Nanosize Tungsten Trioxide Produced by Electro-Pyrolytic from Ammonium Paratungstate

Tungsten trioxide (WO₃) is yellow powder, a kind of important tungsten oxide, also known as yellow tungsten oxide. At present, it’s mainly used in the manufacture of tungsten powder (W) and tungsten carbide powder (WC). The main final products of WO₃ are tungsten rod, tungsten wire and tungsten carbide and so on. In order to obtain WO₃ with better chemical activity, and meet the demand of special alloy with superior properties, we propose a new method--Electro-Pyrolytic to prepare nanosize tungsten trioxide.

Equipment: electromagnetic stirrer; evaporator; drying equipment; grinding equipment; crucible.
Reaction materials: high purity of ammonium paratungstate (APT) with size about 5 μm, purity greater than 99.9%; distilled water; citric acid; ammonia; oxygen.

Specific steps as follows:
1. Adding distilled water into the reaction vessel, and use electromagnetic stirrer for mixing, adding citric acid solution with stirring;
2. When the citric acid solution and distilled water are mixed evenly, adding high purity of APT with stirring, the molar ratio of APT and citric acid is 1:3;
3. Adding ammonia with concentration of 30% to APT solution, stirring at the speed of 180-200r/min;
4. Place the reaction solution in the evaporator to concentrate, drying the concentrated liquid in the drying equipment at the temperature of 150~160°C, and then get the precursor;
5. Precursor grinded in the grinding equipment, heating it in a crucible with oxygen, finally gets nanosize tungsten trioxide. Calculate the flow of oxygen at each gram of precursor for 50-60ml/min, heating temperature for 500~520 °C, time for 1.2~1.5h.

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