Intelligent thermal control device with high emissivity change value and low solar absorptivity and preparation method thereof

Abstract

The invention relates to an intelligent thermal control device with a high emissivity change value and a low solar absorptivity and a preparation method thereof. The intelligent thermal control device with the high emissivity change value and the low solar absorptivity is of a multi-layer composite structure and sequentially comprises a light base material, an infrared high-reflection metal layer, a transparent medium layer, a VO2 phase change layer, an infrared antireflection layer and a visible light reflection increasing layer from bottom to top. The infrared antireflection layer is made of germanium or silicon; the visible light reflection increasing layer is of a multi-layer structure formed by alternating high-refractive-index material films and low-refractive-index material films, and the materials are at least two of HfO2, Al2O3, TiO2, Ta2O5, SiO2, CaF2, MgF2, ZnSe and ZnS.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft thermal control technology, specifically relating to a smart thermal control device with high emissivity variation and low solar absorptivity and its preparation method. Background Technology

[0002] Spacecraft operating in a high-vacuum environment exchange heat with the space environment through thermal radiation. Due to the large fluctuations in external ambient temperature, effective thermal control technology is needed to maintain a suitable internal temperature and ensure the normal operation of all equipment and components. Currently, spacecraft thermal control systems mainly use passive thermal control materials with fixed thermal radiation properties. However, deep space probes, microsatellites, and other spacecraft face complex and variable external heat flow environments, making passive thermal control materials insufficient to meet the requirements of thermal control design. Therefore, there is an urgent need to significantly improve active thermal control capabilities. Active thermal control systems, such as motorized blinds and electrochromic materials, suffer from drawbacks such as large weight, high energy consumption, and complex mechanical movement devices, severely impacting the limited payload capacity of spacecraft.

[0003] Intelligent thermal control devices based on thermotropic phase change materials can effectively control the heat radiated into deep space by changing their emissivity according to ambient temperature variations. These devices do not require complex sensor control systems or additional electric heating equipment, thus offering advantages such as simple structure, light weight, and zero energy consumption. Intelligent thermal control designs for spacecraft typically require devices to have low infrared emissivity at low temperatures to reduce outward heat radiation, and high infrared emissivity at high temperatures to increase radiative heat dissipation. By intelligently adjusting emissivity changes based on temperature sensing, the spacecraft's temperature can be maintained. Research on intelligent thermal control devices contributes to the development of lightweight, low-energy, and low-cost spacecraft.

[0004] VO2 is a typical thermo-induced phase change material. It undergoes a reversible semiconductor-metal phase transition at 68℃, accompanied by significant changes in infrared optical properties. The phase transition temperature can be flexibly changed by doping. Therefore, its phase transition properties can be used to prepare intelligent thermal control devices with adjustable emissivity. However, at present, intelligent thermal control devices based on VO2 have the following problems that restrict their practical application: (1) The phase transition temperature of VO2 is higher than the actual temperature regulation range required by spacecraft. The phase transition temperature can be reduced by tungsten doping, but the change in emissivity will decrease significantly; (2) The preparation process is difficult. V has many oxidation states and a narrow process window, making it difficult to achieve stable preparation; (3) The solar absorptivity is high at high temperatures, which may cause the device to continuously absorb heat at high temperatures and thus remain in the post-phase transition state, losing its temperature regulation capability.

[0005] Against this backdrop, there is an urgent need to develop intelligent thermal control devices that can achieve low solar absorptivity while maintaining high emissivity variation, and whose fabrication process is stable and reliable, in order to meet the actual thermal control requirements of spacecraft. Summary of the Invention

[0006] To address the problems of the aforementioned vanadium dioxide-based intelligent thermal control devices, such as the emissivity variation range not matching the actual emissivity regulation temperature range required by spacecraft, low emissivity variation values, and excessively high solar absorptivity, the present invention aims to provide an intelligent thermal control device with high emissivity variation values ​​and low solar absorptivity, as well as its preparation method.

[0007] Specifically, the present invention provides a smart thermal control device with high emissivity variation and low solar absorptivity. The smart thermal control device with high emissivity variation and low solar absorptivity has a multi-layer composite structure, which includes, from bottom to top: a lightweight substrate, an infrared high reflectivity metal layer, a transparent dielectric layer, a VO2 phase change layer, an infrared antireflection layer, and a visible light antireflection layer; the infrared antireflection layer is made of germanium or silicon. The visible light antireflection layer is a multilayer structure consisting of alternating thin films of high and low refractive index materials, and the materials are at least two of HfO2, Al2O3, TiO2, Ta2O5, SiO2, CaF2, MgF2, ZnSe, and ZnS.

[0008] Preferably, the lightweight substrate is a quartz wafer, silicon wafer, or metal foil with a thickness not exceeding 150 μm.

[0009] Preferably, the infrared high-reflectivity metal layer is a metal film material with high reflectivity in the solar radiation band, preferably a gold, silver, aluminum or platinum film; the thickness is 80-250 nm.

[0010] Preferably, the material of the transparent dielectric layer is one or more of HfO2, Al2O3, SiO2, CaF2, MgF2, ZnSe, ZnS, and TiO2; and the thickness is 500-1500 nm.

[0011] Preferably, the VO2 phase transition layer is a doped VO2 layer, preferably a tungsten-doped VO2 layer, with a W doping amount of 0.8–3 at%; the thickness of the VO2 phase transition layer is 30–80 nm.

[0012] Preferably, the thickness of the infrared antireflection layer is 150–3000 nm.

[0013] Preferably, the thickness of the visible light antireflection layer is 300–2000 nm.

[0014] Preferably, the high refractive index (@450nm) of the visible light antireflective layer ranges from 1.9 to 2.5, and the low refractive index (@450nm) ranges from 1.3 to 1.6; the difference between the high and low refractive indices (@450nm) is 0.3 to 1.2.

[0015] Preferably, the visible light antireflection layer is a structure of 8 to 30 layers of alternating high and low refractive index material thin films, with each layer having a thickness of 20 to 300 nm.

[0016] Preferably, the infrared antireflection layer is prepared by electron beam evaporation or magnetron sputtering; the background vacuum of the electron beam evaporation process is better than 1×10⁻⁶. -3 Pa, sample stage temperature 100-250℃, deposition rate 2-6 A / s; the background vacuum of the magnetron sputtering process is better than 1×10⁻⁶. -3 Pa, sample stage temperature is room temperature, deposition rate is 3-10 A / s; The visible light antireflection layer is prepared by electron beam evaporation or resistance evaporation; the background vacuum of the electron beam evaporation process is better than 1×10⁻⁶. -3 Pa, sample stage temperature 100-300℃, deposition rate 2-8 A / s; background vacuum of resistance evaporation process better than 1×10 -3 Pa, sample stage temperature 100-300℃, deposition rate 2-8A / s.

[0017] Beneficial effects (1) The emissivity of the low solar absorptivity intelligent thermal control device prepared by the present invention has a change value of up to 0.44 within the temperature regulation range required by the spacecraft (-20℃ to 40℃), which is beneficial to improve thermal control efficiency. At the same time, the solar absorptivity is less than 0.4 at high temperature, which can meet the actual needs of intelligent thermal control of spacecraft. (2) By precisely controlling the thickness of each layer, including the substrate, the present invention effectively reduces the weight of the device and achieves an areal density of less than 600 g / m². 2 (Including the substrate) helps reduce the impact on the spacecraft's payload; (3) The low solar absorptivity intelligent thermal control device provided by the present invention has a simple structure, a stable and controllable manufacturing process, and is easy to achieve large-scale manufacturing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a smart thermal control device with high emissivity variation and low solar absorptivity, as exemplified by the present invention; the visible light and infrared light path diagrams in the figure correspond to the high temperature state. Figure 2 This is a schematic diagram illustrating the working mechanism of the infrared antireflection layer; Figure 3 The graph shows the emissivity variation of the high emissivity and low solar absorptivity intelligent thermal control device prepared in Example 1 at different temperatures. Figure 4 The image shows the simulated reflectance curves of the intelligent thermal control devices prepared in Example 1 and Comparative Example 1 in the visible light band at high temperatures. Detailed Implementation

[0019] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0020] First, combined Figure 1 This invention provides an exemplary description of a smart thermal control device with high emissivity variation and low solar absorptivity. The device has a multi-layered composite structure, comprising, from bottom to top: a lightweight substrate, an infrared high-reflectivity metal layer, a transparent dielectric layer, a VO2 phase change layer, an infrared anti-reflection layer, and a visible light anti-reflection layer.

[0021] In some embodiments, the lightweight substrate may be a quartz wafer, a silicon wafer, or a metal foil, and its thickness may be controlled to not exceed 150 μm.

[0022] In some embodiments, the infrared high-reflectivity metal layer can be a metal film material with high reflectivity in the solar radiation band (0.3–2.5 μm), preferably a gold, silver, aluminum, or platinum thin film; the thickness can be 80–250 nm. If the thickness is too small, the metal layer is semi-transparent and cannot effectively reflect solar radiation, thus failing to form an effective resonant cavity structure, resulting in insufficient emissivity of the device at low temperatures, and consequently a decrease in the emissivity change value; if the thickness is too large, it has no effect on the emissivity and solar absorptivity performance of the device, but it will increase the overall weight of the device, affecting its lightweight performance.

[0023] By employing an infrared-high reflectivity metal layer, the overall emissivity variation trend of the device can be ensured to meet the requirements of thermal control: at low temperatures, VO2 is in an infrared transparent state, and light passing through is reflected by the infrared-high reflectivity metal layer, resulting in low emissivity; at high temperatures, VO2 is in an infrared semi-transparent state, exhibiting higher emissivity. This structure can make the emissivity variation trend of the system conform to the requirements of thermal control, but the amount of emissivity variation is small, so it is necessary to add a transparent dielectric layer, which will be discussed later.

[0024] In some embodiments, the material of the transparent dielectric layer can be one or more of HfO2, Al2O3, SiO2, CaF2, MgF2, ZnSe, ZnS, and TiO2; the thickness of the transparent dielectric layer can be 500-1500 nm.

[0025] For the selection of materials for the transparent dielectric layer, it is generally required that the absorption in the infrared band be as low as possible (i.e., to exhibit a transparent effect). If the dielectric layer absorbs infrared light, it will lead to an increase in the emissivity of the device at low temperatures, thereby reducing the emissivity variation. Furthermore, its thickness directly affects at which wavelength the light achieves destructive interference. According to the fundamental law of blackbody radiation, at room temperature, the peak wavelength of blackbody radiation is around 10 μm. Therefore, to achieve optimal emissivity modulation performance, the maximum destructive interference effect needs to be achieved near the 10 μm wavelength. If the thickness of the transparent dielectric layer is too low, the destructive interference occurs at a shorter wavelength; if the thickness is too high, the destructive interference occurs at a longer wavelength. Only when the thickness of the transparent dielectric layer is in the range of 500-1500 nm does the device exhibit the maximum destructive interference effect near the 10 μm wavelength, thus achieving the maximum emissivity variation.

[0026] The amount of change in device emissivity can be adjusted by using a transparent dielectric layer: at low temperatures, both the VO2 phase transition layer and the transparent dielectric layer are infrared transparent. The incident infrared light is highly reflected by the metal layer after passing through the VO2 phase transition layer and the dielectric layer, resulting in a low emissivity. At high temperatures, VO2 is in an infrared semi-transparent state. At the same time, by reasonably designing the thickness of the dielectric layer, the light undergoes multiple reflections and absorptions in the film layer. Due to the principle of "interference cancellation", the reflectivity will be greatly reduced at the target wavelength, thereby achieving a high emissivity.

[0027] In some embodiments, the VO2 phase change layer is a doped VO2 layer, preferably a tungsten-doped VO2 layer, and the W doping amount can be 0.8 to 3 at%; the thickness of the VO2 phase change layer can be 30 to 80 nm.

[0028] It should be noted that when the VO2 phase transition layer is undoped, the device's phase transition temperature is 68°C, while the actual phase transition temperature range required by spacecraft is typically -20°C to 40°C. By doping with W, the device's phase transition temperature can be reduced, but the emissivity variation decreases with increasing doping concentration. If the W doping concentration is too high, although the phase transition temperature can be significantly reduced, the emissivity variation decreases; if the W doping concentration is too low, although the emissivity variation is higher, the phase transition temperature cannot be reduced to the range required by the spacecraft's actual phase transition temperature. Furthermore, the thickness of the VO2 phase transition layer needs to be matched with the thickness of the transparent dielectric layer during the design process to achieve the maximum destructive interference effect near the wavelength of 10 μm. Too large or too small a thickness will cause the overall radiation modulation range of the device to deviate from the vicinity of 10 μm, resulting in a decrease in the emissivity variation.

[0029] In the intelligent thermal control device with high emissivity variation and low solar absorptivity provided by this invention, the key film layer that plays a role in autonomous emissivity adjustment is the VO2 phase change layer. VO2, as a thermally induced phase change material, exhibits a semiconductor state with high emissivity at low temperatures and a metallic state with low emissivity at high temperatures. Its emissivity variation trend is exactly the opposite of the requirements of intelligent thermal control design. Therefore, it is necessary to add the aforementioned infrared high-reflectivity metallic layer to reverse its emissivity variation trend.

[0030] In some embodiments, the infrared antireflection layer can be made of germanium or silicon, and its thickness can be 150–3000 nm.

[0031] The mechanism of infrared antireflection layers is to achieve infrared antireflection by selecting an infrared-transparent material with a refractive index that matches the underlying layer (i.e., VO2). For example... Figure 2 As shown, the intensity of light reflection follows the formula: R1=((n0-n1) / (n0+n1)) 2 (1) R2=((n1-n2) / (n1+n2)) 2 (2) Where R1 and R2 are the reflectivities of infrared light on the first and second surfaces, respectively, n0 is the air refractive index (n0 = 1), n1 is the refractive index of the first layer material (i.e., the infrared antireflection layer), and n2 is the refractive index of the second layer material (i.e., the VO2 layer).

[0032] To achieve anti-reflection, R1 and R2 need to have similar intensities and opposite phases so that the two reflected beams can interfere destructively, thus reducing reflection. Therefore, n1 should be as close as possible to the arithmetic square root of n2 (that is, to make R1 = R2, (n0-n1) / (n0+n1) = (n1-n2) / (n1+n2)). The refractive index of VO2 at a wavelength of 10 micrometers is approximately 8.5. Therefore, the material of the antireflection layer should be chosen with a refractive index close to the square root of 8.5, i.e., around 2.9, and should be infrared transparent, not affecting the transmission performance of infrared light. Based on these conditions, silicon or germanium is selected as the infrared antireflection layer. Furthermore, its thickness directly determines the phase difference between the two reflected beams; therefore, the thickness needs to be controlled between 150 and 3000 nm to achieve good destructive interference, thereby reducing infrared reflection and improving the high-temperature emissivity of the device.

[0033] Adding an infrared antireflection layer to the surface of the VO2 phase transition layer can further improve the emissivity variation of the device. At low temperatures, the infrared antireflection layer has almost no effect on the device emissivity; however, at high temperatures, it helps reduce infrared reflection, thereby improving the high-temperature emissivity. In other words, this invention causes the infrared light reflected from the germanium or silicon layer to interfere destructively with the infrared light reflected from the VO2 layer, thereby reducing infrared reflection, improving the high-temperature emissivity, and achieving a larger overall emissivity variation.

[0034] In some embodiments, the visible light antireflection layer can be a multilayer structure of alternating thin films of high and low refractive index materials, preferably at least two of the following materials: HfO2, Al2O3, TiO2, Ta2O5, SiO2, CaF2, MgF2, ZnSe, and ZnS; the thickness can be 300–2000 nm.

[0035] In some embodiments, the high refractive index (@450nm) of the visible light antireflection layer can be in the range of 1.9-2.5, and the low refractive index (@450nm) can be in the range of 1.3-1.6; the difference between the high and low refractive indices (@450nm) can be 0.3-1.2.

[0036] In some embodiments, the visible light antireflection layer is an 8-30 layer structure of alternating high and low refractive index material thin films, with each layer having a thickness of 20-300 nm.

[0037] Generally, in antireflective coating systems, the higher the refractive index of the high-refractive-index material, the better, and the lower the refractive index of the low-refractive-index material, the better. In other words, the greater the difference in refractive indices between the two materials, the better the antireflective effect. However, the refractive index of a material is an intrinsic property; therefore, materials with inherently high or low refractive indices can be selected. The thickness of each layer needs to be specifically designed to meet the antireflective requirements of a particular wavelength. Multiple layers must be stacked to achieve overall antireflective performance in the visible light band. If the number of layers is too small, the antireflective effect will be weak; if the number of layers is too large, it becomes redundant and may lead to problems such as thin-film stress cracking and increased overall device weight.

[0038] The principle of antireflection enhancement is to increase the intensity of reflected light by utilizing the optical interference effect of thin films. According to the principle of light reflection, when light is incident on the surface of a two-layer thin-film structure composed of two materials with different refractive indices, the reflected light from the first surface and the reflected light from the second surface can interfere constructively, achieving antireflection at a specific wavelength. The greater the difference in refractive index between the two thin films, the stronger the antireflection effect. Therefore, visible light antireflection layers need to be structures of alternating high- and low-refractive-index thin films. However, each "high-refractive-index layer + low-refractive-index layer" double-layer structure can only enhance reflection at a specific wavelength. To achieve antireflection across the entire visible light band, multiple such double-layer structures need to be stacked, each with a different film thickness, thus exerting antireflection effects at different wavelengths, ultimately achieving a continuous, broadband antireflection effect in the visible light band. Therefore, visible light antireflection layers must be multi-layered structures of alternating high- and low-refractive-index thin films, and cannot be made of a single material.

[0039] By adding a visible light antireflection layer to the surface of the device, based on the principle of "constructive interference" in a multi-layer structure, the reflection of energy in the visible light band is enhanced, thereby reducing the solar absorptivity of the device.

[0040] The following is an exemplary description of the preparation method of the intelligent thermal control device with high emissivity variation and low solar absorptivity provided by the present invention. The preparation method may include the following steps: (1) An infrared high reflectance metal layer was prepared on a lightweight substrate by physical vapor deposition. (2) A transparent dielectric layer is prepared on the surface of the infrared high reflectivity metal layer prepared in step (1) by physical vapor deposition. (3) On the surface of the transparent dielectric layer prepared in step (2), a VO2 phase change layer is prepared by reactive magnetron sputtering. (4) On the surface of the VO2 phase change layer prepared in step (3), an infrared antireflection layer is prepared by physical vapor deposition to improve the emissivity change value of the smart coating device. (5) On the surface of the infrared antireflection layer prepared in step (4), a visible light antireflection layer is prepared by physical vapor deposition to reduce the solar absorptivity of the smart coating device, thereby obtaining the smart thermal control device with high emissivity change value and low solar absorptivity.

[0041] In some embodiments, in step (1), the physical vapor deposition method can be electron beam evaporation or magnetron sputtering. The electron beam evaporation process has a base vacuum better than 1×10⁻⁶. -3 Pa, sample stage temperature 20-150℃, deposition rate 30-100 A / s; background vacuum of magnetron sputtering process better than 1×10 -3 Pa, sample stage temperature 20-100℃, deposition rate 10-80A / s.

[0042] In some embodiments, in step (2), the physical vapor deposition method can be electron beam evaporation, magnetron sputtering, or resistance evaporation. The electron beam evaporation process has a base vacuum better than 1×10⁻⁶. -3 Pa, stage temperature 100-300℃, deposition rate 2-8 A / s; background vacuum of magnetron sputtering process better than 1×10 -3 Pa, sample stage temperature 20-200℃, deposition rate 0.1-2 A / s; the background vacuum of the resistance evaporation process is better than 1×10 -3 Pa, sample stage temperature 100-300℃, deposition rate 2-8A / s.

[0043] In some embodiments, in step (3), the oxygen injection rate can be dynamically controlled using a plasma glow discharge monitoring and feedback system during the preparation of the VO2 phase change layer by reactive magnetron sputtering. Since vanadium has multiple oxidation states, preparing pure vanadium dioxide is difficult. However, using a plasma glow discharge monitoring and feedback system to dynamically control the oxygen injection rate can achieve stable preparation of VO2. The background vacuum of the magnetron sputtering process is better than 1×10⁻⁶. -3 Pa, sample stage temperature 450-550℃, deposition rate 0.4-2A / s.

[0044] The oxygen injection rate is related to various factors such as equipment size, deposition temperature, and intracavitary pressure. The typical control method is dynamic control based on plasma glow discharge monitoring feedback. The principle is as follows: the sputtered target emits glow discharge, and its intensity is negatively correlated with the degree of oxidation on the target surface; that is, the higher the oxidation degree, the lower the glow discharge intensity. Based on previous process exploration, when the glow discharge intensity is controlled within a certain range, the corresponding vanadium oxidation state is +4, i.e., VO2. Therefore, in actual implementation, a probe is used to monitor the target glow discharge intensity in real time, and the data is transmitted to the monitoring equipment via optical fiber. If the glow discharge intensity exceeds the set range, the oxygen injection rate is increased; if the glow discharge intensity is below the set range, the oxygen injection rate is decreased, thereby achieving stable VO2 preparation.

[0045] In some embodiments, in step (4), the physical vapor deposition method can be electron beam evaporation or magnetron sputtering. The electron beam evaporation process has a base vacuum better than 1×10⁻⁶. -3 Pa, sample stage temperature 100-250℃, deposition rate 2-6 A / s; the background vacuum of the magnetron sputtering process is better than 1×10⁻⁶. -3 Pa, sample stage temperature is room temperature (20-30℃), deposition rate is 3-10A / s.

[0046] In some embodiments, step (5) of the physical vapor deposition method may include electron beam evaporation or resistance evaporation. The background vacuum of the electron beam evaporation process is better than 1×10⁻⁶. -3 Pa, sample stage temperature 100-300℃, deposition rate 2-8 A / s; background vacuum of resistance evaporation process better than 1×10 -3 Pa, stage temperature 100-300℃, deposition rate 2-8 A / s. The main reason why magnetron sputtering is not suitable for this layer is that the visible light antireflection layer is composed of multiple alternating dielectric films, with a large number of layers and a large total thickness, and requires precise control of the thickness of each layer. However, the preparation of dielectric films by magnetron sputtering has problems such as low rate and difficulty in real-time monitoring of the thickness of different materials, so it is not suitable to use the magnetron sputtering method.

[0047] The intelligent thermal control device with high emissivity variation and low solar absorptivity obtained by the preparation method provided by this invention exhibits an emissivity variation Δε as high as 0.44 within the temperature regulation range required by spacecraft (-20℃ to 40℃), which is beneficial to improving thermal control efficiency. Simultaneously, the solar absorptivity is less than 0.4 at high temperatures (40℃), meeting the actual requirements of intelligent thermal control for spacecraft. Furthermore, this invention effectively reduces the device weight by precisely controlling the thickness of each layer, including the substrate, achieving an areal density of less than 600 g / m². 2 (Including substrate) helps reduce the impact on spacecraft payload and can be applied to the actual needs of intelligent thermal control of spacecraft.

[0048] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0049] Example 1

[0050] The intelligent thermal control device with high emissivity variation and low solar absorptivity, and its fabrication method, provided in this embodiment, are as follows: (1) The intelligent thermal control device with high emissivity variation and low solar absorptivity provided in this embodiment consists of the following layers from bottom to top: a lightweight substrate (150 μm thick quartz glass), an infrared high reflectivity metal layer (200 nm thick silver film), a transparent dielectric layer (600 nm thick HfO2 film), a phase change layer (50 nm thick tungsten-doped VO2 film), an infrared antireflection layer (450 nm thick germanium film), and a visible light antireflection layer (17 layers of alternating CaF2 / TiO2 film with a total thickness of 1900 nm). (2) The method for preparing the intelligent thermal control device with high emissivity variation and low solar absorptivity provided in this embodiment includes the following steps: A 200 nm thick silver film was prepared on a clean quartz glass substrate with a thickness of 150 μm using DC magnetron sputtering. The sputtering conditions were: a background vacuum better than 5 × 10⁻⁶. -4 Pa, deposition rate is 30 A / s; A 600 nm thick HfO2 thin film was prepared on a silver film using electron beam evaporation. The electron beam evaporation process conditions were: background vacuum better than 1 × 10⁻⁶. -3 Pa, stage temperature 180℃, deposition rate 2A / s; A 50 nm thick tungsten-doped VO2 film was prepared on HfO2 film using reactive magnetron sputtering. A tungsten-vanadium alloy target with a W doping amount of 1% at was used. The sputtering conditions were: a background vacuum better than 5 × 10⁻⁶. -4 Pa, the reaction gas is oxygen, the sputtering gas is argon, the substrate temperature is 450-500℃, and the deposition rate is 0.7A / s; A 450 nm thick germanium infrared antireflection layer was deposited on the surface of a tungsten-doped VO2 layer using magnetron sputtering. The sputtering conditions were: a background vacuum better than 5 × 10⁻⁶. -4 Pa, deposition rate is 7 A / s; A visible light antireflection layer was deposited on the surface of the infrared antireflection layer using electron beam evaporation. The electron beam evaporation process conditions were: background vacuum better than 1×10⁻⁶. -3 Pa, the stage temperature was 160℃, and the deposition rates of TiO2 and CaF2 were both 4A / s.

[0051] Figure 3 The graph shows the emissivity variation curves of the intelligent thermal control device with high emissivity variation and low solar absorptivity prepared in Example 1 at different temperatures. As can be seen from the graph, when the temperature increases from -20℃ to 40℃, the normal emissivity of the device in the 2-20μm band increases from 0.21 to 0.65, and the emissivity variation value reaches 0.44.

[0052] Figure 4The graph shows the simulated reflectance curves of the high emissivity variation and low solar absorptivity intelligent thermal control device prepared in Example 1 in the visible light band at high temperatures. As can be seen from the graph, the simulated solar absorptivity of the device prepared in Example 1 is 0.29 at low temperatures and 0.31 at high temperatures.

[0053] Example 2

[0054] The intelligent thermal control device with high emissivity variation and low solar absorptivity, and its fabrication method, provided in this embodiment, are as follows: (1) The intelligent thermal control device with high emissivity variation and low solar absorptivity provided in this embodiment consists of the following layers from bottom to top: a lightweight substrate (150 μm thick silicon wafer), an infrared high reflectivity metal layer (150 nm thick gold film), a transparent dielectric layer (900 nm thick CaF2 film), a phase change layer (50 nm thick tungsten-doped VO2 film), an infrared antireflection layer (320 nm thick silicon film), and a visible light antireflection layer (17 layers of alternating CaF2 / TiO2 film with a total thickness of 1900 nm). (2) The method for preparing the intelligent thermal control device with high emissivity variation and low solar absorptivity provided in this embodiment includes the following steps: A 150 nm thick gold film was prepared on a clean, polished silicon wafer substrate with a thickness of 150 μm using DC magnetron sputtering. The sputtering conditions were: a base vacuum better than 5 × 10⁻⁶. -4 Pa, deposition rate is 20 A / s; A 900 nm thick CaF2 thin film was prepared on a gold film using resistance evaporation. The resistance evaporation process conditions were: a background vacuum better than 1 × 10⁻⁶. -3 Pa, the stage temperature is 180℃, and the deposition rate is 2A / s; A 50 nm thick tungsten-doped VO2 film was prepared on CaF2 film using reactive sputtering. A tungsten-vanadium alloy target with a W doping concentration of 1% at was used. The sputtering conditions were: a background vacuum better than 5 × 10⁻⁶. -4 Pa, the reaction gas is oxygen, the sputtering gas is argon, the substrate temperature is 450-500℃, and the deposition rate is 0.7A / s; A 320 nm thick silicon infrared antireflection layer was deposited on the surface of a tungsten-doped VO2 layer using magnetron sputtering. The sputtering conditions were: a base vacuum better than 5 × 10⁻⁶. -4 Pa, deposition rate is 5 A / s; A visible light antireflection layer was deposited on the surface of the infrared antireflection layer using electron beam evaporation. The electron beam evaporation process conditions were: background vacuum better than 1×10⁻⁶. -3 Pa, the stage temperature was 160℃, and the deposition rates of TiO2 and CaF2 were both 4A / s.

[0055] Tests show that the high emissivity variation and low solar absorptivity intelligent thermal control device prepared in Example 2 has an emissivity variation of 0.42 in the temperature range of -20 to 40°C, a simulated solar absorptivity of 0.25 at low temperatures, and a simulated solar absorptivity of 0.31 at high temperatures.

[0056] Comparative Example 1

[0057] The intelligent thermal control device and its preparation method provided in this comparative example are the same as those in Example 1, the main difference being that the device provided in this comparative example does not contain a visible light anti-reflection layer.

[0058] Figure 4 The figure shows the simulated reflectance curves of the intelligent thermal control device prepared in Comparative Example 1 in the visible light band at high temperatures. As can be seen from the figure, the simulated solar absorptivity of the intelligent thermal control device prepared in this comparative example is 0.51 at low temperatures and 0.53 at high temperatures.

[0059] Comparative Example 2

[0060] The intelligent thermal control device and its preparation method provided in this comparative example are the same as those in Example 1, the main difference being that the device provided in this comparative example does not contain an infrared anti-reflection layer.

[0061] Tests show that the intelligent thermal control device prepared in Comparative Example 2 has an emissivity variation of 0.35 in the temperature range of -20 to 40℃, a simulated solar absorptivity of 0.22 at low temperatures, and a simulated solar absorptivity of 0.28 at high temperatures.

[0062] Comparative Example 3

[0063] The intelligent thermal control device and its preparation method provided in this comparative example are the same as those in Example 1, the main difference being that the device provided in this comparative example does not contain an infrared anti-reflection layer and a visible light anti-reflection layer.

[0064] Tests show that the intelligent thermal control device prepared in Comparative Example 3 has an emissivity variation of 0.39 in the temperature range of -20 to 40℃, a simulated solar absorptivity of 0.45 at low temperatures, and a simulated solar absorptivity of 0.53 at high temperatures.

[0065] Comparative Example 4

[0066] The intelligent thermal control device and its preparation method provided in this comparative example are the same as those in Example 1. The main difference is that the visible light anti-reflection layer in the device provided in this comparative example is replaced with a single TiO2 layer, and the thickness is the same as that of the visible light anti-reflection layer in Example 1, which is 1900 nm.

[0067] The intelligent thermal control device prepared in Comparative Example 4 has a simulated solar absorptivity of 0.70 at low temperatures and 0.73 at high temperatures.

[0068] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A smart thermal control device with high emissivity variation and low solar absorptivity, characterized in that, The intelligent thermal control device with high emissivity variation and low solar absorptivity is a multi-layer composite structure, which includes, from bottom to top: a lightweight substrate, an infrared high reflectivity metal layer, a transparent dielectric layer, a VO2 phase change layer, an infrared anti-reflection layer, and a visible light anti-reflection layer. The infrared antireflection layer is made of germanium or silicon. The visible light antireflection layer is a multilayer structure consisting of alternating thin films of high and low refractive index materials, and the materials are at least two of HfO2, Al2O3, TiO2, Ta2O5, SiO2, CaF2, MgF2, ZnSe, and ZnS.

2. The intelligent thermal control device with high emissivity variation and low solar absorptivity as described in claim 1, characterized in that, The lightweight substrate is a quartz wafer, silicon wafer, or metal foil with a thickness not exceeding 150 μm.

3. The intelligent thermal control device with high emissivity variation and low solar absorptivity as described in claim 1 or 2, characterized in that, The infrared high-reflectivity metal layer is a metal film material with high reflectivity in the solar radiation band, preferably a gold, silver, aluminum or platinum film; the thickness is 80-250 nm.

4. The intelligent thermal control device with high emissivity variation and low solar absorptivity according to any one of claims 1-3, characterized in that, The transparent dielectric layer is made of one or more of the following materials: HfO2, Al2O3, SiO2, CaF2, MgF2, ZnSe, ZnS, and TiO2; and has a thickness of 500-1500 nm.

5. The intelligent thermal control device with high emissivity variation and low solar absorptivity according to any one of claims 1-4, characterized in that, The VO2 phase transition layer is a doped VO2 layer, preferably a tungsten-doped VO2 layer, with a W doping amount of 0.8–3 at%; the thickness of the VO2 phase transition layer is 30–80 nm.

6. The intelligent thermal control device with high emissivity variation and low solar absorptivity according to any one of claims 1-5, characterized in that, The thickness of the infrared antireflection layer is 150–3000 nm.

7. The intelligent thermal control device with high emissivity variation and low solar absorptivity according to any one of claims 1-6, characterized in that, The thickness of the visible light antireflection layer is 300–2000 nm.

8. The intelligent thermal control device with high emissivity variation and low solar absorptivity according to any one of claims 1-7, characterized in that, The high refractive index (@450nm) of the visible light antireflective layer ranges from 1.9 to 2.5, and the low refractive index (@450nm) ranges from 1.3 to 1.6; the difference between the high and low refractive indices (@450nm) is 0.3 to 1.

2.

9. The intelligent thermal control device with high emissivity variation and low solar absorptivity according to any one of claims 1-8, characterized in that, The visible light antireflection layer is a structure of 8 to 30 layers of alternating high and low refractive index material thin films, with each layer having a thickness of 20 to 300 nm.

10. The intelligent thermal control device with high emissivity variation and low solar absorptivity ratio according to any one of claims 1-9, characterized in that, The infrared antireflection layer is prepared by electron beam evaporation or magnetron sputtering; the background vacuum of the electron beam evaporation process is better than 1×10⁻⁶. -3 Pa, sample stage temperature 100-250℃, deposition rate 2-6 A / s; the background vacuum of the magnetron sputtering process is better than 1×10⁻⁶. -3 Pa, sample stage temperature is room temperature, deposition rate is 3-10 A / s; The visible light antireflection layer is prepared by electron beam evaporation or resistance evaporation; the background vacuum of the electron beam evaporation process is better than 1×10⁻⁶. -3 Pa, sample stage temperature 100-300℃, deposition rate 2-8 A / s; background vacuum of resistance evaporation process better than 1×10 -3 Pa, sample stage temperature 100-300℃, deposition rate 2-8A / s.

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