Synthesis of Si-C-N amorphous powder by imide method and its crystallization behavior

The imide powders of Si-C-N-H system were formed by liquid phase reaction in SiCl₄-CH₃SiCl₃-NH₃ or SiCl₄-(C₂H₅)₂NH system in n-hexane and decomposed at 900°C in vacuum to amorphous powder of Si-C-N system. The powders were heat-treated in N₂ at 1400 - 1800°C. Si₃N₄ was crystallized above 1500°C and SiC was formed at higher temperatures. The formation temperature of SiC lowered with an increase of the carbon content in the synthesis system. The SEM-EDX indicated that the detected carbon content was small, when Si₃N₄ phase was predominant, and increased according to SiC formation at high temperatures. This means that carbon may be included inside Si₃N₄ particles, reacting with Si₃N₄ to form SiC at higher temperatures. This results suggests that Si₃N₄-SiC composite can be fabricated from the Si-C-N amorphous powder by optimizing starting materials and heat treatment condition.