High-pressure synthesis of diamond from phenolic resin

Two kinds of phenolic resin, novolak and resols, have been studied with an addition of cobalt at pressures between 2 and 4 GPa and at temperatures from 1300 to 1900 °C, all under thermodynamically graphite-stable conditions. Diamond was synthesized from these resins which had been pre-fired at 500–1000 °C. From such resins, carbon precursors carrying a great number of radicals, being nearly free of hydrogen and oxygen, and turbostratic in structure, can be constructed. The pressure–temperature conditions suitable for the diamond synthesis were dependent on the pre-firing temperatures. The cobalt served as a catalyst–solvent, similar to the case of conventional diamond synthesis from graphite under diamond-stable conditions. Well-defined single crystals cubo-octahedral in shape, measuring 0.3–0.7 mm across and classified as type Ib were obtained.