Preheating-assisted combustion synthesis of β-Si3N4 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.