View source for Chemistry:Titanium

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{{Infobox titanium}}

'''Titanium''' is a [[Chemistry:Chemical element|chemical element]]; it has [[Chemistry:Symbol|symbol]] '''Ti''' and [[Physics:Atomic number|atomic number]] 22. Found in nature only as an [[Chemistry:Oxide|oxide]], it can be reduced to produce a lustrous [[Chemistry:Transition metal|transition metal]] with a silver [[Color|color]], low [[Physics:Density|density]], and high strength, resistant to [[Chemistry:Corrosion|corrosion]] in sea water, [[Chemistry:Aqua regia|aqua regia]], and [[Chemistry:Chlorine|chlorine]].

Titanium was discovered in [[History:Cornwall|Cornwall]], [[Place:Kingdom of Great Britain|Great Britain]], by [[Biography:William Gregor|William Gregor]] in 1791 and was named by [[Biography:Martin Heinrich Klaproth|Martin Heinrich Klaproth]] after the Titans of [[Religion:Greek mythology|Greek mythology]]. The element occurs within a number of [[Earth:Mineral|mineral]]s, principally [[Chemistry:Rutile|rutile]] and [[Chemistry:Ilmenite|ilmenite]], which are widely distributed in the [[Earth:Earth's crust|Earth's crust]] and [[Earth:Lithosphere|lithosphere]]; it is found in almost all living things, as well as bodies of water, rocks, and soils.<ref name="EBC" /> The metal is extracted from its principal mineral ores by the [[Chemistry:Kroll process|Kroll]] and [[Chemistry:Hunter process|Hunter]] processes.<ref name="LANL" /> The most common compound, [[Chemistry:Titanium dioxide|titanium dioxide]], is a popular [[Physics:Photocatalysis|photocatalyst]] and is used in the manufacture of white pigments.<ref name="HistoryAndUse">{{cite book|last=Krebs|first=Robert E.|title=The History and Use of Our Earth's Chemical Elements: A Reference Guide|edition=2nd|publisher=Greenwood Press|location=Westport, CT|isbn=978-0-313-33438-2|year=2006|url=https://books.google.com/books?id=yb9xTj72vNAC}}</ref> Other compounds include [[Chemistry:Titanium tetrachloride|titanium tetrachloride]] (TiCl<sub>4</sub>), a component of smoke screens and [[Chemistry:Catalyst|catalyst]]s; and [[Chemistry:Titanium(III) chloride|titanium trichloride]] (TiCl<sub>3</sub>), which is used as a catalyst in the production of [[Chemistry:Polypropylene|polypropylene]].<ref name="EBC" />

Titanium can be [[Chemistry:Alloy|alloy]]ed with [[Chemistry:Iron|iron]], [[Chemistry:Aluminium|aluminium]], [[Chemistry:Vanadium|vanadium]], and [[Chemistry:Molybdenum|molybdenum]], among other elements, to produce strong, lightweight alloys for aerospace ([[Engineering:Jet engine|jet engine]]s, [[Engineering:Missile|missile]]s, and [[Engineering:Spacecraft|spacecraft]]), military, industrial processes (chemicals and petrochemicals, desalination plants, [[Chemistry:Pulp (paper)|pulp]], and [[Chemistry:Paper|paper]]), automotive, [[Earth:Agriculture|agriculture]] (farming), medical prostheses, orthopedic [[Medicine:Implant|implants]], dental and endodontic instruments and files, [[Engineering:Dental implant|dental implant]]s, sporting goods, jewelry, [[Engineering:Mobile phone|mobile phone]]s, and other applications.<ref name="EBC" />

The two most useful properties of the metal are corrosion resistance and [[Engineering:Specific strength|strength-to-density ratio]], the highest of any metallic element.<ref>{{harvnb|Donachie|1988|p=11}}</ref> In its unalloyed condition, titanium is as strong as some steels, but less dense.<ref name="Barksdale1968p738">{{harvnb|Barksdale|1968|p=738}}</ref> There are two [[Physics:Allotropy|allotropic]] forms<ref name="TICE6th" /> and five naturally occurring [[Physics:Isotope|isotope]]s of this element, [[Physics:Isotopes of titanium|{{sup|46}}Ti]] through {{sup|50}}Ti, with {{sup|48}}Ti being the most [[Chemistry:Natural abundance|abundant]] (73.8%).<ref name="EnvChem">{{cite web |url=http://environmentalchemistry.com/yogi/periodic/Ti-pg2.html#Nuclides |title=Periodic Table of Elements: Ti – Titanium |access-date=26 December 2006 |author=Barbalace, Kenneth L. |year=2006}}</ref>

==Characteristics==

===Physical properties===
<section begin=properties/>
As a [[Chemistry:Metal|metal]], titanium is recognized for its high strength-to-weight ratio.<ref name=TICE6th>{{cite encyclopedia |title=Titanium |encyclopedia=[[Columbia Encyclopedia]] |edition=6th |date=2000–2006 |publisher=Columbia University Press |url=https://archive.org/details/columbiaencyclop00laga |location=New York |isbn=978-0-7876-5015-5 |url-access=registration }}</ref> It is a strong metal with low [[Physics:Density|density]] that is quite [[Physics:Ductility|ductile]] (especially in an [[Chemistry:Oxygen|oxygen]]-free environment),<ref name="EBC">{{cite encyclopedia|encyclopedia=Encyclopædia Britannica|title=Titanium|year=2006|url=http://www.britannica.com/eb/article-9072643/titanium|access-date=19 January 2022}}</ref> lustrous, and metallic-white in [[Color|color]].<ref name="Stwertka1998">{{cite book|title=Guide to the Elements|edition=Revised|first=Albert|last=Stwertka|publisher=[[Organization:Oxford University Press|Oxford University Press]]|year=1998|chapter=Titanium|pages= 81–82|isbn=978-0-19-508083-4|chapter-url=https://books.google.com/books?id=K3RWAAAAYAAJ}}</ref> The relatively high melting point (1,668&nbsp;°C or 3,034&nbsp;°F) makes it useful as a [[Chemistry:Refractory metals|refractory metal]]. It is [[Physics:Paramagnetism|paramagnetic]] and has fairly low [[Physics:Electrical conductivity|electrical]] and [[Physics:Thermal conductivity|thermal conductivity]] compared to other metals.<ref name="EBC" /> Titanium is [[Physics:Superconductivity|superconducting]] when cooled below its critical temperature of 0.49&nbsp;K.<ref>{{Cite journal | doi = 10.1103/PhysRev.92.243| journal = Phys. Rev.| volume = 92| issue = 2| pages = 243–247| year = 1953| title = Superconductivity of Titanium| last1 = Steele | first1 = M. C. | last2 = Hein | first2 = R. A.| bibcode = 1953PhRv...92..243S}}</ref><ref>{{Cite journal | doi = 10.1103/PhysRevB.97.214516| journal = Phys. Rev. B| volume = 97| issue = 21| page = 214516| year = 2018| title = Complete electrodynamics of a BCS superconductor with μeV energy scales: Microwave spectroscopy on titanium at mK temperatures| last1 = Thiemann | first1 = M. |display-authors=0| arxiv = 1803.02736| bibcode = 2018PhRvB..97u4516T| s2cid = 54891002}}</ref><section end=properties/>

{{anchor|Commercially pure titanium}}
Commercially pure (99.2% pure) [[Chemistry:Titanium alloy#Grades of titanium|grades]] of titanium have [[Physics:Ultimate tensile strength|ultimate tensile strength]] of about 434&nbsp;MPa (63,000&nbsp;[[Pounds per square inch|psi]]), equal to that of common, low-grade steel alloys, but are less dense. Titanium is 60% denser than aluminium, but more than twice as strong<ref name=Barksdale1968p738/> as the most commonly used [[Chemistry:6061 aluminium alloy|6061-T6 aluminium alloy]]. Certain titanium alloys (e.g., [[Chemistry:Titanium Beta C|Beta C]]) achieve tensile strengths of over 1,400&nbsp;MPa (200,000&nbsp;psi).<ref>{{harvnb|Donachie|1988|loc=Appendix J, Table J.2}}</ref> However, titanium loses strength when heated above {{convert|430|°C|°F}}.<ref name="Barksdale1968p734">{{harvnb|Barksdale|1968|p=734}}</ref>

Titanium is not as hard as some grades of heat-treated steel; it is non-magnetic and a poor conductor of heat and electricity. Machining requires precautions, because the material can [[Physics:Galling|gall]] unless sharp tools and proper cooling methods are used. Like steel structures, those made from titanium have a [[Physics:Fatigue limit|fatigue limit]] that guarantees longevity in some applications.<ref name="Stwertka1998" />

The metal is a dimorphic [[Physics:Allotropy|allotrope]] of an hexagonal α form that changes into a body-centered cubic (lattice) β form at {{convert|882|°C|°F}}.<ref name="Barksdale1968p734" /> The [[Physics:Specific heat capacity|specific heat]] of the α form increases dramatically as it is heated to this transition temperature but then falls and remains fairly constant for the β form regardless of temperature.<ref name="Barksdale1968p734" />

===Chemical properties===
[[File:Titanium in water Pourbaix diagram.png|thumb|[[Chemistry:Pourbaix diagram|Pourbaix diagram]] for titanium in pure water, perchloric acid, or sodium hydroxide<ref name="medusa">Puigdomenech, Ignasi (2004) [https://web.archive.org/web/20130605034847/http://www.kth.se/che/medusa ''Hydra/Medusa Chemical Equilibrium Database and Plotting Software''], KTH Royal Institute of Technology.</ref>]]
Like [[Chemistry:Aluminium|aluminium]] and [[Chemistry:Magnesium|magnesium]], the surface of titanium metal and its alloys oxidize immediately upon exposure to air to form a thin non-porous [[Engineering:Passivation|passivation]] layer that protects the bulk metal from further oxidation or corrosion.<ref name="EBC" /> When it first forms, this protective layer is only 1–2&nbsp;[[Nanometre|nm]] thick but it continues to grow slowly, reaching a thickness of 25&nbsp;nm in four years.<ref name="Emsley2001p453" /> This layer gives titanium excellent resistance to corrosion against oxidizing acids, but it will dissolve in dilute hydrofluoric acid, hot hydrochloric acid, and hot sulfuric acid.

Titanium is capable of withstanding attack by dilute [[Chemistry:Sulfuric acid|sulfuric]] and [[Chemistry:Hydrochloric acid|hydrochloric acid]]s at room temperature, chloride solutions, and most organic acids.<ref name=LANL/> However, titanium is corroded by concentrated acids.<ref>{{cite journal |author1=Casillas, N. |author2=Charlebois, S. |author3=Smyrl, W.H. |author4=White, H.S. |year=1994 |title=Pitting corrosion of titanium |journal=J. Electrochem. Soc. |volume=141 |issue=3 |pages=636–642 |doi=10.1149/1.2054783 |bibcode=1994JElS..141..636C |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/a274980.pdf |url-status=live |archive-url=https://web.archive.org/web/20200827231129/https://apps.dtic.mil/dtic/tr/fulltext/u2/a274980.pdf |archive-date=27 August 2020}}</ref> Titanium is a very reactive metal that burns in normal air at lower temperatures than the melting point. Melting is possible only in an inert atmosphere or vacuum. At {{convert|550|°C|°F}}, it combines with chlorine.<ref name=LANL/> It also reacts with the other halogens and absorbs hydrogen.<ref name=HistoryAndUse/>

Titanium readily reacts with oxygen at {{convert|1200|°C|°F}} in air, and at {{convert|610|°C|°F}} in pure oxygen, forming [[Chemistry:Titanium dioxide|titanium dioxide]].<ref name="TICE6th" /> Titanium is one of the few elements that burns in pure nitrogen gas, reacting at {{convert|800|°C|°F}} to form [[Chemistry:Titanium nitride|titanium nitride]], which causes embrittlement.<ref name=titaniumindustry>{{cite book |title=Industrial Applications of Titanium and Zirconium|chapter-url= https://books.google.com/books?id=0Adr4zleybgC&pg=PA112 |page= 112|first= A.L. |last= Forrest |chapter= Effects of Metal Chemistry on Behavior of Titanium in Industrial Applications |year=1981}}</ref> Because of its high reactivity with oxygen, nitrogen, and many other gases, titanium that is evaporated from filaments is the basis for titanium sublimation pumps, in which titanium serves as a scavenger for these gases by chemically binding to them. Such pumps inexpensively produce extremely low pressures in [[Physics:Ultra-high vacuum|ultra-high vacuum]] systems.

===Occurrence===
Titanium is the ninth-most [[Earth:Abundance of elements in Earth's crust|abundant]] element in [[Astronomy:Earth|Earth]]'s crust (0.63% by [[Physics:Mass|mass]])<ref name="Barksdale1968p732" /> and the seventh-most abundant metal. It is present as oxides in most [[Earth:Igneous rock|igneous rock]]s, in [[Earth:Sedimentary rock|sediments]] derived from them, in living things, and natural bodies of water.<ref name="EBC" /><ref name="LANL">{{RubberBible86th}}</ref> Of the 801 types of igneous rocks analyzed by the United States Geological Survey, 784 contained titanium. Its proportion in soils is approximately 0.5–1.5%.<ref name="Barksdale1968p732" />

Common titanium-containing [[Earth:Mineral|mineral]]s are [[Chemistry:Anatase|anatase]], [[Chemistry:Brookite|brookite]], [[Chemistry:Ilmenite|ilmenite]], [[Chemistry:Perovskite|perovskite]], [[Chemistry:Rutile|rutile]], and [[Chemistry:Titanite|titanite]] (sphene).<ref name="Emsley2001p453">{{harvnb|Emsley|2001|p=453}}</ref> [[Chemistry:Akaogiite|Akaogiite]] is an extremely rare mineral consisting of titanium dioxide. Of these minerals, only rutile and ilmenite have economic importance, yet even they are difficult to find in high concentrations. About 6.0 and 0.7 million tonnes of those minerals were mined in 2011, respectively.<ref name="USGS" /> Significant titanium-bearing ilmenite deposits exist in {{wipe|Australia}}, {{wipe|Canada}}, {{wipe|China}}, {{wipe|India}}, Mozambique, [[Earth:New Zealand|New Zealand]], {{wipe|Norway}}, Sierra Leone, {{wipe|South Africa}}, and {{wipe|Ukraine}}.<ref name="Emsley2001p453" /> About 210,000 tonnes of titanium metal sponge were produced in 2020, mostly in China (110,000 t), Japan (50,000 t), Russia (33,000 t) and Kazakhstan (15,000 t). Total reserves of anatase, ilmenite, and rutile are estimated to exceed 2 billion tonnes.<ref name="USGS" />

{|class="wikitable floatleft"
|+ 2017 production of titanium minerals and slag<ref name="USGS" />
! Country !! thousand <br />tonnes !! % of total
|-
|{{wipe|China}}||3,830||33.1
|-
|{{wipe|Australia}}||1,513||13.1
|-
|Mozambique||1,070||9.3
|-
|{{wipe|Canada}}||1,030||8.9
|-
|{{wipe|South Africa}}||743||6.4
|-
|Kenya||562||4.9
|-
|{{wipe|India}}||510||4.4
|-
|Senegal||502||4.3
|-
|{{wipe|Ukraine}}||492||4.3
|-
|'''World'''||'''11,563'''||'''100'''
|}

The concentration of titanium is about 4 [[Physics:Molar concentration|picomolar]] in the ocean. At 100&nbsp;°C, the concentration of titanium in water is estimated to be less than 10<sup>−7</sup> M at pH 7. The identity of titanium species in aqueous solution remains unknown because of its low solubility and the lack of sensitive spectroscopic methods, although only the 4+ oxidation state is stable in air. No evidence exists for a biological role, although rare organisms are known to accumulate high concentrations of titanium.<ref>{{cite journal |doi= 10.1021/cr1002886 |pmid= 22074443 |title= Bioinorganic Chemistry of Titanium |journal= Chemical Reviews |volume= 112 |issue= 3 |pages= 1863–81 |year= 2012 |last1= Buettner |first1= K. M. |last2= Valentine |first2= A. M.}}</ref>

Titanium is contained in [[Astronomy:Meteorite|meteorite]]s, and it has been detected in the [[Astronomy:Sun|Sun]] and in [[Astronomy:Stellar classification|M-type]] [[Astronomy:Star|star]]s<ref name="LANL" /> (the coolest type) with a surface temperature of {{convert|3200|°C|°F}}.<ref name="Emsley2001p451">{{harvnb|Emsley|2001|p=451}}</ref> [[Earth:Rock (geology)|Rocks]] brought back from the [[Astronomy:Moon|Moon]] during the [[Engineering:Apollo 17|Apollo 17]] mission are composed of 12.1% TiO<sub>2</sub>.<ref name="LANL" /> Native titanium (pure metallic) is very rare.<ref>[http://www.mindat.org/min-7339.html Titanium]. Mindat</ref>

===Isotopes===
{{Main|Physics:Isotopes of titanium}}
Naturally occurring titanium is composed of five stable [[Physics:Isotope|isotope]]s: <sup>46</sup>Ti, <sup>47</sup>Ti, <sup>48</sup>Ti, <sup>49</sup>Ti, and <sup>50</sup>Ti, with <sup>48</sup>Ti being the most abundant (73.8% [[Chemistry:Natural abundance|natural abundance]]). At least 21 radioisotopes have been characterized, the most stable of which are [[Physics:Titanium-44|<sup>44</sup>Ti]] with a [[Physics:Half-life|half-life]] of 63 years; <sup>45</sup>Ti, 184.8 minutes; <sup>51</sup>Ti, 5.76 minutes; and <sup>52</sup>Ti, 1.7 minutes. All other [[Physics:Radioactive|radioactive]] isotopes have half-lives less than 33 seconds, with the majority less than half a second.<ref name="EnvChem" />

The isotopes of titanium range in [[Physics:Atomic weight|atomic weight]] from 39.002 [[Physics:Unified atomic mass unit|u]] (<sup>39</sup>Ti) to 63.999 u (<sup>64</sup>Ti).{{AME2016 II|ref}} The primary decay mode for isotopes lighter than <sup>46</sup>Ti is [[Physics:Positron emission|positron emission]] (with the exception of <sup>44</sup>Ti which undergoes [[Physics:Electron capture|electron capture]]), leading to [[Physics:Isotopes of scandium|isotopes of scandium]], and the primary mode for isotopes heavier than <sup>50</sup>Ti is [[Physics:Beta emission|beta emission]], leading to [[Physics:Isotopes of vanadium|isotopes of vanadium]].<ref name="EnvChem" />

Titanium becomes radioactive upon bombardment with deuterons, emitting mainly positrons and hard gamma rays.<ref name="LANL" />

==Compounds==
{{Category see also|Titanium compounds|Titanium minerals}}
[[File:Titanium nitride coating.jpg|thumb|upright=0.25|alt=A steel colored twist drill bit with the spiral groove colored in a golden shade.|TiN-coated drill bit]]
The +4 [[Chemistry:Oxidation state|oxidation state]] dominates titanium chemistry,<ref name="Greenwood1997p958">{{harvnb|Greenwood|Earnshaw|1997|p=958}}</ref> but compounds in the +3 oxidation state are also numerous.<ref name="Greenwood1997p970">{{harvnb|Greenwood|Earnshaw|1997|p=970}}</ref> Commonly, titanium adopts an octahedral coordination geometry in its complexes,<ref name="Greenwood1997p960">{{harvnb|Greenwood|Earnshaw|1997|p=960}}</ref><ref name="Greenwood1997p967">{{harvnb|Greenwood|Earnshaw|1997|p=967}}</ref> but tetrahedral TiCl<sub>4</sub> is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of [[Chemistry:Covalent bond|covalent bond]]ing.<ref name="Greenwood1997p958" />

===Oxides, sulfides, and alkoxides===
The most important oxide is TiO<sub>2</sub>, which exists in three important [[Physics:Polymorphism (materials science)|polymorphs]]; anatase, brookite, and rutile. All three are white diamagnetic solids, although mineral samples can appear dark (see [[Chemistry:Rutile|rutile]]). They adopt polymeric structures in which Ti is surrounded by six [[Chemistry:Oxide|oxide]] ligands that link to other Ti centers.<ref name="Greenwood1997p961">{{harvnb|Greenwood|Earnshaw|1997|p=961}}</ref>

The term ''[[Chemistry:Titanate|titanate]]s'' usually refers to titanium(IV) compounds, as represented by [[Chemistry:Barium titanate|barium titanate]] (BaTiO<sub>3</sub>). With a perovskite structure, this material exhibits piezoelectric properties and is used as a transducer in the interconversion of [[Physics:Sound|sound]] and [[Physics:Electricity|electricity]].<ref name="TICE6th" /> Many minerals are titanates, such as ilmenite (FeTiO<sub>3</sub>). Star sapphires and [[Chemistry:Ruby|rubies]] get their asterism (star-forming shine) from the presence of titanium dioxide impurities.<ref name="Emsley2001p453" />

A variety of reduced oxides ([[Chemistry:Suboxide|suboxide]]s) of titanium are known, mainly reduced [[Chemistry:Stoichiometry|stoichiometries]] of titanium dioxide obtained by atmospheric plasma spraying. Ti<sub>3</sub>O<sub>5</sub>, described as a Ti(IV)-Ti(III) species, is a purple semiconductor produced by reduction of TiO<sub>2</sub> with hydrogen at high temperatures,<ref>{{cite journal |last1=Liu |first1=Gang |last2=Huang |first2=Wan-Xia |last3=Yi |first3=Yong |title=Preparation and Optical Storage Properties of λTi<sub>3</sub>O<sub>5</sub> Powder |journal=Journal of Inorganic Materials |date=26 June 2013 |volume=28 |issue=4 |pages=425–430|doi=10.3724/SP.J.1077.2013.12309}}</ref> and is used industrially when surfaces need to be vapor-coated with titanium dioxide: it evaporates as pure TiO, whereas TiO<sub>2</sub> evaporates as a mixture of oxides and deposits coatings with variable refractive index.<ref>{{cite journal |last1=Bonardi |first1=Antonio |last2=Pühlhofer |first2=Gerd |last3=Hermanutz |first3=Stephan |last4=Santangelo |first4=Andrea |year=2014 |title=A new solution for mirror coating in {{mvar|γ}}-ray Cherenkov Astronomy |journal=Experimental Astronomy |volume=38 |issue=1–2 |pages=1–9 |doi=10.1007/s10686-014-9398-x |bibcode=2014ExA....38....1B |s2cid=119213226 |arxiv=1406.0622}}</ref> Also known is [[Chemistry:Titanium(III) oxide|Ti<sub>2</sub>O<sub>3</sub>]], with the [[Chemistry:Corundum|corundum]] structure, and [[Chemistry:Titanium(II) oxide|TiO]], with the rock salt structure, although often nonstoichiometric.{{sfn|Greenwood|Earnshaw|1997|p=962}}

The [[Chemistry:Alkoxide|alkoxide]]s of titanium(IV), prepared by treating TiCl<sub>4</sub> with alcohols, are colorless compounds that convert to the dioxide on reaction with water. They are industrially useful for depositing solid TiO<sub>2</sub> via the sol-gel process. [[Chemistry:Titanium isopropoxide|Titanium isopropoxide]] is used in the synthesis of chiral organic compounds via the [[Chemistry:Sharpless epoxidation|Sharpless epoxidation]].<ref>{{cite journal |author1=Ramón, Diego J. |author2=Yus, Miguel |year=2006 |title=In the arena of enantioselective synthesis, titanium complexes wear the laurel wreath |journal=Chem. Rev. |volume=106 |issue=6 |pages=2126–2308 |doi=10.1021/cr040698p |pmid=16771446}}</ref>

Titanium forms a variety of sulfides, but only [[Chemistry:Titanium disulfide|TiS<sub>2</sub>]] has attracted significant interest. It adopts a layered structure and was used as a cathode in the development of lithium batteries. Because Ti(IV) is a [[Chemistry:HSAB theory|"hard cation"]], the sulfides of titanium are unstable and tend to hydrolyze to the oxide with release of hydrogen sulfide.<ref>{{cite book | last1 = McKelvy | first1 = M.J. | last2 = Glaunsinger | first2 = W.S. | year = 1995 | title = Inorganic Syntheses | chapter = Titanium Disulfide | volume = 30 | pages = 28–32 | doi = 10.1002/9780470132616.ch7 | isbn = 978-0-470-13261-6 }}</ref>

===Nitrides and carbides===
[[Chemistry:Titanium nitride|Titanium nitride]] (TiN) is a refractory solid exhibiting extreme hardness, thermal/electrical conductivity, and a high melting point.<ref>{{Cite journal |last=Saha |first=Naresh |year=1992 |title=Titanium nitride oxidation chemistry: An x-ray photoelectron spectroscopy study |journal=Journal of Applied Physics |volume=72 |issue=7 |pages=3072–3079 |doi=10.1063/1.351465 |bibcode=1992JAP....72.3072S}}</ref> TiN has a hardness equivalent to [[Chemistry:Sapphire|sapphire]] and carborundum (9.0 on the [[Physics:Mohs scale|Mohs scale]]),<ref>{{cite web |author=Schubert, E.F. |title=The hardness scale introduced by Friederich Mohs |series=Educational resources |publisher=[[Organization:Rensselaer Polytechnic Institute|Rensselaer Polytechnic Institute]] |place=Troy, NY |url=https://www.ecse.rpi.edu/~schubert/Educational-resources/Materials-Hardness.pdf |url-status=live |archive-url=https://web.archive.org/web/20100603075632/http://www.rpi.edu/~schubert/Educational-resources/Materials-Hardness.pdf |archive-date=3 June 2010}}</ref> and is often used to coat cutting tools, such as [[Engineering:Drill bit|drill bit]]s.<ref>{{cite magazine |last=Truini |first=Joseph |date=May 1988 |title=Drill bits |magazine=Popular Mechanics |volume=165 |issue=5 |page=91 |issn=0032-4558 |url=https://books.google.com/books?id=Z-QDAAAAMBAJ}}</ref> It is also used as a gold-colored decorative finish and as a [[Engineering:Copper interconnects#Barrier metal|barrier layer]] in semiconductor fabrication.<ref>{{cite book|last=Baliga |first=B. Jayant |year=2005 |title=Silicon carbide power devices |publisher=World Scientific |page=91 |isbn=978-981-256-605-8 |url=https://books.google.com/books?id=LNLVwAzhN7EC}}</ref> [[Chemistry:Titanium carbide|Titanium carbide]] (TiC), which is also very hard, is found in cutting tools and coatings.<ref>{{cite web |title=Titanium carbide product information |publisher=H.C. Starck |url=http://www.hcstarck.com/titanium_carbide_tic  |access-date=16 November 2015 |archive-url=https://web.archive.org/web/20170922194330/https://www.hcstarck.com/titanium_carbide_tic |archive-date=22 September 2017}}</ref>

===Halides===
[[File:TiCl3.jpg|thumb|left|upright=0.4|Titanium(III) compounds are characteristically violet, illustrated by this aqueous solution of titanium trichloride.]]
[[Chemistry:Titanium tetrachloride|Titanium tetrachloride]] (titanium(IV) chloride, TiCl<sub>4</sub><ref>{{cite report |author1=Seong, S. |author2=Younossi, O. |author3=Goldsmith, B.W. |year=2009 |title=Titanium: Industrial base, price trends, and technology initiatives |publisher=Rand Corporation |isbn=978-0-8330-4575-1 |page=10 |url=https://books.google.com/books?id=tIPFfYW304IC&pg=PA10}}</ref>) is a colorless volatile liquid (commercial samples are yellowish) that, in air, hydrolyzes with spectacular emission of white clouds. Via the [[Chemistry:Kroll process|Kroll process]], TiCl<sub>4</sub> is used in the conversion of titanium ores to titanium metal. Titanium tetrachloride is also used to make titanium dioxide, e.g., for use in white paint.<ref>{{cite book |last=Johnson |first=Richard W. |year=1998 |title=The Handbook of Fluid Dynamics |publisher=Springer |pages=38–21 |isbn=978-3-540-64612-9 |url=https://books.google.com/books?id=JBTlucgGdegC}}</ref> It is widely used in [[Chemistry:Organic chemistry|organic chemistry]] as a [[Chemistry:Lewis acids and bases|Lewis acid]], for example in the Mukaiyama aldol condensation.<ref>{{cite book |last=Coates |first=Robert M. |author2=Paquette, Leo A. |year=2000 |title=Handbook of Reagents for Organic Synthesis |publisher=John Wiley and Sons |page=93|isbn=978-0-470-85625-3|url=https://books.google.com/books?id=xxYjJgupBSMC}}</ref> In the [[Physics:Van Arkel–de Boer process|van Arkel–de Boer process]], [[Chemistry:Titanium tetraiodide|titanium tetraiodide]] (TiI<sub>4</sub>) is generated in the production of high purity titanium metal.<ref name="Greenwood1997p965">{{harvnb|Greenwood|Earnshaw|1997|p=965}}</ref>

Titanium(III) and titanium(II) also form stable chlorides. A notable example is [[Chemistry:Titanium(III) chloride|titanium(III) chloride]] (TiCl<sub>3</sub>), which is used as a [[Chemistry:Catalyst|catalyst]] for production of [[Chemistry:Polyolefin|polyolefin]]s (see [[Chemistry:Ziegler–Natta catalyst|Ziegler–Natta catalyst]]) and a reducing [[Biology:Reagent|agent]] in organic chemistry.<ref>{{cite encyclopedia |first1=Lise-Lotte |last1=Gundersen |first2=Frode |last2=Rise |first3=Kjell |last3=Undheim |first4=José |last4=Méndez Andino |year=2007 |title=Titanium(III) Chloride |encyclopedia=[[Chemistry:Encyclopedia of Reagents for Organic Synthesis|Encyclopedia of Reagents for Organic Synthesis]] |doi=10.1002/047084289X.rt120.pub2 |isbn=978-0-471-93623-7 }}</ref>

===Organometallic complexes===
Owing to the important role of titanium compounds as [[Chemistry:Polymerization|polymerization]] catalyst, compounds with Ti-C bonds have been intensively studied. The most common organotitanium complex is [[Chemistry:Titanocene dichloride|titanocene dichloride]] ((C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>TiCl<sub>2</sub>). Related compounds include [[Chemistry:Tebbe's reagent|Tebbe's reagent]] and [[Chemistry:Petasis reagent|Petasis reagent]]. Titanium forms [[Chemistry:Metal carbonyl|carbonyl complexes]], e.g. [[Chemistry:Titanocene dicarbonyl|(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>Ti(CO)<sub>2</sub>]].<ref>{{cite book |author=Hartwig, J.F. |year=2010 |title=Organotransition Metal Chemistry, from Bonding to Catalysis |publisher=University Science Books |place=New York, NY |isbn=978-1-891389-53-5}}</ref>

===Anticancer therapy studies===
Following the success of [[Biology:Cisplatin|platinum-based]] chemotherapy, titanium(IV) complexes were among the first non-platinum compounds to be tested for cancer treatment. The advantage of titanium compounds lies in their high efficacy and low toxicity ''[[Biology:In vivo|in vivo]]''.<ref name=Tshuva-Miller/> In biological environments, hydrolysis leads to the safe and inert titanium dioxide. Despite these advantages the first candidate compounds failed clinical trials due to insufficient efficacy to toxicity ratios and formulation complications.<ref name=Tshuva-Miller/> Further development resulted in the creation of potentially effective, selective, and stable titanium-based drugs.<ref name=Tshuva-Miller>{{cite book |last1=Tshuva |first1=Edit Y. |last2=Miller |first2=Maya |editor1-last=Sigel |editor1-first=Astrid |editor2-last=Sigel |editor2-first=Helmut|editor3-last=Freisinger |editor3-first=Eva |editor4-last=Sigel |editor4-first=Roland K.O. |year=2018 |title=Metallo-drugs: Development and action of anticancer agents |journal=Metal Ions in Life Sciences |volume=18 |doi=10.1515/9783110470734-014 |pmid=29394027 |publisher=de Gruyter GmbH |location=Berlin, DE |chapter=Chapter&nbsp;8. Coordination complexes of titanium(IV) for anticancer therapy |pages=219–250 |isbn=978-3-11-047073-4 |chapter-url=https://books.google.com/books?id=4nBLDwAAQBAJ}}</ref>

==History==
[[File:Martin Heinrich Klaproth.jpg|thumb|upright|alt=Engraved profile image of a mid-age male with high forehead. The person is wearing a coat and a neckerchief.|Martin Heinrich Klaproth named titanium for the Titans of Greek mythology.]]

Titanium was discovered in 1791 by the [[Social:Clergy|clergy]]man and [[Geologist|geologist]] [[Biography:William Gregor|William Gregor]] as an [[Earth:Inclusion (mineral)|inclusion]] of a mineral in [[History:Cornwall|Cornwall]], Great Britain.<ref name=Emsley2001p452/> Gregor recognized the presence of a new element in ilmenite<ref name=HistoryAndUse/> when he found black sand by a stream and noticed the sand was attracted by a [[Physics:Magnet|magnet]].<ref name=Emsley2001p452/> Analyzing the sand, he determined the presence of two metal oxides: [[Chemistry:Iron oxide|iron oxide]] (explaining the attraction to the magnet) and 45.25% of a white metallic oxide he could not identify.<ref name="Barksdale1968p732">{{harvnb|Barksdale|1968|p=732}}</ref> Realizing that the unidentified oxide contained a metal that did not match any known element, in 1791 Gregor reported his findings in both German and French science journals: ''[[Chemistry:Crell's Annalen|Crell's Annalen]]'' and ''Observations et Mémoires sur la Physique''.<ref name=Emsley2001p452/><ref>{{cite journal |author=Gregor, William |year=1791 |title=Beobachtungen und Versuche über den Menakanit, einen in Cornwall gefundenen magnetischen Sand |lang=de |trans-title=Observations and experiments regarding menaccanite [i.e., ilmenite], a magnetic sand found in Cornwall |journal=Chemische Annalen |volume=1 |pages=[https://books.google.com/books?id=ZFAyAQAAMAAJ&pg=PA40 pp. 40–54], [https://books.google.com/books?id=ZFAyAQAAMAAJ&pg=PA103 103–119]}}</ref><ref>{{cite journal |author=Gregor, William |year=1791 |title=Sur le menakanite, espèce de sable attirable par l'aimant, trouvé dans la province de Cornouilles |trans-title=On menaccanite, a species of magnetic sand, found in the county of Cornwall |lang=fr |journal=Observations et Mémoires sur la Physique |volume=39 |pages=[https://archive.org/stream/journaldephysiq23unkngoog#page/n77/mode/1up 72–78], [https://archive.org/stream/journaldephysiq23unkngoog#page/n159/mode/1up 152–160]}}</ref><!-- <ref>{{cite book |url= https://books.google.com/books?id=pqc5AAAAcAAJ&pg=PA40 }}</ref>--> He named this oxide manaccanite.<ref>{{cite journal |last1=Habashi |first1=Fathi |title=Historical Introduction to Refractory Metals |journal=Mineral Processing and Extractive Metallurgy Review |date=January 2001 |volume=22 |issue=1 |pages=25–53 |doi=10.1080/08827509808962488|bibcode=2001MPEMR..22...25H |s2cid=100370649 }}</ref>

Around the same time, [[Biography:Franz-Joseph Müller von Reichenstein|Franz-Joseph Müller von Reichenstein]] produced a similar substance, but could not identify it.<ref name="HistoryAndUse" /> The oxide was independently rediscovered in 1795 by [[Place:Prussia|Prussia]]n chemist [[Biography:Martin Heinrich Klaproth|Martin Heinrich Klaproth]] in rutile from Boinik (the German name of Bajmócska), a village in Hungary (now Bojničky in Slovakia).<ref name="Emsley2001p452" />{{efn|
''"Diesem zufolge will ich den Namen für die gegenwärtige metallische Substanz, gleichergestalt wie bei dem Uranium geschehen, aus der Mythologie, und zwar von den Ursöhnen der Erde, den Titanen, entlehnen, und benenne also diese neue Metallgeschlecht: Titanium;&nbsp;... "''<ref name=Klaproth-1795>{{cite journal |author=Klaproth, Martin Heinrich |year=1795 |url=https://books.google.com/books?id=5zFGAAAAYAAJ&pg=PA233 |title=Chemische Untersuchung des sogenannten hungarischen rothen Schörls |trans-title=Chemical investigation of the so-called Hungarian red tourmaline [rutile] |journal=Beiträge zur chemischen Kenntniss der Mineralkörper [Contributions to the chemical knowledge of mineral substances] |volume=1 |pages=233–244 |place=Berlin, DE |publisher=Heinrich August Rottmann}}</ref>{{rp|style=ama|p= 244}}
:
[By virtue of this I will derive the name for the present metallic substance — as happened similarly in the case of uranium — from mythology, namely from the first sons of the Earth, the Titans, and thus [I] name this new species of metal: "titanium";&nbsp;... ]
}}
Klaproth found that it contained a new element and named it for the Titans of [[Religion:Greek mythology|Greek mythology]].<ref name=Emsley2001p451/> After hearing about Gregor's earlier discovery, he obtained a sample of manaccanite and confirmed that it contained titanium.<ref>{{cite report |title=Twenty-five years of Titanium news: A concise and timely report on titanium and titanium recycling |year=1995 |publisher=Suisman Titanium Corporation |via=[[Organization:Pennsylvania State University|Pennsylvania State University]] / Google Books |page=37 |url=https://books.google.com/books?id=amIQAQAAMAAJ}}</ref>

The currently known processes for extracting titanium from its various ores are laborious and costly; it is not possible to reduce the ore by heating with [[Chemistry:Carbon|carbon]] (as in iron smelting) because titanium combines with the carbon to produce titanium carbide.<ref name=Emsley2001p452/> Pure metallic titanium (99.9%) was first prepared in 1910 by Matthew A. Hunter at [[Organization:Rensselaer Polytechnic Institute|Rensselaer Polytechnic Institute]] by heating TiCl<sub>4</sub> with [[Chemistry:Sodium|sodium]] at {{convert|700-800|°C|°F}} under great pressure<ref name=Roza2008p9>{{harvnb|Roza|2008|p=9}}</ref> in a batch process known as the [[Chemistry:Hunter process|Hunter process]].<ref name=LANL/> Titanium metal was not used outside the laboratory until 1932 when William Justin Kroll produced it by reducing titanium tetrachloride (TiCl<sub>4</sub>) with [[Chemistry:Calcium|calcium]].<ref name=Greenwood1997p955>{{harvnb|Greenwood|Earnshaw|1997|p=955}}</ref> Eight years later he refined this process with magnesium and with sodium in what became known as the Kroll process.<ref name=Greenwood1997p955/> Although research continues to seek cheaper and more efficient routes, such as the [[Chemistry:FFC Cambridge process|FFC Cambridge process]], the Kroll process is still predominantly used for commercial production.<ref name=LANL/><ref name=HistoryAndUse/>

[[File:Titanium metal.jpg|thumb|left|Titanium "sponge", made by the Kroll process]]

Titanium of very high purity was made in small quantities when Anton Eduard van Arkel and Jan Hendrik de Boer discovered the iodide process in 1925, by reacting with iodine and decomposing the formed vapors over a hot filament to pure metal.<ref>{{cite journal |author1=van&nbsp;Arkel, A.E. |author2=de&nbsp;Boer, J.H. |year=1925 |title=Preparation of pure titanium, zirconium, hafnium, and thorium metal |journal=[[Chemistry:Zeitschrift für anorganische und allgemeine Chemie|Zeitschrift für anorganische und allgemeine Chemie]] |volume=148 |pages=345–50 |doi=10.1002/zaac.19251480133}}</ref>

In the 1950s and 1960s, the Soviet Union pioneered the use of titanium in military and submarine applications<ref name=Roza2008p9/> ([[Engineering:Alfa-class submarine|Alfa class]] and Mike class)<ref>{{cite web |last=Yanko |first=Eugene |year=2006 |title=Submarines: General information |publisher=Omsk VTTV Arms Exhibition and Military Parade JSC |url=http://warfare.be/db/catid/243/linkid/1756/ |access-date=2 February 2015 |archive-url=https://web.archive.org/web/20160406114504/http://warfare.be/db/catid/243/linkid/1756/ |archive-date=6 April 2016 }}</ref> as part of programs related to the Cold War.<ref>{{cite news |title=VSMPO stronger than ever |date=July–August 2001 |website=Stainless Steel World |pages=16–19 |publisher=KCI Publishing B.V. |url=http://www.stainless-steel-world.net/pdf/ssw0107.pdf?issueID=30 |access-date=2 January 2007 |archive-date=5 October 2006 |archive-url=https://web.archive.org/web/20061005041506/http://www.stainless-steel-world.net/pdf/ssw0107.pdf?issueID=30  }}</ref> Starting in the early 1950s, titanium came into use extensively in military aviation, particularly in high-performance jets, starting with aircraft such as the F-100 Super Sabre and [[Engineering:Lockheed A-12|Lockheed A-12]] and SR-71.<ref>{{cite book |editor=Jasper, Adam |year=2020 |title=Architecture and Anthropology |isbn=978-1-351-10627-6 |publisher=Taylor & Francis |page=42}}</ref>

Throughout the Cold War period, titanium was considered a [[Social:Strategic material|strategic material]] by the U.S. government, and a large stockpile of titanium [[Chemistry:Metal foam|sponge]] (a porous form of the pure metal) was maintained by the Defense National Stockpile Center, until the stockpile was dispersed in the 2000s.<ref>{{cite report |title=Strategic and Critical Materials Report to the Congress. Operations under the Strategic and Critical Materials Stock Piling Act during the Period October 2007 through September 2008 |year=2008 |publisher=United States Department of Defense |page=3304 |author=Defense National Stockpile Center |url=https://www.dnsc.dla.mil/Uploads/Materials/esolomon_5-21-2009_13-29-4_2008OpsReport.pdf |archive-url=https://web.archive.org/web/20100211093359/https://www.dnsc.dla.mil/Uploads/Materials/esolomon_5-21-2009_13-29-4_2008OpsReport.pdf |archive-date=11 February 2010 }}</ref> As of 2021, the four leading producers of titanium sponge were China (52%), Japan (24%), Russia (16%) and Kazakhstan (7%).<ref name="USGS" />

==Production==
{{Main|Chemistry:Kroll process|Chemistry:Hunter process}}
[[File:TitaniumUSGOV.jpg|thumb|alt=A small heap of uniform black grains smaller than 1mm diameter.|Titanium (mineral concentrate)]]
[[File:Titanium products.jpg|thumb|Basic titanium products: plate, tube, rods, and powder]]

The processing of titanium metal occurs in four major steps: reduction of titanium ore into "sponge", a porous form; melting of sponge, or sponge plus a master alloy to form an ingot; primary fabrication, where an ingot is converted into general mill products such as [[Engineering:Bar stock|billet]], bar, plate, [[Engineering:Sheet metal|sheet]], strip, and [[Engineering:Tube (fluid conveyance)|tube]]; and secondary fabrication of finished shapes from mill products.<ref>{{harvnb|Donachie|1988|loc=Ch. 4}}</ref>

Because it cannot be readily produced by reduction of titanium dioxide,<ref name=Stwertka1998/> titanium metal is obtained by reduction of TiCl<sub>4</sub> with magnesium metal in the Kroll process. The complexity of this batch production in the Kroll process explains the relatively high market value of titanium,<ref name=Barksdale1968p733>{{harvnb|Barksdale|1968|p=733}}</ref> despite the Kroll process being less expensive than the Hunter process.<ref name=Roza2008p9/> To produce the TiCl<sub>4</sub> required by the Kroll process, the dioxide is subjected to carbothermic reduction in the presence of [[Chemistry:Chlorine|chlorine]]. In this process, the chlorine gas is passed over a red-hot mixture of rutile or ilmenite in the presence of carbon.
After extensive purification by [[Fractional distillation|fractional distillation]], the TiCl<sub>4</sub> is reduced with {{convert|800|C}} molten magnesium in an [[Chemistry:Argon|argon]] atmosphere.<ref name=TICE6th/> Titanium metal can be further purified by the van Arkel–de Boer process, which involves thermal decomposition of titanium tetraiodide.
:<chem>2FeTiO3 + 7Cl2 + 6C ->[900^oC] 2FeCl3 + 2TiCl4 + 6CO</chem>
:<chem>TiCl4 + 2Mg ->[1100^oC] Ti + 2MgCl2</chem>

Common [[Chemistry:Titanium alloy|titanium alloy]]s are made by reduction. For example, cuprotitanium (rutile with [[Chemistry:Copper|copper]] added is reduced), ferrocarbon titanium (ilmenite reduced with [[Chemistry:Coke (fuel)|coke]] in an electric furnace), and manganotitanium (rutile with manganese or manganese oxides) are reduced.<ref name=TI_Encarta2005>{{cite encyclopedia |title=Titanium |year=2005 |encyclopedia=Microsoft Encarta |url=http://encarta.msn.com/encyclopedia_761569280/Titanium.html |access-date=29 December 2006  |archive-url= https://web.archive.org/web/20061027112633/http://encarta.msn.com/encyclopedia_761569280/Titanium.html |archive-date=27 October 2006}}</ref>

About fifty grades of [[Chemistry:Titanium alloy|titanium alloy]]s are designed and currently used, although only a couple of dozen are readily available commercially.<ref>{{harvnb|Donachie|1988|p=16, Appendix&nbsp;J}}</ref> The [[Organization:ASTM International|ASTM International]] recognizes 31&nbsp;grades of titanium metal and alloys, of which grades one through four are commercially pure (unalloyed). Those four vary in tensile strength as a function of oxygen content, with grade 1 being the most ductile (lowest tensile strength with an oxygen content of 0.18%), and grade&nbsp;4 the least ductile (highest tensile strength with an oxygen content of 0.40%).<ref name=Emsley2001p453/> The remaining grades are alloys, each designed for specific properties of ductility, strength, hardness, electrical resistivity, [[Physics:Creep (deformation)|creep]] resistance, specific corrosion resistance, and combinations thereof.<ref>{{cite book |title=Annual Book of ASTM Standards |section=Volume&nbsp;02.04: Non-ferrous Metals |year=2006 |publisher=[[Organization:ASTM International|ASTM International]] |location=West Conshohocken, PA |at=section&nbsp;2 |isbn=978-0-8031-4086-8 |url=https://books.google.com/books?id=yCGIPQAACAAJ}} {{cite book |title=Annual Book of ASTM Standards |year=1998 |section=Volume&nbsp;13.01: Medical Devices; Emergency Medical Services |publisher=[[Organization:ASTM International|ASTM International]] |location=West Conshohocken, PA |at=sections&nbsp;2 & 13 |isbn=978-0-8031-2452-3}}</ref>

In addition to the ASTM specifications, titanium alloys are also produced to meet aerospace and military specifications (SAE-AMS, MIL-T), ISO standards, and country-specific specifications, as well as proprietary end-user specifications for aerospace, military, medical, and industrial applications.<ref>{{harvnb|Donachie|1988|pp=13–16, Appendices H and J}}</ref>

[[Chemistry:Titanium powder|Titanium powder]] is manufactured using a flow production process known as the Armstrong process<ref name=Roza2008p25>{{harvnb|Roza|2008|p=25}}</ref> that is similar to the batch production Hunter process. A stream of titanium tetrachloride gas is added to a stream of molten sodium; the products (sodium chloride salt and titanium particles) is filtered from the extra sodium. Titanium is then separated from the salt by water washing. Both sodium and chlorine are recycled to produce and process more titanium tetrachloride.<ref name="ECI online">{{cite web |title=Titanium |date=15 January 2015 |website=The Essential Chemical Industry online |series=CIEC Promoting Science |publisher=[[Organization:University of York|University of York]] |location=York, UK |url=http://www.essentialchemicalindustry.org/metals/titanium.html}}</ref>

===Fabrication===
All [[Chemistry:Welding|welding]] of titanium must be done in an inert atmosphere of argon or [[Chemistry:Helium|helium]] to shield it from contamination with atmospheric gases (oxygen, nitrogen, and hydrogen).<ref name=Barksdale1968p734/> Contamination causes a variety of conditions, such as [[Chemistry:Embrittlement|embrittlement]], which reduce the integrity of the assembly welds and lead to joint failure.<ref>{{Cite book |year=1955 |title=Arc-welding Titanium |author1= Engel, Abraham L. |author2=Huber, R.W. |author3=Lane, I.R. |publisher=U.S. Department of the Interior, Bureau of Mines }}</ref>

Titanium is very difficult to [[Chemistry:Solder|solder]] directly, and hence a solderable metal or alloy such as steel is coated on titanium prior to soldering.<ref>{{cite book | title=Report on Brazing and Soldering of Titanium |year=1956 |publisher=Titanium Metallurgical Laboratory, Battelle Memorial Institute |author1=Lewis, W.J. |author2=Faulkner, G.E. |author3=Rieppel, P.J. | url=https://books.google.com/books?id=316b7CW_HOMC&dq=Titanium+soldering&pg=PA2}}</ref> Titanium metal can be machined with the same equipment and the same processes as [[Chemistry:Stainless steel|stainless steel]].<ref name="Barksdale1968p734" />

====Forming and forging====
Commercially pure flat product (sheet, plate) can be formed readily, but processing must take into account of the tendency of the metal to springback. This is especially true of certain high-strength alloys.<ref>{{cite book|title=AWS G2.4/G2.4M:2007 Guide for the Fusion Welding of Titanium and Titanium Alloys |year=2006 |publisher=American Welding Society |place=Miami |url=http://pdfcast.org/pdf/titanium-design-and-fabrication-handbook-for-industrial-applications |archive-url=https://web.archive.org/web/20101210022045/http://pdfcast.org/pdf/titanium-design-and-fabrication-handbook-for-industrial-applications |archive-date=10 December 2010 }}</ref><ref>{{cite book|title=Titanium design and fabrication handbook for industrial applications |year=1997 |publisher=Titanium Metals Corporation |location=Dallas |url=http://www.timet.com/design%26fabframe.html |archive-url=https://web.archive.org/web/20090209014255/http://www.timet.com/design%26fabframe.html |archive-date=9 February 2009 }}</ref> Exposure to the oxygen in air at the elevated temperatures used in forging results in formation of an brittle oxygen-rich metallic surface layer called "[[Chemistry:Alpha case|alpha case]]" that worsens the fatigue properties, so it must be removed by milling, etching, or electrochemical treatment.<ref name='"Chen 2001"'>{{cite journal |last1=Chen |first1=George Z. |last2=Fray |first2=Derek J. |last3=Farthing |first3=Tom W. |year=2001 |title=Cathodic deoxygenation of the alpha case on titanium and alloys in molten calcium chloride |journal=Metall. Mater. Trans.&nbsp;B |volume=32 |issue=6 |page=1041 |doi=10.1007/s11663-001-0093-8 |s2cid=95616531 |url=https://link.springer.com/article/10.1007/s11663-001-0093-8}}</ref>

==Applications==
[[File:Titanzylinder.jpg|thumb|right|A titanium cylinder of quality "grade&nbsp;2"]]
Titanium is used in steel as an alloying element (ferro-titanium) to reduce [[Earth:Crystallite|grain size]] and as a deoxidizer, and in stainless steel to reduce carbon content.<ref name="EBC" /> Titanium is often alloyed with aluminium (to refine grain size), [[Chemistry:Vanadium|vanadium]], copper (to harden), [[Chemistry:Iron|iron]], [[Chemistry:Manganese|manganese]], [[Chemistry:Molybdenum|molybdenum]], and other metals.<ref name=ECE738>{{cite book |last=Hampel |first=Clifford A. |year=1968 |title=The Encyclopedia of the Chemical Elements |page=738 |publisher=Van Nostrand Reinhold |isbn=978-0-442-15598-8}}</ref> Titanium mill products (sheet, plate, bar, wire, forgings, castings) find application in industrial, aerospace, recreational, and emerging markets. Powdered titanium is used in [[Pyrotechnics|pyrotechnics]] as a source of bright-burning particles.<ref>{{cite book |author1=Mocella, Chris |author2=Conkling, John A. |year=2019 |title=Chemistry of Pyrotechnics|publisher=CRC Press |page=86 |isbn=978-1-351-62656-9}}</ref>

===Pigments, additives, and coatings===
[[File:Titanium(IV) oxide.jpg|thumb|alt=Watch glass on a black surface with a small portion of white powder|[[Chemistry:Titanium dioxide|Titanium dioxide]] is the most commonly used compound of titanium.]]
About 95% of all titanium ore is destined for refinement into titanium dioxide ({{chem|TiO|2}}), an intensely white permanent pigment used in paints, paper, toothpaste, and plastics.<ref name="USGS">{{cite web |title=Titanium |publisher=United States Geological Survey (USGS) |website=USGS Minerals Information |url=http://minerals.usgs.gov/minerals/pubs/commodity/titanium/}}</ref> It is also used in cement, in gemstones, as an optical opacifier in paper,<ref>{{cite book |last=Smook |first=Gary A. |year=2002 |title=Handbook for Pulp & Paper Technologists |edition=3rd |publisher=Angus Wilde Publications |isbn=978-0-9694628-5-9 |page=223 |url=https://books.google.com/books?id=TgtFPgAACAAJ}}</ref> and a strengthening agent in graphite composite fishing rods and golf clubs.<ref>{{cite press release |title=Cheap, environmentally friendly extraction method for titanium dioxide developed |date=13 February 2008 |publisher=[[Organization:University of Leeds|University of Leeds]] |url=https://www.sciencedaily.com/releases/2008/02/080211090311.htm |access-date=12 November 2021 |via=ScienceDaily}}</ref>

{{chem|TiO|2}} pigment is chemically inert, resists fading in sunlight, and is very opaque: it imparts a pure and brilliant white color to the brown or grey chemicals that form the majority of household plastics.<ref name=HistoryAndUse/> In nature, this compound is found in the minerals anatase, brookite, and rutile.<ref name=EBC/> Paint made with titanium dioxide does well in severe temperatures and marine environments.<ref name=HistoryAndUse/> Pure titanium dioxide has a very high [[Physics:Refractive index|index of refraction]] and an optical dispersion higher than [[Chemistry:Diamond|diamond]].<ref name=LANL/> In addition to being a very important pigment, titanium dioxide is also used in sunscreens.<ref name=Stwertka1998/>

===Aerospace and marine===
[[File:A12-flying.jpg|thumb|Lockheed A-12, first plane made of 93% titanium]]
Because titanium alloys have high [[Physics:Tensile strength|tensile strength]] to density ratio,<ref name="TICE6th" /> high corrosion resistance,<ref name=LANL/> fatigue resistance, high crack resistance,<ref name=Moiseyev>{{cite book |last=Moiseyev |first=Valentin N. |year=2006 |title=Titanium Alloys: Russian Aircraft and Aerospace Applications |publisher=Taylor and Francis, LLC |page=196 |isbn=978-0-8493-3273-9 |url=https://books.google.com/books?id=legtmQEACAAJ}}</ref> and ability to withstand moderately high temperatures without creeping, they are used in aircraft, armor plating, naval ships, spacecraft, and missiles.<ref name=LANL/><ref name=HistoryAndUse/> For these applications, titanium is alloyed with aluminium, zirconium, nickel,<ref name=Kramer-2013-07-05/> vanadium, and other elements to manufacture a variety of components including critical structural parts, fire walls, landing gear, exhaust ducts (helicopters), and hydraulic systems. In fact, about two thirds of all titanium metal produced is used in aircraft engines and frames.<ref name=Emsley2001p454/> The titanium 6AL-4V alloy accounts for almost 50% of all alloys used in aircraft applications.<ref>{{harvnb|Donachie|1988|p=13}}</ref>

The [[Engineering:Lockheed A-12|Lockheed A-12]] and the SR-71 "Blackbird" were two of the first aircraft frames where titanium was used, paving the way for much wider use in modern military and commercial aircraft. A large amount of titanium mill products are used in the production of many aircraft, such as (following values are amount of raw mill products used ... only a fraction of this ends up in the finished aircraft): 116&nbsp;metric tons are used in the Boeing 787, 77 in the [[Engineering:Airbus A380|Airbus A380]], 59 in the [[Engineering:Boeing 777|Boeing 777]], 45 in the [[Engineering:Boeing 747|Boeing 747]], 18 in the [[Engineering:Boeing 737|Boeing 737]], 32 in the [[Engineering:Airbus A340|Airbus A340]], 18 in the [[Engineering:Airbus A330|Airbus A330]], and 12 in the [[Engineering:Airbus A320|Airbus A320]].<ref>{{cite book |editor=Froes, F.H. |year=2015 |title=Titanium Physical Metallurgy, Processing, and Applications |page=7 |isbn=978-1-62708-080-4 |publisher=[[Organization:ASM International (society)|ASM International]] }}</ref> In aero engine applications, titanium is used for rotors, compressor blades, hydraulic system components, and [[Engineering:Nacelle|nacelle]]s.{{cn|date=January 2022}} An early use in jet engines was for the Orenda Iroquois in the 1950s.{{bcn|date=January 2022}}<ref>{{cite web |title=Iroquois |year=1957 |website=Flight Global (archive) |page=412 |url=https://www.flightglobal.com/pdfarchive/view/1957/1957%20-%201324.html |archive-url=https://web.archive.org/web/20091213041629/https://www.flightglobal.com/pdfarchive/view/1957/1957%20-%201324.html |archive-date=13 December 2009 }}</ref>

Because titanium is resistant to corrosion by sea water, it is used to make propeller shafts, rigging, and [[Physics:Heat exchanger|heat exchanger]]s in desalination plants;<ref name="LANL" /> heater-chillers for salt water aquariums, fishing line and leader, and divers' knives. Titanium is used in the housings and components of ocean-deployed surveillance and monitoring devices for science and the military. The former [[Place:Soviet Union|Soviet Union]] developed techniques for making submarines with hulls of titanium alloys{{cn|date=January 2023}} forging titanium in huge vacuum tubes.<ref name=Kramer-2013-07-05>{{cite news |author=Kramer, Andrew E. |date=5 July 2013 |title=Titanium Fills Vital Role for Boeing and Russia |newspaper={{wipe|The New York Times}} |url=https://www.nytimes.com/2013/07/06/business/global/titanium-fills-vital-role-for-boeing-and-russia.html |access-date=6 July 2013}}</ref>

===Industrial===
[[File:Titanium-stamps.jpg|thumb|Titanium [[Seal (East Asia)|sealing stamps]]]]

Welded titanium pipe and process equipment (heat exchangers, tanks, process vessels, valves) are used in the chemical and petrochemical industries primarily for corrosion resistance. Specific alloys are used in oil and gas downhole applications and [[Chemistry:Nickel|nickel]] [[Chemistry:Hydrometallurgy|hydrometallurgy]] for their high strength (e. g.: titanium beta C alloy), corrosion resistance, or both. The pulp and paper industry uses titanium in process equipment exposed to corrosive media, such as [[Chemistry:Sodium hypochlorite|sodium hypochlorite]] or wet chlorine gas (in the bleachery).<ref>{{harvnb|Donachie|1988|pp=11–16}}</ref> Other applications include [[Physics:Ultrasonic welding|ultrasonic welding]], [[Engineering:Wave soldering|wave soldering]],<ref>{{cite book |title= Industrial Application of Titanium and Zirconium |publisher=[[Organization:ASTM International|ASTM International]] |editor= Kleefisch, E.W. |isbn= 978-0-8031-0745-8 |location= West Conshohocken, PA |year=1981 |url=https://books.google.com/books?id=cX2HK0osYA4C}}</ref> and [[Physics:Sputtering|sputtering]] targets.<ref>{{cite book |title=Handbook of Hard Coatings |publisher=William Andrew Inc. |chapter=chapter&nbsp;8 |editor=Bunshah, Rointan F. |isbn=978-0-8155-1438-1 |location=Norwich, NY |chapter-url=https://books.google.com/books?id=daamnz8el2sC&pg=PA413 |year=2001}}</ref>

Titanium tetrachloride (TiCl<sub>4</sub>), a colorless liquid, is important as an intermediate in the process of making TiO<sub>2</sub> and is also used to produce the Ziegler–Natta catalyst. Titanium tetrachloride is also used to iridize glass and, because it fumes strongly in moist air, it is used to make smoke screens.<ref name="Stwertka1998" />

===Consumer and architectural===
[[File:Tweeter with Titanium membrane of loudspeaker box JBL TI 5000, 1990s.jpg|thumb|[[Engineering:Tweeter|Tweeter]] loudspeaker driver with a membrane with 25 mm diameter made from titanium; from a JBL TI 5000 loudspeaker box, c. 1997]]
Titanium metal is used in automotive applications, particularly in automobile and motorcycle racing where low weight and high strength and rigidity are critical.<ref>{{cite conference |author=Funatani, K. |date=9–12 October 2000 |title=Recent trends in surface modification of light metals §&nbsp;Metal matrix composite technologies |publication-date=2001 |conference=20th ASM Heat Treating Society Conference |book-title=Heat Treating, an International ... Symposium on Residual Stresses in the Heat Treatment Industry |editor1=Funatani, Kiyoshi |editor2=Totten, George E. |place=St.&nbsp;Louis, MO |publisher=[[Organization:ASM International (society)|ASM International]] |volume=1 & 2 |pages=138–144, esp.&nbsp;141 |isbn=978-0-87170-727-7 |url=https://books.google.com/books?id=4F1zYT4FHyMC}}</ref>{{rp|style=ama|p= 141}} The metal is generally too expensive for the general consumer market, though some late model [[Engineering:Chevrolet Corvette|Corvettes]] have been manufactured with titanium exhausts,<ref>{{cite web |title=Titanium exhausts |publisher=National Corvette Museum |year=2006 |url=http://www.iglou.com/corvette/specs/2001/exhaust.htm |access-date=26 December 2006  |archive-url=https://archive.today/20130103075117/http://www.iglou.com/corvette/specs/2001/exhaust.htm |archive-date=3 January 2013}}</ref> and a Corvette Z06's LT4 supercharged engine uses lightweight, solid titanium intake valves for greater strength and resistance to heat.<ref>{{cite press release |title=Compact powerhouse: Inside Corvette Z06's LT4 engine 650-hp supercharged 6.2L V-8 makes world-class power in more efficient package |date=20 August 2014 |publisher=[[Company:General Motors|General Motors]] |website=media.gm.com |url=http://media.gm.com/media/us/en/chevrolet/vehicles/corvette-z06/2015.detail.html/content/Pages/news/us/en/2014/Aug/0820-8speed/0820-compact-powerhouse.html}}</ref>

Titanium is used in many sporting goods: tennis rackets, golf clubs, lacrosse stick shafts; cricket, hockey, lacrosse, and football helmet grills, and bicycle frames and components. Although not a mainstream material for bicycle production, titanium bikes have been used by racing teams and adventure cyclists.<ref>{{cite book |last=Davis |first=Joseph R. |year=1998 |title=Metals Handbook |publisher=[[Organization:ASM International (society)|ASM International]] |isbn=978-0-87170-654-6 |page=[https://archive.org/details/metalshandbook00davi/page/584 584] |url=https://archive.org/details/metalshandbook00davi |url-access=registration |via=[[Internet Archive]] (archive.org)}}</ref>

Titanium alloys are used in spectacle frames that are rather expensive but highly durable, long lasting, light weight, and cause no skin allergies. Titanium is a common material for backpacking cookware and eating utensils. Though more expensive than traditional steel or aluminium alternatives, titanium products can be significantly lighter without compromising strength. Titanium horseshoes are preferred to steel by farriers because they are lighter and more durable.<ref name=Donachie2000>{{harvnb|Donachie|1988|pp=11, 255}}</ref>

[[File:El Guggenheim vizcaíno. (1454058701).jpg|thumb| Titanium cladding of Frank Gehry's Guggenheim Museum, Bilbao]]
Titanium has occasionally been used in architecture. The {{convert|42.5|m|ft|adj=on|abbr=on}} Monument to Yuri Gagarin, the first man to travel in space ({{coord|55|42|29.7|N|37|34|57.2|E|region:CN-62_type:landmark|display=inline}}), as well as the {{convert|110|m|ft|adj=on|abbr=on}} Monument to the Conquerors of Space on top of the [[Astronomy:Memorial Museum of Cosmonautics|Cosmonaut Museum]] in Moscow are made of titanium for the metal's attractive color and association with rocketry.<ref>{{cite book|author=Mike Gruntman|title=Blazing the Trail: The Early History of Spacecraft and Rocketry|page=457|isbn=978-1-56347-705-8|url=https://books.google.com/books?id=2XY9KXxF8OEC|publisher=American Institute of Aeronautics and Astronautics|location=Reston, VA|year=2004|author-link=Mike Gruntman}}</ref><ref>{{cite book|chapter-url=https://books.google.com/books?id=41EqJFxjA4wC&pg=PA408|title=Titanium |chapter= Appearance Related Applications|isbn=978-3-540-71397-5|author1=Lütjering, Gerd|author2=Williams, James Case|date=12 June 2007|publisher=Springer }}</ref> The Guggenheim Museum Bilbao and the Cerritos Millennium Library were the first buildings in Europe and North America, respectively, to be sheathed in titanium panels.<ref name="Emsley2001p454">{{harvnb|Emsley|2001|p=454}}</ref> Titanium sheathing was used in the Frederic C. Hamilton Building in Denver, Colorado.<ref>{{cite web |url=http://www.designbuild-network.com/projects/dam/ |title=Denver Art Museum, Frederic C. Hamilton Building |access-date=26 December 2006 |publisher=SPG Media |year=2006}}</ref>

Because of titanium's superior strength and light weight relative to other metals (steel, stainless steel, and aluminium), and because of recent advances in metalworking techniques, its use has become more widespread in the manufacture of firearms. Primary uses include pistol frames and revolver cylinders. For the same reasons, it is used in the body of some laptop computers (for example, in [[Company:Apple Inc.|Apple]]'s PowerBook G4).<ref>{{cite web|access-date=8 August 2009|url=http://www.everymac.com/systems/apple/powerbook_g4/stats/powerbook_g4_400.html|title=Apple PowerBook G4 400 (Original – Ti) Specs|work=everymac.com}}</ref><ref name=use/>

In 2023, Apple launched the iPhone 15 Pro, which uses a titanium enclosure.<ref>{{Cite web |title=Apple Announces iPhone 15 Pro Models With Titanium Enclosure |url=https://www.cnet.com/tech/mobile/apple-announces-iphone-15-pro-models-with-titanium-enclosure/ |access-date=2023-09-19 |website=CNET |language=en}}</ref>

Some upmarket lightweight and corrosion-resistant tools, such as shovels, knife handles and flashlights, are made of titanium or titanium alloys.<ref name=use>{{cite book |pages=7–8 |year=2019 |isbn=978-0-12-815820-3 |publisher=Elsevier Science |title=Real-World Use of Titanium |author1=Qian, Ma |author2=Niinomi, Mitsuo}}</ref>

=== Jewelry ===

[[File:Anodized titanium table.jpg|thumb|left|Relation between voltage and color for anodized titanium]]
Because of its durability, titanium has become more popular for designer jewelry (particularly, [[Chemistry:Titanium ring|titanium ring]]s).<ref name=Donachie2000/> Its inertness makes it a good choice for those with allergies or those who will be wearing the jewelry in environments such as swimming pools. Titanium is also [[Chemistry:Titanium gold|alloyed with gold]] to produce an alloy that can be marketed as [[Fineness|24-karat]] gold because the 1% of alloyed Ti is insufficient to require a lesser mark. The resulting alloy is roughly the hardness of 14-karat gold and is more durable than pure 24-karat gold.<ref>{{cite journal |url=http://goldbulletin.org/assets/file/goldbulletin/downloads/Gafner_4_22.pdf |title=The development of 990 Gold-Titanium: its Production, use and Properties |author=Gafner, G. |journal=Gold Bulletin |year=1989 |volume=22 |issue=4 |pages=112–122 |doi=10.1007/BF03214709 |doi-access=free |s2cid=114336550 |archive-url=https://web.archive.org/web/20101129195740/http://goldbulletin.org/assets/file/goldbulletin/downloads/Gafner_4_22.pdf |archive-date=29 November 2010 }}</ref>

Titanium's durability, light weight, and dent and corrosion resistance make it useful for [[Engineering:Watch|watch]] cases.<ref name="Donachie2000" /> Some artists work with titanium to produce sculptures, decorative objects and furniture.<ref>{{cite web|access-date=8 August 2009 |url=http://www.titanium-arts.com/home.html |title=Fine Art and Functional Works in Titanium and Other Earth Elements  |archive-url=https://web.archive.org/web/20080513171451/http://www.titanium-arts.com/home.html |archive-date=13 May 2008 }}</ref>

Titanium may be anodized to vary the thickness of the surface oxide layer, causing optical interference fringes and a variety of bright colors.<ref>{{cite web|url=http://electrochem.cwru.edu/ed/encycl/art-a02-anodizing.htm |title=Electrochemistry Encyclopedia |publisher=Chemical Engineering Department, Case Western Reserve University, U.S.|author=Alwitt, Robert S. |year=2002 |access-date=30 December 2006 |archive-url=https://web.archive.org/web/20080702001336/http://electrochem.cwru.edu/ed/encycl/art-a02-anodizing.htm |archive-date=2 July 2008}}</ref> With this coloration and chemical inertness, titanium is a popular metal for body piercing.<ref>{{cite web |url=http://www.doctorgoodskin.com/tp/bodypiercing/|work=doctorgoodskin.com |title=Body Piercing Safety |date=1 August 2006}}</ref>

Titanium has a minor use in dedicated non-circulating coins and medals. In 1999, Gibraltar released the world's first titanium coin for the millennium celebration.<ref>{{Cite web|url=https://www.pobjoy.com/us/world-firsts|title=World Firsts 
|publisher= British Pobjoy Mint|access-date=11 November 2017}}</ref> The Gold Coast Titans, an Australian rugby league team, award a medal of pure titanium to their player of the year.<ref>{{cite news|last=Turgeon |first=Luke |title=Titanium Titan: Broughton immortalised |url=http://www.goldcoast.com.au/article/2007/09/20/2947_gold-coast-titans.html |newspaper=The Gold Coast Bulletin |date=20 September 2007 |archive-url=https://web.archive.org/web/20130928082012/http://www.goldcoast.com.au/article/2007/09/20/2947_gold-coast-titans.html |archive-date=28 September 2013}}</ref>

===Medical===
{{Main|Chemistry:Titanium biocompatibility}}
Because titanium is [[Chemistry:Biocompatibility|biocompatible]] (non-toxic and not rejected by the body), it has many medical uses, including surgical implements and implants, such as hip balls and sockets ([[Medicine:Joint replacement|joint replacement]]) and [[Engineering:Dental implant|dental implant]]s that can stay in place for up to 20 years.<ref name="Emsley2001p452">{{harvnb|Emsley|2001|p=452}}</ref> The titanium is often alloyed with about 4% aluminium or 6% Al and 4% vanadium.<ref>{{cite web|url=http://www.totaljoints.info/orthopaedic_metal_alloys.htm|title=Orthopaedic Metal Alloys|publisher=Totaljoints.info|access-date=27 September 2010}}</ref>
[[File:Titanium plaatje voor pols.jpg|thumb|Medical screws and plate used to repair wrist fractures. Scale is in centimeters.]]
Titanium has the inherent ability to [[Medicine:Osseointegration|osseointegrate]], enabling use in dental implants that can last for over 30 years. This property is also useful for orthopedic implant applications.<ref name="Emsley2001p452" /> These benefit from titanium's lower modulus of elasticity ([[Physics:Young's modulus|Young's modulus]]) to more closely match that of the bone that such devices are intended to repair. As a result, skeletal loads are more evenly shared between bone and implant, leading to a lower incidence of bone degradation due to stress shielding and [[Medicine:Periprosthetic|periprosthetic]] bone fractures, which occur at the boundaries of orthopedic implants. However, titanium alloys' stiffness is still more than twice that of bone, so adjacent bone bears a greatly reduced load and may deteriorate.<ref>{{cite journal |url=http://www.fraunhofer.de/en/press/research-news/2010/09/titanium-foams-replace-injured-bones.jsp|title=Titanium foams replace injured bones|journal=Research News |date=1 September 2010|archive-url=https://web.archive.org/web/20100904045008/http://www.fraunhofer.de/en/press/research-news/2010/09/titanium-foams-replace-injured-bones.jsp|access-date=27 September 2010|archive-date=4 September 2010}}</ref><ref>{{cite journal | last=Lavine | first=Marc S. | editor-last=Vignieri | editor-first=Sacha | editor-last2=Smith | editor-first2=Jesse | title=Make no bones about titanium | journal=Science | volume=359 | issue=6372 | date=11 January 2018 | doi=10.1126/science.359.6372.173-f | pages=173.6–174| bibcode=2018Sci...359..173L | doi-access=free }}</ref>

Because titanium is non-[[Physics:Ferromagnetic|ferromagnetic]], patients with titanium implants can be safely examined with [[Physics:Magnetic resonance imaging|magnetic resonance imaging]] (convenient for long-term implants). Preparing titanium for implantation in the body involves subjecting it to a high-temperature [[Physics:Plasma|plasma]] arc which removes the surface atoms, exposing fresh titanium that is instantly oxidized.<ref name="Emsley2001p452" />

Modern advancements in additive manufacturing techniques have increased potential for titanium use in orthopedic implant applications.<ref>{{cite journal | last1=Harun | first1=W.S.W. | last2=Manam | first2=N.S. | last3=Kamariah | first3=M.S.I.N. | last4=Sharif | first4=S. | last5=Zulkifly | first5=A.H. | last6=Ahmad | first6=I. | last7=Miura | first7=H. | title=A review of powdered additive manufacturing techniques for Ti-6al-4v biomedical applications | journal=Powder Technology |  volume=331 | year=2018 | doi=10.1016/j.powtec.2018.03.010 | pages=74–97| url=http://irep.iium.edu.my/64319/1/A%20review%20of%20powdered%20additive%20manufacturing%20techniques%20for%20Ti-6al-4v%20biomedical%20applications.pdf }}</ref> Complex implant scaffold designs can be 3D-printed using titanium alloys, which allows for more patient-specific applications and increased implant osseointegration.<ref>{{cite journal | last1=Trevisan | first1=Francesco | last2=Calignano | first2=Flaviana | last3=Aversa | first3=Alberta | last4=Marchese | first4=Giulio | last5=Lombardi | first5=Mariangela | last6=Biamino | first6=Sara | last7=Ugues | first7=Daniele | last8=Manfredi | first8=Diego | year=2017 | title=Additive manufacturing of titanium alloys in the biomedical field: processes, properties and applications | journal=Journal of Applied Biomaterials & Functional Materials | volume=16 | issue=2 |pmid=28967051 | doi=10.5301/jabfm.5000371 | pages=57–67| s2cid=27827821 | doi-access=free }}</ref>

Titanium is used for the [[Engineering:Surgical instrument|surgical instrument]]s used in image-guided surgery, as well as wheelchairs, crutches, and any other products where high strength and low weight are desirable.<ref>{{Cite book |year=2019 |isbn=978-0-12-815820-3 |publisher=Elsevier Science |title=Real-World Use of Titanium |author1=Qian, Ma |author2=Niinomi, Mitsuo |pages=51, 128 }}</ref>

Titanium dioxide [[Physics:Nanoparticle|nanoparticle]]s are widely used in electronics and the delivery of pharmaceuticals and cosmetics.<ref>{{cite journal |last1=Pinsino |first1=Annalisa |last2=Russo |first2=Roberta |last3=Bonaventura |first3=Rosa |last4=Brunelli |first4=Andrea |last5=Marcomini |first5=Antonio |last6=Matranga |first6=Valeria |date=28 September 2015 |title=Titanium dioxide nanoparticles stimulate sea urchin immune cell phagocytic activity involving TLR/p38 MAPK-mediated signalling pathway |journal=Scientific Reports |volume=5 |doi=10.1038/srep14492 |pmc=4585977 |pmid=26412401 |page=14492 |bibcode=2015NatSR...514492P}}</ref>

===Nuclear waste storage===
Because of its corrosion resistance, containers made of titanium have been studied for the long-term storage of nuclear waste. Containers lasting more than 100,000 years are thought possible with manufacturing conditions that minimize material defects.<ref>{{cite journal |doi= 10.1515/CORRREV.2000.18.4-5.331 |title= Hydrogen Absorption and the Lifetime Performance of Titanium Nuclear Waste Containers |journal= Corrosion Reviews |volume= 18 |issue= 4–5 |year= 2000 |last1= Shoesmith |first1= D. W. |last2= Noel |first2= J. J. |last3= Hardie |first3= D. |last4= Ikeda |first4= B. M.|pages= 331–360 |s2cid= 137825823 }}</ref> A titanium "drip shield" could also be installed over containers of other types to enhance their longevity.<ref>{{cite journal |title=Proof of Safety at Yucca Mountain |journal=Science |year=2005|volume= 310 |issue=5747 |pages=447–448 |author1=Carter, L.J. |author2=Pigford, T.J. |doi=10.1126/science.1112786 |pmid=16239463 |s2cid=128447596}}</ref>

==Precautions==
Titanium is non-toxic even in large doses and does not play any natural role inside the [[Medicine:Human body|human body]].<ref name="Emsley2001p451" /> An estimated quantity of 0.8 milligrams of titanium is ingested by humans each day, but most passes through without being absorbed in the tissues.<ref name="Emsley2001p451" /> It does, however, sometimes bio-accumulate in tissues that contain [[Chemistry:Silica|silica]]. One study indicates a possible connection between titanium and [[Medicine:Yellow nail syndrome|yellow nail syndrome]].<ref>{{cite journal |last1=Berglund |first1=Fredrik |author2=Carlmark, Bjorn |title=Titanium, Sinusitis, and the Yellow Nail Syndrome |journal=Biological Trace Element Research |date=October 2011 |pmc=3176400 |volume=143 |issue=1 |pages=1–7 |doi=10.1007/s12011-010-8828-5 |pmid=20809268}}</ref>

As a powder or in the form of metal shavings, titanium metal poses a significant fire hazard and, when heated in air, an explosion hazard.<ref>{{cite book |last=Cotell |first=Catherine Mary |author2=Sprague, J.A. |author3=Smidt, F.A. |title=ASM Handbook: Surface Engineering |publisher=[[Organization:ASM International (society)|ASM International]] |year=1994 |edition=10th |page=836 |isbn=978-0-87170-384-2 |url=https://books.google.com/books?id=RGtsPjqUwy0C}}</ref> Water and [[Chemistry:Carbon dioxide|carbon dioxide]] are ineffective for extinguishing a titanium fire; Class D dry powder agents must be used instead.<ref name="HistoryAndUse" />

When used in the production or handling of chlorine, titanium should not be exposed to dry chlorine gas because it may result in a titanium–chlorine fire.<ref>{{cite book |author=Compressed Gas Association |title=Handbook of compressed gases |publisher=Springer |year=1999 |edition=4th |page=323 |isbn=978-0-412-78230-5 |url=https://books.google.com/books?id=WSLULtCG9JgC}}</ref>

Titanium can catch fire when a fresh, non-oxidized surface comes in contact with [[Physics:Liquid oxygen|liquid oxygen]].<ref>{{cite book |last=Solomon |first=Robert E. |others=National Fire Prevention Association |title=Fire and Life Safety Inspection Manual |publisher=Jones & Bartlett Publishers |year=2002 |edition=8th |page=45 |isbn=978-0-87765-472-8 |url=https://books.google.com/books?id=2fHsoobsCNwC}}</ref>

==Function in plants==
[[File:Kopiva.JPG|thumb|alt=The dark green dentated elliptic leaves of a nettle|[[Biology:Urtica dioica|Nettles]] contain up to 80 parts per million of titanium.<ref name="Emsley2001p451" />]]
An unknown mechanism in [[Biology:Plant|plant]]s may use titanium to stimulate the production of [[Chemistry:Carbohydrate|carbohydrate]]s and encourage growth. This may explain why most plants contain about 1 part per million (ppm) of titanium, food plants have about 2&nbsp;ppm, and horsetail and [[Biology:Urtica|nettle]] contain up to 80&nbsp;ppm.<ref name="Emsley2001p451" />

==See also==
{{Colbegin|colwidth=20em}}
* [[Chemistry:List of countries by titanium production|List of countries by titanium production]]
* [[Chemistry:Suboxide|Suboxide]]
* Titanium in Africa
* [[Earth:Titanium in zircon geothermometry|Titanium in zircon geothermometry]]
* Titanium Man
* VSMPO-AVISMA
{{Colend}}

==Footnotes==
{{notelist}}

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

== Bibliography ==
{{Refbegin |colwidth=25em |small=yes}}

* {{cite book |title=The Encyclopedia of the Chemical Elements|publisher=Reinhold Book Corporation |location=New York, NY |year=1968 |editor=Clifford A. Hampel |last=Barksdale |first=Jelks |chapter=Titanium |pages=[https://archive.org/details/encyclopediaofch00hamp/page/732 732–738] |lccn=68029938 |chapter-url=https://archive.org/details/encyclopediaofch00hamp |chapter-url-access=registration}}
* {{cite book |title=Titanium: A technical guide |year=1988 |last1=Donachie| first1=Matthew J. Jr. |publisher=[[Organization:ASM International (society)|ASM International]] |location=Metals Park, OH |page=11 |isbn=978-0-87170-309-5 |url=https://books.google.com/books?id=Ct9RAAAAMAAJ}}
* {{cite book |title=Nature's Building Blocks: An A-Z guide to the elements |last=Emsley |first=John |publisher=Oxford University Press |year=2001 |location=Oxford, England, UK |isbn=978-0-19-850340-8 |chapter=Titanium |chapter-url=https://books.google.com/books?id=j-Xu07p3cKwC|url-access=registration|url=https://archive.org/details/naturesbuildingb0000emsl}}
* {{cite journal |last=Flower |first=Harvey M.|title=Materials Science: A moving oxygen story |journal=Nature |volume=407 |year=2000 |issue=6802 |pmid=11014169 |pages=305–306 |doi=10.1038/35030266 |s2cid=4425634 }}
* {{cite book|last1=Greenwood|first1=N. N.|last2=Earnshaw|first2=A. |title=Chemistry of the Elements|edition=2nd|publisher=Butterworth-Heinemann|location=Oxford|year=1997|isbn=978-0-7506-3365-9}}
* {{cite book |last1=Roza |first1=Greg |title=Titanium |year=2008 |publisher=The Rosen Publishing Group |location=New York, NY |isbn=978-1-4042-1412-5 |edition=1st |url=https://books.google.com/books?id=rsAGRf7j7fQC}}
{{Refend}}

== External links ==
* [https://books.google.com/books?id=7iwDAAAAMBAJ&pg=RA2-PA46 "Titanium: Our Next Major Metal"] in ''Popular Science'' (October 1950), one of first general public detailed articles on Titanium
* [http://www.periodicvideos.com/videos/022.htm Titanium] at ''[[Biography:Periodic Videos|Periodic Videos]]'' (University of Nottingham)
* [https://titanium.org/ Titanium.org]: official website of the International Titanium Association, an industry association
* [https://www.phase-trans.msm.cam.ac.uk/2003/titanium.movies/titanium.html Metallurgy of Titanium and its Alloys] - slide presentations, movies, and other material from Harshad Bhadeshia and other Cambridge University metallurgists 

{{Periodic table (navbox)}}
{{Titanium compounds}}
{{Titanium minerals}}
{{Jewellery}}

[[Category:Titanium| ]]
[[Category:Aerospace materials]]
[[Category:Biomaterials]]
[[Category:Chemical elements]]
[[Category:Native element minerals]]
[[Category:Pyrotechnic fuels]]
[[Category:Transition metals]]

{{Sourceattribution|Titanium}}