Effect of Y2O3 addition on ammono sol–gel synthesis and sintering of Si3N4–SiC nanocomposite powder

An ammono sol–gel and carbothermal reduction process was employed to prepare silicon nitride–silicon carbide (Si3N4–SiC) nanocomposite powder using silica sol, urea and carbon black as starting materials. When yttria (Y2O3) was introduced into the silica sol, a Si3N4–SiC–Y2O3 composite powder was obtained. Results showed Y2O3 addition led to substantial change in the synthesizing temperature and the morpyology and size of Si3N4–SiC powder. The state of Y presented in Si3N4–SiC composite powder was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effect of addition method and amount of additives on densification and microstructure of sintered Si3N4–SiC ceramics was examined. In comparison with mixed powders of Si3N4–SiC and Y2O3, the evaluated densification of Si3N4–SiC–Y2O3 composite powder can be carried out with a smaller amount of Y2O3, since Y2O3 was dispersed more homogeneously with Si3N4–SiC.