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      20 October 2019, Volume 47 Issue 10 Previous Issue    Next Issue
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    Research progress in nickel-rich ternary materials for lithium-ion batteries
    Song-dong YUAN, Can-xing YANG, Guo-dong JIANG, Jian XIONG, Qing AI, Ren-zhong HUANG
    2019, 47 (10): 1-9.   DOI: 10.11868/j.issn.1001-4381.2018.001301
    Abstract ( 1474 ( PDF (1893KB)( 984 Citation

    Nickel-rich ternary materials for lithium ion batteries are the preferred cathode materials for automotive power batteries at present and in the future, due to their low cost, high energy density, high reversible capacity and environmental friendliness. On the basis of reviewing the crystal structure and electrochemical properties of nickel-rich ternary materials, the main preparation methods at home and abroad, modification methods such as doping, coating and others were introduced. Meanwhile, the effect of different kinds of coating materials on rate performance, cycling performance and good thermal stability of nickel-rich ternary was discussed in details. Finally, the issues about nickel-rich ternary electrolyte solution, safety, compaction density and cycle life were analyzed and prospected.

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    Research progress of piezoelectric nanogenerators and their hybrid devices
    Yao-hong TAN, Cheng-kun LIU, Xue MAO, Jia LIU
    2019, 47 (10): 10-21.   DOI: 10.11868/j.issn.1001-4381.2018.000665
    Abstract ( 901 ( PDF (6290KB)( 639 Citation

    The energy crisis and environmental pollution from excessive use of traditional fossil fuel have been prompting a number of researchers and institutes to develop new technology, emerging mat-erials, and potential applications for green, sustainable and renewable power source. There is a rich source of energy in the environment and therefore it is very promising to collect energy from the envir-onment. The mechanical energy can be transformed into electric energy when the piezoelectric material experiences mechanical deformation due to the transfer of internal electron. Therefore, as a potential sustainable, green energy source, piezoelectric nanogenerator has received extensive attention in rec-ent years. Some research achievements in recent years were reviewed in this paper, starting from the classification of piezoelectric materials and combining with their preparation methods, structure and properties. The effects of different preparation methods and structures on piezoelectric properties of piezoelectric nano-generators were evaluated in detail. The future development was also prospected.

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    Graphene oxide and its composites for adsorption of radionuclides in water
    Hong-juan LIU, Ren-jie WU, Shui-bo XIE, Ying-jiu LIU
    2019, 47 (10): 22-32.   DOI: 10.11868/j.issn.1001-4381.2018.001369
    Abstract ( 724 ( PDF (2858KB)( 265 Citation

    With the rapid development and application of nuclear energy and technology, a large number of radioactive wastewater was produced, which caused potential pollution to the ecological environment. The research on radioactive wastewater treatment is of great significance to environmental protection. Graphene oxide and its composites have attracted much attention in the field of radioactive wastewater treatment because of their high specific surface area, abundant functional groups, strong adsorption capacity and good chemical stability. Recent research status and progress on adsorption of radionuclides in water by graphene oxide and its composites were reviewed. The adsorption capacity, adsorption isothermal model, adsorption thermodynamics, influencing factors and adsorption mechanism of graphene oxide and its composites for radionuclides were introduced. In the end, the problems and challenges faced by the research on graphene oxide and its composites in the treatment of radionuclides in terms of radiation stability and high adsorption selectivity were analyzed. The key research directions for promoting the application of the graphene oxide and its composites in practical radioactive wastewater treatment projects in the future were discussed, such as the perfect industrial system and actively developing a set of matching water treatment processes and equipments.

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    Research progress in high-entropy alloy coatings by laser cladding
    Hai-chao ZHAO, Xiu-bing LIANG, Yu-lin QIAO, Jian LIU, Zhi-bin ZHANG, Yong-gang TONG
    2019, 47 (10): 33-43.   DOI: 10.11868/j.issn.1001-4381.2018.000998
    Abstract ( 1083 ( PDF (1119KB)( 671 Citation

    High-entropy alloy(HEA) coatings with high thermal stability and high temperature resistance of HEA coatings show a new attraction in the field of high temperature coating. The method of preparing HEA coating(HEAc) by laser cladding technology is one of the best preparation methods which can achieve superior performance. The latest research results of HEAc prepared by laser cladding technology were summarized from the view of component design, microstructure, annealing process and properties, high temperature oxidation resistance and other properties. The problems existing in the preparation of HEAc by laser cladding technology were analyzed. It was put forward that the scientific research system should be perfected from the aspects of component design, basic theory, performance law and processing technology in the future. The high-entropy alloy coatings with excellent performance are expected to be prepared.

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    Research Article
    Relationship among processing technology, microstructure and properties of Cu-Ni-Si alloy prepared by temperature controlled mold continuous casting and mechanism
    Wan-neng LIAO, Xue-feng LIU, Si-qing WANG
    2019, 47 (10): 44-52.   DOI: 10.11868/j.issn.1001-4381.2018.000905
    Abstract ( 544 ( PDF (6664KB)( 229 Citation

    Temperature controlled mold continuous casting (TCMCC) technology was used to produce C70250 copper alloy strips. The strips were cold rolled and aged at different temperatures and time. The relationships among processing technology, microstructure, mechanical properties and electrical conductivity were investigated to reveal the mechanism. The results show that the C70250 copper alloy strips prepared by TCMCC have coarse columnar grain structure with less transverse grain boundaries. After cold rolling with the deformation of 97.5%, the fibrous microstructure is formed along the rolling direction. When the aging temperature and the aging time are 450℃ and 60min, the tensile strength and the electrical conductivity of the alloy are 758MPa and 54.5%IACS. Compared with the alloy prepared by traditional process, the tensile strength and the electrical conductivity increase by 5.3% and 36.3% respectively, which means the strength and electrical conductivity are improved simultaneously. Under this condition, the alloy retains the fibrous microstructure and a large number of Ni2Si phases are uniformly precipitated with the size of 6-10nm. The strength of the alloy is improved with the joint action of work hardening and Orowan strengthening. The electrical conductivity of the C70250 copper alloy is significantly improved by the fully precipitated solute atoms and the reduced transverse grain boundaries.

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    Effect of two-step aging on microstructure and properties of high-strength aluminum alloys for automobile
    Cheng-bo LI, Jian-guo TANG, Yun-lai DENG, Jian-xiang LI, Xin-ming ZHANG
    2019, 47 (10): 53-59.   DOI: 10.11868/j.issn.1001-4381.2018.001077
    Abstract ( 613 ( PDF (4495KB)( 202 Citation

    The application of high-strength aluminum alloy on the vehicle body will be the development trend of automobile lightweight in the future.The effects of two-step aging on the microstructure and properties of high-strength aluminum alloys for automobile were investigated by tensile tests, electrical conductivity, and transmission electron microscopy (high resolution). The effect of aging temperature on the overall performance is greater than the aging time. The effect of the second-stage aging temperature in the two-step aging parameters is the greatest. As the aging temperature and aging time of the second-stage increase, the size of the aging strengthening phase increases. The mechanical properties decrease and the conductivity increases. The optimized T76 aging system is 120℃/6h+160℃/12h. The precipitation phase is completely coherent with the matrix. The size of length is about 5-8nm, and the size of thickness is about 3-5nm. The optimized T73 aging system is 120℃/6h+170℃/12h, the precipitation phase is semi-coherent with the matrix.The size of length is about 8-15nm, and the size of thickness is about 4-8nm.

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    Effect of extrusion ratio on microstructure and properties of Al-0.68Mg-0.60Si alloy
    Zi-fu LI, Yun-lai DENG, Zhen ZHANG, Lin SUN, Yi-dan ZHANG, Quan SUN
    2019, 47 (10): 60-67.   DOI: 10.11868/j.issn.1001-4381.2018.001074
    Abstract ( 531 ( PDF (4527KB)( 167 Citation

    The effects of extrusion ratio on microstructure and properties of Al-0.68Mg-0.60Si alloy were studied by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), transmission electron microscope (TEM), hardness test and tensile test at room temperature. The results show that with the increase of extrusion ratio, the size of the dispersed particles in the matrix of Al-0.68Mg-0.60Si alloy profile decreases gradually, the degree of dispersion increases, the fraction of small angle grain boundaries decreases, but the recrystallization fraction increases. When the extrusion ratio reaches above 39.6, the texture of the alloy is cubic texture. In addition, in the extrusion deformation process, the hardness and tensile strength of the alloy profile increase first and then decrease with the increase of extrusion ratio (λ=26.8-55.7);when λ is 39.6, the maximum tensile strength of the alloy reaches 284.00MPa.

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    Microstructure and corrosion-wear resistance of laser cladding Al-Ni-TiC-CeO2 composite coatings
    Xing HE, De-jun KONG, Ren-guo SONG
    2019, 47 (10): 68-75.   DOI: 10.11868/j.issn.1001-4381.2018.000274
    Abstract ( 551 ( PDF (7105KB)( 161 Citation

    Al-Ni-TiC-CeO2 composite coatings were prepared by laser cladding technique on S355 offshore steel.The surface-interface morphologies, chemical element distribution, phase compositions, microhardness of the as-prepared coatings were analyzed by means of scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), X-ray diffractometer (XRD) and microhardness tester. Also, the corrosive wear resistance and stress corrosion cracking (SCC) of the coatings in 3.5%(mass fraction)NaCl solution were studied. The results show that the coating is mainly composed of TiC and AlNi3 phases as well as AlFe3 phase. The surface of the coating is relatively smooth, there is no obvious crack, and the dilution rate is 5%. The surface hardness of the coating is 809.3HV0.2, which is 2.3 times as high as the substrate. The interaction is mainly corrosion accelerating abrasion in the substrate, while it is wear accelerating corrosion in the coating. The SCC susceptibility of the substrate and coating are 35.01% and 17.69% respectively, which indicates that the coating can inhibit the SCC obviously.

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    Effect of extrusion temperature on mechanical properties and biological corrosion resistance of Mg-5.3Gd-2.6Y-1.1Nd-0.3Zr alloy
    Xin XIE, Jian-guo TANG, Hong-ji SHI, Li-qun GUAN, Liu YANG, Yun-lai DENG, Chang-ping TANG, Yi-dan ZHANG
    2019, 47 (10): 76-81.   DOI: 10.11868/j.issn.1001-4381.2017.001426
    Abstract ( 486 ( PDF (4425KB)( 203 Citation

    The homogenized Mg-5.3Gd-2.6Y-1.1Nd-0.3Zr(mass fraction/%) ingots were extruded at different temperatures.The microstructures and mechanical properties of the solution-treated ingot and those extruded at different temperatures were investigated by optical microscopy(OM) and tensile test. The corrosion resistance of the alloys in Hank's solutions was evaluated by mass loss, hydrogen evolution and Tafel polarization tests. The surface corrosion morphology of the specimens after immersion was examined by scanning electron microscopy. The results show that the grains of the investigated alloy are refined substantially after extrusion, and their strength and ductility increase along with the decrease of the extrusion temperature, and the yield strength of the extruded alloy under 450℃ reaches 223.4MPa, which is about 60% higher than that of T4 alloy (139.8MPa). The extrusion deformation also has positive effects on the alloys' corrosion resistance, and corrosion resistance of the alloy increases first and then decreases along with the decrease of the extrusion temperature. The one extruded under 450℃ seems to show the best corrosion resistance, whose corrosion rate is 0.74mm/a.

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    Microstructural stability of Q460FRW fire-resistant steel
    Long-teng MA, Yan-feng WANG, Guo-biao DI, Yong-da YANG, Le-qing HUANG, Chun-zhi LI
    2019, 47 (10): 82-89.   DOI: 10.11868/j.issn.1001-4381.2018.001141
    Abstract ( 533 ( PDF (5953KB)( 164 Citation

    The precipitates in Q460FRW fire-resistant steel under equilibrium state were calculated using Thermo-Calc thermodynamic software. The evolutions of matrix and precipitates in this steel before and after high temperature exposure at 600℃ were experimentally observed and analyzed using optical microscopy(OM), scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The results show that the precipitates under equilibrium state at 600℃ are carbides including M23C6, M7C3 (M=Fe, Cr, Mo, Mn) and MX (M=Nb, Ti; X=C, N). The matrix of this steel at TMCP (thermo-mechanical control process) state consists of granular ferrite and acicular ferrite. After soaking at 600℃, M/A constitutes decompose gradually, while the acicular ferrite is transformed into bulk ferrite. Besides, longer exposure time brings about larger size of M7C3 particles, while the size of MX particles increases after short time heating and keeps constant with longer exposing time. During the heating process, no M23C6 particles are found, while most of Mo addition contributes to solid-solution strengthening effect.

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    Catalytic effect of rare earth oxides with variable valences on hydrogen storage properties of Mg2Ni alloy
    Guo-fang ZHANG, Han-feng SUN, Jian-yi XU, Yang-huan ZHANG
    2019, 47 (10): 90-96.   DOI: 10.11868/j.issn.1001-4381.2018.000266
    Abstract ( 662 ( PDF (3864KB)( 232 Citation

    Mg2Ni-Ni-5%RExOy(CeO2, Nd2O3, Tb4O7) composites were synthesized via ball milling method. The microstructure and hydrogen storage properties of the materials were analyzed systematically by XRD, SEM, EDS, the electrochemical and kinetic measurements. The results show that the crystallinities of the composites with rare earth oxides decrease, and the distribution of the rare earth oxide catalysts on the surface of alloys is uniform. The maximum discharge capacities of the composites with rare earth oxides rise evidently, the discharge capacity of the sample containing Tb4O7 reaches to 871mAh·g-1 at room temperature, and the composites can also keep higher cycling stability. The CeO2 and Tb4O7 catalysts can enhance the abilities of charge transfer on the surface of alloys, and improve the transmission rate of H atoms in the bulk of Mg2Ni alloy obviously. The rare earth oxides catalysts can also increase the gaseous hydrogen absorption capacity. The hydrogen storage capacity of the sample with Tb4O7 reaches to 2.02%(mass fraction) at 250℃, which is the maximum hydrogen absorption capacity among these samples, but the hydriding rate is relatively slow at lower temperature. The catalytic effect of the rare earth oxides is mainly related to the changeable valences of the rare earth ions, that is, the more likely of the valences change of the ions, the better the catalytic activities exhibit. The catalytic activities in descending order are Tb4O7, CeO2 and Nd2O3.

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    Preparation and electrochemical properties of algae-based super activated carbon based on "egg-box" structure
    Shi-jie LI, Kui-hua HAN
    2019, 47 (10): 97-104.   DOI: 10.11868/j.issn.1001-4381.2018.001438
    Abstract ( 615 ( PDF (3063KB)( 237 Citation

    Different with terrestrial plants, algae contains alginic acid and alginate, and the alginate mainly exists in cell walls in the form of calcium alginate and magnesium alginate. Six kinds of algae, sargassum, enteromorpha, asparagus, undaria, kelp and ulva, were used as raw materials, carbon products from algae carbonization were pickled with hydrochloric acid to remove Ca2+ and Mg2+ ions, etc. from alginate and form "egg-box" initial pore structure. Then the algae-based super activated carbon was prepared by KOH activation method, the effect of pickling pretreatment on the pore structure and electrochemical properties of algae-based activated carbon was studied. The results show that the hydrochloric acid pretreatment can not only increase the specific surface area, but also improve the number of mesoporous of the algae-based activated carbons. The electrochemical performance of algae-based activated carbons is improved after hydrochloric acid pretreatment.

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    Synthesis and electrochemical property of NaV6O15 nanorods
    Yu TIAN, Tao-tao DING, Xiao-long ZHU, Guang ZHENG, Zhi-ming ZHAN
    2019, 47 (10): 105-112.   DOI: 10.11868/j.issn.1001-4381.2018.001481
    Abstract ( 6 ( PDF (0KB)( 0 Citation

    A hydrothermal method was employed to synthetise NaV6O15 nanobelts, then nanobelts were annealed in air, the nanorods (NRs) were obtained at 350℃, which possess a length and diameter of 500nm and 100nm, respectively. NaV6O15 NRs as the electrode of supercapacitor exhibit significantly improved electrochemical performance compared with the untreated NaV6O15 electrode, and yield a high specific capacitance (402.8F/g at 300mA/g). Furthermore, the annealing treated nanorods show excellent cycling stability (80% capacitance retention after 1000 cycles at a scan rate of 100mV/s), this can be ascribed to that annealing turns the amorphous NaV6O15 into crystalline. These findings may further broaden the application of NaV6O15-based materials for high performance supercapacitors (SCs), aqueous rechargeable lithium batteries and Li-ion capacitors.

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    Property characterization of spinel structure Ni-doped ZnFe2O4 nanoparticles
    Jia-hao LIANG, Zhi-qiang WEI, Xue-liang ZHU, Xu-dong ZHANG, Xiao-juan WU, Jin-long JIANG
    2019, 47 (10): 113-119.   DOI: 10.11868/j.issn.1001-4381.2018.000042
    Abstract ( 709 ( PDF (2483KB)( 216 Citation

    Pure and Ni-doped Zn1-xNixFe2O4 nanoparticles with different contents were successfully prepared via hydrothermal method. The influence of nickel doping concentration on the microstructure, morphology, optical and magnetic properties of Zn1-xNixFe2O4(x=0, 0.1, 0.3, 0.5) nanocrystals were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction(SAED), X-ray energy dispersive spectroscopy(XEDS), ultraviolet-visible absorption spectrum(UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and the vibrating sample magnetometer (VSM) and etc. The results show that all Zn1-xNixFe2O4 nanoparticles are with good crystallization, Ni2+ enters into ZnFe2O4 lattice in the form of replacing Zn2+, and generating cubic spinel structure ZnFe2O4. With the increase of Ni content, the crystalline size increases and the lattice constant shrinks. The morphology of the samples exhibits irregular ellipsoid with uniform particle size. The absorption peak position of FT-IR spectra does not change with the increase of Ni doping concentration. The energy band gap of Zn1-xNixFe2O4 nanocrystals increases with the increase of Ni doping concentration, and blue shift occurs compared with the corresponding bulk. Pure ZnFe2O4 nanocrystals exhibit super paramagnetic properties and the doped samples show obvious ferromagnetism at room temperature.

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    Process research on preparation of MoO3-doped BiSmMoO6 microwave ceramic sheet by nonaqueous tape casting
    Li-na ZHAN, Yao LIU, Hao LI, Shao-jun LIU
    2019, 47 (10): 120-125.   DOI: 10.11868/j.issn.1001-4381.2018.000006
    Abstract ( 472 ( PDF (2317KB)( 240 Citation

    BiSmMoO6 microwave ceramics were prepared by solid-phase reaction method using Bi2O3-Sm2O3-MoO3 as raw materials. The rheological properties of the slurry and the microstructure and phase composition of the cast film were characterized. The results show that under the conditions of selecting the alcohol/isopropanol as the solvent, when pH=6 and the solid phase content is 60% (mass fraction, the same below), and with the additives of the slurry 2% tributyl phosphate dispersant, 8% PVB binder, and 4.8% polyethylene glycol plasticizer, the casting slurry has excellent rheological properties. After sintering, the cast film is dense in microstructure, and the phase composition does not change compared to the press-formed sample.

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    Preparation of corundum-spinel-mullite porous ceramics with high strength and thermal insulation
    Lin MA, Dan-ni WEN
    2019, 47 (10): 126-132.   DOI: 10.11868/j.issn.1001-4381.2019.000050
    Abstract ( 544 ( PDF (2015KB)( 376 Citation

    Composite ceramics with high strength and thermal insulation were fabricated via an in-situ reaction sintering method using alumina, silica and fused magnesia as starting raw materials, and sulphite liquor as binders. The effect of MgO addition on apparent porosity, flexural and compressive strength, and thermal shock resistance of samples was investigated. The phase compositions, microstructure characteristics and mechanical properties were characterized by means of X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electronic universal testing machine, the apparent porosity and thermal shock resistance of porous ceramics were also characterized. The results show that corundum-spinel-mullite porous composite ceramics are fabricated with 5%(mass fraction) fused magnesia, alumina, and silica sintering at 1450℃ for 3h via an in-situ reaction. The porous ceramics possess high compressive strength of 270.25 MPa, high flexural strength of over 45MPa and apparent porosity of 26.46%. It exhibits good thermal insulation performance with a thermal conductivity of 1.469W·m-1·K-1 at room temperature, and the retention percent of residual flexural strength exceeds 27% after 3 thermal shocks. It is a promising lining material for kilns. The change of MgO content influences directly the three-phase compositions, phase morphology, pores size and distribution, which leads to non-monotonic variation of flexural strength, compressive strength and thermal shock resistance of the porous ceramics.

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    Experiment and finite element simulation on thermo-mechanically coupled deformation behavior of shape memory polyurethane
    Zhi-hong LIANG, Jian LI, Qian-hua KAN, Guo-zheng KANG
    2019, 47 (10): 133-140.   DOI: 10.11868/j.issn.1001-4381.2018.001334
    Abstract ( 559 ( PDF (5315KB)( 219 Citation

    Monotonic tensile tests of shape memory polyurethane (SMPU) at different strain rates were carried out at room temperature, and the surface temperature of samples was monitored synchronously with the infrared thermometer to investigate the thermo-mechanical coupling effect during stretching. The results show that the post-yield softening is observed due to the disentanglement of molecular chains, after the stress approaches the yield peak, and a localized temperature rise is induced by the friction between molecular chains; with the progressive increasing of load, the strain hardening occurs due to the preferred orientation of molecular chains in the direction of stretching, which induces the stress and temperature rise increase. In the meantime, it is found that both the yield peak and localized temperature rise are increased significantly with the increase of strain rates; however, the competition exists between the strain softening induced by the dissipation heat generation and the strain hardening, making the sensitivity of localized plastic flow on the strain rate decreased. Based on the finite element software ABAQUS, the finite element model of a plate specimen was established to study the thermo-mechanically coupled behavior on the tensile deformation of SMPU. By comparing the contours of plastic strain field with that of temperature field at different moments, it is found that the forming of the localized plastic flow and temperature rise start from the initial defect and gradually move towards the middle and the expand to the entire sample, simultaneously. Furthermore, the simulated average temperature rise curves at different loading rates are in good agreement with the experimental ones.

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    Preparation and mechanical property of CIP/GF/CF/EP absorbing composites
    Xue-fei ZHANG, Jin-tang ZHOU, Zheng-jun YAO, Hai-shuo CAI, Bo WEI
    2019, 47 (10): 141-147.   DOI: 10.11868/j.issn.1001-4381.2018.000622
    Abstract ( 620 ( PDF (2989KB)( 217 Citation

    In order to prepare structural absorbing materials with mechanical properties and electromagnetic absorption properties, a kind of absorbing composites with carbonyl iron powders (CIP) as absorbent, glass fiber(GF) as the transmittance layer, carbon fiber(CF) as the reflective layer, and epoxy resin(EP) as matrix was designed and fabricated by vacuum assisted resin infusion process. The effect of different mass ratios of CIP/EP on the mechanical properties and microwave absorption properties of the composites was studied. The results of FTIR and DSC suggest that there is not a chemical reaction between CIP and EP. SEM shows that CIP can be dispersed uniformly in EP resin matrix and not toward the surface of the fibers. The results of mechanical tests indicate that the best mechanical properties of the CIP/GF/CF/EP composites are at a mass ratio of 3:10 of CIP to EP. The tensile strength and tensile modulus are 347.56MPa and 25.99GPa, 4.3% and 5.7% higher than that of GF/CF/EP composites. The flexural strength and the flexural modulus are 339.6MPa and 23.7GPa, 18.2% and 71.2% higher than that of GF/CF/EP composites. Vector network analysis proves that the absorbing performance of composites absorbing plate is increased and the peak of reflection absorbing loss is moved toward the low frequency band with the increase of CIP.

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    Numerical analysis on effect of PNF interlayer on CFRP delamination
    Guo-wei ZHU, Hong-yan LI, Yun-zhi XU, Xiao-jun ZHANG
    2019, 47 (10): 148-153.   DOI: 10.11868/j.issn.1001-4381.2019.000384
    Abstract ( 454 ( PDF (3508KB)( 194 Citation

    It is proved that porous polyamide non-woven fabric (PNF) can achieve an excellent toughness of the composites while keeping a good processibility. However, there is less research about the interlaminar toughening mechanism of PNF up to now. The finite element model based on cohesive zone model (CZM), which represents the PNF thickness and property, was constructed to predict the delamination onset and propagation of CFRP. In the double cantilever beams test, the main conclusions are as follows:There is little effect of thickness of PNF on the peak load in modeⅠdelamination of CFRP, but the resistance of propagation reaches the maximum when the thickness is equal to 20μm. The shape of the delamination front can be directly obtained from the simulations by studying the distribution of the normal traction. For a specific ply-orientation composite, once delamination begins to propagate, the figure of delamination front is consistent. With the increase of the PNF/CFRP ply angle from[012/012] to[012/9012], the propagation distance and peak load are reduced correspondingly.

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    Rheological properties of a mixture of cyclic butylene terephthalate and catalyst
    Wang-qing WU, Yi LIU, Yang-hui XIANG, Ji-xian FU
    2019, 47 (10): 154-159.   DOI: 10.11868/j.issn.1001-4381.2018.000806
    Abstract ( 479 ( PDF (2186KB)( 127 Citation

    A new strategy with gradient cooling method was proposed for characterizing the rheological properties of CBT pure resin and CBT/catalyst mixture system under special molding conditions based on a digital high-temperature rotary viscometer. The results show that the apparent viscosity of CBT pure resin can be accurately obtained by using the gradient cooling method. The apparent viscosity of CBT pure resin is increased with the decrease of temperature, and is decreased with the increase of the rotating speed, and shows a significant shear thinning phenomenon at 170-180℃.The reaction rate of the CBT/catalyst resin system is increased with the increase of the catalyst content, and the molding window time is shortened. Under the same concentration conditions, the CBT/T9 system with higher tin content has a faster reaction rate than the CBT500/DBTL system. With the increase of molding temperature, the reaction rate of CBT/catalyst system shows the trend of slowing down. This may be due to the increased volatilization of the catalyst and the decreased crystallization rate at higher molding temperature. Finally, the effects of different catalyst types, different concentrations and molding temperatures on the molding window time of CBT resin system were studied.

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    Damage coupling mechanical behaviors of 2D-SiC/SiC composite
    Hong-bao GUO, Jun XIE
    2019, 47 (10): 160-165.   DOI: 10.11868/j.issn.1001-4381.2018.000674
    Abstract ( 690 ( PDF (2366KB)( 251 Citation

    By using axial and off-axis loading tests with off-axis angle as 45°, the tensile, compressive and in-plane shear stress-strain behaviors along the fiber bundles directions of a 2D-SiC/SiC composite were obtained, and the damage coupling mechanical behaviors of composite under combined stress condition were studied. The results show that the initial stress levels for the damage coupling mechanical behaviors of composite under 45° off-axis tensile and compressive loading conditions are 40MPa and -110MPa, separately. Under combined stress conditions, there exists obvious mutual acceleration between the tensile and the in-plane shear damage evolutions in the fibre bundles directions of composite, and the in-plane shear damage has accelerative effect on the compressive damage evolution, but the in-plane shear damage evolution is suppressed by compressive stress components obviously. These coupling effects become more significant with increasing stress level. The SEM (scanning electron microscope) pictures of fractured surfaces on off-axis loading specimens indicate that, in the fiber bundles directions, the mutual effects between the three stress components and the cracking evolutions of the three kinds of matrix cracks (oriented at 0°, 90° and 45°) are the main micro-damage mechanisms for the damage coupling mechanical behaviors of 2D-SiC/SiC composite under combined stress conditions.

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