Converting a carbon preform object to a silicon carbide object

A process for converting a carbon or graphite object partially or entirely to a silicon carbide object, by contacting said carbon or graphite object with silicon liquid and vapor in a reaction chamber for a selected period of time said process comprising the steps of:

• (a) passing a stream of gaseous precursor material through a hole within a high emissivity, thin, insulating septum into said reaction chamber, said gaseous precursor material comprised of silicon-containing material in a gaseous phase below the decomposition temperature of said gas and selected from the group consisting of silane, halosilane, and halosilicon, and accompanying gas that has at least one of the properties of a co-reactant, a carrier and a diluent, said reaction chamber being maintained at a temperature above the melting point of silicon of at least 1412.degree. C., said thin septum having one face below the decomposition temperature of said gas and an opposite face exposed to said reaction chamber, so that said silicon containing gaseous precursor material is decomposed directly to silicon in said reaction chamber;
• (b) removing a stream of any decomposition gas, unreacted precursor gas and diluent gas from said reaction chamber;
• (c) contacting said carbon or graphite object in said reaction chamber with said silicon liquid for a period of time depending upon temperature, concentration of said gaseous precursor material, flow rate and porosity of said carbon or graphite object to convert said carbon or graphite object partially or entirely to silicon carbide;
• (d) controlling the quantity of silicon containing precursor material and co-reactant gas passing into the reaction chamber so that an excess of free silicon can remain, and voids in said object can be filled, thereby forming a non-porous body;
• and
• (e) recovering the resulting converted carbon or graphite object.