Volume 43,Issue 3,2014 Table of Contents
2014, 43(3):530-534.
Abstract:
We presented a method to improve the first discharge capacity and the cycling performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 which was synthesized by a coprecipitation-hydrothermal-calcinations method and coated by a V2O5 layer on the surface of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The crystal structure and the charge/discharge performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and electrochemical performance measurement. Results show that V2O5 exists only on the surface, and has no effect on the crystal structure; the Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with V2O5 exhibits better first discharge capacity than the bared Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The electrochemical tests demonstrate that Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with 3 wt% V2O5 shows the best electrochemical performance with the discharge capacity 200.3 mAh/g after 50 cycles, while the bared sample has 194.0 mAh/g only. CV results indicate that the V2O5 coating can suppress the phase transitions and prevent the surface of cathode materials from the direct contact with the electrolyte
We presented a method to improve the first discharge capacity and the cycling performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 which was synthesized by a coprecipitation-hydrothermal-calcinations method and coated by a V2O5 layer on the surface of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The crystal structure and the charge/discharge performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and electrochemical performance measurement. Results show that V2O5 exists only on the surface, and has no effect on the crystal structure; the Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with V2O5 exhibits better first discharge capacity than the bared Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The electrochemical tests demonstrate that Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with 3 wt% V2O5 shows the best electrochemical performance with the discharge capacity 200.3 mAh/g after 50 cycles, while the bared sample has 194.0 mAh/g only. CV results indicate that the V2O5 coating can suppress the phase transitions and prevent the surface of cathode materials from the direct contact with the electrolyte
2014, 43(3):540-543.
Abstract:
Three point bending (3PB) fracture tests and unload tests of lamellar TiAl alloys containing B2 phase were carried out to investigate the toughening mechanisms of the TiAl alloy. Double notched 4PB tests were used to evaluate the critical event of cleavage fracture of this alloy. To observe the morphology of fracture surface and crack path, scanning electron microscope (SEM) and energy spectrum analyses were also carried out. The results reveal the following aspects: (1) The load-displacement curve of 3PB fracture tests presents linear elastic relationship, and B2 phase has no effect on the crack initiation. (2) B2 phase is an obstacle to the crack propagation. The crack is arrested by B2 phase at low applied load and bypasses the B2 phase by skipping over B2 phase or crosses B2 phase at high applied load. (3) The critical event of the cleavage fracture of a notched specimen is a propagation of the nucleated interlamellar crack at the notch root. And trans-lamellar propagation is the key factor affecting the whole process of cleavage fracture. (4) The toughening mechanisms of the current alloy include B2 phase toughening, crack deflection, shear ligament toughening and trans-lamellar toughening
Three point bending (3PB) fracture tests and unload tests of lamellar TiAl alloys containing B2 phase were carried out to investigate the toughening mechanisms of the TiAl alloy. Double notched 4PB tests were used to evaluate the critical event of cleavage fracture of this alloy. To observe the morphology of fracture surface and crack path, scanning electron microscope (SEM) and energy spectrum analyses were also carried out. The results reveal the following aspects: (1) The load-displacement curve of 3PB fracture tests presents linear elastic relationship, and B2 phase has no effect on the crack initiation. (2) B2 phase is an obstacle to the crack propagation. The crack is arrested by B2 phase at low applied load and bypasses the B2 phase by skipping over B2 phase or crosses B2 phase at high applied load. (3) The critical event of the cleavage fracture of a notched specimen is a propagation of the nucleated interlamellar crack at the notch root. And trans-lamellar propagation is the key factor affecting the whole process of cleavage fracture. (4) The toughening mechanisms of the current alloy include B2 phase toughening, crack deflection, shear ligament toughening and trans-lamellar toughening
2014, 43(3):544-547.
Abstract:
This study mainly analyzed the effect of CeO2 on the hydrogen release capacity of LiAlH4 by PCT (Pressure-Composition-Temperature) device and SEM (Scanning Electron Microscope) analysis method. The results show that with CeO2 doping shortens markedly the time of hydrogen release of LiAlH4. Among all samples, the dehydrogenation time of the sample doped with 2 mol% CeO2 is the earliest. The study on the amount of hydrogen release finds that the sample doped with 1 mol% CeO2 presents the largest dehydrogenation amount. And with the increase of the doping amount from 1 mol% to 5 mol%, the total hydrogen release amount of the samples presents a decrease trend. Furthermore, the study on microstructures show that doping with CeO2 does not cause any obvious change of the microstructure of LiAlH4, and all samples show a kind of flocculent structure
This study mainly analyzed the effect of CeO2 on the hydrogen release capacity of LiAlH4 by PCT (Pressure-Composition-Temperature) device and SEM (Scanning Electron Microscope) analysis method. The results show that with CeO2 doping shortens markedly the time of hydrogen release of LiAlH4. Among all samples, the dehydrogenation time of the sample doped with 2 mol% CeO2 is the earliest. The study on the amount of hydrogen release finds that the sample doped with 1 mol% CeO2 presents the largest dehydrogenation amount. And with the increase of the doping amount from 1 mol% to 5 mol%, the total hydrogen release amount of the samples presents a decrease trend. Furthermore, the study on microstructures show that doping with CeO2 does not cause any obvious change of the microstructure of LiAlH4, and all samples show a kind of flocculent structure
2014, 43(3):548-552.
Abstract:
The relationship among the microstructure, the defects and the performance of the Ti60 alloy samples fabricated by the process of laser solid forming (LSF) was studied, The results indicate that for Ti60 alloy the laser power input has a remarkable effect on the microstructure of LSF samples. Concretely a large power input forms a Widmanstatten microstructure, while a small power input causes a basket weave microstructure. The stress rupture property of the Widmanstatten structure is significantly lower than that of the basketweave structure, the former shows obvious intergranular fracture, while the later shows dimple rupture. At the same time the stress rupture properties are affected by metallurgy defects such as porosities. When the gas atomized powder (powder B) is used as cladding materials, the porosities will be formed within the microstructure of LSF Ti60. When the plasma rotation electrode preparation powder (powder A) is used, there is no such defects observed. The high temperature endurance test results show that the rupture life will significantly decrease from more than 100 h (samples deposited with powder A) to less than 25 h (samples deposited with powder B)
The relationship among the microstructure, the defects and the performance of the Ti60 alloy samples fabricated by the process of laser solid forming (LSF) was studied, The results indicate that for Ti60 alloy the laser power input has a remarkable effect on the microstructure of LSF samples. Concretely a large power input forms a Widmanstatten microstructure, while a small power input causes a basket weave microstructure. The stress rupture property of the Widmanstatten structure is significantly lower than that of the basketweave structure, the former shows obvious intergranular fracture, while the later shows dimple rupture. At the same time the stress rupture properties are affected by metallurgy defects such as porosities. When the gas atomized powder (powder B) is used as cladding materials, the porosities will be formed within the microstructure of LSF Ti60. When the plasma rotation electrode preparation powder (powder A) is used, there is no such defects observed. The high temperature endurance test results show that the rupture life will significantly decrease from more than 100 h (samples deposited with powder A) to less than 25 h (samples deposited with powder B)
2014, 43(3):559-562.
Abstract:
Plasma surface copper and nickel alloying was applied to Ti6Al4V alloy. The effects of treatment temperatures on the microstructures were investigated by scanning electron microscope (SEM). The chemical composition and phase constituents of the alloyed layer were analyzed using glow discharge spectrum (GDS) and X-ray diffraction (XRD). The results show that the alloyed layer prepared at 850 oC with about 7 μm in thickness is bonded strongly to the Ti6Al4V substrate and consists of unbound Ti, Ti2Ni, TiNi, Cu0.81Ni0.19 and CuTi. The results indicate that the treated samples exhibit excellent antibacterial properties within 12 h. The wear resistance of titanium alloy is also improved.
Plasma surface copper and nickel alloying was applied to Ti6Al4V alloy. The effects of treatment temperatures on the microstructures were investigated by scanning electron microscope (SEM). The chemical composition and phase constituents of the alloyed layer were analyzed using glow discharge spectrum (GDS) and X-ray diffraction (XRD). The results show that the alloyed layer prepared at 850 oC with about 7 μm in thickness is bonded strongly to the Ti6Al4V substrate and consists of unbound Ti, Ti2Ni, TiNi, Cu0.81Ni0.19 and CuTi. The results indicate that the treated samples exhibit excellent antibacterial properties within 12 h. The wear resistance of titanium alloy is also improved.
6 Ammonia-Alkali Solution Coordination-Precipitation Route for Preparation of β-Ni(OH)2 Nano-Particles
2014, 43(3):563-566.
Abstract:
Nano-sized nickel hydroxide particles were synthesized at room temperature by a facile coordination precipitation method, through simply dropping sodium hydroxide solution to dissociate the complex of nickel-hexammonia, using nickel chloride, ammonia and sodium hydroxide as raw materials. Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetry and derivative thermo-gravimetry (TG-DTG), X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to characterize the products. It is demonstrated that the product is pure β-type nickel hydroxide, which contains more nickel and fewer intercalated anions comparatively, and likely boosts its electrochemical activity. The average size of β-type nickel hydroxide nano-particles is about 100 nm
Nano-sized nickel hydroxide particles were synthesized at room temperature by a facile coordination precipitation method, through simply dropping sodium hydroxide solution to dissociate the complex of nickel-hexammonia, using nickel chloride, ammonia and sodium hydroxide as raw materials. Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetry and derivative thermo-gravimetry (TG-DTG), X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to characterize the products. It is demonstrated that the product is pure β-type nickel hydroxide, which contains more nickel and fewer intercalated anions comparatively, and likely boosts its electrochemical activity. The average size of β-type nickel hydroxide nano-particles is about 100 nm
2014, 43(3):567-569.
Abstract:
Based on the particle morphology of beryllium (Be) powders produced by impact attrition, a physics model has been established for describing the particle size distribution, which has only one parameter with the definite physical meaning. Two important internal mechanisms are considered: firstly, the distribution of existing state of particles with different original kinetic energy should obey the Maxwell-Boltzmann distribution after impacting, which means that big particles are unstable for their being at higher energy level, therefore they are easy to be fractured into smaller pieces in impact attrition process, and this influencing factor can be described as the negative exponential function of particles size; secondly, the tendency to remain low surface energy requires that Be powders should keep big volume as much as possible, and this influencing factor is defined as the cube function of particles size. The actual size distribution of Be particles is resulted from the competition between these two factors. Calculating result from the model is in good agreement with data from measurement
Based on the particle morphology of beryllium (Be) powders produced by impact attrition, a physics model has been established for describing the particle size distribution, which has only one parameter with the definite physical meaning. Two important internal mechanisms are considered: firstly, the distribution of existing state of particles with different original kinetic energy should obey the Maxwell-Boltzmann distribution after impacting, which means that big particles are unstable for their being at higher energy level, therefore they are easy to be fractured into smaller pieces in impact attrition process, and this influencing factor can be described as the negative exponential function of particles size; secondly, the tendency to remain low surface energy requires that Be powders should keep big volume as much as possible, and this influencing factor is defined as the cube function of particles size. The actual size distribution of Be particles is resulted from the competition between these two factors. Calculating result from the model is in good agreement with data from measurement
2014, 43(3):570-574.
Abstract:
The microstructures and the mechanical properties of the Mg-2Y-xZn (x = 1, 2, 3 at%) alloys in as-cast, as-annealed and as-extruded conditions have been investigated. The results show that the 18R-LPSO phases are distributed in a continuous network mainly along the grain boundaries in the alloy with 1 at% Zn. With increasing of Zn content, the 18R-LPSO phase and W-phase coexist in Mg-2Y-2Zn alloy but only W-phase remains in Mg-2Y-3Zn alloy. The 14H-lamellas are precipitated from the block-shaped 18R-LPSO phases into the matrix, and W-phases are broken into particles during homogenizing annealing. After extrusion, the LPSO phases and W-particles are rearranged along the direction of extrusion. The tensile tests show that the as-extruded Mg-2Y-1Zn alloy exhibits the supreme UTS of 320 MPa, with an elongation of 11.2% at room temperature
The microstructures and the mechanical properties of the Mg-2Y-xZn (x = 1, 2, 3 at%) alloys in as-cast, as-annealed and as-extruded conditions have been investigated. The results show that the 18R-LPSO phases are distributed in a continuous network mainly along the grain boundaries in the alloy with 1 at% Zn. With increasing of Zn content, the 18R-LPSO phase and W-phase coexist in Mg-2Y-2Zn alloy but only W-phase remains in Mg-2Y-3Zn alloy. The 14H-lamellas are precipitated from the block-shaped 18R-LPSO phases into the matrix, and W-phases are broken into particles during homogenizing annealing. After extrusion, the LPSO phases and W-particles are rearranged along the direction of extrusion. The tensile tests show that the as-extruded Mg-2Y-1Zn alloy exhibits the supreme UTS of 320 MPa, with an elongation of 11.2% at room temperature
2014, 43(3):575-578.
Abstract:
The effect of catalyst systems Co2B/rare earth oxides on the properties of hydrogen generation of NaBH4 was studied. The results show that doping with Co2B/CeO2 and Co2B/Sm2O3 increases the amount of hydrogen generation of NaBH4 obviously. Among all samples, the sample doped with Co2B/CeO2 with ratio of 1:1 has the largest amount of hydrogen release reaching about 274 mL. However, the investigation on the rate of hydrogen release indicates that doping with Co2B/rare earth oxides decreases the rate of hydrogen release obviously. Furthermore, the analysis on the microstructures of the reaction products of the samples doped with Co2B/rare earth oxides shows that, doping with Co2B/rare earth oxides makes the microstructures of the reaction products looser compared with doping with Co2B. Significantly, the investigation on doping with Co2B/CeO2 shows that the porous structure is helpful for improving the amount of hydrogen generation. However, the investigation on the samples doped with Co2B/La2O3 and Co2B/ Sm2O3 indicates that there is no direct relationship between the amount of hydrogen generation and the porous structure
The effect of catalyst systems Co2B/rare earth oxides on the properties of hydrogen generation of NaBH4 was studied. The results show that doping with Co2B/CeO2 and Co2B/Sm2O3 increases the amount of hydrogen generation of NaBH4 obviously. Among all samples, the sample doped with Co2B/CeO2 with ratio of 1:1 has the largest amount of hydrogen release reaching about 274 mL. However, the investigation on the rate of hydrogen release indicates that doping with Co2B/rare earth oxides decreases the rate of hydrogen release obviously. Furthermore, the analysis on the microstructures of the reaction products of the samples doped with Co2B/rare earth oxides shows that, doping with Co2B/rare earth oxides makes the microstructures of the reaction products looser compared with doping with Co2B. Significantly, the investigation on doping with Co2B/CeO2 shows that the porous structure is helpful for improving the amount of hydrogen generation. However, the investigation on the samples doped with Co2B/La2O3 and Co2B/ Sm2O3 indicates that there is no direct relationship between the amount of hydrogen generation and the porous structure
2014, 43(3):595-600.
Abstract:
The stability, electronic structure, elasticity, and heat capacity of titanium borides were calculated by first-principles density functional theory. The results show that TiB with the space group of and are unstable, and the most stable stucture belongs to TiB2. All of the borides show a mixed character of metallic, covalent and ionic bonds, Ti2B shows high metallic property, while TiB2 has high level of covalent bonding. The values of bulk moduli, shear moduli and Young’s moduli are 251.4, 260.1 and 564.6 GPa, respectively, which are obviously higher than that of other borides. The calculated B/G values clearly imply that TiB2 is more brittle than other borides. The brittle nature of TiB2 (B/G=0.97) constrains its application as potential cutting tools or wear resistant parts. Thus TiB2-based composites should be designed in order to improve the ductile property. Finally, the anisotropy index and heat capacity of the titanium borides were also predicted
The stability, electronic structure, elasticity, and heat capacity of titanium borides were calculated by first-principles density functional theory. The results show that TiB with the space group of and are unstable, and the most stable stucture belongs to TiB2. All of the borides show a mixed character of metallic, covalent and ionic bonds, Ti2B shows high metallic property, while TiB2 has high level of covalent bonding. The values of bulk moduli, shear moduli and Young’s moduli are 251.4, 260.1 and 564.6 GPa, respectively, which are obviously higher than that of other borides. The calculated B/G values clearly imply that TiB2 is more brittle than other borides. The brittle nature of TiB2 (B/G=0.97) constrains its application as potential cutting tools or wear resistant parts. Thus TiB2-based composites should be designed in order to improve the ductile property. Finally, the anisotropy index and heat capacity of the titanium borides were also predicted
2014, 43(3):621-626.
Abstract:
Using the unbalanced magnetron sputter ion plating technique graphite-like coatings with Al, Zr and W as transition layers on the surface of magnesium substrate were prepared. The section microstructure and phase composition of the coatings were analyzed by TEM and the binding force and tribological performance were tested by a scratch tester and a wear machine. The results show that a mixing layer with magnesium and β-Mg17Al12 phase is formed in the interface between Al transition layer and magnesium substrate; there is a partial continuous interface between Zr transition layer and magnesium substrate; the interface between W transition layer and magnesium substrate is a mixed interface layer with magnesium phase and tungsten clusters of about 20nm because of the implantation of tungsten particles into magnesium substrate. The binding force of the three kinds of doped (aluminum, zirconium, tungsten) carbon coatings on the surface of magnesium substrate is 10.2, 11.0 and 4.8 N, respectively. The different work layers of three kinds of doped carbon coatings result in different wear-resistant and anti-friction performances. The Al-doped carbon coating has low friction between 0.1~0.18, so its wear resistance is good and the coating will not fail even after the ball-disc experiment. The work layer of zirconium-doped carbon coating fails around 1600 s when the friction coefficient begins to increase sharply. Its friction coefficient is between 0.08~0.18 before the failure, and it has good wear-resistant and anti-friction performance. The friction coefficient of the tungsten doped carbon coating increases dramatically from the beginning and the coating fails completely in 250 s with a large area of spalling; therefore its wear and friction reducing effect among the three coatings is the worst
Using the unbalanced magnetron sputter ion plating technique graphite-like coatings with Al, Zr and W as transition layers on the surface of magnesium substrate were prepared. The section microstructure and phase composition of the coatings were analyzed by TEM and the binding force and tribological performance were tested by a scratch tester and a wear machine. The results show that a mixing layer with magnesium and β-Mg17Al12 phase is formed in the interface between Al transition layer and magnesium substrate; there is a partial continuous interface between Zr transition layer and magnesium substrate; the interface between W transition layer and magnesium substrate is a mixed interface layer with magnesium phase and tungsten clusters of about 20nm because of the implantation of tungsten particles into magnesium substrate. The binding force of the three kinds of doped (aluminum, zirconium, tungsten) carbon coatings on the surface of magnesium substrate is 10.2, 11.0 and 4.8 N, respectively. The different work layers of three kinds of doped carbon coatings result in different wear-resistant and anti-friction performances. The Al-doped carbon coating has low friction between 0.1~0.18, so its wear resistance is good and the coating will not fail even after the ball-disc experiment. The work layer of zirconium-doped carbon coating fails around 1600 s when the friction coefficient begins to increase sharply. Its friction coefficient is between 0.08~0.18 before the failure, and it has good wear-resistant and anti-friction performance. The friction coefficient of the tungsten doped carbon coating increases dramatically from the beginning and the coating fails completely in 250 s with a large area of spalling; therefore its wear and friction reducing effect among the three coatings is the worst
2014, 43(3):627-630.
Abstract:
Zn-22Al-Mg-RE alloy coating was prepared on Q345 steel substrate by arc spraying with alloy wires which were researched and designed independently. The microstructure and corrosion resistance of the Zn-22Al-Mg-RE alloy coating were investigated and compared with that of Zn coating by SEM, Copper-accelerated acetic acid salt spray, XRD and Polarization curves. Results show that the bonding strength of Zn-22Al-Mg-RE alloy coating is increased by 40% compared with that of pure zinc coating?, and the first rust appearing time is prolonged by 1 time in Copper-accelerated acetic acid salt spray test. Electrochemical experiment results show that the corrosion resistance of Zn-22Al-Mg-RE alloy coating is superior to that of pure Zn coating. It is indicated that the appearance of much Zn6Al2(OH)16CO3·4H2O which is stable and dense, is one of the main reasons for the enhanced corrosion resistance of the Zn-22Al-Mg-RE alloy coating
Zn-22Al-Mg-RE alloy coating was prepared on Q345 steel substrate by arc spraying with alloy wires which were researched and designed independently. The microstructure and corrosion resistance of the Zn-22Al-Mg-RE alloy coating were investigated and compared with that of Zn coating by SEM, Copper-accelerated acetic acid salt spray, XRD and Polarization curves. Results show that the bonding strength of Zn-22Al-Mg-RE alloy coating is increased by 40% compared with that of pure zinc coating?, and the first rust appearing time is prolonged by 1 time in Copper-accelerated acetic acid salt spray test. Electrochemical experiment results show that the corrosion resistance of Zn-22Al-Mg-RE alloy coating is superior to that of pure Zn coating. It is indicated that the appearance of much Zn6Al2(OH)16CO3·4H2O which is stable and dense, is one of the main reasons for the enhanced corrosion resistance of the Zn-22Al-Mg-RE alloy coating
2014, 43(3):631-635.
Abstract:
Using a density functional theory B3LYP method and on the 6-311+G(d, p) basis set level the hydrogenation reaction mechanism of Mg(NH2)2 and MgH2 was studied and the geometric configuration of the reactants, intermediates, transition states and products were optimized. To get more precise energy information, the single point energies of stationary points along the pathways were also calculated by QCISD/6-311+G(d, p) method, and the zero-point energy correction was performed for the total energy. Intermediates, transition states and the processes of the reaction were confirmed by the results of vibration analysis and the IRC calculation. Analyses indicate that the “a” of the first step hydrogen substitution reaction →the “f” of the second step hydrogen substitution reaction →the heterogeneous reactions of Mg3N2 was the main pathway, the activation energy of which was the lowest
Using a density functional theory B3LYP method and on the 6-311+G(d, p) basis set level the hydrogenation reaction mechanism of Mg(NH2)2 and MgH2 was studied and the geometric configuration of the reactants, intermediates, transition states and products were optimized. To get more precise energy information, the single point energies of stationary points along the pathways were also calculated by QCISD/6-311+G(d, p) method, and the zero-point energy correction was performed for the total energy. Intermediates, transition states and the processes of the reaction were confirmed by the results of vibration analysis and the IRC calculation. Analyses indicate that the “a” of the first step hydrogen substitution reaction →the “f” of the second step hydrogen substitution reaction →the heterogeneous reactions of Mg3N2 was the main pathway, the activation energy of which was the lowest
2014, 43(3):636-640.
Abstract:
The cast AZ61 magnesium alloy and the extruded alloy were chosen to study the corrosion morphology and mechanism by means of SEM, XRD and electrochemical testing, under the NaCl atmosphere at 120 oC and 1.8 MPa. The results show that due to the multi-factor coupling effects of NaCl atmosphere, temperature, pressure and microstructure, the corrosion rate of the extruded AZ61 magnesium alloy is larger than that of the cast AZ61 alloy, because of the re-distribution of β phases and smaller grain size. But both of the corrosion products are mainly Mg(OH)2. The environmental factors play an important role in the corrosion behavior of magnesium alloys. Higher temperature and sodium chloride atmosphere work together to accelerate the corrosion rate of Mg alloys
The cast AZ61 magnesium alloy and the extruded alloy were chosen to study the corrosion morphology and mechanism by means of SEM, XRD and electrochemical testing, under the NaCl atmosphere at 120 oC and 1.8 MPa. The results show that due to the multi-factor coupling effects of NaCl atmosphere, temperature, pressure and microstructure, the corrosion rate of the extruded AZ61 magnesium alloy is larger than that of the cast AZ61 alloy, because of the re-distribution of β phases and smaller grain size. But both of the corrosion products are mainly Mg(OH)2. The environmental factors play an important role in the corrosion behavior of magnesium alloys. Higher temperature and sodium chloride atmosphere work together to accelerate the corrosion rate of Mg alloys
2014, 43(3):646-649.
Abstract:
High-quality single crystals of UFeGa5 were grown by the Ga-flux method. The structure of UFeGa5 single crystal was studied by X-ray diffraction and Rietveld method. The results show that the structure of as-grown UFeGa5 single crystal is good and its crystallinity is well. The UFeGa5 has the HoCoGa5 type-structure with space group P4/mmm (No.123). The lattice constants are a=0.42533(2) nm and c=0.67298(3) nm. The crystal structure results are confirmed by transmission electron microscopy
High-quality single crystals of UFeGa5 were grown by the Ga-flux method. The structure of UFeGa5 single crystal was studied by X-ray diffraction and Rietveld method. The results show that the structure of as-grown UFeGa5 single crystal is good and its crystallinity is well. The UFeGa5 has the HoCoGa5 type-structure with space group P4/mmm (No.123). The lattice constants are a=0.42533(2) nm and c=0.67298(3) nm. The crystal structure results are confirmed by transmission electron microscopy
2014, 43(3):650-654.
Abstract:
Nitrogen insertion into the LaFe11.58Si1.42 compound with NaZn13-type crystal structure was carried out in a vacuum quartz tube under a high-purity N2 atmosphere. The crystal structure and the magnetocaloric effect of the nitrides were investigated. It is found that nitrogenation pressure is a very important parameter to obtain LaFe11.58Si1.42 nitrides. In the experimental conditions of lower nitrogen pressure, increasing nitrogenation temperature could cause an obvious nitriding effect. The insertion of interstitial nitrogen atoms leads to lattice expansion and the increase of TC. The Arrott plots of samples show that the magnetic phase transition of the samples changes from the first order to the second order. The nitrogen insertion reduces the magnetic entropy change of LaFe11.58Si1.42 compound
Nitrogen insertion into the LaFe11.58Si1.42 compound with NaZn13-type crystal structure was carried out in a vacuum quartz tube under a high-purity N2 atmosphere. The crystal structure and the magnetocaloric effect of the nitrides were investigated. It is found that nitrogenation pressure is a very important parameter to obtain LaFe11.58Si1.42 nitrides. In the experimental conditions of lower nitrogen pressure, increasing nitrogenation temperature could cause an obvious nitriding effect. The insertion of interstitial nitrogen atoms leads to lattice expansion and the increase of TC. The Arrott plots of samples show that the magnetic phase transition of the samples changes from the first order to the second order. The nitrogen insertion reduces the magnetic entropy change of LaFe11.58Si1.42 compound
2014, 43(3):660-664.
Abstract:
The effects of Mn and Ce on the Fe-rich intermetallics in secondary Al-Si alloys were studied. Microstructure morphology and phase-transition temperature of samples were examined and analyzed by optical microscope (OM), scanning electric microscope (SEM), energy dispersive X-ray (EDX) and differential scanning calorimetric (DSC). The results show that when Mn content was 1wt%, the primary α-Fe was formed in the alloys. At the same time, the addition of 0.1wt% Ce could cause a great increase of primary α-Fe particles
The effects of Mn and Ce on the Fe-rich intermetallics in secondary Al-Si alloys were studied. Microstructure morphology and phase-transition temperature of samples were examined and analyzed by optical microscope (OM), scanning electric microscope (SEM), energy dispersive X-ray (EDX) and differential scanning calorimetric (DSC). The results show that when Mn content was 1wt%, the primary α-Fe was formed in the alloys. At the same time, the addition of 0.1wt% Ce could cause a great increase of primary α-Fe particles
2014, 43(3):665-670.
Abstract:
Based on the density functional theory (DFT), the plane-wave pseudo-potential method was used to calculate structural stabilities, elastic properties and electronic structures of Fe3Si and Fe3Si-X (X=Ni, Co, Cr) compounds. The stability of the solid solution alloy increases with the addition of Ni or Cr, especially Fe3Si-Ni, and the stability of the solid solution alloy decreases with the addition of Co. The calculated elastic constants show that addition of Ni or Cr could enhance the plasticity and ductility, and Co could improve the hardness of compounds. Fe3Si-Ni has a better plasticity, but Fe3Si-Co has the best high temperature stability. Calculation of the density of states and Mulliken electronic populations shows that the reason why Fe3Si-Ni has the highest structural stability and optimal plasticity is attributed to its Fermi level close to the bottom of the pseudogap. And Fe3Si-Ni has the biggest Mulliken population with the metallic bonding of the alloying system increasing.
Based on the density functional theory (DFT), the plane-wave pseudo-potential method was used to calculate structural stabilities, elastic properties and electronic structures of Fe3Si and Fe3Si-X (X=Ni, Co, Cr) compounds. The stability of the solid solution alloy increases with the addition of Ni or Cr, especially Fe3Si-Ni, and the stability of the solid solution alloy decreases with the addition of Co. The calculated elastic constants show that addition of Ni or Cr could enhance the plasticity and ductility, and Co could improve the hardness of compounds. Fe3Si-Ni has a better plasticity, but Fe3Si-Co has the best high temperature stability. Calculation of the density of states and Mulliken electronic populations shows that the reason why Fe3Si-Ni has the highest structural stability and optimal plasticity is attributed to its Fermi level close to the bottom of the pseudogap. And Fe3Si-Ni has the biggest Mulliken population with the metallic bonding of the alloying system increasing.
2014, 43(3):676-681.
Abstract:
In order to solve the corrosion issues that occur in the weld zone (WZ) of zirconium material applied in the industrial community, X-ray diffraction (XRD), electrochemical analysis, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to investigate the microstructure and corrosion resistance of the zirconium butt joint by tungsten inert gas (TIG) welding. Also, the mechanism of corrosion was discussed. It is found that the corrosion pattern of zirconium butt joint is intergranular corrosion. The factors that cause intergranular corrosion are the inadequate protection of argon and a trace amount of oxygen existing in the soldering wires, which facilitates the generation of zirconium composite oxides that result in the electrochemical inhomogeneity between crystal boundaries and particles. Consequently, the dissolve current density of crystal boundaries is larger than that of the grains, which leads to intergranular corrosion
In order to solve the corrosion issues that occur in the weld zone (WZ) of zirconium material applied in the industrial community, X-ray diffraction (XRD), electrochemical analysis, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to investigate the microstructure and corrosion resistance of the zirconium butt joint by tungsten inert gas (TIG) welding. Also, the mechanism of corrosion was discussed. It is found that the corrosion pattern of zirconium butt joint is intergranular corrosion. The factors that cause intergranular corrosion are the inadequate protection of argon and a trace amount of oxygen existing in the soldering wires, which facilitates the generation of zirconium composite oxides that result in the electrochemical inhomogeneity between crystal boundaries and particles. Consequently, the dissolve current density of crystal boundaries is larger than that of the grains, which leads to intergranular corrosion
2014, 43(3):682-685.
Abstract:
An explosive welding experiment with small inclination was performed for researching the influence of explosive welding parameters on the interfacial waves. The interfacial waves of continuous change were obtained under the different impact velocities and impact angles. Through observing the OM morphology of interfacial waves, the wave length and wave height were measured. Explosive welding with small inclination was numerically simulated using SPH method, and the parameters such as impact velocity, impact angle and specific pressure were calculated. The results show that the impact velocity and the impact angle are the key parameters affecting interfacial waves. When the impact velocity is 493 m/s and impact angle is 9.8o, the interfacial waves begin to form. The wave length increases with higher impact velocity and larger impact angle, but the specific wavelength first increases and then decreases
An explosive welding experiment with small inclination was performed for researching the influence of explosive welding parameters on the interfacial waves. The interfacial waves of continuous change were obtained under the different impact velocities and impact angles. Through observing the OM morphology of interfacial waves, the wave length and wave height were measured. Explosive welding with small inclination was numerically simulated using SPH method, and the parameters such as impact velocity, impact angle and specific pressure were calculated. The results show that the impact velocity and the impact angle are the key parameters affecting interfacial waves. When the impact velocity is 493 m/s and impact angle is 9.8o, the interfacial waves begin to form. The wave length increases with higher impact velocity and larger impact angle, but the specific wavelength first increases and then decreases
2014, 43(3):686-691.
Abstract:
Based on the cubic model developed by Ashby, the effects of the topology structure of light metallic foam such as porosity and cell size on its effective thermal conductivities were investigated. Using the least thermal resistance method, the expression of effective thermal conductivities was derived, and the approximate analytic solution was first obtained by employing the simplified integral method. The distribution of heat flux across the open-cell metallic foam and the steady Fourier law were simulated by ABAQUS software in order to determine the influence of porosity and cell size on the thermal conductivities of the open-cell metallic foam materials. The finding of this paper indicates that the effective thermal conductivities of porous metallic foam almost linearly decrease with the increase of porosity, and they have no change with the cell size when the porosity keeps constant. The theoretical study agrees well with the numerical data. The research results are significant to the practical engineering application of metallic foams.
Based on the cubic model developed by Ashby, the effects of the topology structure of light metallic foam such as porosity and cell size on its effective thermal conductivities were investigated. Using the least thermal resistance method, the expression of effective thermal conductivities was derived, and the approximate analytic solution was first obtained by employing the simplified integral method. The distribution of heat flux across the open-cell metallic foam and the steady Fourier law were simulated by ABAQUS software in order to determine the influence of porosity and cell size on the thermal conductivities of the open-cell metallic foam materials. The finding of this paper indicates that the effective thermal conductivities of porous metallic foam almost linearly decrease with the increase of porosity, and they have no change with the cell size when the porosity keeps constant. The theoretical study agrees well with the numerical data. The research results are significant to the practical engineering application of metallic foams.
2014, 43(3):692-697.
Abstract:
The solid-state boriding of new damage tolerance TC21 titanium alloy was carried out to harden surface layers through rare earth (RE) B diffusion process. By means of SEM, XRD, OM and EDS, the microstructure and morphology of boride coatings were investigated. The results indicate that boride layers include a monolithic titanium diboride (TiB2) at the top and a titanium boride (TiB) sub-layer that mostly consisted of TiB whiskers combining with titanium matrix closely. Meanwhile, the contents of RE in boriding medium possess a considerably optimal value. B and C surface co-diffusion with RE on TC21 alloy can be realized by this method
The solid-state boriding of new damage tolerance TC21 titanium alloy was carried out to harden surface layers through rare earth (RE) B diffusion process. By means of SEM, XRD, OM and EDS, the microstructure and morphology of boride coatings were investigated. The results indicate that boride layers include a monolithic titanium diboride (TiB2) at the top and a titanium boride (TiB) sub-layer that mostly consisted of TiB whiskers combining with titanium matrix closely. Meanwhile, the contents of RE in boriding medium possess a considerably optimal value. B and C surface co-diffusion with RE on TC21 alloy can be realized by this method
2014, 43(3):698-702.
Abstract:
Using the cast tungsten carbide particles (CTCP) and reduced iron powder as the raw materials, the porous ceramic preforms with honeycomb structure were prepared by the loose sintering process; then, CTCp/Cr26 ferrous matrix composites with honeycomb structure were prepared by the casting infiltration process. The microstructure of the perform and the composites were analyzed by SEM, XRD and EPMA. The results show that a sintered shell is formed from the reaction of Fe and W2C in the CTCP during loose sintering process; finally, WC plus Fe3W3C phases are located on the inside surface of the shell and the Fe3W3C shell is located between the particles. Therefore, the strength of preforms is enhanced because the shell layer is connected to each other by sintered shell. Besides, the preform can resist the rush of liquid metal and maintain the honeycomb structure during cast infiltration process. A transition layer is formed in the interface of CTCp and the matrix, which is constituted by WC and Fe3W3C. The formation mechanism of the transition layer is the dissolution and precipitation result of the sintered shell in the hot liquid metal.
Using the cast tungsten carbide particles (CTCP) and reduced iron powder as the raw materials, the porous ceramic preforms with honeycomb structure were prepared by the loose sintering process; then, CTCp/Cr26 ferrous matrix composites with honeycomb structure were prepared by the casting infiltration process. The microstructure of the perform and the composites were analyzed by SEM, XRD and EPMA. The results show that a sintered shell is formed from the reaction of Fe and W2C in the CTCP during loose sintering process; finally, WC plus Fe3W3C phases are located on the inside surface of the shell and the Fe3W3C shell is located between the particles. Therefore, the strength of preforms is enhanced because the shell layer is connected to each other by sintered shell. Besides, the preform can resist the rush of liquid metal and maintain the honeycomb structure during cast infiltration process. A transition layer is formed in the interface of CTCp and the matrix, which is constituted by WC and Fe3W3C. The formation mechanism of the transition layer is the dissolution and precipitation result of the sintered shell in the hot liquid metal.
2014, 43(3):703-706.
Abstract:
Considering the limit of equipment technology of Low Pressure Casting (LPC) to shape the large magnesium alloy components, an improved LPC equipment technology, including equipment mechanical part, control system and protective gaseous mixture system has been developed. The melting capacity of 1000 kg of molten magnesium and the maximum weight of 850 kg of the unit casting piece were realized. The protective gaseous mixture system with a good ignition-proof effect can mix SF6, CO2 and compressed air in a certain proportion. The Fuzzy-PID hybrid control technology and the digital assemble valves have been applied in the control system to obtain a high pressure control precision
Considering the limit of equipment technology of Low Pressure Casting (LPC) to shape the large magnesium alloy components, an improved LPC equipment technology, including equipment mechanical part, control system and protective gaseous mixture system has been developed. The melting capacity of 1000 kg of molten magnesium and the maximum weight of 850 kg of the unit casting piece were realized. The protective gaseous mixture system with a good ignition-proof effect can mix SF6, CO2 and compressed air in a certain proportion. The Fuzzy-PID hybrid control technology and the digital assemble valves have been applied in the control system to obtain a high pressure control precision
Wei Xiangfei
,
Zhang Pingze
,
Wei Dongbo
,
Zhou Peng
,
Zhang Yang
,
Chen Xiaohu
,
Wang Qiong
,
Wang Ruonan
2014, 43(3):707-711.
Abstract:
Chromium coatings were deposited on γ-TiAl alloy by multi-arc ion plating (MAIP). The high temperature oxidation resistance of the coatings was tested by SEM, EDX and XRD. The results show that the coating at high temperature can form a protective oxide film. The oxide film is mainly divided into two layers. The outer part at 650 oC is Cr2O3, at 750 oC is TiO2 and at 950 oC is Al2O3. The inner oxide film is Ti-Al-Cr mixed oxide film. The Ti-Al-Cr diffusion layer can effectively prevent the diffusion of oxygen into the substrate, and thus significantly improve the γ-TiAl high-temperature oxidation resistance ability
Chromium coatings were deposited on γ-TiAl alloy by multi-arc ion plating (MAIP). The high temperature oxidation resistance of the coatings was tested by SEM, EDX and XRD. The results show that the coating at high temperature can form a protective oxide film. The oxide film is mainly divided into two layers. The outer part at 650 oC is Cr2O3, at 750 oC is TiO2 and at 950 oC is Al2O3. The inner oxide film is Ti-Al-Cr mixed oxide film. The Ti-Al-Cr diffusion layer can effectively prevent the diffusion of oxygen into the substrate, and thus significantly improve the γ-TiAl high-temperature oxidation resistance ability
2014, 43(3):712-716.
Abstract:
In order to study the effect of the heating rate on the microstructure of TC4 titanium alloy during high temperature compression deformation under the condition of electric field, cylinder samples with grain size of 8 μm and 20 μm were compressed with different heating rates at 700 oC using Gleeble-1500D thermal simulation instrument. The results show that grain size of 8 μm samples becomes finer and more equiaxial after high temperature compression deformation under the action of AC current, equiaxial α phase increases and flake β phase decreases. In addition, the distribution of equiaxial α phase and flake β phase becomes narrow. Both low current and high current heated TC4 titanium alloys of 20 μm have honeycomb structures, and honeycomb structures of low current heated TC4 titanium alloy is more pronounced. With the same grain size of TC4 titanium alloy, the higher the current, the finer the microstructure, and the more equiaxial.
In order to study the effect of the heating rate on the microstructure of TC4 titanium alloy during high temperature compression deformation under the condition of electric field, cylinder samples with grain size of 8 μm and 20 μm were compressed with different heating rates at 700 oC using Gleeble-1500D thermal simulation instrument. The results show that grain size of 8 μm samples becomes finer and more equiaxial after high temperature compression deformation under the action of AC current, equiaxial α phase increases and flake β phase decreases. In addition, the distribution of equiaxial α phase and flake β phase becomes narrow. Both low current and high current heated TC4 titanium alloys of 20 μm have honeycomb structures, and honeycomb structures of low current heated TC4 titanium alloy is more pronounced. With the same grain size of TC4 titanium alloy, the higher the current, the finer the microstructure, and the more equiaxial.
2014, 43(3):722-726.
Abstract:
Two types of Ni-Co-P coatings were synthesized by electroless deposition on p-type Si (100) substrates. Microstructures and properties of the coatings were studied and compared. A mixture of amorphous and nanocrystal structures was found in Ni48Co46P6 coatings, while Ni22Co74P4 coatings contained a nanocrystalline hexagonal closed packed phase with a strong (0002) texture. Surfaces of both coatings were composed of clusters. In Ni48Co46P6 coatings, the clusters were 0.2 ~ 3.5 μm nodules that distributed uniformly, whereas in Ni22Co74P4 coatings there were nano-sized shuttle clusters mixed with micro-sized bud clusters. Both coatings exhibited activation-passivation-transpassivation processes in 3.5% NaCl solution, and Ni48Co46P6 coatings showed a better corrosion resistance. However, corrosion resistance of both Ni-Co-P coatings was decreased remarkably in 1.0% H2SO4 solution. Compared with Ni48Co46P6 coatings, Ni22Co74P4 coatings showed a much improved saturation magnetization and coercivity with a slightly decreased electrical conductivity.
Two types of Ni-Co-P coatings were synthesized by electroless deposition on p-type Si (100) substrates. Microstructures and properties of the coatings were studied and compared. A mixture of amorphous and nanocrystal structures was found in Ni48Co46P6 coatings, while Ni22Co74P4 coatings contained a nanocrystalline hexagonal closed packed phase with a strong (0002) texture. Surfaces of both coatings were composed of clusters. In Ni48Co46P6 coatings, the clusters were 0.2 ~ 3.5 μm nodules that distributed uniformly, whereas in Ni22Co74P4 coatings there were nano-sized shuttle clusters mixed with micro-sized bud clusters. Both coatings exhibited activation-passivation-transpassivation processes in 3.5% NaCl solution, and Ni48Co46P6 coatings showed a better corrosion resistance. However, corrosion resistance of both Ni-Co-P coatings was decreased remarkably in 1.0% H2SO4 solution. Compared with Ni48Co46P6 coatings, Ni22Co74P4 coatings showed a much improved saturation magnetization and coercivity with a slightly decreased electrical conductivity.
2014, 43(3):733-736.
Abstract:
This paper discussed the technical process of mechanical alloying-spark plasma sintering-hot isostatic pressing (MA-SPS-HIP) to fabricate vanadium alloy V-4Cr-4Ti-1.8YH2, and the properties of the alloy after annealing treatment at 1000~1200 oC were tested. The XRD and SEM analyses show that it can reach the purpose of mechanical alloying after 50 h milling. The tensile test shows that V-4Cr-4Ti-1.8YH2 alloy has a better mechanical property which can reach the optimum when the annealing temperature is 1100 oC. Microstructure analysis shows that the grain size of the vanadium alloy is mostly below 0.5 μm, and YH2 transforms into Y2O3 during sintering process which are less than 50 nm particles distributing in the matrix
This paper discussed the technical process of mechanical alloying-spark plasma sintering-hot isostatic pressing (MA-SPS-HIP) to fabricate vanadium alloy V-4Cr-4Ti-1.8YH2, and the properties of the alloy after annealing treatment at 1000~1200 oC were tested. The XRD and SEM analyses show that it can reach the purpose of mechanical alloying after 50 h milling. The tensile test shows that V-4Cr-4Ti-1.8YH2 alloy has a better mechanical property which can reach the optimum when the annealing temperature is 1100 oC. Microstructure analysis shows that the grain size of the vanadium alloy is mostly below 0.5 μm, and YH2 transforms into Y2O3 during sintering process which are less than 50 nm particles distributing in the matrix
Yan Meng
,
Li Yi
,
Fang Baoying
,
Liang Qian
,
Ding Jie
,
Wang Feng
,
Qin Yuan
,
Tong Guoxiang
,
Wang Xiaohua
,
Chen Shaojuan
,
Chen Jiankun
,
Zheng Hongzhu
,
Zheng Hongzhu
2014, 43(3):737-742.
Abstract:
The thermo-optic effect and infrared optical properties of VO2 nano array were studied in order to obtain high quality optical material widely used in the field of smart windows. Reflectance and transmittance spectra of VO2 nano array at different duty ratios were calculated with a modificatory Sellmeier dispersion model and equivalent refractive index of two-dimensional periodic structure. The vanadium nano array was deposited on the glass substrate by magnetic reactive sputtering with the mask of porous alumina, and then VO2 nano array was formed by annealing under air condition. Its microstructure and optical properties were characterized by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and spectrophotometer. The results show that the phase transition temperature of VO2 nano array with duty ratio 0.83 drops to 43 oC and its optical contrast between the metallic and semiconducting states at 1700 nm is 29%, which exhibits a significant thermochromic property. Contrast to VO2 film, the transmittance of VO2 nano array has been noticeably improved. The decrease of phase change temperature and enhancement of optical properties demonstrate that VO2 nano array with decent duty ratio is a competitive candidate material for smart windows
The thermo-optic effect and infrared optical properties of VO2 nano array were studied in order to obtain high quality optical material widely used in the field of smart windows. Reflectance and transmittance spectra of VO2 nano array at different duty ratios were calculated with a modificatory Sellmeier dispersion model and equivalent refractive index of two-dimensional periodic structure. The vanadium nano array was deposited on the glass substrate by magnetic reactive sputtering with the mask of porous alumina, and then VO2 nano array was formed by annealing under air condition. Its microstructure and optical properties were characterized by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and spectrophotometer. The results show that the phase transition temperature of VO2 nano array with duty ratio 0.83 drops to 43 oC and its optical contrast between the metallic and semiconducting states at 1700 nm is 29%, which exhibits a significant thermochromic property. Contrast to VO2 film, the transmittance of VO2 nano array has been noticeably improved. The decrease of phase change temperature and enhancement of optical properties demonstrate that VO2 nano array with decent duty ratio is a competitive candidate material for smart windows
2014, 43(3):743-746.
Abstract:
The ionic liquid CO(NH2)2-NaBr-KBr-CH3NO-ZnCl2 was adopted for electroplating zinc on NdFeB magnet. All the pre-processing of the matrix, the solvents and power supply were authenticated through experiments and the coating was characterized by means of neutral salt spray experiment, SEM and XRD. The results show that when the current density is 1 A/dm2, the temperature 30 oC, the electroplating time 20 min and the additives 10 mL·L-1, a comparatively bright, uniform zinc coating with good corrosion resistance can be obtained by means of digital pulse plating power supply. Therefore it supplies a new idea for electroplating of zinc on NdFeB magnet.
The ionic liquid CO(NH2)2-NaBr-KBr-CH3NO-ZnCl2 was adopted for electroplating zinc on NdFeB magnet. All the pre-processing of the matrix, the solvents and power supply were authenticated through experiments and the coating was characterized by means of neutral salt spray experiment, SEM and XRD. The results show that when the current density is 1 A/dm2, the temperature 30 oC, the electroplating time 20 min and the additives 10 mL·L-1, a comparatively bright, uniform zinc coating with good corrosion resistance can be obtained by means of digital pulse plating power supply. Therefore it supplies a new idea for electroplating of zinc on NdFeB magnet.
2014, 43(3):752-756.
Abstract:
Germanium was extracted from coal dust by manganese dioxide oxidation-hydrochloric acid distillation, and then germanium dioxide with high purity was obtained via purification process. Meanwhile, gallium in the coal dust dissolved fully into germanium distillation residual liquid. After the filtering process, gallium and residual germanium got into the vinasse. The vinasse acidity was adjusted to 5.6 mol/L to extract gallium by 260# solvent oil solution of tributyl phosphate (TBP). A small amount of germanium in the vinasse was extracted as well, and subsequently went into the organic phase. Then sodium hydroxide solution was taken to conduct re-extraction. Afterwards, its pH was adjusted to 6.5~6.7 and it was heated up to 85~95 oC to hydrolyze gallium and germanium. As a result, hydrogen gallium oxide precipitation and germanium dioxide precipitation were produced. Finally germanium and gallium concentrates were obtained via filtering and drying process. By taking the above procedures, the distillation recovery rate of germanium is as high as 92.37%, and the recovery rate of germanium in the vinasse is 86.18%. Hydrochloric acid leaching rate of gallium is above 81.23% and tributyl phosphate recovery rate and re-extraction rate of gallium is 98.81% and 99.11%, respectively. And the neutralized precipitation straight yield rate is 93.20%. Thus, the hydrochloric acid distillation-tributyl phosphate extraction process is a kind of economic and efficient extraction method, enjoying the qualities of short procedures, easier process control, high recovery rate, less time and less assumption of material.
Germanium was extracted from coal dust by manganese dioxide oxidation-hydrochloric acid distillation, and then germanium dioxide with high purity was obtained via purification process. Meanwhile, gallium in the coal dust dissolved fully into germanium distillation residual liquid. After the filtering process, gallium and residual germanium got into the vinasse. The vinasse acidity was adjusted to 5.6 mol/L to extract gallium by 260# solvent oil solution of tributyl phosphate (TBP). A small amount of germanium in the vinasse was extracted as well, and subsequently went into the organic phase. Then sodium hydroxide solution was taken to conduct re-extraction. Afterwards, its pH was adjusted to 6.5~6.7 and it was heated up to 85~95 oC to hydrolyze gallium and germanium. As a result, hydrogen gallium oxide precipitation and germanium dioxide precipitation were produced. Finally germanium and gallium concentrates were obtained via filtering and drying process. By taking the above procedures, the distillation recovery rate of germanium is as high as 92.37%, and the recovery rate of germanium in the vinasse is 86.18%. Hydrochloric acid leaching rate of gallium is above 81.23% and tributyl phosphate recovery rate and re-extraction rate of gallium is 98.81% and 99.11%, respectively. And the neutralized precipitation straight yield rate is 93.20%. Thus, the hydrochloric acid distillation-tributyl phosphate extraction process is a kind of economic and efficient extraction method, enjoying the qualities of short procedures, easier process control, high recovery rate, less time and less assumption of material.
2014, 43(3):757-761.
Abstract:
TiAl intermetallic compounds have attracted wide attention as a new kind of lightweight high-temperature structural material in aerospace industrial and automotive fields for the low density, high specific strength and specific modulus, good oxidation resistance and excellent fatigue resistance. The paper focuses on several preparation methods of TiAl intermetallic compounds and their application, and the development trend for TiAl intermetallic compounds is also summarized
TiAl intermetallic compounds have attracted wide attention as a new kind of lightweight high-temperature structural material in aerospace industrial and automotive fields for the low density, high specific strength and specific modulus, good oxidation resistance and excellent fatigue resistance. The paper focuses on several preparation methods of TiAl intermetallic compounds and their application, and the development trend for TiAl intermetallic compounds is also summarized
