To exploit the combined strengthening effects of nanotwins and carbon nanotubes(CNTs)in Cu matrix composites,the nanotwins with a width ranging from 3 to 30 nm were incorporated into the CNTs-reinforced Cu matrix comp...To exploit the combined strengthening effects of nanotwins and carbon nanotubes(CNTs)in Cu matrix composites,the nanotwins with a width ranging from 3 to 30 nm were incorporated into the CNTs-reinforced Cu matrix composites using cryogenic rolling and optimizing the initial particle size of the raw Cu powders.The formation of nanotwins in the Cu matrix composite reinforced by only 0.2 wt.%CNTs is accompanied by the increased dislocation density and refined Cu grain size,resulting in much better strength−ductility synergy than the referenced composite without significant nanotwins formation.The analysis of strengthening and toughening mechanisms demonstrates that the strength increment mainly derives from grain refinement strengthening,dislocation strengthening,and nanotwin strengthening.The strength increment from the contribution of the nanotwins accounts for 19.9%of the overall strength increment for the composite.Meanwhile,the retention of good tensile ductility can be reasonably explained by the increased dislocation accommodation ability due to the formed nanotwins and the decreased induced dislocation proliferation.展开更多
Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excell...Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excellent mechanical properties,and heat dissipation.However,the different characteristics of C_(sf)and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites.Here,Cu coating with different thicknesses is introduced to modify the C_(sf)/Mg interface,so as to simultaneously enhance the thermal and mechanical performances,which can combine the advantages of coating modification and matrix alloying.Results reveal that thermal diffusivity(TD)of 3-C_(sf)-Cu/Mg composites is as high as 22.12 mm^(2)/s and an enhancement of 52.97%is achieved compared with C_(sf)/Mg composites,as well as 16.3%enhancement of ultimate compressive strength(UCS)in the longitudinal direction,8.84%improvement of UCS in the transverse direction,and 53.08%increasement of ultimate tensile strength(UTS).Such improvement can be ascribed to the formation of intermetallic compounds.The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance,but also bear the loads.Our work is of great significance for designing C_(sf)/Mg composites with integrated structure and function.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
The Cu/1010 steel bimetal laminated composites(BLCs)were rolled to different thicknesses to investigate the effect of rolling direction and reduction on the microstructure evolution and mechanical properties.The diffe...The Cu/1010 steel bimetal laminated composites(BLCs)were rolled to different thicknesses to investigate the effect of rolling direction and reduction on the microstructure evolution and mechanical properties.The difference of mechanical properties between the Cu and 1010 steel causes different thickness reductions,percentage spread,and cladding ratios.The formation of strong texture induces larger strength of the rolled samples,and as the volume fraction of 1010 steel is larger in Route-A,its strength is consistently greater than that in Route-B.The obstruction of interface to crystal and dislocation slip results in the formation of interface distortion,inducing dislocation density gradient when the rolling reduction is low in Route-A.The slip planes of the Cu and 1010 steel are more prone to suffer the normal strain,while the shear strain of other crystal planes is obviously larger than the normal strain under rolling load near the interface.展开更多
The Cu/Invar composites of 40% Cu were prepared by powder metallurgy, and the composites were rolled with 70% reduction and subsequently annealed at 750 ℃. Phases, microstructures and properties of the composites wer...The Cu/Invar composites of 40% Cu were prepared by powder metallurgy, and the composites were rolled with 70% reduction and subsequently annealed at 750 ℃. Phases, microstructures and properties of the composites were then studied. After that, the amount of a-Fe（Ni,Co） in the composites is reduced, because a-Fe（Ni,Co） partly transfers into y-Fe（Ni,Co） through the diffusion of the Ni atoms into a-Fe（Ni,Co） from Cu. When the rolling reduction is less than 40%, the deformation of Cu takes place, resulting in the movement of the Invar particles and the seaming of the pores. When the rolling reduction is in the range from 40% to 60%, the deformations of Invar and Cu occur simultaneously to form a streamline structure. After rolling till 70% and subsequent annealing, the Cu/Invar composites have fine comprehensive properties with a relative density of 98.6%, a tensile strength of 360 MPa, an elongation rate of 50%, a thermal conductivity of 25.42 W/（m.K） （as-tested） and a CTE of 10.79× 10-6/K （20-100 ℃）.展开更多
采用光学显微镜(optical microscope,OM)、扫描电子显微镜(scanning electron microscope,SEM)、透射电子显微镜(transmission electron microscope,TEM)、硬度和电导率试验仪器,研究了Cu-Ni-Fe-P合金成分设计、微观结构和性能之间的构...采用光学显微镜(optical microscope,OM)、扫描电子显微镜(scanning electron microscope,SEM)、透射电子显微镜(transmission electron microscope,TEM)、硬度和电导率试验仪器,研究了Cu-Ni-Fe-P合金成分设计、微观结构和性能之间的构效关系。结果表明,Ni/Fe质量比对合金性能具有显著调控作用,当Ni/Fe质量比为3.00时,Cu-Ni-Fe-P合金在500℃时效0.50 h条件下维氏硬度达到峰值,为171.5,此时析出相平均尺寸为2.2 nm,随着时效时间延长至12.00 h时,析出相平均尺寸增大到5.6 nm。Fe元素的添加降低了溶质原子的固溶度,有效抑制了基体晶格畸变,提高了合金导电性,当Ni/Fe质量比为1.00时,Cu-Ni-Fe-P合金电导率在500℃/12.00 h时效条件下可达峰值63.6%IACS。其中,当Ni/Fe质量比为1.00时,500℃/6.00 h时效条件下,Cu-Ni-Fe-P合金的综合性能最好。展开更多
The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechan...The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.展开更多
Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study...Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature(either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3 vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.展开更多
The microstructural evolvement and friction performance of Cu/FeS self-lubricating composites within electric field were studied by molecular dynamics simulation.The atoms distribution and movement of the Cu/FeS compo...The microstructural evolvement and friction performance of Cu/FeS self-lubricating composites within electric field were studied by molecular dynamics simulation.The atoms distribution and movement of the Cu/FeS composite under different electric field strengths were considered.The results show that some Fe atoms and S atoms break away from the original structure and move along the electric field,but the movement of Fe atoms and S atoms is not synchronized in stronger electric field strength.Thus,the whole material system becomes chaotic and its temperature rises.The unevenly electric field force appears in the material for the nonuniform FeS distribution,so the internal stress of the composite is generated.For the internal solid lubricating phases move along the direction of the electric field to the surface of the composite,the adhesive wear and the friction coefficient reduce.The movement of the phases leaves over some voids in the composite,which induces arc wear easily.展开更多
The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and Mo...The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and MoS2 on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS2 separately.The results show that the nickel wrapping around the MoS2 particles decreases the reaction rate of MoS2 with the copper matrix,and greatly improves the bonding of the matrix.The composites with 12 wt.%Ni-coated MoS2(C12)show the optimum performance including the mechanical properties and tribological behaviors.Under oil lubrication conditions,the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s.The average dry friction coefficient,sliding against 40Cr steel disc,is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa,respectively.展开更多
FeS2/Fe composites were mechanochemically prepared with iron powder and pyrite for the stabilization of ferrite arsenate sludge(FAS).The effects of preparation parameters on stabilization performance were investigated...FeS2/Fe composites were mechanochemically prepared with iron powder and pyrite for the stabilization of ferrite arsenate sludge(FAS).The effects of preparation parameters on stabilization performance were investigated.The results show that the optimum conditions are FeS2/Fe molar ratio of 5:5,milling time of 2 h,ball-to-material mass ratio of 15:1 and milling with stainless steel ball.Then,the composites were characterized by XRD,SEM,FTIR,etc.The physicochemical properties of FeS2/Fe mixture change dramatically,which is responsible for its excellent performance.Finally,the stabilization process of FAS was optimized.When the FAS is mixed with composites at mass ratio of 4:1 and milled for 30 min,the As leaching concentration of FAS can be reduced from 639.15 to 4.74 mg/L with the stabilization ratio of 99.2%.展开更多
Magnetic Cuº/Fe_(3)O_(4)submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate(PMS)and the degradation of organic pollutants.The...Magnetic Cuº/Fe_(3)O_(4)submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate(PMS)and the degradation of organic pollutants.The as-prepared magnetic Cu/Fe_(3)O_(4)submicron composites were composed of Cu°and FesO+crystals and had an average size of approximately 220 nm.The Cu/FesO+composites could efficiently catalyze the activation of PMS to generate singlet oxygen,and thusinduced the rapid degradation of rhodamine B,methylene blue,orange 1l,phenol and 4-chlorophenol.The use of 0.1 g/L of the Cu°/Fe_(3)O_(4)composites induced the complete removal of rhodamine B(20μmol/L)in 15 min,methylene blue(20μmol/L)in 5 min,orange II(20μmol/L)in 10 min,phenol(0.1 mmol/L)in 30 min and 4-chlorophenol(0.1 mmol/L)in 15 min with an initial pH value of 7.0 and a PMS concentration of 0.5 mmol/L.The total organic carbon(TOC)removal higher than 85%for all of these five pollutants was obtained in 30 min when the PMS concentration was 2.5 mmol/L.The rate of degradation was considerably higher than that obtained with Cuªor FezO4 particles alone.The enhanced catalytic activity of the Cu°/Fe_(3)O_(4)composites in the activation of PMS was attributed to the synergistic effect of the Cu*and Fe_(3)O_(4)crystals in the composites.Singlet oxygen was identi-fied as the primary reactive oxygen species responsible for pollutant degradation by electron spin resonance and radical quenching experiments.A possible mechanism for the activation of PMS by Cu°/Fe_(3)O_(4)composites is proposed as electron transfer from the organic pollutants to PMS induces the activation of PMS to generate 10z,which induces the degradation of the organic pollutants.As a magnetic catalyst,the Cu°/Fe_(3)O_(4)composites were easily recovered by magnetic separation,and exhibited excellent stability over five successive degradation cycles.The present study provides a facile and green heterogeneous catalysis method for the oxidative removal of organic pollutants.展开更多
Cu-6%Fe（mass fraction） microcomposites containing（0-0.30）% rare earth elements were prepared by cold drawing and intermediate heat treatments.Microstructure was observed, and mechanical properties and electrical c...Cu-6%Fe（mass fraction） microcomposites containing（0-0.30）% rare earth elements were prepared by cold drawing and intermediate heat treatments.Microstructure was observed, and mechanical properties and electrical conductivity were measured for alloys at various drawing strain levels.Adding rare earth elements could reduce the size of primary Fe and Cu dendrites of Cu-6%Fe.Ultimate tensile strength increased but electrical conductivity decreased with the increase of drawing strain.Rare earth additions in Cu-6%Fe slightly increased the strength at low strain and effectively improved the conductivity at high strain.Both strain hardening rate and conductivity loss of Cu-6%Fe containing rare earths were reduced at lower strain than Cu-6%Fe.展开更多
Cu/Al laminar composite was prepared by dipping Zn layer and then electroplating Cu thick layer on pure Al sheet.During annealing the Cu/Al composites at temperature from 473 to 673 K, the Cu/Al interfacial diffusion ...Cu/Al laminar composite was prepared by dipping Zn layer and then electroplating Cu thick layer on pure Al sheet.During annealing the Cu/Al composites at temperature from 473 to 673 K, the Cu/Al interfacial diffusion and reaction and itskinetics and also the electrical resistivity of the composites were studied. The results show that no Cu?Al IMC layer is observable asthe composites are annealed at 473 K for time till 360 h, indicating that the Zn intermediate layer can effectively suppress the Cu/Alinterfacial diffusion. However, as the composites are annealed at 573 K and above, Zn atoms in the Zn layer dissolve into the Culayer. Tri-layered reaction product of CuAl2/CuAl/Cu9Al4 then forms from the Al side to the Cu side. The IMC layer follows thediffusion-controlled growth kinetics. Electrical resistivity of the Cu/Al composites increases with the increase of the annealingtemperature and time.展开更多
Ni(Co/Zn/Cu)Fe_2O_4/SiC@SiO_2, a microwave absorber, was prepared by the sol-gel method. The phase structure and the morphology of the microwave absorbers were characterized by X-Ray Diffraction(XRD) and scanning elec...Ni(Co/Zn/Cu)Fe_2O_4/SiC@SiO_2, a microwave absorber, was prepared by the sol-gel method. The phase structure and the morphology of the microwave absorbers were characterized by X-Ray Diffraction(XRD) and scanning electron microscopy(SEM), respectively. Laser sizer(LS) and X-ray photoelectron spectroscopy(XPS) analysis show the core-shell structure of SiC@SiO_2. Coaxial method was used to measure the microwave absorption properties of the prepared composites in the frequency range of 2-18 GHz. When 70 wt% SiC is wrapped by 30 wt% SiO_2,and 50 wt% NiFe_2O_4 is added into 50 wt% SiC@SiO_2, the as-prepared powders are found to have advanced microwave absorption properties with a minimum reflection loss(RL) of -32.26 dB at about 6.08 GHz, and the available bandwidth is approximately 2.1 GHz when the RL is below -10 dB.展开更多
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.21624408)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2023A1515012850,2024A1515010416)+2 种基金Guangzhou Science and Technology Planning Project,China(No.2024A04J9966)the National Natural Science Foundation of China(Nos.52271132,52004101)the Key Laboratory of Advanced Materials of Yunnan Province,China(No.2024KF02)。
文摘To exploit the combined strengthening effects of nanotwins and carbon nanotubes(CNTs)in Cu matrix composites,the nanotwins with a width ranging from 3 to 30 nm were incorporated into the CNTs-reinforced Cu matrix composites using cryogenic rolling and optimizing the initial particle size of the raw Cu powders.The formation of nanotwins in the Cu matrix composite reinforced by only 0.2 wt.%CNTs is accompanied by the increased dislocation density and refined Cu grain size,resulting in much better strength−ductility synergy than the referenced composite without significant nanotwins formation.The analysis of strengthening and toughening mechanisms demonstrates that the strength increment mainly derives from grain refinement strengthening,dislocation strengthening,and nanotwin strengthening.The strength increment from the contribution of the nanotwins accounts for 19.9%of the overall strength increment for the composite.Meanwhile,the retention of good tensile ductility can be reasonably explained by the increased dislocation accommodation ability due to the formed nanotwins and the decreased induced dislocation proliferation.
基金supported by the National Natural Science Foundation of China(grant no.52231004 and 52072305).
文摘Mg alloy matrix composites reinforced with short carbon fibers(C_(sf)/Mg)are considered as potential candidates for integrated structural-functional electronic parts that satisfy the requirements of lightweight,excellent mechanical properties,and heat dissipation.However,the different characteristics of C_(sf)and Mg alloy make the interface a critical issue affecting the synergistic improvement of thermal and mechanical properties of the composites.Here,Cu coating with different thicknesses is introduced to modify the C_(sf)/Mg interface,so as to simultaneously enhance the thermal and mechanical performances,which can combine the advantages of coating modification and matrix alloying.Results reveal that thermal diffusivity(TD)of 3-C_(sf)-Cu/Mg composites is as high as 22.12 mm^(2)/s and an enhancement of 52.97%is achieved compared with C_(sf)/Mg composites,as well as 16.3%enhancement of ultimate compressive strength(UCS)in the longitudinal direction,8.84%improvement of UCS in the transverse direction,and 53.08%increasement of ultimate tensile strength(UTS).Such improvement can be ascribed to the formation of intermetallic compounds.The formation of intermetallic compounds can not only effectively alleviate the lattice distortion of the matrix and decrease interfacial thermal resistance,but also bear the loads.Our work is of great significance for designing C_(sf)/Mg composites with integrated structure and function.
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.
基金the National Key Research and Development Program of China(No.2018YFE0306103)the National Natural Science Foundation of China(No.52071050)+1 种基金the Science and Technology Innovation Project of Ningbo,China(No.2021Z032)the Program of China Scholarships Council(No.202106060148).
文摘The Cu/1010 steel bimetal laminated composites(BLCs)were rolled to different thicknesses to investigate the effect of rolling direction and reduction on the microstructure evolution and mechanical properties.The difference of mechanical properties between the Cu and 1010 steel causes different thickness reductions,percentage spread,and cladding ratios.The formation of strong texture induces larger strength of the rolled samples,and as the volume fraction of 1010 steel is larger in Route-A,its strength is consistently greater than that in Route-B.The obstruction of interface to crystal and dislocation slip results in the formation of interface distortion,inducing dislocation density gradient when the rolling reduction is low in Route-A.The slip planes of the Cu and 1010 steel are more prone to suffer the normal strain,while the shear strain of other crystal planes is obviously larger than the normal strain under rolling load near the interface.
文摘The Cu/Invar composites of 40% Cu were prepared by powder metallurgy, and the composites were rolled with 70% reduction and subsequently annealed at 750 ℃. Phases, microstructures and properties of the composites were then studied. After that, the amount of a-Fe（Ni,Co） in the composites is reduced, because a-Fe（Ni,Co） partly transfers into y-Fe（Ni,Co） through the diffusion of the Ni atoms into a-Fe（Ni,Co） from Cu. When the rolling reduction is less than 40%, the deformation of Cu takes place, resulting in the movement of the Invar particles and the seaming of the pores. When the rolling reduction is in the range from 40% to 60%, the deformations of Invar and Cu occur simultaneously to form a streamline structure. After rolling till 70% and subsequent annealing, the Cu/Invar composites have fine comprehensive properties with a relative density of 98.6%, a tensile strength of 360 MPa, an elongation rate of 50%, a thermal conductivity of 25.42 W/（m.K） （as-tested） and a CTE of 10.79× 10-6/K （20-100 ℃）.
基金Foundation of Northwest Institute for Nonferrous Metal Research(ZZXJ2203)Capital Projects of Financial Department of Shaanxi Province(YK22C-12)+3 种基金Innovation Capability Support Plan in Shaanxi Province(2023KJXX-083)Key Research and Development Projects of Shaanxi Province(2024GXYBXM-351,2024GX-YBXM-356)National Natural Science Foundation of China(62204207,12204383)Xi'an Postdoctoral Innovation Base Funding Program。
文摘The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.
文摘Layered composites have attracted considerable interest in the recent literature on metal composites. Their mechanical properties depend on the quality of the bonding provided by the intermediate layers. In this study, we analyzed the mechanical properties and bond strengths provided by the nickel layer with respect to its thickness and nature(either powder or coating). The results suggest that bond strength decreases with an increase in the content of nickel powder. At 0.3 vol% of nickel coating, we found the nature of nickel to be less efficient in terms of bond strength. A different picture arose when the content of nickel was increased and the bond strength increased in nickel coated samples. In addition, the results demonstrate that mechanical properties such as bend strength are strongly dependent on bond strength.
基金financially supported by the State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals(No.SKL-SPM-201510)
文摘The microstructural evolvement and friction performance of Cu/FeS self-lubricating composites within electric field were studied by molecular dynamics simulation.The atoms distribution and movement of the Cu/FeS composite under different electric field strengths were considered.The results show that some Fe atoms and S atoms break away from the original structure and move along the electric field,but the movement of Fe atoms and S atoms is not synchronized in stronger electric field strength.Thus,the whole material system becomes chaotic and its temperature rises.The unevenly electric field force appears in the material for the nonuniform FeS distribution,so the internal stress of the composite is generated.For the internal solid lubricating phases move along the direction of the electric field to the surface of the composite,the adhesive wear and the friction coefficient reduce.The movement of the phases leaves over some voids in the composite,which induces arc wear easily.
基金Projects(51371099,51501091)supported by the National Natural Science Foundation of China。
文摘The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and MoS2 on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS2 separately.The results show that the nickel wrapping around the MoS2 particles decreases the reaction rate of MoS2 with the copper matrix,and greatly improves the bonding of the matrix.The composites with 12 wt.%Ni-coated MoS2(C12)show the optimum performance including the mechanical properties and tribological behaviors.Under oil lubrication conditions,the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s.The average dry friction coefficient,sliding against 40Cr steel disc,is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa,respectively.
基金Projects(2018YFC1900305,2018YFC1903301)supported by the National Key R&D Program of ChinaProject(51825403)supported by the National Natural Science Foundation for Distinguished Young Scholars of China+1 种基金Project(51634010)supported by the National Natural Science Foundation of ChinaProject(2017RS3010)supported by the Science and Technology Program of Hunan Province,China
文摘FeS2/Fe composites were mechanochemically prepared with iron powder and pyrite for the stabilization of ferrite arsenate sludge(FAS).The effects of preparation parameters on stabilization performance were investigated.The results show that the optimum conditions are FeS2/Fe molar ratio of 5:5,milling time of 2 h,ball-to-material mass ratio of 15:1 and milling with stainless steel ball.Then,the composites were characterized by XRD,SEM,FTIR,etc.The physicochemical properties of FeS2/Fe mixture change dramatically,which is responsible for its excellent performance.Finally,the stabilization process of FAS was optimized.When the FAS is mixed with composites at mass ratio of 4:1 and milled for 30 min,the As leaching concentration of FAS can be reduced from 639.15 to 4.74 mg/L with the stabilization ratio of 99.2%.
文摘Magnetic Cuº/Fe_(3)O_(4)submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate(PMS)and the degradation of organic pollutants.The as-prepared magnetic Cu/Fe_(3)O_(4)submicron composites were composed of Cu°and FesO+crystals and had an average size of approximately 220 nm.The Cu/FesO+composites could efficiently catalyze the activation of PMS to generate singlet oxygen,and thusinduced the rapid degradation of rhodamine B,methylene blue,orange 1l,phenol and 4-chlorophenol.The use of 0.1 g/L of the Cu°/Fe_(3)O_(4)composites induced the complete removal of rhodamine B(20μmol/L)in 15 min,methylene blue(20μmol/L)in 5 min,orange II(20μmol/L)in 10 min,phenol(0.1 mmol/L)in 30 min and 4-chlorophenol(0.1 mmol/L)in 15 min with an initial pH value of 7.0 and a PMS concentration of 0.5 mmol/L.The total organic carbon(TOC)removal higher than 85%for all of these five pollutants was obtained in 30 min when the PMS concentration was 2.5 mmol/L.The rate of degradation was considerably higher than that obtained with Cuªor FezO4 particles alone.The enhanced catalytic activity of the Cu°/Fe_(3)O_(4)composites in the activation of PMS was attributed to the synergistic effect of the Cu*and Fe_(3)O_(4)crystals in the composites.Singlet oxygen was identi-fied as the primary reactive oxygen species responsible for pollutant degradation by electron spin resonance and radical quenching experiments.A possible mechanism for the activation of PMS by Cu°/Fe_(3)O_(4)composites is proposed as electron transfer from the organic pollutants to PMS induces the activation of PMS to generate 10z,which induces the degradation of the organic pollutants.As a magnetic catalyst,the Cu°/Fe_(3)O_(4)composites were easily recovered by magnetic separation,and exhibited excellent stability over five successive degradation cycles.The present study provides a facile and green heterogeneous catalysis method for the oxidative removal of organic pollutants.
基金supported by the National Natural Science Foundation of China (50671092)
文摘Cu-6%Fe（mass fraction） microcomposites containing（0-0.30）% rare earth elements were prepared by cold drawing and intermediate heat treatments.Microstructure was observed, and mechanical properties and electrical conductivity were measured for alloys at various drawing strain levels.Adding rare earth elements could reduce the size of primary Fe and Cu dendrites of Cu-6%Fe.Ultimate tensile strength increased but electrical conductivity decreased with the increase of drawing strain.Rare earth additions in Cu-6%Fe slightly increased the strength at low strain and effectively improved the conductivity at high strain.Both strain hardening rate and conductivity loss of Cu-6%Fe containing rare earths were reduced at lower strain than Cu-6%Fe.
基金Project(2012QTXM0751)supported by the Scientific and Technological Research Project,State Grid,China
文摘Cu/Al laminar composite was prepared by dipping Zn layer and then electroplating Cu thick layer on pure Al sheet.During annealing the Cu/Al composites at temperature from 473 to 673 K, the Cu/Al interfacial diffusion and reaction and itskinetics and also the electrical resistivity of the composites were studied. The results show that no Cu?Al IMC layer is observable asthe composites are annealed at 473 K for time till 360 h, indicating that the Zn intermediate layer can effectively suppress the Cu/Alinterfacial diffusion. However, as the composites are annealed at 573 K and above, Zn atoms in the Zn layer dissolve into the Culayer. Tri-layered reaction product of CuAl2/CuAl/Cu9Al4 then forms from the Al side to the Cu side. The IMC layer follows thediffusion-controlled growth kinetics. Electrical resistivity of the Cu/Al composites increases with the increase of the annealingtemperature and time.
基金financially supported by the Military Project of the Ministry of National Defense of China (No. JPPT-125-2-168)
文摘Ni(Co/Zn/Cu)Fe_2O_4/SiC@SiO_2, a microwave absorber, was prepared by the sol-gel method. The phase structure and the morphology of the microwave absorbers were characterized by X-Ray Diffraction(XRD) and scanning electron microscopy(SEM), respectively. Laser sizer(LS) and X-ray photoelectron spectroscopy(XPS) analysis show the core-shell structure of SiC@SiO_2. Coaxial method was used to measure the microwave absorption properties of the prepared composites in the frequency range of 2-18 GHz. When 70 wt% SiC is wrapped by 30 wt% SiO_2,and 50 wt% NiFe_2O_4 is added into 50 wt% SiC@SiO_2, the as-prepared powders are found to have advanced microwave absorption properties with a minimum reflection loss(RL) of -32.26 dB at about 6.08 GHz, and the available bandwidth is approximately 2.1 GHz when the RL is below -10 dB.
