Gordeyev S. Directional control of the nucleation density of diamond single crystals in spontaneous solution-molel crystallization with increased homogeneity of properties

The actual scientific and technical problem of growing diamond single crystals of type IIa with sizes up to 3 mm with increased homogeneity of properties due to the development of basic principles of directed control of nucleation by selecting the particle size distribution of the reaction charge and changing thermobaric parameters during cycles cultivation was decided. Developed technological aspects for the production of diamonds with increased uniformity in habit shape, size, strength and absence of inclusions of the solvent alloy as well as scientific and technical problem of studying the patterns of stimulated diamond nucleation with the required density and subsequent cultivation of structurally perfect single crystals 3 mm in mortar-molten systems metal - carbon at high pressures and temperatures. It is shown that the developed methods, along with the use of fine fractions of scaly graphite up to 3 - 5 μm, allow to ensure the density of nucleation with subsequent growth of structurally perfect diamond single crystals at the level from 0 to 300 pcs/cm3 in the volume of growth cells . The kinetics of crystal growth and its influence on the formation of different habitual types have been studied; The defect-impurity composition of crystals, the conditions for preventing the capture of solvent inclusions during growth and the possibility of classifying crystals relative to the number of such defects using the determination of the values of magnetic susceptibility of the obtained diamond crystals were studied. The static strength and thermal stability at temperatures of 1150 °C of single crystals with a size of 1 - 3 mm were determined. Tests have shown the high efficiency of using diamonds obtained by the method of spontaneous stimulated nucleation to develop new types of diamond tools. The results developed in the work were successfully implemented at the production of Instech LLC, Kyiv and at the Diamond Tool Plant LLC, Poltava.