Boron nitride hexagonal boron nitride | cubic boron nitride | crystal lattice | photo |
Fig. 1. SEM-image (secondary electrons) of hexagonal boron nitride powder. Fig. 2. Crystal lattice of boron nitride (left) and graphite (right). |
Chemical formula BN, further chemical data in separate table. Boron-nitogen-compound with hexagonal (graphite-like) or cubic (diamond-like) crystal lattice structure. Hexagonal boron nitride crystallizes like graphite in a layer lattice and is therefore often called "white graphite". Its very good thermal (high melting- or sublimation point and good thermal shock stability) and physical characteristics (good electrical insulator, good heat conductivity and good high temperature lubrication qualities) make it an interesting ceramic material. One of the most well-known characteristics of hexagonal boron nitride is the very bad wettability by metal melts (like Al, Mg, Zn, Pb and Cu), slags as well as salt melts. Boron nitride is stable at air to approx. 1000°C, under reduced conditions or inert gases it can be used up to 1800°C. Refractory materials on boron nitride base are available in the form of powders, hot isostatic pressed shaped parts and as suspensions (boron-nitride-coatings) for coating by dipping, brushing or spraying. Cubic boron nitride, also called borazon, is a hard material of high microhardness and used for grinding applications. |
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