Lightweight flexible wave-absorbing / heat-conducting bifunctional film material and preparation method thereof

Abstract

The invention provides a light flexible wave-absorbing / heat-conducting bifunctional thin film material and a preparation method thereof, GO and CoFe2O4 are uniformly dispersed in DMF and PAN spinning solutions respectively, CNF-CoFe2O4 and CNF-GO thin films are obtained through electrostatic spinning, the CNF-GO thin films are subjected to reduction treatment, and then the CNF-CoFe2O4 thin films and the CNF-CoFe2O4 thin films are subjected to hot pressing to obtain the flexible sandwich structure thin film wave-absorbing / heat-conducting material. The preparation process is simple, the raw materials are cheap and easy to obtain, and the prepared film material has the advantages of flexibility, wide effective absorption frequency band, good heat-conducting property, environmental friendliness and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbing material preparation, and in particular relates to a flexible broadband wave absorbing / heat conducting dual-function thin film material with a sandwich structure. Background Art

[0002] With the rapid development of precision electronic devices such as 5G or 6G communication equipment, supercomputers, wireless energy transmission devices, AI intelligence, quantum storage, VR technology, and microwave medical devices, these devices are moving towards miniaturization and high integration. This trend brings two major challenges: electromagnetic compatibility and heat dissipation. In particular, achieving the simultaneous absorption of electromagnetic radiation and efficient heat dissipation within the limited space of the equipment has become a difficult hurdle that scientific researchers must overcome. Traditional absorbing materials often have problems such as heavy weight, poor flexibility, narrow absorption bandwidth, and poor thermal conductivity, which limit their scope of application. Therefore, it is particularly important to develop new materials with both absorbing and thermally conductive functions to meet actual engineering needs.

[0003] Electrospinning is a technique for producing micro- and nano-scale fibers using a high-voltage electric field. Its core principle is to overcome the surface tension of a polymer solution or melt through the electric field, forming a jet. The jet solidifies after solvent evaporation or melt cooling, ultimately forming a nanofiber web on a collection device. Due to its simplicity and efficiency, electrospinning demonstrates potential in a variety of cutting-edge fields, with future developments focusing on green manufacturing, intelligent manufacturing, and large-scale applications.

[0004] Ferrite is a well-developed and mature microwave absorbing material. Its advantages include high saturation magnetization, high Snoek cutoff frequency, and low cost, and it remains a popular absorber in various fields. CoFe2O4, a typical ferrite material, offers advantages such as excellent chemical stability, wear resistance, and corrosion resistance. Furthermore, CoFe2O4 maintains high real and imaginary complex conductivity at microwave frequencies in the C and Ku bands, indicating that it can simultaneously generate dielectric and hysteresis losses.

[0005] Graphene is a two-dimensional, single-atom-thick carbon nanomaterial. Due to its unique electrical, optical, and mechanical properties, it can be used as an energy storage material, catalytic material, electromagnetic material, stealth material, and optical material. Reduced graphene oxide (RGO), with its unique two-dimensional layered structure and abundant surface active sites, can serve as an excellent substrate material for the preparation of composite absorber materials with excellent electromagnetic wave absorption properties.

[0006] Currently, there is little research on dual-functional wave-absorbing / heat-conducting thin films. Patent CN119143123A applied for by Jiangsu University of Technology discloses "a graphene magnetic wave-absorbing material, its preparation method and application", which has the characteristics of high absorption intensity and wide effective absorption bandwidth. However, it still requires the addition of substances such as sodium acetate and polyethylene glycol, the preparation process is complicated, and there is a lack of research and exploration on the thermal conductivity of the material. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention provides a lightweight, flexible, wave-absorbing / heat-conducting dual-function thin film material with a simple preparation process and cheap and easily available raw materials. The prepared thin film material has the advantages of flexibility, wide effective absorption bandwidth, good thermal conductivity, and environmental friendliness.

[0008] The technical solution adopted by the present invention to solve its technical problems is: a lightweight and flexible wave-absorbing / heat-conducting dual-functional film material, including a CNF-CoFe2O4 film and a CNF-RGO film, a CNF-RGO film is sandwiched between the two layers of the CNF-CoFe2O4 film, and hot-pressed to form a sandwich structure stack.

[0009] The thickness of the CNF-CoFe2O4 film is 300±50 μm; the thickness of the CNF-RGO film is 300±50 μm.

[0010] The present invention also provides a method for preparing the lightweight flexible wave absorbing / heat conducting dual-function film material, comprising the following steps:

[0011] 1) mixing CoFe2O4 magnetic nanoparticles with a PAN solution to obtain a CoFe2O4 / PAN dispersion as a spinning solution, electrospinning the spinning solution, and drying the obtained CNF-CoFe2O4 film for later use;

[0012] 2) mixing GO powder with PAN solution to obtain a GO / PAN dispersion as a spinning solution, and electrospinning the spinning solution to obtain a CNF-GO film;

[0013] 3) The CNF-GO film is reduced and hot-pressed with the CNF-CoFe2O4 film to obtain the lightweight, flexible, wave-absorbing / heat-conducting dual-functional film material.

[0014] The PAN solution is prepared by adding PAN powder to DMF and stirring in a 60° C. water bath until the PAN is completely dissolved.

[0015] The mass ratio of the CoFe2O4 magnetic nanoparticles to PAN in the PAN solution is 1:2; and the mass concentration of PAN in the PAN solution is 10%.

[0016] The mass ratio of the GO powder to PAN in the PAN solution is (0-2):2; the mass concentration of the PAN solution is 10%; if the GO powder ratio is 0, only the PAN solution is used as the spinning solution.

[0017] The mass ratio of the CoFe2O4 magnetic nanoparticles to GO is 2:(0-2).

[0018] The electrospinning temperature is 15-25° C., the relative humidity is 20-25%, the positive pressure is +7kV-+9kV, the negative pressure is -2--2.5kV, the injection speed is 0.04-0.05mm / min, the receiving speed is 100-600r / min, and the receiving distance is 15-20cm.

[0019] The hot pressing pressure is 5-7 MPa and the temperature is 50-60°C.

[0020] The spinning solution is replaced by polyvinyl alcohol and prepared by adding ultrapure water.

[0021] The beneficial effects of the present invention are:

[0022] The lightweight, flexible, dual-function absorbent / thermal conductive film material combines the advantages of flexibility, wide effective absorption bandwidth, excellent thermal conductivity, and environmental friendliness. The film, produced by electrospinning, is composed of high-aspect-ratio CNFs and compacted using a multilayer stacking method. This macroscopic multilayer stacking structure increases the material's effective absorption area, enhancing the multiple reflections of electromagnetic waves between the CNF films and the interfacial effects. The addition of RGO improves the film's interfacial polarization loss and dipole polarization loss. Simultaneously, the RGO-loaded CNFs form a fast conductive and thermal network, providing a channel for induced currents, generating the thermal effects of induced currents, reducing electrical and polarization relaxation losses, and improving the material's thermal conductivity. Furthermore, the addition of CoFe2O4 nanoparticles, a magnetic matrix, contributes to the material's eddy current and resonance losses, synergizing with the RGO's electrical and magnetic losses to adjust the material's electromagnetic parameters for good impedance matching, thereby achieving excellent absorbent performance.

[0023] The preparation method has simple operation steps, and adopts electrospinning technology to prepare the modified carbon fiber, which has broadband wave absorbing performance and can cover a wide frequency range from low frequency to high frequency. For example, in the test range of 2-18 GHz in Example 4, at a thickness of 1.6 mm, the effective bandwidth of RL<-10 dB (90% electromagnetic wave loss) reaches 6.5 GHz, which fully covers the engineering application requirements of the Ku band (12-18 GHz) and has good thermal conductivity, with a thermal conductivity of 4.983 W / (m·K).

[0024] The materials CoFe2O4, GO, PAN and DMF required by the present invention are inexpensive, and the steps for preparing the modified carbon fiber using electrospinning technology are simple, with low equipment requirements, little environmental pollution, low production cost, and the ability to improve industrial production efficiency.

[0025] The lightweight, flexible, absorbing / thermal-conducting film material prepared by this invention offers significant advantages for electromagnetic wave absorption and heat dissipation in small electronic devices. Due to its unique physical and chemical properties, this material can be customized to produce absorbing materials with varying performance by adjusting the ratio of the magnetic and dielectric matrices and electrospinning parameters. This provides a highly efficient and flexible electromagnetic wave absorption and heat dissipation solution for small electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart for the preparation of CNF-CoFe2O4 / RGO according to the present invention;

[0027] Figure 2 is a graph showing the wave absorption performance of Example 4 of the present invention;

[0028] Figure 3 are spectra of the materials described in the present invention, wherein (ac) are SEM spectra of CNF-(CoFe2O4 / RGO) at different resolutions; (df) are SEM spectra of CNF-RGO at different resolutions; (gh) are TEM spectra of CNF-RGO at different resolutions; (i1-i3) are elemental energy spectra of CNF-(CoFe2O4 / RGO); (j1-j3) are elemental energy spectra of CNF-RGO.

[0029] Figure 4 2 is a graph showing thermal conductivity of various embodiments of the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the accompanying drawings and examples. The present invention includes but is not limited to the following examples.

[0031] The purpose of the present invention is to use electrospinning technology to prepare carbon fiber (CNF) films loaded with magnetic matrix CoFe2O4 nanoparticles and dielectric matrix RGO respectively, and to adjust the electromagnetic parameters of the composite film material by adjusting the addition ratio of RGO and CoFe2O4 to achieve good impedance matching, thereby achieving excellent wave absorption and thermal conductivity.

[0032] The technical solution adopted by the present invention is to uniformly disperse GO and CoFe2O4 into N,N-dimethylformamide (DMF) + polyacrylonitrile (PAN) spinning solution respectively, obtain CNF-CoFe2O4 and CNF-GO films by electrospinning, and then reduce the CNF-GO film and hot-press it with the CNF-CoFe2O4 film through a flat vulcanizer to obtain a flexible sandwich structure thin film absorbing / thermal conductive material, including a CNF-CoFe2O4 film, a CNF-RGO film and a CNF-CoFe2O4 film stacked in sequence from top to bottom.

[0033] The thickness of the CNF-CoFe2O4 film is 300±50 μm; the thickness of the CNF-RGO film is 300±50 μm.

[0034] In order to achieve the above object, the present invention comprises the following preparation steps:

[0035] CoFe2O4 magnetic nanoparticles were mixed with polyacrylonitrile (PAN) solution to obtain CoFe2O4 / PAN dispersion;

[0036] The CoFe2O4 / PAN dispersion is subjected to a first electrospinning process to obtain a CNF-CoFe2O4 film;

[0037] Then, GO powder was mixed with PAN solution to obtain GO / PAN dispersion;

[0038] The GO / PAN dispersion is subjected to a second electrospinning to obtain a CNF-GO film;

[0039] The CNF-GO film was reduced at 800° C. for 2 h under an Ar atmosphere to obtain a CNF-RGO film;

[0040] The CNF-CoFe2O4 film and the CNF-RGO film are stacked in a sandwich structure with a CNF-RGO film sandwiched between two CNF-CoFe2O4 films, and hot pressed to obtain a CNF-(CoFe2O4 / RGO) flexible sandwich structure film absorbing / thermal conductive material.

[0041] The mass ratio of the CoFe2O4 magnetic nanoparticles to the PAN in the PAN solution is 1:2, and the mass concentration of PAN in the PAN solution is 10%.

[0042] The temperature of the first electrospinning is 15-25° C., and the relative humidity is 20-25%.

[0043] During the first electrospinning process, the positive pressure is +7kV to +9kV, the negative pressure is -2 to -2.5kV, the injection speed is 0.04 to 0.05mm / min, the receiving speed is 100 to 600r / min, and the receiving distance is 15 to 20cm.

[0044] The GO powder may not be added; if GO powder is added, the mass ratios of GO powder to PAN in the PAN solution are 1:2 and 1:1, and the mass concentration of the polyacrylonitrile solution is 10%.

[0045] The mass ratio of the CoFe2O4 magnetic nanoparticles to GO is 2:(0-2).

[0046] The temperature of the second electrospinning is 15-25° C., and the relative humidity is 20-25%.

[0047] During the second electrospinning process, the positive pressure is +7kV to +9kV, the negative pressure is -2 to -2.5kV, the injection speed is 0.04 to 0.05mm / min, the receiving speed is 100 to 600r / min, and the receiving distance is 15 to 20cm.

[0048] The hot pressing pressure is 5-7 MPa and the temperature is 50-60°C.

[0049] As an embodiment of the present invention, the following steps are included:

[0050] 1. Weigh 0.4 g of PAN powder into a sample bottle, add 4 ml of DMF, and stir in a 60°C water bath until the PAN is completely dissolved. Then, weigh 0.2 g of CoFe2O4 powder and add it to the PAN solution. Ultrasonicate for 8 hours. The sonicated spinning solution is drawn into a syringe for electrospinning. After spinning, transfer the film to an oven to dry.

[0051] 2. Weigh 0.2g of PAN powder into a sample bottle, add 2ml of DMF, and stir in a 60°C water bath until the PAN is completely dissolved. Weigh GO powder separately and add it to the PAN solution (the amounts of GO added are: none, 0.1g, and 0.2g, respectively). The sonicated spinning solution is drawn into a syringe for electrospinning. After spinning, the film is transferred to an oven for drying. It is then reduced under an inert gas atmosphere.

[0052] 3. The CNF-CoFe2O4 film and the CNF-RGO film are stacked in a sandwich structure with a layer of CNF-RGO film sandwiched between two layers of CNF-CoFe2O4 film, and hot pressed using a flat vulcanizer to obtain the CNF-(CoFe2O4 / RGO) film.

[0053] As a further illustration of the present invention, the spinning solution system is preferably polyacrylonitrile + N,N-dimethylformamide (DMF), and polyvinyl alcohol + ultrapure water can also be used.

[0054] As a further illustration of the present invention, the water bath heating temperature is preferably 60°C.

[0055] As a further illustration of the present invention, the stirring method is magnetic stirring, and the time is preferably 2 hours.

[0056] As a further illustration of the present invention, the ultrasonic time is preferably 8 hours.

[0057] As a further illustration of the present invention, the syringe is a 10ml medical syringe.

[0058] As a further illustration of the present invention, the electrospinning instrument parameter settings are preferably 7 kV positive voltage, 2.5 kV negative voltage, 0.05 mm / min propulsion speed, and 10 mm translation stroke.

[0059] As a further explanation of the present invention, the reduction method is preferably to reduce the sample at 800°C for 2 h under an Ar atmosphere.

[0060] As a further illustration of the present invention, the parameters of the plate vulcanizing press are preferably set as pressure 5 MPa, temperature 50° C., and holding time 5 min.

[0061] As a further illustration of the present invention, the temperature of the drying oven is 60° C. and the drying time is 6 hours.

[0062] As a further illustration of the present invention, the thermal conductivity test method of each embodiment is as follows: the film is cut into a size of 1.2 mm*1.2 mm, placed in a mold, and tested using a laser thermal conductivity meter under vacuum and 30°C conditions.

[0063] In order to explore the effect of RGO on the improvement of the wave absorption and thermal conductivity of the film material, the present invention prepared samples according to the following components:

[0064] Example 1: CoFe2O4:PAN=1:2 CNF film;

[0065] Example 2: The upper and lower layers are CNF films with a ratio of CoFe2O4:PAN=1:2, and the middle layer is a CNF film without GO added;

[0066] Example 3: The upper and lower layers are CNF films with a ratio of CoFe2O4:PAN=1:2, and the middle layer is CNF film with a ratio of GO:PAN=1:2;

[0067] Example 4: The upper and lower layers are CNF films with a ratio of CoFe2O4:PAN=1:2, and the middle layer is a CNF film with a ratio of GO:PAN=1:1.

[0068] The preparation steps of each embodiment are as follows:

[0069] Example 1:

[0070] ① Weigh 0.4 g of PAN powder into a sample bottle, add 4 ml of DMF, and stir magnetically in a 60°C water bath for 2 h until PAN is completely dissolved.

[0071] ② Add 0.2g CoFe2O4 to the homogeneous spinning solution obtained in step 1 and sonicate at room temperature for 8h until it is completely dissolved;

[0072] ③ The sonicated spinning solution was drawn into a 10ml syringe and spun into a CNF-CoFe2O4 film using an electrospinning apparatus. The electrospinning apparatus parameters were set to a positive voltage of 7kV, a negative voltage of 2.5kV, a propulsion speed of 0.05mm / min, and a translational stroke of 10mm.

[0073] ④ After spinning, the film was transferred to an oven and dried at 60℃ for 6 hours. The final test results showed that the absorption performance was 1.0GHz with an effective bandwidth of 3.0mm and a minimum reflection loss (RL min )-25dB. Thermal conductivity 0.00049W / (m·K)

[0074] Example 2: ① The preparation of CNF-CoFe2O4 film is the same as that of Example 1.

[0075] ② Weigh 0.2 g of PAN powder into a sample bottle, add 2 ml of DMF, and stir magnetically in a 60°C water bath for 2 h until PAN is completely dissolved.

[0076] ③ The homogeneous spinning solution of step ② was ultrasonically treated at room temperature for 8 hours until it was completely dissolved.

[0077] ④ The sonicated spinning solution was drawn into a 10ml syringe and spun into a CNF film using an electrospinning apparatus. The electrospinning apparatus parameters were set to a positive voltage of 7kV, a negative voltage of 2.5kV, a propulsion speed of 0.05mm / min, and a translation stroke of 10mm. After spinning, the film was transferred to an oven and dried at 60°C for 6 hours.

[0078] ⑤ In an Ar gas atmosphere, the CNF film was reduced using chemical vapor deposition, the temperature was set to 800°C, and the time was 2h to obtain the CNF film.

[0079] ⑥ The CNF-CoFe2O4 film and the CNF-RGO film were stacked in a sandwich structure and hot-pressed using a flat-plate vulcanizer to obtain Example 2. The parameters of the flat-plate vulcanizer were set to 50°C, 5 MPa, and a holding time of 5 min. The final test results showed that the minimum reflection loss (RL) in the 2-18 GHz frequency band wasmin )<-10dB. Thermal conductivity 0.0804W / (m·K)

[0080] Example 3: ① The preparation of CNF-CoFe2O4 film is the same as that of Example 1.

[0081] ② Weigh 0.2 g of PAN powder into a sample bottle, add 2 ml of DMF, and stir magnetically in a 60°C water bath for 2 h until PAN is completely dissolved.

[0082] ③ Add 0.1 g of GO to the homogeneous spinning solution obtained in step ② and ultrasonicate at room temperature for 8 h until it is completely dissolved.

[0083] ④ The sonicated spinning solution was drawn into a 10ml syringe and spun into a CNF-GO film using an electrospinning apparatus. The electrospinning apparatus parameters were set to a positive voltage of 7 kV, a negative voltage of 2.5 kV, a propulsion speed of 0.05 mm / min, and a translation stroke of 10 mm. After spinning, the film was transferred to an oven and dried at 60°C for 6 hours.

[0084] ⑤ In an Ar gas atmosphere, the CNF-GO film was reduced using chemical vapor deposition, the temperature was set to 800℃, and the time was 2h to obtain the CNF-RGO film.

[0085] ⑥ The CNF-CoFe2O4 film and the CNF-RGO film were stacked in a sandwich structure and hot-pressed using a flat-plate vulcanizer to obtain Example 3. The flat-plate vulcanizer parameters were set to 50°C, 5 MPa, and a holding time of 5 min. The final test results showed that the effective bandwidth of the absorption performance at 1.5 mm was 6.5 GHz, and the minimum reflection loss (RL min )-12.9dB. Thermal conductivity 0.692W / (m·K)

[0086] Example 4: ① The preparation of CNF-CoFe2O4 film is the same as that of Example 1.

[0087] ② Weigh 0.2 g of PAN powder into a sample bottle, add 2 ml of DMF, and stir magnetically in a 60°C water bath for 2 h until PAN is completely dissolved.

[0088] ③ Add 0.2 g GO to the homogeneous spinning solution obtained in step ② and ultrasonicate at room temperature for 8 h until it is completely dissolved.

[0089] ④ The sonicated spinning solution was drawn into a 10ml syringe and spun into a CNF-GO film using an electrospinning apparatus. The electrospinning apparatus parameters were set to a positive voltage of 7 kV, a negative voltage of 2.5 kV, a propulsion speed of 0.05 mm / min, and a translation stroke of 10 mm. After spinning, the film was transferred to an oven and dried at 60°C for 6 hours.

[0090] ⑤ In an Ar gas atmosphere, the CNF-GO film was reduced using chemical vapor deposition, the temperature was set to 800℃, and the time was 2h to obtain the CNF-RGO film.

[0091] ⑥ The CNF-CoFe2O4 film and the CNF-RGO film were stacked in a sandwich structure and hot-pressed using a flat-plate vulcanizer to obtain the film of Example 4. The parameters of the flat-plate vulcanizer were set to 50°C, 5 MPa, and a holding time of 5 minutes. The final test results showed that the effective bandwidth of the absorption performance at 1.6 mm was 6.5 GHz, and the minimum reflection loss (RL min )-38.1dB, thermal conductivity 4.983W / (m·K).

[0092] Table 1 Comparison of performance parameters between comparative examples and examples

[0093]

[0094] In the present invention, unless otherwise specified, the required raw materials or reagents can be prepared according to methods well known in the art or can be commercially available products.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A lightweight, flexible, wave-absorbing / heat-conducting dual-function film material, characterized in that: The method comprises a CNF-CoFe2O4 film and a CNF-RGO film, wherein a CNF-RGO film is sandwiched between the two CNF-CoFe2O4 films and the two films are hot-pressed to form a sandwich structure stack.

2. The lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 1, characterized in that: The thickness of the CNF-CoFe2O4 film is 300±50 μm; the thickness of the CNF-RGO film is 300±50 μm.

3. A method for preparing the lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 1, characterized in that: The following steps are involved: 1) mixing CoFe2O4 magnetic nanoparticles with a PAN solution to obtain a CoFe2O4 / PAN dispersion as a spinning solution, electrospinning the spinning solution, and drying the obtained CNF-CoFe2O4 film for later use; 2) mixing GO powder with PAN solution to obtain a GO / PAN dispersion as a spinning solution, and electrospinning the spinning solution to obtain a CNF-GO film; 3) The CNF-GO film is reduced and hot-pressed with the CNF-CoFe2O4 film to obtain the lightweight, flexible, wave-absorbing / heat-conducting dual-functional film material.

4. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The PAN solution is prepared by adding PAN powder to DMF and stirring in a 60° C. water bath until the PAN is completely dissolved.

5. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The mass ratio of the CoFe2O4 magnetic nanoparticles to PAN in the PAN solution is 1:2; and the mass concentration of PAN in the PAN solution is 10%.

6. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The mass ratio of the GO powder to PAN in the PAN solution is (0-2):2; the mass concentration of the PAN solution is 10%; if the GO powder ratio is 0, only the PAN solution is used as the spinning solution.

7. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The mass ratio of the CoFe2O4 magnetic nanoparticles to GO is 2:(0-2).

8. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The electrospinning temperature is 15-25° C., the relative humidity is 20-25%, the positive pressure is +7kV-+9kV, the negative pressure is -2--2.5kV, the injection speed is 0.04-0.05mm / min, the receiving speed is 100-600r / min, and the receiving distance is 15-20cm.

9. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The hot pressing pressure is 5-7 MPa and the temperature is 50-60°C.

10. The method for preparing a lightweight, flexible, wave-absorbing / heat-conducting dual-function film material according to claim 3, characterized in that: The spinning solution is replaced by polyvinyl alcohol and prepared by adding ultrapure water.

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