Study on Tungsten Oxide Nanorods

Tungsten trioxide has shown good sensing properties towards various gases. Recently thin nanostructured WO3 films have been tested. Due to their large surface area to volume ratio they exhibit good sensitivity depending on the grain size. However in conventional WO3 thin films the average grain size exceeds the thickness of the surface space charge layer, so the electrical conduction is mainly controlled by the carriers transport across the grain boundaries. An alternative way seems to be in a monocrystalline material with nanometric dimensions. Our objective is to fabricate nanosized tungsten oxide rods and to test their sensing properties under gas adsorption. We focus on the growth, the structure and the electrical properties of tungsten nanorods. The tungsten oxide nanorods were grown by vapour transport from a WO3 layer onto a substrate (Mica). The nanorods growth was controlled by the temperature gradient between the WO3 layer and the substrate.
 
 
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Electrical Properties of Tungsten Trioxide Films

Selectively doped semiconducting metal oxide (SMO) films have been shown to have applications as the sensing element in gas microsensors. Critical to the design and operation of these sensors is the SMO film. The electrical properties of both intrinsic and extrinsic (doped with gold) tungsten trioxide (WO3) films, which selectively sorb hydrogen sulfide (H2S), are investigated. Hall effect measurements are performed as a function of film thickness, temperature, gold-doping concentration, and H2S gas concentration. The conductivity was found to be n type and strongly dependent on temperature, gold doping concentration, and H2S gas concentration and less dependent on film thickness. The mobility was relatively high while the intrinsic carrier concentration was low when compared to typical semiconductor materials. The conductivity was shown to exhibit anomalous behavior at certain temperatures and H2S gas concentrations.
 
 
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Tungsten Oxide Powder Typical Applications and Packaging

Tungsten Oxide Powder Typical Applications:
Used in the manufacture of tungsten and tungstates, in alloys, in fire-proofing fabrics and as a ceramic pigment.
 
Tungsten Oxide Powder Packaging:
Jars, pails, drums, multiply paper bags, bulk bags and fiberboard containers. For further information on packaging options contact Chinatungsten Online.
 
 
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Tungsten Oxide Powder

Tungsten Oxide Powder Synonyms:
tungsten oxide, tungsten(IV) oxide (WO2), tungsten(VI) oxide (WO3), tungsten trioxide, tungsten(VI) trioxide, tungstic anhydride, CAS#1314-35-8  (WO3), ditungsten pentaoxide, tetratungsten undecaoxide, tungsten oxide, tungsten oxide (W2O5), scheelite, wolframite, ferberitetungsten oxide (W4O11)
 
Chemical Names:
Tungsten oxide, Tungsten trioxide, Tungsten (VI) trioxide
 
Chemical Formulas:
W2O5, WO2 and WO3
 
Tungsten Oxide Powder Description:
Tungsten oxide is obtained from the minerals scheelite, wolframite, ferberite. It is insoluble in H2O and acids, but soluble in hot alkalis.
 
Tungsten Oxide Powder Chemical Properties Available:
99.9% up to 99.99%
 
Tungsten Oxide Powder Physical Properties Available:
Targets, pieces, and powder to customer specifications
 
 
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What the Difference of the Ammoniu Metatungstate and Ammonium Paratungstate ?

The thermal decomposition of ammonium paratungstate tetrahydrate (APT·4H2O), (NH4)10[H2W12O42]·4H2O, in air to tungsten trioxide, WO3, was investigated under non-isothermal conditions using thermal analysis coupled on-line by a Skimmer® system to a quadrupole mass spectrometer (TA-MS) for evolved gas analysis (EGA), with X-ray powder diffraction (XRD), with Fourier

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Preparation of Tungsten Trioxide

Tungsten trioxide can be prepared in several different ways. CaWO4, or scheelite, is allowed to react with HCl to produce tungstic acid, which decomposes to WO3 and water at high temperatures.
 
CaWO4 + 2 HCl → CaCl2 + H2WO4
H2WO4 → H2O + WO3
 
Another common way to synthesize WO3 is by calcination of ammonium paratungstate (APT) under oxidizing conditions:
 
(NH4)10[H2W12O42]•4H2O → 12 WO3 + 10 NH3 + 10 H2O
 
 
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History of Tungsten Trioxide

Tungsten has a rich history dating back to its discovery during the 18th century. Peter Woulfe was the first to recognize a new element in the naturally occurring mineral wolframite. Tungsten was originally known as wolfram, explaining the choice of "W" for its elemental symbol. Swedish chemist Carl Wilhelm Scheele contributed to its discovery as well with his studies on the mineral scheelite.

In 1841, a chemist named Robert Oxland gave the first procedures for preparing tungsten trioxide and sodium tungstate.He was granted patents for his work soon after, and is considered to be the founder of systematic tungsten chemistry.

 

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Some Techniques Used to Ammonium Metatungstate

Several techniques have been used to study the structure of the Keggin-type polyoxometalate salt ammonium metatungstate(AMT)—(NH4)6[H2W12O40]*nH2O, a potential fuel cell catalyst. The dehydrated salt is comprised of a mixture of crystallites of different unit cells in a centered eutactic cubic configuration, with an average unit cell of a≅12.295. Varied orientations of the Keggin ions in the cubic arrangement create the differences, and orientational variation within each unit cell size represents an energy well.

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A New Production Method of Pure Ammonium Metatungstate

Using a coupling process of neutralization–nanofiltration–crystallization, pure  is producted . The effects of chemical neutralization of ammonium paratungstate (APT) by nitric acid, operating pressure, the concentration of AMT and the volume of washing water on the coupling process were systematically discussed. It was found that the better conditions of AMT

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The Thermal Decomposition of Ammoniu Metatungstate

The thermal decomposition of ammoniu metatungstate(AMT)involved several steps in inert atmosphere: (i)That is release of crystal water between 25°C and 200°C resulte in dehydrated AMT. (ii) The formation of an amorphous phase between 200°C and 380 °C.

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