Ammonium Paratungstate Preparing Tungsten Trioxide

Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH₄)₁₀(H₂W₁₂O₄₂)·4H₂O. Its shape is like sheet or needle.

Ammonium paratungstate being calcined in the air can produce tungsten trioxide. During the drying process, water was removed under about 100 degree Celsius. When temperature is above 240 degree Celsius, it turns into ammonium metatungstate. Under 300-350 degree Celsius, it becomes ammonium tungsten bronze. When temperature reaches 400 degree Celsius, hexagonal crystal tungsten trioxide comes into being. Finally triclinic crystal tungsten trioxide forms under 500 degree Celsius.

Calcination temperature and speed also affect the property of tungsten trioxide. The higher the temperature is, the larger the grain size of tungsten trioxide. The heating speed will cause the different superficial area of tungsten trioxide particle. Tungsten trioxide can be used to made tungsten product and shielding matirials which is widely used in industry.



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