Volume 38,Issue 12,2009 Table of Contents
2009, 38(12):2069-2074.
Abstract:
The effect of grain refinement and trace yttrium addition on dynamic behavior of 93W-4.9Ni-2.1Fe alloy was investigated. The true stress-strain curves obtained from dynamic compression tests show that strain hardening and thermal softening effects are present in the alloy, and the maximum dynamic strength and elongation increase with increasing of strain rates. Compared with the conventional 93W-4.9Ni-2.1Fe alloy, the fine-grained 93W-4.9Ni-2.1Fe alloy exhibits relatively higher strength and elongation under the same compression condition. In particular, the occurrence of obvious adiabatic shear bands in fine-grained alloy under lower high-strain-rate (1900 s-1) indicates that the propensity to adiabatic shear localization are enhanced significantly by grain refinement. Additionally, trace yttrium addition can improve the dynamic strength and elongation of tungsten heavy alloy.
The effect of grain refinement and trace yttrium addition on dynamic behavior of 93W-4.9Ni-2.1Fe alloy was investigated. The true stress-strain curves obtained from dynamic compression tests show that strain hardening and thermal softening effects are present in the alloy, and the maximum dynamic strength and elongation increase with increasing of strain rates. Compared with the conventional 93W-4.9Ni-2.1Fe alloy, the fine-grained 93W-4.9Ni-2.1Fe alloy exhibits relatively higher strength and elongation under the same compression condition. In particular, the occurrence of obvious adiabatic shear bands in fine-grained alloy under lower high-strain-rate (1900 s-1) indicates that the propensity to adiabatic shear localization are enhanced significantly by grain refinement. Additionally, trace yttrium addition can improve the dynamic strength and elongation of tungsten heavy alloy.
2009, 38(12):2075-2079.
Abstract:
The flawless nanocrystalline (nc) Ni with a broad grain size distribution ranging from 5 to 120 nm and an average grain size of 20-30 nm were prepared by direct current and pulse electrodeposition, respectively. In the region of room-temperature static tensile strain rates, for the nc Ni prepared by direct current electrodeposition, the average ultimate tensile strength and the average elongation to failure are 1176 MPa and 10.6%, respectively. While for the nc Ni prepared by pulse electrodeposition, the ultimate tensile strength exceeds 1500 MPa and the max elongation to failure reaches 13.3%. In contrast to the typical electrodeposited nc Ni with a narrow grain size distribution below 50 nm, the ductility is increased by more than 100% for the present nc Ni samples. This enhancement can be interpreted by the reason that dislocations can exist and multiply in the large grains by the mechanism of Frank-Read source in the plastic deformation process revealed by theoretical calculation.
The flawless nanocrystalline (nc) Ni with a broad grain size distribution ranging from 5 to 120 nm and an average grain size of 20-30 nm were prepared by direct current and pulse electrodeposition, respectively. In the region of room-temperature static tensile strain rates, for the nc Ni prepared by direct current electrodeposition, the average ultimate tensile strength and the average elongation to failure are 1176 MPa and 10.6%, respectively. While for the nc Ni prepared by pulse electrodeposition, the ultimate tensile strength exceeds 1500 MPa and the max elongation to failure reaches 13.3%. In contrast to the typical electrodeposited nc Ni with a narrow grain size distribution below 50 nm, the ductility is increased by more than 100% for the present nc Ni samples. This enhancement can be interpreted by the reason that dislocations can exist and multiply in the large grains by the mechanism of Frank-Read source in the plastic deformation process revealed by theoretical calculation.
2009, 38(12):2080-2084.
Abstract:
Nearly monodispersive nickel 3D nanostructures were synthesized using a improved hydrothermal route with poly-(N-vinyl-pyrrolidone) as capping reagent. The obtained products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and field-emission scanning electron microscopy (FE-SEM). Results reveal that cubic nickel crystals possess flower-like 3D nanostructures with nanospearheads growing radially from the core and a uniform diameter of about 1.5 μm. These nanospearheads have almost uniform shapes: the root in (120±20) nm, the tip in (15±5) nm, the length in (400±50) nm, and the thickness in (10±2) nm. Contrast experiments demonstrate that flower-like shape of nickel 3D nanocrystals is controlled by the cooperative effects of time, temperature and surfactant. The good catalytic effects indicate these flower-like nickel 3D nanocrystals are likely to be applied as a better catalyst in the future.
Nearly monodispersive nickel 3D nanostructures were synthesized using a improved hydrothermal route with poly-(N-vinyl-pyrrolidone) as capping reagent. The obtained products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and field-emission scanning electron microscopy (FE-SEM). Results reveal that cubic nickel crystals possess flower-like 3D nanostructures with nanospearheads growing radially from the core and a uniform diameter of about 1.5 μm. These nanospearheads have almost uniform shapes: the root in (120±20) nm, the tip in (15±5) nm, the length in (400±50) nm, and the thickness in (10±2) nm. Contrast experiments demonstrate that flower-like shape of nickel 3D nanocrystals is controlled by the cooperative effects of time, temperature and surfactant. The good catalytic effects indicate these flower-like nickel 3D nanocrystals are likely to be applied as a better catalyst in the future.
2009, 38(12):2089-2092.
Abstract:
The chopping SiCf/LAS composites were prepared by the hot-pressing method. The effects of hot-pressing time and pressures on the microstructures and the dielectric properties of the composites were researched. Compared with the LAS matrix and the SiC fibre, the results of dielectric constant testing in the range of 8-12 GHz indicate that the dielectric constant real part, imaginary part and dielectric dissipation of all samples increase by 1-3 orders of magnitude, and show obvious frequency dispersion effect. Their real parts increase while their imaginary parts and dielectric dissipations decline with the increase of the hot-pressing time or pressures. The SEM fractographs show that the composite interfacial films between the fibre and the matrix are thickened with the increase of the hot-pressing time or pressures.
The chopping SiCf/LAS composites were prepared by the hot-pressing method. The effects of hot-pressing time and pressures on the microstructures and the dielectric properties of the composites were researched. Compared with the LAS matrix and the SiC fibre, the results of dielectric constant testing in the range of 8-12 GHz indicate that the dielectric constant real part, imaginary part and dielectric dissipation of all samples increase by 1-3 orders of magnitude, and show obvious frequency dispersion effect. Their real parts increase while their imaginary parts and dielectric dissipations decline with the increase of the hot-pressing time or pressures. The SEM fractographs show that the composite interfacial films between the fibre and the matrix are thickened with the increase of the hot-pressing time or pressures.
2009, 38(12):2093-2099.
Abstract:
Two kinds of Al-Zn-Mg-Cu alloys containing Sc and Cr, Mn, Ti as well as Zr were prepared. The precipitation free zone (PFZ) around the second phase particle and the precipitation free band at grain boundary as well as the interaction between them were studied by transmitting electron microscopy (TEM). The equation for pinning force of single second phase particle to grain boundary was presented. Results show that when driving force for grain boundary migration exceeds the encumbrance force of particles and their circumference PFZs against the boundaries, grain boundaries are penetrated by particles to form holes. During grain boundaries sweep particles, their movement, e.g. acceleration stage and deceleration stage, undergoes two different stages. When the hole diameter is equal to the particle size, the encumbrance force is the least and the velocity of boundary migration is the highest. When the sum of grain boundary energy and surface phase boundary energy is equal to driving force, grain boundary is pinned by the particle and stops moving. Solute atoms diffusion takes on the trend from high-concentration zone to low-concentration zone; PFZ around grain boundaries and particles have great effect on migration of grain boundary.
Two kinds of Al-Zn-Mg-Cu alloys containing Sc and Cr, Mn, Ti as well as Zr were prepared. The precipitation free zone (PFZ) around the second phase particle and the precipitation free band at grain boundary as well as the interaction between them were studied by transmitting electron microscopy (TEM). The equation for pinning force of single second phase particle to grain boundary was presented. Results show that when driving force for grain boundary migration exceeds the encumbrance force of particles and their circumference PFZs against the boundaries, grain boundaries are penetrated by particles to form holes. During grain boundaries sweep particles, their movement, e.g. acceleration stage and deceleration stage, undergoes two different stages. When the hole diameter is equal to the particle size, the encumbrance force is the least and the velocity of boundary migration is the highest. When the sum of grain boundary energy and surface phase boundary energy is equal to driving force, grain boundary is pinned by the particle and stops moving. Solute atoms diffusion takes on the trend from high-concentration zone to low-concentration zone; PFZ around grain boundaries and particles have great effect on migration of grain boundary.
2009, 38(12):2100-2105.
Abstract:
The error distribution between Miedema-calculated values and reference-reported values for formation enthalpies of binary Al-RE intermetallics was analyzed and it is known that the calculated results are commonly negative compared with those in references. Therefore, an important influencing factor, radius ratio of RE atom to aluminum atom should be considered to modify the thermodynamic calculation model in the study. The calculation results of the modified model are more closed to the reported experiment results and the error was found to be reduced from 33.6% to 5%. The enthalpies of some common intermetallics of aluminum and rare earth were also checked by MTDATA for comparison. All that proved the modified calculating model are much more accurate and reliable. The common formation enthalpies of intermetallics of aluminum and rare earth as well as Al-Er, Al-Tb, Al-Gd, which are studied less, are calculated by the modified Miedema model.
The error distribution between Miedema-calculated values and reference-reported values for formation enthalpies of binary Al-RE intermetallics was analyzed and it is known that the calculated results are commonly negative compared with those in references. Therefore, an important influencing factor, radius ratio of RE atom to aluminum atom should be considered to modify the thermodynamic calculation model in the study. The calculation results of the modified model are more closed to the reported experiment results and the error was found to be reduced from 33.6% to 5%. The enthalpies of some common intermetallics of aluminum and rare earth were also checked by MTDATA for comparison. All that proved the modified calculating model are much more accurate and reliable. The common formation enthalpies of intermetallics of aluminum and rare earth as well as Al-Er, Al-Tb, Al-Gd, which are studied less, are calculated by the modified Miedema model.
7 Fractal Analysis of Pore Structure and Its Application for Prediction of Permeability and Porosity
2009, 38(12):2106-2110.
Abstract:
Fractal theory was applied to characterize pore structure. By image processing and fractal analysis for SEM images of sintered stainless steel fiber porous materials, the influence of image resolution, magnification, and the threshold value from grayscale image to binary image on fractal analysis results of pore structure is investigated and their qualitative relationship with fractal dimension was also studied. The results indicate that sintered porous fiber materials have typical fractal nature; the image resolution, magnification and threshold value obviously impact fractal dimension: the larger the difference between original and applied resolution is, or the smaller the magnification is, the larger the fractal dimension becomes; there is a best threshold value for SEM image conversion from grayscale image to binary image, and with the threshold value increasing, the fractal dimension increases and then decreased. The mathematical relations between fractal dimension of pore structure and porosity as well as permeability of porous materials are also discussed. It is feasible to predict the porosity and permeability through the fractal dimension, surface porosity, pore size and other parameters reasonably and the predicted results are in good agreement with the measured results.
Fractal theory was applied to characterize pore structure. By image processing and fractal analysis for SEM images of sintered stainless steel fiber porous materials, the influence of image resolution, magnification, and the threshold value from grayscale image to binary image on fractal analysis results of pore structure is investigated and their qualitative relationship with fractal dimension was also studied. The results indicate that sintered porous fiber materials have typical fractal nature; the image resolution, magnification and threshold value obviously impact fractal dimension: the larger the difference between original and applied resolution is, or the smaller the magnification is, the larger the fractal dimension becomes; there is a best threshold value for SEM image conversion from grayscale image to binary image, and with the threshold value increasing, the fractal dimension increases and then decreased. The mathematical relations between fractal dimension of pore structure and porosity as well as permeability of porous materials are also discussed. It is feasible to predict the porosity and permeability through the fractal dimension, surface porosity, pore size and other parameters reasonably and the predicted results are in good agreement with the measured results.
Zhou Xiaolong
,
Cao Jianchun
,
Chen Jingchao
,
Yu Jie
,
Du Yan
,
Du Yeping
,
Zhang Kunhua
,
Fen Jing
2009, 38(12):2111-2115.
Abstract:
Gibbs’ function of metal oxide from the reaction between elements as well as sub-metal oxides and 1 mol oxygen in Ag/CuO composites by reactive synthesis was calculated thermodynamically; through the calculation, the relation diagram was drawn for Gibbs’ function and temperature. Considering oxygen pressure influencing the reaction greatly, the oxygen pressure line with temperature change was also drawn in the diagram above. Results show that the reactions between Ag and O2, and Cu2O and O2 are reversible, whose temperature for reversible transition are 586.818 K and 667.663 K, respectively. The oxygen pressure is important for decomposition of metal oxides: the lower the oxygen pressure is, the more easily the oxides decompose. The reactive synthesis sintering technology of Ag/CuO composite was determined by thermodynamic analysis.
Gibbs’ function of metal oxide from the reaction between elements as well as sub-metal oxides and 1 mol oxygen in Ag/CuO composites by reactive synthesis was calculated thermodynamically; through the calculation, the relation diagram was drawn for Gibbs’ function and temperature. Considering oxygen pressure influencing the reaction greatly, the oxygen pressure line with temperature change was also drawn in the diagram above. Results show that the reactions between Ag and O2, and Cu2O and O2 are reversible, whose temperature for reversible transition are 586.818 K and 667.663 K, respectively. The oxygen pressure is important for decomposition of metal oxides: the lower the oxygen pressure is, the more easily the oxides decompose. The reactive synthesis sintering technology of Ag/CuO composite was determined by thermodynamic analysis.
2009, 38(12):2116-2120.
Abstract:
With reasonable simplification on microcosmic pore structures of metal rubber filtering materials, theoretical formula describing maximum pore size of metal rubber filtering material is derived by statistics and is verified by bubble test pore size determination method. Results illustrate that the formula perfectly reflects influencing factors on maximum pore size of metal rubber filtering material and their interrelation, which will provide reliable foundation in theory for metal rubber filter.
With reasonable simplification on microcosmic pore structures of metal rubber filtering materials, theoretical formula describing maximum pore size of metal rubber filtering material is derived by statistics and is verified by bubble test pore size determination method. Results illustrate that the formula perfectly reflects influencing factors on maximum pore size of metal rubber filtering material and their interrelation, which will provide reliable foundation in theory for metal rubber filter.
2009, 38(12):2121-2125.
Abstract:
High temperature deformation behavior and microstructure evolution of stoichiometry single phase Ni-50Al intermetallics with an initial grain size of 220 mm was investigated. Results show that the alloy exhibits good plastic behavior under initial strain rate from 7.5×10-4 to 1×10-3 s-1 in the temperature range of 1000-1100 ℃. A maximum elongation of 139% was obtained under initial strain rate of 8.75×10-4 s-1 at 1075℃. Optical metallography (OM) shows that the grains were refined during plastic deformation from initial 220 μm to less than 30 μm. Electron back-scattered diffraction（EBSD）and transmission electron microscopy (TEM) observations show that small-angle boundaries formed continuously during deformation, and changed to large-angle boundaries, resulting in finer grains finally. Microstructure analyses reveal that high-temperature plastic deformation could be attributed to continuously dynamic recovery and recrystallization (CDRR), which was caused by the interaction among gliding and climbing of dislocation.
High temperature deformation behavior and microstructure evolution of stoichiometry single phase Ni-50Al intermetallics with an initial grain size of 220 mm was investigated. Results show that the alloy exhibits good plastic behavior under initial strain rate from 7.5×10-4 to 1×10-3 s-1 in the temperature range of 1000-1100 ℃. A maximum elongation of 139% was obtained under initial strain rate of 8.75×10-4 s-1 at 1075℃. Optical metallography (OM) shows that the grains were refined during plastic deformation from initial 220 μm to less than 30 μm. Electron back-scattered diffraction（EBSD）and transmission electron microscopy (TEM) observations show that small-angle boundaries formed continuously during deformation, and changed to large-angle boundaries, resulting in finer grains finally. Microstructure analyses reveal that high-temperature plastic deformation could be attributed to continuously dynamic recovery and recrystallization (CDRR), which was caused by the interaction among gliding and climbing of dislocation.
2009, 38(12):2126-2130.
Abstract:
In order to improve the frictional wear resistance and corrosion resistance of Ti-6Al-4V alloy surface, argentine(Ag) ions with different dose were implanted into the polished alloy sample surface by plasma immersion ion implantation (PIII) technique. The chemical composition and element concentration distribution of the modified layer were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), and Auger electron spectrum (AES). Frictional wear resistance, corrosion resistance, microhardness and elastic modulus of sample alloy surface were studied after argentine ions implantation. Results show that the modified layer consists of Ag phase mainly and a few TiAg phase. The microhardness and elastic modulus increases by 62.5% and 54.5%, respectively, for the sample with 1× 1017 ions/cm2 argentine ions dose. The wear area decreases by 57.6%, and the friction coefficient reduces to 0.2 from 0.78 of the matrix alloy. In addition, the corrosion resistance of treated alloys in 3.5% NaCl solution is also improved significantly, with increasing corrosion potential and remarkably decreasing corrosion current density.
In order to improve the frictional wear resistance and corrosion resistance of Ti-6Al-4V alloy surface, argentine(Ag) ions with different dose were implanted into the polished alloy sample surface by plasma immersion ion implantation (PIII) technique. The chemical composition and element concentration distribution of the modified layer were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), and Auger electron spectrum (AES). Frictional wear resistance, corrosion resistance, microhardness and elastic modulus of sample alloy surface were studied after argentine ions implantation. Results show that the modified layer consists of Ag phase mainly and a few TiAg phase. The microhardness and elastic modulus increases by 62.5% and 54.5%, respectively, for the sample with 1× 1017 ions/cm2 argentine ions dose. The wear area decreases by 57.6%, and the friction coefficient reduces to 0.2 from 0.78 of the matrix alloy. In addition, the corrosion resistance of treated alloys in 3.5% NaCl solution is also improved significantly, with increasing corrosion potential and remarkably decreasing corrosion current density.
12 High-Temperature XRD Study and Rietveld Refinement of A2W3O12(A=Y, Er, Ho, Yb) Rare-Earth Tungstate
2009, 38(12):2131-2135.
Abstract:
A2W3O12(A=Y, Er, Ho, Yb) rare-earth tungstate materials were synthesized by solid state method at high temperature. The structures, lattice constants and cell volumes of A2W3O12 were determined by room temperature and high temperature XRD at different temperatures, and their Rietveld refinements were performed by TOPAS software. It is found that Y2W3O12, Er2W3O12 and Yb2W3O12 all possess orthorhombic structure and show negative thermal expansion; whereas Ho2W3O12 has monoclinic structure and shows positive thermal expansion. According to A. W. Sleight prediction, Ho2W3O12 should have large negative thermal expansion, but it shows no negative thermal expansion but large positive thermal expansion coefficient in the present experiment.
A2W3O12(A=Y, Er, Ho, Yb) rare-earth tungstate materials were synthesized by solid state method at high temperature. The structures, lattice constants and cell volumes of A2W3O12 were determined by room temperature and high temperature XRD at different temperatures, and their Rietveld refinements were performed by TOPAS software. It is found that Y2W3O12, Er2W3O12 and Yb2W3O12 all possess orthorhombic structure and show negative thermal expansion; whereas Ho2W3O12 has monoclinic structure and shows positive thermal expansion. According to A. W. Sleight prediction, Ho2W3O12 should have large negative thermal expansion, but it shows no negative thermal expansion but large positive thermal expansion coefficient in the present experiment.
2009, 38(12):2136-2140.
Abstract:
Hot workability of metal molybdenum was investigated by means of hot compression tests carried out in the temperature range of 900~1450 ℃ and strain rate range of 0.01~10 s-1. A constitutive equation of molybdenum for the flow stress was presented. The radial precision forging process of the molybdenum bar was simulated by COGGING modular of FEM software DEFORM. Reasonable process parameters were determined, and the forging penetration efficiency was explored from the strain-effective state. The results show that the forging penetration efficiency criterion put forward for the simulation result analysis is reasonable. Determination methods of the process and parameters are correct. Research shows that the main factors influencing forging penetration efficiency are reduction in pass and the dip angle of the hammer, and the main factors influencing forged piece surface quality are axle feeding speed and rotation angle.
Hot workability of metal molybdenum was investigated by means of hot compression tests carried out in the temperature range of 900~1450 ℃ and strain rate range of 0.01~10 s-1. A constitutive equation of molybdenum for the flow stress was presented. The radial precision forging process of the molybdenum bar was simulated by COGGING modular of FEM software DEFORM. Reasonable process parameters were determined, and the forging penetration efficiency was explored from the strain-effective state. The results show that the forging penetration efficiency criterion put forward for the simulation result analysis is reasonable. Determination methods of the process and parameters are correct. Research shows that the main factors influencing forging penetration efficiency are reduction in pass and the dip angle of the hammer, and the main factors influencing forged piece surface quality are axle feeding speed and rotation angle.
2009, 38(12):2146-2150.
Abstract:
The as-deposited microstructure and heat-treated microstructure of Ti-6.5Al-3.5Mo-1.5Zr-0.25Si alloys (TC11) by Laser Solid Forming (LSF) were compared, and approaches to improve LSF microstructure and high-temperature combination properties of TC11 alloys were researched. Results show the as-deposited microstructure of TC11 alloy consists of coarse columnar grains and equiaxed grains throughout cladding layers, and the prior columnar β-Ti grains are composed of lathlike α and residual β. The microstructure of as-deposited samples after 950 ℃ heat treatment is a similar triplex mixture of equiaxed α, basketweave α lath and transformed b. The majority of continuous prior α boundary is broken, and become spheroidized and illegible; α laths grow up to bunch on some unbroken boundary; the equiaxed α in coarse β grains is related with subgrains. The microstructure after heat treated at 970 ℃ is a certain basketweave structure consisting of a few equiaxed-α and α laths which have coarsening tendency; the microstructure after recrystallization at 1030 ℃ followed by 950 ℃ heat treatment is typical Widmanst?tten structure consisting of coarse α laths, and lots of β-Ti is found to separate out inside α and on α boundaries without breaking basically.
The as-deposited microstructure and heat-treated microstructure of Ti-6.5Al-3.5Mo-1.5Zr-0.25Si alloys (TC11) by Laser Solid Forming (LSF) were compared, and approaches to improve LSF microstructure and high-temperature combination properties of TC11 alloys were researched. Results show the as-deposited microstructure of TC11 alloy consists of coarse columnar grains and equiaxed grains throughout cladding layers, and the prior columnar β-Ti grains are composed of lathlike α and residual β. The microstructure of as-deposited samples after 950 ℃ heat treatment is a similar triplex mixture of equiaxed α, basketweave α lath and transformed b. The majority of continuous prior α boundary is broken, and become spheroidized and illegible; α laths grow up to bunch on some unbroken boundary; the equiaxed α in coarse β grains is related with subgrains. The microstructure after heat treated at 970 ℃ is a certain basketweave structure consisting of a few equiaxed-α and α laths which have coarsening tendency; the microstructure after recrystallization at 1030 ℃ followed by 950 ℃ heat treatment is typical Widmanst?tten structure consisting of coarse α laths, and lots of β-Ti is found to separate out inside α and on α boundaries without breaking basically.
2009, 38(12):2151-2154.
Abstract:
It is possible on thermodynamics to prepare TiAl alloy in CaH2-TiO2-Al system by Reduction-Diffusion method. It is a first-class reaction, whose mechanism was discussed by liquid-solid contracting core model. Results show that TiO2 is reduced to Ti rapidly, which is not the rate-controlling step of the reaction. The interfacial chemical reaction is the rate-controlling step of the reaction. The apparent activation energy of the reduction-diffusion reaction is 76.84 kJ/mol. There is sufficient reaction when the entering quantity of CaH2 is 1.5 times of theoretic quantity. Al powder granularity doesn’t influence the reaction. The transformation efficiency of TiAl alloy is about 100% when the reaction temperature is 1423 K and the reaction time is 8 h.
It is possible on thermodynamics to prepare TiAl alloy in CaH2-TiO2-Al system by Reduction-Diffusion method. It is a first-class reaction, whose mechanism was discussed by liquid-solid contracting core model. Results show that TiO2 is reduced to Ti rapidly, which is not the rate-controlling step of the reaction. The interfacial chemical reaction is the rate-controlling step of the reaction. The apparent activation energy of the reduction-diffusion reaction is 76.84 kJ/mol. There is sufficient reaction when the entering quantity of CaH2 is 1.5 times of theoretic quantity. Al powder granularity doesn’t influence the reaction. The transformation efficiency of TiAl alloy is about 100% when the reaction temperature is 1423 K and the reaction time is 8 h.
2009, 38(12):2155-2158.
Abstract:
Effects of two different deformation manners, martensite reorientation (MR) and stress-induced martensitic transformation (SIM) on the tensile properties and recovery properties after pre-strain of Ni50.2Ti49.8 alloy were investigated. Results show that the strain deformed via MR is higher than that via SIM at the end of the stress plateau in the tensile deformation process. When tensile pre-strain is in the stress plateau, the two manners after the same pre-strain followed by heating have the same recovery properties; however, when the tensile pre-strain is higher than stress plateau, SIM has higher reversed transformation temperatures and recovery strain than MR after the same pre-strain followed by heating.
Effects of two different deformation manners, martensite reorientation (MR) and stress-induced martensitic transformation (SIM) on the tensile properties and recovery properties after pre-strain of Ni50.2Ti49.8 alloy were investigated. Results show that the strain deformed via MR is higher than that via SIM at the end of the stress plateau in the tensile deformation process. When tensile pre-strain is in the stress plateau, the two manners after the same pre-strain followed by heating have the same recovery properties; however, when the tensile pre-strain is higher than stress plateau, SIM has higher reversed transformation temperatures and recovery strain than MR after the same pre-strain followed by heating.
2009, 38(12):2159-2162.
Abstract:
AlN ceramics and Mo-Ni-Cu alloy were brazed actively by Ag70-Cu28-Ti2 active solder in vacuum. The microstructure and phase composition of the brazed zone were analyzed and its mechanical properties and gas leakage were tested. Results show that Cu content is relatively high in the interface between the solder layer and the alloy; while Ti-rich layer with 1-2 μm thickness forms in the interface between the solder layer and AlN ceramics, where TiN is found by XRD, which indicates that there is chemical bonding in the AlN-solder interface. The gas leakage rate of the sample was 1.0 ×10-11 Pa·m3/s, and the bending strength and shear strength were σｂ=78.55 MPa, and στ=189.58 MP, respectively.
AlN ceramics and Mo-Ni-Cu alloy were brazed actively by Ag70-Cu28-Ti2 active solder in vacuum. The microstructure and phase composition of the brazed zone were analyzed and its mechanical properties and gas leakage were tested. Results show that Cu content is relatively high in the interface between the solder layer and the alloy; while Ti-rich layer with 1-2 μm thickness forms in the interface between the solder layer and AlN ceramics, where TiN is found by XRD, which indicates that there is chemical bonding in the AlN-solder interface. The gas leakage rate of the sample was 1.0 ×10-11 Pa·m3/s, and the bending strength and shear strength were σｂ=78.55 MPa, and στ=189.58 MP, respectively.
2009, 38(12):2163-2166.
Abstract:
FePt nanoparticles were prepared by multi-step reduction method. Effects of annealing temperatures on the magnetic properties of the nanoparticles were investigated. The results of XRD and TEM confirm that the as-synthesized FePt nanoparticles were fcc structure and monodisperse, with spherical shape and around 5.0 nm particle size. The results of DSC and VSM show that FePt nanoparticles would change into ordered fct structure after annealing at 500 °C for 30 min from disordered fcc structure. With the temperature increasing, the coercivity was increased, which was 240 kA/m at 600 °C. However, it changed slightly in the high-temperature region (550 °C and above it), which was attributed to the agglomeration of nanoparticles during the annealing treatment.
FePt nanoparticles were prepared by multi-step reduction method. Effects of annealing temperatures on the magnetic properties of the nanoparticles were investigated. The results of XRD and TEM confirm that the as-synthesized FePt nanoparticles were fcc structure and monodisperse, with spherical shape and around 5.0 nm particle size. The results of DSC and VSM show that FePt nanoparticles would change into ordered fct structure after annealing at 500 °C for 30 min from disordered fcc structure. With the temperature increasing, the coercivity was increased, which was 240 kA/m at 600 °C. However, it changed slightly in the high-temperature region (550 °C and above it), which was attributed to the agglomeration of nanoparticles during the annealing treatment.
2009, 38(12):2167-2170.
Abstract:
Characterization of Zr-based bulk metallic glass (BMG) corroded by spout electroanalysis was investigated by transmission electronic microscopy (TEM) and energy depressive X-ray spectroscopy (EDS) analysis. Results show that during the spout electroanalysis corrosion process, the nanocrystallines in the amorphous region are corroded more easily than bulk metallic glass. In addition, there are some special amorphous regions in the amorphous specimens by electroanalysis corrosion of perchloric acid solution in alcohol, where a lot of amorphous oxides were observed, and Ni content decreased. The region formation was resulted from nano-pitting of chlorine ion.
Characterization of Zr-based bulk metallic glass (BMG) corroded by spout electroanalysis was investigated by transmission electronic microscopy (TEM) and energy depressive X-ray spectroscopy (EDS) analysis. Results show that during the spout electroanalysis corrosion process, the nanocrystallines in the amorphous region are corroded more easily than bulk metallic glass. In addition, there are some special amorphous regions in the amorphous specimens by electroanalysis corrosion of perchloric acid solution in alcohol, where a lot of amorphous oxides were observed, and Ni content decreased. The region formation was resulted from nano-pitting of chlorine ion.
2009, 38(12):2171-2174.
Abstract:
Low-cost titanium alloy Ti8LC was heat treated by duplex annealing. Its tensile properties were tested, and the fatigue crack propagation behavior as well as fatigue fracture mechanism were studied. Results show that the strength of the alloy increases a little but the ductility decreases with the increase of the first annealing temperature. SEM analysis on the fatigue crack propagation was performed, and the analysis results indicate that the fatigue crack propagates in three modes of three regions. The presplitting region was cleavage fracture. In the stationary state growth region, fatigue crack grew ahead in the form of striation mechanism and many second fatigue cracks were observed in the meantime. In the fast-growth region is mainly dimple. The temperature of duplex annealing has little influence on fatigue crack propagation behavior.
Low-cost titanium alloy Ti8LC was heat treated by duplex annealing. Its tensile properties were tested, and the fatigue crack propagation behavior as well as fatigue fracture mechanism were studied. Results show that the strength of the alloy increases a little but the ductility decreases with the increase of the first annealing temperature. SEM analysis on the fatigue crack propagation was performed, and the analysis results indicate that the fatigue crack propagates in three modes of three regions. The presplitting region was cleavage fracture. In the stationary state growth region, fatigue crack grew ahead in the form of striation mechanism and many second fatigue cracks were observed in the meantime. In the fast-growth region is mainly dimple. The temperature of duplex annealing has little influence on fatigue crack propagation behavior.
2009, 38(12):2179-2182.
Abstract:
Microstructure evolution of biphase TC21 alloy before and after hydrogenation as well as dehydrogenation was investigated by XRD, OM and TEM. The results show that the amount of β phase increases gradually as the hydrogen content increases; fcc δ hydrides appear when the hydrogen content reaches above 0.319%. Hydrides mainly precipitate by eutectoid transformation through diffusion during the cooling process after high-temperature hydrogenation. Because of the lattice distortion caused by eutectoid transformation, recrystallization occurs after the dehydrogenation, so the grains are refined and become much more homogenous.
Microstructure evolution of biphase TC21 alloy before and after hydrogenation as well as dehydrogenation was investigated by XRD, OM and TEM. The results show that the amount of β phase increases gradually as the hydrogen content increases; fcc δ hydrides appear when the hydrogen content reaches above 0.319%. Hydrides mainly precipitate by eutectoid transformation through diffusion during the cooling process after high-temperature hydrogenation. Because of the lattice distortion caused by eutectoid transformation, recrystallization occurs after the dehydrogenation, so the grains are refined and become much more homogenous.
2009, 38(12):2183-2186.
Abstract:
High-temperature oxidation behavior of Ti-22Al-26Nb alloy was studied by thermogravimetry at 800 and 900℃. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) were employed to characterize the phase composition and morphology of oxide films. Results show that the oxidation of the alloy was parabolic at the transient stage, while it was approximately linear from 20 h to the end of the oxidation. Oxides mainly composed of TiO2, AlNbO4 and Nb2TiO7, and the oxide scale was stratified, which became more obvious with oxidation temperature increasing.
High-temperature oxidation behavior of Ti-22Al-26Nb alloy was studied by thermogravimetry at 800 and 900℃. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) were employed to characterize the phase composition and morphology of oxide films. Results show that the oxidation of the alloy was parabolic at the transient stage, while it was approximately linear from 20 h to the end of the oxidation. Oxides mainly composed of TiO2, AlNbO4 and Nb2TiO7, and the oxide scale was stratified, which became more obvious with oxidation temperature increasing.
2009, 38(12):2187-2190.
Abstract:
Effects of Ga and Al additions on the corrosion resistance of Sn-9Zn lead free solder in 3.5% NaCl solution were researched by erosion mass loss evaluation. Effects of the additions on high-temperature oxidation resistance of the solder were investigated by TGA and AES. Results indicate that the corrosion resistance of Sn-Zn solders is improved by addition of Ga, for the corrosion products exhibit better adhesiveness on the solder surface after adding Ga; however, with Al addition, the corrosion resistance deteriorates for the selective erosion of Al and Zn. The TGA results show that the high-temperature oxidation resistance of Sn-9Zn solder is observably improved by adding Ga or Al; the AES analysis shows that Ga could form a protective skin on the solder surface, while Al can form a dense protective oxidation layer, both of which can hinder diffusion of the oxygen to the inner.
Effects of Ga and Al additions on the corrosion resistance of Sn-9Zn lead free solder in 3.5% NaCl solution were researched by erosion mass loss evaluation. Effects of the additions on high-temperature oxidation resistance of the solder were investigated by TGA and AES. Results indicate that the corrosion resistance of Sn-Zn solders is improved by addition of Ga, for the corrosion products exhibit better adhesiveness on the solder surface after adding Ga; however, with Al addition, the corrosion resistance deteriorates for the selective erosion of Al and Zn. The TGA results show that the high-temperature oxidation resistance of Sn-9Zn solder is observably improved by adding Ga or Al; the AES analysis shows that Ga could form a protective skin on the solder surface, while Al can form a dense protective oxidation layer, both of which can hinder diffusion of the oxygen to the inner.
2009, 38(12):2191-2194.
Abstract:
含钪扩散阴极；活性层；扩散；氧化钪
含钪扩散阴极；活性层；扩散；氧化钪
2009, 38(12):2195-2198.
Abstract:
Solidification microstructure of AZ61 magnesium alloys with different electric-magnetic fields was studied. It was found that solidification microstructure of magnesium alloys were equiaxed grains and the Mg-Al-Zn compound phases appeared as meshes on grains boundaries under magnetostatic filed. Solidified under the magnetostatic-power current field, the microstructure was mainly consisted of equiaxed grains similar to that under the magnetostatic field. But the grains were refined obviously and the mesh structure of compound phases became fine due to the applied power current; while in the solidification process of Mg alloys under the magnetostatic-direct current field, the solidification microstructure was mainly rosette grain and purified significantly; the mesh structure of the compound phases disappeared entirely and they were distributed as discontinuous ribbons and spots; they were the results of the directional force inside melts caused by the combination fields.
Solidification microstructure of AZ61 magnesium alloys with different electric-magnetic fields was studied. It was found that solidification microstructure of magnesium alloys were equiaxed grains and the Mg-Al-Zn compound phases appeared as meshes on grains boundaries under magnetostatic filed. Solidified under the magnetostatic-power current field, the microstructure was mainly consisted of equiaxed grains similar to that under the magnetostatic field. But the grains were refined obviously and the mesh structure of compound phases became fine due to the applied power current; while in the solidification process of Mg alloys under the magnetostatic-direct current field, the solidification microstructure was mainly rosette grain and purified significantly; the mesh structure of the compound phases disappeared entirely and they were distributed as discontinuous ribbons and spots; they were the results of the directional force inside melts caused by the combination fields.
2009, 38(12):2199-2201.
Abstract:
Colloidal gold nanoshells prepared by wet chemical method were irradiated using 800 nm femtosecond laser and their shape change was investigated. Results show that the gold nanoparticles of quasi-sphere-shells with 20~50 nm diameter changed to tube structure of 100~200 nm length and 10 nm diameter after femtosecond laser exposure. In the adsorption spectra, the absorption peak of the gold nanoshell at about 800 nm disappeared and a new absorption peak appeared at about 450 nm. The shape change can be attributed to the electrostatic field from the femtosecond laser exposure. With the force of the electrostatic field, nearby gold nanoshells linked each other, and extended along the electrostatic filed direction to form tube structure.
Colloidal gold nanoshells prepared by wet chemical method were irradiated using 800 nm femtosecond laser and their shape change was investigated. Results show that the gold nanoparticles of quasi-sphere-shells with 20~50 nm diameter changed to tube structure of 100~200 nm length and 10 nm diameter after femtosecond laser exposure. In the adsorption spectra, the absorption peak of the gold nanoshell at about 800 nm disappeared and a new absorption peak appeared at about 450 nm. The shape change can be attributed to the electrostatic field from the femtosecond laser exposure. With the force of the electrostatic field, nearby gold nanoshells linked each other, and extended along the electrostatic filed direction to form tube structure.
2009, 38(12):2202-2206.
Abstract:
In the DMD-450 vacuum deposition system, the evaporation time and cycle times for Sr2CO3, Al2O3, Eu2O3, and Dy2O3 targets were changed by Alternate Electron Beam Evaporation method to prepare the blue-green film(GF) and the blue-purple film(PF). Variation of Al2O3/SrO molar ratio in the light-storing ceramic films with aluminate base will produce many different crystal phases which induce the various broadband 4f65d1→4f7 transitions of Eu2+ and the narrowband 5D0→7FJ transitions of Eu3+. Annealing conditions has great influence on the luminescent properties of the films, among which annealing temperature affects crystallization and the H2 proportion in annealing atmosphere has little influence on the film color but will affect its intensity.
In the DMD-450 vacuum deposition system, the evaporation time and cycle times for Sr2CO3, Al2O3, Eu2O3, and Dy2O3 targets were changed by Alternate Electron Beam Evaporation method to prepare the blue-green film(GF) and the blue-purple film(PF). Variation of Al2O3/SrO molar ratio in the light-storing ceramic films with aluminate base will produce many different crystal phases which induce the various broadband 4f65d1→4f7 transitions of Eu2+ and the narrowband 5D0→7FJ transitions of Eu3+. Annealing conditions has great influence on the luminescent properties of the films, among which annealing temperature affects crystallization and the H2 proportion in annealing atmosphere has little influence on the film color but will affect its intensity.
2009, 38(12):2207-2211.
Abstract:
Strontium-barium titanate based on glass fiber filter (BBST) was prepared by the citrate acid complex sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and fourier transform infrared spectrophotometer (FT-IR). The adsorption behavior of BBST for cadmium ion in distilled water was investigated. The results show that the strontium-barium titanate could bond with glass fiber filter through Si-O-Ti and B-O-Ti bonding to produce a new sort of porous block adsorbent. The cadmium ion could be quantitatively retained in the medium with pH value range of 4-8, and the capacity of adsorption was 9.8 mg·g-1. The adsorption behavior followed Freundlich adsorption isotherm model and HO pseudo-second-order kinetic equation. The enthalpy changes (△H) of the adsorption process was 17.241 kJ·mol-1. At various temperatures, Gibbs free energy changes (△G) were negative, and entropy changes (△S) were positive. These showed that the adsorption of cadmium ion by BBST was endothermic and spontaneous physical process.
Strontium-barium titanate based on glass fiber filter (BBST) was prepared by the citrate acid complex sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and fourier transform infrared spectrophotometer (FT-IR). The adsorption behavior of BBST for cadmium ion in distilled water was investigated. The results show that the strontium-barium titanate could bond with glass fiber filter through Si-O-Ti and B-O-Ti bonding to produce a new sort of porous block adsorbent. The cadmium ion could be quantitatively retained in the medium with pH value range of 4-8, and the capacity of adsorption was 9.8 mg·g-1. The adsorption behavior followed Freundlich adsorption isotherm model and HO pseudo-second-order kinetic equation. The enthalpy changes (△H) of the adsorption process was 17.241 kJ·mol-1. At various temperatures, Gibbs free energy changes (△G) were negative, and entropy changes (△S) were positive. These showed that the adsorption of cadmium ion by BBST was endothermic and spontaneous physical process.
29 Effects of Alkali and Heat Treatment on Bioactivity of Micro-Arc Oxidized Coating on Ti6Al4V Alloy
2009, 38(12):2212-2216.
Abstract:
Porous TiO2 coating containing calcium and phosphate was prepared on Ti6Al4V alloy substrate using micro-arc oxidation, which was termed as MAO. And the MAO coating was treated by alkali and annealing, which was termed as MAONH. The morphology, element content and phase composition of the two kinds of coatings were analyzed by SEM, EDS and XRD, respectively. The results show that the MAONH coating is mainly composed of anatase, rutile and CaTiO3 phases, which is very different from the MAO coating. It is found that Ca2+ and P5+ ion deposit on the MAONH coating more easily than that on the MAO coating. The reason could be the hydrolysis of CaTiO3 soaking in Hank’s solution, which results in abundant Ca2+ and OH- ions. The apatite is deposited on the MAONH coating by ionic exchanges between OH-, Na+ ions of the MAONH coating and Ca2+, PO43- ions in the Hank’s solution.
Porous TiO2 coating containing calcium and phosphate was prepared on Ti6Al4V alloy substrate using micro-arc oxidation, which was termed as MAO. And the MAO coating was treated by alkali and annealing, which was termed as MAONH. The morphology, element content and phase composition of the two kinds of coatings were analyzed by SEM, EDS and XRD, respectively. The results show that the MAONH coating is mainly composed of anatase, rutile and CaTiO3 phases, which is very different from the MAO coating. It is found that Ca2+ and P5+ ion deposit on the MAONH coating more easily than that on the MAO coating. The reason could be the hydrolysis of CaTiO3 soaking in Hank’s solution, which results in abundant Ca2+ and OH- ions. The apatite is deposited on the MAONH coating by ionic exchanges between OH-, Na+ ions of the MAONH coating and Ca2+, PO43- ions in the Hank’s solution.
2009, 38(12):2217-2221.
Abstract:
Films with gradient pores (gradient layer) were prepared on rough-pore substrate materials by centrifugal deposition process. The relationship between the filtration performance of the composites and the particle size as well as the thickness of gradient layers was investigated. Results show the particle size of gradient layers should be less than the mean flow pore size of substrate materials so as to obtain the optimum filtration performance. With the thickness of gradient layers increasing, the permeability of the composites decreased while the filtration precision increased. There is optimum matching thickness of gradient layers for the optimum matching of the two performances, which has linear relation with the particle size of gradient layers, and the mean flow pore size of substrate materials is the intercept of the straight line.
Films with gradient pores (gradient layer) were prepared on rough-pore substrate materials by centrifugal deposition process. The relationship between the filtration performance of the composites and the particle size as well as the thickness of gradient layers was investigated. Results show the particle size of gradient layers should be less than the mean flow pore size of substrate materials so as to obtain the optimum filtration performance. With the thickness of gradient layers increasing, the permeability of the composites decreased while the filtration precision increased. There is optimum matching thickness of gradient layers for the optimum matching of the two performances, which has linear relation with the particle size of gradient layers, and the mean flow pore size of substrate materials is the intercept of the straight line.
Feng Jianqing
,
Lu Yafeng
,
Xu Xiaoyan
,
Xiong Xiaomei
,
Liu Guoqing
,
Zhang Cuiping
,
Chen Shaokai
,
Zhang Pingxiang
,
Zhou Lian
2009, 38(12):2222-2225.
Abstract:
The morphology of powder melting processed Y2BaCuO5 particles quenched in different heat treatment system was investigated, and compared with that of the Y2BaCuO5 particles in melt texture growth process and melt powder melt growth process. The forming mechanism of equiaxed Y2BaCuO5 particles in powder melting process was revealed. The results show that the composition of precursor powder make the excess liquid phase in powder melting process decrease, which inhibits the preferential growth of Y2BaCuO5 particles.
The morphology of powder melting processed Y2BaCuO5 particles quenched in different heat treatment system was investigated, and compared with that of the Y2BaCuO5 particles in melt texture growth process and melt powder melt growth process. The forming mechanism of equiaxed Y2BaCuO5 particles in powder melting process was revealed. The results show that the composition of precursor powder make the excess liquid phase in powder melting process decrease, which inhibits the preferential growth of Y2BaCuO5 particles.
2009, 38(12):2226-2229.
Abstract:
Ti6Al4V alloy surface was multi-alloyed by a double-glow plasma technique, and the homogeneous and dense Cr-Mo modified layer was formed. The phase structure and composition of the modified layer was characterized by XRD and GDOES, and its properties were tested by microhardness meter and ball-plate wear instrument. The results show that the composition in the modified layer are Cr and a few Mo, and decrease gradually from the surface to the underlying substrate. The layer is composed of Cr1.93Ti1.07, Cr2Ti, Cr2Ti4O11 and a few FeCrMo phase. Surface hardness of the modified Ti6Al4V alloy is increased greatly, and the wear resistance is improved significantly.
Ti6Al4V alloy surface was multi-alloyed by a double-glow plasma technique, and the homogeneous and dense Cr-Mo modified layer was formed. The phase structure and composition of the modified layer was characterized by XRD and GDOES, and its properties were tested by microhardness meter and ball-plate wear instrument. The results show that the composition in the modified layer are Cr and a few Mo, and decrease gradually from the surface to the underlying substrate. The layer is composed of Cr1.93Ti1.07, Cr2Ti, Cr2Ti4O11 and a few FeCrMo phase. Surface hardness of the modified Ti6Al4V alloy is increased greatly, and the wear resistance is improved significantly.
2009, 38(12):2230-2233.
Abstract:
TiV alloys were prepared by electro-deoxidization method. Using molten CaCl2 as electrolyte, mixed oxides of sintered V2O5 and TiO2 as cathode, and graphite rod as anode, the samples were electrolyzed at 900 ℃ under 3.0-3.2 V. The electrolysis principle was studied. Results show the reaction process is gradual reduction of mixed oxides to produce content-controllable TiV alloys. The process is prior production of Ti subsequent to gradual production of TiV alloy. The intermediate products include CaTiO3, V4O9 and TiO et al.
TiV alloys were prepared by electro-deoxidization method. Using molten CaCl2 as electrolyte, mixed oxides of sintered V2O5 and TiO2 as cathode, and graphite rod as anode, the samples were electrolyzed at 900 ℃ under 3.0-3.2 V. The electrolysis principle was studied. Results show the reaction process is gradual reduction of mixed oxides to produce content-controllable TiV alloys. The process is prior production of Ti subsequent to gradual production of TiV alloy. The intermediate products include CaTiO3, V4O9 and TiO et al.
2009, 38(12):2234-2237.
Abstract:
A new rare-earth-based catalytic material with low loading precious metals, used for catalytic coating of the three-way catalysts was prepared by co-precipitation method and precious metals modifier technology. The catalyst activities were evaluated by engine-bench test technology; their purify capabilities for vehicle exhaust and durability were evaluated by rotary drum test and vehicle road test according to the critical Europe IV emission rule. The results demonstrate that the catalysts prepared by the catalytic material have not only excellent light-off characteristic, air-fuel ratio characteristic, and high purify capability for the vehicle exhaust but also low degradation coefficient and high anti-aging performance, which ensure the vehicle emission level and durability meeting the Europe IV standard requirement for the matching vehicle entirely.
A new rare-earth-based catalytic material with low loading precious metals, used for catalytic coating of the three-way catalysts was prepared by co-precipitation method and precious metals modifier technology. The catalyst activities were evaluated by engine-bench test technology; their purify capabilities for vehicle exhaust and durability were evaluated by rotary drum test and vehicle road test according to the critical Europe IV emission rule. The results demonstrate that the catalysts prepared by the catalytic material have not only excellent light-off characteristic, air-fuel ratio characteristic, and high purify capability for the vehicle exhaust but also low degradation coefficient and high anti-aging performance, which ensure the vehicle emission level and durability meeting the Europe IV standard requirement for the matching vehicle entirely.
2009, 38(12):2238-2241.
Abstract:
The influences of boron addition on secondary phase α-Fe in LaFe11.5Si1.5 melt-spun ribbons were investigated by SEM, TEM and XRD. The magnetic transition and magnetocaloric effect of LaFe11.5Si1.5Bx compound (x = 0.5, 0.7, and 1.0) were discussed. Compared with LaFe11.5Si1.5, the melt-spun ribbons have much finer microstructure after B addition, and even amorphous structure is obtained when B content is higher. The melt-spun specimens were crystallized into La(Fe,Si)13 compound structure of cubic NaZn13-type after annealing at 1000 °C for 2-10 h. The annealing time can be reduced after B atom introduction to get single phase structure and the amount of residual α-Fe is decreased significantly. Magnetic property test show that Curie temperature of the LaFe11.5Si1.5Bx compound (x = 0.5, 0.7, and 1.0) increased slightly with B content increasing; the LaFe11.5Si1.5B0.5, i.e. low-B-content compound, exhibited first-order magnetic transition characteristics and had the same giant magnetocaloric effect with LaFe11.5Si1.5.
The influences of boron addition on secondary phase α-Fe in LaFe11.5Si1.5 melt-spun ribbons were investigated by SEM, TEM and XRD. The magnetic transition and magnetocaloric effect of LaFe11.5Si1.5Bx compound (x = 0.5, 0.7, and 1.0) were discussed. Compared with LaFe11.5Si1.5, the melt-spun ribbons have much finer microstructure after B addition, and even amorphous structure is obtained when B content is higher. The melt-spun specimens were crystallized into La(Fe,Si)13 compound structure of cubic NaZn13-type after annealing at 1000 °C for 2-10 h. The annealing time can be reduced after B atom introduction to get single phase structure and the amount of residual α-Fe is decreased significantly. Magnetic property test show that Curie temperature of the LaFe11.5Si1.5Bx compound (x = 0.5, 0.7, and 1.0) increased slightly with B content increasing; the LaFe11.5Si1.5B0.5, i.e. low-B-content compound, exhibited first-order magnetic transition characteristics and had the same giant magnetocaloric effect with LaFe11.5Si1.5.
2009, 38(12):2242-2245.
Abstract:
The preproduction situation of commercial pure titanium (Gr.2) cross-rolled boring seamless tube was introduced, and the problems in it were analyzed. The effect of Q value on tube inner surface quality and boring problems were discussed. Results show that the suitable Q value and boring in finished-product-near pass can eliminate inner surface micro-crack effectively and ensure quality of finished products.
The preproduction situation of commercial pure titanium (Gr.2) cross-rolled boring seamless tube was introduced, and the problems in it were analyzed. The effect of Q value on tube inner surface quality and boring problems were discussed. Results show that the suitable Q value and boring in finished-product-near pass can eliminate inner surface micro-crack effectively and ensure quality of finished products.
2009, 38(12):2246-2249.
Abstract:
The exchange coupled dense nanocomposite Nd2Fe14B/α-Fe isotropic bulk magnets were prepared by Spark Plasma Sintering (SPS) method. Influence of sintering temperature, time and pressure on the magnetic properties and microstructure was investigated. It is found that the density and magnetic energy product increased with the sintering temperature and pressure increasing; but the coercivity decreased with the temperature or time further increasing. After sintered at 700 ℃, 500 MPa, and held for 3 min, dense bulk magnets with fine grains of about 20 nm were achieved, whose magnetic properties were: Br=0.81T , Hci =856 kA·m-1, (BH)m =106 kJ·m-3; the density was 7.6 g/cm3.
The exchange coupled dense nanocomposite Nd2Fe14B/α-Fe isotropic bulk magnets were prepared by Spark Plasma Sintering (SPS) method. Influence of sintering temperature, time and pressure on the magnetic properties and microstructure was investigated. It is found that the density and magnetic energy product increased with the sintering temperature and pressure increasing; but the coercivity decreased with the temperature or time further increasing. After sintered at 700 ℃, 500 MPa, and held for 3 min, dense bulk magnets with fine grains of about 20 nm were achieved, whose magnetic properties were: Br=0.81T , Hci =856 kA·m-1, (BH)m =106 kJ·m-3; the density was 7.6 g/cm3.
2009, 38(12):2250-2252.
Abstract:
Y2Zr2O7:Tb3+ nano-phosphors were fabricated by combustion synthesis method using glycine as incendiary agent. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and fluorescence spectrometer were used to characterize the phase structure, surface morphology and luminescence property of Y2Zr2O7:Tb3+ nano-phosphors. The results show that the prepared samples have uniform crystallinity and fine crystalline, with a cubic fluorite structure. Typical Tb3+ emission peaks were observed in the fluorescence spectra and the strongest emission at about 542 nm with green color corresponded to the 5D4--→7F5 transition. The doping concentration of Tb3+ was in the range of 0.5%-6%, with the optimum of 3%.
Y2Zr2O7:Tb3+ nano-phosphors were fabricated by combustion synthesis method using glycine as incendiary agent. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and fluorescence spectrometer were used to characterize the phase structure, surface morphology and luminescence property of Y2Zr2O7:Tb3+ nano-phosphors. The results show that the prepared samples have uniform crystallinity and fine crystalline, with a cubic fluorite structure. Typical Tb3+ emission peaks were observed in the fluorescence spectra and the strongest emission at about 542 nm with green color corresponded to the 5D4--→7F5 transition. The doping concentration of Tb3+ was in the range of 0.5%-6%, with the optimum of 3%.
2009, 38(12):2253-2256.
Abstract:
The ammonia leaching residue sample was dissolved by HNO3-H2SO4-H3PO4 mixed acid and separated by NaOH. With Cu2+ and 2 mol/L H2SO4, Mo(VI) was reduced to Mo(V) by thiourea, then reacted with thiocyanate to form amber complexes which was used for the determination of Mo by spectrophotometric method. The sample digestion method, co-existence elements interference and their elimination were studied. The 8-time experimental results of the same samples by the proposed method were compared with that of gravimetric method and full-differential spectrophotometric method. The results indicate that the proposed method is simple, accurate and high-precision, and fit to the determination of Mo in ammonia leaching residue with satisfactory effects, prior to gravimetric method.
The ammonia leaching residue sample was dissolved by HNO3-H2SO4-H3PO4 mixed acid and separated by NaOH. With Cu2+ and 2 mol/L H2SO4, Mo(VI) was reduced to Mo(V) by thiourea, then reacted with thiocyanate to form amber complexes which was used for the determination of Mo by spectrophotometric method. The sample digestion method, co-existence elements interference and their elimination were studied. The 8-time experimental results of the same samples by the proposed method were compared with that of gravimetric method and full-differential spectrophotometric method. The results indicate that the proposed method is simple, accurate and high-precision, and fit to the determination of Mo in ammonia leaching residue with satisfactory effects, prior to gravimetric method.
2009, 38(12):2085-2088.
Abstract:
Effects of thermal treatment temperatures from 323 K to 473 K in air atmosphere on the Au/CdZnTe contacts fabricated by thermal vacuum evaporation was investigated systematically. The results show that the optimized performances of the Au/CdZnTe contacts after thermal treatment in air at a range of 353-373 K can be obtained, that is, the contacts possess lower barrier height, smaller contact resistance and better ohmic coefficient, without damaging bulk CdZnTe properties. Nevertheless, performing thermal treatment over 400 K, the deposited surface of Au electrodes will grow worse apparently, and the leakage current of CdZnTe samples enhances significantly. This might be attributed to the increase of the Cd vacancies produced by Cd sublimation from the CdZnTe into air atmosphere with the increase of temperature.
Effects of thermal treatment temperatures from 323 K to 473 K in air atmosphere on the Au/CdZnTe contacts fabricated by thermal vacuum evaporation was investigated systematically. The results show that the optimized performances of the Au/CdZnTe contacts after thermal treatment in air at a range of 353-373 K can be obtained, that is, the contacts possess lower barrier height, smaller contact resistance and better ohmic coefficient, without damaging bulk CdZnTe properties. Nevertheless, performing thermal treatment over 400 K, the deposited surface of Au electrodes will grow worse apparently, and the leakage current of CdZnTe samples enhances significantly. This might be attributed to the increase of the Cd vacancies produced by Cd sublimation from the CdZnTe into air atmosphere with the increase of temperature.
