Ultrahigh-transparency large-size block silicon dioxide aerogel and preparation method and application thereof

Abstract

The invention relates to an ultrahigh-transparency large-size block silicon dioxide aerogel and a preparation method and application thereof. The method comprises the following steps: uniformly mixingtetramethyl orthosilicate, long-chain alkyl trimethoxy silane, an alcohol solvent, water and an alkali catalyst, carrying out hydrolysis reaction to obtain sol, and putting the sol into a mold to carry out sol-gel reaction to obtain wet gel; carrying out gradient heating aging on the wet gel to obtain skeleton-reinforced wet gel; and sequentially carrying out solvent replacement and supercriticaldrying on the skeleton-reinforced wet gel to obtain the ultrahigh-transparency large-size block silicon dioxide aerogel. According to the preparation method disclosed by the invention, superfine silicon dioxide sol generated by hydrolyzing long-chain alkyl trimethoxy silane stable tetramethyl orthosilicate is introduced, and the reaction activity of the sol is controllably adjusted so that the accurate regulation and control of a gelling process are realized; the aerogel prepared by the method has the characteristics of ultrahigh transparency, large size, super heat insulation capability, super hydrophobicity and the like, and has great economic value in the field of transparent heat insulation.

Description

technical field

[0001] The invention belongs to the technical field of nanoporous materials, and relates to a method for preparing silica airgel, in particular to an ultrahigh-transparency large-size bulk silica airgel and its preparation method and application. Background technique

[0002] Silica airgel is the most typical representative of the airgel family, and it is also the most mature and widely used type of airgel material. The particles are interconnected to form a three-dimensional continuous nanoporous network structure. This structural feature endows silica aerogels with properties including ultra-low density, ultra-large specific surface area, ultra-high porosity, ultra-low dielectric constant, especially ultra-low thermal conductivity, etc. Many unique properties make silica airgel widely known as a super thermal insulation material. In addition, by controlling the particles and pores of silica airgel to be small and uniform, it has good light transmittance to...

Examples

preparation example Construction

[0034] In a first aspect, the present invention provides a method for preparing an ultrahigh-transparency large-size bulk silica aerogel, the method comprising the following steps:

[0035] (1) Silicon source methyl orthosilicate (TMOS silicon source), additive long-chain alkyl trimethoxysilane (C n TMOS), an alcohol solvent, water and an alkali catalyst are mixed uniformly and then hydrolyzed to obtain a sol, and then the sol is placed in a mold to perform a sol-gel reaction to obtain a wet gel;

[0036] (2) subjecting the wet gel to a gradient temperature aging step to obtain a skeleton-reinforced wet gel;

[0037] (3) Perform the steps of solvent replacement (such as solvent replacement in ethanol) and supercritical drying (such as supercritical carbon dioxide drying) of the skeleton-reinforced wet gel in sequence to obtain ultra-high transparency and large-size block silica gas gel.

[0038] The invention provides a method for preparing super-high transparency and large-...

Embodiment 1

[0061] ①Add 152g of methyl orthosilicate, 11.2g of octadecyltrimethoxysilane (additive) and 224g of methanol into a beaker, and stir mechanically at -20°C for 30min to obtain mixed solution A. Add 72g of deionized water and 710 μL of ammonia-methanol solution (concentration is 7mol / L) into the beaker, utilize mechanical stirring at room temperature for 3min, obtain mixed solution B (in this example, each component in the raw material is calculated by molar ratio of methyl orthosilicate Esters: Octadecyltrimethoxysilane: Methanol: Water: Ammonia (1:0.03:7:4:0.005). Add the mixed solution B to the mixed solution A drop by drop, and continue to maintain the hydrolysis reaction at -20°C for 90 minutes to obtain a sol; inject the above-mentioned cold sol close to the gel state into a detachable tetrafluoroethylene plate with an area of ​​16cm×16cm The sol-gel reaction was carried out in the mold at -20°C for 90 min to form a wet gel.

[0062] ②Put the above-mentioned flat mold wit...

Embodiment 2

[0067] Embodiment 2 is basically the same as Embodiment 1, the difference is:

[0068] In step ①, 152g of methyl orthosilicate, 3.73g of octadecyltrimethoxysilane and 64g of methanol were respectively added into the beaker, and stirred mechanically at -20°C for 30min to obtain a mixed solution A. Add 36g of deionized water and 426μL ammonia-methanol solution (concentration is 7mol / L) in the beaker, utilize mechanical stirring at room temperature for 3min, obtain mixed solution B (in this example, each component in the raw material is calculated by molar ratio of methyl orthosilicate Esters: Octadecyltrimethoxysilane: Methanol: Water: Ammonia (1:0.01:2:2:0.003). Add the mixed solution B to the mixed solution A drop by drop, and continue to maintain the hydrolysis reaction at -20°C for 90 minutes to obtain a sol. The above-mentioned cold sol close to the gel state is injected into a removable tetrafluoroethylene flat mold at -20°C The sol-gel reaction was carried out for 90 min...

technical field

[0001] The invention belongs to the technical field of nanoporous materials, and relates to a method for preparing silica airgel, in particular to an ultrahigh-transparency large-size bulk silica airgel and its preparation method and application. Background technique

[0002] Silica airgel is the most typical representative of the airgel family, and it is also the most mature and widely used type of airgel material. The particles are interconnected to form a three-dimensional continuous nanoporous network structure. This structural feature endows silica aerogels with properties including ultra-low density, ultra-large specific surface area, ultra-high porosity, ultra-low dielectric constant, especially ultra-low thermal conductivity, etc. Many unique properties make silica airgel widely known as a super thermal insulation material. In addition, by controlling the particles and pores of silica airgel to be small and uniform, it has good light transmittance to...

Examples

preparation example Construction

[0034] In a first aspect, the present invention provides a method for preparing an ultrahigh-transparency large-size bulk silica aerogel, the method comprising the following steps:

[0035] (1) Silicon source methyl orthosilicate (TMOS silicon source), additive long-chain alkyl trimethoxysilane (C n TMOS), an alcohol solvent, water and an alkali catalyst are mixed uniformly and then hydrolyzed to obtain a sol, and then the sol is placed in a mold to perform a sol-gel reaction to obtain a wet gel;

[0036] (2) subjecting the wet gel to a gradient temperature aging step to obtain a skeleton-reinforced wet gel;

[0037] (3) Perform the steps of solvent replacement (such as solvent replacement in ethanol) and supercritical drying (such as supercritical carbon dioxide drying) of the skeleton-reinforced wet gel in sequence to obtain ultra-high transparency and large-size block silica gas gel.

[0038] The invention provides a method for preparing super-high transparency and large-...

Embodiment 1

[0061] ①Add 152g of methyl orthosilicate, 11.2g of octadecyltrimethoxysilane (additive) and 224g of methanol into a beaker, and stir mechanically at -20°C for 30min to obtain mixed solution A. Add 72g of deionized water and 710 μL of ammonia-methanol solution (concentration is 7mol / L) into the beaker, utilize mechanical stirring at room temperature for 3min, obtain mixed solution B (in this example, each component in the raw material is calculated by molar ratio of methyl orthosilicate Esters: Octadecyltrimethoxysilane: Methanol: Water: Ammonia (1:0.03:7:4:0.005). Add the mixed solution B to the mixed solution A drop by drop, and continue to maintain the hydrolysis reaction at -20°C for 90 minutes to obtain a sol; inject the above-mentioned cold sol close to the gel state into a detachable tetrafluoroethylene plate with an area of ​​16cm×16cm The sol-gel reaction was carried out in the mold at -20°C for 90 min to form a wet gel.

[0062] ②Put the above-mentioned flat mold wit...

Embodiment 2

[0067] Embodiment 2 is basically the same as Embodiment 1, the difference is:

[0068] In step ①, 152g of methyl orthosilicate, 3.73g of octadecyltrimethoxysilane and 64g of methanol were respectively added into the beaker, and stirred mechanically at -20°C for 30min to obtain a mixed solution A. Add 36g of deionized water and 426μL ammonia-methanol solution (concentration is 7mol / L) in the beaker, utilize mechanical stirring at room temperature for 3min, obtain mixed solution B (in this example, each component in the raw material is calculated by molar ratio of methyl orthosilicate Esters: Octadecyltrimethoxysilane: Methanol: Water: Ammonia (1:0.01:2:2:0.003). Add the mixed solution B to the mixed solution A drop by drop, and continue to maintain the hydrolysis reaction at -20°C for 90 minutes to obtain a sol. The above-mentioned cold sol close to the gel state is injected into a removable tetrafluoroethylene flat mold at -20°C The sol-gel reaction was carried out for 90 min...

Images