Gan Guoyou

Direct Electrodeposition of Fe-Ni Alloy Films on Silicon Substrate

Abstract The direct electroplating of Fe-Ni alloy films onto (100) n-type Si substrates were conducted. The electrodeposition phases, the film structure and the performance were investigated. The results show that when the current density is above 1.0 A/dm2, continuous films are formed and show an anomalous co-deposition progress occurs. When films are prepared with the current density from 1.0 to 4.0 A/dm2 the nickel composition can be adjusted from 45% to 78% (mass fraction), and the corresponding current efficiencies are from about 60% to 66%. The films consisting of 10∼30 nm nanocrystallites show the fcc structure of solid solution of Fe-Ni. The magnetic hystersis loops of the alloy films exhibit a higher saturation magnetization and a very low coercive filed approaching zero, indicating that nanosized alloy films have very good soft magnetic performance.

Study on Preparation Technology of Nickel Powder with Liquid Phase Reduction Method

Abstract Ultrafine nickel powder was prepared without dispersant by liquid phase reduction method. The hydrazine hydrate was used as the reductant, the nickel sulfate as the raw material and NaOH was the pH regulator. The influences of the reaction temperature, pH, concentration of Ni2+ ions, mole ratio of N2H4·H2O/Ni2+ on the particle size, the morphology and the dispersion of nickel powder were studied. The samples were characterized by the scanning electron microscope (SEM), X-ray diffraction (XRD), laser particle size analysis etc. The results show that the high purity and spherical nickel powder with face-centered cubic structure can be prepared when the temperature is 80 C, pH is 11, the concentration of Ni2+ ions is 0.5 mol/L, the mole ratio of N2H4·H2O/Ni2+is 4. The average particle size of nickel powder is about 400 nm.

Effect of Electrolytic Solution Concentrations on Surface Hydrophilicity of Micro-Arc Oxidation Ceramic Film Based on Ti6Al4V Titanium Alloy

Abstract The present work focuses on the surface of Ti6Al4V titanium alloy to improve its microstructure and hydrophilic property using micro-arc oxidation (MAO) in a mixed electrolyte system with different concentrations of calcium salt and phosphate salt. The morphology, the crystalline structure, the thickness and the hydrophilic property of the MAO film were detected by scanning electron microscopy(SEM), X-ray diffraction(XRD), eddy current thickness meter and electrochemical work station. Results show that the MAO film surface is porous and composed of anatase, rutile and a small amount of hydroxyapatite. The amount of hydroxyapatite phase increases with increasing of potassium dihydrogen phosphate concentration. The thickness of MAO film will not change until it increases to a certain value. The ratio of the surface loose zone to the inner compact zone changes with increasing of the potassium dihydrogen phosphate concentration. The thicker loose layer surface is porous and has the hydroxyapatite phase with more Ca and P, which can improve the hydrophilic property and biological compatibility of MAO ceramic film.

Preparation and characterization of layered low-voltage ZnO varistors

Double-layered, low-voltage ZnO varistors have been fabricated by feeding two kinds of ZnO powders into a die using dry extrusion molding. Compared with ZnO varistors fabricated by the conventional route, the layered ZnO varistors have larger non-linear coefficients, lower breakdown electric fields, and lower leakage current densities. The improvement in electrical performance of the layered low-voltage ZnO varistors is attributed to the asymmetric band structure at grain boundary between the two layers.