Nanometer violet tungsten oxide may be applied for preparing transparent thermal insulation material, such as thermal insulation film for building, cars, and so on. Violet tungsten oxide can also be used in the preparation of nano particle size WC-Co composite powder by spray drying-direct carbonization method. Then, the SEM image of the precursor powder prepared by spray drying is studied. And it was found that:
In the image (a), the powder particle size is 10~100μm; and in the image (b), the powder has an average particle size of 50μm. Spray drying to form spherical precursor powder is based on the spherical skeleton of violet tungsten oxide and carbon source, and the binder of cobalt acetate and water crystallization. The powder contains crystal water. It is non-conductive with smooth surface. And there are a small number of large particles. The damaged particles are mainly concentrated on large particles. The large particles and small particles are bonded to each other under the action of crystal water. And many small grains are formed on the large particles. Cobalt acetate is evenly coated on the surface of violet tungsten oxide, which provides a prerequisite for the preparation of cobalt-coated hollow spherical nano WC-Co composite powder.
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