Formation of Si3N4 coating on SiC substrate by gas transporting self‐propagating high‐temperature synthesis with the addition of NH4Cl

Abstract

AbstractUnder the urgent demand of high‐performance silicon nitride substrate (Si3N4), this paper reports a new gas transporting self‐propagating high‐temperature synthesis technology (GTST) to form Si3N4 coating on silicon carbide (SiC) substrate with the addition of NH4Cl, which may partly be a candidate of high‐performance Si3N4 substrate. The effect of NH4Cl on the formation of the Si3N4 coating is investigated, and the reaction mechanism with the participation of NH4Cl is discussed. The addition of the NH4Cl promotes the formation of the compact Si3N4 coating with a thickness of 20–80 μm on both sides of SiC substrate. During the reaction, NH4Cl acts as a carrier to convert solid and liquid Si particles into gas phase SiCl4, and transport it to SiC substrate. Finally, SiCl4 is nitride into Si3N4 coating under the higher temperature generated by the combustion wave. Moreover, the research mechanism can provide a guide for other complex ceramic coatings by GTST.