Carbothermal reduction and nitridation synthesis of silicon nitride by using solution combustion synthesized precursors

摘要

Carbothermal reduction and nitridation synthesis of Si₃N₄ was investigated by using precursor powders prepared by a solution combustion synthesis method. Glycine or urea (fuel), ammonium nitrate (oxidizer), silicic acid (Si source), and sucrose (major carbon source) were dissolved completely in water. This solution was dried and then heated to undergo the solution combustion synthesis reaction, resulting in a homogeneous mixture of nano-sized carbon and SiO₂ particles, which was used as the precursor powder for the carbothermal reduction and nitridation synthesis of Si₃N₄. When the carbothermal reduction and nitridation reaction was carried out at 1,425–1,450 °C for 4 h, formation of Si₃N₄ can be detected only when the C/SiO₂ weight ratio is greater than ~2.0. The Si₃N₄ yield increases rapidly as the C/SiO₂ weight ratio is increased from ~2.0 to 2.8 and decreases with further increase in the C/SiO₂ ratio. The α-phase content increases with increasing C/SiO₂ weight ratio and decreases with increasing temperature. Depending on the C/SiO₂ ratio, a Si₃N₄ yield of ~80 wt% and an α-phase content of ~90 wt% could be obtained.