Tungsten has three kinds of stoichiometric oxide which are WO2, W2O5 and WO3. WO3 has many isomers which possesses good electrical and optical property. It has been widely applied in the fields of manufacturing optical devices, electrochromic smart window, field emission display, gas sensor, humidity and temperature sensor, catalyst, solar photovoltaic chemical cell and water separation hydrogen production.
Tungsten is a transmission metal, with partial recovery of WO3, it has W-O Magneli phase substoichiometric ratio tungsten oxides such as W32O54(WO2.625), W3O8(WO2.667), W18O49(WO2.722), W17O47(WO2.765), W5O14 (WO2.8), W20O58 (WO2.9) and W25O73 (WO2.92).
Tungsten oxide WOX(X=2.625~3) has drawn attention of many researchers due to its special chemical and physical properties such as electrochromic, photochromic, catalytic activity, super conductivity and large loading capability. High currency stability of carbon loading material has becoming problems that people are encountering. So they are now focus on preparing of nano low dimension transmission metal W-O Magneli tungsten oxide as catalyst carrier for fuel cell electrode.
Ultrasonic disperse tungsten hexafluoride into anhydrous N-butanol, using 150ml anhydrous N-butanol for per gram of tungsten hexafluoride. Stop ultrasonic process when the system turns from yellow to blue. Then add sodium nitrate, the amount is 1.53 times of WF6. Load the mixing system into the reactor, the reaction temperature is controlled at 180-220°c, reaction time is 6-12 hour. And the product is washed, centrifuged and dried by water and ethanol after the reaction is cooled to room temperature, and the white W18O49 powder is obtained.
Advantages of this method:
Adding sodium nitrate to modify the surface of tungsten oxide can obtain white tungsten oxide, which is significantly different from the conventional preparing method. It has more excellent proeprties: It can change to blue under the irradiation of ultraviolet light, and can be resotred to the original white after the light disappeared. It can be used in smart glass and heat insulation membrane industry.
