Catalyst-free synthesis of Si3N4 powders via direct nitridation of Si: influence of particle size and nitridation parameters on the α-phase fraction

초록

This study presents a catalyst-free methodology for synthesizing silicon nitride (Si3N4) powders through the direct nitridation of Si. The influence of key parameters, including Si particle sizes (1 mu m, 5 mu m, 20 mu m, and 100 mu m), nitridation temperatures (1390-1450 degrees C), holding times (0-6 h), and gas composition (N2 with or without H2), on the degree of nitridation and alpha-phase fraction of Si3N4 was investigated. The experimental phase contents and microstructural properties were evaluated using X-ray diffraction and scanning electron microscopy. The alpha-phase fraction of Si3N4 was quantitively assessed via Rietveld refinement of the XRD data, ensuring precise phase composition analysis. The results demonstrated that the optimal conditions for achieving phase-pure Si3N4 with a predominant alpha-phase of 95.1% were a Si particle size of 5 mu m, a temperature of 1450 degrees C, no additional holding time, and a gas composition of 96% N2 and 4% H2. These findings highlight the critical role of particle size and process parameters in tailoring the phase composition of Si3N4 powders. The promising results from this study could pave the way for large-scale production of high-purity Si3N4 powders with a high alpha-phase content.

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