Tungsten oxide of pyrochlore phase is a compound having many microporous channel structure, which has the chemical formula M2B2O6O ', where M, B is a metal atom, and O' is monohydrate crystals. Tungsten oxide of pyrochlore phase distorted on the WO6 octahedral structural basic, through the top angle of the tungsten oxide rigid skeleton to build a layered structure having a six-membered ring channels, and has a three-dimensional channel in the direction of. Because of its mesh sieve and metastable structure, physical and chemical properties of tungsten oxide pyrochlore type changed significantly, not only to make it conductive, adsorption performance enhancements, and catalysis, sensors, electrochromic, electromagnetic and other fuels in wait until applications. This kind of phase synthesis method is mainly two: one is soft chemical synthesis, and the other is hydrothermal synthesis.

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Ultrasonic cavitation method due to its unique physical and chemical effects in the production of nanometer tungsten trioxide can gain good results. Because using ultrasonic cavitation method will cause high temperature and a lot of bubbles in the solid particles surface and all of this will reduce the nucleation specific surface. Thereby it can inhibit the nucleation coalescence and growth. In addition, because using ultrasonic cavitation method it will cause shock waves and microjets crushing effect so the gel precipitation will be molecule. Using ultrasonic cavitation technology, through the cavitation will cause local temperature, high pressure or strong shock waves and microjets and so on, and all these can greatly reduce the binding force between nanoparticles, thereby effectively preventing agglomeration phenomenon.

It is useful to prepare a microporous structure with a high specific surface area, highly crystalline nano tungsten trioxide. The preparation method is: adding configured sodium tungstate into cation exchange resin column with uniform and then putting the tungsten acid solution which is exchanged in the beaker. It will form a gel after cooling. Place 1 or 2 days, adding distilled water ultrasonic dispersion gel 20min, centrifuged at 8000r / min 1h to obtain a precipitate. Then repeat the process after 1,4,7,10 times were 100 ℃ vacuum drying or drying, it can be obtained with a small amount of water of crystallization of nano-porous tungsten trioxide different samples at room temperature.

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Non-sag tungsten wire background, it was initially developed prior to 1920 and the introduction of the non-sag tungsten wire had a great impact on the incandescent lamp industry.In explanation of the term "non-sag," if a tungsten wire elongates when it is operated, and thus sags, the individual turns between wire coils will tend to contact one another and short out, thereby shortening the life of the wire. In the practices of the prior art, non-sag tungsten has been fabricated by including therein a very small amount of so-called "dopant," which dopant is added in the form of alkali silicates. Because of this dopant addition, when the wire is initially incandesced, the crystals or grains which are formed therein are elongated and interlocking and generally disposed along the axial dimension of the wire. Within recent years, it has been discovered that the non-sag characteristic which is imparted by the alkali silicate doping is due to the formation of very minute potassium particles, which form potassium bubbles when the wire is incandesced. A substantial portion of these bubbles are generally aligned along the axial dimension of the wire and serve to inhibit the recrystallization and control the grain growth of the wire due to dislocation and grain boundary pinning by the potassium bubbles.

These potassium-formed bubbles are generally submicroscopic in nature and a representative diameter of same is in the order of 100 to 500A. While the performance of such a wire is generally satisfactory, a major problem in the manufacture of the tungsten is the uniform incorporation of the doping impurity into the metal, and the attainment of the consistency of the required concentration, in order to produce the best wire material. 

 

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Tungsten oxide films can render color by light irradiated with appropriate energy (photochromic) or by using an electric field (electrochromic), this property makes it be widely used at electrochromic windows, large information display and automotive mirrors and so on. There are many ways to product tungsten trioxide films including physical deposition method and chemical deposition method, but these methods are high production costs and it is difficult to form a large-area film. But electrodeposition method produce WO3 films that not only economic and then prepared and easy production of large-area thin film, the most important is photochromic and electrochromic properties of WO3 films is well. WO3 Films setting method is : Pt plate as an anode, BP conductive glass as cathode, cathodic electrodeposition in the greenhouse, reacting with 0.5mol / L NA2WO4 solution, the constant current density is 2.00A / cm2, obtained WO3 film dry at red light first, then heat-treated for 3 hours at 400 ℃, the film after the heat treatment is uniform, good adhesion, is displayed in the X-ray diffraction results, the WO3 film amorphous crystalline film.

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Because of tungsten powder and tungsten carbide powder chemical purity and physical properties has high requirement so producing tungsten powder and tungsten carbide powder process is very complex and the cost is higher too. But tungsten powder composition when not strictly required in most cases where there are a lot of impurities so using industrial pure carbon reduction tungsten powder is an economical and easy way. In a vacuum furnace use carbon reducing tungsten trioxide making high purity tungsten powder and tungsten carbide powder provided by melting and casting. According to current science and technology, using industrial pure carbon or tungsten carbide powder as a casting material is fully meet the requirements. Using carbon restore tungsten trioxide is similar with using hydrogen restore tungsten trioxide. At atmospheric pressure, at a temperature condition of 750 ℃ heating tungsten trioxide so it will mix with carbon black or graphite powder occurring reduction. The reaction chemical equation is: WO3 + 3C = W + 3CO, WO3 + 4C = WC + 3CO. The temperature under 1000 ℃, mainly using CO participate in a reaction and chemical equation is: WO3 + 3CO = W + 3CO2, CO2 + C = 2CO. The main process includes milling mixing, compression molding, dried at 200 ℃ temperature, then vacuum carburizing, and then filtered through milling.  

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Non-sag tungsten wire, namely doped tungsten wire, which is widely applied to lighting industry.

Large elongated grains are obtained by primary and secondary recrystallization, which are regarded as the desired microstructure to gain necessary creep resistance. A few of the grains will grow massive in secondary recrystallization, which often called abnormal grain growth. The mechanisms of normal and abnormal grain growth are basically the same, involving high angle boundary migration and driven by the reduction of surface energy. For a few of the grains, the abnormal grain growth can be visualized as a growth advantage while growth disadvantage for the majority. Such an advantage/disadvantage may be caused by (1) differences in grain size and/or(2) differences in grain boundary character distribution (GBCD). In other words, a grain may grow massive if it has large size and/or possibilities of more favorable (i.e., of higher mobility) grain boundaries with the matrix grains.

 

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Non-sag tungsten wire, also namely doped tungsten wire, which was classified in different content of thorium they doped, has different types with different properties and applications

Normally application of non-sag tungsten wire:

Non-sag tungsten wire is widely used to car light and motorbike light due to its property of anti-shaking, so that car light can direct the drivers with stable light source. 

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Sputtering method is a physical vapor deposition method. It is through energetic particle impact a solid so the solid atoms emitted from the surface and deposited onto a substrate or surface film to form films. Sputtering method is divided into DC sputtering, screen shot sputtering, magnetron sputtering, and ion beam sputtering and so on. Wherein the magnetron sputtering method deposition technology is a faster, lower operating pressure sputtering technique, because of its unique features is widely used. Using magnetron sputtering method produces tungsten trioxide film the thickness from tens of nanometers to several hundred nanometers range. Produced by magnetron sputtering of tungsten trioxide films main control several conditions are: first, a tungsten target with a purity of 99.9% by the tungsten powder pressed secondly, the substrate is transparent flat glass (25mm), then the working gas is argon gas (> 99.99%), and reactive gas is oxygen (> 99.99%), where pressure ratio of oxygen and argon is 75%. Finally, set the operating pressure is 1.5 Pa, sputtering current of 0.12 A, the sputtering voltage of 520V, the target distance of 7cm, the sputtering time was 45min. 

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Tungsten trioxide (WO3) because of its unique nature has been widely applied in all aspects of industry and technology. Besides the morphology and structure of WO3 has a direct relationship with applications, now, people have many ways to prepare different pore size of the porous oxide, including large hole, mesoporous and microporous. But the porous foam structure material for fragile so little research and application.

After the expert study, they can produce tungsten trioxide dimensional network structure having a supporting force. Typical synthetic methods for producing tungsten trioxide dimensional network structure are as follows:
(1) 1g metal tungsten powder dissolved in mixed liquor which includes 15ml30% H2O2 and 15ml methanol. In this process to keep stirring then make it to form a clear solution.
(2) Put 0.12g polyvinyl pyrrolidone into clear solution which made from pervious task to form a transparent slightly viscous solution.
(3) The solution was concentrated under 333K, when the solution was concentrated to 5ml, foam-like structure of WO3 is begin to form.
(4) Calcining the foam-like structure at 773K for 6 hours, at a heating rate control at 1K / min.   

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Tungsten trioxide crystal structure satisfies stoichiometric ratio strictly should be distorted perovskite structure, namely the absence of cation A pattern appears in the ABO3 perovskite structure. Oxygen atom is octahedron, and a tungsten atom in the center of the octahedron. All single phases of tungsten are octahedral structure but the structural is different. Since tungsten trioxide varying degrees of oxygen vacancy and therefore the stoichiometric become more complicated, so that the tungsten trioxide chemical formula is usually written as WO3-X. With the increase in the number of oxygen vacancies, which are distributed in the crystals of WO3-X becomes ordered together, a so-called shear surface. When X <0.02 the shear surface is randomly distributed. When X≥0.02 shear surface become parallel arranged, with the increasing degree of reduction of the degree of ordering shear surface arrangement is also increasing. These compounds have different crystal structures, and vacancies, such that the tungsten trioxide having a variety of properties, photocatalytic activity which has not the same.

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