A radar wave absorbing material, a preparation method and application thereof

Abstract

The application belongs to the technical field of electromagnetic wave absorbing materials, and discloses a radar wave absorbing material and a preparation method and application thereof. The radar wave absorbing material comprises a base body and a functional coating arranged on the base body. The functional coating contains N wave absorbing coatings. A coating formed by the same wave absorbing material is defined as one wave absorbing coating. Each wave absorbing coating is named as a first wave absorbing coating, a second wave absorbing coating, an Nth wave absorbing coating, and N is an integer not less than 2. The overlapping area of any two wave absorbing coatings in the vertical projection direction is not more than 10%. The N wave absorbing coatings form a periodic array structure. The periodic array includes a geometric periodic array or a circuit simulation periodic array. The application solves the problems of narrow bandwidth and low efficiency of a single wave absorbing material coating, and the problems of difficult precise regulation of electromagnetic parameters of multi-material mixed spraying and inability to form a regular and ordered structure.

Description

Technical Field

[0001] This invention relates to a radar wave absorbing material, its preparation method, and its application, belonging to the technical field of electromagnetic wave absorbing materials and functional coatings. Background Technology

[0002] As one of the core materials for electromagnetic protection and stealth technology, absorbing materials are widely used in aerospace, military equipment, electronic communications and other fields. Their main function is to absorb or attenuate incident electromagnetic waves, reduce the reflection and scattering of electromagnetic waves, thereby achieving the stealth of the target or the purification of the electromagnetic environment.

[0003] Among them, radar-absorbing coatings, due to their strong adaptability and other characteristics, convert electromagnetic waves into heat energy or other forms of energy through internal dielectric loss, magnetic loss, and composite loss mechanisms, thus becoming one of the important ways to achieve radar stealth.

[0004] Currently, existing methods for preparing microwave absorbing coatings mainly fall into two categories: one is the overall spraying process of a single microwave absorbing material, which involves uniformly coating a single microwave absorbing material onto the substrate surface using spraying equipment to form a single-component microwave absorbing coating; the other is a spraying process that attempts to combine multiple microwave absorbing materials, but this often involves directly spraying a mixture of various materials. Both of these processes have significant drawbacks: the electromagnetic parameters (dielectric constant, permeability) of a single microwave absorbing material are fixed, making it difficult to simultaneously match the absorption requirements of a wide frequency range of electromagnetic waves, resulting in a narrow absorption bandwidth, limited absorption efficiency, and a single electromagnetic wave loss mechanism, relying solely on the material's own dielectric or magnetic loss to achieve absorption; while after spraying a mixture of multiple materials, the electromagnetic parameters of the materials are difficult to precisely control, making it impossible to form a regular and orderly structure. This not only fails to fully utilize the synergistic absorption effect between different materials but may also lead to mutual interference of loss mechanisms due to component mixing, resulting in poor improvement in absorption performance. Furthermore, neither of these processes utilizes the control of electromagnetic waves through structural design, making it difficult to improve loss efficiency by enhancing multiple reflections and scattering of electromagnetic waves, thus failing to achieve ideal microwave absorption performance.

[0005] Therefore, it is necessary to develop an absorbing coating that can achieve excellent microwave absorption performance. Summary of the Invention

[0006] To address the problems existing in the prior art, one of the objectives of this invention is to provide a radar wave absorbing material. This radar wave absorbing material solves the problems of narrow bandwidth and low efficiency of single-material coatings and the difficulty in precisely controlling electromagnetic parameters and forming a regular and orderly structure in multi-material mixed spraying through a dual mechanism of "material synergy + structural enhancement". The radar wave absorbing material provided by this invention can achieve high-efficiency absorption in a wide frequency range (such as 2~18GHz), with a reflection loss of less than -15dB. The absorption bandwidth can be widened by more than 30% compared to unstructured material coatings, which can better meet the stealth and protection requirements in complex electromagnetic environments.

[0007] The second objective of this invention is to provide a method for preparing radar wave absorbing materials, which is simple and easy to industrialize.

[0008] The third objective of this invention is to provide an application of radar wave absorbing materials in aerospace or electronic communications.

[0009] To achieve the above objectives, a first aspect of the present invention provides a radar wave absorbing material, the radar wave absorbing material comprising a substrate and a functional coating disposed on the substrate; wherein the functional coating contains N absorbing coatings, a coating formed of the same absorbing material is defined as an absorbing coating, and each absorbing coating is named a first absorbing coating, a second absorbing coating, ..., an Nth absorbing coating, where N is an integer not less than 2; the overlapping area of ​​any two absorbing coatings in the vertical projection direction does not exceed 10%, and the N absorbing coatings form a periodic array structure, the periodic array including a geometric periodic array or a circuit analog periodic array;

[0010] The microwave absorbing material forming any microwave absorbing coating contains component A and a binder; component A is a dielectric microwave absorbing material or a magnetic loss microwave absorbing material; among N microwave absorbing coatings, at least one microwave absorbing coating formed by dielectric microwave absorbing material and binder and at least one microwave absorbing coating formed by magnetic loss microwave absorbing material and binder are included.

[0011] When the periodic array is a geometric periodic array, any two adjacent structural units contain at least two absorbing coatings;

[0012] When the periodic array is a circuit-simulated periodic array, each structural unit contains at least two absorbing coatings.

[0013] In existing technologies, single-material monolithic spraying or mixed-material monolithic spraying is often used. This invention, however, employs a periodic array structure and the synergistic spraying of different materials to enhance the absorption of specific waves and increase reflection and scattering, thereby further attenuating electromagnetic waves and enhancing the coating's wave absorption capability. This invention introduces multiple coatings of different materials into the same layer and designs these coatings in a periodic array arrangement. Its core principle is a dual wave absorption mechanism of "material synergistic loss + structural regulation enhancement," which can be divided into two parts: First, the synergistic loss mechanism of multiple absorbing materials. The wave absorbing materials selected in this invention (dielectric absorbing materials and magnetic loss absorbing materials) have different electromagnetic loss characteristics (dielectric loss or magnetic loss) and different electromagnetic parameters. When electromagnetic waves are incident, the dielectric absorbing material attenuates mid-to-high frequency electromagnetic waves through polarization loss, while the magnetic loss absorbing material attenuates low-frequency electromagnetic waves through hysteresis loss and eddy current loss. The synergistic effect of multiple materials can cover a wider frequency range, achieving broadband wave absorption. Second, the electromagnetic wave regulation mechanism of the periodic structure. The periodic structure (geometric periodic array and / or circuit-simulated periodic array) designed in this invention can generate resonance, scattering, and multiple reflection effects on incident electromagnetic waves. The periodic array, through the design of unit shape, size, and arrangement, enhances the absorption of electromagnetic waves of specific frequencies through the resonance effect of the periodic structure. Furthermore, the electromagnetic waves undergo multiple reflections and scattering between different material units of the periodic structure, prolonging the propagation path within the coating and increasing the interaction time between the electromagnetic waves and the absorbing material. This allows the energy of the electromagnetic waves to be fully dissipated and converted into heat energy, further improving absorption efficiency and thus strengthening the energy loss and conversion of electromagnetic waves. By employing a coating preparation technique that synergistically combines multiple absorbing materials with a periodic structure, the orderly arrangement of various absorbing materials through a regular periodic structure fully leverages the synergistic absorption effect of the materials and the electromagnetic modulation effect of the periodic structure, thereby significantly improving the absorption performance of the coating. Moreover, experiments have shown that simultaneously incorporating dielectric and magnetically depleted absorbing materials into the functional coating further enhances its absorption performance.

[0014] In this invention, the structural unit refers to the smallest geometric functional unit that constitutes the periodic array of radar wave absorbing coating. This unit is designed according to the resonance matching principle of the target absorption frequency band.

[0015] In this invention, in a periodic array, any two adjacent structural units refer to the two structural units that are closest to each other in the longitudinal or transverse direction.

[0016] As a preferred option, component A is a single component. If a mixture of multiple dielectric materials is used instead of a single material, the dielectric constants and losses of different dielectric materials will vary significantly. This will result in irregular dielectric properties after mixing, leading to a phenomenon where one loss is interfered with by another, affecting the stability of the absorbing coating. The same applies to magnetic loss absorbing materials.

[0017] In this invention, "single component" means that component A is composed of only one substance, rather than a physical mixture of multiple substances under the same functional category. For example, when component A is a dielectric absorbing material, it can only be selected from a single substance in that category. For instance, dielectric absorbing materials include carbon-based materials, which in turn include carbon nanotubes, graphite, and carbon fibers. Component A must be one of these three substances, and cannot be a mixture of them.

[0018] As a preferred embodiment, the same absorbing material has the same component A, and the mass ratio of component A to binder is the same.

[0019] As a preferred embodiment, the spacing between any two adjacent structural units is 0-1 mm. Experiments have shown that when any two adjacent structural units are closely spaced, electromagnetic waves can seamlessly alternately pass through the two coatings during propagation, avoiding the leakage problem of "electromagnetic waves directly penetrating the gap" caused by the spacing, resulting in low electromagnetic wave absorption loss. A more preferred spacing is ≤0.05 mm.

[0020] As a preferred embodiment, the structural unit is square, and the side length of the structural unit of the periodic array structure is 2mm to 40mm.

[0021] As a preferred embodiment, the absorbing coatings do not overlap with each other on a two-dimensional plane, and the absorbing coatings in any structural unit are continuous absorbing coatings. In this invention, "continuous absorbing coating" means that all absorbing coatings in any structural unit completely cover the substrate surface, and there are no obvious gaps or uncovered areas between them.

[0022] As another preferred option, the various absorbing coatings do not overlap with each other and share edges on a two-dimensional plane.

[0023] As a preferred embodiment, N is an integer from 2 to 6.

[0024] As a preferred embodiment, when the periodic array is a geometric periodic array and N is 2, 4 or 6, the functional coating contains N / 2 absorbing coatings formed by dielectric absorbing material and binder;

[0025] When the periodic array is a geometric periodic array and N is 3 or 5, the absorbing coatings of adjacent structural units are arranged alternately in the transverse or longitudinal direction of the periodic array; and the functional coating contains [(N+1) / 2] or [(N-1) / 2] absorbing coatings formed by dielectric absorbing materials and binders.

[0026] When N is an odd number, the number of absorbing coatings formed by dielectric or magnetic loss absorbing materials cannot be equal; however, one more of either type is acceptable, with no special requirements. Experiments have shown that when the types of dielectric and magnetic loss absorbing materials are nearly equal, the absorption of specific waves can be further enhanced, and reflection and scattering can be increased to further dissipate electromagnetic waves, thereby enhancing the absorption capability of the coating.

[0027] As a preferred embodiment, when the periodic array is a geometric periodic array and N is an even number, any two adjacent structural units contain at least two absorbing coatings; the absorbing material forming one of the absorbing coatings is a combination of dielectric absorbing material and adhesive, and the absorbing material forming the other absorbing coating is a combination of magnetic loss absorbing material and adhesive.

[0028] When the periodic array is a circuit-simulated periodic array, each structural unit contains at least two absorbing coatings. One absorbing coating consists of a dielectric absorbing material and an adhesive, while the other absorbing coating consists of a magnetic loss absorbing material and an adhesive. Experiments have shown that the absorption capability of the coating is further enhanced when both dielectric and magnetic loss absorbing materials are present and alternately distributed.

[0029] As a preferred embodiment, the dielectric absorbing material is selected from carbon-based materials and ceramic-based materials.

[0030] As a more preferred embodiment, the carbon-based material is selected from carbon nanotubes, graphite and carbon fibers, and the ceramic material is selected from silicon carbide, alumina and zinc oxide.

[0031] As a preferred embodiment, the magnetic loss absorbing material is selected from one of ferrite, metallic magnetic powder, and carbonyl iron powder.

[0032] As a more preferred embodiment, the metallic magnetic powder is selected from one of yttrium cobalt powder, iron cobalt powder, and nickel cobalt powder.

[0033] As a more preferred embodiment, the functional coating comprises at least one microwave-absorbing coating formed by carbon nanotubes and a binder and another microwave-absorbing coating formed by carbonyl iron powder and a binder, or at least one microwave-absorbing coating formed by carbon nanotubes and a binder and another microwave-absorbing coating formed by metallic magnetic powder and a binder. Experiments have shown that the coating in this preferred embodiment exhibits superior microwave absorption performance.

[0034] As a preferred option, the thickness of any absorbing coating can be independently 0.5~2mm.

[0035] As a preferred embodiment, the substrate is selected from one of aluminum alloy plate, iron plate, copper plate and plastic plate.

[0036] As a preferred embodiment, the mass ratio of component A to adhesive is 1:0.2~5.

[0037] As a preferred embodiment, the adhesive is selected from at least one of epoxy resin, phenolic resin, and vinyl ester resin.

[0038] As a preferred embodiment, the geometric periodic array is a planar regular tessellation or a planar semi-regular tessellation, and the circuit simulation periodic array includes a cross shape, a back shape, and a square ring.

[0039] As a preferred option, planar regular tessellation includes rectangular array structures, hexagonal array structures, or triangular array structures.

[0040] As a preferred embodiment, when the periodic array is a rectangular array structure, the top left structural unit is taken as the first structural unit, the type of absorbing coating of the first structural unit is the first absorbing coating, and the types of absorbing coatings along the horizontal direction of the first structural unit are arranged alternately as the second absorbing coating... the Nth absorbing coating, the first absorbing coating, the second absorbing coating, the Nth absorbing coating...; and the types of absorbing coatings along the vertical direction of the first structural unit are arranged alternately as the second absorbing coating... the Nth absorbing coating, the first absorbing coating, the second absorbing coating, the Nth absorbing coating...

[0041] A second aspect of the present invention is to provide a method for preparing the radar wave absorbing material described in the second aspect above, the method comprising:

[0042] (1) Design a periodic arrangement, and fabricate the first shield, the second shield... the Nth shield according to the designed periodic array, and configure the first absorbing material, the second absorbing material... the Nth absorbing material;

[0043] (2) Using the first shield as a template, the first absorbing material is coated onto the substrate surface and then the first shield is removed for the first curing treatment; using the second shield as a template, the second absorbing material is coated onto the substrate surface and then the second shield is removed for the second curing treatment; repeat this step until the Nth shield is used as a template, the Nth absorbing material is coated onto the substrate surface and then the Nth shield is removed for the Nth curing treatment, to obtain the radar wave absorbing material.

[0044] As a preferred embodiment, the first absorbing material, the second absorbing material, ... the Nth absorbing material contain component A and a binder.

[0045] As a preferred embodiment, the substrate is first cleaned, polished, and dried before the coating is applied. The present invention does not specify any particular method for cleaning, polishing, and drying; any method known in the art is acceptable.

[0046] As a preferred embodiment, the temperature of the first curing treatment, the second curing treatment, ... and the Nth curing treatment are each independently 40℃~80℃, and the time is 1~4h.

[0047] A third aspect of the present invention is to provide the application of the radar wave absorbing material described in the first aspect above in aerospace or electronic communications.

[0048] Compared with the prior art, the present invention has at least the following advantages:

[0049] (1) This invention sprays different absorbing materials in a regular periodic structure in different areas, and utilizes the differences in electromagnetic parameters of different materials and the electromagnetic wave modulation effect of the periodic structure to achieve the dual effect of material synergistic wave absorption and structure-enhanced wave absorption, thereby significantly improving the wave absorption performance of the absorbing coating.

[0050] (2) The radar wave absorbing material structure provided by the present invention has strong design flexibility. Different types and parameters of absorbing materials can be accurately selected according to the target absorbing frequency requirements, and the periodic structure shape and size can be flexibly designed to achieve customized matching of absorbing performance.

[0051] (3) The radar wave absorbing material provided by the present invention has significantly improved the absorption performance: Through the dual mechanism of "material synergy + structural enhancement", the problem of narrow bandwidth and low efficiency of single absorbing material coating is solved. It can achieve high efficiency absorption in a wide frequency range (such as 2-18GHz), and the reflection loss can reach below -15dB. The absorption bandwidth can be widened by more than 30% compared with the unstructured material coating, which can better meet the stealth and protection requirements in complex electromagnetic environments. Attached Figure Description

[0052] Figure 1This is a schematic diagram of the radar wave absorbing material coating of Example 1;

[0053] Figure 2 This is a schematic diagram of the radar wave absorbing material absorbing coating of Example 3;

[0054] Figure 3 This is a schematic diagram of the radar wave absorbing material coating of Example 4;

[0055] Figure 4 This is a schematic diagram of the radar wave absorbing material absorbing coating of Example 5;

[0056] Figure 5 This is a schematic diagram of the radar wave absorbing material absorbing coating of Example 6;

[0057] Figure 6 This is the reflection loss curve of the radar wave absorbing material in Example 1;

[0058] Figure 7 This is the reflection loss curve of the radar wave absorbing material in Example 2;

[0059] Figure 8 This is the reflection loss curve of the radar wave absorbing material in Example 3;

[0060] Figure 9 This is the reflection loss curve of the radar wave absorbing material in Example 4;

[0061] Figure 10 This is the reflection loss curve of the radar wave absorbing material in Example 5;

[0062] Figure 11 The reflection loss curve of the radar wave absorbing material in Comparative Example 1 is shown.

[0063] Figure 12 The reflection loss curve of the radar wave absorbing material in Comparative Example 2 is shown.

[0064] Figure 13 The reflection loss curve of the radar wave absorbing material in Comparative Example 3 is shown.

[0065] Figure 14 The reflection loss curve of the radar wave absorbing material in Comparative Example 4 is shown.

[0066] Figure 15 The reflection loss curve of the radar wave absorbing material in Comparative Example 5 is shown.

[0067] Figure 16 This is a physical image of the radar wave absorbing material prepared according to the present invention. Detailed Implementation

[0068] The endpoints and any values within the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoints of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0069] The following further illustrates the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative efforts still fall within the protection scope of the present invention.

[0070] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0071] Example 1

[0072] (1) Select an aluminum alloy sheet as the substrate, and successively perform ultrasonic cleaning with acetone, sandpaper polishing, and rinsing with deionized water, and then dry it at 80 °C for 1 h to obtain a substrate with a clean and flat surface;

[0073] (2) Design a "hui" - shaped array structure pattern. The size of the unit is 20 mm × 20 mm, and the distance between any two adjacent structural units is less than 0.05 mm. Select carbon nanotube / epoxy resin absorbing material (dielectric absorbing material, mass ratio of carbon nanotubes to epoxy resin is 1:2) as the first absorbing material, and carbonyl iron powder / epoxy resin absorbing material (magnetic loss absorbing material, mass ratio of carbonyl iron powder to epoxy resin is 1:2) as the second absorbing material;

[0074] (3) Fabricate a hollowed - out wood pulp paper (the hollowed - out area is Figure 1 the gray area, with dimensions consistent with the design) that matches the first absorbing coating of the "hui" - shaped array. Fix the template on the surface of the substrate, and coat the carbon nanotube / epoxy resin absorbing material on the hollowed - out area through a high - pressure air spraying device; after coating, remove the template, and put the substrate into an oven and cure it at 80 °C for 1 h to form the first absorbing coating;

[0075] (4) Fabricate a hollowed - out metal template (the hollowed - out area is Figure 1 the black area, with dimensions consistent with the design) that matches the second absorbing coating of the "hui" - shaped array. Fix the template on the surface of the substrate, and coat the carbonyl iron powder / epoxy resin absorbing material on the hollowed - out area through a high - pressure air spraying device; after coating, remove the template, and put the substrate into an oven and cure it at 80 °C for 1 h to form the second absorbing coating;

[0076] (5) Gently polish the cured coating to remove surface burrs, obtaining a "hui"-shaped array multi-material absorbing coating. The coating thicknesses of the first absorbing coating and the second absorbing coating are 1.15 mm.

[0077] After testing, within the frequency range of 2 - 18 GHz, the absorbing bandwidth with a reflection loss ≤ -10 dB of this absorbing coating reaches 8.12 GHz, and the maximum reflection loss is -21.42 dB. The absorbing performance is significantly better than that of a single carbon nanotube coating, a single carbonyl iron powder coating, and a carbon nanotube / carbonyl iron powder hybrid coating.

[0078] Example 2

[0079] This example is carried out by referring to a method similar to that of Example 1. The difference is that the magnetic loss type absorbing material is replaced with a combination of yttrium cobalt powder and epoxy resin with a mass ratio of 1:2.

[0080] After testing, within the frequency range of 2 - 18 GHz, the absorbing bandwidth with a reflection loss ≤ -10 dB of this absorbing coating reaches 5.62 GHz, and the maximum reflection loss is -16.82 dB.

[0081] Example 3

[0082] This example is carried out by referring to a method similar to that of Example 1. The difference is that in this example, the periodic array structure is a rectangular array structure (the spacing between any two adjacent structural units is 0 mm), the absorbing materials forming the first absorbing coating and the second absorbing coating are kept unchanged, and the coating thicknesses of the first absorbing coating and the second absorbing coating are adjusted to 1.06 mm.

[0083] After testing, within the frequency range of 2 - 18 GHz, the absorbing bandwidth with a reflection loss ≤ -10 dB of this absorbing coating reaches 6.14 GHz, and the maximum reflection loss is -17.42 dB.

[0084] Example 4

[0085] This example is carried out by referring to a method similar to that of Example 1. The difference is that in this example, the periodic array structure is a cross-shaped array structure (the spacing between any two adjacent structural units is less than 0.05 mm), the absorbing materials forming the first absorbing coating and the second absorbing coating are kept unchanged, and the coating thicknesses of the first absorbing coating and the second absorbing coating are adjusted to 1.04 mm.

[0086] After testing, within the frequency range of 2 - 18 GHz, the absorbing bandwidth with a reflection loss ≤ -10 dB of this absorbing coating reaches 7.10 GHz, and the maximum reflection loss is -18.62 dB.

[0087] Example 5

[0088] This embodiment is carried out using a method similar to that of Embodiment 1, except that: firstly, the periodic array structure in this embodiment is a hexagonal array structure (the spacing between any two adjacent structural units is 0 mm); secondly, the magnetic loss type absorbing material is replaced with a combination of yttrium cobalt powder and epoxy resin with a mass ratio of 1:2; and thirdly, the coating thickness of the first absorbing coating and the second absorbing coating is adjusted to 1.11 mm.

[0089] Tests showed that the absorbing coating achieved an absorption bandwidth of 5.23 GHz with a reflection loss ≤ -10 dB in the 2-18 GHz frequency range, and a maximum reflection loss of -15.99 dB.

[0090] Example 6

[0091] This embodiment is carried out using a method similar to that of Embodiment 1. The differences are as follows: First, the periodic array structure in this embodiment is a rectangular array structure (the spacing between any two adjacent structural units is 0 mm). Second, the material forming the first microwave absorbing coating is a combination of carbonyl iron powder and epoxy resin in a mass ratio of 1:2 (material A). The material forming the second microwave absorbing coating is a combination of carbon nanotubes and epoxy resin in a mass ratio of 1:2 (material B). The material forming the third microwave absorbing coating is a combination of ferrite and epoxy resin in a mass ratio of 1:2 (material C).

[0092] The structure of the periodic array in this embodiment is as follows: the top left structural unit is the first structural unit, the type of absorbing material of the first structural unit is material A, and the types of absorbing materials along the horizontal direction of the first structural unit are material B, material C, material A, material B, material C... arranged alternately; the types of absorbing materials along the vertical direction of the first structural unit are material B, material C, material A, material B, material C... arranged alternately.

[0093] Tests showed that the absorbing coating achieved an absorption bandwidth of 7.56 GHz with a reflection loss ≤ -10 dB in the 2-18 GHz frequency range, and a maximum reflection loss of -19.87 dB.

[0094] Comparative Example 1

[0095] Step (1) is the same as in Example 1;

[0096] (2) Carbon nanotubes and epoxy resin with a mass ratio of 1:2 are used as microwave absorbing materials. The overall spraying process is adopted. The carbon nanotube / epoxy resin microwave absorbing material is coated on the substrate by high pressure air spraying equipment. The substrate is placed in an oven and cured at 80°C for 1 hour to form a microwave absorbing coating with a coating thickness of 1.15 mm.

[0097] Tests showed that the absorbing coating achieved an absorbing bandwidth of 0 GHz with a reflection loss of ≤-10dB in the 2-18 GHz frequency range, and a maximum reflection loss of only -7.83dB.

[0098] Comparative Example 2

[0099] Step (1) is the same as in Example 1;

[0100] (2) Carbonyl iron powder and epoxy resin with a mass ratio of 1:2 are used as microwave absorbing materials. The whole spraying process is adopted. The carbonyl iron powder / epoxy resin microwave absorbing material is coated on the substrate by high pressure air spraying equipment. The substrate is placed in an oven and cured at 80°C for 1 hour to form a microwave absorbing coating with a coating thickness of 1.15 mm.

[0101] Tests showed that the absorbing coating achieved an absorption bandwidth of 2.76 GHz with a reflection loss ≤ -10 dB in the 2-18 GHz frequency range, and a maximum reflection loss of only -11.37 dB.

[0102] Comparative Example 3

[0103] Step (1) is the same as in Example 1;

[0104] (2) Carbon nanotubes and epoxy resin with a mass ratio of 1:2 and carbonyl iron powder and epoxy resin with a mass ratio of 1:2 are mixed in a mass ratio of 1:1 as microwave absorbing material. The whole spraying process is adopted. The microwave absorbing material is coated on the substrate by high pressure air spraying equipment. The substrate is placed in an oven and cured at 80°C for 1 hour to form a microwave absorbing coating with a coating thickness of 1.15 mm.

[0105] Tests showed that the absorbing coating achieved an absorbing bandwidth of 4.59 GHz with a reflection loss of ≤-10dB in the 2-18 GHz frequency range, and a maximum reflection loss of only -12.90dB.

[0106] Comparative Example 4

[0107] Step (1) is the same as in Example 1;

[0108] (2) Yttrium cobalt powder and epoxy resin with a mass ratio of 1:2 are used as microwave absorbing materials. The whole spraying process is adopted. The Yttrium cobalt powder / epoxy resin microwave absorbing material is coated on the substrate by high pressure air spraying equipment. The substrate is placed in an oven and cured at 80°C for 1 hour to form a microwave absorbing coating with a coating thickness of 1.15 mm.

[0109] Tests showed that the absorbing coating achieved an absorbing bandwidth of 0 GHz with a reflection loss of ≤-10dB in the 2-18 GHz frequency range, and a maximum reflection loss of only -6.32dB.

[0110] Comparative Example 5

[0111] Step (1) is the same as in Example 1;

[0112] (2) Carbon nanotubes and epoxy resin with a mass ratio of 1:2 and yttrium cobalt powder and epoxy resin with a mass ratio of 1:2 are mixed in a mass ratio of 1:1 as microwave absorbing material. The whole spraying process is adopted. The microwave absorbing material is coated on the substrate by high pressure air spraying equipment. The substrate is placed in an oven and cured at 80°C for 1 hour to form a microwave absorbing coating with a coating thickness of 1.15 mm.

[0113] Tests showed that the absorbing coating achieved an absorption bandwidth of 3.14 GHz with a reflection loss of ≤-10dB in the 2-18 GHz frequency range, and a maximum reflection loss of only -10.45dB.

[0114] Comparative Example 6

[0115] Step (1) is the same as in Example 1;

[0116] (2) Carbon nanotubes and epoxy resin with a mass ratio of 1:2 are used as microwave absorbing materials. The overall spraying process is adopted. The carbon nanotube / epoxy resin microwave absorbing material is coated on the substrate by high pressure air spraying equipment. The substrate is placed in an oven and cured at 80°C for 1 hour to form the first microwave absorbing coating with a coating thickness of 1.15 mm.

[0117] (3) Carbonyl iron powder and epoxy resin with a mass ratio of 1:2 are used as microwave absorbing materials. The overall spraying process is adopted. The carbonyl iron powder / epoxy resin microwave absorbing material is coated on the first microwave absorbing coating by high pressure air spraying equipment. Then it is placed in an oven and cured at 80°C for 1 hour to form the second microwave absorbing coating with a coating thickness of 1.15 mm.

[0118] Tests showed that the absorbing coating achieved an absorbing bandwidth of 5.10 GHz with a reflection loss ≤ -10 dB in the 2-18 GHz frequency range, and a maximum reflection loss of only -11.42 dB.

[0119] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A radar wave absorbing material, characterized by: The radar wave absorbing material comprises a substrate and a functional coating arranged on the substrate; in the functional coating, the functional coating contains N wave-absorbing coatings, a coating formed by the same wave-absorbing material is defined as one wave-absorbing coating, each wave-absorbing coating is respectively named as a first wave-absorbing coating, a second wave-absorbing coating,..., and an Nth wave-absorbing coating, N is an integer not less than 2; each wave-absorbing coating is mutually non-overlapped in a two-dimensional plane, and the wave-absorbing coating in any structural unit is a continuous wave-absorbing coating; meanwhile, the N wave-absorbing coatings form a periodic array structure, the periodic array comprises a geometric periodic array or a circuit simulation periodic array; The wave-absorbing material forming any wave-absorbing coating contains component A and a binder; the component A is a dielectric type wave-absorbing material or a magnetic loss type wave-absorbing material; in the N wave-absorbing coatings, at least one wave-absorbing coating is formed by the dielectric type wave-absorbing material and the binder, and at least one wave-absorbing coating is formed by the magnetic loss type wave-absorbing material and the binder; When the periodic array is the geometric periodic array, at least 2 wave-absorbing coatings are contained in any two adjacent structural units; When the periodic array is the circuit simulation periodic array, at least 2 wave-absorbing coatings are contained in each structural unit.

2. A radar wave absorbing material according to claim 1, characterized in that: The structural unit is a square, and the side length of the structural unit of the periodic array structure is 2 mm to 40 mm; And / or, the N is an integer of 2 to 6.

3. A radar wave absorbing material according to claim 2, characterized in that: When the periodic array is the geometric periodic array, and the N is 2, 4 or 6, the functional coating contains N / 2 wave-absorbing coatings formed by the dielectric type wave-absorbing material and the binder; When the periodic array is the geometric periodic array, and the N is 3 or 5, in the transverse or longitudinal direction of the periodic array, the wave-absorbing coatings of adjacent structural units are arranged alternately; and the functional coating contains [(N+1) / 2] or [(N-1) / 2] wave-absorbing coatings formed by the dielectric type wave-absorbing material and the binder.

4. The radar wave absorbing material according to claim 1 or 2, characterized in that: When the periodic array is the geometric periodic array, and the N is an even number, at least 2 wave-absorbing coatings are contained in any two adjacent structural units; the wave-absorbing material forming one of the wave-absorbing coatings is a combination of the dielectric type wave-absorbing material and the binder, and the wave-absorbing material forming the other wave-absorbing coating is a combination of the magnetic loss type wave-absorbing material and the binder; When the periodic array is the circuit simulation periodic array, at least 2 wave-absorbbing coatings are contained in each structural unit, the wave-absorbing material forming one of the wave-absorbing coatings is a combination of dielectric type wave-absorbing material and binder, and the wave-absorbing material forming the other wave-absorbing coating is a magnetic loss type wave-absorbing material and a binder.

5. A radar wave absorbing material according to claim 1 or 2, characterized in that: The dielectric type wave-absorbing material is selected from one of carbon-based materials and ceramic-based materials; And / or, the magnetic loss type wave-absorbing material is selected from one of ferrite, metal magnetic powder and carbonyl iron powder.

6. A radar wave absorbing material according to claim 1 or 2, characterized in that: The thickness of any wave-absorbing coating is independently 0.5 to 2 mm.

7. A radar wave absorbing material according to claim 1 or 2, characterized in that: The mass ratio of the amount of the component A to the amount of the binder is 1:0.2 to 5.

8. A radar wave absorbing material according to claim 1 or 2, characterized in that: The wave-absorbing material is applied in aerospace or electronic communication.

9. A method of producing the radar wave absorbing material according to any one of claims 1 to 8, characterized by: The method comprises: (1) Design a periodic arrangement, and fabricate the first shield, the second shield... the Nth shield according to the designed periodic array, and configure the first absorbing material, the second absorbing material... the Nth absorbing material; (2) Using the first shield as a template, the first absorbing material is coated onto the substrate surface and then the first shield is removed for the first curing treatment; using the second shield as a template, the second absorbing material is coated onto the substrate surface and then the second shield is removed for the second curing treatment; repeat this step until the Nth shield is used as a template, the Nth absorbing material is coated onto the substrate surface and then the Nth shield is removed for the Nth curing treatment, to obtain the radar wave absorbing material.

10. A method of producing a radar wave absorbing material according to claim 9, wherein: The temperature of the first curing treatment, the second curing treatment, ... and the Nth curing treatment are each independently 40℃~80℃, and the time is 1~4h.

Images