Method for preparing hydrophobic SiO2 aerogel by virtue of normal pressure drying

A technology of normal pressure drying and hydrophobicity, applied in the direction of silica, silicon oxide, etc., can solve the problems of low block integrity of airgel, waste of solvent, and restriction of practical application value, and achieve an uncomplicated experimental environment and block The effect of good body integrity and low cost

Active Publication Date: 2014-07-23
NANJING UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] At present, the atmospheric pressure drying technology has been improved to some extent, but due to the large waste of solvents and other wastes in the process, and compared with supercritical drying, the integrity of the airgel block obtained is relatively low, so it is restricted to a certain extent. its practical value

Method used

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  • Method for preparing hydrophobic SiO2 aerogel by virtue of normal pressure drying
  • Method for preparing hydrophobic SiO2 aerogel by virtue of normal pressure drying
  • Method for preparing hydrophobic SiO2 aerogel by virtue of normal pressure drying

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0032] Mix 10ml tetraethyl orthosilicate, 4.0ml deionized water, and 18.0ml absolute ethanol, then add hydrochloric acid (1mol / L) to adjust the pH value between 3 and 4, and fully stir the mixed solution at room temperature for 30min , and then add ammonia water (0.1 mol / L) to adjust the pH value between 6 and 8. Put the solution into an airtight container to form a gel, and then age it in absolute ethanol at about 20°C for one day. Add n-hexane to the aged gel for solvent replacement for 12 hours, and replace the ethanol and excess water in the pores. Pour off the remaining n-hexane, add n-hexane modification solution with a volume concentration of 8% TMCS, and carry out surface modification at 50°C for 12h. Then the gel was washed with n-hexane at 50 °C for 8 h. Finally, after drying, the hydrophobic SiO 2 airgel.

[0033] The drying process is as follows: the gel samples are dried at 60°C, 80°C, 100°C, 120°C, and 150°C for 1.5 hours respectively, and then cooled to room...

Embodiment 2

[0037] Mix 10ml of tetraethyl orthosilicate, 4.0ml of deionized water, and 16.0ml of absolute ethanol, then add hydrochloric acid (1mol / L) to adjust the pH value between 3 and 4, and fully stir the mixed solution at room temperature for 30min , and then add ammonia water (0.1 mol / L) to adjust the pH value between 6 and 8. Place the solution in an airtight container to form a gel. Then aged at about 20°C for one day, and selected TEOS / absolute ethanol with a volume ratio of 1:4 as the aging solution. Add n-hexane to the aged gel for solvent replacement for 12 hours, and replace the ethanol and excess water in the pores. Pour off the remaining n-hexane, add n-hexane modification solution with a volume concentration of 12% HMDZ, and modify the surface of the gel at 50°C for 12 hours. Then the gel was washed with n-hexane at 50 °C for 8 h. Finally, after drying, the hydrophobic SiO 2 airgel.

[0038] The drying process is as follows: the gel samples are dried at 50°C, 70°C, 9...

Embodiment 3

[0041] Mix 10ml of tetraethyl orthosilicate, 3.5ml of deionized water, and 20.0ml of absolute ethanol, then add oxalic acid (0.1mol / L) to adjust the pH value between 3 and 4, and fully stir the mixed solution at room temperature After 1 h, aqueous ammonia (0.01 mol / L) was added to adjust the pH value between 6 and 8. Put the solution in an airtight container to form a gel, and then at about 20°C in H with a volume ratio of 1:1.5 2 Aged in O / absolute ethanol for two days. Add n-hexane to the aged gel for solvent replacement for 24 hours to replace excess solvent. Pour off the remaining n-hexane, add n-hexane modification solution with a volume concentration of 10% TMCS, and carry out surface modification at 60°C for 12 hours. Then the gel was washed with n-hexane at 60°C for 10 h. Finally, after drying, the hydrophobic SiO 2 airgel.

[0042] The drying process is as follows: the gel samples are dried at 60°C, 80°C, 100°C, 120°C, and 150°C for 2 hours respectively, and then...

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Abstract

The invention belongs to the field of aerogel material preparation technologies, and relates to a method for preparing a hydrophobic SiO2 aerogel by virtue of normal pressure drying. During the preparation, a two-step method is adopted, an organic silicon source as precursor, water as a hydrolysis agent, absolute ethyl alcohol as a solvent, acid and alkali as catalysts, and an organic silicon solution and a surface modifier. The preparation method comprises the following steps: mixing and stirring the organic silicon source, the water and the absolute ethyl alcohol in proportion, and respectively adding an acid catalyst and an alkaline catalyst by virtue of an acid and alkali two-step method to regulate pH value so as to form gel; performing solvent replacement on the aged gel, carrying out surface hydrophobic modification, replacing a hydrophilic group on the surface of the gel through a hydrophobic group, so that the gel is hydrophobic; finally, performing normal pressure drying to obtain the hydrophobic SiO2 aerogel. The method disclosed by the invention can be used for reducing the preparation cost of the aerogel; moreover, according to a hydrophobicity test, the contact angle can reach about 158 degrees, thereby showing that the hydrophobicity is good.

Description

technical field [0001] The invention belongs to the field of preparation technology of airgel materials, and in particular relates to the preparation of hydrophobic SiO by atmospheric pressure drying using a two-step sol-gel method combined with an atmospheric pressure drying process 2 Airgel method. Background technique [0002] Airgel is an ultra-light porous condensed matter with a three-dimensional network structure that uses gas as a dispersion medium. SiO 2 Airgel is a new type of structure-controllable porous material with various unique properties. It has ultra-low density (0.003~0.2g / cm 3 ), ultra-high porosity (80%-99.8%) and ultra-fine structure (microscopic network skeleton and pores generally enter the nanometer category, and the specific surface area can reach 800m 2 / g or more), and its surface polarity is controllable, and its hydrophilicity and hydrophobicity can be adjusted according to needs. This brings a series of excellent performances in heat, lig...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/16
Inventor 张毅刘洋李东旭
Owner NANJING UNIV OF TECH
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