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Titanium dioxide

physical science Maturity 5-7 Next article →

Titanium dioxide is an inorganic compound made from titanium and oxygen. It is also known as titanium(IV) oxide or titania. This white solid is highly valued for its unique optical properties. It has a very high refractive index, which means it bends light very effectively. This quality makes it the most widely used white pigment in the world. It is used to provide brightness and opacity to many different products.

TiO2crystals
TiO2crystals

The way titanium dioxide works depends on its particle size and purity. To achieve maximum reflection of visible light, the ideal crystal size is approximately 220 nanometers. When it is used as a pigment, it acts as an opacifier. This means it makes surfaces like paint or plastic look solid and white. In sunscreens, the material is often used in nano-scaled forms, between 20 and 40 nanometers. These tiny particles scatter much less visible light, so they do not look white on the skin. Instead, they absorb and scatter ultraviolet (UV) light to protect the skin from sun damage.

Anatase crystal structure
Anatase crystal structure

Titanium dioxide exists in several different crystal structures called polymorphs. The three most common natural polymorphs are rutile, anatase, and brookite. In these forms, each titanium atom is bonded to six oxygen atoms in an octahedral geometry. Rutile has a tetragonal symmetry and a distorted hexagonal close-packing of oxide anions. Anatase also has tetragonal symmetry but uses a structure close to cubic close-packing. Brookite is different because it has an orthorhombic crystal system. There are twelve known polymorphs in total, including rare high-pressure forms like akaogiite and riesite.

Anatase crystal structure
Anatase crystal structure

Industrial production of titanium dioxide usually begins with minerals like ilmenite. Ilmenite is the most widespread ore containing titanium dioxide. Rutile is another important source because it contains about 98% titanium dioxide. There are two primary industrial methods for creating synthetic pigment. The chloride process is a continuous method where ore is treated with chlorine and carbon. This creates titanium tetrachloride, a volatile liquid that is purified by distillation before being treated with oxygen. The sulfate process is a batch process that uses sulfuric acid to extract iron(II) sulfate pentahydrate from ilmenite.

Evolution production dioxyde de titane
Evolution production dioxyde de titane

The history of mass production for this pigment began in 1916. Since then, it has become a massive global industry. In 2014, world production exceeded 9 million tonnes. It is estimated that titanium dioxide is used in two-thirds of all pigments produced globally. The market for these oxide-based pigments has been valued at approximately $13.2 billion. Major industrial players in this field include companies like Chemours, Venator, and Tronox.

Industrial key players in the production of titanium dioxide
Industrial key players in the production of titanium dioxide

Beyond simple white coloring, titanium dioxide is used for specialized visual effects. It can be used to create pearlescent or iridescent pigments. This is often done by coating minerals like mica with layers of titanium dioxide or iron oxide. These layers cause light interference, which creates a shimmering effect in cosmetics and sparkly paints. It can also be used in thin films to create dielectric mirrors or decorative coatings. In these applications, the thickness of the oxide layer determines which colors are reflected.

Relevant patent families describing titanium dioxide production from ilmenite, 2002–2021
Relevant patent families describing titanium dioxide production from ilmenite, 2002–2021

Because it is so versatile, titanium dioxide is found in many everyday items. It is used in paints, coatings, plastics, inks, and even toothpastes. In 2019, it was present in two-thirds of the toothpastes sold on the French market. It is also used as a food coloring, labeled as E171. However, its use in food has changed in some places; the European Union banned it for food use in 2022. In the United States, some companies like Mars have also removed it from products like Skittles. Despite these changes, its role in sunscreens and industrial coatings remains essential.

Industrial key players in the production of titanium dioxide
Industrial key players in the production of titanium dioxide
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File:Anatase crystal structure.png
Anatase crystal structure.png
File:Industrial key players in the production of titanium dioxide.png
Industrial key players in the production...
File:Evolution production dioxyde de titane.svg
Evolution production dioxyde de titane.svg
File:Relevant patent families describing titanium dioxide production from ilmenite, 2002–2021.png
Relevant patent families describing...
File:Public Institutions patent activity in titanium dioxide production.png
Public Institutions patent activity in...
File:TiO2crystals.JPG
TiO2crystals.JPG
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