Tungsten 30046 225795850 2008-07-15T13:07:33Z Rvbuilder 4876762 /* Applications */ {{otheruses}} {{infobox tungsten}} '''Tungsten''' ({{pronEng|ˈtʌŋstən}}), also known as '''wolfram''' ({{IPA|/ˈwʊlfrəm/}}), is a [[chemical element]] that has the symbol '''W''' and [[atomic number]] 74. A steel-gray [[metal]], tungsten is found in several [[ore]]s, including [[wolframite]] and [[scheelite]]. It is remarkable for its robust physical properties, especially the fact that it has the highest [[melting point]] of all the non-[[alloy]]ed metals and the second highest of all the elements after [[carbon]].<ref name="daintith">Daintith, John. <u>Facts on File Dictionary of Chemistry</u>. 4th ed. New York, New York: Checkmark Books, 2005</ref> Tungsten is often [[brittle]] and hard to [[metalworking|work]] in its raw state; however, if pure, it can be cut with a [[hacksaw]].<ref name="albert">Stwertka, Albert <u>A Guide to the elements</u>. 2nd ed. New York: Oxford University Press, 2002.</ref> The pure form is used mainly in electrical applications, but its many compounds and alloys are used in many applications, most notably in [[light bulb]] filaments, [[X-ray tube]]s (as both the filament and target), and [[superalloys]]. Tungsten is also the only metal from the third transition series that is known to occur in [[biomolecule]]s.<ref>{{cite journal | title = The active sites of molybdenum- and tungsten-containing enzymes | author = J McMaster and John H Enemark | journal = Current Opinion in Chemical Biology | volume = 2 | issue = 2 | pages = 201&ndash;207 | year = 1998 | url = | doi = 10.1016/S1367-5931(98)80061-6 | accessdate = }}</ref><ref>{{cite journal | title = Molybdenum and tungsten in biology | author = Russ Hille | journal = Trends in Biochemical Sciences | volume = 27 | issue = 7 | pages = 360&ndash;367 | year = 2002 | url = | doi = 10.1016/S0968-0004(02)02107-2 | accessdate = }}</ref> ==Etymology== "Tungsten" (from the [[Swedish language|Swedish]] ''tung sten'', meaning "heavy stone") is commonly accepted as the name of the material, although some chemists (primarily in [[Germany]] but also e.g. in [[Sweden]]) refer to it as "wolfram", from its ore [[wolframite]]. The name "wolframite" was derived from "''volf rahm''", the word [[Johan Gottschalk Wallerius]] used to refer to it in 1747. This, in turn, was translated from "''Lupi spuma''", the word [[Georg Agricola]] used to refer to the element in 1546. Its English translation is "wolf's froth", so named because the mineral consumed a large amount of [[tin]] in its extraction.<ref name="sweetums">{{cite web | url = http://elements.vanderkrogt.net/elem/w.html | publisher = Elementymology & Elements Multidict | title = Wolframium Wolfram Tungsten | author = Peter van der Krogt | accessdate = 2008-05-09 }}</ref> Its chemical symbol, '''W''', is derived from wolfram as well.<ref name="albert"/> ==Physical properties== In its raw form, tungsten is a steel-gray [[metal]] that is often [[brittle]] and hard to [[metalworking|work]]. However, if pure, it is much easier to work.<ref name="albert"/> It is worked by [[forging]], [[drawing (manufacturing)|drawing]], [[extrusion|extruding]], or [[sinter]]ing. Of all metals in pure form, tungsten has the highest [[melting point]] (3,422&nbsp;°[[Celsius|C]], 6,192&nbsp;°[[Fahrenheit|F]]), lowest [[vapor pressure]] and (at temperatures above 1,650&nbsp;°C) the highest [[tensile strength]].<ref name="desu">{{cite web | url = http://periodic.lanl.gov/elements/74.html | publisher = Los Alamos National Laboratory | title = Tungsten | date = 2003-12-15 | accessdate = 2008-05-09 }}</ref> Tungsten has the lowest [[coefficient of thermal expansion]] of any pure metal. Alloying small quantities of tungsten with [[steel]] greatly increases its toughness.<ref name="daintith"/> ==Isotopes== {{main|Isotopes of tungsten}} Naturally occurring tungsten consists of five [[isotope]]s whose [[half-life|half-lives]] are so long that they can be considered [[stable isotope|stable]]. Theoretically, all five can decay into isotopes of element 72 ([[hafnium]]) by [[alpha emission]], but only <sup>180</sup>W has been observed to do so with a [[half-life]] of (1.8 ± 0.2)·10<sup>18</sup> yr; on average, this yields about two alpha decays of <sup>180</sup>W in one gram of natural tungsten per year.<ref name=isotopes/> The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be:<ref name=isotopes>{{citeweb|url=http://www.nndc.bnl.gov/chart/|title=Interactive Chart of Nuclides|publisher=Brookhaven National Laboratory|author=Alejandro Sonzogni|location,National Nuclear Data Center|accessdate=2008-06-06}}</ref> :<sup>182</sup>W, ''T''<sub>1/2</sub> > 8.3·10<sup>18</sup> years :<sup>183</sup>W, ''T''<sub>1/2</sub> > 29·10<sup>18</sup> years :<sup>184</sup>W, ''T''<sub>1/2</sub> > 13·10<sup>18</sup> years :<sup>186</sup>W, ''T''<sub>1/2</sub> > 27·10<sup>18</sup> years Another 30 artificial [[radioisotope]]s of tungsten have been characterized, the most stable of which are <sup>181</sup>W with a [[half-life]] of 121.2&nbsp;days, <sup>185</sup>W with a half-life of 75.1&nbsp;days, <sup>188</sup>W with a half-life of 69.4&nbsp;days, <sup>178</sup>W with a half-life of 21.6&nbsp;days, and <sup>187</sup>W with a half-life of 23.72 h.<ref name=isotopes> All of the remaining [[radioactive]] isotopes have half-lives of less than 3&nbsp;hours, and most of these have half-lives that are less than 8&nbsp;minutes.<ref name=isotopes/> Tungsten also has 4&nbsp;[[meta state]]s, the most stable being <sup>179m</sup>W (''T''<sub>½</sub> 6.4&nbsp;minutes). ==Chemical properties== Elemental tungsten resists attack by [[oxidization|oxygen]], [[acid]]s, and [[alkali]]s.<ref name="emsley">Emsley, John E. <u>The elements</u>. 2nd ed. New York: Oxford University Press, 1991</ref> ===Compounds=== :<div class="noprint relarticle mainarticle">''Main article: [[:Category:Tungsten compounds|Tungsten compounds]] The most common formal [[oxidation state]] of tungsten is +6, but it exhibits all oxidation states from -1 to +6.<ref name="emsley">Emsley, John E. <u>The elements</u>. 2nd ed. New York: Oxford University Press, 1991</ref> Tungsten typically combines with oxygen to form the yellow [[tungsten trioxide|tungstic oxide]], WO<sub>3</sub>, which dissolves in aqueous alkaline solutions to form tungstate ions, WO<sub>4</sub><sup>2&minus;</sup>. [[Tungsten carbide]]s (W<sub>2</sub>[[carbon|C]] and WC) are produced by heating powdered tungsten with [[carbon]] and are some of the hardest [[carbide]]s, with a melting point of 2770&nbsp;°C for WC and 2780&nbsp;degrees C for W<sub>2</sub>C. WC is an efficient [[electrical conductor]], but W<sub>2</sub>C is not as efficient. Tungsten carbide behaves in a manner very similar to that of unalloyed tungsten and is resistant to chemical attack, although it reacts strongly with [[chlorine]] to form [[tungsten hexachloride]] (WCl<sub>6</sub>).<ref name="daintith"/> ====Aqueous polyoxoanions==== Aqueous tungstate solutions are noted for the formation of heteropoly acids and [[polyoxometalate]] [[anion]]s under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, [[metastable]] "paratungstate A" [[anion]], {{chem|W|7|O|24|<sup>6&minus;</sup>}}, which over hours or days converts to the less soluble "paratungstate B" anion, {{chem|H|2|W|12|O|42|<sup>10&minus;</sup>}}.<ref name="SmithBJ">{{cite journal|last=Smith|first=Bradley J.|date=2000|title=Quantitative Determination of Sodium Metatungstate Speciation by 183W N.M.R. Spectroscopy |journal=Australian Journal of Chemistry|publisher=CSIRO|volume=53|issue=12|url=http://www.publish.csiro.au/paper/CH00140.htm|accessdate=2008-06-17}}</ref> Further acidification produces the very soluble metatungstate anion, {{chem|H|2|W|12|O|40|<sup>6&minus;</sup>}}, after equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-[[oxygen]] [[octahedron|octahedra]] known as the "Keggin" anion. Many other polyoxometalate anions exist as metastable species. The inclusion of a different atom such as [[phosphorus]] in place of the two central [[hydrogen]]s in metatungstate produces a wide variety of [[heteropoly acid]]s, such as [[phosphotungstic acid]] H<sub>3</sub>P W<sub>12</sub>O<sub>40</sub> in this example. ==Biological role== Tungsten is an [[essential nutrient]] for some organisms. For example, [[enzyme]]s called [[oxidoreductase]]s use tungsten in a way that is similar to [[molybdenum]] by using it in a tungsten-[[pterin]] complex.<ref name="tungsten_orgs">{{cite book|last=Lassner|first=Erik|title=Tungsten: Properties, Chemistry, Technology of the Element, Alloys and Chemical Compounds|publisher=Springer|date=1999|pages=409-411|isbn=0306450534|url=http://books.google.com/books?id=foLRISkt9gcC&pg=PA409&lpg=PA409&dq=tungsten+nutrient+organisms&source=web&ots=-rtHF9sWBY&sig=CoCD7Wp0HS-QRzQEoiPCisLaP04&hl=en&sa=X&oi=book_result&resnum=1&ct=result}}</ref> On [[August 20]], [[2002]], officials representing the U.S.-based [[Centers for Disease Control and Prevention]] announced that [[urine]] tests on [[leukemia]] patient families and control group families in the [[Fallon, Nevada]] area had shown elevated levels of tungsten in the bodies of both groups.<ref>{{cite web | url = http://www.cdc.gov/nceh/clusters/Fallon/study.htm | publisher = Centers for Disease Control and Prevention | title = Cross-Sectional Exposure Assessment of Environmental Contaminants in Churchill County, Nevada | date = 2003-02-06 | accessdate = 2008-05-09 }}</ref> Sixteen recent cases of [[cancer]] in children were discovered in the Fallon area, which has now been identified as a [[cancer cluster]]; although the majority of the cancer victims are not longtime residents of Fallon. However, there is not enough data to support a link between tungsten and leukemia at this time.<ref name="MullenFrankX">{{cite web |url = http://www.familiesagainstcancer.org/?id=344 | publisher = Reno Gazette-Journal | last = Mullen | first = Frank X. | title = Mouse Study Findings key in Fallon Cancer Cases, Scientists Say | date = [[April 27]], [[2006]] | accessdate = 2008-06-17}}</ref> ==Applications== [[Image:Tungsten filament in halogen lamp.JPG|thumb|Closeup of a tungsten filament inside a [[halogen lamp]].]] Because of its ability to produce hardness at high temperatures and its high [[melting point]] (the second highest of any known element), elemental tungsten is used in many high-temperature applications.<ref>DeGarmo, E. Paul. <u>Materials and Processes in Manufacturing</u>. 5th ed. New York, New York: MacMillan Publishing, 1979.</ref> These include [[light bulb]], [[cathode-ray tube]], and [[vacuum tube]] filaments, as well as [[heating element]]s and nozzles on [[rocket engine]]s.<ref name="albert"/> The high melting point also makes tungsten suitable for aerospace and high temperature uses which include electrical, heating, and welding applications, notably in the [[gas tungsten arc welding]] process (also called [[TIG]] welding). Due to its conductive properties, as well as its relative chemical inertia, tungsten is also used in [[electrode]]s, and in the emitter tips of [[field emission]] electron-beam instruments, such as [[focused ion beam]] (FIB) and [[electron microscope]]s. In electronics, tungsten is used as an interconnect material in [[integrated circuit]]s, between the [[silicon dioxide]] [[dielectric]] material and the transistors. Additionally, it is used in the manufacture of metallic films, which replace the wiring used in conventional electronics with a coat of tungsten (or [[molybdenum]]) on [[silicon]].<ref name="manny">Schey, John A. <u>Introduction to Manufacturing Processes.</u> 2nd ed. McGraw-Hill, Inc, 1987.</ref> The electronic structure of tungsten makes it one of the main sources for [[X-ray]] targets,<ref name="patent">{{cite web|url=http://www.patentstorm.us/patents/6428904/description.html|title=US Patent 6428904 - X-ray target|date=[[August 6]], [[2002]]|publisher=[http://www.patentstorm.us/ PatentStorm]|accessdate=2008-06-18}}</ref> and also for shielding from high-energy radiations (such as in the [[radiopharmaceutical]] industry for shielding radioactive samples of [[FDG]]). Tungsten powder is used as a filler material in [[plastic]] composites, which are used as a nontoxic substitute for [[lead]] in [[bullet]]s, shot, and radiation shields. Since this element's thermal expansion is similar to [[borosilicate glass]], it is used for making glass-to-metal seals.<ref name="desu"/> The hardness and density of tungsten are applied in obtaining [[heavy metal]] [[alloy]]s. A good example is [[high speed steel]], which may contain as much as 18% tungsten.<ref name="w-apps">{{cite web|url=http://www.azom.com/details.asp?ArticleID=1264|title=Tungsten Applications - Steel|date=2000-2008|publisher=[http://www.azom.com/ azom.com]|accessdate=2008-06-18}}</ref> [[Superalloy]]s containing tungsten, like [[Hastelloy]] and [[Stellite]], are used in [[turbine]] blades and wear resistant parts and coatings. Applications requiring its high density include [[heat sink]]s, weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, and as ballast in high level race cars in series, such as [[NASCAR]] and [[Formula 1]]. It is an ideal material to use as a bucking bar for [[Riveting]], where the mass necessary for good results can be achieved in a small, easy to wield bar. In armaments, tungsten, usually alloyed with nickel and iron or cobalt to form heavy alloys, is used in [[kinetic energy penetrator]]s as an alternative to [[depleted uranium]] but may also be used in cannon shells, grenades and missiles to create supersonic shrapnel. High-density alloys of tungsten may be used in [[darts]] (to allow for a smaller diameter and thus tighter groupings) or for [[fishing lure]]s (tungsten bead heads allow the fly to sink rapidly). Some types of [[Strings (music)|strings]] for musical instruments are wound with tungsten wires. Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to [[gold]] or [[platinum]].<ref name="albert"/> Its hardness makes it ideal for [[ring (finger)|rings]] that will resist scratching, and are [[hypoallergenic]] and will not need polishing, which is especially useful in designs with a brushed finish.<ref name="popsci">{{cite news|url=http://www.popsci.com/diy/article/2008-03/how-make-convincing-fake-gold-bars|title=How to Make Convincing Fake-Gold Bars|last=Gray|first=Theo|date=[[March 14]], [[2008]]|publisher=[[Popular Science]]|accessdate=2008-06-18}}</ref> Tungsten chemical compounds are used in [[catalyst]]s, inorganic pigments (e.g. [[tungsten oxide]]s), and also as high-temperature [[lubricant]]s ([[Tungsten(IV) sulfide|tungsten disulfide]]). [[Tungsten carbide]] (WC) is used to make wear-resistant [[abrasive]]s and cutters and knives for drills, [[circular saw]]s, [[Milling machine|milling]] and [[Lathe (metal)|turning]] tools used by the metalworking, woodworking, [[mining]], [[petroleum]] and construction industries.<ref name="daintith"/> Tungsten oxides are used in [[ceramic]] glazes and [[calcium]]/[[magnesium]] tungstates are used widely in [[fluorescent lighting]]. Crystal [[tungstate]]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]] industries.<ref name="desu"/> ==Production== [[Image:Tungsten (mined)2.PNG|thumb|right|Tungsten output in 2005]] Tungsten is found in the [[mineral]]s [[wolframite]] ([[iron]]-[[manganese]] tungstate, FeW[[oxygen|O]]<sub>4</sub>/MnWO<sub>4</sub>), [[scheelite]] ([[calcium]] tungstate, (CaWO<sub>4</sub>), [[ferberite]] and [[hübnerite]]. These are mined and used to produce about 37,400 tons of tungsten concentrates per year in 2000.<ref name="production">{{cite news|url=http://minerals.usgs.gov/minerals/pubs/commodity/tungsten/680400.pdf|title=Tungsten|last=Shedd|first=Kim B.|date=2000|publisher=[[United States Geological Survey]]|accessdate=2008-06-18}}</ref> Over 75% of this production came from [[China]], while most of the remaining production is done in Austria, Bolivia, Portugal, and Russia, while [[United States]] produces none.<ref name="production"/> The extraction of tungsten has several stages, the ore eventually being converted to tungsten (VI) oxide (WO<sub>2</sub>), which is heated with [[hydrogen]] or [[carbon]], producing powdered tungsten.<ref name="SaundersN">{{cite book|last=Saunders|first=Nigel|title=Tungsten and the Elements of Groups 3 to 7 (The Periodic Table)|publisher=Heinemann Library|location=[[Chicago, Illinois]]|date=February 2004|isbn=1403435189}}</ref> It can be used in that state or converted into solid bars. Tungsten can also be extracted by hydrogen reduction of WF<sub>6</sub> (WF<sub>6</sub> + 3H<sub>2</sub> = W + 6HF) or [[pyrolytic decomposition]] (WF<sub>6</sub> + energy = W + 3F<sub>2</sub>).<ref name="manny"/> ==History== In 1781, [[Carl Wilhelm Scheele]] ascertained that a new [[acid]] could be made from scheelite (at the time named tungstenite): [[tungstic acid]]. Scheele and [[Torbern Bergman]] suggested that it could be possible to obtain a new metal by reducing this acid.<ref name="SaundersN"/> In 1783, [[José Elhuyar|José]] and [[Fausto Elhuyar]] found an acid made from wolframite that was identical to tungstic acid. Later that year, in [[Spain]], the brothers succeeded in isolating tungsten through reduction of this acid with [[charcoal]]. They are credited with the discovery of the element.<ref name="ITIAnews_0605">{{cite news|url=http://www.itia.info/FileLib/ITIA_Newsletter_June05.pdf|title=ITIA Newsletter|date=June 2005|publisher=International Tungsten Industry Association|accessdate=2008-06-18}}</ref><ref name="ITIAnews_1205">{{cite news|url=http://www.itia.info/FileLib/ITIA_Newsletter_December05.pdf|title=ITIA Newsletter|date=December 2005|publisher=International Tungsten Industry Association|accessdate=2008-06-18}}</ref> In World War II, tungsten played a 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 sources of wolframite ore. The resistance to high temperatures, as well as the extreme strength of its alloys, made the metal into a very important raw material for the weaponry industry.<ref name="portugal">{{cite journal|last=Stevens|first=Donald G.|date=1999|title=World War II Economic Warfare: The United States, Britain, and Portuguese Wolfram|journal=The Historian|publisher=[http://www.questia.com Questia]|url=http://www.questia.com/googleScholar.qst;jsessionid=LY1PyzmCc1D256Gvh5wpbhxKyTyvcm2FHpMwpcs2wW2XyytCh4pW!956463030?docId=5001286099}}</ref> ==See also== * [[Field emission gun]] * ''[[Uncle Tungsten: Memories of a Chemical Boyhood]]'' by [[Oliver Sacks]] ==References== {{reflist|2}} ==Further reading== * DC/AC Circuits and Electronics: Principles & Applications by Robert K. Herrick, Published by Delmar Learning 2003 for Purdue University ==External links== {{Commons|Tungsten}} {{wiktionary|tungsten}} * [http://www.ws2.eagerlearning.com Tungsten Disulfide Applications WS2] * [http://www.webelements.com/webelements/elements/text/W/index.html WebElements.com – Tungsten] * [http://www.tungsten.com/mtstung.html Properties, Photos, History, MSDS] * [http://www.sciencelab.com/data/elements/W.shtml ScienceLab.com – Tungsten] * [http://www.pniok.de/w.htm Picture in the collection from Heinrich Pniok] * [http://www.vanderkrogt.net/elements/elem/w.html Elementymology & Elements Multidict by Peter van der Krogt – Tungsten] * [http://xxx.lanl.gov/abs/nucl-ex/0408006 Detection of the Natural Alpha Decay of Tungsten] * [http://www.itia.info/ International Tungsten Industry Association] {{clear}} {{Compact periodic table}} [[Category:Chemical elements]] [[Category:Transition metals]] [[Category:Refractory materials]] [[Category:Tungsten|*]] [[ar:تنجستن]] [[az:Volfram]] [[be:Вальфрам]] [[bs:Volfram]] [[bg:Волфрам]] [[ca:Tungstè]] [[cs:Wolfram]] [[co:Tungstenu]] [[cy:Twngsten]] [[da:Wolfram]] [[de:Wolfram]] [[et:Volfram]] [[el:Βολφράμιο]] [[es:Wolframio]] [[eo:Volframo]] [[fa:تنگستن]] [[fr:Tungstène]] [[fur:Tungsten]] [[gv:Tungsten]] [[ko:텅스텐]] [[hy:Վոլֆրամ]] [[hr:Volfram]] [[io:Wolframo]] [[id:Wolfram]] [[is:Volfram]] [[it:Tungsteno]] [[he:טונגסטן]] [[ku:Tûngsten]] [[la:Wolframium]] [[lv:Volframs]] [[lb:Wolfram]] [[lt:Volframas]] [[jbo:jarjinme]] [[hu:Volfrám]] [[mr:टंग्स्टन]] [[nl:Wolfraam]] [[ja:タングステン]] [[no:Wolfram]] [[nn:Wolfram]] [[nds:Wolfram]] [[pl:Wolfram]] [[pt:Tungstênio]] [[ro:Wolfram (element)]] [[ru:Вольфрам]] [[simple:Tungsten]] [[sk:Volfrám]] [[sl:Volfram]] [[sr:Волфрам]] [[sh:Volfram]] [[fi:Volframi]] [[sv:Volfram]] [[ta:டங்க்ஸ்டன்]] [[th:ทังสเตน]] [[vi:Volfram]] [[tg:Волфрам]] [[tr:Volfram]] [[uk:Вольфрам]] [[zh:钨]]