Pressureless sintering of beta silicon carbide nanoparticles

This study reports the pressureless sintering of cubic phase silicon carbide nanoparticles (beta-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 degrees C) and the pressureless sintering studied between 1900 and 2100 degrees C. The nearly theoretical density (98% relative density) was obtained after 30 min at 2100 degrees C. The structural and microstructural evolutions during the heat treatment were characterised. The high temperatures needed for the sintering result in the beta-SiC to alpha-SiC transformation which is revealed by the change of the composite microstructure. From 1900 degrees C, dense samples are composed of beta-SiC grains surrounding alpha-SiC platelets in a well-defined orientation. TEM investigations and calculation of the activation energy of the sintering provided insight to the densification mechanism. (C) 2012 Elsevier Ltd. All rights reserved.