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...

  With the development of high and new technology, the requirement of pure tungsten and its alloy material is higher and higher. There are many methods to prepare   tungsten powder , and spray drying is one of the most important methods. The spray drying method or chemical synthesis method, it is a method of physical and chemical solution atomization obtain ultrafine particles through physical means of combining the process, including the original solution was prepared with solution blending, mixing, spray drying and subsequent processing.  In recent years, the influence of nozzle structure, spray drying speed and temperature on particle size has attracted extensive attention. It is found that the concentration of precursor solution plays an important role in the morphology and particle size of ultrafine tungsten powder during ultrasonic spray drying. In order to prove this theory, some scholars have used 2 different concentrations of ammonium tungstate solution to spray ...

The preparation of tungsten powder from APT is usually calcined in the weak reducing atmosphere to produce yellow tungsten, blue tungsten or purple tungsten. Then, the reduction of hydrogen to produce tungsten powder is a commonly used method in industry. The tungsten powder prepared by this process is a kind of very regular polycrystal, which is the main raw material for preparing tungsten alloy and tungsten carbide. But some scholars believe that the traditional process is long, easy to bring in impurities, production costs are relatively high, so he proposed a step through tungsten oxide process, the direct preparation of tungsten powder from ammonium paratungstate one step reduction method. The main process of one-step reduction method is as follows: 1. In the first step to control the formation of the intermediate of blue tungsten, a certain proportion of hydrogen and nitrogen mixed gas is replaced into ammonia in the reduction furnace. 2. Loading the amount of 50g, hydrogen flow ...

Ultra coarse tungsten powder is an important raw material for the preparation of ultra coarse tungsten carbide. Compared with ultrafine tungsten powder, it has a series of advantages, such as less high-temperature defects, higher microhardness and smaller micro strain. The common process of reduction of ultra coarse tungsten powder by ammonium paratungstate is usually the reduction of ammonium paratungstate into blue tungsten or yellow tungsten, and then by hydrogen reduction furnace. The tungsten powder prepared by this method is regular polycrystalline, and the particle size is mostly controlled between 2 microns and 5 microns, and the powder size is moderate. In order to prepare ultra coarse tungsten powder, Li or Na was added to tungsten oxide, as far as the average degree of tungsten powder is concerned, the process of adding Li to ammonium paratungstate is the most effective, but there is a large amount of residue in the powder; At the same time, studies have shown that adding a ...

EDTA is a highly effective chelating agent. It has been widely used in chemical analysis, electroplating, medicine, industrial washing products, photographic products and other industries. Unfortunately, EDTA can chelate with Mg 2+ , Ca 2+ , Mn2+, Cu 2+ , Fe 2+  and other 50 kinds of metal ions to form water soluble chelates, especially the formation and some toxic metal ions is harmful and difficult from the material, excellent stability, will cause heavy metal diffusion, thus adding heavy environmental pollution. Due to the stability of chelating agents, the degradation of EDTA is more difficult than traditional treatment methods, so bismuth tungstate photocatalyst has become a hot choice again. The fact that bismuth tungstate is can play a big role, especially in the petal like Bi 2 WO 6 , visible light catalytic activity is high, can split water to produce oxygen and organic matter degradation, is a kind of photocatalytic agent ideal for environmental pollution control.  ...

Four hydrogen sulfide is a chemical intermediate of nitro spray paint, rubber and other solvents, so is often used in the protection of hydroxyl groups. The catalysts, Lewis acid and ion exchange resin used in the preparation of the four - hydrogen catalyst, all of which have good catalytic effect. However, there are some shortcomings in these methods, such as longer reaction time, reflux, solvent, complex catalyst preparation procedure and unsatisfactory yield. Phosphotungstates have copper phosphotungstic acid , zinc phosphotungstate and aluminum phosphotungstate. As a kind of heteropoly acid salts, phosphotungstates are widely used as catalysts. It has been proved by experiments that the catalytic activity of phosphotungstic acid for the catalytic hydrogenation of four hydrogen peroxide is better than that of the four hydrogenation of alcohol, thus, a green environmental reaction route is provided for the four hydrogen alkylation reaction better than other methods. The results show ...

Chlorothalonil is an efficient fungicide absorbed in organic pesticide, organic compounds but it is also easy to cause pollution of soil. In the process of agricultural operations, the land often contains chlorothalonil which is difficult to degrade, not only the soil ecological structure is affected, but it is often washed by rainwater to enter the river or infiltrate the ground water, causing serious pollution. In recent years, with the tungsten based photocatalyst for environmental, economic, effective and has become a new method for the treatment of organic wastewater, some scholars have found that most of the organic pesticides is easily degraded and mineralized into H 2 O and CO 2  and other small molecules, so the photocatalytic degradation of chlorothalonil is feasible. . Tungsten photocatalysts mainly consist of tungstate and tungsten heteropoly acids, the commonly used method is to use a combination of loading and photocatalyst to form a new composite preparation for ph...

Bismuth tungstate (Bi 2 WO 6 ) is the most common Aurivillius type oxide and is a hot spot in the field of photocatalysis. Most of the traditional photocatalytic reactions are carried out in the suspensions of bismuth tungstate catalyst powders. Although they have high photocatalytic activity, bismuth tungstate powders are easy to agglomerate and difficult to separate and recover. In practice, it was recognized that some measures had enabled bismuth tungstate to work, and some scholars had thought of loading bismuth tungstate onto the cloth. Of course, loading bismuth tungstate on cloth is not a simple mix, and it also requires a series of chemical procedures that combine bismuth tungstate with cloth to function. Acrylic, polyester fiber and so on, have the same effect at last, and their main difference is synthetic method. Some scholars used polyester as the carrier of bismuth tungstate and prepared them by hydrothermal method, the polyester fabric was treated with acetone and eth...