Synthesis of α-Si3N4 powder by high energy ball milling assisting molten salt nitridation method at low temperature

A new method for synthesizing high purity α-Si3N4 powder is introduced in this paper. α-Si3N4 powder was synthesized by high energy ball milling assisting molten salt nitridation method at low temperature, using Si powder as starting material and mixed powder of NaCl–NaF as molten salt. The effects of synthesis temperature and holding time on phase composition and micro-morphology of the samples were discussed. The results showed that Si powder will be completely nitrided at 1200 °C for 4 h, and the content of α-Si3N4 in the sample is 96%. It indicates that this method can effectively reduce the synthesis temperature of silicon nitride and improve the purity of product. The growth of α-Si3N4 whiskers occurs via a vapor-solid (VS) mechanism.