Volume 41,Issue 1,2012 Table of Contents
2012, 41(1):1-4.
Abstract:
Recently, nanocrystal nonvolatile memory (NVM) devices using nanocrystals (NCs) have attracted great research interest. In this work, we investigated the feasibility of Ni nanocrystals embedded in metal–oxide–semiconductor (MOS) capacitor structure for NVM application. Ni NCs embedded in the gate oxide was fabricated. Ni nanocrystals with an average size of 7 nm and density of 1.5×1012 cm?2 were synthesized by e-beam evaporation technique followed by rapid thermal annealing. Distinct frequency-dependent capacitance peaks were observed. High-frequency capacitance versus voltage (C-V) and conductance versus voltage (G-V) measurements were also characterized. These results demonstrate that electrons can be loaded onto Ni nanocrystals by direct tunneling and can be stored in the fabricated MOS structure.
Recently, nanocrystal nonvolatile memory (NVM) devices using nanocrystals (NCs) have attracted great research interest. In this work, we investigated the feasibility of Ni nanocrystals embedded in metal–oxide–semiconductor (MOS) capacitor structure for NVM application. Ni NCs embedded in the gate oxide was fabricated. Ni nanocrystals with an average size of 7 nm and density of 1.5×1012 cm?2 were synthesized by e-beam evaporation technique followed by rapid thermal annealing. Distinct frequency-dependent capacitance peaks were observed. High-frequency capacitance versus voltage (C-V) and conductance versus voltage (G-V) measurements were also characterized. These results demonstrate that electrons can be loaded onto Ni nanocrystals by direct tunneling and can be stored in the fabricated MOS structure.
2012, 41(1):5-8.
Abstract:
C10H8-doped MgB2 wires were fabricated by in-situ PIT (Powder in Tube) method. The Nb/Cu tube was filled with the uniformly mixed precursor powders of magnesium, boron and C10H8 with the stoichiometry of MgB2+xwt%C10H8 ,where x=0, 2, 5, 8 and drawn to diameter Φ2 mm and Φ1 mm, respectively, and then heat treated in argon atmosphere at three different temperatures (650, 700, 750 ℃) for 2.5 h. The phase formation and microstructures of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and so on. It is found that the critical transition temperature (Tc) changes little with increasing of C10H8 doping content, while normal resistance decreases to some degree. At 20, 25 K and in zero external field, the critical current density (Jc) the sample of x=8 achieves 1.1×105 and 3.8×104 A/cm2, respectively, and the Jc of the sample of x=5 reaches 3.1×104 and 1.2×104 A/cm2, respectively.
C10H8-doped MgB2 wires were fabricated by in-situ PIT (Powder in Tube) method. The Nb/Cu tube was filled with the uniformly mixed precursor powders of magnesium, boron and C10H8 with the stoichiometry of MgB2+xwt%C10H8 ,where x=0, 2, 5, 8 and drawn to diameter Φ2 mm and Φ1 mm, respectively, and then heat treated in argon atmosphere at three different temperatures (650, 700, 750 ℃) for 2.5 h. The phase formation and microstructures of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and so on. It is found that the critical transition temperature (Tc) changes little with increasing of C10H8 doping content, while normal resistance decreases to some degree. At 20, 25 K and in zero external field, the critical current density (Jc) the sample of x=8 achieves 1.1×105 and 3.8×104 A/cm2, respectively, and the Jc of the sample of x=5 reaches 3.1×104 and 1.2×104 A/cm2, respectively.
2012, 41(1):9-13.
Abstract:
Al-Mg alloy, as a kind of promising solid fuel applied in impact-initiated energetic materials, was fabricated by bi-direction rotation ball milling. Structure characterization reveals that the surface of Al0.8Mg0.2 granular particles exhibits a mass of nanostructure with size of 15-30 nm and the crystallite size decreases from more than 100 nm (raw Al) to 22.7 nm (Al0.8Mg0.2) after mechanical alloying. Thermal analysis indicates that Al0.8Mg0.2 presents excellent thermal reactivity. In the air, Al0.8Mg0.2 will be oxidized by O2 distinctly before melting. Moreover, the high temperature reaction of Al0.8Mg0.2-O2 is advanced by 33 °C compared with Al-O2 system. TG traces show that about 69.13% of Al0.8Mg0.2 are oxidized when the temperature increases to 1100 °C, but the value is merely 15.52% for raw Al. Using the alloy in thermites, other than Al-Fe2O3, Al0.8Mg0.2-Fe2O3 system presents a considerable solid-solid reaction. In addition, for Al0.8Mg0.2-Fe2O3, the average active energy of solid-solid reaction is lower by 331.664 kJ·mol-1 than that of the liquid-solid reaction, which means an advantage in ignition.
Al-Mg alloy, as a kind of promising solid fuel applied in impact-initiated energetic materials, was fabricated by bi-direction rotation ball milling. Structure characterization reveals that the surface of Al0.8Mg0.2 granular particles exhibits a mass of nanostructure with size of 15-30 nm and the crystallite size decreases from more than 100 nm (raw Al) to 22.7 nm (Al0.8Mg0.2) after mechanical alloying. Thermal analysis indicates that Al0.8Mg0.2 presents excellent thermal reactivity. In the air, Al0.8Mg0.2 will be oxidized by O2 distinctly before melting. Moreover, the high temperature reaction of Al0.8Mg0.2-O2 is advanced by 33 °C compared with Al-O2 system. TG traces show that about 69.13% of Al0.8Mg0.2 are oxidized when the temperature increases to 1100 °C, but the value is merely 15.52% for raw Al. Using the alloy in thermites, other than Al-Fe2O3, Al0.8Mg0.2-Fe2O3 system presents a considerable solid-solid reaction. In addition, for Al0.8Mg0.2-Fe2O3, the average active energy of solid-solid reaction is lower by 331.664 kJ·mol-1 than that of the liquid-solid reaction, which means an advantage in ignition.
2012, 41(1):14-18.
Abstract:
Titanium alloy is sensitive to strain rate, so motions of rolls are crucial to the hot rolling process of titanium alloy large rings. In the study, firstly, the relative velocity vr was proposed to synthesize motion parameters of rolls, including the rotational velocity of the driver roll n1 and the feed rate of the idle roll v, and then the reasonable range of vr was determined analytically based on the stable forming condition. Secondly, a reliably coupled thermo-mechanical 3D-FE model of the process was developed in the dynamic explicit code ABAQUS/Explicit. Finally, the effect of vr on the process was studied using FE simulation. The results obtained show that although increasing vr by two different ways, i.e., by decreasing n1 or by increasing v, makes the feed amount per revolution Δhi increase, not all of their effects on the process are in agreement, such as for the nonuniformity of strain distribution. An appropriately larger value of vr is helpful to improve the end-plane quality and make strain and temperature distributions in a deformed ring more uniform, but has an adverse influence on the roll force.
Titanium alloy is sensitive to strain rate, so motions of rolls are crucial to the hot rolling process of titanium alloy large rings. In the study, firstly, the relative velocity vr was proposed to synthesize motion parameters of rolls, including the rotational velocity of the driver roll n1 and the feed rate of the idle roll v, and then the reasonable range of vr was determined analytically based on the stable forming condition. Secondly, a reliably coupled thermo-mechanical 3D-FE model of the process was developed in the dynamic explicit code ABAQUS/Explicit. Finally, the effect of vr on the process was studied using FE simulation. The results obtained show that although increasing vr by two different ways, i.e., by decreasing n1 or by increasing v, makes the feed amount per revolution Δhi increase, not all of their effects on the process are in agreement, such as for the nonuniformity of strain distribution. An appropriately larger value of vr is helpful to improve the end-plane quality and make strain and temperature distributions in a deformed ring more uniform, but has an adverse influence on the roll force.
2012, 41(1):19-23.
Abstract:
M-T curves, and M-H curves of La0.67-xGdxSr0.33CoO3, La0.67-xGdxSr0.33MnO3 (x=0.00, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.67) systems were measured. The results show that with increasing of doping Gd, magnetic structure of the La0.67-xGdxSr0.33CoO3 system exhibits cluster glass state, and the M-T curves of samples with x>0.10 exhibit a peculiar phenomenon that M value rises sharply in a low temperature range; magnetic structure of La0.67-xGdxSr0.33MnO3 system changes from long-rang ferromagnetic order to cluster glass state, anti-ferromagnetic state, and the M-T curves of samples with x≥0.50 decline sharply in a low temperature range. The different phenomena shown by the two systems come from different coupling function between Gd and Co, Mn and from spin state transition of Co.
M-T curves, and M-H curves of La0.67-xGdxSr0.33CoO3, La0.67-xGdxSr0.33MnO3 (x=0.00, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.67) systems were measured. The results show that with increasing of doping Gd, magnetic structure of the La0.67-xGdxSr0.33CoO3 system exhibits cluster glass state, and the M-T curves of samples with x>0.10 exhibit a peculiar phenomenon that M value rises sharply in a low temperature range; magnetic structure of La0.67-xGdxSr0.33MnO3 system changes from long-rang ferromagnetic order to cluster glass state, anti-ferromagnetic state, and the M-T curves of samples with x≥0.50 decline sharply in a low temperature range. The different phenomena shown by the two systems come from different coupling function between Gd and Co, Mn and from spin state transition of Co.
2012, 41(1):24-27.
Abstract:
Silver nanoparticles modified by silane coupling agent KH-560 were used as conductive filler to prepare conductive adhesive at 180 ℃ in epoxide resin vehicles. The as-modified Ag nanoparticles and conductive adhesive were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC). The effects of silver content and curing time on the properties of conductive adhesive were studied. The results show that KH-560 modified Ag powders with a particle size of approximately 20 nm are uniformly dispersed and KH-560 molecules are adsorbed on silver particle surface. Silver content and curing time could influence the properties of conductive adhesive significantly. The bulk resistivity of conductive adhesive with 55 wt% silver nanoparticle and curing time of 15 min reaches a minimal value of 2.5×10-3 ?·cm. Compared with the conductive adhesive filled with unmodified silver nano-powders, the bulk resistivity of conductive adhesive filled with modified silver nano-powders increases by 3-5 times.
Silver nanoparticles modified by silane coupling agent KH-560 were used as conductive filler to prepare conductive adhesive at 180 ℃ in epoxide resin vehicles. The as-modified Ag nanoparticles and conductive adhesive were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC). The effects of silver content and curing time on the properties of conductive adhesive were studied. The results show that KH-560 modified Ag powders with a particle size of approximately 20 nm are uniformly dispersed and KH-560 molecules are adsorbed on silver particle surface. Silver content and curing time could influence the properties of conductive adhesive significantly. The bulk resistivity of conductive adhesive with 55 wt% silver nanoparticle and curing time of 15 min reaches a minimal value of 2.5×10-3 ?·cm. Compared with the conductive adhesive filled with unmodified silver nano-powders, the bulk resistivity of conductive adhesive filled with modified silver nano-powders increases by 3-5 times.
2012, 41(1):28-32.
Abstract:
The microstructure of a [001] orientated single crystal Ni-based superalloy was observed during tensile creep. By the stress-strain finite element method (FEM) for calculating the von Mises stress distribution in the coherent interface of the cubic γ/γ′ phases, the influence of the applied stress on the regularity of γ′ phase directional coarsening was investigated. Results show that the distribution of the von Mises stress in the cubic γ/γ′ interfaces is changed by the applied tensile stress, which may bring the lattice contraction or expanding of the various crystal planes in the cubical γ′ phase. Thereinto, the lattice contraction strain on (001) plane may repel the Al and Ti atoms with bigger radius, while the lattice expanding strain on (100) and (010) planes may trap the Al and Ti atoms to promote the directional growth of γ′ phase into the mesh-like layer structure along the normal of the expanding lattice. This is thought to be the regularity of γ′ phase directional coarsening during creep of the alloy. Furthermore, the driving force of the elements diffusing and γ′ phase directional coarsening was proposed.
The microstructure of a [001] orientated single crystal Ni-based superalloy was observed during tensile creep. By the stress-strain finite element method (FEM) for calculating the von Mises stress distribution in the coherent interface of the cubic γ/γ′ phases, the influence of the applied stress on the regularity of γ′ phase directional coarsening was investigated. Results show that the distribution of the von Mises stress in the cubic γ/γ′ interfaces is changed by the applied tensile stress, which may bring the lattice contraction or expanding of the various crystal planes in the cubical γ′ phase. Thereinto, the lattice contraction strain on (001) plane may repel the Al and Ti atoms with bigger radius, while the lattice expanding strain on (100) and (010) planes may trap the Al and Ti atoms to promote the directional growth of γ′ phase into the mesh-like layer structure along the normal of the expanding lattice. This is thought to be the regularity of γ′ phase directional coarsening during creep of the alloy. Furthermore, the driving force of the elements diffusing and γ′ phase directional coarsening was proposed.
2012, 41(1):28-32.
Abstract:
The microstructure of a [001] orientated single crystal Ni-based superalloy was observed during tensile creep. By the stress-strain finite element method (FEM) for calculating the von Mises stress distribution in the coherent interface of the cubic γ/γ′ phases, the influence of the applied stress on the regularity of γ′ phase directional coarsening was investigated. Results show that the distribution of the von Mises stress in the cubic γ/γ′ interfaces is changed by the applied tensile stress, which may bring the lattice contraction or expanding of the various crystal planes in the cubical γ′ phase. Thereinto, the lattice contraction strain on (001) plane may repel the Al and Ti atoms with bigger radius, while the lattice expanding strain on (100) and (010) planes may trap the Al and Ti atoms to promote the directional growth of γ′ phase into the mesh-like layer structure along the normal of the expanding lattice. This is thought to be the regularity of γ′ phase directional coarsening during creep of the alloy. Furthermore, the driving force of the elements diffusing and γ′ phase directional coarsening was proposed.
The microstructure of a [001] orientated single crystal Ni-based superalloy was observed during tensile creep. By the stress-strain finite element method (FEM) for calculating the von Mises stress distribution in the coherent interface of the cubic γ/γ′ phases, the influence of the applied stress on the regularity of γ′ phase directional coarsening was investigated. Results show that the distribution of the von Mises stress in the cubic γ/γ′ interfaces is changed by the applied tensile stress, which may bring the lattice contraction or expanding of the various crystal planes in the cubical γ′ phase. Thereinto, the lattice contraction strain on (001) plane may repel the Al and Ti atoms with bigger radius, while the lattice expanding strain on (100) and (010) planes may trap the Al and Ti atoms to promote the directional growth of γ′ phase into the mesh-like layer structure along the normal of the expanding lattice. This is thought to be the regularity of γ′ phase directional coarsening during creep of the alloy. Furthermore, the driving force of the elements diffusing and γ′ phase directional coarsening was proposed.
2012, 41(1):33-37.
Abstract:
TiAl-based alloys with Nb/Mo were obtained by the cold crucible induction levitation melting method. The oxidation behavior in air at 900℃ for various time were investigated. The phase composition, microstructure and the interface of oxidation film and matrix were investigated with the help of XRD, SEM equipped with EDS. Combined with the oxidation kinetic analysis, it is expected to explore the synergistic effect of Nb and Mo on the oxidation behavior of TiAl-based alloys. With the addition of Nb and Mo, the continuous compact oxidation film decreases the oxidating rate and the mass gain which makes alloy preserve better oxidation properties comparing with that of Ti-46Al-6Nb. Due to the synergistic effect of Nb and Mo, the indiffusion of oxygen atoms could be prevented and the oxidation properties of TiAl-based alloys could be improved significantly.
TiAl-based alloys with Nb/Mo were obtained by the cold crucible induction levitation melting method. The oxidation behavior in air at 900℃ for various time were investigated. The phase composition, microstructure and the interface of oxidation film and matrix were investigated with the help of XRD, SEM equipped with EDS. Combined with the oxidation kinetic analysis, it is expected to explore the synergistic effect of Nb and Mo on the oxidation behavior of TiAl-based alloys. With the addition of Nb and Mo, the continuous compact oxidation film decreases the oxidating rate and the mass gain which makes alloy preserve better oxidation properties comparing with that of Ti-46Al-6Nb. Due to the synergistic effect of Nb and Mo, the indiffusion of oxygen atoms could be prevented and the oxidation properties of TiAl-based alloys could be improved significantly.
2012, 41(1):33-37.
Abstract:
TiAl-based alloys with Nb/Mo were obtained by the cold crucible induction levitation melting method. The oxidation behavior in air at 900 oC for long time was investigated. The phase composition, microstructure and the interface of the oxidation film and the matrix were investigated by means of XRD and SEM equipped with EDS. Combined with the oxidation kinetic analysis, the synergistic effect of Nb and Mo on the oxidation behavior of TiAl-based alloys was explored. With the addition of Nb and Mo, the continuous compact oxidation film decreases the oxidating rate and the mass gain which makes the alloy preserve better oxidation properties compared with that of Ti-46Al-6Nb. Due to the synergistic effect of Nb and Mo, the indiffusion of oxygen atoms can be prevented and the oxidation properties of TiAl-based alloys can be improved.
TiAl-based alloys with Nb/Mo were obtained by the cold crucible induction levitation melting method. The oxidation behavior in air at 900 oC for long time was investigated. The phase composition, microstructure and the interface of the oxidation film and the matrix were investigated by means of XRD and SEM equipped with EDS. Combined with the oxidation kinetic analysis, the synergistic effect of Nb and Mo on the oxidation behavior of TiAl-based alloys was explored. With the addition of Nb and Mo, the continuous compact oxidation film decreases the oxidating rate and the mass gain which makes the alloy preserve better oxidation properties compared with that of Ti-46Al-6Nb. Due to the synergistic effect of Nb and Mo, the indiffusion of oxygen atoms can be prevented and the oxidation properties of TiAl-based alloys can be improved.
2012, 41(1):38-41.
Abstract:
Three types of Ti-Al-Nb ternary alloys were prepared by arc-melting and heat treatment, i.e. γ-TiAl single phase alloy (alloy A), γ-TiAl + α2-Ti3Al duplex phase alloy (alloy B) and γ-TiAl + α2-Ti3Al + Nb2Al multiple phase alloy (alloy C). The phase stability was studied using SEM, XRD and electron probe microanalyzer. Mechanical properties were investigated through tensile tests at room temperature and 1173 K. Results show that their tensile properties are closely related to their microstructures. The deformability of alloy B is better than that of alloy A and C at room temperature due to small grain size caused by α2 phase appearance, lamellar microstructure of (γ+α2) and tremendous γ/α2 interface. The deformability of alloy B increases significantly with increasing temperature and its elongation achieves 40.4% at 1173 K. The fracture mode of alloy B changes from brittle transgranular failure at room temperature to ductile failure at 1173 K. While, both of alloys A and C have no increased deformability at 1173 K and show brittle transgranular failure at the two temperatures. Alloy C is a kind of very brittle material at room and elevated temperature, due to Nb2Al phase appearance reducing the continues degree of (γ+α2) lamellar structure.
Three types of Ti-Al-Nb ternary alloys were prepared by arc-melting and heat treatment, i.e. γ-TiAl single phase alloy (alloy A), γ-TiAl + α2-Ti3Al duplex phase alloy (alloy B) and γ-TiAl + α2-Ti3Al + Nb2Al multiple phase alloy (alloy C). The phase stability was studied using SEM, XRD and electron probe microanalyzer. Mechanical properties were investigated through tensile tests at room temperature and 1173 K. Results show that their tensile properties are closely related to their microstructures. The deformability of alloy B is better than that of alloy A and C at room temperature due to small grain size caused by α2 phase appearance, lamellar microstructure of (γ+α2) and tremendous γ/α2 interface. The deformability of alloy B increases significantly with increasing temperature and its elongation achieves 40.4% at 1173 K. The fracture mode of alloy B changes from brittle transgranular failure at room temperature to ductile failure at 1173 K. While, both of alloys A and C have no increased deformability at 1173 K and show brittle transgranular failure at the two temperatures. Alloy C is a kind of very brittle material at room and elevated temperature, due to Nb2Al phase appearance reducing the continues degree of (γ+α2) lamellar structure.
2012, 41(1):42-44.
Abstract:
Effect of high pressure on the lamellar spacing and mechanical properties of Ti-48Al alloy was investigated. The results indicate that when solidified under high pressure, the lamellar spacing decreases with the increasing of pressure. The average lamellar spacings are 495, 345 and 227 nm, respectively, when solidified under normal pressure, 2 GPa and 4 GPa. Also the microhardness increases with the pressure increasing. It provides a new way to refine the lamellar structure.
Effect of high pressure on the lamellar spacing and mechanical properties of Ti-48Al alloy was investigated. The results indicate that when solidified under high pressure, the lamellar spacing decreases with the increasing of pressure. The average lamellar spacings are 495, 345 and 227 nm, respectively, when solidified under normal pressure, 2 GPa and 4 GPa. Also the microhardness increases with the pressure increasing. It provides a new way to refine the lamellar structure.
2012, 41(1):45-48.
Abstract:
An examination of the effects of microstructures on the adiabatic shear banding sensitivity of Ti-6Al-4V-4Zr-Mo alloy was reported. Using the technology of split Hopkinson bar, the dynamic shearing experiments on Ti-6Al-4V-4Zr-Mo alloy with different heat treatments were conducted. The obtained microstructures are divided into the lamellar, the equiaxed and the bimodal according to heat-treatment conditions. The results indicate that the lamellar microstructure has the lowest adiabatic shear banding sensitivity, while the bimodal microstructure has the highest. In the bimodal microstructure, small cracks are found in the α/β interface located in the matrix region near the adiabatic shear band, which is considered as the main reason why the bimodal ones have the highest adiabatic shear banding sensitivity.
An examination of the effects of microstructures on the adiabatic shear banding sensitivity of Ti-6Al-4V-4Zr-Mo alloy was reported. Using the technology of split Hopkinson bar, the dynamic shearing experiments on Ti-6Al-4V-4Zr-Mo alloy with different heat treatments were conducted. The obtained microstructures are divided into the lamellar, the equiaxed and the bimodal according to heat-treatment conditions. The results indicate that the lamellar microstructure has the lowest adiabatic shear banding sensitivity, while the bimodal microstructure has the highest. In the bimodal microstructure, small cracks are found in the α/β interface located in the matrix region near the adiabatic shear band, which is considered as the main reason why the bimodal ones have the highest adiabatic shear banding sensitivity.
2012, 41(1):49-53.
Abstract:
Ti-supported Nd-doped RuO2-Co3O4 electrodes were prepared by thermal decomposition at 400 oC. The parameters of Nd-doping content were optimized. The morphology, the composition and the structure of the coating anode were characterized by SEM, EDX, and XRD. The electrocatalytic activity for oxygen evolution and the stability of the electrodes were studied by open-potential, cyclic voltammetry, polarization curve and damaged checking. The results show that Nb doping can lead to fine grains of surfaces and full crystals, promote RuO2 enrichment, and increase the active sites. Catalytic performance of the mixed oxide electrodes containing 20:1 Nd-doping content is the best, with the greatest voltammetric charge, 686 mC·cm-2, and the lowest apparent activation energy for oxygen evolution, 16.76 kJ/mol. The increase of binding force between the electrode substrate and the coating contribute to a longer electrode life than the blank electrode, reaching to 158 h.
Ti-supported Nd-doped RuO2-Co3O4 electrodes were prepared by thermal decomposition at 400 oC. The parameters of Nd-doping content were optimized. The morphology, the composition and the structure of the coating anode were characterized by SEM, EDX, and XRD. The electrocatalytic activity for oxygen evolution and the stability of the electrodes were studied by open-potential, cyclic voltammetry, polarization curve and damaged checking. The results show that Nb doping can lead to fine grains of surfaces and full crystals, promote RuO2 enrichment, and increase the active sites. Catalytic performance of the mixed oxide electrodes containing 20:1 Nd-doping content is the best, with the greatest voltammetric charge, 686 mC·cm-2, and the lowest apparent activation energy for oxygen evolution, 16.76 kJ/mol. The increase of binding force between the electrode substrate and the coating contribute to a longer electrode life than the blank electrode, reaching to 158 h.
2012, 41(1):54-57.
Abstract:
Ti/RuO2-TiO2-SnO2 electrode with IrO2-MnO2 interlayer was prepared via thermal decomposition. SEM, EDX, XRD and CV were employed to characterize the interlayer, and electrochemical stability was characterized by acceleration life time test. Results show that precursors are completed decomposed at 450 oC. The interlay shows fine grains, compact surface structure and low electrochemical porosity. Acceleration life time is greatly increased form 7.5 h to 995.8 h by adding interlay, much higher than the national standard of 20 h.
Ti/RuO2-TiO2-SnO2 electrode with IrO2-MnO2 interlayer was prepared via thermal decomposition. SEM, EDX, XRD and CV were employed to characterize the interlayer, and electrochemical stability was characterized by acceleration life time test. Results show that precursors are completed decomposed at 450 oC. The interlay shows fine grains, compact surface structure and low electrochemical porosity. Acceleration life time is greatly increased form 7.5 h to 995.8 h by adding interlay, much higher than the national standard of 20 h.
2012, 41(1):58-63.
Abstract:
Carbon supported nano-nickel-platinum electrocatalyst samples of Ni-Pt (5wt%)/C were prepared by the colloidal-gelatin method. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the metal particles’ morphology, crystal configuration, superficial element constitution and value. Moreover, cyclic voltammeter was employed to measure the catalytic activity for the electro-catalytic oxidation of methanol in an alkaline medium. The results show that Ni-Pt particles are distributed homogeneously on the carbon, with the particle sizes of 3-6 nm; the Pt doping improves largely the activity of Ni nano-particles, and the peak current density of alloy Ni-Pt(5wt%)/C catalyst reaches 85.6 mA/mg in the solution of 1.0 mol/L NaOH + 1.0 mol/L CH3OH, which is 8.7 times of that of Ni/C, and 15.3% of that of Pt/C. The current of Pt per unit mass is increased obviously.
Carbon supported nano-nickel-platinum electrocatalyst samples of Ni-Pt (5wt%)/C were prepared by the colloidal-gelatin method. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the metal particles’ morphology, crystal configuration, superficial element constitution and value. Moreover, cyclic voltammeter was employed to measure the catalytic activity for the electro-catalytic oxidation of methanol in an alkaline medium. The results show that Ni-Pt particles are distributed homogeneously on the carbon, with the particle sizes of 3-6 nm; the Pt doping improves largely the activity of Ni nano-particles, and the peak current density of alloy Ni-Pt(5wt%)/C catalyst reaches 85.6 mA/mg in the solution of 1.0 mol/L NaOH + 1.0 mol/L CH3OH, which is 8.7 times of that of Ni/C, and 15.3% of that of Pt/C. The current of Pt per unit mass is increased obviously.
2012, 41(1):64-68.
Abstract:
The Pd/γ-Al2O3 catalyst was prepared by a dipping method. The catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The catalytic properties of the Pd/γ-Al2O3 catalyst for the hydrogen-deuterium exchange of methane were tested with a fixed-bed micro-reactor. The results indicate that the Pd atoms are in the support interior of the Pd/γ-Al2O3 catalyst and the strong interaction between Pd and the support on the Pd/γ-Al2O3 catalyst occurs. The Pd/γ-Al2O3 catalyst possesses high catalytic activity in the hydrogen-deuterium exchange of methane.
The Pd/γ-Al2O3 catalyst was prepared by a dipping method. The catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The catalytic properties of the Pd/γ-Al2O3 catalyst for the hydrogen-deuterium exchange of methane were tested with a fixed-bed micro-reactor. The results indicate that the Pd atoms are in the support interior of the Pd/γ-Al2O3 catalyst and the strong interaction between Pd and the support on the Pd/γ-Al2O3 catalyst occurs. The Pd/γ-Al2O3 catalyst possesses high catalytic activity in the hydrogen-deuterium exchange of methane.
2012, 41(1):69-73.
Abstract:
The tensile property and fracture appearance of U-2.5%Nb alloy (mass fraction) were studied under the conditions with relative humidity of 3.5%, 50%, 100%, underwater, hot water and water vapor, together with hydrogen pressure of 0.4, 1.0, and 2.0 MPa. The results show that when the strain rate is 3′10-5/s, with the environment humidity and hydrogen pressure increasing, the tensile strength of U-2.5%Nb alloy decreases, the proof strength non-proportional extension increases, and the plasticity decreases sharply. In the underwater environment, at the strain rate of 3′10-5/s the elongation after fracture decreases by about 84% and the reduction of area decreases by about 79% compared with those at the strain rate of 1′10-4/s. At the strain rate of 3′10-5/s and in the 2.0 MPa hydrogen pressure environment, the elongation after fracture decreases by about 20% and the reduction of area decreases by about 13% compared with those in the 0.4 MPa hydrogen pressure environment. The fracture surface of U-2.5%Nb alloy shows a ductile feature in the environment with 3.5% relative humidity. However, dimples of the alloy fracture surface reduce obviously and a brittle fracture appears in the underwater environment. The fracture surface of the alloy shows an evident cleavage and brittle feature in water vapor environment. The brittle feature of the alloy fracture surface is enhanced with the hydrogen pressure increasing.
The tensile property and fracture appearance of U-2.5%Nb alloy (mass fraction) were studied under the conditions with relative humidity of 3.5%, 50%, 100%, underwater, hot water and water vapor, together with hydrogen pressure of 0.4, 1.0, and 2.0 MPa. The results show that when the strain rate is 3′10-5/s, with the environment humidity and hydrogen pressure increasing, the tensile strength of U-2.5%Nb alloy decreases, the proof strength non-proportional extension increases, and the plasticity decreases sharply. In the underwater environment, at the strain rate of 3′10-5/s the elongation after fracture decreases by about 84% and the reduction of area decreases by about 79% compared with those at the strain rate of 1′10-4/s. At the strain rate of 3′10-5/s and in the 2.0 MPa hydrogen pressure environment, the elongation after fracture decreases by about 20% and the reduction of area decreases by about 13% compared with those in the 0.4 MPa hydrogen pressure environment. The fracture surface of U-2.5%Nb alloy shows a ductile feature in the environment with 3.5% relative humidity. However, dimples of the alloy fracture surface reduce obviously and a brittle fracture appears in the underwater environment. The fracture surface of the alloy shows an evident cleavage and brittle feature in water vapor environment. The brittle feature of the alloy fracture surface is enhanced with the hydrogen pressure increasing.
2012, 41(1):74-77.
Abstract:
Protium and deuterium permeation measurements were carried out with Pd8.5Y0.19Ru alloy membrane of 40 μm in thickness between 573 K-723 K. Fick's 1st pervasion law can be used to describe the hydrogen permeation behavior. The protium and deuterium permeability of the membrane and separation factors for the H-D gas mixture were obtained. The permeability expression of protium and deuterium are ΦH＝2.566×10-6exp(-3542.45/T) mol/m·s·Pa0.5 and ΦD＝1.398×10-6exp(-3443.72/T) mol/m·s·Pa0.5, respectively. Compared with Pd-Y binary alloy membrane, Ru element addition decreases the membrane’s permeability and the separation factors. Besides, CH4 has strong poison effect to the membrane.
Protium and deuterium permeation measurements were carried out with Pd8.5Y0.19Ru alloy membrane of 40 μm in thickness between 573 K-723 K. Fick's 1st pervasion law can be used to describe the hydrogen permeation behavior. The protium and deuterium permeability of the membrane and separation factors for the H-D gas mixture were obtained. The permeability expression of protium and deuterium are ΦH＝2.566×10-6exp(-3542.45/T) mol/m·s·Pa0.5 and ΦD＝1.398×10-6exp(-3443.72/T) mol/m·s·Pa0.5, respectively. Compared with Pd-Y binary alloy membrane, Ru element addition decreases the membrane’s permeability and the separation factors. Besides, CH4 has strong poison effect to the membrane.
2012, 41(1):78-81.
Abstract:
The transportation of Pd((II) through a dispersion supported liquid membrane (DSLM) system consisting of N, N di(1-methylheptyl) acetamide (N503) in kerosene, supported on the polyvinylidene fluoride membrane(PVDF), was studied. The effects of HCl concentration in the feed phase, the volume ratio of liquid membrane phase to stripping phase, and KSCN concentration in the stripping phase were also researched. The results show that palladium ion can be transported effectively when the HCl concentration in the feed phase is 0.10 mol·L-1, the volume ratio is 30:30, and KSCN concentrations in the stripping phase is 1.60 mol·L-1. The transport rate of Pd(II) can reach to 79.8% through DSLM, while it is only 67.8% through traditional SLM, under the optimum condition of 130 min transport time and initial Pd(II) concentration of 5.00×10-5 mol·L-1.
The transportation of Pd((II) through a dispersion supported liquid membrane (DSLM) system consisting of N, N di(1-methylheptyl) acetamide (N503) in kerosene, supported on the polyvinylidene fluoride membrane(PVDF), was studied. The effects of HCl concentration in the feed phase, the volume ratio of liquid membrane phase to stripping phase, and KSCN concentration in the stripping phase were also researched. The results show that palladium ion can be transported effectively when the HCl concentration in the feed phase is 0.10 mol·L-1, the volume ratio is 30:30, and KSCN concentrations in the stripping phase is 1.60 mol·L-1. The transport rate of Pd(II) can reach to 79.8% through DSLM, while it is only 67.8% through traditional SLM, under the optimum condition of 130 min transport time and initial Pd(II) concentration of 5.00×10-5 mol·L-1.
2012, 41(1):82-86.
Abstract:
The deformation behavior of powder metallurgy (P/M) superalloy FGH4096 has been investigated at the temperatures (Td) of 1050-1140 oC and strain rates (
The deformation behavior of powder metallurgy (P/M) superalloy FGH4096 has been investigated at the temperatures (Td) of 1050-1140 oC and strain rates (
Tian Hui
,
Suo Hongli
,
Zhou Jingyi
,
Gao Mangmang
,
Ma Lin
,
Qiu Huoqin
,
Wang Zhao
,
Liu Min
,
Yuan Dongmei
,
Wang Yingxia
2012, 41(1):87-91.
Abstract:
The deformation and recrystallization texture of the hot rolled Ni9W substrates (Ni-9.3at%W) were analyzed by four circle X-ray diffraction and EBSD measurements. The formation and transformation of hot rolling texture in Ni9W substrates were systematically studied. The results show that the hot rolling process can effectively increase the fractions of S- and C-type textures in the Ni9W tape. With the increase of the deformation reduction, the deformation texture of Ni9W tape is transformed from Brass to Brass and Copper hybrid texture, which is beneficial for the further formation of a strong cube texture after recrystallization annealing in these Ni9W substrates.
The deformation and recrystallization texture of the hot rolled Ni9W substrates (Ni-9.3at%W) were analyzed by four circle X-ray diffraction and EBSD measurements. The formation and transformation of hot rolling texture in Ni9W substrates were systematically studied. The results show that the hot rolling process can effectively increase the fractions of S- and C-type textures in the Ni9W tape. With the increase of the deformation reduction, the deformation texture of Ni9W tape is transformed from Brass to Brass and Copper hybrid texture, which is beneficial for the further formation of a strong cube texture after recrystallization annealing in these Ni9W substrates.
2012, 41(1):92-95.
Abstract:
Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), equipped with an energy dispersive X-ray spectroscopy (EDS) were employed for examining the existing form of Cu in Zr-2.5Nb-0.5Cu alloys and the oxide films during corrosion testing in SCW (supercritical water) at 550 oC/25 MPa. In Zr-2.5Nb-0.5Cu alloy, Cu exists mainly in the form of tetragonal second phase CuZr2, rich in impurity element Fe. The CuZr2 are transferred and agglomerated with the β phase transformation of the alloy induced by hydrogen during the corrosion testing. In the form of amorphous cuprous oxide, Cu segregates on the grain boundaries of zirconia in the oxide films during corrosion testing.
Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM), equipped with an energy dispersive X-ray spectroscopy (EDS) were employed for examining the existing form of Cu in Zr-2.5Nb-0.5Cu alloys and the oxide films during corrosion testing in SCW (supercritical water) at 550 oC/25 MPa. In Zr-2.5Nb-0.5Cu alloy, Cu exists mainly in the form of tetragonal second phase CuZr2, rich in impurity element Fe. The CuZr2 are transferred and agglomerated with the β phase transformation of the alloy induced by hydrogen during the corrosion testing. In the form of amorphous cuprous oxide, Cu segregates on the grain boundaries of zirconia in the oxide films during corrosion testing.
2012, 41(1):96-99.
Abstract:
Mg60Cu16Ni10Nd14 bulk amorphous alloy with a diameter of 5 mm was prepared by copper mould casting. Its microstructure, phase structure and thermal stability were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the alloy is completely composed of amorphous phase, and phase-separated regions are homogeneously distributed in the as-cast sample. The glass transition temperature Tg and the crystallization temperature Tx of the alloy are 431 and 488 K, respectively, and the temperature interval of the supercooled liquid region ?Tx is 57 K, which means the quaternary amorphous alloy has great glass forming ability. The compressive test shows that the fracture strength of 653 MPa and the plastic elongation of 2.5% are obtained. The good plasticity is because of lots of dimples on fracture surface.
Mg60Cu16Ni10Nd14 bulk amorphous alloy with a diameter of 5 mm was prepared by copper mould casting. Its microstructure, phase structure and thermal stability were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the alloy is completely composed of amorphous phase, and phase-separated regions are homogeneously distributed in the as-cast sample. The glass transition temperature Tg and the crystallization temperature Tx of the alloy are 431 and 488 K, respectively, and the temperature interval of the supercooled liquid region ?Tx is 57 K, which means the quaternary amorphous alloy has great glass forming ability. The compressive test shows that the fracture strength of 653 MPa and the plastic elongation of 2.5% are obtained. The good plasticity is because of lots of dimples on fracture surface.
2012, 41(1):100-104.
Abstract:
The phase structure and electrochemical characteristics of CeMn0.25Al0.25Ni1.5+x (x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1) alloys with Ni overstoichiometric addition were studied. XRD, SEM and electrochemical testing have revealed that all alloys mostly contain hexagonal CeAl phase and cubic CeNi phase, and the grain size of the alloys becomes larger with increasing Ni content. The electrochemical activity of CeMn0.25Al0.25Ni1.5+x alloys has been greatly improved by Ni overstoichiometric addition and the discharge capacity can increase from 118.3 mAh·g-1 (x=0.0) to 200.7 mAh·g-1 (x=1.1) at 298 K and from 170.4 mAh·g-1 (x=0.0) to 271.4 mAh·g-1 (x=0.9) at 338 K, respectively. The P-C-T curves show that the slopes of equilibrium hydrogen pressure plateau of CeMn0.25Al0.25Ni1.5+ x (x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1) alloys become flatter, longer and higher with increasing Ni content, and therefore this may be the key factor that enhances the discharge capacity of the alloys. CeMn0.25Al0.25Ni2.4 alloy is a kind of candidate anode material for MH-Ni with further optimizing compositions.
The phase structure and electrochemical characteristics of CeMn0.25Al0.25Ni1.5+x (x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1) alloys with Ni overstoichiometric addition were studied. XRD, SEM and electrochemical testing have revealed that all alloys mostly contain hexagonal CeAl phase and cubic CeNi phase, and the grain size of the alloys becomes larger with increasing Ni content. The electrochemical activity of CeMn0.25Al0.25Ni1.5+x alloys has been greatly improved by Ni overstoichiometric addition and the discharge capacity can increase from 118.3 mAh·g-1 (x=0.0) to 200.7 mAh·g-1 (x=1.1) at 298 K and from 170.4 mAh·g-1 (x=0.0) to 271.4 mAh·g-1 (x=0.9) at 338 K, respectively. The P-C-T curves show that the slopes of equilibrium hydrogen pressure plateau of CeMn0.25Al0.25Ni1.5+ x (x=0.0, 0.3, 0.5, 0.7, 0.9, 1.1) alloys become flatter, longer and higher with increasing Ni content, and therefore this may be the key factor that enhances the discharge capacity of the alloys. CeMn0.25Al0.25Ni2.4 alloy is a kind of candidate anode material for MH-Ni with further optimizing compositions.
2012, 41(1):105-109.
Abstract:
The vacuum-free semi-solid stirring brazing process of SiCp/A356 composites was investigated. Under a certain stirring and brazing condition, the effects of the solid fraction in filler metal on the microstructure, bonded ratio and the tensile strength of bonded joints were investigated. Results show that with stirring the solid fraction of the semi-solid filler metal has a significant influence on the break of the substrate oxide film. And, with increasing of the solid fraction in filler metal, the bonded ratio of the interface and the tensile strength of the bonded joints increases, until up to the maximum values of 91.2% and 160 MPa respectively when the solid fraction is 60%; afterwards they start to decrease. At that time, a good bond between filler metal and composites appears.
The vacuum-free semi-solid stirring brazing process of SiCp/A356 composites was investigated. Under a certain stirring and brazing condition, the effects of the solid fraction in filler metal on the microstructure, bonded ratio and the tensile strength of bonded joints were investigated. Results show that with stirring the solid fraction of the semi-solid filler metal has a significant influence on the break of the substrate oxide film. And, with increasing of the solid fraction in filler metal, the bonded ratio of the interface and the tensile strength of the bonded joints increases, until up to the maximum values of 91.2% and 160 MPa respectively when the solid fraction is 60%; afterwards they start to decrease. At that time, a good bond between filler metal and composites appears.
2012, 41(1):110-114.
Abstract:
Magnesium matrix nanocomposites reinforced with nano-sized SiC particles (n-SiCp) were fabricated by mechanical stirring and high intensity ultrasonic dispersion processing. The dry sliding friction and wear behavior of the magnesium alloy and its nanocomposites were investigated. The results show that the wear resistance of the nanocomposites is higher than that of pure AZ91D alloy due to the nanoparticles reinforced effects. The wear rate increases linearly with the increase of the load for the matrix and its nanocomposites. The wear process of the matrix and the nanocomposites consists of two stages, i.e. running and stable wear stages. The SEM and LSCM analysis results on the worn surface indicate that the main wear mechanism is adhesive wear, abrasive wear and delamination wear. The load has an important effect on the wear mechanism.
Magnesium matrix nanocomposites reinforced with nano-sized SiC particles (n-SiCp) were fabricated by mechanical stirring and high intensity ultrasonic dispersion processing. The dry sliding friction and wear behavior of the magnesium alloy and its nanocomposites were investigated. The results show that the wear resistance of the nanocomposites is higher than that of pure AZ91D alloy due to the nanoparticles reinforced effects. The wear rate increases linearly with the increase of the load for the matrix and its nanocomposites. The wear process of the matrix and the nanocomposites consists of two stages, i.e. running and stable wear stages. The SEM and LSCM analysis results on the worn surface indicate that the main wear mechanism is adhesive wear, abrasive wear and delamination wear. The load has an important effect on the wear mechanism.
2012, 41(1):115-119.
Abstract:
The possibility of minitype titanium alloy impeller cast preparation by bottom vacuum suction casting was studied. At first, the effects of the processing parameters of bottom pouring vacuum suction casting on the horizontal flowability of TA15 alloy in a spiral mold cavity were investigated; then their effects on the filling ratio in gravity direction of a 1 mm thick plate was researched; finally a TA15 impeller was produced by employing reasonable processing parameters. The impeller cast has an integrated structure and fine edges and corners. Results show that gas pressure has a predominant effect on the filling process. The melt has a good filling ability both in vertical and horizontal direction.
The possibility of minitype titanium alloy impeller cast preparation by bottom vacuum suction casting was studied. At first, the effects of the processing parameters of bottom pouring vacuum suction casting on the horizontal flowability of TA15 alloy in a spiral mold cavity were investigated; then their effects on the filling ratio in gravity direction of a 1 mm thick plate was researched; finally a TA15 impeller was produced by employing reasonable processing parameters. The impeller cast has an integrated structure and fine edges and corners. Results show that gas pressure has a predominant effect on the filling process. The melt has a good filling ability both in vertical and horizontal direction.
2012, 41(1):120-123.
Abstract:
TiAl/NiCoCrAl microlaminated sheet prepared by EB-PVD have been oxygenized in air at 850 oC, and its oxidation property has been studied. The phase composition and microstructure have been analyzed by XRD and SEM. The results show TiAl/NiCoCrAl microlaminated sheet has good oxidation resistance and the oxidation kinetics curves follow the parabolic law. The oxidation mechanisms of TiAl/NiCoCrAl microlaminated sheet at high temperature is that Al on the surface will generate the Al2O3 monolayer oxide film with porous structure firstly, subsequently some Ti element in the inner TiAl layers will cross over the NiCoCrAl layers and reach the surface to generate the (TiO2 + Al2O3) oxide layer, and finally Ni and Cr in the NiCoCrAl layers can generate compact outer oxide film composed of Cr2O3 and NiCr2O4 phase, which is the essential reason why the oxidation resistance of the sheet increases obviously.
TiAl/NiCoCrAl microlaminated sheet prepared by EB-PVD have been oxygenized in air at 850 oC, and its oxidation property has been studied. The phase composition and microstructure have been analyzed by XRD and SEM. The results show TiAl/NiCoCrAl microlaminated sheet has good oxidation resistance and the oxidation kinetics curves follow the parabolic law. The oxidation mechanisms of TiAl/NiCoCrAl microlaminated sheet at high temperature is that Al on the surface will generate the Al2O3 monolayer oxide film with porous structure firstly, subsequently some Ti element in the inner TiAl layers will cross over the NiCoCrAl layers and reach the surface to generate the (TiO2 + Al2O3) oxide layer, and finally Ni and Cr in the NiCoCrAl layers can generate compact outer oxide film composed of Cr2O3 and NiCr2O4 phase, which is the essential reason why the oxidation resistance of the sheet increases obviously.
2012, 41(1):124-128.
Abstract:
At atmospheric pressure, diamond-like carbon (DLC) thin films were deposited on the Ti6Al4V alloy surface by a DBD plasma gun at low temperature (<350 oC), with CH4 as a precursor and Ar as dilution gas. The structure of the DLC thin film was analyzed by Laser Raman spectroscope and X-ray photoelectron spectroscopy. The surface morphology was observed through scanning electron microscopy. The adhesion between the DLC thin film and the substrate was investigated with the scribe testing. The friction and wear behavior of the DLC thin films under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results show that it is feasible to prepare a DLC thin film of 1.0 μm thickness by a plasma gun. The film is uniform and dense and the surface roughness Ra is about 13.23 nm. The critical load of adhesion force between the DLC thin film and the substrate is 31.0 N. It has been found that the DLC thin film has excellent friction- and wear-resistant behavior. The friction coefficient of the Ti6Al4V substrate is about 0.50 under dry sliding against steel, while the DLC thin film experiences much abated friction coefficient to 0.15 under the same testing condition.
At atmospheric pressure, diamond-like carbon (DLC) thin films were deposited on the Ti6Al4V alloy surface by a DBD plasma gun at low temperature (<350 oC), with CH4 as a precursor and Ar as dilution gas. The structure of the DLC thin film was analyzed by Laser Raman spectroscope and X-ray photoelectron spectroscopy. The surface morphology was observed through scanning electron microscopy. The adhesion between the DLC thin film and the substrate was investigated with the scribe testing. The friction and wear behavior of the DLC thin films under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results show that it is feasible to prepare a DLC thin film of 1.0 μm thickness by a plasma gun. The film is uniform and dense and the surface roughness Ra is about 13.23 nm. The critical load of adhesion force between the DLC thin film and the substrate is 31.0 N. It has been found that the DLC thin film has excellent friction- and wear-resistant behavior. The friction coefficient of the Ti6Al4V substrate is about 0.50 under dry sliding against steel, while the DLC thin film experiences much abated friction coefficient to 0.15 under the same testing condition.
2012, 41(1):129-133.
Abstract:
Electron beam self-melting brazing experiments of TA15/QCr0.8 dissimilar metals with a copper side beam offset were carried out. Microstructure of the weld was examined by optical microscopy and scanning electron microscopy. Mechanical properties of joints were evaluated by tensile strength tests. Results show that copper content of the weld is increased by adopting copper side beam offset. So the population of Cu-Ti compounds is decreased and solid solution of copper is increased. Consequently, mechanical property of the joint is improved. There is just a little titanium alloy on the top of the weld melted when beam offset is up to 1 mm. And the joint is formed by brazing process according to the filling of the top fluid metal into the butt-weld. Finally, the tensile strength of the joint can reach to 300 MPa. Fracture occurs in copper alloy during tensile strength tests with plastic fracture mode.
Electron beam self-melting brazing experiments of TA15/QCr0.8 dissimilar metals with a copper side beam offset were carried out. Microstructure of the weld was examined by optical microscopy and scanning electron microscopy. Mechanical properties of joints were evaluated by tensile strength tests. Results show that copper content of the weld is increased by adopting copper side beam offset. So the population of Cu-Ti compounds is decreased and solid solution of copper is increased. Consequently, mechanical property of the joint is improved. There is just a little titanium alloy on the top of the weld melted when beam offset is up to 1 mm. And the joint is formed by brazing process according to the filling of the top fluid metal into the butt-weld. Finally, the tensile strength of the joint can reach to 300 MPa. Fracture occurs in copper alloy during tensile strength tests with plastic fracture mode.
2012, 41(1):134-138.
Abstract:
A direct metal rapid prototyping process based on the plasma arc welding was presented. The effects of 6 important processing parameters, such as pulse current, wire-feeding speed etc, on the ratio of width to height of the deposited track cross-section (λ) was investigated by Taguchi method and temperature contrast experiments. The results show that pulse current, duty circle, wire-feeding speed and scanning speed exert significant influences on λ. The plasma gas flow-rate has a great effect on λ, while pulse frequency has no obvious effects on λ. The tensile strength and density of Ti-6Al-4V parts fabricated with the optimized parameters was tested. The results show their test data is similar to that of the parts fabricated with laser deposited process.
A direct metal rapid prototyping process based on the plasma arc welding was presented. The effects of 6 important processing parameters, such as pulse current, wire-feeding speed etc, on the ratio of width to height of the deposited track cross-section (λ) was investigated by Taguchi method and temperature contrast experiments. The results show that pulse current, duty circle, wire-feeding speed and scanning speed exert significant influences on λ. The plasma gas flow-rate has a great effect on λ, while pulse frequency has no obvious effects on λ. The tensile strength and density of Ti-6Al-4V parts fabricated with the optimized parameters was tested. The results show their test data is similar to that of the parts fabricated with laser deposited process.
2012, 41(1):139-142.
Abstract:
Aluminum tube and TA1 tube were cladded by explosive welding. The morphology and phases of the bonding interface were studied by SEM and XRD, respectively. The bonding strength and the microhardness distribution of the transition region were measured. The axial compression test and the radial flattening test were also carried out. The results indicate that the linear and the wavy bonding interface coexist. Meanwhile, obvious element diffusion occurs in the interfacial zone. In addition, the bonding strength can get no less than the shear strength of Al. No separation happens after the compression test and flattening test, indicating that the clad tube has excellent bonding properties and can endure large plastic deformation.
Aluminum tube and TA1 tube were cladded by explosive welding. The morphology and phases of the bonding interface were studied by SEM and XRD, respectively. The bonding strength and the microhardness distribution of the transition region were measured. The axial compression test and the radial flattening test were also carried out. The results indicate that the linear and the wavy bonding interface coexist. Meanwhile, obvious element diffusion occurs in the interfacial zone. In addition, the bonding strength can get no less than the shear strength of Al. No separation happens after the compression test and flattening test, indicating that the clad tube has excellent bonding properties and can endure large plastic deformation.
Zhou Sheng
,
Li Yi
,
Zhu Huiqun
,
Sun Ruoxi
,
Zhang Yuming
,
Huang Yize
,
Li Liu
,
Shen Yujian
,
Zheng Qiuxin
,
Tong Guoxiang
,
Fang Baoying
2012, 41(1):143-147.
Abstract:
Tungsten-vanadium (W-V) co-sputtered thermochromic thin films of low-cost were designed in order to solve the problems of pure vanadium dioxide (VO2) thin films including high phase transition temperature, broad width of thermal hysteresis loop and low infrared transmittance after being doped. The metal thin films of 1.4% tungsten concentration were prepared on the glass substrates by magnetron co-sputtering at room temperature, and then the prepared metal thin films were sufficiently oxidized to the thermochromic thin films by annealing under the air condition. The structure and morphology of the samples collected from the prepared thin films were analyzed by XPS, XRD and SEM, which shows that W-V co-sputtering approach does not modify the preferred orientation growth of VO2 thin films on glass substrates, but significantly changes the surface morphologies of VO2 thin films. The optical properties of W-V co-sputtered thin films were compared with that of VO2 thin films by spectrophotometer, and the phase transition temperature drops from 68 oC to 40 oC, the width of thermal hysteresis loop narrows from 6 oC to 3 oC, and the infrared transmittances at low temperature are 62% and 57%, respectively. Results demonstrate W-V co-sputtering approach can reduce the phase transition temperature, limit the thermal hysteresis loop and gently change the infrared transmittance.
Tungsten-vanadium (W-V) co-sputtered thermochromic thin films of low-cost were designed in order to solve the problems of pure vanadium dioxide (VO2) thin films including high phase transition temperature, broad width of thermal hysteresis loop and low infrared transmittance after being doped. The metal thin films of 1.4% tungsten concentration were prepared on the glass substrates by magnetron co-sputtering at room temperature, and then the prepared metal thin films were sufficiently oxidized to the thermochromic thin films by annealing under the air condition. The structure and morphology of the samples collected from the prepared thin films were analyzed by XPS, XRD and SEM, which shows that W-V co-sputtering approach does not modify the preferred orientation growth of VO2 thin films on glass substrates, but significantly changes the surface morphologies of VO2 thin films. The optical properties of W-V co-sputtered thin films were compared with that of VO2 thin films by spectrophotometer, and the phase transition temperature drops from 68 oC to 40 oC, the width of thermal hysteresis loop narrows from 6 oC to 3 oC, and the infrared transmittances at low temperature are 62% and 57%, respectively. Results demonstrate W-V co-sputtering approach can reduce the phase transition temperature, limit the thermal hysteresis loop and gently change the infrared transmittance.
Li Xiuyan
,
Shen Jun
,
Du Ai
,
Guan Dayong
,
Zhang Zhihua
,
Zhou Bin
,
Wu Guangming
,
Ni Xingyuan
,
Gao Guohua
2012, 41(1):148-151.
Abstract:
Silver colloid nanoparticles, with high Ag+ concentration (up to 0.025 mol/L) and high stability (up to 5 months), have been synthesized via one step reduction of AgNO3 by glucose in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The reaction process, size distribution, morphology, and structure of particles have been characterized by UV/Visible absorption spectrophotometry, transmission electron microscopy (TEM) and X-ray diffractometer (XRD). Results indicate that CTAB accelerates the reaction between silver ions and glucose, because it stabilizes H+. TEM images show that silver sol consists of well-dispersed agglomerates of spherical nanoparticles with particle size from 10 to 40 nm.
Silver colloid nanoparticles, with high Ag+ concentration (up to 0.025 mol/L) and high stability (up to 5 months), have been synthesized via one step reduction of AgNO3 by glucose in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The reaction process, size distribution, morphology, and structure of particles have been characterized by UV/Visible absorption spectrophotometry, transmission electron microscopy (TEM) and X-ray diffractometer (XRD). Results indicate that CTAB accelerates the reaction between silver ions and glucose, because it stabilizes H+. TEM images show that silver sol consists of well-dispersed agglomerates of spherical nanoparticles with particle size from 10 to 40 nm.
2012, 41(1):152-156.
Abstract:
The electrochemical corrosion behavior of Fe44Cr16Mo16C18B6 amorphous alloy coatings in different concentration NaOH solutions (10%, 20% and 30%) at room temperature was evaluated by electrochemical polarization curves, EIS, and scanning electronic microscopy (SEM). Potentiodynamic experiment shows that the coatings exhibit a second wide passive region in the polarization curves, and the passive region gradually gets narrower with the increase of NaOH concentration. The EIS of Fe44Cr16Mo16C18B6 amorphous alloy coatings are composed of high-frequency inductive loop and low-frequency capacitance arc. The corrosion phenomenon of Fe44Cr16Mo16C18B6 amorphous alloy coating can be better interpreted by R(RL)(Q(R(CW))) equivalent circuit model. SEM observation shows that the shed corrosion products of Fe44Cr16Mo16C18B6 amorphous alloy coatings get thicker with the increase of NaOH solution concentration.
The electrochemical corrosion behavior of Fe44Cr16Mo16C18B6 amorphous alloy coatings in different concentration NaOH solutions (10%, 20% and 30%) at room temperature was evaluated by electrochemical polarization curves, EIS, and scanning electronic microscopy (SEM). Potentiodynamic experiment shows that the coatings exhibit a second wide passive region in the polarization curves, and the passive region gradually gets narrower with the increase of NaOH concentration. The EIS of Fe44Cr16Mo16C18B6 amorphous alloy coatings are composed of high-frequency inductive loop and low-frequency capacitance arc. The corrosion phenomenon of Fe44Cr16Mo16C18B6 amorphous alloy coating can be better interpreted by R(RL)(Q(R(CW))) equivalent circuit model. SEM observation shows that the shed corrosion products of Fe44Cr16Mo16C18B6 amorphous alloy coatings get thicker with the increase of NaOH solution concentration.
2012, 41(1):157-160.
Abstract:
Effect of high temperature (T1) tempering on sintered NdFeB magnets was investigated. With increased T1 tempering of magnets, both Br and iHc are improved after low temperature T2 tempering at 600 oC, and optimum T1 is 900 oC. As T1 increases further, Br and iHc begin to decrease. Magnets experiencing T1 tempering own higher iHc but lower Br compared with magnets of free T1 tempering. Whether the magnets experience T1 tempering or not, both Br and (BH)m increase gradually while iHc increases greatly when low temperature T2 tempering increases. The optimum T2 is 600 oC. Microstructure analysis shows that there is a large amount of non-uniform phases in the main phase of sintered magnets, and they act as nuclear centers of reversal magnetism and result in iHc decreasing. After T1 tempering, the non-uniform phases disappear in the main phase and the grain boundary becomes clear and smooth, inhabiting the interaction between Nd2Fe14B grains. So the value of iHc for the tempered magnets is improved a lot.
Effect of high temperature (T1) tempering on sintered NdFeB magnets was investigated. With increased T1 tempering of magnets, both Br and iHc are improved after low temperature T2 tempering at 600 oC, and optimum T1 is 900 oC. As T1 increases further, Br and iHc begin to decrease. Magnets experiencing T1 tempering own higher iHc but lower Br compared with magnets of free T1 tempering. Whether the magnets experience T1 tempering or not, both Br and (BH)m increase gradually while iHc increases greatly when low temperature T2 tempering increases. The optimum T2 is 600 oC. Microstructure analysis shows that there is a large amount of non-uniform phases in the main phase of sintered magnets, and they act as nuclear centers of reversal magnetism and result in iHc decreasing. After T1 tempering, the non-uniform phases disappear in the main phase and the grain boundary becomes clear and smooth, inhabiting the interaction between Nd2Fe14B grains. So the value of iHc for the tempered magnets is improved a lot.
2012, 41(1):161-164.
Abstract:
The microstructure change of Mo70-Cu sheet rolled at room temperature in different deformation degrees and the effect of different annealing temperatures on its plasticity was studied. The results show that the main deformation mechanisms of Mo70-Cu sheet rolled at room temperature are the sliding deformation of Cu and Mo and the twinning deformation of Mo and its plasticity can be recovered with uniform microstructure after annealed at 1000-1100 oC for 1 h.
The microstructure change of Mo70-Cu sheet rolled at room temperature in different deformation degrees and the effect of different annealing temperatures on its plasticity was studied. The results show that the main deformation mechanisms of Mo70-Cu sheet rolled at room temperature are the sliding deformation of Cu and Mo and the twinning deformation of Mo and its plasticity can be recovered with uniform microstructure after annealed at 1000-1100 oC for 1 h.
2012, 41(1):165-168.
Abstract:
The Er-containing Al-Mg alloy was welded by laser beam welding. Microstructures and mechanical properties of the joints were analyzed, and the effects of erbium on the microstructure and properties of the weld and the heat affected zone were investigated. The results show that due to the addition of rare earth element Er, the grain size of the weld center reduces to about 30 μm; a “fine grain layer” appears near the fusion line; no significant grain growth occur in the heat-affected zone; the micro-hardness in the cross section distributes in W-shape. The effect of Er on the tensile strength of welded joints is not obvious, and the tensile strength is 70% of that of the base material.
The Er-containing Al-Mg alloy was welded by laser beam welding. Microstructures and mechanical properties of the joints were analyzed, and the effects of erbium on the microstructure and properties of the weld and the heat affected zone were investigated. The results show that due to the addition of rare earth element Er, the grain size of the weld center reduces to about 30 μm; a “fine grain layer” appears near the fusion line; no significant grain growth occur in the heat-affected zone; the micro-hardness in the cross section distributes in W-shape. The effect of Er on the tensile strength of welded joints is not obvious, and the tensile strength is 70% of that of the base material.
2012, 41(1):169-172.
Abstract:
The monolithic foamed gold was synthesized by seed-mediated growth with polystyrene (PS) template and casting procedure and heat treatment. The results indicate that the PS could be coated by gold colloid with average grain size of 4.6 nm which was made in toluene by the electrostatic effect. The deposited gold with thickness of 70-90 nm and grain size of 30-60 nm were obtained by electroless plating. It can be self-supported after the template removing. The casting procedure is analogous to slip-casting of ceramic that results in randomly-packed PS/Au spheres with void spaces between individual particles. The columniform foamed gold with hollow spheres of 8-9 μm, diameter of 4 mm, density of 1.5 g/cm3, and porosity of 92% was obtained after heat treatment.
The monolithic foamed gold was synthesized by seed-mediated growth with polystyrene (PS) template and casting procedure and heat treatment. The results indicate that the PS could be coated by gold colloid with average grain size of 4.6 nm which was made in toluene by the electrostatic effect. The deposited gold with thickness of 70-90 nm and grain size of 30-60 nm were obtained by electroless plating. It can be self-supported after the template removing. The casting procedure is analogous to slip-casting of ceramic that results in randomly-packed PS/Au spheres with void spaces between individual particles. The columniform foamed gold with hollow spheres of 8-9 μm, diameter of 4 mm, density of 1.5 g/cm3, and porosity of 92% was obtained after heat treatment.
2012, 41(1):173-177.
Abstract:
Ti5Si3 alloy powders were extracted from Ti-bearing blast furnace slag by solid oxygen ionic membrane controlled oxygen flow metallurgy technology. XRD, SEM and EDX analyses show that calcium, magnesium and aluminum impurities are effectively removed during electrolysis. The products Ti5Si3 from Ti-bearing blast furnace slag have similar microstructure and components with the products from the electrolysis of the mixture of TiO2-SiO2 powder (TiO2:SiO2=5:3). The removal mechanism of impurities was analyzed.
Ti5Si3 alloy powders were extracted from Ti-bearing blast furnace slag by solid oxygen ionic membrane controlled oxygen flow metallurgy technology. XRD, SEM and EDX analyses show that calcium, magnesium and aluminum impurities are effectively removed during electrolysis. The products Ti5Si3 from Ti-bearing blast furnace slag have similar microstructure and components with the products from the electrolysis of the mixture of TiO2-SiO2 powder (TiO2:SiO2=5:3). The removal mechanism of impurities was analyzed.
2012, 41(1):178-183.
Abstract:
The functional composite coatings on Ti6Al4V alloy surface prepared by laser cladding can greatly improve the friction and wear behavior and high temperature oxidation resistance, which resu1ts in a widespread application in aeronautics and astronautics, energy resources, chemical industry and biomedical materials fields. In this paper, the research of functional composite coatings on the surface of Ti6Al4V alloy prepared by laser cladding is reviewed. In addition, a variety of performance characteristics, applications and development of the material systems about functional composite coatings are summarized. The deficiency and new design philosophy of functional composite coatings by laser cladding are also proposed.
The functional composite coatings on Ti6Al4V alloy surface prepared by laser cladding can greatly improve the friction and wear behavior and high temperature oxidation resistance, which resu1ts in a widespread application in aeronautics and astronautics, energy resources, chemical industry and biomedical materials fields. In this paper, the research of functional composite coatings on the surface of Ti6Al4V alloy prepared by laser cladding is reviewed. In addition, a variety of performance characteristics, applications and development of the material systems about functional composite coatings are summarized. The deficiency and new design philosophy of functional composite coatings by laser cladding are also proposed.
2012, 41(1):184-188.
Abstract:
Kinds of noble metal catalysts, and the influencing factors of catalytic activity, such as preparation methods, carriers, particle size and the structure of active center have been summarized. Meanwhile, the appropriate reactions of the noble metal catalysts have been introduced.
Kinds of noble metal catalysts, and the influencing factors of catalytic activity, such as preparation methods, carriers, particle size and the structure of active center have been summarized. Meanwhile, the appropriate reactions of the noble metal catalysts have been introduced.
2012, 41(1):878-882.
Abstract:
A direct metal rapid prototyping process based on the plasma arc welding is presented. The impacts of six important process parameters, such as pulse current, wire-feeding speed etc, on the ratio of width to height of the deposited track cross-section (λ) is investigated by Taguchi method and temperature contrast experiments. The experimental results showed that pulse current, duty circle, wire-feeding speed, scanning speed exert significant effects on λ. The plasma gas flow-rate has significant effect on λ, and pulse frequency has not significant effects on λ. The tensile strength and density of Ti-6Al-4V part fabricated with the optimized parameters is tested. The results show the test data is similar to the parts fabricated with laser deposited process.
A direct metal rapid prototyping process based on the plasma arc welding is presented. The impacts of six important process parameters, such as pulse current, wire-feeding speed etc, on the ratio of width to height of the deposited track cross-section (λ) is investigated by Taguchi method and temperature contrast experiments. The experimental results showed that pulse current, duty circle, wire-feeding speed, scanning speed exert significant effects on λ. The plasma gas flow-rate has significant effect on λ, and pulse frequency has not significant effects on λ. The tensile strength and density of Ti-6Al-4V part fabricated with the optimized parameters is tested. The results show the test data is similar to the parts fabricated with laser deposited process.
2012, 41(1):902-905.
Abstract:
The possibility of minitype titanium alloy impeller cast preparation by bottom vacuum suction casting was studied. At first, the effects of the processing parameters of bottom pouring vacuum suction casting on the horizontal flowability of TA15 alloy in a spiral mold cavity were investigated; then their effects on the filling ratio in gravity direction of a 1 mm thick plate was researched; finally a TA15 impeller was produced by employing reasonable processing parameters. The impeller cast has an integrated structure and fine edges and corners. Results show that gas pressure has a predominant effect on the filling process. The melt has a good filling ability both in vertical and horizontal direction.
The possibility of minitype titanium alloy impeller cast preparation by bottom vacuum suction casting was studied. At first, the effects of the processing parameters of bottom pouring vacuum suction casting on the horizontal flowability of TA15 alloy in a spiral mold cavity were investigated; then their effects on the filling ratio in gravity direction of a 1 mm thick plate was researched; finally a TA15 impeller was produced by employing reasonable processing parameters. The impeller cast has an integrated structure and fine edges and corners. Results show that gas pressure has a predominant effect on the filling process. The melt has a good filling ability both in vertical and horizontal direction.
2012, 41(1):919-923.
Abstract:
The microstructure change of Mo70-Cu sheet rolled at room temperature in different deformation degrees and the effect of different annealing temperatures on its plasticity was studied. The results show that the main deformation mechanisms of Mo70-Cu sheet rolled at room temperature are the sliding deformation of Cu and Mo and the twinning deformation of Mo and its plasticity can be recovered with uniform microstructure after annealed at 1000-1100 ºC for 1 h.
The microstructure change of Mo70-Cu sheet rolled at room temperature in different deformation degrees and the effect of different annealing temperatures on its plasticity was studied. The results show that the main deformation mechanisms of Mo70-Cu sheet rolled at room temperature are the sliding deformation of Cu and Mo and the twinning deformation of Mo and its plasticity can be recovered with uniform microstructure after annealed at 1000-1100 ºC for 1 h.
