Title: Boron Nitride
CAS Registry Number: 10043-11-5
Molecular Formula: BN
Molecular Weight: 24.82
Percent Composition: B 43.56%, N 56.43%
Literature References: Prepd by igniting compds of boron with compds of nitrogen: Taylor, US 2855316 (1958 to Carborundum Co.). Reviews: Giardini, Bur. Mines Inf. Circ. No. 7664, 13 pp (1953); K. Niedenzu, J. W. Dawson, Boron-Nitrogen Compounds (Academic Press, New York, 1965) pp 147-153.
Properties: Crystals with hexagonal, graphite lattice is most common form. Borazon, cubic crystalline modification, is probably the hardest substance known. There exists also an amorphous modification. mp 3000°. Begins to sublime at a temp slightly below 3000°. Begins to dissociate in vacuo at about 2700°. The chemical behavior of BN is dependent on the method of prepn. Not attacked by mineral acids, water; in general resistant to chemical attack. Hot concd alkali cleaves boron-nitrogen bond. Oxidation in air begins above 1200°. See Niedenzu, Dawson, loc. cit.
Melting point: mp 3000°
Use: Manuf of alloys; in semiconductors, nuclear reactors, lubricants. |