Synthesis and performance of nano-polycrystalline diamond

Traditional polycrystalline diamond (PCD) has been widely used in the fields of mechanical processing and mineral exploration. However, due to the existence of binders or sintering aids, the deterioration of mechanical properties greatly limits its applications. Nano-polycrystalline diamond (NPD), which is non-adhesive with ultra-fine grain size and strong grain boundary, performs excellent properties superior to those of traditional PCD and single diamond in the field of high precision machining hard materials, etc. Hereby, the synthesis routes and mechanical properties of NPD are reviewed. The method and technology of preparing NPD from different carbon precursors under high temperature and high pressure (HPHT) are introduced. It is focused on the technology of direct converting graphite and carbon onions to NPD, which will provide reference for further research on its synthesis and application.