Synthesis of Chromium Silicides in Ionic Melts

Abstract

We study the currentless diffusion saturation, metal-thermal reduction, and the electrochemical behaviors of chromium- and silicon-containing melts and establish the conditions of synthesis of chromium silicides in the form of superfine powders and coatings. It is shown that the role of limiting stage of the process of diffusion saturation of chromium, molybdenum, and tungsten with silicon in chloride-fluoride melts is played by the diffusion of silicon atoms in the solid phase. In the course of currentless transfer of silicon to metals of group VIB, silicide coatings are formed on their surfaces. The combined reduction of chromium (III) chloride and sodium fluorine-silicate by metallic sodium or magnesium makes it possible to obtain silicide powders. We formulate the conditions required for getting powders of chromium silicides by electrolysis of chloride-fluoride melts containing fluorine-silicate and potassium chromate. The oxidation resistance of the obtained silicide powders is explained by the formation of silicon-oxide layers on their surfaces.