High-pressure, high-temperature synthesis of SiC-diamond nanocrystalline ceramics

Dense and entirely nanocrystalline diamond-SiC ceramics were synthesized by the infiltration of liquid Si into the nanodiamond body under high-pressur e (77 kbar) and high-temperature (1400-2000 degrees C) conditions. Based on x-ray diffraction and transmission electron microscopy observations, a mod el of as-synthesized material is proposed, where individual polycrystalline diamond particles are bonded via SiC-diamond nanolayers. The nanolayers pr ovide a very high hardness of the entire specimen up to 51 GPa. The phenome non of self-stop Si infiltration was detected in this system. This phenomen on can be explained by the closure of pores near the boundary between molte n Si and diamond nanopowder due to the formation of SiC inside the pores. ( C) 2000 American Institute of Physics. [S0003-6951(00)00633-1].