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

Abstract

The invention relates to a SiO2-coated TiO2 / PMMA (polymethyl methacrylate) radiation refrigeration film and a preparation method thereof. The preparation method comprises the following steps: weighing SiO2 powder into a beaker, adding ethanol and water, then dropwise adding tetrabutyl titanate, uniformly stirring, transferring the solution into a Teflon reaction kettle lining, carrying out hydrothermal reaction for 4 hours, washing and drying to obtain SiO2-coated TiO2; the preparation method comprises the following steps: preparing a PMMA (polymethyl methacrylate) solution, adding SiO2-coated TiO2, uniformly stirring, dispensing on a glass plate, and drying to obtain the SiO2-coated TiO2 / PMMA radiation refrigeration film. The preparation method is characterized in that SiO2-coated TiO2 core-shell particles are prepared through a hydrothermal reaction, so that the back scattering capability of the film is improved, the solar waveband reflectivity and the infrared emissivity of the film are greatly improved, the reflectivity of the film in the ultraviolet-visible-near infrared waveband is as high as 96.7%, and the emissivity of the film in the infrared waveband is 95.8%. In an outdoor radiation refrigeration test, 10 DEG C sub-environment refrigeration is realized.

Description

Technical Field

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

[0002] With the rapid population growth and industrial development in recent decades, energy consumption has risen sharply and global warming has become increasingly serious. This trend has not only intensified the demand for refrigeration technology, but also brought about the dual challenges of energy crisis and environmental problems. However, traditional compression refrigeration systems, such as air conditioners, not only consume a lot of energy, but also emit a lot of carbon dioxide, exacerbating the energy crisis and environmental problems. Therefore, it has become crucial to develop a refrigeration technology that is both environmentally friendly and efficient.

[0003] Passive daytime radiative cooling (PDRC) technology has attracted much attention due to its unique advantages. This technology uses the ability of objects on the earth's surface to radiate heat into outer space through the transparent window of the atmosphere (wavelength range of 8-13um) to discharge heat into outer space close to absolute zero (about 3K). This process can effectively reduce the surface temperature of objects to close to ambient temperature (about 300K) without external energy input. Due to its passivity and sustainability, PDRC technology shows great application potential in many fields such as energy-saving buildings, solar panel cooling, personal thermal management, water collection systems, and wearable device cooling. However, it is still challenging to achieve PDRC effects below ambient temperature under direct sunlight. The strong incidence of solar radiation causes most thermal radiation materials to absorb a large amount of energy and heat up rapidly, thus hindering the effective heat dissipation process. Therefore, designing and manufacturing radiative cooling materials that have high solar reflectivity in the solar radiation region (wavelength range of 0.3-2.5um) and high thermal emittance in the mid-infrared region (8-13um) is crucial to achieve efficient PDRC.

[0004] In 2014, Fan et al. experimentally demonstrated that PDRC materials with multilayer photonic structures have high solar reflectivity and thermal radiation. The material is composed of alternating hafnium dioxide (HfO2) and silicon dioxide (SiO2), achieving a solar reflectivity of 97%, while showing strong selective emission in the atmospheric window, and reducing the ambient temperature by 4.9°C relative to the ambient temperature under direct sunlight. Since then, the development of PDRC materials has aroused great interest among researchers, and various radiative cooling materials with high solar reflectivity and high atmospheric emissivity have been reported, including nanophotonic structures, particles or polymer coatings, porous polymers, and nanoparticle-polymer composites. Among them, nanoparticle-polymer composites are simple and easy to prepare, and have high material selectivity, so PDRC materials with different preparation processes and different components emerge in an endless stream. Nanoparticle-polymer composites are nanoparticles introduced into polymers, and nanoparticles are used to improve the material's ability to reflect sunlight, while the absorption of polymer functional groups and the phonon polarization vibration of micro-nanoparticles are used to synergistically enhance the emissivity at the atmospheric window. In 2017, Yang et al. randomly encapsulated SiO2 microbeads in polymethylpentene (TPX) and used SiO2 to enhance the mid-infrared emissivity. 2 Under the solar radiation, it shows 93W / m 2 The radiation cooling power of nanoparticles is 100%. However, due to their limited scattering ability, traditional solid nanoparticles are difficult to achieve high reflectivity, which limits the radiation cooling effect. Therefore, it is particularly important to develop radiation cooling materials with high scattering efficiency, superior performance, simple preparation and environmental protection. Summary of the invention

[0005] In order to avoid the shortcomings of the prior art, the present invention provides a method for preparing a SiO2@TiO2 / PMMA radiation cooling film. No metal reflective layer is required, the preparation method is simple, and it has good adaptability, and has broad application prospects in cooling the surface of objects, cooling buildings, etc.

[0006] One of the purposes of the present invention is to provide a SiO2@TiO2 / PMMA radiation refrigeration film which is efficient, low-cost and can be mass-produced and a preparation method thereof.

[0007] The second purpose of the present invention is to propose a new core-shell structure SiO2@TiO2 as a filler, which has a high backscattering ability, effectively improves the reflectivity in the ultraviolet visible band, and enhances the comprehensive radiation cooling performance.

[0008] The SiO2@TiO2 / PMMA radiation refrigeration film material synthesized by the present invention uses SiO2@TiO2 as filler, polymer polymethyl methacrylate (PMMA) as raw material, and N,N-dimethylformamide (DMF) as solvent. The specific preparation process includes the following steps: 1. Weigh 0.1-0.3g SiO2 powder into a beaker, add 10mL ethanol and 300uL water, and stir evenly; 2. Add 200-400uL tetrabutyl titanate dropwise to the above solution and stir evenly; 3. Transfer the above solution to the Teflon-lined reactor and perform hydrothermal reaction at 120-160°C for 4 hours; 4. Wash and dry the product obtained from the above reaction to obtain a white product, namely SiO2@TiO2; 5. Weigh 1-2 g PMMA and 8-9 g DMF into a flask and stir at 80 °C for 1-3 h to obtain a transparent solution; 6. Weigh 0.1-0.3g SiO2@TiO2 into the above transparent solution and stir evenly to obtain a white solution; 7. Drop the above solution on a clean glass plate and apply it with a scraper to obtain a white coating with a thickness of 100-300um; 8. Place the coating in a ventilated place for drying and curing to obtain the SiO2@TiO2 / PMMA radiation cooling film. Beneficial effects of the present invention

[0009] 1. The present invention provides a SiO2@TiO2 / PMMA radiation refrigeration film and a preparation method thereof, which is characterized in that SiO2@TiO2 is used as filler, PMMA is used as raw material, and DMF is used as solvent. Only common laboratory equipment is required, and no special equipment is required. The process is simple and easy to operate. 2. The SiO2@TiO2 / PMMA radiative cooling film obtained by this method has a reflectivity of up to 96.7% in the ultraviolet-visible-near infrared band and an emissivity of 95.8% in the infrared band; 3. The SiO2@TiO2 / PMMA radiative cooling film obtained by this method can achieve sub-ambient cooling of up to 10°C in outdoor tests; 4. The drugs used in the present invention are non-toxic, harmless and inexpensive, and do not require complicated and tedious steps after preparation. They are particularly suitable for batch and low-cost preparation, and are suitable for industrial-scale production and commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments or the description of the prior art will be briefly introduced with drawings below, but the drawings in the following description are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1This is a transmission electron microscope (TEM) photograph of SiO2@TiO2 prepared in Example 1 of the present invention.

[0012] Figure 2 This is the X-ray diffraction pattern (XRD) of SiO2@TiO2 prepared in Example 1 of the present invention.

[0013] Figure 3 This is a photograph of the appearance of the SiO2@TiO2 / PMMA radiation cooling film prepared in Example 1 of the present invention.

[0014] Figure 4 It is the ultraviolet-visible-near infrared reflection spectrum and infrared emission spectrum of the SiO2@TiO2 / PMMA radiation cooling film prepared in Example 1 of the present invention.

[0015] Figure 5 It is a schematic diagram of the test device and the temperature change curve used in the outdoor cooling effect test of the radiant cooling film prepared in Example 1 of the present invention and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0018] Unless otherwise specified, the experimental methods described in the following examples are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified.

[0019] Embodiment 1: Weigh 0.2g SiO2 powder into a beaker, add 10mL ethanol and 300uL water, then add 300uL tetrabutyl titanate dropwise, transfer the solution to the Teflon reactor liner, hydrothermally react at 140℃ for 4h, wash and dry the product to obtain SiO2@TiO2; weigh 1.5g PMMA and 8.5g DMF into a flask, stir at 80℃ for 2h to obtain a transparent solution, add 0.2g SiO2@TiO2 powder, stir evenly and drop it on a clean glass plate, apply a transparent coating with a thickness of 200um by scraping with a scraper, place it in a ventilated place to dry, and obtain SiO2@TiO2 / PMMA radiation cooling film after curing.

[0020] Comparative Example 1: Weigh 1.5 g PMMA and 8.5 g DMF into a flask, stir at 80 °C for 2 h to obtain a transparent solution, drop the solution onto a clean glass plate, and apply it with a scraper to obtain a transparent coating with a thickness of 200 um. Place the coating in a ventilated place to dry, and after curing, you can get a PMMA radiation cooling film.

[0021] Comparative Example 2: Weigh 1.5g PMMA and 8.5g DMF into a flask, stir at 80℃ for 2h to obtain a transparent solution, add 0.2g SiO2 to the above transparent solution, stir evenly, then drop the above solution on a clean glass plate, and apply it with a scraper to obtain a white coating with a thickness of 200um. Place the above white coating in a ventilated place to dry, and after curing, peel off the film from the glass plate to obtain the SiO2 / PMMA radiation cooling film.

[0022] Figure 1 This is a TEM photo of SiO2@TiO2 prepared in Example 1 of the present invention. It can be observed from the photo that the surface of SiO2 is coated with a layer of TiO2 particles.

[0023] Figure 2 This is the XRD diffraction pattern of SiO2@TiO2 prepared in Example 1 of the present invention. From the results, it can be seen that the diffraction pattern of SiO2@TiO2 prepared in Example 1 corresponds to the TiO2 standard card, indicating that SiO2@TiO2 was successfully prepared.

[0024] Figure 3 This is a photograph of the appearance of the SiO2@TiO2 / PMMA radiation cooling film prepared in Example 1 of the present invention. The film appears white in appearance.

[0025] Figure 4 The UV-visible-near infrared reflectivity spectrum and infrared emissivity spectrum of the SiO2@TiO2 / PMMA radiative cooling film prepared in Example 1 of the present invention are shown in FIG. 1. The radiative cooling film prepared in Example 1 has a reflectivity of up to 96.7% in the UV-visible-near infrared band and an emissivity of 95.8% in the infrared band.

[0026] Figure 5 The figure is a schematic diagram of the test device and the temperature change curve used in the outdoor cooling effect test of the radiative cooling film prepared by Example 1 of the present invention and Comparative Examples 1 and 2. The results show that the cavity temperature covered with Example 1 is the lowest, 10°C lower than the ambient temperature.

Claims

1. A method for preparing a SiO2@TiO2 / PMMA radiation cooling film, the specific preparation process comprising the following steps: Weigh 0.1-0.3g SiO2 powder into a beaker, add 10mL ethanol and 300uL water, then add 200-400uL tetrabutyl titanate dropwise, stir evenly and transfer the solution to the lining of a Teflon reactor, perform a hydrothermal reaction at 120-160°C for 4h, wash and dry the resulting product to obtain SiO2@TiO2; weigh 1-2g PMMA and 8-9g DMF into a flask, stir at 80°C for 1-3h to obtain a transparent solution, add 0.1-0.3g SiO2@TiO2 to the above transparent solution and stir evenly, drop the above solution onto a clean glass plate, apply a coating with a thickness of 100-300um by scraping with a scraper, place the coating in a ventilated place, dry it, and obtain a SiO2@TiO2 / PMMA radiation cooling film after curing.

2. The method for preparing the SiO2@TiO2 / PMMA radiation cooling film according to claim 1, characterized in that: SiO2@TiO2 takes SiO2 as the core and coats a layer of TiO2 particles on the surface through a hydrothermal reaction.

3. The method for preparing the SiO2@TiO2 / PMMA radiation cooling film according to claim 1, characterized in that: The amount of PMMA used was 1.5 g, and the amount of DMF used was 8.5 g.

4. The method for preparing the SiO2@TiO2 / PMMA radiation cooling film according to claim 1, characterized in that: The added amount of SiO2@TiO2 in the radiation cooling film is 10wt%.

5. The method for preparing the SiO2@TiO2 / PMMA radiation cooling film according to claim 1, characterized in that: The prepared radiative cooling film has a reflectivity of up to 96.7% in the ultraviolet-visible-near infrared band and an emissivity of 95.8% in the infrared band.

6. The method for preparing the SiO2@TiO2 / PMMA radiation cooling film according to claim 1, characterized in that: The prepared radiative cooling film was able to reduce the temperature by 10°C in outdoor tests at noon.

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