Tungsten Oxide

  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.  ...