Tungsten trioxide is widely used in modern industry, not only development in gas-sensitive materials, electrochromic and other fields but also development and applied in catalysis which is also very extensive. And tungsten trioxide insoluble in water and acid, but in excess of H2O2 solution, since [O₂] ^2- has strong electronegativity will cause coordination interaction with WO3 forming an oxide tungstate (H₂ [W₂O₃ (O₂) ₄ (H₂O) ₂]) ^{11-12}. Reaction with oxide tungstate the cyclohexythanoids will turn into cyclohexanone. Oxide tungstate not only brings active oxygen but also brings acidity to reaction system. What’s more suitable acidity has for H₂O₂ oxidizing reaction has a strong catalytic effect.

When the amount of tungsten trioxide at 0.50mmol, the acidic of solution is lower, the active centers number less, and cyclohexanone yield is very low. With the tungsten trioxide dosage increased, acidity of the solution and the number of active centers are also increase. So product yield increased accordingly. When the amount of tungsten trioxide increased 1mmol, has been able to provide the number of active centers required for the reaction, cyclohexanone yield arrived at 73.5%, and increases the amount of tungsten trioxide, cyclohexanone yield no significant increase. That is unlimited increase in the amount of catalyst can not increase the yield of cyclohexanone.

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Using XRD-600 diffractometer analysis films structure and morphology which producing by different methods. Different forms of tungsten trioxide film were annealed at different temperatures.

After studies found films light transmittance is similar which produced by sol-gel method and magnetron sputtering method before annealing. the transmittance of thin film samples decreased after annealing at above 300 ℃, the light transmittance will reduce. Besides, annealing temperature more high the light transmittance will lower. Tungsten trioxide film are amorphous  which annealed at 350℃ below, within the range of 350 ~ 400 ℃ annealing, the amorphous film gradually complete transition to crystalline, annealing at 400 ℃ above, the substrate also had a diffraction peak. Morphology and optical properties of tungsten trioxide films have a great impact on its gas sensing properties, such as relatively porous amorphous film, which will help the adsorbed gas so the sensitivity of hydrogen may be higher than the crystalline structure of the film, so that the results of the study have some guidance on hydrogen Sensitivities.

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By comparing the magnetron sputtering method and sol-gel method producing tungsten trioxide films respectively found little difference in light transmittance. But the films producing by magnetron sputtering method the spectrum peaks and valleys more obvious that is the film producing by magnetron sputtering absorb different wavelengths light greater than the sol- gel method.

Analysis films transmission spectra which are producing by gel-sol method at different annealing temperatures before and after. Tungsten trioxide film producing by sol-gel method, the annealing temperature is higher, the lower the light transmittance of it. At 300℃ annealing for 30min, film transmittance fell by an average of 10%, peaks and valleys wavelength position will move to ultraviolet wave slightly which is not obvious. At 380℃ annealing transmittance of the film was reduced by 20% to 25%, and in the infrared portion the light transmittance decline rapidly, the peak number did not change, the difference between the peaks and troughs of the light transmittance becomes smaller. After annealing at 400 ℃ film transmittance decreased by 25% to 30%, and in the infrared portion the light transmittance decline was particularly pronounced.

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Using WGZ-8 double-beam UV - visible spectrophotometer to analysis transmittance of film, the incident light wavelength range of 200 ~ 800nm, light transmission rate of 0% to 150%. Using sol-gel method produce tungsten trioxide films and the transmission spectra showed maximum light transmittance and wavelength corresponding respectively: 85.3%, 556nm, peaks and troughs in the 350 ~ 600nm wavelength range, light transmittance difference at the peaks and valleys value of 4.4%, the wavelength range which is less than 300nm the light transmittance almost all zeros.

And use magnetron sputtering method produce tungsten trioxide films found maximum light transmittance and the corresponding wavelength ranges were: 90.1%, 572 ~ 582nm which peaks and valleys within the 350 to 650nm wavelength and the difference between the peaks and troughs in the light transmittance is about 21.2%. Comparison two lines of transmittance spectra will know the light transmittance difference is not big which produced by sol-gel method and magnetron sputtering method.

When films produce by magnetron sputtering at 450 ℃ the transmittance of the films dropped by an average of about 8% to 10%, peak shape and position almost unchanged. When the annealing temperature at 500 ℃, the light transmittance films dropped by an average of about 8%, the peak position and peak shape has not changed much.

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Tungsten carbide ball burs can create concave cuts at any angle in work pieces and get into the material at any angle or tight areas, and it is also a proper choice for shaping or hollowing out an area. The commonly sizes refer to the ball burs are varied, the smallest one could be as tiny as 0.5mm, which are ideal for intricate carving projects.

By adopting tungsten carbide ball burs, operator could easily make recesses for sweat-soldering, engrave, texture, debur, drill and enlarge holes, cut rounded notches for stone-setting and refine bezels and prongs. Since tungsten carbide ball burs offer so many purposes, they are widely used in wood carving, stone carving and metal engraving, which are also very well accepted among the jewelers.   
 

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Tungsten carbide burs are used to deal with cutting, shaping, grinding and removing the sharp edges, burs and excess material in practices and end mills for metalworking as well as for holes of all sorts. During the operation, for the safety consideration, here are some usage recommendation to review.



1.Make sure the bur shank is always well inserted int o the collet, and it is clamped down tightly enough.

2.Ensure the pressure is light and always ensure the bur moving focusing on the highest material first.

3.Make sure the work piece and the work bench is well secured.

4.Ensure the burs don't snag or jam into the work.

5.Always wear eye protection as a bottom line, whereas a full shield for face is recommended.


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Co-precipitation method is to add a suitable precipitant in a mixed metal solution, a homogeneous precipitation reaction product. It is an important method for produce ultrafine tungsten oxide which including two or more metal elements. using co-precipitation method producing tungsten trioxide, first step is taking 1mol /L Na2WO4 solution and Na2SnO4 solution slowly drop after mixing to dilute H2SO4 in boiling, stirring constantly generate precipitation. Then after aging, washing, filtering, drying and calcining to obtain SnO2-WO3 gas sensing powder materials. The study found the addition inhibited the growth of SnO2 WO3 grains, increase the sensitivity of its gas, wherein the doping amount of 0.5% is optimum.

Some researchers also use Sol-co-precipitation produce tungsten trioxide, in WCl6 and TiCl (4wt %) aqueous solution adding ammonium hydroxide and suitable surfactants to formW (OH) 6 and Ti (OH) 4, then after centrifuged and calcining to obtain the tungsten trioxide powder in 3 ~ 9nm. The study found that the smaller the particle, the more uniform particle size. Agglomeration, the higher the sensitivity of the respective gas and recovery time is shorter accordingly.

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Study on magnetic properties of tungsten trioxide material no much better than the electrical and optical properties. But the object of study the magnetic properties of tungsten trioxide are mainly to clarify their electronic structure and electrical transport properties through the relevant magnetic measurements. After the study of the magnetic properties of WO3-X, researchers found that such materials have Pauli paramagnetic type, and further consider the impact of structural factors may be. By measurement magnetic and electrical parameters, the researchers believe the simple quasi-free electron gas model uniformly distributed in the lattice can explain the observed magnetic behavior. Researchers studied with crystalline structure of the low-temperature paramagnetic WO3 found until the ultra-low temperature of the sample 9 × 10-5K did not appear superconductivity, showing a magnetic behavior.

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Structure of tungsten trioxide can well be described as a common apex WO6 octahedron three-dimensional network structure. However WO3 symmetry relatively quite low because it is a modification by ReO3 ideal structure, embodied in WO6 octahedra tilt and tungsten atoms replacing the central position of the octahedron. The various change of phonon lattice and electronic structure let tungsten trioxide produced several crystalline phase, these types of crystalline phases with increasing temperature is evolved from the low to the high symmetry change.

After the studies, now researchers get more recognized tungsten trioxide phase change order: monoclinic Pc (ε-WO3) → triclinic PT (ζ-WO3) → monoclinic P21 / n (λ-WO3) → orthogonal Pbcn (β-WO3) → Quartet P4 / ncc (α-WO3) → P4 / nmm. In 2002, after continuous research, found new crystalline phase. Also through high resolution neutron powder diffraction method confirmed the existence of a new phase in the monoclinic temperature zone of 720 ℃ to 790 ℃.

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Solid-phase method is blending a proportion of metal salt or metal oxide, calcined after grinding. According to studies, calcined APT under different conditions will obtain different structure tungsten trioxide. Using ammonium tungstate (NH4) 2WO4 as raw materials producing tungsten trioxide by solid phase out method the reaction condition different the WO3 structure is different. A certain amount of (NH4) 2WO4 calcined for 3 hours at 600 ℃ condition, and cooled to obtain WO3 powders which is monoclinic and triclinic two crystal phases. Or using (NH4) 2WO4 as the raw material by calcination, low temperature hardening and calcination, nature cooling method for preparing monoclinic phase and quadrature phase of WO3 respectively. Found that higher activity quadrature phase WO3 than monoclinic WO3. While changing the calcination temperature to 700 ℃ to resolve (NH4) 2WO4 producing WO3 catalyst. After studies theWO3 catalyst in electron acceptor Fe3 + solution system photocatalytic activity found that the increasing of Ar content, the WO3 catalyst surface oxygen vacancies increase, catalytic oxygen evolution increases. And in pure Ar conditions it has been the most active WO3 catalyst.

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