Preheating-assisted combustion synthesis of β-Si₃N ₄ powders at low N₂ pressure

High-purity Si₃N₄ powder with no free Si was prepared at a low N₂ pressure of 140-200 kPa by preheating-assisted combustion synthesis with a heating temperature of 500-750°C. The effects of diluent proportion, preheating temperature, and N₂ pressure on the combustion parameters were investigated. By increasing the N₂ pressure, both the combustion temperature and propagation velocity of combustion wave were enhanced, and the lower limit of preheating temperature for successful combustion synthesis was decreased. As a compromise between direct nitridation and conventional combustion synthesis, preheating-assisted combustion synthesis provides an efficient and practical method for industrial production of Si₃N₄ powders under a moderate condition and on a large scale.