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Hexagonal Boron nitride

The graphite-like polymorph of boron nitride, hexagonal boron nitride, h-BN, α-BN, or g-BN (graphitic BN), sometimes called "white graphite," is the most widely used. The hexagonal polymorph is composed of layers of hexagonal sheets analogous to graphite. However, the interlayer "registry" of these sheets differs from the pattern seen for graphite because the atoms are eclipsed, with boron atoms laying over and above nitrogen atoms. This registry reflects the polarity of the B-N bonds. The diminished covalency in BN results in diminished electrical conductivity relative to graphite, a semimetal that conducts electricity through a network of pi-bonds in the plane of its hexagonal sheets. The diminished electron-delocalization in hexagonal-BN is indicated by its absence of color, which signals a large band gap. Hexagonal BN is a lubricant at low and high temperatures (up to 900 °C), even in an oxidizing atmosphere). It is a beneficial lubricant where graphite's electrical conductivity or chemical reactivity would be problematic. Since the lubricity mechanism does not involve water molecules trapped between the layers, boron nitride lubricants can be used even in a vacuum, e.g., for space applications. Hexagonal boron nitride is stable in temperatures up to 1000 °C in air, 1400 °C in vacuum, and 2800 °C in an inert atmosphere. It has one of the best thermal conductivities of all-electric insulators. It is chemically inert and is not wetted by many melted materials (e.g., aluminum, copper, zinc, iron and steel, germanium, silicon, boron, cryolite, glass, and halide salts). Fine-grained h-BN is used in cosmetics, paints, dental cement, and pencil leads. If you are looking for high quality, high purity, and cost-effective Boron nitride, or if you require the latest price of Boron nitride, please feel free to email contact mis-asia.

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