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

Abstract

Dense and entirely nanocrystalline diamond–SiC ceramics were synthesized by the infiltration of liquid Si into the nanodiamond body under high-pressure (77 kbar) and high-temperature (1400–2000 °C) conditions. Based on x-ray diffraction and transmission electron microscopy observations, a model of as-synthesized material is proposed, where individual polycrystalline diamond particles are bonded via SiC–diamond nanolayers. The nanolayers provide a very high hardness of the entire specimen up to 51 GPa. The phenomenon of self-stop Si infiltration was detected in this system. This phenomenon can be explained by the closure of pores near the boundary between molten Si and diamond nanopowder due to the formation of SiC inside the pores.