Method for preparing silica aerogel under atmospheric pressure and prepared silica aerogel

Abstract

The invention provides a method for preparing silica aerogel under atmospheric pressure and the prepared silica aerogel. The method comprises the following steps: (1) diluting an inorganic silicon source with water, and then mixing the diluted inorganic silicon source with an acid to carry out an acid-base reaction to obtain silicic acid sol; (2) gelling the silicic acid sol, and conducting aging treatment on the formed gel to obtain a wet gel; (3) adding modifier base fluid to the wet gel to completely infiltrate the wet gel; then adding a concentrated acid or concentrated alkali solution to the system; and conducting surface modification treatment under an airtight condition or in an installation with a condensing reflux device until the gel is completely modified from hydrophilicity to hydrophobicity; and (4) conducting drying treatment on the modified aerogel obtained in the step (3) to obtain the silica aerogel. The method also comprises a step of adding a polar organic solvent or a polar organic solvent aqueous solution to the silicic acid sol obtained in the step (1), and/or to the system before addition of the concentrated acid or concentrated alkali solution in the step (3).

Description

technical field [0001] The invention relates to a method for preparing silicon dioxide airgel under normal pressure in an industrialized manner and the prepared silicon dioxide airgel, belonging to the technical field of nanometer materials. Background technique [0002] Silica airgel is a lightweight nanoporous material with high porosity, large specific surface area, low density and low thermal conductivity, these characteristics make silica airgel materials in thermal, acoustic, optical, micro Electronics and particle detection have very broad application potential. Although silica airgel has excellent performance, its preparation cost is too high, which greatly limits its popularization and application. [0003] At present, the preparation of silica airgel mostly adopts supercritical drying process. However, the supercritical process equipment is complicated, the cost is high, and there are certain risks. Therefore, the atmospheric pressure drying process has gradually ...

AI Technical Summary

Problems solved by technology

Although, using water glass as a silicon source can prepare airgel with good performance under normal pressure conditions, the preparation cycle is long (the steps of aging, solvent exchange, surface modification, etc. need several days) and the organic solvent consumption is large (multiple times) Inherent shortcomings such as solvent exchange) have not been resolved

[0005] In order to solve these problems, some researchers tried to use solvent exchange and surface modification to prepare silica airgel in one step, such as Ni Wen et al. SiO 2 Airgel bulk material, Henan Chemical Industry, 24, 2007) using water glass as the silicon source, a one-step method was used to prepare silicon airgel, and its specific surface area was 643m 2 / g, but the amount of modification consumed by the one-step method is too large, and it is difficult to recover

Liu Guangwu of Tongji University et al. 2 Preparation and characterization of airgel blocks, Journal of China Ceramics, 40(1), 2012) using water glass as the silicon source, using ethanol / hexamethyldisiloxane / concentrated hydrochloric acid instead of ethanol / trimethylchlorosilane / One-step preparation of silica airgel blocks with n-hexane, but the preparation process is complicated and takes a long time