Precise spatial control of 2D materials is the key capability of engineering their optical,electronic,and mechanical properties.However,growth of novel 2D Mo2C on Cu surface by chemical vapor deposition method was rev...Precise spatial control of 2D materials is the key capability of engineering their optical,electronic,and mechanical properties.However,growth of novel 2D Mo2C on Cu surface by chemical vapor deposition method was revealed to be seed-induced 2D growth,limiting further synthesis of complex Mo2C spatial structures.In this research,we demonstrate the controlled growth of Mo2C pyramids with numerous morphologies,which are characterized with clear terraces within the structures.The whole evolution for Mo2C pyramids in the coursed of CVD process has been detected,posing significant potential in probing growth mechanism.The formation of the Mo2C pyramids arises from the supersaturation-induced nucleation and concentration-gradient driven diffused growth of a new Mo2C layer on the edged areas of intrinsic ones,as supported by STEM imaging.This work provides a novel Mo2C-based pyramid structure and further reveals a sliding growth mechanism,which could offer impetus for the design of new 3D spatial structures of Mo2C and other 2D materials.展开更多
We report a new kagome quantum spin liquid candidate CuaZn(OH)6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (-20...We report a new kagome quantum spin liquid candidate CuaZn(OH)6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (-200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fraetionalization in the fractional quantum Hall state.展开更多
The transport of Cu(II)from aqueous solutions containing buffer media through hollow fiber supported liquid membrane(HFSLM)using di(2-ethylhexyl)phosphoric acid(D2EHPA)dissolved in kerosene as membrane phase and hydro...The transport of Cu(II)from aqueous solutions containing buffer media through hollow fiber supported liquid membrane(HFSLM)using di(2-ethylhexyl)phosphoric acid(D2EHPA)dissolved in kerosene as membrane phase and hydrochloric acid as striping phase was investigated.A set of factors were studied,including tube side velocity,shell side velocity,pH of the feed phase,Cu(II)concentration in the feed phase,buffer media concentration and D2EHPA concentration in the membrane phase.Experimental results indicate that the mass transfer coefficient increases with increasing both carrier concentration in the organic phase and flow rates on the tube side and shell side,and decreases with increasing initial Cu(II)concentration in the feed phase.With increasing pH value and acetate concentration in the feed phase,the mass transfer coefficient reaches a maximum value then decreases.The optimal operating conditions are obtained at pH value of 4.44 and 0.1 mol·L -1 acetic ion concentration in feed phase,and carrier volume fraction of around 10%in kerosene as organic phase.A mathematical model of the transport mechanism through HFSLM is developed.The modeled results agree well with the experimental ones.展开更多
During the process of liquid forging, a host of hot cracking defects were found in the Al-CuMg-Zn aluminum alloy. Therefore, mechanical tests and analyses by optical microscope, scanning electron microscope, and X-ray...During the process of liquid forging, a host of hot cracking defects were found in the Al-CuMg-Zn aluminum alloy. Therefore, mechanical tests and analyses by optical microscope, scanning electron microscope, and X-ray diffraction were performed to research the influences of zinc, magnesium, and copper(three main alloying elements) on hot cracking tendency and mechanical properties. It was concluded that all the three alloying elements exerted different effects on the performances of newly designed alloys. And the impact of microstructures on properties of alloys was stronger than that of solution strengthening. Among new alloys, Al-5 Cu-4.5 Mg-2.5 Zn alloy shows better properties as follows: σb=327 MPa, δ=2.7%, HB=107 N/mm^2, and HCS=40.展开更多
The ribbons of Cu-Cr alloys with high Cr content (15%- 35%, mass fraction) were prepared by rapid solidification. The microstructures of solidified samples were analyzed by scanning electron microscopy and transmissio...The ribbons of Cu-Cr alloys with high Cr content (15%- 35%, mass fraction) were prepared by rapid solidification. The microstructures of solidified samples were analyzed by scanning electron microscopy and transmission electron microscopy. The results reveal that a representative liquid phase separation microstructures are observed in Cu75Cr25 ribbons solidified at a cooling rate of about 104K/s. The liquid phase separation is not restrained when the cooling rate is enhanced to about 107K/s. However, the size of Cr particles solidified from Cr-rich liquid or Cr-rich regions in alloy melts could be refined by increasing the cooling rates. The size of Cr particles increases with increasing Cr contents when the ribbons contain 15% to 35%Cr.展开更多
Thermodynamics of Cu-Ce-O,Cu-Ce-S and Cu-Ce-0-S solutions at 1200℃ were studied by using solid electrolyte cell and chemical equilibrium method.The equilibrium constant of deoxidation,desulfurization and deoxysulfuri...Thermodynamics of Cu-Ce-O,Cu-Ce-S and Cu-Ce-0-S solutions at 1200℃ were studied by using solid electrolyte cell and chemical equilibrium method.The equilibrium constant of deoxidation,desulfurization and deoxysulfurization by Ce,the Gibbs standard reaction free energies of the formation of Ce_2O_3,CeS and Ce_2O_2S in Cu-base solution,activity interaction coefficients of S and Ce,temperature dependence of standard reaction free energy of solution of Ce in Cu,self-interaction coefficients of Ce in liquid Cu have been obtained.The phase precipitation diagram for Cu-CeS-O system has been plotted.The thermodynamic condition of the existence of Ce_2O_3,CeS and Ce_2O_2S in liquid Cu has been determined.It provides the basis for predicting the sequence and the type of equilibrium inclusions of Ce formed in Cu-base solution.展开更多
The conversion of methane to liquid fuels is still in the development process. The modified HZSM-5 by loading with Tungsten (W) enhanced its heat resistant performance, and the high reaction temperature (800℃) di...The conversion of methane to liquid fuels is still in the development process. The modified HZSM-5 by loading with Tungsten (W) enhanced its heat resistant performance, and the high reaction temperature (800℃) did not lead to the loss of W component by sublimation. The loading of ZSM-5 with Tungsten and Copper (Cu) resulted in an increment in the methane conversion, CO2, and C5+ selectivities. The high methane conversion and C5+ selectivity, and low H2O selectivity are obtained by using W/3.0Cu/ZSM-5. The optimization of methane conversion over 3.0 W/3.0Cu/ZSM-5 under different temperature and oxygen concentration using response surface methodology (RSM) are studied. The optimum point for methane conversion is 19% when temperature is 753 ℃, and oxygen concentration is 12%. The highest C5+ selectivity is 27% when temperature is 751 ℃. and oxwen concentration is 11%.展开更多
The solid-liquid method was used to prepare the continuous casting of copper cladding aluminium by liquid aluminum alloy and solid copper, and the interfacial phase formation of Al-Cu bimetal at different pouring temp...The solid-liquid method was used to prepare the continuous casting of copper cladding aluminium by liquid aluminum alloy and solid copper, and the interfacial phase formation of Al-Cu bimetal at different pouring temperatures(700, 750, 800 oC) was investigated by means of metallograph, scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS) methods. The results showed that the pouring temperature of aluminum melt had an important influence on the element diffusion of Cu from the solid Cu to Al alloy melt and the reactions between Al and Cu, as well as the morphology of the Al-Cu interface. When the pouring temperature was 800 oC, there were abundant Al-Cu intermetallic compounds(IMCs) near the interface. However, a lower pouring temperature(700 oC) resulted in the formation of cavities which was detrimental to the bonding and mechanical properties. Under the conditions in this study, the good metallurgical bonding of Al-Cu was achieved at a pouring temperature of 750 oC.展开更多
The interaction between Cu and liquid Sn was studied by microstructure observation.The curve of the dipping time with related to dissolving and diffusion of Cu in liquid Sn is given. The Cu dissolves rapidly in liquid...The interaction between Cu and liquid Sn was studied by microstructure observation.The curve of the dipping time with related to dissolving and diffusion of Cu in liquid Sn is given. The Cu dissolves rapidly in liquid Sn at the beginning,then an intermetallic compound Cu_6Sn_5 forms,and the dissolving follows to slow down.At temperature up to 350℃,the hard feather-like Cu_6Sn_5 is sharply growing up and speads through the dipped Sn laver.The way to inhibit the growth of the intermetallic compound Cu_6Sn_5 was also approached.Thus,on the above mentioned basis,the physical meaning of the wetting curve traced by the meniscograph wettability tester has been derived as film detaching,Cu dissolying and Cu_6Sn_5 growing.展开更多
The features of Cu_6Sn_5 growing slowly at lower temperature and growing rapidly up over 350℃,and or Cu_3Sn growing at higher temperatures,bave been detailedly observed under SEM.The increase of Pb content seems to i...The features of Cu_6Sn_5 growing slowly at lower temperature and growing rapidly up over 350℃,and or Cu_3Sn growing at higher temperatures,bave been detailedly observed under SEM.The increase of Pb content seems to inhibit sequentially the growth of Cu_6Sn_5 in Pb-Sn alloy.展开更多
The compact oxide on the surface of SiCp/Al metal matrix composite (SiCp/Al MMC) greatly depends on the property of the joint. Inlaid sputtering target was applied to etch the oxide completely on the bonding surface...The compact oxide on the surface of SiCp/Al metal matrix composite (SiCp/Al MMC) greatly depends on the property of the joint. Inlaid sputtering target was applied to etch the oxide completely on the bonding surface of SiCp/Al MMC by plasma erosion. Cu/Ni/Cu film of 5μm in thickness was prepared by magnetron sputtering method on the clean bonding surface in the same vacuum chamber, which was acted as an interlayer in transient liquid phase (TLP) bonding process. Compared with the same thickness of single Cu foil and Ni foil interlayer, the shear strength of 200 MPa was obtained using Cu/Ni/Cu film interlayer during TLP bonding, which was 89.7% that of base metal. In addition, homogenization of the bonding region and no particle segregation in interfacial region were found by analysis of the joint microstructure. Scanning electron microscopy (SEM) was used to observe the micrograph of the joint interface. The result shows that a homogenous microstructure of joint was achieved, which is similar with that of based metal.展开更多
By using the Ti/Cu contact reaction couples, the dissolution behavior of Ti and Cu in the eutectic reaction process was investigated under different conditions. The results show that the formation of eutectic liquid p...By using the Ti/Cu contact reaction couples, the dissolution behavior of Ti and Cu in the eutectic reaction process was investigated under different conditions. The results show that the formation of eutectic liquid phase has a directional property, i.e. the eutectic liquid phase forms first at the Cu side and then spreads along the depth direction of Cu. The width of the eutectic liquid zone when Ti is placed on Cu is wider than that when Ti is placed under Cu. The shape of the upside liquid zone is wave-like. This phenomenon indicates that the formation process and spreading behavior in the upside are different from those in the underside, and there exists void effect in the Cu side of underside liquid zone, this will result in the delaying phenomenon of the contact reaction between Ti and Cu, and distinctly different shapes of the both liquid zones. The formation process of Ti/Cu eutectic liquid zone is similar to that of the traditional solid-state diffusion layer, and the relationship between the width of liquid zone and holding time obeys a square root law.展开更多
A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders.The precipitates were first obtained by adding ammonium heptamolybdate((NH4)6Mo7O24·4H2O) solution into excess hydrazine h...A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders.The precipitates were first obtained by adding ammonium heptamolybdate((NH4)6Mo7O24·4H2O) solution into excess hydrazine hydrate solution,and then mixed the copper chloride solution.The precipitates were subsequently washed,dried,followed by reducing in H2 atmosphere to convert into Mo-Cu composite powders.The composition,morphology and particle size of the Mo-Cu composite powders were characterized by the XRD,SEM and TEM.The effects of the chemical reaction temperature and the magnetic stirring on the morphology of the Mo-Cu powders were also studied.The results show that Mo-Cu powders produced by the chemical liquid reduction process are nearly spherical shape and dispersive distribution state,with particle size ranging from 50 to 100 nm.The chemical reaction temperature and magnetic stirring will change the particle feature of the powders.Because of the Cu3Mo2O9,the reduction process in H2 is the one-stage reduction from the precipitates to the Mo-Cu composite powders.展开更多
The kinetic characteristics of W grain growth operated by diffusion controlled Oswald ripening (DOR) during liquid phase sintering were studied. A liquid phase sintering of W-15wt%Cu was carried out by pushing compa...The kinetic characteristics of W grain growth operated by diffusion controlled Oswald ripening (DOR) during liquid phase sintering were studied. A liquid phase sintering of W-15wt%Cu was carried out by pushing compacts into a furnace at the moment when the temperature increased to 1340℃ for different sintering times. The results show that liquid phase sintering produces the compacts with considerably low relative density and inversely, rather high homogeneity. On the basis of the data extracted from the SEM images, the kinetic equation of W grain growth, G^n = G0^n + kt, is determined in which the grain growth exponent n is 3 and the grain growth rate constant k is 0.15 μm^3/s. The cumulative normalized grain size distributions produced by different sintering times show self-similar. The cumulative distribution function is extracted from the curves by non-linear fitting. In addition, the sintering kinetic characteristics of W-15wt%Cu compacts were also investigated.展开更多
The effect of cooling liquid used for heat exchangers on the Cu alloy corrosion products has been examined using potential-time measurements under applied current condition (anodizing), potentiodynamic polarization, X...The effect of cooling liquid used for heat exchangers on the Cu alloy corrosion products has been examined using potential-time measurements under applied current condition (anodizing), potentiodynamic polarization, X-ray diffraction (XRD) and infrared spectroscopy (IR) The corrosion products formed on the Cu alloy surface during anodizing, are Cu2O, Cu2(OH)3Cl, and Cu2S. NaCl is detected in the corrosion products. The film formation depends on the applied current and the shift of potential to nobler direction indicates its formation progress.展开更多
文摘Precise spatial control of 2D materials is the key capability of engineering their optical,electronic,and mechanical properties.However,growth of novel 2D Mo2C on Cu surface by chemical vapor deposition method was revealed to be seed-induced 2D growth,limiting further synthesis of complex Mo2C spatial structures.In this research,we demonstrate the controlled growth of Mo2C pyramids with numerous morphologies,which are characterized with clear terraces within the structures.The whole evolution for Mo2C pyramids in the coursed of CVD process has been detected,posing significant potential in probing growth mechanism.The formation of the Mo2C pyramids arises from the supersaturation-induced nucleation and concentration-gradient driven diffused growth of a new Mo2C layer on the edged areas of intrinsic ones,as supported by STEM imaging.This work provides a novel Mo2C-based pyramid structure and further reveals a sliding growth mechanism,which could offer impetus for the design of new 3D spatial structures of Mo2C and other 2D materials.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0300502,2016YFA0300503,2016YFA0300604,2016YF0300300 and 2016YFA0300802the National Natural Science Foundation of China under Grant Nos 11421092,11474330,11574359,11674406,11374346 and 11674375+3 种基金the National Basic Research Program of China(973 Program)under Grant No 2015CB921304the National Thousand-Young-Talents Program of Chinathe Strategic Priority Research Program(B) of the Chinese Academy of Sciences under Grant Nos XDB07020000,XDB07020200 and XDB07020300supported by DOE-BES under Grant No DE-FG02-04ER46148
文摘We report a new kagome quantum spin liquid candidate CuaZn(OH)6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (-200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fraetionalization in the fractional quantum Hall state.
基金Supported by the Program for New Century Excellent Talents in University (NCET-05-0122) the National Natural Science Foundation of China(20576008 20706003) the Ph.D.Programs Foundation of Ministry of Education of China(200800100001) The authors are grateful to Prof. Xiaolong Lii of Tianjin Polytechnic University for supplying PVDF hollow fibers.
文摘The transport of Cu(II)from aqueous solutions containing buffer media through hollow fiber supported liquid membrane(HFSLM)using di(2-ethylhexyl)phosphoric acid(D2EHPA)dissolved in kerosene as membrane phase and hydrochloric acid as striping phase was investigated.A set of factors were studied,including tube side velocity,shell side velocity,pH of the feed phase,Cu(II)concentration in the feed phase,buffer media concentration and D2EHPA concentration in the membrane phase.Experimental results indicate that the mass transfer coefficient increases with increasing both carrier concentration in the organic phase and flow rates on the tube side and shell side,and decreases with increasing initial Cu(II)concentration in the feed phase.With increasing pH value and acetate concentration in the feed phase,the mass transfer coefficient reaches a maximum value then decreases.The optimal operating conditions are obtained at pH value of 4.44 and 0.1 mol·L -1 acetic ion concentration in feed phase,and carrier volume fraction of around 10%in kerosene as organic phase.A mathematical model of the transport mechanism through HFSLM is developed.The modeled results agree well with the experimental ones.
基金Funded by the International Cooperation Project of the Ministry of Science and Technology of China(No.2014DFR50320)the National Natural Science Foundation of China(No.51174064).
文摘During the process of liquid forging, a host of hot cracking defects were found in the Al-CuMg-Zn aluminum alloy. Therefore, mechanical tests and analyses by optical microscope, scanning electron microscope, and X-ray diffraction were performed to research the influences of zinc, magnesium, and copper(three main alloying elements) on hot cracking tendency and mechanical properties. It was concluded that all the three alloying elements exerted different effects on the performances of newly designed alloys. And the impact of microstructures on properties of alloys was stronger than that of solution strengthening. Among new alloys, Al-5 Cu-4.5 Mg-2.5 Zn alloy shows better properties as follows: σb=327 MPa, δ=2.7%, HB=107 N/mm^2, and HCS=40.
基金Project(50371066) supported by the National Natural Science Foundation of China
文摘The ribbons of Cu-Cr alloys with high Cr content (15%- 35%, mass fraction) were prepared by rapid solidification. The microstructures of solidified samples were analyzed by scanning electron microscopy and transmission electron microscopy. The results reveal that a representative liquid phase separation microstructures are observed in Cu75Cr25 ribbons solidified at a cooling rate of about 104K/s. The liquid phase separation is not restrained when the cooling rate is enhanced to about 107K/s. However, the size of Cr particles solidified from Cr-rich liquid or Cr-rich regions in alloy melts could be refined by increasing the cooling rates. The size of Cr particles increases with increasing Cr contents when the ribbons contain 15% to 35%Cr.
基金supported by the National Natural Science Foundation of China
文摘Thermodynamics of Cu-Ce-O,Cu-Ce-S and Cu-Ce-0-S solutions at 1200℃ were studied by using solid electrolyte cell and chemical equilibrium method.The equilibrium constant of deoxidation,desulfurization and deoxysulfurization by Ce,the Gibbs standard reaction free energies of the formation of Ce_2O_3,CeS and Ce_2O_2S in Cu-base solution,activity interaction coefficients of S and Ce,temperature dependence of standard reaction free energy of solution of Ce in Cu,self-interaction coefficients of Ce in liquid Cu have been obtained.The phase precipitation diagram for Cu-CeS-O system has been plotted.The thermodynamic condition of the existence of Ce_2O_3,CeS and Ce_2O_2S in liquid Cu has been determined.It provides the basis for predicting the sequence and the type of equilibrium inclusions of Ce formed in Cu-base solution.
文摘The conversion of methane to liquid fuels is still in the development process. The modified HZSM-5 by loading with Tungsten (W) enhanced its heat resistant performance, and the high reaction temperature (800℃) did not lead to the loss of W component by sublimation. The loading of ZSM-5 with Tungsten and Copper (Cu) resulted in an increment in the methane conversion, CO2, and C5+ selectivities. The high methane conversion and C5+ selectivity, and low H2O selectivity are obtained by using W/3.0Cu/ZSM-5. The optimization of methane conversion over 3.0 W/3.0Cu/ZSM-5 under different temperature and oxygen concentration using response surface methodology (RSM) are studied. The optimum point for methane conversion is 19% when temperature is 753 ℃, and oxygen concentration is 12%. The highest C5+ selectivity is 27% when temperature is 751 ℃. and oxwen concentration is 11%.
基金financially supported by the National Natural Science Foundation of China(Nos.51074031 and 51501027)the China Postdoctoral Science Foundation(No.2015M570246)the Fundamental Research Funds for the Central Universities of China[DUT15RC(3)065]
文摘The solid-liquid method was used to prepare the continuous casting of copper cladding aluminium by liquid aluminum alloy and solid copper, and the interfacial phase formation of Al-Cu bimetal at different pouring temperatures(700, 750, 800 oC) was investigated by means of metallograph, scanning electron microscopy(SEM) and energy dispersive spectrometry(EDS) methods. The results showed that the pouring temperature of aluminum melt had an important influence on the element diffusion of Cu from the solid Cu to Al alloy melt and the reactions between Al and Cu, as well as the morphology of the Al-Cu interface. When the pouring temperature was 800 oC, there were abundant Al-Cu intermetallic compounds(IMCs) near the interface. However, a lower pouring temperature(700 oC) resulted in the formation of cavities which was detrimental to the bonding and mechanical properties. Under the conditions in this study, the good metallurgical bonding of Al-Cu was achieved at a pouring temperature of 750 oC.
文摘The interaction between Cu and liquid Sn was studied by microstructure observation.The curve of the dipping time with related to dissolving and diffusion of Cu in liquid Sn is given. The Cu dissolves rapidly in liquid Sn at the beginning,then an intermetallic compound Cu_6Sn_5 forms,and the dissolving follows to slow down.At temperature up to 350℃,the hard feather-like Cu_6Sn_5 is sharply growing up and speads through the dipped Sn laver.The way to inhibit the growth of the intermetallic compound Cu_6Sn_5 was also approached.Thus,on the above mentioned basis,the physical meaning of the wetting curve traced by the meniscograph wettability tester has been derived as film detaching,Cu dissolying and Cu_6Sn_5 growing.
文摘The features of Cu_6Sn_5 growing slowly at lower temperature and growing rapidly up over 350℃,and or Cu_3Sn growing at higher temperatures,bave been detailedly observed under SEM.The increase of Pb content seems to inhibit sequentially the growth of Cu_6Sn_5 in Pb-Sn alloy.
基金The work was financially supported by the National Natural Science Foundation of China under grant Nos. 50275076 and 50075039.
文摘The compact oxide on the surface of SiCp/Al metal matrix composite (SiCp/Al MMC) greatly depends on the property of the joint. Inlaid sputtering target was applied to etch the oxide completely on the bonding surface of SiCp/Al MMC by plasma erosion. Cu/Ni/Cu film of 5μm in thickness was prepared by magnetron sputtering method on the clean bonding surface in the same vacuum chamber, which was acted as an interlayer in transient liquid phase (TLP) bonding process. Compared with the same thickness of single Cu foil and Ni foil interlayer, the shear strength of 200 MPa was obtained using Cu/Ni/Cu film interlayer during TLP bonding, which was 89.7% that of base metal. In addition, homogenization of the bonding region and no particle segregation in interfacial region were found by analysis of the joint microstructure. Scanning electron microscopy (SEM) was used to observe the micrograph of the joint interface. The result shows that a homogenous microstructure of joint was achieved, which is similar with that of based metal.
基金Project(JKLSDT 02 01) supported by the Open Fund of the Jiangsu Key Laboratory of Ship Designing Technology
文摘By using the Ti/Cu contact reaction couples, the dissolution behavior of Ti and Cu in the eutectic reaction process was investigated under different conditions. The results show that the formation of eutectic liquid phase has a directional property, i.e. the eutectic liquid phase forms first at the Cu side and then spreads along the depth direction of Cu. The width of the eutectic liquid zone when Ti is placed on Cu is wider than that when Ti is placed under Cu. The shape of the upside liquid zone is wave-like. This phenomenon indicates that the formation process and spreading behavior in the upside are different from those in the underside, and there exists void effect in the Cu side of underside liquid zone, this will result in the delaying phenomenon of the contact reaction between Ti and Cu, and distinctly different shapes of the both liquid zones. The formation process of Ti/Cu eutectic liquid zone is similar to that of the traditional solid-state diffusion layer, and the relationship between the width of liquid zone and holding time obeys a square root law.
基金Project(51274246) supported by the National Natural Science Foundation of China
文摘A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders.The precipitates were first obtained by adding ammonium heptamolybdate((NH4)6Mo7O24·4H2O) solution into excess hydrazine hydrate solution,and then mixed the copper chloride solution.The precipitates were subsequently washed,dried,followed by reducing in H2 atmosphere to convert into Mo-Cu composite powders.The composition,morphology and particle size of the Mo-Cu composite powders were characterized by the XRD,SEM and TEM.The effects of the chemical reaction temperature and the magnetic stirring on the morphology of the Mo-Cu powders were also studied.The results show that Mo-Cu powders produced by the chemical liquid reduction process are nearly spherical shape and dispersive distribution state,with particle size ranging from 50 to 100 nm.The chemical reaction temperature and magnetic stirring will change the particle feature of the powders.Because of the Cu3Mo2O9,the reduction process in H2 is the one-stage reduction from the precipitates to the Mo-Cu composite powders.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50174007).
文摘The kinetic characteristics of W grain growth operated by diffusion controlled Oswald ripening (DOR) during liquid phase sintering were studied. A liquid phase sintering of W-15wt%Cu was carried out by pushing compacts into a furnace at the moment when the temperature increased to 1340℃ for different sintering times. The results show that liquid phase sintering produces the compacts with considerably low relative density and inversely, rather high homogeneity. On the basis of the data extracted from the SEM images, the kinetic equation of W grain growth, G^n = G0^n + kt, is determined in which the grain growth exponent n is 3 and the grain growth rate constant k is 0.15 μm^3/s. The cumulative normalized grain size distributions produced by different sintering times show self-similar. The cumulative distribution function is extracted from the curves by non-linear fitting. In addition, the sintering kinetic characteristics of W-15wt%Cu compacts were also investigated.
文摘The effect of cooling liquid used for heat exchangers on the Cu alloy corrosion products has been examined using potential-time measurements under applied current condition (anodizing), potentiodynamic polarization, X-ray diffraction (XRD) and infrared spectroscopy (IR) The corrosion products formed on the Cu alloy surface during anodizing, are Cu2O, Cu2(OH)3Cl, and Cu2S. NaCl is detected in the corrosion products. The film formation depends on the applied current and the shift of potential to nobler direction indicates its formation progress.