- Multiphase materials, including the B 6 N boron subnitride, B 6 O boron suboxide, and cBN cubic boron nitride, have been obtained from the initial β-rhombohedral or amorphous boron, hBN hexagonal graphite-like boron nitride and B 2 O 3 amorphous boron oxide at a pressure of 8 GPa and temperatures from 2100 to 2900 K in a toroid high-pressure apparatus. The hardness of the resulting materials has been measured. The formation of ternary phases in the B-BN-B 2 O 3 system has not been observed. The wettability of the resultant materials with copper-based melts has been studied. An addition of 10 mol% Ti to the copper melt has been found to decrease the contact angle to a value lower than 20 deg.