首页>
外国专利>
Improved Method for production of cubic Boron Nitride from hexagonal Boron Nitride Powder, in the absence of Catalyst
Improved Method for production of cubic Boron Nitride from hexagonal Boron Nitride Powder, in the absence of Catalyst
展开▼
机译:在没有催化剂的情况下由六方氮化硼粉末生产立方氮化硼的改进方法
展开▼
页面导航
摘要
著录项
相似文献
摘要
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 DEG C. to the reconversion temperature. The high pressure reaction cell has a special design which prevents the entrance of impurities into the sample. This cell, referring to FIG. 2, comprises, for example, a carbon tube (8) enclosing concentric titanium sleeve (9). Within the cylinder defined by the tube and sleeve are: the HBN sample (4), carbon filler (3), shielding tantalum foil discs (2) and carbon end plugs (10). The vacuum firing is done at pressures of 10-5-10-10 mm Hg, 1400 DEG -1900 DEG 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.
展开▼