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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After the study found that tungsten trioxide producing method, reaction conditions, there will affect the structure and properties of the product. At the same time, the different precursor also has some impact on producing WO3. Depending on the reaction environment of raw materials, methods for producing WO3 can be roughly divided into solid, liquid and gas phase method.

Solid-phase method is a traditional powder technology, using solid-phase for producing tungsten trioxide is usually obtained by calcination APT, but due to different firing conditions there was not the same reactant. Such as at 400 ℃condition calcinate APT with oxidizing atmosphere will obtain an orange powder. And it is characterized by XRD as black bronze (NH4) 0.33WO3 which also contains sixty WO3. Continued calcination at 500 ℃ for 2 hours, the resulting yellow-green product, XRD characterization of monoclinic WO3. In at 400 ℃ with reducing atmosphere calcined APT will obtain blue tungsten oxide. It is a mixture of bronze ATB, WO3, WO2.9, W2.72, W3O other phase composition.

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Tungsten trioxide molecular weight is 231.85, the theoretical density of 7.16g / cm3, insoluble in water, soluble in acid, slightly soluble in HF, soluble in hot alkali, ammonia. Outer electron structure of tungsten is 5d⁴6s², and therefore the compounds may be presented  +2, +3, +4, +5 and +6 valence state, but different valence states coexist kind of this situation often occurs. Tungsten trioxide is the highest price of tungsten oxide. The oxygen content of WO3 is not usually meet stringent stoichiometric ratio so using WO3-X to represent the type. Because there is different degrees oxygen deficiency, making some W6 + ions are reduced to W5 + ions, forming five or six price of tungsten oxide mixed valence state. After studies, in fact, and W5 + W6 + is present in all of the crystalline tungsten oxide. For example: W18O49 (= WO2.72) can be expressed as W86 + W105 + O49 of patterns. Dopting in WO3-X were pentavalent oxides (such as Nb2O5) can make tungsten in the highest valence state. Under certain conditions, it may be the presence tetravalent oxide of tungsten.

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Compare APT and H2WO4 as raw material producing tungsten trioxide (WO3-X) photocatalyst found that different performance WO3-X photocatalyst produce by different materials. After further studies found that different performance WO3-X photocatalyst obtained from different producing methods.

Using solid phase method and the H2WO4 as raw material the production of WO3-X photocatalyst are monoclinic.  Photocatalytic performance influence by temperature was very little. And there have been sixty thousand phase and orthorhombic in the WO3-X which is produced by hydrothermal synthesis method. Oxygen index is 2.50 and photocatalytic performance has been greatly improved. The product of hydrothermal synthesis method 24 hours reaction has highest rate of photolysis. At 365nm ultraviolet light, oxygen production rate arrive at 140umol / L / h O2. However, hydrothermal method, with the reaction temperature, the raw material has undergone transformation which is orthogonal WO3-X • 0.33H2O → sixty thousand WO3-X → monoclinic WO3-X's. Photocatalytic performance will continue to reduce when the WO3-X sixty phase content continue to reduce.

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