Boron Nitride, Chemical Composition, Hexagonal Boron Nitride, Cubic Boron Nitride

What is Boron Nitride?

Boron Nitride is a ceramic material with exceptional properties. It does not occur naturally. Even though Boron Nitride was synthesized as early as in the mid-nineteenth century, its industrial “career” only started after the first hot pressed sintered Boron Nitride parts became available (Carborundum Co., US-Patent 2808314, 1957).Further details are available in the pages covering Production.

Chemical Composition

Boron Nitride is made up of Boron (B) and Nitrogen (N). In the periodic system these elements are located to the immediate left and right of Carbon (C). Carbon and Boron have identical outer electron shells, but while the outer electrons of carbon are mobile, those of boron are bound firmly by the nitrogen in the Boron Nitride molecule.

Crystalline Modifications

Just as with Carbon there exist two allotropic modifications of Boron Nitride, a hexagonal form which corresponds to Graphite, and a cubic form analogous to Diamond.

Hexagonal Boron Nitride (h-BN)

Hexagonal Boron Nitride has a microstructure similar to that of Graphite. In both materials this structure, made up of layers of tiny platelets, is responsible for excellent machinability and
low-friction properties. However, while Graphite is black, Boron Nitride is white in colour. There are other important differences. Both Graphite and Boron Nitride have good thermal conductivity, but Graphite is an electrical conductor whereas Boron Nitride is an excellent electrical insulator, both in its pure form and as a constituent of ceramic composites. Moreover while Graphite needs humidity to act as a lubricant, Boron Nitride is an excellent dry lubricant which will maintain its low coefficient of friction up to 900°C in air, and at even much higher temperatures in a vacuum or under a protective atmosphere.

Link to: Technical properties of Boron Nitride
Link to: Technical applications of Boron Nitride

Cubic Boron Nitride (c-BN)

The crystal lattice structure of cubic Boron Nitride is similar to that of Diamond; its hardness is second only to diamond, which is the hardest material known. Cubic Boron Nitride was first synthesized in 1957. However, important commercial applications were developed only in the Nineties. HENZE supplies hexagonal Boron Nitride only, but will gladly refer you to sources of cubic Boron Nitride upon request.