Panasiuk T. Regularities in the effect of the configuration and composition of the elements of the six-punch high-pressure apparatus cell for the growth of diamond single crystals on its thermal state.

The dissertation is devoted to solving an important scientific and technical problem, which consists in the determination by computer modeling of the regularities of the thermal state formation of a six-punch high-pressure apparatus (HPA) growth cell, depending on cell elements configuration and their composition as well as ambient temperature. It was determined that by changing the sizes and configuration of the corresponding growth cell elements it is possible to exclude the potential spontaneous nucleation of diamonds by minimizing temperature to 1000 °С in the contact area of the metal and graphite elements. Increasing the concentration of composite heater components from 50 to 93 % w/w allows to change the axial temperature gradient from 7 to 16 deg/mm. A change in the ambient temperature from 5 to 35 °C increases the temperature in different zones of the growth cell up to 70 °C and decreases the axial temperature drop in the growth volume by 6 С. To eliminate the negative effect of changing the ambient temperature on the thermal state of the growth volume, it is necessary to carry out thermostating of the press equipment. During the growth of diamond crystals the calculated average value of the axial temperature gradient in growth volume decreases from initial 10 to 3 deg/mm when growing 21 crystals weighing 2 carats each and from 10 to 7 deg/mm when growing 5 crystals weighing 5 carats each. On the basis of the calculated data, a growth cell for a six-punch CCP-type HPA was designed, experiments were carried out to grow diamond single crystals by the temperature gradient method, and diamond crystals of Ib-type weighing up to 5 carats were obtained.