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
The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics...The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.展开更多
Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high ther...Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. The nano-Al2O3/Cu composite was produced by internal oxidation. The microstructures of the composite were analyzed by the TEM and its hot deformation behavior was investigated by means of continuous compression tests performed on a Gleeble 1500 thermo-simulator. Making use of the modified algorithm-Levenberg-Marquardt （L-M） algorithm BP neural network, a model for predicting the flow stresses during hot deformation was set up on the base of the experimental data. Results show that the microstructures of the composite are characterized by uniform distribution of nano-Al2O3 particles in Cu-matrix. The sliding of dislocations is the main deformation mechanism. The dynamic recovery is the main softening mode with the flow stress decreasing gently from 500℃ to 850 ~C. The recrystallization of Cu-matrix can be retarded late into as high as 850 ℃, when it happens only partially. The well-trained BP neural network model can accurately describe the influence of the temperature, strain rate, and true strain on the flow stresses, therefore, it can precisely predict the flow stresses of the composite under given deforming conditions and provide a new way to optimize hot deforming process parameters.展开更多
Silver as a highly conductive metal is usually doped in YBa2Cu3O7-x superconductor bulks to improve critical current density of YBa2Cu3O7-x superconductor.The valuable metal elements silver,yttrium,barium and copper i...Silver as a highly conductive metal is usually doped in YBa2Cu3O7-x superconductor bulks to improve critical current density of YBa2Cu3O7-x superconductor.The valuable metal elements silver,yttrium,barium and copper in waste YBa2Cu3O7-x/Ag composite superconductor bulks were recovered,respectively.Silver was recovered with process at first,the waste was dissolved by nitric acid and silver chloride was precipitated by adding chloride acid,then silver pig was obtained by melting silver chloride together with sodium carbonate at 1 000℃.The effective factors on recovery ratio and purity of silver were studied.The chemical analysis proves that the purity of silver ingot is 95.86%.The recovery ratio of silver is calculated to be 92.56%.The loss of silver may be due to the loss of silver chloride during filtering and the volatilization of silver when silver chloride and sodium carbonate are smelted at high temperature.For other three metal elements,Y3 +,Ba 2+and Cu 2+,in the surplus waste liquid after recovering silver, they were separated with the sequence of barium,copper and then yttrium step by step.First,sulfate acid was used to precipitate barium sulfate.Then,sodium sulfide was added to the surplus solution so that copper could be separated as copper sulfide.During this separation procedure,it was important to control the pH value to be 1-2.After that,oxalic acid was added into the surplus solution to obtain yttrium oxalate.Finally,yttrium oxide was formed by burning yttrium oxalate.The XRD results indicate that the final products are all single-phase compounds as BaSO4,CuS and Y2O3,respectively.展开更多
This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size the...This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high temperature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.展开更多
Chemical solution route was used to synthesize Bi3.1La0.9Ti3O12 and CoFe2O4. Alternate CoFe2O4/Bi3.1La0.9Ti3O12 layers were deposited on Pt substrate （Pt/TiO2/SiO2/Si） by spin coating. X-ray diffraction and SEM （sc...Chemical solution route was used to synthesize Bi3.1La0.9Ti3O12 and CoFe2O4. Alternate CoFe2O4/Bi3.1La0.9Ti3O12 layers were deposited on Pt substrate （Pt/TiO2/SiO2/Si） by spin coating. X-ray diffraction and SEM （scanning electron microscopy） studies show composite-like polycrystalline films. Films were studied for leakage current, dielectric response, ferroelectric and ferromagnetic properties. Leakage current was low （〈 10^-8 A） in electric field below 120 kV/cm, and the dielectric response shows relaxation. Dielectric loss （tan 8） reduces 〈 3% at 10^6 Hz. Two and four layer structures showed room temperature FE （ferroelectric） and FM （ferromagnetic） responses with FE Pr （polarization） 〉 25℃/cm2 and ferromagnetic Mr （memory） 〉 52 emu/cm3. Co-existence of FE and FM can be attributed to stress due to different crystal structures of the material involved in composite film structure.展开更多
采用固相法制备了Ca Cu3Ti4O12多晶块体,研究了其介电常数随温度和频率的变化。结果表明,在温度为300 K、频率为1 k Hz时,多晶块的介电常数高达14 000;频率为1 k Hz时,介电常数基本不随温度的变化而改变。动态变化的极化弛豫使Ca Cu3Ti4...采用固相法制备了Ca Cu3Ti4O12多晶块体,研究了其介电常数随温度和频率的变化。结果表明,在温度为300 K、频率为1 k Hz时,多晶块的介电常数高达14 000;频率为1 k Hz时,介电常数基本不随温度的变化而改变。动态变化的极化弛豫使Ca Cu3Ti4O12多晶块具有巨介电常数,混合价Ti离子导致极化子的热激活使Ca Cu3Ti4O12多晶块的介电特性出现反常效应。展开更多
Aluminium matrix composite reinforced by Al2O3 particles was produced by adding NH4AlO（OH）HCO3 into molten aluminum.The mechanical properties and wear behavior of the as-fabricated composites were studied.The result...Aluminium matrix composite reinforced by Al2O3 particles was produced by adding NH4AlO（OH）HCO3 into molten aluminum.The mechanical properties and wear behavior of the as-fabricated composites were studied.The results show that during stirring γ-Al2O3 particles were formed via decomposition reaction of NH4AlO（OH）HCO3,and the distribution of Al2O3 particles is more uniform in the matrix aluminum than directly added Al2O3 into molten aluminum.The density and the hardness values of the as-fabricated composites increase with increasing the particle volume fraction,while the tensile strength of the composites decreases with increasing the volume fraction of the Al2O3 particles.The wear rate of the composites decreases with increasing the volume fraction of the particle and loading.The in situ formed Al2O3/Al composite by adding NH4AlO（OH）HCO3 shows more superior mechanical and wear behaviors than that prepared by directly adding Al2O3 particles.展开更多
以Cu_3(BTC)_2负载磷钨酸H_3PW_(12)O_(40)/Cu_3(BTC)_2催化剂催化,环己酮和乙二醇为原料合成环己酮乙二醇缩酮.探讨H_3PW_(12)O_(40)/Cu_3(BTC)_2对环己酮乙二醇缩酮的催化活性,较系统地研究了酮醇物质的量比、催化剂用量、带水剂用量...以Cu_3(BTC)_2负载磷钨酸H_3PW_(12)O_(40)/Cu_3(BTC)_2催化剂催化,环己酮和乙二醇为原料合成环己酮乙二醇缩酮.探讨H_3PW_(12)O_(40)/Cu_3(BTC)_2对环己酮乙二醇缩酮的催化活性,较系统地研究了酮醇物质的量比、催化剂用量、带水剂用量、反应时间等因素对产物收率的影响.实验表明:H_3PW_(12)O_(40)/Cu_3(BTC)_2是合成环己酮乙二醇缩酮的良好催化剂,在n(环己酮)∶n(乙二醇)=1∶1.4,催化剂用量占反应物料总质量0.6%,带水剂环己烷的用量为8 m L,反应时间45 min的最佳条件下,环己酮乙二醇缩酮的收率可达75.9%.展开更多
Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of AI2O3 short fiber reinforced AI-Mg alloy matrix composite at elevated temperatures were researched. The interfacial micr...Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of AI2O3 short fiber reinforced AI-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally, the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideration of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300℃) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.展开更多
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.
文摘The preferred internal oxidation of aluminum in Cu Al alloy was used to obtain in situ Al 2O 3/Cu composites. The reinforcement particles were mainly γ Al 2O 3, some θ Al 2O 3 and a little α Al 2O 3. Thermodynamics analyses show that the chemical reactions are 3Cu 2O+2Al=6Cu+Al 2O 3 or 3CuO+2Al=3Cu+Al 2O 3. A related equilibrium diagram was drawn. The experiments and investigation show that the formation rate of Al 2O 3 was controlled by the diffusion of oxygen in matrix.
基金Henan Innovation Project for University Prominent Research Talents (2007KYCX008)Henan Major Science and Technol-ogy Project (0523021500)+1 种基金Henan University of Science and Technology Major Pre-research Foundation (2005ZD003)Henan University of Science and Technology Personnel Scientific Research Foundation
文摘Alumina dispersion strengthened copper composite （nano-Al2O3/Cu composite） was recently emerged as a kind of potentially viable and attractive engineering material for applications requiring high strength, high thermal and electrical conductivities and resistance to softening at elevated temperatures. The nano-Al2O3/Cu composite was produced by internal oxidation. The microstructures of the composite were analyzed by the TEM and its hot deformation behavior was investigated by means of continuous compression tests performed on a Gleeble 1500 thermo-simulator. Making use of the modified algorithm-Levenberg-Marquardt （L-M） algorithm BP neural network, a model for predicting the flow stresses during hot deformation was set up on the base of the experimental data. Results show that the microstructures of the composite are characterized by uniform distribution of nano-Al2O3 particles in Cu-matrix. The sliding of dislocations is the main deformation mechanism. The dynamic recovery is the main softening mode with the flow stress decreasing gently from 500℃ to 850 ~C. The recrystallization of Cu-matrix can be retarded late into as high as 850 ℃, when it happens only partially. The well-trained BP neural network model can accurately describe the influence of the temperature, strain rate, and true strain on the flow stresses, therefore, it can precisely predict the flow stresses of the composite under given deforming conditions and provide a new way to optimize hot deforming process parameters.
基金Project(50702012)supported by the National Natural Science Foundation of ChinaProject(20060145030)supported by Doctoral Foundation of Chinese Education Ministry
文摘Silver as a highly conductive metal is usually doped in YBa2Cu3O7-x superconductor bulks to improve critical current density of YBa2Cu3O7-x superconductor.The valuable metal elements silver,yttrium,barium and copper in waste YBa2Cu3O7-x/Ag composite superconductor bulks were recovered,respectively.Silver was recovered with process at first,the waste was dissolved by nitric acid and silver chloride was precipitated by adding chloride acid,then silver pig was obtained by melting silver chloride together with sodium carbonate at 1 000℃.The effective factors on recovery ratio and purity of silver were studied.The chemical analysis proves that the purity of silver ingot is 95.86%.The recovery ratio of silver is calculated to be 92.56%.The loss of silver may be due to the loss of silver chloride during filtering and the volatilization of silver when silver chloride and sodium carbonate are smelted at high temperature.For other three metal elements,Y3 +,Ba 2+and Cu 2+,in the surplus waste liquid after recovering silver, they were separated with the sequence of barium,copper and then yttrium step by step.First,sulfate acid was used to precipitate barium sulfate.Then,sodium sulfide was added to the surplus solution so that copper could be separated as copper sulfide.During this separation procedure,it was important to control the pH value to be 1-2.After that,oxalic acid was added into the surplus solution to obtain yttrium oxalate.Finally,yttrium oxide was formed by burning yttrium oxalate.The XRD results indicate that the final products are all single-phase compounds as BaSO4,CuS and Y2O3,respectively.
基金The work was financiaIly supported hy the NaturalScience Foundation of Hebei Province (No.94087) alld Pd-ucation Conlmittee of
文摘This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high temperature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.
文摘Chemical solution route was used to synthesize Bi3.1La0.9Ti3O12 and CoFe2O4. Alternate CoFe2O4/Bi3.1La0.9Ti3O12 layers were deposited on Pt substrate （Pt/TiO2/SiO2/Si） by spin coating. X-ray diffraction and SEM （scanning electron microscopy） studies show composite-like polycrystalline films. Films were studied for leakage current, dielectric response, ferroelectric and ferromagnetic properties. Leakage current was low （〈 10^-8 A） in electric field below 120 kV/cm, and the dielectric response shows relaxation. Dielectric loss （tan 8） reduces 〈 3% at 10^6 Hz. Two and four layer structures showed room temperature FE （ferroelectric） and FM （ferromagnetic） responses with FE Pr （polarization） 〉 25℃/cm2 and ferromagnetic Mr （memory） 〉 52 emu/cm3. Co-existence of FE and FM can be attributed to stress due to different crystal structures of the material involved in composite film structure.
文摘采用固相法制备了Ca Cu3Ti4O12多晶块体,研究了其介电常数随温度和频率的变化。结果表明,在温度为300 K、频率为1 k Hz时,多晶块的介电常数高达14 000;频率为1 k Hz时,介电常数基本不随温度的变化而改变。动态变化的极化弛豫使Ca Cu3Ti4O12多晶块具有巨介电常数,混合价Ti离子导致极化子的热激活使Ca Cu3Ti4O12多晶块的介电特性出现反常效应。
基金Project(2009BAE80B01)supported by the Ministry of Science and Technology,China
文摘Aluminium matrix composite reinforced by Al2O3 particles was produced by adding NH4AlO（OH）HCO3 into molten aluminum.The mechanical properties and wear behavior of the as-fabricated composites were studied.The results show that during stirring γ-Al2O3 particles were formed via decomposition reaction of NH4AlO（OH）HCO3,and the distribution of Al2O3 particles is more uniform in the matrix aluminum than directly added Al2O3 into molten aluminum.The density and the hardness values of the as-fabricated composites increase with increasing the particle volume fraction,while the tensile strength of the composites decreases with increasing the volume fraction of the Al2O3 particles.The wear rate of the composites decreases with increasing the volume fraction of the particle and loading.The in situ formed Al2O3/Al composite by adding NH4AlO（OH）HCO3 shows more superior mechanical and wear behaviors than that prepared by directly adding Al2O3 particles.
基金国家自然科学基金(批准号:11004129,11204171)留学回国人员科研启动基金(SRF for ROCS,SEM)+2 种基金上海市教育委员会科研创新项目(批准号:11YZ197,12ZZ174)上海市教育发展基金会晨光计划(批准号:12CG63)上海高校选拔培养优秀青年教师科研专项基金(批准号:sdl10005)资助的课题~~
文摘以Cu_3(BTC)_2负载磷钨酸H_3PW_(12)O_(40)/Cu_3(BTC)_2催化剂催化,环己酮和乙二醇为原料合成环己酮乙二醇缩酮.探讨H_3PW_(12)O_(40)/Cu_3(BTC)_2对环己酮乙二醇缩酮的催化活性,较系统地研究了酮醇物质的量比、催化剂用量、带水剂用量、反应时间等因素对产物收率的影响.实验表明:H_3PW_(12)O_(40)/Cu_3(BTC)_2是合成环己酮乙二醇缩酮的良好催化剂,在n(环己酮)∶n(乙二醇)=1∶1.4,催化剂用量占反应物料总质量0.6%,带水剂环己烷的用量为8 m L,反应时间45 min的最佳条件下,环己酮乙二醇缩酮的收率可达75.9%.
文摘Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of AI2O3 short fiber reinforced AI-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally, the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideration of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300℃) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.
