2015年7月30日星期四

Ammonium Paratungstate Preparing Blue Tungsten Oxide

In 1950s, tungsten powder is often prepared by tungsten acid and yellow tungsten oxide. In 1960-1970s, America, France, Netherlands and Britain used blue tungsten oxide to produce tungsten powder instead of tungsten acid and yellow tungsten oxide. China started to do the research on blue tungsten oxide in 1970-80s. Tungsten powder property is being affected by a lot of factors including producing method and raw material. When producing super fine tungsten powder, the oxide content of tungsten oxide should be low. When producing fine tungsten powder, oxide content of tungsten oxide should be higher. Thus the producing method of blue tungsten oxide which is of low cost, high property and environmental friendly is under investigation.
Use ammonium paratungstate as raw material, under specific preparing technology and certain temperature, ammonia cracked into hydrogen, ammonium paratungstate is under micro reduction and then blue tungsten oxide is prepared.

Analyzing Blue Tungsten Oxide Appearance


Learning blue tungsten oxide (BTO) phase morphology, size and uniformity, help to improve the performance blue tungsten oxide, so that it can be applied in more areas. To produce blue tungsten oxide is boat loading ammonium paratungstate (APT) to the hot zone and during the process to control the hydrogen flow, temperature and holding time these three parameters to produced blue tungsten oxide.



By using hydrogen reduction method to produce blue tungsten oxide and the surface of it has a large number of cracks and voids star, breakage obviously, it has lost the characteristics of hexagonal grains, forming a loose rule like appearance. Blue tungsten oxide surface has cracks is due to a large amount of water molecules and ammonium molecules which is produced from APT decomposition during the reaction. So the crystal inside of APT will cause inner stress to make crystal lattice mutation, resulting in cracks. At the same time, the external hydrogen to penetrate APT inside promoted deepening and expanding of cracks. Because of this crack APT generating vacancies and in baking time it caused partial intense contractions to make further fragmentation then to produce a fine particle powder.

2015年7月24日星期五

Tungsten Oxide Applications

Tungsten oxide is a kind of tungsten acid anhydride, tungsten acid salts products, including tungsten trioxide and tungsten oxide, and in practical industrial production there is no tungsten oxide product, tungsten oxide is widely used in modern industrial production and processing. Tungsten oxide applications are listed as below:

1.Tungsten oxide is used for many purposes in everyday life. It is often used for industrial X-ray phosphor screen and fireproof fabric manufacturing tungstic acid salt, also used as ceramic and paint in the paint.

2.Tungsten oxide was also used to produce electrochromic window and smart window. The window is automatically switch glass, pervious to light performance and the change of the applied voltage, allows the user to tone their window, through the change of quantity of heat and light.

3.Tungsten oxide is used in the production of chemical products, such as paint and coatings, and catalyst in the oil industry. But oxide is a kind of intermediate products, a large number of tungsten oxide is used for metal tungsten powder and tungsten carbide powder, and then used in the manufacture of metal tungsten products in the production, application and production of tungsten alloy products, and a large number of the tungsten copper, nickel, tungsten, tungsten nickel iron, silver, tungsten rhenium tungsten and tungsten thorium, etc., while the most widely used in the industrial field is tungsten base material in the production of various grades and by way of cemented carbide products.



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2015年7月16日星期四

Blue Tungsten Oxide

Tungsten oxide (W2O3) is a compound of tungsten and oxygen. It has beenreported (2006) as being grown as a thin film by atomic layer deposition at temperatures between 140-240 °C using W2(N(CH3)2)6 as a precursor. It is not referred to in major text books e.g. Some older literature refers to the compound W2O3 but as the atomic weight of tungsten was believed at the time to be 92, i.e approximately half the modern accepted value of 183.84 the compound actually being referred to was WO3.
Blue tungsten oxide is is also called tungsten blue oxide (TBO). It is used primarily for the production of tungsten metal power and tungsten carbide. The formula of blue tungsten is H0.5WO3. Blue tungsten oxide is finely divided blue-violet crystalline powder and it is produced by rotary calcining ammonium paratungstate at closely controlled temperatures in a reducing atmosphere. And we usually use APT to manufacture it by calcination. Blue tungsten oxide paly an important role in the line from oxide to W and WC powder. The color varies between deep dark blue to blue,faint blue and green blue. Also the TBO particles are pseudomorphous to the original APT crystals, as described for tungsten trioxide. It is not a chemically defined compound, but consists of various different constituents, like trioxide, tungsten bronzes and different lower tungsten oxides. The relative amount of these compounds in TBO depends on the calcination parameters.

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