A preparation method of high temperature resistant stealth metamaterial

Abstract

The present application discloses a method for preparing a high-temperature resistant stealth metamaterial, and relates to the technical field of stealth materials. The method comprises the following steps: determining the shape of the conductive pattern and the type of ceramic substrate of the target metamaterial according to the performance parameters of the target metamaterial to be prepared; based on the calculation of the Jones matrix, rotating the conductive pattern by an angle θ along the center origin to obtain two units with a phase difference of 180°, and combining the conductive patterns corresponding to the two units to form a unit array; using a conductive slurry to prepare a conductive structure on a ceramic substrate according to the form of the unit array, a high-temperature resistant stealth metamaterial is obtained; wherein the preparation process of the conductive structure includes one of a screen printing process, a plasma spraying process, a high-temperature adhesive bonding process, and a magnetron sputtering process. The present application realizes a 180° phase difference of the polarization conversion wave by rotating the conductive pattern, thereby realizing a broadband low-reflection metamaterial applied to different temperature conditions, and can realize high-temperature stealth characteristics in different frequency bands.

Description

Technical Field

[0001] The present application relates to the technical field of stealth materials, and in particular to a method for preparing a high-temperature resistant stealth metamaterial. Background Art

[0002] With the development of military detection, stealth technology can reduce the probability of targets being discovered, but the application of stealth materials in certain special occasions must meet more stringent requirements. For example, the operating temperature of conventional aircraft tail covers and supersonic aircraft wing leading edges can reach 200-400°C, and the operating temperature of aerospace aircraft wing leading edges, supersonic aircraft tail nozzles, and cruise missile nose cone caps can reach 800°C or even above 1000°C. The demand for high-temperature stealth materials has increased dramatically. However, due to the limitation of the Curie temperature, the absorption performance of magnetic absorbing materials deteriorates sharply with increasing temperature, making it difficult to apply them to high-temperature occasions; the electromagnetic mechanism and temperature characteristics of dielectric absorbing materials are incompatible. As the temperature increases, the electromagnetic parameters of the materials gradually change, and the impedance matching characteristics and electromagnetic wave absorption performance change, making it difficult to achieve broadband stealth from room temperature to high temperature.

[0003] Metamaterials are artificial periodic materials with unique electromagnetic properties. By designing key physical dimensions, they can effectively control the transmission characteristics of electromagnetic waves and are expected to be used in the field of high-temperature stealth. However, current research on metamaterials is mainly focused on the field of room-temperature stealth. This is attributed to the fact that the dielectric materials of metamaterial units are generally FR4, F4B, etc., and the conductive materials are generally copper, aluminum, etc., which will fail under high-temperature conditions because the constituent materials are destroyed. However, most existing high-temperature stealth metamaterials have disadvantages such as poor stealth performance, narrow operating frequency band, and single preparation process. The temperature stability of their reflectivity is poor, and there are differences in reflectivity at different temperatures, making it difficult to meet broadband stealth performance from room temperature to high temperature. Summary of the invention

[0004] The main purpose of this application is to provide a method for preparing a high-temperature resistant stealth metamaterial, aiming to solve the technical problem that existing stealth metamaterials are difficult to meet the broadband stealth performance from room temperature to high temperature.

[0005] To achieve the above objectives, the present application proposes a method for preparing a high temperature resistant stealth metamaterial, comprising the following steps:

[0006] Determining the conductive pattern shape and ceramic substrate type of the target metamaterial according to the performance parameters of the target metamaterial to be prepared;

[0007] Based on Jones matrix calculation, the conductive pattern of the target metamaterial is rotated along the central origin by an angle θ to obtain two units with a phase difference of 180°, and the conductive patterns corresponding to the two units are combined to form a unit array;

[0008] According to the form of the unit array, a conductive slurry is used to prepare a conductive structure on the ceramic substrate to obtain a high-temperature resistant stealth metamaterial;

[0009] The preparation process of using conductive slurry to prepare a conductive structure on the ceramic substrate includes one of a screen printing process, a plasma spraying process, a high-temperature adhesive bonding process and a magnetron sputtering process.

[0010] Optionally, the step of rotating the conductive pattern of the target metamaterial by an angle θ along the center origin based on Jones matrix calculation to obtain two units with a phase difference of 180° includes:

[0011] Based on the conductive pattern shape and ceramic substrate type of the target metamaterial, the calculation formula of the linear polarization wave reflection matrix of the metamaterial is determined, which is expressed as:

[0012]

[0013] In the formula, R x and R y are the reflection characteristics of x-polarized waves and y-polarized waves, R lin is the reflection matrix of electromagnetic wave, r xx 、r xy 、r yx 、r yy is the reflection coefficient, r xx 、r xy 、r yx 、r yy The simplified forms correspond to the four characters A, B, C, and D respectively. x and i y represents the polarization state of the incident wave;

[0014] Based on the linear polarization wave reflection matrix of the metamaterial, the Jones matrix and the rotation matrix, the linear polarization wave reflection matrix R of the metamaterial after rotation by an angle θ is obtained. lin (θ), where the rotation matrix D θ Calculated according to the following formula:

[0015]

[0016] The linear polarization wave reflection matrix R of the metamaterial after rotating by angle θ lin (θ) is calculated according to the following formula:

[0017]

[0018] In the formula, r uu 、r uv 、r vu 、r vv represents the reflection coefficient of the metamaterial after rotation, D θ The reciprocal of

[0019] Based on the linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ lin (θ), and two units with a phase difference of 180° are obtained after the conductive pattern is rotated about the center origin by an angle of θ.

[0020] Optionally, the linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ is lin (θ), the step of obtaining two units with a phase difference of 180° after the conductive pattern is rotated about the center origin by an angle of θ, comprises:

[0021] For metamaterials along the z-axis in the thickness direction, when the metamaterial is mirror-symmetric about the xz plane or the yz plane, it is expressed as C1 symmetry. After symmetric design, the working matrices are and Get M -1 R lin M=R lin , in the reflection matrix, B=C=0, that is, the reflection matrix when C1 is symmetric

[0022] When the metamaterial is rotated 2π / 2 along the center origin and becomes symmetrical, it is expressed as C2 symmetry, and the working matrix is ​​D π , that is, the rotation matrix D θ Here θ is π, which is the same as the reflection matrix before rotation. The reflection matrix when C2 is symmetric is

[0023] When the metamaterial is rotated 2π / 3 along the center origin and becomes symmetrical, it is expressed as C3 symmetry, and the working matrix is ​​D 2π / 3 , that is, the rotation matrix D θ Where θ is 2π / 3, A=D, B=-C, and the reflection matrix when C3 is symmetric is

[0024] When the metamaterial is rotated π / 2 along the center origin and becomes symmetrical, it is expressed as C4 symmetry, and the working matrix is ​​D π / 2 , that is, the rotation matrix D θ Where θ is π / 2, A=D, B=-C, and the reflection matrix when C4 is symmetric is

[0025] Based on the reflection matrix R when C1 is symmetric lin (C1), the reflection matrix R when C2 is symmetric lin (C2), the reflection matrix R when C3 is symmetric lin (C3), the reflection matrix R when C4 is symmetric lin(C4) and the linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ lin (θ), for a metamaterial with mirror symmetry along the xz plane or the yz plane, when the conductive pattern of the metamaterial is rotated by an angle θ, the reflection matrix R lin-θ Calculated according to the following formula:

[0026]

[0027] Based on the reflection matrix R lin-θ , without changing the amplitude, the conductive pattern is rotated by an angle θ to construct two units with opposite phases.

[0028] Optionally, the reflection matrix R lin-θ , without changing the amplitude, the conductive pattern is rotated by an angle θ to construct two units with opposite phases, including:

[0029] Based on the reflection matrix R lin-θ ,set up Matrix r uu and r vv When the amplitude is the same and the phase difference is 180°, θ=θ0, that is, two units of θ=0° and θ=θ0 are obtained.

[0030] Optionally, the step of obtaining two units of θ=0° and θ=θ0 includes:

[0031] Set θ0 to 90° and obtain two units with θ=0° and θ=90°;

[0032] Based on the reflection matrix R lin-θ , the Jones matrices of the two units are expressed as and That is, the phase difference between the two units is 180°.

[0033] Optionally, the step of combining the conductive patterns corresponding to the two units to form a unit array includes:

[0034] The conductive patterns corresponding to the two units are respectively combined in a form of 5×5 or 10×10 to form two super units;

[0035] Then, the two super units are arranged in a chessboard pattern to form a unit array.

[0036] Optionally, the ceramic substrate includes one of silicon oxide ceramics, aluminum oxide ceramics, zirconium oxide ceramics, magnesium oxide ceramics, calcium oxide ceramics, boron nitride ceramics, silicon nitride ceramics, silicon carbide ceramics or composite ceramics.

[0037] Optionally, the conductive pattern has a shape of a rectangle, a circle, a ring, an open ring, a zigzag line, a diagonal line, a multi-shape superposition or a fractal pattern.

[0038] Optionally, the conductive paste includes one of the metal materials gold, silver, platinum, tungsten, rhodium, titanium, titanium alloy, silver-copper alloy or the semiconductor materials carbon black, single-layer graphene, redox graphene or ionic compounds titanium boride, zirconium boride, titanium carbide.

[0039] Optionally, the steps of the screen printing process include:

[0040] The ceramic substrate is ultrasonically cleaned for 0.5h-1.5h, and then dried at 90°C-110°C for 0.3h-0.8h;

[0041] Printing a mask plate that matches the ceramic substrate, determining the shape of the conductive pattern, and drawing a pattern on the mask plate in the form of the unit array;

[0042] Drawing a screen printing screen, coating the screen printing screen with photoresist and drying the screen printing screen at 65° C. to 75° C. for 0.3 h to 0.8 h;

[0043] Combine the screen printing plate coated with photoresist with the mask plate with the pattern drawn, and expose for 8-12 minutes, then wash away the unexposed pattern part with water;

[0044] Covering the exposed silk screen on the ceramic substrate, adding a conductive paste, and printing on the two surfaces of the ceramic substrate respectively, forming a conductive structure on one surface where the ceramic substrate is combined with the silk screen, and forming a conductive backplane on the other surface;

[0045] The silk screen on the printed ceramic substrate is removed, and then the substrate is dried at 550° C. to 650° C. for 1.5 h to 2.5 h to obtain a high-temperature resistant stealth metamaterial.

[0046] Optionally, the steps of the plasma spraying process include:

[0047] The conductive slurry is mixed with silicon oxide powder, and deionized water and anhydrous ethanol are added as ball milling media, and the ball milling is performed for 1.5 h to 2.5 h at a ball milling speed of 250 r / min to 350 r / min to obtain a ball milled slurry;

[0048] Drying the ball-milled slurry at 85° C. to 95° C. for 0.5 h to 1.5 h to obtain a mixed powder;

[0049] Grinding the mixed powder and passing it through a 180-220 mesh sieve to obtain a mixed powder;

[0050] Printing a mask plate that matches the ceramic substrate, determining the shape of the conductive pattern, and drawing a pattern on the mask plate in the form of the unit array;

[0051] A steel film corresponding to the mask plate is prepared, and after combining the steel film with the mask plate, the steel film is attached to the ceramic substrate, and the two surfaces of the ceramic substrate are sprayed respectively, one surface at the junction with the steel film forms a conductive structure, and the other surface forms a conductive backplane, to obtain a high-temperature resistant stealth metamaterial. The voltage during the spraying process is 30V-40V, the current is 300A-400A, the air flow rate is 2000L / h-3000L / h, and the spraying distance is 50mm-100mm.

[0052] Optionally, the steps of the high temperature adhesive bonding process include:

[0053] Making two plates matching the ceramic substrate by using conductive slurry, and cutting one of the plates into a plurality of square pieces by using electric spark technology;

[0054] Using deionized water, ethanol and acetone to ultrasonically clean the plate, the square sheet and the ceramic substrate in sequence, and then drying them;

[0055] Determining the shape of the conductive pattern and performing 3D printing in the form of the unit array to obtain a polymer template;

[0056] Laminating the polymer template to the ceramic substrate, applying high temperature glue on one side of the square sheet and placing it on the ceramic substrate at a position corresponding to the polymer template;

[0057] Then, the polymer template is removed, and the ceramic substrate after the polymer template is removed is left to stand for 15h-17h, then kept at 80°C-100°C for 0.5h-1.5h, and then heated to 110°C-130°C and kept for 0.5h-1.5h to obtain a conductive structure;

[0058] The plate is bonded to the side of the ceramic substrate away from the conductive structure by applying high-temperature glue, and then allowed to stand for 15h-17h, and then kept warm at 80℃-100℃ for 0.5h-1.5h, and then heated to 110℃-130℃ and kept warm for 0.5h-1.5h to form a conductive backplane, thereby obtaining a high-temperature resistant stealth metamaterial.

[0059] Optionally, the steps of the magnetron sputtering process include:

[0060] The ceramic substrate is ultrasonically cleaned for 0.5 h to 1.5 h using detergent, acetone, ethanol and deionized water in sequence, and then dried using an inert gas;

[0061] The resistor target is placed in a magnetron sputtering coating machine and vacuumed for 0.3h-0.8h, and the ceramic substrate is coated for 0.5h-1.5h at a power of 90W-110W and a normal temperature DC condition to obtain a ceramic substrate with resistor films attached to both surfaces;

[0062] The shape of the conductive pattern is determined, and the pattern is drawn in the form of the unit array and introduced into a laser etching device, and one of the surfaces of the ceramic substrate with the attached resistor film is laser etched to obtain a conductive structure. The other surface of the ceramic substrate with the attached resistor film is not laser etched, that is, a conductive backplane, and a high-temperature resistant stealth metamaterial is obtained; wherein, during the laser etching process, the laser power is 2W-6W, and the scanning speed is 40mm / s-60mm / s.

[0063] Optionally, the average resistance value of the resistor film in the conductive structure is R1=200Ω, and the average square resistance of the resistor film in the conductive structure is R s1 =312.5Ω; the average resistance value of the resistor film in the conductive backplane R2=1Ω, the average square resistance of the resistor film in the conductive backplane R s2 =1Ω.

[0064] The present application first determines the conductive pattern shape and ceramic substrate type of the target metamaterial according to the requirements for the temperature resistance characteristics and stealth characteristics of different working frequency bands of the target metamaterial. Since different conductive pattern shapes maintain higher conductivity or loss in different temperature ranges, and the dielectric constant of the low-dielectric ceramic substrate is insensitive to temperature changes, it can correspond to the requirements of different temperature resistance characteristics and stealth characteristics of different working frequency bands. Then, based on Jones matrix calculation, the conductive pattern is rotated by a certain angle to match two units with a phase difference of 180°, and the two units are combined to form a unit array. A conductive structure is prepared on the ceramic substrate in the form of a unit array, so as to realize the electromagnetic scattering function of the metamaterial. After the conductive pattern is rotated, the polarization conversion of the electromagnetic wave can be realized. When it is rotated by a certain angle, a 180° phase difference of the polarization conversion wave can be realized. When the phase difference is 180°, due to the opposite phase, the energy deflection in the transmission direction can be realized by phase cancellation, thereby reducing the echo intensity in the vertical direction, so that the metamaterial has good electromagnetic properties. The present application realizes a 180° phase difference of the polarization conversion wave by selecting different types of ceramic substrates and different types of conductive pattern shapes, and rotating the conductive pattern of the metamaterial, thereby realizing a broadband low-reflection metamaterial that can be applied to different temperature conditions, and can achieve high-temperature stealth characteristics in different frequency bands. The reflectivity is stable at different temperatures, and can meet broadband stealth performance from normal temperature to high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0066] Figure 1 It is a schematic diagram of the arrangement of the unit array of the high temperature resistant stealth metamaterial described in the embodiment of the present application;

[0067] Figure 2 A schematic diagram of a reflectivity curve of the high temperature resistant stealth metamaterial described in Example 1 of the present application;

[0068] Figure 3 A schematic diagram of a reflectivity curve of the high temperature resistant stealth metamaterial described in Example 2 of the present application;

[0069] Figure 4 A schematic diagram of a reflectivity curve of the high temperature resistant stealth metamaterial described in Example 3 of the present application;

[0070] Figure 5 This is a schematic diagram of the reflectivity curve of the high-temperature resistant stealth metamaterial described in Example 4 of the present application.

[0071] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0072] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0073] At present, metamaterials are mainly used in the field of room-temperature stealth. This is attributed to the fact that the dielectric materials of metamaterial units are generally FR4, F4B, etc., and the conductive materials are generally copper, aluminum, etc., which will fail under high-temperature conditions because the constituent materials are destroyed. However, most of the existing high-temperature stealth metamaterials have disadvantages such as poor stealth performance, narrow working frequency band, and single preparation process. The temperature stability of their reflectivity is poor, and there are differences in reflectivity at different temperatures, which makes it difficult to meet the broadband stealth performance from room temperature to high temperature.

[0074] In view of the technical problems existing in the above-mentioned existing stealth metamaterials, an embodiment of the present application provides a method for preparing a high temperature resistant stealth metamaterial, comprising the following steps:

[0075] Determining the conductive pattern shape and ceramic substrate type of the target metamaterial according to the performance parameters of the target metamaterial to be prepared;

[0076] Based on Jones matrix calculation, the conductive pattern of the target metamaterial is rotated along the central origin by an angle θ to obtain two units with a phase difference of 180°, and the conductive patterns corresponding to the two units are combined to form a unit array;

[0077] According to the form of the unit array, a conductive slurry is used to prepare a conductive structure on the ceramic substrate to obtain a high-temperature resistant stealth metamaterial;

[0078] The preparation process of using conductive slurry to prepare a conductive structure on the ceramic substrate includes one of a screen printing process, a plasma spraying process, a high-temperature adhesive bonding process and a magnetron sputtering process.

[0079] The present application first determines the conductive pattern shape and ceramic substrate type of the target metamaterial according to the requirements for the temperature resistance characteristics and stealth characteristics of different working frequency bands of the target metamaterial. Since different conductive pattern shapes maintain higher conductivity or loss in different temperature ranges, and the dielectric constant of the low-dielectric ceramic substrate is insensitive to temperature changes, it can correspond to the requirements of different temperature resistance characteristics and stealth characteristics of different working frequency bands. Then, based on Jones matrix calculation, by rotating the conductive pattern by a certain angle, two units with a phase difference of 180° are matched, and the two units are combined to form a unit array, and a conductive structure is prepared on the ceramic substrate in the form of a unit array, the electromagnetic scattering function of the metamaterial can be realized, and after the conductive pattern is rotated, the polarization conversion of the electromagnetic wave can be realized, and when it is rotated by a certain angle, a phase difference of 180° of the polarization conversion wave can be realized. When the phase difference is 180°, due to the opposite phase, the energy deflection in the transmission direction can be achieved through phase cancellation, and the echo intensity in the vertical direction is reduced, so that the metamaterial has good electromagnetic properties. The present application realizes a 180° phase difference of the polarization conversion wave by selecting different types of ceramic substrates and different types of conductive pattern shapes, and rotating the conductive pattern of the metamaterial, thereby realizing a broadband low-reflection metamaterial that can be applied to different temperature conditions, and can achieve high-temperature stealth characteristics in different frequency bands. The reflectivity is stable at different temperatures, and can meet broadband stealth performance from normal temperature to high temperature.

[0080] As an implementable embodiment of the present application, the step of rotating the conductive pattern of the target metamaterial by an angle θ along the center origin based on Jones matrix calculation to obtain two units with a phase difference of 180° includes:

[0081] Based on the conductive pattern shape and ceramic substrate type of the target metamaterial, the calculation formula of the linear polarization wave reflection matrix of the metamaterial is determined, which is expressed as:

[0082]

[0083] In the formula, R x and R y are the reflection characteristics of x-polarized waves and y-polarized waves, R lin is the reflection matrix of electromagnetic wave, r xx 、r xy 、r yx 、r yy is the reflection coefficient, r xx 、r xy 、r yx 、r yy The simplified forms correspond to the four characters A, B, C, and D respectively. x and i y represents the polarization state of the incident wave;

[0084] Based on the linear polarization wave reflection matrix of the metamaterial and the Lorentz reciprocity theory, the Jones matrix R lin b The calculation formula is expressed as:

[0085]

[0086] Based on the Jones matrix, when the conductive pattern is rotated by an angle θ along the center origin, the rotation matrix D θ Applied to the Jones matrix calculation, the linear polarization wave reflection matrix R of the metamaterial after rotation by angle θ is obtained: lin (θ), where the rotation matrix D θ Calculated according to the following formula:

[0087]

[0088] The linear polarization wave reflection matrix R of the metamaterial after rotating by angle θ lin (θ) is calculated according to the following formula:

[0089]

[0090] In the formula, r uu 、r uv 、r vu 、r vv represents the reflection coefficient of the metamaterial after rotation, D θ -1 D θ The reciprocal of

[0091] For metamaterials along the z-axis in the thickness direction, when the metamaterial is mirror-symmetric about the xz plane or the yz plane, it is expressed as C1 symmetry. After symmetric design, the working matrices are and Get M-1 R lin M=R lin , in the reflection matrix, B=C=0, that is, the reflection matrix when C1 is symmetric

[0092]

[0093] When the metamaterial is rotated 2π / 2 along the center origin and becomes symmetrical, it is expressed as C2 symmetry, and the working matrix is ​​D π , that is, the rotation matrix D θ Here θ is π, which is the same as the reflection matrix before rotation. The reflection matrix when C2 is symmetric is

[0094] When the metamaterial is rotated 2π / 3 along the center origin and becomes symmetrical, it is expressed as C3 symmetry, and the working matrix is ​​D 2π / 3 , that is, the rotation matrix D θ Where θ is 2π / 3, A=D, B=-C, and the reflection matrix when C3 is symmetric is

[0095]

[0096] When the metamaterial is rotated π / 2 along the center origin and becomes symmetrical, it is expressed as C4 symmetry, and the working matrix is ​​D π / 2 , that is, the rotation matrix D θ Where θ is π / 2, A=D, B=-C, and the reflection matrix when C4 is symmetric is

[0097]

[0098] Based on the reflection matrix R when C1 is symmetric lin (C1), the reflection matrix R when C2 is symmetric lin (C2), the reflection matrix R when C3 is symmetric lin (C3), the reflection matrix R when C4 is symmetric lin (C4) and the linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ lin (θ), for a metamaterial with mirror symmetry along the xz plane or the yz plane, when the conductive pattern of the metamaterial is rotated by an angle θ, the reflection matrix R lin-θ Calculated according to the following formula:

[0099]

[0100] Based on the reflection matrix R lin-θ , without changing the amplitude, rotate the conductive pattern by an angle of θ and set Matrix r uu and r vvWhen the amplitude is the same and the phase difference is 180°, θ=θ0, and θ0 is set to 90° to obtain two units with θ=0° and θ=90°;

[0101] Based on the reflection matrix R lin-θ , the Jones matrices of the two units are expressed as and That is, the phase difference between the two units is 180°.

[0102] The present application uses Jones matrix calculation to obtain the reflection matrix R when the conductive pattern of the metamaterial is rotated by an angle θ: lin-θ The calculation formula is to obtain two units with a phase difference of 180° based on R lin-θ The calculation formula is as follows. When θ = 0° and θ = 90°, the Jones matrices of the two units are expressed as and "1" and "-1" indicate that the phase difference between the two is 180°, that is, the phase difference of the cross-polarized wave is 180°, so the phase difference between the two units of θ=0° and θ=90° is 180°, and the conductive patterns corresponding to the two units of θ=0° and θ=90° are combined to form a unit array.

[0103] As an implementation method of the present application, the step of combining the conductive patterns corresponding to the two units to form a unit array includes:

[0104] The conductive patterns corresponding to the two units are respectively combined in a form of 5×5 or 10×10 to form two super units;

[0105] Then, the two super units are arranged in a chessboard pattern to form a unit array.

[0106] The present application combines the conductive patterns corresponding to the two units with opposite phases in the form of 5×5 or 10×10, and then arranges them in a chessboard pattern, such as Figure 1 As shown, the scattering function of electromagnetic waves can be realized.

[0107] As an implementation method of the present application, the ceramic substrate includes one of silicon oxide ceramics, aluminum oxide ceramics, zirconium oxide ceramics, magnesium oxide ceramics, calcium oxide ceramics, boron nitride ceramics, silicon nitride ceramics, silicon carbide ceramics or composite ceramics.

[0108] In order to adjust the electromagnetic properties of the metamaterial so that the metamaterial can be applied to broadband low reflection under different temperature conditions, the ceramic substrate can be selected from silicon oxide ceramics, aluminum oxide ceramics, zirconium oxide ceramics, magnesium oxide ceramics, calcium oxide ceramics, boron nitride ceramics, silicon nitride ceramics, silicon carbide ceramics or composite ceramics made of the above ceramic materials. Preferably, the quartz ceramic substrate has good impedance matching characteristics, which can make the stealth performance of the metamaterial better; the impedance matching characteristics of the silicon carbide ceramic substrate are worse than those of the quartz ceramic substrate; the zirconium oxide ceramic substrate has a small thermal expansion coefficient and high strength, and is suitable for the preparation of high temperature resistant materials; the aluminum oxide ceramic substrate has good temperature resistance and good water resistance, and can work for a long time in a high temperature environment.

[0109] As an implementation method of the present application, the conductive pattern includes a rectangular, circular, annular, open annular, zigzag, diagonal, multi-shape superposition or fractal pattern.

[0110] According to the requirements for the electromagnetic properties of metamaterials under different working conditions, the present application further adjusts the electromagnetic properties of metamaterials by adjusting the shape of the conductive pattern. Preferably, the open circular conductive pattern is an asymmetric design, which can deflect the transmission direction of the electromagnetic wave and reduce the echo energy to achieve radar stealth; the zigzag conductive pattern can increase the equivalent capacitance and inductance of the conductive pattern to achieve high-temperature stealth performance; the diagonal conductive pattern can also achieve high-temperature stealth performance, and the reflectivity is relatively stable under high temperature conditions.

[0111] As an implementation method of the present application, the conductive paste includes metal materials such as gold, silver, platinum, tungsten, rhodium, titanium, titanium alloy, silver-copper alloy or semiconductor materials such as carbon black, single-layer graphene, redox graphene or ionic compounds such as titanium boride, zirconium boride and titanium carbide.

[0112] The present application is a metamaterial that maintains high conductivity or loss at different temperatures. The conductive paste uses gold, silver, platinum, tungsten, rhodium, titanium, titanium alloy, silver-copper alloy, carbon black, single-layer graphene, redox graphene, titanium boride, zirconium boride or titanium carbide. Different conductive pastes can maintain high conductivity or loss in different temperature ranges. Preferably, silver paste still has high conductivity or loss at 800°C, and platinum paste can achieve low reflection performance that can withstand 1000°C or even higher temperatures.

[0113] As an implementation method of the present application, the steps of the screen printing process include:

[0114] The ceramic substrate is ultrasonically cleaned for 0.5h-1.5h, and then dried at 90°C-110°C for 0.3h-0.8h;

[0115] Printing a mask plate that matches the ceramic substrate, determining the shape of the conductive pattern, and drawing a pattern on the mask plate in the form of the unit array;

[0116] Drawing a screen printing screen, coating the screen printing screen with photoresist and drying the screen printing screen at 65° C. to 75° C. for 0.3 h to 0.8 h;

[0117] Combine the screen printing plate coated with photoresist with the mask plate with the pattern drawn, and expose for 8-12 minutes, then wash away the unexposed pattern part with water;

[0118] Covering the exposed silk screen on the ceramic substrate, adding a conductive paste, and printing on the two surfaces of the ceramic substrate respectively, forming a conductive structure on one surface where the ceramic substrate is combined with the silk screen, and forming a conductive backplane on the other surface;

[0119] The silk screen on the printed ceramic substrate is removed, and then the substrate is dried at 550° C. to 650° C. for 1.5 h to 2.5 h to obtain a high-temperature resistant stealth metamaterial.

[0120] The present application adopts a screen printing process, screen-prints a conductive paste on one surface of a ceramic substrate and sintered to obtain a conductive structure, and brushes the conductive paste on the other surface and sintered to obtain a conductive backplane, thereby preparing the final high-temperature stealth metamaterial. The process is simple and feasible, and can obtain a metamaterial that meets broadband stealth performance from room temperature to high temperature.

[0121] As an implementable method of the present application, the steps of the plasma spraying process include:

[0122] The conductive slurry is mixed with silicon oxide powder, and deionized water and anhydrous ethanol are added as ball milling media, and the ball milling is performed for 1.5 h to 2.5 h at a ball milling speed of 250 r / min to 350 r / min to obtain a ball milled slurry;

[0123] Drying the ball-milled slurry at 85° C. to 95° C. for 0.5 h to 1.5 h to obtain a mixed powder;

[0124] Grinding the mixed powder and passing it through a 180-220 mesh sieve to obtain a mixed powder;

[0125] Printing a mask plate that matches the ceramic substrate, determining the shape of the conductive pattern, and drawing a pattern on the mask plate in the form of the unit array;

[0126] A steel film corresponding to the mask plate is prepared, and after combining the steel film with the mask plate, the steel film is attached to the ceramic substrate, and the two surfaces of the ceramic substrate are sprayed respectively, one surface at the junction with the steel film forms a conductive structure, and the other surface forms a conductive backplane, to obtain a high-temperature resistant stealth metamaterial. The voltage during the spraying process is 30V-40V, the current is 300A-400A, the air flow rate is 2000L / h-3000L / h, and the spraying distance is 50mm-100mm.

[0127] The present application adopts a plasma spraying process, sprays a conductive slurry on one surface of a ceramic substrate and forms a conductive structure, and sprays the other surface with a conductive slurry and forms a conductive backplane to prepare the final high-temperature stealth metamaterial. The process is simple and feasible, and can prepare a metamaterial with broadband stealth performance under different temperature conditions.

[0128] As an implementation method of the present application, the steps of the high temperature adhesive bonding process include:

[0129] Making two plates matching the ceramic substrate by using conductive slurry, and cutting one of the plates into a plurality of square pieces by using electric spark technology;

[0130] Using deionized water, ethanol and acetone to ultrasonically clean the plate, the square sheet and the ceramic substrate in sequence, and then drying them;

[0131] Determining the shape of the conductive pattern and performing 3D printing in the form of the unit array to obtain a polymer template;

[0132] Laminating the polymer template to the ceramic substrate, applying high temperature glue on one side of the square sheet and placing it on the ceramic substrate at a position corresponding to the polymer template;

[0133] Then, the polymer template is removed, and the ceramic substrate after the polymer template is removed is left to stand for 15h-17h, then kept at 80°C-100°C for 0.5h-1.5h, and then heated to 110°C-130°C and kept for 0.5h-1.5h to obtain a conductive structure;

[0134] The plate is bonded to the side of the ceramic substrate away from the conductive structure by applying high-temperature glue, and then allowed to stand for 15h-17h, and then kept warm at 80℃-100℃ for 0.5h-1.5h, and then heated to 110℃-130℃ and kept warm for 0.5h-1.5h to form a conductive backplane, thereby obtaining a high-temperature resistant stealth metamaterial.

[0135] The present application adopts cutting and high-temperature adhesive bonding process to realize the preparation of stealth metamaterials. The process is simple and feasible, and can realize broadband stealth performance of metamaterials from room temperature to high temperature.

[0136] As an implementable method of the present application, the steps of the magnetron sputtering process include:

[0137] The ceramic substrate is ultrasonically cleaned for 0.5 h to 1.5 h using detergent, acetone, ethanol and deionized water in sequence, and then dried using an inert gas;

[0138] The resistor target is placed in a magnetron sputtering coating machine and vacuumed for 0.3h-0.8h, and the ceramic substrate is coated for 0.5h-1.5h at a power of 90W-110W and a normal temperature DC condition to obtain a ceramic substrate with resistor films attached to both surfaces;

[0139] The shape of the conductive pattern is determined, and the pattern is drawn in the form of the unit array and introduced into a laser etching device, and one of the surfaces of the ceramic substrate with the attached resistor film is laser etched to obtain a conductive structure. The other surface of the ceramic substrate with the attached resistor film is not laser etched, that is, a conductive backplane, and a high-temperature resistant stealth metamaterial is obtained; wherein, during the laser etching process, the laser power is 2W-6W, and the scanning speed is 40mm / s-60mm / s.

[0140] This application adopts magnetron sputtering technology and introduces a resistive film to improve the impedance matching characteristics, and realizes radar stealth based on microwave absorption. The magnetron sputtering and laser etching processes can greatly improve the low-frequency stealth performance of the metamaterial.

[0141] As an implementation method of the present application, the average resistance value R1 of the resistor film in the conductive structure is 200Ω, and the average square resistance R s1 =312.5Ω; the average resistance value of the resistor film in the conductive backplane R2=1Ω, the average square resistance of the resistor film in the conductive backplane R s2 =1Ω.

[0142] The above technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0143] Example 1

[0144] A high temperature resistant stealth metamaterial comprises the following steps:

[0145] Select thickness 3mm and area 300mm 2 ×300mm 2 The quartz ceramic substrate is made of silver paste, and the conductive pattern is determined to be an open circular ring (such as Figure 2 lower right corner);

[0146] Set θ to 0° and 90°, based on the reflection matrix R lin-θ , the Jones matrices of the two units are expressed as and "1" and "-1" indicate that the phase difference between the two units is 180°. The conductive patterns corresponding to the two units are combined in a 5×5 form to form two super units, and then the two super units are arranged in a chessboard pattern to form a unit array, such as Figure 1 As shown ("1" and "2" are two units respectively);

[0147] The quartz ceramic substrate was ultrasonically cleaned for 1 h and then dried at 100 °C for 0.5 h;

[0148] Printing a mask plate that matches the quartz ceramic substrate, and drawing a conductive pattern on the mask plate in the form of the unit array;

[0149] Drawing a screen printing plate, coating the screen printing plate with photoresist and drying the screen printing plate at 70° C. for 0.5 h;

[0150] Combine the screen printing plate coated with photoresist with the mask plate with the pattern drawn, and expose for 10 minutes, then wash away the unexposed pattern part with water;

[0151] Covering the exposed silk screen on the quartz ceramic substrate, adding silver paste, and printing on the two surfaces of the ceramic substrate respectively, forming a conductive structure on one surface where the silk screen is combined with the silk screen, and forming a conductive backplane on the other surface;

[0152] The silk screen on the printed ceramic substrate is removed, and then the substrate is dried at 600°C for 2 hours to obtain a high-temperature resistant stealth metamaterial.

[0153] The dimensions of the conductive pattern are: unit period p=10 mm, outer ring radius r=4.6 mm, ring diameter s=0.9 mm, opening gap w=4.9 mm; the thickness of the conductive structure and the conductive backplane are both 0.03 mm.

[0154] The high temperature resistant stealth metamaterial of this embodiment rotates the conductive pattern by a specific angle, and there is a stable phase difference between the two units. After testing, the measured reflectivity of the high temperature resistant stealth metamaterial is as follows: Figure 2 As shown, its reflectivity in the range of 25℃-800℃ and 8GHz-18GHz frequency band is less than -10dB, and the reflectivity curve is basically consistent and is insensitive to temperature. Among them, the average reflectivity in the 8GHz-18GHz frequency band at 25℃ is -16.7dB, the average reflectivity in the 8GHz-18GHz frequency band at 400℃ is -17.3dB, and the average reflectivity in the 8GHz-18GHz frequency band at 800℃ is -17.4dB, which can meet the broadband stealth performance from normal temperature to high temperature.

[0155] Example 2

[0156] A high temperature resistant stealth metamaterial comprises the following steps:

[0157] Select thickness 2.5mm and area 300mm 2 ×300mm 2 The silicon carbide ceramic substrate is selected, the conductive paste is selected as platinum powder, and the conductive pattern shape is determined to be a broken line shape (such as Figure 3 lower right corner);

[0158] Obtain two units with a phase difference of 180°, combine the conductive patterns corresponding to the two units in a 5×5 form to form two super units, and then arrange the two super units in a checkerboard pattern to form a unit array;

[0159] Platinum powder and silicon oxide powder were mixed, and deionized water and anhydrous ethanol were added as ball milling media, and the ball milling was performed for 2 hours at a ball milling speed of 300 r / min to obtain ball milling slurry;

[0160] Drying the ball-milled slurry at 90° C. for 1 h to obtain a mixed powder;

[0161] Grinding the mixed powder and passing it through a 200-mesh sieve to obtain a mixed powder;

[0162] Printing a mask plate that matches the ceramic substrate, and drawing a conductive pattern on the mask plate in the form of the unit array;

[0163] A steel film corresponding to the mask is prepared, and after the steel film is combined with the mask, the steel film is attached to the ceramic substrate, and the two surfaces of the ceramic substrate are sprayed respectively, one surface of the combination with the steel film forms a conductive structure, and the other surface forms a conductive backplane, to obtain a high-temperature resistant stealth metamaterial, the voltage during the spraying process is 34V, the current is 370A, the gas flow rate is 2400L / h, and the spraying distance is 80mm;

[0164] The dimensions of the conductive pattern are: unit period p = 10 mm, fold line length r = 6 mm, fold line width s = 0.5 mm, opening gap w = 1.5 mm, fold length a = 1.5 mm, fold width b = 1 mm; the thickness of the conductive structure and the conductive backplane are both 0.015 mm.

[0165] The high temperature resistant stealth metamaterial of this embodiment adopts a zigzag conductive pattern, which can further improve the pattern equivalent capacitance and inductance compared with Example 1, and achieves stealth performance on the basis that the impedance matching characteristics of the silicon carbide ceramic substrate are worse than those of the quartz ceramic substrate. After testing, the measured reflectivity of the high temperature resistant stealth metamaterial is as follows: Figure 3As shown, its reflectivity in the range of 25℃-1200℃ and 8GHz-13.5GHz frequency band is less than -10dB, and the reflectivity curve is basically consistent, and it is insensitive to temperature, wherein the average reflectivity in the 8GHz-13.5GHz frequency band and 25℃ is -15.0dB, the average reflectivity in the 8GHz-13.5GHz frequency band and 400℃ is -15.0dB, the average reflectivity in the 8GHz-13.5GHz frequency band and 800℃ is -15.4dB, and the average reflectivity in the 8GHz-13.5GHz frequency band and 1200℃ is -14.8dB. Compared with Example 1, it can work for a long time in a high temperature environment of 1200℃, and can be applied to more harsh living environments.

[0166] Example 3

[0167] A high temperature resistant stealth metamaterial comprises the following steps:

[0168] Select thickness 2.5mm and area 300mm 2 ×300mm 2 The zirconia ceramic substrate is selected, the conductive paste is titanium boride, and the conductive pattern shape is determined to be a broken line shape (such as Figure 4 lower right corner);

[0169] Obtain two units with a phase difference of 180°, respectively combine the conductive patterns corresponding to the two units in a 10×10 form to form two super units, and then arrange the two super units in a checkerboard pattern to form a unit array;

[0170] Two plates matching the ceramic substrate are made by titanium boride slurry and polished to a thickness of 0.5 mm, and one of the plates is cut into a plurality of square pieces by electric spark technology;

[0171] Using deionized water, ethanol and acetone to ultrasonically clean the plate, the square sheet and the ceramic substrate in sequence, and then drying them;

[0172] Perform 3D printing in the form of a unit array to obtain a polymer template;

[0173] Laminating the polymer template to the ceramic substrate, applying high temperature glue on one side of the square sheet and placing it on the ceramic substrate at a position corresponding to the polymer template;

[0174] The polymer template is then removed, and the ceramic substrate after the polymer template is removed is left to stand for 16 hours, then kept at 90° C. for 1 hour, and then heated to 120° C. and kept for 1 hour to obtain a conductive structure;

[0175] The plate is bonded to the side of the ceramic substrate away from the conductive structure by applying high temperature glue, and then left to stand for 16 hours, and then kept at 90° C. for 1 hour, and then heated to 120° C. and kept for 1 hour to form a conductive backplane, thus obtaining a high temperature resistant stealth metamaterial;

[0176] The dimensions of the conductive pattern are: unit period p=5 mm, diagonal length a=4 mm, diagonal width b=1 mm, diagonal height h=0.5 mm; the thickness of the reflective backplane is 1 mm.

[0177] The high temperature resistant stealth metamaterial of this embodiment adopts a zirconium oxide ceramic substrate, which has a small thermal expansion coefficient and high strength, and is suitable for the preparation of high temperature resistant materials. After testing, the measured reflectivity of the high temperature resistant stealth metamaterial is as follows: Figure 4 As shown, the reflectivity in the range of 25°C-800°C and the frequency band of 8-12GHz is less than -10dB, and the reflectivity curve is relatively insensitive to temperature, wherein the average reflectivity in the frequency band of 8-12GHz and 25°C is -18.4dB, the average reflectivity in the frequency band of 8-12GHz and 400°C is -23.5dB, and the average reflectivity in the frequency band of 8-12GHz and 800°C is -18.0dB. Comparing Examples 1 and 2, the preparation of stealth metamaterials is achieved by cutting and high-temperature adhesive bonding processes, which can meet the broadband stealth performance from room temperature to high temperature.

[0178] Example 4

[0179] A high temperature resistant stealth metamaterial comprises the following steps:

[0180] Select thickness 2mm and area 300mm 2 ×300mm 2 The alumina ceramic substrate is made of inorganic aluminosilicate and graphite powder, and the conductive pattern is rectangular (such as Figure 5 shown);

[0181] Get two units with a phase difference of 180°, combine the two units in the form of 10×10 to form two super units, and then arrange the two super units in a chessboard pattern to form a unit array, such as Figure 1 As shown;

[0182] The ceramic substrate is ultrasonically cleaned for 1 hour using detergent, acetone, ethanol and deionized water in sequence, and then dried using an inert gas;

[0183] A 200Ω resistance target is placed in a magnetron sputtering coating machine and vacuumed for 0.5 h, and a resistance film is coated on the ceramic substrate for 1 h under a power of 100 W and a normal temperature direct current condition to obtain a ceramic substrate with resistance films attached to both surfaces;

[0184] A pattern is drawn in the form of the unit array and introduced into a laser etching device, and one surface of the ceramic substrate with the resistor film attached is laser-etched to obtain a conductive structure, and the other surface of the ceramic substrate with the resistor film attached is not laser-etched, that is, a conductive backplane, and a high-temperature resistant stealth metamaterial is obtained; wherein, during the laser etching process, the laser power is 4W and the scanning speed is 50mm / s;

[0185] Resistor film pattern size: period p = 15mm, rectangular side length s = 12mm, average resistance value of the resistor film in the conductive structure R1 = 200Ω, average square resistance R s1 =312.5Ω; the average resistance of the resistor film in the conductive backplane is R2 = 1Ω, the average square resistance is R s2 =1Ω.

[0186] The high temperature resistant stealth metamaterial of this embodiment introduces a resistive film to improve the impedance matching characteristics, realizes radar stealth based on microwave absorption, and realizes more excellent stealth performance under the condition of reducing the thickness of the ceramic substrate. The alumina ceramic substrate has good temperature resistance and waterproofness and can work for a long time in a high temperature environment. After testing, the measured reflectivity of the high temperature resistant stealth metamaterial is as follows: Figure 5 As shown, its reflectivity in the range of 25℃-400℃ and 2GHz-18GHz frequency band is less than -10dB, and the reflectivity curve is basically consistent, which is insensitive to temperature. Among them, the average reflectivity in the 2GHz-18GHz frequency band and 25℃ is -11.3dB, the average reflectivity in the 2GHz-18GHz frequency band and 200℃ is -11.2dB, and the average reflectivity in the 2GHz-18GHz frequency band and 400℃ is -10.9dB. Compared with Examples 1-3, the stealth metamaterial is prepared by magnetron sputtering and laser etching process. Although the operating temperature range is reduced, the low-frequency stealth performance can be greatly improved.

[0187] The above description is only an optional embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the inventive concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for preparing a high temperature resistant stealth metamaterial, It is characterized in that The following steps are involved: Determining the conductive pattern shape and ceramic substrate type of the target metamaterial according to the performance parameters of the target metamaterial to be prepared; Based on the conductive pattern shape and ceramic substrate type of the target metamaterial, the calculation formula of the linear polarization wave reflection matrix of the metamaterial is determined, which is expressed as: In the formula, R x and R y are the reflection characteristics of x-polarized waves and y-polarized waves, R lin is the reflection matrix of electromagnetic wave, r xx 、r xy 、r yx 、r yy is the reflection coefficient, r xx 、r xy 、r yx 、r yy The simplified forms correspond to the four characters A, B, C, and D respectively. x and i y represents the polarization state of the incident wave; Based on the linear polarization wave reflection matrix of the metamaterial, the Jones matrix and the rotation matrix, the linear polarization wave reflection matrix R of the metamaterial after rotation by an angle θ is obtained. lin (θ), where the rotation matrix D θ Calculated according to the following formula: The linear polarization wave reflection matrix R of the metamaterial after rotating by angle θ lin (θ) is calculated according to the following formula: In the formula, r uu 、r uv 、r vu 、r vv represents the reflection coefficient of the metamaterial after rotation, D θ -1 D θ The reciprocal of Based on the linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ lin (θ), obtaining two units with a phase difference of 180° after the conductive pattern is rotated about the center origin by an angle of θ; Combining the conductive patterns corresponding to the two units to form a unit array; According to the form of the unit array, a conductive slurry is used to prepare a conductive structure on the ceramic substrate to obtain a high-temperature resistant stealth metamaterial; The preparation process of using conductive slurry to prepare a conductive structure on the ceramic substrate includes one of a screen printing process, a plasma spraying process, a high-temperature adhesive bonding process and a magnetron sputtering process.

2. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ lin (θ), the step of obtaining two units with a phase difference of 180° after the conductive pattern is rotated about the center origin by an angle of θ, comprises: For metamaterials with thickness along the z-axis, when the metamaterial is mirror-symmetric about the xz plane or the yz plane, it is expressed as C 1 Symmetrical, the working matrices after symmetrical design are and Get M -1 R lin M=R lin , in the reflection matrix, B=C=0, that is, C 1 Symmetric reflection matrix When the metamaterial is rotated 2π / 2 along the center origin, it is symmetrical and is expressed as C 2 Symmetric, the working matrix is ​​D π , that is, the rotation matrix D θ In this case, θ is π, which is the same as the reflection matrix before rotation. 2 Symmetric reflection matrix When the metamaterial is rotated 2π / 3 along the center origin and then becomes symmetrical, it is expressed as C 3 Symmetric, the working matrix is ​​D 2π / 3 , that is, the rotation matrix D θ Where θ is 2π / 3, A=D, B=-C, and C 3 Symmetric reflection matrix When the metamaterial is rotated π / 2 along the center origin and becomes symmetrical, it is expressed as C 4 Symmetric, the working matrix is ​​D π / 2 , that is, the rotation matrix D θ Where θ is π / 2, A=D, B=-C, and C 4 Symmetric reflection matrix Based on the C 1 Symmetric reflection matrix R lin (C 1 ), said C 2 Symmetric reflection matrix R lin (C 2 ), said C 3 Symmetric reflection matrix R lin (C 3 ), said C 4 Symmetric reflection matrix R lin (C 4 ) and the linear polarization wave reflection matrix R of the metamaterial after the rotation angle θ lin (θ), for a metamaterial with mirror symmetry along the xz plane or the yz plane, when the conductive pattern of the metamaterial is rotated by an angle θ, the reflection matrix R lin-θ Calculated according to the following formula: Based on the reflection matrix R lin-θ , without changing the amplitude, the conductive pattern is rotated by an angle θ to construct two units with opposite phases.

3. The method for preparing the high temperature resistant stealth metamaterial according to claim 2, It is characterized in that The reflection matrix R lin-θ The steps of rotating the conductive pattern by an angle θ without changing the amplitude to construct two units with opposite phases include: Based on the reflection matrix R lin-θ ,set up Matrix r uu and r vv When the amplitude is the same and the phase difference is 180°, θ = θ 0 , that is, to obtain θ=0° and θ=θ 0 two units.

4. The method for preparing the high temperature resistant stealth metamaterial according to claim 3, It is characterized in that The acquisition of θ=0° and θ=θ 0 The two-unit steps, include: θ 0 Set it to 90° and obtain two units with θ = 0° and θ = 90°; Based on the reflection matrix R lin-θ , the Jones matrices of the two units are expressed as and That is, the phase difference between the two units is 180°.

5. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The step of combining the conductive patterns corresponding to the two units to form a unit array comprises: The conductive patterns corresponding to the two units are respectively combined in a form of 5×5 or 10×10 to form two super units; Then, the two super units are arranged in a chessboard pattern to form a unit array.

6. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The ceramic substrate includes one of silicon oxide ceramics, aluminum oxide ceramics, zirconium oxide ceramics, magnesium oxide ceramics, calcium oxide ceramics, boron nitride ceramics, silicon nitride ceramics, silicon carbide ceramics or composite ceramics.

7. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The conductive pattern shapes include rectangle, circle, ring, open ring, broken line, diagonal line, multi-shape superposition or fractal pattern.

8. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The conductive paste includes one of the metal materials gold, silver, platinum, tungsten, rhodium, titanium, titanium alloy, silver-copper alloy or the semiconductor materials carbon black, single-layer graphene, redox graphene or ionic compounds titanium boride, zirconium boride and titanium carbide.

9. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The steps of the screen printing process include: The ceramic substrate is ultrasonically cleaned for 0.5h-1.5h, and then dried at 90°C-110°C for 0.3h-0.8h; Printing a mask plate that matches the ceramic substrate, determining the shape of the conductive pattern, and drawing a pattern on the mask plate in the form of the unit array; Drawing a screen printing screen, coating the screen printing screen with photoresist and drying the screen printing screen at 65° C. to 75° C. for 0.3 h to 0.8 h; Combine the screen printing plate coated with photoresist with the mask plate with the pattern drawn, and expose for 8-12 minutes, then wash away the unexposed pattern part with water; Covering the exposed silk screen on the ceramic substrate, adding a conductive paste, and printing on the two surfaces of the ceramic substrate respectively, forming a conductive structure on one surface where the ceramic substrate is combined with the silk screen, and forming a conductive backplane on the other surface; The silk screen on the printed ceramic substrate is removed, and then the substrate is dried at 550° C. to 650° C. for 1.5 h to 2.5 h to obtain a high-temperature resistant stealth metamaterial.

10. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The steps of the plasma spraying process include: The conductive slurry is mixed with silicon oxide powder, and deionized water and anhydrous ethanol are added as ball milling media, and the ball milling is performed for 1.5 h to 2.5 h at a ball milling speed of 250 r / min to 350 r / min to obtain a ball milled slurry; Drying the ball-milled slurry at 85° C. to 95° C. for 0.5 h to 1.5 h to obtain a mixed powder; Grinding the mixed powder and passing it through a 180-220 mesh sieve to obtain a mixed powder; Printing a mask plate that matches the ceramic substrate, determining the shape of the conductive pattern, and drawing a pattern on the mask plate in the form of the unit array; A steel film corresponding to the mask plate is prepared, and after combining the steel film with the mask plate, the steel film is attached to the ceramic substrate, and the two surfaces of the ceramic substrate are sprayed respectively, one surface at the junction with the steel film forms a conductive structure, and the other surface forms a conductive backplane, to obtain a high-temperature resistant stealth metamaterial. The voltage during the spraying process is 30V-40V, the current is 300A-400A, the air flow rate is 2000L / h-3000L / h, and the spraying distance is 50mm-100mm.

11. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The steps of the high temperature adhesive bonding process include: Making two plates matching the ceramic substrate by using conductive slurry, and cutting one of the plates into a plurality of square pieces by using electric spark technology; Using deionized water, ethanol and acetone to ultrasonically clean the plate, the square sheet and the ceramic substrate in sequence, and then drying them; Determining the shape of the conductive pattern and performing 3D printing in the form of the unit array to obtain a polymer template; Laminating the polymer template to the ceramic substrate, applying high temperature glue on one side of the square sheet and placing it on the ceramic substrate at a position corresponding to the polymer template; Then, the polymer template is removed, and the ceramic substrate after the polymer template is removed is left to stand for 15h-17h, then kept at 80°C-100°C for 0.5h-1.5h, and then heated to 110°C-130°C and kept for 0.5h-1.5h to obtain a conductive structure; The plate is bonded to the side of the ceramic substrate away from the conductive structure by applying high-temperature glue, and then allowed to stand for 15h-17h, and then kept warm at 80℃-100℃ for 0.5h-1.5h, and then heated to 110℃-130℃ and kept warm for 0.5h-1.5h to form a conductive backplane, thereby obtaining a high-temperature resistant stealth metamaterial.

12. The method for preparing the high temperature resistant stealth metamaterial according to claim 1, It is characterized in that The steps of the magnetron sputtering process include: The ceramic substrate is ultrasonically cleaned for 0.5 h to 1.5 h using detergent, acetone, ethanol and deionized water in sequence, and then dried using an inert gas; The resistor target is placed in a magnetron sputtering coating machine and vacuumed for 0.3h-0.8h, and the ceramic substrate is coated for 0.5h-1.5h at a power of 90W-110W and a normal temperature DC condition to obtain a ceramic substrate with resistor films attached to both surfaces; The shape of the conductive pattern is determined, and the pattern is drawn in the form of the unit array and introduced into a laser etching device, and one of the surfaces of the ceramic substrate with the attached resistor film is laser etched to obtain a conductive structure. The other surface of the ceramic substrate with the attached resistor film is not laser etched, that is, a conductive backplane, and a high-temperature resistant stealth metamaterial is obtained; wherein, during the laser etching process, the laser power is 2W-6W, and the scanning speed is 40mm / s-60mm / s.

13. The method for preparing the high temperature resistant stealth metamaterial according to claim 12, It is characterized in that The average resistance value R of the resistor film in the conductive structure 1 =200Ω, the average square resistance R of the resistor film in the conductive structure s1 =312.5Ω; the average resistance value R of the resistor film in the conductive backplane 2 =1Ω, the average square resistance R of the resistive film in the conductive backplane s2 =1Ω.

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