Abstract:Silicon nitride (Si ₃N ₄) powders were synthesized with silica sol, urea and carbon black by ammono sol gel processing. Urea was dissolved in water and mixed homogeneously with silica sol. Ammonoly sis of the aqueous solution could form a precursor, which was then mixed with carbon black and nitrided at1 300～1 600 ℃ under a flowing N ₂ atmosphere. The precursor and final powder were characterized by X ray diffractometry, infrared spectroscopy and transmission electron microscopy. Results showed that Si ₃N ₄ powders with a size of 50～80nm and a content of more than 37% nitrogen can be obtained from the precursor annealed at 1 500 ℃ under a N ₂ flow of 3 L/min for 2 h. Effects of ammonolysis and synthesizing conditions on the final products were investigated.

Key words: silicon nitride nanosized powder ammonolysis sol gel