Study Of Si₃N₄/SiC Ceramic Composite Material

This paper addresses a possible route, Self-propagating High-temperature Synthesis (acronym:SHS), for the manufacturing of Si3N4/SiC composite ceramic powder, The main reactant material including silicon powder, carbon powder and nitrogen and using Si3N4as diluent, NH4Cl as addition. By adjusting the content of silicon powder, carbon powder and diluent can obtain composite powder with different composition. Add the sintering additives (alumina and yttrium oxide), process the SHS composite powder, compression molding, and use gas pressure sintering to obtain dense Si3N4/SiC in phase ceramic material. The microstructure of SHS Si3N4/SiC powder and ceramic had been studied by means of X-ray difraction (XRD), Scanning electron microscopy(SEM). The sintering characteristics of in phase ceramic can be studied through the test of density, hardness, flexural strength, and the fracture toughness.Composite powder preparation research results show that the carbon powder quality score, the higher during the high temperature burning reaction, burning the faster the speed, the greater the particle size of the powders synthesis average; When the carbon content increases, β phase was obviously changed, but (3phase grain size fell. In the reaction process, a part of the a phase transformation into β phase. At the same time because of the existence of NH4Cl additive, promote the formation of the reaction, decrease the reaction temperature, and for the generation of a phase. Due to the existence of Si3N4, SiC generation reaction is carbon and silicon nitride reaction.In phase ceramic preparation results show that in the certain nitrogen pressure, suitable sintering additives and the right sintering temperature, can manufacturing Si3N4/SiC In phase ceramic. The fracture toughness of the In phase ceramic can be improved, but the hardness and flexural strength has not changed much. Main toughening mechanism for SiC particle toughening and β-Si3N4toughening; The main way should be enhanced particles reinforced SiC.