A combustion synthesis method for the synthesis of α-Si 3 N 4 from a reactant compact composed of Si, NaN 3 , and NH 4 X and wrapped up with an igniting agent was investigated. Wrapping the reactant compact with the igniting agent (i.e., a mixture of Ti and C powders) was found necessary for the synthesis of Si 3 N 4 . In addition to NH 4 Cl, which was considered previously to function as a catalytic agent, other ammonium halides (i.e., NH 4 F, NH 4 Br, and NH 4 I) were found to be capable of catalyzing the synthesis reaction with NH 4 Cl being the most effective. Si 3 N 4 could not be produced when NaN 3 was replaced by C 3 H 6 N6NaN 3 was thus considered to exert an essential effect on the combustion synthesis reaction other than functioning as a solid-state nitrogen source as considered previously. It was proposed that Na vapor produced by decomposition of NaN 3 reduces SiX x (formed by reaction of Si and NH 4 X), promoting the nitridation reaction to form Si 3 N 4 . NaN 3 thus plays a role as a reducing agent in the synthesis reaction.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering