C - Chemistry – Metallurgy – 01 – B
Patent
C - Chemistry, Metallurgy
01
B
18/1123, 57/15,
C01B 21/064 (2006.01) B01J 3/06 (2006.01) B24D 3/00 (2006.01) C04B 35/5831 (2006.01) C09K 3/14 (2006.01)
Patent
CA 1140728
ABSTRACT OF THE DISCLOSURE 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°C to the reconversion temperature. This process may be carried out in a high pressure reaction cell having a special design which presents the entrance of impuritize into the sample. This cell, comprises, for example, a carbon tube enclosing concentric titanium sleeve. Within the cylinder defined by the tube and sleeve are: the HBN sample, carbon filler, shielding tantalum foil discs and carbon end plugs. The vacuum firing is done at pressures of 10-5-10-10 mm ?, 1400 - 1900°C, for 5 minutes - 4 hours, and is believed to form a thin, free-boron coating on the HBN particles. The process works on both pyrolytic (turbostratic) and graphitic hexagonal boron nitride. Grinding grits formed by milling cubic boron nitride chunks recovered from the high pressure-high temperature process have resulted in higher grinding ratios than commercially available CBN.
352170
Company General Electric
Eckersley Raymond A.
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