View source for Titanium nitride

{{Short description|Ceramic material}}
{{redirect|TiN|the chemical element|Tin}}
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 449174994
| Name = Titanium nitride
| ImageFile = File:Titanium nitride TiN.jpg
| ImageAlt = Brown powdered titanium nitride
| ImageSize = 280
| ImageFile2 = Titanium-nitride-crystal-3D-vdW.png
| ImageAlt2 = The structure of sodium chloride; titanium nitride's structure is similar.
| IUPACName = Titanium nitride
| OtherNames = Titanium(III) nitride
| Section1 = {{Chembox Identifiers
| CASNo = 25583-20-4
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 6RW464FEFF
| PubChem = 93091
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 84040
| RTECS = 
| EINECS = 247-117-5
| InChI = 1S/N.Ti
| SMILES = N#[Ti]
}}
| Section2 = {{Chembox Properties
| Formula = TiN
| MolarMass = 61.874 g/mol
| Appearance = Brown as a pure solid, coating of golden color
| Odor = Odorless
| Solubility = insoluble
| SolubleOther = 
| Density = 5.21 g/cm<sup>3</sup><ref name=crc>{{cite book |editor-last=Haynes |editor-first=William M. |year=2016 |title=CRC Handbook of Chemistry and Physics |edition=97th |page=4.92 |publisher=[[CRC Press]] |isbn=9781498754293 |title-link=CRC Handbook of Chemistry and Physics}}</ref>
| MeltingPtC = 2947
| MeltingPt_ref= <ref name=crc/>
| ThermalConductivity = 29&nbsp;W/(m·K) (323&nbsp;K)<ref name=th2/>
| MagSus = +38{{e|-6}} emu/mol
| BoilingPt = 
| RefractIndex = 
}}
| Section3 = {{Chembox Structure
| Structure_ref=<ref>{{cite journal |last=Lengauer |first=Walter |year=1992 |title=Properties of bulk δ-TiN<sub>1−x</sub> prepared by nitrogen diffusion into titanium metal |journal=Journal of Alloys and Compounds |volume=186 |issue=2 |pages=293–307 |doi=10.1016/0925-8388(92)90016-3}}</ref>
| CrystalStruct = [[Face-centered cubic]] (FCC), [[Pearson symbol|cF8]]
| SpaceGroup = Fm<u style="text-decoration:overline">3</u>m, No. 225
| Coordination = Octahedral 
| LattConst_a = 0.4241 nm
| UnitCellFormulas =4
}}
| Section4 = {{Chembox Thermochemistry
| Thermochemistry_ref =
| HeatCapacity = 24 J/(K·mol) (500 K)<ref name=th2>{{cite journal |last1=Lengauer |first1=W. |last2=Binder |first2=S. |last3=Aigner |first3=K. |last4=Ettmayer |first4=P. |last5=Guillou |first5=A. |last6=de&nbsp;Buigne |first6=J. |last7=Groboth |first7=G. |year=1995 |title=Solid state properties of group IV‑b carbonitrides |journal=Journal of Alloys and Compounds |volume=217 |pages=137–147 |doi=10.1016/0925-8388(94)01315-9}}</ref>
| Entropy = −95.7 J/(K·mol)<ref name=th1>{{cite journal |last=Wang |first=Wei-E |year=1996 |title=Partial thermodynamic properties of the Ti-N system |journal=Journal of Alloys and Compounds |volume=233 |issue=1–2 |pages=89–95 |doi=10.1016/0925-8388(96)80039-9}}</ref>
| DeltaHform = −336 kJ/mol<ref name=th1/>
| DeltaGfree = 
| DeltaHcombust =
| DeltaHfus =
| DeltaHvap =
| DeltaHsublim =
| HHV =
| LHV =
 }}
| Section8 = {{Chembox Related
| OtherFunction = [[Titanium aluminum nitride]]
| OtherFunction_label = coating
}}
}}
'''Titanium nitride''' ('''TiN'''; sometimes known as '''tinite''') is an extremely hard [[ceramic]] material, often used as a [[physical vapor deposition]] (PVD) coating on [[titanium alloy]]s, [[steel]], [[carbide]], and [[aluminium]] components to improve the substrate's surface properties.

Applied as a thin coating, TiN is used to harden and protect cutting and sliding surfaces, for decorative purposes (for its golden appearance), and as a non-toxic exterior for [[implant (medicine)|medical implants]]. In most applications a coating of less than {{nowrap| {{convert|5|um|in}} }} is applied.<ref>{{Cite web |title=TiN (Titanium Nitride) – Surface Coating |url=http://www.surftech.com.au/coating-types/tin/ |access-date=2024-02-17 |language=en-US}}</ref>

==Characteristics==
TiN has a [[Vickers hardness]] of 1800–2100, hardness of {{val|31|4|u=GPa}},<ref name=":0" /> a [[modulus of elasticity]] of {{val|550|50|u=GPa}},<ref name=":0" /> a [[thermal expansion coefficient]] of 9.35{{e|-6}}&nbsp;K<sup>−1</sup>, and a superconducting transition temperature of 5.6&nbsp;K.<ref name=prop>{{cite book |editor-first=Hugh O. |editor-last=Pierson |year=1996 |title=Handbook of Refractory Carbides and Nitrides: Properties, characteristics, processing, and applications |publisher=William Andrew |isbn=978-0-8155-1392-6 |page=193 |via=Google Books |url=https://books.google.com/books?id=pbt-RWodmVAC&pg=PA193}}</ref><ref name=":0">{{cite journal |doi=10.1116/1.577270 |first1=D. S. |last1=Stone |first2=K. B. |last2=Yoder |first3=W. D. |last3=Sproul |year=1991 |title=Hardness and elastic modulus of TiN based on continuous indentation technique and new correlation |journal=Journal of Vacuum Science and Technology A |volume=9 |issue=4 |pages=2543–2547 |bibcode=1991JVSTA...9.2543S |doi-access=free }}</ref>

TiN oxidizes at 800&nbsp;°C in a normal atmosphere. It is chemically stable at 20&nbsp;°C, according to laboratory tests, but can be slowly attacked by concentrated acid solutions with rising temperatures.<ref name=prop/> TiN has a brown color and appears gold when applied as a coating. Depending on the substrate material and surface finish, TiN has a [[coefficient of friction]] ranging from 0.4 to 0.9 against another TiN surface (non-lubricated). The typical TiN formation has a [[crystal structure]] of [[Rock-salt structure|NaCl type]] with a roughly 1:1 [[stoichiometry]]; TiN<sub>''x''</sub> compounds with ''x'' ranging from 0.6 to 1.2 are, however, thermodynamically stable.<ref>{{cite book |first=L. E. |last=Toth |year=1971 |title=Transition Metal Carbides and Nitrides |publisher=Academic Press |location=New York, NY |isbn=978-0-12-695950-5}}</ref>

TiN becomes [[superconductivity|superconducting]] at cryogenic temperatures, with critical temperature up to 6.0&nbsp;K for single crystals.<ref>{{cite journal |last1=Spengler |first1=W. |display-authors=etal |year=1978 |title=Raman scattering, superconductivity, and phonon density of states of stoichiometric and nonstoichiometric TiN |journal=Physical Review B |volume=17 |issue=3 |pages=1095–1101 |doi=10.1103/PhysRevB.17.1095 |bibcode=1978PhRvB..17.1095S}}</ref> Superconductivity in thin-film TiN has been studied extensively, with the superconducting properties strongly varying depending on sample preparation, up to complete suppression of superconductivity at a [[superconductor–insulator transition]].<ref>{{cite journal |last1=Baturina |first1=T. I. |display-authors=etal |year=2007 |title=Localized superconductivity in the quantum-critical region of the disorder-driven superconductor-insulator transition in TiN thin films |journal=Physical Review Letters |volume=99 |issue=25 |pages=257003 |pmid=18233550 |arxiv=0705.1602 |doi=10.1103/PhysRevLett.99.257003 |bibcode=2007PhRvL..99y7003B |s2cid=518088}}</ref> A thin film of TiN was chilled to near [[absolute zero]], converting it into the first known [[superinsulator]], with resistance suddenly increasing by a factor of 100,000.<ref>{{cite news |title=Newly discovered 'superinsulators' promise to transform materials research, electronics design |date=2008-04-07 |website=PhysOrg.com |url=http://www.physorg.com/news126797387.html}}</ref>

==Natural occurrence==<!--Osbornite redirects here-->
[[Osbornite]] is a very rare natural form of titanium nitride, found almost exclusively in meteorites.<ref>{{cite web |title=Osbornite |publisher=Hudson Institute of Mineralogy |website=Mindat.org |url=http://www.mindat.org/min-3035.html |access-date=Feb 29, 2016}}</ref><ref>{{cite web |title=Osbornite mineral data |date=Sep 5, 2012 |website=Mineralogy Database |publisher=David Barthelmy |url=http://webmineral.com/data/Osbornite.shtml#.V_cFauArJaQ |access-date=Oct 6, 2015}}</ref>

==Uses==
{{Multiple image|total_width=160 |align=left |image1=Titanium nitride coating.jpg |caption1=TiN-coated drill bit |image2=Paraframe.jpg |caption2=Dark gray TiCN coating on a [[Gerber Legendary Blades|Gerber]] pocketknife}}
A well-known use for TiN coating is for edge retention and corrosion resistance on machine tooling, such as [[drill bit]]s and [[milling cutter]]s, often improving their lifetime by a factor of three or more.<ref>{{cite web |title=Titanium Nitride (TiN) Coating |date=June 2014 |publisher=Surface Solutions |url=http://www.tincoat.net/TiN.html
}}</ref>

Because of the metallic gold color of TiN, this material is used to coat [[costume jewelry]] and automotive trim for decorative purposes. TiN is also widely used as a top-layer coating, usually with [[nickel]]- or [[chromium]]-plated substrates, on consumer plumbing fixtures and door hardware. As a coating, it is used in [[aerospace]] and military applications and to protect the sliding surfaces of [[suspension (vehicle)|suspension]] forks of [[bicycle]]s and [[motorcycle]]s, as well as the shock shafts of [[radio-controlled car]]s. TiN is also used as a protective coating on the moving parts of many rifles and semi-automatic firearms, as it is extremely durable. As well as being durable, it is also extremely smooth, making removing the carbon build-up extremely easy. TiN is non-toxic, meets [[Food and Drug Administration|FDA]] guidelines,<ref>{{cite web |url=https://www.accessdata.fda.gov/cdrh_docs/pdf2/k022795.pdf |title=Titanium-Nitride Coating Special |website=Food and Drug Administration |date=Aug 21, 2002 |access-date=Sep 22, 2024}}</ref> and has seen use in [[medical device]]s such as [[scalpel]] blades and orthopedic [[Bone cutter|bone-saw]] blades, where sharpness and edge retention are important.<ref>{{cite web |url=https://www.sputtertargets.net/blog/titanium-nitride-overview-properties-production-and-uses.html |title=Titanium Nitride Overview: Properties, Production, and Uses |last=Green |first=Julissa |date=Feb 23, 2024 |website=Sputter Targets |access-date=Sep 22, 2024}}</ref> TiN coatings have also been used in implanted [[prosthesis|prostheses]] (especially [[hip replacement]] implants) and other medical implants.

Though less visible, [[thin film]]s of TiN are also used in [[microelectronics]], where they serve as a [[electrical conductivity|conductive]] connection between the active device and the metal contacts used to operate the circuit, while acting as a [[diffusion barrier]] to block the [[diffusion]] of the metal into the silicon. In this context, TiN is classified as a "barrier metal" (electrical resistivity ~ 25&nbsp;μΩ·cm<ref name=th2/>), even though it is clearly a [[ceramic]] from the perspective of [[chemistry]] or mechanical behavior. Recent chip design in the 45&nbsp;nm technology and beyond also makes use of TiN as a "metal" for improved [[transistor]] performance. In combination with [[gate dielectric]]s (e.g. [[Hafnium(IV) silicate|HfSiO<sub>4</sub>]]) that have a higher [[permittivity]] compared to standard [[Silicon dioxide|SiO<sub>2</sub>]], the gate length can be scaled down with low [[Subthreshold leakage|leakage]], higher drive current and the same or better [[threshold voltage]].<ref>{{cite journal |first1=Thaddeus G. |last1=Dziura |first2=Benjamin |last2=Bunday |first3=Casey |last3=Smith |first4=Muhammad M. |last4=Hussain |first5=Rusty |last5=Harris |first6=Xiafang |last6=Zhang |first7=Jimmy M. |last7=Price |year=2008 |title=Measurement of high-''k'' and metal film thickness on FinFET sidewalls using scatterometry |journal=Proceedings of SPIE |volume=6922 |issue=2 |page=69220V |doi=10.1117/12.773593 |series=Metrology, Inspection, and Process Control for Microlithography XXII |bibcode=2008SPIE.6922E..0VD |s2cid=120728898}}</ref> Additionally, TiN thin films are currently under consideration for coating [[zirconium alloy]]s for accident-tolerant nuclear fuels.<ref>{{Cite journal |last1=Tunes |first1=Matheus A. |last2=da&nbsp;Silva |first2=Felipe C. |last3=Camara |first3=Osmane |last4=Schön |first4=Claudio G. |last5=Sagás |first5=Julio C. |last6=Fontana |first6=Luis C. |last7=Donnelly |first7=Stephen E. |last8=Greaves |first8=Graeme |last9=Edmondson |first9=Philip D. |display-authors=6 |date=December 2018 |title=Energetic particle irradiation study of TiN coatings: are these films appropriate for accident tolerant fuels? |journal=Journal of Nuclear Materials |volume=512 |pages=239–245 |doi=10.1016/j.jnucmat.2018.10.013 |bibcode=2018JNuM..512..239T |url=https://pure.hud.ac.uk/ws/files/14781227/preprint_TiN.pdf}}</ref><ref>{{Cite journal |last1=Alat |first1=Ece |last2=Motta |first2=Arthur T. |last3=Comstock |first3=Robert J. |last4=Partezana |first4=Jonna M. |last5=Wolfe |first5=Douglas E. |date=September 2016 |title=Multilayer (TiN, TiAlN) ceramic coatings for nuclear fuel cladding |journal=Journal of Nuclear Materials |volume=478 |pages=236–244 |doi=10.1016/j.jnucmat.2016.05.021 |doi-access=free |bibcode=2016JNuM..478..236A}}</ref> It is also used as a coating on some [[compression driver]] diaphragms to improve performance. 

Owing to their high biostability, TiN layers may also be used as electrodes in [[bioelectronics|bioelectronic applications]]<ref name= SCT2010>{{cite journal | last1 = Birkholz | first1 = M. | last2 = Ehwald | first2 = K.-E. | last3 = Wolansky | first3 = D. | last4 = Costina | first4 = I. | last5 = Baristiran-Kaynak | first5 = C. | last6 = Fröhlich | first6 = M. | last7 = Beyer | first7 = H. | last8 = Kapp | first8 = A. | last9 = Lisdat | first9 = F. |display-authors=6 | year = 2010 | title = Corrosion-resistant metal layers from a CMOS process for bioelectronic applications | journal = Surf. Coat. Technol. | volume = 204 | issue = 12–13 | pages = 2055–2059 | doi = 10.1016/j.surfcoat.2009.09.075 | url = https://www.researchgate.net/publication/230817001}}</ref> like in intelligent [[implant (medicine)|implants]] or in-vivo [[biosensors]] that have to withstand the severe corrosion caused by [[body fluid]]s. TiN electrodes have already been applied in the [[visual prosthesis|subretinal prosthesis project]]<ref name= Haem2002>{{cite journal | last1 = Hämmerle | first1 = Hugo | last2 = Kobuch | first2 = Karin | last3 = Kohler | first3 = Konrad | last4 = Nisch | first4 = Wilfried | last5 = Sachs | first5 = Helmut | last6 = Stelzle | first6 = Martin | year = 2002 | title = Biostability of micro-photodiode arrays for subretinal implantation | journal = Biomaterials | volume = 23 | issue = 3 | pages = 797–804 | doi = 10.1016/S0142-9612(01)00185-5 | pmid = 11771699}}</ref> as well as in biomedical microelectromechanical systems ([[BioMEMS]]).<ref name= AdFM2011>{{cite journal | last1 = Birkholz | first1 = M. | last2 = Ehwald | first2 = K.-E. | last3 = Kulse | first3 = P. | last4 = Drews | first4 = J. | last5 = Fröhlich | first5 = M. | last6 = Haak | first6 = U. | last7 = Kaynak | first7 = M. | last8 = Matthus | first8 = E. | last9 = Schulz | first9 = K. | last10 = Wolansky | first10 = D. |display-authors=6 | year = 2011 | title = Ultrathin TiN membranes as a technology platform for CMOS-integrated MEMS and BioMEMS devices | journal = Advanced Functional Materials | volume = 21 | issue = 9 | pages = 1652–1654 | doi = 10.1002/adfm.201002062 | doi-access = free }}</ref>

==Fabrication==
[[File:TiNCoatedPunches NanoShieldPVD Thailand.JPG|thumb|right|Punches TiN-coated using cathodic arc deposition technique]]

The most common methods of TiN thin film creation are [[physical vapor deposition]] (PVD, usually [[sputter deposition]], [[cathodic arc deposition]] or [[Electron-beam physical vapor deposition|electron-beam heating]]) and [[chemical vapor deposition]] (CVD).<ref>{{cite web |url=http://www.diffusion-alloys.com/our-services/wear-coatings-for-industrial-products/ |title=Wear coatings for industrial products |publisher=Diffusion Alloys |access-date=2013-06-14 |url-status=dead |archive-url=https://web.archive.org/web/20130519024447/http://www.diffusion-alloys.com/our-services/wear-coatings-for-industrial-products/ |archive-date=2013-05-19}}</ref> In both methods, pure titanium is [[Sublimation (chemistry)|sublimed]] and reacted with nitrogen in a high-energy, [[vacuum]] environment. TiN film may also be produced on Ti workpieces by reactive growth (for example, [[Annealing (metallurgy)|annealing]]) in a [[nitrogen]] atmosphere. PVD is preferred for steel parts because the deposition temperatures exceeds the [[Austenite|austenitizing]] temperature of steel. TiN layers are also sputtered on a variety of higher-melting-point materials such as [[stainless steel]]s, [[titanium]] and [[titanium alloy]]s.<ref>{{cite web |title=Coatings |publisher=Coating Services Group |url=http://coatingservicesgroup.com/coatings |access-date=2009-06-25}}</ref> Its high [[Young's modulus]] (values between 450 and 590&nbsp;[[gigapascal|GPa]] have been reported in the literature<ref name= SCT2008>{{cite journal | last = Abadias | first = G. | year = 2008 | title = Stress and preferred orientation in nitride based PVD coatings | journal = Surf. Coat. Technol. | volume = 202 | issue = 11 | pages = 2223–2235 | doi = 10.1016/j.surfcoat.2007.08.029}}</ref>) means that thick coatings tend to flake away, making them much less durable than thin ones. Titanium-nitride coatings can also be deposited by [[thermal spraying]] whereas TiN powders are produced by nitridation of titanium with nitrogen or ammonia at 1200&nbsp;°C.<ref name=prop/>

Bulk ceramic objects can be fabricated by packing powdered metallic titanium into the desired shape, compressing it to the proper density, then igniting it in an atmosphere of pure nitrogen. The heat released by the chemical reaction between the metal and gas is sufficient to [[sintering|sinter]] the nitride reaction product into a hard, finished item. See [[powder metallurgy]].

==Other commercial variants==
[[File:Smith&Wesson CKLPR.jpg|thumb|right|A knife with a titanium oxynitride coating]]

There are several commercially used variants of TiN that have been developed since 2010, such as titanium carbon nitride (TiCN), [[titanium aluminium nitride]] (TiAlN or AlTiN), and titanium aluminum carbon nitride, which may be used individually or in alternating layers with TiN. These coatings offer similar or superior enhancements in corrosion resistance and hardness, and additional colors ranging from light gray to nearly black, to a dark, [[Iridescence|iridescent]], bluish-purple, depending on the exact process of application. These coatings are becoming common on sporting goods, particularly [[knife|knives]] and [[handgun]]s, where they are used for both aesthetic and functional reasons.

==As a constituent in steel==
Titanium nitride is also produced intentionally, within some steels, by judicious addition of titanium to the [[alloy]]. TiN forms at very high temperatures because of its very low [[Standard enthalpy change of formation|enthalpy of formation]], and even [[Nucleation|nucleates]] directly from the melt in secondary steel-making. It forms discrete, micrometre-sized [[Cubic crystal system|cubic]] particles at [[Grain boundary|grain boundaries]] and triple points, and prevents [[grain growth]] by [[Ostwald ripening]] up to very high [[homologous temperature]]s. Titanium nitride has the lowest [[Solubility equilibrium|solubility product]] of any metal nitride or carbide in austenite, a useful attribute in [[microalloyed steel]] formulas.

==References==
{{reflist|25em}}

{{Titanium compounds}}
{{Nitrides}}
{{Authority control}}

[[Category:Nitrides]]
[[Category:Titanium(III) compounds]]
[[Category:Semiconductor device fabrication]]
[[Category:Superhard materials]]
[[Category:Rock salt crystal structure]]
[[Category:Coatings]]