Synthesis of High-Pressure Diamond Using Graphite Over Which CVD Diamond Grains Were Grown

CVD diamond grains have been grown on polycrystalline graphite pieces by the hot-filament CVD method using mixtures of methane and hydrogen, and high-pressure diamond was synthesized by 66 MN (6600 t) cubic high pressure apparatus using CVD diamond-grown graphite. The experimental results show that growth features of CVD diamond on the polycrystalline graphite substrate depended largely on the total pressure when other conditions were same, growth of CVD diamond grains on the graphite pieces used as starting material is a possible way of increasing transformation rate of graphite to diamond and of lowering the synthesis pressure at the synthesis of high-pressure diamond.