Titanium [Ti]

Characteristics

An: 22 N: 26
Am: 47.867 g/mol
Group No: 4
Group Name: Transition metals
Block: d-block Period: 4
State: solid at 298 K
Colour: silvery metallic
Classification: Metallic
Boiling Point: 3560K (3287^oC)
Melting Point: 1941K (1668^oC)
Superconducting temperature: 0.40K (-272.7°C)
Density: 4.506g/cm³

Discovery Information

Who: William Gregor
When: 1791
Where: England

Name Origin

Greek: titanos (Titans). "Titanium" in different languages.

Sources

Usually occurs in the minerals ilmenite (FeTiO₃) or rutile (TiO₂). Also in Titaniferous magnetite (Fe₃O₄), titanite (CaTiSiO₅), and iron ores. The primary deposits of titanium ore are in Australia, Scandinavia, North America and Malaysia.

 

A large piece of rutile, a mineral source of titanium.

World wide production is around 99 thousand tons.

Abundance

Universe: 3 ppm (by weight)
Sun: 4 ppm (by weight)
Carbonaceous meteorite: 550 ppm
Earth’s Crust: 6600 ppm
Seawater: 4.8 x 10^-4 ppm

Uses

Titanium is well known for its excellent resistance to corrosion; it is almost as resistant as platinum, being able to withstand attack by acids, moist chlorine gas, and by common salt solutions.
Because of its high tensile strength (even at high temperatures), light weight, extraordinary corrosion resistance, and ability to withstand extreme temperatures, titanium alloys are used in aircraft (a Boeing 737 contains around 18 tons, a 777 around 58 tons), armour plating, naval ships, spacecraft and missiles. It is used in steel alloys 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 with other metals.
Because it is considered to be physiologically inert, the metal is used in joint replacement implants such as hip ball and sockets and to make medical equipment and in pipe/tank lining in food processing. Since titanium is non-ferromagnetic patients with titanium implants can be safely examined with magnetic resonance imaging, which makes it convenient for long term implants and surgical instruments for use in image-guided surgery.
95% of titanium production is consumend in the form of titanium dioxide (TiO₂), a white pigment that covers surfaces very well, is used in paint, rubber, paper and many other materials. Also used in heat exchangers, airplane motors, bone pins and other things requiring light weight metals or metals that resist corrosion or high temperatures. Titanium oxide is used extensively in paints and in suncreens.
Due to excellent resistance to sea water, it is used to make propeller shafts and rigging and in the heat exchangers of desalination plants and in heater-chillers for salt water aquariums, and lately diver knives as well.
Titanium tetrachloride (TiCl₄), a colourless liquid, is used to iridize glass and because it fumes strongly in moist air it is also used to make smoke screens and in skywriting.

History

Titanium was discovered combined in a mineral in Cornwall, England in 1791 by amateur geologist William Gregor, the then vicar of Creed village. He recognized the presence of a new element in ilmenite (FeTiO₃) when he found black sand by a stream in the nearby parish of Manaccan and noticed the sand was attracted by a magnet. Analysis of the sand 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. Gregor, realizing that the unidentified oxide contained a metal that did not match the properties of any known element, reported his findings to the Royal Geological Society of Cornwall and in the German science journal Crell’s Annalen.
Around the same time, Franz Joseph Muller also produced a similar substance, but could not identify it. The oxide was independently rediscovered in 1795 by German chemist Martin Heinrich Klaproth in rutile from Hungary. 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 it contained titanium.
The processes required to extract titanium from its various ores are laborious and costly; it is not possible to reduce in the normal manner, by heating in the presence of carbon, because that produces titanium carbide. Pure metallic titanium (99.9%) was first prepared in 1910 by Matthew A. Hunter by heating TiCl₄ with sodium in a steel bomb at 700 - 800^oC in the Hunter process. Titanium metal was not used outside the laboratory until 1946 when William Justin Kroll proved that it could be commercially produced by reducing titanium tetrachloride with magnesium in what came to be known as the Kroll process. Although research continues into more efficient and cheaper processes (FFC Cambridge, e.g.), the Kroll process is still used for commercial production.
Titanium of very high purity was made in small quantities when Anton Eduard van Arkel and Jan Hendrik de Boer discovered the iodide, or crystal bar, process in 1925, by reacting with iodine and decomposing the formed vapours over a hot filament to pure metal.

Notes

Pure titanium is a lustrous white metal, as strong as steel, 45% lighter, 60% heavier than aluminium.
Titanium is Latin and refers to the Titans, the first sons of the earth in Mythology. It was discovered by Gregor in 1791 and named by Klaproth four years later. It was nearly a hundred years later (1887) when impure titanium was first prepared by Nilson and Pettersson. About 20 years later Hunter heated Titanium Chloride TiCl₄ with sodium in a steel bomb and isolated 99.6% pure titanium. It is the ninth most abundant element in the Earth’s crust and is also found in meteorites and in the sun. It is found in the ash of coal, in plants and even in the human body. It occurs in the minerals rutile (TiO₂), ilmenite (FeTiO₃) and sphene (CaTiSiO₅).
As a compound, it is found as Titanium dioxide TiO₂ in star sapphires and rubies (it is TiO₂ that gives them their asterism). It is also found as titanium chloride (TiCl₄). When it is red hot the metal combines with oxygen, and when it reaches 550^oC it combines with chlorine. It also reacts with the other halogens and absorbs hydrogen.

Hazards

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-based methods to extinguish fires are ineffective on burning titanium.
Titanium powder is harmful if inhaled and is also an eye irritant.

Titanium Compounds

Titanium boride TiB₂

An extremely hard ceramic material with excellent corrosion resistance at high temperatures and very good wear resistance which does not occur naturally in earth. Many TiB₂ applications are inhibited by economic factors, particularly the costs of densifying a high melting point material. Current use of this material appears to be limited to specialized applications in such areas as impact resistant armour, cutting tools, crucibles and wear resistant coatings.

Titanium carbide TiC

An extremely hard refractory ceramic material, similar to tungsten carbide. It is commercially used in tool bits cutting tools. It is mainly used in preparation of cermets, which are frequently used to machine steel materials at high cutting speed.

Tool bits without tungsten content can be made of titanium carbide in nickel-cobalt matrix cermet, enhancing the cutting speed and precision and smoothness of the workpiece. This material is sometimes called high-tech ceramics and is used as a heat shield for atmospheric re-entry of space shuttles and similar vehicles. The substance may be also polished and used in scratch-proof watches.

Titanium dioxide TiO₂

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. When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for dielectric mirrors. 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, and most toothpastes. In cosmetic and skin care products, titanium dioxide is used both as a pigment and a thickener, and in almost every sunblock 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. Titanium dioxide is used as a white food dye. In that use, its E number is E171.

Titanium nitride TiN

An extremely hard ceramic material, often used as a coating on titanium alloy, steel, carbide, and aluminium components to improve the substrate’s surface properties. Far and away the most common use for TiN coating is for edge retention and corrosion resistance on machine tooling, such as drill bits and milling cutters, often improving their lifetime by a factor of three or more.

Because of its metallic gold colour, it is used to coat costume jewellery and automotive trim for decorative purposes. TiN is also widely used as a top-layer coating, usually with nickel or chromium plated substrates, on consumer plumbing fixtures and door hardware.

Reactions of Titanium

Reactions with water

Titanium is coated with a thin oxide layer that under normal circumstances renders inert in air. However, titanium will react with steam to form titanium(IV) oxide and hydrogen.

Ti_(s) + 2H₂O_(g) --> TiO_2(s) + 2H_2(g)

Reactions with air

Titanium is coated with a thin oxide layer that under normal circumstances renders inert in air. However, once titanium starts to burn in air it burns with a bright white flame to form titanium oxide and titanium nitride. It will burn in pure nitrogen to form titanium nitride.

Ti_(s) + O_2(g) --> TiO_2(s)

2Ti_(s) + N_2(g) --> TiN_(s)

Reactions with halogens

Titanium does react with the halogens upon warming to form titanium(IV) halides. The reaction with fluorine requires heating to 200^oC.

Ti_(s) + 2F_2(g) --> TiF_4(s)

Ti_(s) + 2C_l2(g) --> TiCl_4(s)

Ti_(s) + 2Br_2(l) --> TiBr_4(s)

Ti_(s) + 2I_2(s) --> TiI_4(s)

Reactions with acids

Dilute aqueous hydrofluoric acid reacts with titanium to form the complex anion [TiF₆]^3- together with hydrogen.

2Ti_(s) + 12HF_(aq) --> 2[TiF₆]^3-_(aq) + 3H_2(g) + 6H⁺_(aq)

Titanium metal does not react with mineral acids at ambient temperature but does react with hot hydrochloric acic to form titanium(III) complexes.

Reactions with bases

Titanium does not appear to react wih alkalis under normal conditions, even when hot.

Occurrence of Titanium

Titanium is always bonded to other elements in nature. It is the ninth-most abundant element in the Earth’s crust (0.63% by mass) and the seventh-most abundant metal. It is present in most igneous rocks and in sediments derived from them (as well as in living things and natural bodies of water). In fact, 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 to 1.5%.
It is widely distributed and occurs primarily in the minerals anatase, brookite, ilmenite (FeTiO₃), perovskite, rutile (TiO₂), titanite ( CaTiSiO₅) (sphene), as well in many iron ores. Of these minerals, only rutile and ilmenite have any economic importance, yet even they are difficult to find in high concentrations. Significant titanium-bearing ilmenite deposits exist in western Australia, Canada, New Zealand, Norway, and Ukraine. Large quantities of rutile are also mined in North America and South Africa and help contribute to the annual production of 90,000 tonnes of the metal and 4.3 million tonnes of titanium dioxide. Total known reserves of titanium are estimated to exceed 600 million tonnes.
Titanium is contained in meteorites and has been detected in the sun and in M-type stars; the coolest type of star with a surface temperature of 3,200^oC (5792^oF). Rocks brought back from the moon during the Apollo 17 mission are composed of 12.1% TiO₂. It is also found in coal ash, plants, and even the human body.

Isotopes of Titanium

⁴⁴Ti [22 neutrons]

Abundance: synthetic
Half life: 63 years [ Electron Capture ]
Decay Energy: ? MeV
Decays to ⁴⁴Sc.
Half life: 63 years [ Gamma Radiation ]
Decay Energy: 0.07D, 0.08D MeV
Decays to ?.

⁴⁶Ti [24 neutrons]

Abundance: 8.0%
Stable with 24 neutrons

⁴⁷Ti [25 neutrons]

Abundance: 7.3%
Stable with 25 neutrons

⁴⁸Ti [26 neutrons]

Abundance: 73.8%
Stable with 26 neutrons

⁴⁹Ti [27 neutrons]

Abundance: 5.5%
Stable with 27 neutrons

⁵⁰Ti [28 neutrons]

Abundance: 5.4%
Stable with 28 neutrons

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