A surface hydrophobic type heat-conducting and wave-absorbing multifunctional flexible composite film and a preparation method and application thereof

Abstract

This invention belongs to the technical field of multifunctional materials for electromagnetic protection and thermal management, and discloses a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film, its preparation method, and its application. This invention uses a hydrothermal-annealing process to prepare Ni@WO3. 3‑x @C layered nanosheet arrays, used as thermally conductive and microwave-absorbing multifunctional fillers, were uniformly mixed with thermoplastic polyurethane (TPU) matrix in a certain ratio using 1,4-dioxane as solvent, and the mixture was then evaporated to obtain a novel high-strength, hydrophobic Ni@WO3. 3‑x @C Thermally Conductive and Microwave-Absorbing Multifunctional Flexible Composite Membrane. The hydrothermal-annealing preparation process used in this invention is simple, and the product morphology is novel, filling the gap in the application of tungsten-based materials in electromagnetic wave absorption and thermal conductivity. The product structure is novel, and its morphology, phase structure, and properties can all be controlled. The prepared composite membrane possesses high strength, good flexibility, excellent hydrophobicity, high thermal conductivity, and broadband lightweight microwave absorption performance, showing good prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the technical field of multifunctional materials for electromagnetic protection and thermal management, and relates to an integrated thermally conductive and microwave-absorbing material and its thermally conductive and microwave-absorbing applications. Specifically, it discloses a tungsten-based multifunctional filler (Ni@WO3). 3-x @C / TPU (0 < x < 1), thermally conductive, microwave absorbing, and hydrophobic surface multifunctional flexible composite membrane, its preparation method and application. Background Technology

[0002] Tungsten atoms have a unique electronic configuration ([Xe] 4f). 14 5d 4 6s²), rich in oxidation states, can form WO3, W 18 O 49 Tungsten oxides include various forms such as WO2, W2O5, and WO3·H2O. Tungsten oxides possess unique physicochemical properties and broad prospects for multifunctional applications. Their abundant oxidation states and defect structures readily induce interfacial polarization and dipole polarization, giving them excellent application potential in the field of electromagnetic wave absorption. Furthermore, tungsten oxide crystal structures are stable, and thermal conduction is primarily phonon-based.

[0003] Currently, tungsten-based materials used for electromagnetic wave absorption mainly include metallic phase compound-based composite materials such as tungsten carbide and tungsten nitride, as well as semiconductor phase compound-based composite materials such as tungsten oxide and tungsten sulfide. Among existing related patents, Chinese patent CN114014366A discloses a method for preparing a WO3 / WC core-shell hollow structure microwave absorbing material. This method employs a ball milling-annealing process, with a milling time of 48-72 hours, relying on specialized equipment, and a filler filling ratio as high as 75%. Chinese patent CN115896737A reports a high-temperature resistant tungsten / carbon core silicon carbide fiber microwave absorbing material, with a preparation annealing temperature as high as 1200℃ and using acetylene and argon as carrier gases, posing certain safety risks. Chinese patent CN 109206925A proposes a WS2-multi-walled carbon nanotube three-dimensional self-assembled microwave absorbing material, but its effective absorption bandwidth is only 3.08 GHz under a matching thickness of 3.0 mm. Furthermore, research and application of tungsten-based materials in the field of integrated thermal conductivity and microwave absorption are still largely unexplored.

[0004] Therefore, developing a novel thermally conductive and microwave-absorbing integrated tungsten-based microwave absorbing filler with simple preparation process, low filling ratio, excellent microwave absorption performance, low cost and industrial scalability has become a key scientific and technological problem that urgently needs to be solved in this field. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film, its preparation method, and its application, which is a tungsten-based flexible Ni@WO3 film. 3-x@C / TPU (0 < x < 1) is a multifunctional composite membrane with thermal conductivity, microwave absorption, and hydrophobic surface. It combines novel filler, high flexibility, hydrophobic properties, and thermal conductivity / microwave absorption performance. The thermally conductive / microwave-absorbing filler is Ni@WO3. 3-x The C-layered nanosheet array has a length of 0.51~8.27 μm and a width of 0.20~1.17 μm. The thermally conductive and microwave-absorbing filler is prepared by hydrothermal method in the first step and annealing method in the second step. This not only effectively avoids the disadvantages of poor experimental repeatability and insufficient performance in the previous preparation process, but also fills the gap of tungsten-based materials as integrated microwave-absorbing and thermally conductive materials.

[0006] To achieve the above objectives, the present invention discloses the following technical content:

[0007] The first technical objective of this invention is to disclose a tungsten-based flexible thermally conductive and microwave-absorbing multifunctional flexible composite membrane, specifically a Ni@WO3-based membrane. 3-x @C / TPU (0 < x < 1) thermally conductive and microwave-absorbing multifunctional composite film is made by dispersing thermally conductive and microwave-absorbing multifunctional fillers and thermoplastic polyurethane (TPU) matrix in an organic solvent and forming a film by evaporating the solvent.

[0008] The thermally conductive and microwave-absorbing multifunctional filler is magnetic Ni@WO3. 3-x The @C complex has a structure of layered nanosheet arrays with a length of 0.51~8.27 μm and a width of 0.20~1.17 μm, and a Ni / W atomic ratio of (0~1):1.

[0009] The multifunctional flexible composite membrane has high flexibility, high strength, high thermal conductivity, strong absorption, and hydrophobic surface. Its fracture strain is 643.52%, tensile strength is 17.84 MPa, and thermal conductivity is 2.52~3.73 W / (m·K). The effective absorption bandwidth of the thermally conductive and microwave-absorbing multifunctional filler is 3.12~9.04 GHz, and the maximum absorption is -21.5~-53.3 dB. The static water contact angle is 93.3~104.249°.

[0010] The second technical objective of this invention is to disclose a method for preparing the multifunctional flexible composite membrane as described above. The multifunctional flexible composite membrane is prepared by solvent evaporation. TPU particles and 1,4-dioxane organic solvent are added to a container in a certain stoichiometric ratio and stirred at 60°C to 70°C for 8 to 12 hours to dissolve and obtain a TPU solution. Then, the ground thermally conductive and microwave-absorbing multifunctional filler is added to the TPU solution and stirred to obtain a uniform thermally conductive and microwave-absorbing slurry. The thermally conductive and microwave-absorbing slurry is poured into a mold, and the solvent is evaporated to obtain the surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite membrane.

[0011] Specifically, the method for preparing a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film disclosed in this invention includes the following steps: (1) A certain mass of TPU particles was added to 1,4-dioxane solvent and allowed to stand at room temperature for 3 hours to obtain gel-like TPU; (2) At room temperature, the thermally conductive and microwave-absorbing multifunctional filler (Ni@WO) 3-x The C-layered nanosheet array was poured into a 1,4-dioxane solvent and ultrasonically stirred until uniformly dispersed. (3) Pour the solution described in step (2) into the TPU gel in step (1) and stir in an oil bath at 60°C to 70°C for 2 hours until a uniform thermally conductive and microwave-absorbing slurry is obtained. (4) Pour the thermally conductive and microwave-absorbing slurry into the mold, remove the gas in the system under vacuum, and after the surface is flat, put it into an electric heating drying oven and heat it at 70°C until it is dry. Demold to obtain the tungsten-based flexible thermally conductive and microwave-absorbing, hydrophobic multifunctional composite film.

[0012] Optionally, the concentration of the TPU solution is 0.03~0.1 g / mL, preferably 0.05~0.06 g / mL, and the filler content in the TPU substrate is 5~40% by mass.

[0013] The preparation method of the thermally conductive and microwave-absorbing multifunctional filler is as follows: Ni@WO is prepared using a hydrothermal-high-temperature annealing process. 3-x @C layered nanosheet array. The specific steps of the hydrothermal-high temperature annealing process are as follows: (1) Take an appropriate amount of deionized water in the reactor, dissolve nickel nitrate hexahydrate in the deionized water, stir magnetically for 20 min at room temperature, add ammonium paratungstate to the green transparent solution, continue stirring for 30 min to obtain a milky white suspension; add hydrochloric acid dropwise into the stirred suspension, cover the reactor and stir for 20 min, remove the stir bar and transfer to an electric heating drying oven, react at 165℃~200℃ for 6~10 h, cool naturally to room temperature, wash several times with deionized water and industrial alcohol, dry at 60℃ for 8 h to obtain Ni-WO3·0.5H2O / WO3 precursor; (2) Prepare a certain concentration of nickel acetate tetrahydrate solution in a centrifuge tube, add an appropriate amount of Ni-WO3·0.5H2O / WO3 precursor obtained in step (1), impregnate and transfer to an alumina boat, dry at 80°C for 4 h, and obtain green crystals after drying. Place the alumina boat in a tube furnace, program the temperature to 550°C, anneal for two hours, and take it out after natural cooling to obtain the thermally conductive and microwave-absorbing multifunctional filler.

[0014] This invention first prepares Ni-WO3·0.5H2O / WO3 precursors with different morphologies by controlling the content of nickel nitrate hexahydrate and utilizing an acid precipitation reaction. As the content of nickel nitrate hexahydrate is adjusted to 9.7 × 10⁻⁶, the precursors are further differentiated. -4 ~1.9×10 -2 The precursor morphology gradually changes from a layered nanosheet array to nanofibers as the g / mL range increases. The nanosheets have a length of 0.47–2.30 μm and a width of 0.64–0.71 μm; the nanofibers have a length of 1.3–3.6 μm and a diameter of 30–244 nm.

[0015] Furthermore, Ni@WO3 with different Ni loadings was prepared by high-temperature annealing and reduction. 3-x @C layered nanosheet arrays: This method is low-cost, high-yield, and exhibits excellent reproducibility. By varying the molar ratio of nickel acetate tetrahydrate to the Ni-WO3·0.5H2O / WO3 precursor, the loading of elemental Ni on the surface of the Ni-WO3·0.5H2O / WO3 precursor was positively correlated with the molar ratio, with the following molar ratios: 0:1, 0.125:1, 0.25:1, 0.5:1, and 1:1. Ni@WO 3-x The @C layered nanosheet array has a length of 0.51–8.27 μm and a width of 0.26–1.17 μm.

[0016] Furthermore, the present invention also provides an application of the surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite film as described above in the field of microwave absorption and thermal conduction.

[0017] It should be noted that the Ni@WO material disclosed in this invention is prepared using a high-temperature annealing process. 3-x The @C layered nanosheet array structure is innovative, allowing for the manipulation of its morphology, electrical conductivity, static water contact angle, and thermal conductivity-wave absorption properties by varying the Ni(CH3COO)2·4H2O content. The resulting Ni@WO 3-x The C-layered nanosheet array has a length of 0.51–8.27 μm and a width of 0.26–1.17 μm; its electrical conductivity is 1.5 × 10⁻⁶. -3 ~1000 S / m; static water contact angle range is 93.3°~104.249°; elemental nickel is reduced in the gap, which not only improves the electrical conductivity, but also forms a continuous thermally conductive network with a good electron transport path, enhancing electron thermal conductivity; in the field of microwave absorption, magnetic metal doping increases the magnetic loss mechanism of electromagnetic waves, and the introduction of surface carbon elements enhances dielectric loss, making it have great potential in the fields of thermal conduction and microwave absorption.

[0018] The Ni@WO prepared in this invention 3-x@C layered nanosheet arrays exhibit excellent thermal conductivity and microwave absorption properties, with a thermal conductivity of 2.52~3.73 W / (m·K); the effective absorption bandwidth of the thermally conductive and microwave-absorbing multifunctional filler is 3.12~9.04 GHz, the maximum absorption is -21.5~-53.3 dB, and the thickness is 2.3~5.0 mm.

[0019] The preparation method disclosed in this invention is simple to operate and produces novel and controllable product morphology with high experimental repeatability. It effectively avoids the disadvantages of poor experimental repeatability and insufficient performance in previous preparation processes. It also fills the gap in tungsten-based materials as integrated heat-absorbing and heat-conducting materials, and opens up the beginning of tungsten-based materials as new integrated heat-conducting and heat-absorbing materials, with good potential for industrial application.

[0020] As can be seen from the above technical solution, compared with the prior art, the present invention provides a tungsten-based flexible thermally conductive and microwave-absorbing, hydrophobic multifunctional composite film and its preparation and application, which has the following excellent effects: 1) This invention employs a hydrothermal-high temperature annealing process to prepare Ni@WO with a layered nanosheet array structure. 3-x @C Thermally Conductive and Microwave-Absorbing Filler. This preparation method is safe, controllable, and easy to operate, and can achieve uniform loading of nickel on a tungsten oxide substrate; increasing the nickel content can effectively improve the material's electrical conductivity, achieving a synergistic enhancement of thermal conductivity and microwave absorption performance.

[0021] 2) The Ni@WO prepared in this invention 3-x @C features a novel structure, tunable heterojunction interface, high conductivity, magnetic / dielectric double loss, and electron / phonon dual carriers, exhibiting excellent electromagnetic wave absorption and heat transfer performance.

[0022] 3) The Ni@WO of this invention 3-x @C materials have a simple preparation process, strong chemical stability, are environmentally friendly, and have low requirements for equipment precision, making them promising for industrial production.

[0023] 4) Ni@WO prepared in this invention 3-x @C / TPU composite film possesses multiple properties such as excellent flexibility, hydrophobicity, mechanical strength, high thermal conductivity, and broadband lightweight microwave absorption, and has broad application potential in electromagnetic protection, thermal management and other fields. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figures 1-3 The phase and morphology of the product obtained in Example 1 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0026] Figures 4-6 The phase and morphology of the product obtained in Example 2 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0027] Figures 7-9 The phase and morphology of the product obtained in Example 3 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0028] Figures 10-12 The phase and morphology of the product obtained in Example 4 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0029] Figures 13-15 The phase and morphology of the product obtained in Example 5 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0030] Figures 16-18 The phase and morphology of the product obtained in Example 6 of this invention were measured under XRD, EDX and scanning electron microscope, respectively.

[0031] Figure 19 The morphology of the product obtained in Example 7 of this invention was measured under a scanning electron microscope.

[0032] Figure 20 The morphology of the product obtained in Example 8 of this invention is measured under a scanning electron microscope.

[0033] Figure 21 The morphology of the product obtained in Example 9 of this invention is measured under a scanning electron microscope.

[0034] Figure 22 The morphology of the product obtained in Example 10 of this invention was measured under a scanning electron microscope.

[0035] Figure 23 The morphology of the product obtained in Example 11 of this invention is measured under a scanning electron microscope.

[0036] Figure 24 The morphology of the product obtained in Example 12 of this invention was measured under a scanning electron microscope.

[0037] Figure 25 The morphology of the product obtained in Example 13 of this invention is measured under a scanning electron microscope.

[0038] Figure 26 This refers to the static water contact angle of the pure TPU membrane prepared in Example 2 of the present invention.

[0039] Figure 27This refers to the static water contact angle of the multifunctional composite membrane prepared in Embodiment 2 of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0041] This invention discloses a flexible, high-strength, hydrophobic, and thermally conductive-wave-absorbing multifunctional composite membrane with good thermal conductivity and microwave absorption properties, as well as its preparation method and application.

[0042] To better understand the present invention, the following embodiments are provided for further detailed description of the invention, but they should not be construed as limiting the invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description are also considered to fall within the protection scope of the present invention.

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0044] Example 1 A method for preparing a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film specifically includes the following steps: Take 80 mL of deionized water and add 0.0776 g of nickel nitrate hexahydrate to a polytetrafluoroethylene liner. Stir magnetically at room temperature for 30 min until a clear solution is formed. Then add 1.3867 g of ammonium paratungstate to the solution and continue stirring for 30 min. Add 0.1333 mL of concentrated hydrochloric acid (36.0%–38.0% by mass) to the suspension, cover, and continue stirring for 30 min. Then transfer the reactor to an oven and react at 165 °C for 6 h. After naturally cooling to room temperature, remove the solution, wash it several times with deionized water and industrial alcohol, and dry it at 60 °C for 8 h to obtain the Ni-WO3·0.5H2O / WO3 precursor.

[0045] 2 g of TPU and 20 mL of 1,4-dioxane solvent were placed in a beaker and stirred at 80 °C for 8 h to obtain a clear TPU solution. The above Ni-WO3·0.5H2O / WO3 was added to the 1,4-dioxane solvent at a mass filling ratio of 15% (approximately 0.35 g), and ultrasonically stirred until uniformly dispersed. This solution was poured into the TPU gel solution and stirred in an oil bath at 60 °C to 70 °C for 2 hours until a uniform thermally conductive and microwave-absorbing slurry was obtained. The thermally conductive and microwave-absorbing slurry was poured into a mold, and the gas in the system was removed under vacuum. After the surface was smoothed, it was placed in an electric heating drying oven and heated at 70 °C until dry. The mold was then removed to obtain the hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film.

[0046] Figures 1-3 The images show the phase and morphology of the product obtained in Example 1 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0047] The above analysis shows that the product is Ni-WO3·0.5H2O / WO3, and the nanosheet array has a length of 0.47~2.3 μm and a width of 0.64~0.71 μm.

[0048] The thermal conductivity and microwave absorption properties are shown in Table 1. The obtained Ni-WO3·0.5H2O / WO3 exhibits good microwave absorption and thermal conductivity. The maximum effective bandwidth with a reflectivity of less than or equal to -10 dB is 3.12 GHz at a thickness of 5.0 mm, and the maximum absorption reaches -21.5 dB at a matched thickness of 3.0 mm. The thermal conductivity is 2.52 W / (m²). K).

[0049] Example 2 A method for preparing a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film involves annealing the Ni-WO3·0.5H2O / WO3 precursor prepared in Example 1 to prepare Ni@WO3. 3-x The specific steps for using a C-layered nanosheet array are as follows: 0.5 g of Ni-WO3·0.5H2O / WO3 precursor was added to 10 mL of 0.2 M nickel acetate tetrahydrate solution and impregnated for 1 h. The mixture was then transferred to an alumina boat and dried at 80 °C for 4 h. After drying, a green powder was obtained. The alumina boat was placed in a tube furnace and heated to 550 °C under argon protection at a rate of 5 °C / min. After annealing for two hours and allowing to cool naturally, the powder was removed. This is the thermally conductive and microwave-absorbing multifunctional filler.

[0050] Ni@WO3 was prepared by laminating a thermally conductive and microwave-absorbing multifunctional filler onto TPU using the method shown in Example 1. 3-x @C / TPU composite film.

[0051] Figures 4-6 The figures show the phase composition and morphology of the product obtained in Example 2 of this invention as measured by XRD, EDX, and scanning electron microscopy. As can be seen from the above analysis, the product is Ni, WO. 3-x The C complex (named Ni@WO) 3-x @C), the nanosheet array is 0.51~1.35 μm long and 0.26~0.33 μm wide, and a large number of nickel nanoparticles are loaded on the surface of the layered nanosheet array.

[0052] Figure 26 The static water contact angle of the pure TPU film is 78.607°. Figure 27 The Ni@WO obtained in Example 2 of this invention 3-x The static water contact angle of the @C / TPU composite membrane is 104.249°.

[0053] The thermal conductivity and microwave absorption properties are shown in Table 1. The obtained Ni@WO 3-x @C layered nanosheet arrays exhibit excellent microwave absorption and thermal conductivity. The maximum effective bandwidth with a reflectivity of -10 dB or less reaches 8.96 GHz at a thickness of 2.3 mm, and the maximum absorption reaches -44.5 dB at a matched thickness of 2.7 mm; the thermal conductivity is 3.73 W / (m²). K).

[0054] Example 3 A method for preparing a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite membrane, with other conditions remaining unchanged, except that the concentration of nickel acetate tetrahydrate is changed to 0.1 M based on Example 2.

[0055] Figures 7-9 The images show the phase and morphology of the product obtained in Example 3 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0056] The above analysis shows that the product is Ni, WO. 3-x The C complex (named Ni@WO) 3-x @C), the nanosheet array is 5.74~8.27 μm long and 0.78~1.17 μm wide, and a large number of nickel nanoparticles are loaded on the surface of the layered nanosheet array.

[0057] The thermal conductivity and microwave absorption properties are shown in Table 1. The obtained Ni@WO 3-x @C layered nanosheet arrays exhibit excellent microwave absorption and thermal conductivity. The maximum effective bandwidth with a reflectivity of -10 dB or less reaches 7.52 GHz at a thickness of 2.9 mm, and the maximum absorption reaches -53.3 dB at a matched thickness of 1.9 mm. The thermal conductivity is 3.53 W / (m²). K).

[0058] Example 4 A method for preparing a surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite membrane, with other conditions remaining unchanged, except that the concentration of nickel acetate tetrahydrate is changed to 0.05 M based on Example 2.

[0059] Figures 10-12 The images show the phase and morphology of the product obtained in Example 4 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0060] The above analysis shows that the product is Ni, WO. 3-x The C complex (named Ni@WO) 3-x @C), the nanosheet array is 2.02~2.59 μm long and 0.20~0.35 μm wide, and a small amount of nickel nanoparticles are loaded on the surface of the layered nanosheet array.

[0061] The thermal conductivity and microwave absorption properties are shown in Table 1. The obtained Ni@WO 3-x @C layered nanosheet arrays exhibit excellent microwave absorption and thermal conductivity. The maximum effective bandwidth with a reflectivity of -10 dB or less reaches 9.04 GHz at a thickness of 2.4 mm, and the maximum absorption reaches -49.0 dB at a matched thickness of 2.6 mm. The thermal conductivity is 3.36 W / (m²). K).

[0062] Example 5 A method for preparing a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite membrane, with other conditions remaining unchanged, except that the concentration of nickel acetate tetrahydrate is changed to 0.025 M based on Example 2.

[0063] Figures 13-15 The images show the phase and morphology of the product obtained in Example 5 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0064] The above analysis shows that the product is Ni, WO. 3-x The C complex (named Ni@WO) 3-x @C), the nanosheet array is 1.66~3.73 μm long and 0.46~0.57 μm wide, and a small amount of nickel nanoparticles are loaded on the surface of the layered nanosheet array.

[0065] The thermal conductivity and microwave absorption properties are shown in Table 1. The obtained Ni@WO 3-x @C layered nanosheet arrays exhibit excellent microwave absorption and thermal conductivity. The maximum effective bandwidth with a reflectivity of -10 dB or less reaches 8.40 GHz at a thickness of 2.3 mm, and the maximum absorption reaches -47.9 dB at a matched thickness of 2.4 mm; the thermal conductivity is 3.02 W / (m²). K).

[0066] Example 6 A method for preparing a surface-hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite membrane involves directly transferring 0.5 g of Ni-WO3·0.5H2O / WO3 precursor into an alumina boat, placing it in a tube furnace, and then heating it to 550°C under argon protection at a heating rate of 5°C / min. After annealing for two hours and allowing it to cool naturally, the membrane is removed, which is the aforementioned thermally conductive and microwave-absorbing multifunctional filler.

[0067] Figures 16-18 The images show the phase and morphology of the product obtained in Example 6 of this invention as measured by XRD, EDX, and scanning electron microscopy.

[0068] The above analysis shows that the product is WO. 3-x @Ni layered nanosheet arrays with dimensions of 1.01~1.79 μm in length and 0.53~0.95 μm in width better preserve the layered structure of the Ni-WO3·0.5H2O / WO3 precursor.

[0069] The thermal conductivity and microwave absorption properties are shown in Table 1. The obtained WO 3-x @Ni layered nanosheet arrays exhibit excellent microwave absorption and thermal conductivity. The maximum effective bandwidth with a reflectivity of -10 dB or less reaches 6.56 GHz at a thickness of 3.1 mm, and the maximum absorption reaches -37.2 dB at a matched thickness of 5.0 mm. The thermal conductivity is 2.81 W / (m²). K).

[0070] Example 7 A method for preparing the precursor Ni-WO3·0.5H2O / WO3, with other conditions remaining unchanged, based on Example 1, wherein the mass of nickel nitrate hexahydrate is 0.3877 g.

[0071] Figure 19 The morphology of the product obtained in Example 7 of this invention is shown under a scanning electron microscope. As can be seen from the above analysis, the product is Ni-WO3·0.5H2O / WO3, with a spun fiber length of 1.3 μm and a diameter of 105 nm.

[0072] Example 8 A method for preparing the precursor Ni-WO3·0.5H2O / WO3, with other conditions remaining unchanged, based on Example 1, wherein the mass of nickel nitrate hexahydrate is 1.5509 g.

[0073] Figure 20The morphology of the product obtained in Example 8 of this invention was measured under a scanning electron microscope. As can be seen from the above analysis, the product is Ni-WO3·0.5H2O / WO3, and the nanofibers constituting the three-dimensional porous structure have a length of 3.6 μm and a diameter of 53 nm.

[0074] Example 9 A method for preparing the precursor Ni-WO3·0.5H2O / WO3, with other conditions remaining unchanged, but based on Example 1, the concentration of all substances is doubled.

[0075] Figure 21 The morphology of the product obtained in Example 9 of this invention is shown under a scanning electron microscope. As can be seen from the above analysis, the product is Ni-WO3·0.5H2O / WO3, with a nanorod length of 2.3 μm and a diameter of 140 nm.

[0076] Example 10 A method for preparing the precursor Ni-WO3·0.5H2O / WO3, with other conditions remaining unchanged, is based on Example 1, but the concentration of all substances is reduced to half of the original concentration.

[0077] Figure 22 The morphology of the product obtained in Example 10 of this invention was measured under a scanning electron microscope. As can be seen from the above analysis, the product is Ni-WO3·0.5H2O / WO3, with a nanorod length of 0.55 μm and a diameter of 54 nm.

[0078] Example 11 A method for preparing the precursor Ni-WO3·0.5H2O / WO3, with other conditions unchanged, is based on Example 1, wherein after the hydrothermal reaction is completed for 6 hours, the reaction vessel is cooled to room temperature and then heated at 180°C for 4 hours.

[0079] Figure 23 The morphology of the product obtained in Example 11 of this invention was measured under a scanning electron microscope. As can be seen from the above analysis, the product is Ni-WO3·0.5H2O / WO3, and the size of the sunflower-shaped annular product is 10.4 μm.

[0080] Example 12 A method for preparing a surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite film, with other conditions remaining unchanged, except that the annealing temperature is increased to 650℃ based on Example 2.

[0081] Figure 24 The morphology of the product obtained in Example 12 of this invention is measured under a scanning electron microscope. As can be seen from the above analysis, the product is Ni@WO. 3-x @C, the diameter of the random product is 277 nm.

[0082] Example 13 A method for preparing a surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite film, with other conditions remaining unchanged, except that the annealing temperature is increased to 750°C based on Example 2.

[0083] Figure 25 The morphology of the product obtained in Example 13 of this invention is measured under a scanning electron microscope. As can be seen from the above analysis, the product is Ni@WO. 3-x @C, the rod-shaped product has a length of 8.1 μm and a diameter of 228 nm.

[0084] Table 1. Microwave absorption and thermal conductivity properties of the products obtained in Examples 1-6 of this invention.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite membrane, characterized in that, The multifunctional flexible composite membrane is formed by dispersing a thermally conductive and microwave-absorbing multifunctional filler and a thermoplastic polyurethane (TPU) matrix in an organic solvent, followed by solvent evaporation; the thermally conductive and microwave-absorbing multifunctional filler is a magnetic Ni@WO3. 3-x The @C complex has a structure of layered nanosheet arrays with a length of 0.51~8.27 μm and a width of 0.20~1.17 μm, and a Ni / W atomic ratio of (0~1):

1.

2. The surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite membrane according to claim 1, characterized in that, The multifunctional flexible composite membrane has a fracture strain of 643.52% and a tensile strength of 17.84 MPa; a thermal conductivity of 2.52~3.73 W / (m·K); an effective absorption bandwidth of 3.12~9.04 GHz for the thermally conductive and microwave-absorbing multifunctional filler, a maximum absorption of -21.5 ~ -53.3 dB; and a static water contact angle of 93.3~104.249°.

3. A method for preparing a surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film as described in claim 1, characterized in that, The multifunctional flexible composite membrane is formed using a solvent evaporation method, as detailed below: TPU particles and 1,4-dioxane organic solvent are added to a container according to a certain stoichiometric ratio and stirred at 60℃~70℃ for 8~12 hours to dissolve and obtain a TPU solution. Then, the ground thermally conductive and microwave-absorbing multifunctional filler is added to the TPU solution and stirred to obtain a uniform thermally conductive and microwave-absorbing slurry. The thermally conductive and microwave-absorbing slurry is poured into a mold and the solvent is evaporated to obtain the surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite film.

4. The method for preparing the surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film according to claim 3, characterized in that, The concentration of the TPU solution is 0.03~0.1 g / mL.

5. The method for preparing the surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film according to claim 3, characterized in that, The thermally conductive and microwave-absorbing multifunctional filler accounts for 5-40% of the mass percentage in the TPU substrate.

6. The method for preparing the surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film according to claim 3, characterized in that, The preparation of a thermally conductive and microwave-absorbing multifunctional filler using a hydrothermal-annealing method includes the following steps: (1) A certain amount of nickel nitrate hexahydrate and deionized water were placed in a reaction vessel and magnetically stirred at room temperature to obtain a green transparent solution; then an appropriate amount of ammonium paratungstate was added and stirred to obtain a milky white suspension; hydrochloric acid was added dropwise and stirred further, sealed and transferred to an oven, heated to react, and naturally cooled to room temperature. The solution was washed several times with deionized water and industrial alcohol, dried, and Ni-WO3·0.5H2O / WO3 precursor was obtained. (2) Prepare a certain concentration of nickel acetate tetrahydrate solution in a centrifuge tube, add an appropriate amount of Ni-WO3·0.5H2O / WO3 precursor obtained in step (1), impregnate and transfer to an alumina boat, dry at 80°C for 4 hours, and obtain green crystals after drying. Place the alumina boat in a tube furnace, heat it to 550~750°C under argon protection, anneal for two hours, and take it out after natural cooling to obtain the thermally conductive and microwave-absorbing multifunctional filler.

7. The method for preparing the surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film according to claim 6, characterized in that, The concentration of the nickel nitrate hexahydrate is 9.7 × 10⁻⁶. -4 ~1.9×10 -2 g / mL, the morphology of the precursor gradually transforms from layered nanosheets to nanofibers. The length of the Ni-WO3·0.5H2O / WO3 nanosheet array is 0.47 ~ 2.30 μm and the width is 0.64 ~ 0.71 μm; the length of the nanofiber structure is 1.3 ~ 3.6 μm and the diameter is 30 ~ 244 nm.

8. The method for preparing the surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film according to claim 6, characterized in that, The concentration of ammonium paratungstate in the milky white suspension was 8.7 × 10⁻⁶. -3 ~ 6.9×10 -2 g / mL, heating temperature is 165 ℃ ~ 200 ℃, heating time is 6 ~ 10 h; drying temperature is 60 ℃ ~ 80 ℃, drying time is 8 ~ 10 h.

9. The method for preparing the surface-hydrophobic, thermally conductive, and microwave-absorbing multifunctional flexible composite film according to claim 6, characterized in that, The molar ratio of nickel acetate tetrahydrate to ammonium paratungstate is 0~1, and the concentration of the nickel acetate tetrahydrate solution is 0.025~0.2mol / L.

10. The application of a surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite film as described in claim 3 to 9, or a surface hydrophobic thermally conductive and microwave-absorbing multifunctional flexible composite film prepared by any one of claims 3 to 9, in the field of microwave absorption and thermal conduction.

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