Tungsten, or wolfram, is a

chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...

with the

symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...

W and

atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...

74. Tungsten is a

rare metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lustr ...

found naturally on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolated as a metal in 1783. Its important

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 April 2 ...

s include

scheelite Scheelite is a calcium tungstate mineral with the chemical formula Ca W O4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist K. Scheele (1742-1786). Well-formed crystals are sought by collectors a ...

and

wolframite Wolframite is an iron, manganese, and tungstate mineral with a chemical formula of that is the intermediate between ferberite ( rich) and hübnerite ( rich). Along with scheelite, the wolframite series are the most important tungsten ore minerals ...

, the latter lending the element its alternate name. The

free element In chemistry, a free element is a chemical element that is not combined with or chemical bond, chemically bonded to other elements. Examples of elements which can occur as free elements include the oxygen molecule (O) and carbon.A. Earnshaw and No ...

is remarkable for its robustness, especially the fact that it has the highest

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...

of all known elements barring

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

(which sublimes at normal pressure), melting at . It also has the highest

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envir ...

, at . Its density is , comparable with that of

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

and

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...

, and much higher (about 1.7 times) than that of

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

. Polycrystalline tungsten is an intrinsically

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Bre ...

and

hard Hard may refer to: * Hardness, resistance of physical materials to deformation or fracture * Hard water, water with high mineral content Arts and entertainment * ''Hard'' (TV series), a French TV series * Hard (band), a Hungarian hard rock supe ...

material (under standard conditions, when uncombined), making it difficult to

work Work may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community ** Manual labour, physical work done by humans ** House work, housework, or homemaking ** Working animal, an animal tr ...

. However, pure single-crystalline tungsten is more

ductile Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...

and can be cut with a hard-steel

hacksaw A hacksaw is a fine-toothed saw, originally and mainly made for cutting metal. The equivalent saw for cutting wood is usually called a bow saw. Most hacksaws are hand saws with a C-shaped walking frame that holds a blade under tension. Such h ...

. Tungsten occurs in many alloys, which have numerous applications, including incandescent

light bulb An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...

filaments,

X-ray tube An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast ...

s, electrodes in

gas tungsten arc welding Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode are protected from oxidation or other atmo ...

superalloy A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Several key characteristics of a superalloy are excellent mechanical strength, resistance to thermal creep deformation, g ...

s, and

radiation shielding Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposur ...

. Tungsten's hardness and high

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

make it suitable for military applications in penetrating projectiles. Tungsten compounds are often used as industrial

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

s. Tungsten is the only metal in the third transition series that is known to occur in

biomolecule A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large ...

s, being found in a few species of bacteria and

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

. However, tungsten interferes with

molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...

and

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

metabolism and is somewhat toxic to most forms of animal life.

Characteristics

Physical properties

In its raw form, tungsten is a hard steel-grey

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

that is often

and hard to

. Purified, monocrystalline tungsten retains its

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

(which exceeds that of many steels), and becomes

malleable Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...

enough that it can be worked easily. It is worked by

forging Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which i ...

drawing Drawing is a form of visual art in which an artist uses instruments to mark paper or other two-dimensional surface. Drawing instruments include graphite pencils, pen and ink, various kinds of paints, inked brushes, colored pencils, crayons, ...

, or

extruding Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex ...

but it is more commonly formed by

sintering Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing ...

. Of all metals in pure form, tungsten has the highest

(), lowest

vapor pressure Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases ...

(at temperatures above ), and the highest

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...

. Although

remains solid at higher temperatures than tungsten, carbon sublimes at

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...

instead of melting, so it has no melting point. Moreover, tungsten's most stable

crystal phase A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

does not exhibit any high-pressure-induced structural transformations for pressures up to at least 364 gigapascals. Tungsten has the lowest

coefficient of thermal expansion Thermal expansion is the tendency of matter to change its shape A shape or figure is a graphics, graphical representation of an object or its external boundary, outline, or external Surface (mathematics), surface, as opposed to other pro ...

of any pure metal. The low thermal expansion and high melting point and

of tungsten originate from strong

metallic bond Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be descri ...

s formed between tungsten atoms by the 5d electrons. Alloying small quantities of tungsten with

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...

greatly increases its

toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. Tungsten exists in two major

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

forms: α and β. The former has a

body-centered cubic In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of ...

structure and is the more stable form. The structure of the β phase is called A15 cubic; it is

metastable In chemistry and physics, metastability denotes an intermediate Energy level, energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of me ...

, but can coexist with the α phase at ambient conditions owing to non-equilibrium synthesis or stabilization by impurities. Contrary to the α phase which crystallizes in isometric grains, the β form exhibits a columnar

habit A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously.

. The α phase has one third of the

electrical resistivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...

and a much lower superconducting transition temperature T_C relative to the β phase: ca. 0.015 K vs. 1–4 K; mixing the two phases allows obtaining intermediate T_C values. The T_C value can also be raised by

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

ing tungsten with another metal (e.g. 7.9 K for W- Tc). Such tungsten alloys are sometimes used in low-temperature superconducting circuits.

Isotopes

Naturally occurring tungsten consists of four stable

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

s (¹⁸²W, ¹⁸³W, ¹⁸⁴W, and ¹⁸⁶W) and one very long-lived radioisotope, ¹⁸⁰W. Theoretically, all five can decay into isotopes of element 72 (

hafnium Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri M ...

) by

alpha emission Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atom ...

, but only ¹⁸⁰W has been observed to do so, with a half-life of years; on average, this yields about two alpha decays of ¹⁸⁰W per gram of natural tungsten per year. This rate is equivalent to a

specific activity Specific activity is the activity per unit mass of a radionuclide and is a physical property of that radionuclide. Activity is a quantity (for which the SI unit is the becquerel) related to radioactivity, and is defined as the number of radi ...

of roughly 63 micro-

becquerel The becquerel (; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. For applications relatin ...

per kilogram. This rate of decay is orders of magnitude lower than that observed in carbon or potassium as found on earth, which likewise contain small amounts of long-lived radioactive isotopes.

Bismuth Bismuth is a chemical element with the Symbol (chemistry), symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental ...

was long thought to be non-radioactive, but (its longest lived isotope) actually decays with a half life of years or about a factor 10 slower than . However, due to naturally occurring bismuth being 100% , its specific activity is actually higher than that of natural tungsten at 3 milli-becquerel per kilogram. The other naturally occurring isotopes of tungsten have not been observed to decay, constraining their half-lives to be at least 4 × 10²¹ years - if they decay at all. Another 30 artificial

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s of tungsten have been characterized, the most stable of which are ¹⁸¹W with a half-life of 121.2 days, ¹⁸⁵W with a half-life of 75.1 days, ¹⁸⁸W with a half-life of 69.4 days, ¹⁷⁸W with a half-life of 21.6 days, and ¹⁸⁷W with a half-life of 23.72 h. All of the remaining

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...

isotopes have half-lives of less than 3 hours, and most of these have half-lives below 8 minutes. Tungsten also has 11

meta state A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ha ...

s, with the most stable being ^179mW (''t''_1/2 6.4 minutes).

Chemical properties

Tungsten is a mostly non-reactive element: it does not react with water, is immune to attack by most acids and bases, and does not react with oxygen or air at room temperature. At elevated temperatures (i.e., when red-hot) it reacts with oxygen to form the trioxide compound tungsten(VI), WO₃. It will, however, react directly with fluorine (F₂) at room temperature to form

tungsten(VI) fluoride Tungsten(VI) fluoride, also known as tungsten hexafluoride, is an inorganic compound with the formula W F6. It is a toxic, corrosive, colorless gas, with a density of about (roughly 11 times heavier than air). It is one of the densest known ga ...

(WF₆), a colorless gas. At around 250 °C it will react with chlorine or bromine, and under certain hot conditions will react with iodine. Finely divided tungsten is

pyrophoric A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...

. The most common formal

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...

of tungsten is +6, but it exhibits all oxidation states from −2 to +6. Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO₃, which dissolves in aqueous alkaline solutions to form tungstate ions, .

Tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...

s (W₂C and WC) are produced by heating powdered tungsten with carbon. W₂C is resistant to chemical attack, although it reacts strongly with

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

to form

tungsten hexachloride Tungsten hexachloride is the chemical compound of tungsten and chlorine with the formula WCl6. This dark violet blue species exists as a volatile solid under standard conditions. It is an important starting reagent in the preparation of tungsten ...

(WCl₆). In aqueous solution, tungstate gives the

heteropoly acid In chemistry, the heteropolymetalates are a subset of the polyoxometalates, which consist of three or more transition metal oxyanions linked together by shared oxygen atoms to form a closed 3-dimensional molecular framework. In contrast to isopo ...

s and

polyoxometalate In chemistry, a polyoxometalate (abbreviated POM) is a polyatomic ion, usually an anion, that consists of three or more transition metal oxyanions linked together by shared oxygen atoms to form closed 3-dimensional frameworks. The metal atoms are ...

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s under neutral and acidic conditions. As

tungstate In chemistry, a tungstate is a compound that contains an oxyanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is , "orthotungstate". Many other tungstates belong to a large group of polyatomic ions that are ter ...

is progressively treated with acid, it first yields the soluble,

"paratungstate A"

, , which over time converts to the less soluble "paratungstate B" anion, . Further acidification produces the very soluble metatungstate anion, , after which equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

octahedra In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...

known as the Keggin anion. Many other polyoxometalate anions exist as metastable species. The inclusion of a different atom such as

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

in place of the two central

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

s in metatungstate produces a wide variety of heteropoly acids, such as

phosphotungstic acid Phosphotungstic acid (PTA) or tungstophosphoric acid (TPA), is a heteropoly acid with the chemical formula . It forms hydrates . It is normally isolated as the ''n'' = 24 hydrate but can be desiccated to the hexahydrate (''n'' = 6). EPTA is the nam ...

H₃PW₁₂O₄₀. Tungsten trioxide can form intercalation compounds with alkali metals. These are known as ''bronzes''; an example is

sodium tungsten bronze Sodium tungsten bronze is a form of insertion compound with the formula Na''x''WO3, where ''x'' is equal to or less than 1. So named because of its metallic lustre, its electrical properties range from semiconducting to metallic depending on the ...

. In gaseous form, tungsten forms the diatomic species W₂. These molecules feature a

sextuple bond A sextuple bond is a type of covalent bond involving 12 bonding electrons and in which the bond order is 6. The only known molecules with true sextuple bonds are the diatomic dimolybdenum ( Mo2) and ditungsten ( W2), which exist in the gaseous pha ...

between tungsten atoms — the highest known bond order among

stable A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate stalls for individual animals and livestock. There are many different types of stables in use today; the ...

atoms.

History

In 1781,

Carl Wilhelm Scheele Carl Wilhelm Scheele (, ; 9 December 1742 – 21 May 1786) was a Swedish German pharmaceutical chemist. Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hydrog ...

discovered that a new

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...

tungstic acid Tungstic acid refers to hydrated forms of tungsten trioxide, WO3. Both a monohydrate (WO3·H2O) and hemihydrate (WO3·1/2 H2O) are known. Molecular species akin to sulfuric acid, i.e. (HO)2WO2 are not observed. The solid-state structure of ...

, could be made from

(at the time called tungsten). Scheele and

Torbern Bergman Torbern Olaf (Olof) Bergman (''KVO'') (20 March 17358 July 1784) was a Swedish chemist and mineralogist noted for his 1775 ''Dissertation on Elective Attractions'', containing the largest chemical affinity tables ever published. Bergman was the ...

suggested that it might be possible to obtain a new metal by reducing this acid. In 1783,

José José is a predominantly Spanish and Portuguese form of the given name Joseph. While spelled alike, this name is pronounced differently in each language: Spanish ; Portuguese (or ). In French, the name ''José'', pronounced , is an old vernacul ...

and

Fausto Elhuyar Fausto de Elhuyar (11 October 1755 – 6 February 1833) was a Spanish chemist, and the first to isolate tungsten with his brother Juan José Elhuyar in 1783. He was in charge, under a King of Spain commission, of organizing the School of Mines i ...

found an acid made from

that was identical to tungstic acid. Later that year, at the Royal Basque Society in the town of

Bergara es, vergarés, vergaresa , population_note = , population_density_km2 = auto , blank_name_sec1 = Official language(s) , blank_info_sec1 = BasqueSpanish , timezone = CET , utc_offset = +1 ...

, Spain, the brothers succeeded in isolating tungsten by reduction of this acid with

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...

, and they are credited with the discovery of the element (they called it "wolfram" or "volfram"). The strategic value of tungsten came to notice in the early 20th century. British authorities acted in 1912 to free the Carrock mine from the German owned Cumbrian Mining Company and, during

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

, restrict German access elsewhere. In

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, tungsten played a more significant role in background political dealings. Portugal, as the main European source of the element, was put under pressure from both sides, because of its deposits of wolframite ore at

Panasqueira Minas da Panasqueira or Mina da Panasqueira (Panasqueira Mine) is the generic name for a set of mining operations between Cabeço do Pião ( Fundão Municipality) and the village of Panasqueira (Covilhã Municipality), which operated in a techni ...

. Tungsten's desirable properties such as resistance to high temperatures, its hardness and density, and its strengthening of alloys made it an important raw material for the arms industry, both as a constituent of weapons and equipment and employed in production itself, e.g., in

tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...

cutting tools for machining steel. Now tungsten is used in many more applications such as aircraft & motorsport ballast weights, darts, anti-vibration tooling, and sporting equipment. Tungsten is unique amongst the elements in that it has been the subject of patent proceedings. In 1928, a US court rejected

General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...

's attempt to patent it, overturning granted in 1913 to

William D. Coolidge William David Coolidge (; October 23, 1873 – February 3, 1975) was an American physicist and engineer, who made major contributions to X-ray machines. He was the director of the General Electric Research Laboratory and a vice-president of t ...

Etymology

The name "tungsten" (which means "heavy stone" in

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

) is used in English, French, and many other languages as the name of the element, but not in the

Nordic countries The Nordic countries (also known as the Nordics or ''Norden''; literal translation, lit. 'the North') are a geographical and cultural region in Northern Europe and the Atlantic Ocean, North Atlantic. It includes the sovereign states of Denmar ...

. "Tungsten" was the old Swedish name for the mineral

. "Wolfram" (or "volfram") is used in most European (especially Germanic, Spanish and Slavic) languages and is derived from the mineral

, which is the origin of the chemical symbol W. The name "wolframite" is derived from German "''wolf rahm''" ("wolf soot" or "wolf cream"), the name given to tungsten by

Johan Gottschalk Wallerius Johan Gottschalk Wallerius (11 July 1709 – 16 November 1785) was a Swedish chemist and mineralogist. Biography Wallerius was born at Stora Mellösa in Närke (now Örebro County), Sweden. He was a son of provost Erik Nilsson Wallerius and hi ...

in 1747. This, in turn, derives from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

"''lupi spuma''", the name

Georg Agricola Georgius Agricola (; born Georg Pawer or Georg Bauer; 24 March 1494 – 21 November 1555) was a German Humanist scholar, mineralogist and metallurgist. Born in the small town of Glauchau, in the Electorate of Saxony of the Holy Roman Empire ...

used for the element in 1546, which translates into English as "wolf's froth" and is a reference to the large amounts of

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

consumed by the mineral during its extraction, as though the mineral devoured it like a wolf. This naming follows a tradition of colorful names miners from the Ore Mountains would give various minerals, out of a superstition that certain ones that looked as if they contained then-known valuable metals but didn't were somehow "hexed".

Cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

(c.f.

Kobold A kobold (occasionally cobold) is a mythical sprite. Having spread into Europe with various spellings including "goblin" and "hobgoblin", and later taking root and stemming from Germanic mythology, the concept survived into modern times in Ger ...

pitchblende Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes th ...

(c.f. German " blenden" for "to blind" or "to deceive") and

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

(c.f. "Old Nick") derive their names from the same miner's idiom.

Occurrence

Tungsten has thus far not been found in nature in its pure form. Instead, tungsten is found mainly in the minerals

and

. Wolframite is

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

–

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

tungstate , a solid solution of the two minerals

ferberite Ferberite is the iron endmember of the manganese - iron wolframite solid solution series. The manganese endmember is hübnerite. Ferberite is a black monoclinic mineral composed of iron(II) tungstate, Fe W O4. Ferberite and hübnerite often cont ...

(FeWO₄) and

hübnerite Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (chemical formula MnWO4). It is the manganese endmember of the manganese–iron wolframite solid solution series. It forms reddish brown to black monoclinic prismatic ...

(MnWO₄), while

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

tungstate (CaWO₄). Other tungsten minerals range in their level of abundance from moderate to very rare, and have almost no economic value.

Chemical compounds

upStructure of W₆Cl₁₈ ("tungsten trichloride") Tungsten forms chemical compounds in oxidation states from -II to VI. Higher oxidation states, always as oxides, are relevant to its terrestrial occurrence and its biological roles, mid-level oxidation states are often associated with

metal cluster In chemistry, an atom cluster (or simply cluster) is an ensemble of bound atoms or molecules that is intermediate in size between a simple molecule and a nanoparticle; that is, up to a few nanometers (nm) in diameter. The term ''microcluster ...

s, and very low oxidation states are typically associated with CO complexes. The chemistries of tungsten and

show strong similarities to each other, as well as contrasts with their lighter congener,

chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...

. The relative rarity of tungsten(III), for example, contrasts with the pervasiveness of the chromium(III) compounds. The highest oxidation state is seen in

tungsten(VI) oxide Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid . It is a light ye ...

(WO₃). Tungsten(VI) oxide is soluble in aqueous base, forming tungstate (WO₄²⁻). This

oxyanion An oxyanion, or oxoanion, is an ion with the generic formula (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determine ...

condenses at lower pH values, forming polyoxotungstates. The broad range of

s of tungsten is reflected in its various chlorides: * Tungsten(II) chloride, which exists as the hexamer W₆Cl₁₂ * Tungsten(III) chloride, which exists as the hexamer W₆Cl₁₈ *

Tungsten(IV) chloride Tungsten(IV) chloride is an inorganic compound with the formula WCl4. It is a diamagnetic black solid. The compound is of interest in research as one of a handful of binary tungsten chlorides. Structure and preparation WCl4 is usually prepar ...

, WCl₄, a black solid, which adopts a polymeric structure. *

Tungsten(V) chloride Tungsten(V) chloride is an inorganic compound with the formula W2 Cl10. This compound is analogous in many ways to the more familiar molybdenum pentachloride. The material is prepared by reduction of tungsten hexachloride. One method involves ...

WCl₅, a black solid which adopts a dimeric structure. * Tungsten(VI) chloride WCl₆, which contrasts with the instability of MoCl₆. Organotungsten compounds are numerous and also span a range of oxidation states. Notable examples include the trigonal prismatic and octahedral .

Production

A full trolly coming from one of the galleries (27072015764)

Reserves

The world's reserves of tungsten are 3,200,000 tonnes; they are mostly located in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

(1,800,000 t),

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

(290,000 t),

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

(160,000 t),

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

(95,000 t) and

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

. As of 2017, China, Vietnam and Russia are the leading suppliers with 79,000, 7,200 and 3,100 tonnes, respectively. Canada had ceased production in late 2015 due to the closure of its sole tungsten mine. Meanwhile, Vietnam had significantly increased its output in the 2010s, owing to the major optimization of its domestic refining operations, and overtook Russia and Bolivia. China remains the world's leader not only in production, but also in export and consumption of tungsten products. Tungsten production is gradually increasing outside China because of the rising demand. Meanwhile, its supply by China is strictly regulated by the Chinese Government, which fights illegal mining and excessive pollution originating from mining and refining processes.Tungsten
''Mineral Commodity Summaries''. USGS (2018) There is a large deposit of tungsten ore on the edge of

Dartmoor Dartmoor is an upland area in southern Devon, England. The moorland and surrounding land has been protected by National Park status since 1951. Dartmoor National Park covers . The granite which forms the uplands dates from the Carboniferous ...

in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

, which was exploited during

and

as the

Hemerdon Mine Drakelands Mine, also known as Hemerdon Mine or Hemerdon Ball Mine, is a tungsten and tin mine. It is located northeast of Plymouth, near Plympton, in Devon, England. It lies to the north of the villages of Sparkwell and Hemerdon, and adjacen ...

. Following increases in tungsten prices, this mine was reactivated in 2014, but ceased activities in 2018. Within the EU, the

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

n Felbertal scheelite deposit is one of the few producing tungsten mines.

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

is one of Europe's main tungsten producers, with 121 kt of contained tungsten in mineral concentrates from 1910 to 2020, accounting for roughly 3.3% of the global production. Tungsten is considered to be a

conflict mineral The eastern Democratic Republic of the Congo (DRC) has a history of conflict, where various armies, rebel groups, and outside actors have profited from mining while contributing to violence and exploitation during wars in the region. The four mai ...

due to the unethical mining practices observed in the

Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...

Extraction

Tungsten is extracted from its ores in several stages. The ore is eventually converted to

(WO₃), which is heated with

or carbon to produce powdered tungsten. Because of tungsten's high melting point, it is not commercially feasible to cast tungsten

ingot An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of sh ...

s. Instead, powdered tungsten is mixed with small amounts of powdered nickel or other metals, and

sintered Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing ...

. During the sintering process, the nickel diffuses into the tungsten, producing an alloy. Tungsten can also be extracted by hydrogen reduction of WF₆: :WF₆ + 3 H₂ → W + 6 HF or pyrolytic decomposition: :WF₆ → W + 3 F₂ ( Δ''H''_r = +) Tungsten is not traded as a futures contract and cannot be tracked on exchanges like the

London Metal Exchange The London Metal Exchange (LME) is a futures and forwards exchange with the world's largest market in standarised forward contracts, futures contracts and options on base metals. The exchange also offers contracts on ferrous metals and precious ...

. The tungsten industry often uses independent pricing references such as

Argus Media Argus (formerly known as Petroleum Argus Ltd) is an independent provider of price information, consultancy services, conferences, market data and business intelligence for the global petroleum, natural gas, electricity, emissions, biofuels, bi ...

Metal Bulletin Fastmarkets MB, previously known as Metal Bulletin, is a specialist international publisher and information provider for the global steel, non-ferrous and scrap metals markets. History What was later known as ''Metal Bulletin'' was started in 191 ...

as a basis for contracts. The prices are usually quoted for tungsten concentrate or WO₃.Shedd, Kim B. (December 2018
Tungsten
''2016 Minerals Yearbook''. USGS

Applications

Approximately half of the tungsten is consumed for the production of hard materials – namely

– with the remaining major use being in alloys and steels. Less than 10% is used in other

chemical compounds A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

. Because of the high ductile-brittle transition temperature of tungsten, its products are conventionally manufactured through

powder metallurgy Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes can reduce or eliminate the need for subtractive processes in manufacturing, lowering material losses and ...

spark plasma sintering Spark plasma sintering (SPS), also known as field assisted sintering technique (FAST) or pulsed electric current sintering (PECS), or plasma pressure compaction (P2C) is a sintering technique. The main characteristic of SPS is that the pulsed or u ...

chemical vapor deposition Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (substra ...

hot isostatic pressing Hot isostatic pressing (HIP) is a manufacturing process, used to reduce the porosity of metals and increase the density of many ceramic materials. This improves the material's mechanical properties and workability. The process can be used to pro ...

, and

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...

routes. A more flexible manufacturing alternative is

selective laser melting Selective laser melting (SLM) is one of many proprietary names for a metal additive manufacturing (AM) technology that uses a bed of powder with a source of heat to create metal parts. Also known as direct metal laser sintering (DMLS), the ASTM ...

, which is a form of 3D printing and allows creating complex three-dimensional shapes.

Industrial

Tungsten is mainly used in the production of hard materials based on

(WC), one of the hardest carbides. WC is an efficient electrical conductor, but W₂C is less so. WC is used to make wear-resistant abrasives, and "carbide" cutting tools such as knives, drills, circular saws, Die (manufacturing), dies, Milling machine, milling and Lathe (metal), turning tools used by the metalworking, woodworking, mining, petroleum and construction industries. Carbide tooling is actually a ceramic/metal composite, where metallic cobalt acts as a binding Metal matrix composite, (matrix) material to hold the WC particles in place. This type of industrial use accounts for about 60% of current tungsten consumption. The jewelry industry makes rings of sintered

, tungsten carbide/metal composites, and also metallic tungsten. WC/metal composite rings use nickel as the metal matrix in place of cobalt because it takes a higher luster when polished. Sometimes manufacturers or retailers refer to

as a metal, but it is a ceramic. Because of tungsten carbide's hardness, rings made of this material are extremely abrasion resistant, and will hold a burnished finish longer than rings made of metallic tungsten. Tungsten carbide rings are brittle, however, and may crack under a sharp blow.

Alloys

The hardness and heat resistance of tungsten can contribute to useful

s. A good example is high-speed steel, which can contain as much as 18% tungsten. Tungsten's high melting point makes tungsten a good material for applications like Rocket engine nozzle, rocket nozzles, for example in the UGM-27 Polaris submarine-launched ballistic missile. Tungsten alloys are used in a wide range of applications, including the aerospace and automotive industries and radiation shielding. Superalloys containing tungsten, such as Hastelloy and Stellite, are used in turbine blades and wear-resistant parts and coatings. Tungsten's heat resistance makes it useful in arc welding applications when combined with another highly-conductive metal such as silver or copper. The silver or copper provides the necessary conductivity and the tungsten allows the welding rod to withstand the high temperatures of the arc welding environment.

Permanent magnets

Quenched (martensitic) tungsten steel (approx. 5.5% to 7.0% W with 0.5% to 0.7% C) was used for making hard permanent magnets, due to its high remanence and coercivity, as noted by John Hopkinson (1849–1898) as early as 1886. The magnetic properties of a metal or an alloy are very sensitive to microstructure. For example, while the element tungsten is not ferromagnetic (but

is), when it is present in steel in these proportions, it stabilizes the martensite phase, which has greater ferromagnetism than the Allotropes of iron, ferrite (iron) phase due to its greater resistance to Domain wall (magnetism), magnetic domain wall motion.

Military

Tungsten, usually alloyed with

, or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium, in applications where uranium's radioactivity is problematic even in depleted form, or where uranium's additional

properties are not desired (for example, in ordinary small arms bullets designed to penetrate body armor). Similarly, tungsten alloys have also been used in shell (projectile), shells, grenades, and missiles, to create supersonic shrapnel. Germany used tungsten during World War II to produce shells for anti-tank gun designs using the Gerlich squeeze bore principle to achieve very high muzzle velocity and enhanced armor penetration from comparatively small caliber and light weight field artillery. The weapons were highly effective but a shortage of tungsten used in the shell core, caused in part by the Wolfram Crisis, limited their use. Tungsten has also been used in Dense inert metal explosives, which use it as dense powder to reduce collateral damage while increasing the lethality of explosives within a small radius.

Chemical applications

Tungsten(IV) sulfide is a high temperature lubricant and is a component of catalysts for hydrodesulfurization. MoS₂ is more commonly used for such applications. Tungsten oxides are used in ceramic glazes and

/magnesium tungstates are used widely in fluorescent lighting. Crystal

s are used as scintillator, scintillation detectors in nuclear physics and nuclear medicine. Other salts that contain tungsten are used in the chemical and Tanning (leather), tanning industries. Tungsten oxide (WO₃) is incorporated into selective catalytic reduction (SCR) catalysts found in coal-fired power plants. These catalysts convert nitrogen oxides (NOx, NO_x) to nitrogen (N₂) and water (H₂O) using ammonia (NH₃). The tungsten oxide helps with the physical strength of the catalyst and extends catalyst life. Tungsten containing catalysts are promising for epoxidation, oxidation, and hydrogenolysis reactions. Tungsten heteropoly acids are key component of multifunctional catalysts. Tungstates can be used as photocatalyst, while the tungsten sulfide as electrocatalyst.

Niche uses

Applications requiring its high density include weights, Mallory metal, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, rotor weights for civil and military helicopters, and as ballast in race cars for NASCAR and Formula One. Being slightly less than twice the density, Tungsten is seen as an alternative (albeit more expensive) to lead fishing sinkers. Depleted uranium is also used for these purposes, due to similarly high density. Seventy-five-kg blocks of tungsten were used as "cruise balance mass devices" on the entry vehicle portion of the 2012 Mars Science Laboratory spacecraft. It is an ideal material to use as a dolly (tool), dolly for riveting, where the mass necessary for good results can be achieved in a compact bar. High-density alloys of tungsten with nickel, copper or iron are used in high-quality darts (to allow for a smaller diameter and thus tighter groupings) or for Fly tying, artificial flys (tungsten beads allow the fly to sink rapidly). Tungsten is also used as a heavy bolt to lower the rate of fire of the Cobray Company, SWD M11/9 sub-machine gun from 1300 RPM to 700 RPM. Tungsten has seen use recently in nozzles for 3D printing; the high wear resistance and thermal conductivity of tungsten carbide improves the printing of abrasive filaments. Some string instrument strings are wound with tungsten. Tungsten is used as an absorber on the electron telescope on the Cosmic Ray System of the two Voyager program, Voyager spacecraft.

Gold substitution

Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to

or platinum. Metallic tungsten is hypoallergenic, and is harder than gold alloys (though not as hard as tungsten carbide), making it useful for ring (finger), rings that will resist scratching, especially in designs with a brushed finish. Because the density is so similar to that of gold (tungsten is only 0.36% less dense), and its price of the order of one-thousandth, tungsten can also be used in counterfeiting of gold bars, such as by plating a tungsten bar with gold, which has been observed since the 1980s, or taking an existing gold bar, drilling holes, and replacing the removed gold with tungsten rods. The densities are not exactly the same, and other properties of gold and tungsten differ, but gold-plated tungsten will pass superficial tests. Gold-plated tungsten is available commercially from China (the main source of tungsten), both in jewelry and as bars.

Electronics

Because it retains its strength at high temperatures and has a high

, elemental tungsten is used in many high-temperature applications, such as incandescent light bulb, cathode-ray tube, and vacuum tube filaments, heating elements, and rocket engine nozzles. Its high melting point also makes tungsten suitable for aerospace and high-temperature uses such as electrical, heating, and welding applications, notably in the

process (also called tungsten inert gas (TIG) welding). TIG torch breakdown

Because of its conductive properties and relative chemical inertness, tungsten is also used in electrodes, and in the emitter tips in electron-beam instruments that use field emission guns, such as electron microscopes. In electronics, tungsten is used as an interconnect material in integrated circuits, between the silicon dioxide dielectric material and the transistors. It is used in metallic films, which replace the wiring used in conventional electronics with a coat of tungsten (or

) on silicon. The electronic structure of tungsten makes it one of the main sources for X-ray targets,Hasz, Wayne Charles ''et al.'' (August 6, 2002) "X-ray target" and also for shielding from high-energy radiations (such as in the radiopharmaceutical industry for shielding radioactive samples of Fludeoxyglucose (18F), FDG). It is also used in gamma imaging as a material from which coded apertures are made, due to its excellent shielding properties. Tungsten powder is used as a filler material in plastic composites, which are used as a nontoxic substitute for

in bullets, lead shot, shot, and radiation shields. Since this element's thermal expansion is similar to borosilicate glass, it is used for making glass-to-metal seals. In addition to its high melting point, when tungsten is doped with potassium, it leads to an increased shape stability (compared with non-doped tungsten). This ensures that the filament does not sag, and no undesired changes occur.

Nanowires

Through top-down nanofabrication processes, tungsten nanowires have been fabricated and studied since 2002. Due to a particularly high surface to volume ratio, the formation of a surface oxide layer and the single crystal nature of such material, the mechanical properties differ fundamentally from those of bulk tungsten. Such tungsten nanowires have potential applications in nanoelectronics and importantly as pH probes and gas sensors. In similarity to silicon nanowires, tungsten nanowires are frequently produced from a bulk tungsten precursor followed by a thermal oxidation step to control morphology in terms of length and aspect ratio. Using the Deal–Grove model it is possible to predict the oxidation kinetics of nanowires fabricated through such thermal oxidation processing.

Fusion power

Due to its high melting point and good erosion resistance, tungsten is a lead candidate for the most exposed sections of the plasma-facing inner wall of nuclear fusion Fusion power, reactors. It will be used as the plasma-facing material of the divertor in the ITER reactor, and is currently in use in the Joint European Torus, JET test reactor.

Biological role

Tungsten, at atomic number ''Z'' = 74, is the heaviest element known to be biologically functional. It is used by some bacteria and

, but not in eukaryotes. For example, enzymes called oxidoreductases use tungsten similarly to

by using it in a tungsten-pterin complex with molybdopterin (molybdopterin, despite its name, does not contain molybdenum, but may complex with either molybdenum or tungsten in use by living organisms). Tungsten-using enzymes typically reduce carboxylic acids to aldehydes. The tungsten oxidoreductases may also catalyse oxidations. The first tungsten-requiring enzyme to be discovered also requires selenium, and in this case the tungsten-selenium pair may function analogously to the molybdenum-sulfur pairing of some molybdopterin-requiring enzymes. One of the enzymes in the oxidoreductase family which sometimes employ tungsten (bacterial formate dehydrogenase H) is known to use a selenium-molybdenum version of molybdopterin. Acetylene hydratase is an unusual metalloenzyme in that it catalyzes a hydration reaction. Two reaction mechanisms have been proposed, in one of which there is a direct interaction between the tungsten atom and the C≡C triple bond. Although a tungsten-containing xanthine dehydrogenase from bacteria has been found to contain tungsten-molydopterin and also non-protein bound selenium, a tungsten-selenium molybdopterin complex has not been definitively described. In soil, tungsten metal oxidizes to the

anion. It can be selectively or non-selectively imported by some Prokaryote, prokaryotic organisms and may substitute for molybdenum, molybdate in certain enzymes. Its effect on the action of these enzymes is in some cases inhibitory and in others positive. The soil's chemistry determines how the tungsten polymerizes; alkaline soils cause monomeric tungstates; acidic soils cause polymeric tungstates. Sodium tungstate and

have been studied for their effect on earthworms. Lead was found to be lethal at low levels and sodium tungstate was much less toxic, but the tungstate completely inhibited their Reproduction, reproductive ability. Tungsten has been studied as a biological copper metabolic Receptor antagonist, antagonist, in a role similar to the action of molybdenum. It has been found that salts may be used as biological copper chelation chemicals, similar to the tetrathiomolybdates.

In archaea

Tungsten is essential for some archaea. The following tungsten-utilizing enzymes are known: * Aldehyde ferredoxin oxidoreductase (AOR) in ''Thermococcus'' strain ES-1 * Formaldehyde ferredoxin oxidoreductase (FOR) in ''Thermococcus litoralis'' * Glyceraldehyde-3-phosphate ferredoxin oxidoreductase (GAPOR) in ''Pyrococcus furiosus'' A ''wtp'' system is known to selectively transport tungsten in archaea: * WtpA is tungsten-binding protein of ABC transporter, ABC family of transporters * WptB is a permease * WtpC is ATPase

Health factors

Because tungsten is a rare metal and its compounds are generally inert, the effects of tungsten on the environment are limited. The abundance of tungsten in the Earth's crust is thought to be about 1.5 parts per million. It is one of the rarer elements. It was at first believed to be relatively inert and an only slightly toxic metal, but beginning in the year 2000, the risk presented by tungsten alloys, its dusts and particulates to induce cancer and several other adverse effects in animals as well as humans has been highlighted from in vitro and in vivo experiments. The median lethal dose LD₅₀ depends strongly on the animal and the method of administration and varies between 59 mg/kg (intravenous, rabbits) and 5000 mg/kg (tungsten metal powder, Intraperitoneal injection, intraperitoneal, rats). People can be exposed to tungsten in the workplace by breathing it in, swallowing it, skin contact, and eye contact. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 5 mg/m³ over an 8-hour workday and a short term limit of 10 mg/m³.

References

External links

Properties, Photos, History, MSDS

at ''The Periodic Table of Videos'' (University of Nottingham)
Picture in the collection from Heinrich Pniok

Elementymology & Elements Multidict by Peter van der Krogt – Tungsten

International Tungsten Industry Association
{{Authority control Tungsten, Chemical elements Transition metals Refractory metals Chemical elements with body-centered cubic structure Native element minerals