Tungsten
[17] Polycrystalline tungsten is an intrinsically brittle[18][19][20] and hard material (under standard conditions, when uncombined), making it difficult to work into metal.Contrary to the α phase which crystallizes in isometric grains, the β form exhibits a columnar habit.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 was long thought to be non-radioactive, but 209Bi (its longest lived isotope) actually decays with a half life of 2.01×1019 years or about a factor 10 slower than 180W.It will, however, react directly with fluorine (F2) at room temperature to form tungsten(VI) fluoride (WF6), a colorless gas.Later that year, at the Royal Basque Society in the town of Bergara, Spain, the brothers succeeded in isolating tungsten by reduction of this acid with charcoal, and they are credited with the discovery of the element (they called it "wolfram" or "volfram").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.Now tungsten is used in many more applications such as aircraft and motorsport ballast weights, darts, anti-vibration tooling, and sporting equipment.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.[69] Tungsten is considered to be a conflict mineral due to the unethical mining practices observed in the Democratic Republic of the Congo.[23] Because of the high ductile-brittle transition temperature of tungsten, its products are conventionally manufactured through powder metallurgy, spark plasma sintering, chemical vapor deposition, hot isostatic pressing, and thermoplastic routes.A more flexible manufacturing alternative is selective laser melting, which is a form of 3D printing and allows creating complex three-dimensional shapes.[17] Carbide tooling is actually a ceramic/metal composite, where metallic cobalt acts as a binding (matrix) material to hold the WC particles in place.[78] WC/metal composite rings use nickel as the metal matrix in place of cobalt because it takes a higher luster when polished.[82] Tungsten alloys are used in a wide range of applications, including the aerospace and automotive industries and radiation shielding.Tungsten's heat resistance makes it useful in arc welding applications when combined with another highly-conductive metal such as silver or copper.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.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.[26] Tungsten oxide (WO3) is incorporated into selective catalytic reduction (SCR) catalysts found in coal-fired power plants.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.[108] 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.Tungsten powder is used as a filler material in plastic composites, which are used as a nontoxic substitute for lead in bullets, shot, and radiation shields.[112] These motors are integral components that provide tactile feedback to users, alerting them to incoming calls, messages, and notifications.[113] Tungsten’s high density, hardness, and wear resistance property helps to endure the high-speed rotational vibrations these motors generate.[120] 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 reactors.[125] 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.[127] 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.[136] 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.[137][138] The median lethal dose LD50 depends strongly on the animal and the method of administration and varies between 59 mg/kg (intravenous, rabbits)[139][140] and 5000 mg/kg (tungsten metal powder, intraperitoneal, rats).
Tungsten (disambiguation)AllotropesStandard atomic weightperiodic tableHydrogenHeliumLithiumBerylliumCarbonNitrogenOxygenFluorineSodiumMagnesiumAluminiumSiliconPhosphorusSulfurChlorinePotassiumCalciumScandiumTitaniumVanadiumChromiumManganeseCobaltNickelCopperGalliumGermaniumArsenicSeleniumBromineKryptonRubidiumStrontiumYttriumZirconiumNiobiumMolybdenumTechnetiumRutheniumRhodiumPalladiumSilverCadmiumIndiumAntimonyTelluriumIodineCaesiumBariumLanthanumCeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumRheniumOsmiumIridiumPlatinumMercury (element)ThalliumBismuthPoloniumAstatineFranciumRadiumActiniumThoriumProtactiniumUraniumNeptuniumPlutoniumAmericiumCuriumBerkeliumCaliforniumEinsteiniumFermiumMendeleviumNobeliumLawrenciumRutherfordiumDubniumSeaborgiumBohriumHassiumMeitneriumDarmstadtiumRoentgeniumCoperniciumNihoniumFleroviumMoscoviumLivermoriumTennessineOganessonAtomic numbergroup 6Periodperiod 6Electron configurationMelting pointBoiling pointDensityHeat of fusionkJ/molHeat of vaporizationMolar heat capacityVapor pressureOxidation statesElectronegativity