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definitions - Tungsten

tungsten (n.)

1.a heavy grey-white metallic element; the pure form is used mainly in electrical applications; it is found in several ores including wolframite and scheelite

Tungsten (n.)

1.(MeSH)Tungsten. A metallic element with the atomic symbol W, atomic number 74, and atomic weight 183.85. It is used in many manufacturing applications, including increasing the hardness, toughness, and tensile strength of steel; manufacture of filaments for incandescent light bulbs; and in contact points for automotive and electrical apparatus.

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Merriam Webster

TungstenTung"sten (tŭng"stĕn), n. [Sw. tungsten (cf. Dan. tungsteen, G. tungstein); tung heavy (akin to Dan. tung, Icel. þungr) + sten stone. See Stone.]
1. (Chem.) A rare element of the chromium group found in certain minerals, as wolfram and scheelite, and isolated as a heavy steel-gray metal which is very hard and infusible. It has both acid and basic properties. When alloyed in small quantities with steel, it greatly increases its hardness. Symbol W (Wolframium). Atomic weight, 183.6. Specific gravity, 18.

2. (Min.) Scheelite, or calcium tungstate. [Obs.]

Tungsten ocher, or Tungstic ocher (Min.), tungstite.

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definition of Wikipedia

synonyms - Tungsten

Tungsten (n.) (MeSH)

Wolfram  (MeSH)

tungsten (n.)

atomic number 74, W, wolfram

phrases

-Bürentsogt Tungsten Mine • Copper-tungsten • Daehan Tungsten FC • Di-tungsten tetra(hpp) • Drake Tungsten • Eka-Tungsten • Eka-tungsten • Gas tungsten arc welding • Isotopes of tungsten • Operation Tungsten • Tungsten (Cantung) Airport • Tungsten (disambiguation) • Tungsten (handheld) • Tungsten (music) • Tungsten PDA • Tungsten borides • Tungsten carbide • Tungsten carbonate • Tungsten chloride • Tungsten dichloride dioxide • Tungsten disilicide • Tungsten film • Tungsten hexacarbonyl • Tungsten hexachloride • Tungsten hexafluoride • Tungsten inert gas welding • Tungsten nitride • Tungsten ore • Tungsten oxide • Tungsten oxide (disambiguation) • Tungsten pentoxide • Tungsten trioxide • Tungsten(III) oxide • Tungsten(IV) oxide • Tungsten(IV) sulfide • Tungsten(IV) telluride • Tungsten(V) bromide • Tungsten(V) chloride • Tungsten(VI) oxytetrabromide • Tungsten(VI) oxytetrachloride • Tungsten(VI) oxytetrafluoride • Tungsten, Northwest Territories • Tungsten-158 • Tungsten-159 • Tungsten-160 • Tungsten-161 • Tungsten-162 • Tungsten-163 • Tungsten-164 • Tungsten-165 • Tungsten-166 • Tungsten-167 • Tungsten-168 • Tungsten-169 • Tungsten-170 • Tungsten-171 • Tungsten-172 • Tungsten-173 • Tungsten-174 • Tungsten-175 • Tungsten-176 • Tungsten-177 • Tungsten-178 • Tungsten-179 • Tungsten-180 • Tungsten-181 • Tungsten-182 • Tungsten-183 • Tungsten-184 • Tungsten-185 • Tungsten-186 • Tungsten-187 • Tungsten-188 • Tungsten-189 • Tungsten-190 • Tungsten-191 • Tungsten-192 • Tungsten-carbide • Tungsten-halogen bulb • Tungsten-halogen lamp • Tungsten-halogen light • Tungsten-halogen light bulb • Uncle Tungsten

analogical dictionary

 

Metals - Elements[Hyper.]

Tungsten (n.) [MeSH]



tungsten (n.)


Wikipedia

Tungsten

                   
tantalumtungstenrhenium
Mo

W

Sg
Appearance
grayish white, lustrous
General properties
Name, symbol, number tungsten, W, 74
Pronunciation /ˈtʌŋstən/;
alternatively, /ˈwʊlfrəm/ WOOL-frəm
Element category transition metal
Group, period, block 66, d
Standard atomic weight 183.84
Electron configuration [Xe] 4f14 5d4 6s2[1]
Electrons per shell 2, 8, 18, 32, 12, 2 (Image)
Physical properties
Phase solid
Density (near r.t.) 19.25 g·cm−3
Liquid density at m.p. 17.6 g·cm−3
Melting point 3695 K, 3422 °C, 6192 °F
Boiling point 5828 K, 5555 °C, 10031 °F
Critical point 13892 K, MPa
Heat of fusion 35.3 kJ·mol−1
Heat of vaporization 806.7 kJ·mol−1
Molar heat capacity 24.27 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 3477 3773 4137 4579 5127 5823
Atomic properties
Oxidation states 6, 5, 4, 3, 2, 1, 0, −1, -2
(mildly acidic oxide)
Electronegativity 2.36 (Pauling scale)
Ionization energies 1st: 770 kJ·mol−1
2nd: 1700 kJ·mol−1
Atomic radius 139 pm
Covalent radius 162±7 pm
Miscellanea
Crystal structure body-centered cubic
Magnetic ordering paramagnetic[2]
Electrical resistivity (20 °C) 52.8 nΩ·m
Thermal conductivity 173 W·m−1·K−1
Thermal expansion (25 °C) 4.5 µm·m−1·K−1
Young's modulus 411 GPa
Shear modulus 161 GPa
Bulk modulus 310 GPa
Poisson ratio 0.28
Mohs hardness 7.5
Vickers hardness 3430 MPa
Brinell hardness 2570 MPa
CAS registry number 7440-33-7
Most stable isotopes
Main article: Isotopes of tungsten
iso NA half-life DM DE (MeV) DP
180W 0.12% 1.8×1018 y α 2.516 176Hf
181W syn 121.2 d ε 0.188 181Ta
182W 26.50% 182W is stable with 108 neutrons
183W 14.31% 183W is stable with 109 neutrons
184W 30.64% 184W is stable with 110 neutrons
185W syn 75.1 d β 0.433 185Re
186W 28.43% 186W is stable with 112 neutrons
· r

Tungsten /ˈtʌŋstən/, also known as wolfram /ˈwʊlfrəm/ (WUUL-frəm), is a chemical element with the chemical symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten directly translatable to heavy stone,[3] though it is commonly called volfram in Swedish.

A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important ores include wolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Also remarkable is its high density of 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead.[4] Tungsten with minor amounts of impurities is often brittle[5] and hard, making it difficult to work. However, very pure tungsten, though still hard, is more ductile, and can be cut with a hard-steel hacksaw.[6]

The unalloyed elemental form is used mainly in electrical applications. Tungsten's many alloys have numerous applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), electrodes in TIG welding, and superalloys. Tungsten's hardness and high density give it military applications in penetrating projectiles. Tungsten compounds are most often used industrially as catalysts.

Tungsten is the only metal from the third transition series that is known to occur in biomolecules, where it is used in a few species of bacteria. It is the heaviest element known to be used by any living organism. Tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life.[7][8]

Contents

  History

In 1781, Carl Wilhelm Scheele discovered that a new acid, tungstic acid, could be made from scheelite (at the time named tungsten). Scheele and Torbern Bergman suggested that it might be possible to obtain a new metal by reducing this acid.[9] In 1783, 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 by reduction of this acid with charcoal, and they are credited with the discovery of the element.[10][11]

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 deposits of wolframite ore at Panasqueira. Tungsten's resistance to high temperatures and its strengthening of alloys made it an important raw material for the arms industry.[12]

  Etymology

The name "tungsten" (from the Nordic tung sten, meaning "heavy stone") is used in English, French, and many other languages as the name of the element. Tungsten was the old Swedish name for the mineral scheelite. The other name "wolfram" (or "volfram"), used for example in most European (especially Germanic and Slavic) languages, is derived from the mineral wolframite, and this is also the origin of its chemical symbol, W.[6] The name "wolframite" is derived from German "wolf rahm" ("wolf soot" or "wolf cream"), the name given to tungsten by Johan Gottschalk Wallerius in 1747. This, in turn, derives from "Lupi spuma", the name Georg Agricola used for the element in 1546, which translates into English as "wolf's froth" or "cream" (the etymology is not entirely certain), and is a reference to the large amounts of tin consumed by the mineral during its extraction.[13]

  Characteristics

  Physical properties

In tungsten's raw form, it is a hard steel-gray metal that is often brittle and hard to work. If made very pure, tungsten retains its hardness (which exceeds that of many steels), and becomes malleable enough that it can be worked easily.[6] It is worked by forging, drawing, extruding or sintering.

Of all metals in pure form, tungsten has the highest melting point (3,422 °C, 6,192 °F), lowest vapor pressure (at temperatures above 1,650 °C, 3,000 °F) and the highest tensile strength.[14] Tungsten has the lowest coefficient of thermal expansion of any pure metal. The low thermal expansion and high melting point and strength of tungsten originate from strong covalent bonds formed between tungsten atoms by the 5d electrons.[15] Alloying small quantities of tungsten with steel greatly increases its toughness.[4]

Tungsten exists in two major crystalline forms: α and β. The former has a body-centered cubic structure and is the most stable form. The structure of the β phase is called A15 cubic; it is metastable, 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. The α phase has a three times lower electrical resistivity[16] and a much lower superconducting transition temperature TC than the β phase: ca. 0.015 K vs. 1–4 K; mixing the two phases allows obtaining intermedicate TC values.[17][18] The TC value can also be raised by alloying tungsten with another metal (e.g. 7.9 K for W-Tc).[19] Such tungsten alloys are sometimes used in low-temperature superconducting circuits.[20][21][22]

  Isotopes

Naturally occurring tungsten consists of five isotopes whose half-lives are so long that they can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed[23] to do so with a half-life of (1.8 ± 0.2)×1018 years; on average, this yields about two alpha decays of 180W in one gram of natural tungsten per year.[24] The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be[24]

182W, T1/2 > 8.3×1018 years
183W, T1/2 > 2.9×1019 years
184W, T1/2 > 1.3×1019 years
186W, T1/2 > 2.7×1019 years

Another 30 artificial radioisotopes 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.[24] All of the remaining radioactive isotopes have half-lives of less than 3 hours, and most of these have half-lives below 8 minutes.[24] Tungsten also has 4 meta states, the most stable being 179mW (T½ 6.4 minutes).

  Chemical properties

Main article: Tungsten compounds

Elemental tungsten resists attack by oxygen, acids, and alkalis.[25]

The most common formal oxidation state of tungsten is +6, but it exhibits all oxidation states from −2 to +6.[25][26] Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO3, which dissolves in aqueous alkaline solutions to form tungstate ions, WO2−
4
.

Tungsten carbides (W2C and WC) are produced by heating powdered tungsten with carbon. W2C is resistant to chemical attack, although it reacts strongly with chlorine to form tungsten hexachloride (WCl6).[4]

In aqueous solution, tungstate gives the heteropoly acids and polyoxometalate anions under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, metastable "paratungstate A" anion, W7O6–
24
, which over time converts to the less soluble "paratungstate B" anion, H2W12O10–
42
.[27] Further acidification produces the very soluble metatungstate anion, H2W12O6–
40
, after which equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-oxygen 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 hydrogens in metatungstate produces a wide variety of heteropoly acids, such as phosphotungstic acid H3PW12O40.

Tungsten trioxide can form intercalation compounds with alkali metals. These are known as bronzes; an example is sodium tungsten bronze.

  Occurrence

Tungsten is found in the minerals wolframite (iron-manganese tungstate, (Fe,Mn)WO4), scheelite (calcium tungstate, (CaWO4), ferberite (FeWO4) and hübnerite (MnWO4). China produced 51,000 tonnes of tungsten concentrate in 2009, which was 83% of the world output. In the prelude to WWII China's production of tungsten played a role as China could use this leverage to demand material assistance from the US government.[28] Most of the remaining production originated from Russia (2,500 t), Canada (1,964 t), Bolivia (1,023 t), Austria (900 t), Portugal (900 t), Thailand (600 t), Brazil (500 t), Peru (500 t) and Rwanda (500 t).[29] Tungsten is also considered to be a conflict mineral due to the unethical mining practices observed in the Democratic Republic of the Congo.[30][31]

  Biological role

Tungsten, at atomic number 74, is the heaviest element known to be biologically functional, with the next heaviest being iodine (Z = 53). Although not in eukaryotes, tungsten is used by some bacteria. For example, enzymes called oxidoreductases use tungsten similarly to molybdenum 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.[32] 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 molybdenum cofactor-requiring enzymes.[33] 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.[34] 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.[35]

In soil, tungsten metal oxidizes to the tungstate anion. It can be selectively or non-selectively imported by some prokaryotic organisms and may substitute for molybdate in certain enzymes. Its effect on the action of these enzymes is in some cases inhibitory and in others positive.[36] The soil's chemistry determines how the tungsten polymerizes; alkaline soils cause monomeric tungstates; acidic soils cause polymeric tungstates.[37]

Sodium tungstate and lead 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 reproductive ability.[38]

Tungsten has been studied as a biological copper metabolic antagonist, in a role similar to the action of molybdenum. It has been found that tetrathiotungstates may be used as biological copper chelation chemicals, similar to the tetrathiomolybdates.[39]

  Production

  Wolframite, scale in cm
  Tungsten output in 2005

About 61,300 tonnes of tungsten concentrates were produced in the year 2009.[29] Tungsten is extracted from its ores in several stages. The ore is eventually converted to tungsten(VI) oxide (WO3), which is heated with hydrogen or carbon to produce powdered tungsten.[9] Because of tungsten's high melting point, it is not commercially feasible to cast tungsten ingots. Instead, powdered tungsten is mixed with small amounts of powdered nickel or other metals, and sintered. 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:[40]

WF6 → W + 3 F2 (ΔHr = +)

Tungsten is not traded as a futures contract and cannot be tracked on exchanges like the London Metal Exchange. The price for pure metal is around $20,075 per tonne as of October 2008.[41]

  Applications

  Close-up of a tungsten filament inside a halogen lamp
  Tungsten carbide ring (jewelry)

Approximately half of the tungsten is consumed for the production of hard materials — namely tungsten carbide — with the remaining major use being in alloys and steels. Less than 10% is used in other chemical compounds.[42]

  Hard materials

Tungsten is mainly used in the production of hard materials based on tungsten carbide, one of the hardest carbides, with a melting point of 2770 °C. WC is an efficient electrical conductor, but W2C is less so. WC is used to make wear-resistant abrasives and cutters and knives for drills, circular saws, milling and turning tools used by the metalworking, woodworking, mining, petroleum and construction industries[4] and accounts for about 60% of current tungsten consumption.[43]

The jewelry industry makes rings of sintered tungsten carbide, tungsten carbide/metal composites, and also metallic tungsten. Sometimes manufacturers or retailers refer to tungsten carbide as a metal, but it is a ceramic.[44] Because of tungsten carbide's hardness, rings made of this material are extremely abrasion resistant, and will hold a burnished finish much longer than rings made of metallic tungsten. Tungsten carbide rings are brittle, however, and may crack under a sharp blow.[45]

  Alloys

The hardness and density of tungsten are applied in obtaining heavy metal alloys. A good example is high speed steel, which can contain as much as 18% tungsten.[46] Tungsten's high melting point makes tungsten a good material for applications like rocket nozzles, for example in the UGM-27 Polaris submarine-launched ballistic missile.[47] Superalloys containing tungsten, such as Hastelloy and Stellite, are used in turbine blades and wear-resistant parts and coatings.

  Armaments

Tungsten, usually alloyed with nickel and iron or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium, in applications where uranium's additional pyrophoric properties are not required (for example, in ordinary small arms bullets designed to penetrate body armor). Similarly, tungsten alloys have also been used in cannon shells, grenades and missiles, to create supersonic shrapnel. 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.[48]

  Chemical applications

Tungsten(IV) sulfide is a high temperature lubricant and is a component of catalysts for hydrodesulfurization.[49] MoS2 is more commonly used for such applications.[50]

Tungsten oxides are used in ceramic glazes and calcium/magnesium tungstates are used widely in fluorescent lighting. Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine. Other salts that contain tungsten are used in the chemical and tanning industries.[14]

Tungsten oxide (WO3) is incorporated into selective catalytic reduction (SCR) catalysts found in coal-fired power plants. These catalysts convert nitrogen oxides (NOx) to nitrogen (N2) and water (H2O) using ammonia (NH3). The tungsten oxide helps with the physical strength of the catalyst and extends catalyst life.[51]

  Niche uses

Applications requiring its high density include weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, and as ballast in race cars for NASCAR and Formula One; depleted uranium is also used for these purposes, due to similarly high density. It is an ideal material to use as a 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[52] (to allow for a smaller diameter and thus tighter groupings) or for fishing lures (tungsten beads allow the fly to sink rapidly). Some types of strings for musical instruments are wound with tungsten wires.

  Gold substitution

Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to gold or platinum.[6][53] Metallic tungsten is harder than gold alloys (though not as hard as tungsten carbide), and is hypoallergenic, making it useful for rings that will resist scratching, especially in designs with a brushed finish.

Because the density is so similar to gold (tungsten is only 0.36% less dense), tungsten can also be used in counterfeiting of gold bars, such as by plating a tungsten bar with gold,[54][55][56] which has been observed since the 1980s,[57] or taking an existing gold bar, drilling holes, and replacing the removed gold with tungsten rods.[58] The densities are not exactly the same, and other properties of gold and tungsten differ, but gold-plated tungsten will pass superficial tests.[54]

Gold-plated tungsten is available commercially from China (the main source of tungsten), both in jewelry and as bars.[59]

  Electronics

Because it retains its strength at high temperatures and has a high melting point, elemental tungsten is used in many high-temperature applications,[60] such as light bulb, cathode-ray tube, and vacuum tube filaments, heating elements, and rocket engine nozzles.[6] Its high melting point also makes tungsten suitable for aerospace and high-temperature uses such as electrical, heating, and welding applications, notably in the gas tungsten arc welding process (also called tungsten inert gas (TIG) welding).

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 molybdenum) on silicon.[40]

The electronic structure of tungsten makes it one of the main sources for X-ray targets,[61][62] 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 bullets, shot, and radiation shields. Since this element's thermal expansion is similar to borosilicate glass, it is used for making glass-to-metal seals.[14]

  Precautions

Because tungsten is rare and its compounds are generally inert, the effects of tungsten on the environment are limited.[63] The median lethal dose LD50 depends strongly on the animal and the method of administration and varies between 59 mg/kg (intravenous, rabbit)[64][65] and 5000 mg/kg (tungsten metal powder, intraperitoneal, rats).[66][67]

  Patent claim

Tungsten is unique amongst the elements in that it has been the subject of legal proceedings. In 1928, a US court rejected General Electric's attempt to patent it, overturning U.S. Patent 1,082,933 granted in 1913 to William D. Coolidge.[68][69]

  See also

  References

  1. ^ "Why does Tungsten not 'Kick' up an electron from the s sublevel ?". http://www.madsci.org/posts/archives/2000-02/951518136.Ch.r.html. Retrieved 2008-06-15. 
  2. ^ Magnetic susceptibility of the elements and inorganic compounds, in Handbook of Chemistry and Physics 81st edition, CRC press.
  3. ^ "Tungsten". Oxford English Dictionary. Oxford University Press. 3rd ed. 2001.
  4. ^ a b c d Daintith, John (2005). Facts on File Dictionary of Chemistry (4th ed.). New York: Checkmark Books. ISBN 0-8160-5649-8. 
  5. ^ Lassner, Erik; Schubert, Wolf-Dieter (1999). "low temperature brittleness". Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds. Springer. p. 256. ISBN 978-0-306-45053-2. http://books.google.com/?id=foLRISkt9gcC&pg=PA20. 
  6. ^ a b c d e Stwertka, Albert (2002). A Guide to the elements (2nd ed.). New York: Oxford University Press. ISBN 0-19-515026-0. 
  7. ^ McMaster, J. and Enemark, John H (1998). "The active sites of molybdenum- and tungsten-containing enzymes". Current Opinion in Chemical Biology 2 (2): 201–207. DOI:10.1016/S1367-5931(98)80061-6. PMID 9667924. 
  8. ^ Hille, Russ (2002). "Molybdenum and tungsten in biology". Trends in Biochemical Sciences 27 (7): 360–367. DOI:10.1016/S0968-0004(02)02107-2. PMID 12114025. 
  9. ^ a b Saunders, Nigel (2004). Tungsten and the Elements of Groups 3 to 7 (The Periodic Table). Chicago, Illinois: Heinemann Library. ISBN 1-4034-3518-9. 
  10. ^ "ITIA Newsletter" (PDF). International Tungsten Industry Association. June 2005. http://web.archive.org/web/20110721214335/http://www.itia.info/FileLib/Newsletter_2005_06.pdf. Retrieved 2008-06-18. 
  11. ^ "ITIA Newsletter" (PDF). International Tungsten Industry Association. December 2005. http://web.archive.org/web/20110721214335/http://www.itia.info/FileLib/Newsletter_2005_12.pdf. Retrieved 2008-06-18. 
  12. ^ Stevens, Donald G. (1999). "World War II Economic Warfare: The United States, Britain, and Portuguese Wolfram". The Historian (Questia). http://www.questia.com/googleScholar.qst;jsessionid=LY1PyzmCc1D256Gvh5wpbhxKyTyvcm2FHpMwpcs2wW2XyytCh4pW!956463030?docId=5001286099. 
  13. ^ van der Krogt, Peter. "Wolframium Wolfram Tungsten". Elementymology & Elements Multidict. http://elements.vanderkrogt.net/element.php?sym=W. Retrieved 2010-03-11. 
  14. ^ a b c C. R. Hammond (2004). The Elements, in Handbook of Chemistry and Physics 81st edition. CRC press. ISBN 0-8493-0485-7. 
  15. ^ Erik Lassner, Wolf-Dieter Schubert (1999). Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds. Springer. p. 9. ISBN 0-306-45053-4. http://books.google.com/?id=foLRISkt9gcC&pg=PA9. 
  16. ^ Heather Bean Material Properties and Analysis Techniques for Tungsten Thin Films. October 19, 1998
  17. ^ Lita, A. E.; Rosenberg, D.; Nam, S.; Miller, A.; Balzar, D.; Kaatz, L. M.; Schwall, R. E. "Tuning of Tungsten Thin Film Superconducting Transition Temperature for Fabrication of Photon Number Resolving Detectors". IEEE Transactions on Applied Superconductivity 15 (2): 3528–3531. DOI:10.1109/TASC.2005.849033. http://mysite.du.edu/~balzar/IEEE-Adriana%20-2005.pdf. 
  18. ^ Johnson, R. T.; O. E. Vilches, J. C. Wheatley, Suso Gygax (1966). "Superconductivity of Tungsten". Physical Review Letters 16 (3): 101–104. Bibcode 1966PhRvL..16..101J. DOI:10.1103/PhysRevLett.16.101. 
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