Tungsten [vÉlfram] is a chemical element with the element symbol W and atomic number 74. It is one of the transition metals, in the periodic table it is in the 6. Subgroup (group 6) Chrome or group. Tungsten is a brittle white shiny heavy metal in the pure state of high density. It possesses all pure metals the highest melting point and the second highest boiling point. His best-known use is therefore the filament in light bulbs.
Already in 16. Century described the Freiberger mineralogist Georgius Agricola, the occurrence of a mineral in Saxon tin ore, which the tin production by slagging the tin sometimes considerably more difficult. The part of the name "Wolf" comes from this property, since the tin ore, the mineral as a wolf "ate". Whether it is acting to wolframite, is still controversial, as he spoke of the "lightness" of the mineral. He called the Mineral wolves foam, which translated from Latin means "wolf(s)-Foam does ". Later it was called tungsten, by mhd. ram "Soot, Dirt ", because the gray-black mineral can easily grind and then reminded of soot. Its chemical symbol W is from tungsten.
That, in English, Italian and French common word Tungsten derived from Tung Sten (Swedish word for "heavy stone") from. This was in Sweden at that time not even tungsten (Swedish Volfram), but calcium tungstate denotes. Recognized in this 1781 the German-Swedish chemist Carl Wilhelm Scheele, a hitherto unknown salt. Pure tungsten was first 1783 by the Spanish brothers Juan JosĂ© Elhuyar Faustound (who worked under the direction Scheele) by reduction of tungsten trioxide, which is obtained from wolframite, produced.
The tungsten content in the earth's crust is about 0,0001 g / t or 0,0064 Weight percent (Clarke-Wert). The metal has not been dignified in nature (in pure form) proved to be. Published the "Doklady Akademii Nauk" in Russia 1995 a report on solid tungsten, without this mineral by the IMA belonging "Commission on new, Nomenclature and Classificationâ (CNMNC) was tested. There are some minerals, especially oxides and tungstates known. The most important tungsten ores are Wolframite (Mn, Faith)WHERE4 and scheelite CaWO4. There are other tungsten minerals, as Stolzit PbWO4 und Tuneptit WO3 Â· H2The.
The largest deposits are found in China, Peru, USA, Korea, Bolivia, Kazakhstan, Russia, Austria and Portugal. Even in the Ore finds tungsten ores. Proved and probable reserves currently amount to the world 2,9 My. Tons of pure tungsten.
The largest known deposits of tungsten in Europe is located in Felbertal in the Hohe Tauern (Province of Salzburg in Austria).
2006 was the world's production of pure tungsten 73.300 Tons. By far the largest producer of tungsten, China. More than 80 % of tungsten produced in the world is made there. The states with the biggest promotion of tungsten (2006):
|Rank||Land||Flow(in tonnes per year )|
Promotion in Austria
In Austria, the scheelite tungsten ore was first already 1815/16 on the gold deposit in the municipality Schellgaden Muhr (Province of Salzburg) discovered. As a result, many were found in crevices of the beautiful Hohe Tauern, sometimes several centimeters in size Scheelitkristalle. These findings were all of no practical benefit. The large deposit in Felbertal remained initially undetected.
1950 was known, that in the already since 1927 already exploited in the magnesite Wanglalm at Lanersbach / Tux (Tyrol) in the Zillertal scheelite occurred in larger amounts. These were tough to, intergrown with magnesite and quartz scheelite. In the following years, each about 10.000 Tonnes of ore with an average of tungsten oxide 1,8 % won, representing a globally unique high quality. Because of the low market price, the tungsten mining in the late 1960s set, but 1971 resumed until its closure of Magnesitbergbaues 1976 continued.
1967 eventually became the largest ever discovered in Europe Scheelitvorkommen Felbertal. Existing in streams ErzstĂŒcken was traced with the aid of UV light (Scheelite fluoresces). The difficult exploration work in the high alpine terrain (highest point on the reduction in Brent Ling 2100 m above sea level) started 1971, the first day of mine was in Felbertal 1976 recorded (from 1979 and underground mining, Surface Mining 1986 set). From the beginning 1993 to mid- 1995 Mining was suspended because of the low market price for tungsten.
Tungsten ore from the Felbertal is processed in the near Mittersill. From here, the scheelite arrived in St. Martin in Sulmtal (Styria). On the site of 1976 closed underground lignite mine of PĂ¶lfing Bergla was a tungsten-hut, since in the 1977 of tungsten oxide concentrates from several countries, Tungsten metal- and tungsten carbide are produced.
Processors are important German H.C. Starck and Longyear GmbH.
Extraction and representation
Tungsten can not be obtained by reduction with coal from the oxide ores, since this tungsten carbide produced.
By adding ammonia solution results in a complex called ammonium paratungstate (APW). This is filtered off and then at 600 Â° C transferred to relatively pure tungsten. By annealing tungsten is obtained(WE)-oxide (WHERE3), at the 800 Â° C is reduced under a hydrogen atmosphere to steel-gray tungsten:
This produces gray tungsten powder, this is usually compacted into molds and sintered electrically bars. At temperatures above 3400 Â° C, in special electric furnaces with reducing hydrogen atmosphere a compact tungsten metal are melted (Zone melting process).
Tungsten is a shiny white, expandable metal in its pure state high hardness, Density and strength. The density is almost as high as that of gold, the Brinell hardness is 250 HB, the tensile strength 550-620 N/mm2 (soft) to 1920 N/mm2 (hart). The metal exists in a stable body-centered cubic Î±-modification with a lattice spacing (= Lattice constant) of 316 pm bei Raumtemperatur. This crystal structure type is often called tungsten-type. Than at a ÎČ-Modifikation metastabile of tungsten (distorted body-centered cubic) it is substance called contrast to the tungsten-rich oxide W3The.
Tungsten has after the element with carbon 3422 Â° C, the second highest melting point of all chemical elements. The boiling point of 5555 Â° C with only by the rare metal rhenium 5596 Â° C to 41 K surpassed.
The metal is a superconductor with a transition temperature of 15 mK.
Tungsten is a very chemically resistant metal, the self-hydrofluoric acid and aqua regia (at least at room temperature) is hardly affected. It dissolves but in mixtures of river- undSalpetersĂ€ure and molten mixtures of alkali nitrates and carbonates on.
Are of tungsten 33 Isotope and 5 Kernisomere known. Get away in nature 5 Isotope vor 180In, 182In, 183In, 184W and 186In. The tungsten isotope 184W in this case has the highest frequency at. All 5 natural isotopes have long been considered to be stable. Only 2004 managed the CRESST experiment at Gran Sasso Laboratori nazionali as a side result of the search for dark matter detection, that the isotope 180W If the alpha decay under. The half-life is extremely long 1,8 Trillions of years, Therefore, this decay is not detectable in normal laboratory environment. The natural radioactivity of this isotope is so small, that they can be ignored for all practical purposes. The artificial radioactive isotopes of tungsten, however, have short half-lives between 0,9 ms 185W and 121,2 Days at 181In.
The most important use of tungsten is due to its high melting point in the lighting industry as the filament in light bulbs and as an electrode in gas discharge lamps and electron tubes.
In light bulbs makes you look this advantage, that the electrical conductivity of tungsten is significantly lower than those of the metals copper and aluminum cable. This heats up the thin filament of tungsten, until it glows, while the thicker line leads from the metals are barely warm.
It has its second major importance as an alloying metal in ferrous metallurgy. It forms in tool steels, tungsten carbides, which increase the secondary hardness.
Due to its high density it is for balance weights and for use of radiation shielding. Though its density and thus the shielding effect is significantly higher than that of lead, it is rarely used as a lead for this purpose, as it is to process more costly and less. Is also due to the high density of this material in some armies armor piercing projectile with a core made of tungsten instead of the cheaper, but radioactive and toxic depleted uranium used. In World War II was important for the construction of the tungsten German tank shell 40, which had a tungsten core. In the future, be used with tungsten core ammunition from the new Puma armored protect, which will replace the Marder.
Because of its high corrosion resistance of tungsten can be used in chemical plants as material for equipment. However, this application form due to the poor machinability of tungsten (Tungsten can only by means of laser- or electron beam welded to) rarely used. The same is true for a possible application in medical.
In physiology, particularly in neurophysiology, be made of tungsten microelectrodes used for extracellular recordings.
Furthermore, electrodes made of tungsten for welding processes. E.g.. in resistance welding, especially when materials such as copper, Bronze or brass are to be welded. Even the universal TIG (Tungsten-inert-gas) Welding is an electrode made of tungsten or an alloy thereof. These electrodes are not there melted in the welding process. The arc is burning as a plasma in an inert gas between the electrode and the component. The filler material is fed in the form of bars separately.
In sports comes to producing high quality tungsten barrels for the game of darts used, in archery are tips for special arrows made therefrom, and the hammer throw hammer heads were at times to reduce the air resistance and the rotation radius is also made of tungsten. In addition, tungsten plates as additional weights in the formula 1 used, around the required minimum weight of Formula 1 car (including. Beer, Brake- and cooling liquid, and driver in racing overalls and helmet) of 620 kg (Stand: 2010) to achieve. Even in sailing, it is for some time in the great racer keel bombs used. Here, the water resistance due to the greater density compared to conventional materials such as lead or cast iron greatly reduced. Likewise, there are already racket in tennis, were incorporated into the carbon frame braided tungsten fibers. Thus, all targeted at specific areas of the racket frame is additionally stabilized by the game to increase precision.
When fly fishing nymphs and streamers are (under water baits fished) with pierced and weighed down on the hook shank pushed tungsten beads, so they plunge faster and deeper.
Strings for musical instruments are partly wrapped with tungsten, to increase their weight and thereby reduce the pitch.
Tungsten is also in diagnostic radiology as a target material in the anode using. There are - and -Lines of characteristic X-rays to be 59 keV and. 67 keV.
In scanning tunneling microscopy, tungsten is often used as material for the probe tip.
Since the beginning of the 21. Century is tungsten carbide, incorrectly referred to as tungsten, also jewelry (Tungsten Jewelry), of. B. Rings processed. This is very easily detected by the hardness and density. WC has MohshĂ€rte9, 5, Tungsten only 7,5. So far, all produced on the market jewelery parts of tungsten carbide.
Tungsten is a positive bioelement of anaerobic bacteria of the type Eubacterium acidaminophilum used and installed as a cofactor in some enzymes. It. acidaminophilum is an amino acid bacteria fermented, tungsten which uses in the enzymes formate dehydrogenase and aldehyde dehydrogenase. In these organisms replaces tungsten, molybdenum, because in their natural environment (Vulkanschlote am Meeresboden) much more common.
According to current knowledge tungsten and its compounds are considered to be non-toxic. Lung diseases in workers in hard metal manufacturing or processing operations due to the also anwesendeCobalt.
In an animal model was established, that the greatest amount of orally absorbed tungsten compounds excreted quickly in the urine. A small portion of the tungsten is in the blood plasma and thence into erythrocytes. It is then deposited in the kidneys and the skeletal system. Three months after administration, the largest proportion of the total found only in very small amount of tungsten in the recorded body bone.
2003 were in Fallon / Nevada 16 since 1997 leukemia and children in Sierra Vista / Arizona with nine children also suffering from blood cancer two so-called cancer cluster - which is a local area with a higher than average rate of cancer - identified. In both places the water has to unusually high concentrations of tungsten. In the urine of the population were significantly elevated tungsten concentrations detected. Both places are known for their occurrence of tungsten ores. In the subsequent, about the year-long investigation of the Centers for Disease Control (CDC) However, no direct link between tungsten and leukemia are found. Wolfram show carcinogenic effects in any test method, Nevada and other locations with similar high levels of tungsten in the urine of the population had no detectable cancer cluster.
As a powder or dust is highly flammable, in a compact form of non-combustible.
Tungsten forms several oxides. Between the initial term:
- Tungsten(WE)-oxide WO3 - Lemon yellow
and the end member:
- Tungsten(IV)-oxide WO2 â braun
There are still following intermediate oxides:
- In10The29 blue violet, WHERE homogeneity region2,92-WHERE2,88
- In4The11 rotviolett, WHERE homogeneity region2,76-WHERE2,73
- In18The49, WHERE2,72
- In20The50, WHERE2,50
- That Natriumwolframat2WHERE4
- Zirkoniumwolframat were also asked2The8 shows an anomaly when heated.
- Tungsten bronzes MxWHERE3; M = Alkali, Erdalkalimetall,Lanthanoid, as. 0.3 < x < 0.9 colored possess electrical conductivity and are intense and varied depending on the metal content.
- Calciumwolframat CaWO4 is known as a mineral under the name of scheelite.
- WC tungsten carbide is an extremely hard metal-like compound. There are also ditungsten W2C.
- Wolframhexafluorid WF6
- Lead tungstate PbWO4
- Wolframdisulfid WS2 Use as a dry lubricant (Similar to MoS2)
Use of the compounds
Tungsten carbide is used as a neutron reflector in nuclear weapons, reduce the critical mass. Tungsten Carbide (Carbide) be used due to their high hardness in materials processing.
Tungstates are used for the impregnation of fabrics, to make them flame retardant.
Tungsten-containing colors in painting and ceramics in the- Porcelain and industrial uses.
Lead tungstate scintillator is used as a modern particle physics.
|Name, Symbol,Atomic number||Tungsten, In, 74|
|group, Period, Block||6, 6, d|
|Appearance||grayish white, shiny|
|Mass fraction of derErdhĂŒlle||64 ppm|
|Atomic mass||183,84 you|
|Atomradius (calculated)||135 (193) pm|
|Kovalenter Radius||162 pm|
|Electron configuration||[Car] 4f145d46s2|
|1. Ionization||770 kJ / mol|
|2. Ionization||1700 kJ / mol|
|Crystal structure||body centered cubic|
|Density||19,3 g/cm3 (20 Â° C)|
|Magnetism||paramagnetisch ( = 7,8 Â· 10â5)|
|Melting point||3695 K (3422 Â° C)|
|Boiling point||5828 K (5555 Â° C)|
|Molar Volume||9,47 Â· 10â6 m3/mol|
|Heat of vaporization||824 kJ / mol|
|SchmelzwĂ€rme||35,4 kJ / mol|
|Speed ââof sound||5174 m/s|
|Specific heat capacity||138 J/(kg Â· K)|
|Electrical conductivity||18,52 Â· 106 A/(In Â· m)|
|Thermal conductivity||170 W /(m Â· K)|
|Oxidation states||6, 5, 4, 3, 2|
|Normalpotential||-0.119 V (WHERE2 + 4H+ + 4andâ
â W + 2H2The)
GefahrH- and P-SĂ€tzeH: 228EUH: no EUH setsP: 210-240 - 241 - 280 to 370 378 for materials
PulverR- and S-SĂ€tzeR: 11S: 43