Preparation method of MXene-NiO-PPy ternary composite wave-absorbing material

Abstract

The invention relates to the technical field of wave-absorbing materials, in particular to a preparation method of an MXene-NiO-PPy ternary composite wave-absorbing material. The invention provides a preparation method of an MXene-NiO-PPy ternary composite wave-absorbing material, which comprises the following steps of: etching titanium aluminum carbide powder through a LiF / HCl mixture, and performing ultrasonic stripping to prepare a uniform dispersion of MXene nanosheets; the preparation method comprises the following steps: dispersing MXene nanosheets in a solution of water and absolute ethyl alcohol, and adding a pyrrole monomer and a FeCl3. 6H2O aqueous solution for reaction; after the reaction, washing is performed to obtain a PPy-MXene composite material; the preparation method comprises the following steps: by taking NiCl2. 6H2O as a nickel source and sodium oxalate as a precipitator, preparing NiO nanowires by adopting a hydrothermal method combined with a calcining process; the invention discloses a preparation method of an MXene-NiO-PPy ternary composite wave-absorbing material.According to the method, the MXene-NiO-PPy ternary composite wave-absorbing material with rich heterogeneous interfaces and a porous micro-nano structure is constructed, cooperation of dielectric loss, magnetic loss and interface polarization loss is achieved, and finally the light, efficient and broadband wave-absorbing performance is obtained.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and in particular to a method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material. Background Technology

[0002] With the rapid development of 5G, IoT, and military stealth technologies, electromagnetic pollution and information security issues are becoming increasingly prominent, making the demand for high-performance electromagnetic wave absorbing materials more urgent. Absorbing coatings can absorb, scatter, or reflect electromagnetic waves, weakening their propagation and reflection, thereby reducing interference between devices and improving electromagnetic compatibility, ensuring the stable operation of electronic systems. At the same time, the concept of green manufacturing is driving the rise of environmentally friendly absorbing materials. An ideal absorbing material should possess the characteristics of being "thin, light, wide, and strong," meaning thin, lightweight, with a wide absorption bandwidth and strong absorption capacity, while also meeting good impedance matching to minimize electromagnetic wave reflection.

[0003] MXene (such as Ti3C2T) x As a novel two-dimensional material, MXene, due to its extremely high electrical conductivity and abundant surface functional groups, can attenuate electromagnetic waves through a powerful dielectric polarization relaxation and conductivity loss mechanism. However, the high electrical conductivity of a single MXene leads to poor impedance matching characteristics, making electromagnetic waves more likely to be reflected on its surface rather than being consumed internally, and its single dielectric loss mechanism limits the effective absorption bandwidth (EAB).

[0004] To overcome the aforementioned shortcomings, introducing magnetic components and components with modulated dielectric properties are effective strategies. Polypyrrole (PPy) as an adhesive layer can modulate the interfacial interaction between MXene and NiO, suppress MXene stacking, form porous or layered structures, and enhance multiple reflections and scattering of electromagnetic waves. Nickel oxide (NiO) is magnetic and can compensate for the dielectric loss of MXene through hysteresis loss and natural resonance, forming a dielectric-magnetic synergistic effect, improving impedance matching, and broadening the absorption bandwidth.

[0005] Therefore, developing a microwave absorbing material and its preparation method that is simple to process, environmentally friendly, and can fully leverage the synergistic advantages of the three components is of great significance for promoting the practical application of high-performance microwave absorbing materials. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, a simple, low-cost, and environmentally friendly method for preparing MXene-NiO-PPy ternary composite microwave absorbing materials is provided. This method constructs a composite material with abundant heterogeneous interfaces and porous micro / nano structures, achieving synergistic effects of dielectric loss, magnetic loss, and interfacial polarization loss, ultimately obtaining lightweight, efficient, and broadband microwave absorption performance.

[0007] In a first aspect, this application provides a method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: Synthesis of S1 MXene nanosheets: A uniform dispersion of MXene nanosheets was prepared by etching aluminum titanium carbide powder with a LiF / HCl mixture and then ultrasonically exfoliating. Preparation of S2 PPy-MXene composite material: MXene nanosheets were dispersed in a solution of water and anhydrous ethanol, pyrrole monomer was added, and FeCl3·6H2O aqueous solution was added dropwise under ice-water bath and high-speed stirring conditions. After the reaction was completed, the PPy-MXene mixture was centrifuged to obtain precipitate B. Precipitate B was washed alternately with anhydrous ethanol and deionized water, and the washed precipitate B was vacuum dried to obtain the PPy-MXene composite material. Preparation of S3 NiO nanowires: Nickel monoxide nanowires were prepared by hydrothermal method combined with calcination, using NiCl2·6H2O as the nickel source and sodium oxalate as the precipitant. Preparation of S4 MXene-NiO-PPy composite material: The PPy-MXene composite material from step S2 is dispersed in deionized water and ultrasonically dispersed to achieve uniform dispersion. Then, NiO nanowires from step S3 are added, and after ultrasonic dispersion treatment, the mixture is filtered and dried to obtain the MXene-NiO-PPy ternary composite microwave absorbing material.

[0008] The above-described scheme is not a simple, crude physical mixing process, but rather a carefully designed multi-step chemical preparation process. Step S2 uses an "in-situ polymerization method" to prepare the PPy-MXene composite material, instead of synthesizing PPy particles first and then mixing them with MXene nanosheets. This method ensures that PPy is uniformly coated on the surface of MXene nanosheets, forming a denser heterojunction interface, which greatly promotes interfacial polarization and electron transport, thereby enhancing dielectric loss. Controlling the ratio of pyrrole monomer (Py) to MXene is key to optimizing the interfacial structure and conductivity. Step S3 uses a hydrothermal method to synthesize the precursor and then calcines it to obtain one-dimensional NiO nanowires. One-dimensional materials are more likely to form conductive networks or act as "bridges" in composite materials than zero-dimensional particles, which helps to enhance loss and mechanical properties. The final step, S4, uses low-temperature ultrasonic mixing to composite PPy-MXene with NiO nanowires. This method ensures uniform mixing of the two materials while minimizing damage to the already formed structure, preventing performance degradation of the high-performance material. The combination of these preparation methods (etching, in-situ polymerization, hydrothermal synthesis, and ultrasonic composite) ensures the full utilization of the advantages of each component and the maximization of the interface effect, which is the key to achieving high performance, rather than simply stacking up processes.

[0009] Preferably, step S1 specifically includes: slowly adding 1.5-3 parts of aluminum titanium carbide powder to a LiF / HCl mixture, stirring and reacting at 35°C for 36-48 hours, centrifuging at 3500 rpm for 5-10 minutes to obtain precipitate A, adding 3 times the volume of deionized water to precipitate A, ultrasonicating and centrifuging at 3500 rpm for 5-10 minutes, adding 3 times the volume of anhydrous ethanol to precipitate A, performing intercalation ultrasonicating and centrifuging at 3500 rpm for 5-10 minutes, repeating the ethanol intercalation step 2-5 times, and collecting the precipitate to obtain MXene nanosheets.

[0010] Preferably, in step S1, the LiF / HCl mixture is prepared by dissolving 1.5-2.5 parts of lithium fluoride in 35-45 parts of 9 mol / L hydrochloric acid and stirring at room temperature for 30 min.

[0011] Preferably, the precipitate A obtained in step S1 is subjected to ultrasonic treatment with deionized water at 500W for 5-10 minutes and then centrifuged; then anhydrous ethanol is added for intercalation and ultrasonic treatment at 500W for 50-70 minutes, followed by centrifugation.

[0012] By adopting the above scheme and precisely controlling the reaction conditions and adjustable range, the preparation process of monolayer MXene nanosheets was standardized, reproducible, and high-performance was achieved. The ultrasonic power was fixed at 500W, which ensured that the energy input for each intercalation and exfoliation was consistent, avoiding batch-to-batch differences in MXene sheet size and exfoliation efficiency caused by power fluctuations. The ethanol intercalation step was repeated 2-5 times, which ensured that impurity ions and byproducts were fully removed to obtain pure MXene nanosheets.

[0013] Preferably, step S2 specifically includes: dispersing MXene nanosheets in 40-60 parts of water, adding Py to a solution containing 40-60 parts of anhydrous ethanol, and then adding FeCl3·6H2O aqueous solution dropwise under ice-water bath and high-speed stirring conditions, maintaining the reaction in an ice-water bath for 24 hours; obtaining a PPy-MXene mixture, centrifuging to obtain a PPy-MXene precipitate, washing twice with anhydrous ethanol and deionized water, centrifuging at 7000 rpm for 5-10 minutes, and vacuum drying the washed and centrifuged PPy-MXene precipitate at 40-60℃ for 10-12 hours to obtain a PPy-MXene composite material.

[0014] Preferably, in step S2, the mass ratio of Py to MXene nanosheets is (0.25-1):1; and the molar ratio of oxidant FeCl3·6H2O to pyrrole monomer in step S2 is 1:1.

[0015] Preferably, in step S2, the FeCl3·6H2O aqueous solution is prepared by mixing 1.5-2.0 parts of FeCl3·6H2O oxidant into 10 parts of deionized water.

[0016] Preferably, in step S2, the PPy-MXene mixture is centrifuged at 7000 rpm for 8-10 minutes.

[0017] By employing the above-described scheme and precisely controlling the temperature, concentration, ratio, and post-processing of the polymerization reaction, uniform and dense coating of polypyrrole (PPy) on the surface of MXene nanosheets was achieved, constructing a PPy-MXene secondary heterostructure with strong interfacial bonding and an excellent conductive network. Step S2 demonstrates an upgrade from "simple mixing reaction" to "precise control." Through the synergistic control of solvent, temperature, and stirring, the close composite between PPy and MXene was promoted, enhancing the interfacial polarization effect, which is key to improving dielectric loss and microwave absorption performance. By adjusting the Py / MXene ratio, the electromagnetic properties of the final composite material can be fine-tuned. Strict stoichiometry and standardized post-processing ensure that the prepared PPy-MXene composite material has high purity, high conductivity, and excellent batch stability.

[0018] Preferably, step S3 specifically includes: mixing 30-34 parts of ethylene glycol with 18-20 parts of deionized water, then adding 0.4-0.5 parts of NiCl2·6H2O and mixing, then adding 0.1-0.15 parts of sodium oxalate and mixing, transferring to a high-pressure reactor, reacting at 180-210℃ for 18-24 hours, heating and then naturally cooling, centrifuging to obtain precipitate B, washing precipitate B with ethanol 2-3 times and centrifuging again, drying the centrifuged precipitate B under vacuum to obtain NiO nanowire precursor, calcining the NiO nanowire precursor in air atmosphere to obtain NiO nanowires.

[0019] Preferably, in step S3, precipitate B is washed with ethanol 2-3 times, then centrifuged at 5000-7000 rpm for 5-10 min, and the washed precipitate B is vacuum dried at 50-70℃ for 18-24 hours to obtain NiO nanowire precursor. The NiO nanowire precursor is then calcined in air at 350-450℃ for 1-3 hours to obtain polycrystalline NiO nanowires.

[0020] Using the above scheme, one-dimensional NiO nanowires (NiC2O4) were successfully prepared through a two-step method combining efficient and controllable hydrothermal synthesis and calcination. .The unique morphology of the 2H2O nanoparticles allows them to not only provide magnetic loss in the final ternary composite material but also serve as a crucial structural bridge and support, thereby significantly enhancing the overall microwave absorption performance of the composite material. A mixed solvent system of ethylene glycol and water is used. Ethylene glycol is a mild reducing and complexing agent; its high viscosity slows down the diffusion rate of reacting ions, effectively controlling the generation and growth rate of crystal nuclei, which is beneficial for forming uniform and well-crystallized nanostructures. The optimized mixing ratio of ethylene glycol and water is one of the key factors in achieving the nanowire morphology. Sodium oxalate, as a precipitant and structure directing agent, allows oxalate ions to react with Ni... 2+ The reaction produces nickel oxalate precipitate, which is itself an excellent structure-directing agent. Its selective adsorption on specific crystal planes guides the crystal to preferentially grow along the one-dimensional direction, which is the fundamental reason for forming nanowires rather than nanoparticles or cubic blocks. The final product is one-dimensional nanowires. These nanowires can bridge each other or establish connections between MXene sheets, forming a more complete three-dimensional conductive network inside the composite material, which greatly promotes electron transport and enhances conductivity loss. At the same time, the one-dimensional structure greatly increases the aspect ratio of the material. Incident electromagnetic waves are repeatedly reflected and scattered between the nanowires, and the propagation path is effectively extended, thus increasing the chance of loss. A large number of two-dimensional and one-dimensional heterogeneous interfaces are formed between the nanowires, the two-dimensional MXene sheets, and the coated PPy. These interfaces are ideal sites for interfacial polarization, which is a very important dielectric loss mechanism.

[0021] Preferably, in step S4, the PPy-MXene composite material and NiO nanowires are prepared at a mass ratio of (1.25-2):1.

[0022] Preferably, in step S4, the PPy-MXene composite material and deionized material are prepared at a mass ratio of (1.25-2):5.

[0023] Preferably, in step S4, the ultrasonic treatment conditions are: 80-120W, 40-60min, and the ultrasonic process temperature is controlled to not exceed 40℃ to avoid overheating.

[0024] By adopting the above scheme, step S4 successfully combines three nanomaterials (PPy-MXene and NiO nanowires) with different functions (dielectric loss, conductive loss, and magnetic loss) in a preset ratio using a mild and controllable liquid-phase ultrasonic-assisted mixing technology. This maximizes the preservation of the inherent advantages of each component and creates a strong synergistic effect, ultimately resulting in a high-performance ternary composite microwave absorbing material.

[0025] Secondly, this application provides an MXene-NiO-PPy ternary composite microwave absorbing material, which adopts the following technical solution: An MXene-NiO-PPy ternary composite microwave absorbing material is prepared by the method for preparing the MXene-NiO-PPy ternary composite microwave absorbing material.

[0026] By employing the above scheme, a conductive MXene substrate, a PPy conductive polymer interface layer, and magnetic NiO nanowires are organically combined, simultaneously modulating dielectric and magnetic properties, providing a new material system for achieving efficient broadband microwave absorption. Among these, MXene nanosheets, as the substrate material, have the advantage of extremely high electrical conductivity and abundant surface functional groups. High conductivity tends to generate strong dielectric loss, but excessively high conductivity can lead to impedance mismatch, with most electromagnetic waves being reflected by the surface and unable to penetrate the material's interior. The main role of MXene nanosheets is to provide a conductive network and structural framework, enhancing the material's physical shielding performance. Polypyrrole (PPy), as the adhesive layer, can regulate the interfacial interaction between MXene nanosheets and NiO, suppressing MXene stacking and forming porous or layered structures, enhancing multiple reflections and scattering of electromagnetic waves, while also strengthening the adhesion between the composite material and the substrate. NiO, being magnetic, can compensate for the dielectric loss of MXene through hysteresis loss and natural resonance, forming a dielectric-magnetic synergistic effect, improving impedance matching, and broadening the absorption bandwidth. The morphology of NiO nanowires also helps to construct a three-dimensional network in the composite material, enhancing multiple reflections and scattering.

[0027] The MXene-NiO-PPy ternary composite microwave absorbing material prepared by adopting the above scheme can effectively solve the problem of electromagnetic wave pollution, improve electromagnetic compatibility, ensure green development of the environment, adapt to diverse needs, and has the characteristics of structural stability, which is conducive to large-scale production and application.

[0028] In summary, this application has the following beneficial effects: 1. The MXene-NiO-PPy ternary composite microwave absorbing material prepared in this application can effectively solve the problem of electromagnetic wave pollution, improve electromagnetic compatibility, ensure green development of the environment, adapt to diverse needs, and has the characteristics of structural stability, which is conducive to large-scale production and application.

[0029] 2. This application organically combines a conductive MXene substrate, a PPy conductive polymer interface layer, and magnetic NiO nanowires, simultaneously modulating dielectric and magnetic properties, providing a new material system for achieving efficient broadband microwave absorption. MXene, as the substrate material, has the advantage of extremely high electrical conductivity and abundant surface functional groups. High conductivity tends to generate strong dielectric loss, but excessively high conductivity can lead to impedance mismatch, with most electromagnetic waves being reflected by the surface and unable to penetrate the material's interior. The main role of MXene is to provide a conductive network and structural framework, improving the material's physical shielding performance. Polypyrrole (PPy), as the adhesive layer, can regulate the interfacial interaction between MXene and NiO, suppressing MXene stacking and forming porous or layered structures, enhancing multiple reflections and scattering of electromagnetic waves, while also strengthening the adhesion between the composite material and the substrate. NiO, being magnetic, can compensate for the dielectric loss of MXene through hysteresis loss and natural resonance, forming a dielectric-magnetic synergistic effect, improving impedance matching, and broadening the absorption bandwidth. The morphology of the NiO nanowires also helps to construct a three-dimensional network in the composite material, enhancing multiple reflections and scattering. Attached Figure Description

[0030] Figure 1 The image shows a scanning electron microscope image of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 1. Figure 2 This is a scanning electron microscope image of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 4; Figure 3 The image shows a scanning electron microscope image of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 5. Figure 4 The image shows a scanning electron microscope image of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 6. Figure 5 Infrared images of the MXene-NiO-PPy ternary composite absorbing materials prepared in Examples 1 and 4-6 (wherein, the gray line represents the MXene-NiO-PPy ternary composite absorbing material prepared in Example 1, the red line represents the MXene-NiO-PPy ternary composite absorbing material prepared in Example 4, the blue line represents the MXene-NiO-PPy ternary composite absorbing material prepared in Example 5, and the green line represents the MXene-NiO-PPy ternary composite absorbing material prepared in Example 6); Figure 6 The image shows the three-dimensional reflection loss of the MXene-NiO-PPy ternary composite absorbing material prepared in Example 1. Figure 7The above is a contour plot of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 1. Figure 8 The image shows the three-dimensional reflection loss of the MXene-NiO-PPy ternary composite absorbing material prepared in Example 4. Figure 9 The above is a contour plot of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 4. Figure 10 The image shows the three-dimensional reflection loss of the MXene-NiO-PPy ternary composite absorbing material prepared in Example 5. Figure 11 The above is a contour plot of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 5. Figure 12 The image shows the three-dimensional reflection loss of the MXene-NiO-PPy ternary composite absorbing material prepared in Example 6. Figure 13 The image shows the contour plot of the MXene-NiO-PPy ternary composite microwave absorbing material prepared in Example 6. Detailed Implementation

[0031] The technical solution of this application is further illustrated by specific embodiments below. These specific embodiments do not represent a limitation on the scope of protection of this application. Any non-essential modifications and adjustments made by others based on the concept of this application still fall within the scope of protection of this application.

[0032] Unless otherwise specified, the experimental methods shown in the following examples are conventional methods. All reagents and materials shown are commercially available products.

[0033] Lithium fluoride: Wuhan Jixin Yibang Biotechnology Co., Ltd., CAS NO: 7789-24-4; Aluminum titanium carbide powder (Ti3AlC2): Jinzhou Haixin Metal Materials Co., Ltd., CAS NO: 196506-01-1, Grade: ZJHX; Pyrrole monomer (Py): Zaozhuang Jiuxing Biotechnology Co., Ltd., FEMA: 3386, CAS: 109-97-7; NiCl2·6H2O: Jilin Jien Nickel Industry Co., Ltd., 99% purity; Ethylene glycol: Shandong Binteng Chemical Co., Ltd. CAS107-21-1, Product No.: 55; Sodium oxalate: Wujiang Jinjin Light Chemical Co., Ltd., Product No.: 546354, Content > 99%.

[0034] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0035] Example 1 A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: Synthesis of S1 MXene: 2.0 g of lithium fluoride was dissolved in 40 mL of 9 mol / L hydrochloric acid and stirred at room temperature for 30 min to obtain a LiF / HCl mixture; 2.0 g of aluminum titanium carbide powder was slowly added to the LiF / HCl mixture and stirred at 35 °C for 48 h. The mixture after reaction was centrifuged at 3500 rpm for 10 min to remove the supernatant and obtain precipitate A. Three times the volume of deionized water was added to precipitate A, and the mixture was sonicated at 500 W for 10 min and centrifuged at 3500 rpm for 10 min. Then, three times the volume of anhydrous ethanol was added to precipitate A for intercalation, and the mixture was sonicated at 500 W for 60 min and centrifuged at 3500 rpm for 10 min. The ethanol intercalation step was repeated three times to ensure the separation of MXene. The precipitate was collected to obtain an MXene dispersion. (2) Preparation of PPy-MXene composite material The mass ratio of Py to MXene nanosheets is 0.25:1, and the molar ratio of FeCl3·6H2O to Py is 1:1; the specific operation steps are as follows: 1.772 g of MXene nanosheets were first dispersed in 50 g of water. Then, 0.443 ml of pyrrole monomer was added to a solution containing 50 g of anhydrous ethanol. Under ice-water bath and high-speed stirring conditions, a prepared FeCl3·6H2O aqueous solution (with a mass of 1.785 g of FeCl3·6H2O) was added dropwise. The reaction was maintained in an ice-water bath for 24 hours to obtain a PPy-MXene mixture. The mixture was centrifuged at 7000 rpm for 8-10 min to remove the supernatant and obtain a PPy-MXene precipitate. The precipitate was washed twice with anhydrous ethanol and deionized water, and centrifuged at 7000 rpm for 5-10 min. The washed and centrifuged PPy-MXene precipitate was vacuum dried at 50 °C for 12 hours to obtain a PPy-MXene composite material. (3) Preparation of NiO nanowires: 32 mL of ethylene glycol and 18 mL of deionized water were mixed, and 0.47 g of NiCl2·6H2O was added to dissolve the mixture. 0.12 g of sodium oxalate was added and mixed. The mixture was then transferred to a high-pressure reactor and heated at 200 °C for 24 hours. After the heating treatment, the mixture was naturally cooled. The resulting product was centrifuged at 7000 rpm for 5 min to obtain precipitate B. Anhydrous ethanol was added for washing, and the supernatant was removed by centrifugation at 7000 rpm for 5 min. This process was repeated twice. The washed precipitate B was vacuum dried at 60 °C for 24 h to obtain NiO nanowire precursor. The NiO nanowire precursor was calcined in air at 400 °C for 2 hours to obtain polycrystalline NiO nanowires. (4) Preparation of MXene-NiO-PPy composite material PPy-MXene composite material and NiO nanowires were prepared at a mass ratio of 1.25:1.

[0036] The specific operation steps are as follows: 1.25g of PPy-MXene composite material is dispersed in 5mL of deionized water, ultrasonically dispersed at 100W for 5min, 1g of NiO nanowires from step S3 is added, and ultrasonically treated at 100W for 50min for mixing, controlling the ultrasonic temperature to not exceed 40℃, and then filtered and dried to obtain the MXene-NiO-PPy ternary composite microwave absorbing material.

[0037] The FeCl3·6H2O aqueous solution was prepared by mixing 1.785g of FeCl3·6H2O oxidant into 10ml of deionized water.

[0038] Example 2 A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: The difference from Example 1 is that: Synthesis of S1 MXene nanosheets: 1.5 g of lithium fluoride was dissolved in 35 mL of 9 mol / L hydrochloric acid and stirred at room temperature for 30 min to obtain a LiF / HCl mixture; 1.5 g of aluminum titanium carbide powder was slowly added to the LiF / HCl mixture, and the mixture was stirred at 35 °C for 36 h. The reaction mixture was centrifuged at 3500 rpm for 5 min to remove the supernatant and obtain precipitate A. Three times the volume of deionized water was added to precipitate A, and the mixture was sonicated at 500 W for 10 min, centrifuged at 3500 rpm for 5 min, and then three times the volume of anhydrous ethanol was added to precipitate A for intercalation. The mixture was sonicated at 500 W for 50 min, centrifuged at 3500 rpm for 5 min, and the ethanol intercalation step was repeated 5 times to ensure the separation of MXene. The precipitate was collected to obtain an MXene nanosheet dispersion. (2) Preparation of PPy-MXene composite material 1.772 g of MXene nanosheets were first dispersed in 40 g of water. Then, 0.443 ml of pyrrole monomer was added to a solution containing 60 g of anhydrous ethanol. Under ice-water bath and high-speed stirring conditions, a prepared FeCl3·6H2O aqueous solution (containing 1.785 g of FeCl3·6H2O) was added dropwise. The reaction was maintained in an ice-water bath for 24 hours, resulting in a PPy-MXene mixture. The mixture was centrifuged at 7000 rpm for 8 min to remove the supernatant. The PPy-MXene precipitate was washed twice with anhydrous ethanol and deionized water, and centrifuged at 7000 rpm for 5 min. The centrifuged precipitate B was then vacuum-dried at 40 °C for 10 hours to obtain the PPy-MXene composite material. (3) Preparation of NiO nanowires: 30 mL of ethylene glycol and 18 mL of deionized water were mixed, and 0.4 g of NiCl2·6H2O was added to dissolve the mixture. 0.1 g of sodium oxalate was added and mixed. The mixture was then transferred to a high-pressure reactor and heated at 180 °C for 24 hours. After the heating treatment, the mixture was naturally cooled. The resulting product was centrifuged at 5000 rpm for 10 min to obtain precipitate B. Anhydrous ethanol was added for washing, and the supernatant was removed by centrifugation at 7000 rpm for 5 min. This process was repeated twice. The washed precipitate B was vacuum dried at 50 °C for 24 hours to obtain NiO nanowire precursor. The NiO nanowire precursor was calcined at 350 °C in air atmosphere for 3 hours to obtain polycrystalline NiO nanowires. (4) Preparation of MXene-NiO-PPy composite material: Ultrasonic treatment conditions: 80W, 40min.

[0039] Example 3 A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: The difference from Example 1 is that: Synthesis of S1 MXene: 2.5 g of lithium fluoride was dissolved in 45 mL of 9 mol / L hydrochloric acid and stirred at room temperature for 30 min to obtain a LiF / HCl mixture; 3 g of aluminum titanium carbide powder was slowly added to the LiF / HCl mixture, and the mixture was stirred at 35 °C for 48 h. The reaction mixture was centrifuged at 3500 rpm for 10 min to remove the supernatant and obtain precipitate A. Three times the volume of deionized water was added to precipitate A, and the mixture was sonicated at 500 W for 10 min, centrifuged at 3500 rpm for 10 min, and then three times the volume of anhydrous ethanol was added to precipitate A for intercalation. The mixture was sonicated at 500 W for 70 min, centrifuged at 3500 rpm for 10 min, and the ethanol intercalation step was repeated twice to ensure the separation of MXene. The precipitate was collected to obtain an MXene nanosheet dispersion. (2) Preparation of PPy-MXene composite material 1.772 g of MXene nanosheets were first dispersed in 60 g of water. Then, 0.443 ml of pyrrole monomer was added to a solution containing 40 g of anhydrous ethanol. Under ice-water bath and high-speed stirring conditions, a prepared FeCl3·6H2O aqueous solution (containing 1.785 g of FeCl3·6H2O) was added dropwise. The reaction was maintained in an ice-water bath for 24 hours, resulting in a PPy-MXene mixture. The mixture was centrifuged at 7000 rpm for 10 min to remove the supernatant. The PPy-MXene precipitate was washed twice with anhydrous ethanol and deionized water, and centrifuged at 7000 rpm for 10 min. The centrifuged precipitate B was then vacuum-dried at 40 °C for 12 hours to obtain the PPy-MXene composite material. (3) Preparation of NiO nanowires: 34 mL of ethylene glycol and 20 mL of deionized water were mixed, and 0.5 g of NiCl2·6H2O was added to dissolve the mixture. 0.15 g of sodium oxalate was added and mixed. The mixture was then transferred to a high-pressure reactor and heated at 210 °C for 24 hours. After the heating treatment, the mixture was naturally cooled. The resulting product was centrifuged at 7000 rpm for 5 min to obtain precipitate B. Anhydrous ethanol was added for washing, and the supernatant was removed by centrifugation at 7000 rpm for 5 min. This process was repeated twice. The washed precipitate B was vacuum dried at 70 °C for 18 hours to obtain the NiO nanowire precursor. The NiO nanowire precursor was calcined at 450 °C in air atmosphere for 1 hour to obtain polycrystalline NiO nanowires. (4) Preparation of MXene-NiO-PPy composite material: Ultrasonic treatment conditions: 120W, 60min.

[0040] Example 4 A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: The difference from Example 1 is that: The Py and MXene nanosheets were prepared at a mass ratio of 0.5:1, and the PPy-MXene composite material and NiO nanowires were prepared at a mass ratio of 1.5:1. The specific addition amounts were: 0.5g Py, 1g MXene nanosheets, 1.5g PPy-MXene composite material, and 1g NiO nanowires.

[0041] Example 5 A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: The difference from Example 1 is that: The Py and MXene nanosheets were prepared at a mass ratio of 0.75:1, and the PPy-MXene composite material and NiO nanowires were prepared at a mass ratio of 1.75:1. The specific addition amounts were: 0.75g Py, 1g MXene nanosheets, 1.75g ​​PPy-MXene composite material, and 1g NiO nanowires.

[0042] Example 6 A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, employing the following technical solution: The difference from Example 1 is that: The Py and MXene nanosheets were prepared at a mass ratio of 1:1, and the PPy-MXene composite material and NiO nanowires were prepared at a mass ratio of 2:1. The specific addition amounts were: 1g Py, 1g MXene nanosheets, 2g PPy-MXene composite material, and 1g NiO nanowires.

[0043] Comparative Example Comparative Example 1 Similar to Example 5, except that in step S2, MXene nanosheets are not added, and pyrrole is polymerized only in a water / ethanol mixed solvent to obtain pure PPy. Then, PPy and NiO nanowires are ultrasonically dispersed, filtered and dried to prepare NiO-PPy binary composite material.

[0044] Comparative Example 2 Similar to Example 5, except that no pyrrole monomer is added, and MXene is only dispersed and centrifuged in the same way. Specifically, the MXene-NiO composite material is prepared through steps S1, S3 and S4.

[0045] Comparative Example 3 Similar to Example 5, except that in step S4, the composite with NiO nanowires is not performed. Instead, the PPy-MXene binary composite material is prepared through steps S1 and S2.

[0046] Comparative Example 4 Similar to Example 5, except that the pure PPy powder, MXene dispersion, and NiO nanowires are physically mixed according to the proportions of Example 1 and sonicated for 50 minutes, instead of in-situ polymerization-step composite.

[0047] Comparative Example 5 Similar to Example 5, except that in step S2, the mass ratio of Py to MXene nanosheets is 1.5:1, and the specific amount added is 1.5g of Py and 1g of MXene nanosheets.

[0048] Comparative Example 6 Similar to Example 5, except that the anhydrous ethanol intercalation and ultrasonication steps are omitted in step S1.

[0049] Comparative Example 7 Similar to Example 5, except that the MXene dispersion obtained in step S1 is calcined at 400°C for 2 hours under an Ar atmosphere before being used for compounding.

[0050] Comparative Example 8 Similar to Example 5, except that in step S2, APS is used instead of FeCl3·6H2O as the oxidant for Py.

[0051] Comparative Example 9 Similar to Example 5, except that the absorbing material is the pure NiO nanowires prepared in step S3.

[0052] Performance testing The MXene-NiO-PPy ternary composite microwave absorbing materials prepared by the methods of Examples 1-6 and Comparative Examples 1-9 were subjected to performance tests on minimum reflection loss (RLmin, dB), effective absorption bandwidth (EAB, GHz), matching thickness (d, mm), and conductivity (σ, S / cm). The results are shown in Table 1.

[0053] Table 1 Performance Measurement Results serial number Electrical conductivity (S / cm) <![CDATA[RL min (dB)]]> EAB(GHz) Matching thickness (mm) Example 1 51.4 -4.46 16.00 7.7 Example 2 52.3 -5.72 16.00 7.8 Example 3 55.4 -4.98 16.00 7.7 Example 4 68.5 -26.10 16.00 7.5 Example 5 62.3 -36.8 16.16 7.6 Example 6 55.1 -11.15 6.96 5.6 Comparative Example 1 8.2 -15.8 3.5 4 Comparative Example 2 135 -10.5 2 4.5 Comparative Example 3 95.7 -30.5 5.2 2.8 Comparative Example 4 40.1 -21.2 4.5 3.2 Comparative Example 5 55.1 -11.15 6.96 5.6 Comparative Example 6 28.9 -19.5 3.8 3.5 Comparative Example 7 14.7 -23.1 4.2 3 Comparative Example 8 30.5 -25.9 5.5 3.3 Comparative Example 9 ＜0.01 -10.5 1 3 The MXene-NiO-PPy ternary composite microwave absorbing materials prepared in Examples 1 and 4-6 were tested using scanning electron microscopy. The scanning electron microscope images are shown below. Figure 1-4 As shown, PPy is tightly bonded to MXene nanosheets, and NiO is uniformly dispersed between the layers.

[0054] The MXene-NiO-PPy ternary composite microwave absorbing materials prepared in Examples 1 and 4-6 were tested using infrared spectroscopy. The infrared spectra are shown below. Figure 5 As shown, it can be seen that 1640cm -1 The peak at 3247 cm⁻¹ is related to the vibration of Ti-O bonds, indicating the presence of -O functional groups on the MXene surface. Due to the interfacial bonding effect, PPy and MXene are covalently bonded, causing Ti-O to shift to higher frequencies; -1 The peak at 1303 cm⁻¹ is related to the stretching vibration of the NH bond. The OH group of MXene and the NH group of PPy are bonded through hydrogen bonds, causing the peak position to shift to lower frequencies and the peak shape to broaden. The peak at 1551 cm⁻¹ is related to the bending vibration of the CH surface. -1 The peak at 1026 cm⁻¹ is related to the skeletal vibration of the C=C bond, indicating that the pyrrole ring has a conjugated structure; -1 The appearance of a CO-Ti bond vibration peak at 738 cm⁻¹ confirms the covalent bonding between MXene and PPy; -1 The presence of a weak Ti-O-Ni bond absorption peak at 440 cm⁻¹ confirms the successful bonding of the ternary material; -1 The peak at the point is related to the lattice vibration peak of Ni-O; analysis of the infrared spectrum shows that there are abundant functional groups on the MXene-NiO-PPy surface.

[0055] As shown in Table 1, the performance test results indicate that in Examples 1-3, the Py to MXene nanosheets were prepared at a mass ratio of 1:1, and the PPy-MXene composite material and NiO nanowires were prepared at a mass ratio of 2:1, although the specific operating conditions differed, the performance differences were not significant. The MXene-NiO-PPy nanosheets prepared in Example 1... 0.25Three-dimensional reflection loss diagrams and contour plots of ternary composite microwave absorbing materials (Py:MXene = 0.25:1, PPy-MXene:NiO nano = 1.25:1) at 2-18 GHz are shown below. Figure 6 and Figure 7 As shown, MXene-NiO-PPy 0.25 At a thickness of 7.70 mm, the RLmin reaches -4.46 dB, and the effective absorption bandwidth at this thickness is 16.00 GHz, demonstrating the effectiveness of MXene-NiO-PPy. 0.25 It has certain wave-absorbing properties.

[0056] Examples 4-6: The preparation conditions for the MXene-NiO-PPy ternary composite microwave absorbing materials are the same as in Example 1, but the proportions of MXene-NiO-PPy materials are different, wherein: MXene-NiO-PPy prepared in Example 5 0.75 (Py:MXene = 0.75:1, PPy-MXene:NiO nanoparticles = 1.75:1) exhibits the best overall performance, achieving extremely strong absorption intensity (-36.80 dB) and an extremely wide effective absorption bandwidth (16.16 GHz), covering almost the entire test frequency band. Its moderate conductivity indicates an optimal balance between dielectric and magnetic losses, meaning the ratio of PPy-MXene to NiO nanoparticles achieves optimal impedance matching. Although not the thinnest, this is a reasonable trade-off for achieving ultra-wideband strong absorption. The prepared MXene-NiO-PPy... 0.75 Three-dimensional reflection loss diagrams and contour plots of ternary composite absorbing materials in the 2-18 GHz range, such as... Figure 10 and Figure 11 As shown.

[0057] MXene-NiO-PPy prepared in Example 4 0.5 (Py:MXene = 0.5:1, PPy-MXene:NiO nano = 1.5:1): Excellent performance, but slightly inferior to Example 5; its absorption intensity (-26.10dB) is sufficiently strong, and it also has the same ultrawide bandwidth; the prepared MXene-NiO-PPy 0.5 Three-dimensional reflection loss diagrams and contour plots of ternary composite absorbing materials in the 2-18 GHz range, such as... Figure 8 and Figure 9 As shown.

[0058] MXene-NiO-PPy prepared in Example 6 1.0(Py:MXene = 1:1, PPy-MXene:NiO nano = 2:1): Performance showed a significant decline. Although the thickness was thinner, its absorption intensity (-11.15dB) barely passed the acceptable level, and the bandwidth was significantly narrowed (6.96GHz). This is because excessive PPy leads to an excessively high overall dielectric constant of the composite material. Electromagnetic waves are largely reflected at the material surface and are difficult to penetrate and be consumed, severely disrupting impedance matching. This proves that "the higher the PPy content, the better" is a misconception, and there exists an optimal threshold. The prepared MXene-NiO-PPy... 1.0 Three-dimensional reflection loss diagrams and contour plots of ternary composite absorbing materials in the 2-18 GHz range, such as... Figure 12 and Figure 13 As shown.

[0059] The performance results from Examples 1-6 show that the reflectivity of the MXene-NiO-PPy ternary composite microwave absorbing material first increases and then decreases with the increase of PPy content. It can be seen that the MXene-NiO-PPy0.75 ternary composite material has the highest reflectivity, with RLmin reaching -36.80dB. It can absorb more than 99.9% of electromagnetic waves and has a suitable thickness while ensuring high absorption rate, thus exhibiting excellent microwave absorption performance.

[0060] Comparative Example 1 (the difference is the absence of MXene), Comparative Example 2 (the difference is the absence of PPy), and Comparative Example 3 (the difference is the absence of NiO) clearly demonstrate the necessity of the ternary synergistic effect due to the absence of components. The performance of any binary system (Comparative Examples 1, 2, and 3) cannot be compared with that of the ternary system (Example 5). Comparative Examples 1-3 have serious shortcomings in terms of absorption intensity and bandwidth.

[0061] Comparative Example 4 (the difference being that MXene, PPy powder, and NiO nanowires were physically mixed): its performance was far inferior to that of Example 5, demonstrating that in-situ chemical polymerization can construct a tighter heterojunction interface and generate stronger interfacial polarization, which cannot be achieved by physical mixing.

[0062] Comparative Example 5 (the difference lies in the excessive PPy): Compared with Examples 5 and 6, it is shown that the ratio of Py:MXene = 1.5:1 leads to performance degradation. Excessive PPy results in an excessively high overall dielectric constant of the composite material. Electromagnetic waves are largely reflected on the material surface and are difficult to penetrate and be consumed, which seriously damages impedance matching. This again proves that "the higher the PPy content, the better" is a misconception and there is an optimal threshold.

[0063] Comparative Example 6 (the difference being the absence of the ethanol intercalation step): performance was significantly reduced, demonstrating that a complete MXene stripping process is fundamental to achieving high performance. Unstripped MXenes were severely stacked and could not provide an effective conductive network and interface.

[0064] Comparative Example 7 (the difference lies in calcined MXene): the conductivity decreased sharply and the performance deteriorated, proving that the high conductivity of MXene is the core factor contributing to dielectric loss, and calcination and oxidation cause it to lose this advantage.

[0065] Comparative Example 8 (the difference lies in the different oxidants): FeCl3 is far superior to APS as both an oxidant and a dopant, resulting in better conductivity of the prepared PPy and ultimately superior performance of the composite material.

[0066] The performance of pure NiO in Comparative Example 9 was far inferior to that of all the embodiments and comparative examples.

[0067] The above performance tests demonstrate that this technical solution overcomes the shortcomings of existing technologies and provides a simple, low-cost, and environmentally friendly method for preparing MXene-NiO-PPy ternary composite microwave absorbing materials. It constructs a composite material with abundant heterogeneous interfaces and porous micro / nano structures, achieving synergistic effects of dielectric loss, magnetic loss, and interfacial polarization loss. Ultimately, it obtains lightweight, efficient, and wideband microwave absorption performance, achieving extremely strong absorption intensity (-36.80dB) and an extremely wide effective absorption bandwidth (16.16GHz), covering almost the entire test frequency band, as well as excellent performance with moderate conductivity.

[0068] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the present invention, they are protected by patent law.

Claims

1. A method for preparing an MXene-NiO-PPy ternary composite microwave absorbing material, characterized in that, The following technical solution is adopted: Synthesis of S1 MXene nanosheets: A uniform dispersion of MXene nanosheets was prepared by etching aluminum titanium carbide powder with a LiF / HCl mixture and then ultrasonically exfoliating. Preparation of S2 PPy-MXene composite material: MXene nanosheets were dispersed in a solution of water and anhydrous ethanol, pyrrole monomer was added, and FeCl3·6H2O aqueous solution was added dropwise under ice-water bath and high-speed stirring conditions. After the reaction was completed, the PPy-MXene mixture was centrifuged to obtain precipitate B. Precipitate B was washed alternately with anhydrous ethanol and deionized water, and the washed precipitate B was vacuum dried to obtain the PPy-MXene composite material. Preparation of S3 NiO nanowires: Nickel monoxide nanowires were prepared by hydrothermal method combined with calcination, using NiCl2·6H2O as the nickel source and sodium oxalate as the precipitant. Preparation of S4 MXene-NiO-PPy composite material: The PPy-MXene composite material from step S2 is dispersed in deionized water and ultrasonically dispersed to achieve uniform dispersion. Then, NiO nanowires from step S3 are added, and after ultrasonic dispersion treatment, the mixture is filtered and dried to obtain the MXene-NiO-PPy ternary composite microwave absorbing material.

2. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 1, characterized in that, Step S1 specifically includes: slowly adding 1.5-3 parts of aluminum titanium carbide powder to a LiF / HCl mixture, stirring and reacting at 35°C for 36-48 hours, centrifuging at 3500 rpm for 5-10 min to obtain precipitate A, adding 3 times the volume of deionized water to precipitate A, ultrasonicating and centrifuging at 3500 rpm for 5-10 min, then adding 3 times the volume of anhydrous ethanol to precipitate A, performing intercalation ultrasonicating and centrifuging at 3500 rpm for 5-10 min, repeating the ethanol intercalation step 2-5 times, and collecting the precipitate to obtain MXene nanosheets.

3. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 1, characterized in that, Step S2 specifically includes: dispersing MXene nanosheets in 40-60 parts of water, adding Py to a solution containing 40-60 parts of anhydrous ethanol, and then adding FeCl3·6H2O aqueous solution dropwise under ice-water bath and high-speed stirring conditions, maintaining the reaction in an ice-water bath for 24 hours; obtaining a PPy-MXene mixture, centrifuging to obtain a PPy-MXene precipitate, washing twice with anhydrous ethanol and deionized water, centrifuging at 7000 rpm for 5-10 minutes, and vacuum drying the washed and centrifuged PPy-MXene precipitate at 40-60℃ for 10-12 hours to obtain a PPy-MXene composite material.

4. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 3, characterized in that, In step S2, the mass ratio of Py to MXene nanosheets is (0.25-1):1; and the molar ratio of oxidant FeCl3·6H2O to pyrrole monomer in step S2 is 1:

1.

5. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 3, characterized in that, In step S2, the FeCl3·6H2O aqueous solution is prepared by mixing 1.5-2.0 parts of FeCl3·6H2O oxidant into 10 parts of deionized water.

6. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 1, characterized in that, Step S3 specifically includes: mixing 30-34 parts of ethylene glycol with 18-20 parts of deionized water, then adding 0.4-0.5 parts of NiCl2·6H2O and mixing, then adding 0.1-0.15 parts of sodium oxalate and mixing, transferring to a high-pressure reactor, reacting at 180-210℃ for 18-24 hours, heating and then naturally cooling, centrifuging to obtain precipitate B, washing precipitate B with ethanol 2-3 times and centrifuging again, drying the centrifuged precipitate B under vacuum to obtain NiO nanowire precursor, calcining the NiO nanowire precursor in air atmosphere to obtain NiO nanowires.

7. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 6, characterized in that, In step S3, precipitate B is washed with ethanol 2-3 times, then centrifuged at 5000-7000 rpm for 5-10 min. The washed precipitate B is then vacuum dried at 50-70℃ for 18-24 hours to obtain NiO nanowire precursor. The NiO nanowire precursor is then calcined in air at 350-450℃ for 1-3 hours to obtain polycrystalline NiO nanowires.

8. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 1, characterized in that, In step S4, PPy-MXene composite material and NiO nanowires are prepared at a mass ratio of (1.25-2):

1.

9. The preparation method of the MXene-NiO-PPy ternary composite microwave absorbing material according to claim 1, characterized in that, In step S4, the PPy-MXene composite material and deionized material are prepared at a mass ratio of (1.25-2):

5.

10. A ternary composite microwave absorbing material of MXene-NiO-PPy, characterized in that: It is prepared by the preparation method described in any one of claims 1-9.

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