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Abstract

A method for producing a high yield of free-flowing alpha-phase single crystal silicon carbide platelets. Through the use of various parameter and composition values, the size range of the platelets can be controlled. For example, small size platelets can be prepared by first heating a mixture of finely divided silicon dioxide and carbon to a temperature of about 1600.degree..+-.100.degree. C. for a duration of about 5-10 hours to produce a silicon carbide product, referred to as a 'prefire' product. This prefire product is mixed with a platelet-enhancing material in the form of powdered carbon or aluminum metal (and mixtures thereof) and then further heated to about 1900.degree.-2400.degree. C. for 2-10 hours to make the platelets. Also, small platelets can be made by substituting silicon carbide whiskers for the intermediate prefire material and adding a platelet enhancing material. Large platelets are formed by mixing the prefire product and a platelet-enhancing material of a mixture of powdered aluminum metal and anhydrous boric oxide. This mixture is heated to about 2150.degree..+-.250.degree. C. for 2-10 hours. During any of the heating steps the gaseous products of the reaction are maintained at substantially steady state by flowing an inert gas, e.g., argon, through the furnace.

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