PREPARATION OF SI3N4 POWDER FROM THE SYSTEM SIO2-C-N-2 WITH SI3N4 SEED

The effects of adding a small amount of S3N4 less than 0.1 mass% as se ed crystals on the particle size and the alpha-content in resulting Si 3N4 powders were investigated. A small quantity of only 0.02 mass% see d increased the alpha-content to more than 90%. This seems to be due t o the high partial pressure of gaseous SiO evolved by reduction of SiO 2. The particle sizes of the products decreased as the amount of seed increased, Finer particles were obtained when a hind of seed powder pr oduced through pulverization process was used, which can be ascribed t o significantly finer particles in the seed. With addition of less tha n 0.1 mass% seed, the relation between the number of seed (N) and the resultant particle size (D) was confirmed to obey the equation, D=k(1/ N)(1/3), where k is a constant.