SYNTHESIS OF COMPOSITES BASED ON SILICON-MODIFIED DETONATION NANODIAMONDS

Abstract

Scientific approaches to the formation of composite materials such as «nanodiamond-nanostructured SiC» have been developed. It is shown that, as a result of vacuum heat treatment, nanodiamonds are graphitized and nanostructured graphite-like coating forms on their surface. In this case, the reduction in the mass of the nanodiamond powder after vacuum annealing reaches 20 – 30 wt. % by removing oxygen-containing surface functional groups, physically and chemically adsorbed water. In accordance with the developed technology chemical-thermal modifying of nanodiamonds by silicon is carried out by annealing in a reducing atmosphere in the temperature range of 873–1273 К in the presence of silicon halides. On the basis of carbon and silicon modified nanodiamonds under vacuum annealing conditions a composite nanostructured powder of nanodiamond-SiC with particles of size from 0.1 to 5 μm is obtained. As a result of thermobaric sintering of the modified powder in the pressure range of 1.0 – 2.5 GPa, a compact diamond composite material consisting of polycrystalline diamond grains of 0.2 – 0.5 μm in size is formed. The size of diamond subgrains is 50 – 100 nm, and the presence of nanodiamonds measuring 10 – 20 nm is noted between large polycrystalline grains. As a result of grinding of the synthesized compacts, a polycrystalline diamond micropowder with particles of size up to 50 μm, characterized by submicron- and nanocrystalline structure is obtained. Due to the hierarchical structure of the sintered particles (particle-grain-subgrain-nanodiamond crystallite), powders based on the obtained material are promising in finishing technologies for brittle nonmetallic materials.