- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
The cork composite (RC16) is prepared by using one-component moisture curing polyurethane (U030) as cork adhesive, and the cork composite exhibits excellent mechanical properties and flexibility, and its density is 0.40g/cm3. The effect of adhesive content, moisture content in cork granules, and curing condition on the thermal insulation property, flexibility, and mechanical properties of the RC16 cork was investigated. The results show that:the synthetic adhesive U030 has good compatibility and adhesion with cork granules, which can wrap the cork granules completely and distribute evenly; the mechanical properties of the cork composite exhibit first increasing and then decreasing with increasing moisture content in cork granules, and the maximum value is reached at 7.0%; with the increase of U030 content, each performance of the RC16 cork show rising firstly, and then towards a stabilizing trend, but the thermal conductivity increases correspondingly, so when U030 content is 30%, the comprehensive performance of composite is the best; the optimum curing condition of the RC16 cork is defined:curing temperature is 110℃ and curing time is 1.5h. RC16 exhibits good heat resistance, which can bear 800℃ ablation within 20s.
The process technology and the mechanical and electrical properties of the "metamaterial"structural absorbing composites were studied, in which metal periodic structure units were produced on the organic carrier film and then combined with medium. Through the breakthrough of key technologies involving producing different size metal periodic structure, the transfer of metal periodic structure, and optimizing process parameters, the "metamaterial" structural absorbing composite with good wave-absorbing and mechanical stabilities that contained multi-layer metal periodic structure was prepared. The "metamaterial" structural absorbing composite has a high broadband absorbing property in the frequency range of 2-18GHz.
Based on electrochemical anodic oxidation, an innovative technique was developed to efficiently obtain the uniform catalyst coating on continuous carbon fibers. Through systematic investigation on the effect of electrochemical modified strength on the physical and chemical characteristics of carbon fiber surface, catalyst particles and the morphology of CNTs-grafted carbon fibers, tensile strength of multi-scale reinforcement and the interlaminar shear strength of its reinforced composites, the electrochemical modification process on carbon fibre surface was optimized. The results show that the morphology and distribution of catalyst particles not only affect the morphology of CNTs deposited on the surface of carbon fibres, but also affect the mechanical properties of multi-scale reinforcement and its reinforced composites of CNTs-grafted carbon fibers.
PI pre-polymerization method was adopted to synthesize the rigid polyurethane-imide (PUI) foams flame retarded by kaolin(KL) and APP. The effect of content and ratio of KL/APP on the limited oxygen index, smoke density rank, char layer morphology, density and mechanical properties was analyzed. The results show that with the increase of content of KL/APP, the limited oxygen index, density, compressive strength and modulus and surface chalking degree of the rigid polyurethane-imide foams increase. The density exponent values for compression strength and compression modulus are fitted respectively as 1.999 and 1.764; while the smoke density rank of foams decreases with the increasing addition of KL. Moreover, the disadvantage of porous char layer of foams can be improved with the addition of KL/APP.
The effect of the different stress ratios (R) and annealing treatment on the fatigue properties of the transparent polycarbonate (PC) sheet and the mechanism behind were studied, the fatigue crack propagation (FCP) process and mechanism were analyzed. The results show that after annealing, the residual stress of the PC samples decreases obviously and the fatigue properties are greatly improved. This is because the machining process results in tensile stress in the PC samples, eliminating the tensile stress can improve the fatigue property of PC effectively; under the positive stress ratio (tensile-tensile fatigue), as the stress amplitude increases, the fatigue properties of PC decreases obviously, however, the negative stress ratio (tensile-compression fatigue) causes complex influence on the fatigue properties of PC. The fatigue fracture morphology suggests that distinct crack source, stable crack extension zone and instability zone exist obviously in fatigue fracture of PC. The mechanism of the fatigue crack propagation of PC indicates that crazes are initiated at first under the cycling stress, when the stress is higher than the strength of the fibrils in crazes or the fibrils are broken under the cycling stress, crazes develop into cracks.
A single layer of titanate was prepared by high temperature solid phase hydrothermal synthesis. To fabricate mesoporous nanocomposite-Ni-doped Zr-pillared titanate(NZPT), the exfoliated layered titanate in aqueous solution was reassembled in the presence of the hydroxyl-Zr oligocations and nickel cation by exfoliation-restacking technology. The crystal structure, chemical composition, microstructure and pore structure were characterized by powder X-ray diffraction, N2 asbsorption analysis, scanning electron microscope/transmission electron microscopy and UV-vis spectra. The influence of doping Ni cations on the catalytic activity of the Zr-pillared composites (ZPT) was investigated by the degradation of acid red G under ultraviolet and visible radiation. The results show that the Ni-containing pillared nanocomposite exhibits higher photocatalytic activities than that of ZPT without doping Ni cations, and the NZPT-0.10 has the best photocatalytic activities of them, which are based on the bigger specific surface area and electronic coupling between the host and the guest species.
The highly ordered porous anodic alumina was prepared by anodic oxidation technology, after being treated by AC phosphoric pore broadening, the Cu-Ni nano composite particles were deposited into anodic alumina pores by AC frequency with 50Hz in different voltages, different time and different temperatures. The spectra result shows that the coating prepared under the conditions of voltage is 12V, time is 600s, temperature is 25℃ has good solar absorption performance, the absorptivity is 0.91, emissivity is 0.18, quality factor is 4.9. The SEM and XRD analysis show that CuAl2O4/Cu-Ni composite nanorods were deposited on the surface of the composite oxide coating. After heat treatment at 600℃, the solar absorption and infrared emission of target coating have a small fluctuation and the thermal stability of the coating system is greatly improved. The existing of CuAl2O4 limits the diffusion of metal particles under high temperature environment at the interface, which prevents the Cu/Ni from being oxidized.
Layered LiNi0.5Co0.2Mn0.3O2 coated with homogeneous nano FePO4 suspension was prepared by using co-precipitation method. XRD, TG-DTA and TEM were adopted to characterize the structure, morphology and liquid state of FePO4 prepared. The structure, morphology and electrochemical performance of the coated materials prepared were characterized by the means such as XRD, SEM, EDS, TEM, ICP, galvanostatic charge-discharge cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy(EIS) tests. The effect of heat treatment temperature and coating quantity on the structure and electrochemical performance of coated LiNi0.5Co0.2Mn0.3O2 by co-precipitation method was explored. The results show that 400℃ and 2%(mass fraction, the same below) FePO4 coating can significantly improve cycle performance and rate capability of LiNi0.5Co0.2Mn0.3O2, CV and EIS testing results reveal that FePO4 coating can improve the reversibility and dynamic performance for LiNi0.5Co0.2Mn0.3O2. ICP results show that FePO4 coating layer can effectively reduce the electrolyte to dissolute and erode cathode materials, stabilize its layered structure, then improve the electrochemical performance of cathode materials.
VO2 sol was firstly prepared using vanadyl sulfate as a vanadium source by precipitation-peptization method. Then tungsten(W) doping vanadium dioxide(W-VO2) was prepared by hydrothermal crystallization of prepared sol with the presence of ammonium metatungstate. The morphologies, crystal structure of the as-prepared samples and phase transition properties were studied by X-ray diffraction(XRD), field emission scanning electron microscope(FESEM)and differential scanning calorimetry(DSC) analysis. The results indicate that rod-like W-VO2(B) crystal with length of 1-2μm and radius of 100-200nm is firstly formed during hydrothermal treatment for 4-48h at 280℃, then the rod-like crystal dissolves gradually and sheet-like or snowflake-like crystal is formed with the phase transition from W-VO2(B) to W-VO2(M) and eventually, the W-VO2(M) crystals can further grow up while the W-VO2(B) gradually dissolves; the phase transition temperature of VO2 decreases with the increase in W doping content, and the phase transition temperature of W-VO2(M) reduces to about 28℃ when the nominal dopant concentration is 6.0%(atom fraction).The "nucleation-growth-transformation-ripening" mechanism is proposed as the formation mechanism based on the hydrothermal crystallization and morphological evolution process of W-VO2(M).
In order to improve the thermal conductivity of paraffin widely applied in phase change energy storage field, metal Na with high thermal conductivity, low melting point and low density was compounded to paraffin to form a new phase change energy storage material (Na/paraffin) in glove box, and the thermal conductivity, latent heat and heat storage/release characteristics of Na/paraffin were studied. The results show that thermal conductivity of 5%Na/95% paraffin composite phase change energy storage materials is improved 17.6 times compared to pure paraffin and the heat storage/release ratio of 5%Na/95% paraffin is two times of pure paraffin. After 200 cycles experiment, the phase transition temperature of 3%Na/97% paraffin composite phase change energy storage materials falls from 60.58℃ to 59.65℃. The phase transformation latent heat and thermal conductivity rate are reduced from 166.7520J·g-1 to 160.5632J·g-1 and from 2.33W·m-1·K-1 to 1.98W·m-1·K-1, respectively.
The Ni-5%RExOy (CeO2, La2O3, Eu2O3) as composite additives, Mg2Ni-Ni-5%RExOy composites were prepared by the ball milling method. The effects of different additives on the structure, morphology, electrochemistry and kinetic properties of Mg2Ni alloy were studied systematically. The results show that composite additives can improve the proportion of amorphous and nanocrystalline structure of Mg2Ni alloy. The particle size is homogeneous but the agglomeration is observed in the sample with Ni-5%CeO2 additives. The composites with additives show higher maximum discharge capacity and better cycle stabilities. All of these three kinds of composite additives can improve the kinetic properties of the composites effectively, including optimizing the charge-transfer ability, the reversibility of the electrochemical reaction on the alloy surface, and enhancing the diffusion coefficients of H atoms in the bulk of alloy. Among these three kinds of additives, Ni-5%CeO2 additive shows the best catalysis effect on promoting the kinetic properties of the composites.
The extrusion process parameters were optimized based on Deform 2D finite element simulation, aluminum magnesium bimetal composite extrusion experiment was conducted under the extrusion rate of 2mm/s and extrusion temperature of 470℃. The microstructure of interface bonding layer was observed and analyzed by using scanning electron microscopy(SEM), microhardness test and electron backscattering diffraction(EBSD).The results show that interface layer generates in the contact region of aluminum and magnesium alloys, new phases in the layer are Al12Mg17 which is close to the AZ31 magnesium substrate and Al3Mg2 which is close to the aluminum substrate. The average microhardness value of Al3Mg2 phase is the highest, the average value is about 210HV, and that of Al12Mg17 is 170HV, the interface area forms a typical brittle layer as the hardness is higher than the parent metal on both substrate sides, the EBSD test shows that the average grain size of Al12Mg17 phase is 30μm, the average grain size of Al3Mg2 phase is about 20μm, different grain orientation can be observed in composite interface bonding layer regional and the grain size is not uniform, the outer pure aluminum matrix composite orientation area is uniform, some recrystallization of new generation phase occurs on the grain boundary.
Experiments were carried out with TIG welding-brazing of AZ31B magnesium alloy to PRO500 steel using TIG arc as heat source. The interfacial reaction characteristics and mechanical properties of the welding-brazing bonding were investigated. The results show that an effective bonding is achieved between AZ31B magnesium alloy and PRO500 steel by using TIG welding-brazing method. Some spontaneous oxidation reactions result in the formation of a transition zone containing AlFe3 phase with rich oxide. The micro-hardness value of the interfacial transition zone is between that of the AZ31B and the PRO500. Temper softening zone appears due to the welding thermal cycle nearby the bonding position in the interface. A higher heat input makes an increase of the brittle phases and leads to an obvious decrease of the bonding strength.
Two typical cross-section of welds, including nail shape and near X shape, are obtained in the process of fiber laser welding 2024-T4 Al alloy with filler wire. The correlations of the two weld appearances and other elements (such as microstructure, microhardness, and joint's tensile properties) were analyzed. The results show that the weld with near X shape cross-section during the welding process is more stable than that with nail shape cross-section, and the welding spatter of the former is smaller than that of the latter. The microstructure of the weld zone is columnar grains and equiaxed grains, the columnar grains are formed near the fusion line and growing along the vertical direction of the fusion line, the equiaxed grains are distributed in the center of the weld zone. The secondary dendrite of the grains in the center of the weld with nail shape cross-section grows better, and gradually forms to equiaxed dendrite, while the grains size of the weld with near X shape cross-section is relatively finer, exhibiting equiaxed cellular grain. Compared with the joint with nail shape cross-section of the weld, the joint with near X shape cross-section of the weld have some different characteristics, the precipitation strengthening phase θ(Al2Cu) content in weld zone of the latter is more than that of the former, the average microhardness value of the weld zone of the latter is higher than that of the former, the softening phenomenon of heat affect zone (HAZ) of the latter is weaker than that of the former, and the joint's tensile strength and plasticity of the latter are lower than that of the former slightly.
In view of the problem that paste flux is difficult to spread uniformly on the surface of filler metal, the adhesion behavior of the different concentrations of paste flux on the surface of filler metal was studied by the equipment of OM, wetting angle tester and surface tensiometer. The results show that adhesive layer is gradually thickened with the increase of the concentration of paste flux. A small amount of shrinkage appears in the thin adhesive layer. however, mass paste flux slides off filler metal when adhesive layer is thicker, accompanying by severe aggregation and shrinkage. For the ideal surface, the adhesive tension of paste flux with different concentrations of paste flux is the same. For the actual surface, the stripe groove additional pressure is formed when paste flux wets stripe groove, and the additional pressure is the main reason for the lagging phenomenon of the shrinkage of the adhesive layer. With the increase of paste flux concentration, the additional pressure decreases, the hysteresis resistance decreases, and the shrinkage increases. A relationship is satisfied when the shrinkage takes place in thin adhesive layer, this is ΔWC ≥ A+ΔP. Whether the shrinkage occurs mainly depends on the adhesion tension and the additional pressure.
Through using XRD, DSC, SEM, EDS and other modern analysis methods, the effects of rare earth element Ce on microstructure and solidification temperature of Al-Zn-Mg-Cu under different cooling rates were studied, the principle of Ce on grain refining and melt cleaning of alloys was analyzed and discussed. The results show that MgZn2 phase and α-Al matrix are the main precipitations, Al, Cu, Mg and other elements dissolve in MgZn2 phase, a new phase Mg(Zn, Cu, Al)2 is formed, solute elements in the grain boundary have higher concentration, eutectic reaction takes place between MgZn2 and α-Al, lamellar eutectic structure is generated. The addition of Ce decreases the dendritic arm spacing, reduces the layer spacing between eutectic phases and refines the eutectic structure and the grain significantly, and inhibits the appearance of the impurity phase Al7Cu2Fe in aluminum alloys. The addition of Ce also reduces the precipitation temperature of α-Al matrix and eutectic phase by 6.4℃ and 5.6℃ respectively.
The behaviors of deformation and recrystallization and textures evolution of 3% (mass fraction) Si columnar-grained electrical steel slabs were investigated by electron backscatter diffractometer technique and X-ray diffraction. The results indicate that the three columnar-grained samples have different initial textures with the long axes arranged along rolling, transverse and normal directions. Three shear orientations can be obtained in surface layer after hot rolling, of which Goss orientation is formed easily. The α and γ fibre rolling orientations are obtained in RD sample, while strong γ fibre orientations in TD sample and sharp {100} orientations in ND sample are developed respectively. In addition, cube orientation can be found in all the three samples. The characteristics of hot rolled orientations in center region reveal distinct dependence on initial columnar-grained orientations. Strong {111}〈112〉 orientation in RD and TD samples separately comes from Goss orientation of hot rolled sheets, and sharp rotated cube orientation in ND sample originates from the initial {100} orientation of hot rolled sheets after cold rolling. Influenced by initial deviated orientations and coarse grain size, large orientation gradient of rotated cube oriented grain can be observed in ND sample. The coarse {100} orientated grains of center region in the annealed sheets show the heredity of the initial columnar-grained orientations.
The W-4.9Ni-2.1Fe alloy with different addition of Y2O3 was prepared by high energy ball milling and spark plasma sintering techniques, the microstructure, mechanical property, friction and wear behavior of the high density alloy were investigated by the Rockwell hardness tester, X-ray diffractometer, reciprocating friction and wear tester, 3D profiler, etc. The results show that adequate doping of the trace Y2O3 can effectively inhibit the grain size, promote the γ-(Ni, Fe) bonding phase and tungsten particles uniformly distribute, increase the relative density, hardness, friction and wear properties. But the excessive Y2O3 addition can easily aggregate at grain boundary, weaken the inhibition effect, and decrease the mechanical and wear properties of the alloy. So the addition of Y2O3 should be appropriate. When the adding mass fraction of Y2O3 particles is 0.4%, the comprehensive performance of the alloy is the best.
Carbon nanotubes (CNTs, mass fraction of 0%-2%) reinforced Al5083 composites were fabricated by horizontal high-energy ball milling. The effects of ball milling time and CNTs contents on the properties of composite materials were studied. The micro morphology of CNTs/Al5083 composites was characterized by scanning electron microscopy(SEM) and transmission electron microscopy(TEM), the tensile strength and microhardness of the composites were tested. The results indicate that after high-energy ball milling for 1.5h, the carbon nanotubes are dispersed homogeneously in the Al5083 matrix, and good interfacial bonding strength between CNTs and Al5083 is obtained at the addition of 1.5%CNTs. Under these conditions, the tensile strength and microhardness of CNTs/Al5083 composites are 188.8MPa and 136HV, respectively. Compared to Al5083 matrix without CNTs reinforcement, tensile strength and microhardness of CNTs/Al5083 composites are increased by 32.2% and 36%, respectively.
The current high entropy alloys' studies are most in block, powder, coating, film and other areas. There are few studies of high entropy alloys in other areas and they are lack of unified classification. According to the current high entropy alloys' research situation, The paper has focused on the classification on all kinds of high entropy alloys having been researched, introduced the selecting principle of elements, summarized the preparation methods, reviewed the research institutions, research methods and research contents of high entropy alloys, prospected the application prospect of high entropy alloys, put forward a series of scientific problems of high entropy alloys, including less research on mechanism, incomplete performance research, unsystematic thermal stability study, preparation process parameters to be optimized, lightweight high entropy alloys' design, the expansion on the research field, etc, and the solutions have been given. Those have certain guiding significance for the expansion of the application of high entropy alloys subjects in the future research direction.
Based on years of airworthiness regulations research, combined with the experience of airworthiness certification of civil aviation products, the airworthiness requirement to materials for civil aviation products was analyzed. The key airworthiness requirement for materials is that materials should conform to some material specification to ensure their having the strength and other properties adopted in the design data. The shortcomings of domestic airworthiness management methods for civil aviation materials was discussed and three recommendations for improvement were proposed:(1) conduct individual airworthiness management for civil aviation materials according to CCAR 21.351 through 371 and CCAR 37; (2) develop and promote statistical-based material specification developing methods, to establish material specifications which could ensure material having the strength and other properties adopted in the design data; (3) establish a cooperation mechanism for developing material design value data base for civil aviation materials to reduce the cost of airworthiness certification activities. At the end of this paper, statistical methods used for establishing material specifications were discussed.
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