Applied Mechanics and Materials Vol. 778

Abstract: The glass frits were prepared via high temperature melting and water quenching method and nano zirconia powders were synthesized via coprecipitation method. XRD and SEM were utilized to analyze the phase composition and microstructures. The results revealed that when the additive amount of frits was 5%, the samples sintered at 1400 °C for 1 h had homogeneous microstructure.

Abstract: The mesoporous CeO₂ were prepared via a surfactant-assisted method of nanoparticle assembly, CTAB was used as surfactant. The mesoporous CeO₂ were used as the supports for preparing xAu/CeO₂ catalysts by the chemical reduction method, and the catalytic activities of the total oxidation of propane were studied. The prepared catalysts were characterized by XRD, TEM and N₂ adsorption techniques. The content of Au can affect the catalytic properties of the xAu/CeO₂ catalysts. 4Au/CeO₂ exhibited the highest catalytic activity in propane complete oxidation with the T₁₀₀ of 420 °C.

Abstract: Oxide particles of Fe-77Ni alloy scraps were reduced by hydrogen gas on the effect of temperature and time. The chemical composition of metallic powder was examined by X-ray diffraction (XRD) and FeNi₃ alloy was finally obtained with a mean particle size of 10μm.

Abstract: Ceramics is a material of hardness and brittle, so crack arises easily when it is machined. To improve its cutting performance and enhance machining quality, a dynamic model based on constant-shearing-stress is built for milling ceramics, therefore some cutting parameters can be optimized by the model for no crack machining; moreover, an algorithm of 5 axis tool-path designed with constant-shearing-stress is put forward. According to the model and the algorithm, 5 axis tool paths of decreasing-cutting-depth and decreasing-feed-rate are realized; these are really accurate and smooth through VERICUT software simulating. Using Mikron high-speed machining center, several experiments were done to find a good method of crack control in milling thin-wall ceramics. The results show that the experiment based on the 5 axis tool paths with high pressure air cooling and regional cutting is rather successful because of no cracking in cutting thin-wall ceramics, compared to others.

Abstract: This paper deals with the study of automobile parts laser cutting process and high power laser oxidation melting cutting technology. Laser oxidation melting cutting and perforation technology was studied and laser cutting process was established. Take automobile part back end plate for example, back end plate and the material is carbon steel, the CAD/CAM simulation software was used, reasonable processing parameters, cutting parameters and perforation parameters were designed. The experimental results show that laser oxidation cutting is very effective method for automobile parts of carbon steel. The laser oxidation laser cutting technical problems and carbon materials processing technology were solved and improvement measures were summarized for the high laser oxidation melting cutting.

Abstract: In this study, the anti-corrosion properties of nickel-based coatings on the surface of copper alloy were investigated, and damages caused by corrosion on the copper surface were resolved. Researchers prepared nickel-based coatings by supersonic particles deposition, and tested the anti-corrosion properties of brass substrate and nickel-based coating by electrochemical technology and neutral salt spray. The results show that, the corrosion current of coating decreased 35 times than that of matrix. The successive and pyknotic oxide film on the surface of coating prevented reaction of corrosion further. When it reached 500 hours, the corrosion rate closed to 0. Nickel-based coatings prepared by supersonic particles deposition contribute to the increase of corrosion resistance significantly, which verifies that it is feasible to prepare outstanding corrosion resisting nickel-based coating by supersonic particles deposition.

Abstract: In order to get homogeneously dispersed carbon nanotubes suspension for composite plating, carbon nanotubes were ball milled for different times and polycyclic acid (PA) was used as dispersant in this work. Sedimentation ratio was calculated by measuring the absorbance of suspensions and friction coefficient of the composite coatings was measured by friction tester. Dispersant content and ball milling time on the dispersive stability of suspension were studied. The dispersion mechanisms were discussed. The results showed that PA could effectively disperse carbon nanotubes in Pb-Sn electroplating solution. When the volume percent of PA was 0.3%, milling time was 6h and the milling speed was 300r/min, the sedimentation ratio was the smallest. The composite coatings had the smallest friction coefficient. Besides, the mechanism of PA effectively dispersing CNTs in Pb-Sn electro plating solution was electrostatics stabilization.

Abstract: Ni-diamond nanocomposite electroforming films were prepared in supercritical fluids. The effect of process parameters to wear-resisting property of composite electroforming films was analyzed by orthogonal tests, which included current density, working time, diamond content and working pressure. It has been found that the composite electroforming films prepared in supercritical CO₂ fluids have spherical crystallization with refined crystalline grain and small internal stress. Then it can be that the wear-resisting property of supercritical electroforming films is far higher than that of conventional electroforming by detecting the wear scar cross-sectional area, and the wear-resisting property increased by 18.8%.

Abstract: The thiourea (T) -formaldehyde (F) resins with different lamellar crystal structures were synthesized by varying the relative T/F molar ratio in acidic aqueous solution at 55°C. By maintaining the amount of formaldehyde more than that of thiourea, the polymerization reaction allows one to transform the lamellar crystal fragments into cross-linked microspheres, TF resin that has a somewhat high absorption capability to Cr³⁺.

Abstract: Ce³⁺ doped cubic KLaF₄ system was synthesized by co-precipitation method. The sample was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectrophotometer and fluorescence spectrophotometer. The result indicated the nanoparticle diameter of KLaF₄:Ce³⁺ was 12.5 nm. The KLaF₄:Ce³⁺ had a stronger absorption at 250 nm, which could be explained by d elecronic transition of Ce³⁺ . The maximum emission peak of KLaF₄:Ce³⁺ was 355 nm in its luminescent spectrum, and emission band of Ce³⁺ also belonged to 5d→4f transition.