Cubic boron nitride has been made from powdered hexagonal boron nitride by a process which comprises vacuum firing of the HBN and conversion by high pressure-high temperature processing at 55-80 kilobars and 1600.degree. C. to the reconversion temperature....http://www.google.fr/patents/US4289503?utm_source=gb-gplus-shareBrevet US4289503 - Polycrystalline cubic boron nitride abrasive and process for preparing same in the absence of catalyst
Polycrystalline cubic boron nitride abrasive and process for preparing same ...
