The influences of N and H on diamond synthesized with Ni-Mn-Co catalyst by HPHT

The elements of nitrogen and hydrogen are the main impurities in natural and synthetic diamond and can significantly affect the physical properties of diamond. In this paper, the effects of nitrogen and hydrogen, which came from decomposition of melamine (C3N6H6) at 5.3 GPa and 1500 K for 15 min, on diamond synthesized with powder catalysts by high pressure and high temperature (HPHT) were investigated. Our results indicated that the nucleation of diamond was disturbed and the graphite/diamond conversion could be completely prevented by high concentrations of nitrogen and hydrogen. These results could be explained by changes in characteristics of catalysts due to different chemical reactions between the elements in Ni-Mn-Co catalyst and nitrogen and hydrogen.