| 摘要 |
PURPOSE:To obtain superhigh purity BN without damaging heating furnaces by heating BN powder to a specified temp. in a heating furnace using a graphite furnace material and further heating it in a heating furnace using a furnace material generating no gas contg. carbon under specified conditions. CONSTITUTION:BN powder or a sintered BN body is heat treated at 2,000- 2,200 deg.C, preferably 2,050-2,150 deg.C in a heating furnace using a graphite furnace material such as a graphite heater to remove most of hydrogen, carbon impurities and oxygen. It is further heated to 2,000-2,200 deg.C, preferably 2,050-2,150 deg.C in an atmosphere having a higher partial pressure of nitrogen than the decomposition pressure of BN in a heating furnace using a furnace material generating no gas contg. carbon such as an Mo heater. Thus, superhigh purity BN can be manufactured over a long term without damaging the Mo heater, etc. |
