Transformation of polysilicon cutting waste into SiC/α-Si3N4 composite powders via electromagnetic induction heating

In order to use polysilicon cutting waste more efficiently, SiC/α-Si₃N₄ composite powders were prepared via electromagnetic induction heating at ambient pressure. Factors affecting synthesis and reaction mechanisms of the SiC/α-Si₃N₄ composite powders were investigated. Results show that the morphology of obtained α-Si₃N₄ consists of particles equiaxed with diameter in the micron range and one-dimensional Si₃N₄ nanowires with diameter of tens to hundreds of nanometers and length of up to tens of microns. It was found that the addition of NH₄Cl can promote nitridation by controlling reaction temperature and participating in the reaction. In addition, the existence of Fe₂O₃ impurities was found to be beneficial to the formation of α-Si₃N₄ in reaction process by removing the SiO₂ film from silicon and providing FeSi₂ liquid phase as effective pass for vapor phase. Mechanisms used to grow Si₃N₄-NWs were vapor-solid (VS) and vapor-liquid-solid (VLS) depositions.