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AssigneeNational Institute for Researches in Inorganic Materials
InventorsTadao Sato, Tadashi Endo, Osamu Fukunaga, Minoru Iwata
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A process for preparing cubic boron nitride comprises heating hexagonal boron nitride and magnesium boron nitride at a temperature of at least 1350.degree. C. under a pressure at which the cubic boron nitride is thermodynamically stable, whereby the cubic boron having high strength and high purity can readily be obtainable. Also disclosed is a process for the preparation of magnesium boron useful as a starting material for the above process. This process comprises mixing hexagonal boron nitride and magnesium nitride or metal magnesium in a molar ratio of hexagonal boron nitride/magnesium being at least 0.6, and heating the mixture thus obtained, at a temperature of from 950.degree. to 1250.degree. C. under atmospheric pressure in a non-oxidizing atmosphere, e.g. a nitrogen atmosphere.
A process for preparing cubic boron nitride which comprises heating hexagonal boron nitride and magnesium boron nitride at a temperature of at least 1350.degree. C. under pressure at which the cubic boron nitride is thermodynamically stable, said magnesium boron nitride having lattice spacings obtained from the major x-ray diffraction lines thereof as designated in Table 2 of the specification.
A process for preparing magnesium boron nitride which comprises mixing hexagonal boron nitride and magnesium nitride or metal magnesium in a molar ratio of hexagonal boron nitride/magnesium being at least 0.6, and heating the mixture thus obtained, at a temperature of from 950.degree. to 1250.degree. C. under atmospheric pressure in a non-oxidizing atmosphere.
A process for preparing cubic boron nitride which comprises:
Dependencies are inferred from the claim text.