Volume 39,Issue 4,2010 Table of Contents
Wang Kaixuan
,
Zeng Weidong
,
ZhaoYongqing
,
Shao Yitao
,
Zhou Jianhua
,
Wang Xiaoying
,
Zhou Yigang
2010, 39(4):565-569.
Abstract:
To quantitatively research the microstructural evolution of lamellar α phase in titanium alloys, large size cakes of Ti-17 alloy with initial lamellar microstructure were isothermally-forged at different strains in α+β phase field followed by solid-solution and aging treatment. The changes of α thickness and morphology in different locations (center, midradius, edge) of the cakes deformed to different strain levels were measured and the imposed strain was estimated using finite element analysis. It is found that increasing of forging strains causes an increase in thickness of α phase. The modification of α morphology depends strongly on the forging strains and the locations in the cakes. The distribution curves of α morphology parameter Feret Ratio were characterized by no peak at lower strains, and a single peak appears at Feret Ratio 1.5-2.5 at larger strains. Moreover, the peak values increased with increasing of the height reduction, and the distribution curves at the center have the largest peak values. Increasing of forging strains will cause the high-Feret-Ratio lamellae to decrease but low-Feret-Ratio α to increase noticeably. Sufficiently imposed strains also can improve the microstructure homogeneity in different locations of the cakes. The effect of the effective strains on the percentage of α phase with different morphologies is also quantificationally summarized. The average strains for initiation of globalization are of the order of 0.4 and those for completion are of the order of 1.0, which are lower than that of conventional α+β titanium alloys
To quantitatively research the microstructural evolution of lamellar α phase in titanium alloys, large size cakes of Ti-17 alloy with initial lamellar microstructure were isothermally-forged at different strains in α+β phase field followed by solid-solution and aging treatment. The changes of α thickness and morphology in different locations (center, midradius, edge) of the cakes deformed to different strain levels were measured and the imposed strain was estimated using finite element analysis. It is found that increasing of forging strains causes an increase in thickness of α phase. The modification of α morphology depends strongly on the forging strains and the locations in the cakes. The distribution curves of α morphology parameter Feret Ratio were characterized by no peak at lower strains, and a single peak appears at Feret Ratio 1.5-2.5 at larger strains. Moreover, the peak values increased with increasing of the height reduction, and the distribution curves at the center have the largest peak values. Increasing of forging strains will cause the high-Feret-Ratio lamellae to decrease but low-Feret-Ratio α to increase noticeably. Sufficiently imposed strains also can improve the microstructure homogeneity in different locations of the cakes. The effect of the effective strains on the percentage of α phase with different morphologies is also quantificationally summarized. The average strains for initiation of globalization are of the order of 0.4 and those for completion are of the order of 1.0, which are lower than that of conventional α+β titanium alloys
2010, 39(4):570-573.
Abstract:
The ternary Ag0.405Sb0.532Te alloy was prepared by spark plasma sintering, and its transport properties involving Seebeck coefficients, electrical and thermal conductivities were evaluated. The results reveal that the electrical conductivity mildly decreases from 7.6′104 S·m-1 to 6.6′104 S·m-1 when the temperature increases from 316 K, to 548 K. Above 438 K, the thermal conductivity gradually increases with the increase of the temperature, and below 438 K, a relative stable value of about 0.86 W·K-1·m-1 is obtained. The maximum thermoelectric figure of merit ZT is up to 0.65 at 548 K, a little higher than 0.61 of the ternary alloy Ag0.365Sb0.558Te. The thermoelectric properties have been improvement compared with the Ag-doped AgxBi0.5Sb1.5-xTe3 alloys (x=0-0.4). The action mechanism of the second phase Ag-Sb-Te ternary alloy precipitated in the AgxBi0.5Sb1.5-xTe3 alloys has been re-discussed
The ternary Ag0.405Sb0.532Te alloy was prepared by spark plasma sintering, and its transport properties involving Seebeck coefficients, electrical and thermal conductivities were evaluated. The results reveal that the electrical conductivity mildly decreases from 7.6′104 S·m-1 to 6.6′104 S·m-1 when the temperature increases from 316 K, to 548 K. Above 438 K, the thermal conductivity gradually increases with the increase of the temperature, and below 438 K, a relative stable value of about 0.86 W·K-1·m-1 is obtained. The maximum thermoelectric figure of merit ZT is up to 0.65 at 548 K, a little higher than 0.61 of the ternary alloy Ag0.365Sb0.558Te. The thermoelectric properties have been improvement compared with the Ag-doped AgxBi0.5Sb1.5-xTe3 alloys (x=0-0.4). The action mechanism of the second phase Ag-Sb-Te ternary alloy precipitated in the AgxBi0.5Sb1.5-xTe3 alloys has been re-discussed
2010, 39(4):574-577.
Abstract:
Ultra-fine Gd2BaCuO5(Gd211) powders were prepared by three different routes including low temperature combustion synthesis (LCS), coprecipitation and solid state reaction. The powders were characterized in terms of morphology, chemical purity, specific surface area and particle size. The results show that LCS process yields the most weakly agglomerated powder with smallest average particle size. The microstructure and superconductor property of GdBa2Cu3O5(Gd123) bulk material fabricated from the precursor of Gd211 powders were also studied. It is found that the employment of fine Gd211 starting powder is effective for the size reduction of Gd211 particles in the bulk samples. Gd123 bulk produced from LCS powder achieved the largest critical current density (Jc) value compared with those from other two powders.
Ultra-fine Gd2BaCuO5(Gd211) powders were prepared by three different routes including low temperature combustion synthesis (LCS), coprecipitation and solid state reaction. The powders were characterized in terms of morphology, chemical purity, specific surface area and particle size. The results show that LCS process yields the most weakly agglomerated powder with smallest average particle size. The microstructure and superconductor property of GdBa2Cu3O5(Gd123) bulk material fabricated from the precursor of Gd211 powders were also studied. It is found that the employment of fine Gd211 starting powder is effective for the size reduction of Gd211 particles in the bulk samples. Gd123 bulk produced from LCS powder achieved the largest critical current density (Jc) value compared with those from other two powders.
2010, 39(4):578-581.
Abstract:
The purpose of this paper is to investigate the corrosion and the tarnish behaviour of 925Ag75Cu and 925Ag40Cu35Zn alloys in synthetic sweat at 37 oC and H2S atmosphere at room temperature. The alloys were in two hardening states, viz., aging at 250 ℃ for 4 h and 70 % cold rolling + aging at 200 ℃ for 4 h, and tested by means of static corrosion, examined by XRD, SEM, EDS and XPS. The results show the corrosion and the tarnish in synthetic sweat at 37 ℃ of these two 925Ag alloys are induced by Cl- and OH- anions. The tarnish of 925Ag40Cu35Zn alloy is much slower than that of 925Ag75Cu alloy, and the white AgCl and the grayish black Ag2O produced by corrosion are difficult to deposit on the surface of 925Ag40Cu35Zn alloy resulting in grayish black corrosion film. The corrosion and the tarnish in H2S atmosphere at room temperature of these two 925Ag alloys are induced by S2- anion. The corrosion and the tarnish of 925Ag40Cu35Zn alloy are much slower than 925Ag75Cu alloy. This is because Zn in 925Ag40Cu35Zn alloy reacts earliest with H2S to form white ZnS, which significantly retards the reaction between Ag or/and Cu and H2S to form grayish black Ag2S and black Cu2S
The purpose of this paper is to investigate the corrosion and the tarnish behaviour of 925Ag75Cu and 925Ag40Cu35Zn alloys in synthetic sweat at 37 oC and H2S atmosphere at room temperature. The alloys were in two hardening states, viz., aging at 250 ℃ for 4 h and 70 % cold rolling + aging at 200 ℃ for 4 h, and tested by means of static corrosion, examined by XRD, SEM, EDS and XPS. The results show the corrosion and the tarnish in synthetic sweat at 37 ℃ of these two 925Ag alloys are induced by Cl- and OH- anions. The tarnish of 925Ag40Cu35Zn alloy is much slower than that of 925Ag75Cu alloy, and the white AgCl and the grayish black Ag2O produced by corrosion are difficult to deposit on the surface of 925Ag40Cu35Zn alloy resulting in grayish black corrosion film. The corrosion and the tarnish in H2S atmosphere at room temperature of these two 925Ag alloys are induced by S2- anion. The corrosion and the tarnish of 925Ag40Cu35Zn alloy are much slower than 925Ag75Cu alloy. This is because Zn in 925Ag40Cu35Zn alloy reacts earliest with H2S to form white ZnS, which significantly retards the reaction between Ag or/and Cu and H2S to form grayish black Ag2S and black Cu2S
2010, 39(4):582-586.
Abstract:
Three types of fatty acids—oleic acid, stearic acid, and 12-hydroxystearic acid—were used to disperse nano-sized bismuth powders in octane solvents. The surface characteristics of bismuth powders were modified to be hydrophobic in nature, and the bismuth-fatty acid formed on the surface. Stability property of the suspension was measured by ultraviolet-visible spectrophotometer. Results indicate that better suspension stabilization can be achieved when the 12-hydroxystearic acid is used. Adsorption behavior reveals that a greater affinity at the solid/liquid interface occurred for the 12-hydroxystearic acid than that for stearic acid or oleic acid. This observation suggests that the adsorption of 12-hydroxystearic acid may lead to a better packing of the acid molecules onto the solid surface than others and also results in better suspension stability. It is also evidenced by the results of theoretical calculation of potential energies that the colloidal stability of organic bismuth suspension is caused by fatty acid reducing the attractive interparticle potential and by steric repulsion mechanism
Three types of fatty acids—oleic acid, stearic acid, and 12-hydroxystearic acid—were used to disperse nano-sized bismuth powders in octane solvents. The surface characteristics of bismuth powders were modified to be hydrophobic in nature, and the bismuth-fatty acid formed on the surface. Stability property of the suspension was measured by ultraviolet-visible spectrophotometer. Results indicate that better suspension stabilization can be achieved when the 12-hydroxystearic acid is used. Adsorption behavior reveals that a greater affinity at the solid/liquid interface occurred for the 12-hydroxystearic acid than that for stearic acid or oleic acid. This observation suggests that the adsorption of 12-hydroxystearic acid may lead to a better packing of the acid molecules onto the solid surface than others and also results in better suspension stability. It is also evidenced by the results of theoretical calculation of potential energies that the colloidal stability of organic bismuth suspension is caused by fatty acid reducing the attractive interparticle potential and by steric repulsion mechanism
6 Hollow Ceramic Microsphere Coated with Co by Electroless Plating and Its Electromagnetic Properties
2010, 39(4):587-592.
Abstract:
Functional microspheres with size of 1-20 μm were produced by plating Co on hollow ceramic microspheres for the application of lightweight microwave absorbers. Using Sn-Pd solution as active agent, the surface of hollow microspheres was activated. Co plating was carried out in an alkaline bath with sodium hypophosphite as a reducing agent. The coating of Co was characterized by field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The electromagnetic properties were improved by adjusting the molar ratio of main salt to complexing agent and the concentration of the main salt in a certain range. Furthermore, the processing conditions such as pH value and plating temperature were optimized. Due to the conductive and ferromagnetic behavior of Co coating which is dense and uniform, high dielectric constant can be obtained in the microwave frequency range of 2-18 GHz and the functional hollow micorsphere has certain microwave absorption performance
Functional microspheres with size of 1-20 μm were produced by plating Co on hollow ceramic microspheres for the application of lightweight microwave absorbers. Using Sn-Pd solution as active agent, the surface of hollow microspheres was activated. Co plating was carried out in an alkaline bath with sodium hypophosphite as a reducing agent. The coating of Co was characterized by field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The electromagnetic properties were improved by adjusting the molar ratio of main salt to complexing agent and the concentration of the main salt in a certain range. Furthermore, the processing conditions such as pH value and plating temperature were optimized. Due to the conductive and ferromagnetic behavior of Co coating which is dense and uniform, high dielectric constant can be obtained in the microwave frequency range of 2-18 GHz and the functional hollow micorsphere has certain microwave absorption performance
2010, 39(4):593-597.
Abstract:
According to the gradient-enhanced Johnson-Cook model to investigate the evolution of the ASB width (w5%) with the average plastic shear strain for Ti-6Al-4V alloy. Results show that w5% decreases rapidly and then approaches a constant with the increasing of average plastic shear strain. When the total width of the ASB is 0.3235 mm, the critical value of w5% approaches the upper bound (55 μm) measured for Ti-6Al-4V, while when the total width of the ASB is 0.0705 mm, the critical value of w5% approaches the lower bound (12 μm). It is found that the ASB width is influenced by many factors such as material properties, loading rate, ambient temperature, stress and strain states. In the paper, the key assumption of the balance of heat diffusion and plastic work is not adopted and the present analysis is in adiabatic condition
According to the gradient-enhanced Johnson-Cook model to investigate the evolution of the ASB width (w5%) with the average plastic shear strain for Ti-6Al-4V alloy. Results show that w5% decreases rapidly and then approaches a constant with the increasing of average plastic shear strain. When the total width of the ASB is 0.3235 mm, the critical value of w5% approaches the upper bound (55 μm) measured for Ti-6Al-4V, while when the total width of the ASB is 0.0705 mm, the critical value of w5% approaches the lower bound (12 μm). It is found that the ASB width is influenced by many factors such as material properties, loading rate, ambient temperature, stress and strain states. In the paper, the key assumption of the balance of heat diffusion and plastic work is not adopted and the present analysis is in adiabatic condition
2010, 39(4):598-602.
Abstract:
According to the empirical electron theory of solids and molecules (EET) and Gerold’s terminal-state atom model of GP zone of Al-Cu alloy, the calculation model of valence electron structure of GP zone was set up and the evolution process was investigated. Moreover, the calculation method of lattice constant of GP zone during precipitation was proposed, and the valence electron structure of GP zone was calculated. Furthermore, the effect of Cu content on the valence electron structure was also studied. The results show that the formation of GP zone in Al-Cu alloy in early aging is a progressive process. In the initial development of GP zone, the Spinodal decomposition is the dominant mechanism, and in its later period, the dominant mechanism is the normal nucleation-growth mechanism. With aggregating of Cu atom, the covalent electron pairs nA on the strongest covalent bond A increase gradually, but the covalent electron pairs nB, nC and nD on the covalent bonds B, C and D decrease bit by bit. The strengthening of A bond in GP zone is by means of the transfer to A bond of covalent electrons on B, C and D bonds
According to the empirical electron theory of solids and molecules (EET) and Gerold’s terminal-state atom model of GP zone of Al-Cu alloy, the calculation model of valence electron structure of GP zone was set up and the evolution process was investigated. Moreover, the calculation method of lattice constant of GP zone during precipitation was proposed, and the valence electron structure of GP zone was calculated. Furthermore, the effect of Cu content on the valence electron structure was also studied. The results show that the formation of GP zone in Al-Cu alloy in early aging is a progressive process. In the initial development of GP zone, the Spinodal decomposition is the dominant mechanism, and in its later period, the dominant mechanism is the normal nucleation-growth mechanism. With aggregating of Cu atom, the covalent electron pairs nA on the strongest covalent bond A increase gradually, but the covalent electron pairs nB, nC and nD on the covalent bonds B, C and D decrease bit by bit. The strengthening of A bond in GP zone is by means of the transfer to A bond of covalent electrons on B, C and D bonds
2010, 39(4):603-607.
Abstract:
The fundamental thermodynamic functions of nanograin boundaries in nanocrystalline metal were derived. The Gibbs free energy as a function of the excess volume and the temperature of the nanograin boundary was simulated and calculated. Using nanocrystalline Cu as an example, the thermodynamic stability and the nanograin growth behavior of nanocrystalline microstructure were predicted by the nanocrystalline thermodynamic model. The thermodynamic functions of nanograin boundaries were introduced into the Cellular Automation algorithm, and the temperature-varying nanograin growth process of nanocrystalline Cu was simulated. The kinetics features of the nanograin growth of the nanocrystalline Cu confirm the predictions from the thermodynamic model
The fundamental thermodynamic functions of nanograin boundaries in nanocrystalline metal were derived. The Gibbs free energy as a function of the excess volume and the temperature of the nanograin boundary was simulated and calculated. Using nanocrystalline Cu as an example, the thermodynamic stability and the nanograin growth behavior of nanocrystalline microstructure were predicted by the nanocrystalline thermodynamic model. The thermodynamic functions of nanograin boundaries were introduced into the Cellular Automation algorithm, and the temperature-varying nanograin growth process of nanocrystalline Cu was simulated. The kinetics features of the nanograin growth of the nanocrystalline Cu confirm the predictions from the thermodynamic model
2010, 39(4):613-617.
Abstract:
Cyclic and discontinuous high-temperature oxidation behavior and the residual stress of thermal growth oxide (TGO) of modified aluminide bond coating with different Pt contents in nickel base superalloys for TBC (thermal barrier coating) application were studied in air at 1100 °C. It was found that the continuous and compact α-Al2O3 layers formed over Pt modified aluminide bond coating in the process of the cyclic oxidation, and the two Pt-modified aluminide coatings with different Pt contents had similar morphology and thickness. Thermal growth stress of α-Al2O3 layers increased quickly during initial discontinuous oxidation and a peak value of the residual stress appeared when the coating oxidation was prolonged to 100 h; at the same time, the high content of Pt promoted the diffusion of element Al, resulting in changing the mechanical property of the coating, and exhibiting a relatively great residual stress in the coating with high content of Pt, but the high content of Pt had no influence upon the change trend of the residual stress curve of α-Al2O3 layers. In addition, γ′-Ni3Al phase usually grew along β-NiAl grain boundary, while the high content of Pt would refine coating grains, resulting in γ′-Ni3Al growth in the way of dispersion distribution, and thus a net-like high velocity diffusion channel for element Al would form
Cyclic and discontinuous high-temperature oxidation behavior and the residual stress of thermal growth oxide (TGO) of modified aluminide bond coating with different Pt contents in nickel base superalloys for TBC (thermal barrier coating) application were studied in air at 1100 °C. It was found that the continuous and compact α-Al2O3 layers formed over Pt modified aluminide bond coating in the process of the cyclic oxidation, and the two Pt-modified aluminide coatings with different Pt contents had similar morphology and thickness. Thermal growth stress of α-Al2O3 layers increased quickly during initial discontinuous oxidation and a peak value of the residual stress appeared when the coating oxidation was prolonged to 100 h; at the same time, the high content of Pt promoted the diffusion of element Al, resulting in changing the mechanical property of the coating, and exhibiting a relatively great residual stress in the coating with high content of Pt, but the high content of Pt had no influence upon the change trend of the residual stress curve of α-Al2O3 layers. In addition, γ′-Ni3Al phase usually grew along β-NiAl grain boundary, while the high content of Pt would refine coating grains, resulting in γ′-Ni3Al growth in the way of dispersion distribution, and thus a net-like high velocity diffusion channel for element Al would form
2010, 39(4):618-622.
Abstract:
NiCoCuZn spinel ferrites were prepared by a low-temperature sintering procedure with adding different composite additives, Bi2O3-V2O5 and Bi2O3-PbO. The effect of different composite additives on their magnetic permeability dispersion behaviors was investigated. Results show that for the samples with Bi2O3-V2O5 additive, the grain size increases with increasing of the Bi2O3 content in the composite additive. The microstructure change results in variations of initial magnetic permeability values and cutoff frequencies. Their permeability dispersion behaviors are ascribed to the domain wall movement mechanism. However, for the samples with Bi2O3-PbO additive, the grain size decreases with increasing of the Bi2O3 content in the composite additive. Compared with samples with Bi2O3-V2O5 additive, their initial magnetic permeability values are smaller, but the cutoff frequencies are higher
NiCoCuZn spinel ferrites were prepared by a low-temperature sintering procedure with adding different composite additives, Bi2O3-V2O5 and Bi2O3-PbO. The effect of different composite additives on their magnetic permeability dispersion behaviors was investigated. Results show that for the samples with Bi2O3-V2O5 additive, the grain size increases with increasing of the Bi2O3 content in the composite additive. The microstructure change results in variations of initial magnetic permeability values and cutoff frequencies. Their permeability dispersion behaviors are ascribed to the domain wall movement mechanism. However, for the samples with Bi2O3-PbO additive, the grain size decreases with increasing of the Bi2O3 content in the composite additive. Compared with samples with Bi2O3-V2O5 additive, their initial magnetic permeability values are smaller, but the cutoff frequencies are higher
12 Study on Silver Tin Oxide Composite Powder Preparation by Hydrothermal Method in Different Systems
2010, 39(4):623-627.
Abstract:
The silver tin oxide powders were prepared by hydrothermal method using ammonia and citric acid as complex of silver ions, and oxalic acid, sulfuric acid and citric acid as reductant. The Ag-SnO2 composite powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy(SEM) and energy spectrum analysis. The results show that the silver tin oxide composite powders could be synthesized in different hydrothermal systems. In the system with ammonia as complex of silver ions, sodium sulfuric and oxalic acid as reductant, respectively, silver and tin oxide deposit completely. In the system with sodium sulfuric as reductant, the prepared composite powder is mainly flake structure with about 300 nm thickness. While in the system with oxalic acid as reductant, the prepared composite powder is spherical structure with about 100 nm particle size. In the system with citric acid as both complex and reductant, the tin oxide do not deposit completely and the prepared composite powder is irregularly spherical particle with smaller size of about 30 nm
The silver tin oxide powders were prepared by hydrothermal method using ammonia and citric acid as complex of silver ions, and oxalic acid, sulfuric acid and citric acid as reductant. The Ag-SnO2 composite powders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy(SEM) and energy spectrum analysis. The results show that the silver tin oxide composite powders could be synthesized in different hydrothermal systems. In the system with ammonia as complex of silver ions, sodium sulfuric and oxalic acid as reductant, respectively, silver and tin oxide deposit completely. In the system with sodium sulfuric as reductant, the prepared composite powder is mainly flake structure with about 300 nm thickness. While in the system with oxalic acid as reductant, the prepared composite powder is spherical structure with about 100 nm particle size. In the system with citric acid as both complex and reductant, the tin oxide do not deposit completely and the prepared composite powder is irregularly spherical particle with smaller size of about 30 nm
2010, 39(4):628-632.
Abstract:
The bulk nanocrystalline nickel was prepared by DC arc plasma evaporation method and pre-press sintering. The grain size and porosity was characterized; the compression strength, the strain-rate sensitivity and the influence of the compression process on the grain size and lattice distortion of the specimens were investigated. The results show that the grain size increases with higher sintering temperature. At 725 oC, the relative density of the bulk nanocrystalline nickel is 97%. The compression strength increases with smaller grain size and it is proportional to the strain rate, and the highest compression fracture strength is 600 MPa. The specimen exhibits lower sensitivity to strain rate and lower working hardening exponent. The damage mechanism of the bulk nanocrystalline nickel is intergranular fracture, and the compression leads to the decrease of the grain size and lattice distortion
The bulk nanocrystalline nickel was prepared by DC arc plasma evaporation method and pre-press sintering. The grain size and porosity was characterized; the compression strength, the strain-rate sensitivity and the influence of the compression process on the grain size and lattice distortion of the specimens were investigated. The results show that the grain size increases with higher sintering temperature. At 725 oC, the relative density of the bulk nanocrystalline nickel is 97%. The compression strength increases with smaller grain size and it is proportional to the strain rate, and the highest compression fracture strength is 600 MPa. The specimen exhibits lower sensitivity to strain rate and lower working hardening exponent. The damage mechanism of the bulk nanocrystalline nickel is intergranular fracture, and the compression leads to the decrease of the grain size and lattice distortion
2010, 39(4):633-637.
Abstract:
The effects of Co on the transition and the deformation characteristics of Ti-49.8Ni shape memory alloy were investigated by thermal gravity, X-ray diffraction, differential scanning calorimetry and tensile test. The results indicate that the phase transformation types of intermediate-temperature annealed Ti-49.8Ni alloy during cooling/heating cycle is A→R→M/M→A (A—parent phase, R—R phase, M—martensite phase). With the annealing temperature increasing, the M-phase transformation temperature of Ti-49.8Ni alloy increases, and the R-phase transition temperature increases first and then decreases. The phase of Ti-49.8Ni alloy at room temperature is martensite and shows shape memory effect (SME). After adding 1% Co, the transformation type of Ti-49.8Ni-1Co alloy is A→R→M/M→R→A upon cooling/heating, and the transition temperature of the alloy is low. The phase of Ti-49.8Ni-1Co alloy at room temperature is parent phase, and shows superelasticity (SE). The excellent SME and SE can be obtained in Ti-Ni base alloys when the annealing temperature is below 600 ℃. When the annealing temperature is over 600℃, the oxidation of Ti-Ni alloys speeds up, SME and SE become bad, but the plasticity of the alloy is improved significantly
The effects of Co on the transition and the deformation characteristics of Ti-49.8Ni shape memory alloy were investigated by thermal gravity, X-ray diffraction, differential scanning calorimetry and tensile test. The results indicate that the phase transformation types of intermediate-temperature annealed Ti-49.8Ni alloy during cooling/heating cycle is A→R→M/M→A (A—parent phase, R—R phase, M—martensite phase). With the annealing temperature increasing, the M-phase transformation temperature of Ti-49.8Ni alloy increases, and the R-phase transition temperature increases first and then decreases. The phase of Ti-49.8Ni alloy at room temperature is martensite and shows shape memory effect (SME). After adding 1% Co, the transformation type of Ti-49.8Ni-1Co alloy is A→R→M/M→R→A upon cooling/heating, and the transition temperature of the alloy is low. The phase of Ti-49.8Ni-1Co alloy at room temperature is parent phase, and shows superelasticity (SE). The excellent SME and SE can be obtained in Ti-Ni base alloys when the annealing temperature is below 600 ℃. When the annealing temperature is over 600℃, the oxidation of Ti-Ni alloys speeds up, SME and SE become bad, but the plasticity of the alloy is improved significantly
2010, 39(4):638-641.
Abstract:
Pure Mo and Mo-La2O3 bars with high transverse ductility were prepared by forging and upsetting. The microstructure and transverse bending properties of both bars were investigated after different annealing treatments. The results show that the pure Mo bars forged and upset by 85% possess good transverse ductility and the elongation reaches 5%, while that of the forged and upset Mo-La2O3 bars is only 2%. It is because the mobility of dislocations in the Mo bars is better than that of Mo-La2O3 bars in this condition. As the annealing temperature increases, the transverse ductility of the two kinds of bars is improved gradually; particularly the elongation of Mo-La2O3 bars annealed at 1200 oC for 1 h exceeds 10%, higher than that of pure Mo bars. In the upsetting process, many dislocation cells can be observed in the Mo-La2O3 bars, which disappeared little by little as the annealing temperature increased, and still there were a lot of tangled dislocations in the cells which were pinned by the dispersed La2O3 particles. The improvement of the transverse ductility of Mo-La2O3 bars is relative with the interaction between the La2O3 particles and dislocations. Both the Mo bars and Mo-La2O3 bars have recovery recrystallization process, and similar dislocation structure change
Pure Mo and Mo-La2O3 bars with high transverse ductility were prepared by forging and upsetting. The microstructure and transverse bending properties of both bars were investigated after different annealing treatments. The results show that the pure Mo bars forged and upset by 85% possess good transverse ductility and the elongation reaches 5%, while that of the forged and upset Mo-La2O3 bars is only 2%. It is because the mobility of dislocations in the Mo bars is better than that of Mo-La2O3 bars in this condition. As the annealing temperature increases, the transverse ductility of the two kinds of bars is improved gradually; particularly the elongation of Mo-La2O3 bars annealed at 1200 oC for 1 h exceeds 10%, higher than that of pure Mo bars. In the upsetting process, many dislocation cells can be observed in the Mo-La2O3 bars, which disappeared little by little as the annealing temperature increased, and still there were a lot of tangled dislocations in the cells which were pinned by the dispersed La2O3 particles. The improvement of the transverse ductility of Mo-La2O3 bars is relative with the interaction between the La2O3 particles and dislocations. Both the Mo bars and Mo-La2O3 bars have recovery recrystallization process, and similar dislocation structure change
2010, 39(4):642-646.
Abstract:
Porous Ti-50.8 at%Ni shape memory alloys (SMA) with high porosity were prepared by the powder metallurgical technique, and the microstructure and shape memory behavior of the porous alloys were investigated. The results indicate that the porous alloys prepared by this method exhibit a homogenous pore-space structure with a high open-cell ratio, and the average pore size is about 200 mm. The microstructure is mainly composed of Austenitic NiTi phase (B2) and monoclinic Martensite NiTi (B19’). The cyclic load-unload recovery curves reveal that the porous alloy can exhibit certain shape-memory effect, which decreases with the increase of the porosity
Porous Ti-50.8 at%Ni shape memory alloys (SMA) with high porosity were prepared by the powder metallurgical technique, and the microstructure and shape memory behavior of the porous alloys were investigated. The results indicate that the porous alloys prepared by this method exhibit a homogenous pore-space structure with a high open-cell ratio, and the average pore size is about 200 mm. The microstructure is mainly composed of Austenitic NiTi phase (B2) and monoclinic Martensite NiTi (B19’). The cyclic load-unload recovery curves reveal that the porous alloy can exhibit certain shape-memory effect, which decreases with the increase of the porosity
2010, 39(4):647-651.
Abstract:
Pt-W-Ru-Se catalysts with different Pt contents were fabricated by low-temperature synthesis and their catalysis effect on the oxygen reduction reaction was tested by the rotating-disk-electrode potential sweep method. The microstructure and surface composition of the obtained catalysts were characterized by XRD, EDS and XPS. Results show that Pt can greatly enhance the catalysis activity of W-Ru-Se to oxygen reduction. In particular, Pt-W-Ru-Se with 5% Pt (mass fraction, similarly hereinafter) is the most obvious one, whose catalysis activity to oxygen reduction is superior to that of W-Ru-Se and Pt in 0.5 mol·L-1 H2SO4. Its stability and resistance-methanol is better than that of Pt when there is methanol
Pt-W-Ru-Se catalysts with different Pt contents were fabricated by low-temperature synthesis and their catalysis effect on the oxygen reduction reaction was tested by the rotating-disk-electrode potential sweep method. The microstructure and surface composition of the obtained catalysts were characterized by XRD, EDS and XPS. Results show that Pt can greatly enhance the catalysis activity of W-Ru-Se to oxygen reduction. In particular, Pt-W-Ru-Se with 5% Pt (mass fraction, similarly hereinafter) is the most obvious one, whose catalysis activity to oxygen reduction is superior to that of W-Ru-Se and Pt in 0.5 mol·L-1 H2SO4. Its stability and resistance-methanol is better than that of Pt when there is methanol
Meng Mianwu
,
Ji Xiaomei
,
Liu Qingye
,
Hu Changhua
,
Huang Siyu
,
HuangYing
,
Zhao Yongming
,
Liao Qinhong
,
Kang Caiyan
2010, 39(4):652-655.
Abstract:
he phase structure, the morphology, activation performance and cycle stability of the rare-earth-doped lithium manganese oxygen cathode materials prepared by Pechini process were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and battery testing system. The results show that the prepared LiMn2O4, LiLa0.03Mn1.97O4, LiLa0.012Ce0.012Mn1.976O4, LiLa0.012Nd0.012Mn1.976O4 and LiCe0.012Nd0.012Mn1.976O4 samples are composed of single-phase spinel LiMn2O4 structure only when the content of rare earth is strictly controlled in a certain range. The LiLa0.015Ce0.015Mn1.97O4, LiLa0.015Nd0.015Mn1.97O4 and LiCe0.015Nd0.015Mn1.97O4 specimens consist of the LiMn2O4 and trace CeO2, Nd2O3, CeO2+Nd2O3 phases when the content of the rare earth exceeds the range. The particles of all the specimens are regularly spheroid or near-sphere, and the size of the particles is 0.5-2.8 μm. The initial discharge capacity of the specimens would be decreased, and the ratio of discharge/charge capacity and cyclic stability of the specimens would be increased with the suitable rare earth element doping. The LiCe0.012Nd0.012Mn1.976O4 cathode materials has good comprehensive electrochemical performances whose initial discharge capacity is 123.5 mAh/g, and whose capacity is 113.2 mAh/g after the 30th cycle, 1.27 times as high as that of LiMn2O4 material
he phase structure, the morphology, activation performance and cycle stability of the rare-earth-doped lithium manganese oxygen cathode materials prepared by Pechini process were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and battery testing system. The results show that the prepared LiMn2O4, LiLa0.03Mn1.97O4, LiLa0.012Ce0.012Mn1.976O4, LiLa0.012Nd0.012Mn1.976O4 and LiCe0.012Nd0.012Mn1.976O4 samples are composed of single-phase spinel LiMn2O4 structure only when the content of rare earth is strictly controlled in a certain range. The LiLa0.015Ce0.015Mn1.97O4, LiLa0.015Nd0.015Mn1.97O4 and LiCe0.015Nd0.015Mn1.97O4 specimens consist of the LiMn2O4 and trace CeO2, Nd2O3, CeO2+Nd2O3 phases when the content of the rare earth exceeds the range. The particles of all the specimens are regularly spheroid or near-sphere, and the size of the particles is 0.5-2.8 μm. The initial discharge capacity of the specimens would be decreased, and the ratio of discharge/charge capacity and cyclic stability of the specimens would be increased with the suitable rare earth element doping. The LiCe0.012Nd0.012Mn1.976O4 cathode materials has good comprehensive electrochemical performances whose initial discharge capacity is 123.5 mAh/g, and whose capacity is 113.2 mAh/g after the 30th cycle, 1.27 times as high as that of LiMn2O4 material
2010, 39(4):656-659.
Abstract:
A series of ternary amorphous Ni-Co-B alloys were prepared by a chemical reduction codeposition method with Ni introduction and influence of Ni on electrochemical hydrogen storage property of the amorphous Co-B alloys was investigated. Results show that at a charge/discharge rate of 650 mA/g, the amorphous Ni-Co-B alloy with Ni content of 23.8 at% has a reversible discharge capacity of about 250 mAh/g, 20 mAh/g lower than amorphous Co-B alloy does. Discharge capacity of the two samples keeps almost unchanged after 60 cycles. Nevertheless, the amorphous Ni-Co-B alloy with Ni content of 35.8 at% shows much lower discharge capacity and capacity retention during cycling than amorphous Co-B alloy does under the same condition. However, a positive effect of Ni on electrochemical hydrogen storage of Co-B alloy is also found, i.e. element Ni could suppress H2 evolution on the surface of the amorphous Co-B alloy at a high charge rate and reduce the fluctuation of discharge potential plateau and discharge capacity during cycling. It could be attributed to that Ni decreases electrocatalytic activity for H2O dissociation on the surface and improves hydrogen diffusion rate for amorphous Co-B alloy bulk
A series of ternary amorphous Ni-Co-B alloys were prepared by a chemical reduction codeposition method with Ni introduction and influence of Ni on electrochemical hydrogen storage property of the amorphous Co-B alloys was investigated. Results show that at a charge/discharge rate of 650 mA/g, the amorphous Ni-Co-B alloy with Ni content of 23.8 at% has a reversible discharge capacity of about 250 mAh/g, 20 mAh/g lower than amorphous Co-B alloy does. Discharge capacity of the two samples keeps almost unchanged after 60 cycles. Nevertheless, the amorphous Ni-Co-B alloy with Ni content of 35.8 at% shows much lower discharge capacity and capacity retention during cycling than amorphous Co-B alloy does under the same condition. However, a positive effect of Ni on electrochemical hydrogen storage of Co-B alloy is also found, i.e. element Ni could suppress H2 evolution on the surface of the amorphous Co-B alloy at a high charge rate and reduce the fluctuation of discharge potential plateau and discharge capacity during cycling. It could be attributed to that Ni decreases electrocatalytic activity for H2O dissociation on the surface and improves hydrogen diffusion rate for amorphous Co-B alloy bulk
2010, 39(4):660-663.
Abstract:
The longitudinal thermal expansion characteristics of SiCf/Cu matrix composites without or with Ti6Al4V interlayers were studied, and the microstructures of the specimens after thermal cycles were observed by the scanning electronic microscopy. The results reveal that the interfacial bonding strength between the fiber and the matrix has significant influence on the longitudinal thermal expansion behavior of fiber-enhanced metal-matrix composites. The composites without Ti6Al4V interlayers have unstable thermal expansion behavior and exhibit positive thermal hysteresis behavior after the two continuous thermal cycles due to the interfacial debonding, sliding and expansion of the matrix. While the composites with Ti6Al4V interlayers keep dimensional stable after the two thermal cycles, and their longitudinal coefficients of thermal expansion (CTE) are greatly reduced as well as the fiber/matrix interface keeps stable.
The longitudinal thermal expansion characteristics of SiCf/Cu matrix composites without or with Ti6Al4V interlayers were studied, and the microstructures of the specimens after thermal cycles were observed by the scanning electronic microscopy. The results reveal that the interfacial bonding strength between the fiber and the matrix has significant influence on the longitudinal thermal expansion behavior of fiber-enhanced metal-matrix composites. The composites without Ti6Al4V interlayers have unstable thermal expansion behavior and exhibit positive thermal hysteresis behavior after the two continuous thermal cycles due to the interfacial debonding, sliding and expansion of the matrix. While the composites with Ti6Al4V interlayers keep dimensional stable after the two thermal cycles, and their longitudinal coefficients of thermal expansion (CTE) are greatly reduced as well as the fiber/matrix interface keeps stable.
2010, 39(4):664-667.
Abstract:
The alkaline earth metal magnesium chlorosilicate M7Mg2(SiO4)4C12:0.08Eu2+(M=Ca,Sr,Ba) phosphors activated by Eu2+ were synthesized by high-temperature solid-state reaction, and the luminescence properties of the phosphors were studied. Results show that all the three phosphors have broadband excitation spectra with ranges of 250-500 nm, 250-450 nm, 250-430 nm, respectively. The composition dependence of the radiation transitions of Eu2+ in the host was discussed. The position of emission peak of Eu2+ moved to short-wavelength and the phosphors emit green (507 nm) and blue (458 nm, 445 nm) light with increasing of radius size of Ca, Sr and Ba ions in sequence
The alkaline earth metal magnesium chlorosilicate M7Mg2(SiO4)4C12:0.08Eu2+(M=Ca,Sr,Ba) phosphors activated by Eu2+ were synthesized by high-temperature solid-state reaction, and the luminescence properties of the phosphors were studied. Results show that all the three phosphors have broadband excitation spectra with ranges of 250-500 nm, 250-450 nm, 250-430 nm, respectively. The composition dependence of the radiation transitions of Eu2+ in the host was discussed. The position of emission peak of Eu2+ moved to short-wavelength and the phosphors emit green (507 nm) and blue (458 nm, 445 nm) light with increasing of radius size of Ca, Sr and Ba ions in sequence
2010, 39(4):668-671.
Abstract:
On the basis of the calculation results of Phase Diagram Thermodynamics, the phase diagrams of Mg-6Al-XGd alloy system including vertical section, isothermal section at 200 and 500 oC were calculated using Calphad software Pandat. Five kinds of AM60 alloys with different Gd additions (0wt%, 0.8wt%, 1.2wt%, 1.6wt% and 2.0wt%) were prepared and the microstructures and mechanical properties were investigated. The results show that the grain sizes of the tested alloys are greatly reduced by addition of Gd. The mechanical properties such as ultimate tensile strength (UTS) and elongation (EL) are also improved at room temperature. The alloy containing 1.6wt% Gd exhibits the finest microstructure and best mechanical properties
On the basis of the calculation results of Phase Diagram Thermodynamics, the phase diagrams of Mg-6Al-XGd alloy system including vertical section, isothermal section at 200 and 500 oC were calculated using Calphad software Pandat. Five kinds of AM60 alloys with different Gd additions (0wt%, 0.8wt%, 1.2wt%, 1.6wt% and 2.0wt%) were prepared and the microstructures and mechanical properties were investigated. The results show that the grain sizes of the tested alloys are greatly reduced by addition of Gd. The mechanical properties such as ultimate tensile strength (UTS) and elongation (EL) are also improved at room temperature. The alloy containing 1.6wt% Gd exhibits the finest microstructure and best mechanical properties
Geng Yonghong
,
Guo Yingchun
,
Bi Jun
,
Zhang Jiming
,
Wang Chuanjun
,
Chen Song
,
Guan Weiming
,
Zhang Kunhua
2010, 39(4):670-701.
Abstract:
Ag-20Cu macro-composite wires (volume fraction, %, similarly hereinafter), a new DMMCs(Deformation Metal-Metal Composites), were fabricated by metal clad metal method and post-severe plastic deformation. The mechanical properties of the composite wires were tested at different true strains η, and the size change of the Ag layer and the Cu layer and fracture morphology were observed by SEM. The deformation characteristics of the Ag layer and the Cu layer for the Ag-20Cu composite were studied by the above experiments. The results indicate that the deformation process of the composite mainly contains cooperating deformation between Ag and Cu layers due to their different mechanical properties and the modes of cooperating deformation at different stages are different. Because of work-hardening and recovery to different degrees during deformation, the property change trend of the composite is different and the effects of Ag and Cu layers on the properties of the composites are unlike
Ag-20Cu macro-composite wires (volume fraction, %, similarly hereinafter), a new DMMCs(Deformation Metal-Metal Composites), were fabricated by metal clad metal method and post-severe plastic deformation. The mechanical properties of the composite wires were tested at different true strains η, and the size change of the Ag layer and the Cu layer and fracture morphology were observed by SEM. The deformation characteristics of the Ag layer and the Cu layer for the Ag-20Cu composite were studied by the above experiments. The results indicate that the deformation process of the composite mainly contains cooperating deformation between Ag and Cu layers due to their different mechanical properties and the modes of cooperating deformation at different stages are different. Because of work-hardening and recovery to different degrees during deformation, the property change trend of the composite is different and the effects of Ag and Cu layers on the properties of the composites are unlike
24 Effect of Rare-Earth Y on Microstructure and Mechanical Properties of As-Cast Mg-2.0Zn-0.3Zr Alloy
2010, 39(4):672-677.
Abstract:
The effect of rare earth element Y and its content on the microstructure and mechanical properties of the Mg-2.0Zn-0.3Zr alloy and the mechanism were investigated by adding different contents of Y in the alloy. The results indicate that when the Y content changes from 0.9% to 1.9 % (mass fraction, similarly hereinafter), the microstructure becomes finer obviously and the intercrystalline compound looks like a continuous thin net; while when the Y content increases to 3.7%, the compound shows discontinuous thick net. The strength of the alloy is improved gradually when the Y content increases from 1.9% to 5.8%. The preferable plasticity with a maximal elongation of 24.8% is obtained when the Y content is 0.9%, due to the refinement effect of Y and proper W-phase content. When the Y content is 3.7%, the W-phase is less due to the presence of X-phase, while the intercrystalline compound becomes discontinuous thick net, which are favorable to improving plasticity of the alloy. The alloy with 3.7% Y has better comprehensive mechanical properties than others, with the tensile strength of 232 MPa, the yield strength of 124 MPa and the elongation of 23.5%. The Y element addition can lead to an increase of the flow stress and the deformation resistance of the alloy; annealing at 420 oC for 12 h and hot deformation at 450 oC can improve the extrudability and better comprehensive mechanical properties for the alloy can be obtained
The effect of rare earth element Y and its content on the microstructure and mechanical properties of the Mg-2.0Zn-0.3Zr alloy and the mechanism were investigated by adding different contents of Y in the alloy. The results indicate that when the Y content changes from 0.9% to 1.9 % (mass fraction, similarly hereinafter), the microstructure becomes finer obviously and the intercrystalline compound looks like a continuous thin net; while when the Y content increases to 3.7%, the compound shows discontinuous thick net. The strength of the alloy is improved gradually when the Y content increases from 1.9% to 5.8%. The preferable plasticity with a maximal elongation of 24.8% is obtained when the Y content is 0.9%, due to the refinement effect of Y and proper W-phase content. When the Y content is 3.7%, the W-phase is less due to the presence of X-phase, while the intercrystalline compound becomes discontinuous thick net, which are favorable to improving plasticity of the alloy. The alloy with 3.7% Y has better comprehensive mechanical properties than others, with the tensile strength of 232 MPa, the yield strength of 124 MPa and the elongation of 23.5%. The Y element addition can lead to an increase of the flow stress and the deformation resistance of the alloy; annealing at 420 oC for 12 h and hot deformation at 450 oC can improve the extrudability and better comprehensive mechanical properties for the alloy can be obtained
2010, 39(4):678-681.
Abstract:
A new β-type alloy Ti30Nb5Ta6Zr for dental implant with low Young’s modulus, medium-high tensile strength, good plasticity and biocompatibility was designed according to β coefficient of stabilization kβ and d-electron theory. The change of microstructures and mechanical properties for the alloy after solution treatment followed by aging in β phase region was investigated. It is found that the alloy is composed of metastable β phase after solution treatment in β phase region; ω phase precipitates when aged at low temperature, while α phase precipitates gradually when the aging temperature increases. With the aging temperature increasing, the strength and Young’s modulus of the alloy increase first and then decrease, while the elongation of the alloy decreases first and then increases. The alloy after 800 oC, 30 min solution treatment and 500 oC, 12 h aging possesses excellent integrated mechanical properties and can meet the requirement for dental implant
A new β-type alloy Ti30Nb5Ta6Zr for dental implant with low Young’s modulus, medium-high tensile strength, good plasticity and biocompatibility was designed according to β coefficient of stabilization kβ and d-electron theory. The change of microstructures and mechanical properties for the alloy after solution treatment followed by aging in β phase region was investigated. It is found that the alloy is composed of metastable β phase after solution treatment in β phase region; ω phase precipitates when aged at low temperature, while α phase precipitates gradually when the aging temperature increases. With the aging temperature increasing, the strength and Young’s modulus of the alloy increase first and then decrease, while the elongation of the alloy decreases first and then increases. The alloy after 800 oC, 30 min solution treatment and 500 oC, 12 h aging possesses excellent integrated mechanical properties and can meet the requirement for dental implant
26 Crystallization Process of Nanocrystalline (FeCo)78Nb6B15Cu1 Alloy and Its Magnetic Characterization
2010, 39(4):682-686.
Abstract:
(FeCo)78Nb6B15Cu1 amorphous ribbons were prepared by a melt-quenching method; crystallization characteristics of the ribbons were tested by DSC, and accordingly annealing at 400, 500, 700 and 750 oC for 1 h were carried out. Crystallization behavior of the ribbons at different annealing temperatures was analyzed by XRD and SEM and the static magnetic parameters of the ribbon and the powder were measured by VSM. The results show that for the Hitperm alloy with a fixed composition, a suitable annealing temperature can control the grain size and phase ratio and adjust disorder magnetic moment of the grain surface, thereby improving the specific saturation magnetization of material. Moreover, the small nano-grain is favorable for depressing the coercivity. Due to the introduction of ultracrystallite when quenching, there is crystallization on the surface of the ribbon, which will worsen the static magnetic properties of materials to a certain extent
(FeCo)78Nb6B15Cu1 amorphous ribbons were prepared by a melt-quenching method; crystallization characteristics of the ribbons were tested by DSC, and accordingly annealing at 400, 500, 700 and 750 oC for 1 h were carried out. Crystallization behavior of the ribbons at different annealing temperatures was analyzed by XRD and SEM and the static magnetic parameters of the ribbon and the powder were measured by VSM. The results show that for the Hitperm alloy with a fixed composition, a suitable annealing temperature can control the grain size and phase ratio and adjust disorder magnetic moment of the grain surface, thereby improving the specific saturation magnetization of material. Moreover, the small nano-grain is favorable for depressing the coercivity. Due to the introduction of ultracrystallite when quenching, there is crystallization on the surface of the ribbon, which will worsen the static magnetic properties of materials to a certain extent
2010, 39(4):687-691.
Abstract:
Nanostructured Ti/IrO2-Ta2O5-SnO2 oxide anodes with different Sn content were prepared by Pechini method. The surface morphology and microstructure were analyzed by SEM, EDX and XRD. The electrochemical activity and stability were investigated by electrochemical testing including oxygen evolving potential measurement, cyclic voltammetry, and accelerated life test. The results indicate that the oxide coatings are composed of (IrSn)O2 solid solution and amorphous Ta2O5, with the composition close to the nominal one. With the increase of Sn content, more microcracks appear on the anode surface. The addition of Sn into the IrO2-Ta2O5-SnO2 oxide coating increases the oxygen evolving potential and lowers the electrochemical stability
Nanostructured Ti/IrO2-Ta2O5-SnO2 oxide anodes with different Sn content were prepared by Pechini method. The surface morphology and microstructure were analyzed by SEM, EDX and XRD. The electrochemical activity and stability were investigated by electrochemical testing including oxygen evolving potential measurement, cyclic voltammetry, and accelerated life test. The results indicate that the oxide coatings are composed of (IrSn)O2 solid solution and amorphous Ta2O5, with the composition close to the nominal one. With the increase of Sn content, more microcracks appear on the anode surface. The addition of Sn into the IrO2-Ta2O5-SnO2 oxide coating increases the oxygen evolving potential and lowers the electrochemical stability
2010, 39(4):692-696.
Abstract:
The activity of Au catalyst supported by activated carbon (Au/AC) for decomposition of low-level ozone was evaluated. The influence of preparation conditions such as pH value of precursor solution, drying mode and calcining temperature on the catalytic activity was studied, and the ozone removal ratio was tested under different space velocity at ambient temperature. The results show that the procedure of controlling the precursor pH=10, drying catalysts by microwave and being reduced at 200℃ with H2 can improve the dispersion of gold particle, decrease particle sizes and significantly enhance the activity of Au/AC for ozone decomposition. When the catalytic activity test was carried out under the condition of 50 mg/m3 ozone in air, relative humidity 45%, space velocity 72 000 h-1 and ambient temperature, the ozone removal ratio could be maintained above 90% (within 2400 min). The results of N2 adsorption-desorption and XPS show that, after the reaction with ozone the specific surface area and pore volume of Au/AC decrease slightly; Au/AC remains active although the spectrum peaks of Au4f shift toward higher. Furthermore, the fact that C content decreased notably while O increased, reveals that the Au supported on AC is concerned with the catalytic reaction and can concurrently promote another reaction between ozone and graphitic C
The activity of Au catalyst supported by activated carbon (Au/AC) for decomposition of low-level ozone was evaluated. The influence of preparation conditions such as pH value of precursor solution, drying mode and calcining temperature on the catalytic activity was studied, and the ozone removal ratio was tested under different space velocity at ambient temperature. The results show that the procedure of controlling the precursor pH=10, drying catalysts by microwave and being reduced at 200℃ with H2 can improve the dispersion of gold particle, decrease particle sizes and significantly enhance the activity of Au/AC for ozone decomposition. When the catalytic activity test was carried out under the condition of 50 mg/m3 ozone in air, relative humidity 45%, space velocity 72 000 h-1 and ambient temperature, the ozone removal ratio could be maintained above 90% (within 2400 min). The results of N2 adsorption-desorption and XPS show that, after the reaction with ozone the specific surface area and pore volume of Au/AC decrease slightly; Au/AC remains active although the spectrum peaks of Au4f shift toward higher. Furthermore, the fact that C content decreased notably while O increased, reveals that the Au supported on AC is concerned with the catalytic reaction and can concurrently promote another reaction between ozone and graphitic C
2010, 39(4):702-706.
Abstract:
Amorphous MgNi hydrogen storage alloy was synthesized by mechanically alloying (MA) with the proper milling parameters. The mechanism of amorphous formation by milling was discussed. The surface morphology and phases were analyzed by SEM and XRD. The effect of different parameters such as the mass ratio of ball to powder, the number and size of the balls, and the milling rate and time on electrochemical properties was tested. The maximum discharge capacity of the prepared amorphous MgNi alloy electrode was 450 mAh/g, but the capacity deteriorated fast
Amorphous MgNi hydrogen storage alloy was synthesized by mechanically alloying (MA) with the proper milling parameters. The mechanism of amorphous formation by milling was discussed. The surface morphology and phases were analyzed by SEM and XRD. The effect of different parameters such as the mass ratio of ball to powder, the number and size of the balls, and the milling rate and time on electrochemical properties was tested. The maximum discharge capacity of the prepared amorphous MgNi alloy electrode was 450 mAh/g, but the capacity deteriorated fast
2010, 39(4):707-710.
Abstract:
Epitaxial DyBa2Cu3O7-x(DyBCO) superconductive thin film was fabricated via a F-free metal organic deposition (MOD) method on the (00l) single crystal substrate of LaAlO3. Because of the fluorine-free metal organic system, harmful gas by the normal TFA-MOD approach was avoided during the heat treatment. A high temperature treatment was introduced during the growth of DyBCO film and then the SEM observation shows denser microstructure and better texture of the film. X-ray diffraction pattern reveals the c-axis oriented grains. φ-scan also shows an excellent in-plane texture in the DyBCO film with a high temperature treatment. The DyBCO film fabricated by F-free MOD with a high temperature treatment has a superconductivity transition temperature of 92 K and a critical current density of 1.8 MA/cm2 at 77 K in self-field
Epitaxial DyBa2Cu3O7-x(DyBCO) superconductive thin film was fabricated via a F-free metal organic deposition (MOD) method on the (00l) single crystal substrate of LaAlO3. Because of the fluorine-free metal organic system, harmful gas by the normal TFA-MOD approach was avoided during the heat treatment. A high temperature treatment was introduced during the growth of DyBCO film and then the SEM observation shows denser microstructure and better texture of the film. X-ray diffraction pattern reveals the c-axis oriented grains. φ-scan also shows an excellent in-plane texture in the DyBCO film with a high temperature treatment. The DyBCO film fabricated by F-free MOD with a high temperature treatment has a superconductivity transition temperature of 92 K and a critical current density of 1.8 MA/cm2 at 77 K in self-field
2010, 39(4):711-714.
Abstract:
Gold single-crystal nanobelts were synthesized by a nitric-acid-induced seed-mediated growth method. The morphologies and structures of the products were characterized by TEM and HRTEM; the absorption property was analyzed by UV-vis spectrum. TEM observation shows that nanobelts are dominant morphology with perfect fcc single-crystal structure and there are some nanoplates and nanoparticles. The UV-vis spectra reveal a strong longitudinal surface plasma resonance (SPR) band and a weak transverse SPR band centered at ~975 nm and ~550 nm, respectively. The growth mechanism of the nanobelts is the self-assembly of the adjacent nanoplates through surface dipole-dipole interaction with nitric acid induction
Gold single-crystal nanobelts were synthesized by a nitric-acid-induced seed-mediated growth method. The morphologies and structures of the products were characterized by TEM and HRTEM; the absorption property was analyzed by UV-vis spectrum. TEM observation shows that nanobelts are dominant morphology with perfect fcc single-crystal structure and there are some nanoplates and nanoparticles. The UV-vis spectra reveal a strong longitudinal surface plasma resonance (SPR) band and a weak transverse SPR band centered at ~975 nm and ~550 nm, respectively. The growth mechanism of the nanobelts is the self-assembly of the adjacent nanoplates through surface dipole-dipole interaction with nitric acid induction
2010, 39(4):715-718.
Abstract:
he vacuum infiltration casting technique was adopted to prepare high-Cr white cast iron based composites with particle-reinforced wear resistant layer. The composition and phases of the interface were analyzed by means of XRD, EDX, etc. The WC-TiC-Co particles distribute uniformly in the composite layer of the material. The casting technique ensures metallurgical bonding of the interface between the high-Cr white cast iron and the particles. Owing to partial dissolution of the WC-TiC-Co particles and the interdiffusion of elements such as W, C, Ti, Co, Fe and Cr, compounds containing Fe, W and Co were formed in the interface region of composites. Finally, wear resistance of the composites was studied
he vacuum infiltration casting technique was adopted to prepare high-Cr white cast iron based composites with particle-reinforced wear resistant layer. The composition and phases of the interface were analyzed by means of XRD, EDX, etc. The WC-TiC-Co particles distribute uniformly in the composite layer of the material. The casting technique ensures metallurgical bonding of the interface between the high-Cr white cast iron and the particles. Owing to partial dissolution of the WC-TiC-Co particles and the interdiffusion of elements such as W, C, Ti, Co, Fe and Cr, compounds containing Fe, W and Co were formed in the interface region of composites. Finally, wear resistance of the composites was studied
2010, 39(4):719-722.
Abstract:
Effect of minor Sc, Zr and Ti co-addition and Mg content on the microstructure and Brinell hardness of Al-Mg alloys was investigated by means of Brinell hardness tester, optical microscope, SEM and TEM. Results show that the grain size of the as-cast alloys was refined by the addition of Sc and Zr, and it can be further refined by the addition of Ti. With the same Sc, Zr and Ti content, the increase of Mg content is beneficial to the refinement of microstructure, which is due to the solid solution strengthening of Mg in α-Al. The refined microstructures of the as-cast alloys were favorable for the improvement of the Brinell hardness. After homogenization annealing treatment of Al-10Mg-Sc-Zr-Ti, the Brinell hardness of alloys increased by 10% owing to second precipitations of Al3(Sc1-xZrx), Al3(Sc1-xTix) and Al3(Sc1-x-yZrxTiy), increased dispersity and more homogeneous distribution
Effect of minor Sc, Zr and Ti co-addition and Mg content on the microstructure and Brinell hardness of Al-Mg alloys was investigated by means of Brinell hardness tester, optical microscope, SEM and TEM. Results show that the grain size of the as-cast alloys was refined by the addition of Sc and Zr, and it can be further refined by the addition of Ti. With the same Sc, Zr and Ti content, the increase of Mg content is beneficial to the refinement of microstructure, which is due to the solid solution strengthening of Mg in α-Al. The refined microstructures of the as-cast alloys were favorable for the improvement of the Brinell hardness. After homogenization annealing treatment of Al-10Mg-Sc-Zr-Ti, the Brinell hardness of alloys increased by 10% owing to second precipitations of Al3(Sc1-xZrx), Al3(Sc1-xTix) and Al3(Sc1-x-yZrxTiy), increased dispersity and more homogeneous distribution
2010, 39(4):723-726.
Abstract:
Microstructure and properties of a near β titanium alloy after different heat treatments were studied. The results show that different match of strength and plasticity can be obtained by different heat treatments. After α+β solution and aging treatment, excellent strength (ultimate tensile strength of 1200-1500 MPa) and plasticity can be achieved. The mechanical property of the alloy is mainly controlled by the shape of primary α. The alloy also has the aging characteristics of common near-β titanium alloy, i.e. its strength decreases and plasticity increases with aging temperature rising
Microstructure and properties of a near β titanium alloy after different heat treatments were studied. The results show that different match of strength and plasticity can be obtained by different heat treatments. After α+β solution and aging treatment, excellent strength (ultimate tensile strength of 1200-1500 MPa) and plasticity can be achieved. The mechanical property of the alloy is mainly controlled by the shape of primary α. The alloy also has the aging characteristics of common near-β titanium alloy, i.e. its strength decreases and plasticity increases with aging temperature rising
2010, 39(4):727-730.
Abstract:
Fe(NO3)3·9H2O and Sr(NO3)2 were used as starting materials to form sol in the water solvent and then the sol formed gel on the surface of the absorbent cotton template. The strontium ferrite micropipe was prepared by calcining the gel. The SrLaxFe12-xO19(x=0-0.3) micropipe sample with excellent magnetic properties was obtained by doping La. The microstructure, morphology and magnetic properties of the sample were characterized by XRD, SEM and VSM. Results show that the morphology of the La-doped strontium ferrite remained the organism morphology of cotton fiber on the whole. The external diameter of the micropipe was between 8 μm and 13 μm, and the wall thickness was between 0.5 μm and 1 μm. When the calcining temperature was constant, the coercive force and the saturation magnetization of the sample increased first, and then decreased with the increase of x value. But the change of the saturation magnetization lagged the coercive force
Fe(NO3)3·9H2O and Sr(NO3)2 were used as starting materials to form sol in the water solvent and then the sol formed gel on the surface of the absorbent cotton template. The strontium ferrite micropipe was prepared by calcining the gel. The SrLaxFe12-xO19(x=0-0.3) micropipe sample with excellent magnetic properties was obtained by doping La. The microstructure, morphology and magnetic properties of the sample were characterized by XRD, SEM and VSM. Results show that the morphology of the La-doped strontium ferrite remained the organism morphology of cotton fiber on the whole. The external diameter of the micropipe was between 8 μm and 13 μm, and the wall thickness was between 0.5 μm and 1 μm. When the calcining temperature was constant, the coercive force and the saturation magnetization of the sample increased first, and then decreased with the increase of x value. But the change of the saturation magnetization lagged the coercive force
2010, 39(4):731-734.
Abstract:
The electromagnetic interfering (EMI) shielding properties of open-pore Fe-Ni foams prepared by a patented technique in the frequency range from 0.03 MHz to 1500 MHz was investigated using a coaxial cable method. The results indicate that the open-pore Fe-Ni foams exhibit high shielding effectiveness (SE) between 60 dB and 85 dB in the whole frequency range, but the SE value of the foams is similar to that of aluminum alloy sheets in the frequency range from 0.03 MHz to 400 MHz. Moreover, the SE value of open-pore Fe-Ni foams is determined by the foam structure such as pore size and porosity. The SE value increases significantly with the open-pore size and porosity decreasing. However, the porosity change influences the SE value less than other factors when the pore size and thickness is certain
The electromagnetic interfering (EMI) shielding properties of open-pore Fe-Ni foams prepared by a patented technique in the frequency range from 0.03 MHz to 1500 MHz was investigated using a coaxial cable method. The results indicate that the open-pore Fe-Ni foams exhibit high shielding effectiveness (SE) between 60 dB and 85 dB in the whole frequency range, but the SE value of the foams is similar to that of aluminum alloy sheets in the frequency range from 0.03 MHz to 400 MHz. Moreover, the SE value of open-pore Fe-Ni foams is determined by the foam structure such as pore size and porosity. The SE value increases significantly with the open-pore size and porosity decreasing. However, the porosity change influences the SE value less than other factors when the pore size and thickness is certain
2010, 39(4):735-738.
Abstract:
Pr0.3TbxDy0.7-xFe1.9Ti0.1(x=0.18-0.21) alloys were prepared by arc melting and then the samples were annealed under different conditions. Their magnetostriction was studied. The results indicate that the second phase exists in all samples before annealing and greatly influences the magnetostriction of samples. The second phase cannot be eliminated and the magnetostriction can not be improved by 700 oC, 6 d annealing. However, the second phase can be efficiently eliminated by 900 oC, 3 d annealing. In particular, for the sample of Pr0.3Tb0.21Dy0.49Fe1.9Ti0.1, the pure cubic Laves phase with MgCu2-type structure was obtained and its magnetization and magnetostriction coefficient increased. It has a high magnetostriction coefficient of about 1.12×10-3 at 900 kA/m
Pr0.3TbxDy0.7-xFe1.9Ti0.1(x=0.18-0.21) alloys were prepared by arc melting and then the samples were annealed under different conditions. Their magnetostriction was studied. The results indicate that the second phase exists in all samples before annealing and greatly influences the magnetostriction of samples. The second phase cannot be eliminated and the magnetostriction can not be improved by 700 oC, 6 d annealing. However, the second phase can be efficiently eliminated by 900 oC, 3 d annealing. In particular, for the sample of Pr0.3Tb0.21Dy0.49Fe1.9Ti0.1, the pure cubic Laves phase with MgCu2-type structure was obtained and its magnetization and magnetostriction coefficient increased. It has a high magnetostriction coefficient of about 1.12×10-3 at 900 kA/m
2010, 39(4):739-742.
Abstract:
The ceramic coatings on Zr-4 alloy were prepared by micro-arc oxidation in phosphate electrolyte system and silicate electrolyte system respectively. The microstructure, the phase composition and the wear resistance of the ceramic coatings in different electrolyte systems were compared. The results indicate that for the ceramic coating prepared in the phosphate electrolyte, it has thicker dense layers, about 2/3 of the whole layers, than that prepared in the silicate electrolyte; its surface micro-morphology shows typically volcano-shape character, rougher than that prepared in the silicate, but the hole is fewer, and the inner layer is compacter. The ceramic coatings in both electrolyte systems are mainly composed of t-ZrO2 and m-ZrO2, but the mass fraction of m-ZrO2 is higher in phosphate electrolyte and there may be a few zirconium silicate in the outside of the coating in the silicate electrolyte. After the micro-arc oxidation treatment, the wear-resistance of zirconium alloy has a large increase and the wear-resistance of the coating prepared in the phosphate electrolyte is superior to that prepared in the silicate electrolyte
The ceramic coatings on Zr-4 alloy were prepared by micro-arc oxidation in phosphate electrolyte system and silicate electrolyte system respectively. The microstructure, the phase composition and the wear resistance of the ceramic coatings in different electrolyte systems were compared. The results indicate that for the ceramic coating prepared in the phosphate electrolyte, it has thicker dense layers, about 2/3 of the whole layers, than that prepared in the silicate electrolyte; its surface micro-morphology shows typically volcano-shape character, rougher than that prepared in the silicate, but the hole is fewer, and the inner layer is compacter. The ceramic coatings in both electrolyte systems are mainly composed of t-ZrO2 and m-ZrO2, but the mass fraction of m-ZrO2 is higher in phosphate electrolyte and there may be a few zirconium silicate in the outside of the coating in the silicate electrolyte. After the micro-arc oxidation treatment, the wear-resistance of zirconium alloy has a large increase and the wear-resistance of the coating prepared in the phosphate electrolyte is superior to that prepared in the silicate electrolyte
2010, 39(4):743-746.
Abstract:
Bi2Sb3Cex and Bi2Sb3Ndx alloy films were prepared by PRC method (Pulse Reverse Current) in carbamide-NaBr-KBr-methanamide system. Their chemical composition was determined by EDS and the crystalline structure was analyzed by XRD. Under the optimal processing condition, there is a maximum filling quantity of the REE and the alloy films are composed of Bi2Sb3Ce2 and Bi2Sb3Nd0.1, which are rhombic hexahedral BiSb and tetrahedral cubic monoplasmatic Ce and Nd. The conductivity of Bi-Sb semiconductor pyroelectric materials stuffed by different REEs was also discussed
Bi2Sb3Cex and Bi2Sb3Ndx alloy films were prepared by PRC method (Pulse Reverse Current) in carbamide-NaBr-KBr-methanamide system. Their chemical composition was determined by EDS and the crystalline structure was analyzed by XRD. Under the optimal processing condition, there is a maximum filling quantity of the REE and the alloy films are composed of Bi2Sb3Ce2 and Bi2Sb3Nd0.1, which are rhombic hexahedral BiSb and tetrahedral cubic monoplasmatic Ce and Nd. The conductivity of Bi-Sb semiconductor pyroelectric materials stuffed by different REEs was also discussed
2010, 39(4):747-749.
Abstract:
The electrochemical corrosion properties of welded joints of H65 brass alloy by friction stir welding and manual arc welding were studied by measuring open potentials and polarization curves in 3.5% NaCl solution. The result shows that the corrosion resistance of the friction stir welded joint is better than that of manual arc welded joint, because microstructural refinement, homogenization and densification reduced the electrochemical heterogeneity of grains and grain boundaries. The tensile stress between the dezincification layer and substrate has great effect on the corrosion resistance of the manual arc welded joint
The electrochemical corrosion properties of welded joints of H65 brass alloy by friction stir welding and manual arc welding were studied by measuring open potentials and polarization curves in 3.5% NaCl solution. The result shows that the corrosion resistance of the friction stir welded joint is better than that of manual arc welded joint, because microstructural refinement, homogenization and densification reduced the electrochemical heterogeneity of grains and grain boundaries. The tensile stress between the dezincification layer and substrate has great effect on the corrosion resistance of the manual arc welded joint
2010, 39(4):750-752.
Abstract:
W-TiC alloys were prepared by means of the mechanical alloying method and their main physical properties were tested. It is found that TiC particle introduction can strengthen the grain boundary notably and enhance the mechanical properties of the alloys. Particularly, the relative density, flexural strength, Vickers microhardness and elastic modulus of W-1wt%TiC alloy is 98.4%, 1065 MPa, 4.33 and 396 GPa, respectively. Meanwhile, the electron-beam heat-flux test show that TiC particles can effectively improve the heat flux properties of W-TiC alloy below the re-crystallization temperature; however, when the alloy is used above the re-crystallization temperature due to the higher grain strain energy, the effect is not notable. Therefore, the results indicate W-1wt%TiC is the suitable plasma facing material as the heat flux material below the re-crystallization temperature
W-TiC alloys were prepared by means of the mechanical alloying method and their main physical properties were tested. It is found that TiC particle introduction can strengthen the grain boundary notably and enhance the mechanical properties of the alloys. Particularly, the relative density, flexural strength, Vickers microhardness and elastic modulus of W-1wt%TiC alloy is 98.4%, 1065 MPa, 4.33 and 396 GPa, respectively. Meanwhile, the electron-beam heat-flux test show that TiC particles can effectively improve the heat flux properties of W-TiC alloy below the re-crystallization temperature; however, when the alloy is used above the re-crystallization temperature due to the higher grain strain energy, the effect is not notable. Therefore, the results indicate W-1wt%TiC is the suitable plasma facing material as the heat flux material below the re-crystallization temperature
2010, 39(4):608-612.
Abstract:
The effects of hot working parameters on flow stress and microstructure of GH864 superalloy were studied by isothermal compressive deformation at deformation temperatures from 1000 to 1160 oC, strain rates of 1 and 10 s-1 and engineering strain of 30%, 50% and 70%. The results show that the deformation temperature has great influence on the ultimate as-heat treated grain size and morphology of carbides on grain boundary. When the temperature is below the γ′ precipitation temperature, the dynamic recrystallization capability is bad. While when the temperature is high enough to resolve MC carbides, severely duplex grain structure and feather-like carbide around smaller grains can be easily formed because of the non-uniform pinning effect of re-precipitated fine MC particles on grain boundary, and all these unfavorable characteristics can be partially eliminated by improving hot deformed structure through increasing strain and decreasing strain rate. The ideal deformation temperature should be confined between γ′ precipitation temperature and dissolution of MC carbide
The effects of hot working parameters on flow stress and microstructure of GH864 superalloy were studied by isothermal compressive deformation at deformation temperatures from 1000 to 1160 oC, strain rates of 1 and 10 s-1 and engineering strain of 30%, 50% and 70%. The results show that the deformation temperature has great influence on the ultimate as-heat treated grain size and morphology of carbides on grain boundary. When the temperature is below the γ′ precipitation temperature, the dynamic recrystallization capability is bad. While when the temperature is high enough to resolve MC carbides, severely duplex grain structure and feather-like carbide around smaller grains can be easily formed because of the non-uniform pinning effect of re-precipitated fine MC particles on grain boundary, and all these unfavorable characteristics can be partially eliminated by improving hot deformed structure through increasing strain and decreasing strain rate. The ideal deformation temperature should be confined between γ′ precipitation temperature and dissolution of MC carbide
