Cherniyenko A. Peculiarities of synthesis of thermally stable electrically conductive diamond pow-ders in the Mg-Zn-B-C system

The dissertation is dedicated to solution of important physical technical problem - obtaining diamond powder with high level of thermal stability by researching of fea-tures of the diamond crystallization in Mg-Zn-B-C system by method of spontaneous crystallization. The phase transformations that occur at prepare of alloy-solvent, and the phase transformations that accompany the process of the diamond crystallization are studied. The structure of alloy-solvent, and the properties of diamond crystals are researched. The processes of forming the acceptor centers and the inclusions in dia-mond crystals because of the boron addition to the charge are described. It is estab-lished that the boron does not interact with the magnesium. Solubility of the boron in the Mg-Zn melt is limited at low value. Strength index and thermal stability coefficient of diamond powders are researched. It is shown, that the curve of index strength of the diamond powders has a minimum (when the boron concentration 20 % at.), and thermal stability coefficient increases with increasing boron content in the charge. The distribution compressive strength of diamond particles described under Weibull func-tion. We identified strength indexes of the diamond powders and corresponding con-fidence intervals. It is established that using of diamond powders, obtained in Mg-Zn-B-C system, for abrasive surface treatment of sapphire body increases productivity and quality of the processing compared to the powder, obtained in the Ni-Mn-C sys-tem.