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white powder(s), 1μm or less 99.5% pure; hexagonal, most common form: a=0.2504 nm, c=0.6661nm; fcc: a=0.3615nm; hardness: hexagonal like graphite,?cub approaches that of diamond; band gap ~7.5 eV at 300K; dielectric 7.1; used in furnace insulation and in crucibles for melting aluminum, boron, iron, and silicon, also as sputtering target for dielectrics, diffusion masks, passivation layers [KIR81] [HAW93] [MER06] [CER91]

White powder, hexagonal graphite-like form or cubic crystal; cubic form similar to diamond in its crystal structure, and reverts to graphite form when heated above 1,700°C; density 2.18 g/cm³; melts at 2,975°C (under nitrogen pressure); sublimes at 2,500°C at atmospheric pressure; insoluble in water and acid; attacked by hot alkalies and fused alkali carbonates; not wetted by most molten metals or glasses.
Cubic boron nitride (c-BN) does not exist in nature but it is a novel substance created by human. It is synthesized under high pressure and high temperature just like diamond counterpart and has the wurzite crystal structure. The tables below compare reference hardness and heat conductivity for a couple of abrasive materials. Apparently c-BN is excellent in these properties, second only to diamond, the highest.

Boron nitride finds applications in shaping tools in industries due to its ability to withstand temperatures greater than 2,000°C. Cutting tools and abrasive components, designed specifically for use with low-carbon ferrous metals, have been developed using cubic boron nitride. These tools perform similarly to polycrystalline diamond (PCD) tools but can be utilized on iron and low-carbon alloys without the risk of a reaction occurring.

boron nitride: A solid, BN, insolublein cold water and slowly decomposedby hot water; r.d. 2.25 (hexagonal);sublimes above 3000°C. Boronnitride is manufactured by heatingboron oxide to 800°C on an acid-solublecarrier, such as calcium phosphate,in the presence of nitrogen orammonia. It is isoelectronic with carbonand, like carbon, it has a veryhard cubic form (borazon) and asofter hexagonal form; unlikegraphite this is a nonconductor. It isused in the electrical industrieswhere its high thermal conductivityand high resistance are of especialvalue.

Boron nitride is prepared by heating boric oxide with ammonia:
B₂O₃ + 2NH₃ → 2BN + 3H₂O
Alternatively, the compound can be prepared by heating boric oxide or boric acid with ammonium chloride or an alkali metal cyanide. Purified product can be obtained by high temperature reaction of boron halide with ammonia:
BCl₃ + NH₃ → BN + 3HCl
Boron nitride can also be made from the elements by heating boron and nitrogen at red heat.

In tonnage production, acetaldehyde may be manufactured by:
1. The direct oxidation of ethylene, requiring a catalytic solution of copper chloride plus small quantities of palladium chloride Cl2Pd.
2. The oxidation of ethyl alcohol C2H6O with sodium dichromate Cr2Na2O7, and
3. The dry distillation of calcium acetate C4H6CaO4 with calcium formate C2H2CaO4.

Boron nitride (BN) has many potential commercial applications. It is a white, fluffy powder with a greasy feel. It is used for heat-resistant parts by molding and pressing the powder without a binder to a specific gravity of 2.1 to 2.25.
BN may be prepared in a variety of ways, for example, by the reaction of boron oxide with ammonia, alkali cyanides, and ammonium chloride, or of boron halides and ammonia. The usually high chemical and thermal stability, combined with the high electrical resistance of BN, suggests numerous uses for this compound in the field of high-temperature technology. BN can be hot-pressed into molds and worked into desired shapes.
BN powders can be used as mold-release agents, high-temperature lubricants, and additives in oils, rubbers, and epoxies to improve thermal conductance of dielectric compounds. Powders also are used in metal- and ceramicmatrix composites (MMC and CMC) to improve thermal shock and to modify wetting characteristics.
The platy habit of the particles and the fact that boron nitride is not wet by glass favors use of the powder as a mold wash, e.g., in the fabrication of high-tension insulators. It is also useful as thermal insulation in induction heating. A cubic form of boron nitride (Borazon) similar to diamond in hardness and structure has been synthesized by the high-temperature, high-pressure process for making synthetic diamonds. Any uses it may find as a substitute for diamonds will depend on its greatly superior oxidation resistance.

Boron nitride exists as three different poly-morphs:
Alpha-boron nitride (α-BN), a soft and ductile polymorph (ρ = 2280 kg.m^–3 and m.p. = 2700°C) with a hexagonal crystal lattice similar to that of graphite, also called hexagonal boron nitride (HBN) or white graphite;
Beta-boron nitride (β-BN), the hardest manmade material and densest polymorph (ρ = 3480 kg.m^–3, m.p. = 3027°C), with a cubic crystal lattice similar to that of diamond, also called cubic boron nitride (CBN) or borazon;
Pyrolitic boron nitride (PBN). From a chemical point of view, boron nitride oxidizes readily in air at temperatures above 1100°C, forming a thing protective layer of boric acid (H₃BO₃) on its surface that prevents further oxidation as long as it coats the material. Boron nitride is stable in reducing atmospheres up to 1500°C.