Transition metal
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. The metal is extracted from its principal mineral ores by the Kroll and Hunter processes. The most common compound, titanium dioxide (TiO2), is a popular photocatalyst and is used in the manufacture of white pigments. 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.
Titanium can be alloyed with iron, aluminium, vanadium, and molybdenum, among other elements. …
Titanium was discovered in 1791 by the clergyman and geologist William Gregor as an inclusion of a mineral in Cornwall, Great Britain. Gregor recognized the presence of a new element in ilmenite when he found black sand by a stream and noticed the sand was attracted by a magnet. 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. 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. He named this oxide manaccanite.
Around the same time, Franz-Joseph Müller von Reichenstein produced a similar substance, but could not identify it. 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).
Klaproth found that it contained a new element and named it for the Titans of Greek mythology. After hearing about Gregor's earlier discovery, he obtained a sample of manaccanite and confirmed that it contained titanium. …
As a metal, titanium is recognized for its high strength-to-weight ratio. It is a strong metal with low density that is quite ductile (especially in an oxygen-free environment), lustrous, and metallic-white in color. 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. It is paramagnetic and has fairly low electrical and thermal conductivity compared to other metals. Titanium is superconducting when cooled below its critical temperature of 0.49 K.
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 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). However, titanium loses strength when heated above 430 °C (806 °F).
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. …
Titanium is the ninth-most abundant element in Earth's crust (0.63% by mass) 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. 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%.
Common titanium-containing minerals are anatase, brookite, ilmenite, perovskite, rutile, and titanite (sphene). 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. Significant titanium-bearing ilmenite deposits exist in Australia, Canada, China, India, Mozambique, New Zealand, Norway, Sierra Leone, South Africa, and Ukraine. Total reserves of anatase, ilmenite, and rutile are estimated to exceed 2 billion tonnes.
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 10−7 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. …
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. Titanium is often alloyed with aluminium (to refine grain size), vanadium, copper (to harden), iron, manganese, molybdenum, and other metals. 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.
Titanium dioxide (TiO2) 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. It is also used in cement, in gemstones, and as an optical opacifier in paper.
TiO2 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. In nature, this compound is found in the minerals anatase, brookite, and rutile. Paint made with titanium dioxide does well in severe temperatures and marine environments. Pure titanium dioxide has a very high index of refraction and an optical dispersion higher than diamond. Titanium dioxide is used in sunscreens because it reflects and absorbs UV light. …
Naturally occurring titanium is composed of five stable isotopes: 46Ti, 47Ti, 48Ti, 49Ti, and 50Ti, with 48Ti being the most abundant (73.8% natural abundance). Twenty-three radioisotopes have been characterized, the most stable of which are 44Ti with a half-life of 63 years; 45Ti, 184.8 minutes; 51Ti, 5.76 minutes; and 52Ti, 1.7 minutes. All other radioactive isotopes have half-lives less than 33 seconds, with the majority less than half a second.
The isotopes of titanium range from 39Ti to 66Ti. The primary decay mode for isotopes lighter than 46Ti is positron emission (with the exception of 44Ti, which undergoes electron capture), leading to isotopes of scandium, and the primary mode for isotopes heavier than 50Ti is beta emission, leading to isotopes of vanadium. Titanium becomes radioactive upon bombardment with deuterons, emitting mainly positrons and hard gamma rays.
Titanium is non-toxic, even in large doses, and does not play any natural role inside the human body. An estimated 0.8 milligrams of titanium is ingested by humans each day, but most passes through the digestive system without being absorbed in the tissues. 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.
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. Water and carbon dioxide are ineffective for extinguishing a titanium fire; Class D dry powder agents must be used instead. When used in the production or handling of chlorine, titanium exposed to dry chlorine gas may result in a titanium–chlorine fire. Titanium can also catch fire when a fresh, non-oxidized surface comes in contact with liquid oxygen.