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2024, Volume 41,  Issue 2

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2024, 41(2): 533-1093.
Abstract:
Review
Research progress of 4D printing based on strain mismatch
LIU Xiaoyan, ZHANG Yaling, GENG Chengzhen, LIAO Enze, LIU Yu, LU Ai
2024, 41(2): 533-547. doi: 10.13801/j.cnki.fhclxb.20230724.002
Abstract:
4D printing is an emerging technology that aims to endow objects produced by additive manufacturing with the ability to change shape or function over time. By converting planar precursor patterns into 3D structures with complex geometric shapes, 4D printing provides a flexible and efficient manufacturing method for the field. The design of the precursor structure is a crucial factor that affects the deformation effect of 4D printing. In this article, we aim to review the development of 4D printing based on strain mismatch from the perspective of precursor structure design. Firstly, we provided a brief overview of the current research situation on 4D printing. Then, we classified research related to structural design from the perspective of precursor structures in different dimensions, providing a comprehensive overview of 4D printing by different dimensions of precursor structures. Additionally, we discussed several auxiliary design methods for the precursor structure, including theoretical calculation models and simulation analysis to predict shape transformation, as well as reverse design tools to accurately design the precursor structure. Finally, we summarized and prospected the application prospects and challenges faced by 4D printing.
Recent progress on 3D graphene aerogel based microwave absorbing materials
QIAO Mingtao, QI Jingbo, WANG Jiani, SHI Jinxuan, LI Xiang, LEI Wanying, WEI Jian
2024, 41(2): 548-560. doi: 10.13801/j.cnki.fhclxb.20230815.001
Abstract:
With the development of information technology, electromagnetic pollution has become increasingly severe. Therefore, the development of high-performance microwave absorbing materials with "thin, light, wide, and strong" characteristics has become a top priority. Graphene's excellent properties, such as high conductivity, high specific surface area, and low density, have attracted widespread attention from researchers. To solve the problem of impedance mismatch and single loss mechanism caused by single graphene material, other components are introduced to prepare multi-component composite materials, which improve impedance matching and create diverse loss mechanisms, making it a common design solution. This paper briefly discusses the absorption mechanism, describing four categories: Dielectric type, magnetic composite type, ordered type, and pressure-induced type. Through material selection (metals, ceramics, ferrites, conductive polymers, biomass materials, etc.), structural design, mechanism analysis, and combining with recent research results in the field, the research progress of graphene aerogel based microwave absorbing materials is summarized, and future research directions are also proposed.
Research progress on thermal conductivity of carbon fiber/polymer composites in recent ten years
XIE Shihong, GAO Jie, NING Laiyuan, ZHENG Ke, MA Yong, YU Shengwang, HE Zhiyong
2024, 41(2): 561-571. doi: 10.13801/j.cnki.fhclxb.20230714.001
Abstract:
In this paper, the progress made by researchers in improving the thermal conductivity of carbon fiber-reinforced polymer (CFRP) composites in the past decade is summarized. Based on the principle of thermal conductivity of polymer composites, this paper focuses on the analysis of the influence of carbon fiber (CFs) on the thermal conductivity of CFRP composites, including content, length, and orientation. In addition, four methods to improve the thermal conductivity of CFRP composites are summarized, including surface modification of CFs, directional treatment of CFs, adding thermal conductive fillers and designing three-dimensional continuous thermal channels, which have an impact on the thermal conductivity of CFRP composites. Finally, the prospect of carbon fibers arranged in the same direction and combined with high thermal conductivity fillers with different shapes and sizes to construct continuous thermal conduction channels is prospected. The preparation of CFRP composites with low filling content and high thermal conductivity will become the research direction in the future, which will provide guidance for the development and optimization of the next generation of thermal conductivity materials.
Research and application of electromagnetic shielding conductive coating
LI Mingzhan, LI En, PAN Yamin, LIU Xianhu
2024, 41(2): 572-591. doi: 10.13801/j.cnki.fhclxb.20230530.003
Abstract:
In order to deeply understand the preparation and properties of electromagnetic shielding conductive coatings and promote the large-scale production of high-efficiency and low-cost coatings, this paper first introduces the conductive mechanism of coatings and the basic principles of electromagnetic shielding. Secondly, focusing on different types of conductive fillers and resin matrices that constitute coatings, the effects of various materials on the overall performance of coatings due to differences in structure and properties are systematically introduced. The current research progress and multi-functional improvement for practical applications are reviewed. Finally, the problems of electromagnetic shielding coatings in filler structure, filler synthesis, compatibility of polymer matrix and filler are summarized and the prospect of future industrial development is expressed.
Research progress in photothermal conversion mechanism and performance enhancement of the microencapsulated phase change materials
WANG Chengyao, LI Zhaojun, ZHANG Tao, ZHU Qunzhi
2024, 41(2): 592-608. doi: 10.13801/j.cnki.fhclxb.20230802.004
Abstract:
Microencapsulated phase change materials (MPCM) can effectively prevent leakage and corrosion of phase change materials, which are widely utilized in the fields of solar energy utilization, thermo-regulated fibers and fabrics, energy saving buildings and heat transfer fluids. However, there is a problem that the core-shell structure of conventional MPCM weakens the photothermal conversion performance. The poor performance can be effectively improved by modifying MPCM with the addition of photothermal materials. In this paper, the materials of MPCM’s core and shell and their characteristics are summarized. The characteristics and photothermal conversion mechanisms of photothermal materials, including organic photothermal materials, carbon-based materials, semiconductor materials, metal-based materials and other photothermal materials, are illustrated. Additionally, photothermal conversion efficiency is introduced to evaluate the enhancement of photothermal properties of modified MPCM with different modified photothermal materials. Finally, future trend of modified MPCM with photothermal conversion is prospected.
Research progress on influencing factors and control methods of drying shrinkage of alkali-activated foam concrete
SUN Haoyang, ZHANG Xiuzhi, TAO Wenhong, YAN Xiaowei, HOU Jie, ZHENG Peiqi, FENG Shuxia, DU Peng
2024, 41(2): 609-624. doi: 10.13801/j.cnki.fhclxb.20230817.001
Abstract:
Alkali-activated foam concrete is a type of green, low-carbon and energy-saving material which combines the advantages of alkali-activated materials and foam concrete. The application and development of alkali-activated foam concrete are limited by its complex drying shrinkage values which affected by its complicated pores structure and hydration products that unlike cement. In this review, the capillary tension theory, the surface tension theory, the separation pressure theory and the interlayer water transfer theory were analyzed. Contrast the similarities and differences of contraction mechanism between alkali-activated foam concrete, cement base material and alkali-activated material. Meanwhile, the latest research progress of inhibiting drying shrinkage of alkali-activated foam concrete is summarized. Compared with cement-based materials, alkali-activated materials have larger drying shrinkage because of the different hydration products. The drying shrinkage of alkali-activated foam concrete is mainly related to the amount of foam, and the less slurry, the smaller the drying shrinkage value. Finally, this review points out the research and application of alkali-activated foam concrete and provides an effective way for its development economically and environmentally.
Research progress of biomimetic biomass-based adhesives
LUO Jing, LI Renjie, MA Rui, CHEN Linyu, ZHOU Ying, ZENG Guodong, GAO Qiang, GUO Yongsheng
2024, 41(2): 625-639. doi: 10.13801/j.cnki.fhclxb.20230926.004
Abstract:
Currently, industrial synthetic resin adhesives, which mainly use petroleum-based chemicals as raw materials, dominate the market. However, their unsustainable development and the release of volatile organic compounds during synthesis and application lead to environmental pollution. Therefore, it is of significant research significance and development prospects to develop environmentally friendly adhesives using renewable biomass resources. However, biomass-based adhesives generally suffer from high viscosity, poor adhesive performance, low water resistance, and poor product stability, which limit their practical application. To address these issues, researchers have used physical and chemical methods to modify these adhesives, aiming to improve their bonding and usage performance. Inspired by nature, the use of biomimetic approaches to modify adhesives is one of the hotspots in research. This article reviews the research progress on biomimetic modification of soy protein adhesives, lignin adhesives, tannin adhesives, and polysaccharide adhesives, discusses the research prospects of biomimetic modification of biomass-based adhesives, and provides an outlook on their applications. These efforts aim to provide new ideas and methods for the modification and performance improvement of biomass-based adhesives and promote their large-scale application.
Research progress of medical magnesium alloy properties and its alloying improvement path
SHI Chenchen, YUAN Kezhen, GAO Dongfang, QIAO Yang
2024, 41(2): 640-655. doi: 10.13801/j.cnki.fhclxb.20231018.001
Abstract:
The corrosion resistance and strength of magnesium alloys are poor compared to traditional medical metal materials, which seriously limits their application in the field of medical devices. Studies have shown that alloying can significantly improve the properties of medical magnesium alloys, but due to the different effects of the addition of different alloying elements on the mechanical properties, corrosion resistance and biocompatibility of magnesium alloys, and there are differences in the improvement effect of the elements on the alloys. Therefore, it is of great significance to study the effects of the addition of different elements on the properties of medical magnesium alloys. This paper firstly reviews the comprehensive studies on the mechanical properties, corrosion degradation properties and their biocompatibility of magnesium-based alloys in recent years, and secondly analyses the differences in the properties of magnesium-based alloys with the addition of different alloying elements, and puts forward suggestions for the future development of medical magnesium-based alloy materials in view of the limitations of alloying and expects to provide valuable experience for future clinical applications.
Status and prospects of research on vibration reduction performance of metaconcrete
XIONG Jianrong, REN Fengming, TIAN Shiyu, LI Yongsheng
2024, 41(2): 656-671. doi: 10.13801/j.cnki.fhclxb.20231007.002
Abstract:
Metaconcrete, a new type of material with vibration attenuation characteristics, is formed by replacing natural coarse aggregates with a heavy metal core wrapped with an elastic soft coating and mixed with mortar. When subjected to dynamic loads, metaconcrete could attenuate the vibration response of concrete using the bandgap generated by the local resonance of artificial aggregates. Recently, metaconcrete has received great attention in the field of blast and impact resistance due to its remarkable vibration reduction performance under high-frequency dynamic action vibration, and various forms of metaconcrete have been developed by changing the structure and arrangement of aggregates. Systematic theoretical derivation, numerical analysis and experimental studies have been carried out for the vibration attenuation performance of metaconcrete. In order to accelerate the research and application of metaconcrete in the civil engineering, the research work on its vibration reduction performance was systematically summarized, the problems and bottlenecks in the engineering performance were discussed, and the future vibration attenuation research and application prospects of metaconcrete were prospected in this paper.
Recent progress in special infiltrating nanocellulose-based aerogel for oil-water separation
GAO Jiannan, WANG Wei, WU Jianbing, SUN Yinyin, LU Xin
2024, 41(2): 672-684. doi: 10.13801/j.cnki.fhclxb.20230918.001
Abstract:
The development of petrochemical, textile industry, steel and other industries has produced oily wastewater that has seriously damaged the eco-logical environment of humans and has aggravated the shortage of water resources. How to effectively separate oil-water mixture has become a current research hotspot under the global consensus of carbon peaking and carbon neutral. The special infiltrating nanocellulose-based aerogel has the characteristics of different infiltration to oil and water phases and has high efficiency of oil-water separation, so it has a broad application prospect in the field of oil-water separation. This article systematically summarized several infiltration models and basic action mechanisms, focusing on detailed analysis of nanocellulose-based aerogels in oil-water separation field and preparation process. Finally, the existing problems of special infiltrating nanocellulose-based aerogels are discussed with looking forward to their future development.
Resin Polymer Composite
Modified silicone alkyne hybrid resin for RTM and its composite
HU Wenjie, ZHANG Junjun, GAO Mingyu, JIANG Fengguang, LIU Min, ZHOU Quan
2024, 41(2): 685-693. doi: 10.13801/j.cnki.fhclxb.20230524.002
Abstract:
Resin transfer molding (RTM) forming process is a liquid closed mold forming process, which has a smooth surface of the finished product, safety and environmentally friendly, low cost, and has great development potential. Silicone alkyne hybrid resin is an organic-inorganic hybrid resin with excellent high-temperature resistance, widely used in aerospace field, but its poor bonding performance with fibers and poor mechanical properties of composites have become the main factors restricting its development and application. Poly(m-diacetylbenzene-methylhydrosilane) resin (PSA) was modified by blending benzoxazine resin (PBZ) and amino diluent (PAD) to prepare modified silicone alkyne hybrid resin (PPA) suitable for RTM molding process. The RTM molding process, curing behavior, and heat resistance of PPA resin were analyzed by DSC, FTIR, rheometer, rotational viscometer, and thermogravimetry. The results show that the processing window of PPA resin is wide, which can achieve the goal of RTM molding, but the curing temperature is higher than that of PSA resin. The heat resistance of PPA resin is excellent, and the temperature of 5% mass loss (Td5) of PPA-1 resin (PSA∶PBZ∶PAD mass ratio 5∶1∶2) resin is 585.4℃ and 568.3℃, respectively. The mass retention rates at 1000℃ is 88.3% and 26.0%, respectively. The mechanical property tests show that the mechanical properties of quartz fiber reinforced PPA resin composites (QF/PPA) gradually increase with the increase of PBZ content. The flexural strength of QF/PPA-1 at room temperature is 346.2 MPa, and the interlaminar shear strength is 21.4 MPa, which is 120.6% and 72.6% higher than that of QF/PSA composites, respectively. After thermal aging at 400℃ for 2 h, the flexural strength and interlaminar shear strength are 256.5 MPa and 17.1 MPa, respectively, and the retention rate of mechanical properties after thermal aging at 400℃ for 2 h exceeds 70%.
Effect of glass fibers and coupling agents on the degradation properties of polylactic acid
LYU Dongyang, CHEN Li, WANG Jing
2024, 41(2): 694-701. doi: 10.13801/j.cnki.fhclxb.20230627.002
Abstract:
Polylactic acid (PLA) is widely used in the field of fracture internal fixation because of its excellent performance, but it has the problem of degradation of flexural and shear properties due to rapid degradation rate, so compound modification is one of the ways to improve its performance. In this study, glass fiber (GF) and PLA blended preforms were prepared by the three-dimensional braiding technique, followed by modification of the preforms using coupling agent KH550. The composite materials were prepared using a hot-press molding technique. The composite materials were subjected to in vitro degradation experiments by immersing them in phosphate buffered saline (PBS) solution at 37℃. The results reveal that an increase in GF content leads to a decrease in the quality loss rate and water absorption of the composite. After 28 days of degradation, the crystallinity of samples with 40wt%GF content increases by 12.3% compared to samples with 30wt%GF content. Additionally, the flexural strength decreases by 32.3%, 28.13%, and 16.16% for samples with GF contents of 30wt%, 35wt%, and 40wt%. Similarly, the shear strength decrease by 53.74%, 51.1%, and 47.18% for samples with GF contents of 30wt%, 35wt%, and 40wt%, respectively. This finding indicates that increasing the GF content helps to preserve the mechanical properties of the composite material and alleviate interface damage caused by degradation. The introduction of KH550 resulted in a minimal decrease in the pH value of the degradation medium (PBS buffer solution). After 28 days of degradation, the modified composite material exhibits a decrease in flexural strength of 22.85% and a decrease in shear strength of 56.11%. While combined with SEM images, it is observed that the sample with 30wt%GF content exhibits small fissures on the surface after 7 days of degradation, while significant surface damage is observed after 28 days. In contrast, the sample with 40wt%GF content exhibits less degradation damage, which corroborates the testing results of flexural strength and shear strength. It can be observed that GF promoted the mechanical properties and crystallinity of PLA composites while inhibiting the degradation of PLA. KH550 improved the interface between GF and PLA and had less effect on the pH change of the degradation medium.
Low dielectric nanoporous composites based on epoxy-based POSS modification: Effect of microstructure on dielectric properties
LI Xiaodan, LIU Xiaoqing, HE Rui, LIU Hongyu, WANG Feng, MENG Shiyun
2024, 41(2): 702-711. doi: 10.13801/j.cnki.fhclxb.20230812.001
Abstract:
With the rapid development of ultra-large-scale integrated circuits, micro-integrated high-density semiconductor components urgently require low dielectric materials. In this work, epoxy sesquisiloxane (EOVS) with cage structure was synthesized and blended with epoxy resin E51 to obtain the nanoporous EOVS/E51composite. As shown by SEM, EOVS nanoparticles are uniformly dispersed in the E51 matrix. With the increase of EOVS, the nanopores introduced by its cage structure make the free volume of EOVS/E51 composite increase and the density of polarized molecules per unit volume decrease, so that the dielectric constant decreases from 4.21 to 2.51 (1 MHz) when the EOVS content is 15wt%. However, the epoxy groups on EOVS provide new reaction sites, so the crosslink density of the EOVS/E51 composite system increases with the increase of EOVS, and the free volume of the composite decreases and the dielectric constant turns to increase when the EOVS content reaches 20wt%. In addition, the hydrophobicity of the Si—O—Si bond of EOVS enhances the moisture resistance of EOVS/E51 composites, while the thermal stability of the inorganic backbone and the nano-toughening effect lead to a significant increase in the heat and impact resistance of the composite, which is promising for applications in microelectronics.
Synthesis of a self-crosslinking flame retardant and its performance on solid epoxy resin
LOU Gaobo, DAI Jinfeng, LIU Lina, FU Shenyuan
2024, 41(2): 712-722. doi: 10.13801/j.cnki.fhclxb.20230629.003
Abstract:
Epoxy resin (EP) is widely used in various fields of national production and life due to its excellent chemical stability, electrical properties, adhesive properties, and mechanical strength. But its flammable properties pose a threat to people's lives and property safety, thus, the flame retardancy modification of epoxy resin has always been a research hotspot. Using 3-aminophenol, 4-nitrophthalonitrile, 4-formylphenylboronic acid, and 9, 10-dihydro-9-oxa-10-phosphazephenanthroline-10 oxide (DOPO) as raw materials, a self-crosslinking flame retardant (DBPN) was synthesized through substitution, condensation, including addition reactions, and was used for flame retardancy of solid epoxy resin. The thermal stability, flame retardancy, and flame retardancy mechanism of epoxy resin composites were systematically studied. The results show that adding 6.4wt%DBPN advance the initial thermal decomposition temperature of epoxy resin composite from 372.6℃ of neat epoxy resin (EP) to 351.5℃, which is conducive to the formation of a carbon layer barrier during the combustion process, isolating the mass and heat transfer processes. Its UL-94 vertical combustion test increased from N.R to V-2 level, with peak heat release rate (PHRR), total heat release (THR), peak smoke production rate (PSPR), and total smoke production (TSP) decreased by 34.2%, 29.5%, 20.8%, and 17.8%, respectively, compared to neat EP. The flame retardancy mechanism of epoxy resin composites was proposed through the analysis of residual carbon. This work provides innovative ideas for the preparation of new halogen-free flame retardants.
Functional Composite
Preparation and electrochemical properties of MOF/polypyrrole/graphene ternary composite aerogel
PANG Qihan, SONG Huimin, LIU Jiahao, WANG Kai, HAN Yongqin
2024, 41(2): 723-734. doi: 10.13801/j.cnki.fhclxb.20230707.001
Abstract:
The poor electrical conductivity of metal organic frameworks (MOF) with rich porous structures limits their practical application in supercapacitor electrode materials. With MOF crystalline material and polypyrrole (PPy) chains embedded in the 3D network structure of graphene (GE) aerogel, 3D hierarchical porous structure can be successfully constructed. Simultaneously, high level and stable doping of conductive PPy, which can further improve the supercapacitive performance of the composite aerogel. Co-MOF, Ni-MOF and bimetallic CoNi-MOF were obtained by hydrothermal method with Co(NO3)2·6H2O and Ni(NO3)2·6H2O as metal source and trimesic acid (H3BTC) as organic ligand. Then MOF/PPy/GE ternary composite aerogels were prepared with MOF crystal material pyrrole (Py) and graphene oxide (GO) by one-step hydrothermal method. The composite morphology, chemical structure, and doping structures were characterized by SEM, TEM, FTIR, XRD, Raman and XPS techniques. The results show that the bimetallic CoNi-MOF material is more easily embedded in the three-dimensional network structure of the composite aerogel, and could effectively suppress the accumulation of GE layers by constructing a stable three-dimensional porous network structure together with graphene layers and PPy conjugated long chains. The electrochemical test results show that the specific capacitance of the CoNi-MOF/GE/PPy composite aerogel (GPMOF-CoNi) can reach 447 F/g, and the capacitance retention rate of 10000 cycles is up to 97%, showing good supercapacitive performance.
Preparation of modified hydroxyapatite/mixed acid-oxidized multi-walled carbon nanotubes and applications
HE Yingying, WANG Ruixue, ZHOU Yuan, FAN Linkui, DOU Yan
2024, 41(2): 735-747. doi: 10.13801/j.cnki.fhclxb.20230825.001
Abstract:
The development of nanocomposites with high dispersion and good adsorption properties is important for the removal of heavy metal ions from water bodies. Fluorine/carbon-doped hydroxyapatite (FCHAP) was prepared stepwise by microwave/light-wave combined heating assisted chemical precipitation using mixed-acid oxidized multi-walled carbon nanotubes (AO-MWCNTs) as the matrix and hydroxyapatite (HAP) was introduced and loaded onto AO-MWCNTs to synthesize FCH/AO-MWCNTs composites. The results show that the theoretical maximum adsorption capacity of FCH/AO-MWCNTs for Mn(II) is 317.5 mg/g, which is higher than that of AO-MWCNTs and each preparation intermediate. Combined with the characterization results of SEM-EDS, FTIR, XPS, Zeta, and BET, it is speculated that the new material FCH/AO-MWCNTs form more abundant pore structure and adsorption sites, and their dispersion and stability performance are excellent, and at the same time, the new material has broad application prospects in the removal of other heavy metals and recycling.
Preparation and characterization of Basil essential oil nanoparticles/polyvinylpyrrolidone-polyvinyl alcohol hydrogel wound dressing
XU Mi, ZHANG Liang, HE Zhixian
2024, 41(2): 748-760. doi: 10.13801/j.cnki.fhclxb.20230629.002
Abstract:
Basil essential oil (BEO) is a green and safe antibacterial agent. However, the high volatility of BEO has limited its application in the field of antibacterial wound dressings. BEO nanoparticles (BEO@Zein) were prepared by nanoprecipitation method. They were then loaded on the hydrogel based on polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) to form BEO@Zein/PVP-PVA hydrogel wound dressing by freeze-thaw cycle. The microscopic morphology and structure of BEO@Zein and hydrogel were characterized. The antibacterial property, mechanical property, swelling and moisturizing, degradability and blood compatibility of hydrogel were studied. The results show that BEO@Zein forms a nano-spherical structure with BEO as core and Zein as shell (mean particle size is 56.3 nm), which significantly reduces the volatility of BEO. BEO@Zein/PVP-PVA hydrogel can release BEO slowly, thus exhibiting excellent slow-release antibacterial property. Therefore, BEO@Zein/PVP-PVA hydrogel has excellent antimicrobial persistence (over 72 h). In addition, the hydrogel shows remarkable antibacterial biofilm property. BEO@Zein/PVP-PVA hydrogel has good mechanical property, swelling and moisturizing, degradability, and blood compatibility. Studies have shown that BEO@Zein/PVP-PVA hydrogel can be used as a good wound dressing material.
Electrochemical oxidation mechanism of high modulus carbon fibers in ammonium electrolyte solution
GONG Haoting, QIAN Xin, GUO Mei, LI Chunjie, ZHANG Yonggang
2024, 41(2): 761-774. doi: 10.13801/j.cnki.fhclxb.20230616.004
Abstract:
Polyacrylonitrile-based high-modulus carbon fibers (HMCFs) have excellent properties such as high specific strength, high specific modulus, and low coefficient of thermal expansion. So far, HMCFs have been widely used in aerospace and high-end sports equipment, etc. However, it is really difficult for HMCFs to effectively bond with the matrix owing to their extremely high surface inertness, which directly affects the performance of the corresponding composites. At present, electrochemical oxidation is one feasible surface modification process of carbon fiber which has been equipped online, whereas there is a lack of systematic research on the surface electrochemical oxidation of HMCFs, especially the oxidation mechanism of HMCF surface oxidized by different electrolyte solutions. In this paper, the electrochemical oxidation of HMCFs in four ammonium solutions with different acid-base characteristics was conducted. Changes in fiber surface structure, mechanical properties and composite interfacial properties before and after treatment were characterized and analyzed in detail. The results showed that after the treatment with ammonium electrolyte solutions, the fiber surface was oxidized together with the introduction of N elements and the generation of nitrogen-containing functional groups. Meantime, the degree of fiber surface disordering and the oxygen content also increased with the enhancement of the acidity and alkalinity of the electrolyte solutions. The fiber modulus increased to varying degrees after electrochemical treatment, while the fiber samples oxidized in NH4HCO3 and NH4H2PO4 electrolyte solutions showed an increase in fiber tensile strength after treatment, from 4.21 GPa to 4.82 GPa and 4.75 GPa, respectively, and the interfacial shear strength of their compo-sites also increased by 49.86% and 49.02%, respectively, compared with composites reinforced by untreated fibers. It is demonstrated that moderate oxidative etching during electrochemical oxidation can improve the tensile strength of fibers while modifying the fiber surface.
Preparation of boehmite sol modified HGMs and properties of water-based composite coatings
WANG Zhaoyang, GONG Guifen, CUI Weiwei, WANG Yidi, LOU Chenxia
2024, 41(2): 775-786. doi: 10.13801/j.cnki.fhclxb.20230614.007
Abstract:
Thermal insulation is of great strategic importance for energy saving and emission reduction, and energy consumption. In this paper, the surface modification of hollow glass microbeads (HGMs) with boehmite sol was used to introduce the air cavity structure to improve the thermal insulation performance of the coating and to prepare a high-performance water-based composite coating that can be produced continuously. The microscopic morphology and structure of the composite microspheres were analyzed by FTIR, XRD, SEM and other characterization methods. Thermal weight loss analysis, thermal conductivity, infrared thermography and other technical means were used to systematically study the microstructure, comprehensive performance, thermal insulation and heat preservation mechanism of the coating. The results show that the surface modification of HGMs is successfully carried out by boehmite sol, and HGMs@Al2O3 retains the basic structure and characteristics of HGMs, enhances the interfacial compatibility with the aqueous polymer matrix, and solves the practical problem of poor interfacial bonding between HGMs and the aqueous matrix, resulting in large fluctuations of its thermal conductivity. Compared with the composite coating without added thermal insulation filler, when the content of HGMs@Al2O3 is 7wt%, it reaches the over-permeability threshold, and the comprehensive performance of the coating is the best, which significantly improves the thermal insulation of the composite coating and reduces the thermal conductivity by 58.7%. The application potential and commercialization prospect are huge.
Application of porous conductive gel PAM/CNTs-PEG in zinc-air batteries
LI Peizhi, YANG Haichao, CHENG Xiaoliang, CHEN Zhigang, ZHANG Kang, WANG Chen
2024, 41(2): 787-794. doi: 10.13801/j.cnki.fhclxb.20230625.002
Abstract:
In order to realize the industrial production of zinc-air battery, the performance of its air diffusion electrode is optimized to make it conducive to the diffusion of gas and to form more three-phase interfaces. The conductive hydrogel is composed of a conductive material and a cross-linked polymer network, the polymer network provides the scaffold, and the conductive material gives the hydrogel good electrical conductivity. The porous structure can give more diffusion paths to the gas, and is also conducive to the load of the catalytic layer, forming more three-phase interfaces. In this paper, polyacrylamide hydrogel was used to synthesize porous polyacrylamide/carbon nanotubes-polyethylene glycol (PAM/CNTs-PEG) conductive hydrogel with polyethylene glycol 2000 (PEG2000) as pore-making agent. The prepared PAM/CNTs-PEG conductive hydrogels were immersed in ethanol solution to form different numbers of mesopores. The effect of different immersion time on the properties of porous PAM/CNTs-PEG conductive hydrogels in flexible zinc-air cells was studied. The experimental results show that the electrochemistry performance of the conductive gel soaked in ethanol for 5 h is the best. When the voltage changes from 1.23 V at 1 mA/cm2 to 1.11 V at 5 mA/cm2, the attenuation is only 0.12 V. The maximum power density is 77.35 mW/cm2 at 8.5 mA/cm2, and the high gram capacity of 1104.85 mA·h/g at discharge is much higher than that of other conductive gels. It has good electrical conductivity and strain sensitivity and can be used in sensing and other fields.
Morphology modulation and photo-Fenton degradation of RhB properties in spinel-structured ZnFe2O4 nanocrystals
LI Zhiming, WEI Zhiqiang, LI Chao, HAN Mingjun, WANG Qing, ZHAO Yufeng
2024, 41(2): 795-803. doi: 10.13801/j.cnki.fhclxb.20230627.001
Abstract:
The shortage of water resources and the increase of water demand for human production and life have made the topic of wastewater purification and treatment hot. The advanced oxidation process has become a proven method to treat wastewater because it is efficient, environmentally friendly and free of secondary pollution. The most representative ones are photocatalytic technology and Fenton technology. Three different morphologies of ZnFe2O4 nanocrystals, namely microspherical (ZFO-1), hollow spherical (ZFO-2) and orthohexagonal (ZFO-3), were prepared by hydrothermal and calcination methods by adjusting the process parameters. The microstructure, morphology, elemental composition and photoelectrochemical properties of the samples were characterized by XRD, SEM, HRTEM, UV-vis, electrochemical impedance spectroscopy (EIS) and transient photocurrent response tests. Furthermore, the ZnFe2O4 nanocrystal photo-Fenton properties were derived from the degradation of rhodamine B (RhB). The results show that all three prepared ZnFe2O4 nanocrystals have cubic spinel structure and good crystallinity. ZFO-2 exhibits excellent visible light absorption and the narrowest band gap with red-shift phenomenon. EIS tests show that ZFO-2 has the lowest internal resistance to transfer and the highest transient photocurrent, with excellent migration and separation of photogenerated carriers. The photo-Fenton degradation efficiencies of ZFO-1, ZFO-2 and ZFO-3 catalysts are 88.2%, 97.6% and 48.1% in order, indicating good degradation performance. The comprehensive obtained, ZFO-2 has excellent photodegradation performance. And the possible catalytic mechanism of photo-Fenton degradation of RhB was discussed.
Rare earth cerium oxide reinforced cobalt based catalysts for electrolysed water and their properties
QIU Wenjie, HU Zhen, ZHOU Qihong, CHEN Jian, QI Xiaopeng
2024, 41(2): 804-815. doi: 10.13801/j.cnki.fhclxb.20230703.003
Abstract:
The exploration and development of efficient and low-cost electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are crucial but challenging for addressing the energy crisis and environmental pollution. In this paper, a self-supporting electrode composed of ultrathin ceria and cobalt phosphide nanosheets (CeO2-CoP/NF) was designed and fabricated on a three-dimensional nickel foam substrate. At 10 mA·cm−2, the hydrogen evolution overpotential of CeO2-CoP/NF is 124 mV and 142 mV at 1 mol/L KOH and 0.5 mol/L H2SO4, respectively. In addition, CeO2-CoP/NF can also demonstrate superior OER activity at 100 mA·cm−2, exhibiting an oxygen evolution overpotential of 328 mV in 1 mol/L KOH, and also has superior cycle stability. The experimental results show that the introduction of CeO2 can reduce the erosion of the electrolyte and significantly improve the electrochemical performance of the CoP material. This work provides new insights into the development of high-performance electrocatalysts for water splitting.
Preparation and H2S sensing performance of Co(CO3)0.5(OH)·0.11H2O/WO3 nanomaterials
GUI Yanghai, WU Jintao, TIAN Kuan, GUO Huishi, ZHANG Xinhua
2024, 41(2): 816-826. doi: 10.13801/j.cnki.fhclxb.20230703.001
Abstract:
In recent years, H2S as a novel biomarker for asthma and chronic obstructive pulmonary disease is of great significance to human health monitoring, so it is urgent to study H2S sensors with low power consumption, high selectivity, low detection limit and high stability. Co(CO3)0.5(OH)·0.11H2O/WO3 nanomaterials were synthesized by a two-step in situ growth method. Different Co(CO3)0.5(OH)·0.11H2O/WO3 nanomaterials were grown in situ on WO3 nanosheets by regulating the water bath reaction time using WO3 nanosheets as a substrate synthesized by in situ hydrothermal method. The composites were characterized by FE-SEM, FTIR, XRD and TG, and then tested for gas sensing performance. The results show that the Co(CO3)0.5(OH)·0.11H2O/WO3 composite prepared after 20 min reaction has the best gas-sensitive property, and the response value to 50×10−6 H2S gas at the optimal working temperature (90℃) is as high as 109. The response and recovery time are 130 s and 182 s respectively, showing excellent selectivity for H2S gas. The composite still has a good response/recovery curve in low concentration H2S (3×10−6) atmosphere. In three repeated tests conducted in one month, it showed good repeatability and long-term stability. The in-situ preparation of Co(CO3)0.5(OH)·0.11H2O/WO3 gas sensing materials and the study of gas sensing properties provide a new idea for the preparation of gas sensing devices and a new way for the diversity of gas sensing materials. It has potential application value in environmental detection and intelligent medical treatment.
Civil Construction Composite
Pore structure and mechanical properties of foam concrete under freeze-thaw environment
GAO Zhihan, CHEN Bo, CHEN Jialin, YUAN Zhiying
2024, 41(2): 827-838. doi: 10.13801/j.cnki.fhclxb.20230608.001
Abstract:
The freeze-thaw tests of four kinds of foam concrete samples with different density were carried out. The pore structure of foam concrete was scanned with X-CT equipment, and the acoustic emission characteristics of foam concrete during uniaxial compression were tested by acoustic emission device. The results show that obvious stages exist in the process of uniaxial compression test and the acoustic emission events in the process of uniaxial compression are mainly concentrated in the contact period and steep growth period. After freeze-thaw cycles, the porosity and average pore diameter of foam concrete increase, the pore size distribution is more discrete, and the thickness of pore wall decreases, which leads to the decrease of mechanical properties. The freeze-thaw cycle reduces the brittleness of the samples, and the cumulative ring count curve of acoustic emission is smoother. Besides, the signal activity decreases with the increase of freeze-thaw times. After 100 freeze-thaw cycles, most of the pore size of the sample with 1000 kg/m3 density is less than 1000 μm, and the compressive strength is only reduced by 23.7%. It has a good ability to resist freeze-thaw erosion.
In-plane compression properties of negative Poisson's ratio structure of rotating thin-walled multi-cell square tubes with foam concrete filler
LIU Hao, ZHOU Hongyuan, WANG Xiaojuan, ZHANG Hong
2024, 41(2): 839-857. doi: 10.13801/j.cnki.fhclxb.20230531.001
Abstract:
To improve the mechanical and energy absorption properties of thin-walled metal tubular structures, a type of negative Poisson's ratio structure of rotating thin-walled multi-cell square tubes with foam concrete filler (RSTFC) was proposed. Firstly, quasi-static compressive test on the thin-walled multi-cell square tubes (TMST), rotating thin-walled multi-cell square tubes (RTMST), and RSTFC specimens were carried out, and their deformation mode, load-displacement curve, and energy absorption performance were experimentally investigated. The test results show that the TMST, RTMST, and RSTFC specimens all exhibit compressive failure. Furthermore, it is found that the rotational deformation of the RTMST specimen can effectively reduce its peak load and improve the energy absorption by 73.2% and 33.6% in comparison to the TMST specimen. Moreover, due to the presence of foam concrete, the aluminum tubes undergo a certain degree of deformation during the rotational process, accompanied by continuous compression deformation of the foam concrete. As a result, the crushing force efficiency and energy absorption of the RSTFC specimen filled with 200 kg/m3 foam concrete increase by 22.5% and 8.9% respectively compared to those of the RTMST specimen. Based on the validated numerical model by test data, it is observed that the matching of bearing capacity between aluminum tube and foam concrete significantly influence the mechanical properties and energy absorption of the RSTFC specimen. Therefore, the deformation mode, load transfer, and energy absorption performance of the RSTFC specimen could be regulated by adjusting the density of foam concrete, the wall thickness of the aluminum tube, and the filling mode of foam concrete. It was recommended to apply RSTFC with two periodic structures in practical engineering due to their relatively higher specific energy absorption and crushing force efficiency.
Experimental study on bonding behavior between CFRP smooth bar and UHPC under impact loading
JIANG Zhengwen, LIU Pengjie, FANG Zhi, FANG Yawei, WANG Zhiwei
2024, 41(2): 858-870. doi: 10.13801/j.cnki.fhclxb.20230612.002
Abstract:
To investigate effect of strain rate on chemical adhesion force and friction on the bonding interface between carbon fiber-reinforced polymer (CFRP) bars and ultra-high performance concrete (UHPC) under impact load, both static pull-out tests and longitudinal impact tests with the 4.0 s−1 strain rate were conducted on UHPC-filled anchorage for CFRP smooth bars. Totally, 24 specimens for eight test groups with 20d-35d (d is CFRP bars diameter) embedded lengths were prepared. The results show that both static and longitudinal impact specimens fail in a similar pattern, that is, all CFRP bars slide out UHPC regardless of the embedded lengths and load types. However, the damage on the surface of CFRP bar is slightly severer in static tests than in impact tests. Under the impact, the chemical bond strength at the bonding interface between CFRP smooth bar and UHPC increases, thereby leading to an improved peak bond strength; however, the residual bonding strength (i.e., friction) at the bond interface decreases. Compared with the corresponding static test specimens, the chemical bond strength and peak bond strength approximately increase by 53% and 17%, respectively, while the average residual bonding strength decreases by about 38%. Besides, a prediction formula for predicting the dynamic bonding strength between CFRP smooth bar and UHPC under impact loads was established.
Experiment of bonding performance of inclined embedded section of RC structure reinforced with near-end enhanced embeded CFRP strip
LOU Yiqun, PENG Hui, LAN Chuanyun, CHOU Jiaxuan
2024, 41(2): 871-883. doi: 10.13801/j.cnki.fhclxb.20230530.001
Abstract:
Near-end enhanced embedment (NEEE) prestressed carbon fibre reinforced polymer (CFRP) strip is an innovative, efficient and economical technique to reinforce the concrete structure. The CFRP-concrete interfacial bonding performance in NEEE section is the key factor to anchor prestressed CFRP and ensure high efficiency of reinforcement. To clarify the bonding performance of CFRP-concrete interface in the inclined embedded section, which is a part of the NEEE section, nine single-shear pull-out tests with respect to concrete prism specimens were carried out. Factors such as the angle of oblique grooves, embedded depth of CFRP strips and bond length of strengthened region were investigated. Additionally, a bond-slip model of the local interface was presented. The test results show that the load-bearing capacity and fracture energy of specimens increase with the increase of oblique groove angle. The interfacial bonding performance has a positive correlation with the embedded depth of CFRP strips and reaches a maximum with the embedment ratio of 50%, and do not change significantly thereafter. The proposed bond-slip model based on test results could accurately predict the debonding process of CFRP strips in the inclined embedded section.
Experimental study on bending properties of modified aggregate-steel fibre recycled concrete under low temperature
SU Jun, HUANG Fu, WANG Songbo, XU Ziyang, YANG Haixin, LI Yang
2024, 41(2): 884-897. doi: 10.13801/j.cnki.fhclxb.20230531.002
Abstract:
In order to study the effect of low temperature on bending property of modified aggregate-steel fiber recycled aggregate concrete, the replacement rates of 30wt% and 60wt% recycled aggregate were set, mixed with appropriate amount of steel fiber to make cement recycled aggregate concrete (CRAC), temperature gradients of 20℃, 0℃, −20℃, −40℃ and −60℃ were set in the cold area of northern China. CRAC was subjected to compressive strength and four-point bending performance tests by low-temperature action, and its equivalent bending strength and bending toughness were analysed, together with SEM to reveal its macroscopic performance change mechanism from the microstructure perspective, on the basis of which an expression for the fibre reinforcement effect of recycled concrete under low-temperature was proposed. The test results show that after low temperature treatment, the flexural strength of CRAC is significantly increased by 168%, respectively. With the further decrease of temperature, the bending property of 60wt% CRAC is better than that of 30wt% CRAC. At the same time, CRAC with 1.5vol% steel fibres has the best strength and toughness properties at low temperatures. The conclusion of the study is expected to provide reference for the performance design and application of recycled concrete in low temperature environment.
Basic mechanical properties and constitutive model of recycled brick-concrete aggregate
ZHU Chao, ZHAO Wentao, YU Weihang, LIU Chao
2024, 41(2): 898-910. doi: 10.13801/j.cnki.fhclxb.20230531.004
Abstract:
Recycled concrete aggregate is often mixed with recycled brick aggregate, which is difficult to separate. The mixed use of recycled brick and recycled concrete aggregate is more in line with the actual situation. Different water-binder ratios (0.3 and 0.4) and different recycled aggregate replacement rates (0%, 50%, 100% replaced by volume method) were used as control parameters to study the compressive strength, splitting tensile strength, flexural strength, prism compressive strength and uniaxial compressive stress-strain relationship of eight groups of recycled brick-concrete aggregate concrete with different mix ratios. The results show that compared with natural aggregate concrete, the mechanical properties of recycled concrete with different mix ratios decrease to varying degrees. With the increase of recycled brick aggregate content, the mechanical properties decrease significantly. When the replacement rate of brick aggregate reaches 100%, the compressive strength decreases by up to 29.9%, but it can still ensure a certain mechanical property reserve. In this paper, the influence mechanism of water-binder ratio and recycled brick aggregate content on the mechanical properties of concrete is explored. Based on the experimental data, the uniaxial compression constitutive model of recycled brick concrete and the conversion formula of mechanical properties of recycled brick concrete are established. The research results can provide reference for the analysis and design of such recycled concrete structures.
Uniaxial constitutive relation of ultra-high performance fiber reinforced concrete and the effect of steel fiber reinforcement on it
DENG Jinlan, YANG Jian, CHEN Baochun, XU Gang, LI Yang
2024, 41(2): 911-924. doi: 10.13801/j.cnki.fhclxb.20230613.001
Abstract:
The uniaxial constitutive relation of ultra-high performance fiber reinforced concrete (UHPFRC) is the basis for under-standing its material properties and nonlinear structural design. From the perspective of the constitutive equation function model, this paper reviews the existing research on the uniaxial constitutive relationship of UHPFRC. It was found that the empirical model of constitutive relation is suitable for structural design calculation, and the constitutive equations of uniaxial tension and compression should adopt rational fractions. The simplified model of constitutive relation is suitable for simplified force analysis and numerical simulation. The three-fold line model is suitable for uniaxial tension, and the double-fold line model is suitable for uniaxial compression. The damage model of constitutive relation is suitable for the study of material properties, and the damage evolution function is mostly Weibull distribution. In addition, it is found that the constitutive equations obtained by various existing studies do not contain fiber parameters, which cannot fully reflect the influence of steel fibers. Therefore, uniaxial tension and compression tests were carried out on UHPFRC with three aspect ratios and six volume fractions to analyze the influence of fibers on the constitutive relationship. The results show that the rational fraction is more suitable for the empirical model function of the uniaxial tension and compression constitutive model of UHPFRC. Combined with the test and the collected literature data, the influence of fiber on the coefficient of the empirical model equation was analyzed, and the equation of the empirical model of the uniaxial constitutive relationship was proposed. The influence of steel fiber parameters on the uniaxial damage constitutive relation was also explored. The experimental results show that there is a strong correlation between the steel fiber enhancement factor and the control coefficient of the damage model. Based on the experimental data, the relationship between the parameters of steel fiber and the control coefficient of constitutive equation is obtained by numerical analysis, and then the damage constitutive equations of uniaxial tension and compression including steel fiber variables are proposed. The literature data are collected for verification and correction, indicating that the constitutive relation proposed in this paper is in better agreement with the experimental results.
Effect mechanism of temperature on the interface properties of CFRP-steel bondedby self-developed adhesive
LI Chuanxi, GAO Youwei, WANG Xiaoyao, LI You, SIDU Yinghu
2024, 41(2): 925-936. doi: 10.13801/j.cnki.fhclxb.20230614.006
Abstract:
Bonding interface is the weak link of carbon fiber reinforced polymer (CFRP) reinforced steel structure, which is significantly affected by adhesive and temperature. In order to investigate the effect of temperature on the interfacial properties of CFRP-steel bonded by a self-developed high-performance adhesive, 28 CFRP-steel double lap specimens were prepared. The tensile shear tests of self-developed high-performance adhesive G3 and typical commercial adhesive Sika30 were carried out at 7 ambient temperatures (−20℃, −5℃, 10℃, 25℃, 40℃, 55℃ and 70℃). The failure mode, ultimate bearing capacity, load-displacement curve, interface shear stress and bond-slip curve of the specimens were analyzed. The results show that the strength of the adhesive decreases and the toughness increases with the increase of temperature. When the temperature is close to or exceeds the glass transition temperature of the adhesive, the colloidal performance decreases sharply, and the failure mode of the lap joint specimen changes from CFRP layer separation failure to steel-adhesive interface failure, and the interface performance decreases significantly. The low temperature performance of G3 specimen is comparable to that of Sika30 specimen, but the high temperature performance of G3 adhesive specimen is significantly better than that of Sika30 adhesive specimen. The interface performance of the specimen at low temperature is significantly lower than that at 25℃. The adverse effects of brittleness of the reinforcement system at low temperature should be considered in the steel structure strengthened with adhesive CFRP.
Effect of capillary crystalline cement additive on the mechanical, anti-chloride ion permeability, and self-healing properties of PE/ECC
TAN Yan, LONG Xiong, YU Jiangtao, ZHAO Ben
2024, 41(2): 937-951. doi: 10.13801/j.cnki.fhclxb.20230614.005
Abstract:
To study the effects of capillary crystalline cement additive (CCCA) on the mechanical, chloride ion penetration resistance and self-healing properties of polyethylene (PE) fiber reinforced engineered cementitious composites (ECC), PE/ECC was used as the control group and mixed with different mass fractions of CCCA (2wt%, 4wt%, 6wt%, 8wt%, 10wt%), and the mechanical, anti-chloride ion permeability and self-healing properties of PE/ECC were investigated by compressive, flexural, tensile, electric flux method and pre-loaded strain damage method, and the self-healing products were analyzed by XRD and SEM-EDS for their physical composition, microscopic morphology and elemental composition. The results show that: The mechanical and anti-chloride ion permeability of PE/ECC increase and then decrease with the increase of CCCA doping, and when the doping of CCCA is 4wt%, the mechanical and anti-chloride ion permeability of PE/ECC is most obviously improved by CCCA, and the compressive strength, flexural strength and ultimate tensile stress increase by 55.5%, 10.8%, and 79.4%, respectively. The ultimate tensile strain does not change much, and the electrical flux decreases by 38.6%. The self-healing test shows that the recovery rate of tensile strength and strain energy of PE/ECC is significantly improved after doping with CCCA, and the self-healing performance is enhanced. When the pre-damage strain is 0.5%, the tensile strength and strain energy of PE/ECC specimens doped with CCCA are higher than those of the original matrix after 84 days of maintenance, which are 10.41% and 2.83% higher than those of the original matrix, respectively. The tensile strength and strain energy of PE/ECC specimens without CCCA are lower than those of undamaged specimens under three strain damages. The XRD and SEM-EDS results show that the CaCO3, calcium silicate hydrate (C-S-H), and ettringite (AFt) intensity diffraction peaks increase in the hydration products of PE/ECC with CCCA, and the self-healing products are mainly C-S-H crystals, and the distribution is denser in the PE/ECC with CCCA.
Early shrinkage characteristics of high performance geopolymer concrete
WAN Congcong, JIANG Tianhua
2024, 41(2): 952-964. doi: 10.13801/j.cnki.fhclxb.20230529.001
Abstract:
In order to study the early shrinkage performance of high performance geopolymer concrete, a series of experimental research and analysis were carried out. The results show that the influence of silica fume content and water glass modulus on the early drying shrinkage of high performance geopolymer concrete is consistent within the range of test content, which decreases first and then increases. The influence of silica fume content and steel fiber content on the early autogenous shrinkage of high performance geopolymer concrete is consistent, which increases first and then decreases, and then increases. In the range of water glass modulus, the water glass modulus has a negative effect on the early autogenous shrinkage of high performance geopolymer concrete. Increasing the water glass modulus, the early autogenous shrinkage of high performance geopolymer concrete increases in turn. In the range of steel fiber content in the test, the steel fiber content has a positive effect on the early drying shrinkage of high performance geopolymer concrete. With the increase of steel fiber content, the early drying shrinkage of high performance geopolymer concrete decreases in turn. The early drying shrinkage of high performance geopolymer concrete specimens is between 1411×10−6-4387×10−6, and the early autogenous shrinkage is between 856×10−6-1188×10−6. With the increase of age, the drying shrinkage of high performance geopolymer concrete increases rapidly in the early stage, and the autogenous shrinkage decreases slightly first and then increases rapidly, and then gradually tends to be gentle. The early shrinkage curve can be divided into three stages (rapid growth stage, slow growth stage and stable stage). Based on the measured values of early drying shrinkage, the applicability of GL2000 model to the early drying shrinkage curve of high performance geopolymer concrete was verified.
Effect of freeze-thaw cycles on thermoelectric properties of expanded graphite-boron-doped carbon nanotubes/cement composites
WANG Taotao, WEI Jian, HUI Jiawei, GUO Yupeng, ZHANG Siqing, ZHANG Yanbin, QIAO Xinyu
2024, 41(2): 965-977. doi: 10.13801/j.cnki.fhclxb.20230616.001
Abstract:
Thermoelectric cementitious composites using temperature difference power generation can realize the mutual conversion of thermal and electrical energy to reduce urban environmental temperature and resource consumption, but the low efficiency of thermoelectric conversion and vulnerability to environmental impact have restricted its large-scale application. To address this issue, this study proposes the addition of highly conductive expanded graphite (EG) to boron-doped carbon nanotubes (B-CNTs) with high Seebeck coefficients to improve the overall power factor of cementitious composites by the synergistic effect of multi-scale hybridization of B-CNTs and EG. The power factor of the cementitious composites was improved by 10 times to 1.49 μW·m−1·℃−2 compared with that of the cementitious composites without the addition of expanded graphite. The EG-B-CNTs/cement composites after freeze-thaw cycling result in increased porosity and the presence of moisture, which introduce high-density defect interfaces such as solid-solid and liquid-solid, resulting in an increase in carrier scattering intensity and an enhanced Seebeck coefficient for freeze-thaw cycling of cement matrix composites. The power factor of 10.0wt%EG-5.0wt%B-CNTs/cement composite is 1.54 μW·m−1·℃−2 when freeze-thaw cycles are performed 15 times. The research in this paper provides a theoretical basis for improving the performance and environmental conditions of thermoelectric cement matrix composites for future viable applications.
Mechanical behavior of bamboo scrimber filled steel tube under different loading modes
WU Fengyi, WEI Yang, WANG Gaofei, LIN Yu, DING Mingmin
2024, 41(2): 978-989. doi: 10.13801/j.cnki.fhclxb.20230616.002
Abstract:
By means of structural innovation, a new type of bamboo scrimber filled steel tube was formed by composite materials of bamboo scrimber and steel tube. Axial compression tests were carried out on 24 cylindrical specimens of the new type of bamboo scrimber filled steel tube to study the effect of steel tube thickness and loading mode (full section and core loading) on its axial compression performance. The test results show that the external steel tube can effectively improve the structural bearing capacity and deformation capacity, and the main failure mode of the bamboo scrimber filled steel tube is shear failure. The peak stress and peak strain of the structure are positively correlated with the steel tube thickness. As the steel tube thickness increases, the maximum increase in peak stress of the specimens reaches 22.4%, while the maximum increase in peak strain is 6.1%. The core loading specimens exhibit better load bearing potential and deformation capacity than the full section loading specimens. Based on the different curves of full section loading and core loading, and considering the steel tube confinement factor, the prediction models of ultimate stress, ultimate strain, peak stress and peak strain of the new type of bamboo scrimber filled steel tube under different loading modes are proposed, and the error of the stress calculation model is less than 10%. Finally, the stress-strain full curve model is proposed, and the stress-strain variation of the new bamboo scrimber filled steel tube under different loading modes is predicted.
Accelerated creep testing of tensile properties of glued laminated bamboo
LIU Yanyan, SHENG Baolu, HUANG Dongsheng, WANG Wendao, ZHANG Kun
2024, 41(2): 990-1000. doi: 10.13801/j.cnki.fhclxb.20230625.003
Abstract:
The tensile creep behavior of glued laminated bamboo was experimentally studied by the conventional creep test with a time duration of 500 h. The Findley creep model was used to fit the creep curves. The accelerated test using the stepped isothermal method (SIM) was applied to characterize the long-term tensile behavior of glued laminated bamboo. The SIM master curves display the creep characteristics of several decades beyond the test duration. The results show that the tensile creep curve of glued laminated bamboo has two stages under different stress levels: The primary and the secondary creep stages. The tensile creep behavior of glued laminated bamboo conforms to linear viscoelasticity, and its creep deformation is proportional to the stress level at any time. When the stress level is high (reaching 60% of the ultimate strength), the glued laminated bamboo undergoes creep fracture, presenting a brittle failure mode. The Findley creep model can well fit the short-term tensile creep behavior of glued laminated bamboo, and its extrapolation agrees well with the SIM creep master curve. Based on the test results and analysis, the isochronous stress-strain curves were established. The coefficient of elastic modulus of laminated bamboo for different design service life was further discussed and compared with the recommended values in GB/T 50005—2017 standard for design of timber structures.
Effect of carbonation curing on the performance of cement paste added with carbide slag
QIN Ling, MAO Xingtai, XIE Qijie, CUI Yifei, BAO Jiuwen, CHEN Tiefeng, GAO Xiaojian, ZHANG Peng
2024, 41(2): 1001-1010. doi: 10.13801/j.cnki.fhclxb.20230616.003
Abstract:
In order to reduce the carbon footprint of cement industry and recycle carbide slag, carbide slag was added into carbonation curing cement as the mineral admixture. The influence of carbonation curing on the compressive strength, drying shrinkage, chloride ion penetration of cement paste added with carbide slag was studied, and the microstructure of cement paste was analyzed by X-ray diffraction, thermal analysis, mercury intrusion porosimetry, scanning electron microscopy, etc. The results show that carbonation curing can improve the compressive strength and chloride ion erosion resistance of cement paste added with carbide slag, reduce the electric flux by 38.17%-50.08%, reduce the 56 days drying shrinkage by 8.8%-25.2%, and refine the pore structure. About 10% of carbide slag can be used as resource under the premise that the strength of cement paste is not reduced, and the carbon fixation rate of cement paste can reach 11.19%-15.87%. The purpose of capturing and solidifying carbon dioxide, recycling carbide slag and improving the performance of cement paste are achieved by carbonation curing.
Biological and Nano-composite
Construction of PAMAM-PQQ functional layer on titanium surface and its effect on biological behavior of endocardial cells
WANG Yilong, HUANG Jinquan, YUAN Yating, SONG Siqi, CHEN Junying
2024, 41(2): 1011-1020. doi: 10.13801/j.cnki.fhclxb.20230607.002
Abstract:
Implantation/interventional surgery is the main treatment for cardiovascular diseases. Direct contact with blood during device implantation and damage to the implantation site can cause complications such as thrombosis and inflammation. Surface modification of materials is one of the main methods to improve the biocompatibility of materials. In this study, the dendrimer polyamide amine (PAMAM) was immobilized on the surface of alkaline activated Ti, and pyrroloquinoline quinone (PQQ), an anti-inflammatory and anti-oxidative molecule, was grafted on the amino group of PAMAM to construct the PAMAM-PQQ functional layer. The effects of different concentrations of PQQ on the surface biocompatibility of the materials were also investigated. FTIR, XPS and amino quantification demonstrated that PQQ was successfully grafted to the surface of the material. SEM and water contact angle detection proved that the surface of the material has porous mesh structure and high hydrophilicity. Blood tests showed that the functional layer reduced the number of platelet adhesion and activation degree, showing good anticoagulant ability, and the best effect was when the PQQ concentration was 300 nmol/mL. Static cell culture results showed that the functional layer improved the activity of endothelial cells and myocardial cells, and promoted the proliferation and migration of the two kinds of cells. Oxidative damage experiment showed that the functional layer could reduce the damage of H2O2 on endothelial cells and myocardial cells, and the best protective effect was achieved when the concentration of PQQ was 300 nmol/mL. In summary, the functional layer of PAMAM-PQQ was successfully constructed on the Titanium surface, which has good blood compatibility, cell compatibility and antioxidant damage ability, and is expected to be used for the development and application of surface modification of cardiac implantable devices.
Preparation and drug release evaluation of spider fibroin membrane
LIU Xinxin, ZENG Huina, JI Chenran, GAO Pengfei, ZHAO Yu, ZHANG Chenggui
2024, 41(2): 1021-1029. doi: 10.13801/j.cnki.fhclxb.20230822.003
Abstract:
Natural spider silk has superior mechanical properties, and its various forms have excellent antibacterial activity, biocompatibility, and good thermal conductivity. It is of great significance to develop natural biological drug-loaded materials with good biocompatibility for reducing the strong immunogenicity reaction of patients. By exploring the dissolution and membrane-forming methods of spider silk in different solvents, the reaction conditions were optimized, hexafluoroisopropanol was used as the dissolution solvent, the material ratio was 1∶1 (mg∶mL), the spider silk was dissolved at 60℃ for 8 h, and the membrane was formed by solvent casting, and the drug release in vitro of rhodamine B (RhB) as the model drug was explored with the correlation characterization. The cytotoxicity of the material was tested by extraction method. The spider fibroin membrane extract co-culture with cells showed that the material had no potential cytotoxicity to mouse embryonic osteoblasts cells. The drug-loaded spider silk fibroin membrane prepared by this method has high yield, uniform thickness and simple operation, which provides a simple and feasible technology for the dissolution of natural spider silk protein and the preparation of membrane agent.
Metal and Ceramic Matrix Composite
Research on microstructure and site preference of NiTi alloy coating on 316L by laser cladding
FENG Yuqiang, HU Zhengfei
2024, 41(2): 1030-1037. doi: 10.13801/j.cnki.fhclxb.20230614.003
Abstract:
60 NiTi (60wt%Ni-40wt%Ti) alloy presents higher hardness, high elastic modulus, good abrasion performance and excellent corrosion resistance, making it suitable for various applications in different fields. This paper investigated the microstructure and phase composition of NiTi alloy coating on 316L stainless steel prepared by laser cladding. It shows that the main alloying elements Fe and Cr in the substrate are significantly doped into the cladding coating, which obviously affect the microstructure and properties of Ni-Ti coating. The main phases in the coating are NiTi and Ni3Ti phases. Increase the content of Ni can inhibit the precipitation of NiTi2. First-principles calculation based on density functional theory was used to study the phase preference and site preference occupations of the alloying elements Fe and Cr from substrate in NiTi and Ni3Ti phases. The microstructure and phase composition of the coatings were investigated as well. The results show that, NiTi and Ni3Ti are the major phases in the coating. Both Fe and Cr atoms prefer to substitute Ni atom in the NiTi (B2) crystal structure. However, in the Ni3Ti crystal structure, each Ni and Ti atom has two different crystal positions, Fe atom prefers to substitute position Ni-1 and Cr atom prefers to substitute position Ni-2 instead. Combined the experiment and calculation results, the major phases in the coatings after element doping are supposed to be Ni5Ti8Fe2Cr and Ni9Ti4Fe2Cr.
Tensile fatigue of three-dimensional needling SiO2f/SiO2 composites at high temperatures
WANG Heng, ZHANG Peiwei, XU Peifei, CHEN Qiang, FEI Qingguo
2024, 41(2): 1038-1046. doi: 10.13801/j.cnki.fhclxb.20230710.001
Abstract:
Three-dimensional needled SiO2f/SiO2 composite material is suitable for aircraft radome. Tensile fatigue tests at 600℃ and 800℃ and tensile tests after fatigue loading were carried out to obtain the stress-strain curves of the corresponding tests. By analyzing the shape and size of hysteresis loops under different cycles and the variation of stiffness with cycles, the tensile fatigue mechanical behavior of 3D needled SiO2f/SiO2 composites at high temperature was investigated. The results show that temperature has great influence on fatigue stress of 3D needled SiO2f/SiO2 composites, and the fatigue properties of the composites are different at 600℃ and 800℃. The modulus of most specimens decreases gradually with the increase of the number of cycles, but the modulus of some specimens fluctuates with the cyclic loading.
Preparation process and bending properties of CFRP/stainless steel ultra-thin strip fiber metal laminates
MA Wei, GUAN Hailu, ZHANG Xiaoqiong, WANG Tao
2024, 41(2): 1047-1057. doi: 10.13801/j.cnki.fhclxb.20230609.002
Abstract:
A new type of foil material of stainless steel ultra-thin strip with light mass (thickness only 0.01-0.1 mm), high strength, easy to form, corrosion resistance and many other advantages, is a kind of light and high strength material with great application prospects. In order to investigate the feasibility of stainless steel ultra-thin strip as a component material of fiber metal laminates and evaluate its mechanical properties, six different surface treatment processes of stainless steel ultra-thin strip were compared. It is proved that mechanical grinding + acetone cleaning + 10wt% sodium hydroxide solution corrosion + 1wt% coupling agent is the best surface treatment technology for the composite of stainless steel ultra-thin strip and carbon fiber prepreg, the single lap tensile shear strength is 21.3 MPa. Based on this technology, fiber metal laminates containing different layers and different types of stainless steel ultra-thin strips were prepared by using T700 carbon fiber unidirectional prepreg, T300 plain braid prepreg and soft, semi-hard and hard stainless steel ultra-thin strips with thickness of 0.1 mm. The bending properties and deformation failure mechanism of the laminates were systematically studied by three-point bending experiments. The results show that the bending failure mode of carbon fiber/stainless steel ultra-thin strip fiber metal laminates is mainly affected by the change of steel strip strength and toughness, the bending deformation is mainly affected by the content of steel strip.
Preparation and microwave absorption performance of hollow iron-based carbon fiber composites
MA Qian, QIANG Rong, SHAO Yulong, YANG Xiao, XUE Rui, CHEN Bowen
2024, 41(2): 1058-1069. doi: 10.13801/j.cnki.fhclxb.20230613.002
Abstract:
In order to improve the increasingly serious electromagnetic pollution caused by the rapid development of communication and electronic devices, and solve the problems of complicated preparation methods and high energy consumption of magnetic carbon-based absorbing materials, this project proposes a new method for developing iron-based carbon fiber absorbing materials. Using hollow poplar catkin fibers as carriers, Fe3+ as the metal source, and wet chemical adsorption and high-temperature carbon thermal reduction methods, Fe-FexOy/C composite materials with excellent microwave absorption properties were obtained. The experimental results show that as the calcination temperature increases, different iron oxides (Fe/Fe3O4/FeO) are generated by combining the iron component with oxygen-containing groups in the Yangxu fibers, and the coercivity and saturation magnetization of the material are enhanced, and the ferromagnetic properties are obvious. Fe-FexOy/C-600 has the best absorption performance, and the effective absorption bandwidth can reach 8.4 GHz (7.2-15.6 GHz) when the thickness of the absorber is 3 mm. The excellent absorption performance of the composite material is attributed to the synergy of impedance matching and dielectric loss and magnetic loss, and the mutually carried fiber structure builds a suitable attenuation space for electromagnetic waves and quickly attenuates in the carbon fiber conductive network. The research will provide reference for the design and development of new iron based carbon fiber absorbing materials.
Composite Micro-mechanics
Global sensitivity analysis of forming wrinkle defects in thermoplastic prepregs
ZHANG Jiachen, GUO Yuan, LYU Bingyi, XIAO Jinyou, WEN Lihua, HOU Xiao
2024, 41(2): 1070-1079. doi: 10.13801/j.cnki.fhclxb.20230920.003
Abstract:
Wrinkles are easily produced during the forming process of complex composite structures, which affect the forming quality and load-bearing performance of the components. It is urgent to establish the quantitative mapping relationship between forming process parameters and prepreg wrinkles to support the low-defect forming manufacturing of components. In this paper, a global sensitivity analysis method for wrinkled defects in thermoplastic prepregs coupled with multiple process parameters is proposed. A finite element simulation method based on a non-orthogonal constitutive model is developed for the wide temperature domain deformation of thermoplastic prepreg. Combining the distance between the prepreg and the mold and the curvature of the out of plane bending of the prepreg improves the reliability of quantitative characterization of crease defects. Finally, a global sensitivity analysis method was established using the Sobol global sensitivity index based on variance, which can quantitatively calculate the impact of forming process parameters on wrinkle defects. It is verified through the typical carbon fiber/polycarbonate (CF/PC) material single dome forming process. The results show that in the temperature range of 200-250℃ and the pressure range of 0.2-2.0 kPa, the influence of temperature on the wrinkling defects of CF/PC prepreg is greater than that of pressure, and there is a dual parameter coupling effect of temperature and pressure during the forming process.
Probabilistic residual strength model for composite materials considering stress levels
MA Huidong, ZENG Shilong, MA Qiang, BAI Xuezong, AN Zongwen
2024, 41(2): 1080-1091. doi: 10.13801/j.cnki.fhclxb.20230614.002
Abstract:
To address the problems of low generalization and high testing costs of most current residual strength models for composites, a probabilistic residual strength model that accounts for the effect of stress level and is independent of stress level was proposed. Firstly, the normalized strength reserve was defined and a deterministic residual strength model was derived based on the normalized strength reserve. Then, a fatigue life probability model was coupled into the deterministic residual strength model, and then a new residual strength probability model was derived. Finally, the accuracy and applicability of the proposed probabilistic residual strength model was verified using constant-amplitude and variable-amplitude residual strength experimental data from the open literatures. The results show that almost all the constant amplitude experimental data points are distributed between the upper 95% confidence limit and lower 5% confidence limit of the prediction curves, and the prediction curves with 50% reliability have high goodness-of-fit values for the experimental data: 0.94, 0.84 and 0.97. The proposed model accurately describes strength degradation at multiple stress levels using only one set of model parameters, with sufficient consideration of the statistical characteristics of the residual strength of the composite. The relative error between the predicted values of the proposed model and experimental values for both ascending and descending variable-amplitude loading is less than 6%.
2024, 41(2): 1092-1092.
Abstract:
2024, 41(2): 1093-1093.
Abstract: