12 4月 Physical properties and physical structure of boron nitride coating
Boron nitride coating is a crystal composed of nitrogen atoms and boron atoms. Chemical composition of 43.6% boron and 56.4% nitrogen in four different variants: hexagonal boron nitride coating (HBN), rhombohedral boron nitride (RBN), cubic boron nitride (CBN) and wurtzite nitrogen Boron Nitride (WBN).
CBN is usually a black, brown, or dark red crystal with a sphalerite structure and good thermal conductivity. Second, only to diamond in hardness, it is a superhard material, often used as tool material and abrasive. the
Boron nitride coating has chemical resistance properties and is not attacked by inorganic acids and water. The boron-nitrogen bond is broken in hot concentrated alkali. It begins to oxidize in the air above 1200°C. The melting point is 3000°C, and sublimation starts at slightly lower than 3000°C. It begins to decompose at about 2700°C in a vacuum. Slightly soluble in hot acid, insoluble in cold water, relative density 2.25. The compressive strength is 170MPa. The maximum operating temperature is 900°C in an oxidizing atmosphere, and up to 2800°C in an inactive reducing atmosphere, but the lubricating performance is poor at room temperature. Most of the properties of boron carbide are better than carbon materials. For hexagonal boron nitride: very low friction coefficient, good high-temperature stability, good thermal shock resistance, high strength, high thermal conductivity, low expansion coefficient, high resistivity, corrosion resistance, microwave or Transparent to infrared rays.
Boron nitride coating hexagonal crystal system, the most common graphite lattice, also has amorphous deformation, in addition to hexagonal crystal form, boron carbide has other crystal forms, including rhombohedral boron nitride (referred to as r-BN, or Name: trigonal bn coating, whose structure is similar to h-BN, will be produced in the process of converting h-BN into c-BN), cubic boron nitride [abbreviation: c-BN, or |3-BN, or z -BN (that is, sphalerite-type boron nitride), the texture is very hard], wurtzite-type boron nitride (abbreviation: w—BN, h—a hard state of BN under high pressure). People have even found two-dimensional boron nitride crystals like graphene (similar to MoS: two-dimensional crystals).