Flexible multifunctional electromagnetic shielding film and preparation method and application thereof

Abstract

The application discloses a flexible multifunctional electromagnetic shielding film and a preparation method and application thereof. The electromagnetic shielding film comprises a carbon nanotube film, a high magnetic permeability layer and a high electrical conductivity layer combined with a first surface and a second surface of the carbon nanotube film respectively, and the electrical conductivity of the high magnetic permeability layer, the carbon nanotube film and the high electrical conductivity layer increases in turn, and the magnetic permeability decreases in turn. The application provides an electromagnetic shielding material with a three-layer structure. Due to the difference in the electrical conductivity and the magnetic permeability of the materials between the three layers, the electromagnetic wave experiences an 'absorption-reflection-reabsorption' process after entering the material, so that the material presents a low reflection characteristic. The Joule heating performance of the electromagnetic shielding film is good, the temperature response speed is fast when a voltage is applied, the stability of the electromagnetic shielding film during heating is excellent, the electromagnetic shielding film can remain stable for a long time, and the electromagnetic shielding film shows great application potential in the electromagnetic protection field and the thermal management field of high-integration electronic equipment.

Description

Technical Field

[0001] This invention relates to a method for preparing an electromagnetic shielding material, specifically to a flexible, multifunctional electromagnetic shielding film, its preparation method, and its application, belonging to the field of carbon-based electromagnetic shielding technology. Background Technology

[0002] With the rapid development of 5G mobile communication, electronic devices are evolving towards lighter weight, greater flexibility, and portability. To ensure their normal operation, electromagnetic shielding materials are essential for protection. Traditional metal shielding materials, due to their excellent electrical conductivity, can effectively shield electromagnetic waves. However, their high density, poor corrosion resistance, poor flexibility, and processing difficulties are becoming increasingly prominent, failing to meet the demands of modern technology. Therefore, polymer composite materials doped with conductive components have entered the research field due to their lightweight and high flexibility. Currently, both traditional metal shielding materials and highly conductive polymer composite materials utilize their high electrical conductivity to increase electromagnetic wave reflection on the material surface, thus exhibiting excellent electromagnetic shielding performance. However, high conductivity often increases the material's electromagnetic wave reflection loss, and such electromagnetic shielding materials relying on strong surface reflection inevitably cause secondary pollution. Therefore, the development of flexible electromagnetic shielding materials with low reflection and high shielding properties is becoming increasingly important. Furthermore, many high-precision electronic instruments inevitably need to operate in extreme environments, such as extremely cold weather. Under these conditions, the stability of electromagnetic shielding materials is also particularly crucial.

[0003] Electromagnetic shielding materials generally attenuate electromagnetic waves through electrical loss, magnetic loss, and dielectric loss. Introducing ferromagnetic nanoparticles is a feasible method to address the secondary pollution caused by reflected electromagnetic waves. Zhang et al. reported a Fe3O4@MWCNT / PMMA composite material with an X-band EMI SE of 25.11 dB and an R-value of 0.47 (Compos Part A 2017; 100: 128-38). Sharif et al. introduced Fe3O4@rGO magnetic nanoparticles into a PMMA matrix and found an EMI SE of 29.3 dB and an R-value of 0.6 (ACS Appl Mater Interfaces 2017; 9(16): 14171-9). Although composite materials with added magnetic hybrid fillers can reduce reflection to some extent, under fixed impedance mismatch conditions, these uniformly conductive network composites always exhibit uniform conductivity, which is not very effective in reducing electromagnetic wave reflection. In response, various structural designs have been developed in recent years, such as layered structures, split structures, and porous structures. Studies have found that EMI shielding materials with isolated conductive networks, such as Fe3O4@rGO / natural rubber composites (NRMG) and CNT / RGF@Fe3O4 / PC composites, form a special structure integrating reflection and absorption. This allows electromagnetic waves to undergo an "absorption-reflection-reabsorption" process within the material, achieving a lower electromagnetic wave reflection efficiency (Chem.Eng.J.344(2018)184-193.Chem.Eng.J.393(2020), 124644.). However, these materials only focus on their electromagnetic shielding performance and do not describe other properties such as Joule heating performance, stability, and durability, failing to meet the multi-functional requirements of protective materials for precision instruments.

[0004] Furthermore, in high-end manufacturing industries such as aviation, aerospace, microelectronics, and portable communications, lightweight, flexible, high-performance, and multifunctional electromagnetic shielding materials are increasingly favored. This requires electromagnetic shielding materials to withstand harsh environments and exhibit a certain degree of flexibility for various practical applications. Summary of the Invention

[0005] The main objective of this invention is to provide a flexible, multifunctional electromagnetic shielding film with a multilayer composite structure, high stability, and good thermal management performance and low reflection characteristics, as well as its preparation method, to overcome the shortcomings of the prior art.

[0006] Another object of the present invention is to provide the application of the aforementioned flexible and multifunctional electromagnetic shielding film.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] This invention provides a flexible, multifunctional electromagnetic shielding film, comprising:

[0009] Carbon nanotube films, and

[0010] A high magnetic permeability layer and a high electrical conductivity layer are respectively bonded to the first surface and the second surface of the carbon nanotube film, with the first surface and the second surface arranged back to back;

[0011] The conductivity of the high magnetic permeability layer, the carbon nanotube thin film, and the high electrical conductivity layer increases sequentially, while the magnetic permeability decreases sequentially.

[0012] In some embodiments, the high magnetic permeability layer comprises a polymer matrix and magnetic nanoparticles dispersed in the polymer matrix.

[0013] In some embodiments, the magnetic nanoparticles include NiCo particles or Fe3O4 particles.

[0014] This invention also provides a method for preparing a flexible, multifunctional electromagnetic shielding film, comprising: depositing a high magnetic permeability layer and a high electrical conductivity layer on the first and second surfaces of a carbon nanotube film, respectively;

[0015] The first surface and the second surface are arranged opposite to each other, and the conductivity of the high magnetic permeability layer, the carbon nanotube film and the high electrical conductivity layer increases sequentially, while the magnetic permeability decreases sequentially.

[0016] In some embodiments, the preparation method specifically includes:

[0017] Magnetic nanoparticles are uniformly dispersed in a polymer solution to form a magnetic nanoparticle dispersion.

[0018] The magnetic nanoparticle dispersion is coated onto the first surface of the carbon nanotube film, and then dried to form the high magnetic permeability layer.

[0019] The present invention also provides a flexible, multifunctional electromagnetic shielding film prepared by the aforementioned method.

[0020] This invention also provides applications of the flexible, multifunctional electromagnetic shielding film in electromagnetic protection or thermal management of highly integrated electronic devices.

[0021] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0022] 1) This invention provides a multifunctional electromagnetic shielding film with excellent flexibility, high electromagnetic shielding performance, and durability. The conductivity of this composite film increases with the increase of carbon nanotube thickness. When the CNT thickness is 30 μm, the conductivity of the sample can reach 3.22 × 10⁻⁶. 4S / m. Due to the introduction of a high-conductivity metallic layer as a reflective layer, when electromagnetic waves penetrate the asymmetric composite material, a special "absorption-reflection-reabsorption" process is generated, and the material's shielding performance can reach 75dB in the X-band range;

[0023] 2) This invention prepares an electromagnetic shielding material with a three-layer structure through structural design. Due to the difference in conductivity and permeability between the three layers, electromagnetic waves will undergo a process of "absorption-reflection-reabsorption" after entering the material, thus making the material exhibit low reflection characteristics.

[0024] 3) The flexible multifunctional electromagnetic shielding material provided by this invention has good Joule heating performance, fast temperature response when voltage is applied, and excellent stability during heating. It can remain stable even after long-term heating, showing great application potential in the fields of electromagnetic protection and thermal management of highly integrated electronic devices. Attached Figure Description

[0025] 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 some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the preparation process of a flexible, multifunctional electromagnetic shielding film (Fe3O4-PDMS / CNT / Cu composite film) in a typical embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the electromagnetic shielding mechanism of the Fe3O4-PDMS / CNT / Cu composite film in a typical embodiment of the present invention;

[0028] Figure 3 This is a time-temperature curve of the Fe3O4-PDMS / CNT / Cu composite film at a constant voltage of 3V in a typical embodiment of the present invention. Detailed Implementation

[0029] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, which mainly provides a flexible, multifunctional electromagnetic shielding film with a multi-layered composite structure, high stability, and combining good thermal management performance and low reflection characteristics, as well as its preparation method. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0030] One aspect of this invention provides a flexible, multifunctional electromagnetic shielding film, comprising:

[0031] Carbon nanotube films, and

[0032] A high magnetic permeability layer and a high electrical conductivity layer are respectively bonded to the first surface and the second surface of the carbon nanotube film, with the first surface and the second surface arranged back to back;

[0033] The conductivity of the high magnetic permeability layer, the carbon nanotube thin film, and the high electrical conductivity layer increases sequentially, while the magnetic permeability decreases sequentially.

[0034] Wherein, the first surface can be understood as the upper surface of the carbon nanotube film, and the second surface can be understood as the lower surface of the carbon nanotube film.

[0035] In some embodiments, the high magnetic permeability layer comprises a polymer matrix and magnetic nanoparticles dispersed in the polymer matrix.

[0036] Furthermore, the polymer matrix material may include polydimethylsilane (PDMS), and polyvinyl alcohol (PVA), polyethylene (PVP), or polyvinylidene fluoride (PVDF) may be used instead of polydimethylsilane (PDMS).

[0037] Furthermore, the magnetic nanoparticles may include Fe3O4 particles, and the aforementioned thin film structure may also be prepared using different materials, such as replacing Fe3O4 particles with other magnetic nanoparticles such as NiCo particles.

[0038] Furthermore, the magnetic nanoparticles have a particle size of 10–15 nm.

[0039] Furthermore, the high permeability layer contains 10–20 wt% magnetic nanoparticles.

[0040] In some embodiments, the material of the high conductivity layer is selected from metals, which may include copper, or other metals may be vapor-deposited onto the underside of the carbon nanotube film, such as silver or nickel instead of copper.

[0041] Furthermore, the thickness of the carbon nanotube film is 10–30 μm.

[0042] Furthermore, the thickness of the high magnetic permeability layer is 300–400 μm.

[0043] Furthermore, the thickness of the high conductivity layer is 300–900 nm.

[0044] This invention prepares an electromagnetic shielding material with a three-layer structure through structural design. Due to the difference in conductivity and permeability between the three layers, electromagnetic waves will undergo a process of "absorption-reflection-reabsorption" after entering the material, thus making the material exhibit low reflection characteristics.

[0045] Furthermore, the flexible multifunctional electromagnetic shielding film provided by the present invention has good Joule heating performance, fast temperature response when voltage is applied, and excellent stability during heating, remaining stable even after long-term heating.

[0046] Another aspect of the present invention provides a method for preparing a flexible multifunctional electromagnetic shielding film, which includes: depositing a high magnetic permeability layer and a high electrical conductivity layer on a first surface and a second surface of a carbon nanotube film, respectively.

[0047] The first surface and the second surface are arranged opposite to each other, and the conductivity of the high magnetic permeability layer, the carbon nanotube film and the high electrical conductivity layer increases sequentially, while the magnetic permeability decreases sequentially.

[0048] Wherein, the first surface can be understood as the upper surface of the carbon nanotube film, and the second surface can be understood as the lower surface of the carbon nanotube film.

[0049] In some implementation schemes, the preparation method specifically includes:

[0050] Magnetic nanoparticles are uniformly dispersed in a polymer solution to form a magnetic nanoparticle dispersion.

[0051] The magnetic nanoparticle dispersion is coated onto the first surface of the carbon nanotube film, and then dried to form the high magnetic permeability layer.

[0052] Furthermore, the polymer solution contains polymers including polydimethylsilane (PDMS), and polyvinyl alcohol (PVA), polyethylene (PVP), and polyvinylidene fluoride (PVDF) can be used instead of polydimethylsilane (PDMS).

[0053] In some embodiments, the magnetic nanoparticles may include Fe3O4 particles, and the aforementioned thin film structure may also be prepared using different materials, such as replacing Fe3O4 particles with other magnetic nanoparticles such as NiCo particles.

[0054] Furthermore, the magnetic nanoparticles have a particle size of 10–15 nm.

[0055] Furthermore, the magnetic nanoparticle dispersion contains 10-20 wt% magnetic nanoparticles.

[0056] Furthermore, the drying process is carried out at a temperature of 80–120°C.

[0057] In some embodiments, the preparation method specifically includes: forming a metal film on the second surface of the carbon nanotube film by physical and / or chemical deposition, thereby obtaining the high conductivity layer.

[0058] Furthermore, the thickness of the carbon nanotube film is 10–30 μm.

[0059] Furthermore, the thickness of the high magnetic permeability layer is 300–400 μm.

[0060] Furthermore, the thickness of the high conductivity layer is 300–900 nm.

[0061] In summary, this invention has prepared a flexible, multifunctional electromagnetic shielding film with excellent flexibility, high electromagnetic shielding performance, and durability. Its conductivity increases with increasing carbon nanotube film thickness; when the carbon nanotube film thickness is 30 μm, the sample conductivity reaches 3.22 × 10⁻⁶. 4 S / m. Due to the introduction of a metal layer as a reflective layer, when electromagnetic waves penetrate the asymmetric composite material, a special "absorption-reflection-reabsorption" process is generated, and the material's shielding performance can reach 75dB in the X-band range.

[0062] Another aspect of the present invention provides a flexible, multifunctional electromagnetic shielding film prepared by the aforementioned method.

[0063] Another aspect of the present invention provides the application of the aforementioned flexible multifunctional electromagnetic shielding film in the fields of electromagnetic protection and thermal management.

[0064] Furthermore, the flexible, multifunctional electromagnetic shielding film possesses excellent electrothermal performance and stability, demonstrating great application potential in the fields of electromagnetic protection and thermal management of highly integrated electronic devices.

[0065] The flexible, multifunctional electromagnetic shielding film of the present invention maintains essentially the same electromagnetic shielding performance under heating conditions and exhibits good flexibility.

[0066] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0067] Example 1

[0068] 1. The specific technical steps of the preparation method of a flexible multifunctional electromagnetic shielding film (taking Fe3O4-PDMS / CNT / Cu composite film as an example in this embodiment) are as follows:

[0069] Please see Figure 1 The diagram shows the preparation process of Fe3O4-PDMS / CNT / Cu composite films with different copper thicknesses. First, Fe3O4 nanoparticles with a mass content of 10–20 wt% were added to a PDMS solution, and a homogeneous mixture was formed with the aid of ultrasonic stirring. Then, the mixture was uniformly coated onto a CNT film using a blade coating method, and the film was placed in a vacuum oven at 80–120 °C for 4 hours to prepare the Fe3O4-PDMS / CNT film. Finally, metallic Cu was deposited onto the lower surface of the CNT film using electron beam evaporation to form the Fe3O4-PDMS / CNT / Cu composite film.

[0070] The inventors of this case prepared a series of Fe3O4-PDMS / CNT / Cu composite films with different carbon nanotube film thicknesses, namely 10μm, 20μm and 30μm. The prepared samples were named Fe3O4-PDMS / CNT / Cu-1, Fe3O4-PDMS / CNT / Cu-2 and Fe3O4-PDMS / CNT / Cu-3, respectively, and the copper plating thickness was 300nm.

[0071] 2. Conductivity test

[0072] The multilayer structure of the thin film resulted in different conductivity levels on the upper and lower surfaces of the Fe3O4-PDMS / CNT / Cu composite film. The conductivity of the upper surface of the Fe3O4-PDMS / CNT / Cu composite film was 1.12 × 10⁻⁶. -5 S / m, lower surface conductivity is 3.21×10 4 The conductivity of the lower surface is eight orders of magnitude higher than that of the upper surface, mainly because the conductivity of the copper layer at the bottom of the composite film is much higher than that of the Fe3O4-PDMS layer at the top. The difference in conductivity between the upper and lower surfaces confirms the unique layered structure of the flexible composite film. Furthermore, Table 1 shows that the conductivity of the composite film increases with the increase of the carbon nanotube film thickness. When the carbon nanotube thickness in the composite film is 10 μm, the conductivity is 1.26 × 10⁻⁶ m. 4 The conductivity of the composite film reaches 3.22 × 10⁻⁶ S / m when the carbon nanotube thickness increases to 30 μm. 4 The high conductivity (S / m) is primarily due to the dense and continuous conductive network formed by the copper layer and carbon nanotube film at the bottom of the composite film, rather than a uniform distribution within the film. Ideal conductivity is a necessary prerequisite for the composite material to achieve excellent electromagnetic interference shielding performance. This unique layered structure ensures that the composite film possesses highly efficient electromagnetic shielding capabilities.

[0073] 3. Electromagnetic Shielding Performance (EMI SE) Test

[0074] The inventors also tested the EMI shielding performance of the Fe3O4-PDMS / CNT / Cu composite film prepared in this embodiment in the X-band. Table 1 shows the overall electromagnetic shielding performance of the Fe3O4-PDMS / CNT film prepared in this embodiment, where the thickness of the CNT film gradually increases in Fe3O4-PDMS / CNT / Cu-1, Fe3O4-PDMS / CNT / Cu-2, and Fe3O4-PDMS / CNT / Cu-3. As shown in Table 1, the Fe3O4-PDMS / CNT / Cu film exhibits good electromagnetic shielding performance. The average EMI SE of the Fe3O4-PDMS / CNT / Cu-1 film in the X-band is 59.6 dB, which is higher than the standard for commercial electromagnetic shielding materials (20 dB). Furthermore, the electromagnetic shielding performance of Fe3O4-PDMS / CNT / Cu can be changed by adjusting the thickness of the CNT film. When the CNT film thickness is 30 μm, the EMI SE of the Fe3O4-PDMS / CNT / Cu-3 film reaches 75.1 dB, with 99.999% of electromagnetic waves being shielded. Furthermore, with increasing CNT film thickness, the EMI SE of the Fe3O4-PDMS / CNT / Cu composite film significantly increases, even with a sample thickness of only 0.35 mm, which is significantly superior to previously reported carbon-based and metallic materials.

[0075] Table 1. Conductivity and electromagnetic shielding performance of Fe3O4-PDMS / CNT / Cu composite films

[0076] 4. Electromagnetic shielding mechanism

[0077] To analyze the electromagnetic shielding mechanism of the Fe3O4-PDMS / CNT / Cu composite film prepared in this embodiment, the inventors compared the reflection loss (SER) and absorption loss (SE). A The contribution of CNT film thickness to the overall electromagnetic shielding efficiency (SET) of flexible composite films. Table 1 shows that as the CNT film thickness increases, the SET of all samples... T and SE A The values ​​all show an increasing trend, and SE A The value is much higher than the corresponding SE. R Value. For Fe3O4-PDMS / CNT / Cu composite films, as the CNT film thickness increases, the SE value... R Maintaining a low constant value, SE T and SE R The relative value of SE gradually increases. Therefore, it can be concluded that SE... T The increase in value is entirely based on SE AThe increase in SE. For example, the SE of Fe3O4-PDMS / CNT / Cu-3 composite films. A and SE R The values ​​were 64.8 dB and 10.3 dB, respectively. These results indicate that the Fe3O4-PDMS / CNT / Cu composite film can effectively absorb incident electromagnetic waves, and its shielding mechanism is dominated by absorption, suggesting that the Fe3O4-PDMS / CNT / Cu composite material maintains an electromagnetic wave shielding mechanism dominated by absorption.

[0078] The asymmetric structure of the Fe3O4-PDMS / CNT composite film and the Cu layer significantly improves the electromagnetic shielding mechanism of the material (see reference). Figure 2 (As shown). When electromagnetic waves are incident on one side of the Fe3O4-PDMS / CNT composite material, due to the relatively low surface conductivity and good impedance matching, the electromagnetic waves are reflected with weak reflection (low SE). R The electromagnetic waves penetrate the composite material. The penetrating microwaves are absorbed by the conductive network through electrical and dielectric losses, and attenuated through multiple reflections between the conductive networks. When the electromagnetic waves pass through the Fe3O4-PDMS / CNT film, they are significantly attenuated and absorbed. The remaining electromagnetic waves reaching the other side of the Fe3O4-PDMS / CNT composite material are reflected by the highly conductive Cu layer and reabsorbed by the Fe3O4-PDMS / CNT composite material. Due to the rational design of the high permeability and high conductivity layers, a special "absorption-reflection-reabsorption" process is formed when the electromagnetic waves penetrate the composite layer.

[0079] 5. Joule heating performance test

[0080] The Fe3O4-PDMS / CNT / Cu composite film prepared in this embodiment exhibits flexibility and high electromagnetic shielding performance, along with good thermal management properties. To explore the reliability and durability of the Fe3O4-PDMS / CNT / Cu composite film under Joule heating, a long-term stability test was conducted at 3V. Figure 3 Under a constant voltage of 3V, the temperature curves showed little change after the 1st, 20th, and 50th heating / cooling cycles, demonstrating good performance stability. The Fe3O4-PDMS / CNT / Cu composite film maintained a stable temperature for over 1800 seconds after reaching its saturation temperature of 83℃, proving its good reliability.

[0081] In this embodiment, the material for the high conductivity layer can be silver, nickel, or other materials besides copper. Fe3O4 nanoparticles can also be replaced with NiCo nanoparticles. For the polymer matrix material, polyvinyl alcohol, polyethylene, polyvinylidene fluoride, etc., can be used besides PDMS.

[0082] The Fe3O4-PDMS has a thickness of 300–400 μm, and the Cu layer has a thickness of 300 nm.

[0083] The flexible, multifunctional electromagnetic shielding film described in this embodiment has potential application value in the fields of electromagnetic protection and thermal management of highly integrated electronic devices.

[0084] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0085] Compare with Example 1

[0086] In this comparative example, a series of Fe3O4-PDMS / CNT composite films with different carbon nanotube film thicknesses were prepared, namely 10 μm, 20 μm and 30 μm, and the prepared samples were named Fe3O4-PDMS / CNT-1, Fe3O4-PDMS / CNT-2 and Fe3O4-PDMS / CNT-3, respectively.

[0087] 2. Conductivity test

[0088] As shown in Table 2, the conductivity of the Fe3O4-PDMS / CNT composite film increases with increasing carbon nanotube film thickness. When the carbon nanotube thickness of the composite film is 10 μm, the composite film exhibits a conductivity of 0.64 × 10⁻⁶. 4 The conductivity was S / m; however, when the thickness of the thin-film carbon nanotubes increased to 30 μm, the conductivity of the composite film was 1.33 × 10⁻⁶. 4 S / m.

[0089] 3. Electromagnetic Shielding Performance (EMI SE) Test

[0090] As shown in Table 2, the average EMI SE of Fe3O4-PDMS / CNT-1 film in the X-band is 36.1 dB, and the EMI SE of Fe3O4-PDMS / CNT-3 film is 63.9 dB when the thickness of CNT film is 30 μm.

[0091] Table 2. Conductivity and electromagnetic shielding performance of Fe3O4-PDMS / CNT composite films

[0092]

[0093] Compare with Example 2

[0094] In this comparative example, a series of CNT / Cu composite films with different carbon nanotube film thicknesses were prepared, namely 10 μm, 20 μm and 30 μm, and the prepared samples were named CNT / Cu-1, CNT / Cu-2 and CNT / Cu-3, respectively.

[0095] 2. Conductivity test

[0096] As shown in Table 3, when the thickness of the composite thin film carbon nanotubes is 10 μm, the composite thin film exhibits a density of 2.64 × 10⁻⁶. 4 The conductivity (S / m) of the composite film is 4.53 × 10⁻⁶ when the thickness of the carbon nanotube film increases to 30 μm. 4 S / m.

[0097] 3. Electromagnetic Shielding Performance (EMI SE) Test

[0098] As shown in Table 3, the average EMI SE of the CNT / Cu-1 film in the X-band is 50.4 dB. When the thickness of the CNT film is 30 μm, the EMI SE of the CNT / Cu-3 film is 62.4 dB.

[0099] As the CNT film thickness increased, the SE of all samples... T The values ​​all show an increasing trend, among which SE A Although compared to SE R High, but compared with Fe3O4-PDMS / CNT / Cu films, the SE of CNT / Cu films is lower. R This accounts for a large portion. These results indicate that the CNT / Cu composite film does not primarily employ an absorption-based shielding mechanism.

[0100] Table 3. Conductivity and electromagnetic shielding performance of CNT / Cu composite films

[0101]

[0102] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A flexible, multifunctional electromagnetic shielding film, characterized in that... include: Carbon nanotube films, and A high magnetic permeability layer and a high electrical conductivity layer are respectively bonded to the first and second surfaces of the carbon nanotube film, with the first and second surfaces facing away from each other. The high magnetic permeability layer comprises a polymer matrix and magnetic nanoparticles dispersed in the polymer matrix. The magnetic nanoparticles are selected from NiCo particles or Fe3O4 particles, and the particle size of the magnetic nanoparticles is 10-15 nm. The high magnetic permeability layer contains 10-20 wt% magnetic nanoparticles. The high electrical conductivity layer is made of any one or more combinations of copper, silver, and nickel. The thickness of the high magnetic permeability layer is 300-400 μm, and the thickness of the high electrical conductivity layer is 300-900 nm. The conductivity of the high magnetic permeability layer, the carbon nanotube thin film, and the high electrical conductivity layer increases sequentially, while the magnetic permeability decreases sequentially.

2. The electromagnetic shielding film according to claim 1, characterized in that: The polymer matrix is ​​selected from polyvinyl alcohol, polyethylene, polyvinylidene fluoride or polydimethylsilane.

3. The electromagnetic shielding film according to claim 1, characterized in that: The thickness of the carbon nanotube film is 10~30 μm.

4. The method for preparing the flexible multifunctional electromagnetic shielding film according to any one of claims 1-3, characterized in that... include: Magnetic nanoparticles are uniformly dispersed in a polymer solution to form a magnetic nanoparticle dispersion, wherein the magnetic nanoparticle dispersion contains 10-20 wt% magnetic nanoparticles. The magnetic nanoparticle dispersion is coated onto the first surface of a carbon nanotube film and then dried to form a high magnetic permeability layer. A metal film is formed on the second surface of the carbon nanotube film using physical and / or chemical deposition methods, thereby obtaining a high conductivity layer and a flexible, multifunctional electromagnetic shielding film; the first surface and the second surface are arranged back to back, and the conductivity of the high magnetic permeability layer, the carbon nanotube film, and the high conductivity layer increases sequentially, while the magnetic permeability decreases sequentially.

5. The preparation method according to claim 4, characterized in that: The polymer solution contains polymers selected from polyvinyl alcohol, polyethylene, polyvinylidene fluoride, or polydimethylsilane.

6. The preparation method according to claim 4, characterized in that: The drying process is carried out at a temperature of 80~120℃.

7. The application of the flexible multifunctional electromagnetic shielding film according to any one of claims 1-3 in the fields of electromagnetic protection or thermal management.

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