View source for Boron nitride

{{Short description|Refractory compound of boron and nitrogen with formula BN}}
{{Multiple issues|
{{primary sources|date=June 2024}}
{{expert needed|Chemicals|date=June 2024}}
}}

{{Chembox
| Verifiedfields = changed
| Watchedfields  = changed
| verifiedrevid  = 476994982
| ImageFile      = Hbncrystals.jpg
| ImageFile_Ref  = {{chemboximage|correct|??}}
| ImageSize      = 140
| ImageName      = Magnified sample of crystalline hexagonal boron nitride
| IUPACName      = Boron nitride
| Section1       = {{Chembox Identifiers
| CASNo = 10043-11-5
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 2U4T60A6YD
| PubChem = 66227
| ChemSpiderID = 59612
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 233-136-6
| MeSHName = Elbor
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 50883
| RTECS = ED7800000
| Gmelin = 216
| SMILES = B#N
| StdInChI = 1S/BN/c1-2
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1S/B2N2/c1-3-2-4-1
| InChI1 = 1S/B3N3/c1-4-2-6-3-5-1
| InChI2 = 1/BN/c1-2
| StdInChIKey = PZNSFCLAULLKQX-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = AMPXHBZZESCUCE-UHFFFAOYSA-N
| InChIKey1 = WHDCVGLBMWOYDC-UHFFFAOYSA-N
| InChIKey2 = PZNSFCLAULLKQX-UHFFFAOYAL
}}
| Section2       = {{Chembox Properties
| B=1 | N=1
| MolarMassUnit = g/mol
| Appearance = Colorless crystals
| Density = 2.1&nbsp;g/cm<sup>3</sup> (h-BN); 3.45&nbsp;g/cm<sup>3</sup> (c-BN)
| MeltingPtC = 2973
| MeltingPt_notes = sublimates (c-BN)
| ElectronMobility = 200&nbsp;cm<sup>2</sup>/(V·s) (c-BN)
| RefractIndex = 1.8 (h-BN); 2.1 (c-BN)
| Solubility = Insoluble
}}
| Section3       = {{Chembox Structure
| CrystalStruct = [[Hexagonal crystal system|Hexagonal]], [[zincblende (crystal structure)|sphalerite]], [[wurtzite (crystal structure)|wurtzite]]
| Coordination =
| MolShape =
}}
| Section4       = {{Chembox Thermochemistry
| DeltaHf = −254.4&nbsp;kJ/mol<ref name="auto">for h-BN</ref><ref name=b92t/>
| DeltaGf = −228.4&nbsp;kJ/mol<ref name="auto"/><ref name=b92t/>
| Entropy = 14.8&nbsp;J/K mol<ref name="auto"/><ref name=b92t/>
| HeatCapacity = 19.7&nbsp;J/(K·mol)<ref name="auto"/><ref name=b92t>{{RubberBible92nd|page=5.6}}</ref>
}}
| Section5       = {{Chembox Hazards
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|319|335|413}}
| PPhrases = {{P-phrases|261|264|271|273|280|304+340|305+351+338|312|337+313|403+233|405|501}}
| NFPA-H = 0
| NFPA-F = 0
| NFPA-R = 0
}}
| Section8       = {{Chembox Related
| OtherCompounds = {{ubli
 | [[Boron arsenide]]
 | [[Boron carbide]]
 | [[Boron phosphide]]
 | [[Boron trioxide]]
 }}
}}
}}

'''Boron nitride''' is a thermally and chemically resistant [[refractory]] compound of [[boron]] and [[nitrogen]] with the [[chemical formula]] '''[[Boron|B]][[Nitrogen|N]]'''. It exists in various [[Polymorphism (materials science)|crystalline forms]] that are [[isoelectronic]] to a similarly structured [[carbon]] lattice. The [[Hexagonal crystal system|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 (crystal structure)#Zincblende structure|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 [[Hexagonal_crystal_family#Wurtzite_structure|wurtzite]] BN modification is similar to [[lonsdaleite]] but slightly harder than the cubic form. It has been reported to be 18% stronger than diamond.<ref name="ReferenceA">{{Cite journal |arxiv = 1811.09503|doi = 10.1063/1.5082739|title = Myths about new ultrahard phases: Why materials that are significantly superior to diamond in elastic moduli and hardness are impossible|journal = Journal of Applied Physics|volume = 125|issue = 13|page = 130901|year = 2019|last1 = Brazhkin|first1 = Vadim V.|last2 = Solozhenko|first2 = Vladimir L.|bibcode = 2019JAP...125m0901B|s2cid = 85517548}}</ref>

Because of excellent thermal and chemical stability, boron nitride ceramics are used in high-temperature equipment and [[Casting (metalworking)|metal casting]]. Boron nitride has potential use in nanotechnology.

== History ==
Boron nitride was discovered by chemistry teacher of the [[Liverpool Institute]] {{Ill|William Henry Balmain|de}} in 1842 via reduction of [[boric acid]] with charcoal in the presence of [[potassium cyanide]].<ref>{{Cite journal |last=Balmain |first=W. H. |date=October 1842 |title=Observations on the formation of compounds of boron and silicon with nitrogen and certain metals |url=https://books.google.com/books?id=7XiUObxbsYQC&pg=RA2-PA270 |journal=The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science |language=en |volume=21 |issue=138 |pages=270–277 |doi=10.1080/14786444208621545 |issn=1941-5966}}</ref> Boron nitride is now used to make nanotubes, and used for mechanical insulation, and other nanomaterials used in the industry and occasionally pharmaceutical purposes, as well as recent development in electronics.<ref>{{Cite journal |last=Izyumskaya |first=Natalia |date=n.d. |title=Recent Development of Boron Nitride towards Electronic Applications |journal=Advanced Electronic Materials |volume=3 |issue=5 |article-number=1600485 |doi=10.1002/aelm.201600485 |doi-access=free }}</ref>
{{Expand section|date=November 2024}}

==Structure==
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.<ref>{{Cite web |title=HBN, CBN, and WBN: A Comparative Analysis of Boron Nitride Polymorphs |url=https://www.samaterials.com/content/hbn-cbn-wbn-boron-nitride-polymorphs-comparison.html |access-date=2025-07-18 |website=www.samaterials.com |language=en}}</ref>

=== 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, graphitic boron nitride and "white graphite". Hexagonal boron nitride (point group = D<sub>3h</sub>; space group = P6<sub>3</sub>/mmc) has a layered structure similar to graphite. Within each layer, boron and nitrogen atoms are bound by strong [[covalent bond]]s, whereas the layers are held together by weak [[van der Waals force]]s. 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. BC<sub>6</sub>N hybrids have been synthesized, where carbon substitutes for some B and N atoms.<ref>{{cite journal | author = Kawaguchi, M. | title = Electronic Structure and Intercalation Chemistry of Graphite-Like Layered Material with a Composition of BC6N | journal = Journal of Physics and Chemistry of Solids | volume = 69 | year = 2008 | page = 1171 | doi = 10.1016/j.jpcs.2007.10.076 |issue = 5–6 |bibcode = 2008JPCS...69.1171K |display-authors=etal}}</ref> Hexagonal boron nitride monolayer is analogous to [[graphene]], having a honeycomb lattice structure of nearly the same dimensions. Unlike graphene, which is black and an electrical conductor, h-BN monolayer is white and an insulator. It has been proposed for use as an atomic flat insulating substrate or a [[tunnel diode|tunneling]] dielectric barrier in 2D electronics.<ref>{{cite journal
| vauthors = Ba K, Jiang W, Cheng J, Bao J, ''et al.''
| date = 2017
| title = Chemical and Bandgap Engineering in Monolayer Hexagonal Boron Nitride
| journal = Scientific Reports
| volume = 7
| issue = 1
| article-number = 45584
| doi = 10.1038/srep45584
| pmid = 28367992
| bibcode = 2017NatSR...745584B
| s2cid = 22951232
| doi-access = free
| pmc = 5377335
}}</ref>

Studies into the optical properties of [[hexagonal boron nitride|h-BN]] at the few- and mono-layer level have been conducted using specialized techniques like [[deep ultraviolet]] (DUV) [[hyperspectral imaging]] due to its very wide bandgap. Research at low temperatures revealed that [[monolayer]] h-BN exhibits [[photoluminescence]] consistent with a [[direct and indirect bandgaps|direct bandgap]] semiconductor, with emission observed around 6.1 eV. In contrast to observations in other 2D materials like [[transition metal dichalcogenide monolayers|TMDs]], the photoluminescence intensity remains remarkably high in few-layer h-BN, which has been attributed to a high radiative efficiency despite the [[direct and indirect bandgaps|indirect bandgap]] nature of bulk h-BN. Complementary [[atomic force microscopy|AFM]] investigations, particularly in tapping and Kelvin probe modes, have provided nanoscale insight into surface morphology and potential distribution across mono- and few-layer regions. These AFM-based techniques not only assist in confirming flake thickness and uniformity but also support optoelectronic analyses by correlating topographical and electrical variations with luminescence behavior.<ref name="Rousseau2021DUV">{{cite journal | last1=Rousseau | first1=Adrien | last2=Ren | first2=Lei | last3=Durand | first3=Alrik | last4=Valvin | first4=Pierre | last5=Gil | first5=Bernard | last6=Watanabe | first6=Kenji | last7=Taniguchi | first7=Takashi | last8=Urbaszek | first8=Bernhard | last9=Marie | first9=Xavier | last10=Robert | first10=Cédric | last11=Cassabois | first11=Guillaume | title=Monolayer Boron Nitride: Hyperspectral Imaging in the Deep Ultraviolet | journal=Nano Letters | volume=21 | issue=23 | pages=10133–10138 | date=September 16, 2021 | doi=10.1021/acs.nanolett.1c02531 | pmid=34529455 | pmc=12345805 | bibcode=2021NanoL..2110133R }}</ref>

=== Functionalization and heterostructures ===
Modifications of hexagonal boron nitride have led to novel materials like hBNCF, a vertical heterostructure involving [[graphene]] and [[hexagonal boron nitride|h-BN]] functionalized with [[fluorine]]. This material, synthesized from h-BN via graphitization and fluorination, was found to exhibit room-temperature [[ferromagnetism]]. Crucially, [[magnetic force microscopy]] (MFM), a specialized mode of [[atomic force microscopy]] (AFM), was employed to investigate the magnetic properties at the nanoscale. These MFM studies confirmed the ferromagnetic nature of the hBNCF powder. Furthermore, the MFM analysis provided evidence that the observed magnetism was intrinsic to the hBNCF structure, helping to exclude extrinsic [[magnetic impurity|metallic magnetic impurities]] as the origin.<ref name="Sahoo2021hBNCF">{{cite journal | last1=Sahoo | first1=Krishna Rani | last2=Sharma | first2=Rahul | last3=Bawari | first3=Sumit | last4=Vivek | first4=S. | last5=Rastogi | first5=Pankaj Kumar | last6=Nair | first6=Swapna S. | last7=Grage | first7=Stephan L. | last8=Narayanan | first8=Tharangattu N. | title=Room-temperature ferromagnetic wide bandgap semiconducting fluorinated Graphene-hBN vertical heterostructures | journal=Materials Today Physics | volume=21 | article-number=100547 | year=2021 | doi=10.1016/j.mtphys.2021.100547 | bibcode=2021MTPhy..2100547S | issn=2542-5293}}</ref> The material was also characterized as a wide [[band gap]] semiconductor (~3.89 eV) with potential applications as an [[MRI contrast agent]].<ref name="Sahoo2021hBNCF"/>

=== Cubic form (c-BN) ===
[[File:Cubic Boron Nitride.jpg|thumb|c-BN crystal structure]]
Cubic boron nitride has a crystal structure analogous to that of [[diamond]]. Consistent with diamond being less stable than graphite, the cubic form is less stable than the hexagonal form, but the conversion rate between the two is negligible at room temperature, as it is for diamond. The cubic form has the [[Cubic crystal system#Zincblende structure|sphalerite crystal structure]] (space group = F{{overline|4}}3m), the same as that of diamond (with ordered B and N atoms), and is also called β-BN or c-BN.

=== Wurtzite form (w-BN) ===
The [[Wurtzite crystal structure|wurtzite]] form of boron nitride (w-BN; point group = C<sub>6v</sub>; space group = P6<sub>3</sub>mc) has the same structure as [[lonsdaleite]], a rare hexagonal polymorph of carbon. As in the cubic form, the boron and nitrogen atoms are grouped into [[tetrahedra]].<ref>{{cite book | author = Silberberg, M. S. | title = Chemistry: The Molecular Nature of Matter and Change | edition = 5th | location = New York | publisher = McGraw-Hill | year = 2009 | page = 483 |isbn=978-0-07-304859-8}}</ref> In the wurtzite form, the boron and nitrogen atoms are grouped into 6-membered rings. In the cubic form all rings are in the [[chair configuration]], whereas in w-BN the rings between 'layers' are in [[boat configuration]]. Earlier optimistic reports predicted that the wurtzite form was very strong, and was estimated by a simulation as potentially having a strength 18% stronger than that of diamond. Since only small amounts of the mineral exist in nature, this has not yet been experimentally verified.<ref>{{Cite web |url=https://www.newscientist.com/article/dn16610-diamond-no-longer-natures-hardest-material/ |title=Diamond no longer nature's hardest material |last=Griggs |first=Jessica |date=2014-05-13 |website=New Scientist |access-date=2018-01-12}}</ref> Its hardness is 46 GPa, slightly harder than commercial borides but softer than the cubic form of boron nitride.<ref name="ReferenceA" />

<gallery mode="packed">
File:Boron-nitride-(hexagonal)-side-3D-balls.png|Hexagonal form (h-BN)<br/>[[Hexagonal crystal family|hexagonal]] analogous to [[graphite]]
File:Boron-nitride-(sphalerite)-3D-balls.png|Cubic form (c-BN)<br/>[[sphalerite]] structure<br/> analogous to [[diamond]]
File:Boron-nitride-(wurtzite)-3D-balls.png|Wurtzite form (w-BN)<br/>[[Wurtzite crystal structure|wurtzite]] structure<br/>analogous to [[lonsdaleite]]
</gallery>

== Properties ==

===Physical===
{| class="wikitable" style="margin:0;"
|+ Properties of amorphous and crystalline BN, graphite and diamond.<br /><small>Some properties of h-BN and graphite differ within the basal planes (∥) and perpendicular to them (⟂)</small>
! rowspan=2 | Material
! colspan=4 | Boron nitride (BN)
! rowspan=2 | Graphite<ref>{{cite book | author = Delhaes, P. | title = Graphite and Precursors | publisher = CRC Press | year = 2001 | isbn = 978-90-5699-228-6}}</ref>
! rowspan=2 | Diamond<ref name=ioffe>{{cite web | url = http://www.ioffe.ru/SVA/NSM/Semicond/BN/index.html | title = BN – Boron Nitride | work = Ioffe Institute Database}}</ref>
|-
! a-<ref>{{cite journal | doi = 10.1016/0022-3093(95)00748-2 | title = Properties of Amorphous Boron Nitride Thin Films | year = 1996 | author = Zedlitz, R. | journal = Journal of Non-Crystalline Solids | volume = 198–200 | issue = Part 1 | page = 403 |bibcode = 1996JNCS..198..403Z}}</ref><ref>{{cite journal | doi = 10.1364/AO.32.000091 | pmid = 20802666 | title = Thermal Conductivities of Thin, Sputtered Optical Films | year = 1993 | author = Henager, C. H. Jr. | journal = Applied Optics | volume = 32 | issue = 1 | pages = 91–101 |bibcode = 1993ApOpt..32...91H | url = https://digital.library.unt.edu/ark:/67531/metadc1108231/}}</ref><ref>{{cite journal | doi = 10.1016/S0925-9635(98)00394-X | title = Microstructure and Mechanical Properties of Pulsed Laser Deposited Boron Nitride Films | year = 1999 | author = Weissmantel, S. | journal = Diamond and Related Materials | volume = 8 | page = 377 | issue = 2–5 |bibcode = 1999DRM.....8..377W}}</ref>
! h-
! c-<ref name=BN>{{cite book | title = Landolt-Börnstein – Group VIII Advanced Materials and Technologies: Powder Metallurgy Data. Refractory, Hard and Intermetallic Materials | chapter = 13.5 Properties of diamond and cubic boron nitride | volume = 2A2 | doi = 10.1007/b83029 | isbn = 978-3-540-42961-6 | pages = 118–139 | editor = P. Beiss | author = Leichtfried, G. | year = 2002 | publisher = Springer | location = Berlin |display-authors=etal|display-editors=etal| series = Landolt-Börnstein - Group VIII Advanced Materials and Technologies}}</ref><ref name=ioffe/>
! w-
|-
! Density (g/cm<sup>3</sup>)
| 2.28
| ~2.1
| 3.45
| 3.49
| ~2.1
| 3.515
|-
! [[Knoop hardness test|Knoop hardness]] (GPa)
| 10
|
| 45
| 34
|
| 100
|-
! [[Bulk modulus]] (GPa)
| 100
| 36.5
| 400
| 400
| 34
| 440
|-
! [[Thermal conductivity]] <br/>(W/m·K)
| 3
| 600 ∥, <br/>30 ⟂
| 740
|
| 200–2000 ∥, <br/>2–800 ⟂
| 600–2000
|-
! [[Thermal expansion]] (10<sup>−6</sup>/K)
|
| −2.7 ∥, 38 ⟂
| 1.2
| 2.7
| −1.5 ∥, 25 ⟂
| 0.8
|-
! [[Band gap]] (eV)
| 5.05
| 5.9–6.4 <ref>{{cite journal |author=Su, C. | title = Tuning colour centres at a twisted hexagonal boron nitride interface | journal = Nature Materials | volume = 21 | year = 2022 | issue = 8 | pages = 896–902 | doi = 10.1038/s41563-022-01303-4| pmid = 35835818 | bibcode = 2022NatMa..21..896S | osti = 1906698 | s2cid = 250535073 | url = https://escholarship.org/uc/item/98b013nr}}</ref>
| 10.1-10.7 <ref>{{cite journal |author1= Tararan, Anna |author2=di Sabatino, Stefano |author3=Gatti, Matteo |author4=Taniguchi, Takashi |author5=Watanabe, Kenji |author6=Reining, Lucia |author7=Tizei, Luiz H. G. |author8=Kociak, Mathieu |author9=Zobelli, Alberto| title = Optical gap and optically active intragap defects in cubic BN | journal = Phys. Rev. B | volume = 98| year = 2018| issue = 9 | article-number = 094106 | doi =10.1103/PhysRevB.98.094106 | arxiv = 1806.11446 | bibcode = 2018PhRvB..98i4106T | s2cid = 119097213 | url = https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.094106}}</ref>
| 4.5–5.5
| 0
| 5.5
|-
! [[Refractive index]]
| 1.7
| 1.8
| 2.1
| 2.05
|
| 2.4
|-
! [[Magnetic susceptibility]] <br/>(µemu/g)<ref>{{cite journal |author1=Crane, T. P. |author2=Cowan, B. P. | title = Magnetic Relaxation Properties of Helium-3 Adsorbed on Hexagonal Boron Nitride | journal = Physical Review B | volume = 62 | article-number = 11359 | year = 2000 | doi = 10.1103/PhysRevB.62.11359 | issue = 17 |bibcode = 2000PhRvB..6211359C}}</ref> 
|
| −0.48 ∥, <br/>−17.3 ⟂
|
|
| −0.2 – −2.7 ∥, <br/>−20 – −28 ⟂
| −1.6
|}
{{clear}}
The partly [[ionic bond|ionic]] structure of BN layers in h-BN reduces covalency and electrical conductivity, whereas the interlayer interaction increases resulting in higher hardness of h-BN relative to graphite. The reduced electron-delocalization in hexagonal-BN is also indicated by its absence of color and a large [[band gap]]. Very different bonding – strong covalent within the [[basal plane]]s (planes where boron and nitrogen atoms are covalently bonded) and weak between them – causes high [[anisotropy]] of most properties of h-BN.

For example, the hardness, electrical and thermal conductivity are much higher within the planes than perpendicular to them. On the contrary, the properties of c-BN and w-BN are more homogeneous and isotropic.

Those materials are extremely hard, with the hardness of bulk c-BN being slightly smaller and w-BN even higher than that of diamond.<ref>{{cite journal | author = Pan, Z. | title = Harder than Diamond: Superior Indentation Strength of Wurtzite BN and Lonsdaleite | journal = Physical Review Letters | volume = 102 | article-number = 055503 | year = 2009 | doi = 10.1103/PhysRevLett.102.055503 | pmid = 19257519 | bibcode = 2009PhRvL.102e5503P | issue = 5 |display-authors=etal}}</ref> Polycrystalline c-BN with grain sizes on the order of 10&nbsp;nm is also reported to have [[Vickers hardness]] comparable or higher than diamond.<ref>{{cite journal|author=Tian, Yongjun |doi=10.1038/nature11728|title=Ultrahard nanotwinned cubic boron nitride|year=2013|journal=Nature|volume=493|issue=7432|pages=385–8|pmid=23325219|display-authors=etal|bibcode = 2013Natur.493..385T |s2cid=4419843}}</ref> Because of much better stability to heat and transition metals, c-BN surpasses diamond in mechanical applications, such as machining steel.<ref name=dkg>{{cite journal | title = Hexagonal Boron Nitride (hBN) – Applications from Metallurgy to Cosmetics | url = http://www.esk.com/uploads/tx_userjspresseveroeff/PR_0712_CFI_12-2007_Hexagonales-BN_e_01.pdf | author = Engler, M. | journal = Cfi/Ber. DKG | volume = 84 | year = 2007 | page = D25 | issn = 0173-9913 | archive-date = 2013-06-13 | access-date = 2009-06-12 | archive-url = https://web.archive.org/web/20130613174727/http://www.esk.com/uploads/tx_userjspresseveroeff/PR_0712_CFI_12-2007_Hexagonales-BN_e_01.pdf }}</ref> The thermal conductivity of BN is among the highest of all electric insulators (see table).

Boron nitride can be doped p-type with beryllium and n-type with boron, sulfur, silicon or if co-doped with carbon and nitrogen.<ref name=BN/> Both hexagonal and cubic BN are wide-gap semiconductors with a band-gap energy corresponding to the UV region. If voltage is applied to h-BN<ref>{{cite journal | author = Kubota, Y. | title = Deep Ultraviolet Light-Emitting Hexagonal Boron Nitride Synthesized at Atmospheric Pressure | doi = 10.1126/science.1144216 | journal = Science | pmid = 17702939 | volume = 317 | issue = 5840 | year = 2007 | pages = 932–4 |bibcode = 2007Sci...317..932K |display-authors=etal| doi-access = free}}</ref><ref name="taniguchi">{{cite journal |author1=Watanabe, K. |author2=Taniguchi, T. |author3=Kanda, H. | title = Direct-Bandgap Properties and Evidence for Ultraviolet Lasing of Hexagonal Boron Nitride Single Crystal | doi = 10.1038/nmat1134 | journal = Nature Materials | pmid = 15156198 | volume = 3 | issue = 6 | year = 2004 | pages = 404–9 |bibcode = 2004NatMa...3..404W |s2cid=23563849}}</ref> or c-BN,<ref>{{cite journal | author = Taniguchi, T. | title = Ultraviolet Light Emission from Self-Organized p–n Domains in Cubic Boron Nitride Bulk Single Crystals Grown Under High Pressure | doi = 10.1063/1.1524295 | journal = Applied Physics Letters | volume = 81 | year = 2002 | page = 4145 | issue = 22 |bibcode = 2002ApPhL..81.4145T |display-authors=etal}}</ref> then it emits UV light in the range 215–250&nbsp;nm and therefore can potentially be used as [[light-emitting diode]]s (LEDs) or lasers.

Little is known on melting behavior of boron nitride. It degrades at 2973&nbsp;°C, but melts at elevated pressure.<ref>{{cite journal | doi = 10.1021/j100814a515 | title = Sublimation and Decomposition Studies on Boron Nitride and Aluminum Nitride | year = 1962 | author = Dreger, Lloyd H. | journal = The Journal of Physical Chemistry | volume = 66 | page = 1556 | issue = 8 |display-authors=etal | bibcode = 1962JPhCh..66.1556D }}</ref><ref name=wentorf1957>{{cite journal | doi = 10.1063/1.1745964 | title = Cubic Form of Boron Nitride | year = 1957 | author= Wentorf, R. H. | journal = The Journal of Chemical Physics | volume = 26 | issue = 4 | page = 956 | bibcode=1957JChPh..26..956W}}</ref>

===Thermal stability===
Hexagonal and cubic BN (and probably w-BN) show remarkable chemical and thermal stabilities. For example, h-BN is stable to decomposition at temperatures up to 1000&nbsp;°C in air, 1400&nbsp;°C in vacuum, and 2800&nbsp;°C in an inert atmosphere. The reactivity of h-BN and c-BN is relatively similar, and the data for c-BN are summarized in the table below. 
{| class="wikitable" style="margin:10px;"
|+ Reactivity of c-BN with solids<ref name=BN/>
! Solid
! Ambient
! Action
! Threshold temperature (°C)
|-
| Mo 
| {{val|e=-2|u=Pa}} vacuum
| Reaction 
| 1360
|-
| Ni 
| {{val|e=-2|u=Pa}} vacuum
| [[Wetting]]{{efn|Here wetting refers to the ability of a molten metal to keep contact with solid BN}}
| 1360
|-
| Fe, Ni, Co 
| Argon 
| React
| 1400–1500
|-
| Al 
| {{val|e=-2|u=Pa}} vacuum 
| Wetting and reaction 
| 1050
|-
| Si
| {{val|e=-3|u=Pa}} vacuum
| Wetting 
| 1500
|-
| Cu, Ag, Au, Ga, In, Ge, Sn 
| {{val|e=-3|u=Pa}} vacuum
| No wetting
| 1100
|-
| B 
|
| No wetting
| 2200
|-
| {{chem2|Al2O3 + B2O3}}
| {{val|e=-2|u=Pa}} vacuum
| No reaction 
| 1360
|}
{{clear}}

Thermal stability of c-BN can be summarized as follows:<ref name=BN/>
* In air or oxygen: {{chem2|B2O3}} protective layer prevents further oxidation to ~1300&nbsp;°C; no conversion to hexagonal form at 1400&nbsp;°C.
* In nitrogen: some conversion to h-BN at 1525&nbsp;°C after 12&nbsp;h.
* In vacuum ({{val|e=-5|u=Pa}}): conversion to h-BN at 1550–1600&nbsp;°C.

===Chemical stability===
Boron nitride is not attacked by the usual acids, but it is soluble in alkaline molten salts and nitrides, such as [[Lithium hydroxide|LiOH]], [[Potassium hydroxide|KOH]], [[Sodium hydroxide|NaOH]]-[[Sodium carbonate|{{chem2|Na2CO3}}]], [[Sodium nitrate|{{chem2|NaNO3}}]], [[Lithium nitride|{{chem2|Li3N}}]], [[Magnesium nitride|{{chem2|Mg3N2}}]], [[Strontium nitride|{{chem2|Sr3N2}}]], [[Barium nitride|{{chem2|Ba3N2}}]] or [[Lithium boron nitride|{{chem2|Li3BN2}}]], which are therefore used to etch BN.<ref name=BN/>

===Thermal conductivity===
The theoretical thermal conductivity of hexagonal boron nitride nanoribbons (BNNRs) can approach 1700–2000&nbsp;[[watt|W]]/([[metre|m]]⋅[[kelvin|K]]), which has the same order of magnitude as the experimental measured value for [[graphene]], and can be comparable to the theoretical calculations for graphene nanoribbons.<ref>{{cite journal | author = Lan, J. H. | title = Thermal Transport in Hexagonal Boron Nitride Nanoribbons | doi = 10.1103/PhysRevB.79.115401 | journal = Physical Review B | volume = 79 | issue = 11 | year = 2009 | article-number = 115401 |bibcode = 2009PhRvB..79k5401L |display-authors=etal | url = http://scholarbank.nus.edu.sg/handle/10635/96285 }}</ref><ref>{{cite journal | vauthors = Hu J, Ruan X, Chen YP| title = Thermal Conductivity and Thermal Rectification in Graphene Nanoribbons: A Molecular Dynamics Study | doi = 10.1021/nl901231s| journal = Nano Letters | volume = 9 | issue = 7 | year = 2009 | pages = 2730–5 | pmid = 19499898 |arxiv = 1008.1300 |bibcode = 2009NanoL...9.2730H | s2cid = 1157650}}</ref> Moreover, the thermal transport in the BNNRs is [[anisotropic]]. The thermal conductivity of zigzag-edged BNNRs is about 20% larger than that of armchair-edged nanoribbons at room temperature.<ref>{{cite journal | title = Thermal Transport in Hexagonal Boron Nitride Nanoribbons | doi = 10.1088/0957-4484/21/24/245701 | pmid = 20484794 | journal = Nanotechnology | volume = 21 | issue = 24 | year = 2010 | article-number = 245701 |bibcode = 2010Nanot..21x5701O | last1 = Ouyang | first1 = Tao | last2 = Chen | first2 = Yuanping | last3 = Xie | first3 = Yuee | last4 = Yang | first4 = Kaike | last5 = Bao | first5 = Zhigang | last6 = Zhong | first6 = Jianxin | s2cid = 12898097}}</ref>

=== Mechanical properties ===
BN nanosheets consist of hexagonal boron nitride (h-BN). They are stable up to 800&nbsp;°C in air. The structure of monolayer BN is similar to that of [[graphene]], which has exceptional strength,<ref name=":0">{{Cite journal |last1=Falin |first1=Aleksey |last2=Cai |first2=Qiran |last3=Santos |first3=Elton J. G. |last4=Scullion |first4=Declan |last5=Qian |first5=Dong |last6=Zhang |first6=Rui |last7=Yang |first7=Zhi |last8=Huang |first8=Shaoming |last9=Watanabe |first9=Kenji |last10=Taniguchi |first10=Takashi |last11=Barnett |first11=Matthew R. |last12=Chen |first12=Ying |last13=Ruoff |first13=Rodney S. |last14=Li |first14=Lu Hua |date=2017-06-22 |title=Mechanical properties of atomically thin boron nitride and the role of interlayer interactions |journal=Nature Communications |language=en |volume=8 |issue=1 |article-number=15815 |doi=10.1038/ncomms15815 |pmid=28639613 |pmc=5489686 |issn=2041-1723|arxiv=2008.01657 |bibcode=2017NatCo...815815F }}</ref> a high-temperature lubricant, and a substrate in electronic devices.<ref>{{Cite journal |last1=Bosak |first1=Alexey |last2=Serrano |first2=Jorge |last3=Krisch |first3=Michael |last4=Watanabe |first4=Kenji |last5=Taniguchi |first5=Takashi |last6=Kanda |first6=Hisao |date=2006-01-19 |title=Elasticity of hexagonal boron nitride: Inelastic x-ray scattering measurements |url=https://link.aps.org/doi/10.1103/PhysRevB.73.041402 |journal=Physical Review B |language=en |volume=73 |issue=4 |article-number=041402 |doi=10.1103/PhysRevB.73.041402 |bibcode=2006PhRvB..73d1402B |issn=1098-0121}}</ref>

The anisotropy of Young's modulus and [[Poisson's ratio]] depends on the system size.<ref>{{Cite journal |last1=Thomas |first1=Siby |last2=Ajith |first2=K M |last3=Valsakumar |first3=M C |date=2016-07-27 |title=Directional anisotropy, finite size effect and elastic properties of hexagonal boron nitride |url=https://iopscience.iop.org/article/10.1088/0953-8984/28/29/295302 |journal=Journal of Physics: Condensed Matter |volume=28 |issue=29 |article-number=295302 |doi=10.1088/0953-8984/28/29/295302 |pmid=27255345 |bibcode=2016JPCM...28C5302T |issn=0953-8984|url-access=subscription }}</ref> h-BN also exhibits strongly anisotropic strength and [[toughness]],<ref>{{Cite journal |last1=Ahmed |first1=Tousif |last2=Procak |first2=Allison |last3=Hao |first3=Tengyuan |last4=Hossain |first4=Zubaer M. |date=2019-04-17 |title=Strong anisotropy in strength and toughness in defective hexagonal boron nitride |url=https://link.aps.org/doi/10.1103/PhysRevB.99.134105 |journal=Physical Review B |language=en |volume=99 |issue=13 |article-number=134105 |doi=10.1103/PhysRevB.99.134105 |bibcode=2019PhRvB..99m4105A |issn=2469-9950|url-access=subscription }}</ref> and maintains these over a range of [[vacancy defect]]s, showing that the anisotropy is independent to the defect type.

==Natural occurrence==
In 2009, cubic form (c-BN) was reported in [[Tibet]], and the name [[qingsongite]] proposed. The substance was found in dispersed [[micron]]-sized inclusions in chromium-rich rocks. In 2013, the International Mineralogical Association affirmed the mineral and the name.<ref>{{cite journal|author=Dobrzhinetskaya, L.F. |year=2013|title=Qingsongite, IMA 2013-030|journal=CNMNC Newsletter|volume=16|page=2708|display-authors=etal}}</ref><ref>{{cite journal|author=Dobrzhinetskaya, L.F. |year=2014|title=Qingsongite, natural cubic boron nitride: The first boron mineral from the Earth's mantle|journal=American Mineralogist|volume=99|issue=4|pages=764–772|url=http://www.minsocam.org/msa/ammin/toc/Abstracts/2014_Abstracts/APR14_Abstracts/Dobr_p764_14.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.minsocam.org/msa/ammin/toc/Abstracts/2014_Abstracts/APR14_Abstracts/Dobr_p764_14.pdf |archive-date=2022-10-09 |url-status=live|doi=10.2138/am.2014.4714|display-authors=etal|bibcode=2014AmMin..99..764D|s2cid=130947756}}</ref><ref>{{Cite web|url=https://www.mindat.org/min-43792.html|title = Qingsongite}}</ref><ref>{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}}</ref>

==Synthesis==
===Preparation and reactivity of hexagonal BN===
Hexagonal boron nitride is obtained by the treating boron trioxide ({{chem2|B2O3}}) or boric acid ({{chem2|H3BO3}}) with [[ammonia]] ({{chem2|NH3}}) or [[urea]] ({{chem2|CO(NH2)2}}) in an inert atmosphere:<ref name=prod>{{cite journal | author = Rudolph, S. | journal = American Ceramic Society Bulletin | volume = 79 | year = 2000 | page = 50 | url = http://www.a-m.de/deu/literatur/cb0600.html | title = Boron Nitride (BN) | archive-url = https://web.archive.org/web/20120306221940/http://www.a-m.de/deu/literatur/cb0600.html | archive-date = 2012-03-06}}</ref>

:{{chem2|B2O3 + 2 NH3 → 2 BN + 3 H2O}} (''T'' = 900&nbsp;°C)
:{{chem2|B(OH)3 + NH3 → BN + 3 H2O}} (''T'' = 900&nbsp;°C)
:{{chem2|B2O3 + CO(NH2)2 → 2 BN + CO2 + 2 H2O}} (''T'' > 1000&nbsp;°C)
:{{chem2|B2O3 + 3 CaB6 + 10 N2 → 20 BN + 3 CaO}} (''T'' > 1500&nbsp;°C)

The resulting disordered ([[amorphous solid|amorphous]]) material contains 92–95% BN and 5–8% {{chem2|B2O3}}. The remaining {{chem2|B2O3}} can be evaporated in a second step at temperatures {{nowrap|> 1500 °C}} in order to achieve BN concentration >98%. Such annealing also crystallizes BN, the size of the crystallites increasing with the annealing temperature.<ref name=dkg/><ref>{{cite web | url = http://hubacek.jp/bn/bn.htm | access-date = 2009-06-06 | title = Synthesis of Boron Nitride from Oxide Precursors | archive-url = https://web.archive.org/web/20071212115253/http://hubacek.jp/bn/bn.htm | archive-date = December 12, 2007 }}</ref>

h-BN parts can be fabricated inexpensively by hot-pressing with subsequent machining. The parts are made from boron nitride powders adding boron oxide for better compressibility. Thin films of boron nitride can be obtained by [[chemical vapor deposition]] from [[borazine]].<ref>A. J. R. Payne, N. F. X. Jr, A. Tamtögl, M. Sacchi, Unravelling the Epitaxial Growth Mechanism of Hexagonal and Nanoporous Boron Nitride: A First-Principles Microkinetic Model. Small 2025, 2405404. https://doi.org/10.1002/smll.202405404</ref> [[ZYP Coatings (company)|ZYP Coatings]] also has developed boron nitride coatings that may be painted on a surface. Combustion of boron powder in nitrogen [[plasma (physics)|plasma]] at 5500&nbsp;°C yields [[Ultrafine particles|ultrafine]] boron nitride used for lubricants and [[toner (printing)|toner]]s.<ref>{{cite journal |author1=Paine, Robert T. |author2=Narula, Chaitanya K. | title = Synthetic Routes to Boron Nitride | journal = Chemical Reviews | year = 1990 | volume = 90 | pages = 73–91 | doi= 10.1021/cr00099a004}}</ref>

Boron nitride reacts with [[iodine monofluoride|iodine fluoride]] to give {{chem2|NI3}} in low yield.<ref>{{cite journal |author1=Tornieporth-Oetting, I. |author2=Klapötke, T. | journal = Angewandte Chemie International Edition | year = 1990 | volume = 29 | pages =677–679 | doi = 10.1002/anie.199006771 | title = Nitrogen Triiodide | issue = 6}}</ref>
Boron nitride reacts with nitrides of lithium, alkaline earth metals and lanthanides to form [[nitridoborate]]s.<ref name = "Housecroft2d">{{cite book |author1=Housecroft, Catherine E. |author2=Sharpe, Alan G. | year=2005 |title=Inorganic Chemistry|edition=2d |publisher=Pearson education|page=318|isbn=978-0-13-039913-7}}</ref> For example:
:{{chem2|Li3N + BN → Li3BN2}}

===Intercalation of hexagonal BN===
{{see also|Graphite intercalation compound|Graphene boron nitride nanohybrid materials}}
[[Image:BN8Kstructure.jpg|150px|thumb|Structure of hexagonal boron nitride intercalated with potassium ({{chem2|B4N4K}})]]

Various species intercalate into hexagonal BN, such as {{chem2|NH3}} intercalate<ref>{{cite journal | author = Solozhenko, V. L. | journal = Physical Chemistry Chemical Physics | year = 2002 | page = 5386 | doi = 10.1039/b206005a | title = ''In situ'' Studies of Boron Nitride Crystallization from BN Solutions in Supercritical N–H Fluid at High Pressures and Temperatures | volume = 4 | issue = 21 |bibcode = 2002PCCP....4.5386S |display-authors=etal}}</ref> or alkali metals.<ref>{{cite journal | author = Doll, G. L. | title = Intercalation of Hexagonal Boron Nitride with Potassium | journal = Journal of Applied Physics | volume = 66 | page = 2554 | year = 1989 | doi = 10.1063/1.344219 | issue = 6 |bibcode = 1989JAP....66.2554D |display-authors=etal}}</ref>

===Preparation of cubic BN===
c-BN is prepared analogously to the preparation of [[synthetic diamond]] from graphite. Direct conversion of hexagonal boron nitride to the cubic form has been observed at pressures between 5 and 18&nbsp;GPa and temperatures between 1730 and 3230&nbsp;°C, that is similar parameters as for direct graphite-diamond conversion.<ref name=wentorf>{{cite journal | author = Wentorf, R. H. Jr. | author-link = Robert H. Wentorf, Jr. |date=March 1961 | title = Synthesis of the Cubic Form of Boron Nitride | journal = Journal of Chemical Physics | volume = 34 | issue = 3 | pages = 809–812 | doi = 10.1063/1.1731679 |bibcode = 1961JChPh..34..809W}}</ref> The addition of a small amount of boron oxide can lower the required pressure to 4–7&nbsp;GPa and temperature to 1500&nbsp;°C. As in diamond synthesis, to further reduce the conversion pressures and temperatures, a catalyst is added, such as lithium, potassium, or magnesium, their nitrides, their fluoronitrides, water with ammonium compounds, or hydrazine.<ref name=vel>{{cite journal | doi = 10.1016/0921-5107(91)90121-B | title = Cubic Boron Nitride: Synthesis, Physicochemical Properties and Applications | author = Vel, L. | journal = Materials Science and Engineering: B | volume = 10 | year = 1991 | page = 149 | issue = 2 |display-authors=etal}}</ref><ref>{{cite journal | author = Fukunaga, O. | title = Science and Technology in the Recent Development of Boron Nitride Materials | year = 2002 | journal = Journal of Physics: Condensed Matter | volume = 14 | page = 10979 | doi = 10.1088/0953-8984/14/44/413 | issue = 44 |bibcode = 2002JPCM...1410979F | s2cid = 250835481}}</ref> Other industrial synthesis methods, again borrowed from diamond growth, use crystal growth in a temperature gradient, or explosive [[shock wave]]. The shock wave method is used to produce material called [[heterodiamond]], a superhard compound of boron, carbon, and nitrogen.<ref>{{cite journal | author = Komatsu, T. | title = Creation of Superhard B–C–N Heterodiamond Using an Advanced Shock Wave Compression Technology | journal = Journal of Materials Processing Technology | volume = 85 | issue = 1–3 | year = 1999 | page = 69 | doi = 10.1016/S0924-0136(98)00263-5 |display-authors=etal}}</ref>

Low-pressure deposition of thin films of cubic boron nitride is possible. As in diamond growth, the major problem is to suppress the growth of hexagonal phases (h-BN or graphite, respectively). Whereas in diamond growth this is achieved by adding hydrogen gas, [[boron trifluoride]] is used for c-BN. [[Ion beam deposition]], [[plasma-enhanced chemical vapor deposition]], [[pulsed laser deposition]], [[Sputter deposition|reactive sputtering]], and other [[physical vapor deposition]] methods are used as well.<ref name=cvd>{{cite journal | title = Review of Advances in Cubic Boron Nitride Film Synthesis | author = Mirkarimi, P. B. | volume = 21 | year = 1997 | pages = 47–100 | doi = 10.1016/S0927-796X(97)00009-0 | journal = Materials Science and Engineering: R: Reports | issue = 2 |display-authors=etal| url = https://zenodo.org/record/1260151}}</ref>

===Preparation of wurtzite BN===
Wurtzite BN can be obtained via static high-pressure or dynamic shock methods.<ref>{{cite journal | title = Characterization of Wurtzite Type Boron Nitride Synthesized by Shock Compression | author = Soma, T. | journal = Materials Research Bulletin | volume = 9 | year = 1974 | page = 755 | doi = 10.1016/0025-5408(74)90110-X | issue = 6 |display-authors=etal}}</ref> The limits of its stability are not well defined. When pressure is decreased to atmospheric pressure, w-BN produced by conversion of h-BN at high pressures have shown the tendency to recover back to h-BN. However, it has been found that 3D networks of planar defects, constructed by high densities of intrinsic stacking faults and inversion domain boundaries, facilitated the stability of millimeter-size w-BN crystals at atmospheric pressure.<ref>{{cite journal |author = Chen, C. |title=Stabilizing the metastable superhard material wurtzite boron nitride by three-dimensional networks of planar defects |journal=Proc. Natl. Acad. Sci. |year=2019 |volume=116 |issue=23 |pages=11181-11186 |doi=10.1073/pnas.1902820116 |display-authors=etal|pmc=6561256 }}</ref> Both c-BN and w-BN are formed by compressing h-BN, but formation of w-BN occurs at much lower temperatures close to 1700&nbsp;°C.<ref name=vel/>

===Production statistics===
Whereas the production and consumption figures for the raw materials used for BN synthesis, namely boric acid and boron trioxide, are well known (see [[boron]]), the corresponding numbers for the boron nitride are not listed in statistical reports. An estimate for the 1999 world production is 300 to 350 [[metric tons]]. The major producers and consumers of BN are located in the United States, Japan, China and Germany. In 2000, prices varied from about $75–120/kg for standard industrial-quality h-BN and were about up to $200–400/kg for high purity BN grades.<ref name=prod/>

==Applications==
===Hexagonal BN===
{{Main|Synthesis of hexagonal boron nitride}}

[[Image:BNcrucible.jpg|thumb|right|Ceramic BN crucible]]
Hexagonal BN (h-BN) is the most widely used polymorph. It is a good lubricant at both low and high temperatures (up to 900&nbsp;°C, even in an oxidizing atmosphere). h-BN lubricant is particularly useful when the electrical conductivity or chemical reactivity of graphite (alternative lubricant) would be problematic. In internal combustion engines, where graphite could be oxidized and turn into carbon sludge, h-BN with its superior thermal stability can be added to engine lubricants. As with all nano-particle suspensions, Brownian-motion settlement is a problem. Settlement can clog engine oil filters, which limits solid lubricant applications in a combustion engine to automotive racing, where engine re-building is common. Since carbon has appreciable solubility in certain alloys (such as steels), which may lead to degradation of properties, BN is often superior for high temperature and/or high pressure applications. Another advantage of h-BN over graphite is that its lubricity does not require water or gas molecules trapped between the layers. Therefore, h-BN lubricants can be used in vacuum, such as space applications. The lubricating properties of fine-grained h-BN are used in [[cosmetics]], [[paint]]s, [[dental cement]]s, and [[pencil]] leads.<ref name=b1>{{cite book |author1=Greim, Jochen |author2=Schwetz, Karl A. | chapter = Boron Carbide, Boron Nitride, and Metal Borides | title = Ullmann's Encyclopedia of Industrial Chemistry | publisher = Wiley-VCH | location = Weinheim | year = 2005 | doi = 10.1002/14356007.a04_295.pub2 |isbn=978-3-527-30673-2}}</ref>

Hexagonal BN was first used in cosmetics around 1940 in [[Japan]]. Because of its high price, h-BN was abandoned for this application. Its use was revitalized in the late 1990s with the optimization h-BN production processes, and currently h-BN is used by nearly all leading producers of cosmetic products for [[Foundation (cosmetics)|foundations]], [[make-up]], [[eye shadow]]s, blushers, [[eye liner|kohl pencils]], [[lipstick]]s and other skincare products.<ref name=dkg/>

Because of its excellent thermal and chemical stability, boron nitride ceramics and coatings are used high-temperature equipment. h-BN can be included in ceramics, alloys, resins, plastics, rubbers, and other materials, giving them self-lubricating properties. Such materials are suitable for construction of e.g. [[Bearing (mechanical)|bearings]] and in steelmaking.<ref name=dkg/> Many quantum devices use multilayer h-BN as a substrate material. It can also be used as a dielectric in resistive random access memories.<ref>{{Cite journal|last1=Pan|first1=Chengbin|last2=Ji|first2=Yanfeng|last3=Xiao|first3=Na|last4=Hui|first4=Fei|last5=Tang|first5=Kechao|last6=Guo|first6=Yuzheng|last7=Xie|first7=Xiaoming|last8=Puglisi|first8=Francesco M.|last9=Larcher|first9=Luca|date=2017-01-01|title=Coexistence of Grain-Boundaries-Assisted Bipolar and Threshold Resistive Switching in Multilayer Hexagonal Boron Nitride|journal=Advanced Functional Materials|volume=27|issue=10|article-number=1604811|doi=10.1002/adfm.201604811|hdl=11380/1129421|s2cid=100500198 |hdl-access=free}}</ref><ref>{{Cite book|last1=Puglisi|first1=F. M.|last2=Larcher|first2=L.|last3=Pan|first3=C.|last4=Xiao|first4=N.|last5=Shi|first5=Y.|last6=Hui|first6=F.|last7=Lanza|first7=M.|title=2016 IEEE International Electron Devices Meeting (IEDM) |chapter=2D h-BN based RRAM devices |date=2016-12-01|pages=34.8.1–34.8.4|doi=10.1109/IEDM.2016.7838544|hdl=11380/1129447 |isbn=978-1-5090-3902-9|s2cid=28059875}}</ref>

Hexagonal BN is used in [[Xerography|xerographic process]] and [[laser printer]]s as a charge leakage barrier layer of the photo drum.<ref>{{cite journal | author = Schein, L. B. | title = Electrophotography and Development Physics | journal = Physics Today | series = Springer Series in Electrophysics | volume = 14 | issue = 12 | pages = 66–68 |publisher = Springer-Verlag | location = Berlin | year = 1988 | isbn = 978-0-387-18902-4 | bibcode = 1989PhT....42l..66S | doi = 10.1063/1.2811250}}</ref> In the automotive industry, h-BN mixed with a binder (boron oxide) is used for sealing [[oxygen sensor]]s, which provide feedback for adjusting fuel flow. The binder utilizes the unique temperature stability and insulating properties of h-BN.<ref name=dkg/>

Parts can be made by [[hot pressing]] from four commercial grades of h-BN. Grade HBN contains a [[boron trioxide|boron oxide]] [[binder (material)|binder]]; it is usable up to 550–850&nbsp;°C in oxidizing atmosphere and up to 1600&nbsp;°C in vacuum, but due to the boron oxide content is sensitive to water. Grade HBR uses a [[calcium borate]] binder and is usable at 1600&nbsp;°C. Grades HBC and HBT contain no binder and can be used up to 3000&nbsp;°C.<ref>{{cite book | author = Harper, Charles A. | title = Handbook of Ceramics, Glasses and Diamonds | publisher = McGraw-Hill | year = 2001 | isbn = 978-0-07-026712-1}}</ref>

[[Boron nitride nanosheet]]s (h-BN) can be deposited by catalytic decomposition of [[borazine]] at a temperature ~1100&nbsp;°C in a [[chemical vapor deposition]] setup, over areas up to about 10&nbsp;cm<sup>2</sup>. Owing to their hexagonal atomic structure, small lattice mismatch with graphene (~2%), and high uniformity they are used as substrates for graphene-based devices.<ref name=nn>{{cite journal|doi=10.1021/nn503140y|pmid=25094030|title=Large-Area Monolayer Hexagonal Boron Nitride on Pt Foil|journal=ACS Nano|volume=8|issue=8|pages=8520–8|year=2014|last1=Park|first1=Ji-Hoon|last2=Park|first2=Jin Cheol|last3=Yun|first3=Seok Joon|last4=Kim|first4=Hyun|last5=Luong|first5=Dinh Hoa|last6=Kim|first6=Soo Min|last7=Choi|first7=Soo Ho|last8=Yang|first8=Woochul|last9=Kong|first9=Jing|last10=Kim|first10=Ki Kang|last11=Lee|first11=Young Hee |bibcode=2014ACSNa...8.8520P }}</ref> BN nanosheets are also excellent [[proton conductor]]s. Their high proton transport rate, combined with the high electrical resistance, may lead to applications in [[fuel cells]] and [[water electrolysis]].<ref>{{cite journal | author = Hu, S. |display-authors=etal | title = Proton transport through one-atom-thick crystals | journal = Nature | year = 2014 | volume = 516 | issue = 7530 | pages = 227–230 | doi = 10.1038/nature14015|pmid=25470058 |arxiv = 1410.8724 |bibcode = 2014Natur.516..227H |s2cid=4455321}}</ref>

h-BN has been used since the mid-2000s as a bullet and bore lubricant in precision target rifle applications as an alternative to [[molybdenum disulfide]] coating, commonly referred to as "moly". It is claimed to increase effective barrel life, increase intervals between bore cleaning and decrease the deviation in point of impact between clean bore first shots and subsequent shots.<ref>{{cite web | url = http://bulletin.accurateshooter.com/2014/09/hexagonal-boron-nitride-hbn-how-well-does-it-work/ | title = Hexagonal Boron Nitride (HBN)—How Well Does It Work? | author = <!--Staff writer(s); no by-line.--> | date = 8 September 2014 | website = AccurateShooter.com | access-date = 28 December 2015}}</ref>

h-BN is used as a release agent in molten metal and glass applications. For example, [[ZYP Coatings (company)|ZYP Coatings]] developed and currently produces a line of paintable h-BN coatings that are used by manufacturers of molten aluminium, non-ferrous metal, and glass.<ref>{{Cite web|url=http://www.colourdeverre.com/img/projects/advancedpriming.pdf|title=colourdeverre.com/img/projects/advancedpriming.pdf}}</ref> Because h-BN is nonwetting and lubricious to these molten materials, the coated surface (i.e. mold or crucible) does not stick to the material.<ref>{{Cite web|url=https://www.researchgate.net/publication/234787198|title=Wettability, Spreading, and Interfacial Phenomena in High-Temperature Coatings}}</ref><ref>{{Cite web|url=https://hal.science/hal-02113581/document|title=Substrate Release Mechanisms for Gas Metal Arc 3-D Aluminum Metal Printing. 3D Printing &Additive Manufacturing}}</ref><ref>{{Cite web|url=https://www.researchgate.net/publication/265172365|title=Wear properties of squeeze cast in situ Mg2Si–A380 alloy}}</ref><ref>{{Cite web|url=http://www.jwri.osaka-u.ac.jp/~dpt9/Acta(1993)BNAl.pdf|title=INTERFACIAL REACTION WETTING IN THE BORON NITRIDE/MOLTEN ALUMINUM SYSTEM}}</ref>

Exfoliated h-BN shows the ability to improved mechanical and thermal properties of polypropylene. One process used Resonant Acoustic Mixing to coat polypropylene with the h-BN. Then the h-BN was exfoliated by running the material through a high-pressure homogenizer, effectively creating nanosheets. This melt process also caused the h-BN to have a more uniform distribution through the polypropylene. Improvements were especially noted in oxidative thermal stability, enhanced oxidative induction time and reduct carbonyl index values.<ref>{{Cite journal |last1=Sonker |first1=Amit Kumar |last2=Tran |first2=Man Hieu |last3=Park |first3=Nathan |last4=Das |first4=Gouri Sankar |last5=Mahajan |first5=Hansa |last6=Lee |first6=Tae Hee |last7=Kim |first7=TaeYoung |date=2025-01-14 |title=Enhancement of Thermal, Mechanical, and Oxidative Properties of Polypropylene Composites with Exfoliated Hexagonal Boron Nitride Nanosheets |journal=ACS Omega |volume=10 |issue=1 |pages=1853–1861 |doi=10.1021/acsomega.4c10677 |pmc=11740118 |pmid=39829589}}</ref>

===Cubic BN===
Cubic boron nitride (CBN or c-BN) is widely used as an [[abrasive]].<ref name="mprg">{{Cite book | vauthors = Todd RH, Allen DK, Dell KAlting L | year = 1994 | title = Manufacturing Processes Reference Guide | publisher = Industrial Press Inc. | pages = 43–48 | url = https://books.google.com/books?id=6x1smAf_PAcC | isbn = 978-0-8311-3049-7}}</ref> Its usefulness arises from its insolubility in [[iron]], [[nickel]], and related [[alloy]]s at high temperatures, whereas diamond is soluble in these metals. Polycrystalline c-BN ('''PCBN''') abrasives are therefore used for machining steel, whereas diamond abrasives are preferred for aluminum alloys, ceramics, and stone. When in contact with oxygen at high temperatures, BN forms a [[Passivation (chemistry)#Surface passivation|passivation layer]] of boron oxide. Boron nitride binds well with metals due to formation of interlayers of metal borides or nitrides. Materials with cubic boron nitride crystals are often used in the [[tool bit]]s of [[cutting tool]]s. For grinding applications, softer binders such as resin, porous ceramics and soft metals are used. Ceramic binders can be used as well. Commercial products are known under names "[[Borazon]]" (by Hyperion Materials & Technologies<ref>{{cite web |title=Diamond and Cubic Boron Nitride (CBN) Abrasives |url=https://www.hyperionmt.com/products/Abrasives/mesh-cbn |website=Hyperion Materials & Technologies |access-date=21 June 2022}}</ref>), and "Elbor" or "Cubonite" (by Russian vendors).<ref name=b1/>

Contrary to diamond, large c-BN pellets can be produced in a simple process (called sintering) of annealing c-BN powders in nitrogen flow at temperatures slightly below the BN decomposition temperature. This ability of c-BN and h-BN powders to fuse allows cheap production of large BN parts.<ref name=b1/>

Similar to diamond, the combination in c-BN of highest thermal conductivity and electrical resistivity is ideal for [[heat spreader]]s.

As cubic boron nitride consists of light atoms and is very robust chemically and mechanically, it is one of the popular materials for X-ray membranes: low mass results in small X-ray absorption, and good mechanical properties allow usage of thin membranes, further reducing the absorption.<ref>{{cite journal |author1=El Khakani, M. A. |author2=Chaker, M. | title = Physical Properties of the X-Ray Membrane Materials | journal = Journal of Vacuum Science and Technology B | volume = 11 | pages = 2930–2937 | year = 1993 | doi = 10.1116/1.586563 | issue = 6 |bibcode = 1993JVSTB..11.2930E}}</ref>

===Amorphous BN===
Layers of amorphous boron nitride (a-BN) are used in some [[semiconductor device]]s, e.g. [[MOSFET]]s. They can be prepared by chemical decomposition of [[trichloroborazine|trichloro]][[borazine]] with [[caesium]], or by thermal chemical vapor deposition methods. Thermal CVD can be also used for deposition of h-BN layers, or at high temperatures, c-BN.<ref>{{cite journal | author = Schmolla, W. | title = Positive Drift Effect of BN-InP Enhancement N-Channel MISFET | doi =10.1080/00207218508939000 | journal = International Journal of Electronics | volume = 58 | year = 1985 | page = 35}}</ref>

==Other forms of boron nitride==
=== Atomically thin boron nitride ===
{{Main|Boron nitride nanosheet}}
Hexagonal boron nitride can be exfoliated to mono or few atomic layer sheets. Due to its analogous structure to that of graphene, atomically thin boron nitride is sometimes called ''white graphene''.<ref name="LiChen2016">{{cite journal|last1=Li|first1=Lu Hua|last2=Chen|first2=Ying|title=Atomically Thin Boron Nitride: Unique Properties and Applications|journal=Advanced Functional Materials|volume=26|issue=16|year=2016|pages=2594–2608|doi=10.1002/adfm.201504606|arxiv=1605.01136|bibcode=2016arXiv160501136L|s2cid=102038593}}</ref>

====Mechanical properties====
Atomically thin boron nitride is one of the strongest electrically insulating materials. Monolayer boron nitride has an average Young's modulus of 0.865TPa and fracture strength of 70.5GPa, and in contrast to graphene, whose strength decreases dramatically with increased thickness, few-layer boron nitride sheets have a strength similar to that of monolayer boron nitride.<ref>{{Cite journal|last1=Falin|first1=Aleksey|last2=Cai|first2=Qiran|last3=Santos|first3=Elton J.G.|last4=Scullion|first4=Declan|last5=Qian|first5=Dong|last6=Zhang|first6=Rui|last7=Yang|first7=Zhi|last8=Huang|first8=Shaoming|last9=Watanabe|first9=Kenji|date=2017-06-22|title=Mechanical properties of atomically thin boron nitride and the role of interlayer interactions|journal=Nature Communications|volume=8|article-number=15815|doi=10.1038/ncomms15815|pmid=28639613|pmc=5489686|arxiv=2008.01657|bibcode=2017NatCo...815815F}}</ref>

====Thermal conductivity====
Atomically thin boron nitride has one of the highest thermal conductivity coefficients (751 W/mK at room temperature) among semiconductors and electrical insulators, and its thermal conductivity increases with reduced thickness due to less intra-layer coupling.<ref>{{Cite journal|last1=Cai|first1=Qiran|last2=Scullion|first2=Declan|last3=Gan|first3=Wei|last4=Falin|first4=Alexey|last5=Zhang|first5=Shunying|last6=Watanabe|first6=Kenji|last7=Taniguchi|first7=Takashi|last8=Chen|first8=Ying|last9=Santos|first9=Elton J. G.|date=2019|title=High thermal conductivity of high-quality monolayer boron nitride and its thermal expansion|journal=Science Advances|language=en|volume=5|issue=6|article-number=eaav0129|doi=10.1126/sciadv.aav0129|issn=2375-2548|pmc=6555632|pmid=31187056|arxiv=1903.08862|bibcode=2019SciA....5..129C}}</ref>

====Thermal stability====
The air stability of graphene shows a clear thickness dependence: monolayer graphene is reactive to oxygen at 250&nbsp;°C, strongly doped at 300&nbsp;°C, and etched at 450&nbsp;°C; in contrast, bulk graphite is not oxidized until 800&nbsp;°C.<ref name="LiSantos2014"/> Atomically thin boron nitride has much better oxidation resistance than graphene. Monolayer boron nitride is not oxidized till 700&nbsp;°C and can sustain up to 850&nbsp;°C in air; bilayer and trilayer boron nitride nanosheets have slightly higher oxidation starting temperatures.<ref name="LiCervenka2014">{{cite journal|last1=Li|first1=Lu Hua|last2=Cervenka|first2=Jiri|last3=Watanabe|first3=Kenji|last4=Taniguchi|first4=Takashi|last5=Chen|first5=Ying|title=Strong Oxidation Resistance of Atomically Thin Boron Nitride Nanosheets|journal=ACS Nano|volume=8|issue=2|year=2014|pages=1457–1462|doi=10.1021/nn500059s|pmid=24400990|arxiv=1403.1002|bibcode=2014ACSNa...8.1457L|s2cid=5372545}}</ref> The excellent thermal stability, high impermeability to gas and liquid, and electrical insulation make atomically thin boron nitride potential coating materials for preventing surface oxidation and corrosion of metals<ref name="LiXing2014">{{cite journal|last1=Li|first1=Lu Hua|last2=Xing|first2=Tan|last3=Chen|first3=Ying|last4=Jones|first4=Rob|title=Nanosheets: Boron Nitride Nanosheets for Metal Protection (Adv. Mater. Interfaces 8/2014)|journal=Advanced Materials Interfaces|volume=1|issue=8|article-number=admi.201470047 |year=2014|pages=n/a|doi=10.1002/admi.201470047|doi-access=free}}</ref><ref>{{Cite journal|last1=Liu|first1=Zheng|last2=Gong|first2=Yongji|last3=Zhou|first3=Wu|last4=Ma|first4=Lulu|last5=Yu|first5=Jingjiang|last6=Idrobo|first6=Juan Carlos|last7=Jung|first7=Jeil|last8=MacDonald|first8=Allan H.|last9=Vajtai|first9=Robert|date=2013-10-04|title=Ultrathin high-temperature oxidation-resistant coatings of hexagonal boron nitride|journal=Nature Communications|volume=4|issue=1|page=2541|doi=10.1038/ncomms3541|pmid=24092019|bibcode=2013NatCo...4.2541L|doi-access=free}}</ref> and other two-dimensional (2D) materials, such as [[black phosphorus]].<ref>{{Cite journal|last1=Chen|first1=Xiaolong|last2=Wu|first2=Yingying|last3=Wu|first3=Zefei|last4=Han|first4=Yu|last5=Xu|first5=Shuigang|last6=Wang|first6=Lin|last7=Ye|first7=Weiguang|last8=Han|first8=Tianyi|last9=He|first9=Yuheng|date=2015-06-23|title=High-quality sandwiched black phosphorus heterostructure and its quantum oscillations|journal=Nature Communications|volume=6|issue=1|page=7315|doi=10.1038/ncomms8315|pmid=26099721|pmc=4557360|arxiv=1412.1357|bibcode=2015NatCo...6.7315C}}</ref>

====Better surface adsorption====
Atomically thin boron nitride has been found to have better surface adsorption capabilities than bulk hexagonal boron nitride.<ref>{{Cite journal|last1=Cai|first1=Qiran|last2=Du|first2=Aijun|last3=Gao|first3=Guoping|last4=Mateti|first4=Srikanth|last5=Cowie|first5=Bruce C. C.|last6=Qian|first6=Dong|last7=Zhang|first7=Shuang|last8=Lu|first8=Yuerui|last9=Fu|first9=Lan|author9-link=Lan Fu (engineer)|date=2016-08-29|title=Molecule-Induced Conformational Change in Boron Nitride Nanosheets with Enhanced Surface Adsorption|journal=Advanced Functional Materials|volume=26|issue=45|pages=8202–8210|doi=10.1002/adfm.201603160|arxiv=1612.02883|bibcode=2016arXiv161202883C|s2cid=13800939}}</ref> According to theoretical and experimental studies, atomically thin boron nitride as an adsorbent experiences conformational changes upon surface adsorption of molecules, increasing adsorption energy and efficiency. The synergic effect of the atomic thickness, high flexibility, stronger surface adsorption capability, electrical insulation, impermeability, high thermal and chemical stability of BN nanosheets can increase the [[Raman spectroscopy|Raman sensitivity]] by up to two orders, and in the meantime attain long-term stability and reusability not readily achievable by other materials.<ref>{{Cite journal|last1=Cai|first1=Qiran|last2=Mateti|first2=Srikanth|last3=Yang|first3=Wenrong|last4=Jones|first4=Rob|last5=Watanabe|first5=Kenji|last6=Taniguchi|first6=Takashi|last7=Huang|first7=Shaoming|last8=Chen|first8=Ying|last9=Li|first9=Lu Hua|date=2016-05-20|title=Inside Back Cover: Boron Nitride Nanosheets Improve Sensitivity and Reusability of Surface-Enhanced Raman Spectroscopy (Angew. Chem. Int. Ed. 29/2016)|journal=Angewandte Chemie International Edition|volume=55|issue=29|page=8457|doi=10.1002/anie.201604295|doi-access=free|hdl=10536/DRO/DU:30086239|hdl-access=free}}</ref><ref>{{Cite journal|last1=Cai|first1=Qiran|last2=Mateti|first2=Srikanth|last3=Watanabe|first3=Kenji|last4=Taniguchi|first4=Takashi|last5=Huang|first5=Shaoming|last6=Chen|first6=Ying|last7=Li|first7=Lu Hua|date=2016-06-14|title=Boron Nitride Nanosheet-Veiled Gold Nanoparticles for Surface-Enhanced Raman Scattering|journal=ACS Applied Materials & Interfaces|volume=8|issue=24|pages=15630–15636|doi=10.1021/acsami.6b04320|pmid=27254250|arxiv=1606.07183|bibcode=2016AAMI....815630C|s2cid=206424168}}</ref>

====Dielectric properties====
Atomically thin hexagonal boron nitride is an excellent dielectric substrate for graphene, molybdenum disulfide ({{chem2|MoS2}}), and many other 2D material-based electronic and photonic devices. As shown by electric force microscopy (EFM) studies, the electric field screening in atomically thin boron nitride shows a weak dependence on thickness, which is in line with the smooth decay of electric field inside few-layer boron nitride revealed by the first-principles calculations.<ref name="LiSantos2014">{{Cite journal|last1=Li|first1=Lu Hua|last2=Santos|first2=Elton J. G.|last3=Xing|first3=Tan|last4=Cappelluti|first4=Emmanuele|last5=Roldán|first5=Rafael|last6=Chen|first6=Ying|last7=Watanabe|first7=Kenji|last8=Taniguchi|first8=Takashi|year=2015|title=Dielectric Screening in Atomically Thin Boron Nitride Nanosheets|journal=Nano Letters|volume=15|issue=1|pages=218–223|doi=10.1021/nl503411a|pmid=25457561|arxiv=1503.00380|bibcode=2015NanoL..15..218L|s2cid=207677623}}</ref>

====Raman characteristics====
Raman spectroscopy has been a useful tool to study a variety of 2D materials, and the Raman signature of high-quality atomically thin boron nitride was first reported by Gorbachev et al. in 2011.<ref>{{Cite journal|last1=Gorbachev|first1=Roman V.|last2=Riaz|first2=Ibtsam|last3=Nair|first3=Rahul R.|last4=Jalil|first4=Rashid|last5=Britnell|first5=Liam|last6=Belle|first6=Branson D.|last7=Hill|first7=Ernie W.|last8=Novoselov|first8=Kostya S.|last9=Watanabe|first9=Kenji|date=2011-01-07|title=Hunting for Monolayer Boron Nitride: Optical and Raman Signatures|journal=Small|volume=7|issue=4|pages=465–468|doi=10.1002/smll.201001628|pmid=21360804|arxiv=1008.2868|bibcode=2011Small...7..465G |s2cid=17344540}}</ref> and Li et al.<ref name="LiCervenka2014"/> However, the two reported Raman results of monolayer boron nitride did not agree with each other. Cai et al., therefore, conducted systematic experimental and theoretical studies to reveal the intrinsic Raman spectrum of atomically thin boron nitride.<ref>{{Cite journal|last1=Cai|first1=Qiran|last2=Scullion|first2=Declan|last3=Falin|first3=Aleksey|last4=Watanabe|first4=Kenji|last5=Taniguchi|first5=Takashi|last6=Chen|first6=Ying|last7=Santos|first7=Elton J. G.|last8=Li|first8=Lu Hua|date=2017|title=Raman signature and phonon dispersion of atomically thin boron nitride|journal=Nanoscale|volume=9|issue=9|pages=3059–3067|doi=10.1039/c6nr09312d|pmid=28191567|url=https://pure.qub.ac.uk/portal/en/publications/raman-signature-and-phonon-dispersion-of-atomically-thin-boron-nitride(5f58d958-22ab-450f-97fb-cd7c0f25f5b4).html|arxiv=2008.01656|s2cid=206046676}}</ref> It reveals that atomically thin boron nitride without interaction with a substrate has a G band frequency similar to that of bulk hexagonal boron nitride, but strain induced by the substrate can cause Raman shifts. Nevertheless, the Raman intensity of G band of atomically thin boron nitride can be used to estimate layer thickness and sample quality.[[Image:STMnm-2.JPG|thumb|left|150px|BN nanomesh observed with a [[scanning tunneling microscope]]. The center of each ring corresponds to the center of the pores]]
[[File:Oil absorption by BN aerogel.jpg|thumb|upright=1.5|Top: absorption of [[cyclohexane]] by BN aerogel. Cyclohexane is stained with [[Sudan II]] red dye and is floating on water. Bottom: reuse of the aerogel after burning in air.<ref name=nat>{{cite journal|doi=10.1038/srep10337|pmid=25976019|title=Ultralight boron nitride aerogels via template-assisted chemical vapor deposition|journal=Scientific Reports|volume=5|article-number=10337|year=2015|last1=Song|first1=Yangxi|last2=Li|first2=Bin|last3=Yang|first3=Siwei|last4=Ding|first4=Guqiao|last5=Zhang|first5=Changrui|last6=Xie|first6=Xiaoming|pmc=4432566|bibcode=2015NatSR...510337S}}</ref>]]

===Boron nitride nanomesh===
{{Main|Nanomesh}}
[[nanomesh|Boron nitride nanomesh]] is a nanostructured two-dimensional material. It consists of a single BN layer, which forms by [[self-assembly]] a highly regular mesh after high-temperature exposure of a clean [[rhodium]]<ref name="corso04">{{cite journal | author = Corso, M. | title = Boron Nitride Nanomesh | journal = Science | volume = 303 | pages = 217–220 | doi = 10.1126/science.1091979 | year = 2004 | pmid = 14716010 | issue = 5655 |bibcode = 2004Sci...303..217C | s2cid = 11964344 |display-authors=etal}}</ref> or [[ruthenium]]<ref name="goriachko07">{{cite journal | author = Goriachko, A. | title = Self-Assembly of a Hexagonal Boron Nitride Nanomesh on Ru(0001) | journal = Langmuir | volume = 23 | issue = 6 | pages = 2928–2931 | doi = 10.1021/la062990t | pmid = 17286422 | year = 2007 |display-authors=etal}}</ref> surface to [[borazine]] under [[ultra-high vacuum]]. The nanomesh looks like an assembly of hexagonal pores. The distance between two pore centers is 3.2&nbsp;nm and the pore diameter is ~2&nbsp;nm. Other terms for this material are boronitrene or white graphene.<ref>[http://jacobs.physik.uni-saarland.de/forschung/Graphene.htm Graphene and Boronitrene (White Graphene)] {{Webarchive|url=https://web.archive.org/web/20180528042221/http://jacobs.physik.uni-saarland.de/forschung/Graphene.htm |date=2018-05-28}}. physik.uni-saarland.de</ref>

The boron nitride nanomesh is air-stable<ref name="bunk07">{{cite journal | author = Bunk, O. | title = Surface X-Ray Diffraction Study of Boron-Nitride Nanomesh in Air | journal = Surface Science | volume = 601 | pages = L7–L10 | doi = 10.1016/j.susc.2006.11.018 | year = 2007 | issue = 2 |bibcode = 2007SurSc.601L...7B | url = https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A18158 |display-authors=etal}}</ref> and compatible with some liquids.<ref name="berner07">{{cite journal | author = Berner, S. | title = Boron Nitride Nanomesh: Functionality from a Corrugated Monolayer | journal = Angewandte Chemie International Edition | volume = 46 | issue = 27 | pages = 5115–5119 | doi = 10.1002/anie.200700234 | pmid = 17538919 | year = 2007 |display-authors=etal | bibcode = 2007ACIE...46.5115B }}</ref><ref name="widmer07">{{cite journal | author = Widmer, R. | title = Electrolytic ''in situ'' STM Investigation of h-BN-Nanomesh |url=http://webmail.physik.unizh.ch/groups/osterwalder/zz_publications_old/EC_Widmer.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://webmail.physik.unizh.ch/groups/osterwalder/zz_publications_old/EC_Widmer.pdf |archive-date=2022-10-09 |url-status=live| journal = Electrochemical Communications | volume = 9 | pages = 2484–2488 | doi = 10.1016/j.elecom.2007.07.019 | year = 2007 | issue = 10 |display-authors=etal}}</ref> up to temperatures of 800&nbsp;°C.<ref name="corso04"/>

[[File:Flame test of buckypapers.jpg|thumb|upright=1.5|BN nanotubes are flame resistant, as shown in this comparative test of airplanes made of cellulose, carbon [[buckypaper]] and BN nanotube buckypaper.<ref name="BNpaper">{{cite journal|doi=10.1039/C5RA02988K |title=Polymer nanocomposites from free-standing, macroscopic boron nitride nanotube assemblies |journal=RSC Adv |volume=5 |issue=51 |page=41186 |year=2015 |last1=Kim |first1=Keun Su |last2=Jakubinek |first2=Michael B. |last3=Martinez-Rubi |first3=Yadienka |last4=Ashrafi |first4=Behnam |last5=Guan |first5=Jingwen |last6=O'Neill |first6=K. |last7=Plunkett |first7=Mark |last8=Hrdina |first8=Amy |last9=Lin |first9=Shuqiong |last10=Dénommée |first10=Stéphane |last11=Kingston |first11=Christopher |last12=Simard |first12=Benoit |bibcode=2015RSCAd...541186K}}</ref>]]

===Boron nitride nanotubes===
{{Main|Boron nitride nanotube}} Boron nitride tubules were first made in 1989 by Shore and Dolan This work was patented in 1989 and published in 1989 thesis (Dolan) and then 1993 Science. The 1989 work was also the first preparation of amorphous BN by B-trichloroborazine and cesium metal.

Boron nitride nanotubes were predicted in 1994<ref>{{cite journal | doi = 10.1103/PhysRevB.49.5081 | pmid = 10011453 | title = Theory of Graphitic Boron Nitride Nanotubes | year = 1994 | author = Rubio, A. | journal = Physical Review B | volume = 49 | issue = 7 | pages = 5081–5084 |bibcode = 1994PhRvB..49.5081R | url = https://zenodo.org/record/1233727 |display-authors=etal}}</ref> and experimentally discovered in 1995.<ref name="N.G. Chopra, R.J. Luyken 1995">{{cite journal | doi = 10.1126/science.269.5226.966 | title = Boron Nitride Nanotubes | year = 1995 | author = Chopra, N. G. | journal = Science | volume = 269 | pages = 966–7 | pmid = 17807732 | issue = 5226 |bibcode = 1995Sci...269..966C | s2cid = 28988094 |display-authors=etal}}</ref> They can be imagined as a rolled up sheet of h-boron nitride. Structurally, it is a close analog of the [[carbon nanotube]], namely a long cylinder with diameter of several to hundred nanometers and length of many micrometers, except carbon atoms are alternately substituted by nitrogen and boron atoms. However, the properties of BN nanotubes are very different: whereas carbon nanotubes can be metallic or semiconducting depending on the rolling direction and radius, a BN nanotube is an electrical insulator with a bandgap of ~5.5 eV, basically independent of tube chirality and morphology.<ref>{{cite journal | doi = 10.1209/0295-5075/28/5/007 | title = Stability and Band Gap Constancy of Boron Nitride Nanotubes | year = 1994 | author = Blase, X. | s2cid = 120010610 | journal = Europhysics Letters | volume = 28 | page = 335 | issue = 5 |bibcode = 1994EL.....28..335B |display-authors=etal}}</ref> In addition, a layered BN structure is much more thermally and chemically stable than a graphitic carbon structure.<ref>{{cite journal | url = http://www.glue.umd.edu/~cumings/PDF%20Publications/15.APL81han.pdf | doi = 10.1063/1.1498494 | title = Transformation of B<sub>x</sub>C<sub>y</sub>N<sub>z</sub> Nanotubes to Pure BN Nanotubes | year = 2002 | author = Han, Wei-Qiang | journal = Applied Physics Letters | volume = 81 | page = 1110 | issue = 6 |bibcode = 2002ApPhL..81.1110H |display-authors=etal}}</ref><ref name="golberg">{{cite journal | title = Boron Nitride Nanotubes | doi = 10.1002/adma.200700179 | journal = Advanced Materials | volume = 19 | year = 2007 | page = 2413 | issue = 18 | last1 = Golberg | first1 = D. | last2 = Bando | first2 = Y. | last3 = Tang | first3 = C. C. | last4 = Zhi | first4 = C. Y. | bibcode = 2007AdM....19.2413G | s2cid = 221149452}}</ref>

===Boron nitride aerogel===
{{Main|Boron nitride aerogel}}
Boron nitride aerogel is an [[aerogel]] made of highly porous BN. It typically consists of a mixture of deformed BN nanotubes and [[Boron nitride nanosheet|nanosheets]]. It can have a density as low as 0.6&nbsp;mg/cm<sup>3</sup> and a specific surface area as high as 1050&nbsp;m<sup>2</sup>/g, and therefore has potential applications as an [[Absorption (chemistry)|absorbent]], catalyst support and gas storage medium. BN aerogels are highly [[hydrophobic]] and can absorb up to 160 times their weight in oil. They are resistant to oxidation in air at temperatures up to 1200&nbsp;°C, and hence can be reused after the absorbed oil is burned out by flame. BN aerogels can be prepared by template-assisted [[chemical vapor deposition]] using [[borazine]] as the feed gas.<ref name=nat/>

===Composites containing BN===
Addition of boron nitride to [[silicon nitride]] ceramics improves the [[thermal shock]] resistance of the resulting material. For the same purpose, BN is added also to silicon nitride-[[alumina]] and [[titanium nitride]]-alumina ceramics. Other materials being reinforced with BN include alumina and [[zirconia]], [[borosilicate glass]]es, [[glass ceramic]]s, [[vitreous enamel|enamels]], and composite ceramics with [[titanium boride]]-boron nitride, titanium boride-[[aluminium nitride]]-boron nitride, and [[silicon carbide]]-boron nitride composition.<ref>{{cite book | title = Handbook of Composite Reinforcements | author = Lee, S. M. | publisher = John Wiley and Sons | year = 1992 | isbn = 978-0-471-18861-2}}</ref>

Zirconia Stabilized Boron Nitride (ZSBN) is produced by adding [[zirconia]] to BN, enhancing its thermal shock resistance and mechanical strength through a [[sintering]] process.<ref>{{cite web |url=https://www.preciseceramic.com/blog/boron-nitride-variants-pbn-hbn-cbn-zsbn.html |title=Diverse Classification Factors of Boron Nitride and Their Correlation with PBN, HBN, CBN, and ZSBN Variants
 |last=Lisa |first=Ross |website=Precise Ceramics |access-date=June 8, 2024}}</ref> It offers better performance characteristics including Superior [[corrosion]] and [[erosion]] resistance over a wide temperature range.<ref>{{cite book |author=<!-- Not Stated --> |title=New Steel: Mini & Integrated Mill Management and Technologies |date=1996 |publisher=Chilton Publishing |pages=51–56}}</ref> Its unique combination of thermal conductivity, [[lubricity]], mechanical strength, and stability makes it suitable for various applications including cutting tools and wear-resistant coatings, thermal and electrical insulation, aerospace and defense, and high-temperature components.<ref>{{cite journal |last1=Hayat |first1=Asif |last2=Sohail |first2=Muhammad |last3=Hamdy |first3=Mohamed |date=2022 |title=Fabrication, characteristics, and applications of boron nitride and their composite nanomaterials |url=https://www.sciencedirect.com/science/article/abs/pii/S2468023022000062 |journal=Surfaces and Interfaces |volume=29 |article-number=101725 |doi=10.1016/j.surfin.2022.101725 |access-date=June 8, 2024|url-access=subscription }}</ref><ref>{{cite journal |last1=Eichler |first1=Jens |last2=Lesniak |first2=Cristoph |date=2008 |title=Boron nitride (BN) and BN composites for high-temperature applications |url=https://www.sciencedirect.com/science/article/abs/pii/S0955221907004700 |journal=Journal of the European Ceramic Society |volume=28 |issue=5 |pages=1105–1109 |doi=10.1016/j.jeurceramsoc.2007.09.005|url-access=subscription }}</ref>

===Pyrolytic boron nitride (PBN)===

Pyrolytic boron nitride (PBN), also known as [[Chemical vapor deposition|Chemical vapour-deposited]] Boron Nitride(CVD-BN),<ref>{{cite web |url=https://www.preciseceramic.com/blog/introduction-of-pyrolytic-boron-nitride-pbn.html |title=About Pyrolytic Boron Nitride |last=Rose |first=Lisa |website=Precise Ceramic |access-date=May 31, 2024}}</ref> is a high-purity [[ceramic]] material characterized by exceptional chemical resistance and mechanical strength at high temperatures.<ref>{{cite web |title=Pyrolytic Boron Nitride (PBN) |url=https://www.shinetsu.co.jp/en/products/electronics-materials/pyrolytic-boron-nitride-pbn/ |website=Shin-Etsu Chemical Co., Ltd. |access-date=May 31, 2024}}</ref>
Pyrolytic boron nitride is typically prepared through the thermal decomposition of [[boron trichloride]] and [[ammonia]] vapors on [[graphite]] substrates at 1900&nbsp;°C.<ref>{{cite journal |last1=Moore |first1=A. |title=Compression Annealing of Pyrolytic Boron Nitride |journal=Nature |volume=221 |pages=1133–1135 |date=1969-03-22 |issue=5186 |doi=10.1038/2211133a0 |bibcode=1969Natur.221.1133M |url=https://www.nature.com/articles/2211133a0 |access-date=May 31, 2024|url-access=subscription }}</ref>

Pyrolytic boron nitride (PBN) generally has a hexagonal structure similar to hexagonal boron nitride (hBN), though it can exhibit stacking faults or deviations from the ideal lattice.<ref>{{cite web |title=An Overview of Pyrolytic Boron Nitride (PBN) |url=https://www.sputtertargets.net/an-overview-of-pyrolytic-boron-nitride-pbn.html |website=Sputter Targets |date=3 December 2018 |access-date=May 31, 2024}}</ref> Pyrolytic boron nitride (PBN) shows some remarkable attributes, including exceptional chemical inertness, high [[dielectric]] strength, excellent thermal shock resistance, non-wettability, non-toxicity, oxidation resistance, and minimal [[outgassing]].
<ref>{{cite journal |last1=Lipp |first1=A. |last2=Schwetz |first2=K.A. |last3=Hunold |first3=K. |title=Hexagonal boron nitride: Fabrication, properties and applications |journal=Journal of the European Ceramic Society |volume=5 |issue=1 |pages=3–9 |date=1989 |doi=10.1016/0955-2219(89)90003-4 }}</ref><ref>{{cite journal |last1=Moore |first1=A.W. |title=Characterization of pyrolytic boron nitride for semiconductor materials processing |journal=Journal of Crystal Growth |volume=106 |issue=1 |pages=6–15 |date=1990 |doi=10.1016/0022-0248(90)90281-O |bibcode=1990JCrGr.106....6M }}</ref>

Due to a highly ordered planar texture similar to pyrolytic graphite (PG), it exhibits anisotropic properties such as lower [[dielectric]] constant vertical to the [[crystal]] plane and higher bending strength along the [[crystal]] plane.<ref>{{cite journal |last1=Rebillat |first1=F. |last2=Guette |first2=A. |title=Highly ordered pyrolytic BN obtained by LPCVD |journal=Journal of the European Ceramic Society |volume=17 |issue=12 |pages=1403–1414 |date=1997 |doi=10.1016/S0955-2219(96)00244-0}}</ref> PBN material has been widely manufactured as [[crucibles]] of compound [[semiconductor]] crystals, output windows and [[dielectric]] rods of traveling-wave tubes, high-temperature [[Jig (tool)|jigs]] and [[Insulator (electricity)|insulator]].<ref>{{cite journal |last1=Gao |first1=Shitao |last2=Li |first2=Bin |title=Micromorphology and structure of pyrolytic boron nitride synthesized by chemical vapor deposition from borazine |journal=Ceramics International |volume=44 |issue=10 |pages=11424–11430 |date=2018 |doi=10.1016/j.ceramint.2018.03.201}}</ref>

==Health issues==
Boron nitride (along with {{chem2|Si3N4}}, NbN, and BNC) is generally considered to be non-toxic and does not exhibit chemical activity in biological systems. Due to its excellent safety profile and lubricious properties, boron nitride finds widespread use in various applications, including cosmetics and food processing equipment.<ref>{{Cite web |title=UNII - 2U4T60A6YD |url=https://precision.fda.gov/uniisearch/srs/unii/2u4t60a6yd |access-date=2023-07-26 |website=precision.fda.gov}}</ref><ref>{{Cite web|url=https://info.nsf.org/USDA/letters/153558.pdf|title=NSF International / Nonfood Compounds Registration Program}}</ref>

==See also==
* [[Beta-carbon nitride]]
* [[Borazon]]
* [[Borocarbonitrides]]
* [[Boron suboxide]]
* [[Superhard materials]]
* [[Wide-bandgap semiconductor]]s

==Notes==
{{notelist}}

==References==
{{Reflist|30em}}

==External links==
{{Commons category|Boron nitride}}
*[http://www.npi.gov.au/resource/boron-and-compounds National Pollutant Inventory: Boron and Compounds]
*[https://web.archive.org/web/20061014174243/http://ptcl.chem.ox.ac.uk/MSDS/BO/boron_nitride.html Materials Safety Data Sheet] at University of Oxford

{{Boron compounds}}
{{Nitrides}}

{{Authority control}}

{{DEFAULTSORT:Boron Nitride}}
[[Category:Boron compounds]]
[[Category:Ceramic materials]]
[[Category:Nitrides]]
[[Category:III-V semiconductors]]
[[Category:Non-petroleum based lubricants]]
[[Category:Dry lubricants]]
[[Category:Abrasives]]
[[Category:Superhard materials]]
[[Category:Neutron poisons]]
[[Category:Monolayers]]
[[Category:III-V compounds]]
[[Category:Boron–nitrogen compounds]]
[[Category:Zincblende crystal structure]]
[[Category:Wurtzite structure type]]