View source for Titanium dioxide

{{Chembox new
|   Name = Titanium dioxide
|   ImageFile = Titanium(IV)_oxide.jpg
|   ImageSize = 200px
|   ImageName = Titanium(IV) oxide
|   ImageFile1 = Rutile-unit-cell-3D-balls.png
|   ImageSize1 = 200px
|   ImageName1 = The unit cell of rutile
|   IUPACName = Titanium dioxide<br />Titanium(IV) oxide
|   OtherNames = Titania<br />[[Rutile]]<br />[[Anatase]]<br />[[Brookite]]
| Section1 = {{Chembox Identifiers
|   CASNo = 13463-67-7
|   RTECS = XR2775000
  }}
| Section2 = {{Chembox Properties
|   Formula = [[titanium|Ti]][[oxygen|O]]<sub>2
|   MolarMass = 79.87 g/mol
|   Appearance = White solid
|   Density = 4.23 g/cm<sup>3</sup>
|   MeltingPt = 1870 °C (3398 °F)
|   BoilingPt = 2972 °C (5381.6 °F)
|   Solvent = other solvents
|   SolubleOther = Insoluble
  }}
| Section4 = {{Chembox Thermochemistry
|   DeltaHf = &minus;249 [[joule|kJ]]/[[mole (unit)|mol]]
|   DeltaHf = &minus;879 [[joule|kJ]]/[[mole (unit)|mol]]
|   DeltaHf = &minus;944 [[joule|kJ]]/[[mole (unit)|mol]]     }}
| Section7 = {{Chembox Hazards
|   EUClass = not listed
|   NFPA-H = 1
|   NFPA-F =
|   NFPA-R =
|   FlashPt = non-flammable
  }}
| Section8 = {{Chembox Related
|   OtherCations = [[Titanium(II) oxide]]<br />[[Titanium(III) oxide]]<br />[[Titanium(III,IV) oxide]]<br />[[Zirconium dioxide]]<br />[[Hafnium dioxide]]
  }}
}}
{{SI}}



'''Titanium dioxide''', also known as '''titanium(IV) oxide''' or '''titania''', is the naturally occurring [[oxide]] of [[titanium]], chemical formula [[titanium|Ti]][[oxygen|O]]<sub>2</sub>. When used as a [[pigment]], it is called '''titanium white''', '''Pigment White 6''', or '''[[Colour Index International|CI 77891]]'''. It is noteworthy for its wide range of applications, from paint to sunscreen to [[food colouring]].

==Natural occurrence==

Titanium dioxide occurs in four forms:
* [[rutile]], a [[tetragon]]al mineral usually of prismatic habit, often twinned;
* [[anatase]] or octahedrite, a tetragonal mineral of dipyramidal habit;
* [[brookite]], an [[orthorhombic]] mineral. Both anatase and brookite are relatively rare minerals;
* [[Titanium dioxide (B)]] or TiO<sub>2</sub>(B), a [[monoclinic]] mineral.

Titanium dioxide occurrences in nature are never pure; it is found with contaminant metals such as [[iron]]. The oxides can be mined and serve as a source for commercial [[titanium]]. The metal can also be mined from other minerals such as [[ilmenite]] or [[leucoxene]] [[ore]]s, or one of the purest forms, [[rutile]] beach sand.

==Production==
Crude titanium dioxide is purified via [[titanium tetrachloride]] in the [[Chloride process]]. In this process, the crude ore (containing at least 90% TiO<sub>2</sub>) is reduced with [[carbon]], oxidized with [[chlorine]] to give [[titanium tetrachloride]]. This titanium tetrachloride is distilled, and re-oxidized with [[oxygen]] to give pure titanium dioxide.<ref>{{cite web | publisher = Millenium Inorganic Chemicals | title = Titanium Dioxide Manufacturing Processes | url = http://www.millenniumchem.com/Products+and+Services/Products+by+Type/Titanium+Dioxide+-+Paint+and+Coatings/r_TiO2+Fundamentals/Titanium+Dioxide+Manufacturing+Processes_EN.htm | accessdate = 2007-09-05}}</ref>

==Applications==
Titanium dioxide is the most widely used white pigment because of its brightness and very high [[refractive index]] (''n''=2.4), in which it is surpassed only by a [[List of indices of refraction|few other]] materials.  When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for [[dielectric mirrors]] and some [[gemstone|gemstones]], for example "mystic fire [[topaz]]".  TiO<sub>2</sub> is also an effective [[opacifier]] in powder form, where it is employed as a pigment to provide whiteness and [[opacity]] to products such as [[paint]]s, [[coating]]s, [[plastic]]s, [[paper]]s, [[ink]]s, [[food]]s, [[medicine]]s (i.e. pills and tablets) as well as most [[toothpaste]]s. Used as a white [[food coloring|food colouring]], it has [[E number]] E171. In [[Cosmetics|cosmetic]] and [[skin care]] products, titanium dioxide is used both as a pigment and a [[thickener]]. It is also used as a [[tattoo]] pigment and [[styptic pencil]]s.

This pigment is used extensively in plastics and other applications for its UV resistant properties where it acts as a UV reflector.

In [[ceramic glaze]]s titanium dioxide acts as an opacifier and seeds [[crystal]] formation. In almost every [[sunscreen]] with a physical blocker, titanium dioxide is found both because of its refractive index and its resistance to discolouration under [[ultraviolet]] light.  This advantage enhances its stability and ability to protect the skin from ultraviolet light. Sunscreens designed for infants or people with sensitive skin are often based on titanium dioxide and/or [[zinc oxide]], as these mineral UV blockers are less likely to cause skin irritation than chemical UV [[absorber]] ingredients, such as [[avobenzone]].

Titanium oxide is also used as a semi-conductor.<ref>http://prola.aps.org/abstract/PR/v61/i1-2/p56_1</ref>

===As a photocatalyst===
Titanium dioxide, particularly in the anatase form, is a [[photocatalysis|photocatalyst]] under ultraviolet light. Recently it has been found that titanium dioxide, when spiked with nitrogen ions, is also a photocatalyst under visible light. The strong [[redox|oxidative potential]] of the [[electron hole|positive holes]] oxidizes [[water]] to create [[hydroxyl radical]]s. It can also oxidize oxygen or organic materials directly. Titanium dioxide is thus added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and anti-fouling properties and is also used as a [[hydrolysis]] [[catalyst]]. It is also used in the [[Graetzel cell]], a type of chemical solar cell.

Titanium dioxide has potential for use in energy production: as a photocatalyst, it can:
# carry out [[hydrolysis]], i.e., break water into hydrogen and oxygen.  Were the hydrogen collected, it could be used as a fuel.  The efficiency of this process can be greatly improved by doping the oxide with carbon, as described in "Carbon-doped titanium dioxide is an effective photocatalyst" [http://www.highbeam.com/doc/1G1-110587279.html].
# produce electricity when in nanoparticle form. Research suggests that by using these nanoparticles to form the pixels of a screen, they generate electricity when transparent and under the influence of light. If subjected to electricity on the other hand, the nanoparticles blacken, forming the basic characteristics of a LCD screen. According to creator Zoran Radivojevic, Nokia has already built a functional 200 by 200 pixels monochromatic screen which is energetically self-sufficient.

As TiO<sub>2</sub> is exposed to UV light, it becomes increasingly [[hydrophilic]]; thus, it can be used for [[anti-fog]]ging coatings or self-cleaning windows. TiO<sub>2</sub> incorporated into outdoor building materials, such as paving stones in [[noxer block]]s, can substantially reduce concentrations of airborne pollutants such as [[volatile organic compound]]s and [[nitrogen oxide]]s.

====For wastewater remediation====
TiO<sub>2</sub> offers great potential as an industrial technology for detoxification or [[remediation]] of [[wastewater]] due to several factors.
# The process occurs under ambient conditions.
# The formation of photocyclized intermediate products, unlike direct [[photolysis]] techniques, is avoided.
# Oxidation of the substrates to CO<sub>2</sub> is complete.
# The photocatalyst is inexpensive and has a high turnover.
# TiO<sub>2</sub> can be supported on suitable reactor substrates.

===Other applications===
It is also used in resistance-type [[lambda probe]]s (a type of [[oxygen sensor]]).

Titanium dioxide is what allows [[osseointegration]] between an [[Implant (medicine)|artificial medical implant]] and [[bone]].

Titanium dioxide in solution or suspension can be used to cleave [[protein]] that contains the amino acid [[proline]] at the site where proline is present. This breakthrough in cost-effective protein splitting took place at [[ASU]] in 2006.<ref>http://pubs.acs.org/cgi-bin/article.cgi/ancham/2007/79/i04/pdf/ac0613737.pdf</ref>

Titanium dioxide on silica is being developed as a form of odor control in [[cat litter]]. The purchased photocatalyst is vastly cheaper than the purchased silica beads, per usage, and prolongs their effective odor-eliminating life substantially.

The Pilkington Activ glass has a special nano-scale, extremely thin [[hydrophobic]] coating of microcrystalline titanium oxide which catalyses the break-down of organic surface contamination by ultraviolet light from the sun. [http://news.bbc.co.uk/1/hi/technology/3770353.stm]

==Historical uses==
The [[Vinland map]], the map of [[North America|America]] ("[[Vinland]]") that was supposedly drawn during mid-15th century based on data from the [[Viking Age]], has been declared a forgery on the basis that the ink on it contains traces of the TiO<sub>2</sub>-form anatase; TiO<sub>2</sub> was not synthetically produced before the 1920s. Recently (1992) a counter-claim has been made that the compound can be formed from ancient ink.

Titanium dioxide white paint was used to paint the [[Saturn V]] rocket, which is so far the only rocket that has sent astronauts to the moon. In [[2002]], a spectral analysis of [[J002E3]], a celestial object, showed that it had titanium dioxide on it, giving evidence it may be a Saturn V [[S-IVB]].

==See also==

* [[Noxer]], a building material incorporating TiO<sub>2</sub>.

==References==
<div class="references-small" style="-moz-column-count:2; column-count:2;">
<references/>
</div>

==External links==
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0338.htm International Chemical Safety Card 0338]
* [http://www.cdc.gov/niosh/npg/npgd0617.html NIOSH Pocket Guide to Chemical Hazards]
* [http://news.bbc.co.uk/1/hi/health/2162248.stm "Fresh doubt over America map", ''bbc.co.uk'', 30 July, 2002]
* [http://www.threebond.co.jp/en/technical/technicalnews/pdf/tech62.pdf A description of TiO<sub>2</sub> photocatalysis]
* [http://www.newscientist.com/article.ns?id=dn4636 "Smog-busting paint soaks up noxious gases", Jenny Hogan, 'newscientist.com'', 04 February 2004]
* [http://ruby.colorado.edu/~smyth/min/tio2.html Crystal structures of the three forms of TiO<sub>2</sub>]
* Kutal, C., Serpone, N. (1993). Photosensitive Metal Organic Systems: Mechanistic Principles and Applications. American Chemical Society, Washington D.C
* [http://www.iht.com/articles/2006/11/22/news/smog.php "Architecture in Italy goes green", Elisabetta Povoledo, ''International Herald Tribune'', November 22, 2006]
* [http://www.businessweek.com/innovate/content/nov2006/id20061108_116412.htm?campaign_id=bier_innv.g3a.rss1109c "A Concrete Step Toward Cleaner Air", Bruno Giussani, ''BusinessWeek.com'', November 8, 2006]


[[Category:Titanium compounds]]
[[Category:Oxides]]
[[Category:Inorganic pigments]]
[[Category:Food colorings]]
[[Category:Sunscreening agents]]

[[ar:ثاني أكسيد التيتانيوم]]
[[de:Titandioxid]]
[[es:Dióxido de titanio]]
[[fr:Dioxyde de titane]]
[[it:Diossido di titanio]]
[[hu:Titán-dioxid]]
[[nl:Titaanwit]]
[[ja:二酸化チタン]]
[[pl:Tlenek tytanu(IV)]]
[[pt:Dióxido de titânio]]
[[ru:Оксид титана(IV)]]
[[fi:Titaanidioksidi]]
[[sv:Titandioxid]]
[[zh:二氧化鈦]]

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