A flexible hydrophilic silica aerogel and a preparation method and application thereof

Abstract

The application discloses a flexible hydrophilic silica aerogel and a preparation method and application thereof. The preparation method of the flexible hydrophilic silica aerogel comprises the following steps: uniformly mixing amphiphilic organosilicon molecules, an alkali catalyst and an acid catalyst, then adding an auxiliary silicon source, uniformly stirring, and standing to obtain a silica wet gel; and performing aging treatment and solvent replacement on the silica wet gel, and obtaining the flexible hydrophilic silica aerogel through normal pressure drying. The flexible hydrophilic silica aerogel is prepared through a normal pressure drying method, a series of flexible hydrophilic silica aerogels with good sphericity can be prepared through a one-pot method without using any traditional surfactant and emulsification process, and the method can save a large amount of surfactant and is very friendly to the environment.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a flexible hydrophilic silica aerogel, its preparation method, and its application. Background Technology

[0002] Aerogels are porous solid nanomaterials composed of colloidal particles or polymers aggregated into a network structure, possessing a three-dimensional continuous and open porous network. Due to their low packing density (0.003-0.6 g / cm³), hydrophobicity, low thermal conductivity (0.001-0.06 W / m·K), high surface area (400-1500 m² / g), and optical transparency, they have broad application prospects in numerous fields such as thermal insulation, drug carriers, catalysts, high-efficiency rechargeable batteries, low-dielectric-constant insulating layers, Cherenkov detectors, and ultra-high-speed integrated circuit substrates. Since the first invention of silica aerogel in 1931, various methods for its preparation have been developed over the decades. The most common preparation method is the sol-gel method. The prepared wet gel needs to be further dried to obtain an aerogel. Current drying methods include supercritical drying, freeze drying, and atmospheric pressure drying. However, supercritical drying has harsh production conditions, requires special equipment, and is difficult to operate, costly, and poses significant safety hazards. Freeze drying usually requires a longer aging time to stabilize the network structure of the wet gel, thereby reducing volume shrinkage during the drying process. Atmospheric pressure drying, on the other hand, has a short drying time, is simple to operate, and has a relatively high degree of precision.

[0003] Surfactants are essential in aerogel synthesis. Surfactants are amphiphilic and readily form different aggregation states in water, effectively controlling the assembly of nanostructures with varying morphologies. The most important surfactant in aerogel synthesis is hexadecyltrimethylammonium bromide (CTAB), but its drawback is that it requires replacement with ethanol and deionized water for approximately 4-5 days during each gelation process, making complete removal difficult. Summary of the Invention

[0004] The main objective of this invention is to provide a flexible hydrophilic silica aerogel, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a method for preparing a flexible hydrophilic silica aerogel, comprising:

[0007] After the amphiphilic organosilicon molecules, the base catalyst and the acid catalyst are mixed evenly, an auxiliary silicon source is added and mixed evenly. After standing, a silica wet gel is obtained.

[0008] The silica wet gel was subjected to aging treatment, solvent replacement and drying at normal pressure to obtain a flexible hydrophilic silica aerogel.

[0009] Furthermore, the preparation method of the flexible hydrophilic silica aerogel specifically includes: coupling a propyltriethoxysilane cyanate with a terminal hydroxyl oligoether in a molar ratio of 1:2.0 to 2.08 to obtain the amphiphilic organosilicon molecule.

[0010] Furthermore, the volume ratio of the alkaline catalyst to the auxiliary silicon source is 1:1 to 2:1.

[0011] Furthermore, the volume ratio of the acid catalyst to the auxiliary silicon source is 1:1 to 3:1.

[0012] Furthermore, the solvent used for solvent replacement includes any one or a combination of two or more of anhydrous ethanol, deionized water, or n-hexane, and the solvent replacement time is 2 to 3 days.

[0013] Furthermore, the atmospheric pressure drying method includes any one or a combination of two or more of the following: forced air drying, spray drying, or rotary drying, with a drying pressure of 0.9 to 1.1 atmospheres, a temperature of 60 to 100°C, and a time of 10 to 20 hours.

[0014] The present invention also provides a flexible hydrophilic silica aerogel, the flexible hydrophilic silica aerogel comprising a gel skeleton mainly composed of oligoether and silica, and the flexible hydrophilic silica aerogel having a porous structure with a porosity of 80-95%, a maximum compression resilience of 80%, a water contact angle of 0°, a UV-Vis reflectance of >80%, and an average emissivity of 0.8-0.95 in the 8-13 micrometer band.

[0015] The present invention also provides the use of the aforementioned flexible hydrophilic silica aerogel in daytime passive radiative cooling or atmospheric water capture.

[0016] The present invention also provides a method for obtaining water, comprising: capturing water from the atmosphere using the aforementioned flexible hydrophilic silica aerogel, and then squeezing the flexible hydrophilic silica aerogel to obtain liquid water.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The preparation method of the flexible hydrophilic silica aerogel of the present invention uses amphiphilic organosilicon molecules that can be used as both surfactants and silicon source precursors. In this way, the surfactant molecules can be used as reactants and directly become one of the main components of the gel, which does not need to be removed in the future, thus alleviating the environmental pressure. The present invention is prepared by atmospheric pressure drying method, which can prepare a series of flexible hydrophilic silica aerogels with good sphericity in one pot without the use of any additional traditional surfactants and emulsification processes. This method can save a lot of surfactants and is also environmentally friendly.

[0019] (2) The preparation method of the present invention breaks through the bottleneck of normal pressure drying preparation of flexible hydrophilic silica aerogel, and can be used for passive radiation cooling and atmospheric water capture. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is the Fourier transform infrared spectrum of the flexible hydrophilic silica aerogel obtained in Example 1 of the present invention.

[0022] Figure 2 This is a scanning electron microscope image of the flexible hydrophilic silica aerogel obtained in Example 1 of the present invention.

[0023] Figure 3 This is a particle size distribution diagram of the flexible hydrophilic silica aerogel obtained in Example 1 of the present invention.

[0024] Figure 4 This is the Fourier transform infrared spectrum of the flexible hydrophilic silica aerogel obtained in Example 2 of the present invention.

[0025] Figure 5 This is a scanning electron microscope image of the flexible hydrophilic silica aerogel obtained in Example 2 of the present invention.

[0026] Figure 6 This is a particle size distribution diagram of the flexible hydrophilic silica aerogel obtained in Example 2 of the present invention.

[0027] Figure 7 This is the Fourier transform infrared spectrum of the flexible hydrophilic silica aerogel obtained in Example 3 of the present invention.

[0028] Figure 8 This is a scanning electron microscope image of the flexible hydrophilic silica aerogel obtained in Example 3 of the present invention.

[0029] Figure 9 This is a particle size distribution diagram of the flexible hydrophilic silica aerogel obtained in Example 3 of the present invention.

[0030] Figure 10 This is the Fourier transform infrared spectrum of the flexible hydrophilic silica aerogel obtained in Example 4 of the present invention.

[0031] Figure 11 This is a scanning electron microscope image of the flexible hydrophilic silica aerogel obtained in Example 4 of the present invention.

[0032] Figure 12 This is a particle size distribution diagram of the flexible hydrophilic silica aerogel obtained in Example 4 of the present invention.

[0033] Figure 13 This is the Fourier transform infrared spectrum of the flexible hydrophilic silica aerogel obtained in Example 5 of the present invention.

[0034] Figure 14 This is a scanning electron microscope image of the flexible hydrophilic silica aerogel obtained in Example 5 of the present invention.

[0035] Figure 15 This is a particle size distribution diagram of the flexible hydrophilic silica aerogel obtained in Example 5 of the present invention. Detailed Implementation

[0036] Given the numerous shortcomings of current methods for preparing flexible hydrophilic silica aerogels, the inventors of this case, through long-term research and practice, have proposed a flexible hydrophilic silica aerogel, its preparation method, and its applications. The method primarily uses an organosilicon precursor as an auxiliary silicon source, mixing amphiphilic organosilicon molecules, an alkaline catalyst, and an acid catalyst, then adding the auxiliary silicon source. After standing for a period of time, a wet gel is obtained, which is then aged, solvent-replaced, and dried at atmospheric pressure to obtain a flexible hydrophilic silica aerogel. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0037] One aspect of this invention provides a method for preparing a flexible hydrophilic silica aerogel, comprising:

[0038] After the amphiphilic organosilicon molecules, the base catalyst and the acid catalyst are mixed evenly, an auxiliary silicon source is added and mixed evenly. After standing, a silica wet gel is obtained.

[0039] The silica wet gel was subjected to aging treatment, solvent replacement and drying at normal pressure to obtain a flexible hydrophilic silica aerogel.

[0040] In some preferred embodiments, the preparation method of the flexible hydrophilic silica aerogel specifically includes: coupling a propyltriethoxysilane cyanate with a terminal hydroxyl oligoether in a molar ratio of 1:2.0 to 2.08 to obtain the amphiphilic organosilicon molecule.

[0041] In some more preferred embodiments, the preparation method specifically includes: mixing propyltriethoxysilane cyanate and hydroxyl-terminated oligoether at a molar ratio of 1:(2.0-2.08) until homogeneous, and reacting completely under hydrothermal conditions to obtain an amphiphilic organosilicon molecule that serves as both a silicon source and a surfactant.

[0042] Furthermore, the temperature of the hydrothermal treatment is 60–80°C.

[0043] Furthermore, the reaction time is 3 to 6 hours.

[0044] In some preferred embodiments, the auxiliary silicon source may include any one or a combination of two or more of methyltrimethoxysilane, dimethyldimethoxysilane, tetramethylsilane, epoxysilane or tetraethoxysilane, but is not limited thereto.

[0045] In some preferred embodiments, the alkaline catalyst may include any one or a combination of two or more of urea, ammonia, sodium hydroxide solution, etc., but is not limited thereto.

[0046] In some preferred embodiments, the volume ratio of the alkaline catalyst to the auxiliary silicon source is 1:1 to 2:1.

[0047] Furthermore, the volume content of the alkaline catalyst in the silica wet gel is 1-20% (V / V).

[0048] In some preferred embodiments, the acid catalyst may include any one or a combination of two or more of acetic acid, hydrochloric acid, nitric acid, oxalic acid, etc., but is not limited thereto.

[0049] In some preferred embodiments, the volume ratio of the acid catalyst to the auxiliary silicon source is 1:1 to 3:1.

[0050] Furthermore, the volume content of the acid catalyst in the silica wet gel is 1-60% (V / V).

[0051] Furthermore, the volume content of the auxiliary silicon source in the silica wet gel is 10-40% (V / V).

[0052] In some preferred embodiments, the settling temperature is 40–80°C and the settling time is 2–6 hours.

[0053] In some preferred embodiments, the aging treatment is performed at a temperature of 40–80°C for 1–2 days.

[0054] In some preferred embodiments, the solvent used for solvent replacement includes any one or a combination of two or more of anhydrous ethanol, deionized water or n-hexane, and the solvent replacement time is 2 to 3 days.

[0055] In some preferred embodiments, the atmospheric pressure drying method includes any one or a combination of two or more of the following: forced air drying, spray drying, or rotary drying, with a drying pressure of 0.9 to 1.1 atmospheres, a temperature of 60 to 100°C, and a time of 10 to 20 hours.

[0056] In some more preferred embodiments, the method for preparing the flexible hydrophilic silica aerogel includes:

[0057] The preparation of amphiphilic organosilicon molecules, which can act as both surfactants and silicon source precursors for the synthesis of aerogels; and,

[0058] A base catalyst, amphiphilic organosilicon molecules, and an acid catalyst were mixed thoroughly, followed by the addition of an auxiliary silicon source. The mixture was stirred until homogeneous, allowed to stand, and then subjected to a gelation reaction at 40–80°C to obtain a wet silica gel.

[0059] The silica wet gel was aged at 40–80°C, solvent replaced, and then dried at 60–100°C under normal pressure for 10–20 h to obtain a flexible hydrophilic silica aerogel. The drying pressure was 0.9–1.1 atmospheres.

[0060] In some more specific embodiments, the preparation method of the flexible hydrophilic silica aerogel includes:

[0061] (1) Prepare amphiphilic organosilicon molecules, which can act as both surfactants and silicon source precursors for the synthesis of aerogels;

[0062] (2) Mix the alkaline catalyst (e.g., urea), amphiphilic organosilicon molecules, and acid catalyst (e.g., acetic acid) evenly, then add the auxiliary silicon source (e.g., methyltrimethoxysilane, dimethyldimethoxysilane), stir evenly, and let stand (e.g., gel at 40°C for 2 hours) to obtain silica wet gel.

[0063] (3) The silica wet gel is subjected to aging treatment (e.g., aging at 70°C for 1.5 days), solvent replacement (e.g., replacement in deionized water for 1 day, replacement in ethanol for 2 days), and atmospheric pressure drying (e.g., drying at 70°C for 12 hours, drying pressure of 1.0 atmosphere) to obtain flexible hydrophilic silica aerogel.

[0064] In summary, the embodiments of the present invention propose a simple method for preparing flexible hydrophilic silica aerogels that is simple in process, low in cost, short in production cycle, and requires only simple equipment, providing a simple method for the atmospheric pressure drying preparation of flexible silica aerogels.

[0065] The preparation method of this invention enables the industrial production of flexible hydrophilic silica aerogels, and yields flexible hydrophilic silica aerogels with good sphericity without the use of any traditional surfactants. This method is simple, has a short production process, uses few organic reagents, and is low in cost.

[0066] Another aspect of the present invention provides a flexible hydrophilic silica aerogel, the flexible hydrophilic silica aerogel comprising a gel skeleton mainly composed of oligoethers and silica, and the flexible hydrophilic silica aerogel having a porous structure with a porosity of 80-95%, a maximum compression resilience of 80%, a water contact angle of 0°, a UV-Vis reflectance of >80%, and an average emissivity of 0.8-0.95 in the 8-13 micrometer band.

[0067] Another aspect of the present invention provides the use of the aforementioned flexible hydrophilic silica aerogel in daytime passive radiative cooling or atmospheric water capture.

[0068] Another aspect of the present invention provides a method for obtaining water, comprising: capturing water from the atmosphere using the aforementioned flexible hydrophilic silica aerogel, and then squeezing the flexible hydrophilic silica aerogel to obtain liquid water.

[0069] In summary, the preparation method of this invention overcomes the bottleneck of atmospheric pressure drying preparation of flexible hydrophilic silica aerogels and can be used for passive radiation cooling and atmospheric water capture.

[0070] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate understanding of the present invention, and do not constitute any limitation thereof. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0071] Example 1

[0072] (1) Preparation of amphiphilic organosilicon molecules: Polyethylene glycol-400 and propyltriethoxysilane isocyanate were mixed evenly at a molar ratio of 1:2.0 and reacted at 60℃ under hydrothermal conditions for 3h to obtain an amphiphilic organosilicon molecule that can act as a surfactant and as a silicon source precursor for the synthesis of aerogels.

[0073] (2) Preparation of silica wet gel: 1.0 g of the above amphiphilic organosilicon molecules, 5 g of urea, and 15 ml of acetic acid (concentration of 0.05 mol / L) were weighed and stirred at 500 r / min for 0.5 h. Then, 3 ml of methyltrimethoxysilane and 2 ml of dimethyldimethoxysilane were added dropwise while stirring. The mixture was then gelled in an oven at 40 °C for 2 h to form silica wet gel.

[0074] (3) Aging: The silica wet gel was aged at 40°C for 24 hours.

[0075] (4) Solvent replacement: The aged gel was placed in deionized water for 48 hours for replacement.

[0076] (5) Drying: The solvent-displaced silica wet gel was dried in a blower dryer for 10 hours at a drying pressure of 0.9 atm and a temperature controlled at 60℃ to obtain a flexible hydrophilic silica aerogel. Characterization by SEM and other methods revealed that the average particle size of this flexible hydrophilic silica aerogel was 4-7 μm, and the particles were spherical. For the Fourier transform infrared spectrum of this flexible hydrophilic silica aerogel, please refer to [link to Fourier transform infrared spectrum]. Figure 1 Please refer to the separate documents for scanning electron microscopy and particle size distribution. Figure 2 and Figure 3 Other parameters are shown in Table 1.

[0077] Example 2

[0078] (1) Preparation of amphiphilic organosilicon molecules: Polyethylene glycol-400 and propyltriethoxysilane isocyanate were mixed evenly at a molar ratio of 1:2.02 and reacted at 65℃ under hydrothermal conditions for 4h to obtain an amphiphilic organosilicon molecule that can be used as a surfactant and as a silicon source precursor for the synthesis of aerogels.

[0079] (2) Preparation of silica wet gel: 1.5g of the above amphiphilic organosilicon molecules, 5g of urea, and 15ml of acetic acid (concentration of 0.05mol / L) were weighed and stirred at 500r / min for 0.5h. Then, 3ml of methyltrimethoxysilane and 2ml of dimethyldimethoxysilane were added dropwise while stirring. The mixture was then gelled in an oven at 50℃ for 3h to form silica wet gel.

[0080] (3) Aging: The silica wet gel was aged at 50°C for 30 hours.

[0081] (4) Solvent replacement: The aged gel was placed in deionized water for 54 hours for replacement.

[0082] (5) Drying: The solvent-displaced silica wet gel was dried in a blower dryer for 12 hours at a drying pressure of 0.95 atm and a temperature controlled at 70℃ to obtain a flexible hydrophilic silica aerogel. Characterization by SEM and other methods revealed that the average particle size of this flexible hydrophilic silica aerogel was 3-5 μm, and the particles were spherical. For the Fourier transform infrared spectrum of this flexible hydrophilic silica aerogel, please refer to [link to Fourier transform infrared spectrum]. Figure 4 Please refer to the separate documents for scanning electron microscopy and particle size distribution. Figure 5 and Figure 6 Other parameters are shown in Table 1.

[0083] Example 3

[0084] (1) Preparation of amphiphilic organosilicon molecules: Polyethylene glycol-400 and propyltriethoxysilane isocyanate were mixed evenly at a molar ratio of 1:2.04 and reacted at 70℃ under hydrothermal conditions for 4h to obtain an amphiphilic organosilicon molecule that can be used as a surfactant and as a silicon source precursor for the synthesis of aerogels.

[0085] (2) Preparation of silica wet gel: 2.0g of the above amphiphilic organosilicon molecules, 5g of urea, and 15ml of acetic acid (concentration of 0.05mol / L) were weighed and stirred at 500r / min for 0.5h. Then, 3ml of methyltrimethoxysilane and 2ml of dimethyldimethoxysilane were added dropwise while stirring. The mixture was then gelled in an oven at 60℃ for 4h to form silica wet gel.

[0086] (3) Aging: The silica wet gel was aged at 60°C for 36 hours.

[0087] (4) Solvent replacement: The aged gel was placed in anhydrous ethanol for 60 h for replacement.

[0088] (5) Drying: The solvent-displaced silica wet gel was dried in a blower dryer for 15 hours at a drying pressure of 1.0 atm and a temperature controlled at 80℃ to obtain a flexible hydrophilic silica aerogel. Characterization by SEM and other methods revealed that the average particle size of this flexible hydrophilic silica aerogel was 3-4 μm, and the particles were spherical. For the Fourier transform infrared spectrum of this flexible hydrophilic silica aerogel, please refer to [link to Fourier transform infrared spectrum]. Figure 7 Please refer to the separate documents for scanning electron microscopy and particle size distribution. Figure 8 and Figure 9 Other parameters are shown in Table 1.

[0089] Example 4

[0090] (1) Preparation of amphiphilic organosilicon molecules: Polyethylene glycol-400 and propyltriethoxysilane isocyanate were mixed evenly at a molar ratio of 1:2.06 and reacted at 75°C under hydrothermal conditions for 5 hours to obtain an amphiphilic organosilicon molecule that can act as a surfactant and as a silicon source precursor for the synthesis of aerogels.

[0091] (2) Preparation of silica wet gel: 2.5g of the above amphiphilic organosilicon molecules, 5g of urea, and 15ml of acetic acid (concentration of 0.05mol / L) were weighed and stirred at 500r / min for 0.5h. Then, 3ml of methyltrimethoxysilane and 2ml of dimethyldimethoxysilane were added dropwise while stirring. The mixture was then gelled in an oven at 70℃ for 5h to form silica wet gel.

[0092] (3) Aging: The silica wet gel was aged at 70°C for 42 hours.

[0093] (4) Solvent replacement: The aged gel was placed in anhydrous ethanol for 66 hours for replacement.

[0094] (5) Drying: The solvent-displaced silica wet gel was dried in a spray dryer for 17 h at a drying pressure of 1.05 atm and a temperature controlled at 90 °C to obtain a flexible hydrophilic silica aerogel. Characterization by SEM and other methods revealed that the average particle size of this flexible hydrophilic silica aerogel was 3-5 μm, and the particles were spherical. For the Fourier transform infrared spectrum of this flexible hydrophilic silica aerogel, please refer to [reference needed]. Figure 10 Please refer to the separate documents for scanning electron microscopy and particle size distribution. Figure 11 and Figure 12 Other parameters are shown in Table 1.

[0095] Example 5

[0096] (1) Preparation of amphiphilic organosilicon molecules: Polyethylene glycol-400 and propyltriethoxysilane isocyanate were mixed evenly at a molar ratio of 1:2.08 and reacted at 80℃ under hydrothermal conditions for 6 hours to obtain an amphiphilic organosilicon molecule that can act as a surfactant and as a silicon source precursor for the synthesis of aerogels.

[0097] (2) Preparation of silica wet gel: 3.0g of the above amphiphilic organosilicon molecules, 5g of urea, and 15ml of acetic acid (concentration of 0.05mol / L) were weighed and stirred at 500r / min for 0.5h. Then, 3ml of methyltrimethoxysilane and 2ml of dimethyldimethoxysilane were added dropwise while stirring. The mixture was then gelled in an oven at 80℃ for 6h to form silica wet gel.

[0098] (3) Aging: The silica wet gel was aged at 80°C for 48 hours.

[0099] (4) Solvent replacement: The aged gel was placed in n-hexane for 72 hours for replacement.

[0100] (5) Drying: The solvent-displaced silica wet gel was dried in a rotary dryer for 20 h at a drying pressure of 1.1 atm and a temperature controlled at 100 °C to obtain a flexible hydrophilic silica aerogel. Characterization by SEM and other methods revealed that the average particle size of this flexible hydrophilic silica aerogel was 4-6 μm, and the particles were spherical. For the Fourier transform infrared spectrum of this flexible hydrophilic silica aerogel, please refer to [link to Fourier transform infrared spectrum]. Figure 13 Please refer to the separate documents for scanning electron microscopy and particle size distribution. Figure 14 and Figure 15 Other parameters are shown in Table 1.

[0101] Table 1. Parameters of the flexible hydrophilic silica aerogels obtained in Examples 1-5

[0102]

[0103] As shown in Table 1, the flexible hydrophilic silica aerogel prepared by the embodiments of the present invention has a porous structure with a porosity of 80-95%, a UV-Vis reflectance of >80%, and an average emissivity of 0.8-0.95 in the 8-13 micrometer band.

[0104] Comparative Example 1

[0105] Preparation of silica wet gel: 5g of urea and 15ml of acetic acid (concentration 0.05mol / L) were measured and stirred at 500r / min for 0.5h. While stirring, 3ml of methyltrimethoxysilane and 2ml of dimethyldimethoxysilane were added dropwise, and the mixture was gelled in an oven at 80℃ for 6h. Without the presence of amphiphilic organosilicon molecules, gel formation is impossible.

[0106] Comparative Example 2

[0107] Preparation of traditional aerogels: 5g of urea, 15ml of acetic acid (0.05mol / L), and 1g of CTAB were mixed at 500r / min for 0.5h. While stirring, 3ml of methyltrimethoxysilane and 2ml of dimethyldimethoxysilane were added dropwise. The mixture was then gelled in an oven at 80℃ for 6h to form a silica wet gel. After replacement with deionized water for 24h and ethanol for 72h, the gel was dried in an oven at 70℃ for 8h to obtain a silica aerogel. This aerogel has a contact angle of 124°, is completely hydrophobic, has an average emissivity of 0.91 in the 8–13 μm wavelength range, an average particle size of 6.3 μm, and a density of 0.147 g / cm³. 3 .

[0108] Application Example 1

[0109] Application of the flexible hydrophilic silica aerogel in Example 1 for daytime passive radiative cooling. Testing showed that the aerogel can lower the temperature by 10°C during the day and 6°C at night.

[0110] Application Example 2

[0111] Application of the flexible hydrophilic silica aerogel in atmospheric water capture according to Example 2. After fog absorption testing, the aerogel was able to absorb 200% of its own weight in fog within 10 hours.

[0112] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0113] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. The use of a flexible hydrophilic silica aerogel in daytime passive radiative cooling or atmospheric water capture, characterized in that, The preparation method of the flexible hydrophilic silica aerogel includes: A mixture of propyltriethoxysilane cyanate and hydroxyl-terminated oligoether at a molar ratio of 1:(2.0-2.08) was prepared and reacted under hydrothermal conditions at 60-80°C to obtain an amphiphilic organosilicon molecule. After the amphiphilic organosilicon molecules, the base catalyst, and the acid catalyst are mixed evenly, an auxiliary silicon source is added and mixed evenly. After standing, a silica wet gel is obtained. The silica wet gel is subjected to aging treatment, solvent replacement, and drying at normal pressure to obtain a flexible hydrophilic silica aerogel. The flexible hydrophilic silica aerogel comprises a gel skeleton composed of oligoether and silica, and has a porous structure with a porosity of 80-95%, a maximum compression resilience of 80%, a water contact angle of 0°, a UV-Vis reflectance of >80%, and an average emissivity of 0.8-0.95 in the 8-13 micrometer band.

2. The use according to claim 1, characterized in that: The auxiliary silicon source includes any one or a combination of two or more of methyltrimethoxysilane, dimethyldimethoxysilane, tetramethylsilane, epoxysilane, or tetraethoxysilane.

3. The use according to claim 1, characterized in that: The alkaline catalyst includes any one or a combination of two or more of urea, ammonia, or sodium hydroxide solution.

4. The use according to claim 1, characterized in that: The acid catalyst includes any one or a combination of two or more of acetic acid, hydrochloric acid, nitric acid, or oxalic acid.

5. The use according to claim 1, characterized in that: The volume ratio of the alkaline catalyst to the auxiliary silicon source is 1:1 to 2:

1.

6. The use according to claim 1, characterized in that: The volume ratio of the acid catalyst to the auxiliary silicon source is 1:1 to 3:

1.

7. The use according to claim 1, characterized in that: The settling temperature is 40~80℃, and the time is 2~6h.

8. The use according to claim 1, characterized in that: The aging treatment is performed at a temperature of 40-80℃ for 1-2 days.

9. The use according to claim 1, characterized in that, The solvent used for solvent replacement includes any one or a combination of two or more of anhydrous ethanol, deionized water, or n-hexane, and the solvent replacement time is 2 to 3 days.

10. The use according to claim 1, characterized in that, The atmospheric pressure drying method includes any one or a combination of two or more of the following: forced air drying, spray drying, or rotary drying, with a drying pressure of 0.9 to 1.1 atmospheres, a temperature of 60 to 100°C, and a time of 10 to 20 hours.

11. The use according to claim 1, characterized in that, include: The flexible hydrophilic silica aerogel is used to capture water from the atmosphere, and then the flexible hydrophilic silica aerogel is squeezed to obtain liquid water.

Images