Study on rapid nitridation process of molten silicon by thermogravimetry and in situ Raman spectroscopy

Abstract The melt of silicon, hindering nitridation for its agglomeration, should be avoided in the direct nitridation of silicon to synthesize silicon nitride powders, although liquid phase facilitates nitridation. Therefore, we proposed a method to nitride molten silicon without agglomeration. Thermogravimetric and in situ Raman studies on the nitridation process of molten silicon were performed. The as‐prepared silicon nitride samples were found to be micron clusters composed of submicron grains with high α‐Si 3 N 4 content. The nitridation of molten silicon at 1500°C was completed after 500 s and 109 times faster than the nitridation of solid silicon at 1350°C. β‐Si 3 N 4 is produced dominantly by α–β‐phase transition. Less nitridation time and low temperature can decrease the β‐Si 3 N 4 content. The rapid nitridation was owning to core–shell structure Si@Si 3 N 4 , which was formed after the initial nitridation of silicon particles and hindered the agglomeration of molten silicon.