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Treatment Methods for Complicated Materials Containing Selenium, Tellurium and Precious Metals

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 15-18
Advantages and disadvantages are summarized of the conventional treatment methods for complicated materials containing selenium,tellurium and precious metals. The improved process in a Russian precious metal refinery and its efficiency is emphatically introduced, including leaching of initial materials in NaOH solution to enrich precious metal in alkali leaching residue, step-by-step adjustment of alkali leaching solution pH to precipitate and separate base metals such as selenium and tellurium,precious metal replacement and removal from mother liquor, and mixing smelting of alkali leaching residue and replacement product. Using the improved process, both precious and base metals are effectively recovered, and displacer consumption is also reduced during subsequent mother liquor replacement.
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Synthesis of TiO_2 Nanoparticles by Hydrothermal Hydrolysis with Titanium Sulfate and Their Optical Absorption Properties

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 19-22
Anatase TiO2 nanoparticles were synthesized by hydrothermal hydrolysis with Ti(SO4)2 as the titanium source and strong ammonia as the precipitant. The samples were analyzed through XRD, SEM, TEM and spectrophotometer. The results show that without strong ammonia, the increase of the reaction time results in little change of TiO2 particle size. By adding strong ammonia,with the increase of pH Value the particle size of TiO2 significantly decreases,but it doesn't change when pH value is more than 7. UVVIS analysis shows that the decrease of TiO2 particle size is beneficial to the blue shift of TiO2 absorption peak. Under the conditions of 240 ℃ ,48 h and pH9, square or elliptical TiO2 nanoparticles,with better dispersity and diameter of 20 nm,are synthesized.
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Effects of Thermal Hydrogenation on Microstructure and Phase Transition of TB8 Alloy

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 23-26
Hydrogen element was implanted into TB8 titanium alloy by thermal hydrogenation. Microstructure and phase composition of hydrogenation TB8 titanium alloy were studied by OM, SEM and XRD. Effects of hydrogen on the phase transition point and elemental distribution of TB8 titanium alloy were analyzed by DTA and EDS. The results show that with hydrogen content increasing,β phase in the alloy decreases at first and then increases. Hydrogenation on the one hand reduces the critical cooling rate of co phase generation in the alloy,on the other hand reduces (α+β)/β phase transition temperature of TB8 titanium alloy. In addition, Hydrogenation promotes alloy element redistribution and phase transition from a
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Effects of Ti Doping Amount on Microstructure and Properties of TZM Alloy

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 27-30
TZM alloys doped with different amount of Ti were prepared by powder metallurgy,their micro- structure is observed by SEM, and their microhardness was also measured. Gleeble 1500 thermal/mechanical testing machine was employed to simulate the heating and deformation process of the alloys at high temperature,and then stress-strain curves were drawn. The results show that higher Ti doping amount results in more and more obvious enrichment of Ti and Zr oxide or simple substance at the alloy grain boundaries to strengthen the alloy. The alloy microhardness increases first and then decreases with Ti doping amount increasing,and reaches a maximum with 0.6% TiH2 content. High temperature deformation resistance of the alloys is improved with higher Ti doping amount.
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Simulation and Experimental Study of Cutting Deformation of TC4 Titanium Alloy

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 31-34
In view of poor cutting performance of titanium alloy materials, simulation and experimental study on cutting deformation of the common titanium alloy TC4 were carried out. Cutting deformation process of the titanium alloy and its chip formation mechanism were reproduced by finite element analysis. The simulation results indicate that the material nearby the knifepoint softens because of high temperature and high stress,and thermoplastic instability happens at chip root resulting in the upper part of the chip squeezed to form cracks but the lower part still joined. Therefore, the chip appears serrated. The results from fast cutting tests show that with high distortion degree and temperature of the material nearby the knifepoint, centralized shear slip of the chip occurs resulting in obvious indentation of the chip. Meanwhile, original crisscross and basket-like microstructure changes into the stripe-like along the cutting direction. Tiny microcracks are also observed at chip root by SEM, and chip morphology and simulation results are almost uniform.
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Effects of Annealing Treatment on the Charge/Discharge Performance of RE-Mg-Ni-based Alloy Electrode

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 35-39
Charge/discharge performance of La0.75 Mg0. 25 Ni3.44 Co0. 2 Al0.03 Ti0.03 cast alloy or annealed alloys was investigated. The results show that with annealing temperature rising, the alloy charge/discharge potential difference decreases at first and then increases during electrode activation,contrary to the discharge efficiency. All the annealed alloys have higher specific discharge capacity than the cast alloy, and the alloy annealed at 1 223 K has obvious advantage. The maximum specific discharge capacity of the cast alloy or annealed alloys decreases with charge/discharge current density increasing. The cycling performance of annealed alloys is improved,attributed to phase composition change of the alloy,microstructure homogeneity improvement and content increase of hydrogen-absorbing element on particle surface.
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Effect of Bias on Composition and Microstructure of Zr-Nb-N Diffusion Barrier

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 40-43
The Zr-Nb-N diffusion barrier films were deposited at different bias by radio-frequency reaction magnetron sputtering. The effect of bais on the microstructure and electric properties of Zr-Nb-N thin films is analyzed by EDS, XRD, TEM and resistance tester, etc. The results show that the bias has an obvious effect on the composition,resistivity and microstructure of Zr-Nb-N thin films. With the increase of bias, Nb/Zr mole ratio increases and resistivity rises in advance then falls. The Zr-Nb-N thin films of singlephase nanocrystalline, with the microstructure of substitutional solid solution, can be obtained at the bias of- 150 V.
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Analysis of the Influencing Factors of Density and Microstructure of W-Cu Alloy

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 44-48
The basic performances and common preparation methods of W-Cu alloy are briefly introduced, and the relevant influencing factors of alloy density and microstructure are analyzed. The major measures to improve the density of W-Cu alloy are pointed out,including controlling the via hole structure of tungsten matrix skeleton for infiltration process, improving the activity and decreasing the size of the powder for direct sintering process,and with as little as possible additives. Homogeneity of the W-Cu alloy microstructure can be improved by using the raw material of fine and homogeneous mixed powder, the process of isostatic pressing or injection molding,and appropriate follow-up treatment.
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The Latest Development of Super Capacitor and its Electrode Material of Nanometer MoO_3

Rare Metals and Cemented Carbides | Vol., Issue 6, 2012 | pp. 53-55
The working principle and application development of super capacitor are introduced, and the latest development of three series of electrode materials is summarized including carbon materials, metal oxides and conductive polymers. The future application of nanometer MoO3 as the electrode material of super capacitor is intensively analyzed.
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