Niobium

identified the element columbium in 1801 within a mineral discovered in Connecticut, US.|alt=Oval black and white painting of a man with a prominent shirt collar and necktie |alt=Black and white image of a marmor sculpture of a bowing woman with a child nestling in her lap Niobium was identified by English chemist Charles Hatchett in 1801. He found a new element in a mineral sample that had been sent to England from Connecticut, United States in 1734 by John Winthrop (grandson of John Winthrop the Younger) and named the mineral "columbite" and the new element "columbium" after Columbia, the poetic name for the United States. The columbium discovered by Hatchett was probably a mixture of the new element with tantalum. Subsequently, there was considerable confusion over the difference between columbium (niobium) and the closely related tantalum. In 1809, English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm, and tantalum—tantalite, with a density over 8 g/cm, and concluded that the two oxides, despite the significant difference in density, were identical; thus he kept the name tantalum. This confusion arose from the minimal observed differences between tantalum and niobium. The claimed new elements pelopium, ilmenium, and dianium were in fact identical to niobium or mixtures of niobium and tantalum. in 1866, who all proved that there were only two elements. Articles on ilmenium continued to appear until 1871. Christian Wilhelm Blomstrand was the first to prepare the metal in 1866, when he reduced niobium chloride by heating it in an atmosphere of hydrogen. Although de Marignac was able to produce tantalum-free niobium on a larger scale by 1866, it was not until the early 20th century that niobium was used in incandescent lamp filaments, the first commercial application. Naming the element Columbium (symbol Cb) was the name originally given by Hatchett upon his discovery of the metal in 1801. This name remained in use in American journals—the last paper published by American Chemical Society with columbium in its title dates from 1953—while niobium was used in Europe. To end this confusion, the name niobium was chosen for element 41 at the 15th Conference of the Union of Chemistry in Amsterdam in 1949. A year later this name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) after 100 years of controversy, despite the chronological precedence of the name columbium. ==Characteristics==

Physical Niobium is a lustrous, grey, ductile, paramagnetic metal in group 5 of the periodic table (see table), with an electron configuration in the outermost shells atypical for group 5. Similarly atypical configurations occur in the neighborhood of ruthenium (44) and rhodium (45). Although it is thought to have a body-centered cubic crystal structure from absolute zero to its melting point, high-resolution measurements of the thermal expansion along the three crystallographic axes reveal anisotropies which are inconsistent with a cubic structure. Therefore, further research and discovery in this area is expected. Niobium becomes a superconductor at cryogenic temperatures. At atmospheric pressure, it has the highest critical temperature of the elemental superconductors at . Niobium has the greatest magnetic penetration depth of any element. In addition, it is one of the three elemental type II superconductors, along with vanadium and technetium. The superconductive properties are strongly dependent on the purity of the niobium metal. When very pure, it is comparatively soft and ductile, but impurities make it harder. Chemical The metal takes on a bluish tinge when exposed to air at room temperature for extended periods. Despite a high melting point in elemental form (), it is less dense than other refractory metals. Furthermore, it is corrosion-resistant, exhibits superconductivity properties, and forms dielectric oxide layers. Niobium is slightly less electropositive and more compact than its predecessor in the periodic table, zirconium, whereas it is virtually identical in size to the heavier tantalum atoms, as a result of the lanthanide contraction. Although its corrosion resistance is not as outstanding as that of tantalum, the lower price and greater availability make niobium attractive for less demanding applications, such as vat linings in chemical plants. Isotopes lighter than the stable {{chem2|^{93}Nb}} tend to β decay, and those that are heavier tend to β decay, with β-delayed proton emission observed for isotopes as heavy as {{chem2|^{84}Nb}}. The most stable of isomeric state of a niobium isotope is {{chem2|^{93m}Nb}} with half-life . The long-lived fission product {{chem2|^{93}Zr}} decays, mainly through this isomer, to stable niobium. Occurrence Niobium is estimated to be the 33rd most abundant element in the Earth's crust, at . Some believe that the abundance on Earth is much greater, and that the element's high density has concentrated it in Earth's core. Minerals that contain niobium often also contain tantalum. Examples include ferrocolumbite () and coltan ().) that are most usually found as accessory minerals in pegmatite intrusions, and in alkaline intrusive rocks. Less common are the niobates of calcium, uranium, thorium and the rare earth elements. Examples of such niobates are pyrochlores () and euxenite (). These large deposits of niobium have been found associated with carbonatites (carbonate-silicate igneous rocks) and as a constituent of pyrochlore. The three largest currently mined deposits of pyrochlore, two in Brazil and one in Canada, were found in the 1950s, and are still the major producers of niobium mineral concentrates. Brazil also has a large but still unexploited deposit near São Gabriel da Cachoeira, state of Amazonas, as well as a few smaller deposits, notably in the state of Roraima. The third largest producer of niobium is the carbonatite-hosted Niobec mine, in Saint-Honoré, Quebec, Canada, owned by Magris Resources. It produces between 7% and 10% of the world's supply. ==Production==

After the separation from the other minerals, the mixed oxides of tantalum () and niobium () are obtained. The first step in the processing is the reaction of the oxides with hydrofluoric acid: Ferroniobium contains between 60 and 70% niobium. , CBMM from Brazil controlled 85 percent of the world's niobium production. The United States Geological Survey estimates that the production increased from 38,700 tonnes in 2005 to 44,500 tonnes in 2006. Worldwide resources are estimated to be 4.4 million tonnes. Between 2009 and 2011, production was stable at 63,000 tonnes per year, with a slight decrease in 2012 to only 50,000 tonnes per year. Lesser amounts are found in Malawi's Kanyika Deposit (Kanyika mine). ==Compounds==

In many ways, niobium is similar to tantalum and zirconium. It reacts with most nonmetals at high temperatures; with fluorine at room temperature; with chlorine at and hydrogen at ; and with nitrogen at , with products that are frequently interstitial and nonstoichiometric. It resists corrosion by acids, including aqua regia, hydrochloric, sulfuric, nitric and phosphoric acids. Although niobium exhibits all of the formal oxidation states from +5 to −1, the most common compounds have niobium in the +5 state. Oxides, niobates and sulfides Niobium forms oxides in the oxidation states +5 (Niobium pentoxide|), +4 (Niobium dioxide|), and the rarer oxidation state, +2 (NbO). Most common is the pentoxide, precursor to almost all niobium compounds and alloys. Niobates are generated by dissolving the pentoxide in basic hydroxide solutions or by melting it in alkali metal oxides. Examples are lithium niobate () and lanthanum niobate (). Lithium niobate has a trigonally distorted perovskite-like structure, whereas the lanthanum niobate contains lone ions. Halides Niobium forms halides in the oxidation states of +5 and +4 as well as diverse substoichiometric compounds. The pentahalides () feature octahedral Nb centres. Niobium pentafluoride () is a white solid with a melting point of and niobium pentachloride () is yellow (see image at right) with a melting point of . Both are hydrolyzed to give oxides and oxyhalides, such as . The pentachloride is a versatile reagent used to generate the organometallic compounds, such as niobocene dichloride (). The tetrahalides () are dark-coloured polymers with Nb-Nb bonds; for example, the black niobium tetrafluoride () and dark violet niobium tetrachloride (). Anionic halide compounds of niobium are well known, owing in part to the Lewis acidity of the pentahalides. The most important is , an intermediate in the separation of Nb and Ta from the ores. This heptafluoride tends to form the oxopentafluoride more readily than does the tantalum compound. Other halide complexes include octahedral []: : As with other metals with low atomic numbers, a variety of reduced halide cluster ions is known, the prime example being . Nitrides and carbides Other binary compounds of niobium include niobium nitride (NbN), which becomes a superconductor at low temperatures and is used in detectors for infrared light. The main niobium carbide is NbC, an extremely hard, refractory, ceramic material, commercially used in cutting tool bits. ==Applications==

Out of of niobium mined in 2006, an estimated 90% was used in high-grade structural steel. The second-largest application is superalloys. Niobium alloy superconductors and electronic components account for a very small share of the world production. but important addition to high-strength low-alloy steels that are widely used structurally in modern automobiles. Niobium is sometimes used in considerably higher quantities for highly wear-resistant machine components and knives, as high as 3% in Crucible CPM S110V stainless steel. These same niobium alloys are often used in pipeline construction. Superalloys Quantities of niobium are used in nickel-, cobalt-, and iron-based superalloys in proportions as great as 6.5% One example superalloy is Inconel 718, consisting of roughly 50% nickel, 18.6% chromium, 18.5% iron, 5% niobium, 3.1% molybdenum, 0.9% titanium, and 0.4% aluminium. These superalloys were used, for example, in advanced air frame systems for the Gemini program. Another niobium alloy was used for the nozzle of the Apollo Service Module. Because niobium is oxidized at temperatures above 400 °C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle. The reactivity of niobium with oxygen requires it to be worked in a vacuum or inert atmosphere, which significantly increases the cost and difficulty of production. Vacuum arc remelting (VAR) and electron beam melting (EBM), novel processes at the time, enabled the development of niobium and other reactive metals. The project that yielded C-103 began in 1959 with as many as 256 experimental niobium alloys in the "C-series" that could be melted as buttons and rolled into sheet. Wah Chang Corporation had an inventory of hafnium, refined from nuclear-grade zirconium alloys, that it wanted to put to commercial use. The 103rd experimental composition of the C-series alloys, Nb-10Hf-1Ti, had the best combination of formability and high-temperature properties. Wah Chang fabricated the first of C-103 in 1961, ingot to sheet, using EBM and VAR. The intended applications included turbine engines and liquid metal heat exchangers. Competing niobium alloys from that era included FS85 (Nb-10W-28Ta-1Zr) from Fansteel Metallurgical Corp., Cb129Y (Nb-10W-10Hf-0.2Y) from Wah Chang and Boeing, Cb752 (Nb-10W-2.5Zr) from Union Carbide, and Nb1Zr from Superior Tube Co. Niobium-based superalloys are used to produce components of hypersonic missile systems. Superconducting magnets clinical magnetic resonance imaging scanner using niobium superconducting alloy|alt=Room-high yellow-grey medical machine with a man-size hole in the middle and a stretcher directly in front of it Niobium-germanium (), niobium–tin (), as well as the niobium–titanium alloys are used as a type II superconductor wire for superconducting magnets. These superconducting magnets are used in magnetic resonance imaging and nuclear magnetic resonance instruments as well as in particle accelerators. For example, the Large Hadron Collider uses of superconducting strands, while the International Thermonuclear Experimental Reactor uses an estimated of strands and of NbTi strands. In 1992 alone, more than one billion US dollars' worth of clinical magnetic resonance imaging systems were constructed with niobium-titanium wire. A cryomodule team at Fermilab used the same SRF technology from the FLASH project to develop nine-cell SRF cavities made from pure niobium. The cavities will be used in the linear particle accelerator of the International Linear Collider. The same technology will be used in LCLS-II at SLAC National Accelerator Laboratory and PIP-II at Fermilab. The high sensitivity of superconducting niobium nitride bolometers make them an ideal detector for electromagnetic radiation in the THz frequency band. These detectors were tested at the Heinrich Hertz Submillimeter Telescope, the South Pole Telescope, the Receiver Lab Telescope, and at Atacama Pathfinder Experiment (APEX), and are now used in the HIFI instrument on board the Herschel Space Observatory. Other uses Electroceramics Lithium niobate, which is a ferroelectric, is used extensively in mobile telephones and optical modulators, and for the manufacture of surface acoustic wave devices. It belongs to the perovskite () structure ferroelectrics like lithium tantalate and barium titanate. Niobium capacitors are available as alternatives to tantalum capacitors, but tantalum capacitors still predominate. Niobium is added to glass to obtain a higher refractive index, making possible thinner and lighter corrective lenses for eyeglasses. Hypoallergenic applications: medicine and jewelry Niobium and some niobium alloys are physiologically inert and hypoallergenic. For this reason, niobium is used in prosthetics and implant devices, such as pacemakers. Niobium treated with sodium hydroxide forms a porous layer that aids osseointegration. Like titanium, tantalum, and aluminium, niobium can be heated and anodized to produce a wide array of iridescent colours for jewelry, where its hypoallergenic property is highly desirable. Numismatics Niobium is used as a precious metal in commemorative coins, often with silver or gold. For example, Austria produced a series of silver niobium euro (€) coins starting in 2003; the colour in these coins is created by the diffraction of light by a thin anodized oxide layer. In 2012, ten coins are available showing a broad variety of colours in the centre of the coin: blue, green, brown, purple, violet, or yellow. Two more examples are the 2004 Austrian €25 150-Year Semmering Alpine Railway commemorative coin, and the 2006 Austrian €25 European Satellite Navigation commemorative coin. The Austrian mint produced for Latvia a similar series of coins starting in 2004, with one following in 2007. In 2011, the Royal Canadian Mint started production of a $5 sterling silver and niobium coin named ''Hunter's Moon'' in which the niobium was selectively oxidized, thus creating unique finishes where no two coins are exactly alike. Other The arc-tube seals of high pressure sodium vapor lamps are made from niobium, sometimes alloyed with 1% of zirconium; niobium has a very similar coefficient of thermal expansion, matching the sintered alumina arc tube ceramic, a translucent material which resists chemical attack or reduction by the hot liquid sodium and sodium vapour contained inside the operating lamp. Niobium is used in arc welding rods for some stabilized grades of stainless steel and in anodes for cathodic protection systems on some water tanks, which are then usually plated with platinum. Niobium is used to make the high voltage wire of the solar corona particles receptor module of the Parker Solar Probe. Niobium is a constituent of a lightfast chemically stable inorganic yellow pigment that has the trade name NTP Yellow. It is Niobium Sulfur Tin Zinc Oxide, a pyrochlore, produced via high-temperature calcination. The pigment is also known as pigment yellow 227, commonly listed as PY 227 or PY227. Niobium is employed in the atomic energy industry for its high temperature and corrosion resistance, as well as its stability under radiation. It is used in nuclear reactors for components like fuel rods and reactor cores. Nickel niobium alloys are used in aerospace, oil and gas, construction. They are used in components of jet engines, in ground gas turbines, elements of bridges and high-rise buildings. ==Precautions==

}} Niobium has no known biological role. While niobium dust is an eye and skin irritant and a potential fire hazard, elemental niobium on a larger scale is physiologically inert (and thus hypoallergenic) and harmless. It is often used in jewelry and has been tested for use in some medical implants. Short- and long-term exposure to niobates and niobium chloride, two water-soluble chemicals, have been tested in rats. Rats treated with a single injection of niobium pentachloride or niobates show a median lethal dose (LD) between 10 and 100 mg/kg. For oral administration the toxicity is lower; a study with rats yielded a LD after seven days of . ==References==