Transparent passive radiation cooling film and preparation method thereof

Abstract

The invention discloses a transparent passive radiation cooling film and a preparation method thereof.The film is obtained by mixing Cs0. 33MoO3 and polymethyl methacrylate in a solvent and then forming the film, and the preparation method of the transparent passive radiation cooling film comprises the steps that 1, Cs0. 33MoO3 nano-particle powder and polymethyl methacrylate are added into the solvent, heating is conducted to enable the polymethyl methacrylate to be dissolved, and a transparent passive radiation cooling film is obtained; a mixed solution of Cs0. 33MoO3 and polymethyl methacrylate is obtained; and (2) uniformly coating a substrate with the mixed solution obtained in the step (1), drying, and demolding to obtain the transparent passive radiation cooling film. The thin film formed by combining Cs0. 33MoO3 and polymethyl methacrylate is transparent in a visible light wave band, that is, transmission of the visible light wave band of incident sunlight is allowed, but transmission of a near-infrared wave band is prevented at the same time, and the thin film has high emissivity in an atmospheric window wave band and can achieve a transparent passive radiation cooling effect.

Description

Technical Field

[0001] The invention relates to the technical field of passive radiation cooling films, and in particular to a transparent passive radiation cooling film and a preparation method thereof. Background Art

[0002] With the development of human society, widely used active cooling systems such as air conditioners consume a lot of energy, accounting for about 15% of global electricity consumption. Passive radiative cooling is an emerging cooling technology that reflects sunlight with a wavelength range of about 0.3-2.5μm back and dissipates its own heat through an atmospheric transparent window with a wavelength of 8-13μm into the cold outer space. Energy-free passive radiative cooling is increasingly being explored as an environmentally friendly alternative to electric cooling to alleviate the various effects caused by global warming. It is expected to replace air compression-based refrigeration systems and will have a significant impact on the world's energy structure and global warming. However, existing conventional passive radiative cooling materials often present an opaque white or ivory color due to the need to achieve efficient reflection of the solar spectrum, which is a single color and seriously limits practical applications. Moreover, in the cold winter, conventional passive radiative cooling materials are often prone to excessive cooling, further hindering their application. In addition, due to the opaque white color, traditional passive radiative cooling materials are also difficult to apply to some application fields that require transparency in the visible light band, such as greenhouses for ecological agriculture and automotive heat shielding films. In order to achieve proper temperature regulation, a transparent passive radiation cooling film is developed that can transmit in the visible light band, block transmission in the near-infrared band, and has a high emissivity in the atmospheric window band, which is of great practical significance for promoting the advancement and application of passive radiation cooling technology.

[0003] The patent application with publication number CN202211225096.2 discloses "A passive radiation cooling film and its preparation method" and discloses a method for preparing a passive radiation cooling film from hexagonal boron nitride micron particles and ultraviolet (UV) light-curing adhesive, dipentaerythritol hexaacrylate (DPHA) and polyethylene terephthalate (PET). However, the passive radiation cooling film prepared by this method cannot achieve visible light transmission.

[0004] The document "Thin lamellar films with enhanced mechanical properties for durable radiative cooling" (Nature Communications, 2023, 14.1: 6129.) reports a layered passive radiative cooling film of aramid nanofibers mixed with TiO2 nanoparticles. The film has an average reflectivity of 92% for the solar spectrum and an emissivity of 87% at the atmospheric window, which can achieve a cooling effect of 3.35°C lower than the ambient temperature on a clear day. However, the film is still a traditional passive radiative cooling film, and its appearance is white, which means that visible light cannot be transmitted. In other words, the film is not a transparent passive radiative cooling film. Summary of the invention

[0005] Purpose of the invention: The first purpose of the present invention is to provide a transparent passive radiation cooling film that can transmit the visible light band of incident sunlight while preventing the transmission of the near-infrared band; the second purpose of the present invention is to provide a method for preparing the film.

[0006] Technical solution: The transparent passive radiation cooling film of the present invention is composed of Cs 0.33 MoO3 and polymethyl methacrylate are mixed in a solvent to form a film.

[0007] Preferably, the Cs 0.33 The mass of MoO3 is 1 to 6% of the mass of polymethyl methacrylate. 0.33 If the mass ratio of MoO3 is too large (eg, more than 6%), it is easy to cause the visible light transmittance of the film to be low.

[0008] Preferably, the Cs 0.33 The particle size of MoO3 is 40 to 120 nm. 0.33 As the particle size of MoO3 increases, the particle size in the visible light range (380-680nm) easily causes strong light scattering, seriously affecting the transmission of visible light and causing the film to be opaque.

[0009] Preferably, the thickness of the film is 200 μm to 800 μm. The thickness of the film affects the transmission of visible light. Too large a thickness will cause a decrease in visible light transmittance, and the bending and folding properties of the film will also decrease, restricting practical applications.

[0010] The method for preparing the transparent passive radiation cooling film of the present invention comprises the following steps:

[0011] (1) Cs 0.33 MoO3 nanoparticle powder and polymethyl methacrylate are added to the solvent and heated to dissolve the polymethyl methacrylate to obtain Cs0.33 A mixed solution of MoO3 and polymethyl methacrylate;

[0012] (2) The mixed solution of step (1) is evenly coated on a substrate, dried, and stripped to obtain the transparent passive radiation cooling film.

[0013] Preferably, in step (1), the solvent is toluene and the heating temperature is 60-80°C.

[0014] Preferably, in step (2), the drying is carried out at a constant temperature, and the drying temperature is 40°C to 50°C.

[0015] Preferably, the Cs 0.33 The preparation method of MoO3 comprises the following steps:

[0016] (1) ammonium molybdate (H8MoN2O4) and cesium carbonate (Cs2CO3) are added to a solvent, mixed evenly, and dried to obtain a powder. The powder is heated at a high temperature in a vacuum furnace while introducing H2 and N2 gases, and then annealed under N2 gas protection to obtain a compound Cs 0.33 MoO3;

[0017] (2) Compound Cs from step (1) 0.33 MoO3 grinding, obtain Cs 0.33 MoO3 nanoparticles.

[0018] Preferably, the high temperature heating in the vacuum furnace in step (1) is 450-500°C, the flow ratio of the H2 and N2 gases introduced is H2 / N2=80-90 / 10-20cc / min; the annealing temperature under N2 gas protection is 550-650°C, and the annealing time is 1-1.5h.

[0019] Preferably, in step (1), the solvent is water; the uniform mixing is as follows: dissolving the ammonium molybdate and the metallic cesium carbonate in water and stirring at room temperature (20-35° C.) for about 1-2 hours, and then fully mixing the two feed solutions in a ceramic crucible.

[0020] Preferably, in step (1), the drying is: drying the uniformly mixed solution with air in a heating chamber at 150-180° C. for 8-10 hours.

[0021] Preferably, in step (1), the purity of the ammonium molybdate and the metallic cesium carbonate is greater than 99%.

[0022] Preferably, in step (2), the grinding is: using a turbo mill to grind the Cs prepared in step (1) 0.33MoO3 is mixed with the grinding medium and then ground for 2 to 4 hours. Preferably, the grinding medium is iron balls, zirconium oxide beads, or a mixture of iron balls and zirconium oxide beads.

[0023] Invention mechanism: The inventor discovered that Cs 0.33 MoO3 nanoparticles have high transmittance in the visible light band and high absorption characteristics in the near-infrared band. The film prepared by combining the high transmittance of polymethacrylic acid in the visible light band and the high emissivity characteristics of the atmospheric window band is transparent in the visible light band and blocks the transmission of the near-infrared band. It is a transparent passive radiation cooling film, such as Figure 2 shown.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) Through Cs 0.33 The film formed by combining MoO3 and polymethyl methacrylate is transparent in the visible light band, that is, it allows the visible light band of incident sunlight to be transmitted, but at the same time blocks the transmission of the near-infrared band, and has a high emissivity in the atmospheric window band, which can achieve a transparent passive radiation cooling effect; (2) The preparation method is simple and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the preparation process of the present invention;

[0026] Figure 2 It is a schematic diagram of the passive radiation cooling film principle of the present invention;

[0027] Figure 3 The CS of the present invention 0.33 SEM test image of MoO3 nanoparticles;

[0028] Figure 4 is the transmittance test curve of Example 1;

[0029] Figure 5 is the atmospheric window emissivity test curve of Example 1;

[0030] Figure 6 is the transmittance test curve of Example 2;

[0031] Figure 7 is the atmospheric window emissivity test curve of Example 2;

[0032] Figure 8 is the environmental temperature drop test curve of Example 2;

[0033] Fig. 9 This is the transmittance test curve of Comparative Example 1. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with embodiments.

[0035] Example 1

[0036] The transparent passive radiation cooling film of the present invention comprises the following steps:

[0037] (S1) Preparation of Compound Cs 0.33 MoO3;

[0038] (1) 20 g of ammonium molybdate (H8MoN2O4, purity 99%) and 10 g of cesium carbonate (Cs2CO3, purity 99%) were dissolved in 200 mL of water, and stirred at room temperature (20-35° C.) for about 1 h, and then the solution was fully mixed in a clean ceramic crucible; the mixed solution was dried in a heating chamber at 180° C. with air for 8 h to obtain a powder;

[0039] (2) The powder prepared in step (1) was heated at 450° C. in a vacuum furnace and H2 and N2 gases were introduced simultaneously, with the flow ratio of H2 to N2 being H2 / N2=80 / 10 cc / min; then, under the protection of N2 gas, the annealing temperature was maintained at 550° C. and the annealing time was 1 h to obtain compound Cs 0.33 MoO3.

[0040] (S2) Grinding to obtain Cs 0.33 MoO3 nanoparticles;

[0041] In this step, the compound Cs obtained in step S1 is milled by a turbo mill. 0.33 MoO3 was mixed with grinding media zirconium oxide beads (diameter about 0.3 mm) and ground for 2 h to obtain Cs 0.33 MoO3 nanoparticles.

[0042] (S3)Configure Cs 0.33 A mixed solution of MoO3 and polymethyl methacrylate (PMMA);

[0043] 1g Cs 0.33 MoO3 nanoparticle powder was mixed with 100g polymethyl methacrylate (PMMA) (i.e. Cs 0.33 MoO3 (1 wt% of PMMA) was added to 200 mL of toluene solution (purity 99.9%) and magnetically stirred at 70 °C for 2 h to obtain CS 0.33 Mixed solution of MoO3 and polymethyl methacrylate (PMMA).

[0044] (S4) applying the mixed solution and drying it to form a film;

[0045] In this step, the Cs obtained in step (S3) 0.33The mixed solution of MoO3 and polymethyl methacrylate (PMMA) is transported to the coating head as the coating liquid, and the gap between the coating head scraper is controlled so that the target thickness of the film is 200μm. It is evenly coated on the base quartz glass by a coating method and dried at a constant temperature of 40°C. After demolding, a transparent passive radiation cooling film with a thickness of 200μm is obtained.

[0046] The Cs obtained in Example 1 0.33 MoO3 nanopowder was tested by scanning electron microscope. Figure 3 As shown, it can be seen that Cs 0.33 The average particle diameter of MoO3 nanopowder is about 40nm. The average transmittance of the passive radiation cooling film obtained in the visible light band of 400nm to 780nm is about 64%, and the average transmittance in the near infrared band of 780nm to 1450nm is about 25% ( Figure 4 ). At the same time, the average emissivity in the atmospheric window 8μm ~ 13μm band is 92.3% ( Figure 5 ).

[0047] Example 2

[0048] The transparent passive radiation cooling film of the present invention comprises the following steps:

[0049] (S1) Preparation of Compound Cs 0.33 MoO3;

[0050] (1) 20 g of ammonium molybdate (H8MoN2O4, purity 99%) and 10 g of cesium carbonate (Cs2CO3, purity 99%) were dissolved in 200 mL of water, and stirred at room temperature (20-35° C.) for about 1 h, and then the solution was fully mixed in a clean ceramic crucible; the mixed solution was dried in a heating chamber at 180° C. with air for 8 hours to obtain a powder;

[0051] (2) The powder prepared in step (1) was heated at 500°C in a vacuum furnace and H2 and N2 gases were introduced simultaneously, with the flow ratio of H2 to N2 being H2 / N2=90 / 20cc / min; then, under the protection of N2 gas, the annealing temperature was maintained at 650°C and the annealing time was 1.5h to obtain Cs 0.33 MoO3.

[0052] (S2) Grinding to obtain Cs 0.33 MoO3 nanoparticles;

[0053] The compound Cs obtained in step S1 is treated by a turbo mill. 0.33 MoO3 was mixed with grinding media iron balls (about 4 mm in diameter) and zirconium oxide beads (about 0.3 mm in diameter) and ground for 2 h to obtain Cs0.33 MoO3 nanoparticles.

[0054] (S3)Configure Cs 0.33 A mixed solution of MoO3 and polymethyl methacrylate (PMMA);

[0055] 6g Cs 0.33 MoO3 nanoparticle powder was mixed with 100g polymethyl methacrylate (PMMA) (i.e. Cs 0.33 MoO3 (6 wt% of PMMA) was added to 200 mL of toluene solution (purity 99.9%) and magnetically stirred at 70 ° C for 3 h to obtain CS 0.33 Mixed solution of MoO3 and polymethyl methacrylate (PMMA).

[0056] (S4) applying the mixed solution and drying it to form a film;

[0057] The Cs obtained in step (S3) 0.33 A mixed solution of MoO3 and polymethyl methacrylate (PMMA) is transported to the coating head as a coating liquid, and the gap between the coating head scraper is controlled so that the target thickness of the film is 800μm. It is evenly coated on the base quartz glass by a coating method and dried at a constant temperature of 50°C. After demolding, a transparent passive radiation cooling film with a thickness of 800μm is obtained.

[0058] The passive radiation cooling film obtained in Example 2 was tested for its optical properties and cooling performance. Figures 6 to 8 shown.

[0059] Depend on Figure 6 It can be seen that the average transmittance of the passive radiation cooling film in the visible light band of 400nm-780nm is about 46%, and the average transmittance in the near infrared band of 780nm-1450nm is about 19%. At the same time, the average emissivity in the atmospheric window band of 8μm to 13μm is 92.8% ( Figure 7 ).

[0060] Passive cooling experiments were conducted on a clear summer day. The test results showed that from 10 a.m. to 3 p.m., the film could achieve a cooling effect that was 3.9°C lower than the average ambient temperature.

[0061] Comparative Example 1

[0062] Based on Example 1, in step (S3), Cs is changed 0.33 The mass of MoO3 nanoparticle powder is 10g (i.e. Cs 0.33MoO3 is 10wt% of PMMA), and other conditions remain unchanged. The average transmittance of the passive radiation cooling film in the visible light band of 400nm-780nm is only about 18% ( Fig. 9 ), the film is opaque under visible light.

Claims

1. A transparent passive radiation cooling film, characterized in that: The film is composed of Cs 0.33 MoO3 and polymethyl methacrylate are mixed in a solvent to form a film.

2. The transparent passive radiation cooling film according to claim 1, characterized in that: The Cs 0.33 The mass of MoO3 is 1 to 6% of the mass of polymethyl methacrylate.

3. The transparent passive radiation cooling film according to claim 1, characterized in that: The Cs 0.33 The particle size of MoO3 is 40 to 120 nm.

4. The transparent passive radiation cooling film according to claim 1, characterized in that: The film has a thickness of 200 μm to 800 μm.

5. A method for preparing a transparent passive radiation cooling film according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Cs 0.33 MoO3 nanoparticle powder and polymethyl methacrylate are added to the solvent and heated to dissolve the polymethyl methacrylate to obtain Cs 0.33 A mixed solution of MoO3 and polymethyl methacrylate; (2) The mixed solution of step (1) is evenly coated on a substrate, dried, and stripped to obtain the transparent passive radiation cooling film.

6. The method for preparing a transparent passive radiation cooling film according to claim 5, characterized in that: In step (2), the drying is carried out at a constant temperature, and the drying temperature is 40°C to 50°C.

7. The method for preparing a transparent passive radiation cooling film according to claim 5, characterized in that: In step (1), the solvent is toluene and the heating temperature is 60-80°C.

8. The method for preparing a transparent passive radiation cooling film according to claim 5, characterized in that: The Cs 0.33 The preparation method of MoO3 comprises the following steps: (1) adding ammonium molybdate and cesium carbonate into a solvent, mixing evenly, and drying to obtain a powder; heating the powder at a high temperature in a vacuum furnace while introducing H2 and N2 gases; and then annealing the powder under N2 gas protection to obtain a compound Cs 0.33 MoO3; (2) Compound Cs prepared in step (1) 0.33 MoO3 grinding, obtain Cs 0.33 MoO3 nanoparticles.

9. The method for preparing a transparent passive radiation cooling film according to claim 8, characterized in that: In step (1), the high temperature heating in the vacuum furnace is at a temperature of 450-500°C, and the annealing temperature under N2 gas protection is at a temperature of 550-650°C.

10. The method for preparing a transparent passive radiation cooling film according to claim 8, characterized in that: In step (1), the drying step is: drying the uniformly mixed solution with air in a heating chamber at 150 to 180° C. for 8 to 10 hours.

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