Absorbent and metamaterial combined high-temperature-resistant radar wave-absorbing coating and preparation method thereof

Abstract

The invention discloses an absorbent and metamaterial combined high-temperature-resistant radar wave-absorbing coating and a preparation method thereof, belongs to the field of radar stealth materials, and relates to a scheme of combining an absorbent (formed by mixing oxide ceramics such as YSZ or aluminum oxide with La1-xSrxMnO3 or La1-xSrxCoO3) and a metamaterial. Starting from the surface of the metal base material, a metal bonding layer, a first radar wave-absorbing layer, a metamaterial layer and a second radar wave-absorbing layer are sequentially arranged from bottom to top. According to the invention, the high reliability of oxide ceramic is combined with the dielectric controllability and high electronic conductivity of La1-xSrxMnO3 or La1-xSrxCoO3, and meanwhile, the metamaterial layer is introduced, so that strong absorption of electromagnetic waves is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of radar stealth materials, and particularly relates to a high-temperature-resistant radar wave-absorbing coating combined with an absorbing agent and a metamaterial and a preparation method thereof. BACKGROUND

[0002] With the diversification of detection technology, strict requirements are put forward for the effective absorption of electromagnetic waves in research and design to reduce the possibility of being detected by radar. However, the absorption capacity of ordinary absorbing materials is limited, and their performance depends on a specific wavelength range, which is difficult to adapt to complex shapes or dynamic deformation requirements, so it is of great significance to find new absorbing materials.

[0003] The existing high-temperature-resistant radar wave-absorbing coating materials include radar wave-absorbing coatings for use at temperatures below 400℃, which have been very mature in application, using ferrite, carbonyl iron powder and other absorbing agents plus resin-based adhesives, and have achieved a large number of applications on aircraft. For application scenarios with a temperature resistance requirement of ≥500℃, the current radar wave-absorbing stealth coating mainly adopts two technical solutions, one of which is to use high-temperature-resistant absorbing agents, and the other is to use structural design, adopting a multilayer gradient structure or a sandwich structure (such as a ceramic base layer + a resistance type periodic pattern layer + a ceramic surface layer”), which takes into account impedance matching, thermal protection and structural strength.

[0004] Technical features of the existing high-temperature-resistant radar wave-absorbing coating: ① The dielectric constant of the high-temperature-resistant absorbing agent, the total thickness of the coating, the position of the metamaterial in the thickness and the sheet resistance of the pattern can be adjusted to achieve strong absorption in different frequency bands.

[0005] ② The temperature resistance can meet the requirements from room temperature to 1100℃.

[0006] ③ Environmental adaptability: resistant to oxidation, ablation, thermal shock and other characteristics, suitable for re-entry into the atmosphere and other extreme environments.

[0007] Application scenarios of the high-temperature-resistant radar wave-absorbing coating: ① High-speed aircraft: high-temperature-resistant wave-absorbing coating is used to achieve high-Mach number penetration.

[0008] ② Hypersonic aircraft: used for waveriders, gliders and other aircraft, taking into account the requirements for thermal protection and stealth.

[0009] ③ Aircraft engines and tail nozzles: reduce the radar signal characteristics of high-temperature components.

[0010] Yttrium-stabilized zirconia (YSZ) and alumina oxide ceramics have been very maturely applied in engine thermal barrier coatings, but both are typical insulating dielectric layers, and pure coating alone cannot achieve wave-absorbing function. La 1-xSr x MnO3 or La 1-x Sr x CoO3 has the characteristics of high electron conductivity, and still maintains structural stability at 800-1000℃. La 1-x Sr x MnO3 or La 1-x Sr x CoO3, the obtained material can maintain high temperature stability, and can improve the dielectric constant and dielectric loss of the coating, which is beneficial to the stealth requirement of different frequency bands of the coating in the case of thin thickness.

[0011] In summary, by adding La 1-x Sr x MnO3 or La 1-x Sr x CoO3 to YSZ and other oxide ceramics such as alumina, the dielectric properties of the coating are adjusted, and the absorption performance of the resistive periodic pattern layer is further improved, and it is a difficult problem for those skilled in the art to prepare a coating with adjustable stealth performance, thin thickness and high service temperature. SUMMARY

[0012] In view of the problem that there is no La 1-x Sr x MnO3 or La 1-x Sr x CoO3 content and dielectric properties in the prior art, and the stealth performance of the resistive periodic pattern layer is adjustable, the thickness is thin, and the service temperature is high, the present application provides a high-temperature-resistant radar absorbing coating combined with an absorbing agent and a super material, and a preparation method thereof, which is also a radar absorbing coating with adjustable dielectric constant, high-temperature resistance and strong absorption, and a preparation method thereof. The present application adopts a combination of high-temperature-resistant absorbing agent and electromagnetic periodic structure layer, wherein the high-temperature-resistant absorbing agent adopts La 1-x Sr x MnO3 or La 1-x Sr x CoO3, and is prepared by plasma spraying process.

[0013] The technical scheme of the present application is as follows: A high-temperature-resistant radar absorbing coating combined with an absorbing agent and a super material is a kind of absorbing agent (oxide ceramic such as YSZ or alumina and La 1-x Sr x MnO3 or La 1-x Sr xCoO3 powder is mixed, X is 0.2-0.4)and the scheme of combining with super material, the high reliability of oxide ceramic is combined with La 1-x Sr x MnO3 or La 1-x Sr x CoO3, the dielectric adjustable property and the characteristic of high electron conductivity are combined, and meanwhile, the super material layer is introduced, so that strong absorption of electromagnetic wave is realized.

[0014] The purpose of the application is realized by the following technical scheme: A high-temperature-resistant radar wave-absorbing coating combined with an absorber and super material, which is coated on the surface of a metal base material and sequentially comprises, from the surface of the metal base material and from bottom to top, a metal bonding layer, a first radar wave-absorbing layer, a super material layer and a second radar wave-absorbing layer. The metal bonding layer has a thickness of 20-80 microns. The raw material used in the radar wave-absorbing layer is prepared by mixing oxide ceramic powder and La 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder, X is 0.2-0.4, and the La 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder has a content of 10%-70% of the mass of the mixed powder. The first radar wave-absorbing layer has a thickness of 500-1300 microns. The second radar wave-absorbing layer has a thickness of 200-1000 microns. The super material layer has a thickness of 10-50 microns and is prepared by screen printing and high-temperature heat treatment and has a patch form; the raw material of the super material layer is a high-temperature-resistant resistance type paste prepared by taking RuO2 as a conductive phase and Bi2O3-SiO2-B2O3 glass as a bonding phase. The metal bonding layer is a NiCrAlY or CoCrAlY coating layer and has a thickness of 20-80 microns. The high-temperature-resistant radar wave-absorbing coating combined with the absorber and super material has the following performance indexes, according to the content of La 1-x Sr x MnO3 or La 1-x Sr x CoO3, the periodic pattern and the distribution position of the super material are realized: 12GHz~18GHz reflectivity ≤-5dB, or 8GHz~12GHz reflectivity ≤-5dB; coating bonding strength ≥8MPa at room temperature, 500 times of thermal shock at 900℃ without damage.

[0015] Further, the oxide ceramic powder is selected from YSZ or alumina powder.

[0016] The metamaterial layer is a resistive periodic structure layer, containing patches, and the patch periodic size is 3mm~30mm.

[0017] The preparation method of the above-mentioned high-temperature-resistant radar wave-absorbing coating combined with an absorbent and a metamaterial includes the following steps: S1, granulation: S1-1, mixing the oxide ceramic powder with La 1-x Sr x MnO3 powder or La 1-x Sr x CoO3 powder according to the proportion, then adding gum arabic, citric acid triamine and deionized water, and ball milling for 48h~60h to obtain a slurry; S1-2, then atomizing and granulating the slurry obtained by ball milling, the atomizer frequency is 24Hz~35Hz, the inlet temperature is 240℃, the outlet temperature is 120℃, the pulse needle pressing force is 0.2MPa, and the mixed powder is obtained by granulation, and the powder obtained after granulation is screened, and the powder between 150 meshes and 400 meshes is collected and heat treated at 1000℃ for 2h; S2, sandblasting roughening treatment is performed on the superalloy substrate; S3, a metal bonding layer is prepared on the surface of the sandblasted superalloy substrate by plasma spraying process; 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 process through drying and heat treatment of the high-temperature resistive slurry; S6, a second radar wave-absorbing layer is prepared on the surface of the metamaterial layer obtained in S5 by plasma spraying, and the spraying process is the same as that in S4, to obtain a high-temperature-resistant radar wave-absorbing coating combined with an absorbent and a metamaterial.

[0018] Further, in S1, the gum arabic accounts for 2% of the mass of the mixed powder, the citric acid triamine 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.

[0019] Further, the sand blasting roughening treatment of the high-temperature alloy substrate in S2 has the following process parameters: pressure 0.2-0.5 MPa, sand blasting medium white corundum sand, mesh size 24-40, sand blasting distance 80-150 mm, and sand blasting angle 30-60°.

[0020] Further, the metal bonding layer prepared on the surface of the sand-blasted high-temperature alloy substrate in S3 has the following process parameters: carrier gas flow rate 1-4 L / min, main gas flow rate 40-50 L / min, 5 min powder feeding amount 80-100 g, current 500-600 A, and power 30-50 kW.

[0021] Further, the first radar wave-absorbing layer prepared on the surface of the metal bonding layer obtained in S3 in S4 has the following process parameters: carrier gas flow rate 1-4 L / min, main gas flow rate 40-50 L / min, 5 min powder feeding amount 40-150 g (determined by different oxide powders and powder doping amounts), current 500-600 A, and power 30-50 kW. Further, the super material layer prepared in S5 is prepared by screen printing of high-temperature resistance paste on the surface of the first radar wave-absorbing layer, and has the following process parameters: screen mesh size 200 or 250, drying temperature 150-250 °C, drying time 0.5-2 h, sintering temperature 900 °C ± 10 °C, and sintering time 30 min.

[0022] Further, the second radar wave-absorbing layer prepared on the surface of the super material layer obtained in S5 in S6 has the following process parameters: carrier gas flow rate 1-4 L / min, main gas flow rate 40-50 L / min, 5 min powder feeding amount 40-150 g, current 500-600 A, and power 30-50 kW.

[0023] Compared with the prior art, the present application has the following advantages: 1. The preparation method of the high-temperature-resistant radar wave-absorbing coating combined with an absorbent and a super material has the following advantages: mainly using atmospheric plasma spraying technology and other environmentally friendly technologies; no toxic and harmful substances are generated during powder synthesis, and the environment is not polluted, which is an environmentally friendly preparation method; no harmful gas is generated during coating preparation, only a small amount of dust and waste gas are generated, which are collected by dust removal and filtration, and do not pollute the environment.

[0024] 2. The high-temperature-resistant radar wave-absorbing coating combined with an absorbent and a super material has the following advantages: the addition of La1-x Sr x MnO3 or La 1-x Sr x The selection of the ratio of CoO3 realizes accurate control of the dielectric constant, and the pattern size, position and sheet resistance of the super material are combined to control the wave absorption performance.

[0025] 3、The high-temperature radar wave absorbing coating combined with the absorbing agent and the super material can realize strong absorption of a certain frequency band, and has high reliability. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a high-temperature wave absorbing coating panel using the high-temperature radar wave absorbing coating combined with the absorbing agent and the super material prepared by the application; Figure 2 is a reflectivity test result graph of the high-temperature radar wave absorbing coating combined with the absorbing agent and the super material prepared in Example 1 of the application; Figure 3 is a reflectivity test result graph of the high-temperature radar wave absorbing coating combined with the absorbing agent and the super material prepared in Example 2 of the application at room temperature; Figure 4 is a reflectivity test graph of the high-temperature radar wave absorbing coating combined with the absorbing agent and the super material prepared in Example 3 of the application; Figure 5 is a structural schematic view of the high-temperature radar wave absorbing coating combined with the absorbing agent and the super material prepared in Example 1 of the application; Figure 6 is a reflectivity test result graph of the high-temperature radar wave absorbing coating combined with the absorbing agent and the super material prepared in Example 4 of the application; Figure 7 is a reflectivity test result graph of a pure YSZ coating (without a periodic structure) prepared in the comparative example of the application; Figure 8 is a reflectivity test result graph of a pure YSZ coating doped with La 0.8 Sr 0.2 MnO3 (without a periodic structure) prepared in the comparative example of the application. DETAILED DESCRIPTION

[0027] The application will be described in detail below in combination with the drawings and examples, and it should be noted that the examples and drawings are only used to exemplarily describe the application and do not limit the protection scope of the application.

[0028] Unless otherwise defined, all terms used in the description employed herein have the same meaning as commonly understood by one of ordinary skill in the art. As used herein, the following professional terms are intended to have the following meanings.

[0029] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0030] Example 1 A high-temperature-resistant radar absorbing coating combined with an absorbent and a metamaterial, the coating is applied to the surface of a metal substrate, and from the surface of the metal substrate, the coating includes, in order from bottom to top, a metal bonding layer, a first radar absorbing layer, a metamaterial layer, and a second radar absorbing layer. The metal bonding layer has a thickness of 80 μm. The raw materials used in the radar absorbing layer are prepared by ball milling and granulation of oxide ceramic powder and La 0.8 Sr 0.2 CoO3, wherein the content of La 0.8 Sr 0.2 CoO3 is 50%. The first radar absorbing layer has a thickness of 1300 μm. The second radar absorbing layer has a thickness of 200 μm. The metamaterial layer has a thickness of 20 μm and is prepared by screen printing and high-temperature heat treatment, and is in the form of a patch; the raw materials of the metamaterial layer are high-temperature-resistant resistance type paste prepared by taking RuO2 as the conductive phase and Bi2O3-SiO2-B2O3 system glass as the bonding phase. The metal bonding layer is a NiCrAlY coating layer, and has a thickness of 80 μm. The oxide ceramic powder is selected from alumina. The patch period size in the metamaterial layer is 9.5 mm.

[0031] The above-mentioned method for preparing a high-temperature-resistant radar absorbing coating combined with an absorbent and a metamaterial includes the following steps: S1, granulation: S1-1, mixing oxide ceramic powder and La 0.8 Sr 0.2 CoO3 in proportion, then adding gum arabic, citric acid triamine and deionized water, and ball milling for 48 h to obtain the paste. S1-2, the slurry obtained by ball milling is then atomized and granulated, the atomizer frequency is 35 Hz, the inlet temperature is 240 DEG C, the outlet temperature is 120 DEG C, the pulse needle pressure is 0.2 MPa, the mixed powder is obtained by granulation, and the powder obtained after granulation is screened, the powder between 150 meshes and 400 meshes is collected and is subjected to high temperature heat treatment at 1000 DEG C for 2h; S2, the high-temperature alloy substrate is subjected to sand blasting roughening treatment, the process parameters are: pressure 0.2 MPa, sand blasting medium is white corundum sand, the mesh number is 24-40, the sand blasting distance is 150 mm, and the sand blasting angle is 30 DEG; S3, a metal bonding layer is prepared on the surface of the sand-blasted high-temperature alloy substrate by plasma spraying process, the preparation process parameters are: carrier gas flow 2 L / min, main gas flow 46 L / min, 5 min powder feeding amount 100 g, current size 550 A, power 34 Kw; S4, a first radar wave-absorbing layer is prepared on the surface of the metal bonding layer obtained by plasma spraying S3, the preparation process parameters are: carrier gas flow 43 L / min, main gas flow 46 L / min, 5 min powder feeding amount 50 g, current size 580 A, power 42 Kw; S5, a high-temperature resistance type slurry is prepared on the surface of the first radar wave-absorbing layer by screen printing process through drying and heat treatment to prepare a metamaterial layer, and a resistance type periodic structure layer is prepared on the surface of the first radar wave-absorbing layer by screen printing process through drying and heat treatment, in the screen printing process, the screen mesh number is 200 meshes, the drying temperature is 150 DEG C, the time is 2h, the sintering temperature is 900 DEG C ± 10 DEG C, and the sintering time is 30 min; S6, a second radar wave-absorbing layer is prepared on the surface of the metamaterial layer obtained in S5, the spraying process is the same as S4, and a high-temperature resistant radar wave-absorbing coating combined with an absorber and a metamaterial is obtained.

[0032] The high-temperature resistant radar wave-absorbing coating combined with an absorber and a metamaterial has the following performance indexes: the reflectivity is less than or equal to -5 dB at 12 GHz-18 GHz; the coating bonding strength is greater than or equal to 8 MPa at room temperature, and is not damaged after 500 times of thermal shock at 900 DEG C.

[0033] Figure 1 It is a picture of a high-temperature wave-absorbing coating panel using the high-temperature wave-absorbing coating combined with an absorber and a metamaterial prepared in Example 1, and it can be seen that the coating surface is smooth and flat.

[0034] Figure 2is a reflectivity test result graph of a high-temperature resistant radar absorbing coating prepared by combining the absorbent prepared in Example 1 with a metamaterial, 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; from Figure 2 It can be seen that the overall reflectivity of the coating is ≤-6 dB in the range of 10-18 GHz.

[0035] Figure 5 is a structural schematic diagram of a high-temperature resistant radar absorbing coating prepared by combining an absorbent with a metamaterial, and it can be seen that the coating is coated on the surface of a metal substrate, and from the surface of the metal substrate, it includes a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer from bottom to top.

[0036] Example 2: A high-temperature resistant radar absorbing coating prepared by combining an absorbent with a metamaterial, the coating is coated on the surface of a metal substrate, and from the surface of the metal substrate, it includes a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer from bottom to top. The thickness of the metal bonding layer is 80 μm. The raw materials used in the radar absorbing layer are prepared by ball milling and granulation of an oxide ceramic powder and La 0.8 Sr 0.2 CoO3, wherein the content of La 0.8 Sr 0.2 CoO3is 70%; The thickness of the first radar absorbing layer is 1300 μm. The thickness of the second radar absorbing layer is 200 μm. The thickness of the metamaterial layer is 20 μm, which 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 resistance type paste prepared by taking RuO2as the conductive phase and Bi2O3-SiO2-B2O3glass as the bonding phase; The metal bonding layer is a CoCrAlY coating with a thickness of 80 μm. The oxide ceramic powder is selected from alumina. The patch period size in the metamaterial layer is 9.5 mm.

[0037] The preparation method of the above-mentioned high-temperature resistant radar absorbing coating prepared by combining an absorbent with a metamaterial includes the following steps: S1, granulation: S1-1, mix an oxide ceramic powder and La 0.8 Sr 0.2 MnO3or La 0.8 Sr 0.2CoO3 were mixed in proportion, then gum arabic, citric acid triamine and deionized water were added, the ball milling time was 60h, and the slurry was obtained; S1-2, then the slurry obtained by ball milling was atomized and granulated, the atomizer frequency was 24Hz, the inlet temperature was 240℃, the outlet temperature was 120℃, the pulse needle pressure was 0.2MPa, the mixed powder was obtained by granulation, and the powder obtained after granulation was sieved, the powder between 150mesh and 400mesh was collected and high temperature heat treatment was carried out at 1000℃ for 2h; S2, the high-temperature alloy substrate was subjected to sand blasting roughening treatment, the process parameters were: pressure 0.5MPa, sand blasting medium was white corundum sand with mesh size of 24mesh~40mesh, sand blasting distance was 80mm, and sand blasting angle was 60°; S3, a metal bonding layer was prepared on the surface of the sand blasted high-temperature alloy substrate by plasma spraying process, the preparation process parameters were: carrier gas flow 2L / min, main gas flow 46L / min, 5min powder feeding amount 100g, current size 550A, and power 34Kw; S4, a first radar wave absorbing layer was prepared on the surface of the metal bonding layer obtained by plasma spraying S3, the preparation process parameters were: carrier gas flow 3L / min, main gas flow 46L / min, 5min powder feeding amount 60g, current size 550A, and power 38Kw; S5, a metamaterial layer was prepared on the surface of the first radar wave absorbing layer by drying and heat treatment of high-temperature resistance type slurry by screen printing process, and a resistance type periodic structure layer was prepared on the surface of the first radar wave absorbing layer by drying and heat treatment of high-temperature resistance type slurry by screen printing process, in the screen printing process, the screen mesh size was 250mesh, the drying temperature was 250℃, the time was 0.5h, the sintering temperature was 900℃±10℃, and the sintering time was 30min; S6, a second radar wave absorbing layer was prepared on the surface of the metamaterial layer obtained in S5, the spraying process was the same as S4, and a high-temperature resistant radar wave absorbing coating combined with an absorber and a metamaterial was obtained; The high-temperature resistant radar wave absorbing coating combined with an absorber and a metamaterial has the following performance indexes: 6GHz~12GHz reflectivity≤-4dB, 7GHz~10GHz overall≤-6dB, coating bonding strength at room temperature≥8MPa, and no damage after 500 times of thermal shock at 900℃.

[0038] Figure 3 It is the measured reflectivity result graph of the high-temperature resistant radar wave absorbing coating combined with an absorber and a metamaterial prepared in example 2 at room temperature, the dielectric constant is 18, the thickness of the first radar wave absorbing layer is 1.3mm, the thickness of the second radar wave absorbing layer is 0.2mm, and the metamaterial layer is prepared on the surface of the first radar layer; ByFigure 2 and Figure 3 It can be seen that the high-temperature resistant radar absorbing coating prepared by combining the absorbent of Example 2 with the metamaterial has the same thickness as the high-temperature resistant radar absorbing coating prepared by combining the absorbent of Example 1 with the metamaterial, but is less than -4dB in the range of 7GHz~12GHz as a whole; the position of the absorption peak is adjusted, so that the application can achieve strong absorption in different frequency bands by adjusting the dielectric constant according to different absorption requirements.

[0039] Example 3: A high-temperature resistant radar absorbing coating combined with an absorbent and a metamaterial, which is coated on the surface of a metal substrate and sequentially comprises, from the surface of the metal substrate and from bottom to top, a metal bonding layer, a first radar absorbing layer, a metamaterial layer and a second radar absorbing layer. The metal bonding layer has a thickness of 80μm. The raw material for the radar absorbing layer is prepared by ball milling and granulation of an oxide ceramic powder and La 0.8 Sr 0.2 MnO3, wherein the content of La 0.8 Sr 0.2 MnO3 is 10%; The first radar absorbing layer has a thickness of 650μm. The second radar absorbing layer has a thickness of 1050μm. The metamaterial layer has a thickness of 20μm and 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 system glass as a bonding phase; The metal bonding layer is a CoCrAlY coating layer and has a thickness of 80μm. The oxide ceramic powder is selected from YSZ. The patch period size of the metamaterial layer is 5.33mm.

[0040] The preparation method of the above-mentioned high-temperature resistant radar absorbing coating combined with an absorbent and a metamaterial comprises the following steps: S1, granulation: S1-1, mixing the oxide ceramic powder and La 0.8 Sr 0.2 MnO3 according to the proportion, then adding gum arabic, citric acid triamine and deionized water, and ball milling for 60h to obtain a paste; S1-2, then the slurry obtained by ball milling is atomized and granulated, the atomizer frequency is 24 Hz, the inlet temperature is 240 DEG C, the outlet temperature is 120 DEG C, the pulse needle pressure is 0.2 MPa, the mixed powder is obtained by granulation, the powder obtained after granulation is screened, the powder between 150 meshes and 400 meshes is collected and high-temperature heat treatment at 1000 DEG C for 2h is carried out; S2, the high-temperature alloy substrate is subjected to sand blasting roughening treatment, the process parameters are: pressure 0.5 MPa, sand blasting medium is white corundum sand, the mesh number is 24-40, the sand blasting distance is 80 mm, and the sand blasting angle is 60 DEG; S3, a metal bonding layer is prepared on the surface of the sand-blasted high-temperature alloy substrate by plasma spraying process, the preparation process parameters are: carrier gas flow 2 L / min, main gas flow 46 L / min, 5 min powder feeding amount 100 g, current size 550 A, power 34 Kw; S4, a first radar wave-absorbing layer is prepared on the surface of the metal bonding layer obtained by plasma spraying S3, the preparation process parameters are: carrier gas flow 3 L / min, main gas flow 46 L / min, 5 min powder feeding amount 135 g, current size 600 A, power 42 Kw; S5, a high-temperature resistance type slurry is prepared on the surface of the first radar wave-absorbing layer by screen printing process through drying and heat treatment to prepare a metamaterial layer, and a resistance type periodic structure layer is prepared on the surface of the first radar wave-absorbing layer by screen printing process through drying and heat treatment, in the screen printing process, the screen mesh number is 250 meshes, the drying temperature is 250 DEG C, the time is 0.5 h, the sintering temperature is 900 DEG C±10 DEG C, and the sintering time is 30 min; S6, a second radar wave-absorbing layer is prepared on the surface of the metamaterial layer obtained in S5, the spraying process is the same as S4, and a high-temperature resistant radar wave-absorbing coating combined with an absorber and a metamaterial is obtained.

[0041] Figure 4 It is the reflectivity measurement diagram of the high-temperature resistant radar wave-absorbing coating combined with an absorber and a metamaterial prepared in Example 3, the total thickness is 1.7 mm, higher than 1.5 mm of Examples 1 and 2, can realize ≤-6 dB in most of 8 GHz-18 GHz frequency band, and ≤-5 dB in the whole, and ≤-2 dB at 5 GHz, ≤-3 dB at 6 GHz, and the whole presents the characteristics of wideband wave-absorbing.

[0042] Example 4: A high-temperature resistant radar wave-absorbing coating combined with an absorber and a metamaterial, the coating is coated on the surface of a metal substrate, and from the surface of the metal substrate, the coating comprises 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 metal bonding layer has a thickness of 80 μm; The raw material for the radar wave absorbing layer is prepared from oxide ceramic powder and La 0.8 Sr 0.2 CoO3, wherein the content of La 0.8 Sr 0.2 CoO3 is 50%; The first radar wave absorbing layer has a thickness of 550 μm; The second radar wave absorbing layer has a thickness of 950 μm; The metamaterial layer has a thickness of 20 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 resistance type paste prepared from RuO2 as a conductive phase and Bi2O3-SiO2-B2O3 system glass as a bonding phase; The metal bonding layer is a CoCrAlY coating layer, and has a thickness of 80 μm; The oxide ceramic powder is selected from alumina; The patch period size of the metamaterial layer is 9.5 mm.

[0043] The above method for preparing the high-temperature-resistant radar wave absorbing coating combined with an absorber and a metamaterial comprises the following steps: S1, granulation: S1-1, mixing oxide ceramic powder and La 0.8 Sr 0.2 CoO3 according to a proportion, then adding gum arabic, citric acid triamine and deionized water, and ball milling for 60 h to obtain a paste; S1-2, then performing atomization granulation on the paste obtained by ball milling, wherein the frequency of an atomizer is 24 Hz, the inlet temperature is 240 °C, the outlet temperature is 120 °C, the pulse needle pressing force is 0.2 MPa, the mixed powder is obtained by granulation, the powder obtained after granulation is sieved, the powder between 150 meshes and 400 meshes is collected, and high-temperature heat treatment at 1000 °C for 2 h is performed on the powder; S2, performing sand blasting roughening treatment on the superalloy substrate, wherein the process parameters are as follows: pressure 0.5 MPa, sand blasting medium white corundum sand with a mesh size of 24 mesh to 40 mesh, sand blasting distance 80 mm, and sand blasting angle 60°; S3, preparing a metal bonding layer on the surface of the sand blasted and roughened superalloy substrate by using a plasma spraying process, wherein the preparation process parameters are as follows: carrier gas flow 2 L / min, main gas flow 46 L / min, 5 min powder feeding amount 100 g, current size 550 A, and power 34 Kw; S4, a first radar wave absorbing layer is prepared on the surface of the metal bonding layer obtained in S3 by plasma spraying, and the process parameters are as follows: carrier gas flow 3 L / min, main gas flow 46 L / min, powder feeding amount 50 g for 5 min, current 580 A, and power 38 Kw; S5, a high-temperature resistance type paste is prepared on the surface of the first radar wave absorbing layer by screen printing, drying, and heat treatment, and a resistance type periodic structure layer is prepared on the surface of the first radar wave absorbing layer by screen printing, drying, and heat treatment, wherein the screen mesh number is 250 mesh, the drying temperature is 250 DEG C, the time is 0.5 h, the sintering temperature is 900 DEG C ± 10 DEG C, and the sintering time is 30 min; S6, a second radar wave absorbing layer is prepared on the surface of the super material layer obtained in S5 by spraying, and the spraying process is the same as that in S4, to obtain a high-temperature resistant radar wave absorbing coating combined with an absorbing agent and a super material.

[0044] Figure 6 is a reflectivity test result graph of the high-temperature resistant radar wave absorbing coating combined with an absorbing agent and a super material prepared in Example 4, Figure 6 The overall thickness of the measured coating is 1.5 mm, and the dielectric constant of the radar wave absorbing layer is the same as that in Example 1, wherein the thickness of the first radar layer is 550 μm, the thickness of the second radar layer is 950 μm, the super material layer is prepared on the surface of the first radar layer, and the dielectric constant is 14, which is the same as that in Example 1. Figure 2 Figure 6 The measured curve can achieve strong absorption of ≤-5 dB within 11 GHz to 18 GHz, and the test result shows that under the same dielectric constant, the position of the super material layer can be adjusted to achieve strong absorption in different frequency bands, which further illustrates that the wave absorbing performance of the present application is jointly achieved by the absorbing agent layer and the super material layer, and not only depends on the super material layer or the absorbing agent layer.

[0045] It can be seen from Examples 1 to 4 that the coating structure has both an absorbing agent layer and a super material layer, and strong absorption of radar waves can be achieved by the joint action of the two, and not only depends on the super material layer or the absorbing agent layer.

[0046] Comparative Example: The difference between the comparative example and Example 1 is that: (1) The main body of the coating is an oxide ceramic, and La 1-x Sr x MnO3 or La 1-x Sr x CoO3 is not added.

[0047] (2) In the comparative example, the raw material powder is not subjected to a process of heat treatment at 1000 DEG C for 2 h. ​

[0048] In the comparative example, the radar function layer was heat treated at 900℃ for 30 min, and different sintering times resulted in different sheet resistance values of the metamaterial layer.

[0049] Figure 7 is a reflectivity test result graph of the pure YSZ coating prepared in the comparative example; the 1.2 mm thick pure ceramic (without periodic structure) wave absorption performance is as shown in Figure 7 Therefore, the wave absorption performance is only realized by the metamaterial layer, and in the case of the same thickness, the wave absorption function of the coating can only be realized by adjusting the position and parameters of the metamaterial layer, and the wave absorption performance is limited.

[0050] Figure 8 is a reflectivity test result graph of the 1.2 mm thick pure YSZ coating prepared in the comparative example after doping La 0.8 Sr 0.2 MnO3 (without periodic structure), and by comparing the comparative example and example 3, the wave absorption performance of example 3 is more excellent due to the addition of La 0.8 Sr 0.2 MnO3.

[0051] In the comparative example, 2 layers of periodic structure layers are used to realize wideband wave absorption, and in example 1, La 0.8 Sr 0.2 CoO3 is doped in the oxide ceramic, and the wave absorption performance is more excellent, so that only one layer of metamaterial layer can realize more excellent wave absorption effect.

[0052] The above is only a preferred embodiment of the present application, and the protection scope of the present application is not limited to the above examples. Any technical solution falling within the concept of the present application belongs to the protection scope of the present application. It should be noted that improvements and refinements made by ordinary skilled in the art without departing from the principles of the present application should also be considered as the protection scope of the present application.

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 metal bonding layer has a thickness of 20-80 microns. 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 microns. The second radar wave absorbing layer has a thickness of 200-1000 microns. The metamaterial layer has a thickness of 10-50 microns, is prepared by screen printing and high-temperature heat treatment, and has a patch form; the raw material of the metamaterial layer is a high-temperature resistant resistance type paste prepared by taking RuO2 as a conductive phase and Bi2O3-SiO2-B2O3 glass as a bonding phase. The metal bonding layer is a NiCrAlY or CoCrAlY coating layer, and has a thickness of 20-80 microns. 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 less than or equal to -5 dB at 12-18 GHz or 8-12 GHz, the coating bonding strength is greater than or equal to 8 MPa at normal temperature, and the coating is not damaged after thermal shock for 500 times at 900 DEG C.

2. The high-temperature radar-absorbing coating combining an absorber and metamaterials according to claim 1, characterized in that, The oxide ceramic powder is selected from yttria-stabilized zirconia powder or alumina powder.

3. The high-temperature radar-absorbing coating combining an absorber and metamaterials according to claim 1, characterized in that, The metamaterial layer is a resistance type periodic structure layer, and 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 DEG C, the outlet temperature is 120 DEG C, the pulse needle pressure is 0.2 MPa, the mixed powder is obtained by granulation, the powder obtained after granulation is screened, and the powder between 150 and 400 meshes is collected, and the powder is high-temperature heat-treated at 1000 DEG C for 2 h; S2, sand blasting roughening treatment is performed on the superalloy substrate; S3, a metal bonding layer is prepared on the surface of the sand blasted and roughened superalloy substrate by plasma spraying process; 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 high-temperature resistance type paste is prepared on the surface of the first radar wave absorbing layer by screen printing process through drying and heat treatment to prepare a metamaterial layer; 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 citric acid triamine 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 sand blasting roughening treatment is performed on the superalloy substrate, and the process parameters are as follows: the pressure is 0.2-0.5 MPa, the sand blasting medium is white corundum sand with a mesh size of 24-40, the sand blasting distance is 80-150 mm, and the sand blasting angle is 30-60 DEG.

7. The method according to claim 4, wherein the method is characterized by, The metal bonding layer is prepared on the sandblasted high-temperature alloy substrate surface by the plasma spraying process, and the preparation process parameters are as follows: carrier gas flow 1L / min-4L / min, main gas flow 40L / min-50L / min, 5min powder feeding amount 80g-100g, current size 500A-600A, and power 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 metal bonding layer obtained in S3 by the plasma spraying process, and the preparation process parameters are as follows: carrier gas flow 1L / min-4L / min, main gas flow 40L / min-50L / min, 5min powder feeding amount 40g-150g, current size 500A-600A, and power 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 size is 200 mesh or 250 mesh, the drying temperature is 150 DEG C-250 DEG C, the time is 0.5h-2h, the sintering temperature is 900 DEG C+ / -10 DEG C, 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 material layer obtained in S5 by the plasma spraying process, and the preparation process parameters are as follows: carrier gas flow 1L / min-4L / min, main gas flow 40L / min-50L / min, 5min powder feeding amount 40g-150g, current size 500A-600A, and power 30Kw-50Kw.

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