Synthesis of SiC@Al2O3 core–shell nanoparticles for dense SiC sintering

Abstract

Owing to the difficulty for dense SiC sintering, high sintering temperatures and pressures are usually needed. Lowering the sintering temperature by adding Al2O3 as a sintering additive has previously been shown to be beneficial. However, traditional addition methods limit the effect of the Al2O3 owing to inhomogeneous mixing at the nanoscale. A SiC@Al2O3 composite nanoparticle with a core–shell structure is designed and prepared using the slow co-precipitation method. The differences between this method and the traditional mechanical ball milling method are interpreted by different experimental parameters, such as temperature, pressure, amount of additive, and mixing type. It is found that the method of slow co-precipitation enables homogeneous mixing of Al2O3 and SiC at a smaller scale, and makes the sintered SiC much denser and more homogeneous, when compared with the traditional method. The parameters of sintering at 1900°C and 30MPa for 30min are recommended. The conclusions here are also beneficial for the sintering research of other ceramic materials.