Synthesis of Si3N4 by silicon combustion in air

The silicon mixture mechanically activated for 20 h could combust in air. It was found that the burning of silicon powder occurred via two-stage self-propagating regime. The surface and center of the synthesized products are demonstrated to be with different features. On the surface of the product, alpha-Si3N4 is the major phase coexisting with minor Si2N2O and amorphous SiO2, while in the center of the lump, loose grey powders are Si3N4 powders whose phase composition depends on the reaction conditions. The whole combustion process of silicon powders in air after mechanical activation approves the feasibility of silicon combustion in air. The qualitative discussion given shows the formation of Si3N4 instead of SiO2 in air. Furthermore, the phase composition of product can be controlled by adjusting the composition of the reactant mixtures.