Preparation method of intelligent device capable of regulating and controlling sunlight reflectivity in large range

Abstract

The invention discloses a thermosensitive intelligent device capable of regulating and controlling sunlight reflectivity in a large range and a preparation method of the thermosensitive intelligent device, and belongs to the field of intelligent materials and energy-saving buildings. The device is composed of an upper thermosensitive phase change layer and a lower sunlight reflecting layer. Wherein the lower layer takes polyvinylidene fluoride (PVDF) as a matrix, Al2O3 and SiO2 nanoparticles with two different sizes are doped, and a composite structure with a multi-stage scattering effect is formed through curing, so that the full-band sunlight reflecting capacity can be remarkably improved. And the upper layer is a reversible thermochromic interlayer formed by dissolving crystal violet lactone (CVL), bisphenol A and tetradecanol in a transparent substrate. The core mechanism is that at low temperature, the lower layer can serve as a light trap layer, light absorption of the upper layer is enhanced through multiple reflections, and the heating efficiency is improved; at high temperature, the upper layer becomes transparent, the overall reflectivity of the device is dominated by the lower layer, and efficient refrigeration is achieved. The device can regulate and control the sunlight reflectivity (greater than 60%) according to the environment temperature, and has a good application prospect in the field of energy conservation.

Description

Technical Field

[0001] This invention relates to the field of smart materials and energy-saving buildings, and provides a method for preparing a smart device with adjustable solar reflectivity over a wide range. Background Technology

[0002] Building heating and cooling account for a significant portion of global energy consumption (approximately 30%-40%), and this trend is expected to continue to grow in the context of global warming. Traditional thermal management methods that rely on fossil fuels or air conditioning are not only energy-intensive but also generate additional CO2 emissions and environmental burdens, hindering the progress of "dual carbon" goals. Therefore, passive thermal management strategies that utilize the sun and outer space as "clean heat and cold sources" (such as radiative cooling and solar heating) have attracted attention. The core of these strategies lies in controlling the spectral selectivity of materials / devices: cooling requires high reflectivity in the 0.3-2.5μm solar wavelength band and high emission in the 8-13μm atmospheric window; heating requires higher solar absorption and suppression of heat radiation loss, thereby alleviating building heat load and reducing energy consumption under conditions of no or low energy consumption.

[0003] However, real-world climates exhibit significant seasonal and diurnal temperature variations. A singular "cooling only" or "heating only" strategy may lead to over-cooling / over-heating at inappropriate times, thereby increasing energy consumption. To address this, various switchable thermal management materials (mechanical, electrochromic, thermochromic, etc.) and passive thermochromic systems (such as thermosensitive hydrogels, perovskites, and microcapsules) have emerged in recent years. However, these systems generally suffer from problems such as the need for external energy assistance for switching, complex and costly processes, or narrow control ranges. Therefore, there is an urgent need to develop a photothermal synergistic intelligent device that requires no external energy, automatically switches between "high absorption heating" and "high reflection cooling" based on ambient temperature, and achieves wide-range solar reflectivity regulation for all-season energy saving, carbon reduction, and sustainable thermal comfort management in buildings. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for fabricating a smart device with a wide range of adjustable solar reflectivity.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The intelligent device capable of wide-range control of solar reflectivity includes a thermosensitive phase change layer and a solar reflective layer. The fabrication method includes the following steps:

[0007] (1) Preparation of thermosensitive phase change layer: Crystal violet lactone (CVL), bisphenol A and tetradecyl alcohol are mixed and dissolved to form a thermochromic phase change mixture; then the mixture is injected between two transparent substrates to form a reversible thermochromic interlayer, and the edges of the interlayer are sealed to obtain the thermosensitive phase change upper layer.

[0008] (2) Preparation of the precursor solution for the solar reflective layer: Polyvinylidene fluoride (PVDF) is dissolved in a specific polar solvent and stirred until clear to obtain a PVDF solution; then silicon dioxide (SiO2) as the first scattering particle and aluminum oxide (Al2O3) as the second scattering particle are added to the solution, and after stirring and ultrasonic dispersion treatment, a uniform radiation-cooled lower layer solution is obtained.

[0009] (3) Composite of intelligent device: The radiation cooling lower layer solution obtained in step (2) is coated on a quartz glass substrate and dried to form a PVDF-SiO2 / Al2O3 solar reflective film layer; finally, the solar reflective layer is composited with the thermosensitive phase change layer obtained in step (1) to obtain the intelligent device with a wide range of adjustable solar reflectivity.

[0010] As a preferred technical solution of the present invention, the following further limitations or optimizations are made:

[0011] In the thermochromic phase change mixture, the mass ratio of CVL, bisphenol A and tetradecyl alcohol is (0.1-10):(0.5-50):(10-100).

[0012] The transparent substrate can be selected from transparent organic polymer materials such as transparent quartz glass, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), or cyclic olefin polymers (COC / COP).

[0013] The polar solvent mentioned in step (2) may be selected from one or a blend of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc).

[0014] In step (2), the mass ratio of PVDF to polar solvent is 5%-50%.

[0015] In step (2), the median particle size of SiO2 is 0.5-15 μm, and the median particle size of Al2O3 is 0.3-10 μm.

[0016] In step (2), the mass ratio of SiO2 to Al2O3 is 1:(0.1-5).

[0017] In step (2), the total mass of SiO2 and Al2O3 particles is 0.5%-60% of the mass of PVDF.

[0018] The present invention also provides a smart device with adjustable solar reflectivity over a wide range, prepared by any of the above-described methods.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) Adaptive intelligent control: The device utilizes the reversible thermochromic properties of the thermosensitive phase change layer to automatically switch between low-temperature heat absorption mode and high-temperature reflective cooling mode according to changes in ambient temperature, without the need for external energy or complex control devices.

[0021] (2) Wide spectrum high amplitude dimming: Through the collaborative design of multi-scale scattering particles in the lower solar reflective layer and the state switching of the upper thermosensitive layer, the device realizes wide range and high efficiency control of solar spectrum reflectivity, with significant dynamic adjustment amplitude (>60%).

[0022] (3) Photothermal synergy and energy efficiency: The device integrates passive temperature management function. In low temperature environment, the upper heat absorption and lower reflective structure form a "light trap" to enhance photothermal conversion and improve the active heating effect; in high temperature environment, the upper layer becomes highly transparent and the high reflectivity of the lower layer dominates, realizing efficient radiative cooling and providing an innovative solution for building energy conservation and carbon reduction. Attached Figure Description

[0023] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0024] Figure 1 This is a graph showing the solar reflectance curves of the smart device prepared in Example 1 at high and low temperatures;

[0025] Figure 2 This is a solar reflectance curve of the solar reflective layer prepared in Comparative Example 1;

[0026] Figure 3 This is a differential scanning calorimetry (DSC) curve of the thermosensitive phase change layer prepared in Comparative Example 2;

[0027] Figure 4 This is the absorption curve of sunlight by the thermosensitive phase change layer prepared in Comparative Example 2;

[0028] Figure 5 This is a graph showing the solar reflection curves of the smart device prepared in Comparative Example 3 at high and low temperatures. Detailed Implementation

[0029] The following detailed description of the effects of a smart device for wide-range control of solar reflectivity according to the present invention is provided in conjunction with specific embodiments. However, the specific implementation methods mentioned in these embodiments are merely illustrative examples of the technical solutions of the present invention and are not intended to limit the scope of implementation of the present invention. Any improvements or substitutions made based on the above principles and on the basis of the present invention should be within the protection scope of the present invention.

[0030] Example 1

[0031] A method for fabricating a smart device with wide-range adjustable solar reflectivity includes the following steps: This invention provides a method for fabricating a smart device with wide-range adjustable solar reflectivity, the device being composed of a thermosensitive phase change upper layer and a solar reflective (radiative cooling) lower layer: First, crystal violet lactone (CVL), bisphenol A, and tetradecyl alcohol are mixed and dissolved to form a thermochromic phase change mixture with a mass ratio of 1:5:50, and injected between two quartz glass substrates to form a reversible thermochromic interlayer, followed by sealing the edges to obtain the thermosensitive phase change layer; Second, a radiative cooling lower layer solution is prepared by dissolving PVDF at a mass fraction of 10% in the polar solvent DMF and stirring until clear, then adding the first scattering particle SiO2 and the second scattering particle A. A homogeneous solution of SiO2 / Al2O3 was obtained by stirring and ultrasonic dispersion. The median particle size of SiO2 was 3 μm, and the median particle size of Al2O3 was 0.5 μm, with a SiO2 to Al2O3 mass ratio of 1:2. The total mass of both particles was 10% of the mass of PVDF. The lower layer solution was then radiatively cooled, coated onto a quartz glass substrate, and dried to form a PVDF-SiO2 / Al2O3 solar reflective film. This film was then combined with the thermosensitive phase change layer to create a smart device capable of wide-range control of solar reflectivity under different temperature conditions. Finally, solar reflectivity was measured using a UV-Vis-NIR spectrophotometer in the wavelength range of 0.25-2.5 μm. Figure 1 ).

[0032] Comparative Example 1

[0033] Polyvinylidene fluoride (PVDF) was dissolved in the polar solvent DMF at a mass fraction of 10% and stirred until clear. Then, first scattering particles SiO2 and second scattering particles Al2O3 were added, and the mixture was stirred and ultrasonically dispersed to obtain a homogeneous solution. The median particle size of SiO2 was 3 μm, and the median particle size of Al2O3 was 0.5 μm. The mass ratio of SiO2 to Al2O3 was 1:2, and the total mass of both particles was 10% of the mass of PVDF. Finally, the lower layer solution was radiatively cooled and coated onto a quartz glass substrate and dried to form a PVDF-SiO2 / Al2O3 solar reflective film. Solar reflectance was measured using a UV-Vis-NIR spectrophotometer in the wavelength range of 0.25–2.5 μm (corresponding to…). Figure 2 ).

[0034] Comparative Example 2

[0035] Crystal violet lactone (CVL), bisphenol A, and tetradecyl alcohol were mixed and dissolved to form a thermochromic phase transition mixture in a mass ratio of 1:5:50. This mixture was then injected between two quartz glass substrates to form a reversible thermochromic interlayer, followed by edge sealing to obtain a thermosensitive phase transition layer. The phase transition temperature range (corresponding to...) was characterized by DSC. Figure 3The absorbance was measured using a UV-Vis-NIR spectrophotometer, with a test wavelength range of 0.25-2.5 μm (corresponding to...). Figure 4 ).

[0036] Comparative Example 3

[0037] Crystal violet lactone (CVL), bisphenol A, and tetradecyl alcohol were mixed and heated and stirred until dissolved to obtain a thermochromic phase change mixture, wherein the mass ratio of CVL, bisphenol A, and tetradecyl alcohol was 1:5:50. Polyvinylidene fluoride (PVDF) was dissolved in the polar solvent DMF to a mass fraction of 10%, and stirred until clear to obtain a PVDF solution. Subsequently, first scattering particles silica (SiO2) and second scattering particles alumina (Al2O3) were added to the PVDF solution, wherein the median particle size of SiO2 was 3 μm and the median particle size of Al2O3 was 0.5 μm; the mass ratio of SiO2 to Al2O3 was 1:2, and the total mass of the two particles to the mass ratio of PVDF was 10%. The mixture was stirred and ultrasonically dispersed to obtain a uniform radiation-cooled lower layer solution. The thermochromic phase change mixture and the radiation-cooled lower layer solution were blended in a predetermined ratio (1:3 by mass). The mixture was mechanically stirred and then ultrasonically dispersed to ensure homogeneity, resulting in an "upper / lower layer blended coating liquid." This blended coating liquid was directly coated onto the surface of a quartz glass substrate and dried / cured to form a single-layer composite film. Finally, solar reflectance was measured using a UV-Vis-NIR spectrophotometer, with a wavelength range of 0.25-2.5 μm (corresponding to...). Figure 5 ).

[0038] (1) Comparative Example 1 shows that a high solar band reflection capability can be obtained by using only the multi-level scattering structure constructed with the PVDF–SiO2 / Al2O3 system. Figure 2 This indicates that the lower high-reflectivity film layer can provide strong scattering and high reflection when sunlight is incident, which is the basis for the device to realize the high-temperature reflective cooling mode.

[0039] (2) Comparative Example 2 shows that the CVL / bisphenol A / tetradecyl alcohol system has a clear phase transition thermal behavior and can produce a reversible thermochromic absorption response with temperature change. Figure 3 , Figure 4 This indicates that the upper thermosensitive phase change layer can provide a temperature-triggered optical state switching mechanism, which is the switch for the device to realize high-temperature cooling and low-temperature heating modes.

[0040] (3) Example 1 combines the above two types of functions in a layered and synergistic manner: at low temperatures, the upper thermosensitive phase change layer is in a colored absorption state, and the lower high-reflectivity structure generates multiple reflections and scattering of incident light, forming a "light trap" effect, thereby enhancing the absorption of sunlight by the upper layer and improving heating efficiency; at high temperatures, the upper phase change layer becomes highly transparent, and the overall solar reflectivity of the device is dominated by the lower high-reflectivity film layer, achieving a highly efficient reflective cooling effect, thus obtaining a wider range of solar reflectivity control ( Figure 1 Comparative Example 3 serves as a reference for existing blending schemes. Figure 5 Since scattering particles and thermochromic phase change components are mixed in the same system, the introduction of scattering particles will cause significant scattering extinction, resulting in ineffective loss of light energy, thereby reducing the effective absorption of the color-changing component and weakening its ability to control sunlight. In contrast, this invention adopts a layered structure design of a thermochromic phase change layer and a high-reflectivity layer, achieving a more stable and wider range of adaptive hot and cold switching effects.

[0041] For any points not covered above, existing technologies shall apply.

[0042] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for fabricating a smart device with widely adjustable solar reflectivity, characterized in that: The smart device comprises an upper thermosensitive phase change layer and a lower solar reflective layer, and the fabrication method includes the following steps: (1) Preparation of thermosensitive phase change layer: Crystal violet lactone (CVL), bisphenol A and tetradecyl alcohol are mixed and dissolved to form a thermochromic phase change mixture. The thermochromic phase change mixture is injected between transparent substrates to form a reversible thermochromic interlayer. The edges of the interlayer are sealed to obtain the thermosensitive phase change upper layer. (2) Preparation of the precursor solution for the solar reflective layer: Polyvinylidene fluoride (PVDF) is dissolved in a polar solvent and stirred until clear to obtain a PVDF solution; the first scattering particles, silicon dioxide (SiO2), and the second scattering particles, aluminum oxide (Al2O3), are added to the PVDF system, and the solution is stirred and ultrasonically dispersed to obtain a radiation-cooled lower layer solution; (3) Composite of intelligent device: The radiation-cooled lower layer solution obtained in step (2) is coated on a quartz glass substrate and dried to prepare a PVDF-SiO2 / Al2O3 solar reflective film layer; the solar reflective layer is composited with the thermosensitive phase change upper layer obtained in step (1) to obtain the intelligent device with a wide range of adjustable solar reflectivity.

2. The preparation method according to claim 1, characterized in that: In the thermochromic phase change mixture described in step (1), the mass ratio of CVL, bisphenol A and tetradecyl alcohol is (0.1-10):(0.5-50):(10-100).

3. The preparation method according to claim 1, characterized in that: The transparent substrate mentioned in step (1) can be transparent quartz glass, transparent organic polymers such as polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS) or cyclic olefin polymers (COC / COP) and other transparent organic polymer materials.

4. The preparation method according to claim 1, characterized in that: In step (2), the polar solvent can be one or a blend of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), or N,N-dimethylacetamide (DMAc).

5. The preparation method according to claim 1, characterized in that: In step (2), the ratio of PVDF to polar solvent is 5%-50%.

6. The preparation method according to claim 1, characterized in that: The median particle size of SiO2 in step (2) is 0.5-15 μm, and the median particle size of Al2O3 is 0.3-10 μm.

7. The preparation method according to claim 1, characterized in that: The mass ratio of SiO2 to Al2O3 in step (2) is 1:(0.1-5).

8. The preparation method according to claim 1, characterized in that: The total mass ratio of SiO2 and Al2O3 to PVDF in step (2) is 0.5%-60%.

9. A smart device with adjustable solar reflectivity, prepared by the method described in any one of claims 1-8.

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