Tungsten Oxide

Halotungstate is a kind of tungstate which is mainly composed of oxyhalide, it is a new type of visible light response photocatalyst. In alkaline earth tungstate, the luminescent intensity of barium tungstate is very weak. Therefore, people try to modify its structure. In 1982, domele and others synthesized barium tungstate with BaF 2  and WO 3  as raw materials. Ba 2 WO 3 F 4  is a kind of halotungstate. Through the improvement of its structure. It has been found that ba2wo3f4 has strong fluorescence intensity and strong blue-green luminescence under UV excitation. It can be developed into practical UV and X-ray luminescent materials. It has also been found that the rare earth tungsten composite halide oxide, which is made by the preparation of the halide tungstate, can glow stronger luminescence performance. For example, the study of lawo4cl shows that it has a strong absorption of X-ray, and its absorption wavelength is just within the range of medical usefulness. It is suitable fo

Sodium hydroxide decomposition is the main process for tungsten mineral raw materials. In the alkaline system, phosphorus, arsenic, silicon, molybdenum, tin and other elements contained in the mineral are leached to varying degrees and become the main impurities in the crude sodium tungstate solution. Some scholars have found that when sodium hydroxide decomposes tungsten ore, the calcium content of raw materials is beneficial to inhibit the leaching of impurities such as phosphorus, arsenic and silicon, and the leaching rate of these impurities decreases with the increase of calcium content. The results show that the oxy acids of phosphorus, arsenic and silicon can form insoluble compounds with calcium, and these precipitates can still exist stably under the condition that scheelite has been decomposed. Because of this, in the purification process of crude sodium tungstate solution, adding appropriate amount of Ca(OH) 2  can also remove the above three impurities. The precipitation ra

Cadmium tungstate (CdWO 4 , CWO) single crystal is a scintillation crystal material with excellent comprehensive properties, which can be widely used in nuclear medicine imaging, safety inspection, industrial CT, oil logging, high energy physics and other technical fields, especially in medical X-CT, container inspection system. Up to now, it has been reported that the single crystal of cadmium tungstate has been grown by Czochralski method at home and abroad. It is very difficult to grow high-quality large-scale cadmium tungstate single crystal. The main problem is that the optical transmittance of the grown single crystals is not uniform at the beginning and the end, the repeatability of the single crystals grown in different batches is poor, and there are many crystal defects such as cracking, inclusions, color centers, etc.  In view of the technical problems existing in the current Czochralski growth of cadmium tungstate single crystal, a transparent and complete CdWO 4  single cr

Theoretically, many of the carriers found at present can be used as the carriers of tungstophosphoric acid, but most of them use oxidants as the carriers of oxidants or are easy to decompose when alkali is azeotropic. At present, SiO 2 , HZSM-5 molecular sieve, Y-type molecular sieve, HP, HMS molecular sieve, worm like molecular sieve, activated carbon, silica gel and so on are the main carriers of phosphotungstic acid catalyst. At present, the main preparation methods of phosphotungstic acid include impregnation method, adsorption method and sol gel method. 1. Impregnation method The impregnation method is to dissolve tungstophosphoric acid in water, then impregnate the carrier with this solution and stir it. After a certain period of time, take it out for drying, and then obtain the supported tungstophosphoric acid catalyst. Or the active component is directly loaded on the carrier by physical mixing, hydrothermal dispersion, CO impregnation or ion exchange. However, there are some p