Effects of Silicon Particle Size on the Morphology of Rod-Like Si 3 N 4 Crystals Prepared by SHS Method

Silicon nitride whiskers or rod-like crystals have a wide range application due to its excellent mechanical properties and high temperature performance. Two different silicon powders with different size (mesh 200 and mesh 300, respectively) were chosen to prepare rod-like Si3N4 crystals by SHS method and the effects of silicon particle size on the morphology of rod-like Si3N4 crystals were investigated. The results indicate that rod-like Si3N4 crystals could be formed with either kind of silicon powders when no more than 9wt% extra Y2O3 was introduced, which could effectively promote the growth of rod-like Si3N4 crystals. The residual free silicon was detected when using coarse silicon powders, while the silicon could be reacted completely with nitrogen gas when using fine silicon powders. The morphology of samples with coarse Si powders as starting materials is more uniform and regular than that of fine Si powders samples. Fine silicon powders are not ideal candidates for forming uniform and regular rod-like Si3N4 crystals.