Explosive shock synthesis of polycrystalline diamond powders

Research and development for manufacturing micro polycrystalline diamond powders by use of explosives has been carried out. At first, basic research was conducted by a plane shock compression method using a flyer plate. The sample material, which is a mixture of carbon and copper powders, was shock compressed at pressures of 30 to 60 GPa. Under the best conditon of shock pressure and temperature, the conversion yield from graphite to diamond amounted to more than 60%. Next, cylindrical compression methods have been developed in order to treat a large amount of smaple compared with the plane method. It was found that an increase of shock duration time, which needs a much larger size of explosive charge, gave a good conversion yield. An explosion chamber which has a firing capability of a 100 kg-explosive without any damage was constructed. Many tests with large charge shots have been conducted without any environmental problems.