Ti_(3)AlC_(2)was added into Cu-graphite composites to enhance their tribological properties.The impact of sintering temperature on properties of Cu-graphite-Ti_(3)AlC_(2)composites(CGTCs)fabricated by spark plasma sin...Ti_(3)AlC_(2)was added into Cu-graphite composites to enhance their tribological properties.The impact of sintering temperature on properties of Cu-graphite-Ti_(3)AlC_(2)composites(CGTCs)fabricated by spark plasma sintering(SPS)was studied,including microstructure,density,hardness,electrical conductivity,interfacial properties,and tribological behavior.The results indicate that mutual diffusion between Ti_(3)AlC_(2)and Cu occurs during sintering,leading to metallurgical bonding.Moreover,titanium atoms originating from Ti_(3)AlC_(2)undergo a reaction with carbon atoms on the graphite surface,facilitating enhanced bonding between Cu and graphite.CGTCs exhibit promising lubrication performance at different sintering temperatures,with friction coefficients ranging from 0.15 to 0.25.The wear rate decreases and then increases with the increase of sintering temperature.Optimal tribological properties are achieved at 980℃,when the average friction coefficient and wear rate are 0.18 and 4.82×10^(−6) mm^(3)·(N·m)^(−1),respectively.展开更多
To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis(PIP)method,the low-temperature reactive melt infiltration(RMI)process was used to seal the composite...To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis(PIP)method,the low-temperature reactive melt infiltration(RMI)process was used to seal the composites using Zr_(2)Cu as the filler.The microstructure,mechanical properties,and ablation properties of the Zr_(2)Cu packed composites were analyzed.Results show that during Zr_(2)Cu impregnation,the melt efficiently fills the large pores of the composites and is converted to ZrCu due to a partial reaction of zirconium with carbon.This results in an increase in composite density from 1.91 g/cm^(3)to 2.24 g/cm^(3)and a reduction in open porosity by 27.35%.Additionally,the flexural strength of Zr_(2)Cu packed C/C-SiC-ZrC composites is improved from 122.78±8.09 MPa to 135.53±5.40 MPa.After plasma ablation for 20 s,the modified composites demonstrate superior ablative resistance compared to PIP C/C-SiC-ZrC,with mass ablation and linear ablation rates of 2.77×10^(−3)g/s and 2.60×10^(−3)mm/s,respectively.The“selftranspiration”effect of the low-melting point copper-containing phase absorbs the heat of the plasma flame,further reducing the ablation temperature and promoting the formation of refined ZrO_(2)particles within the SiO_(2)melting layer.This provides more stable erosion protection for Zr_(2)Cu packed C/C-SiC-ZrC composites.展开更多
Photocatalysis is an important process in energy conversion and environmental usage because of its feasible,profitable,and environmentally safe benefits.Coordination chemistry of the CeO_(2)is gaining significant inte...Photocatalysis is an important process in energy conversion and environmental usage because of its feasible,profitable,and environmentally safe benefits.Coordination chemistry of the CeO_(2)is gaining significant interest because its nanocomposites show unique characteristics namely optically active,wide bandgap(Eg),reversible valence states(Ce^(3+/4+)),rich defect architectures,high O_(2)storage capability,ionic conductivity,and exceptional chemical resistance.Systematically summarized the importance of synthesis methods,particle morphology,and crystal structure aiming at how to heighten the efficacy of CeO_(2)-derived hybrid heterojunction(HHJ)photocatalyst.Selection of an appropriate synthesis method and morphology of the composite materials are beneficial in inhibiting the rapid electron-hole(e^(−)-h^(+))recombination,improvement in visible light adsorption,and large generation of e^(−)-h^(+)pairs to accelerate the photocatalysts activities.Various modification approaches include elemental doping(metal/non-metal doping),heterojunction construction(lower/wide Eg semiconductors(SCD),carbon,conducting polymeric materials),imperfection engineering,and multicomponent hybrid composites.These methods assist as a valuable resource for the rational design of effective CeO_(2)-based composite photocatalysts for sustainable development owing to the enhancement of oxygen species mobility,rapid charge transfer,maximum visible light captivation and slow down the charge recombination rate with increase photogeneration of e−-h+pairs.Also examines the advancements made in CeO_(2)conjugated hybrid composites in photo-oxidation of wastewater effluents(antibiotic/organic dyes/chemical/pharmaceutical),heavy metal removal,H2 production,CO_(2)reduction,and H2O splitting applications.Subsequently,the difficulties and fundamental ideas behind several heterojunction photocatalysts encountered by CeO_(2)-based composites are examined,and future directions for their development are suggested.展开更多
Unmanaged wood waste,particularly in countries like Nepal,presents serious environmental concerns due to open burning and improper disposal,leading to carbon emissions,air pollution and land degradation.This study int...Unmanaged wood waste,particularly in countries like Nepal,presents serious environmental concerns due to open burning and improper disposal,leading to carbon emissions,air pollution and land degradation.This study introduces an environmentally sustainable strategy to upcycle Toona ciliata wood scrap—an abundant and underutilized lignocellulosic biomass—into high performance carbon electrodes for green energy storage applications.Activated carbon(TCWAC)was synthesized via single-step pyrolytic carbonization followed by phosphoric acid activation,yielding a material with high specific surface area,hierarchical porosity,and excellent electrical conductivity.Electrochemical measurements using a three-electrode configuration in 6 M KOH revealed optimized potential windows of -1.0 to -0.2 V(TCWAC),-1.2 to 0 V(TCWAC-Mn),and -1.15 to -0.4 V(TCWAC-Fe).TCWAC exhibited a specific capacitance of 156.3 Fg^(-1)at 1 Ag^(-1),with an energy density of 3.5 Whkg^(-1),and 80.2% capacity retention after 1000 charge-discharge cycles.Composites with MnO_(2)and Fe_(2)O_(3)were also evaluated.TWAC-Mn delivered 489.4 Fg^(-1),25.1 Whkg^(-1),and 99.1% retention,whereas,TWAC-Fe achieved 321.3 Fg^(-1),6.3 Whkg^(-1),and 90.3% retention.The superior performance of MnO_(2)is attributed to its multiple oxidation states,facilitating reversible faradaic redox and enhanced pseudocapacitance.This work offers the first direct,systematic comparison of MnO_(2)and Fe_(2)O_(3)composites on a common biomass-carbon matrix under identical synthesis and testing conditions.The finding provides mechanistic insight into charge storage behaviour and demonstrate a scalable route for converting biomass waste into sustainable electrode materials,contributing to cleaner energy solutions and improved biomass valorization.展开更多
B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites...B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites show better macroscopic plastic deformability and obvious work-hardening behavior compared to the conventional amorphous alloy matrix composites reinforced with ductile phases.However,the in-situ metastable B2-CuZr phase tends to undergo eutectoid decomposition during solidification,and the volume fraction,size,and distribution of B2-CuZr phase are difficult to control,which limits the development and application of these materials.To date,much efforts have been made to solve the above problems through composition optimization,casting parameter tailoring,and post-processing technique.In this study,a review was given based on relevant studies,focusing on the predictive approach,reinforcing mechanism,and microstructure tailoring methods of B2-CuZr phase reinforced amorphous alloy matrix composites.The research focus and future prospects were also given for the future development of the present composite system.展开更多
Ultrasonic vibration treatment(UVT)at varying power was successfully applied to the Cu–TiB_(2) composite melt using a SiAlON ceramic sonotrode.The results indicate that TiB_(2) particles are more evenly dispersed in ...Ultrasonic vibration treatment(UVT)at varying power was successfully applied to the Cu–TiB_(2) composite melt using a SiAlON ceramic sonotrode.The results indicate that TiB_(2) particles are more evenly dispersed in the Cu matrix with increasing ultrasonic power,leading to improved mechanical properties of as-cast composites(≤1000 W).With 1000 W UVT,the distribution of TiB_(2) particles becomes the remarkably uniform and well dispersed,with the size of TiB_(2) particle aggregates decreasing from~50μm without UVT to~5μm.The ultimate tensile strength,yield strength,and elongation of the as-cast composite are 201 MPa,85 MPa,and 28.6%,respectively,representing increases of 21.1%,27.3%,and 43%,respectively,compared to the as-cast composite without UVT.However,when the power is increased to 1500 W,thermal efects are likely to emerge,and the ultrasonic attenuation efect is enhanced,resulting in the re-agglomeration of TiB_(2) particles and a deterioration in performance.By quantitatively analyzing the relationships between sound pressure(Pk),sound energy density(I),sound pulse velocity(V),and ultrasonic power,the infuence mechanism of ultrasonic power on the composite microstructure has been further elucidated and characterized.This study provides crucial guidance for the industrial application of UVT in the fabrication of Cu matrix composites.展开更多
The Al-Mg_(2)Si in-situ composite is a lightweight material with great potential for application in fields such as automotive lightweighting,aerospace,and electronic components.In this research,the modification,semi-s...The Al-Mg_(2)Si in-situ composite is a lightweight material with great potential for application in fields such as automotive lightweighting,aerospace,and electronic components.In this research,the modification,semi-solid technology coupled with different types of electromagnetic stirring was applied to regulate the undesirable solidified dendritic microstructure and facilitate the composites’mechanical properties.The spheroidization and refinement of Mg_(2)Si andα-Al matrix in SM(semi-solid)+RES(rotate electromagnetic stirring)sample and SM+SHES(single winding helical electromagnetic stirring)sample are realized under the effect of fused dendrite arm,the decreased critical nucleate radius,and the increased nucleation rate and extra supercooling degree induced by electromagnetic stirring.The Mg_(2)Si phase in the SM+RES sample and SM+SHES sample is refined by 73.4%and 75.7%,respectively compared to the AC(as-cast)sample.Besides,the single winding electromagnetic stirring can lead to more homogeneously distributed physical fields,lower temperature gradient,and more significant mass transfer,mainly responsible for the more homogeneous distributed reinforced finer Mg_(2)Si particles in the SM+SHES sample.Moreover,both the tensile properties and hardness of modified semi-solid composites are improved through electromagnetic stirring.Compared with RES,the improvement effect of SHES is more excellent.The SM+SHES sample possesses the highest Brinell hardness(124.7 HB),and its quality index of tensile properties is 5.73%and 82.2%higher than that of the SM+RES and AC samples,respectively.展开更多
A novel mechanical stirring-assisted double-melt in-situ reaction casting process was developed to prepare Cu-1TiB2(wt%)composites.The effects of preparation parameters(melting reaction temperature,stirring rate and s...A novel mechanical stirring-assisted double-melt in-situ reaction casting process was developed to prepare Cu-1TiB2(wt%)composites.The effects of preparation parameters(melting reaction temperature,stirring rate and stirring time)on the microstructure and properties of Cu-1TiB2 composites were investigated.The melt viscosity and particle motion during stirring process were analyzed.The strong turbulence and shear effects generated by mechanical stirring in the melt not only significantly improve the particle distribution but also contribute to adequate in-situ reactions and precise control of the chemical composition.The optimal preparation parameters were 1200℃,a stirring rate of 100 r·min^(−1) and a stirring time of 1 min.Combined with the cold rolling process,the tensile strength,elongation and electrical conductivity of the composite reached 475 MPa,6.0%and 88.4%IACS,respectively,which were significantly better than the composite prepared by manual stirring.The good plasticity is attributed to the uniform distribution of TiB_(2) particles,effectively retarding the crack propagation.The dispersion of particles promotes heterogeneous nucleation of Cu matrix and inhibits grain growth.On the other hand,dispersed particles contribute to grain shear fracture and dislocation multiplication during cold deformation.Therefore,the composite achieves higher dislocation strengthening and grain boundary strengthening.展开更多
Cost-effective CO_(2) adsorbents are gaining increasing attention as viable solutions for mitigating climate change.In this study,composites were synthesized by electrochemically combining the post-gasification residu...Cost-effective CO_(2) adsorbents are gaining increasing attention as viable solutions for mitigating climate change.In this study,composites were synthesized by electrochemically combining the post-gasification residue of Macadamia nut shell with copper benzene-1,3,5-tricarboxylate(CuBTC).Among the different composites synthesized,the ratio of 1:1 between biochar and CuBTC(B 1:1)demonstrated the highest CO_(2) adsorption capacity.Under controlled laboratory conditions(0℃,1 bar,without the influence of ambient moisture or CO_(2) diffusion limitations),B 1:1 achieved a CO_(2) adsorption capacity of 9.8 mmol/g,while under industrial-like conditions(25℃,1 bar,taking into account the impact of ambient moisture and CO_(2) diffusion limitations within a bed of adsorbent),it reached 6.2 mmol/g.These values surpassed those reported for various advanced CO_(2) adsorbents investigated in previous studies.The superior performance of the B 1:1 composite can be attributed to the optimization of the number of active sites,porosity,and the preservation of the full physical and chemical surface properties of both parentmaterials.Furthermore,the composite exhibited a notable CO_(2)/N_(2) selectivity and improved stability under moisture conditions.These favorable characteristics make B 1:1 a promising candidate for industrial applications.展开更多
Mg alloys have the defects of low stiffness,low strength,and high coefficient of thermal expansion(CTE).The composites strategy and its architecture design are effective approaches to improve the comprehensive perform...Mg alloys have the defects of low stiffness,low strength,and high coefficient of thermal expansion(CTE).The composites strategy and its architecture design are effective approaches to improve the comprehensive performance of materials,but the processing difficulty,especially in ceramics forming,limits the control and innovation of material architecture.Here,combined with 3D printing and squeeze infiltration technology,two precisely controllable architectures of AZ91/Al_(2)O_(3)interpenetrating phase composites(IPC)with ceramic scaffold were prepared.The interface,properties and impact of different architecture on IPC performance were studied by experiments and finite element simulation.The metallurgical bonding of the interface was realized with the formation of MgAl_(2)O_(4)reaction layer.The IPC with 1 mm circular hole scaffold(1C-IPC)exhibited significantly improved elastic modulus of 164 GPa,high compressive strength of 680 MPa,and good CTE of 12.91×10^(-6)K^(−1),which were 3.64 times,1.98 times and 55%of the Mg matrix,respectively.Their elastic modulus,compressive strength,and CTE were superior to the vast majority of Mg alloys and Mg based composites.The reinforcement and matrix were bicontinuous and interpenetrating each other,which played a critical role in ensuring the potent strengthening effect of the Al_(2)O_(3)reinforcement by efficient load transfer.Under the same volume fraction of reinforcements,compared to IPC with 1 mm hexagonal hole scaffold(1H-IPC),the elastic modulus and compressive strength of 1C-IPC increased by 15%and 28%,respectively,which was due to the reduced stress concentration and more uniform stress distribution of 1C-IPC.It shows great potential of architecture design in improving the performance of composites.This study provides architectural design strategy and feasible preparation method for the development of high performance materials.展开更多
Ti_(2)AlC/TiAl composites with a network structure were successfully prepared with carbon nanotubes and Ti-45Al-8Nb pre-alloyed powder using spark plasma sintering.The effects of sintering temperature(1200-1350℃)on t...Ti_(2)AlC/TiAl composites with a network structure were successfully prepared with carbon nanotubes and Ti-45Al-8Nb pre-alloyed powder using spark plasma sintering.The effects of sintering temperature(1200-1350℃)on the microstructural evolution and mechanical properties were systematically investigated.The microstructure of Ti_(2)AlC/TiAl composites exhibits duplex,near-lamellar,and fully lamellar structures,as the sintering temperature increases from 1200 to 1350℃.The network structured Ti_(2)AlC phase can refine the microstructure and the phase becomes discontinuous at high sintering temperatures.Notably,composites sintered at 1300℃ exhibit excellent mechanical properties,with the highest compressive strength(1921 MPa)and fracture strain(26%)at room temperature.Moreover,the ultimate tensile strength and fracture strain reach 537 MPa and 3.1%at 900℃,and 485 MPa and 3.3%at 950℃,respectively.The enhancement of the mechanical properties is attributed primarily to the load bearing,particle pull-out,and inhibition of crack propagation induced by Ti_(2)AlC particles.展开更多
To improve the oxidation resistance of carbon/carbon composites,ZrB2-MoSi2/SiC coating on the carbon/carbon substrate was prepared.The inner coating of SiC was prepared by pack cementation and the outer coating of ZrB...To improve the oxidation resistance of carbon/carbon composites,ZrB2-MoSi2/SiC coating on the carbon/carbon substrate was prepared.The inner coating of SiC was prepared by pack cementation and the outer coating of ZrB2-MoSi2 was prepared by slurry painting.The phase compositions and microstructures of the coating were characterized by XRD and SEM,respectively.The preparation and the high temperature oxidation property of the coated composites were investigated.The results show that the outer coating of carbon/carbon composites is composed of ZrB2,MoSi2 and SiC phases.The mass losses of the ZrB2-MoSi2/SiC coated samples with SiC nano-whiskers after 30 h and 10 h of oxidation at 1 273 K and 1 773 K were,respectively,5.3% and 3.0%.The ZrB2-MoSi2/SiC coated samples exhibit self-sealing performance and good oxidation resistance at high temperature.展开更多
To improve the oxidation resistance of carbon/carbon （C/C） composites in air at high temperatures, a SiC- MoSi2/ZrO2-MoSi2 coating was prepared on the surface of C/C composites by pack cementation and slurry method....To improve the oxidation resistance of carbon/carbon （C/C） composites in air at high temperatures, a SiC- MoSi2/ZrO2-MoSi2 coating was prepared on the surface of C/C composites by pack cementation and slurry method. The microstructures and phase compositions of the coated C/C composites were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The result shows that the SiC-MoSi2/ZrO2-MoSi2 coating is dense and crack-free with a thickness of 250-300 μm. The preparation and the high temperature oxidation property of the coated composites were investigated. The as-received coating has excellent oxidation protection ability and can protect C/C composites from oxidation for 260 h at 1773 K in air. The excellent anti-oxidation performance of the coating is considered to come from the formation of ZrSiO4, which improves the stability of the coating at high temperatures.展开更多
To improve the anti-oxidation ability of silicon-based coating for carbon/carbon （C/C） composites at high temperatures, a ZrB2 modified silicon-based multilayer oxidation protective coating was prepared by pack ceme...To improve the anti-oxidation ability of silicon-based coating for carbon/carbon （C/C） composites at high temperatures, a ZrB2 modified silicon-based multilayer oxidation protective coating was prepared by pack cementation. The phase composition, microstructure and oxidation resistance at 1773, 1873 and 1953 K in air were investigated. The prepared coating exhibits dense structure and good oxidation protective ability. Due to the formation of stable ZrSiO4-SiO2 compound, the coating can effectively protect C/C composites from oxidation at 1773 K for more than 550 h. The anti-oxidation performance decreases with the increase of oxidation temperature. The mass loss of coated sample is 2.44% after oxidation at 1953 K for 50 h, which is attributed to the decomposition of ZrSiO4 and the volatilization of SiO2 protection layer.展开更多
TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstru...TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni＋Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.展开更多
Four kinds of Cu-based composites with different mass ratios of graphite and WS2 as lubricants were fabricated by hot-pressing method. Electrical sliding wear behaviors of the composites were investigated using a bloc...Four kinds of Cu-based composites with different mass ratios of graphite and WS2 as lubricants were fabricated by hot-pressing method. Electrical sliding wear behaviors of the composites were investigated using a block-on-ring tribometer rubbing against Cu-5%Ag alloy ring. The results demonstrated that 800 ~C was the optimum sintering temperature for Cu-graphite-WS2 dual-lubricant composites to obtain the best comprehensive properties of mechanical strength and lubrication performance. Contact voltage drops of the Cu-based composites increased with increasing the mass ratio of WS2 to graphite. The Cu-based composite with 20% graphite and 10% WS2 showed the best wear resistance due to the excellent synergetic lubricating effect of graphite and WS2. The reasonable addition of WS2 into the Cu-graphite composite can remarkably improve the wear resistance without much rise of electrical energy loss which provides a novel principle of designing suitable sliding electrical contact materials for industrial applications.展开更多
Zn-Al-Cu-TiB2（ZA27-TiB2） in situ composites were fabricated via reactions between molten aluminum and mixed halide salts（K2TiF6 and KBF4） at temperature of 875 °C. The microstructure, mechanical properties an...Zn-Al-Cu-TiB2（ZA27-TiB2） in situ composites were fabricated via reactions between molten aluminum and mixed halide salts（K2TiF6 and KBF4） at temperature of 875 °C. The microstructure, mechanical properties and wear behavior of the composites were investigated. Microstructure analysis shows that fine and clean TiB2 particles distribute uniformly through the matrix. The mechanical properties of the composites increase with the increase in TiB2 content. As TiB2 content increases to 5%（mass fraction）, an improvement of HB 18 in hardness and 49 MPa in ultimate tensile strength（UTS） is achieved. The overall results reveal that the composites possess low friction coefficients and the wear rate is reduced from 5.9×10-3 to 1.3×10-3 mm3/m after incorporating 5% TiB2. Friction coefficient and worn surface analysis indicate that there is a change in the wear mechanism in the initial stage of wear test after introducing in situ TiB2 particles into the matrix.展开更多
C/SiC/MoSi2-SiC-Si oxidation protective multilayer coating for carbon/carbon （C/C） composites was prepared by pack cementation and slurry method. The microstructure, element distribution and phase composition of the...C/SiC/MoSi2-SiC-Si oxidation protective multilayer coating for carbon/carbon （C/C） composites was prepared by pack cementation and slurry method. The microstructure, element distribution and phase composition of the as-received coating were analyzed by scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS） and X-ray diffraction （XRD）. The results show that the multilayer coating was composed of MoSi2, SiC and Si. It could effectively protect C/C composites against oxidation for 200 h with the mass loss of 3.25% at 1873 K in static air. The mass loss of the coated C/C composites results from the volatilization of SiO2 and the formation of cracks and bubble holes in the coating.展开更多
Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and coppe...Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.展开更多
Microstructures of Ti2AlN/TiAl composites prepared by in-situ method were characterized in in-situ and aging treatment conditions and the nitride precipitation was investigated in Ti2AlN/TiAl composites aged at 900 ℃...Microstructures of Ti2AlN/TiAl composites prepared by in-situ method were characterized in in-situ and aging treatment conditions and the nitride precipitation was investigated in Ti2AlN/TiAl composites aged at 900 ℃ for 24 h after being heat treated at 1400 ℃ for 0.5 h. The in-situ composites consist of γ＋α2 lamellar colonies, equiaxed y grains and Ti2AlN reinforcements. Matrix with nearly fully lamellar structure formed after solution and subsequently aging treatment. With the increase of Ti2AlN content, the nearly fully lamellar structure becomes instable for the aged composites. According to TEM study, fine Ti2AlN precipitates are found to distribute at the grain boundaries of lamellar colony. Needle-like Ti3AlN precipitates arrange in line with growing axis parallel to [001] direction of the γ-TiAl matrix and another needle-like Ti3AlN precipitates with lager size distribute at the dislocations. Key words：展开更多
基金Open subject of State Key Laboratory of Heavy-Duty and Express High-Power Electric Locomotive(QZKFKT2023-007)。
文摘Ti_(3)AlC_(2)was added into Cu-graphite composites to enhance their tribological properties.The impact of sintering temperature on properties of Cu-graphite-Ti_(3)AlC_(2)composites(CGTCs)fabricated by spark plasma sintering(SPS)was studied,including microstructure,density,hardness,electrical conductivity,interfacial properties,and tribological behavior.The results indicate that mutual diffusion between Ti_(3)AlC_(2)and Cu occurs during sintering,leading to metallurgical bonding.Moreover,titanium atoms originating from Ti_(3)AlC_(2)undergo a reaction with carbon atoms on the graphite surface,facilitating enhanced bonding between Cu and graphite.CGTCs exhibit promising lubrication performance at different sintering temperatures,with friction coefficients ranging from 0.15 to 0.25.The wear rate decreases and then increases with the increase of sintering temperature.Optimal tribological properties are achieved at 980℃,when the average friction coefficient and wear rate are 0.18 and 4.82×10^(−6) mm^(3)·(N·m)^(−1),respectively.
基金Open Fund of Zhijian Laboratory,Rocket Force University of Engineering(2024-ZJSYS-KF02-09)National Natural Science Foundation of China(51902028,52272034)+1 种基金Key Research and Development Program of Shaanxi(2023JBGS-15)Fundamental Research Funds for the Central Universities(Changan University,300102313202,300102312406)。
文摘To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis(PIP)method,the low-temperature reactive melt infiltration(RMI)process was used to seal the composites using Zr_(2)Cu as the filler.The microstructure,mechanical properties,and ablation properties of the Zr_(2)Cu packed composites were analyzed.Results show that during Zr_(2)Cu impregnation,the melt efficiently fills the large pores of the composites and is converted to ZrCu due to a partial reaction of zirconium with carbon.This results in an increase in composite density from 1.91 g/cm^(3)to 2.24 g/cm^(3)and a reduction in open porosity by 27.35%.Additionally,the flexural strength of Zr_(2)Cu packed C/C-SiC-ZrC composites is improved from 122.78±8.09 MPa to 135.53±5.40 MPa.After plasma ablation for 20 s,the modified composites demonstrate superior ablative resistance compared to PIP C/C-SiC-ZrC,with mass ablation and linear ablation rates of 2.77×10^(−3)g/s and 2.60×10^(−3)mm/s,respectively.The“selftranspiration”effect of the low-melting point copper-containing phase absorbs the heat of the plasma flame,further reducing the ablation temperature and promoting the formation of refined ZrO_(2)particles within the SiO_(2)melting layer.This provides more stable erosion protection for Zr_(2)Cu packed C/C-SiC-ZrC composites.
文摘Photocatalysis is an important process in energy conversion and environmental usage because of its feasible,profitable,and environmentally safe benefits.Coordination chemistry of the CeO_(2)is gaining significant interest because its nanocomposites show unique characteristics namely optically active,wide bandgap(Eg),reversible valence states(Ce^(3+/4+)),rich defect architectures,high O_(2)storage capability,ionic conductivity,and exceptional chemical resistance.Systematically summarized the importance of synthesis methods,particle morphology,and crystal structure aiming at how to heighten the efficacy of CeO_(2)-derived hybrid heterojunction(HHJ)photocatalyst.Selection of an appropriate synthesis method and morphology of the composite materials are beneficial in inhibiting the rapid electron-hole(e^(−)-h^(+))recombination,improvement in visible light adsorption,and large generation of e^(−)-h^(+)pairs to accelerate the photocatalysts activities.Various modification approaches include elemental doping(metal/non-metal doping),heterojunction construction(lower/wide Eg semiconductors(SCD),carbon,conducting polymeric materials),imperfection engineering,and multicomponent hybrid composites.These methods assist as a valuable resource for the rational design of effective CeO_(2)-based composite photocatalysts for sustainable development owing to the enhancement of oxygen species mobility,rapid charge transfer,maximum visible light captivation and slow down the charge recombination rate with increase photogeneration of e−-h+pairs.Also examines the advancements made in CeO_(2)conjugated hybrid composites in photo-oxidation of wastewater effluents(antibiotic/organic dyes/chemical/pharmaceutical),heavy metal removal,H2 production,CO_(2)reduction,and H2O splitting applications.Subsequently,the difficulties and fundamental ideas behind several heterojunction photocatalysts encountered by CeO_(2)-based composites are examined,and future directions for their development are suggested.
文摘Unmanaged wood waste,particularly in countries like Nepal,presents serious environmental concerns due to open burning and improper disposal,leading to carbon emissions,air pollution and land degradation.This study introduces an environmentally sustainable strategy to upcycle Toona ciliata wood scrap—an abundant and underutilized lignocellulosic biomass—into high performance carbon electrodes for green energy storage applications.Activated carbon(TCWAC)was synthesized via single-step pyrolytic carbonization followed by phosphoric acid activation,yielding a material with high specific surface area,hierarchical porosity,and excellent electrical conductivity.Electrochemical measurements using a three-electrode configuration in 6 M KOH revealed optimized potential windows of -1.0 to -0.2 V(TCWAC),-1.2 to 0 V(TCWAC-Mn),and -1.15 to -0.4 V(TCWAC-Fe).TCWAC exhibited a specific capacitance of 156.3 Fg^(-1)at 1 Ag^(-1),with an energy density of 3.5 Whkg^(-1),and 80.2% capacity retention after 1000 charge-discharge cycles.Composites with MnO_(2)and Fe_(2)O_(3)were also evaluated.TWAC-Mn delivered 489.4 Fg^(-1),25.1 Whkg^(-1),and 99.1% retention,whereas,TWAC-Fe achieved 321.3 Fg^(-1),6.3 Whkg^(-1),and 90.3% retention.The superior performance of MnO_(2)is attributed to its multiple oxidation states,facilitating reversible faradaic redox and enhanced pseudocapacitance.This work offers the first direct,systematic comparison of MnO_(2)and Fe_(2)O_(3)composites on a common biomass-carbon matrix under identical synthesis and testing conditions.The finding provides mechanistic insight into charge storage behaviour and demonstrate a scalable route for converting biomass waste into sustainable electrode materials,contributing to cleaner energy solutions and improved biomass valorization.
基金supported by the National Natural Science Foundation of China(No.52101138,No.52201075)the Natural Science Foundation of Hubei Province(No.2023AFB798,No.2022CFB614)+3 种基金the Shenzhen Science and Technology Program(No.JCYJ20220530160813032)the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202309,No.SKLSP202308)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011227)the State Key Laboratory of Powder Metallurgy of Central South University(No.SklpmKF-05)。
文摘B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites show better macroscopic plastic deformability and obvious work-hardening behavior compared to the conventional amorphous alloy matrix composites reinforced with ductile phases.However,the in-situ metastable B2-CuZr phase tends to undergo eutectoid decomposition during solidification,and the volume fraction,size,and distribution of B2-CuZr phase are difficult to control,which limits the development and application of these materials.To date,much efforts have been made to solve the above problems through composition optimization,casting parameter tailoring,and post-processing technique.In this study,a review was given based on relevant studies,focusing on the predictive approach,reinforcing mechanism,and microstructure tailoring methods of B2-CuZr phase reinforced amorphous alloy matrix composites.The research focus and future prospects were also given for the future development of the present composite system.
基金supported by the National Key Research and Development Program of China(No.2021YEA1600702)the Natural Science Foundation of Guangxi(ZY24212052)+1 种基金the National Natural Science Foundation of China(Nos.52174356,52301061,52271024,U24A2028 and U22A20174)the Fundamental Research Funds for the Central Universities.
文摘Ultrasonic vibration treatment(UVT)at varying power was successfully applied to the Cu–TiB_(2) composite melt using a SiAlON ceramic sonotrode.The results indicate that TiB_(2) particles are more evenly dispersed in the Cu matrix with increasing ultrasonic power,leading to improved mechanical properties of as-cast composites(≤1000 W).With 1000 W UVT,the distribution of TiB_(2) particles becomes the remarkably uniform and well dispersed,with the size of TiB_(2) particle aggregates decreasing from~50μm without UVT to~5μm.The ultimate tensile strength,yield strength,and elongation of the as-cast composite are 201 MPa,85 MPa,and 28.6%,respectively,representing increases of 21.1%,27.3%,and 43%,respectively,compared to the as-cast composite without UVT.However,when the power is increased to 1500 W,thermal efects are likely to emerge,and the ultrasonic attenuation efect is enhanced,resulting in the re-agglomeration of TiB_(2) particles and a deterioration in performance.By quantitatively analyzing the relationships between sound pressure(Pk),sound energy density(I),sound pulse velocity(V),and ultrasonic power,the infuence mechanism of ultrasonic power on the composite microstructure has been further elucidated and characterized.This study provides crucial guidance for the industrial application of UVT in the fabrication of Cu matrix composites.
基金supported by the National Key R&D Projects(No.2021YFB3702000)the Institute Projects of Ansteel Beijing Research Institute(No.2023BJC-06)the Regional Company Projects in Ansteel Beijing Research Institute(No.2022BJB-18BG&No.2022BJB-13GF).
文摘The Al-Mg_(2)Si in-situ composite is a lightweight material with great potential for application in fields such as automotive lightweighting,aerospace,and electronic components.In this research,the modification,semi-solid technology coupled with different types of electromagnetic stirring was applied to regulate the undesirable solidified dendritic microstructure and facilitate the composites’mechanical properties.The spheroidization and refinement of Mg_(2)Si andα-Al matrix in SM(semi-solid)+RES(rotate electromagnetic stirring)sample and SM+SHES(single winding helical electromagnetic stirring)sample are realized under the effect of fused dendrite arm,the decreased critical nucleate radius,and the increased nucleation rate and extra supercooling degree induced by electromagnetic stirring.The Mg_(2)Si phase in the SM+RES sample and SM+SHES sample is refined by 73.4%and 75.7%,respectively compared to the AC(as-cast)sample.Besides,the single winding electromagnetic stirring can lead to more homogeneously distributed physical fields,lower temperature gradient,and more significant mass transfer,mainly responsible for the more homogeneous distributed reinforced finer Mg_(2)Si particles in the SM+SHES sample.Moreover,both the tensile properties and hardness of modified semi-solid composites are improved through electromagnetic stirring.Compared with RES,the improvement effect of SHES is more excellent.The SM+SHES sample possesses the highest Brinell hardness(124.7 HB),and its quality index of tensile properties is 5.73%and 82.2%higher than that of the SM+RES and AC samples,respectively.
基金supported by the National Natural Science Foundation of China(Nos.U2202255 and 52371038)the Science and Technology Innovation Program of Hunan Province(No.2023RC1019).
文摘A novel mechanical stirring-assisted double-melt in-situ reaction casting process was developed to prepare Cu-1TiB2(wt%)composites.The effects of preparation parameters(melting reaction temperature,stirring rate and stirring time)on the microstructure and properties of Cu-1TiB2 composites were investigated.The melt viscosity and particle motion during stirring process were analyzed.The strong turbulence and shear effects generated by mechanical stirring in the melt not only significantly improve the particle distribution but also contribute to adequate in-situ reactions and precise control of the chemical composition.The optimal preparation parameters were 1200℃,a stirring rate of 100 r·min^(−1) and a stirring time of 1 min.Combined with the cold rolling process,the tensile strength,elongation and electrical conductivity of the composite reached 475 MPa,6.0%and 88.4%IACS,respectively,which were significantly better than the composite prepared by manual stirring.The good plasticity is attributed to the uniform distribution of TiB_(2) particles,effectively retarding the crack propagation.The dispersion of particles promotes heterogeneous nucleation of Cu matrix and inhibits grain growth.On the other hand,dispersed particles contribute to grain shear fracture and dislocation multiplication during cold deformation.Therefore,the composite achieves higher dislocation strengthening and grain boundary strengthening.
基金funded by the University of Science and Technology of Hanoi for the emerging research group“Sustainable Energy and Environmental Development” (SEED).
文摘Cost-effective CO_(2) adsorbents are gaining increasing attention as viable solutions for mitigating climate change.In this study,composites were synthesized by electrochemically combining the post-gasification residue of Macadamia nut shell with copper benzene-1,3,5-tricarboxylate(CuBTC).Among the different composites synthesized,the ratio of 1:1 between biochar and CuBTC(B 1:1)demonstrated the highest CO_(2) adsorption capacity.Under controlled laboratory conditions(0℃,1 bar,without the influence of ambient moisture or CO_(2) diffusion limitations),B 1:1 achieved a CO_(2) adsorption capacity of 9.8 mmol/g,while under industrial-like conditions(25℃,1 bar,taking into account the impact of ambient moisture and CO_(2) diffusion limitations within a bed of adsorbent),it reached 6.2 mmol/g.These values surpassed those reported for various advanced CO_(2) adsorbents investigated in previous studies.The superior performance of the B 1:1 composite can be attributed to the optimization of the number of active sites,porosity,and the preservation of the full physical and chemical surface properties of both parentmaterials.Furthermore,the composite exhibited a notable CO_(2)/N_(2) selectivity and improved stability under moisture conditions.These favorable characteristics make B 1:1 a promising candidate for industrial applications.
基金supported by the National Key Research and Development Program of China(No.2022YFB3708400)the National Natural Science Foundation of China(No.52305158)+1 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)the Science Innovation Foundation of Shanghai Academy of Spaceflight Technology(No.USCAST2021-18).
文摘Mg alloys have the defects of low stiffness,low strength,and high coefficient of thermal expansion(CTE).The composites strategy and its architecture design are effective approaches to improve the comprehensive performance of materials,but the processing difficulty,especially in ceramics forming,limits the control and innovation of material architecture.Here,combined with 3D printing and squeeze infiltration technology,two precisely controllable architectures of AZ91/Al_(2)O_(3)interpenetrating phase composites(IPC)with ceramic scaffold were prepared.The interface,properties and impact of different architecture on IPC performance were studied by experiments and finite element simulation.The metallurgical bonding of the interface was realized with the formation of MgAl_(2)O_(4)reaction layer.The IPC with 1 mm circular hole scaffold(1C-IPC)exhibited significantly improved elastic modulus of 164 GPa,high compressive strength of 680 MPa,and good CTE of 12.91×10^(-6)K^(−1),which were 3.64 times,1.98 times and 55%of the Mg matrix,respectively.Their elastic modulus,compressive strength,and CTE were superior to the vast majority of Mg alloys and Mg based composites.The reinforcement and matrix were bicontinuous and interpenetrating each other,which played a critical role in ensuring the potent strengthening effect of the Al_(2)O_(3)reinforcement by efficient load transfer.Under the same volume fraction of reinforcements,compared to IPC with 1 mm hexagonal hole scaffold(1H-IPC),the elastic modulus and compressive strength of 1C-IPC increased by 15%and 28%,respectively,which was due to the reduced stress concentration and more uniform stress distribution of 1C-IPC.It shows great potential of architecture design in improving the performance of composites.This study provides architectural design strategy and feasible preparation method for the development of high performance materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52171120,52271106,52071188)the Natural Science Foundation of Zhejiang Province,China(No.LZY23E050001)。
文摘Ti_(2)AlC/TiAl composites with a network structure were successfully prepared with carbon nanotubes and Ti-45Al-8Nb pre-alloyed powder using spark plasma sintering.The effects of sintering temperature(1200-1350℃)on the microstructural evolution and mechanical properties were systematically investigated.The microstructure of Ti_(2)AlC/TiAl composites exhibits duplex,near-lamellar,and fully lamellar structures,as the sintering temperature increases from 1200 to 1350℃.The network structured Ti_(2)AlC phase can refine the microstructure and the phase becomes discontinuous at high sintering temperatures.Notably,composites sintered at 1300℃ exhibit excellent mechanical properties,with the highest compressive strength(1921 MPa)and fracture strain(26%)at room temperature.Moreover,the ultimate tensile strength and fracture strain reach 537 MPa and 3.1%at 900℃,and 485 MPa and 3.3%at 950℃,respectively.The enhancement of the mechanical properties is attributed primarily to the load bearing,particle pull-out,and inhibition of crack propagation induced by Ti_(2)AlC particles.
基金Project(50721003) supported by the Innovation Community Foundation of National Natural Science of ChinaProject(2011CB605805) supported by the National Basic Research Program of China
文摘To improve the oxidation resistance of carbon/carbon composites,ZrB2-MoSi2/SiC coating on the carbon/carbon substrate was prepared.The inner coating of SiC was prepared by pack cementation and the outer coating of ZrB2-MoSi2 was prepared by slurry painting.The phase compositions and microstructures of the coating were characterized by XRD and SEM,respectively.The preparation and the high temperature oxidation property of the coated composites were investigated.The results show that the outer coating of carbon/carbon composites is composed of ZrB2,MoSi2 and SiC phases.The mass losses of the ZrB2-MoSi2/SiC coated samples with SiC nano-whiskers after 30 h and 10 h of oxidation at 1 273 K and 1 773 K were,respectively,5.3% and 3.0%.The ZrB2-MoSi2/SiC coated samples exhibit self-sealing performance and good oxidation resistance at high temperature.
基金Projects(51221001,51222207)supported by the National Natural Science Foundation of ChinaProject(090677)supported by the Program for New Century Excellent Talents in University of ChinaProject(B08040)supported by Program of Introducing Talents of Discipline to Universities,China
文摘To improve the oxidation resistance of carbon/carbon （C/C） composites in air at high temperatures, a SiC- MoSi2/ZrO2-MoSi2 coating was prepared on the surface of C/C composites by pack cementation and slurry method. The microstructures and phase compositions of the coated C/C composites were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The result shows that the SiC-MoSi2/ZrO2-MoSi2 coating is dense and crack-free with a thickness of 250-300 μm. The preparation and the high temperature oxidation property of the coated composites were investigated. The as-received coating has excellent oxidation protection ability and can protect C/C composites from oxidation for 260 h at 1773 K in air. The excellent anti-oxidation performance of the coating is considered to come from the formation of ZrSiO4, which improves the stability of the coating at high temperatures.
基金Projects(51221001,50972120)supported by the National Natural Science Foundation of ChinaProject(73-QP-2010)supported by the Research Fund of the State Key Laboratory of Solidification Processing of Northwestern Polytechnical University,ChinaProject(B08040)supported by Program of Introducing Talents of Discipline to Universities,China
文摘To improve the anti-oxidation ability of silicon-based coating for carbon/carbon （C/C） composites at high temperatures, a ZrB2 modified silicon-based multilayer oxidation protective coating was prepared by pack cementation. The phase composition, microstructure and oxidation resistance at 1773, 1873 and 1953 K in air were investigated. The prepared coating exhibits dense structure and good oxidation protective ability. Due to the formation of stable ZrSiO4-SiO2 compound, the coating can effectively protect C/C composites from oxidation at 1773 K for more than 550 h. The anti-oxidation performance decreases with the increase of oxidation temperature. The mass loss of coated sample is 2.44% after oxidation at 1953 K for 50 h, which is attributed to the decomposition of ZrSiO4 and the volatilization of SiO2 protection layer.
基金Projects(51072104,51272141)supported by the National Natural Science Foundation of ChinaProject(ts20110828)supported by Taishan Scholars Project of Shandong,China
文摘TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni＋Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.
基金Projects(9102601860979017) supported by the National Natural Science Foundation of ChinaProject(20110111110015) supported by the Doctoral Fund of Ministry of Education of China
文摘Four kinds of Cu-based composites with different mass ratios of graphite and WS2 as lubricants were fabricated by hot-pressing method. Electrical sliding wear behaviors of the composites were investigated using a block-on-ring tribometer rubbing against Cu-5%Ag alloy ring. The results demonstrated that 800 ~C was the optimum sintering temperature for Cu-graphite-WS2 dual-lubricant composites to obtain the best comprehensive properties of mechanical strength and lubrication performance. Contact voltage drops of the Cu-based composites increased with increasing the mass ratio of WS2 to graphite. The Cu-based composite with 20% graphite and 10% WS2 showed the best wear resistance due to the excellent synergetic lubricating effect of graphite and WS2. The reasonable addition of WS2 into the Cu-graphite composite can remarkably improve the wear resistance without much rise of electrical energy loss which provides a novel principle of designing suitable sliding electrical contact materials for industrial applications.
基金Projects(51071035,51274054,51375070)supported by the National Natural Science Foundation of ChinaProject(313011)supported by the Key Project of Ministry of Education of China
文摘Zn-Al-Cu-TiB2（ZA27-TiB2） in situ composites were fabricated via reactions between molten aluminum and mixed halide salts（K2TiF6 and KBF4） at temperature of 875 °C. The microstructure, mechanical properties and wear behavior of the composites were investigated. Microstructure analysis shows that fine and clean TiB2 particles distribute uniformly through the matrix. The mechanical properties of the composites increase with the increase in TiB2 content. As TiB2 content increases to 5%（mass fraction）, an improvement of HB 18 in hardness and 49 MPa in ultimate tensile strength（UTS） is achieved. The overall results reveal that the composites possess low friction coefficients and the wear rate is reduced from 5.9×10-3 to 1.3×10-3 mm3/m after incorporating 5% TiB2. Friction coefficient and worn surface analysis indicate that there is a change in the wear mechanism in the initial stage of wear test after introducing in situ TiB2 particles into the matrix.
基金Projects(51272213,51221001)supported by the National Natural Science Foundation of ChinaProject(73-QP-2010)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU)Project(B08040)supported by Program of Introducing Talents of Discipline to Universities,China
文摘C/SiC/MoSi2-SiC-Si oxidation protective multilayer coating for carbon/carbon （C/C） composites was prepared by pack cementation and slurry method. The microstructure, element distribution and phase composition of the as-received coating were analyzed by scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDS） and X-ray diffraction （XRD）. The results show that the multilayer coating was composed of MoSi2, SiC and Si. It could effectively protect C/C composites against oxidation for 200 h with the mass loss of 3.25% at 1873 K in static air. The mass loss of the coated C/C composites results from the volatilization of SiO2 and the formation of cracks and bubble holes in the coating.
基金National Natural Science Foundation of China (50432020)Henan Innovation Project for University Prominent Re- search Talents (2007KYCX008)+3 种基金Henan Education Department Science and Technology Project (2007430004)Henan Plan Project for College Youth Backbone TeacherHenan University of Science and Technology Major Pre-research Foundation (2005ZD003)Henan University of Science and Technology Personnel Scientific Research Foundation (of023)
文摘Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.
基金Project(2011CB605502)supported by the National Basic Research Program of ChinaProject(51001086)supported by the National Natural Science Foundation of China
文摘Microstructures of Ti2AlN/TiAl composites prepared by in-situ method were characterized in in-situ and aging treatment conditions and the nitride precipitation was investigated in Ti2AlN/TiAl composites aged at 900 ℃ for 24 h after being heat treated at 1400 ℃ for 0.5 h. The in-situ composites consist of γ＋α2 lamellar colonies, equiaxed y grains and Ti2AlN reinforcements. Matrix with nearly fully lamellar structure formed after solution and subsequently aging treatment. With the increase of Ti2AlN content, the nearly fully lamellar structure becomes instable for the aged composites. According to TEM study, fine Ti2AlN precipitates are found to distribute at the grain boundaries of lamellar colony. Needle-like Ti3AlN precipitates arrange in line with growing axis parallel to [001] direction of the γ-TiAl matrix and another needle-like Ti3AlN precipitates with lager size distribute at the dislocations. Key words：
