Sinterability of nano-sized silicon carbide powders

The sinterability of three kinds of commercially available nano-sized SiC powders and a treated nano-sized SiC powder was investigated using Al2O3-Y2O3-CaO as a sintering additive. The commercially available, as-received nano-sized SiC powders were difficult to sinter to a relative density of > 95% by conventional hot pressing. The effects of the free carbon and SiO2 impurities in the starting powders on the sinterability of the nano-sized SiC powders were identical to those on the submicron SiC powders. However, both the extremely high free carbon content and low green density of the commercially available nano-sized SiC powders were responsible for their poor sinterability. The reduction of the free carbon content by oxidation and the control of the SiO2 content by acid treatment were beneficial for enhancing the sinterability of the nano-sized SiC powder during liquid-phase sintering.