SHOCK SYNTHESIS OF TERNARY DIAMOND-LIKE PHASES IN THE B - C - N SYSTEM

摘要

Nanodispersed powders of the ternary graphite-like phases BC_(1.28)N and BC_(2.14)N have been used along with mixtures of powders of turbostratic BN and C in high-temperature shock compression followed by sharp quenching. The yield of diamond-like phases has attained 50 percent by volume. The excess of the graphite-like phase has been removed by treatment with molten alkalis containing nitrates and then with concentrated HclO_4. The shock and chemical treatments alter the compositions of the diamond-like phases towards BCN in both of the BC_xN specimens on account of the segregation of the excess carbon followed by the dissolution of it. Precision lattice-parameter measurements and line shape analysis indicate that the diamond-like phase is a BN - C substitutional solid solution. Treatment of a mechanical mixture of the graphite-like phases of carbon and BN under the same p and T conditions led to the formation of a mixture of cubic boron nitride and diamond.