High-efficiency aluminum veneer radiation refrigeration coating based on nano composite particles and preparation method of high-efficiency aluminum veneer radiation refrigeration coating

Abstract

The invention relates to the technical field of coatings, in particular to an efficient aluminum veneer radiation refrigeration coating based on nano-composite particles, which is composed of a base material, a nano-composite functional filler, an auxiliary agent and deionized water, the base material is a hybrid system of fluorosilicone emulsion and water-based inorganic ceramic, the nano-composite functional filler is a nano-composite functional filler, and the auxiliary agent is a nano-composite functional filler. The nano composite functional filler is a combination of nano particles with a core-shell structure and composite nano particles, the nano particles with the core-shell structure are Ag coated SiO2, and the composite nano particles are TiO2 / SiO2; the auxiliaries comprise a thickening agent, a defoaming agent, a coalescing agent, a sterilizing agent, a dispersing agent, a pH (Potential of Hydrogen) regulator and a nanoscale SiO2 wear-resistant agent. The nano-composite functional filler formed by combining the Ag-coated SiO2 core-shell structure nano-particles and the TiO2 / SiO2 composite nano-particles is adopted, and due to the synergistic effect of the dual mechanisms, the coating shows excellent optical performance in the solar spectrum range and the infrared spectrum range, and therefore the efficient radiation refrigeration effect is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coatings, in particular to an aluminum veneer coating with high-efficiency radiative cooling performance applied in the field of building and a preparation method thereof. BACKGROUND

[0002] With the global warming and the increasing demand for energy, the problem of building energy consumption is becoming increasingly prominent. In particular, in summer, the air conditioning energy consumption inside the building accounts for a large part of the total energy consumption. Traditional building materials will absorb a lot of heat under solar radiation, causing the indoor temperature to rise and increasing the air conditioning load. In order to reduce the building energy consumption, the radiative cooling technology emerges as the times require. The core principle of radiative cooling is to use the characteristics of high reflectivity in the solar spectrum range and high emissivity in the atmospheric window (8-13 microns) of the material, to radiate heat from the building surface to the cold outer space through the radiation of the three heat dissipation modes of convection, conduction and radiation, thereby achieving passive cooling without consuming energy.

[0003] At present, the research on radiative cooling coating mainly focuses on how to improve the reflectivity of the coating in the solar spectrum range and the emissivity in the atmospheric window. In the prior art, high-reflectivity pigments (such as TiO2) are usually added to improve the solar reflectivity, and specific infrared emissivity materials are introduced to enhance the infrared emissivity. However, these coatings often have some problems in practical application: first, the optical performance of a single component pigment in a wide band is difficult to meet the requirements of high reflectivity and high emissivity at the same time, resulting in poor cooling effect; second, the mechanical properties, weather resistance and adhesion of the coating and other properties related to actual application are often ignored, and problems such as cracking, powdering and peeling are prone to occur in long-term use, affecting the service life and stability of the cooling effect; third, the dispersion of nanoparticles is not well controlled in the preparation process of the existing radiative cooling coating, which easily leads to the agglomeration of nanoparticles, thereby affecting the optical performance and uniformity of the coating. In addition, there is also a lack of a systematic and effective method for surface treatment of aluminum veneer, a commonly used building material, to ensure the adhesion of the coating and the durability of the coating. Therefore, it is urgent to develop a special coating for aluminum veneer with excellent comprehensive performance, controllable preparation process and long-term high-efficiency radiative cooling performance and a preparation method thereof. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a high-efficiency aluminum veneer radiative cooling coating based on nano-composite particles and a preparation method thereof, which solves the problems of insufficient optical performance, poor mechanical properties and weather resistance of the radiative cooling coating in the prior art.

[0005] To achieve the above object, the application is implemented by the following technical scheme: the high-efficiency aluminum single board radiation refrigeration coating based on nano composite particles is composed of the following raw materials in mass percentage: base material 35-50%, nano composite functional filler 15-30%, additive 8-25%, deionized water 10-20%; the additive includes thickening agent 0.5-4%, defoaming agent 1-4%, film forming aid 2-8%, bactericide 0.5-1%, dispersant 1-2%, pH regulator 1-3%, nano SiO2 wear-resistant agent 1-3%.

[0006] The application also provides a preparation method of the high-efficiency aluminum single board radiation refrigeration coating based on nano composite particles, including the following steps: (1) aluminum single board pretreatment: first, surface degreasing treatment is performed on the aluminum single board, and alkaline cleaning agent is used for ultrasonic cleaning for 10-15 minutes; then, phosphating treatment is performed, the aluminum single board is immersed in a phosphating solution added with fluoride, and the temperature is 50-60 DEG C, and the treatment time is 5-8 minutes; finally, silane coupling agent treatment is performed, the aluminum single board after phosphating is immersed in a KH-570 silane coupling agent solution with a mass fraction of 1-3%, and the treatment time is 3-5 minutes at room temperature, and the aluminum single board is taken out and dried for standby use; (2) preparation of nano composite functional filler: Ag@SiO2 core-shell structure nanoparticles and TiO2 / SiO2 composite nanoparticles are mixed in proportion, a dispersant and a proper amount of deionized water are added, a high-speed shearing dispersion machine is used for dispersion at a rotating speed of 2000-3000 r / min for 15-20 minutes, and then ultrasonic treatment is performed for 30-40 minutes, and the ultrasonic power is 300-500 W, to obtain a nano composite functional filler dispersion liquid; (3) preparation of coating: fluorosilicon emulsion and water-based inorganic ceramic are added in a reaction kettle in proportion, and are uniformly mixed at a stirring speed of 500-800 r / min; then, the nano composite functional filler dispersion liquid is slowly added, and stirring is continuously performed for 30-40 minutes; then, thickening agent, defoaming agent, film forming aid, bactericide and pH regulator are sequentially added, and stirring is performed at a rotating speed of 800-1000 r / min for 20-30 minutes; finally, nano SiO2 wear-resistant agent is added, and stirring is performed for 15-20 minutes, to obtain a coating primary product; the coating primary product is subjected to sand milling treatment by using a sand mill, and the grinding particle size is controlled to be 50-200 nm, to obtain a radiation refrigeration coating finished product; (4) coating and solidification: the coating is uniformly coated on the surface of the pretreated aluminum single board by using spraying or roller coating, and the wet film thickness is controlled to be 60-100 mu m; after coating, pre-solidification is performed at 80 DEG C for 30 minutes, and then complete solidification is performed at 120 DEG C for 60 minutes, to form a radiation refrigeration coating layer with a dry film thickness of 30-50 mu m.

[0007] The application provides a high-efficiency aluminum single board radiation refrigeration coating based on nano composite particles and a preparation method thereof. 1、The present application adopts the nanocomposite functional filler combined by Ag@SiO2 core-shell structure nanoparticles and TiO2 / SiO2 composite nanoparticles. The high reflectivity of Ag@SiO2 core-shell structure nanoparticles to visible light ensures effective blocking of solar radiation by the coating, avoiding heat absorption; the high radiance of TiO2 / SiO2 composite nanoparticles in the atmospheric window band ensures effective heat dissipation. This dual mechanism synergistically works, so that the coating exhibits excellent optical performance in the solar spectrum and infrared spectrum range, thereby realizing efficient radiation refrigeration effect.

[0008] 2、The present application adopts the hybrid system of fluorosilicone emulsion and water-based inorganic ceramic as the base material. The fluorosilicone emulsion endows the coating with excellent weather resistance, water resistance, and stain resistance, and the water-based inorganic ceramic provides excellent hardness, adhesion, and heat resistance. The addition of nanoscale SiO2 wear-resistant agent further improves the wear resistance and mechanical strength of the coating, effectively solving the problems of easy cracking, powdering, and peeling of the coating in the prior art, greatly prolonging the service life of the coating. At the same time, the step of combining high-speed shearing dispersion and ultrasonic treatment is introduced in the preparation method to prepare the nanocomposite functional filler dispersion liquid, effectively solving the problem of nanoparticle agglomeration, ensuring the uniform dispersion of the functional filler in the coating, and thus ensuring the stability and uniformity of the optical performance of the coating. DETAILED DESCRIPTION

[0009] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0010] Embodiment one: The present application provides a kind of high efficiency aluminum veneer radiation refrigeration coating based on nanocomposite particle, it is composed of the following mass percentage of raw materials: base material 35%, nanocomposite functional filler 30%, auxiliary agent 25%, deionized water 10%.

[0011] The base material is a hybrid system of fluorosilicon emulsion and water-based inorganic ceramic. In the hybrid system, the fluorosilicon emulsion accounts for 60% of the total amount of the base material, and the water-based inorganic ceramic accounts for 40%. The fluorosilicon emulsion is a single-component fluorosilicon emulsion, and the latex particle size is 150 nm. The water-based inorganic ceramic is a nano ceramic emulsion. The fluorosilicon emulsion, as the organic part, introduces fluorine and silicon elements, which can give the coating excellent weather resistance, water resistance, UV aging resistance and self-cleaning performance. The coating formed has low surface energy and is not easy to be contaminated. The water-based inorganic ceramic, as the inorganic part, can significantly improve the hardness, adhesion, scratch resistance and high temperature resistance of the coating, and increase the density of the coating. The advantages of the two base materials are complementary, forming a composite matrix with excellent mechanical properties, weather resistance and adhesion.

[0012] The nano-composite functional filler is a combination of core-shell structure nanoparticles and composite nanoparticles, with a total mass percentage of 30%. Among them, the core-shell structure nanoparticles are Ag@SiO2, accounting for 40% of the total amount of nano-composite functional fillers. Ag@SiO2 nanoparticles have a core-shell structure, and the silver (Ag) core has a plasmonic resonance effect, which can efficiently reflect solar radiation in the visible light band, thereby reducing the absorption of solar heat by the coating. The silica (SiO2) shell not only protects the stability of the silver core and prevents oxidation of silver, but also has low refractive index characteristics, which helps to improve the scattering efficiency. The reflectivity of the Ag@SiO2 nanoparticles to 390-750 nm visible light is ≥85%, and the particle size range is 60 nm. The composite nanoparticles are TiO2 / SiO2, accounting for 60% of the total amount of nano-composite functional fillers. TiO2 / SiO2 composite nanoparticles are the key to realizing high-efficiency radiation cooling in the present application. TiO2 has a high refractive index and can effectively scatter sunlight, while SiO2 has a high infrared emissivity in the atmospheric window band (8-13 μm). This composite structure utilizes the synergistic effect of the two materials to achieve a radiance of more than 93% in the atmospheric window band, effectively dissipating heat in the form of infrared radiation, and achieving self-cooling of the coating. The particle size range is 4 nm, which ensures uniform dispersion in the coating and stability of optical performance.

[0013] The total mass percentage of the auxiliary agent is 25%. Specifically, it includes: Thickening agent 0.5%, cellulose ether is selected in this embodiment. The thickening agent is used to adjust the viscosity of the coating, improve the construction performance, prevent the coating from sagging and settling, and ensure the uniformity of the coating thickness.

[0014] Defoamer 1%, silicone defoamer is selected in this embodiment. The defoamer is used to eliminate bubbles generated during the production and construction of the coating, ensuring a smooth and defect-free coating surface.

[0015] Film forming aid 2%, dodecanol ester is selected in the embodiment. The film forming aid can reduce the minimum film forming temperature (MFFT) of the coating, promote the emulsion particles to form a dense and uniform coating film at room temperature, and improve the adhesion and mechanical properties of the coating.

[0016] Bactericide 0.5%, isothiazolinone salt is selected in the embodiment. The bactericide is used to inhibit the growth of microorganisms in the coating during storage and use, and prevent the coating from deteriorating.

[0017] Dispersant 1%, butyric acid carboxymethyl cellulose acetate is selected in the embodiment. The key role of the dispersant is to effectively disperse the nanocomposite functional filler, prevent the agglomeration of nanoparticles, and ensure the uniform and stable dispersion of the nanoparticles in the coating system, thereby ensuring the optical properties and stability of the coating.

[0018] pH regulator 1%, AMP-95 (2-amino-2-methyl-1-propanol) is selected in the embodiment. The pH regulator is used to control the pH value of the coating system, and maintain the stability of the system and the optimal performance of each component.

[0019] Nanoscale SiO2 wear-resistant agent 1%, with an average particle size of 15 nm, is a nanoscale SiO2 particle. The addition of the nanoscale SiO2 wear-resistant agent as a nanoscale reinforcing filler can significantly improve the hardness, wear resistance and scratch resistance of the coating, and further enhance the mechanical durability of the coating.

[0020] Deionized water accounts for 10% of the total mass of the coating, which is used as a solvent and dispersion medium to ensure the stability and fluidity of the coating system.

[0021] In the present application, the synergistic effect of each component enables the coating to not only have high-efficiency radiation cooling capacity, but also have excellent mechanical properties, weather resistance and construction performance, which is suitable for the application of building aluminum veneer under various climate conditions.

[0022] The preparation method of the high-efficiency aluminum veneer radiation cooling coating based on nanocomposite particles comprises the following steps: (1) Aluminum veneer pretreatment: ① Surface degreasing treatment: first, the surface of the aluminum veneer is degreased. The aluminum veneer is immersed in a tank containing an alkaline cleaning agent, and ultrasonic cleaning is used. Under the action of ultrasonic waves, the aluminum veneer is cleaned for 10 minutes. Ultrasonic cleaning uses the cavitation effect generated by rapid vibration to efficiently remove oil, dust and impurities on the surface of the aluminum veneer, providing a clean substrate for subsequent processing.

[0023] ② Phosphating: After degreasing, remove the aluminum veneer and rinse it with deionized water. Then, immerse it in a fluoride-added phosphating solution. The solution is kept at 50°C for 5 minutes. Phosphating forms a dense phosphate conversion coating on the surface of the aluminum veneer. This coating offers excellent corrosion resistance and reduces roughness, significantly improving adhesion between the coating and the substrate. The addition of fluoride helps activate the aluminum surface, improving the uniformity and density of the phosphate film.

[0024] ③ Silane coupling agent treatment: The phosphated aluminum veneer is rinsed again with deionized water. Next, the phosphated aluminum veneer is immersed in a 1% by weight solution of KH-570 silane coupling agent. Treatment is performed at room temperature (approximately 25°C) for 3 minutes. KH-570, an organic-inorganic hybrid molecule, undergoes a hydrolysis-condensation reaction with hydroxyl groups on the aluminum veneer surface, forming a strong covalent bond. The other end contains a reactive functional group (such as a methacryloyloxy group) that cross-links with the organic polymer matrix in the coating, creating a "molecular bridge" between the metal surface and the coating. This significantly improves the coating's wet adhesion, salt spray corrosion resistance, and long-term durability. Remove the treated aluminum veneer and dry it in a 70°C oven for later use.

[0025] (2) Preparation of nanocomposite functional fillers: Ag@SiO2 core-shell nanoparticles and TiO2 / SiO2 composite nanoparticles were mixed in a mass ratio of 4:6. Appropriate amounts of a dispersant (carboxymethyl cellulose acetate butyrate, representing 1% of the total mass of the nanocomposite functional filler) and deionized water were added. A high-speed shear disperser was used for 15 minutes at 2000 rpm to break up any agglomerated nanoparticles. The dispersion was then transferred to an ultrasonic device and sonicated for 30 minutes at 300 W. The mechanical force of the high-speed shear effectively reduced the size of the initial aggregates. Subsequent ultrasonic treatment, through the cavitation effect, generated shock waves and jets, further disrupted the van der Waals forces between the nanoparticles, achieving uniform and stable dispersion of the nanoparticles in the dispersion. This resulted in a transparent and clear nanocomposite functional filler dispersion, ensuring the optical uniformity and performance of the final coating.

[0026] (3) Preparation of coating: First, in a reactor equipped with a stirring device, fluorosilicone emulsion and water-based inorganic ceramics were added in a mass ratio of 6:4, and mixed evenly at a stirring speed of 500 r / min for 15 minutes to allow the two base materials to be fully miscible.

[0027] Then, under continuous stirring, the nanocomposite functional filler dispersion prepared in step (2) is slowly added into the reactor and stirred for 30 minutes to ensure that the nanofunctional filler is evenly dispersed in the base material system.

[0028] Then, the thickening agent, defoaming agent, film forming aid, bactericide and pH regulator are added in turn, the stirring speed is increased to 800 r / min, and stirring is performed for 20 minutes to make the additives fully dissolved and play a role, and the rheological property and stability of the coating are adjusted.

[0029] Finally, the nano-sized SiO2 wear-resistant agent is added, and stirring is performed for 15 minutes to make the wear-resistant agent uniformly dispersed, and the coating primary product is obtained.

[0030] The coating primary product is subjected to sand milling treatment by using a sand mill to control the grinding particle size to 50 nm, and the radiation refrigeration coating finished product is obtained. The sand milling treatment can further reduce the particle size of pigments and fillers in the coating, improve the fineness and dispersion uniformity of the coating, and optimize the optical performance and hand feeling of the coating.

[0031] (4) Coating and curing: The prepared radiation refrigeration coating finished product is uniformly coated on the surface of the pretreated aluminum veneer by using a spraying method. In the coating process, the wet film thickness is strictly controlled to be 60 μm to ensure the consistency of the coating thickness.

[0032] After the coating is completed, pre-curing is first performed at 80℃ for 30 minutes. The pre-curing is aimed at rapidly evaporating the moisture and part of the solvent in the coating, and making the coating preliminarily film-forming to form a certain strength to prevent sagging and finger dryness.

[0033] Finally, the aluminum veneer after pre-curing is transferred to an oven at 120℃ for complete curing for 60 minutes. The high-temperature complete curing ensures that the polymerization reaction in the coating is thoroughly performed to form a highly cross-linked dense coating, so that the mechanical performance, weather resistance and adhesion reach the best state, and finally a radiation refrigeration coating layer with a dry film thickness of 30 μm is formed, which is firmly combined with the aluminum veneer substrate.

[0034] Example Two: The embodiment of the present application provides a kind of high-efficiency aluminum veneer radiation refrigeration coating based on nano composite particle, by following mass percentage of raw materials: base material 45%, nano composite functional filler 20%, auxiliary agent 15%, deionized water 20%; Auxiliary agent includes: thickening agent 2% (polyurethane thickening agent), defoaming agent 2% (silicone defoaming agent), film forming aid 4% (dodecanol ester), bactericide 0.7% (isothiazolinone salt), dispersing agent 1.5% (carboxymethyl cellulose acetate butyrate), pH regulator 2% (AMP-95), nano-sized SiO2 wear-resistant agent 2%.

[0035] The preparation method of the high-efficiency aluminum veneer radiation refrigeration coating based on nano composite particle includes the following steps: (1) Pretreatment of aluminum veneer: first, the surface of the aluminum veneer is degreased, and ultrasonic cleaning is performed for 15 minutes with an alkaline cleaning agent; then, phosphating treatment is performed, the aluminum veneer is immersed in a phosphating solution added with fluoride, and the temperature is 60℃, the treatment time is 8 minutes; finally, silane coupling agent treatment is performed, the phosphated aluminum veneer is immersed in a KH-570 silane coupling agent solution with a mass fraction of 3%, and the treatment time is 5 minutes at room temperature, and then the aluminum veneer is dried for standby; (2) Preparation of nano-composite functional filler: Ag@SiO2 core-shell structure nanoparticles and TiO2 / SiO2 composite nanoparticles are mixed in a mass ratio of 6:4, a dispersing agent and a proper amount of deionized water are added, and high-speed shearing dispersion is performed for 20 minutes at a speed of 3000 r / min, and then ultrasonic treatment is performed for 40 minutes at an ultrasonic power of 500 W to obtain a nano-composite functional filler dispersion liquid; (3) Preparation of coating: fluorosilicon emulsion and water-based inorganic ceramic are added to a reaction kettle in a mass ratio of 8:2, and stirred uniformly at a stirring speed of 800 r / min; then, the nano-composite functional filler dispersion liquid is slowly added, and stirring is continued for 40 minutes; then, thickening agent, defoaming agent, film-forming aid, bactericide and pH regulator are sequentially added, and stirring is performed at a speed of 1000 r / min for 30 minutes; finally, nano-sized SiO2 wear-resistant agent is added, and stirring is performed for 20 minutes to obtain a coating primary product; the coating primary product is subjected to sand milling treatment with a sand mill to control the grinding particle size to 200 nm, and a radiation refrigeration coating finished product is obtained; (4) Coating and curing: the coating is uniformly coated on the surface of the pretreated aluminum veneer by spraying or rolling, and the wet film thickness is controlled to be 100 μm; after coating, pre-curing is performed at 80℃ for 30 minutes, and then complete curing is performed at 120℃ for 60 minutes to form a radiation refrigeration coating layer with a dry film thickness of 50 μm.

[0036] The performance of the aluminum veneer radiation refrigeration coating prepared in Example 1 is tested, and the results are as follows: 1. Solar reflectance: under AM1.5G standard solar spectrum, the total solar reflectance of the coating is 92%. This data shows that the coating can significantly reflect solar radiation and effectively reduce heat input.

[0037] 2. Atmospheric window emissivity: in the 8-13 μm atmospheric window band, the infrared emissivity of the coating is 94%. The high emissivity ensures that the coating can efficiently radiate its own heat to outer space, achieving passive cooling.

[0038] 3. Surface temperature difference: in the clear and windless summer afternoon, the aluminum veneer coated with the coating of the present application is compared with the ordinary white (without radiation refrigeration function) coating of the aluminum veneer, and the surface temperature of the coating of the present application is 4-6℃ lower than the ambient temperature, and 10-15℃ lower than the surface temperature of the ordinary white coating, which proves the excellent radiation refrigeration effect.

[0039] 4. Adhesion: According to GB / T 9286-1998 "Paints and varnishes - Cross-cut test for coating films", the adhesion of the coating is 0 level, indicating that the coating is firmly combined with the aluminum veneer substrate and has no peeling phenomenon.

[0040] 5. Hardness: The hardness of the coating reaches the HB level, showing good scratch resistance.

[0041] 6. Weather resistance: After 2000 hours of testing in an accelerated aging test (such as a Q-SUN accelerated aging test machine simulating outdoor exposure and rain), the coating has no obvious loss of luster, cracking or powdering phenomenon, and the optical performance attenuation is less than 5%, showing excellent outdoor durability.

[0042] Through the detailed description of the above examples, the present application not only discloses the component composition of the high-efficiency radiation refrigeration coating, but also provides specific preparation process and parameter range, as well as optimized formula and performance verification. These contents are sufficient to enable those skilled in the art to fully understand and implement the present application, and to obtain technical effects consistent with the purpose of the present application.

[0043] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. High-efficiency aluminum veneer radiant cooling coating based on nanocomposite particles, characterized by: The composition is composed of the following raw materials in the following mass percentages: base material 35-50%, nano-composite functional filler 15-30%, additive 8-25%, deionized water 10-20%; The auxiliary agents include: thickener 0.5-4%, defoamer 1-4%, film-forming auxiliary agent 2-8%, bactericide 0.5-1%, dispersant 1-2%, pH regulator 1-3%, nano-SiO2 wear-resistant agent 1-3%.

2. The high-efficiency aluminum veneer radiant cooling coating based on nanocomposite particles according to claim 1 is characterized in that: The thickener is a cellulose ether or polyurethane thickener, the defoamer is an organosilicon defoamer, the film-forming aid is lauryl alcohol ester, the bactericide is an isothiazolinone salt, the dispersant is carboxymethyl cellulose acetate butyrate, and the pH regulator is AMP-95.

3. The high-efficiency aluminum veneer radiant cooling coating based on nanocomposite particles according to claim 1 is characterized in that: The base material is a hybrid system of fluorosilicone emulsion and water-based inorganic ceramics, with the fluorosilicone emulsion accounting for 60%-80% of the total base material and the water-based inorganic ceramics accounting for 20%-40%. The fluorosilicone emulsion is a single-component fluorosilicone emulsion with a latex particle size of 100-300nm, and the water-based inorganic ceramics are nano-scale ceramic emulsions.

4. The high-efficiency aluminum veneer radiant cooling coating based on nanocomposite particles according to claim 1, characterized in that: The nano-composite functional filler is a combination of core-shell structured nanoparticles and composite nanoparticles. The core-shell structured nanoparticles are Ag@SiO2, accounting for 40%-60% of the total amount of the nano-composite functional filler, and their reflectivity to visible light of 390-750nm is ≥85%, and the particle size range is 45-80nm; the composite nanoparticles are TiO2 / SiO2, accounting for 40%-60% of the total amount of the nano-composite functional filler, and their emissivity in the atmospheric window band is ≥93%, and the particle size range is 3-5nm.

5. The method for preparing a high-efficiency aluminum veneer radiant cooling coating based on nanocomposite particles according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Pretreatment of aluminum veneer: First, degrease the surface of the aluminum veneer and use an alkaline cleaning agent to ultrasonically clean it for 10-15 minutes; then perform phosphating treatment, immerse the aluminum veneer in a phosphating solution with fluoride added, and treat it at a temperature of 50-60°C for 5-8 minutes; finally, perform silane coupling agent treatment, immerse the phosphated aluminum veneer in a KH-570 silane coupling agent solution with a mass fraction of 1-3%, treat it at room temperature for 3-5 minutes, take it out and dry it for use; (2) Preparation of nanocomposite functional fillers: Ag@SiO2 core-shell structure nanoparticles and TiO2 / SiO2 composite nanoparticles were mixed in proportion, a dispersant and an appropriate amount of deionized water were added, and a high-speed shear disperser was used to disperse the mixture at a speed of 2000-3000 r / min for 15-20 minutes, followed by ultrasonic treatment for 30-40 minutes at an ultrasonic power of 300-500 W to obtain a nanocomposite functional filler dispersion. (3) Preparation of coating: Add fluorosilicone emulsion and water-based inorganic ceramics into the reactor in proportion and mix them evenly at a stirring speed of 500-800 r / min; then slowly add the nano-composite functional filler dispersion and continue stirring for 30-40 minutes; then add thickener, defoamer, film-forming aid, bactericide and pH regulator in sequence and stir at a speed of 800-1000 r / min for 20-30 minutes; finally add nano-scale SiO2 wear-resistant agent and stir for 15-20 minutes to obtain the initial coating; the initial coating is sand-milled with a sand mill to control the grinding particle size to 50-200 nm to obtain the finished radiant cooling coating; (4) Coating and curing: Use spraying or roller coating to evenly apply the coating on the surface of the pretreated aluminum veneer, and control the wet film thickness to be 60-100 μm; after coating, pre-cure it at 80 ° C for 30 minutes, and then fully cure it at 120 ° C for 60 minutes to form a radiant cooling coating with a dry film thickness of 30-50 μm.