Superhard materials based on the solid solution SiC–C

Abstract

Recently, a fine powder of the SiC–C solid solution, where superstoichiometric carbon atoms in the SiC crystal structure are arranged either as planar defects (diamond-like layers) or as non-correlated point defects, was synthesised. The dynamics of the SiC–C powder sintering and different sintering conditions under high pressures (2–8 GPa) and temperatures (1273–2073 K) are analysed by hardness measurements and by X-ray powder diffraction methods. The strains of the SiC–C crystal structure are characterised by classical and modified Williamson–Hall plots and by the dislocation model of the strain anisotropy. A correlation between microstructure parameters and the hardness of the material was established. The main cause of the work hardening of the SiC–C ceramics is the growth of the dislocation density in the SiC–C crystal structure during high pressure and temperature sintering. The presence of the planar carbon defects plays a key role in the work hardening of the SiC–C ceramics. The highest hardness found for ceramics based on the SiC–C solid solution was 41.4 GPa (Vickers indentation at 2 kg loading).