Diamond synthesis from a system of chromium-carbide and Ni₇₀Mn₂₅Co₅ alloy

Abstract

In order to ascertain the mechanism of interaction between carbide and metallic catalyst and formation of diamond under high pressure and high temperature, and find a new method to synthesize diamond with special properties, it is necessary to investigate the reaction behavior of different carbides and metallic solvent-catalysts under high pressure and high temperature. A system of Cr₃C₂ powder and Ni₇₀Mn₂₅Co₅ alloy in weight ratio of 1:6 was treated under 6.0 GPa and 1 500°C for 20, 30 or 60 min respectively. X-ray diffraction of the samples indicated the Cr₃C₂ decomposed partially after high pressure and temperature treatment, and Cr₇, C₃, Cr and diamond formed respectively. There was not any trace of graphite in the samples. The result suggested that the separated carbon atoms could form diamond directly without conversion process of graphite into diamond. The observation of SEI, WDX and EDX also showed that diamond crystals were synthesized in the system, which have perfect surfaces and shapes, with the average grain size of about 40 μm. The properties of the crystals are being investigated.