阅读说明：本技术 一种硅气凝胶的制备方法 (Preparation method of silicon aerogel ) 是由 徐嘉鹏 王克 于 2021-02-03 设计创作，主要内容包括：本发明公开了一种硅气凝胶的制备方法,涉及气凝胶制备领域,包括以下步骤：按质量份,将1份水玻璃、10～15份有机硅烷化合物、2～4份碳酸钴加入pH值为3～3.5的有机酸水溶液中,搅拌10～60min至均匀后,在室温下静置10～15h,使水玻璃和有机硅烷化合物部分水解,同时,钴离子与水解后的硅离子结合,再加入5～8份甲基三甲氧基硅烷,加入氨水调节溶液pH值至5～5.5,搅拌15～30min至均匀,在室温下静置10～20h继续水解并形成凝胶,同时,-CH3大量分布在SiO2形成疏水基团,将凝胶干燥；本发明具有较坚硬的骨骼结构,能够在低温下干燥不变形。(The invention discloses a preparation method of silicon aerogel, relating to the field of aerogel preparation and comprising the following steps: adding 1 part by mass of water glass, 10-15 parts by mass of an organosilane compound and 2-4 parts by mass of cobalt carbonate into an organic acid aqueous solution with the pH value of 3-3.5, stirring for 10-60 min until the mixture is uniform, standing at room temperature for 10-15 h to hydrolyze the water glass and the organosilane compound partially, simultaneously, combining cobalt ions with hydrolyzed silicon ions, adding 5-8 parts by mass of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5-5.5, stirring for 15-30 min until the mixture is uniform, standing at room temperature for 10-20 h to continue hydrolyzing and form gel, simultaneously, distributing a large amount of-CH 3 on SiO2 to form hydrophobic groups, and drying the gel; the invention has a harder skeleton structure and can be dried at low temperature without deformation.)

1. A method of preparing a silicone aerogel comprising the steps of:

(1) adding 1 part by mass of water glass, 10-15 parts by mass of an organosilane compound and 2-4 parts by mass of cobalt carbonate into an organic acid aqueous solution with the pH value of 3-3.5, and stirring for 10-60 min until the mixture is uniform;

(2) standing for 10-15 h at room temperature to hydrolyze part of the water glass and the organosilane compound, and simultaneously, combining cobalt ions with hydrolyzed silicon ions;

(3) adding 5-8 parts of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5-5.5, and stirring for 15-30 min to be uniform;

(4) standing for 10-20 h at room temperature for continuous hydrolysis to form gel, and simultaneously distributing a large amount of-CH 3 on SiO2 to form hydrophobic groups;

(5) the gel is dried.

2. A method of preparing a silica aerogel as claimed in claim 1, wherein: the organosilane compound is tetraethoxysilane or methyltriethoxysilane.

3. A method of preparing a silica aerogel as claimed in claim 1, wherein: the organic acid is acetic acid, tartaric acid or benzoic acid.

4. A method of preparing a silica aerogel as claimed in claim 1, wherein: the method also comprises the following steps before the gel is dried: and (3) placing the gel in a methanol solution for standing for 5-10 h.

5. A method of preparing a silica aerogel as claimed in claim 1, wherein: the gel drying method comprises the following specific steps: drying for 15-20 h at room temperature, and drying for 5h at 80 ℃, 100 ℃ and 150 ℃ respectively to obtain the silica aerogel.

Technical Field

The invention relates to the field of aerogel preparation, in particular to a preparation method of silicon aerogel.

Background

The aerogel is a porous network structure formed by mutually aggregating colloidal particles or high polymer molecules, and gaseous dispersion media are arranged in pores of the aerogel, so that the aerogel has high porosity, light weight and excellent heat insulation performance.

At present, a silicon source (such as TEOS) is usually added into water or ethanol to form a gel structure, and then the water or ethanol in pores is removed through supercritical drying, because the cost of the supercritical drying is high, the supercritical drying is developed into freeze drying and normal-temperature drying, because the drying technology is to replace gas with liquid in the pores, and the framework structure of the gel is kept unchanged, but in the drying process, the gel inevitably shrinks to further damage the framework structure, the reason is that the pores are different in size, the shrinkage stress of each pore is uneven during drying, the pressure of different pores is different, and when the pressure difference is greater than the bearing pressure of the framework structure, the pores crack can be generated to collapse.

In order to avoid the above problems, it is necessary to make the pores uniform and increase the strength of the skeleton structure, and at present, in order to increase the strength, the gel is usually soaked in a mother liquor or a silicon alkoxide and aged to enhance the structural strength, but at the same time, the density of the aerogel is also increased, and the quality is increased.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method of a silicon aerogel, which has a harder skeleton structure and can be dried at a low temperature without deformation.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:

a preparation method of silicon aerogel comprises the steps of adding 1 part by mass of water glass, 10-15 parts by mass of an organosilane compound and 2-4 parts by mass of cobalt carbonate into an organic acid aqueous solution with a pH value of 3-3.5, stirring for 10-60 min to be uniform, standing for 10-15 h at room temperature to hydrolyze the water glass and the organosilane compound partially, simultaneously combining cobalt ions with hydrolyzed silicon ions, adding 5-8 parts by mass of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5-5.5, stirring for 15-30 min to be uniform, standing for 10-20 h at room temperature to hydrolyze continuously and form gel, and simultaneously, -CH₃Distributed in large amount in SiO₂Hydrophobic groups are formed and the gel is dried.

On the basis of the technical scheme, the organosilane compound is tetraethoxysilane or methyltriethoxy.

On the basis of the technical scheme, the organic acid is acetic acid, tartaric acid or benzoic acid.

On the basis of the technical scheme, the gel is placed in a methanol solution and stands for 5-10 hours.

On the basis of the technical scheme, drying is carried out for 15-20 h at room temperature, and then drying is carried out for 5h under the conditions that the temperature is 80 ℃, 100 ℃ and 150 ℃ respectively, so as to obtain the silicon aerogel.

Compared with the prior art, the invention has the advantages that:

(1) according to the preparation method of the silicon aerogel, water glass, an organic silane compound and cobalt carbonate react for 10-15 hours under an acidic condition, at the moment, the water glass and the organic silane compound are gradually hydrolyzed (partially hydrolyzed) to generate an Si-OH structure, and free Co in the cobalt carbonate²⁺Ions can react with Si to generate Si-Co-Si chains and repeatedly expand to form a network structure to construct a skeleton structure of gel, and the structure is firm and is not easy to collapse in the drying process; after addition of ammonia and methyltrimethoxysilane, -CH₃The silicon aerogel has the advantages that the silicon aerogel reacts with unreacted Si-OH and attacks Si to form a Si-CH3 hydrophobic structure, so that hydrophobic groups are distributed on the surface of a pore structure of the silicon aerogel, when the silica aerogel is placed in a methanol solution to interact with water, the methanol can effectively displace the water, and due to the fact that the surface tension of the methanol is small, the shrinkage stress of pores is small during drying, and collapse of a framework structure due to overlarge stress difference can be avoided; through the mode, the silicon aerogel prepared by the embodiment has fewer cracks, shorter preparation period, milder drying condition and lower cost.

Detailed Description

The present invention will be described in further detail with reference to examples.

The embodiment of the invention provides a preparation method of silica aerogel

Adding 1 part by mass of water glass, 10-15 parts by mass of an organosilane compound and 2-4 parts by mass of cobalt carbonate into an organic acid aqueous solution with the pH value of 3-3.5, stirring for 10-60 min until the mixture is uniform, standing at room temperature for 10-15 h to hydrolyze the water glass and the organosilane compound partially, simultaneously combining cobalt ions with hydrolyzed silicon ions, adding 5-8 parts by mass of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5-5.5, stirring for 15-30 min until the solution is uniform, standing at room temperatureStanding for 10-20 h for continuous hydrolysis to form gel, and simultaneously-CH₃Distributed in large amount in SiO₂Forming a hydrophobic group.

And (3) standing the gel in a methanol solution for 5-10 h, drying at room temperature for 15-20 h, and drying at 80 ℃, 100 ℃ and 150 ℃ for 5h respectively to obtain the silicon aerogel.

In this embodiment, the organosilane compound is tetraethoxysilane or methyltriethoxysilane; the organic acid is acetic acid, tartaric acid or benzoic acid.

In the embodiment, water glass, an organosilane compound and cobalt carbonate react for 10-15 hours under an acidic condition, at the moment, the water glass and the organosilane compound are gradually hydrolyzed (partially hydrolyzed) to generate an Si-OH structure, and free Co in the cobalt carbonate²⁺Ions can react with Si to generate Si-Co-Si chains and repeatedly expand to form a network structure to construct a skeleton structure of gel, and the structure is firm and is not easy to collapse in the drying process; after addition of ammonia and methyltrimethoxysilane, -CH₃Reacts with unreacted Si-OH and attacks Si to form Si-CH₃The hydrophobic structure enables the surface of the pore structure of the silicon aerogel to be fully distributed with hydrophobic groups, when the gel is placed in a methanol solution to interact with water, the methanol can effectively displace the water, and due to the fact that the surface tension of the methanol is small, the shrinkage stress of pores is small when the drying is carried out, and collapse of the framework structure caused by overlarge stress difference can be avoided; through the mode, the silicon aerogel prepared by the embodiment has fewer cracks, shorter preparation period, milder drying condition and lower cost.

Hereinafter, the present invention will be described in detail by way of 3 examples and 3 comparative examples.

Example 1

Adding 1 part of water glass, 10 parts of ethyl orthosilicate and 4 parts of cobalt carbonate into acetic acid aqueous solution with the pH value of 3 according to parts by mass, stirring for 60min to be uniform, standing for 10h at room temperature to hydrolyze the water glass and the organosilane compound partially, simultaneously combining cobalt ions with hydrolyzed silicon ions, adding 5 parts of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5, and stirring for 15min to be uniformStanding at room temperature for 20 hr for hydrolysis and gel formation, and simultaneously-CH₃Distributed in large amount in SiO₂Forming a hydrophobic group.

And (3) placing the gel in a methanol solution for standing for 10h, drying at room temperature for 15h, and respectively drying at the temperature of 80 ℃, 200 ℃ and 500 ℃ for 5h to obtain the silicon aerogel.

Example 2

Adding 1 part of water glass, 15 parts of methyltriethoxy and 2 parts of cobalt carbonate into aqueous solution of tartaric acid with the pH value of 33.5 according to parts by mass, stirring for 10min until the mixture is uniform, standing for 15h at room temperature to hydrolyze the water glass and the organosilane compound partially, simultaneously combining cobalt ions with the hydrolyzed silicon ions, adding 8 parts of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5.5, stirring for 30min until the mixture is uniform, standing for 10h at room temperature to continue hydrolysis and form gel, and simultaneously, -CH₃Distributed in large amount in SiO₂Forming a hydrophobic group.

And (3) placing the gel in a methanol solution, standing for 50h, drying at room temperature for 20h, and respectively drying at the temperature of 80 ℃, 100 ℃ and 150 ℃ for 5h to obtain the silicon aerogel.

Example 3

Adding 1 part of water glass, 12 parts of ethyl orthosilicate and 3 parts of cobalt carbonate into tartaric acid aqueous solution with the pH value of 3.3 according to parts by mass, stirring for 40min until the mixture is uniform, standing for 12h at room temperature to hydrolyze the water glass and the organosilane compound partially, simultaneously combining cobalt ions with the hydrolyzed silicon ions, adding 7 parts of methyltrimethoxysilane, adding ammonia water to adjust the pH value of the solution to 5.3, stirring for 25min until the mixture is uniform, standing for 15h at room temperature to continue hydrolysis and form gel, and simultaneously, -CH₃Distributed in large amount in SiO₂Forming a hydrophobic group.

And (3) standing the gel in a methanol solution for 8h, drying at room temperature for 18h, and drying at 80 ℃, 100 ℃ and 150 ℃ for 5h respectively to obtain the silicon aerogel.

Comparative example 1

Adding 1 part of water glass and 12 parts of tetraethoxysilane into a tartaric acid aqueous solution with the pH value of 3.3 according to the parts by mass,stirring for 40min, standing at room temperature for 12 hr to hydrolyze water glass and organic silane, adding 7 parts of methyltrimethoxysilane, adding ammonia water to adjust pH to 5.3, stirring for 25min, standing at room temperature for 15 hr to hydrolyze, forming gel, and simultaneously-CH₃Distributed in large amount in SiO₂Forming a hydrophobic group.

And (3) standing the gel in a methanol solution for 8h, drying the gel at room temperature for 18h, and drying the gel at the temperature of 80 ℃, 200 ℃ and 500 ℃ for 5h respectively to obtain the silicon aerogel.

Comparative example 2

Adding 1 part of water glass, 12 parts of ethyl orthosilicate and 3 parts of cobalt carbonate into a tartaric acid aqueous solution with the pH value of 3.3 according to parts by mass, stirring for 40min until the mixture is uniform, standing for 12h at room temperature to hydrolyze the water glass and the organosilane compound partially, simultaneously combining cobalt ions with hydrolyzed silicon ions, adding ammonia water to adjust the pH value of the solution to 5.3, stirring for 25min until the mixture is uniform, standing for 15h at room temperature to continue hydrolysis and form gel.

And (3) standing the gel in a methanol solution for 8h, drying at room temperature for 18h, and drying at 80 ℃, 100 ℃ and 150 ℃ for 5h respectively to obtain the silicon aerogel.

Comparative example 3

Adding 1 part of water glass and 12 parts of tetraethoxysilane into a tartaric acid aqueous solution with the pH value of 3.3 according to the parts by mass, stirring for 40min until the mixture is uniform, standing for 12h at room temperature to hydrolyze the water glass and the organosilane compound partially, adding ammonia water to adjust the pH value of the solution to 5.3, stirring for 25min until the mixture is uniform, standing for 15h at room temperature to continue hydrolysis, and forming gel.

And (3) standing the gel in a methanol solution for 8h, drying at room temperature for 18h, and drying at 80 ℃, 100 ℃ and 150 ℃ for 5h respectively to obtain the silicon aerogel.

The silica aerogels prepared in examples 1 to 3 all had no cracks, the pore size was relatively uniform, and the gel time of example 3 was the shortest, example 1 followed by example 3; whereas the volume shrinkage of example 2 was larger.

The silica aerogels obtained in comparative examples 1 and 3 both had cracks, and comparative example 3 was easily broken.

The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.