High pressure synthesis of cubic boron nitride from Si-hBN system

Cubic boron nitride (cBN) was synthesized from hexagonal boron nitride (hBN) in the presence of silicon. The cBN forming pressure-temperature region was determined at pressures up to 7.7 GPa. Near perfect octahedral cBN crystals could be synthesized under the P-T conditions near the low temperature boundary of the cBN-forming region. When the temperature was above 1700 degreesC at 6.5 GPa, the transformation rate of cBN from hBN was very high and the cBN crystals had an oriented columnar morphology. This suggests that silicon has strong catalytic ability for cBN formation from hBN. The energy-disperse X-ray analysis (EDXA) identified that silicon was homogeneously distributed in the cBN crystals. (C) 2001 Elsevier Science B.V. All rights reserved.