Polycrystalline silicon nitride fibers by combustion synthesis

SHS nitriding of Si in the presence of added (NН 4 ) 2 (COO) 2 ∙ H 2 O and FeCl 3 ∙ 6Н 2 О under pressure of nitrogen gas was explored by XRD and SEM. The additives were used with an intention to transpose the nitriding reaction into the gas phase and thus to allow the deposition of Si 3 N 4 from the gas phase. Thus prepared Si 3 N 4 had a shape of polycrystalline fibers formed by 1D crystals of varied morphology and by the assemblies of nanosized crystals. Phase composition, fiber length, and shape of nanocrystals were found to depend on nitrogen pressure. Synthesized fibers can find their application in heat insulation of aircrafts, fabrication of coatings, deep purification filters, etc.