Titanium (Ti)
Titanium (Ti) is a transition metal with the atomic number 22, known for its strength, low density, and resistance to corrosion. It is the ninth most abundant element in Earth’s crust, comprising about 0.63 percent of the planet's total mass. Titanium is primarily found in the form of titanium dioxide (TiO2), which occurs in minerals like ilmenite and rutile, and it is commonly extracted from igneous, metamorphic, and sedimentary rocks. The metal is predominantly utilized in the aerospace industry for aircraft construction due to its favorable mechanical properties.
Additionally, titanium dioxide serves as a critical white pigment in various products, particularly paints and varnishes, with annual global production exceeding five million metric tons. While titanium is generally non-toxic, some organic titanium compounds can exhibit toxicity. Historical milestones in titanium research include its discovery in the late 18th century and the development of the Kroll process in the mid-20th century for producing metallic titanium. Today, titanium's versatility extends beyond aerospace to applications in medical equipment, chemical processing, and sports gear, making it an essential material in multiple industries.
Titanium (Ti)
Where Found
Titanium is the ninth most abundant element in Earth’s crust and accounts for 0.63 percent of the planet’s total mass. It is never found uncombined. It is usually found in igneous, metamorphic, and sedimentary rocks and is most frequently obtained from ilmenite or rutile deposits. Titanium also occurs in seawater in a concentration of 4.8 × 10-4 parts per million (about 1.5 metric tons per cubic kilometer). Commercially important producers of titanium and titanium dioxide include Australia, the United States (especially Florida), Canada, China, Argentina, Japan, Russia, Kazakhstan, Ukraine, and several African and European nations.
Primary Uses
The main uses for titanium metal are in aircraft construction. Smaller amounts are used for the manufacture of chemical plant equipment. Titanium is usually alloyed with 10 to 15 percent of other metals. Large quantities of titanium compounds, principally titanium dioxide, are used for a variety of commercial purposes, especially paints and varnishes.
Technical Definition
Titanium (symbol Ti), atomic number 22, belongs to group 4 of the periodic table of the elements. It is a transition metal in period 4 of the table, located between scandium and vanadium. It has five naturally occurring isotopes, all stable, and a relative atomic mass of 47.867. Pure titanium is a hard, lustrous, brittle, silvery metal with a density of 4.506 grams per cubic centimeter at 20 degrees Celsius. It has a melting point of 1,668 degrees Celsius and a boiling point of 3,280 degrees Celsius. Titanium is used in three basic forms: titanium mineral compounds, titanium dioxide (TiO2), and titanium sponge metal.
Description, Distribution, and Forms
Titanium is found nearly everywhere in Earth’s crust, in seawater, and even in plants and animals. It occurs in nature primarily as titanium dioxide, which frequently is combined with metal oxides (potassium, iron, zinc, lead, barium) to produce titanates, such as FeTiO3 (ilmenite), a major commercial source of metallic titanium. Another source, rutile, contains titanium dioxide uncombined. Separation procedures used with rutile can yield 95 percent titanium dioxide for further processing into metal.
Commercially, titanium in the form of titanium dioxide is used as a white pigment for paints and other products. Annual global production of titanium dioxide is more than five million metric tons.
Titanium is widely distributed in nature, but the difficulty in producing the relatively pure metal limited its use until the twentieth century. However, titanium dioxide has been the principal white pigment for commercial applications for much longer because of its ready availability, chemical inertness, and extraordinarily high refractive index. The dioxide is found as black or brown rutile most frequently; other forms are anatase and brookite. Anatase and rutile yield relatively white titanium dioxide directly, but titanium metal in purer states is best obtained from ilmenite, a black titanate resulting from the fusion of titanium and iron oxides. Since the known reserves of ilmenite are more than fifty times greater than those of rutile, the choice is clear. Processes for production of titanium from lower-content ores should make titanium easily available; testing of igneous rocks by the US Geological Survey found titanium in 784 out of 801. Soil titanium content of 0.5 to 1.5 percent is common. Titanium is found in clay, sand, volcanic materials and meteorite fragments. Although rutile (and increasingly, ilmenite) is mined mainly in Australia, commercial-scale operations in Florida and Virginia are prevalent. Outside the United States and Australia, many countries of the world have extensive titanium deposits, with primary mineral producers including Brazil, Canada, China, India, Kenya, Madagascar, Mozambique, Norway, Russia, Senegal, Sierra Leone, South Africa, Ukraine, and Vietnam. In addition to the titanium dioxide (rutile) and iron titanate (ilmenite) previously described, titanium dioxide and other titanium oxides are also found combined with other metals, frequently with silicon dioxide (such as in calcium silicotitanite, CaTiSiO5).
Although small amounts of titanium exist in biological systems, no confirmed role has been identified. Daily dietary intake of titanium for an average human adult is 0.8 milligram, and it locates mainly in muscle tissue (0.9–2.2 parts per million). At higher levels some investigators suspect carcinogenicity. Titanium dioxide is apparently nontoxic to test animals and humans, but some organic titanium compounds show toxicity. Various titanium compounds are able to catalyze oxidation reactions in plant cells. Titanium may be involved in soil formation processes.
History
In 1791, English vicar and mineralogist William Gregor first identified an unknown white metallic oxide as a constituent of black sands found on Cornish beaches. In 1795, German chemist Martin Heinrich Klaproth identified the oxide as that of a new element; he named it "titanium" after the Titans, the giants of ancient Greek mythology who gave birth to the Olympian gods. Metallic titanium was first isolated at 95 percent purity by Lars Nilson and Otto Pettersson in 1887, then at 99.9 percent purity by New Zealand–born metallurgist Matthew Hunter at the Rensselaer Polytechnic Institute in 1910; the process he used, now known as the Hunter process, involved reacting titanium tetrachloride with sodium at high temperatures. In 1932, Luxembourgish metallurgist William Kroll improved the process by switching to calcium, and by 1940 he had refined the process further by using magnesium in an argon atmosphere. This magnesium-argon process, now called the Kroll process, became the dominant method of production.
Obtaining Titanium
Rutile or ilmenite is charged into a continuous chlorination chamber and converted into titanium tetrachloride, a liquid, which is then heated to more than 750 degrees Celsius with molten magnesium. The titanium is obtained along with magnesium chloride, which can be recycled to magnesium and chlorine for reuse. Other methods use other metals, such as sodium, or subject the titanium tetrachloride to electrolysis.
Uses of Titanium
In the United States in 2015, about 95 percent of titanium mineral concentrates were used in the production of titanium dioxide pigment. Welding-rod coatings and the production of carbides, chemicals, and metals accounted for the remaining 5 percent.
Because of its low density and high strength, titanium sponge metal is mainly used in aerospace production. Since it is both strong and chemically resistant, titanium is widely used for the manufacture of chemical reactors. Other uses include armor, chemical processing, marine applications, medical equipment, energy production, and sports equipment.
Titanium dioxide is used in great quantities as a whitener for paints. It is also used in plastics, paper, catalysts, ceramics, coated fabrics, floor coverings, printer’s ink, sunscreen, and roofing granules.
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