High purity high surface area silicon nitride

Abstract

A process is disclosed for producing high purity high surface area silicon nitride. The process involves contacting silicon tetrachloride with water to form a two phase system consisting essentially of a solid phase which is essentially silica gel and a liquid phase, heating the two phase system at a sufficient temperature for a sufficient time to partially dehydrate the silica gel followed by removing the solid phase from the liquid phase. A slurry is then formed of the solid phase in an aqueous solution of a water soluble organic carbon source. A dispersing agent is added to the slurry to disperse the silica gel, and the pH of the slurry is adjusted to greater than about 7, followed by heating the slurry at a sufficient temperature for a sufficient time to remove essentially all of the water and to decompose the carbon source. The resulting powder mixture of silicon dioxide and carbon is deagglomerated and heated in a nitrogen atmosphere at a sufficient temperature for a sufficient time to form a reaction product the major portion of which is silicon nitride. The reaction product is heated in an air atmosphere at a sufficient temperature for a sufficient time to remove essentially all of the carbon and form the high purity high surface area silicon nitride.