Double-selectivity all-inorganic radiation refrigeration film and preparation method thereof

Abstract

The invention discloses a double-selectivity all-inorganic radiation refrigeration film and a preparation method thereof.The film comprises an adhesion layer, a metal reflection layer and a multi-layer dielectric film layer, the adhesion layer is arranged on a bottom layer, the metal reflection layer is arranged on the upper surface of the adhesion layer, and the multi-layer dielectric film layer is arranged on the upper surface of the metal reflection layer; the multi-layer dielectric film layer comprises a quasi-periodic multi-layer film structure which is formed by two materials of which the refractive index difference is greater than a preset threshold value according to a preset thickness in a preset arrangement mode; wherein the number of layers, the preset arrangement mode and the preset thickness of the multiple dielectric film layers are obtained by optimizing an ideal spectrum selectively emitted by the double atmospheric transmission windows as an optimization target. The radiation refrigeration film has the characteristic of high reflection in the solar spectrum range, and can selectively emit infrared rays at the first atmospheric window and the second atmospheric window at the same time, so that the radiation refrigeration film has higher refrigeration potential than an existing radiation refrigeration emitter.

Description

Technical Field

[0001] The present invention relates to the field of radiation refrigeration technology, and more specifically, to a dual-selective all-inorganic radiation refrigeration film and a preparation method thereof. Background Art

[0002] On the basis of the continuous increase in energy consumption, global warming has become a prominent issue, and the demand for energy-saving technologies is also increasing at a corresponding rate. According to statistics, among all aspects of energy consumption, cooling systems consume 15% of the world's electricity generation and account for 10% of global greenhouse gas emissions. Passive daytime radiative cooling (PDRC) is a green refrigeration technology that can achieve sub-ambient cooling (lowering the temperature of an object below the ambient temperature) under direct sunlight. It does not consume any energy and does not emit any greenhouse gases. It is an ideal alternative technology to traditional vapor compression-based refrigeration systems. This technology reflects most of the incident solar energy during the day and transmits infrared (IR) energy to the external space with a low temperature of 3K through an atmospheric transparent window. Due to the zero-energy cooling advantage of daytime radiative cooling technology, it has a wide range of applications in wearable devices, smart windows, thermoelectric materials, solar cells and other fields.

[0003] In previous studies, carefully designed multilayer thin films, photonic crystals, and metamaterials have been actively investigated for radiative cooling systems. Typically, Aaswath P. Raman et al. reported a PDRC of seven alternating layers of hafnium dioxide and silicon dioxide on a silicon substrate with a Ag solar reflective layer. Experimentally, this multilayer radiative cooling system was demonstrated to be effective at 850 W m -2 The solar irradiance provided a cooling temperature of 4.9°C and a cooling rate of 40.1W m -2 The cooling power. Although the introduction of surface microstructures can improve the high emissivity of the atmospheric transparent window and the reflectivity of the solar spectrum region (0.3-2.5 μm), this type of PDRC is difficult to apply on a large scale due to its complex structure and high price. Yao Zhai et al. introduced a radiation cooling system based on microparticles embedded in metamaterials. They uniformly incorporated randomly dispersed SiO2 microparticles into a polymer matrix. The microspheres of a specific size strongly scattered infrared light (due to high-order resonances), achieving the goal of providing high emissivity in the atmospheric transparent window. In outdoor experiments, silver (200nm) was plated on the back of the hybrid metamaterial as a sunlight reflection layer, showing superior daytime radiative cooling performance. The advantage of daytime radiative cooling systems based on hybrid metamaterials is that they can be easily manufactured at low cost and on a large scale, and have broad commercial application prospects. However, existing radiative cooling system designs usually only focus on the main atmospheric transparent window (8μm~13μm) and ignore the other window (16μm~25μm), without fully exploring their cooling potential. Only a few research works have paid attention to this. For example, the Chinese patent with publication number CN116790087 A discloses a dual-selective radiative cooling material and its preparation method. They realized a high-performance dual-selective thermal emitter by combining polyoxymethylene fibers and polytetrafluoroethylene particles of specific sizes, demonstrating the great potential of the dual-selective PDRC design in improving radiative cooling performance. The Chinese patent with publication number CN118703042 A discloses a dual-band high-emissivity radiation cooling film and a preparation method. The material is a first polymer filler powder, a second inorganic filler powder, an organic film base material and other auxiliary additives, mixed evenly in proportion, defoamed, made into a film, and cured to obtain a radiation cooling film material. It can achieve high emissivity and greater than 90% solar reflectivity in dual atmospheric window bands. However, the polymer-based radiation cooling system has a limited life due to oxidation, degradation and peeling problems. Summary of the invention

[0004] One of the purposes of the present invention is to provide a dual-selective all-inorganic radiation cooling film to solve the problems that existing radiation cooling materials are mostly single-band high-emissivity materials, have low radiation cooling power, limited application scenarios, and low service life; the second purpose of the present invention is to provide a method for preparing a dual-selective all-inorganic radiation cooling film.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] The first aspect of the present invention provides a dual-selective all-inorganic radiation cooling film, comprising an adhesive layer, a metal reflective layer and a multi-layer dielectric film layer, wherein:

[0007] The adhesive layer is arranged on the bottom layer, the metal reflective layer is arranged on the upper surface of the adhesive layer, and the multi-layer dielectric film layer is arranged on the upper surface of the metal reflective layer;

[0008] The multilayer dielectric film layer comprises a quasi-periodic multilayer thin film structure composed of two materials with a refractive index difference greater than a preset threshold value, with a preset thickness and a preset arrangement, wherein the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film layer are optimized based on the ideal spectrum selectively emitted by the double atmospheric transmission windows as the optimization target.

[0009] In the above technical means, the adhesive layer is used to adhere the substrate and the radiation cooling film; the metal reflective layer has high reflectivity and low absorption rate for the solar light band spectrum; the multi-layer dielectric film layer enables the radiation cooling film to have selective emission peaks at the two atmospheric windows. At the same time, the radiation cooling system composed of all inorganic materials has significant advantages in system life.

[0010] Furthermore, the adhesion layer includes a film layer made of metal titanium.

[0011] Furthermore, the metal reflective layer includes a film layer made of a metal film, and the metal film includes a film made of Ag or Al.

[0012] Furthermore, the two materials with a refractive index difference greater than a preset threshold, wherein the high refractive index material includes AlON, Al2O3, SiN x , TiO2 or HfO2, low refractive index materials include SiO2, MgF2 or AlF3.

[0013] Furthermore, the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film are optimized based on the ideal spectrum selectively emitted by the double atmospheric transmission windows as the optimization target, including:

[0014] The simulated annealing genetic algorithm and the transfer matrix method are used as structural optimization tools, the ideal spectrum of the ideal dual-selective radiation cooling film is taken as the optimization target spectrum, the parameter of the thickness of each layer is set to 0-000 nanometers, and the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film layer are determined.

[0015] Furthermore, in the simulated annealing genetic algorithm, the fitness function of each generation is defined as:

[0016]

[0017] In the formula, Φ represents the fitness function, μ j represents the weight, ∈0(λ j ) represents the target emissivity / absorbance spectrum, ∈(λ j ) represents the current emissivity / absorbance spectrum.

[0018] Furthermore, the multilayer dielectric film layer includes six sub-layers with different thicknesses.

[0019] Furthermore, the multilayer dielectric film layer includes six sub-layers of SiO2 and Si3N4 of different thicknesses which are alternately arranged.

[0020] Furthermore, the dual atmospheric transmission windows include a first atmospheric window and a second atmospheric window, the first atmospheric window is 8 microns to 13 microns, and the second atmospheric window is 16 microns to 25 microns.

[0021] The second aspect of the present invention provides a method for preparing a dual-selective all-inorganic radiation refrigeration film, the method for preparing the dual-selective all-inorganic radiation refrigeration film as claimed in the claims comprises the following steps:

[0022] Using a metal target, a uniform adhesion layer is deposited on the working surface by magnetron sputtering or electron beam evaporation;

[0023] Using a metal target, a uniform metal reflective layer is deposited on the adhesion layer by a magnetron sputtering method or an electron beam evaporation process;

[0024] Using a preset ratio of reaction gas, an inductively coupled plasma chemical vapor deposition process, a pure target DC or radio frequency reactive magnetron sputtering technology, a multilayer dielectric film layer consisting of two materials with a refractive index difference greater than a preset threshold is sequentially grown on the metal reflective layer.

[0025] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0026] The present invention provides a high-performance all-inorganic dual-selective radiation cooling film, which can selectively emit infrared rays in a first atmospheric window and a second atmospheric window, wherein the first atmospheric window is 8 μm to 13 μm, and the second atmospheric window is 16 μm to 25 μm; and the radiation cooling film has a high reflective property in the solar spectrum range, wherein the solar spectrum range is 0.3 μm to 2.5 μm; the radiation cooling film of the present invention has high selective thermal emissivity in both atmospheric windows, and can be used as a dual-selective heat emitter, and while eliminating atmospheric parasitic heat, it can efficiently dissipate heat to outer space through the two atmospheric windows, thereby having a higher cooling potential than existing radiation cooling emitters. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the structure of a dual-selective all-inorganic radiation cooling film provided by an embodiment of the present invention;

[0028] Figure 2 A schematic flow chart of a method for preparing a dual-selective all-inorganic radiation refrigeration film provided by an embodiment of the present invention;

[0029] Figure 3A schematic diagram of the spectral response of a dual-selective all-inorganic radiative cooling film provided in an embodiment of the present invention, in which the experimental values ​​include the solar band emissivity (ultraviolet-visible-near infrared spectrophotometer) and the mid-infrared emissivity (Fourier transform infrared spectrometer) and the theoretical value based on the optical transmission matrix method;

[0030] Figure 4 is the theoretical value of the emissivity of the dual-selective all-inorganic radiation cooling film provided in the embodiment of the present invention at different angles at two atmospheric windows;

[0031] Figure 5 A physical picture of an outdoor refrigeration performance test system for a dual-selective all-inorganic radiative refrigeration film provided in an embodiment of the present invention, and an illustration of a physical picture of the radiative refrigeration film and two physical pictures of a control group;

[0032] Figure 6 This is a diagram showing the actual cooling effect of the dual-selective all-inorganic radiation cooling film provided in an embodiment of the present invention outdoors, including the solar power density and the relative humidity of the environment during the test;

[0033] Figure 7 The specific effect of the dual-selective all-inorganic radiation cooling film provided in the embodiment of the present invention on sub-ambient cooling outdoors;

[0034] Figure 8 It is a diagram of the actual passive radiative cooling power of the dual-selective all-inorganic radiative cooling film provided in an embodiment of the present invention outdoors, including the solar power density and the relative humidity of the environment during the test;

[0035] Fig. 9 This is the monthly energy saving of cooling energy in a year when the dual-selective all-inorganic radiation cooling film provided in the embodiment of the present invention is used as the outer material of a building.

[0036] In the figure, 1 is an adhesion layer, 2 is a metal reflective layer, 3 is a multilayer dielectric film layer, and 3-1 to 3-6 are six sublayers of the multilayer dielectric film layer. DETAILED DESCRIPTION

[0037] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0038] In order to better illustrate the present embodiment, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product;

[0039] It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0040] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0041] Example 1

[0042] This embodiment provides a dual-selective all-inorganic radiation cooling film, such as Figure 1 As shown, it includes an adhesion layer 1, a metal reflective layer 2 and a multi-layer dielectric film layer 3, wherein:

[0043] The adhesive layer 1 is arranged on the bottom layer, the metal reflective layer 2 is arranged on the upper surface of the adhesive layer 1, and the multi-layer dielectric film layer 3 is arranged on the upper surface of the metal reflective layer 2;

[0044] The multilayer dielectric film layer 3 comprises a quasi-periodic multilayer thin film structure composed of two materials with a refractive index difference greater than a preset threshold value, arranged in a preset thickness, wherein the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film layer 3 are optimized based on the ideal spectrum selectively emitted by the dual atmospheric transmission windows as the optimization target.

[0045] In a further embodiment, the adhesion layer 1 comprises a film layer made of metal titanium.

[0046] In a further embodiment, the metal reflective layer 2 includes a film layer made of a metal film, and the metal film includes a film made of Ag or Al.

[0047] In this embodiment, a metal film made of silver is used as the metal reflective layer 2 .

[0048] In a further embodiment, the two materials with a refractive index difference greater than a preset threshold, wherein the material with a high refractive index includes AlON, Al2O3, SiN x , TiO2 or HfO2, low refractive index materials include SiO2, MgF2 or AlF3.

[0049] In a further embodiment, the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film layer 3 are optimized based on the ideal spectrum selectively emitted by the dual atmosphere transmission windows as an optimization target, including:

[0050] The simulated annealing genetic algorithm and the transfer matrix method are used as structural optimization tools, the ideal spectrum of the ideal dual-selective radiation cooling film is taken as the optimization target spectrum, the parameter of the thickness of each layer is set to 10-1000 nanometers, and the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film layer 3 are determined.

[0051] In a specific embodiment, layered thin film photonic structures have many advantages in design due to their simple planar geometry, precisely controllable dimensions, flexible combination of different materials, and potential scalable manufacturing. In this study, the number of layers and layer thickness of the photonic radiation cooler were determined and optimized using a simulated annealing genetic algorithm (a method widely used in the field of layered thin film photonic structure optimization). The transmittance, reflectance, and absorptivity of the layered thin film photonic structure were calculated by the transfer matrix method.

[0052] Genetic algorithm is a random search algorithm based on biological evolution mechanisms such as natural selection and genetic mutation. It simulates the process of biological evolution. First, the solution to the problem is encoded to form a chromosome, and then a population is initialized. In each generation, the fitness of each chromosome is evaluated by the fitness function. Then the chromosomes with higher fitness are selected, and genetic operations (such as crossover and mutation) are performed to generate new chromosomes to form a new population. This process is repeated continuously, so that the population gradually evolves and eventually the optimal solution is found. In principle, the genetic algorithm can obtain the global optimal solution to the optimization problem, and it has strong robustness.

[0053] In the embodiment of the present invention, silicon (Si) is set as the substrate layer, silver (Ag) is set as the reflective layer, and silicon dioxide (SiO2) and silicon nitride (Si3N4) are used as materials for the alternating insertion layers. The number of layers, arrangement, and thickness of silicon dioxide (SiO2) and silicon nitride (Si3N4) are optimized with the ideal spectrum of selective emission of the double atmospheric transmission window as the optimization target.

[0054] In a further embodiment, in the simulated annealing genetic algorithm, the fitness function of each generation is defined as:

[0055]

[0056] In the formula, Φ represents the fitness function, μ j represents the weight, ∈0(λ j ) represents the target emissivity / absorbance spectrum, ∈(λ j ) represents the current emissivity / absorbance spectrum.

[0057] During the process of structural optimization, the fitness of each generation gradually decreased. At about the 50th generation, the fitness reached a low level and tended to be stable. The structural parameters at this time were extracted. Considering the feasibility of preparing the sample, the following were obtained: Figure 1 The final structure shown exhibits broadband low absorption in the solar spectrum and selective high emissivity in two atmospheric transparency windows.

[0058] In a further embodiment, the multilayer dielectric film layer 3 includes six sub-layers of different thicknesses.

[0059] In a further embodiment, the multilayer dielectric film layer 3 includes six sub-layers of SiO2 and Si3N4 of different thicknesses which are alternately arranged.

[0060] In a further embodiment, the dual atmospheric transmission windows include a first atmospheric window and a second atmospheric window, the first atmospheric window is 8 microns to 13 microns, and the second atmospheric window is 16 microns to 25 microns.

[0061] The dual-selective all-inorganic radiation cooling film prepared by the embodiment of the present invention has the characteristic of high reflection in the solar spectrum range, and the solar spectrum range is 0.3μm to 2.5μm. The radiation cooling film of the embodiment of the present invention has high selective thermal emissivity in both atmospheric windows, and can be used as a dual-selective heat emitter, and while eliminating atmospheric parasitic heat, it can efficiently dissipate heat to outer space through two atmospheric windows, thereby having a higher cooling potential than existing all-inorganic radiation cooling emitters. Since the designed high-performance all-inorganic dual-selective radiation cooling film has a simple structure, the materials used have excellent stability and are easy to obtain, the high-performance all-inorganic dual-selective radiation cooling film described in the embodiment of the present invention has great application potential, and can be used for heat dissipation and cooling of electronic components, outdoor equipment and buildings.

[0062] According to an embodiment of the present invention, the emissivity of the radiative cooling film at the first atmospheric window is greater than or equal to 70%, the emissivity at the second atmospheric window is greater than or equal to 90%, and the solar reflectivity of the radiative cooling material is greater than or equal to 95%. In addition, the radiative cooling film has a high average solar reflectivity and a high average emissivity over a wide angle range, which is a useful feature for maximizing the radiative cooling power of the film. The calculation of the average reflectivity and the average emissivity is based on the equations Among them, I AM1.5 (λ) is the standard solar spectrum intensity under an atmospheric quality factor of 1.5, is the spectral radiance of a black body at temperature T, where h is Planck's constant, k B is the Boltzmann constant, c is the speed of light in vacuum, and λ is the wavelength.

[0063] According to an embodiment of the present invention, the radiative cooling film has an ultra-high radiative cooling capacity, which can achieve a sub-ambient temperature drop of 12.6°C and a power consumption of about 150W m -2 The maximum radiant cooling power.

[0064] According to the embodiments of the present invention, the radiant cooling film has great application potential in the field of building energy conservation. Based on the optical properties measured in the experiment, the refrigeration energy saving of the radiant cooling film when used as the exterior wall and roof of the building is numerically simulated. Under hot climate conditions, the annual refrigeration energy saving can reach about 129.1MJ / m 2 , which has the potential to greatly reduce fossil energy consumption and greenhouse gas emissions.

[0065] Example 2

[0066] This embodiment provides a method for preparing a dual-selective all-inorganic radiation refrigeration film. Figure 2 As shown, the preparation method is used to prepare the dual-selective all-inorganic radiation refrigeration film described in Example 1, comprising the following steps:

[0067] Using a metal target, a uniform adhesion layer is deposited on the working surface by magnetron sputtering or electron beam evaporation process 1;

[0068] Using a metal target, a uniform metal reflective layer 2 is deposited on the adhesion layer 1 by a magnetron sputtering method or an electron beam evaporation process;

[0069] Using a preset ratio of reaction gas, an inductively coupled plasma chemical vapor deposition process, a pure target DC or RF reactive magnetron sputtering technology, a multilayer dielectric film layer 3 consisting of two materials with a refractive index difference greater than a preset threshold is sequentially grown on the metal reflective layer 2.

[0070] Table 1 shows the material composition, thickness and preparation process of each functional layer of the dual-selective all-inorganic radiation refrigeration film in Example 2.

[0071] Table 1

[0072]

[0073] Combination Figure 1 The cross-sectional diagram of the high-performance dual-selective all-inorganic radiation refrigeration film is shown. The preparation process of the refrigeration film is as follows:

[0074] (1) Prime-grade four-inch silicon wafers were used as substrates. Before coating, the substrates were cleaned with pure water, a mixed solution of hydrogen peroxide and concentrated sulfuric acid (ratio 1:3), and pure water in sequence, and then dried with a nitrogen gun and a hot plate.

[0075] (2) The substrate was attached to a carrier and sent into the transition chamber (Loadlock) of an electron beam evaporator (DE400 DE Technology, Inc.) with a vacuum degree of 3.5×10 -6Pa or lower, the substrate is then sent into the process chamber. Set the evaporation program to evaporate metal titanium (Ti) at a rate of 1A / s. Switch the crucible to the crucible where the Ti target is placed, turn on the high voltage and filament of the equipment, and adjust the electric field so that the metal target is heated evenly. Based on the above method, a Ti adhesion layer (film 1) with a thickness of 15-25 nanometers is prepared.

[0076] (3) After the preparation of film 1 is completed, turn off the filament and the high voltage of the equipment. Adjust the evaporation program to evaporate metal silver (Ag) at a rate of 2A / s. Replace the crucible with a crucible containing an Ag target, turn on the high voltage and filament of the equipment again, and adjust the electric field so that the metal target is evenly heated. Based on the above method, a Ag solar light reflection layer (film 2) with a thickness of 150-250 nm is prepared.

[0077] (4) After the preparation of film 2 is completed, turn off the filament and the high voltage of the equipment, and take out the substrate for retention. After the substrate is cooled, it is placed in an inductively coupled plasma chemical vapor deposition system (ICP-CVD, PlasmaPro System100 ICP180, Oxford Instruments) and pretreated with oxygen-free gas to help ignition. Subsequently, SiH4 and N2 are introduced at the same time, and the ratio is controlled to be 1.333:1.000, the gas pressure is 10mTorr, and the temperature is 300°C, and a Si3N4 film (film 3-1) with a thickness of 850-1000 nanometers and a refractive index of about 1.96@632.8nm is prepared.

[0078] (5) After the deposition of film 3-1 is completed, the substrate is taken out and placed in a drying oven for temporary storage. A cleaning sheet is sent into the ICP-CVD and a mixed gas of CF4 and O2 is introduced to clear the cavity. Then, the substrate is sent back into the ICP-CVD to prepare film 3-2 and film 3-3. The substrate surface is pretreated with a short period of N2O to help with ignition. Subsequently, N2O and SiH4 are introduced simultaneously to prepare a SiO2 film with a thickness of 15-30 nanometers (film 3-2), wherein the gas ratio is 3.25:1.00, the gas pressure is 10mTorr, and the temperature is 300°C. After the deposition of film 3-2 is completed, the process parameters are adjusted, and SiH4 and N2 are introduced simultaneously in a ratio of 1.333:1.000 to prepare a Si3N4 film with a thickness of 800-950 nanometers (film 3-3).

[0079] (6) After the deposition of film 3-3 is completed, the substrate is taken out and temporarily stored in a drying oven. A cleaning sheet is sent into the ICP-CVD and a mixed gas of CF4 and O2 is introduced to clear the cavity. Then, the substrate is sent back into the ICP-CVD to prepare films 3-4, 3-5 and 3-6. First, the substrate surface is pretreated with N2O similar to step (5), and then N2O and SiH4 are introduced at a ratio of 3.25:1.00 to prepare a SiO2 film with a thickness of 70-85 nanometers (film 3-4). Subsequently, after inserting a gas filling process in the middle, SiH4 and N2 are introduced at a ratio of 1.333:1.000 to prepare a Si3N4 film with a thickness of 80-95 nanometers (film 3-5). Finally, N2O and SiH4 are introduced again at a ratio of 3.25:1.00 to prepare a SiO2 film with a thickness of 15-25 nanometers (film 3-6).

[0080] Example 3

[0081] In this example, the dual-selective all-inorganic radiation refrigeration film prepared in Example 2 is experimentally tested.

[0082] The solar reflectivity and infrared emissivity of the dual-selective all-inorganic radiative cooling film prepared in the embodiment were tested as follows: A UV-visible-near infrared spectrophotometer (Lambda 950, PerkinElmer) was used to characterize the reflectivity of the DS-PDRC in the visible and near infrared ranges using a non-polarized light source and a calibrated high specular reflectivity standard. In the infrared region, a Fourier transform infrared spectrometer (Vertex 70, Bruker) with a non-polarized light source was used to characterize the reflectivity of the cooler using a gold (Au) film as a reflectivity standard. The test results are shown in Figure 2. Figure 3 The results show that the emissivity of the radiation cooling film in the first atmospheric window is greater than or equal to 70%, the emissivity in the second atmospheric window is greater than or equal to 90%, and the solar reflectivity of the radiation cooling material is greater than or equal to 95%.

[0083] The dual-selective all-inorganic radiation cooling film prepared in the embodiment was tested for outdoor cooling performance. The test contents included ambient temperature, ambient humidity, temperature of the dual-selective all-inorganic radiation cooling film, and solar radiation intensity. The test results are shown in Figure 5 , Figure 6 , Figure 7 and Figure 8 The specific test method is as follows:

[0084] (1) Sub-ambient cooling effect test of dual-selective all-inorganic radiation cooling film:

[0085] A test system was built on the rooftop of a building at Sun Yat-sen University (Guangzhou, Guangdong, 113.3°E, 23.1°N). Figure 5 ). A cavity was made of Ethylene Vinyl Acetate Copolymer (EVA) foam for thermal insulation. On the outside of the foam, an aluminum reflective film was wrapped to reflect sunlight. The aluminum reflective film left a window with a diameter of 8 cm at the sample. In order to avoid air convection and test uncertainty caused by disordered natural wind, the sample cavity was covered with a layer of low-density polyethylene (LDPE) film. This design creates a well-sealed air pocket around the sample. The surface in contact with the air pocket absorbs the least sunlight, minimizing the heat load on the sample and facilitating the measurement of radiative cooling performance. A thermocouple was placed on the back surface of the radiative cooler, installed in the center of the dual-selective all-inorganic radiative cooling film, and connected to a multi-channel temperature patrol meter (DC5516U, DCUU). Near the radiative cooler, a foam cavity without any sample and a reference sample of carbon black coating were also placed, also installed on the same test platform. The entire device was placed on a platform 1.2m above the roof ground to reduce the impact of building thermal radiation. During the experiment, ambient temperature, ambient humidity (JB913F001, Anymetre), and solar power density (TES-132, TES) were collected synchronously. The experiment was carried out outdoors under direct sunlight on October 4, 2024. The experiment lasted from 9 am to 4 pm, a continuous test of up to seven hours. The experimental results are as follows Figure 6 and Figure 7 As shown, the cooling effect of the dual-selective all-inorganic radiation cooling film prepared in the example is up to about 12.6°C.

[0086] (2) Radiative cooling power test of dual-selective all-inorganic radiative cooling film:

[0087] In order to test the cooling power of the dual-selective all-inorganic radiation cooling film, an intelligent heating system was independently built. A polyimide (PI) electric heating film (50mm in diameter and 250μm in thickness) was selected as the heating device and powered by a programmable DC power supply (eTM-305DP, eTOMMENS). During the experiment, the heating film was adhered to a high-purity copper sheet (1mm in thickness) to evenly heat the sample. A layer of high thermal conductivity silicone grease was applied between the sample and the copper sheet to ensure good thermal contact between the radiation cooling film and the copper sheet. On October 7, 2024, a self-designed intelligent temperature heating system was used to keep the radiation cooling film consistent with the ambient temperature at all times, and then the electric heating power was collected at each moment. According to the principle of energy compensation, at each moment, the cooling power is equal to the heating power. During the experiment, the temperature control effect was good. In an open outdoor environment, the temperature difference between the two curves was maintained at ±2°C. The experimental results are as follows Figure 8 As shown, the radiation intensity exceeds 900W m -2 At noon, the maximum radiative cooling power of the dual-selective all-inorganic radiative cooling film prepared in the embodiment is about 150W m -2 .

[0088] (3) Numerical simulation of energy saving when dual-selective all-inorganic radiative cooling film is used as the outer layer material of buildings:

[0089] Based on the experimental data of the dual-selective all-inorganic radiant cooling film, the potential energy-saving capacity of the material was calculated as a building outer layer material. First, a standard office building model of 8m×4m×3m was established, and the actual weather in Guangzhou was used as the weather input file. Based on EnergyPlus-24.1.0, the monthly cooling energy consumption when the dual-selective all-inorganic radiant cooling film was used / not used as the building outer layer material in a year was obtained ( Fig. 9 Among them, the building cooling energy saving in Guangzhou was the highest in July, about 20.4MJ / m 2 Similarly, the energy saving value of cooling in each provincial capital city was used as a representative of the whole province to calculate the energy saving of cooling when using dual-selective all-inorganic radiation cooling film as the outer material of buildings across the country. It can be found that Hainan Province, the southernmost province, has the highest energy saving, about 129.1MJ / m 2 Every year. Through numerical simulation, the great application potential of dual-selective all-inorganic radiation cooling film in the field of building energy conservation is further revealed, which can reduce the consumption of fossil energy and greenhouse gas emissions to a certain extent.

[0090] The same or similar reference numerals correspond to the same or similar components;

[0091] The terms used in the drawings to describe positional relationships are only used for illustrative purposes and should not be construed as limiting this patent;

[0092] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A dual-selective all-inorganic radiation cooling film, characterized in that: It comprises an adhesive layer (1), a metal reflective layer (2) and a multi-layer dielectric film layer (3), wherein: The adhesive layer (1) is arranged on the bottom layer, the metal reflective layer (2) is arranged on the upper surface of the adhesive layer (1), and the multilayer dielectric film layer (3) is arranged on the upper surface of the metal reflective layer (2); The multilayer dielectric film layer (3) comprises a quasi-periodic multilayer thin film structure composed of two materials with a refractive index difference greater than a preset threshold value, with a preset thickness and a preset arrangement, wherein the number of layers, the preset arrangement and the preset thickness of the multilayer dielectric film layer (3) are optimized based on an ideal spectrum selectively emitted by a double atmospheric transmission window as an optimization target.

2. The dual-selective all-inorganic radiation cooling film according to claim 1, characterized in that: The adhesion layer (1) comprises a film layer made of metal titanium.

3. The dual-selective all-inorganic radiation cooling film according to claim 1, characterized in that: The metal reflective layer (2) comprises a film layer made of a metal film, wherein the metal film comprises a film made of Ag or Al.

4. The dual-selective all-inorganic radiation cooling film according to claim 1, characterized in that: The two materials with a refractive index difference greater than a preset threshold, wherein the high refractive index material includes AlON, Al2O3, SiN x , TiO2 or HfO2, low refractive index materials include SiO2, MgF2 or AlF3.

5. The dual-selective all-inorganic radiation cooling film according to claim 1, characterized in that: The number of layers, the preset arrangement mode and the preset thickness of the multilayer dielectric film layer (3) are optimized based on the ideal spectrum of the selective emission of the double atmospheric transmission window as the optimization target, and include: A simulated annealing genetic algorithm and a transfer matrix method are used as structural optimization tools, the ideal spectrum of an ideal dual-selective radiation cooling film is used as the optimization target spectrum, the thickness parameter of each layer is set to 10-1000 nanometers, and the number of layers, the preset arrangement mode and the preset thickness of the multilayer dielectric film layer (3) are determined.

6. The dual-selective all-inorganic radiation cooling film according to claim 5, characterized in that: In the simulated annealing genetic algorithm, the fitness function of each generation is defined as: In the formula, Φ represents the fitness function, μ j represents the weight, ∈0(λ j ) represents the target emissivity / absorbance spectrum, ∈(λ j ) represents the current emissivity / absorbance spectrum.

7. The dual-selective all-inorganic radiation cooling film according to claim 6, characterized in that: The multilayer dielectric film layer (3) comprises six sub-layers of different thicknesses.

8. The dual-selective all-inorganic radiation cooling film according to claim 7, characterized in that: The multilayer dielectric film layer (3) comprises six sub-layers of SiO2 and Si3N4 of different thicknesses which are alternately arranged.

9. The dual-selective all-inorganic radiation cooling film according to claim 1, characterized in that: The dual atmospheric transmission window includes a first atmospheric window and a second atmospheric window, wherein the first atmospheric window is 8 microns to 13 microns, and the second atmospheric window is 16 microns to 25 microns.

10. A method for preparing a dual-selective all-inorganic radiation refrigeration film, characterized in that: The preparation method is used to prepare the dual-selective all-inorganic radiation refrigeration film according to any one of claims 1 to 9, comprising the following steps: Using a metal target, a uniform adhesion layer (1) is deposited on the working surface by a magnetron sputtering method or an electron beam evaporation process; Using a metal target, a magnetron sputtering method or an electron beam evaporation process is used to deposit a uniform metal reflective layer (2) on the adhesion layer (1); Using a preset ratio of reaction gas, an inductively coupled plasma chemical vapor deposition process, a pure target DC or radio frequency reactive magnetron sputtering technology, a multilayer dielectric film layer (3) composed of two materials with a refractive index difference greater than a preset threshold is sequentially grown on the metal reflective layer (2).

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