Method for preparing silicon carbide

Claim 1

An improved method of preparing silicon carbide which consists of (A) treating organohalogendisilanes with 0.1 to 10 percent by weight of a catalyst selected from the group consisting of quaternary ammonium halides having the formula (R') 4 NX, quaternary phosphonium halides having the formula (R') 4 PX and hexamethylphosphoramide wherein R' is a member selected from the class consisting of alkyl and aryl radicals and X is a halogen, at a temperature of from 150° C. to 340° C. for a period of 1 to 48 hours while distilling by-produced volatile materials until there is produced a polysilane, which is a solid at 25° C., having the average formula {(CH.sub.3).sub.2 Si}{CH.sub.3 Si} in which polysilane there is from 0 to 60 mole percent (CH 3 ) 2 Si═units and 40 to 100 mole percent CH 3 Si.tbd.units, wherein the remaining bonds on the silicon are attached to either another silicon atom, a chlorine atom or a bromine atom such that the polysilane contains from 10-38 weight percent, based on the weight of the polysilane, of hydrolyzable chlorine or 21-58 weight percent based on the weight of the polysilane of hydrolyzable bromine, (B) forming a shape from said polysilane, (C) heating the shape in an inert atmosphere or in a vacuum to an elevated temperature in the range of 1150° C. to 1600° C. until said polysilane is converted to silicon carbide.