Boron nitride

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**Properties**
General
Name	Boron nitride
Chemical formula	B N
Appearance	White solid
CAS Number	10043-11-5
Physical
Formula weight	24.818 g/mol
Melting Point	2967 ° C
Boiling point	3273 °C
Density	2.18 ×10³ kg/m³
Crystal structure	hexagonal or cubic
Solubility	insoluble
Thermochemistry
Δ_fH⁰_gas	476.98 kJ/mol
Δ_fH⁰_solid	-250.91 kJ/mol
S⁰_{gas, 1 bar}	212.36 J/mol·K
S⁰_solid	14.77 J/mol·K
Heat of Fusion	3263.8 J/g
Safety
Risk Phrases	R36 R37
Ingestion	Classified "not hazardous"
Inhalation	?
Skin	?
Eyes	?
More info	?
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references

Boron nitride is a binary chemical compound, consisting of equal proportions of boron and nitrogen, with formula BN. Structurally, it is isoelectronic to carbon and takes on similar physical forms: a hexagonal, graphite-like one, and a cubic, diamond-like one. Cubic boron nitride is one of the hardest materials known, behind only diamond , ultrahard fullerite, and aggregated diamond nanorods. It is widely used for grinding and as a material for tools in industry. This is in part because it does not dissolve into iron, nickel, and related alloys at high temperatures like diamond does. Hexagonal boron nitride finds use as a high-temperature lubricant where the electrical conductivity or reactivity of graphite would be problematic.

Boron nitride can also be synthesized in forms analogous to carbon fullerenes and nanotubes. BN nanotubes are a new important nanostructure mostly due to their homogeneous electronic behavior: tubes of different chiralities are all semiconductors with almost the same band gap.

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Synthesis

Hexagonal boron nitride is produced by the nitridation or ammonolysis of boron trioxide. Cubic boron nitride is produced by treating hexagonal boron nitride at high pressure and temperature, much as synthetic diamond is produced from graphite.

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