Titanium dioxide

Titanium dioxide, also known as titanium(IV) oxide or titania /taɪˈteɪniə/, is the inorganic compound with the chemical formula TiO
₂. When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891.^[4] It is a white solid that is insoluble in water, although mineral forms can appear black. As a pigment, it has a wide range of applications, including paint, sunscreen, and food coloring. When used as a food coloring, it has E number E171. World production in 2014 exceeded 9 million tonnes.^[5][6][7] It has been estimated that titanium dioxide is used in two-thirds of all pigments, and pigments based on the oxide have been valued at a price of $13.2 billion.^[8]

Titanium dioxide

Unit cell of titanium dioxide (rutile form)   Titanium   Oxygen
Names
IUPAC names Titanium dioxide Titanium(IV) oxide
Other names Titania Rutile Anatase Brookite
Identifiers
CAS Number	13463-67-7^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:32234^Y
ChEMBL	ChEMBL1201136^N
ChemSpider	24256^Y
ECHA InfoCard	100.033.327
E number	E171 (colours)
KEGG	C13409^N
PubChem CID	26042
RTECS number	XR2775000
UNII	15FIX9V2JP^Y
CompTox Dashboard (EPA)	DTXSID3021352
InChI InChI=1S/2O.Ti^Y Key: GWEVSGVZZGPLCZ-UHFFFAOYSA-N^Y InChI=1/2O.Ti/rO2Ti/c1-3-2 Key: GWEVSGVZZGPLCZ-TYTSCOISAW
SMILES O=[Ti]=O
Properties
Chemical formula	TiO 2
Molar mass	79.866 g/mol
Appearance	White solid
Odor	Odorless
Density	4.23 g/cm^3 (rutile) 3.78 g/cm^3 (anatase)
Melting point	1,843 °C (3,349 °F; 2,116 K)
Boiling point	2,972 °C (5,382 °F; 3,245 K)
Solubility in water	Insoluble
Band gap	3.05 eV (rutile)^[1]
Magnetic susceptibility (χ)	+5.9·10^−6 cm^3/mol
Refractive index (nD)	2.488 (anatase) 2.583 (brookite) 2.609 (rutile)
Thermochemistry
Std molar entropy (S^⦵298)	50 J·mol^−1·K^−1^[2]
Std enthalpy of formation (ΔfH^⦵298)	−945 kJ·mol^−1^[2]
Hazards
NFPA 704 (fire diamond)	1 0 0
Flash point	not flammable
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 15 mg/m^3^[3]
REL (Recommended)	Ca^[3]
IDLH (Immediate danger)	Ca [5000 mg/m^3]^[3]
Safety data sheet (SDS)	ICSC 0338
Related compounds
Other cations	Zirconium dioxide Hafnium dioxide
Related Titanium oxides	Titanium(II) oxide Titanium(III) oxide Titanium(III,IV) oxide
Related compounds	Titanic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

Structure

In all three of its main dioxides, titanium exhibits octahedral geometry, being bonded to six oxide anions. The oxides in turn are bonded to three Ti centers. The overall crystal structures of rutile and anatase are tetragonal in symmetry whereas brookite is orthorhombic. The oxygen substructures are all slight distortions of close packing: in rutile, the oxide anions are arranged in distorted hexagonal close-packing, whereas they are close to cubic close-packing in anatase and to "double hexagonal close-packing" for brookite. The rutile structure is widespread for other metal dioxides and difluorides, e.g. RuO₂ and ZnF₂.

Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms.^[9] This is distinct from the crystalline forms in which Ti coordinates to 6 oxygen atoms.

 

Structure of anatase. Together with rutile and brookite, one of the three major polymorphs of TiO₂.

Synthetic and geologic occurrence

Synthetic TiO₂ is mainly produced from the mineral ilmenite. Rutile, and anatase, naturally occurring TiO₂, occur widely also, e.g. rutile as a 'heavy mineral' in beach sand. Leucoxene, fine-grained anatase formed by natural alteration of ilmenite, is yet another ore. Star sapphires and rubies get their asterism from oriented inclusions of rutile needles.^[10]

Mineralogy and uncommon polymorphs

Titanium dioxide occurs in nature as the minerals rutile and anatase. Additionally two high-pressure forms are known minerals: a monoclinic baddeleyite-like form known as akaogiite, and the other has a slight monoclinic distortion of the orthorhombic α-PbO₂ structure and is known as riesite. Both of which can be found at the Ries crater in Bavaria.^[11][12][13] It is mainly sourced from ilmenite, which is the most widespread titanium dioxide-bearing ore around the world. Rutile is the next most abundant and contains around 98% titanium dioxide in the ore. The metastable anatase and brookite phases convert irreversibly to the equilibrium rutile phase upon heating above temperatures in the range 600–800 °C (1,110–1,470 °F).^[14]

Titanium dioxide has twelve known polymorphs – in addition to rutile, anatase, brookite, akaogiite and riesite, three metastable phases can be produced synthetically (monoclinic, tetragonal, and orthorhombic ramsdellite-like), and four high-pressure forms (α-PbO₂-like, cotunnite-like, orthorhombic OI, and cubic phases) also exist:

Form	Crystal system	Synthesis
Rutile	Tetragonal
Anatase	Tetragonal
Brookite	Orthorhombic
TiO2(B)^[15]	Monoclinic	Hydrolysis of K2Ti4O9 followed by heating
TiO2(H), hollandite-like form^[16]	Tetragonal	Oxidation of the related potassium titanate bronze, K0.25TiO2
TiO2(R), ramsdellite-like form^[17]	Orthorhombic	Oxidation of the related lithium titanate bronze Li0.5TiO2
TiO2(II)-(α-PbO2-like form)^[18]	Orthorhombic
Akaogiite (baddeleyite-like form, 7 coordinated Ti)^[19]	Monoclinic
TiO2 -OI^[20]	Orthorhombic
Cubic form^[21]	Cubic	P > 40 GPa, T > 1600 °C
TiO2 -OII, cotunnite(PbCl2)-like^[22]	Orthorhombic	P > 40 GPa, T > 700 °C

The cotunnite-type phase was claimed to be the hardest known oxide with the Vickers hardness of 38 GPa and the bulk modulus of 431 GPa (i.e. close to diamond's value of 446 GPa) at atmospheric pressure.^[22] However, later studies came to different conclusions with much lower values for both the hardness (7–20 GPa, which makes it softer than common oxides like corundum Al₂O₃ and rutile TiO₂)^[23] and bulk modulus (~300 GPa).^[24][25]

Titanium dioxide (B) is found as a mineral in magmatic rocks and hydrothermal veins, as well as weathering rims on perovskite. TiO₂ also forms lamellae in other minerals.^[26]

Production

 

Evolution of the global production of titanium dioxide according to process

The largest TiO
₂ pigment processors are Chemours, Venator, Kronos [de], and Tronox.^[27][28] Major paint and coating company end users for pigment grade titanium dioxide include Akzo Nobel, PPG Industries, Sherwin Williams, BASF, Kansai Paints and Valspar.^[29] Global TiO
₂ pigment demand for 2010 was 5.3 Mt with annual growth expected to be about 3–4%.^[30]

The production method depends on the feedstock. In addition to ores, other feedstocks include upgraded slag. Both sulfate and chloride processes produce the titanium dioxide pigment in the rutile crystal form, but the Sulfate Process can be adjusted to produce the anatase form. Anatase, being softer, is used in fiber and paper applications. The Sulfate Process is run as a batch process; the Chloride Process is run as a continuous process.^[31]

Chloride process

In chloride process, the ore is treated with chlorine and carbon to give titanium tetrachloride, a volatile liquid that is further purified by distillation. The TiCl4 is treated with oxygen to regenerate chlorine and produce the titanium dioxide.

Sulfate process

Chemical manufacturing plants using the sulfate process, require ilmenite concentrate (45–60% TiO₂) or pretreated feedstocks as a suitable source of titanium.^[32] In the sulfate process, ilmenite is treated with sulfuric acid to extract iron(II) sulfate pentahydrate. The resulting synthetic rutile is further processed according to the specifications of the end user, i.e. pigment grade or otherwise.^[33] In another method for the production of synthetic rutile from ilmenite the Becher process first oxidizes the ilmenite as a means to separate the iron component.

Specialized methods

For specialty applications, TiO₂ films are prepared by various specialized chemistries.^[34] Sol-gel routes involve the hydrolysis of titanium alkoxides, such as titanium ethoxide:

Ti(OEt)₄ + 2 H₂O → TiO₂ + 4 EtOH

This technology is suited for the preparation of films. A related approach that also relies on molecular precursors involves chemical vapor deposition. In this application, the alkoxide is volatilized and then decomposed on contact with a hot surface:

Ti(OEt)₄ → TiO₂ + 2 Et₂O

Applications

Pigment

Main article: Titanium white

First mass-produced in 1916,^[35] titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index, in which it is surpassed only by a few other materials (see list of indices of refraction). Titanium dioxide crystal size is ideally around 220 nm (measured by electron microscope) to optimize the maximum reflection of visible light. However, abnormal grain growth is often observed in titanium dioxide, particularly in its rutile phase.^[36] The occurrence of abnormal grain growth brings about a deviation of a small number of crystallites from the mean crystal size and modifies the physical behaviour of TiO₂. The optical properties of the finished pigment are highly sensitive to purity. As little as a few parts per million (ppm) of certain metals (Cr, V, Cu, Fe, Nb) can disturb the crystal lattice so much that the effect can be detected in quality control.^[37] Approximately 4.6 million tons of pigmentary TiO₂ are used annually worldwide, and this number is expected to increase as use continues to rise.^[38]

TiO₂ is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, supplements, medicines (i.e. pills and tablets), and most toothpastes; in 2019 it was present in two-thirds of toothpastes on the French market.^[39] In food, it is commonly found in products like ice creams, chocolates, all types of candy, creamers, desserts, marshmallows, chewing gum, pastries, spreads, dressings, cakes, and many other foods.^[40] In paint, it is often referred to offhandedly as "brilliant white", "the perfect white", "the whitest white", or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles.

Thin films

When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for dielectric mirrors; it is also used in generating decorative thin films such as found in "mystic fire topaz".

Some grades of modified titanium based pigments as used in sparkly paints, plastics, finishes and cosmetics – these are man-made pigments whose particles have two or more layers of various oxides – often titanium dioxide, iron oxide or alumina – in order to have glittering, iridescent and or pearlescent effects similar to crushed mica or guanine-based products. In addition to these effects a limited colour change is possible in certain formulations depending on how and at which angle the finished product is illuminated and the thickness of the oxide layer in the pigment particle; one or more colours appear by reflection while the other tones appear due to interference of the transparent titanium dioxide layers.^[41] In some products, the layer of titanium dioxide is grown in conjunction with iron oxide by calcination of titanium salts (sulfates, chlorates) around 800 °C^[42] One example of a pearlescent pigment is Iriodin, based on mica coated with titanium dioxide or iron (III) oxide.^[43]

The iridescent effect in these titanium oxide particles is unlike the opaque effect obtained with usual ground titanium oxide pigment obtained by mining, in which case only a certain diameter of the particle is considered and the effect is due only to scattering.

Sunscreen and UV blocking pigments

In cosmetic and skin care products, titanium dioxide is used as a pigment, sunscreen and a thickener. As a sunscreen, ultrafine TiO₂ is used, which is notable in that combined with ultrafine zinc oxide, it is considered to be an effective sunscreen that lowers the incidence of sun burns and minimizes the premature photoaging, photocarcinogenesis and immunosuppression associated with long term excess sun exposure.^[44] Sometimes these UV blockers are combined with iron oxide pigments in sunscreen to increase visible light protection.^[45]

Titanium dioxide and zinc oxide are generally considered to be less harmful to coral reefs than sunscreens that include chemicals such as oxybenzone, octocrylene and octinoxate.^[46]

Nanosized titanium dioxide is found in the majority of physical sunscreens because of its strong UV light absorbing capabilities and its resistance to discolouration under ultraviolet light. This advantage enhances its stability and ability to protect the skin from ultraviolet light. Nano-scaled (particle size of 20–40 nm)^[47] titanium dioxide particles are primarily used in sunscreen lotion because they scatter visible light much less than titanium dioxide pigments, and can give UV protection.^[38] 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 believed to cause less skin irritation than other UV absorbing chemicals. Nano-TiO₂ blocks both UV-A and UV-B radiation, which is used in sunscreens and other cosmetic products. It is safe to use and it is better to environment than organic UV-absorbers.^[48]

The risk assessment of different titanium dioxide nanomaterials in sunscreen is currently evolving as nano-sized TiO₂ is different from the well-known micronized form.^[49] The rutile form is generally used in cosmetic and sunscreen products due to it not possessing any observed ability to damage the skin under normal conditions^[50] and having a higher UV absorption.^[51] In 2016 Scientific Committee on Consumer Safety (SCCS) tests concluded that the use of nano titanium dioxide (95–100% rutile, ≦5% anatase) as a UV filter can be considered to not pose any risk of adverse effects in humans post-application on healthy skin,^[52] except in the case the application method would lead to substantial risk of inhalation (ie; powder or spray formulations). This safety opinion applied to nano TiO₂ in concentrations of up to 25%.^[53]

Initial studies indicated that nano-TiO₂ particles could penetrate the skin causing concern over the use of nano-TiO₂. These studies were later refuted, when it was discovered that the testing methodology couldn't differentiate between penetrated particles and particles simply trapped in hair follicles and that having a diseased or physically damaged dermis could be the true cause of insufficient barrier protection.^[49]

SCCS research found that when nanoparticles had certain photostable coatings (eg. alumina, silica, cetyl phosphate, triethoxycaprylylsilane, manganese dioxide) the photocatalytic activity was attenuated and no notable skin penetration was observed; the sunscreen in this research was applied at amounts of 10 mg/cm2 for exposure periods of 24 hours.^[53] Coating TiO₂ with alumina, silica, zircon or various polymers can minimize avobenzone degradation^[54] and enhance UV absorption by adding an additional light diffraction mechanism.^[51]

TiO
₂ is used extensively in plastics and other applications as a white pigment or an opacifier and for its UV resistant properties where the powder disperses light – unlike organic UV absorbers – and reduces UV damage, due mostly to the particle's high refractive index.^[55]

Other uses of titanium dioxide

In ceramic glazes, titanium dioxide acts as an opacifier and seeds crystal formation.

It is used as a tattoo pigment and in styptic pencils. Titanium dioxide is produced in varying particle sizes which are both oil and water dispersible, and in certain grades for the cosmetic industry. It is also a common ingredient in toothpaste.

The exterior of the Saturn V rocket was painted with titanium dioxide; this later allowed astronomers to determine that J002E3 was likely the S-IVB stage from Apollo 12 and not an asteroid.^[56]

Research

Photocatalyst

Nanosized titanium dioxide, particularly in the anatase form, exhibits photocatalytic activity under ultraviolet (UV) irradiation. This photoactivity is reportedly most pronounced at the {001} planes of anatase,^[57][58] although the {101} planes are thermodynamically more stable and thus more prominent in most synthesised and natural anatase,^[59] as evident by the often observed tetragonal dipyramidal growth habit. Interfaces between rutile and anatase are further considered to improve photocatalytic activity by facilitating charge carrier separation and as a result, biphasic titanium dioxide is often considered to possess enhanced functionality as a photocatalyst.^[60] It has been reported that titanium dioxide, when doped with nitrogen ions or doped with metal oxide like tungsten trioxide, exhibits excitation also under visible light.^[61] The strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. It can also oxidize oxygen or organic materials directly. Hence, in addition to its use as a pigment, titanium dioxide can be added to paints, cements, windows, tiles, or other products for its sterilizing, deodorizing, and anti-fouling properties, and is used as a hydrolysis catalyst. It is also used in dye-sensitized solar cells, which are a type of chemical solar cell (also known as a Graetzel cell).

The photocatalytic properties of nanosized titanium dioxide were discovered by Akira Fujishima in 1967^[62] and published in 1972.^[63] The process on the surface of the titanium dioxide was called the Honda-Fujishima effect (ja:本多-藤嶋効果).^[62] Titanium dioxide, in thin film and nanoparticle form has potential for use in energy production: as a photocatalyst, it can break water into hydrogen and oxygen. With 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.^[64] Further efficiency and durability has been obtained by introducing disorder to the lattice structure of the surface layer of titanium dioxide nanocrystals, permitting infrared absorption.^[65] Visible-light-active nanosized anatase and rutile has been developed for photocatalytic applications.^[66][67]

In 1995 Fujishima and his group discovered the superhydrophilicity phenomenon for titanium dioxide coated glass exposed to sun light.^[62] This resulted in the development of self-cleaning glass and anti-fogging coatings.

Nanosized TiO₂ incorporated into outdoor building materials, such as paving stones in noxer blocks^[68] or paints, could reduce concentrations of airborne pollutants such as volatile organic compounds and nitrogen oxides.^[69] A TiO₂-containing cement has been produced.^[70]

Using TiO₂ as a photocatalyst, attempts have been made to mineralize pollutants (to convert into CO₂ and H₂O) in waste water.^[71][72][73] The photocatalytic destruction of organic matter could also be exploited in coatings with antimicrobial applications.^[74]

Hydroxyl radical formation

Although nanosized anatase TiO₂ does not absorb visible light, it does strongly absorb ultraviolet (UV) radiation (hv), leading to the formation of hydroxyl radicals.^[75] This occurs when photo-induced valence bond holes (h⁺_vb) are trapped at the surface of TiO₂ leading to the formation of trapped holes (h⁺_tr) that cannot oxidize water.^[76]

TiO₂ + hv → e⁻ + h⁺_vb

h⁺_vb → h⁺_tr

O₂ + e⁻ → O₂^•−

O₂^•− + O₂^•−+ 2 H⁺ → H₂O₂ + O₂

O₂^•− + h⁺_vb → O₂

O₂^•− + h⁺_tr → O₂

 OH⁻ + h⁺_vb → HO•

e⁻ + h⁺_tr → recombination

Note: Wavelength (λ)= 387 nm^[76] This reaction has been found to mineralize and decompose undesirable compounds in the environment, specifically the air and in wastewater.^[76]

 

Synthetic single crystals of TiO₂, ca. 2–3 mm in size, cut from a larger plate

Nanotubes

 

Titanium oxide nanotubes, SEM image

 

Nanotubes of titanium dioxide (TiO₂-Nt) obtained by electrochemical synthesis. The SEM image shows an array of vertical self-ordered TiO₂-Nt with closed bottom ends of tubes.

Anatase can be converted into non-carbon nanotubes and nanowires.^[77] Hollow TiO₂ nanofibers can be also prepared by coating carbon nanofibers by first applying titanium butoxide.^[78]

 

SEM (top) and TEM (bottom) images of chiral TiO₂ nanofibers^[78]

Health and safety

As of 2006, titanium dioxide has been regarded as "completely nontoxic".^[4] Widely-occurring minerals and even gemstones are composed of TiO₂. All natural titanium, comprising more than 0.5% of the earth's crust, exists as oxides. Although no evidence points to acute toxicity, recurring concerns have been expressed about nanophase forms of these materials. Studies of workers with high exposure to TiO₂ particles indicate that even at high exposure there is no adverse effect to human health.^[79]

The European Union removed the authorization to use titanium dioxide (E 171) in foods, effective 7 February 2022, with a six months grace period.^[80]

Titanium dioxide dust, when inhaled, has been classified by the International Agency for Research on Cancer (IARC) as an IARC Group 2B carcinogen, meaning it is possibly carcinogenic to humans.^[81][82] The US National Institute for Occupational Safety and Health recommends two separate exposure limits. NIOSH recommends that fine TiO
₂ particles be set at an exposure limit of 2.4 mg/m³, while ultrafine TiO
₂ be set at an exposure limit of 0.3 mg/m³, as time-weighted average concentrations up to 10 hours a day for a 40-hour work week.^[83]

As of May 2023 (and as a result of the European Union already having banned it in 2022), U.S. states California and New York are considering banning the use of Titanium dioxide in foods.^[84]

Environmental waste introduction

Titanium dioxide (TiO₂) is mostly introduced into the environment as nanoparticles via wastewater treatment plants.^[85] Cosmetic pigments including titanium dioxide enter the wastewater when the product is washed off into sinks after cosmetic use. Once in the sewage treatment plants, pigments separate into sewage sludge which can then be released into the soil when injected into the soil or distributed on its surface. 99% of these nanoparticles wind up on land rather than in aquatic environments due to their retention in sewage sludge.^[85] In the environment, titanium dioxide nanoparticles have low to negligible solubility and have been shown to be stable once particle aggregates are formed in soil and water surroundings.^[85] In the process of dissolution, water-soluble ions typically dissociate from the nanoparticle into solution when thermodynamically unstable. TiO₂ dissolution increases when there are higher levels of dissolved organic matter and clay in the soil. However, aggregation is promoted by pH at the isoelectric point of TiO₂ (pH= 5.8) which renders it neutral and solution ion concentrations above 4.5 mM.^[86][87]

National policies on food additive use

TiO₂ whitener in food was banned in France from 2020, due to uncertainty about what quantities were safe for human consumption.^[88]

In 2021, the European Food Safety Authority (EFSA) ruled that as a consequence of new understandings of nanoparticles, titanium dioxide could "no longer be considered safe as a food additive", and the EU health commissioner announced plans to ban its use across the EU, with discussions beginning in June 2021. EFSA concluded that genotoxicity—which could lead to carcinogenic effects—could not be ruled out, and that a "safe level for daily intake of the food additive could not be established".^[89] In 2022, the UK Food Standards Agency and Food Standards Scotland announced they disagreed with the EFSA ruling, and would therefore not follow the EU in banning titanium dioxide as a food additive.^[90] Health Canada has similarly reviewed the available evidence and decided not to change their position on titanium dioxide as a food additive at this time.^[91]

Research as an ingestible nanomaterial

Due to the potential that long-term ingestion of titanium dioxide may be toxic, particularly to cells and functions of the gastrointestinal tract, preliminary research is assessing its possible role in disease development, such as inflammatory bowel disease and colorectal cancer, as of 2021.^[92]

Culture and society

Companies such as Dunkin' Donuts dropped titanium dioxide from their merchandise in 2015 after public pressure.^[93] Andrew Maynard, director of Risk Science Center at the University of Michigan, rejected the supposed danger from use of titanium dioxide in food. He says that the titanium dioxide used by Dunkin' Brands and many other food producers is not a new material, and it is not a nanomaterial either. Nanoparticles are typically smaller than 100 nanometres in diameter, yet most of the particles in food grade titanium dioxide are much larger.^[94] Still, size distribution analyses showed that batches of food-grade TiO₂ always include a nano-sized fraction as inevitable byproduct of the manufacturing processes.^[95]

See also

• Delustrant
• Dye-sensitized solar cell
• List of inorganic pigments
• Noxer blocks, TiO₂-coated pavers that remove NO_x pollutants from the air
• Suboxide
• Surface properties of transition metal oxides
• Titanium dioxide nanoparticle

References

1. Nowotny, Janusz (2011). Oxide Semiconductors for Solar Energy Conversion: Titanium Dioxide. CRC Press. p. 156. ISBN 9781439848395.
2. Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A23. ISBN 978-0-618-94690-7.
3. NIOSH Pocket Guide to Chemical Hazards. "#0617". National Institute for Occupational Safety and Health (NIOSH).
4. Völz, Hans G.; et al. (2006). "Pigments, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a20_243.pub2.
5. "Titanium" in 2014 Minerals Yearbook. USGS
6. "Mineral Commodity Summaries, 2015" (PDF). U.S. Geological Survey. U.S. Geological Survey 2015.
7. "Mineral Commodity Summaries, January 2016" (PDF). U.S. Geological Survey. U.S. Geological Survey 2016.
8. Schonbrun, Zach. "The Quest for the Next Billion-Dollar Color". Bloomberg.com. Retrieved 24 April 2018.
9. Alderman, O. L. G., Skinner, L. B., Benmore, C. J., Tamalonis, A., Weber, J. K. R. (2014). "Structure of Molten Titanium Dioxide". Physical Review B. 90 (9): 094204. Bibcode:2014PhRvB..90i4204A. doi:10.1103/PhysRevB.90.094204.{{cite journal}}: CS1 maint: multiple names: authors list (link)
10. Emsley, John (2001). Nature's Building Blocks: An A–Z Guide to the Elements. Oxford: Oxford University Press. pp. 451–53. ISBN 978-0-19-850341-5.
11. El, Goresy; Chen, M; Dubrovinsky, L; Gillet, P; Graup, G (2001). "An ultradense polymorph of rutile with seven-coordinated titanium from the Ries crater". Science. 293 (5534): 1467–70. Bibcode:2001Sci...293.1467E. doi:10.1126/science.1062342. PMID 11520981. S2CID 24349901.
12. El Goresy, Ahmed; Chen, Ming; Gillet, Philippe; Dubrovinsky, Leonid; Graup, GüNther; Ahuja, Rajeev (2001). "A natural shock-induced dense polymorph of rutile with α-PbO2 structure in the suevite from the Ries crater in Germany". Earth and Planetary Science Letters. 192 (4): 485. Bibcode:2001E&PSL.192..485E. doi:10.1016/S0012-821X(01)00480-0.
13. Akaogiite. mindat.org
14. Hanaor, Dorian A. H.; Sorrell, Charles C. (February 2011). "Review of the anatase to rutile phase transformation". Journal of Materials Science. 46 (4): 855–874. Bibcode:2011JMatS..46..855H. doi:10.1007/s10853-010-5113-0. S2CID 97190202.
15. Marchand R.; Brohan L.; Tournoux M. (1980). "A new form of titanium dioxide and the potassium octatitanate K₂Ti₈O₁₇". Materials Research Bulletin. 15 (8): 1129–1133. doi:10.1016/0025-5408(80)90076-8.
16. Latroche, M; Brohan, L; Marchand, R; Tournoux (1989). "New hollandite oxides: TiO₂(H) and K_0.06TiO₂". Journal of Solid State Chemistry. 81 (1): 78–82. Bibcode:1989JSSCh..81...78L. doi:10.1016/0022-4596(89)90204-1.
17. Akimoto, J.; Gotoh, Y.; Oosawa, Y.; Nonose, N.; Kumagai, T.; Aoki, K.; Takei, H. (1994). "Topotactic Oxidation of Ramsdellite-Type Li_0.5TiO₂, a New Polymorph of Titanium Dioxide: TiO₂(R)". Journal of Solid State Chemistry. 113 (1): 27–36. Bibcode:1994JSSCh.113...27A. doi:10.1006/jssc.1994.1337.
18. Simons, P. Y.; Dachille, F. (1967). "The structure of TiO₂II, a high-pressure phase of TiO₂". Acta Crystallographica. 23 (2): 334–336. doi:10.1107/S0365110X67002713.
19. Sato H; Endo S; Sugiyama M; Kikegawa T; Shimomura O; Kusaba K (1991). "Baddeleyite-Type High-Pressure Phase of TiO₂". Science. 251 (4995): 786–788. Bibcode:1991Sci...251..786S. doi:10.1126/science.251.4995.786. PMID 17775458. S2CID 28241170.
20. Dubrovinskaia N. A.; Dubrovinsky L. S.; Ahuja R.; Prokopenko V. B.; Dmitriev V.; Weber H.-P.; Osorio-Guillen J. M.; Johansson B. (2001). "Experimental and Theoretical Identification of a New High-Pressure TiO₂ Polymorph". Phys. Rev. Lett. 87 (27 Pt 1): 275501. Bibcode:2001PhRvL..87A5501D. doi:10.1103/PhysRevLett.87.275501. PMID 11800890.
21. Mattesini M.; de Almeida J. S.; Dubrovinsky L.; Dubrovinskaia L.; Johansson B.; Ahuja R. (2004). "High-pressure and high-temperature synthesis of the cubic TiO₂ polymorph". Phys. Rev. B. 70 (21): 212101. Bibcode:2004PhRvB..70u2101M. doi:10.1103/PhysRevB.70.212101.
22. Dubrovinsky, LS; Dubrovinskaia, NA; Swamy, V; Muscat, J; Harrison, NM; Ahuja, R; Holm, B; Johansson, B (2001). "Materials science: The hardest known oxide". Nature. 410 (6829): 653–654. Bibcode:2001Natur.410..653D. doi:10.1038/35070650. hdl:10044/1/11018. PMID 11287944. S2CID 4365291.
23. Oganov A.R.; Lyakhov A.O. (2010). "Towards the theory of hardness of materials". Journal of Superhard Materials. 32 (3): 143–147. arXiv:1009.5477. Bibcode:2010arXiv1009.5477O. doi:10.3103/S1063457610030019. S2CID 119280867.
24. Al-Khatatbeh, Y.; Lee, K. K. M. & Kiefer, B. (2009). "High-pressure behavior of TiO₂ as determined by experiment and theory". Phys. Rev. B. 79 (13): 134114. Bibcode:2009PhRvB..79m4114A. doi:10.1103/PhysRevB.79.134114.
25. Nishio-Hamane D.; Shimizu A.; Nakahira R.; Niwa K.; Sano-Furukawa A.; Okada T.; Yagi T.; Kikegawa T. (2010). "The stability and equation of state for the cotunnite phase of TiO₂ up to 70 GPa". Phys. Chem. Minerals. 37 (3): 129–136. Bibcode:2010PCM....37..129N. doi:10.1007/s00269-009-0316-0. S2CID 95463163.
26. Banfield, J. F., Veblen, D. R., and Smith, D. J. (1991). "The identification of naturally occurring TiO₂ (B) by structure determination using high-resolution electron microscopy, image simulation, and distance–least–squares refinement" (PDF). American Mineralogist. 76: 343.{{cite journal}}: CS1 maint: multiple names: authors list (link)
27. "Top 5 Vendors in the Global Titanium Dioxide Market From 2017-2021: Technavio" (Press release). 20 April 2017.
28. Hayes, Tony (2011). "Titanium Dioxide: A Shining Future Ahead" (PDF). Euro Pacific Canada. p. 5. Retrieved 16 August 2012.^{[permanent dead link]}
29. Hayes (2011), p. 3
30. Hayes (2011), p. 4
31. "Titanium dioxide".
32. Vartiainen, Jaana (7 October 1998). "Process for preparing titanium dioxide" (PDF).
33. Winkler, Jochen (2003). Titanium Dioxide. Hannover: Vincentz Network. pp. 30–31. ISBN 978-3-87870-148-4.
34. Chen, Xiaobo; Mao, Samuel S. (2007). "Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications". Chemical Reviews. 107 (7): 2891–2959. doi:10.1021/cr0500535. PMID 17590053.
35. St. Clair, Kassia (2016). The Secret Lives of Colour. London: John Murray. p. 40. ISBN 9781473630819. OCLC 936144129.
36. Hanaor, D. A. H.; Xu, W.; Ferry, M.; Sorrell, C. C. (2012). "Abnormal grain growth of rutile TiO₂ induced by ZrSiO₄". Journal of Crystal Growth. 359: 83–91. arXiv:1303.2761. Bibcode:2012JCrGr.359...83H. doi:10.1016/j.jcrysgro.2012.08.015. S2CID 94096447.
37. Anderson, Bruce (1999). Kemira pigments quality titanium dioxide. Savannah, Georgia. p. 39.{{cite book}}: CS1 maint: location missing publisher (link)
38. Winkler, Jochen (2003). Titanium Dioxide. Hannover, Germany: Vincentz Network. p. 5. ISBN 978-3-87870-148-4.
39. Margaux de Frouville (28 March 2019). "Deux dentifrices sur trois contiennent du dioxyde de titane, un colorant au possible effet cancérogène" [Two out of three toothpastes contain titanium dioxide, a possibly carcinogenic colouring material] (in French). BFMTV.com.
40. "Titanium Dioxide (E171) – Overview, Uses, Side Effects & More". HealthKnight. 10 April 2022. Retrieved 9 June 2022.
41. Koleske, J. V. (1995). Paint and Coating Testing Manual. ASTM International. p. 232. ISBN 978-0-8031-2060-0.
42. Koleske, J. V. (1995). Paint and Coating Testing Manual. ASTM International. p. 229. ISBN 978-0-8031-2060-0.
43. , pearl-effect.com, archived from the original on 17 January 2012
44. Gabros, Sarah; Nessel, Trevor A.; Zito, Patrick M. (2021), "Sunscreens And Photoprotection", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30725849, retrieved 6 March 2021
45. Dumbuya, Hawasatu; Grimes, Pearl E.; Lynch, Stephen; Ji, Kaili; Brahmachary, Manisha; Zheng, Qian; Bouez, Charbel; Wangari-Talbot, Janet (1 July 2020). "Impact of Iron-Oxide Containing Formulations Against Visible Light-Induced Skin Pigmentation in Skin of Color Individuals". Journal of Drugs in Dermatology. 19 (7): 712–717. doi:10.36849/JDD.2020.5032. ISSN 1545-9616. PMID 32726103.
46. "US Virgin Islands bans sunscreens harming coral reefs". www.downtoearth.org.in. Retrieved 6 March 2021.
47. Dan, Yongbo et al. Measurement of Titanium Dioxide Nanoparticles in Sunscreen using Single Particle ICP-MS. perkinelmer.com
48. "Health_scientific_committees" (PDF).
49. Jacobs, J. F.; Van De Poel, I.; Osseweijer, P. (2010). "Sunscreens with Titanium Dioxide (TiO₂) Nano-Particles: A Societal Experiment". Nanoethics. 4 (2): 103–113. doi:10.1007/s11569-010-0090-y. PMC 2933802. PMID 20835397.
50. cosmeticsdesign-europe.com. "Scientists encourage 'safer' rutile form of TiO₂ in cosmetics". cosmeticsdesign-europe.com. Retrieved 6 March 2021.
51. Jaroenworaluck, A.; Sunsaneeyametha, W.; Kosachan, N.; Stevens, R. (29 March 2006). "Characteristics of silica‐coated TiO₂ and its UV absorption for sunscreen cosmetic applications". Wiley Analytical Science. 38 (4): 473–477. doi:10.1002/sia.2313. S2CID 97137064 – via Wiley Online Library.
52. Dréno, Alexis, Chuberre, & Marinovich (2019). "Safety of Titanium Dioxide Nanoparticles in Cosmetics". Journal of the European Academy of Dermatology and Venereology. 33 (Suppl 7): 34–46. doi:10.1111/jdv.15943. PMID 31588611. S2CID 203849903.{{cite journal}}: CS1 maint: multiple names: authors list (link)
53. "OPINION ON additional coatings for Titanium Dioxide (nano form) as UV-filter in dermally applied cosmetic products" (PDF). Scientific Committee on Consumer Safety (SCCS). European Commission. 7 November 2016 – via ec.europa.eu.
54. Wang, Can; Zuo, Shixiang; Liu, Wenjie; Yao, Chao; Li, Xiazhang; Li, Zhongyu (2016). "Preparation of rutile TiO₂@avobenzone composites for the further enhancement of sunscreen performance". RSC Advances. 6 (113): 111865. Bibcode:2016RSCAd...6k1865W. doi:10.1039/C6RA23282E – via Royal society of chemistry.
55. Polymers, Light and the Science of TiO₂ 29 March 2017 at the Wayback Machine, DuPont, pp. 1–2
56. Jorgensen, K.; Rivkin, A.; Binzel, R.; Whitely, R.; Hergenrother, C.; Chodas, P.; Chesley, S.; Vilas, F. (May 2003). "Observations of J002E3: Possible Discovery of an Apollo Rocket Body". Bulletin of the American Astronomical Society. 35: 981. Bibcode:2003DPS....35.3602J.
57. Liang Chu (2015). "Anatase TiO₂ Nanoparticles with Exposed {001} Facets for Efficient Dye-Sensitized Solar Cells". Scientific Reports. 5: 12143. Bibcode:2015NatSR...512143C. doi:10.1038/srep12143. PMC 4507182. PMID 26190140.
58. Li Jianming and Dongsheng Xu (2010). "tetragonal faceted-nanorods of anatase TiO₂ single crystals with a large percentage of active {100} facets". Chemical Communications. 46 (13): 2301–3. doi:10.1039/b923755k. PMID 20234939.
59. M Hussein N Assadi (2016). "The effects of copper doping on photocatalytic activity at (101) planes of anatase TiO 2: A theoretical study". Applied Surface Science. 387: 682–689. arXiv:1811.09157. Bibcode:2016ApSS..387..682A. doi:10.1016/j.apsusc.2016.06.178. S2CID 99834042.
60. Hanaor, Dorian A. H.; Sorrell, Charles C. (2014). "Sand Supported Mixed-Phase TiO₂ Photocatalysts for Water Decontamination Applications". Advanced Engineering Materials. 16 (2): 248–254. arXiv:1404.2652. Bibcode:2014arXiv1404.2652H. doi:10.1002/adem.201300259. S2CID 118571942.
61. Kurtoglu M. E.; Longenbach T.; Gogotsi Y. (2011). "Preventing Sodium Poisoning of Photocatalytic TiO₂ Films on Glass by Metal Doping". International Journal of Applied Glass Science. 2 (2): 108–116. doi:10.1111/j.2041-1294.2011.00040.x.
62. . Japan Nanonet Bulletin Issue 44, 12 May 2005.
63. Fujishima, Akira; Honda, Kenichi (1972). "Electrochemical Photolysis of Water at a Semiconductor Electrode". Nature. 238 (5358): 37–8. Bibcode:1972Natur.238...37F. doi:10.1038/238037a0. PMID 12635268. S2CID 4251015.
64. . Advanced Ceramics Report. 1 December 2003. Archived from the original on 4 February 2007. This carbon-doped titanium dioxide is highly efficient; under artificial visible light, it breaks down chlorophenol five times more efficiently than the nitrogen-doped version.
65. Cheap, Clean Ways to Produce Hydrogen for Use in Fuel Cells? A Dash of Disorder Yields a Very Efficient Photocatalyst. Sciencedaily (28 January 2011)
66. Karvinen, Saila (2003). "Preparation and Characterization of Mesoporous Visible-Light-Active Anatase". Solid State Sciences. 5 2003 (8): 1159–1166. Bibcode:2003SSSci...5.1159K. doi:10.1016/S1293-2558(03)00147-X.
67. Bian, Liang; Song, Mianxin; Zhou, Tianliang; Zhao, Xiaoyong; Dai, Qingqing (June 2009). "Band gap calculation and photo catalytic activity of rare earths doped rutile TiO2". Journal of Rare Earths. 27 (3): 461–468. doi:10.1016/S1002-0721(08)60270-7.
68. Advanced Concrete Pavement materials 20 June 2013 at the Wayback Machine, National Concrete Pavement Technology Center, Iowa State University, p. 435.
69. Hogan, Jenny (4 February 2004) "Smog-busting paint soaks up noxious gases". New Scientist.
70. TIME's Best Inventions of 2008. (31 October 2008).
71. Winkler, Jochen (2003). Titanium Dioxide. Hannover: Vincentz Network. pp. 115–116. ISBN 978-3-87870-148-4.
72. Konstantinou, Ioannis K; Albanis, Triantafyllos A (2004). "TiO₂-assisted photocatalytic degradation of azo dyes in aqueous solution: Kinetic and mechanistic investigations". Applied Catalysis B: Environmental. 49: 1–14. doi:10.1016/j.apcatb.2003.11.010.
73. Hanaor, Dorian A. H.; Sorrell, Charles C. (2014). "Sand Supported Mixed-Phase TiO₂ Photocatalysts for Water Decontamination Applications". Advanced Engineering Materials. 16 (2): 248–254. arXiv:1404.2652. doi:10.1002/adem.201300259. S2CID 118571942.
74. Ramsden, Jeremy J. (2015). "Photocatalytic antimicrobial coatings". Nanotechnology Perceptions. 11 (3): 146–168. doi:10.4024/N12RA15A.ntp.15.03.
75. Jones, Tony; Egerton, Terry A. (2000). "Titanium Compounds, Inorganic". Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. doi:10.1002/0471238961.0914151805070518.a01.pub3. ISBN 9780471238966.
76. Hirakawa, Tsutomu; Nosaka, Yoshio (23 January 2002). "Properties of O2•-and OH• formed in TiO₂ aqueous suspensions by photocatalytic reaction and the influence of H2O2 and some ions". Langmuir. 18 (8): 3247–3254. doi:10.1021/la015685a.
77. Mogilevsky, Gregory; Chen, Qiang; Kleinhammes, Alfred; Wu, Yue (2008). "The structure of multilayered titania nanotubes based on delaminated anatase". Chemical Physics Letters. 460 (4–6): 517–520. Bibcode:2008CPL...460..517M. doi:10.1016/j.cplett.2008.06.063.
78. Wang, Cui (2015). "Hard-templating of chiral TiO₂ nanofibres with electron transition-based optical activity". Science and Technology of Advanced Materials. 16 (5): 054206. Bibcode:2015STAdM..16e4206W. doi:10.1088/1468-6996/16/5/054206. PMC 5070021. PMID 27877835.
79. Warheit DB, Donner EM (November 2015). "Risk assessment strategies for nanoscale and fine-sized titanium dioxide particles: Recognizing hazard and exposure issues". Food Chem Toxicol (Review). 85: 138–47. doi:10.1016/j.fct.2015.07.001. PMID 26362081.
80. 'amending Annexes II and III to Regulation (EC) No 1333/2008 of the European Parliament and of the Council as regards the food additive titanium dioxide (E 171)'. COMMISSION REGULATION (EU) 2022/63, 14 January 2022
81. "Titanium dioxide" (PDF). 93. International Agency for Research on Cancer. 2006. {{cite journal}}: Cite journal requires |journal= (help)
82. "Titanium Dioxide Classified as Possibly Carcinogenic to Humans". Canadian Centre for Occupational Health & Safety. August 2006.
83. National Institute for Occupational Safety and Health. "Current Intelligence Bulletin 63: Occupational Exposure to Titanium Dioxide (NIOSH Publication No. 2011-160)" (PDF). National Institute for Occupational Safety and Health.
84. Two States Have Proposed Bans on Common Food Additives Linked to Health Concerns by Dana G. Smith, April 13, 2023 on the New York Times website. Last access 5/23/2023.
85. Tourinho, Paula S.; van Gestel, Cornelis A. M.; Lofts, Stephen; Svendsen, Claus; Soares, Amadeu M. V. M.; Loureiro, Susana (1 August 2012). "Metal-based nanoparticles in soil: Fate, behavior, and effects on soil invertebrates". Environmental Toxicology and Chemistry. 31 (8): 1679–1692. doi:10.1002/etc.1880. ISSN 1552-8618. PMID 22573562. S2CID 45296995.
86. Swiler, Daniel R. (2005). "Pigments, Inorganic". Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. doi:10.1002/0471238961.0914151814152215.a01.pub2. ISBN 9780471238966.
87. Preočanin, Tajana; Kallay, Nikola (2006). "Point of Zero Charge and Surface Charge Density of TiO₂ in Aqueous Electrolyte Solution as Obtained by Potentiometric Mass Titration". Croatica Chemica Acta. 79 (1): 95–106. ISSN 0011-1643.
88. France to ban titanium dioxide whitener in food from 2020. Reuters, 2019-04-17
89. Boffey, Daniel (6 May 2021). "E171: EU watchdog says food colouring widely used in UK is unsafe". the Guardian.
90. 'UK disagrees with EU position on titanium dioxide'. Food Safety News, 2022-03-09
91. 'Titanium dioxide (TiO2) as a food additive: Current science report'. Health Canada, 2022-06-20
92. Barreau F, Tisseyre C, Ménard S, Ferrand A, Carriere M (July 2021). "Titanium dioxide particles from the diet: involvement in the genesis of inflammatory bowel diseases and colorectal cancer". Particle and Fibre Toxicology. 18 (1): 26. doi:10.1186/s12989-021-00421-2. PMC 8323234. PMID 34330311.
93. "Dunkin' Donuts to remove titanium dioxide from donuts". CNN Money. March 2015.
94. Dunkin' Donuts ditches titanium dioxide – but is it actually harmful? The Conversation. 12 March 2015
95. Winkler, Hans Christian; Notter, Tina; Meyer, Urs; Naegeli, Hanspeter (December 2018). "Critical review of the safety assessment of titanium dioxide additives in food". Journal of Nanobiotechnology. 16 (1): 51. doi:10.1186/s12951-018-0376-8. ISSN 1477-3155. PMC 5984422. PMID 29859103.

External links

 

Look up titanium suboxide in Wiktionary, the free dictionary.

 

Wikiquote has quotations related to Titanium dioxide.

• International Chemical Safety Card 0338
• (PDF). nano-oxides.com. Archived from the original (PDF) on 13 October 2017.
• NIOSH Pocket Guide to Chemical Hazards
• "Fresh doubt over America map", bbc.co.uk, 30 July 2002
• "Titanium Dioxide Classified as Possibly Carcinogenic to Humans", Canadian Centre for Occupational Health and Safety, August, 2006 (if inhaled as a powder)
• Crystal structures of the three forms of TiO₂
• "Architecture in Italy goes green", Elisabetta Povoledo, International Herald Tribune, 22 November 2006
• "A Concrete Step Toward Cleaner Air", Bruno Giussani, BusinessWeek.com, 8 November 2006
• Sunscreen in the Sky? Reflective Particles May Combat Warming
• Titanium and titanium dioxide production data (US and World)