Abstract: High-density SiC ceramics doped with 2wt% Al₂O₃ additives were fabricated by ultra-high
pressure and high temperature technique (4.5GPa,1250℃,20min). The structures, grain size, lattice parameters, chemical component, morphology and mechanical property of the sintered SiC ceramics were characterized by X-ray diffraction
(XRD), X-ray photoelectron energy spectroscope (XPS), scanning electron microscope (SEM), energy dispersive X-ray
spectroscope (EDX) and nano impress indenter. The results show that nano-SiC ceramic is fully densified by ultra-high
pressure technique at relative low temperature (1250±50℃). No phase transfer or holes is found in the sintered nano-SiC
ceramic. The hardness and elastic modulus of the sintered SiC ceramic with grain size of 22nm and lattice parameters of 0.4355nm are 33.7GPa and 407GPa, respectively.

Key words: ultra-high pressure, sinter, silicon carbide, alumina