Preparation method of electromagnetic shielding material, electromagnetic shielding material and application of electromagnetic shielding material

Abstract

The embodiment of the invention relates to the technical field of electromagnetic shielding materials, in particular to a preparation method of an electromagnetic shielding material, the electromagnetic shielding material and application of the electromagnetic shielding material. After a plurality of electromagnetic shielding sponges are subjected to multi-layer lamination through a hot pressing process, each electromagnetic shielding sponge forms a corresponding hot pressing sponge layer. The hot-pressed sponge layer comprises hot-pressed polyurethane sponge, and MXene and ferrite which are distributed in pores of the hot-pressed polyurethane sponge. And the content of MXene and the content of ferrite between the hot-pressed sponge layers are in gradient change. The porous structure of the hot-pressed sponge layer can reduce impedance mismatch between the electromagnetic shielding material and air; the ferrite can carry out magnetic loss on electromagnetic waves; the MXene can attenuate electromagnetic waves in the modes of conductive loss, multiple reflection, polarization loss and the like; and meanwhile, the content of MXene and the content of ferrite in each layer of hot-pressed sponge are changed in a gradient manner, so that the absorption effect of the electromagnetic shielding material on electromagnetic waves is improved, and the reflection coefficient of the electromagnetic shielding material on the electromagnetic waves is reduced.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of electromagnetic shielding materials, and in particular, to a preparation method of an electromagnetic shielding material, the electromagnetic shielding material and its application. Background Art

[0002] With the rapid development of electronic information technology, electromagnetic waves have been widely used in various fields. However, many negative impacts have also arisen. Electromagnetic waves in the environment can cause electromagnetic pollution, interfere with the normal operation of the electromagnetic systems of devices, and the electromagnetic wave radiation of digital transmission systems can lead to information leakage. At the same time, electromagnetic radiation may also have direct or indirect adverse effects on human health.

[0003] The high conductivity of conductive polymers is usually beneficial to enhancing their electromagnetic shielding effect, but the high conductivity will lead to an increase in the reflection of electromagnetic waves by them, thus causing secondary electromagnetic pollution. Therefore, it is usually very difficult for electromagnetic shielding materials to have a low reflection coefficient while meeting high electromagnetic shielding performance. Summary of the Invention

[0004] In order to reduce the reflection coefficient of electromagnetic shielding materials for electromagnetic waves, the embodiments of the present application provide a preparation method of an electromagnetic shielding material, the electromagnetic shielding material and its application, which can enable the electromagnetic shielding material to have both high electromagnetic shielding performance and a low electromagnetic wave reflection coefficient.

[0005] To solve the above technical problems, the embodiments of the present application provide the following technical solutions:

[0006] In the first aspect of the present application, a preparation method of an electromagnetic shielding material is provided. The method includes: obtaining a plurality of electromagnetic shielding sponges; performing multi-layer lamination on the plurality of electromagnetic shielding sponges through a hot pressing process to obtain the electromagnetic shielding material; wherein, the electromagnetic shielding sponge includes a polyurethane sponge and MXene and ferrite distributed in the pores of the polyurethane sponge, and the content of MXene and the content of ferrite between each electromagnetic shielding sponge show a gradient change.

[0007] In the embodiments of the present application, after multiple electromagnetic shielding sponges are laminated in multiple layers through a hot pressing process, each electromagnetic shielding sponge forms a corresponding hot-pressed sponge layer, and an electromagnetic shielding material is obtained. The hot-pressed sponge layer includes a hot-pressed polyurethane sponge and MXene and ferrite distributed in the pores of the hot-pressed polyurethane sponge. Since the contents of MXene and ferrite between the electromagnetic shielding sponges show a gradient change, the contents of MXene and ferrite in each hot-pressed sponge layer also show a gradient change. The porous structure of the hot-pressed sponge layer can reduce the impedance mismatch between the electromagnetic shielding material and air; the ferrite can cause magnetic loss to electromagnetic waves; MXene can attenuate electromagnetic waves through ways such as conductive loss, multiple reflections, and polarization loss; at the same time, the gradient change of the contents of MXene and ferrite in each layer of the hot-pressed sponge is beneficial to improving the absorption effect of the electromagnetic shielding material on electromagnetic waves and reducing the reflection coefficient of the magnetic shielding material to electromagnetic waves, so that the electromagnetic shielding material provided by the embodiments of the present application has both high electromagnetic shielding performance and low electromagnetic wave reflection coefficient.

[0008] In some embodiments, the obtaining of the multiple electromagnetic shielding sponges includes: respectively immersing multiple polyurethane sponges in MXene dispersions with different MXene concentrations to obtain multiple first immersed sponges; respectively drying the multiple first immersed sponges, and then respectively immersing the multiple first immersed sponges in ferrite dispersions with different ferrite concentrations to obtain multiple second immersed sponges; respectively freeze-drying the multiple second immersed sponges to obtain multiple electromagnetic shielding sponges.

[0009] In some embodiments, the multiple electromagnetic shielding sponges include a first electromagnetic shielding sponge and a second electromagnetic shielding sponge; the concentration of MXene in the MXene dispersion corresponding to the first electromagnetic shielding sponge is 5 mg·mL -1 ~10 mg·mL -1 , and the concentration of ferrite in the ferrite dispersion corresponding to the first electromagnetic shielding sponge is 5 mg·mL -1 ~10 mg·mL -1 ; the concentration of MXene in the MXene dispersion corresponding to the second electromagnetic shielding sponge is 10 mg·mL -1 ~20 mg·mL -1 , and the concentration of ferrite in the ferrite dispersion corresponding to the second electromagnetic shielding sponge is 10 mg·mL -1 ~20 mg·mL -1 .

[0010] In some embodiments, the separately freeze-drying of the plurality of second impregnated sponges includes: separately freezing the plurality of second impregnated sponges under a temperature condition of -70°C to -60°C, and then separately freeze-drying the plurality of second impregnated sponges in a freeze dryer, where the temperature of the freeze-drying is -35°C to -45°C, and the time of the freeze-drying is 23h to 25h.

[0011] In some embodiments, the separately drying treatment of the plurality of first impregnated sponges includes: under a vacuum condition, separately drying the plurality of first impregnated sponges, where the temperature of the drying treatment is 55°C to 65°C, and the time of the drying treatment is 1.5h to 2.5h.

[0012] In some embodiments, the pore size of the polyurethane sponge is 1000μm to 1200μm.

[0013] In some embodiments, the pressure of the hot pressing process is 5kg to 10kg, the temperature of the hot pressing process is 50°C to 60°C, and the pressing time of the hot pressing process is 0.5min to 1.5min.

[0014] In some embodiments, the MXene includes Ti 3 C 2 T x and the ferrite includes CoFe 2 O 4 .

[0015] In the second aspect of the present application, there is also provided an electromagnetic shielding material, which is prepared according to the method described in the first aspect.

[0016] In the third aspect of the present application, there is also provided an application of an electromagnetic shielding material prepared according to the method described in the first aspect in the field of anti-electromagnetic interference.

[0017] It should be understood that the content described in the Summary of the Invention section is not intended to limit the key or important features of the present disclosure, nor to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1It is a schematic flow chart of a method for preparing an electromagnetic shielding material provided by an embodiment of the present application. Detailed implementation manners

[0020] The principles and spirit of the present disclosure will be described below with reference to several exemplary embodiments shown in the accompanying drawings. It should be understood that describing these specific embodiments is only to enable those skilled in the art to better understand and implement the present disclosure, and does not limit the scope of the present disclosure in any way. In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure belongs.

[0021] As used herein, the term "comprising" and its like should be understood as an open inclusion, that is, "including but not limited to". The term "based on" should be understood as "at least partially based on". The term "an embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects, and are only used to distinguish the objects referred to, without implying a specific spatial order, temporal order, importance order, etc. of the objects referred to.

[0022] Exemplarily, Figure 1 The flow of a method for preparing an electromagnetic shielding material provided by some embodiments of the present application is shown. Please refer to Figure 1 , and the method includes the following steps:

[0023] Step 11: Obtain a plurality of electromagnetic shielding sponges; wherein, the electromagnetic shielding sponges include polyurethane sponges and MXene and ferrite distributed in the pores of the polyurethane sponges, and the content of MXene and the content of ferrite between each of the electromagnetic shielding sponges show a gradient change.

[0024] In some embodiments, step 11 specifically includes: respectively immersing a plurality of polyurethane sponges in MXene dispersion liquids with different MXene concentrations to obtain a plurality of first immersed sponges; respectively performing a drying treatment on the plurality of first immersed sponges, and then respectively immersing the plurality of first immersed sponges in ferrite dispersion liquids with different ferrite concentrations to obtain a plurality of second immersed sponges; respectively performing freeze-drying on the plurality of second immersed sponges to obtain a plurality of electromagnetic shielding sponges.

[0025] In some embodiments, before respectively immersing a plurality of polyurethane sponges in MXene dispersion liquids with different MXene concentrations, it is also necessary to clean the plurality of polyurethane sponges. Specifically, the plurality of polyurethane sponges can be placed in a detergent, ultrasonically cleaned, and then the polyurethane sponges are placed in a vacuum condition at 55°C to 65°C and dried for 1.5 to 2.5 h; wherein, the detergent can specifically be an ethanol solution.

[0026] In some embodiments, the plurality of electromagnetic shielding sponges include a first electromagnetic shielding sponge and a second electromagnetic shielding sponge. In order to improve the electromagnetic shielding performance of the electromagnetic shielding material and reduce the electromagnetic wave reflection coefficient of the electromagnetic shielding material, the concentration of MXene in the MXene dispersion corresponding to the first electromagnetic shielding sponge is 5 mg·mL -1 ~10 mg·mL -1 , and the concentration of ferrite in the ferrite dispersion corresponding to the first electromagnetic shielding sponge is 5 mg·mL -1 ~10 mg·mL -1 ; the concentration of MXene in the MXene dispersion corresponding to the second electromagnetic shielding sponge is 10 mg·mL -1 ~20 mg·mL -1 , and the concentration of ferrite in the ferrite dispersion corresponding to the second electromagnetic shielding sponge is 10 mg·mL -1 ~20 mg·mL -1 .

[0027] In the above example, step 11 specifically includes: impregnating the first polyurethane sponge in the MXene dispersion with a concentration of 5 mg·mL -1 ~10 mg·mL -1 , drying the first polyurethane sponge impregnated with the MXene dispersion, then impregnating it in the ferrite dispersion with a concentration of 5 mg·mL -1 ~10 mg·mL -1 , and then performing freeze-drying to obtain the first electromagnetic shielding sponge. Impregnating the second polyurethane sponge in the MXene dispersion with a concentration of 10 mg·mL -1 ~20 mg·mL -1 , drying the second polyurethane sponge impregnated with the MXene dispersion, then impregnating it in the ferrite dispersion with a concentration of 10 mg·mL -1 ~20 mg·mL -1 , and then performing freeze-drying to obtain the second electromagnetic shielding sponge.

[0028] In some embodiments, in order to improve the electromagnetic shielding performance of the electromagnetic shielding material and reduce the electromagnetic wave reflection coefficient of the electromagnetic shielding material, freeze-drying the plurality of second impregnated sponges respectively includes: freezing the plurality of second impregnated sponges respectively under the temperature condition of -70 °C to -60 °C, and then placing the plurality of second impregnated sponges respectively in a freeze dryer for freeze-drying, the temperature of the freeze-drying is -35 °C to -45 °C, and the time of the freeze-drying is 23 h to 25 h.

[0029] In some embodiments, to improve the electromagnetic shielding performance of the electromagnetic shielding material and reduce the electromagnetic wave reflection coefficient of the electromagnetic shielding material, multiple first impregnated sponges are respectively dried, including: drying multiple first impregnated sponges respectively under vacuum conditions, the drying temperature is 55°C to 65°C, and the drying time is 1.5 h to 2.5 h.

[0030] In some embodiments, the pore size of the polyurethane sponge is 1000 μm to 1200 μm. The pore size refers to the diameter of the pores in the polyurethane sponge. When the pore size of the polyurethane sponge is higher than 1200 μm or lower than 1000 μm, it is not conducive to improving the electromagnetic interference resistance performance of the electromagnetic shielding material. In some embodiments, to make the comprehensive performance of the electromagnetic shielding material better, the thickness of the polyurethane sponge can specifically be 2 mm to 4 mm.

[0031] In the embodiments of the present application, MXene is a type of metal carbon / nitride with a two-dimensional layered structure, and its chemical general formula is M n+1 X n T x , where (n = 1 - 3), M represents early transition metals such as Ti, Zr, V, Mo, etc.; X represents C or N element, and T x is a surface group, usually -OH, -O, -F or -Cl. Due to its similar lamellar structure to graphene, it is named MXene.

[0032] In some embodiments, MXene can specifically be Ti 3 C 2 T x . Ti 3 C 2 T x has characteristics such as high electrical conductivity, special morphological structure and adjustable surface functional groups, enabling it to attenuate electromagnetic waves through ways such as conductive loss, multiple reflections, and polarization loss.

[0033] Since ferrite is both a magnetic medium and an electric medium, it has two functions of magnetic absorption and electric absorption, and is an excellent wave-absorbing material. Ferrite has characteristics such as large magnetic saturation intensity and coercivity, small volume, large specific surface area and good impedance matching, and can cause interface polarization and magnetic resonance. Compared with other wave-absorbing materials, it has the characteristics of small volume, good wave-absorbing effect and low cost. According to the crystal structure, ferrite can be divided into three categories: spinel structure type, garnet structure type and magnetoplumbite type hexagonal ferrite. In some embodiments of the present application, the ferrite is spinel structure type ferrite, and the chemical composition of the spinel structure type ferrite is MeFe 2 0 4 , where Me is a metal ion such as cobalt ion (Co2+ ) or magnesium ions (Mg 2+ ), etc. Spinel-structured ferrites have characteristics such as high magnetocrystalline anisotropy and high saturation magnetization, which are beneficial to improving the wave absorption performance of electromagnetic shielding materials.

[0034] In some embodiments, the ferrite may specifically be CoFe 2 0 4 . The dielectric constant and magnetic permeability of the ferrite are moderate, which can better improve the wave absorption ability of the electromagnetic shielding material.

[0035] Step 12: Multilayer laminate the plurality of electromagnetic shielding sponges through a hot pressing process to obtain the electromagnetic shielding material.

[0036] In some embodiments, in order to further improve the electromagnetic shielding performance of the electromagnetic shielding material and reduce the electromagnetic wave reflection coefficient of the electromagnetic shielding material, the pressure of the hot pressing process is 5 kg to 10 kg, the temperature of the hot pressing process is 50 °C to 60 °C, and the pressing time of the hot pressing process is 0.5 min to 1.5 min.

[0037] In some embodiments, the plurality of electromagnetic shielding sponges may specifically be 2 electromagnetic shielding sponges; in other embodiments, the plurality of electromagnetic shielding sponges may also specifically refer to 3 or more electromagnetic shielding sponges. Those skilled in the art can set the specific number of electromagnetic shielding sponges according to actual needs, and the embodiments of the present application do not limit this.

[0038] In the embodiments of the present application, by multilayer laminating a plurality of electromagnetic shielding sponges in the thickness direction of the electromagnetic shielding sponge through a hot pressing process, a plurality of electromagnetic shielding sponges can be correspondingly formed into stacked multilayer hot-pressed sponge layers; that is, the electromagnetic shielding material includes multilayer hot-pressed sponge layers, wherein the hot-pressed sponge layer includes hot-pressed polyurethane sponge (formed by hot-pressing polyurethane sponge) and MXene and ferrite distributed in the pores of the hot-pressed polyurethane sponge.

[0039] In the embodiments of the present application, since the contents of MXene and ferrite between the electromagnetic shielding sponges both show gradient changes, the contents of MXene and ferrite between the hot-pressed sponge layers also show gradient changes, such that the contents of MXene and ferrite in the electromagnetic shielding material show gradient changes in its own thickness direction. The porous structure of the hot-pressed sponge layer can reduce the impedance mismatch between the electromagnetic shielding material and air; the ferrite can cause magnetic loss to electromagnetic waves; MXene can achieve the attenuation of electromagnetic waves through ways such as conductive loss, multiple reflections, and polarization loss; at the same time, in the thickness direction of the electromagnetic shielding material, the content of MXene shows a gradient change, and the content of ferrite also shows a gradient change, which is beneficial to improving the absorption effect of the electromagnetic shielding material on electromagnetic waves and reducing the reflection coefficient of the magnetic shielding material to electromagnetic waves, so that the electromagnetic shielding material provided by the embodiments of the present application has both high electromagnetic shielding performance and low electromagnetic wave reflection coefficient.

[0040] In the embodiments of the present application, an electromagnetic shielding material is also provided, and this electromagnetic shielding material is prepared according to the method provided in the above embodiments.

[0041] In the embodiments of the present application, an application of an electromagnetic shielding material prepared according to the method provided in the above embodiments in the field of anti-electromagnetic interference is also provided.

[0042] Several embodiments of the present application are provided below.

[0043] Example 1

[0044] The preparation method of the electromagnetic shielding material includes:

[0045] Step 1: Place the first polyurethane sponge and the second polyurethane sponge in an ethanol solution with a mass fraction of 50%, and perform ultrasonic cleaning on the first polyurethane sponge and the second polyurethane sponge; then, place the first polyurethane sponge and the second polyurethane sponge in a vacuum oven at 60 °C and dry for 2 hours. Among them, the pore diameters of the first polyurethane sponge and the second polyurethane sponge are approximately 1100 μm, the thicknesses of the first polyurethane sponge and the second polyurethane sponge are 3 mm, and the sizes of the first polyurethane sponge and the second polyurethane sponge are 22.86 mm (length) × 10.16 mm (width).

[0046] Step 2: Immerse the first polyurethane sponge obtained in Step 1 repeatedly in 2 mL of Ti 3 C 2 T x nanosheets with a concentration of 5 mg·mL -1 of Ti 3 C 2 T xIn the dispersion liquid, the first impregnated sponge was obtained; after drying the first impregnated sponge in a vacuum oven at 60 °C for 2 hours, the first impregnated sponge was then repeatedly impregnated in 2 mL of CoFe 2 O 4 with a concentration of 5 mg·mL -1 of CoFe 2 O 4 dispersion liquid to obtain the second impregnated sponge; after quickly freezing the second impregnated sponge at -60 °C, the second impregnated sponge was then placed in a freeze dryer at -40 °C and freeze-dried for 24 h to obtain the first electromagnetic shielding sponge.

[0047] Step 3: The second polyurethane sponge obtained in Step 1 was repeatedly impregnated in 2 mL of Ti 3 C 2 T x nanosheet with a concentration of 10 mg·mL -1 of Ti 3 C 2 T x dispersion liquid to obtain the first impregnated sponge; after drying the first impregnated sponge in a vacuum oven at 60 °C for 2 hours, the first impregnated sponge was then repeatedly impregnated in 2 mL of CoFe 2 O 4 with a concentration of 10 mg·mL -1 of CoFe 2 O 4 dispersion liquid to obtain the second impregnated sponge; after quickly freezing the second impregnated sponge at -60 °C, the second impregnated sponge was then placed in a freeze dryer at -40 °C and freeze-dried for 24 h to obtain the second electromagnetic shielding sponge.

[0048] Step 4: The first electromagnetic shielding sponge and the second electromagnetic shielding sponge were laminated together in the thickness direction by a hot pressing process to obtain an electromagnetic shielding material in which the content of MXene and the content of ferrite changed in a gradient in the thickness direction; wherein, the pressure of the hot pressing process was 5 kg, the temperature of the hot pressing process was 60 °C, and the pressing time of the hot pressing process was 1 min.

[0049] Example 2

[0050] The preparation method of the electromagnetic shielding material includes:

[0051] Step 1: Place the first polyurethane sponge and the second polyurethane sponge in an ethanol solution with a mass fraction of 50%, and ultrasonically clean the first polyurethane sponge and the second polyurethane sponge; then, place the first polyurethane sponge and the second polyurethane sponge in a vacuum oven at 60 °C and dry for 2 hours. Among them, the pore size of the first polyurethane sponge and the second polyurethane sponge is ≈1100 μm, the thickness of the first polyurethane sponge and the second polyurethane sponge is 3 mm, and the size of the first polyurethane sponge and the second polyurethane sponge is 22.86 mm (length) × 10.16 mm (width).

[0052] Step 2: Immerse the first polyurethane sponge obtained in Step 1 repeatedly in 2 mL of a Ti 3 C 2 T x dispersion with a concentration of 10 mg·mL -1 of Ti 3 C 2 T x to obtain the first impregnated sponge; after drying the first impregnated sponge in a vacuum oven at 60 °C for 2 hours, then immerse the first impregnated sponge repeatedly in 2 mL of a CoFe 2 O 4 dispersion with a concentration of 10 mg·mL -1 of CoFe 2 O 4 to obtain the second impregnated sponge; quickly freeze the second impregnated sponge at -70 °C, and then freeze-dry the second impregnated sponge in a freeze dryer at -40 °C for 24 h to obtain the first electromagnetic shielding sponge.

[0053] Step 3: Immerse the second polyurethane sponge obtained in Step 1 repeatedly in 2 mL of a Ti 3 C 2 T x dispersion with a concentration of 20 mg·mL -1 of Ti 3 C 2 T x to obtain the first impregnated sponge; after drying the first impregnated sponge in a vacuum oven at 60 °C for 2 hours, then immerse the first impregnated sponge repeatedly in 2 mL of a CoFe 2 O 4 dispersion with a concentration of 20 mg·mL -1 of CoFe 2 O 4 to obtain the second impregnated sponge; quickly freeze the second impregnated sponge at -70 °C, and then freeze-dry the second impregnated sponge in a freeze dryer at -40 °C for 24 h to obtain the second electromagnetic shielding sponge.

[0054] Step 4: Stack the first electromagnetic shielding sponge and the second electromagnetic shielding sponge together in the thickness direction through a hot pressing process to obtain an electromagnetic shielding material with a gradient change in the content of MXene and the content of ferrite in the thickness direction; wherein, the pressure of the hot pressing process is 10 kg, the temperature of the hot pressing process is 50 °C, and the pressing time of the hot pressing process is 30 s.

[0055] Comparative Example 1

[0056] The preparation method of the electromagnetic shielding material includes:

[0057] Step 1: Place the polyurethane sponge in an ethanol solution with a solute mass fraction of 50% and ultrasonically clean the polyurethane sponge; then, place the polyurethane sponge in a vacuum oven at 60 °C and dry it for 2 hours. Among them, the pore size of the polyurethane sponge is approximately 1100 μm, the thickness of the polyurethane sponge is 6 mm, and the size of the polyurethane sponge is 22.86 mm (length) × 10.16 mm (width).

[0058] Step 2: Immerse the polyurethane sponge obtained in Step 1 repeatedly in 2 mL of Ti 3 C 2 T x dispersion with a concentration of 10 mg·mL -1 of Ti 3 C 2 T x to obtain the first impregnated sponge; after drying the first impregnated sponge in a vacuum oven at 60 °C for 2 hours, then immerse the first impregnated sponge repeatedly in 2 mL of CoFe 2 O 4 dispersion with a concentration of 10 mg·mL -1 of CoFe 2 O 4 to obtain the second impregnated sponge; after quickly freezing the second impregnated sponge at -70 °C, then freeze-dry the second impregnated sponge in a freeze dryer at -40 °C for 24 h to obtain the electromagnetic shielding material.

[0059] Perform anti-electromagnetic interference performance tests on the electromagnetic shielding materials provided in Example 1, Example 2, and Comparative Example 1 respectively, and the test results are shown in Table 1:

[0060] Table 1

[0061] Electromagnetic shielding effectiveness (dB) Reflection coefficient Example 1 46.5 0.15 Example 2 53.2 0.20 Comparative Example 1 43.0 0.61

[0062] As can be seen from Table 1, the electromagnetic shielding effectiveness of the electromagnetic shielding material provided in Example 1 reaches 46.5 dB, and the reflection coefficient is only 0.15; the electromagnetic shielding effectiveness of the electromagnetic shielding material provided in Example 2 reaches 53.2 dB, and the reflection coefficient is only 0.20. The electromagnetic shielding effectiveness of the electromagnetic shielding material provided in Comparative Example 1 can reach 43.0 dB, but the reflection coefficient is 0.61; due to the relatively large reflection coefficient of the electromagnetic shielding material provided in Comparative Example 1, it is likely to cause secondary electromagnetic radiation pollution. Compared with Comparative Example 1, the electromagnetic shielding materials of Example 1 and Example 2 have higher electromagnetic shielding effectiveness and lower reflection coefficients. That is to say, the electromagnetic shielding materials of Example 1 and Example 2 have more excellent electromagnetic shielding performance and more excellent wave absorption performance.

[0063] Compared with Comparative Example 1, the Ti 3 C 2 T x concentration in the dispersion liquid of Ti 3 C 2 T x nanosheets, and the concentration of CoFe 2 O 4 in the CoFe 2 O 4 dispersion liquid are both lower than those in Comparative Example 1. Although the electromagnetic shielding material in Example 1 has a lower content of Ti 3 C 2 T x and a lower content of CoFe 2 O 4 , the electromagnetic shielding material provided in Example 1 instead has higher electromagnetic shielding effectiveness and lower reflection coefficients. The main reason is that the content of Ti 3 C 2 T x and the content of CoFe 2 O 4 in the electromagnetic shielding material of Comparative Example 1 are uniformly distributed in its thickness direction, while the content of Ti 3 C 2 T x and the content of CoFe 2 O 4 in the electromagnetic shielding material of Example 1 change in a gradient in its thickness direction. The gradient change of the content of Ti 3 C 2 T x and the content of CoFe 2 O 4 in the thickness direction of the electromagnetic shielding material is beneficial to improving the absorption effect of the electromagnetic shielding material on electromagnetic waves and reducing the reflection coefficient of the magnetic shielding material to electromagnetic waves.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; under the idea of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an electromagnetic shielding material, characterized in that: The method comprises: Obtain a plurality of electromagnetic shielding sponges; The electromagnetic shielding material is obtained by laminating the plurality of electromagnetic shielding sponges in multiple layers through a hot pressing process; The electromagnetic shielding sponge includes a polyurethane sponge and MXene and ferrite distributed in the pores of the polyurethane sponge, and the content of the MXene and the content of the ferrite between each electromagnetic shielding sponge varies in a gradient.

2. The method according to claim 1, characterized in that The obtaining of a plurality of electromagnetic shielding sponges comprises: impregnating a plurality of polyurethane sponges in MXene dispersions having different MXene concentrations, respectively, to obtain a plurality of first impregnated sponges; Drying the plurality of first impregnated sponges respectively, and then immersing the plurality of first impregnated sponges respectively in ferrite dispersions with different ferrite concentrations to obtain a plurality of second impregnated sponges; The plurality of second impregnated sponges are freeze-dried respectively to obtain a plurality of electromagnetic shielding sponges.

3. The method according to claim 2, characterized in that The plurality of electromagnetic shielding sponges include a first electromagnetic shielding sponge and a second electromagnetic shielding sponge; The concentration of MXene in the MXene dispersion corresponding to the first electromagnetic shielding sponge is 5 mg·mL -1 ~10 mg mL -1 The concentration of ferrite in the ferrite dispersion corresponding to the first electromagnetic shielding sponge is 5 mg·mL -1 ~10 mg mL -1 ; The concentration of MXene in the MXene dispersion corresponding to the second electromagnetic shielding sponge is 10 mg·mL -1 ~20 mg mL -1 The concentration of ferrite in the ferrite dispersion corresponding to the second electromagnetic shielding sponge is 10 mg·mL -1 ~20 mg mL -1 .

4. The method according to claim 2, characterized in that: The freeze-drying of the plurality of second impregnated sponges respectively comprises: The plurality of second impregnated sponges are respectively placed at a temperature of -70°C to -60°C for freezing, and then the plurality of second impregnated sponges are respectively placed in a freeze dryer for freeze drying, the freeze drying temperature is -35°C to -45°C, and the freeze drying time is 23h to 25h.

5. The method according to claim 2, characterized in that: The drying process of the plurality of first impregnated sponges respectively comprises: Under vacuum conditions, the plurality of first impregnated sponges are dried respectively, the drying temperature is 55° C. to 65° C., and the drying time is 1.5 h to 2.5 h.

6. The method according to any one of claims 1 to 5, characterized in that: The pore diameter of the polyurethane sponge is 1000 μm to 1200 μm.

7. The method according to any one of claims 1 to 5, characterized in that: The pressure of the hot pressing process is 5kg to 10kg, the temperature of the hot pressing process is 50°C to 60°C, and the pressing time of the hot pressing process is 0.5min to 1.5min.

8. The method according to any one of claims 1 to 5, characterized in that: The MXene includes Ti3C2T x , the ferrite includes CoFe2O4.

9. An electromagnetic shielding material, characterized in that: The electromagnetic shielding material is prepared according to the method according to any one of claims 1-8.

10. Use of the electromagnetic shielding material prepared by the method according to any one of claims 1 to 8 in the field of anti-electromagnetic interference.

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