China Hexagonal Boron Nitride

Boron nitride is chemically resistant to attack by inorganic acids and water. Boron - nitrogen bonds are broken in hot concentrated alkali. Above 1200 degree begins to oxidize in air. Melting point is 3000 degree , slightly lower than 3000 degree begins to sublimate. Decomposition begins at about 2700 degree in 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 degree in oxidizing atmosphere and 2800 degree in inactive reducing atmosphere, but the lubrication performance is poor at room temperature. Most properties of boron carbide are better than those of carbon materials. For hexagonal boron nitride: very low friction coefficient, high temperature stability, good thermal shock resistance, high strength, high thermal conductivity, low expansion coefficient, high resistivity, corrosion resistance, microwave or infrared penetration.