Broadband wave-absorbing material based on MAX phase metasurface structure and impedance matching optimization method thereof

Abstract

The invention discloses a broadband wave-absorbing material based on an MAX-phase metasurface structure and an impedance matching optimization method of the broadband wave-absorbing material. The wave-absorbing material comprises an MAX-phase ceramic substrate and periodic metasurface structures which are arranged on the surface of the MAX-phase ceramic substrate in an array mode and composed of conductive resonance units. The resonance units are isolated through gaps, an equivalent R1L1C1 series resonance circuit is formed in an electromagnetic field, and a base body is equivalent to a parallel resistor R2. By establishing an equivalent circuit model and optimizing parameters R1, L1, C1 and R2, impedance matching of the wave-absorbing material in a target frequency band can be regulated and controlled, so that the wave-absorbing material at least has an absorption peak of which the reflection loss is less than-10 dB. According to the optimization method, electromagnetic simulation and circuit simulation are combined, optimized circuit parameters are reversely mapped into structure geometric parameters, material preparation is guided, and accurate design and broadband absorption of the wave absorbing performance are achieved.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a broadband absorbing material based on a MAX phase metasurface structure and its impedance matching optimization method. Background Technology

[0002] With the rapid development of electronic technology, electromagnetic waves are increasingly used in communication, remote sensing, and detection, which has also led to increasingly serious electromagnetic pollution and safety problems. The research and application of electromagnetic absorbing materials has become particularly urgent. In the military field, they can be used to reduce the reflection of radar detection signals to improve the survivability of military targets, while in the civilian field, they are used to protect precision equipment and electronic components from electromagnetic interference.

[0003] Traditional electromagnetic absorbing materials primarily rely on their inherent electromagnetic properties, namely dielectric constant and permeability, to absorb electromagnetic waves. However, these materials generally suffer from limitations such as large thickness, narrow absorption bandwidth, and difficulty in adapting to complex and variable electromagnetic environments.

[0004] In recent years, metamaterial absorbers have attracted much attention due to their ability to acquire electromagnetic properties (such as negative permeability and negative permittivity) that are not found in natural materials through artificial structures, thereby enabling efficient manipulation of incident electromagnetic waves. Nevertheless, existing metamaterial absorbers still face challenges such as complex manufacturing processes, poor integrability, and insufficient absorption stability. In particular, for materials like Ti3AlC2, which possess inherently high conductivity, although they exhibit good fracture toughness and high-temperature oxidation resistance, the high conductivity leads to a severe mismatch between its conductivity and free-space impedance. This makes it difficult for electromagnetic waves to penetrate the material's interior, resulting in low reflection loss and a narrow effective absorption bandwidth. The single absorption mechanism makes it unsuitable for applications that integrate absorbing structures with load-bearing functions.

[0005] To improve the microwave absorption performance of MAX phase materials, researchers have explored novel absorbing structure designs. For example, metasurface design is considered an effective way to optimize material impedance matching. Chinese invention patent CN114336069A discloses a low-frequency broadband absorbing metastructure based on conductive composite materials, which employs a metal substrate and a periodically stacked multi-layered ring resonant structure to broaden the absorption bandwidth through the superposition of multiple resonant structures. However, this scheme still has room for optimization in the design of the resonant structure (such as ring width) and the gradient variation of material conductivity, failing to fully realize its potential for achieving wider bandwidth and higher efficiency. Another patent, CN113013629A, provides a scheme combining electromagnetic metasurfaces with functional absorbing substrates to improve electromagnetic compatibility in complex environments, but its metal microstructure design (such as the matching of trace length and wavelength) still shows insufficient improvement in absorption performance and bandwidth migration capability.

[0006] In summary, the existing technologies still have the following main drawbacks: pure MAX phase materials have poor impedance matching due to their high conductivity, resulting in poor absorption performance; existing metamaterial absorbers have complex structures and are difficult to integrate; traditional absorber materials have narrow bandwidth and large thickness; and existing absorber structure design methods are not yet perfect in terms of fine control of resonant units, making it difficult to achieve wide-bandwidth and high-efficiency electromagnetic absorption while maintaining the lightweight nature of the materials. Summary of the Invention

[0007] To address the poor absorption performance of existing MAX phase materials due to impedance mismatch, this invention provides a broadband absorbing material based on metasurface structures and its impedance matching optimization method.

[0008] The specific technical solution of the present invention is as follows: This invention provides a broadband absorbing material based on a MAX phase metasurface structure, comprising: MAX phase ceramic matrix; and periodic metasurface structure disposed on the surface of the MAX phase ceramic matrix; The periodic metasurface structure is composed of multiple arrayed conductive resonant units. The conductive resonant units are isolated from each other and / or from the MAX phase ceramic substrate by gaps, thereby forming a resonant circuit with equivalent inductance L1, equivalent capacitance C1 and equivalent resistance R1 under alternating electromagnetic field. The structural parameters of the absorbing material are determined based on an equivalent circuit model. The equivalent circuit model equates the periodic metasurface structure to a series branch of R1L1C1 and the MAX phase ceramic substrate to a parallel resistor R2. By adjusting the values ​​of the equivalent circuit parameters R1, L1, C1, and R2, the absorbing material is made to have at least one absorption peak with a reflection loss of less than -10 dB in the target frequency band.

[0009] The material of the MAX phase ceramic matrix is ​​selected from the general formula M. n+1 AX n MAX phase materials, where M is a transition metal, A is a main group element, X is carbon, nitrogen or carbon-nitrogen solid solution, and n=1, 2, 3.

[0010] The MAX phase ceramic matrix is ​​a solid solution and is selected from at least one of the following: A-site high-entropy solid solution, wherein the A-site contains at least three main group elements; mixing entropy ΔS mix ≥ 1.5R, where R is the gas constant; M-site high-entropy solid solution, wherein the M-site contains at least three transition metal elements; X-position solid solution, where the X-position is C 1-y N y , where 0 ≤ y ≤ 1.

[0011] The MAX phase ceramic matrix is ​​a composite material of MAX phase material and dielectric modulating material, wherein the dielectric modulating material is selected from one or more of oxide ceramics, nitride ceramics, and polymers.

[0012] The conductive resonant unit can be a planar structure or a three-dimensional structure.

[0013] The conductive resonant unit includes prism-shaped, cross-shaped, open ring, I-shaped, H-shaped, or biomimetic gradient resonant cavity structures.

[0014] The period a of the periodic metasurface structure satisfies: 1 mm ≤ a ≤ 30 mm; the circumscribed circle diameter r of the characteristic dimension of the resonant unit satisfies: 0.1 mm ≤ r ≤ 10 mm; the thickness h of the MAX phase ceramic substrate satisfies: 0.5 mm ≤ h ≤ 6 mm; and the height d of the resonant unit satisfies: 0.01 mm ≤ d ≤ 4 mm.

[0015] This invention provides a method for optimizing the impedance matching of a broadband absorbing material based on a MAX phase metasurface structure, comprising the following steps: S1: Determine the initial geometric parameters of the periodic metasurface structure based on the target absorption frequency band; S2: Establish an electromagnetic simulation model of the absorbing material containing the initial geometric parameters, and calculate its reflection coefficient S11; S3: Based on the reflection coefficient S11, extract the equivalent circuit parameters of the absorbing material according to the equivalent circuit model. The equivalent circuit model equates the periodic metasurface structure to a series branch of R1L1C1 and the MAX phase ceramic substrate to a parallel resistor R2. S4: In circuit simulation software, adjust the values ​​of the equivalent circuit parameters R1, L1, C1, and R2 to optimize the impedance matching characteristics of the absorbing material in the target frequency band; S5: The optimized equivalent circuit parameters R1, L1, C1, and R2 are reverse-mapped to the final geometric parameters of the periodic metasurface structure to guide the preparation of the absorbing material.

[0016] In step S3, the imaginary part of the impedance Im[Z] at two frequencies f1 and f2 near the resonant point is obtained. h (f1)] and Im[Z h (f2)], calculate the equivalent capacitance C1 and equivalent inductance L1; The equivalent resistance R2 of the MAX phase ceramic matrix is ​​determined by calculating the overall impedance Z of the absorber based on the reflection coefficient S11 at the resonant point. total And by solving the overall impedance Z totalThe value of R2 is derived by reversing the equation that is equal to the parallel impedance of the periodic metasurface structure impedance and the substrate resistance R2.

[0017] In step S4, the strategies for adjusting the equivalent circuit parameters include: Increase the equivalent inductance L1 or equivalent capacitance C1 to shift the absorption peak to lower frequencies; Increasing the equivalent resistance R1 of the metasurface structure or the equivalent resistance R2 of the MAX phase ceramic matrix will reduce the absorption peak intensity.

[0018] Compared with the prior art, the beneficial technical effects of this invention are reflected in: 1. By optimizing the impedance matching performance of the material through metasurface design, the impedance matching difference problem of MAX phase material is effectively improved, making it easier for electromagnetic waves to enter the interior of the material, significantly improving the absorption performance of the material, and overcoming the shortcomings of insufficient absorption performance of pure MAX phase material. 2. The effects of the compound components on the mechanical properties and antioxidant properties of the material were studied. By optimizing the ratio design, the material properties were balanced, effectively solving the problems of thick thickness and narrow absorption bandwidth of traditional microwave absorbing materials. 3. Four types of resonant unit structures—triangular prism, square prism, hexagonal prism, and dodecagonal prism—were designed. The influence mechanism of the superstructure on the microwave absorption performance was studied using HFSS finite element simulation software. The correctness of the equivalent circuit model was verified, and the microwave absorption performance of the material was further improved. 4. The electromagnetic absorption mechanism of the resonant unit was analyzed using equivalent circuit theory. By changing the RLC parameters in the equivalent circuit, the electromagnetic properties of the material were further optimized, achieving efficient absorption of electromagnetic waves. Attached Figure Description

[0019] Figure 1 : Schematic diagram of the metasurface structure and resonant unit of the present invention (showing period a, radius r, substrate thickness h, and unit height d); Figure 2 Schematic diagrams of resonant units of different shapes (triangular prism, square prism, hexagonal prism, dodecagonal prism); Figure 3 : Simulation results of reflection loss under different structural parameters; Figure 4 : Electric field distribution diagram of the metasurface at the resonance peak; Figure 5 : Magnetic field distribution diagram of the metasurface at the resonance peak; Figure 6 The equivalent circuit model diagram of this invention (showing R1, L1, C1, R2); Figure 7 Comparison of reflection loss results between ADS circuit simulation and HFSS full-wave simulation; Figure 8 The graph shows the effect of changes in various parameters (R1, L1, C1, R2) on reflection loss in the equivalent circuit. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] The core of the microwave absorbing material provided by this invention is the construction of a periodically arranged prismatic metasurface structure on a MAX phase ceramic matrix. In the embodiments, the matrix is ​​a composite ceramic of Ti3AlC2 and 48 wt% mullite, which provides optimal dielectric loss and oxidation resistance while ensuring mechanical properties.

[0025] Example 1: Design and Verification of Ti3AlC2 / Mullite Composite Matrix Metasurface Absorbing Material This embodiment details the broadband absorbing material based on Ti3AlC2 metasurface structure and its design method provided by the present invention.

[0026] 1. Preparation of matrix materials First, a Ti3AlC2 ceramic matrix was prepared. The ceramic matrix was a composite material of Ti3AlC2 and mullite, with mullite comprising 48% by mass. This ratio was an optimized scheme determined after previous systematic research, aiming to achieve the best balance between the material's microwave absorption properties, oxidation resistance, and mechanical properties. A dense composite ceramic bulk was then prepared using powder metallurgy and sintering processes.

[0027] 2. Metasurface Structure Design and Initial Modeling On the surface of the composite ceramic block, periodically arranged prism-shaped resonant units are designed. In this embodiment, a quadrangular prism is selected as the shape of the resonant unit for detailed description.

[0028] The initial geometric parameters of the metasurface structure are set as follows: Period a = 10 mm; The circumcircle radius of the prism is r = 3.5 mm; The substrate thickness h = 4.5 mm; The height of the prism structure is d = 3 mm; Use 3D modeling software to create a metasurface structure model that includes the above parameters.

[0029] The three-dimensional model was imported into the high-frequency electromagnetic simulation software ANSYS HFSS for full-wave simulation analysis.

[0030] Settings: Simulation frequency range is 2-18 GHz; background is set to air; master-slave boundary conditions are set in the x and y directions to simulate an infinite periodic array; electromagnetic waves are incident perpendicularly from the +z axis in the form of plane waves.

[0031] Results: Simulation calculations yielded the scattering parameters S11 and S21 of the structure. The absorptivity of the absorber... Calculated using the following formula: (1) Since the thickness of the substrate is much greater than the skin depth of electromagnetic waves in the material, the transmission coefficient S 21 Since the absorptivity is approximately zero, the absorptivity is mainly determined by the reflectance coefficient S. 11 The above formula simplifies to: ≈

[0032] Simulation results show that the structure exhibits a distinct absorption resonance peak at 11.2 GHz.

[0033] To further investigate the electromagnetic wave absorption mechanism of this metasurface structure, the electromagnetic field distribution at the resonance peak (11.2 GHz) was analyzed.

[0034] Figure 4 The electric field distribution at this frequency is shown. From Figure 4 It can be seen that the electric field energy is highly concentrated on the sides and corners of the quadrangular prism resonant unit. More importantly, the two opposite faces between adjacent prisms and the air gap between them together form a highly efficient "equivalent capacitance" (C1), which will undergo a continuous charging and discharging process in the alternating electromagnetic field, thereby dissipating electromagnetic wave energy through dielectric polarization.

[0035] Figure 5The magnetic field distribution at the same frequency is shown. The results show that, except for the depth of the substrate and the very center of the prism, the magnetic field is strongly distributed throughout the entire structural region, especially within the prism structure itself. This indicates that the tetragonal prism structure itself constitutes an "equivalent inductance" (L1), in which the changing magnetic field induces eddy currents, and the inherent resistance (R1) of the material converts this current energy into Joule heat dissipation.

[0036] Based on the above distribution characteristics of electric and magnetic fields, and combined with the equivalent circuit theory, we constructed the following... Figure 6 The equivalent circuit model shown is used to accurately describe the physical mechanism of the absorbing material. The model simplifies the entire system into two parallel branches: one branch represents the metasurface structure, which consists of its equivalent resistance R1, equivalent inductance L1, and equivalent capacitance C1 connected in series; the other branch represents the Ti3AlC2 / mullite composite ceramic matrix at the bottom, which is equivalent to a resistor R2.

[0037] 4. Equivalent circuit model construction and parameter extraction Based on the above electromagnetic mechanism analysis, a structure is constructed as follows: Figure 6 The equivalent circuit model is shown. The impedance characteristics of this model are described by the following formula: The impedance of the metasurface structure (2) The impedance of the ceramic matrix (3) Where Z0 is the free space impedance, approximately 377 Ω. Therefore, the overall composite impedance of the absorber (4) To verify the correctness of the model and quantify the circuit parameters, two frequency points were selected near the resonant point (11.2 GHz): f1 = 11.16 GHz and f2 = 11.24 GHz.

[0038] The composite impedance at these two frequency points was obtained through HFSS simulation. Z (f1) and Z (f2), and substitute into formulas (4) and (2) to deduce Z. h ( f1 ) and Z h ( f2 Subsequently, the values ​​of the equivalent elements are extracted using the following set of formulas: the resistance R1 of the superstructure layer is determined by the real part of the impedance near the resonant point: (5) Its reactance part satisfies: (6) in, =2π f ω is the angular frequency.

[0039] By substituting the impedance values ​​at f1 and f2 into Formula 6, the value of the equivalent element can be calculated. The formula for calculating the equivalent capacitance C1 is as follows: (7) Substitute the calculated C1 into formula (6) and take f=f2 to solve for the equivalent inductance L1.

[0040] The formula for calculating L1 is: (8) The calculated parameters are: R1 = 96 Ω, L1 = 30 nH, C1 = 0.007 pF.

[0041] Subsequently, based on the principle that the overall impedance of the absorber should achieve optimal matching with free space at the resonant frequency, the equivalent resistance R2 of the substrate is calculated. The specific method is as follows: First, based on the reflection coefficient S obtained from HFSS simulation... 11 The overall impedance Z of the absorber at the resonant point (11.2 GHz) was calculated. total Then, the previously determined metasurface structure impedance (approximately a pure resistance R1 at this point) and the substrate resistance R2 are considered to be in parallel. By solving this parallel circuit, the total impedance is equal to Z. total Therefore, the value of R2 can be derived in reverse as 77 Ω.

[0042] Based on the above complete calculations, the final set of equivalent circuit parameters are: R1 = 96 Ω, L1 = 30 nH, C1 = 0.007 pF, R2 = 77 Ω.

[0043] 5. Verification of the equivalent circuit model The extracted R, L, and C parameters are input into the circuit simulation software ADS (Advanced Design System) for circuit simulation. The simulation results of ADS (based on the equivalent circuit model) are compared with the full-wave electromagnetic simulation results of HFSS, as shown in the comparison figure. Figure 7 As shown in the figure. The results show that the peak position, peak intensity, and bandwidth of the two are basically the same near the resonant frequency (11.2 GHz), thus verifying the correctness of the equivalent circuit model. The large difference in S11 values ​​near the resonant point is because the equivalent circuit model is a simplified representation of complex electromagnetic resonance phenomena. Its accuracy will naturally decrease when it is far from the central resonant frequency band, but this does not affect its core role in the optimization design of the target frequency band. 6. Performance optimization and reverse design based on equivalent circuits Using the validated equivalent circuit model, the influence of various circuit parameters on the absorption performance was systematically studied in ADS software. The results are as follows: Figure 8As shown in Figure 8(a), the effect of equivalent resistance variation on electromagnetic performance in the superstructure layer is observed. It can be seen that the change in equivalent resistance only affects the absorption peak intensity, having no effect on bandwidth or absorption peak position. As the equivalent resistance increases, the absorption peak intensity gradually decreases. Figure 8(b) shows the effect of equivalent inductance on electromagnetic performance. The change in equivalent inductance only affects the absorption peak position, having no effect on absorption peak intensity or bandwidth. As the equivalent inductance increases, the absorption peak position gradually shifts towards lower frequencies. Figure 8(c) shows the effect of equivalent capacitance variation on electromagnetic performance. The equivalent capacitance also only affects the absorption peak position, having no effect on absorption peak intensity or bandwidth. As the equivalent capacitance increases, the absorption peak position gradually shifts towards lower frequencies. Figure 8 (d) is the effect of the equivalent resistance of the substrate on electromagnetic performance. The change of the equivalent resistance R2 affects the absorption peak intensity and bandwidth, but has no effect on the absorption peak position. As the equivalent resistance increases, the absorption peak intensity decreases and the bandwidth narrows.

[0044] Increasing the equivalent inductance L1 or equivalent capacitance C1 shifts the absorption peak to lower frequencies, but has little effect on peak intensity and bandwidth. Increasing the equivalent resistance R1 of the metasurface structure or the equivalent resistance R2 of the substrate reduces the absorption peak intensity, and increasing R2 narrows the bandwidth.

[0045] Based on the above principles, if the absorption peak position needs to be adjusted to a lower 10 GHz, it can be achieved by increasing L1 or C1. For example, increasing L1 from 30 nH to 35 nH can be quickly predicted through circuit simulation. Subsequently, this change in circuit parameters is mapped inversely to adjustments in the physical structure (such as increasing L1 by increasing the prism height d, or increasing C1 by decreasing the prism spacing), and then verified using HFSS, thus quickly completing the directional optimization design of the absorbing material.

[0046] Example 2: Comparison of different resonant unit shapes This embodiment aims to illustrate that the shape of the resonant unit has a relatively small impact on the absorption performance.

[0047] In addition to the tetragonal prism in Example 1, three other resonant unit structures—triangular prism, hexagonal prism, and dodecagonal prism—were designed and simulated using HFSS. The simulation results are as follows: Figure 3 As shown, where Figure 3 (a) Set a=10 mm, r=2 mm, h=1 mm, d=3 mm; Figure 3 (b) Set a=10 mm, r=3mm, h=1 mm, d=3 mm; Figure 3(c) Set a=10 mm, r=2 mm, h=2 mm, d=3 mm. Simulation results show that the peak position and intensity of the absorption peak do not change significantly under different unit shapes and similar sizes. This confirms that the equivalent circuit model described in this invention has universality, and its absorption performance mainly depends on the equivalent R, L, C parameters, rather than the specific shape of the resonant unit, providing flexibility for design.

[0048] In summary, this invention provides an effective approach for the rapid and accurate design of high-performance, wideband Ti3AlC2-based absorbing materials through the method of "electromagnetic simulation—equivalent circuit extraction—circuit optimization—structural parameter reverse mapping".

[0049] Example 3: Verification of microwave absorption performance of different MAX phase material matrices In the experiment, sample A (pure Ti3AlC2 ceramic matrix) exhibited a severe impedance mismatch with free space due to its excessively high conductivity. According to the equivalent circuit principle, a complex circuit can be simplified to a simpler circuit with identical external performance. For pure Ti3AlC2, its high conductivity resulted in excessively low resistance in the equivalent circuit, causing reflection losses consistently above -5 dB in the 2–18 GHz frequency band, rendering it almost entirely devoid of wave absorption capability. This result confirms the common challenges faced by single MAX phases in electromagnetic functional applications without impedance modulation.

[0050] Sample B (a composite ceramic matrix of Ti2AlC and 50 wt% SiO2) exhibits a significant performance improvement. By introducing SiO2 into the Ti2AlC matrix, we effectively modulated the equivalent resistance and equivalent capacitance networks of the composite material. Based on the equivalent circuit method, complex circuits can be simplified into simpler circuits with the same function through resistance equivalence and capacitance equivalence. This resulted in a strong absorption peak at 10.8 GHz, a minimum reflection loss of -58.1 dB, and an effective bandwidth of -10 dB of 3.5 GHz. This demonstrates that the equivalent circuit design method of this patent can precisely control the impedance matching characteristics of MAX phase-based composite materials by introducing appropriate dielectric components. Although Ti2AlC and Ti3AlC2 differ in specific electrical parameters, our method is successfully applied to the Ti2AlC system, initially demonstrating its cross-composition applicability.

[0051] The most compelling evidence comes from sample C (A-site high-entropy MAX phase Ti2(Al)). 0.2 Sn 0.2 In 0.2 Bi 0.2 Ag 0.2(A composite material of C and 45wt% Al2O3). The sample exhibits dual absorption peaks at 8.5 GHz and 14.2 GHz, with a minimum reflection loss of -45.3 dB and an overall -10 dB bandwidth exceeding 5 GHz. The lattice distortion and numerous interface effects caused by various A-site elements in the high-entropy MAX phase are abstracted into a more complex resistor-capacitor network in the equivalent circuit. This method of simplifying the complex network into a simple network with the same output voltage and current to the external circuit through equivalent transformation, especially by applying Thevenin's theorem to convert the linear source-containing one-port network into a model of a voltage source and a resistor in series, effectively describes the multi-relaxation mechanism brought about by the high-entropy component, thereby achieving broadband absorption performance. This shows that the equivalent circuit method of this patent can not only handle traditional MAX phases, but also adapt to the compositional complexity and structural heterogeneity brought about by high entropy, and its model framework has the ability to describe the layered structure-related polarization mechanism common to the MAX phase family.

[0052] Sample D is a high-entropy solid solution MAX phase at the M-site, with the chemical formula (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)3AlC2, meaning the M-site is formed by the solid solution of five transition metal elements in an equimolar ratio. Both samples were compounded with 40 wt% SiO2 and employed the exact same cross-shaped metasurface resonant unit structure (period 10 mm, unit height 3 mm, total substrate thickness 4.5 mm) to ensure that the performance differences mainly stemmed from variations in the M-site composition of the MAX phase.

[0053] The test results from the vector network analyzer clearly demonstrate the performance impact of M-site solid solution, showing dual absorption peaks near 9.6 GHz and 14.1 GHz, a minimum reflection loss of -49.8 dB, and a significant expansion of the overall -10 dB effective bandwidth to 5.2 GHz. In summary, from traditional Ti3AlC2 to Ti2AlC, and then to the cutting-edge A-site high-entropy MAX phase, the equivalent circuit design method of this patent can effectively guide the impedance matching design and performance optimization of composite materials by adjusting key circuit parameters. This series of results strongly demonstrates the universality of this method, making it a general design and analysis tool for the MAX phase material family in electromagnetic functional applications.

[0054] This embodiment strongly demonstrates that the equivalent circuit design method of this patent is not only applicable to traditional single-M-element MAX phases, but also provides precise guidance for complex systems where the M-site is a solid solution (including high-entropy designs). The universality of the method stems from its grasp of the physical essence of the electromagnetic response of MAX phase materials and its abstraction into quantifiable circuit parameters. Regardless of the combination of M-site elements, their final impact on absorption performance can be understood and optimized by adjusting the R, L, and C parameters in the equivalent circuit. This provides reliable theoretical and tool support for directional electromagnetic function design of the MAX phase material family within a broader compositional space.

[0055] Sample E is Ti n+1 Al(C 1-y N y ) n (n=1,2,3; 0≤y≤1). This series of materials achieves continuous tunability of the chemical composition at the X-site by partially replacing carbon atoms with nitrogen atoms, while maintaining the basic crystal structure of the MAX phase. We focused on comparing composites of Ti3AlC2 (y=0), Ti3Al(C0.5N0.5)2 (y=0.5), and Ti3AlN2 (y=1) ceramic matrices with 40 wt% SiO2. All samples employed the same cross-shaped metasurface resonant unit structure to ensure that performance differences primarily stemmed from variations in the X-site composition of the MAX phase.

[0056] Test results show that the solid solution at the X-site has a systematic impact on the microwave absorption performance. As the nitrogen content y increases from 0 to 1, the minimum reflection loss of the material first optimizes and then slightly decreases, reaching its optimal value near y=0.5. Specifically, the minimum reflection loss of the Ti3AlC2 / SiO2 sample is -48.5 dB; while that of the Ti3Al(C 0.5 N 0.5 The Ti3AlN2 / SiO2 sample exhibited the best performance, with a minimum reflection loss of -55.2 dB and an effective bandwidth of -10 dB extended to 4.2 GHz; when completely converted to nitride Ti3AlN2 / SiO2, the minimum reflection loss was -51.8 dB. More importantly, the position of the absorption peak shifted continuously and predictably with changes in nitrogen content y.

[0057] This embodiment strongly demonstrates that the equivalent circuit design method of this patent is not only applicable to traditional carbide or nitride MAX phases, but also possesses accurate prediction and guidance capabilities for continuously modulated systems where the X-site is a carbon-nitride solid solution. The method's universality stems from its grasp of the intrinsic relationship between the electromagnetic response and composition-structure of MAX phase materials, abstracting it into quantifiable circuit parameters. Regardless of the variation in the C / N ratio at the X-site, its ultimate impact on absorption performance can be understood and optimized by adjusting the R and C parameters in the equivalent circuit. This provides strong theoretical and tool support for customizing electromagnetic functions through precise X-site solid solution design within the MAX phase material family.

[0058] Example 4: Performance Verification of Different Dielectric Modulation Materials This embodiment aims to demonstrate that the function of adjusting the equivalent resistance R2 of the substrate can be achieved by a variety of dielectric materials, and mullite is not the only choice.

[0059] To verify the universality of the equivalent circuit method of this patent, we designed three sets of experiments using Ti3AlC2 as a unified MAX phase matrix, respectively combined with oxide ceramics (SiO2), nitride ceramics (Si3N4), and polymers (high-entropy engineered polymer HEP-B1). All samples adopted the same cross-shaped metasurface resonant unit structure (period 10 mm, unit height 3 mm, total substrate thickness 4.5 mm) to ensure that the performance differences mainly stemmed from the properties of the dielectric modulation material itself.

[0060] 1. The regulating effect of oxide ceramics (SiO2) SiO2, a classic insulating oxide ceramic, has extremely high resistivity. When combined with high-conductivity Ti3AlC2 (sample A: Ti3AlC2 / 40 wt% SiO2), significant interfacial polarization occurs at the interface. In the equivalent circuit, this effect manifests as an increase in the equivalent capacitance C1. Test results show that sample A exhibits a strong absorption peak at 11.5 GHz, with a minimum reflection loss of -52.3 dB and an effective bandwidth of -10 dB of 3.8 GHz. The introduction of SiO2 not only optimizes impedance matching through interfacial polarization but also significantly reduces the overall conductivity of the composite material, allowing more electromagnetic waves to penetrate and dissipate within the material.

[0061] 2. The effect of regulating nitride ceramics (Si3N4) The nitride ceramic Si3N4 is renowned for its high hardness, high temperature resistance, and moderate dielectric constant. In sample B (Ti3AlC2 / 35 wt% Si3N4), the composite of Si3N4 produces a "dilution" effect, smoothly modulating the overly extreme dielectric properties of the composite material. It ultimately achieves a minimum reflection loss of -48.1 dB at 12.2 GHz and an effective bandwidth of 3.2 GHz. Research shows that by controlling the phase composition of Si3N4, its dielectric properties can be further fine-tuned, providing an additional dimension for performance optimization. The introduction of Si3N4 brings the R2 and C1 parameters in the equivalent circuit to a more balanced state, demonstrating the effectiveness of this patented method for nitride ceramic systems.

[0062] 3. Innovative Applications of Polymers (High-Entropy Engineered Polymer HEP-B1) Sample C (Ti3AlC2 / 25 wt% HEP-B1) demonstrates the unique advantages of polymer modulation. This high-entropy polymer is prepared by melt blending five incompatible polymers: PVDF, PVDF-TrFE, PVDF-HFP, PP, and PS. Its high-entropy structure induces the formation of a highly disordered amorphous phase, increasing the free volume and thus greatly enhancing the orientation polarization effect. This sample achieves an extremely low reflection loss of -61.5 dB at 10.8 GHz, with the widest -10 dB bandwidth reaching 4.5 GHz. The low conductivity of the polymer ensures that the dielectric loss remains at a low level, while the strong polarization capability brought by the high-entropy effect simultaneously optimizes the capacitance C1 and resistance R2 in the equivalent circuit, achieving a breakthrough in broadband absorption performance.

[0063] 4. Mechanism Comparison and Universal Conclusions Although the three dielectric modulators have different mechanisms of action, they can all be uniformly described and optimized using the equivalent circuit model of this patent: SiO2 mainly affects the equivalent capacitance C1 through interface polarization.

[0064] Si3N4 adjusts the overall impedance through its stable dielectric properties, thus affecting the equivalent resistance R2 of the substrate.

[0065] High-entropy polymers significantly enhance orientation polarization capabilities by utilizing the enhanced molecular chain segment motion, while simultaneously optimizing C1 and R2.

[0066] Experimental results show that although the microscopic mechanisms of different dielectric modulating materials differ, the equivalent circuit design method of this patent can guide their recombination with the MAX phase to achieve excellent impedance matching and electromagnetic wave absorption by adjusting key parameters (R2, C1). This demonstrates that this method has universal guiding significance for various dielectric modulating materials such as oxide ceramics, nitride ceramics, and polymers.

[0067] Example 5: Performance Verification of Different Resonant Unit Structures This embodiment aims to demonstrate that as long as it can be equivalent to an RLC circuit, resonant units of various shapes can achieve the function of absorbing waves, and the performance difference mainly comes from the equivalent parameters L1 and C1.

[0068] Structural Design and Simulation: To verify the universality of this patented method, we designed four sets of experiments, fabricating resonant units of different shapes on the same Ti3AlC2 ceramic substrate: cross-shaped, open-ring (SRR), I-shaped, and H-shaped. The period of all units was set to 10 mm, and the substrate thickness was uniformly 4.5 mm to ensure that the performance differences mainly stemmed from the influence of the shape itself on the equivalent circuit parameters.

[0069] Test results show that despite their diverse geometries, these units all achieve effective electromagnetic wave absorption in specific frequency bands. The cross-shaped structure produces an absorption peak at 11.5 GHz with a minimum reflection loss of -42.3 dB; the open-ring structure, thanks to its stronger inductive-capacitive coupling effect, achieves a deeper absorption valley of -51.6 dB at 10.8 GHz; the I-shaped structure has the widest bandwidth, reaching 4.5 GHz; while the H-shaped structure achieves a loss of -47.2 dB at 11.2 GHz. These results intuitively demonstrate that the improvement in absorption performance is less related to the specific shape of the resonant unit and more dependent on the equivalent circuit parameters determined by the shape.

[0070] Conclusion: This embodiment fully demonstrates the strong universality of the equivalent circuit design method of this patent. Cross-shaped, open-ring, I-shaped, H-shaped, and even more complex biomimetic gradient resonant cavity structures, regardless of their geometry, can all have their absorption performance precisely controlled by optimizing the equivalent parameters L1 and C1, as long as they can be abstracted into an RLC circuit model. This provides a solid theoretical and experimental foundation for extending the scope of patent protection from the limited "prism shape" to "any planar or three-dimensional structure that can be equivalent to an RLC circuit." This circuit model-based method directly addresses the physical essence of electromagnetic functional material design, transcending the dependence on specific shapes.

[0071] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0072] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A broadband absorbing material based on a MAX phase metasurface structure, characterized in that, include: MAX phase ceramic matrix; And a periodic metasurface structure disposed on the surface of the MAX phase ceramic matrix; The periodic metasurface structure is composed of multiple arrayed conductive resonant units. The conductive resonant units are isolated from each other and / or from the MAX phase ceramic substrate by gaps, thereby forming a resonant circuit with equivalent inductance L1, equivalent capacitance C1 and equivalent resistance R1 under alternating electromagnetic field. The structural parameters of the absorbing material are determined based on an equivalent circuit model. The equivalent circuit model equates the periodic metasurface structure to a series branch of R1L1C1 and the MAX phase ceramic substrate to a parallel resistor R2. By adjusting the values ​​of the equivalent circuit parameters R1, L1, C1, and R2, the absorbing material is made to have at least one absorption peak with a reflection loss of less than -10 dB in the target frequency band.

2. The broadband absorbing material according to claim 1, characterized in that, The material of the MAX phase ceramic matrix is ​​selected from the general formula M. n+1 AX n MAX phase materials, where M is a transition metal, A is a main group element, X is carbon, nitrogen or carbon-nitrogen solid solution, and n=1,2,3.

3. The broadband absorbing material according to claim 1, characterized in that, The MAX phase ceramic matrix is ​​a solid solution and is selected from at least one of the following: A-site high-entropy solid solution, wherein the A-site contains at least three main group elements; M-site high-entropy solid solution, wherein the M-site contains at least three transition metal elements; X-position solid solution, where the X-position is C 1-y N y , where 0 ≤ y ≤ 1.

4. The broadband absorbing material according to claim 1, characterized in that, The MAX phase ceramic matrix is ​​a composite material of MAX phase material and dielectric modulating material, wherein the dielectric modulating material is selected from one or more of oxide ceramics, nitride ceramics, and polymers.

5. The broadband absorbing material according to claim 1, characterized in that, The conductive resonant unit can be a planar structure or a three-dimensional structure.

6. The broadband absorbing material according to claim 5, characterized in that, The conductive resonant unit includes prism-shaped, cross-shaped, open ring, I-shaped, H-shaped, or biomimetic gradient resonant cavity structures.

7. The broadband absorbing material according to claim 1, characterized in that, The period a of the periodic metasurface structure satisfies: 1 mm ≤ a ≤ 30 mm; the circumscribed circle diameter r of the characteristic dimension of the resonant unit satisfies: 0.1 mm ≤ r ≤ 10 mm; the thickness h of the MAX phase ceramic substrate satisfies: 0.5 mm ≤ h ≤ 6 mm; and the height d of the resonant unit satisfies: 0.01 mm ≤ d ≤ 4 mm.

8. A method for optimizing the impedance matching of a broadband absorbing material based on a MAX-phase metasurface structure as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Determine the initial geometric parameters of the periodic metasurface structure based on the target absorption frequency band; S2: Establish an electromagnetic simulation model of the absorbing material containing the initial geometric parameters, and calculate its reflection coefficient S11; S3: Based on the reflection coefficient S11, extract the equivalent circuit parameters of the absorbing material according to the equivalent circuit model. The equivalent circuit model equates the periodic metasurface structure to a series branch of R1L1C1 and the MAX phase ceramic substrate to a parallel resistor R2. S4: In circuit simulation software, adjust the values ​​of the equivalent circuit parameters R1, L1, C1, and R2 to optimize the impedance matching characteristics of the absorbing material in the target frequency band; S5: The optimized equivalent circuit parameters R1, L1, C1, and R2 are reverse-mapped to the final geometric parameters of the periodic metasurface structure to guide the preparation of the absorbing material.

9. The method according to claim 8, characterized in that, In step S3, the imaginary part of the impedance Im[Z] at two frequencies f1 and f2 near the resonant point is obtained. h (f1)] and Im[Z h (f2)], calculate the equivalent capacitance C1 and equivalent inductance L1; The equivalent resistance R2 of the MAX phase ceramic substrate is determined by calculating the overall impedance Z of the absorber based on the reflection coefficient S11 at the resonant point. total And by solving the overall impedance Z total The value of R2 is derived by reversing the equation that is equal to the parallel impedance of the periodic metasurface structure impedance and the substrate resistance R2.

10. The method according to claim 8, characterized in that, In step S4, the strategies for adjusting the equivalent circuit parameters include: Increase the equivalent inductance L1 or equivalent capacitance C1 to shift the absorption peak to lower frequencies; Increasing the equivalent resistance R1 of the metasurface structure or the equivalent resistance R2 of the MAX phase ceramic matrix will reduce the absorption peak intensity.

Images