A band-selective infrared regulation and radiative cooling coating and a preparation method thereof

Abstract

The application discloses a waveband-selective infrared regulation and radiative cooling coating and a preparation method thereof. The coating comprises, from bottom to top, a reflective layer and a nanoparticle composite layer. The nanoparticle composite layer is composed of a dielectric constant near-zero ceramic nanoparticle mixed medium composite material. The preparation method comprises the following steps: (1) preparing a ceramic nanoparticle mixed solution; (2) depositing a metal reflective layer on a substrate; and (3) preparing a nanoparticle composite layer on the reflective layer. Compared with the prior art, the application has excellent waveband-selective infrared regulation and radiative cooling performance. The infrared emissivity of the coating is 0.79-0.82 in a 5-8 mu m non-atmospheric detection window, 0.11-0.16 in a 3-5 mu m atmospheric detection window, and 0.21-0.25 in an 8-14 mu m atmospheric detection window. The application realizes thermal radiation regulation through a simple double-layer structure, the material source is wide, the preparation method is simple, the preparation process is simple, and large-area and low-cost production can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of selective radiation heat control, and particularly relates to a waveband-selective infrared regulation and radiative cooling coating and a preparation method thereof, in particular to an infrared regulation and radiative cooling coating based on a dielectric constant near-zero ceramic and a preparation method thereof. BACKGROUND

[0002] With the continuous development of science and technology, various frequency band detection technology means emerge as the times require. Signal suppression technology occupies a pivotal position in modern warfare. Among them, the infrared suppression technology aims to suppress the infrared signal and minimize the difference with the background radiation, thereby reducing the probability of being discovered. According to the Stefan-Boltzmann law, the infrared characteristics of an object are proportional to the fourth power of its emissivity and surface temperature. Therefore, to achieve infrared suppression of the target object, two ways can be generally used: one is to reduce the surface temperature of the target, which is often achieved by heat insulation, heat dissipation or phase change of phase change materials; the other is to reduce the surface emissivity of the target. Among them, in order to reduce the infrared emissivity, some materials such as flaky powder, two-dimensional materials and super surfaces are proposed and applied. However, the low emissivity of the entire infrared waveband will hinder the outward heat dissipation, resulting in the accumulation of energy and causing thermal instability. Therefore, the traditional low emissivity material cannot meet the needs of suppressing infrared and heat dissipation. Based on this, researchers proposed the concept of ideal selective radiator, which is high broadband radiation covering the entire non-atmospheric window (5-8 μm), and low radiation in the atmospheric window (3-5 μm and 8-14 μm), which can achieve waveband-selective infrared regulation and radiative cooling.

[0003] In recent years, waveband-selective infrared regulation and radiative cooling coatings have emerged in an endless stream, and can be achieved by using metamaterials, photonic crystals and multilayer films. Generally, selective infrared emitter devices contain patterned metals and dielectrics or alternating stacks of metals and dielectrics. However, these structures are usually complex, requiring a system of more than 3 layers of films to achieve, and limiting their application in large areas and low-cost fields. For example, a spectral selective radiation infrared stealth material and preparation disclosed in publication No. CN111158069A, the spectral radiator is composed of high refractive index materials and low refractive index materials arranged alternately, the structure and process of the material are relatively complex, the number of film layers is more than 4-7 layers, the internal stress of the material increases, making the product prone to film peeling due to different thermal expansion coefficients and reducing performance. For example, a Ge2Sb2Te5-based infrared stealth and radiative heat dissipation film and a preparation method thereof disclosed in publication No. CN115747740A, which requires a four-layer structure, the plating process is complex and expensive, and it is difficult to produce in large quantities, which seriously limits its popularization and application in the market.

[0004] Therefore, it is urgent to explore a process using a simple structure and providing a large-area preparation to realize a coating with excellent waveband-selective infrared regulation and radiation cooling. SUMMARY

[0005] The present application aims to overcome the deficiencies of the prior art, and provides a waveband-selective infrared regulation and radiation cooling coating and a preparation method thereof, in particular to a coating with simple structure, low-cost large-area preparation, excellent waveband-selective infrared regulation and radiation cooling, based on a dielectric constant near-zero ceramic. The selective infrared regulation and radiation cooling coating of the dielectric constant near-zero ceramic realizes a wideband radiation cooling performance of 5-8 mu m based on the coupling effect of surface plasmons and dielectric constant near-zero mode. It has excellent compatible selective infrared regulation and radiation cooling characteristics, and is widely used, safe and reliable, with excellent radiation heat regulation performance. Only two layers of structure are used to realize excellent selective emission performance.

[0006] The object of the present application can be achieved by the following scheme:

[0007] The present application provides a waveband-selective infrared regulation and radiation cooling coating, which comprises a reflective layer and a nanoparticle composite layer on the reflective layer.

[0008] The reflective layer is an Al metal reflective layer, and the material of the nanoparticle composite layer comprises dielectric constant near-zero ceramic particles, a dielectric substrate and an adhesive resin. The mass ratio of the dielectric constant near-zero ceramic particles, the dielectric substrate and the adhesive resin is 0.1-1.2:0.2-1.2:0.02-0.03.

[0009] Further, the dielectric constant near-zero ceramic particles are Al-doped ZnO nanoparticles (AZO); the average particle size of the Al-doped ZnO nanoparticles is 20-25 nm, and the filling rate of the Al-doped ZnO nanoparticles in the dielectric substrate is 5-8%.

[0010] Further, the dielectric substrate comprises one or more of inorganic substances and organic substances; the inorganic substances comprise one or more of Al2O3 and ZnO, and the organic substances comprise one or more of PE, PVC and PMMA.

[0011] Further, the thickness of the nanoparticle composite layer is 1-1.2 mu m.

[0012] Further, the adhesive resin comprises PEO.

[0013] Further, the thickness of the Al metal reflective layer is 150-200 nm.

[0014] The cooling coating of the present application comprises a two-layer structure of Al and dielectric constant near-zero ceramic nanoparticle small ball mixed medium. The present application utilizes the bottommost Al metal layer to provide reflection, Al-doped ZnO nanoparticles (AZO) with dielectric constant near zero and plasmonic characteristics to provide broadband radiation performance of 5-8 mu m. The medium around the Al-doped ZnO nanoparticles provides higher plasmonic absorption. The selected medium material can be inorganic substances such as Al2O3 and ZnO, or organic substances such as PE, PVC and PMMA, so that appropriate materials can be selected according to requirements, thereby realizing flexible large-scale preparation and angle insensitivity in the full wave band. The non-atmospheric detection window radiation of 5-8 mu m is as high as 0.79-0.82, the 3-5 mu m atmospheric detection window infrared radiation is only 0.11-0.16, and the 8-14 mu m atmospheric detection window infrared radiation is only 0.21-0.25;

[0015] The present application also provides a preparation method of the above-mentioned wave band selective infrared regulation and radiation cooling coating, comprising the following steps:

[0016] S1, preparing a spin coating solution of dielectric constant near-zero ceramic particles

[0017] The medium substrate is prepared into a medium dispersion solution, dielectric constant near-zero ceramic particles are added, and then adhesive resin is added, so as to obtain the spin coating solution of dielectric constant near-zero ceramic particles;

[0018] S2, preparing an Al metal reflection layer

[0019] The reflection aluminum substrate is deposited on the substrate by magnetron sputtering, so as to obtain the Al metal reflection layer;

[0020] S3, preparing a wave band selective infrared regulation and radiation cooling coating (top layer ENZ nanocomposite thermal radiation regulator)

[0021] The obtained spin coating solution is prepared into a thin film on the Al metal reflection layer by a spin coating method, and then drying treatment is carried out, so as to obtain the wave band selective infrared regulation and radiation cooling coating.

[0022] Further, the use amount ratio of the medium to the solvent in the medium solution is 0.1-1.2 g:10 ml. The solvent is water.

[0023] Further, the substrate is a silicon wafer; the power of magnetron sputtering is 80-120 w, and the sputtering pressure is 0.5-0.6 Pa.

[0024] Further, the spin coating parameters are 1000-2000 rmp for 50-80 s.

[0025] Further, the drying treatment is: drying in an oven at 90-110 DEG C for 20-40 minutes, or annealing in a tube furnace at 450-550 DEG C for 2-3 hours.

[0026] The application adopts a metal reflection layer and a dielectric constant near zero nanoparticle mixed dielectric material system double-layer structure, can realize excellent waveband selective infrared regulation and radiation cooling performance; the emissivity in the 5-8 mu m non-atmosphere transparent window can reach 0.79-0.82, the infrared transmittance in the 3-5 mu m and 8-14 mu m infrared transparent window is 0.11-0.16 and 0.21-0.25 respectively.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] (1) The application utilizes the unique dielectric constant near zero effect of the dielectric constant near zero material, and couples the localized surface plasmon effect, realizes the wideband high emissivity in the 5-8 mu m non-atmosphere transparent window;

[0029] (2) The application reduces the number of layers and the total thickness of the film system, can avoid the stress mismatch film peeling problem caused by the different expansion coefficients of the materials at high temperature;

[0030] (3) The application can select the wide source of the dielectric material, cooperates the preparation method of spin coating, makes the preparation process simple, realizes the large-area low-cost production. BRIEF DESCRIPTION OF DRAWINGS

[0031] Other features, objects and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0032] Figure 1 It is a structure schematic diagram of the waveband selective infrared regulation and radiation cooling coating based on the dielectric constant near zero ceramic in the application; wherein 1-AZO nanoparticle, 2-dielectric substrate, 3-Al metal reflection layer. DETAILED DESCRIPTION

[0033] The application will be described in detail below in combination with the embodiments. The following embodiments will help the person skilled in the art to further understand the application, but do not limit the application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the application, a number of adjustments and improvements can be made. These all belong to the protection scope of the application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the application can be purchased from the market.

[0034] The design idea of the waveband-selective infrared regulation and radiative cooling coating based on the dielectric constant near-zero ceramic in the application is: the Al metal reflection layer is used to provide low infrared emissivity, and the dielectric constant near-zero effect and the localized surface plasmon resonance effect of the dielectric constant near-zero ceramic are used to realize high emissivity of a wide-band non-atmosphere transparent infrared window.

[0035] Embodiment 1

[0036] In this embodiment, a waveband-selective infrared regulation and radiative cooling coating based on the dielectric constant near-zero ceramic is prepared, and the specific preparation method is as follows:

[0037] Firstly, an AZO nanoparticle spin coating liquid is prepared: 0.8 g of Al2O3 is added to 10 ml of water, and stirred until uniformly dispersed, and 0.2 g of AZO nanoparticles is added to the Al2O3 solution, and 0.02 g of PEO is added to increase the adhesion of the slurry and improve the bonding force between the films.

[0038] Then, an Al metal reflection layer is prepared: the reflection aluminum substrate is deposited on a silicon wafer by magnetron sputtering, the power is 100 w, and the sputtering pressure is 0.5 Pa.

[0039] Finally, a double-layer ENZ nanocomposite thermal radiation regulator is prepared: the top ENZ nanocomposite structure is prepared by the spin coating method. Then, the AZO nanoparticle slurry obtained above is spin coated at 3000 rpm for 60 s to prepare a film, and then the film is annealed in a tube furnace at 500 DEG C for 2 hours.

[0040] The schematic diagram of the coating structure is shown in Figure 1 The coating structure is shown in the figure, which includes a nanoparticle composite layer and an Al metal reflection layer 3, and the nanoparticle composite layer is composed of a dielectric substrate 2, AZO nanoparticles 1 and adhesive resin. In this example, the thickness of the Al reflection layer is 200 nm, the radius of the dielectric constant near-zero ceramic nanoparticles is 25 nm, the filling rate is 6%, and the thickness of the top layer of dielectric constant near-zero ceramic nanoparticles mixed with Al2O3 dielectric is 1.2 μm.

[0041] In this embodiment, the 5-8 μm non-atmosphere detection window emissivity of the waveband-selective infrared regulation and radiative cooling coating is as high as 0.81, the 3-5 μm atmosphere detection window infrared emissivity is only 0.16, and the 8-14 μm atmosphere detection window infrared emissivity is only 0.21.

[0042] Embodiment 2

[0043] First, the AZO nanoparticle spin coating liquid was prepared: 1 g of PVC was added to 10 ml of water, stirred until uniformly dispersed, and 0.2 g of AZO nanoparticles was added to the PVC solution. In order to increase the adhesion of the slurry, 0.03 g of PEO was added to improve the bonding between the films.

[0044] Next, the Al metal reflection layer was prepared by depositing a reflective aluminum substrate on a silicon wafer by magnetron sputtering, with a power of 100 w and a sputtering pressure of 0.5 Pa.

[0045] Finally, the double-layer dielectric constant near-zero nano-composite thermal radiation regulator was prepared: the top ENZ nano-composite structure was prepared by the spin coating method. Then the AZO nanoparticle slurry obtained above was spin-coated at 1500 rpm for 60 s to prepare a thin film, which was then dried in a 100°C oven for 20 minutes.

[0046] In this example, the thickness of the Al reflection layer was 200 nm, the radius of the dielectric constant near-zero ceramic nanoparticles was 25 nm, the filling rate was 6%, and the thickness of the top layer of dielectric constant near-zero ceramic nanoparticles mixed with PVC medium was 1.2 μm.

[0047] The 5-8 μm non-atmospheric detection window emissivity of the band-selective infrared regulation and radiation cooling coating prepared in this example was as high as 0.82, the 3-5 μm atmospheric detection window infrared emissivity was only 0.12, and the 8-14 μm atmospheric detection window infrared emissivity was only 0.24.

[0048] Example 3

[0049] First, the AZO nanoparticle spin coating liquid was prepared: 1.2 g of PE was added to 10 ml of water, stirred until uniformly dispersed, and 0.2 g of AZO nanoparticles was added to the PE solution. In order to increase the adhesion of the slurry, 0.03 g of PEO was added to improve the bonding between the films.

[0050] Next, the Al metal reflection layer was prepared by depositing a reflective aluminum substrate on a silicon wafer by magnetron sputtering, with a power of 100 w and a sputtering pressure of 0.5 Pa.

[0051] Finally, the double-layer dielectric constant near-zero nano-composite thermal radiation regulator was prepared: the top ENZ nano-composite structure was prepared by the spin coating method. Then the AZO nanoparticle slurry obtained above was spin-coated at 2000 rpm for 60 s to prepare a thin film, which was then dried in a 100°C oven for 20 minutes.

[0052] In this example, the thickness of the Al reflection layer was 200 nm, the radius of the dielectric constant near-zero ceramic nanoparticles was 25 nm, the filling rate was 6%, and the thickness of the top layer of dielectric constant near-zero ceramic nanoparticles mixed with PVC medium was 1.2 μm.

[0053] The 5-8 pm non-atmospheric detection window emissivity of the band-selective infrared regulation and radiative cooling coating prepared in this embodiment is as high as 0.80, the 3-5 pm atmospheric detection window infrared emissivity is only 0.11, and the 8-14 pm atmospheric detection window infrared emissivity is only 0.23.

[0054] Example 4

[0055] First, the AZO nanoparticle spin coating solution was prepared: 0.3 g of ZnO was added to 10 ml of water, stirred until uniformly dispersed, and 0.2 g of AZO nanoparticles was added to the ZnO solution. In order to increase the adhesion of the slurry, 0.02 g of PEO was added to improve the bonding force between the films.

[0056] Then, the Al metal reflection layer was prepared. The reflective aluminum substrate was deposited on the silicon wafer by magnetron sputtering, with a power of 100 w and a sputtering pressure of 0.5 Pa.

[0057] Finally, the double-layer dielectric constant near-zero nano-composite thermal radiation regulator was prepared: the top ENZ nano-composite structure was prepared by spin coating. Then, the AZO nanoparticle slurry obtained above was spin-coated at 2000 rpm for 60 s to prepare a film, and then dried in an oven at 100°C for 20 minutes.

[0058] In this example, the thickness of the Al reflection layer is 200 nm, the radius of the dielectric constant near-zero ceramic nanoparticles is 25 nm, the filling rate is 6%, and the thickness of the top layer of dielectric constant near-zero ceramic nanoparticles mixed with ZnO medium is 1.2 pm.

[0059] The 5-8 pm non-atmospheric detection window emissivity of the band-selective infrared regulation and radiative cooling coating prepared in this embodiment is as high as 0.79, the 3-5 pm atmospheric detection window infrared emissivity is only 0.15, and the 8-14 pm atmospheric detection window infrared emissivity is only 0.25.

[0060] Example 5

[0061] First, the AZO nanoparticle spin coating solution was prepared: 0.3 g of ZnO was added to 10 ml of water, stirred until uniformly dispersed, and 0.2 g of AZO nanoparticles was added to the ZnO solution. In order to increase the adhesion of the slurry, 0.02 g of PEO was added to improve the bonding force between the films.

[0062] Then, the Al metal reflection layer was prepared. The reflective aluminum substrate was deposited on the silicon wafer by magnetron sputtering, with a power of 100 w and a sputtering pressure of 0.5 Pa.

[0063] Finally, the double-layer dielectric constant near-zero nanocomposite thermal radiation controller was prepared: the top layer ENZ nanocomposite structure was prepared by spin coating. Then the AZO nanoparticle slurry obtained above was spin coated at 1000 rpm for 60 s to prepare a thin film, and then dried in an oven at 100°C for 20 minutes.

[0064] In this example, the thickness of the Al reflective layer is 200 nm, the radius of the dielectric constant near-zero ceramic nanoparticles is 25 nm, the filling rate is 6%, and the thickness of the top layer dielectric constant near-zero ceramic nanoparticle mixed PMMA medium is 1.2 μm.

[0065] The 5-8 μm non-atmospheric detection window emissivity of the band-selective infrared regulation and radiation cooling coating prepared in this example is as high as 0.82, the 3-5 μm atmospheric detection window infrared emissivity is only 0.16, and the 8-14 μm atmospheric detection window infrared emissivity is only 0.25.

[0066] Comparative Example 1

[0067] A band-selective infrared regulation and radiation cooling coating was prepared in this comparative example, and the preparation method was basically the same as that of Example 1, except that the AZO nanoparticles were replaced with an equal amount of undoped ZnO.

[0068] The 5-8 μm non-atmospheric detection window emissivity of the band-selective infrared regulation and radiation cooling coating prepared in this example is as high as 0.53, the 3-5 μm atmospheric detection window infrared emissivity is 0.4, and the 8-14 μm atmospheric detection window infrared emissivity is only 0.45. Compared with Example 1, the stealth and radiation cooling effect is poorer.

[0069] Comparative Example 2

[0070] A band-selective infrared regulation and radiation cooling coating was prepared in this comparative example, and the preparation method was basically the same as that of Example 1, except that the nanoparticles in the spin coating liquid were all Al2O3, i.e. no AZO nanoparticles were added, and an equal amount of Al2O3 was used.

[0071] The 5-8 μm non-atmospheric detection window emissivity of the band-selective infrared regulation and radiation cooling coating prepared in this example is as high as 0.84, the 3-5 μm atmospheric detection window infrared emissivity is 0.82, and the 8-14 μm atmospheric detection window infrared emissivity is only 0.85. Compared with Example 1, there is no infrared stealth effect.

[0072] Comparative Example 3

[0073] A band-selective infrared regulation and radiation cooling coating was prepared in this comparative example, and the preparation method was basically the same as that of Example 4, except that the nanoparticles in the spin coating liquid were all ZnO.

[0074] The 5-8 μm non-atmospheric detection window radiation of the band-selective infrared regulation and radiation cooling coating prepared in the embodiment is as high as 0.32, the 3-5 μm atmospheric detection window infrared radiation is 0.34, and the 8-14 μm atmospheric detection window infrared radiation is only 0.61. Compared with the embodiment 1, the stealth and radiation cooling effect is poorer.

[0075] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be combined with each other in any way without conflict.

Claims

1. A band-selective infrared regulation and radiative cooling coating, characterized in that, The coating comprises a reflective layer and a nanoparticle composite layer on the reflective layer; the reflective layer is an Al metal reflective layer, and the material of the nanoparticle composite layer comprises near-zero dielectric constant ceramic particles, a dielectric substrate and adhesive resin; The near-zero dielectric constant ceramic particles are Al-doped ZnO nanoparticles with an average particle size of 20-25 nm; the filling rate of the Al-doped ZnO nanoparticles in the dielectric substrate is 5-8%. The dielectric substrate is an inorganic substance; the inorganic substance comprises one or more of Al2O3 and ZnO.

2. The band-selective infrared regulation and radiative cooling coating of claim 1, wherein, The thickness of the nanoparticle composite layer is 1-1.2 microns; and the thickness of the reflective layer is 150-200 nm.

3. The band-selective infrared regulation and radiative cooling coating of claim 1, wherein, The adhesive resin comprises PEO.

4. The band-selective infrared regulation and radiative cooling coating of claim 1, wherein, The 5-8 micron non-atmospheric detection window emissivity of the waveband-selective infrared regulation and radiation cooling coating is 0.79-0.82, the 3-5 micron atmospheric detection window infrared emissivity is 0.11-0.16, and the 8-14 micron atmospheric detection window infrared emissivity is 0.21-0.

25.

5. A method of making a band-selective infrared regulation and radiative cooling coating as claimed in claim 1, wherein, The method comprises the following steps: S1. Preparing a spin coating solution of near-zero dielectric constant ceramic particles The dielectric substrate is prepared into a dielectric dispersion liquid, the near-zero dielectric constant ceramic particles are added, and then the adhesive resin is added, to obtain the spin coating solution of the near-zero dielectric constant ceramic particles; S2. Preparing an Al metal reflective layer An Al metal reflective layer is prepared by depositing a reflective Al substrate on a substrate by magnetron sputtering; S3. Preparing a waveband-selective infrared regulation and radiation cooling coating The obtained spin coating solution is prepared into a thin film on the Al metal reflective layer by a spin coating method, and then subjected to drying treatment, to obtain the waveband-selective infrared regulation and radiation cooling coating.

6. The preparation method according to claim 5, characterized in that, The use amount ratio of the dielectric substrate to the solvent in the dielectric dispersion liquid is 0.1-1.2 g:10 ml.

7. The preparation method according to claim 5, characterized in that, The substrate is a silicon wafer; the power of the magnetron sputtering is 80-120 W, the sputtering pressure is 0.5-0.6 Pa, and the spin coating parameters are 1000-2000 rpm for 50-80 s.

8. The preparation method according to claim 5, characterized in that, The drying treatment is drying for 20-40 minutes in an oven at 90-110℃, or annealing for 2-3 hours in a tube furnace at 450-550℃.

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