A multi-stage heterogeneous composite based on cf@mxene@nanomagnetic particles and a preparation method thereof

Abstract

This application discloses a hierarchical heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles and its preparation method, specifically relating to the field of thermally conductive and electromagnetic wave absorbing composite materials. This hierarchical heterogeneous composite material is formed by encapsulating and curing carbon fibers, MXene nanosheets, and magnetic nanoparticles in a polymer matrix. The carbon fibers are arranged vertically in an array structure within the composite material; MXene nanosheets are loaded onto the carbon fiber surface to form a wrinkled layer structure; and magnetic nanoparticles are loaded onto the surface of MXene or carbon fibers. The MXene nanosheets and magnetic nanoparticles form a hierarchical heterogeneous composite structure on the carbon fiber surface. This invention provides a hierarchical heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles and its preparation method. This hierarchical heterogeneous composite material integrates electromagnetic absorption, efficient thermal conductivity, and mechanical reinforcement into a single material, better meeting the urgent needs of modern high-end electronic equipment for lightweight and multifunctional materials.

Description

Technical Field

[0001] This application relates to the field of thermally conductive and electromagnetic wave absorbing composite materials, and in particular to a multi-level heterogeneous composite material based on CF@MXene@ nanomagnetic particles and its preparation method. Background Technology

[0002] With the rapid development of 5G, artificial intelligence servers, electric vehicles, aerospace equipment, and radar communication systems, electronic devices are continuously evolving towards higher power density, higher integration, and miniaturization. This trend leads to more significant electromagnetic radiation and heat accumulation problems during the operation of electronic devices. Electromagnetic interference can not only cause signal distortion and system malfunctions, but may also lead to the failure of critical electronic components and even safety risks. At the same time, the continuous accumulation of localized heat can accelerate device aging and reduce operational stability, and in severe cases, even cause thermal runaway. Therefore, developing structural-functional integrated materials that simultaneously possess efficient electromagnetic wave absorption capabilities and good thermal management performance has become an important research direction in the field of electronic equipment.

[0003] Carbon fiber is a structural material with high strength, high specific modulus, and excellent electrical and thermal conductivity, widely used in aerospace, automotive, and high-performance composite materials. In recent years, the application of carbon fiber in electromagnetic shielding, thermally conductive composites, and functional structural materials has gradually attracted attention. Its high aspect ratio and continuous conductive network are beneficial for forming stable electromagnetic loss paths and heat conduction channels. However, some limitations still exist in practical applications. For example, traditional carbon fiber reinforced composites are difficult to recycle effectively after their service life ends, and large amounts of waste materials are usually disposed of through landfill or incineration, easily leading to resource waste and environmental pollution.

[0004] To improve resource utilization efficiency, researchers have proposed preparing recycled carbon fibers through methods such as pyrolysis or chemical recycling, and attempting to reuse them in functional composite material systems. However, during the recycling process, the surface dimensional integrity and surface structure of carbon fibers are often damaged, such as increased surface defects, shortened fiber length, and reduced interfacial activity. This leads to a decline in the mechanical, electrical, and thermal properties of carbon fibers in composite materials, thus limiting their high-value-added utilization.

[0005] To this end, Chinese invention patent publication number CN113174751B discloses a multi-level heterogeneous composite material, its preparation method, and its application. In this scheme, flexible cotton fabric is used as a substrate, MXene nanosheets are sequentially coated onto it, followed by in-situ growth of sheet-like Co-MOF, and finally, nitrogen-doped carbon nanotubes (Co-NCNTs) are grown via pyrolysis catalysis, forming a "sandwich"-like multi-level heterogeneous three-dimensional network structure (Co-NCNTs@MXene@CF). The conductive layer of MXene is used to transmit induced current, and the three-dimensional network constructed using Co-NCNTs provides numerous heterogeneous interfaces to generate polarization loss and optimize impedance matching, causing electromagnetic waves to undergo multiple reflections and scatterings.

[0006] However, the above-mentioned solution has the following drawbacks in practical applications: 1. The sole objective of this solution is to improve electromagnetic absorption performance, such as minimum reflection loss RL and effective absorption bandwidth EAB. However, modern electronic devices such as 5G base stations, AI servers, and electric vehicles simultaneously face the dual challenges of electromagnetic interference (EMI) and heat accumulation, requiring materials to possess wave absorption, thermal conductivity, and structural load-bearing capacity. 2. This composite material is a three-dimensional growth structure based on a planar substrate, which limits impedance matching and functional scalability, making it difficult to introduce magnetic losses and relying solely on the dielectric losses of Co-NCNTs derived from Co-MOF. 3. Cotton fabric is a disposable, low-value material that cannot be recycled to reduce costs or achieve green manufacturing. The insulating properties of cotton fabric mean that its interface bonding with MXene relies on physical impregnation, making it impossible to form strong covalent / ionic bonds. Furthermore, the low mechanical strength of cotton fabric prevents it from being used as a structural reinforcement, limiting its application to scenarios with low strength requirements, such as flexible wave-absorbing coatings, and hindering its expansion into fields with high structural load-bearing requirements, such as aerospace and automotive.

[0007] Therefore, under the premise of taking into account the sustainable use of resources, how to construct a carbon fiber composite system with stable structure and multifunctional synergistic effect remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] This invention provides a multi-level heterogeneous composite material based on CF@MXene@ nanomagnetic particles and its preparation method. This multi-level heterogeneous composite material innovatively integrates the three major requirements of electromagnetic absorption, efficient thermal conductivity and mechanical reinforcement into one material, which better meets the urgent needs of modern high-end electronic equipment for lightweight and multifunctional materials.

[0009] The objective of this invention is achieved through the following technical solution: A multi-level heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles is formed by encapsulating and curing carbon fibers, MXene nanosheets and magnetic nanoparticles in a polymer matrix; In this composite material, carbon fibers are arranged vertically to form an array structure, MXene nanosheets are loaded on the surface of carbon fibers to form a wrinkled layer structure, magnetic nanoparticles are loaded on the surface of MXene or carbon fibers, and MXene nanosheets and magnetic nanoparticles form a multi-level heterogeneous composite structure on the surface of carbon fibers.

[0010] Preferably, the carbon fiber is in the form of chopped fiber or continuous fiber, and the fiber length is preferably 0.5–5 mm.

[0011] As a preferred option, the general formula for MXene nanosheets is M n+1 X n T x Where n = 1, 2, 3 or 4, M is one of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta or W; X is carbon, nitrogen or CN.

[0012] Preferably, the general formula of MXene nanosheets is Ti3C2T. x T x It is at least one of -OH, -O, and -F.

[0013] Preferably, the magnetic nanoparticles can be selected from at least one of NiFe2O4, Fe3O4, CoFe2O4, and MnFe2O4.

[0014] Preferably, the polymer matrix is ​​selected from any one of silicone rubber, epoxy resin, and polyurethane.

[0015] Preferably, the chemical formula of this multi-level heterogeneous composite material is CF@Ti3C2T. x @NiFe2O4@PDMS.

[0016] This invention also provides a method for preparing a hierarchical heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles, the method comprising the following steps: (1) Preparation of MXene nanosheets: MXene nanosheets were prepared by etching the MAX phase precursor with LiF-HCl and then exfoliating. The MXene nanosheet dispersion was obtained by ultrasonic exfoliation after etching. Ti3C2T prepared by this method... x The resulting product is a mixture of three end groups: -OH, -O, and -F. The proportions of these three functional groups vary among different MXene nanosheets.

[0017] (2) Surface modification of carbon fiber: Carbon fiber is acid-treated to obtain short carbon fiber; the surface of the short carbon fiber is rough and rich in oxygen functional groups; the carbon fiber is dispersed in MXene nanosheet dispersion. After surface modification by APTES, the carbon fiber is positively charged and combines with the negatively charged MXene through electrostatic self-assembly to form MXene@CF structure.

[0018] The specific steps for cleaning or surface oxidation of carbon fibers are as follows: Step A: Desizing and Cleaning. Place the carbon fiber in acetone, ethanol or deionized water and ultrasonically clean it at 25℃-80℃ for 30-120 minutes to remove the sizing agent and impurities on the surface; then vacuum dry it at 60℃-100℃ for 6-12 hours.

[0019] Step B: Acid Oxidation (Core Parameter) The cleaned carbon fibers are immersed in an oxidizing acid solution, wherein the acid solution is selected from concentrated nitric acid, concentrated sulfuric acid, or a mixture of both (volume ratio 1:1-1:3). Reaction temperature: controlled at 60℃-110℃ (preferably 80℃-90℃); Reaction time: continuous reflux or stirring for 1-6 hours (preferably 2-4 hours); Acid concentration: 65%-68% concentrated nitric acid or 95%-98% concentrated sulfuric acid by mass fraction.

[0020] Step C: After washing until the neutral reaction is complete, separate the carbon fibers by centrifugation or filtration, and wash repeatedly with deionized water until the pH of the washing solution reaches 6.5-7.5. Finally, freeze-dry or vacuum-dry.

[0021] (3) Magnetic particles load to form a hierarchical interface structure: Magnetic nanoparticles are added to the dispersion containing MXene@CF structure. The magnetic nanoparticles are adsorbed on the surface of MXene nanosheets, thereby forming a multi-level heterogeneous coating structure CF@MXene@nanomagnetic particles.

[0022] (4) Electrostatic flocking to construct a vertical array: Through the electrostatic flocking process, a high voltage electric field is applied between the upper and lower electrodes, so that the CF@MXene@ magnetic particles are vertically arranged on the elastic substrate along the direction of the electric field to form a controllable array structure.

[0023] (5) Matrix encapsulation and curing: The adjusted carbon fiber array structure is impregnated in a polymer matrix and cured to obtain a structurally stable composite material.

[0024] Preferably, in step (3), the pre-stretching degree of the substrate is set to 0%-100%; by adjusting the pre-stretching degree, the fiber array areal density is achieved at 5 mg / cm². 2 -65mg / cm 2 Precise control within the range, and the fiber volume fraction increases synchronously within the range of 2vol%-18vol% as the degree of pre-stretching increases.

[0025] Compared with the prior art, the advantages or beneficial effects of the technical solution of this application include: This application goes beyond a single wave-absorbing function, and instead proactively integrates the three major requirements of electromagnetic absorption, efficient thermal conductivity and mechanical reinforcement into a single material, which better meets the urgent needs of modern high-end electronic equipment, such as 5G base stations, AI servers and electric vehicles, for lightweight and multifunctional materials.

[0026] The solution provided by this invention greatly optimizes the impedance matching of composite materials to electromagnetic waves by constructing a vertical array, enabling more electromagnetic waves to enter the interior of the material instead of being reflected by the surface; at the same time, it provides a fast channel for heat conduction along the thickness direction, realizing anisotropic improvement of thermal conductivity.

[0027] The multi-level structure of carbon fiber-MXene-magnetic particles in the design creates numerous interfaces, significantly enhancing interfacial polarization loss. The combination of MXene (dielectric loss) and magnetic particles (magnetic loss) achieves complementarity and synergy in the loss mechanism, which is beneficial for broadening the effective absorption bandwidth (EAB).

[0028] This plan explicitly includes and uses recycled carbon fiber (rCF), which has significant environmental and cost advantages and is in line with the trends of green manufacturing and circular economy. Attached Figure Description

[0029] Figure 1 This invention describes the complete process from the preparation of MXene from MAX precursors, rCF treatment, hierarchical interface construction, electrostatic flocking to form a vertical array, encapsulation and molding, and the final implementation of a multi-loss mechanism.

[0030] Figure 2 : A macroscopic photograph of the vMNrCF@PDMS composite material prepared in this invention.

[0031] Figure 3 : Hysteresis loop diagram of NiFe2O4 and NMrCF.

[0032] Figure 4 : for Ti3C2T x Statistical distribution of particle size of NiFe2O4.

[0033] Figure 5 : A polar coordinate statistical diagram of the fiber orientation distribution in NMrCF.

[0034] Figure 6 : This is a polar coordinate statistical diagram of the fiber orientation of vMNrCF.

[0035] Figure 7 (f): Cross-sectional view of pure PDMS matrix. Figure 7 (g): Cross-sectional view of vMNrCF prepared on an unstretched substrate. Figure 7 (h): A cross-sectional view of the randomly arranged recycled carbon fiber (rCF). Figure 7 (i): Cross-sectional view of the vMNrCF structure without PDMS encapsulation. Figure 7 (j): A cross-sectional view of the NMrCF (random distribution) encapsulated structure. Figure 7 (k): Cross-sectional view of the structure after vMNrCF encapsulation. Figure 7 (l–m): The structural morphology of NMrCF(l) and vMNrCF(m) under external compression (20N).

[0036] Figure 8 The electromagnetic wave reflection loss (RL) properties of vertically aligned composite materials vMNrCF1, vMNrCF2, and vMNrCF3 with different filler contents are shown in three-dimensional and two-dimensional characteristics as a function of sample thickness and frequency.

[0037] Figure 9 : This is a finite element simulation diagram of the electromagnetic field of the vertical wave-absorbing structure of the present invention.

[0038] Figure 10 The electromagnetic energy density distributions of rCF, MNrCF, and vMNrCF in the CST model are shown.

[0039] Figure 11 : Comparison of experimental RL curve test, transmission line model (TL) calculation and CST simulation results for vMNrCF1 (10wt%, t=2.5mm).

[0040] Figure 12 : To compare the experimental and simulated RL curves of vMNrCF samples with different thicknesses.

[0041] Figure 13 : These are curves showing the variation of the loss factor α with frequency for different samples.

[0042] Figure 14 : Impedance matching characteristics of the sample Trends with frequency variation.

[0043] Figure 15 : RL-frequency curves for rCF, MNrCF series and vMNrCF series.

[0044] Figure 16 : A bar chart showing the RLmin and EABmax of rCF, MNrCF1-3, and vMNrCF1-3. Figure 17 : This is a two-dimensional comparison of the maximum effective absorption bandwidth (EABmax) and the deepest absorption value (RLmin) of the material of this invention and typical microwave absorbing materials in the literature.

[0045] Figure 18 This is a bar chart showing the thermal conductivity of different samples under room temperature conditions.

[0046] Figure 19 The thermal conductivity of the carbon fiber-MXene-magnetic particle composite material of the present invention is shown. Detailed Implementation

[0047] The following detailed description of the embodiments of this application, in conjunction with the accompanying drawings, will provide a thorough understanding of how this application uses technical means to solve technical problems and achieve corresponding technical effects, enabling its implementation. The embodiments of this application and the various features within them can be combined with each other without conflict, and all resulting technical solutions are within the protection scope of this application.

[0048] It should be clearly stated that the embodiments described below are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. Example 1

[0049] like Figure 1 As shown, this invention demonstrates the complete process from the preparation of MXene from MAX precursors, rCF treatment, hierarchical interface construction, electrostatic flocking to form a vertical array, encapsulation and molding, and the final realization of the multi-loss mechanism, as well as its core structural features and functional advantages.

[0050] Specifically, as shown in the figure, the present invention includes the following key steps and structural features: 1) Surface treatment of recycled carbon fiber (hereinafter referred to as rCF) The pretreated short-cut recycled carbon fibers (0.3-3mm) are ultrasonically cleaned in deionized water and dried at 60-100℃.

[0051] The dried rCF was immersed in a cationic surfactant solution to obtain rCF with a positively charged surface. After immersion and stirring for 0.5-6 hours, the rCF was washed and dried to obtain positively modified rCF. Cationic treatment agents such as APTES, APS, PEI, PDDA, and PDDA / APTES co-modification can be used.

[0052] 2) Preparation of MXene nanosheets MXene was prepared using Ti3AlC2MAX phase as a precursor and employing LiF-HCl, NH4HF2, or other mild etching processes. In this embodiment, LiF-HCl etching was selected.

[0053] Subsequently, ultrasonic exfoliation and centrifugation were used to obtain a suspension of MXene nanosheets with a thickness of <5 nm and a side length of 200 nm-10 µm. Due to the negative charge of the -OH, -O, and -F end groups on the surface of MXene in aqueous systems, it can bind to the positively charged rCF surface via electrostatic adsorption.

[0054] 3) Assembly of magnetic particles The magnetic particles can be: NiFe2O4, Fe3O4, CoFe2O4, MnFe2O4. These magnetic particles can be modified with APTES / APS / PEI and then bonded to MXene nanosheets.

[0055] MXene nanosheet suspension was slowly added dropwise to a positively charged rCF suspension, followed by the addition of positively charged NiFe2O4 nanoparticles. A hierarchical heterogeneous interface structure of rCF@MXene@magnetic particles was formed by electrostatic-hydrogen bonding, which can be obtained as powder by freeze-drying or low-temperature drying.

[0056] 4) Construction of array orientation structure Electrostatic flocking technology is employed: modified rCF@MXene@magnetic particle composite fibers are placed between two electrodes, and a 1-50kV high-voltage electric field is applied, causing the fibers to align along the direction of the electric field and flock onto an elastic substrate. Suitable substrates include natural rubber, SBS, SEBS, and PU.

[0057] By pre-stretching the substrate, allowing for springback, and adjusting the array density, structural parameters such as array density and tilt angle can be made adjustable. An array angle ≤30° is considered "vertical orientation".

[0058] 5) Packaging The orientation array can be further encapsulated to form a structurally stable composite material. The encapsulation material is not limited to PDMS; options include PDMS, PU, ​​PI, epoxy resin, silicone-containing, fluoroelastomers, thermoplastic rubber, curable gels, and thermoplastic plastics. The composite structure material is obtained through casting, degassing, and curing.

[0059] 6) Performance Typical performance: RLmin ≤ −60 dB; EAB ≥ 6–9 GHz; thermal conductivity ≥ 1–3 W / m·K Example 2

[0060] like Figure 2 As shown, the vertically oriented composite structure of the present invention (hereinafter referred to as vMNrCF, i.e., rCF@Ti3C2T as mentioned above) is illustrated. x A comparison of the morphology control, magnetic properties, and structural stability of NiFe2O4 (NiFe2O4) with its substrate encapsulation and stress deformation.

[0061] in, Figure 2This is a macroscopic photograph of the vMNrCF@PDMS composite material prepared in this invention. It can be seen that it has good flexibility, can bend without breaking, and is suitable for flexible structural devices.

[0062] Figure 3 The figure shows the hysteresis loops of NiFe2O4 and NMrCF, which indicate that NiFe2O4 exhibits typical ferrite magnetic behavior, while the hysteresis is significantly reduced after NMrCF is combined. This suggests that NiFe2O4 was successfully modified into the rCF@MXene structure and contributed to the overall magnetic response.

[0063] Figure 4 : for Ti3C2T x The particle size distribution diagrams of NiFe2O4 show the typical size ranges of MXene sheets and magnetic particles, respectively, proving that the magnetic particles are at the nanoscale and uniformly distributed, which is beneficial for constructing a uniform hierarchical interface structure.

[0064] Figure 5 The figure shows a polar coordinate statistical diagram of the fiber orientation distribution in NMrCF. It can be seen that the fiber orientation is randomly distributed, indicating that the fiber arrangement is irregular before the orientation process.

[0065] Figure 6 The graph shows the polar coordinates of the fiber orientation of vMNrCF. It can be seen that the fiber orientation is highly concentrated and the orientation along the vertical direction is obvious, indicating that electrostatic flocking achieves the formation of a fiber array and forms a stable directional guiding channel.

[0066] Figure 7 (f): This is a cross-sectional view of a pure PDMS matrix, showing no fiber filling and a uniform structure. Figure 7 (g): Cross-sectional view of vMNrCF prepared on an unstretched substrate, with fibers arranged in a vertical orientation. The inset is further magnified to show the fiber array structure. Figure 7 (h): A cross-sectional view of the randomly arranged recycled carbon fiber (rCF). The fibers are randomly distributed and it is difficult to form a continuous transport channel. Figure 7 (i): A cross-sectional view of the vMNrCF structure without PDMS encapsulation. It can be seen that the fibers still maintain a good array structure, indicating that the array structure is stable; the inset is a magnified view of a part. Figure 7 (j): This is a cross-sectional view of the NMrCF (randomly distributed) structure after encapsulation. The surface and internal fiber arrangement are still disordered. Figure 7 (k): This is a cross-sectional view of the structure after vMNrCF packaging. The fibers are arranged regularly along the thickness direction to form a vertical conductive path, which is beneficial for the transmission of electromagnetic waves and heat. Figure 7(l–m): The structural morphology of NMrCF (l) and vMNrCF (m) under external compression (20N). It can be seen that the array structure of vMNrCF still maintains the orientation consistency after being compressed, while the fibers in ordinary NMrCF are still randomly distributed. This indicates that the vertically arranged vMNrCF has superior structural stability and deformation adaptability.

[0067] In summary: 1) Electrostatic flocking can effectively construct a vertical fiber array structure; 2) Array structures significantly improve directional consistency, while randomly distributed structures have no directional control; 3) The array structure remains stable after encapsulation and external force application; 4) The nano-sized NiFe2O4 particles have a moderate size and are well dispersed; 5) Vertically arranged vMNrCF maintains structural integrity after bending, exhibiting both flexibility and mechanical stability; This demonstrates that the structural construction strategy of the present invention is effective, controllable, and has process reliability, providing a foundation for the realization of high-performance electromagnetic absorption, heat conduction, and other functions. Example 3

[0068] Figure 8 The electromagnetic wave reflection loss (RL) characteristics of vertically aligned composite materials vMNrCF1, vMNrCF2, and vMNrCF3 with different filler contents (10%, 15%, and 20%) are shown in both three-dimensional and two-dimensional configurations as a function of sample thickness and frequency. Specifically, vMNrCF1 = 10 wt% filled with magnetic nanoparticles, vMNrCF2 = 15 wt% filled with magnetic nanoparticles, and vMNrCF3 = 20 wt% filled with magnetic nanoparticles. All three are vertically oriented rCF@MXene@magnetic nanoparticle array structures and are encapsulated in PDMS.

[0069] Figure 8 (ac): Two-dimensional reflection loss (RL) distribution contour plots for vMNrCF1, vMNrCF2, and vMNrCF3, respectively. The horizontal axis represents frequency (GHz), the vertical axis represents thickness (mm), and the color indicates loss intensity (dB). All three show significant absorption bands, and the depth of the minimum RL value varies with the filling amount, indicating that the filling ratio has a significant synergistic effect on the interface and magnetic loss.

[0070] Figure 8 (df): Three-dimensional RL distribution diagrams of vMNrCF1, vMNrCF2, and vMNrCF3, respectively, further showing the distribution of absorption peak positions and absorption intensities under different thicknesses. The absorption valley regions shift slightly in position depending on the structure.

[0071] The 3D visualization material exhibits broadband deep absorption capability in the C-Ku band.

[0072] Figure 8 (gi): RL-frequency curves of vMNrCF1, vMNrCF2, and vMNrCF3 under different thickness conditions (0.5-5.0 mm). With varying thickness, the absorption peaks undergo significant tuning, with the peak positions shifting generally towards lower frequencies, consistent with the thickness-matching law of electromagnetic absorption. Figure 8 In summary: 1) All three batches of samples showed good absorption performance, indicating that the vertical orientation array and hierarchical interface structure played a significant role; 2) The position of the reflection loss peak can be adjusted with the thickness, and the material thickness provides additional degrees of freedom for the tuning of the absorption peak; 3) As the filling amount decreases from 20-10 wt%, impedance matching is optimized, and the absorption depth and bandwidth of the sample are significantly improved; 4) vMNrCF3 (10%) can achieve optimal depth absorption at moderate thickness, indicating better impedance matching, synergistic magnetic loss, and interface polarization; 5) The array structure enhances multiple scattering and channel transmission, which helps with deep absorption and bandwidth expansion.

[0073] The vertical array structure, combined with the hierarchical interface design, can achieve excellent and tunable microwave absorption performance by adjusting the filling ratio and thickness, making it suitable for broadband microwave absorption applications. Example 4

[0074] Figure 9 This is a finite element simulation diagram of the electromagnetic field of the vertical absorbing structure of the present invention. From the front, side, and rear views, it can be observed that the electromagnetic energy is mainly concentrated around the vertical array, indicating that the fiber array structure forms a continuous dissipation channel, which is beneficial for enhancing interface polarization and loss.

[0075] Figure 10 The image shows the electromagnetic energy density distribution of rCF, MNrCF, and vMNrCF using the CST model. It is evident that the energy density of vMNrCF is significantly enhanced near the fiber array, indicating that vertical alignment facilitates energy introduction and transmission, and induces a stronger polarization effect; the random structure, on the other hand, exhibits a weak and dispersed energy distribution. The overall electromagnetic wave loss performance of vMNrCF is significantly enhanced compared to rCF and MNrCF.

[0076] Figure 11 The image shows a comparison of experimental RL curves, transmission line model (TL) calculations, and CST simulation results for vMNrCF1 (10wt%, t=2.5mm). The three methods show a high degree of consistency in absorption peak position and intensity, demonstrating the rationality of the model construction and the reliability of the experimental results.

[0077] Figure 12 The experimental and simulated RL curves of vMNrCF samples with different thicknesses (2.0-4.9 mm) are superimposed and compared. The absorption peak shifts towards lower frequencies with increasing thickness, which is consistent with the electromagnetic matching law. The experimental and simulated curves are highly consistent, verifying the effectiveness of the theoretical model and the rationality of the structural design. Example 5

[0078] The figure below shows the microwave absorption performance parameters of different samples (rCF, MNrCF1-3, vMNrCF1-3), including loss factor, impedance matching degree, reflection loss (RL) value, effective absorption bandwidth (EAB), and performance comparison results with representative microwave absorbing materials in existing literature.

[0079] Figure 13 The figures show the loss factor α as a function of frequency for different samples (rCF, MNrCF1-3, vMNrCF1-3). The vMNrCF series exhibits a significantly improved loss factor in the 4-16 GHz range, indicating that the hierarchical interface and vertical array structure can significantly promote electromagnetic wave dissipation.

[0080] Figure 14 : Impedance matching characteristics of the sample Trend of variation with frequency. When At this time, better absorption effect can be achieved. The vMNrCF series has a wider matching region and the area close to 1 is significantly expanded, indicating that it has good impedance matching capability in the C-Ku band.

[0081] Figure 15 Figure : RL-frequency curves for rCF, MNrCF series and vMNrCF series. The vMNrCF series consistently outperforms the random structure MNrCF and rCF, with vMNrCF2 (15%) showing the best performance, with the deepest reflection loss of approximately −60.71 dB, compared to only −18.22 to −51.17 dB for MNrCF and only −2.91 dB for rCF.

[0082] Figure 16 : RL for rCF, MNrCF1-3, vMNrCF1-3 min With EAB max Bar chart. vMNrCF2 (15%) has the deepest absorption and the widest effective absorption bandwidth, RL min ≈−60.71dB, EAB max The ≈7.82GHz indicates that the hierarchical structure and vertical array bring synergistic enhancement.

[0083] Figure 17 : This represents the maximum effective absorption bandwidth (EAB) of the material in this invention and typical absorbing materials in the literature. max ) and deepest absorption value (RL) minTwo-dimensional distribution comparison diagram. The material of this invention (marked in red) is located in the deep absorption + broadband region, which is significantly better than most existing reported systems such as MXene, carbon fiber, and ferrite, showing that the composite structure of this invention has significant advantages in microwave absorption performance.

[0084] Figure 13-17 The system reveals: 1) The vertical array structure and the hierarchical interface work together to construct an electromagnetic dissipation channel; 2) The MXene+NiFe2O4 composite enhances both dielectric and magnetic losses; 3) Fiber arrays improve impedance matching, allowing more electromagnetic waves to enter the material; 5) Absorption intensity and bandwidth can be adjusted by changing the filler ratio and thickness; 6) vMNrCF2 (15%) performed best: RLmin ~−60.71dB, EABmax ~7.82GHz, achieving both deep absorption and broadband absorption; 7) The performance is significantly better than most reported MXene / ferrite / carbon fiber composites, indicating that the present invention is significantly innovative.

[0085] Example 6 Figure 18 The results show that the thermal conductivity of the composite material gradually increases as the composite filler structure changes from random distribution to vertical orientation. Specifically, the thermal conductivity of the vertical array structure sample is significantly higher than that of the unoriented sample and the pure PDMS matrix.

[0086] Figure 18 The graphs show the thermal conductivity variations of different samples at different temperatures, ranging from approximately 20℃ to 125℃. The results indicate that the thermal conductivity of the composite material is significantly improved after adding vertical fillers compared to the pure PDMS matrix. Among them, the samples containing vertically oriented carbon fiber / MXene / magnetic particle structures (vMNrCF1–vMNrCF3) exhibited high thermal conductivity throughout the entire temperature range. Figure 18 and Figure 19 This invention is used to illustrate the thermal conductivity of the carbon fiber-MXene-magnetic particle composite material. Test results show that the composite structure can significantly improve the thermal conductivity of the material.

Claims

1. A hierarchical heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles, characterized in that, It is made by encapsulating and solidifying carbon fiber, MXene nanosheets and magnetic nanoparticles in a polymer matrix; In this composite material, carbon fibers are arranged vertically to form an array structure, MXene nanosheets are loaded on the surface of carbon fibers to form a wrinkled layer structure, magnetic nanoparticles are loaded on the surface of MXene or carbon fibers, and MXene nanosheets and magnetic nanoparticles form a multi-level heterogeneous composite structure on the surface of carbon fibers.

2. The multi-level heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles according to claim 1, characterized in that, The carbon fiber is in the form of chopped fibers or continuous fibers, and the fiber length is preferably 0.5–5 mm.

3. The multi-level heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles according to claim 1, characterized in that, The general formula for MXene nanosheets is M n+1 X n T x Where n = 1, 2, 3 or 4, M is one of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta or W; X is carbon, nitrogen or CN.

4. The multi-level heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles according to claim 3, characterized in that, The general formula for MXene nanosheets is Ti3C2T x T x It is at least one of -OH, -O, and -F.

5. The multi-level heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles according to claim 1, characterized in that, The magnetic nanoparticles can be selected from at least one of NiFe2O4, Fe3O4, CoFe2O4, and MnFe2O4.

6. The multi-level heterogeneous composite material based on CF@MXene@nanomagnetic nanoparticles according to claim 1, characterized in that, The polymer matrix is ​​selected from any one of silicone rubber, epoxy resin, and polyurethane.

7. The multi-level heterogeneous composite material according to any one of claims 1-6, characterized in that, The chemical formula is CF@Ti3C2T x @NiFe2O4@PDMS.

8. A method for preparing hierarchical heterogeneous composite materials based on CF@MXene@nanomagnetic nanoparticles, characterized in that, Includes the following steps: (1) Preparation of MXene nanosheets: MXene nanosheets were prepared by etching the MAX phase precursor with LiF-HCl and then exfoliating. After etching, the MXene nanosheet dispersion was obtained by ultrasonic exfoliation. (2) Surface modification of carbon fiber: Acid treatment is performed on carbon fiber to obtain short-cut carbon fiber; The surface of the short-cut carbon fiber is rough and rich in oxygen-containing functional groups; Carbon fibers were dispersed in MXene nanosheet dispersion. After surface modification with APTES, the carbon fibers became positively charged and then electrostatically self-assembled with the negatively charged MXene to form an MXene@CF structure. (3) Magnetic particles load to form a hierarchical interface structure: Magnetic nanoparticles are added to the dispersion containing MXene@CF structure. The magnetic nanoparticles are adsorbed on the surface of MXene nanosheets, thereby forming a multi-level heterogeneous coating structure CF@MXene@nanomagnetic particles. (4) Electrostatic flocking to construct a vertical array: Through electrostatic flocking, a high voltage electric field is applied between the upper and lower electrodes, so that the CF@MXene@ magnetic particles are vertically arranged on the elastic substrate along the direction of the electric field to form a controllable array structure. (5) Matrix encapsulation and curing: The adjusted carbon fiber array structure is impregnated in a polymer matrix and cured to obtain a structurally stable composite material.

9. The preparation method according to claim 8, characterized in that, In step (3), the pre-stretching degree of the substrate is set to 0%-100%; by adjusting the pre-stretching degree, the fiber array areal density is achieved at 5 mg / cm². 2 -65mg / cm 2 Precise control within the range, and the fiber volume fraction increases synchronously within the range of 2vol%-18vol% as the degree of pre-stretching increases.

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