Chemistry of inorganic compounds – Boron or compound thereof – Binary compound
Patent
1982-04-27
1982-11-30
Peters, G. O.
Chemistry of inorganic compounds
Boron or compound thereof
Binary compound
C01B 2106
Patent
active
043615430
ABSTRACT:
A process for producing polycrystals of cubic boron nitride which comprises exposure of hexagonal boron nitride to a pressure of from 40 to 70 kbar at a temperature of from 1,200.degree. to 1,800.degree. C. When the conversion of hexagonal boron nitride to cubic boron nitride reaches 20 to 65% by weight, the heating is switched off and pressure is increased to a value of from 80 to 120 kbar. Then the heating is resumed and temperature is elevated to 1,800.degree.-3,000.degree. C. Under these conditions the process is continued to full conversion of hexagonal boron nitride to cubic modification thereof.
The process can be conducted in the presence of 0.5 to 10% by weight of a catalyst contributing to the conversion of hexagonal boron nitride into its cubic modification. The main portion of the catalyst is concentrated in the central portion of the volume of hexagonal boron nitride, the remainder - in the peripheral portion.
The present invention is useful in the manufacture of super-hard materials which, in turn, can be used in the industry of cutting tools.
REFERENCES:
patent: 3876751 (1975-04-01), Alexeevsky et al.
patent: 4150098 (1979-04-01), Sirota et al.
Baraban Vladimir P.
Dudyak Alexandr I.
Galkov Mikhail I.
Zhdanovich Gennady M.
Zherebtsov Jury V.
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