Preparation of Tungsten Trioxide Thin Films by Sol - Gel Method
Sol gel method is widely used abroad, a kind of nano material preparation method, its principle is the prepared precursor (such as inorganic salt or metal alkoxide) dissolved in small molecule solvent in solution by mixing made uniform, solute and solvent hydrolysis reaction, hydrolysis condensation the reaction of nano particles and the formation of integrated sol.
On the basis of the prepared sol, different processes can be used to prepare nano thin films and ultrafine powders with different properties. There are several ways to prepare tungsten trioxide thin films by sol-gel method: 1. Tungstic acid hydrochloric acid method; 2. Tungsten powder peroxide polytungstic acid method; 3. Tungstic acid colloid solution is prepared by ion exchange; 4. Polymer method.
The traditional sol-gel method mostly controls the particle size of powders by controlling pH value, temperature and adding surfactants. Recently, some scholars have successfully controlled the particle size of WO3 powders by increasing the viscosity of the reaction medium. After aging, filtration, drying and crystallization at 60 ℃, WO3 between 20 and 30 nm was obtained. Compared with the traditional gel method, CMC increased the viscosity of the hydrolyzate and inhibited the growth of colloidal particles , so using this method can be made of small size nanoparticles.
The sol-gel method has the advantages of low reaction temperature, easy control of product composition, smaller particle size, narrow and uniform particle size distribution and high purity of powder. At the same time, there are also many problems, such as the price of raw materials more expensive, the product is easy to agglomerate in the drying process, the synthesis period is very long, so time is money in the moment, even if the gas sensing properties of tungsten oxide films prepared by the sol-gel method is excellent, but the cost is difficult to control, so it is difficult to scale production.
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