Editing Titanium (section)

== Characteristics ==

=== Physical properties ===
<section begin=properties/>
As a [[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 [[density]] that is quite [[ductility|ductile]] (especially in an [[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]].<ref name="Stwertka1998">{{cite book|title=Guide to the Elements|edition=Revised|first=Albert|last=Stwertka|publisher=[[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> Due to its relatively high melting point (1,668&nbsp;°C or 3,034&nbsp;°F) it has sometimes been described as a [[refractory metals|refractory metal]], but this is not the case.<ref>{{cite web|website=Special Metal Fabrication|url=https://special-metals.co.uk/is-titanium-a-refractory-metal|title=Is Titanium A Refractory Metal|date=3 August 2021 }}</ref> It is [[paramagnetism|paramagnetic]] and has fairly low [[electrical conductivity|electrical]] and [[thermal conductivity]] compared to other metals.<ref name="EBC" /> Titanium is [[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=etal| arxiv = 1803.02736| bibcode = 2018PhRvB..97u4516T| s2cid = 54891002}}</ref><section end=properties/>

{{anchor|Commercially pure titanium}}
Commercially pure (99.2% pure) [[titanium alloy#Grades of titanium|grades]] of titanium have [[ultimate tensile strength]] of about 434&nbsp;[[megapascal|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 [[6061 aluminium alloy|6061-T6 aluminium alloy]]. Certain titanium alloys (e.g., [[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 [[galling|gall]] unless sharp tools and proper cooling methods are used. Like steel structures, those made from titanium have a [[fatigue limit]] that guarantees longevity in some applications.<ref name="Stwertka1998" />

The metal is a dimorphic [[allotrope]] of a [[hexagonal close packed]] α form that changes into a [[body-centered cubic]] (lattice) β form at {{convert|882|°C|°F}}.<ref name="Barksdale1968p734" /><ref name="schmidt65">{{cite book |last1=Schmidt |first1=F. F. |last2=Wood |first2=R. A. |title=HEAT TREATMENT OF TITANIUM AND TITANIUM ALLOYS BY |date=1965 |publisher=NASA |location=GEORGE C. MARSHALL SPACE FLIGHT CENTER |edition=TECHNICAL MEMORANDUM X-53445 |url=https://ntrs.nasa.gov/api/citations/19660015720/downloads/19660015720.pdf}}</ref> The [[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 products.jpg|thumb|left|Titanium products: plate, tube, rod, powder]]
[[File:Titanium in water Pourbaix diagram.png|thumb|[[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 [[aluminium]] and [[magnesium]], the surface of titanium metal and its alloys [[oxidize]] immediately upon exposure to air to form a thin non-porous [[Passivation (chemistry)|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 [[sulfuric acid|sulfuric]] and [[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 [[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 [[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 [[electrical filament|filaments]] is the basis for [[titanium sublimation pump]]s, in which titanium serves as a scavenger for these gases by chemically binding to them. Such pumps inexpensively produce extremely low pressures in [[ultra-high vacuum]] systems.

=== Occurrence ===
Titanium is the ninth-most [[abundance of elements in Earth's crust|abundant]] element in [[Earth]]'s crust (0.63% by [[mass]])<ref name="Barksdale1968p732" /> and the seventh-most abundant metal. It is present as oxides in most [[igneous rock]]s, in [[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 [[mineral]]s are [[anatase]], [[brookite]], [[ilmenite]], [[perovskite]], [[rutile]], and [[titanite]] (sphene).<ref name="Emsley2001p453">{{harvnb|Emsley|2001|p=453}}</ref> [[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 [[Australia]], [[Canada]], [[China]], [[India]], [[Mozambique]], [[New Zealand]], [[Norway]], [[Sierra Leone]], [[South Africa]], and [[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
|-
|[[China]]||3,830||33.1
|-
|[[Australia]]||1,513||13.1
|-
|[[Mozambique]]||1,070||9.3
|-
|[[Canada]]||1,030||8.9
|-
|[[South Africa]]||743||6.4
|-
|[[Kenya]]||562||4.9
|-
|[[India]]||510||4.4
|-
|[[Senegal]]||502||4.3
|-
|[[Ukraine]]||492||4.3
|-
|'''World'''||'''11,563'''||'''100'''
|}

The concentration of titanium is about 4 [[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 [[meteorite]]s, and it has been detected in the [[Sun]] and in [[stellar classification|M-type]] [[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> [[Rock (geology)|Rocks]] brought back from the [[Moon]] during the [[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|Isotopes of titanium}}
Naturally occurring titanium is composed of five stable [[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% [[natural abundance]]). At least 21 [[radioisotope]]s have been characterized, the most stable of which are [[titanium-44|<sup>44</sup>Ti]] with a [[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 [[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 [[atomic weight]] from {{val|39.002|ul=Da}} (<sup>39</sup>Ti) to {{val|63.999|u=Da}} (<sup>64</sup>Ti).{{AME2016 II|ref}} The primary [[decay mode]] for isotopes lighter than <sup>46</sup>Ti is [[positron emission]] (with the exception of <sup>44</sup>Ti which undergoes [[electron capture]]), leading to [[isotopes of scandium]], and the primary mode for isotopes heavier than <sup>50</sup>Ti is [[beta emission]], leading to [[isotopes of vanadium]].<ref name="EnvChem" />

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