Light ultra-wideband visible light-infrared-radar multi-spectrum compatible metamaterial

Abstract

The invention discloses a light ultra-wideband visible light-infrared-radar multi-spectrum compatible metamaterial. The metamaterial sequentially comprises an infrared visible layer, a cross-shaped wave absorbing layer and a bottom reflecting metal layer from top to bottom, the infrared visible layer comprises a first array composed of a plurality of first units with the same structure, each first unit is composed of a conducting layer and a dielectric layer, the first units are in a regular hexagon shape, the first array is formed by closely arranging regular hexagons at certain intervals, and the conducting layers are made of MXene; the cross-shaped wave absorbing layer comprises a second array composed of a plurality of second units of the same structure, each second unit comprises two resistive film plates with gaps, and the two resistive film plates intersect to form a cross-shaped structure; the resistive film plate comprises a dielectric layer, and a first conductive layer and a second conductive layer which are respectively positioned on the upper surface and the lower surface of the dielectric layer. The invention has the advantages of light weight, ultra wide band, low infrared emissivity, low visible emissivity, high microwave absorptivity, polarization insensitivity, angle stability and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metamaterial multi-spectrum compatible design, in particular to a lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial. BACKGROUND

[0002] Modern detection system has been expanded from single radar to "radar-infrared-visible light-laser-acoustic" full spectrum cooperation, and the traditional means for a certain frequency band is easy to be complemented by the remaining frequency band. The radar high absorption requires high loss and low reflection of the material, the infrared band requires low emission and low temperature, and the visible light requires low reflection. The physical requirements of radar, infrared and visible light are often mutually exclusive. The traditional multi-spectrum compatible metamaterial is layered on the metal structure and coated with different functional coatings, resulting in large thickness, high surface density, easy to fall off, high maintenance cost, and difficult to meet the comprehensive requirements of lightweight, thin and loadable for aviation / aerospace platform. Therefore, the multi-spectrum compatible technology is an advanced direction under the triple pressure of threat escalation, frequency band mechanism exclusion and platform lightweight demand.

[0003] Currently, the infrared-visible compatible reduces the infrared emissivity to below 0.2, and the infrared-radar compatible layer also realizes-30dB microwave absorption, but if the infrared-visible-radar multi-spectrum compatible is to be realized, the coating needs to be added respectively, and the surface density is too large after stacking. It is difficult to realize lightweight, so it is necessary to develop a lightweight multi-spectrum compatible metamaterial. Currently, the infrared-radar compatible metamaterial intelligently realizes 90% absorption of Ku band, but the bandwidth is insufficient to adapt to the demand of multi-spectrum complementation, so it is necessary to develop an ultra-wideband multi-spectrum compatible metamaterial. SUMMARY

[0004] The present application relates to the field of metamaterial multi-spectrum compatible design, in particular to a lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial.

[0005] Technical solution: To achieve the above-mentioned purposes, the light-weight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial provided by the application comprises, from top to bottom, an infrared-visible layer, a cross-shaped wave-absorbing layer, and a bottom reflective metal layer; the infrared-visible layer comprises a first array of a plurality of first units with the same structure, each first unit being composed of a conductive layer and a dielectric layer, the first units being regular hexagons, and the first array being formed by closely arranging the regular hexagons at a certain distance; the material of the conductive layer is MXene; the cross-shaped wave-absorbing layer comprises a second array of a plurality of second units with the same structure, each second unit comprising two resistance film plates with slits, and the two resistance film plates intersecting to form a cross-shaped structure; the resistance film plate comprises a dielectric layer and a first conductive layer and a second conductive layer located on the upper and lower surfaces of the dielectric layer, respectively.

[0006] As a preferred, in the infrared-visible layer, the proportion of the area occupied by the conductive layer to the total size of the first unit is 80.2%-92.6%.

[0007] As a preferred, in the infrared-visible layer, the side length of the regular hexagon is 0.5mm-0.6mm, and the interval is 0.04-0.1mm.

[0008] As a preferred, in the infrared-visible layer, the sheet resistance of the conductive layer MXene is 1-6Ω / sq.

[0009] Further preferably, in the infrared-visible layer, the thickness of the conductive layer MXene is 2μm, after laser etching, the side length of the regular hexagon is 0.6mm, and the slit of laser etching is 0.1mm.

[0010] As a preferred, in the cross-shaped wave-absorbing layer, the materials of the first conductive layer and the second conductive layer are conductive carbon paste.

[0011] As a preferred, in the cross-shaped wave-absorbing layer, the sheet resistance of the first conductive layer and the second conductive layer is 380-440Ω / sq.

[0012] As a preferred, in the cross-shaped wave-absorbing layer, the unit side length is 8cm, and the height is 16mm.

[0013] As a preferred, in the infrared-visible layer, the material of the dielectric layer is PET; in the material of the cross-shaped wave-absorbing layer, the material of the dielectric layer is FR4.

[0014] As a preferred, the emissivity of the metamaterial in the infrared frequency band of 3-14μm ranges from 0.3 to 0.5, the average reflectivity in the visible light frequency band of 400-800nm ranges from 12% to 15%, and the absorption rate in the range of 1.82-18.41GHz is greater than 90%.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant effects:

[0016] (1) This invention can reduce the scattering of electromagnetic waves incident on a target within a wide frequency band. Simulation results show that the absorption rate is greater than 90% in the range of 1.82-18.41 GHz, and the relative absorption bandwidth reaches 164%. Since the performance of visible light, infrared and radar microwave is always mutually restrictive and mutually exclusive, this invention can achieve a wide frequency band while maintaining the requirements of low reflectivity of visible light and low emissivity of infrared, thus further expanding the application range.

[0017] (2) The absorbing layer of the present invention adopts a three-dimensional hollow structure, similar to a honeycomb structure, but lighter than a honeycomb structure, with a larger unit spacing, a thinner dielectric substrate, and a conductive carbon paste layer at the micrometer level, with an overall thickness of only 0.097λ. L , λ L For the maximum operating wavelength. Surface density less than 0.26 g / cm³. -2 It achieves lightweight design, which can meet the comprehensive requirements of aviation / aerospace platforms for lightweight, thinness, and load-bearing capacity.

[0018] (3) By using MXene as the infrared-visible layer, this invention can simultaneously achieve low infrared emissivity and low visible reflectivity. MXene itself has a low infrared emissivity, with an experimentally verified high duty cycle of 80.2%-92.6%. Combined with its dense hexagonal structure, it can achieve infrared emissivity of 0.3-0.5 in the 3-5μm and 8-14μm ranges. Because MXene is black and has a certain surface roughness, its average reflectivity in the visible light 400-800nm ​​range is 12%-15%. Low visible light reflectivity and low infrared emissivity provide more possibilities for multi-band collaborative protection, which can be extended to diverse application scenarios and is one of the key technologies for improving target concealment and tactical advantages. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a periodic structural unit according to an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the infrared visible layer unit according to an embodiment of the present invention.

[0022] Figure 3A unit diagram of a cross-shaped wave-absorbing layer of an embodiment of the present application.

[0023] Figure 4 An emissivity graph of an embodiment of the present application in the infrared 3-14 μm.

[0024] Figure 5 A reflectivity graph of an embodiment of the present application in the visible light 400-800 nm.

[0025] Figure 6 A reflection amplitude curve graph of an embodiment of the present application in the case of horizontal incidence TE and vertical incidence TM.

[0026] Figure 7 A reflection amplitude curve graph of an embodiment of the present application in the case of horizontal incidence TE at different angles.

[0027] Figure 8 A reflection amplitude curve graph of an embodiment of the present application in the case of horizontal incidence TM at different angles. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the embodiments and drawings, and the exemplary embodiments of the present application and their descriptions are only used to explain the present application, and do not limit the present application.

[0029] It should be noted that the relationship terms such as "first" and "second" and the like in the text are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0030] As shown in Figure 1 , an embodiment of the present application discloses a lightweight ultra-wideband visible light-infrared-radar multi-spectrum compatible metamaterial, which comprises, from top to bottom, an infrared-visible layer, a cross-shaped wave-absorbing layer and a bottom reflective metal layer. As shown in Figure 2 , the infrared-visible layer comprises a first array composed of a plurality of identical first units, each first unit being composed of a conductive layer and a dielectric layer, the first units being regular hexagons, and the first array being formed by closely arranging the regular hexagons at a certain distance, the material of the conductive layer being MXene. Figure 2 In the figure, the black part is MXene, which is arranged in a close regular hexagonal honeycomb shape. The chemical composition of Mxene is two-dimensional transition metal carbide / nitride ), microstructure two-dimensional layered structure, with metal-level conductivity ( ), ceramic-level strength (Young's modulus ≈ 0.33 TPa) and large specific surface area similar to graphene.

[0031] To achieve low infrared emissivity, low visible light reflectivity and high microwave transmittance, the proportion of the area occupied by the conductive layer to the total size of the first unit in the infrared-visible layer is 80.2%-92.6%. In specific implementation, the side length of the regular hexagon is 0.5mm-0.6mm, the interval is 0.04-0.1mm, the MXene film thickness of the conductive layer is 1.5-2.5μm, and the square resistance is 1-6Ω / sq.

[0032] In this embodiment, a regular hexagon with a side length of 0.6mm and an interval of 0.1mm is selected as an example for illustration.

[0033] Figure 2 In this embodiment, the white part is the dielectric layer, and PET substrate is used in this embodiment. The dielectric constant of PET is 2.2, the loss tangent is 0.02, and the thickness is 0.2mm.

[0034] The unit structure of the cross-shaped wave-absorbing layer is shown in Figure 3 , which includes two slotted resistive film plates, each of which includes a first conductive layer, a dielectric layer and a second conductive layer. The black part is the conductive layer, and the square resistance of the first conductive layer and the second conductive layer is 380-440Ω / sq. In this embodiment, the dielectric layer material is FR4, the relative dielectric constant is 4.4, the loss tangent is 0.025, the thickness is 0.5mm, and the square resistance of the conductive layer is 380Ω / sq. The unit size of the cross-shaped wave-absorbing layer is 8mm. The periodic array size is 50×50.

[0035] In some embodiments, the MXene film of the infrared-visible layer can be prepared by stirring powder in hydrofluoric acid at 35°C for 24h to selectively dissolve Al, obtaining multilayer ; after centrifugal washing to pH ≈ 6, intercalation with solution for 17h to make the flakes delaminate and float on the water surface to form a high-concentration colloid; then the colloid is suction-filtered onto a microporous membrane by vacuum-assisted filtration to obtain a self-supporting paper-like film, or uniformly scraped on a PET substrate with a scraper; then 60-120°C hot pressing is performed to improve the density, and 200-300°C inert annealing is performed to remove functional group defects, and finally the MXene film is obtained, which can be directly peeled off or used by roll-to-roll transfer.

[0036] The hexagonal structure in the infrared-visible layer is obtained by laser etching of a whole prepared MXene film. The laser etching machine is a fiber laser marking machine. The laser etching speed is 1000 mm / s, the power is 20%, and the frequency is 30 kHz. The laser etching pattern is a CAD drawing imported into the CAD software, in which a hexagonal periodic pattern is drawn.

[0037] In this embodiment, the infrared-visible layer adopts a regular hexagonal periodic structure. The reason for using a regular hexagon is that the internal angle of a regular hexagon is 120°, which can be seamlessly tiled on a plane. Similarly, a triangle and a square can also be seamlessly tiled on a plane. However, the unique advantage of a regular hexagon is that it has a larger area than a regular triangle and a square under the same perimeter. Moreover, for a square and a regular hexagon, the regular hexagon has a higher microwave transmittance under the same duty cycle. Since compatibility with visible light, infrared, and microwave is required, the visible light and infrared shielding layer is required to have a microwave transmittance, so that electromagnetic waves can pass through the visible light and infrared shielding layer to the microwave absorbing layer to achieve multi-spectrum compatibility. Due to the right-angle edges of the square Mxene patch, current is concentrated and scattered at the edges, resulting in strong near-field coupling and parasitic resonance, reducing the transmittance, and easily exciting grating lobes and high-order modes, causing energy to scatter in non-transmission directions. The 120° internal angle of the hexagon reduces the electric field concentration, the edge capacitance is smaller, the symmetric current path is lengthened, the edge scattering is reduced, the current distribution is more uniform, the energy is more easily transmitted through the patch gap, the honeycomb arrangement suppresses the grating lobes, and the main lobe energy is more concentrated in the normal transmission direction.

[0038] In this embodiment, the final thickness of the Mxene film of the infrared-visible layer is 2 μm, and the sheet resistance is about 1 Ω / sq, which is the best choice after repeated attempts. A larger sheet resistance leads to a thinner Mxene layer, a more transparent material, which is not conducive to low visible light reflectivity. In addition, an increase in sheet resistance leads to a decrease in surface defects or poor interlayer contact, enhancing infrared absorption, which will cause the infrared emissivity to increase. A smaller sheet resistance leads to a too thick Mxene layer, which is not conducive to improving the transmittance of the laser etching gap.

[0039] The substrate of the Mxene film of the infrared-visible layer is PET. Compared with F4B, PET has a lower cost and a comparable infrared emissivity. The use of PET also facilitates the observation of whether the MXene is completely etched according to the given pattern when using laser etching, and whether the substrate PET is also etched to cause uneven thickness of the substrate, thereby summarizing experience to set appropriate etching speed and frequency. According to the idea of the present application, a suitable substrate can be selected, and experience in laser etching can be obtained.

[0040] The side length of the regular hexagonal unit of the infrared-visible layer is 0.6 mm, and the interval is 0.1 mm. The size is selected because a suitable transmittance is required. Based on the formula wherein represents the infrared emissivity of the whole, represents the infrared emissivity of MXene, represents the infrared emissivity of PET, represents the duty cycle of MXene, in order to ensure the lower infrared emissivity requirement, the duty cycle of MXene is large, but due to the requirement of microwave transmittance, the duty cycle cannot be too large, so in order to balance the infrared emissivity and microwave transmittance, the length of the regular hexagon unit is 0.6mm, the interval is 0.1mm, the duty cycle of MXene is 83.2%, and the finally obtained infrared emissivity is as shown in Figure 4 , the infrared emissivity of 3-14um is lower than 0.3, and the lower infrared emissivity is realized.

[0041] The reflectivity of visible light is as shown in Figure 5 , the reflectivity of 400-800nm is lower than 12%, due to the surface defect structure and multi-layer structure of MXene, it has good absorption effect on visible light, and the lower reflectivity of visible light can be realized, which is also suitable for night scene.

[0042] For microwave performance, as shown in Figure 6 , S11 is less than-10dB in the range of 1.82-18.41GHz, the absorption rate is greater than 90%, and the relative bandwidth is 164%, realizing microwave absorption in a wide frequency band. Moreover, the reflection parameter curves of TE wave incidence and TM wave incidence are basically coincided, which shows that the present application has polarization insensitivity. Due to the high symmetry of the cross-shaped wave absorbing layer, the infrared visible layer is also almost symmetrical, so the two polarization directions are almost completely the same. As shown in Figure 7 , in the TE wave incidence, 0-30° can basically maintain the angle stability, and the absorption rate of 45° decreases slightly, which can show that the angle stability is maintained. As shown in Figure 8 , in the TM wave incidence, with the increase of the angle, the absorption performance is better, which is related to the asymmetry of the TE and TM polarization directions of the regular hexagon, and also shows the angle stability.

[0043] The above is only a preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial, characterized in that, From top to bottom, it includes an infrared-visible layer, a cross-shaped wave-absorbing layer and a bottom reflective metal layer; the infrared-visible layer includes a first array composed of a plurality of first units with the same structure, each first unit is composed of a conductive layer and a dielectric layer, the first unit is a regular hexagon, the first array is formed by closely arranging regular hexagons with a certain distance, the material of the conductive layer is MXene; the cross-shaped wave-absorbing layer includes a second array composed of a plurality of second units with the same structure, each second unit includes two resistive film plates with slits, and the two resistive film plates cross to form a cross-shaped structure; the resistive film plate includes a dielectric layer and a first conductive layer and a second conductive layer located on the upper and lower surfaces of the dielectric layer respectively.

2. The lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial of claim 1, wherein, In the infrared-visible layer, the proportion of the area occupied by the conductive layer to the total size of the first unit is 80.2%-92.6%.

3. The LWIR-Radar-VIS multi-spectrum compatible metamaterial of claim 1, wherein, In the infrared-visible layer, the side length of the regular hexagon is 0.5mm-0.6mm, and the interval is 0.04-0.1mm.

4. The lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial of claim 1, wherein, In the infrared-visible layer, the sheet resistance of the conductive layer MXene is 1-6Ω / sq.

5. The lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial of claim 1, wherein, In the infrared-visible layer, the thickness of the conductive layer MXene is 2μm, after laser etching, the side length of the regular hexagon is 0.6mm, and the laser etching gap is 0.1mm.

6. The LWIR-Radar-VIS multi-spectrum compatible metamaterial of claim 1, wherein, In the cross-shaped wave-absorbing layer, the materials of the first conductive layer and the second conductive layer are conductive carbon paste.

7. The LWIR-Radar-VIS multi-spectrum compatible metamaterial of claim 1, wherein, In the cross-shaped wave-absorbing layer, the sheet resistance of the first conductive layer and the second conductive layer is 380-440Ω / sq.

8. The LWIR-Radar-VIS multi-spectrum compatible metamaterial of claim 1, wherein, In the cross-shaped wave-absorbing layer, the unit side length is 8cm, and the height is 16mm.

9. The LWIR-Radar-VIS multi-spectrum compatible metamaterial of claim 1, wherein, In the infrared-visible layer, the material of the dielectric layer is PET; in the cross-shaped wave-absorbing layer, the material of the dielectric layer is FR4.

10. The lightweight ultra-wideband visible-infrared-radar multi-spectrum compatible metamaterial of claim 1, wherein, The emissivity in the infrared frequency band of 3-14μm is in the range of 0.3-0.5, the average reflectivity in the visible light frequency band of 400-800nm is in the range of 12%-15%, and the absorption rate in the range of 1.82-18.41GHz is greater than 90%.

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