7440-33-7 Usage
Uses
Used in Ferrous and Nonferrous Alloys:
Tungsten is used to increase the hardness, toughness, elasticity, and tensile strength of steel. It is also used in the manufacturing of heavy metal alloys with nickel, copper, and iron, which can be made machineable and moderately ductile for applications as high-density materials.
Used in Filaments for Incandescent Lamps and Electron Tubes:
Tungsten is used in the filaments of common light bulbs, as well as in TV tubes, cathode ray tubes, and computer monitors. Its ability to be "pulled" into thin wire makes it useful in the electronics industry.
Used in Heating Elements and Welding Electrodes:
Tungsten's ability to withstand high temperatures makes it ideal for rocket engines and electric-heater filaments of all kinds. It is also used as electrodes in arc welding.
Used in Abrasives and Tools:
Tungsten carbide is used as a substitute for diamonds for drills and grinding equipment. This attribute is important in the manufacture of exceptionally hard, high-speed cutting tools.
Used in Textiles and Ceramics:
Tungsten is used in the manufacture of textiles and ceramics due to its high melting temperature and resistance to corrosion.
Used in Solar Energy Products and X-ray Equipment:
Tungsten is used in solar energy products and X-ray equipment due to its ability to glow white hot when heated without melting.
Used as a Catalyst in Chemical Reactions:
Tungsten is used as a catalyst in chemical reactions, with tungsten carbides (W2C, WC) used in rock drills, metal-cutting tools, wire-drawing dies, and as a catalyst instead of platinum.
Used in Aerospace Components:
Tungsten's alloys with molybdenum are used in aerospace components.
Used in Electric Lamp Filaments, Glass-to-Metal Seals, and Solar Energy Devices:
Unalloyed tungsten has several major applications, including electric lamp filaments for light bulbs, electrodes in arc welding, heating elements for high-temperature furnaces, electron and television tubes, glass-to-metal seals, and solar energy devices.
Used in Automotive, Telegraph, Radio, and Television Apparatus:
Tungsten is used in contact points for automotive, telegraph, radio, and television apparatus.
Used in Phonograph Needles:
Tungsten is used in phonograph needles due to its hardness and durability.
Used as a Lead Substitute in Ammunition and Sporting Goods:
A recent use for tungsten is as a lead substitute during the manufacturing of ammunition and sporting good products.
Used in the Production of Wedding Bands:
Another recent commercial use for tungsten is in the production of wedding bands.
History and Occurrence
The discovery of tungsten occurred in the 1780’s. Peter Woulfe, in 1779, while examining the mineral now known as wolframite, established that it contained a new substance. Around the same time, Swedish chemist Carl Wilhelm Scheele was investigating another mineral, scheelite. This mineral was known at that time as tungsen, which in Swedish meant heavy stone. Scheele, in 1781, determined that tungsen contained lime and a new acid similar to molybdic acid. This new acid was tungstic acid. Scheele and Bergman predicted that reduction of this acid could produce a new metal. Two years later in 1783, J. J. de Elhuyar and his brother F. deElhuyar of Spain first prepared metallic tungsten from wolframite. They derived an acid from wolframite which was similar to acid obtained by Scheele from tungsten (scheelite), and succeeded in producing a new metal by reduction of this acid with charcoal. Also, they determined that the mineral wolframite contained iron and manganese. The metal took over the old name of its mineral tungsten. Also the metal is known as wolfram, derived from the name of its other mineral, wolframite. The word wolfram originated from the wolf-like nature of the mineral that it devoured tin during the tin smelting operation causing low recoveries. The element was given the symbol W for its old name wolfram.
Tungsten is widely distributed in nature, occurring in several minerals. It is found in scheelite, CaWO4; wolframite, (Fe,Mn)WO4; huebnerite, MnWO4; ferberite, FeWO4; tungstite, H2WO4; and cuprotungstite, CuWO4. Its abundance in the earth’s crust is estimated to be 1.25 mg/kg and average concentration in seawater is about 0.1 μg/L.
Production
Tungsten is recovered mostly from mineral scheelite and wolframite. The recovery process depends on the mineral, the cost, and the end use; i.e., the commercial products to be made. Typical industrial processes have been developed to convert tungsten ores to tungsten metal and alloy products, tungsten steel, non-ferrous alloys, cast and cemented tungsten carbides, and tungsten compounds. A few processes are mentioned briefly below.
The first step in recovery is opening the ore. If the ore is scheelite, CaWO4, it is digested with hydrochloric acid:
CaWO4 + 2HCl → H2WO4 + CaCl2
Tungstic acid, H2WO4 precipitates out. The precipitate is washed and dissolved in sodium or ammonium hydroxide solution during heating:
H2WO4 + 2NaOH → Na2WO4 + 2H2O
Sodium tungstate is crystallized, separated from any impurities in the solution, and digested again with hydrochloric acid to form tungstic acid in purified form. The pure acid is dried, ignited and reduced with carbon to form tungsten powder from which most non-ferrous alloys are made.
Reactions
Tungsten exhibits several oxidation states, +6 being most stable. Compounds of lower oxidation states show alkaline properties. They also are less stable than those produced in higher oxidation states. Tungsten exhibits remarkable stability to practically all substances at ambient temperature. The metal is not attacked by nonoxidizing mineral acid. Concentrated hydrochloric acid, dilute sulfric acid and hydrofluoric acid attack the metal very slightly even when heated to 100°C. Tungsten is stable to dilute or concentrated nitric acid under cold conditions. Cold acid passivates the surface forming a slight oxide film. Hot dilute nitric acid corrodes the metal, while hot concentrated acid slowly dissolves bulk metal but rapidly oxidizes metal in powder form. At room temperature, aqua regia oxidizes metal only on the surface forming tungsten trioxide. A hydrofluoric-nitric acid mixture rapidly oxidizes tungsten to its trioxide. Chromic acid-sulfuric acid mixture does not react with tungsten metal in ductile form at ambient temperatures.
Isotopes
There are 36 isotopes of tungsten. Five are naturally stable and therefore contributeproportionally to tungsten’s existence on Earth, as follows: W-180 = 0.12%, W-182 = 26.50%, W-183 = 14.31%, W-184 = 30.64%, and W-186 = 28.43%. The other31 isotopes are man-made in nuclear reactors and particle accelerators and have halflivesranging from fractions of a second to many days.
Origin of Name
Tungsten was originally named “Wolfram” by German scientists, after
the mineral in which it was found, Wolframite—thus, its symbol “W.” Later, Swedish scientists
named it tung sten, which means “heavy stone,” but it retained its original symbol
of “W.”
Characteristics
Tungsten is considered part of the chromium triad of group six (VIB), which consists of24Cr, 42Mo, and 74W. These elements share many of the same physical and chemical attributes.Tungsten’s high melting point makes it unique insofar as it can be heated to the point thatit glows with a very bright white light without melting. This makes it ideal as a filamentfor incandescent electric light bulbs. Most metals melt long before they reach the point ofincandescence.Chemically, tungsten is rather inert, but it will form compounds with several other elementsat high temperatures (e.g., the halogens, carbon, boron, silicon, nitrogen, and oxygen).Tungsten will corrode in seawater.
History
In 1779 Peter Woulfe examined the mineral now
known as wolframite and concluded it must contain a new substance.
Scheele, in 1781, found that a new acid could be made
from tung sten (a name first applied about 1758 to a mineral
now known as scheelite). Scheele and Berman suggested the
possibility of obtaining a new metal by reducing this acid. The
de Elhuyar brothers found an acid in wolframite in 1783 that
was identical to the acid of tungsten (tungstic acid) of Scheele,
and in that year they succeeded in obtaining the element by
reduction of this acid with charcoal. Tungsten occurs in wolframite,
(Fe, Mn)WO4; scheelite, CaWO4; huebnerite, MnWO4;
and ferberite, FeWO4. Important deposits of tungsten occur in
California, Colorado, Bolivia, Russia, and Portugal. China is
reported to have about 75% of the world’s tungsten resources.
Natural tungsten contains five stable isotopes. Thirty-two
other unstable isotopes and isomers are recognized. The metal
is obtained commercially by reducing tungsten oxide with hydrogen
or carbon. Pure tungsten is a steel-gray to tin-white
metal. Very pure tungsten can be cut with a hacksaw, and can
be forged, spun, drawn, and extruded. The impure metal is
brittle and can be worked only with difficulty. Tungsten has the
highest melting point of all metals, and at temperatures over
1650°C has the highest tensile strength. The metal oxidizes
in air and must be protected at elevated temperatures. It has
excellent corrosion resistance and is attacked only slightly by
most mineral acids. The thermal expansion is about the same
as borosilicate glass, which makes the metal useful for glass-to-metal seals. Tungsten and its alloys are used extensively for
filaments for electric lamps, electron and television tubes, and
for metal evaporation work; for electrical contact points for
automobile distributors; X-ray targets; windings and heating
elements for electrical furnaces; and for numerous spacecraft
and high-temperature applications. High-speed tool steels,
Hastelloy?, Stellite?, and many other alloys contain tungsten.
Tungsten carbide is of great importance to the metal-working,
mining, and petroleum industries. Calcium and magnesium
tungstates are widely used in fluorescent lighting; other salts
of tungsten are used in the chemical and tanning industries.
Tungsten disulfide is a dry, high-temperature lubricant, stable
to 500°C. Tungsten bronzes and other tungsten compounds
are used in paints. Zirconium tungstate has found recent applications
(see under Zirconium). Tungsten powder (99.999%)
costs about $2900/kg.
Production Methods
Tungsten occurs principally in the minerals wolframite (Fe,Mn)WO4, scheelite (CaWO4), ferberite (FeWO4), and hubnerite (MnWO4). These ores are found in China, Russia, Canada, Austria, Africa, Bolivia, Columbia, and Portugal. Wolframite is the most important oreworldwide; scheelite is the principal domestic U.S. ore. Scheelite, when pure, contains 80.6% WO3, the most common impurity being MoO3. The percentages of FeO and MnO in wolframite vary considerably; hubnerite is the term applied to ore containing more than 20% MnO and ferberite and to ore containing more than 20% FeO. Intermediate samples are called wolframite.
Reactivity Profile
Tungsten is stable at room temperature. Very slowly attacked by nitric acid, sulfuric acid, and aqua regia. Dissolved by a mixture of hydrofluoric acid and nitric acid. No reaction with aqueous bases. Attacked rapidly by motlen alkaline melts such as Na2O2 or KNO3/NaOH. Vigorous reactions with bromine trifluoride and chlorine trifluoride. Becomes incandescent upon heating with lead oxide; becomes incandescent in cold fluorine and with iodine pentafluoride. Combustible in the form of finely divided powder and may ignite spontaneously.
Hazard
Tungsten dust, powder, and fine particles will explode, sometimes spontaneously, in air.The dust of many of tungsten’s compounds is toxic if inhaled or ingested.
Health Hazard
The soluble compounds of
tungsten are distinctly more toxic than the
insoluble forms.
Flammability and Explosibility
Flammable
Safety Profile
An inhalation hazard.
Mildly toxic by an unspecified route. An
experimental teratogen. Experimental
reproductive effects. A skin and eye irritant.
Flammable in the form of dust when
exposed to flame. The powdered metal may
ignite on contact with air or oxidants (e.g.,
bromine pentafluoride, bromine, chlorine
trifluoride, potassium perchlorate, potassium
dichromate, nitryl fluoride, fluorine, oxygen
difluoride, iodine pentafluoride, hydrogen
sulfide, sodlum peroxide, lead (IV)oxide).
See also TUNGSTEN COMPOUNDS and
POWDERED METALS.
Potential Exposure
Tungsten is used in ferrous and
nonferrous alloys, and for filaments in incandescent lamps.
It has been stated that the principal health hazards from
tungsten and its compounds arise from inhalation of aerosols
during mining and milling operations. The principal
compounds of tungsten to which workers are exposed are
ammonium paratungstate, oxides of tungsten (WO3, W2O5,
WO2); metallic tungsten; and tungsten carbide. In the production
and use of tungsten carbide tools for machining, exposure
to the cobalt used as a binder or cementing substance
may be the most important hazard to the health of the
employees. Since the cemented tungsten carbide industry
uses such other metals as tantalum, titanium, niobium, nickel,
chromium, and vanadium in the manufacturing process, the
occupational exposures are generally to mixed dust.
Carcinogenicity
Tungsten has been suspected to be involved in the occurrence of childhood leukemia, with the discovery of a cluster of diseases in Fallon, Nevada, associated with elevated levels of tungsten in urine and drinking water. The exact environmental source of exposure to tungsten was not clearly identi?ed and there is little evidence for an etiological role of tungsten in eliciting leukemia.
Environmental Fate
Tungsten in the environment largely exists as ions in
compounds and primarily insoluble solids. The potential for
particulate matter to spread is low as wet and dry deposition
removes it from the atmosphere. If released to air, most
tungsten compounds have low vapor pressures and are expected
to exist solely in the particulate phase in the ambient
atmosphere. Volatization is not expected to be an important
fate process.
Shipping
UN3089 Metal powders, flammable, n.o.s.,
Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN3189
Metal powder, self heating, n.o.s., Hazard Class: 4.2;
Labels: 4.2-Spontaneously combustible material.
Purification Methods
Clean the solid with conc NaOH solution, rub it with very fine emery paper until its surface is bright, wash it with previously boiled and cooled conductivity water and dry it with filter paper. [Hein & Herzog in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II p 1417 1965.]
Toxicity evaluation
Reported inhalation effects are probably due to cobalt in
exposures, a competitive inhibitor of molybdenum utilization.
Incompatibilities
Tungsten: The finely divided powder is
combustible and may ignite spontaneously in air.
Incompatible with bromine trifluoride; chlorine trifluoride;
fluorine, iodine pentafluoride.
Waste Disposal
Recovery of tungsten from
sintered metal carbides, scrap and spent catalysts has been
described as an alternative to disposal.
Check Digit Verification of cas no
The CAS Registry Mumber 7440-33-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 3 and 3 respectively.
Calculate Digit Verification of CAS Registry Number 7440-33:
(6*7)+(5*4)+(4*4)+(3*0)+(2*3)+(1*3)=87
87 % 10 = 7
So 7440-33-7 is a valid CAS Registry Number.
InChI:InChI=1/W
7440-33-7Relevant articles and documents
(W6I8)Cl4– A Basic Model Compound for Photophysically Active [(W6I8)L6]2–Clusters?
Str?bele, Markus,Enseling, David,Jüstel, Thomas,Meyer, H.-Jürgen
, p. 1435 - 1438 (2016)
The heteroleptic cluster compound (W6I8)Cl4was prepared by thermal conversion of the homoleptic clusters W6I12and W6Cl12at 700 °C to yield a bright yellow powder. The presence of the smaller chlorido ligands in apical positions of [(W6I8)Cl6]2–creates nearly spherically clusters showing thermal and chemical inertness. Photoluminescence studies revealed a strong red phosphorescence from excited spin-triplet states.
Reduction of WO3 to W-metal by mechanochemical reaction
Kano, Junya,Kobayashi, Eiko,Tongamp, William,Miyagi, Shoko,Saito, Fumio
, p. 666 - 669 (2009)
A new non-thermal route for reduction of tungsten oxide (WO3) to metallic tungsten (W) by a milling operation in ammonia (NH3) gas atmosphere in the presence of lithium nitride (Li3N) is proposed in this paper. A sample of
Reduction of tungsten oxides with carbon. Part 1: Thermal analyses
Venables, Dean S.,Brown, Michael E.
, p. 251 - 264 (1996)
The kinetics and mechanism of the reduction of WO3 with carbon (in the form of graphite and of lamp black) were studied using isothermal thermogravimetry of small sample masses (2 and the final product of the reduction was tungsten. The CO/CO2 ratio in the gaseous products had a considerable influence on the reactions occurring. The rate of the first stage of the reduction under isothermal conditions could be described by diffusion models, and is proposed to involve diffusion of CO(g) and CO2(g) through the pores of the reacting tungsten oxides. The activation energies of the graphite and lamp black systems differed significantly for this first stage of reduction (386 compared to 465 kJ mol-1). These activation energies are high for a diffusion process and may be inflated by changes in the structure of the product and the CO/CO2 equilibrium ratio as the temperature increases. The rate of the second stage of reaction can be described by a first-order rate equation, and it is proposed that the second stage of reaction is limited by the reaction of carbon with carbon dioxide, rather than by the reduction of a tungsten oxide. The measured activation energy of 438 kJ mol-1 is slightly higher than the reported values for the carbon-carbon dioxide reaction (up to 400 kJ mol-1).
On the formation of defects and morphology during chemical vapor deposition of tungsten
Wang,Cao,Wang,Zhang
, p. 2192 - 2198 (1994)
Face-to-face wafers were used to observe anomalous tungsten deposition in the gap-edge between wafers. In the WF6-H2 atmosphere, three regions are identified: (i) an open-deposition region (region A), (ii) a half-sealed deposition region (region B), and (iii) an etching or tunnel region (region C). In the WF6-Ar atmosphere, there are only two regions: (i) an open deposition region (region A'), and (ii) a half-sealed deposition region (region B'). The third region disappears because HF does not form in the absence of H2. Different chemical reactions are expected in different regions, dictated by the local gas composition. A half-sealed structure model proposed here is supported by thermodynamic calculations, and applied to explain encroachment, wormholes, and other well-known effects during the chemical vapor deposition of tungsten from tungsten hexafluoride.
Zirconium carbide-tungsten cermets prepared by in situ reaction sintering
Zhang,Hilmas,Fahrenholtz
, p. 1930 - 1933 (2007)
Zirconium carbide-tungsten (ZrC-W) cermets were prepared by a novel in situ reaction sintering process. Compacted stoichiometric zirconium oxide (ZrO2) and tungsten carbide (WC) powders were heated to 2100°C, which produced cermets with 35 vol% ZrC and 65 vol% W consisting of an interpenetrating-type microstructure with a relative density of ～95%. The cermets had an elastic modulus of 274 GPa, a fracture toughness of 8.3 MPa·m1/2, and a flexural strength of 402 MPa. The ZrC content could be increased by adding excess ZrC or ZrO2 and carbon to the precursors, which increased the density to >98%. The solid-state reaction between WC and ZrO2 and W-ZrC solid solution were also studied thermodynamically and experimentally.
Preparation of tungsten and tungsten carbide submicron powders in a chlorine-hydrogen flame by the chemical vapor phase reaction
Zhao, G. Y.,Revankar, V. V. S.,Hlavacek, V.
, p. 269 - 280 (1990)
A hydrogen-chlorine flame chemical vapor deposition reactor has been developed to synthesize ultrafine powders of refractory compounds (e.g. carbides and nitrides). At the laboratory scale, synthesis of tungsten and tungsten carbides (both (WC)1-x and α - W2C) gave encouraging results. The collected refractory powders do not have internal porosity, they exhibit spherical shape and have a very narrow size distribution. The size of the particles and the crystalline structure depends on the flame temperature, flow rate of the reactants and residence time of particles. In short, they depend on the flame characteristics. Thermochemical calculations were carried out to obtain the optimum conditions for different carbide powder synthesis. The flame is completely characterized and the temperature distribution within the reactor is obtained.
Structural evolution of W nano clusters with increasing cluster size
Oh,Huh,Kim,Park,Lee
, p. 7402 - 7404 (1999)
We have recorded.the x-ray diffraction (XRD) patterns of nanometer-size W metal clusters prepared at different average cluster sizes. Nanometer-size W metal clusters were produced through a collision induced clustering mechanism of W metal atoms generated by decomposing W(CO)6 vapors. The XRD patterns clearly showed that structure changed from amorphous→face-centered-cubic (fcc)→body-centered-cubic (bcc) with increasing average cluster size. This implies that W metal clusters do not simply approach the bulk bcc structure but pass through an intermediate fcc structure before they reach the bulk structure, as predicted by Tomanek, Mukherjee, and Bennemann [Phys. Rev. B 28, 665 (1983)].
Carbon nanotubes produced by tungsten-based catalyst using vapor phase deposition method
Lee, Cheol Jin,Lyu, Seung Chul,Kim, Hyoun-Woo,Park, Jong Wan,Jung, Hyun Min,Park, Jaiwook
, p. 469 - 472 (2002)
We have demonstrated that W-based catalysts can produce carbon nanotubes (CNTs) effectively. Well-aligned, high-purity CNTs were synthesized using the catalytic reaction of C2H2 and W(CO)6 mixtures. The CNTs had a multiwalled structure with a hollow inside. The graphite sheets of CNTs were highly crystalline but the outmost graphite sheets were defective.
Sc2O3-W matrix impregnated cathode with spherical grains
Wang, Jinshu,Li, Lili,Liu, Wei,Wang, Yanchun,Wang, Yiman,Zhou, Meiling
, p. 2103 - 2108 (2008)
Sc2O3-W matrix cathodes have been prepared by using a liquid-liquid doping method combined with high-temperature sintering. The microstructure and physical behavior of active substances of scandia-doped tungsten matrix and impregnated cathode has been studied by SEM and AES methods. The results show that the matrix has a homogeneous structure composed of W grains with spherical shape and superfine Sc2O3 particles dispersed uniformly over and among W grains. After impregnation, this Sc-type impregnated cathode has high emission capability. Space-charge-limited current density could reach 52 A/cm2 at 850 °Cb. The high emission results from a Ba-Sc-O active layer with a thickness of about 80 nm, which is formed at the cathode surface during the activation period. Both the decrease of the thickness of active surface layer and the decrease of the content of Sc at the surface could lead to the degradation of current density during operation.
Electrodeposition of tungsten from ZnCl2-NaCl-KCl-KF-WO3 melt and investigation on tungsten species in the melt
Nitta, Koji,Nohira, Toshiyuki,Hagiwara, Rika,Majima, Masatoshi,Inazawa, Shinji
, p. 1278 - 1281 (2010)
The electrodeposition of tungsten in ZnCl2-NaCl-KCl-KF-WO3 melt at 250 °C was further studied to obtain a thicker deposit. In the ordinary electrolysis at 0.08 V vs. Zn(II)/Zn, the current density decreased from 1.2 mA cm-2 to 0.3 mA cm-2 in 6 h. A thickness of the obtained tungsten layer was 2.1 μm and the estimated current efficiency was 93%. A supernatant salt and a bottom salt were sampled after 6 h from the melting and were analyzed by ICP-AES and XRD. It was found that the soluble tungsten species slowly changes to insoluble ones in the melt. The soluble species was suggested to be WO3F- anion. One of the insoluble species was confirmed to be ZnWO4 and the other one was suggested to be K2WO2F4. Electrodeposition was carried out under the same condition as above except for the intermittent addition of WO3 every 2 h. The current density was kept at the initial value and the thickness was 4.2 μm. The intermittent addition of WO3 was confirmed to be effective to obtain a thicker tungsten film.
