Combustion synthesis of α-Si3N4 powders using in-situ nano-SiO2 coated Si and Si3N4 reactants

Alpha phase silicon nitride (α-Si₃N₄) powders were synthesized by combustion reaction of the in-situ nano-SiO₂ coated Si and Si₃N₄ reactants with pressurized nitrogen. The combustion temperature profile as well as the product phase composition and morphology were investigated. Regardless of the combustion temperature reached as high as 1800 °C, up to 86 wt% α-Si₃N₄ was obtained in the combustion-synthesized product from the reactants with only 6 wt% SiO₂ addition, which is three times higher than that of without SiO₂ coating, meanwhile, the morphology of Si₃N₄ grains changed from rod-like to equiaxed grain，indicating the in-situ coated SiO₂ tailored the nitridation reaction path of Si successfully by enhancing the silicon monoxide (SiO) gas phase formation.