Composite material with brick mortar structure as well as preparation method and application of composite material

Abstract

The invention provides a composite material with a brick mortar structure and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbing materials. The method comprises the following steps: preparing a Ti < 3 > C < 2 > T < x > MXene material by using an HF etching method; preparing a Fe3O4 / PDA composite material by using an in-situ mineralization technology; and preparing the brick-mortar-shaped multifunctional Fe3O4 / PDA / Ti < 3 > C < 2 > T < x > Mxene composite electromagnetic wave absorbing material by utilizing an electrostatic adsorption effect. The interface stability of the composite material is regulated and controlled through a unique brick mortar structure, the compressive strength is improved, the electromagnetic wave path is prolonged, and the internal wave absorbing performance of the material is improved; by combining the synergistic effect of interface polarization and defect regulation and control, the wave-absorbing advantages of being wide, light, thin and strong are shown. The material can be applied to the field of electromagnetic wave absorption.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbing materials, and in particular relates to a composite material with a "brick mortar" structure, a preparation method thereof, and an application thereof. Background Art

[0002] With the advent of the 5G / 6G era, electromagnetic pollution is becoming increasingly severe, necessitating the development of highly efficient absorbing materials. Ideal absorbing materials require the absorption characteristics of "broadband absorption (wide), lightweight (light), thin thickness (thin), and high loss (strong)", but this remains elusive. Furthermore, drawbacks such as high density, heavy loads, and poor stability severely limit their application. Therefore, balancing absorbing performance with applicability has been a hot topic in recent years in the field of electromagnetic wave absorbing materials.

[0003] Ti3C2T x MXene (hereinafter referred to as Ti3C2T x ) is a newly emerged two-dimensional transition metal carbide and / or nitride material with a layered structure, excellent electrical conductivity, good mechanical properties and rich surface functional groups. Its layered structure is conducive to extending the propagation path of electromagnetic waves and enhancing the interface polarization effect. The bulk defects caused by the surface functional groups are conducive to increasing the dipole polarization to enhance the electromagnetic attenuation capability. Therefore, it is considered to be a very promising absorbing material. However, according to the electromagnetic loss mechanism, a single loss mechanism is not conducive to achieving broadband absorption. Therefore, the combination of dielectric loss and magnetic loss is considered to be an effective method to precisely control electromagnetic parameters, meet electromagnetic synergy, and achieve broadband. Among various magnetic materials, Fe3O4 is low-cost, environmentally friendly, and abundant in sources. x It is widely used in absorbing materials. Studies have shown that Fe3O4 nanoparticles have high magnetic properties, good compatibility and good compatibility with Ti3C2T x The synergistic effect of the magnetic components and Ti3C2T x The lack of chemical bonding during compounding results in poor structural and interfacial stability. In addition, the preparation of magnetic materials still requires high-temperature treatment. x The chemical properties are unstable and easily oxidized. Therefore, the magnetic particles and Ti3C2T x Interface stability and Ti3C2T x The chemical stability of the material itself is an issue that must be considered when designing electromagnetic composite materials. x The polymer that can interact and be in situ mineralized at room temperature is used as Ti3C2T x Coupling agents with magnetic particles can effectively improve interface stability and maintain chemical stability.

[0004] Polydopamine is a mussel biomimetic material that contains a large amount of catechol in its structure, which fully meets the conditions for in-situ mineralization. Its structure contains a large number of hydroxyl groups and primary and secondary amines, which are used to bind to Ti3C2T through hydrogen bonds, van der Waals forces and electrostatic adsorption. x Through the functional groups in polydopamine, the in-situ growth of magnetic particles and the interaction with Ti3C2T x The coupling ensures that the complex has proper impedance matching to reduce reflection and enhance absorption.

[0005] In order to improve the mechanical properties, scientists have found that the excellent mechanical properties of pearl shells in nature are mainly due to their unique layered "brick-mortar" structure and the strong interfacial adhesion between "bricks" and "mortar". x The strong interfacial adhesion between the two materials can improve the strength of the composite material by simulating the biological assembly process of pearl shells. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that a single loss mechanism is not conducive to achieving broadband absorption, magnetic particles and Ti3C2T x To solve the problem of limited absorption performance caused by insufficient interface stability and insufficient mechanical properties, a composite material with a "brick mortar" structure and a preparation method and application thereof are provided.

[0007] The present invention first provides a method for preparing a composite material having a "brick mortar" structure, comprising:

[0008] Step 1: Preparation of Ti3C2T by HF etching x Mxene powder;

[0009] Step 2: Mixing ferric chloride (FeCl3) solution and polydopamine (PDA) dispersion to form a first mixed solution, then adding NaOH solution to adjust the pH value of the system, and finally adding ferrous chloride tetrahydrate (FeCl2·4H2O) solution to allow static precipitation, and finally separating, washing, and drying to obtain Fe3O4 / PDA powder;

[0010] Step 3: Prepare the Ti3C2T x After MXene powder is added into deionized water and evenly dispersed, Ti3C2T x MXene solution, the Fe3O4 / PDA powder prepared in step 2 is added to the above solution for stirring, allowed to settle, and finally separated, washed, and dried to obtain a composite material with a "brick mortar" structure.

[0011] Preferably, the concentration of the FeCl3 solution in step 2 is 0.2 mol·L-1 , the concentration of PDA dispersion is 200 mg·mL -1 The concentration of ferrous chloride tetrahydrate (FeCl2·4H2O) solution is 0.2 mol·L -1 .

[0012] Preferably, the volume ratio of the FeCl3 solution, the PDA dispersion and the FeCl2·4H2O solution is 24:0.5:8.

[0013] Preferably, in step 2, the ferric chloride (FeCl 3 ) solution and the polydopamine (PDA) dispersion are mixed by stirring at room temperature for 1-3 minutes.

[0014] Preferably, the concentration of the NaOH solution in step 2 is 4 mol·L -1 , adjust the pH value of the system to 12.

[0015] Preferably, the static sedimentation time in step 2 is 30-35 minutes.

[0016] Preferably, the stirring time in step 3 is 20-25 minutes, and the static sedimentation time is 40-45 minutes.

[0017] Preferably, in step 3, Ti3C2T x The mass ratio of MXene powder to Fe3O4 / PDA powder is 1:(1.5-3).

[0018] The present invention also provides a composite material with a "brick mortar" structure obtained by the above preparation method.

[0019] The present invention also provides the use of the composite material with the "brick-mortar" structure as an electromagnetic wave absorbing material.

[0020] Beneficial effects of the present invention

[0021] The present invention first provides a composite material with a "brick mortar" structure and a preparation method thereof. The composite material is a multifunctional Fe3O4 / PDA / Ti3C2T x MXene composite material, which is prepared by HF etching method of Ti3C2T x MXene materials; then Fe3O4 / PDA composite materials were prepared using in-situ mineralization technology; finally, electrostatic adsorption was used to prepare "brick mortar" multifunctional Fe3O4 / PDA / Ti3C2T x MXene composite electromagnetic wave absorbing material.

[0022] First, the present invention uses in-situ mineralization technology to use PDA as a coupling agent to directly generate magnetic particles on Ti3C2T at room temperature. x Between the layers, it solves the problem of most magnetic components and Ti3C2T x The lack of chemical bonding during the composite process results in poor structural and interface stability. x The problem of easy oxidative decomposition.

[0023] Second, through the unique “brick-mortar” structure of the composite material, Ti3C2T x The rich heterogeneous interface formed by MXene ("brick") and Fe3O4 / PDA ("mortar") dissipates energy through interfacial polarization, and Ti3C2T x Surface functional groups (-OH, -F) and PDA polar groups (-NH2, -OH) induce dipole polarization, while the high conductivity of MXene and the Fe3O4 / PDA network contribute to conductive losses through eddy current effects. Regarding magnetic losses, Fe3O4 nanoparticles dissipate electromagnetic waves through natural resonance and exchange resonance, while their magnetic coupling with MXene enhances hysteresis losses. Furthermore, the "brick-and-mortar" design utilizes the MXene layered structure to extend the electromagnetic wave path, regulate the stability of the composite material interface, enhance compressive strength, and improve the material's internal absorption properties, demonstrating its "wide, light, thin, and strong" absorption advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are scanning electron microscope images of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention.

[0025] Figure 2 These are the XRD patterns of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention.

[0026] Figure 3 These are the infrared spectra of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention.

[0027] Figure 4 It is the electrical conductivity of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention.

[0028] Figure 5 This is a diagram of the effective absorption bandwidth of PFM-1.5 prepared in Example 1 of the present invention.

[0029] Figure 6 This is a diagram of the effective absorption bandwidth of PFM-2.0 prepared in Example 2 of the present invention.

[0030] Figure 7 This is a diagram of the effective absorption bandwidth of PFM-3.0 prepared in Example 3 of the present invention.

[0031] Figure 8 This is the RL-F curve of PFM-1.5 prepared in Example 1 of the present invention.

[0032] Figure 9 This is the RL-F curve of PFM-2.0 prepared in Example 2 of the present invention.

[0033] Figure 10 This is the RL-F curve of PFM-3.0 prepared in Example 3 of the present invention.

[0034] Figure 11 This is a physical diagram of the stress conditions of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention.

[0035] Figure 12 This is a scanning electron microscope image of the Fe3O4 / PDA composite prepared in Comparative Example 1 of the present invention.

[0036] Figure 13 SEM and EDS element mapping images of the Fe3O4 / PDA composite prepared in Comparative Example 1 of the present invention.

[0037] Figure 14 This is the XRD pattern of the Fe3O4 / PDA composite prepared in Comparative Example 1 of the present invention.

[0038] Figure 15 The In-situ Fe3O4 / PDA composite material (Comparative Example 1) and Fe 3+ -Raman spectra of PDA composite material (Comparative Example 2) and Ex-situ Fe3O4 / PDA composite material (Comparative Example 3). DETAILED DESCRIPTION

[0039] The present invention first provides a method for preparing a composite material having a "brick mortar" structure, comprising:

[0040] Step 1: Prepare Ti3C2T by classic HF etching method x MXene; specifically preferably includes:

[0041] First, dilute the HF solution with deionized water to obtain an HF solution. Then, slowly add Ti3AlC2 powder to the HF solution and stir with a magnetic stirrer, preferably at room temperature for 5 hours. Many bubbles appear during the etching process. After the reaction is completed, add the product to deionized water and repeat centrifugation until the pH value reaches about 7. After centrifugation, remove the supernatant and dry the product under vacuum to obtain a black powder product. The mass g of the Ti3AlC2 powder: the volume mL of the HF solution is 0.5:10; the mass fraction of the HF solution is preferably 40%;

[0042] Step 2: In situ generation of Fe3O4 magnetic nanoparticles on the surface of PDA microspheres by in situ mineralization technology, specifically comprising: mixing ferric chloride (FeCl3) solution with polydopamine (PDA) dispersion to form a first mixed solution, wherein the concentration of the FeCl3 solution is preferably 0.2 mol·L -1 The concentration of the PDA dispersion is preferably 200 mg·mL -1 Then, the first mixed solution is physically stirred, preferably at room temperature for 1 minute. Then, NaOH solution is added to adjust the pH value of the system. The concentration of the NaOH solution is 4 mol·L -1 , the pH value is preferably 12, and finally ferrous chloride tetrahydrate (FeCl2·4H2O) solution is added for static precipitation, wherein the concentration of the FeCl2·4H2O solution is 0.2 mol·L -1 The static sedimentation time is preferably 30 minutes. The sediment is obtained by magnetic separation and the supernatant is removed. After repeated washing with deionized water and repeated sedimentation, the product is collected by vacuum filtration and vacuum dried. The pore size of the polytetrafluoroethylene (PVDF) filter membrane used in the filtration process is preferably 0.221 μm, the vacuum drying temperature is preferably 60°C, and the reaction time is preferably 24 hours to obtain black Fe3O4 / PDA powder. The volume ratio of the FeCl3 solution, PDA dispersion, NaOH solution and FeCl2·4H2O solution is 24:0.5:3.3:8.

[0043] Step 3: Add Ti3C2T x After MXene powder is added into deionized water and evenly dispersed, Ti3C2T xMXene solution, the Fe3O4 / PDA powder in step 2 is added to the above solution and stirred, the stirring temperature is preferably room temperature, the stirring time is preferably 20 minutes, and then static sedimentation is performed, the static sedimentation time is preferably 40 minutes, the sediment is obtained by magnetic separation and the supernatant is removed, and after repeated washing with deionized water and repeated deposition, the product is collected by vacuum filtration and vacuum dried. The pore size of the polytetrafluoroethylene (PVDF) filter membrane used in the filtration process is preferably 0.221 μm, the vacuum drying temperature is preferably 60°C, and the reaction time is preferably 24 hours to obtain Fe3O4 / PDA / Ti3C2T x MXene composite electromagnetic wave absorbing material. Ti3C2T x The mass ratio of MXene powder to Fe3O4 / PDA powder is preferably 1:(1.5-3).

[0044] The present invention also provides a composite material with a "brick mortar" structure obtained by the above preparation method.

[0045] The present invention also provides the use of the composite material with the "brick-mortar" structure as an electromagnetic wave absorbing material.

[0046] The present invention is further described in detail below with reference to specific examples, in which the raw materials involved are all commercially available.

[0047] Example 1: A multifunctional Fe3O4 / PDA / Ti3C2T with a "brick mortar" structure x MXene composite material (I) is prepared according to the following steps:

[0048] Step 1: Ti3C2T was prepared by classic HF etching method. x MXene. First, the HF solution was diluted with deionized water to obtain a 40% HF solution by mass. Then, 0.5 g of Ti3AlC2 powder was slowly added to 10 mL of HF solution over 5 minutes and stirred at room temperature for 5 hours using a magnetic stirrer. Many bubbles appeared during the etching process. After the reaction, the product was added to deionized water and centrifuged repeatedly at 3500 rpm for 10 minutes until the pH reached approximately 7. After centrifugation, the supernatant was removed, and the product was dried under vacuum at 80°C for 24 hours to obtain a black powder product.

[0049] Step 2: In situ generation of Fe3O4 magnetic nanoparticles on the surface of PDA microspheres by in situ mineralization technology. -1 0.5 ml of FeCl3 solution with a concentration of 200 mg mL -1 The PDA dispersion was mixed and physically stirred for 1 min at room temperature, and then 3.3 ml of 4 mol·L-1 NaOH solution to raise the pH value of the reaction system to 12. Then 8 ml of 0.2 mol·L -1 A FeCl2·4H2O solution was added to the reaction solution and allowed to settle for half an hour. The sediment was adsorbed using a magnet, the supernatant removed, and washed several times with deionized water. The settling process was repeated. The product was vacuum-filtered through a 0.221μm pore size polytetrafluoroethylene (PVDF) membrane using 200ml of deionized water and then dried under vacuum at 65°C for 24 hours to obtain a black powder.

[0050] Step 3: Take Ti3C2T x After MXene powder was evenly dispersed in 20ml of deionized water, Fe3O4 / PDA powder was added to the solution, stirred at room temperature for 20 minutes, and allowed to settle for 40 minutes. The sediment was then adsorbed with a magnet, the supernatant removed, and washed several times with deionized water, repeating the settling process. The product was vacuum-filtered and dried at 65°C for 24 hours to obtain a black powder. x The mass ratio of MXene to Fe3O4 / PDA is 1:1.5, and the composite with this ratio is represented by PFM-1.5.

[0051] Figure 1 a and Figure 1 b is a scanning electron microscope image of the PFM-1.5 and the oblique section of PFM-1.5 prepared in Example 1 of the present invention. Figure 1 a is the overall morphology of the PFM-1.5 sample, showing that it has a continuous and dense composite layered structure; Figure 1 b is an enlarged view of the cross section after bevel cutting. This special sample preparation process can clearly show the typical "brick mortar" structural characteristics. It can be seen from the figure that the Fe3O4 / PDA microspheres in the sample are tightly adhered to the multi-layer Ti3C2T x The interlayer and surface of MXene form a "brick-mortar" structure, in which Ti3C2T x MXene is used as "bricks" to stack layer by layer, and Fe3O4 / PDA microspheres are used as "mortar" to mix Ti3C2T x MXene sheets are connected. In the PFM-1.5 sample, due to the Ti3C2T x The content of MXene is the least, and Fe3O4 / PDA microspheres are relatively excessive, except for the distribution on Ti3C2T x There are also a large number of microspheres distributed between the MXene layers on the Ti3C2T x On the outer surface of the MXene block, the interlayer microspheres are tightly packed and in contact with each other, with pores between the spheres.

[0052] Figure 5 This is a graph showing the effective absorption bandwidth of PFM-1.5 prepared in Example 1 of the present invention. The graph shows that within the frequency range of 2.0-18.0 GHz, as the material thickness increases from 1.0 mm to 5.5 mm, when the thickness of the PFM-1.5 is 2.5 mm, the minimum reflection loss value is -28.82 dB at a corresponding frequency of 9.44 GHz, and the effective absorption bandwidth is 2.24 GHz.

[0053] Figure 8 This is the RL-F curve of PFM-1.5 prepared in Example 1 of the present invention. It can be seen from the figure that the electron beam loss capability of the composite samples is relatively strong. For the PFM-1.5 composite sample, when its thickness varies in the range of 1.5-5.5mm, the RL in the range of 3.76-18GHz exceeds -10dB. At the same time, the sample's t at 1 / 4λ is m The experimental value is consistent with the simulation value. This shows that the multi-layer Ti3C2T x The construction of a conductive network and the formation of multiple interfaces between MXene and Fe3O4 / PDA microspheres help achieve quarter-wavelength attenuation and improve electromagnetic wave absorption performance.

[0054] Example 2: A multifunctional Fe3O4 / PDA / Ti3C2T with a "brick mortar" structure x MXene composite material (II) is prepared according to the following steps:

[0055] The preparation method and conditions are the same as those in Example 1, except that in step 3, Ti3C2T x The mass ratio of MXene to Fe3O4 / PDA is 1:2, and the composite with this ratio is represented by PFM-2.0.

[0056] Figure 1 c and Figure 1 d is a scanning electron microscope image of the PFM-2.0 and the oblique section of PFM-2.0 prepared in Example 2 of the present invention. Figure 1 c is the overall morphology of the PFM-2.0 sample, showing that it has a continuous and dense composite layered structure; Figure 1 d is an enlarged view of the cross section after bevel cutting. This special sample preparation process can clearly show the typical structural characteristics of "brick mortar". It can be seen from the figure that in the PFM-2.0 sample, as Ti3C2T x With the increase of MXene content, the number of microspheres on the Ti3C2Tx MXene surface decreases, and the Fe3O4 / PDA microspheres are mainly distributed between the layers and have good dispersion. The Fe3O4 / PDA microspheres firmly adhere the layers, making the stacking of "bricks" more solid. xAs the MXene content increases, some exposed holes appear between the layers. These holes are beneficial to increase the specific surface area of the material.

[0057] Figure 6 This is a graph showing the effective absorption bandwidth of PFM-2.0 prepared in Example 2 of the present invention. The graph shows that within the frequency range of 2.0-18.0 GHz, as the material thickness increases from 1.0 mm to 5.5 mm, when the PFM-2.0 thickness is 1.5 mm, the minimum reflection loss reaches -33.71 dB at a corresponding frequency of 13.6 GHz, resulting in an effective absorption bandwidth of 3.36 GHz.

[0058] Figure 9 This is the RL-F curve of PFM-2.0 prepared in Example 2 of the present invention. From the figure, it can be observed that the electron beam loss capability of the composite samples is relatively strong. When the thickness of the PFM-2.0 composite sample varies in the range of 1.5-5.5mm, the RL in the range of 2.88-18GHz exceeds -10dB, which shows that the electromagnetic absorption bandwidth (EAB) of PFM-2.0 is relatively wide. At the same time, the t m The experimental value is consistent with the simulation value. This shows that the multi-layer Ti3C2T x The construction of a conductive network and the formation of multiple interfaces between MXene and Fe3O4 / PDA microspheres help achieve quarter-wavelength attenuation and improve electromagnetic wave absorption performance.

[0059] Figure 9 This is the RL-F curve of PFM-2.0 prepared in Example 2 of the present invention. From the figure, it can be observed that the electron beam loss capability of the composite samples is relatively strong. When the thickness of the PFM-2.0 composite sample varies in the range of 1.5-5.5mm, the RL in the range of 2.88-18GHz exceeds -10dB, which shows that the electromagnetic absorption bandwidth (EAB) of PFM-2.0 is relatively wide. At the same time, the t m The experimental value is consistent with the simulation value. This shows that the multi-layer Ti3C2T x The construction of a conductive network and the formation of multiple interfaces between MXene and Fe3O4 / PDA microspheres help achieve quarter-wavelength attenuation and improve electromagnetic wave absorption performance.

[0060] Example 3: A multifunctional Fe3O4 / PDA / Ti3C2T with a "brick mortar" structure x MXene composite material (III) is prepared according to the following steps:

[0061] The preparation method and conditions are the same as those in Example 1, except that in step 3, Ti3C2T xThe mass ratio of MXene to Fe3O4 / PDA is 1:3, and the composite with this ratio is represented by PFM-3.0.

[0062] Figure 1 e and Figure 1 f is a scanning electron microscope image of the oblique section of PFM-3.0 and PFM-3.0 prepared in Example 3 of the present invention. Figure 1 e is the overall morphology of the PFM-3.0 sample, showing that it has a continuous and dense composite layered structure; Figure 1 f is an enlarged view of the cross section after bevel cutting. This special sample preparation process can clearly show the typical "brick mortar" structural characteristics. It can be observed from the figure that in the PFM-3.0 sample, as Ti3C2T x As the MXene content continues to increase, the number of microspheres is relatively the least, which is similar to that of Ti3C2T x During MXene self-assembly, the amount of microspheres is insufficient, resulting in only a small amount of microspheres adhering to the Ti3C2T x A large number of unfilled, exposed pores appear between the layers of MXene. The increase in pores will help increase the specific surface area of the material, but it may also have a negative impact on the enhancement of mechanical properties.

[0063] Figure 2 The XRD patterns of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) of the present invention are shown in Figure 1. It can be observed from the figure that Ti3C2T x The characteristic peak of the (002) crystal plane of MXene and the angles are slightly shifted. This is because in the composite material, Fe3O4 / PDA microspheres act as mortar and adhere to Ti3C2T x The interlayer spacing between MXene layers is widened. The crystal diffraction peaks appearing near 28.86°, 35.7°, 38.7°, 57.4°, and 61.2° are characteristic peaks of Fe3O4, and their corresponding crystal planes are (220), (311), (400), (511), and (440), respectively. This indicates that the Ti3C2T x MXene and Fe3O4 / PDA were successfully composited. It can be seen from the figure that Ti3C2T x The characteristic peak intensity of MXene is significantly higher than that of Fe3O4, indicating that the material is based on Ti3C2T x MXene is the main component and Fe3O4 is the auxiliary component, and the results are consistent with the scanning electron microscopy results.

[0064] Figure 3The infrared spectra of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) of the present invention are shown in FIG. It can be observed from the figure that the three composite samples have an infrared spectrum at 3423 cm -1 A strong functional group absorption peak appeared at 1629cm, which was caused by the stretching vibration of OH and NH in Fe3O4 / PDA. -1 、1399cm -1 、1081cm -1 The absorption peaks generated at x The absorption peaks of surface functional groups C=O, CF, and CO in MXene are at 578 cm -1 445cm -1 There are two absorption peaks at 3+ -O stretching vibration and Fe 2+ -O stretching vibration. It can be observed from the figure that Ti3C2T exists in all three composite samples. x The characteristic functional group absorption peaks of MXene and Fe3O4 further prove that Ti3C2T x MXene was successfully composited with Fe3O4 / PDA.

[0065] Figure 4 The conductivity of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention. It can be observed from the figure that as Ti3C2T x With the increase of MXene content, the electrical conductivity of the three composite samples increases. This result further illustrates that the x The "brick mortar" structure formed by MXene and Fe3O4 / PDA microspheres is interconnected to form a good conductive network, which improves the conductivity of the material and helps to improve the conductive loss of the material.

[0066] Figure 7 This is a graph showing the effective absorption bandwidth of PFM-3.0 prepared in Example 3 of the present invention. The graph shows that within the frequency range of 2.0-18.0 GHz, as the material thickness increases from 1.0 mm to 5.5 mm, when the PFM-3.0 thickness is 1.5 mm, the minimum reflection loss value is -27.49 dB at a corresponding frequency of 14.32 GHz, and the effective absorption bandwidth is 2.8 GHz.

[0067] Figure 10This is the RL-F curve of PFM-3.0 prepared in Example 3 of the present invention. From the figure, we can see that the electron beam loss capability of the composite samples is relatively strong. When the thickness of the PFM-3.0 composite sample changes in the range of 1.5-5.5mm, the RL in the range of 2.88-18GHz also exceeds -10dB, which shows that the electromagnetic absorption bandwidth (EAB) of PFM-3.0 is also relatively wide. At the same time, the sample t m The experimental value is consistent with the simulation value. This shows that the multi-layer Ti3C2T x The construction of a conductive network and the formation of multiple interfaces between MXene and Fe3O4 / PDA microspheres help achieve quarter-wavelength attenuation and improve electromagnetic wave absorption performance.

[0068] Figure 11 The following are the actual images of the stress conditions of PFM-1.5 (Example 1), PFM-2.0 (Example 2), and PFM-3.0 (Example 3) described in the present invention. It can be observed from the figure that the three composite samples can maintain their original shape under the pressure of a 20g weight, and the overall structure remains good without collapse, indicating that the Fe3O4 / PDA / Ti3C2T x MXene composites for improving Ti3C2T x The mechanical properties of MXene-based composites offer possibilities.

[0069] Comparative Example 1: Preparation of an in-situ synthesized Fe3O4 / PDA composite material was carried out according to the following steps:

[0070] Step 1: Add 24 ml of 0.2 mol·L -1 0.5 ml of FeCl3 solution with a concentration of 200 mg mL -1 The PDA dispersion was mixed and physically stirred for 1 min at room temperature, and then 3.3 ml of 4 mol·L -1 of NaOH solution to raise the pH value of the reaction system to 12.

[0071] Step 2: Add 8ml of 0.2mol·L -1 A FeCl2·4H2O solution was added to the reaction solution and allowed to settle for half an hour. The sediment was adsorbed using a magnet, the supernatant removed, and washed several times with deionized water. The settling process was repeated. The product was vacuum-filtered through a 0.221μm pore size polytetrafluoroethylene (PVDF) membrane using 200ml of deionized water and then dried under vacuum at 65°C for 24 hours to obtain a black powder.

[0072] Figure 12This is a scanning electron micrograph of the Fe₃O₄ / PDA composite prepared in Comparative Example 1 of the present invention. The image shows that the sample is composed of small spheres with particles attached to their surfaces. The lumps connect to form a coating that encapsulates a large number of well-dispersed microspheres.

[0073] Figure 13 (a) is the SEM image of the Fe3O4 / PDA composite prepared in comparative example 1 of the present invention, and 13(b) is the corresponding EDS element mapping image. It can be observed from the figure that the composite mainly contains four elements: Fe, O, N, and C. Among them, the C element and a small amount of N and O elements belong to the PDA microspheres, and the O element also mainly belongs to Fe3O4. Fe, O, and N are distributed around the C element of the PDA microspheres, proving that Fe3O4 is generated on the surface of the PDA microspheres. During the synthesis process, PDA was used as a carrier and a certain stoichiometric amount of Fe was mixed. 3+ , coordinate cross-linking with the catechol groups on PDA, and then adjust the pH value of the cross-linking system to 12 by adding NaOH solution to form a Fe 3+ -catechol coordination crosslinking and covalent catechol crosslinking combined crosslinking network. 2+ According to Fe 2+ :Fe 3+ =1:3 stoichiometric ratio, introduced into the cross-linking system, and finally triggered the in-situ mineralization of Fe3O4. 2+ First, with 2 stoichiometric Fe 3+ The reaction generates 1 stoichiometric amount of Fe3O4 and the remaining 1 stoichiometric amount of Fe 2+ Then with Fe 3+ -catechol coordination complex. Therefore, the particles on the surface of PDA microspheres are composed of Fe 2+ with Fe 3+ -Fe3O4 produced by coordination and complexation of catechol.

[0074] Figure 14 This is the XRD pattern of the Fe3O4 / PDA composite prepared in Comparative Example 1 of the present invention. It can be observed that all diffraction peak positions completely overlap with those of the Fe3O4 standard card. The diffraction peaks appear at 30.3°, 35.6°, 43.2°, 57.1°, and 62.7°, corresponding to the 220, 311, 400, 511, and 440 crystal planes of Fe3O4 (PDF#88-0866), respectively. This indicates that the in-situ mineralization method successfully prepared Fe3O4.

[0075] Comparative Example 2: A Fe 3+ The preparation of the PDA composite material is carried out according to the following steps:

[0076] Step 1: Add 24 ml of 0.2 mol·L-1 0.5 ml of FeCl3 solution with a concentration of 200 mg mL -1 The PDA dispersion was mixed and physically stirred for 1 min at room temperature, and then 3.3 ml of 4 mol·L -1 of NaOH solution to raise the pH value of the reaction system to 12.

[0077] Step 2: Allow to settle for half an hour. Use a magnet to attract the sediment, remove the supernatant, and wash repeatedly with deionized water several times. Repeat the settling process. Vacuum-filter the product using 200 ml of deionized water through a 0.221 μm pore size polytetrafluoroethylene (PVDF) filter membrane. Dry at 65°C under vacuum for 24 hours to obtain a black powder.

[0078] Comparative Example 3: Preparation of a non-in-situ synthesized Fe3O4 / PDA (Ex-situ) composite material, according to the following steps:

[0079] Step 1: Add 24 ml of 0.2 mol·L -1 FeCl3 solution with a concentration of 4 mol·L -1 of NaOH solution to raise the pH value of the reaction system to 12.

[0080] Step 2: Add 8ml of 0.2mol·L -1 Add FeCl2·4H2O solution to the reaction solution and let it settle for half an hour. Use a magnet to adsorb the sediment, remove the supernatant, and wash it several times with deionized water. Repeat the settling process.

[0081] Step 3: Add 20 ml of deionized water to the sediment and stir thoroughly for 10 min, then add 0.5 ml of 200 mg mL -1 The PDA dispersions were mixed, stirred at room temperature for 20 min, and then vacuum-filtered. The resulting product was dried at 65°C under vacuum for 24 h.

[0082] Figure 15 The In-situ Fe3O4 / PDA composite material (Comparative Example 1) and Fe 3+ -PDA composite material (Comparative Example 2), Ex-situ Fe3O4 / PDA composite material (Comparative Example 3) Raman spectra. 3+ -PDA, available at 526, 588, 650cm -1 Three absorption peaks were observed at the 400 nm t-type ion exchanger, which were not observed in the ex-situ product. These three characteristic peaks were attributed to the Fe 3+The coordination bonding interaction between the catechol ligand and the oxygen of the catechol ligand was confirmed in the in-situ product and Fe 3+ -PDA has Fe-catechol coordination interaction. After in situ mineralization reaction, both in-situ product and ex-situ product have the peak at 680cm -1 A resonance peak appears at . This peak corresponds to Fe3O4 (magnetite) mineral. This indicates that in the In-situ product, the initial Fe 3+ The catechol-coordinated complex was transformed into a cross-linked structure of catechol-bound Fe₃O₄ mineral particles, indicating direct interaction between catechol and mineral particles in the cross-linked network. Pre-prepared Fe₃O₄ was also present in the ex-situ product. Raman spectroscopy confirmed the formation of metal cross-links during the in situ mineralization reaction.

Claims

1. A method for preparing a composite material having a "brick mortar" structure, characterized in that: include: Step 1: Preparation of Ti3C2T by HF etching x Mxene powder; Step 2: Mixing the ferric chloride solution and the PDA dispersion to form a first mixed solution, then adding a NaOH solution to adjust the pH value of the system, and finally adding a ferrous chloride tetrahydrate solution to allow static precipitation, and finally separating, washing, and drying to obtain Fe3O4 / PDA powder; Step 3: Prepare the Ti3C2T x After MXene powder is added into deionized water and evenly dispersed, Ti3C2T x MXene solution, the Fe3O4 / PDA powder prepared in step 2 is added to the above solution for stirring, allowed to settle, and finally separated, washed, and dried to obtain a composite material with a "brick mortar" structure.

2. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: The concentration of FeCl3 solution in step 2 is 0.2 mol·L -1 , the concentration of PDA dispersion is 200 mg·mL -1 The concentration of ferrous chloride tetrahydrate solution is 0.2 mol·L -1 .

3. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: The volume ratio of the FeCl3 solution, the PDA dispersion and the ferrous chloride tetrahydrate solution is 24:0.5:

8.

4. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: In the step 2, the ferric chloride solution and the PDA dispersion are mixed and stirred at room temperature for 1-3 minutes.

5. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: The concentration of NaOH solution in step 2 is 4 mol·L -1 , adjust the pH value of the system to 12.

6. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: The time for static sedimentation in step 2 is 30-35 minutes.

7. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: The stirring time in step 3 is 20-25 minutes, and the static sedimentation time is 40-45 minutes.

8. The method for preparing a composite material having a "brick mortar" structure according to claim 1, characterized in that: Ti3C2T in step 3 x The mass ratio of MXene powder to Fe3O4 / PDA powder is 1:(1.5-3).

9. The composite material having a "brick mortar" structure obtained by the preparation method according to claim 1.

10. Use of the composite material having a "brick-mortar" structure according to claim 9 as an electromagnetic wave absorbing material.

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