Catalytic Effects in the Transformation of Graphite to Diamond

The transformation graphite to diamond is catalyzed by the Group VIII metals, manganese and chromium. The fact that these metals are good solvents for carbon tends to obscure their catalytic role in this transformation. It was found that copper-rich copper—nickel alloys capable of dissolving less than 0.06 at. % carbon catalyzed the formation of diamond whereas lead and antimony having about equal solvent capacity did not. The diamond nucleation rate increased exponentially with nickel concentration in the copper-rich alloys. Hence, on the basis of the theory that nucleation catalysts provide surfaces of low interfacial energy, one important role of the nickel in these alloys may be interpreted as that of reducing the interfacial energy between diamond and alloy.