Thermal management film capable of realizing zero energy consumption and dual modes as well as preparation method and application of thermal management film

Abstract

The invention relates to the technical field of heat management, and discloses a zero-energy-consumption dual-mode heat management film and a preparation method and application thereof.The method comprises the steps that vanadium pentoxide and hydrazine hydrochloride are added into deionized water to be evenly mixed for a hydrothermal reaction, cooling, washing, suction filtration and drying are conducted at the cooling rate of 0.08-0.4 DEG C / min after the reaction is finished, and star-shaped VO2 powder is obtained; the preparation method comprises the following steps: dissolving poly (4-methyl-1-pentene) in cyclohexane to prepare a first coating solution; dissolving poly (4-methyl-1-pentene) in cyclohexane, adding star-shaped VO2 powder, and uniformly dispersing the star-shaped VO2 powder to prepare a second coating solution; and sequentially coating the first coating liquid and the second coating liquid on the ITO side of an ITO-PET film to form a film, so as to obtain the zero-energy-consumption dual-mode thermal management film. Compared with traditional modes such as magnetron sputtering, atomic layer deposition, electron beam evaporation, ion beam etching and pulse laser deposition, the coating method (such as a blade coating method) has the advantages that the preparation method is simple, the prepared sample is large in size, and large-scale industrial production is facilitated.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, specifically to a thermal management thin film that achieves zero-energy dual-mode operation, its preparation method, and its application. Background Technology

[0002] Global demand for advanced thermal management solutions continues to grow. Traditional methods relying on fossil fuels face significant sustainability challenges, as thermal management accounts for nearly 50% of global annual energy consumption. Radiative thermal management systems achieve passive temperature regulation without external energy input by utilizing the cold universe (~3 K) as a thermodynamic cold source through mid-infrared (MIR) radiation within an atmospheric transparency window (8–13 μm). However, static radiative cooling systems with fixed emissivity have operational limitations, particularly in suboptimal thermal environments where overcooling can occur, increasing the need for auxiliary heating. Therefore, developing materials capable of spontaneously switching between cooling and heating modes is crucial for achieving dynamic thermal regulation that adapts to fluctuating environmental conditions.

[0003] Vanadium dioxide (VO2) is a temperature-responsive phase change material that has been extensively studied for applications such as smart windows, building insulation coatings, and camouflage due to its dynamically tunable infrared (IR) emissivity within the atmospheric window (ATW). However, its reliance on precision manufacturing techniques such as magnetron sputtering or pulsed laser deposition, along with the complex metasurface design requirements, significantly limits its scalability and practical applications.

[0004] Hydrothermal synthesis has emerged as a promising approach for preparing vanadium dioxide-based thin films due to its scalability, morphology tunability, and ease of processing. Typically, hydrothermal processes require precise control of temperature and atmosphere to ensure high purity and well-defined crystal structures in vanadium dioxide, crucial for effective mid-infrared modulation. However, most hydrothermally synthesized vanadium dioxide powders exhibit layered, blocky, or flake-like morphologies and limited thermochromic modulation (Δε < 0.5) in the mid-infrared region. Optimizing the emissivity spectrum in the atmospheric transmission window region remains essential for advancing radiative thermal management systems. Summary of the Invention

[0005] This invention proposes a simplified hydrothermal synthesis and multi-material coating strategy for VO2 to fabricate large-size dual-mode radiative thermal management films. By controlling the cooling rate of hydrothermal synthesis, star-shaped VO2(M) powder was synthesized, solving the problem of low emissivity change before and after phase transition caused by the small specific surface area of ​​blocky, sheet-like, and layered VO2(M) powders. Furthermore, a mixed solution of PMP-VO2 was coated onto an ITO-PET film, overcoming the problems of complex preparation processes, difficulty in mass production, and lack of flexibility in traditional VO2-based phase change radiative cooling materials.

[0006] This invention prepares star-shaped VO2(M) nanoparticles with a high surface area to volume ratio (SA:V) by controlling the cooling rate during the hydrothermal reaction process; subsequently, radiative thermal management films reaching the meter scale (lengths exceeding 1 meter) are prepared by a blade coating method. These films achieve autonomous temperature regulation by realizing spectral modulation with an average Δε = 0.64 in the atmospheric transmission wavelength (ATW) band, and can spontaneously and reversibly switch between cooling and heating modes. This technical solution combines radiative thermal management and camouflage through a simple and scalable manufacturing strategy, laying the foundation for multifunctional adaptive thermal management in dynamic environments.

[0007] To achieve the above objectives, the present invention provides a method for preparing a thermal management thin film with zero energy consumption dual modes, characterized by comprising the following steps: S1. Vanadium pentoxide (V2O5) and hydrazine hydrochloride (N2H4·HCl) were added to deionized water and mixed to prepare a hydrothermal synthesis precursor suspension. Then, a hydrothermal reaction was carried out. After the reaction was completed, the mixture was cooled at a cooling rate of 0.08~0.4 ℃ / min. After washing, filtration and drying, star-shaped VO2 powder in the M phase was obtained. S2. Dissolve poly(4-methyl-1-pentene) (PMP) in cyclohexane to prepare the first coating solution; dissolve poly(4-methyl-1-pentene) in cyclohexane and add star-shaped VO2 powder to disperse evenly to prepare the second coating solution. S3. Using ITO-PET film as the high-reflectivity layer of Fabry-Perot structure, the first coating liquid and the second coating liquid are sequentially coated on the ITO side of the ITO-PET film to form the intermediate layer and phase change layer of Fabry-Perot structure, respectively, and finally a thermal management film with zero energy consumption dual mode is obtained.

[0008] As a further preferred embodiment of the present invention, the stoichiometric ratio of vanadium pentoxide and hydrazine hydrochloride is 1:0.6 to 1:0.7.

[0009] As a further preferred embodiment of the present invention, the hydrothermal reaction temperature is 270~290 ℃, and the reaction time is 24~72 h. After the reaction is completed, the target cooling temperature is below 45 ℃ and room temperature.

[0010] As a further preferred technical solution of the present invention, the washing process is as follows: the product after the hydrothermal reaction is completed is mixed with deionized water, first ultrasonicated in a water bath for 10-30 min, then centrifuged at 6000-8000 rpm for 1-5 min, the supernatant is discarded and deionized water is added again to repeat the washing process.

[0011] As a further preferred embodiment of the present invention, the concentration of poly4-methyl-1-pentene in the first coating solution is 5~15 mg / mL, and the coating film thickness of the first coating solution is 1.0~5.0 μm; the concentration of poly4-methyl-1-pentene in the first coating solution is 5~15 mg / mL, the concentration of VO2 is 20~35 mg / mL, and the coating film thickness of the second coating solution is 10~20 μm.

[0012] As a further preferred technical solution of the present invention, the preparation process of the second coating liquid is as follows: poly-4-methyl-1-pentene and star-shaped VO2 powder are added to cyclohexane, and the poly-4-methyl-1-pentene is first dissolved by magnetic stirring on a hot table at 50~70 °C, and then the star-shaped VO2 powder is uniformly dispersed by ultrasonication with a probe in an ice-water bath. As a further preferred technical solution of the present invention, after the ultrasonic treatment of the ice-water bath probe is completed, the second coating solution is allowed to stand at room temperature before coating.

[0013] As a further preferred technical solution of the present invention, the coating is performed by any one of spin coating, blade coating or spray coating.

[0014] According to a second aspect of the present invention, the present invention also provides a thermal management thin film that achieves zero-energy dual-mode operation, which is prepared by the above-described preparation method.

[0015] According to a third aspect of the invention, the invention also provides an application of a thermal management thin film that achieves zero-energy dual-mode thermal management for thermal management.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: 1) The VO2(M) nanoparticles of the present invention are prepared by hydrothermal synthesis. By precisely controlling the cooling rate of hydrothermal synthesis, star-shaped VO2(M) can be synthesized. Due to its high specific surface area, it significantly improves the change of infrared emissivity of the material compared with other VO2(M) powders such as block, sheet, and layer. 2) Compared with traditional methods such as magnetron sputtering, atomic layer deposition, electron beam evaporation, ion beam etching, and pulsed laser deposition, the coating method of the present invention (such as the blade coating method) has the advantages of simple preparation method and large sample size, and is easy to mass industrial production. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 This is a schematic diagram of the hydrothermal synthesis of star-shaped VO2(M) nanoparticles in Example 1; Figure 2The fabrication process and SEM image of the cross-section of the large-size zero-energy dual-mode radiative thermal management film prepared in Example 1 are shown. Figure 3 The images shown are (a) a photograph of the thermal management film, (b) a schematic cross-sectional view of the infrared characterization device, and (c) data on the changes in infrared absorption / emissivity in Example 1. Figure 4 Infrared absorption / emissivity characterization of thermal management films prepared from VO2(M) nanoparticles synthesized at different cooling rates in Examples 1-6; Figure 5 SEM images of VO2(M) nanoparticles synthesized at different cooling rates in Examples 1-6.

[0019] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0021] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0022] Example 1 Depend on Figure 1 As shown, this embodiment provides a method for preparing a large-size, zero-energy-consumption dual-mode radiative thermal management thin film, as detailed below: 1) Mix 1.82 g V₂O₅, 0.44 g N₂H₄·HCl, and 30 mL deionized water, add the mixture to a 100 mL PPL hydrothermal reactor, and place it in a muffle furnace. React at 285 °C for 48 h, then cool to 40 °C at a cooling rate of 0.1 °C / min. Transfer the product from the reactor to centrifuge tubes, and alternately sonicate with deionized water for 20 min three times, centrifuge at 8000 rpm for 180 s to wash the product, then filter to collect the product. Finally, place the filtered powder in an 80 °C vacuum oven to dry for 24 h to obtain star-shaped VO₂(M) powder.

[0023] 2) Dissolve 100 mg of PMP particles in 10 mL of cyclohexane under magnetic stirring at 80 °C to obtain a 10 mg / mL first coating solution. Figure 2 As shown in a1), the solution is scraped onto the ITO side of the ITO-PET film ( Figure 1 (a) is dried to obtain a PMP-ITO-PET film forming the intermediate PMP layer. Figure 2 In b), the thickness of the intermediate layer is 2.1 μm.

[0024] 3) Add 300 mg VO2(M) powder and 100 mg PMP to 10 mL cyclohexane, stir magnetically at 60 °C for 30 min to dissolve, then sonicate at 400 W probe in an ice-water bath for 60 min to uniformly disperse the VO2(M) powder, obtaining the second coating solution. Figure 2 (As shown in c1). The solution was coated onto PMP-ITO-PET to form a phase change layer PMP-VO2 layer with a thickness of 18.9 μm. Figure 2 In the case of e), a large-size dual-mode radiation thermal management film VO2-PMP-ITO-PET was finally obtained. Figure 2 (d) is also known as meter-scale radiative thermal management film.

[0025] The thermal management film VO2-PMP-ITO-PET prepared by the present invention has a Fabry-Perot structure, including a phase change layer PMP-VO2, an intermediate layer PMP, and a high-reflectivity layer ITO-PET stacked sequentially along the thickness.

[0026] like Figure 1 As shown, the VO2(M) nanoparticles prepared by hydrothermal synthesis in Example 1 have a star-shaped crystal structure under SEM.

[0027] like Figure 3 As shown in a, Example 1 prepared a large-area zero-energy dual-mode radiative thermal management film with a width of about 0.4 m and a length of about 1 m by a scraping coating method.

[0028] like Figure 3 As shown in b, the infrared emissivity spectrum of Example 1 was tested using the illustrated apparatus. Due to the presence of the ITO layer, the sample does not have infrared transmittance; therefore, a heating element was placed above the sample to facilitate testing its emissivity at room temperature and 90 °C. The test results are as follows. Figure 3 As shown in c, the film of Example 1 exhibits a high infrared emissivity variation between the two different modes.

[0029] Examples 2-6 Based on Example 1, a series of thermal management films were prepared by simply changing the cooling rate after the hydrothermal reaction. The cooling rates of Examples 2-6 were 0.8 ℃ / min, 0.6 ℃ / min, 0.47 ℃ / min, 0.28 ℃ / min, and 0.05 ℃ / min, respectively. The other similarities with Example 1 will not be repeated.

[0030] The following tests were conducted on the radiative heat management films of Examples 1-6 above: like Figure 4 As shown, the infrared emissivity of the thermal management films prepared in Examples 1-6 was characterized. It can be seen that the infrared emissivity of Example 1 has the largest change, with an average emissivity change rate of about 0.64 in the 8~13 μm band. This is because the star-shaped VO2(M) powder selected in Example 1 has a higher specific surface area than bulk, layered and sheet-like VO2 powders, so it can achieve a larger absorption cross-section. The crystal form of VO2 is controlled by the cooling rate.

[0031] like Figure 5 As shown in Figure af, as the cooling rate decreases, the prepared VO2(M) powder gradually changes from a blocky state (as shown in Figure af). Figure 5 In the middle (a), it becomes sheet-like (such as...). Figure 5 (b) As the cooling rate further decreases, the content of star-shaped VO2(M) phase powder in the prepared VO2(M) increases. Due to its high specific surface area, the infrared spectral density also increases. This continues until the reaction rate is controlled at 0.1 °C / min, at which point the amount of star-shaped VO2(M) reaches its maximum, and the infrared spectral density of the radiation heat management film prepared from it is also the highest (~0.64). When the cooling rate is further reduced to 0.05 °C / min, it is observed that the prepared powder contains no star-shaped VO2(M) or very little of it. This is because the cooling rate is too low, resulting in an excessively long reaction time (>94 h), and the excessively low cooling rate cannot effectively control the crystal form of the reaction product. Therefore, the preferred cooling rate of this invention is 0.08~0.4 °C / min, with 0.1 °C / min being optimal.

[0032] Comparative Example 1 As a control experiment for Example 1, the only difference from Example 1 is the composition of the second coating solution; the rest is the same as Example 1 and will not be repeated here. Specifically, 300 mg of the VO2(M) powder prepared in Example 1 was added to 10 mL of cyclohexane, and after dissolution by magnetic stirring at 60 °C for 30 min, it was sonicated in an ice-water bath at 400 W for 60 min to uniformly disperse the VO2(M) powder, thus obtaining the second coating solution.

[0033] The spectral performance of the samples from Example 1 and Comparative Example 1 was tested after being placed under the same conditions for 6 months. The VO2(M) powder in Example 1 was coated with PMP and did not come into direct contact with oxygen, so the change in infrared absorption emissivity was not significant. However, the VO2(M) in Comparative Example 1 lacked coating and was oxidized by direct contact with air on the top layer, so the change in infrared absorption emissivity was significantly reduced.

[0034] The above test results effectively demonstrate that a strategy for preparing star-shaped VO2(M) nanoparticles is provided by precisely controlling the cooling rate during hydrothermal synthesis; large-size dual-mode radiative thermal management films can be prepared by blade coating. Therefore, this invention can effectively solve the problems of complex preparation processes, difficulty in mass production, and lack of flexibility in traditional VO2-based phase change radiative cooling materials by hydrothermally synthesizing VO2(M) powder and configuring it into a suspension for blade coating.

[0035] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A method for preparing a thermal management thin film achieving zero-energy dual-mode operation, characterized in that, Includes the following steps: S1. Vanadium pentoxide and hydrazine hydrochloride were added to deionized water and mixed to prepare a hydrothermal synthesis precursor suspension. Then, a hydrothermal reaction was carried out. After the reaction was completed, the mixture was cooled at a cooling rate of 0.08~0.4 ℃ / min. After washing, filtration and drying, star-shaped VO2 powder in the M phase was obtained. S2. Dissolve poly4-methyl-1-pentene in cyclohexane to prepare the first coating solution; dissolve poly4-methyl-1-pentene in cyclohexane and add star-shaped VO2 powder to disperse evenly to prepare the second coating solution. S3. The first coating liquid and the second coating liquid are sequentially coated onto the ITO side of the ITO-PET film to form a film, and finally a thermal management film with zero energy consumption dual mode is obtained.

2. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 1, characterized in that, The stoichiometric ratio of vanadium pentoxide and hydrazine hydrochloride is 1:0.6 to 1:0.

7.

3. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 1, characterized in that, The hydrothermal reaction temperature is 270~290 ℃, and the reaction time is 24~72 h.

4. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 1, characterized in that, The washing process is as follows: after the hydrothermal reaction is completed, the product is mixed with deionized water, first ultrasonicated in a water bath for 10-30 min, then centrifuged at 6000-8000 rpm for 1-5 min, the supernatant is discarded and deionized water is added again to repeat the washing process.

5. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 1, characterized in that, The concentration of poly4-methyl-1-pentene in the first coating solution is 5~15 mg / mL, and the coating film thickness of the first coating solution is 1.0~5.0 μm; the concentration of poly4-methyl-1-pentene in the first coating solution is 5~15 mg / mL, the concentration of VO2 is 20~35 mg / mL, and the coating film thickness of the second coating solution is 10~20 μm.

6. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 1, characterized in that, The preparation process of the second coating solution is as follows: poly4-methyl-1-pentene and star-shaped VO2 powder are added to cyclohexane, and the poly4-methyl-1-pentene is first dissolved by magnetic stirring on a hot table at 50~70°C, and then the star-shaped VO2 powder is uniformly dispersed by ultrasonication with a probe in an ice-water bath.

7. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 6, characterized in that, After the probe is sonicated in an ice-water bath, the second coating solution is allowed to stand at room temperature before coating.

8. The method for preparing a thermal management thin film with zero energy consumption dual mode according to claim 1, characterized in that, The coating is applied using any one of the following methods: spin coating, scraping coating, or spray coating.

9. A thermal management thin film achieving zero-energy dual-mode operation, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The thermal management film of claim 9, which achieves zero energy consumption dual-mode, is used for thermal management applications.

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