Shielding material and preparation method thereof

Abstract

The invention relates to the field of electromagnetic wave shielding materials, in particular to a shielding material and a preparation method thereof.The material comprises MXene nanosheets, magnetic nanoparticles and carbon nanotubes, the broadband electromagnetic shielding effect is achieved through the synergistic effect of the three nanomaterials, the surface of the material contains the MXene nanosheets and the magnetic nanoparticles with the low concentration, and therefore the electromagnetic shielding effect is achieved. Good impedance matching is realized, so that reflection of electromagnetic waves is reduced. In the material, the concentration of the MXene nanosheets and the magnetic particles is gradually increased, a high-loss area is formed, and electromagnetic waves are converted into heat energy to be consumed to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic wave shielding materials, in particular to a shielding material and a preparation method thereof. BACKGROUND

[0002] With the wide application of electronic devices, electromagnetic interference (EMI) problems are becoming increasingly serious, especially in the spectral gap region between high frequency bands (such as 8 GHz to 18 GHz) and low frequency bands (such as 100 MHz to 2 GHz). Traditional electromagnetic shielding materials, such as metal foils, metal meshes and carbon-based composites, although have good shielding effectiveness in certain frequency bands, generally have the following defects: limited frequency band coverage: the electromagnetic shielding effectiveness of traditional materials is uneven in a wide frequency band (from low frequency to high frequency), and it is difficult to meet the needs of different frequency bands at the same time. Insufficient mechanical properties: many high-efficiency shielding materials, while achieving excellent electromagnetic shielding performance, often sacrifice mechanical properties, resulting in fragile materials that are difficult to apply to flexible electronic devices and wearable devices. Secondary pollution problem: some materials shield electromagnetic waves through reflection mechanism, which may cause secondary reflection of electromagnetic waves in the environment, causing secondary pollution.

[0003] Chinese patent CN108811478A discloses a three-dimensional layered MXene electromagnetic shielding foam. This material uses a combination of MXene nanosheets and magnetic nanoparticles, aiming to improve electromagnetic shielding performance, and through three-dimensional structure design, enhances the material's electromagnetic wave absorption capacity. However, this scheme does not fully utilize the dielectric loss mechanism, which may result in insufficient shielding effectiveness at high frequencies.

[0004] Chinese patent CN110499142A discloses a MXene / metal ion composite material with high efficiency electromagnetic interference shielding and a preparation method thereof. This material optimizes the absorption and reflection performance of electromagnetic waves through gradient structure design, but does not consider the dielectric loss mechanism.

[0005] In summary, it is particularly important to design a material that has high shielding effectiveness in multiple frequency bands. SUMMARY

[0006] The purpose of the present application is to provide a shielding material and a preparation method thereof. This material includes MXene nanosheets, magnetic nanoparticles and carbon nanotubes, and through the synergistic effect of these three nanomaterials, a wide frequency band electromagnetic shielding effect is achieved. The material surface contains a low concentration of MXene nanosheets and magnetic particles, achieving good impedance matching, thereby reducing electromagnetic wave reflection. In the interior of the material, the concentration of MXene nanosheets and magnetic particles gradually increases, forming a high loss area, which maximizes the conversion of electromagnetic waves into heat energy consumption.

[0007] In order to achieve the above purpose, the present application provides the following technical solutions: A shielding material, consisting of: MXene nanosheets, magnetic nanoparticles, carbon nanotubes and a PU matrix, the magnetic nanoparticles comprising Fe3O4 or NiFe2O4.

[0008] Further, the mass ratio of the MXene nanosheets, the magnetic nanoparticles and the carbon nanotubes is 1.5-5.0:3.0-8.0:0.5-2.0 Further, the mass ratio of the MXene nanosheets, the magnetic nanoparticles and the carbon nanotubes is 2.0:5.0:1.0.

[0009] Further, the PU matrix is a polyurethane or polyester fabric.

[0010] A method for preparing the above-mentioned shielding material, comprising the following steps: Preparation of MXene nanosheet aqueous solution, magnetic nanoparticle aqueous solution, carbon nanotube aqueous solution and PU matrix solution respectively; Mixing the MXene nanosheet aqueous solution, the magnetic nanoparticle aqueous solution, the carbon nanotube aqueous solution and the PU matrix solution to obtain a mixed solution; Uniformly coating a thin film of the obtained mixed solution on the PU matrix; Drying after coating to obtain the shielding material.

[0011] Further, the preparation of the MXene nanosheet aqueous solution comprises the following steps: taking MXene nanosheets, mixing with deionized water according to a mass percentage of 1.5%-5.0%, using an ultrasonic cleaning instrument for ultrasonic treatment for 30 minutes to 1 hour to obtain the MXene nanosheet aqueous solution.

[0012] Further, the preparation of the magnetic nanoparticle aqueous solution comprises the following steps: mixing the magnetic nanoparticles with deionized water according to a mass percentage of 3.0%-8.0%, using an ultrasonic cleaning instrument for treatment for 30 minutes to 1 hour to obtain the magnetic nanoparticle aqueous solution.

[0013] Further, the preparation of the carbon nanotube aqueous solution comprises the following steps: removing surface impurities of the carbon nanotubes through acidification treatment, mixing the carbon nanotubes with deionized water according to a mass percentage of 0.5%-2.0%, using an ultrasonic cleaning instrument for treatment for 30 minutes to 1 hour to obtain the carbon nanotube aqueous solution.

[0014] Further, the solvent of the PU matrix solution is dimethyl sulfoxide.

[0015] Further, the step of uniformly coating a thin film of the obtained mixed solution on the PU matrix is: uniformly coating the mixed solution on the surface of the PU matrix using a doctor blade method or a coating machine. After coating, a gradient structure is formed by gradient coating method, and the coated material is dried and high-temperature cured to obtain a shielding material.

[0016] The shielding material can be applied to the fields of textile fabrics, communication equipment, etc.

[0017] MXene nanoplatelets: MXene is a two-dimensional material composed of metal carbide or nitride, which generally appears in the form of Ti3C4Tx, where T represents surface functional groups (such as -OH, -O, -F, etc.). MXene has excellent electrical conductivity and chemical activity, and is widely used in electronics, catalysis, energy storage, etc. In the present application, due to its highly conductive properties, MXene plays a key role in the absorption of electromagnetic waves in the high frequency band (such as 8GHz to 18GHz), absorbing and reflecting electromagnetic waves through the conductive loss mechanism. Enhance the electrical conductivity of the composite material: The introduction of MXene nanoplatelets makes the composite material have higher electrical conductivity, which can effectively improve the electromagnetic shielding effectiveness, especially in the shielding of high frequency electromagnetic waves. MXene nanoplatelets contain a large number of functional groups on their surface, which can interact well with other materials (such as magnetic particles, carbon nanotubes, etc.), promoting the uniform dispersion of the composite material.

[0018] Magnetic nanoparticles refer to metal oxides with a particle size in the nanometer scale (1-100nm), specifically Fe3O4 or NiFe2O4 in this application, which have good magnetic properties. Such particles can be arranged or magnetized under the action of an external magnetic field, and are used for low frequency electromagnetic wave absorption in this application: Magnetic nanoparticles mainly absorb low frequency electromagnetic waves (such as 100MHz to 2GHz) through magnetic loss mechanism, improving the shielding effectiveness of the composite material in the low frequency band. Magnetic loss effect: Magnetic particles have characteristics such as magnetic hysteresis loss and eddy current loss, which help to reduce the intensity of electromagnetic waves and thus improve the shielding effect. Improve the stability of the composite material: The introduction of magnetic particles makes the composite material have higher stability in external environment (such as magnetic field, electric field), which is suitable for electromagnetic shielding applications in high magnetic field environment.

[0019] Carbon nanotubes (CNTs) are hollow nanoscale tubular structures formed by carbon atoms arranged in a hexagonal structure. They are generally classified into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes possess excellent electrical conductivity, mechanical strength, and thermal stability. In this invention, carbon nanotubes play an important role in electromagnetic shielding at high frequencies (e.g., 8 GHz to 18 GHz), primarily absorbing electromagnetic waves through dielectric loss mechanisms. The conductivity of carbon nanotubes enables them to effectively absorb electromagnetic waves, and the interfacial polarization effect enhances the electromagnetic wave absorption capacity of the composite material. The introduction of carbon nanotubes can significantly improve the mechanical strength and flexibility of the composite material, making it more suitable for applications such as flexible electronic devices and wearable devices. Furthermore, carbon nanotubes provide structural support to the composite material, enhancing its mechanical strength and contributing to improved durability and stability.

[0020] The present invention has the following beneficial effects: This invention achieves highly efficient electromagnetic shielding across multiple frequency bands through the synergistic effect of MXene nanosheets, magnetic nanoparticles, carbon nanotubes, and a PU matrix. MXene provides conductivity loss and primarily absorbs high-frequency electromagnetic waves; magnetic nanoparticles absorb low-frequency electromagnetic waves through magnetic loss mechanisms; and carbon nanotubes enhance absorption capacity in the high-frequency band through dielectric loss mechanisms. Through the synergistic effect of these materials, the composite material provides excellent shielding performance across multiple frequency bands from low to high frequencies.

[0021] The principle of synergistic enhancement lies in the complementary mechanisms of conductivity, magnetic loss, and dielectric loss among the components, thereby optimizing the electromagnetic wave absorption capability of the composite material. Through gradient structure design, the material distributes different concentrations of components in different regions, achieving optimal impedance matching and electromagnetic wave absorption. This combination of multiple mechanisms enables the composite material to achieve highly efficient electromagnetic shielding across a wide frequency range.

[0022] In the preparation process, the synergistic effect is closely related to steps such as uniform dispersion, gradient coating, and directional drying of the materials. First, ultrasonic dispersion and high-shear stirring ensure the uniform distribution of MXene nanosheets, magnetic nanoparticles, and carbon nanotubes in the solution, allowing the properties of each material to interact effectively. Second, gradient coating is used to form different concentrations of MXene and magnetic particles in the composite material, optimizing the absorption and reflection properties of electromagnetic waves. Finally, directional drying and high-temperature curing ensure the structural stability of the composite material and promote the synergistic effect of the materials, providing more efficient electromagnetic shielding in applications. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Shielding materials consist of the following key components: MXene nanosheets (Ti3C2Tx): possess excellent electrical conductivity and surface activity, providing conductivity loss at high frequencies and effectively reflecting and absorbing electromagnetic waves.

[0025] Magnetic nanoparticles: absorb low-frequency electromagnetic waves through magnetic loss mechanism, and are used for shielding low-frequency (100MHz-2GHz) electromagnetic waves. Magnetic nanoparticles include Fe3O4 or NiFe2O4.

[0026] Carbon nanotubes (CNTs) or graphene: improve the absorption efficiency of high-frequency electromagnetic waves (such as 8GHz-18GHz) through dielectric loss mechanisms.

[0027] High-strength matrix (polyurethane (PU) or polyester fabric): As a load-bearing structure, it provides the composite material with mechanical strength, flexibility and durability.

[0028] Example 1 The steps for preparing the shielding material are as follows: Preparation of MXene nanosheets: An appropriate amount of Ti3AlC2 (titanium aluminum carbide) raw material was taken and added to an appropriate amount of ammonium fluoride (NH4HF2) solution with a concentration of 10 mol / L. The reaction was carried out at 60℃ for 24 hours, followed by washing with deionized water until the pH of the solution was neutral. Then, the treated Ti3C2 sample was subjected to ultrasonic treatment under nitrogen protection using an ultrasonic cleaner at a frequency of 40 kHz for 1 hour to obtain an aqueous solution of MXene nanosheets with a concentration of 3%.

[0029] Preparation of Fe3O4 nanoparticles: Ferric chloride (FeCl3) and ferrous chloride (FeCl2) were mixed in a 2:1 mass ratio and dissolved in deionized water to obtain a solution concentration of 0.1 mol / L. Under a nitrogen atmosphere, the mixed solution was added to a reactor at 80°C, and ammonia was slowly added dropwise until the pH reached 11. The reaction proceeded for 2 hours, followed by filtration and washing with deionized water. The resulting Fe3O4 nanoparticles were dried in a vacuum drying oven for 12 hours to obtain Fe3O4 nanoparticles with a concentration of 6%.

[0030] Preparation of aqueous solutions of carbon nanotubes: Carbon nanotubes (CNTs) were acidified in a concentrated nitric acid (HNO3) solution at 70°C for 3 hours to remove impurities from their surface. The acidified CNTs were then mixed with deionized water at a mass ratio of 1% and treated with an ultrasonic cleaner at a frequency of 40 kHz for 1 hour to obtain an aqueous solution of carbon nanotubes.

[0031] Preparation of PU matrix solution: Polyurethane (PU) was dissolved in dimethyl thionamide (DMF) at a mass ratio of 10% and stirred until completely dissolved to obtain a PU matrix solution.

[0032] Preparation and coating of mixed solutions: An aqueous solution of MXene, an aqueous solution of magnetic nanoparticles, an aqueous solution of carbon nanotubes, and a PU matrix solution were mixed at a volume ratio of 3:6:1:10 to obtain a homogeneous mixed solution. The mixed solution was then uniformly coated onto the surface of the PU matrix using a doctor blade method or a coating machine to form a thin film. After coating, the film was dried at 80°C for 1 hour, followed by high-temperature curing at 150°C for 2 hours to obtain a high-shielding material.

[0033] Example 2 The only difference between Example 2 and Example 1 is the preparation of the aqueous solution of carbon nanotubes: The preparation of aqueous solutions of carbon nanotubes includes the following steps: Take an appropriate amount of carbon nanotubes (CNTs) and add them to a concentrated nitric acid (HNO3) solution for acidification treatment at 70℃ for 3 hours to remove impurities from the surface of the carbon nanotubes. After acidification, thoroughly wash the carbon nanotubes with deionized water until the washing solution is neutral.

[0034] The acidified carbon nanotubes were mixed with deionized water at a mass ratio of 1%, and ultrasonically treated with an ultrasonic cleaner at a frequency of 40 kHz for 1 hour to obtain an aqueous solution of carbon nanotubes.

[0035] Next, WO3 (tungsten oxide) was incorporated into the carbon nanotube aqueous solution at a mass ratio of 2%. First, WO3 powder was weighed and dissolved in a small amount of deionized water to prepare a 2% WO3 solution. Then, the WO3 solution was added to the carbon nanotube aqueous solution, and the solution was treated using an ultrasonic cleaner at a frequency of 40 kHz for 30 minutes to ensure that the WO3 was uniformly dispersed on the surface of the carbon nanotubes, resulting in a WO3-doped carbon nanotube aqueous solution.

[0036] Comparative Example 1 Preparation of MXene nanosheets: An appropriate amount of Ti3AlC2 (titanium aluminum carbide) raw material was taken and added to an appropriate amount of ammonium fluoride (NH4HF2) solution with a concentration of 10 mol / L. The reaction was carried out at 60℃ for 24 hours, followed by washing with deionized water until the pH of the solution was neutral. Then, the treated Ti3C2 sample was subjected to ultrasonic treatment under nitrogen protection using an ultrasonic cleaner at a frequency of 40 kHz for 1 hour to obtain an aqueous solution of MXene nanosheets with a concentration of 3%.

[0037] Preparation of Fe3O4 nanoparticles: Ferric chloride (FeCl3) and ferrous chloride (FeCl2) were mixed in a 2:1 mass ratio and dissolved in deionized water to obtain a solution concentration of 0.1 mol / L. Under a nitrogen atmosphere, the mixed solution was added to a reactor at 80°C, and ammonia was slowly added dropwise until the pH reached 11. The reaction proceeded for 2 hours, followed by filtration and washing with deionized water. The resulting Fe3O4 nanoparticles were dried in a vacuum drying oven for 12 hours to obtain Fe3O4 nanoparticles with a concentration of 6%.

[0038] Preparation of PU matrix solution: Polyurethane (PU) was dissolved in dimethyl thionamide (DMF) at a mass ratio of 10% and stirred until completely dissolved to obtain a PU matrix solution.

[0039] Preparation and coating of mixed solutions: An aqueous solution of MXene, an aqueous solution of magnetic nanoparticles, and a PU matrix solution were mixed at a volume ratio of 3:6:10 to obtain a homogeneous mixture. The mixture was then uniformly coated onto the surface of the PU matrix using a doctor blade or a coating machine to form a thin film. After coating, the film was dried at 80°C for 1 hour, followed by high-temperature curing at 150°C for 2 hours to obtain a high-shielding material.

[0040] Comparative Example 2 Preparation of MXene nanosheets: An appropriate amount of Ti3AlC2 (titanium aluminum carbide) raw material was taken and added to an appropriate amount of ammonium fluoride (NH4HF2) solution with a concentration of 10 mol / L. The reaction was carried out at 60℃ for 24 hours, followed by washing with deionized water until the pH of the solution was neutral. Then, the treated Ti3C2 sample was subjected to ultrasonic treatment under nitrogen protection using an ultrasonic cleaner at a frequency of 40 kHz for 1 hour to obtain an aqueous solution of MXene nanosheets with a concentration of 3%.

[0041] Preparation of Fe3O4 nanoparticles: Ferric chloride (FeCl3) and ferrous chloride (FeCl2) were mixed in a 2:1 mass ratio and dissolved in deionized water to obtain a solution concentration of 0.1 mol / L. Under a nitrogen atmosphere, the mixed solution was added to a reactor at 80°C, and ammonia was slowly added dropwise until the pH reached 11. The reaction proceeded for 2 hours, followed by filtration and washing with deionized water. The resulting Fe3O4 nanoparticles were dried in a vacuum drying oven for 12 hours to obtain Fe3O4 nanoparticles with a concentration of 6%.

[0042] Preparation of graphene aqueous solution: Take an appropriate amount of graphene powder and mix it with deionized water at a mass ratio of 1%. Use an ultrasonic cleaner to perform ultrasonic treatment at a frequency of 40kHz for 1 hour to obtain a graphene aqueous solution.

[0043] Preparation of PU matrix solution: Polyurethane (PU) was dissolved in dimethyl thionamide (DMF) at a mass ratio of 10% and stirred until completely dissolved to obtain a PU matrix solution.

[0044] Preparation and coating of mixed solutions: An aqueous solution of MXene, an aqueous solution of magnetic nanoparticles, an aqueous solution of graphene, and a PU matrix solution were mixed at a volume ratio of 3:6:1:10 to obtain a homogeneous mixed solution. The mixed solution was then uniformly coated onto the surface of the PU matrix using a doctor blade method or a coating machine to form a thin film. After coating, the film was dried at 80°C for 1 hour, followed by high-temperature curing at 150°C for 2 hours to obtain a high-shielding material.

[0045] Comparative Example 3 Preparation of MXene nanosheets: An appropriate amount of Ti3AlC2 (titanium aluminum carbide) raw material was taken and added to an appropriate amount of ammonium fluoride (NH4HF2) solution with a concentration of 10 mol / L. The reaction was carried out at 60℃ for 24 hours, followed by washing with deionized water until the pH of the solution was neutral. Then, the treated Ti3C2 sample was subjected to ultrasonic treatment under nitrogen protection using an ultrasonic cleaner at a frequency of 40 kHz for 1 hour to obtain an aqueous solution of MXene nanosheets with a concentration of 3%.

[0046] Preparation of Fe3O4 nanoparticles: Ferric chloride (FeCl3) and ferrous chloride (FeCl2) were mixed in a 2:1 mass ratio and dissolved in deionized water to obtain a solution concentration of 0.1 mol / L. Under a nitrogen atmosphere, the mixed solution was added to a reactor at 80°C, and ammonia was slowly added dropwise until the pH reached 11. The reaction proceeded for 2 hours, followed by filtration and washing with deionized water. The resulting Fe3O4 nanoparticles were dried in a vacuum drying oven for 12 hours to obtain Fe3O4 nanoparticles with a concentration of 6%.

[0047] Preparation of aqueous solutions of carbon nanotubes: Carbon nanotubes (CNTs) were acidified in a concentrated nitric acid (HNO3) solution at 70°C for 3 hours to remove impurities from their surface. The acidified CNTs were then mixed with deionized water at a mass ratio of 1% and ultrasonically treated at 40 kHz for 1 hour. Cobalt powder was then added to the solution at a mass ratio of 1% and ultrasonically treated again at 40 kHz for 30 minutes to ensure uniform metal doping, resulting in a metal-doped aqueous solution of carbon nanotubes.

[0048] Preparation of PU matrix solution: Polyurethane (PU) was dissolved in dimethyl thionamide (DMF) at a mass ratio of 10% and stirred until completely dissolved to obtain a PU matrix solution.

[0049] Preparation and coating of mixed solutions: An aqueous solution of MXene, an aqueous solution of magnetic nanoparticles, an aqueous solution of carbon nanotubes, and a PU matrix solution were mixed at a volume ratio of 3:6:1:10 to obtain a homogeneous mixed solution. The mixed solution was then uniformly coated onto the surface of the PU matrix using a doctor blade method or a coating machine to form a thin film. After coating, the film was dried at 80°C for 1 hour, followed by high-temperature curing at 150°C for 2 hours to obtain a high-shielding material.

[0050] Sample preparation The composite materials prepared in Examples 1, 2, 1, 2, and 3 were cut into film samples of specified dimensions, generally 10cm × 10cm, with the thickness controlled at around 0.3mm to ensure that the thickness of each sample was consistent.

[0051] Electromagnetic shielding effectiveness test According to the GJB6190 standard, the electromagnetic shielding effectiveness (EMISE) tester is used for testing.

[0052] Place the sample between the electromagnetic wave source and receiver of the test equipment.

[0053] Test frequency range: 100MHz to 18GHz.

[0054] The attenuation value (dB) of the electromagnetic wave was recorded during each frequency band measurement.

[0055] The test data for each frequency band were compiled, and the average attenuation value of each sample in each frequency band was calculated.

[0056] Tensile strength test Tensile strength tests were performed using the GB / T3923.1 standard.

[0057] Cut the sample into strips of 10cm × 2cm, and ensure that the sample is uniform and flat during testing.

[0058] The maximum tensile strength of a sample during the tensile process is measured using a tensile testing machine.

[0059] Measure the tensile strength in the warp and weft directions and record the maximum tensile force (unit: N).

[0060] Calculate and record the average tensile strength.

[0061] Tear strength test Tear strength test was performed using GB / T3917.3 standard.

[0062] The sample was cut into strips measuring 10cm x 2cm.

[0063] The tear strength of the sample is tested using a tear testing machine, and the tear force in the warp and weft directions is measured (unit: N).

[0064] Record the maximum tear strength and calculate the average tear strength.

[0065] Elongation at break test The elongation at break was tested using the GB / T3923.1 standard.

[0066] The sample was cut into strips of 10cm × 2cm to ensure the uniformity of the sample.

[0067] The elongation of the sample at the point of fracture during the tensile process is tested using a tensile testing machine, and the elongation in the warp and weft directions is recorded.

[0068] Calculate and record the average elongation at break.

[0069] Peel strength test Peel strength testing was performed using the GB / T532-2008 standard.

[0070] The sample was cut into small pieces of 2.5cm × 2.5cm.

[0071] The 2.5cm peel strength of the sample was tested using a peel strength tester, and the peel force in the warp and weft directions was measured (unit: N).

[0072] Record the peel strength of each sample and calculate the average value.

[0073] Material thickness and basis weight testing The thickness of each sample was measured using the GB / T3820 standard to ensure that the sample thickness was approximately 0.3 mm.

[0074] The weight of each sample (unit: g / m³) was measured using the GB / T4669 standard. 2 ), and record the weight data of each sample.

[0075] Data Recording and Analysis Record the test results, compile them into a table, and calculate the average value of each performance indicator.

[0076] The shielding effectiveness, mechanical properties (tensile strength, tear strength, elongation at break, peel strength) and physical parameters (thickness, basis weight) of different materials were compared and analyzed.

[0077] Low-frequency experimental data are shown in Table 1. Table 1

[0078] High-frequency experimental data are shown in Table 2. Table 2

[0079] As can be seen from Tables 1 and 2 Example 2 (WO3-doped carbon nanotubes) It provides optimal high-frequency electromagnetic shielding performance, especially in the 5150-5250MHz and 5715-5850MHz frequency bands, where it performs exceptionally well.

[0080] Example 1 It has good shielding effectiveness in the low and mid frequency bands, but its performance is slightly inferior in the high frequency band.

[0081] Metal-doped carbon nanotubes It provides a good shielding effect in the low-frequency band, but its effect in the high-frequency band is slightly inferior to that of WO3 doping and is lower than that of Example 1.

[0082] Graphene-doped and pure carbon nanotubes The shielding effectiveness is weak in both high and low frequency bands, especially in the high frequency band where the absorption capacity is poor.

[0083] WO3 tungstate is a material with strong dielectric loss characteristics. When electromagnetic waves interact with the material, WO3 can generate dielectric loss through polarization, converting the energy of the electromagnetic wave into heat energy, which helps to increase the material's electromagnetic wave absorption capability. WO3 doping enhances the absorption capability of composite materials in high-frequency bands, such as above 2 GHz, especially in high-frequency electromagnetic waves, where it can more effectively convert electromagnetic energy into heat, reduce electromagnetic wave reflection, and improve overall shielding effectiveness. By doping carbon nanotubes with WO3, not only can interfacial polarization be increased, but the thermal stability of the material can also be improved, giving it better anti-interference capabilities in high-frequency electromagnetic wave environments.

[0084] Doping with WO3 can effectively improve the shielding performance of high-frequency electromagnetic waves, such as those above 2 GHz, because WO3 has a high electromagnetic wave absorption capacity, which can reduce the transmission of electromagnetic waves and increase the absorption effect of the shielding material. In the high-frequency band of 8 GHz to 18 GHz, the shielding effect of traditional materials such as pure MXene or carbon nanotubes is often weak, while WO3 doping can significantly improve the shielding performance, thereby significantly improving the shielding capability of composite materials in multiple frequency bands.

[0085] Doping with WO3 not only improves the electromagnetic shielding effectiveness of the material, but also enhances its mechanical strength and thermal stability, making the doped composite material more durable and suitable for applications in various high-frequency and high-temperature environments.

[0086] Cobalt (Co) is a metallic element that, while exhibiting good magnetic loss in certain situations, primarily functions as a shield for low-frequency electromagnetic waves through magnetic loss mechanisms. Compared to WO3, cobalt has weaker electromagnetic wave absorption and dielectric loss characteristics, especially at higher frequencies such as above 8 GHz, where it performs worse than WO3.

[0087] WO3 has a stronger dielectric loss mechanism than cobalt, especially in the absorption of high-frequency electromagnetic waves, resulting in WO3-doped composite materials providing better electromagnetic shielding performance in the high-frequency band than cobalt-doped composite materials.

[0088] Although cobalt has strong magnetic loss characteristics, making it suitable for shielding low-frequency electromagnetic waves, the effectiveness of magnetic materials in shielding high-frequency electromagnetic waves is limited by frequency dependence. In high-frequency bands such as 8 GHz to 18 GHz, the magnetic loss effect of cobalt weakens, thus its shielding effect against electromagnetic waves is not as good as WO3. This may be one of the reasons why the shielding effectiveness of cobalt-doped materials is lower than that of Example 1.

[0089] Differences in the synergistic effect between cobalt-doped carbon nanotubes and MXene: In Example 1, the MXene-magnetic particle composite material, through the high conductivity of MXene and the magnetic loss mechanism of the magnetic particles, synergistically provides good shielding effectiveness for both low-frequency and high-frequency electromagnetic waves. In contrast, cobalt-doped carbon nanotubes in the composite material have a weaker shielding effect on high-frequency electromagnetic waves, which may result in its overall shielding effectiveness being lower than that of Example 1.

[0090] While cobalt, as a metallic element, can enhance the magnetism of materials, excessive metal doping may lead to unstable mechanical properties of composite materials, especially under high stress conditions. This may affect the overall structure and performance of the material, resulting in mechanical properties that are inferior to those of WO3-doped carbon nanotubes.

Claims

1. A shielding material, characterized by, The material is a shielding material, characterized in that the material is composed of MXene nanosheets, magnetic nanoparticles, carbon nanotubes and a PU matrix, wherein the magnetic nanoparticles include Fe3O4 or NiFe2O4.

2. The shielding material of claim 1, wherein, The mass ratio of the MXene nanosheets, the magnetic nanoparticles and the carbon nanotubes is 1.5-5.0:3.0-8.0:0.5-2.

0.

3. The shielding material of claim 1, wherein, The mass ratio of the MXene nanosheets, the magnetic nanoparticles and the carbon nanotubes is 2.0:5.0:1.

0.

4. The shielding material of claim 1, wherein, The PU matrix is a polyurethane or polyester fabric.

5. A method for preparing the shielding material according to any one of claims 1-4, comprising the following steps: respectively preparing a MXene nanosheet aqueous solution, a magnetic nanoparticle aqueous solution, a carbon nanotube aqueous solution and a PU matrix solution; mixing the MXene nanosheet aqueous solution, the magnetic nanoparticle aqueous solution, the carbon nanotube aqueous solution and the PU matrix solution to obtain a mixed solution; uniformly coating a thin film of the obtained mixed solution on the PU matrix; drying after the coating is completed to obtain the shielding material.

6. The production method according to claim 5, wherein The preparation of the MXene nanosheet aqueous solution comprises the following steps: mixing MXene nanosheets with deionized water at a mass percentage of 1.5%-5.0%, and using an ultrasonic cleaning instrument for ultrasonic treatment for 30 minutes to 1 hour to obtain the MXene nanosheet aqueous solution.

7. The preparation method according to claim 5, characterized in that, The preparation of the magnetic nanoparticle aqueous solution comprises the following steps: mixing magnetic nanoparticles with deionized water at a mass percentage of 3.0%-8.0%, and using an ultrasonic cleaning instrument for treatment for 30 minutes to 1 hour to obtain the magnetic nanoparticle aqueous solution.

8. The production method according to claim 5, characterized by, The preparation of the carbon nanotube aqueous solution comprises the following steps: removing surface impurities of the carbon nanotubes by acid treatment, mixing the carbon nanotubes with deionized water at a mass percentage of 0.5%-2.0%, and using an ultrasonic cleaning instrument for treatment for 30 minutes to 1 hour to obtain the carbon nanotube aqueous solution.

9. The preparation method according to claim 5, characterized in that, The solvent of the PU matrix solution is dimethyl sulfoxide.

10. The method of claim 5, wherein, The step of uniformly coating a thin film of the obtained mixed solution on the PU matrix is: uniformly coating the mixed solution on the surface of the PU matrix by using a doctor blade method or a coating machine; after the coating, a gradient structure is formed by a gradient coating method, and the coated material is dried and subjected to high-temperature curing treatment to obtain the shielding material.

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