Influence of water agent on high-pressure/high-temperature transformation of graphitic BC2N

Graphitic BC2N has been exposed to high pressure (7.7 GPa) and high tempera ture (800-2200 degreesC) in the presence of water as a fluid agent to explo re the reactivity of the graphitic BC2N and crystallization behavior to cub ic compounds in a B-C-N ternary system. The graphitic BC2N reacted with wat er above 1200 degreesC, which describes that the graphitic BC2N is similar to graphite in reactivity rather than hexagonal boron nitride (hBN). The di ssolved BC2N was not recrystallized as a cubic B-C-N compound but was dispr oportionated into graphite and cubic boron nitride (cBN) in the temperature range of 1200-1800 degreesC. Then, the precipitated graphite was transform ed into diamond above 2000 degreesC. The precipitation behavior of the cubi c compounds in the BC2N-H2O system can be explained by the simple sum of th e formation of cBN in hBN-H2O and that of diamond in graphite-H2O.