Boron nitride is a crystal composed of nitrogen atoms and boron atoms. Chemistry; 43.6% boron and 56.4% nitrogen, with four different variants: hexagonal boron nitride (HBN), rhombohedral boron nitride (RBN), cubic boron nitride (CBN) and wurtzite F boron nitride (WBN).
BN can be obtained by melting B2O3 with NH4CI or burning boron in NH3. The usual boron nitride is graphite structure.
It is commonly known as white graphite. The other type is diamond, similar to the principle of graphite transforming into diamond, graphite boron chloride at high temperature (1800C).
Boron nitride has good corrosion resistance, electrical insulation, specific resistance greater than 10-60.cm, compressive strength 170 MPa, thermal expansion coefficient in the c-axis direction is 41X10-6/C and in the d-axis direction is -2.3X10-6. The maximum service temperature is 900C in the oxidizing atmosphere and 2800C in the inactive reducing atmosphere, but its lubricity is poor at room temperature, so it is often mixed with graphite fluoride, graphite and molybdenum disulfide. As a high temperature lubricant, dispersing boron nitride powder in oil or water can be used as a lubricant for wire drawing or pressing, as well as for sliding parts of high temperature furnace. Boron nitride sinter can be used as a material for bearings and sliding parts with self-lubricating properties.
Boron nitride is usually white, sphalerite structure, with good thermal conductivity. Hardness is second only to diamond, which is a kind of super hard material. It is often used as tool materials and abrasives. Below for you to introduce the material properties of boron nitride.
Boron chloride has chemical resistance and is not corroded by inorganic acids and water. The boron-nitrogen bond is broken in hot concentrated alkali. Over 1200C begins to oxidize in the air. The melting point is 3000C, and sublimation begins when the melting point is slightly below 3000C. About 2700C begins to decompose in vacuum. It is slightly soluble in hot acid and insoluble in cold water with relative density of 2.25. The compressive strength is 170MPa. The maximum operating temperature is 900C in oxidizing atmosphere and 2800C in inactive reducing atmosphere, but the lubrication performance is poor at room temperature. Most of the properties of boron carbide are better than those of carbon materials. For hexagonal boron nitride: 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 infrared transmission.
Boron nitride hexagonal products are most commonly graphite and amorphous. In addition to hexagonal products, boron carbide has other crystalline forms, including rhombohedral boron nitride (r - BN, or trigonal boron nitride), whose structure is similar to that of H - BN, which is produced during the conversion of H - BN to C - BN, and cubic boron nitride [abbreviated as "cubic boron nitride" C - BN, or | 3 - BN, or Z - BN (sphalerite boron nitride), very hard texture], wurtzite boron nitride (abbreviated as w - BN, a hard state under high pressure of H - BN). People even found two-dimensional boron nitride like graphite (similar to MoS: two-dimensional).
Boron nitride is usually made of graphite structure, commonly known as white graphite。 The other is diamond type, which is similar to the principle of graphite transforming into diamond。 Graphite type boron nitride can be transformed into diamond type boron nitride at high temperature (1800C) and high pressure (8000Mpa) [5-18GPa]。 It is a new type of superhard material with high temperature resistance, which is used to make drills, abrasives and cutting tools。
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The six party
The six party