Based on experimental data,machine learning(ML) models for Young's modulus,hardness,and hot-working ability of Ti-based alloys were constructed.In the models,the interdiffusion and mechanical property data were hi...Based on experimental data,machine learning(ML) models for Young's modulus,hardness,and hot-working ability of Ti-based alloys were constructed.In the models,the interdiffusion and mechanical property data were high-throughput re-evaluated from composition variations and nanoindentation data of diffusion couples.Then,the Ti-(22±0.5)at.%Nb-(30±0.5)at.%Zr-(4±0.5)at.%Cr(TNZC) alloy with a single body-centered cubic(BCC) phase was screened in an interactive loop.The experimental results exhibited a relatively low Young's modulus of(58±4) GPa,high nanohardness of(3.4±0.2) GPa,high microhardness of HV(520±5),high compressive yield strength of(1220±18) MPa,large plastic strain greater than 30%,and superior dry-and wet-wear resistance.This work demonstrates that ML combined with high-throughput analytic approaches can offer a powerful tool to accelerate the design of multicomponent Ti alloys with desired properties.Moreover,it is indicated that TNZC alloy is an attractive candidate for biomedical applications.展开更多
The effect of electroslag refining on iron reduction from commercial aluminum was investigated.Cast electrodes of commercial aluminum were electroslag refined using KCl-NaCl-Na3AlF6 slag containing Na2B4O7.Experimenta...The effect of electroslag refining on iron reduction from commercial aluminum was investigated.Cast electrodes of commercial aluminum were electroslag refined using KCl-NaCl-Na3AlF6 slag containing Na2B4O7.Experimental results indicate that the iron content decreases with increasing Na2B4O7 addition and remelting time,and the iron content decreases from 0.400% to 0.184% under 9% Na2B4O7 addition for 30 min remelting.The elastic modulus,yield strength and ultimate tensile strength commercial aluminum are improved,and the tensile elongation is increased by 43% after electroslag refining.The chemical reaction between melt and slag to form Fe2B is the main reason for iron reduction and the thermodynamic calculation of the chemical reaction theoretically accounts for the formation of Fe2B.展开更多
Structural features, aging behavior, precipitation kinetics and mechanical properties of a 6013 Al–Mg–Si aluminum alloy subjected to equal channel angular pressing (ECAP) at different temperatures were comparative...Structural features, aging behavior, precipitation kinetics and mechanical properties of a 6013 Al–Mg–Si aluminum alloy subjected to equal channel angular pressing (ECAP) at different temperatures were comparatively investigated with that in conventional static aging by quantitative X-ray diffraction (XRD) measurements, differential scanning calorimetry (DSC) and tensile tests. Average grain sizes measured by XRD are in the range of 66-112 nm while the average dislocation density is in the range of 1.20×10^14-1.70×10^14 m^-2 in the deformed alloy. The DSC analysis reveals that the precipitation kinetics in the deformed alloy is much faster as compared with the peak-aged sample due to the smaller grains and higher dislocation density developed after ECAP. Both the yield strength (YS) and ultimate tensile strength (UTS) are dramatically increased in all the ECAP samples as compared with the undeformed counterparts. The maximum strength appears in the samples ECAP treated at room temperature and the maximum YS is about 1.6 times that of the statically peak-aged sample. The very high strength in the ECAP alloy is suggested to be related to the grain size strengthening and dislocation strengthening, as well as the precipitation strengthening contributing from the dynamic precipitation during ECAP.展开更多
In order to investigate the influences of the stoichiometric ratio of La/Mg (increasing La and decreasing Mg on the same mole ratio) on the structure and electrochemical performances of the La-Mg-Ni-based A2B7-type ...In order to investigate the influences of the stoichiometric ratio of La/Mg (increasing La and decreasing Mg on the same mole ratio) on the structure and electrochemical performances of the La-Mg-Ni-based A2B7-type electrode alloy, the as-cast and the annealed ternary Lao.8+xMgo.2_xNi3.5 (x=0-0.05) electrode alloys were prepared. The characterization of electrode alloys by X-ray diffraction (XRD) and scanning electron microscopy (SEM) shows that all the as-cast and the annealed alloys hold two major phases of (La,Mg)2Ni7 and LaNi5 as well as a residual phase of LaNi3. Moreover, the increase of La/Mg ratio brings on a decline of (La,Mg)2Ni7 phase and a rise of LaNi5 and LaNi3 phases. The variation of La/Mg ratio gives rise to an evident change of the electrochemical performances of the alloys. The discharge capacities of the as-cast and the annealed alloys evidently decrease with growing the La/Mg ratio, while the cycle stabilities of the alloys visibly augment under the same condition. Furthermore, the high rate discharge ability (HRD), the electrochemical impedance spectrum (EIS), the Tafel polarization curves, and the potential step measurements all indicate that the electrochemical kinetic properties of the alloy electrodes increase with the La/Mg ratio rising.展开更多
Thermoplastic starch is a kind of modified starch produced by mixing starch with additives and processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, biod...Thermoplastic starch is a kind of modified starch produced by mixing starch with additives and processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, biodegradability and rheological properties were studied. Glycerol and urea, to some extent, can both decrease the tensile strength and increase percentage elongation at break, because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. Thermoplastic starch shows thermoplasticity and its melt behaves as a pseudoplastic liquid at a low shear rate. Its biodegrading extent is slightly higher than that of native starch. The molecular weight of starch displays a decreasing tendency after thermoplastic modification.展开更多
La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex (x=0-0.20) hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were inves...La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex (x=0-0.20) hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were investigated. All alloys consist of a single LaNi5 phase with CaCu5 structure, and the lattice constant a and the cell volume (V) of the LaNi5 phase increase with increasing x value. The maximum discharge capacity gradually decreases from 319.0 mA?h/g (x=0) to 291.9 mA?h/g (x=0.20) with the increase in x value. The high-rate dischargeability at the discharge current density of 1200 mA/g decreases monotonically from 53.1% (x=0) to 44.2% (x=0.20). The cycling stability increases with increasing x from 0 to 0.20, which is mainly ascribed to the improvement of the pulverization resistance.展开更多
Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon (C/C)...Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon (C/C) composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.展开更多
Molecular dynamics simulations have been performed to investigate well-known energetic material cyelotrimethylene trinitramine (RDX) crystal, 3-azidomethyl-3-methyloxetane (AMMO) and RDX/AMMO propellant. The resul...Molecular dynamics simulations have been performed to investigate well-known energetic material cyelotrimethylene trinitramine (RDX) crystal, 3-azidomethyl-3-methyloxetane (AMMO) and RDX/AMMO propellant. The results show that the binding energies on different crystalline surface of RDX changes in the order of (010)〉(100)〉 (001). The interactions between RDX and AMMO have been analyzed by means of pair correlation functions. The mechanical properties of RDX/AMMO propellant, i.e. elastic coefficients, modulus, Cauchy pressure, and Poisson's ratio, etc., have been obtained. It is found that mechanical properties are effectively improved by adding some amounts of AMMO polymers, and the overall effect of AMMO on three crystalline surfaces of RDX changes in the order of (100)〉(010)〉(001). The energetic properties of RDX/AMMO propellant have also been calculated and the results show that compared with the pure RDX crystal, the standard theoretical specific impulse of RDX/AMMO propellant decrease, but they are still superior to those of double base propellant.展开更多
The structural, elastic, electronic and optical properties for U3Si2-type AlSc2Si2 compound under pressure were systematically investigated by using the first-principles calculations. The values of elastic constants a...The structural, elastic, electronic and optical properties for U3Si2-type AlSc2Si2 compound under pressure were systematically investigated by using the first-principles calculations. The values of elastic constants and elastic moduli indicate that AlSc2Si2 keeps mechanical stability under high pressure. The mechanical properties of AISc2Si2 are compared with those of Al3Sc. The results indicate that AlSc2Si2 is harder than AI3Sc. Anisotropic constant AU and 3D curved surface of elastic moduli predict that AISc2Si2 is obviously anisotropic under pressure. The electronic structure of AlSc2Si2 exhibits metallic character and the metallicity decreases with the elevated pressure. In addition, optical properties as a function of pressure were calculated and analyzed. The present work provides theoretical support for further experimental work and industrial applications.展开更多
In situ TiB2/7055 composites were successfully synthesized via magnetic chemical direct melt reaction from 7055 (Al-3B)?Ti system. The phase composition and the microstructure of the composites were investigated by...In situ TiB2/7055 composites were successfully synthesized via magnetic chemical direct melt reaction from 7055 (Al-3B)?Ti system. The phase composition and the microstructure of the composites were investigated by XRD, OM and SEM technologies, and the mechanical and wear properties were tested. The results indicate that with the pulsed magnetic field assistance, the morphologies of in situ TiB2 particles are mainly hexagonal-shape or nearly spherical, the sizes are less than 1 μm, and the distribution of the matrix is uniform. Compared the microstructures of the 7055 aluminum matrix composites synthesized without pulsed magnetic field, the average size ofα(Al) phase with pulsed magnetic field assistance is decreased from 20 to 10μm, the array of the second phase is changed from continuous net-shape to discontinuous shape. With the pulsed magnetic field, the tensile strengths of the composites are enhanced from 310 to 330 MPa, and the elongations are increased from 7.5%to 8.0%. In addition, compared with matrix alloy, the wear mass loss of the composites is decreased from 111 to 78 mg under a load of 100 N for 120 min.展开更多
BN interphase was successfully synthesized on SiC fiber fabrics by dip-coating process using boric acid and urea as precursors under N2 atmosphere. The morphology of BN interphase was observed by SEM, and the structur...BN interphase was successfully synthesized on SiC fiber fabrics by dip-coating process using boric acid and urea as precursors under N2 atmosphere. The morphology of BN interphase was observed by SEM, and the structure was characterized by XRD and FT-IR spectra. The SiCf/SiC composites with dip-coated BN interphase were fabricated by chemical vapor infiltration (CVI) process, and the effects ofBN interphase on the mechanical properties of composites were investigated. The results show that the SiC fibers are fully covered by BN interphase with smooth surface and turbostratic structure (t-BN), and the thickness is about 0.4 μm. The flexural strengths of SiCf/SiC composites with and without BN interphase are about 180 and 95 MPa, respectively. Compared with the as-received SiCf/SiC composites, the composites with BN interphase exhibit an obvious toughened fracture behavior. From the microstructural analysis, it can be confirmed that the BN interphase plays a key part in protecting the fibers from chemical attack during matrix infiltration and weakening interfacial bonding, which can improve the mechanical properties of SiCf/SiC composites remarkably.展开更多
The effects of SiCp surface modifications(Cu coating,Ni coating and Ni/Cu coating)on the microstructures and mechanical properties of Al matrix composites were investigated.Surface modification of SiC particles with C...The effects of SiCp surface modifications(Cu coating,Ni coating and Ni/Cu coating)on the microstructures and mechanical properties of Al matrix composites were investigated.Surface modification of SiC particles with Cu,Ni and Cu/Ni,respectively,was carried out by electroless plating method.SiCp/Al composites were prepared by hot pressed sintering followed by hot extrusion.The results show that the surface modification of SiC particles plays an effective role,which is relative to the type of surface coating,and the interfacial bonding become stronger in the following order:untreated SiCp<Ni(Cu)-coated SiCp<Ni/Cu-coated SiCp.The Ni/Cu-coated SiCp/Al composites exhibit the best comprehensive mechanical properties,with ultimate tensile strength(σUTS)and fracture strain(εf)of 389 MPa and 6.3%,respectively.Compared with that of untreated-SiCp/Al composites,theσUTS andεf are enhanced by 19.3%and 57.5%.展开更多
Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was...Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was prepared by powder metallurgy method.The composite powder was prepared by molecular blending method and ball milling method at first,and then densified into bulk material by spark plasma sintering(SPS).X-ray diffraction,Raman spectroscopy,infrared spectroscopy,and nuclear magnetic resonance were employed to characterize the CQD synthesized under different temperature conditions,and then CQDs with a higher degree of sp^(2)were utilized as the reinforcement to prepare composite materials with different contents.Mechanical properties and electrical conductivity results show that the tensile strength of the 0.2 CQD/Cu composite material is~31%higher than that of the pure copper sample,and the conductivity of 0.4 CQD/Cu is~96%IACS,which is as high as pure copper.TEM and HRTEM results show that good interface bonding of CQD and copper grain is the key to maintaining high mechanical and electrical conductivity.This research provides an important foundation and direction for new carbon materials reinforced metal matrix composites.展开更多
The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimenta...The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimental alloys were characterized by X-ray diffractometry and scanning electron microscopy. The hydrogen storage kinetics and thermodynamics, and P-C-I curves were tested using a Sievert apparatus. It is found that increasing Ni content remarkably improves hydrogen storage kinetics but reduces the hydrogen storage capacity of alloys. The highest hydrogen absorption/desorption rate is observed in the La5Mg80Ni15 alloy, with the lowest hydrogen desorption activation value being 57.7 kJ/mol. By means of P-C-I curves and the van’t Hoff equation, it is determined that the thermodynamic performance of the alloy is initially improved and then degraded with increasing Ni content. The La5Mg85Ni10 alloy has the best thermodynamics properties with a hydrogenation enthalpy of -72.1 kJ/mol and hydrogenation entropy of -123.2 J/(mol·K).展开更多
In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the...In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.展开更多
The effect of iron addition on the microstructure, mechanical and magnetic properties of Al-matrix composite was studied. Mechanical mixing was used for the preparation of 0, 5%, 10% and 15% Fe-Al composites(mass fra...The effect of iron addition on the microstructure, mechanical and magnetic properties of Al-matrix composite was studied. Mechanical mixing was used for the preparation of 0, 5%, 10% and 15% Fe-Al composites(mass fraction). Mixtures of Al-Fe were compacted and sintered in a vacuum furnace at 600 °C for 1 h. X-ray diffraction(XRD) of the samples containing 5% and 10% Fe indicates the presence of Al and Fe peaks, while sample containing 15% Fe reveals Al and Al13Fe4 peaks. The results show that both densification and thermal conductivity of the composites decrease by increasing the iron content. The presence of iron in the composite improves the compressive strength and the hardness. The strengthening mechanism is associated with the grain refinement of the matrix and uniform distribution of the Fe particles, as well as the formation of Al13Fe4 intermetallic. The measured magnetization values are equal to 0.3816×10-3 A·m2/g for 5% Fe sample and increases up to 0.6597×10-3 A·m2/g for 10% Fe sample, then decreases to 0.0702×10-3 A·m2/g for 15% Fe sample. This can be explained by the formation of the diamagnetic Al13Fe4 intermetallic compound in the higher Fe content sample detected by XRD analysis.展开更多
Phase decomposition kinetics and the corresponding mechanical properties of the severe cold-rolled(SCRed) carbon-doped(1.3 at.%) equimolar FeCoCrNiMn high-entropy alloy(HEA) after being annealed at 500 ℃ were investi...Phase decomposition kinetics and the corresponding mechanical properties of the severe cold-rolled(SCRed) carbon-doped(1.3 at.%) equimolar FeCoCrNiMn high-entropy alloy(HEA) after being annealed at 500 ℃ were investigated. This single face-centered cubic(FCC) solid-solution HEA decomposed to M23 C6+L10, B2, and σ in chronological order. The formation kinetics of the L10, B2, and σ phases followed the Johnson-Mehl-AvramiKolmogorov(JMAK) equation. The yield strength of the HEA was 1520 MPa and increased to 1920 MPa after being annealed at 500 ℃ for 1 h, as a result of the formation of nanosized M23 C6 and L10. Both strength and ductility decreased after 2 d of annealing due to the increase of volume fractions and the coarsening of the M23C6 and L10 precipitates. From 4 to 32 d, the hardness was found to increase, which is ascribed to the rapid formation of the B2 and σ phases. From 32 to 64 d, the hardness increased further to finally reach about HV 760, with the FCC matrix almost exhausted to form the M23 C6, L10, B2, and σ phases. The results of this work may serve as a guide for the heat-treatment of carbon-doped HEAs.展开更多
基金the financial supports from the National Key Research and Development Program of China (No. 2022YFB3707501)the National Natural Science Foundation of China (No. 51701083)+1 种基金the GDAS Project of Science and Technology Development, China (No. 2022GDASZH2022010107)the Guangzhou Basic and Applied Basic Research Foundation, China (No. 202201010686)。
文摘Based on experimental data,machine learning(ML) models for Young's modulus,hardness,and hot-working ability of Ti-based alloys were constructed.In the models,the interdiffusion and mechanical property data were high-throughput re-evaluated from composition variations and nanoindentation data of diffusion couples.Then,the Ti-(22±0.5)at.%Nb-(30±0.5)at.%Zr-(4±0.5)at.%Cr(TNZC) alloy with a single body-centered cubic(BCC) phase was screened in an interactive loop.The experimental results exhibited a relatively low Young's modulus of(58±4) GPa,high nanohardness of(3.4±0.2) GPa,high microhardness of HV(520±5),high compressive yield strength of(1220±18) MPa,large plastic strain greater than 30%,and superior dry-and wet-wear resistance.This work demonstrates that ML combined with high-throughput analytic approaches can offer a powerful tool to accelerate the design of multicomponent Ti alloys with desired properties.Moreover,it is indicated that TNZC alloy is an attractive candidate for biomedical applications.
基金Project (50825401) supported by the National Natural Science Foundation of ChinaProject (2012CB61905) supported by the National Basic Research Program of China
文摘The effect of electroslag refining on iron reduction from commercial aluminum was investigated.Cast electrodes of commercial aluminum were electroslag refined using KCl-NaCl-Na3AlF6 slag containing Na2B4O7.Experimental results indicate that the iron content decreases with increasing Na2B4O7 addition and remelting time,and the iron content decreases from 0.400% to 0.184% under 9% Na2B4O7 addition for 30 min remelting.The elastic modulus,yield strength and ultimate tensile strength commercial aluminum are improved,and the tensile elongation is increased by 43% after electroslag refining.The chemical reaction between melt and slag to form Fe2B is the main reason for iron reduction and the thermodynamic calculation of the chemical reaction theoretically accounts for the formation of Fe2B.
基金Project(BK2012715)supported by the Basic Research Program(Natural Science Foundation)of Jiangsu Province,ChinaProject(14KJA430002)supported by the Key University Science Research Project of Jiangsu Province,China+3 种基金Project(50971087)supported by the National Natural Science Foundation of ChinaProjects(11JDG070,11JDG140)supported by the Senior Talent Research Foundation of Jiangsu University,ChinaProject(hsm1301)supported by the Foundation of the Jiangsu Province Key Laboratory of High-end Structural Materials,ChinaProject(Kjsmcx2011004)supported by the Foundation of the Jiangsu Province Key Laboratory of Materials Tribology,China
文摘Structural features, aging behavior, precipitation kinetics and mechanical properties of a 6013 Al–Mg–Si aluminum alloy subjected to equal channel angular pressing (ECAP) at different temperatures were comparatively investigated with that in conventional static aging by quantitative X-ray diffraction (XRD) measurements, differential scanning calorimetry (DSC) and tensile tests. Average grain sizes measured by XRD are in the range of 66-112 nm while the average dislocation density is in the range of 1.20×10^14-1.70×10^14 m^-2 in the deformed alloy. The DSC analysis reveals that the precipitation kinetics in the deformed alloy is much faster as compared with the peak-aged sample due to the smaller grains and higher dislocation density developed after ECAP. Both the yield strength (YS) and ultimate tensile strength (UTS) are dramatically increased in all the ECAP samples as compared with the undeformed counterparts. The maximum strength appears in the samples ECAP treated at room temperature and the maximum YS is about 1.6 times that of the statically peak-aged sample. The very high strength in the ECAP alloy is suggested to be related to the grain size strengthening and dislocation strengthening, as well as the precipitation strengthening contributing from the dynamic precipitation during ECAP.
基金Projects(51161015,51371094) supported by the National Natural Science Foundation of China
文摘In order to investigate the influences of the stoichiometric ratio of La/Mg (increasing La and decreasing Mg on the same mole ratio) on the structure and electrochemical performances of the La-Mg-Ni-based A2B7-type electrode alloy, the as-cast and the annealed ternary Lao.8+xMgo.2_xNi3.5 (x=0-0.05) electrode alloys were prepared. The characterization of electrode alloys by X-ray diffraction (XRD) and scanning electron microscopy (SEM) shows that all the as-cast and the annealed alloys hold two major phases of (La,Mg)2Ni7 and LaNi5 as well as a residual phase of LaNi3. Moreover, the increase of La/Mg ratio brings on a decline of (La,Mg)2Ni7 phase and a rise of LaNi5 and LaNi3 phases. The variation of La/Mg ratio gives rise to an evident change of the electrochemical performances of the alloys. The discharge capacities of the as-cast and the annealed alloys evidently decrease with growing the La/Mg ratio, while the cycle stabilities of the alloys visibly augment under the same condition. Furthermore, the high rate discharge ability (HRD), the electrochemical impedance spectrum (EIS), the Tafel polarization curves, and the potential step measurements all indicate that the electrochemical kinetic properties of the alloy electrodes increase with the La/Mg ratio rising.
文摘Thermoplastic starch is a kind of modified starch produced by mixing starch with additives and processing the mixture in an extruder. The mechanical properties, including tensile strength and elongation at break, biodegradability and rheological properties were studied. Glycerol and urea, to some extent, can both decrease the tensile strength and increase percentage elongation at break, because the former acts as a plasticizer and the latter can break down interactions among starch macromolecules. Thermoplastic starch shows thermoplasticity and its melt behaves as a pseudoplastic liquid at a low shear rate. Its biodegrading extent is slightly higher than that of native starch. The molecular weight of starch displays a decreasing tendency after thermoplastic modification.
基金Project (51001043) supported by the National Natural Science Foundation of ChinaProject (NCET2011) supported by Program for New Century Excellent Talents in University, China+4 种基金Project (201104390) supported by China Postdoctoral Science Special FoundationProject (20100470990) supported by China Postdoctoral Science FoundationProject (2012IRTSTHN007) supported by Program for Innovative Research Team (in Science and Technology) in the University of Henan Province, ChinaProject (2011J1003) supported by Baotou Science and Technology Project, ChinaProject (B2010-13) supported by the Doctoral Foundation of Henan Polytechnic University, China
文摘La0.7Ce0.3Ni3.75Mn0.35Al0.15Cu0.75-xFex (x=0-0.20) hydrogen storage alloys were synthesized by induction melting and subsequent annealing treatment, and phase structure and electrochemical characteristics were investigated. All alloys consist of a single LaNi5 phase with CaCu5 structure, and the lattice constant a and the cell volume (V) of the LaNi5 phase increase with increasing x value. The maximum discharge capacity gradually decreases from 319.0 mA?h/g (x=0) to 291.9 mA?h/g (x=0.20) with the increase in x value. The high-rate dischargeability at the discharge current density of 1200 mA/g decreases monotonically from 53.1% (x=0) to 44.2% (x=0.20). The cycling stability increases with increasing x from 0 to 0.20, which is mainly ascribed to the improvement of the pulverization resistance.
基金Projects(51221001,50972121)supported by the National Natural Science Foundation of ChinaProject(B08040)supported by the Introducing Talents of Discipline to Universities,ChinaProject(11-BZ-2012)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),China
文摘Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon (C/C) composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.
文摘Molecular dynamics simulations have been performed to investigate well-known energetic material cyelotrimethylene trinitramine (RDX) crystal, 3-azidomethyl-3-methyloxetane (AMMO) and RDX/AMMO propellant. The results show that the binding energies on different crystalline surface of RDX changes in the order of (010)〉(100)〉 (001). The interactions between RDX and AMMO have been analyzed by means of pair correlation functions. The mechanical properties of RDX/AMMO propellant, i.e. elastic coefficients, modulus, Cauchy pressure, and Poisson's ratio, etc., have been obtained. It is found that mechanical properties are effectively improved by adding some amounts of AMMO polymers, and the overall effect of AMMO on three crystalline surfaces of RDX changes in the order of (100)〉(010)〉(001). The energetic properties of RDX/AMMO propellant have also been calculated and the results show that compared with the pure RDX crystal, the standard theoretical specific impulse of RDX/AMMO propellant decrease, but they are still superior to those of double base propellant.
基金Projects(L2014051,LT2014004)supported by the Program for Scientific Technology Plan of the Educational Department of Liaoning Province,China
文摘The structural, elastic, electronic and optical properties for U3Si2-type AlSc2Si2 compound under pressure were systematically investigated by using the first-principles calculations. The values of elastic constants and elastic moduli indicate that AlSc2Si2 keeps mechanical stability under high pressure. The mechanical properties of AISc2Si2 are compared with those of Al3Sc. The results indicate that AlSc2Si2 is harder than AI3Sc. Anisotropic constant AU and 3D curved surface of elastic moduli predict that AISc2Si2 is obviously anisotropic under pressure. The electronic structure of AlSc2Si2 exhibits metallic character and the metallicity decreases with the elevated pressure. In addition, optical properties as a function of pressure were calculated and analyzed. The present work provides theoretical support for further experimental work and industrial applications.
基金Projects(50971066,51174098)supported by the National Natural Science Foundation of ChinaProject(2008-46)supported by Jiangsu Provincial"333"Project of Training the High-level Talents Foundation,China+3 种基金Project(BE2009127)supported by Jiangsu Provincial Science Supporting Item,ChinaProject(2011-11)supported by Jiangsu Provincial College Excellent Science and Technology Innovation Team,ChinaProject(kjsmcx0903)supported by Jiangsu Key Laboratory of Tribology Project,ChinaProject(1201220072)supported by Jiangsu Province Undergraduate Practice-Innovation Training,China
文摘In situ TiB2/7055 composites were successfully synthesized via magnetic chemical direct melt reaction from 7055 (Al-3B)?Ti system. The phase composition and the microstructure of the composites were investigated by XRD, OM and SEM technologies, and the mechanical and wear properties were tested. The results indicate that with the pulsed magnetic field assistance, the morphologies of in situ TiB2 particles are mainly hexagonal-shape or nearly spherical, the sizes are less than 1 μm, and the distribution of the matrix is uniform. Compared the microstructures of the 7055 aluminum matrix composites synthesized without pulsed magnetic field, the average size ofα(Al) phase with pulsed magnetic field assistance is decreased from 20 to 10μm, the array of the second phase is changed from continuous net-shape to discontinuous shape. With the pulsed magnetic field, the tensile strengths of the composites are enhanced from 310 to 330 MPa, and the elongations are increased from 7.5%to 8.0%. In addition, compared with matrix alloy, the wear mass loss of the composites is decreased from 111 to 78 mg under a load of 100 N for 120 min.
基金Project(51072165)supported by the National Natural Science Foundation of ChinaProject(KP201307)supported by the Fund of the State Key Laboratory of Solidification Processing in NWPU
文摘BN interphase was successfully synthesized on SiC fiber fabrics by dip-coating process using boric acid and urea as precursors under N2 atmosphere. The morphology of BN interphase was observed by SEM, and the structure was characterized by XRD and FT-IR spectra. The SiCf/SiC composites with dip-coated BN interphase were fabricated by chemical vapor infiltration (CVI) process, and the effects ofBN interphase on the mechanical properties of composites were investigated. The results show that the SiC fibers are fully covered by BN interphase with smooth surface and turbostratic structure (t-BN), and the thickness is about 0.4 μm. The flexural strengths of SiCf/SiC composites with and without BN interphase are about 180 and 95 MPa, respectively. Compared with the as-received SiCf/SiC composites, the composites with BN interphase exhibit an obvious toughened fracture behavior. From the microstructural analysis, it can be confirmed that the BN interphase plays a key part in protecting the fibers from chemical attack during matrix infiltration and weakening interfacial bonding, which can improve the mechanical properties of SiCf/SiC composites remarkably.
基金Project(2017zzts111)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The effects of SiCp surface modifications(Cu coating,Ni coating and Ni/Cu coating)on the microstructures and mechanical properties of Al matrix composites were investigated.Surface modification of SiC particles with Cu,Ni and Cu/Ni,respectively,was carried out by electroless plating method.SiCp/Al composites were prepared by hot pressed sintering followed by hot extrusion.The results show that the surface modification of SiC particles plays an effective role,which is relative to the type of surface coating,and the interfacial bonding become stronger in the following order:untreated SiCp<Ni(Cu)-coated SiCp<Ni/Cu-coated SiCp.The Ni/Cu-coated SiCp/Al composites exhibit the best comprehensive mechanical properties,with ultimate tensile strength(σUTS)and fracture strain(εf)of 389 MPa and 6.3%,respectively.Compared with that of untreated-SiCp/Al composites,theσUTS andεf are enhanced by 19.3%and 57.5%.
基金Project(52064032)supported by the National Natural Science Foundation of ChinaProjects(2019ZE001,202002AB080001)supported by the Yunnan Science and Technology Projects,ChinaProject(YNWR-QNBJ-2018-005)supported by the Yunnan Ten Thousand Talents Plan Young&Elite Talents,China。
文摘Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was prepared by powder metallurgy method.The composite powder was prepared by molecular blending method and ball milling method at first,and then densified into bulk material by spark plasma sintering(SPS).X-ray diffraction,Raman spectroscopy,infrared spectroscopy,and nuclear magnetic resonance were employed to characterize the CQD synthesized under different temperature conditions,and then CQDs with a higher degree of sp^(2)were utilized as the reinforcement to prepare composite materials with different contents.Mechanical properties and electrical conductivity results show that the tensile strength of the 0.2 CQD/Cu composite material is~31%higher than that of the pure copper sample,and the conductivity of 0.4 CQD/Cu is~96%IACS,which is as high as pure copper.TEM and HRTEM results show that good interface bonding of CQD and copper grain is the key to maintaining high mechanical and electrical conductivity.This research provides an important foundation and direction for new carbon materials reinforced metal matrix composites.
基金Projects(51761032,51471054) supported by the National Natural Science Foundation of China
文摘The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimental alloys were characterized by X-ray diffractometry and scanning electron microscopy. The hydrogen storage kinetics and thermodynamics, and P-C-I curves were tested using a Sievert apparatus. It is found that increasing Ni content remarkably improves hydrogen storage kinetics but reduces the hydrogen storage capacity of alloys. The highest hydrogen absorption/desorption rate is observed in the La5Mg80Ni15 alloy, with the lowest hydrogen desorption activation value being 57.7 kJ/mol. By means of P-C-I curves and the van’t Hoff equation, it is determined that the thermodynamic performance of the alloy is initially improved and then degraded with increasing Ni content. The La5Mg85Ni10 alloy has the best thermodynamics properties with a hydrogenation enthalpy of -72.1 kJ/mol and hydrogenation entropy of -123.2 J/(mol·K).
基金supported by the National Key Technology R&D Program(No.2013BAD13B03)the Key R&D Project from Science and Technology Department of Zhejiang Province(Nos.2018C02026,2018C02040)+1 种基金the National Natural Science Foundation of China(No.31072246)the Fundamental Research Funds for the Central Universities(No.201564020)
文摘In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.
文摘The effect of iron addition on the microstructure, mechanical and magnetic properties of Al-matrix composite was studied. Mechanical mixing was used for the preparation of 0, 5%, 10% and 15% Fe-Al composites(mass fraction). Mixtures of Al-Fe were compacted and sintered in a vacuum furnace at 600 °C for 1 h. X-ray diffraction(XRD) of the samples containing 5% and 10% Fe indicates the presence of Al and Fe peaks, while sample containing 15% Fe reveals Al and Al13Fe4 peaks. The results show that both densification and thermal conductivity of the composites decrease by increasing the iron content. The presence of iron in the composite improves the compressive strength and the hardness. The strengthening mechanism is associated with the grain refinement of the matrix and uniform distribution of the Fe particles, as well as the formation of Al13Fe4 intermetallic. The measured magnetization values are equal to 0.3816×10-3 A·m2/g for 5% Fe sample and increases up to 0.6597×10-3 A·m2/g for 10% Fe sample, then decreases to 0.0702×10-3 A·m2/g for 15% Fe sample. This can be explained by the formation of the diamagnetic Al13Fe4 intermetallic compound in the higher Fe content sample detected by XRD analysis.
基金Project(51901134)supported by the National Natural Science Foundation of ChinaProject(SJTU.18X100040023)supported by the Program of Scientific Research Ability Cultivation for Young Researchers,China。
文摘Phase decomposition kinetics and the corresponding mechanical properties of the severe cold-rolled(SCRed) carbon-doped(1.3 at.%) equimolar FeCoCrNiMn high-entropy alloy(HEA) after being annealed at 500 ℃ were investigated. This single face-centered cubic(FCC) solid-solution HEA decomposed to M23 C6+L10, B2, and σ in chronological order. The formation kinetics of the L10, B2, and σ phases followed the Johnson-Mehl-AvramiKolmogorov(JMAK) equation. The yield strength of the HEA was 1520 MPa and increased to 1920 MPa after being annealed at 500 ℃ for 1 h, as a result of the formation of nanosized M23 C6 and L10. Both strength and ductility decreased after 2 d of annealing due to the increase of volume fractions and the coarsening of the M23C6 and L10 precipitates. From 4 to 32 d, the hardness was found to increase, which is ascribed to the rapid formation of the B2 and σ phases. From 32 to 64 d, the hardness increased further to finally reach about HV 760, with the FCC matrix almost exhausted to form the M23 C6, L10, B2, and σ phases. The results of this work may serve as a guide for the heat-treatment of carbon-doped HEAs.