Radiation refrigeration material preparation method, radiation refrigeration material and radiation refrigeration method

Abstract

The invention relates to the technical field of radiation refrigeration, and particularly provides a radiation refrigeration material preparation method, a radiation refrigeration material and a radiation refrigeration method. The preparation method of the radiation refrigeration material comprises the following steps: putting a material to be foamed into a supercritical foaming device; after the internal temperature of the supercritical foaming device reaches the set temperature, foaming gas is introduced into the supercritical foaming device; the foaming gas comprises supercritical carbon dioxide or supercritical nitrogen; and the internal gas pressure of the supercritical foaming device is adjusted to the set pressure, and after the reaction time is maintained, the radiation refrigeration material is prepared through pressure relief. According to the method, the radiation refrigeration material is prepared through the expansion behavior of carbon dioxide or nitrogen permeating into the to-be-foamed material in the supercritical state in the pressure relief foaming process, pollutants or toxic and harmful substances cannot be generated in the preparation process, the ecological environment can be prevented from being damaged in the preparation process of the radiation refrigeration material, and the service life of the radiation refrigeration material is prolonged. The wide application of the radiation refrigeration material is facilitated.

Description

Technical Field

[0001] This application relates to the field of radiation cooling technology, and more specifically, to methods for preparing radiation cooling materials, radiation cooling materials, and radiation cooling methods. Background Technology

[0002] Radiative cooling is a technology that uses thermal radiation to dissipate heat from the Earth's surface into the cold outer space. Materials possessing this function are called radiative cooling materials. Radiative cooling materials exhibit unique spectral selectivity, specifically including high reflectivity in the solar radiation band and high emissivity through the mid-infrared atmospheric window. Therefore, based on the ability of radiative cooling materials to modulate the optical properties of an object's surface, making it reflect solar heat and continuously radiate heat into the upper atmosphere through atmospheric windows, the surface temperature of the object can be significantly reduced, thus decreasing the energy consumption of cooling equipment such as air conditioners.

[0003] However, current radiative cooling materials use a large amount of toxic and harmful chemical reagents in their preparation, which can damage the ecological environment during the production process and hinder the widespread application of radiative cooling materials. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a method for preparing a radiation cooling material, a radiation cooling material, and a radiation cooling method to solve the above-mentioned technical problems.

[0005] In a first aspect, embodiments of this application provide a method for preparing a radiation-cooling material, the method comprising: Place the material to be foamed into the supercritical foaming device; After the internal temperature of the supercritical foaming device reaches the set temperature, foaming gas is introduced into the supercritical foaming device; wherein, the foaming gas includes supercritical carbon dioxide or supercritical nitrogen. The internal gas pressure of the supercritical foaming device is adjusted to a set pressure, and after maintaining the reaction time, the radiative cooling material is prepared by depressurization.

[0006] In the above-described process, the method for preparing the radiation-cooling material involves placing the material to be foamed into a supercritical foaming device; after the internal temperature of the supercritical foaming device reaches a set temperature, a foaming gas is introduced into the device; wherein the foaming gas includes supercritical carbon dioxide or supercritical nitrogen; the internal gas pressure of the supercritical foaming device is adjusted to a set pressure, and after maintaining the reaction time, the radiation-cooling material is prepared by depressurization. This method utilizes only the expansion behavior of carbon dioxide or nitrogen gas that permeates into the material under supercritical conditions during the depressurization foaming process to create the internal porous structure of the material. The preparation process does not generate pollutants or toxic substances, thus avoiding the environmental damage caused by the preparation of radiation-cooling materials and facilitating their widespread application.

[0007] Optionally, in this embodiment of the application, the material to be foamed includes a biodegradable material.

[0008] In the above-mentioned process, since the material to be foamed includes biodegradable materials, the radiative cooling material prepared by this method through foaming is also biodegradable, which can further reduce the damage to the ecological environment caused by radiative cooling materials.

[0009] Optionally, in the embodiments of this application, the material to be foamed specifically includes polycaprolactone material; the set temperature of the supercritical foaming device is 31.1℃~55℃, the set pressure is greater than or equal to 7.38MPa, and the reaction time is greater than or equal to 1.5 hours.

[0010] In the above-mentioned process, by adjusting the set temperature of the supercritical foaming device to 31.1℃~55℃, the set pressure to be greater than or equal to 7.38MPa, and the reaction time to be greater than or equal to 1.5 hours, a more uniform and dense cell structure can be prepared to obtain a radiative cooling material with better radiative cooling effect.

[0011] Optionally, in this embodiment of the application, before placing the material to be foamed into the supercritical foaming device, the method further includes: placing the material to be foamed into a heat processor; raising the internal temperature of the heat processor to the heat elimination temperature and maintaining it for a period of time to eliminate the thermal history of the material to be foamed; wherein the heat elimination temperature is higher than the melting temperature of the material to be foamed and lower than the decomposition temperature of the material to be foamed.

[0012] In the above implementation process, by placing the material to be foamed into a heat processor, raising the internal temperature of the heat processor to the heat elimination temperature and maintaining it for a period of time, the thermal history of the material to be foamed is eliminated; this can reduce the differences in material properties caused by different processing or storage conditions, and make the performance of the radiation cooling material prepared based on the material to be foamed after eliminating the thermal history more stable.

[0013] Secondly, embodiments of this application provide a radiation cooling material, which is prepared based on any of the methods described in the first aspect above.

[0014] In the above-described process, the method for preparing radiative cooling materials utilizes only the expansion behavior of carbon dioxide or nitrogen gas, which permeates into the material under supercritical conditions, during the depressurization foaming process to create the internal porous structure of the material. This process does not generate pollutants or toxic substances, thus avoiding the environmental damage caused by the preparation of radiative cooling materials. Therefore, radiative cooling materials prepared using any of the methods described in the first aspect above are more environmentally friendly and conducive to their widespread application.

[0015] Optionally, in an embodiment of this application, the radiative cooling material includes a plurality of internal pores; wherein the pore size of the internal pores includes 5μm to 15μm; and the pore walls of the internal pores are distributed with holes of a preset pore size.

[0016] In the above implementation process, since the pores with preset diameters are distributed on the walls of the internal foam, the reflectivity of the radiative cooling material to the solar light band can be improved, resulting in a better radiative cooling effect.

[0017] Optionally, in the embodiments of this application, the preset aperture includes 0.1μm to 3μm.

[0018] In the above implementation process, by limiting the preset aperture to 0.1μm~3μm, the reflectivity of the radiation cooling material to the solar light band is further improved.

[0019] Thirdly, embodiments of this application provide a radiative cooling method, the method comprising: The radiative cooling material is made into material particles of a predetermined particle size; wherein the radiative cooling material is prepared based on any of the methods described in the first aspect above; The material particles are placed in the area to be cooled.

[0020] In the above-described process, by forming the radiative cooling material into particles of a predetermined size and placing these particles in the area to be cooled, the surface temperature of the area can be reduced without relying on cooling equipment such as air conditioners, thus reducing energy consumption. Furthermore, since the radiative cooling material is prepared based on any of the methods described in the first aspect above—that is, by using carbon dioxide or nitrogen gas that permeates into the material under supercritical conditions and expands during the depressurization foaming process to create the internal porous structure of the material—no pollutants or toxic or harmful substances are generated during the preparation process. Therefore, the radiative cooling method provided in this application can also reduce energy consumption while minimizing the environmental damage caused by the preparation process of the radiative cooling material.

[0021] Optionally, in this embodiment of the application, the step of forming the radiative cooling material into material particles of a preset particle size includes: cooling the radiative cooling material; wherein the temperature of the cooling treatment is lower than the glass transition temperature of the radiative cooling material; and crushing the cooled radiative cooling material to obtain material particles of the preset particle size.

[0022] In the above implementation process, by cooling the radiative cooling material before it is formed into particles of a predetermined size, the internal structure of the radiative cooling material can be prevented from being damaged due to temperature rise during the crushing process. By setting the cooling temperature below the glass transition temperature of the radiative cooling material, the radiative cooling material can maintain a rigid solid glassy state during the crushing process, ensuring that the internal structure of the radiative cooling material is not damaged during the crushing process, thereby guaranteeing the radiative cooling effect of the material particles of the predetermined size obtained through the crushing process.

[0023] Optionally, in this embodiment of the application, the preset particle size is greater than 300 μm.

[0024] In the above implementation process, by limiting the preset particle size to be greater than 300μm, the internal structural integrity of the material particles can be improved, thereby obtaining a better radiative cooling effect.

[0025] The beneficial effects of this application include at least the following: the method for preparing the radiative cooling material involves placing the material to be foamed into a supercritical foaming device; after the internal temperature of the supercritical foaming device reaches a set temperature, introducing a foaming gas into the supercritical foaming device; wherein the foaming gas includes supercritical carbon dioxide or supercritical nitrogen; adjusting the internal gas pressure of the supercritical foaming device to a set pressure; maintaining the reaction time; and then releasing the pressure to prepare the radiative cooling material. This method for preparing the radiative cooling material utilizes only the expansion behavior of carbon dioxide or nitrogen gas that permeates into the material to be foamed in a supercritical state during the pressure-release foaming process to achieve the preparation of the internal porous structure of the material. No pollutants or toxic or harmful substances are generated during the preparation process, thus avoiding the damage to the ecological environment caused by the preparation of radiative cooling materials and facilitating the widespread application of radiative cooling materials. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic flowchart illustrating a method for preparing a radiation-cooling material according to an embodiment of this application; Figure 2 This is a spectral schematic diagram of a radiation cooling material provided in an embodiment of this application; Figure 3 A schematic flowchart illustrating another method for preparing a radiation-cooling material provided in this application embodiment; Figure 4 This is a schematic diagram of the structure of a radiation cooling material provided in an embodiment of this application; Figure 5 An electron microscope image of a radiation-cooling material provided in an embodiment of this application; Figure 6 This is a schematic flowchart of a radiation cooling method provided in an embodiment of this application. Detailed Implementation

[0028] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0030] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0031] See Figure 1 The illustrated diagram shows a process flow diagram of a method for preparing a radiation-cooling material according to an embodiment of this application. This method for preparing a radiation-cooling material may include the following steps: S101. Place the material to be foamed into the supercritical foaming device; S102. After the internal temperature of the supercritical foaming device reaches the set temperature, foaming gas is introduced into the supercritical foaming device; wherein, the foaming gas includes supercritical carbon dioxide or supercritical nitrogen. S103. Adjust the internal gas pressure of the supercritical foaming device to the set pressure, and after maintaining the reaction time, prepare the radiation cooling material by depressurization.

[0032] In step S101, the material to be foamed can be a foamable material such as polycaprolactone, ethylene-vinyl acetate copolymer, thermoplastic polyurethane, thermoplastic polyester elastomer, or polylactic acid. A supercritical foaming device refers to a device capable of foaming materials using gas under supercritical conditions.

[0033] In step S102, the set temperature can be adjusted according to the actual material to be foamed. For example, when the material to be foamed is polycaprolactone, the set temperature can be 35°C, 40°C, 50°C, or other reasonable temperature values. The foaming gas can be supercritical carbon dioxide or supercritical nitrogen; this application does not specifically limit it.

[0034] In step S103, the set pressure can be adjusted according to the actual material to be foamed. For example, when the material to be foamed is polycaprolactone, the set pressure can be 10 MPa, or 12 MPa, 20 MPa, 30 MPa, or other reasonable pressure values. The reaction time can be 1 hour, 1.5 hours, 2 hours, or other time values, and the specific reaction time can be adjusted according to the actual application conditions such as the material to be foamed and the required foaming state. After maintaining the reaction time, the pressure relief valve of the supercritical foaming device can be quickly opened, and after depressurization to atmospheric pressure, the prepared radiative cooling material can be taken out.

[0035] Please refer to Figure 2 , Figure 2 This is a spectral schematic diagram of a radiation cooling material provided in an embodiment of this application. Figure 2 Specifically, the diagram shows the spectrum of a radiation-cooling material prepared under the following conditions: the material to be foamed is polycaprolactone, the set temperature is 35°C, the set pressure is 15 MPa, and the foaming gas is supercritical carbon dioxide. Figure 2 The purple curve on the left represents the variation of the reflectivity of the radiative cooling material to sunlight with the wavelength of sunlight (0.3 μm to 2.5 μm); Figure 2 The yellow shaded area on the left represents the spectral distribution of solar energy received on the ground. Figure 2 The blue curve on the right represents the emissivity of the radiation-cooling material as a function of wavelength (3.8 μm to 16 μm); Figure 2 The blue shaded area on the right represents the atmospheric transmittance when the air mass is 1.5. Figure 2 The red curve on the right represents blackbody radiation at a temperature of 300K. Therefore, at room temperature, the peak blackbody radiation of an object falls within the atmospheric window of 8μm-13μm.

[0036] The following is a method for calculating solar reflectance according to embodiments of this application:

[0037] in, It's the wavelength. It is the ASTM G173 global solar intensity spectrum. It is the diffuse reflectance of the radiation-cooled material.

[0038] Based on the above calculation formula and... Figure 2It can be seen that the radiation-cooling material prepared by the method provided in this application has a maximum reflectivity of over 98% for sunlight. That is, it can be understood that for an incident light energy of 1000 W / m², it can reflect 980 W / m² of sunlight energy. Simultaneously, its emissivity within the atmospheric window of 8 μm-13 μm is higher than 92%. Therefore, the radiation-cooling material prepared by the method provided in this application exhibits high reflectivity in the solar band and high emissivity in the mid-infrared atmospheric window, resulting in a superior radiation-cooling effect. Furthermore, the internal pore structure of the material can be prepared solely through the expansion behavior of carbon dioxide or nitrogen gas that permeates into the material under supercritical conditions during the depressurization foaming process, thus obtaining a radiation-cooling material with a good radiation-cooling effect. No pollutants or toxic substances are generated during the preparation process, avoiding the damage to the ecological environment caused by the preparation of radiation-cooling materials and facilitating their widespread application.

[0039] Therefore, the method for preparing radiative cooling materials provided in this application involves placing the material to be foamed into a supercritical foaming device; after the internal temperature of the supercritical foaming device reaches a set temperature, introducing a foaming gas into the supercritical foaming device; wherein the foaming gas includes supercritical carbon dioxide or supercritical nitrogen; adjusting the internal gas pressure of the supercritical foaming device to a set pressure; maintaining the reaction time; and then releasing the pressure to prepare the radiative cooling material. This method for preparing radiative cooling materials utilizes only the expansion behavior of carbon dioxide or nitrogen gas that permeates into the material to be foamed in a supercritical state during the pressure-release foaming process to achieve the preparation of the internal porous structure of the material. No pollutants or toxic or harmful substances are generated during the preparation process, thus avoiding the damage to the ecological environment caused by the preparation of radiative cooling materials and facilitating the widespread application of radiative cooling materials.

[0040] In some alternative embodiments, the material to be foamed includes a biodegradable material.

[0041] The material to be foamed can be a biodegradable material, specifically polycaprolactone or polylactic acid. Since the material to be foamed includes biodegradable materials, the radiative cooling material prepared by this method through foaming is also biodegradable, further reducing the damage to the ecological environment caused by radiative cooling materials.

[0042] In some optional embodiments, the material to be foamed specifically includes polycaprolactone; the set temperature of the supercritical foaming device is 31.1℃~55℃, the set pressure is greater than or equal to 7.38MPa, and the reaction time is greater than or equal to 1.5 hours.

[0043] The set temperature can be 31.1℃, 31.7℃, 45℃, or 55℃, etc. The set pressure can be 7.38 MPa, 16 MPa, 35 MPa, or 50 MPa, etc. The reaction time can be 1.5 hours, 2 hours, 2.5 hours, or 3 hours, etc. This application does not specifically limit any of these. By adjusting the set temperature of the supercritical foaming device to 31.1℃~55℃, the set pressure to be greater than or equal to 7.38 MPa, and the reaction time to be greater than or equal to 1.5 hours, this application can prepare a more uniform and dense cell structure, thereby obtaining a radiative cooling material with better radiative cooling effect.

[0044] In the above implementation process, 31.1℃ and 7.38MPa are the critical values ​​for the supercritical state of carbon dioxide. Therefore, the temperature and pressure must be greater than these values. According to the experience of polycaprolactone foaming in the material to be foamed, the lower the temperature, the smaller the foam cell size and the higher the reflectivity; the higher the pressure, the smaller the foam cell size and the higher the reflectivity; a penetration time of less than 1.5 hours will result in incomplete foaming, that is, the cell size inside the material and the surface are inconsistent.

[0045] Furthermore, at lower pressures, such as 10 MPa, temperature changes have a significant impact on the cell size of the material. However, at higher pressures, such as 20 MPa, the reflectivity of samples at 35°C and 55°C changes less. This is because higher pressures increase the solubility of the material in supercritical carbon dioxide, leading to an increase in bubble nuclei. Although higher temperature settings reduce the number of bubble nuclei and the viscosity of the material to some extent, the number of bubble nuclei under high pressure is similar, so the impact is minimal.

[0046] It is known that blindly pursuing high pressure will actually increase costs: for example, requiring more robust reactors, more powerful pressurization equipment, more carbon dioxide, and longer pressurization times. Meanwhile, the polycaprolactone radiation cooling material prepared at 35℃ and 20MPa has achieved a reflectivity of 98.18% (92.31% at 10MPa and 96.36% at 15MPa), which is already among the highest values ​​for radiation cooling materials currently available.

[0047] While lower temperatures are more advantageous for preparing radiation cooling materials with small pores, the critical temperature of 31.1℃ cannot guarantee that a supercritical state can be reached, considering the possible temperature measurement errors of the experimental instruments. Furthermore, considering the parameter interval of 5℃, 35℃ can be chosen as the lower limit.

[0048] Please refer to Figure 3 , Figure 3 This is a schematic flowchart illustrating another method for preparing a radiation-cooling material provided in an embodiment of this application. Figure 3As shown, in some optional embodiments, before placing the material to be foamed into the supercritical foaming device, the method further includes: S104, placing the material to be foamed into a heat processor; S105, raising the internal temperature of the heat processor to the heat elimination temperature and maintaining it for a period of time to eliminate the thermal history of the material to be foamed; wherein the heat elimination temperature is higher than the melting temperature of the material to be foamed and lower than the decomposition temperature of the material to be foamed.

[0049] The heat elimination temperature can be adjusted according to the selected foaming material. Specific adjustments can be based on the melting and decomposition temperatures of the material. For example, using polycaprolactone as the foaming material, the heat elimination temperature can be 70℃, 80℃, 100℃, or other suitable values. By placing the foaming material inside a heat processor and raising its internal temperature to the heat elimination temperature and maintaining it for a period of time, the thermal history of the material is eliminated. This reduces material performance differences caused by variations in processing or storage conditions, resulting in more stable performance of the radiative cooling material prepared from the foaming material after heat history elimination.

[0050] Specifically, different foaming materials require different temperatures. For example, the melting temperature of polycaprolactone is about 60°C, and the heat treatment temperature is generally 80 to 100°C; while for polylactic acid, the melting temperature reaches 176°C, and the heat treatment generally requires more than 200°C.

[0051] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the structure of a radiative cooling material provided in an embodiment of this application. This application provides a radiative cooling material prepared based on the radiative cooling material preparation method described in any of the first aspects above.

[0052] in, Figure 4 The material in the substrate refers to the material to be foamed. Since the above-mentioned method for preparing radiative cooling materials utilizes only supercritical carbon dioxide or nitrogen gas to permeate into the material to be foamed, and achieves the internal porous structure of the material through expansion during the depressurization foaming process, no pollutants or toxic substances are generated during the preparation process, thus avoiding the environmental damage caused by the preparation of radiative cooling materials. Therefore, radiative cooling materials prepared based on any of the methods described in the first aspect above are more environmentally friendly and conducive to the widespread application of radiative cooling materials.

[0053] In some optional embodiments, the radiative cooling material includes a plurality of internal pores; wherein the pore size of the internal pores includes 5μm to 15μm; and the pore walls of the internal pores are distributed with holes of a predetermined pore size.

[0054] The pore size of the internal bubbles can be 5μm, 10μm, 15μm, or other suitable sizes. The pore sizes of multiple internal bubbles do not need to be exactly the same. Because the walls of the internal bubbles have pores of a predetermined diameter, the reflectivity of the radiative cooling material to the solar spectrum can be further improved, resulting in better radiative cooling performance.

[0055] Please refer to Figure 5 , Figure 5 An electron microscope image of a radiation cooling material provided in an embodiment of this application. Figure 5 The image above shows a local structural image of a radiation-cooling material taken using a scanning electron microscope. Figure 5 The image below shows an image of the internal pores in a radiation-cooled material, taken using a scanning electron microscope. Figure 5 It can be seen that the radiative cooling material includes multiple internal pores, and the walls of the internal pores have pores of a predetermined diameter. It should be noted that the internal pores or pores are not necessarily regular circles or spheres, and the pore size can be the equivalent pore size of the internal pores, while the predetermined pore size can be the equivalent pore size of the pores.

[0056] In some optional embodiments, the preset aperture includes 0.1 μm to 3 μm.

[0057] The preset pore size can be 0.1 μm, 0.3 μm, 1 μm, 3 μm, or other reasonable pore sizes. One or more pores with preset pore sizes can be distributed on the wall of any internal bubble. When multiple pores with preset pore sizes are distributed on the wall of an internal bubble, the pore sizes of these pores do not need to be completely identical. By limiting the preset pore size to 0.1 μm to 3 μm, the reflectivity of the radiative cooling material to the solar wavelength range can be further improved.

[0058] Please refer to Figure 6 , Figure 6 This is a schematic flowchart illustrating a radiative cooling method provided in an embodiment of this application. Figure 6 As shown, the radiative cooling method includes: S201. The radiative cooling material is formed into material particles of a predetermined particle size; wherein the radiative cooling material is prepared based on any of the radiative cooling material preparation methods described in the first aspect above; S202. Place the material particles in the area to be cooled.

[0059] The preset particle size can be adjusted according to actual application needs (e.g., the type of area to be cooled). The area to be cooled can be an agricultural production area or a desert area, etc., and this application does not specifically limit this. By making the radiation cooling material into particles of the preset particle size and placing the particles in the area to be cooled, the surface temperature of the area to be cooled can be reduced without relying on cooling equipment such as air conditioning, thus reducing energy consumption. Furthermore, since the radiation cooling material is prepared based on any of the methods described in the first aspect above; that is, the internal porous structure of the material is achieved solely through the expansion behavior of carbon dioxide or nitrogen gas that permeates into the interior of the material under supercritical conditions during the depressurization foaming process; no pollutants or toxic or harmful substances are generated during the preparation process. Therefore, the radiation cooling method provided by this application can reduce energy consumption while avoiding damage to the ecological environment caused by the radiation cooling material during its preparation process. For example, in agricultural production or desert ecological management, by making the radiation cooling material into particles of the preset particle size and scattering them in the corresponding area, the surface temperature can be reduced, thereby reducing water evaporation, increasing soil moisture, and promoting plant growth and sand fixation. Moreover, the material particles can naturally degrade in the environment, achieving eco-friendly agriculture or desertification control.

[0060] The distribution of xenon lamp power at different wavelengths is quite similar to that of solar radiation. Xenon lamps are used to simulate solar radiation, specifically employing a power output of 1000 W / m². 2 The power was applied to bare soil samples and soil samples treated with the radiation cooling method (i.e., soil samples prepared by placing particles of a predetermined particle size from the radiation cooling material prepared using the above-mentioned radiation cooling material preparation method on the surface of bare soil) for 3 hours each. The humidity of the bare soil sample decreased by 7.38%, while the humidity of the soil sample decreased by only 0.665%. Furthermore, this embodiment of the application also conducted a 24-hour humidity test by placing the bare soil sample, the soil sample, and the sample covered with PE mulch film outdoors. The results showed that the humidity of the bare soil sample decreased by 17.48%, the humidity of the sample covered with PE mulch film decreased by 11.94%, while the humidity of the soil sample decreased by only 3.71%. This indicates that the radiation cooling method provided in this application can reduce surface temperature, thereby reducing water evaporation, increasing soil humidity, promoting plant growth and sand fixation, and thus achieving eco-friendly agriculture or desertification control.

[0061] In some optional embodiments, step S201, forming the radiative cooling material into material particles of a preset particle size, includes: cooling the radiative cooling material; wherein the temperature of the cooling treatment is lower than the glass transition temperature of the radiative cooling material; and crushing the cooled radiative cooling material to obtain material particles of the preset particle size.

[0062] The cooling temperature can be adjusted based on the material to be foamed used in the actual preparation of the radiative cooling material. By cooling the radiative cooling material before it is formed into particles of a predetermined size, the internal structure of the radiative cooling material can be prevented from being damaged due to temperature rise during the crushing process. By setting the cooling temperature below the glass transition temperature of the radiative cooling material, the radiative cooling material can maintain a rigid, glassy state during the crushing process, ensuring that the internal structure of the radiative cooling material is not damaged during crushing, thereby guaranteeing the radiative cooling effect of the material particles of the predetermined size obtained through crushing.

[0063] In some optional embodiments, the preset particle size is greater than 300 μm.

[0064] The preset particle size can be 300 μm, or it can be 350 μm, 400 μm, 600 μm, or other reasonable particle sizes. By limiting the preset particle size to greater than 300 μm, the internal structural integrity of the material particles can be improved, thereby obtaining a better radiative cooling effect.

[0065] It should be understood that the disclosed materials and methods can also be implemented in other ways, as provided in the embodiments of this application. The method embodiments described above are merely illustrative. For example, the flowcharts in the accompanying drawings show the architecture, functions, and operations of possible implementations of methods according to various embodiments of this application. In this regard, each block in the flowchart can represent a module, segment, or part of code, which contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, or they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the flowchart, and combinations of blocks in the flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0066] In addition, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0067] The above description is only an optional implementation of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be covered within the protection scope of the embodiments of this application.

Claims

1. A method for preparing a radiation-cooling material, characterized in that, The method includes: Place the material to be foamed into the supercritical foaming device; After the internal temperature of the supercritical foaming device reaches the set temperature, foaming gas is introduced into the supercritical foaming device; wherein, the foaming gas includes supercritical carbon dioxide or supercritical nitrogen. The internal gas pressure of the supercritical foaming device is adjusted to a set pressure, and after maintaining the reaction time, the radiative cooling material is prepared by depressurization.

2. The method according to claim 1, characterized in that, The material to be foamed includes biodegradable materials.

3. The method according to claim 1, characterized in that, in, The material to be foamed specifically includes polycaprolactone material; The set temperature of the supercritical foaming device is 31.1℃~55℃, the set pressure is greater than or equal to 7.38MPa, and the reaction time is greater than or equal to 1.5 hours.

4. The method according to claim 1, characterized in that, Before placing the material to be foamed into the supercritical foaming device, the method further includes: Place the material to be foamed into the heat processor; The internal temperature of the heat processor is raised to the heat elimination temperature and maintained for a period of time to eliminate the thermal history of the material to be foamed; wherein the heat elimination temperature is higher than the melting temperature of the material to be foamed and lower than the decomposition temperature of the material to be foamed.

5. A radiative cooling material, characterized in that, The radiation cooling material is prepared based on the method according to any one of claims 1-4.

6. The material according to claim 5, characterized in that, The radiative cooling material includes multiple internal pores; wherein the pore size of the internal pores ranges from 5μm to 15μm; The walls of the internal pores are provided with holes of a predetermined diameter.

7. The material according to claim 6, characterized in that, The preset aperture ranges from 0.1μm to 3μm.

8. A radiative cooling method, characterized in that, The method includes: The radiative cooling material is made into material particles of a predetermined particle size; wherein the radiative cooling material is prepared based on the method according to any one of claims 1-4 above; The material particles are deployed in the area to be cooled.

9. The method according to claim 8, characterized in that, The process of forming radiative cooling material into material particles of a predetermined particle size includes: The radiative cooling material is subjected to a cooling treatment; wherein the temperature of the cooling treatment is lower than the glass transition temperature of the radiative cooling material. The radiative cooling material after cooling treatment is crushed to obtain material particles of the preset particle size.

10. The method according to claim 8, characterized in that, The preset particle size is greater than 300 μm.

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