Structure and Morphology of Si3N4 Powders Prepared by Carbon Thermal Reduction and Nitriding Method with Silicic Acid Gel

Taking sodium silicate as silicon source and carbon black as carbon source, the Si3N4 powders were prepared by carbon thermal reduction and nitriding method, and the effects of nitriding temperature, nitriding time and mole ratio of carbon to silicon on structure were studied, and the morphology was observed. The results show that all products were Si3N4 when nitriding temperature was over 1 400 ℃, the fairly pure α-Si3N4 could be obtained when nitriding time was more than 5 h, and all products were Si3N4 when the mole ratio of carbon to silicon was 3∶1. The Si3N4 powders prepared by nitriding the precursor with mole ratio of carbon to silicon of 4∶1 at 1 400 ℃ for 5 h had irregular particles and good dispersity, the particles size was 0.3-1 μm, and the Si3N4 powders prepared by nitriding the precursor with mole ratio of carbon to silicon of 3∶1 at 1 450 ℃ for 5 h had good dispersity and appeared regular hammer-like.