SiO2 / TiO2 / PMMA radiation refrigeration film and preparation method thereof

Abstract

The invention provides a SiO2 / TiO2 / PMMA radiation refrigeration film and a preparation method thereof, and relates to the technical field of passive daytime radiation refrigeration films. The radiation refrigeration film is prepared from the following raw materials: N, N-dimethylformamide, polymethyl methacrylate, silicon dioxide and titanium dioxide. The invention relates to a preparation method of a SiO2 / TiO2 / PMMA radiation refrigeration film. The preparation method comprises the steps of preparing silicon dioxide, preparing titanium dioxide, synthesizing composite sol and preparing the SiO2 / TiO2 / PMMA radiation refrigeration film. The SiO2 / TiO2 / PMMA radiation refrigeration film prepared by the invention has high reflectivity in the ultraviolet-visible-near infrared band and high emissivity in the infrared band, can realize 8.4 DEG C sub-environment refrigeration, and is low in cost and simple in process flow.

Description

Technical Field

[0001] The present invention relates to the technical field of passive daytime radiation cooling films, and in particular to a SiO2 / TiO2 / PMMA radiation cooling film and a preparation method thereof. Background Art

[0002] Global industrialization and population expansion continue to drive up energy demand, exacerbating urban heat islands and the greenhouse effect. Despite an increasing share of clean energy, fossil fuels still dominate global energy supply, contributing to rising global temperatures and an energy crisis, necessitating urgent action to address environmental heat loads. Current traditional refrigeration technologies have significant drawbacks: their heavy reliance on electricity and high energy consumption indirectly exacerbate fossil fuel consumption and greenhouse gas emissions like CO2, creating a vicious cycle. In contrast, radiant cooling technology, with its zero-energy and pollution-free properties, is poised to become a disruptive alternative, demonstrating significant potential for applications in building energy conservation, electronics cooling, and personal thermal management.

[0003] With the innovative development of functional materials, radiative cooling technology has achieved important breakthroughs. Based on the design and application of photonic crystals, nanocomposites and metamaterials, efficient all-weather cooling has been achieved. However, current high-performance radiative cooling materials still face the challenges of complex preparation processes and high costs, which seriously restrict their industrialization process. The prior art with publication number CN113985674A discloses a method for preparing an electrochromic radiative cooling device. This technology has the following defects: complex structure, cumbersome process, low reflectivity in the ultraviolet-visible-near-infrared band, low emissivity in the infrared band, and high cost. The prior art with publication number CN109135599A discloses a reflective radiative cooling film. This technology has the following problems: the metal layer is easily oxidized and corroded, has poor stability, the interface adhesion between the PET layer and the coating layer is insufficient, the preparation process is complex, the equipment investment is large, and the production cycle is long.

[0004] In summary, although the current existing technical solutions have improved the radiative cooling film to a certain extent, the following technical problems still exist: low reflectivity in the solar spectrum band, low emissivity in the infrared band, limited application scenarios, high cost, and complex process. Summary of the Invention

[0005] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a SiO2 / TiO2 / PMMA radiation cooling film and a preparation method thereof, and achieves the following invention objectives: the prepared SiO2 / TiO2 / PMMA radiation cooling film has high reflectivity in the ultraviolet-visible-near infrared band and high emissivity in the infrared band, can achieve sub-ambient cooling of 8.4°C, and has low cost and simple process flow.

[0006] To achieve the above objectives, the technical solutions adopted are as follows: A SiO2 / TiO2 / PMMA radiation refrigeration film comprises the following raw materials in parts by weight: 80-90 parts of N,N-dimethylformamide, 10-20 parts of polymethyl methacrylate, 1-5 parts of silicon dioxide, and 1-5 parts of titanium dioxide.

[0007] The present invention also provides a method for preparing a SiO2 / TiO2 / PMMA radiation refrigeration film, comprising the following steps: Step 1: Preparation of silicon dioxide Deionized water, ammonia water, and isopropanol are uniformly stirred in a volume ratio of (4-6):(1-2):(20-30) to obtain a mixed solution; tetraethyl orthosilicate is added to the mixed solution in a volume ratio of tetraethyl orthosilicate to ammonia water of 1:1, stirred at a rate of 200-300 rpm, and stirred for 2-2.5 hours; after the reaction, the mixture is centrifuged at a speed of 5000-6000 rpm for 5-10 minutes to retain a solid phase; the solid phase is then washed 3-5 times with a 50% by volume ethanol solution; dried at a temperature of 80-85°C for 6-7 hours, and then ground for 2-3 minutes to obtain silica. The ammonia water concentration is 28% (mass percent).

[0008] Step 2: Preparation of titanium dioxide The weight ratio of the raw materials used is: 0.4-0.6 parts of hexadecylamine, 30-40 parts of ethylamine, 0.9-1.8 parts of ammonia water, and 0.58-1.15 parts of isopropyl titanate.

[0009] Hexadecylamine and ethylamine are uniformly mixed to obtain a mixed solution; aqueous ammonia is added to the mixed solution, stirred at a speed of 200-300 rpm, and stirred for 10-15 minutes; isopropyl titanate is then slowly added dropwise at a rate of 50-100 μl / s. After the addition is complete, the reaction is continued at room temperature for 1.5-2 hours; after the reaction is completed, the mixture is centrifuged at a speed of 5000-6000 rpm for 5-10 minutes to retain a solid phase; the solid phase is then washed 3-5 times with a 50% by volume ethanol solution; the mixture is dried at a temperature of 80-85°C for 6-7 hours, and then ground for 2-3 minutes to obtain titanium dioxide. The aqueous ammonia concentration is 28% (mass percent).

[0010] Step 3: Synthesize composite sol Polymethyl methacrylate and N,N-dimethylformamide are mixed evenly, heated to 80-85°C, stirred at a rate of 200-300 rpm, and stirred for reaction for 2-2.5 hours; after the reaction is completed, silicon dioxide and titanium dioxide are added, stirred evenly, and a composite sol is obtained.

[0011] The raw material dosage is as follows: 80-90 parts of N,N-dimethylformamide, 10-20 parts of polymethyl methacrylate, 1-5 parts of silicon dioxide, and 1-5 parts of titanium dioxide, in parts by weight.

[0012] Step 4: Prepare SiO2 / TiO2 / PMMA radiative cooling film The composite sol was dropped onto the surface of a clean glass plate and scraped with a scraper to obtain a preliminary coating with a coating thickness of 300 μm. The preliminary coating was dried under ventilation at room temperature for 6-7 hours to obtain a SiO2 / TiO2 / PMMA radiation cooling film.

[0013] The beneficial effects of the present invention are as follows: 1. The SiO2 / TiO2 / PMMA radiative cooling film prepared by the present invention has high reflectivity in the ultraviolet-visible-near-infrared band and high emissivity in the infrared band. The reflectivity in the ultraviolet-visible-near-infrared band is 95.2%, and the emissivity in the infrared band is 95.1%.

[0014] 2. The SiO2 / TiO2 / PMMA radiative cooling film prepared by the present invention can achieve sub-ambient cooling of 8.4°C in outdoor tests.

[0015] 3. The raw materials used in the present invention are non-toxic, harmless and inexpensive, the process is simple and easy to operate, suitable for batch and low-cost preparation, and suitable for industrial-scale production and commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attachment Figure 1 This is a transmission electron microscope image of the silicon dioxide prepared in the present invention.

[0017] Attachment Figure 2 a is a transmission electron microscope image of titanium dioxide prepared in the present invention.

[0018] Attachment Figure 2 b is the X-ray diffraction pattern of titanium dioxide prepared in the present invention.

[0019] Attachment Figure 3 a is an optical photograph of the SiO2 / TiO2 / PMMA radiation refrigeration film prepared in the present invention.

[0020] Attachment Figure 3 b is a scanning electron microscope image of the SiO2 / TiO2 / PMMA radiation cooling film prepared in the present invention.

[0021] Attachment Figure 4 a is the UV-visible-near-infrared reflectivity spectrum of the SiO2 / TiO2 / PMMA radiative cooling film prepared in Example 1.

[0022] Attachment Figure 4b is the infrared emissivity spectrum of the SiO2 / TiO2 / PMMA radiative cooling film prepared in Example 1.

[0023] Attachment Figure 5 a is a schematic diagram of the test device used in the outdoor cooling effect test of the radiative cooling film prepared in Example 1 and Comparative Example 1.

[0024] Attachment Figure 5 b is the temperature change curve of the outdoor cooling effect test of the radiative cooling films prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0026] Example 1 A SiO2 / TiO2 / PMMA Radiative Refrigeration Film A SiO2 / TiO2 / PMMA radiation refrigeration film comprises the following raw materials in parts by weight: 85 parts of N,N-dimethylformamide, 15 parts of polymethyl methacrylate, 5 parts of silicon dioxide and 5 parts of titanium dioxide.

[0027] A method for preparing a SiO2 / TiO2 / PMMA radiative cooling film, comprising the following steps: Step 1: Preparation of silicon dioxide Deionized water, ammonia water, and isopropanol were stirred uniformly in a volume ratio of 4:1:20 to obtain a mixed solution. Ethyl orthosilicate was added to the mixed solution in a volume ratio of 1:1 to ammonia water, stirred at 300 rpm, and stirred for 2 hours. After the reaction, the mixture was centrifuged at 5000 rpm for 5 minutes to retain a solid phase. The solid phase was then washed three times with a 50% by volume ethanol solution. The solid phase was dried at 80°C for 6 hours and then ground for 2 minutes to obtain silica. The ammonia water concentration was 28% (mass percent).

[0028] Step 2: Preparation of titanium dioxide The weight ratio of the raw materials used is: 0.4 parts of hexadecylamine, 30 parts of ethylamine, 0.9 parts of ammonia water, and 0.58 parts of isopropyl titanate.

[0029] Hexadecylamine and ethylamine were uniformly mixed to obtain a mixed solution; aqueous ammonia was added to the mixed solution, stirred at 300 rpm for 10 minutes; isopropyl titanate was then slowly added dropwise at a rate of 50 μl / s. After the addition was complete, the reaction was continued at room temperature for 1.5 hours; after the reaction, the mixture was centrifuged at 5000 rpm for 5 minutes to retain a solid phase; the solid phase was then washed three times with a 50% by volume ethanol solution; the mixture was dried at 80°C for 6 hours, and then ground for 2 minutes to obtain titanium dioxide. The aqueous ammonia concentration was 28% (mass percent).

[0030] Step 3: Synthesize composite sol Polymethyl methacrylate and N,N-dimethylformamide were mixed evenly, heated to 80° C., stirred at a rate of 300 rpm, and stirred for 2 hours; after the reaction, silicon dioxide and titanium dioxide were added, stirred evenly, and a composite sol was obtained.

[0031] The raw material amounts in parts by weight are: 85 parts of N,N-dimethylformamide, 15 parts of polymethyl methacrylate, 5 parts of silicon dioxide, and 5 parts of titanium dioxide.

[0032] Step 4: Prepare SiO2 / TiO2 / PMMA radiative cooling film The composite sol was dropped onto the surface of a clean glass plate and a preliminary coating was obtained by scraping with a scraper. The coating thickness was 300 μm. The preliminary coating was dried under ventilation at room temperature for 6 hours to obtain a SiO2 / TiO2 / PMMA radiative cooling film.

[0033] Example 2 A SiO2 / TiO2 / PMMA Radiative Refrigeration Film A SiO2 / TiO2 / PMMA radiation refrigeration film comprises the following raw materials in parts by weight: 88 parts of N,N-dimethylformamide, 10 parts of polymethyl methacrylate, 3 parts of silicon dioxide and 3 parts of titanium dioxide.

[0034] A method for preparing a SiO2 / TiO2 / PMMA radiative cooling film, comprising the following steps: Step 1: Preparation of silicon dioxide Deionized water, ammonia, and isopropanol were stirred uniformly in a volume ratio of 5:1:25 to obtain a mixed solution. Ethyl orthosilicate was added to the mixed solution in a volume ratio of 1:1 to ammonia, stirred at 200 rpm, and stirred for 2.5 hours. After the reaction, the mixture was centrifuged at 5000 rpm for 10 minutes to retain a solid phase. The solid phase was then washed four times with a 50% by volume ethanol solution. The solid phase was dried at 80°C for 7 hours and then ground for 3 minutes to obtain silica. The ammonia concentration was 28% (mass percent).

[0035] Step 2: Preparation of titanium dioxide The weight ratio of the raw materials used is: 0.5 parts of hexadecylamine, 35 parts of ethylamine, 1.2 parts of ammonia water, and 1 part of isopropyl titanate.

[0036] Hexadecylamine and ethylamine were uniformly mixed to obtain a mixed solution; aqueous ammonia was added to the mixed solution, stirred at 200 rpm for 15 minutes; isopropyl titanate was then slowly added dropwise at a rate of 50 μl / s. After the addition was complete, the reaction was continued at room temperature for 2 hours; after the reaction, the mixture was centrifuged at 5000 rpm for 10 minutes to retain a solid phase; the solid phase was then washed four times with a 50% by volume ethanol solution; the mixture was dried at 80°C for 7 hours, and then ground for 3 minutes to obtain titanium dioxide. The aqueous ammonia concentration was 28% (mass percent).

[0037] Step 3: Synthesize composite sol Polymethyl methacrylate and N,N-dimethylformamide were mixed evenly, heated to 80° C., stirred at a rate of 200 rpm, and stirred for 2 hours; after the reaction, silicon dioxide and titanium dioxide were added, stirred evenly, and a composite sol was obtained.

[0038] The raw material amounts are as follows, in parts by weight: 88 parts of N,N-dimethylformamide, 10 parts of polymethyl methacrylate, 3 parts of silicon dioxide, and 3 parts of titanium dioxide.

[0039] Step 4: Prepare SiO2 / TiO2 / PMMA radiative cooling film The composite sol was dropped onto the surface of a clean glass plate and a preliminary coating was obtained by scraping with a scraper. The coating thickness was 300 μm. The preliminary coating was dried under ventilation at room temperature for 6 hours to obtain a SiO2 / TiO2 / PMMA radiative cooling film.

[0040] Example 3 A SiO2 / TiO2 / PMMA Radiative Refrigeration Film A SiO2 / TiO2 / PMMA radiation refrigeration film comprises the following raw materials in parts by weight: 90 parts of N,N-dimethylformamide, 20 parts of polymethyl methacrylate, 1 part of silicon dioxide, and 1 part of titanium dioxide.

[0041] A method for preparing a SiO2 / TiO2 / PMMA radiative cooling film, comprising the following steps: Step 1: Preparation of silicon dioxide Deionized water, ammonia water, and isopropanol were stirred uniformly in a volume ratio of 6:2:30 to obtain a mixed solution. Ethyl orthosilicate was added to the mixed solution in a volume ratio of 1:1 to ammonia water, stirred at 200 rpm, and stirred for 2.5 hours. After the reaction, the mixture was centrifuged at 6000 rpm for 10 minutes to retain a solid phase. The solid phase was then washed five times with a 50% by volume ethanol solution. The solid phase was dried at 85°C for 7 hours and then ground for 3 minutes to obtain silica. The ammonia water concentration was 28% (mass percent).

[0042] Step 2: Preparation of titanium dioxide The weight ratio of the raw materials used is: 0.6 parts of hexadecylamine, 40 parts of ethylamine, 1.8 parts of ammonia water, and 1.15 parts of isopropyl titanate.

[0043] Hexadecylamine and ethylamine were uniformly mixed to obtain a mixed solution; aqueous ammonia was added to the mixed solution, stirred at 200 rpm for 15 minutes; isopropyl titanate was then slowly added dropwise at a rate of 100 μl / s. After the addition was complete, the reaction was continued at room temperature for 2 hours; after the reaction, the mixture was centrifuged at 6000 rpm for 10 minutes to retain a solid phase; the solid phase was then washed five times with a 50% by volume ethanol solution; after washing, the mixture was dried at 85°C for 7 hours, and then ground for 3 minutes to obtain titanium dioxide. The aqueous ammonia concentration was 28% (mass percent).

[0044] Step 3: Synthesize composite sol Polymethyl methacrylate and N,N-dimethylformamide were mixed evenly, heated to 85° C., stirred at a rate of 200 rpm, and stirred for 2.5 hours; after the reaction was completed, silicon dioxide and titanium dioxide were added and stirred evenly to obtain a composite sol.

[0045] The raw material dosage is as follows, in parts by weight: 90 parts of N,N-dimethylformamide, 20 parts of polymethyl methacrylate, 1 part of silicon dioxide, and 1 part of titanium dioxide.

[0046] Step 4: Prepare SiO2 / TiO2 / PMMA radiative cooling film The composite sol was dropped onto the surface of a clean glass plate and a preliminary coating was obtained by scraping with a scraper. The coating thickness was 300 μm. The preliminary coating was dried under ventilation at room temperature for 7 hours to obtain a SiO2 / TiO2 / PMMA radiation cooling film.

[0047] Comparative Example 1

[0048] A radiation refrigeration film comprises the following raw materials, calculated in parts by weight: 85 parts of N,N-dimethylformamide and 15 parts of polymethyl methacrylate.

[0049] A method for preparing a radiative cooling film, comprising the following steps: Step 1: Synthesize sol Polymethyl methacrylate and N,N-dimethylformamide were mixed evenly, heated to 80° C., stirred at a rate of 300 rpm, and reacted for 2 h to obtain a sol.

[0050] The raw material usage is as follows: 85 parts of N,N-dimethylformamide and 15 parts of polymethyl methacrylate.

[0051] Step 2: Prepare radiative cooling film The sol was dropped onto the surface of a clean glass plate and scraped with a scraper to obtain a preliminary coating with a coating thickness of 300 μm. The preliminary coating was dried under ventilation at room temperature for 6 hours to obtain a radiative cooling film.

[0052] Example 4 Performance Test (1) The morphology of the silicon dioxide, titanium dioxide, and SiO2 / TiO2 / PMMA radiation cooling films prepared by the present invention was characterized and analyzed. The silicon dioxide was analyzed by transmission electron microscopy, and the transmission electron microscopy image of the silicon dioxide was obtained as shown in the attached figure. Figure 1 As shown in the attached Figure 1 It can be seen that silicon dioxide is a regular spherical particle with a particle size of about 200nm. Titanium dioxide was analyzed by transmission electron microscopy, and the transmission electron microscopy image of titanium dioxide was obtained as shown in the attached figure. Figure 2 As shown in a, Figure 2 It can be seen from a that titanium dioxide is a regular spherical particle with a particle size of about 150nm. X-ray diffraction analysis of titanium dioxide was performed and the X-ray diffraction pattern was obtained as shown in the attached figure. Figure 2 As shown in b; the X-ray diffraction pattern shows that the characteristic peaks of titanium dioxide correspond to the standard card, proving the successful preparation of titanium dioxide. The appearance of the SiO2 / TiO2 / PMMA radiation cooling film was analyzed, and its optical photograph is shown in the attached Figure 3 As shown in a; Figure 3As can be seen from a, the SiO2 / TiO2 / PMMA radiation cooling film is white in appearance. The SEM image of the SiO2 / TiO2 / PMMA radiation cooling film is obtained by scanning electron microscopy (SEM) analysis as shown in the attached figure. Figure 3 As shown in b; through the scanning electron microscope image, it can be observed that there are obvious particles on the surface of the PMMA film, which proves the successful preparation of the SiO2 / TiO2 / PMMA radiation cooling film.

[0053] (2) The SiO2 / TiO2 / PMMA radiative cooling film prepared in Example 1 was subjected to UV-visible-near-infrared reflectivity test, and the UV-visible-near-infrared reflectivity spectrum of the SiO2 / TiO2 / PMMA radiative cooling film was obtained as shown in the attached figure. Figure 4 As shown in a; Figure 4 It can be seen that the radiative cooling film prepared in Example 1 has a reflectivity of up to 95.2% in the ultraviolet-visible-near infrared band. The SiO2 / TiO2 / PMMA radiative cooling film prepared in Example 1 was subjected to an infrared emissivity test, and the infrared emissivity spectrum of the SiO2 / TiO2 / PMMA radiative cooling film was obtained as shown in the attached figure. Figure 4 As shown in b; Figure 4 b It can be seen that the radiative cooling film prepared in Example 1 has an emissivity of 95.1% in the infrared band.

[0054] (III) The radiative cooling films prepared in Example 1 and Comparative Example 1 were subjected to outdoor cooling effect tests. The schematic diagram of the device used in the outdoor cooling effect test is shown in the attached figure. Figure 5 The temperature change curve is shown in the attached Figure 5 As shown in b; Figure 5 b It can be seen that when the solar radiation intensity is about 600W / m 2 Under the condition of , the temperature of the cavity covered with Example 1 is significantly lower than the temperature of the cavity covered with Comparative Example 1 and the ambient temperature, and is 8.4°C lower than the ambient temperature.

[0055] Obviously, there are many specific implementation methods that can be changed under the concept of the present invention. Here, it should be stated that any changes made under the inventive concept of the present invention will fall within the scope of protection of the present invention.

Claims

1. A SiO2 / TiO2 / PMMA radiative cooling film, characterized by: The raw materials of the radiation refrigeration film are composed of: N,N-dimethylformamide, polymethyl methacrylate, silicon dioxide and titanium dioxide.

2. The SiO2 / TiO2 / PMMA radiative cooling film according to claim 1, characterized in that: The weight ratio of the raw materials is: 80-90 parts of N,N-dimethylformamide, 10-20 parts of polymethyl methacrylate, 1-5 parts of silicon dioxide, and 1-5 parts of titanium dioxide.

3. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to any one of claims 1-2, characterized in that: The method comprises the steps of preparing silicon dioxide, preparing titanium dioxide, synthesizing composite sol, and preparing SiO2 / TiO2 / PMMA radiation cooling film; The method for preparing silica comprises the following steps: uniformly stirring deionized water, ammonia water, and isopropyl alcohol to obtain a mixed solution; adding ethyl orthosilicate to the mixed solution, stirring and reacting for 2-2.5 hours; centrifuging after the reaction to retain a solid phase; then washing the solid phase 3-5 times with a 50% by volume ethanol solution; and drying and grinding to obtain silica.

4. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 3, characterized in that: The volume ratio of the deionized water, ammonia water and isopropyl alcohol is (4-6): (1-2): (20-30).

5. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 3, characterized in that: The volume ratio of the tetraethyl orthosilicate to the ammonia water is 1:

1.

6. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 3, characterized in that: Preparation of titanium dioxide: Hexadecylamine and ethylamine are mixed uniformly to obtain a mixed solution; ammonia water is added to the mixed solution and stirred for 10-15 minutes; Then, isopropyl titanate is slowly added dropwise. After the addition is completed, the reaction is continued at room temperature for 1.5-2 hours. After the reaction is completed, centrifugation is performed to retain the solid phase. The solid phase is then washed 3-5 times with a 50% by volume ethanol solution. After washing, titanium dioxide is obtained by drying and grinding.

7. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 6, characterized in that: The weight ratio of the raw materials used for preparing titanium dioxide is: 0.4-0.6 parts of hexadecylamine, 30-40 parts of ethylamine, 0.9-1.8 parts of ammonia water, and 0.58-1.15 parts of isopropyl titanate.

8. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 6, characterized in that: The droplet acceleration rate of the isopropyl titanate is 50-100 μl / s.

9. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 3, characterized in that: The composite sol is synthesized by mixing polymethyl methacrylate and N,N-dimethylformamide uniformly, heating to 80-85° C., and stirring for reaction for 2-2.5 hours; after the reaction is completed, adding silicon dioxide and titanium dioxide, and stirring uniformly to obtain a composite sol.

10. The method for preparing a SiO2 / TiO2 / PMMA radiative cooling film according to claim 3, characterized in that: The SiO2 / TiO2 / PMMA radiative cooling film is prepared by dropping the composite sol onto the surface of a clean glass plate and applying it with a scraper to obtain a preliminary coating with a coating thickness of 300 μm; The preliminary coating was dried under ventilation at room temperature to obtain a SiO2 / TiO2 / PMMA radiative cooling film.

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