Cesium tungsten bronze is an important compound of the transition metal tungsten. Its molecular formula is Cs0.33WO3. It has a crystal structure similar to that of tungsten bronze, which is an oxygen octahedral structure. It has the characteristics of good performance, and has excellent near-infrared absorption characteristics, weather resistance and low-temperature superconductivity. In terms of optical performance, Cs0.33WO3 powder has a blocking rate of up to 95% in the near-infrared region and a light transmittance of 70% in visible light. Currently, citric acid-induced hydrothermal synthesis and solvothermal liquid phase methods are often used to prepare the chemical.
Needle-shaped purple tungsten oxide (VTO), as its name implies, is an oxide of tungsten, and its molecular formula is WO2.72 or W18O49. In addition to being different from other tungsten oxides in color, its particle shape is also very different, that is, violet tungsten particles The shape is needle-like or rod-like, and the shape of the rest of the tungsten oxide is nearly spherical. Violet tungsten powder has remarkable surface effect, quantum size effect and small size effect due to its unique particle shape, and the blocking rate of ultraviolet rays can reach 98%-99%, so it is suitable for use in energy-saving films. At present, the compound is often prepared by closed calcination method of tungsten trioxide, hydrogen reduction method of ammonium paratungstate and direct synthesis method.
As a typical oxide of non-ferrous metal tungsten, acicular violet tungsten particles are finely divided purple tungsten oxide powder crystals, which are popular in many fields because of their excellent physical and chemical properties. In addition to being an important raw material for tungsten products such as metal tungsten powder and tungsten carbide powder, violet tungsten is also an important additive for products such as energy storage electrodes, photocatalysts, shielding materials, resistor components, dimming glass and energy-saving films.
A preparation method of a high-purity homogeneous acicular purple tungsten oxide powder comprises the following steps: raw material preparation, uniform high-purity single-crystal ammonium paratungstate crystals are obtained, raw material pretreatment, and then ammonia gas is introduced. The total amount of impurity elements in APT should be controlled below 60ppm, so that violet tungsten powder with better physical and chemical properties in all aspects can be produced, such as single phase, large specific surface area, good fluidity, and the content of impurity elements K and Na are lower than 1ppm etc. By controlling the particle size composition of high-purity single crystal ammonium paratungstate raw materials, it is more beneficial to control the morphology and uniformity of subsequent purple tungsten, ultra-fine tungsten powder and ultra-fine tungsten carbide powder.
In addition, the process of preparing violet tungsten powder by high-temperature micro-reduction of high-purity single-crystal ammonium paratungstate in a rotary furnace has the characteristics of simple operation. During the reaction process, ammonia replaces hydrogen for reduction, which is beneficial to control the atmosphere of micro-reduction and eliminate the safety hazards brought by hydrogen.
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