Titanium
Template:Good article Template:Other uses Template:Pp-semi-indef Template:Pp-move Template:Use dmy dates Template:Infobox titanium
Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength that is resistant to corrosion in sea water, aqua regia, and chlorine.
Titanium was discovered in Cornwall, Great Britain, by William Gregor in 1791 and was named by Martin Heinrich Klaproth after the Titans of Greek mythology. The element occurs within a number of minerals, principally rutile and ilmenite, which are widely distributed in the Earth's crust and 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 Kroll and Hunter processes.<ref name="LANL" /> The most common compound, titanium dioxide (TiO2), is a popular photocatalyst and is used in the manufacture of white pigments.<ref name="HistoryAndUse">Template:Cite book</ref> Other compounds include titanium tetrachloride (TiCl4), a component of smoke screens and catalysts; and titanium trichloride (TiCl3), which is used as a catalyst in the production of polypropylene.<ref name="EBC" />
Titanium can be alloyed with iron, aluminium, vanadium, and molybdenum, among other elements. The resulting titanium alloys are strong, lightweight, and versatile, with applications including aerospace (jet engines, missiles, and spacecraft), military, industrial processes (chemicals and petrochemicals, desalination plants, pulp, and paper), automotive, agriculture (farming), sporting goods, jewelry, and consumer electronics.<ref name="EBC" /> Titanium is also considered one of the most biocompatible metals, leading to a range of medical applications including prostheses, orthopedic implants, dental implants, and surgical instruments.<ref name="Medical University 2022 v636">Template:Cite web</ref>
The two most useful properties of the metal are its corrosion resistance and strength-to-density ratio, the highest of any metallic element.<ref>Template:Harvnb</ref> In its unalloyed condition, titanium is as strong as some steels, but less dense.<ref name="Barksdale1968p738">Template:Harvnb</ref> There are two allotropic forms<ref name="TICE6th" /> and five naturally occurring isotopes of this element, [[isotopes of titanium|Template:SupTi]] through Template:SupTi, with Template:SupTi being the most abundant (73.8%).<ref name="EnvChem">Template:Cite web</ref>
Characteristics
Physical properties
<section begin=properties/> As a metal, titanium is recognized for its high strength-to-weight ratio.<ref name=TICE6th>Template:Cite encyclopedia</ref> It is a strong metal with low density that is quite ductile (especially in an oxygen-free environment),<ref name="EBC">Template:Cite encyclopedia</ref> lustrous, and metallic-white in color.<ref name="Stwertka1998">Template:Cite book</ref> Due to its relatively high melting point (1,668 °C or 3,034 °F) it has sometimes been described as a refractory metal, but this is not the case.<ref>Template:Cite web</ref> It is paramagnetic and has fairly low electrical and thermal conductivity compared to other metals.<ref name="EBC" /> Titanium is superconducting when cooled below its critical temperature of 0.49 K.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><section end=properties/>
Template:Anchor Commercially pure (99.2% pure) grades of titanium have ultimate tensile strength of about 434 MPa (63,000 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-T6 aluminium alloy. Certain titanium alloys (e.g., Beta C) achieve tensile strengths of over 1,400 MPa (200,000 psi).<ref>Template:Harvnb</ref> However, titanium loses strength when heated above Template:Convert.<ref name="Barksdale1968p734">Template:Harvnb</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 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 Template:Convert.<ref name="Barksdale1968p734" /><ref name="schmidt65">Template:Cite book</ref> The 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
Like aluminium and magnesium, the surface of titanium metal and its alloys oxidizes immediately upon exposure to air to form a thin non-porous 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 nm thick but it continues to grow slowly, reaching a thickness of 25 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.<ref name=":0">Template:Citation</ref>
Titanium is capable of withstanding attack by dilute sulfuric and hydrochloric acids at room temperature, chloride solutions, and most organic acids.<ref name=LANL/> However, titanium is corroded by concentrated acids.<ref>Template:Cite journal</ref> Titanium burns in normal air at temperatures lower than its melting point, so melting the metal is possible only in an inert atmosphere or vacuum.<ref name="LANL" /> At room temperature, titanium is fairly inert to halogens, but will violently combine with chlorine and bromine at Template:Convert to form titanium tetrachloride and titanium tetrabromide, respectively.<ref name=":0" />
Titanium readily reacts with oxygen at Template:Convert in air, and at Template:Convert in pure oxygen, forming titanium dioxide.<ref name="TICE6th" /> This oxide is also formed by reaction between titanium and pure oxygen at room temperature and pressure of Template:Convert.<ref name=":0" /> Titanium is one of the few elements that burns in pure nitrogen gas, reacting at Template:Convert to form titanium nitride, which causes embrittlement.<ref name=titaniumindustry>Template:Cite book</ref>
Occurrence
Titanium is the ninth-most 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 rocks, in sediments derived from them, in living things, and natural bodies of water.<ref name="EBC" /><ref name="LANL">Template: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 minerals are anatase, brookite, ilmenite, perovskite, rutile, and titanite (sphene).<ref name="Emsley2001p453">Template:Harvnb</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" /> Total reserves of anatase, ilmenite, and rutile are estimated to exceed 2 billion tonnes.<ref name="USGS" />
The concentration of titanium is about 4 picomolar in the ocean. At 100 °C, the concentration of titanium in water is estimated to be less than 10Template: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>Template:Cite journal</ref>
Titanium is contained in meteorites, and it has been detected in the Sun and in M-type stars<ref name="LANL" /> (the coolest type) with a surface temperature of Template:Convert.<ref name="Emsley2001p451">Template:Harvnb</ref> Rocks brought back from the Moon during the Apollo 17 mission are composed of 12.1% TiO2.<ref name="LANL" /> Native titanium is only found in rocks that have been exposed to pressures between roughly 2.8 to 4.0Template:Spacesgigapascal on Earth,<ref>Template:Cite journal</ref> but it has been identified in nanocrystals on the Moon.<ref>Template:Cite journal</ref>
Isotopes
Template:Main Naturally occurring titanium is composed of five stable isotopes: Template:SupTi, Template:SupTi, Template:SupTi, Template:SupTi, and Template:SupTi, with Template:SupTi being the most abundant (73.8% natural abundance). Twenty-three radioisotopes have been characterized,Template:Efn the most stable of which are [[titanium-44|Template:SupTi]] with a half-life of 63 years; Template:SupTi, 184.8 minutes; Template:SupTi, 5.76 minutes; and Template:SupTi, 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" /><ref name=nubase2020>Template:NUBASE2020</ref>
The isotopes of titanium range from Template:SupTi to Template:SupTi.Template:AME2016 II<ref name=Tarasov2025 /> The primary decay mode for isotopes lighter than Template:SupTi is positron emission (with the exception of Template:SupTi which undergoes electron capture), leading to isotopes of scandium, and the primary mode for isotopes heavier than Template:SupTi 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" />
Compounds
Template:Category see also Template:See also
The +4 oxidation state dominates titanium chemistry,<ref name="Greenwood1997p958">Template:Harvnb</ref> but compounds in the +3 oxidation state are also numerous.<ref name="Greenwood1997p970">Template:Harvnb</ref> Commonly, titanium adopts an octahedral coordination geometry in its complexes,<ref name="Greenwood1997p960">Template:Harvnb</ref><ref name="Greenwood1997p967">Template:Harvnb</ref> but tetrahedral TiCl4 is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of covalent bonding.<ref name="Greenwood1997p958" />
Oxides, sulfides, and alkoxides
The most important oxide is TiO2, which exists in three important polymorphs; anatase, brookite, and rutile. All three are white diamagnetic solids, although mineral samples can appear dark, as in rutile. They adopt polymeric structures in which Ti is surrounded by six oxide ligands that link to other Ti centers.<ref name="Greenwood1997p961">Template:Harvnb</ref>
The term titanates usually refers to titanium(IV) compounds, as represented by barium titanate (BaTiO3). With a perovskite structure, this material exhibits piezoelectric properties and is used as a transducer in the interconversion of sound and electricity.<ref name="TICE6th" /> Many minerals are titanates, such as ilmenite (FeTiO3). Star sapphires and rubies get their asterism (star-forming shine) from the presence of titanium dioxide impurities.<ref name="Emsley2001p453" />
A variety of reduced oxides (suboxides) of titanium are known, mainly reduced stoichiometries of titanium dioxide obtained by atmospheric plasma spraying. Ti3O5, described as a Ti(IV)-Ti(III) species, is a purple semiconductor produced by reduction of TiO2 with hydrogen at high temperatures,<ref>Template:Cite journal</ref> and is used industrially when surfaces need to be vapor-coated with titanium dioxide: it evaporates as pure TiO, whereas TiO2 evaporates as a mixture of oxides and deposits coatings with variable refractive index.<ref>Template:Cite journal</ref> Also known is Ti2O3, with the corundum structure, and TiO, with the rock salt structure, although often nonstoichiometric.Template:Sfn
The alkoxides of titanium(IV), prepared by treating TiCl4 with alcohols, are colorless compounds that convert to the dioxide on reaction with water. They are industrially useful for depositing solid TiO2 via the sol-gel process. Titanium isopropoxide is used in the synthesis of chiral organic compounds via the Sharpless epoxidation.<ref>Template:Cite journal</ref>
Titanium forms a variety of sulfides, but only TiS2 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 "hard cation", the sulfides of titanium are unstable and tend to hydrolyze to the oxide with release of hydrogen sulfide.<ref>Template:Cite book</ref>
Nitrides and carbides
Titanium nitride (TiN) is a refractory solid exhibiting extreme hardness, thermal/electrical conductivity, and a high melting point.<ref>Template:Cite journal</ref> TiN has a hardness equivalent to sapphire and carborundum (9.0 on the Mohs scale),<ref>Template:Cite web</ref> and is often used to coat cutting tools, such as drill bits.<ref>Template:Cite magazine</ref> It is also used as a gold-colored decorative finish and as a barrier layer in semiconductor fabrication.<ref>Template:Cite book</ref> Titanium carbide (TiC), which is also very hard, is found in cutting tools and coatings.<ref>Template:Cite web</ref>
Halides
Titanium tetrachloride (titanium(IV) chloride, TiCl4<ref>Template:Cite report</ref>) is a colorless volatile liquid (commercial samples are yellowish) that, in air, hydrolyzes with spectacular emission of white clouds. Via the Kroll process, TiCl4 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>Template:Cite book</ref> It is widely used in organic chemistry as a Lewis acid, for example in the Mukaiyama aldol condensation.<ref>Template:Cite book</ref> In the van Arkel–de Boer process, titanium tetraiodide (TiI4) is generated in the production of high purity titanium metal.<ref name="Greenwood1997p965">Template:Harvnb</ref>
Titanium(III) and titanium(II) also form stable chlorides. A notable example is titanium(III) chloride (TiCl3), which is used as a catalyst for production of polyolefins (see Ziegler–Natta catalyst) and a reducing agent in organic chemistry.<ref>Template:Cite encyclopedia</ref>
Organometallic complexes
Template:Main Owing to the important role of titanium compounds as polymerization catalyst, compounds with Ti-C bonds have been intensively studied. The most common organotitanium complex is titanocene dichloride ((C5H5)2TiCl2). Related compounds include Tebbe's reagent and Petasis reagent. Titanium forms carbonyl complexes, e.g. (C5H5)2Ti(CO)2.<ref>Template:Cite book</ref>
History
Titanium was discovered in 1791 by the clergyman and geologist William Gregor as an inclusion of a mineral in 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 magnet.<ref name=Emsley2001p452/> Analyzing the sand, he determined the presence of two metal oxides: iron oxide (explaining the attraction to the magnet) and 45.25% of a white metallic oxide he could not identify.<ref name="Barksdale1968p732">Template:Harvnb</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: Crell's Annalen and Observations et Mémoires sur la Physique.<ref name=Emsley2001p452/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> He named this oxide manaccanite.<ref>Template:Cite journal</ref>
Around the same time, 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 Prussian chemist Martin Heinrich Klaproth in rutile from Boinik (the German name of Bajmócska), a village in Hungary (now Bojničky in Slovakia).<ref name="Emsley2001p452" />Template:Efn Klaproth found that it contained a new element and named it for the Titans of 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>Template:Cite report</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 carbon (as in iron smelting) because titanium combines with the carbon to produce titanium carbide.<ref name=Emsley2001p452/> An extraction of 95% pure titanium was achieved by Lars Fredrik Nilson and Otto Petterson. To achieve this they chlorinated titanium oxide in a carbon monoxide atmosphere with chlorine gas before reducing it to titanium metal by the use of sodium.<ref>Template:Citation</ref> Pure metallic titanium (99.9%) was first prepared in 1910 by Matthew A. Hunter at Rensselaer Polytechnic Institute by heating TiCl4 with sodium at Template:Convert under great pressure<ref name=Roza2008p9>Template:Harvnb</ref> in a batch process known as the 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 (TiCl4) with calcium.<ref name=Greenwood1997p955>Template:Harvnb</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 FFC Cambridge process, the Kroll process is still predominantly used for commercial production.<ref name=LANL/><ref name=HistoryAndUse/>
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>Template:Cite journal</ref>
In the 1950s and 1960s, the Soviet Union pioneered the use of titanium in military and submarine applications<ref name=Roza2008p9/> (Alfa class and Mike class)<ref>Template:Cite web</ref> as part of programs related to the Cold War.<ref>Template:Cite news</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 Lockheed A-12 and SR-71.<ref>Template:Cite book</ref>
Throughout the Cold War period, titanium was considered a strategic material by the U.S. government, and a large stockpile of titanium 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>Template:Cite report</ref> Even so, the U.S. government annually allocates 15,000Template:Spacesmetric tons of titanium sponge as potential acquisitions for the stockpile.<ref name=":3" />
Production
| Country | thousand tonnes |
% of total |
|---|---|---|
| ChinaTemplate:Efn | 3,300 | 35.3 |
| Mozambique | 1,908 | 20.4 |
| South Africa | 1,400 | 15.0 |
| Australia | 600 | 6.4 |
| NorwayTemplate:Efn | 360 | 3.8 |
| CanadaTemplate:Efn | 350 | 3.7 |
| SenegalTemplate:Efn | 300 | 3.2 |
| MadagascarTemplate:Efn | 240 | 2.6 |
| India | 222 | 4.3 |
| Ukraine | 130 | 1.4 |
| United States | 100 | 1.1 |
| Sierra LeoneTemplate:Efn | 60 | 0.6 |
| KenyaTemplate:Efn | 40 | 0.4 |
| Other countries | 350 | 3.7 |
| World | 9,360 | 100 |
Titanium production is largely divided into three measured categories: manufacture of porous titanium metal "sponge", titanium oxide pigment, and titanium mineral concentrates used for the production of sponge, pigment, metal ingots, and other titanium products such as coatings. These concentrates are largely made up of the mineral ilmenite, but also include anatase, natural and synthetic rutile, tailings, slag, and leucoxene. As of 2024, the largest producers of titanium mineral concentrates were China, Mozambique, and South Africa.<ref name=":3">Template:Cite web</ref>
Most of the world's titanium is produced in China. The United States Geological Survey's 2025 report on mineral commodities estimated that out of the Template:Convert of titanium sponge produced globally in 2024, 220,000 (69%) were produced in China, with the second-largest producer being Japan (which produced 55,000Template:Spacesmetric tons in the same year, 17% of the total). Japan was the largest exporter of titanium sponge in 2024, but did not produce any titanium minerals on its own.<ref name=":3" /> A prior report in 2021 noted that the four leading producers of titanium sponge were China (52%), Japan (24%), Russia (16%) and Kazakhstan (7%).<ref name="USGS" /> Russia remains the third-largest producer of titanium sponge<ref name=":3" /> through the efforts of the metallurgy company VSMPO-AVISMA, despite international sanctions during the Russian invasion of Ukraine.<ref>Template:Cite news</ref> Production statistics on titanium dioxide pigment are not as clear-cut, but estimates placed the maximum capacity on global pigment production at Template:Convert in 2024.<ref name=":3" />
Various methods have been developed to extract and refine titanium from ore since the metal was first purified in 1910.<ref name=":0" /><ref name=":4" />
Mineral beneficiation processes
Several processes have been developed to extract titanium and usable titanium-containing minerals from ore. The Becher process is an industrial process used to produce synthetic rutile, a form of titanium dioxide, from the ore ilmenite by removing iron.<ref>Template:Cite web</ref> It is not used at scale.<ref name=":4">Template:Cite book</ref> The chloride process produces titanium tetrachloride through treatment of rutile ore with chlorine and carbon at high heat,<ref name="Greenwood1997p960" /> then oxidizes the product with an oxygen flame or plasma to produce titanium dioxide.<ref name=UllmannPigments>Template:Cite encyclopedia</ref> The sulfate process uses sulfuric acid (H2SO4) to leach titanium from ilmenite ore (FeTiO3), producing titanyl sulfate (Template:Chem2). This sulfate is broken into two hydrates, Template:Chem2 and Template:Chem2, through addition of water, and this water is removed by adding heat, which produces titanium dioxide as the end product.<ref name="bar1">Template:Cite news</ref>
Purification processes
Hunter process
The Hunter process was the first industrial process to produce pure metallic titanium. It was invented in 1910 by Matthew A. Hunter, a chemist born in New Zealand who worked in the United States.<ref>Template:Cite journal</ref> The process involves reducing titanium tetrachloride (TiCl4) with sodium (Na) in a batch reactor with an inert atmosphere at a temperature of 1,000 °C. Dilute hydrochloric acid is then used to leach the salt from the product.<ref>Template:Cite encyclopedia</ref>
- TiCl4(g) + 4 Na(l) → 4 NaCl(l) + Ti(s)
Kroll process
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 billet, bar, plate, sheet, strip, and tube; and secondary fabrication of finished shapes from mill products.<ref>Template:Harvnb</ref>
Because it cannot be readily produced by reduction of titanium dioxide,<ref name=Stwertka1998/> titanium metal is obtained by reduction of titanium tetrachloride (TiCl4) 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>Template:Harvnb</ref> despite the Kroll process being less expensive than the Hunter process.<ref name=Roza2008p9/> To produce the TiCl4 required by the Kroll process, the dioxide is subjected to carbothermic reduction in the presence of 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, the TiCl4 is reduced with Template:Convert molten magnesium in an argon atmosphere.<ref name=TICE6th/>
- <chem>2FeTiO3 + 7Cl2 + 6C ->[900^oC] 2FeCl3 + 2TiCl4 + 6CO</chem>
- <chem>TiCl4 + 2Mg ->[1100^oC] Ti + 2MgCl2</chem>
Arkel-Boer process
The van Arkel–de Boer process was the first semi-industrial process developed to produce pure titanium, invented by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925 for the electronics company Philips.<ref name=":1">Template:Cite journal</ref> It is a closed-loop process<ref name=":2">Template:Cite book</ref> that involves thermal decomposition of titanium tetraiodide.<ref>Template:Cite book</ref> This same process is used to purify other metals, such as thorium, hafnium, and zirconium,<ref name=":1" /> and a similar process using further refined iodide was used to refine chromium. A desire to develop processes that could be run continuously led to the development of commercial processes to refine titanium.<ref name=":2" />
Armstrong process
Titanium powder is manufactured using a flow production process known as the Armstrong process<ref name=Roza2008p25>Template:Harvnb</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) are filtered from the extra sodium. Titanium is then separated from the salt by water washing. Both the sodium and chlorine are recycled to produce and process more titanium tetrachloride.<ref name="ECI online">Template:Cite web</ref>
Other processes
The titanium tetrachloride used as an intermediate in both the Hunter and Kroll process is a volatile and corrosive liquid, and is thus hazardous to work with. The processes involving the tetrachloride, both its formation and the vacuum distillation processes used to purify the final material, are slow, and have prompted development of other techniques.<ref name=flower>Template:Cite journal</ref>
Methods for electrolytic production of Ti metal from Template:Chem2 using molten salt electrolytes have been proposed starting in the 1990s,<ref name=flower /> and have been researched and tested at laboratory and small pilot plant scales.<ref name="fray17">Template:Cite journal</ref> While some metals such as nickel and copper can be refined by electrowinning at room temperature, titanium must be in the molten state, which is likely to damage the refractory lining of a reaction vessel.<ref name="sohn23">Template:Cite journal</ref> Zhang and colleagues concluded in 2017 that despite industry interests in finding new ways to manufacture titanium metal, no method had yet been developed to commercially replace the Kroll process.<ref name="zhang17">Template:Cite journal</ref> One manufacturer in Virginia has developed a method to recycle scrap titanium metal back into powder, though their scale remains small, having the goal of producing only 125 tons of titanium per year as of 2025.<ref name=":3" />
One method that has been developed to potentially supplant the Kroll process is known as hydrogen-assisted magnesiothermic reduction and makes use of magnesium, hydrochloric acid, and a hydrogen atmosphere to directly reduce titanium dioxide to pure titanium. The reduction of titanium dioxide powder by magnesium in an atomphere of hydrogen can be followed by a leaching step with hydrochloric acid, which removes magnesium and residual non-titanium oxides. This is followed by additional reduction and leaching steps, and eventually results in pure titanium powder or titanium hydride.<ref>Template:Cite journal</ref>
Fabrication
All welding of titanium must be done in an inert atmosphere of argon or helium to shield it from contamination with atmospheric gases (oxygen, nitrogen, and hydrogen).<ref name=Barksdale1968p734/> Contamination causes a variety of conditions, such as embrittlement, which reduce the integrity of the assembly welds and lead to joint failure.<ref>Template:Cite book</ref>
Titanium is very difficult to solder directly, and hence a solderable metal or alloy such as steel is coated on titanium prior to soldering.<ref>Template:Cite book</ref> Titanium metal can be machined with the same equipment and the same processes as stainless steel.<ref name="Barksdale1968p734" />
Titanium alloys
Common titanium alloys are made by reduction. For example, cuprotitanium (rutile with copper added), ferrocarbon titanium (ilmenite reduced with coke in an electric furnace), and manganotitanium (rutile with manganese or manganese oxides) are reduced.<ref name=TI_Encarta2005>Template:Cite encyclopedia</ref>
About fifty grades of titanium alloys are designed and currently used, although only a couple of dozen are readily available commercially.<ref>Template:Harvnb</ref> The ASTM International recognizes 31 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 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, creep resistance, specific corrosion resistance, and combinations thereof.<ref>Template:Cite book Template:Cite book</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>Template:Harvnb</ref>
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>Template:Cite book</ref><ref>Template:Cite book</ref> Exposure to the oxygen in air at the elevated temperatures used in forging results in formation of a brittle oxygen-rich metallic surface layer called "alpha case" that worsens the fatigue properties, so it must be removed by milling, etching, or electrochemical treatment.<ref name=""Chen 2001"">Template:Cite journal</ref> The working of titanium may include friction welding,<ref name="mti1">Template:Cite web</ref> cryo-forging,<ref name="mdes1">Template:Cite news</ref> and vacuum arc remelting.<ref>Template:Cite journal</ref>
Applications
Titanium is used in steel as an alloying element (ferro-titanium) to reduce 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), vanadium, copper (to harden), iron, manganese, molybdenum, and other metals.<ref name=ECE738>Template:Cite book</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 as a source of bright-burning particles.<ref>Template:Cite book</ref>
Pigments, additives, and coatings
Titanium dioxide (Template:Chem) is the most common compound of the element, being the end point of 95% of the world's refined titanium. It is a widely used white pigment.<ref name="USGS">Template:Cite web</ref> It is also used in cement, in gemstones, and as an optical opacifier in paper.<ref>Template:Cite book</ref>
Template:Chem 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 index of refraction and an optical dispersion higher than diamond.<ref name=LANL/> Titanium dioxide is used in sunscreens because it reflects and absorbs UV light.<ref name=Stwertka1998/>
Aerospace and marine
Because titanium alloys have high tensile strength to density ratio,<ref name="TICE6th" /> high corrosion resistance,<ref name=LANL/> fatigue resistance, high crack resistance,<ref name=Moiseyev>Template:Cite book</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, landing gear, firewalls, exhaust ducts (helicopters), and hydraulic systems. About two thirds of all titanium metal produced is used in aircraft frames and engines.<ref name=Emsley2001p454/> The titanium 6AL-4V alloy accounts for almost 50% of all alloys used in aircraft applications.<ref>Template:Harvnb</ref>
The 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 metric tons are used in the Boeing 787, 77 in the Airbus A380, 59 in the Boeing 777, 45 in the Boeing 747, 32 in the Airbus A340, 18 in the Boeing 737, 18 in the Airbus A330, and 12 in the Airbus A320.<ref>Template:Cite book</ref> In aero engine applications, titanium is used for rotors, compressor blades, hydraulic system components, and nacelles.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> An early use in jet engines was for the Orenda Iroquois in the 1950s.<ref>Template:Cite book</ref><ref>Template:Cite web</ref><ref>Template:Cite book</ref>
Because titanium is resistant to corrosion by sea water, it is used to make propeller shafts, rigging, heat exchangers 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 military. The former Soviet Union developed techniques for making submarines with hulls of titanium alloys,<ref>Template:Cite web</ref> forging titanium in huge vacuum tubes.<ref name=Kramer-2013-07-05>Template:Cite news</ref>
Industrial
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 nickel 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 sodium hypochlorite or wet chlorine gas (in the bleachery).<ref>Template:Harvnb</ref> Titanium is also used in sputtering targets.<ref>Template:Cite book</ref>
Powdered titanium acts as a non-evaporative getter, and is one of several gas-reactive materials used to remove gases from ultra-high vacuum systems.<ref>Template:Cite journal</ref> This application manifested in titanium sublimation pumps<ref>Template:Cite journal</ref> first employed in 1961,<ref>Template:Cite report</ref> though the metal was first used in vacuum systems to prevent chambers from oxidizing in a design created by Raymond Herb in 1953.<ref>Template:Cite web</ref>
Titanium tetrachloride (TiCl4), a colorless liquid, is important as an intermediate in the process of making TiO2 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" /> In many industrial applications, titanium and its alloys can serve as a potential substitute for other metals, such as nickel, niobium, scandium, silver, tantalum, and tungsten.<ref>Template:Cite web</ref>
Consumer and architectural
Titanium metal is used in automotive applications, particularly in automobile and motorcycle racing where low weight and high strength and rigidity are critical.<ref>Template:Cite conference</ref> The metal is generally too expensive for the general consumer market, though some late model Corvettes have been manufactured with titanium exhausts.<ref>Template:Cite web</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>Template:Cite book</ref> Titanium is used in spectable frames, as it is durable and protect the lenses, though it may be less flexible than alternatives.<ref>Template:Cite book</ref> Its biocompatibility is a potential benefit over other glasses frame materials.<ref>Template:Cite journal</ref> Titanium is a common material for backpacking cookware and eating utensils. Titanium horseshoes are preferred to steel by farriers because they are lighter and more durable.<ref name=Donachie2000>Template:Harvnb</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>Template:Cite book</ref>
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Titanium has occasionally been used in architecture. The Template:Convert Monument to Yuri Gagarin, the first man to travel in space, as well as the upper part of the Template:Convert Monument to the Conquerors of Space on top of the Cosmonaut Museum in Moscow are made of titanium.<ref>Template:Cite book</ref><ref>Template:Cite book</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">Template:Harvnb</ref> Titanium sheathing was used in the Frederic C. Hamilton Building in Denver, Colorado.<ref>Template:Cite web</ref>
Because of titanium's superior strength and light weight relative to other metals (steel, stainless steel, and aluminium), and because of advances in metalworking techniques, its use has become 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 Apple's PowerBook G4)<ref>Template:Cite web</ref><ref name="use" /> and phones (such as the iPhone 15 Pro).<ref>Template:Cite web</ref>
Jewelry
Because of its durability, titanium is used in some designer jewelry, such as titanium rings.<ref name=Donachie2000/> Its inertness makes it hypoallergenic and wearable in environments such as swimming pools. Titanium is also alloyed with gold to produce an alloy that can be marketed as 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>Template:Cite journal</ref>
Titanium's durability, light weight, and dent and corrosion resistance make it useful for watch cases.<ref name="Donachie2000" /> Some artists work with titanium to produce sculptures, decorative objects and furniture.<ref>Template:Cite web</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>Template:Cite web</ref> With its variable coloration and chemical inertness, titanium is a popular metal for body piercing.<ref>Template:Cite web</ref>
Titanium has a minor use in dedicated non-circulating coins and medals. In 1999, the world's first titanium coin was minted for Gibraltar's millennium celebration.<ref>Template:Cite web</ref> Pobjoy Mint, the British mint that produced the coin, continued to manufacture anodized titanium coins<ref>Template:Cite web</ref> until its closure in 2023.<ref>Template:Cite web</ref> The Gold Coast Titans, an Australian rugby league team, award a medal of pure titanium to their player of the year.<ref>Template:Cite news</ref>
Medical
Template:Main Because titanium is 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 (joint replacement) and dental implants.<ref name="Emsley2001p452">Template:Harvnb</ref> Titanium and titanium alloy implants have been used in surgery since the 1950s, and are favored due to their low rate of corrosion, long life, and low Young's modulus. A titanium alloy that contains 6% aluminium and 4% vanadium commonly used in the aerospace industry is also a common material for artificial joints.<ref name="e429">Template:Cite journal</ref>
Titanium has the inherent ability to 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 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 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>Template:Cite journal</ref><ref>Template:Cite journal</ref> Biomedical implants coated with a combination of silver and titanium have been researched as a potential option for load-bearing implants that need antimicrobial surfaces.<ref name="e429" />
Modern advancements in additive manufacturing techniques have increased potential for titanium use in orthopedic implant applications.<ref>Template:Cite journal</ref> Complex implant scaffold designs can be 3D-printed using titanium alloys, which allows for more patient-specific applications and increased implant osseointegration.<ref>Template:Cite journal</ref> Because titanium is non-ferromagnetic, patients with titanium implants can be safely examined with magnetic resonance imaging (convenient for long-term implants). Preparing titanium for implantation in the body involves subjecting it to a high-temperature plasma arc which removes the surface atoms, exposing fresh titanium that is instantly oxidized.<ref name="Emsley2001p452" /> Titanium is used for the surgical instruments used in image-guided surgery, as well as wheelchairs, crutches, and any other products where high strength and low weight are desirable.<ref>Template:Cite book</ref>
Titanium dioxide nanoparticles are widely used in electronics and the delivery of pharmaceuticals and cosmetics.<ref>Template:Cite journal</ref>
Anticancer therapy studies
Following the success of platinum-based chemotherapy, titanium(IV) complexes were among the first non-platinum compounds to be tested and accepted for clinical trials in cancer treatment.<ref>Template:Cite journal</ref> The advantage of titanium compounds lies in their high efficacy and low toxicity in vivo. 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. Further development resulted in the creation of potentially effective, selective, and stable titanium-based drugs.<ref name=Tshuva-Miller>Template:Cite book</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>Template:Cite journal</ref> A titanium "drip shield" has been considered for installation over containers of other types to enhance their longevity.<ref>Template:Cite journal</ref>
Hazards and safety
Titanium is non-toxic, even in large doses, and does not play any natural role inside the human body.<ref name="Emsley2001p451" /> An estimated 0.8Template:Spacesmilligrams of titanium is ingested by humans each day, but most passes through the digestive system without being absorbed in the tissues.<ref name="Emsley2001p451" /> However, it can sometimes bioaccumulate in tissues that contain silica. Yellow nail syndrome has been reported in individuals that have been exposed to titanium, though the disorder's rarity have made it difficult to determine a direct association between exposure and disorder development.<ref>Template:Cite journal</ref><ref>Template:Cite journal</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>Template:Cite book</ref> Water and 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 exposed to dry chlorine gas may result in a titanium–chlorine fire.<ref>Template:Cite book</ref> Titanium can also catch fire when a fresh, non-oxidized surface comes in contact with liquid oxygen.<ref>Template:Cite book</ref>
Function in plants
An unknown mechanism in plants may use titanium to stimulate the production of carbohydrates and encourage growth. This may explain why most plants contain about 1 part per million (ppm) of titanium, food plants have about 2 ppm, and horsetail and nettle contain up to 80 ppm.<ref name="Emsley2001p451" />
See also
Footnotes
References
Bibliography
External links
- "Titanium: Our Next Major Metal" in Popular Science (October 1950), one of first general public detailed articles on Titanium
- Titanium at Periodic Videos (University of Nottingham)
- Titanium.org: official website of the International Titanium Association, an industry association
- Metallurgy of Titanium and its Alloys - slide presentations, movies, and other material from Harshad Bhadeshia and other Cambridge University metallurgists
Template:Periodic table (navbox) Template:Titanium compounds Template:Titanium minerals Template:Jewellery Template:Authority control