Latest Accepted Articles

Prediction of elastic properties of short fiber reinforced composites based on machine learning
WANG Jiling, JIN Hao, GUO Ruiwen, SHI Chenxi, YANG Lifang, LI Meie, ZHOU Jinxiong
, Available online  
Abstract:
The elastic and mechanical properties of short fiber reinforced composites are significantly affected by their internal structure and the properties of the underlying materials, and the parametric analysis of these effects requires extremely high experimental or numerical analysis costs. In order to solve this problem, this paper combines the numerical homogenization method based on periodic representative volume units (RVE) and artificial neural network (ANN) to construct three forms of mechanical property prediction surrogate models of short fiber reinforced composites: spatial random distribution, intralayer random distribution and aligned distribution, respectively. Each surrogate model can quickly predict the equivalent elastic properties of composites under different parameter combinations (fiber length, aspect ratio, volume fraction, and fiber and matrix material properties), and the goodness of fit R2 is above 0.98, the calculation time is negligible compared to conventional simulation calculations, which greatly saves experimental and computational costs and creates important conditions for the design and customization of short fiber-reinforced composites.
Influence of multiple process parameters on the friction coefficient of prepregs and machine learning prediction method
SONG Feng, ZHANG Jiachen, LV Bingyi, WANG Shiyu, XIAO Jinyou, WEN Lihua, HOU Xiao
, Available online  
Abstract:
During the forming process of composites, the friction-sliding behavior between prepreg ply-ply and ply-tool may lead to defects such as wrinkles and pores, which seriously affect the mechanical properties of the components. However, there are many factors affecting the inter-ply friction of the prepreg plies in the forming process of complex components. The existing theoretical models contain insufficient process parameters, resulting in the accuracy of forming process simulation not meeting high-quality forming requirements. In this paper, a friction test method for carbon fiber prepregs was designed for multiple process parameters. The influence of sliding velocity, normal force, viscosity, surface roughness, contact material, and fiber orientation on the friction coefficient were studied. Taking the typical fiber orientations of \begin{document}$ {{\text{0}}^{\text{o}}}{\text{/4}}{{\text{5}}^{\text{o}}}{\text{/9}}{{\text{0}}^{\text{o}}} $\end{document} as examples, the inter-ply friction mechanism in different fiber orientations was revealed. In order to predict the friction coefficient of prepreg corresponding to multiple process parameters rapidly and accurately, a prediction model for the friction coefficient of prepreg was established using the support vector regression (SVR) method. Taking the prepreg ply-ply friction behavior with relative fiber orientation of \begin{document}$ {\text{[3}}{{\text{0}}^{\text{o}}}{\text{/}}{{\text{0}}^{\text{o}}}{\text{]}} $\end{document} and \begin{document}$ {\text{[6}}{{\text{0}}^{\text{o}}}{\text{/}}{{\text{0}}^{\text{o}}}{\text{]}} $\end{document} as examples, the experiments and predictions were conducted, and the error was less than 7%.
Research progress on energy absorption mechanism and damage mode of fiber reinforced resin based bulletproof composites
ZHAO Yun, YANG Bo, TAO Ziwei, NING Huiming, CHENG Yehong, HU Ning, ZHAO Libin
, Available online  
Abstract:
This article reviews the energy absorption mechanism and damage modes of fiber reinforced resin matrix composites in the field of impact resistance. Firstly, the applications of fiber reinforced composites in the fields of ballistic protection and aerospace are introduced. In addition, the advantages and disadvantages of high-performance fibers such as ultra-high molecular weight polyethylene fiber (UHMWPE), aramid fibers and carbon fibers are compared. Secondly, based on ballistic experiments and theoretical simulations of various fiber reinforced resin matrix composites, the energy absorption mechanism and damage mode of bulletproof composites are analyzed. It is found that tensile deformation is the main energy absorption mode of composites, and delamination is its main damage mode. Finally, the classification and characteristics of fabric structures and their influence on the ballistic performance of composites are summarized and the development prospect of fiber reinforced resin matrix composites is prospected.
Research progress of modified epoxy resin anticorrosive composite coatings
TONG Qingling, YANG Jianjun, WU Qingyun, WU Mingyuan, ZHANG Jianan, LIU Jiuyi
, Available online  
Abstract:
In the field of anti-corrosion, epoxy resin anti-corrosion composite coating is an excellent material to prevent metal corrosion. The epoxy coating forms a barrier between the metal and the corrosive ions, but the anti-corrosion effect of the epoxy resin does not last long during curing due to mechanical breakage and the formation of micropores. Three strategies for enhancing the anticorrosive properties of epoxy resin are introduced in this paper, namely nanoparticle modification, micro/nano container modification, and bio-based material modification. The research progress of epoxy resin anticorrosive composite coating modification is reviewed, and the future development direction of epoxy resin anticorrosive composite coating is prospected. In the future, a green epoxy anticorrosive composite coating with intelligent self-warning and self-repair, multi-function and cost-effective should be developed.
Simulation and experimental study of CFRTP orthogonal cutting considering the influence of temperature
WEI Gang, WANG Fuji, JIA Zhenyuan, JU Pengcheng, HU Xiaohang, FU Rao
, Available online  
Abstract:
Carbon fiber reinforced thermoplastic composites (CFRTP) is the preferred material for weight loss and efficiency improvement of high-end equipment. However, CFRTP is a typical difficult-to-machine material, and damage occurs frequently during processing. In this paper, the process of material removal and damage formation during cutting CFRTP was simulated and experimentally studied. CFRTP is prone to plastic deformation during cutting, and the material properties are greatly affected by temperature. In this paper, a three-dimensional orthogonal cutting simulation model of CFRTP was established, and the J-C model was introduced to characterize the elastic-plastic deformation of resin at different temperatures. The effects of temperature and fiber orientation angle on the cutting removal process of CFRTP were analyzed. The results show that when cutting at room temperature, and the fiber orientation angles are 0° and 45°, the machined surface is relatively flat and the processing quality is better; when the fiber orientation angles are 90° and 135°, the bending degree of the fiber increases obviously, and there are cracks on the machined surface, and the processing quality is poor. When cutting at room temperature, and the fiber orientation angle is 0°, the unremoved material appears on the machined surface; when the fiber orientation angle is 45°, cracks and fiber pull-out phenomenon appear on the machined surface. When the fiber orientation angles are 90° and 135°, the machined surface is more cracked, and the workpiece has obvious out-of-plane deformation along the thickness direction. The material with out-of-plane deformation is difficult to be effectively removed.
Preparation and characterization on carbon fiber composites with high thermal conductivity based on multifunctional intercalation structures
CAO Hongtao, CHENG Tao, SUN Zhenghao, CHEN Li, LI Yaoyao, HU Bingsheng
, Available online  
Abstract:
With the extensive application of carbon fiber reinforced resin matrix composites in aerospace field, structure/function integrated composites will play a crucial part. In this paper, asphalt based carbon fiber (CF) reinforced cyanate ester composites with high thermal conductivity were prepared by functional interlayer technology (Functional Interlayer Technology, FIT). The film material graphene sheets (GNPs)-Al2O3/CF prepared by electrophoretic deposition of GNPs and Al2O3 on the surface of the short-cut carbon fiber film was used as the functional interlayer film to replace the resin-rich layer region between the fiber layers. The in-plane thermal conductivity and through-plane thermal conductivity of orthogonal lamination composites are increased by 123.1% and 77.5%. The in-plane thermal conductivity and through-plane thermal conductivity of quasi-anisotropic lamination composites are increased by 119.0% and 50.0%, respectively. In addition, the addition of multifunctional intercalation structure can prevent the propagation of cracks and improve the interlaminar toughness of composites. Therefore, the multifunctional intercalation structure can not only form an effective thermal network structure between the layers to improve the in-plane and out-of-plane thermal conductivity of the composite, but also improve the toughening efficiency of the interlayer region.
Considering the influence of temperature and stress levels on the nonlinear creep model of GFRP in a water environment
ZHANG Yanfeng, LU Qi, LI Xingen, ZHU Sirong
, Available online  
Abstract:
This study investigates the influence of temperature and stress levels on the creep behavior of GFRP composite materials in deionized water environment. After treating the specimens with resin edge sealing, long-term creep tests were conducted at 20%, 30%, 40%, 50%, and 60% stress levels under 20°C, 30°C, 40°C, 50°C, and 60°C conditions using a constant load bending corrosion test machine. Furthermore, long-term creep tests were also performed at 20%, 30%, 40%, and 50% stress levels under 30°C conditions. The study separately examines the effects of different temperatures and stress levels on the creep performance of GFRP, quantifies the comprehensive impact of temperature and stress levels on the creep behavior of GFRP in deionized water environment, and establishes an improved Findley nonlinear creep model. Additionally, the study assesses the influence of deionized water environment on the interlaminar shear strength of GFRP using the short beam shear method. The results indicate that the improved Findley nonlinear creep model can accurately describe the creep performance of GFRP at temperatures ranging from 20°C to 60°C and below its creep fracture stress level, showing a broad applicability and high accuracy with good agreement with experimental results. Based on this model, the long-term creep performance of GFRP composite materials under different temperatures and stress levels in deionized water environment can be predicted, with prediction errors within 2%. Deionized water has minimal impact on the interlaminar shear strength of edge-sealed GFRP specimens. The findings of this study provide a basis for the design of GFRP structures.
Axial compressive property of 3 D braided-unidirectional hybrid tubes
SUN Houli, SUN Lin, WANG Xiaobo, CUI Jian, LI Zherui, ZHA Yibin, QIN Cheng, YAN Hongxia, LIU Yong, ZHANG Hui, YU Jianyong
, Available online  
Abstract:
Using the method of combining quasi-static axial compression experiment with finite element simulation, the axial compression characteristics and failure mechanisms of 3D braided-unidirectional ply (3D-UD) hybrid tubes were investigated. Test results show that the peak load, total absorbed energy and specific energy absorption (SEA) of 3D-UD hybrid tube are increased by 20.3%, 109.2% and 67.1% respectively compared to the UD tube, and the compression energy absorption mode becomes more stable. In addition, the failure process of 3D-UD hybrid tubes was simulated by finite element method. The results show that load-displacement curves curve are in good accordance with experiment results so that the reliability of the simulation model is verified. Combined with the experimental results and the simulation analysis of the damage deformation of the mixed tube, it is found that the binding and supporting effects of the outer layer 3D and the inner layer 3D on the sandwich UD inhibit the breakage of the UD tube wall due to excessive bending. At the same time, the stability failure and energy absorption of the sandwich UD tube prevent the 3D tube from serious braided layer crimp. Therefore, the mixed tube can effectively resist the wall deformation and improve the stability and energy absorption under axial compression.
Deep learning based tensile-shear damage evolution mechanism of quasi-isotropic satin weave C/SiC composites
CHEN Peng, WANG Long, ZHANG Daxu, DU Yonglong, GUO Weiyu, CHEN Chao
, Available online  
Abstract:
4D X-ray CT in-situ tensile testing, along with deep learning technology, was used to characterize the damage and failure process of quasi-isotropic lay-up satin C/SiC composites under tensile loading, and to reveal the damage evolution mechanism under the coupled action of (0°/90°) lay-up tension and (±45°) lay-up shear. Using the deep learning image segmentation method, damages were extracted for quantitative analysis based on intelligent detection of matrix cracks, delamination of the material under loading. Furthermore, damage and failure mechanisms were investigated by examining the fracture morphology. It is found that ±45° oblique cracks account for the major part of matrix cracks. Oblique cracks were mainly induced by small cracks at the initial loading stage. Although transverse cracks were less than oblique ones, their lengths and crack opening distance developed rapidly. Delamination was induced by the deflection of matrix cracks along the interfaces between adjacent layers. For a (0°/90°) satin lay-up, transverse split took place in the tissue point region of 90° fibre tows, and accompanied by bending in the floating length region of 90° fibre tows. Fractures occurred in the tissue point region of 0° fibre tows, and accompanied by longitudinal split in the floating length region of 0° tows. For a (±45°) satin lay-up, oblique split and relatively sliding occurred in −45° (or +45°) tows. While fractures accompanied by fibre tow bridging and bending took place in the +45° (or −45°) tows of the same lay-up.
Nonlinear transient heat transfer analysis of functionally graded material sandwich slabs by incremental differential quadrature element method
ZHANG Zhong, XU Jiajing, CAO Xiaojian, WANG Yanchao, ZHU Jun, YAO Lu
, Available online  
Abstract:
As a first attempt, the incremental differential quadrature element method (IDQEM) was adopted to perform the one-dimensional nonlinear transient heat transfer analysis of functionally graded material (FGM) sandwich slabs. The thermophysical properties of the slab were considered to be position- and temperature-dependent. To implement the IDQEM, the sandwich slab was divided into three spatial sub-domains along the layer interfaces, and the entire heating process was also divided into several temporal sub-domains. For each temporal sub-domain, the governing equations as well as the initial condition, interfacial condition, and boundary condition were discretized by the differential quadrature technique. Because the obtained discrete equations were built in different regions of grid points, a modification of the equations was proposed which were then expressed in the matrix forms so that they can be built in the same regions. Using the Kronecker product, the simultaneous matrix equations were transformed into a set of nonlinear algebraic equations, which were then solved by the Newton-Raphson iteration method to obtain the temperature profile for each temporal sub-domain. Because the initial condition of each temporal sub-domain was defined by the temperature results at the end of the previous sub-domain, the temperature profile of the slab during the entire heating process can be obtained by repeating the calculation procedure from the first temporal sub-domain to the last one. Numerical examples were carried out to verify the fast convergence of the present method. The correctness of the present method was verified through comparison with the analytical and numerical results reported in previous works. The effects of temperature-dependent thermophysical properties, volume fraction index, and thermal boundary on the temperature profile of the slab were discussed.
Extraction of plant long fiber and its application in biodegradable composites
HUANG Jingxu, LI Minwen, LI Zhihan, HUANG Haibo
, Available online  
Abstract:
Plant fibers have the advantages of eco-friendliness, lightweight, high strength, sound and heat insulating, and low carbon footprint, etc. These attributes make them highly sought-after for applications in sectors such as automotive, aerospace, construction, packaging, and transportation, particularly when plant fibers are processed into composites with polymers. This paper briefly describes the effects of the types of plant long fibers and extraction methods on their physical properties, and at the same time outlines the effects of plant long fibers on the physical properties of composites when they are used as reinforcement in combination with the fiber orientation distribution, fiber surface modification, composite molding process, and failure modes under tensile loading, as well as summarizes and looks forward to the application of plant long fiber-reinforced biodegradable composites.
Study on the mechanism of radiation heat dissipation behavior of rubber/steel cord composites based on multi-scale simulation
ZHOU Jiazhi, XIAO Huiping, XIE Xiaolin, ZHOU Zhisong, AN Lin, LI Wenbo
, Available online  
Abstract:
Heat transfer and temperature field analysis of rubber steel/cord composites are important for the study of vulcanization molding, thermo-oxidative aging, and thermal fatigue life of rubber products. In this paper, the heat transfer and heat dissipation mechanisms of rubber/steel cord composites with different steel cord ratios, laminate angles and temperature rise operating conditions are investigated based on a multi-scale heat transfer model and experimentally verified. The results show that the rubber/steel cord composites exhibit obvious anisotropic heat transfer behavior, and the heat flow aggregation effect at the heat transfer interface accelerates the interlayer diffusion of heat for more uniform temperature distribution. The radiative heat dissipation emissivity obtained from the simulation is as high as 0.95, and the radiative heat dissipation behavior is more pronounced as the percentage of steel cord increases and the temperature rises. Compared to the series-parallel heat transfer model, the prediction error of the multiscale heat transfer model is reduced from 10.1% to 2.5%.
Impact of the morphological evolution of SEBS based on external field effects on the mechanical properties of PPS composite materials
YI Chenghong, XIE Linsheng, JI Huajian, LI Guo, MA Yulu, WANG Yu
, Available online  
Abstract:
Polyphenylene sulfide (PPS) stands as a thermoplastic engineering material, renowned for its high strength and excellent stability. It has found extensive applications in both defense and civilian sectors. However, the intrinsic lack of toughness in PPS necessitates toughness enhancement for broadening its application scope, typically achieved through the incorporation of elastomers. In this study, a melt-blending technique utilizing a high-stretch chaotic flow rotor was employed to prepare hydrogenated styrene-butadiene-styrene block copolymer/polyphenylene sulfide (SEBS/PPS) composite materials. The research aimed to investigate the microstructural evolution of the materials under the influence of high-stretch external forces and analyze the impact of varying SEBS content on the mechanical properties of the PPS-based composite materials. The results indicate that with an increase in SEBS content, the impact strength and fracture elongation of the PPS-based composite materials exhibit an initial rise followed by a subsequent decline. When the SEBS content reaches 6wt%, the composite material demonstrates a ductile fracture behavior, achieving the highest impact strength and fracture elongation at 67.8 J/m and 6.1%, respectively. Microstructural analysis of the composite material reveals that within the SEBS content range of 0~6wt%, under the action of the high-stretch blending rotor, SEBS particles exhibit smaller and more uniformly distributed sizes. The droplet morphology undergoes a transition to elongated rod shapes, indicating a brittle-to-ductile transformation and a significant improvement in toughness. In the composite material with 6wt% SEBS content, multiple silver streaks are induced upon impact, leading to shear yielding and exhibiting plastic deformation. Continued increase in SEBS content intensifies the aggregation behavior of SEBS, resulting in an enlargement of particle sizes and broader distribution. At this stage, numerous void regions appear at the two-phase interfaces, triggering the development of silver streaks and concurrently causing fracture failure in the composite material, leading to a decrease in impact strength.
Preparation of curved carbon/carbon honeycomb and its mechanical properties under uniform load
WU Hao, LI Weijie, ZHANG Zhongwei, LIU Yu, LEI Yu, SHI Wentong, DONG Zhichao
, Available online  
Abstract:
With the increasing demand of precision instruments on the bearing platform structure, honeycomb structure has been widely concerned because of its light weight and ultra-high stability. In order to meet the requirements of the special-shaped composite bearing platform, this paper uses the combination of hot pressing and resin impregnation carbonization and chemical vapor deposition (CVD) to prepare the curved carbon/carbon honey-comb structure samples of different specifications. Then, according to the structural characteristics of curved honeycomb and the service environment, a test method of uniform load is designed to conduct compression tests on different samples. The influences of honeycomb thickness, layering angle and curvature radius on the mechanical properties of curved honeycomb were analyzed. The results show that when the radial thickness of honeycomb increases, the bending degree of honeycomb wall increases, the load on honeycomb double-walled space increases, and the cracking tendency of adhesive surface becomes more obvious. When the orientation of honeycomb fiber changes from 0° to 45°, the bending mode of honeycomb wall changes to non-buckling, ductile buckling and plastic buckling. When the curvature radius of curved honeycomb decreases, the failure mode gradually changes from decudation cracking to buckling fracture of honeycomb wall. The curved carbon/carbon honeycomb prepared in this paper has a compressive strength of 1.48 MPa, and has good mechanical properties, which can meet the requirements of increasingly complex aerospace structures.
Advances in silica aerogel composites and their research in aerospace
Mu Rui, LIU Yuanxue, LIU Xiaoying, ZHANG Yuxin, YAO Weilai, REN Junru, CHEN Jinfeng, CHENG Xinlei, YANG Xiuming, GONG Hongwei
, Available online  
Abstract:
As the most cutting-edge, basic and influential science and technology research field, the level of scientific research development is an important symbol to measure the innovation of national science and technology. However, aerospace thermal insulation materials are the most important technical support for the development of aerospace technology, and how to prepare materials with good thermal insulation properties and mechanical strength is of great significance for the development of aerospace technology. Silicon dioxide aerogel with ultra-low thermal conductivity, high porosity, high specific surface area and ultra-low density and other excellent properties, in the deep space probe, solar panels, space shuttle engines, solid rocket boosters and return capsule base and other special engineering equipment materials have a better application prospects.. In recent years, with the continuous development of silica aerogel research methods and preparation technology, by compounding it with functional materials with high strength and high temperature resistance, it can synergistically enhance its properties such as thermal insulation and mechanical strength, which is crucial for the development of aerospace special engineering materials. In view of this, this paper briefly describes the development history of silica aerogel, analyzes and summarizes in detail the research progress of aerogel composites formed by compositing silica aerogel with common oxides, fiber-reinforced and organic polymers and other reinforcing materials in the field of aerospace, and mainly comments on the preparation method, structural characteristics, heat insulation, mechanical properties, etc., and looks ahead to the problems, challenges, and future directions of the research and application of silica aerogel composites in this field.
Preparation of S−BiOI/BiOBr adsorption photocatalyst and its removal properties for 2,4−dichlorophenoxyacetic acid
YAO Dan, YANG Yi, ZHENG Anni, WANG Shaobing, YU Guanlong
, Available online  
Abstract:
Pesticide pollution of water body is a potential threat to human health. In this study, a new S0.1−(0.3/0.7)BiOI/BiOBr (S0.1BBI0.3) photocatalyst was synthesized by one−step solvothermal method. The structure, morphology and optical properties were characterized by XRD, SEM, XPS, UV−Vis DRS, EIS and other methods. S0.1BBI0.3 is a flower−like microsphere structure formed by the accumulation of two−dimensional nanosheets. Z−type heterojunction and S−doped dual−strategy co−modification broaden the photoresponse range of BiOBr, effectively prevent the photogenerated electron−hole pair recombination in S0.1BBI0.3, improve the photogenerated carrier redox ability, and increase the specific surface area. It provides more mesoporous structures, significantly improves adsorption properties, and provides more active sites for photocatalytic reactions. The photocatalytic experiment results showed that S0.1BBI0.3 had the best adsorption and photocatalytic performance for 2,4−dichlorophenoxyacetic acid (2,4−D) under visible light, and the removal rate of 2,4−D was up to 91.8% under 45 min darkness and 120 min light conditions. ESR technology confirmed that ·O2 is a photocatalytic active substance of S0.1BBI0.3.
Flexible capacitive pressure sensor based on carbon black/barium titanate/polyurethane
CHEN Xufeng, ZHANG Yu, QIN Yafei, WANG Mengyan, SUI Zhiyuan
, Available online  
Abstract:
With the rapid development and application of smart wearable flexible electronic technology in biomedicine, electronic skin, human-computer interaction and other fields, the research demand of flexible pressure sensors with high sensitivity and wide detection range has been put on the agenda. In this paper, a CB-BTO/PU flexible capacitive pressure sensor was prepared by using the polyurethane sponge (PU) as the base and combining CB-BTO/ BTO composite material on the polyurethane sponge by ultrasonic dipping coating. After testing, the sensor combines high sensitivity (~0.7911 kPa−1) and wide detection range (0~300 kPa). At the same time, the response time, the minimum detection limit and the stability of the sensor are studied. In addition, the sensor has been tested in four different pressure ranges, which verifies the potential of the sensor in high sensitivity and wide detection range, and provides a new possibility for low-cost and large-scale fabrication of high-performance flexible sensors.
Effects of high temperature heat treatment on the micro structure and mechanical performance of C/C-SiC composite materials
MA Fei, LUO Hao, SUN Shouye, SHI Xiangdong, LUO Ruiying, GUO Lingyan
, Available online  
Abstract:
The microstructure and properties of C/C-SiC composites prepared by reactive melt infiltration (RMI) are significantly affected by post-heat treatment. In order to study the effect and mechanism of post-heat treatment on the microstructure and mechanical properties of C/C-SiC composites prepared by RMI, the isothermal chemical vapor infiltration (CVI) process was used to deposit pyrolytic carbon matrix in the carbon fiber preform, and C/C porous bodies with a density of 1.2 g/cm3 were prepared by using natural gas as carbon source gas and nitrogen as carrier gas and dilution gas. Then C/C-SiC composites were prepared by reactive melt infiltration method. The effects of different post-heat treatment temperatures on the phase composition, internal stress and mechanical properties of C/C-SiC composites were studied. The prepared C/C-SiC composites were treated at 1300℃, 1500℃ and 1700℃ respectively. The effects of post-high temperature heat treatment on the density, porosity, matrix composition, internal stress and bending properties of the C/C-SiC composites were investigated. The results show that after heat treatment at 1300℃, 1500℃ and 1700℃, the density of C/C-SiC composites decreases, the porosity increases, the content of SiC matrix increases, the distribution of SiC matrix becomes more extensive, and the residual Si content decreases significantly with large pores caused by residual Si volatilization. At 1300℃, 1500℃ and 1700℃, the bending strength increases first and then decreases. At 1500℃, the bending strength reaches a maximum of 296.52 MPa. With the increase of the post-treatment temperature, the bending modulus decreases, and at 1700℃, the bending strength decreases the most.
Preparation and microwave absorption properties of ultra-fluffy doped graphene aerogel composites
REN Peiyong, CHEN Miao, ZHAO Ke, GAO Xiaoping
, Available online  
Abstract:
With the rapid advancement of intelligent communication, the issue of electromagnetic radiation caused by information transmission is becoming increasingly severe. However, traditional microwave absorption materials have limitations such as poor attenuation ability and difficulties in impedance matching, which no longer meet practical applications. In this paper, graphene aerogel (GA) was prepared by hydrothermal synthesis based on the theory of electromagnetic loss, the design strategy of multi-component synergistic loss and the construction of three-dimensional porous aerogel. To enhance its properties, we incorporated MnO2-coated Ni-Zn ferrite (NiZnFe2O4@MnO2) microspheres with graphene dielectric material to prepare ultra-fluffy magnetically doped graphene-based composite aerogel (NiZnFe2O4@MnO2/GA) powders. The impact of heat treatment temperature and magnetic doping on the wave absorption capability of the composite aerogel was analyzed. Our results demonstrate that at a heat treatment temperature of 300 ℃ and a nickel-zinc ferrite doping amount of 15 wt%, the composite aerogel exhibits optimal absorption performance. At a matching thickness of 2.9 mm, it achieves a minimum reflection loss (RLmin) value of -47.27 dB at a frequency of 8.72 GHz, providing an effective absorption bandwidth (EAB) spanning 3.2 GHz covering most X-band frequencies while maintaining only a packing load rate of 10 wt%. The problem of poor material impedance matching is solved, the dielectric loss and magnetic loss capacity of the absorbing materials are optimized,The application requirements of the wave absorbing material for "thin, light, wide and strong" are met.
Cement-based structural batteries: mechanism, influencing factors, and application
XIE Wenjian, GAO Wanyang, HU Nantao
, Available online  
Abstract:
Structural energy storage integrated composite materials provide an innovative approach to the integrated development of structure and energy storage. Using cement-based materials as a structural electrolyte and combining it with electrode material can produce cement-based structural batteries. This review paper provides an overview of research on cement-based structural batteries. The paper introduced the conductive and discharge mechanism and discussed the key factors that affect resistivity and discharge performance from the major aspects of electrode and electrolyte. Research indicates that cement-based structure batteries can achieve a voltage of 1.5 V and a capacity density of 8.45×105 mA·h·m−1, and are rechargeable. With the characteristics of integrated structural and energy storage functions, it demonstrates the potential for applications in energy storage green building, smart concrete, and energy-harvesting concrete. Finally, the paper points out current problems and future research directions.
Flexible capacitive pressure sensor with a wide detection range based on porous carbon nanotube、carboxyl iron powder/silicone composite
YUAN Lin, HUNG Chengyi, HUANG Pei, LI Yuanqing, FU Shaoyun
, Available online  
Abstract:
Featured by simple structure, fast response, high sensitivity, and low cost, etc., flexible capacitive pressure sensor has been widely used in the fields of health care, robotics, wearable devices and so on. However, the trade-off between the effective upper and lower detection limits greatly restricts the applications of the flexible capacitive pressure sensor. In this work, a flexible and porous carbon nanotube (CNT)/carbonyl iron particle (CIP)/silicone composite was produced by using sugar particles (SPs) as the as pore-forming agents, CIPs as the magneto-responsive fillers, CNTs as the conductive fillers and silicone rubber as the flexible matrix. After serving as the dielectric layer, the porous CNT、CIP/silicone composite endows the capacitive pressure sensor produced a wide effective detection range of 0.07-180 kPa (at the frequency range of 0-5 Hz), much wider than most capacitive pressure sensors reported. In virtue of the wide detection range, long-term stability and fast response, the sensor produced is capable of monitoring human breath, arm movement, talking, and robotic movement, thus showing great promise in health monitoring, wearable electronic devices, and intelligent robotics, etc.
Preparation and properties of Silicone polymer-Graphene oxide reinforced glass fiber/epoxy resin composites
XU Huan, YE Bei, LU Jing Jing, GUAN Ji Peng, DANG Rui Qiong, SHEN Xiao Jun
, Available online  
Abstract:
In this study, different proportions of Silicon polymer-Graphene oxide (PSOL-GO) were used as nano-fillers to modify Glass fiber/epoxy resin(GF/EP )composites, the composites with different PSOL-GO contents were prepared, The microstructure and strengthening mechanism of epoxy composites were analyzed by observing morphology, measuring contact Angle, infrared analysis, mechanical properties and dynamic mechanical analysis (DMA). The experimental results show that the mechanical properties of PSOL-GO@GF/EP composites are the best when the ratio of PSOL-GO is 1∶0.1: The interlayer shear strength of modified GF/EP composites is 13.19% higher than that of pure GF/EP composites; Its bending strength increased by 33.12%; Its tensile strength increased by 35.32%; Its impact strength increased by 16.95%. The glass transition temperature (Tg) of GF/EP composites was increased by 7.1℃ by adding PSOL-GO at 1∶0.1 ratio, and the heat resistance of GF/EP composites was improved. The epoxy resin with the introduction of PSOL-GO nano-filler has better wettability to glass fibers, and can fill the gap of pure GF/EP composite itself to enhance the performance of the composite materials.
Adsorption performance and mechanism of MnO2/Ti3C2TX composite towards U(VI) in water
ZHOU guolin, XIE shuibo, HU lian
, Available online  
Abstract:
To address the shortcomings of Ti3C2TX nanosheets, which tend to stack and have limited adsorption sites, a MnO2/Ti3C2TX composite was prepared using the hydrothermal method. The influence of uranium initial concentration, dosage, pH, time, and interfering ions on U(VI) adsorption was investigated through single-factor adsorption experiments. Modern characterization techniques were employed to analyze the surface properties of MnO2/Ti3C2TX and the mechanism of U(VI) adsorption. Experimental results revealed that with an initial U(VI) concentration of 5 mg·L−1, MnO2/Ti3C2TX dosage of 0.1 g·L−1, and a temperature of 303 K, pH of 6, the U(VI) concentration dropped to 0.41mg·L−1 within 30 seconds. Adsorption equilibrium was reached after 30 minutes, with an adsorption rate of 99.15% and an adsorption capacity of 49.58 mg·g−1. After five cycles, the adsorption efficiency of MnO2/Ti3C2TX remained at 96.3%, demonstrating its potential for regeneration and reuse.The entire adsorption process was endothermic and spontaneous, fitting the pseudo-second-order kinetic model and the Freundlich isotherm model. BET analysis showed that the specific surface area of MnO2/Ti3C2TX reached 318.3 m2·g−1, which is 55.9 times higher than that of Ti3C2TX. FTIR and XPS analyses indicated that the primary mechanism of U(VI) adsorption on MnO2/Ti3C2TX is the coordination complexation between surface oxygen-containing groups and uranium.
Research progress of electrolytes for aluminum ion batteries
LEI Xin, CHENG Cheng, SUN Tao, FAN Hognyu, SHEN Xuejing, WU Zhanjun
, Available online  
Abstract:
Due to the rapid development of society, demands for secondary ion batteries are gradually increasing. Aluminum-ion battery has a lot of advantages, such as low cost, high safety and good cycle performance. Thus, it is an ideal energy storage system to replace lithium-ion battery in the future. As an important component of battery system, electrolyte plays a key role in transferring ions and connecting circuits, and has a direct impact on battery performance. Therefore, designing and preparing of electrolytes with good overall performance has become a research hotspot in aluminum-ion batteries. This article summarizes the current research status of liquid electrolytes, inorganic solid electrolytes and polymer electrolytes for aluminum-ion batteries, analyzes their performance in terms of cost, electrochemical window, chemical stability and ionic conductivity. The future development direction of aluminum-ion battery electrolytes is prospected.
Research on the Uranium ion Removal Performance of Polyethyleneimine/Ramie Fiber Self-Supporting Membranes
ZHANG Shuang, TANG Yong, AN Zaixu, CHEN Xixi, NA Bing, LIU Hesheng, LIU Yuhui
, Available online  
Abstract:
In order to deal with the increasingly serious energy and environmental pollution problems, the treatment of uranium containing wastewater has become an urgent matter. In order to treat uranium containing wastewater efficiently and conveniently, polyethylenimide/ramie fiber self-sustaining membrane (PEI/RAM) was prepared by grafting polyethylimide (PEI) onto ramie fiber after treatment with low eutic solvent (DES, choline chloride-oxalic acid system), and was used to remove uranyl ion (UO22+) in aqueous solution. The effects of initial concentration of UO22+, pH value of solution, adsorption time and temperature on the properties of the adsorbent were studied. When the initial concentration of uranyl ion is 20 mg/L and the solution pH is 6, the adsorption equilibrium capacity of uranium reaches 302 mg·g−1. The uranium adsorption process of PEI/RAM is closer to Langmuir model and quasi-second-order kinetic model. In the presence of interfering metal ions (Ca2+, K+, Mg2+, Na+), the polyethylenimide/Ramie fiber self-supported film (PEI/RAM) adsorbent showed good selectivity for uranyl ions, and its adsorption capacity for UO22+ (20 mg/L) was nearly 70 times that of other metal ions (20 mg/L).
Electromagnetic performance and microstructure of amorphous/Fe-Si soft magnetic composites
GUO Hai, NIE Min, YANG Yiting, ZHAO Fengxiang, HE Jiayi
, Available online  
Abstract:
This work optimizes the electromagnetic properties of Fe-Si based soft magnetic composites by both modifying the composition and particle size distribution. The relationship between soft magnetic properties and microstructure is investigated. Great comprehensive electromagnetic properties can be obtained by firstly composing the Fe-Si powders with different sizes, and then partly replacing the coarse Fe-Si powder by Fe-Si-B-C amorphous powder with similar particle size. The amorphous/Fe-Si soft magnetic composites have good frequency stability within 1 MHz. When the mass ratio among Fe-Si-B-C amorphous powder, Fe-Si coarse powder, Fe-Si fine powder is 25∶25∶50, the effective permeability at 100 kHz is 47.6, the DC bias capacity at 100 Oe is 79.5%, and the power loss at 100 kHz/100mT is 1806 mW/cm3. Compared with other reported amorphous-containing soft magnetic composites, the amorphous Fe-Si-B-C/Fe-Si soft magnetic composites in this work have significant advantages in cost and combined electromagnetic properties. The Fe-Si fine powder can fill the gap between the coarse powder, which is conducive to improving the density and permeability of the soft magnetic composite, while the addition of amorphous powder can significantly reduce the power loss. The amorphous/Fe-Si soft magnetic composites prepared in this work have good comprehensive electromagnetic properties and can provide potential solutions for industrial production.
Pore structure and mechanical properties of steel fiber reinforced geopolymer recycled aggregate concrete
LI Zhenjun, LIU Xi, ZHAO Chenyu, WANG Chi, TIAN Xin
, Available online  
Abstract:
To study the pore characteristics and macroscopic performance of steel fiber reinforced geopolymer recycled aggregate concrete (SFGRC), the internal pore structure, mechanical properties and shrinkage performance of SFGRC were tested. The influences of recycled aggregate content and calcium silicon ratio on the pore structure, strength, stress-strain curve shape and characteristic parameters of concrete were analyzed. Based on fractal theory, a correlation model between pore structure and the macroscopic performance of SFGRC was established. The research results indicate that recycled aggregate significantly increases the porosity and harmful pore proportion of SFGRC and deteriorates its mechanical properties. The high ground granulated blast furnace slag (GGBS) content refines the pore structure of SFGRC, increasing the complexity of the material's pore size and spatial distribution. The GGBS and recycled aggregate significantly increase the shrinkage rate of SFGRC. The pore structure of SFGRC exhibits obvious fractal characteristics, with fractal dimensions ranging from 2.623 to 2.731. It strongly correlates with pore structure characteristic parameters and mechanical properties, which can effectively evaluate the pore structure characteristics of SFGRC. A prediction model based on fractal dimension for characteristic parameters such as SFGRC elastic modulus, ultimate stress, ultimate strain and drying shrinkage was established using the Bayesian- markov chain monte carlo (Bayesian-MCMC) method, with a goodness of fit of 0.51-0.98 and high prediction accuracy. This provides a theoretical basis for optimizing the pore structure and macroscopic performance of GRC concrete.
Construction and drug release performance of thermosensitive copolymer-modified hollow mesoporous silica and the composite nanofibers
PEI Wenxiang, MA Shijie, YANG Langfei, GAO Yujie, WU Jindan
, Available online  
Abstract:
Traditional drug-loaded nanofibers face challenges such as unstable drug loading and excessively rapid release. In light of these issues, this study employs a thermosensitive copolymer (P(NIPAM-co-AM)) to coat hollow mesoporous silica nanoparticles (HMSN), incorporating them as drug carriers in conjunction with poly(ε-caprolactone) (PCL) nanofibers. The drug release and antibacterial performance of the composite nanofiber membrane were investigated. Firstly, the HMSN surface was functionalized through free radical polymerization by grafting a copolymer of isopropylacrylamide (NIPAM) and acrylamide (AM) (P(NIPAM-co-AM)). Hydrophobic drug ciprofloxacin (CIP) was loaded into the modified nanoparticles (P(NIPAM-co-AM)-HMSN or PHMSN). The analysis of the microstructure, composition, and temperature-responsibility of the drug-loaded particles were performed using SEM, TEM, TG, BET analysis, FTIR, UV-Vis spectroscopy, etc. Blending PCL with drug-loaded PHMSN, a composite fibrous membrane (CIP@PHMSN-PCL) was fabricated using electrospinning. CIP@PHMSN-PCL exhibited temperature-stimulated drug releasing, with cumulative release rates of CIP reaching 90.78% and 72.67% at 45℃ and 25℃ after 72 hours, respectively. The Korsmeyer-Peppas model aptly described the drug release kinetics, suggesting the diffusion as the primary mechanisms for drug release from the composite fiber membrane. At 45℃, the drug-loaded fiber membrane exhibited a 100% inhibition rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). At 25℃, the inhibition rates were 92.34% and 95.83% against E. coli and S. aureus, respectively, demonstrating temperature-dependent drug release performance of the CIP@PHMSN-PCL membrane. In summary, the drug-loaded PHMSN composite nanofiber membrane exhibits temperature-regulated drug release functionality and excellent antibacterial activity, holding potential application value in the biomedical field.
Research progress of hydrogen permeation palladium composite membranes
ZHU Xiaoxin1, ZHANG Zhenqiang, CAO Mei, TIAN Yiran, HAN Fei, ZHANG Bin
, Available online  
Abstract:
Palladium composite membranes have highly selective permeability to hydrogen due to their special dissolution/diffusion mechanism of hydrogen permeation, and are an ideal material for hydrogen separation in membrane reactors. In order to promote the research and application of palladium composite membranes with high hydrogen permeability and stability, the preparation method of the membranes via electroless plating and its combined with other methods, and different types of the membranes are reviewed in this paper. Electroless plating is the most common preparation method of palladium composite membranes, and the quality of the membranes can be improved by combining with vacuum and continuous flow. Using group ⅤB metals, porous ceramics and stainless steel as the matrix of electroless Pd membranes, the membrane thickness can be reduced, mechanical strength and hydrogen permeability can be improved; The thickness of Pd membranes can be further reduced by adding refractory oxide, zeolite, natural mineral and polymer between Pd membrane and porous matrix, and the thermal and chemical stability can be improved. Compared with pure Pd membrane, Pd-Ag, Pd-Cu, Pd-Au binary alloy membranes and Pd-Au-Ag ternary alloy membrane have no hydrogen embrittlement phenomenon at low temperature, and can improve the hydrogen permeability and sulfur resistance of Pd membranes to a certain degrees. Finally, the future research direction of palladium composite membranes is prospected.
Study on plastic yield strength of gyroid lattice structures based on functional principleson
WU Fenghe, WANG Chaoshi, SUN Yingbing, LIU Lei, ZHANG Tongqing, WANG Zhaohua
, Available online  
Abstract:
One of the differences in mechanical properties between lattice structures and dense structures lies in the plastic yield response. Therefore, studying their yield behavior can provide important theoretical basis for the design and application of lattice structures. Firstly, The Gyroid lattice structure was simplified and its mechanical model was established based on the principle of deformable body function, obtaining the mapping relationship between the plastic yield strength and volume fraction of the Gyroid lattice structure. Then, based on the finite element analysis software Abaqus, simulation experiments were conducted on the quasi-static compression process of Gyroid lattice structures to preliminarily verify the accuracy of the theoretical model. Finally, different volume fractions of 316L stainless steel Gyroid lattice structures were prepared by selective laser melting (SLM), and uniaxial compression experiments were conducted to analyze their deformation mechanism and mechanical properties. The results show that the error between theoretical derivation, finite element simulation results and experimental results is within 25%, and the coefficients of the Gibson-Ashby model fitted based on the results of the three methods have good consistency, indicating the effectiveness of the Gyroid lattice structure plastic yield strength prediction model established based on theoretical derivation. The construction method of theoretical models can be transformed into other complex types of lattice structures, providing a theoretical basis for quickly calculating the mechanical properties of lattice structures and applying them in engineering equipment.
Performance and mechanism of biochar loaded magnetic nanocarbon hydroxyapatite(CHAP-γ-Fe2O3/BC) for the removal of U(VI) from water
SHAO Xiongbin, XIE Shuibo, MAI Yingqing, JIANG Peixuan
, Available online  
Abstract:
To address the efficiency of removing U(VI) from water using functional materials and the susceptibility of nanoparticles to agglomeration, biochar-loaded magnetic nanocarbon hydroxyapatite (CHAP-γ-Fe2O3/BC ) composites were prepared by dynamic oil-heating and impregnation methods using corn stover, egg shells, and magnetic γ-Fe2O, and the experiments were carried out to investigate the performances and used for the removal of U(Ⅵ) from water. When the initial concentration of U(Ⅵ) is 5 mg/L, the dosage of CHAP-γ-Fe2O3/BC is 0.1 g/L, the pH value is 6, the temperature is 30°, and the reaction time is 1 h, the experimental results show that the maximum adsorption capacity of CHAP-γ-Fe2O3/BC for U(Ⅵ) reaches 324.4 mg/g, and the removal rate reaches 95.93%. The proposed secondary kinetic model and Langmuir model could fit the adsorption process of CHAP-γ-Fe2O3/BC on U(Ⅵ) better, indicating that the monomolecular layer chemisorption is dominated. The materials are realized to attenuate the agglomeration by surface modification technique. The composite material shows good separation recovery and recyclability in the magnetic field. The characterization results of FTIR and XPS prove that the removal mechanism of uranium by this material mainly includes ion exchange, dissolution-precipitation chemisorption and surface complexation.
Preparation and properties of micromodulation-based polypropylene/polybutylene terephthalate/carbon nanotube electromagnetic shielding materials
ZHANG Xu, XIE LinSheng, ZHU HuiHao, LI Guo, MA YuLu, WANG Yu
, Available online  
Abstract:
The electromagnetic pollution caused by electronic equipment to the external environment has become another major public hazard after noise pollution, air pollution, water pollution and solid waste pollution, so the research and development of high-performance electromagnetic shielding materials has become a hot spot in materials science research. In this paper, the phase domain size of the polymer phases in the PP/PBT/CNTs blends was regulated by adjusting the blending methods of polypropylene (PP), polybutylene terephthalate (PBT) and carbon nanotubes (CNTs) during the melt blending process. The influence of the microscopic morphology of the composites on their electromagnetic shielding properties was studied by morphology analysis, dynamic rheology and crystallization behavior tests. The results show that compared with the PP phase, CNTs have a stronger affinity for the PBT phase, and are always located in the PBT phase domain among the four blending methods. When the PP/PBT/CNTs composites are prepared by PP/CNTs masterbatch method, the phase domain size of the PBT inside the obtained composites is smaller, the compatibility between PP and PBT is higher, the conductive path and interface area are significantly increased, and a denser and uniform conductive network structure is formed inside the composites, so the conductivity of the prepared polymer matrix composites is significantly improved, reaching 29.60 s/m, and the electromagnetic shielding efficiency is in the X-band (8.2-12.4 GHz) to 35.6 dB, far exceeding the demand for commercial electromagnetic shielding materials.
Preparation of polyvinylpyrrolidone water-based hybrid coating and its sizing treatment of recycled glass fiber
SHEN Yang, XIE Jiaqi, FU Yaqin
, Available online  
Abstract:
In order to effectively utilize recycled glass fiber, two polyvinylpyrrolidone water-based hybrid coatings were synthesized under acid catalysis and without adding catalyst using ethyl orthosilicate and coupling agent as precursors and polyvinylpyrrolidone as film-forming agent. The recycled glass fibers were sized separately using the prepared hybrid coatings. The results showed that the surface roughness of the recycled glass fibers after the sizing treatment of the hybrid coatings prepared under acid-catalyzed conditions was greater compared with that of the hybrid coatings prepared under the condition of no added catalyst; The single-fiber tensile strengths of the recycled glass fibers after sizing treatment of the hybrid coatings prepared under acid-catalyzed conditions and conditions without added catalysts were 1322.7 ± 98.5 MPa and 1093.8 ± 53.8 MPa, which were increased by 39.8% and 15.6%, compared with the single-fiber tensile strengths of the recycled glass fibers. The use of single fiber fragmentation method to evaluate the interfacial properties of recycled glass fiber and epoxy resin shows that single fiber epoxy resin composite materials prepared from recycled glass fiber after sizing with hybrid coating prepared under acid catalytic conditions and without adding catalytic conditions The interfacial shear strengths are 53.5 MPa and 35.7 MPa respectively, which are 200.5% and 100.8% higher than the interfacial shear strengths of single fiber epoxy resin composites of recycled glass fibers without sizing treatment. Aqueous hybrid coatings prepared under acid-catalyzed conditions are shown to be feasible for recycling glass fibers.
Carboxymethyl cellulose-MgCl2 composite based humidity sensor: self-powered, flexible, and multifunctional sensing applications
WANG Haoxiang, TANG Chengli
, Available online  
Abstract:
Humidity sensors have been widely used in fields of agriculture, industrial production, precision instruments and human health monitoring. To address the problem that humidity sensors need to be driven by an external power source, a self-powered flexible humidity sensor based on the principle of primary battery was proposed in this paper. The carboxymethyl cellulose with moisture-sensitive properties and MgCl2 with moisture-absorbent properties were applied as the sensitive layer. And commercialized conductive copper and nickel adhesive tapes were used as the positive and negative electrodes. The micro-morphology and surface elements of the sensitive layer of the sensor were characterized by SEM and EDS, the moisture sensitivity mechanism was analyzed based on complex impedance spectroscopy, and the multifunctional applications of the sensor was demonstrated. The sensor sensitive layer has good hydrophilicity, which can ionize the MgCl2 in it to produce carriers such as Mg2+ and Cl after contacting the water molecules in the environment. The directional movement of these carriers can generate output voltage. The response value can reach 177% when the relative humidity changes from 11% to 95%. The sensor can be used for human respiratory frequency and characteristic detection, soil moisture and urinary moisture detection, finger distance detection, and providing electrical energy. Experimental results show its potential for applications in health monitoring, environmental humidity monitoring, non-contact switching, and power-supply areas.
Influence of the rheological properties of paste on the early-age tensile creep of high-volume fly ash concrete
NI Tongyuan, YAO Shuifeng, CHEN Weizhong, YANG Yang, LIU Jintao, NIE Haibo
, Available online  
Abstract:
It is one of important factors affecting on concrete tensile creep that the rheological properties of concrete paste. The microscopic mechanical properties and rheological characteristics of cementitious paste containing high volume fly ash (60%) were analyzed by nanoindentation. And the same time, the tensile creep law dependent on ages of high-volume fly ash concrete containing same cementitious paste was experimental studied. The predictive function expressions of the HVFAC tensile creep considering the rheological properties of paste were proposed. The nanoindentation results show that the fly ash promotes the paste’s micro creep development of paste at the same test ages, and the micro creep of paste tends to converge quickly with the delay of test age which the cement is replaced with the same quality fly ash. The influence of fly ash and loading age on the development of HVFAC creep is consistent with the influence law of cementitious paste’s micro creep without aggregate. Base on the correlation analysis on the parameters of Et,28d/(EV+EH), Et,28d/χφ, φ and relative compressive strength fc(t0)/fc,28d, the parameters of C, τ and test ages, it shows that these parameters are in good agreement with the function y = axb. The tensile creep prediction expression of ZC model considering the rheological properties of cement paste can reflect the structure of the model unit cell.
Advances in photoelectrocatalysis and artificial photosynthesis for the reduction of CO2
LIU Jinrui, ZHANG Yan, SUN Shishu, SHI Jianjun, SUN Tianyi, SHI Zaifeng
, Available online  
Abstract:
With the continuous development of industrialization, CO2 produced by the excessive use of fossil fuels has led to problems such as the greenhouse effect, which has attracted great attention from the international community and a series of countermeasures have been formulated. Therefore, the research and development of technology for the reduction and recovery of CO2 from the atmosphere is urgent and important. Photoelectrocatalysis is one of the technologies with good application prospects that can be used to reduce CO2. In order to carry out a more in-depth research on this technology and promote its practical application, this paper firstly describes the basic principles and advantages and disadvantages of photocatalysis, electrocatalysis, and photoelectrocatalysis for CO2 reduction, and gives examples of the efficiency of various types of catalysts for CO2 reduction. Because photocatalysis is one of the important steps in photosynthesis, it then focuses on analyzing the current status and prospects of photosynthesis in reducing CO2 research, and proposes the feasibility and potential of artificial photosynthesis for CO2 reduction. The aim of this paper is to provide new ideas and references for the reduction of CO2 by artificial photosynthesis, and to provide new insights and perspectives for reducing the accumulation of CO2 in the atmosphere and addressing current environmental challenges.
Research Progress of Magnetic Silicate Nanomaterials for Photocatalytic Degradation of Organic Pollutants
ZHU Hao, DU Chunyan, CAO Jiao, ZHOU Lu, YU Guanlong, YAN Rong, YANG Yu
, Available online  
Abstract:
Photocatalysis is an effective method for removing recalcitrant organic pollutants from water, demonstrating significant potential due to its high mineralization efficiency. However, the practical application of most photocatalysts is hindered by their powder form, posing challenges for large-scale use. Recently, magnetic silicate composite materials have garnered increasing attention in the field of materials science due to their stability and recyclability. In this review, we examine the current state of research on magnetic silicate composite materials as photocatalysts, exploring the latest advancements in synthesis, modification, and degradation mechanisms. Finally, we provide an outlook on the research findings and future challenges associated with magnetic silicate composite materials.
Research progress on the regulation of filler particle alignment during physics-assisted 3D printing
LI Yang, ZHENG Xinmei, MEI Xin, REN Yan, CHEN Gang, PENG Biyou
, Available online  
Abstract:
3D printing is a bottom-up, layer-by-layer material additive manufacturing technique. Currently, 3D printing is evolving from prototype manufacturing towards high-performance and functionalization, placing higher demands on the control of printing materials and processes. The orderly arrangement of nanoparticles in 3D printing materials is crucial for enhancing the performance of printed components, yet effectively controlling the orientation of nanoparticles remains challenging. Incorporating physical fields (magnetic, electric, and ultrasonic fields) into the 3D printing process emerges as one of the effective strategies for precise microstructure manipulation of printed items. This approach not only endows the printed components with specific functions but also provides new insights for fabricating multi-scale and multi-responsive structured components. Therefore, physical field-assisted 3D printing has become a research hotspot in recent years. This article begins by briefly describing the types and characteristics of 3D printing technology, emphasizing the importance of physical field assistance in controlling the orientation of nanoparticles. Subsequently, it reviews and summarizes the fundamental principles, material requirements, applications, and performance of physical field-assisted 3D printing in controlling nanoparticle orientation. Finally, the problems and challenges existing in controlling the orientation of filler particles in physical field-assisted 3D printing are summarized, and its future development direction is prospected.
Low frequency bandgap characteristics and application of a novel two-dimensional three-component cement-based phononic-like crystal composite material
XIAO Peng, MIAO Linchang, ZHENG Haizhong, LEI Lijian
, Available online  
Abstract:
In order to widen the width and number of elastic bandgap of concrete metamaterials, a novel two-dimensional three-component cement-based phononic-like crystal was designed based on local resonance theory. Firstly, the finite element method was used to calculate and study the energy band structure, vibration mode, displacement field and attenuation characteristics of the novel two-dimensional three-component cement-based phononic-like crystal. Secondly, the formation mechanism and influencing factors of the bandgap were analyzed, and the theoretical estimation of the bandgap range was derived according to the mass-spring system model. Finally, the cement-based phononic-like crystal was applied to the subway track bed, and the vibration reduction performance of the cement-based phononic-like crystal subway track bed was analyzed. The results show that the novel two-dimensional three-component cement-based phononic-like crystal opens 5 low-frequency bandgaps in the 200 Hz frequency range, and the attenuation values are mostly above 10 dB within the bandgap frequency range, and the attenuation effect is good. The opening of the bandgap corresponds to the vibration characteristics of each primitive cell, which is triggered by the translational vibration of a specific primitive cell and controlled by the strength of the coupling between the specific primitive cell and the matrix. The density of scatterer material, elastic modulus and thickness of cladding material are the main factors affecting the bandgap. In the 1-200 Hz frequency band, the vibration acceleration of the cement-based phononic-like crystal subway track bed composed of the novel two-dimensional three-component cement-based phononic-like crystal is lower than that of the ordinary concrete subway track bed, and the maximum insertion loss is 10.22 dB and the average insertion loss is 8.76 dB, which has remarkable vibration reduction performance.
Biomass carbon tubes/kaolin rock - dual wastes derived composite for efficient microwave absorption
KONG Xiangkai, WU Peikun, YAN Han, ZHENG Fangyu, WANG Lizhi, LIU Qiangchun, JU Zhicheng
, Available online  
Abstract:
Low cost, high performance, and good environmental stability are the key factors to determine the application of microwave absorbent. In this study, the wasted platanus tree fruits were taken as raw biomass materials, which were combined with the kaolin rock, one kind of abandoned coal mine resources, to construct the dual wastes-derived composite for microwave absorption. The obtained carbon microtubes/kaolin rock composite was optimized by controlling their interfacial interaction followed by high-temperature pyrolysis to reach efficient absorbing capability towards microwave radiation. The experimental results showed that the acid-modified carbon microtubes (CMT-ac) and the alkali-decorated kaolin rock (KR-al) combined well to supply a large number of heterogeneous interfaces to strengthen the interfacial polarization mechanism. As a result, their conductivity difference under the irradiation of electromagnetic wave enabled greatly attenuating electromagnetic wave. The final KR-al@CMT-ac sample achieved an effective absorption bandwidth of 6.3 GHz (11.7~18.0 GHz) at a matching thickness of only 2.0 mm and a minimum reflection loss of -51.5 dB at 8.08 GHz at a thickness of 3.0 mm. The improvement in microwave absorption performance is due to the enhanced interface polarization and conduction loss. This study will provide an effective strategy for the design of low-cost and high-performance dielectric absorbents.
Design and processing of wear-resistant and ice-resistant PTFE surface
HE Zhihao, ZHANG Bingzhen, PAN Weihao, SUN Jing, SONG Jinlong
, Available online  
Abstract:
The icing on the surface of the silo of the ice jet cleaning equipment often causes the equipment to shutdown for maintenance, but how to reduce the icing adhesion on the silo surface is a difficulty of current research. In this work, CO2 laser was used to etch polytetrafluoroethylene (PTFE) to obtain a superhydrophobic surface, and a rhombus support rib array structure was designed to improve the wear resistance of the superhydrophobic PTFE surface. CO2 laser etching could form a multi-layer staggered stacked fiber structure on the PTFE surface, and there was no obvious change in the chemical composition of the surface after laser etching. The superhydrophobic PTFE surface with contact angle of 164° and rolling angle of 4° can be obtained at laser scanning line spacing of 50 μm, scanning speed of 300 mm/s, and laser power of 9 W. The designed rhombus support rib array structure with crest angle of 30°, length of side of 3 mm and rib width of 0.05 mm can effectively improve the wear resistance of superhydrophobic PTFE surface. Even after being rubbed by sandpaper for 6 m, the superhydrophobic PTFE surface with rhombus support rib array structure can still maintain excellent superhydrophobicity, and the icing adhesion of it is only 50% of that of ordinary PTFE surface. The wear-resistant and ice-resistant PTFE surface is expected to be used in ice jet cleaning equipment.
Mechanical properties of basalt fiber reinforced polymer grids reinforced magnesium phosphate cement mortar composite
XIE Jian, LIU Jiawang, LI Wei, JIN Lingyi
, Available online  
Abstract:
To investigate the influences of basalt fiber reinforced polymer (BFRP) grid and steel fibers on the mechanical properties of magnesium phosphate cement mortar (MPCM), BFRP grid reinforced magnesium phosphate cement mortar (GRMM) composite was prepared. The effects of material forms (steel fiber reinforced, BFRP grid reinforced and composite reinforced), BFRP grid thicknesses (1mm, 2mm and 3mm), and BFRP grid surface forms (untreated and sand-sticked) on the tensile stress-strain curves, bending stress-deflection curves, and key indexes of GRMM were investigated by the axial tensile test and four-point bending test. Moreover, the roles of steel fibers and BFRP grid in GRMM were also studied. The results show that steel fibers mainly play a role in the early stage, which can effectively inhibit the generation of cracks and improve the strength and toughness of GRMM. The incorporation of steel fibers increases the tensile and bending capacity by 24.23% and 215.33%, respectively, and improves the crack resistance, ductility and energy consumption of both types of specimens. The tensile stress is the mainly borne by BFRP grid, which plays a role throughout the whole loading process of GRMM. The incorporation of the BFRP grid improves the peak deformation of both tests by more than 70 times, but the BFRP grid is not coordinated with the MPCM in the specimen. Combined with the strengthening effects of steel fibers on the matrix and the good deformation of BFRP grid, the cracking resistance, strength, ductility and energy dissipation capacity of MPCM matrix are improved. As the thickness of the BFRP grid increases, the strength and energy dissipation capacity of the GRMM specimens are further improved. Sticking sand on the BRFP grid does not significantly affect the mechanical properties of GRMM.
Review of process defects and failure behaviors of continuous fiber-reinforced composite materials via 3D printing
ZHANG Xin, ZHENG Xitao, YANG Tiantian, SONG Luyang, YAN Leilei
, Available online  
Abstract:
Constraint-free design, rapid production, and the absence of mold requirements are just a few of the reasons why continuous fiber-reinforced 3D printing (CFR3DP) has emerged as one of the most innovative advanced composite manufacturing technologies nowadays. This study examines the recent developments in research concerning process defects and the failure behaviors of CFR3DP. In order to systematically categorize the printing process, the notion of “dry/wet/dry-wet-mixed” has been introduced, with an emphasis on the three distinct groups of defects that may be introduced during the additive manufacturing process. Following this, an analysis was conducted to summarize the failure behaviors of CFR3DP while also identifying the primary causes of failure. In conclusion, we propose the prospect of CFR3DP with respect to cost reduction, efficiency, the mitigation of process defects, and improvement of failure mode.
Configuration design and thermal properties of diamond reinforced graphite film/aluminum composite
ZHANG Qingyun, HUANG Junchen, YANG Bing, LYU Zheng, OU Yun, TANG Siwen, SONG Dian, LIU Qian
, Available online  
Abstract:
To improve the low longitudinal thermal conductivity of graphite film/aluminum composites, this study employed high-thermal diamond to penetrate the aluminum layer and establish a thermal conduction channel within the composites to effectively enhance their longitudinal thermal conductivity. To enhance the interface bonding between diamond and aluminum matrix. Tungsten coating was applied on the diamond surface using physical vapor deposition (PVD) technology. Subsequently, diamond-reinforced graphite film/aluminum composites were fabricated through fast hot pressing sintering (FHP) method. The influence of interfacial bonding and diamond volume fraction on the thermal conductivity of the composite were investigated. The results demonstrate that at a 10% volume fraction of W-coated diamond, the in-plane thermal conductivity reaches its peak value at 658 W/(m·K), which is 7% higher than that of an uncoated corundum reinforced composite. However, when the volume fraction of tungsten diamond plating exceeds 10%, the in-plane thermal conductivity shows a decreasing trend. The in-plane thermal conductivity is reduced to 535 W/(m·K) for composites with a high volume fraction of tungsten diamond coated (30 vol%). Nevertheless, as the diamond volume fraction increases, more thermal conduction channels are formed within the composite leading to an increase in longitudinal thermal conductivity up to its highest value at 177 W/(m·K), which is 34% higher than that of uncoated diamond reinforced composites. The present study demonstrates that the incorporation of diamond thermal conduction channels between graphite film and aluminum effectively enhances the longitudinal thermal conductivity of composites.
Preparation and properties of artificial auricles based on PVA/BNC composites
HUANG Lina, CHEN Lin, HONG Feng
, Available online  
Abstract:
The key to auricle reconstruction is to achieve a biomechanical fit between the implanted material and the natural tissue. So far, an ideal auricle substitute has not been found. In this study, bacterial nanocellulose (BNC) homogenate was added into polyvinyl alcohol (PVA) aqueous solutions of different concentrations, and the freeze-thaw method was used to form PVA/BNC composite materials with both high elastic flexibility and high mechanical strength via physically cross-linking. The physical and chemical properties and cytocompatibility of the composites were characterized. The results show that the material has the characteristics of high water absorption, low swelling ratio, as well as high toughness, elasticity and suture strength. The maximum compressive modulus reaches 6.98 ± 0.49 MPa, which matches the biomechanics of natural auricle tissue. The maximum suture strength reaches 7.06 ± 0.33 N, which fully meets the needs of clinical suture. Addition of BNC promotes the adhesion, growth and proliferation of cells on the surface of the material, giving the PVA/BNC composite material higher cell density and vitality. All the results show that the PVA/BNC composite is a promising biomaterial for artificial auricles.
A method of enhancing honeycomb absorbing performance based on metamaterial
JING Zhi, ZHANG Peng, ZHANG Jian, GUO Cean
, Available online  
Abstract:
Absorbing honeycomb, which has the characteristics of lightweight, load-bearing, and microwave absorbing, is widely used in radar absorbing structure design. But it has shortcoming in low-frequency absorption performance. In this paper, a metamaterial with strong electromagnetic wave absorption performance was designed using square open resonant ring units. The metamaterial was applied to modify the electromagnetic performance of an absorbing honeycomb, and realized significant improvement on broadband microwave absorption performance. First, the square split ring resonator unit was designed. The variation of electromagnetic scattering characteristics with the shape parameters of the square split ring resonator unit was studied. The influence of the four main design parameters, including the thickness of the dielectric layer, the width of the square ring, the opening width of the square ring and the length of the square ring, on the absorption performance of the metamaterial was explored through simulation. The change rules of the electromagnetic absorption peak with the shape of the square split ring resonator unit were analyzed. A scheme with strong narrow-band absorbing ability was proposed. Then, a design method for metamaterial absorbing honeycomb was proposed by combining the square split ring resonator metamaterial with the absorbing honeycomb. Research shows that compared with the absorbing honeycomb, the reflection loss of the metamaterial absorbing honeycomb is improved by 4.4 dB in 1~10 GHz on average. The absorption performance of the absorbing honeycomb has been significantly enhanced.
Improved Extraction Performance of SnO2 ETL for Perovskite Solar Cells by a Combined Hydrolysis Oxidation and Sol-Gel Method
ZHAO Hang, CHENG Zetong, Lü Kuanxin, CHEN Lize, YANG Yuyun, HUANG Xing, LI Zhenzhen
, Available online  
Abstract:
Tin dioxide (SnO2) is widely used in perovskite solar cells (PSCs) due to its high electron mobility, suitable conduction band and low-temperature preparation characteristics. Currently, the two most commonly used methods for preparing SnO2 are SnCl2 hydrolysis oxidation or SnO2 sol-gel preparation. However, although SnCl2 hydrolysis oxidation can produce well-crystallized SnO2, its controllability is poor, resulting in low device performance repeatability. On the other hand, the devices based on SnO2 electronic transport layer prepared by the sol-gel method have good repeatability, but usually have poor crystallinity, leading to a decrease in electron transport performance. In this study, a combination of hydrolysis oxidation and sol-gel methods was used to prepare SnO2 electronic transport layers. The results of the study demonstrate that using SnCl2 hydrolysis oxidation to prepare high-quality SnO2 crystalline layers can serve as a pre-growth template to improve the crystalline quality of sol-gel generated SnO2. Additionally, covering the hydrolysis oxidation-based SnO2 layer with sol-gel prepared SnO2 crystalline layer can improves the repeatability of device preparation. The electron transport layers prepared by this method can effectively enhance the quality of thin film crystal growth and charge extraction capability, ultimately contributing to improving the efficiency, stability, and reducing hysteresis of the devices.
Humidity-resistant ammonia sensor based on PTFE/ZnO/Ti3C2Tx composite films
GAO Fengjiao, CHANG Xueting, LI Junfeng, WANG Dongsheng, GAO Weixiang, SUN Shibin
, Available online  
Abstract:
The development of moisture-resistant room-temperature gas sensors based on semiconductor functional materials has always been a hot and difficult research topic in the field of gas sensors. Considering the high sensitivity and stability of metal oxide semiconductor, the room-temperature gas-sensing behaviors of Mxene (Ti3C2Tx) and the hydrophobicity of polytetrafluoroethylene (PTFE), we here prepared the PTFE/ZnO/Mxene composite films by depositing the PTFE and ZnO layers orderly onto the Mxene film surface via a magnetron sputtering method, followed by the construction of the gas sensors based on the composite films. The PTFE/ZnO/Mxene composite films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), and the gas-sensing and humidity-resistant properties of the composite films-based gas sensors were investigated. Results showed that the PTFE/ZnO/Ti3C2Tx composite films-based gas sensors exhibited good selectivity, high sensitivity, and excellent reproducibility towards ammonia at room temperature. With the increase of the thickness of the PTFE layers, the humidity resistance of the composite films-based gas sensors gradually increased, but at the cost of sensitivity.
Research progress of cathode materials for aluminum-ion batteries
CHENG Cheng, LEI Xin, SUN Tao, FAN Hognyu, SHEN Xuejing, WU Zhanjun
, Available online  
Abstract:
With high theoretical specific capacity, high safety, low cost, and sufficient raw material sources, aluminum-ion batteries have been regarded as potential alternatives to lithium-ion batteries. However, the shortcomings of the inherent characteristics of the cathode material have greatly limited the further development of aluminum-ion batteries. In this paper, the important role of cathode materials in the application filed of aluminum ion battery was summarized, the mechanism of action and research progress of aluminum ion electrode materials were reviewed, and the effects of various cathode materials such as carbon-based, transition metal oxides and sulfides, organic materials and metal-organic skeletal compounds on the electrochemical performance of aluminum ion batteries were summarize. Finally, the problems that need to be solved urgently in the field of positive electrode materials for aluminum ion batteries are discussed, and the future development direction of positive electrode materials for aluminum ion batteries is proposed.
Fatigue assessment for composites by using piezoelectric signal
XIAO Yushan, WU Zhen, REN Xiaohui
, Available online  
Abstract:
Considering the strain characteristics of the composite structures changing with fatigue loading, so that this paper attempts to monitor the strain characteristics in real time during the fatigue cycle and assesses the fatigue life through the strain signals. However, from the published literatures, resistance strain gauge often suffered from early fatigue failure in the long-time dynamic testing, which is not suitable for strain signal acquisition during the full fatigue cycle. Therefore, the novel polyvinylidene fluoride piezoelectric film (PVDF) with high fatigue resistance is used to acquire fatigue characteristic signals of composite structures. The piezoelectric signals during the fatigue process of the composite laminates are obtained by pasting PVDF on the surface of carbon fiber reinforced plastic (CFRP) plates (T700/9A16). Based on the piezoelectric effect, the strain information during the fatigue process is converted into the piezoelectric signal from PVDF. Then, a Random Forest Regression (RFR) algorithm is trained based on the database generated from the experimental tests to efficiently establish the correlation between the piezoelectric signals and fatigue cycles of composite laminates. Through the trained RFR network, the actual fatigue cycles of the test pieces can be accurately predicted based on the piezoelectric signals, in which the maximum percentage error of logarithms of fatigue cycles is controlled within 5%. This paper provides a new research idea and technical support for the fatigue life assessment of composite materials.
Recent Progress on Silicon Source Materials and the Related Preparation Process of Silicon-Based Anodes in Lithium-Ion Batteries
GONG Jun, SONG Peng, LIU Xinghan, TANG Yanhong, TAN Kaiwen, LI Yejun
, Available online  
Abstract:
With the rapid development of new energy vehicles, the traditional graphite carbon-based anodes can no longer meet the increasing demand for high performance lithium-ion battery, especially in terms of capacity. Silicon, boasting an exceptionally high theoretical capacity, serves as a promising anode material capable of significantly enhancing battery performance, showcasing tremendous development potential, where the silicon source materials, the morphology and size of the silicon particles, and the fabrication process play dominant roles on the performance of silicon-based anodes. The present review provides a comprehensive overview of the recent research progresses on the silicon-based anode materials, with a specific emphasis on the selection of silicon source materials, silicon nanostructuring technologies, and the preparation processes. Moreover, it accentuates the challenges and existing problems associated with the different silicon sources as well as the related preparation processes for the silicon-based anode materials, which will eventually provide deep insights for the advancement of silicon-based anodes in lithium-ion battery.
Phase-field fracture model of anisotropic materials based on strain energy volumetric-deviatoric split
ZHANG Zhichao, DONG Hongcheng, WANG Fangxin
, Available online  
Abstract:
The phase field method, recognized for its effectiveness in fracture analysis, particularly of isotropic and composite materials, remains a key research focus when considering the intricacies of fractures in anisotropic materials and their composites. In this study, a refined approach to decomposing elastic strain energy was presented. This method excludes the compressive volumetric strain energy influence on crack propagation and accounts for asymmetries in material constitutive relationships under tension and compression. Leveraging this, a tailored phase field analysis model for orthotropic material fractures was constructed. To validate our model's robustness and applicability, we conducted analyses on unidirectional opening plates made of isotropic and orthotropic materials, focusing on tensile and shear boundary conditions. For composite plates with unidirectional fiber reinforcement, the Hashin criterion was incorporated to refine the quantification of damage-induced crack driving forces. This facilitated accurate simulations of tensile behavior in composite plates with varying carbon fiber orientations. Our findings demonstrate the profound capability of our theoretical framework in simulating crack propagation in anisotropic materials and unidirectional fiber-reinforced composites. The predicted crack propagation paths align with those from established models for both isotropic and orthotropic materials, attesting to the model's fidelity. Within composites, we observed a strong alignment between crack propagation and fiber orientation, highlighting a robust correlation between our predictions and experiment results.
Microstructure and high-temperature tensile properties of Ti2AlNb/TA15 laminated composites prepared by vacuum hot pressing
SHAO Xinxiang, ZHANG Shouyin, ZHANG Kun, WAN Junjie, LU Baiping
, Available online  
Abstract:
In order to improve the intrinsic brittleness of Ti2AlNb alloy without sacrificing its high-temperature performance, a composite material was prepared by combining it with high-temperature titanium alloy TA15 using vacuum hot pressing. The effects of different hot pressing temperatures on the microstructure and tensile properties of Ti2AlNb/TA15 laminated composite materials were investigated. The results show that the pore defects in the interface layer gradually decrease with the increase of the hot pressing temperature. A defect-free metallurgical bonding interface can be achieved at temperatures of 1050°C and above. The thickness of the interface reaction layer increases with the rise of the hot pressing temperature. Under the diffusion conditions at 1050℃ and above, a transition layer of certain width formed between the reaction zone and the Ti2AlNb layers, which improve the properties of the interface bonding. Tensile tests indicate that the room and high-temperature tensile properties of the Ti2AlNb/TA15 laminated composite material are significantly improved compared with Ti2AlNb alloy. The laminated composite material under the hot pressing temperature condition of 1050℃ exhibits excellent comprehensive performance, with a high-temperature tensile strength and strain of 667.85 MPa and 16.2%, respectively.
Optimization of the high-temperature strong plasticity of the new precipitation-enhanced nickel-iron-based superalloy GH4650T
WANG Xitong, ZHOU Yongli, YAN Yingbo, LIU Yeng, YUAN Yong, DOU Zizhuo, NAN Yanli, ZHANG Peng
, Available online  
Abstract:
The tensile properties and deformation mechanisms of a new precipitate-hardened Ni-Fe-base superalloy GH4650T are investigated after solutionizing and thermal aging at 750℃ for different hours. It is found that the strength increases firstly and decreases with time, whereas the tensile plasticity shows the opposite changing trend. After thermal aging for 48 h, the tensile strength is the best, whereas the elongation to fracture is the minimum at 5 h. Microstructural observations reveal that the grow kinetics of γ′ precipitates in the experimental alloy meet the Lifshitz-Slyozov-Wagner law, and the dominant deformation mechanism changes from particle shearing by weekly-coupled dislocations to by strongly-coupled dislocations and then to Orowan looping with increasing the γ′ precipitate size. Meanwhile, it is also found the fracture mechanism changes from transcrystalline fracture to intercrystalline fracture and then to ductile and brittle mixed fracture and the feature of ductile fractures becomes more and more obvious with precipitate size. Give these observations, the relationship between the tensile properties and the operative deformation and fracture mechanisms is discussed.
Inter-laminar stress modeling and validation on multi-layer composite cylinders under thermal loading
LI Xiang, ZHAO Xianhang, ZHONG Hua, XIE Yu, RU Jiasheng, LIU Xin, LI Xudong, LI Yuefang
, Available online  
Abstract:
The inter-laminar stress in multi-layer composite cylindrical structures can cause internal delamination, structural instability, etc. It is necessary to study the internal stress formation mechanism. An analytical model for prediction of the inter-laminar stress in multi-layer composite cylinders subjected to thermal loading was developed based on an anisotropic constitutive model and the plane stress assumption. The analytical model was validated by means of finite element analyses and a thermal expansion experiment performed on a composite cylinder. Using this validated model, the inter-laminar stress between layers and the thermal expansion behavior were investigated. Results show that the special geometric constraint of the cylinder itself plays an important role in the residual stress development. The thermal expansion behavior in the cylinders is much different compared to that in planer laminated composites. Due to the difference of modulus and coefficient of thermal expansion along hoop and radial direction, a significant inter-laminar tensile stress will generate during cooling down process. Furthermore, the hoop thermal expansion deformation shows an evident increasing trend from the inner layer to the outer layer. The hoop thermal expansion deformation in the inner layer is much smaller than that of the composite. With the increment of the cylinder thickness, the inter-laminar tensile stress, and the difference in coefficient of thermal expansion between inner layer and outermost layer increase. The developed model could be useful to disclose the stress-induced inter-laminar crack and optimize stress distribution in multi-layer composite cylinders.
Load-bearing mechanism and full-process response characterization of a GFRP square tube bonded-bolted sleeve connection
LI Ruoyu, ZHANG Hengming, LIU Chenglin, HAO Xulong, LI Da, LI Feng
, Available online  
Abstract:
The connection region of FRP components is a potential weak link in structures. Accurately reflecting the full-process behavior of the joint in structural scale calculations is a challenging aspect in the design of FRP composite structures. In this study, assembled GFRP lattice columns subject to compression loads were used as the structural background, and the focus was on the research of bonded-bolted sleeve connections for pultruded GFRP square tubes. Four hybrid joint specimens and two pure bolted joint specimens were designed and prepared. Axial compression static load tests were conducted, and a solid FE model considering the failure behavior of the adhesive layer was established. The results indicate that the connection form exhibits a secondary load-carrying characteristic, and the overall mechanical behavior is derived from the superposition of the adhesive shear and bolt shear load transmitting mechanisms; regarding specimens in this paper, the secondary peak load reaches 92% of the first, and the bearing failure load is on average increased by 49% compared to pure bolted connection specimens. For the bonded-bolted sleeve connection, a simplified modeling approach is proposed. Based on the continuous damage model and the plastic potential theory, a macroscopic constitutive model in terms of force and displacement is established. This model distills constitutive parameters with clear physical meanings, enabling an accurate consideration of the full-process behavior of the joint in structural-scale calculations at a relatively low computational cost. The phenomenological nature of the macroscopic constitutive model leads to a relatively accurate description of the mechanical behavior of the joint, and the computational cost is small, making it suitable for structural scale calculation analysis of assembled GFRP latticed columns subject to compression loads.
Preparation and microwave absorption properties of ferrite/ reed charcoal composites
JIAN Yu, FAN Xune, QIU Baiyang, TIAN Xundong, YANG Xi
, Available online  
Abstract:
In order to solve the problems of high density and narrow absorption bandwidth of ferrite absorbing materials, the ferrite/reed charcoal (Ferrite/RC) composites were prepared from reed stalks by impregnation and high temperature in-situ growth methods. The electromagnetic characteristics and electromagnetic wave absorption properties of the composites were controlled by tailoring the carbonization temperature. The results of SEM, TEM, XRD, and VNA showed that the Ferrite/RC composites retained the natural three-dimensional honeycomb network structures of the reed stalks, and Fe3O4 and iron nanoparticles were uniformly distributed in the charcoal wall and pores of the reed stem; Raising the carbonization temperature (650~690℃) can increase the conductivity and dielectric loss ability of composites, but excessive temperature can lead to impedance mismatch of the material and reduce its electromagnetic attenuation ability. The composites prepared at a carbonization temperature of 670℃ exhibit the best absorption performance, with a reflection loss of -45.7 dB at a thickness of only 1.7 mm and an effective absorption bandwidth of 5.7 GHz (12.1-17.8 GHz) at a thickness of 2 mm, which is attributed to the good conductivity loss, polarization relaxation, and the synergistic effect of electrical and magnetic losses of composite materials. The excellent absorption performance of Ferrite/RC composites has good prospects in the field of electromagnetic wave absorption, which can promote the high-value and functional application of reed resources.
Investigation on numerical analysis method of fatigue delamination damage of plane woven composites
WAN Aoshuang, ZHU Feiyang, YUN Xinyao, LI Dinghe
, Available online  
Abstract:
Based on bilinear constitutive relationship, a cohesive model considering fatigue damage was established. Integrating with finite element analysis technology, the numerical analysis method of delamination propagation behavior of composite laminates was developed to simulate the mode II delamination propagation behavior of plane woven composite laminates under static and fatigue loading. The simulated load-displacement curve under quasi-static loading has good agreement with the experimental results. The simulated delamination propagation rate-strain energy release rate curve under fatigue loading is also in good agreement with the experimental results. Thus, the cohesive model considering fatigue damage has been validated. On this basis, the fatigue failure criteria for plane woven composites were established. Then the residual life prediction method of plane woven composite laminates with initial delamination damage was developed by integrating with the intralaminar progressive fatigue damage model. Using the developed method, the residual life and fatigue damage propagation of laminates with initial delamination damage were predicted, showing good correlation with the experimental results. In addition, the simulation results indicate that the fatigue damage initiates from the initial delamination damage which then propagates to the edges. The fatigue damage in both warp and weft directions appear early within the two layers of 0° adjacent to the initial delamination damage. And more damage occurs within the 0° layers than the 45° layers in general. Finally, the 0° layers show warp damage dominated failure mode while the 45° layers show weft damage dominated failure mode, and large area of damage appear at all the interlaminar interfaces.
Bonding properties of UHPC-high strength rebar based on beam test
DENG Mingke, YAO Xin, ZHANG Yangxi, JIN Mengna, CAO Jitao
, Available online  
Abstract:
To study the bonding properties of high-strength steel bars and ultra-high-performance concrete (UHPC), nine groups of lap beams were designed and fabricated. The influences of specific variables on the bonding properties were analyzed, including lap length, steel fiber volume content, and mechanical anchoring measures. The experimental results show that the tensile steel bars in the lap section of the lap beams connected with UHPC have better performance on the bonding properties with concrete. Increasing the lap length promotes peak load but the average bonding strength of the lap beams on the contrary. With the increase of steel fiber volume content, the peak load and bond strength of the lap beams increase. Mechanical anchoring adopted lap beams show a higher peak load and bonding strength, where bent hooks treated lap beam shows the highest enhancement, with peak load and bond strength improved by 212.4% and 199.4%, respectively, and it is worth mentioning that the hooked lap steel bars yielded. Based on the equilibrium condition of axial force and bending moment at the peak point, the maximum tensile stress of the steel bar in the lap beam was calculated. A calculation method of the average bonding strength between the steel bar and UHPC was then established. The proposed method calculation results were compared with the centre pull-out test and brace lap test results subsequently.
Fabrication of Magnetic Fe3O4@SiO2@TiO2-Au with Core-shell Structure and Its Photocatalytic Reduction Activity
GUO Xiaohua, MA Jianqi
, Available online  
Abstract:
TiO2-based photocatalysts have been widely used for photoxidation of various organic pollutants and photoreduction of Cr(VI) in aqueous solution. However, less attention has been paid to the photocatalyzed reduction of nitro group to amino group of nitroaromatics. In this study, liquid-phase deposition (LPD) technique was adopted to deposit anatase TiO2 shell on amorphous SiO2-coated Fe3O4 to form core-shell Fe3O4@SiO2@TiO2 magnetic photocatalyst. To further promote its photocatalytic activity, uniformly dispersed Au nanoparticles (NPs) were decorated on its surface to obtain Fe3O4@SiO2@TiO2-Au composite. Both the TiO2-based magnetic composites were characterized and used as photocatalysts. To evaluate their photocatalytic performance, the photocatalyzed reduction of p-nitroaniline (p-NA) to p-phenylenediamine (p-PDA) was chosen as a model reaction under UV irradiation using HCOONH4 as a hole scavenger and H source. Although p-NA can be completely reduced to p-PDA by the two photocatalysts, Fe3O4@SiO2@TiO2-Au exhibits much superior photocatalytic activity to Fe3O4@SiO2@TiO2. The is because Au NPs decorated on the TiO2 can efficiently facilitate the photoexcited electron-transfer from the conduction band of TiO2 to Au, which is favorable for minimizing the recombination rate of electrons and holes and prolong the lifetime of the photoelectrons. In addition, HCOONH4 plays an indispensable role in improving the photocatalytic reduction of p-NA via capturing photo-generated holes.
Preparation and Thermal Conductivity Study of Hydroxylated Boron Nitride Nanosheets/Nanocellulose Composite
ZHANG Yu, LI Lei, HU Zhixun, LI Shengjuan, ZHU Yingjie
, Available online  
Abstract:
The potential of boron nitride nanosheets (BNNS) in thermal management materials is significantly hindered by the inherent surface chemical inertness that leads to a substantial interfacial thermal resistance. To overcome this limitation, hydroxyl-functionalized boron nitride nanosheets (BNNS-OH) were successfully synthesized through a high-temperature alkali treatment coupled with liquid-phase assisted ultrasonication. Subsequently, a vacuum filtration combined with compression drying technique was employed to fabricate hydroxyl-functionalized boron nitride nanosheet/cellulose nanofiber (BNNS-OH/CNF) composites. The hydroxyl groups on the surface of BNNS enhance compatibility with CNF and improve the dispersion of BNNS, thereby reducing the interfacial thermal resistance. Furthermore, the one-dimensional structure of CNF does not fully cover the thermal fillers, and the compression drying method effectively minimizes the voids between the fillers and polymer, resulting in a dense layered structure. This facilitates better contact between fillers, forming continuous thermal conduction pathways and enhancing the thermal conductivity of the composite material. When loaded with 30wt% BNNS-OH, the thermal conductivity of the BNNS-OH/CNF composite reaches as high as 14.571 W·m−1·K−1, approximately 819% higher than that of pure CNF films. In practical heat dissipation applications, compared to CNF films, LED chips encapsulated with BNNS-OH/CNF composite films exhibited a temperature reduction of 29.5°C within 150 seconds.
Mechanical behavior of 2D braided composites under the coupling effect of moisture and load
CHENG Zhaohui, LIU Bin, XIANG Dong, XU Fei, FENG Wei
, Available online  
Abstract:
In order to study the moisture absorption behavior and performance degradation law of 2D braided composites under long-term moisture-load coupling, a moisture-load coupled aging device was designed. The moisture absorption test and tensile test after moisture absorption of T300/H69 plain woven composite material under different stress levels were carried out. The results show that the moisture absorption of T300/H69 braided composites is positively correlated with the tensile prestress, and increases with the increase of tensile prestress. Compared with the effect of water alone, the elastic modulus and strength degradation of the material under moisture -load coupling are more obvious. After 432 hours at 140% σs prestress, the elastic modulus and failure strength of the braided composites decreased by 55.9% and 35.4%, respectively. In addition, the degradation mechanism of braided composites under long-term moisture-load coupling is further revealed by macro and micro section analysis. Based on Shiva 's residual strength theory, the residual strength model of composites under moisture-load is improved, and the prediction results are good, which provides guidance for the durability design of composites in complex environment.
Seismic performance of ECC shell-RC composite pier column and its plastic hinge developing mechanism
WANG Jin, XU Weibing, DU Xiuli, DING Mengjia, CHEN Yanjiang, FANG Rong, YAN Xiaoyu
, Available online  
Abstract:
To improve the seismic performance of reinforced concrete (RC) pier column and fully utilize the mechanical properties of Engineered Cementitious Composites (ECC), an innovative ECC shell -RC composite pier column was proposed. The numerical analysis model of the composite pier column was established and verified based on ABAQUS platform and existing experimental results, respectively. On this basis, the influence of common design parameters on the seismic performance of the composite pier column was systematically investigated, including the ECC segment height, ECC shell thickness, longitudinal reinforcement ratio, volume stirrup ratio and axial compression ratio. Finally, the plastic hinge development mechanism of the composite pier column was clarified. The results show that compared with RC pier column, the bearing capacity, displacement ductility and energy dissipating capacity of ECC shell -RC composite pier columns are improved. The peak loads of the composite pier columns increase with the ECC segment height increasing. The seismic performance of the composite pier columns can approach to that of the ECC pure pier column when the height of the ECC shell-RC composite segment is larger than 1.4h (transverse dimension of the pier column). The peak load and ductility of the composite pier column increase with the ECC shell thickness and longitudinal reinforcement ratio increasing. However, the seismic performance of the composite pier column will not significantly change when the ECC shell thickness is larger than 1/5h. The increase of the axial compression ratio can increase the initial stiffness and peak load of the specimen, while has a negative impact on its ductility. The decreasing of the volume stirrup ratio around the plastic hinge zone will significantly decrease the ductility of the specimen, but little affect its bearing capacity. The plastic hinge development mechanism of the composite pier column is significantly influenced by the height of the ECC shell- RC composite segment. There is a minimum critical height of the composite segment to make the plastic hinge zone not transfer.
Axial compressive performance and design model of fiber wound GFRP tube confined concrete
YE Hanhui, XU Shengliang, MAO Ming, BU Zhanyu
, Available online  
Abstract:
54 fiber-wound GFRP tube confined concrete cylindrical specimens classified in eighteen groups were designed and manufactured, and the parameters included the number of fiber layers (6, 10), fiber angle (\begin{document}$ \pm 45^\circ $\end{document}, \begin{document}$ \pm 60^\circ $\end{document}, \begin{document}$ \pm 80^\circ $\end{document}), slenderness ratio (2, 4) and compression section (full section, core concrete). Based on the axial compression test results, a design-oriented peak stress prediction model in terms of fiber angle was proposed. The results show that GFRP tube can effectively improve the strength and ductility of confined specimens. The peak strength of the specimen increases with the increase of fiber angle and layer number, and the increase of the peak strength of the specimen with large slenderness ratio is larger. The full section compression will adversely affect the circumferential properties of the confined specimen. The confined pattern is mainly determined by the fiber angle. The specimens with ±60° and ±80° angles are strong confinement, and reveal brittle failure mode. The specimens with ±45° angle are weak confinement, and reveal ductile failure mode. By studying the mathematical relationship between the peak strength and the effective confinement strength, the simplified design-oriented model was derived, which has sufficient precision for solving the peak strength of specimens with different fiber angles, and can provide reference for relevant engineering applications.
Mechanical properties and damage mechanisms of novel variable stiffness laminates
CAO Zhongliang, DING Xiaoxiao
, Available online  
Abstract:
Laminated composite panels, widely employed in aerospace, aviation and transportation, face challenges in terms of load-bearing capacity and stability in practical applications. To address these issues, this study adopts an automated variable stiffness layup approach and investigates the mechanical properties and failure mechanisms of the resulting laminated composite panels. Firstly, a novel periodic linear extrapolation algorithm was proposed based on a linear variable angle function to optimize the fiber placement paths, achieving more detailed and precise variations in fiber trajectories. Subsequently, a finite element model for the new variable stiffness laminated panel was constructed using Python/Abaqus. Finally, the damage mechanisms under three-point bending for both constant and variable stiffness laminated panels were analyzed, revealing the impact of different fiber orientation angles on the mechanical properties, stress distribution and damage scenarios. The research findings indicate that the orientation angle of the central fiber significantly influences bending performance under three-point conditions, with 0° favoring performance enhancement and 90° leading to a decline in performance. Compared to the baseline with a central fiber orientation angle (T0) of 5°, employing a variable angle design effectively suppresses further extension of bending damage, ensures a uniform stress distribution within the laminated panel, and further enhances the ultimate bending stress, with a maximum improvement of 28.31%. This study provides crucial insights and a systematic approach for the subsequent design and optimization of laminated composite panels, contributing to advancements in bending resistance design for composite materials.
Construction of Se@TiO2 nanostructures on polyester surface and investigation of the photocatalytic and antibacterial properties
ZHAO Ziyao, LUAN Rui, MO Huilin, NIE Hao, REN Yu, LI Meixian
, Available online  
Abstract:
Surface pretreatment of polyester fabric was carried out using plasma technology. Nano-TiO2 was loaded on the surface of the polyester fabric, and then Se nanospheres (SeNPs) and Se nanowires (SeNWs) were grown on the surface of the TiO2/ Polyethylene terephthalate (PET) through molecular assembly method. Se@TiO2 binary composite structure was constructed on the surface of the PET(SeNPs@TiO2/PET and SeNWs@TiO2/PET). The crystal structure, surface morphology, chemical composition, photocatalytic and antibacterial properties of the material were characterized by SEM, XRD, XPS, UV vis, PL, and photocatalytic and antibacterial experiments. Characterize the wetting performance of composite photocatalytic materials through contact angle testing. The results indicate that SeNPs@TiO2/PET and SeNWs@TiO2/PET composite photocatalytic materials have been successfully prepared. The photocatalytic degradation experiment shows that SeNWs@TiO2/PET has a higher degradation rate under sunlight simulation. After 90 minutes of degradation of the model pollutant methylene blue, the degradation rate reached 98.3%. PL spectrum indicates SeNWs@TiO2/PET separation rate of electron hole pairs is higher than SeNPs@TiO2/PET. The UV-vis spectrum indicates that relative bandgap widths of SeNPs@TiO2/PET and SeNWs@TiO2/PET are 2.8 eV and 2.7 eV, respectively. The antibacterial rates of composite materials against S.aureus and E.coli can reach over 99% and 90%, respectively.
High sensitivity flexible piezoresistive sensor of PDMS porous elastomer decorated by MXene-PEDOT:PSS
SHI Feifei, XIONG Juan, DAN Zhigang
, Available online  
Abstract:
Flexible piezoresistive sensors have great application demands in wearable devices, electronic skins, man-computer interaction, and other fields. The common conductive sensitive media of flexible piezoresistive sensors suffer from high cost and complex preparation processes, which limit their practical application and mass production. A porous polydimethylsiloxane (PDMS) elastomer was prepared using gelatin as a sacrificial agent, and a MXene- Poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS)/PDMS composite piezoresistive sensor was obtained by impregnation method. Experimental results demonstrated that when the composite concentrations of PEDOT:PSS and MXene are 15 mg/mL and 10 mg/mL, respectively, the sensor has the highest sensitivity, reaching up to 29.1 kPa−1 under the force range of 12-40 kPa. The response and recovery time of the piezoresistive sensor are 0.36 s and 0.6 s, respectively. After verification, the sensor can detect the movement of human joints (finger, elbow and knee), indicating that the developed piezoresistive sensor exhibits good application prospects in the fields of smart clothing, flexible wearable electronic devices, and human-computer interaction.
Preparation of stretchable graphene/PDMS composite films with excellent electromagnetic performance
LIN Shaofeng, SU Meng, ZHANG Jianwei, JIANG Dazhi
, Available online  
Abstract:
Aircraft, satellites and other aircraft with key electronic components, are susceptible to interference from strong electromagnetic field. And some structures of aircraft need to meet mechanical requirements such as large deformation and stretchability in work. Therefore, highly conductive and stretchable electromagnetic shielding materials have attracted widespread attention. Using graphene oxide as raw material and through casting method and high-temperature graphitization treatment, a highly conductive and flexible GP-4 film with the thickness of 13.5 μm was prepared, whose electrical conductivity and electromagnetic shielding efficiency were 6010 S/cm and 68.4 dB, respectively. Using polydimethylsilane (PDMS) as the base, GP-4/PDMS-50.5 composite film with stretchable bilayer structure was prepared, whose elongation was as high as 50.5%. When the axial tensile strain of the composite film is 50.5% and the number of stretching cycles is 500, the composite film could still maintain excellent conductivity and electromagnetic shielding performance. Among them, the resistance of the composite film is 1.04 Ω and 1.06 Ω, keeping constant with the GP-4 film almost. The electromagnetic shielding efficiency of the composite film is as high as 68.5 dB and 67.7 dB. These excellent properties indicate that GP-4/PDMS-50.5 composite film has great application prospects in the electromagnetic shielding field of flexible electronic devices.
Mechanical properties of micro silicon powder -rubber/cement mortar under dynamic and static loading
ZHANG Jinsong, TANG Yulun, ZHAN Jiajia, PANG Jianyong
, Available online  
Abstract:
In order to study the mechanical properties of micro silicon powder (MP)-rubber/cement mortar, 16 sets of specimens were designed and analyzed by uniaxial compression test and impact test (SHPB) for peak stress, peak strain, modulus of elasticity, impact strength, damage morphology and stress-strain curves of the specimens with different micro silicon powder dosage, rubber particle sizes and curing ages. The uniaxial compressive test shows that the addition of rubber particles decreases the compressive strength and modulus of elasticity of mortar specimens and increases the peak strain at the same age of maintenance, and the strength and modulus of elasticity of the specimens recover after the addition of micro silica powder. The impact resistance test shows that: rubber will reduce the impact strength of mortar, but can improve the damage morphology of mortar, and micro silica powder not only enhances this improvement, but also improves the impact strength of rubber/cement mortar, in addition, after the addition of micro silica powder, the peak load of the stress-strain curve of the specimen will be shifted to the left due to the shortening of the elastic deformation and elasto-plastic deformation stages, but the damage stage is obviously prolonged.
Preparation and properties of high specific strength carbon/carbon composites based on carbon fiber/carbon foam preforms
WANG Xingjun, JIA Jiangang, PAN Zikang, LIU Diqiang, ZANG Shujun
, Available online  
Abstract:
Carbon/carbon composites has been widely used in aerospace, weaponry and other fields with their excellent properties. However, the development of carbon/carbon composites has been limited by the high cost of carbon fiber preforms. Carbon foam has a three-dimensional network structure, and its ligaments show similar properties to carbon fibers, which can be used as the reinforcing phase to prepare carbon/carbon composites. In this paper, carbon foams with different carbon fiber volume contents (0vol%, 1vol%, 3vol%, 5vol%, 7vol%) were prepared as carbon/carbon composites preforms by using phenolic resin as the carbon source and NaCl as the pore-forming agent, and the carbon/carbon composites were prepared by using the rapid densification technique of thermal gradient chemical vapour infiltration (TG-CVI), which investigated the effects of carbon fiber content on the carbon fiber/carbon foam preform and its density, microstructure and mechanical properties after densification. The effects of carbon fiber content on the density, microstructure and mechanical properties of the carbon fiber/carbon foam preform and its densification were investigated. The results showed that with the increase of carbon fiber content, the number of microcracks in the carbon fiber/carbon foam precast body increased significantly, the density gradually decreased from 0.51 g/cm3 to 0.31 g/cm3, and the compressive strength decreased from 51.30 MPa to 1.30 MPa, flexural strength decreased from 42.53 MPa to 6.32 MPa. The compressive and flexural strengths of the carbon/carbon composites were significantly increased after densification, up to 183.67 MPa and 123.46 MPa, respectively, while the density was 1.09 g/cm3, resulting in high specific strength. The thermal conductivity of the composites increased from 0.298 W/(m·K) (before densification) to 2.484 W/(m·K), an increase of 734%, which was attributed to the formation of a three-dimensional thermal conductivity network between the carbon fibers and pyrolytic carbon after densification.
Radar-IR dual band compatible carbon fiber/aluminum powder /modified EPDM composite coating
Ning Liang, DONG Chunlei, WANG Xiangming, WU Lianfeng, YU Meijie, WANG Chengguo
, Available online  
Abstract:
Multi-band compatible composite coating materials are in urgent demand in the field of civil-military integration and are a current research hotspot. Coating binder is an important component affecting the mechanical, infrared and dielectric properties of coatings. However, most organic binders have high infrared emissivity, and the low emissivity fillers often fail to harmonize the contradiction between mechanical properties, infrared stealth and radar transmittance properties. A composite coating with low infrared emissivity and low dielectric loss characteristics was prepared by modifying EPDM binder with acrylic acid (AA) and maleic anhydride (MAH) as grafting monomers, and using EPDM rubber as binder before and after modification, floating aluminum powder and short-cut antistatic carbon fiber as fillers. The influence laws of modified monomer type and dosage on the binder itself and on the performance of the composite coating with added filler were systematically investigated. The results show that the infrared emissivity of the composite coatings slightly increases with the increase of the content of grafted monomers, while the radar transmittance properties remain basically unchanged. The graft modification of the binder improves the compatibility, wettability and interfacial bonding between the filler and binder, which significantly improves the mechanical and comprehensive properties of the composite coating. The tensile strength (σb) and elongation at break (e) of the composite coating can be increased by 32% and 18%, respectively, by appropriate graft modification. The mechanism of the effect of AA and MAH graft modification on the coating properties was revealed from the aspects of polarity, branching and cross-linking.
Experimental and mechanism exploration of alkali-silica reaction inhibition by microbial mineralization
ZHENG Yulong, LIN Hongru, LU Chunhua, WANG Jingquan
, Available online  
Abstract:
Alkali-silica reaction (ASR) is a reaction between alkaline pore solutions in concrete and reactive non-crystalline SiO2 in aggregates, which leads to expansion and cracking of the concrete, and degradation of mechanical properties. In this study, based on the microbial induced calcium carbonate precipitation (MICP) technique of Bacillus pasteurus, various treatment frequencies and methods, including surface treatments of potentially active aggregates and mortar bars made by them, to comprehensively evaluate the inhibition law and mechanism of MICP on ASR. The results showed that the MICP treatment could form a dense CaCO3 layer with adhesive effect on the surface of aggregates and mortar bars, thus preventing the intrusion of alkaline ions and water, and the inhibiting effect became stronger with the treatment numbers; Compared with the control group, the maximum increase in mechanical properties of 13.8%, and the decrease in expansion rate of 35% were observed when the mortar bars were treated; When treating the aggregate, the mechanical properties were improved by 25.3% and the expansion rate was reduced by 59.6% with a better inhibition effect, as the surface CaCO3 layer could simultaneously block the alkaline ions and water existing in the pore solution and invading from outside. Microstructural and compositional analyses showed that the proportion of Si and Na atoms on the aggregate surface decreased by 69.6% and 88.9%, respectively, after treatment, indicating a significant reduction in the ASR gel.
Research progress on FRP confined recycled aggregate concrete components
LIU Chunyang, YAN Kai, LI Xiuling, SUI Yuwu
, Available online  
Abstract:
Promoting the use of recycled aggregate concrete is an important way to recycle the of building solid waste and promote the sustainable development of ecological environment. Fiber reinforced polymer (FRP) is an effective way to improve the mechanical properties of recycled concrete. Domestic and overseas researchers have carried out experimental research on and theoretical analysis of the characteristic of compressive strength, stress-strain curve, mechanical properties and seismic performance of the FRP wrapped recycled concrete materials and structural member with the different design parameters, such as the replacement rate of recycled aggregate, FRP type, lateral confinement stiffness (number of FRP layers), FRP fully wrapped or strip wrapped, etc. The applicability of the ultimate strength and ultimate strain model of FRP confined ordinary concrete to the test results of FRP confined recycled concrete is also compared. This paper analyzes the research status and shortcomings of FRP confined recycled concrete materials and components, and summarizes the problems that need to be further researched, so as to provide references for the subsequent research and engineering application of FRP confined recycled concrete structures.
Comparison of aging properties of starch/ PBAT degradable mulching film in different environments
LIN Jun, LI Xiaoxuan, CHAI Xicun, HE Chunxia
, Available online  
Abstract:
In order to develop a biodegradable mulching film to reduce the pollution of traditional mulching film, starch(TPS) and PBAT were used as raw materials to prepare two biodegradable mulching films TPS/PBAT-A and TPS/PBAT-B with a ratio of raw materials, and study their thermal aging (60, 80, 100 ℃) and multi-factor aging (temperature, humidity, and light intensity are 40℃-65%-310 W/m2、60℃-65%-310 W/m2 and 60℃-65%-648 W/m2). Before aging, the tensile strength of the two mulching films TPS/PBAT-A and TPS/PBAT-B are 16.3 MPa and 20.8 MPa, respectively, and the elongation at break is 1222.7% and 564.5%, respectively. After high temperature thermal aging, the mechanical properties of the two mulching films decreased. After thermal aging at 100 ℃, the tensile strength of the two mulching films TPS/PBAT-A and TPS/PBAT-B decreased to 11.2 MPa and 18.2 MPa, respectively; TPS/PBAT-B mulching films have relatively few surface defects after thermal aging, and their properties are well preserved. In the comparative environment of 60℃-65%-310 W/m2 and 60℃-65%-648 W/m2, the tensile strength of the two mulching films decreased by 23.0% and 22.4% after 24 days, respectively. When the two kinds of mulching films are aged, the amorphous area of the mulching films decomposes first, the molecular chain structure is destroyed, the existence of internal voids after molecular fracture reduces the bonding quality, and there are many holes and cracks on the surface.
Bacteriostatic performance and mechanism of Ag quantum dots synergistic tetracycline
GUO Shaobo, CHEN Huihui, LIU Ke, HU Ruiling, WANG Jiawei, YU Fan, LIU Zhifeng, SHI Juan, GUO Ting, JI Xiaohui, ZHANG Tianlei
, Available online  
Abstract:
Tetracycline antibiotics are widely used because of their high efficiency, low toxicity and broad-spectrum bacteriostasis, but with the abuse of antibiotics leading to the emergence of a large number of resistant bacteria, the medicinal value of tetracycline antibiotics gradually decreases. Although the ultra-small particle size of Ag can inactivate bacteria and even drug-resistant bacteria, it is highly toxic and easy to agglomerate when used alone. Therefore, in this study, the core-shell mesoporous Fe3O4@SiO2@mTiO2@Ag-tetracycline (FSmTA-T) composite was designed to solve the problems of antibiotic resistance, Ag nanoparticles agglomeration and strong toxicity by using the principle that the d orbital of Ag is a full electron structure and can be coordinated with the electron donor group. The results showed that the particle size of the Ag quantum dots in the prepared composite was 2.84 nm, which could be bonded with the carbonyl group in tetracycline ring 3, and compared with tetracycline, the composite material had high bacteriostatic activity against Escherichia coli, Staphylococcus aureus, tetracycline-resistant Salmonella and Candida albicans, and could effectively destroy the bacterial cell wall and make it die, while the toxicity was reduced to 1/3 of the original. Therefore, its superior bacteriostatic activity can be applied to sewage treatment.
Effect of graphene quantum dots on mechanical properties and microstructure of serpentine concrete
YANG Zhao, SHI Jianjun, ZHANG Zhiheng, CHEN Lei
, Available online  
Abstract:
In order to explore the feasibility of using graphene quantum dots (GQDs) as admixtures to improve the properties of serpentine concrete, effects of GQDs dosage on strength, crystal water loss rate, and microstructure of serpentine concrete were investigated at 25, 150, 300, 450, and 600℃. The results show that strength of serpentine concrete at room temperature (25 ℃) is enhanced with the increase in the dosage of GQDs, and the best enhancement is achieved when the dosage is 0.12wt%, and its 7 d and 28 d compressive strength and 28 d splitting tensile strength are increased by 26.4%, 20.9%, and 27.7%, respectively, compared with the baseline group. The addition of 0.12wt% GQDs reduces the crystal water loss rate of serpentine concrete by 1.8%~20.0%, and increases the compressive strength and splitting tensile strength by 18.0%~34.0% and 29.4%~39.8%, respectively, as compared to serpentine concrete without GQDs during the entire heating period. Microscopic tests show that high temperature environment promotes the hydration of serpentine concrete, as well as GQDs possess better thermal conductivity and nano-filling properties, which together significantly improve the micro-density of serpentine concrete, and the micro-density is highest at 300 ℃.
Research progress of bacterial cellulose and its composites for electrochemical energy storage and sensing
, Available online  
Abstract:
Bacterial cellulose ( BC ) is a green and renewable material with abundant sources. BC has outstanding physical and chemical properties and is considered to be a biopolymer material with diverse application potential. With the continuous deterioration of energy and ecological environment, it is urgent to develop advanced energy storage technology. BC shows broad application prospects in the fields of electrochemical energy storage, sensing and energy conversion, and has gained a lot of attention. In this review, BC is briefly introduced. Based on the types of BC and its composites in the field of electrochemical energy storage and sensing, as well as the effects of different treatments and modification methods on the structure and properties of BC, the application progress of BC in the field of electrochemical energy storage and sensing is systematically summarized. In addition, in terms of the composite matrix and reinforcement concept, the construction process of BC and its composites was systematically introduced. The application status of BC in the field of electrochemical energy storage and sensing is mainly reviewed, and the strengths and weaknesses of its application are analyzed and summarized. Meantime, the different applications of BC in new electronic devices and energy conversion are also involved. Finally, the existing challenges and prospects of BC in electrochemical energy storage and sensing are summarized.
Preparation and properties of Zr-MOF-NH2 and doped Nafion composite proton exchange membranes synthesized by microwaves
GAO Qian, ZHANG Liujie, ZHANG Hui, XU Jingkai, XIAO Wei, LI Ying
, Available online  
Abstract:
Vanadium liquid flow batteries require proton exchange membranes with excellent ion selectivity and physicochemical stability. In this work, UIO-66-NH2 was prepared by microwave and traditional hydrothermal method, respectively, and UIO-66-NH2/Nafion composite proton exchange membranes were prepared by the casting method, and the physicochemical properties of the membranes and the cell performance were systematically characterized. The results show that the hydrogen bonding network formed by UIO-66-NH2 within the composite membrane, acid-base pairs and its own pore size synergistically strengthened the ion selectivity of the composite membrane. The comprehensive performance of the composite membranes base on both microwave (M/N) and traditional hydrothermal (T/N) methods is superior to that of the pure resin membrane (P-N). At the addition amount of 3 wt%, the tensile strength of the M/N-3 membrane reaches 27 MPa, the proton conductivity and vanadium ion permeability are 122.18 mS·cm−1 and 0.83 × 10−7 cm2·min−1, respectively, and the ion selectivity is 15.6 × 105 S min cm−3, which is about 30 times of that of the P-N membrane, and the cell energy efficiency of this membrane reaches 83.8% - 71.7% (100-200 mA·cm−2), which is superior to T/N-3 membrane (82.7%-71.0%) and P-N membrane (79.4%-69.0%). The cell also shows superior cycling stability and capacity retention. Therefore, UIO-66-NH2 synthesized by microwave method can effectively improve the comprehensive performance of proton exchange membranes, which is promising in optimizing the performance of vanadium liquid flow batteries.
Preparation of lignin surface-functionalized MXene nanosheets and its U(VI)adsorption properties
Li Shiyou, Qiao Jishuai, Yang Yubiao, Xiong Zhiyu, Wang Guohua
, Available online  
Abstract:
In order to further improve the adsorption performance of MXene nanomaterials on U(Ⅵ) in simulated radioactive wastewater, the surface functionalization of MXene was carried out by using natural resources of enzymatically hydrolyzed lignin (EHL) as a biosurfactant, and the materials before and after the modification were characterized and analyzed by using SEM-EDS, XRD, and FTIR, and the effects of pH, temperature, and the adsorption experiments were explored, reaction time, interfering ions and different initial U(VI) concentrations on the effect of U(VI) removal. The results show that EHL prevents the re-stacking of MXene nanosheets and introduces a large number of active functional groups, which improves the adsorption performance of EHL-functionalized MXene nanosheets. The maximum adsorption capacity for U(VI) is 231.95 mg·g−1 at the mass ratio of MXene to EHL of 1∶5, the dosage of 0.1 g·L−1, pH = 5, and the temperature of 303 K. In addition, the adsorption kinetic and isotherm analyses show that the proposed second-order kinetic model and the Frendlich isotherm model fit this adsorption process well, and the thermodynamic analyses indicate that its adsorption process is spontaneous heat absorption. After five cycles of regeneration, the removal rate of U(VI) is still above 80%. Characterization results reveals that the interaction mechanisms between MX/EHL and U(VI) involve ion exchange, electrostatic attraction, and complexation with oxygen-containing functional groups. Based on this study, MX/EHL has great potential as an environmentally friendly adsorbent material for the removal of U(VI) from wastewater.
Modification of coconut shell biochar by ball milling with an alkali for enrofloxacin adsorption
XIAO Dao, ZHENG Lili, ZHENG Xiaoyan, YANG Yang, AI Binling, SHENG Zhanwu
, Available online  
Abstract:
In order to efficiently adsorb enrofloxacin (EFA) in water, coconut shell biocharC(BM-KOH-BC) was prepared by modifying coconut shell through ball milling and KOH activation, and in-depth research was conducted on the adsorption of EFA. BM-KOH-BC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The results revealed that KOH activation and ball milling modification significantly improved the pore structure and specific surface area of BM-KOH-BC. under optimized conditions (initial EFA concentration is 80 mg·L−1, pH value is 7, temperature is 25°C, adsorbent dosage is 0.14 g·mg·L−1, stirring speed is 200 r/min, contact time Under the conditions of 35 h), BM-KOH-BC showed good adsorption performance, with a removal rate of 77.4% and a maximum adsorption capacity of 481.1 mg·g−1. The adsorption process is consistent with the second-order kinetic model and Freundlich isotherm model. In addition, BM-KOH-BC still maintains efficient EFA removal rate after 5 adsorption-desorption cycles. This low-cost, efficient adsorption and recyclability feature makes BM-KOH-BC show potential application prospects in treating EFA in water bodies.
Research progress of single/dual network liquid crystal elastomers based on dynamic bonds
LEI Lan, HAN Wenjia, LOU Jiang
, Available online  
Abstract:
Liquid crystal elastomers (LCEs) containing dynamic cross-linking bonds are capable of undergoing macroscopic motion through alterations in volume or shape in response to external stimuli, including light, electricity, or heat. These materials demonstrate remarkable molecular cooperative effects and adaptive properties, offering considerable potential in the fields of soft robotics, artificial muscles, and microfluidics. Effective control of the internal liquid crystal orientation in LCEs is essential for achieving reversible deformation. The breakage and reformation of dynamic bonds not only decouples the construction of cross-linked networks and orientation control, but also enhances the reprocessing properties of materials, enabling new functionalities like remodeling deformation, self-healing, and shape memory. Therefore, the deliberate design and construction of cross-linked network structures, including the selection of cross-linking agents, their structures, and cooperative effects of various networks, are crucial for producing liquid crystal elastomers with exceptional performance and multifunctional integration. This review comprehensively discusses advancements in the preparation and application of LCEs, encompassing liquid crystal orientation control and single/double dynamic cross-linking networks (involving dynamic non-covalent and covalent bonds), and delineates future prospects for development in this field.
Research progress of specific structural composites derived catalysts in dry reforming of methane
XIE Xuanlan, LU Zhiheng, LI Wenzhi
, Available online  
Abstract:
Specific structural composites such as perovskite, spinel and hydrotalcite have attracted widespread research interest in catalytic applications due to their flexible composition, controllable structure, and better thermal stability. Dry reforming of methane is a technology with great application prospect for converting CH4 and CO2 into syngas with low H2/CO molar ratio simultaneously. Conventional supported catalysts are susceptible to face the challenge of catalyst deactivation caused by carbon deposition and active component sintering under high-temperature reforming conditions, whereas supported catalysts derived from specific structural composites have attracted much attention owing to their superiority in terms of catalytic activity and stability. In this paper, the characteristics of dry reforming of methane, the challenges faced and the current research status of the reaction mechanism are first briefly outlined, and then elaborates on the structural characteristics of perovskite, spinel and hydrotalcite these three composites, the advantages and disadvantages of applying them as catalyst precursors in this reaction, their performance and the current status of research on the catalytic pathway. Perovskite structure is relatively more stable, but high calcination temperatures may easily lead to a lower surface area of its derived catalyst; hydrotalcite-derived catalysts usually have a high specific surface area and can restore partially ordered layered structures when calcined under certain circumstances; hydrotalcite and spinel are relatively more sensitive to temperature, and the presence of inverse spinel structure is beneficial for improving the reducibility of the derived catalysts. Additionally, the catalytic mechanisms of these three specific structural composites derived catalysts are summarized. The clear one is that CH4 is activated at the active metal sites, and due to the influence of catalysts and operating conditions, researchers have not reached a clear consensus on the details of the reaction mechanism at the catalyst surface for the time being. Finally, some advice is put forward on the application of these specific structural composites derived catalysts in dry reforming of methane.
Structure and properties of chitosan enhanced cellulose nanofiber-montmorillonite composite membrane
WANG Yunyi, ZOU Chuwen, YIN Ran, YOU Zhengtong, WANG Haigang
, Available online  
Abstract:
The way of mimicking the ordered “brick and mortar” structure in natural shells to prepare high-strength functional composite materials with cellulose and inorganic substances of which the interface bonding is the key to achieving ideal structure and performance is a potential excellent choice for producing naturally degradable packaging films. The single interfacial binding force between nanocellulose and montmorillonite results in insufficient mechanical properties. In this work, carboxymethyl cellulose nanofibers (CNFMG) and montmorillonite (MTM) nanosheets were used to prepare pearl layer films in which chitosan (CS) enhanced interface bonding through electrostatic interaction. The effects of electrostatic interactions between CS, CNFMG, and MTM on the structure, mechanical properties, and thermal stability of nanocomposites were studied. The results indicate that MTM in the composite membrane was orderly dispersed in nanosheet form between CNFMG networks. Compared with the CNFMG-MTM binary film, the tensile strength of the ternary film with the addition of CS reached 119.2 MPa, which doubled the strength. The fracture energy reached 10.9 MJ/m3, and the toughness was increased by four times. The composite film was semitransparent and had good UV shielding properties. The addition of CS also enhanced the thermal stability of the composite film. The research results of this article can provide ideas for the research and application of cellulose based pearl layer biomimetic materials.
Advances in flexible wearable bismuth telluride-based Materials thermoelectric devices
ZHANG Tong, LI Jie, YE Shiying, WU Kai, REN Song, FANG Jian
, Available online  
Abstract:
As the global energy consumption increasing rapidly, development and application of thermoelectric devices have become one of the effective ways to solve the problem. Among them, bismuth telluride-based flexible devices attract widespread attention because they have been applied in the wearable sector gradually. However, due to the limitations of high material cost, rigid structure, and other factors, it is difficult for bismuth telluride-based flexible thermoelectric devices to achieve flexible wearable applications while maintaining efficient thermoelectric properties. This paper systematically reviews the current research progress of bismuth telluride-based flexible thermoelectric devices in terms of material composites and flexible structure design, especially in terms of flexible structure design, which covers three types of structures: ingot-, film- and yarn- shaped. Finally, it summarizes and analyzes the possible future challenges and development trends of bismuth telluride-based flexible thermoelectric devices, to facilitate the realization of a wide range of applications for thermoelectric devices in the wearable field.
Preparation and electrical properties of recyclable high performance dual-curing epoxy resin
WANG Haohuan, QIN Ling, WANG Tianxing, SHI Lingna, WU Jinsuo, WEN Sen
, Available online  
Abstract:
Epoxy resins play a crucial role in providing insulation, support, and protection for the electrification process in transportation. However, the conventional methods of recycling epoxy resins are quite complex and do not align with the sustainability goals of green transportation. There is an urgent need to develop environmentally friendly and recyclable epoxy resins. To address the issues related to the physical, chemical, and electrical properties of recyclable epoxy resins, this paper introduces a novel photothermal dual-curing method that combines photosensitive oil-based resin with epoxy resin. This innovative approach leverages the transesterification mechanism to recover the dual-curing epoxy resin under high-temperature and high-pressure conditions without the need for a catalyst. Remarkably, the recovered resin retains excellent physical, chemical, and electrical properties. The study demonstrates that the initial properties of the dual-curing epoxy resin are promising. The quality of the recovered resin improves with smaller resin particle sizes and higher hot pressing pressures. After undergoing a hot pressing process at 220℃ and 10 MPa for 3 hours, the recovered resin exhibits its best comprehensive properties, with recovery rates of 92.0% for bending strength and 93.7% for tensile strength. Furthermore, the dielectric constant and dielectric loss at power frequency remain largely unchanged compared to their values before recovery, with a remarkable breakdown strength recovery rate of 98.4%. This research highlights the significant potential and application prospects of dual-curing epoxy resin in advancing the electrification of transportation.
Research progress in the preparation of functional fluorescent transparent wood composite materials
LONG Shoufu, ZHANG Ming, AN Congcong
, Available online  
Abstract:
With the continuous development of society, there is an urgent need for a green composite material with environmental protection, low cost, good toughness, high strength, and high added value - functional fluorescent transparent wood composite material, to replace traditional glass doors and windows, building and home materials. Functional fluorescent transparent wood composite materials have advantages such as green, high transmittance, high strength, good toughness, excellent fluorescence effect, good UV shielding, antibacterial, and good mechanical properties, and have broad application fields. This article summarizes the luminescence principle and influencing factors of fluorescent materials, various preparation methods of wood substrates, and the application of functional fluorescent transparent wood composite materials. It also introduces the applications of functional fluorescent transparent wood composite materials in LED lamps, sensors, encryption and anti-counterfeiting, UV conversion, and formaldehyde detection. Finally, it looks forward to future application scenarios and proposes the urgent problems to be solved at present.
Research Status of AgNPs Composite Antibacterial Agent and its Carriers
JIN Jing, ZHANG Fan
, Available online  
Abstract:
In recent years, the development of antibacterial materials has received great attention in various fields. The application of antibacterial technology is closely related to human health and has a great development prospect. AgNPs antibacterial agent is one of the most widely used antibacterial agents at present. In this paper, the antibacterial mechanism of AgNPs antibacterial agent is discussed. Besides, the research progress of composite antibacterial agent composed of Ag-NPs and natural antibacterial agent, organic antibacterial agent and inorganic antibacterial agent respectively is introduced. At the same time, the carrier of AgNPs antibacterial agent was introduced from three aspects: Inorganic Carrier, Organic Carrier and new carrier, which can provide reference for further research and application of AgNPs antibacterial agent.
Preparation and properties of nano-SiO2/anthocyanidin/ regenerated cellulose smart colorimetric sensing film for food freshness monitoring
CAO Jiali, DONG Huilin, XU Yanglei, XU Feng
, Available online  
Abstract:
Smart food packaging can make up for the shortcomings of traditional packaging in real-time quality monitoring, so exploiting a low cost, harmless to human health and green food freshness intelligent indicator label is of great significance for food safety. Therefore, in this study, we employed regenerated cellulose (RC) films, anthocyanidin extracted from red cabbage and nano-SiO2 to fabricate a biodegradable smart colorimetric sensing film (RCG-PCE-Si). This film has good mechanical properties (maximum stress is 67.1 MPa, and maximum tensile strain is 45.50%) and super-hydrophobicity (water contact angle is 152.8°), and has a certain barrier ability to ultraviolet light, which can be used for real-time monitoring of fresh food freshness. In addition, the effectiveness of the film in detecting the freshness of shrimp was confirmed by measuring the total volatile basic nitrogen (TVBN) and pH value, and its color obviously changes from magenta to water-red, then to grey-purple, and then to grey-green, effectively indicating the spoilage of shrimp. The colorimetric sensing film developed here would be used as an intelligent colorimetric label with good mechanical properties and super-hydrophobicity, and can be applied to intelligent packaging that can monitor the freshness of food in real time.
Numerical research on magnetostrictive deformation of hard magnetic soft materials
PENG Fan, MA Weili
, Available online  
Abstract:
Smoothed finite element method is based on strain-smoothed technology; it avoids using the isoparametric transformations during numerical integration, and has certain advantages in simulating large deformation problems of soft materials. A numerical format for simulating large deformation of hard magnetic soft materials based on strain-smoothed technology has been established, and the necessary stress tensors and constitutive tensors have been provided. The bending characteristics of hard magnetic soft material beams with different aspect ratios under external magnetic field were studied, and the magnetic load displacement curves obtained were compared with experimental results; evolution process of the morphological of hard magnetic soft material structures with different directions of residual magnetic field under the action of an external magnetic field was simulated, and the calculated final deformation morphology was compared with experimental results. The numerical results indicate that the results obtained by using this numerical format are in good agreement with the experimental results; there is significant deformation at the sudden change in the direction of the residual magnetic field inside hard magnetic soft materials. The research results can provide reference for the mechanical analysis and deformation control design of soft robots and intelligent flexible structures composed of hard magnetic soft materials.
Experimental study on strength and deformation characteristics of polymers treated sand
BAI Yuxia, LIU Jin, SONG Zezhuo, ZHANG Chenyang, HE Chengzong, DENG Yongfeng
, Available online  
Abstract:
Polymer has broad application prospects in soil stabilization. However, there is currently little research on the strength and deformation characteristics of polymer treated soil, as well as the degree of influence of different influencing factors. In this work, a series of unconfined compression strength and shear strength tests were performed on a water-soluble polymer treated sand, and subsequently, the effects of polymer content, curing time and dry density on the strength and deformation characteristics of the treated sand were analyzed. Also, the degree of influence of the three research variables was elucidated using correlation analysis. And finally, the related mechanism of treated sand was revealed using electron microscopy scanning (SEM) observations. The results show that, (1) The three studied variables significantly enhance the unconfined compression strength and shear strength, and the influence of polymer content and curing time on shear strength was mainly reflected in the cohesion. The strength of polymer treated sand is significantly and positively correlated with curing time, and moderately and positively correlated with polymer content and dry density. In addition, these relationships can be represented by a logarithmic function or linear function. (2) As the polymer content, curing time and dry density increase, the shear characteristics of treated sand change from shear hardening type to shear softening type, and the shear failure displacement of treated sand decreases gradually (as dry densities decreases). Also, its axial stress-strain curve shows obvious post-peak easing phenomenon and then produces obvious changes, and the compression failure pattern is dominated by bulging and accompanied by cracks, what’s more, this pattern gradually changes from E-type to G-type (as dry densities decreases). (3) The deformation capacity of treated sand is strongly and positively correlated with curing time, moderately and positively correlated with dry density, while the correlation with polymer content is not significant. Additionally, the peak strain has a polynomial (or linear) relationship with three studied variables. (4) For this polymer treated sand, the optimum mixing content is about 2%, and when the curing time reaches 24h and above, it shows a better treatment effect. (5) The polymer forms an effective and stable three-dimensional membrane structure in the sand particles by adsorption, bonding and filling effects, and thus effectively improves the microstructure of sand. The proportion of changes in the types of polymers under load determines the strength, deformation capacity, and failure mode of treated sand, which is closely related to polymer content, curing time and dry density.
Mechanical properties of concrete modified by graphene oxide grafted carbon fiber reinforcement
WANG Zhihang, BAI Erlei, REN Biao, LIU Chaojia, ZHOU Junpeng
, Available online  
Abstract:
In order to enhance the interface properties of carbon fiber/concrete matrix, and investigate the effects of graphene oxide grafted carbon fiber reinforcement (CF-GO) on the mechanical properties of concrete, by using amino silane as bridge material, carbon fiber and graphene oxide were tightly bonded through chemical bonds and graphene oxide grafted carbon fiber reinforcement (CF-GO) was prepared. The microstructure and functional groups of CF-GO were characterized by scanning electron microscopy and infrared spectroscopy. Graphene oxide was successfully grafted to the surface of carbon fiber and the interfacial shear strength of CF-GO was tested. CF-GO modified concrete (CF-GO/C) was prepared, its mechanical properties were tested and compared with those of carbon fiber modified concrete. In addition, the modification mechanism of CF-GO on the mechanical properties of concrete was analyzed. The results show that the interfacial shear strength of CF-GO increases by 25.37% compared with that of carbon fiber. With the increase of CF-GO content, the flexural and compressive strength of CF-GO/C first increase and then decrease. The optimal content of CF-GO is 0.3%, and the optimal content of carbon fiber is 0.2%. The flexural and compressive strength of CF-GO/C increase by 33.21% and 24.63% respectively with the optimal CF-GO content. Graphene oxide on the surface of CF-GO enhances the interface of CF-GO/concrete matrix physically and chemically by improving the mechanical bite between CF-GO and concrete matrix and promoting the formation of hydration products on the surface of CF-GO.
Effect of matrix modification on the properties of continuous glass fiber reinforced nylon composites
ZHANG Xinting, YIN Hongfeng, WEI Ying, TANG Yun, YUAN Hudie, REN Xiaohu, YANG Shun
, Available online  
Abstract:
One of the important ways to improve the mechanical properties of continuous glass fiber (cGF) reinforced nylon 6 composites (cGF/PA6) is to improve the interface interactions between glass fiber and nylon 6. In this study, star-branched polyamide 6 (SPA6) was applied to cGF/PA6 composite system, and continuous glass fiber reinforced nylon composites with different contents of SPA6 (cGF/PA6-SPA6) were prepared by melt extrusion combined with hot pressing. The characterization of Contact Angle indicates that the polarity between SPA6 and cGF is more similar. DSC results show that there is not much difference in the melting temperature among PA6, SPA6 and PA6-SPA6 composite matrix, and both the crystallization temperature and crystallinity of PA6-SPA6 are increased. The flexural strength of PA6-SPA6 matrix is lower than that of PA6 and SPA6 measured by three-point flexural tests. However, compared with cGF/70wt.%PA6, the flexural strength of cGF/5wt.%SPA6 and cGF/10wt.%SPA6 composites increased by 4.9% and 6.4%, respectively, and the shearing strength of cGF/5wt.%SPA6 and cGF/10wt.%SPA6 composites increased by 16.7% and 15.6%, respectively. The impact strength of cGF/PA6 and cGF/SPA6 composites is 12 times and 26.3 times that of PA6 and SPA6, respectively. Combined with the observation of impact fracture morphology, it can be inferred that adding 5wt.% or 10wt.% SPA6 to cGF/PA6 composites can improve the flexural and shearing strength of the composites, while having little influence on the impact strength, and considering its cost-effectiveness, it proves to be of practical value for applications.
Research progress on multiaxial fatigue of continuous fiber reinforced polymer matrix composite
CAO Duanxing, YANG Yang, CHEN Xinwen, ZHU He, LI Shaolin, SHI Duoqi, QI Hongyu
, Available online  
Abstract:
Currently, continuous fiber-reinforced polymer matrix composite find extensive applications in aerospace and various other industries. These materials undergo intricate multiaxial stress states during usage, with a predominant presence of fatigue loads. Consequently, delving into the multiaxial fatigue study of composite materials becomes imperative. Research on the multiaxial fatigue of composite materials is presently categorized into three primary domains: exploration of multiaxial fatigue behavior across different specimens, identification of factors influencing such behavior, and the development of multiaxial fatigue life prediction methods. The investigation into multiaxial fatigue testing of composite materials encompasses tube-shaped, cross-shaped, and plate-shaped specimens. Among these, cross-shaped and tube-shaped specimen tests are the most prevalent. The impact of factors such as stacking sequence, multiaxial degree, and load loading methods on the multiaxial fatigue strength of composite materials under varying multiaxial fatigue loading conditions are discussed in this article. Concerning the prediction of biaxial fatigue life in composite materials, available methods predominantly consist of phenomenological models and non-classical models. While akin to uniaxial fatigue life prediction methods, these models overlook damage evolution under biaxial fatigue loads and the damage mechanisms controlling final failure. A comprehensive overview of the progress in researching multiaxial fatigue of fiber-reinforced composite materials is furnished, and an in-depth introduction is provided for the three dimensions of multiaxial fatigue. Through the synthesis and analysis of existing research findings, prospective directions for future research on multiaxial fatigue in composite materials are discussed.
Silver nanoparticle/nanocellulose composites antibacterial strain-responsive hydrogels
WANG Qinwen, WANG Wenjun, CHEN Wenjin, TANG Aimin
, Available online  
Abstract:
The antibacterial and conductive hydrogels based on silver nanoparticles (AgNPs) have important applications in wearable devices, electronic skin, biosensors, and other areas, and their green manufacturing is currently the focus of much research. Nanocellulose has attracted more attention relating to the preparation and application of the smart hydrogels due to its unique physico-chemical properties. When AgNPs are combined with nanocellulose and applied to hydrogels, it is expected to lead to fabrication of antibacterial hydrogels with good mechanical properties, which has guiding significance for the application of hydrogels in the area of intelligent wearable systems. In the present study, AgNPs/nanocellulose composites (Ag-CNF) were in situ synthesized using TEMPO-oxidized nanocellulose (TOCNF) as a composite substrate and silver nitrate (AgNO3) as a source of silver. Ag-CNF and tannic acid (TA) were introduced to polyacrylamide (PAM) hydrogels as functional additives to prepare the Ag-CNF/PAM hydrogel (AP hydrogel) with good tensile properties, adhesion, antibacterial properties, and UV-shielding properties. The AP hydrogels were then packaged into a strain-responsive sensor. The electrical and sensing properties were studied. AP hydrogels can maintain stable and repeated electrical output under 100% strain cycle and can also be used for wrist motion and head motion detection, which has potential for use as a strain-responsive sensor.
Enhanced modification of interface performance of polyethersulfone resin matrix carbon fiber composite by thermosetting resin transition layer
XU Peijun, LI Zhao, GUO Xinliang, LIU Ronghai, WU Daosheng
, Available online  
Abstract:
Polyether Sulfone (PES) resin possesses excellent heat resistance, mechanical properties, and high-temperature stability, making it suitable for the production of high-performance thermoplastic resin-based carbon fiber composite materials. However, due to the poor interfacial adhesion between PES resin and commercial grade carbon fibers, PES resin based carbon fiber composites exhibit poor interfacial properties. In previous studies, we discovered that thermosetting cyanate ester (CE) resin had advantages such as good melt flowability, a curing temperature close to that of PES resin, and some compatibility with PES resin. In this paper, CE resin is utilized as an interface transition layer for PES resin-based carbon fiber composite materials, Leveraging the transition layer resin's excellent bonding capability with the carbon fiber surface sizing agents and its strong mechanical interlocking with PES resin, the impact of the thermosetting resin transition layer on the interface performance of thermoplastic resin-based composite materials is investigated by us. The results demonstrate that introducing a CE resin transition layer can enhance the interfacial bonding performance of PES-based carbon fiber composite materials. Compared to carbon fiber (CF)/PES composite materials, the CF/(10%CE-PES)-L composite material with a 10wt% CE resin transition layer exhibits an 18.7% increase in flexural strength, a 24.2% increase in interlaminar shear strength, additionally, the glass transition temperature (Tg) of the CF/(5%CE-PES)-L composite material increased from 167℃ to 179℃. The method of preparing thermoplastic resin-based carbon fiber composites by adding an interlayer between the thermoplastic resin matrix and commercial carbon fibers has addressed the issue of poor interface performance in thermoplastic resin-based carbon fiber composites. This investigation important research insights and a theoretical basis for its engineering applications.
Effect of polyethylene glycol on fluoride removal performance of hydroxyapatite
MA Mingming, CUI Shuhui, YANG Jiaqin
, Available online  
Abstract:
The removal efficiency of hydroxyapatite (HAP ) to fluoride was low due to its easy agglomeration during the synthesis process. Based on this, a clean,simple, green and environmentally fiendly electrochemcial synthesis method was applied to improve the fluoride removal efficiency. Polyethylene glycol (PEG), a non ionic surfactant with strong hydrophilicity and excellent dispersion,was added to the mixed support electrolyte for preparing HAP. A new type of HAP composite (PEG/(HAP) was prepared on the surface of copper sheet as the working electrode. By contrast to HAP, the crystal structure, pore size, specific surface area, surface morphology, elemental proportion, and functional groups of PEG/HAP were analyzed to reveal the instrinsic mechnism of the higher fluoride removal efficiency of PEG/HAP than HAP. The results showed that PEG/HAP and HAP had the same crystal plane structure characteristics, elements and chemical bonds, while the proportion of various elements as well as the absorption peaks and instensity of hydroxyl and phosphate ion functional groups in PEG/HAP had certain differences compared to HAP. PEG transformed HAP from a short rod-shaped surface morphology to a porous and porous structure that facilitated the exchange and adsorption of fluoride ions. Average pore size of PEG/HAP decreased from 16.58 nm of HAP to 11.93 nm, and its specific surface area increased from 24.29 m2/g OF HAP to 29.83 m2/g. Although the adsorption types of PEG/HAP and HAP were both IV type H3 hysteresis loop, and their mesoporous distribution ranges were consistent, the number of micropores and mesopores in PEG/HAP were significantly higher than those in HAP. Although the adsorption reactions of both materials for fluoride ions exhibited entropy increase, endothermic, and spontaneous process characteristics with the adsorption isotherm model conforming to Langmuir-Freundlich, the intra particle diffusion rate constant of PEG/HAP was slightly higher than HAP. Therefore, the maximum adsorption capacity of PEG/HAP for fluoride ions can reach 9.56 mg/g, which was higher than that of HAP of 8.36 mg/g. Compared with 4 times of recycle regeneration for removing fluoride ions of HAP, PEG/HAP can arrived at 6. In addition, the presence of PEG did not affect the change trend of preparation parameters such as electrolyte pH on the adsorption capacity of HAP for fluoride ions. However, PEG increased the adsorption capacity of HAP for fluoride ions. All coexisiting ions such as Cl, NO3−, SO4 2−, and CO3 2− did not interfere with the adsorption of fluoride ions for PEG/HAP and HAP.
In-situ modification of laser-induced graphene with silver nanoparticles and its electronic conductivity modulation
WANG Wenbo, SONG Yanping, LI Nian, WANG Zhenyang
, Available online  
Abstract:
With the rapid development of high-frequency communication technology, electromagnetic interference (EMI) issue has been increasing. Hence, EMI shielding materials for the 5G frequency band are in high demand. Here, a two-step laser-induced strategy was developed to rapidly prepare silver nanoparticles/porous graphene flexible composite in a solid-phase synthesis process. AgNO3 solution can be efficiently adsorbed by hydrophilic laser-induced graphene (LIG) obtained by the first laser irradiation with tuned parameters, which provides favorable conditions for the abundant and homogeneous loading of Ag nanoparticles on LIG after in-situ the second laser irradiation. Furthermore, the microstructures, structural properties and electronic conductivity of the prepared Ag/LIG composites with different AgNO3 additive concentrations are detailedly analyzed. As a result, with a 0.5 mol/L AgNO3 additive concentration, Ag nanoparticles in the composite film maintain small size while exhibiting the best dispersion, exhibiting a high conductivity of 2788 S/m. In the 18-27 GHz frequency band, the EMI shielding effectiveness increases from 18-26 dB of LIG to 36-40 dB of composite materials. The EMI shielding effectiveness of Ag/LIG-0.5 at the 26 GHz reaches 38 dB with an over 90% shielding effectiveness retention rate after 200 bending cycles.
Preparation and self-healing property of phenolic modified epoxy vitrimer
LIAN Weiqiang, ZHAO Xiaojia, PENG Guirong, ZHANG Siqi
, Available online  
Abstract:
Vitrimer can undergo plastic deformation while maintaining a cross-linked state, which means that traditional thermosetting resins have the ability to undergo secondary thermal processing and molding, which will effectively reduce scrap rates and reduce waste from the beginning. The plastic deformation of vitrimer can also endow item self-healing ability and extended its service life, and so contribute to environmental protection and emission reduction. In the paper stannous iso-octanoate as a catalyst and phenolic resin as a modifier was used to prepare anhydride cured epoxy vitrimer materials. The research results indicate that the increase in catalyst content could make the system cure more completely, so there is a certain improvement in the bending strength of the material, up to 87.5 MPa. With introduction of phenolic resin, the bending strength increases from 87.5 MPa before modification to 126.9 MPa, and the tensile strength reaches 63.3 MPa. When the amount of phenolic resin added is too high, the crosslinking density of the material decreases, and the mechanical properties of the material show a downward trend. The study on the relaxation behavior of the epoxy vitrimer system cured with pure anhydride shows that increasing the catalyst content reduces the relaxation time of the materials, but the post curing reaction at high temperature could inhibit the relaxation process and suppress the self-welding strength. The stress relaxation of epoxy vitrimer material modified with phenolic resin is significantly faster than that of epoxy vitrimer system cured with pure anhydride. The relaxation of the samples with 10% catalyst shows a sudden change, and there is a significant acceleration when the temperature rises to 190 ℃, and the introduction of phenolic resin could advance the sudden change temperature Ts to 180 ℃. Under no pressure conditions, scratches are repaired. The tensile shear strength and scratches repair effect of the samples repaired above Ts are significantly improved. Compared to samples without phenolic resin, phenolic modified samples could be repaired better. Catalyst have a significant impact on the repair strength and repair speed of the samples.
Progress in the structural design and properties of Ti3C2Tx-based electromagnetic shielding composites
WANG Heng, FENG Shuyue, HU Junhao, LIU Mengzhu, WANG Yongpeng
, Available online  
Abstract:
With the popularity of 5G network and the miniaturization of electromagnetic equipment, electromagnetic radiation has brought certain harm to the surrounding environment and human body. Therefore, it is of great significance to develop new electromagnetic interference shielding materials with excellent comprehensive performance. Ti3C2Tx MXene is a new type of two-dimensional material with unique layered structure, adjustable active surface, ultra-high conductivity and other characteristics. Thus, it exhibits an excellent electromagnetic shielding performance. In recent years, many researches on its preparation method and filler selection have been reported. However, there is little work to summarize Ti3C2Tx matrix composites from the structural design level. High-efficiency structural design can not only reduce the amount of filler, but also improve shielding effectiveness. This article takes the structure as the main thread and summarizes the development trend of Ti3C2Tx based electromagnetic shielding materials in recent years. By analyzing the shielding effectiveness and mechanism, the article focuses on summarizing the influence and role of different structures such as porous structure, layered structure, core-shell structure, other special structures, and their composite structures on the electromagnetic shielding performance of Ti3C2Tx based materials. And key scientific and technical issues that urgently need to be addressed when Ti3C2Tx and its composite materials are used as electromagnetic shielding materials were proposed. Finally, the development prospect of Ti3C2Tx MXene is prospected.
Preparation of nickel ferrite loaded fir sawdust biochar to activate peroxymonosulfate for Chloroquine Phosphate degradation
WANG Junhui, ZHANG Jingwei, SUN Jing, YAN Jingyuan, XU Zisong, JIANG Luying, HUANG Yan, HAN Biao, ZHANG Hanbing, HAO Gerile, HE Sijing, ZHU Huafeng
, Available online  
Abstract:
In recent years, chloroquine phosphate (CQP) has been widely used as a specific drug for the treatment of COVID-19. Even after the epidemic ended, it still plays an important role because of its anti-inflammatory and anti-malaria capabilities. The widespread use of chloroquine phosphate poses serious potential hazards to the environment. Utilizing waste wood chips as resources, a nickel ferrite loaded biochar composite material (NiFe2O4@BC) with magnetic recovery was prepared by co precipitation anaerobic calcination method, and study the performance of activating peroxymonosulfate (PMS) to degrade CQP. The compositional structure, surface functional groups, and degree of graphitization of the NiFe2O4@BC composite were analyzed using various characterizations. Compared with unmodified fir sawdust biochar (Fir sawdust biochar, BC), the loading of magnetic NiFe2O4 on the biochar resulted in an increase in the degree of graphitization of the composite, and an increase in the number of defective active sites, which led to a tremendous increase in the effectiveness of the removal of CQP. The effects of NiFe2O4@BC dosing, PMS concentration, initial pH of the solution, inorganic anions, and humic acid in the degradation of CQP were mainly investigated. Research shows that when NiFe2O4@BC Under the conditions of 0.5 g/L dosage, 1.0 mmol/L PMS concentration, and 10 mg/L CQP concentration, the CQP removal rate reaches 89% in 120 minutes. The degradation of CQP is more favorable under acidic or alkaline conditions, and humic acid (HA) has a promoting effect on the degradation of CQP by NiFe2O4@BC-activated PMS. Quenching experiments confirm that •OH and 1O2 generated by the radical and non-radical pathways dominated the degradation of CQP by the NiFe2O4@BC/PMS system. Under the same conditions, it can achieve more than 80% degradation effect for many kinds of pollutants. In addition, the efficiency of CQP removal by activated PMS could still reach about 74% after NiFe2O4@BC was recycled 5 times. This study provides new strategies and reference significance for the efficient and green resource utilization of discarded fir sawdust.
Preparation of MXene-based composites and their applications in sodium and potassium-ion batteries
LIU Na, WANG Ya-ting, XIU Shi-jian, LI Ren-zhe, QUAN Bo
, Available online  
Abstract:
MXene and its composite materials have been widely used in the field of secondary batteries. As a new two-dimensional transition metal carbide layered material, MXene has been widely used in energy storage, adsorption, catalysis and other fields. Constructing composites based on MXene not only improves conductivity and alleviates volume expansion, but in turn inhibits MXene stacking and obtains better electrochemical performance. In this paper, the synthesis methods of MXene containing fluorine and fluorine-free are reviewed, and the application and performance of MXene and its composites in sodium and potassium-ion batteries are analyzed. Finally, the challenges and prospects of MXene and its composites are elaborated.
Antibacterial mechanism of MXene and its composite hydrogel application in infective wound healing
WU Xiaona, WANG Yiyu, ZHAO Kai
, Available online  
Abstract:
Infected wounds seriously endanger the quality of life and even life and health of human beings, so the development of antimicrobial biomaterials with high efficiency and few side effects for the repair of infected wounds has broad market prospects. Two-dimensional transition metal carbide (MXene) is a new type of two-dimensional sheet material with excellent antibacterial properties, and its antibacterial mechanism mainly includes physical capture theory, infrared thermal effect, reactive oxygen species (ROS) generation theory, intercellular molecular leakage theory, etc., so MXene is expected to become a safer, effective and broad-spectrum antibacterial method. Compared with simple hydrogels, MXene composite hydrogels made of hydrogels encapsulated with MXene have better antibacterial, antioxidant properties and photothermal effects. In this paper, the antimicrobial mechanism of MXene was reviewed, and the researches on the repair of infected wounds by MXene composite hydrogels were comprehensively reviewed and summarized in recent years.
In-plane shear behavior characterization of unidirectional thermoset prepreg and its viscoelastic constitutive modeling
GAO Sasa, WANG Zeyu, HE Liang, YU Zuwang, ZHAO Zizhao, LIANG Biao
, Available online  
Abstract:
The in-plane shear deformation behavior of unidirectional thermoset prepreg has significant effect on the forming quality and mechanical properties of composite parts after hot diaphragm forming. In this paper, the in-plane shear and stress relaxation behavior of unidirectional thermoset prepreg at different forming temperatures and loading rates were investigated. The test results show that the unidirectional thermoset prepreg exhibits a nonlinear in-plane shear deformation behavior strongly related to temperature and loading rate, and the sensitivity of shear deformation to loading rate decreases with the increasing of temperature. The relaxation rate of unidirectional thermoset prepreg accelerates with the increasing of temperature, and the sooner it is in a stable state. Based on the in-plane shear stress relaxation behavior of unidirectional thermoset prepreg, a generalized Maxwell viscoelastic constitutive model was constructed, which could accurately track fiber orientation change. The viscoelastic constitutive model was implemented in the user material subroutine VUMAT in Abaqus. The off-axis tensile stress relaxations were simulated. It is in good agreement with the experimental results, indicating the effectiveness of the viscoelastic constitutive model.
Preparation and microwave absorbing properties of 2.5D woven SiCf/SiC composites
ZHAO Majuan, WANG Xiaomeng, WANG Ling, QIU Haipeng, ZHANG Diantang
, Available online  
Abstract:
2.5D woven SiCf/SiC composites were designed and prepared to meet the requirements of high temperature microwave absorbing structural composites, and the microwave absorbing properties were studied by combining experiment and simulation. The reflection loss of the material was measured by means of the bow method, and the geometrical parameters of the material were extracted by X-ray computed tomography (Micro-CT) to establish a full-thickness mesoscopic model. The reflection loss of the material was simulated and calculated on the CST electromagnetic simulation software, and compared with the experiment results. Based on the theory of equivalent electromagnetic parameters and field distribution map, the microwave-absorbing mechanism is analyzed, and the effects of geometric structure parameters, electromagnetic parameters, electromagnetic field polarization direction and incidence angle on the microwave-absorbing property of materials are studied.The experimental results show that the 2.5D woven SiCf/SiC composites prepared in this paper have an effective absorption bandwidth of 3 GHz in the frequency range of 1-18 GHz, and the maximum reflection loss reaches −17 dB at the absorption peak of 9.3 GHz, which is basically consistent with the simulation results.The composite absorbs electromagnetic microwave mainly through the way of electrical loss, and its good microwave absorption performance is the result of the synergistic effect of structural design and material characteristics. The overall material thickness and fiber dielectric constant are the key factors affecting the microwave absorption performance of 2.5D woven SiCf/SiC composites.
Adsorption of heavy metals by agricultural solid waste based hydrogel : A review
HOU Wenjing, HE Caiqing, CHEN Wenqing
, Available online  
Abstract:
With the rapid development of economy, the pollution of heavy metal ions in water poses a threat to human health and ecosystem. Hydrogels have great potential in the treatment of heavy metal ions because of their good adsorption properties, renewability and low toxicity.This paper discusses the research progress in recent years on the preparation of hydrogels (cellulose-based hydrogels, hemicellulose-based hydrogels, lignin-based hydrogels, etc.) for the adsorption of heavy metals from agricultural solid wastes at home and abroad. The synthesis of agricultural solid waste based hydrogels, the adsorption effect, adsorption mechanism, and analytical methods for the removal of heavy metals are also discussed, and the effects of heavy metal adsorption by industrial solid waste based and other solid waste based hydrogels are enumerated. In order to help the researchers to have a deeper understanding of the investigation of heavy metal adsorption by agricultural solid waste based hydrogels.
Research progress of MXene materials in the application of heavy metal electrochemical detection
LI Shangshang, WANG Hongmei, HE Kaiyu, WANG Liu, LAN Hangzhen, XU Xiahong
, Available online  
Abstract:
Detecting heavy metal pollution has become an essential technical guarantee in risk prevention and control, agricultural green development, food safety, and ecological protection. At present, there are many technologies to detect heavy metal ions, among which electrochemical detection methods have the advantages of high sensitivity, fast analysis, and simultaneous detection of a variety of metal ions, which have become a research area in the field of rapid detection of heavy metals. MXene is a transition metal-carbon/nitride material with a graphene-like structure with good hydrophilicity, electrical conductivity, and rich adjustable surface terminations. The focus of this study is the research progress of MXenes in the electrochemical detection of heavy metal ions. The sources, hazards, and detection methods of heavy metal contaminants are briefly described. Secondly, the synthesis methods of MXene are summarized, and the research progress of MXene in the electrochemical detection of heavy metals in recent years is reviewed, including the sensing mechanism and detection performance analysis. Finally, the challenges and prospects of MXene materials in the electrochemical detection of heavy metals are discussed.
Research Progress in Biomass-based Monolithic Catalytic Microreactors
YAO Sisi, GUO Dengkang, LI Jingpeng, JIANG Zehui
, Available online  
Abstract:
Natural biomass materials are favored in the field of heterogeneous catalysis due to their wide resources, strong carbon sequestration capacity, high mechanical strength, renewability, environmental friendliness, as well as their unique fine structure and chemical composition. The inherent pore channel system and chemical compositions of biomass materials can not only improve the chemical reaction rate, but also participate in the heterogeneous catalytic reaction as the catalysts carrier. The resource, structural and chemical advantages of biomass such as bamboo, wood and rattan as catalyst carriers were briefly introduced in this paper. The basic concepts, types of catalysts, construction strategies and mechanisms, catalytic activity and failure mechanism of biomass-based monolithic catalytic microreactors were reviewed, as well as the research progress in advanced functional fields such as water treatment, energy generation, chemical synthesis, Fischer-Tropsch synthesis, and bioanalysis. Finally, in view of the limitations and existing problems of the current research, the future development trend of biomass-based monolithic catalytic microreactor is prospected in terms of construction strategy optimization, functional catalyst design, structure regulation improvement and stability performance improvement, in order to provide new scientific ideas and technical references for the construction and efficient utilization of functional interfaces of biomass materials under the strategic goals of carbon peak and carbon neutrality.
Effect of opening position on the connection performance of 3D woven composite materials
ZHANG Yifan, SHI Zhiwei, ZHANG Qian, LIU Yanfeng, ZHANG Daijun, CHEN Li
, Available online  
Abstract:
To reveal the effect of opening position on pinned-joints mechanical properties and failure mechanism of 3D woven composites, three different 3D woven composite structures were designed and prepared, and the load-bearing performance and damage modes of these composites with different opening positions was discussed. The results shows that there are differences in the effect of end-diameter ratio (E/D) on composites with different structural parameters. When the E/D decreases from 3 to 2, the ultimate compressive strength of three structural composites decreases by 5.3%, 9.9%, and 5.9%, respectively. When the E/D decreases from 2 to 1, the ultimate compressive strength decreases by 73.3%, 68.9%, and 69.8%, respectively. When the E/D changes from 3 to 1, the damage mode of the composites changes from extrusion damage to interfacial debonding, and the damage propagation of each yarn layer presents obvious angle features.
Research progress of MXenes for second near-infrared window photothermal diagnosis and therpay of tumors
LI Jianfeng, ZHAO Lu, BAI Yunfeng, FENG Feng
, Available online  
Abstract:
Photothermal tumor therapy with second near-infrared (NIR-II, 1000-1350 nm) phototriggered photothermal agents is a promising emerging method of tumor therapy. Transition metal carbides, nitrides, and carbonitridges compounds (MXenes) have advantages such as ultra-thin layered structure, unique electronic properties, large specific surface area, high photothermal conversion efficiency, good hydrophilicity, and easy surface functionalization, making them suitable as photothermal agents for tumor photothermal therapy. This review introduces the advantages of NIR-Ⅱ photothermal therapy, summarizes the photothermal performance of MXenes and the stability of MXenes colloidal solution. At the same time, the research progress of MXenes in NIR-Ⅱ tumor photothermal therapy was discussed, and the challenges and opportunities faced in the future development of this field were elaborated.
Study on the evolution of pore structure of manufactured aggregate concrete under sulfate freeze-thaw based on nuclear magnetic resonance technology
ZHU Xiangchen, ZHANG Yunsheng, LIU Zhiyong, QIAO Hongxia, XUE Cuizhen, FENG Qiong, ZHOU Qiming
, Available online  
Abstract:
There is a large temperature difference between day and night in the northwest region of China and there is a large amount of saline soil environment. Therefore, a large number of buildings in the northwest region are inevitably subjected to the coupling effect of sulfate and freeze-thaw, resulting in a large number of pores inside the structure and ultimately leading to its damage and failure. Nuclear Magnetic Resonance (NMR) was used to analyze the pore size distribution, porosity and other pore structure parameters of manufactured aggregate concrete under the coupling effect of sulfate and freeze-thaw, and the influences of sulfate concentration, freeze-thaw cycles and stone powder content on the pore structure of manufactured aggregate concrete were explored. The results show that sulfate reduces the freeze-thaw deterioration rate of the mechanism aggregate concrete, and the deterioration effect is more significant with the increase of sulfate concentration. The porosity of machine-made aggregate concrete increases with the increase of freeze-thaw cycles. The porosity of mechanism aggregate concrete decreases first and then increases with the increase of stone powder content. It has the best pore structure when the content of stone powder is controlled at about 10%. In addition to ettringite and gypsum, there is also anhydrous mirabilite in the chemical erosion products under the coupling effect of sulfate freeze-thaw, but the low temperature inhibits the chemical erosion of sulfate and makes physical erosion dominant.
Preparation of nickel-doped ZnFe2O4 composites and their algal removal properties
DENG Dongzhu, LI Ling, CAO Chuanqi, LIAO Danling, MO Chuangrong, LI Xuetang
, Available online  
Abstract:
Harmful algal blooms (HABs) outbreaks due to eutrophication of water bodies are becoming increasingly serious, posing a great threat to the water environment and human health. In this paper, magnetic and recoverable nickel-doped ZnFe2O4 (Ni-ZFO) adsorbents were prepared by a simple hydrothermal method for the removal of Microcystis aeruginosa from water bodies. The materials were characterized by SEM, XRD, EDS, XPS and VSM. The algal cell removal of Ni-ZFO composites was up to 99.09% within 30 min and remained above 90.41% at 25℃ and pH = 3-8. In addition, the saturation magnetization intensity of Ni-ZFO was 67.93 emu/g, which was 10.74 emu/g higher than that of ZnFe2O4 (ZFO), and it was easy to be recycled. The content of algal bile proteins did not increase in the adsorption process, and the algal cells would not be ruptured during the adsorption process, which avoids the secondary pollution caused by Microcystins entering the water environment. The algal removal rate remained above 75% after four times of recycling. The Ni-ZFO adsorbent synthesized in this paper has strong removal efficiency for algal cells and does not cause secondary pollution, which shows great potential in the practical application of mitigating eutrophication of water bodies, and also enriches the application of modified ZFO in the field of adsorption.
Application research of multi-functional sensor based on cellulose nanocrystals
YU Meng, LIN Tao, YIN Xuefeng, LIU Feiya, LI Jie, LU Lulu
, Available online  
Abstract:
Cellulose Nanocrystals (CNC) are nanomaterials with excellent mechanical properties, optical properties and surface chemical properties, which have attracted wide attention from researchers in recent years. CNC-based sensors have a single, double and multiple response to external environmental stimuli, such as humidity, gas, pH, solvent, temperature, light and other drive sensing, which makes it in the information encryption, health detection, food, environmental monitoring, energy storage, wearable and other fields show great application potential. In this paper, the key characteristics of CNC are briefly introduced, and the important application development and research mechanism of multi-functional sensors based on CNC are analyzed. Finally, the main problems and challenges in the preparation process of CNC-based sensor materials are summarized, and the reference is provided for improving their performance and functional innovative applications.
Cyclic compression test and stress-strain constitutive relationship of polypropylene fiber coral seawater concrete
CHEN Zongping, QIN Qinquan, LIANG Ying, ZHOU Ji
, Available online  
Abstract:
The stress-strain characteristics and damage evolution of polypropylene fiber coral seawater concrete (PPF/CAC) under uniaxial cyclic compression were studied. A total of 20 samples with different fiber volume fractions were tested. The failure form of PPF/CAC was observed in the test, and the stress-strain curve, peak stress-strain, plastic strain and other important indexes were obtained. The results show that the strength of specimens under cyclic loading is reduces by 1.21%-3.67% compared with that under monochrome loading, and the degradation can be slowed down with the increase of fiber content. The peak stress and peak strain increases are the largest when the polypropylene fiber volume fraction is 0.15%, which are 10.45% and 6.45%, respectively. In addition, the increase of PPF volume fraction can significantly reduce the accumulation of plastic strain and increase the elastic stiffness ratio. According to the test results, four characteristic points of hysteresis curve are defined: unloading point, common point, residual point and end point. And the relationship between residual strain, common point strain and end point strain and unloading strain is established. Finally, the stress-strain constitutive equation and damage constitutive model of PPF/CAC under cyclic load are proposed, and the simplified stress-strain constitutive equation based on the damage evolution law can effectively predict the stress-strain behavior of PPF/CAC under cyclic load.
Preparation and properties of self-healing photochromic polyurethane composite fabric
LI Han, GUO Yang, BAI Song, WU Huanling, LIN Ling, MAO Haiyan
, Available online  
Abstract:
In order to improve the durability of photochromic coated fabrics, the photochromic microcapsules (PM) and zwitterionic polyurethane (ZPU) were used to prepare PM/ZPU films, which were then hot-pressed onto cotton fabrics to obtain the self-healing PM/ZPU composite fabrics. The structure and morphology of PM/ZPU composite fabric were characterized, and the photochromic properties, self-healing and recycling ability of PM/ZPU composite fabric were discussed in detail. The results show that the maximum absorption wavelength of PM/ZPU composite fabric changes from 470 nm to 530 nm, the color changes from yellow-orange to reddish-brown, and the fabric has good fatigue resistance. Based on the dynamic reversibility of zwitterionic, the scratches of PM/ZPU composite fabric can be completely repaired at 80 ℃, and the bond strength of the fractured composite fabric reaches 1.47 MPa at 60 ℃, showing excellent self-healing properties. The coating on the waste fabric can be recycled and reused by a simple dissolution method, and the PM/ZPU composite fabric can still be prepared with good photochromic properties.
Preparation and properties of multifunctional MXene-CCNT/polyimide electromagnetic shielding films
CHU Na, LUO Chunjia, CHAO Min, YANG Xuexue, YAN Luke
, Available online  
Abstract:
Conductive polymer composites (CPCs) are widely used for the preparation of electromagnetic shielding materials due to their good comprehensive performance such as good corrosion resistance, high specific strength, low cost and easy processing. In this paper, MXene-carboxylated carbon nanotube (CCNT)/polyimide (MXene-CCNT/PI) composite films with good comprehensive performance were prepared by a simple scraping and thermal imidization method. The synergistic action of MXene and CCNT constructed a good conductive network, which gave the films high efficient electromagnetic shielding performance (EMI SE). When the contents of both MXene and CCNT were 12.5wt%, the film thickness was 80 μm, the conductivity was 5.88 S/cm, the EMI SE was 26.49 dB, and the ratio of electromagnetic shielding effectiveness to thickness (EMI SE/t) was 331.13 dB/mm. Moreover, the film showed long-lasting and stable EMI SE under extreme environments (acid-alkali treatment, high and low temperature treatment, and repetitive bending). At the same time, the MXene-CCNT/PI film still have a tensile strength of 53.17 MPa, excellent thermal stability (>500 ℃), and flame retardancy. Convenient and efficient preparation of polymer-based EMI shielding composites is realized, taking into account their excellent mechanical properties and heat resistance.
Effect of Al powder content on the properties and microstructure of Y2O3-based ceramic core
LU Gang, WU Qian, CHEN Xiao, CHEN Yisi, WEN Yanbo, YAN Qingsong
, Available online  
Abstract:
In order to obtain ceramic core with high chemical reaction resistance for titanium alloy investment casting, the Al powders were introduced into Y2O3-based ceramic core as the sintering aids, and then the modified ceramic core was prepared by hot injection molding. The effects of Al powder content on the densification characteristic, mechanical properties, microstructure and phase composition of Y2O3-based ceramic cores were studied. The results indicate that the sintering shrinkage and high temperature deflection of Y2O3-based ceramic core decrease with the increasing of Al powder content. The oxidation of Al element led to the expansion of the Al powders, which is beneficial to resist the shrinkage of Y2O3-based ceramic core during the sintering process. The densification of ceramic core is enhanced by liquid-phase sintering of Al powder melting and the interface reaction sintering of Al-Y2O3, as well as the diffusion sintering between Al2O3 and Y2O3 matrix. The formation of Al2Y4O9 crystals in matrix inhibits the secondary sintering of intergranular fine Y2O3 particles, which improves the high temperature creep resistance of the ceramic core. With a small amount of Al powder introducing, the Al2Y4O9 and Y2Al crystals are formed and then coated on the surface of the matrix Y2O3 particles, and the interfacial bonding strength is improved by the second phase strengthening. The Y2O3-based ceramic core modified by 2wt%Al powder, exhibits the optimal flexural strength about 34.38 MPa with a typical cleavage fracture, which is 49.15% higher than that of the ceramic core without Al powder. However, the expansion caused by excessive oxidation of Al powder can expands the distance between the ceramic particles. Therefore, the interfacial bonding strength of Y2O3-based ceramic core is weakened obviously, and then the ceramic core tends to fracture along the grain boundaries, resulting in the decrease of the bearing capacity under the load.
Preparation and properties of phase change energy storage composite with microcapsules and desulfurized gypsum
LIU Fengli, BAI Jianxia, LIU Junhua, LI Qiaoli
, Available online  
Abstract:
Micro-encapsulated phase change materials (MPCM) was used as energy storage elements and combined with desulfurized gypsum. Effects of MPCM on the mechanical properties, thermal properties and thermal cycle stability of desulfurized gypsum-based composites were investigated. Results show that the latent heat energy storage capacity of MPCM can not only adjust the hydration temperature rise of the slurry, but also gave the composite the power to store energy and regulate temperature. However, the addition of MPCM has a negative effect on the strength of the composite. When the MPCM content is 50wt%, the comprehensive properties of the composite are better. At this time, the phase transition temperature and enthalpy of the composite are 24.51℃ and 28.47 J·g−1, respectively. The temperature peak during heat storage stage and the time to reach the peak temperature are reduced and delayed by 6.4℃ and 980 s, when compared with pure gypsum. The effect of heat storage and temperature control is obvious. The thermal conductivity of the composite is 0.451 W·(m·K)−1 and its 28-day compressive strength is 25.05 MPa. The mass loss rate, phase change temperature change rate and phase change enthalpy change rate of 250 cold hot cycles are 0.67%, 0.08% and 2.3%, respectively, and the thermal cycle stability is good. Phase change energy storage gypsum has good mechanical properties, thermal properties and thermal cycle stability, and has broad application prospects in building envelope structure.
Research progress on thermally conductive polymer matrix composites reinforced by three-dimensional network fillers
ZHOU Zhengrong, YAN Xiuwen, HE Feng, XU Dong, HUANG Rongjin, LI Laifeng
, Available online  
Abstract:
Polymer materials find wide applications in various fields such as superconducting technology, aerospace, electronic circuits, power batteries, heat exchangers, among others. With the increasing demands for miniaturization, densification, and high power of devices, the overall heat dissipation requirements have escalated. However, polymers, serving as crucial materials in device encapsulation and bonding processes, exhibit a low thermal conductivity of only 0.2 W/(m∙K), which falls significantly short of current heat dissipation needs. Therefore, there is an urgent need to enhance the thermal conductivity of polymers. Constructing continuous thermal pathways within the polymer matrix has been shown to significantly improve the thermal conductivity, often increasing it several times or even tens of times. Hence, utilizing three-dimensional network fillers to reinforce the thermal conductivity of polymers stands out as one of the most commonly employed methods. Accordingly, this paper organizes relevant studies on enhancing the thermal conductivity of polymeric materials through the construction of three-dimensional network fillers. Based on different preparation methods, these are categorized into self-assembly, phase-separation, template-methods, oriented-distribution methods, among others. Finally, a summary analysis is provided from aspects such as the increase in thermal conductivity values due to preparation methods, feasibility, stability, and prospects for the future development of polymer-based thermally conductive composites reinforced by three-dimensional network fillers.
Mechanism of fiber grid reinforced with end self-locking anchorage
ZHOU Chaoyang, DENG Kai, LIN Guozhi, WANG Yi
, Available online  
Abstract:
In order to solve the problem of interface end peeling of textile reinforced concrete (TRC) reinforced concrete beam structures, an end self-locking technique was proposed to anchor the TRC slabs at the bottom of the beams. Thanks to the end anchorage provided by this technique, the TRC slab can continue to carry the load even if interfacial spalling occurs. However, compared with the fiber cloth, the fiber mesh has poor synergistic stress performance due to much larger gaps between the fiber bundles, and it is doubtful whether self-locking can be achieved without treatment. In order to improve the utilization of fiber mesh strength, this paper investigates the end-anchor self-locking enhancement effect through the end self-locking anchored fiber mesh tensile test. Measures such as increasing physical friction or adding chemical bonding to the fiber grid are taken to stretch it to failure. The failure modes and load-strain curves of each specimen are analyzed and compared, and a formula for calculating the bearing capacity of the fiber grid after enhancement is proposed. The results show that even if the size of the fiber grid is limited, the strength utilization rate of the fiber grid under end anchoring is increased by 60.66% by reinforcement measures, and the tensile bearing capacity of the three-layer grid can be similar to that of the fiber sheet. The application of the self-locking anchorage technology is expected to solve the problem of end-interface spalling in TRC-reinforced concrete beams, enhance the material utilization, and improve the reinforcement effect. The proposed formula for calculating the bearing capacity after fiber mesh reinforcement can provide a useful reference for related engineering practice.
Friction and wear properties of TC4 titanium alloy with high-speed nitriding treatment
DING Xu, WANG Yun, DU Daozhong, ZHOU Hong, YU Chao, LIU Weili, LIU Zhenqiang, LI Ruitao
, Available online  
Abstract:
In order to improve the surface hardness and wear resistance of TC4 titanium alloy, a high-speed nitriding treatment (HSNT) based on Ultrafast High-temperature Sintering (UHS) process was proposed. HSNT was ap-plied to the surface of TC4 titanium alloy, and the microstructure of the sample was studied by X-ray diffractometer and scanning electron microscope. The mechanical properties of the sample were tested by Vickers microhardness tester and friction and wear test device. The modified layer can be formed on the surface of TC4 titanium alloy in 2 min. The modified layer consists of two parts. The outermost layer is the nitride layer, the thickness is about 10 μm, the average microhardness is 973.55 HV0.1, and the main component is TiN. The sub-surface layer is nitriding layer, the thickness is also about 10 μm, the average microhardness is 774.53 HV0.1, the cross-section microhardness overall shows a trend of ladder distribution. The friction and wear test shows that under 20 N load, the friction coefficient of TC4 with HSNT is 0.406, which is reduced by 24.4%, and the wear volume of TC4 with HSNT is 0.302 mm3, which is reduced by 86.7%. The friction coefficient and wear volume of TC4 with HSNT under different loads are always smaller than that of TC4 titanium alloy, and all increase with the increase of load. Under 20 N load, the wear mechanism of TC4 is mainly abrasive wear and oxidative wear, while the wear mechanism of TC4 with HSNT is mainly adhesive wear and oxidative wear. The performance of TC4 titanium alloy with HSNT has been significantly improved, making up for the shortcomings of low hard-ness and poor wear resistance of TC4.
Fast prediction of 2D C/SiC compression performance based on self-consistent clustering analysis
DAI Xinhang, XU Chenghai, WANG Kunjie, GAO Bo
, Available online  
Abstract:
In this paper, the self-consistent clustering analysis (SCA) method was used to investigate the progressive damage behavior of 2D C/SiC under uniaxial compression load. The SCA method clusters the grid elements by strain concentration tensor, which greatly reduces the degree of freedom of the model and improves the computational efficiency of the model without significantly reducing the computational accuracy. The whole method consists of two stages: offline and online. In the offline stage, the k-means algorithm was used to decompose and cluster the high-fidelity composite unit cells and calculate the interaction tensor between different clusters, and finally the reduced-order model was generated. At the online stage, the mechanical response was obtained by solving the discrete Lippmann-Schwinger equations based on the reduced-order model. The SCA method was applied to predict the compressive strength of 2D C/SiC. When the total number of clusters is 64, compared with the experiment, the calculation accuracy of the compressive strength solution is reduced by 1% compared with the traditional finite element method, but the overall calculation efficiency is improved by 34 times. When the clustering time spent in the offline stage is not considered, that is, the meso-structure of the material is known in advance to solve its mechanical behavior, the time of one-time online calculation is only 6s, and the calculation efficiency is 104 times higher than that of the traditional finite element method. It has broad application prospects in the fields of rapid design of structural performance and rapid prediction of structural state.
Research progress on wood-based porous materials for dye wastewater treatment
MEI Zekai, DING Yi, FENG Shu, YANG Weisheng, HAN Jingquan
, Available online  
Abstract:
Dyes are extensively utilized in various industries, such as textiles, leather, plastics, and paper, and are currently one of the major sources of water pollution. Dye wastewater is characterized by its complex composition, high toxicity, and significant amounts of organic pollutants and heavy metals, which pose a serious threat to the ecological environment. Consequently, the removal of water-soluble organic dyes from water bodies has become a crucial challenge in wastewater treatment. Wood is a renewable, biodegradable, and environmentally friendly natural material that possesses a well-structured and hierarchically organized multiscale structure, as well as abundant pore structures. This porous hierarchical structure serves as a natural basis for the creation of new materials and devices intended for removing dyes. The physicochemical adsorption and catalytic degradation of dyes by wood-based composites can be promoted by loading active substances such as graphene, MOF, noble metal nanoparticles (Ag, Au, Pd) and polyoxometalates on the surface of the internal lumen of the wood, which can lead to the effective removal of dyes from wastewater. In this paper, the characteristics of dye wastewater and its hazards are firstly outlined, and the special microstructure of wood and its advantages in dye wastewater treatment are introduced in detail; subsequently, the principles and research status of wood-based porous materials loaded with active substances for the two treatments of adsorption and catalytic degradation of dye wastewater are overviewed, and the future development prospects of wood-based porous materials for the treatment of dye wastewater are also prospected and summarized.
PVDF/MWCNTs-AgNWs@MXene bilayer 3 D networks electromagnetic shielding composite films with highly conductive
SHI Ouling, TAN Yanyan, WU Xiao, LONG Xuebin, QIN Shuhao
, Available online  
Abstract:
With the development of communication networks, wireless devices and aerospace industries. Electromagnetic wave hazards become prevalent. Therefore, it is essential to develop composites with better electromagnetic shielding properties. In this paper, highly conductive three-dimensional (conductivity up to 1.4×104 S·m−1) networked electromagnetic shielding composite films (Ti3C2Tx MXene-based functional composite films) were constructed using MXene (Ti3C2Tx), silver nanowires (AgNWs) and multi-walled carbon nanotubes (MWCNTs) in a bilayer. In particular, the aqueous solutions of 10 mL AgNWs and 15 mL Ti3C2Tx MXene were adsorbed on top of poly(vinylidene fluoride) (PVDF)/MWCNTs composite films by vacuum-assisted filtration (VAF), and the total electromagnetic interference shielding effectiveness (EMI SET) of the Ti3C2Tx MXene-based functional composite film was as high as 69.0 dB, which was 245% higher than that of the commercial standard (20 dB), of which the absorption loss effectiveness (SEA) accounted for 85.1%. It is shown that the main electromagnetic loss mechanism of Ti3C2Tx MXene-based functional composite films is absorption loss, with a specific electromagnetic shielding effectiveness (SSE/t) of up to 2719.8 dB/(cm−2·g). This work provides structural design and research ideas for the application of novel MXene materials in electromagnetic shielding composites.
Influence of granite stone powder on the basic properties and gas permeability characteristics of mechanism sand concrete
ZHOU Aoxiang, ZHANG Yunsheng, QIAN Rusheng, MIAO Gaixia, XUE Cuizhen, ZHANG Yu, QIAO Hongxia
, Available online  
Abstract:
Granite powder (0%-32%) was used to replace part of cement clinker to prepare machine-made sand concrete. The Isothermal Calorimetry, Mercury Intrusion Porosimetry as well as Gas Penetration testing-methods were employed to measure the hydration heat, pore structure, mechanical strength and gas permeability of the concrete. Combined with the gray-correlation analysis method, the relationship between gas permeability properties and pore-structure characteristics was established for concrete at various curing ages (28-130 d). The results show that appropriate granite powder added can slow down the hydration heat release rate, refine pore structure, increase compressive strength, and reduce gas permeability. The compressive strength value of the concrete with 8% granite powder is the highest while its gas permeability coefficient reaches the lowest. The gray-correlation analysis shows that the effective porosity and the pore with the size less than 100 nm play the most significant impact on gas permeability.
Research progress of high-temperature baseline seal with hybrid structure of multiple materials
WEI Yuhan, ZENG Qin, BAI Hongbai, XUE Xin
, Available online  
Abstract:
The high temperature baseline seal with hybrid structure of multiple materials is a novel porous composite, which is composed of thermal insulation core material, metal braided spring tube and ceramic fiber braided tube. It has excellent multi-functional performances, including flexibility, high temperature resistance, abrasion resistance and sealing. It is vital for improving the comprehensive performance of the hot end components, especially for the new generation of high-speed aircraft. Hybrid structure of multiple materials can take advantage of specific attributes of each material to enhance the performance of a product or introduce new functionalities. For the proposed high-temperature baseline, the inner core material plays a role on thermal insulation, and the intermediate superalloy braided spring tube play a dominative effect on the elastic deformation recovery during the dynamic seal condition, and the outer ceramic fiber tube makes a function on heat and wear resistance. The major problem of hybrid structure is emanated from the different property of each component material, the internal relationship between hybrid structure and performance regulation is still unclear. To end this, the characteristics of each component material and fabrication technology of high temperature baseline seal with hybrid structure of multiple materials are firstly introduced. Then, the current research on the theory and numerical model of high temperature baseline are sorted out and summarized. Once more, the main challenges for the key fabrication technology of high-temperature baseline seal and its service ability in the high-temperature and dynamic loading are expounded. Finally, the research development trend and engineering application potentials of novel high-temperature baseline seal with hybrid structure of multiple materials are prospected.
Performance of Cu-BTC-derived CuOx/C for methanol oxidative carbonylation to dimethyl carbonate
LI Wenjie, GAO Shanlin, LAI Chunbo, XIAO Wanjing, LI Xinling, LIN Huibo, WANG Xinyu, XU Chenghua, DEN Zhiyong
, Available online  
Abstract:
Carbon-based material supported Cu is an efficient catalyst for methanol oxidative carbonylation to dimethyl carbonate, but Cu nanoparticles are prone to agglomeration and oxidation. Cu-BTC were prepared by hydrothermal method. And then CuOx/C catalysts was prepared by pyrolysis Cu-BTC under N2 atmosphere. The effect of pyrolysis temperature on Cu nanoparticle size, Cu valence state and performance for methanol oxidative carbonylation to dimethyl carbonate were investigated. The characterization results show that increasing the pyrolysis temperature is beneficial to the reduction of Cu2+ to (Cu0+Cu+), but would lead to the agglomeration of Cu nanoparticles. Catalytic activity decreases with the increasing of pyrolysis temperature. CuOx/C-300, prepared by pyrolysis of Cu-BTC at 300 ℃, shows the optimized catalytic activity and the space-time yield of dimethyl carbonate is 1209 mg·g−1·h−1. This is attributed to the smallest particle size of Cu nanoparticles (7.5 nm). In addition, the space-time yield of dimethyl carbonate decreased to 468 mg·g−1·h−1 after 6 cycle experiments. The main reasons for catalyst inactivation are the oxidation of (Cu0+Cu+) and the agglomeration of Cu nanoparticles.
Degradation mechanism of tensile properties and life prediction of hybrid carbon/basalt fiber reinforced polymer bars in seawater sea-sand concrete
XU Aiyan, DU Yunxing, PAN Liujingtai, ZHU Deju
, Available online  
Abstract:
To investigate the degradation pattern of tensile properties of epoxy resin-based hybrid carbon-basalt fiber reinforcing bars (CF-BF/Epoxy) in seawater sea-sand concrete (SSC) under seawater immersion, the CF-BF/Epoxy in SSC were soaked in seawater at different temperatures (25°C, 40°C, and 55°C) for durations of 60, 90 and 120 days. The tensile performance of the CF-BF/Epoxy in SSC was examined through tensile tests, and the changes in their microstructure were analyzed by SEM and FTIR. The results indicate that ambient temperature significantly affects the tensile properties of CF-BF/Epoxy. After 120 days of immersion at 55°C, the tensile strength decreases by 13.84%, the elastic modulus experiences a slight fluctuation within a 3% range, and pseudo-ductility is observed in the CF-BF/Epoxy. Additionally, blending of basalt fibers and carbon fibers delay the further intrusion of OH- from SSC into CF-BF/Epoxy, while the hydrolysis of the resin in the outer basalt fiber region and the degradation of the resin-fiber interface are identified as the primary causes of the decline in the tensile properties of CF-BF/Epoxy. Lastly, based on the Arrhenius equation, it is predicted that the tensile strength retention rate of CF-BF/Epoxy embedded in SSC will drop to 70% between 584 and 803 days.
Synergistic flame retardant effect of lignin containing silicon-nitrogen with ammonium polyphosphate on polylactic acid
SONG Yan, LIN Ken, ZHOU Yutong, SHAN Xueying, LI Jinchun, ZHAO Caixia
, Available online  
Abstract:
Polylactic acid (PLA) as a biobased degradable plastic has increasingly become a research hotspot. However, PLA’s application in packaging and electrical appliances is limited due to its high combustibility. In order to solve the above problem, lignin containing silicon-nitrogen synergistic(Si-NLig) was synthesized by modification of alkali lignin (Lig), and its thermogravimetric analysis (TGA) results showed that the T5% increased by 20℃ and the high temperature residue increased from 2.3% to 25.5% in air. And Si-NLig was used as a charring agent, and compounded with ammonium polyphosphate (APP) to prepared flame retardant polylactic acid (Si-NLig-APP/PLA) by melt blending and hot-press molding, and the PLAs’ flame retardant properties, mechanical properties, and combustion behavior, were investigated. The results showed that addition of 10wt% Si-NLig-APP with the mass ratio 1∶4 made Si-NLig-8%APP/PLA reach the limiting oxygen index (LOI) value of 27% and the vertical burning UL-94 V-0 level, while the LOI value of Lig-8%APP/PLA with Lig as charring agent at the same condition was 26% and the vertical burning UL-94 only passed V-2 rating. Meanwhile, the peak heat release rate (PHRR) reduced by 27% compared to Lig-8%APP/PLA. Raman spectroscopy was used to characterize the structure of the residual char after cone calorimeter testing, it was found that the degree of graphitization of Si-NLig-8%APP/PLA increased by 36.7% compared to that of Lig-8%APP/PLA, which provides a theoretical basis for its good flame retardancy. Introduction of Si-NLig led to the enhancement of mechanical properties of the flame retardant PLA with tensile strength increasing by 21%. It can be seen that Si-NLig has potential application prospect in the field of halogen-free flame retardant PLA.
Preparation and properties of lignocellulose network ionic thermoelectric gels
GUAN Jilun, LI Wenjing, FANG Huayang, CHENG Fangchao
, Available online  
Abstract:
Thermoelectric materials enable the direct conversion of thermal energy into electrical energy and are increasingly used in domestic and industrial waste heat reuse. However, traditional inorganic thermoelectric materials suffer from low thermal power (or Seebeck coefficient) and high thermal conductivity, and do not offer advantages in low-grade waste heat (<130℃) collection. Using the ionic thermal diffusion effect (Soret effect), cellulose network ionic thermoelectric gels were prepared by a simple syringe injection method using cellulose as the network and poly(vinyl alcohol) (PVA) as the electrolyte matrix, and the differences in the thermoelectric properties of different contents of NaOH and LiOH as the ion donor were investigated. FTIR was used to characterize the internal groups of the material, while a homemade thermoelectric test setup proved its higher thermopower. The results showed that the incorporation of cellulose resulted in an ionic conductivity of 3.31 mS·cm−1, which was enhanced by 98.2% compared to the pure PVA ionogel. At the same time, the addition of cellulose reduced the thermal conductivity to keep the upper and lower temperature difference constant for a longer period of time under the temperature difference between human body temperature and 26℃ room temperature. The ionic Seebeck coefficient reaches +12 mV·k−1 at 2℃ temperature difference. This research proposes a cost-effective and environmentally friendly solution for the reuse of low-grade waste heat, which is of greater significance for the sustainable development of human society.
A review of the effect of ceramic wastes on mechanical properties and mechanisms of cementitious composites
ZHANG Liqing, XIAO Zhenrong, LIU Sha, WANG Yunyang, XU Kaicheng, HAN Baoguo
, Available online  
Abstract:
As one of the solid wastes, ceramic wastes have a hard texture, and their main chemical composition are SiO2 and Al2O3. These characteristics make properly treated ceramic wastes have the potential to replace natural sand, gravel aggregates and act as admixtures. Application of ceramic wastes into cementitious composites will contribute to alleviate the problems of environmental pollution caused by the overexploitation of natural sand and gravel, high energy consumption and pollution in cement production, and the accumulation of ceramic wastes. This paper first briefly describes the physical and chemical properties of various types of ceramic wastes. Then, from the different application forms of ceramic wastes in cementitious composites, this paper comprehensively reviews the research status of the effect of ceramic waste aggregates and ceramic waste powders on the basic mechanical properties of cementitious composites, reveals the influencing mechanisms of ceramic wastes on the basic mechanical properties of cementitious composites. Finally, suggestions for further application and research of cementitious composites with ceramic wastes, especially in green and ultra-high-performance concrete and mechanical property retention after high temperature refractory concrete, are put forward based on the problems existing in the current research.
Recycled carbon fiber layering orientation optimization and its performance of composites
HUANG Haihong, KONG Lingcheng, LIU Weihao, RUAN Haoda
, Available online  
Abstract:
Recycled carbon fibers (RCF) are mostly fluffy and disorganized short fiber bundles, which can be reoriented based on wet fiber orientation technology. Conventional fiber-reinforced composites are usually layered with fibers in a unidirectional direction, which makes it difficult to fully utilize the gain effect of the fibers on open-hole parts, but the structural properties of the composites can be improved by curved layups of the fibers. The optimal configuration parameters of certain RCF content with different concentrations of hydroxyethyl cellulose (HEC) were investigated by designing fiber dispersion experiments. Using the self-constructed fiber orientation path control device, the prepared dispersion was spread to obtain fiber mats with different trajectories and shapes, and the orientation effect of RCF was evaluated based on a two-dimensional fast Fourier transform (2D FFT). The open-hole specimens of Recycled carbon fiber/Epoxy resin (RCF/EP) composites were prepared by molding, and the effects of different layup paths on the load-bearing capacity of the open-hole specimens were analyzed. The results show that the optimal HEC concentration is 14 g/L when the 6 mm RCF content is 6 g/L. The open-hole specimens prepared according to the curved path effectively reduce the stress concentration at the open hole, and the ultimate load is increased by 69.5% and 35.9% compared with the open-hole specimens prepared according to the unordered path and the horizontal path, respectively. The study broadens the design freedom of RCF/EP composite structures and provides a reference for realizing high-performance reuse of RCF.
Synthesis and properties of red mud/polydimethylsiloxane composites
LU Ben, Li Anmin, HUANG Zhuofang
, Available online  
Abstract:
Red mud/polydimethylsiloxane composites were prepared by filling red mud in flexible polydimethylsiloxane by mechanical stirring, vacuum magnetic stirring defoamination and heating curing. The structure, microstructure, mechanical and thermal properties of the composites were characterized and analyzed. The results showed that, Red mud as a cross-linked node and self-lubricating particle improved the elastic modulus, tensile strength, hardness Shore, impact strength and friction and wear properties of the composites, among which the impact strength increased significantly, from 41.13 kJ·m−2 to 273.33 kJ·m−2, an increase of 565%. In addition, red mud as a non-combustible also improved the flame retardant performance of the composites, the limiting oxygen index increased from 25.7% to 34.7%, an increase of 35%, into the range of refractory materials (> 27%). This is expected to expand the application field of this silicone material, and provide a reference for the resource utilization of red mud and the research of new red mud/polymer composites.
Discrete element simulation of foam concrete under uniaxial compression considering non-spherical pores
ZHOU Chengtao, CHEN Bo, GAO Zhihan, CHEN Jialin, CHEN Kai
, Available online  
Abstract:
In order to study the fitness of discrete element method (DEM) in the simulation of mechanical properties of foam concrete and the influence of non-spherical pores on the uniaxial compression characteristics of foam concrete, X-CT test and uniaxial compression-acoustic emission joint test were carried out on foamed concrete with density of 500 kg/m3. Based on the measured pore structure characteristics, a series of three-dimensional mesoscopic DEM models with different non-spherical particle proportions were established and the uniaxial compression process was simulated. The results show that the uniaxial compression damage process of the model is basically consistent with the acoustic emission test results, which has obvious stage characteristics. The non-spherical particle discrete element model can characterize the oscillation of the stress-strain curve in the initial compaction stage, and simulate the shear and interlocking of the matrix in the stress dissipation stage. When establishing the discrete element model of foam concrete, the influence of pore shape should be considered. The compressive strength of the DEM model decreases linearly with the increase of the non-spherical rate of the pores in the model while the correlation coefficient is 0.94.
Effects of resin coating and seawater immersion on mechanical performance of basalt textile reinforced seawater sea sand concrete
ZHU Deju, HUANG Wei, GUO Shuaicheng
, Available online  
Abstract:
In order to study the effects of different resin (epoxy resin, furan resin, vinyl resin) coatings and seawater immersion on the mechanical properties of basalt textile reinforced seawater sea sand concrete (BTR-SSC), a universal testing machine was used to perform static tensile tests on the fiber yarns of each resin coating and the BTR-SSC specimens immersed in seawater for different time, and the fiber-matrix interface bonding performance was evaluated by pull-out test. The crack and strain distribution were obtained by digital image correlation analysis, and the damage mechanism was analyzed by scanning electron microscopy. The long-term performance of the interface was evaluated by crack distribution and matrix strength through the calculation formula of interface bond strength. The results show that the reinforcing effects of the three resins on the fiber yarns are significant and similar (around 32%), which could significantly improve the mechanical properties of BTR-SSC. The vinyl resin coating had the best performance, and the tensile properties and interfacial bonding properties are increased by 77% and 180%, respectively. The mechanical properties of BTR-SSC specimens are significantly degraded under seawater immersion. The untreated specimens are brittle after 14 days of high temperature immersion. The tensile strength of epoxy resin, furan resin and vinyl resin coated specimens increase by 81%, 48% and 94% respectively after 7 days of immersion compared with untreated specimens. After 28 days of immersion, there are still multiple cracks developed, and the interfacial bonding properties are lost by 64%, 57% and 55%, respectively. The results will help to improve the long-term performance of BTR-SSC in the marine environment and promote its application in marine structures.
Research Progress of Electrospinning flame Retardant Nanofiber
BAO Yan, ZHAO Haihang, GAO Lu, ZHANG Wenbo
, Available online  
Abstract:
Electrospinning nanofiber exhibits several advantages, such as adjustable fiber diameter and distribution, interconnected pore structure, high porosity, high specific surface area, and controllable fiber packing density, which is a prominent research hot spot in recent years. Flame-retardant is an important characteristic of polymer materials, and flame-retardant fibers have the characteristic of higher safety in use compared to ordinary fibers. The development of nanofibers with flame-retardant properties is of great significance. Electrospinning technology refers to the jet spinning of polymer solutions or melts under strong electric fields, providing technical support for constructing nanofibers with special functions. It not only provides the possibility of combining functional fillers into polymers, but also provides the possibility of uniform dispersion of functional fillers within the polymer, which helps to more conveniently produce nanocomposites with special properties in situ. Based on this, this review introduced the development of flame-retardant nanofibers via electrospinning technology. Specially, the structure of electrospinning flame-retardant nanofibers was discussed, mainly including blend structure, core-shell structure, side-by-side structure, and porous structure. Their advantages and disadvantages were also emphasized. Moreover, the application status of flame-retardant nanofibers in lithium-ion battery separators, air filtration systems, fire alarm sensors, and protective materials were introduced. Finally, the future development directions of electrospinning flame-retardant nanofibers were foreseen.
Finite element modelling considering the bending behavior of uncured unidirectional prepregs
HE Liang, ZHAO Anan, XU Xiaowei, WANG Xiaokai, HU Dabao, LIANG Biao
, Available online  
Abstract:
Thermoset resin based prepregs exhibit very high tensile modulus and relatively low bending stiffness, and the accurate characterization of such special properties of prepregs is critical to predict and avoid the wrinkle defect during forming process, and improve the accuracy of finite element simulation of composite forming process. In the present paper, a finite element model that accurately tracks the fiber directions was built considering the nonlinear in-plane shear behavior of unidirectional prepregs, and the high tensile stiffness and significantly lower bending stiffness of the prepreg were decoupled using superimposed membrane-shell elements. Besides, the tensile stiffness, no-linear shear stiffness, and bending stiffness of the domestic prepreg system AC531/CCF800H were characterized experimentally. Finally, the 30° off-axis tensile test and axial compression test were used to prove the validity of the proposed model, respectively.
Preparation and performance of PVDF/PPy flexible DC nano-generator
LI Jinhui, LIU Xiaodong, JIN Xin, SHI Shanjing, WANG Wenyu
, Available online  
Abstract:
To address the difficulty of high integration, flexibility and low power density caused by the traditional nanogenerators with AC output and still need to use external rectifiers for DC conversion, in this paper, poly(vinylidene fluoride) (PVDF) electrostatically spun film is used as a substrate and polypyrrole (PPy) is gas-phase polymerized on the surface of the film to produce a composite nanofibrous film of PVDF/PPy, and based on the Schottky collation principle, a DC nanogenerator is constructed by this composite nanofibrous film. The composite nanofiber membrane was used to construct a DC nanogenerator based on Schottky finishing principle. The effects of oxidant concentration on the morphology of PVDF/PPy composite nanofiber membrane and the electromechanical performance of DC nanogenerator were investigated under different polymerization times. The results show that when the oxidant concentration is 2 mol/L and the polymerization time is 90 min, the electrical output performance is optimal, corresponding to a peak voltage output of 1.23 V, a peak current output of 210.55 μA, and a theoretical power density of 28.77 μW/cm2. In this study, this PVDF/PPy DC nanogenerator was demonstrated, and the energy conversion The mechanism originates from the piezoelectric effect of piezoelectric polymer and the rectification effect of Schottky junction. These DC nanogenerators are flexible, integrated and self-rectifying, and can be flexibly used in various places to provide power directly to electronic devices.
Structural and property modulation of cyclohexanedimethanol-based polycarbonates by bio-based tetrahydrofuran dimethanol with cyclic ether structures
YU Huatong, CAI Xiaodong, YANG Yexin, JIAO Danhua, ZHANG Daohai
, Available online  
Abstract:
1,4-Cyclohexanedimethanol-based polycarbonates have desired thermodynamic property yet poor degradation capability. Introducing aliphatic units into the molecular chains could effectively improve the degradability at the severe expense of thermodynamic properties. For this reason, biobased 2,5-tetrahydrofurandimethanol (THFDM) with cyclic ether rigidity was selected as the modification unit and Poly(1,4-cyclohexyldimethylene-co-2,5-tetrahydrofurandimethanol carbonate) (PCThC) copolymers with higher molecular weights were synthesized via melt ester exchange polycondensation method. The composition and microstructure were investigated by NMR, which confirms the random distribution among the copolymer components. DSC and WAXD results revealed that the introduction of THFDM units break the regular arrangement of the molecular chains in PCThCs, reduce the crystallisation ability, which promote the transition from the semi-crystalline to amorphous. Furthermore, the rigid ring structure in THFDM prevents the rapid declination of Tg and keeps the good thermal stability. The ring structure in the THFDM endow higher stiffness and better mechanical performance for the polymer. The ether bonds in THFDM enhance the hydrophilicity of the PCThC copolymers, resulting in a gradual acceleration of the hydrolysis rate. The copolymers exhibit pleasant degradation ability either under acidic or alkaline environment.
Design of Hybridized Network Structure and Photoelectric Thermal Conversion Performance of polyethylene glycol-based Phase Change Composites
ZHAO Zhongguo, WANG Chouxuan, XUE Rong, SHEN Siyang
, Available online  
Abstract:
PEG60PLA40CNT0.6X(y) phase-change energy storage composites were prepared in this paper by physically hybridizing carbon nanotubes (CNTs) with boron nitride (BN), aluminum trioxide (Al2O3), and copper powder (Cu), respectively, to investigate the effects of nanoparticles with different structures on the shape stability and photovoltaic conversion efficiency of polyethylene glycol (PEG) based phase-change composites. The incorporation of Al2O3 and Cu nanofillers has a minor effect on the electrical conductivity of the PEG/PLA/CNT/X(y) composites; however, the introduction of BN drastically reduces the electrical conductivity of the composites. When the mass ratio of BN reaches 40%, the electrical conductivity of the PEG60-PLA40-CNT0.6-BN40 composites is only 8.71×10-7 S/m, indicating obvious insulating properties. The spherical Al2O3 nanoparticles were found to be uniformly distributed inside the composites by SEM and EDS energy spectroscopy, and the thermal conductivity and enhancement factor (\begin{document}$ \varPhi $\end{document}) values of PEG60-PLA40-CNT0.6-Al2O3(40) composites were as high as 5.81 W/m·K and 363.6%, respectively. Compared to the PEG60-PLA40 composites, the addition of Al2O3 improves the photothermal conversion efficiency (\begin{document}$ \eta $\end{document}), photosensitive response rate, and current stability of PEG60-PLA40-CNT0.6-Al2O3(40) composites, raising the value from 42.9% to 72.9%.
Damage accumulation simulation and residual performance evaluation of ceramic ballistic plate under the multi-hit strikes
HE Chenglong, HUO Ziyi, LIU Yaqing, YANG Kexu, MAO Xiang
, Available online  
Abstract:
The ceramic/fibre composite ballistic panels are widely used in personal protection equipment, and the performance of the ballistic plate under multiple impact loadings are important to keep soldiers safe. The numerical simulation was used to analyze the failure distribution and residual ballistic performance of ballistic panels subjected to multiple impacting, and specifically focusing on the operating condition of 53-type 7.62 mm armor-piercing bullet impacting SiC/UHMWPE ballistic panels. The damage of the ballistic plate was characterized by the ceramic failure, fiber deformation and bond surface stripping, and the residual properties of the bulletproof plate with different damage were established. The results show that the damage radius (R) of ballistic panels is 30 mm under the first impact, and the damage (D) is greater than 0.6 when R<15 mm, and the target can't resist the second bullet impacting. Under two impacts, the damage in the middle zone becomes seriously when the distance between two bullets (ΔL) is less than 50 mm, and the cumulative effect of damage is not significant when ΔL>50 mm. Ballistic panels are discretized with 5 mm×5 mm grid, and the proportions of different damage areas are obtained. The penetration probability of the integral ballistic plate is 0.94% under the two impacts' loadings. The penetration probability of the integral ballistic plate under the third impacting is decided by the striking distance of the first two impacts, and the penetration probability by the third impacting is 1.94% when ΔL=20 mm.
Preparation of polypyrrole/chitosan-sodium alginate composite microspheres and their slow-release properties
LI Sha, ZHANG Xinhao, JIA Rui, LUO Yu, XING Jianyu
, Available online  
Abstract:
The development of novel drug controlled release composite materials is of great significance in the fields of medicine and agriculture. Using chitosan and sodium alginate (CS-Alg) gel network as carrier, PPy/CS-Alg composite slow-release material was prepared by in-situ oxidation of polypyrrole (PPy). The microstructure, structure composition and photothermal conversion properties were studied by SEM, FT-IR, XPS and UV-vis-NIR. Indolebutyric acid (IBA) was used as a model drug molecule to study its sustained release performance. The results show that the porous morphology of PPy/CS-Alg microspheres is conducive to the loading and release of IBA. The PPy oxidized state formed by in-situ oxidation can be slowly reduced in the CS-Alg gel network, and changes from a positive state to an uncharged state. As a result, IBA can be slowly released from the gel network of PPy/CS-Alg microspheres, with the long-term release rate of 56.12%. In addition, the temperature of PPy/CS-Alg microspheres under simulated sunlight can rise from 26℃ to 37℃ based on the photothermal effect of PPy, which is conducive to the formation of temperature gradients inside and outside the microspheres and further enhancing the slow-release of IBA. The controlled release material of auxin IBA based on the slow reduction and photothermal effect of PPy has broad application prospects in the agricultural field.
Preparation of Honeycomb Porous Carbon Nanofibers via Electro-blowing spinning and Investigation of their Supercapacitor Performance
ZHU Lin, WANG Yifan, HAN Lu, ZHOU Xinghai, SHAN Xiya, CUI Wenqi, GAO Yuan, LYU Lihua
, Available online  
Abstract:
One-dimensional porous carbon nanofibers have become a popular choice for supercapacitor electrode materials due to their high specific surface area, large aspect ratio, and efficient electron transport. In this study, honeycomb porous carbon nanofibers were synthesized using electrospinning technique, where polyvinylpyrrolidone (PVP) served as the carbon precursor and polytetrafluoroethylene (PTFE) emulsion acted as the pore-forming agent, followed by a high-temperature carbonization process. The morphology and structure of the prepared electrode materials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM)、Raman spectroscopy, X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. Furthermore, the influence of pore-forming agent content on the fiber morphology, pore structure, and electrochemical performance was investigated. The results revealed that when the m PVP∶m PTFE ratio in the spinning solution was 1∶10 (mass ratio), the resulting electrode material exhibited the maximum specific surface area of 165 m²/g. Moreover, at a current density of 0.5 A·g−1, it achieved a high specific capacitance of 277.5 F·g−1. In a two-electrode system, the power density reached 250 w/kg, resulting in an energy density of 31.6 wh/kg. Additionally, after 10,000 charge-discharge cycles, the capacitance retention remained as high as 98.4%, indicating excellent capacitive and cycling performance of the fabricated electrode material. Such a unique porous carbon nanofibers electrode material with its high porosity and honeycomb-like structure can offer abundant active sites for charge storage and provide convenient pathways for fast electron/ion transport, which holds significant reference and guidance for the development of high-performance supercapacitor electrode materials.
Construction of a synergistic photothermic/chemotherapeutic nanosystem for anti-tumor and study of its drug controlled release behavior
HUANG Run, WU Liujun, SHI Hongqi, GU Yingjian, PAN Yusong
, Available online  
Abstract:
Traditional methods of cancer treatment include surgery, radiotherapy, and chemotherapy. The surgical treatment is highly traumatic and easy to recur, while the period of radiotherapy is too long. Although chemotherapy is considered as the first choice to destroy tumor cells, it has obvious toxic and side effects, and the long-term chemotherapy can seriously affect the quality of the patients’ life. In this study, CuS was selected as a photothermal agent, and mesoporous silica (mSiO2) was coated on the surface of CuS using the solvothermal and template removal methods. With the aid of the large specific surface area of mSiO2, a highly doxorubicin hydrochloride (DOX) loaded nanodrug system was prepared (CuS@mSiO2-DOX). XRD, UV-Vis, SEM, TEM, and DLS results jointly confirm that the CuS@mSiO2-DOX nanosystem with a particle size of approximately 300-400 nm is successfully synthesized, and the loading efficiency of DOX in this system can reach up to 99.76%. The 24 h-drug release rate of CuS@mSiO2-DOX reaches 63.44% under the conditions of pH=5.5 and t=45℃, which is nearly 20 times higher than that under the normal physiological environment (pH=7.4 and t=35℃), indicating that the CuS@mSiO2-DOX nanosystem possesses obvious pH and temperature responsive release characteristics. In addition, the photothermal performance and in-vitro cytotoxicity of the CuS@mSiO2 nanodrug delivery system was tested, and the results show that CuS@mSiO2 exhibits a good photothermal stability with a photothermal conversion efficiency of 31.67%, and which also reveals low toxicity to normal human liver cells (HL-7702). CuS@mSiO2 nanosystem has good biocompatibility, outstanding photothermal conversion and drug loading properties, and after DOX adsorption, the system exhibits excellent pH and laser responsive drug controlled release performance, which is expected to be widely used in the field of combining the photothermal-chemotherapy to synergistically resist tumor.
Preparation of carbon fiber heating elements and their effects on the properties of resistance welding joints in thermoplastic composite materials
YAO Xin, HUO Hongyu, AN Xuefeng, ZHANG Baoyan
, Available online  
Abstract:
This paper presents the preparation of two types of thin-layer carbon fiber stretched-width cloth heating elements using the suspension impregnation process with polyether-ether-ketone (PEEK) powder and the melt impregnation process with PEEK resin film. The resistance welding technology for carbon fiber reinforced polyether-ether-ketone composite laminates was experimentally investigated. The results demonstrated that employing an “embedded type” electrode arrangement effectively mitigates the “edge effect” caused by exposed heating elements during resistance welding. Moreover, it was found that the heating time significantly influences the strength of welded joints, which initially increases and then decreases, reaching a maximum value of 28.1 MPa at 120 s. Additionally, the fracture failure mode has changed from initial adhesive failure to a mixed failure mode of implant and fiber. Furthermore, compared to melt impregnation, powder suspension impregnation process enhance joint strength by 15% under identical welding conditions.
Microstructure and damage characteristics of basalt fiber reinforced foam concrete
ZHOU Chengtao, CHEN Bo, ZHANG Juan, LI Song
, Available online  
Abstract:
In order to study the microstructure characteristics of basalt fiber reinforced foam concrete and the influence of different fiber content on its damage characteristics, this paper carried out X-CT test and uniaxial compression acoustic emission joint test on basalt fiber reinforced foam concrete with density grade of 1000kg/cm3. Based on Avizo image processing and acoustic emission basic parameters and \begin{document}$ {b}_{\mathrm{i}} $\end{document} values (Improved b value), the microstructure characteristics of fibers and pores and the damage evolution characteristics of materials were analyzed. The results show that the addition of basalt fiber can effectively improve the mechanical properties of foam concrete. The average compressive strength of the specimens with 0.5vol%, 1.5vol% and 2.5vol% fibers increase by 1.37 MPa, 4.58 MPa and 2.77 MPa, respectively. The fiber fractal dimension of the specimen with 2.5vol% content is mainly in the range of 1.0-1.3, the fiber agglomeration is obvious, the fiber angle is concentrated, and the performance of the specimen is reduced. After adding basalt fiber, the trend of acoustic emission \begin{document}$ {b}_{\mathrm{i}} $\end{document} value of the specimen is gentler, and basalt fiber can effectively inhibit crack development.
Mechanical properties and failure prediction of three-dimensional orthogonal fiber reinforced nanoporous resin composites
LI Tong, QIAN Zhen, CHEN Zixuan, LI Liang, CAI Hongxiang, CAO Yu, ZHANG Yayun, NIU Bo, LONG Donghui
, Available online  
Abstract:
To meet the extreme thermal protection and load-bearing requirement of aerospace vehicle, three-dimensional orthogonal fiber reinforced nanoporous resin composites (3DIPC) have been prepared using three-dimensional quartz fiber preform as reinforcement and high-strength nanoporous phenolic resin as matrix. The as-prepared 3DIPC exhibit a mid-density of ~1.46 g·cm−3, low room-temperature thermal conductivity (<0.30 W·(m·K)−1), low linear ablation rate (~0.15 mm·s−1) and excellent mechanical properties with tensile strength >400 MPa, compressive strength >390 MPa, bending strength >300 MPa and interlaminar shear strength >30 MPa. By adjusting the yarn fineness in different directions, the effects of meso-structure variations in fiber preforms on the mechanical properties of 3DIPC were systematically studied. The results show increasing the fineness of the Z yarn can enhance the compressive modulus and interlaminar shear strength of composite materials, but it leads to a deterioration of tensile properties and compressive strength. Increasing the fineness of the warp yarn can improve the tensile and bending properties in the warp direction, but the tensile and flexural properties in the weft direction will be reduced. Finally, a mesoscale finite element model incorporating both surface and internal structures was established based on the actual morphology of 3DIPC. Combining with the progressive damage model of the composite material, the tensile failure behavior of the 3DIPC was simulated using the finite element software ABAQUS. The results show that the damage in 3DIPC initiates at the matrix of yarns and propagates to pure matrix and the fibers of yarns as the strain increases. The failure of 3DIPC under tensile loading in the warp and weft direction is dominated by the fracture of fibers of warp and weft yarns, respectively. Furthermore, the fracture of fibers of surface-Z yarns and surface-weft yarns is the primary cause of early-stage damage in 3DIPC under tensile loading in the weft direction.
Research Progress on Microwave Absorption Stealth Technology of Honeycomb Sandwich Structure Composites
LI Xuguang, WU Xuemeng, SHI Junxi, YANG Jin
, Available online  
Abstract:
With the rapid development of detection technology and the demand for operational performance, higher requirements have been put forward for radar stealth technology, honeycomb sandwich structure as a classical structural wave-absorbing material has made great development in recent years, this paper aims to comprehensively analyse and summarize the characteristics, research status and application of honeycomb sandwich structure composites in the field of wave-absorbing stealth technology at home and abroad. This paper focuses on the key factors affecting the wave-absorbing performance of honeycomb sandwich structures, including the performance of absorbers, the design of honeycomb structures and the wave-transparent performance of skins, etc. It also analyses the advantages and disadvantages of different honeycomb sandwich structure wave-absorbing materials with respect to the key indexes of wave-absorbing bandwidth and absorption rate. In addition, this paper summarises the current development trend of honeycomb sandwich structure wave-absorbing stealth composites, summarises the current status of development, and gives an outlook on the future development direction.
Effect of sulfate corrosion on the fracture properties of PVA fiber reinforced cement-based composite materials with steel slag powder
SU Jun, FAN Zikang, CAI Xinhua
, Available online  
Abstract:
In order to study the fracture characteristics of cement-based composite materials under the solid waste steel slag and erosion of sulfate solution, the PVA fiber reinforced cement-based composite materials were prepared by adding different mass fractions of steel slag powder. Three-point bending performance test was conducted on prefabricated initial crack beam specimens after sulfate erosion. Combined with the apparent morphology and microstructure characteristics of steel slag powder PVA/ECC in Na2SO4 solution (mass fraction of 5%), the effect of sulfate corrosion on the fracture performance of steel slag powder PVA/ECC was investigated. The results show that when the content of steel slag powder without sulfate attack is 20%, the cracking load and instability load of the specimen are the best, with an increase of about 61% and 110% compared to the specimens without steel slag powder, respectively; The fracture toughness of PVA/ECC first increases and then decreases with erosion time, reaching its peak after 60 days of erosion. After 120 days, the S80 group shows the most obvious degradation, with the initiation toughness \begin{document}$ {K}^{\mathrm{u}\mathrm{n}} $\end{document}and instability toughness \begin{document}$ {K}^{\mathrm{u}\mathrm{n}} $\end{document}decreasing by about 23% and 13%, respectively; The addition of an appropriate amount of steel slag powder can effectively alleviate the erosion damage of PVA fiber reinforced cement-based composite materials. When the amount of steel slag powder does not exceed 60%, there is no significant deterioration of the material within the age range of the experimental study. On this basis, the durability life of the specimens was predicted using a Weibull distribution model, PVA/ECC with a 20% steel slag powder content having the longest service life, reaching around 444 cycles.
Experimental investigation on discreteness of quasi-static and dynamic compressive strength of recycled aggregate concrete
WANG Xiaojuan, LI Runlin, ZHOU Hongyuan, MU Chongyuan, QIAO Qiyun
, Available online  
Abstract:
To explore the influence of the substitute rate of recycled coarse aggregate (RCA) and strain rate on the discreteness of the compressive strength of recycled aggregate concrete (RAC), RAC specimens with three different RCA substitute rates were prepared for both quasi-static compression and split Hopkinson pressure bar (SHPB) tests. The test results show that despite the limited change in the discreteness of compressive strength of RAC with increasing RCA substitution rate, it still tends to initially increase and then decrease as the RCA substitution rate increases. The results of the SHPB test indicate that both the RCA substitute rate and the strain rate exert a significant influence on the variability of the dynamic compressive strength of RAC. The dynamic compressive strength discreteness of RAC with the same RCA substitute rate gradually decreases with increasing strain rate, while it increases with increasing RCA substitute rate under the same strain rate. In addition, the traditional Weibull distribution model was modified by introducing the parameters of RCA substitute rate and strain rate, and a dynamic compressive strength prediction formula for RAC with different RCA substitute rates at any given probability level was proposed.
Lubrication-reinforcement microcapsules reinforce UHMWPE material
XIAO Yang, WEI Bin, CHEN Yan Yan, LI Ling
, Available online  
Abstract:
Lubrication-reinforcement bifunctional microcapsules PTFE@Al(OH)3 using polytetrafluoroethylene (PTFE) as the core material and Al(OH)3 as the shell material were prepared by in-situ polymerization of sodium bicarbonate and aluminum sulfate solutions. Its surface was treated with vinyl trimethoxysilane (VTMS) and used as a reinforcing filler for ultra-high molecular weight polyethylene (UHMWPE). After it was evenly mixed, processed into composite materials using spark plasma sintering (SPS). The dispersion properties of microcapsules in the matrix, tribological properties and mechanical properties of composite materials were characterized by scanning electron microscope (SEM), transmission Electron Microscope (TEM), fourier transform infrared (FT-IR), universal micro tribometer (UMT-5), three-dimensional white light interferometer and methods of tensile compression testing machine. It was demonstrated that the addition of microcapsules effectively improved the tribological properties (friction coefficient decreased by 35%, wear amount decreased by 20%) and mechanical properties (compression strength increased by 2.5 times) of the composites. In addition, the dispersibility of the microcapsules is also greatly improved by surface modification.
Flexural creep test and prediction of GFRP-balsa sandwich beams
LI Xiaolong, FANG Hai, WU Peng
, Available online  
Abstract:
The application scope of the glass fiber reinforced plastic (GFRP)-balsa sandwich structure composed of GFRP facings and a balsa wood core is constantly expanding in the field of infrastructure. However, GFRP-balsa sandwich structures are susceptible to creep deformation due to their viscoelasticity. Under the controlled temperature of (25±1)°C and relative humidity of 55%±5%, the three-point flexural creep performance of the GFRP-balsa sandwich beams at 20%, 25% and 30% load levels were tested for a period of 3000~8760 h using the self-designed flexural creep loading devices. Various models were used to simulate and predict the creep response of the GFRP-balsa sandwich beams. The results show that the GFRP-balsa sandwich beams exhibit linear viscoelasticity at the test load levels. Flexural creep has an important impact on the mid-span deflection of the GFRP-balsa sandwich beams, and the creep coefficients at 3000 h of all the specimens are not less than 0.35. The Findley model is applicable for fitting the time-dependent total deflection of the GFRP-balsa sandwich beams at a single load level, and the maximum relative error between the fitting value and the test value at 3000 h is only 0.7%. The Bailey-Norton model and the general power law model are applicable for predicting the creep deflection and the time-dependent total deflection of the GFRP-balsa sandwich beams when the load level does not exceed 30%, respectively. At one year, the maximum relative error between the predicted value of the Bailey-Norton model and the test value is 8.3%, and the maximum relative error between the predicted value of the general power law model and the test value is 5.9%.
Design, preparation and mechanical properties of microwave sintered TiB2-based ceramic tools with complex edge shape
JI Wenbin, WANG Zihao, DAI Shijie, CHENG Pengxiang, WU Runhe
, Available online  
Abstract:
The structural parameters of TiB2-based ceramic tools with complex edge shapes were designed based on microwave sintering characteristics. The effect of tool design parameters on turning forces and temperatures when turning QT450 ductile cast iron was investigated using finite element simulation. For TiB2-based ceramic tools with complex cutting edges, the optimum tool front angle was found to be 5°, the optimum back angle was found to be 6° and the optimum tip radius was found to be 0.8mm. Complex edge-shaped TiB2-based ceramic tools were prepared by microwave sintering technology, and the effects of pressing pressure and holding time on the relative density, mechanical properties and microstructure of complex edge-shaped TiB2-based ceramic tools were investigated. The results show that the pressing pressure has a great influence on the abnormal growth of grains, and a reasonable pressing pressure can inhibit the abnormal growth of grains, improve the tool fracture mode, and then improve the tool performance. A reasonable holding time can make the white phase on the surface of the tool partition uniform and prevent aggregation, which is conducive to improving the fracture toughness of the tool. When the pressing pressure is 200MPa and the holding time is 4min, the dimensional shrinkage of each part of the tool is more average, the forming accuracy is higher, the densification is the highest, the microstructure is more uniform, the grain arrangement is more compact, and the overall mechanical properties are optimal.
Durability of CFRP-steel interface modified by liquid rubber under chlorine salt erosion
PANG Yuyang, LV Yuanchen, WANG Qiang
, Available online  
Abstract:
Fifty-four carbon fiber reinforced resin composite (CFRP)-steel double lap specimens were designed to study the effects of liquid rubber modifier content and corrosion age on the mechanical properties of CFRP-steel modified interface under the erosion of two kinds of chlorine salts: high temperature water bath and dry-wet cycles at normal temperature. The results show that: Under the action of high temperature water bath and dry-wet cycles at normal temperature, the unmodified specimens show CFRP interlayer stripping failure and steel/binder interface stripping failure, respectively, while the liquid rubber modified specimens could transform the failure mode into adhesive cohesion failure, among which 10% liquid rubber has the best effect on improving interface durability. After 180 days of high temperature water bath and dry-wet cycles chloride salt erosion at normal temperature, the ultimate load retention rates of the specimens increase by 28.11% and 29.94%, respectively, compared with that of the unmodified specimens. Based on the experimental results, modified interface bond-slip models were established which are suitable for two kinds of chlorine salt erosion environments, and the predicted results are in good agreement with the experimental results.
Effect of bolt preload on bearing response of single-lap, countersunkcomposite bolted joints
LI Rupeng, XIAO Ruiheng, GE Ende
, Available online  
Abstract:
Experimental and numerical studies on the bearing response of single-lap, countersunk composite joints which were designed according to ASTM 5961 under various bolt preload were presented. The specimens were manufactured from carbon fiber/epoxy unitapes with quasi-isotropic lay-ups. To obtain a more accurate hole strain, 2D DIC measurement technique was used. Three-dimensional finite element model was constructed using ABAQUS/Standard and validated by comparing to the experiment. The validated model was used to provide a detailed stress analysis around the hole boundary considering various bolt preload and friction conditions. The results show that countersunk hole is the region where the severest damage occurs, and bolt preload could significantly improve the 2% hole deformation bearing strength but only slightly increase the ultimate bearing strength. Through stress analysis, increasing either bolt preload or friction between laminates are found to have an active effect on relieving stress concentration, and will make a better bearing performance of single-lap, single-bolt, countersunk composite joints.
Controllable preparation and upconversion luminescence properties of Tm3+/Ho3+ doped NaErF4@NaYF4 core-shell nanocrystals with bright red emission
YIN Yu, CHEN Jie, LIU Rong, ZHAO Wei
, Available online  
Abstract:
In order to obtain upconversion nanomaterials with bright red emission for deep bioimaging applications, a series of Tm3+/Ho3+ doped NaErF4@NaYF4 core-shell upconversion nanocrystals were prepared by thermal decomposition method, and their morphology, structure and luminescence properties were characterized. The results show that NaErF4, NaErF4:Tm3+ and NaErF4:Ho3+ bare core all exhibit hexagonal phase structure and good spherical morphology, with average sizes of 23.19 nm, 28.01 nm and 27.89 nm, respectively. After coating NaYF4 inert shell, the crystal phase remains unchanged, but the morphology became short rod-like, and the average length increases to 38.51 nm, 37.82 nm, 42.65 nm. Under the excitation of 980 nm near-infrared light, NaErF4, NaErF4:Tm3+ and NaErF4:Ho3+ show obvious red emission due to the 4F9/24I15/2 transition of Er3+, and the luminescence intensity and lifetime increase significantly after coating NaYF4 inert shell. In particular, the luminescence intensity of NaErF4@NaYF4 core-shell sample is about 1787 times that of NaErF4 bare core, and the lifetime is 2.04 ms. In addition, compared with NaErF4@NaYF4, the Tm3+/Ho3+ ions in the NaErF4:Tm3+/Ho3+@NaYF4 system act as energy trapping centers and generate energy transfer with Er3+, resulting in a larger red-green emission peak ratio (R/G), and the luminescence color is closer to red, which is consistent with the CIE color coordinate color region. Finally, according to the relationship between luminescence intensity and excitation power, the upconversion luminescence enhanced mechanism and the possible energy transfer process are analyzed in detail.
Tensile and compressive properties and crack characteristics of rice husk ash and crumb rubber particles modified engineered cementitious composites
TENG Xiaodan, LI Yonghong, WEI Xiaoning, ZHOU Junjie
, Available online  
Abstract:
Rice husk ash is the primary supplementary cementitious material, with rubber particles injected as artificial flaws. CR-RHA/ECC (Rice Husk Ash and Crumb Rubbers Engineered Cementitious Composites) are low carbon, ecologically friendly cementitious composites with good ductility. The effects of rubber content (0, 10%, 20%, 30%) on the ductility and cracking characteristics of CR-RHA/ECC at each curing ages (7 d and 28 d) were explored employing macroscopic mechanical properties and microscopic investigations. The results show that: With the increase of age, there is a great difference in the ductility of CR-RHA/ECC. The replacement of 10% river sand by CR weakens the ductility of CR-RHA/ECC at 7 days by 54% and increases the ductility of CR-RHA/ECC at 28 days by 67%. With the increase of age (28 days), When CR replaces 30% river sand, the ductility of CR-RHA/ECC can reach 6%, and the tensile fracture width of CR-RHA/ECC decreases by 53% compared with that of CR-RHA/ECC without CR replacement.
Prediction of in-plane mechanical properties of auxetic honeycombs based onmachine learning
MA Pei, ZHANG Junhua, QUAN Tiehan
, Available online  
Abstract:
It is well known that honeycombs with negative Poisson’s ratio have excellent mechanical properties. In this paper, two kinds of multi-input and multi-output artificial neural network models (ANN) were developed and compared to predict the energy absorption characteristics of honeycombs with negative Poisson's ratio under different geometric parameters. The cell angle θ, the ratio of straight wall length to cell height L/H and the thickness t of honeycomb cells are used as the inputs of ANN, and the outputs are the initial peak force, platform force and total energy absorption of honeycombs. The error in the verification set is all within 8%, and the average correlation coefficient R2 of the verification set and the test set is greater than 98.2%, which shows that the neural network can obtain good prediction effect and it has the ability to learn and capture the potential physical mechanism that relates the topology structure and mechanical properties of the honeycombs. Compared with ANN1, ANN2 has more network parameters, more complex network structure and better prediction accuracy and training speed. By quickly predicting the mechanical properties of the honeycomb with given geometric parameters, an optimized honeycomb was obtained. A reversed design network was established to reverse design the honeycomb, and it is found that the network has a good prediction effect on the cell angle θ and wall thickness t of the honeycomb, but the prediction effect of L/H is relatively weak, because the parameter L/H has little effect on the initial peak force, platform force and total energy absorption. In addition, the sensitivity analysis of input parameters was carried out. The results show that the sensitivity trend of geometric parameters of the honeycombs to initial peak force, platform force and total energy absorption is the same, the sensitivity of honeycomb cell thickness t is the highest, and the ratio of straight wall length to cell height L/H is the lowest. The reverse design network has good prediction performance for parameters with high sensitivity, while the prediction performance for parameters with low sensitivity is relatively poor. In a word, ANN provides a fast and accurate method for the study of energy absorption performance of honeycombs, which is expected to accelerate the optimization and design process of honeycomb structures.
Application of layered double hydroxide-biochar composite in wastewater treatment
LV Peng-fei, CHEN Que, WANG Jia-cheng, YE Quan-yun, WU Gen-yi, LIU Min, DAI Shi-qin, HUANG Jie
, Available online  
Abstract:
Layered double hydroxide-biochar (LDH-BC) composites, novel biochar-based composite nanomaterials that have been shown to be highly effective in adsorbing pollutants and catalyzing degradation in wastewater treatment. This review provides a thorough and organized overview of the current research on LDH-BC composites, which can be used to inform future studies. The research content provides a summary of the synthesis method of LDH-BC composites, the modification strategy, and the application and mechanism of the composites in wastewater treatment. It is suggested in the outlook section that LDH-BC composites have problems inadequate research such as unclear degradation paths of specific components, less application of composite pollutant systems, and lack of field scale tests. The next step is to explore the above shortages of research further in order to promote the research and application of LDH-BC composites.
Flame retardant and mechanical properties of wood-plastic composites with multi-layer sandwich structures
GUO Yujia, XU Jingwen, CHEN Wenli, FAN Qi, SUN Lichao, WANG Qingwen
, Available online  
Abstract:
In order to solve the problems of high flame-retardant addition and deterioration of mechanical properties in the modification of wood-plastic composites (WPCs) by traditional expandable graphite, flame-retardant reinforced wood-plastic composites with a multilayered sandwich structure were prepared by laminated hot pressing process and structure optimization design using poplar wood flour (WF), high-density polyethylene (HDPE), expandable graphite (EG) and nano-silicon dioxide (n-SiO2) as the main raw materials. And the appropriate characterization and equipment such as cone calorimeter, vertical burner, limiting oxygen index tester and mechanical testing machine were used to investigate the effects of single layer, double layer and triple layer sandwich structures on the flame retardant and mechanical properties of wood-plastic composites, respectively. The experimental results showed that compared with the control wood-plastic composite (WPC-0), the multilayer structure wood-plastic composites exhibited significant reduction of peak heat release rate, total heat release rate, smoke production rate and total smoke production, and remarkable improvement of residue yield in the cone test when the contents of EG in the flame-retardant layer and n-SiO2 in the reinforcement layer were 10% and 5%, respectively. Among all the multilayer wood-plastic composites, WPC-E3B with a triple layer sandwich structure improved its LOI from 20.8% to 30.6% and passed the UL-94 test with a V-0 rating. Moreover, it also showed better mechanical properties compared with WPC-0, such as a 61.9% increase in impact strength and 16.2% and 13.4% increases in tensile and flexural strength, respectively.
Preparation and anisotropic conduction behavior of polyethylene/carbonfiber composites
SHI Suyu, LV Jiansheng, ZHANG Chenhui, REN Zhilin, XU Qiankun, ZHENG Guoqiang
, Available online  
Abstract:
The anisotropic conductive polymer composites (ACPCs) have great application potential in integrated circuits, sensors, thermal management and other fields because of their unique anisotropic conductive and thermal properties. In this experiment, the carbon fiber (CF) and high-density polyethylene (HDPE) films are used as raw materials. The CF was pretreated at high temperature firstly and then used to make a carbon fiber network by ultrasonic dispersion and vacuum filtration technology. Subsequently, the HDPE/CF composites with anisotropic conductivity were fabricated by hot-pressing molding technique. DSC, SEM, TG and conductivity test was performed to analyze the microstructure, thermal and conductive properties of composites. Then the anisotropic conduction behavior of HDPE/CF was monitored by the integrated circuits and IR thermal camera. HDPE layer and CF web layer are arranged alternately and closely combined. The alternating multilayer structure endows HDPE/CF composites with special intra layer conductivity and interlayer insulation, showing typical anisotropic conductivity. HDPE/CF composites exhibit excellent electrical conductivity in the X and Y directions (with conductivity up to 85.71 S/m), which is 5-7 orders of magnitude higher than the Z direction. The introduction of alternating multilayer structure and CF web significantly improves the thermal stability of HDPE/CF composite, and its initial thermal decomposition temperature is increased by about 35℃ compared with that of HDPE film. It exhibits excellent current-carrying capability and remarkable conductive anisotropy, exhibiting great application potential in circuit connection, directional conduction, thermal management and other fields.
Ecofriendly and antibacterial poly(lactic acid) nanofibrous membranes forhigh-efficiency and low-resistance filtration of airborne particulate matters
LI Feng, JIANG Liang, LI Xiao-Peng, TANG Mengke, HUANG Rongting, ZHU Jintuo, HE Xinjian, LI Heguo, XU Huan
, Available online  
Abstract:
Fine particulate matters (PMs) generated during industrial production pose a serious threat to human health and are one of the main hazards causing occupational diseases at work. The contemporary traditional masks have poor filtration effect, high breathing resistance, low dust holding capacity, not easy to degrade as well as insignificant antibacterial effect, for this reason, a high-efficiency and low-resistance poly(lactic acid) (PLA) antibacterial biodegradable nanofibrous filtration membrane has been developed. Structurally ordered nanohybrid structure (CNT@ZIF-8) with large specific surface area were successfully synthesized by inducing the growth of zeolitic imidazolium ester framework-8 (ZIF-8) on carbon nanotubes (CNTs) by microwave-assisted synthesis method. Based on the electrospinning-electrospray technology, CNT@ZIF-8 was successfully embedded onto PLA fiber, and PLA composite fibrous membranes (PLA/CNT@ZIF) with different fiber diameters were prepared by regulating the mass fraction of CNT@ZIF-8. The filtration performance and air resistance of PLA/CNT@ZIF nanofibrous membranes at different flow rates were investigated, and the effects of different mass fractions of CNT@ZIF-8 on the mechanical properties and antibacterial properties were investigated. The results showed that the tensile strength of PLA/CNT@ZIF nanofibrous membrane increased up to 47% (18.5 MPa) and the fracture toughness increased 100% (2.9 MJ/m3) compared with that of pure PLA membrane. As the mass fraction of CNT@ZIF-8 increases, the air resistance gradually decreases, and at the test flow rate of 32 L/min, the air resistance of PLA/CNT@ZIF12% nanofibrous membrane is only 78.7 Pa, which is 40.8% less than that of Pure PLA fiber membrane, and after the 180 minutes long filtration test, there was no significant change observed in the filtration efficiency of PMs. At the test flow rate of 85 L/min, the filtration efficiency of PLA/CNT@ZIF nanofibrous membrane for PM0.3 was more than 89%, and after 5 min of irradiation by the sunlight simulator, the antibacterial efficiency against both E. coli and S. aureus reached 100%.
Effect of interfacial agents on the mechanical properties of the interface between full lightweight ceramsite concrete and ordinary concrete
ZHU Hongbing, FU Zhenghao, WANG Ye, CHEN Jingyi
, Available online  
Abstract:
Five types of full lightweight ceramsite concrete and ordinary concrete composite specimens with different interfacial agents were produced. Moreover, mechanical tests (splitting tensile, shear and bending tests) and scanning electron microscopy (SEM) tests were performed to investigate the effect of interfacial agents on the mechanical properties of the interface between full lightweight ceramsite concrete and ordinary concrete. The mechanical test results show that firstly, the applying interfacial agent can effectively improve the structure of the interfacial zone and substantially enhance the mechanical properties of the interface. For interfacial splitting tensile strength and flexural strength, epoxy resin is the optimal interfacial agent and the strength values will be increased by 56.5% and 37.3%, respectively. The polymer mortar has the most significant effect on the improvement of interfacial shear strength, which can be improved by 71.2%. The mechanical properties of the interface coated with cement paste can also meet the requirements of industry standards. As an interfacial agent, cement paste containing silica fume is superior to cement mortar. Secondly, the influence degree of interface agent on mechanical indexes from strong to weak is splitting tensile strength, flexural strength and shear strength. Thirdly, based on the mechanical indexes of full lightweight ceramsite concrete, a formula for calculating the mechanical strength of the interface between old and new concrete considering the influence of interfacial agents was established. Finally, SEM testing provides a good explanation of the conclusions of mechanical performance testing at the micro level. The use of interfacial agent can reduce the microcrack width between new and old concrete. Among them, the effect of epoxy resin interfacial agent and polymer mortar is more obvious. Besides, it can effectively reduce the porosity of the interfacial transition zone, with a decrease of 46.44% -60.81%. The research conclusions have reference value for the interface treatment of concrete structure reinforcement.
Preparation and properties of anisotropic cellulose nanofiber/aramidnanofiber composite foam
LIN Xu, MAI Xueyan, WANG Jun, YU Yan, ZHANG Xuexia
, Available online  
Abstract:
Cellulose nanofibers (CNF) foam has gained attention in the field of thermal insulation due to its lightweight, biodegradable, renewable nature, and excellent insulation properties.. However, CNF foam suffers from drawbacks such as poor mechanical properties, flammability, and limited thermal stability, which restrict their practical applications. This study prepares anisotropic CNF/ANF composite foam by introducing aramid nanofibers (ANF) into nanocellulose fibers, using ice templating method combined with freeze-drying technique. The effects of ANF content and the introduction of anisotropic structure on the microstructure, mechanical properties, thermal stability, and thermal insulation performance of the composite foam were investigated. The results showed that,when the mass ratio of CNF to ANF is 2∶1, the CNF/ANF composite foam exhibits an ultra-low density (12.25 mg/cm3), good mechanical strength (axial compressive strength of 74.56 kPa), and excellent thermal insulation performance (25.2 mW/mk). Additionally, this composite foam also possesses good thermal stability and flame retardant properties, which endow it with broad prospects for applications in areas such as insulation and self-extinguishing property.
Intelligent identification of micro components and defects of 3D braided C/C composites based on deep learning of X-ray CT images
QIAN Qiwei, ZHANG Xin, YANG Zhenjun, SHEN Zhen, XIAO Jinyou
, Available online  
Abstract:
Four 20 mm cubic 3D braided carbon/carbon (C/C) composite specimens were scanned by micro X-ray computed tomography (XCT) to obtain internal microstructure images with a voxel resolution of 18 μm. A deep learning based semantic segmentation algorithm was then used to train a large number of 2D XCT images to achieve intelligent identification and segmentation of rods, fiber bundles, matrix, pores, delamination and cracks of these specimens. The results show that (1) the XCT scanning can characterize the distribution and morphology of the above components and defects with high resolutions, and the dominant defect is delamination between adjacent fiber bundle layers; (2) Since the grey values in the CT images of all micro components of C/C composites are very close, it is impossible for the traditional threshold segmentation method to segment the different components, whereas the deep learning based algorithm is able to effectively filter noise and artifacts and segment all the components and defects with high accuracy and at a prediction speed of about two orders faster than manual image labelling. This deep learning algorithm thus provides a promising tool to construct high-resolution numerical models for further studies such as performance optimization of C/C composites.
Study on Stretched Aramid Honeycomb cell Structure Based on the Viscoelastic Constitutive Model of Adhesive
XIA Siyu, LI Yan, FU Kunkun, Li Zhaopeng
, Available online  
Abstract:
Stretching process is one of the critical procedures that affect the honeycomb cell structure of Aramid honeycomb. In this study, the viscoelastic constitutive relationship of node bond adhesive was determined by a fitting method based on nanoindentation, and a finite element model of honeycomb biaxial stretching process was established. The validity of the model was verified by the honeycomb stretching-holding experiment. The study found that the stress relaxation behavior of the adhesive caused an increase in the radius of the inscribed circles at both ends of the honeycomb and a decrease in the middle. Meanwhile, during the holding process, the node bond adhesive fillet radius decreased, leading to a decrease in the internal angle of the honeycomb cell. Finally, the influence of gluing process parameters on the size of honeycomb cell after stretching was explored based on the finite element model. The study showed that the increase in gluing width and thickness would lead to a decrease in the diameter of the inscribed circle of the honeycomb cell, and the honeycomb cell's internal angle was only affected by the gluing width, which increased with the gluing width.
Photocatalytic reduction and cyclic adsorption of Cr (VI) by nanocellulose-polyethylenimine-polypyrrole composite aerogel
YANG Mingyan, CAI Xiaodan, CHEN Xinyue, AN Linyu, XING Jianyu
, Available online  
Abstract:
The combined method of adsorption-reduction is a promising method for chromium pollution control. In this paper, nanocellulose-polyethylenimine-polypyrrole (CPP-F) photosensitive composite aerogel was prepared by in-situ oxidation polymerization of pyrrole using CPA as skeleton. The aerogel was characterized by SEM, FT-IR, UV-vis and XPS. The adsorption, in-situ reduction and cyclic adsorption properties of CPP-F composite aerogel on Cr(VI) were studied by comparing the dark and light conditions, and the cyclic adsorption mechanism was analyzed. The results show that CPP-F is a black porous aerogel with uniform and stable structure, and has strong light absorption effect in ultraviolet, visible and near infrared region. After light treatment, Cr(III) content in Cr(VI) loaded CPP-F increase from 29.76% under dark conditions to 72.33%, and its reduction rate is 2.43 times that of dark conditions, indicating that PPy has excellent photocatalytic performance, and light treatment can promote the in-situ reduction of Cr(VI). After 6 cycles of adsorption, the cyclic adsorption capacity of Cr(VI) by CPP-F under light treatment is 64.97% higher than that under dark treatment, indicating that photocatalytic reduction of Cr(III) provid a new adsorption site for Cr(VI) and realized the cyclic adsorption of Cr(VI). The combination of adsorption-photocatalytic reduction-cyclic adsorption has more advantages than adsorption method, and has great application potential in Cr(VI) pollution control.
Ti3C2Tx MXene-modified domestic high-modulus high-strength carbon fibers based on electrophoretic deposition method
CAO Hongshuo, HUANG Ling, LIU Zhe, TIAN Yanhong, ZHANG Xuejun
, Available online  
Abstract:
In order to improve the surface properties of domestic high-modulus high-strength carbon fibers and the interfacial properties of their composites, Ti3C2Tx MXene nanosheets were constructed on the surface of domestic high-modulus high-strength carbon fibers (BHM5 carbon fibers) using a continuous electrophoretic deposition process. The surface morphology, surface element content, surface wettability of BHM5 carbon fibers and the mechanical properties and cross-section morphology of their composites before and after modification were characterized by SEM, XPS, dynamic contact angle, and INSTRON universal material tester, and the interfacial enhancement mechanism of the Ti3C2Tx MXene-modified BHM5 carbon fiber composites was investigated. The results showed that the surface roughness and specific surface area of the Ti3C2Tx MXene-modified BHM5 carbon fibers increased, possessing a good mechanical interlocking ability with the epoxy resin matrix. The content of polar groups on the surface of the carbon fiber increased significantly, and the surface wettability was enhanced. After treating the BHM5 carbon fibers at 15 V for 2 min, the interlaminar shear strength of the composites reached 82.54 MPa, which was enhanced by 28.2% compared with the composites made of untreated carbon fibers.
FFT-based investigation of transverse tensile behavior of unidirectional composites with voids at different temperatures
LI Menglei, WANG Bing, HU Jiqiang
, Available online  
Abstract:
This study investigates the mechanical behavior of the transverse tensile properties of unidirectional carbon fiber-reinforced epoxy resin composites with varying fiber and void volume fractions, focusing on the influence of tem-perature and void volume fractions. For this purpose, an algorithm based on the maximum offset method for the generation of representative volume elements (RVE) was developed. A series of high-fidelity RVE models were con-structed for unidirectional composites with different fiber and void volume fractions. To address the localization problems in damage models and to overcome the inefficiency of traditional finite element methods (FEM), a coupled non-local damage model with fast Fourier transform (FFT) computational framework was proposed. After comparative analysis with reported models and results, the proposed computational framework was validated to have good accuracy and reliability. Based on the validation, we investigated the influence of temperature, void and fiber volume fraction on the transverse tensile performance of composites. Specifically, elevated temperatures correspond to a decrease in the transverse tensile strength and modulus of the composites. In addition, an increase in voids results in a significant reduction in both tensile strength and modulus. Furthermore, as the fiber volume fraction increases, the transverse modulus of the composite material increases significantly while the tensile strength remains relatively constant. The computational framework and research findings presented in this study are expected to play a significant guiding role in the design and manufacturing of composite materials, aiming to enhance material performance and reliability.
Numerical simulation of progressive damage of single-lap CFRP/Al connected by blind rivet under interference condition
WANG Bingbing, ZHOU Zhaoyuan, JIN Wanjun, HE Chao, TANG Zhengqiang
, Available online  
Abstract:
Interference fit has advantages in improving the mechanical performance of blind rivet in connections for composite materials. However, the installation of blind rivets under interference fit leads to the damage of carbon fiber reinforced plastic (CFRP) laminates, weakening the mechanical performance of the joints. In this paper, based on continuous damage mechanics, extended three-dimensional failure criteria and strain rate effect, a complete blind rivet model, which combining finite element method and secondary development of Abaqus was developed to study the effect of interference and installation speed on the damage of composite materials. From the simulation results, the installation resistance force exhibits two typical stages, which are generated by the friction between the aluminum alloy and the CFRP laminate with the blind rivet, respectively. Under interference fit conditions, a higher installation speed is highly advantageous in reducing installation resistance. However, excessive installation speed can lead to increased damage to the hole walls, which is especially noticeable in cases of high interference fit. The failure mode of the joint is mainly caused by CFRP damage and is significantly influenced by the interference size.
Compressive performance of bamboo scrimber and concrete-filled steel tube columns
WEI Baoxing, WEI Yang, WANG Gaofei, XING Ze, LIN Yu
, Available online  
Abstract:
The light and high strength bamboo scrimber was buried in the core of concrete-filled steel tube (CFST) to form bamboo scrimber and concrete-filled steel tube columns (BCFSTs), which was expected to give full play to the compressive strength of the bamboo scrimber and delay its crushing and splitting. In order to study the axial compression performance of BCFSTs, on the basis of three groups of axial compression tests, the corresponding model was established by using ABAQUS finite element software and the nonlinear finite element analysis was carried out. The reliability and applicability of the finite element model were verified by comparing the failure forms and load-displacement curves of the specimens. Based on the verified finite element model, the two key design variables of bamboo scrimber dimension and diameter to thickness ratio of steel tube were parameterized. The analysis results show that: for CFSTs with the same wall thickness, increasing the dimension of bamboo scrimber can inhibit the decline of load-displacement curve after peak point. Compared with CFSTs, the peak load of BCFSTs is increased by more than 8%, and the maximum increase is 16%. The ultimate load of the specimens show a clear growth trend, and the ultimate bearing capacity of the specimens with built-in bamboo scrimber could reach 33.2% compared with that of the CFSTs. With the increase of wall thickness of steel tube, the circumferential constraint of bamboo scrimber and concrete is strengthened, and the core section strength is improved. When the wall thickness of steel tube changes from 4.5 mm to 6.0 mm, the ultimate load of the specimen is increased by 18.2%.
In-plane compression properties of foam-filled anti-tetrachiral structure and re-entrant structure
SHI Nannan, ZHANG Weichen, LI Zhenbao, WANG Lihui, LIU Han, ZHANG Lei, XIA Yang
, Available online  
Abstract:
Negative Poisson's ratio honeycomb structure has excellent mechanical properties including indentation resistance, impact resistance and energy absorption. In order to better study the mechanical properties of negative Poisson's ratio structure, this paper selects two kinds of negative Poisson's ratio structure: anti-tetrachiral structure and re-entrant structure for comparative analysis. In order to improve the mechanical properties of honeycomb structure, polyurethane foam was filled in the structure. The deformation modes and mechanical properties of the foam- filled anti-tetrachiral structure and re-entrant structure were experimentally studied. In addition, through the parametric study of the foam-filled anti-tetrachiral structure, the effects of wall thickness ‘t’ and node radius ‘r’ on the energy absorption and Poisson's ratio of the structure were analyzed. The results show that the energy absorption and bearing capacity of anti-tetrachiral structure is better than that of the re-entrant structure. After filling the two kinds of structures respectively, the structure has higher stiffness and energy absorption, but the ‘auxetics’ effect is weakened. With the increase of wall thickness ‘t’ and node radius ‘r’, the stiffness and energy absorption capacity of the foam-filled anti-tetrachiral structure increase, the Poisson's ratio increases, and the ‘auxetics’ effect decreases. However, the brittle failure of the structure is enhanced and its specific energy absorption is weakened when the wall thickness is too thick. In addition, the compaction strain of the four-ligament backhand structure decreases with the increase of the wall thickness ‘t’ and the decrease of the node radius ‘r’.
Designed growth of hollow WO3/PEDOT bilayer hybrid nanosphere arrays film with superior electrochromic and capacitive performance
SHI Yingdi, MA Kai, FAN Mengxiang, WANG Lirong, TANG Kai, KE Xiang, LIU Taikang, LIAO Zhaoying, DONG Yingchun
, Available online  
Abstract:
In this work, hollow tungsten trioxide (WO3)/poly (3,4-ethylenedioxythiophene)(PEDOT)bilayer hybrid nanosphere arrays film is constructed by template-assisted magnetron sputtering combined with electrochemical deposition. The hollow nanosphere arrays can provide large contact area with electrolyte to benefit ion exchange. The prepared WO3 layer is responsible for offering a lot of ions binding sites due to the large capacity of amorphous WO3 for small ions, and the PEDOT layer is prepared to construct a unique conductive network which can effectively facilitate electron transportation and connect separated color centers. The obtained hollow hybrid nanosphere film exhibits outstanding electrochromic performance with high contrast (77.4% at 633 nm), fast response speed (3.2 s for coloring and 4.2 s for bleaching), good cycling stability (lose 14.5% optical modulation after 2000 cycles) and decent coloring efficiency (116.2 cm2·C−1) at low colored/bleached potentials (−1.0/1.0 V). The hollow hybrid nanospheres also display high areal capacitance (54.6 mF/cm2), superior rate capability and cyclic stability (areal capacitance remains 79.6% after 2000 cycles).
Microstructure and self-repairing performance of granular loaded graphene oxide composite cement-based materials
HU Dexin, SHAN Yuxi, WANG Hailiang, LI Dongxu, ZHANG Yi
, Available online  
Abstract:
To improve the dispersion performance of graphene oxide(GO) in the cement materials, nano SiO2 and CaCO3 powder were used as support of the GO and the SiO2-GO(SG) and SiO2-CaCO3-GO(SCG) were prepared. The effects of the SG and SCG on the mechanical strength, self-repairing performance, hydration products and microstructure of the cement materials were studied. The results show that the mechanical strength of the cement material is improved as the addition of SG and SCG, the flexural strength and compressive strength of the cement-based materials with SCG at 28d are improved by 7.3% and 18.7%, respectively. The self-repairing performance of SCG composite cement is also improved which shows a higher compressive strength repairing rate of about 110.6% and a higher water permeability repairing rate of 100%. The crack area testing shows that SCG has a more significant repair effect on cracks in the cement materials. XRD analysis shows that the early stage cement hydration is accelerated as the addition of SG and SCG, especially for the SCG, the hydration degree at 3d is obviously improved. TG analysis shows that with the extension of hydration age, a higher reaction degree of Ca(OH)2 and SiO2 is achieved in the SCG composite cement, compared with the early 3d hydration stage, the Ca(OH)2 content of SCG composite cement at 28d reduces to 14.90%. Microstructure analysis shows that the SCG has better compatibility with the cement, more C-S-H gels in the late hydration stage is generated and the microcracks of cement could be filled, which makes the excellent self-repairing performance of the SCG composite cement.
Experimental and simulational study on tensile mechanical property of carbon nanotubes/epoxy resin composite
ZENG Lijian, LI Renfu, CHEN Yuxuan
, Available online  
Abstract:
Due to the excellent mechanical, electrical and thermal properties, carbon nanotubes (CNTs) are widely used in the research and preparation of high-performance composite. However, with the high aspect ratio, high specific surface energy and strong van der Waals force, CNTs intend to form agglomeration during the preparation process, causing a decrease in the mechanical property of the composite material at high concentration. In order to accurately characterize the tensile mechanical property of CNTs/EP nanocomposite, the tensile mechanical properties of different kinds of CNTs/EP were characterized by experiment and finite element analysis. Considering the influence of agglomeration on the material parameter of epoxy, a method for reducing the materials parameter of epoxy in the agglomeration region was proposed to improve the numerical analysis method of agglomeration distribution model. The result show that the uniform distribution numerical analysis method can accurately predict the tensile strength and elastic modulus of CNTs/EP at a low content of 0.5wt%. The agglomeration analysis method accurately predicts the tensile mechanical property, the error of elastic modulus and tensile strength of CNTs/EP are no more than 5% at a high concentration of 1.5wt%.
A method for predicting dome thickness layer by layer of filament wound composite pressure vessel
ZHANG Hang, REN Mingfa, WANG Lei, ZU Lei, HE Jingxuan
, Available online  
Abstract:
Due to the influence of fiber winding molding process and the variable curvature/thickness of the dome, the stress state of the dome of the composite pressure vessel was relatively complicated. It was of great significance to accurately predict the thickness of the winding layer of the dome, which was of great significance for constructing a high-precision finite element model and guiding engineering applications. In order to solve the above problems, this study developed a layer-by-layer prediction method for the winding layer thickness of composite pressure vessel dome based on the dual formula method and cubic spline function method. The effects of polar hole radius, the thickness of single-layer yarn thickness and number of winding layers on the thickness and winding angle of the dome were studied. The results show that as the polar hole radius increases, the thickness of the single-layer yarn sheet in the dome decreases gradually, the extreme value of the fiber winding layer of the dome gradually decreases, and the variation of winding angle at the equatorial circle decreases with the decrease of the radius of the polar hole and the thickness of single-layer yarn. Furthermore, by comparing the thickness of each layer of the dome, it is found that the thickness of each winding layer from the inner layer to the outer increases first, then decreases, and finally tends to be the same as the radius of parallel circle increases.
Axial compression performance of precast UHPC-RAC composite short column
QIN Chaogang, DU Jinlin
, Available online  
Abstract:
The combination design of ultra-high performance concrete (UHPC) and recycled aggregate concrete (RAC) forms the precast UHPC-RAC composite columns. Seven precast UHPC-RAC composite short columns were designed and fabricated with the parameters of stirrup position, UHPC thickness and UHPC-RAC interface roughness. The failure form, material strain, load-displacement curve, bearing capacity, Poisson’s ratio and damage were analyzed through the axial compression experiments. The results show that the precast UHPC-RAC composite short columns improve the failure pattern, which can be divided into strong confining shear collapse failure and weak confining of UHPC splitting due to the difference in the binding effect of the combination of external UHPC and stirrup on internal RAC. The increase thickness of hooped UHPC ensures the enhancement of external UHPC restraint. The restraint effect of the outer UHPC is enhanced with the increase of the hoop UHPC and its thickness. The axial compressive stiffness and compression capacity of the prefabricated UHPC-RAC short column are increased by 93.3% and 97.4% at the maximum, and the Poisson's ratio and damage index are decreased, with the Poisson's ratio varying from 0.26 to 0.18. The roughness of UHPC-RAC bonding surface has little difference on the favorable influence of axial compression performance parameters. The strong constraint effect can make full use of the mechanics of high performance materials. Based on the superposition principle, the calculation formula of the compression capacity of
Design of carbon fiber prepreg electromagnetic wave absorbing and load-bearing integrated laminated structure for aircraft skin
JI Zhengjiang, DONG Jiachen, LIANG Liang, CHENG Linhao, YAN Leilei, ZHENG Xitao
, Available online  
Abstract:
In response to the difficulty in balancing load-bearing and electromagnetic (EM) wave absorbing performance in the design of existing aircraft composite skin, the unique mechanical and electrical characteristics of carbon fiber prepreg were utilized to enhance the mechanical and electrical properties of Glass Fiber Laminated Structure (GFLS). Gradient carbon fiber arrays were designed with excellent absorbing performance based on the impedance gradient principle, endowing the structure with EM wave absorbing performance; Carbon Fiber Reinforced Polymer (CFRP) back sheet with excellent load-bearing performance was utilized to achieve enhanced design of mechanical properties. By enhancement design of both magnetic and mechanical properties of GFLS, the EM wave absorbing and load-bearing Integrated Laminated Structure (ILS) was finally constructed. EM simulation and experiment show that the ILS realizes a broadband (5-18 GHz), multiangle (0-70°), and efficient (average absorptivity>94%) absorption effects for EM wave under thin thickness (<5 mm). Through study of absorption mechanisms, it is discovered that the resonant frequency of a structure is inversely proportional to the width of carbon fibers. The layer-by-layer gradual change of the width of the carbon fibers in the ILS is designed to produce multiple adjacent strong absorption frequency points in a wide range of frequency band, which achieves a broadband and strong EM wave absorption. The mechanical experiment results show that the specific bending strength and specific stiffness of the ILS have increased by 86.8% and 76.3% respectively, compared to the GFLS of the same size. Through the introduction of carbon fiber prepreg in glass fiber prepreg layup and structural design in this paper , the EM wave absorbing and load-bearing performance of the GFLS have significantly been enhanced, providing a novel solution for the EM wave absorbing and load-bearing integrated design of aircraft composite skin.
Study on interfacial compatibility and resilient creep resistance of silane-modified collagen fiber/polyvinyl chloride composites
LEI Chao, XU Weixing, ZENG Yunhang, SHI Bi
, Available online  
Abstract:
The three-dimensional hierarchical structure of collagen fiber (CF) has the natural advantage of resilient creep-resistant modification of polyvinyl chloride (PVC), but the hydrophilic CF is difficult to be compatible with the hydrophobic PVC effectively, which limits the modification efficacy of PVC by CF. Modified CF (M-CF) was prepared with amino-silane coupling agent (APTES). The structural transformation pattern of M-CF, and the structure, creep behavior, and fracture behavior of M-CF/PVC were investigated by FESEM, FTIR, and DMA. The results showed that APTES improved the hydrophobicity of CF and formed ionic and covalent bonds with PVC chains, thereby greatly improving the compatibility between CF and PVC. In addition, APTES modification fully opened the three-dimensional hierarchical structure of M-CF, which allowed PVC to better penetrate into the M-CF phase region and form more blocking sites between PVC and M-CF. As a result, the movement of PVC chains was obviously inhibited, the deformation activation energy of M-CF/PVC was increased by 30.7% compared with that of pure PVC, the creep lifetime of M-CF/PVC was extended to 80.5 times that of pure PVC and 2.3 times that of CF/PVC, and the reversible deformation (11.50%) of M-CF/PVC was increased to more than 1.4 times that of the conventional modified PVC. In summary, the improved compatibility between CF and PVC endowed M-CF/PVC with ideal resilient creep-resistance.
Effect of temperature on mechanical properties of metal-compositehybrid multi-bolt joint
WANG Dong, DONG Chuanrui, ZHU Hongmin, DING Guoyuan, HUANG Heyuan, ZHAO Meiying
, Available online  
Abstract:
Taking the aluminum alloy-carbon fiber/bismaleimide (BMI) resin composite multi-bolt double-lap structure as the research object, combined with digital image correlation (DIC) technology, quasi-static tensile tests under different temperature environments (−100°C, 25°C, 150°C) were carried out. The elastic-plastic model of metal and the progressive damage model of composite were used for numerical simulation. A UMAT subroutine considering the influence of temperature was developed to predict the damage of composite materials. The influence of temperature on load-bearing capacity, failure mode, damage evolution and bolt-load distribution of metal-composite hybrid multi-bolt joint structure was studied. The results show that the maximum load of the structure in the environment of 150°C and −100°C is reduced by 4.46% and 2.06% compared with the room temperature environment of 25°C, respectively. The failure modes of three temperature environments are all tensile fracture of the hole edge of the composite. The delamination and extrusion phenomenon of the hole edge are more serious at the high temperature, but the fiber and the matrix are tightly bonded and the extrusion and delamination of the hole edge are weaker in the cryogenic temperature environment. The unevenness of the multi-bolt hole edge damage is weakened at 150°C and is enhanced at −100°C, compared with at the room temperature. Due to the difference in thermal expansion between metal and composite, the bolt load distribution of the three bolts at high and cryogenic temperatures is different.
CsPbBr3 Quantum Dots Passivated by Acetylacetone Indium and Their Room-Temperature Methanol Gas Sensitivity
HUANG Sheng, WEI Tianle, GU Xiuquan, HUO Yumeng, WAN Zixin, WANG Yanyan
, Available online  
Abstract:
Methanol gas is toxic gas that can harm the human nerve system and blood circulation system. Developing devices capable of detecting methanol gas is of great significance. The use of sensors to detect methanol gas has the advantages of low cost, high sensitivity, and real-time monitoring. However, the mainstream methanol gas sensors mainly rely on metal oxides, which have the drawback of high operating temperatures. Therefore, we synthesized perovskite QDs CsPbBr3 through a simple solution synthesis method, and passivated their surface defects using an acetylacetone indium ligand (In(Acac)3), obtaining a material with good gas sensitivity to methanol gas at room temperature. The sensitivity to a volume fraction of 100×10–6 methanol gas at room temperature is 0.33, and the response/recovery time is 11.0 s/17.0 s,gas sensitivity is further improved under ultraviolet light irradiation. It also has good reproducibility and stability, the sensitivity of the sensor has been maintained at around 0.25 after multiple tests at a volume fraction of 80×10–6 methanol gas, and the sensor sensitivity has remained at a high level for 15 days. At the same time, it still has a good response to methanol gas under harsh conditions such as high humidity and no light. Considering that the structure of metal halide perovskite can easily adjust its properties by changing elements, this research method and experimental process can be applied to the detection of other gases.
The “forming-bending” coupling numerical model for the carbon fiber reinforced polypropylene composite tube
WANG Zhen, REN Haoqian, CAO Xi’ao, MEI Xuan, ZHU Guohua, CHEN Yisong, GUO Yingshi
, Available online  
Abstract:
Currently, composite automotive body components still face the challenge of isolated analysis of manufacturing process and structural performance in the research and development process, developing the “forming-performance” coupling model for woven fabric reinforced thermoplastics (WFRTPs) shows great significances to promote the industrial application of WFRTPs in the field of new energy vehicles. In this study, using the carbon fiber reinforced polypropylene (CF/PP) prepregs as the raw materials, two kinds of thin-walled CF/PP tubes with different fiber angles were manufactured by hot molding process, and the quasi-static bias-extension tests for CF/PP prepregs and CF/PP laminates, and the three-point bending (TPB) tests for CF/PP tubes were preformed, and experimental results show that the increase in fabric fiber angle caused by the forming process leads to the decrease in shear strength and the increase in failure strain of the CF/PP laminates, which further results in the reduction in peak force and the increase in failure displacement of CF/PP tubes. Then, the hypoelastic forming constitutive model for CF/PP prepreg, the progressive damage bending constitutive model for CF/PP laminate and the “forming-bending” coupling constitutive model for CF/PP tube were developed and validated. The numerical results indicate that the shear plastic strain of the non-orthogonal CF/PP tube manufactured with restraints of blank holding force (BHF) is 69% higher than that of the orthogonal sample without BHF, and the increase in fiber angle results in the significant increase in shear plastic strain, which further significantly increases the bending failure displacement of the non-orthogonal CF/PP tube.
Response and damage characteristics of composite laminates under high-energywide-area blunt impact
ZOU Jun, LIU Jiaxin, WANG Jizhen, GUO Yazhou, LI Lingling, FENG Zhenyu
, Available online  
Abstract:
High-energy wide-area blunt impact (HEWABI) can lead to severe internal damage to the composite aircraft, which is barely visible from the outside of fuselage and cause a significant threat to flight safety. High energy quasi-static loading tests were carried out on the laminates with different shapes of rigid impactors and rubber impactors, then the finite element simulation models based on Continuum Damage Mechanics (CDM) were developed. The results show that the established simulation analysis models can effectively predict the response and damage of the laminated panels under rigid or rubber impactors. When the load reaches 40 kN, severe delamination damages will occur in the laminated panel for the rigid impactors. On the other hand, no damage can be observed at 90 kN for the rubber impactors, which can be attributed to the significant deformation of rubber impactors and the reduced local contact loads. The shape of rigid impactors has great effect on the damage to laminated panels, while the shape of the rubber impactors has almost no impact on the damages.
Constitutive model of recycled brick aggregate geopolymer concrete under compression before and after elevated temperature
WANG Huailiang, OU Rui
, Available online  
Abstract:
Recycled brick aggregate geopolymer concrete (RBGC) is a sustainable building material with great potential, but there are few studies on the performance of RBGC before and after high temperatures. Firstly, the influence of the amount of cementitious material and the type of coarse aggregate on the axial compression constitutive model of geopolymer concrete was explored. It is found that with the increase of cementitious material, the compressive strength, split tensile strength, elastic modulus and peak compressive strength of RBGC decrease. The change amplitude of strain is smaller than that of ordinary aggregate geopolymer concrete (NAGC). The linear section of the rising section of the stress-strain curve of RBGC is longer, and the stress decreases faster in the falling section. Secondly, the mechanical properties of RBGC and NAGC after high temperature were studied. At 800°C, the strength and stiffness loss of RBGC are 22.1% and 18.3% smaller than that of NAGC respectively. And it is found that RBGC shows better high temperature resistance, and different models should be used to calculate the mechanical performance indicators of the two concretes. This is because the temperature expansion coefficient of brick aggregate is close to that of geopolymer mortar, and the internal temperature gradient of RBGC is small at high temperatures. Finally, by correcting the shape parameters of the descending section, the stress-strain relationship model of RBGC and NAGC before and after high temperature is determined, and the model is in good agreement with the test results.
Effect of various nucleating agents on mechanical properties and crystallizationbehavior of poly (lactic acid)
LV Chao, LUO Shupin, GUO Wenjing
, Available online  
Abstract:
The aim of this study was to investigate the effect of poplar wood fiber as a bio-nucleating agent on the mechanical properties and crystallization behaviors of poly (lactic acid) (PLA), and compare with common nucleating agents talc powder and hydrazide compounds. Poplar wood fiber (WF), talc powder (Talc) and hydrazide compounds (TMC-300) were blended with PLA to prepare composite at 0.5-4, 1-8 and 0.3-2wt% contents by extrusion and molding process, respectively. The optimal content of each nucleating agent was determined based on mechanical properties of composites. The effect of WF, Talc and TMC-300 under optimal content on the crystallization properties including crystallization behaviors, crystal morphology and structure of PLA-based composites was compared. All the three types of nucleating agents can improve the notched impact strength of PLA. Compared with Talc and TMC-300, the addition of WF results in more significant improvement in tensile and flexural properties of PLA-based composite. Under the optimal addition content (1wt%) of WF, the elongation at break, tensile and flexural strength increase by 27%, 17% and 18% in comparison with neat PLA, respectively. The effect of WF, Talc and TMC-300 on the crystallization behaviors of PLA is studied through differential scanning calorimetry. Results show that adding 1wt% WF could improve the crystallinity of PLA in the non-isothermal crystallization, but it is much lower than that of 1Talc/PLA and 0.5TMC/PLA. According to the isothermal crystallization kinetic analysis, WF could also reduce the half-crystallization time of PLA matrix, and improve the crystallization rate. The half-crystallization time under isothermal crystallization at 110℃ is reduced from 23.6 min (neat PLA) to 7.2, 2.7 and 1.4 min when adding 1wt% WF, 1wt% Talc and 0.5wt% TMC-300, respectively. Hot-stage polarized light microscope observation shows that the crystal morphology of PLA induced by various nucleating agents is different during 110℃ isothermal crystallization. WF and Talc provide a large number of nucleation sites for PLA crystallization, which promotes the grain refinement of PLA. TMC-300 induces PLA to form fibrous bundle-like crystals accompanied with higher crystallization rate, which is consistent with isothermal crystallization kinetic analysis results. The SEM observation of impact facture morphology after etching treatment indicates that the accumulation of crystals with different morphologies is one reason for the difference of mechanical properties. Wide angle X-diffraction analysis shows that all the three types of nucleating agents can promote the generation of orderly α-crystal. The 1WF/ PLA composite exhibits the strongest diffraction intensity. Besides, WF could significantly decrease the crystal size of PLA. This study demonstrates that poplar wood fiber can be used as a bio-nucleating agent for PLA, which plays dual effect of reinforcement and nucleation. This study provides a basis for optimizing the nucleation ability of WF for PLA, and also provides references for further promoting the green development of wood-plastic composite.
Microstructure and properties investigation of B4C/Al composite materialsfabricated by selective laser melting
DENG Yunqi, HU Qiyao
, Available online  
Abstract:
In order to solve the problems of uneven distribution of B4C particles, agglomeration and violent reaction with Al matrix during the preparation of B4C/Al composites. In this paper, B4C/Al composites were prepared by selective laser melting method. The effects of laser power and Ti elements on microstructure and mechanical properties of B4C/Al composites were studied. The results show that the density of B4C/Al composites increases first and then decreases with the increase of laser power, and reaches the maximum density of 94.1% at 240 W. During the preparation process, B4C particles are prone to interfacial reaction with Al matrix and increase with the increase of laser power, resulting in brittle phases and micro-cracks of Al3BC and Al3B48C2, resulting in decreased interfacial bonding properties. The density of B4C/Al composite with Ti increased to 95.2%, the resulting interface products TiC and TiB2 could effectively inhibit the interface reaction, and the interface was clear and complete with high bonding properties. The tensile strength and elongation of the composite were increased by 41% and 49.3%, respectively, and the tensile fracture mode changed from brittle fracture to ductile fracture.
Design and performance of hollow mesoporous SiO2-based nanodrug carrier materials with controllable particle size
YIN Chengwu, CHEN Yuxin, WANG Yujie, ZHU Dehui, YIN Fulin, CHENG Lin, ZHAO Yu, ZHOU Guoyong
, Available online  
Abstract:
In this study, polyacrylic acid (PAA), ethyl orthosilicate (TEOS), silane coupling agent Si-69, fluorescein isothiocyanate (FITC) were used as soft templates, the main raw materials, fluorescent agents, and fluorescent agents were used to prepare hollow mesoporous SiO2 nanocarriers (HMSNs-69-FITC) with fluorescent labeling by self-template method. The structure and particle size of nanocarriers were determined by FTIR, DLS, BET, Raman and TEM, their reduction-sensitive properties were characterized by ultraviolet spectrophotometer and TEM, and sorafenib (SOR) was loaded with solvent volatilization, and calculate its load efficiency. The results show that the amount of regulating PAA can achieve controllable particle size of HMSNs in the range of 25~380 nm, among which, HMSNs with 0.024 g/mL PAA and an average particle size of 100 nm have excellent stability performance, HMSNS-69-FITC has a loading efficiency of 280.0 μg/mg for SOR, and in PBS solution containing 0.0083 g/mL dithiothreitol (DTT), 48 The cumulative release rate of h was about 82.4%; In the absence of DTT, the cumulative release rate at 48 h was about 25.1%, which had significant disulfide bond reduction sensitivity. This work helps advance research in the field of particle size controllable and reduction-sensitive SiO2 nanocarriers.
Preparation of graphene (carbon nanotubes) -cellulose/keratin composite sensing films
SUN Zeying, JIANG Dawei, SUN Caiying
, Available online  
Abstract:
Cellulose (CE) and keratin (FK) are abundant natural materials. Cellulose has been used in various fields of production and life, while keratin, which is the main component of feathers, has mostly been discarded. Compounding keratin into cellulose can make good use of waste materials and improve the properties of cellulose materials. Firstly, cellulose and keratin were dissolved with ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), and epichlorohydrin (ECH) was used as a crosslinking agent to connect CE and FK into a network. The ionic liquid can shield the π-π deposition of graphene or carbon nanotubes, so that the carbon nanotubes or graphene can be well dispersed into the cellulose/keratin cross-linked network composite system to improve the electrical and mechanical properties of the material. The tensile strength and strain of the prepared composite film can reach 64.8 MPa and 58.0% respectively. When bending 30º, 60º and 90º, the resistance would increase by 10%, 14% and 35%. The change of human motion behavior can be monitored by the change of resistance caused by the deformation of the film. Therefore, the composite film is very promising to be applied to wearable electronic devices that monitor motion, for sports, medical and other fields.
Buckling of metallic cylindrical shells stiffened with helical CFRP stripes
ZUO Xinlong, TANG Wenxian
, Available online  
Abstract:
Buckling of metallic cylindrical shells stiffened with helical composite stripes was investigated in the current study. A mathematical relationship between area ratio and thickness ratio of composite layer for externally pressurized metallic cylinder stiffened with helical composite stripes was proposed. An analytical formula for collapse load of such hybrid structure was derived. Numerical analysis and experimental verification were conducted. Furthermore, depth chart for full-scale hybrid cylinder was designed using analytical formulae. The results indicate that the maximum and minimum difference between numerical and theoretical results obtained using interpolation method are 5.2% and 0.9%, respectively. The theoretical, numerical and experimental data for samples agree favorably. The difference between theoretical and numerical results is 3.20%; The difference between theoretical and experimental results is 3.46%. Metallic cylindrical shells stiffened with multiple helical composite stripes is satisfy for a wide range of depths. Composite stripe stiffeners have vast potential for application in installed and reusable tubes.
Preparation, Modification and Application of Laser-Induced Graphene
ZHANG Ziyang, LI Zhao
, Available online  
Abstract:
Laser-induced graphene (LIG) is a novel graphene preparation technique, which is a process for the rapid transformation of three-dimensional network-structured graphene by irradiating carbon-containing substrates with high-energy beams. Compared with the conventional graphene preparation process, LIG has attracted broad research interest because of its rapid preparation, designable patterning, environmental friendliness, controlled microscopic morphology, and controlled composition. This review summarizes the synthesis process of LIG, including the composition of precursors, the selection of light sources, and the structural modulation of LIG. It also explores the in-situ and non-in-situ modification methods of LIG in recent years, describes the applications of LIG in the field of flexible electrodes and sensors, and provides an outlook on the development of LIG in the direction of integrated energy, sensing, and detection devices.
Tribological performance study of carbon fibre-carbon nanotube multiscale reinforced polytetrafluoroethylene composites
Hao TANG, Ying XU, Xianhua CHENG
, Available online  
Abstract:
To avoid the fibre damage and serious pollution caused by the traditional chemical methods, this study synthesized the carbon fibre (CF)-carbon nanotube (CNT) micro-nano multiscale reinforcer by rare-earth LaCl3 surface treatment method, and then prepared CF-CNT multiscale reinforced polytetrafluoroethylene (PTFE) composites via sintering process. The morphology and surface microcrystalline structure of the reinforcer, and the hardness, crystal structure and wettability of the composite were characterized, and the influence mechanism of the CF-CNT multiscale reinforcer on the crystallinity and surface energy of the PTFE composite was revealed. The coefficient of friction and wear rate of the composites were tested under different reciprocating tribological test parameters, every stage of the friction process was thoroughly discussed with the proposition of corresponding friction and wear mechanism. These results demonstrate that: the avoidance of fibre damage and toxic raw materials distinguishes the proposed CF-CNT reinforcer synthesis method from the traditional methods. The lower surface energy of CF-CNT reinforced composite decreases its initial friction coefficient. The wear rate of the CF-CNT reinforced composite is reduced by 75.3%, which is superior to the counterpart in similar studies. The multiscale structure and La(III) on CF-CNT improve the interface bonding performance of the CF-CNT reinforced composites, prevent the generation of large and hard wear debris during the surface yielding process as well as promoting the formation of high strength and stable transfer film. The tribological behaviors of the CF-CNT reinforced composites is sensitive to the reciprocating frequency and load, the higher frequency and lower load favour the lower wear rate. This study synthesized CF-CNT multiscale reinforcer via rare-earth LaCl3 surface treatment method to enhance the tribological properties of PTFE composite, the obtained research conclusions are instructive for the design of high-performance polymer composite.
A review of the studies on concrete structures prestressed with external fiber reinforced polymer (FRP) tendons
   , A A
, Available online  
Abstract:
The studies on concrete structures prestressed with external FRP tendons are reviewed in the aspects of FRP tendon, key technology and structural component, in this review. Firstly, the tensile properties and long-term behaviors of FRP tendon are introduced. The design-oriented values of creep-rupture stress, relaxation rate and the limits of maximum fatigue stress and fatigue stress range are provided. Secondly, the advantages and deficiencies of three main types of anchor for FRP tendon, and the methods of reducing the stress concentration on FRP tendon at anchor are elaborated. The newly-developed composite-wedge anchor is emphasized, which possesses an anchor efficiency coefficient exceeding 90%. Meanwhile, the deviation radius is recommended to be larger than 200 times of the radius the cross-section of FRP tendons, and the deviation angle of FRP tendons should not exceed 5°, based on the experimental results on the mechanical properties of deviated FRP tendons. Thirdly, the experimental results of concrete beams prestressed with external FRP tendons are reviewed, including monotonic loading, sustained loading and cyclic loading. The design methodologies in the codes at home and overseas are introduced. The accuracies of the calculating methods in the codes are evaluated using the experimental data of forty-two beams, and the methods in the Chinese code GB 50608—2020 are validated to be accurate in the design calculation for concrete structures prestressed with external FRP tendons. This paper is expected to actively promote the popularization and application of concrete structures prestressed with external FRP tendons.