Effect of detonation nanodiamonds on the properties of diamond microcrystals grown from carbon black in a C–O–H medium at high pressure and high temperature

In this work, an attempt was made to optimize the process of synthesizing diamond powders without metal catalysts at high pressures and temperatures and to determine the features of diamond crystallization in C–O–H fluid. For this purpose, a comparative study of diamond powders synthesized at a pressure of 7.5 GPa from a mixture of carbon black (55wt%) with pentaerythritol (45wt%) and the same mixture modified with detonation nanodiamonds (DNDs) (5wt%) was carried out. The addition of DND leads to the formation of aggregates with a size of ∼10 μm, consisting of high quality diamond crystals with a size of ∼0.5–3 µm, and a decrease in the synthesis temperature from ∼1600 to ∼1500 °C. The addition of DNDs into the reaction medium has no effect on the concentration of N0, N2 and NV– centers in the synthesized diamonds, while the content of N3VH0 increases.