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7440-33-7

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7440-33-7 Usage

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.

Chemical Properties

Different sources of media describe the Chemical Properties of 7440-33-7 differently. You can refer to the following data:
1. Tungsten is a steel-gray to tin-white metal. It is a heavy metal. It is a very hard metal that is stable in dry air at ordinary temperatures. Although very difficult to work with, tungsten can be cut with a hacksaw, forged, or spun. Commercially, tungsten is obtained via the reduction of tungsten oxide with hydrogen or carbon. Due to its hardness, tungsten has the highest boiling point and highest tensile strength of all metals. Although the metal shows resistance to corrosion, it can oxidize in air with an increase in temperature (Robert and Golden, 1980; Gbaruko and Igwe, 2007). Tungsten is a very hard metal with similar properties and functions to molybdenum and chromium. Unlike molybdenum, tungsten is not an essential trace metal. However, tungsten is a competitive inhibitor of molybdenum in bacteria, plants, and animals (Hainline and Rajagopalan, 1983; Smith, 1991).
2. Tungsten is a hard, brittle, steel-gray to tinwhite metal or fine powder.

Uses

Different sources of media describe the Uses of 7440-33-7 differently. You can refer to the following data:
1. Industrially tungsten is a very important metal having wide applications. This is due to many outstanding physical properties. Among all the metals, tungsten has the highest melting point and the lowest vapor pressure. Also at high temperatures it has the highest tensile strength. The metal has an excellent resistance to corrosion and attack by mineral acids. Also it has a thermal expansion comparable to that of borosilicate glass. Tungsten is extensively used in alloy steel to impart high strength and hardness to steel. Heavy metal alloys with nickel, copper and iron, produced by powder metallurgy, can be made machineable and moderately ductile for applications as high-density materials. Tungsten carbides are extremely hard and are excellent cutting materials. They are used extensivly in the tool and die industry for drilling and cutting tools, sand blasting nozzels, armor-piercing bullets, and studs to increase traction of tires. Among the nonferrous tungsten alloys, its alloys with copper and silver are used as electrical contacts and switches and with molybdenum in aerospace components. Unalloyed tungsten has several major applications. An important use is in the electric lamp filaments for light bulbs. Also, it is used as electrodes in arcwelding, in heating elements for high-temperature furnaces, in electron and television tubes, in glass-tometal seals, and in solar energy devices.
2. Tungsten, also known as wolfram, occurs as wolframite (FeWO4). It can be found in the earth’s crust but not in its pure metal form. It combines with other chemicals and compounds within the rocky earth’s crust. It is a transitional hard metal with physicochemical properties and can also be manufactured commercially (Lassner and Schnubert, 1999; Gbaruko and Igwe, 2007; Stefaniak, 2010; Strigul et al., 2010). Tungsten is most commonly used to increase the hardness of steel. It is available commercially in the form of powder, single crystal, and ultrapure granule grades. It is also used in the manufacturing of alloys, light filaments, and X-ray tubes. A recent use for tungsten is as a lead substitute during the manufacturing of ammunition and sporting good products. Another recent commercial use for tungsten is in the production of wedding bands. It is also used as a catalyst in chemical reactions (Lassner and Schnubert, 1999; Gbaruko and Igwe, 2007; Stefaniak, 2010; Strigul et al., 2010). To increase hardness, toughness, elasticity, and tensile strength of steel; manufacture of alloys; manufacture of filaments for incandescent lamps and in electron tubes; in contact points for automotive, telegraph, radio and television apparatus; in phonograph needles. Tungsten carbides (W2C, WC) used in rock drills, metal-cutting tools, wire-drawing dies. WC used as catalyst instead of platinum: Bennett et al., Science 184, 563 (1974).
3. Since its melting temperature is over 3,400°C, tungsten is one of the few metals that canglow white hot when heated without melting. This factor makes it the second most frequentlyused industrial metal (the first is iron). Tungsten is used in the filaments of common lightbulbs, 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. It is also used in solarenergy products and X-ray equipment. Its ability to withstand high temperatures makes itideal for rocket engines and electric-heater filaments of all kinds. Tungsten carbide is used as asubstitute for diamonds for drills and grinding equipment. This attribute is important in themanufacture of exceptionally hard, high-speed cutting tools.
4. Ferrous and nonferrous alloys, filaments in incandescent lamps, heating elements, welding electrodes, manufacture of abrasives and tools, manufacture of textiles and ceramics.

Physical Properties

Grayish-white metal; body-centered cubic crystalline structure; density 19.3 g/cm3; melts at 3,422°C; vaporizes at 5,555°C; vapor pressure 1 torr at 3,990°C; electrical resistivity 5.5 microhm-cm at 20°C; modulus of elasticity about 50 to 57 × 106 psi (single crystal); Poisson’s ratio 0.17; magnetic susceptibilty +59 × 10–6; thermal neutron absorption cross section 19.2 + 1.0 barns (2,200m/sec); velocity of sound, about 13,000 ft/sec; insoluble in water; practically insoluble in most acids and alkalies; dissolves slowly in hot concentrated nitric acid; dissolves in saturated aqueous solution of sodium chlorate and basic solution of potassium ferricyanide; also solubilized by fusion with sodium hydroxide or sodium carbonate in the presence of potassium nitrate followed by treatment with water.

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.

Description

Tungsten was recognized as a distinct element in 1779 by Peter Woulfe, but not isolated until 1783, by Jose and Fausto d’Elhuyar. The average tungsten concentration in the earth’s crust is ~0.006%. Tungsten occurs naturally as tungstate, mainly in compounds such as wolframites and scheelites.

Physical properties

Extremely pure samples of tungsten are rather soft and can be cut easily with a simple saw.Pure tungsten can be drawn into fine wires (ductile). On the other hand, if there are even a fewimpurities in the sample, the metal becomes very hard and brittle. It is a very dense metal witha whitish-to-silvery-grayish color when freshly cut. It has the highest melting point of all metalsat 3,422°C, making it a useful metal where high temperatures are required. Incidentally,the transition metals on both sides of it in period 6 (73Ta and 75Re) have the second- and thirdhighestmelting points. Tungsten’s boiling point is also high at 5,927°C.

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.”

Occurrence

Tungsten is the 58th most abundant element found on Earth. It is never found in 100%pure form in nature. Its major ore is called wolframite or tungsten tetroxide, (Fe,Mn)WO4,which is a mixture of iron and manganese and tungsten oxide. During processing, the ore ispulverized and treated with strong alkalis resulting in tungsten trioxide (WO3), which is thenheated (reduced) with carbon to remove the oxygen. This results in a variety of bright colorchanges and ends up as a rather pure form of tungsten metal: 2WO3 + 3C → 2WO + 3CO2.Or, if hydrogen is used as the reducing agent, a more pure form of metal is produced: WO3+ 3H2 → W + 3H2O. Tungsten ores (oxides) are found in Russia, China, South America, Thailand, and Canada.In the United States, the ores are found in Texas, New Mexico, Colorado, California, Arizona,and Nebraska.

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.

Definition

Different sources of media describe the Definition of 7440-33-7 differently. You can refer to the following data:
1. A transition metal occurring naturally in wolframite ((Fe,Mn)WO4) and scheelite (CaWO4). It was formerly called wolfram. It is used as the filaments in electric lamps and in various alloys. Symbol: W; m.p. 3410 ± 20°C; b.p. 5650°C; r.d. 19.3 (20°C); p.n. 74; r.a.m. 183.84.
2. tungsten: Symbol W. A white orgrey metallic transition element(formerly called wolfram); a.n. 74;r.a.m. 183.85; r.d. 19.3; m.p. 3410°C;b.p. 5660°C. It is found in a numberof ores, including the oxides wolframite,(Fe,Mn)WO4, and scheelite,CaWO4. The ore is heated with concentratedsodium hydroxide solutionto form a soluble tungstate. Theoxide WO3 is precipitated from thisby adding acid, and is reduced to themetal using hydrogen. It is used invarious alloys, especially high-speedsteels (for cutting tools) and in lampfilaments. Tungsten forms a protectiveoxide in air and can be oxidizedat high temperature. It does not dissolvein dilute acids. It forms compoundsin which the oxidation stateranges from +2 to +6. The metal wasfirst isolated by Juan d’Elhuyer andFausto d’Elhuyer (1755–1833) in1783.

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

7440-33-7 Well-known Company Product Price

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7440-33-7SDS

SAFETY DATA SHEETS

According to Globally Harmonized System of Classification and Labelling of Chemicals (GHS) - Sixth revised edition

Version: 1.0

Creation Date: Aug 16, 2017

Revision Date: Aug 16, 2017

1.Identification

1.1 GHS Product identifier

Product name tungsten atom

1.2 Other means of identification

Product number -
Other names Tungsten ICPStd.

1.3 Recommended use of the chemical and restrictions on use

Identified uses For industry use only.
Uses advised against no data available

1.4 Supplier's details

1.5 Emergency phone number

Emergency phone number -
Service hours Monday to Friday, 9am-5pm (Standard time zone: UTC/GMT +8 hours).

More Details:7440-33-7 SDS

7440-33-7Synthetic route

sodium tungstate

sodium tungstate

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With hydrogen byproducts: NaOH, H2O; redn. at 1100°C;100%
With hydrogen byproducts: Na, O2; no reaction until 700°C, 900°C;100%
With hydrogen byproducts: Na, O2; no reaction until 700°C, 900°C;100%
5Na2O*12WO3*28H2O

5Na2O*12WO3*28H2O

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
in hydrogen stream at 900°C;100%
in hydrogen stream at 900°C;100%
tungsten(IV) sulfide

tungsten(IV) sulfide

A

sulfur
7704-34-9

sulfur

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
2000°C, fast react.;A n/a
B 100%
2000°C, fast react.;A n/a
B 100%
1200°C, 2 h;A n/a
B 60%
1200°C, 2 h;A n/a
B 60%
tungsten(VI) oxide

tungsten(VI) oxide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With magnesium In solid byproducts: MgO; (Ar) milled at room temp. and reaction times from few min up to several h; leached (HCl) under stirring; centrifuged; wached (HCl); wached several times (water); dried at 120°C (air);84%
With hydrogen fluoride In not given Electrolysis; in 4.6 n soln. at 95°C, 0.65-1A per cm2 on mercury cathode, with H2SO4 and HCl complete scale pptn.;20%
With hydrogen fine powder at 80 atm, 550-600°C;
tungsten(VI) chloride
13283-01-7

tungsten(VI) chloride

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With magnesium hydride In toluene byproducts: H2; (argon); refluxing WCl6 and MgH2 in toluene in a mill under continuous grinding (8.5 h); washing (toluene), trituration with EtOH, filtration, boiling with concd. HCl, filtration, washing (H2O; EtOH), drying;82.9%
on annealing single crystal tungsten wire covered with Mo single crystal layer;
pptn. on glowing tungsten wire in vac. at 1600-1700 °C;
tungsten dichloride

tungsten dichloride

magnesium
7439-95-4

magnesium

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
redn. at beginning red heat, leaching with water;61.03%
redn. at beginning red heat, leaching with water;61.03%
incomplete reaction at red head;;
incomplete reaction at red head;;
W6I12

W6I12

W6(12+)*12Cl(1-)=W6Cl12

W6(12+)*12Cl(1-)=W6Cl12

A

4Cl(1-)*W6I8(4+)

4Cl(1-)*W6I8(4+)

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
at 600℃; for 12h; Milling; Sealed tube;A 60%
B n/a
tungsten hexacarbonyl
14040-11-0

tungsten hexacarbonyl

1-[{[Bis-(2-diethylphosphanyl-ethyl)-phosphanyl]-methyl}-(2-diethylphosphanyl-ethyl)-phosphanyl]-2-diethylphosphanyl-ethane
99035-49-1

1-[{[Bis-(2-diethylphosphanyl-ethyl)-phosphanyl]-methyl}-(2-diethylphosphanyl-ethyl)-phosphanyl]-2-diethylphosphanyl-ethane

W2(CO)7(C19H43P5)
120120-97-0

W2(CO)7(C19H43P5)

fac,fac-(tungsten)2(carbonyl)6(eHTP)
114221-42-0

fac,fac-(tungsten)2(carbonyl)6(eHTP)

C

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In xylene N2- or Ar atmosphere; addn. of W(CO)6 and org. compd. to xylol, refluxing (5 d); cooling, evapn. (vac.), filtn., dissoln. CH2Cl2, filtn., recrystn. (CH2Cl2/toluene);A 40%
B n/a
C n/a
tungsten diselenide

tungsten diselenide

A

selenium
7782-49-2

selenium

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In neat (no solvent, solid phase) heating of WSe2 single crystal flakes enclosed in envelopes made by thin Ta plates by passing current;A 30%
B n/a
In neat (no solvent, solid phase) heating single crystal flakes of WSe2 by current in high vac.;
tungsten hexacarbonyl
14040-11-0

tungsten hexacarbonyl

Hexamethylbenzene
87-85-4

Hexamethylbenzene

A

W(CO)3(η6-Me6C6)
33505-53-2

W(CO)3(η6-Me6C6)

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In decane under Ar, educts added to n-decane, slowly heated to reflux, refluxed for 20 h with periodical shaking, cooled; filtered through SiO2 with CH2Cl2, evapd. in vac., crystals filtered, washed with pentane, dried in vac.;A 28%
B n/a
iron silicon

iron silicon

tungsten(VI) oxide

tungsten(VI) oxide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With calcium carbide byproducts: CaO, CO; Electric Arc; redn. with carbide ferrosilicium mixt. in elec. oven or arc at 2800-2900°C; carbon free tungsten;
With calcium carbide In melt
In melt in elec. oven;
iron silicon

iron silicon

wolframite MnWO4

wolframite MnWO4

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With calcium carbide In melt
In melt in elec. oven;
sodium tungstate

sodium tungstate

disodium telluride

disodium telluride

A

tellurium

tellurium

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With hydrogenchloride In water adding HCl, pptn.;
With HCl In water adding HCl, pptn.;
boron trioxide

boron trioxide

tungsten(VI) oxide

tungsten(VI) oxide

A

tungsten boride

tungsten boride

B

tungsten monoboride

tungsten monoboride

C

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In further solvent(s) Electrolysis; melt composition: NaCl (39.5 wt-%), Na3AlF6 (39.5 wt-%), WO3 (1.0 wt-%),B2O3 (20.0 wt-%), 950°C, graphite crucible (container and anode) , W- or Ni-bars as cathode, U=4.0 V, t=20 min; products sepn. by hot water and 10% H2SO4 at 50-70°C; powder XRD;
boron trioxide

boron trioxide

tungsten(VI) oxide

tungsten(VI) oxide

A

tungsten monoboride

tungsten monoboride

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In further solvent(s) Electrolysis; melt composition: NaCl (39.5 wt-%), Na3AlF6 (39.5 wt-%), WO3 (1.0 wt-%),B2O3 (20.0 wt-%), 950°C, graphite crucible (container and anode) , W- or Ni-bars as cathode, U=4.0 V, t=10 min; products sepn. by hot water and 10% H2SO4 at 50-70°C; powder XRD;
boron trioxide

boron trioxide

tungsten(VI) oxide

tungsten(VI) oxide

A

tungsten boride

tungsten boride

B

tungsten tetraboride

tungsten tetraboride

C

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In further solvent(s) Electrolysis; melt composition: NaCl (39.5 wt-%), Na3AlF6 (39.5 wt-%), WO3 (1.0 wt-%),B2O3 (20.0 wt-%), 950°C, graphite crucible (container and anode) , W- or Ni-bars as cathode, U=4.0 V, t=30 min; products sepn. by hot water and 10% H2SO4 at 50-70°C; powder XRD;
boron trioxide

boron trioxide

tungsten(VI) oxide

tungsten(VI) oxide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In further solvent(s) Electrolysis; melt composition: NaCl (39.5 wt-%), Na3AlF6 (39.5 wt-%), WO3 (1.0 wt-%),B2O3 (20.0 wt-%), 950°C, graphite crucible (container and anode) , W- or Ni-bars as cathode, U=4.0 V, t=5 min;
sodium azide

sodium azide

tungsten(VI) chloride
13283-01-7

tungsten(VI) chloride

A

tungsten nitride

tungsten nitride

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
byproducts: N2, NaCl; vac., heating in ampoule (300-400°C); cooling, washing (MeOH), drying (vac.), powder XRD, FT IR;
potassium tungstate

potassium tungstate

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In melt Electrolysis; neutral or light alk. raw material, 900-1000°C, 60-80% yield of current, light pptn. of tungsten powder or single crystal; 99.3% tungsten content, impurities: SiO2 and alk.;
With hydrogen0%
In melt Electrochem. Process; electrodeposition (LiF-KF eutectic melt, 973 K); scanning electron microscopy, electron probe anal.;
potassium tungstate

potassium tungstate

sodium tungstate

sodium tungstate

lithium tungstate

lithium tungstate

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In melt Electrolysis; neutral or light alk. raw material, 900-1000°C, 60-80% yield of current, light pptn. of tungsten powder or single crystal; 99.3% tungsten content, impurities: SiO2 and alk.;
In melt Electrolysis; m. 500°C, 6 A per cm2; product mixt. of α and β modifikation;
ammonium iodide

ammonium iodide

tungsten hexaiodide
33963-20-1

tungsten hexaiodide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In further solvent(s) Electrolysis; in furfural soln.;0%
tungsten monocarbide

tungsten monocarbide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
repeated thermic and mech. treatments; carbon free product;
heating;
repeated thermic and mech. treatments; carbon free product;
heating;
manganese oxide

manganese oxide

tungsten(VI) oxide

tungsten(VI) oxide

aluminium
7429-90-5

aluminium

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With manganese(IV) oxide violent aluminothermic react.; very pure product by dissolving other metals from tungsten manganese alloy;
thorium(IV) nitrate

thorium(IV) nitrate

ceric nitrate

ceric nitrate

tungsten(VI) oxide

tungsten(VI) oxide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
With hydrogen mixing of WO3 with soln. of additives, drying paste and redn. at 1000°C;
sodium tungstate

sodium tungstate

A

sodium polytungstate

sodium polytungstate

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In melt Electrolysis; electrolysis in NaCl electrolyte under Ar, cathode current density of 0.2 A/cm**2, anode current density of 0.04 A/cm**2, at 850-950°C; emf: 1.2-1.8 V;
sodium tungstate

sodium tungstate

lithium tungstate

lithium tungstate

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In neat (no solvent) Electrolysis; 1123 - 1173 K, U = 1.9 V;
sodium tungstate

sodium tungstate

lithium tungstate

lithium tungstate

tungsten(VI) oxide

tungsten(VI) oxide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In melt Electrolysis; on tungsten single crystal cathode at 900°C, 6 or 8 angular single crystal formation;
sodium tungstate

sodium tungstate

lithium tungstate

lithium tungstate

lithium carbonate
554-13-2

lithium carbonate

A

tungsten carbide

tungsten carbide

B

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In neat (no solvent) Electrolysis; 1 mol % of carbonate, 1123 - 1173 K, U = 1.9 V;
sodium tungstate

sodium tungstate

tungsten(VI) oxide

tungsten(VI) oxide

tungsten
7440-33-7

tungsten

Conditions
ConditionsYield
In melt Electrolysis; with lower current density, with higher current density bronze formation;
lanthanum(III) oxide

lanthanum(III) oxide

tungsten(VI) oxide

tungsten(VI) oxide

cobalt
7440-48-4

cobalt

sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

La3CoS3(6+)*WO6(6-)=La3CoWS3O6

La3CoS3(6+)*WO6(6-)=La3CoWS3O6

Conditions
ConditionsYield
In melt stoich. amts. of La2O3, S, W, WO3, Co mixed with KCl flux; sealed in carbon coated SiO2 ampoule under vac.; heated from 200 to 400°C in 24 h; held for 48 h; heated to 950°C in 12 h; held for 120 h; cooled to room temp. within 24 h; soaked in H2O overnight; washed with H2O; detn. by EDX, XRD;100%
tungsten(VI) fluoride
7783-82-6

tungsten(VI) fluoride

sodium fluoride

sodium fluoride

tungsten
7440-33-7

tungsten

sodium hexafluorotungstate(V)
55822-76-9

sodium hexafluorotungstate(V)

Conditions
ConditionsYield
In neat (no solvent) in an inert atmosphere under N2; 850°C for 30 min; before use NaFdried at 300°C overnight (vac.), recrystd. from molten state;98%
sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

tungsten thiobromide complex

tungsten thiobromide complex

Conditions
ConditionsYield
With Br2 In neat (no solvent) heating in an evacuated sealed quartz ampoule at 300°C for 48 h, stirring thoroughly and heating for another 72 h; opening, washing of the solid with CHCl3 and hot benzene and drying (vac.); elem. anal.;97%
potassium fluoride

potassium fluoride

tungsten(VI) fluoride
7783-82-6

tungsten(VI) fluoride

tungsten
7440-33-7

tungsten

A

potassium octafluorotungstate(VI)

potassium octafluorotungstate(VI)

B

potassium hexafluorotungstate(V)
34629-85-1

potassium hexafluorotungstate(V)

Conditions
ConditionsYield
In neat (no solvent) in an inert atmosphere under N2; 850°C for 30 min; before use KF dried at 300°C overnight (vac.), recrystd. from molten state; K2WF8 identified by Raman spectrum;A n/a
B 97%
rubidium fluoride

rubidium fluoride

tungsten(VI) fluoride
7783-82-6

tungsten(VI) fluoride

tungsten
7440-33-7

tungsten

rubidium hexafluorotungstate(V)
53639-97-7

rubidium hexafluorotungstate(V)

Conditions
ConditionsYield
In neat (no solvent) in an inert atmosphere under N2; 800°C for 2 h; RbF before use dried in situ at 600°C for 5 h (vac.) before addition WF6;96%
chromium
7440-47-3

chromium

nickel
7440-02-0

nickel

aluminium
7429-90-5

aluminium

tungsten
7440-33-7

tungsten

A

Ni(77.1),Cr(2.0),Al(17.9),W(3.0) (A%)

Ni(77.1),Cr(2.0),Al(17.9),W(3.0) (A%)

B

Ni(79.8),Cr(5.8),Al(12.2),W(2.2) (A%)

Ni(79.8),Cr(5.8),Al(12.2),W(2.2) (A%)

Conditions
ConditionsYield
In melt Electric Arc; ingots by arc melting of Ni(75)-Cr(2.5)-Al(20)-W(2.5) (at%), several remelts, sealed in silica tube under vac. with partial pressure of Ar, 1573K (2 weeks), furnace cooled to 1523K, 4 weeks, 1273K (6 weeks), quenched in iced water; electron microscopy, electron probe microanalysis, x-ray diffraction;A 95%
B 5%
tungsten(VI) fluoride
7783-82-6

tungsten(VI) fluoride

cesium fluoride
13400-13-0

cesium fluoride

tungsten
7440-33-7

tungsten

cesium hexafluorotungstate(V)
19175-38-3

cesium hexafluorotungstate(V)

Conditions
ConditionsYield
In neat (no solvent) in an inert atmosphere under N2; 800°C for 2 h; CsF before use dried in situ at 600°C for 5 h (vac.) before addition WF6;94%
bis(cyclopentadienyl)tungsten dichloride

bis(cyclopentadienyl)tungsten dichloride

tungsten(VI) fluoride
7783-82-6

tungsten(VI) fluoride

tungsten
7440-33-7

tungsten

2{WCl2(C5H5)2}(1+)*{W4F18}(2-)={WCl2(C5H5)2}2{W4F18}

2{WCl2(C5H5)2}(1+)*{W4F18}(2-)={WCl2(C5H5)2}2{W4F18}

Conditions
ConditionsYield
In sulfur dioxide Sonication; condensing WF6 onto a frozen mixture (10ml) of W(C5H5)Cl2 and activated W in SO2 at -196°C; warming react. mixture to room temp., stirring, 30min in an ultrasonic bath; allowing to react, 12h;; filtration; removal of sulfur dioxide; elem. anal.; IR;;94%
tungsten
7440-33-7

tungsten

tungstic acid

tungstic acid

Conditions
ConditionsYield
With CH3OH; Br2 In methanol byproducts: CH3OBr, HCOOCH3, H2O; a mixt. of Br2, MeOH and powdered W was stirred at 45-60°C for 12 h, additional Br2 may be added; further by-products; rinsed with MeOH, filtered, dried in vac.;93%
With CH3OH; Br2 In methanol byproducts: HBr, (CH3)2O, CH3Br; a mixt. of Br2, MeOH and powdered W was stirred at 45-60°C for 12 h, additional Br2 may be added; further by-products; rinsed with MeOH, filtered, dried in vac.;93%
polysilazane

polysilazane

tungsten
7440-33-7

tungsten

W(90.86),Si(6.18),C(1.55) (X%)

W(90.86),Si(6.18),C(1.55) (X%)

Conditions
ConditionsYield
In toluene ultrasoning mixing soln. of org. polymer and W (30 min); solvent removal (vac.); residue breaking; pyrolysis to 1500°C (argon stream, 5°C/min, 4 h hold); X-ray diffraction;93%
tungsten(VI) chloride
13283-01-7

tungsten(VI) chloride

tungsten
7440-33-7

tungsten

tungsten(IV) chloride
13470-13-8

tungsten(IV) chloride

Conditions
ConditionsYield
In 1,2-dichloro-ethane at 20℃; for 17h;93%
diguanidine carbonate
593-85-1

diguanidine carbonate

tungsten
7440-33-7

tungsten

guanidinium tetrafluorodioxowolframate

guanidinium tetrafluorodioxowolframate

Conditions
ConditionsYield
With 65percent HNO3; HF In hydrogen fluoride aq. HF; dissolution of W powder in 40% HF and 65% HNO3, slow addn. of (C(NH2)3)2CO3 in 40% HF under stirring; filtn., washing with water, drying in air, elem. anal.;92%
disulfur dichloride
10025-67-9

disulfur dichloride

sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

tungsten(VI) sulfide tetrachloride
25127-53-1

tungsten(VI) sulfide tetrachloride

Conditions
ConditionsYield
In neat (no solvent) heating (2E-4 Torr, 425°C, 48 h), slow cooling;89%
polysilazane

polysilazane

ammonia
7664-41-7

ammonia

tungsten
7440-33-7

tungsten

pentatungsten trisilicide

pentatungsten trisilicide

Conditions
ConditionsYield
In toluene ultrasoning mixing soln. of org. polymer and W (30 min); solvent removal (vac.); residue breaking; pyrolysis to 800°C (ammonia stream, 5°C/min, 4 h hold); further heating to 1500°C (5°C/min, argon stream); X-ray diffraction;89%
silicon
7440-21-3

silicon

tungsten
7440-33-7

tungsten

A

tungsten silicide

tungsten silicide

B

pentatungsten trisilicide

pentatungsten trisilicide

Conditions
ConditionsYield
at 1350℃; for 4h; Inert atmosphere;A 85%
B 15%
In neat (no solvent, solid phase) react. of tungsten and silicon above 1070 K;
In melt under Ar; mixt. of W and Si melted in siliconized graphite crucible at 2100°C; held no longer than 2 min with vibration stirring; detd. by X-ray microanalysis;
potassium fluoride

potassium fluoride

hydrogen fluoride
7664-39-3

hydrogen fluoride

dihydrogen peroxide
7722-84-1

dihydrogen peroxide

tungsten
7440-33-7

tungsten

2K(1+)*WO(O2)F4(2-)*H2O = K2{WO(O2)F4}*H2O

2K(1+)*WO(O2)F4(2-)*H2O = K2{WO(O2)F4}*H2O

Conditions
ConditionsYield
In water Electrolysis; electrolysis of H2O2 and HF solns. for 120 min (anode: metal rod, cathode: Pt foil), voltage 5-10 V, current 0.05 A, temp. 0-5°C, soln. remained colorless; filtered, addn. of KF in HF, pptn., filtered, washed with ethanol, dried over KOH; elem. anal.;84%
In water metal dissolved in a mixt. of HF and H2O2 solns. with stirring, temp. maintained below 10°C; filtered, addn. of KF in HF;60-70
methanol
67-56-1

methanol

tungsten
7440-33-7

tungsten

A

tungsten hexamethoxide
35869-33-1

tungsten hexamethoxide

B

tungsten oxomethoxide
19174-06-2

tungsten oxomethoxide

Conditions
ConditionsYield
With LiCl In methanol Electrochem. Process; anodic oxidation of W in MeOH in the presence of LiCl (110 V, 12 h); evapn. to dryness (vac.), extn. (hexane), drying (vac.); mixture of the 2 compds.;A 81%
B 17%
2-chloro-4-fluorotoluene
452-73-3

2-chloro-4-fluorotoluene

tungsten
7440-33-7

tungsten

2-chloro-4-fluorobenzylbromide
45767-66-6

2-chloro-4-fluorobenzylbromide

Conditions
ConditionsYield
With bromine In tetrachloromethane80%
lanthanum(III) oxide

lanthanum(III) oxide

manganese
7439-96-5

manganese

tungsten(VI) oxide

tungsten(VI) oxide

sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

La3MnS3(6+)*WO6(6-)=La3MnWS3O6

La3MnS3(6+)*WO6(6-)=La3MnWS3O6

Conditions
ConditionsYield
In melt stoich. amts. of La2O3, S, W, WO3, Mn mixed with KCl flux; sealed in carbon coated SiO2 ampoule under vac.; heated from 200 to 400°C in 24 h; held for 48 h; heated to 950°C in 12 h; held for 120 h; cooled to room temp. within 24 h; soaked in H2O overnight; washed with H2O; detn. by EDX, XRD;80%
lanthanum(III) oxide

lanthanum(III) oxide

tungsten(VI) oxide

tungsten(VI) oxide

nickel
7440-02-0

nickel

sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

La3NiS3(6+)*WO6(6-)=La3NiWS3O6

La3NiS3(6+)*WO6(6-)=La3NiWS3O6

Conditions
ConditionsYield
In melt stoich. amts. of La2O3, S, W, WO3, Ni mixed with KCl flux; sealed in carbon coated SiO2 ampoule under vac.; heated from 200 to 400°C in 24 h; held for 48 h; heated to 950°C in 12 h; held for 120 h; cooled to room temp. within 24 h; soaked in H2O overnight; washed with H2O; detn. by EDX, XRD;80%
lanthanum(III) oxide

lanthanum(III) oxide

chromium
7440-47-3

chromium

tungsten(VI) oxide

tungsten(VI) oxide

sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

La3CrS3(6+)*WO6(6-)=La3CrWS3O6

La3CrS3(6+)*WO6(6-)=La3CrWS3O6

Conditions
ConditionsYield
In melt stoich. amts. of La2O3, S, W, WO3, Cr mixed with KCl flux; sealed in carbon coated SiO2 ampoule under vac.; heated from 200 to 400°C in 24 h; held for 48 h; heated to 950°C in 12 h; held for 120 h; cooled to room temp. within 24 h; soaked in H2O overnight; washed with H2O; detn. by EDX, XRD;80%
lanthanum(III) oxide

lanthanum(III) oxide

tungsten(VI) oxide

tungsten(VI) oxide

sulfur
7704-34-9

sulfur

tungsten
7440-33-7

tungsten

La3FeS3(6+)*WO6(6-)=La3FeWS3O6

La3FeS3(6+)*WO6(6-)=La3FeWS3O6

Conditions
ConditionsYield
In melt stoich. amts. of La2O3, S, W, WO3, Fe mixed with KCl flux; sealed in carbon coated SiO2 ampoule under vac.; heated from 200 to 400°C in 24 h; held for 48 h; heated to 950°C in 12 h; held for 120 h; cooled to room temp. within 24 h; soaked in H2O overnight; washed with H2O; detn. by EDX, XRD;80%
cyclopentene
142-29-0

cyclopentene

tungsten
7440-33-7

tungsten

trimethylphosphane
594-09-2

trimethylphosphane

A

(η-cyclopentadienyl)trihydridobis(trimethylphosphine)tungsten

(η-cyclopentadienyl)trihydridobis(trimethylphosphine)tungsten

B

(W(η-C5H5)(PMe3)H5)

(W(η-C5H5)(PMe3)H5)

C

(tungsten)(triphenylphosphane)4(hydride)(P(CH3)2CH2)

(tungsten)(triphenylphosphane)4(hydride)(P(CH3)2CH2)

D

W(C5H5)(C5H8)(P(CH3)3)2H

W(C5H5)(C5H8)(P(CH3)3)2H

Conditions
ConditionsYield
-196°C; not isolated, detected by NMR;A 10%
B <1
C 20%
D 70%
bromine
7726-95-6

bromine

tungsten
7440-33-7

tungsten

Br12W6

Br12W6

Conditions
ConditionsYield
In neat (no solvent) byproducts: WBr4, WO2Br2; W powder and Br2 in evacuated and sealed ampule cooled to liq. N2; I endof ampole heated to 750°C, II - to 40°C; WBr5 formed; the n ampole heated at gradient of 750-540°C for 40 h, cooled to roomtemp.; purified by sublimation at 540°C in dynamic vac.; detd. by powderXRD;67%

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.

Gruenert, W.,Shpiro, E. S.,Feldhaus, R.,Anders, K.,Antoshin, G. V.,Minachev, Kh. M.

, p. 522 - 534 (1987)

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.

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.

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.

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.

Kinetic study of tungsten atoms (a 7S3 and a 5DJ) in the presence of C2H4 and NH3 at room temperature

Ishikawa, Yo-ichi,Matsumoto, Yoshitaka

, p. 1145 - 1153 (2003)

The gas-phase reactivity of W (a 7S3 and a 5DJ) with C2H4 and NH3 at room temperature was investigated using a time-resolved laser induced fluorescence (LIF) spectroscopy. Tungsten atoms were produced by a 266-nm multiphoton decomposition (MPD) of W(CO)6. The reactant pressure dependence of the pseudo-first-order depletion rates of W (a 7S3) could allow an estimation of the pseudo-second-order depletion rate constant of W (a 7S3), (4.5 ± 0.5) × 10-10 cm3 molecule-1 s-1 for C2H4 and (0.73 ± 0.10) × 10-10 for NH3 at 6.0-Torr total pressure with an Ar buffer. A simulation of the transient curves based on a modification of the observed apparent decay rate constants, involving nearby a 5DJ states in the presence of C2H4 and NH3, allowed us to separately estimate the contribution of the chemical quenching (W (a 7S3) + R → product(s)) and the physical quenching (W (a 7S3) + R → W (a 5D1) + R) processes. In the case of C2H4, chemical quenching appeared to dominate over the physical quenching, while the physical quenching was the main depletion process in the case of NH3. The large reactivity of the W (a 7S3) state not only for C2H4, but also for NH3, is discussed in terms of the relativistic effects.

Study of the preparation of bulk powder tungsten carbides by temperature programmed reaction with CH4 + H2 mixtures

Leclercq,Kamal,Giraudon,Devassine,Feigenbaum,Leclercq,Frennet,Bastin,Loefberg,Decker,Dufour

, p. 142 - 169 (1996)

The synthesis of bulk tungsten carbides by carburization of W metal or of WO3 with mixtures of CH4 in hydrogen at various pressures has been studied in temperature programmed experiments. The resulting solids have been characterized by elemental analysis, X-ray diffraction, XPS analysis, and specific surface area measurements. The carburization occurs in two distinct steps: W2C is formed in the first step taking place at about 650°C at atmospheric pressure with a 20% CH4-H2 mixture, while the formation of WC occurs only at higher temperatures. During carburization some free carbon is deposited, the importance of which is very much dependent on CH4 partial pressure and on the temperature of carburization. It has also been shown that direct carburization of WO3 by CH4-H2 does not take place, but that the carburization occurs via the reduction of WO3 to W metal. The rate of reduction of WO3 and that of carburization of W metal are very much dependent on, respectively, hydrogen partial pressure and CH4 partial pressure. The extent of reduction of WO3 into W metal required for carburization which takes place also depends on CH4 partial pressure, indicating a competition between carburization of W metal at the surface and diffusion of W metal into the bulk of the Solid.

Zhang, S.-L.,Palmas, R.,Keinonen, J.,Petersson, C. S.,Maex, K.

, p. 2998 - 3000 (1995)

Mechanism for selectivity loss during tungsten CVD

Creighton

, p. 271 - 276 (1989)

We have investigated possible mechanisms for the loss of selectivity (i.e., deposition on silicon dioxide) during tungsten CVD by reduction of tungsten hexafluoride and found strong evidence that selectivity loss is initiated by desorption of tungsten sub

LOW PRESSURE CHEMICAL VAPOR DEPOSITION OF TUNGSTEN ON POLYCRYSTALLINE AND SINGLE-CRYSTAL SILICON VIA THE SILICON REDUCTION.

Tsao,Busta

, p. 2702 - 2708 (1984)

High purity metallic tungsten films are deposited on phosphorus-doped and undoped polycrystalline and single-crystal silicon by the silicon reduction of WF//6. Depositions are performed in a commercial LPCVD hot wall reactor at temperatures ranging from 310 degree -540 degree C. Film formation is self-limiting, meaning that after a given film thickness any further reaction between WF//6 and the underlying silicon is inhibited. Obtainable film thickness depends strongly on the doping condition of silicon and on surface preparation prior to LPCVD. Conventional wet chemical cleaning limits the maximum obtainable film thickness to approximately 400A, whereas with a low power argon plasma treatment approximately 900A thick films can be obtained reproducibly. The resistivity of these films is 18. 3 plus or minus 4. 5 mu OMEGA cm.

Oxidation resistance of hafnium diboride ceramics with additions of silicon carbide and tungsten boride or tungsten carbide

Carney, Carmen M.,Parthasarathy, Triplicane A.,Cinibulk, Michael K.

, p. 2600 - 2607 (2011)

Dense samples of HfB2-SiC, HfB2-SiC-WC, and HfB 2-SiC-WB were prepared by field-assisted sintering. The WB and WC additives were incorporated by solid solution into the HfB2 and the HfC that formed during sintering. Oxidation of the samples was studied using isothermal furnace oxidation between 1600° and 2000°C. Sample microstructure and chemistry before and after oxidation were analyzed by scanning electron microscopy and X-ray diffraction. The addition of WC and WB did not alter oxidation kinetics of the baseline HfB2-SiC composition below 1800°C; however, at 2000°C, HfB2-SiC-WC and HfB 2-SiC-WB had oxide scales that were 30% thinner than the oxide scale of HfB2-SiC. It is believed that WC and WB promoted liquid-phase densification of the HfO2 scale, thereby reducing the path of oxygen ingress, during oxidation.

Temperature-programmed and X-ray diffractometry studies of hydrogen-reduction course and products of WO3 powder: Influence of reduction parameters

Zaki,Fouad,Mansour,Muftah

, p. 90 - 96 (2011)

The hydrogen-reduction course and products of synthetic tungsten(VI) oxide (WO3) were examined by means of temperature-programmed reduction (TPR) and X-ray powder diffractometry (XRD) studies. A set of model tungsten compounds was procured and examined similarly for reference purposes. Results obtained could help resolving two subsequent reduction stages: (i) a low-temperature stage (3 is reduced to the tetravalent state (WO2) via formation and subsequent reduction of intermediate WO2.96, WO2.9, WO2.72 oxides; and (ii) a high-temperature stage (>1050 K) through which WO2 thus produced is reduced to the metallic state (Wo) via two intermediate oxide species (tentatively, WO and W2O-W3O). Reduction events involved in the high-temperature stage were found to be relatively more sensitive to the reduction parameters; namely, the starting oxide mass, heating temperature and rate, and gas flow rate and composition. They were also found to require lower activation energies than those required by events occurring throughout the low-temperature stage, a fact that may suspect compliance of the high-temperature reduction events to autocatalytic effects.

Diffusion barrier properties of tungsten nitride films grown by atomic layer deposition from bis(tert-butylimido)bis(dimethylamido)tungsten and ammonia

Becker, Jill S.,Gordon, Roy G.

, p. 2239 - 2241 (2003)

The synthesis of the highly uniform, smooth and conformal coatings of tungsten nitride (WN) using atomic layer deposition (ALD) from vapors of bis(tert-butylimido)bis(dimethylamido)tungsten and ammonia was discussed. The diffusion barrier properties of th

Size control of tungsten powder synthesized by self-propagating high temperature synthesis process

Won, Chang-Whan,Jung, Joong-Chai,Ko, Seog-Gueon,Lee, Jong-Hyeon

, p. 2239 - 2245 (1999)

Tungsten powder was prepared by self-propagating high temperature synthesis (SHS) from a mixture of WO3 and Mg. The MgO in the product was leached with an HCl solution. The complete reduction of WO3 required a 33% excess of magnesium over the stoichiometric molar ratio Mg/WO3 of 3. The tungsten product had a purity of 99.98%, which was higher than that of the reactants. The high purity resulted because the impurities in the reactants were volatilized during the highly exothermic reaction and dissolved during leaching of the product. Size distribution and the shape of the tungsten particles produced was affected by compaction pressure on the green pellet.

Bryant, W. A.

, p. 37 - 44 (1976)

ENTHALPY OF FORMATION OF PENTACARBONYL(TRIPHENYLPHOSPHINE) TUNGSTEN AND OF PENTACARBONYL(METHOXY(PHENYL)METHYLENE)TUNGSTEN

Al-Takhin, Ghassan,Connor, Joseph A.,Pilcher, Geoffrey,Skinner, Henry A.

, p. 263 - 270 (1984)

Microcalorimetric studies on the sublimation, thermal decomposition and bromination of W(CO)6, and of the complexes and > have provided standard enthalpies of formation (in kJ mol-1) of the crystalline and vapour

Characterization of selective tungsten films prepared by photo-chemical vapor deposition

Fang,Hwang,Sun

, p. 1720 - 1723 (1991)

Selective photo-chemical vapor deposition (CVD) of tungsten films decomposed by direct photoexcitation of WF6 have been studied. Film deposition rate increased with increasing temperature but was only slightly dependent on WF6 gas concentration. The selectivity deteriorated with increasing deposition temperature, WF6 concentration, and deposition time. Typically, in order to achieve selectivity, the flow rate of WF6 must be lower than 35 sccm and the deposition temperature must be lower than 230°C. No encroachment and self-limited thickness problems were found as in the low-pressure chemical vapor deposition method. In general, tungsten films prepared by photo-CVD were amorphous as observed by x-ray diffraction analysis. After annealing, the tungsten had a polycrystalline structure with a resistivity of 18 μΩ-cm.

Vacuum annealing of nanocrystalline WC powders

Kurlov,Gusev

, p. 680 - 690 (2012)

The effect of vacuum annealing temperature on the chemical and phase compositions, particle size, and lattice strain of nanocrystalline tungsten carbide (WC) powders with a particle size from 20 to 60 nm has been studied by X-ray diffraction and electron microscopy. The results demonstrate that vacuum annealing of WC nanopowders at tann ≤ 1400°C is accompanied by a marked decrease in carbon content and changes in phase composition due to carbon desorption from the surface of the powder as a result of the interaction of carbon with oxygen impurities. In addition, annealing leads to an increase in particle size due to coalescence of aggregated nanoparticles and reduces the lattice strain of the powder. Pleiades Publishing, Ltd., 2012.

Nucleation on SiO2 during the selective chemical vapor deposition of tungsten by the hydrogen reduction of tungsten hexafluoride

Desatnik,Thompson

, p. 3532 - 3539 (1994)

A horizontal hot-wall chemical vapor deposition (CVD) quartz reactor with rectangular cross section was used to study the effect of different process conditions on the nucleation of tungsten on SiO2 during selective WCVD by the H2 reduction of WF6. The experimental procedure included placing a metallic surface at the center of the reactor, and small samples of SiO2 at different positions both upstream and downstream with respect to the metallic surface. Digitized scanning electron microscopy micrographs were used to determine the particle size distributions of nuclei on the SiO2 surfaces. We found that the amount of nucleation on SiO2 decreases when smaller metallic surfaces are present and for lower temperatures and shorter process times. Although nucleation was always greatest on SiO2 samples closest to the metal sample, the effect of flow rate depended on the position of the SiO2. A statistical nearest neighbor analysis indicated a clustering of W nuclei on the SiO2. A simplified mathematical model was developed to predict concentration profiles of a gaseous intermediate generated at the metal surface during the thermal decomposition of the source gas. This intermediate has been proposed as being the reactive species that causes nucleation on SiO2 surface. Qualitative agreement between experimental and theoretical results reinforce the proposed role of the intermediate with this species being characterized by a short lifetime.

Electrolytes for tungsten refining

Pavlovskii

, p. 372 - 375 (2004)

Chloride-fluoride and phosphate-fluoride salts of alkali metals with additions of sodium tungstate and tungstic anhydride are studied as electrolyte systems for tungsten refining. The results demonstrate that the melts of these systems are suitable for el

Nanoscale electron-beam-stimulated processing

Rack,Randolph,Deng,Fowlkes,Choi,Joy

, p. 2326 - 2328 (2003)

Electron beam stimulated deposition and etching were investigated. These processes find application in nanoscale selective processing. During etching of silicon and silicon dioxide, inelastic scattering of the electron beam with the gas was found to take

Reactivity of hexanes (2MP, MCP and CH) on W, W2C and WC powders. Part II. Approach to the reaction mechanisms using concepts of organometallic chemistry

Hemming,Wehrer,Katrib,Maire

, p. 39 - 56 (1997)

The reactivity of 2-methylpentane (2MP), methyleyelopentante (MCP) and cyclohexane (CH) on reproducible and well-characterized surfaces of W, W2C and WC has been studied. A great deal of effort was put on the characterizations by physisorption, chemisorption and photoemission spectroscopy. The results obtained with these reference materials can be used for comparison with those appearing in the literature and sometimes debated because of the inconstancy of the active states due to non-stoichiometric compositions (excess of carbon, decarburization, oxidation by oxygen impurities). In agreement with the work of Boudart et al. [F.H. Ribeiro, R.A. Dalla Betta, M. Boudart, J. Baumbgartner, E. Iglesia, J. Catal. 130 (1991) 86; F.H. Ribeiro, M. Boudart, R.A. Dalla Betta, E. Iglesia, J. Catal. 130 (1991) 498; E. Iglesia, J.E. Baumgartner, E.H. Ribeiro, M. Boudart, J. Catal. 131 (1991) 523; E. Iglesia, F.H. Ribeiro, M. Boudart, J.E. Baumgartner, Catal, Today 15 (1992) 307.] we confirmed that reforming reactions do not take place in the temperature range 80-400°C and four experimental conditions. They dehydrogenation of cyclohexane appeared only when a strong position by carbonaceous residues occurred. For 2-methylpentane and methylcyclopentane the extensive hydrogenolysis character of WC is higher than for W2C and WC surfaces are interpreted by different possible reaction intermediates deduced from concepts of organometallic chemistry.

A reflectometric study of the reaction between Si and WF6 during W-LPCVD on Si and of the renucleation during the H2 reduction of WF6

Holleman,Hasper,Middelhoek

, p. 783 - 788 (1991)

The formation of W through the reduction of WF6 by Si is monitored in situ using a wavelength adjustable reflectometer. The reflectance-time relation can be understood and modeled by assuming island growth and a statistical distribution of the island thickness. The model is supported by SEM and Auger observations. The effect of surface layers like native oxides or a plasma treatment on the inhomogeneous Si consumption by the reaction between Si and WF6 (gouging) and its effect on the reflectance-time relation are understood. The model is also applicable in the case of renucleation during the H2 reduction of WF6. A renucleation step consists of the deposition of SiH4 followed by the Si consumption by WF6. A renucleation step reduces the surface roughing which occurs during the H2 reduction process.

Tungsten fluorides: Syntheses and electrochemical characterization in the FLINAK molten salt eutectic

Eklund,Chambers,Mamantov,Diminnie,Barnes

, p. 715 - 722 (2001)

The following tungsten fluorides have been synthesized by simple addition reactions or by reduction with tungsten metal at elevated temperature: KWFT7, K2WF8, MWF6 (M = K, Na, Rb, Cs), K2WF7, M3WF8 (M = K, Na, Rb), and K3WF6. The compounds were characterized by their Raman spectra and by cyclic voltammetry in the molten FLINAK eutectic melt (46.5, 11.5, and 42.0 mol % of LiF, NaF, and KF, respectively) at 475-800 °C. X-ray crystal structures are reported for two new compounds K2WF7 and K3WF6. The crystals of K2WF7 were orthorhombic, space group Pnma (No. 62) with a = 9.800(2) A, b = 5.7360(11) A, c = 11.723(2) A, and Z = 4. Crystals of K3WF6 were cubic, space group Fm3 (No. 225) with a = b = c = 8.9160(10) A, Z = 4. Electrodeposition of tungsten metal on Pt from FLINAK, prepared by the addition of WF6 gas and metallic tungsten to the melt, is suggested to result from reduction of an equilibrium mixture of WF83- and WF63-.

Structural Transformations of [CuEn 3]WO4 Complex Salt in the Range 100–390 K and Its Degradation to [CuEn 2](WO4)·2H2O

Khranenko,Sukhikh,Komarov, V. Yu.,Gromilov

, p. 1790 - 1798 (2019/12/24)

The crystal structure of [CuEn3]WO4 (En is ethylenediamine) is studied in the temperature range 100–390 K. Crystallographic data at 100 K are: a = 27.6903(8) ?, c = 9.9405(3) ?, space group P3?, V = 6600.8(4) ?3, Z = 18. Copper atomic coordination is a distorted square bipyramid. Four short Cu–N distances are within 2.038(5)–2.110(6) ?; two long distances are within 2.374(8)–2.514(7) ?. The lengths of N–H…O interionic contacts lie within 1.96–2.17 ?. A temperature elevation makes the Cu–N distances equal: at 298 K they are within 2.066(2)–2.256(3) ?(a = 16.0391(8) ?, c = 9.9608(6) ?, space group P3?c1, V = 2219.1(3) ?3, Z = 6), and at 390 K they are 2.151(6) ?(a = 9.2986(10) ?, c = 10.0520(14) ?, P3?1c, V = 752.7(2) ?3, Z = 2). In the range from 100 K to 390 K the average W–O distances decrease from 1.776 ? to 1.734 ?. Hirshfeld surfaces of complex cations are analyzed. It is shown that with increasing temperature the number of interionic N–H…O contacts decreases. The [CuEn3]WO4 phase is found to be unstable and on storing in air it transforms into [CuEn2](WO4)·2H2O.

Novel aluminum-graphene and aluminum-graphite metallic composite materials: Synthesis and properties

Yolshina,Muradymov,Korsun,Yakovlev,Smirnov

, p. 449 - 459 (2016/01/09)

A novel method of creating new lightweight, aluminum-metallic, composite materials under halides melt at temperatures 973-1073 K under air atmosphere is proposed. The method for synthesizing aluminum-based metallic composite materials, containing up to 2 wt. % graphene sheets uniformly distributed in a metal matrix, is entirely new, having no analogies in current science and practice. The synthesis of graphene nanosheets in a metal matrix is one-step, simultaneous process, taking place directly in molten aluminum under alkali halides melt without the necessity of a separate stage of synthesis and introduction of graphene. This has the potential to facilitate the inexpensive synthesis of aluminum-graphene composites with a high concentration of graphene. The aluminum-graphene composites formed according to this method are characterized by a high uniformity of graphene films with linear dimensions from 100 nm to 50 μm and a thickness from one to three nm in the metal bulk. No aluminum carbide forms under synthesis; the aluminum-graphene and aluminum-graphite composites are resistant to corrosion in NaCl solution. The hardness, strength and ductility of aluminum-graphene composites are at least 2-3 times higher than the initial aluminum material, proportional to the concentration of graphene.

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