Boron nitride is a crystal composed of nitrogen atoms and boron atoms. The chemical composition is 43.6% boron and 56.4% nitrogen, with four different variants: hexagonal (hBN), rhombic (RBN), cubic boron nitride (CBN) and wurtzite boron nitride (WBN). Its cubic crystalline variant (wurtzite replacement shape of boron nitride) is considered to be a known very hard material. It is widely used in the manufacture of alloys, high temperature resistant materials, semiconductors, nuclear reactors, lubricants, etc.

　　We should know that there are four common crystal types in the category of boron nitride: ionic crystal, atomic crystal, molecular crystal and metal crystal. Ionic crystal is a topic composed of cations and anions combined by ionic bonds. All atoms in atomic crystal are a spatial network structure combined by covalent bonds. Molecular crystal is a solid substance formed by intermolecular forces. Metal crystal refers to metal elemental and alloy.

　　Boron nitride has great hardness, high temperature resistance of 2000 ℃, melting point of 3000 ℃ under nitrogen pressure, insoluble in cold water, slightly soluble in hot acid and so on. From the perspective of molecular structure, nitrogen atoms and boron atoms in BN are combined by covalent bond. To sum up, boron nitride is an atomic crystal.

　　Hexagonal boron nitride is a common stable phase, which is similar to graphite. It has only layered structure and can be used as high temperature lubricant. Cubic boron nitride is a superhard material with excellent damage resistance. Boron nitride belongs to atomic crystal. What boron nitride Du damages when melting is covalent bond. The force between particles defeated when the given material melts is different from that defeated when boron nitride melts.

　　Source: semiconductor chemical manufacturer  www.sun-chem.cn