Pressureless sintering of beta silicon carbide nanoparticles

This study reports the pressureless sintering of cubic phase silicon carbide nanoparticles (β-SiC). Green blended compounds made of SiC nano-sized powder, a fugitive binder and a sintering agent (boron carbide, B4C), have been prepared. The binder is removed at low temperature (e.g. 800°C) and the pressureless sintering studied between 1900 and 2100°C. The nearly theoretical density (98% relative density) was obtained after 30min at 2100°C. The structural and microstructural evolutions during the heat treatment were characterised. The high temperatures needed for the sintering result in the β-SiC to α-SiC transformation which is revealed by the change of the composite microstructure. From 1900°C, dense samples are composed of β-SiC grains surrounding α-SiC platelets in a well-defined orientation. TEM investigations and calculation of the activation energy of the sintering provided insight to the densification mechanism.