Radiative cooling coating and method of making the same

Abstract

The present application relates to the technical field of radiative cooling, and particularly relates to a radiative cooling coating and a preparation method thereof. Embodiments of the present application provide a radiative cooling coating, which comprises a functional layer, wherein the functional layer comprises ceramic particles, and the particle size of the ceramic particles ranges from 0.2 to 2 microns. The present application provides a radiative cooling coating and a preparation method thereof, and the radiative cooling coating has a long service life and good effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiative cooling, in particular to a radiative cooling coating and a preparation method thereof. BACKGROUND

[0002] Radiative cooling is a passive cooling effect that does not require energy support. Radiative cooling requires a material to reflect visible light and radiate infrared light.

[0003] In the related art, the radiative cooling coating is a convenient and efficient use mode. In order to reflect visible light, the coating material is usually a semiconductor material with high refractive index. However, the band gap of the material with high refractive index is relatively narrow, and the ultraviolet absorption edge of the material moves to the visible band, and the ultraviolet absorption is higher. High ultraviolet absorption generates electron-hole pairs. The holes move freely in the semiconductor and can diffuse to the surface of the material, oxidize the adhesive, and cause the coating to oxidize and turn yellow, reducing the service life of the coating. The change of color affects the reflectivity of the coating, and further reduces the radiative cooling performance of the coating.

[0004] Therefore, there is an urgent need for a radiative cooling coating with long service life and good effect. SUMMARY

[0005] The embodiments of the present application provide a radiative cooling coating and a preparation method thereof, which can provide a radiative cooling coating with long service life and good effect.

[0006] In a first aspect, the embodiments of the present application provide a radiative cooling coating, comprising:

[0007] A functional layer, the functional layer comprising ceramic particles, the particle size of the ceramic particles being in a range of 0.2-2 microns.

[0008] In a possible design, in the ceramic particles, the mass ratio between the particles with a particle size of 0.2-0.5 microns, the particles with a particle size of 0.5-1 micron and the particles with a particle size of 1-2 microns is 1:2:1.

[0009] In a possible design, the ceramic particles comprise alumina particles.

[0010] In a possible design, the functional layer further comprises an inorganic adhesive.

[0011] In a possible design, a hydrophobic layer is arranged on the functional layer.

[0012] In a second aspect, the embodiments of the present application provide a preparation method of a radiative cooling coating, which is used to prepare any of the above radiative cooling coatings, and the preparation method comprises:

[0013] Mix ceramic particles with particle size ranging from 0.2 to 2 microns uniformly and coat on the material to be coated to obtain a functional layer.

[0014] In a possible design, the mass ratio between the 0.2-0.5 micron particles, the 0.5-1 micron particles and the 1-2 micron particles in the ceramic particles is 1:2:1.

[0015] In a possible design, the ceramic particles include alumina particles.

[0016] In a possible design, the mixing of the ceramic particles with particle size ranging from 0.2 to 2 microns uniformly and coating on the material to be coated includes:

[0017] Mix the ceramic particles with particle size ranging from 0.2 to 2 microns, inorganic adhesive and deionized water uniformly to obtain a suspension;

[0018] Coat the suspension on the material to be coated.

[0019] In a possible design, after the coating of the suspension on the material to be coated, further includes:

[0020] Dry the material to be coated coated with the functional layer;

[0021] Spray silicate adhesive uniformly on the dried functional layer, and obtain a hydrophobic preform after drying;

[0022] Soak the hydrophobic preform in a silane coupling agent solution with a hydrophobic group, and obtain a hydrophobic layer after drying and curing.

[0023] Compared with the prior art, the present application has at least the following beneficial effects:

[0024] By preparing the radiation cooling coating, the low ultraviolet band (0.25-0.4 microns) absorption, visible light band (0.3-1.35 microns) full reflection, and high radiation in the atmospheric window band (8-13 microns) are obtained, the heat absorption of the cooled medium is reduced, the heat radiation of the cooled medium is improved, and the purpose of passive cooling is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0026] Figure 1is a reflectivity graph of a coating in the ultraviolet-visible band provided by an embodiment of the present application;

[0027] Figure 2 is a reflectivity graph of a coating in the infrared band provided by an embodiment of the present application;

[0028] Figure 3 is a graph of the relationship between the scattering ability and the particle size of the alumina provided by an embodiment of the present application;

[0029] Figure 4 is a reflectivity comparison graph of a coating prepared by alumina particles and a coating prepared by titanium dioxide particles provided by an embodiment of the present application;

[0030] Figure 5 is a reflectivity comparison graph of coatings prepared by different mass ratios of multiple particle sizes provided by an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0032] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" means two or more; the terms "connection", "fixation" and the like should be understood in a broad sense, for example, "connection" can be fixed connection, can be detachable connection, or integrally connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0033] The embodiment of the present application provides a radiation cooling coating, which comprises:

[0034] The functional layer comprises ceramic particles, and the particle size of the ceramic particles ranges from 0.2 to 2 microns.

[0035] In the embodiment, the ceramic material with a particle size range of 0.2-2 μm is used to prepare the coating layer that reflects visible light and radiates infrared light, which can prevent the aging of the coating layer, increase the service life of the coating layer, and improve the performance of the coating layer. This is because the ceramic material has a wide band gap, low ultraviolet band absorption, can reduce the occurrence of electron-hole pairs, and prevent the aging of the coating layer caused by ultraviolet light. Although the ceramic material has excellent infrared radiation performance, the visible light reflectivity of the ceramic material is low. In order to improve the reflectivity of the ceramic material, the particle size of the ceramic material is limited to 0.2-2 μm. In this way, the multiple interfaces of multiple ceramic particles are superimposed and reflected, which effectively increases the reflectivity of the material in the visible band. The specific effects of the product are shown in Figure 1 and Figure 2 .

[0036] It should be noted that, as shown in Figure 3 , as the particle size increases, the scattering ability also increases, but after reaching a certain particle size, the improvement of the scattering ability slows down. Using ceramic particles with too large a particle size not only has limited improvement in the scattering ability of the material, but also leads to a decrease in the number of particles per unit volume, i.e., a decrease in the number of scatterers, which further leads to a decrease in the number of scattering cross sections, and thus affects the overall scattering ability. Therefore, only by limiting the particle size of the particles to 0.2-2 μm can a good scattering effect be achieved.

[0037] In some embodiments of the present application, the mass ratio between the 0.2-0.5 μm particles, the 0.5-1 μm particles, and the 1-2 μm particles in the ceramic particles is 1:2:1.

[0038] In the embodiment, experiments show that the mass ratio of different particle sizes also affects the performance of the material. In order to further improve the reflectivity of the material in the visible light band, the mass ratio of different particle sizes is limited to the above range. In this way, the particles of different particle sizes are combined according to the above mass ratio, which can increase the reflection effect. The samples made of the above three particle sizes with different mass ratios are tested, and the test results are shown in Figure 5 . In the figure, the mass ratios of the above three particle sizes are (a) 1:1:1; (b) 1:2:1; (c) 1:2:2; and (d) 1:2:3. According to Figure 5 , it can be seen that when the mass ratio of each particle size is 1:2:1, the product has the highest visible light reflectivity and the best effect.

[0039] In some embodiments of the present application, the ceramic particles include alumina particles.

[0040] In the embodiment, alumina particles are selected as the ceramic particles, which have the advantages of good performance, stable properties, and low cost. Of course, other ceramic particles, such as titanium dioxide, can also be selected. However, as shown inFigure 4 As shown in the figure, the titanium dioxide has poor reflectivity in the ultraviolet band, and when the titanium dioxide coating is irradiated by photons with energy less than the band gap width of the titanium dioxide, electrons are excited, holes are generated, and diffuse in the material. Water and organic matter on the interface or in the material adsorb the holes, and the hydrogen atoms in the water and organic matter are replaced to generate protons. The protons combine with the titanium dioxide, and Ti is easily changed from divalent to trivalent to generate titanium bronze, generate color centers, and cause the material to discolor, thereby reducing the reflectivity of the material.

[0041] In some embodiments of the present application, the functional layer further comprises an inorganic adhesive.

[0042] In the present embodiment, the inorganic adhesive is preferably a silicate adhesive. In the inorganic adhesive, there is no volatilization of organic small molecules, and the inorganic silicate adhesive is used, which has the advantages of being non-toxic, environmentally friendly, inexpensive and easy to obtain. The main body of the silicate adhesive is silicon dioxide, which has high emissivity in the infrared band, and at the same time as an inorganic adhesive, has higher light aging resistance in the ultraviolet band than organic adhesives.

[0043] In some embodiments of the present application, a hydrophobic layer is provided on the functional layer.

[0044] The inorganic coating often has poor moisture resistance and the structure is easily damaged when encountering water, so a hydrophobic layer is built on the inorganic coating to achieve water resistance, moisture resistance and self-cleaning effect. In addition, the present application can be uniformly dispersed without adding additives and is not prone to foaming.

[0045] The present application provides a preparation method of a radiative cooling coating, which is used for preparing any one of the above radiative cooling coatings, and the preparation method comprises the following steps:

[0046] The ceramic particles with a particle size range of 0.2-2 mu m are mixed and uniformly coated on the material to be coated to obtain a functional layer.

[0047] In some embodiments of the present application, in the ceramic particles, the mass ratio between the particles with a particle size of 0.2-0.5 mu m, the particles with a particle size of 0.5-1 mu m and the particles with a particle size of 1-2 mu m is 1:2:1.

[0048] In some embodiments of the present application, the ceramic particles comprise alumina particles.

[0049] In some embodiments of the present application, the ceramic particles with a particle size range of 0.2-2 mu m are mixed and uniformly coated on the material to be coated, which comprises the following steps:

[0050] The ceramic particles with a particle size range of 0.2-2 mu m, the inorganic adhesive and the deionized water are mixed and uniformly obtained to obtain a suspension;

[0051] The suspension is coated on the material to be coated.

[0052] In some embodiments of the present application, after the suspension is applied on the material to be coated, the following steps are further included:

[0053] The material to be coated with the functional layer is subjected to a drying process;

[0054] A silicate adhesive is uniformly sprayed on the dried functional layer, and a hydrophobic preform is obtained after drying;

[0055] The hydrophobic preform is soaked in a silane coupling agent solution with a hydrophobic group, and a hydrophobic layer is obtained after oven drying and curing.

[0056] In order to more clearly illustrate the technical solutions and advantages of the present application, the preparation method of a radiative cooling coating is described in detail below through several embodiments.

[0057] Embodiment 1

[0058] (1) Preparation of alumina suspension

[0059] Alumina powder and inorganic water glass adhesive are mixed with deionized water to prepare an alumina suspension. Among them, alumina: water glass: deionized water = 4g: 1ml: 3ml.

[0060] (2) The prepared suspension is uniformly dispersed on a magnetic stirrer for 2-3h to uniformly mix the alumina powder and the adhesive.

[0061] (3) The uniformly mixed suspension is uniformly sprayed on a clean aluminum sheet using a spray gun, and the spraying time is 1-2min.

[0062] (4) A uniform layer of adhesive is sprayed on the surface of the coating, and the coating is naturally dried at room temperature for 12h.

[0063] (5) The inorganic coating is soaked in a 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane solution in n-hexane (2wt%) for 24h, washed with ethanol three times, and cured in an oven at 150℃ for 2h.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A radiation cooling coating, characterized in that, include: The functional layer includes ceramic particles with a particle size ranging from 0.2 to 2 μm. The mass ratio of 0.2~0.5μm particles, 0.5~1μm particles and 1~2μm particles in the ceramic particles is 1:2:

1. The ceramic particles include alumina particles; The functional layer also includes an inorganic adhesive, which is a silicate adhesive.

2. The radiation cooling coating according to claim 1, characterized in that, A hydrophobic layer is provided on the functional layer.

3. A method for preparing a radiation-cooled coating, characterized in that, The method for preparing any one of the radiation-cooled coatings according to claims 1-2 includes: Ceramic particles with a particle size range of 0.2~2μm are mixed and uniformly coated onto the material to be coated to obtain a functional layer; The process of uniformly mixing and coating ceramic particles with a particle size range of 0.2~2μm onto the material to be coated includes: Ceramic particles with a particle size range of 0.2~2μm, inorganic adhesive, and deionized water are mixed evenly to obtain a suspension. The suspension is coated onto the material to be coated.

4. The method for preparing the radiation cooling coating according to claim 3, characterized in that, After coating the suspension onto the material to be coated, the method further includes: The material to be coated with the functional layer is dried. A silicate adhesive is uniformly sprayed onto the dried functional layer, and after drying, a hydrophobic preform is obtained. The hydrophobic preform is immersed in a silane coupling agent solution with hydrophobic groups, and then dried and cured to obtain a hydrophobic layer.

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