Volume 43,Issue 9,2014 Table of Contents
2014, 43(9):2055-2059.
Abstract:
Five kinds of Ni(OH)2 positive materials with different chemical compositions were prepared by a chemical coprecipitation method. The compounds with Co, Zn, Ca, Mg, Cu or Mn elements were mixed with nickel sulfate and reacted with each other at a special temperature and pH value under stirring. The XRD analysis indicates that the microstructure of as-prepared materials is β-Ni(OH)2. SEM images show the particles are spherical with a little rough surface. The electrochemical results indicate that the Ni(OH)2 B has the best performances at different rates and temperatures. The discharge capacities for Ni(OH)2 B sample can achieve more than 285 mAh·g-1 at 1 C/3 C rate both at 25 and 65 oC. The experiment shows that the Ni(OH)2 positive materials with perfect properties can be synthesized by coprecipitating other elements, which is helpful for the improvement of Ni-MH batteries
Five kinds of Ni(OH)2 positive materials with different chemical compositions were prepared by a chemical coprecipitation method. The compounds with Co, Zn, Ca, Mg, Cu or Mn elements were mixed with nickel sulfate and reacted with each other at a special temperature and pH value under stirring. The XRD analysis indicates that the microstructure of as-prepared materials is β-Ni(OH)2. SEM images show the particles are spherical with a little rough surface. The electrochemical results indicate that the Ni(OH)2 B has the best performances at different rates and temperatures. The discharge capacities for Ni(OH)2 B sample can achieve more than 285 mAh·g-1 at 1 C/3 C rate both at 25 and 65 oC. The experiment shows that the Ni(OH)2 positive materials with perfect properties can be synthesized by coprecipitating other elements, which is helpful for the improvement of Ni-MH batteries
2014, 43(9):2064-2068.
Abstract:
The effects of trace yttrium oxidation on the properties and the microstructures of 9Cr-1Mo steel welds for super critical generation units and USC units have been studied. Yttrium has been added into weld metal by coating transition (e. g. molten droplet method). The yttrium content for optimized properties and structures has been determined. Comparison tests including room temperature and high temperature tensile tests, serials impact test, metallographic analysis, diffusion hydrogen measuring, phase transformation point, SEM, XDR etc. have been performed on the welds with and without yttrium. It is found that second phase particles make an important contribution to improving the properties of the weld metal, especially low temperature impact performance
The effects of trace yttrium oxidation on the properties and the microstructures of 9Cr-1Mo steel welds for super critical generation units and USC units have been studied. Yttrium has been added into weld metal by coating transition (e. g. molten droplet method). The yttrium content for optimized properties and structures has been determined. Comparison tests including room temperature and high temperature tensile tests, serials impact test, metallographic analysis, diffusion hydrogen measuring, phase transformation point, SEM, XDR etc. have been performed on the welds with and without yttrium. It is found that second phase particles make an important contribution to improving the properties of the weld metal, especially low temperature impact performance
2014, 43(9):2075-2078.
Abstract:
The effect of the catalysts LaCl3 and La2O3 on the dehydrogenation properties of the LiAlH4-NH4Cl system was analyzed. The results show that La2O3 doping shortens the starting time of hydrogen release, and improves the rate of hydrogen release. While, LaCl3 doping induces an obvious decrease of the rate of hydrogen release. Furthermore, the study shows that with the increase of the amounts of LaCl3 and La2O3, the hydrogen release amounts of the samples present a gradual decrease within 180 min except for the sample doped with 3 mol% LaCl3. However, the maximum hydrogen release amount of the sample doped with La2O3 is obviously higher than that of the sample doped with LaCl3. In addition, the analysis of the SEM images of the undoped sample and the doped samples indicates that the microstructure of all the samples seems to be similar and obvious differences are not found
The effect of the catalysts LaCl3 and La2O3 on the dehydrogenation properties of the LiAlH4-NH4Cl system was analyzed. The results show that La2O3 doping shortens the starting time of hydrogen release, and improves the rate of hydrogen release. While, LaCl3 doping induces an obvious decrease of the rate of hydrogen release. Furthermore, the study shows that with the increase of the amounts of LaCl3 and La2O3, the hydrogen release amounts of the samples present a gradual decrease within 180 min except for the sample doped with 3 mol% LaCl3. However, the maximum hydrogen release amount of the sample doped with La2O3 is obviously higher than that of the sample doped with LaCl3. In addition, the analysis of the SEM images of the undoped sample and the doped samples indicates that the microstructure of all the samples seems to be similar and obvious differences are not found
2014, 43(9):2079-2082.
Abstract:
Preparation of Mg-Li alloys by vacuum silicothermic reduction process was investigated. XRD was employed to analyze the phase composition of the product and slag. SEM was used to characterize the condensation morphology of the product. The results show that the main phase of the product is Mg and that of slag is Ca2SiO4. The product successively presents lamellar, short rod-like and flocculent shape along with the condensation. When adding no fluorite, the impacts of extraction conditions, including ferrosilicon addition, temperature, compacting pressure and holding time, on Mg and Li recoveries were evaluated. Under the conditions of temperature of 1250 °C, ferrosilicon addition of 110%, compacting pressure of 15 MPa and holding time of 150 min, Mg and Li recoveries are 81.38% and 99.58%, respectively
Preparation of Mg-Li alloys by vacuum silicothermic reduction process was investigated. XRD was employed to analyze the phase composition of the product and slag. SEM was used to characterize the condensation morphology of the product. The results show that the main phase of the product is Mg and that of slag is Ca2SiO4. The product successively presents lamellar, short rod-like and flocculent shape along with the condensation. When adding no fluorite, the impacts of extraction conditions, including ferrosilicon addition, temperature, compacting pressure and holding time, on Mg and Li recoveries were evaluated. Under the conditions of temperature of 1250 °C, ferrosilicon addition of 110%, compacting pressure of 15 MPa and holding time of 150 min, Mg and Li recoveries are 81.38% and 99.58%, respectively
2014, 43(9):2089-2094.
Abstract:
A composite material β-SiCp/Al was fabricated by a novel manufacturing process of bottom-vacuum pressureless infiltration. The β-SiC perform was oxidized at 1373 K and the infiltration in molten Al with the addition of Si and Mg. To evaluate the microstructure and the fractograph of the prepared composites, metallographic and scanning electron microscopes (SEM) were applied. The results reveal that SiC particles can be distributed in the aluminum matrix uniformly, the SiC preform can be completely infiltrated by the molten aluminum. X-ray diffraction (XRD) shows that the main crystalline phases in the composites are β-SiC and Al. There exist Mg2Si, MgAl2O4 interface products, brittle phases such as Al4C3 are not formed within the interface zone. Mechanical properties of the β-SiCp/Al composites were investigated by the wear and friction, Brinell hardness tests. The results prove that the wear mechanisms of the composites are abrasive and adhesive wear. With the increased of SiC volume fraction the wear rate of the composite decreases while the hardness increases
A composite material β-SiCp/Al was fabricated by a novel manufacturing process of bottom-vacuum pressureless infiltration. The β-SiC perform was oxidized at 1373 K and the infiltration in molten Al with the addition of Si and Mg. To evaluate the microstructure and the fractograph of the prepared composites, metallographic and scanning electron microscopes (SEM) were applied. The results reveal that SiC particles can be distributed in the aluminum matrix uniformly, the SiC preform can be completely infiltrated by the molten aluminum. X-ray diffraction (XRD) shows that the main crystalline phases in the composites are β-SiC and Al. There exist Mg2Si, MgAl2O4 interface products, brittle phases such as Al4C3 are not formed within the interface zone. Mechanical properties of the β-SiCp/Al composites were investigated by the wear and friction, Brinell hardness tests. The results prove that the wear mechanisms of the composites are abrasive and adhesive wear. With the increased of SiC volume fraction the wear rate of the composite decreases while the hardness increases
2014, 43(9):2095-2099.
Abstract:
LiMnBO3 and its carbon coated material LiMnBO3/C were synthesized by a microwave method. The influences of sintering temperature and feed composition on the structure and the morphology of materials were investigated. XRD, SEM and HR-TEM were used to characterize the structure and the morphology of the materials. The electrochemical properties of materials were tested by constant charge-discharge and electrochemical impedance spectroscopy. The results show that LiMnBO3 has a hexagonal crystal structure (h-LiMnBO3). The good crystalline structure with small grain size can be obtained under the reaction conditions of 750 oC, 25 min and nLi:nB:nMn=1:1:1(molar ratio). The charge-discharge capacity and the conductivity of the carbon coated material are enhanced after carbon coating. The initial discharge capacity of LiMnBO3/C is 50.3 mAh/g
LiMnBO3 and its carbon coated material LiMnBO3/C were synthesized by a microwave method. The influences of sintering temperature and feed composition on the structure and the morphology of materials were investigated. XRD, SEM and HR-TEM were used to characterize the structure and the morphology of the materials. The electrochemical properties of materials were tested by constant charge-discharge and electrochemical impedance spectroscopy. The results show that LiMnBO3 has a hexagonal crystal structure (h-LiMnBO3). The good crystalline structure with small grain size can be obtained under the reaction conditions of 750 oC, 25 min and nLi:nB:nMn=1:1:1(molar ratio). The charge-discharge capacity and the conductivity of the carbon coated material are enhanced after carbon coating. The initial discharge capacity of LiMnBO3/C is 50.3 mAh/g
2014, 43(9):2104-2107.
Abstract:
TG/DSC tests of non-hydrogenated and hydrogenated Ti-6Al-4V alloys were carried out in order to investigate the dehydrogenation behavior of hydrogenated titanium alloys. Results indicate that mass losses of the hydrogenated Ti-6Al-4V alloys are significantly different with that of the non-hydrogenated Ti-6Al-4V alloy when the heating temperature is higher than 600 oC. Mass loss of the hydrogenated Ti-6Al-4V alloy increases with the increasing of hydrogen content when the heating temperature is in the range of 600 oC to 900 oC due to the decomposition of metastable phases. The maximum mass loss of the hydrogenated Ti-6Al-4V alloy is in correspondence with its hydrogen content upon no consideration of oxidation. The optimal dehydrogenation temperature among hydrogenated Ti-6Al-4V alloys is 750 oC. The dehydrogenation process for all hydrogenated Ti-6Al-4V alloys is the same
TG/DSC tests of non-hydrogenated and hydrogenated Ti-6Al-4V alloys were carried out in order to investigate the dehydrogenation behavior of hydrogenated titanium alloys. Results indicate that mass losses of the hydrogenated Ti-6Al-4V alloys are significantly different with that of the non-hydrogenated Ti-6Al-4V alloy when the heating temperature is higher than 600 oC. Mass loss of the hydrogenated Ti-6Al-4V alloy increases with the increasing of hydrogen content when the heating temperature is in the range of 600 oC to 900 oC due to the decomposition of metastable phases. The maximum mass loss of the hydrogenated Ti-6Al-4V alloy is in correspondence with its hydrogen content upon no consideration of oxidation. The optimal dehydrogenation temperature among hydrogenated Ti-6Al-4V alloys is 750 oC. The dehydrogenation process for all hydrogenated Ti-6Al-4V alloys is the same
2014, 43(9):2108-2111.
Abstract:
The transient liquid-phase densification behavior and the mechanical performance of W-Ni-Fe alloy were investigated. This results show that the excellent mechanical properties and the quick densification of 93W-Ni-Fe alloy can be obtained via the microwave-assisted sintering approach in a 2.45 GHz microwave furnace. The tensile strength, the elongation, the relative density and the hardness (HRC) of samples are 1200 MPa, 16.6%, 98.6% and 42.0, respectively after the compacts are sintered at 1500 oC for only 5 min. The compacts can be successfully sintered in a microwave furnace with above 80% reduction in the overall processing time. Transient liquid-phase sintering by microwave-assisted heating is beneficial to saving of a lot of sintering time and accelerating of densification process, which results in W grains refinement, homogeneous microstructure and high comprehensive performances of W-Ni-Fe alloy
The transient liquid-phase densification behavior and the mechanical performance of W-Ni-Fe alloy were investigated. This results show that the excellent mechanical properties and the quick densification of 93W-Ni-Fe alloy can be obtained via the microwave-assisted sintering approach in a 2.45 GHz microwave furnace. The tensile strength, the elongation, the relative density and the hardness (HRC) of samples are 1200 MPa, 16.6%, 98.6% and 42.0, respectively after the compacts are sintered at 1500 oC for only 5 min. The compacts can be successfully sintered in a microwave furnace with above 80% reduction in the overall processing time. Transient liquid-phase sintering by microwave-assisted heating is beneficial to saving of a lot of sintering time and accelerating of densification process, which results in W grains refinement, homogeneous microstructure and high comprehensive performances of W-Ni-Fe alloy
2014, 43(9):2130-2135.
Abstract:
The extrusion process for large-scale thick-walled INCONEL625 pipe was investigated by DEFORM-2D simulations. The influent significances of the process parameters including initial temperature of billet (P), initial temperature of dies (M), extrusion speed (V), friction factor (F) as well as extrusion ratio (λ) and die structure geometrical parameters angle of bottom die (β), profile radius of bottom die (R1, R2) as well as bear length (L) to the extrusion load peak (ELP) and temperature peak (TP) at the die exit of the pipe were obtained through orthogonal regression analysis. The results show that the parameters of P, F, V, β and λ have more significant influences than other parameters. The regression models of ELP and TP related to the parameters of P, F, V, β and λ are created through stepwise regression, and using the developed regression models the reasonable span of these parameters are obtained as following: F=0.01~0.02, V=100~200 mm/s, P=1000~1250 oC, β=35°~50° and λ=4.5~7. Based on the above results, the extrusion limit map has been established for the extrusion process of large-scale thick-walled INCONEL625 pipe, which can be used to fast design the feasible extrusion parameters
The extrusion process for large-scale thick-walled INCONEL625 pipe was investigated by DEFORM-2D simulations. The influent significances of the process parameters including initial temperature of billet (P), initial temperature of dies (M), extrusion speed (V), friction factor (F) as well as extrusion ratio (λ) and die structure geometrical parameters angle of bottom die (β), profile radius of bottom die (R1, R2) as well as bear length (L) to the extrusion load peak (ELP) and temperature peak (TP) at the die exit of the pipe were obtained through orthogonal regression analysis. The results show that the parameters of P, F, V, β and λ have more significant influences than other parameters. The regression models of ELP and TP related to the parameters of P, F, V, β and λ are created through stepwise regression, and using the developed regression models the reasonable span of these parameters are obtained as following: F=0.01~0.02, V=100~200 mm/s, P=1000~1250 oC, β=35°~50° and λ=4.5~7. Based on the above results, the extrusion limit map has been established for the extrusion process of large-scale thick-walled INCONEL625 pipe, which can be used to fast design the feasible extrusion parameters
2014, 43(9):2136-2140.
Abstract:
Cu-Ag alloys were prepared by an integrated technique of continuous casting and equal channel angular pressing (ECAP). Their mechanical properties and tensile fracture morphology were studied. Results show that the strength of Cu-Ag alloys increases with the increase of ECAP passes and Ag content, but their elongation decreases. Static toughness of ECAPed alloys by continuous casting is improved compared with that of ECAPed alloys by traditional casting before necking. Meanwhile, it is found that the alloys only by continuous casting exhibits necking before failure, while the alloys subjected to ECAP fail in shear mode with different shear fracture angles as the number of ECAP passes increases. Based on the experimental results, the tensile failure mechanisms of the ECAPed Cu-Ag alloys by continuous casting were discussed
Cu-Ag alloys were prepared by an integrated technique of continuous casting and equal channel angular pressing (ECAP). Their mechanical properties and tensile fracture morphology were studied. Results show that the strength of Cu-Ag alloys increases with the increase of ECAP passes and Ag content, but their elongation decreases. Static toughness of ECAPed alloys by continuous casting is improved compared with that of ECAPed alloys by traditional casting before necking. Meanwhile, it is found that the alloys only by continuous casting exhibits necking before failure, while the alloys subjected to ECAP fail in shear mode with different shear fracture angles as the number of ECAP passes increases. Based on the experimental results, the tensile failure mechanisms of the ECAPed Cu-Ag alloys by continuous casting were discussed
2014, 43(9):2157-2161.
Abstract:
The hot deformation behavior of Ti600 alloy at deformation temperatures ranging from 25 to 800 oC and strain rates of 10-4 and 10-3 s-1 was studied by isothermal compression on a WDW-300 electronic universal testing machine. GW-1200A controller and high-temperature furnace were used to provide an accurate temperature control and measurement during testing. The true stress-true strain curves of Ti600 alloy were obtained. The results show that the flow stress of Ti600 alloy does not change obviously with the increasing of strain rate at lower temperatures (25 and 300 oC), while it increases with the increasing of strain rate at higher temperatures (600 and 800 oC), and the flow stress decreases with the increasing of temperature at the same strain rate. Based on the experimental results of true stress-true strain curves of Ti600 alloy at different temperatures, a modified Inoue Katsuro constitutive model was established to explore the flow stress of Ti600 alloy at elevated temperatures. A good agreement between the model predictions and the experimental results is derived, which verifies the reliability of the model. The fracture mode of Ti600 alloy at room temperature after the quasi-static compression was analyzed using scanning electron microscopy (SEM) and results show that the alloy is mainly of brittle fracture with some ductile fracture in the local region of the fracture surface
The hot deformation behavior of Ti600 alloy at deformation temperatures ranging from 25 to 800 oC and strain rates of 10-4 and 10-3 s-1 was studied by isothermal compression on a WDW-300 electronic universal testing machine. GW-1200A controller and high-temperature furnace were used to provide an accurate temperature control and measurement during testing. The true stress-true strain curves of Ti600 alloy were obtained. The results show that the flow stress of Ti600 alloy does not change obviously with the increasing of strain rate at lower temperatures (25 and 300 oC), while it increases with the increasing of strain rate at higher temperatures (600 and 800 oC), and the flow stress decreases with the increasing of temperature at the same strain rate. Based on the experimental results of true stress-true strain curves of Ti600 alloy at different temperatures, a modified Inoue Katsuro constitutive model was established to explore the flow stress of Ti600 alloy at elevated temperatures. A good agreement between the model predictions and the experimental results is derived, which verifies the reliability of the model. The fracture mode of Ti600 alloy at room temperature after the quasi-static compression was analyzed using scanning electron microscopy (SEM) and results show that the alloy is mainly of brittle fracture with some ductile fracture in the local region of the fracture surface
2014, 43(9):2172-2176.
Abstract:
Hot deformation behavior and microstructure evolution of a new high strength Al-Zn-Mg-Cu alloy were studied in a temperatures range of 300~450 oC, a strain rates range of 0.001~10 s-1, and a reductions range of 30%~80% by high-temperature compression tests. Characteristics of stress-strain curves were investigated. Kinetics analyses indicate that the stress exponent and hot deformation activation energy are 4.97 and 150.07 kJ/mol, respectively, suggesting that deformation would be controlled by diffusion mainly. Microstructure observation by OM shows that precipitates in the deformed grain dissolve into the matrix and microstructure in the deformed grain become homogeneous gradually at higher temperatures or lower strain rates, while the prior coarse grains elongate along the deformation direction, and coarse un-dissolved phases at grain boundaries become smaller and more dispersive at the same time. The results of TEM and EBSD show that microstructure evolution during hot deformation of the alloy is characterized by generation and formation of sub-grains, and mechanisms of microstructure evolution during hot deformation is dynamic recovery and geometric dynamic recrystallization at large reductions.
Hot deformation behavior and microstructure evolution of a new high strength Al-Zn-Mg-Cu alloy were studied in a temperatures range of 300~450 oC, a strain rates range of 0.001~10 s-1, and a reductions range of 30%~80% by high-temperature compression tests. Characteristics of stress-strain curves were investigated. Kinetics analyses indicate that the stress exponent and hot deformation activation energy are 4.97 and 150.07 kJ/mol, respectively, suggesting that deformation would be controlled by diffusion mainly. Microstructure observation by OM shows that precipitates in the deformed grain dissolve into the matrix and microstructure in the deformed grain become homogeneous gradually at higher temperatures or lower strain rates, while the prior coarse grains elongate along the deformation direction, and coarse un-dissolved phases at grain boundaries become smaller and more dispersive at the same time. The results of TEM and EBSD show that microstructure evolution during hot deformation of the alloy is characterized by generation and formation of sub-grains, and mechanisms of microstructure evolution during hot deformation is dynamic recovery and geometric dynamic recrystallization at large reductions.
2014, 43(9):2177-2181.
Abstract:
Ni-diamond composite coatings were prepared by co-electrodeposition. The effect of the particle content in suspension on the mass fraction of codeposited diamond was investigated. Codeposition process of Ni-diamond system was discussed according to two-step adsorption, particles transmission and interfacial force. The results show that the diamond contents in coatings increase firstly and then decrease slowly with the increasing of particles contents in baths. Co-deposition mechanism for Ni-diamond does not match well with N. Guglielmi’s two-step adsorption model and Yeh’s particles transmission model. Further analysis indicates that the codeposition process of Ni-diamond system could be divided into two periods. During the first period, particles in the baths are transferred to cathode surface by stirring. At the second period, particles are buried in matrix metal by the action of interfacial force with the help of high field intensity of electric double layer.
Ni-diamond composite coatings were prepared by co-electrodeposition. The effect of the particle content in suspension on the mass fraction of codeposited diamond was investigated. Codeposition process of Ni-diamond system was discussed according to two-step adsorption, particles transmission and interfacial force. The results show that the diamond contents in coatings increase firstly and then decrease slowly with the increasing of particles contents in baths. Co-deposition mechanism for Ni-diamond does not match well with N. Guglielmi’s two-step adsorption model and Yeh’s particles transmission model. Further analysis indicates that the codeposition process of Ni-diamond system could be divided into two periods. During the first period, particles in the baths are transferred to cathode surface by stirring. At the second period, particles are buried in matrix metal by the action of interfacial force with the help of high field intensity of electric double layer.
2014, 43(9):2182-2186.
Abstract:
A NiCuFeBSi alloy layer was fabricated by laser cladding on HT250 substrate through a Nd:YAG laser. And each carbon structure in the cladding layer, semi-melt zone and heat affected zone (HAZ) was investigated. Results show that carbon distributes in the cladding layers in the form of graphite, CO and C atom solid soluted in [Ni,Cu]. However, carbon distributing in the semi-melt zone are in the form of Fe3C and micro graphite pebble. And in the HAZ, carbon diffuses around graphite and solid solutes in the acicular martensite due to the extremely high cooling rate of molten pool. Moreover, with increasing of the distance to the bonding interface, the content of martensite decreases gradually. Graphite in the substrate fuses less and keeps to be flake
A NiCuFeBSi alloy layer was fabricated by laser cladding on HT250 substrate through a Nd:YAG laser. And each carbon structure in the cladding layer, semi-melt zone and heat affected zone (HAZ) was investigated. Results show that carbon distributes in the cladding layers in the form of graphite, CO and C atom solid soluted in [Ni,Cu]. However, carbon distributing in the semi-melt zone are in the form of Fe3C and micro graphite pebble. And in the HAZ, carbon diffuses around graphite and solid solutes in the acicular martensite due to the extremely high cooling rate of molten pool. Moreover, with increasing of the distance to the bonding interface, the content of martensite decreases gradually. Graphite in the substrate fuses less and keeps to be flake
2014, 43(9):2192-2196.
Abstract:
The uncompleted pole figures of W80Cu20 and W80Cu20 alloy sheets after multi-pass hot-rolling were measured by XRD texture instrument at angles from 0° to 90°. And their texture evolution law was analyzed by the orientation distribution functions (ODF). The results indicate that W80Cu20 alloy before rolling has no texture, because its orientation density value is closely to 1 with poor and non-obvious texture. But hot-rolled W80Cu20 alloy sheets have obvious rolling texture and preferred orientation with greater orientation density. As well, the sheets have their stable texture components: Brass type texture {110}<112>, Copper type texture{211}<111> and rotating cubic texture {200}<011>
The uncompleted pole figures of W80Cu20 and W80Cu20 alloy sheets after multi-pass hot-rolling were measured by XRD texture instrument at angles from 0° to 90°. And their texture evolution law was analyzed by the orientation distribution functions (ODF). The results indicate that W80Cu20 alloy before rolling has no texture, because its orientation density value is closely to 1 with poor and non-obvious texture. But hot-rolled W80Cu20 alloy sheets have obvious rolling texture and preferred orientation with greater orientation density. As well, the sheets have their stable texture components: Brass type texture {110}<112>, Copper type texture{211}<111> and rotating cubic texture {200}<011>
2014, 43(9):2203-2208.
Abstract:
The influences of substrate temperature and sputtering pressure on microstructure and optical properties of ZnO thin film buffer layer deposited by magnetron sputtering were investigated. The results show that the substrate temperature and the sputtering pressure have a great effect on the surface morphology, average grain size, forbidden band width and optical transmittance of ZnO buffer layer. Through the comprehensive analysis, it is concluded that the optimal ZnO buffer layer film can be deposited at substrate temperature of 250 oC and sputtering pressure of 0.6 Pa. Under this technical condition, ZnO buffer layer film presents well (002) preferred orientation in c axis, compact and uniform structure with the forbidden band width of 3.24 eV and average visible light transmittance of 86.93%, satisfying the requirement of the buffer layer of CIGS solar cell
The influences of substrate temperature and sputtering pressure on microstructure and optical properties of ZnO thin film buffer layer deposited by magnetron sputtering were investigated. The results show that the substrate temperature and the sputtering pressure have a great effect on the surface morphology, average grain size, forbidden band width and optical transmittance of ZnO buffer layer. Through the comprehensive analysis, it is concluded that the optimal ZnO buffer layer film can be deposited at substrate temperature of 250 oC and sputtering pressure of 0.6 Pa. Under this technical condition, ZnO buffer layer film presents well (002) preferred orientation in c axis, compact and uniform structure with the forbidden band width of 3.24 eV and average visible light transmittance of 86.93%, satisfying the requirement of the buffer layer of CIGS solar cell
2014, 43(9):2209-2214.
Abstract:
采用化学共还原法制备了聚乙烯吡咯烷酮（PVP）稳定的Pt/Co双金属纳米溶胶，利用UV-Vis、TEM等对所合成的Pt/Co双金属纳米溶胶进行了表征，并系统研究了PVP用量，还原剂用量，双金属比例对该溶胶型纳米双金属催化剂活性的影响。结果表明：所制备的Pt/Co双金属纳米溶胶的平均粒径在2~3 nm之间，大部分双金属纳米溶胶催化剂催化NaBH4制氢的活性都优于单金属Pt和Co纳米溶胶，Pt10Co90双金属纳米溶胶的催化活性最高，其催化NaBH4制取氢气的活性可以达到8800 mol-H2·mol-催化剂-1·h-1，该双金属纳米溶胶催化NaBH4水解反应的活化能为61.8 kJ/mol。所制备的Pt/Co双金属纳米溶胶催化剂具有很好的稳定性，即使在4次催化试验后该催化剂仍然保持着较高的催化活性
采用化学共还原法制备了聚乙烯吡咯烷酮（PVP）稳定的Pt/Co双金属纳米溶胶，利用UV-Vis、TEM等对所合成的Pt/Co双金属纳米溶胶进行了表征，并系统研究了PVP用量，还原剂用量，双金属比例对该溶胶型纳米双金属催化剂活性的影响。结果表明：所制备的Pt/Co双金属纳米溶胶的平均粒径在2~3 nm之间，大部分双金属纳米溶胶催化剂催化NaBH4制氢的活性都优于单金属Pt和Co纳米溶胶，Pt10Co90双金属纳米溶胶的催化活性最高，其催化NaBH4制取氢气的活性可以达到8800 mol-H2·mol-催化剂-1·h-1，该双金属纳米溶胶催化NaBH4水解反应的活化能为61.8 kJ/mol。所制备的Pt/Co双金属纳米溶胶催化剂具有很好的稳定性，即使在4次催化试验后该催化剂仍然保持着较高的催化活性
2014, 43(9):2227-2231.
Abstract:
ZrAl alloys with three different Al contents (6.0, 7.0, 8.0, wt%) were melted by the non-consumable electric-arc furnace. Zr3Al-based alloys with different phase compositions were obtained by peritectoid reaction during the annealing process. Microstructures and phase compositions of alloys was studied by optical microscope and XRD, and then its microhardnesses and tensile properties were tested. The results show that the microhardness of as-cast ZrAl alloys increases with the increase of Al content. Homogeneous microstructure of Zr3Al-based alloys can be obtained by annealing. Its microhardness and tensile strength are relative to matrix grain size and phase composition, but independent of the form and distribution of the second phases. Microhardness and tensile strength of the annealed alloy increase with the increase of Zr3Al content, while the elongation decreases. In addition, microhardness, tensile strength and elongation of the annealed alloys increase with Zr3Al grain refinement
ZrAl alloys with three different Al contents (6.0, 7.0, 8.0, wt%) were melted by the non-consumable electric-arc furnace. Zr3Al-based alloys with different phase compositions were obtained by peritectoid reaction during the annealing process. Microstructures and phase compositions of alloys was studied by optical microscope and XRD, and then its microhardnesses and tensile properties were tested. The results show that the microhardness of as-cast ZrAl alloys increases with the increase of Al content. Homogeneous microstructure of Zr3Al-based alloys can be obtained by annealing. Its microhardness and tensile strength are relative to matrix grain size and phase composition, but independent of the form and distribution of the second phases. Microhardness and tensile strength of the annealed alloy increase with the increase of Zr3Al content, while the elongation decreases. In addition, microhardness, tensile strength and elongation of the annealed alloys increase with Zr3Al grain refinement
2014, 43(9):2232-2236.
Abstract:
The heating treatment technical parameters and the microstructure of diffusion layer was investigated after cold-rolling bonding for the Cu/Al composite strips by a tensile testing machine, metalloscope, XRD, EMPA, etc. Results show that with the increasing of the annealing temperature or prolonging of the holding time, the Cu/Al composite strips have a lower strength and higher plasticity, and the interface width of composite strips is from 1.5 μm to 6.5 μm. In a conclusion, 410 oC/10 min is the best heating treatment parameter. There are five intermediate phases, Cu9Al4, Cu4Al3, Cu3Al2, CuAl, and CuAl2. The size of these intermediate phases is relatively small and at the quality grade of 10-4~10-8mm2. The morphology of Cu9Al4, Cu4Al3 and Cu3Al2 is polygonal lump. Also there are a lot of parallel laths in the Cu9Al4. The form of CuAl2 phase is similar to ovoid and that of CuAl phase is dispersive grain
The heating treatment technical parameters and the microstructure of diffusion layer was investigated after cold-rolling bonding for the Cu/Al composite strips by a tensile testing machine, metalloscope, XRD, EMPA, etc. Results show that with the increasing of the annealing temperature or prolonging of the holding time, the Cu/Al composite strips have a lower strength and higher plasticity, and the interface width of composite strips is from 1.5 μm to 6.5 μm. In a conclusion, 410 oC/10 min is the best heating treatment parameter. There are five intermediate phases, Cu9Al4, Cu4Al3, Cu3Al2, CuAl, and CuAl2. The size of these intermediate phases is relatively small and at the quality grade of 10-4~10-8mm2. The morphology of Cu9Al4, Cu4Al3 and Cu3Al2 is polygonal lump. Also there are a lot of parallel laths in the Cu9Al4. The form of CuAl2 phase is similar to ovoid and that of CuAl phase is dispersive grain
2014, 43(9):2237-2241.
Abstract:
Zr4+ doped Li4Ti5O12 was synthesized from Li2CO3, ZrO2 and tetrabutyl titanate by a modified solid-state method. The effects of the in-situ coating, high energy ball-milling and Zr-doping on crystalline structure, particle size, morphology and electrochemical performance of Li4Ti5O12 were investigated. The samples were tested by XRD, SEM and electrochemical workstation. The results show that the in-situ coating and ball-milling can decrease the particle size and prevent the aggregation of nanoparticles. Zr-doping obviously improves the rate capability of Li4Ti5O12 via the generation of less electrode polarization and higher Li+ diffusion coefficient. Li4Ti4.95Zr0.05O12 exhibits an excellent rate capability and cycling stability. At the charge-discharge rate of 0.5 and 40C, its discharge capacities are 176 and 52 mAh·g-1, respectively. After 10 cycles, there is less than 0.5% reduction in reversible capacity at 1, 2, 5, 10, 20 and 40 C. Compared to Ce-doping, it also shows better crystallization and electrochemical performance due to its smaller ionic radius.
Zr4+ doped Li4Ti5O12 was synthesized from Li2CO3, ZrO2 and tetrabutyl titanate by a modified solid-state method. The effects of the in-situ coating, high energy ball-milling and Zr-doping on crystalline structure, particle size, morphology and electrochemical performance of Li4Ti5O12 were investigated. The samples were tested by XRD, SEM and electrochemical workstation. The results show that the in-situ coating and ball-milling can decrease the particle size and prevent the aggregation of nanoparticles. Zr-doping obviously improves the rate capability of Li4Ti5O12 via the generation of less electrode polarization and higher Li+ diffusion coefficient. Li4Ti4.95Zr0.05O12 exhibits an excellent rate capability and cycling stability. At the charge-discharge rate of 0.5 and 40C, its discharge capacities are 176 and 52 mAh·g-1, respectively. After 10 cycles, there is less than 0.5% reduction in reversible capacity at 1, 2, 5, 10, 20 and 40 C. Compared to Ce-doping, it also shows better crystallization and electrochemical performance due to its smaller ionic radius.
2014, 43(9):2242-2246.
Abstract:
Titanium nitride (Ti-N) thin films were deposited by unbalanced magnetron sputtering under conditions of various N2 flow rates at room temperature. The morphologies and optical properties of the films were studied. Four layers of solar selective absorbing coatings based on Ti-N were designed and then optimized by optical design software of SCOUT. Results show that various characteristics such as bubble precipitates, bubble bursting, and amorphous morphologies are observed in the films with the increasing of N2 flow rate. The UV-Visible-NIF spectra show that the optical properties of the films can be improved using appropriate sputtering parameters and software optimization. Absorptance of the optimized films is enhanced from 0.8209 to 0.9048 after optimization, which are suitable as solar selective absorbing coatings
Titanium nitride (Ti-N) thin films were deposited by unbalanced magnetron sputtering under conditions of various N2 flow rates at room temperature. The morphologies and optical properties of the films were studied. Four layers of solar selective absorbing coatings based on Ti-N were designed and then optimized by optical design software of SCOUT. Results show that various characteristics such as bubble precipitates, bubble bursting, and amorphous morphologies are observed in the films with the increasing of N2 flow rate. The UV-Visible-NIF spectra show that the optical properties of the films can be improved using appropriate sputtering parameters and software optimization. Absorptance of the optimized films is enhanced from 0.8209 to 0.9048 after optimization, which are suitable as solar selective absorbing coatings
2014, 43(9):2247-2251.
Abstract:
The effects of stibium element on microscopic structure and mechanical properties of Mg-5Sn-2Al-1.5Zn-0.8Si magnesium alloy were studied when Sb was added into melt in the form of pure metal. The results indicate that Sb element and Mg matrix combine to form Mg3Sb2 phases. The addition of 0.9% Sb has a strong modification for Chinese script morphology of Mg2Si phases. Sn can replace Si of Mg2Si phase to form Mg2(Si,Sn) composite phases, whose physical properties lie between Mg2Si and Mg2Sn. With the increase of Sb content, the elongations of the as-cast alloy and the extruded gradually decrease, while tensile strengths increase firstly and then decrease. Strength and plasticity of the extruded alloy are better than that of the cast alloy, and the increase of Sb content is beneficial to improve the heat resistance of Mg-5Sn-2Al-1.5Zn-0.8Si alloy
The effects of stibium element on microscopic structure and mechanical properties of Mg-5Sn-2Al-1.5Zn-0.8Si magnesium alloy were studied when Sb was added into melt in the form of pure metal. The results indicate that Sb element and Mg matrix combine to form Mg3Sb2 phases. The addition of 0.9% Sb has a strong modification for Chinese script morphology of Mg2Si phases. Sn can replace Si of Mg2Si phase to form Mg2(Si,Sn) composite phases, whose physical properties lie between Mg2Si and Mg2Sn. With the increase of Sb content, the elongations of the as-cast alloy and the extruded gradually decrease, while tensile strengths increase firstly and then decrease. Strength and plasticity of the extruded alloy are better than that of the cast alloy, and the increase of Sb content is beneficial to improve the heat resistance of Mg-5Sn-2Al-1.5Zn-0.8Si alloy
2014, 43(9):2252-2256.
Abstract:
The texture of the extrusion tube of super-alloy IN690 was analyzed by electron backscatter diffraction (EBSD) test. The results indicate that the orientation error between twinning and maternal grains is <111>/60° for the extrusion tube of super-alloy IN690, and it results in much 60° large grain boundary after extrusion deformation. The grain boundary of IN690 is coherent twin boundary (Σ3) coincidence site lattice. Comparing the Σ3 volume and texture in different extrusion parameters, the tube of super-alloy IN690 has excellent corrosion resistance and plasticity when the extrusion temperature is 1200 oC and extrusion ratio is 5
The texture of the extrusion tube of super-alloy IN690 was analyzed by electron backscatter diffraction (EBSD) test. The results indicate that the orientation error between twinning and maternal grains is <111>/60° for the extrusion tube of super-alloy IN690, and it results in much 60° large grain boundary after extrusion deformation. The grain boundary of IN690 is coherent twin boundary (Σ3) coincidence site lattice. Comparing the Σ3 volume and texture in different extrusion parameters, the tube of super-alloy IN690 has excellent corrosion resistance and plasticity when the extrusion temperature is 1200 oC and extrusion ratio is 5
2014, 43(9):2257-2261.
Abstract:
A 2-D axisymmetric finite element model of vacuum hot bulge forming of rotor cans was established. With the aid of user subroutine of non-linear finite element software MSC.Marc, the creep constitutive model of Hastelloy C-276 was coupled with the FEM model to simulate the vacuum hot bulge forming process of the rotor can. The transient temperature field and the radius-direction displacement field of the rotor can and the die during vacuum hot bulge forming process were calculated. The bulging dimension of the rotor can was predicted. The effects of process parameters such as die thickness, holding time and holding temperature on the bulging dimension of the rotor can were studied on the basis of the developed model. The vacuum hot bulge forming experiment was conducted. The simulated results are in good agreement with the experimental ones
A 2-D axisymmetric finite element model of vacuum hot bulge forming of rotor cans was established. With the aid of user subroutine of non-linear finite element software MSC.Marc, the creep constitutive model of Hastelloy C-276 was coupled with the FEM model to simulate the vacuum hot bulge forming process of the rotor can. The transient temperature field and the radius-direction displacement field of the rotor can and the die during vacuum hot bulge forming process were calculated. The bulging dimension of the rotor can was predicted. The effects of process parameters such as die thickness, holding time and holding temperature on the bulging dimension of the rotor can were studied on the basis of the developed model. The vacuum hot bulge forming experiment was conducted. The simulated results are in good agreement with the experimental ones
2014, 43(9):2262-2266.
Abstract:
TiAl alloy workpieces were prepared using titanium powder or titanium hydride power and aluminum powder as raw material by low-temperature sintering, gel-casting, batching out and pressureless sintering. The results show that the TiAl alloy powder can be obtained by heating titanium powder and aluminum power for 2 h at 500 oC and 3 h at 600 oC, or heating titanium hydride power and aluminum powder for 3 h at 750 oC. The last sintering process is 2 h at 1450 oC and 2 h at 1400 oC for the two kinds of processing. The relative density are 91% and 96.75%, respectively
TiAl alloy workpieces were prepared using titanium powder or titanium hydride power and aluminum powder as raw material by low-temperature sintering, gel-casting, batching out and pressureless sintering. The results show that the TiAl alloy powder can be obtained by heating titanium powder and aluminum power for 2 h at 500 oC and 3 h at 600 oC, or heating titanium hydride power and aluminum powder for 3 h at 750 oC. The last sintering process is 2 h at 1450 oC and 2 h at 1400 oC for the two kinds of processing. The relative density are 91% and 96.75%, respectively
2014, 43(9):2267-2271.
Abstract:
In order to improve the resistance of titanium alloy on antifouling of halobios, a laser etching technique was used to build micro-structure with different spacing on Ti6Al4V alloy surface. Polymer-based nanocomposites were coated on the micro-structure to build the micro-nano structure for the superhydrophobic surface of Ti6Al4V alloy. The morphology was investigated by optical microscope and scanning electron microscopy. The contact angles and roll angles were measured by contact angle measurement. Sea-site exposure test was conducted to evaluate its antifouling performance. The results show that the Ti6Al4V alloy surface with a single micro structure is hydrophobic. The contact angles increase with spacing decreasing. When the spacing is 50 μm, the contact angle is as high as 131.8°. But the roll angle is large. Even if the surface is placed vertically or invert, the droplet does not roll. The Ti6Al4V alloy surface with the micro-nano structure is superhydrophobic. The contact angles increase and the roll angles decrease with the spacing decreasing. When the spacing is 50 μm, the contact angle is as high as 163.8°, while the roll angle is only 1.89°. The antifouling performance of superhydrophobic surface with micro-nano structure is significantly superior to that of polishing surface and the surface with a single micro structure
In order to improve the resistance of titanium alloy on antifouling of halobios, a laser etching technique was used to build micro-structure with different spacing on Ti6Al4V alloy surface. Polymer-based nanocomposites were coated on the micro-structure to build the micro-nano structure for the superhydrophobic surface of Ti6Al4V alloy. The morphology was investigated by optical microscope and scanning electron microscopy. The contact angles and roll angles were measured by contact angle measurement. Sea-site exposure test was conducted to evaluate its antifouling performance. The results show that the Ti6Al4V alloy surface with a single micro structure is hydrophobic. The contact angles increase with spacing decreasing. When the spacing is 50 μm, the contact angle is as high as 131.8°. But the roll angle is large. Even if the surface is placed vertically or invert, the droplet does not roll. The Ti6Al4V alloy surface with the micro-nano structure is superhydrophobic. The contact angles increase and the roll angles decrease with the spacing decreasing. When the spacing is 50 μm, the contact angle is as high as 163.8°, while the roll angle is only 1.89°. The antifouling performance of superhydrophobic surface with micro-nano structure is significantly superior to that of polishing surface and the surface with a single micro structure
2014, 43(9):2277-2280.
Abstract:
The effects of semi-solid isothermal heat treatment temperature and holding time on microstructures evolution of extruded AZ91 magnesium alloy were studied. The microstructures of hot extrusion AZ91 magnesium alloy are characterized by streamline structure and small recrystallized α-Mg equiaxed grain. In the semi-solid isothermal treatment, the phase of low melting point begins to melt firstly, then permeates along the grain boundary, and finally the semi-solid structure which is liquid phase surrounded by solid-phase particles is formed. With the increase of isothermal temperature, melt and separation of the solid phases become faster. At the isothermal temperature of 560 oC, with the extension of isothermal holding time, the liquid phases increase obviously, solid phases separate and tend spheroid constantly. After holding for 20 min, the alloy reaches the solid-liquid equilibrium state, Ostwald ripening mechanism begins to be clear, and grains coarsening become the main mechanism. The better semi-solid processing technological parameters of extruded AZ91 alloy are 560 oC and 20~30 min
The effects of semi-solid isothermal heat treatment temperature and holding time on microstructures evolution of extruded AZ91 magnesium alloy were studied. The microstructures of hot extrusion AZ91 magnesium alloy are characterized by streamline structure and small recrystallized α-Mg equiaxed grain. In the semi-solid isothermal treatment, the phase of low melting point begins to melt firstly, then permeates along the grain boundary, and finally the semi-solid structure which is liquid phase surrounded by solid-phase particles is formed. With the increase of isothermal temperature, melt and separation of the solid phases become faster. At the isothermal temperature of 560 oC, with the extension of isothermal holding time, the liquid phases increase obviously, solid phases separate and tend spheroid constantly. After holding for 20 min, the alloy reaches the solid-liquid equilibrium state, Ostwald ripening mechanism begins to be clear, and grains coarsening become the main mechanism. The better semi-solid processing technological parameters of extruded AZ91 alloy are 560 oC and 20~30 min
2014, 43(9):2281-2284.
Abstract:
The Mg12Al1.5Zn6.5Ca1Nd alloy was prepared by spray forming. The microstructure and mechanical properties of the as-extruded experimental alloy were investigated by XRD, SEM, TEM and EDS. The results show that the microstructure of the experimental alloy consists of α-Mg and Al2Ca, the microstructure is equiaxial grain, and the grain size is about 2 μm. The size of dispersive Al2Ca phase is less than 1 μm, which distributes mainly along the grain boundaries of the primary Mg. The dislocation pile-up in matrix Mg and twin structure in Al2Ca are observed by TEM. The σb, σ0.2 and δ of the alloy reach 470 MPa, 350 MPa and 4.7%, respectively. The main strengthening methods are fine grain strengthening, dispersion strengthening and solid solution strengthening. The fracture morphologies indicate the micro cracks nucleate between the impurity at the bottom of holes or the hard phase around the holes and the matrix. Holes are formed through micropores aggregation in the fracture. The fracture mechanism is microporous polymeric intergranular fracture
The Mg12Al1.5Zn6.5Ca1Nd alloy was prepared by spray forming. The microstructure and mechanical properties of the as-extruded experimental alloy were investigated by XRD, SEM, TEM and EDS. The results show that the microstructure of the experimental alloy consists of α-Mg and Al2Ca, the microstructure is equiaxial grain, and the grain size is about 2 μm. The size of dispersive Al2Ca phase is less than 1 μm, which distributes mainly along the grain boundaries of the primary Mg. The dislocation pile-up in matrix Mg and twin structure in Al2Ca are observed by TEM. The σb, σ0.2 and δ of the alloy reach 470 MPa, 350 MPa and 4.7%, respectively. The main strengthening methods are fine grain strengthening, dispersion strengthening and solid solution strengthening. The fracture morphologies indicate the micro cracks nucleate between the impurity at the bottom of holes or the hard phase around the holes and the matrix. Holes are formed through micropores aggregation in the fracture. The fracture mechanism is microporous polymeric intergranular fracture
2014, 43(9):2285-2288.
Abstract:
TiO2 nanotube arrays (TNA) were fabricated by anodization of Ti in fluoride containing electrolytes. Then Ag-TiO2 nanotube arrays (Ag-TNA) were prepared by loading silver nanoparticles into TiO2 nanotube via photochemical reduction of AgNO3 solution with different Ag contents. The as-prepared samples were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy (UV-Vis). The result shows Ag-TNA have the best efficiency of photocatalytic degradation with methyl blue (MB) as probing molecule in aqueous solution and good anti-bacterial properties.
TiO2 nanotube arrays (TNA) were fabricated by anodization of Ti in fluoride containing electrolytes. Then Ag-TiO2 nanotube arrays (Ag-TNA) were prepared by loading silver nanoparticles into TiO2 nanotube via photochemical reduction of AgNO3 solution with different Ag contents. The as-prepared samples were characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectroscopy (UV-Vis). The result shows Ag-TNA have the best efficiency of photocatalytic degradation with methyl blue (MB) as probing molecule in aqueous solution and good anti-bacterial properties.
2014, 43(9):2297-2304.
Abstract:
The high voltage cathode material, LiMnPO4, has gained a lot of attention, because of its properties of non-toxicity, high voltage, excellent cycle performance and security. But the shortages of this material limit its application, such as the bad electronic conductivity, intrinsic conductivity and rate capability. In recent years, the electrochemical performance of LiMnPO4 has been improved significantly by increasing the electronic conductivity between the particles, the intrinsic conductivity of particles and decreasing the size of particles. In this paper, we mainly introduced the structure and properties of LiMnPO4 and the methods of synthesizing and improving LiMnPO4 material, including high temperature solid-phase, sol-gel, hydrothermal method and spray drying, surface coating, doping and nano-structure synthesis. We also concluded the current situation and the problems of the research of LiMnPO4 material and gave some comments of the main research direction
The high voltage cathode material, LiMnPO4, has gained a lot of attention, because of its properties of non-toxicity, high voltage, excellent cycle performance and security. But the shortages of this material limit its application, such as the bad electronic conductivity, intrinsic conductivity and rate capability. In recent years, the electrochemical performance of LiMnPO4 has been improved significantly by increasing the electronic conductivity between the particles, the intrinsic conductivity of particles and decreasing the size of particles. In this paper, we mainly introduced the structure and properties of LiMnPO4 and the methods of synthesizing and improving LiMnPO4 material, including high temperature solid-phase, sol-gel, hydrothermal method and spray drying, surface coating, doping and nano-structure synthesis. We also concluded the current situation and the problems of the research of LiMnPO4 material and gave some comments of the main research direction
