Fabrication of dense Si3N4 ceramics via coating amorphous Si3N4 nano-powders by sodium reduction in liquid ammonia

Abstract

Commercial Si3N4 powders coated with 030% amorphous Si3N4 nano-powders were fabricated successfully. Amorphous Si3N4 nano-powders coating were prepared through the reduction of silicon tetrachloride (SiCl4) by sodium in liquid ammonia at 45C. Dense Si3N4 ceramics with 97.2% relative density of theoretic value were obtained from Si3N4 micro-powders coated with 30% nano-powders sintered by spark plasma sintering at 1500C without sintering additives.