Preparation of Intelligent Equipment for Vanadium Dioxide Doped Tungsten Powder
- Details
- Category: Tungsten Information
- Published on Wednesday, 25 October 2017 17:05
Among the vanadium oxides, two vanadium oxide is distinguished by its rapid and abrupt phase transition, and its phase transition temperature is 68 °C.
The reversible change from low temperature monoclinic system to high temperature tetragonal system leads to great changes in physical properties such as resistivity, optical transmittance, permeability and so on. This feature makes it very promising in intelligent switches, electronic devices and optoelectronic devices.
However, in daily life, the application temperature of 68 degrees is still too high, so it is necessary to reduce the VO2 phase transition temperature, so that VO2 can be widely used. In recent years, many studies have shown that doping of other elements in VO2 can effectively reduce its phase transition point. Especially the high valence metal ions, such as MO6+, W6+ and so on, doping effect is particularly significant.
The amount of ammonium metatungstate was mixed with vanadium oxide by hydrothermal method. According to the molar mass ratio of tungsten ion to VO2 of 0%, 1% and 2%, a certain amount of ammonium metavanadate and ammonium metatungstate powder, successively added to the 40mL deionized water, stirring on the magnetic stirrer, a certain amount of oxalic acid (and ammonium vanadate molar ratio 1.5: 1) as a reducing agent. When the solution is added into the solution, the liquor is mixed with red wine, and the mixed solution is transferred to a reactor lined with polytetrafluoroethylene in 100 mL, and the filling degree is 60%, In the drying box under 180 DEG C for 24 h insulation, get powder black precipitate, removed and cooled to room temperature, using deionized water and anhydrous ethanol by centrifugal washing 3 times. Then after centrifugation sediment in Petri dish, and the dish is put in a drying box, heat 8 h into dry powder under 80 degrees, with agate mortar grinding. The dried powder is placed in the porcelain boat and placed in the quartz tube. In the quartz tube through the argon, the gas flow rate of 15 mL / min, at 600 °C for 6 h. With the furnace cooled to room temperature, to be doped with different molar mass of tungsten ions than the vanadium dioxide powder.
The test results show that the phase transition temperature of W doped VO2 powders decreases with the increase of tungsten doping content. When the doping amount of tungsten increases from 0% to 2%, the phase transition temperature decreases about 12.5 degrees when the doping content increases by 1%, and the phase transition temperature of the powder decreases to 43.17 degrees when doping 2%, and the phase transition temperature is close to the daily temperature. Among the vanadium oxides, two vanadium oxide is distinguished by its rapid and abrupt phase transition, and its phase transition temperature is 68 degrees centigrade.
The reversible change from low temperature monoclinic system to high temperature tetragonal system leads to great changes in physical properties such as resistivity, optical transmittance, permeability and so on. This feature makes it very promising in intelligent switches, electronic devices and optoelectronic devices.
However, in daily life, the application temperature of 68 degrees is still too high, so it is necessary to reduce the VO2 phase transition temperature, so that VO2 can be widely used. In recent years, many studies have shown that doping of other elements in VO2 can effectively reduce its phase transition point. Especially the high valence metal ions, such as MO6+, W6+ and so on, doping effect is particularly significant.
The amount of ammonium metatungstate was mixed with vanadium oxide by hydrothermal method. According to the molar mass ratio of tungsten ion to VO2 of 0%, 1% and 2%, a certain amount of ammonium metavanadate and ammonium metatungstate powder, successively added to the 40mL deionized water, stirring on the magnetic stirrer, a certain amount of oxalic acid (and ammonium vanadate molar ratio 1.5: 1) as a reducing agent. When the solution is added into the solution, the liquor is mixed with red wine, and the mixed solution is transferred to a reactor lined with polytetrafluoroethylene in 100 mL, and the filling degree is 60%, In the drying box under 180 DEG C for 24 h insulation, get powder black precipitate, removed and cooled to room temperature, using deionized water and anhydrous ethanol by centrifugal washing 3 times. Then after centrifugation sediment in Petri dish, and the dish is put in a drying box, heat 8 h into dry powder under 80 degrees, with agate mortar grinding. The dried powder is placed in the porcelain boat and placed in the quartz tube. In the quartz tube through the argon, the gas flow rate of 15 mL / min, at 600 °C for 6 h. With the furnace cooled to room temperature, to be doped with different molar mass of tungsten ions than the vanadium dioxide powder.
The test results show that the phase transition temperature of W doped VO2 powders decreases with the increase of tungsten doping content. When the doping amount of tungsten increases from 0% to 2%, the phase transition temperature decreases about 12.5 degrees when the doping content increases by 1%, and the phase transition temperature of the powder decreases to 43.17 degrees when doping 2%, and the phase transition temperature is close to the daily temperature.
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