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

Abstract

Abstract An ammono sol–gel and carbothermal reduction process was employed to prepare silicon nitride–silicon carbide (Si 3 N 4 –SiC) nanocomposite powder using silica sol, urea and carbon black as starting materials. When yttria (Y 2 O 3 ) was introduced into the silica sol, a Si 3 N 4 –SiC–Y 2 O 3 composite powder was obtained. Results showed Y 2 O 3 addition led to substantial change in the synthesizing temperature and the morpyology and size of Si 3 N 4 –SiC powder. The state of Y presented in Si 3 N 4 –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 Si 3 N 4 –SiC ceramics was examined. In comparison with mixed powders of Si 3 N 4 –SiC and Y 2 O 3 , the evaluated densification of Si 3 N 4 –SiC–Y 2 O 3 composite powder can be carried out with a smaller amount of Y 2 O 3 , since Y 2 O 3 was dispersed more homogeneously with Si 3 N 4 –SiC.