Boron nitride

**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	?
Inhalation	?
Skin	?
Eyes	?
More info	?
SI units were used where possible. Unless otherwise stated, standard conditions were used.

Boron nitride is a binary chemical compound, consisting of equal proportions of boron and nitrogen. The empirical formula is therefore BN. Boron nitride is isoelectronic to the elemental forms of carbon and isomorphism occurs between the two species. That is boron nitride possess three polymorphic forms; one analogous to diamond, one analogous to graphite and ones analogous to the fullerenes. The diamond-like allotrope of boron nitride, known as Borazon, is one of the hardest materials known but is softer than materials such as diamond, ultrahard fullerite, and aggregated diamond nanorods.

The diamond-like allotrope of boron nitride is widely used as an abrasive for industrial tools. Such usefulness is derived from the insolubility of boron nitride in iron, nickel and related alloys at high temperatures (unlike diamond).

The graphite-like allotrope of boron nitride is useful as a high-temperature lubricant in situations where the electrical conductivity or reactivity of graphite would be problematic.

The fullerene-like allotropes of boron nitride can be synthesized and resemble those of carbon. The recently discovered boron nitride nanotubes are an important development due to their homogeneous electronic behavior. That is, tubes of different chiralities are all semiconductor materials with the same (approximate) band gap.

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.

External links

National Pollutant Inventory - Boron and Compounds
Fiz Chimie Berlin thermophysical database
Materials Safety Data Sheet at University of Oxford

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Synthesis

See also

External links