A wave-absorbing material, a preparation method and application thereof

Abstract

The application belongs to the technical field of communication materials, and particularly relates to a wave-absorbing material and a preparation method and application thereof. The wave-absorbing material has a core-shell structure; the composition of the core in the core-shell structure comprises a two-dimensional layered material and magnetic nanoparticles, and the magnetic nanoparticles are distributed in the interlayer and surface of the two-dimensional layered material; and the composition of the shell layer in the core-shell structure comprises a low-dielectric material. The intercalation structure of the magnetic nanoparticles distributed in the interlayer and surface of the two-dimensional layered material can enhance electromagnetic absorption, the coating of the low-dielectric material can further reduce reflection loss, enhance electromagnetic absorption, so that the use frequency of the wave-absorbing material is in the 16-18 GHz frequency band, and the wave-absorbing material has good electromagnetic absorption performance. In addition, the reaction is carried out at room temperature during preparation of the application, so that more functional groups can be reserved, polarization relaxation loss is good, and magnetic absorption is increased.

Description

Technical Field

[0001] This invention belongs to the field of communication materials technology, and specifically relates to a microwave absorbing material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of emerging technologies such as 5G communication, artificial intelligence, and the Internet of Things, high-frequency electromagnetic waves (such as the GHz band), as the core medium for information transmission, have been widely used in many fields such as military, science and technology, and people's livelihood, marking the full arrival of the era of the Internet of Everything and human-computer interaction. However, the widespread application of high-frequency electromagnetic waves has also caused many problems, among which electromagnetic radiation and electromagnetic interference (EMI) are particularly prominent, becoming the fifth largest environmental problem after air pollution, water pollution, solid waste pollution, and noise pollution. Electromagnetic radiation not only interferes with the normal operation of communication equipment, leading to signal distortion and information leakage, but may also pose potential harm to human health, such as causing nervous system disorders and decreased immune function.

[0003] With the rapid development of 5G, artificial intelligence and other fields, high-frequency electromagnetic waves (GHz band electromagnetic waves), which are low-latency, high-bandwidth and high-speed, have been widely used in many fields such as military, science and technology and people's livelihood as a bridge for information transmission. The era of Internet of Things and human-computer interaction has arrived.

[0004] Currently, the PCIe 7.0 transmission standard, used in data-intensive markets (such as 800G Ethernet, artificial intelligence / machine learning, hyperscale data centers, high-performance computing, quantum computing, and cloud computing), operates at frequencies up to 32GHz. However, current research on electromagnetic loss materials remains largely confined to the sub-16GHz band, with research on higher frequency electromagnetic loss materials almost nonexistent. Furthermore, the fabrication of most high-performance electromagnetic loss materials requires high-temperature heat treatment. This process is problematic because it demands specialized equipment and carries inherent risks, hindering practical applications. It also consumes significant energy, leading to high costs. Additionally, the fabrication process is difficult to control and has poor repeatability.

[0005] Therefore, it is of great significance to provide a microwave absorbing material that can be used in the 16-18GHz frequency band, has good electromagnetic absorption performance, and is simple to prepare, requiring no high-temperature heat treatment or special equipment. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a microwave absorbing material that operates in the 16-18 GHz frequency band, has good electromagnetic absorption performance, and has a simple preparation process that requires no high-temperature heat treatment or special equipment, making it easy for industrial applications.

[0007] The inventive concept of this invention is as follows: The microwave absorbing material of this invention has a core-shell structure. The core of the core-shell structure comprises a two-dimensional layered material and magnetic nanoparticles, wherein the magnetic nanoparticles are distributed between the layers and on the surface of the two-dimensional layered material. The shell of the core-shell structure comprises a low-dielectric material. This intercalation structure, in which the magnetic nanoparticles are distributed between the layers and on the surface of the two-dimensional layered material, facilitates multiple reflections of electromagnetic waves between the layers, enhancing electromagnetic absorption. The core-shell structure formed by encapsulating the material with low-dielectric material enhances impedance matching, forms a shell with good wave transmission performance, promotes the entry of electromagnetic waves into the material's interior, further reduces reflection loss, and enhances electromagnetic absorption. This allows the microwave absorbing material to be used in the 16-18 GHz frequency band with excellent electromagnetic absorption performance.

[0008] Therefore, a first aspect of the present invention provides a microwave absorbing material.

[0009] Specifically, the absorbing material has a core-shell structure; The core in the core-shell structure comprises a two-dimensional layered material and magnetic nanoparticles, wherein the magnetic nanoparticles are distributed between the layers and on the surface of the two-dimensional layered material. The shell layer in the core-shell structure is composed of low-dielectric materials.

[0010] Preferably, the electrical conductivity of the two-dimensional layered material is greater than 1 S / m; more preferably, the electrical conductivity of the two-dimensional layered material is greater than 100 S / m and less than 10 S / m. 9 S / m.

[0011] Preferably, the dielectric constant of the two-dimensional layered material is greater than 10 F / m; more preferably, the dielectric constant of the two-dimensional layered material is greater than 10 F / m and less than 2000 F / m.

[0012] Preferably, the dielectric constant of the low-dielectric material is 1-3 F / m.

[0013] Preferably, the two-dimensional layered material comprises MXene material; more preferably, the two-dimensional layered material comprises Ti3C2T. x .

[0014] Preferably, the magnetic nanoparticles include at least one of metal nanoparticles, alloy nanoparticles, and ferrite nanoparticles; more preferably, the magnetic nanoparticles include magnetic ferrite nanoparticles.

[0015] Preferably, the metal nanoparticles include at least one of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles.

[0016] Preferably, the alloy nanoparticles include at least one of iron-nickel alloy nanoparticles, iron-cobalt alloy nanoparticles, and cobalt-nickel alloy nanoparticles.

[0017] Preferably, the ferrite nanoparticles include at least one of cobalt ferrite nanoparticles, manganese ferrite nanoparticles, and zinc ferrite nanoparticles.

[0018] Preferably, the low-dielectric material includes at least one of titanium dioxide and silicon dioxide; more preferably, the low-dielectric material includes titanium dioxide.

[0019] Preferably, in the microwave absorbing material, the mass fraction of the magnetic nanoparticles is 82-85%, the mass fraction of the two-dimensional layered material is 5-8%, and the mass fraction of the low dielectric material is 7-13%.

[0020] Preferably, the frequency range of the absorbing material is 16-18 GHz.

[0021] A second aspect of the present invention provides a method for preparing the microwave absorbing material described in the first aspect of the present invention.

[0022] Specifically, the preparation method of the microwave absorbing material includes the following steps: (1) Mix the precursor of magnetic nanoparticles, reducing agent and two-dimensional layered material, stir to obtain intermediate product 1; or mix the precursor of magnetic nanoparticles, two-dimensional layered material and solvent, adjust pH to alkaline, react, freeze dry to obtain intermediate product 2. (2) Mix the polarity regulator, pH regulator and intermediate product 1 or intermediate product 2 obtained in step (1), sonicate, then add low dielectric material precursor, react at room temperature to obtain the microwave absorbing material.

[0023] Specifically, the present invention utilizes a room-temperature reaction, which retains more functional groups, exhibits better polarization relaxation loss, increases magnetic absorption, and improves the microwave absorption performance of the absorbing material. Furthermore, room-temperature reactions consume less energy, saving costs, and the preparation process is safe, easy to control, and highly reproducible. In contrast, current technologies that use heating or heat treatment to prepare absorbing materials face inherent risks at high temperatures, consume significant amounts of energy, and suffer from difficulty in controlling the process and poor reproducibility.

[0024] Preferably, in step (1), the precursor of the magnetic nanoparticles is a metal salt.

[0025] Preferably, when the magnetic nanoparticles in the absorbing material are metal nanoparticles, the metal salt includes at least one of iron salt, cobalt salt, and nickel salt.

[0026] Preferably, when the magnetic nanoparticles in the absorbing material are alloy nanoparticles, the metal salt includes at least two of iron salt, cobalt salt, and nickel salt.

[0027] Preferably, when the magnetic nanoparticles in the absorbing material are ferrite nanoparticles, the metal salt includes iron salt, and at least one of cobalt salt, nickel salt, manganese salt, and zinc salt.

[0028] Specifically, when the magnetic nanoparticles in the microwave absorbing material are metal nanoparticles or alloy nanoparticles, step (1) involves mixing the precursor of the magnetic nanoparticles, the reducing agent, and the two-dimensional layered material, stirring, and obtaining intermediate product 1; when the magnetic nanoparticles in the microwave absorbing material are ferrite nanoparticles, step (1) involves mixing the precursor of the magnetic nanoparticles, the two-dimensional layered material, and the solvent, adjusting the pH to alkaline, reacting, and freeze-drying to obtain intermediate product 2.

[0029] Preferably, in step (1), the reducing agent includes sodium borohydride.

[0030] Preferably, in step (1), the solvent includes water.

[0031] Preferably, in step (1), the temperature at which the precursor of the magnetic nanoparticles, the two-dimensional layered material, and the solvent are mixed is 40-60°C, and the mixing time is 25-35 min; more preferably, the temperature at which the precursor of the magnetic nanoparticles, the two-dimensional layered material, and the solvent are mixed is 45-55°C, and the mixing time is 27-33 min; even more preferably, the temperature at which the precursor of the magnetic nanoparticles, the two-dimensional layered material, and the solvent are mixed is 50°C, and the mixing time is 30 min.

[0032] Preferably, in step (1), the reaction temperature is 40-60℃ and the reaction time is 22-26h; more preferably, the reaction temperature is 45-55℃ and the reaction time is 23-25h; even more preferably, the reaction temperature is 50℃ and the reaction time is 24h.

[0033] Preferably, in step (1), the reaction is first centrifuged and then freeze-dried.

[0034] Preferably, in step (1), the freeze-drying temperature is -60~-40℃ and the freeze-drying time is 40-55h; more preferably, the freeze-drying temperature is -55~-45℃ and the freeze-drying time is 44-52h; even more preferably, the freeze-drying temperature is -50℃ and the freeze-drying time is 48h.

[0035] Preferably, in step (2), the polarity modifier includes acetonitrile and ethanol.

[0036] Preferably, in step (2), the pH adjuster includes ammonia.

[0037] Preferably, in step (2), the low dielectric precursor includes at least one of tetrabutyl titanate and tetraethyl silicate.

[0038] Preferably, in step (2), the room temperature reaction time is 3-5 hours; more preferably, the room temperature reaction time is 3.5-4.5 hours; even more preferably, the room temperature reaction time is 4 hours.

[0039] A third aspect of the present invention provides an electromagnetic absorbing material or an electromagnetic absorbing device.

[0040] Specifically, the electromagnetic absorbing material or electromagnetic absorbing device includes the wave-absorbing material described in the first aspect of the present invention.

[0041] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) The magnetic nanoparticles of the present invention are distributed in the interlayer and surface of the two-dimensional layered material. This interlayer structure is conducive to multiple reflections of electromagnetic waves in the interlayer and enhances electromagnetic absorption. The core-shell structure formed by coating with low dielectric material is conducive to enhancing impedance matching, forming a shell with good wave transmission performance, promoting electromagnetic waves to enter the interior of the material, further reducing reflection loss, enhancing electromagnetic absorption, so that the wave absorbing material can be used in the 16-18 GHz frequency band and has good electromagnetic absorption performance.

[0042] (2) The present invention uses a reaction method carried out at room temperature. Room temperature reaction can retain more functional groups, has better polarization relaxation loss, increases magnetic absorption, avoids the danger of heating or heat treatment, and consumes less energy. The preparation process is easy to control and has good repeatability. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the preparation process of the microwave absorbing material in Embodiment 1 of the present invention; Figure 2 The Ti3C2T prepared in Example 1 of this invention x Scanning electron microscope image; Figure 3 The Ti3C2T prepared in Example 1 of this invention x Scanning electron microscope image of CoFe2O4 in CoFe2O4; Figure 4 The Ti3C2T prepared in Example 1 of this invention x Scanning electron microscope image of CoFe2O4@TiO2 absorbing material; Figure 5 The Ti3C2T prepared as Comparative Example 1 of this invention x Scanning electron microscope image of CoFe2O4 microwave absorbing material; Figure 6 The Ti3C2T prepared in step (2) of Example 1 of this invention x / CoFe2O4, Ti3C2T prepared in step (3) x X-ray photoelectron spectrum of / CoFe2O4@TiO2 microwave absorbing material; Figure 7 The Ti3C2T prepared in step (2) of Example 1 of this invention x / CoFe2O4, Ti3C2T prepared in step (3) x Fine spectrum of titanium in CoFe2O4@TiO2 microwave absorbing material; Figure 8 This is a diagram showing the microwave absorption performance of the microwave absorbing material in Embodiment 1 of the present invention; Figure 9 This is a diagram showing the microwave absorption performance of the microwave absorbing material in Comparative Example 1 of the present invention; Figure 10 This is a diagram showing the microwave absorption performance of the microwave absorbing material in Comparative Example 2 of the present invention; Figure 11 This is a diagram showing the microwave absorption performance of the microwave absorbing material in Comparative Example 3 of the present invention; Figure 12 This is a diagram showing the microwave absorption performance of the microwave absorbing material in Comparative Example 4 of the present invention; Figure 13 This is a diagram showing the microwave absorption performance of the microwave absorbing material in Comparative Example 5 of the present invention. Detailed Implementation

[0044] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0045] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0046] Example 1 A microwave absorbing material having a core-shell structure; the core in the core-shell structure is composed of a two-dimensional layered material Ti3C2T. x Composed of magnetic nanoparticles CoFe2O4, which are distributed in the two-dimensional layered material Ti3C2T x Interlayers and surfaces; The shell in the core-shell structure is titanium dioxide.

[0047] A method for preparing a microwave absorbing material includes the following steps: (1) Ti3C2T x Preparation: Weigh 40 mL of HF into a container, and slowly pour in 4 g of TiAlC2 powder in small amounts several times. Stir magnetically at room temperature (25 °C) for 24 h. After the reaction, centrifuge and wash repeatedly until the pH of the supernatant is greater than 6. Freeze-dry the obtained solid at -50 °C for 48 h to obtain Ti3C2T. x powder; (2) Ti3C2T x Preparation of / CoFe2O4: Weigh 2 mmol Co(NO3)2·6H2O (0.58 g), 4 mmol Fe(NO3)3·9H2O (1.62 g), and 0.197 g Ti3C2T x The mixture was placed in 100 mL of deionized water and stirred at 50 °C for 30 min. Sodium hydroxide was then added to adjust the pH to 12, and the reaction was allowed to proceed for 24 h. After centrifugation, the mixture was washed three times with ethanol and water, and then freeze-dried at -50 °C for 48 h to obtain black Ti3C2T. x / CoFe2O4; (3) Ti3C2T x Preparation of / CoFe2O4@TiO2: It was prepared by sol-gel method. 0.5g of Ti3C2T obtained in step (2) was weighed. x / CoFe2O4 was placed in a mixed solution of 100 mL ethanol and 120 mL acetonitrile, and 2 mL ammonia was added. After ultrasonic dispersion for 15 min, 2 mL tetrabutyl titanate was slowly added, and the reaction was carried out at room temperature for 4 h. Subsequently, the mixture was filtered and washed three times with ethanol and water to obtain a grayish-white Ti3C2T x / CoFe2O4@TiO2 microwave absorbing material, denoted as TC3-T.

[0048] Example 1: Schematic diagram of the preparation process of the microwave absorbing material. Figure 1 As shown.

[0049] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not perform step (3), that is, it does not encapsulate titanium dioxide, and the microwave absorbing material does not have a core-shell structure. Otherwise, it is the same as Example 1. The microwave absorbing material of Comparative Example 1 is denoted as TC3.

[0050] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, after adding 2 mL of tetrabutyl titanate in step (3), it is heat-treated at 550°C for 4 h in an argon atmosphere. The rest is the same as in Example 1. The microwave absorbing material of Comparative Example 2 is denoted as S-TC3-T.

[0051] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the amount of Ti3C2Tx used in Comparative Example 3 is 0.115g, while the rest is the same as in Example 1, denoted as TC2-T.

[0052] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, Ti3C2T x The dosage was 0.31g, and the rest was the same as in Example 1, denoted as TC4-T.

[0053] Comparative Example 5 Comparative Example 5 uses Ti3C2T x The microwave absorbing material obtained by directly mixing CoFe2O4 and TiO2 is denoted as TCT.

[0054] Among them, Ti3C2T x The preparation process is the same as in Example 1.

[0055] The preparation process of CoFe2O4 is as follows: Weigh 2 mmol Co(NO3)2·6H2O and 4 mmol Fe(NO3)3·9H2O, place them in 100 mL of deionized water, stir at 50 °C for 30 min, then add sodium hydroxide to adjust the pH to 12, and react for 24 h; centrifuge, wash three times with ethanol and water, and freeze dry at -50 °C for 48 h to obtain black CoFe2O4.

[0056] The preparation process of TiO2 is as follows: The solution was prepared by the sol-gel method. 100 mL of ethanol and 120 mL of acetonitrile were mixed, 2 mL of ammonia water was added, and 2 mL of tetrabutyl titanate was slowly added. The mixture was reacted at room temperature for 4 h. The mixture was then filtered and washed three times with ethanol and water to obtain white TiO2.

[0057] Performance testing 1. Scanning electron microscopy observation The Ti3C2T prepared in Example 1 x Ti3C2Tx CoFe2O4 and Ti3C2T in CoFe2O4 x / CoFe2O4@TiO2 microwave absorbing material, and Ti3C2T prepared in Comparative Example 1 x The / CoFe2O4 absorbing material was observed using scanning electron microscopy (SEM), and the SEM images are shown below. Figure 2-5 As shown.

[0058] Depend on Figure 2 It can be seen that the two-dimensional material Ti3C2T x It exhibits a distinct layered structure.

[0059] Depend on Figure 3 It can be seen that Ti3C2T x The CoFe2O4 in / CoFe2O4 consists of nanoparticles with a particle size of approximately 42 nm.

[0060] Depend on Figure 4 It can be seen that Ti3C2T x The / CoFe2O4@TiO2 microwave absorbing material exhibits an intercalation structure of magnetic nanoparticles located between layers and on the surface of a two-dimensional layered material, as well as a coating structure.

[0061] Depend on Figure 5 It can be seen that Ti3C2T x / CoFe2O4 microwave absorbing material has an intercalation structure in which magnetic nanoparticles are located between layers and on the surface of a two-dimensional layered material.

[0062] 2. Elemental Analysis The Ti3C2T prepared in step (2) of Example 1 x / CoFe2O4 (before coating titanium dioxide), Ti3C2T prepared in step (3) x Elemental analysis of the / CoFe2O4@TiO2 microwave absorbing material (after coating with titanium dioxide) was performed, and the results are shown in Table 1.

[0063] Table 1: Ti3C2T prepared in Example 1 x / CoFe2O4、Ti3C2T x Elemental analysis results of / CoFe2O4@TiO2 microwave absorbing material

[0064] As shown in Table 1, after step (3), the content of titanium and oxygen elements increased, indicating that the titanium dioxide coating was successful.

[0065] 3. XPS Analysis The Ti3C2T prepared in step (2) of Example 1 x / CoFe2O4 (before coating titanium dioxide), Ti3C2T prepared in step (3) x X-ray photoelectron spectroscopy (XPS) analysis was performed on the / CoFe2O4@TiO2 microwave absorbing material (after coating with titanium dioxide). The results are as follows: Figure 6 As shown. Among them, Figure 6 The image at the top center shows Ti3C2T prepared by coating with titanium dioxide. x XPS image of CoFe2O4@TiO2 microwave absorbing material; Figure 6 The lower center image shows Ti3C2T prepared before coating with titanium dioxide. x XPS plot of / CoFe2O4.

[0066] Depend on Figure 6 It can be seen that after the coating in step (3), the peaks of titanium and oxygen elements are greatly enhanced, indicating that the titanium dioxide coating was successful.

[0067] Among them, the Ti3C2T prepared before coating titanium dioxide in step (2) of Example 1 x / CoFe2O4, Ti3C2T prepared after coating titanium dioxide in step (3) x Fine spectrum of titanium in / CoFe2O4@TiO2 microwave absorbing material as follows Figure 7 As shown. Among them, Figure 7 The image at the top center shows Ti3C2T prepared by coating with titanium dioxide. x Fine spectrum of titanium in CoFe2O4@TiO2 microwave absorbing material; Figure 7 The lower center image shows Ti3C2T prepared before coating with titanium dioxide. x Fine spectrum of titanium in / CoFe2O4.

[0068] Depend on Figure 7 The fine elemental spectrum of titanium shows that the number of titanium-oxygen bonds increased significantly after coating, confirming that titanium dioxide was successfully coated.

[0069] In summary, elemental analysis and XPS analysis show that titanium dioxide was successfully coated, giving the microwave absorbing material a core-shell structure.

[0070] 4. Electromagnetic absorption test Electromagnetic absorption tests were conducted on the microwave absorbing materials prepared in Example 1 and Comparative Examples 1-5. The specific testing method involved using a vector network analyzer for coaxial method testing. The above materials were mixed with paraffin wax (each material accounted for 80%), heated to 60°C and mixed evenly. After cooling, the mixture was placed in a mold and pressed into a coaxial ring with an outer diameter of 7.0 mm, an inner diameter of 3.04 mm, and a thickness of 2 mm using a hydraulic press at 5 MPa. The ring was then tested using a vector network analyzer in the 1-18 GHz range to obtain the electromagnetic parameters of different materials at different frequencies. The reflection loss value at different thicknesses was then calculated according to the reflection loss formula.

[0071] Example 1: The microwave absorption performance of the absorbing material is as follows Figure 8 As shown. The microwave absorption properties of the microwave absorbing materials in Comparative Examples 1-5 are respectively as follows. Figure 9 , 10 As shown in 11, 12, and 13.

[0072] Depend on Figure 8 It can be seen that the absorbing material in Example 1 can achieve an absorption performance of -52.99dB at 18GHz.

[0073] Depend on Figure 9 It can be seen that the absorbing material of Comparative Example 1 can achieve an absorption performance of -40.64dB at 1.53GHz; Depend on Figure 10 It can be seen that the absorbing material of Comparative Example 2 can achieve an absorption performance of -41.29dB at 1.52GHz.

[0074] Depend on Figure 11 It can be seen that the absorbing material in Comparative Example 3 can achieve an absorption performance of -38.72dB at 9.06GHz; Depend on Figure 12 It can be seen that the absorbing material in Comparative Example 4 can achieve an absorption performance of -28.68 dB at 5.80 GHz; Depend on Figure 13 It can be seen that the absorbing material of Comparative Example 5 can achieve an absorption performance of -16.3dB at 1.51GHz.

[0075] As can be seen from the comparison between Example 1 and Comparative Example 1, the absorption intensity and absorption frequency are improved after coating with titanium dioxide.

[0076] As can be seen from the comparison between Example 1 and Comparative Example 2, the high-temperature heat treatment method reduces the absorption intensity of Comparative Example 5 from -52.99dB to -41.3dB and the absorption frequency from 18GHz to 1.52GHz.

[0077] As can be seen from the comparison between Example 1 and Comparative Examples 3-4, changing the amount of two-dimensional material during the preparation process reduces the absorption intensity and absorption frequency.

[0078] As can be seen from the comparison between Example 1 and Comparative Example 5, directly applying Ti3C2T x The absorption intensity of the microwave absorbing material obtained by physically mixing CoFe2O4 and TiO2 is significantly worse than that of Example 1, and the absorption frequency decreases from 18GHz to 1.51GHz. This indicates that the microwave absorbing material of this application needs to have a specific structure in order to obtain good microwave absorption performance.

[0079] In summary, the microwave absorbing material prepared by this invention has a specific structure. The intercalation structure of magnetic nanoparticles distributed between the layers and on the surface of the two-dimensional layered material is conducive to multiple reflections of electromagnetic waves between the layers, enhancing electromagnetic absorption. At the same time, the core-shell structure formed by the low-dielectric material coating is conducive to enhancing impedance matching, forming a shell with good wave transmission performance, promoting the entry of electromagnetic waves into the interior of the material, further reducing reflection loss, and enhancing electromagnetic absorption. This allows the microwave absorbing material to be used in the 16-18 GHz frequency band and has good electromagnetic absorption performance.

[0080] Furthermore, compared to high-temperature heat treatment, the present invention prepares microwave absorbing materials through room-temperature reaction, which can retain more functional groups, has better polarization relaxation loss, and can significantly improve the microwave absorption intensity and absorption frequency of the microwave absorbing material. At the same time, room-temperature reaction also has the advantages of reducing energy consumption, reducing costs, and being safer.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A microwave absorbing material, characterized in that, The microwave absorbing material has a core-shell structure; The core in the core-shell structure comprises a two-dimensional layered material and magnetic nanoparticles, wherein the magnetic nanoparticles are distributed between the layers and on the surface of the two-dimensional layered material. The shell layer in the core-shell structure is composed of low-dielectric materials.

2. The microwave absorbing material according to claim 1, characterized in that, The conductivity of the two-dimensional layered material is greater than 1 S / m; and / or the dielectric constant of the two-dimensional layered material is greater than 10 F / m; and / or the dielectric constant of the low dielectric material is 1-3 F / m.

3. The microwave absorbing material according to claim 2, characterized in that, The two-dimensional layered material includes MXene material; and / or, the magnetic nanoparticles include at least one of metal nanoparticles, alloy nanoparticles, and ferrite nanoparticles; and / or, the low dielectric material includes at least one of titanium dioxide and silicon dioxide.

4. The microwave absorbing material according to claim 3, characterized in that, The metal nanoparticles include at least one of iron nanoparticles, cobalt nanoparticles, and nickel nanoparticles; and / or, the alloy nanoparticles include at least one of iron-nickel alloy nanoparticles, iron-cobalt alloy nanoparticles, and cobalt-nickel alloy nanoparticles; and / or, the ferrite nanoparticles include at least one of cobalt ferrite nanoparticles, manganese ferrite nanoparticles, and zinc ferrite nanoparticles.

5. The microwave absorbing material according to claim 1, characterized in that, In the microwave absorbing material, the mass fraction of the magnetic nanoparticles is 82-85%, the mass fraction of the two-dimensional layered material is 5-8%, and the mass fraction of the low dielectric material is 7-13%.

6. The microwave absorbing material according to any one of claims 1-5, characterized in that, The frequency range of the absorbing material is 16-18 GHz.

7. The method for preparing the microwave absorbing material according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Mix the precursor of magnetic nanoparticles, reducing agent and two-dimensional layered material, stir to obtain intermediate product 1; or mix the precursor of magnetic nanoparticles, two-dimensional layered material and solvent, adjust pH to alkaline, react, freeze dry to obtain intermediate product 2. (2) Mix the polarity regulator, pH regulator and intermediate product 1 or intermediate product 2 obtained in step (1), sonicate, then add low dielectric material precursor, react at room temperature to obtain the microwave absorbing material.

8. The preparation method according to claim 7, characterized in that, In step (1), the precursor of the magnetic nanoparticles is a metal salt; and / or, the reducing agent includes sodium borohydride; and / or, the reaction temperature is 40-60℃ and the reaction time is 116-132h; and / or, the freeze-drying temperature is -60~-40℃ and the freeze-drying time is 40-55h.

9. The preparation method according to claim 7, characterized in that, In step (2), the polarity regulator includes acetonitrile and ethanol; and / or, the pH regulator includes ammonia; and / or, the low dielectric material precursor includes at least one of tetrabutyl titanate and tetraethyl silicate; and / or, the room temperature reaction time is 3-5 h.

10. An electromagnetic absorbing material or electromagnetic absorbing device, characterized in that, Includes the microwave absorbing material according to any one of claims 1-6.

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