Formation of Carbon Coatings on SiC Fibers by Selective Etching in Halogens and Supercritical Water

Abstract

Carbon coatings can be obtained on silicon carbide fibers by selective etching that removes silicon from the surface layer of the fiber. A gas or fluid (chlorine, supercritical water, etc.) can be used. This approach allows us to solve the problems of uniformity and adherence of coatings, as well as avoid bridging of filaments. The principal difference between the suggested method and other approaches is that the coating is not deposited on the surface of the carbide; rather the carbide surface is converted into carbon. This method can provide a simple and inexpensive route to carbon coatings (thickness from 10 nm to several microns) for a wide range of applications. It is shown that hydrothermal leaching produces a smooth and uniform carbon film on the surface of polymer-derived SiC fibers, however treatment of CVD fibers requires more efforts. Similar carbon coatings have been obtained by halogenation of SiC fibers in chlorine-containing environments.