A high-temperature-resistant radar absorbing coating combined with an absorbent and a metamaterial and a preparation method thereof

Abstract

The application discloses a high-temperature-resistant radar wave-absorbing coating combined with an absorbent and a super material and a preparation method thereof, belongs to the field of radar stealth materials, and is a scheme in which an absorbent (an oxide ceramic such as YSZ or alumina and LaSrMnO3 or LaSrCoO3 are mixed) is combined with a super material, the coating is coated on the surface of a metal base material, and from the surface of the metal base material, the coating sequentially comprises a metal bonding layer, a first radar wave-absorbing layer, a super material layer and a second radar wave-absorbing layer from bottom to top. The high reliability of the oxide ceramic is combined with the dielectric controllability and the high electronic conductivity characteristics of LaSrMnO3 or LaSrCoO3, and a super material layer is introduced, so that strong absorption of electromagnetic waves is realized. 1‑x Sr x MnO3 or La 1‑x Sr x CoO3 is mixed) is combined with a super material, the coating is coated on the surface of a metal base material, and from the surface of the metal base material, the coating sequentially comprises a metal bonding layer, a first radar wave-absorbing layer, a super material layer and a second radar wave-absorbing layer. 1‑x Sr x MnO3 or La 1‑x Sr x CoO3 of the oxide ceramic, and the dielectric controllability and the high electronic conductivity characteristics of LaSrMnO3 or LaSrCoO3 are combined, and a super material layer is introduced, so that strong absorption of electromagnetic waves is realized.

Description

Technical Field

[0001] This invention belongs to the field of radar stealth materials, specifically relating to a high-temperature radar absorbing coating that combines an absorber with metamaterials and its preparation method. Background Technology

[0002] With the diversification of detection technologies, stringent requirements have been placed on the effective absorption of electromagnetic waves in the research and design of equipment to reduce the possibility of radar detection. However, ordinary absorbing materials have limited absorption capacity, and their performance depends on a specific wavelength range, making it difficult to adapt to complex shapes or dynamic deformation requirements. Therefore, the search for new absorbing materials is of great significance.

[0003] Existing high-temperature radar-absorbing coating materials, including those for operating temperatures below 400℃, utilize ferrite, carbonyl iron powder, and other absorbers combined with resin-based binders, a mature technology that has been widely adopted in aircraft. For applications requiring temperatures ≥500℃, radar-absorbing stealth coatings currently employ two main technical solutions: one uses high-temperature resistant absorbers, and the other utilizes structural design, employing multi-layered gradient structures or sandwich structures (such as a ceramic substrate layer + resistive periodic pattern layer + ceramic surface layer), balancing impedance matching, thermal protection, and structural strength.

[0004] The technical characteristics of existing high-temperature radar absorbing coatings are as follows:

[0005] ① Strong absorption at different frequency bands can be achieved by adjusting the dielectric constant of the high-temperature absorber, the total thickness of the coating, the position of the metamaterial in the thickness, and the sheet resistance of its pattern, according to specific needs.

[0006] ② Its temperature resistance can meet the requirements from room temperature to 1100℃.

[0007] ③ Environmental adaptability: It has properties such as oxidation resistance, ablation resistance, and thermal shock resistance, and is suitable for extreme environments such as atmospheric reentry.

[0008] Application scenarios of high-temperature radar absorbing coating:

[0009] ① High-speed aircraft: High-temperature resistant radar-absorbing coating is used to achieve high Mach number penetration.

[0010] ② Hypersonic aircraft: used for waveriders, gliders, etc., taking into account both thermal protection and stealth requirements.

[0011] ③ Aero engines and exhaust nozzles: Reduce the radar signature of high-temperature components.

[0012] Yttrium-stabilized zirconia (YSZ) and alumina, among other oxide ceramics, have been widely used in engine thermal barrier coatings. However, both are typical insulating dielectric layers, and pure coatings alone cannot achieve microwave absorption. La... 1-x Sr x MnO3 or La 1-x Sr x CoO3 possesses high electronic conductivity and maintains structural stability at temperatures ranging from 800℃ to 1000℃. The addition of La to oxide ceramics such as YSZ and alumina... 1-x Sr x MnO3 or La 1-x Sr x CoO3 can be used to obtain materials that maintain high-temperature stability while improving the dielectric constant and dielectric loss of the coating, which is beneficial for the coating to meet the stealth requirements of different frequency bands even with a thinner coating.

[0013] In summary, by incorporating La into oxide ceramics such as YSZ and alumina... 1-x Sr x MnO3 or La 1-x Sr x Adjusting the dielectric properties of the coating with CoO3 and further improving its microwave absorption performance by combining it with a resistive periodic pattern layer is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0014] The existing technology lacks a method for precisely controlling the La content of YSZ and oxide ceramics such as alumina. 1-x Sr x MnO3 or La 1-x Sr x Considering the CoO3 content and dielectric properties, and the controllable stealth performance of resistive periodic patterned layers, this invention addresses the challenges of thin coatings with high service temperatures. It provides a high-temperature resistant radar absorbing coating combining an absorber and metamaterials, along with its preparation method. This invention also offers a radar absorbing coating with adjustable dielectric constant, high temperature resistance, and strong absorption, along with its preparation method. The invention employs a combination of a high-temperature resistant absorber and an electromagnetic periodic structure layer, wherein the high-temperature resistant absorber is La... 1-x Sr x MnO3 or La 1-x Sr x CoO3 is prepared using a plasma spraying process.

[0015] The technical solution of the present invention is as follows:

[0016] A high-temperature radar-absorbing coating combining an absorbent and a metamaterial, wherein the absorbent is an oxide ceramic such as YSZ or alumina and La1-x Sr x MnO3 or La 1-x Sr x A scheme combining CoO3 powder (X = 0.2~0.4) with metamaterials combines the high reliability of oxide ceramics with La 1-x Sr x MnO3 or La 1-x Sr x The combination of CoO3's dielectric tunability and high electronic conductivity, along with the introduction of a metamaterial layer, enables strong absorption of electromagnetic waves.

[0017] The objective of this invention is achieved through the following technical solution:

[0018] A high-temperature resistant radar absorbing coating combining an absorbent and a metamaterial, the coating being applied to the surface of a metal substrate, and from bottom to top, including a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer.

[0019] The raw materials used in the radar absorbing layer are oxide ceramic powder and La 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder, with X of 0.2~0.4, was prepared by ball milling granulation, wherein La 1-x Sr x MnO3 powder or La 1-x Sr x The CoO3 powder content is 10% to 70% of the mass of the mixed powder;

[0020] The thickness of the first radar absorbing layer is 500μm~1300μm;

[0021] The thickness of the second radar absorbing layer is 200μm~1000μm;

[0022] The metamaterial layer has a thickness of 10μm~50μm and is prepared by screen printing and high-temperature heat treatment in the form of a patch. The raw material of the metamaterial layer is a high-temperature resistive paste prepared with RuO2 as the conductive phase and Bi2O3-SiO2-B2O3 glass as the binder phase.

[0023] The metal bonding layer is a NiCrAlY or CoCrAlY coating with a thickness of 20μm~80μm;

[0024] The high-temperature radar-absorbing coating combining the absorber and metamaterial has the following performance indicators, based on La 1-x Sr x MnO3 or La 1-x Srx The selection of CoO3 content, and the realization of the periodic pattern and distribution location of metamaterials:

[0025] The reflectivity is ≤-5dB for 12GHz~18GHz or ≤-5dB for 8GHz~12GHz; the coating bonding strength is ≥8MPa at room temperature and it can withstand 500 thermal shocks at 900℃ without damage.

[0026] Furthermore, the oxide ceramic powder is selected from YSZ or alumina powder.

[0027] The metamaterial layer is a resistive periodic structure layer containing patches with a patch period size of 3mm to 30mm.

[0028] The preparation method of the above-mentioned high-temperature radar absorbing coating combining an absorber and a metamaterial includes the following steps:

[0029] S1. Granulation:

[0030] S1-1, Mix oxide ceramic powder with La 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder was mixed in a certain proportion, and then gum arabic, triamine citrate and deionized water were added. The mixture was ball-milled for 48-60 hours to obtain a slurry.

[0031] S1-2. Subsequently, the slurry obtained from ball milling is atomized and granulated. The atomizer frequency is 24Hz~35Hz, the inlet temperature is 240℃, the outlet temperature is 120℃, and the pulse needle pressure is 0.2MPa. The mixed powder is obtained by granulation. The granulated powder is sieved and the powder between 150 mesh and 400 mesh is collected. The powder is then heat-treated at 1000℃ for 2 hours.

[0032] S2. The high-temperature alloy substrate is roughened by sandblasting.

[0033] S3. A metal bonding layer is prepared on the surface of the high-temperature alloy substrate after sandblasting and roughening by plasma spraying process.

[0034] S4. The first radar absorbing layer is prepared by plasma spraying onto the surface of the metal bonding layer obtained in S3.

[0035] S5. A metamaterial layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment.

[0036] S6. A second radar absorbing layer is prepared on the surface of the metamaterial layer obtained in S5 by plasma spraying. The spraying process is the same as that in S4, resulting in a high-temperature radar absorbing coating that combines an absorber and a metamaterial.

[0037] Furthermore, in S1, the gum arabic accounts for 2% of the mass of the mixed powder, the triamine citrate accounts for 0.8% of the mass of the mixed powder, and the ratio of deionized water to the mass of the mixed powder is 1:1.

[0038] Furthermore, the process parameters for the sandblasting roughening treatment of the high-temperature alloy substrate described in S2 are as follows: pressure 0.2MPa~0.5MPa, sandblasting medium is white corundum sand with a mesh size of 24~40 mesh, sandblasting distance 80 mm~150 mm, and sandblasting angle 30°~60°.

[0039] Furthermore, as described in S3, a metal bonding layer is prepared on the surface of the sandblasted and roughened high-temperature alloy substrate using a plasma spraying process. The preparation process parameters are as follows: carrier gas flow rate 1L / min~4L / min, main gas flow rate 40L / min~50L / min, powder feeding amount 80g~100g per 5min, current 500A~600A, and power 30kW~50kW.

[0040] Furthermore, in step S4, the first radar absorbing layer is prepared by plasma spraying onto the surface of the metal bonding layer obtained in step S3. The preparation process parameters are as follows: carrier gas flow rate 1L / min~4L / min, main gas flow rate 40L / min~50L / min, powder feeding amount 40g~150g per 5min (determined by different oxide powders and powder doping amount), current 500A~600A, and power 30kW~50kW.

[0041] Furthermore, the preparation of the metamaterial layer described in S5 involves using a high-temperature resistive paste to prepare a resistive periodic structure layer on the surface of the first radar absorbing layer through a screen printing process followed by drying and heat treatment. During the screen printing process, the mesh size is 200 or 250, the drying temperature is 150℃~250℃, the drying time is 0.5h~2h, the sintering temperature is 900℃±10℃, and the sintering time is 30min.

[0042] Furthermore, in step S6, a second radar absorbing layer is prepared on the surface of the metamaterial layer obtained in step S5 by plasma spraying. The preparation process parameters are as follows: carrier gas flow rate 1L / min~4L / min, main gas flow rate 40L / min~50L / min, powder feeding amount 40g~150g in 5min, current 500A~600A, and power 30kW~50kW.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The method for preparing a high-temperature resistant radar absorbing coating combining an absorbent and metamaterials as described in this invention mainly adopts environmentally friendly technologies such as atmospheric plasma spraying. At the same time, no toxic or harmful substances are generated during the powder synthesis process, and there is no pollution to the environment, making it an environmentally friendly preparation method. No harmful gases are generated during the coating preparation process, only splashed dust and a small amount of waste gas are generated, which are collected by dust removal filtration and will not cause environmental pollution.

[0045] 2. The high-temperature radar-absorbing coating combining an absorbent and metamaterials described in this invention, through the addition of La... 1-x Sr x MnO3 or La 1-x Sr x By selecting the CoO3 ratio, the dielectric constant can be precisely controlled. At the same time, the absorption performance can be specifically controlled by combining the size, position and sheet resistance of the metamaterial pattern.

[0046] 3. The high-temperature radar absorbing coating combining an absorbent and metamaterials described in this invention can achieve strong absorption in a certain frequency band while maintaining high reliability. Attached Figure Description

[0047] Figure 1 This is a diagram of a high-temperature absorbing coating plate that uses the absorber prepared in this invention combined with metamaterials to form a high-temperature absorbing radar coating.

[0048] Figure 2 This is a graph showing the measured reflectivity of the high-temperature radar absorbing coating prepared in Example 1 of this invention, which combines the absorber with metamaterials.

[0049] Figure 3 This is a diagram showing the measured reflectivity at room temperature of the high-temperature radar absorbing coating prepared in Example 2 of this invention, which combines the absorber with metamaterials.

[0050] Figure 4 This is a measured reflectance diagram of the high-temperature radar absorbing coating prepared in Example 3 of this invention, which combines the absorber with metamaterials.

[0051] Figure 5 This is a schematic diagram of the high-temperature radar absorbing coating prepared in Example 1 of the present invention, which combines the absorber with metamaterials;

[0052] Figure 6 This is a graph showing the reflectivity test results of the high-temperature radar absorbing coating prepared in Example 4 of this invention, which combines the absorber with metamaterials.

[0053] Figure 7 This is a graph showing the reflectance test results of the pure YSZ coating (without periodic structure) prepared in the comparative example of this invention;

[0054] Figure 8 The pure YSZ coating prepared in the comparative example of this invention is doped with La. 0.8 Sr 0.2 The reflectance test results of MnO3 (excluding periodic structure) are shown in the figure. Detailed Implementation

[0055] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the embodiments and drawings are only used for illustrative description of the present invention and do not limit the scope of protection of the present invention.

[0056] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0057] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0058] Example 1:

[0059] A high-temperature resistant radar absorbing coating combining an absorbent and a metamaterial, the coating being applied to the surface of a metal substrate, and from bottom to top, including a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer.

[0060] The raw materials used in the radar absorbing layer are oxide ceramic powder and La 0.8 Sr 0.2 CoO3 was prepared by ball milling granulation, in which La 0.8 Sr 0.2 The CoO3 content is 50%;

[0061] The thickness of the first radar absorbing layer is 1300 μm;

[0062] The thickness of the second radar absorbing layer is 200 μm;

[0063] The metamaterial layer is 20 μm thick and is prepared by screen printing and high-temperature heat treatment in the form of a patch. The raw material of the metamaterial layer is a high-temperature resistive paste prepared with RuO2 as the conductive phase and Bi2O3-SiO2-B2O3 glass as the binder phase.

[0064] The metal bonding layer is a NiCrAlY coating with a thickness of 80 μm;

[0065] The oxide ceramic powder mentioned above is selected from alumina;

[0066] The patch period size in the metamaterial layer is 9.5 mm.

[0067] The preparation method of the above-mentioned high-temperature radar absorbing coating combining an absorber and a metamaterial includes the following steps:

[0068] S1. Granulation:

[0069] S1-1, Mix oxide ceramic powder with La 0.8 Sr 0.2 CoO3 was mixed in a certain proportion, and then gum arabic, triamine citrate and deionized water were added. The mixture was ball-milled for 48 hours to obtain a slurry.

[0070] S1-2. Subsequently, the slurry obtained from ball milling is atomized and granulated. The atomizer frequency is 35Hz, the inlet temperature is 240℃, the outlet temperature is 120℃, and the pulse needle pressure is 0.2MPa. The mixed powder is obtained through granulation. The granulated powder is sieved, and the powder between 150 mesh and 400 mesh is collected and subjected to high-temperature heat treatment at 1000℃ for 2 hours.

[0071] S2. The high-temperature alloy substrate is subjected to sandblasting roughening treatment. The process parameters are: pressure 0.2MPa, sandblasting medium is white corundum sand with a mesh size of 24 to 40 mesh, sandblasting distance 150mm, and sandblasting angle 30°.

[0072] S3. A metal bonding layer is prepared on the surface of the high-temperature alloy substrate after sandblasting and roughening by plasma spraying. The preparation process parameters are: carrier gas flow rate 2L / min, main gas flow rate 46L / min, powder feeding amount 100g in 5min, current 550A, power 34kW.

[0073] S4. The first radar absorbing layer is prepared by plasma spraying the metal bonding layer obtained in S3. The preparation process parameters are: carrier gas flow rate 43L / min, main gas flow rate 46L / min, powder feeding amount 50g in 5min, current 580A, power 42kW.

[0074] S5. A metamaterial layer is prepared on the surface of the first radar absorbing layer by screen printing, drying and heat treatment. A resistive periodic structure layer is prepared on the surface of the first radar absorbing layer by screen printing, drying and heat treatment. In the screen printing process, the screen mesh number is 200 mesh, the drying temperature is 150℃, the time is 2h, the sintering temperature is 900℃±10℃, and the sintering time is 30min.

[0075] S6. Prepare a second radar absorbing layer on the surface of the metamaterial layer obtained in S5. The spraying process is the same as in S4, resulting in a high-temperature radar absorbing coating that combines the absorber and the metamaterial.

[0076] The high-temperature radar absorbing coating combining the absorber and metamaterial has the following performance indicators: reflectivity ≤-5dB at 12GHz~18GHz; coating bonding strength ≥8MPa at room temperature; and no damage after 500 thermal shocks at 900℃.

[0077] Figure 1 The image shows a high-temperature absorbing coating plate made by combining the absorber prepared in Example 1 with metamaterials. As can be seen, the coating surface is smooth and flat.

[0078] Figure 2 This is a measured reflectivity image of the high-temperature radar absorbing coating combining the absorber and metamaterial prepared in Example 1. The dielectric constant is 14, the thickness of the first radar absorbing layer is 1.3 mm, the thickness of the second radar absorbing layer is 0.2 mm, and the metamaterial layer is prepared on the surface of the first radar layer. Figure 2 It can be seen that the overall reflectivity of the coating is ≤-6dB in the 10~18GHz range.

[0079] Figure 5 This is a schematic diagram of the high-temperature radar absorbing coating that combines the absorber and metamaterial prepared in Example 1. It can be seen that the coating is applied to the surface of a metal substrate. Starting from the surface of the metal substrate, from bottom to top, it includes a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer.

[0080] Example 2:

[0081] A high-temperature resistant radar absorbing coating combining an absorbent and a metamaterial, the coating being applied to the surface of a metal substrate, and from bottom to top, including a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer.

[0082] The raw materials used in the radar absorbing layer are oxide ceramic powder and La 0.8 Sr 0.2 CoO3 was prepared by ball milling granulation, in which La 0.8 Sr 0.2 The CoO3 content is 70%;

[0083] The thickness of the first radar absorbing layer is 1300 μm;

[0084] The thickness of the second radar absorbing layer is 200 μm;

[0085] The metamaterial layer is 20 μm thick and is prepared by screen printing and high-temperature heat treatment in the form of a patch. The raw material of the metamaterial layer is a high-temperature resistive paste prepared with RuO2 as the conductive phase and Bi2O3-SiO2-B2O3 glass as the binder phase.

[0086] The metal bonding layer is a CoCrAlY coating with a thickness of 80 μm;

[0087] The oxide ceramic powder mentioned above is selected from alumina;

[0088] The patch period size in the metamaterial layer is 9.5 mm.

[0089] The preparation method of the above-mentioned high-temperature radar absorbing coating combining an absorber and a metamaterial includes the following steps:

[0090] S1. Granulation:

[0091] S1-1, Mix oxide ceramic powder with La 0.8 Sr 0.2 CoO3 was mixed in a certain proportion, and then gum arabic, triamine citrate and deionized water were added. The mixture was ball-milled for 60 hours to obtain a slurry.

[0092] S1-2. Subsequently, the slurry obtained from ball milling is atomized and granulated. The atomizer frequency is 24Hz, the inlet temperature is 240℃, the outlet temperature is 120℃, and the pulse needle pressure is 0.2MPa. The mixed powder is obtained by granulation. The granulated powder is sieved, and the powder between 150 mesh and 400 mesh is collected and subjected to high-temperature heat treatment at 1000℃ for 2 hours.

[0093] S2. The high-temperature alloy substrate is subjected to sandblasting roughening treatment. The process parameters are: pressure 0.5 MPa, sandblasting medium is white corundum sand with a mesh size of 24 to 40 mesh, sandblasting distance 80 mm, and sandblasting angle 60°.

[0094] S3. A metal bonding layer is prepared on the surface of the high-temperature alloy substrate after sandblasting and roughening by plasma spraying. The preparation process parameters are: carrier gas flow rate 2L / min, main gas flow rate 46L / min, powder feeding amount 100g in 5min, current 550A, power 34kW.

[0095] S4. The first radar absorbing layer is prepared by plasma spraying the metal bonding layer obtained in S3. The preparation process parameters are: carrier gas flow rate 3L / min, main gas flow rate 46L / min, powder feeding amount 60g in 5min, current 550A, power 38kW.

[0096] S5. A metamaterial layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment. A resistive periodic structure layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment. In the screen printing process, the mesh size is 250 mesh, the drying temperature is 250℃, the time is 0.5h, the sintering temperature is 900℃±10℃, and the sintering time is 30min.

[0097] S6. Prepare a second radar absorbing layer on the surface of the metamaterial layer obtained in S5. The spraying process is the same as in S4, and a high-temperature radar absorbing coating combining absorber and metamaterial is obtained.

[0098] The high-temperature radar-absorbing coating combining the absorbent and metamaterial has the following performance indicators:

[0099] The reflectivity is ≤-4dB in the 6GHz~12GHz range and ≤-6dB in the 7GHz~10GHz range; the coating bonding strength is ≥8MPa at room temperature and it can withstand 500 thermal shocks at 900℃ without damage.

[0100] Figure 3 The image shows the measured reflectivity of the high-temperature radar absorbing coating prepared in Example 2, which combines the absorber with metamaterials, at room temperature. The dielectric constant is 18, the thickness of the first radar absorbing layer is 1.3 mm, the thickness of the second radar absorbing layer is 0.2 mm, and the metamaterial layer is prepared on the surface of the first radar layer.

[0101] pass Figure 2 and Figure 3 As can be seen, the high-temperature radar absorbing coating combining absorber and metamaterial prepared in Example 2 has the same overall thickness as the high-temperature radar absorbing coating combining absorber and metamaterial prepared in Example 1, but its thickness is less than -4dB in the range of 7GHz to 12GHz. The position of the absorption peak has been adjusted. Therefore, this invention can achieve strong absorption in different frequency bands by adjusting the dielectric constant according to different absorption requirements.

[0102] Example 3:

[0103] A high-temperature resistant radar absorbing coating combining an absorbent and a metamaterial, the coating being applied to the surface of a metal substrate, and from bottom to top, including a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer.

[0104] The raw materials used in the radar absorbing layer are oxide ceramic powder and La 0.8 Sr 0.2 MnO3 was prepared by ball milling granulation, in which La 0.8 Sr 0.2 The MnO3 content is 10%;

[0105] The thickness of the first radar absorbing layer is 650 μm;

[0106] The thickness of the second radar absorbing layer is 1050 μm;

[0107] The metamaterial layer is 20 μm thick and is prepared by screen printing and high-temperature heat treatment in the form of a patch. The raw material of the metamaterial layer is a high-temperature resistive paste prepared with RuO2 as the conductive phase and Bi2O3-SiO2-B2O3 glass as the binder phase.

[0108] The metal bonding layer is a CoCrAlY coating with a thickness of 80 μm;

[0109] The oxide ceramic powder mentioned above is selected from YSZ;

[0110] The patch period size in the metamaterial layer is 5.33 mm.

[0111] The preparation method of the above-mentioned high-temperature radar absorbing coating combining an absorber and a metamaterial includes the following steps:

[0112] S1. Granulation:

[0113] S1-1, Mix oxide ceramic powder with La 0.8 Sr 0.2 MnO3 was mixed in a certain proportion, and then gum arabic, triamine citrate and deionized water were added. The mixture was ball-milled for 60 hours to obtain a slurry.

[0114] S1-2. Subsequently, the slurry obtained from ball milling is atomized and granulated. The atomizer frequency is 24Hz, the inlet temperature is 240℃, the outlet temperature is 120℃, and the pulse needle pressure is 0.2MPa. The mixed powder is obtained by granulation. The granulated powder is sieved, and the powder between 150 mesh and 400 mesh is collected and subjected to high-temperature heat treatment at 1000℃ for 2 hours.

[0115] S2. The high-temperature alloy substrate is subjected to sandblasting roughening treatment. The process parameters are: pressure 0.5MPa, sandblasting medium is white corundum sand with a mesh size of 24 to 40 mesh, sandblasting distance 80mm, and sandblasting angle 60°.

[0116] S3. A metal bonding layer is prepared on the surface of the high-temperature alloy substrate after sandblasting and roughening by plasma spraying. The preparation process parameters are: carrier gas flow rate 2L / min, main gas flow rate 46L / min, powder feeding amount 100g in 5min, current 550A, power 34kW.

[0117] S4. The first radar absorbing layer is prepared by plasma spraying the metal bonding layer obtained in S3. The preparation process parameters are: carrier gas flow rate 3L / min, main gas flow rate 46L / min, powder feeding amount 135g in 5min, current 600A, power 42kW.

[0118] S5. A metamaterial layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment. A resistive periodic structure layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment. In the screen printing process, the mesh size is 250 mesh, the drying temperature is 250℃, the time is 0.5h, the sintering temperature is 900℃±10℃, and the sintering time is 30min.

[0119] S6. Prepare a second radar absorbing layer on the surface of the metamaterial layer obtained in S5. The spraying process is the same as in S4, resulting in a high-temperature radar absorbing coating that combines the absorber and the metamaterial.

[0120] Figure 4 The image shows the measured reflectance of the high-temperature radar absorbing coating prepared in Example 3, which combines the absorber with metamaterials. Its total thickness is 1.7 mm, which is higher than the 1.5 mm in Examples 1 and 2. It can achieve a wave absorption effect of ≤-6dB in most frequency bands from 8GHz to 18GHz and ≤-5dB overall. It also has a wave absorption effect of ≤-2dB in 5GHz and ≤-3dB in 6GHz, exhibiting broadband wave absorption characteristics.

[0121] Example 4:

[0122] A high-temperature resistant radar absorbing coating combining an absorbent and a metamaterial, the coating being applied to the surface of a metal substrate, and from bottom to top, including a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer.

[0123] The raw materials used in the radar absorbing layer are oxide ceramic powder and La 0.8 Sr 0.2 CoO3 was prepared by ball milling granulation, in which La 0.8 Sr 0.2 The CoO3 content is 50%;

[0124] The thickness of the first radar absorbing layer is 550 μm;

[0125] The thickness of the second radar absorbing layer is 950 μm;

[0126] The metamaterial layer is 20 μm thick and is prepared by screen printing and high-temperature heat treatment in the form of a patch. The raw material of the metamaterial layer is a high-temperature resistive paste prepared with RuO2 as the conductive phase and Bi2O3-SiO2-B2O3 glass as the binder phase.

[0127] The metal bonding layer is a CoCrAlY coating with a thickness of 80 μm;

[0128] The oxide ceramic powder mentioned above is selected from alumina;

[0129] The patch period size in the metamaterial layer is 9.5 mm.

[0130] The preparation method of the above-mentioned high-temperature radar absorbing coating combining an absorber and a metamaterial includes the following steps:

[0131] S1. Granulation:

[0132] S1-1, Mix oxide ceramic powder with La 0.8 Sr 0.2 CoO3 was mixed in a certain proportion, and then gum arabic, triamine citrate and deionized water were added. The mixture was ball-milled for 60 hours to obtain a slurry.

[0133] S1-2. Subsequently, the slurry obtained from ball milling is atomized and granulated. The atomizer frequency is 24Hz, the inlet temperature is 240℃, the outlet temperature is 120℃, and the pulse needle pressure is 0.2MPa. The mixed powder is obtained by granulation. The granulated powder is sieved, and the powder between 150 mesh and 400 mesh is collected and subjected to high-temperature heat treatment at 1000℃ for 2 hours.

[0134] S2. The high-temperature alloy substrate is subjected to sandblasting roughening treatment. The process parameters are: pressure 0.5MPa, sandblasting medium is white corundum sand with a mesh size of 24 to 40 mesh, sandblasting distance 80mm, and sandblasting angle 60°.

[0135] S3. A metal bonding layer is prepared on the surface of the high-temperature alloy substrate after sandblasting and roughening by plasma spraying. The preparation process parameters are: carrier gas flow rate 2L / min, main gas flow rate 46L / min, powder feeding amount 100g in 5min, current 550A, power 34kW.

[0136] S4. The first radar absorbing layer is prepared by plasma spraying the metal bonding layer obtained in S3. The preparation process parameters are: carrier gas flow rate 3L / min, main gas flow rate 46L / min, powder feeding amount 50g in 5min, current 580A, power 38kW.

[0137] S5. A metamaterial layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment. A resistive periodic structure layer is prepared on the surface of the first radar absorbing layer by screen printing of high-temperature resistive paste, followed by drying and heat treatment. In the screen printing process, the mesh size is 250 mesh, the drying temperature is 250℃, the time is 0.5h, the sintering temperature is 900℃±10℃, and the sintering time is 30min.

[0138] S6. Prepare a second radar absorbing layer on the surface of the metamaterial layer obtained in S5. The spraying process is the same as in S4, resulting in a high-temperature radar absorbing coating that combines the absorber and the metamaterial.

[0139] Figure 6 This is a graph showing the reflectivity test results of the high-temperature radar absorbing coating prepared in Example 4, which combines the absorber with metamaterials. Figure 6 The overall thickness of the coating measured was 1.5 mm. The dielectric constant of the radar absorbing layer was consistent with that of Example 1. The thickness of the first radar layer was 550 μm, and the thickness of the second radar layer was 950 μm. The metamaterial layer was prepared on the surface of the first radar layer, with a dielectric constant of 14. Its dielectric constant is consistent with that of Example 1. Figure 2 same, Figure 6 The measured curve surface can achieve strong absorption of ≤-5dB overall within the range of 11GHz to 18GHz. The test results show that, under the same dielectric constant, strong absorption in different frequency bands can be achieved by adjusting the position of the metamaterial layer. This further illustrates that the wave absorption performance of the present invention is due to the combined effect of the absorber layer and the metamaterial layer, rather than relying solely on the metamaterial layer or the absorber layer.

[0140] As can be seen from Examples 1 to 4, the coating structure has both an absorbent layer and a metamaterial layer, and can achieve strong absorption of radar waves through the combined effect of the two, rather than relying solely on the metamaterial layer or the absorbent layer.

[0141] Comparative example:

[0142] The difference between the comparative example and Example 1 is as follows:

[0143] (1) The coating is mainly composed of oxide ceramic and does not contain La. 1-x Sr x MnO3 or La 1-x Sr x CoO3.

[0144] (2) In the comparative example, there was no process of heat treatment at 1000℃ for 2 hours on the raw material powder for spraying.

[0145] In the comparative example, the heat treatment time for the radar functional layer was 900℃ for 30 minutes. Different sintering times can yield different sheet resistance values ​​for the metamaterial layer.

[0146] Figure 7 The graph shows the reflectivity test results of the pure YSZ coating prepared in the comparative example; the microwave absorption performance of 1.2mm thick pure ceramic (without periodic structure) is as follows. Figure 7 As shown, its wave absorption performance is achieved solely through the metamaterial layer. With the thickness remaining constant, the wave absorption function of the coating can only be achieved by adjusting the position and parameters of the metamaterial layer, and the wave absorption performance is limited.

[0147] Figure 8 The 1.2 mm thick pure YSZ coating prepared in the comparative example was doped with La. 0.8 Sr 0.2 The reflectance test results after adding MnO3 (without periodic structure) are shown in the figure. By comparing the example and Example 3, the reflectance of Example 3 is better due to the addition of La. 0.8 Sr 0.2 MnO3 has even better microwave absorption properties.

[0148] In the comparative example, a two-layer periodic structure was used to achieve broadband absorption. In Example 1, La was doped into the oxide ceramic. 0.8 Sr 0.2 CoO3 itself has superior wave absorption properties, so only one layer of metamaterial is needed to achieve a better wave absorption effect.

[0149] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that improvements and refinements made by those skilled in the art without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high temperature resistant radar absorbing coating combining an absorber with a metamaterial, characterized in that, The coating is coated on the surface of the metal substrate, and sequentially comprises, from the surface of the metal substrate, a metal bonding layer, a first radar wave absorbing layer, a metamaterial layer and a second radar wave absorbing layer from bottom to top; The raw material used in the radar wave absorbing layer is prepared by mixing La 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder, X is 0.2-0.4, and the mixture is granulated by ball milling. 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder, X is 0.2-0.4, and the mixture is granulated by ball milling. The first radar wave absorbing layer has a thickness of 500-1300 μm; The second radar wave absorbing layer has a thickness of 200-1000 μm; The metamaterial layer has a thickness of 10-50 μm, is prepared by screen printing and high-temperature heat treatment, and is in the form of a patch; the raw material of the metamaterial layer is a high-temperature-resistant resistive type paste prepared by taking RuO2 as a conductive phase and Bi2O3-SiO2-B2O3-based glass as a bonding phase; The metal bonding layer is a NiCrAlY or CoCrAlY coating layer, and has a thickness of 20-80 μm; The high-temperature-resistant radar-absorbing coating combined with the absorbent and the metamaterial has the following performance indexes: according to La 1- x Sr x MnO3 or La 1-x Sr x CoO3 content selection, periodical pattern and distribution position of the metamaterial The reflectivity is ≤-5 dB at 12-18 GHz or ≤-5 dB at 8-12 GHz; the coating bonding strength is ≥8 MPa at normal temperature, and the coating is not damaged after thermal shock for 500 times at 900°C.

2. The high temperature resistant radar absorbing coating of claim 1, wherein, The oxide ceramic powder is selected from yttria-stabilized zirconia powder or alumina powder.

3. The high temperature resistant radar absorbing coating of claim 1, wherein the absorbing agent is combined with a metamaterial. The metamaterial layer is a resistive type periodic structure layer, contains a patch, and the patch has a periodic size of 3-30 mm.

4. A method for preparing a high temperature resistant radar absorbing coating of an absorbent combined with a metamaterial according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, granulation: S1-1, mixing oxide ceramic powder with La 1-x Sr x MnO3powder or La 1-x Sr x CoO3powder in proportion, then adding gum arabic, citric acid triamine and deionized water, ball milling for 48h~60h, to obtain slurry; S1-2, then the slurry obtained by ball milling is atomized and granulated, the atomizer frequency is 24-35 Hz, the inlet temperature is 240°C, the outlet temperature is 120°C, the pulse needle pressure is 0.2 MPa, the mixed powder is obtained by granulation, the powder obtained after granulation is sieved, and the powder between 150 and 400 meshes is collected and subjected to high-temperature heat treatment at 1000°C for 2 h; S2, sandblasting roughening treatment is performed on the superalloy substrate; S3, a metal bonding layer is prepared on the surface of the sandblasting-roughened superalloy substrate by plasma spraying; S4, a first radar wave absorbing layer is prepared on the surface of the metal bonding layer obtained in S3 by plasma spraying; S5, a metamaterial layer is prepared on the surface of the first radar wave absorbing layer by screen printing of a high-temperature resistive type paste, drying and heat treatment; S6, a second radar wave absorbing layer is prepared on the surface of the metamaterial layer obtained in S5 by plasma spraying, the spraying process is the same as that in S4, and a high-temperature-resistant radar wave absorbing coating combined with an absorber and a metamaterial is obtained.

5. The method for preparing a high-temperature resistant radar-absorbing coating combined with an absorbent and a metamaterial according to claim 4, characterized in that, In S1, the gum arabic accounts for 2% of the mass of the mixed powder, the triaminocitrate accounts for 0.8% of the mass of the mixed powder, and the mass ratio of deionized water to the mixed powder is 1:

1.

6. The method for preparing a high-temperature resistant radar-absorbing coating combined with an absorbent and a metamaterial according to claim 4, characterized in that, In S2, the sandblasting roughening treatment of the superalloy substrate is performed by using a white corundum sand having a mesh size of 24-40 meshes as the sandblasting medium, at a pressure of 0.2-0.5 MPa, at a sandblasting distance of 80-150 mm, and at a sandblasting angle of 30-60°.

7. The method according to claim 4, wherein the method is characterized by, The metal bonding layer is prepared on the surface of the sandblasted high-temperature alloy substrate by the plasma spraying process, and the preparation process parameters are as follows: carrier gas flow is 1L / min-4L / min, main gas flow is 40L / min-50L / min, 5min powder feeding amount is 80g-100g, current size is 500A-600A, and power is 30kW-50kW.

8. The method according to claim 4, wherein the method is characterized by, The first radar wave-absorbing layer is prepared on the surface of the metal bonding layer obtained in S3 by the plasma spraying process, and the preparation process parameters are as follows: carrier gas flow is 1L / min-4L / min, main gas flow is 40L / min-50L / min, 5min powder feeding amount is 40g-150g, current size is 500A-600A, and power is 30kW-50kW.

9. The method according to claim 4, wherein the method is characterized by, The material layer is prepared by adopting the screen printing process to dry and heat treat the high-temperature resistance type paste on the surface of the first radar wave-absorbing layer to prepare the resistance type periodic structure layer, in the screen printing process, the screen mesh number is 200 meshes or 250 meshes, the drying temperature is 150℃-250℃, the time is 0.5h-2h, the sintering temperature is 900℃±10℃, and the sintering time is 30min.

10. The method according to claim 4, wherein the method is characterized by, The second radar wave-absorbing layer is prepared on the surface of the material layer obtained in S5 by the plasma spraying process, and the preparation process parameters are as follows: carrier gas flow is 1L / min-4L / min, main gas flow is 40L / min-50L / min, 5min powder feeding amount is 40g-150g, current size is 500A-600A, and power is 30kW-50kW.

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