Preparation method and application of multifunctional spongy N-doped MXene-coated AgMFs composite material

Abstract

The invention discloses a preparation method and application of a multifunctional spongy N-doped MXene-coated AgMFs composite material, and belongs to the technical field of electromagnetic shielding materials. Two-dimensional transition metal carbide MXene and industrial-grade silver microchips AgMFs are driven by a solvent to complete interface self-assembly, a composite film is obtained in a vacuum-assisted filtering mode, and then the spongy N-doped MXene-coated AgMFs composite material is prepared through hydrazine hydrate treatment. The composite material prepared by the invention can ensure extremely high electromagnetic shielding effectiveness (79.1 dB, 8-12 GHz) of the material under the conditions of extremely thinness (86 microns) and extremely low density, and meanwhile, the shielding behavior is mainly dominated by absorption, so that the situation that electromagnetic pollution in a module is caused by over-strong reflection performance of most of current high-conductivity materials is avoided.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding materials technology, and more specifically, relates to a method for preparing and applying a multifunctional sponge-like N-doped MXene@AgMFs composite material. Background Technology

[0002] The evolution of high-speed communication technologies has driven an urgent need for flexible electronics, miniaturized components, and high-frequency devices adapted for portable smart terminals. However, the resulting electromagnetic pollution poses a dual risk to sensitive devices and biological systems. Traditional metal-based shielding materials (such as Ag, Al, and Cu) possess high conductivity and excellent shielding performance, but are limited by their high density, mechanical inflexibility, and corrosion sensitivity. More importantly, their reflection-dominated shielding mechanism generates secondary electromagnetic pollution, making them incompatible with the modern requirements of integrated and multifunctional electronic products.

[0003] MXene is a two-dimensional material discovered in 2016, with the general formula M. n+1 X n T x (n = 1-4), where M, X, and Tx are early transition metals (groups 3-6 of the periodic table), C and / or N, and surface terminals (= O, -OH, -F, -Cl or combinations thereof), possessing unique advantages: 1) abundant polar functional groups, resulting in excellent dispersibility and film-forming ability; 2) combined with metallic conductivity (σ ~ 4500 S cm- 1 The high efficiency of electromagnetic shielding achieved through conduction and abundant interfacial polarization loss allows MXene nanosheets to dissipate electromagnetic waves through the synergistic effect of conduction and polarization losses, thus establishing a shielding mechanism primarily based on absorption. However, during processing, MXene nanosheets are susceptible to dense stacking driven by van der Waals forces and hydrogen bonding, resulting in limited interlayer spacing and porosity. This dense structure not only restricts the multiple reflection and scattering paths of electromagnetic waves within the material but also reduces the density of the effective polarization interface, severely limiting further improvements in its electromagnetic shielding effectiveness (EMI SE) and absorption performance.

[0004] To overcome these limitations, researchers designed MXene composites, strategically assembling them with metals, carbon, or polymers to amplify interfacial polarization and porous scattering properties. For example, a directionally freeze-dried Ti3C2Tx-silver nanowire composite, with its porous network, achieved an EMI SE of 79.3 dB, but its high electrical conductivity resulted in a reflection advantage (R = 0.8). Similarly, an MXene / rGO / PUDA composite achieved an EMI SE of 40 dB, but its low absorption coefficient (A = 0.3, R = 0.7) highlighted the reflection-dominated mechanism. These results indicate that achieving absorption-controlled shielding under high SE conditions is challenged by σ-induced interfacial impedance mismatch, which promotes reflection. Furthermore, thermal conductivity and mechanical flexibility are crucial for applications in advanced electronics. Silver, with its unparalleled electrical conductivity (15.87 nΩ·m) and thermal conductivity (429 W / m·K), is an ideal candidate material. In particular, micron-sized silver sheets (AgMFs) demonstrate advantages on an industrial scale, with their high aspect ratio enabling highly efficient permeation networks, as proven in RFID systems and membrane switches. Paradoxically, achieving absorption-controlled shielding under high SE conditions is challenged by σ-induced interfacial impedance mismatch, which promotes reflection.

[0005] Therefore, a method is needed to effectively improve the interlayer spacing and porosity of MXene-based composite materials, thereby enhancing the overall EMI SE of the material. Simultaneously, while maintaining high shielding effectiveness, the absorption coefficient should be increased to prevent secondary electromagnetic pollution caused by reflection-dominated shielding mechanisms between modules in dense electron systems. Furthermore, by endowing the material with additional functions, such as thermal conductivity, flame retardancy, and sensing properties, integrated applications in microelectronics or flexible electronics can be achieved. Summary of the Invention

[0006] To address the aforementioned problems in existing technologies, the technical problem this invention aims to solve is to provide a method for preparing a multifunctional sponge-like N-doped MXene@AgMFs composite material. This method is simple and can further improve the material's porosity, specific surface area, and scattering space. Another technical problem this invention aims to solve is to provide a sponge-like N-doped MXene@AgMFs composite material prepared by the above method. This composite material achieves high electromagnetic shielding effectiveness dominated by absorption, efficient thermal conductivity, and multifunctional integration, meeting the dynamic environmental requirements of advanced electronic devices. A further technical problem this invention aims to solve is to provide applications of the sponge-like N-doped MXene@AgMFs composite material in the preparation of electromagnetic shielding materials, microwave absorbing materials, thermally conductive materials, and integrated electronic devices.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a multifunctional sponge-like N-doped MXene@AgMFs composite material involves solution-driven interfacial self-assembly of AgMFs and MXene, followed by treatment with hydrazine hydrate to obtain the sponge-like N-doped MXene@AgMFs composite material; wherein the MXene is a single-layer Ti3C2T x T x It has O, F or OH functional groups.

[0009] Preferably, the mass ratio of AgMFs to MXene is 1:1.

[0010] Preferably, in the hydrazine hydrate treatment, the amount of hydrazine hydrate added is 1-4 mL, and the concentration of hydrazine hydrate is 40%-80%.

[0011] The preparation method of the aforementioned multifunctional sponge-like N-doped MXene@AgMFs composite material includes the following steps:

[0012] 1) AgMFs were fully dispersed in diethyl ether, and ethanol was added to obtain mixed liquid A; the obtained mixed liquid was slowly added dropwise to MXene dispersion under ultrasonic conditions, and after the addition was completed, ultrasonication was continued for 15 min to obtain mixed liquid B;

[0013] 2) The mixed liquid B obtained in step 1) was subjected to a self-assembly reaction under water bath conditions. The reaction was stopped after observing that there were no micron-sized silver flakes on the surface of the liquid and no obvious stratification. The self-assembled mixed liquid was filtered to obtain a self-supporting membrane.

[0014] 3) The self-supporting membrane obtained in step 2) is dried to obtain the MXene@AgMFs composite film;

[0015] 4) The MXene@AgMFs composite film obtained in step 3) is treated with hydrazine hydrate. The hydrazine hydrate is evenly distributed on the surface of the dry MXene@AgMFs composite film. After standing, the nitrogen doping reaction is carried out in a vacuum oven. After naturally cooling to room temperature, the sponge-like N-doped MXene@AgMFs composite material is obtained after washing and drying.

[0016] Preferably, in step 1), the ratio of AgMFs to diethyl ether, ethanol, and MXene dispersion is 30:4:4:3.5, and the concentration of MXene dispersion is 8.6 mg / mL.

[0017] Preferably, in step 2), the water bath is carried out at 50°C for 10 minutes.

[0018] Preferably, in step 4), after standing, the temperature is increased to 90°C at 8°C / min in a vacuum oven, and dried at 90°C for 6 hours.

[0019] The sponge-like N-doped MXene@AgMFs composite material prepared by the aforementioned method is a sponge-like N-doped MXene@AgMFs composite material.

[0020] The thickness of the sponge-like N-doped MXene@AgMFs composite material is 45–95 μm.

[0021] The sponge-like N-doped MXene@AgMFs composite material is used in the preparation of electromagnetic shielding materials, microwave absorbing materials, thermal conductive materials, and integrated electronic devices.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1) This invention uses a two-dimensional transition metal carbide MXene (Ti3C2Tx) and industrial-grade silver microplates (AgMFs) to achieve interfacial self-assembly via solvent driving. The self-assembled material is then formed into a composite film using vacuum-assisted methods. The composite material is optimized by treating it with hydrazine hydrate, which replaces some oxygen functional groups (-OH, -O) on the MXene surface with nitrogen atoms to form Ti-N bonds, introducing polarization sites and enhancing electromagnetic wave polarization loss. In addition, the high temperature causes the parallel shielding units to bend under the influence of overflow gas and water vapor, thus presenting a spatial morphology of longitudinal and transverse overlap, further improving the porosity, specific surface area and scattering space of the material.

[0024] 2) The embedded AgMFs network of the present invention solves the inherent thermal limitation of MXene by reducing the surface temperature of the component through enhanced thermal conductivity; in addition, the N-doped MXene@AgMFs composite material has multiple functions, including flame retardancy, electrothermal conversion, infrared stealth and condition monitoring, demonstrating great potential for advanced integrated flexible electronics in dynamic environments.

[0025] 3) This invention constructs a sponge-like porous structure and a nitrogen-doped composite material interface through hydrazine hydrate treatment. Compared with traditional metal-based and ordinary carbon-based shielding materials, it can ensure extremely high electromagnetic shielding efficiency (79.1dB, 8-12GHz) under extremely thin (86μm) and low temperature conditions. At the same time, the shielding behavior is mainly dominated by absorption (absorption coefficient A = 0.82), avoiding the situation of electromagnetic pollution inside the module caused by the excessive reflection performance of most high conductivity materials. It also avoids the shielding status quo of "thick and inefficient" high electromagnetic absorption materials.

[0026] 4) This invention overcomes the problem of heat accumulation caused by the layering of pure MXene materials, making them difficult to apply in precision electronics. Compared to exposed electronic component surfaces and pure MXene films, the thermal conductivity is improved by 57.9% and 13.4%, respectively. Furthermore, the multifunctional properties of the composite material, such as infrared shielding, flame retardancy, sensing, and weather resistance, compensate for the single-function problem of traditional shielding materials, giving this material great potential for application in current advanced thin and light integrated electronic products. Attached Figure Description

[0027] Figure 1 Combustion test diagram of industrial flexible aluminum fabric and N-doped MXene@AgMFs composite material prepared in Example 9 on the surface of an alcohol lamp at room temperature;

[0028] Figure 2 The Raman spectrum of the residue after combustion test of the N-doped MXene@AgMFs composite material prepared in Example 9;

[0029] Figure 3 The sensing performance of the N-doped MXene@AgMFs composite material prepared in Example 9, which was applied to the finger joint, at different bending angles of the finger;

[0030] Figure 4 A graph showing pulse-sensing data of the N-doped MXene@AgMFs composite material prepared in Example 9 and applied to the wrist;

[0031] Figure 5 A sensor data graph showing the letters A to N written on the surface of the N-doped MXene@AgMFs composite material prepared in Example 9;

[0032] Figure 6 Sensing response diagram of the vibration of a ruler with the N-doped MXene@AgMFs composite material prepared in Example 9 for surface coating;

[0033] Figure 7 The images show infrared shielding (camouflage) test results of the N-doped MXene@AgMFs composite material prepared in Example 9. Specifically, f-1 shows the change in infrared thermal imaging of a mobile phone surface covered with the N-doped MXene@AgMFs composite material on grass at night; f-2 shows the change in infrared thermal imaging of a car engine casing covered with the N-doped MXene@AgMFs composite material at noon; f-3 shows the change in infrared thermal imaging of a mobile phone screen running a large game covered with the N-doped MXene@AgMFs composite material; and f-4 shows the change in infrared thermal imaging of a human hand surface covered with the N-doped MXene@AgMFs composite material outdoors at noon.

[0034] Figure 8 Optical photographs of the N-doped MXene@AgMFs composite material prepared in Example 9 after immersion in different organic solvents for 36 hours;

[0035] Figure 9 Infrared thermograms showing the changes over time of an exposed LED chip with MXene, MXene@AgMFs, and the N-doped MXene@AgMFs composite material prepared in Example 9 after energization.

[0036] Figure 10 Cold field electron microscopy image of the cross section of the M@A-H80% composite material prepared in Example 9. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0038] The AgMFs used in the following examples are industrial-grade micron-sized silver powders with a particle size of 0.5-3 μm. The hydrazine hydrate is commercially available 80% hydrazine hydrate, CAS number 10217-52-4.

[0039] The preparation process of MXene is as follows: Ti3AlC2MAX (1g) was gradually added to a mixture of HCl (20mL, 9M) and LiF (1.6g) in a polypropylene bottle (100mL). The mixture was stirred continuously at 40℃ for 24h. The resulting mixture was washed twice by centrifugation with HCl (1M) at 3500rpm, and then washed nine times by centrifugation with deionized water at 10000rpm until pH=6. The mixture was then dispersed by ultrasonication (100W) for 4h to separate monolayer Ti3C2T. x MXene; centrifuge at 3500 rpm for 1 h, collect the supernatant to obtain a stable and well-dispersed monolayer of Ti3C2T. x MXene thin film suspension.

[0040] The preparation process of pure MXene shielding membrane is as follows: 7 mL of 8.6 mg / mL MXene dispersion is taken and filtered into a membrane using a vacuum-assisted device. The membrane is then dried at 40°C for 5 h to obtain pure MXene shielding membrane.

[0041] The preparation process of the MXene@AgMFs membrane without hydrazine hydrate treatment is as follows: the ether dispersion of AgMFs and the aqueous dispersion of MXene are self-assembled in the presence of ethanol as an intermediate solvent. The resulting self-assembled mixed liquid is then passed through a PP filter membrane with a pore size of 0.45 μm and filtered under vacuum to obtain a self-supported membrane. The membrane is then dried at 40 °C for 4 h to obtain the MXene@AgMFs composite film, denoted as M@A-H0.

[0042] The preparation process of pure micron-sized silver sheet membrane is as follows: 60 mg of AgMFs is dispersed in diethyl ether, and then the dispersion is filtered into a membrane by vacuum-assisted means. The membrane is dried at 40°C for 4 hours to obtain pure micron-sized silver sheet membrane.

[0043] The shielding effectiveness test used in the following embodiments is as follows: The shielding effectiveness of the sponge-like composite film is tested using vector network analysis. The multifunctional sponge-like N-doped MXene@AgMFs-H film, cut to standard size, is precisely fixed in the test fixture (waveguide fixture) with conductive adhesive to ensure tight contact and avoid signal leakage. Then, the target frequency band (i.e., X-band, 8-12GHz) is set and the S-parameters (S11 / S21) are scanned and collected. The shielding effectiveness is quantified by calculating the insertion loss (SE=-|S21|) and reflection coefficient (R=|S11|2). At the same time, the absorption coefficient (A=1-RT) is combined to analyze the absorption-dominant characteristics. During the test, the temperature and humidity need to be controlled and the data stability needs to be repeatedly verified. Finally, the electromagnetic response characteristics and multi-mechanism shielding performance of the material in a wide frequency range are accurately characterized.

[0044] The apparatus structure for hydrazine hydrate treatment in the following embodiments mainly includes a mold shell, which is an openable quartz sealed container containing a double-layer ceramic sheet assembly (made of alumina). The double-layer structure achieves horizontal support by setting ceramic gaps of 2mm height at each of the four corners of the ceramic sheets, and the thickness difference between the bottom and top ceramic sheets is 3mm. In use, the quartz shell and the double-layer ceramic sheet assembly are opened, and hydrazine hydrate is sprayed onto the surface of the bottom ceramic sheet. After the hydrazine hydrate is evenly dispersed, a dry MXene@AgMFs composite film is placed on it. After closing the device, it needs to stand for 5 minutes to ensure that the hydrazine hydrate permeates the composite material from the outside to the internal unit space through capillary action. Then, the device is placed in a vacuum oven for heating treatment to complete the nitrogen doping process. After the mold surface cools down naturally to room temperature, the composite material is removed.

[0045] Example 1

[0046] A method for preparing a multifunctional sponge-like N-doped MXene@AgMFs composite material includes the following steps:

[0047] 1) Disperse 30 mg AgMFs thoroughly in 4 mL of diethyl ether, add 4 mL of ethanol, and then disperse thoroughly on a vortex mixer to obtain a mixed liquid;

[0048] 2) Place the mixed liquid obtained in step 1) into an ultrasonic cleaner, and slowly add 3.5 mL of 8.6 mg / mL MXene deionized water dispersion under ultrasonic conditions of 40 W. After the addition is complete, continue to maintain ultrasonication at 40 W for 15 min.

[0049] 3) The mixed liquid obtained in step 2) was subjected to a self-assembly reaction in a water bath at 50°C for 10 min. The reaction was stopped after observing that there were no micron-sized silver flakes on the surface of the liquid and no obvious stratification. The self-assembled mixed liquid was then passed through a PP filter membrane with a pore size of 0.45 μm and a self-supporting membrane was obtained under vacuum-assisted filtration.

[0050] 4) Place the self-supporting film obtained in step 3) into an oven and dry it at 40°C for 4 hours to obtain the MXene@AgMFs composite film;

[0051] 5) The MXene@AgMFs composite film obtained in step 4) was treated with hydrazine hydrate. 1 mL of 70% hydrazine hydrate was evenly distributed on the surface of the dried MXene@AgMFs composite film. After standing for 5 min, the film was heated to 90 °C at 8 °C / min in a vacuum oven and dried at 90 °C for 6 h. After naturally cooling to room temperature, the film was washed with deionized water and ethanol in sequence. After drying at 35 °C for 3 h, a multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H1) with a thickness of 47 μm was obtained.

[0052] Example 2

[0053] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the amount of hydrazine hydrate added in step 5) was 2 mL, and the remaining preparation methods and parameters were the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H2) with a thickness of 65 μm was prepared.

[0054] Example 3

[0055] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the amount of hydrazine hydrate added in step 5) was 3 mL, and the remaining preparation methods and parameters were the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H3) with a thickness of 76 μm was prepared.

[0056] Example 4

[0057] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the amount of hydrazine hydrate added in step 5) was 4 mL, and the remaining preparation methods and parameters were the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H4) with a thickness of 94 μm was prepared.

[0058] Example 5

[0059] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the concentration of hydrazine hydrate in step 5) was 40%, and the remaining preparation methods and parameters were the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H40%) was prepared with a thickness of 46 μm.

[0060] Example 6

[0061] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the concentration of hydrazine hydrate in step 5) is 50%, and the remaining preparation methods and parameters are the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H50%) was prepared with a thickness of 57 μm.

[0062] Example 7

[0063] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the concentration of hydrazine hydrate in step 5) is 60%, and the remaining preparation methods and parameters are the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H60%) was prepared with a thickness of 67 μm.

[0064] Example 8

[0065] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the concentration of hydrazine hydrate in step 5) is 70%, and the remaining preparation methods and parameters are the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H70%) was prepared with a thickness of 76 μm.

[0066] Example 9

[0067] When preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material, the concentration of hydrazine hydrate in step 5) is 80%, and the remaining preparation methods and parameters are the same as in Example 1. The multifunctional sponge-like N-doped MXene@AgMFs composite material (denoted as M@A-H80%) was prepared with a thickness of 84 μm.

[0068] Example 10

[0069] The electromagnetic shielding effectiveness of the multifunctional sponge-like N-doped MXene@AgMFs composite material prepared in Examples 1-9, pure MXene shielding film, MXene@AgMFs film without hydrazine hydrate treatment (denoted as M@A-H0), and pure micron silver film were compared, and the results are shown in Tables 1-3.

[0070] Table 1. Shielding effectiveness of Example 1, pure MXene shielding film, pure AgMFs shielding film, and M@A-H0.

[0071]

[0072] Table 2 shows the shielding effectiveness results of Examples 2-5.

[0073]

[0074] Table 3 shows the shielding effectiveness results of Examples 6-9.

[0075]

[0076] As shown in Table 1-3, when the hydrazine hydrate treatment dose is 1 mL, the EMI SE of MA-H1 is improved by 2.9 dB compared to M@A-H0. At this point, the porous internal structure greatly extends the propagation path of electromagnetic waves, and the layer-by-layer attenuation and numerous multiple reflections compensate for the loss caused by the decrease in conductivity. Subsequently, with further increases in the hydrazine hydrate treatment dose, the hydrazine hydrate liquid penetrates into the interlayer of MXene@AgMFs through isotropic inward capillary forces within the film. Then, when the vapor products are discharged from each side of the sample, the gas and heat diffuse and propagate in all directions within the sample, forming unique and denser pores. A large amount of oxygen-containing functional groups (-OH, -COOH) and bound water on the surface are removed, and the material thickness is further increased. When the hydrazine hydrate treatment dose is 2 mL, the absorption coefficient increases to 0.73, and absorption shielding plays an absolute dominant role in the shielding mechanism.

[0077] When the hydrazine hydrate treatment dose was 3 mL, the shielding effectiveness of M@A-H3 improved by 5.5 dB (7.95%) compared to M@A-H0. The hydrazine treatment process also changed the main shielding mechanism of the material, transforming it from reflection shielding to absorption shielding. With increasing hydrazine hydrate dosage, under high-temperature conditions, N2H4·H2O reacts with MXene surface groups to form pyrrole nitrogen or amino nitrogen. The incorporated nitrogen atoms, due to their high electronegativity, provide additional electrons to the outer layer of MXene, enhancing the overall electron density of the material. Simultaneously, the addition of nitrogen atoms may lead to hybridization of the p orbitals with the d orbitals of carbon and titanium in MXene, lowering the conduction band energy and making it easier for electrons to transition from the valence band to the conduction band, enabling the material to effectively absorb low-frequency electromagnetic waves. At a hydrazine hydrate treatment dose of 3 mL, the composite material reached its highest absorption coefficient of 0.79, representing a 364.7% improvement in absorption performance compared to M@A-H0, significantly higher than the 0.01 absorption coefficient of the pure AgMFs sample. However, treating the composite material (M@A-H4) with excessive hydrazine hydrate leads to an increase in internal collapse and leakage flux, resulting in a reduction in shielding effectiveness to 73.2 dB. At this point, the weakening effect of this change on the absorption coefficient is greater than the contribution effect of N doping, and the absorption coefficient (0.7) reaches an inflection point, but the overall shielding mechanism is still dominated by absorption.

[0078] Given the aqueous nature of hydrazine hydrate and the intense heat release and gas ejection during the reaction, the final structural integrity of the M@AH composite material is related to the concentration of hydrazine hydrate. Therefore, after determining the appropriate hydrazine treatment dosage, it is necessary to investigate the effect of different concentrations of hydrazine hydrate treatment on the electromagnetic shielding effectiveness of the M@AH composite material. The electromagnetic shielding effectiveness of M@A-H40% was improved to 70.2 dB. The lower concentration of hydrazine hydrate itself carries more water, diluting the active components in the reaction process, reducing the intensity of local reactions, and leading to mild foaming. M@A-H40% exhibits a structure with open spatial channels formed by overlapping parallel units, effectively expanding the absorption and propagation path of electromagnetic waves. At the same time, the widely dispersed contact interface between the generated dielectric material and MXene can accumulate a large amount of charge when electromagnetic waves are incident, completing significant Maxwell-Wagner polarization to help convert electromagnetic energy into heat energy, ultimately improving the electromagnetic wave absorption efficiency of the material. Therefore, the final material exhibits an ultra-high absorption shielding effect of 73%, at which point the improvement in overall shielding effectiveness mainly depends on the increase in polarization sites and the opening of the spatial structure.

[0079] With further increases in hydrazine hydrate concentration, the shielding effectiveness of the composite material improved to 71.6 dB and 72.3 dB. Higher hydrazine hydrate concentrations resulted in lower moisture carrying capacity and stronger reducing ability, leading to simultaneous oxidation and reduction on the MXene surface at high temperatures, thus increasing the overall shielding effectiveness. However, the continuous loss of numerous polarization sites caused the absorption coefficient to decrease from 0.73 to 0.71 and 0.69. When the hydrazine hydrate concentration reached 70%, the critical point of redox reaction equilibrium was exceeded. At this point, the reduction reaction dominated, and large amounts of hydrogen, nitrogen, and water vapor rapidly accumulated during the reaction. The increased pressure caused further expansion and foaming of the internal space of the MA shielding unit overlap, ultimately resulting in a distinct sponge-like curved shape in the overlap layer. This phenomenon was particularly pronounced when using a hydrazine hydrate concentration of 80% (e.g., ...). Figure 10 (As shown). M@A-H80% achieves a maximum shielding effectiveness of 79.1 dB, representing a 14.3% improvement in shielding effect compared to M@A-H0 while maintaining flexibility and thinness. Furthermore, thanks to the amino nitrogen and pyrrole nitrogen generated by N doping, polarization sites are widely distributed again, resulting in improved dielectric loss and impedance matching capabilities, leading to a significant increase in the absorption coefficient A. M@A-H80% achieves a high absorption coefficient of 0.82 with extremely low sheet thickness, and its absorption shielding effect is 382.4% better than the original sample. This absorption-based shielding mechanism effectively avoids secondary electromagnetic pollution between highly integrated module circuits, making it suitable for next-generation flexible precision electronic products.

[0080] like Figure 1 As shown, under extreme conditions, the N-doped MXene@AgMF composite material prepared in Example 9 exhibits excellent flame retardancy: commonly used industrial aluminum fabric shielding materials burn completely within 10 seconds, while the N-doped MXene@AgMF composite material retains its structural integrity after 50 seconds of direct contact with a flame.

[0081] Depend on Figure 2 It can be seen that the Raman spectral peaks of the residue of the N-doped MXene@AgMFs composite material prepared in Example 9 after the combustion test are at 145, 399, 442, 518 and 624 cm⁻¹. -1 This confirms that the elasticity originates from the high-temperature oxidation of MXene to form a dense anatase TiO2 layer, which acts as a thermal barrier and prevents heat propagation.

[0082] Depend on Figure 3 It is evident that attaching the N-doped MXene@AgMFs composite material prepared in Example 9 to a finger allows for tracking of human movement during cyclic bending, with current changes correlated with the bending angle. The maximum current change gradually decreases as the bending angle increases. The stress-induced changes in the conduction pathways of the sponge-like structure result in a consistent and reliable signal response.

[0083] Depend on Figure 4 As demonstrated, when placed on the wrist, the N-doped MXene@AgMFs composite material prepared in Example 9 detected subtle pulsations caused by cardiac activity, generating a stable and repeatable electrical signal. A heart rate of 72 beats per minute was determined from radial artery pulses recorded over 10 seconds, highlighting its practicality in wearable devices for real-time health monitoring.

[0084] Depend on Figure 5 and Figure 6 It was found that writing letters on the N-doped MXene@AgMFs composite material prepared in Example 9 with a ballpoint pen generated electrical signals of varying intensities depending on the pressure and trajectory. Furthermore, placing the material on an insulating ruler subjected to mechanical stress produced repeatable damped vibration signals over multiple cycles. These results demonstrate the material's potential for interactive sensing applications in integrated electronics and human protection monitoring.

[0085] Based on the fact that infrared shielding and electromagnetic shielding follow the same fundamental electromagnetic principles within the Maxwell framework, the N-doped MXene@AgMFs composite material prepared in Example 9 of this invention exhibits infrared stealth performance under different dynamic environments, such as... Figure 7 As shown.

[0086] Depend on Figure 7 It is known that under nighttime conditions (26.3-30℃), this composite material, through randomized infrared reflection via its disordered M@A heterostructure, reduces the surface temperature of uncovered devices from 30-31℃ to <28.3℃, effectively camouflaging devices from infrared detection. In nighttime outdoor environments with temperatures between 26.3 and 30℃, uncovered electronic devices with surface temperatures of 30-31℃ are highly visible under infrared imaging. Applying the M@AH shielding film further reduces the surface temperature to below 28.3℃, allowing the device to seamlessly integrate into the environment. This is due to the effective superposition of the M@A heterostructure and the variability of its composition, which increases the disorder of infrared wave reflection, thereby reducing the probability of detection by infrared sensors. Under midday sunlight, the composite material, through the synergistic effect of MXene's low emissivity and agmf's high thermal conductivity, suppresses the infrared characteristics of metal surfaces, reducing the temperature from 55.9-58.5℃ to 42.1-43.7℃. This dual mechanism of "infrared reflection scattering and heat dissipation" enables seamless environmental integration even under strong sunlight. When applied to electronic devices operating in intensive applications or directly to the human body, this composite material also maintains an infrared emission frequency close to the environmental level (Figures f-3 and f-4), demonstrating its excellent stealth capability for flexible electronic devices under complex conditions.

[0087] Depend on Figure 8As can be seen, the N-doped MXene@AgMFs composite material prepared in Example 9 further exhibits excellent weather resistance, even without the addition of any conventional polymer binders. Even after immersion in water, ethanol, acetone, diethyl ether, ethyl acetate, or N,N-dimethylformamide for 36 hours, the composite material retains its morphology without peeling or damage. This demonstrates its exceptional adaptability to extreme environments.

[0088] Efficient heat dissipation is crucial for highly integrated flexible electronic products, directly impacting component efficiency and lifespan. To investigate the heat conduction mechanism of the M@AH composite material in electronic components, the surface temperatures of LED chips covered with pure MXene, MXene@AgMFs composite material, and the MXene@AgMFs-H composite material prepared in Example 9 were monitored after 10, 20, 30, 40, and 50 seconds of illumination. Measurements were taken using an infrared camera and a thermocouple thermometer, and the results are shown below. Figure 9 As shown.

[0089] Depend on Figure 9 It was found that the uncovered LED chip reached a surface temperature of 105.9℃ after 50 seconds. For pure MXene films, the interlayer stacking structure limited their heat dissipation capacity. Introducing AgMFs into the composite material to form M@A self-assembly units significantly enhanced the material's heat dissipation capacity. AgMFs provide an efficient electronic pathway, overcoming the limitations of MXene in electronically mediated heat conduction by utilizing their superior electronic thermal conductivity. When the AgMFs content was 50%, the M@A composite material reduced the LED chip surface temperature to 41.7℃, with thermal conductivity increased by 60% and 19% respectively compared to the uncovered chip and pure MXene film, significantly extending the lifespan of the electronic components. When nitrogen doping is introduced into M@A materials via hydrazine treatment, the resulting sponge-like structure increases internal porosity. While enhancing absorption and shielding, this poses a challenge to heat dissipation. The surface temperatures of LED chips covered by N-doped MXene@AgMFs composites after 10, 20, 30, 40, and 50 seconds of illumination were 33.5℃, 38.4℃, 40.4℃, 43.8℃, and 44.6℃, respectively, higher than those of MXene@AgMFs composites under the same conditions. Nevertheless, the heat dissipation performance of the M@AH composite is still superior to pure MXene (51.5℃) and significantly better than that of bare LED chips (105.9℃). Given the excellent electromagnetic shielding performance of the M@AH composite, primarily through absorption mechanisms, and its outstanding integration properties, it can be considered a preferred material for advanced flexible and integrated electronic device applications.

[0090] Depend on Figure 10It is known that when the concentration of hydrazine hydrate is increased to 80%, the extensive spatial structure prolongs the propagation path of electromagnetic waves and increases the multiple scattering effect. At the same time, hundreds or thousands of MA shielding elements work together to completely dissipate the incident electromagnetic waves through layer-by-layer attenuation and spatial reflection.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional sponge-like N-doped MXene@AgMFs composite material, characterized in that, AgMFs and MXene were subjected to solution-driven interfacial self-assembly, followed by hydrazine hydrate treatment to prepare a sponge-like N-doped MXene@AgMFs composite material; the MXene was a monolayer Ti3C2T. x T x It has O, F or OH functional groups.

2. The preparation method of the multifunctional sponge-like N-doped MXene@AgMFs composite material according to claim 1, characterized in that, The mass ratio of AgMFs to MXene is 1:

1.

3. The method for preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material according to claim 1, characterized in that, In the hydrazine hydrate treatment, the amount of hydrazine hydrate added is 1-4 mL, and the concentration of hydrazine hydrate is 40%-80%.

4. The preparation method of the multifunctional sponge-like N-doped MXene@AgMFs composite material according to claim 1, characterized in that, Includes the following steps: 1) Disperse AgMFs thoroughly in diethyl ether, add ethanol to obtain mixed liquid A; slowly add MXene dispersion dropwise to the obtained mixed liquid under ultrasonic conditions, and continue ultrasonication for 15 min after the addition is complete to obtain mixed liquid B; 2) The mixed liquid B obtained in step 1) was subjected to a self-assembly reaction under water bath conditions. The reaction was stopped after observing that there were no micron-sized silver flakes on the surface of the liquid and no obvious stratification. The self-assembled mixed liquid was filtered to obtain a self-supporting membrane. 3) The self-supporting membrane obtained in step 2) is dried to obtain the MXene@AgMFs composite film; 4) The MXene@AgMFs composite film obtained in step 3) is treated with hydrazine hydrate. The hydrazine hydrate is evenly distributed on the surface of the dry MXene@AgMFs composite film. After standing, the nitrogen doping reaction is carried out in a vacuum oven. After naturally cooling to room temperature, the sponge-like N-doped MXene@AgMFs composite material is obtained after washing and drying.

5. The method for preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material according to claim 4, characterized in that, In step 1), the ratio of AgMFs to diethyl ether, ethanol, and MXene dispersion is 30:4:4:3.5, and the concentration of MXene dispersion is 8.6 mg / mL.

6. The method for preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material according to claim 4, characterized in that, In step 2), the water bath is carried out at 50°C for 10 minutes.

7. The method for preparing the multifunctional sponge-like N-doped MXene@AgMFs composite material according to claim 4, characterized in that, In step 4), after standing, the temperature is increased to 90°C at 8°C / min in a vacuum oven, and dried at 90°C for 6 hours.

8. The sponge-like N-doped MXene@AgMFs composite material prepared by the preparation method of any one of claims 1-7.

9. The sponge-like N-doped MXene@AgMFs composite material according to claim 8, characterized in that, The thickness of the sponge-like N-doped MXene@AgMFs composite material is 45–95 μm.

10. The application of the sponge-like N-doped MXene@AgMFs composite material according to claim 8 or 9 in the preparation of electromagnetic shielding materials, microwave absorbing materials, thermal conductive materials, and integrated electronic devices.

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