Preparation method of silicon dioxide aerogel

Abstract

The invention provides a preparation method of a silicon dioxide aerogel, which comprises the following steps: regulating the pH value of a silicasol to 4-10 with reducing acid, adding ethanol, heating, and keeping the temperature to obtain a wet gel; mixing the wet gel with ethyl orthosilicate and ethanol to carry out aging; and finally, mixing with a drying-control chemical additive, and drying to obtain the silicon dioxide aerogel. In the aging process, the active hydroxy groups and ethyl orthosilicate on the wet gel surface and the region with weak network skeleton structure react to reinforce the silicon-oxygen bridge bond and enhance the networking degree and strength of the gel skeleton, thereby reducing the shrinkage and cracking phenomena in the drying process. Atoms with large electronegativity and small radius in the drying-control chemical additive and SiOH on the colloidal particle surface form a hydrogen bond, thereby generating a wide shielding network on the periphery; polycondensation is also generated in the system under the action of the hydrogen bond, thereby reducing the polycondensation speed; and many branched chains are increased in the skeleton network structure formation process, thereby promoting the formation of large and uniform nanopores.

Description

technical field [0001] The invention belongs to the technical field of chemical materials, in particular to a preparation method of silica airgel. Background technique [0002] Airgel material is the product obtained after drying the internal solvent while keeping its gel skeleton unchanged. It is a nanoporous lightweight material with controllable structure, 99% of which is composed of gas, so air condensation Glue is also the lightest solid substance known at present, and the lightest silica airgel weighs only 3mg / cm 3 , also known as "frozen smoke" or "blue smoke". [0003] Among them, silica airgel generally refers to the amorphous silica material with air as the dispersion medium, especially the silica material with low density, high porosity and high specific surface area, which has powder and block , The porosity rate is as high as 80% to 99.8%. Since silica airgel contains nanoscale particles and pore structure (1-100nm), it has a very large specific surface area ...

AI Technical Summary

Problems solved by technology

From the perspective of product performance, supercritical drying has advantages and has been industrialized, but the critical pressure of tens of hundreds of atmospheres has caused a significant burden on equipment, cost, operation technology and safety, and even equipment explosion accidents have limited this technology. The promotion of the method, and the supercritical drying technology also leads to the higher cost of the produced silica aerogel

[0006] In order to solve the defects of supercritical drying technology, the processes of subcritical drying, freeze drying and even atmospheric pressure drying have been gradually developed, but each has its own shortcomings: subcritical drying is similar to supercritical drying, except that the temperature and pressure are lower than the critical point, and Some problems caused by supercritical drying are not solved; freeze drying is the reverse thinking of supercritical drying, which relies on low temperature to convert the liquid-gas interface into a solid-gas interface, and removes the solvent by sublimation, which can also avoid the adverse effects of surface tension, but strict Low temperature and low pressure are also the bottleneck of the technology, and the product also has to bear the additional internal stress brought by the transformation of the liquid into a solid; normal pressure drying is generally based on solvent replacement with low surface tension, the process cycle is long, the solvent consumption is large, and the product low quality

This method obtains aerogels with excellent performance, but the hydrophobic modification leads to an increase in cost

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