Spacecraft variable infrared emissivity thermal control intelligent film and preparation method thereof

Abstract

The application provides a variable infrared emissivity thermal control intelligent film for a spacecraft and a preparation method thereof, and belongs to the technical field of functional film coating in the field of spaceflight. The thermal control intelligent film is sequentially provided with a metal reflection layer, a substrate layer, a phase change layer and a dielectric layer from bottom to top. When the temperature of the thermal control intelligent film is higher than the phase change temperature of vanadium dioxide of the phase change layer, the average emissivity in the infrared wave band of 8-13 um is greater than 0.6, and the thermal control intelligent film is in a cooling mode. When the temperature of the thermal control intelligent film is lower than the phase change temperature of vanadium dioxide of the phase change layer, the average emissivity in the infrared wave band of 8-13 um is less than 0.3, and the thermal control intelligent film is in a heat preservation mode. The thermal control intelligent film can cope with different cold and hot requirements of the sun-facing surface and the back-sun surface of the spacecraft, so that the stability of the spacecraft in the running process is maintained, and the problems that the phase change material in the traditional structure is easily damaged under sunlight for a long time and is difficult to prepare are overcome. The thermal control intelligent film is easy to prepare and has a long service life, and has great application potential in the fields of spaceflight and military industry.

Description

Technical Field

[0001] This invention relates to the field of functional thin film coating technology in the aerospace industry, specifically to the optical design and preparation method of multilayer thin films. Background Technology

[0002] Spacecraft operating in space are affected by solar radiation, Earth's radiation, and their own heat sources, causing drastic fluctuations in their surface temperature, which in turn affects their normal operation and lifespan. For example, the surface temperature of a space station located approximately 400 km above the Earth can reach over 150°C on its sun-facing side, while the temperature on its shaded side can drop below -100°C. Therefore, spacecraft thermal management has become a critical technology in aerospace engineering.

[0003] Traditional variable emissivity thermal control devices primarily employ electrically driven mechanical thermal control mechanisms, such as louvers. These typically require components like temperature sensors, actuators, drive elements, control circuits, and power supply systems, increasing not only the weight and size of the spacecraft and energy consumption but also manufacturing and launch costs. They also suffer from long color-change response times. Preliminary research has been conducted on thin-film-based intelligent radiation devices, such as placing a phase-change coating with infrared modulation capabilities on the outermost surface of the control device to achieve variable emissivity thermal control. (See also...) Figure 9 This is currently the most widely used vanadium dioxide (VO2) phase change layer-dielectric layer-metal reflective layer-substrate layer smart thermal control material. Although this phase change control material shortens the response time to within nanoseconds, its structural design makes the surface functional layer, vanadium dioxide (VO2), prone to failure or even damage under prolonged sunlight or space irradiation, greatly affecting the emissivity modulation capability of smart radiation devices and thus failing to meet practical applications. Test results show that under continuous natural conditions for one month, the material's performance degrades by 30%, and it completely fails after 5 months. Therefore, achieving highly efficient new spacecraft thermal control thin-film devices with long lifespan, good thermal stability, light weight, and high reliability remains a major demand and research challenge in the field of aerospace thermal control technology. Summary of the Invention

[0004] To address the problems of traditional coatings being easily damaged under prolonged sunlight exposure and being difficult to prepare, and to achieve the stability and infrared control capability of thin film materials, this invention provides a thermally controlled smart thin film with variable infrared emissivity for spacecraft and its preparation method.

[0005] The specific technical solutions are as follows:

[0006] A spacecraft-grade thermal control smart thin film with variable infrared emissivity is provided from bottom to top with a metal reflective layer, a substrate layer, a phase change layer and a dielectric layer;

[0007] The material of the metal reflective layer is a material with an average reflectivity greater than 0.9 in the infrared band of 8-13 μm;

[0008] The substrate layer is made of a material with an average transmittance greater than 0.6 in the infrared band of 8–13 μm.

[0009] The phase change layer is made of vanadium dioxide, and the phase change temperature is 35℃~80℃;

[0010] The dielectric layer is made of a material with an average absorption rate of less than 0.1 in the infrared band of 8–13 μm.

[0011] When the temperature of the thermal control smart film is lower than the phase transition temperature of vanadium dioxide, the average emissivity in the infrared band of 8-13 μm is greater than 0.6, and it is in cooling mode; when the temperature of the thermal control smart film is higher than the phase transition temperature of vanadium dioxide, the average emissivity in the infrared band of 8-13 μm is less than 0.3, and it is in heat preservation mode.

[0012] The technical requirements for thermal control smart thin films are further defined as follows:

[0013] The material of the metal reflective layer is one of silver, copper, aluminum, and gold;

[0014] The substrate layer is made of one of silicon, germanium, or flexible polyethylene film.

[0015] The dielectric layer is made of one of silicon, germanium, or hafnium dioxide.

[0016] The preparation steps of a thermal control smart thin film with variable infrared emissivity for spacecraft are as follows:

[0017] (1) Clean the substrate

[0018] The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, and then dried; the substrate is the substrate layer; (2) Preparation of phase change layer (2.1) The cleaned substrate was placed on the sample stage in the vacuum chamber of the radio frequency magnetron sputtering coating equipment, with one side of the substrate in close contact with the sample stage. The sample stage was located 60 cm directly above the vanadium target. The vacuum chamber pressure was evacuated to 1.0 × 10⁻⁶. -4 Below Pa;

[0019] (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 2.0-10.0 Pa, open the target baffle, and pre-sputter clean the vanadium target.

[0020] (2.3) After cleaning, adjust the growth gas pressure to 1.0 to 2.0 Pa, and perform sputtering deposition on one side of the substrate for 5 to 40 minutes under a power of 110 W to 200 W to form a vanadium thin film layer on one side of the substrate.

[0021] (2.4) The substrate with the vanadium thin film layer is placed in a tube furnace and annealed to obtain a vanadium dioxide phase change layer.

[0022] (3) Preparation of dielectric layer (3.1) Place the substrate with phase change layer on the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric target; pre-sputter clean the dielectric target;

[0023] (3.2) Sputtering deposition is performed for 1 to 2 hours at a power of 110W to 200W; a dielectric layer is formed on the phase change layer, wherein the dielectric layer is an amorphous thin film;

[0024] (4) Fabrication of the metal reflective layer

[0025] In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate positioned directly above the metal reflective layer target. Under a power of 110W to 200W, the other side of the substrate is sputtered for 10 to 50 minutes to form a metal reflective layer on the other side of the substrate, thus obtaining a thermally controlled smart thin film with variable infrared emissivity for spacecraft.

[0026] The further defined preparation conditions are as follows:

[0027] The thickness of the substrate layer is 5–500 μm.

[0028] In step (2.3), the thickness of the phase change layer is 42–200 nm.

[0029] In step (2.4), when the substrate material is silicon or germanium, the annealing temperature is 550℃; when the substrate material is flexible polyethylene film, the annealing temperature is 50~80℃; and the annealing time is 2~3h.

[0030] In step (3.2), when the sputtering coating has been completed for 45 minutes, the sputtering is stopped for 15 minutes, and then the sputtering coating is resumed.

[0031] In step (3.2), the thickness of the dielectric layer is 500 to 1050 nm.

[0032] In step (4), the thickness of the metal reflective layer is 50-300 nm.

[0033] The purity of the vanadium target, the dielectric target, and the metal target are all greater than 99.95%.

[0034] The beneficial technical effects of this invention are reflected in the following aspects:

[0035] 1. This invention utilizes the thermally induced phase transition properties of vanadium dioxide to achieve automatic adjustment of the infrared spectral characteristics of thin film materials according to temperature changes. In heat preservation mode, the temperature of the thin film material is below the vanadium dioxide phase transition temperature. Vanadium dioxide is in an insulating state, and the film exhibits high transmittance in the 8-13 μm infrared band. Most of the infrared light passes through the dielectric layer, phase transition layer, and substrate layer before being reflected by the metal layer. Therefore, the coated thin film material exhibits high reflectivity and low emissivity in the infrared band, achieving intelligent heat preservation. In cooling mode, due to the absorption of solar radiation energy, the temperature of the thin film material is above the vanadium dioxide phase transition temperature. Vanadium dioxide transforms into a metallic state, and the film exhibits high reflectivity in the infrared band. At this time, the dielectric layer and the vanadium dioxide layer form a novel Fabry-Perot resonant microcavity, enhancing infrared absorption. Therefore, the thin film material exhibits high emissivity in the infrared band, increasing radiative heat dissipation. The thin film can meet the different heating and cooling requirements of the sun-facing and shaded sides of spacecraft and other equipment, alleviating the pressure on the temperature control system to some extent.

[0036] 2. See Figure 9 Compared to traditional control films, which typically grow the phase change layer on top, making them susceptible to damage and failure under prolonged exposure to ultraviolet light, this method offers a significant advantage. (See also...) Figure 1 By optimizing the structure, a novel Fabry-Perot resonant microcavity was designed. The uppermost dielectric layer can prevent ultraviolet radiation from damaging vanadium dioxide, ensuring its stability during use.

[0037] 3. This invention eliminates the need for temperature sensor drive circuits, power supply systems, and other components, overcoming the problems of large size, weight, and high manufacturing costs associated with traditional temperature control systems. It features rapid response, simple structure, small weight, and requires no energy input, helping spacecraft and other extraterrestrial exploration equipment alleviate the pressure from extreme temperatures in space. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the thin film structure of the present invention;

[0039] Figure 2 An ideal infrared spectral emissivity diagram of a spacecraft's thermal control film;

[0040] Figure 3 The infrared emissivity spectra of the thin film in Example 1 are shown in cooling mode and heat preservation mode.

[0041] Figure 4 The infrared emissivity spectra of the thin film in Example 2 are shown in cooling mode and heat preservation mode.

[0042] Figure 5 The infrared emissivity spectra of the thin film in Example 3 are shown in cooling mode and heat preservation mode.

[0043] Figure 6The infrared emissivity spectra of the thin film in Example 4 are shown in cooling mode and heat preservation mode.

[0044] Figure 7 The infrared emissivity spectra of the thin film in Example 5 are shown in cooling mode and heat preservation mode.

[0045] Figure 8 The infrared emissivity spectra of the thin film in Example 6 are shown in cooling mode and heat preservation mode.

[0046] Figure 9 This is a schematic diagram of a thermally controlled thin film structure based on vanadium dioxide variable infrared emissivity, as shown in other studies.

[0047] Figure 1 The layers are numbered as follows: 1. Metal reflective layer; 2. Substrate layer; 3. Phase change layer; and 4. Dielectric layer. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0049] See Figure 1 and Figure 2 A spacecraft-grade variable infrared emissivity thermal control smart thin film comprises, from bottom to top, a metal reflective layer 1, a substrate layer 2, a phase transition layer 3, and a dielectric layer 4. The thin film exhibits different spectral characteristics in different modes and can adjust its spectral characteristics according to temperature changes to meet the thermal management requirements of spacecraft. This helps spacecraft and other extraterrestrial exploration equipment alleviate the stress of extreme temperatures in space, and provides a fast response time. When the coating temperature is below the vanadium dioxide thin film phase transition temperature, it exhibits high emission in the 8–13 μm infrared band, indicating a cooling mode; when the coating temperature is above the vanadium dioxide thin film phase transition temperature, it exhibits low emission in the 8–13 μm infrared band, indicating a heat preservation mode.

[0050] Example 1

[0051] The preparation steps of a thermal control smart thin film with variable infrared emissivity for spacecraft are as follows:

[0052] (1) Clean the substrate

[0053] The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, each time for 10 minutes, and then dried. The substrate is the base layer, which is a 500um thick silicon substrate.

[0054] (2) Preparation of Phase Change Layer (2.1) Place the cleaned substrate onto the sample stage in the vacuum chamber of the RF magnetron sputtering coating equipment. One side of the substrate should be in close contact with the sample stage, which should be positioned 60 cm directly above the vanadium target. Evacuate the vacuum chamber to 1.0 × 10⁻⁶. -4 Below Pa.

[0055] (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 5.0 Pa, open the target baffle, and pre-sputter clean the vanadium target; the pre-sputter cleaning power is 50 W, and the pre-sputter cleaning is performed for 10 minutes to remove contaminants from the target surface.

[0056] (2.3) After cleaning, adjust the growth gas pressure to 1.0 Pa and perform sputtering deposition on one side of the substrate for 40 min at a power of 110 W. Turn off the power to form a 100 nm thick vanadium thin film layer on one side of the substrate.

[0057] (2.4) The substrate with the vanadium thin film layer was placed in a tube furnace and annealed at 550°C for 3 hours with an argon flow rate of 1.0 SCCM to obtain a vanadium dioxide phase change layer with a thickness of 200 nm. The substrate was then naturally cooled to room temperature and removed.

[0058] (3) Preparation of the dielectric layer (3.1) Place the substrate with the phase change layer on the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric target; pre-sputter clean the dielectric target with a power of 50W for 10 minutes. (3.2) Adjust and control the AC power supply of the silicon target. Sputter coating for 2 hours at a power of 110W, with a 15-minute interval between every 45 minutes; deposit a 600nm thick silicon dielectric layer on the phase change layer. The silicon dielectric layer is an amorphous thin film, which protects the phase change layer.

[0059] (4) Fabrication of the metal reflective layer

[0060] In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate directly above the aluminum target. Under a power of 150W, the other side of the substrate is sputtered for 50 minutes to form a 200nm thick aluminum film. A thermal control smart thin film with variable infrared emissivity for spacecraft is obtained.

[0061] See Figure 1 The thermal control smart film prepared in Example 1 consists of a metal reflective layer 1, a substrate layer 2, a phase change layer 3, and a dielectric layer 4 from bottom to top.

[0062] Its infrared spectral emissivity in the 8–13 μm band during cooling and heat preservation modes, such as Figure 3 As shown. In the cooling model, when the film temperature is higher than the transition temperature, the average emissivity of the film in the infrared band is 0.61; in the heat preservation model, when the film temperature is lower than the transition temperature, the average emissivity of the film in the infrared band is 0.11, and the modulation amplitude can reach 0.50.

[0063] Example 2

[0064] The preparation steps of a thermal control smart thin film with variable infrared emissivity for spacecraft are as follows:

[0065] (1) Clean the substrate

[0066] The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, each time for 10 minutes, and then dried. The substrate is the base layer, which is a 5µm thick polyethylene substrate.

[0067] (2) Preparation of Phase Change Layer (2.1) Place the cleaned substrate onto the sample stage in the vacuum chamber of the RF magnetron sputtering coating equipment. One side of the substrate should be in close contact with the sample stage, which should be positioned 60 cm directly above the vanadium target. Evacuate the vacuum chamber to 1.0 × 10⁻⁶. -4 Below Pa.

[0068] (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 3.0 Pa, open the target baffle, and pre-sputter clean the vanadium target; the pre-sputter cleaning power is 50 W, and the pre-sputter cleaning is performed for 10 minutes to remove contaminants from the target surface.

[0069] (2.3) After cleaning, adjust the growth gas pressure to 1.0 Pa and perform sputtering deposition on one side of the substrate for 20 min at a power of 150 W. Turn off the power to form a 90 nm thick vanadium thin film layer on one side of the substrate.

[0070] (2.4) The substrate with the vanadium thin film layer was placed in a tube furnace and annealed at 550°C for 2 hours with an argon flow rate of 1.0 SCCM to obtain a vanadium dioxide phase change layer with a thickness of 180 nm; it was then naturally cooled to room temperature and removed.

[0071] (3) Preparation of the dielectric layer (3.1) Place the substrate with the phase change layer on the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric target; pre-sputter clean the dielectric target with a power of 50W for 10 minutes. (3.2) Adjust and control the AC power supply of the germanium target. Sputter coating is performed for 1.5 hours at a power of 170W, with a 15-minute interval between every 45 minutes; deposit a 550nm thick germanium dielectric layer on the phase change layer. The germanium dielectric layer is an amorphous thin film, which protects the phase change layer.

[0072] (4) Fabrication of the metal reflective layer

[0073] In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate directly above the aluminum target. Under a power of 120W, the other side of the substrate is sputtered for 30 minutes to form a 100nm thick aluminum film on the other side of the substrate, thus obtaining a thermal control smart thin film with variable infrared emissivity for spacecraft.

[0074] See Figure 1 The thermal control smart film prepared in Example 2 consists of a metal reflective layer 1, a substrate layer 2, a phase change layer 3, and a dielectric layer 4 from bottom to top.

[0075] See Figure 4 In the cooling model, when the film temperature is above the transition temperature, the average emissivity of the film in the infrared band is 0.85; in the heat preservation model, when the film temperature is below the transition temperature, the average emissivity of the film in the infrared band is 0.05. Compared to Example 1, not only is the modulation amplitude increased to 0.8, but the use of a polyethylene film makes the coating flexible, reducing weight and enabling more applications.

[0076] Example 3

[0077] The preparation steps of a thermal control smart thin film with variable infrared emissivity for spacecraft are as follows:

[0078] (1) Clean the substrate

[0079] The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, each time for 10 minutes, and then dried. The substrate is the base layer, which is a 100um thick polyethylene substrate.

[0080] (2) Preparation of Phase Change Layer (2.1) Place the cleaned substrate onto the sample stage in the vacuum chamber of the RF magnetron sputtering coating equipment. One side of the substrate should be in close contact with the sample stage, which should be positioned 60 cm directly above the vanadium target. Evacuate the vacuum chamber to 1.0 × 10⁻⁶. -4 Below Pa.

[0081] (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 4.0 Pa, open the target baffle, and pre-sputter clean the vanadium target; the pre-sputter cleaning power is 50 W, and the pre-sputter cleaning is performed for 10 minutes to remove contaminants from the target surface.

[0082] (2.3) After cleaning, adjust the growth gas pressure to 1.5 Pa and perform sputtering deposition on one side of the substrate for 5 min at a power of 200 W. Turn off the power to form a 21 nm thick vanadium thin film layer on one side of the substrate.

[0083] (2.4) The substrate with the vanadium thin film layer was placed in a tube furnace and annealed at 80°C for 2 hours with an argon flow rate of 1.0 SCCM to obtain a vanadium dioxide phase change layer with a thickness of 42 nm; it was then naturally cooled to room temperature and removed.

[0084] (3) Preparation of dielectric layer (3.1) Place the substrate with phase change layer into the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric hafnium dioxide target; pre-sputter clean the dielectric target, the pre-sputter cleaning power is 50W, and the pre-sputter cleaning is 10 minutes.

[0085] (3.2) Adjust and control the AC power supply of the hafnium dioxide target material. Under the power of 110W, sputtering coating is carried out for 2 hours with a 15-minute interval between every 45 minutes. A 1050nm thick hafnium dioxide dielectric layer is deposited on the phase change layer, which plays a protective role for the phase change layer.

[0086] (4) Fabrication of the metal reflective layer

[0087] In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate directly above the silver target. Under a power of 200W, the other side of the substrate is sputtered for 15 minutes to form a 120nm thick silver film. A thermal control smart thin film with variable infrared emissivity for spacecraft is obtained.

[0088] See Figure 1 The thermal control smart film prepared in Example 3 consists of a metal reflective layer 1, a substrate layer 2, a phase change layer 3, and a dielectric layer 4, from bottom to top.

[0089] Its infrared spectral emissivity in the 8–13 μm band during cooling and heat preservation modes is as follows: Figure 5 As shown. In the cooling model, when the film temperature is higher than the transition temperature, the average emissivity of the film in the infrared band is 0.91; in the heat preservation mode, when the film temperature is lower than the transition temperature, the average emissivity of the film in the infrared band is 0.26, and the modulation amplitude can reach 0.65, which is 0.15 higher than that in Example 1.

[0090] Example 4

[0091] The preparation steps of a thermal control smart thin film with variable infrared emissivity for spacecraft are as follows:

[0092] (1) Clean the substrate

[0093] The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, each time for 10 minutes, and then dried. The substrate is the base layer, which is a 5µm thick polyethylene substrate.

[0094] (2) Preparation of Phase Change Layer (2.1) Place the cleaned substrate onto the sample stage in the vacuum chamber of the RF magnetron sputtering coating equipment. One side of the substrate should be in close contact with the sample stage, which should be positioned 60 cm directly above the vanadium target. Evacuate the vacuum chamber to 1.0 × 10⁻⁶. -4 Below Pa.

[0095] (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 8.0 Pa, open the target baffle, and pre-sputter clean the vanadium target; the pre-sputter cleaning power is 50 W, and the pre-sputter cleaning is performed for 10 minutes to remove contaminants from the target surface.

[0096] (2.3) After cleaning, adjust the growth gas pressure to 1.0 Pa and perform sputtering deposition on one side of the substrate for 25 min at a power of 130 W. Turn off the power to form an 85 nm thick vanadium thin film layer on one side of the substrate.

[0097] (2.4) The substrate with the vanadium thin film layer was placed in a tube furnace and annealed at 60°C for 2 hours with an argon flow rate of 1.0 SCCM to obtain a vanadium dioxide phase change layer with a thickness of 170 nm; it was then naturally cooled to room temperature and removed.

[0098] (3) Preparation of the dielectric layer (3.1) Place the substrate with the phase change layer on the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric target; pre-sputter clean the dielectric target with a power of 50W for 10 minutes. (3.2) Adjust and control the AC power supply of the silicon target. Under the power of 130W, sputter coating for 1.7 hours with a 15-minute interval between every 45 minutes; deposit a 650nm thick silicon dielectric layer on the phase change layer. The silicon dielectric layer is an amorphous thin film, which protects the phase change layer.

[0099] (4) Fabrication of the metal reflective layer

[0100] In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate directly above the copper target. Under a power of 190W, the other side of the substrate is sputtered for 40 minutes to form a 300nm thick copper film. A thermal control smart thin film with variable infrared emissivity for spacecraft is obtained.

[0101] See Figure 1 The thermal control smart film prepared in Example 4 consists of a metal reflective layer 1, a substrate layer 2, a phase change layer 3, and a dielectric layer 4, from bottom to top.

[0102] Its infrared spectral emissivity in the 8–13 μm band during cooling and heat preservation modes is as follows: Figure 6 As shown. In the cooling model, when the film temperature is above the transition temperature, the average emissivity of the film in the infrared band is 0.81; in the heat preservation model, when the film temperature is below the transition temperature, the average emissivity of the film in the infrared band is 0.04, and the modulation amplitude is 0.77.

[0103] Example 5

[0104] Compared to Example 4, only the thickness of the polyethylene substrate was changed to 10 μm, while all other conditions remained unchanged. The infrared spectral emissivity in the 8–13 μm band under both cooling and insulation modes is as follows: Figure 7 As shown. In the cooling model, when the film temperature is above the transition temperature, the average emissivity of the film in the infrared band is 0.78; in the heat preservation model, when the film temperature is below the transition temperature, the average emissivity of the film in the infrared band is 0.06, and the modulation amplitude can reach 0.72.

[0105] Example 6

[0106] The preparation steps of a thermal control smart thin film with variable infrared emissivity for spacecraft are as follows:

[0107] (1) Clean the substrate

[0108] The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, each time for 10 minutes, and then dried. The substrate is the base layer, which is a 500um thick germanium substrate.

[0109] (2) Preparation of Phase Change Layer (2.1) Place the cleaned substrate onto the sample stage in the vacuum chamber of the RF magnetron sputtering coating equipment. One side of the substrate should be in close contact with the sample stage, which should be positioned 60 cm directly above the vanadium target. Evacuate the vacuum chamber to 1.0 × 10⁻⁶. -4 Below Pa.

[0110] (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 3.0 Pa, open the target baffle, and pre-sputter clean the vanadium target; the pre-sputter cleaning power is 50 W, and the pre-sputter cleaning is performed for 10 minutes to remove contaminants from the target surface.

[0111] (2.3) After cleaning, adjust the growth gas pressure to 1.0 Pa and perform sputtering deposition on one side of the substrate for 30 min at a power of 140 W. Turn off the power to form a 90 nm thick vanadium thin film layer on one side of the substrate.

[0112] (2.4) The substrate with the vanadium thin film layer was placed in a tube furnace and annealed at 550°C for 3 hours with an argon flow rate of 1.0 SCCM to obtain a vanadium dioxide phase change layer with a thickness of 180 nm; it was then naturally cooled to room temperature and removed.

[0113] (3) Preparation of the dielectric layer (3.1) Place the substrate with the phase change layer on the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric target; pre-sputter clean the dielectric target with a power of 50W for 10 minutes. (3.2) Adjust and control the AC power supply of the germanium target. Sputter coating is performed for 1.5 hours at a power of 150W, with a 15-minute interval between every 45 minutes; deposit a 500nm thick germanium dielectric layer on the phase change layer. The germanium dielectric layer is an amorphous thin film, which protects the phase change layer.

[0114] (4) Fabrication of the metal reflective layer

[0115] In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate directly above the gold target. Under a power of 110W, the other side of the substrate is sputtered for 10 minutes to form a 50nm thick gold film. A thermal control smart thin film with variable infrared emissivity for spacecraft is obtained.

[0116] See Figure 1 The thermal control smart film prepared in Example 6 consists of a metal reflective layer 1, a substrate layer 2, a phase change layer 3, and a dielectric layer 4, from bottom to top.

[0117] Its infrared spectral emissivity in the 8–13 μm band during cooling and heat preservation modes is as follows: Figure 8 As shown. In the cooling model, when the film temperature is above the transition temperature, the average emissivity of the film in the infrared band is 0.76; in the heat preservation model, when the film temperature is below the transition temperature, the average emissivity of the film in the infrared band is 0.06, and the modulation amplitude is 0.70.

[0118] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a thermally controlled smart thin film with variable infrared emissivity for spacecraft, characterized in that: The thermal control smart film is provided with a metal reflective layer, a substrate layer, a phase change layer and a dielectric layer from bottom to top; The material of the metal reflective layer is a material with an average reflectivity greater than 0.9 in the infrared band of 8-13 μm; The substrate layer is made of a material with an average transmittance greater than 0.6 in the infrared band of 8–13 μm. The phase change layer is made of vanadium dioxide, and the phase change temperature is 35℃~80℃; The dielectric layer is made of a material with an average absorption rate of less than 0.1 in the infrared band of 8–13 μm. When the temperature of the thermal control smart film is higher than the phase transition temperature of vanadium dioxide, the average emissivity in the infrared band of 8-13 μm is greater than 0.6, and it is in cooling mode; when the temperature of the thermal control smart film is lower than the phase transition temperature of vanadium dioxide, the average emissivity in the infrared band of 8-13 μm is less than 0.3, and it is in heat preservation mode. The material of the metal reflective layer is one of silver, copper, aluminum, and gold; The material of the base layer is one of silicon, germanium, or flexible polyethylene film; The material of the dielectric layer is one of silicon, germanium, or hafnium dioxide; The preparation steps of the thermal control smart thin film are as follows: (1) Clean the substrate The substrate was ultrasonically cleaned twice with deionized water and anhydrous ethanol, and then dried; the substrate is the base layer. (2) Preparation of phase change layer (2.1) Place the cleaned substrate onto the sample stage in the vacuum chamber of the RF magnetron sputtering coating equipment, with one side of the substrate in close contact with the sample stage. The sample stage is located 60 cm directly above the vanadium target. Evacuate the vacuum chamber to 1.0 × 10⁻⁶. -4 Below Pa; (2.2) Introduce argon gas at a flow rate of 80 SCCM; open the flow limiting valve, adjust the gas pressure to 2.0-10.0 Pa, open the target baffle, and pre-sputter clean the vanadium target; (2.3) After cleaning, adjust the growth gas pressure to 1.0 to 2.0 Pa, and perform sputtering deposition on one side of the substrate for 5 to 40 minutes under a power of 110 W to 200 W to form a vanadium thin film layer on one side of the substrate. (2.4) The substrate with the vanadium thin film layer is placed in a tube furnace and annealed to obtain a vanadium dioxide phase change layer; (3) Preparation of dielectric layer (3.1) Place the substrate with the phase change layer on the sample stage in the vacuum chamber of the coating equipment, so that the phase change layer is directly above the dielectric target. Pre-sputtering cleaning medium target; (3.2) Sputtering deposition is performed for 1 to 2 hours at a power of 110W to 200W; a dielectric layer is formed on the phase change layer, wherein the dielectric layer is an amorphous thin film; (4) Preparation of metal reflective layer In a vacuum chamber, the dielectric layer of the substrate is fixed on the sample stage, with the other side of the substrate positioned directly above the metal reflective layer target. Under a power of 110W to 200W, the other side of the substrate is sputtered for 10 to 50 minutes to form a metal reflective layer on the other side of the substrate, thus obtaining a thermally controlled smart thin film with variable infrared emissivity for spacecraft.

2. The preparation method according to claim 1, characterized in that: The thickness of the substrate layer is 5–500 μm.

3. The preparation method according to claim 1, characterized in that: In step (2.3), the thickness of the phase change layer is 42–200 nm.

4. The preparation method according to claim 1, characterized in that: In step (2.4), when the substrate material is silicon or germanium, the annealing temperature is 550℃; when the substrate material is flexible polyethylene film, the annealing temperature is 50~80℃; and the annealing time is 2~3h.

5. The preparation method according to claim 1, characterized in that: In step (3.2), when the sputtering coating has been completed for 45 minutes, the sputtering is stopped for 15 minutes, and then the sputtering coating is resumed.

6. The preparation method according to claim 1, characterized in that: In step (3.2), the thickness of the dielectric layer is 500 to 1050 nm.

7. The preparation method according to claim 1, characterized in that: In step (4), the thickness of the metal reflective layer is 50-300 nm.

8. The preparation method according to claim 1, characterized in that: The purity of the vanadium target, the dielectric target, and the metal target are all greater than 99.95%.

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