2023 Vol. 40, No. 7

Additive manufacturing for continuous fiber-reinforced polymer composites: A review on processing technique
XING Yue, HE Pengfei, LI Jinglong, WANG Rong, CHEN Yongxiong, LIANG Xiubing
2023, 40(7): 3703-3721. doi: 10.13801/j.cnki.fhclxb.20230224.001
Compared with metal, ceramic or other structural materials, continuous fiber-reinforced polymer composites can offer significant advantage for their excellent design tailorability, mechanical properties, fracture toughness, good resistance to corrosion and fatigue, and are widely used in aerospace, transportation, energy, machinery and other fields. The organic combination of continuous fiber-reinforced polymer composites and additive manufacturing technology has the potential to promote new revolution for weight saving and structure-function integrated manufacturing of high-end equipment. This paper reviewed the recent research progress of extrusion and impregnation methods, printing temperature, auxiliary process, printing speed, printing spacing and geometric construction methods in additive manufacturing of continuous fiber composites. The influence of various process parameters on properties of the formed parts was emphatically discussed. Finally, the present challenges and future development directions have been prospected for reference.
Research progress of nanomaterials in flexible piezoresistive pressure sensors
TANG Guijun, YIN Keke, YUAN Huiyu
2023, 40(7): 3722-3737. doi: 10.13801/j.cnki.fhclxb.20230225.001
With the rapid development of flexible pressure sensors in the fields of health detection, electronic skin and wearable electronic devices, the research on fabrication of high-performance flexible piezoresistive sensors has become prevalent. The performance of flexible pressure sensors can be optimized by nanomaterials because of their surface and interface effects, small size effects and macroscopic quantum tunneling effects. Nanomaterials based pressure sensor has the advantages of small size, wide detection range and high sensitivity. In this paper, the latest research progress of nanomaterials in flexible pressure sensors in recent years is reviewed.
Recent advances in carbon dots and their antibacterial composite materials
ZHANG Wenli, CHEN Lin, XUE Baoxia, YANG Yongzhen, ZHANG Li, LIU Xuguang
2023, 40(7): 3738-3755. doi: 10.13801/j.cnki.fhclxb.20230306.001
Antimicrobials are indispensable drugs to inhibit bacterial infection. The overuse of conventional antibacterial (antibiotics) leads to the gradual enhancement of antimicrobial resistance of bacteria, which poses a serious threat to human health. As a new type of nano antibacterial material, carbon dots have the advantages of high anti antibacterial ability, wide range of raw materials, low cytotoxicity and good biocompatibility. Novel nano composite materials constructed by combining carbon dots with traditional antibacterial agents show great application prospects in the antibacterial field. This paper reviews the research progress on antibacterial mechanisms and applications of carbon dots and their composites. Firstly, the main factors affecting on the antibacterial performance of carbon dots are systematically analyzed by summarizing their antibacterial mechanisms. Secondly, the new nano composite materials combining carbon dots with traditional antibacterial agents and their applications in the antibacterial field are introduced. Finally, problems in the antibacterial application research of carbon dots and their composites are summarized and prospects are put forward, so as to provide reference experience for the design and synthesis of carbon dot composites with efficient and long-time antibacterial properties.
Research progress of aqueous magnesium ion battery
TU Tiancheng, LI Longyan, DAI Qihang
2023, 40(7): 3756-3770. doi: 10.13801/j.cnki.fhclxb.20221206.001
As a newly developed energy storage system, aqueous magnesium ion battery takes its edge by lower cost, more abundant source of raw materials, higher theoretical energy storage capacity. However, the problems brought by aqueous electrolytes and magnesium themselves greatly limit the further development of aqueous magnesium ion batteries. Here, the influence of the type and concentration of anions in aqueous electrolyte and electrolyte additives on the battery performance is described, and the research of some electrode materials, including new materials and new theories, is introduced. Finally, some efficient characterization and analysis methods are summarized.
Research progress in reinforcement design and analysis of composite bolted joints
SHAN Meijuan, ZHAO Libin
2023, 40(7): 3771-3784. doi: 10.13801/j.cnki.fhclxb.20221123.002
Bolted joint is the weak link of composite structures, and determines the load-carrying capacity of the entire structures. The reinforcement design of composite bolted joints can significantly improve the application efficiency of composites. For this reason, researchers at home and abroad have developed design methods for the overall or local improvement of composite bolted joints, and evaluated the strengthening effects of these methods by using experimental and numerical simulation methods. Some of the reinforcement design methods have been applied in the design of advanced aerospace vehicles abroad. In this paper, the existing reinforcement design methods of composite bolted joints are classified and summarized in detail, and the evaluation methods for the strengthening effect are analyzed. Finally, the existing problems are summarized, and the future development direction is proposed.
Research progress of lightweight polymer electromagnetic shielding materials
YANG Jifei, LIU Shan, FAN Qiao, HE Lulu, HE Min
2023, 40(7): 3785-3794. doi: 10.13801/j.cnki.fhclxb.20230119.002
With the continuous progress of science and technology, the rapid popularization of 5G technology and the rapid development of wearable devices, life is becoming more and more convenient. Meanwhile, electromagnetic interference poses a threat to the health of people and the operation of precision electronic devices. Nowadays, traditional electromagnetic interference shielding materials can no longer meet the daily needs of people's life, lightweight polymer-based electromagnetic interference shielding materials have attracted more and more attention. This study summarized the electromagnetic interference shielding mechanism, and the influence of polymer structures on electromagnetic interference shielding performance, reviewed the preparation methods, electromagnetic shielding properties, and related mechanisms of advanced carbon/polymer materials, metal/polymer materials, and novel MXene/polymer materials, discussed their advantages and limitations, and prospected the key challenges, potential applications and development prospects of lightweight polymer-based electromagnetic shielding materials in the future.
Recent progress in enhancement of physical properties of organic phase change materials and optimization of coupling thermal management of batteries
XIAO Xin, FENG Ze, WANG Yunfeng, ZHANG Ying, GAO Feng
2023, 40(7): 3795-3811. doi: 10.13801/j.cnki.fhclxb.20221024.001
To meet the demand for thermal management of lithium-ion batteries in electric vehicle, the cooling method with phase change materials (PCM) on battery modules has gradually become a research hotspot. Based on the poor physical properties of organic PCM, the preparation and improvement directions of composite organic PCM for battery thermal management (BTM) are summarized, including adding multi-dimensional materials such as carbon materials, nano-metals and metal foams to enhance the heat transfer, and adding copolymer such as polyethylene and thermoplastic elastomer to improve the flexibilities. Additionally, flame retardants such as red phosphorus and ammonium polyphosphate are used to improve the flame retardance for better practicabilities. Among them, expanded graphite, styrene-ethylene-butadiene-styrene, and the composite of red phosphorus and ammonium polyphosphate significantly improve the thermal conductivity, flexibility and flame retardancy respectively. Subsequently, the heat transfer enhancement effects of the system after coupling organic PCM with heat pipe, liquid cooling or air cooling are evaluated, indicating that various arrangements of heat pipe and appropriate flow channels of air and liquid should be considered. Then the optimal operating conditions of organic PCM used in BTM system is determined with numerical calculation. Finally, the progress and shortcomings of organic PCM used in BTM are summarized. It is pointed out that the difficulties of composite organic PCM used in BTM are still accounted for the improvement of flammability and conductivity and the insufficient flexibility of flexible organic PCM at room temperature. Furthermore, the reliability and cycle feasibility of PCM and traditional heat dissipation system in the process of vehicle use are still lack of verification. Totally, several suggestions are put forward for the application of organic PCM in BTM in the future.
Research progress of biomass carbon@MnO2-based electrode materials for supercapacitors
ZHANG Yalin, CHEN Xinggang, WANG Mengqian, REN Mengya, CAI Yanqing, XU Ying
2023, 40(7): 3812-3823. doi: 10.13801/j.cnki.fhclxb.20221109.001
Based on the problems of energy crisis and environmental pollution, it is very important to develop new high-performance energy storage devices. Supercapacitors are favored by researchers because of their high specific energy and good stability. Biomass carbon is obtained by pre-carbonization and activation of biomass materials, with developed pore size, high active specific surface area, and rich resources, which has good application prospects as a supercapacitor material. In order to meet the high specific capacity and high cycle stability of supercapacitors, the current effective method is to combine biomass carbon materials with pseudo capacitor materials. Transition metal oxide MnO2 has become the most promising pseudocapacitor material due to its high theoretical specific capacitance, wide potential window, low cost and environmental friendliness. The research shows that the specific capacitance and energy density of the supercapacitor made of the composite material of biomass carbon and transition metal oxide are significantly improved. This paper mainly introduces the source, characteristics and preparation methods of biomass carbon, also introduces the composite methods of biomass carbon and MnO2 and the research progress of biomass carbon@MnO2 composite materials, and finally looks forward to the development trend of biomass carbon@MnO2 based supercapacitors.
Research progress of water responsive compound material in the field of green writing and anti-counterfeiting
WU Ping, REN Hong
2023, 40(7): 3824-3836. doi: 10.13801/j.cnki.fhclxb.20230103.003
Water stimulus responsive materials can undergo reversible color or fluorescence emission change process under the external stimulus of water. Because of its low cost, non-toxic, compatibility with existing inkjet printing technology and other advantages, it is an ideal choice to achieve rewritable. Meanwhile, it shows great application potential in information storage, security and anti-counterfeiting. In this review, the research progress of water responsive compound material based on organic small molecules in the past five years is systematically reviewed. Inductive materials are classified from the viewpoints of water induced proton transfer, water induced configuration change, water induced proton transfer combined with configuration change sensing principle. The achievements and technologies in design principles, optical physical properties and information storage applications are summarized. It is hoped to provide ideas for further developing the application of water responsive composites in the field of green writing and anti-counterfeiting, promoting the development of related industries.
Research progress of superhydrophobic flexible strain sensors in human motion monitoring
LUO Linghuan, LIN Xiangde, JIANG Jiayi, YING Na, ZENG Dongdong
2023, 40(7): 3837-3851. doi: 10.13801/j.cnki.fhclxb.20230222.001
A flexible strain sensor is a device that converts changes in external stress into electrical signals. It overcomes the shortcomings of traditional rigid sensors such as high hardness and poor human adaptability. As a wearable device, it has great development prospects in the field of human motion monitoring. However, in harsh conditions or extreme environments, there are still risks such as signal output distortion and easy corrosion. The superhydrophobic flexible strain sensor combines the water repellency, surface self-cleaning, anti-corrosion and anti-fouling of the superhydrophobic coating with the high ductility and high sensitivity of the flexible strain sensor, which enhances the performance of the sensor and broadens the applications in human motion monitoring. This paper reviews the basic performance parameters of superhydrophobic flexible strain sensors, the commonly used construction materials and construction methods as well as their functions and applications in human motion monitoring, and provides perspectives on this field.
Resin Polymer Composite
Preparation and performance of cesium iodide/natural leather wearable X-ray shielding composites
LI Hao, WANG Yaping, YAN Linping, ZHONG Rui, LIAO Xuepin, SHI Bi
2023, 40(7): 3852-3861. doi: 10.13801/j.cnki.fhclxb.20220922.005
With the rapid development of nuclear science and technology, there has been an increasing application of high-energy rays in medicine, industry and other fields, which puts forward higher requirements on the performance of shielding materials, and developing new protective materials to effectively reduce radiation harm has thus become an important goal in the field of radiation protection. Here, an advanced wearable protective composites with excellent shielding performance for low- and medium-energy X-rays which using natural leather (NL) as the substrate and CsI as the high Z elements (Z elements refer to the elements with the plateau subral number) source was constructed via “impregnation-desolvation” strategy. The results indicate that the CsI is stably loaded and well dispersed into the hierarchical structure of NL. A 4.5 mm thickness CsI2.0/NL displays excellent attenuation efficiency of higher than 95% for the low-energy X-ray (16-48 keV) and higher than 85% for the medium-energy X-ray (65 keV), which is comparative or superior than that of 0.25 mm Pb plate, and its density is only 8.6% of Pb plate. In addition, the mechanical strength and water vapor permeability of the prepared material not only meet the requirements of national standard for protective clothing but also exceed those of the commercial lead apron. This work shows promising potential of CsIx/NL to be an ideal wearable X-ray shielding composites which features light weight, convenient and high X-rays shielding capabilities.
Interlaminar toughening of carbon fiber/epoxy composites with graphene oxide-carbon nanotube composite film
DAI Shaowei, ZHOU Yujing, LI Weidong, BAI Weihua, ZHAO Huhu, BAI Hua, HU Xiaolan
2023, 40(7): 3862-3873. doi: 10.13801/j.cnki.fhclxb.20221027.003
The interlayer properties of carbon fiber reinforced resin matrix composites are always the weakness of composites. A composite film was designed and fabricated using graphene oxide (GO) and carbon nanotubes (CNT), which exhibited good permeability and resin wettability. A hybrid carbon fiber/epoxy (CF/EP) composite was prepared using the composite GO-CNT film by interlayer toughening method. The interlaminar toughness of the GO-CNT-CF/EP composites was investigated by open type interlaminar fracture toughness (GIC) and slip type interlaminar fracture toughness (GIIC). The interlayer toughening effect and toughening mechanism of the GO-CNT composite film on the GO-CN-CF/EP composites were analyzed based on the damage micro-morphology and damage/destruction characteristics of the composites. The results show that the composite GO-CNT film prepared with a mass ratio of GO to CNT of 3∶7 has good film-forming processability and resin wettability.The contact angle between EP and GO-CNT composite film is much lower than that between EP and pure GO film. Moreover, GO and oxygen-containing groups such as hydroxyl, carboxyl, and epoxy group in CNT increase their physical affinity and chemical interaction with EP, which is conducive to the toughening of GO-CNT/EP microzone structure between layers of composite materials. The GO-CNT composite film has no enhancement effect on the GIC of the composite. The GIC value of the GO-CNT-CF/EP composite even dropped slightly compared to the CF/EP composites. However, the GO-CNT composite film has a good effect on improving the GIIC of the GO-CNT-CF/EP composite. The GIIC of the composite increased from 1855 J/m2 for the CF/EP composite to 2720 J/m2 for the GO-CNT-CF/EP composite, which has an increase of 47%. This is attributed to the interpenetrating and overlapping network structure formed between the GO-CNT composite film and the resin, which inhibits the propagation of interlayer microcracks caused by slip-type loading. The glass transition temperature of GO-CNT/EP composites is similar to that of CF/EP composites.
Study on dynamic and static mechanical properties of glass beads/epoxy resin composites
LIU Xin, YUAN Ye, QU Jia
2023, 40(7): 3874-3880. doi: 10.13801/j.cnki.fhclxb.20220930.003
Glass bead buoyancy material is a two-phase composite material made of hollow glass bead (HGB) and epoxy resin. Glass bead has been widely used in building materials, navigation, aerospace and other fields because of its low density, high strength and low water absorption. Its static mechanical properties have been fully studied, but its dynamic mechanical properties are less studied, which are not enough to meet the needs of engineering applications. The compression, splitting and pseudo-triaxial compression experiments of HGB/epoxy resin composites under quasi-static/dynamic loading were carried out by INSTRON electronic universal testing machine and split Hopkinson pressure bar (SHPB). The results show that HGB/epoxy composite has strong strain rate sensitivity. The compressive strength and splitting resistance increase with the increase of strain rate, showing strain rate enhancement effect. The failure mode is also rate sensitive, and its brittleness increases with the increase of strain rate. Comparing uniaxial compression with pseudo triaxial compression, it is found that the compressive strength of the material under pseudo triaxial compression is higher than that under uniaxial compression.
Flame retardancy and smoke suppression of poly(lactic acid) composites modified by polyphosphate
YANG Huawei, YANG Xingcai, MIN Yang, BAN Daming
2023, 40(7): 3881-3891. doi: 10.13801/j.cnki.fhclxb.20220917.001
Due to poly(lactic acid) (PLA) was easy to burn and accompanied by serious droplet phenomenon, its application in many fields such as packaging, automotive, electrical and electronic industries were seriously limited. And in order to solve this problem, PLA was used as matrix and poly(2-10-hydrogen-9-oxa-phosphaphenanthrene hydroquinone phenyl phosphate) (POPP) was used as flame retardant. PLA composites with different contents were prepared via melting blending and hot-compression method. The flame retardant properties and smoke suppression of PLA composites were investigated by means of limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TG) and cone calorimetric test etc. The results show that the LOI of PLA composite with 4wt% POPP is 34.8%, and it reaches a UL-94 V-0 rating. Comparing with pure PLA, the smoke production rate and total smoke production of POPP/PLA-4 are respectively reduced by 85.83% and 77.65%, which dramatically improve the smoke suppression performance of PLA materials. Moreover, the results of microstructure of char residues after cone calorimeter and thermal degradation behavior analysis reveal that the excellent flame-retardant performance of PLA composites are followed a flame-retardant mechanism of gaseous phase at superiority. This is attributed to •PO and •PO2 decomposed by POPP quenching •H and •OH. Otherwise, by promoting the intermolecular crosslinking of PLA, a continuous and dense carbon layer on the surface is formed, which improve flame retardancy of PLA composites.
Preparation and properties of BaSO4/TPU nanocomposites
KONG Xuguang, GONG Jinghua, FAN Bing, MA Jinghong
2023, 40(7): 3892-3899. doi: 10.13801/j.cnki.fhclxb.20221012.002
During the operation of the conveyor belt used in the food industry, the plastic particles on the surface layer may fall off and adhere to the food, resulting in unqualified food quality and a negative impact on human health. Therefore, it is of great importance to research the modification of surface layer materials that can be detected by X-rays. In this study, BaSO4/thermoplastic polyurethane (TPU) nanocomposites were prepared by the melt blending method. The phase morphology, thermal stability, and tensile property of BaSO4/TPU nanocomposites were systematically characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), hardness, and tensile property tests. In particular, the X ray developing properties of the composites were characterized by X ray fluoroscopy tests. SEM shows that BaSO4/TPU nanocomposites are the best. The tensile strength, elongation at break and work of fracture improve by 10.19%, 30.09% and 31.92% compared to unmodified TPU. The TGA test results show that the high-temperature thermal stability of BaSO4/TPU nanocomposites is improved. In addition, by adding BaSO4, the X ray developing properties of the composites are also improved, thus realizing the application in the surface layer of conveyor belts.
Modification of carbon fiber by microwave and its effect on interfacial properties of electron beam cured CFRP
ZHANG Jingjing, LIANG Sen, TANG Chao
2023, 40(7): 3900-3911. doi: 10.13801/j.cnki.fhclxb.20220922.004
For carbon fiber reinforced polymer matrix composites (CFRP), the in-situ electron beam (E-Beam) curing meets the requirements of integrated manufacturing of shape and performance, which is low-cost according with the "carbon peak and carbon neutralization" strategy. But the E-Beam technology has not yet been industrialized due to the poor interface quality of cured components. Addressing the weak interface of E-Beam cured CFRP, the mechanism and technology of an efficient and high industrial feasibility strengthening technology by microwave short-time radiation were explored in this study. The evolution of physical morphology, roughness and chemical composition of carbon fiber surface under different microwave radiation process parameters was described, showing that the surface roughness, surface area and the O/C atomic ratio of CFs increased from 4.41 nm,7.5 nm2, 0.2578 at 0 s irradiation to 21.7 nm, 26.4 nm2, and 0.3278 respectively after 180 s microwave irradiation. Furthermore, a molecular dynamics model of the interface was constructed to refine and deepen the nature of the carboxyl and hydroxyl enhanced interface from the molecular level, and then their effects on the interface structure and interface energy. The experimental results show that the interfacial shear strength of carbon fiber/resin is improved by 20.47% under the combined effect of physical and chemical modification of microwave radiation (90 s). This research provides the foundation and support for green forming manufacturing of high-performance E-Beam cured CFRP, and has important scientific significance.
Influence of carbon/glass hybrid fiber layup structure on the bending-twisting coupling behavior of wind turbine blades
FU Lingfeng, JIANG Xin, SUN Zhen, WEN Shidong, GAO Mingze, TIAN Rui
2023, 40(7): 3912-3920. doi: 10.13801/j.cnki.fhclxb.20220915.006
In order to analyze the influence of layer structure of composite material on bending-twisting coupling behavior of wind turbine blade, the carbon/glass biaxial warp knitting fabric with hybrid layer ratio 4∶4 and 2∶6 were selected as reinforcement to fabricate blade. A 2 kW wind turbine blade samples model was established and the strain deform behavior of blade samples was experimental studied by combining classical laminate theory and nodal displacement method. The bending-twisting coupling behavior was also analyzed. The results show that when the carbon/glass hybrid ratio is same and the fiber off-axis angle is 25°, the optimal value of equivalent bending-twisting coupling coefficient of blade samples is 0.186. With same fiber off-axis angle, carbon/glass hybrid ratio 4∶4 blade samples has higher equivalent bending-twisting coupling coefficient than carbon/glass hybrid ratio 2∶6 blade samples. The strain measurement experiment shows that the principal strains decreases gradually along with blade length, and bending-twisting coupling behavior have a good effect on perfecting the principal strain at the blade root.
Bulletproof performance of polyimide/UHMWPE fiber hybrid reinforced composites
JIA Wenxing, JIA Ziqi, TIAN Guofeng, CHEN Junxian, HUANG Xiancong, LIU Shaofei, ZHAN Jiayu, WU Dezhen
2023, 40(7): 3921-3927. doi: 10.13801/j.cnki.fhclxb.20221009.002
Aiming at the deficiency of high back-face signature (BFS) of ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced ballistic composites, a series of polyimide (PI) and UHMWPE fiber hybrid composites were prepared by making full use of the advantages of high temperature resistance and high modulus of PI fibers in this study. The effects of layer structure and mixing ratio on the specific energy absorption (SEA) and BFS values of the hybrid composites and the protective mechanism were investigated. The results show that the use of PI fibers can effectively limit the BFS without affecting the SEA value. The bipolar layer structure (H3, UHMWPE/PI) and the sandwich layer structure (H4, PI/UHMWPE/PI) exhibit positive mixed effect. SEA and BFS values of the two structures can reach 193.2 J·m2/kg, 17.40 mm and 208.9 J·m2/kg, 17.77 mm, respectively, demonstrated excellent bulletproof performance.
Preparation of multi-walled carbon nanotubes@graphene/thermoplastic vulcanizate composites and study on its thermoelectric properties
TANG Qi, HU Shiteng, WANG Xuemeng, SUN Jujie, ZONG Chengzhong
2023, 40(7): 3928-3938. doi: 10.13801/j.cnki.fhclxb.20220919.002
This work mainly used the synergistic effect of one- and two-dimensional fillers (Multi-walled carbon nanotubes (MWCNTs)@graphene (GE)) to improve the thermoelectric and mechanical properties of thermoplastic vulcanizate (TPV). MWCNTs@GE/polypropylene-maleic anhydride (PP-MA) masterbatch were first prepared by melt-graft blending. The structure, crystallinity and microstructure of MWCNTs@GE/PP-MA masterbatch were characterized. Then MWCNTs@GE/TPV composites with unique network structure were prepared by dynamic vulcanization method. The effects of the amount of MWCNTs@GE on the phase structure, electrical conductivity, thermal conductivity and mechanical properties of MWCNTs@GE/TPV composites were studied. The results show that the combination of MWCNTs and GE has a synergistic effect and can be used as nucleating agent to improve crystallization peak temperature (Tc) and crystallinity of PP (Xc) and reduce crystal size of the PP crystal plane (LCrystallite) in the crystallization process, compared with the masterbatch prepared with single filler. In the MWCNTs@GE/PP-MA masterbatch, MWCNTs and GE are uniformly dispersed in PP-MA and have strong bonding force with the matrix. The MWCNTs@GE/TPV composites show an obvious "island" structure, and the cross-linked butyl rubber (IIR) rubber is dispersed in the PP-MA phase as micron size particles. MWCNTs and GE are uniformly dispersed in the continuous phase PP-MA, and the distance between MWCNTs and GE is less than 1 µm, forming the MWCNTs@GE network structure. When the content of MWCNTs@GE in MWCNTs@GE/TPV composites reaches 3wt%, the alternating current (AC) electrical conductivity, thermal conductivity, elongation at break and tensile strength reach the best value.
Functional Composite
Preparation of dual-network MXene hydrogels and their electromagnetic and UV shielding properties
FAN Kefan, LI Kun, YANG Zhijian, CHENG Jue, ZHANG Junying
2023, 40(7): 3939-3949. doi: 10.13801/j.cnki.fhclxb.20220907.005
MXenes show unique advantages in electromagnetic shielding materials due to their high electrical conductivity, abundant active sites (such as —OH, —F, —O), electrochemical behavior, and excellent hydrophilicity. However, hydrogels with both excellent mechanical strength and high electromagnetic shielding efficiency remain to be further studied. Meanwhile, transparent hydrogels often lack the ability to filter ultraviolet light, which greatly limits the application of hydrogel materials. In this work, PAAm-PHEMA/PAA-Fe3+-MXene hydrogels with double shielding mechanism were prepared by using acrylamide (AAm) copolymer hydroxyethyl methacrylate (HEMA) chemical cross-linking as the first network, and polyacrylic acid (PAA)-Fe3+ metal ion complexation as the second network, and two-dimensional MXene as conductive nanofillers. The presence of MXene and Fe3+ makes the hydrogel possess both electromagnetic and UV shielding properties. The structure and three-dimensional network of the composite hydrogel were confirmed by FTIR, SEM and EDS. The as-prepared double-network hydrogel exhibits high mechanical strength (320.1 kPa), high stretchability (1786%), and good electrical conductivity (3.8 S/m). In addition, the composite hydrogel also exhibits excellent UV shielding ability, with transmittances of 0% and 79.2% at characteristic wavelengths of 365 and 550 nm, respectively. At the same time, the composite hydrogel can obtain excellent electromagnetic-interference (EMI) shielding effect of more than 36 dB in the X-band, strong adhesion to various substrates, rapid self-healing performance and high shape adaptability. This work provides a flexible and highly tunable dual-shielding mechanism hydrogel network design and large-scale facile fabrication of new ideas, showing great application prospects in flexible wearable materials.
Improved energy storage performance of PMMA/PVDF blend polymer matrix composites by doping modification
ZHANG Changhai, YAN Weidong, ZHANG Tongqin, ZHANG Tiandong, CHI Qingguo, LIU Xianli
2023, 40(7): 3950-3963. doi: 10.13801/j.cnki.fhclxb.20220913.004
Thin film capacitors have important applications in the fields of electrical engineering and electronic devices such as high voltage transmission converter stations, new energy vehicle electric drive controllers, electromagnetic weapon pulse power supply and so on. At present, thin-film capacitors are developing towards the technical direction of high energy density, voltage resistance, high temperature resistance and so on, which put forward higher requirements for the electrical performance of capacitor films. In this study, ferroelectric polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) blends were selected as the energy storage polymer matrix, and BaTiO3 nanoparticles with high dielectric constant and organic molecular semiconductor [6, 6]-phenyl C61 methyl butyrate (PCBM) with high electron affinity were used as the doping phase. The high dielectric properties of BaTiO3 and the ability of PCBM to capture charge are comprehensively utilized to improve the polarization strength and breakdown field strength of the composite medium and significantly improve the energy storage performance. The results show that when the doping content is 3wt%, the composite media has the best comprehensive performance. On this basis, with the increase of PCBM doping content, its energy storage density and charge-discharge efficiency improved significantly. When PCBM doping content is 2wt%, PMMA/PVDF composite medium containing 3wt% BaTiO3 has excellent energy storage performance. When the electric field is 579.67 kV/mm, the discharge energy density reaches 15.60 J/cm3 and the charge-discharge efficiency is 75.30%. First proposed in this paper, based on a small amount of inorganic high dielectric organic molecules together semiconductor filler modified polymer film energy storage performance of the function, by adding a small amount of BaTiO3 particles, avoids insulation performance degradation caused by the high content of BaTiO3, and ensures the BaTiO3 particle on the properties of composite dielectric permittivity and polarization. At the same time, in order to further improve due to the low dielectric constant substrate with high dielectric constant BaTiO3 particles between the electric field distortion caused by the breakdown strength degradation, consider joining a certain amount of PCBM in a composite medium, use PCBM electron affinity ability, strong in composite medium build deep traps to capture and carrier, inhibit the transfer of carrier.The breakdown field strength of the composite medium is improved, so as to comprehensively improve the energy storage performance of the composite medium, which provides a new idea for the development of polymer composite medium with excellent energy storage performance.
Preparation of Ti3C2/SrTiO3 composites and their photoelectrochemical cathodic protection
SU Xinyue, KONG Cunhui, QING Da, ZHAO Yingna, WANG Jiansheng
2023, 40(7): 3964-3972. doi: 10.13801/j.cnki.fhclxb.20220909.004
Due to the shortcomings of strontium titanate (SrTiO3) with large band gap and low separation rate of photogenerating carriers, its photoelectrochemical cathodic protection performance is limited. And in order to solve this problem, SrTiO3 can be modified with the supporting cocatalyst Ti3C2. Firstly, SrTiO3 was prepared by hydrothermal method and Ti3C2 was obtained by etching. Then, Ti3C2/SrTiO3 composites were prepared by mechanical mixing. XRD, XPS, SEM, UV-vis DRS, and PL had characterized the phase structure, chemical state, microscopic morphology, and light absorption performance of the samples. Finally, the photoelectrochemical cathodic protection performance of Ti3C2/SrTiO3 composites to 304 stainless steel (304SS) was analyzed. The results show that Ti3C2/SrTiO3 composites are broadened to absorb visible light. Among them, the photogenerated carrier separation rate of the 15%-Ti3C2/SrTiO3 composite with a mass fraction of 15wt% of Ti3C2 has a higher separation rate and an optical current density of 2.5 μA·cm−2. In the 3.5wt% NaCl solution, after the coupling of 304SS to the composite, its photomotive potential drops by 200 mV under light conditions, which can effectively protect 304SS. After four open and closed light cycle tests, the performance of Ti3C2/SrTiO3 composites are stable.
One-step solvothermal preparation of Bi-Bi2O3-BiOBr ternary complex and its visible light-driven catalytic degradation of methylene blue
YUAN Xiaoya, YU Lixin, JIA Wen
2023, 40(7): 3973-3985. doi: 10.13801/j.cnki.fhclxb.20220909.002
The construction of surface plasmon resonance (SPR), oxygen vacancies, and heterojunctions is one of the effective ways to enhance the catalytic activity of semiconductor photocatalysts. In this paper, Bi-Bi2O3-BiOBr ternary heterojunction composites with SPR effect and oxygen vacancies were synthesized by a one-step solvothermal method by changing the molar ratio of Bi(NO3)3 to KBr. Used XRD, electron paramagnetic resonance (EPR), XPS, SEM, TEM, UV-vis and other means to characterize and analyze the crystal phase, elemental composition and microscopic morphology of the obtained product, and investigate the effect of the molar ratio of Bi(NO3)3 to KBr on the visible light-driven photocatalytic degradation of methylene blue (MB) activity of the ternary complex. The results show that the catalytic activity of Bi-Bi2O3-BiOBr depends on the molar ratio of Bi(NO3)3 to KBr, but is higher than that of pure Bi2O3 and BiOBr. The 2∶1-Bi-Bi2O3-BiOBr prepared with a molar ratio of Bi(NO3)3 to KBr of 2∶1 exhibited the best photocatalytic activity towards MB. 2∶1-Bi-Bi2O3-BiOBr was irradiated with visible light for 240 min. The removal rate of MB on Bi-Bi2O3-BiOBr is 95.07%, and the degradation kinetics conform to pseudo-first-order kinetics. The degradation rate constant is 2.90 h−1, which is 5 and 6 times that of pure Bi2O3 and BiOBr, respectively. After 4 cycles of experiments, 2∶1-Bi-Bi2O3-BiOBr composite does't significantly reduce the removal efficiency of MB. The excellent visible-light photocatalytic activity of this material can be attributed to the three synergistic effects of SPR effect, semiconductor heterojunction structure and oxygen vacancies. The method for synthesizing photocatalysts with special structures in this paper can be extended to other catalytic materials.
Preparation of composite polyacrylonitrile - nano silver electrospun fiber membrane and its application in controlling microbial deterioration of grotto cultural heritage
HU Yulan, DU Binbin, PAN Liwei, DU Haowei, ZHANG Bingjian, WANG Bowen
2023, 40(7): 3986-3997. doi: 10.13801/j.cnki.fhclxb.20221031.001
Using electrospinning technology to compound antibacterial active ingredients with matrix fibers is seen as an effective means to develop new antibacterial materials. To develop new microbial deterioration control materials for grotto cultural heritage, composite polyacrylonitrile (PAN)-nano silver (AgNPs) electrospun fiber membrane was developed by electrospinning technology. The antibacterial effects of the fiber were further evaluated. Spinning stock solution containing silver particles was prepared by PAN mixing with dimethylformamide, adding silver nitrate and tea polyphenols. Then, the nano fiber membrane containing silver particles was prepared by electrostatic spinning technology. By changing the concentration and reaction temperature of PAN, the physical and chemical properties of electrospun fiber membrane, screening the optimal preparation process of electrospun fiber membrane suitable for the prevention and control of grotto cultural heritage microbial deterioration, the antibacterial effect of fibers was verified in the laboratory and outdoors respectively. The results show that the composite fiber membrane prepared with 12wt% PAN content at 80℃ has the advantages of good fiber mechanical properties and high concentration of silver particles, which is the optimal preparation condition of composite PAN-AgNPs electrospun fiber membrane screened in this study. Silver composite nanofiber material has antibacterial effect on Aspergillus niger and Penicillium ap., two microorganisms related to the deterioration of grotto cultural heritage. Significant antibacterial effect under outdoor rock surface conditions has been detected. These results indicate that the composite PAN-AgNPs electrospun fiber membrane prepared in this study has application value for the control of grotto cultural heritage deterioration.
Preparation and properties of polyvinyl alcohol-carbon black/hollow sphere foam sound absorption composites
ZHOU Xiao, ZHANG Liangmiao, WANG Li, GAO Yanfeng
2023, 40(7): 3998-4007. doi: 10.13801/j.cnki.fhclxb.20221102.002
Noise pollution greatly affects human mental and physical health. Porous sound absorption materials usually perform well in middle and high frequency bands, but improvement still needs in low frequency bands. In this work, hollow sphere foam matrix were prepared with fly-ash hollow sphere and sodium silicate as the raw materials firstly. Subsequently, flexible polyvinyl alcohol-carbon black (PVA-C) composite was introduced into the porous matrix through vacuum impregnation and ordinary heat drying or freeze drying process to obtain PVA-C/hollow sphere foam composites. The results show that the compressive strength of the obtained porous composite is more than 1.65 MPa. The sound absorption performance is improved by 35.2% in the range of 100-1000 Hz, compared with the hollow sphere foam matrix. The noise reduction coefficient reaches 0.523, which is increased by 10.1%. The results of the study provide a basis for the improvement of sound absorption performance and practical application of porous sound absorbing materials.
Preparation of glass microspheres/aluminum matrix syntactic foam and its quasi-static compressive characteristic and energy absorption
LIN Yingfei, SHIL'KO Serge, ZHANG Qiang, LU Jianning, FENG Xiaowei, TIAN Zhuo, YIN Cuicui, FENG Bo
2023, 40(7): 4008-4021. doi: 10.13801/j.cnki.fhclxb.20221116.001
Aluminum matrix syntactic foams are a novel class of cellular materials synthesized by hollow particles and aluminum matrix, which exhibit lightweight and high energy-absorbing capacity. In this study, the glass microspheres/aluminum matrix syntactic foams were prepared by the spark plasma sintering (SPS) method. The effects of the content and size of microspheres on the quasi-static compressive deformation behavior and energy absorption properties of the syntactic foams were analyzed by optical microscope (OM), SEM, quasi-static compression in situ observation, and digital image correlation (DIC) characterization. The results show that the microspheres of aluminum matrix syntactic foams prepared by two-step heating SPS sintering are uniformly embedded in the aluminum matrix, while the aluminum matrix is completely fused with high densification. With the increase of the microsphere content, the compressive stress of the syntactic foam decreases as a whole, meanwhile, the yield plateau expands and changes from smooth to zigzag. In addition, the compressive deformation behavior gradually develops from a relatively uniform drum-shaped deformation to brittle shear. The energy absorption capacity of the syntactic foam with the volume fraction of 50vol% is 23.6 J·cm−3, which is higher than that with the volume fraction of 30vol% and 70vol%. There is an optimal correspondence between the energy absorption capacity and the microsphere content of the syntactic foam. Small-sized microspheres have better compressive resistance. With the increase of the small-sized microsphere proportion, the syntactic foams can withstand higher stress and strain concentration on the microscopic level, as a result, the compressive strain of shear deformation increases on the macro level. In this study, the peak stress and energy absorption capacity of the syntactic foam with small-sized microspheres are 89.4 MPa and 29.0 J·cm−3, which are 23.5% and 22.9% higher than those of the syntactic foam with large-sized microsphere, respectively.
Piezoelectric/triboelectric nanogenerator based on PVDF/SBS flexible composite fiber film
LIU Jingyan, CHEN Zihang, JIANG Qiheng, XIONG Juan
2023, 40(7): 4022-4029. doi: 10.13801/j.cnki.fhclxb.20220915.007
Piezoelectric nanogenerators and friction nanogenerators can convert irregular mechanical energy into electrical energy which have the potential to provide independent and continuous power supply for low-power wearable electronic devices. Combining two kinds nanogenerators can integrate the advantages of their electrical output characteristics and improve the performance of nanogenerators. In this paper, polyvinyl fluoride (PVDF) and styrene butadiene styrene block copolymer (SBS) were selected as positive and negative friction materials, respectively. The PVDF/SBS composite fiber films were prepared by electrospinning and were employed to build a piezoelectric/triboelectric nanogenerator. The results show that when the amount of PVDF is 20wt%, the maximum open circuit voltage and short circuit current of the PVDF/SBS piezoelectric/triboelectric nanogenerator can reach 108 V and 0.34 μA, which are 5 and 6 times that of neat SBS sample, respectively. When the devices were fixed on the palm and sole of the shoe, output voltage signal with different amplitude can be obtained by collecting the mechanical energy of human motion, including clapping, walking and running. 64 commercial blue LED beads were lit up when the device were beaten by palm. The device can also detect the instantaneous pressure and the maximum sensitivity can reach 3.685 V·N−1. The experimental results show that PVDF/SBS piezoelectric/triboelectric nanogenerator exhibits a good application prospect in the fields of sensor monitoring and self-energy supply of electronic devices.
Preparation and research of high capacity/high cycle stability porous waste cotton carbon cloth electrode
WANG Tao, XIA Zhaopeng, ZHANG Huirong, PAN Jiajun, WU Liwei, LIU Xiaochen, LI Jiaxin
2023, 40(7): 4030-4038. doi: 10.13801/j.cnki.fhclxb.20220926.001
With the improvement of productivity level, a large number of waste textiles have been produced. The traditional incineration and burial treatment methods for waste textiles not only cause waste of resources but also generate a lot of pollution. In order to make waste cotton have higher added value, activated carbon is prepared by carbonization technology, which makes it have great application value in the field of soil pollution control, medicine, and energy storage. However, the prepared carbon material has disadvantages such as small specific surface area, low capacity, and poor wettability at the interface with the electrolyte. In this paper, Zn2+ and NO3 ions were first introduced into the waste cotton fabrics, and the hollow porous carbon cloth with a high specific surface area was prepared by adjusting the concentration of Zn2+ and NO3 ions and utilizing impregnation-drying-carbonization technology. The results show that Zn(NO3)2 has an excellent pore-forming ability, and a hollow carbon cloth with a multi-scale pore structure of micropores, mesopores, and macropores is obtained. The specific surface area is as high as 1257.07 m2·g−1, and the interfacial wettability is excellent. The prepared hollow porous carbon cloth electrode has a specific capacitance up to 251.5 F·g−1 and the capacity retention rate of 100% after 5000 cycles, showing a broad application prospect in the field of energy storage.
Preparation and properties of triple shape memory composites based on trans-polyisopren/poly(ethylene-co-vinyl acetate)
XIN Hua, LI Yangfan, PENG Qi, CHEN Yue, LI Xinqi
2023, 40(7): 4039-4047. doi: 10.13801/j.cnki.fhclxb.20221021.002
The TPI-EVA triple shape memory composites were prepared by compounding trans-polyisoprene and poly(ethylene-co-vinyl acetate) (TPI-EVA), and designed cross-linking reaction of dicumyl peroxide to connect the two phases. The TPI-EVA composites were characterized by rheometer, universal testing machine, XRD, DSC and dynamic thermomechanical analyzer (DMA). The effects of the mass ratio of EVA on the mechanical properties, phase structure, crystalline properties and triple shape memory properties of TPI-EVA composites were studied. The results show that with the increase of the mass ratio of EVA, the crystallization temperature (Tc) of TPI decreases from 14.7℃ to 8.2℃, and the Tc of EVA increase slightly. SEM test showed that with the increases of EVA mass ratio, the phase interface of the composites changes from smooth to rough; DMA test shows that the increase of EVA mass ratio increases the first temporary shape memory fixation rate of the samples from 57.6% to 88.5%. Moreover, the TPI-EVA composites exhibit excellent mechanical properties, the tensile strength is as high as 30.3 MPa and the elongation at break reaches 490%.
Adsorption behaviors of magnetic nitrogen-doped graphene-modified persimmon tannins for tetracycline
LIU Songlin, WANG Zhongmin, QIAN Xi, WANG Tong, RAN Zhaojin, HUANG Zhimin, WU Chenxi, LI Guiyin
2023, 40(7): 4048-4059. doi: 10.13801/j.cnki.fhclxb.20221021.001
Tetracycline (TC), as a broad-spectrum class of antibiotics, is used in large quantities in the farming industry and has caused serious water pollution due to its characteristics of not being easily degraded naturally. In this paper, a magnetic composite Fe3O4-NG/PT was produced by hydrothermal method, persimmon tannin (PT) was as the matrix, and modified by nitrogen-doped graphene (NG), Fe3O4 was as a magnetic filler. The application of the composite in TC adsorption was also investigated. NG with its hydrophobicity and the large specific surface area made up for the lack of persistent tannin in adsorption, and Fe3O4 solved the problem of difficult recovery of adsorbent. The mechanism was shown by SEM, chemisorption was dominant. The adsorption isotherm is consistent with the Freundlich model, indicating that it is multilayer adsorption. The maximum capacity of adsorption at 318 K reaches 315.65 mg/g, and the adsorption efficiency reaches 94.5%. The Fe3O4-NG/PT composites have the advantages of large specific surface area, high porosity, and phenolic hydroxyl groups, which will broaden their application fields.
Effect of flux agents on properties of ceramifiable flame retardant room temperature vulcanized silicone rubber foam
SHANG Ke, LIN Guide, JIANG Huijing, JIN Xing, ZHAO Bi, WANG Junsheng
2023, 40(7): 4060-4071. doi: 10.13801/j.cnki.fhclxb.20220915.005
In order to improve the flame retardancy and fire resistance of room temperature vulcanized (RTV) silicone rubber foam, glass powder and zinc borate as flux agent, and mica powder as refractory filler were used to prepare ceramifiable flame retardant RTV silicone rubber foam. The effects of different types and proportions of inorganic fillers on the micromorphology, thermal stability, flame retardancy and combustion behavior of the silicone rubber foam, as well as the ceramifiable behavior of the silicone rubber foam after ablation at different temperatures were studied. The results show that the introduction of glass powder affects the foaming process of the silicone rubber foam, forming a foam structure with large pore size, which is not conducive to the improvement of the flame retardancy, thermal stability and fire safety performances of the silicone rubber foam. But, glass power can remarkably decrease ceramization temperature of the silicone rubber foam. The introduction of zinc borate greatly improves the flame retardancy, thermal stability in high temperature zone and fire safety performances of the silicone rubber foam. Meanwhile, zinc borate and mica powder show good synergistic flame retardant effect. limiting oxygen index (LOI) value of the silicone rubber foam can reach to 33.2, and it can pass the vertical combustion FV-0 level. Carbon residue of the silicone rubber foam at 900℃ can reach up to 75.9% in thermogravimetric analysis in N2 atmosphere. The heat release, smoke release of the silicone rubber foam and the mass loss after the ablation experiment are significantly reduced. In addition, zinc borate also contributes to the formation of ceramic carbon residue.
Preparation and upconversion luminescence properties of SiO2@Gd2O3:Yb3+, Ln3+ (Ln=Er, Tm, Ho) core-shell microspheres
CHEN Jie, WANG Chao, YIN Yu, LIU Rong, ZENG Xiaodan, LIU Zhigang
2023, 40(7): 4072-4081. doi: 10.13801/j.cnki.fhclxb.20220919.001
In order to solve the problem of high price and poor size controllability of rare earth doped upconversion luminescent materials, spherical SiO2@Gd2O3:Yb3+, Ln3+ (Ln=Er, Tm, Ho) core-shell upconversion luminescent materials were successfully synthesized by simple chemical precipitation method using low cost and easy to prepare SiO2 microspheres as cores and uniformly coated with Gd2O3:Yb3+, Ln3+ (Ln=Er, Tm, Ho) shells. XRD results show that the SiO2@Gd(OH)CO3:Yb3+, Ln3+ precursor is firstly obtained by the reaction of urea with rare earth ions, then the Gd(OH)CO3:Yb3+, Ln3+ shell is further transformed into cubic phase Gd2O3:Yb3+, Ln3+ with good crystallinity after calcination at 800℃. SEM and size distribution images show that the prepared samples are ideal core-shell microspheres with uniform size, and the average diameter is about 580 nm. Under the excitation of 980 nm, SiO2@Gd2O3:Yb3+, Ln3+ (Ln=Er, Tm, Ho) core-shell microspheres exhibit red, blue and green emissions respectively, corresponding to the 4F9/24I15/2 transition of Er3+, the 1G43H6 transition of Tm3+, and the 5S25I8 transition of Ho3+, which are consistent with the luminescence color region of chromaticity color coordinates, indicating that three color upconversion luminescence is successfully achieved by simply adjusting the doped rare-earth ion species in the shell of SiO2@Gd2O3:Yb3+, Ln3+ core-shell microspheres.
Preparation and enduring effect oil-water separation performance of water-based superhydrophilic anti-fouling composite mesh membrane
WANG Ronghui, CHEN Junxu, YU Zhaopeng, YU Xinquan, ZHANG Youfa
2023, 40(7): 4082-4094. doi: 10.13801/j.cnki.fhclxb.20230215.001
Oily sewage is ubiquitous in the petrochemical industry, machinery manufacturing and other fields. Direct discharge not only wastes water and oil resources, pollutes the ecological environment, but also affects the survival and health of human beings and other organisms. The traditional oil-water separation method has strong limitations, such as poor economy and low separation efficiency. Based on 316 stainless mesh, a superhydrophilic/underwater oleophobic membrane that was resistant to long-term water immersion and oil pollution was developed. The water-based acrylic acid resin and water-based epoxy topcoat resin were selected as the binder, and the substrate was pretreated with phytic acid. The superhydrophilic/underwater oleophobic membrane coated with water-based coating was prepared using a one-step spraying method. It is found that the separation efficiency of wastewater with different oils can reach more than 98%, the water flux can reach more than 14000 L/(m2·h·bar), and the intrusion pressure of oil is 4.65 kPa. After 50 cycles of separating wastewater with N-hexane, the separation efficiency of the membrane can still reach more than 98%. After 180 days of water immersion, the membrane still maintains superhydrophilicity with a water flux of more than 6500 L/(m2·h·bar). After adding a small amount of surfactant of sodium dodecyl sulfate, the water flux of the membrane decreases by less than 50% after 50 pollution and cleaning cycles. This study provides technical references for the development and preparation of superhydrophilic separation membranes in the field of refined oily wastewater treatment.
Civil Construction Composite
Microwave deicing characteristics and durability of magnetite aggregate concrete
WANG Zhihang, BAI Erlei, YAN Ping, HUANG He, LIU Junliang, WANG Yuxian
2023, 40(7): 4095-4106. doi: 10.13801/j.cnki.fhclxb.20220915.008
In order to improve the microwave deicing efficiency of cement concrete without reducing its service life, the magnetite gravel was used as the microwave absorbing aggregate to prepare 6 kinds of concrete with different magnetite aggregate contents. And the effect of magnetite aggregate on microwave deicing efficiency and durability of concrete was studied. The results show that the magnetite aggregate improves the microwave deicing properties of concrete by increasing its dielectric loss and magnetic loss to microwave. With the increase of magnetite aggregate content, the complex dielectric constant, the complex magnetic permeability, the dielectric loss and the magnetic loss of concrete increase, the time required for the surface of concrete specimen to reach 0℃ decreases, and the temperature rise rate and the deicing effect increase. Magnetite aggregate enhances the abrasion resistance and compressive strength of concrete by improving its compactness, and enhances the frost resistance of concrete by improving its ability to resist crack development. With the increase of magnetite aggregate content, the abrasion mass and abrasion loss per unit area of concrete decrease. And after freeze-thaw cycles, with the increase of magnetite aggregate content, the mass loss rate and compressive strength loss rate of concrete decrease, and the relative dynamic elastic modulus increases. Magnetite aggregate concrete has both good microwave deicing properties and durability.
Composite shear mechanical properties of carbon fiber recycled aggregate concrete
CHEN Yuliang, LI Tang, JIANG Rui, XU Hongfei
2023, 40(7): 4107-4116. doi: 10.13801/j.cnki.fhclxb.20221011.001
To study the mechanical properties of carbon fiber recycled aggregate concrete under composite shear condition, the composite shear test of 102 cube specimens was completed with recycled coarse aggregate replacement rate, compressive stress ratio and carbon fiber content as test parameters. The failure mode of carbon fiber reinforced recycled concrete specimens was observed, and the load-displacement curve under shear state was obtained. The effects of three kinds of change parameters on the shear strength, peak displacement, and damage evolution law of specimens were analyzed. The research shows that the compressive stress ratio has a significant indigenous effect on the failure mode of the carbon fiber reinforced recycled concrete specimen, and the number and angle of cracks increase with the increase of the compressive stress ratio. 0.3vol% content of carbon fiber can improve the shear strength of the specimen by about 12%. When the compressive stress ratio increases from 0 to 0.09 and 0.18, the shear strength of the specimen is 2.34 and 3.25 times that of the specimen, respectively. The recycled coarse aggregate replacement rate has little effect on the peak shear strength. Increasing the compression stress ratio can effectively slow down the development of damage, and the adopted damage constitutive can better reflect the shear-displacement relationship of composite shear.
Characterization of pore structure of foamed concrete and its influence on performance
YUAN Zhiying, CHEN Bo, CHEN Jialin, GAO Zhihan
2023, 40(7): 4117-4127. doi: 10.13801/j.cnki.fhclxb.20221014.001
In order to study the pore structure of foamed concrete and its influence on mechanical properties, the pore structures of three density grades of foamed concrete were tested by X-ray computed tomography (X-CT) technology, and the quantitative characterization of characteristic parameters such as porosity, pore size distribution and pore shape was realized. Based on the grey correlation theory, the correlation degree between different pore structure characteristic parameters and their mechanical properties was analyzed. The results show that the pore size distribution of foamed concrete conforms to the non-standard lognormal distribution, and the pore sphericity has a unimodal distribution, and there is a significant negative correlation between pore volume and pore size. There are obvious differences in the porosity distribution of different densities of foamed concrete in different directions. With the increase of the foamed concrete density, the fractal dimension, median size and median area of pores gradually decrease, and the overall pore sphericity gradually increases. The mechanical properties of foamed concrete are closely related to the pore structure, of which the porosity has the most obvious influence on the strength of foamed concrete, and the grey correlation degree reaches 0.859. The pore size closely related to the strength of foamed concrete is mainly distributed in the range of 100-200 μm, 200-300 μm, and the grey correlation degrees are 0.832 and 0.847 respectively. The closer the pore shape is to spherical shape, the stronger its compressive capacity.
Direct shear mechanical properties and damage evolution of coral seawater sea-sand concrete after high temperature
CHEN Yuliang, LIU Zhihua, YE Peihuan, CHEN Zongping
2023, 40(7): 4128-4138. doi: 10.13801/j.cnki.fhclxb.20221024.002
In order to explore the direct shear mechanical properties and constitutive relationship of coral seawater sea-sand concrete (CSSC) after high temperature, the direct shear test of CSSC after high temperature was designed and completed with maximum high temperature T and constant temperature duration H as changing parameters. The failure mode and stress-displacement curve of CSSC under direct shear were observed, and the effects of T and H on the shear strength, volume expansion and mass loss of CSSC were obtained. Then the damage evolution process of CSSC after high temperature was analyzed and compared. The results show that the high temperature leads to non-uniform temperature fields, surface cracks and corner cracks in CSSC. With the increase of T and H, the shear strength of CSSC decreases gradually while the volume expansion rate and the mass loss rate gradually increase. When T > 400℃, the decrease rate of shear strength accelerates. When T = 800℃, the direct shear strength of CSSC is only 39% of that at room temperature. Finally, the direct shear strength calculation equation of CSSC after high temperature and its damage constitutive model are proposed.
Biological and Nano-composite
Effect of pentaerythritol tetrakis[3-(3, 5-di-tert-butyl-4-hydroxyphenyl)propionate] on mechanical properties and thermal stability of hemp straw powder/polylactic acid wood-plastic composite
LI Yonggang, WU Huawei, WANG Chunhong, WANG Ni
2023, 40(7): 4139-4148. doi: 10.13801/j.cnki.fhclxb.20221013.001
In order to solve the problem of poor mechanical properties and thermal stability of hemp straw powder reinforced polylactic acid composite (HPRPC), Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (PTP) was used to modify HPRPC. The modification mechanism of HPRPC by PTP was investigated by FTIR, mechanical properties analysis, SEM, TG and defect analysis. The results show that PTP enhances the interface compatibility of hemp straw powder (HP) and polylactic acid (PLA), and improves the interfacial properties. When the mass fraction of PTP is 0.6wt%, HPRPC has the best mechanical properties, thermal stability and defects condition. Compared with the untreated composite, the tensile strength and flexural strength of the treated HPRPC are increased by 38.08% and 45.24%, respectively. The mechanical property is significantly improved. And the initial decomposition temperature and maximum weight loss rate temperature are increased by 12.9℃ and 16.8℃, respectively. The thermal stability is improved. And the water absorption rate and the thickness swelling rate of HPRPC are optimized. The water absorption rate of treated HPRPC keeps about 50% of that of the untreated HPRPC. The increase of the thickness swelling rate slows down significantly, and the thickness swelling rate is only 2.11% at 96 h, the defects condition is obviously improved.
Preparation and properties of POSS/sodium polyacrylate conductive composite hydrogels with high stretchability, self-healable and self-adhesive properties
ZHANG Xiaojing, LIU Bo, SHEN Weiwei, WEI Wangchong, FENG Wenbo, FAN Kaiqi
2023, 40(7): 4149-4163. doi: 10.13801/j.cnki.fhclxb.20220930.002
Conductive hydrogels have great potential applications in flexible wearable devices, electronic skin and biological electrodes. However, the complex and changing application scenarios put forward higher requirements on the stretchability, self-healable, self-adhesive and biocompatibility of conductive hydrogels. In this paper, a conductive composite hydrogel (OCAPS/PAA-Na) with high extensibility, self-healable, self-adhesive and excellent biocompatibility was designed by the non-covalent cross-linking between a water-soluble polyhedral oligomeric silsesquioxane (POSS) and sodium polyacrylate (PAA-Na). The elongation at break of OCAPS/PAA-Na hydrogel is 2537.0%-4056.1%. The addition of POSS improves the mechanical properties of hydrogels: The tensile strength increases from 10.5 kPa to 23.8 kPa; The tensile modulus increases from 7.1 kPa to 27.8 kPa; The fracture energy increases from 3.7 kJ·m−2 to 6.8 kJ·m−2. OCAPS/PAA-Na hydrogel has excellent self-healable property, and the self-healable efficiency is up to 97.8%. The hydrogel shows good adhesion to both organic and inorganic materials, with the highest adhesive strength of 19.6 kPa and 18.2 kPa, respectively. Cytotoxicity test and hemolysis test show that the hydrogel has excellent biocompatibility. The conductivity of the hydrogel increases from 0.165 to 0.290 S·m−1 with NaCl crystals is generated in situ during the preparation. OCAPS/PAA-Na hydrogel can be used as a strain resistance sensor material to accurately detect some subtle human actions and the gauge factor value can reach 5.17, which has a good application prospect in the field of flexible intelligent wearable devices and electronic skin.
Sepiolite reinforced carbon foam composite toward phase change energy storage material and its light-thermal-electric conversion performance
ZHUO Zuyou, SONG Shengnan, SHEN Yongkang, CHEN Yandan
2023, 40(7): 4164-4172. doi: 10.13801/j.cnki.fhclxb.20220916.001
Polyethylene glycol (PEG) is an excellent phase change material with high phase change enthalpy, biodegradability, non toxicity and corrosion resistance. However, the easy leakage and poor thermal conductivity hinder its large-scale application. Therefore, with wheat flour as the matrix, a biomass carbon foam composite SCF-X-Y reinforced by sepiolite, where X represents the amount of sepiolite added and Y represents the carbonization temperature) was prepared as the efficient carrier of PEG phase change material by using microbial foaming and high temperature carbonization technology. The experimental results show that the compressive strength of SCF-10-800 can reach 5.42 MPa. The thermal conductivity of SCF-5-1000@PEG reaches 0.39 W/(m·K), and its melting enthalpy and solidification enthalpy are 123.4 J·g−1 and 106.6 J·g−1, respectively. Meanwhile, it has excellent leakage resistance. Using SCF-5-1000@PEG as an optical absorption source, a light driven thermoelectric conversion system was assembled, which showed a light to heat conversion efficiency of 63.2% and could achieve a stable current output for more than 400 s, demonstrating its application potential in the light-thermal-electric energy conversion system.
Metal and Ceramic Matrix Composite
Effect of multi-element alloy-carbide bonding phase on the microstructure of diamond composites
QIU Tianxu, ZHANG Wei, LIU Yong
2023, 40(7): 4173-4183. doi: 10.13801/j.cnki.fhclxb.20221014.006
Diamond composites are widely used in processing, drilling and other fields, and improving the bonding strength of the diamond skeleton is an important research direction. In this work, Co50Ni40Fe10 multi-element alloy-carbide was used as the binder instead of Co to prepare diamond composites under high temperature and high pressure, and the influence of multi-element alloys and carbides on the microstructure of composites was studied by experiments and thermodynamic calculations. The results show that, compared with Co, Co50Ni40Fe10 multi-element alloy has stronger ability to promote the migration and diffusion of C atoms, which can accelerate the formation of diamond skeleton. Under the condition of high temperature and high pressure, the carbon content in WC increased slightly, which has little effect on the formation of diamond skeleton; TiC lost C slightly, which can promote the formation of diamond skeleton to a certain extent; The C produced by Cr3C2 decomposition can promote the formation of diamond skeleton.
Mechanical properties and damage of 2.5D braided SiCf/SiC ceramic matrix composites under different thermal shock conditions
DUAN Hongyu, WANG Hequan, ZHANG Jiaping, ZHENG Wei, CHEN Jing
2023, 40(7): 4184-4194. doi: 10.13801/j.cnki.fhclxb.20221011.002
The effects of different thermal shock conditions (times) on the mechanical properties and damage of 2.5D braided SiCf/SiC (f represents fiber) ceramic matrix composites (CMCs) were analyzed by uniaxial tensile and three-point bending experiments, combined with SEM and EDS. The results show that the tensile stress-strain curves of 2.5D braided SiCf/SiC CMCs exhibit nonlinear changes at room temperature without thermal shock and under different thermal shock conditions at 1200℃. The tensile strength first decreases gradually, and then increases slightly. The tensile strength of the material decreases to 48.39% under 10 thermal shocks, and increases to 54.11% after 30 thermal shocks; The three-point bending displacement-load curves of the material without thermal shock at room temperature and under different thermal shock conditions at 1200℃ also show nonlinear changes, with the increase of the number of thermal shocks, the flexural strength decreases rapidly, the bending strength of the material rapidly drops to 26.06% under 10 thermal shocks, and decreases to 10.77% after 30 thermal shocks. From the macroscopic fracture analysis, it can be seen that the tensile and bending fractures of the material at room temperature without thermal shock show pseudo-brittle fracture characteristics, while the tensile and bending fractures show ductile fracture characteristics under thermal shock conditions. From the microscopic fracture, damage behaviors such as fiber pullout, fiber debonding, interface debonding, crack propagation and fiber fracture are observed, and with the increase of the number of thermal shocks, the interface bonding force is gradually weakened, and the above-mentioned damage behaviors increase significantly.
Composite Micro-mechanics
Numerical simulation and influence factors analysis of cure-induced distortions in resin matrix composites with variable thickness
GAN Jianye, HU Weiye, ZHANG Yicheng, CHU Qiyi, HAO Xiaozhong
2023, 40(7): 4195-4209. doi: 10.13801/j.cnki.fhclxb.20220922.001
The carbon fiber reinforced polymer (CFRP) composite parts with variable thickness possessed the advantages of material saving, weight reduction, and elastic tailoring properties, and were often used in important application such as wing structures. However, dropping-off plies between layers caused a discontinuity inside the part. Therefore, uneven residual stress could be generated after the curing, and the complex cure-induced distortion (CID) appeared after demolding. For the prediction of the CID of CFRP parts with variable thickness, the existing research mainly adopted the modeling method of equivalent material parameters, without considering the structural characteristics of the resin pocket. In this paper, based on the laminated modeling method, the resin pocket structure was introduced at the dropping-off plies position, and the numerical simulation model of the CID was established. Compared with the results of the traditional equivalent modeling method, the traditional laminated modeling method and experiment, it is proved that the proposed model has the preferable accuracy, the error of the simulated CID is only 1.01×10−2 mm compared with the experimental result, and the deformation trend is consistent. The influence of different ply drop-off patterns, taper section slopes, and thickness-to-thin ratios on the CID was analyzed. The part with a dispersed ply drop-off pattern presents the smallest CID, and the part with the overlapped ply drop-off pattern has the largest CID. Increasing the taper section slope and reducing the thickness ratio can effectively reduce the warpage.
Statistical distribution pattern of strength and microstructural damage analysis of unidirectional fiber bundle SiC/SiC composites
ZHANG Chen, SUN Guodong, LEI Bao, LI Xuqin, ZHANG Qing, MENG Zhixin, GAO Xiangyun
2023, 40(7): 4210-4225. doi: 10.13801/j.cnki.fhclxb.20230217.004
The discrete mechanical properties of SiC/SiC composites originate from their structural units and microstructural features. In this paper, for the unidirectional fiber bundle SiC/SiC composites with the simplest structure, the strength distribution pattern was analyzed by the two-parameter Weibull distribution and the median estimated distribution, and the discrete nature was revealed based on the deep learning of the microstructure of each group element (matrix, interface phase, and fiber) of the composites. The results show that the tensile strengths of the unidirectional fiber bundle SiC/SiC prepared in the small and medium test furnaces are located at (331.02 MPa, 407.82 MPa) and (161.09 MPa, 540.95 MPa), respectively. The former Weibull modulus (20.59) is 75.7% higher than the latter (5.01), indicating an increase in the dispersion of the medium test. The results of deep learning of fracture morphology show that matrix cracking, interface deflection and fiber fracture pullout are the main failure mechanisms, and due to the distribution of matrix crack spacing at (83.2 μm, 107.8 μm), the calculation by the micromechanical equation indicates that matrix nonuniformity is the main reason affecting the reliability of the composites.
Low-velocity impact of functional gradient honeycomb sandwich plate with CFRP face sheets
FU Shanshan, CHEN Dong, SHI Jianwei, LI Cheng
2023, 40(7): 4226-4236. doi: 10.13801/j.cnki.fhclxb.20221014.007
The impact process and resistance capability of honeycomb plate with carbon fiber reinforced polymer (CFRP) face sheets were studied by using finite element model (FEM), and the FEM was verified by comparing with impact experiment. The density gradient was introduced into the traditional honeycomb structure by changing the wall thickness and the protection characteristics of functional gradient (FG) honeycomb sandwich plate under low-velocity impact (LVI) were simulated under different impact energies and gradient coefficients α. The energy absorption characteristics of the FG and the traditional sandwich plate were compared through FEM. The results show that, under low impact energy, the honeycomb sandwich plate with α>1 has better energy absorption. With the increase of impact energy, the core with absorbing energy advantages changes gradually from α>1 to α<1, when the whole sandwich plate is penetrated, the sandwich plate with α<1 has better energy absorption characteristics. Under the impact energy of 20 J, 50 J and 100 J, the energy absorptions of functional gradient sandwich plates are 7.54%, 5.33% and 8.65% higher than that of traditional sandwich plates with the same mass.
Atomic scale characterization of interfacial properties of polymer/metal composites
HU Linhui, DUAN Mingzheng, WANG Shuai, LIANG Lihong
2023, 40(7): 4237-4245. doi: 10.13801/j.cnki.fhclxb.20220927.001
The interfacial properties of polymer/metal significantly affect the mechanical properties of composites formed by metal and polymer. Combined with thermodynamic theoretical analysis and molecular dynamics simulation, the interface fracture energy and interface strength of the interface formed by several typical polymers (Polypropylene (PP), polyethylene (PE), polystyrene (PS)) and metals (Al, Ni, Cu, Fe) were systematically calculated. With the increase of interface displacement, the interface stress of polymer/metal interface first increases, then reaches the strength and enters the interface damage stage, and the interface stress decreases until the interface is completely broken, and the stress decreases to zero. The strength change trend of different polymer/metal interfaces is consistent with the interface fracture energy, and the simulation results of interface fracture energy are basically consistent with the theoretical calculation results. The interface fracture energy of polymer/metal interface is related to the surface energy of metal. As the surface energy of metal decreases with the order of Ni, Fe, Cu and Al, the interface fracture energy of polymer/metal interface also decreases with the order of polymer/Ni, polymer/Fe, polymer/Cu and polymer/Al. Under the same metal condition, the interface strength of PE/metal and PP/metal is similar, and both are smaller than that of PS/metal. Furthermore, the interface damage was characterized by the free volume evolution of the polymer. The research results provide a basis for material selection, design and application of polymer/metal composites.
Thermal properties of phase change thermal storage foam concrete
YIN Guansheng, ZHANG Jintao, SHI Minghui, CHEN Wenbo, ZHENG Xiaohai, WEI Pengfei, FENG Junjie, ZHENG Biyu
2023, 40(7): 4246-4259. doi: 10.13801/j.cnki.fhclxb.20221024.005
In order to seek building materials with energy-saving effect, a phase change thermal storage foam concrete with thermal storage and temperature regulation capabilities was prepared by means of experimental design and numerical simulation. Its dry density grade is 700 kg/m3, the content of shaped composite phase change material accounted for 0%, 3%, 6%, 9%, 12% and 15% of the mass of the cementitious material, respectively. The influence of shaped composite phase change materials on the dry density, compressive strength and thermal properties of foam concrete was explored, and the finite element software ABAQUS was used to establish the wall model of phase change thermal storage foam concrete, and the heat storage and temperature regulating performance of phase change thermal storage foam concrete wall was studied. The experiment results show that the dry density, compressive strength and thermal conductivity of the phase change thermal storage foam concrete gradually decrease with the increase of the content of the shaped composite phase change material. When the content of the shaped composite phase change material is 15%, the dry density, compressive strength and thermal conductivity reach the minimum values, which are 661 kg/m3, 2.18 MPa and 0.144 W/(m·K), respectively. With the increase of the content of shaped composite phase change material, the phase change temperature, phase change latent heat and specific heat capacity of foam concrete also increase. When the content of shaped composite phase change material is 15%, the phase change temperature is 24.83℃, the phase change latent heat is 12.320 J/g, and the specific heat capacity is 1462 J/(kg·℃). The finite element simulation results show that when the content of the shaped composite phase change material is 15%, the temperature fluctuation range of the inner surface of the phase change thermal storage foam concrete wall is 25.37-26.57℃, and the maximum temperature difference is 1.20℃, which is 0.46℃ lower than that of pure foam concrete, the time to the highest temperature is delayed by 1.83 h, and the time to reach the lowest temperature is delayed by 1.16 h compared with the pure foam concrete wall. When the phase change thermal storage foam concrete is arranged inside the wall, its thermal storage and temperature regulation effect are the best.
Cure-induced residual stresses assessment of composite materials based on machining deformation
LIU Xueshu, QIAO Renyong
2023, 40(7): 4260-4269. doi: 10.13801/j.cnki.fhclxb.20220922.002
Cure-induced residual stresses are usually unavoidable due to anisotropic properties of composite materials, which have great influence on following machining and assembly process. Therefore, it is necessary to understand the distribution of cure-induced residual stresses in the materials for high performance composite part manufacturing. The traditional slitting method used for residual stresses assessment was analyzed and deformations caused by the slitting process were divided into two groups. One was caused by the release of cure-induced residual stresses and the other was by gravity. After the partial deformation caused by gravity being obtained by using finite element analysis, relationship between the remained deformation and the cure-induced residual stresses was set up by using bending deformation theory, which was used to evaluate the distribution of cure-induced residual stresses. Experimental results show that the proposed method can obtain the same distribution as that of the traditional slitting method and the difference may less than 14% when a proper measurement point is selected.
Effect of fit conditions on mechanical properties of C/SiC online riveting unit
TAN Zhiyong, WANG Jiebing, MENG Fanfu, LI Yanbin, QIAN Yixing, LIU Xiaochong
2023, 40(7): 4270-4281. doi: 10.13801/j.cnki.fhclxb.20220930.004
According to the on-line rivet connection forms widely used in chemical vapor infiltration (CVI) process 2D-C/SiC thermal structures and characteristics shown in ground tests, the effects of different forms of clearance or interference fit between rivets and flat openings on mechanical properties were studied. A typical test piece with rivets was prepared and the microscopic morphology was observed. Through rivet push-out test, the push-out static strength and fatigue rules under different matching conditions were obtained. By comparing the tensile static strength of the specimens with rivets and the specimens with holes under different matching conditions, the rule of in-plane strength performance degradation caused by C/SiC online riveting was obtained. The characteristics of fiber bundle deformation, hole edge pre-stress and local area damage of materials were analyzed, and numerical modeling calculation was carried out according to morphology observation. Then, an improved point stress failure criterion (PSC) considering the effect of stress concentration at the hole edge was proposed for C/SiC interference fit riveting. Research shows that interference fit can improve the connection reliability between rivet and hole, significantly improve the push-out static strength and fatigue strength of rivet. But the interference fit riveting process makes the local carbon fiber at the hole edge extrude and deform, which leads to the prestress at the hole edge.
Crack initiation and propagation mechanism during uniaxial compression of SiC/AZ91D magnesium matrix composites
LIANG Chaoqun, YAO Junping, LI Yiran, XIAO Peng
2023, 40(7): 4282-4293. doi: 10.13801/j.cnki.fhclxb.20220922.003
The crack initiation and propagation mechanism of SiC/AZ91D magnesium matrix composites with different shapes and volume fractions of SiC particles under uniaxial compression was investigated by using the finite element analysis software Abaqus to introduce a cohesive force element into the interface of the finite element model. The introduction of cohesive force element avoids the defects of prefabrication crack and singularity of crack tip in linear elasticity, and provides a new method to solve the problem of crack propagation. The results show that the compressive strengths of circular, original shape and square SiC/AZ91D magnesium matrix composites are 474.853 MPa, 435.783 MPa and 397.211 MPa, respectively. The time of crack initiation and fracture are 15.6 μs, 14.4 μs, 12.6 μs, 22.2 μs, 20.4 μs, 18 μs after loading, respectively. The crack propagation mechanism of circular particle composites is the crack propagation initiated by matrix damage, which leads to material fracture, while the crack propagation mechanism of square and original shape particle composites is the crack initiation at the junction of particle and matrix, and the primary crack and secondary crack are connected with each other, which lead to material fracture. The crack initiation and fracture time of SiC/AZ91D magnesium matrix composites with 10vol%, 15vol% and 20vol% original shape particles are 15.6 μs, 14.4 μs, 11.4 μs, 22.2 μs, 20.4 μs and 18 μs after loading, respectively. The crack propagation process of SiC/AZ91D magnesium matrix composites is accelerated with the increase of particle volume fraction.