Abstract
Polycrystalline diamond was successively synthesized recently at very high pressure and temperature using a Kawai-type apparatus, which turned out to be extremely hard when compared with currently available sintered diamond products and natural single crystal diamonds. Here the author summarizes the results of experiments and reviews aspects of the synthesis of polycrystalline diamonds by the direct conversion of graphite. Some future perspectives and related unsolved problems are also discussed on the basis the results of our and other experimental studies on the synthesis of polycrystalline diamond.
