Broadband wave-absorbing material and preparation method thereof

Abstract

This application provides a broadband absorbing material and its preparation method in its embodiments. Specifically, the wave-transmitting protective layer is a thin fiber-reinforced composite material layer, and the pattern of the intermediate coupling layer includes basic unit regions and scaled unit regions. The intermediate coupling layer is a unit resistive film layer. The basic unit regions and scaled unit regions each include several complete or incomplete regular hexagons. The basic unit region includes a complete first regular hexagon in the center position, and the scaled unit region includes a complete second regular hexagon in the center position and four complete second regular hexagons in non-center positions. The areas of the first and second regular hexagons are different. This application proposes a method for combining patterns and lightweight magnetic materials to obtain a wider effective frequency band and reduce the overall weight of the composite material. The magnetic material contains carbon material, which enhances the dielectric loss of the functional filler while reducing magnetic loss.

Description

Technical Field

[0001] This invention relates to the field of communications, and in particular to a broadband absorbing material and its preparation method. Background Technology

[0002] Metasurface absorbing materials are advanced functional materials based on the design of artificial metasurfaces. Through precise control of subwavelength-scale structures, they achieve efficient absorption and modulation of electromagnetic waves. The core principle is to utilize periodically arranged micro / nano unit structures, such as metal resonators and dielectric layers, to excite localized surface plasmon resonance or magnetic resonance, thereby achieving near-perfect absorption in specific frequency bands such as microwaves, terahertz, or infrared. Compared to traditional absorbing materials, metasurface absorbers offer advantages such as ultra-thinness (less than 1 / 10 of the wavelength), lightweight, tunability, and broadband absorption. Furthermore, the absorption frequency band and polarization characteristics can be flexibly controlled through structural design. These materials hold significant application potential in fields such as stealth technology, electromagnetic compatibility, solar energy utilization, and terahertz imaging.

[0003] Metasurface absorbing materials use traditional absorbing materials as the medium and achieve the control of electromagnetic wave absorption and scattering characteristics through surface pattern design, thereby obtaining absorbing materials with a thickness lower than that of traditional absorbing materials. CN201521139084.3 discloses an I-shaped absorbing pattern; CN 116315731 discloses a centrally symmetric pattern composed of two congruent ellipses intersecting in a cross shape; CN 110190407 discloses a hexagonal metal ring pattern with a loaded resistor; CN 118943744 discloses a tessellated structure with hexagons and squares as units, etc.

[0004] However, existing ultrathin absorbing materials face difficulties in multi-frequency coupling, and multi-layer designs may weaken the interlayer strength of fiber composite materials, affecting their mechanical properties. Summary of the Invention

[0005] In view of the above problems, embodiments of the present invention are proposed to provide a broadband absorbing material and a method for preparing the same, which overcomes or at least partially solves the above problems:

[0006] A broadband absorbing material includes a wave-transmitting protective layer, an intermediate coupling layer, and a wave-absorbing structural layer arranged sequentially.

[0007] The wave-transmitting protective layer is a thin fiber-reinforced composite material layer, and the thickness of the wave-transmitting protective layer ranges from 50μm to 100μm.

[0008] The pattern of the intermediate coupling layer includes a basic unit region and a scaling unit region, and the intermediate coupling layer is a unit resistive film layer; specifically, the basic unit region and the scaling unit region each include a number of complete or incomplete regular hexagons, wherein the basic unit region includes a complete first regular hexagon in the center position, and the scaling unit region includes a complete second regular hexagon in the center position and four complete second regular hexagons in non-center positions; the first regular hexagon and the second regular hexagon have different areas; the basic unit is composed of a first regular hexagon and four right trapezoids.

[0009] Preferably, the right trapezoid is obtained by dividing the first regular hexagon by a quarter radially, and the four right trapezoids are arranged symmetrically around the first regular hexagon.

[0010] Preferably, the scaling unit is composed of four sub-units whose linear dimensions are reduced to one-quarter of the basic unit, joined together in a cross shape.

[0011] Preferably, the side length of the first regular hexagon is in the range of 2 to 4 mm; the vertical distance between the first regular hexagon and the right trapezoid is in the range of 1.3 to 1.5 mm.

[0012] Preferably, the microwave absorbing structure layer comprises a dielectric layer and a metal backplate arranged sequentially.

[0013] One side of the dielectric layer is connected to the intermediate coupling layer, and the other side of the dielectric layer is connected to the metal backplate; the dielectric layer is a magnetic material absorbing composite layer.

[0014] Preferably, the metal backplate is a copper film with a value range of 10μm to 30μm; and / or, the metal backplate is an aluminum film with a value range of 10μm to 30μm.

[0015] Preferably, the magnetic material microwave absorbing composite layer is made of a resin matrix and a magnetic filler, wherein the volume ratio of the magnetic filler to the resin is 0.5:1 to 3:1; and the magnetic filler is a lightweight magnetic microwave absorbing material.

[0016] Preferably, the lightweight magnetic microwave absorbing material comprises a hollow center, a carbon base layer, a silicon oxide layer, and a magnetic layer arranged sequentially; the lightweight magnetic microwave absorbing material is spherical in shape, and the microspheres of the lightweight magnetic microwave absorbing material have a size of 200-800 nm.

[0017] Preferably, the metal backplate is a copper film with a value range of 25 μm; or, the metal backplate is an aluminum film with a value range of 25 μm; or, the metal backplate is a copper film with a value range of 25 μm.

[0018] Preferably, the thin-layer fiber-reinforced composite material layer is made of glass fiber fabric with an areal density of less than or equal to 100 g / m2; or, the thin-layer fiber-reinforced composite material layer is made of aramid fiber fabric with an areal density of less than or equal to 100 g / m2.

[0019] To achieve this, the application also includes a method for preparing the broadband absorbing material, comprising:

[0020] Acrylic acid PS microspheres containing nitrile groups were prepared by emulsion polymerization. The PS microspheres were dispersed in an aqueous ethanol solution, and the pH was adjusted to weakly alkaline by adding surfactant and ammonia. Ethyl silicate was added dropwise for hydrolysis polymerization. After centrifugation and drying, the microspheres were thermally degraded under an inert atmosphere to obtain silica microspheres with carbon-containing inner layers. Then, a lightweight magnetic material with a magnetite magnetic layer was generated on the surface of the microspheres by hydrothermal reaction.

[0021] The lightweight magnetic material described in the step is mixed with resin at a weight ratio of 1:1, a prepreg is prepared using glass fiber cloth, and then molded and combined with a metal substrate to obtain a thin composite material.

[0022] A microwave absorbing material with a thickness of 1.1 mm and a density of 2.3 g / cm³ is obtained by screen printing a pattern on the surface of the thin composite material. 3 .

[0023] This application specifically includes the following advantages:

[0024] In the embodiments of this application, compared with the difficulties in multi-frequency coupling faced by ultra-thin absorbing materials in the prior art, and the potential weakening of interlayer strength and impact on mechanical properties due to multi-layer design, this application provides a solution of pattern combination and lightweight magnetic materials, specifically: including a wave-transparent protective layer, an intermediate coupling layer and a wave-absorbing structure layer arranged sequentially; the wave-transparent protective layer is a thin-layer fiber-reinforced composite material layer, and the thickness of the wave-transparent protective layer ranges from 50μm to 100μm; the pattern of the intermediate coupling layer includes basic unit regions and scaled unit regions, and the intermediate coupling layer is a unit resistive film layer; specifically, the basic unit regions and scaled unit regions each include several complete or incomplete regular hexagons, wherein the basic unit region includes a complete first regular hexagon in the center position, and the scaled unit region includes a complete second regular hexagon in the center position and four complete second regular hexagons in non-center positions; the areas of the first regular hexagon and the second regular hexagon are different. This application proposes a method for combining patterns and using lightweight magnetic materials to address the difficulties faced by ultra-thin microwave absorbing materials in the market in multi-frequency coupling, and the problem that multi-layer designs may weaken the interlayer strength of fiber composite materials, affecting their mechanical properties. By combining patterns, multi-band coupling is achieved, resulting in a wider effective frequency band. The use of lightweight magnetic materials as fillers reduces the overall weight of the composite material, which has a higher specific strength and is suitable for lightweight microwave absorbing structures. The magnetic materials contain carbon materials, which enhance the dielectric loss of the functional filler while reducing magnetic loss, thus helping to reduce the overall thickness of the composite material. Attached Figure Description

[0025] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of a broadband absorbing material according to the present invention;

[0027] Figure 2 This is a schematic diagram of the planar structure of a broadband absorbing material according to the present invention;

[0028] Figure 3 This is a schematic diagram of the planar structure of a broadband absorbing material according to the present invention;

[0029] Figure 4 This is a schematic diagram of the composite material's wave absorption characteristics in Example 1 of a method for preparing a broadband absorbing material according to the present invention;

[0030] Figure 5This is a comparative schematic diagram illustrating a method for preparing a broadband absorbing material according to the present invention.

[0031] 1. Wave-transparent protective layer; 2. Intermediate coupling layer; 21. Basic unit region; 211. First regular hexagon; 212. Right trapezoid; 22. Scaling unit region; 221. Second regular hexagon; 3. Dielectric layer; 4. Metal backplate. Detailed Implementation

[0032] To make the objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. 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.

[0033] The inventors, through analysis of existing technologies, discovered that metasurface absorbing materials use traditional absorbing materials as a medium, and achieve the control of electromagnetic wave absorption and scattering characteristics through surface pattern design, thereby obtaining absorbing materials with a thickness lower than that of traditional absorbing materials. CN201521139084.3 discloses an I-shaped absorbing pattern; CN 116315731 discloses a centrally symmetric pattern composed of two congruent ellipses intersecting in a cross shape; CN 110190407 discloses a hexagonal metal ring pattern with applied resistance; CN 118943744 discloses a tessellated structure using hexagons and squares as units, etc. Due to the frequency band dependence of absorption characteristics, the pattern size and structure do not have broad applicability; therefore, most absorbing materials require pattern design based on specific objectives.

[0034] Furthermore, in existing technologies, when the thickness is much less than a quarter of the wavelength, it is difficult for a single pattern to achieve wide coupling across multiple frequency bands. Thin absorbing composite materials are not suitable for multi-layer design to broaden the bandwidth, especially fiber-reinforced composite materials. Multi-layer structural design may lead to a decrease in interlaminar shear strength of the composite material, affecting the overall mechanical properties of the composite material.

[0035] In the embodiments of this application, compared with the difficulties in multi-frequency coupling faced by ultra-thin absorbing materials in the prior art, and the potential weakening of interlayer strength and impact on mechanical properties due to multi-layer design, this application provides a solution of pattern combination and lightweight magnetic materials, specifically: including a wave-transmitting protective layer 1, an intermediate coupling layer 2, and a wave-absorbing structure layer arranged sequentially; the wave-transmitting protective layer 1 is a thin-layer fiber-reinforced composite material layer, and the thickness of the wave-transmitting protective layer 1 ranges from 50μm to 100μm; the pattern of the intermediate coupling layer 2 includes a basic unit region 21 and a scaling unit region 22, and the intermediate coupling layer 2 is a unit resistive film layer; specifically, the basic unit region 21 and the scaling unit region 22 each include a plurality of complete or incomplete regular hexagons, wherein the basic unit region 21 includes a complete first regular hexagon 211 in the center position, and the scaling unit region 22 includes a complete second regular hexagon 221 in the center position and four complete second regular hexagons 221 in non-center positions; the areas of the first regular hexagon 211 and the second regular hexagon 221 are different. This application proposes a method for combining patterns and using lightweight magnetic materials to address the difficulties faced by ultra-thin microwave absorbing materials in the market in multi-frequency coupling, and the problem that multi-layer designs may weaken the interlayer strength of fiber composite materials, affecting their mechanical properties. By combining patterns, multi-band coupling is achieved, resulting in a wider effective frequency band. The use of lightweight magnetic materials as fillers reduces the overall weight of the composite material, which has a higher specific strength and is suitable for lightweight microwave absorbing structures. The magnetic materials contain carbon materials, which enhance the dielectric loss of the functional filler while reducing magnetic loss, thus helping to reduce the overall thickness of the composite material.

[0036] Reference Figures 1-3 The diagram illustrates the structure of the present invention, which may specifically include the following structure: a wave-transmitting protective layer 1, an intermediate coupling layer 2, and a wave-absorbing structure layer arranged sequentially; the wave-transmitting protective layer 1 is a thin-layer fiber-reinforced composite material layer, and the thickness of the wave-transmitting protective layer 1 ranges from 50 μm to 100 μm; the pattern of the intermediate coupling layer 2 includes a basic unit region 21 and a scaling unit region 22, and the intermediate coupling layer 2 is a unit resistive film layer; specifically, the basic unit region 21 and the scaling unit region 22 each include a plurality of complete or incomplete regular hexagons, wherein the basic unit region 21 includes a complete first regular hexagon 211 in the center position, and the scaling unit region 22 includes a complete second regular hexagon 221 in the center position and four complete second regular hexagons 221 in non-center positions; the areas of the first regular hexagon 211 and the second regular hexagon 221 are different.

[0037] In this embodiment, the structure includes a wave-transmitting protective layer 1, an intermediate coupling layer 2, and a wave-absorbing structural layer arranged sequentially. The wave-transmitting protective layer 1 is a thin-layer fiber-reinforced composite material layer, and its thickness ranges from 50 μm to 100 μm. Preferably, the thickness of the wave-transmitting protective layer 1 is 50 μm; preferably, the thickness is 75 μm; preferably, the thickness is 100 μm. The thin-layer fiber-reinforced composite material layer is made of glass fiber fabric with an areal density of less than or equal to 100 g / m²; or, the thin-layer fiber-reinforced composite material layer is made of aramid fiber fabric with an areal density of less than or equal to 100 g / m².

[0038] As an example, the wave-transparent protective layer 1 is also called a surface wave-transparent layer. The surface wave-transparent layer is a thin-layer fiber-reinforced composite material layer with a thickness of ≤100μm. The thin-layer fiber-reinforced composite material layer is made of glass fiber fabric or aramid fiber fabric with an areal density of less than 100g / m2, and the real part of the dielectric constant of the wave-transparent protective layer 1 is ≤4.0 and the loss tangent is ≤0.02.

[0039] In this embodiment, the pattern of the intermediate coupling layer 2 includes a basic unit region 21 and a scaling unit region 22, and the intermediate coupling layer 2 is a unit resistive film layer. Specifically, the basic unit region 21 and the scaling unit region 22 each include a plurality of complete or incomplete regular hexagons. The basic unit region 21 includes a complete first regular hexagon 211 at the center, and the scaling unit region 22 includes a complete second regular hexagon 221 at the center and four complete second regular hexagons 221 at non-center positions. The first regular hexagon 211 and the second regular hexagons 221 have different areas. Multi-band coupling is achieved through the combination of patterns, resulting in a wider effective frequency band.

[0040] In this embodiment, the basic unit comprises a first regular hexagon 211 and four right trapezoids 212. Each right trapezoid 212 is obtained by dividing the first regular hexagon 211 by a quarter radial division, and the four right trapezoids 212 are symmetrically arranged around the first regular hexagon 211.

[0041] As an example, four right trapezoids 212 and one first regular hexagon 211 together constitute a basic unit, and multi-band absorption performance is optimized through combination and arrangement. The four right trapezoids 212 are respectively set at the four corners of the first regular hexagon 211, and the sides of the first regular hexagon 211 are parallel to the slant sides of the right trapezoids 212. Two right trapezoids 212 are placed upside down at the upper left and upper right corners of the first regular hexagon 211, and two right trapezoids 212 are square at the lower left and lower right corners of the first regular hexagon 211.

[0042] In one specific embodiment, the basic unit consists of a central first regular hexagon 211 and four symmetrically distributed right-angled trapezoids 212 around it. The right-angled trapezoids 212 are obtained by radially dividing the hexagon into four equal parts, forming a geometrically complementary structure. The four right-angled trapezoids 212 are arranged in two sets of mirror images: the two upper ones are inverted, with their top edges facing inwards and respectively attached to the upper left and upper right corners of the hexagon; the two lower ones are upright, with their base edges facing inwards and corresponding to the lower left and lower right corners. The sloping sides of all trapezoids are parallel to the side lines of the first regular hexagon 211. This spatial arrangement, by adjusting the size ratio of the right-angled trapezoids 212 to the first regular hexagon 211, can form a multi-resonance structure. When multiple units are periodically arranged, the electromagnetic coupling of different geometric modules can excite multi-band absorption peaks, thereby optimizing broadband absorption performance. Strict angular symmetry between units and 120° rotational symmetry ensure isotropic response.

[0043] In this embodiment, the side length of the first regular hexagon 211 ranges from 2 to 4 mm. Preferably, the side length of the first regular hexagon 211 is 3 mm; preferably, the side length of the first regular hexagon 211 is 2 mm; preferably, the side length of the first regular hexagon 211 is 2.5 mm; preferably, the side length of the first regular hexagon 211 is 3.5 mm; preferably, the side length of the first regular hexagon 211 is 4 mm.

[0044] In this embodiment, the vertical distance between the first regular hexagon 211 and the right trapezoid 212 ranges from 1.3 to 1.5 mm; preferably, the vertical distance between the first regular hexagon 211 and the right trapezoid 212 is 1.4 mm; preferably, the vertical distance between the first regular hexagon 211 and the right trapezoid 212 is 1.3 mm; preferably, the vertical distance between the first regular hexagon 211 and the right trapezoid 212 is 1.5 mm.

[0045] In this embodiment of the application, the scaling unit is composed of four sub-units whose linear dimensions are reduced to one-quarter of the basic unit, joined together in a cross shape.

[0046] As an example, the scaling unit consists of four scaled-down basic units, each with a linear dimension of one-quarter, arranged symmetrically in a cross shape. Each sub-unit maintains the original hexagonal and right-angled trapezoidal 212 structural proportions, achieving high-frequency resonance through size reduction. The cross-shaped arrangement enhances coupling between units, extends the absorption bandwidth, and forms a multi-scale structure to achieve broadband performance optimization. The scaling unit is located on one side of the basic unit, and the two are joined together.

[0047] In one specific embodiment, the scaling unit consists of four sub-units, with two sub-units arranged side by side and the other two sub-units arranged below the two sub-units, forming a grid pattern with each pair of sub-units connected.

[0048] In this embodiment, the microwave absorbing structure layer includes a dielectric layer 3 and a metal backplate 4 arranged sequentially; one side of the dielectric layer 3 is connected to the intermediate coupling layer 2, and the other side of the dielectric layer 3 is connected to the metal backplate 4; the dielectric layer 3 is a magnetic material microwave absorbing composite layer.

[0049] In this embodiment, the magnetic material absorbing composite layer is made of a resin matrix and a magnetic filler, wherein the volume ratio of the magnetic filler to the resin is 0.5:1 to 3:1; and the magnetic filler is a lightweight magnetic absorbing material. Preferably, the volume ratio of the magnetic filler to the resin is 1:1; preferably, the volume ratio of the magnetic filler to the resin is 0.5:1; and preferably, the volume ratio of the magnetic filler to the resin is 3:1.

[0050] In this embodiment, the lightweight magnetic microwave absorbing material comprises a hollow center, a carbon base layer, a silicon oxide layer, and a magnetic layer arranged sequentially. The lightweight magnetic microwave absorbing material is spherical in shape, and the microsphere size is 200–800 nm. Preferably, the microsphere size is 200 nm; preferably, it is 400 nm; preferably, it is 600 nm; preferably, it is 800 nm. Using lightweight magnetic material as a filler reduces the overall weight of the composite material, resulting in a higher specific strength. This is suitable for lightweight microwave absorbing structures where the magnetic material contains carbon material, which enhances both magnetic loss and dielectric loss of the functional filler, thus reducing the overall thickness of the composite material.

[0051] In one specific embodiment, the absorbing structure layer adopts a multi-layer composite design, wherein the dielectric layer 3 is a magnetic material absorbing composite layer, composed of a resin matrix such as epoxy resin or polyurethane and a lightweight magnetic filler. The volume ratio of filler to resin is controlled between 0.5:1 and 3:1, preferably 1:1, to ensure good impedance matching and electromagnetic loss balance. The lightweight magnetic absorbing material is a core-shell structured microsphere with a sphere size ranging from 200 to 800 nm. Its hollow center reduces density and enhances dielectric loss, the carbon substrate provides conductive loss, the silicon oxide layer adjusts impedance matching, and the magnetic layer, such as Fe3O4 or CoNi alloy, contributes magnetic loss. This multi-component synergistic effect can broaden the effective absorption bandwidth while reducing the overall weight. The dielectric layer 3, combined with the metal backplate 4, forms a reflection loss mechanism, while the intermediate coupling layer 2 optimizes surface impedance, jointly achieving broadband and efficient absorption. This design balances lightweight and high performance, and is suitable for aerospace, stealth technology, and other fields.

[0052] In one specific embodiment, when the thickness is much less than a quarter of the wavelength, it is difficult to obtain a wide effective bandwidth for thin-film composite materials. Most magnetic materials have high density and are not suitable for the preparation of microwave absorbing composite materials. Therefore, by combining the development of lightweight fillers and pattern design, a wider effective absorption bandwidth can be achieved at a lower thickness. The overall structure of the composite material in this application, including the surface pattern and the preparation of lightweight materials, allows for the acquisition of a lightweight composite material with a wide effective bandwidth through pattern design and the preparation of lightweight fillers.

[0053] In this embodiment, the metal backplate 4 is a copper film with a value range of 10μm to 30μm; and / or; the metal backplate 4 is an aluminum film with a value range of 10μm to 30μm. The metal backplate 4 is a copper film with a value range of 25μm; or; the metal backplate 4 is an aluminum film with a value range of 25μm; or; the metal backplate 4 is a copper film with a value range of 25μm. Preferably, the metal backplate 4 is a copper film with a value range of 10μm; or; the metal backplate 4 is an aluminum film with a value range of 10μm. Preferably, the metal backplate 4 is a copper film with a value range of 15μm; or; the metal backplate 4 is an aluminum film with a value range of 15μm. Preferably, the metal backplate 4 is a copper film with a value range of 20μm; or; the metal backplate 4 is an aluminum film with a value range of 20μm. Preferably, the metal backplate 4 is a copper film with a value range of 30 μm; or, the metal backplate 4 is an aluminum film with a value range of 30 μm.

[0054] This application provides a flowchart of the steps involved in the preparation and use of a broadband absorbing material and its method, specifically including the following steps:

[0055] Acrylic acid PS microspheres containing nitrile groups were prepared by emulsion polymerization. The PS microspheres were dispersed in an aqueous ethanol solution, and the pH was adjusted to weakly alkaline by adding surfactant and ammonia. Ethyl silicate was added dropwise for hydrolysis polymerization. After centrifugation and drying, the microspheres were thermally degraded under an inert atmosphere to obtain silica microspheres with carbon-containing inner layers. Then, a lightweight magnetic material with a magnetite magnetic layer was generated on the surface of the microspheres by hydrothermal reaction.

[0056] The lightweight magnetic material described in the step is mixed with resin at a weight ratio of 1:1, a prepreg is prepared using glass fiber cloth, and then molded and combined with a metal substrate to obtain a thin composite material.

[0057] A microwave absorbing material with a thickness of 1.1 mm and a density of 2.3 g / cm³ is obtained by screen printing a pattern on the surface of the thin composite material. 3 .

[0058] As an example:

[0059] 80 parts of styrene, 10 parts of cyanopropyl vinyl acetate and 10 parts of butyl methacrylate were mixed and heated to 70°C for emulsion polymerization for 8 hours, and then dried to obtain nitrile acrylic PS microspheres.

[0060] Four parts of nitrile acrylic acid PS microspheres were added to 100 parts of ethanol aqueous solution, 1 part of dodecyl ammonium bromide and 6 parts of ammonia water and the pH was adjusted to weakly alkaline. Four parts of nitrile acrylic acid PS microspheres were added dropwise with an equal weight of ethyl silicate and the mixture was ultrasonically stirred and polymerized at room temperature for 4 hours. After centrifugation and drying, the mixture was thermally degraded at 800℃ in an argon atmosphere to obtain silica microspheres with carbon-containing inner layer.

[0061] Carbon-containing silica microspheres were dispersed in water, and ferrous chloride and ferric chloride were added in a molar ratio of 1:2. After hydrothermal reaction at 160℃ for 2 hours, the mixture was centrifuged, washed with water, and dried to obtain a lightweight magnetic material.

[0062] Lightweight magnetic material was added to resin at a weight ratio of 1:1, and a prepreg was prepared using glass fiber cloth. The prepreg was then molded at 120°C for 4 hours and molded together with a metal substrate to obtain a thin composite material.

[0063] A broadband absorbing material is obtained by screen printing a pattern onto the surface of a composite material board. The broadband absorbing material has a thickness of approximately 1.1 mm and a density of 2.3 g / cm³. 3 .

[0064] In one specific embodiment, this experiment prepared a lightweight magnetic microsphere with a core-shell structure through a multi-step reaction, and then composited it with a resin matrix to finally produce a microsphere with a thickness of 1.1 mm and a density of 2.3 g / cm³. 3 A broadband absorbing material. The material combines dielectric loss and magnetic loss mechanisms, and optimizes impedance matching through surface patterning design.

[0065] The specific steps include: Terpolymer microspheres are synthesized using emulsion polymerization, with 80 parts benzene and ethylene as the main components, and 10 parts methyl cyanopropyl vinyl acetate and 10 parts butyl methacrylate introduced. The nitrile groups of methyl cyanopropyl vinyl acetate can improve the residual carbon rate during subsequent carbonization, while the flexible segments of butyl methacrylate help improve the processability of the microspheres. The reaction is carried out at 70℃ for 8 hours to ensure sufficient polymerization of the monomers and the formation of polymer microspheres with uniform particle size. A silica shell is then coated onto the surface of the PS microspheres: The microspheres are dispersed in an ethanol-water mixed solvent, and dodecyl ammonium bromide is added as a surfactant to adjust the pH to weakly alkaline (ammonia catalysis). Ethyl silicate is then added dropwise. Dodecyl ammonium bromide promotes the hydrolysis of ethyl silicate and guides the uniform deposition of SiO2 on the surface of the microspheres. Ultrasonic stirring for 4 hours ensures the density of the shell. Subsequently, under argon protection, pyrolysis at 800℃ carbonizes the internal polymer to form a porous carbon core, while the SiO2 shell maintains structural stability, ultimately yielding lightweight hollow carbon / SiO2 microspheres. This structure possesses low density, high specific surface area, and tunable dielectric properties, which are beneficial for multiple scattering of electromagnetic waves and dielectric loss.

[0066] Fe3O4 nanoparticles were loaded onto the surface of carbon / SiO2 microspheres using a hydrothermal method: the microspheres were dispersed in water, and ferrous chloride and ferric chloride were added in a molar ratio of 1:2. The reaction was carried out at 160°C for 2 hours. 2+ / Fe 3 Under alkaline conditions, spinel-type Fe3O4 is co-precipitated, and its high magnetic permeability and natural resonance effect can significantly enhance magnetic loss. The lightweight magnetic microspheres obtained after centrifugation and washing combine the dielectric loss of the carbon core with the magnetic loss of the Fe3O4 shell, forming a "dielectric-magnetic synergistic" absorption mechanism.

[0067] Lightweight magnetic microspheres were mixed with resin at a 1:1 weight ratio, and a prepreg was prepared using glass fiber cloth reinforcement. The mixture was then molded at 120°C for 4 hours and cured. The resin matrix provides mechanical support, while the uniformly dispersed microspheres construct a conductive-magnetic network, optimizing electromagnetic parameters. The molded thin-layer composite material was then bonded to a metal backing plate, extending the electromagnetic wave path through metal reflection and further improving absorption efficiency.

[0068] Periodic patterns were fabricated on the surface of the composite material using screen printing. The surface impedance was then modulated by the resonant characteristics of the geometric units, allowing for better matching with free space. Tests showed that this material achieved broadband absorption at a thickness of only 1.1 mm, with a density of only 2.3 g / cm³. 3 Its efficiency is far lower than that of traditional microwave absorbing materials.

[0069] Embodiment 1 of this application is carried out according to the following steps, as follows: Figure 4 As shown, the wave absorption characteristics of the composite material in Example 1 are within the effective bandwidth range of 8.1 to 12 GHz:

[0070] (1) Preparation of lightweight magnetic materials: Acrylonitrile-containing acrylic PS microspheres were prepared by emulsion polymerization, wherein 80 parts of styrene, 10 parts of cyanopropyl vinyl acetate, and 10 parts of butyl methacrylate were emulsion polymerized at 70℃ for 8 hours and dried to obtain PS microspheres; 4 parts of PS microspheres were added to 100 parts of ethanol aqueous solution, 1 part of dodecyl ammonium bromide and 6 parts of ammonia water were added, the pH was adjusted to weakly alkaline, and an equal weight of ethyl silicate of PS microspheres was added dropwise, and the mixture was ultrasonically stirred and polymerized at room temperature for 4 hours; after centrifugation and drying, the mixture was thermally degraded at 800℃ in an argon atmosphere to obtain silica microspheres with carbon-containing inner layers; the microspheres were dispersed in water, and ferrous chloride and ferric chloride were added at a molar ratio of 1:2, and the mixture was hydrothermally reacted at 160℃ for 2 hours, followed by centrifugation, washing with water and drying to obtain lightweight magnetic materials;

[0071] (2) Lightweight nanomaterials were added to resin at a weight ratio of 1:1, and a prepreg was prepared using glass fiber cloth and molded at 120°C for 4 hours. The prepreg was then molded together with a metal substrate to obtain a thin composite material.

[0072] (3) A pattern is printed on the surface of the composite material board by screen printing to obtain a microwave absorbing composite material with a thickness of about 1.1 mm and a density of 2.3 g / cm3.

[0073] In Comparative Example 1 of this application:

[0074] (1) Preparation of lightweight magnetic materials: Acrylonitrile-containing acrylic PS microspheres were prepared by emulsion polymerization, wherein 80 parts of styrene, 10 parts of cyanopropyl vinyl acetate, and 10 parts of butyl methacrylate were emulsion polymerized at 70℃ for 8 hours and dried to obtain PS microspheres; 4 parts of PS microspheres were added to 100 parts of ethanol aqueous solution, 1 part of dodecyl ammonium bromide and 6 parts of ammonia water were added, the pH was adjusted to weakly alkaline, and an equal weight of ethyl silicate of PS microspheres was added dropwise, and the mixture was ultrasonically stirred and polymerized at room temperature for 4 hours; after centrifugation and drying, the mixture was thermally degraded at 800℃ in an argon atmosphere to obtain silica microspheres with carbon-containing inner layers; the microspheres were dispersed in water, and ferrous chloride and ferric chloride were added at a molar ratio of 1:2, and the mixture was hydrothermally reacted at 160℃ for 2 hours, followed by centrifugation, washing with water and drying to obtain lightweight magnetic materials;

[0075] (2) Lightweight nanomaterials were added to the resin at a weight ratio of 1:1. A prepreg was prepared using glass fiber cloth and molded at 120°C for 4 hours. The prepreg was then molded together with the metal substrate to obtain a thin composite material with a thickness of about 1.1 mm and a density of 2.2 g / cm3.

[0076] In Comparative Example 2 of this application:

[0077] (1) Carbonyl iron powder was added to the resin at a weight ratio of 1:1, and a prepreg was prepared using glass fiber cloth and molded at 120°C for 2 hours. The prepreg was then molded together with the metal substrate to obtain a thin composite material.

[0078] (2) A pattern is printed on the surface of the composite material board by screen printing to obtain a microwave absorbing composite material with a thickness of about 1.1 mm and a density of 3.6 g / cm3.

[0079] In Comparative Example 3 of this application:

[0080] (1) Preparation of lightweight magnetic materials: Acrylonitrile-containing acrylic PS microspheres were prepared by emulsion polymerization, wherein 80 parts of styrene, 10 parts of cyanopropyl vinyl acetate, and 10 parts of butyl methacrylate were emulsion polymerized at 70℃ for 8 hours and dried to obtain PS microspheres; 4 parts of PS microspheres were added to 100 parts of ethanol aqueous solution, 1 part of dodecyl ammonium bromide and 6 parts of ammonia water were added, the pH was adjusted to weakly alkaline, and an equal weight of ethyl silicate of PS microspheres was added dropwise, and the mixture was ultrasonically stirred and polymerized at room temperature for 12 hours; after centrifugation and drying, the mixture was thermally degraded at 800℃ in an argon atmosphere to obtain silica microspheres with carbon-containing inner layers; the microspheres were dispersed in water, and ferrous chloride and ferric chloride were added at a molar ratio of 1:2, and the mixture was hydrothermally reacted at 160℃ for 12 hours, followed by centrifugation, washing with water and drying to obtain lightweight magnetic materials;

[0081] (2) Lightweight nanomaterials were added to resin at a weight ratio of 1:1, and a prepreg was prepared using glass fiber cloth and molded at 120°C for 4 hours. The prepreg was then molded together with a metal substrate to obtain a thin composite material.

[0082] (3) A pattern is printed on the surface of the composite material board by screen printing. The pattern contains only regular hexagonal pattern units to obtain the microwave absorbing composite material. The thickness of the composite material is about 1.1 mm and the density is 2.3 g / cm3.

[0083] The schematic diagrams of Comparative Examples 1-3 are as follows: Figure 5 As shown.

[0084] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0085] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0086] The present invention provides a detailed description of a broadband absorbing material and its preparation method. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A broadband wave-absorbing material, characterized in that, It includes a wave-transmitting protective layer, an intermediate coupling layer, and a wave-absorbing structural layer arranged sequentially; The wave-transmitting protective layer is a thin fiber-reinforced composite material layer, and the thickness of the wave-transmitting protective layer ranges from 50μm to 100μm. The intermediate coupling layer pattern includes a basic unit region and a scaling unit region. The scaling unit is composed of four sub-units whose linear dimensions are reduced to one-quarter of the basic unit, joined together in a cross shape. The intermediate coupling layer is a unit resistive film layer. Specifically, the basic unit region and the scaling unit region each include several complete or incomplete regular hexagons. The basic unit region includes a complete first regular hexagon in the center, and the scaling unit region includes a complete second regular hexagon in the center and four complete second regular hexagons in non-center positions. The first and second regular hexagons have different areas. The basic unit consists of one first regular hexagon and four right trapezoids. The microwave absorbing structure layer includes a dielectric layer and a metal backplate arranged sequentially; one side of the dielectric layer is connected to the intermediate coupling layer, and the other side of the dielectric layer is connected to the metal backplate; the dielectric layer is a magnetic material microwave absorbing composite layer; the magnetic material microwave absorbing composite layer is made of a resin matrix and magnetic filler; the magnetic filler is a lightweight magnetic microwave absorbing material.

2. The broadband wave-absorbing material according to claim 1, wherein, The right trapezoid is obtained by dividing the first regular hexagon by a quarter radially, and the four right trapezoids are arranged symmetrically around the first regular hexagon. 3.The broadband wave-absorbing material according to claim 1, wherein, The side length of the first regular hexagon ranges from 2 to 4 mm; the perpendicular distance between the first regular hexagon and the right trapezoid ranges from 1.3 to 1.5 mm.

4. The broadband absorbing material according to claim 1, characterized in that, The metal backplate is a copper film with a value range of 10μm to 30μm; and / or, the metal backplate is an aluminum film with a value range of 10μm to 30μm.

5. The broadband absorbing material according to claim 1, characterized in that, The volume ratio of the magnetic filler to the resin is 0.5:1 to 3:

1.

6. The broadband absorbing material according to claim 1, characterized in that, The lightweight magnetic microwave absorbing material comprises a hollow center, a carbon base layer, a silicon oxide layer, and a magnetic layer arranged sequentially; the lightweight magnetic microwave absorbing material is spherical in shape, and the microspheres of the lightweight magnetic microwave absorbing material have a size of 200~800nm.

7. The broadband absorbing material according to claim 1, characterized in that, The thin layer of fiber reinforced composite is made of glass fiber fabric with an areal density less than or equal to 100 g / m 2 ; or the thin layer of fiber reinforced composite is made of aramid fiber fabric with an areal density less than or equal to 100 g / m 2 .

8. A method for preparing a broadband absorbing material according to any one of claims 1-7, characterized in that, include: Acrylic acid PS microspheres containing nitrile groups were prepared by emulsion polymerization. The PS microspheres were dispersed in an aqueous ethanol solution, and the pH was adjusted to weakly alkaline by adding surfactant and ammonia. Ethyl silicate was added dropwise for hydrolysis polymerization. After centrifugation and drying, the microspheres were thermally degraded under an inert atmosphere to obtain silica microspheres with carbon-containing inner layers. Then, a lightweight magnetic material with a magnetite magnetic layer was generated on the surface of the microspheres by hydrothermal reaction. The lightweight magnetic material described in the step is mixed with resin at a weight ratio of 1:1, a prepreg is prepared using glass fiber cloth, and then molded and combined with a metal substrate to obtain a thin composite material. A microwave absorbing material with a thickness of 1.1 mm and a density of 2.3 g / cm³ is obtained by screen printing a pattern on the surface of the thin composite material.

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