Interaction During Barothermal Processing of Wurtzite Boron Nitride with Diamonds Obtained under Different Synthesis Conditions

We present the results of a study of the interaction at a pressure p = 7.7 GPa and a temperature T = 1600 °C and 1800 °C of wurtzite boron nitride, previously subjected to deformation processing by 4-fold rolling and having a particle size in the developed plane of 0.1...1.5 microns, and diamond powders of various origin obtained under conditions of static synthesis in the presence of a metal solvent and shock-wave synthesis from carbon material. The diamond component had the following sizes: submicron powders of static synthesis of 0.1/0 microns, dynamic synthesis diamonds 5...12 nm. The initial charge before barothermal treatment consisted of 90 wt. % BNw and 10 wt. % diamonds. The duration of exposure to temperature under pressure was τ = 60 s and τ = 120 s. X-ray photography of the samples was carried out on a DRON-3 diffractometer in copper Cu-Kα radiation with a graphite monochromator and digital recording of reflections in the automatic mode with a step movement of 0.1° and exposure duration at each point of 4°. It was found that in the contact interaction of BNw with diamonds, diamond dissolves in boron nitride with the formation of a BNC solid solution, which depends on p, T of the process parameters and the method for producing diamonds. At a temperature T = 1600 °С, there is no interaction of BNw with the diamond component. An increase in temperature to T = 1800 °C leads to the dissolution of diamonds in boron nitride, and their number depends on the time of exposure to temperature, and the interaction of dynamic synthesis diamonds occurs to a greater extent. Homogenization of the BNC solution is observed. To determine the mutual solubility of substances, Vegard's law was applied, and the quantitative content of dissolved diamond in sphalerite boron nitride was established, which is 2 times greater for dynamic synthesis diamonds than for static synthesis diamonds. The higher activity of dynamic synthesis diamonds is due to the feature of their crystalline structure – high dispersion and distortion. The dissolution of diamonds in BNw has a diffusion character.