Salt-assisted combustion synthesis of silicon nitride with high α-phase content

摘要

This paper presents the results showing the effect of adding varying amounts of additives, such as NaN_3, and NaCl on the ratio of α/β-Si_3N_4 prepared by nitridation of micrometer size silicon powder by combustion synthesis. The nitridation process was performed under 6.0 MPa pressure of nitrogen, and the content of α/β-Si_3N_4 in the final product was examined using intensity of the peaks in the XRD patterns. The resultant was a mixture of α-Si_3N_4 and β-Si_3N_4, where a rapid increase of a-phase was found after addition of NaCl. In the optimized synthesis conditions, micrometer size Si_3N_4powder with –90% of α-phase was obtained. The reaction mechanism is discussed with respect to the combustion temperature and the amount of NaCl.