Combustion synthesis of silicon nitride using ultrafine silicon powders

The paper examines the synthesis of α-Si3N4 using ultrafine powders of silicon and inert diluent (α-Si3N4). It is established that the combustion temperature of the mixture based on silicon particles 200 nm in diameter is lower than the silicon melting point (1420°C). The low combustion temperature is obviously attributed to a nanofraction in the silicon powder. The specific surface area of silicon nitride increases with decreasing silicon fraction in the starting mixture. When Si with Ssp = 6 m2/g and 12 m2/g is used, the maximum specific surface area of Si3N4 is 6.5 m2/g and 9.6 m2/g, respectively. The content of the low-temperature Si3N4 (alpha phase) modification remains the same in the synthesis product: α /(α + β) ⋅ 100% = 89–93% (∼95 wt.%).