A method for preparing a super-transparent aerogel sheet

Abstract

The present application relates to a kind of preparation methods of super-transparent aerogel sheet, by one-step sol-gel method, with super-transparent aerogel sheet, its transparency is comparable to glass.Selecting functional silane precursor as raw material, by uniformly mixing acid catalyst, deionized water, functional silicon precursor, alkali solution, after hydrolysis, condensation, obtain porous material with matrix structure of pore structure and present silk-like fiber.Again after supercritical drying or atmospheric drying, it is prepared into super-transparent, elastic, super-insulating aerogel sheet.The present application innovatively proposes micro-level particle control, pore structure design, silk-like fiber skeleton growth technology, and the aerogel constructed covers super-transparent, elastic, hydrophobic, super-insulating and other properties, realizes the coupling of multiple functions.And raw material source is extensive, preparation process is simple, energy consumption is low, the preparation of sheet material marks its quantifiable production, the characteristics of super-transparency can make its application field expand to building insulation, industrial insulation and other fields, to achieve energy saving and efficiency, high value-added benefit.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of preparation process of aerogel porous materials, and relates to a preparation method of super-transparent aerogel sheet, which is prepared by a simple one-step sol-gel method combined with supercritical drying or atmospheric drying process to prepare a super-transparent, elastic and super-insulating multifunctional aerogel sheet. BACKGROUND

[0002] SiO2 aerogel is a porous material composed of a three-dimensional network of nanoscale, as a gas-solid two-phase material, the solid phase structure gives the condition of aerogel block forming, so it can be prepared into various shaped materials; the gas phase is provided by its almost 95% or more nanopores, which are covered with a large amount of air, and air as a poor conductor of heat, gives the aerogel thermal insulation performance, so it can serve in extreme environments. Today, with the rapid development of science and technology, the exploration of various fields is further improved, and the requirements for materials used in high-tech equipment are also more stringent. Science and technology, chemical industry and other fields often require equipment to work in high temperature environment, and high temperature environment usually affects the performance and service life of the equipment, which requires a protective device to provide protection and isolate the influence of extreme temperature to provide a suitable working environment. Zhou (Advanced Materials, 2023, 35(49): 10) et al. prepared a layered inorganic silicate aerogel with nanocluster pillars, which achieved synergistic improvement in thermal and mechanical properties. The thermal conductivity of the layered silicate aerogel is 0.034 W / (m·K) at room temperature (298K) under air conditions, and 0.187 W / (m·K) at high temperature (1073K) under air conditions, and the compressive strength is 80 kPa at 42% compression, which provides reliable support for its application. The novel columnar layer structure improves the thermal insulation performance and mechanical stability of the layered inorganic silicate aerogel, and opens up a way for exploring advanced inorganic aerogels under extreme conditions.

[0003] In addition to the thermal insulation performance, mechanical elasticity and transparency have a huge driving force for the wide application of SiO2 aerogel. Large cargo ships or cruise ships usually travel on the ocean for several days or even several months. The scorching sun or cold environment on the ocean makes it difficult for the driver and the traveling passengers to bear. By placing the aerogel with high transparency in the glass interlayer of the ship body, its thermal insulation performance can be played, and a comfortable environment can be provided for the inside of the ship. Moreover, the aerogel has mechanical elasticity and can withstand the extrusion of the glass interlayer without breaking. Zhang (Advanced Materials, 2023, 35(29): 11) et al. prepared a nano-composite aerogel with a "porous brick and fiber" structure through multi-scale adaptive synthesis and scalable ambient pressure drying technology. The thermal conductivity is 0.0174 W / (m·K), the high tensile strength and compressive strength (tensile modulus 24 MPa and compressive modulus 2.2 MPa), and the high bending toughness (bending modulus 8.2·10-6MPa) exhibit excellent structural stability under dynamic impact force, fatigue stress / strain cycle and extreme temperature. The aerogel has excellent mechanical and thermal insulation properties and strong thermal insulation performance under extreme conditions.

[0004] Patent CN202211685237.9 prepared a transparent aerogel, the light transmittance of which is between 80% and 90%, and the wet gel needs tedious modification treatment to have hydrophobicity, and the contact angle is about 106°. The transparency and hydrophobicity of the aerogel are not good, so the aerogel with super-transparency, elasticity, super-thermal insulation and other multifunctional integration still needs to be developed and applied. SUMMARY

[0005] The purpose of the present application is to improve the shortcomings of the prior art and provide a preparation method of super-transparent aerogel sheet, which can produce aerogel sheet with super-high transparency comparable to glass. The material has super-transparency, elasticity and super-thermal insulation and other properties. The aerogel material of the prior art usually does not have super-transparency, only covers elasticity and thermal insulation functions, and the application scene is limited. The material prepared by the present patent has the characteristics of ultra-low thermal conductivity, and the characteristics of ultra-low density make its mass advantage more significant compared with most materials of the same volume. The super-transparency of the material makes it applicable to the fields of cruise ship glass interlayer and building glass interlayer, which can ensure the comfortable temperature inside large machinery and buildings without affecting the light transmittance, and has great application value.

[0006] The technical scheme of the present application is as follows:

[0007] (1) uniformly mix the acid and the functionalized silicon precursor, stir at 5-60℃ and a magnetic stirring speed of 200-1000r / min for 0.1-2h to obtain a transparent solution;

[0008] (2) adding water and a surfactant into the solution system obtained in step (1), maintaining the same temperature and stirring speed as in step (1) for 0.1-2 h to obtain a transparent sol system;

[0009] (3) adding a base solution into the sol system obtained in step (2), maintaining the same temperature and stirring speed as in step (1) for 1-60 min to obtain a transparent sol;

[0010] (4) pouring the transparent sol obtained in step (3) into a mold, standing for 0.1-1 h to gel, and then aging at 5-60 °C for 1-12 h;

[0011] (5) adding the wet gel obtained in step (4) into a displacement solution for displacement;

[0012] (6) subjecting the wet gel obtained in step (5) to supercritical carbon dioxide drying or atmospheric pressure drying to obtain an ultratransparent aerogel sheet;

[0013] In step (1), the molar ratio of the acid to the functionalized silicon precursor is (0.001-0.1):1; in step (2), the molar ratio of water, the surfactant and the functionalized silicon precursor is (1-100):(0.002-0.5):1; and in step (3), the molar ratio of the base solute in the base solution to the functionalized silicon precursor is (0.001-1):1.

[0014] Preferably, the acid in step (1) is oxalic acid, acetic acid, hypochlorous acid, hydrochloric acid, sulfuric acid or nitric acid; and the concentration of the acid is 0.001-1 mol / L.

[0015] Preferably, the functionalized silicon precursor in step (1) is one or more of methylsilane, methyltrimethoxysilane, methyltriethoxysilane, diethoxymethylsilane, dimethylchlorosilane, vinyltriethoxysilane, phenyltriethoxysilane, 3-aminopropyltriethoxysilane, isobutyltriethoxysilane, n-octyltriethoxysilane or dodecyltrimethoxysilane.

[0016] Preferably, the surfactant in step (2) is one or more of dodecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, polyether F127, octadecyl trimethyl ammonium chloride, octadecyl amide methyl pyridine chloride or polyquaternary ammonium salt-16.

[0017] Preferably, the base solution in step (3) is one of Na2CO3, NaHCO3, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, ammonia, urea, choline hydroxide or benzyl trimethyl ammonium hydroxide solution; and the concentration of the base solution is 0.01-1 mol / L.

[0018] The displacement liquid in step (5) is preferably one or more of water, methanol, ethanol, t-butanol, n-hexane, isopropanol, carbon tetrachloride, toluene or n-decanol. The displacement in step (5) is preferably carried out 6-12 times at 30-80°C, with an interval of 4-12 hours.

[0019] The supercritical carbon dioxide drying method in step (6) is preferably carried out using carbon dioxide as the drying medium, at a reaction temperature of 45-50°C, a pressure of 8-15 MPa in a high-pressure reaction kettle, a gas release rate of 2-8 L / min, and a drying time of 4-12 hours.

[0020] The atmospheric drying method in step (6) is preferably carried out by drying the wet gel at three temperatures: 40-60°C, 80-100°C and 100-120°C, with a drying time of 2-6 hours at each temperature.

[0021] The present patent realizes the synergistic improvement of the super-transparency, elasticity and super-thermal insulation performance of aerogels through the innovative strategy of regulating the size of gel particle and pore structure. The functionalized silicon precursor containing alkyl groups retains the alkyl groups during hydrolysis, and after condensation, there are mutually repulsive alkyl groups on the aerogel skeleton. The existence of repulsive force makes the skeleton structure exhibit excellent elasticity when it is pressed. At the same time, the existence of alkyl groups makes the aerogel have hydrophobic properties, which can be used in various humid environments without affecting its performance. The basic catalyst as the condensation catalyst effectively balances the formation of fibrous-like skeleton of polysiloxane. The super-transparent aerogel prepared by controlling the micro-skeleton characteristics and structure size has almost comparable transparency to glass, providing a strategy for the preparation of high-transparency, elastic, high-thermal insulation aerogel sheets.

[0022] Advantages:

[0023] The method of the present patent and the super-transparent aerogel sheet prepared by the method have the following characteristics:

[0024] (1) Technological innovation, by adjusting the size of gel particles and pore structure at the micro level, the aerogel has the characteristics of super-transparency, with extremely high transparency, comparable to glass, and a visible light transmittance of 99%, and realizes the multifunctional coupling of super-transparency, elasticity, super-thermal insulation and other properties.

[0025] (2) Simple process route, by one-step sol-gel method combined with supercritical drying process or atmospheric drying process, super-transparent, elastic, super-thermal insulation aerogel sheet can be obtained, and the material has both elasticity and extremely high compressive strength, can withstand a large degree of extrusion, and has a rebound feature.

[0026] (3) Low cost, the various reagents used in the patent are all commercially available raw materials, the raw materials are easy to obtain, the material preparation is efficient, the preparation process has low energy consumption, and has the potential for large-scale or industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a photograph of the ultratransparent aerogel sheet prepared in Example 1, wherein (a) is a top view of the ultratransparent aerogel sheet, and (b) is a side view of the ultratransparent aerogel sheet.

[0028] Figure 2 is a BET test data graph of the ultratransparent aerogel sheet prepared in Example 2; wherein (a) is a nitrogen adsorption-desorption curve, and (b) is a pore size distribution curve. DETAILED DESCRIPTION

[0029] Example 1

[0030] Oxalic acid and methylsilane were mixed uniformly at a molar ratio of 0.008:1. A transparent solution was obtained after stirring at 60°C and a magnetic stirring speed of 850 r / min for 1 h, wherein the concentration of the oxalic acid solution was 1 mol / L. Then water, polyquaternary ammonium salt-16 were added to the transparent solution at a molar ratio of water: polyquaternary ammonium salt-16:methylsilane of 68:0.08:1. A transparent sol system was obtained after stirring at the same temperature and speed for 0.5 h. Choline hydroxide was then added to the sol system at a molar ratio of choline hydroxide:methylsilane of 1:1. A transparent sol was obtained after continuing to stir at the same temperature and speed for 1 min, wherein the concentration of the solute in the choline hydroxide solution was 0.01 mol / L. The transparent sol was poured into a mold and left to gel for 0.5 h, followed by aging at 60°C for 5 h. The gel was first replaced with a mixed solution of water and methanol at a volume ratio of 1:1 at 60°C, and the replacement was performed 8 times, followed by replacement with pure methanol for 2 times, with an interval of 10 h each time. Then the wet gel after methanol replacement was subjected to normal pressure drying at temperatures of 40°C, 80°C and 100°C for 6 h respectively, to obtain an ultratransparent aerogel sheet. The photograph of the ultratransparent aerogel prepared is shown in Figure 1 , the top view shows that the material has very high transparency Figure 1 (a)), and the aerogel sheet has a thickness of about 7 mm Figure 1 (b)), a light transmittance of 97%, a specific surface area of 1037 m2 / g, a compression resilience of 983 times at a deformation of 50%, a thermal conductivity of 0.023 W / (m*K), and a hydrophobic angle of 139°.

[0031] Example 2

[0032] Acetic acid and methyltrimethoxysilane were mixed evenly at a molar ratio of 0.013:1 and stirred at 8°C and 450 rpm for 0.25 h to obtain a transparent solution with an acetic acid concentration of 0.005 mol / L. Water and polyether F127 were then added to the transparent solution at a molar ratio of 5.7:0.002:1 (water, polyether F127, methyltrimethoxysilane). The mixture was stirred at the same temperature and speed for 1.5 h to obtain a transparent sol system. Tetramethylammonium hydroxide was then added to the sol system at a molar ratio of 0.039:1 (tetramethylammonium hydroxide, methyltrimethoxysilane). The mixture was stirred at the same temperature and speed for another 3 min to obtain a transparent sol with a solute concentration of 0.5 mol / L in the tetramethylammonium hydroxide solution. The transparent sol was poured into a mold and allowed to stand for 0.1 h to gel, followed by aging at 8°C for 1 h. The gel was first replaced with a water-ethanol mixture at 50℃ (water to ethanol volume ratio 1:1) six times, followed by two replacements with pure ethanol solvent, with each replacement occurring 12 hours apart. The ethanol-replaced wet gel was then subjected to supercritical carbon dioxide drying at 49℃, with an autoclave pressure of 10 MPa, an outgassing rate of 3 L / min, and a drying time of 6.5 hours, yielding an ultra-transparent aerogel sheet. The nitrogen adsorption-desorption curve of the prepared ultra-transparent aerogel was shown. Figure 2 (a) and aperture distribution curve ( Figure 2 (b) shows that the material exhibits a typical type IV mixing isotherm, with the most probable pore size distribution occurring at 23.45 nm. Figure 2 (b) demonstrates that the material is a mesoporous material, which explains its superior thermal insulation properties. The material has a light transmittance of 99% and a specific surface area of ​​984 m². 2 / g, achieving 1002 compression rebounds under 50% deformation, with a thermal conductivity of 0.018W / (m*K) and a hydrophobic angle of 142°.

[0033] Example 3

[0034] Hydrochloric acid, 3-aminopropyltriethoxysilane were mixed uniformly according to the molar ratio of 0.001:1. The transparent solution was obtained after stirring at 5°C, 1000r / min speed for 0.2h, in which the concentration of hydrochloric acid solution was 0.2mol / L. Then water, cetyltrimethylammonium bromide were added to the transparent solution according to the molar ratio of water, cetyltrimethylammonium bromide, 3-aminopropyltriethoxysilane 1:0.01:1. The transparent sol system was obtained after stirring at the same temperature and speed for 2h. Ammonia was added to the sol system according to the molar ratio of ammonia, 3-aminopropyltriethoxysilane 0.001:1. The transparent sol was obtained after stirring at the same temperature and speed for 60min, in which the concentration of solute in the ammonia solution was 1mol / L. The transparent sol was poured into the mold and gelled after 0.2h, and then aged at 5°C for 5h. The gel was first replaced with a mixed solution of water and t-butyl alcohol at 80°C, in which the volume ratio of water to t-butyl alcohol was 1:1. After 4 times of replacement, t-butyl alcohol pure solvent was used for 2 times of replacement, with an interval of 4h each time. Then the wet gel after t-butyl alcohol replacement was subjected to carbon dioxide supercritical drying, in which the reaction temperature was 45°C, the pressure in the high-pressure reaction kettle was 15MPa, the air release rate was 2L / min, and the drying time was 12h. The ultratransparent aerogel sheet was obtained. The prepared ultratransparent aerogel had a light transmittance of 97.6%, a specific surface area of 892m 2 / g, a compression resilience of 958 times at a deformation of 50%, a thermal conductivity of 0.017W / (m*K), and a hydrophobic angle of 146°.

[0035] Example 4

[0036] The hypochlorous acid, dodecyltrimethoxysilane were mixed uniformly according to the molar ratio of 0.046:1, and a transparent solution was obtained after stirring at 24°C with a magnetic stirring speed of 620r / min for 1.3h, wherein the concentration of the hypochlorous acid solution was 0.06mol / L. Then water, octadecyltrimethylammonium chloride were added to the transparent solution according to the molar ratio of water, octadecyltrimethylammonium chloride, dodecyltrimethylsilane 100:0.2:1, and the same temperature and stirring speed were maintained for 0.8h to obtain a transparent sol system. Then NaHCO3 solution was added to the sol system according to the molar ratio of NaHCO3, dodecyltrimethylsilane 0.72:1, and the same temperature and stirring speed were maintained for 43min to obtain a transparent sol, wherein the concentration of the solute in the NaHCO3 solution was 0.08mol / L. The transparent sol was poured into a mold and left to gel for 0.8h, followed by aging at 24°C for 9h. The gel was replaced with isopropanol pure solvent 10 times at 30°C, with an interval of 8h each time. Then the wet gel after isopropanol replacement was subjected to carbon dioxide supercritical drying, wherein the reaction temperature was 50°C, the pressure in the high-pressure reaction kettle was 8MPa, the air release rate was 8L / min, and the drying time was 4h, to obtain an ultratransparent aerogel sheet. The prepared ultratransparent aerogel had a light transmittance of 98.5%, a specific surface area of 938m 2 / g, a compression and rebound of 1021 times was achieved at a deformation of 50%, a thermal conductivity of 0.020W / (m*K), and a hydrophobic angle of 143°.

[0037] Example 5

[0038] Sulfuric acid, isobutyl triethoxysilane were mixed uniformly according to the molar ratio of 0.1:1, and a transparent solution was obtained after stirring at 48°C with a magnetic stirrer at a speed of 200 r / min for 2h, wherein the concentration of the sulfuric acid solution was 0.001 mol / L. Then water, dodecyl dimethyl benzyl ammonium chloride were added to the transparent solution according to the molar ratio of water, dodecyl dimethyl benzyl ammonium chloride, isobutyl triethoxysilane 22:0.5:1, and a transparent sol system was obtained after stirring at the same temperature and speed for 0.1h. Urea was then added to the sol system according to the molar ratio of urea, isobutyl triethoxysilane 0.093:1, and a transparent sol was obtained after continuing to stir at the same temperature and speed for 26min, wherein the solute concentration in the urea solution was 0.8 mol / L. The transparent sol was poured into a mold and left to gel for 1h at 48°C, followed by aging for 12h. The gel was first replaced with a mixed solution of water and n-hexane at a volume ratio of 1:1 at 45°C, and the replacement was performed 6 times, followed by replacement with pure n-hexane for 6 times, with an interval of 10h each time. Then the wet gel after n-hexane replacement was subjected to normal pressure drying at 60°C, 100°C and 120°C respectively for 2h, and an ultratransparent aerogel sheet was obtained. The prepared ultratransparent aerogel showed a transparent state, a light transmittance of 98%, a specific surface area of 1012m 2 / g, a compression and rebound of 926 times at a deformation of 50%, a thermal conductivity of 0.023 W / (m*K), and a hydrophobic angle of 139°.

Claims

1. A method for preparing a super-transparent aerogel sheet, comprising the following steps: (1) uniformly mixing an acid and a functionalized silicon precursor, stirring at a magnetic stirring speed of 200-1000 r / min at 5-60 ℃ for 0.1-2 h to obtain a transparent solution; wherein the functionalized silicon precursor is one or more of methylsilane, methyltrimethoxysilane, methyltriethoxysilane, diethoxymethylsilane, dimethylchlorosilane, vinyltriethoxysilane, phenyltriethoxysilane, 3-aminopropyltriethoxysilane, isobutyltriethoxysilane, n-octyltriethoxysilane or dodecyltrimethoxysilane; (2) adding water and a surfactant to the solution system obtained in step (1), and stirring at the same temperature and speed as in step (1) for 0.1-2 h to obtain a transparent sol system; (3) adding a base solution to the sol system obtained in step (2), and stirring at the same temperature and speed as in step (1) for 1-60 min to obtain a transparent sol; (4) pouring the transparent sol obtained in step (3) into a mold, and allowing it to gel after standing for 0.1-1 h, and then aging at 5-60 ℃ for 1-12 h; (5) adding a replacement liquid to replace the wet gel obtained in step (4); wherein the replacement liquid is one or more of water, methanol, ethanol, t-butanol, n-hexane, isopropyl alcohol, carbon tetrachloride, toluene or n-decanol; and the replacement is performed 6-12 times at 30-80 ℃, with an interval of 4-12 h each time; (6) subjecting the wet gel obtained in step (5) to supercritical carbon dioxide drying or atmospheric pressure drying to obtain a super-transparent aerogel sheet. In step (1), the molar ratio of the acid to the functionalized silicon precursor is (0.001-0.1):1; in step (2), the molar ratio of water, the surfactant and the functionalized silicon precursor is (1-100):(0.002-0.5):1; and in step (3), the molar ratio of the base solute in the base solution to the functionalized silicon precursor is (0.001-1):

1. In step (1), the acid is oxalic acid, acetic acid, hypochlorous acid, hydrochloric acid, sulfuric acid or nitric acid; and the concentration of the acid is 0.001-1 mol / L. In step (2), the surfactant is one or more of dodecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, polyether F127, octadecyl trimethyl ammonium chloride, octadecyl amide methyl pyridine chloride or polyquaternary ammonium salt-16. In step (3), the base solution is one of Na2CO3, NaHCO3, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, ammonia, urea, choline hydroxide or benzyl trimethyl ammonium hydroxide solution; and the concentration of the base solution is 0.01-1 mol / L. In step (6), the supercritical carbon dioxide drying is performed using carbon dioxide as the drying medium, at a reaction temperature of 45-50 ℃, a pressure of 8-15 MPa in a high-pressure reaction kettle, a gas release rate of 2-8 L / min and a drying time of 4-12 h. ​ ​ ​ ​ ​ ​ wherein: ​ 2. The production method according to claim 1, characterized by ​ 3. The method of claim 1, wherein ​ 4. The production method according to claim 1, characterized by ​ 5. The production method according to claim 1, characterized by ​ 6. The production method according to claim 1, characterized by The atmospheric drying in step (6): drying treatment of the wet gel is carried out at three temperatures: 40~60 ℃, 80~100 ℃, 100~120 ℃, and drying for 2~6 h at each temperature, respectively. The atmospheric drying in step (6): drying treatment of the wet gel is carried out at three temperatures: 40~60 ℃, 80~100 ℃, 100~120 ℃, and drying for 2~6 h at each temperature, respectively.

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