Preparation of high-purity -Si₃N₄ powder via multifunctional synergistic catalysis and pretreatment method

At present, the Si3N4 powder prepared is not pure enough. Therefore, this work introduces a novel method of preparing high-purity alpha-Si3N4 powder. Si3N4 powder with high alpha phase content was prepared via a unique two-stage temperature-rise (TSTR) process, using KCl and metal Co as dual catalysts through low-temperature pretreatment for silicon powder and subsequent high-temperature nitriding reaction. Molten KCl insulates silicon particles in three contact modes during low-temperature pretreatment, promoting complete and uniform nitriding and absorbing the heat released during the reaction. In addition, Co forms a Co-Si liquid phase, causing the reaction to transition into a gas-liquid-solid reaction with lower potential energy, thereby reducing the reaction temperature. Through the synergistic effect of the two catalysts and optimized unique TSTR process, Si3N4 powder can be obtained at 1250 C-degrees, boasting a remarkably high alpha phase content of 99.1%, distinguished by its layered, needle-like, and spherical structures. The detailed experiments first provide a comprehensive explanation of the growth mechanism of alpha-Si3N4 . This innovative method for preparing Si3N4 powder offers a new approach to the facile production of high-purity phase ceramic powder.