Violet tungsten oxide, abbreviated as VTO, is named after the appearance of purple. It is the best raw material for the preparation of ultrafine or nanometer tungsten powder.
It is produced in the process of producing ammonium paratungstate under the condition of precise control of temperature reduction. Violet tungsten oxide is mainly used in the production of tungsten powder and tungsten carbide.
Violet tungsten oxide sample color can be divided into purple, dark purple, dark blue, blue, the color of violet tungsten oxide and its oxygen index, particle degree of tightness, the aspect ratio of the needle.
Some scholars have invented a way to directly control and detect the quality of violet tungsten oxide. The quality of purple tungsten oxide is determined by the unique color of violet tungsten oxide. This method is called "colorimetric method" in the industry.
The color of violet tungsten oxide is related to the oxygen index, the degree of tightness of the particles and the ratio of length to diameter of the needle. A type of violet tungsten oxide is purple, oxygen index is slightly higher and needle is slightly elongated; B violet tungsten oxide is purple red, and the needle is slightly shorter and slightly thicker. A, B class basically maintained the needle-like morphology of violet tungsten oxide, but there are some small particles are not acicular; Category C violet tungsten oxide is black, the needle is severely shrunk and begins to transform into WO2; D and E are produced abnormally, the color of different particles can be seen with a microscope, and the morphology of the sample is also different by scanning electron microscopy.
By colorimetric method, it is found that the quality of violet tungsten oxide with purple and purple color is the best, and the quality of purple black is slightly worse. If it appears purple blue or blue, it has basically declared failure.