Recent development in diamond synthesis

The high pressure-high temperature (HPHT) method led to wide applications of artificial diamonds in industry. Low temperature coating of diamonds has been studied for some time, and chemical vapor deposition has been developed. In this contribution, we will focus on the most recent developments in diamond synthesis, and especially the important progress upon hydrothermal synthesis and the reduction of carbide (HSRC), which has attracted more and more attention due to its great commercial potential. Especially, we will discuss the synthesis of colorless, large diamond crystals from the reduction of carbon dioxide or carbonates. In addition, some recent progress on the theoretical studies of the metastable nucleation and growth of diamonds will also be reviewed. Finally, theories about the genesis of natural diamond were briefly reviewed, and a new theory based on our experimental results was proposed, which suggests that diamond within the Earth could be produced from carbon dioxide wherever carbon dioxide existed and the conditions (e.g., temperature, pressure, and reducing environment) are satisfied.