Preparation method of hydrophobic gadolinium oxide-based radiation refrigeration coating material
By adding specific nanoparticles and chemical modifiers to the gadolinium-based radiation refrigeration coating to form a stable hydrophobic coating, the problem of optical performance degradation of radiation refrigeration materials in high humidity environments is solved, and long-term cooling and self-cleaning effects with low energy consumption are achieved.
Patent Information
- Application Number
- CN202510795256.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-15
- Publication Date
- 2025-08-19
AI Technical Summary
Existing radiation refrigeration materials are susceptible to water vapor erosion in high humidity environments, resulting in deterioration of optical properties and no self-cleaning performance, which affects the refrigeration effect.
The gadolinium-based radiation refrigeration coating was prepared by sol-gel method. By incorporating TiO2, SiO2, ZrO2, SiC nanoparticles and heptadecyl trimethoxysilane, Si-O-Gd chemical bonds were formed to achieve hydrophobic properties, and the coating surface was treated in FAS-17 vapor to form a dense hydrophobic functional layer.
Under low energy consumption conditions, long-term cooling and self-cleaning functions are achieved, the solar light reflectivity and mid-infrared emissivity are improved, and the hydrophobic performance of the coating is maintained.
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Figure CN120504986A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of thermal management material preparation, and in particular to a method for preparing a hydrophobic gadolinium oxide-based radiation refrigeration coating material. Background Art
[0002] As the high energy consumption of traditional active cooling technologies (such as air conditioning and compression refrigeration) becomes increasingly prominent, the development of zero-energy passive radiative cooling (PRC) technology has become a research hotspot. Radiative cooling materials achieve low-power cooling by highly reflecting sunlight (0.3–2.5 μm) and efficiently emitting mid-infrared thermal radiation (8–13 μm), using a transparent window in the atmosphere to radiate heat directly into outer space. However, existing radiative cooling materials are susceptible to surface corrosion by water vapor or accumulation of condensation droplets when exposed to high humidity or long-term outdoor conditions, resulting in degradation of optical performance and severely restricting their practical application.
[0003] Gadolinium oxide (Gd2O3), a rare earth oxide, exhibits extremely high intrinsic emissivity (>0.83) in the mid-infrared band (8–13 μm) due to its wide bandgap (~5.4 eV) and unique lattice vibration modes. The periodic table indicates that Gd has an extremely high absorption coefficient (49700), making it an ideal substrate for radiative cooling. However, pure Gd2O3 coatings are poorly hydrophobic, with water contact angles typically below 90°. In humid environments, they readily adsorb water molecules, resulting in a decrease in optical performance. Furthermore, the attachment of water molecules to the coating surface increases solar absorption, reduces reflectivity, and weakens the cooling effect. Furthermore, its hydrophilic surface easily attracts dust or contaminants, further reducing the efficiency of radiative cooling.
[0004] Therefore, it is necessary to propose a method for preparing a gadolinium oxide (Gd2O3)-based radiation cooling coating material with hydrophobic properties to solve the above technical problems. Summary of the Invention
[0005] The main purpose of the present invention is to provide a method for preparing a hydrophobic gadolinium oxide-based radiative cooling coating material to solve the technical problems of the prior art radiative cooling coatings, such as poor hydrophobicity, low water contact angle, poor cooling effect, and lack of self-cleaning performance.
[0006] To achieve the above object, the present invention provides the following technical solutions:
[0007] A method for preparing a hydrophobic gadolinium oxide (Gd2O3)-based radiation cooling coating material comprises the following steps:
[0008] (1) dissolving gadolinium nitrate (Gd(NO3)3·6H2O) in an ethanol-water mixed solvent, adjusting the pH to 4-6, and heating and stirring to form a transparent sol to obtain a gadolinium oxide precursor;
[0009] (2) TiO2, SiO2, ZrO2, and SiC particles are added to a gadolinium oxide precursor, and heptafluorodecyltrimethoxysilane (FAS-17), a dispersant, a defoaming agent, a film-forming aid, and a leveling agent are added, followed by ultrasonic dispersion treatment, and then heated and stirred to form a coating;
[0010] (3) The substrate is surface treated, and the coating is sprayed on the substrate by air spraying. After curing, the sprayed coating is treated in heptadecafluorodecyltrimethoxysilane (FAS-17) vapor to obtain a gadolinium oxide-based radiation cooling coating with hydrophobic properties.
[0011] Preferably, the weight percentages of the raw materials in step (1) and step (2) are: 30-50wt% gadolinium nitrate; 15-20wt% TiO2, 10-15wt% SiO2, 5-10wt% ZrO2, 2-5wt% SiC; 3-5wt% heptafluorodecyltrimethoxysilane; 0.5-1wt% dispersant, 0.5-1wt% defoamer, 0.5-1wt% film-forming aid, 0.5-1wt% leveling agent; and the balance is ethanol-water mixed solvent.
[0012] Preferably, the volume ratio of ethanol to water in the ethanol-water mixed solvent in step (1) is 2:1; and the pH regulator is one of acetic acid or oxalic acid.
[0013] Preferably, in step (2), the particle sizes of TiO2, SiO2, ZrO2 and SiC are all 20-100 nm; the dispersant is SN-5040 aqueous dispersant; the defoaming agent is aqueous polyvinyl alcohol defoaming agent; the film-forming aid is alcohol lipid twelve; and the leveling agent is silicone leveling agent H421.
[0014] Preferably, the ultrasonic dispersion treatment in step (2) is carried out for an ultrasonic time of 10-30 minutes; and the heating and stirring in steps (1) and (2) are both carried out at 60-80° C. for 60-120 minutes, with a stirring rate of 300-400 r / min.
[0015] Preferably, in step (3), the substrate is surface treated by an acid pickling method; the acid pickling method is to first treat the substrate surface with oxalic acid or acetic acid, and then clean the substrate with water.
[0016] Preferably, the parameters of the air spraying in step (3) are: voltage 220V, power 1-1.5KW; spraying distance 300-350mm, and coating thickness 200-500μm.
[0017] Preferably, the nozzle diameter during air spraying in step (3) is 0.3 mm, the pressure is 0.3 MPa, the spraying distance is 300-350 mm, the curing temperature is 15-80° C., and the curing time is 30-480 minutes.
[0018] Preferably, in step (3), the heptadecafluorodecyltrimethoxysilane is heated to 80-100° C., and the coating reacts in the heptadecafluorodecyltrimethoxysilane vapor for 2-5 hours.
[0019] Preferably, the hydrophobic gadolinium oxide-based radiation cooling coating has a solar reflectivity of ≥92%, an atmospheric window emissivity of ≥91%, and a contact angle of ≥150°C.
[0020] The beneficial effects of the present invention are:
[0021] 1. The present invention introduces heptadecafluorodecyltrimethoxysilane (FAS-17) into the Gd2O3 precursor (Gd(NO3)3·6H2O) to achieve stable anchoring of the hydrophobic group (-CF3) through Si-O-Gd chemical bonding, thereby avoiding thermal decomposition during high-temperature treatment, improving the contact angle (≥150°C), and achieving hydrophobic properties; at the same time, composite TiO2 / SiO2 nanoparticles (enhancing 0.3-2.5μm reflection) and SiC / ZrO2 (broadening the 8-13μm emission peak) to achieve multi-band coordinated regulation, thereby improving the coating's solar reflectivity (≥92%) and atmospheric window emissivity (≥91%).
[0022] 2. The present invention prepares a precursor by a sol-gel method, dissolving gadolinium nitrate (Gd(NO3)3·6H2O) in an ethanol-water mixed solvent, adding acetic acid to adjust the pH to a weak acidic state, and heating and stirring to form a transparent sol; to improve solar reflectivity, TiO2 nanoparticles and SiO2 nanoparticles are added; to enhance mid-infrared emissivity, ZrO2 and SiC nanoparticles are added; and 3 wt% of heptadecafluorodecyltrimethoxysilane (FAS-17) is added simultaneously for hydrophobic modification, forming Si-O-Gd bonds by in-situ reaction to ensure stable binding of the hydrophobic groups. Then, a coating is prepared by air spraying, and cured to obtain a gadolinium oxide (Gd2O3)-based radiative cooling coating with hydrophobic properties; to further achieve the hydrophobic effect, the coating is treated in FAS-17 vapor for several hours to form a dense hydrophobic functional layer on the coating surface; the hydrophobic gadolinium oxide-based radiative cooling coating thus prepared can achieve the dual functions of long-term cooling and self-cleaning under low energy consumption conditions;
[0023] 3. The preparation method of the present invention has simple process, low preparation cost, is suitable for industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a comparison chart of the thermal insulation effect test of the radiant cooling coating prepared in Example 1 of the present invention and Comparative Example 1;
[0025] Figure 2This is a diagram showing the effect of TiO2 on solar reflectivity in Example 1 and Comparative Examples 3-5 of the present invention.
[0026] Figure 3 This is a diagram showing the effect of SiC content on the atmospheric window emissivity in Example 1, Example 4, and Comparative Examples 6-7 of the present invention. DETAILED DESCRIPTION
[0027] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.
[0028] Example 1
[0029] The method for preparing a hydrophobic gadolinium oxide (Gd2O3)-based radiation cooling coating material of this embodiment includes the following steps:
[0030] (1) Preparation of gadolinium oxide precursor: 50 g of gadolinium nitrate (Gd(NO3)3·6H2O) was dissolved in 13 g of ethanol-water mixed solvent, and the pH was adjusted to 4-6 by tube titration with oxalic acid. The mixture was heated and stirred to form a transparent sol. The heating and stirring parameters were: temperature 60°C, stirring rate 300 r / min, and stirring time 60 min.
[0031] (2) Preparation of coating: 15 g TiO2, 10 g SiO2, 5 g ZrO2, and 2 g SiC nanoparticles with a particle size of 20-100 nm were added to the transparent sol formed above; 3 g heptafluorodecyltrimethoxysilane (FAS-17), 0.5 g SN-5040 aqueous dispersant, 0.5 g aqueous polyvinyl alcohol defoamer, 0.5 g alcohol lipid film-forming aid, and 0.5 g organosilicon H421 leveling agent were added at the same time, and then ultrasonically dispersed, heated and stirred to form a coating; the heating and stirring parameters were: temperature 60°C, stirring rate 400 r / min, and stirring time 60 minutes;
[0032] (3) Coating Preparation: After pickling the steel alloy substrate with acetic acid and then washing it with a high-pressure water gun, the coating was sprayed onto the steel alloy substrate using an air spray method. After curing, the coating was treated in FAS-17 vapor for several hours. The air spraying parameters were: 0.3 mm nozzle, 0.3 MPa pressure, spray distance of 300 mm, curing temperature of 25°C, curing time of 480 minutes, and coating thickness of 200 μm. Finally, heptadecafluorodecyltrimethoxysilane was heated to 80°C and the coating was reacted in FAS-17 vapor for 5 hours.
[0033] 1.1 Performance test:
[0034] (1) Solar reflectance: tested in accordance with the standard JG / T235-2014 “Architectural Reflective Thermal Insulation Coatings”, with a wavelength range of 0.3 to 2.5 μm;
[0035] (2) Atmospheric window emissivity: tested in accordance with the standard T / ZZB 2304-2021 “Radiative Cooling Film”, with a wavelength range of 8 to 13 μm;
[0036] (3) Contact angle: optical contact angle measuring instrument (Dataphysics OCA);
[0037] (4) Cooling effect: Place the sample under sunlight or sun lamp to test the radiant cooling effect, and test the front and back temperatures.
[0038] Comparative Example 1
[0039] This comparative example serves as a blank control group, i.e., a 1 mm thick steel alloy substrate is not coated, to compare the thermal insulation performance of the radiant cooling coating.
[0040] Comparing the thermal performance of Example 1 and Comparative Example 1, Figure 1 As shown in Table 1. The results show that under the same heat source test conditions, the inner surface temperature of the coating (Example 1) is 25.7°C, which is 8.5°C lower than that of the pure steel alloy (Comparative Example 1), and the temperature drop effect is obvious.
[0041] Table 1 Temperature drop performance of steel alloy substrate with and without coating
[0042]
[0043] Example 2
[0044] The difference between Example 2 and Example 1 is that in step (1), 30 g of gadolinium nitrate (Gd(NO3)3·6H2O) is dissolved in 11 g of an ethanol-water mixed solvent.
[0045] Comparative Example 2
[0046] The difference between this comparative example and Example 1 is that in step (1), 20 g of gadolinium nitrate (Gd(NO3)3·6H2O) is dissolved in 11 g of ethanol-water mixed solvent.
[0047] Comparative Example 3
[0048] The difference between this comparative example and Example 1 is that in step (1), 60 g of gadolinium nitrate (Gd(NO3)3·6H2O) is dissolved in 11 g of an ethanol-water mixed solvent.
[0049] The effects of (Gd(NO3)3·6H2O) on the performance of the radiative cooling coating materials in Example 1, Example 2, Comparative Example 2, and Comparative Example 3 are shown in Table 2. The results show that when the (Gd(NO3)3·6H2O) content is 50wt% (Example 1) and 30wt% (Example 2), the coating has a high solar reflectivity and atmospheric window emissivity. When the (Gd(NO3)3·6H2O) content is reduced to 20wt% (Comparative Example 2), the atmospheric window emissivity decreases. When the (Gd(NO3)3·6H2O) content is increased to 60wt% (Comparative Example 3), the atmospheric window emissivity reaches 93%, but the solar reflectivity decreases, indicating that Gd 3+ It has a great influence on emissivity and solar reflectivity. In order to balance the performance of the two, the content of (Gd(NO3)3·6H2O) is controlled at 30-50wt%.
[0050] Table 2 Effect of (Gd(NO3)3·6H2O) on the performance of radiative cooling coating materials
[0051]
[0052] Example 3
[0053] The difference between this embodiment and embodiment 1 is that the mass of TiO2 in step (2) is 20g.
[0054] Comparative Example 4
[0055] The difference between this comparative example and Example 1 is that the mass of TiO2 in step (2) is 10g.
[0056] Comparative Example 5
[0057] The difference between this comparative example and Example 1 is that the mass of TiO2 in step (2) is 25g.
[0058] The effects of TiO2 on the performance of the radiative cooling coating materials in Example 1, Example 3, and Comparative Examples 4-5 are shown in Table 3 and Figure 2 The results show that when the TiO2 content is 15wt% (Example 1) and 20wt% (Example 3), the atmospheric window emissivity does not change much. When the TiO2 content is less than 15wt% (Comparative Example 4), the solar reflectivity decreases. When the TiO2 content is 25wt% (Comparative Example 5), the solar reflectivity increases, but the atmospheric window emissivity decreases. In order to balance the two properties, the TiO2 content is controlled at 15-20wt%.
[0059] Table 3 Effect of TiO2 on the performance of radiative cooling coating materials
[0060]
[0061]
[0062] Example 4
[0063] The difference between this embodiment and embodiment 1 is that the mass of SiC in step (2) is 5 g.
[0064] Comparative Example 6
[0065] The difference between this comparative example and Example 1 is that the mass of SiC in step (2) is 10 g.
[0066] Comparative Example 7
[0067] The difference between this comparative example and Example 1 is that the mass of SiC in step (2) is 0 g.
[0068] The effects of SiC in Example 1, Example 3, and Comparative Examples 4-5 on the performance of the radiative cooling coating material are shown in Table 4 and Figure 3 The results show that the SiC content has a significant impact on the atmospheric window emissivity. When the SiC content is 2-5wt%, the atmospheric window emissivity has little effect. When the SiC content is 0, the atmospheric window emissivity is low. When the SiC content is greater than 10wt%, the atmospheric window emissivity increases, but the solar reflectivity decreases. To balance the two, the SiC content is controlled between 2-5wt%.
[0069] Table 4 Effect of SiC on the performance of radiative cooling coating materials
[0070]
[0071] Comparative Example 8
[0072] This comparative example differs from Example 1 in that the coating was not treated in FAS-17 vapor after curing.
[0073] Table 5 shows the effects of whether or not the coatings in Example 1 and Comparative Example 8 were treated in FAS-17 vapor after curing on the radiative cooling coating material properties. The results show that compared to treating the coating in FAS-17 vapor after curing (Example 1), the solar reflectance and atmospheric window emissivity in Comparative Example 8 did not change significantly, but the contact angle decreased, the wettability was poor, and the hydrophobicity was reduced. Therefore, it is necessary to treat the coating in FAS-17 vapor.
[0074] Table 5 Effect of whether or not the coating is treated in FAS-17 vapor after curing on the performance of the radiative cooling coating material
[0075]
[0076] Example 6
[0077] The method for preparing a hydrophobic gadolinium oxide (Gd2O3)-based radiation cooling coating material of this embodiment includes the following steps:
[0078] (1) Preparation of gadolinium oxide precursor: 40 g of gadolinium nitrate (Gd(NO3)3·6H2O) was dissolved in 11 g of ethanol-water mixed solvent, and the pH was adjusted to 4-6 by tube titration with oxalic acid. The mixture was heated and stirred to form a transparent sol. The heating and stirring parameters were: temperature 80°C, stirring rate 400 r / min, and stirring time 120 min.
[0079] (2) Preparation of coating: 20 g TiO2, 10 g SiO2, 10 g ZrO2, and 5 g SiC nanoparticles with a particle size of 20-100 nm were added to the transparent sol formed above; 5 g heptafluorodecyltrimethoxysilane (FAS-17), 1 g SN-5040 aqueous dispersant, 1 g aqueous polyvinyl alcohol defoamer, 1 g alcohol lipid film-forming aid, and 1 g organic silicone H421 leveling agent were added at the same time, and then ultrasonically dispersed, heated and stirred to form a coating. The heating and stirring parameters were: temperature 50 ° C, stirring rate 500 r / min, and stirring time 120 minutes;
[0080] (3) Coating Preparation: After pickling the steel alloy substrate with acetic acid and then washing it with a high-pressure water gun, the coating was sprayed onto the steel alloy substrate using an air spray method. After curing, the coating was treated in FAS-17 vapor for several hours. The air spraying parameters were: 0.3 mm nozzle, 0.3 MPa pressure, spray distance of 350 mm, curing temperature of 80°C, curing time of 30 minutes, and coating thickness of 500 μm. Finally, heptadecafluorodecyltrimethoxysilane was heated to 100°C and the coating was reacted in FAS-17 vapor for 2 hours.
[0081] Example 7
[0082] The method for preparing a hydrophobic gadolinium oxide (Gd2O3)-based radiation cooling coating material of this embodiment includes the following steps:
[0083] (1) Preparation of gadolinium oxide precursor: 40 g of gadolinium nitrate (Gd(NO3)3·6H2O) was dissolved in 12 g of ethanol-water mixed solvent, and the pH was adjusted to 4-6 by tube titration with oxalic acid. The mixture was heated and stirred to form a transparent sol. The heating and stirring parameters were: temperature 70°C, stirring rate 350 r / min, and stirring time 100 min.
[0084] (2) Preparation of coating: 16 g TiO2, 14 g SiO2, 8 g ZrO2, and 3 g SiC nanoparticles with a particle size of 20-100 nm were added to the transparent sol formed above; 4 g heptafluorodecyltrimethoxysilane (FAS-17), 0.8 g SN-5040 aqueous dispersant, 0.8 g aqueous polyvinyl alcohol defoamer, 0.8 g alcohol lipid film-forming aid, and 0.6 g organosilicon H421 leveling agent were added at the same time, and then ultrasonically dispersed, heated and stirred to form a coating. The heating and stirring parameters were: temperature 70°C, stirring rate 480 r / min, and stirring time 100 minutes.
[0085] (3) Coating Preparation: After pickling the steel alloy substrate with acetic acid and then washing it with a high-pressure water gun, the coating was sprayed onto the steel alloy substrate using an air spray method. After curing, the coating was treated in FAS-17 vapor for several hours. The air spray parameters were: 0.3 mm nozzle, 0.3 MPa pressure, spray distance of 330 mm, curing temperature of 70°C, curing time of 120 minutes, and coating thickness of 350 μm. Finally, heptadecafluorodecyltrimethoxysilane was heated to 90°C and the coating was reacted in FAS-17 vapor for 4 hours.
[0086] The radiative cooling coatings prepared in Examples 6 and 7 also have excellent radiative cooling performance and hydrophobic properties.
[0087] In summary, the present invention selects Gd, an element with an extremely high absorption coefficient (49700), as a key material for radiative cooling and improves its hydrophobic properties through modification, resulting in a coating material that combines radiative cooling with self-cleaning properties. Specifically, heptadecafluorodecyltrimethoxysilane (FAS-17) is introduced into the Gd2O3 precursor (Gd(NO3)3·6H2O). Si-O-Gd chemical bonding stabilizes the hydrophobic group (-CF3), preventing thermal decomposition during high-temperature treatment and improving hydrophobic properties. Furthermore, TiO2 / SiO2 nanoparticles (enhancing reflection from 0.3–2.5 μm) and SiC / ZrO2 (broadening the emission peak from 8–13 μm) are combined to achieve multi-band coordinated regulation.
[0088] The above detailed description of the specific embodiments of the invention is intended to be illustrative only, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the invention are also within the scope of the present invention. Therefore, equivalent changes, modifications, and improvements made without departing from the spirit and scope of the present invention are also encompassed within the scope of the present invention.
Claims
1. A method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material, characterized in that: The steps include: (1) dissolving gadolinium nitrate in an ethanol-water mixed solvent, adjusting the pH to 4-6, heating and stirring to form a transparent sol, and obtaining a gadolinium oxide precursor; (2) adding TiO2, SiO2, ZrO2, and SiC particles to a gadolinium oxide precursor, and simultaneously adding heptafluorodecyltrimethoxysilane, a dispersant, a defoaming agent, a film-forming aid, and a leveling agent, followed by ultrasonic dispersion treatment, heating and stirring to form a coating; (3) The substrate is surface treated, and the coating is sprayed on the substrate by air spraying. After curing, the sprayed coating is treated in heptadecafluorodecyltrimethoxysilane vapor to obtain a gadolinium oxide-based radiation cooling coating with hydrophobic properties.
2. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: The weight percentages of the raw materials in step (1) and step (2) are: 30-50wt% gadolinium nitrate; 15-20wt% TiO2, 10-15wt% SiO2, 5-10wt% ZrO2, 2-5wt% SiC; 3-5wt% heptafluorodecyltrimethoxysilane; 0.5-1wt% dispersant, 0.5-1wt% defoamer, 0.5-1wt% film-forming aid, 0.5-1wt% leveling agent; the balance is ethanol-water mixed solvent.
3. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: In step (1), the volume ratio of ethanol to water in the ethanol-water mixed solvent is 2:1; and the pH regulator is one of acetic acid or oxalic acid.
4. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: In step (2), the particle sizes of TiO2, SiO2, ZrO2 and SiC are all 20-100 nm; the dispersant is SN-5040 aqueous dispersant; the defoaming agent is aqueous polyvinyl alcohol defoaming agent; the film-forming aid is alcohol lipid twelve; and the leveling agent is silicone leveling agent H421.
5. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: The ultrasonic dispersion treatment in step (2) is carried out for an ultrasonic time of 10-30 minutes; the heating and stirring in steps (1) and (2) are both carried out at 60-80° C. for 60-120 minutes, wherein the stirring rate is 300-400 r / min.
6. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: In step (3), the substrate is surface treated by an acid pickling method; the acid pickling method is to first treat the substrate surface with oxalic acid or acetic acid, and then clean the substrate with water.
7. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: The parameters of the air spraying in step (3) are: voltage 220V, power 1-1.5KW; spraying distance 300-350mm, and coating thickness 200-500μm.
8. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 7, wherein: In step (3), the nozzle for air spraying is 0.3 mm, the pressure is 0.3 MPa, the spraying distance is 300-350 mm, the curing temperature is 15-80° C., and the curing time is 30-480 minutes.
9. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: In step (3), the temperature of heptadecafluorodecyltrimethoxysilane is heated to 80-100° C., and the coating is reacted in the heptadecafluorodecyltrimethoxysilane vapor for 2-5 hours.
10. The method for preparing a hydrophobic gadolinium oxide-based radiation cooling coating material according to claim 1, wherein: The hydrophobic gadolinium oxide-based radiation cooling coating has a solar reflectivity of ≥92%, an atmospheric window emissivity of ≥91%, and a contact angle of ≥150°C.