Answer:
Boron nitride
Magnified sample of crystalline hexagonal boron nitride
Names
IUPAC name
Boron nitride
Identifiers
CAS Number
10043-11-5 check
3D model (JSmol)
hexagonal (graphite) structure: Interactive image
sphalerite structure: Interactive image
wurtzite structure: Interactive image
ChEBI
CHEBI:50883 check
ChemSpider
59612 check
ECHA InfoCard 100.030.111 Edit this at Wikidata
EC Number
233-136-6
Gmelin Reference 216
MeSH Elbor
PubChem CID
66227
RTECS number
ED7800000
UNII
2U4T60A6YD ☒
CompTox Dashboard (EPA)
DTXSID5051498 Edit this at Wikidata
InChI
SMILES
Properties
Chemical formula BN
Molar mass 24.82 g·mol−1
Appearance Colorless crystals
Density 2.1 (h-BN); 3.45 (c-BN) g/cm3
Melting point 2,973 °C (5,383 °F; 3,246 K) sublimates (cBN)
Solubility in water insoluble
Electron mobility 200 cm2/(V·s) (cBN)
Refractive index (nD) 1.8 (h-BN); 2.1 (c-BN)
Structure
Crystal structure hexagonal, sphalerite, wurtzite
Thermochemistry
Heat capacity (C) 19.7 J/(K·mol)[1]
Std molar
entropy (So298) 14.8 J/K mol[1]
Std enthalpy of
formation (ΔfH⦵298) -254.4 kJ/mol[1]
Gibbs free energy (ΔfG˚) -228.4 kJ/mol[1]
Hazards
GHS labelling:
Pictograms GHS07: Exclamation mark
Signal word Warning
Hazard statements H319, H335, H413
Precautionary statements P261, P264, P271, P273, P280, P304+P340, P305+P351+P338, P312, P337+P313, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
000
Related compounds
Related compounds Boron arsenide
Boron carbide
Boron phosphide
Boron trioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒ verify (what is check☒ ?)
Infobox references
Step-by-step explanation:
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products. The cubic (zincblende aka sphalerite structure) variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior. The rare wurtzite BN modification is similar to lonsdaleite but slightly softer than the cubic form.[2]
Because of excellent thermal and chemical stability, boron nitride ceramics are used in high-temperature equipment. Boron nitride has potential use in nanotechnology.
Boron nitride exists in multiple forms that differ in the arrangement of the boron and nitrogen atoms, giving rise to varying bulk properties of the material.
Amorphous form (a-BN)
The amorphous form of boron nitride (a-BN) is non-crystalline, lacking any long-distance regularity in the arrangement of its atoms. It is analogous to amorphous carbon.
All other forms of boron nitride are crystalline.
Hexagonal form (h-BN)
The most stable crystalline form is the hexagonal one, also called h-BN, α-BN, g-BN, and graphitic boron nitride. Hexagonal boron nitride (point group = D6h; space group = P63/mmc) has a layered structure similar to graphite. Within each layer, boron and nitrogen atoms are bound by strong covalent bonds, whereas the layers are held together by weak van der Waals forces. The interlayer "registry" of these sheets differs, however, from the pattern seen for graphite, because the atoms are eclipsed, with boron atoms lying over and above nitrogen atoms. This registry reflects the local polarity of the B–N bonds, as well as interlayer N-donor/B-acceptor characteristics. Likewise, many metastable forms consisting of differently stacked polytypes exist. Therefore, h-BN and graphite are very close neighbors, and the material can accommodate carbon as a substituent element to form BNCs. BC6N hybrids have been synthesized, where carbon substitutes for some B and N atoms.