Influence of an Ultrasonic Field on the HPHT Synthesis of Natural Carbonado-Type Polycrystalline Diamond

The study investigates the effect of an ultrasonic field on the synthesis of natural carbonado-type polycrystalline diamond in a toroidal high-pressure chamber under constant pressure, temperature, and holding-time conditions. A method for introducing ultrasound into a toroid-type high-pressure apparatus was developed, ensuring the pressure–temperature parameters (P, T) required for carbonado synthesis. The proposed configuration provides acoustic excitation of both the rod and the graphite, implementing an axial waveguide energy-transfer mode and maximizing radial diffusion processes. An optimal range of amplitudes (1–1.5 μm) and frequencies (200–300 kHz) was determined, resulting in up to a 50% increase in product yield compared with synthesis performed without ultrasonic treatment. A significant improvement in the mechanical strength and performance characteristics of the synthesized carbonado-type polycrystalline diamond was also established.