Multifunctional elastic radiation refrigeration aerogel and preparation method thereof

Abstract

The invention discloses a multifunctional elastic radiation refrigeration aerogel and a preparation method thereof, and the preparation method comprises the following steps: carrying out surface modification and nanocrystallization treatment on biomass polysaccharide, and then mixing and dispersing with an inorganic nanomaterial; adding a cross-linking agent into the obtained mixed dispersion liquid, and stirring for reaction; then adding a surfactant, stirring and foaming to obtain a cross-linked dispersion liquid; sequentially carrying out freeze solidification and freeze drying on the cross-linked dispersion liquid to obtain a radiation refrigeration aerogel matrix; and finally, dipping the radiation refrigeration aerogel matrix in a mixed solution of polydimethylsiloxane and a curing agent, and carrying out heat treatment to obtain the multifunctional elastic radiation refrigeration aerogel. The multifunctional elastic radiation refrigeration aerogel prepared by the invention has the advantages of high porosity, excellent mechanical properties, high cooling efficiency and the like, and also has high weather resistance and high safety and degradability.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling materials technology. Specifically, this invention relates to a multifunctional elastic radiation cooling aerogel and its preparation method. Background Technology

[0002] Global energy shortages and rising temperatures pose significant challenges to sustainable development, making refrigeration a crucial means for combating high temperatures and maintaining comfortable living conditions. Traditional refrigeration technologies, such as compression refrigeration, are currently the most widely used. While simple and efficient, these technologies consume vast amounts of electricity from fossil fuels. Furthermore, traditional refrigeration solutions rely on compressors and chemical refrigerants, resulting in enormous electricity consumption. Additionally, fluorinated refrigerants damage the ozone layer, further exacerbating the greenhouse effect and creating a vicious cycle. With increasing focus on sustainable development, finding a highly efficient, energy-saving, and environmentally friendly refrigeration technology is urgently needed. Radiative refrigeration utilizes the Earth's atmospheric window (8-13μm infrared band) to directly radiate heat into the low-temperature outer space, while simultaneously reflecting solar radiation (0.25-2.5μm). It operates entirely passively, requiring no external energy input and using no refrigerants. It operates with zero energy consumption, zero emissions, and low maintenance costs. With continuous technological advancements, radiative refrigeration is emerging as a promising approach to addressing challenges such as climate change and energy consumption.

[0003] Radiative cooling materials are crucial for radiative cooling. Ideal radiative cooling materials should possess characteristics such as high solar spectral reflectivity, high atmospheric window emissivity, low thermal conductivity, and weather resistance. Simultaneously, the materials should be easy to prepare, economical, environmentally friendly, and suitable for large-scale production. In recent years, many radiative cooling materials have been reported. Chinese patent application CN118852813A discloses a porous polymer-based radiative cooling material, obtained by cold pressing the polymer at room temperature and sintering it at high temperature. This material exhibits good radiative cooling performance, but may suffer from the problem of matrix degradation. Chinese patent application CN118636549A discloses a multilayer radiative cooling material with strong resistance to ultraviolet aging, but its preparation process is complex, which may limit its large-scale application.

[0004] Conventional radiative cooling materials are mostly organic polymers or inorganic nanoparticles, with chemical coatings and optical films as the main carriers. They have a wide range of applications, but the products have limited functions and are complex to prepare. In the production process, some toxic and harmful substances are inevitably used, which can cause environmental damage. In particular, current cooling materials are difficult to recycle or biodegrade after long-term use, causing new environmental pollution.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a multifunctional elastic radiation-cooling aerogel and its preparation method. This invention combines natural biodegradable biomass materials and two-dimensional inorganic nanomaterials to prepare an elastic radiation-cooling aerogel through hierarchical multi-scale microstructure regulation and organic / inorganic interface enhancement. This aerogel possesses advantages such as high porosity, excellent mechanical properties, and high cooling efficiency.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: In a first aspect, embodiments of the present invention provide a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) The biomass polysaccharide is first surface modified and then nano-sized to obtain modified biomass polysaccharide; (2) The modified biomass polysaccharide and inorganic nanomaterials are dispersed in water to obtain a mixed dispersion; (3) Add a crosslinking agent to the mixed dispersion and stir to react; (4) Add a surfactant to the reaction solution obtained in step (3), stir and foam to obtain a cross-linked dispersion; (5) The cross-linked dispersion is then subjected to freeze-coagulation and freeze-drying in sequence to obtain a radiation-cooled aerogel matrix; (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of polydimethylsiloxane and curing agent, and the multifunctional elastic radiation-cooled aerogel is obtained after heat treatment.

[0008] In some embodiments, in step (1), the surface modification treatment includes carboxylation modification or sulfonation modification of the biomass polysaccharide; Optionally, the biomass polysaccharide includes at least one of cellulose, hemicellulose, and lignin; Optionally, the carboxylation modification process is as follows: biomass polysaccharide, 4-acetamido-TEMPO and sodium bromide are mixed evenly in water, and then NaClO solution is added. The mixture is stirred and reacted. After the reaction is completed, the reaction product is filtered and washed until neutral to obtain the product. Optionally, the sulfonation modification process is as follows: the biomass polysaccharide is hydrolyzed using sulfuric acid as a catalyst, and then the resulting hydrolysis product is washed with water until neutral to obtain the final product.

[0009] In some embodiments, during the carboxylation modification process, the mass ratio of the biomass polysaccharide, the 4-acetamido-TEMPO, and the sodium bromide is 1:0.016:0.1, and the concentration of the NaClO solution is 1.3~5 mmol / g; the stirring reaction is carried out at a pH of 10, a reaction temperature of 25°C, and a reaction time of 5 h. And / or, in the sulfonation modification process, the concentration of sulfuric acid is 64 wt%, the reaction temperature of the hydrolysis reaction is 45°C, and the reaction time is 30~100 min.

[0010] In some embodiments, in step (1), the nano-processing involves homogenizing the surface-modified biomass polysaccharide in a high-pressure homogenizer for 3 to 5 cycles, and the pressure of the high-pressure homogenizer is controlled at 8000 bar.

[0011] In some embodiments, in step (2), the mass ratio of the modified biomass polysaccharide to the inorganic nanomaterial is 1:(1~5); Optionally, the inorganic nanomaterial is a natural layered silicate mineral, including at least one of kaolin, montmorillonite, and bentonite; And / or, in the mixed dispersion, the sum of the concentrations of the modified biomass polysaccharide and the inorganic nanomaterial is 1.9~5.6 wt.%.

[0012] In some embodiments, in step (3), the crosslinking agent includes at least one of 3-aminopropyltriethoxysilane, polydiglycol diglycidyl ether, and citric acid, and the amount of the crosslinking agent added is 0.1~1g / 100mL; And / or, the stirring speed is 1000 r / min, the reaction temperature is room temperature, and the reaction time is 2 h.

[0013] In some embodiments, in step (4), the surfactant includes at least one of sodium carboxymethyl cellulose, hydroxyethyl cellulose, and methyl cellulose; And / or, the stirring and foaming is carried out in a high-speed shearing machine, and the stirring and foaming speed is 8000~12000 r / min, and the stirring and foaming time is 5~15 min.

[0014] In some embodiments, in step (5), the freezing temperature is -196 to -24°C and the freezing time is 5 to 12 hours. And / or, the freeze-drying temperature is not higher than -56°C, and the drying time is ≥48h.

[0015] In some embodiments, in step (6), the concentration of the mixed solution of polydimethylsiloxane and curing agent is 5~20 wt.%; And / or, in the mixed solution of polydimethylsiloxane and curing agent, the mass ratio of polydimethylsiloxane to curing agent is 10:1; And / or, the immersion time is 10 seconds; And / or, the heat treatment temperature is 60~120℃, and the heat treatment time is 0.5~5h.

[0016] Secondly, embodiments of the present invention also provide a multifunctional elastic radiation-cooling aerogel, which is prepared by the preparation method described in the first aspect.

[0017] The advantages and beneficial effects of the embodiments of the present invention are as follows: This invention provides a porous, biodegradable matrix prepared by combining modified biomass polysaccharides with two-dimensional inorganic nanomaterials under the action of crosslinking agents and surfactants. A radiation-cooling aerogel is then obtained through low-temperature polymerization and high-temperature curing. This aerogel exhibits high solar reflectivity and mid-to-far-infrared emissivity. Furthermore, the hierarchical porous structure formed by the surfactants and freeze-drying process enhances its resistance to external impacts and improves the thermal insulation performance of the resulting aerogel material. Simultaneously, the additional functional layer formed by polydimethylsiloxane imparts high weather resistance to the aerogel material, while the inorganic nanomaterials provide fire resistance. Moreover, the aerogel material utilizes abundant, low-cost, clean, and pollution-free raw materials, exhibiting high safety and degradability. This meets the requirements of high radiation cooling power, long-term stable weather resistance, and environmental friendliness in the field of radiation cooling for building radiation cooling materials. Attached Figure Description

[0018] Figure 1 The images are scanning electron microscope (SEM) images of the radiation-cooled aerogels prepared in Examples 3-5 and Comparative Example 1 of this invention.

[0019] Figure 2 The image shows the cyclic compression curve of the radiation-cooled aerogel prepared in Example 3 of this invention under 30% compressive strain in a dry state at room temperature.

[0020] Figure 3 The contact angle test diagrams are of the radiation-cooled aerogels prepared in Examples 3-5 of this invention.

[0021] Figure 4 The reflectance curves of the radiation-cooled aerogels prepared in Example 3 and Comparative Example 1 of this invention are shown in the range of 0.25-2.5 μm.

[0022] Figure 5The infrared emission curves of the radiation-cooled aerogels prepared in Example 3 and Comparative Example 1 of this invention are shown.

[0023] Figure 6 The data curves show the thermal insulation performance of the radiation-cooled aerogel prepared in Example 4 of this invention.

[0024] Figure 7 This is an optical image of the testing device for the actual radiative cooling performance of the radiative cooling aerogel prepared in Example 3 of the present invention.

[0025] Figure 8 The actual radiation cooling performance test temperature curves of the radiation-cooling aerogels prepared in Example 3 and Comparative Example 1 of this invention are shown.

[0026] Figure 9 The temperature curve of the radiative cooling aerogel simulated house radiative cooling test obtained in Example 4 of the present invention is shown. Detailed Implementation

[0027] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] In this invention, when a value is described as a range, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as specific numerical values ​​falling within that range, regardless of whether specific numerical values ​​or specific subranges are explicitly specified.

[0029] In this invention, the terms “comprising” and “including” and their various variations mean that other elements or wholes may be included but are not specifically described.

[0030] In this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0031] In a first aspect, embodiments of the present invention provide a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) The biomass polysaccharide is first surface modified and then nano-sized to obtain modified biomass polysaccharide; (2) The modified biomass polysaccharide and inorganic nanomaterials are dispersed in water to obtain a mixed dispersion; (3) Add a crosslinking agent to the mixed dispersion and stir to react; (4) Add a surfactant to the reaction solution obtained in step (3), stir and foam to obtain a cross-linked dispersion; (5) The cross-linked dispersion is then subjected to freeze-coagulation and freeze-drying in sequence to obtain a radiation-cooled aerogel matrix; (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of polydimethylsiloxane and curing agent, and the multifunctional elastic radiation-cooled aerogel is obtained after heat treatment.

[0032] This invention combines modified biomass polysaccharides with inorganic nanomaterials to form a strong and tough microscopic framework structure. Furthermore, the introduction of surfactants enables the material to form a unique multi-level porous structure, effectively improving its reflectivity to visible light and infrared emissivity, and enhancing its elasticity. In addition, the additional functional layer formed by the two-dimensional inorganic nanomaterials and polydimethylsiloxane imparts thermal insulation, fire resistance, self-cleaning properties, and good radiative cooling effects. Moreover, the raw materials used in the preparation method of this invention are widely available, low-cost, and environmentally friendly, and the preparation process is simple, clean, and pollution-free, facilitating large-scale production and promotion.

[0033] In some embodiments, in step (1), the surface modification treatment includes carboxylation modification or sulfonation modification of the biomass polysaccharide; Optionally, the biomass polysaccharide includes at least one of cellulose, hemicellulose, and lignin; preferably, the biomass polysaccharide includes at least one of cellulose and lignin; wherein the cellulose is at least one of lyocell fiber, bleached softwood pulp board, and degreased cotton; and the lignin is at least one of softwood lignin, hardwood lignin, and grass lignin. Optionally, the carboxylation modification is performed using the TEMPO oxidation method. The specific process is as follows: biomass polysaccharide, 4-acetamido-TEMPO and sodium bromide are mixed evenly in water, and then NaClO solution is added. The mixture is stirred and reacted. After the reaction is completed, the reaction product is filtered and washed until neutral to obtain the final product. Optionally, the sulfonation modification process is as follows: the biomass polysaccharide is hydrolyzed using sulfuric acid as a catalyst, and then the resulting hydrolysis product is washed with water until neutral to obtain the final product.

[0034] In some embodiments, during the carboxylation modification process, the mass ratio of the biomass polysaccharide, the 4-acetamido-TEMPO, and the sodium bromide is 1:0.016:0.1, and the concentration of the NaClO solution is 1.3~5 mmol / g (i.e., 1.3-5 mmol NaClO per gram of biomass polysaccharide, and the available chlorine content of the NaClO is 10%); the stirring reaction is carried out at a pH of 10, a reaction temperature of 25°C, and a reaction time of 5 h. And / or, in the sulfonation modification process, the concentration of sulfuric acid is 64 wt%, the reaction temperature of the hydrolysis reaction is 45°C, and the reaction time is 30~100 min.

[0035] In some embodiments, in step (1), the nano-processing involves homogenizing the surface-modified biomass polysaccharide in a high-pressure homogenizer for 3 to 5 cycles, and the pressure of the high-pressure homogenizer is controlled at 8000 bar.

[0036] In some embodiments, in step (2), the mass ratio of the modified biomass polysaccharide to the inorganic nanomaterial is 1:(1~5); Optionally, the inorganic nanomaterial is a natural layered silicate mineral with a size of 100-200 nm; further, the silicate mineral includes at least one of kaolin, montmorillonite, and bentonite; preferably, the silicate mineral includes at least one of kaolin and montmorillonite. By adding two-dimensional layered silicate minerals, the material can be endowed with functions such as heat insulation and flame retardancy, making it difficult to burn when exposed to open flames and self-extinguishing in a very short time, thereby effectively preventing fire threats. And / or, in the mixed dispersion, the sum of the concentrations of the modified biomass polysaccharide and the inorganic nanomaterial is 1.9~5.6 wt.%.

[0037] This invention employs plant polysaccharides as biomass polysaccharides, and performs surface modification and nano-sizing treatment to form a one-dimensional nanostructure with abundant negative surface charge, high aspect ratio, and high strength. Simultaneously, by selecting inorganic nanomaterials with a two-dimensional nanolayer structure and combining the two, the one-dimensional plant polysaccharides and the two-dimensional inorganic nanomaterials can form a strong and tough brick-and-mortar structure through surface charge interaction, thereby endowing the material with a strong and tough microscopic framework structure.

[0038] Furthermore, the inventors discovered through research that if the amount of inorganic nanomaterials added is too high, the resulting radiation-cooled aerogel will have poor mechanical elasticity and will be difficult to recover after compression; however, if the amount of inorganic nanomaterials added is too low, the flame retardancy of the resulting radiation-cooled aerogel will be greatly reduced. Therefore, it is advantageous to control the mass ratio of modified biomass polysaccharide to inorganic nanomaterials within the range of 1:(1~5) in the embodiments of the present invention.

[0039] In some embodiments, in step (3), the crosslinking agent includes at least one of 3-aminopropyltriethoxysilane (APTES), polydiglycidyl ether (PEGDE), and citric acid (CA), and the amount of the crosslinking agent added is 0.1~1g / 100mL, preferably 0.5~1g / 100mL; And / or, the stirring speed is 1000 r / min, the reaction temperature is room temperature, and the reaction time is 2 h.

[0040] In some embodiments, in step (4), the surfactant includes at least one of sodium carboxymethyl cellulose, hydroxyethyl cellulose, and methyl cellulose. By introducing the surfactant, the surface tension of water can be significantly reduced, allowing air to form stable bubbles in the dispersion, and the pore structure is preserved after freeze-drying. In addition, the microporous structure formed after the removal of the tiny ice crystals formed during the freezing process also exists in the radiation-cooled aerogel. This process endows the radiation-cooled aerogel with a unique multi-level pore structure, giving it both excellent mechanical properties and low thermal conductivity. This satisfies the requirements of building materials for thermal insulation, sound insulation, etc., and can effectively resist the effects of complex weather. And / or, the stirring and foaming is carried out in a high-speed shearing machine, and the stirring and foaming speed is 8000~12000 r / min, and the stirring and foaming time is 5~15 min.

[0041] In some embodiments, in step (5), the freezing temperature is -196 to -24°C and the freezing time is 5 to 12 hours; preferably, the freezing temperature is -70 to -20°C. And / or, the freeze-drying temperature is not higher than -56°C, and the drying time is ≥48h.

[0042] In some embodiments, in step (6), the concentration of the mixed solution of polydimethylsiloxane (PDMS) and curing agent is 5-20 wt.%, preferably 10-15 wt.%. And / or, in the mixed solution of polydimethylsiloxane and curing agent, the mass ratio of polydimethylsiloxane to curing agent is 10:1; And / or, the immersion time is 10 seconds; And / or, the heat treatment temperature is 60~120℃, and the heat treatment time is 0.5~5h.

[0043] It should be noted that in the curing process of step (6) of this invention, it is only necessary to encapsulate PDMS on the substrate material to form an additional functional layer. The curing time varies at different temperatures; the higher the temperature, the shorter the curing time. This additional functional layer can effectively improve the hydrophobicity, self-cleaning properties, and durability of the radiation-cooling aerogel. In practical applications, it can effectively ensure the cleanliness of its surface, maintain its radiation-cooling effect for a long time, and reduce the cost of use. In addition, it should be noted that the polydimethylsiloxane and curing agent used in the embodiments of this invention are commercially available reagents purchased from Dow Corning SYLGARD 184 silicone resin two-component kit, which includes a basic component (i.e., polydimethylsiloxane) and a curing agent.

[0044] Secondly, embodiments of the present invention also provide a multifunctional elastic radiation-cooling aerogel, which is prepared by the preparation method described in the first aspect.

[0045] The following are non-limiting embodiments and comparative examples of the present invention. It should be noted that the schemes in the comparative examples are not prior art, but are only set up for comparison with the schemes in the embodiments, and are not intended to limit the present invention. Unless otherwise stated, all raw materials used in the embodiments and comparative examples are conventional commercially available products, or can be prepared by known methods.

[0046] Example 1 This embodiment provides a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 2mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, adjust the pH of the reaction system with 0.5mol / L NaOH solution to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 1g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 1.96wt.%. (3) Add 0.1 g of citric acid to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g sodium carboxymethyl cellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (wherein, PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in an 80°C forced-air drying oven for 3 hours to obtain a multifunctional elastic radiation-cooled aerogel.

[0047] Example 2 This embodiment provides a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%), and use 64wt% sulfuric acid to catalyze the hydrolysis reaction of the softwood pulp board under heating conditions of 45℃. After hydrolysis for 30~100min, the hydrolysis product is washed with water until neutral to obtain modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 1g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 1.96wt.%. (3) Add 0.1 g of citric acid to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g of methylcellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (wherein, PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in an 80°C forced-air drying oven for 3 hours to obtain a multifunctional elastic radiation-cooled aerogel.

[0048] Example 3 This embodiment provides a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 2g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 2.91wt.%. (3) Add 0.1 g of citric acid to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g of methylcellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (wherein, PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in an 80°C forced-air drying oven for 3 hours to obtain a multifunctional elastic radiation-cooled aerogel.

[0049] Example 4 This embodiment provides a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 3g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 3.8wt.%. (3) Add 0.1 g of citric acid to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g of methylcellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (wherein, PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in an 80°C forced-air drying oven for 3 hours to obtain a multifunctional elastic radiation-cooled aerogel.

[0050] Example 5 This embodiment provides a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 5g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 5.6wt.%. (3) Add 0.1 g of 3-aminopropyltriethoxysilane (APTES) to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g of methylcellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (wherein, PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in a 100°C forced-air drying oven for 1 hour to obtain a multifunctional elastic radiation-cooled aerogel.

[0051] Example 6 This embodiment provides a method for preparing a multifunctional elastic radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 5g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 5.6wt.%. (3) Add 0.1 g of polydiglycidyl ether (PEGDE) to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g of methylcellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (wherein, PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in a 100°C forced-air drying oven for 1 hour to obtain a multifunctional elastic radiation-cooled aerogel.

[0052] Comparative Example 1 This comparative example provides a method for preparing a radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and add it to 100mL of water. Stir at room temperature until fully dispersed to obtain a modified biomass polysaccharide dispersion with a concentration of about 1wt.%. (3) Pour the modified biomass polysaccharide dispersion obtained in step (2) into a silicone mold, freeze at -80℃ for 12h, and after solidification, freeze-dry the solidified material at -56℃ for 48h to obtain radiation-cooled aerogel.

[0053] Comparative Example 2 This comparative example provides a method for preparing a radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 2g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 2.91wt.%. (3) Pour the mixed dispersion obtained in step (2) into a silicone mold and freeze at -80℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain radiation-cooled aerogel.

[0054] Comparative Example 3 This comparative example provides a method for preparing a radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 2g of montmorillonite and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 2.91wt.%. (3) Add 0.1 g of citric acid to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g of methylcellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24°C for 12 hours. After solidification, freeze-dry the solidified material at -56°C for 48 hours to obtain a radiation-cooled aerogel.

[0055] Comparative Example 4 This comparative example provides a method for preparing a radiation-cooled aerogel, comprising the following steps: (1) Take 1g of bleached softwood pulp board (Yinying Paper Industry, α-cellulose >90%) and add it to 100mL of deionized water. Then add 0.016g of 4-acetamido-TEMPO and 0.1g of sodium bromide and stir evenly. Then add 10mL of NaClO solution with a concentration of 5mmol / g dropwise and stir the reaction at 25℃ for 5h. During the reaction, use 0.5mol / L NaOH solution to adjust the pH value of the reaction system to maintain it at about 10. After the reaction is completed, filter and wash the reaction product until it is neutral. Then place it in a high pressure homogenizer (8000bar) and homogenize it 5 times to obtain a transparent jelly-like modified biomass polysaccharide. (2) Take 1g of the above-mentioned dry weight of modified biomass polysaccharide and 1g of spherical silica and add them to 100mL of water. Stir at room temperature until fully dispersed to obtain a mixed dispersion with a concentration of about 1.96wt.%. (3) Add 0.1 g of citric acid to the mixed dispersion obtained in step (2) and stir at room temperature for 2 h at a stirring speed of 1000 r / min; (4) Add 0.1g sodium carboxymethyl cellulose to the reaction solution obtained in step (3), and put the mixed solution into a high-speed shear machine with a rotation speed of 10000r / min and stir and foam for 10min to obtain the cross-linked dispersion; (5) Pour the cross-linked dispersion into a silicone mold and freeze at -24℃ for 12h. After solidification, freeze-dry the solidified material at -56℃ for 48h to obtain the radiation-cooled aerogel matrix. (6) The radiation-cooled aerogel matrix is ​​immersed in a mixed solution of 10 wt.% polydimethylsiloxane (PDMS) and curing agent (PDMS: curing agent = 10:1) for 10 seconds, and then heated and cured in an 80°C forced-air drying oven for 3 hours to obtain the radiation-cooled aerogel.

[0056] Performance testing: 1) Stress-strain test: The samples prepared in Examples 1-6 and Comparative Examples 1-4 (cut into 2cm×2cm×2cm sizes) were placed in the air for compression-rebound test. The moving speed was 5mm / min. The stress curves at 30~70% strain were recorded to obtain the maximum elastic stress at different strains. The stress loss rate and strain loss rate were further calculated, as shown in Table 1.

[0057] 2) Hydrophobicity test: The samples prepared in Examples 1-6 and Comparative Examples 1-4 (cut into 2cm×2cm×2cm sizes) were placed on the sample stage to test the contact angle. The test solution was deionized water. The contact angle was calculated by the software of the contact angle tester. The results are shown in Table 1.

[0058] 3) Flame retardant test: The samples prepared in Examples 1-6 and Comparative Examples 1-4 (cut into 120mm×13mm×13mm sizes) were fixed on the fixture and the extinguishing time was tested. The results are shown in Table 1.

[0059] Table 1

[0060] As shown in Table 1, the pure biomass polysaccharide aerogel material prepared in Comparative Example 1 is relatively soft overall, with a maximum elastic stress of only 4.3 kPa and a large strain loss rate. It undergoes irreversible deformation after compression and is difficult to restore its original size. Furthermore, this pure biomass polysaccharide aerogel material is highly hydrophilic and easily collapses into a gel state upon contact with water. Compared to Example 1 with added inorganic nanomaterials, it is more flammable and takes longer to extinguish. The aerogel material prepared in Comparative Example 2, due to the addition of inorganic nanomaterials, has a maximum elastic stress increased to 18 kPa, and its mechanical strength is improved. However, compared to Example 3, because it lacks surfactants and crosslinking agents, the material has poor elasticity, a strain loss rate as high as 56%, and insufficient structural stability. The aerogel material prepared in Comparative Example 3, after structural regulation and chemical cross-linking treatment, showed an increase in maximum elastic stress to 21 kPa and a decrease in strain loss rate to 5%, indicating that structural regulation can effectively enhance the mechanical strength and elasticity of the material. However, compared with Example 3, this aerogel, due to the lack of PDMS encapsulation, had a water contact angle of 0°, exhibiting strong hydrophilicity and poor weather resistance. Comparative Example 4 used spherical SiO2 nanoparticles as the inorganic component to prepare an aerogel. The results showed that the maximum elastic stress of the obtained aerogel was only 10 kPa, and its mechanical strength was significantly lower than that of the aerogel prepared in Example 3 using two-dimensional layered silicate minerals as the inorganic component, indicating that layered silicate minerals have a better effect on improving the structural strength of aerogels. In contrast, the radiation-cooled aerogels prepared in Examples 1-6 of this invention are lighter in weight, and the addition of surfactants can adjust the pore structure in the aerogel matrix and improve the elasticity of the aerogel material. At the same time, the addition of two-dimensional sheet-like inorganic nanomaterials continuously enhances the mechanical strength of the aerogel, but adding too high a concentration of inorganic nanomaterials can inhibit the elasticity of the aerogel. In addition, PDMS encapsulation can further improve the hydrophobicity and mechanical strength of the aerogel material, thereby enabling the radiation-cooled aerogel material to adapt to complex environmental conditions when used outdoors and extending the service life of the aerogel material.

[0061] Figure 1 The images shown are scanning electron microscope (SEM) images of the radiation-cooled aerogels prepared in Examples 3-5 and Comparative Example 1 of this invention (where a is the radiation-cooled aerogel prepared in Comparative Example 1, and bd are the multifunctional elastic radiation-cooled aerogels prepared in Examples 3-5 of this invention, respectively). Figure 1 As can be seen from the above, the radiation-cooled aerogel (pure biomass polysaccharide aerogel) prepared in Comparative Example 1 has thinner pore walls and a disordered pore structure. In contrast, the radiation-cooled aerogels prepared in Examples 3-5 of this invention have a more regular pore structure due to the introduction of inorganic nanomaterials and surfactants, with pore sizes between 30 and 50 μm. Furthermore, the higher the amount of inorganic nanomaterials added, the thicker the pore walls.

[0062] Figure 2The figure shows the cyclic compression curve of the radiation-cooled aerogel prepared in Example 3 of this invention under 30% compressive strain in a dry state at room temperature. As can be seen from the figure, its maximum elastic stress is 29 kPa, and after 50 cycles of compression, the maximum elastic stress is 25 kPa, exhibiting good elastic and mechanical properties.

[0063] Figure 3 The figures show the contact angle test results of the radiation-cooled aerogels prepared in Examples 3-5 of this invention. The results show that after PDMS encapsulation, the water contact angles of the radiation-cooled aerogels obtained in Examples 3, 4, and 5 are 123°, 126°, and 129°, respectively, exhibiting excellent hydrophobicity.

[0064] Figure 4 The figures show the reflectance curves of the radiation-cooled aerogels prepared in Example 3 and Comparative Example 1 within the range of 0.25-2.5 μm. Compared with the aerogel prepared in Comparative Example 1, the radiation-cooled aerogel prepared in Example 3 of this invention has a unique porous structure that effectively enhances its Mie scattering, resulting in a higher reflectance to solar radiation. The average reflectance across the entire solar radiation band (0.3-2.5 μm) is 92.53% (>90%), indicating that this radiation-cooled aerogel has extremely high solar radiation reflection capability.

[0065] Figure 5 The figures show the infrared emission curves of the radiation-cooled aerogels prepared in Example 3 and Comparative Example 1 of this invention. As can be seen from the figures, compared to the aerogel prepared in Comparative Example 1, the radiation-cooled aerogel prepared in Example 3 of this invention has an average emissivity of up to 96.27% in the 8-13 μm wavelength range, indicating that the radiation-cooled aerogel has good atmospheric window emissivity.

[0066] Figure 6 The data curves for the thermal insulation performance of the radiation-cooled aerogel prepared in Example 4 of this invention are shown (the test procedure was as follows: the sample was cut into 2cm×2cm×2cm pieces and placed on a heating stage; the heating temperatures were 60℃ and 80℃; and the surface temperature data of the sample was recorded using a thermal imaging camera). The results show that, due to the low thermal conductivity of this radiation-cooled aerogel, its surface temperature only increased by 3℃ after heating at 60℃ for 30 minutes, and by 6℃ after heating at 80℃ for 30 minutes, exhibiting excellent thermal insulation performance.

[0067] Outdoors, by setting up such Figure 7The apparatus shown (four 5cm×5cm×2.5cm cavities were made on the surface of a 30cm×30cm×30cm polystyrene foam box; thermocouples were fixed in the center of the cavities to ensure the sample tightly covered the thermocouples; aluminum foil was wrapped around the foam box to reduce the heating of the test apparatus by sunlight; a polyethylene film was used to cover the top of the apparatus to isolate it from heat convection and heat conduction from the surrounding environment; a mobile weather station was used to test the ambient temperature, and a solar irradiance meter was used to measure the irradiance intensity) was used to test the radiative cooling performance of the radiative cooling aerogels prepared in Example 3 and Comparative Example 1. The test data are as follows: Figure 8 As shown in the figure. The results show that the temperature of the uncovered radiation-cooled aerogel rises faster and is higher; while the radiation-cooled aerogel with a porous structure and additional functional layers has a lower temperature, a more gradual temperature fluctuation, and a significant cooling effect under the same conditions. It exhibits a lower temperature throughout the entire test period, with an average temperature reduction of 8.4℃.

[0068] Figure 9 The cooling effect of the radiative cooling aerogel prepared in Example 4 of this invention was tested using a log cabin to simulate an actual building. The results showed that the log cabin covered with the radiative cooling aerogel prepared in Example 4 of this invention exhibited a lower temperature compared to the uncovered house model.

[0069] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method of making a multifunctional elastomeric radiative cooling aerogel, characterized in that, The method comprises the following steps: (1) performing surface modification treatment on biomass polysaccharide, and then performing nanocrystallization treatment to obtain modified biomass polysaccharide; (2) dispersing the modified biomass polysaccharide and inorganic nanomaterials in water to obtain a mixed dispersion liquid; (3) adding a crosslinking agent to the mixed dispersion liquid and stirring to react; (4) adding a surfactant to the reaction liquid obtained in the step (3) and stirring to foam, to obtain a crosslinked dispersion liquid; (5) sequentially performing freeze coagulation and freeze drying on the crosslinked dispersion liquid to obtain a radiation refrigeration aerogel matrix; (6) immersing the radiation refrigeration aerogel matrix in a mixed solution of polydimethylsiloxane and a curing agent, and performing heat treatment to obtain the multifunctional elastic radiation refrigeration aerogel.

2. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: In the step (1), the surface modification treatment comprises carboxyl modification or sulfonic acid group modification on the biomass polysaccharide; Optionally, the biomass polysaccharide comprises at least one of cellulose, hemicellulose and lignin; Optionally, the carboxyl modification process comprises uniformly mixing biomass polysaccharide, 4-acetylamino-TEMPO and sodium bromide in water, then adding NaClO solution, stirring to react, filtering and washing the reaction product to neutral, and obtaining the product. Optionally, the sulfonic acid group modification process comprises catalyzing biomass polysaccharide to undergo hydrolysis reaction by sulfuric acid, and then washing the obtained hydrolysis reaction product to neutral.

3. The method of claim 2, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: In the carboxyl modification process, the mass ratio of the biomass polysaccharide, the 4-acetylamino-TEMPO and the sodium bromide is 1:0.016:0.1, the concentration of the NaClO solution is 1.3-5 mmol / g, the stirring reaction is performed at a pH value of 10, the reaction temperature is 25°C, and the reaction time is 5 h; And / or, in the sulfonic acid group modification process, the concentration of the sulfuric acid is 64 wt%, the reaction temperature of the hydrolysis reaction is 45°C, and the reaction time is 30-100 min.

4. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: In the step (1), the nanocrystallization treatment is to cycle the surface-modified biomass polysaccharide in a high-pressure homogenizer for 3-5 times, and the pressure of the high-pressure homogenizer is controlled at 8000 bar.

5. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: In the step (2), the mass ratio of the modified biomass polysaccharide to the inorganic nanomaterials is 1:(1-5); Optionally, the inorganic nanomaterials are natural layered silicate minerals, and at least one of kaolin, montmorillonite and bentonite; And / or, in the mixed dispersion liquid, the sum of the concentrations of the modified biomass polysaccharide and the inorganic nanomaterials is 1.9-5.6 wt.%.

6. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: In the step (3), the crosslinking agent comprises at least one of 3-aminopropyl triethoxysilane, polyglycol diglycidyl ether and citric acid, and the addition amount of the crosslinking agent is 0.1-1 g / 100 mL; And / or, the stirring reaction is performed at a rotation speed of 1000 r / min, a reaction temperature of room temperature and a reaction time of 2 h.

7. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: The surface active agent in step (4) comprises at least one of sodium carboxymethyl cellulose, hydroxyethyl cellulose, and methyl cellulose; And / or, the stirring foaming is performed in a high-speed shearing machine, and the rotating speed during the stirring foaming is 8000-12000 r / min, and the stirring foaming time is 5-15 min.

8. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: The freezing and solidification temperature in step (5) is -196 to -24℃, and the solidification time is 5-12 h; And / or, the freezing and drying temperature is not higher than -56℃, and the drying time is ≥48 h.

9. The method of claim 1, wherein the multifunctional elastic radiative cooling aerogel is prepared by the steps of: The concentration of the mixed solution of the polydimethylsiloxane and the curing agent in step (6) is 5-20 wt.%; And / or, in the mixed solution of the polydimethylsiloxane and the curing agent, the mass ratio of the polydimethylsiloxane to the curing agent is 10:1; And / or, the impregnation time is 10 s; And / or, the heat treatment temperature is 60-120℃, and the heat treatment time is 0.5-5 h.

10. A multifunctional elastomeric radiative cooling aerogel, characterized in that, The multifunctional elastic radiative cooling aerogel is prepared by the preparation method in any one of claims 1-9.

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