In situ preparation of SiC/Si3N4-NW composite powders by combustion synthesis

Large-scale composite powders containing SiC particles and silicon nitride nanowires (Si3N4-NWs) were synthesised in situ by combustion synthesis (CS). In this process, a mixture of silicon, carbon black, PTFE and a small amount of iron powder was used as the precursor. The products were characterised by XRD, SEM, EDS and TEM. The particles were equiaxed with diameters in the micron range, and the in-situ formed nanowires were straight with uniform diameters of 20-350 nm and lengths of tens of micron. The Si3N4-NWs were alpha-phase single crystals grown along the [101] or [100] direction. Vapour-liquid-solid (VLS) and solid-liquid-gas-solid (SLGS) processes are proposed as the growth mechanisms of the nanowires. The as-synthesised powders have great potential for use in the preparation of high-performance SiC/Si3N4-NW composites.