High-pressure sintering of a solid solution of carbon in SiC

Submicron powder of a solid solution of carbon in silicon carbide was synth esized and characterized by x-ray diffraction, electron microscopy, and Ram an scattering spectroscopy. The dissolution of carbon was found to reduce t he lattice parameter of SiC from 4.359 to 4.353 Angstrom. The structural pe rfection of the powder particles and the bonding configuration of the disso lved carbon are assessed, and the structural changes induced in the solid s olution by vacuum annealing and high-pressure sintering are considered. Sin tering the SiC-C powder under optimal conditions yields ceramics with a har dness of about 40 GPa and a fracture toughness as high as 9.5 MPa m(1/2).