New catalysts for the high pressure synthesis of cubic BN

The catalytic effect of water on the high pressure synthesis of cubic BN from hexagonal BN is studied in further detail. An amorphous substance is found to coexist with cubic BN thus prepared and is tentatively identified as anhydrous ammonium borate. The idea that a melt of ammonium borate which is formed by the reaction of hexagonal BN and water at high pressures and temperatures might act as a flux for the conversion from hexagonal BN to cubic BN, leads to the discovery of new catalysts such as urea, ammonium borate, and ammonium nitrate. It is also found that cubic BN can be synthesized from boron and urea or ammonium nitrate under the same pressures and temperatures. The results open more efficient ways of synthesizing cubic BN