CN115337875A - Aerogel and preparation method and application thereof - Google Patents
Aerogel and preparation method and application thereof Download PDFInfo
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- CN115337875A CN115337875A CN202110529317.4A CN202110529317A CN115337875A CN 115337875 A CN115337875 A CN 115337875A CN 202110529317 A CN202110529317 A CN 202110529317A CN 115337875 A CN115337875 A CN 115337875A
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- 239000004964 aerogel Substances 0.000 title claims abstract description 106
- 238000002360 preparation method Methods 0.000 title claims abstract description 35
- 239000004372 Polyvinyl alcohol Substances 0.000 claims abstract description 46
- 229920002451 polyvinyl alcohol Polymers 0.000 claims abstract description 46
- 239000000843 powder Substances 0.000 claims abstract description 40
- 238000010041 electrostatic spinning Methods 0.000 claims abstract description 36
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000000835 fiber Substances 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 23
- 239000002243 precursor Substances 0.000 claims abstract description 20
- 239000002270 dispersing agent Substances 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 12
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 239000000243 solution Substances 0.000 claims description 29
- 238000000034 method Methods 0.000 claims description 23
- 239000002202 Polyethylene glycol Substances 0.000 claims description 14
- 229920001223 polyethylene glycol Polymers 0.000 claims description 14
- 239000007864 aqueous solution Substances 0.000 claims description 12
- 238000000498 ball milling Methods 0.000 claims description 12
- 238000002347 injection Methods 0.000 claims description 8
- 239000007924 injection Substances 0.000 claims description 8
- 229920002125 Sokalan® Polymers 0.000 claims description 6
- 239000004584 polyacrylic acid Substances 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000001523 electrospinning Methods 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 239000004115 Sodium Silicate Substances 0.000 claims description 4
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 claims description 4
- 229940048086 sodium pyrophosphate Drugs 0.000 claims description 4
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 4
- 235000019818 tetrasodium diphosphate Nutrition 0.000 claims description 4
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 2
- 238000003801 milling Methods 0.000 claims description 2
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 40
- 239000000377 silicon dioxide Substances 0.000 description 18
- 230000000052 comparative effect Effects 0.000 description 14
- 238000012360 testing method Methods 0.000 description 10
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 239000002131 composite material Substances 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 238000009413 insulation Methods 0.000 description 6
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- 239000010703 silicon Substances 0.000 description 6
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- 235000012239 silicon dioxide Nutrition 0.000 description 5
- 238000003980 solgel method Methods 0.000 description 4
- 238000011282 treatment Methods 0.000 description 4
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- 239000002086 nanomaterial Substances 0.000 description 1
- 239000007783 nanoporous material Substances 0.000 description 1
- 230000005622 photoelectricity Effects 0.000 description 1
- 238000006068 polycondensation reaction Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 229910021426 porous silicon Inorganic materials 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
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- 229920003169 water-soluble polymer Polymers 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0091—Preparation of aerogels, e.g. xerogels
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Abstract
The invention provides an aerogel, a preparation method and application thereof, wherein the aerogel has a porous network structure formed by fiber aerogel; the material of the fiber aerogel comprises a combination of diatom shells, polyvinyl alcohol and alumina. The preparation method of the aerogel comprises the following steps: uniformly mixing the diatom shell powder, the polyvinyl alcohol solution and an optional aqueous dispersant, adding aluminum oxide, heating and optionally ultrasonically dispersing to obtain an electrostatic spinning precursor solution; and carrying out electrostatic spinning on the electrostatic spinning precursor solution to obtain the aerogel. The aerogel provided by the invention has high porosity, light weight, excellent infrared stealth effect and excellent toughness, and can be used in infrared stealth materials.
Description
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to aerogel and a preparation method and application thereof.
Background
All objects in nature radiate infrared rays. The magnitude of an object's ability to radiate infrared light is directly related to its surface temperature. Therefore, the infrared detector can measure the radiation difference between the target and the background no matter day or night, and infrared images of different objects are obtained. The existing infrared stealth technology principle is usually to change the target heat radiation characteristic, but most of the stealth materials have the defects of continuous energy consumption, narrow application range, slow reaction and the like.
In recent years, aerogel is widely studied as a nano-porous material with a controllable structure in the fields of heat insulation, energy storage, sound insulation and the like. The preparation of aerogels generally consists of a sol-gel process and a supercritical drying treatment. In the sol-gel process, nanoclusters with different structures are formed in a solution by controlling hydrolysis and polycondensation reaction conditions of the solution, the clusters are adhered to each other to form a gel, and the periphery of a solid skeleton of the gel is filled with a liquid reagent remaining after chemical reaction. In order to prevent the damage of the material structure caused by the surface tension in the micropore in the gel drying process, a supercritical drying process is adopted for treatment. However, the supercritical drying process has high requirements on equipment, and is not favorable for large-scale preparation of aerogel products at present.
With the development of nanotechnology, electrostatic spinning, as a simple, convenient and effective novel processing technology, will play a great role in biomedical materials, filtration and protection, catalysis, energy, photoelectricity, food engineering, cosmetics and other fields. Meanwhile, the preparation of the fiber aerogel by electrostatic spinning is a future development trend, and the fiber aerogel also occupies a place in the field of infrared stealth materials.
The silicon dioxide aerogel has the porosity as high as 80-99.8 percent due to the nano porous network structure, is the material with the best heat insulation performance so far, has wide application prospect in the fields of aerospace, petrochemical industry, electric metallurgy, building energy conservation, precise instruments and the like, and is a revolutionary substitute product of the traditional heat insulation material. Currently, most of silicon-based aerogels are prepared by a sol-gel method and a post-drying treatment, for example, CN101318659A discloses a method for preparing a silica aerogel composite material by atmospheric drying, which comprises the following steps: (1) Compounding the silicon dioxide sol and a reinforcing material, standing to form composite gel, and then aging; (2) And (3) performing hydrophobic modification on the aged composite gel by using a modifier, and then drying the modified composite gel under normal pressure to obtain the silicon dioxide aerogel composite material. The silica aerogel composite material prepared by the method has extremely low heat conductivity coefficient, the added value of a reinforcing material such as a fibrous body is greatly improved, the product can be widely applied to heat preservation, heat insulation and sound insulation aspects such as building heat preservation and sound insulation, industrial pipeline transportation and the like, and the application fields of silica and the fibrous body are expanded. CN111039295A discloses a one-step method for preparing silica aerogel, comprising: (1) Mixing and stirring a silicon source precursor A, a silicon source precursor B, a solvent and water to obtain a premixed solution; (2) Mixing a gel catalyst with the premixed solution, and carrying out a gel reaction to obtain silica wet gel; (3) And aging and drying the silica wet gel to obtain the silica aerogel. The silica aerogel has a good pore structure, a large specific surface area and low thermal conductivity. However, the products obtained by sol-gel processes and post-drying treatments are generally brittle and have a low porosity.
Therefore, the research on the silicon-based aerogel with higher porosity and better toughness has important practical significance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the aerogel and the preparation method and the application thereof, the diatom shells are selected as the fiber aerogel material, and the diatom shells are natural porous silicon dioxide, so that the porosity of the prepared aerogel is up to more than 90% due to the porous structure of the silicon dioxide and the three-dimensional porous structure formed by the fiber aerogel material, and the aerogel has excellent infrared stealth performance and excellent toughness.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an aerogel having a porous network structure comprised of a fibrous aerogel; the material of the fiber aerogel comprises a combination of diatom shells, polyvinyl alcohol and alumina.
The aerogel provided by the invention is silicon-based aerogel, has a porous network structure formed by fiber aerogel, and the fiber material comprises a combination of diatom shells, polyvinyl alcohol and alumina, wherein the diatom shells are natural porous silica, the polyvinyl alcohol is a water-soluble polymer capable of being subjected to electrostatic spinning, the polyvinyl alcohol and the silica are mixed to enable the porous silica to be subjected to electrostatic spinning forming, and the alumina is added into an aqueous solution to provide an acidic environment, so that the diatom shells can be formed through an electrostatic spinning process. The combination of these three components thus allows for the preparation of an aerogel and allows for its higher porosity and better toughness.
In the present invention, the thickness of the aerogel is 0.1 to 2mm, for example, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.5mm or 1.8mm, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive.
Preferably, the polyvinyl alcohol has a number average molecular weight of 20000 to 100000, which may be 25000, 30000, 35000, 40000, 45000, 50000, 55000, 60000, 65000, 70000, 75000, 80000, 85000, 90000, 95000 or 98000, and the specific values therebetween are not exhaustive, and for the sake of brevity and brevity, the present invention is not intended to list the specific values included in the range.
Preferably, the mass ratio of the frustules to the polyvinyl alcohol is 1 (0.025 to 0.45), and may be, for example, 1.
Preferably, the mass ratio of the diatom shell to the alumina is 1 (0.375-2), and can be, for example, 1.
In the present invention, the porosity of the aerogel is not less than 90%, and may be, for example, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or the like.
In the invention, the material of the fiber aerogel also comprises an aqueous dispersant.
Preferably, the mass ratio of the frustules to the aqueous dispersant is 1 (0.0025 to 0.05), and may be, for example, 1.
Preferably, the aqueous dispersant is selected from any one of or a combination of at least two of polyacrylic acid, polyethylene glycol, sodium pyrophosphate or sodium silicate.
Preferably, the polyacrylic acid has a number average molecular weight of 5000 to 10000, which may be, for example, 5200, 5500, 6000, 6500, 7000, 7200, 7500, 8000, 8200, 8500, 9000, 9500, 9800 or 9000, and specific values therebetween, not to be limited by space and for the sake of brevity, the present invention is not exhaustive of the specific values included in the ranges.
Preferably, the polyethylene glycol has a number average molecular weight of 2000 to 8000, and may be, for example, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 7800 or 7900, and the specific values therebetween, are not exhaustive and are included for brevity.
In a second aspect, the present invention provides a method for preparing the aerogel of the first aspect, the method comprising the steps of: uniformly mixing the diatom shell powder, the polyvinyl alcohol solution and the water-based dispersing agent, adding aluminum oxide, heating and optionally ultrasonically dispersing to obtain an electrostatic spinning precursor solution; and carrying out electrostatic spinning on the electrostatic spinning precursor solution to obtain the aerogel.
In the invention, the diatom shell powder is prepared by grinding diatom shells.
Preferably, the method of milling is ball milling.
Preferably, the rotational speed of the ball mill is 50 to 200r/min, for example, 60r/min, 70r/min, 80r/min, 90r/min, 100r/min, 120r/min, 150r/min, 180r/min or 190r/min, and the specific values therebetween are not exhaustive, but for brevity and conciseness.
Preferably, the ball milling time is 1 to 4 hours, for example, 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h, 3h, 3.2h, 3.5h, 3.8h or 3.9h, and the specific values therebetween are not exhaustive, and for the sake of brevity and brevity, the invention is not intended to be exhaustive of the specific values included in the scope.
Preferably, the particle size of the frustules powder is 10-100 nm, and may be, for example, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 60nm, 70nm, 80nm, 90nm or 95nm, and specific values therebetween, not to be limited by space and for the sake of brevity, and the invention is not intended to be exhaustive of the specific values included in the range.
Preferably, the particle size of the alumina is 10 to 100nm, for example, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 60nm, 70nm, 80nm, 90nm or 95nm, and specific values therebetween, which are not exhaustive for the invention and are included in the range for reasons of brevity and conciseness.
Preferably, the heating temperature is 30 to 50 ℃, for example, 32 ℃, 35 ℃, 40 ℃, 42 ℃, 44 ℃, 46 ℃, 48 ℃ or 49 ℃, and the specific values therebetween are limited for space and simplicity, and the invention is not exhaustive.
In the invention, the solvent of the polyvinyl alcohol solution is water.
Preferably, the polyvinyl alcohol solution has a polyvinyl alcohol content of 10 to 15% by mass, for example, 10.5%, 11%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 14.6%, 14.8% or 14.9%, and specific values therebetween, which are not exhaustive for the invention and for simplicity.
Preferably, the mass ratio of the diatom shell powder to the aqueous dispersant is 1 (0.0025-0.05), and can be, for example, 1.
Preferably, the mass ratio of the diatom shell powder to the polyvinyl alcohol solution is 1 (0.3-3.6), and can be, for example, 1.
Preferably, the mass ratio of the diatom shell powder to alumina is 1 (0.375-2), and can be, for example, 1.
In the present invention, the voltage of the electrostatic spinning is 10 to 18KV, for example, 10.5KV, 11KV, 12KV, 13KV, 14KV, 15KV, 16KV or 17KV, and the specific values therebetween are limited to space and for simplicity, and the present invention does not exhaust the specific values included in the range.
Preferably, the number of the inner diameter of the needle of the electrospinning is 18 to 27G, and may be 22G, for example.
Preferably, the electrospinning jet velocity is 0.5-1.5 mL/h, such as 0.6mL/h, 0.7mL/h, 0.8mL/h, 0.9mL/h, 1.0mL/h, 1.1mL/h, 1.2mL/h, 1.3mL/h, or 1.4mL/h, and the specific points between the above points are limited by space and for brevity, the invention is not exhaustive of the specific points included in the range.
Preferably, the rotational speed of the electrostatic spinning roller is 50-150 r/min, for example, 60r/min, 70r/min, 80r/min, 90r/min, 100r/min, 110r/min, 120r/min, 130r/min or 140r/min, and the specific values therebetween are not exhaustive, but for brevity and conciseness.
In the invention, the preparation method comprises the following steps:
(1) Ball-milling the frustules for 1-4 h at the rotating speed of 50-200 r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1), a polyvinyl alcohol aqueous solution with the concentration of 10-15% and a water-based dispersing agent according to the mass ratio of 1 (0.3-3.6) to (0.0025-0.05), then adding aluminum oxide, heating to 30-50 ℃ and optionally carrying out ultrasonic dispersion to obtain an electrostatic spinning precursor solution; the mass ratio of the diatom shell powder to the aluminum oxide is 1 (0.375-2); the aqueous dispersant is selected from any one or a combination of at least two of polyacrylic acid, polyethylene glycol, sodium pyrophosphate and sodium silicate;
(3) And (3) performing electrostatic spinning on the electrostatic spinning precursor solution obtained in the step (2) by adopting a needle with the inner diameter number of 18-27G under the conditions that the voltage is 10-18 KV, the injection speed is 0.5-1.5 mL/h and the rotating speed of a roller is 50-150 r/min to obtain the aerogel.
In a third aspect, the present invention provides a use of the aerogel according to the first aspect in an infrared stealth material.
Compared with the prior art, the invention has the following beneficial effects:
according to the aerogel provided by the invention, diatom shells with a porous structure are selected as fiber aerogel materials, a three-dimensional porous structure is constructed among the fiber aerogels, and the two materials act together, so that the porosity of the aerogel is remarkably improved, and the porosity is up to more than 90%. Through the screening of each component content, when aerogel thickness was 0.05mm, had apparent infrared stealthy effect, the grey scale value can be as low as 33, can further improve silicon-based aerogel's pliability simultaneously, can be able to bear or endure 500 times of buckling.
Drawings
FIG. 1 is a scanning electron microscope image of the surface morphology of the frustules powder obtained in example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of the surface morphology of a commercially available silica according to comparative example 1 of the present invention.
Detailed Description
The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The following examples and comparative examples of the present invention use materials including:
polyvinyl alcohol: shanghai aladine, 9002-89-5;
polyethylene glycol: shanghai Michelin, 25322-68-3.
Example 1
The embodiment provides an aerogel and a preparation method thereof, wherein the aerogel has a porous network structure formed by fiber aerogel; the fiber aerogel comprises a combination of diatom shells, polyvinyl alcohol and alumina; the mass ratio of the diatom shells to the polyvinyl alcohol is 1; the mass ratio of the diatom shells to the alumina is 1.
The preparation method of the aerogel comprises the following steps:
(1) Ball-milling the frustules for 2h at the rotating speed of 100r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1) and a polyvinyl alcohol aqueous solution with the concentration of 12% according to the mass ratio of 1; the mass ratio of the diatom shell powder to the alumina is 1.2; (3) And (3) performing electrostatic spinning on the electrostatic spinning precursor solution obtained in the step (2) by using a needle with the inner diameter number of 22G under the conditions that the voltage is 14KV, the injection speed is 1mL/h and the rotating speed of a roller is 100r/min to obtain the aerogel.
Example 2
The embodiment provides an aerogel and a preparation method thereof, wherein the aerogel has a porous network structure formed by fiber aerogel; the fiber aerogel material comprises a combination of diatom shells, polyvinyl alcohol and alumina; the mass ratio of the diatom shells to the polyvinyl alcohol is 1; the mass ratio of the diatom shells to the alumina is 1.
The preparation method of the aerogel comprises the following steps:
(1) Ball-milling the frustules for 2h at the rotating speed of 100r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1) and a polyvinyl alcohol aqueous solution with the concentration of 10% according to the mass ratio of 1; the mass ratio of the diatom shell powder to the alumina is 1; (3) And (3) performing electrostatic spinning on the electrostatic spinning precursor solution obtained in the step (2) by adopting a needle with the inner diameter number of 18G under the conditions that the voltage is 10KV, the injection speed is 0.5mL/h and the rotating speed of a roller is 50r/min to obtain the aerogel.
Example 3
The embodiment provides an aerogel and a preparation method thereof, wherein the aerogel has a porous network structure formed by fiber aerogel; the fiber aerogel material comprises a combination of diatom shells, polyvinyl alcohol and alumina; the mass ratio of the diatom shells to the polyvinyl alcohol is 1; the mass ratio of the diatom shells to the alumina is 1.
The preparation method of the aerogel comprises the following steps:
(1) Ball-milling the frustules for 2h at the rotating speed of 100r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1) and a polyvinyl alcohol aqueous solution with the concentration of 15% according to the mass ratio of 1; the mass ratio of the diatom shell powder to the alumina is 1; (3) And (3) performing electrostatic spinning on the electrostatic spinning precursor solution obtained in the step (2) by using a needle with the inner diameter number of 27G under the conditions that the voltage is 18KV, the injection speed is 1.5mL/h and the rotating speed of a roller is 150r/min to obtain the aerogel.
Example 4
The present embodiment provides an aerogel and a preparation method thereof, which are different from example 1 only in that the mass ratio of diatom shells to polyvinyl alcohol is 1; according to the preparation method, the mass ratio of the diatom shell powder to the polyvinyl alcohol aqueous solution is 1.
Example 5
The present embodiment provides an aerogel and a preparation method thereof, which are different from example 1 only in that the mass ratio of the diatom shells to the polyvinyl alcohol is 1; according to the preparation method, the mass ratio of the diatom shell powder to the polyvinyl alcohol aqueous solution is 1.
Example 6
The present embodiment provides an aerogel and a preparation method thereof, which are different from example 1 only in that the mass ratio of diatom shells to alumina is 1; according to the preparation method, the mass ratio of the diatom shell powder to the polyvinyl alcohol aqueous solution is 1.
Example 7
The present embodiment provides an aerogel and a preparation method thereof, which are different from example 1 only in that the mass ratio of the diatom shells to the alumina is 1; according to the preparation method, the mass ratio of the diatom shell powder to the polyvinyl alcohol aqueous solution is 1.
Example 8
The embodiment provides an aerogel and a preparation method thereof, wherein the aerogel has a porous network structure formed by fiber aerogel; the fiber aerogel comprises a combination of diatom shells, polyvinyl alcohol, aluminum oxide and polyethylene glycol; the mass ratio of the diatom shells to the polyvinyl alcohol is 1; the mass ratio of the diatom shells to the alumina is 1.2; the mass ratio of the diatom shells to the polyethylene glycol is 1.
The preparation method of the aerogel comprises the following steps:
(1) Ball-milling the frustules for 2h at the rotating speed of 100r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1) and polyvinyl alcohol aqueous solution polyethylene glycol with the concentration of 12% in a mass ratio of 1; the mass ratio of the diatom shell powder to the alumina is 1.2; (3) And (3) performing electrostatic spinning on the electrostatic spinning precursor solution obtained in the step (2) by adopting a needle with the inner diameter number of 20G under the conditions that the voltage is 14KV, the injection speed is 1mL/h and the rotating speed of a roller is 100r/min to obtain the aerogel.
Example 9
The embodiment provides an aerogel and a preparation method thereof, wherein the aerogel has a porous network structure; the material of the fiber aerogel comprises a combination of diatom shells, polyvinyl alcohol and polyethylene glycol; the mass ratio of the diatom shells to the polyvinyl alcohol is 1; the mass ratio of the diatom shells to the polyethylene glycol is 1.
The preparation method of the aerogel comprises the following steps:
(1) Ball-milling the frustules for 2h at the rotating speed of 100r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1) and polyvinyl alcohol aqueous solution polyethylene glycol with the concentration of 12% in a mass ratio of 1;
(3) And (3) freeze-drying the precursor solution obtained in the step (2) to obtain the aerogel.
Comparative example 1
The present comparative example provides an aerogel and a preparation method thereof, which is different from example 1 in that commercially available silica is used in the material of the fibrous aerogel instead of the diatom shell powder, and other components, contents and preparation methods are the same as example 1; the particle size of the commercially available silica is 10 to 100nm.
Comparative example 2
This comparative example provides an aerogel and a method for preparing the same, which is different from example 1 in that alumina is not included in the material of the fibrous aerogel, alumina is not included in the preparation method, and other components, contents and preparation methods are the same as example 1.
Comparative example 3
This comparative example provides an aerogel and a method for preparing the same, which is different from example 8 in that a frustule component is replaced with a commercially available silica component, and the preparation method is the same as example 8.
And (4) performance testing:
and (3) testing a scanning electron microscope: scanning electron microscope (VEGA 3LMH, tescan) was used to perform scanning electron microscope tests on the frustule powder obtained in step (1) of example 1 and the commercially available silica provided in comparative example 1, respectively; the test results are shown in fig. 1 and 2;
and (3) porosity testing: the aerogels provided in examples 1-9 and comparative examples 1-3 were subjected to porosity testing according to the test method of GB/T33052-2016;
testing infrared stealth performance: average gray values were obtained from the IR thermographs of the output gray patterns of the aerogels provided in examples 1-9 and comparative examples 1-3 using a 320X 240 resolution IR imager. The smaller the average gray value is, the darker the image color is, the less the infrared radiation amount on the surface of the object is, and the better the infrared stealth performance is;
flexibility test: the aerogels provided in examples 1 to 9 and comparative examples 1 to 3 were clamped with a jig having a rubber gasket using a universal tester (model: instron 2367), and the jig interval was adjusted. The stretching and compression of the film is achieved by the up and down displacement of the clamps. One expansion and compression process was considered to be foldable 1 time and the test was repeated until the film was broken.
The test results are shown in table 1:
TABLE 1
According to the data in table 1, it can be known that polyvinyl alcohol is used as an electrospinning forming aid, and is beneficial to preparing the frustule-based fiber aerogel through an electrospinning process. Too low a content thereof is not favorable for molding, too low results in poor toughness of the aerogel (example 4), and too high results in reduced porosity and reduced stealth performance (example 5). The polyethylene glycol is used as the diatom shell dispersing agent, so that the diatom shells can be uniformly dispersed in the precursor solution, the uniformity and stability of the fiber aerogel can be improved, and the porosity and flexibility are further improved (embodiments 1-7 and 8). The alumina is used as an electrostatic spinning forming assistant, so that viscosity adjustment is provided, an acid environment is provided, rapid forming of the diatom shell based fiber aerogel is facilitated through an electrostatic spinning process, and the high content of the alumina can cause the excessive viscosity of a precursor solution and easily block pinholes; the viscosity was too low, which had little effect on the precursor solution and reduced the injection speed (spinning speed) (examples 1 to 5 and examples 6 and 7, comparative example 2). The diatom shells as the porous natural silica have high purity, and compared with the commercially available silica, the multi-level porosity of the diatom shells further improves the porosity of the aerogel, reduces the weight of the aerogel, and shows more excellent infrared stealth and flexibility (example 1 and comparative example 1). Compared with the aerogel prepared by a freeze-drying method, the aerogel prepared by the electrostatic spinning method provided by the invention has higher porosity, more excellent infrared stealth performance and better flexibility (examples 1 and 8).
The applicant states that the present invention is illustrated by the above examples of the process of the present invention, but the present invention is not limited to the above process steps, i.e. it is not meant that the present invention must rely on the above process steps to be carried out. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.
Claims (10)
1. Aerogel, characterized in that it has a porous network structure made of fibrous aerogel; the fiber aerogel comprises a combination of diatom shells, polyvinyl alcohol and alumina.
2. The aerogel of claim 1, wherein said aerogel has a thickness of 0.1 to 2mm;
preferably, the number average molecular weight of the polyvinyl alcohol is 20000 to 100000;
preferably, the mass ratio of the diatom shells to the polyvinyl alcohol is 1 (0.025-0.45);
preferably, the mass ratio of the diatom shells to the alumina is 1 (0.375-2).
3. The aerogel of claim 1 or 2, wherein the aerogel has a porosity of greater than or equal to 90%.
4. The aerogel according to any of claims 1 to 3, wherein the fibrous aerogel material further comprises an aqueous dispersant;
preferably, the mass ratio of the diatom shells to the aqueous dispersant is 1 (0.0025-0.05);
preferably, the aqueous dispersant is selected from any one or a combination of at least two of polyacrylic acid, polyethylene glycol, sodium pyrophosphate or sodium silicate;
preferably, the polyacrylic acid has a number average molecular weight of 5000 to 10000;
preferably, the number average molecular weight of the polyethylene glycol is 2000 to 8000.
5. A method for the preparation of aerogels according to any of claims 1 to 4, comprising the following steps: uniformly mixing the diatom shell powder, the polyvinyl alcohol solution and an optional aqueous dispersant, adding aluminum oxide, heating and optionally ultrasonically dispersing to obtain an electrostatic spinning precursor solution; and carrying out electrostatic spinning on the electrostatic spinning precursor solution to obtain the aerogel.
6. The method according to claim 5, wherein the frustule powder is prepared by grinding frustules;
preferably, the method of milling is ball milling;
preferably, the rotation speed of the ball milling is 50-200 r/min;
preferably, the ball milling time is 1-4 h;
preferably, the particle size of the diatom shell powder is 10-100 nm;
preferably, the particle size of the alumina is 10 to 100nm;
preferably, the heating temperature is 30 to 50 ℃.
7. The method according to claim 5 or 6, wherein the solvent of the polyvinyl alcohol solution is water;
preferably, the mass percentage of the polyvinyl alcohol in the polyvinyl alcohol solution is 10-15%;
preferably, the mass ratio of the diatom shell powder to the aqueous dispersant is 1 (0.0025-0.05);
preferably, the mass ratio of the diatom shell powder to the polyvinyl alcohol solution is 1 (0.3-3.6);
preferably, the mass ratio of the diatom shell powder to the alumina is 1 (0.375-2).
8. The production method according to any one of claims 5 to 7, wherein the voltage for electrospinning is 10 to 18KV;
preferably, the number of the inner diameter of the needle head of the electrostatic spinning is 18-27G;
preferably, the injection speed of the electrostatic spinning is 0.5-1.5 mL/h;
preferably, the rotating speed of the roller for electrostatic spinning is 50-150 r/min.
9. The method of any one of claims 5 to 8, comprising the steps of:
(1) Ball-milling the frustules for 1-4 h at the rotating speed of 50-200 r/min to obtain frustules powder;
(2) Uniformly mixing the diatom shell powder obtained in the step (1), a polyvinyl alcohol aqueous solution with the concentration of 10-15% and a water-based dispersing agent according to the mass ratio of 1 (0.3-3.6) to (0.0025-0.05), then adding aluminum oxide, heating to 30-50 ℃, and optionally carrying out ultrasonic dispersion to obtain an electrostatic spinning precursor solution; the mass ratio of the diatom shell powder to the aluminum oxide is 1 (0.375-2); the aqueous dispersant is selected from any one or combination of at least two of polyacrylic acid, polyethylene glycol, sodium pyrophosphate or sodium silicate;
(3) And (3) performing electrostatic spinning on the electrostatic spinning precursor solution obtained in the step (2) by adopting a needle with the inner diameter number of 18-27G under the conditions that the voltage is 10-18 KV, the injection speed is 0.5-1.5 mL/h and the rotating speed of a roller is 50-150 r/min to obtain the aerogel.
10. Use of an aerogel as claimed in any of claims 1 to 4 in an infrared stealth material.
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