PYROLYTIC RHOMBOHEDRAL BORON NITRIDE AND METHOD OF PRODUCTION OF BORON NITRIDE Russian patent published in 2001 - IPC

FIELD: refractory compound, pyrolytic rhombohedral boron nitride, in particular, and procedure of production of boron nitride by chemical settling from gaseous fraction. SUBSTANCE: pyrolytic rhombohedral boron nitride is used for manufacture of various parts (heat-transfer rods, energy removal ports) for thermionic microwave oscillator tubes. Boron nitride contains from 0 to 25% of hexagonal phase. Separate flows of gaseous boron trifluoride and ammonia are fed to reactor for production of purolytic rhombohedral boron and for increase of rate its settling; prior to mixing boron fluoride with flow of ammonia, it is enriched with boron before formation of lower boron fluorides by passing its flow through boron-containing charge at temperature of 1600 to 2000 C; settling of boron nitride is effect at interaction of gaseous lower boron fluorides with ammonia at temperature of 1550 to 1700 C and pressure of 1 to 5 mm Hg and ratio of λ = 457 hm and BF₃ flows of 1:1 to 1:6. Used as boron containing charge is amorphous boron, boron carbide refuse or their mixture. The method ensures production of highly-oriented pyrolytic boron nitride containing up to 100% of rhombohedral phase in form of set of noncorrugated microlayers at thickness of 50 to 70 Nm at reflection factor of 0.58 to 0.62 and wave length of NH₃=457 Nm density of 2.21 to 2.27. EFFECT: higher efficiency. 5 cl, 3 dwg, 1 tbl, 10 ex