Ultrafine Yellow Tungsten Oxide Producing Method

Yellow tungsten oxide (YTO) is also named as tungsten trioxide, chemical formula is WO3, mainly used to reduce as tungsten powder or tungsten carbide powder which are raw materials of tungsten alloy and tungsten carbide products, such as producing of cutting tools and dies, also for producing tungsten metal products such as tungsten bar, tungsten wire and tungsten electrode.

Calcinating ammonium tungstate is usually used to produce YTO, but the grain size is too coarse to satisfy current application. So use sodium tungstate decomposing crystalline producing method can obtain ultrafine yellow tungsten oxide. Steps are as follows:

1. Seed crystal preparation. Use organic acid or inorganic acid to adjust sodium tungstate solution with concentrate 45%, pH value 4.0~8.0, after hydrothermal reaction for 12 hours, the precipitation is being filtered, concentrated and crystallized to obtain seed crystal.

2. Material ratio. Add seed crystal into sodium tungstate solution with concentrate 10%~55%, the ratio of seed crystal and sodium tungstate is 1:4.5.

3. Hydrothermal reaction. In high pressure reaction still, mix seed crystal and sodium tungstate solution under 200~220℃，after hydrothermal reaction for 12 hours and cool down to room temperature, slurry is obtained.

4. Filter and clean slurry to obtain filtered material and mother liquor.

5. Calcinating the filtered material under 350℃ to obtain ultra yellow tungsten oxide.

6. Mix the remained mother liquor and filtered material to mother liquor with sodium tungstate concentration 3%~20% and then recycle.

The above method is easy to prepare ultrafine yellow tungsten oxide, the process is shortened, energy cost is saving and reduce environmental pollution, the produced YTO has advantages of fine grain, high purity and stable property.

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