Preparation method and application of super-transparent silicon dioxide aerogel thermal insulation material

Abstract

The invention provides a preparation method and application of an ultra-transparent silicon dioxide aerogel thermal insulation material. The method comprises the following steps: dissolving a nonionic surfactant in an acidic solvent, and then adding double silicon sources for hydrolysis to obtain a silicon source precursor; dropwise adding a basic catalyst into the silicon source precursor solution, and carrying out sol-gel reaction to obtain wet gel; and putting the wet gel into a drying oven, carrying out aging treatment, and then carrying out solvent replacement and supercritical drying to obtain the ultra-transparent silicon dioxide aerogel. The prepared aerogel has the heat conductivity coefficient of 0.0259 W / m.K to 0.0339 W / m.K, the light transmittance of 67% to 95% and the water contact angle of 102 degrees to 121 degrees, the temperature of the aerogel is 3.5 DEG C lower than that of a common glass window in simulation of a building energy-saving window, the temperature of the aerogel is 27.3 DEG C higher than that of a common solar heat collection device in simulation of a solar heat collection device, the problem that low heat conductivity coefficient, high light transmittance and water repellency cannot be achieved at the same time is solved, and the aerogel is suitable for being used in a building energy-saving window and a building energy-saving window. The method has huge application value in the fields of building energy conservation, solar heat collection systems, super transparent heat insulation, deep space exploration and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanoporous materials technology, and relates to a method for preparing an ultra-transparent silica aerogel thermal insulation material and its application. Background Technology

[0002] Silica aerogels are a type of solid material with a porous three-dimensional network structure formed by interconnected nano-silica particles. Due to their unique low thermal conductivity, high specific surface area, and low density, they have broad application prospects in fields such as pipe / tank insulation, flame retardant insulation, catalysis, adsorption, and aerospace. Ultra-transparent aerogels, with their unique high light transmittance and thermal insulation properties, have also demonstrated significant application value in deep space exploration, building energy conservation, and solar thermal collection. Transparent aerogels excel in particle capture. The extremely small particle and pore structure within transparent aerogels, along with their low density and high porosity, facilitates the soft landing and complete capture of high-speed particles. NASA's Stardust probe used transparent aerogels to capture comet and interstellar dust particles. Transparent aerogels also offer significant advantages in building energy conservation and solar thermal collection. On the one hand, as an insulation material replacing traditional glass, they can significantly reduce heat loss; on the other hand, as a collector filling material, they ensure efficient solar transmission, and their ultra-low thermal conductivity can suppress heat loss to the environment. Studies have shown that transparent aerogels significantly reduce air conditioning energy consumption and improve solar energy utilization, which reduces electricity consumption in summer and winter as well as the dependence of buildings on fossil fuels for domestic water and heating.

[0003] Therefore, the preparation of ultra-transparent silica aerogels has attracted widespread attention from researchers. Chinese patent CN118456985B discloses a highly transparent, heat-insulating, and sound-insulating aerogel glass, its preparation method, and applications. Bulk aerogels were prepared using tetraethyl orthosilicate and dimethyldiethoxysilane as silicon sources and applied in glass interlayers for heat and sound insulation. However, the aerogel's uneven internal structure and insufficient light transmittance greatly limit its application range. Chinese patent CN115893429B discloses a high- and low-temperature resistant transparent aerogel insulation material with ultraviolet shielding properties and its preparation method. It mainly uses alkoxysilane as the silicon source, first modifying it in a silane coupling agent, then grafting it in a diamine solution, dianhydride solution, and an imidizing agent to finally obtain a transparent aerogel insulation material. Although this aerogel has ultraviolet shielding capabilities, its transmittance in the visible light range is less than 70%, and the modification process is complex, resulting in a relatively limited application and failing to highlight other performance advantages of transparent aerogels.

[0004] Therefore, there are still some challenges in preparing aerogel materials that combine high transparency and low thermal conductivity. Researchers need to consider how to maintain the structural integrity of transparent aerogels while also giving them ultra-transparency so that they can give full play to the unique advantages of transparent aerogels. Summary of the Invention

[0005] To address the challenge of balancing light transmittance and structural integrity in existing technologies, this invention provides a method for preparing an ultra-transparent silica aerogel thermal insulation material and its applications. The ultra-transparent silica aerogel thermal insulation material prepared by this method has a thermal conductivity of 0.0259 W / m·K to 0.0339 W / m·K, a light transmittance of 67% to 95%, and a water contact angle of 102° to 121°. In a simulated energy-efficient building window, it exhibits a temperature 3.5°C lower than ordinary glass windows, and in a simulated solar thermal collector, it shows a temperature 27.3°C higher than ordinary solar thermal collectors. This invention will greatly promote the practical application of transparent aerogels in numerous fields such as building energy conservation, solar thermal systems, and deep space exploration.

[0006] The technical solution of the present invention:

[0007] A method for preparing an ultra-transparent silica aerogel thermal insulation material includes the following steps:

[0008] (1) Preparation of silicon source precursor;

[0009] Dissolve 0.01 to 0.1 parts of nonionic surfactant in a mixed solution of 5 to 10 parts of alcohol solvent, 10 to 20 parts of water, and 0.001 to 0.01 parts of acid catalyst. Then add 2 to 10 parts of dual silicon source and 0.5 to 2 parts of drying control chemical additive to the above mixed solution for hydrolysis reaction to obtain silicon source precursor.

[0010] (2) Preparation of wet gel;

[0011] Add 0.1 to 0.5 parts of alkaline catalyst to the silicon source precursor in step (1), stir for 1 to 5 minutes, pour the sol into the mold, and obtain a wet gel within 15 minutes of reaction;

[0012] (3) Preparation of aerogels;

[0013] The obtained wet gel was placed in an oven at 40℃~80℃ for aging treatment. After aging, the wet gel was subjected to solvent replacement and supercritical drying to obtain an ultra-transparent silica aerogel thermal insulation material.

[0014] Preferably, the alcohol solvent is methanol, the acid catalyst is an acetic acid solution, and the drying chemical additive is N,N-dimethylformamide.

[0015] Preferably, the nonionic surfactant is one or a mixture of two or more of polyether F127, polyether F68, polyether P123, polyether P105, and polyether L64.

[0016] Preferably, one of the silicon sources is methyltrimethoxysilane and / or methyltriethoxysilane containing methyl groups, and the other silicon source is methyl orthosilicate and / or tetraethyl orthosilicate, with a molar ratio of 1:(0.5-3).

[0017] Preferably, the hydrolysis reaction temperature is 20℃~50℃, the hydrolysis reaction time is 0.5h~3h, and the aging time is 12h~36h.

[0018] Preferably, the alkaline catalyst is one or a mixture of two or more of ammonia, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.

[0019] Preferably, the solvent used for solvent replacement is one or a mixture of two or more of ethanol, methanol, isopropanol, and n-hexane; the number of times the solvent replacement is repeated is 1 to 8 times; the supercritical drying is supercritical carbon dioxide drying, and the pressure of supercritical carbon dioxide drying is 8 MPa to 15 MPa, the temperature is 40℃ to 70℃, the time is 2h to 8h, and the pressure relief rate is 0.1 MPa / h to 2 MPa / h.

[0020] The ultra-transparent silica aerogel thermal insulation material prepared by the above method has one or more of the following properties: the thermal conductivity of the ultra-transparent silica aerogel thermal insulation material is 0.0259 W / m·K to 0.0339 W / m·K; the light transmittance of the ultra-transparent silica aerogel thermal insulation material is 67% to 95%; and the water contact angle of the ultra-transparent silica aerogel thermal insulation material is 102° to 121°.

[0021] The ultra-transparent silica aerogel thermal insulation material prepared by the above method has applications in building energy conservation, solar thermal systems, super transparent thermal insulation, and deep space exploration. The building energy conservation material has a temperature 3.5°C lower than that of ordinary glass windows in the simulated building energy conservation window. The solar thermal system has a temperature 27.3°C higher than that of ordinary solar thermal devices in the simulated solar thermal device.

[0022] The beneficial effects of this invention are as follows: The ultra-transparent silica aerogel insulation material prepared by this invention firstly uses a nonionic surfactant to adjust the structure of the aerogel, resulting in an ultra-transparent silica aerogel insulation material with uniform pore structure, excellent light transmittance, and low thermal conductivity. Secondly, this invention employs a dual-silicon source design. One silicon source is a flexible silicon source containing methyl groups, which introduces flexible segments into the aerogel to solve the brittleness problem of transparent aerogels and provides a certain degree of hydrophobicity. The other silicon source is a rigid silicon source, and the resulting aerogel is a highly cross-linked pure inorganic network, providing a high-transmittance framework for the aerogel. The combination of the two silicon sources not only solves the problem of the fragility of pure inorganic silica transparent aerogels, but also maintains the structural integrity of the ultra-transparent aerogel while maintaining high light transmittance, and imparts a certain degree of water resistance to the aerogel. At the same time, the introduction of the nonionic surfactant also gives the aerogel a more uniform skeletal structure, perfectly solving the problem of the inability to balance the light transmittance and structural integrity of transparent aerogels. The ultra-transparent silica aerogel thermal insulation material prepared by this invention will greatly promote the practical application of such materials in many fields such as building energy conservation, solar thermal collection systems, super transparent thermal insulation, and deep space exploration. It will give full play to the unique advantage of the high light transmittance of the high-transparency aerogel itself, and has great scientific value and economic benefits. Attached Figure Description

[0023] Figure 1 This is a photograph of the ultra-transparent silica aerogel insulation material prepared in Example 3 of the present invention placed on a piece of paper covered with aerogel writing.

[0024] Figure 2 This is a scanning electron microscope image of the ultra-transparent silica aerogel thermal insulation material prepared in Example 3 of the present invention.

[0025] Figure 3 This is a transmittance curve of the ultra-transparent silica aerogel thermal insulation material prepared in Example 3 of the present invention.

[0026] Figure 4 This is a water contact angle diagram of the ultra-transparent silica aerogel thermal insulation material prepared in Example 3 of the present invention.

[0027] Figure 5 This is a temperature change curve of an energy-saving window simulated after 2 hours of outdoor sunlight exposure, based on the ultra-transparent silica aerogel thermal insulation material prepared in Example 3 of this invention.

[0028] Figure 6 This is a graph showing the temperature change of a simulated solar collector after 2 hours of direct sunlight exposure on the ultra-transparent silica aerogel insulation material prepared in Example 3 of this invention. Detailed Implementation

[0029] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0030] Example 1

[0031] (1) Preparation of silicon source precursor

[0032] 0.05 g of nonionic surfactant P123 was dissolved in a mixed solution of 10 ml methanol solvent, 15 ml water, and 0.005 ml acetic acid catalyst. Then, 3 ml of methyltrimethoxysilane, 3 ml of tetraethyl orthosilicate, and 1 ml of N,N-dimethylformamide were added to the above mixed solution and hydrolyzed at 40 °C for 2 h to obtain the silicon source precursor.

[0033] (2) Preparation of wet gel

[0034] Add 0.05 ml of ammonia water to the silicon source precursor in step (1), stir for 3 min, and then pour the sol into the mold. The gelation reaction will take place within 15 min to obtain a wet gel.

[0035] (3) Preparation of aerogels

[0036] The obtained wet gel was placed in a 60℃ oven for aging treatment. After aging for 24 hours, the wet gel was subjected to five solvent replacements using n-hexane. Then, the wet gel was subjected to supercritical carbon dioxide drying under the conditions of 9 MPa pressure, 45℃ drying temperature, 5 hours drying time, and 1 MPa / h depressurization rate to obtain an ultra-transparent silica aerogel thermal insulation material.

[0037] Example 2

[0038] (1) Preparation of silicon source precursor

[0039] 0.1 g of nonionic surfactant P123 was dissolved in a mixed solution of 10 ml methanol solvent, 15 ml water, and 0.005 ml acetic acid catalyst. Then, 3 ml of methyltrimethoxysilane, 3 ml of tetraethyl orthosilicate, and 1 ml of N,N-dimethylformamide were added to the above mixed solution and hydrolyzed at 40 °C for 2 h to obtain the silicon source precursor.

[0040] (2) Preparation of wet gel

[0041] Add 0.1 ml of ammonia water to the silicon source precursor in step (1), stir for 3 min, and then pour the sol into the mold. The gelation reaction will take place within 15 min to obtain a wet gel.

[0042] (3) Preparation of aerogels

[0043] The obtained wet gel was placed in a 60℃ oven for aging treatment. After aging for 24 hours, the wet gel was subjected to six solvent replacements using n-hexane. Then, the wet gel was dried with supercritical carbon dioxide under the conditions of 9 MPa pressure, 45℃ drying temperature, 5 hours drying time, and 1 MPa / h depressurization rate to obtain an ultra-transparent silica aerogel thermal insulation material adhesive.

[0044] Example 3

[0045] (1) Preparation of silicon source precursor

[0046] 0.15 g of nonionic surfactant P123 was dissolved in a mixed solution of 10 ml methanol solvent, 15 ml water, and 0.005 ml acetic acid catalyst. Then, 3 ml of methyltrimethoxysilane, 3 ml of tetraethyl orthosilicate, and 1 ml of N,N-dimethylformamide were added to the above mixed solution and hydrolyzed at 40 °C for 2 h to obtain the silicon source precursor.

[0047] (2) Preparation of wet gel

[0048] Add 0.15 ml of ammonia water to the silicon source precursor in step (1), stir for 3 min, and then pour the sol into the mold. The gelation reaction will take place within 15 min to obtain a wet gel.

[0049] (3) Preparation of aerogels

[0050] The obtained wet gel was placed in a 60℃ oven for aging treatment. After aging for 24 hours, the wet gel was subjected to 7 solvent replacements with n-hexane. Then, the wet gel was dried with supercritical carbon dioxide under the conditions of 9 MPa pressure, 45℃ drying temperature, 5 hours drying time and 1 MPa / h depressurization rate to obtain an ultra-transparent silica aerogel thermal insulation material.

[0051] Example 4

[0052] (1) Preparation of silicon source precursor

[0053] 0.15 g of nonionic surfactant F127 was dissolved in a mixed solution of 10 ml methanol solvent, 15 ml water, and 0.005 ml acetic acid catalyst. Then, 3 ml of methyltriethoxysilane, 3 ml of tetraethyl orthosilicate, and 1 ml of N,N-dimethylformamide were added to the above mixed solution and hydrolyzed at 40 °C for 2 h to obtain the silicon source precursor.

[0054] (2) Preparation of wet gel

[0055] Add 0.15 ml of sodium hydroxide to the silicon source precursor in step (1), stir for 3 min, and then pour the sol into the mold. The gelation reaction will take place within 15 min to obtain a wet gel.

[0056] (3) Preparation of aerogels

[0057] The obtained wet gel was placed in a 60℃ oven for aging treatment. After aging for 24 hours, the wet gel was subjected to 7 solvent replacements with isopropanol. Then, the wet gel was dried with supercritical carbon dioxide under the conditions of 9 MPa pressure, 45℃ drying temperature, 5 hours drying time and 1 MPa / h depressurization rate to obtain an ultra-transparent silica aerogel thermal insulation material.

[0058] Example 5

[0059] (1) Preparation of silicon source precursor

[0060] 0.2 g of nonionic surfactant F127 was dissolved in a mixed solution of 10 ml methanol solvent, 15 ml water, and 0.005 ml acetic acid catalyst. Then, 3 ml of methyltrimethoxysilane, 3 ml of methyl orthosilicate, and 1 ml of N,N-dimethylformamide were added to the above mixed solution and hydrolyzed at 40 °C for 2 h to obtain the silicon source precursor.

[0061] (2) Preparation of wet gel

[0062] Add 0.2 ml of sodium hydroxide to the silicon source precursor in step (1), stir for 3 min, and then pour the sol into the mold. The gelation reaction will take place within 15 min to obtain a wet gel.

[0063] (3) Preparation of aerogels

[0064] The obtained wet gel was placed in a 60℃ oven for aging treatment. After aging for 24 hours, the wet gel was subjected to 7 solvent replacements with ethanol. Then, the wet gel was dried with supercritical carbon dioxide under the conditions of 9 MPa pressure, 45℃ drying temperature, 5 hours drying time and 1 MPa / h depressurization rate to obtain an ultra-transparent silica aerogel thermal insulation material.

[0065] Aerogel performance testing

[0066] Method for determining water contact angle: The water contact angle was measured using a JC2000G contact angle / interfacial tension tester. The water contact angle of each sample surface was measured 5 times, and the average value was taken.

[0067] Thermal conductivity testing method: The thermal conductivity of the samples is tested using a thermal conductivity analyzer based on the transient plane source method. The thermal conductivity of each sample is tested 3 times and the average value is taken.

[0068] Transmittance testing method: The transmittance of the sample was measured using a UV-Vis spectrophotometer in the wavelength range of 400nm-800nm.

[0069] Building Energy-Saving Window Application Test: To verify the thermal insulation performance of aerogel as thermal insulation glass, a cooling device consisting of aluminum foil, aerogel sample, glass, thermocouple, and insulating foam box was built for the experiment. The temperature of the glass, aerogel sample, and ambient air was monitored in real time.

[0070] Solar thermal collection application test: In order to evaluate the effect of aerogel solar thermal collection device, we designed a simple simulated solar thermal collection device consisting of thermocouples, thermal insulation foam box, heat-absorbing coating, transparent aerogel and tempered glass.

[0071] Table 1. Performance test results of transparent aerogel

[0072]

[0073] It should be noted that the transmittance described in this invention is the transmittance at a visible light wavelength of 550 nm. The thickness of the sample measured was 5 mm. Higher transmittance indicates better transparency of the sample. The ultra-transparent silica aerogel synthesized in this invention possesses both a uniform pore structure and a continuous, uniform silica framework structure, thus exhibiting excellent thermal insulation and light transmission properties. Its uniform pore structure and silica framework structure... Figure 2 It can be observed under a scanning electron microscope; secondly, due to the introduction of hydrophobic methyl groups in the silicon source, the ultra-transparent silica aerogel of the present invention also has a certain degree of hydrophobicity, which further expands the application scenarios of the ultra-transparent silica aerogel prepared by the present invention.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ultratransparent silica aerogel thermal insulation material, characterized in that, The method comprises the following steps: (1) preparation of a silicon source precursor; 0.01-0.1 parts of a non-ionic surfactant is dissolved in a mixed solution of 5-10 parts of an alcohol solvent, 10-20 parts of water, and 0.001-0.01 parts of an acid catalyst, and then 2-10 parts of a double silicon source and 0.5-2 parts of a dry control chemical additive are added to the mixed solution for hydrolysis reaction to obtain the silicon source precursor; (2) preparation of a wet gel; 0.1-0.5 parts of an alkaline catalyst is added dropwise to the silicon source precursor in step (1), and after stirring for 1-5 min, the sol is poured into a mold to obtain the wet gel within 15 min; (3) preparation of an aerogel; The obtained wet gel is placed in an oven at 40-80°C for aging treatment, and after aging, the wet gel is subjected to solvent replacement and supercritical drying to obtain the ultra-transparent silica aerogel thermal insulation material.

2. The method of claim 1, wherein the super-transparent silica aerogel thermal insulation material is prepared by the steps of: In step (1), the alcohol solvent is methanol; the acid catalyst is an acetic acid solution; the dry chemical additive is N,N-dimethylformamide; the non-ionic surfactant is one or a mixture of two or more of polyether F127, polyether F68, polyether P123, polyether P105, and polyether L64; one of the double silicon sources is methyltrimethoxysilane and / or methyltriethoxysilane containing a methyl group, and the other is tetramethyl orthosilicate and / or tetraethyl orthosilicate, and the molar ratio of the two silicon sources is 1:(0.5-3).

3. The method of claim 1, wherein the super-transparent silica aerogel thermal insulation material is prepared by the steps of: In step (1), the temperature of the hydrolysis reaction is 20-50°C, the time of the hydrolysis reaction is 0.5-3 h, and the aging time is 12-36 h.

4. The method of claim 1, wherein the super-transparent silica aerogel thermal insulation material is prepared by the steps of: In step (2), the alkaline catalyst is one or a mixture of two or more of aqueous ammonia, sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.

5. The method of claim 1, wherein the super-transparent silica aerogel thermal insulation material is prepared by the steps of: In step (3), the solvent used for solvent replacement is one or a mixture of two or more of ethanol, methanol, isopropanol, and n-hexane.

6. The method of claim 1, wherein the super-transparent silica aerogel thermal insulation material is prepared by the steps of: In step (3), the number of repetitions of the solvent replacement is 1-8 times; the supercritical drying is supercritical carbon dioxide drying; the pressure of the supercritical carbon dioxide drying is 8-15 MPa, the temperature is 40-70°C, the time is 2-8 h, and the pressure release rate is 0.1-2 MPa / h.

7. An ultra-transparent silica aerogel thermal insulation material obtained by the preparation method of any one of claims 1-6.

8. The ultratransparent silica aerogel thermal insulation material according to claim 7, characterized in that, The ultra-transparent silica aerogel thermal insulation material has one or more of the following properties: The thermal conductivity of the ultra-transparent silica aerogel thermal insulation material is 0.0259-0.0339 W / m·K; The light transmittance of the ultra-transparent silica aerogel thermal insulation material is 67-95%; The water contact angle of the ultra-transparent silica aerogel thermal insulation material is 102-121°.

9. Use of the ultra-transparent silica aerogel thermal insulation material of claim 7 or 8 in the fields of building energy saving, solar heat collection system, super-transparent thermal insulation, and deep space exploration.

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