Nitrogen-Doped Impact on Tungsten Trioxide Structure

Doping is an important method to improve the efficiency of light energy conversion of photocatalytic material. Numerous of studies show that the rare earth and metal ions by doping can significantly enhance the catalytic activity of the photocatalyst, however, it may lead the stability of metal-doped catalysts thermal to decrease and the introduction of photo-generated electron and hole recombination centers to reduce its optical conversion efficiency. Some non-metal-doped semiconductor material may improve their stability, electrical conductivity, and pass through between the conductive and leave with the formation of "middle level" and to improve the material efficiency of absorption of visible light.Sol-gel - ammonia oxygen atmosphere firing method

Numerous of studies show that, the N-doped can significantly improve the absorption efficiency of TiO2, ZrO2, Ta2O5 and other semiconductor materials belong to visible light, the n-type semiconductor, the same can be improved by N-doped WO3-x of visible light absorption efficiency.

The nitrogen (N) doped tungsten trioxide photocatalyst (WO_ (3-x): N) is prepared by Sol-gel - ammonia oxygen atmosphere firing method. The structural properties of the samples were characterization and analysis by using SEM, XRD, XPS and DRS, comparing the experimental study of nitrogen doping on the tungsten trioxide photolysis aquatic oxygen catalytic activity. The results show that NH_3 / O_2 was mixed atmosphere at 500 ℃ , sintering it 3h , doping N, when N enters tungsten trioxide lattice, it does not change WO_ (3-x) polymorphs and morphology. WO_ (3-x ): N remains monoclinic crystal structure, and are a small amount of an unknown sample new phase that causes thinning size and lattice distortion increases while doping surface W ~ (4+) powder and increase the oxygen vacancy. Certain lattice defects and oxygen vacancies are in favor of catalyst response wavelength red shift. The rate of N average oxygen evolution reaches 66.8μmol / (L • g • h) under UV irradiation 12h, while the rate of photolysis under visible radiation water increase to 24.5% than non-doped sample.

 

Scheelite and Wolframite Mixture Ore and Shizhuyuan Method

Improvement of Shizhuyuan Method
In the national science and technology research of the 8th and the 9th Five-Year Plans, the joint research by the Shizhuyuan Nonferrous Metals Company, Beijing General Research Institute of Mining and Metallurgy, Guangzhou Nonferrous Metal Research Institute, Changsha Nonferrous Metallurgy Design and Research Institute, and other units, is proposed comprehensive new technology beneficiation - Shizhuyuan Method with all float process as the basis and chelation collector flotation as the core, which is the combination of molybdenum and bismuth flotation, bismuth and sulfur mixed election, scheelite and wolframite mixture ore flotation, coarse-grained ore heating selection and wolframite slimes flotation.
 
Successful research of Shizhuyuan Method, made Shizhuyuan Nonferrous Metals Company instantly built and began production for two large-scale concentrators, so that this company became the tungsten ore business with the largest production scale of tungsten mine and the best economic benefits.
 
After ten years of research in science and technology formed the basis of Shizhuyuan Method, currently Shizhuyuan beneficiation technology have a major breakthrough, the first time that use "high gradient magnetic shunt scheelite and wolframite mixture ore - scheelite and wolframite mixture ore flotation respectively" magnetic - floating and floating - magnetic sorting of new technology to replace the original all float process technology, to achieve harmonious, efficient sorting of low-grade scheelite and wolframite mixture ore, and created favorable conditions for the next step of fluorite and garnet comprehensive recovery . Industrial production results showed that the process makes tungsten comprehensive recovery rate increase 5-10%.

scheelite and wolframite mixture ore

 

Tungsten Copper Electrode and Other Materials Comparison

Tungsten copper powder sintered material having high hardness, high density, high strength, wear resistance, adhesion, excellent electrical and thermal conductivity as well as sweating characteristics, making it ideally suited to withstand high stress resistance welding electrode matching, or as automatic submerged arc welding, carbon dioxide CO2 gas shielded arc welding tip conductive or conductive plate. Tungsten copper flash welding electrode and chromium-copper comparison as follow:

tungsten copper electrode








 

From the table we can see that tungsten copper chromium copper compared to flash welding electrode welding electrode flash at the same working hours, higher welding efficiency, the amount of wear smaller, better weld quality, lower cracking rate life more long, the application is more convenient, and therefore wide range of applications. Vertical automatic welding, soldering conditions when the thickness of 22-28mm, wire directly Φ2.4mm, conductive nozzle aperture when 2.8mm, tungsten, copper and chromium copper conductor conductive nozzle tip wear after welding is very different.

Tungsten copper conductive tip after welding 20m, the aperture remains the prototype, you can still continue to work, in contrast, chromium copper conductive soldering tip less than 2m, its conductivity unilateral eccentric bore wear, maximum diameter enlargement ratio of tungsten copper conductor increases 0.6mm, has been unable to proceed with the welding work. Therefore, resistance welding electrodes and welding conductor tungsten copper powder sintered material having a high hardness, high density, high strength, wear resistance, adhesion, excellent electrical and thermal conductivity and a series of advantages, which has a broad prospect.

Detinning Process of APT Production- Controlling the Alkali Decomposition Conditions

Usually the alkali decomposition conditions for wolframite are: alkali concentration of 500 g / L, the base amount of the theoretical amount of 160, reaction time of 4h, each batch of wolframite 1 t. In the various process conditions of alkali decomposition, such as temperature, time and alkali concentration, the temperature has the greatest impact on the leaching rate of tin. In normal decomposition conditions, tin leaching rate increased with temperature increasing and the increase rate is much faster than the increase rate of tungsten leaching rate, the reason of which is the leaching reaction of tin is more inclined to thermodynamically controlled than tungsten. So the production often needs making a balance between the decomposition rate of tungsten requirements and product quality requirements of different minerals to determine the optimum reaction temperature. At this temperature, the low leaching degree of tin and high leaching rate of  tungsten achieves the best combination.
 
However, this detinning process is mainly carried out at high temperatures (160 ~ 170 ℃), because temperature changes have little effect on the leaching rate of tin at low decomposition temperature. Thus, for the atmospheric mechanical agitation leaching process of caustic soda, because the temperature is low (only 105 ~ 110 ℃), this detinning process is not meaningful then.

New Technology of Tungsten Copper Electrode—Microwave Infiltration

Actually, microwave infiltration is one of new methods, which combines microwave sintering with traditional infiltration. It has many advantages, such as selective heating (the coupling ability of material and microwave, the ability of microwave absorption is related to the properties of itself, such as electrical conductivity, magnetic conductivity and dielectric constant, which will get diverse heating properties when the material is different in a given microwave field. ), volume heating (Each portion of the object in the portion of the material is heated after the heat acquired, so that the part of the material temperature rises.), non-thermal effect (It general refers to compared with traditional sintering under the same thermal dynamic conditions has remarkable superiority in physical, such as the active sintering of powder material and atomic diffusion rate.) , and uniform structure of infiltration processing. Therefore, microwave infiltration has higher speed of increasing temperature, shorter sintering time, higher energy utilization ratio and uniform structure or excellent properties of the products. Microwave infiltration of microwave sintering equipment is produced by DC magnetron microwave waveguide by introducing the heating chamber, the sample is placed in the cavity is heated sintering. The sketch of structure of the equipment as follow:

tungsten copper electrode

The major technical parameters of microwave sintering furnace includes work area, the highest working temperature, thermometric, methods, the range of infrared detection, the precision of temperature control, the out power of microwave, vacuum limit of furnace, the leaking of microwave. At present, the use of microwave sintering heating chamber includes a resonant and non-resonant two, while the cavity can be subdivided into single-mode and multi-mode resonant cavity resonator. Under the same electromagnetic power, single-mode resonant cavity having a stronger magnetic field strength is more suitable for low heating medium. The multimode resonator having multiple resonant modes, the electromagnetic field distribution is more uniform, the structure is relatively simple, suitable for a variety of heating load, the more it is difficult to accurately analyze the data.

 

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