Tungsten Oxide

Tungsten powder is the basic raw material for making cemented carbide. Most of the cemented carbides in the market do not have much demand for the size of tungsten powder, but they have strict requirements for the particle size uniformity of tungsten powder. A new method of ammonium tungstate cyclic oxidation reduction method proposed in recent years for producing submicron tungsten powder, it is mainly through a number of ammonium tungstate - tungsten oxide circulation change, submicron tungsten powder and ultimately the average particle size. Therefore, we can also try to use circulating oxidation reduction method to help the common tungsten powder to achieve particle size rebalancing. It is necessary to prepare blue tungsten for reduction of tungsten powder because of the preparation of ordinary particle grade tungsten powder. The general process of ammonium tungstate cycle oxidation reduction method is: the special pure ammonium paratungstate in argon to slowly raise the temperatur...

At present, the industrial production of pure tungsten trioxide or APT is mainly purify the crude sodium tungstate solution. Ammonia purification of a thermal dissociation method is the South China University of Zhang Qixiao et al in the early 21st century proposed purification of ammonium arsenate solution method, it can be achieved by the crude ammonium tungstate solution directly prepared high purity tungsten trioxide. The use of ammonia purification heat from the main base of high pure tungsten trioxide solution is directly preparing high purity tungstic acid (H 2 WO 4 ), the quality of H 2 WO 4  directly affects the quality of the final product and cycle times. The process of ammonia purification by thermal dissociation is: 1.The pulp industry H 2 WO 4  slowly adding ammonia, WO 4  will dissolve (NH 4 )  2 WO 4  solution, and silica, crude H 2 WO 4  of ferric hydroxide, manganese oxide and calcium tungstate are reserved for ammonia dissolution in slag....

Paratungstate B guanidine salt precipitation method is a method for separating molybdenum and tungsten. It is known that there are three kinds of orthopolyacids, namely, paratungstic acid A, paratungstic acid B, paratungstic acid Z, the structure of B is the most special, and its chemical formula is Na 10 [H 2 W 12 O 42 ], containing two H atoms, so the selectivity is strongest. The key point of B guanidine precipitation method is how to convert A into B. Scholars have found that SiO 2  has a significant catalytic effect on the transition reaction, and can shorten the conversion process to a few hours, which makes the feasibility of B guanidine salt precipitation method. After the conversion of sec-tungstic acid A to paratungstic acid B, the pH of the solution was increased from 6.7 to 8.1, ensuring that Mo 4 2-  could be polymerized in a large concentration range, in order to use guanidine salt precipitation agent can effectively separate and in suitable conditions of pH tun...

Tungsten powder is mainly used to manufacture tungsten filament for incandescent lamp, inert gas shielded arc welding and atomic hydrogen welding electrode etc.. Submicron tungsten powder has the advantages of fine particle, well-developed surface, high activity, it is not as stringent as the preparation of nano tungsten powder, and the application range is better than ordinary tungsten powder, so the application scope is more and more widely.  There are many main methods for preparing submicron tungsten powder at home and abroad: they are high-energy ball milling, dry atmosphere reduction, violet tungsten hydrogen reduction, molten salt electrolysis and plasma technology, etc. There are still many shortcomings in the preparation of submicron tungsten powder, such as time consuming, energy consumption, low production efficiency, high production cost, and difficult to realize industrial production. So the next to introduce an innovative submicron tungsten powder preparation method ...

In recent years, tungstate catalysts have attracted more attention for their narrower band gap and larger visible light range. Zinc tungstate (ZnWO 4 ) is a very representative tungstate material. As an efficient photocatalyst, ZnWO 4  has excellent catalytic activity, good stability, low energy consumption and no secondary pollution, it has a wide range of applications in environmental protection, water treatment and many other fields. But inevitably, zinc tungstate, like bismuth tungstate, titanium dioxide and other photocatalysts, is easy to agglomerate and difficult to recover in practical applications, therefore, searching for an effective carrier is an effective way to improve photocatalytic performance and reduce the amount of zinc tungstate. Bamboo charcoal is a three-year-old alpine bamboo as raw material, by nearly 1000 degrees high temperature firing from a charcoal. Bamboo charcoal has porous and porous structure, its molecule is fine and porous, the raw material is ea...

  Many scholars have tried new methods to reduce production cost. The direct synthesis of tungsten cobalt alloy powder from ammonium metatungstate is an innovative attempt. By ammonium metatungstate direct synthesis of WC-CO powder the process is roughly using ammonium metatungstate (APT), soluble cobalt salt and organic carbon source as raw materials, using spray conversion method, preparation of tungsten cobalt precursor by direct carbonization in situ synthesis method, the precursor for WC-CO carbide composite powder. The technology greatly simplifies the process of traditional technology, the cost is also reduced in theory. Some scholars using the preparation of ammonium metatungstate by AMT (WO 3 >92.5%), soluble cobalt salts and ultra pure organic carbon as raw materials, according to the wc-6% (mass fraction) CO composition prepared tungsten cobalt mixed solution, and then the preparation of tungsten cobalt precursor powder in spray drying tower, calcined in N 2  at...

High purity quaternary ammonium paratungstate (APT) is a crystalline powder of ammonium paratungstate with a purity of 99.999% to 99.9999%. At present, the methods of producing high purity APT by controlling impurity content in industrial production are: re dissolution method, ion exchange method, ammonium tungstate method, electrolysis method, recrystallization method, etc.. But because of the different chemical properties of impurity elements, using only one method to achieve the purpose of removing all impurities, so the preparation of high purity APT often need two times of ion exchange, activated carbon adsorption and other means of further purification. It is found that the following three problems should be paid attention to during the purification of high purity ammonium paratungstate (APT). (1). The higher the crystallization rate, the higher the impurity content in APT crystallization. When the crystallization rate is more than 65%, the precipitation of impurities is accelera...

Tungsten trioxide is a transition metal oxide, with a semiconductor character, has great potential for gas-sensitive materials, sensitive to a variety of gases, especially toxic gases. In recent years, with the emergence of nanotechnology, it was found that nano-tungsten trioxide has a higher sensitivity and response speed. There are three main methods for preparing nano tungsten trioxide, gas phase method, liquid phase method and solid phase method. In general, hydrothermal method has become the most widely used method for the preparation of nano WO 3  by virtue of its economical, low cost and easy operation. Commonly used to produce gas-sensing elements of tungsten trioxide mainly nanorods, nano-plate, nano-plate rod-like mixed structure and other forms, as will eventually become what form, are generally in the process of hydrothermal synthesis by adjusting the parameters formed by the results, therefore, even with the same hydrothermal method of nano-tungsten trioxide, often be...