Nano Tungstate Preparation by Sol-Gel Method
Sol-gel method is first used for glass and ceramic production, it refers to metal inorganic compounds, metal organic compounds or a mixture of the two under the action of surfactants.
The process of preparing tungstate by the process of sol-gel and drying, roasting and other heat treatment process. Modern sol-gel method is mainly used to prepare nano film coating, for example, in optical field, some kind of optical film (such as high reflectivity film, low reflectivity film and waveguide film) is often needed. Sol-gel method can prepare nano tungstate by controlling the temperature, colloid composition, particle size of precursor and pH value in liquid.
The advantage of sol-gel method is that: 1. The chemical homogeneity is good. Because the sol is prepared by the solution in the process of sol-gel, the chemical composition between the colloidal particles and the colloidal particles is exactly the same. 2. High purity; 3. Particle size is less than 0.1 um. 4. This method can accommodate the insoluble fractions and pellet fractions, after gelation, insoluble components can be naturally fixed in the gel system.
In view of the above advantages, sol-gel method is widely used in industrial practice, and there are few manufacturers of tungstate using this method. For example, an enterprise using sol-gel method to prepare tungstate film, with six valence tungsten salt and other two valence metal salt as raw material, dissolved in solvents to form a homogeneous solution, the sol is formed by the hydrolysis reaction of solute and solvent, and then converted into gel by certain method. After drying, the dry gel is obtained, and then the nano tungstate powder is obtained by high temperature treatment.
However, the solution-gel method also has some unavoidable defects such as the instability of the sintered spherical agglomerated granular material, the drying shrinkage, and so on. Therefore, no matter how many years the solution gel method has been applied, the scholars in China have been studying and improving it.
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