CN113388305A - Radiation refrigeration composite coating with structural color, application and preparation method - Google Patents
Radiation refrigeration composite coating with structural color, application and preparation method Download PDFInfo
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Abstract
The invention discloses a radiation refrigeration composite coating with structural color, application and a preparation method thereof, wherein the radiation refrigeration composite coating comprises a base layer, reflective nanoparticles and color-forming nanoparticles, wherein the reflective nanoparticles and the color-forming nanoparticles are embedded in the base layer; wherein the reflection valley jointly realized by the broadband high reflection of the reflection nanoparticles and the local plasma resonance of the color-forming nanoparticles presents the structural color of the radiation refrigeration composite coating. The radiation refrigeration composite coating has strong reflection capability in a sunlight wave band (0.3-4 mu m), and the reflectivity in most sunlight wave bands is as high as 0.95. The emissivity of the material in an infrared band (4-24 mu m) can be continuously over 0.9, and the emissivity of the material in most infrared bands can be as high as 0.95. The invention can overcome the problem that the application occasion of the existing radiation refrigeration coating is limited due to single color, thereby having wide application prospect in the fields of building energy conservation, outdoor object and electronic product surface heat management and the like.
Description
Technical Field
The invention belongs to the field of nano-particles with spectral selectivity, and particularly relates to a radiation refrigeration composite coating with structural color, application and a preparation method thereof.
Background
With the development of modern society, the consumption and demand of human energy are increasing day by day. Energy problems have evolved to global problems. Meanwhile, the global demand for refrigeration is increasing due to the increasing global warming and greenhouse effect. The refrigeration process of active refrigeration equipment, such as air conditioners, fans and the like, inevitably has the problem of consuming a large amount of energy.
Radiation refrigeration is a passive refrigeration technology which realizes radiation heat exchange between an object and a low-temperature outer space and an external environment by covering an object with an infrared band (especially an atmospheric window band of 8-13 mu m and 16-24 mu m) high-emissivity structure, so as to cool the object. The technology has wide development and application prospect as a spontaneous refrigeration technology without consuming any energy. The method can be applied to the fields of building energy conservation, electronic device heat dissipation, outdoor object surface heat management, photovoltaic cell cooling and the like. Currently, radiation refrigeration is divided into daytime radiation refrigeration and nighttime radiation refrigeration, and compared with nighttime radiation refrigeration, the daytime radiation refrigeration also needs to consider the problem of absorption of solar radiation energy, so that the daytime radiation refrigeration is more difficult to realize. The daytime radiation refrigeration technology requires that an object has high emission characteristics in an infrared band of 4-24 mu m, and also requires that the object has high reflection characteristics in a sunlight band of 0.3-4 mu m to reduce absorption of solar radiation energy and ensure refrigeration effect. However, due to the performance requirement of high reflectivity of sunlight wave band, almost all daytime radiation refrigeration structures are white or silver in color, and the application space is limited to a great extent by the monotonicity of the color. For example, patent CN 105348892A-a radiation refrigeration double-layer nano coating and the coating structure provided in the preparation method thereof, although have good radiation refrigeration effect, the structure can only present single white color due to the high reflection characteristic of the structure in the full visible light band.
Recently, researchers try to solve the problem of color unity of radiation refrigeration structures by means of doping of absorptive dyes, the studied structures can present vivid colors, but the absorption characteristics of the absorptive dyes on visible light can cause that most of the structures cannot realize radiation refrigeration below the ambient temperature due to too high solar radiation energy absorption, and the color formation of the dyes has the problems of poor stability, easy fading and the like.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a radiation refrigeration composite coating with structural color, application and a preparation method thereof. The radiation refrigeration composite coating can realize large-scale preparation, solves the problem that the application space of the conventional radiation refrigeration structure is limited due to single color, and simultaneously solves the problems that the conventional pigment color-forming radiation refrigeration structure is poor in color-forming stability, easy to fade and low in refrigeration effect.
In order to achieve the above object, the present invention is achieved by the following aspects:
the radiation refrigeration composite coating with structural color is composed of PMMA resin with the thickness of 2mm, embedded randomly distributed reflection nanoparticles for reflecting sunlight and color-forming nanoparticles for presenting the structural color.
The radiation refrigeration composite coating adopts PMMA resin as a dielectric material, and PMMA resin is used as a common coating, so that the radiation refrigeration composite coating has the advantages of low price and suitability for large-scale preparation. The millimeter PMMA resin has good transparency in the main radiation wave band of 0.3-2.5 mu m of sunlight and excellent emission characteristic in the infrared wave band of 4-15 mu m.
Wherein the reflective nanoparticles are rutile TiO2、Zr2O3、Y2O3One or more of the above (B), the particle size range is 200-500 nm, and the volume fraction is 5-10%.
Preferably, the reflective nanoparticles are rutile TiO2Rutile TiO2Is a high-refractivity material, namely TiO of hundred nanometers2The particles have strong scattering property to sunlight with the diameter of 0.5-4 mu m, so the particles can be used as a good sunlight reflector. Final determination of rutile TiO2The particle diameter is 400 nm.
Wherein the structural color property is realized by TiO2@ Ag core-shell structure nanoparticle, pure Ag nanoparticle and TiO2One or more of @ Au core-shell structure nanoparticlesSeveral implementations are provided. In a PMMA resin medium, the color-forming nanoparticles can generate Local Surface Plasmon Resonance (LSPR) in a visible light waveband, so that the color-forming nanoparticles have good dipole characteristics and narrow-band absorption characteristics, a narrow-band absorption peak is formed in a specific waveband in a 0.5-2.5 mu m broadband high reflection peak generated by reflecting nanoparticles, and the structure presents structural color by absorbing light in the specific waveband.
Preferably, TiO is selected2And one of the @ Ag core-shell structure nano-particles and the pure Ag nano-particles is used as the color-forming nano-particles. Wherein, TiO2The dimension design of the @ Ag core-shell structure nano-particles takes the generation of absorption efficiency peaks in a 550nm (green light) band and a 600nm (red light) band as a target, and the absorption efficiency peaks are determined by Mie theoretical calculation. The TiO is2The internal and external diameter size ratio of the @ Ag core-shell structure is 1: 1.7 and 1: 1.5. the size of pure Ag nanoparticles was designed with the aim of generating absorption efficiency peaks in the 450nm (blue) band, determined by Mie theory (Mie scattering theory) calculations. The diameter of the pure Ag nano-particles is 30 nm.
Wherein the size ratio of the inner diameter to the outer diameter is 1: 1.7 TiO2The @ Ag core-shell structure nano-particles are absorbed by a narrow band corresponding to a green light wave band, so that the structure presents a light purple red (Magenta) structural color. The size ratio of the inner diameter to the outer diameter is 1: 1.5 TiO2The @ Ag core-shell structure nano-particles are corresponding to narrow-band absorption of a red light wave band, so that the structure presents light Cyan (Cyan) structural color. The absorption of pure Ag nanoparticles with a diameter of 30nm corresponding to a blue light wave band enables the structure to be in a light Yellow structural color.
Wherein the radiation refrigeration effect of the composite coating is not impaired too much in order to allow absorption of additional solar energy by colored absorption peaks. Preferably, TiO is added2The volume fraction of the @ Ag core-shell structure nano-particles is set to be 0.001%, the size of the nano core-shell structure for presenting a light purple structural color is 20nm/34nm (inner diameter/outer diameter), and the size of the nano core-shell structure for presenting a light cyan structural color is 40nm/60nm (inner diameter/outer diameter); the volume fraction of pure Ag nanoparticles was set to 0.002%, rutile TiO2The volume fraction of the particles is set to 10%, and the composite coating is preferably a coating which can exhibit a subtractive methodRadiation refrigeration composite coating with three primary color structural colors.
The overall reflection capacity of the optimized composite coating in a sunlight wave band (0.3-4 mu m) can reach 85.33% -86.33%, and the reflectivity of the optimized composite coating in most sunlight wave bands can reach more than 0.9. The emissivity of the material in an infrared band (4-24 mu m) can be continuously over 0.9, and the emissivity of the material in most infrared bands can be as high as 0.95.
The reflectance refers to a weighted average of spectral reflectances in the solar wavelength band (the weight function is the spectral irradiation intensity of solar light), that is, an average reflectance.
It will be understood by those skilled in the art that with respect to most infrared bands and most solar bands, it is meant that the spectral emissivity and spectral reflectance of the coating are greater than 0.9 and 0.95 at multiple wavelengths (the spectral radiance parameter integrated over wavelength as we generally speak of radiance parameters such as emissivity, absorptivity, etc.), as can be clearly seen from the emissivity curve of fig. 2.
The preferred composite coating can present three subtractive primary structural colors of light purple (Magenta), light Cyan (Cyan) and light Yellow (Yellow), and the color coordinates (x, Y) in the CIE1931 chromaticity diagram are Magenta (0.32, 0.31, 81.05), Cyan (0.30, 0.33, 87.48) and Yellow (0.33, 0.36, 92.64), respectively.
It should be noted that the light cyan, the light purple red and the light yellow are three subtractive primary colors, the three structural colors are realized by a composite coating only containing a nano core-shell structure, and after the different color forming particles are mixed in pairs in different proportions, the composite coating can also present three structural colors of light red, light green and light purple.
That is, the composite coating may exhibit three structural colors of light Red (Red), light Green (Green), and light purple (Lilac) by mixing different color forming nanoparticles. When the size ratio of the inner diameter to the outer diameter is 1: 1.7 TiO2When the @ Ag nano particles are mixed with pure Ag nano particles with the particle size of 30-50 nm, the composite coating can absorb part of blue light and green light, so that the structure is light red. When in useThe size ratio of the inner diameter to the outer diameter is 1: 1.5 TiO2When the @ Ag nano-particles are mixed with pure Ag nano-particles with the particle size of 30-50 nm, the composite coating can absorb part of blue light and red light, so that the structure is light green. When the size is 1: 1.5 and 1: 1.7 of two TiO species2When the @ Ag nano particles are mixed, the composite coating can absorb a small part of green light and red light, and TiO is used2The structure is light purple due to the slight absorptivity of short-wave-band visible light and the preposed requirements of sub-environment temperature radiation refrigeration. On the basis of ensuring that the coating can radiate and refrigerate, a plurality of different structural colors can be presented by mixing the color-forming nano particles with different volume fractions.
Wherein the theoretical net radiation refrigeration power of the preferred radiation refrigeration composite coating capable of presenting the subtractive primary colors is 26.98W/m2～36.31W/m2. Can realize the reduction of 3-4.2 ℃ compared with the environmental temperature of 30 ℃.
Wherein the theoretical net radiation refrigeration power of the plurality of radiation refrigeration composite coatings capable of presenting three structural colors of light green, light red and light purple is 0W/m2～34W/m2。
Specifically, the theoretical net radiant refrigeration power is 0W/m2～56W/m2The optimized composite coating (containing a nano core-shell structure with one size, the volume fraction of the core-shell structure is 0.001%/0.002%, and the volume fraction of rutile particles is 10%) with subtractive primary colors can realize the cooling effect of reducing the temperature by 3-4.2 ℃ compared with the ambient temperature of 30 ℃.
In fact, the core-shell structure with one size can only present one absorption peak, so that only three primary colors of subtraction can be presented, and the refrigeration power of the core-shell structure is 26.98-36.31W/m of the original refrigeration power2
The structural colors of light purple (different from light purple red), light red and light green are mixed by two core-shell structures with different sizes, so that the increase of the reflection dip causes the increase of the solar radiation absorption amount, which is why the radiation refrigeration coatings of the three colors have lower refrigeration power than the radiation refrigeration coatings of the three subtractive primary colors.
It should be noted that, in practice, a structure which can make both the color forming effect and the cooling effect relatively moderate is selected as an example of the patent within the given size parameter range, and the contents of the parts such as the spectrum curve, the cooling power calculation and the like are given.
In addition, the invention also provides a preparation method of the radiation refrigeration composite coating, and the radiation refrigeration composite coating is prepared by a solution method. Specifically, acetone or chloroform can be used as a solvent to dissolve a matrix material PMMA, then the reflection nanoparticles and the color-forming nanoparticles with specific volume fractions are added, the uniform dispersion of the nanoparticles is realized by a physical dispersion method and an ultrasonic dispersion method, and finally, the required radiation refrigeration composite coating is obtained by drying and volatilizing the solvent. Drying can be carried out, for example, using: spin coating or vacuum drying.
Compared with the prior art, the invention has the following beneficial effects:
the radiation refrigeration composite coating with structural color realizes that the structure presents structural color through a spectrum absorption peak on the basis of ensuring the radiation refrigeration effect through the LSPR effect of the nano core-shell structure/nano metal particles, the strong scattering property of rutile particles to sunlight and the high infrared emission property of PMMA resin. Compared with the conventional radiation refrigeration structure, the composite coating can present various colors, and the problem of limited application space caused by single color of the conventional radiation refrigeration structure is solved. Compared with a pigment color-forming radiation refrigeration structure, the composite coating forms colors through the reflection structure, and has the great advantages of high color-forming stability and fastness in various environments. Meanwhile, the composite coating has low requirement on the accuracy of the structure thickness, and is suitable for large-scale preparation.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic structural view of a radiation-cooled composite coating having a structural color according to the present invention;
FIG. 2 is a graph of emissivity of the preferred radiation refrigeration composite coating showing three subtractive primary colors in a full waveband (0.3-24 μm);
FIG. 3 is a graph comparing reflectance curves of visible light bands of the preferred radiation refrigeration composite coating layer exhibiting three subtractive primary colors and a radiation refrigeration structure of pure rutile particles without a core-shell structure;
FIG. 4 is a color coordinate of a subtractive primary structural color and corresponding structural color in CIE1931 chromaticity space exhibited by the preferred composite coatings;
FIG. 5 is a theoretical diurnal radiant cooling power curve for the preferred radiant cooling composite coating exhibiting subtractive primary colors;
fig. 6(a) -6 (c) show various structural colors and corresponding net cooling power which can be presented by the composite coating on the basis of realizing radiation cooling.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
In the invention, a radiation refrigeration composite coating with structural color is composed of PMMA resin with the thickness of 2mm, embedded reflection nanoparticles which are randomly distributed and used for reflecting sunlight and color-forming nanoparticles used for presenting the structural color. Preferably, rutile TiO is selected2The particles are used as reflective nanoparticles, TiO is selected2And one of the @ Ag core-shell structure nano-particles and the pure Ag nano-particles is used as the color-forming nano-particles. Among these, in a preferred composite coating that can present subtractive primary colors: rutile TiO22The particle diameter is 400nm, the volume fraction is 10%, and the particle is used for reflecting sunlight of 0.3-2.5 mu m. TiO22The @ Ag core-shell structure had a volume fraction of 0.001% and sizes of 20nm/34nm (inner diameter/outer diameter, which is expressed as diameter,while the radial dimension is shown in fig. 2 and 3) and 40nm/60nm (inner diameter/outer diameter, it should be noted that the diameter is shown here, while the radial dimension is shown in fig. 2 and 3); the pure Ag nano-particles have the volume fraction of 0.002 percent and the diameter of 30 nm. Three types of nanoparticles are used to present subtractive primary colors, respectively. The reflection capacity of the preferred radiation refrigeration composite coating with structural color in the sunlight wave band reaches 85.33% -86.33%, and the reflection capacity in most sunlight wave bands reaches 95%. The emissivity of the material in an infrared band (4-24 mu m) can be continuously over 0.9, and the emissivity of the material in most infrared bands can be as high as 0.95. Meanwhile, the absorption peaks generated by the LSPR effect of the preferred composite coating layer can present subtractive primary structural colors of light purple red (0.32, 0.31, 81.05), light cyan (0.30, 0.33, 87.48) and light yellow (0.33, 0.36, 92.64). By mixing the nano-particles with different colors, three structural colors of light red, light green and light purple can be presented. On the basis of presenting the structural color, the composite coating can also maintain better radiation refrigeration performance, and when the structure is the same as the environment temperature of 30 ℃, the net radiation refrigeration power of the three preferable structures is 26.98W/m2～36.31W/m2. When the net refrigerating power is 0, the three composite coatings can reduce the environmental temperature by 3-4.2 ℃ compared with the environmental temperature of 30 ℃. On the basis of ensuring the radiation refrigeration capacity, more structural colors can be presented by adjusting the volume fraction of the color-forming nano particles and the proportion of different color-forming nano particles. The composite coating has low requirement on the accuracy of the structure thickness, and is suitable for large-scale preparation. The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a schematic structural view of a radiation-cooled composite coating having a structural color according to the present invention.
As shown in fig. 1, the composite refrigeration radiation refrigeration composite coating according to the present invention includes a base layer, and reflective nanoparticles and color-forming nanoparticles embedded in the base layer; wherein the reflection valleys, which are jointly realized by broadband high reflection of the reflective nanoparticles and localized plasmon resonance (LSPR) of the color forming nanoparticles, represent the structural color of the radiation cooling composite coating.
The base layer is 2mm PMMA resin, and randomly distributed reflection nanoparticles for reflecting sunlight and color-forming nanoparticles for presenting structural colors are embedded in the PMMA resin, wherein the reflection nanoparticles can adopt rutile TiO2The particles act as reflective nanoparticles for reflecting solar radiation energy. At the same time, the coating passes through the base PMMA and rutile TiO layers2Infrared radiant energy is emitted. TiO is selected as the color-forming nano-particles2And one of the @ Ag core-shell structure nano-particles or the pure Ag nano-particles is taken as the color-forming nano-particles.
FIG. 2 is a graph of emissivity of the preferred radiation refrigeration composite coating showing three subtractive primary colors in a full waveband (0.3-24 μm). Wherein the absorption rate A of 0.3-2.5 μm is obtained by solving the RTE equation directly by adopting a Monte Carlo method (MC method). The absorptivity A of 4-24 mu m is calculated by adopting an Equivalent Medium Theory (EMT) and a Transmission Matrix Method (TMM) together to obtain the reflectivity R and the transmissivity T of the composite coating, and the absorptivity is calculated according to the structure with energy conservation: a is 1T-R. And finally, obtaining an emissivity curve of the composite coating in a 0.3-24 mu m waveband, wherein the absorptivity is equal to the emissivity ratio epsilon-A according to kirchhoff's law.
In the figure 2, Solar irradiance refers to Solar irradiance, Atmospheric Transmittance refers to Atmospheric Transmittance, TiO2@ Ag ri/ro:20nm/30nm refers to TiO serving as color-forming nano particles adopted in the radiation refrigeration composite coating2A @ Ag core-shell structure with a volume fraction of 0.001% and a size of 20nm/30nm (inner radius/outer radius); the TiO2@ Ag ri/ro is 10nm/17nm, which means that the color-forming nano particles adopted in the radiation refrigeration composite coating are TiO2The @ Ag core-shell structure has the volume fraction of 0.001% and the size of 10nm/17nm (inner radius/outer radius).
And Plain Ag r is 15nm, which means that the color-forming nano-particles adopted in the radiation refrigeration composite coating are pure Ag nano-particles, the volume fraction of the color-forming nano-particles is 0.002%, and the radius of the color-forming nano-particles is 15 nm.
Wherein, the calculation result shows that the three preferable radiation refrigeration composite coatings (namely, the adopted color-forming nano particles are one of the following TiO: the2Core-shell structure of @ AgThe integral fraction is 0.001%, and the sizes are respectively 20nm/30nm (inner radius/outer radius) and 10nm/17nm (inner radius/outer radius); the pure Ag nano-particles have the volume fraction of 0.002 percent and the diameter of 15 nm. ) The infrared radiation film has extremely high emissivity in the whole infrared band, and can be kept above 0.9 all the time. In the sunlight wave band of 0.3-1.5 microns, the emissivity of the three preferable composite coatings is below 0.1 except the wave band generated by the LSPR effect, and in the sunlight wave band of 1.5-4 microns, the emissivity of the composite coating is increased due to the intrinsic absorptivity of the PMMA resin medium, but the absorption of the wave band does not cause great influence on the radiation refrigeration effect due to the low sunlight irradiation intensity of the wave band.
Wherein the integral reflection capacity to the solar wave band
Can be determined according to the formula:
is obtained by calculation, wherein IAM1.5(lambda) is the intensity of direct solar radiation, A (lambda, theta)Sun) The absorption rate of the composite coating to sunlight at normal incidence, wherein lambda represents the wavelength of the incident sunlight, and thetaSunRepresenting the angle of incident sunlight to the surface normal direction of the composite coating. The calculation result shows that the three optimized composite coatings designed by the invention have integral sunlight reflection capacity
Can reach 85.33 to 86.33 percent.
Fig. 3 is a graph comparing the reflectance curves of the preferred radiation refrigeration composite coating exhibiting three subtractive primary colors with the visible light band of a pure rutile particle radiation refrigeration structure without a core-shell structure (i.e., pure rutile TiO2 system in fig. 1). Wherein I, II, and III in FIG. 3 respectively represent
And
representing the color matching function in CIE1931 XYZ chromaticity space. The calculation result shows that due to the LSPR effect, compared with the radiation refrigeration structure of pure rutile particles with the same thickness and without a core-shell structure, the three composite coatings comprise: containing TiO2The reflectivity curves of the coating of the @ Ag core-shell structure nano-particles have reflection valleys at the wavelength band of 550nm and the wavelength band of 600nm respectively; due to rutile TiO2Due to the self-short-waveband visible light absorption characteristic, the pure Ag nano particles with absorption coefficient peaks at about 450nm do not cause reflection valleys, but show the whole weakness on the reflectivity curve of 400 nm-500 nm waveband. The selective absorption of the composite coating to specific bands of visible light allows it to exhibit structural color.
FIG. 4 is the color coordinates of the subtractive primary structural colors and corresponding structural colors exhibited by the preferred composite coatings in the CIE1931 xyY chromaticity diagram. Wherein, the color coordinates (x, Y) and the color brightness Y in the CIE1931 xyY chromaticity diagram can be calculated according to the formula:
obtained by calculation, wherein R (lambda) is the reflectivity of the composite coating in a wave band of 0.36-0.83 mu m, D65 (lambda) is the spectral energy distribution of a D65 artificial sunlight source,
and
representing the color matching function of CIE1931 XYZ chromaticity space, k being a normalization coefficient. X, Y and Z represent tristimulus values of the reflection spectrum corresponding to the colors in the CIE1931 XYZ chromaticity space, the size of the tristimulus values corresponding to the size of the components that make up the three hypothetical standard primary colors X (red), Y (green), and Z (blue) of the corresponding color. And finally, carrying out normalization processing on the tristimulus values to obtain the color coordinates (x, y) of the colors corresponding to the reflection spectrums in the CIE1931 xyY chromaticity diagram, wherein the normalization inevitably has a relation z of 1-x-y, so that in the two-dimensional CIE1931 xyY chromaticity diagram, the positions of the corresponding colors can be determined only by two coordinates of x and y. Meanwhile, in the CIE1931 xyY chromaticity diagram, the luminance value Y of a color is the same as the Y value in the corresponding color tristimulus value, and thus, the luminance value Y and the Y value are represented by the same symbol.
The calculation result shows that the composite coating can present light purple red (Magenta), light Cyan (Cyan) and light Yellow (Yellow), namely, subtractive primary structural colors, and the color coordinates (x, Y) in the CIE1931 chromaticity diagram are Magenta (0.32, 0.31, 81.05), Cyan (0.30, 0.33, 87.48) and Yellow (0.33, 0.36, 92.64), respectively. And any color in a triangle formed by the color coordinates of the three colors can be prepared by mixing the three types of nano particles.
Fig. 5 is a theoretical diurnal radiant cooling power curve for the preferred radiant cooling composite coating exhibiting the subtractive primary colors. Net radiation refrigeration power P of composite coatingnetCan be determined according to the formula:
Pnet＝Prad-Patm-Psum-Pconv
Pconv＝hc(Tatm-TS)
is obtained by calculation, wherein theta and
the zenith angle and the azimuth angle in the spherical coordinate system are respectively, and meanwhile, theta can also represent the angle of incident light. PradRadiant energy, P, emitted outwardly of said composite coatingatmIs the atmospheric radiant energy absorption, P, of said composite coatingsunSolar energy absorption, P, for said composite coatingconvThe composite coating absorbs extra energy caused by heat transfer processes such as heat conduction and convection. T isatmThe temperature was set to 30 ℃ (303K), TSIs the surface temperature, epsilon, of the composite coatingatm(λ, θ) is the atmospheric emissivity, ε (λ, θ) is the emissivity of the composite coating, Ibb(TSλ) is the blackbody direction spectral radiation intensity of the composite coating, Ibb(TatmAnd lambda) is the spectral radiation intensity in the black body direction of the atmospheric environment. h iscFor the heat transfer coefficient of the additional convection heat conduction process, the natural air convection condition is considered, hcIs set to 4W/(m)2·K)。
Wherein, the calculation result shows that the theoretical net radiation refrigeration power of the radiation refrigeration composite coating with the structural color is 26.98W/m respectively2(Magenta)、30.86W/m2(Cyan) and 36.31W/m2(Yellow). The reduction of 3 deg.C (Magenta), 3.6 deg.C (Cyan) and 4.2 deg.C (Yellow) from 30 deg.C can be achieved.
Fig. 6(a) -6 (c) show various structural colors and corresponding net cooling power which can be presented by the composite coating on the basis of realizing radiation cooling. In fig. 6(a), the ratio of the inner diameter to the outer diameter is 1: 1.7 TiO2And mixing the @ Ag nano particles with pure Ag nano particles with the particle size of 30-50 nm under different volume fractions to enable the composite coating to have the structural color. The mixing of the two color-forming nano particles can make the structure show light red, and the net radiation refrigeration power of the light red structure is 2W/m2～32W/m2Within the range of (1). Fig. 6(b) shows the ratio of the inner diameter to the outer diameter of 1: 1.5 TiO2And mixing the @ Ag nano particles with pure Ag nano particles with the particle size of 30-50 nm under different volume fractions to enable the composite coating to have the structural color. The mixing of the two color-forming nano particles can make the structure present light green, and the net radiation refrigeration power of the light green structure is 0W/m2～34W/m2Within the range of (1). Fig. 6(c) shows the ratio of the inner diameter to the outer diameter of 1: 1.5 and 1: the two TiO2@ Ag nanoparticles of 1.7 were mixed at different volume fractions to give the composite coating the structural color it exhibited. The mixing of the two color-forming nano particles can make the structure show light purple, and the net radiation refrigeration power of the light purple structure is 0W/m2～26W/m2Within the range of (1).
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. A radiation refrigeration composite coating with structural color is characterized in that: the radiation refrigeration composite coating comprises a base layer, and reflective nano-particles and color-forming nano-particles which are embedded in the base layer;
wherein the reflection valley jointly realized by the broadband high reflection of the reflection nanoparticles and the local plasma resonance of the color-forming nanoparticles presents the structural color of the radiation refrigeration composite coating.
2. The radiation cooled composite coating of claim 1, wherein the base media is PMMA resin.
3. The radiation refrigeration composite coating of claim 1, wherein the thickness of the radiation refrigeration composite coating is 0.5-2 mm.
4. The radiation-cooled composite coating of claim 1, wherein the reflective nanoparticles comprise TiO2、Zr2O3、Y2O3The particle size range of the reflective nanoparticles is 200-500 nm, and the volume fraction of the reflective nanoparticles accounts for 5-10% of the radiation refrigeration composite coating.
5. The radiation-cooled composite coating of claim 1, wherein the color-forming nanoparticles comprise TiO2@ Ag core-shell structure nano-particles and SiO2@ Ag core-shell structure nanoparticle, pure Ag nanoparticle and TiO2One or more of the @ Au core-shell structure nanoparticles; the particle size range of the color-forming nano particles is 30-60 nm, and the volume fraction of the color-forming nano particles in the radiation refrigeration composite coating is 0.0005-0.002%.
6. The radiation-cooled composite coating of claim 5, wherein when the color-forming nanoparticles are TiO2In the case of @ Ag core-shell structured nanoparticles, TiO2The internal and external diameter size ratio of the @ Ag core-shell structure nanoparticles is set to be 1: (1.5 to 1.7);
when the color-forming nanoparticles are SiO2When the @ Ag core-shell structure nano-particles are adopted, the SiO2The internal and external diameter size ratio of the @ Ag core-shell structure nanoparticles is set to be 1: (1.2-1.5);
when the color-forming nanoparticles are pure Ag nanoparticles, the diameter of the pure Ag nanoparticles is set to be 30-50 nm.
7. The radiation refrigeration composite coating according to any one of claims 1 to 6, wherein the average reflectivity of the radiation refrigeration composite coating in the solar band is 0.8533-0.8633;
the emissivity of the radiation refrigeration composite coating in an infrared band is more than or equal to 0.9;
wherein the solar wave band is 0.3-4 μm; the infrared band is 4-24 μm.
8. A radiation refrigerating composite coating according to any one of claims 1-6, characterised in that the structural colours include light red, light green and light purple.
9. Use of a radiation-cooled composite coating having a structured color according to any one of claims 1 to 8, wherein the radiation-cooled composite coating, when used for radiation cooling, has a theoretical net radiation cooling power of 26.98W/m2～36.31W/m2The refrigerating temperature is reduced by 3-4.2 ℃ compared with the ambient temperature of 30 ℃.
10. A method of making a radiation-cooled composite coating according to any one of claims 1 to 8, wherein the radiation-cooled composite coating is made by a solution process.
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