Combustion synthesis of silicon nitride using ultrafine silicon powders

The paper examines the synthesis of alpha-Si3N4 using ultrafine powders of silicon and inert diluent (alpha-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 (1420A degrees 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 S (sp) = 6 m(2)/g and 12 m(2)/g is used, the maximum specific surface area of Si3N4 is 6.5 m(2)/g and 9.6 m(2)/g, respectively. The content of the low-temperature Si3N4 (alpha phase) modification remains the same in the synthesis product: alpha /(alpha + beta) a <... 100% = 89-93% (similar to 95 wt.%).