Method for preparing silicon dioxide aerogel by sublimation method

A technology of silica and airgel, applied in chemical instruments and methods, inorganic chemistry, silicon compounds, etc., can solve the problems of cumbersome preparation process and long cycle, and achieve enhanced network structure, reduced capillary force, and reduced shrinkage Effect

Inactive Publication Date: 2019-04-19
HUAIYIN INSTITUTE OF TECHNOLOGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the atmospheric pressure drying method currently reported requires a large amount of solvents to be exchanged, and the surface of the gel is treated with hydrophobicity, and the preparation process is cumbersome and the cycle is long.

Method used

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  • Method for preparing silicon dioxide aerogel by sublimation method
  • Method for preparing silicon dioxide aerogel by sublimation method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] Dissolve naphthalene in methanol water solvent and stir to obtain a transparent solution, add tetramethyl orthosilicate and ammonia water to the above solution and stir evenly, and let stand to obtain a gel; age the gel at 60°C for 12 h, and then in 10 Carry out vacuum sublimation at ℃ to remove naphthalene in the gel pores to obtain silica airgel; wherein the molar ratio of naphthalene, tetramethylorthosilicate, methanol, water, and ammonia is 1: 0.1:10:0.4:0.001;

[0029] The prepared silica airgel has a density of 0.05 g cm -3 The pore size distribution measured by nitrogen adsorption method is 1~200nm, and the BET specific surface area is as high as 1000 m 2 g -1 , the thermal conductivity measured by the planar heat source method is 0.01 W·m -1 k -1 .

Embodiment 2

[0031] Dissolve naphthalene in ethanol water solvent and stir to obtain a transparent solution, add tetraethylorthosilicate and ammonia water to the above solution and stir evenly, and let it stand to obtain a gel; aging the gel at 80°C for 2 h, and then at 40 Carry out vacuum sublimation at ℃ to remove naphthalene in the gel pores to obtain silica airgel; wherein the molar ratio of naphthalene, tetramethylorthosilicate, ethanol, water, and ammonia is 1: 20:10:10:0.05;

[0032] The prepared silica airgel has a density of 0.65 g cm -3 , the pore size distribution measured by nitrogen adsorption method is 2~80 nm, and the BET specific surface area is as high as 300 m 2 g -1 , the thermal conductivity measured by the planar heat source method is 0.08 W·m -1 k -1 .

Embodiment 3

[0034] Dissolve benzoic acid in ethanol water solvent and stir to obtain a transparent solution, add polysiloxane and urea to the above solution, stir evenly, and let stand to obtain a gel; age the gel at 80°C for 4 h, and then in 30 Carry out vacuum sublimation at ℃ to remove benzoic acid in the pores of the gel to obtain silica airgel; the molar ratio of benzoic acid, polysiloxane, ethanol, water, and urea is 1: 10:50:2:0.02 ;

[0035] The prepared silica airgel has a density of 0.15 g cm -3 , the pore size distribution measured by nitrogen adsorption method is 2~100nm, and the BET specific surface area is as high as 620 m 2 g -1 , the thermal conductivity measured by the planar heat source method is 0.025 W·m -1 k -1 .

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Abstract

The invention discloses a method for preparing silicon dioxide aerogel by a sublimation method. The method comprises the following steps of (1) dissolving a sublimation substance in an alcohol-water solvent to obtain a transparent solution; (2) adding a silicon source and a alkali catalyst into the solution in step (1), uniformly mixing and standing to form gel, and then aging the gel; (3) carrying out vacuum sublimation on the aged gel in step (2) to remove the sublimation substance so as to obtain the silicon dioxide aerogel. According to the method, the sublimation substance can plug the gaps of the gel, plays a role in enhancing the network structure of the gel, and can reduce the shrinkage of the gel; solvent exchange and gel surface modification process are not needed in the preparation process, so that a large amount of organic solvents are saved, and the preparation efficiency of the silicon dioxide aerogel is greatly improved. The silicon dioxide aerogel prepared by the methodis of a nano-pore structure and has the advantages that the pore diameter distribution is 1-200 nanometers; the BET specific surface area is as high as 300-1000 m2/g<1>, the density is 0.05-0.65 g/cm<3>, and the thermal conductivity is 0.01-0.08 W/m<1>/k<1>.

Description

technical field [0001] The invention belongs to the field of preparation of nanoporous new materials, in particular to a method for preparing silica airgel by sublimation. Background technique [0002] Silica airgel is a lightweight solid material with a nanoporous network structure and a large specific surface area (300–1000 m 2 g -1 ), low density (3~500kg·m -3 ), low thermal conductivity (0.01~0.05W·m -1 ·K -1 ) and other excellent physical properties, can be widely used in aerospace, oil pipelines, construction, catalysis, sewage treatment and other fields. Silica aerogels are usually prepared by using a sol-gel method to prepare a gel, and then drying to remove the solvent in the pores of the gel. In order to obtain low-density aerogels, supercritical drying is usually used, but supercritical drying equipment is expensive and maintenance costs are high, resulting in expensive aerogels, which limits the wide application of aerogels. [0003] In order to reduce the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/158B82Y30/00B82Y40/00
CPCB82Y30/00B82Y40/00C01B33/1585C01P2004/30C01P2006/17
Inventor 云山陈全会陈荣郭探张加栋李彦兴李华举洪坤陈静
Owner HUAIYIN INSTITUTE OF TECHNOLOGY
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