Computational modeling of superhard materials synthesis

Two-level theoretical model of the diamond spontaneous crystallization in high pressure apparatus (HPA) has been developed. At the macro level, the model describes the coupled processes of resistance heating, heat transfer, thermoelastoplastic deformation and graphite-to-diamond phase transition at the reaction volume scale. At the diamond grain (micro) level, it describes the thermoelastic fields and conditions of phase transitions in the local diamond–metal melt–graphite system. By applying the methods of continuum thermomechanics and computer simulation, the temperature, stress and mass fraction fields in the reaction volume of HPA and in the local diamond–melt–graphite system under diamond synthesis conditions have been determined. An analysis discovers substantial coupling of the physical fields and interrelation of the solutions for the reaction mixture and for the local system. The pressure self-regulation effect in the HPA reaction volume consisting in pressure oscillation with respect to graphite-to-diamond phase transition line is detected. An efficiency of two types of HPA for diamond synthesis has been compared from numerical study.