NIE Lei, SONG Jin, MA Jingtao, ZHAO Xingyu, HAO Shaochang, LI Jianjun, DENG Changsheng, LIU Bing

(State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China)

Abstract:  Silicon nitride ceramics have excellent performance at high temperatures. Silicon nitride ceramic microspheres have a wide range of industrial applications. In this study, zirconium sol was used as a gel additive and nano-silica powder was used as a silicon source, to prepare silicon nitride ceramic microspheres. The zirconium sol acted as a gelling agent during the formation of the gel balls, while the zirconium oxide promoted the densification of silicon nitride ceramic microspheres during the sintering process. The influences of the concentration of ZrO²⁺ and HNO₃ in the glue formulation on stability of the glue, the washing process on the nitridation reaction and the sintering temperature on the nitridation rate of the gel ball were studied. Finally, silicon nitride ceramic microspheres with a nitriding rate of 80% were obtained after sintering at nitriding temperature of 1450 ℃ for 4 h.

Key words:  silicon nitride microspheres; sol-gel; nitridation reaction; nitridation mechanism