Abstract: Hot isostatically pressed nano-ceramics of monophasic SiC and Si₃N₄/SiC composite were studied,and the phase composition and ndcrostructure were characterized by XRD, TEM and HREM. It is skownthat fine and homogeneous microstructure with average grch size of less than 100nm for monopkasic SiC can be obtained at the HIP conditions of 1850°C, 200MPa for 1h. The starting powder materialssignificantly affect the final microstructure. At 1750°C, 150MPa for 1h, very fine and homogeneous mi-crostructure with the average grain size of about 50nm can be prepared by using the pretreated composed Si₃N₄-SiC nano-powder. Both of the different phase compositions of nano-powder and HIP conditions may be ascribed to the depression of grain growth.

Key words: nano-ceramics, monolithic SiC, Si_3N_4/ SiC composite, hot isostatic pressing （HIP）