An adaptive thermochromic composite coating film for a spacecraft multilayer thermal insulation assembly and a preparation method thereof

Abstract

This invention belongs to the field of aerospace materials technology, specifically relating to an adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft and its preparation method. The film comprises a flexible polymer substrate layer, a metal reflective layer, a titanium nitride anti-diffusion intermediate layer, a tungsten-magnesium co-doped vanadium dioxide thermochromic control layer, and a silicon dioxide protective layer. Preparation involves DC magnetron sputtering to deposit the metal reflective layer, reactive magnetron sputtering to deposit the titanium nitride layer, three-target co-sputtering to deposit the tungsten-magnesium co-doped vanadium dioxide layer in a one-step process, electron beam evaporation to deposit the silicon dioxide layer, and finally thermal curing. This invention adjusts the phase transition temperature of vanadium dioxide to the spacecraft operating temperature range through tungsten-magnesium co-doping, enabling the film's infrared emissivity to automatically change with temperature, achieving adaptive thermal control. Simultaneously, the titanium nitride layer inhibits elemental diffusion and induces low-temperature crystallization of vanadium dioxide. The product exhibits stable thermal control performance and good tolerance to the space environment, making it suitable for multilayer thermal insulation components in spacecraft.

Description

Technical Field

[0001] This invention belongs to the field of aerospace materials technology, specifically relating to an adaptive thermochromic composite coating film for multilayer thermal insulation components of spacecraft and its preparation method. Background Technology

[0002] Spacecraft face extremely drastic thermal environmental changes during their orbital operation. During the orbital period, the temperature on the sun-facing side of the spacecraft can reach over 100 degrees Celsius, while the temperature on the shaded side can plummet to below -100 degrees Celsius. This periodic alternation of hot and cold temperatures poses a severe challenge to the reliable operation of onboard equipment and precision instruments.

[0003] Multilayer thermal insulation components are currently the most widely used passive thermal control products in spacecraft thermal control systems. They typically use polyester film or polyimide film as the substrate and achieve high infrared reflection and low solar absorption by vacuum evaporation of aluminum or silver layers, thereby blocking heat conduction.

[0004] However, with the increasing demands on the thermal control precision and adaptability of spacecraft from missions such as deep space exploration and high-resolution remote sensing, the inherent defects of traditional static multilayer thermal insulation components are becoming increasingly prominent. On the one hand, thermal insulation components using pure silver or pure aluminum as reflective layers face environmental stability issues during long-term service. The literature "Reflective Coating System for High-Temperature Vacuum Use" (NASA Tech Briefs, LEW-16599, May 1998) reports a SiO2 / Ag / Ni reflective coating system for space solar power systems. This literature clearly points out that when a silver layer is directly deposited on a copper substrate and heated, the reflectivity will significantly decrease due to the diffusion of silver into the substrate. However, by sequentially depositing a silver reflective layer and a silicon dioxide protective layer on a nickel substrate, the high-temperature diffusion of silver can be suppressed. On the other hand, in the study of combining high reflectivity layers with flexible polymer substrates, the literature "Highly stable Ag-Ni based transparent electrodes on PET substrates for flexible organic solar cells" (Solar Energy Materials and Solar Cells, Vol. 108, pp. 60-65, 2013) reported a method for preparing silver-nickel bilayer transparent electrodes on polyester substrates. The literature pointed out that when only a single layer of silver is deposited on the polymer substrate, the silver layer will be oxidized due to the penetration of moisture and oxygen through the polymer substrate, resulting in performance degradation. However, adding a nickel capping layer can significantly improve the stability of the silver layer under high temperature and high humidity conditions.

[0005] The aforementioned research has made significant progress in the fields of high-temperature vacuum reflective coatings and flexible polymer substrate electrodes. However, the reflectivity or emissivity of these solutions remains fixed after manufacturing. The thermal load on spacecraft varies greatly under different operating conditions; for example, the heat dissipation during periods of intensive electronic equipment operation can differ by several times from that during standby. Traditional multi-layer thermal insulation components cannot automatically adjust their heat dissipation capacity according to real-time temperature changes. While mechanical thermally controlled louvers can achieve adjustable heat dissipation, the moving parts pose a potential risk to the reliability and lifespan of the spacecraft.

[0006] Therefore, developing a flexible thin-film material that can adaptively adjust infrared emissivity with temperature changes while maintaining the inherent thermal insulation advantages of multilayer thermal insulation components has become a pressing technical problem in the field of aerospace thermal control. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by providing an adaptive thermochromic composite coating film for multilayer thermal insulation components of spacecraft and its preparation method. The purpose is to enable the infrared emissivity of the film to change automatically and reversibly with temperature, thereby upgrading the passive thermal control of spacecraft from static thermal insulation to adaptive thermal regulation without relying on mechanical moving parts. It is especially suitable for spacecraft thermal control scenarios with variable heat flux density or drastic changes in orbital environment.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of this invention provides an adaptive thermochromic composite coating film for a multilayer thermal insulation assembly in a spacecraft, comprising: Flexible polymer substrate layer; A metal reflective layer is disposed on the flexible polymer substrate layer, and the material of the metal reflective layer is silver (Ag) or aluminum (Al). An anti-diffusion intermediate layer is disposed on the metal reflective layer, and the material of the anti-diffusion intermediate layer is titanium nitride (TiN). A thermochromic control layer is disposed on the anti-diffusion intermediate layer, and the material of the thermochromic control layer is tungsten-magnesium co-doped vanadium dioxide; A protective layer is disposed on the thermochromic control layer, and the material of the protective layer is silicon dioxide (SiO2).

[0010] Furthermore, the flexible polymer substrate layer is a polyester (PET) film layer or a polyimide (PI) film layer with a thickness of 12 μm to 25 μm.

[0011] Furthermore, in the tungsten-magnesium co-doped vanadium dioxide, the atomic ratio of tungsten atoms, magnesium atoms and vanadium atoms is W:Mg:V = (0.5-2):(1-3):100.

[0012] Furthermore, the thickness of the metal reflective layer is 60nm to 90nm, the thickness of the anti-diffusion intermediate layer is 8nm to 12nm, the thickness of the thermochromic control layer is 70nm to 120nm, and the thickness of the protective layer is 15nm to 30nm.

[0013] A second aspect of this invention provides a method for preparing the aforementioned adaptive thermochromic composite coating film for a multilayer thermal insulation assembly in a spacecraft, comprising the following steps: (1) Place the flexible polymer substrate into a vacuum winding coating equipment, evacuate the vacuum, and perform plasma pretreatment on the substrate to make the surface tension of the substrate reach more than 50 dyn / cm. (2) A metal reflective layer is deposited on the substrate surface in an argon atmosphere using a DC magnetron sputtering method with a silver or aluminum target as the sputtering target. (3) Maintain vacuum, switch to reactive magnetron sputtering mode, use titanium target as sputtering target material, and carry out reactive sputtering in a mixed atmosphere of argon and nitrogen to deposit titanium nitride anti-diffusion intermediate layer on the surface of metal reflective layer. Radio frequency plasma is used to assist in the deposition process, and the substrate temperature is kept below 150°C by controlling sputtering power and winding speed. (4) Maintain vacuum, switch to three-target co-sputtering mode, use vanadium target, tungsten target and magnesium target as sputtering targets, carry out reactive co-sputtering in a mixed atmosphere of argon and oxygen, and deposit tungsten magnesium co-doped vanadium dioxide thermochromic control layer on the surface of titanium nitride anti-diffusion intermediate layer. (5) Maintaining a vacuum, the silicon dioxide particles are evaporated and deposited on the surface of the thermochromic control layer by electron beam evaporation to form a protective layer, thus obtaining a composite film; (6) The composite film is heat-cured at 80℃-120℃ for 1-3 hours to obtain the product.

[0014] Furthermore, in step (2), the sputtering power density is 3 W / cm². 2 Up to 8 W / cm 2 .

[0015] Furthermore, in step (3), the power density of the reactive sputtering is 5 W / cm². 2 Up to 10 W / cm 2 The radio frequency power of the radio frequency plasma-assisted radio frequency is 100 W-300 W.

[0016] Furthermore, in step (3), the volume flow ratio of argon to nitrogen is 1:2 to 1:3.

[0017] The role of the titanium nitride layer in the thin film is to suppress the interdiffusion of elements between the silver reflective layer and the vanadium dioxide layer. Silver atoms have a high migration tendency in multilayer film structures, especially during long-term service or temperature changes. Silver easily diffuses along grain boundaries into the upper vanadium dioxide layer, leading to structural damage to the silver layer and a decrease in infrared reflectivity. As a dense nitride material, titanium nitride has a dense lattice structure and high chemical stability, forming a reliable physical barrier between silver and vanadium dioxide, preventing the outward diffusion of silver atoms and the penetration of oxygen atoms into the silver layer. Secondly, the titanium nitride layer provides a favorable growth interface for the low-temperature crystallization of vanadium dioxide. Vanadium dioxide is difficult to achieve a good crystallization state when directly deposited on flexible polymer substrates, while titanium nitride has a specific crystal structure. Its surface can induce the orderly arrangement of vanadium dioxide molecules, allowing vanadium dioxide to form a crystalline thin film with phase transition function at a relatively low temperature, thus avoiding damage to the polymer substrate caused by high-temperature annealing. In addition, titanium nitride has a certain electrical conductivity, which can provide a charge discharge path in the direction of film thickness, preventing electrostatic discharge caused by surface charge accumulation due to electron or ion irradiation during spacecraft operation in orbit.

[0018] Furthermore, in the three-target co-sputtering described in step (4), the sputtering power density of the vanadium target is 4 W / cm². 2 Up to 8 W / cm 2 The sputtering power densities of the tungsten and magnesium targets were independently controlled to be 0.5 W / cm². 2 Up to 2 W / cm 2 .

[0019] Furthermore, in step (4), the volume flow ratio of argon to oxygen is 35:1 to 45:1, and the temperature of the substrate is controlled to be 130°C to 145°C during the deposition process.

[0020] Vanadium dioxide, a thermochromic material, undergoes a reversible crystal structure transformation with temperature changes. At low temperatures, vanadium dioxide is in an insulating state with weak infrared radiation emissivity; when the temperature rises above a certain value, it transforms into a metallic state, significantly enhancing its infrared radiation emissivity. Utilizing this property, introducing this material into the reflector of a spacecraft's multilayer thermal insulation assembly allows the reflector's infrared emissivity to be adjusted automatically according to its temperature: maintaining a low infrared emissivity to reduce heat loss when the reflector temperature is low, and automatically increasing the infrared emissivity to enhance heat dissipation when the reflector temperature is high. However, the phase transition temperature of pure vanadium dioxide is too high for the typical operating temperature range of spacecraft, making it difficult to function effectively under normal operating conditions. This solution adjusts its phase transition behavior by simultaneously introducing tungsten and magnesium dopants into the vanadium dioxide lattice: the incorporation of tungsten effectively lowers the phase transition temperature, bringing it into the more common operating temperature range of spacecraft; the incorporation of magnesium helps improve the transmittance characteristics of the thin film in the visible light band, reducing the absorption of solar radiation. The synergistic effect of co-doping allows the thermochromic control layer to adaptively change its infrared emissivity within the actual operating temperature range of the spacecraft, without causing additional temperature rise due to excessive absorption of sunlight. Therefore, this layer endows multi-layer thermal insulation components with dynamic thermal regulation capabilities—automatically switching between heat preservation and heat dissipation states based on its own temperature without relying on any external control or mechanical action, thus overcoming the inherent deficiency of traditional static thermal insulation films in adapting to changes in heat load.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses tungsten and magnesium co-doping of vanadium dioxide to reduce the phase transition temperature to the typical operating temperature range of spacecraft. This allows the thin film to maintain a low infrared emissivity at low temperatures to reduce heat loss, and automatically increase the infrared emissivity at high temperatures to enhance heat dissipation. This achieves all-solid-state adaptive thermal regulation without relying on external control, and makes up for the shortcomings of traditional static multilayer thermal insulation components that cannot adapt to changes in thermal load.

[0022] 2. Using titanium nitride as an anti-diffusion intermediate layer not only effectively prevents silver atoms from migrating to the vanadium dioxide layer and maintains the integrity of the reflective layer structure, but its rock salt-type crystal structure can also induce the upper vanadium dioxide layer to crystallize and grow at a lower temperature, reducing the requirements for the temperature resistance of the flexible substrate during the preparation process.

[0023] 3. The metal reflective layer, titanium nitride layer, vanadium dioxide layer and silicon dioxide protective layer are all continuously deposited in the same vacuum winding equipment without interruption. The process is compact and suitable for large-area industrial production.

[0024] 4. The silicon dioxide protective layer and the titanium nitride anti-diffusion layer together provide atomic oxygen protection and UV radiation resistance. After 200 hours of UV aging, the reflectivity decay is less than 3%, significantly better than traditional aluminum-plated or silver-plated thermal insulation components. Example data shows that the solar absorptivity of the thin film of this invention is as low as 0.24-0.29, and the infrared emissivity can be adjusted within a range of 0.41-0.46, exhibiting excellent overall thermal control performance and meeting the dynamic thermal control requirements of spacecraft in orbit. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the composite coating film of the present invention. In the figure, 1-protective layer, 2-thermochromic control layer, 3-anti-diffusion intermediate layer, 4-metal reflective layer, and 5-flexible polymer substrate layer. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the embodiments are all commercially available products.

[0027] Example 1 This embodiment provides an adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft, the film structure of which is as follows: Figure 1 As shown, its preparation method includes the following steps: (1) A biaxially oriented polyester film with a thickness of 18 μm was selected as the flexible polymer substrate layer 5. It was placed in the unwinding chamber of the vacuum winding coating equipment and evacuated to a vacuum degree of 5 × 10⁻⁶. -3 Pa was used to pretreat the substrate with plasma, and the surface tension of the treated substrate was 52 dyn / cm.

[0028] (2) A DC magnetron sputtering method was used, with a silver target as the sputtering target, to deposit a metal reflective layer 4 on the substrate surface in an argon atmosphere, with a sputtering power density of 5 W / cm². 2 The deposition thickness is 75 nm.

[0029] (3) Maintaining continuous vacuum, switch to reactive magnetron sputtering mode, using a titanium target as the sputtering target, and perform reactive sputtering in a mixed atmosphere of argon and nitrogen to deposit a titanium nitride anti-diffusion intermediate layer 3 on the surface of the metal reflective layer. Radio frequency plasma assistance is used during the deposition process, with a radio frequency power of 200 W, an argon flow rate of 10 sccm, and a nitrogen flow rate of 20 sccm. The sputtering power density is controlled at 7 W / cm². 2The winding speed keeps the substrate temperature below 140°C, and the deposition thickness is 10nm.

[0030] (4) Maintaining uninterrupted vacuum, switch to the three-target co-sputtering mode, using vanadium, tungsten, and magnesium targets as sputtering targets, and perform reactive co-sputtering in a mixed atmosphere of argon and oxygen to deposit a tungsten-magnesium co-doped vanadium dioxide thermochromic control layer 2 on the surface of the titanium nitride anti-diffusion intermediate layer. The sputtering power density of the vanadium target is 6 W / cm². 2 The sputtering power density of the tungsten target is 1.2 W / cm³. 2 The sputtering power density of the magnesium target is 1.5 W / cm³. 2 The argon flow rate was 40 sccm, and the oxygen flow rate was 1 sccm. The substrate temperature was controlled at 135℃ during deposition, and the deposition thickness was 95 nm. The atomic ratio of tungsten, magnesium, and vanadium atoms in the resulting film was 1.2:2.1:100.

[0031] (5) Maintaining a continuous vacuum, the silicon dioxide particles are evaporated and deposited on the surface of the thermochromic control layer to form a protective layer 1 using an electron beam evaporation method. The evaporation rate is 0.5 nm / s and the deposition thickness is 22 nm.

[0032] (6) The composite film after coating is subjected to heat curing treatment at 90°C for 2 hours to obtain the product.

[0033] Example 2 This embodiment provides an adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft, the preparation method of which includes the following steps: (1) A 25 μm thick biaxially oriented polyimide film was selected as the flexible polymer substrate and placed in the unwinding chamber of a vacuum winding coating equipment. The vacuum was then evacuated to a vacuum degree of 3 × 10⁻⁶. -3 Pa was used to pretreat the substrate with plasma, and the surface tension of the treated substrate was 55 dyn / cm.

[0034] (2) A DC magnetron sputtering method was used, with an aluminum target as the sputtering target, to deposit a metal reflective layer on the substrate surface in an argon atmosphere, with a sputtering power density of 3.5 W / cm². 2 The deposition thickness is 60 nm.

[0035] (3) Maintaining continuous vacuum, switch to reactive magnetron sputtering mode, using a titanium target as the sputtering target, and perform reactive sputtering in a mixed atmosphere of argon and nitrogen to deposit a titanium nitride anti-diffusion intermediate layer on the surface of the metal reflective layer. Radio frequency plasma is used for deposition, with a radio frequency power of 150 W, an argon flow rate of 8 sccm, and a nitrogen flow rate of 24 sccm. The sputtering power density is controlled to be 9 W / cm³. 2The winding speed keeps the substrate temperature below 130°C, and the deposition thickness is 8nm.

[0036] (4) Maintaining uninterrupted vacuum, switch to the three-target co-sputtering mode, using vanadium, tungsten, and magnesium targets as sputtering targets, and perform reactive co-sputtering in a mixed atmosphere of argon and oxygen to deposit a tungsten-magnesium co-doped vanadium dioxide thermochromic control layer on the surface of the titanium nitride anti-diffusion intermediate layer. The sputtering power density of the vanadium target is 7.5 W / cm². 2 The sputtering power density of the tungsten target is 0.8 W / cm³. 2 The sputtering power density of the magnesium target is 1.0 W / cm³. 2 The argon flow rate was 45 sccm, and the oxygen flow rate was 1.2 sccm. The substrate temperature was controlled at 142℃ during deposition, and the deposition thickness was 110 nm. The atomic ratio of tungsten, magnesium, and vanadium atoms in the resulting film was 0.7:1.5:100.

[0037] (5) Maintaining a continuous vacuum, the silicon dioxide particles are evaporated and deposited on the surface of the thermochromic control layer to form a protective layer using the electron beam evaporation method. The evaporation rate is 0.7 nm / s and the deposition thickness is 28 nm.

[0038] (6) The composite film after coating is subjected to heat curing treatment at 110°C for 1.5 hours to obtain the product.

[0039] Example 3 This embodiment provides an adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft, the preparation method of which includes the following steps: (1) A 12μm thick biaxially oriented polyester film was selected as the flexible polymer substrate and placed in the unwinding chamber of a vacuum winding coating equipment. The vacuum was then evacuated to a vacuum degree of 7×10. -3 Pa was used to pretreat the substrate with plasma, and the surface tension of the treated substrate was 50 dyn / cm.

[0040] (2) A DC magnetron sputtering method was used, with a silver target as the sputtering target, to deposit a metal reflective layer on the substrate surface in an argon atmosphere, with a sputtering power density of 7 W / cm². 2 The deposition thickness is 85 nm.

[0041] (3) Maintaining continuous vacuum, switch to reactive magnetron sputtering mode, using a titanium target as the sputtering target, and perform reactive sputtering in a mixed atmosphere of argon and nitrogen to deposit a titanium nitride anti-diffusion intermediate layer on the surface of the metal reflective layer. Radio frequency plasma is used for the deposition process, with a radio frequency power of 260 W, an argon flow rate of 12 sccm, and a nitrogen flow rate of 28 sccm. The sputtering power density is controlled at 6 W / cm². 2The winding speed keeps the substrate temperature below 145°C, and the deposition thickness is 12nm.

[0042] (4) Maintaining uninterrupted vacuum, switch to the three-target co-sputtering mode, using vanadium, tungsten, and magnesium targets as sputtering targets, and perform reactive co-sputtering in a mixed atmosphere of argon and oxygen to deposit a tungsten-magnesium co-doped vanadium dioxide thermochromic control layer on the surface of the titanium nitride anti-diffusion intermediate layer. The sputtering power density of the vanadium target is 5 W / cm². 2 The sputtering power density of the tungsten target is 1.8 W / cm³. 2 The sputtering power density of the magnesium target is 2.0 W / cm². 2 The argon flow rate was 36 sccm, and the oxygen flow rate was 0.9 sccm. The substrate temperature was controlled at 128℃ during deposition, and the deposition thickness was 75 nm. The atomic ratio of tungsten, magnesium, and vanadium atoms in the resulting film was 1.8:2.7:100.

[0043] (5) Maintain a continuous vacuum and use an electron beam evaporation method to evaporate and deposit silicon dioxide particles onto the surface of the thermochromic control layer to form a protective layer. The evaporation rate is 0.4 nm / s and the deposition thickness is 18 nm.

[0044] (6) The composite film after coating is subjected to heat curing treatment at 85°C for 3 hours to obtain the product.

[0045] Comparative Example 1 The difference between this comparative example and Example 1 is that the thermochromic control layer uses undoped vanadium dioxide. Step (4) is as follows: maintaining continuous vacuum, switching to single-target sputtering mode, using only a vanadium target as the sputtering target, and performing reactive sputtering in a mixed atmosphere of argon and oxygen to deposit a pure vanadium dioxide thermochromic control layer on the surface of the titanium nitride anti-diffusion intermediate layer. The sputtering power density of the vanadium target is 6 W / cm². 2 The argon flow rate was 40 sccm, the oxygen flow rate was 1 sccm, the substrate temperature was controlled at 135℃ during deposition, and the deposition thickness was 95 nm. The remaining steps were the same as in Example 1.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that step (4) is as follows: The vacuum is maintained continuously, and the process is switched to a three-target co-sputtering mode. Vanadium, tungsten, and magnesium targets are used as sputtering targets, and reactive co-sputtering is performed in a mixed atmosphere of argon and oxygen to deposit a tungsten-magnesium co-doped vanadium dioxide thermochromic control layer on the surface of the titanium nitride anti-diffusion intermediate layer. The sputtering power density of the vanadium target is 6 W / cm². 2 The sputtering power density of the tungsten target is 2.8 W / cm³. 2 The sputtering power density of the magnesium target is 3.5 W / cm². 2The argon flow rate was 40 sccm, and the oxygen flow rate was 1 sccm. The substrate temperature was controlled at 135℃ during deposition, and the deposition thickness was 95 nm. The atomic ratio of tungsten, magnesium, and vanadium atoms in the resulting film was 3.5:5:100. The remaining steps were the same as in Example 1.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that step (3) is as follows: The vacuum is maintained continuously, the process is switched to DC magnetron sputtering mode, a nickel target is used as the sputtering target, sputtering is performed in an argon atmosphere, and a nickel anti-diffusion intermediate layer is deposited on the surface of the metal reflective layer. The sputtering power density is 7 W / cm². 2 The argon flow rate was 30 sccm, and the substrate temperature was controlled below 140°C by controlling the winding speed, with a deposition thickness of 10 nm. The remaining steps were the same as in Example 1.

[0048] Comparative Example 4 The difference between this comparative example and Example 1 is that: steps (1) to (3) of Example 1 are performed, and step (4) is: maintaining continuous vacuum, switching to single-target sputtering mode, using only a vanadium target as the sputtering target, and depositing a pure vanadium dioxide layer in a mixed atmosphere of argon and oxygen, with the same deposition conditions as the pure vanadium dioxide layer deposition parameters in Comparative Example 1. After deposition, the film is removed and placed in an ion implantation device for dual-element ion implantation with tungsten and magnesium ions. The implantation energy and dose are optimized to achieve the same final atomic ratio of tungsten and magnesium as in Example 1. After ion implantation, the film is placed back into the vacuum roll-to-roll coating device, and steps (5) and (6) are performed.

[0049] Performance testing Referring to the relevant testing standards for spacecraft thermal control coatings, the composite coating films prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests: (1) Solar absorptivity (αs): Referring to GJB 2502.2-2006 "Test Methods for Thermal Control Coatings of Spacecraft Part 2: Solar Absorptivity Test", the spectral reflectance of the thin film in the wavelength range of 250nm to 2500nm was measured by a spectrophotometer, and the solar absorptivity was calculated by weighted average of the solar spectrum.

[0050] (2) Infrared emissivity (ε): Referring to GJB 2502.3-2006 "Test Methods for Thermal Control Coatings of Spacecraft Part 3: Emissivity Test", the hemispherical emissivity of the thin film in the 2.5μm to 40μm band was measured by the reflection method, and the emissivity at two temperature points of 25℃ and 70℃ was tested respectively.

[0051] (3) Infrared emissivity adjustment range (Δε): Calculate the difference in infrared emissivity between 70℃ and 25℃, Δε = ε_70℃ - ε_25℃, which reflects the adaptive adjustment capability of the thin film with temperature change.

[0052] (4) Reflectance decay after ultraviolet aging: Referring to GJB 2502.5-2006 "Test Methods for Thermal Control Coatings of Spacecraft Part 5: Vacuum-Ultraviolet Irradiation Test", the film was irradiated for a cumulative 200 hours under vacuum conditions using an ultraviolet light source. The irradiation conditions were set according to the standard. The average reflectance of the film in the visible and near-infrared bands before and after irradiation was tested, and the decay rate was calculated.

[0053] The test results are shown in Table 1.

[0054] Table 1 Performance Test Results

[0055] The test results above show that the films obtained in Examples 1-3 of this invention have a low overall solar absorptivity, low infrared emissivity at room temperature, significantly improved infrared emissivity at high temperatures, a large range of infrared emissivity regulation, and outstanding adaptive thermal regulation capability. Simultaneously, the film structure is stable, and the reflectivity decays little after long-term vacuum ultraviolet irradiation, demonstrating excellent overall thermal control performance and space environment tolerance. Comparative Example 1 did not involve doping or modifying vanadium dioxide. The intrinsic phase transition temperature of pure vanadium dioxide cannot be adapted to the operating temperature range of spacecraft. Its narrow intrinsic band gap leads to strong absorption of visible light, resulting in a high solar absorptivity. Furthermore, the thermochromic response is significantly weakened, and its resistance to ultraviolet aging is also insufficient. In Comparative Example 2, the tungsten and magnesium doping amounts exceed the preferred range of this invention. Excessive doping causes vanadium dioxide lattice distortion and may introduce impurity phases, which not only weakens the effect of reducing solar absorptivity but also inhibits the reversible phase transition process of the crystal, significantly reducing thermal regulation capability and consequently worsening the film's aging resistance. Comparative Example 3 uses metallic nickel instead of titanium nitride as the diffusion-resistant intermediate layer. While the nickel layer provides basic diffusion protection, its ability to induce vanadium dioxide crystal growth is weaker than that of titanium nitride, leading to a decrease in vanadium dioxide crystal quality and a reduced range of infrared emissivity modulation. Furthermore, metallic nickel exhibits lower chemical stability under ultraviolet irradiation than titanium nitride, resulting in more significant degradation of optical performance during long-term service. Comparative Example 4 employs ion implantation for element doping. Compared to in-situ co-sputtering, ion implantation easily causes uneven distribution of dopant components in the thickness direction and introduces lattice damage, resulting in a thin film thermal control effect inferior to that of the embodiments of this invention. There is also a significant difference in structural stability and radiation resistance.

[0056] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft, characterized in that, include: Flexible polymer substrate layer; A metal reflective layer is disposed on the flexible polymer substrate layer, and the material of the metal reflective layer is silver or aluminum; An anti-diffusion intermediate layer is disposed on the metal reflective layer, and the material of the anti-diffusion intermediate layer is titanium nitride; A thermochromic control layer is disposed on the anti-diffusion intermediate layer, and the material of the thermochromic control layer is tungsten-magnesium co-doped vanadium dioxide; A protective layer is disposed on the thermochromic control layer, and the material of the protective layer is silicon dioxide.

2. The adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft according to claim 1, characterized in that: The flexible polymer substrate layer is a polyester film layer or a polyimide film layer with a thickness of 12 μm to 25 μm.

3. The adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft according to claim 1, characterized in that: In the tungsten-magnesium co-doped vanadium dioxide, the atomic ratio of tungsten atoms, magnesium atoms and vanadium atoms is W:Mg:V = (0.5-2):(1-3):

100.

4. The adaptive thermochromic composite coating film for multilayer thermal insulation components in spacecraft according to claim 1, characterized in that: The thickness of the metal reflective layer is 60nm to 90nm, the thickness of the anti-diffusion intermediate layer is 8nm to 12nm, the thickness of the thermochromic control layer is 70nm to 120nm, and the thickness of the protective layer is 15nm to 30nm.

5. The method for preparing the adaptive thermochromic composite coating film for a spacecraft multilayer thermal insulation assembly according to any one of claims 1-4, comprising the following steps: (1) Place the flexible polymer substrate into a vacuum winding coating equipment, evacuate the vacuum, and perform plasma pretreatment on the substrate to make the surface tension of the substrate reach more than 50 dyn / cm. (2) A metal reflective layer is deposited on the substrate surface in an argon atmosphere using a DC magnetron sputtering method with a silver or aluminum target as the sputtering target. (3) Maintain vacuum, switch to reactive magnetron sputtering mode, use titanium target as sputtering target material, and carry out reactive sputtering in a mixed atmosphere of argon and nitrogen to deposit titanium nitride anti-diffusion intermediate layer on the surface of metal reflective layer. Radio frequency plasma is used to assist in the deposition process, and the substrate temperature is kept below 150°C by controlling sputtering power and winding speed. (4) Maintain vacuum, switch to three-target co-sputtering mode, use vanadium target, tungsten target and magnesium target as sputtering targets, carry out reactive co-sputtering in a mixed atmosphere of argon and oxygen, and deposit tungsten magnesium co-doped vanadium dioxide thermochromic control layer on the surface of titanium nitride anti-diffusion intermediate layer. (5) Maintaining a vacuum, the silicon dioxide particles are evaporated and deposited on the surface of the thermochromic control layer by electron beam evaporation to form a protective layer, thus obtaining a composite film; (6) The composite film is heat-cured at 80℃-120℃ for 1-3 hours to obtain the product.

6. The preparation method according to claim 5, characterized in that: In step (2), the sputtering power density is 3 W / cm². 2 Up to 8 W / cm 2 .

7. The preparation method according to claim 5, characterized in that: In step (3), the power density of the reactive sputtering is 5 W / cm². 2 Up to 10 W / cm 2 The radio frequency power of the radio frequency plasma-assisted radio frequency is 100 W-300 W.

8. The preparation method according to claim 5, characterized in that: In step (3), the volume flow ratio of argon to nitrogen is 1:2 to 1:

3.

9. The preparation method according to claim 5, characterized in that: In step (4), during the three-target co-sputtering process, the sputtering power density of the vanadium target is 4 W / cm². 2 Up to 8 W / cm 2 The sputtering power densities of the tungsten and magnesium targets were independently controlled to be 0.5 W / cm². 2 Up to 2 W / cm 2 .

10. The preparation method according to claim 5, characterized in that: In step (4), the volume flow ratio of argon to oxygen is 35:1 to 45:1, and the temperature of the substrate is controlled to be 130°C to 145°C during the deposition process.

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