Applied Mechanics and Materials Vols. 543-547

Abstract: The basic principle of vacuum evaporation deposition was introduced, the factors that influence the coating thickness in the process of evaporation coating has carried out by theoretical calculation and experimental analysis, and the influence law of film thickness was found out.

Abstract: s. Situated in Honghe Municipality of China, a magnetite-bearing cassiterite ore deposit is characterized by iron and tin minerals association in the oxide ores. Magnetite is the main iron mineral containing fine-sized cassiterite that should be recovered. Except for the complex mineral composition, the valuable minerals are finely disseminated in the ore, a joint process of magnetic and gravity concentration was used to process the ore. Results show that, a tin concentrate and a tin middlings can be obtained in processing the tailings of Low-intensity magnetic separation (LIMS), assaying 31.76% Sn and 1.98% Sn at the recovery of 46.18% and 13.36% respectively. The results provide some valuable reference in utilization of the tailings of the ore.

Abstract: Heat-resistant Al-Fe-V-Si aluminum alloys enhanced by in-situ TiC particles have been prepared by spray forming process with suitable process parameters. Research results show that the microstructure of as-deposited alloy is fine and homogeneous. In-situ TiC particles prevent the unsteady phases from coming into being. On the other hand, the TiC particles increase the volume fraction of heat-resistant phases. So the mechanical properties of the enhanced alloy by in-situ TiC particles are better than that of Al-Fe-V-Si alloy without TiC particles. The hot extrusion temperature is also an important parameter to understand. Under the permission, it is better to extrude the alloy at lower temperature. The tensile strength of the alloy without TiC particles is about 435MPa at room temperature and is about 204MPa at 350°C. However, when the alloy is enhanced by in-situ TiC particles, the strength of alloy is about 482MPa at room temperature and is about 224MPa at 350°C temperature.

Abstract: Heat-resistant FVS0812 alloys were prepared by spray forming technique. The effect of temperature on microstructure the alloys was studied by optical microscope (OM), transmission electron microscope (TEM) with energy dispersive spectrometer (EDS), differential scanning calorimeter (DSC) in this paper. The research results show that the microstructure of the material doesnt change obviously after being hold for 3 hours at 420°C temperature. When the temperature is over 420°C, the second coarse phases are found in the alloy. The studies on the microstructure of the alloy exposed at 400°C for 100 hours show that the alloy has excellent high temperature stability.

Abstract: In this study, 8009 heat resistant aluminum alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the alloy were studied using transmission electron microscopy, X-ray diffraction, and tensile tests. The secondary phases in the microstructure of the spray-deposited alloy were examined. The tensile test results indicate that the spray-deposited 8009 alloy both at room and elevated temperature displays superior tensile strength due to the presence of the thermally stable Al₁₂(Fe,V)₃Si particles.

Abstract: The complex perovskite Ba (Zn_1/3Nb_2/3)O₃ was successfully synthesized by the aqueous sol-gel method using niobium pentoxide, nitrate barium and zinc nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized Ba (Zn_1/3Nb_2/3)O₃ powders were successfully obtained at 850 °C with particle size ~100 nm. By comparison, the aqueous sol-gel process was the most effective and least expensive technique used for the preparation of Ba (Zn_1/3Nb_2/3)O₃ nanopowders.

Abstract: The ecandrewsite-type ZnTiO₃ was successfully synthesized by the aqueous sol-gel method using TiO₂ dioxide and zinc nitrate as starting materials instead of expensive organic solvent and metal alkoxides. The as-prepared nanopowders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM), respectively. The results showed that the calcination process of gel consisted of a series of oxidation and combustion reactions, accompanied by significantly exothermal effects. Highly reactive nanosized ZnTiO₃ powders were successfully obtained at 850 °C with particle size ~50 nm. By comparison, the aqueous sol-gel process was the most effective and least expensive technique used for the preparation of ZnTiO₃ nanopowders.

Abstract: The phosphors Bi_1-xPO₄:xEu³⁺(x=0.01-0.08) were synthesized by the conventional solid-state reaction method. The crystal structure,morphology,photoluminescence properties and concentration quenching of these phosphors were systematically investigated. The powder X-ray diffraction revealed that the samples BiPO₄:Eu³⁺ transform from high-temperature monoclinic phase (HTMP) to low-temperature monoclinic phase (LTMP) with the increasing Eu³⁺ content. All the samples show the characteristic red emission of Eu³⁺ ions using the fluorescence spectrometer. The concentration quenching of Eu³⁺ in BiPO₄ phosphor can be mainly attributed to multiple-multiple interaction.

Abstract: Based on the analysis of the sputtering power of field-emission electrons which hit on the end surface of positive electrode, the wear mechanism of electrode materials was studied during positive EDM process The theoretical prediction equations of maximum and minimum electrode wear rate were deduced respectively in this paper.

Abstract: By analyzing the geometry of craters in a single pulse, the model of surface roughness in EDM was established and the main factors impacting on surface roughness were analyzed. On the base of establishment of the roughness model, the effect of discharge parameters on surface roughness was investigated by the process test method during the process of aluminum alloy 2A12 in EDM. At the same time, surface morphology obtained by different discharge parameters was comparatively analyzed. The results show that the effect of peak current and pulse width on the surface roughness is more significant, the crater on the machined surface has larger size while using higher peak current and pulse width, but the number of discharge craters is reduced.