Synthesis of cubic boron nitride from hexagonal boron nitride with AlMg alloy solvent under high pressures and high temperatures

Abstract

An AlMg metallic alloy solvent has been proved to be an effective solvent for the synthesis of cubic BN(cBN) from hexagonal BN(hBN) under high pressures and temperatures. The Mg content in the AlMg solvent ranged from 30 to 70% by weight. The conversion rate from hBN to cBN and morphology of the cBN crystals could be controlled by varying the amount of solvent in the hBN-solvent mixture and the Mg content in the solvent, respectively. The conversion rate increased as the amount of solvent in the hBN-solvent mixture or the Mg content in the solvent increased. The large blocky cBN crystals with well-developed crystallographic surfaces were synthesized by the solvent with high Mg content and the fine cBN crystals, with irregular shape, by the solvent with low Mg content. ？ 1994.