Variable-emissivity radiation refrigeration device with flexible grating structure and preparation method of variable-emissivity radiation refrigeration device

Abstract

The invention provides a variable-emissivity radiation refrigeration device with a flexible grating structure and a preparation method of the variable-emissivity radiation refrigeration device. The variable-emissivity radiation refrigeration device comprises a metal reflecting layer, a substrate, a grating structure layer and a VO2 phase change layer, the metal reflecting layer, the substrate, the grating structure layer and the VO2 phase change layer are sequentially arranged from bottom to top; the grating structure layer is of a rectangular groove structure obtained by etching the surface of the substrate by a preset depth. The method has good substrate applicability, bending performance and operability, and compared with a multilayer film design and preparation technology, the technical method for etching the grating is simpler, more convenient and more efficient to operate.

Description

Technical Field

[0001] The present invention relates to the field of radiation cooling technology, and in particular to a flexible grating structure variable emissivity radiation cooling device and a preparation method thereof, in particular to a preparation method of a variable emissivity radiation cooling device with a flexible grating structure. Background Art

[0002] Traditional gas compression refrigeration not only consumes a lot of energy, but also causes great damage to the environment, exacerbating global warming. Therefore, it is urgent to find a new refrigeration technology that is less energy-consuming and environmentally friendly. Radiative refrigeration is a passive, zero-energy, reusable green refrigeration technology that radiates the heat of an object into deep space in the form of electromagnetic waves to achieve the goal of refrigeration through radiation heat exchange. It has great development prospects in the future.

[0003] Normally, objects mainly absorb solar energy in the 0.3um to 2.5um band, and radiate their own energy to deep space through the "atmospheric window" in the 8um to 13um band. Radiative cooling mainly makes objects highly reflective in the 0.3um to 2.5um solar band to minimize solar radiation absorption; and has high emissivity in the 8um to 13um infrared band to enhance its own infrared radiation, thereby reducing the temperature of the object itself.

[0004] VO2 is a phase change material that changes with temperature. When the temperature is below the phase change temperature of 68°C, it is in the monoclinic phase with high infrared transmittance. When the temperature is above the phase change temperature of 68°C, it is in the rutile phase with high infrared reflectivity. Since 68°C is the phase change temperature point, which is closest to the actual spacecraft operating temperature range, VO2 phase change materials can be well applied to spacecraft intelligent thermal control through reasonable structure and composite design of film layers, increasing the multi-scenario use, adjustability and intelligence of spacecraft thermal control.

[0005] According to the principle of radiation cooling, a glass-type secondary surface mirror is a typical radiation cooling device, with a quartz material as the substrate as the infrared radiation layer and a silver-plated layer on the bottom as the solar reflection layer. If we want to further improve the radiation cooling capacity of glass-type secondary surface mirrors, most of the research focuses on the device film system design. For example, Fan et al. introduced a radiation cooling device that integrates an optical solar reflector and a 7-layer SiO2 / HfO2 multilayer film structure in their paper "Passive radiative cooling below ambient air temperature under direct sunlight", which reduces the solar absorption ratio and improves its infrared emissivity change. However, the control ability of this film system structure is limited and the film system preparation process is relatively cumbersome. In addition, since the substrate is usually glass, it has high rigidity and insufficient flexibility, which makes it difficult to implement on curved and complex surfaces, and the operational reliability is not high. In the published literature, there are few reports on the research of grating etching on the surface of polyimide film, especially colorless polyimide film, and using the composite design of grating structure and VO2 temperature phase change characteristics to improve and change the heat dissipation capacity of radiation cooling devices.

[0006] The patent document with the publication number CN116774332B discloses the application of a directional radiation device in radiation cooling, wherein an asymmetric unit and a porous membrane are combined and arranged, each asymmetric unit includes a reflection surface and a radiation surface, the reflection surface is an infrared reflection material, and the radiation surface is a material that has an absorption effect on the 8-13 micron spectrum; the porous membrane is arranged on the top of the asymmetric unit to have a transmission effect on the 8-13 micron band; the directional radiation device is tilted or vertically arranged, with the radiation surface facing the sky and the reflection surface facing the ground. However, the patent document still has the defects of high rigidity and insufficient flexibility, difficulty in implementation on curved and complex surfaces, and low operational reliability. Summary of the invention

[0007] In view of the defects in the prior art, an object of the present invention is to provide a flexible grating structure variable emissivity radiation cooling device and a preparation method thereof.

[0008] A flexible grating structure variable emissivity radiative cooling device according to the present invention comprises: a metal reflection layer, a substrate, a grating structure layer and a VO2 phase change layer;

[0009] The metal reflective layer, the substrate, the grating structure layer and the VO2 phase change layer are arranged in sequence from bottom to top;

[0010] The grating structure layer is a rectangular groove structure obtained by etching a preset depth on the surface of the substrate.

[0011] Preferably, the substrate is any one of the following: polyimide, poly(perfluoroethylene propylene), and strontium glass.

[0012] Preferably, the substrate is colored polyimide or colorless polyimide.

[0013] Preferably, the metal reflective layer is any one of the following: aluminum, gold, silver, hafnium, nickel, copper, and magnesium.

[0014] Preferably, the period of the grating structure layer is 0.5 μm to 10 μm, and the duty cycle is 0.1 to 1.

[0015] The present invention also provides a method for preparing a flexible grating structure variable emissivity radiative cooling device, which is used to prepare the flexible grating structure variable emissivity radiative cooling device according to any one of claims 1 to 5, and specifically comprises the following steps:

[0016] Step 1: ultrasonically clean the substrate using acetone, ethanol, and ultrapure water in sequence, and blow dry with nitrogen;

[0017] Step 2: sputtering a metal reflective layer on one side of the substrate, and etching a grating structure layer on the other side of the substrate using plasma reactive ion etching;

[0018] Step 3: Magnetron sputtering of VO2 phase change layer on the etched grating structure layer.

[0019] Preferably, the thickness of the metal reflective layer is 100 nm to 300 nm.

[0020] Preferably, the thickness of the substrate is 50 μm to 150 μm.

[0021] Preferably, the thickness of the VO2 phase change layer is 20nm to 80nm.

[0022] Preferably, the process of etching the grating structure layer by plasma reaction is as follows:

[0023] Step a: coating a photoresist on the surface of the substrate by spin coating;

[0024] Step b: etching a rectangular pattern on the photoresist using ultraviolet lithography technology;

[0025] Step c: etching a grating depth of 300 to 700 nm by ion beam reaction according to the rectangular pattern on the photoresist;

[0026] Step d: remove the residual photoresist to obtain a rectangular grating structure layer.

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

[0028] 1. The present invention provides a flexible grating structure variable emissivity radiation cooling device. By combining the grating structure with the surface phonon resonance absorption and the temperature phase change characteristics of VO2, while maintaining the original low solar absorption ratio state, on the one hand, the infrared radiation intensity in the atmospheric window band is increased, and the infrared emissivity can reach a maximum of 0.85, an increase of more than 20%; on the other hand, at high temperatures (temperature>68°C), the infrared emissivity of the device can be changed to a maximum of 0.85, and at low temperatures (temperature<68°C), the infrared emissivity of the device can be changed to a minimum of 0.36, showing the characteristic that the emissivity can change with temperature, which can further significantly improve the heat dissipation capacity of the original simple glass-type secondary surface mirror structure.

[0029] 2. The present invention has a simple manufacturing process, is easy to produce, has strong operability in the implementation process, and has many application scenarios, and can achieve the green and environmentally friendly effect of radiative heat dissipation and refrigeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 It is a schematic diagram of the structure of a flexible grating structure variable emissivity radiation cooling device;

[0032] Figure 2 The present invention is a flowchart of the steps of the method for preparing a flexible grating structure variable emissivity radiation cooling device.

[0033] The figure shows:

[0034] Metal reflective layer 1 Grating structure layer 3

[0035] Substrate 2, VO2 phase change layer 4 DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0037] Embodiment 1:

[0038] like Figure 1 and Figure 2As shown, this embodiment provides a flexible grating structure variable emissivity radiation cooling device, including: a metal reflection layer 1, a substrate 2, a grating structure layer 3 and a VO2 phase change layer 4; the metal reflection layer 1, the substrate 2, the grating structure layer 3 and the VO2 phase change layer 4 are arranged in sequence from bottom to top; the grating structure layer 3 is a rectangular groove structure obtained by etching a preset depth on the surface of the substrate 2. The substrate 2 is any one of the following including: polyimide, polytetrafluoroethylene propylene, and strontium glass. The substrate 2 is a colored polyimide or a colorless polyimide. In this embodiment, the substrate 2 is a colorless polyimide absorption layer.

[0039] The metal reflective layer 1 is any one of the following: aluminum, gold, silver, hafnium, nickel, copper, magnesium. The period of the grating structure layer 3 is 0.5 μm to 10 μm, and the duty cycle is 0.1 to 1.

[0040] This embodiment also provides a method for preparing a flexible grating structure variable emissivity radiative cooling device, which is used for the above-mentioned flexible grating structure variable emissivity radiative cooling device, and specifically comprises the following steps:

[0041] Step 1: ultrasonically clean the substrate 2 using acetone, ethanol, and ultrapure water in sequence, and blow dry with nitrogen; the thickness of the substrate 2 is 50 μm to 150 μm.

[0042] Step 2: sputtering a metal reflective layer 1 on one side of the substrate 2, and etching the grating structure layer 3 on the other side of the substrate 2 by plasma reactive ion etching; the thickness of the metal reflective layer 1 is 100nm to 300nm;

[0043] The process of etching the grating structure layer 3 by plasma reaction is as follows:

[0044] Step a: coating a photoresist on the surface of the substrate 2 by spin coating;

[0045] Step b: etching a rectangular pattern on the photoresist using ultraviolet lithography technology;

[0046] Step c: etching a grating depth of 300 to 700 nm by ion beam reaction according to the rectangular pattern on the photoresist;

[0047] Step d: removing the residual photoresist to obtain a rectangular grating structure layer 3.

[0048] Step 3: magnetron sputtering a VO2 phase change layer 4 on the etched grating structure layer 3; the thickness of the VO2 phase change layer 4 is 20nm to 80nm.

[0049] The present embodiment provides a flexible grating structure variable emissivity radiation cooling device and a preparation method thereof. After a grating structure is modified on the surface of a colorless polyimide silver-plated film by reactive etching, a VO2 phase change layer is sputtered on the grating structure surface by magnetron sputtering. Due to the effect of the grating structure, the radiation cooling performance of the device is greatly improved, and the emissivity of the "atmospheric window" can be increased by up to 17.5% compared with the structure without a grating. Since the VO2 film has the characteristic of phase change due to temperature, the transmittance of the incident light can be changed, and then the emissivity of the radiation cooling device can be changed, which is particularly suitable for the field of spacecraft heat dissipation.

[0050] The device of this embodiment is mainly composed of a metal reflective layer, a colorless polyimide absorption layer, a grating structure layer and a VO2 phase change layer. The ability of radiative cooling does not depend on the type of substrate and the optical properties of the surface. It has good substrate applicability, bendability and operability. At the same time, the technical method of etching the grating is simpler, more convenient and more efficient to operate than the multilayer film design and preparation technology.

[0051] Embodiment 2:

[0052] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0053] The present embodiment provides a flexible grating structure variable emissivity radiative cooling device, comprising: a metal reflective layer, a colorless polyimide absorption layer, a grating structure layer and a VO2 phase change layer are arranged in sequence from bottom to top, wherein the grating structure layer is a rectangular groove obtained by etching a certain depth on the surface of the colorless polyimide absorption layer.

[0054] The metal reflective layer is aluminum, gold, silver, hafnium, nickel, copper or magnesium. The period of the grating structure is 0.5 μm to 10 μm, and the duty cycle is 0.1 to 1.

[0055] This embodiment also provides a method for preparing a flexible grating structure variable emissivity radiation cooling device, and the preparation method is implemented according to the following steps: ultrasonically clean the colorless polyimide with acetone, ethanol, and ultrapure water in sequence, and blow dry it with nitrogen gas, sputter a metal reflective layer on one side of the colorless polyimide, and then use reactive ion etching to etch the grating structure on the other side, and magnetron sputter a VO2 phase change layer on the etched grating structure surface.

[0056] The substrate material is colored polyimide, polyperfluoroethylene propylene and strontium glass. The thickness of the metal reflective layer is 100nm-300nm. The thickness of the colorless polyimide is 50μm-150μm. The thickness of the VO2 phase change layer is 20nm-80nm.

[0057] The process of plasma reaction etching rectangular grating structure is as follows:

[0058] First, photoresist is coated on the surface of the colorless polyimide layer by spin coating, and then a rectangular pattern is etched using ultraviolet photolithography technology. Subsequently, an ion beam reaction is used to etch a grating depth of 300 to 700 nm to remove the residual photoresist, and finally a rectangular grating micro-nano structure is obtained.

[0059] The purpose of this embodiment is to change the radiation cooling capacity of the glass-type secondary surface mirror while realizing that the emissivity changes with temperature, and is independent of the type of base material, and to provide a flexible grating structure variable emissivity radiation cooling device and its preparation method.

[0060] In this embodiment, a flexible grating structure variable emissivity radiation cooling device is prepared. By combining the grating structure with the surface phonon resonance absorption and the temperature phase change characteristics of VO2, while maintaining the original low solar absorption ratio state, on the one hand, the infrared radiation intensity in the atmospheric window band is increased, and the infrared emissivity can reach a maximum of 0.85, an increase of more than 20%; on the other hand, at high temperatures (temperature > 68°C), the device's infrared emissivity can be changed to a maximum of 0.85, and at low temperatures (temperature < 68°C), the device's infrared emissivity can be changed to a minimum of 0.36, showing the characteristic that the emissivity can be changed with temperature, which can further greatly improve the heat dissipation capacity of the original simple glass-type secondary surface mirror structure, and the manufacturing process is simple, easy to produce, the implementation process is highly operable, and there are many application scenarios, which can achieve the green and environmentally friendly effect of radiation heat dissipation and cooling.

[0061] Embodiment 3:

[0062] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0063] like Figure 1 As shown, the flexible grating structure variable emissivity radiation cooling device of this embodiment is composed of a colorless polyimide absorption layer, a metal reflection layer 1 sputtered on one side, and an etched grating structure layer 3 and a sputtered VO2 phase change layer 4 on the other side.

[0064] Taking 100μm colorless polyimide as the substrate, acetone, ethanol and ultrapure water are used to ultrasonically clean the colorless polyimide substrate until the surface is clean. Magnetron sputtering technology is used to use φ60mm, 99.999% purity metallic silver as the sputtering target, and 99.99% purity argon gas is introduced to sputter a metallic silver layer with a thickness of 150nm; on the other side, ion beam etching technology is used to obtain a rectangular grating micro-nano structure with a period of 10μm, a duty cycle of 0.2, and a groove depth of 0.8um; switch to the vanadium target position, introduce 99.99% purity argon gas and oxygen as reaction gases, and plate a 50nm thick VO2 phase change layer on the grating structure layer at a temperature of 300°C.

[0065] The flexible grating structure variable emissivity radiative cooling device prepared in the embodiment was tested to have a solar absorption ratio of 0.25, an emissivity of 0.82 at high temperature in the 8-13 um band, and an emissivity of 0.37 at low temperature.

[0066] Embodiment 4:

[0067] The difference between this embodiment and embodiment 3 is that the period of the rectangular grating structure is 5 μm and the duty cycle is 0.5.

[0068] The flexible grating structure variable emissivity radiative cooling device prepared in the embodiment was tested to have a solar absorption ratio of 0.28, an emissivity of 0.81 at high temperature in the 8-13 um band, and an emissivity of 0.38 at low temperature.

[0069] Embodiment 5:

[0070] The difference between this embodiment and embodiment 3 is that the groove depth of the rectangular grating structure is 1 um.

[0071] The flexible grating structure variable emissivity radiative cooling device prepared in the embodiment was tested to have a solar absorption ratio of 0.24, an emissivity of 0.85 at high temperature in the 8-13 um band, and an emissivity of 0.40 at low temperature.

[0072] Embodiment 6:

[0073] The difference between this embodiment and embodiment 3 is that the base layer is poly(perfluoroethylene propylene).

[0074] The flexible grating structure variable emissivity radiative cooling device prepared in the embodiment was tested to have a solar absorption ratio of 0.20, an emissivity of 0.83 at high temperature in the 8-13 um band, and an emissivity of 0.37 at low temperature.

[0075] Embodiment 7:

[0076] The difference between this embodiment and embodiment 3 is that the thickness of the VO2 phase change layer is 70 nm.

[0077] The flexible grating structure variable emissivity radiative cooling device prepared in the embodiment was tested to have a solar absorption ratio of 0.25, an emissivity of 0.85 at high temperature in the 8-13 um band, and an emissivity of 0.36 at low temperature.

[0078] The present invention has good substrate applicability, bendability and operability, and the technical method of etching the grating is simpler, more convenient and more efficient to operate than the multilayer film design and preparation technology.

[0079] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0080] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A flexible grating structure variable emissivity radiation cooling device, characterized in that: include: A metal reflective layer (1), a substrate (2), a grating structure layer (3) and a VO2 phase change layer (4); The metal reflection layer (1), the substrate (2), the grating structure layer (3) and the VO2 phase change layer (4) are arranged in sequence from bottom to top; The grating structure layer (3) is a rectangular groove structure obtained by etching a preset depth on the surface of the substrate (2).

2. The flexible grating structure variable emissivity radiative cooling device according to claim 1, characterized in that: The substrate (2) is any one of the following: polyimide, poly(perfluoroethylene propylene), and strontium glass.

3. The flexible grating structure variable emissivity radiative cooling device according to claim 2, characterized in that: The substrate (2) is colored polyimide or colorless polyimide.

4. The flexible grating structure variable emissivity radiation cooling device according to claim 1, characterized in that: The metal reflective layer (1) is any one of the following: aluminum, gold, silver, hafnium, nickel, copper, and magnesium.

5. The flexible grating structure variable emissivity radiation cooling device according to claim 1, characterized in that: The period of the grating structure layer (3) is 0.5 μm to 10 μm, and the duty cycle is 0.1 to 1.

6. A method for preparing a flexible grating structure variable emissivity radiation cooling device, characterized in that: The method for preparing the flexible grating structure variable emissivity radiative cooling device according to any one of claims 1 to 5 specifically comprises the following steps: Step 1: ultrasonically clean the substrate (2) using acetone, ethanol, and ultrapure water in sequence, and blow dry with nitrogen; Step 2: sputtering a metal reflective layer (1) on one side of the substrate (2), and etching a grating structure layer (3) on the other side of the substrate (2) using plasma reactive ion etching; Step 3: magnetron sputtering a VO2 phase change layer (4) on the etched grating structure layer (3).

7. The method for preparing the flexible grating structure variable emissivity radiation cooling device according to claim 6, characterized in that: The thickness of the metal reflective layer (1) is 100 nm to 300 nm.

8. The method for preparing the flexible grating structure variable emissivity radiation cooling device according to claim 6, characterized in that: The thickness of the substrate (2) is 50 μm to 150 μm.

9. The method for preparing the flexible grating structure variable emissivity radiative cooling device according to claim 6, characterized in that: The thickness of the VO2 phase change layer (4) is 20nm to 80nm.

10. The method for preparing the flexible grating structure variable emissivity radiative cooling device according to claim 6, characterized in that: The process of etching the grating structure layer (3) by plasma reaction is as follows: Step a: coating a photoresist on the surface of the substrate (2) by spin coating; Step b: etching a rectangular pattern on the photoresist using ultraviolet lithography technology; Step c: etching a grating depth of 300 to 700 nm by ion beam reaction according to the rectangular pattern on the photoresist; Step d: removing the residual photoresist to obtain a rectangular grating structure layer (3).

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