Graphene-based electromagnetic shielding film and preparation method and application thereof

Abstract

The invention discloses a graphene-based electromagnetic shielding film and a preparation method and application thereof, and relates to the technical field of application of electromagnetic shielding materials. The preparation method of the graphene-based electromagnetic shielding film specifically comprises the following steps: placing graphene, a binder and a dielectric medium filler in a dispersing solvent for ultrasonic dispersion to obtain a solid-liquid mixture; the solid-liquid mixture is poured into a mold, then the mold is placed in a horizontal dynamic magnetic field to be treated, meanwhile, heating and curing are conducted, and the graphene-based electromagnetic shielding film is formed. Directional arrangement of graphene is achieved through the synergistic effect of the horizontal dynamic magnetic field, the binder and the dielectric medium filler, the X-waveband electromagnetic shielding performance of the thin film is improved, and roll-to-roll production can be achieved.

Description

Technical Field

[0001] This invention relates to a graphene-based electromagnetic shielding film, its preparation method, and its application, belonging to the field of electromagnetic shielding material application technology. Background Technology

[0002] Graphene nanosheets can be synthesized using a low-cost solution exfoliation method and possess ultra-low density (area density 0.77 mg / m³). 2 ), ultra-high electrical conductivity (electron mobility 15000cm), 2 ·V -1 ·s -1 Excellent thermal conductivity (5300 W·m) -1 ·K -1 With its high mechanical strength (Young's modulus 1 TPa, tensile strength 130 GPa), graphene is considered an ideal filler that can significantly improve the electromagnetic shielding performance of composite materials. In traditional composite materials, graphene nanosheets are randomly distributed, which prevents their anisotropic properties (high in-plane conductivity and weak interlayer interactions) from being manifested on a macroscopic scale, severely limiting the improvement of electromagnetic interference (EMI) shielding effectiveness.

[0003] The EMI shielding effectiveness of graphene is closely related to its orientation and alignment: horizontally ordered graphene can enhance electromagnetic wave reflection, improve in-plane conductivity, and form microcapacitor structures, thereby synergistically strengthening the reflection and absorption of electromagnetic waves. Currently, related technologies (such as self-assembly or mechanical pressing) are difficult to achieve high-precision, large-scale oriented alignment of graphene nanosheets, and the processes are complex and costly. Furthermore, graphene's strong diamagnetic properties provide a theoretical basis for magnetic field-induced orientation, allowing for global ordered alignment within a polymer matrix through magnetic field manipulation, while simultaneously optimizing interfacial interactions. However, EMI shielding composites constructed solely from graphene often suffer from limitations in mechanical strength and electromagnetic wave absorption performance due to weak interlayer interactions and a single reflection shielding mechanism. By introducing binders and dielectric fillers, the resulting three-dimensional support structure not only significantly enhances the mechanical properties of the film, but its multi-interface, multi-component system can also synergistically regulate the electromagnetic response, improving the overall shielding effect by enhancing energy dissipation. Therefore, based on the efficient and controllable graphene nanosheet orientation alignment technology, combined with binders and dielectric fillers, the advantages of graphene in the field of electromagnetic shielding can be fully utilized, thereby promoting the large-scale application of high-performance EMI shielding composite materials in consumer electronics, military equipment and spacecraft. Summary of the Invention

[0004] To address the shortcomings of related technologies, this invention provides a graphene-based electromagnetic shielding film, its preparation method, and its application. It possesses extremely strong electromagnetic wave isolation performance, excellent mechanical properties, and flexibility, thus solving the problem of uncontrollable large-scale, high-precision arrangement of graphene nanosheets in traditional composite materials.

[0005] One objective of this invention is to provide a method for preparing a graphene-based electromagnetic shielding film, specifically comprising the following steps: (1) Place graphene, binder and dielectric filler in a dispersion solvent and ultrasonically disperse (preferably ultrasonically disperse at a frequency of 35 kHz for 12 min) to obtain a solid-liquid mixture.

[0006] (2) Pour the solid-liquid mixture into a mold (preferably a rectangular silicone groove mold), and then place the mold in a horizontal dynamic magnetic field for treatment, while heating and curing to form a graphene-based electromagnetic shielding film.

[0007] Preferably, in step (1), the dispersing solvent is N,N-dimethylformamide (DMF); the binder is polyvinylidene fluoride; the dielectric filler is ethylene carbonate; the graphene, binder, and dielectric filler are weighed according to a mass ratio of (40-95):(1-20):(4-40); the total amount of graphene, binder, and dielectric filler added in the solid-liquid mixture is 0.1-0.125 g / mL.

[0008] Preferably, the conditions for processing the mold in step (2) by placing it in a horizontal dynamic magnetic field are: processing in a horizontal dynamic magnetic field with an intensity of 100-200mT at a frequency that changes periodically at 0.5-5Hz; and the temperature for heating and curing is 25-65℃.

[0009] The second objective of this invention is to provide a graphene-based electromagnetic shielding film prepared using the method of this invention.

[0010] The third objective of this invention is to provide an application of the graphene-based electromagnetic shielding film prepared by the method of this invention in electromagnetic shielding.

[0011] Mechanism of the invention: This invention utilizes a horizontal dynamic magnetic field for processing (see schematic diagram of the horizontally moving magnetic field). Figure 1As shown, the intrinsic diamagnetism of graphene induces its nanosheets to align horizontally, constructing a highly ordered multilayer thin film structure. In this system, the introduction of polyvinylidene fluoride (PVDF), the high dielectric properties of ethylene carbonate (EC), and the oriented graphene form a triple synergistic mechanism, effectively enhancing the mechanical integrity of the oriented structure, ensuring the stability of the functional network, and giving the prepared graphene-based electromagnetic shielding film good flexibility; and forming a large number of microcapacitor structures at the interface. When electromagnetic waves are incident, the horizontally aligned graphene on the surface first reflects the electromagnetic waves; the transmitted portion, after entering the interior of the film, will undergo multiple reflections and scatterings in the conductive network composed of oriented graphene. The microcapacitor structure formed by the graphene-based electromagnetic shielding film of this invention induces significant dielectric loss, thereby converting electromagnetic energy into heat energy for efficient dissipation. This significantly improves the overall electromagnetic shielding effectiveness of the composite material in the X-band.

[0012] The beneficial effects of this invention are: Excellent shielding performance: Graphene is oriented and aligned using a horizontal dynamic magnetic field, and it synergistically interacts with polyvinylidene fluoride and ethylene carbonate to construct a synergistic shielding mechanism, significantly improving the material's electromagnetic shielding effectiveness in the X-band. (Process flow diagram shown...) Figure 12 As shown.

[0013] Achieving continuous production: This invention uses "sequential lamination" or "hot pressing" connection technology to successfully achieve roll-to-roll continuous production of high-performance flexible shielding films, solving the problem of large-scale preparation in this field.

[0014] Integrated Functionality: The graphene-based electromagnetic shielding film prepared by this invention possesses both good flexibility and excellent mechanical properties. Furthermore, by stacking and hot-pressing the films, a bulk material with high thermal conductivity (24 W / (m·K)) can be further prepared, achieving integrated electromagnetic shielding and thermal conductivity functions. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the horizontally moving magnetic field of the present invention.

[0016] Figure 2 This is a schematic diagram illustrating the process of preparing a graphene-based electromagnetic shielding film using a silicone groove mold according to the present invention.

[0017] Figure 3 This is a schematic diagram illustrating the process of preparing a continuous long strip of graphene-based electromagnetic shielding film using the sequential lamination method of this invention.

[0018] Figure 4 This is a schematic diagram of the process for preparing continuous long strips of graphene-based electromagnetic shielding film using the hot pressing method of this invention.

[0019] Figure 5This is a scanning electron microscope image of the graphene-based electromagnetic shielding film prepared in Example 1 of the present invention.

[0020] Figure 6 The image shows the X-band electromagnetic shielding effectiveness of the graphene-based electromagnetic shielding film prepared in Example 1 of this invention.

[0021] Figure 7 The image shows the X-band electromagnetic shielding effectiveness of the graphene-based electromagnetic shielding film prepared in Comparative Example 1 of this invention.

[0022] Figure 8 This is a schematic diagram illustrating the flexibility of the graphene-based electromagnetic shielding film prepared in Example 1 of the present invention.

[0023] Figure 9 The image shows the X-band electromagnetic shielding effectiveness of the graphene-based electromagnetic shielding film prepared in Comparative Example 2 of this invention.

[0024] Figure 10 The image shows the macroscopic morphology of the graphene nanosheet composite thermally conductive bulk material prepared using the graphene-based electromagnetic shielding film of this invention.

[0025] Figure 11 The stress-strain curve of the graphene-based electromagnetic shielding film prepared in Example 1 of this invention is shown.

[0026] Figure 12 This is a process flow diagram for preparing the oriented graphene-based electromagnetic shielding film according to the present invention.

[0027] Figure 13 The image shows the X-band electromagnetic shielding effectiveness of the graphene-based electromagnetic shielding film prepared in Comparative Example 3 of this invention. Detailed Implementation

[0028] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents used were commercially available analytical grade reagents.

[0029] Example 1 A method for preparing a graphene-based electromagnetic shielding film specifically includes the following steps: (1) Graphene, polyvinylidene fluoride and ethylene carbonate were placed in DMF in a mass ratio of 90:7:3 and ultrasonically dispersed at a frequency of 35 kHz for 12 min to obtain a solid-liquid mixture. The total amount of graphene, binder and dielectric filler added in the solid-liquid mixture was 0.11 g / mL.

[0030] (2) Pour the solid-liquid mixture into a rectangular silicone tank mold, and then place the rectangular silicone tank mold in a horizontal dynamic magnetic field with an intensity of 200mT for periodic change treatment of 0.5Hz. At the same time, heat and solidify at 60℃ to evaporate the DMF solvent. The graphene nanosheets are oriented along the cutting of the magnetic field lines, and finally form a graphene-based electromagnetic shielding film with a thickness of 100μm.

[0031] The electromagnetic shielding performance of the graphene-based electromagnetic shielding film prepared in this embodiment was tested (using the flange coaxial method): First, the film sample was made into a standard ring and placed in a special test fixture. Electromagnetic waves were emitted within a set frequency band (e.g., 300MHz to 1.5GHz) using a vector network analyzer. The test consisted of two steps: first, the incident signal power was measured as a reference in a "straight-through" state without the sample, and then the signal power after penetration was measured after the sample was inserted. Finally, the shielding effectiveness (SE) was calculated using the formula SE(dB) = 10log 10 The shielding effectiveness value is obtained by dividing the incident power by the transmitted power, which characterizes the material's ability to attenuate electromagnetic waves. The test results show that the shielding effectiveness of this embodiment can reach 93.7dB. This is because the intrinsic diamagnetism of graphene induces its nanosheets to be horizontally oriented, constructing a highly ordered multilayer thin film structure. The introduction of polyvinylidene fluoride (PVDF) and the high dielectric properties of ethylene carbonate (EC) form a triple synergistic mechanism with the oriented graphene, which effectively enhances the mechanical integrity of the oriented structure, ensures the stability of the functional network, and makes the prepared graphene-based electromagnetic shielding film have good flexibility. Furthermore, a large number of microcapacitor structures are formed at the interface, which improves the electromagnetic shielding effect of the film material.

[0032] Example 2 A method for preparing a graphene-based electromagnetic shielding film specifically includes the following steps: (1) Graphene, polyvinylidene fluoride and ethylene carbonate are placed in DMF in a mass ratio of 40:20:40 and ultrasonically dispersed at a frequency of 35 kHz for 12 min to obtain a solid-liquid mixture. The total amount of graphene, binder and dielectric filler added in the solid-liquid mixture is 0.1 g / mL.

[0033] (2) Pour the solid-liquid mixture into a rectangular silicone tank mold, then place the rectangular silicone tank mold in a horizontal dynamic magnetic field with an intensity of 100mT and perform a periodic change treatment of 5Hz. At the same time, heat and solidify at 25℃ to evaporate the DMF solvent. The graphene nanosheets are oriented along the cutting of the magnetic field lines, and finally form a graphene-based electromagnetic shielding film with a thickness of 100μm.

[0034] The electromagnetic shielding performance of the graphene-based electromagnetic shielding film of this embodiment was tested using the same testing method as in Example 1. The test results showed that the shielding effectiveness of the graphene-based electromagnetic shielding film prepared in this embodiment was 59.3 dB. In this embodiment, the intrinsic diamagnetism of graphene induces its nanosheets to be horizontally oriented, constructing a highly ordered multilayer film structure. The introduction of polyvinylidene fluoride (PVDF) and the high dielectric properties of ethylene carbonate (EC) form a triple synergistic mechanism with the oriented graphene. While ensuring that the graphene-based electromagnetic shielding film has a good electromagnetic shielding effect, it effectively enhances the mechanical integrity of the oriented structure, ensures the stability of the functional network, and makes the prepared graphene-based electromagnetic shielding film have good flexibility.

[0035] Example 3 A method for preparing a graphene-based electromagnetic shielding film specifically includes the following steps: (1) Graphene, polyvinylidene fluoride and ethylene carbonate were placed in DMF in a mass ratio of 95:1:4 and ultrasonically dispersed at a frequency of 35 kHz for 12 min to obtain a solid-liquid mixture. The total amount of graphene, binder and dielectric filler added in the solid-liquid mixture was 0.125 g / mL.

[0036] (2) Pour the solid-liquid mixture into a rectangular silicone tank mold, then place the rectangular silicone tank mold in a horizontal dynamic magnetic field with an intensity of 100mT and perform periodic changes of 1Hz. At the same time, heat and solidify at 30℃ to evaporate the DMF solvent. The graphene nanosheets are oriented along the cutting of the magnetic field lines, and finally form a graphene-based electromagnetic shielding film with a thickness of 100μm.

[0037] The electromagnetic shielding performance of the graphene-based electromagnetic shielding film of this embodiment was tested using the same testing method as in Example 1. The test results showed that the shielding effectiveness of the graphene-based electromagnetic shielding film prepared in this embodiment was 87.6 dB. This is because the intrinsic diamagnetism of graphene induces its nanosheets to be horizontally oriented, constructing a highly ordered multilayer film structure. Furthermore, the introduction of polyvinylidene fluoride (PVDF) and the high dielectric properties of ethylene carbonate (EC) form a triple synergistic mechanism with the oriented graphene, effectively enhancing the mechanical integrity of the oriented structure, ensuring the stability of the functional network, and giving the prepared graphene-based electromagnetic shielding film good flexibility. In addition, a large number of microcapacitor structures are formed at the interface, improving the electromagnetic shielding effect of the film material.

[0038] Comparative Example 1 A method for preparing a graphene-based electromagnetic shielding film specifically includes the following steps: (1) Graphene and polyvinylidene fluoride were placed in DMF at a mass ratio of 90:10 and ultrasonically dispersed at a frequency of 35 kHz for 12 min to obtain a solid-liquid mixture. The total amount of graphene, binder and dielectric filler added in the solid-liquid mixture was 0.11 g / mL.

[0039] (2) Pour the solid-liquid mixture into a rectangular silicone tank mold, and then place the rectangular silicone tank mold in a horizontal dynamic magnetic field with an intensity of 200mT for a periodic change of 0.5Hz. At the same time, heat and solidify at 60℃ to evaporate the DMF solvent. The graphene nanosheets are oriented along the cutting of the magnetic field lines, and finally form a graphene-based electromagnetic shielding film with a thickness of 100μm.

[0040] The electromagnetic shielding performance of the graphene-based electromagnetic shielding film in this comparative example was tested using the same testing method as in Example 1. The test results showed that the shielding effectiveness of the graphene-based electromagnetic shielding film prepared in this comparative example was 81 dB (e.g., Figure 7 As shown in the figure, this is because ethylene carbonate was not used as the dielectric filler in this comparative example, resulting in a single shielding mechanism: the unfilled film mainly relies on the surface reflection mechanism. Although its high conductivity can reflect electromagnetic waves, it is prone to secondary electromagnetic pollution and has a weak ability to suppress low-frequency and near-field interference, resulting in a reduction in the electromagnetic shielding effectiveness of the film.

[0041] Comparative Example 2 A method for preparing a graphene-based electromagnetic shielding film specifically includes the following steps: (1) Graphene, polyvinylidene fluoride and ethylene carbonate were placed in DMF in a mass ratio of 90:7:3 and ultrasonically dispersed at a frequency of 35 kHz for 12 min to obtain a solid-liquid mixture. The total amount of graphene, binder and dielectric filler added in the solid-liquid mixture was 0.11 g / mL.

[0042] (2) Pour the solid-liquid mixture into a rectangular silicone tank mold, and then place the rectangular silicone tank mold on a heating platform at 60°C for heating and curing to evaporate the DMF solvent and form a graphene-based electromagnetic shielding film with a thickness of 100μm.

[0043] The electromagnetic shielding performance of the graphene-based electromagnetic shielding film in this comparative example was tested using the same testing method as in Example 1. The test results showed that the shielding effectiveness of the graphene-based electromagnetic shielding film prepared in this comparative example was 85 dB (e.g., Figure 9 As shown in the figure, this is because the comparative example involves a horizontal dynamic magnetic field treatment during the film curing process, which results in the graphene sheets not being uniformly arranged, thus affecting the shielding performance of the film.

[0044] Comparative Example 3 A method for preparing a graphene-based electromagnetic shielding film specifically includes the following steps: (1) Graphene and ethylene carbonate were placed in DMF at a mass ratio of 90:10 and ultrasonically dispersed at a frequency of 35 kHz for 12 min to obtain a solid-liquid mixture. The total amount of graphene, binder and dielectric filler added in the solid-liquid mixture was 0.11 g / mL.

[0045] (2) Pour the solid-liquid mixture into a rectangular silicone tank mold, and then place the rectangular silicone tank mold in a horizontal dynamic magnetic field with an intensity of 200mT for a periodic change of 0.5Hz. At the same time, heat and solidify at 60℃ to evaporate the DMF solvent. The graphene nanosheets are oriented along the cutting of the magnetic field lines, and finally form a graphene-based electromagnetic shielding film with a thickness of 100μm.

[0046] The electromagnetic shielding performance of the graphene-based electromagnetic shielding film in this comparative example was tested using the same testing method as in Example 1. The test results showed that the shielding effectiveness of the graphene-based electromagnetic shielding film prepared in this comparative example was 91.3 dB (e.g., ...). Figure 13 As shown in the figure, although the graphene-based electromagnetic shielding film prepared in this comparative example has high electromagnetic shielding efficiency, the lack of a binder leads to structural instability of the film, reduced interlayer bonding ability of the graphene sheets, and easy cracking of the film, which is not conducive to practical electromagnetic shielding applications.

[0047] The graphene-based electromagnetic shielding film prepared in this embodiment of the invention can be produced roll-to-roll by sequential lamination or hot pressing, as detailed below: Sequential lamination method: Place an arc-shaped ramp at one end of a silicone groove mold, and then place one end of the graphene-based electromagnetic shielding film prepared in the example back onto the arc-shaped ramp and completely cover it. Figure 2 Then, pour the uniformly dispersed liquid into the mold and repeat the above process to obtain a continuous long strip of graphene-based electromagnetic shielding film, realizing roll-to-roll mass production. Figure 3 ).

[0048] Hot pressing method: Take two sections of graphene-based electromagnetic shielding film prepared in the example, and hot press the two ends of the two sections of graphene-based electromagnetic shielding film at 100°C for 2 hours to connect the two sections of film into a complete long strip film. Figure 4 Repeating this hot-pressing process allows for the production of roll-to-roll oriented graphene-based electromagnetic shielding strips.

[0049] The graphene-based electromagnetic shielding films prepared in the examples were subjected to scanning electron microscopy and X-band electromagnetic shielding effectiveness tests. The scanning electron microscopy image of the graphene-based electromagnetic shielding film prepared in Example 1 is shown below. Figure 5 As shown, by Figure 5The graphene nanosheets in the graphene-based electromagnetic shielding film prepared in Example 1 exhibit a laterally regular arrangement, which is beneficial to improving the electromagnetic shielding reflection efficiency of the film. The graphene nanosheets in the graphene-based electromagnetic shielding films prepared in Examples 2 and 3 also show a laterally regular arrangement, further enhancing the electromagnetic shielding reflection efficiency of the films. X-band electromagnetic shielding performance testing was conducted on the graphene-based electromagnetic shielding film prepared in Example 1. The test results showed that the X-band electromagnetic shielding performance of the graphene-based electromagnetic shielding film prepared in Example 1 was 93.7 dB (e.g., ...). Figure 6 As shown in the figure), where SET is the total shielding efficiency, SER is the electromagnetic shielding efficiency for reflected signals, and SEA is the electromagnetic shielding efficiency for absorbed signals, and as... Figure 8 The graphene-based electromagnetic shielding film shown has good flexibility. Figure 11 The stress-strain curves of the 100 μm thick graphene-based electromagnetic shielding film prepared in Example 1 are shown. The figure shows that the maximum stress of the graphene-based electromagnetic shielding film prepared in Example 1 is 394 MPa, and the maximum strain is 2.4%. This indicates that Example 1 utilizes the intrinsic diamagnetism of graphene to induce the horizontal orientation of its nanosheets, constructing a highly ordered multilayer film structure. Furthermore, the introduction of polyvinylidene fluoride (PVDF) and the high dielectric properties of ethylene carbonate (EC) form a triple synergistic mechanism with the oriented graphene, effectively enhancing the mechanical integrity of the oriented structure. The graphene-based electromagnetic shielding films prepared in Examples 2 and 3 of this invention also exhibit similar mechanical properties to those in Example 1.

[0050] A method for preparing a graphene nanosheet composite thermally conductive material specifically includes the following steps: By stacking multiple layers of the graphene-based electromagnetic shielding film prepared in this invention and then heating and compressing them, a block of horizontally arranged graphene can be obtained (e.g., Figure 10 (As shown). Due to the extremely high thermal conductivity of graphene, and by aligning it with a magnetic field, good contact can be achieved between the graphene particles, forming a thermally conductive pathway. If cut along the normal to the alignment direction, a sample of a material with an interfacial thermal conductivity far exceeding that of currently widely used thermal grease can be obtained.

[0051] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method of preparing a graphene-based electromagnetic shielding film, characterized by, Specifically comprising the following steps: (1) placing graphene, a binder and a dielectric filler in a dispersion solvent and ultrasonically dispersing to obtain a solid-liquid mixture; (2) pouring the solid-liquid mixture into a mold, then placing the mold in a horizontal dynamic magnetic field for treatment, and simultaneously heating and curing to form a graphene-based electromagnetic shielding film.

2. The method of claim 1, wherein the graphene-based electromagnetic shielding film is prepared by the steps of: (a) preparing a graphene-based film by a chemical vapor deposition method; (b) coating a conductive layer on the graphene-based film; and (c) coating a protective layer on the conductive layer. In step (1), the dispersion solvent is N,N-dimethylformamide; the binder is polyvinylidene fluoride; the dielectric filler is ethylene carbonate; the graphene, binder and dielectric filler are weighed according to a mass ratio of (40-95):(1-20):(4-40); and the total amount of graphene, binder and dielectric filler in the solid-liquid mixture is 0.1-0.125 g / mL.

3. The method of claim 1, wherein the graphene-based electromagnetic shielding film is prepared by the steps of: (a) preparing a graphene-based film by a chemical vapor deposition method; (b) coating a conductive layer on the graphene-based film; and (c) coating a protective layer on the conductive layer. In step (2), the mold is placed in a horizontal dynamic magnetic field for treatment under the following conditions: the horizontal dynamic magnetic field has a strength of 100-200 mT, and the treatment is performed at a frequency that periodically varies at 0.5-5 Hz; and the heating and curing temperature is 25-65℃.

4. The graphene-based electromagnetic shielding film prepared by the method of claims 1-3.

5. The graphene-based electromagnetic shielding film of claim 4 for use in electromagnetic shielding.

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