What are the physical properties of boron nitride ceramics?

oron nitride has chemical resistance and is not eroded 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 begins when it is slightly lower than 3000 C. The decomposition begins at about 2700 C in vacuum. It is slightly soluble in hot acid, insoluble in cold water, with a density greater than 2.0 and a bending strength of 30 Mpa.The maximum operating temperature in oxidizing atmosphere is 900 (?) C, while in inactive reducing atmosphere it can reach 2800 (?) C, but its 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.