Volume 38,Issue 9,2009 Table of Contents
2009, 38(9):1505-1508.
Abstract:
A novel type of foundry method for TiAl-based alloy is presented in the present paper. The filling processes of Ti-47Al alloy sheet and blade have been studied via numerical simulation. The investigation results indicate that the filling fraction is enhanced by the increase of filling velocity and graphite throat diameter. The graphite throat diameter is the main parameter for the backward filling location in the process of vacuum suction casting. With the increase of mould temperature, the solid fraction is reduced. The alloy solidification begins from bottom to top. The TiAl sheet and the blade are produced by this method. The grain size of the sheet is in the range from 10 μm to 40 μm. There is no obvious shrinkage cavity
A novel type of foundry method for TiAl-based alloy is presented in the present paper. The filling processes of Ti-47Al alloy sheet and blade have been studied via numerical simulation. The investigation results indicate that the filling fraction is enhanced by the increase of filling velocity and graphite throat diameter. The graphite throat diameter is the main parameter for the backward filling location in the process of vacuum suction casting. With the increase of mould temperature, the solid fraction is reduced. The alloy solidification begins from bottom to top. The TiAl sheet and the blade are produced by this method. The grain size of the sheet is in the range from 10 μm to 40 μm. There is no obvious shrinkage cavity
2009, 38(9):1509-1513.
Abstract:
The diffusion bonding of TC21 titanium alloy with initial grain size of 2 μm was performed at 780-980 oC for 5-90 min. The microstructure, bonding quality, microhardness and deformation ratio of the joints were analyzed. It is found that the interface bonding ratio can achieve 100% and the deformation ratio can be controlled within 10% when diffusion bonding is performed at 880 oC for 15-30 min. The microhardness of the joints increases with increasing of bonding temperature, but it shows a peak value as the bonding time is prolonged. When the joint is bonded at 880-930 oC, fully equiaxed structures are observed, and with increasing of bonding temperature, the sizes of α and β phases are increased; but when bonding temperature is up to 980 ℃, fully lamellar structures are obtained. When the joint is bonded at 880 oC for 5-60 min, the size of α and β phases increases with prolonging of bonding time. However, when the bonding time is prolonged to 90 min, the sizes of α and β phases decrease slightly
The diffusion bonding of TC21 titanium alloy with initial grain size of 2 μm was performed at 780-980 oC for 5-90 min. The microstructure, bonding quality, microhardness and deformation ratio of the joints were analyzed. It is found that the interface bonding ratio can achieve 100% and the deformation ratio can be controlled within 10% when diffusion bonding is performed at 880 oC for 15-30 min. The microhardness of the joints increases with increasing of bonding temperature, but it shows a peak value as the bonding time is prolonged. When the joint is bonded at 880-930 oC, fully equiaxed structures are observed, and with increasing of bonding temperature, the sizes of α and β phases are increased; but when bonding temperature is up to 980 ℃, fully lamellar structures are obtained. When the joint is bonded at 880 oC for 5-60 min, the size of α and β phases increases with prolonging of bonding time. However, when the bonding time is prolonged to 90 min, the sizes of α and β phases decrease slightly
2009, 38(9):1514-1517.
Abstract:
The CdS/TiO2NTs nanocomposite was prepared through ion-exchange and precipitation reactions. The nanostructure properties of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-visible absorption spectra (DRUVAS), fluorescence emission spectra (FES) and X-ray fluorescence analyzer (XRF). SEM results revealed that the lamellar sodium trititanate originating from the TiO2 particles individually curled to form the sodium trititanate nanotubes by self-assembled mechanism. The results of XRD, TEM and DRUVAS demonstrated that hexagonal phase CdS with about 8 nm particle size were homogeneously loaded on the surface of anatase TiO2NTs and the absorption edge of the composite was extended to the visible region. The CdS/TiO2NTs composite exhibited the highest activity of hydrogen production (1708 mL/g) by photocatalytic water decomposition in comparison with TiO2NTs and TiO2 powder under visible light irradiation (l > 400 nm) for 6 h
The CdS/TiO2NTs nanocomposite was prepared through ion-exchange and precipitation reactions. The nanostructure properties of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-visible absorption spectra (DRUVAS), fluorescence emission spectra (FES) and X-ray fluorescence analyzer (XRF). SEM results revealed that the lamellar sodium trititanate originating from the TiO2 particles individually curled to form the sodium trititanate nanotubes by self-assembled mechanism. The results of XRD, TEM and DRUVAS demonstrated that hexagonal phase CdS with about 8 nm particle size were homogeneously loaded on the surface of anatase TiO2NTs and the absorption edge of the composite was extended to the visible region. The CdS/TiO2NTs composite exhibited the highest activity of hydrogen production (1708 mL/g) by photocatalytic water decomposition in comparison with TiO2NTs and TiO2 powder under visible light irradiation (l > 400 nm) for 6 h
2009, 38(9):1518-1525.
Abstract:
By the first-principles calculations method based on the density functional theory, H2 adsorption and dissociation properties on clean, vacancy defective and Pd atom coadsorption Mg(0001) surfaces are investigated systematically. The calculation results show that the model of H2 adsorption on clean surface is weak physisorption, and there is a high energy barrier, i.e., 1.3774 eV, when H2 dissociates into two separate H atoms. Vacancy defect not only benefits enhancing of the physisorption interaction between H2 and Mg surface, but also decreasing of the energy barrier, i.e., 1.2221 eV, of H2 dissociation to some extent. For Pd atom coadsorption Mg(0001) surface, there is a strong chemisorption interaction between Pd atom and H2, and the energy barrier, i.e., 0.2860 eV, of H2 dissociation is reduced significantly. Further analysis of electronic structures shows that the catalytic activity for H2 adsorption and dissociation on three different surfaces is closely related to the bonding electrons number of s orbital of the topmost layer metal atoms which interact directly with H2 around Fermi level
By the first-principles calculations method based on the density functional theory, H2 adsorption and dissociation properties on clean, vacancy defective and Pd atom coadsorption Mg(0001) surfaces are investigated systematically. The calculation results show that the model of H2 adsorption on clean surface is weak physisorption, and there is a high energy barrier, i.e., 1.3774 eV, when H2 dissociates into two separate H atoms. Vacancy defect not only benefits enhancing of the physisorption interaction between H2 and Mg surface, but also decreasing of the energy barrier, i.e., 1.2221 eV, of H2 dissociation to some extent. For Pd atom coadsorption Mg(0001) surface, there is a strong chemisorption interaction between Pd atom and H2, and the energy barrier, i.e., 0.2860 eV, of H2 dissociation is reduced significantly. Further analysis of electronic structures shows that the catalytic activity for H2 adsorption and dissociation on three different surfaces is closely related to the bonding electrons number of s orbital of the topmost layer metal atoms which interact directly with H2 around Fermi level
2009, 38(9):1526-1529.
Abstract:
The phase composition and microstructure evolution of pure and carbon-doped MgB2 bulks exposed to hydrochloric acid (pH=2) for different time were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) systematically. XRD results show the decomposition of pure and carbon-doped MgB2 bulks exposed to acid is rapid decay with exposure time. The decomposition reaction will finish completely after 5 h exposure and the main solid products are B(OH)3 and MgCl2(6H2O). The SEM results demonstrate that the reaction among pure and carbon-doped MgB2 as well as HCl occurs at grain boundaries. But the grain connection of carbon-doped MgB2 is better than that of pure MgB2 after acid exposure. The Tc of MgB2 decreases after 10 min acid exposure, but Tc is almost unchanged in carbon-doped MgB2 after the same exposure. This result indicates that substitution of C for boron in MgB2 can improve of the resistance to the corrosion of acid
The phase composition and microstructure evolution of pure and carbon-doped MgB2 bulks exposed to hydrochloric acid (pH=2) for different time were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) systematically. XRD results show the decomposition of pure and carbon-doped MgB2 bulks exposed to acid is rapid decay with exposure time. The decomposition reaction will finish completely after 5 h exposure and the main solid products are B(OH)3 and MgCl2(6H2O). The SEM results demonstrate that the reaction among pure and carbon-doped MgB2 as well as HCl occurs at grain boundaries. But the grain connection of carbon-doped MgB2 is better than that of pure MgB2 after acid exposure. The Tc of MgB2 decreases after 10 min acid exposure, but Tc is almost unchanged in carbon-doped MgB2 after the same exposure. This result indicates that substitution of C for boron in MgB2 can improve of the resistance to the corrosion of acid
2009, 38(9):1530-1532.
Abstract:
The detail fatigue rating (DFR) valued method is one of the design and prediction methods for fatigue reliability life based on probability fatigue for civil aircrafts. The casting TC4 alloy could not meet the development need for new-type civil turbofan regional aircraft owing to the data deficiency of its fatigue properties. So that the DFRcutoff values of casting TC4 alloy were measured and calculated by double-dot and single dot method, respectively, in this study. The results indicate that the DFRcutoff values are 375.83 MPa by the double-dot method and 387.30 MPa by the single dot method with a relative error lower than 3.1% between them. These test results were accurate and reliable, and can be used to select suitable materials from the fatigue strength design and fatigue life evaluation of the components for new-type turbofan aircraft and the navigability inspection of the civil aircraft
The detail fatigue rating (DFR) valued method is one of the design and prediction methods for fatigue reliability life based on probability fatigue for civil aircrafts. The casting TC4 alloy could not meet the development need for new-type civil turbofan regional aircraft owing to the data deficiency of its fatigue properties. So that the DFRcutoff values of casting TC4 alloy were measured and calculated by double-dot and single dot method, respectively, in this study. The results indicate that the DFRcutoff values are 375.83 MPa by the double-dot method and 387.30 MPa by the single dot method with a relative error lower than 3.1% between them. These test results were accurate and reliable, and can be used to select suitable materials from the fatigue strength design and fatigue life evaluation of the components for new-type turbofan aircraft and the navigability inspection of the civil aircraft
2009, 38(9):1533-1536.
Abstract:
Microstructure evolution of Ti14 (α＋Ti2Cu) alloy during isothermal process at different semi-solid temperatures was researched. It is found that both the semi-solid temperature and holding time would affect the morphology of grain boundary and the grain size. The grains grow obviously and the grain’s shape becomes globular with increasing the holding time, the distribution of liquid on grain boundary changes from discontinuous to continuous to form a latticed structure finally. According to the statistic analysis of experimental data, the grain growth index is 0.88 and 0.97 at 1000 ℃ and 1050 ℃, respectively, indicating that the rising of isothermal temperature would accelerated the microstructure evolution
Microstructure evolution of Ti14 (α＋Ti2Cu) alloy during isothermal process at different semi-solid temperatures was researched. It is found that both the semi-solid temperature and holding time would affect the morphology of grain boundary and the grain size. The grains grow obviously and the grain’s shape becomes globular with increasing the holding time, the distribution of liquid on grain boundary changes from discontinuous to continuous to form a latticed structure finally. According to the statistic analysis of experimental data, the grain growth index is 0.88 and 0.97 at 1000 ℃ and 1050 ℃, respectively, indicating that the rising of isothermal temperature would accelerated the microstructure evolution
2009, 38(9):1537-1541.
Abstract:
By means of similar physical simulation method, the variation of infiltration volume is thoroughly studied during titanium alloy melt feeding in centrifugal field, and compared with the big cross-section filling process. The results show that the infiltration volume in feeding process increases with increasing the feeding time and velocity or decreasing the fluid viscosity and eyelet number of porous medium. When the mould rotates clockwise, the left part relative to the right part in running channel starts feeding and infiltration firstly. The infiltration volume decreases against the big cross-section macro-filling flow in the same time.
By means of similar physical simulation method, the variation of infiltration volume is thoroughly studied during titanium alloy melt feeding in centrifugal field, and compared with the big cross-section filling process. The results show that the infiltration volume in feeding process increases with increasing the feeding time and velocity or decreasing the fluid viscosity and eyelet number of porous medium. When the mould rotates clockwise, the left part relative to the right part in running channel starts feeding and infiltration firstly. The infiltration volume decreases against the big cross-section macro-filling flow in the same time.
2009, 38(9):1542-1546.
Abstract:
In order to improve the properties of the nanostructured Al2O3-13wt%TiO2 composite ceramic coatings fabricated by plasma spraying, a laser remelting experiment was carried out and the effects of laser remelting on the microstructure and properties of coatings were studied. The morphology, microstructure and microhardness of the coatings were investigated by SEM and microhardness. Meanwhile, the wear behavior of the coatings was researched. The results show that the plasma-sprayed nanostructured ceramic coating consists of not only fully melted regions but also partially melted regions, and the total coating has a lamellar-like structure as conventional coating. According to the microstructural difference, the ceramic coating can be divided into the remelted zone (fine equiaxed grains), the sintered zone and remained plasma-sprayed zone after laser remelting. The surface ceramic coating has smaller grains and higher compactness, and the lamellar structure of plasma-sprayed coating is eliminated. Due to the rapid heating and cooling of laser remelting, there are still some nanoparticles coming from the remained nanoparticles of plasma spraying in the remelted zone. The nanostructured ceramic coating has higher hardness, better wear resistance than the conventional ceramic coatings, and the laser–remelted coating has the highest hardness and the best wear resistance
In order to improve the properties of the nanostructured Al2O3-13wt%TiO2 composite ceramic coatings fabricated by plasma spraying, a laser remelting experiment was carried out and the effects of laser remelting on the microstructure and properties of coatings were studied. The morphology, microstructure and microhardness of the coatings were investigated by SEM and microhardness. Meanwhile, the wear behavior of the coatings was researched. The results show that the plasma-sprayed nanostructured ceramic coating consists of not only fully melted regions but also partially melted regions, and the total coating has a lamellar-like structure as conventional coating. According to the microstructural difference, the ceramic coating can be divided into the remelted zone (fine equiaxed grains), the sintered zone and remained plasma-sprayed zone after laser remelting. The surface ceramic coating has smaller grains and higher compactness, and the lamellar structure of plasma-sprayed coating is eliminated. Due to the rapid heating and cooling of laser remelting, there are still some nanoparticles coming from the remained nanoparticles of plasma spraying in the remelted zone. The nanostructured ceramic coating has higher hardness, better wear resistance than the conventional ceramic coatings, and the laser–remelted coating has the highest hardness and the best wear resistance
2009, 38(9):1547-1551.
Abstract:
Nano-SrFe12O19 magnetic powder was preparaed with sol-gel method, and its magnetic properties were detected by a magnetometer. The TiO2 film containing SrFe12O19 powder was coated on the surface of NiTi alloy and 316L stainless steel with sol-gel method and the elements of film were analysed by XRD. The micro-magnetic field magnetization of TiO2 films containing SrFe12O19 powder with different layer numbers were tested and the dynamic clotting time and the hemolysis rate of these different films were tested. All results show that the higher the micro-magnetic field strength of material surface, the better the blood compatibility.
Nano-SrFe12O19 magnetic powder was preparaed with sol-gel method, and its magnetic properties were detected by a magnetometer. The TiO2 film containing SrFe12O19 powder was coated on the surface of NiTi alloy and 316L stainless steel with sol-gel method and the elements of film were analysed by XRD. The micro-magnetic field magnetization of TiO2 films containing SrFe12O19 powder with different layer numbers were tested and the dynamic clotting time and the hemolysis rate of these different films were tested. All results show that the higher the micro-magnetic field strength of material surface, the better the blood compatibility.
2009, 38(9):1552-1555.
Abstract:
The effect of superficial magnetic film on vascular endothelialization for the 316L medical stainless steel stent was investigated in this study. The in vitro endothelial response of human umbilical vein endothelium cell (HUVECs) was investigated on the superficial magnetic film 316L medical stainless steel stent vs bare-metal stent surface；as well as the re-endothelialization and platelet adhesion reaction of superficial magnetic film 316L medical stainless steel stent vs bare-metal stent were evaluated with SEM after animal models implantation for 1 month and 3 months. The consequence indicates that the superficial magnetic film 316L medical stainless steel stent can increase the adhesion and proliferation of HUVECs in vitro，and promote the regenesis of vas endothelialization after implantation in vivo, as well as speed the stent endothelialization and inhibite the platelet adhesion reaction and activation, simultaneously
The effect of superficial magnetic film on vascular endothelialization for the 316L medical stainless steel stent was investigated in this study. The in vitro endothelial response of human umbilical vein endothelium cell (HUVECs) was investigated on the superficial magnetic film 316L medical stainless steel stent vs bare-metal stent surface；as well as the re-endothelialization and platelet adhesion reaction of superficial magnetic film 316L medical stainless steel stent vs bare-metal stent were evaluated with SEM after animal models implantation for 1 month and 3 months. The consequence indicates that the superficial magnetic film 316L medical stainless steel stent can increase the adhesion and proliferation of HUVECs in vitro，and promote the regenesis of vas endothelialization after implantation in vivo, as well as speed the stent endothelialization and inhibite the platelet adhesion reaction and activation, simultaneously
2009, 38(9):1556-1561.
Abstract:
In this paper, rare earth Y-doped amorphous nano-sized nickel hydroxide powder was prepared through the method of micro emulsion deep freeze deposition with the system of Tween-80/n-C4H9OH/c-C6H12/NiSO4 solution. XRD, SAED, SEM, TEM, EDS, Raman, IR, and particle size distribution and specific surface area measurements were used to analyze the structure and morphology of the material samples. Their charge-discharge performance and electrochemical impedance spectroscopy were also studied. The results showed that the disorder intensity of amorphous nickel hydroxide is increased, the average particle size is decreased and the specific surface area is also increased by adding rare earth Y, to the benefit of decreasing solution resistance, charge transfer resistance and Warburg impedance for the sample electrodes due to the increase of discharge specific capacity. The discharge specific capacity is 333.3 mAh·g-1 when adding 4% Y (mass fraction) at a charge-discharge system of 0.2 C and a cut-off voltage of 1 V if used for the anode materials of MH-Ni battery
In this paper, rare earth Y-doped amorphous nano-sized nickel hydroxide powder was prepared through the method of micro emulsion deep freeze deposition with the system of Tween-80/n-C4H9OH/c-C6H12/NiSO4 solution. XRD, SAED, SEM, TEM, EDS, Raman, IR, and particle size distribution and specific surface area measurements were used to analyze the structure and morphology of the material samples. Their charge-discharge performance and electrochemical impedance spectroscopy were also studied. The results showed that the disorder intensity of amorphous nickel hydroxide is increased, the average particle size is decreased and the specific surface area is also increased by adding rare earth Y, to the benefit of decreasing solution resistance, charge transfer resistance and Warburg impedance for the sample electrodes due to the increase of discharge specific capacity. The discharge specific capacity is 333.3 mAh·g-1 when adding 4% Y (mass fraction) at a charge-discharge system of 0.2 C and a cut-off voltage of 1 V if used for the anode materials of MH-Ni battery
2009, 38(9):1562-1566.
Abstract:
Based on the microscopic phase-field model, the evolution of atom morphology of Ni80Al7Cr13 ternary alloy is simulated at 873 K during the aging process. The early stage effect of precipitation is studied and discussed through analysising the changes of microstructure, composition and order parameter with the time. The study shows that the ordering of atom is happened earlier than the clustering of atom in the early time of precipitation, firstly forming the nonstoicheometric L10 ordered domain with very low order parameter, then the order parameter increasing with the increase of the aging time. At the same time, the ordered domain expands toward the nonordered domain, and the nonstoicheometric L10 ordered domain gradually transforms to the nonstoicheometric L12 structure when the order parameter of L10 increases to some degree. At last, the composition and the order parameter of nonstoicheometric L12 ordered domain attain to that of the stoicheometric L12 ordered domain. In the stoicheometric L12 ordered domain, Al priority occupies the αⅠ antisite,Cr priority occupies the αⅡ antisite
Based on the microscopic phase-field model, the evolution of atom morphology of Ni80Al7Cr13 ternary alloy is simulated at 873 K during the aging process. The early stage effect of precipitation is studied and discussed through analysising the changes of microstructure, composition and order parameter with the time. The study shows that the ordering of atom is happened earlier than the clustering of atom in the early time of precipitation, firstly forming the nonstoicheometric L10 ordered domain with very low order parameter, then the order parameter increasing with the increase of the aging time. At the same time, the ordered domain expands toward the nonordered domain, and the nonstoicheometric L10 ordered domain gradually transforms to the nonstoicheometric L12 structure when the order parameter of L10 increases to some degree. At last, the composition and the order parameter of nonstoicheometric L12 ordered domain attain to that of the stoicheometric L12 ordered domain. In the stoicheometric L12 ordered domain, Al priority occupies the αⅠ antisite,Cr priority occupies the αⅡ antisite
2009, 38(9):1567-1569.
Abstract:
ZrO2 thin coatings were deposited on stainless steel substrates by electron beam physical vapor deposition (EB-PVD) under different substrate temperatures. The phase composition, microstructure and residual stress of the deposited coatings were investigated by grazing incidence X-ray diffraction, scanning electron microscopy and atomic force microscope techniques. The results show that all the deposited thin films have a tetragonal structure with a preferred orientation (111). The grain size, surface roughness and residual stress of the ZrO2 coatings increase as the substrate temperature goes up. The residual stress of ZrO2 coatings was induced by the thermal stress due to the difference of thermal expansion coefficients of ZrO2 ceramic coatings and metal substrate
ZrO2 thin coatings were deposited on stainless steel substrates by electron beam physical vapor deposition (EB-PVD) under different substrate temperatures. The phase composition, microstructure and residual stress of the deposited coatings were investigated by grazing incidence X-ray diffraction, scanning electron microscopy and atomic force microscope techniques. The results show that all the deposited thin films have a tetragonal structure with a preferred orientation (111). The grain size, surface roughness and residual stress of the ZrO2 coatings increase as the substrate temperature goes up. The residual stress of ZrO2 coatings was induced by the thermal stress due to the difference of thermal expansion coefficients of ZrO2 ceramic coatings and metal substrate
2009, 38(9):1570-1574.
Abstract:
WOx-Mo thin films have been deposited on the ITO/PET substrates by RF magnetron sputtering. The electrochromic properties of films were investigated by cyclic voltammetry (C-V) and chronoamperometry (CA) methods. It is found that the maximum of oxidation current increases and the oxidation peaks move to plus potential with increasing Mo doping concentration. Furthermore, the coloring response time decreases and the bleaching response time increases with increasing Mo doping concentration in the experimental range. For the film doped 15.4% Mo, the oxidation current reaches the maximum and the coloring response time is 4.53 s, the bleaching response time is 9.8 s. Not all the samples exhibit good reversibility due to the charge left in the film. The best reversibility is 51.2 % in the WOx film doped 7.6% Mo
WOx-Mo thin films have been deposited on the ITO/PET substrates by RF magnetron sputtering. The electrochromic properties of films were investigated by cyclic voltammetry (C-V) and chronoamperometry (CA) methods. It is found that the maximum of oxidation current increases and the oxidation peaks move to plus potential with increasing Mo doping concentration. Furthermore, the coloring response time decreases and the bleaching response time increases with increasing Mo doping concentration in the experimental range. For the film doped 15.4% Mo, the oxidation current reaches the maximum and the coloring response time is 4.53 s, the bleaching response time is 9.8 s. Not all the samples exhibit good reversibility due to the charge left in the film. The best reversibility is 51.2 % in the WOx film doped 7.6% Mo
2009, 38(9):1575-1579.
Abstract:
Metal zirconium was prepared by electro-deoxidization method by using CaCl2 molten as electrolyte, sintered ZrO2 and ZrO2 doped different mole CaCO3 pallets as cathode, graphite rod as anode. The pallets were electrolyzed at 900 ℃ and 3.1 V for 8 h. It is found that the rate of electro-deoxidization reaction for ZrO2 and the current efficiency were increased, and the reaction time of Electro-deoxidization was shortened by adding CaCO3.
Metal zirconium was prepared by electro-deoxidization method by using CaCl2 molten as electrolyte, sintered ZrO2 and ZrO2 doped different mole CaCO3 pallets as cathode, graphite rod as anode. The pallets were electrolyzed at 900 ℃ and 3.1 V for 8 h. It is found that the rate of electro-deoxidization reaction for ZrO2 and the current efficiency were increased, and the reaction time of Electro-deoxidization was shortened by adding CaCO3.
2009, 38(9):1580-1583.
Abstract:
Ytterbium silicate (Yb2SiO5) is a promising oxidation protective coating material for C fiber-reinforced SiC (Cf/SiC) composites. Firstly, the SiC bond coat was prepared on Cf/SiC composites by pulse CVD. The single-phase Yb2SiO5 powders of 200~300 nm in size were synthesized by sol–gel process. Then for the first time, the SiC-Yb2SiO5 intermediate coat was applied on the SiC coated Cf/SiC composites through PCS-SiC-Yb2SiO5 slurry application. The incorporation of PCS could significantly improve the adhesion of the coating because of the great stickiness of PCS and its ability to form SiC ceramic in situ after pyrolysis. The Yb2SiO5 slurry with low viscosity and high solid content was prepared, and the dense Yb2SiO5 top coat with fine crystallites was fabricated by dip-coating and subsequent sintering. The oxidation tests at 1500 ℃ in stationary air indicate that the fabricated SiC/Yb2SiO5 multilayer coatings possess a outstanding oxidation resistance
Ytterbium silicate (Yb2SiO5) is a promising oxidation protective coating material for C fiber-reinforced SiC (Cf/SiC) composites. Firstly, the SiC bond coat was prepared on Cf/SiC composites by pulse CVD. The single-phase Yb2SiO5 powders of 200~300 nm in size were synthesized by sol–gel process. Then for the first time, the SiC-Yb2SiO5 intermediate coat was applied on the SiC coated Cf/SiC composites through PCS-SiC-Yb2SiO5 slurry application. The incorporation of PCS could significantly improve the adhesion of the coating because of the great stickiness of PCS and its ability to form SiC ceramic in situ after pyrolysis. The Yb2SiO5 slurry with low viscosity and high solid content was prepared, and the dense Yb2SiO5 top coat with fine crystallites was fabricated by dip-coating and subsequent sintering. The oxidation tests at 1500 ℃ in stationary air indicate that the fabricated SiC/Yb2SiO5 multilayer coatings possess a outstanding oxidation resistance
2009, 38(9):1584-1588.
Abstract:
Al65Cu15Co20 decagonal quasicrystalline alloys were prepared by an arc-melting furnace. The aluminium-based composites were fabricated by using the Al65Cu15Co20 decagonal quasicrystalline particles as reinforcing phase and Al-4.5 wt%Cu alloy as matrix with mechanical stirring. The microstructures, the phase composition, and the distribution of Al65Cu15Co20 were characterisied by XRD, SEM, SEM and EDS for the Al65Cu15Co20 quasicrystalline alloys and the reinforced composites. And the morphology, chemical composition and structure changes of the quasicrystalline particles before and after adding to the melt were also analysised. As the interdiffusion occurs between the quasicrystalline particles and the melt, the quasicrystalline particles can not exist stably in the melt. The morphology of the particles turns from inregular polygons to block and lath-like in shape as following: D-Al62.10Cu17.46Co20.44 → θ-Al79.58Cu1.10Co19.32 after adding the quasicrystalline particles into the melt. During the solidification process, the θ phase distributes uniformly along the grain boundaries because of the “interfacial pushing effect”
Al65Cu15Co20 decagonal quasicrystalline alloys were prepared by an arc-melting furnace. The aluminium-based composites were fabricated by using the Al65Cu15Co20 decagonal quasicrystalline particles as reinforcing phase and Al-4.5 wt%Cu alloy as matrix with mechanical stirring. The microstructures, the phase composition, and the distribution of Al65Cu15Co20 were characterisied by XRD, SEM, SEM and EDS for the Al65Cu15Co20 quasicrystalline alloys and the reinforced composites. And the morphology, chemical composition and structure changes of the quasicrystalline particles before and after adding to the melt were also analysised. As the interdiffusion occurs between the quasicrystalline particles and the melt, the quasicrystalline particles can not exist stably in the melt. The morphology of the particles turns from inregular polygons to block and lath-like in shape as following: D-Al62.10Cu17.46Co20.44 → θ-Al79.58Cu1.10Co19.32 after adding the quasicrystalline particles into the melt. During the solidification process, the θ phase distributes uniformly along the grain boundaries because of the “interfacial pushing effect”
2009, 38(9):1589-1593.
Abstract:
The one-step ageing behavior of a novel Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy was studied by measuring the mechanical properties and electrical conductivity, and the evolution of microstructure during the aging was investigated by using TEM. The results show that the aging response rate was greatly accelerated with elevating the aging temperature from 100 ℃ to 160 ℃, and the time achieved to over-aged stage was remarkably decreased, while the electrical conductivity of the alloy became higher. After aging for 14 h at 140 °C, the UTS, TYS, Elongation and Electrical conductivity values were achieved to 585 MPa, 560 MPa, 16.1% and 22.6 MS/m, respectively; Comparing with the T6 temper condition performed at 120 ℃ for 24 h, the UTS decreased only by 1%, whereas the TYS and the electrical conductivity obviously increased by 4% and 11%, respectively. The major strengthening precipitates of the peak-aged alloy were the η’ phase and GP zones. The precipitates in both the matrix and the grain boundary became coarser with rising aging temperature. There were obvious PFZs along the grain boundary when the aging treatment was performed at 140 ℃
The one-step ageing behavior of a novel Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy was studied by measuring the mechanical properties and electrical conductivity, and the evolution of microstructure during the aging was investigated by using TEM. The results show that the aging response rate was greatly accelerated with elevating the aging temperature from 100 ℃ to 160 ℃, and the time achieved to over-aged stage was remarkably decreased, while the electrical conductivity of the alloy became higher. After aging for 14 h at 140 °C, the UTS, TYS, Elongation and Electrical conductivity values were achieved to 585 MPa, 560 MPa, 16.1% and 22.6 MS/m, respectively; Comparing with the T6 temper condition performed at 120 ℃ for 24 h, the UTS decreased only by 1%, whereas the TYS and the electrical conductivity obviously increased by 4% and 11%, respectively. The major strengthening precipitates of the peak-aged alloy were the η’ phase and GP zones. The precipitates in both the matrix and the grain boundary became coarser with rising aging temperature. There were obvious PFZs along the grain boundary when the aging treatment was performed at 140 ℃
2009, 38(9):1594-1597.
Abstract:
Cu-Fe-Cr-Ni in-situ composite wires were manufactured by inductive melting, casting, hot rolling and heavily cold drawing. The structure and morphology were analyzed by XRD, SEM and TEM. The magnetic properties were examined by vibrating sample magnetometer. With the ferrite fibers are fined down to submicrometer, obvious magnetic anisotropy and the Perminvar effect were found along the axis of wires. After deformation of higher amount, the rectangle degree increases gradually to a value of 0.33 at η=10.11
Cu-Fe-Cr-Ni in-situ composite wires were manufactured by inductive melting, casting, hot rolling and heavily cold drawing. The structure and morphology were analyzed by XRD, SEM and TEM. The magnetic properties were examined by vibrating sample magnetometer. With the ferrite fibers are fined down to submicrometer, obvious magnetic anisotropy and the Perminvar effect were found along the axis of wires. After deformation of higher amount, the rectangle degree increases gradually to a value of 0.33 at η=10.11
2009, 38(9):1598-1601.
Abstract:
The atomic cluster models of α-Al, η phase and large angle grain boundary of α-Al with η phase in Al-Zn-Mg-Cu alloys have been founded by a computer program. The environment-sensitive embedding energy, and the atom action energy of Zn, Mg, Cu and the atom binding energy, the fermi energy of α-Al and/or η phase have been calculated by a recursion method. The corrosion character of Al-Zn-Mg-Cu alloys has been studied according to the calculated electronic parameter. The results show that Mg and Zn elements are easy to segregate on grain boundaries, and to form η phase. The η phase on grain boundary are large then that in grain due to the segregation of Mg in the grain boundary. The calculated results indicate that the fermi energy of η phase is the highest, will be decomposed firstly in the corrosion as an anode. The alloy element Zn has the function to increase the electrode potential difference between grain boundary and grains, to deteriorate the corrosion character of alloys. The alloy element Cu can reduce the difference of Fermi energy and the potential difference between grain and grain boundary, so as to slow down the corrosion process
The atomic cluster models of α-Al, η phase and large angle grain boundary of α-Al with η phase in Al-Zn-Mg-Cu alloys have been founded by a computer program. The environment-sensitive embedding energy, and the atom action energy of Zn, Mg, Cu and the atom binding energy, the fermi energy of α-Al and/or η phase have been calculated by a recursion method. The corrosion character of Al-Zn-Mg-Cu alloys has been studied according to the calculated electronic parameter. The results show that Mg and Zn elements are easy to segregate on grain boundaries, and to form η phase. The η phase on grain boundary are large then that in grain due to the segregation of Mg in the grain boundary. The calculated results indicate that the fermi energy of η phase is the highest, will be decomposed firstly in the corrosion as an anode. The alloy element Zn has the function to increase the electrode potential difference between grain boundary and grains, to deteriorate the corrosion character of alloys. The alloy element Cu can reduce the difference of Fermi energy and the potential difference between grain and grain boundary, so as to slow down the corrosion process
2009, 38(9):1602-1607.
Abstract:
The microstructure and mechanical properties of AlxCoCrCuFeNi with different Al content have been studied. The results showed that the microstructures exhibit simple dendrite and interdendrite structures. When the content of aluminum was low, the alloy was composed of a simple FCC solid-solution structure. As the aluminum contents increasing, a BCC structure appeared. The high entropy effects and sluggish diffusion enhance the formation of simple solid-solution phases and submicron structures with nanoprecipitates in the alloys. With the addition of aluminum from x=0 to 3.0, the hardness of the alloys increase from 1530 to 7350 MPa Correspondingly, the alloy’s deformability falls and transfers from ductile materials to brittle materials at moderate temperatures.
The microstructure and mechanical properties of AlxCoCrCuFeNi with different Al content have been studied. The results showed that the microstructures exhibit simple dendrite and interdendrite structures. When the content of aluminum was low, the alloy was composed of a simple FCC solid-solution structure. As the aluminum contents increasing, a BCC structure appeared. The high entropy effects and sluggish diffusion enhance the formation of simple solid-solution phases and submicron structures with nanoprecipitates in the alloys. With the addition of aluminum from x=0 to 3.0, the hardness of the alloys increase from 1530 to 7350 MPa Correspondingly, the alloy’s deformability falls and transfers from ductile materials to brittle materials at moderate temperatures.
2009, 38(9):1608-1612.
Abstract:
The continuous castings of wrought magnesium alloy AZ31 with or without the effects of electromagnetic field and Ca microalloying were investigated，and the appearances, microstructures and mechanical properties were compared. The results show that the ingots with the electromagnetic field casting (EMC) and Ca microalloying have smooth surface, and the defects, such as segregation, trapped oxide can be eliminated on the ingot surface. Through EMC and Ca microalloying, the microstructure is improved and the grain in the border and center of the ingot has a same size, the β-Mg17Al12 phases with the shape of dot and approximate dot distribute in the basal body uniformly. The yield strength and elongation increase by 15% and 90%, respectively, for the ingot with EMC and Ca microalloying compared to the ingot without EMC and Ca microalloying
The continuous castings of wrought magnesium alloy AZ31 with or without the effects of electromagnetic field and Ca microalloying were investigated，and the appearances, microstructures and mechanical properties were compared. The results show that the ingots with the electromagnetic field casting (EMC) and Ca microalloying have smooth surface, and the defects, such as segregation, trapped oxide can be eliminated on the ingot surface. Through EMC and Ca microalloying, the microstructure is improved and the grain in the border and center of the ingot has a same size, the β-Mg17Al12 phases with the shape of dot and approximate dot distribute in the basal body uniformly. The yield strength and elongation increase by 15% and 90%, respectively, for the ingot with EMC and Ca microalloying compared to the ingot without EMC and Ca microalloying
2009, 38(9):1613-1617.
Abstract:
The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength
The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength
2009, 38(9):1618-1621.
Abstract:
The effect of Al addition on the hydrogen storage performance of LiBH4 was investigated. It is indicated that the onset dehydrogenation temperature of LiBH4/Al mixture is decreased to about 300 ℃. The main hydrogen release shifts to low temperature with the increase of Al content. Furthermore, the dehydrogenated LiBH4/Al sample can be rehydrogenated at 600 ℃ and 10 MPa, significantly lower than that of the plan LiBH4. The improvement of hydrogen storage properties in LiBH4/Al system is due to the formation of LiAl and AlB2 compounds during the dehydrogenation
The effect of Al addition on the hydrogen storage performance of LiBH4 was investigated. It is indicated that the onset dehydrogenation temperature of LiBH4/Al mixture is decreased to about 300 ℃. The main hydrogen release shifts to low temperature with the increase of Al content. Furthermore, the dehydrogenated LiBH4/Al sample can be rehydrogenated at 600 ℃ and 10 MPa, significantly lower than that of the plan LiBH4. The improvement of hydrogen storage properties in LiBH4/Al system is due to the formation of LiAl and AlB2 compounds during the dehydrogenation
2009, 38(9):1622-1625.
Abstract:
Using the MSC.Marc software, the temperature and stress fields in beryllium during cutting process are studied by employing a thermo-mechanically coupled finite element method (FEM). The constitutive equation of beryllium is fitted with the Johnson-Cook plasticity model, and an user subroutine is written for modeling the chip separation after fracturing. The results show that the temperature in beryllium increases only a little and the highest temperature is about 45 ℃. Both of the residual stress components for parallel and vertical to the cutting direction are tensile on the surface of beryllium after cutting. The cutting force and thrust force are 280 and –250 N/mm, respectively, during the cutting steady state if the cutting process is adopted in this paper. This study is helpful to enhance the understanding for stress formation and the optimizing for the beryllium cutting process.
Using the MSC.Marc software, the temperature and stress fields in beryllium during cutting process are studied by employing a thermo-mechanically coupled finite element method (FEM). The constitutive equation of beryllium is fitted with the Johnson-Cook plasticity model, and an user subroutine is written for modeling the chip separation after fracturing. The results show that the temperature in beryllium increases only a little and the highest temperature is about 45 ℃. Both of the residual stress components for parallel and vertical to the cutting direction are tensile on the surface of beryllium after cutting. The cutting force and thrust force are 280 and –250 N/mm, respectively, during the cutting steady state if the cutting process is adopted in this paper. This study is helpful to enhance the understanding for stress formation and the optimizing for the beryllium cutting process.
27 Microstructure Transformation during Ramp-up of Weld in Brazing Copper with Cu-P Amorphous Fillers
2009, 38(9):1626-1629.
Abstract:
The amorphous fillers with components Cu68.5Ni15.7Sn9.3P6.5 (wt%) are brazed with copper by vacuum brazing. The microstructure transformation during ramp-up are studied by means of XRD, EPMA and DSC. The results show that the crystallstructures of amorphous filler are fully eutectic organizations with small and uniform grains, as a result, its joint mechanical properties are enhanced by different solidification ways
The amorphous fillers with components Cu68.5Ni15.7Sn9.3P6.5 (wt%) are brazed with copper by vacuum brazing. The microstructure transformation during ramp-up are studied by means of XRD, EPMA and DSC. The results show that the crystallstructures of amorphous filler are fully eutectic organizations with small and uniform grains, as a result, its joint mechanical properties are enhanced by different solidification ways
2009, 38(9):1630-1633.
Abstract:
Yb0.05:Gd0.20Y0.75Al3(BO3)4(Yb:GdYAB) and Yb0.05:Y0.95Al3(BO3)4(Yb:YAB) crystals have been grown using the flux method. Their absorption and fluorescence spectra were measured at room temperature and important spectroscopic parameters were calculated. Through the comparison of spectroscopic parameters for the Yb:GdYAB and Yb:YAB, it is indicated that the 5 at% Yb:GdYAB crystal is an excellent self-frequency-doubling laser crystal and potential candidate for compact, efficient thin chip lasers.
Yb0.05:Gd0.20Y0.75Al3(BO3)4(Yb:GdYAB) and Yb0.05:Y0.95Al3(BO3)4(Yb:YAB) crystals have been grown using the flux method. Their absorption and fluorescence spectra were measured at room temperature and important spectroscopic parameters were calculated. Through the comparison of spectroscopic parameters for the Yb:GdYAB and Yb:YAB, it is indicated that the 5 at% Yb:GdYAB crystal is an excellent self-frequency-doubling laser crystal and potential candidate for compact, efficient thin chip lasers.
2009, 38(9):1634-1637.
Abstract:
ZrB2 based ceramic matrix composites containing two kinds of SiC whiskers were produced at 1800 ℃ under a uniaxial load of 30 MPa by hot-pressing. The microstructure and mechanical properties of the two composites were investigated. The results show that the flexural strength and fracture toughness of composites are related with the aspect ratio of SiC whisker: the larger the aspect ratio is, the better of the properties of materials. The maximum flexural strength and the fracture toughness are 651 MPa and 5.97 MPa.m1/2, respectively. The mechanical properties, especially the fracture toughness, are much higher than that of monolithic ZrB2 and SiC particles reinforced ZrB2 composites due to the main toughening mechanisms of crack deflection, whisker bridging and pullout.
ZrB2 based ceramic matrix composites containing two kinds of SiC whiskers were produced at 1800 ℃ under a uniaxial load of 30 MPa by hot-pressing. The microstructure and mechanical properties of the two composites were investigated. The results show that the flexural strength and fracture toughness of composites are related with the aspect ratio of SiC whisker: the larger the aspect ratio is, the better of the properties of materials. The maximum flexural strength and the fracture toughness are 651 MPa and 5.97 MPa.m1/2, respectively. The mechanical properties, especially the fracture toughness, are much higher than that of monolithic ZrB2 and SiC particles reinforced ZrB2 composites due to the main toughening mechanisms of crack deflection, whisker bridging and pullout.
30 Structure and Luminescence Properties of (Y, Gd)Al3(BO3)4:Tb3+ Phosphors by Gel Combustion Synthesis
2009, 38(9):1638-1641.
Abstract:
(Y,Gd)Al3(BO3)4:Tb3+ phosphors were synthesized by a gel combustion method. The phase composition, morphology and luminescent properties of the powders derived from the sintered precursor at different temperatures were analyzed by X–ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescent measurement (PL). The results show that the purified (Y,Gd)Al3(BO3)4:Tb3+ crystalline phase could be obtained at 1000 ℃. The intermediate phases: Yttrium borate (YBO3) , aluminum borate (Al4B2O9) and yttrium aluminum garnet, are generated firstly, then the finally single-phase YAB:Eu3+ is produced. The powder as-prepared at 1100 ℃ consists of relatively homogeneous particles with the average diameter of 1 μm. The luminescent properties of (Y, Gd)Al3(BO3)4:Tb3+ are presented. In the emission spectrum of (Y, Gd)Al3(BO3)4:Tb3+ excited by 229 nm, the main peak is located at about 542 nm due to the transition of 5D0→7F2 of Tb3+ emission. The PL intensity of Tb3+ in Y0.9-xGdxAl3Tb0.1(BO3)4 increases with the increase of x values due to an energy migration process like Gd3+→Tb3+ occurred in the phosphors
(Y,Gd)Al3(BO3)4:Tb3+ phosphors were synthesized by a gel combustion method. The phase composition, morphology and luminescent properties of the powders derived from the sintered precursor at different temperatures were analyzed by X–ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescent measurement (PL). The results show that the purified (Y,Gd)Al3(BO3)4:Tb3+ crystalline phase could be obtained at 1000 ℃. The intermediate phases: Yttrium borate (YBO3) , aluminum borate (Al4B2O9) and yttrium aluminum garnet, are generated firstly, then the finally single-phase YAB:Eu3+ is produced. The powder as-prepared at 1100 ℃ consists of relatively homogeneous particles with the average diameter of 1 μm. The luminescent properties of (Y, Gd)Al3(BO3)4:Tb3+ are presented. In the emission spectrum of (Y, Gd)Al3(BO3)4:Tb3+ excited by 229 nm, the main peak is located at about 542 nm due to the transition of 5D0→7F2 of Tb3+ emission. The PL intensity of Tb3+ in Y0.9-xGdxAl3Tb0.1(BO3)4 increases with the increase of x values due to an energy migration process like Gd3+→Tb3+ occurred in the phosphors
2009, 38(9):1642-1645.
Abstract:
Glass fiber reinforced chitosan-hydroxyapatite (HA-CS) composites (G(f)/HA-CS) were prepared by a in-situ precipitation process. The infulences of the cross linker, HA mass fraction and fiber mass fraction on the structure and flexural strength of the composites were investigated. The structures and properties of the as-prepared composites were characterized by IR, SEM and universal test machine. The results show that the composites with good performances can be obtained by employing the in-situ hybrid process; the toughness of the composites modified by glutaric dialdehyde cross-linking can be remarkably increased, and their flexural strength can be improved by 16% to an optimum value of 84.47 MPa when the monomer ratio (CS/HA) reaches 10/1 and the fiber mass fraction reaches 1.5%. With the increase of glass fiber mass fraction, the microstructure of fractured surfaces changes from smooth to crapy. It can be infered that the toughness of the composites is improved
Glass fiber reinforced chitosan-hydroxyapatite (HA-CS) composites (G(f)/HA-CS) were prepared by a in-situ precipitation process. The infulences of the cross linker, HA mass fraction and fiber mass fraction on the structure and flexural strength of the composites were investigated. The structures and properties of the as-prepared composites were characterized by IR, SEM and universal test machine. The results show that the composites with good performances can be obtained by employing the in-situ hybrid process; the toughness of the composites modified by glutaric dialdehyde cross-linking can be remarkably increased, and their flexural strength can be improved by 16% to an optimum value of 84.47 MPa when the monomer ratio (CS/HA) reaches 10/1 and the fiber mass fraction reaches 1.5%. With the increase of glass fiber mass fraction, the microstructure of fractured surfaces changes from smooth to crapy. It can be infered that the toughness of the composites is improved
2009, 38(9):1646-1649.
Abstract:
Carbon coated nano Co particles were prepared by pyrolysis of Co-exchanged resin (Co/D113) at 400 to 700 ℃. The TG results show that the thermal stability of Co/D113 is better than that of pure D113 resin. The XRD and TEM results reveal that the cobalt particles existed mainly in the form of fcc Co phase, and the particle size of nano-Co increase with the increase of pyrolytic temperature. The magnetic tests show that the coercivity(Hc) of the pyrolyzates obtained at 400 to 700 ℃ at room temperature are much higher than that of the corresponding bulk material, and the Hc value is influenced by the size of the nano particles. The saturation magnetizations (Ms) of all the pyrolyzates are lower than that of bulk material and increase with the increase of pyrolytic temperature
Carbon coated nano Co particles were prepared by pyrolysis of Co-exchanged resin (Co/D113) at 400 to 700 ℃. The TG results show that the thermal stability of Co/D113 is better than that of pure D113 resin. The XRD and TEM results reveal that the cobalt particles existed mainly in the form of fcc Co phase, and the particle size of nano-Co increase with the increase of pyrolytic temperature. The magnetic tests show that the coercivity(Hc) of the pyrolyzates obtained at 400 to 700 ℃ at room temperature are much higher than that of the corresponding bulk material, and the Hc value is influenced by the size of the nano particles. The saturation magnetizations (Ms) of all the pyrolyzates are lower than that of bulk material and increase with the increase of pyrolytic temperature
2009, 38(9):1650-1654.
Abstract:
SiC particulate reinforced aluminium metal matrix composites SiCp/101Al were welded by electron beam welding with different welding parameters, and the structure and properties of welded joints were investigated. The mechanical properties of welded joints with different welding parameters were studied through tensile test. The microstructure of weld metal was analyzed with optical microscope and the morphology of joint fracture was observed by SEM. The interfacial structure of SiC-A1 was analyzed with TEM, and the phase constituent of welded joint was tested by XRD. The results show that the joint strength can be improved by decreasing the heat input power of electron beam when getting the penetration bead. Some pores appeared mainly near in the bond line, but porosity can be suppressed to a great extent by increasing welding speed or electron beam scanning. Moreover, the modification of welding is advantageous to improve the joint qualities.
SiC particulate reinforced aluminium metal matrix composites SiCp/101Al were welded by electron beam welding with different welding parameters, and the structure and properties of welded joints were investigated. The mechanical properties of welded joints with different welding parameters were studied through tensile test. The microstructure of weld metal was analyzed with optical microscope and the morphology of joint fracture was observed by SEM. The interfacial structure of SiC-A1 was analyzed with TEM, and the phase constituent of welded joint was tested by XRD. The results show that the joint strength can be improved by decreasing the heat input power of electron beam when getting the penetration bead. Some pores appeared mainly near in the bond line, but porosity can be suppressed to a great extent by increasing welding speed or electron beam scanning. Moreover, the modification of welding is advantageous to improve the joint qualities.
2009, 38(9):1655-1658.
Abstract:
An Al2O3-modified chromizing coating was produced by chromizing as-electrodeposited Ni-Al2O3 nanocomposite film using pack cementation method at 1100 oC for 3 h. For comparison, the chromizing was also performed in the same condition on as-deposited Ni film without Al2O3 nanoparticles. SEM/EDAX and TEM results indicate that the co-deposited Al2O3 nanoparticles are homogeneously dispersed in the finer-grain nanocrystalline Ni grains. At the same time, the co-deposited Al2O3 nanoparticles restrain the grain growth during chromizing by anchoring the movement of grain boundaries, which leads to the formation of finer grained chromizing coating. It is indicated from oxidation at 900 ℃ for 120 h that although both two chromizing coatings grow chromia scales during oxidation, the Al2O3-modified chromizing coating exhibits an increased oxidation resistance due to the accelerated chromium diffusion to the oxidation front via the increased grain boundaries and consequently accelerated the formation of a continuous chromia layer in a shorter transient time, together with the change of the oxidation mechanism. The effect of Al2O3 on the microstructure and oxidation of the chromizing coatings are discussed in the detail
An Al2O3-modified chromizing coating was produced by chromizing as-electrodeposited Ni-Al2O3 nanocomposite film using pack cementation method at 1100 oC for 3 h. For comparison, the chromizing was also performed in the same condition on as-deposited Ni film without Al2O3 nanoparticles. SEM/EDAX and TEM results indicate that the co-deposited Al2O3 nanoparticles are homogeneously dispersed in the finer-grain nanocrystalline Ni grains. At the same time, the co-deposited Al2O3 nanoparticles restrain the grain growth during chromizing by anchoring the movement of grain boundaries, which leads to the formation of finer grained chromizing coating. It is indicated from oxidation at 900 ℃ for 120 h that although both two chromizing coatings grow chromia scales during oxidation, the Al2O3-modified chromizing coating exhibits an increased oxidation resistance due to the accelerated chromium diffusion to the oxidation front via the increased grain boundaries and consequently accelerated the formation of a continuous chromia layer in a shorter transient time, together with the change of the oxidation mechanism. The effect of Al2O3 on the microstructure and oxidation of the chromizing coatings are discussed in the detail
2009, 38(9):1659-1662.
Abstract:
Fe-B nanoparticles were synthesized by using solution and reverse micelle methods. The structures, the B contents and the magnetic properties of the particles have been characterized by XRD, TEM, ICP, VSM, etc. It is found that the difference in magnetic properties of Fe-B nanoparticles fabricated by the two methods is mainly caused by the structure, the B content and the particle size. The Fe-B particles fabricated by solution method are crystalline with a size range of 20~70 nm, and the B content is about 17.8 at%; and the Fe-B particles prepared by reverse micelle method are usually non-crystalline with a size much smaller (about 5 nm), the B content is about 34.9 at%.
Fe-B nanoparticles were synthesized by using solution and reverse micelle methods. The structures, the B contents and the magnetic properties of the particles have been characterized by XRD, TEM, ICP, VSM, etc. It is found that the difference in magnetic properties of Fe-B nanoparticles fabricated by the two methods is mainly caused by the structure, the B content and the particle size. The Fe-B particles fabricated by solution method are crystalline with a size range of 20~70 nm, and the B content is about 17.8 at%; and the Fe-B particles prepared by reverse micelle method are usually non-crystalline with a size much smaller (about 5 nm), the B content is about 34.9 at%.
2009, 38(9):1663-1666.
Abstract:
The converters with two catalysts in every one were prepared and their catalytic activity and anti-aging ability were studied with the distribution changes of palladium and rhodium contents on the two substrates. The results show that the two metals distribution influences the converter activity and anti-aging ability significantly, and for the different converters, a higher content of Palladium in the catalysts all near to the inlet or the outlet is more helpful to enhance the converter catalytic activity and anti-aging ability. For the same converter, the performances were higher when the catalyst loading more Palladium is near to the inlet, but without obvious performance advantage for the converter with same Pd/Rh ratio on the two substrates. It is indicated that designing a precious metals distribution reasonably on the two substrates is very important for increasing the using life of single converter with two substrates and controlling the vehicle exhaust emission effectively
The converters with two catalysts in every one were prepared and their catalytic activity and anti-aging ability were studied with the distribution changes of palladium and rhodium contents on the two substrates. The results show that the two metals distribution influences the converter activity and anti-aging ability significantly, and for the different converters, a higher content of Palladium in the catalysts all near to the inlet or the outlet is more helpful to enhance the converter catalytic activity and anti-aging ability. For the same converter, the performances were higher when the catalyst loading more Palladium is near to the inlet, but without obvious performance advantage for the converter with same Pd/Rh ratio on the two substrates. It is indicated that designing a precious metals distribution reasonably on the two substrates is very important for increasing the using life of single converter with two substrates and controlling the vehicle exhaust emission effectively
2009, 38(9):1667-1670.
Abstract:
The LiNixCo1-2xMnxO2 cathode materials for lithium-ion batteries were synthesized by an improved high temperature solid-state method. The effects of x values（x=0.20, 0.33, 0.40, 0.45, Li/（Ni+Co+Mn）molar ratios n(Li)/n(M)=(1.00, 1.05, 1.10, 1.15)，sintering temperatures（800, 900, 950, 1000 ℃）and sintering times (8, 12, 16, 20 h) on the performances of LiNixCo1-2xMnxO2 were studied and the structures of products were characterized by X-ray diffraction (XRD). The results showed that the cycling performance was improved for higher Co content. The cathode material with excellent electrochemical performance was obtained by sintering the mixed raw materials with n(Li)/n(M)=1.10 at 950~1000 ℃ for 20 h
The LiNixCo1-2xMnxO2 cathode materials for lithium-ion batteries were synthesized by an improved high temperature solid-state method. The effects of x values（x=0.20, 0.33, 0.40, 0.45, Li/（Ni+Co+Mn）molar ratios n(Li)/n(M)=(1.00, 1.05, 1.10, 1.15)，sintering temperatures（800, 900, 950, 1000 ℃）and sintering times (8, 12, 16, 20 h) on the performances of LiNixCo1-2xMnxO2 were studied and the structures of products were characterized by X-ray diffraction (XRD). The results showed that the cycling performance was improved for higher Co content. The cathode material with excellent electrochemical performance was obtained by sintering the mixed raw materials with n(Li)/n(M)=1.10 at 950~1000 ℃ for 20 h
2009, 38(9):1671-1675.
Abstract:
Ti3SiC2 compound was synthesized by mechanical alloying (MA) using the starting materials consisting of 3Ti/Si/2C/0.2Al powder mixtures, and the effects of ball milling parameters (ball milling time, charge ratio, ball size, process control addition and attrition medium) on the MA synthesis of Ti3SiC2 were studied. The results show that, the powders and bulks product containing TiC and Ti3SiC2 were synthesized by chemical reaction between Ti, Si and C mixed powders after milling at ball size of 10 mm and ball-to-powder ratio of 10:1 for 7 h. Appropriate increase of ball size and charge ratio may obviously shorten the incubation period for reaction. However, using over large ball or high rate of ball-to-powder ratio will reduce the milling efficiency to extend incubation period. Adding alcohol as the process control addition (PCA) may not only prolong the incubation period, but also inhibit the synthesis of Ti3SiC2
Ti3SiC2 compound was synthesized by mechanical alloying (MA) using the starting materials consisting of 3Ti/Si/2C/0.2Al powder mixtures, and the effects of ball milling parameters (ball milling time, charge ratio, ball size, process control addition and attrition medium) on the MA synthesis of Ti3SiC2 were studied. The results show that, the powders and bulks product containing TiC and Ti3SiC2 were synthesized by chemical reaction between Ti, Si and C mixed powders after milling at ball size of 10 mm and ball-to-powder ratio of 10:1 for 7 h. Appropriate increase of ball size and charge ratio may obviously shorten the incubation period for reaction. However, using over large ball or high rate of ball-to-powder ratio will reduce the milling efficiency to extend incubation period. Adding alcohol as the process control addition (PCA) may not only prolong the incubation period, but also inhibit the synthesis of Ti3SiC2
39 Surface Treatment Method of Cathodic Current-Collector and Its Effect on Performances of Batteries
2009, 38(9):1676-1680.
Abstract:
Zn-In alloy material with high hydrogen evolution overpotential was prepared on the cathodic current-collector surface of the alkaline Zn/MnO2 battery by chemical plating. The properties, effects on the battery performances and the composition of the Zn-In alloy material were studied by linear scanning voltammetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electrochemical impedance spectra (EIS) and altimetry. The results indicate that Zn-In alloy material could increase the hydrogen evolution overpotential of current-collector obviously and was capable of restricting hydrogen evolution effectively to improve the performances of batteries, which can reduce the cost and protect the environment well. Therefore, the Zn-In alloy materials have promising application in Ag-free battery industry, as the replacement of the conventional In coated copper current-collector
Zn-In alloy material with high hydrogen evolution overpotential was prepared on the cathodic current-collector surface of the alkaline Zn/MnO2 battery by chemical plating. The properties, effects on the battery performances and the composition of the Zn-In alloy material were studied by linear scanning voltammetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electrochemical impedance spectra (EIS) and altimetry. The results indicate that Zn-In alloy material could increase the hydrogen evolution overpotential of current-collector obviously and was capable of restricting hydrogen evolution effectively to improve the performances of batteries, which can reduce the cost and protect the environment well. Therefore, the Zn-In alloy materials have promising application in Ag-free battery industry, as the replacement of the conventional In coated copper current-collector
2009, 38(9):1681-1686.
Abstract:
The development of metal-N-H hydrogen storage system, Li-N-H and Li-Mg-N-H series, is elucidated, especially for their progress in the reaction mechanism and effect of catalysts on reaction kinetics. Subsequently, the most possible reaction mechanism and the reaction limited steps in this mechanism are explored and summed up. Furthermore, we probe into the effects of different catalysts on the reaction steps in these materials, and then we deeply clear up the catalytic interaction between the additives and reaction kinetics. Therefore, this would be a recommendable reference for the research on reaction kinetics in this hydrogen storage system
The development of metal-N-H hydrogen storage system, Li-N-H and Li-Mg-N-H series, is elucidated, especially for their progress in the reaction mechanism and effect of catalysts on reaction kinetics. Subsequently, the most possible reaction mechanism and the reaction limited steps in this mechanism are explored and summed up. Furthermore, we probe into the effects of different catalysts on the reaction steps in these materials, and then we deeply clear up the catalytic interaction between the additives and reaction kinetics. Therefore, this would be a recommendable reference for the research on reaction kinetics in this hydrogen storage system
2009, 38(9):1687-1692.
Abstract:
LiMn2O4 and LiMPO4 can be used as cathode materials of power battery by judging the security of power lithium ion battery cathode material. Recent progresses on LiMn2O4 and LiMPO4 cathode materials are reviewed. Emphasis is placed on the generalization and discussion between synthesis, structures and properties of the cathode materials. At present, the LiMn2O4 is the mainstreaming cathode material for power lithium ion battery. However, the LiMPO4, especial the Li3V2(PO4)3, is the trend of development for power lithium ion battery cathode materials in long term.
LiMn2O4 and LiMPO4 can be used as cathode materials of power battery by judging the security of power lithium ion battery cathode material. Recent progresses on LiMn2O4 and LiMPO4 cathode materials are reviewed. Emphasis is placed on the generalization and discussion between synthesis, structures and properties of the cathode materials. At present, the LiMn2O4 is the mainstreaming cathode material for power lithium ion battery. However, the LiMPO4, especial the Li3V2(PO4)3, is the trend of development for power lithium ion battery cathode materials in long term.
