Electromagnetic wave-absorbing material and preparation method thereof

Abstract

The invention relates to the field of structural wave absorption, in particular to an electromagnetic wave-absorbing material and a preparation method thereof. The electromagnetic wave-absorbing material comprises: a) a honeycomb substrate having a plurality of honeycomb holes penetrating along the thickness direction; the honeycomb holes are filled with the wave-absorbing medium; wherein the wave-absorbing medium is a condensate formed by cooling after paraffin and an absorbent are uniformly dispersed in a molten state; the absorbent has magnetic loss and / or dielectric loss properties. Impedance is adjusted through paraffin, loss is provided through the absorbent, a propagation path is prolonged through the honeycomb structure, and the electromagnetic wave-absorbing material which is reduced in interface reflection, improved in absorption efficiency, good in structural stability and adjustable in absorption performance is achieved.

Description

Technical Field

[0001] This invention relates to the field of structural wave absorption, and more specifically, to an electromagnetic wave absorbing material and its preparation method. Background Technology

[0002] Electromagnetic wave absorbing materials are widely used in aerospace, radar detection, communication equipment, electromagnetic shielding, and stealth structures. They are primarily used to attenuate and eliminate electromagnetic wave reflections, reduce radar cross-sections, or suppress electromagnetic interference. Existing absorbing materials typically dissipate the energy of incident electromagnetic waves by introducing absorbers with magnetic or dielectric loss properties into the medium, such as carbonyl iron powder, ferrite, carbon black, carbon nanotubes, or graphene. Common absorbing medium systems include resin-based composite materials, rubber-based composite materials, and foam absorbing materials.

[0003] However, resin matrices typically have high dielectric constants. As the amount of absorbent added increases, the overall dielectric constant of the system further rises, easily causing impedance mismatch at the interface between the material and air or skin. This leads to significant reflection of electromagnetic waves at the incident interface, reducing absorption efficiency. Simultaneously, the high viscosity of resins under processing conditions makes it difficult to achieve high volume fraction dispersion of the absorbent, limiting the allowable amount of absorbent to be added. This inhibits the formation of the loss network structure, affecting the material's absorption performance. Furthermore, the resin matrix may contain active functional groups, which can easily react with the absorbent surface during heat curing or affect the absorbent's microstructure, leading to a decrease in absorbent loss capacity and causing material instability.

[0004] In structural microwave absorption applications, honeycomb structures are often used as core materials to balance lightweight and mechanical properties. Existing methods typically involve filling the honeycomb pores with resin systems or using resin composite absorbing coatings. However, the inherent impedance mismatch, insufficient filling, and impaired absorber activity of these resin systems still limit further improvements in their microwave absorption performance.

[0005] Therefore, existing cellular absorbing materials still have clear areas for improvement in terms of efficient absorption of absorbers, interfacial impedance matching, filling uniformity, and absorption performance stability. Summary of the Invention

[0006] This invention covers the following technical solutions:

[0007] One aspect of the present invention relates to an electromagnetic absorbing material, comprising:

[0008] a) a honeycomb substrate having a plurality of honeycomb holes extending along the thickness direction; and b) an absorbing medium filling the honeycomb holes;

[0009] The microwave absorbing medium is a solidified product formed by uniformly dispersing paraffin and absorbent in a molten state and then cooling it; the absorbent has magnetic loss and / or dielectric loss characteristics.

[0010] According to another aspect of the present invention, there is an electromagnetic absorbing structure assembly comprising a support frame and an electromagnetic absorbing material as described above disposed within the support frame.

[0011] According to another aspect of the present invention, a method for preparing the electromagnetic absorbing material as described above is provided, comprising:

[0012] The honeycomb matrix is ​​provided, the paraffin wax and the absorbent are mixed and heated to melt to obtain a microwave absorbing melt; the microwave absorbing melt is introduced into the honeycomb pores of the honeycomb matrix and cooled and solidified.

[0013] This invention achieves an electromagnetic absorbing material with reduced interface reflection, improved absorption efficiency, good structural stability, and adjustable absorption performance by adjusting impedance with paraffin wax, providing loss with absorbent, and extending the propagation path with a honeycomb structure. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 Schematic diagram of a paraffin-filled honeycomb absorbing material. Detailed Implementation

[0016] Reference will now be made to detailed embodiments of the present invention, one or more of which are described below. Each example is provided for explanation and not for limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0017] Unless otherwise stated, all terms used to disclose this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Further guidance is provided below for a better understanding of the teachings of this invention. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0018] In this invention, unless otherwise stated, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the terms and laboratory procedures related to polymer materials and phase change materials, electromagnetic wave absorption, composite materials and structural materials used herein are all widely used terms and routine procedures in their respective fields. To better understand this invention, definitions and explanations of relevant terms are provided below.

[0019] As used herein, the terms “and / or,” “or / and,” and “and / or” encompass any one of two or more of the relevant listed items, as well as any and all combinations of the relevant listed items, including any two of the relevant listed items, any more of the relevant listed items, or a combination of all the relevant listed items.

[0020] The terms “containing,” “comprising,” and “including” as used in this invention are synonyms and are inclusive or open-ended, and do not exclude additional, uncited members, elements, or method steps.

[0021] In this invention, the numerical range represented by endpoints includes all numerical values ​​and fractions contained within that range, as well as the endpoints mentioned.

[0022] In describing representative embodiments of the invention, this specification may present the methods and / or processes of the invention as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that the method or process does not depend on the specific order of steps presented herein. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps presented in the specification should not be construed as a limitation of the claims. Furthermore, the claims relating to the methods and / or processes of the invention should not be limited to the execution of their steps in the order they are written, and those skilled in the art will readily recognize that the sequence may be modified while still remaining within the spirit and scope of the invention.

[0023] The concentration values ​​involved in this invention include fluctuations within a certain range.

[0024] As used in this invention, unless otherwise stated, the singular forms of the articles “a,” “an,” and “the” include plural referents.

[0025] In this invention, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity of 2 or more.

[0026] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0027] In this invention, terms such as "preferred," "better," "more suitable," and "ideal" merely describe implementation methods or embodiments with better effects and should be understood not to limit the scope of protection of this invention. In this invention, terms such as "optionally," "optionally," and "optional" mean that something is optional, that is, selected from either "with" or "without" a parallel solution. If multiple "optional" statements appear in a technical solution, unless otherwise specified and without contradiction or mutual constraint, each "optional" statement is independent.

[0028] In this invention, the "honeycomb matrix" refers to a load-bearing frame composed of regularly arranged walls and having multiple through-pores along the thickness direction. It can be made of dielectric or metallic materials, such as aramid paper phenolic honeycomb, glass fiber honeycomb, polymer honeycomb, ceramic honeycomb, or metal honeycomb. The typical cross-section of the pores is hexagonal, but it can also be a square honeycomb, triangular honeycomb, or other regular / irregular pore shapes. The specific shape is not a limitation of this invention. The function of the honeycomb matrix is ​​to provide through-pores for accommodating the absorbing medium and to maintain the overall thickness and mechanical morphology of the structure, enabling the absorbing medium to achieve a stable spatial distribution on a macroscopic scale. The material and dielectric properties of the honeycomb matrix are not key limitations of this invention; it is sufficient that it can maintain structural stability and support the absorbing medium under the preparation conditions of this invention.

[0029] The first aspect of the present invention relates to an electromagnetic absorbing material, comprising:

[0030] a) a honeycomb substrate having a plurality of honeycomb holes extending along the thickness direction; and b) an absorbing medium filling the honeycomb holes;

[0031] The microwave absorbing medium is a solidified product formed by uniformly dispersing paraffin and absorbent in a molten state and then cooling it; the absorbent has magnetic loss and / or dielectric loss characteristics.

[0032] The paraffin wax exhibits good fluidity when heated, enabling it to fill the spaces within the honeycomb cells and form a structurally stable solid continuum upon cooling. However, there are several engineering limitations to using paraffin wax as a matrix. The main issue is that paraffin wax melts at high temperatures, compromising its basic shape and causing leakage. Therefore, adding a honeycomb matrix is ​​necessary to ensure the overall material shape.

[0033] The absorbent is a functional particulate material with magnetic and / or dielectric loss characteristics. Its dielectric parameters and addition ratio can ensure that the complex dielectric constant of the system falls within the impedance matching controllable range, thereby guaranteeing absorption performance. In some preferred embodiments, the absorbent is selected from carbonyl iron powder, ferrite, carbon black, carbon nanotubes, graphene, and combinations thereof. The absorbent forms a uniform dispersion in the molten paraffin system, which, after solidification, constitutes a uniform loss network structure, thereby achieving energy dissipation of electromagnetic waves. It should be noted that carbon-based absorbents significantly increase the viscosity of the resin system, thus limiting the amount of absorbent added. Similarly, metallic magnetic absorbents (such as carbonyl iron powder and ferrite) are also limited by matrix viscosity and interfacial wettability in resin, often making it difficult to achieve high volume fraction dispersion, resulting in insufficient impedance matching and loss network construction. This invention uses molten paraffin as the matrix, which can achieve high-content uniform dispersion of the absorbent and obtain better absorption performance. Therefore, in some preferred embodiments, the absorbent is selected from carbon-based absorbents (such as carbon black, carbon nanotubes, and graphene).

[0034] By using paraffin, a material with a low dielectric constant, as the matrix material, reflections caused by impedance mismatch at the material interface can be effectively reduced, making it easier for incident electromagnetic waves to penetrate the material's interior. The absorber provides magnetic and / or dielectric loss channels to absorb electromagnetic energy. The honeycomb channel structure extends the propagation path of electromagnetic waves in the material, promoting multiple scattering and loss. Therefore, the electromagnetic absorbing material of this invention has the characteristics of good impedance matching, high absorption efficiency, controllable structural strength, and stable manufacturing process, and is suitable for constructing lightweight structured absorbing components.

[0035] In this invention, the amount of absorbent in the absorbing medium has a significant impact on the electromagnetic loss capability and impedance matching characteristics of the material. When the absorbent content is too low, the loss component is insufficient, and the absorption peak intensity and absorption bandwidth of the material will decrease. When the absorbent content is too high, the overall dielectric constant of the system increases significantly, the interface reflection is enhanced, resulting in a decrease in electromagnetic wave incident coupling efficiency, and the absorbents are prone to agglomeration, which in turn affects the absorption stability and repeatability of the material, and may even prevent the establishment of a uniformly dispersed system. To balance good absorption performance and dielectric parameter stability, in some preferred embodiments, the mass ratio of paraffin to absorbent is 10:(1-30); for example, 10:14, 10:5, 10:7, 10:10, 10:15, 10:20, 10:25, 10:30, preferably 10:(20-30).

[0036] In an optional embodiment of the present invention, the honeycomb substrate can be an absorbing honeycomb. An absorbing honeycomb refers to a honeycomb wall material that inherently possesses magnetic loss and / or dielectric loss characteristics, or whose surface is coated with a functional absorbing coating, or incorporating absorber powder during the honeycomb substrate molding process, so that the honeycomb structure itself participates in energy loss during electromagnetic wave propagation. The absorbing honeycomb can be made from ferrite-based composite materials, conductive filler-reinforced resin honeycombs, carbon-based honeycombs, magnetic ceramic honeycombs, or other honeycomb materials with electromagnetic loss response.

[0037] Compared to dielectric honeycomb, absorbing honeycomb can further enhance the multiple reflections, refractions, and dissipation effects of electromagnetic waves in the material without changing the honeycomb pore structure and the distribution of the paraffin-absorbing medium, thereby increasing the absorption peak intensity and broadening the absorption bandwidth under certain conditions. However, the absorption performance of this invention mainly comes from the paraffin-based impedance matching system and the loss network structure of the absorber; whether the honeycomb matrix has absorption function does not affect the construction of the core technical solution of this invention. Therefore, absorbing honeycomb is an optional reinforcement structure, and its adoption can be selected based on the target frequency band, structural load requirements, or process cost.

[0038] In another embodiment of the present invention, a skin layer may be provided on the upper and / or lower surfaces of the electromagnetic absorbing material. The skin layer primarily serves to protect the structure, assist in shaping the paraffin wax, encapsulate the entire absorbing material to prevent leakage, and provide load-bearing connections. It improves the overall mechanical strength and environmental adaptability of the material while maintaining the stability of the honeycomb structure and the absorbing medium. The skin layer can be integrally prepared with the honeycomb substrate and the absorbing medium through processes such as resin-based film, prepreg curing, or hot-pressing lamination, thereby forming an absorbing component with a sandwich structure.

[0039] The skin can be either a wave-transparent skin or a wave-absorbing skin. Wave-transparent skins typically use materials with low dielectric constants and low losses to ensure that incident electromagnetic waves can pass through the skin layer and enter the honeycomb absorbing structure with minimal energy reflection and phase distortion. These materials may include glass fiber reinforced resin composites, polytetrafluoroethylene composites, nylon fiber reinforced materials, etc. In a preferred embodiment, the real part of the dielectric constant of the wave-transparent skin can be 2.8–3.5, and the dielectric tangent can be 0.004–0.04, to achieve low interface reflection and ensure good wave transmission.

[0040] In contrast, absorbing skins can incorporate absorbers or absorbing fillers into the skin material, giving the surface layer electromagnetic energy dissipation capabilities. This creates a composite absorbing system of "outer primary absorption + inner honeycomb loss enhancement," which can further enhance the absorption peak intensity or broaden the absorption bandwidth. In different application scenarios, either transparent or absorbing skins can be selected based on the target frequency band, structural strength, and wave transmission requirements.

[0041] In another embodiment, a carbon fiber prepreg layer may be disposed on the upper and / or lower surface of the electromagnetic absorbing material to provide additional structural reinforcement and shape stability. The carbon fiber prepreg layer, after curing, forms a high-specific-strength upper / lower load-bearing layer, enabling the material of this invention to serve as a structural absorbing component requiring mechanical support. The carbon fiber layer does not alter the loss mechanism of the paraffin-absorbing medium; its main functions are mechanical reinforcement and interface protection.

[0042] A second aspect of the present invention relates to an electromagnetic absorbing structure assembly, comprising a support frame and an electromagnetic absorbing material as described above disposed within the support frame.

[0043] Typical examples of such structural components include: radomes, wing or fuselage coverings for unmanned aerial vehicles, radar-absorbing layers in the shape of aircraft bulkheads or fairings, stealth structural layers in the shape of missiles and tactical aircraft, shielding panels for electronic equipment bulkheads of ships or vehicles, and radar-absorbing sandwich panels for communication base stations, data centers, or secure spaces.

[0044] In these application scenarios, the electromagnetic absorbing structure component can achieve lightweighting, controllable strength, and synergistic optimization of absorption performance. After electromagnetic waves are incident, they enter the honeycomb absorbing core layer through the support frame and are reflected, scattered, and lost multiple times in the paraffin-absorbent solidified dispersion system, thereby reducing reflection and enhancing absorption. This makes it suitable for engineering needs such as stealth protection, electromagnetic interference suppression, and electromagnetic environment optimization.

[0045] The support frame provides structural support and shape constraint for the electromagnetic absorbing material, enabling it to maintain a stable configuration on a macroscopic scale and achieve reliable connection with other structural components. The electromagnetic absorbing material can be the honeycomb absorbing material described in any of the above embodiments, where the absorbing medium is shaped and solidified within the honeycomb cells, thereby forming a lightweight, customizable thickness absorbing core layer with adjustable loss performance.

[0046] A third aspect of the present invention relates to a method for preparing the electromagnetic absorbing material as described above, comprising:

[0047] The honeycomb matrix is ​​provided, the paraffin wax and the absorbent are mixed and heated to melt to obtain a microwave absorbing melt; the microwave absorbing melt is introduced into the honeycomb pores of the honeycomb matrix and cooled and solidified.

[0048] The embodiments of the present invention will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this invention, or follow experimental manuals or conventional conditions in the art, or other experimental methods known in the art, or follow the conditions recommended by the manufacturer.

[0049] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision.

[0050] The absorbents used in the examples are as follows:

[0051] Carbonyl iron powder is a commercially available product. By weight, 23 parts of absorbent and 10 parts of paraffin are mixed to obtain the following electromagnetic properties of the mixture: in the range of 2 to 18 GHz, the real part of the dielectric constant is 6 to 7, the imaginary part of the dielectric constant is 0 to 0.1, the real part of the permeability is 0.5 to 3.5, and the imaginary part of the permeability is 0.7 to 1.4.

[0052] The carbon black was a commercially available product. By weight, 4 parts of absorbent and 10 parts of paraffin were mixed to obtain the following electromagnetic properties of the mixture: in the range of 2 to 18 GHz, the real part of the dielectric constant was 14 to 68, the imaginary part of the dielectric constant was 3.2 to 3.5, the real part of the permeability was 1, and the imaginary part of the permeability was 0.

[0053] Example 1

[0054] Weigh out the paraffin wax and heat it to a molten state. Add carbonyl iron powder to the molten paraffin wax and stir to make the carbonyl iron powder evenly dispersed in the molten paraffin wax system. By weight, the paraffin wax is 10 parts and the carbonyl iron powder is 23 parts.

[0055] The obtained microwave absorbing melt is introduced into the honeycomb pores of the honeycomb matrix and cooled and solidified to obtain a honeycomb microwave absorbing material. No skin is provided in this structure.

[0056] The honeycomb substrate is hexagonal, the honeycomb frame has a side length of 3mm, a wall thickness of 0.06mm, and a height of 2mm.

[0057] Example 2

[0058] Weigh out the paraffin wax and heat it to a molten state. Add carbonyl iron powder to the molten paraffin wax and stir to make the absorbent evenly dispersed in the molten paraffin wax system. By weight, the paraffin wax is 10 parts and the absorbent is 23 parts (which is a mixture of carbonyl iron powder and carbon black, by weight, the carbonyl iron powder is 40 parts and the carbon black is 1 part).

[0059] The obtained microwave absorbing melt is introduced into the honeycomb pores of the honeycomb matrix and cooled and solidified to obtain a honeycomb microwave absorbing material. The structure is wrapped with a microwave-transparent skin on the top and bottom, with a thickness of 0.2 mm, a real part of dielectric constant of 3.2, and a dielectric tangent of 0.008.

[0060] The honeycomb substrate is hexagonal, the honeycomb frame has a side length of 3mm, a wall thickness of 0.06mm, and a height of 2mm.

[0061] Example 3

[0062] The difference between this embodiment and embodiment 1 is that a wave-transparent skin is respectively applied to the upper and lower surfaces of the honeycomb structure, and the skin is the same as that in embodiment 2.

[0063] Example 4

[0064] The difference between this embodiment and Embodiment 1 is that the absorbent is replaced with carbon black. Due to the different densities of carbon black and iron carbonyl, the weight percentages are 10 parts paraffin and 4 parts carbon black. The height of the honeycomb matrix is ​​1.5 mm.

[0065] Comparative Example 1

[0066] The paraffin-filled honeycomb absorbing material provided in this comparative example has a honeycomb frame internal space (hexagonal column) filled with absorbing paraffin, wherein the hexagonal honeycomb frame has a side length of 3mm, a wall thickness of 0.06mm, and a height of 2mm.

[0067] The microwave-absorbing paraffin is a homogeneous mixture of paraffin and absorbent, with 10 parts paraffin and 1 part absorbent by weight.

[0068] The top and bottom are wrapped with a transparent skin with a thickness of 2.5mm. The measured real part of the dielectric constant is 3.2 and the dielectric tangent is 0.008.

[0069] Comparative Example 2

[0070] The paraffin-filled honeycomb absorbing material provided in this comparative example has a honeycomb frame internal space (hexagonal column) filled with absorbing paraffin, wherein the hexagonal honeycomb frame has a side length of 3mm, a wall thickness of 0.06mm, and a height of 2mm.

[0071] The microwave-absorbing paraffin is a homogeneous mixture of paraffin and absorbent, with 10 parts paraffin and 31 parts absorbent by weight.

[0072] Comparative Example 3

[0073] The only difference between this comparative example and Example 1 is that paraffin wax was replaced with an equal amount of polyamide resin (PA6).

[0074] Comparative Example 4

[0075] The only difference between this comparative example and Example 4 is that paraffin wax was replaced with an equal amount of polyamide resin (PA6).

[0076] Reflection loss measurement results of paraffin / resin filled honeycomb absorbing material samples

[0077]

[0078] A comparison of Example 1 and Comparative Example 3 shows that, under the same absorbent system, the paraffin-based material exhibits significantly better absorption performance than the resin (PA6)-based material. Paraffin has a lower dielectric constant and good melt wettability, enabling the absorbent to achieve high-content uniform dispersion in the system, thereby constructing a continuous loss network; while the resin system has higher viscosity and poorer interfacial compatibility, easily leading to absorbent agglomeration and impedance mismatch, thus limiting its absorption performance.

[0079] Furthermore, a comparison between Example 3 and Comparative Example 3 shows that even with the introduction of transparent skins on the top and bottom of the honeycomb structure for engineering encapsulation, the absorption performance of the paraffin-based microwave absorbing system still maintains a significant advantage. This indicates that the improved absorption performance of the present invention does not rely on an ideal exposed interface; it can still achieve enhanced electromagnetic loss in actual assembly and structured application scenarios, demonstrating engineering applicability.

[0080] A comparison of Example 4 and Comparative Example 4 shows that the carbon-based absorbent exhibits absorption effect in paraffin wax; however, in the resin system, due to the high viscosity and insufficient wettability of the system, a higher concentration of carbon-based absorbent cannot be completely mixed with the resin. This demonstrates that the present invention has universal applicability to absorbent systems, and is particularly suitable for carbon-based absorbents.

[0081] Furthermore, the absorption bandwidth range of the embodiment is different from that of the comparative example, indicating that paraffin can also control the reflectivity by adjusting the absorber, allowing for more flexible customized design for different frequency bands.

[0082] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. An electromagnetic wave absorbing material, characterized by, Comprising: a) a honeycomb substrate having a plurality of honeycomb cells extending through the thickness direction; and b) a wave-absorbing medium filled in the honeycomb cells; wherein the wave-absorbing medium is a solidified product of the paraffin and the absorber uniformly dispersed in a molten state; the absorber has magnetic loss and / or dielectric loss characteristics.

2. The electromagnetic wave absorbing material according to claim 1, characterized in that, The absorber is selected from the group consisting of carbonyl iron powder, ferrite, carbon black, carbon nanotube, graphene and combinations thereof.

3. The electromagnetic wave absorbing material according to claim 1, wherein, The mass ratio of the paraffin to the absorber is 10:(1-30); preferably 10:(20-30).

4. The electromagnetic wave absorbing material according to any one of claims 1-3, characterized in that, The honeycomb substrate is a wave-absorbing honeycomb.

5. The electromagnetic wave absorbing material according to any one of claims 1-3, characterized in that, The upper and / or lower surface is provided with a skin.

6. The electromagnetic wave absorbing material according to claim 5, wherein, The skin is a wave-transparent skin or a wave-absorbing skin.

7. The electromagnetic wave absorbing material according to claim 6, characterized in that, The wave-transparent skin has a dielectric constant real part of 2.8-3.5 and a dielectric tangent value of 0.004-0.

04.

8. The electromagnetic wave absorbing material according to any one of claims 1-3, wherein, The upper and / or lower surface is provided with a carbon fiber prepreg.

9. An electromagnetic wave absorber assembly, characterized by, Comprising a support frame and the electromagnetic wave-absorbing material of any one of claims 1-8 arranged in the support frame.

10. The method for preparing the electromagnetic wave absorbing material according to any one of claims 1-8, characterized in that, Comprising: Providing the honeycomb substrate, mixing the paraffin and the absorber and heating to molten to obtain a wave-absorbing molten body; introducing the wave-absorbing molten body into the honeycomb cells of the honeycomb substrate and cooling to solidify.

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