Synthesis of nano-polycrystalline diamond under high pressure and high temperature

Bulk material of nano-polycrystalline diamond is synthesized by independently developed two-stage large cavity static high-pressure device through the direct transformation from graphite to diamond under ultra-high pressure and high temperature.The synthesis pressure is about 17GPa and temperature is about 2300℃.Micro X-ray diffraction analysis indicates that the graphite has been transformed into cubic phase diamond.The scanning electron microscopic picture and whole spectrum fitting analysis of X-ray shows that the dimension of synthesized diamond crystal is about 16nm.The Vickers hardness of the sample measured by the indentation method is above 100GPa.