Method of manufacturing crystalline silicon carbide employing acid pretreated rice husks

Claim 1

In a method for manufacturing silicon carbide wherein rice husks are employed as a silicon and carbon containing raw material, the improvement comprising: (a) pretreating said rice husk raw material by admixing therewith an acid solution; (b) maintaining said rice husk raw material in the presence of said acid solution for a period of at least one-half hour; (c) removing said acid solution from said rice husk raw material; (d) arranging the acid treated raw material on a gas-permeable, heat-resistant support in a manner allowing the passage of a gas through said raw material; (e) placing the material-bearing support in an air tight furnace, said air tight furnace adapted to provide at least three temperature zones covering the range of about 400° C. to a high of at least 1,350° C., each of said temperature zones having a substantially different temperature; (f) moving said material-bearing support successively through said temperature zones, in the direction of increasing temperature; (g) maintaining said material-bearing support means in each of said temperature zones for at least one hour; (h) passing a non-oxidizing gas through the heated material to remove impurities while the material is in each temperature zone below 1,300° C.; and, (i) removing silicon carbide whisker-containing material from said furnace.