Radiation cooling coating based on multi-scale structure collaborative design and preparation method thereof

Abstract

The invention provides a radiation cooling coating based on multi-scale structure collaborative design, materials of the radiation cooling coating comprise an ethyl cellulose matrix, silicon dioxide nanoparticles, barium titanate nanoparticles and carbon nanotubes, the surface of the radiation cooling coating is provided with a periodic micropore array structure, and the periodic micropore array structure is a gradient refractive index structure. The invention further provides a preparation method of the radiation cooling pattern layer. Through molecular-level compounding of an ethyl cellulose matrix, barium titanate and silicon dioxide nanoparticles and in combination with femtosecond laser surface microstructure processing, collaborative optimization of multi-band spectrum regulation and high-efficiency heat conduction of the radiation cooling coating can be realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of functional materials, and more specifically, to a radiative cooling coating based on multi-scale structure collaborative design and a preparation method thereof. Background Art

[0002] With the intensification of the global energy crisis and the increasing carbon emission pressure, the development of passive radiative cooling technologies that do not require external energy input has become a key research and industrial focus worldwide. In recent years, the research on daytime radiative cooling material systems has mainly focused on three major technical routes: metamaterials such as photonic crystals / surfaces, polymer-based composites, and multi-layer thin film structures. Among them, polymer materials have attracted much attention due to their adjustable molecular structure, low preparation cost, and excellent intrinsic infrared radiation efficiency. However, the existing technologies still face two key contradictions: on the one hand, although three-dimensional porous polymers with metal-free reflective layers can achieve partial sunlight reflection through micro-nano pore scattering, their disordered pore structures result in poor selectivity in the mid-infrared radiation band, severely restricting the active regulation ability of the day-night temperature difference and making it difficult to meet the long-term stable service requirements of outdoor equipment; this leads to limited day-night temperature difference regulation ability and difficulty in meeting long-term outdoor service requirements; on the other hand, the inherently low thermal conductivity of the polymer matrix severely restricts the heat conduction efficiency from the heat source to the radiation layer, and the heat dissipation efficiency of electronic devices covered with traditional coatings is reduced by more than 40% compared with metal-based solutions. To address the above bottlenecks, it is necessary to break through multi-scale collaborative optimization to achieve a synergistic leap in the optical-thermal-mechanical properties at the material intrinsic level. Summary of the Invention

[0003] In view of this, the present disclosure breaks through the technical bottlenecks of traditional radiative cooling materials in infrared emissivity, mechanical stability, and thermal conduction efficiency through molecular-level material compounding and the mechanism of laser-matter interaction, and provides a radiative cooling coating based on multi-scale structure collaborative design and a preparation method thereof.

[0004] One aspect of the present disclosure provides a radiative cooling coating based on multi-scale structure collaborative design. The materials of the radiative cooling coating include: an ethyl cellulose matrix, silica nanoparticles, barium titanate nanoparticles, and carbon nanotubes. Its surface has a periodic microporous array structure, and the periodic microporous array structure is a gradient refractive index structure.

[0005] According to an embodiment of the present disclosure, the mass ratio of the material components of the radiative cooling coating is: 2-5 wt% of ethyl cellulose, 40-50 wt% of barium titanate nanoparticles, 40-50 wt% of silica nanoparticles, and 0.5-2 wt% of carbon nanotubes.

[0006] According to an embodiment of the present disclosure, the particle size of the barium titanate nanoparticles is 50 - 100 nm, and the particle size of the silica nanoparticles is 20 - 50 nm.

[0007] According to an embodiment of the present disclosure, the length of the carbon nanotubes is 5 - 20 μm, and the diameter is 10 - 30 nm.

[0008] According to an embodiment of the present disclosure, the periodic microporous array structure is formed by femtosecond laser ablation. The central wavelength of the femtosecond laser pulse is 1030 nm, the repetition frequency is 50 - 200 kHz, and the pulse width is 35 fs.

[0009] According to an embodiment of the present disclosure, the micropore diameter of the periodic microporous array is 5 - 20 μm, and the depth is 10 - 20 μm.

[0010] Another aspect of the present disclosure provides a method for preparing a radiative cooling coating based on the collaborative design of multi-scale structures, which is applied to the radiative cooling coating according to any one of the above aspects. The method includes: dispersing barium titanate nanoparticles and silica nanoparticles in a water / ethanol mixed solvent with a volume ratio of 1:1 respectively, ultrasonically cleaning for 30 minutes to remove surface adsorbents, centrifuging the barium titanate nanoparticles and the silica nanoparticles at a speed of 8000 rpm with a centrifuge, repeating the cleaning and then drying in an oven at 60 °C to obtain purified barium titanate nanoparticles and silica nanoparticles; dispersing 5 g of ethyl cellulose in a 100 g water / ethanol mixed solvent with a mass ratio of 1:4, magnetically stirring for 2 hours under a water bath condition at 60 °C to form a transparent homogeneous ethyl cellulose solution; dispersing 80 g of the purified barium titanate nanoparticles in a 100 g water / ethanol mixed solvent with a mass ratio of 1:4, ultrasonically treating for 0.5 hour to form a stable barium titanate suspension; dispersing 80 g of the purified silica nanoparticles in a 100 g water / ethanol mixed solvent with a mass ratio of 1:4, ultrasonically treating for 0.5 hour to form a stable silica suspension; adding 2 g of carbon nanotubes to a 50 g water / ethanol mixed solvent with a mass ratio of 1:4, adding 0.5 wt% sodium dodecyl sulfate as a dispersant, ultrasonically treating for 1 hour to form a uniformly dispersed carbon nanotube solution; mixing the transparent homogeneous ethyl cellulose solution, the stable barium titanate suspension, the stable silica suspension and the uniformly dispersed carbon nanotube solution according to a preset mass ratio, magnetically stirring for 1 hour, and then ultrasonically dispersing for 0.5 hour to form a uniform composite slurry; performing plasma cleaning on the substrate, using a spraying process to uniformly coat the uniform composite slurry on the surface of the substrate, and curing at room temperature in a clean environment for 24 hours to form a cured coating; controlling the femtosecond laser pulse with a galvanometer scanning system, processing a periodic microporous array on the surface of the cured coating, and forming a gradient refractive index structure by real-time monitoring of the micropore morphology through an integrated CCD camera.

[0011] According to an embodiment of the present disclosure, through the molecular-level composite of an ethyl cellulose matrix with barium sulfate and silicon dioxide nanoparticles, combined with femtosecond laser surface microstructure processing, the synergistic optimization of multi-band spectral regulation and high-efficiency heat conduction is achieved.

[0012] Specifically, a radiative cooling coating based on the collaborative design of multi-scale structures provided by the present disclosure has the following beneficial effects:

[0013] 1. Based on the collaborative design of multi-scale structures, efficient spectral regulation in the entire band is achieved. Through the phonon polariton resonance effect of barium titanate nanoparticles, a high emissivity is achieved in the 8-10 μm band; silicon dioxide nanoparticles optimize the radiation efficiency in the 10-13 μm band, and the average emissivity in the overall atmospheric window (8-13 μm) reaches above 0.94, significantly enhancing the day-night radiative cooling ability. The periodic micropore array processed by femtosecond laser forms a gradient refractive index structure, effectively suppressing the absorption of solar radiation heat;

[0014] 2. The synergistic optimization of thermal-mechanical-optical properties is achieved. Carbon nanotubes construct a three-dimensional continuous heat conduction network in the matrix, which can quickly conduct the heat of the heat source to the radiation layer. The ethyl cellulose (EC) matrix improves the toughness of the coating through a dynamic cross-linking network and combines the stress dispersion effect of the laser micropore array to meet the long-term outdoor service requirements;

[0015] 3. By optimizing the surface modification and dispersion process of nanoparticles to replace the step-by-step deposition of traditional multi-layer films, it has process scalability and cost advantages. Through the collaborative control of a galvanometer scanning system and femtosecond laser, efficient processing of the micropore array is achieved, avoiding the problems of thermal damage and pollution of chemical etching processes, and eliminating the need for mask assistance, providing a manufacturing solution with high efficiency, high precision, and green sustainability for large-scale industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:

[0017] Figure 1 Schematically shows the infrared emissivity test diagram of the radiative cooling coating of the radiative cooling coating based on the collaborative design of multi-scale structures according to the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure. However, evidently, one or more embodiments can be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present disclosure.

[0019] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0020] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0021] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but not be limited to a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0022] Embodiments of the present disclosure provide a radiative cooling coating based on multi-scale structure co-design. The materials of the radiative cooling coating include: an ethyl cellulose (EC) matrix, silicon dioxide (SiO2) nanoparticles, barium titanate (BaTiO4) nanoparticles, and carbon nanotubes. Its surface has a periodic microporous array structure, and the periodic microporous array structure is a gradient refractive index structure.

[0023] In the embodiments of the present disclosure, the radiative cooling coating is composed of the following components by mass ratio: 2-5 wt% of ethyl cellulose, 40-50 wt% of barium titanate nanoparticles, 40-50 wt% of silicon dioxide nanoparticles, and 0.5-2 wt% of carbon nanotubes.

[0024] In the embodiments of the present disclosure, the particle size of the barium titanate nanoparticles is 50-100 nm, and the particle size of the silicon dioxide nanoparticles is 20-50 nm.

[0025] In the embodiments of the present disclosure, the length of the carbon nanotubes is 5-20 μm, and the diameter is 10-30 nm.

[0026] In the embodiments of the present disclosure, the periodic microporous array structure is formed by femtosecond laser ablation. The central wavelength of the femtosecond laser pulse is 1030 nm, the repetition frequency is 50 - 200 kHz, and the pulse width is 35 fs.

[0027] In the embodiments of the present disclosure, the pore diameter of the periodic microporous array is 5 - 20 μm, and the depth is 10 - 20 μm.

[0028] The embodiments of the present disclosure also provide a method for preparing a radiative cooling coating based on the collaborative design of multi-scale structures, and this method includes Step 1 to Step 8.

[0029] Step 1: Disperse barium titanate nanoparticles and silica nanoparticles separately in a water / ethanol (ethanol purity ≥ 99.9%) mixed solvent with a volume ratio of 1:1, ultrasonically clean for 30 minutes to remove surface adsorbents, centrifuge the barium titanate nanoparticles and silica nanoparticles at a speed of 8000 rpm, repeat the cleaning 3 times, and then place them in an oven at 60 °C for drying for 12 hours to obtain purified barium titanate nanoparticles and silica nanoparticles.

[0030] Step 2: Disperse 5 g of ethyl cellulose (viscosity 4000 cP) in a 100 g water / ethanol mixed solvent with a mass ratio of 1:4, and magnetically stir (rotation speed 500 rpm) for 2 hours under a 60 °C water bath condition to form a transparent homogeneous ethyl cellulose solution.

[0031] Step 3: Disperse 80 g of the purified barium titanate nanoparticles (particle size 50 - 100 nm) in a 100 g water / ethanol mixed solvent with a mass ratio of 1:4, and ultrasonically treat for 0.5 hour to form a stable barium titanate suspension.

[0032] Step 4: Disperse 80 g of the purified silica nanoparticles in a 100 g water / ethanol mixed solvent with a mass ratio of 1:4, and ultrasonically treat for 0.5 hour to form a stable silica suspension.

[0033] Step 5: Add 2 g of carbon nanotubes to a 50 g water / ethanol mixed solvent with a mass ratio of 1:4, add 0.5 wt% of sodium dodecyl sulfate as a dispersant, and ultrasonically treat for 1 hour to form a uniformly dispersed carbon nanotube solution.

[0034] Step 6: Mix the transparent homogeneous ethyl cellulose solution, the stable barium titanate suspension, the stable silica suspension, and the uniformly dispersed carbon nanotube solution according to a preset mass ratio of 1:2:2:0.1, magnetically stir (rotation speed 500 rpm) for 1 hour, and then ultrasonically disperse for 0.5 hour to form a uniform composite slurry.

[0035] Step 7, the substrate is subjected to plasma cleaning (Ar gas, 200 W, 5 minutes) to enhance surface adhesion. The uniform composite slurry is evenly coated on the surface of the substrate by using a high-pressure airless spraying device (nozzle diameter 0.3 mm, pressure 0.5 MPa). The wet film thickness is controlled to be 100 - 120 μm (corresponding to a dry film thickness of 50 - 60 μm, and a volume shrinkage rate of ~50% after curing). The wet film is placed in a clean environment (temperature 25 ± 2°C, humidity 50 ± 5%) and cured at room temperature for 24 hours to form a cured coating;

[0036] Step 8, a galvanometer scanning system is used to control femtosecond laser pulses to process a periodic micropore array on the surface of the cured coating. The micropore morphology is monitored in real time through an integrated CCD camera. The pore diameter is 5 - 20 μm, the depth is 10 - 20 μm, and the pore spacing is 25 μm to form a gradient refractive index structure.

[0037] Figure 1 The infrared emissivity test chart of the radiative cooling coating based on the multi-scale structure collaborative design of the embodiment of the present disclosure is shown. It can be seen from the figure that the average infrared emissivity of the radiative cooling coating with the multi-scale structure collaborative design is as high as 0.943 in the 8 - 13 μm band.

[0038] The embodiments of the present disclosure have been described above. However, these embodiments are only for illustrative purposes and not for limiting the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. A radiative cooling coating based on co - design of multi - scale structures, the material of the radiative cooling coating comprising: An ethyl cellulose matrix, silica nanoparticles, barium titanate nanoparticles, and carbon nanotubes, having a periodic microporous array structure on its surface, and the periodic microporous array structure being a gradient refractive index structure.

2. The radiative cooling coating according to claim 1, wherein, The mass ratio of the material components of the radiative cooling coating is: ethyl cellulose 2 - 5 wt%, barium titanate nanoparticles 40 - 50 wt%, silica nanoparticles 40 - 50 wt%, and carbon nanotubes 0.5 - 2 wt%.

3. The radiative cooling coating according to claim 1, wherein The particle size of the barium titanate nanoparticles is 50 - 100 nm, and the particle size of the silica nanoparticles is 20 - 50 nm.

4. The radiative cooling coating according to claim 1, wherein The length of the carbon nanotubes is 5 - 20 μm, and the diameter is 10 - 30 nm.

5. The radiative cooling coating according to claim 1, wherein the periodic microporous array structure is formed by femtosecond laser ablation. The central wavelength of the femtosecond laser pulse is 1030 nm, the repetition frequency is 50 - 200 kHz, and the pulse width is 35 fs.

6. The radiative cooling coating according to claim 1, wherein the micropore diameter of the periodic microporous array is 5 - 20 μm, and the depth is 10 - 20 μm.

7. A method for preparing a radiative cooling coating based on co - design of multi - scale structures, applied to the radiative cooling coating according to any one of claims 1 to 6, the method comprising: Disperse barium titanate nanoparticles and silica nanoparticles respectively in a water / ethanol mixed solvent with a volume ratio of 1:1, ultrasonically clean for 30 minutes to remove surface adsorbents, centrifuge separate the barium titanate nanoparticles and the silica nanoparticles at a speed of 8000 rpm, repeat the cleaning and then place them in an oven at 60 °C for drying to obtain purified barium titanate nanoparticles and silica nanoparticles; Disperse 5 g of ethyl cellulose in 100 g of a water / ethanol mixed solvent with a mass ratio of 1:4, and magnetically stir for 2 hours under a water bath condition of 60 °C to form a transparent homogeneous ethyl cellulose solution; Disperse 80 g of the purified barium titanate nanoparticles in 100 g of a water / ethanol mixed solvent with a mass ratio of 1:4, and ultrasonically treat for 0.5 hour to form a stable barium titanate suspension; Disperse 80 g of the purified silica nanoparticles in 100 g of a water / ethanol mixed solvent with a mass ratio of 1:4, and ultrasonically treat for 0.5 hour to form a stable silica suspension; Add 2 g of carbon nanotubes to 50 g of a water / ethanol mixed solvent with a mass ratio of 1:4, add 0.5 wt% of sodium dodecyl sulfate as a dispersant, and ultrasonically treat for 1 hour to form a uniformly dispersed carbon nanotube solution; Mix the transparent homogeneous ethyl cellulose solution, the stable barium titanate suspension, the stable silica suspension, and the uniformly dispersed carbon nanotube solution according to a preset mass ratio, magnetically stir for 1 hour, and then ultrasonically disperse for 0.5 hour to form a uniform composite slurry; Perform plasma cleaning on the substrate, and use a spraying process to uniformly coat the uniform composite slurry on the surface of the substrate, and place it in a clean environment for room - temperature curing for 24 hours to form a cured coating; A galvanometer scanning system is used to control femtosecond laser pulses to machine a periodic micropore array on the surface of the solidified coating, and a CCD camera is integrated to monitor the micropore morphology in real time to form a gradient refractive index structure.

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