Volume 39,Issue 6,2010 Table of Contents
2010, 39(6).
Abstract:
The electrodeposited nanocrystalline (nc) Ni with an average grain size of 27.2 nm and with a broad grain size distribution (BGSD) ranging from 5 to 120 nm was prepared. The tensile strain rate () jump test was performed at room temperature to measure the strain rate sensitivity (m). The result shows that m increases with decreasing of . In particular, when is less than 2×10-5 s-1, m increases rapidly which reaches 0.054 at =5×10-6 s-1, indicating that the deformation mechanisms involved in grain boundary diffusion and sliding are possibly activated. The room temperature loading-unloading tensile test was carried out. The results show that the capability of storing dislocations in BGSD nc Ni is very limited and the dislocation density is saturated when the stress reaches 1052 MPa with a strain of 7.8%. From the observation of TEM microstructures in the vicinity of tensile fracture, it is confirmed that there is significant intragranular dislocation sliding similar to that in coarse-grained materials in the process of plastic deformation of BGSD nc Ni
The electrodeposited nanocrystalline (nc) Ni with an average grain size of 27.2 nm and with a broad grain size distribution (BGSD) ranging from 5 to 120 nm was prepared. The tensile strain rate () jump test was performed at room temperature to measure the strain rate sensitivity (m). The result shows that m increases with decreasing of . In particular, when is less than 2×10-5 s-1, m increases rapidly which reaches 0.054 at =5×10-6 s-1, indicating that the deformation mechanisms involved in grain boundary diffusion and sliding are possibly activated. The room temperature loading-unloading tensile test was carried out. The results show that the capability of storing dislocations in BGSD nc Ni is very limited and the dislocation density is saturated when the stress reaches 1052 MPa with a strain of 7.8%. From the observation of TEM microstructures in the vicinity of tensile fracture, it is confirmed that there is significant intragranular dislocation sliding similar to that in coarse-grained materials in the process of plastic deformation of BGSD nc Ni
2010, 39(6):941-944.
Abstract:
Transmission electron microscopy (TEM) specimens of Zr-based metallic glasses were prepared from amorphous ribbons. Shear bands produced by bending these specimens were located by TEM. High resolution transmission electron microscopy analysis indicates the existence of nanoscale void-like defects and high-density areas in shear bands. The formation of these defects is believed resulting from the evolution of stress-activated free volumes during the mechanical loading and the removal of external stress, which can be understood by comparing the stress-induced processes in shear bands in analogy with the thermal annealing effects on similar metallic glasses
Transmission electron microscopy (TEM) specimens of Zr-based metallic glasses were prepared from amorphous ribbons. Shear bands produced by bending these specimens were located by TEM. High resolution transmission electron microscopy analysis indicates the existence of nanoscale void-like defects and high-density areas in shear bands. The formation of these defects is believed resulting from the evolution of stress-activated free volumes during the mechanical loading and the removal of external stress, which can be understood by comparing the stress-induced processes in shear bands in analogy with the thermal annealing effects on similar metallic glasses
2010, 39(6):945-948.
Abstract:
Gold-nickel alloy was synthesized by arc-melted process. The electro-oxidation of formic acid of Au-Ni alloy was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results were compared with those at a polycrystalline gold electrode surface. It is found that Au-Ni alloy is catalytically more active than pure gold according to the comparison of the main peak potential and current density
Gold-nickel alloy was synthesized by arc-melted process. The electro-oxidation of formic acid of Au-Ni alloy was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results were compared with those at a polycrystalline gold electrode surface. It is found that Au-Ni alloy is catalytically more active than pure gold according to the comparison of the main peak potential and current density
2010, 39(6):949-952.
Abstract:
Fe/Pd magnetic films were prepared by vacuum arc ion plating technology on 316L stainless steel vascular stents. The surface morphology, the surface roughness and the magnetism of coated stents were characterized by laser scanning confocal microscope and digital magnetic flux and field measuring instruments, while the biological effects of the Fe/Pd coated magnetic stents were evaluated through animals experiment. The results show that the Fe/Pd coated magnetic stents, which are smooth and which have good biological compatibility, significantly promote vascular endothelium regeneration, and inhibit tunica intima thickening and vascular wall inflammatory
Fe/Pd magnetic films were prepared by vacuum arc ion plating technology on 316L stainless steel vascular stents. The surface morphology, the surface roughness and the magnetism of coated stents were characterized by laser scanning confocal microscope and digital magnetic flux and field measuring instruments, while the biological effects of the Fe/Pd coated magnetic stents were evaluated through animals experiment. The results show that the Fe/Pd coated magnetic stents, which are smooth and which have good biological compatibility, significantly promote vascular endothelium regeneration, and inhibit tunica intima thickening and vascular wall inflammatory
2010, 39(6):958-962.
Abstract:
Influences of amorphous film formation on the growth of nanocrystalline Ag during replacement reactions were investigated. Amorphous films with a thickness of 5-10 nm were observed by HRTEM on the growth tip of Ag nanopaticles. The growth of Ag nanocrytallines depends on the in situ crystallization of amorphous films. Both in situ nucleation of crystalline Ag in amorphous films and without nucleation can take place. The stability of amorphous films depends on the concentration of AgNO3 solution. In 80 mmol·L-1 or lower AgNO3 solution, amorphous films can exist stably, while in 400 mmol·L-1 AgNO3 solution no amorphous films can be detected
Influences of amorphous film formation on the growth of nanocrystalline Ag during replacement reactions were investigated. Amorphous films with a thickness of 5-10 nm were observed by HRTEM on the growth tip of Ag nanopaticles. The growth of Ag nanocrytallines depends on the in situ crystallization of amorphous films. Both in situ nucleation of crystalline Ag in amorphous films and without nucleation can take place. The stability of amorphous films depends on the concentration of AgNO3 solution. In 80 mmol·L-1 or lower AgNO3 solution, amorphous films can exist stably, while in 400 mmol·L-1 AgNO3 solution no amorphous films can be detected
2010, 39(6):963-968.
Abstract:
With the introduction of high by-pass turbofan engines into both commercial and military aircraft industries, the fabrication of large size fan blade through superplastic forming/diffusion bonding (SPF/DB) has become a pivotal technique of turbine fan engine. There are three key steps to form a hollow blade: twisting, hot forming and SPF. In this study, a three dimensional finite element method (FEM) model is established to simulate the forming process of titanium fan blade, in which the mechanical behavior of TC4 obeys Backofen’s equation. Based on the numerical modeling, the influences of key factors such as the twisting rate, descending velocity, frictional coefficient, strain rate, the sheet thickness ratio of core sheet to face sheet on the forming force were studied. The results show that with increasing of the twisting rate, descending velocity, strain rate, the sheet thickness ratio of core sheet to face sheet, the forming forces increase; however the frictional coefficient has little influence on the forming force
With the introduction of high by-pass turbofan engines into both commercial and military aircraft industries, the fabrication of large size fan blade through superplastic forming/diffusion bonding (SPF/DB) has become a pivotal technique of turbine fan engine. There are three key steps to form a hollow blade: twisting, hot forming and SPF. In this study, a three dimensional finite element method (FEM) model is established to simulate the forming process of titanium fan blade, in which the mechanical behavior of TC4 obeys Backofen’s equation. Based on the numerical modeling, the influences of key factors such as the twisting rate, descending velocity, frictional coefficient, strain rate, the sheet thickness ratio of core sheet to face sheet on the forming force were studied. The results show that with increasing of the twisting rate, descending velocity, strain rate, the sheet thickness ratio of core sheet to face sheet, the forming forces increase; however the frictional coefficient has little influence on the forming force
2010, 39(6):969-974.
Abstract:
The dehydrogenating properties of MgH2 systems were improved by the addition of metal fluorides as the catalyst; the energy of substitution for the Mg atom, the Mg vacancy formation energy, the energy to remove H atoms and electronic structure change of MgH2 systems were calculated by Dmol4.1 program based on the density functional theory. The mechanism of improvement of dehydrogenating properties of MgH2 systems by the addition of metal fluorides was discussed. The results show that the Mg vacancy formation energy is significantly higher than that of Fe, Ti, Zr, V, Ni, Nb, Cr or Cu substitution, which means that the substitution of these elements at the Mg site is more favorable for dehydrogenation of MgH2 system than the Mg vacancy formation at lower temperatures. NiF2, NbF5 and ZrF4 all benefit for the dehydrogenation of MgH2 systems, and the calculation results of improvement of the dehydrogenating properties of MgH2 systems are in agreement with experimental results. The Ni, Nb and Zr atoms replace a Mg atom of MgH2 systems respectively, the corresponding reactions of NiF2+3MgH2=MgF2+Mg2NiH4, 2NbF5+5MgH2=5MgF2+2NbH+4H2 and ZrF4+2MgH2=2MgF2+ZrH2 are accelerated; therefore, MgH2 with the higher stability can be changed into the other hydrides, such as Mg2NiH4, NbH and ZrH2. Compared with the density of states (DOS) of MgH2 systems, it is found that when the Ni, Nb or Zr atom replaces Mg atom, the valence electron numbers below Fermi level in octahedral areas made of the supercell center atom and its first-nearest, second-nearest H atom increased in the order of Ni, Ti, Zr, meaning the corresponding structural stability are increased while the dehydrogenating properties are reduced, both of which are in the order of Ni, Ti and Zr. A good agreement between the calculation results of the improvement of the dehydrogenating properties of MgH2 systems by NiF2, NbF5 and ZrF4 as the catalyst and experimental results can also be well explained
The dehydrogenating properties of MgH2 systems were improved by the addition of metal fluorides as the catalyst; the energy of substitution for the Mg atom, the Mg vacancy formation energy, the energy to remove H atoms and electronic structure change of MgH2 systems were calculated by Dmol4.1 program based on the density functional theory. The mechanism of improvement of dehydrogenating properties of MgH2 systems by the addition of metal fluorides was discussed. The results show that the Mg vacancy formation energy is significantly higher than that of Fe, Ti, Zr, V, Ni, Nb, Cr or Cu substitution, which means that the substitution of these elements at the Mg site is more favorable for dehydrogenation of MgH2 system than the Mg vacancy formation at lower temperatures. NiF2, NbF5 and ZrF4 all benefit for the dehydrogenation of MgH2 systems, and the calculation results of improvement of the dehydrogenating properties of MgH2 systems are in agreement with experimental results. The Ni, Nb and Zr atoms replace a Mg atom of MgH2 systems respectively, the corresponding reactions of NiF2+3MgH2=MgF2+Mg2NiH4, 2NbF5+5MgH2=5MgF2+2NbH+4H2 and ZrF4+2MgH2=2MgF2+ZrH2 are accelerated; therefore, MgH2 with the higher stability can be changed into the other hydrides, such as Mg2NiH4, NbH and ZrH2. Compared with the density of states (DOS) of MgH2 systems, it is found that when the Ni, Nb or Zr atom replaces Mg atom, the valence electron numbers below Fermi level in octahedral areas made of the supercell center atom and its first-nearest, second-nearest H atom increased in the order of Ni, Ti, Zr, meaning the corresponding structural stability are increased while the dehydrogenating properties are reduced, both of which are in the order of Ni, Ti and Zr. A good agreement between the calculation results of the improvement of the dehydrogenating properties of MgH2 systems by NiF2, NbF5 and ZrF4 as the catalyst and experimental results can also be well explained
2010, 39(6):975-979.
Abstract:
The influence of heat treatment, specimen orientation and stress ratio on the fatigue crack propagation behavior of Al-Cu-Mg alloy containing Zr was studied. The results show that the difference of fatigue crack propagation rates between T3 and T4 temper specimens was not obvious. The effect of specimen orientation on the crack propagation rates was less significant. The fatigue crack propagation rates of the specimens in the L-T orientation and T-L orientation were similar. However, the stress ratio had a remarkable influence on the fatigue crack propagation rates; at the higher stress ratio, the fatigue crack propagation rates increased and the fatigue crack propagated rapidly into the high crack propagation regime to failure at lower ?K levels. The effect of stress ratio at near-threshold levels could be explained by a crack closure concept
The influence of heat treatment, specimen orientation and stress ratio on the fatigue crack propagation behavior of Al-Cu-Mg alloy containing Zr was studied. The results show that the difference of fatigue crack propagation rates between T3 and T4 temper specimens was not obvious. The effect of specimen orientation on the crack propagation rates was less significant. The fatigue crack propagation rates of the specimens in the L-T orientation and T-L orientation were similar. However, the stress ratio had a remarkable influence on the fatigue crack propagation rates; at the higher stress ratio, the fatigue crack propagation rates increased and the fatigue crack propagated rapidly into the high crack propagation regime to failure at lower ?K levels. The effect of stress ratio at near-threshold levels could be explained by a crack closure concept
2010, 39(6):993-996.
Abstract:
Ta-Si-N(10 nm)/Zr(20 nm) bilayer diffusion barrier was prepared between n-type silicon(100) wafer and Cu film by radio frequency reactive magnetron sputtering. The Cu/Ta-Si-N/Zr/Si samples were subsequently annealed at different temperatures ranging from 600 to 800 oC in high-purity N2 gas for 1 h. The thermal stability of the Cu/Ta-Si-N/Zr/Si system during annealing was investigated by X-ray diffraction(XRD), auger electron spectroscopy(AES), scanning electron microscopy(SEM) and four-point probe technique(FPP). The results show that Ta-Si-N deposited on Zr film is amorphous with low roughness. In addition, the diffusion of Zr atoms into Si substrate results in ZrSi2 formation which decreases effectively the contact resistance between the barrier and Si after annealing of Cu/Ta-Si-N/Zr/Si sample above 650 oC. Ta-Si-N/Zr bilayer can serve as effective diffusion barrier up to 750 oC
Ta-Si-N(10 nm)/Zr(20 nm) bilayer diffusion barrier was prepared between n-type silicon(100) wafer and Cu film by radio frequency reactive magnetron sputtering. The Cu/Ta-Si-N/Zr/Si samples were subsequently annealed at different temperatures ranging from 600 to 800 oC in high-purity N2 gas for 1 h. The thermal stability of the Cu/Ta-Si-N/Zr/Si system during annealing was investigated by X-ray diffraction(XRD), auger electron spectroscopy(AES), scanning electron microscopy(SEM) and four-point probe technique(FPP). The results show that Ta-Si-N deposited on Zr film is amorphous with low roughness. In addition, the diffusion of Zr atoms into Si substrate results in ZrSi2 formation which decreases effectively the contact resistance between the barrier and Si after annealing of Cu/Ta-Si-N/Zr/Si sample above 650 oC. Ta-Si-N/Zr bilayer can serve as effective diffusion barrier up to 750 oC
2010, 39(6):997-1001.
Abstract:
(Ce-La)-Ni-Al bulk amorphous alloys were developed by seeking the eutectic composition and similar element substitution. A series of completely amorphous alloy rods (≥5 mm in diameter) were prepared by casting the melt ingots into a water-cooled copper mould under vacuum. The structures of the alloy samples were determined by X-ray diffraction. The behaviors of glass transition, crystallization and melting were studied by differential scanning calorimetry (DSC). Results show that La addition greatly improves the glass-forming ability (GFA) and thermal stability of Ce-Ni-Al amorphous alloy. The reasons for this change were explained by a thermodynamic model. Compared with Ce-Ni-Al amorphous alloys, the coexistence of Ce and La, which have similar physical and chemical properties, increases the confusion degree and the entropy of the corresponding alloys; consequently it decreases the Gibbs free energy and thus increases the GFA and thermal stability of the alloys
(Ce-La)-Ni-Al bulk amorphous alloys were developed by seeking the eutectic composition and similar element substitution. A series of completely amorphous alloy rods (≥5 mm in diameter) were prepared by casting the melt ingots into a water-cooled copper mould under vacuum. The structures of the alloy samples were determined by X-ray diffraction. The behaviors of glass transition, crystallization and melting were studied by differential scanning calorimetry (DSC). Results show that La addition greatly improves the glass-forming ability (GFA) and thermal stability of Ce-Ni-Al amorphous alloy. The reasons for this change were explained by a thermodynamic model. Compared with Ce-Ni-Al amorphous alloys, the coexistence of Ce and La, which have similar physical and chemical properties, increases the confusion degree and the entropy of the corresponding alloys; consequently it decreases the Gibbs free energy and thus increases the GFA and thermal stability of the alloys
2010, 39(6):1002-1004.
Abstract:
Complex of europium with 5-aminoisophthalic acid was synthesized in the aqueous solution. The complex has bright red light when excited by UV light. UV-Vis absorption spectra of the complex show that the UV absorption is mainly from the ligand. FTIR spectra indicate that in the complex Eu3+ was coordinated with carbonyl oxygen in the form of bidentate chelate. And excellent fluorescence property is confirmed by the fluorescence spectrum. Optimal excitation wavelength is 395 nm, and the emission spectrum is the characteristic spectrum of Eu3+; there is a sharp and strong red peak with 7 nm mid-width at 616 nm, which is attributed to 5D0→7F2 transition from Eu3+ ions; Eu3+ exists in the site without inversion symmetrical center. Meanwhile, the fluorescence spectrum of the complex reveals the M-M fluorescence mechanism
Complex of europium with 5-aminoisophthalic acid was synthesized in the aqueous solution. The complex has bright red light when excited by UV light. UV-Vis absorption spectra of the complex show that the UV absorption is mainly from the ligand. FTIR spectra indicate that in the complex Eu3+ was coordinated with carbonyl oxygen in the form of bidentate chelate. And excellent fluorescence property is confirmed by the fluorescence spectrum. Optimal excitation wavelength is 395 nm, and the emission spectrum is the characteristic spectrum of Eu3+; there is a sharp and strong red peak with 7 nm mid-width at 616 nm, which is attributed to 5D0→7F2 transition from Eu3+ ions; Eu3+ exists in the site without inversion symmetrical center. Meanwhile, the fluorescence spectrum of the complex reveals the M-M fluorescence mechanism
2010, 39(6):1005-1008.
Abstract:
Reinforced Ag nanoparticles were incorporated into Sn-0.7Cu matrix composite solder by a mechanical means in order to improve the creep properties of the solder matrix. The creep-rupture life was studied of Sn-0.7Cu solder joints and composite solder joints reinforced with Ag nanoparticles at different temperatures and applied stresses. Stress exponents and creep activation energy were calculated for Ag nanoparticle reinforced Sn-Cu matrix composite solder joints at different temperatures and stress levels. Steady-state creep constitutive equation of the composite solder joint was established. Results show that at different temperatures and stresses, Ag nanoparticles reinforced Sn-Cu composite solder joints have higher creep rupture life and creep activation energy than Sn-0.7Cu solder joints. It indicates the creep resistance of the composite solder joint with 1 vol% Ag reinforcement addition is better than that of Sn-0.7Cu solder joint
Reinforced Ag nanoparticles were incorporated into Sn-0.7Cu matrix composite solder by a mechanical means in order to improve the creep properties of the solder matrix. The creep-rupture life was studied of Sn-0.7Cu solder joints and composite solder joints reinforced with Ag nanoparticles at different temperatures and applied stresses. Stress exponents and creep activation energy were calculated for Ag nanoparticle reinforced Sn-Cu matrix composite solder joints at different temperatures and stress levels. Steady-state creep constitutive equation of the composite solder joint was established. Results show that at different temperatures and stresses, Ag nanoparticles reinforced Sn-Cu composite solder joints have higher creep rupture life and creep activation energy than Sn-0.7Cu solder joints. It indicates the creep resistance of the composite solder joint with 1 vol% Ag reinforcement addition is better than that of Sn-0.7Cu solder joint
13 Study on Characteristics of Directionally-Solidified Microstructure for NiAl-Mo Eutectic Composites
2010, 39(6):1009-1012.
Abstract:
NiAl-Mo eutectic composites with two kinds of composition, 46.59Ni-45.61Al-7.8Mo and 44.86Ni-46.3Al-9.01Mo(at%), were prepared by directional solidification technology. The characteristics of solidification microstructure for the alloys at different withdrawing rates were studied. Results show that the microstructure of 46.59Ni-45.61Al-7.8Mo alloy was hypoeutectic at different withdrawing rates. The primary NiAl phase was dendritic; those initial dendrites disappeared gradually as their preferred growth direction did not coincide with the direction of heat transfer during the vertical directional solidification. With increase of the withdrawing rate, the dendrite arm spacing of NiAl phases was decreased little by little. For the 44.86Ni-46.3Al-9.01Mo alloy, eutectic microstructure of rod-like Mo phases inserted in NiAl matrix was formed at different withdrawing rates. With the increase of the withdrawing rate, both of the average spacing and the average diameter of the Mo phases decreased. When the withdrawing rate exceeded 14 mm/h, the continuous and regularly-ranged rod-like Mo-phase turned to irregular and discontinuous
NiAl-Mo eutectic composites with two kinds of composition, 46.59Ni-45.61Al-7.8Mo and 44.86Ni-46.3Al-9.01Mo(at%), were prepared by directional solidification technology. The characteristics of solidification microstructure for the alloys at different withdrawing rates were studied. Results show that the microstructure of 46.59Ni-45.61Al-7.8Mo alloy was hypoeutectic at different withdrawing rates. The primary NiAl phase was dendritic; those initial dendrites disappeared gradually as their preferred growth direction did not coincide with the direction of heat transfer during the vertical directional solidification. With increase of the withdrawing rate, the dendrite arm spacing of NiAl phases was decreased little by little. For the 44.86Ni-46.3Al-9.01Mo alloy, eutectic microstructure of rod-like Mo phases inserted in NiAl matrix was formed at different withdrawing rates. With the increase of the withdrawing rate, both of the average spacing and the average diameter of the Mo phases decreased. When the withdrawing rate exceeded 14 mm/h, the continuous and regularly-ranged rod-like Mo-phase turned to irregular and discontinuous
2010, 39(6):1009-1102.
Abstract:
The effects of revolving magnetic field on the microstructure, mechanical properties and corrosion resistance of the AZ91D-0.4%RE alloy were investigated. It is found that under the revolving magnetic field, the grain size of α-Mg dendrite was obviously decreased and became more uniform with the increasing of excitation voltage; the additional phases of Al11RE3 became smaller and changed from fishbone or long-acicular structure to short acicular structure gradually. Under the revolving magnetic field, σb, σ0.2, δ and hardness of the alloy can be increased by 13%, 15%, 44% and 19%, respectively. The room-temperature tensile fracture shows a feature of quasicleavage fracture. Meanwhile, the self-corrosion potential increased from –1.56 V to –1.51 V, indicating that the corrosion resistance was greatly enhanced.
The effects of revolving magnetic field on the microstructure, mechanical properties and corrosion resistance of the AZ91D-0.4%RE alloy were investigated. It is found that under the revolving magnetic field, the grain size of α-Mg dendrite was obviously decreased and became more uniform with the increasing of excitation voltage; the additional phases of Al11RE3 became smaller and changed from fishbone or long-acicular structure to short acicular structure gradually. Under the revolving magnetic field, σb, σ0.2, δ and hardness of the alloy can be increased by 13%, 15%, 44% and 19%, respectively. The room-temperature tensile fracture shows a feature of quasicleavage fracture. Meanwhile, the self-corrosion potential increased from –1.56 V to –1.51 V, indicating that the corrosion resistance was greatly enhanced.
2010, 39(6):1013-1017.
Abstract:
A series of TiO2 thin film electrodes were prepared by a sol-gel method, an anodization method and a thermal oxidation method. The photoelectrochemical properties of these electrodes such as photocurrents and photopotentials were characterized under white light and visible light illumination. Visible-light photoelectrochemical responses were observed for all the TiO2 thin film electrodes prepared by the three methods without any modification. This may be due to many surface states with visible light absorption ability, which was caused by lattice distortion during the annealing treatment. The changes of the visible-light photoelectrochemical response of TiO2 electrodes prepared under different conditions were the same as that of the white light response.
A series of TiO2 thin film electrodes were prepared by a sol-gel method, an anodization method and a thermal oxidation method. The photoelectrochemical properties of these electrodes such as photocurrents and photopotentials were characterized under white light and visible light illumination. Visible-light photoelectrochemical responses were observed for all the TiO2 thin film electrodes prepared by the three methods without any modification. This may be due to many surface states with visible light absorption ability, which was caused by lattice distortion during the annealing treatment. The changes of the visible-light photoelectrochemical response of TiO2 electrodes prepared under different conditions were the same as that of the white light response.
16 Effects of Micropatterned Surface of NiTi Alloy on Adhesion of Endothelial Cells and Blood Platelets
2010, 39(6):1018-1022.
Abstract:
Effects of the surface morphology of micropatterned NiTi alloy, an intravascular stent material, on the adhesion of bovine aortic endothelial cells (BAECs) and blood platelets were investigated. Mechanical polishing, chemical pickling and sandpaper grinding were used to prepare NiTi alloy with micropores and microgrooves. The surface morphologies and average roughness (Ra) were characterized by SEM and surface profilometer. The effects of the material surface with micropores and microgrooves on the adhesion of blood platelets and endothelial cells were determined. Results show the NiTi alloy surface with micropores or microgrooves could be controlled in the range of nanometer. Both of these two micriopatterned surface could enhance BAECs adhesion, but the effect on platelet adhesion is not obvious; the number of BAECs adhesion on surface with micropores were significantly more than that on the surface with microgrooves. Furthermore, the cells in the surface with micropores show a good growth situation. The microgroove structure has contact-induction effect on the early adhesion of the cells
Effects of the surface morphology of micropatterned NiTi alloy, an intravascular stent material, on the adhesion of bovine aortic endothelial cells (BAECs) and blood platelets were investigated. Mechanical polishing, chemical pickling and sandpaper grinding were used to prepare NiTi alloy with micropores and microgrooves. The surface morphologies and average roughness (Ra) were characterized by SEM and surface profilometer. The effects of the material surface with micropores and microgrooves on the adhesion of blood platelets and endothelial cells were determined. Results show the NiTi alloy surface with micropores or microgrooves could be controlled in the range of nanometer. Both of these two micriopatterned surface could enhance BAECs adhesion, but the effect on platelet adhesion is not obvious; the number of BAECs adhesion on surface with micropores were significantly more than that on the surface with microgrooves. Furthermore, the cells in the surface with micropores show a good growth situation. The microgroove structure has contact-induction effect on the early adhesion of the cells
2010, 39(6):1023-1026.
Abstract:
A series of Ti-Ni-Cu brazing alloys with different composition were designed in this experiment. The influence of the alloying elements such as B, Si and Zr on the glass forming ability and performance of the brazing alloys was studied. The results show that the wettablity of Ti-Ni-Cu brazing alloys on the Si3N4 ceramics can be significantly improved by adding traces of B or Si. Under the same experimental conditions, the Ti40Ni15Cu with 0.2% B addition has the largest wetting area. The glass forming ability of Ti-Ni-Cu brazing alloys without Zr is bad. Ti40Zr20Ni20CuB0.2 and Ti40Zr20Ni25CuB0.2 of the experiment have a good wettability as well as a good glass forming ability. The Ti40Zr20Ni20CuB0.2 and Ti40Zr20Ni25CuB0.2 amorphous brazing alloy joints of Si3N4 ceramics are similar in room-temperature strength to Ti40Zr25Ni15Cu amorphous brazing alloy joints, but the high temperature strength has been improved markedly
A series of Ti-Ni-Cu brazing alloys with different composition were designed in this experiment. The influence of the alloying elements such as B, Si and Zr on the glass forming ability and performance of the brazing alloys was studied. The results show that the wettablity of Ti-Ni-Cu brazing alloys on the Si3N4 ceramics can be significantly improved by adding traces of B or Si. Under the same experimental conditions, the Ti40Ni15Cu with 0.2% B addition has the largest wetting area. The glass forming ability of Ti-Ni-Cu brazing alloys without Zr is bad. Ti40Zr20Ni20CuB0.2 and Ti40Zr20Ni25CuB0.2 of the experiment have a good wettability as well as a good glass forming ability. The Ti40Zr20Ni20CuB0.2 and Ti40Zr20Ni25CuB0.2 amorphous brazing alloy joints of Si3N4 ceramics are similar in room-temperature strength to Ti40Zr25Ni15Cu amorphous brazing alloy joints, but the high temperature strength has been improved markedly
2010, 39(6):1027-1030.
Abstract:
Based on the microscopic phase-field theory, the inversion formula of the connection between the first nearest neighbor interchange potential W1 and the long range order parameter η, i.e. was concluded according to the formula for the connection between occupation probability and free energy by Khachaturyan. According to the formula, W1 of L12 structure can be simply calculated under different conditions of atomic concentration and temperature only by substituting the temperature and atomic concentration of L1 structure transformation point. The calculated result is close to the numerical value by first-principle and other methods. At the same time, it is found that W1 of L12 structure was affected by atomic concentration and temperature in the phase diagram range of precipitated L12.
Based on the microscopic phase-field theory, the inversion formula of the connection between the first nearest neighbor interchange potential W1 and the long range order parameter η, i.e. was concluded according to the formula for the connection between occupation probability and free energy by Khachaturyan. According to the formula, W1 of L12 structure can be simply calculated under different conditions of atomic concentration and temperature only by substituting the temperature and atomic concentration of L1 structure transformation point. The calculated result is close to the numerical value by first-principle and other methods. At the same time, it is found that W1 of L12 structure was affected by atomic concentration and temperature in the phase diagram range of precipitated L12.
2010, 39(6):1031-1036.
Abstract:
Artificial Neural Network (ANN) is a feasible method to reflect the complicated nonlinear relationship between β transus temperature and the alloy composition. In this paper, back propagation neural network (BP neural network) was developed and trained using data from various sources of published literature. The influence of aluminum, molybdenum and zirconium on β transus temperature in titanium alloys was assessed on the base of the trained neural network. It is found that the predicted results are in good agreement with experimental values. The effect of element contents on β transus temperature simulated by ANN model presents nonlinear relationship caused by the interaction among the elements, which is different from the results of the traditional equations.
Artificial Neural Network (ANN) is a feasible method to reflect the complicated nonlinear relationship between β transus temperature and the alloy composition. In this paper, back propagation neural network (BP neural network) was developed and trained using data from various sources of published literature. The influence of aluminum, molybdenum and zirconium on β transus temperature in titanium alloys was assessed on the base of the trained neural network. It is found that the predicted results are in good agreement with experimental values. The effect of element contents on β transus temperature simulated by ANN model presents nonlinear relationship caused by the interaction among the elements, which is different from the results of the traditional equations.
2010, 39(6):1037-1040.
Abstract:
CaCu3Ti4O12(CCTO), SrCu3Ti4O12(SCTO) and BaCu3Ti4O12(BCTO) ceramics with ideal molar ratio were prepared by the traditional solid-state reaction method. The temperature dependence of dielectric constant and dielectric loss at different frequencies for the samples were measured. It is found that the dielectric properties of CaCu3Ti4O12 are attributed to Debye relaxation theory, while the great difference of the dielectric properties between SCTO, BCTO and CCTO comes from the aberrance of structure and the appearance of impurity
CaCu3Ti4O12(CCTO), SrCu3Ti4O12(SCTO) and BaCu3Ti4O12(BCTO) ceramics with ideal molar ratio were prepared by the traditional solid-state reaction method. The temperature dependence of dielectric constant and dielectric loss at different frequencies for the samples were measured. It is found that the dielectric properties of CaCu3Ti4O12 are attributed to Debye relaxation theory, while the great difference of the dielectric properties between SCTO, BCTO and CCTO comes from the aberrance of structure and the appearance of impurity
2010, 39(6):1041-1044.
Abstract:
By means of in-situ tension test on notched specimens of the duplex high-Nb-containing TiAl alloy and the corresponding SEM observation, the tensile fracture mechanism and crack propagation dynamic process were investigated. The results indicate that the fracture was dominated by transgranular cleavage. The fracture process was that the main crack occurred firstly, microcrack appeared and then propagated, the main crack and microcrack were linked, and the alloy fractured finally. In the crack propagation process, the obvious fracture characteristic was easy formation of microcracks in γ grains near the crack tip. For notched specimens of duplex microstructure, the stress concentrated at the notch root, and the main crack propagation path was straighter because the grain size was very fine
By means of in-situ tension test on notched specimens of the duplex high-Nb-containing TiAl alloy and the corresponding SEM observation, the tensile fracture mechanism and crack propagation dynamic process were investigated. The results indicate that the fracture was dominated by transgranular cleavage. The fracture process was that the main crack occurred firstly, microcrack appeared and then propagated, the main crack and microcrack were linked, and the alloy fractured finally. In the crack propagation process, the obvious fracture characteristic was easy formation of microcracks in γ grains near the crack tip. For notched specimens of duplex microstructure, the stress concentrated at the notch root, and the main crack propagation path was straighter because the grain size was very fine
2010, 39(6):1045-1049.
Abstract:
Pd-Ag alloy shows high hydrogen permeability and excellent resistance to hydrogen embrittlement, so it is used to separate the products of methane steam reforming to achieve high purity hydrogen. However, Pd is very expensive; therefore it is eagerly desired to develop no-Pd based alloys with low cost and high hydrogen permeation performance. In order to find out Nb-Ti-Ni alloy with higher hydrogen permeability, the Nb-Ti-Ni alloys located at the straight line connecting the primary (Nb, Ti) of Nb40Ti30Ni30 and the eutectic {(Nb,Ti)+TiNi} phases in the Nb-Ti-Ni trinary diagram were prepared. Results show that the alloys located at the straight line consists of the primary (Nb, Ti) and the eutectic {(Nb,Ti)+TiNi} phases, and their hydrogen permeability increase with increasing of Nb content or volume fraction of the primary (Nb,Ti). Moreover, the Nb content increases to 68 mol%. The Nb68Ti17Ni15 alloy, consisting of 74 vol% primary (Nb, Ti) phase and 26 vol% eutectic {(Nb,Ti)+TiNi} phase, show the highest Φ673K of 4.91′10-8 mol H2m-1s-1Pa-0.5, which is 2.5 times as high as that of the Nb40Ti30Ni30, and 3.5 times as high as that of the pure Pd
Pd-Ag alloy shows high hydrogen permeability and excellent resistance to hydrogen embrittlement, so it is used to separate the products of methane steam reforming to achieve high purity hydrogen. However, Pd is very expensive; therefore it is eagerly desired to develop no-Pd based alloys with low cost and high hydrogen permeation performance. In order to find out Nb-Ti-Ni alloy with higher hydrogen permeability, the Nb-Ti-Ni alloys located at the straight line connecting the primary (Nb, Ti) of Nb40Ti30Ni30 and the eutectic {(Nb,Ti)+TiNi} phases in the Nb-Ti-Ni trinary diagram were prepared. Results show that the alloys located at the straight line consists of the primary (Nb, Ti) and the eutectic {(Nb,Ti)+TiNi} phases, and their hydrogen permeability increase with increasing of Nb content or volume fraction of the primary (Nb,Ti). Moreover, the Nb content increases to 68 mol%. The Nb68Ti17Ni15 alloy, consisting of 74 vol% primary (Nb, Ti) phase and 26 vol% eutectic {(Nb,Ti)+TiNi} phase, show the highest Φ673K of 4.91′10-8 mol H2m-1s-1Pa-0.5, which is 2.5 times as high as that of the Nb40Ti30Ni30, and 3.5 times as high as that of the pure Pd
2010, 39(6):1050-1052.
Abstract:
Shuttle-like silver nanoparticles were synthesized in sodium dodecyl sulfate (SDS) solution through reduction of silver nitrate with citric acid (CA). Transmission electron microscopy (TEM) and UV-vis absorption spectroscopy were used to characterize the obtained products. Results show that the silver nanoparticles are shuttle-like when the mass ratio of SDS to CA is fixed at 50:50. The formation of shuttle-like structure is mainly caused by the different growth rates of crystal faces because of SDS adsorption. SDS might play the adsorbent and dispersant roles rather than the template role in the formation process of shuttle-like nanoparticles
Shuttle-like silver nanoparticles were synthesized in sodium dodecyl sulfate (SDS) solution through reduction of silver nitrate with citric acid (CA). Transmission electron microscopy (TEM) and UV-vis absorption spectroscopy were used to characterize the obtained products. Results show that the silver nanoparticles are shuttle-like when the mass ratio of SDS to CA is fixed at 50:50. The formation of shuttle-like structure is mainly caused by the different growth rates of crystal faces because of SDS adsorption. SDS might play the adsorbent and dispersant roles rather than the template role in the formation process of shuttle-like nanoparticles
2010, 39(6):1053-1056.
Abstract:
研究相对密度92%的熔渗烧结85W-Cu板坯冷轧变形行为。通过对板材中孔洞、钨颗粒变形行为的观测及XRD分析，得出85W-Cu板材的塑性变形机制。孔洞变形、弥合实现材料的致密化，钨颗粒经过纵向移动、横向移动、冷焊、变形过程，钨颗粒断裂贯穿整个塑性变形。材料的致密化和铜相、钨颗粒的变形产生的内应力导致材料显微硬度增加，最后材料失去塑性而失效。在800~930 ℃温区内对30%~40%变形量板材的退火能够改善材料的塑性
研究相对密度92%的熔渗烧结85W-Cu板坯冷轧变形行为。通过对板材中孔洞、钨颗粒变形行为的观测及XRD分析，得出85W-Cu板材的塑性变形机制。孔洞变形、弥合实现材料的致密化，钨颗粒经过纵向移动、横向移动、冷焊、变形过程，钨颗粒断裂贯穿整个塑性变形。材料的致密化和铜相、钨颗粒的变形产生的内应力导致材料显微硬度增加，最后材料失去塑性而失效。在800~930 ℃温区内对30%~40%变形量板材的退火能够改善材料的塑性
2010, 39(6):1057-1060.
Abstract:
Mo-15Cu sheets of 90.5% relative density were cold-rolled with deformation by 70% and 90% and then resintered at 1200 oC for 1 and 1.5 h. The microstructure change and XRD patterns of the sheets before and after resintering were analyzed. The thermal conductivity, electrical resistivity and thermal expansion coefficient of the sheets rolled and sintered were measured. Results show that the microstructure defects of the cold-rolled sheets were eliminated significantly by resintering. The thermal conductivity of 70% deformed sheet after resintering was 154.5 W(m·K)-1, electrical resistivity was 4.48 μΩ·cm, and the thermal expansion coefficient was 6.31×10-6 K–1. It is concluded that the resintering technology can improve greatly the microstructure and physical performances of cold-rolled Mo-15Cu sheets to meet the demands of electronic packaging materials
Mo-15Cu sheets of 90.5% relative density were cold-rolled with deformation by 70% and 90% and then resintered at 1200 oC for 1 and 1.5 h. The microstructure change and XRD patterns of the sheets before and after resintering were analyzed. The thermal conductivity, electrical resistivity and thermal expansion coefficient of the sheets rolled and sintered were measured. Results show that the microstructure defects of the cold-rolled sheets were eliminated significantly by resintering. The thermal conductivity of 70% deformed sheet after resintering was 154.5 W(m·K)-1, electrical resistivity was 4.48 μΩ·cm, and the thermal expansion coefficient was 6.31×10-6 K–1. It is concluded that the resintering technology can improve greatly the microstructure and physical performances of cold-rolled Mo-15Cu sheets to meet the demands of electronic packaging materials
26 Influence of Aging Processing on Microstructure and Mechanical Properties of Ti-10V-2Fe-3Al Alloy
Shang Guoqiang
,
Kou Hongchao
,
Fei Yue
,
Chang Hui
,
Zhu Zhishou
,
Wang Xinnan
,
Zhang Fengshou
,
Li Jinshan
2010, 39(6):1061-1065.
Abstract:
Effects of one-step aging, two-step aging of low-temperature and high-temperature and heating rate of aging on the microstructure and mechanical properties of Ti-10V-2Fe-3Al titanium alloy after high temperature deformation were studied. The results show that comparing with one-step aging, in the two-step aging the early precipitated ω particles provided uniform nucleation sites for α phase during the low-temperature aging. As a result, the two-step aging sequences led to much finer and more uniform α+β microstructure to obtain good match of strength and ductility. For a slow heating rate of 0.1 oC/s to the peak aging temperature, a very finely dispersed isothermal ω-phase had enough time to precipitate, and thus provided nucleation sites of high density for the α-phase, resulting in the very fine α plates; therefore, the same match effect of strength and ductility was obtained
Effects of one-step aging, two-step aging of low-temperature and high-temperature and heating rate of aging on the microstructure and mechanical properties of Ti-10V-2Fe-3Al titanium alloy after high temperature deformation were studied. The results show that comparing with one-step aging, in the two-step aging the early precipitated ω particles provided uniform nucleation sites for α phase during the low-temperature aging. As a result, the two-step aging sequences led to much finer and more uniform α+β microstructure to obtain good match of strength and ductility. For a slow heating rate of 0.1 oC/s to the peak aging temperature, a very finely dispersed isothermal ω-phase had enough time to precipitate, and thus provided nucleation sites of high density for the α-phase, resulting in the very fine α plates; therefore, the same match effect of strength and ductility was obtained
2010, 39(6):1066-1070.
Abstract:
For better application of TiO2 nanotube array electrodes in solar cells, TiO2 nanotube arrays were prepared on a titanium substrate in 0.5wt%NH4F/glycerol electrolyte by means of anodic oxidization at a constant potential. The characteristics of the electron transfer and the interface of the TiO2 nanotube array electrodes were researched by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), electron paramagnetic resonance spectrometer (EPR), electrochemical impedance spectra (EIS) and cyclic voltammetry (CV). The impedance curves corresponding to reaction processes of electrodes were determined. Moreover, the dynamic parameters for electron transfer in the electrodes were calculated. The results indicate that the reaction of trivalent titanium compound to tetravalent titanium oxide took place on the surface of the electrodes, leading to great decrease of the resistance of the electrodes. Therefore, the electron pervasion at the electrode-electrolyte interface was accelerated, which was good for the formation of ·OH on the electrode surface
For better application of TiO2 nanotube array electrodes in solar cells, TiO2 nanotube arrays were prepared on a titanium substrate in 0.5wt%NH4F/glycerol electrolyte by means of anodic oxidization at a constant potential. The characteristics of the electron transfer and the interface of the TiO2 nanotube array electrodes were researched by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), electron paramagnetic resonance spectrometer (EPR), electrochemical impedance spectra (EIS) and cyclic voltammetry (CV). The impedance curves corresponding to reaction processes of electrodes were determined. Moreover, the dynamic parameters for electron transfer in the electrodes were calculated. The results indicate that the reaction of trivalent titanium compound to tetravalent titanium oxide took place on the surface of the electrodes, leading to great decrease of the resistance of the electrodes. Therefore, the electron pervasion at the electrode-electrolyte interface was accelerated, which was good for the formation of ·OH on the electrode surface
2010, 39(6):1071-1074.
Abstract:
Cancellous bovine bone (CBB) as starting materials was treated by a series of degreasing and then calcined at low temperature. By adjusting the concentration of soaking solution NH4H2PO4 and the calcination temperature, β-TCP/HAP/Ca2P2O7 multiphasic bioceramic material was prepared with porous structure of natural bone. The phase composition of the calcined specimen was characterized by XRD and the reaction mechanism was discussed by FTIR and TG. Results show that the concentration of soaking solution NH4H2PO4 has a significant effect on the phase composition of the specimen. Porous bioceramic materials with different phase composition can be prepared by controlling the concentration reasonably. The phase composition was also influenced by the amount of OH- which came from HAP decomposition (x) and which reacted with NH4H2PO4 (3m). When x>3m, the product was mainly composed of HAP and β-TCP. When x<3m, the procuct may contain HAP/β-TCP/Ca2P2O7 or β-TCP/Ca2P2O7. Only as x=3m, pure β-TCP could be gained
Cancellous bovine bone (CBB) as starting materials was treated by a series of degreasing and then calcined at low temperature. By adjusting the concentration of soaking solution NH4H2PO4 and the calcination temperature, β-TCP/HAP/Ca2P2O7 multiphasic bioceramic material was prepared with porous structure of natural bone. The phase composition of the calcined specimen was characterized by XRD and the reaction mechanism was discussed by FTIR and TG. Results show that the concentration of soaking solution NH4H2PO4 has a significant effect on the phase composition of the specimen. Porous bioceramic materials with different phase composition can be prepared by controlling the concentration reasonably. The phase composition was also influenced by the amount of OH- which came from HAP decomposition (x) and which reacted with NH4H2PO4 (3m). When x>3m, the product was mainly composed of HAP and β-TCP. When x<3m, the procuct may contain HAP/β-TCP/Ca2P2O7 or β-TCP/Ca2P2O7. Only as x=3m, pure β-TCP could be gained
2010, 39(6):1075-1078.
Abstract:
Carbon-fiber-supported TiO2 photocatalytic material (TiO2/CF) was prepared by sol-gel method with PAN-based carbon fibers as support. Then the TiO2/CF was modified by depositing noble metal Pd particles on its surface by oxidation-redox method at room temperature to obtain carbon-fiber-supported Pd-TiO2 photocatalytic material (Pd-TiO2/CF). XRD analysis shows that TiO2 of anatase was formed on the surface of carbon fibers by sol-gel method. Acid orange II of azo dyes was chosen as the target of photocatalytic degradation, and the photocatalytic activities of TiO2/CF, Pd-TiO2/CF and powder TiO2 of equal load capacity were analyzed by UV absorption spectrum. The results indicate that the photocatalytic activity of powder TiO2 decreased to some extent under the supported condition; Pd particle deposition increased photocatalytic activity efficiently; the Pd-TiO2/CF has much higher photocatalytic activity for Acid orange II solution than TiO2/CF and powder TiO2
Carbon-fiber-supported TiO2 photocatalytic material (TiO2/CF) was prepared by sol-gel method with PAN-based carbon fibers as support. Then the TiO2/CF was modified by depositing noble metal Pd particles on its surface by oxidation-redox method at room temperature to obtain carbon-fiber-supported Pd-TiO2 photocatalytic material (Pd-TiO2/CF). XRD analysis shows that TiO2 of anatase was formed on the surface of carbon fibers by sol-gel method. Acid orange II of azo dyes was chosen as the target of photocatalytic degradation, and the photocatalytic activities of TiO2/CF, Pd-TiO2/CF and powder TiO2 of equal load capacity were analyzed by UV absorption spectrum. The results indicate that the photocatalytic activity of powder TiO2 decreased to some extent under the supported condition; Pd particle deposition increased photocatalytic activity efficiently; the Pd-TiO2/CF has much higher photocatalytic activity for Acid orange II solution than TiO2/CF and powder TiO2
30 TC4 Deep Cylinder with Uniform Thickness by Friction-Changing Direct-Reverse Superplastic Forming
2010, 39(6):1079-1084.
Abstract:
The thickness accuracy of a TC4 deep cylinder is within the limit of (1.6±0.2) mm; hereby different shapes of preforming-dies were designed and the relation between the shape and the thickness distribution of the cylinder side-wall as well as the effect of pre-thinning areas were investigated using MARC finite element method (FEM). And also the influence of surface friction coefficient of the preforming die and the final forming die on the final thickness distribution of the deep cylinder was analyzed. A method of thickness control by friction changing was proposed. The results show that the performing-dies have great effect on the local pre-thinning of the ring band near the periphery and the bottom of the deep cylinder to improve the thickness distribution of the final side wall. Meanwhile the properly higher friction coefficient of the preforming die can efficiently reduce the thickness of the regions which need to be thinned, resulting in a more uniform final thickness distribution. Lower friction coefficient of the forming die can make the sheet tend to integral formation, also resulting in uniform thickness distribution of the side wall. According to the results of the simulation, the surface friction coefficient of the preforming die was increased by machining and the friction coefficient of the forming die was decreased by spraying BN ceramic powder. The aerospace TC4 deep cylinder with uniform thickness of 1.50-1.78 mm was fabricated by direct-reverse superplastic forming experiment
The thickness accuracy of a TC4 deep cylinder is within the limit of (1.6±0.2) mm; hereby different shapes of preforming-dies were designed and the relation between the shape and the thickness distribution of the cylinder side-wall as well as the effect of pre-thinning areas were investigated using MARC finite element method (FEM). And also the influence of surface friction coefficient of the preforming die and the final forming die on the final thickness distribution of the deep cylinder was analyzed. A method of thickness control by friction changing was proposed. The results show that the performing-dies have great effect on the local pre-thinning of the ring band near the periphery and the bottom of the deep cylinder to improve the thickness distribution of the final side wall. Meanwhile the properly higher friction coefficient of the preforming die can efficiently reduce the thickness of the regions which need to be thinned, resulting in a more uniform final thickness distribution. Lower friction coefficient of the forming die can make the sheet tend to integral formation, also resulting in uniform thickness distribution of the side wall. According to the results of the simulation, the surface friction coefficient of the preforming die was increased by machining and the friction coefficient of the forming die was decreased by spraying BN ceramic powder. The aerospace TC4 deep cylinder with uniform thickness of 1.50-1.78 mm was fabricated by direct-reverse superplastic forming experiment
2010, 39(6):1085-1088.
Abstract:
Ultrafine SnO2 nanopowder was prepared by a free arc method and an arc plasma method, respectively. Then the phases, morphology and particle size were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The results show that the powder prepared by the arc plasma method has uniform particles with smaller size and fewer impurities, which are mostly spherical; while the powder prepared by the free arc method has bigger particle size and much C impurities. Nucleation and growth mechanism of the powder was analyzed and it is found that the temperature, temperature gradient and saturation are significant influencing factors. Arc plasma method has easily higher temperature and temperature gradient, so it is favorable for nucleation and growth to obtain high nucleation rate
Ultrafine SnO2 nanopowder was prepared by a free arc method and an arc plasma method, respectively. Then the phases, morphology and particle size were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The results show that the powder prepared by the arc plasma method has uniform particles with smaller size and fewer impurities, which are mostly spherical; while the powder prepared by the free arc method has bigger particle size and much C impurities. Nucleation and growth mechanism of the powder was analyzed and it is found that the temperature, temperature gradient and saturation are significant influencing factors. Arc plasma method has easily higher temperature and temperature gradient, so it is favorable for nucleation and growth to obtain high nucleation rate
2010, 39(6):1089-1093.
Abstract:
CeNi5 and Ni3Sn2 were prepared from NiO-CeO2 and NiO-SnO2 oxides by electro-deoxidization (FFC). The samples of mixed oxides sintered at different temperatures were used as cathode, and the graphite rod was used as anode. Then the reaction was completed under 3.1 V in the CaCl2 solution at 850 oC. The morphology and phase composition of the samples before and after deoxidization were analyzed by SEM and XRD. Results show that the sample has lower porosity and smaller electro-deoxidization current under the condition of higher sintering temperature. The product from samples sintered at different temperatures was pure CeNi5; the product from samples sintered at lower temperature was pure Ni3Sn2 with loose sponginess. The research provides a new method for cell materials preparation
CeNi5 and Ni3Sn2 were prepared from NiO-CeO2 and NiO-SnO2 oxides by electro-deoxidization (FFC). The samples of mixed oxides sintered at different temperatures were used as cathode, and the graphite rod was used as anode. Then the reaction was completed under 3.1 V in the CaCl2 solution at 850 oC. The morphology and phase composition of the samples before and after deoxidization were analyzed by SEM and XRD. Results show that the sample has lower porosity and smaller electro-deoxidization current under the condition of higher sintering temperature. The product from samples sintered at different temperatures was pure CeNi5; the product from samples sintered at lower temperature was pure Ni3Sn2 with loose sponginess. The research provides a new method for cell materials preparation
2010, 39(6):1094-1098.
Abstract:
ZrO2-mullite nano-composite ceramics were prepared by in-situ crystallization of Si-Al-Zr-O (SAZ) amorphous bulk. The amorphous bulk and as-prepared ceramics were characterized by XRD, IR and SEM. The influence of heat-treatment temperature on the structure and mechanical properties of ZrO2-mullite nano-composite ceramics was investigated. The results show that the t-ZrO2 began to form after 960 oC heat treatment of SAZ bulk and mullite was crystallized at 1000 oC in the amorphous bulks. The main phases were identified as t-ZrO2 and mullite, and at the same time cristobalite formed by a two-step gradient heat treatment at 950-1000 oC and 1100-1250 oC. The first-step nucleation temperature has a great effect on the microstructure and fracture toughness, and with the increase of the temperature from 950 oC to 1000 oC, the nano-particle size increases but the fracture toughness decreases sharply. However, the influence of the second-step crystallization temperature on the mechanical properties is not obvious. The fracture toughness and flexural strength increase gradually, and then decreases as the crystallization temperature increasing. The nano-composite ceramics exhibit the best mechanical properties, including the flexural strength up to 521 MPa and the fracture toughness up to 5.13 MPa·m1/2 after 950 oC nucleation and then 1150 oC crystallization
ZrO2-mullite nano-composite ceramics were prepared by in-situ crystallization of Si-Al-Zr-O (SAZ) amorphous bulk. The amorphous bulk and as-prepared ceramics were characterized by XRD, IR and SEM. The influence of heat-treatment temperature on the structure and mechanical properties of ZrO2-mullite nano-composite ceramics was investigated. The results show that the t-ZrO2 began to form after 960 oC heat treatment of SAZ bulk and mullite was crystallized at 1000 oC in the amorphous bulks. The main phases were identified as t-ZrO2 and mullite, and at the same time cristobalite formed by a two-step gradient heat treatment at 950-1000 oC and 1100-1250 oC. The first-step nucleation temperature has a great effect on the microstructure and fracture toughness, and with the increase of the temperature from 950 oC to 1000 oC, the nano-particle size increases but the fracture toughness decreases sharply. However, the influence of the second-step crystallization temperature on the mechanical properties is not obvious. The fracture toughness and flexural strength increase gradually, and then decreases as the crystallization temperature increasing. The nano-composite ceramics exhibit the best mechanical properties, including the flexural strength up to 521 MPa and the fracture toughness up to 5.13 MPa·m1/2 after 950 oC nucleation and then 1150 oC crystallization
2010, 39(6):1103-1106.
Abstract:
Power spinning feasibility of the Ti75 (Ti-3Al-2Mo-2Zr) alloy tube cast by a skull furnace ZHN-100 was studied; effects of parameters such as the spinning temperature (T), spin wheel feed rate (f) and pass thinning rate (ψtn) on the spinning process performance of the alloy tube were discussed and the changes of cast microstructure and properties under different thinning rates were also researched. The results show that the appropriate first-pass spinning temperature is 600-800 oC for the cast Ti75 alloy tube when the multi-pass heating backward spinning was applied; while the spinning temperature of the follow-up passes should be lowered gradually in order to ensure the product performance and accuracy. The spin wheel feed rate of 0.42-0.67 mm/r is proper, for which the higher value can ensure the easy-to-punch, and the smaller one is in favor of the surface quality increase of the product. The first-pass thinning rate should not be more than 30%, in order to ensure the smooth progress of spinning. The maximum thinning rate ψt of wall thickness for the cast Ti75 alloy tube is up to 80%, confirming its excellent spinning properties
Power spinning feasibility of the Ti75 (Ti-3Al-2Mo-2Zr) alloy tube cast by a skull furnace ZHN-100 was studied; effects of parameters such as the spinning temperature (T), spin wheel feed rate (f) and pass thinning rate (ψtn) on the spinning process performance of the alloy tube were discussed and the changes of cast microstructure and properties under different thinning rates were also researched. The results show that the appropriate first-pass spinning temperature is 600-800 oC for the cast Ti75 alloy tube when the multi-pass heating backward spinning was applied; while the spinning temperature of the follow-up passes should be lowered gradually in order to ensure the product performance and accuracy. The spin wheel feed rate of 0.42-0.67 mm/r is proper, for which the higher value can ensure the easy-to-punch, and the smaller one is in favor of the surface quality increase of the product. The first-pass thinning rate should not be more than 30%, in order to ensure the smooth progress of spinning. The maximum thinning rate ψt of wall thickness for the cast Ti75 alloy tube is up to 80%, confirming its excellent spinning properties
2010, 39(6):1107-1110.
Abstract:
The heat decomposition of TiH2 was researched with a thermogravimetry (TGA) method. TiH2 powder was heated up at different heating rates under the vacuum condition, and then it was decomposed. The initial temperature of decomposition was between 550 and 580 oC, and did not greatly increase with increasing of the heating rate; but the termination temperature was increased. The mass loss of TiH2 decomposition increased with increase of the heating rate, but the time of TiH2 decomposition was reduced
The heat decomposition of TiH2 was researched with a thermogravimetry (TGA) method. TiH2 powder was heated up at different heating rates under the vacuum condition, and then it was decomposed. The initial temperature of decomposition was between 550 and 580 oC, and did not greatly increase with increasing of the heating rate; but the termination temperature was increased. The mass loss of TiH2 decomposition increased with increase of the heating rate, but the time of TiH2 decomposition was reduced
2010, 39(6):1111-1115.
Abstract:
RuO2-Co3O4-CeO2(Ru-Co-Ce) composite oxide electrodes were prepared by sol-gel process. The parameters of electrode preparation, including the heat treatment temperature and CeO2 doping content, were optimized. The morphology and composition of the anode surface were characterized by SEM and XRD, respectively. Electrocatalytic activity of these electrodes in 1.0 mol·L-1 KOH solution were studied by means of open-circuit potential (Eoc), cyclic voltammetry (CV), voltammetric charge (q*) and polarization curve. The results show that the preparation temperature influenced electrode surface morphology greatly, and the optimal temperature was 400 oC. The CeO2 of appropriate content could increase the active surface area, reduce the grain size and enhance the electrical conductivity of the electrodes, which was in favor of catalytic reactions and redox transition from RuⅢ to RuⅣ. The anodic overpotential for oxygen evolution was decreased by 60 mV and thus the activity of oxygen evolution was improved. The maximum activity was observed with the Ce content of 0.4 mol%
RuO2-Co3O4-CeO2(Ru-Co-Ce) composite oxide electrodes were prepared by sol-gel process. The parameters of electrode preparation, including the heat treatment temperature and CeO2 doping content, were optimized. The morphology and composition of the anode surface were characterized by SEM and XRD, respectively. Electrocatalytic activity of these electrodes in 1.0 mol·L-1 KOH solution were studied by means of open-circuit potential (Eoc), cyclic voltammetry (CV), voltammetric charge (q*) and polarization curve. The results show that the preparation temperature influenced electrode surface morphology greatly, and the optimal temperature was 400 oC. The CeO2 of appropriate content could increase the active surface area, reduce the grain size and enhance the electrical conductivity of the electrodes, which was in favor of catalytic reactions and redox transition from RuⅢ to RuⅣ. The anodic overpotential for oxygen evolution was decreased by 60 mV and thus the activity of oxygen evolution was improved. The maximum activity was observed with the Ce content of 0.4 mol%
2010, 39(6):1116-1120.
Abstract:
YBCO film was deposited on LaAlO3 (LAO) single crystal substrate of Φ76.2 mm using low-fluorine sol-gel process. The uniformity of microstructure, thickness and superconducting properties of the Φ76.2 mm YBCO film were analyzed. The results show that the whole film has uniform thickness and exhibits good c-axis epitaxial growth orientation and excellent uniform superconducting properties
YBCO film was deposited on LaAlO3 (LAO) single crystal substrate of Φ76.2 mm using low-fluorine sol-gel process. The uniformity of microstructure, thickness and superconducting properties of the Φ76.2 mm YBCO film were analyzed. The results show that the whole film has uniform thickness and exhibits good c-axis epitaxial growth orientation and excellent uniform superconducting properties
2010, 39(6):1121-1124.
Abstract:
α-Fe coated Nd-Fe-B nano-composite magnetic powders were prepared by chemical vapor deposition (CVD), which were then spark plasma sintered to obtain Nd-Fe-B/α-Fe nano-composite magnets. SEM, XRD and XPS researches show that CVD method can realize uniform coating of Nd-Fe-B powders with α-Fe, improve effectively the distribution of hard and soft magnetic properties, and increase the integrated magnetic properties of the magnets. The obtained coating was dense and uniform, and the particle size of α-Fe was about 50-100 nm, when the temperature of CVD was 120 oC and the time was 30 min. Under optimum processing conditions, the SPSed NdFeB magnet can be nearly fully dense and reach the best magnetic properties with Br of 0.81 T, Hcj of 1286 kA/ m and (BH)m of 108.6 kJ/m3
α-Fe coated Nd-Fe-B nano-composite magnetic powders were prepared by chemical vapor deposition (CVD), which were then spark plasma sintered to obtain Nd-Fe-B/α-Fe nano-composite magnets. SEM, XRD and XPS researches show that CVD method can realize uniform coating of Nd-Fe-B powders with α-Fe, improve effectively the distribution of hard and soft magnetic properties, and increase the integrated magnetic properties of the magnets. The obtained coating was dense and uniform, and the particle size of α-Fe was about 50-100 nm, when the temperature of CVD was 120 oC and the time was 30 min. Under optimum processing conditions, the SPSed NdFeB magnet can be nearly fully dense and reach the best magnetic properties with Br of 0.81 T, Hcj of 1286 kA/ m and (BH)m of 108.6 kJ/m3
2010, 39(6):1125-1128.
Abstract:
The solidification process and solidification structures of Fe-B-C alloy containing 1.4%-2.0% B and 0.4%-0.6% C were researched. The change of microstructures, mechanical properties and wear resistance of the alloy at different quenching temperatures were also studied. The results show that the solidification structures of Fe-B-C alloy consist of borides such as Fe2B, Fe3(C, B) and Fe23(C,B)6 and metallic matrix such as martensite, pearlite and ferrite. The part of boride network is broken and there is no new phase after quenching. The matrix transforms into the single martensite completely and the hardness exceeds 55 HRC. The hardness of Fe-B-C alloy increases while the impact toughness has no obvious change with increase of the quenching temperature. Under the conditions of static load pin-on-disc wear and dynamic load impact wear, Fe-B-C alloy has excellent wear resistance and the quenching temperature has no marked effect on the wear resistance
The solidification process and solidification structures of Fe-B-C alloy containing 1.4%-2.0% B and 0.4%-0.6% C were researched. The change of microstructures, mechanical properties and wear resistance of the alloy at different quenching temperatures were also studied. The results show that the solidification structures of Fe-B-C alloy consist of borides such as Fe2B, Fe3(C, B) and Fe23(C,B)6 and metallic matrix such as martensite, pearlite and ferrite. The part of boride network is broken and there is no new phase after quenching. The matrix transforms into the single martensite completely and the hardness exceeds 55 HRC. The hardness of Fe-B-C alloy increases while the impact toughness has no obvious change with increase of the quenching temperature. Under the conditions of static load pin-on-disc wear and dynamic load impact wear, Fe-B-C alloy has excellent wear resistance and the quenching temperature has no marked effect on the wear resistance
2010, 39(6):980-984.
Abstract:
Ag6O2/SnO2 interface bonding of Ag/SnO2 composites was simulated by HRTEM image analysis and first-principles calculations. Results show that there is lattice match between the interfaces of SnO2(10) and Ag6O2(101). According to cohesive energy, population and density of state (DOS), it is found the bonding of the two free interfaces is in good agreement with the experiment results. Furthermore, the electron density difference verifies the undecomposed Ag6O2 provided an oxygen-rich environment for Sn, which is favorable for SnO2 particle formation. At last the relaxation state of surface atoms in the interface was analyzed
Ag6O2/SnO2 interface bonding of Ag/SnO2 composites was simulated by HRTEM image analysis and first-principles calculations. Results show that there is lattice match between the interfaces of SnO2(10) and Ag6O2(101). According to cohesive energy, population and density of state (DOS), it is found the bonding of the two free interfaces is in good agreement with the experiment results. Furthermore, the electron density difference verifies the undecomposed Ag6O2 provided an oxygen-rich environment for Sn, which is favorable for SnO2 particle formation. At last the relaxation state of surface atoms in the interface was analyzed
2010, 39(6):985-988.
Abstract:
Mo-Ti-TiC alloys were fabricated by powder metallurgy process through adding TiH2 powder and ultrafine TiC powder into Mo metal. The influence of the addition of nano-scale TiC particles on the microstructure and tensile properties of Mo-Ti alloy was studied. The results indicate that the tensile strength of Mo-Ti alloy was effectively increased by TiC particles addition. Mo-Ti with 0.05wt% TiC exhibited the highest tensile strength, which is 31.7% higher than that of Mo-Ti alloy. The addition of TiC protects Ti from oxidation, which is produced by decomposition and dehydrogenization of TiH2 particles. The second phase particles containing Mo, Ti, O and C in the alloy were formed with TiC addition. The grain size of the alloy decreased with the increase of the TiC content since the second phase particles can inhibit the grain growth
Mo-Ti-TiC alloys were fabricated by powder metallurgy process through adding TiH2 powder and ultrafine TiC powder into Mo metal. The influence of the addition of nano-scale TiC particles on the microstructure and tensile properties of Mo-Ti alloy was studied. The results indicate that the tensile strength of Mo-Ti alloy was effectively increased by TiC particles addition. Mo-Ti with 0.05wt% TiC exhibited the highest tensile strength, which is 31.7% higher than that of Mo-Ti alloy. The addition of TiC protects Ti from oxidation, which is produced by decomposition and dehydrogenization of TiH2 particles. The second phase particles containing Mo, Ti, O and C in the alloy were formed with TiC addition. The grain size of the alloy decreased with the increase of the TiC content since the second phase particles can inhibit the grain growth
2010, 39(6):989-992.
Abstract:
Mo-30Cu alloy was prepared by liquid sintering. Microstructures and composition of the alloy were analyzed with SEM, TEM and XRD, and the influence of sintering temperatures and relative density on microstructures and properties of the alloy was studied. The results indicate that the microstructure of the Mo-30Cu alloy is homogeneous, in which are only Mo phase and Cu phase for the alloy; a medium changing zone is between Mo phase and Cu phase. The sintering temperature plays the most important role on the microstructures and properties of the alloy. Relative density and thermal conductivity of Mo-30Cu alloy sintered at 1300 oC are 99.6% and 196 W·(m·K)-1, respectively
Mo-30Cu alloy was prepared by liquid sintering. Microstructures and composition of the alloy were analyzed with SEM, TEM and XRD, and the influence of sintering temperatures and relative density on microstructures and properties of the alloy was studied. The results indicate that the microstructure of the Mo-30Cu alloy is homogeneous, in which are only Mo phase and Cu phase for the alloy; a medium changing zone is between Mo phase and Cu phase. The sintering temperature plays the most important role on the microstructures and properties of the alloy. Relative density and thermal conductivity of Mo-30Cu alloy sintered at 1300 oC are 99.6% and 196 W·(m·K)-1, respectively
