Hexagonal element sequential wave-absorbing metamaterial and preparation method and application thereof

Abstract

The invention belongs to the technical field of electromagnetic functional materials, and particularly relates to a hexagonal element sequential wave-absorbing metamaterial and a preparation method and application thereof. Superstructure design is carried out on the surface of the wave-absorbing coating with intrinsic electromagnetic loss, a superstructure wave-absorbing coating for carrying out structural loss on electromagnetic waves is obtained, the superstructure wave-absorbing coating is attached to the metal matrix layer, and the hexagonal element sequential wave-absorbing metamaterial is obtained. The hexagonal primitive sequential wave-absorbing metamaterial breaks through the Rogov limit, solves the problem that a traditional homogeneous wave-absorbing material is limited in the aspects of increasing the bandwidth and reducing the thickness, breaks through the limitation that the thickness and the bandwidth cannot be met at the same time, achieves efficient wave-absorbing and stealth compatibility under the deep sub-wavelength size, and improves the wave-absorbing efficiency. And the thickness of the super-structure wave-absorbing coating is reduced to 2mm, so that practical engineering application is facilitated, and the super-structure wave-absorbing coating can be applied to the fields of communication and national defense.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic functional materials, and in particular is a hexagonal elementary sequence structure wave absorbing metamaterial and a preparation method and application thereof. Background Art

[0002] With the rapid development of electronic technology, electromagnetic waves are increasingly used in the fields of communication, remote sensing, and detection, bringing many conveniences to people's daily lives. However, the pollution and safety issues caused by electromagnetic radiation are also gradually becoming prominent, and the research and development and application of absorbing materials are becoming increasingly urgent. In the civilian field, absorbing materials can be coated on the surface of precision equipment and electronic components to reduce electromagnetic interference and ensure the efficient operation of equipment; in the military field, absorbing materials can reduce the reflection of radar detection signals, thereby enhancing the anti-strike capability of military targets. Therefore, the development of high-performance absorbing materials is of great significance both in the military and civilian fields. With the complexity of the electromagnetic environment, the military and civilian fields have put forward multiple demands on absorbing materials. The development of high-performance absorbing materials with thin thickness, wide absorption bandwidth, and strong absorbing ability has become a research hotspot.

[0003] The prior art discloses homogeneous absorbing materials. However, due to the limitations of the intrinsic physical properties of homogeneous absorbing materials, they are subject to many restrictions in terms of increasing bandwidth and reducing thickness. s / lnρ0|), determined by the absorber material, that is, its magnetic permeability (μ s ) and reflection coefficient (ρ0) are determined, if the effective absorption bandwidth (Δλ) is to be widened, the coating thickness (d) of the absorber needs to be increased. Therefore, when the absorber coating thickness is much smaller than the wavelength of the 2-18GHz frequency band (i.e., the working wavelength is 16.7mm-150mm), that is, when the deep subwavelength thickness (2mm) is reached, the absorbing performance of the coating will be limited by the Lozanov limit, and broadband absorption will not be achieved. Summary of the invention

[0004] In order to solve the problems of the prior art, the present invention provides a hexagonal elementary order structure absorbing metamaterial and its preparation method and application. The present invention performs superstructure design on the surface of the absorbing coating with intrinsic electromagnetic wave loss, obtains a superstructure absorbing coating with structural loss of electromagnetic waves, and then obtains the hexagonal elementary order structure absorbing metamaterial. The hexagonal elementary order structure absorbing metamaterial breaks through the Rozanov limit of traditional homogeneous absorbing materials, and obtains an absorbing metamaterial with thin thickness and broadband absorption performance.

[0005] The present invention is achieved through the following technical solutions:

[0006] A hexagonal elementary structure absorbing metamaterial consists of a metal matrix layer and a superstructure absorbing coating. The superstructure absorbing coating is attached to the surface of the metal matrix layer. Compared with the homogeneous absorbing coating in the prior art, the surface of the superstructure absorbing coating is divided by different intervals, and then a superstructure design is performed to achieve structural loss.

[0007] The superstructure absorbing coating is composed of a plurality of vertically arranged absorbing arrays, the plurality of absorbing arrays are staggered, and there is a lateral interval between two adjacent absorbing arrays, and the lateral interval is composed of two interval units.

[0008] Each absorbing array is composed of a number of absorbing units periodically arranged in the horizontal direction. Each absorbing unit is square and includes an outer hexagonal element, an inner hexagonal element and four triangular elements.

[0009] The outer hexagonal primitive is surrounded by six angular primitives, and there is a gap between every two adjacent angular primitives.

[0010] Four triangular primitives are distributed outside the outer hexagonal primitive, and the outer hexagonal primitive and the four triangular primitives form a square structure, and there is an oblique interval between the outer hexagonal primitive and the triangular primitive; the outer hexagonal primitives of every two adjacent absorbing units are arranged in parallel.

[0011] The inner hexagon primitive is nested in the center of the outer hexagon primitive, and there is a regular hexagonal gap between the two.

[0012] The outer hexagonal element, the inner hexagonal element and the triangular element are all made of radar-absorbing paint, which is a mixture of carbonyl iron, charcoal and epoxy resin.

[0013] Preferably, the radius of the circumscribed circle of the outer hexagonal primitive is 8-12 mm, and the radius of the circumscribed circle of the inner hexagonal primitive is 4-8 mm.

[0014] Preferably, each absorbing unit has a length of 16-20 mm and a width of 15-19 mm.

[0015] Preferably, the width of the strip spacing is 1.0-1.4 mm, the width of the regular hexagon spacing is 1.1-1.5 mm, the width of the oblique spacing is 1.0-1.2 mm, the width of each spacing unit is 0.6-1.0 mm, and the width of the lateral spacing is 1.2-2.0 mm.

[0016] The outer hexagonal element, the inner hexagonal element, the absorbing unit and each interval exceed the above range values, and the absorbing performance is poor.

[0017] Preferably, the thickness of the superstructure absorbing coating is 1.8-2.2 mm, which effectively overcomes the problem that the prior art homogeneous absorbing materials cannot achieve both thin coating and broadband absorbing.

[0018] Preferably, the metal matrix layer is selected from an aluminum matrix layer, a copper matrix layer or an iron matrix layer.

[0019] The present invention also provides a method for preparing the above-mentioned hexagonal primitive sequence structure absorbing metamaterial, which comprises the following steps:

[0020] Carbonyl iron and charcoal are ground and mixed to obtain a carbonyl iron / charcoal composite material, which is an absorbing element of intrinsic electromagnetic wave loss.

[0021] The carbonyl iron / charcoal composite material and epoxy resin are mixed in a solvent to obtain an absorbing coating, which is coated on a metal matrix layer and allowed to stand at room temperature until semi-cured. A superstructure mold is then used for embossing, and the absorbing coating is demoulded after it is completely cured to form a superstructure absorbing coating on the surface of the metal matrix layer, thereby obtaining a hexagonal elementary structure absorbing metamaterial.

[0022] Preferably, the superstructure mold is designed according to the wave absorbing array.

[0023] Preferably, the mass ratio of carbonyl iron, charcoal and epoxy resin is 5:0.2-0.3:1, and the mass ratio of the three is obtained through screening.

[0024] Preferably, the solvent is selected from anhydrous ethanol, toluene, acetone, and ethyl acetate. Any solvent that can disperse carbonyl iron, charcoal, and epoxy resin can be applied to the present invention.

[0025] The present invention also protects the application of the above hexagonal primitive sequence structure absorbing metamaterial in the preparation of electromagnetic wave absorbing metamaterial.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. In order to achieve broadband absorption at a relatively thin superstructure absorbing coating thickness, the present invention designs a superstructure on the surface of the absorbing coating to obtain a superstructure absorbing coating that causes structural loss of electromagnetic waves. The superstructure absorbing coating achieves both intrinsic electromagnetic wave loss and structural electromagnetic wave loss. Then, by introducing an artificial superstructure on the absorbing coating, a hexagonal elementary sequence absorbing metamaterial with a simple structure, simple process and broadband compatibility is prepared.

[0028] The present invention prepares a hexagonal primitive sequence structure absorbing metamaterial by constructing periodically arranged absorbing units on an absorbing coating, wherein the absorbing unit is composed of an outer hexagonal primitive, an inner hexagonal primitive and four triangular primitives, wherein the inner hexagonal primitive is nested in the outer hexagonal primitive, and the outer hexagonal primitive and the four triangular primitives form a square absorbing unit; different primitives generate different induced currents under the irradiation of incident electromagnetic waves, and there is a complex local coupling effect between adjacent primitives, which affects the propagation path of charge and current inside the hexagonal primitive sequence structure absorbing metamaterial, so that the hexagonal primitive sequence structure absorbing metamaterial can better absorb electromagnetic waves. The structural design of the inner hexagonal primitive nested in the outer hexagonal primitive can also make the overall input impedance Zin of the hexagonal primitive sequence structure absorbing metamaterial closer to the air impedance Zair, which is helpful to broaden the effective absorption bandwidth.

[0029] The spacing design on the hexagonal primitive order absorbing metamaterial expands the propagation path of electromagnetic waves in the hexagonal primitive order absorbing metamaterial, increases the interaction between the electromagnetic waves and the hexagonal primitive order absorbing metamaterial, improves the absorption efficiency, and enables the hexagonal primitive order absorbing metamaterial to achieve efficient absorption at deep subwavelength thickness.

[0030] When electromagnetic waves are incident on the superstructure absorbing coating, a large number of periodically arranged absorbing units can improve the impedance matching characteristics of the hexagonal primitive order absorbing metamaterial, reduce the reflection of electromagnetic waves, and thus allow them to better enter the hexagonal primitive order absorbing metamaterial and convert them into other forms of energy, thereby improving the absorption efficiency. At the same time, a large number of air gaps in the absorbing units can reduce the overall weight of the hexagonal primitive order absorbing metamaterial, which is conducive to achieving the lightweight of the hexagonal primitive order absorbing metamaterial.

[0031] The superstructure absorbing coating of the present invention improves the absorbing performance at a low thickness, which becomes a key factor in the breakthrough of absorbing coatings. The obtained hexagonal elementary order absorbing metamaterial is a new type of artificial material composed of periodic absorbing units. By adjusting the size of the absorbing unit to change its electromagnetic parameters, the hexagonal elementary order absorbing metamaterial has the ability to absorb waves in multiple frequency bands.

[0032] The present invention uses carbonyl iron (CIP), charcoal (C) and epoxy resin to mix to obtain an absorbing coating, which is an absorbing coating with intrinsic electromagnetic wave loss. After structural design is performed on the homogeneous absorbing coating with intrinsic electromagnetic wave loss, the hexagonal primitive sequence absorbing metamaterial obtained has both magnetic loss and dielectric loss, which is conducive to widening the effective absorption bandwidth. At the same time, after the absorbing units are arranged periodically, an equivalent electromagnetic resonance cavity is formed, which expands the interference, multiple reflection and resonance action space of electromagnetic waves in the absorbing metamaterial, significantly improves the attenuation loss characteristics of the hexagonal primitive sequence absorbing metamaterial, and then realizes wide-band absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the structure of the absorbing unit of the hexagonal primitive sequence absorbing metamaterial in Example 1 of the present invention.

[0034] Figure 2 In the figure, (a) is a top view of a superstructure absorbing coating of a hexagonal primitive order absorbing metamaterial of Example 1 of the present invention, and (b) is a side view of a hexagonal primitive order absorbing metamaterial of Example 1 of the present invention.

[0035] Figure 3 This is a real picture of the superstructure absorbing coating of the hexagonal primitive sequence absorbing metamaterial in Example 1 of the present invention.

[0036] Figure 4 In the figure, (a) is the microscopic morphology of carbonyl iron particles, and (b) is the microscopic morphology of charcoal particles.

[0037] Figure 5 Graphs of electromagnetic parameters of carbonyl iron / charcoal composite materials; (a) is a graph of relative complex permittivity, and (b) is a graph of relative complex magnetic permeability.

[0038] Figure 6 The simulated reflection loss diagrams are of the superstructure absorbing coatings of Examples 1-3 and the homogeneous absorbing coatings of Comparative Examples 1-3; wherein (a) is the simulated reflection loss diagram of the homogeneous absorbing coatings of Comparative Examples 1-3, and (b) is the simulated reflection loss diagram of the superstructure absorbing coatings of Examples 1-3.

[0039] Figure 7 Schematic diagram of the structure of a single absorbing unit.

[0040] Description of reference numerals:

[0041] 1. Metal matrix layer; 2. Superstructure absorbing coating; 3. Absorbing array; 4. Absorbing unit; 5. Angular primitive; 6. Triangular primitive; 7. Strip spacing; 8. Internal hexagonal primitive; 9. Spacer unit; 10. Oblique spacing; 11. Regular hexagonal spacing. DETAILED DESCRIPTION

[0042] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0043] Compared with homogeneous absorbing coatings, the present invention introduces new electromagnetic resonance and coupling mechanisms in superstructure absorbing coatings by designing special artificial geometric structures. The design of the superstructure significantly improves the overall absorbing performance of the hexagonal primitive order absorbing metamaterial, so that the hexagonal primitive order absorbing metamaterial exhibits absorbing performance far superior to that of homogeneous absorbing coatings. In the hexagonal primitive order absorbing metamaterial sample prepared by the present invention, when the thickness of the superstructure absorbing coating is 2mm and the mass ratio of carbonyl iron, charcoal and epoxy resin is 5:0.2:1, the effective absorbing frequency band is 9.12-18GHz (RL<-10dB, microwave absorption rate exceeds 90%), completely covering most of the X band (8-12GHz) and the entire Ku band (12-18GHz), with a bandwidth of up to 8.88GHz, achieving broadband and efficient absorbing at deep subwavelength thickness, and its absorbing performance far exceeds that of homogeneous coatings.

[0044] The present invention breaks through the Rozanov limit and achieves an effective absorbing bandwidth (RL<-10dB, microwave absorption rate exceeds 90%) of up to 8.88GHz at a deep subwavelength thickness, solving the problems of traditional homogeneous absorbing materials being subject to many limitations in improving bandwidth and reducing thickness, breaking the limitation that thickness and bandwidth cannot be satisfied at the same time, overcoming the defects of traditional homogeneous absorbing materials, achieving high-efficiency absorbing and stealth compatibility at deep subwavelength sizes, and an overall thickness of 2mm, which is conducive to practical engineering applications and can be used in the fields of communications and national defense.

[0045] Hexagonal primitive order structure absorbing metamaterials, such as Figure 7 As shown, it is composed of a metal matrix layer 1 and a superstructure absorbing coating 2, and the superstructure absorbing coating 2 is attached to the surface of the metal matrix layer 1; the superstructure absorbing coating 2 is composed of a plurality of vertically arranged absorbing arrays 3, and the plurality of absorbing arrays 3 are staggered, and there is a lateral interval between two adjacent absorbing arrays 3, and the lateral interval is composed of two spacing units 9.

[0046] Each absorbing array 3 is composed of a number of absorbing units 4 arranged periodically in the horizontal direction, and each absorbing unit 4 is square, including an outer hexagonal primitive, an inner hexagonal primitive 8 and four triangular primitives 6: the outer hexagonal primitive is composed of six angular primitives 5, and there is a spacing 7 between every two adjacent angular primitives 5; the outer hexagonal primitive and the four triangular primitives 6 form a square absorbing unit 4, and there is an oblique spacing 10 between the outer hexagonal primitive and the triangular primitive 6; the outer hexagonal primitives of every two adjacent absorbing units 4 are arranged in parallel; the inner hexagonal primitive 8 is nested in the center of the outer hexagonal primitive, and there is a regular hexagonal spacing 11 between the two.

[0047] The outer hexagonal element, the inner hexagonal element 8 and the triangular element 6 are all radar-absorbing coatings, which are made of a mixture of carbonyl iron, charcoal and epoxy resin.

[0048] The present invention is further explained by using embodiments and comparative examples, which are specifically as follows:

[0049] Example 1

[0050] A method for preparing a hexagonal elementary structure absorbing metamaterial comprises the following steps:

[0051] S1. Preparation of carbonyl iron / charcoal composite material: Carbonyl iron and charcoal were weighed in a mass ratio of 5:0.2, and then placed in a mortar for thorough grinding and mixing to obtain a carbonyl iron / charcoal composite material.

[0052] S2. Select an aluminum plate as the metal matrix layer with a thickness of 1.0 mm and a plane size of 200 mm×200 mm. Use alcohol to rinse its surface to ensure that the absorbing coating can be evenly covered to obtain a metal matrix layer.

[0053] S3. Weigh epoxy resin (ER) and anhydrous ethanol in a mass ratio of 3:4 and mix them thoroughly to obtain an epoxy resin solution.

[0054] The carbonyl iron / charcoal composite material was added to the epoxy resin solution. At this time, the mass ratio of carbonyl iron, charcoal and epoxy resin was 5:0.2:1. Then, stirring and shaking operations were performed to ensure that the carbonyl iron / charcoal composite material was evenly dispersed in the epoxy resin matrix. The stirrer speed was gradually increased from 400 rpm to 1200 rpm to obtain an absorbing coating.

[0055] The absorbing coating is coated on the metal matrix layer, left to stand horizontally at room temperature until semi-solidified, and then embossed using a 3D printed superstructure mold and kept under pressure for a period of time. After the absorbing coating is completely cured, it is demoulded to form a superstructure absorbing coating on the surface of the metal matrix layer, thereby obtaining a hexagonal elementary structure absorbing metamaterial.

[0056] Example 2

[0057] A method for preparing a hexagonal elementary structure absorbing metamaterial, which has the same preparation steps as those in Example 1, except that the mass ratio of carbonyl iron, charcoal and epoxy resin is replaced from 5:0.2:1 to 5:0.25:1, and comprises the following steps:

[0058] S1. Preparation of carbonyl iron / charcoal composite material: Carbonyl iron and charcoal were weighed in a mass ratio of 5:0.2, and then placed in a mortar for thorough grinding and mixing to obtain a carbonyl iron / charcoal composite material.

[0059] S2. Select an aluminum plate as the metal matrix layer with a thickness of 1.0 mm and a plane size of 200 mm×200 mm. Use alcohol to rinse its surface to ensure that the absorbing coating can be evenly covered to obtain a metal matrix layer.

[0060] S3. Weigh epoxy resin (ER) and anhydrous ethanol in a mass ratio of 3:4 and mix them thoroughly to obtain an epoxy resin solution.

[0061] The carbonyl iron / charcoal composite material was added to the epoxy resin solution. At this time, the mass ratio of carbonyl iron, charcoal and epoxy resin was 5:0.25:1. Then, stirring and shaking operations were performed to ensure that the carbonyl iron / charcoal composite material was evenly dispersed in the epoxy resin matrix. The stirrer speed was gradually increased from 400 rpm to 1200 rpm to obtain an absorbing coating.

[0062] The absorbing coating is coated on the metal matrix layer, left to stand horizontally at room temperature until semi-solidified, and then embossed using a 3D printed superstructure mold and kept under pressure for a period of time. After the absorbing coating is completely cured, it is demoulded to form a superstructure absorbing coating on the surface of the metal matrix layer, thereby obtaining a hexagonal elementary structure absorbing metamaterial.

[0063] Example 3

[0064] A method for preparing a hexagonal elementary structure absorbing metamaterial, which has the same preparation steps as those in Example 1, except that the mass ratio of carbonyl iron, charcoal and epoxy resin is replaced from 5:0.2:1 to 5:0.3:1, and comprises the following steps:

[0065] S1. Preparation of carbonyl iron / charcoal composite material: Carbonyl iron and charcoal were weighed in a mass ratio of 5:0.2, and then placed in a mortar for thorough grinding and mixing to obtain a carbonyl iron / charcoal composite material.

[0066] S2. Select an aluminum plate as the metal matrix layer with a thickness of 1.0 mm and a plane size of 200 mm×200 mm. Use alcohol to rinse its surface to ensure that the absorbing coating can be evenly covered to obtain a metal matrix layer.

[0067] S3. Weigh epoxy resin (ER) and anhydrous ethanol in a mass ratio of 3:4 and mix them thoroughly to obtain an epoxy resin solution.

[0068] The carbonyl iron / charcoal composite material was added to the epoxy resin solution. At this time, the mass ratio of carbonyl iron, charcoal and epoxy resin was 5:0.3:1. Then, stirring and shaking operations were performed to ensure that the carbonyl iron / charcoal composite material was evenly dispersed in the epoxy resin matrix. The stirrer speed was gradually increased from 400 rpm to 1200 rpm to obtain an absorbing coating.

[0069] The absorbing coating is coated on the metal matrix layer, left to stand horizontally at room temperature until semi-solidified, and then embossed using a 3D printed superstructure mold and kept under pressure for a period of time. After the absorbing coating is completely cured, it is demoulded to form a superstructure absorbing coating on the surface of the metal matrix layer, thereby obtaining a hexagonal elementary structure absorbing metamaterial.

[0070] Comparative Example 1

[0071] The preparation method of the homogeneous absorbing coating is the same as the preparation steps of Example 1, except that no imprinting is performed, and includes the following steps:

[0072] S1. Preparation of carbonyl iron / charcoal composite material: Carbonyl iron and charcoal were weighed in a mass ratio of 5:0.2, and then placed in a mortar for thorough grinding and mixing to obtain a carbonyl iron / charcoal composite material.

[0073] S2. Select an aluminum plate as the metal matrix layer with a thickness of 1.0 mm and a plane size of 200 mm×200 mm. Use alcohol to rinse its surface to ensure that the homogeneous absorbing material can be evenly covered to obtain a metal matrix layer.

[0074] S3. Weigh epoxy resin (ER) and anhydrous ethanol in a mass ratio of 3:4 and mix them thoroughly to obtain an epoxy resin solution.

[0075] The carbonyl iron / charcoal composite material was added to the epoxy resin solution. At this time, the mass ratio of carbonyl iron, charcoal and epoxy resin was 5:0.3:1. Then, stirring and shaking operations were performed to ensure that the carbonyl iron / charcoal composite material was evenly dispersed in the epoxy resin matrix. The stirrer speed was gradually increased from 400 rpm to 1200 rpm to obtain an absorbing coating.

[0076] The microwave-absorbing coating is coated on the metal matrix layer, and is horizontally placed at room temperature until it is completely cured and then demoulded to form a homogeneous microwave-absorbing coating on the surface of the metal matrix layer.

[0077] Comparative Example 2

[0078] The preparation method of the homogeneous absorbing material is the same as the preparation steps of Comparative Example 1, except that the filler ratio of carbonyl iron, charcoal and epoxy resin is replaced from 5:0.2:1 to 5:0.25:1.

[0079] Comparative Example 3

[0080] The preparation method of the homogeneous absorbing material is the same as the preparation steps of Comparative Example 1, except that the filler ratio of carbonyl iron, charcoal and epoxy resin is replaced from 5:0.2:1 to 5:0.3:1.

[0081] Embodiments 1 to 3 of the present invention all produce hexagonal primitive order absorbing metamaterials with excellent absorbing performance. The hexagonal primitive order absorbing metamaterials of Embodiments 1 to 3 are used as examples for research, and compared with the homogeneous absorbing materials of Comparative Examples 1 to 3. The specific research methods and results are as follows:

[0082] The present invention uses carbonyl iron / charcoal composite materials as absorbers with intrinsic electromagnetic wave loss, and uses 3D printed superstructure molds to obtain superstructure absorbing coatings, and then prepares hexagonal primitive sequence absorbing metamaterials. The hexagonal primitive sequence absorbing metamaterial introduces new electromagnetic resonance and coupling mechanisms through superstructures (i.e., primitive sequence system), which causes loss of incident electromagnetic wave energy, thereby achieving the purpose of expanding the absorbing bandwidth and improving the absorbing performance.

[0083] The hexagonal element-ordered absorbing metamaterial is composed of a superstructure absorbing coating and a metal matrix layer, and the superstructure absorbing coating is composed of a number of periodically arranged absorbing units. Figure 1 As shown, each absorbing unit 4 is composed of an outer hexagonal element, an inner hexagonal element 8 and a triangular element 6. The periodic size of each absorbing unit 4 is a×b=20mm×18.6mm. The outer hexagonal element is arranged at the center of the absorbing unit 4, the inner hexagonal element 8 is nested in the outer hexagonal element, and the triangular element 6 is arranged at the four corners of the absorbing unit 4; the circumscribed circle radius R1 of the outer hexagonal element is 10mm, and the circumscribed circle radius R2 of the inner hexagonal element 8 is 5.2mm; the lengths of the two right-angled sides of the triangular element 6 are L1=3.3mm and L2=6.6mm respectively; the strip spacing 7 is 1.1mm, the regular hexagonal spacing 11 is 1.3mm, the oblique spacing 10 is 1mm, and the spacing unit 9 is 0.65mm.

[0084] like Figure 2 As shown, the superstructure absorbing coating is composed of a plurality of absorbing units 4 arranged periodically in a two-dimensional plane, the arrangement of each absorbing unit is consistent, and two adjacent absorbing arrays 3 are staggered. The thickness of the superstructure absorbing coating is 2.0 mm, and the thickness of the metal matrix layer is 1.0 mm.

[0085] Figure 3 This is a physical picture of the superstructure absorbing coating.

[0086] Figure 4 The scanning electron microscope images of carbonyl iron and charcoal particles are shown respectively. Figure 4 The microscopic morphology of the carbonyl iron particles shown in (a) is a spherical particle with an "onion-like" structure, which is conducive to its uniform distribution inside the matrix epoxy resin and can avoid the skin effect of magnetic iron to a certain extent; Figure 4As shown in (b), the charcoal particles have a flake structure with a high specific surface area, strong adsorption function and interface polarization.

[0087] Figure 5 The curves of electromagnetic parameter changes of carbonyl iron / charcoal composite materials with different mass ratios in the 2-18GHz frequency band are shown. The real parts (ε' and μ') of the complex dielectric constant and complex magnetic permeability can measure the storage capacity of carbonyl iron / charcoal composite materials for electromagnetic waves, and the imaginary parts (ε" and μ") can measure the attenuation capacity of carbonyl iron / charcoal composite materials for electromagnetic waves. Figure 5 As shown in (a), the real part ε' of carbonyl iron / charcoal composite materials with different mass ratios is distributed between 10-12, and the imaginary part ε" is between 0.3-0.7, showing relatively weak dielectric loss characteristics; Figure 5 As shown in (b), the real part of the complex magnetic permeability μ' shows a decreasing trend with increasing frequency, and the fluctuation range is between 0.9-3. The imaginary part μ" first increases slightly with the frequency and then gradually decreases, and the overall distribution is between 0.9-1.2, showing a relatively strong magnetic loss characteristic. It can be concluded that the carbonyl iron / charcoal composite material has good magnetic loss performance and is a good magnetic loss absorber.

[0088] The design of the superstructure absorbing coating introduces new electromagnetic resonance and coupling mechanisms, thereby improving the electromagnetic wave absorption capacity of the hexagonal elementary structure absorbing metamaterial. At the same time, the hexagonal elementary structure is periodically arranged to form an equivalent electromagnetic resonance cavity, which expands the action space of electromagnetic waves inside the hexagonal elementary structure absorbing metamaterial, significantly improves the attenuation and loss characteristics of the hexagonal elementary structure absorbing metamaterial, and thus improves the absorbing performance of the hexagonal elementary structure absorbing metamaterial.

[0089] Figure 6 The reflection loss curves of homogeneous absorbing coatings and superstructure absorbing coatings with different mass ratios at 2mm thickness in the frequency range of 2-18GHz are shown. Figure 6 As shown in (a), the average effective absorbing bandwidth of the homogeneous absorbing coatings with different mass ratios is 4.43 GHz. Figure 6As shown in (b), in terms of effective absorption bandwidth (RL<-10dB), the effective absorption bandwidth of the superstructure absorbing coating with a mass ratio of 5:0.25:1 is 8.3GHz, and the effective absorption bandwidths of the superstructure absorbing coatings with the other two mass ratios are all above 8.3GHz; in terms of peak value, the reflection loss peak value of the superstructure absorbing coating with a mass ratio of 5:0.2:1 is -29dB, which is lower than that of the superstructure absorbing coatings with the other two mass ratios. In summary, when the coating thickness is 2 mm and the mass ratio of carbonyl iron, charcoal and epoxy resin is 5:0.2:1, the prepared hexagonal elementary structure absorbing metamaterial sample has the best absorbing ability and has multi-band broadband and high-efficiency absorbing characteristics. The effective absorbing frequency band is 9.12-18 GHz (RL <-10 dB, microwave absorptivity exceeds 90%), completely covering most of the X band (8-12 GHz) and the entire Ku band (12-18 GHz), and its minimum reflection loss value is -29 dB at 12.5 GHz.

[0090] In summary, the present invention prepares a hexagonal elementary structure absorbing metamaterial by constructing a periodic microstructure on a homogeneous absorbing coating, so that it has both intrinsic loss and structural loss absorbing mechanisms, thereby generating strong losses to the incident electromagnetic waves. The present invention uses carbonyl iron / charcoal composite materials as absorbers of intrinsic electromagnetic waves, so that the superstructure absorbing coating has both magnetic loss and dielectric loss, which is beneficial to broaden the effective absorption bandwidth. At the same time, after the hexagonal elementary structure is arranged periodically, an equivalent electromagnetic resonance cavity is formed, which expands the interference, multiple reflection, resonance and other action spaces of electromagnetic waves in the absorbing metamaterial, significantly improves the attenuation loss characteristics of the absorbing metamaterial, and thus improves the absorbing bandwidth.

[0091] The absorbing unit of the present invention is novel in design, and the absorption and loss degree of electromagnetic waves by the superstructure absorbing coating is regulated by constructing a structure-component regulating mechanism. The superstructure absorbing coating is prepared by using a carbonyl iron / charcoal composite material as an electromagnetic wave absorber. The superstructure absorbing coating broadens the transmission space of electromagnetic waves inside the absorbing metamaterial through a hexagonal primitive sequence structure, increases the probability of electromagnetic wave interference destructiveness and electromagnetic coupling, and realizes the energy consumption of the incident electromagnetic wave. This metamaterial has a strong electromagnetic wave loss capacity, can efficiently absorb electromagnetic waves, and effectively protect related equipment from interference and damage, so that the absorbing performance of the hexagonal primitive sequence absorbing metamaterial is significantly higher than that of the homogeneous absorbing coating, and also breaks the limitation that thickness and bandwidth cannot be satisfied at the same time, and obtains an ultra-thin broadband absorbing coating.

[0092] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, they are also intended to be included.

Claims

1. A hexagonal elementary structure absorbing metamaterial, characterized in that: The invention comprises a metal matrix layer (1) and a superstructure absorbing coating (2), wherein the superstructure absorbing coating (2) is attached to the surface of the metal matrix layer (1); the superstructure absorbing coating (2) comprises a plurality of vertically arranged absorbing arrays (3), wherein the plurality of absorbing arrays (3) are arranged in a staggered manner, and a lateral interval is provided between two adjacent absorbing arrays (3), wherein the lateral interval comprises two interval units (9); Each of the wave absorbing arrays (3) is composed of a plurality of wave absorbing units (4) periodically arranged in a horizontal direction, and each of the wave absorbing units (4) is square, and includes an outer hexagonal unit, an inner hexagonal unit (8) and four triangular units (6): The outer hexagonal primitive is formed by enclosing six angular primitives (5), and there is a spacer (7) between every two adjacent angular primitives (5); Four triangular primitives (6) are distributed outside the outer hexagonal primitive, the outer hexagonal primitive and the four triangular primitives (6) form a square structure, and an oblique interval (10) is provided between the outer hexagonal primitive and the triangular primitive (6); the outer hexagonal primitives of every two adjacent absorbing units (4) are arranged in parallel; The inner hexagonal primitive (8) is nested in the center of the outer hexagonal primitive, and there is a regular hexagonal interval (11) between the two; The outer hexagonal element, the inner hexagonal element (8) and the triangular element (6) are all made of a radar absorbing coating, and the radar absorbing coating is a mixture of carbonyl iron, charcoal and epoxy resin.

2. The hexagonal elementary structure absorbing metamaterial according to claim 1, characterized in that: The circumscribed circle radius of the outer hexagonal primitive is 8-12 mm, and the circumscribed circle radius of the inner hexagonal primitive (8) is 4-8 mm.

3. The hexagonal elementary structure absorbing metamaterial according to claim 1, characterized in that: The length of each of the wave absorbing units (4) is 16-20 mm, and the width is 15-19 mm.

4. The hexagonal elementary structure absorbing metamaterial according to claim 1, characterized in that: The thickness of the superstructure absorbing coating (2) is 1.8-2.2 mm.

5. The hexagonal elementary structure absorbing metamaterial according to claim 1, characterized in that: The width of the strip spacing (7) is 1.0-1.4 mm, the width of the regular hexagonal spacing (11) is 1.1-1.5 mm, the width of the oblique spacing (10) is 1.0-1.2 mm, the width of each spacing unit (9) is 0.6-1.0 mm, and the width of the transverse spacing is 1.2-2.0 mm.

6. A method for preparing the hexagonal elementary structure absorbing metamaterial according to claim 1, characterized in that: The steps include: grinding and mixing carbonyl iron and charcoal to obtain a carbonyl iron / charcoal composite material; The carbonyl iron / charcoal composite material and epoxy resin are mixed in a solvent to obtain an absorbing coating, which is coated on a metal matrix layer and allowed to stand at room temperature until semi-cured. A superstructure mold is then used for embossing, and the absorbing coating is demoulded after it is completely cured to form a superstructure absorbing coating on the surface of the metal matrix layer, thereby obtaining a hexagonal elementary structure absorbing metamaterial.

7. The method for preparing a hexagonal elementary structure absorbing metamaterial according to claim 6, characterized in that: The superstructure mold is designed according to the absorber array.

8. The method for preparing a hexagonal elementary structure absorbing metamaterial according to claim 6, characterized in that: The mass ratio of carbonyl iron, charcoal and epoxy resin is 5:0.2-0.3:

1.

9. The method for preparing a hexagonal elementary structure absorbing metamaterial according to claim 6, characterized in that: The solvent is selected from anhydrous ethanol, toluene, acetone and ethyl acetate.

10. Use of the hexagonal elementary structure absorbing metamaterial according to claim 1 in preparing electromagnetic wave absorbing metamaterial.

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