Low-infrared-emissivity frequency selective surface coating resistant to high temperature of 950 DEG C and preparation method thereof

Abstract

The invention relates to the field of high-temperature functional ceramic materials, and particularly discloses an infrared low-emissivity frequency selective surface coating capable of resisting the high temperature of 950 DEG C. The surface of a substrate material is coated with the infrared low-emissivity frequency selective surface coating, and the infrared low-emissivity frequency selective surface coating sequentially comprises a transition bonding layer, a ceramic matching layer and an infrared low-emissivity frequency selective surface layer from inside to outside; the periodic structure size a of a patch unit of the infrared low-emissivity frequency selective surface layer is 0.5-0.9 mm, the side length of the unit is a * x, x is 0.8-0.95, and the patch unit is composed of high-melting-point Bi2O3-RE2O3-SiO2 series microcrystalline glass serving as a binding phase and high-temperature oxidation-resistant precious metal alloy powder serving as a conductive phase. The 950 DEG C high-temperature-resistant infrared low-emissivity frequency selective surface coating can resist the high temperature not lower than 950 DEG C, has the characteristic of high-temperature infrared low emissivity of two wavebands of 3-5 [mu] m and 8-14 [mu] m, and meanwhile has the advantages of high radar wave-transparent characteristic, high bonding performance, excellent thermal shock resistance, low cost and the like. The contradictory problem between high radar wave transmission and low infrared emissivity of the surface of a single coating is effectively solved, and the radar and infrared compatible stealth performance is promoted to be improved.

Description

Technical Field

[0001] The present invention mainly relates to the field of high-temperature functional ceramic materials, and in particular to a 950°C high-temperature resistant infrared low-emissivity frequency selective surface coating and a preparation method thereof. Background Art

[0002] With the continuous improvement of aero-engine thrust, the engine thermal cavity structure is not only a strong radar scattering source, but also the strongest infrared radiation source behind the aircraft. It is urgent to solve the coating radar absorption and realize the coating's high-temperature infrared low-emissivity characteristics. However, radar absorption requires high absorption and low reflection of electromagnetic waves, while infrared low emissivity requires low absorption and high reflection; limited by the inherent electromagnetic properties of the coating material, a single coating material cannot simultaneously achieve high-efficiency radar absorption and high-temperature infrared low-emissivity characteristics. Therefore, solving the coordinated optimization of high radar transmittance and low infrared emissivity on the coating surface has become a bottleneck technology that restricts the coating from achieving efficient multi-spectrum stealth.

[0003] Chinese patents ZL201910399226.6 and ZL201910399986.7 respectively disclose two thermal barrier / high temperature low infrared emissivity integrated coatings and their preparation methods. Such coatings have good temperature resistance and infrared low emissivity characteristics, but do not have radar absorbing function. In addition, the infrared low emissivity characteristics make it have a strong reflection effect on radar waves, and it is impossible to achieve high transmittance of electromagnetic waves in the radar band. As a type of metamaterial, the frequency selective surface is arranged periodically. Through the macroscopic parameter control of the periodic structure unit size, it can achieve selectivity for electromagnetic waves in the characteristic frequency band. The material characteristics of the frequency selective surface coating are used to achieve high transmittance in the radar band and high reflectivity in the infrared band, which can alleviate the inherent contradiction between radar absorbing and low emissivity. Chinese Patents No. ZL201711498947.X and No. ZL201710943403.3 respectively disclose two types of radar and infrared compatible stealth coatings and their preparation methods. Such coating materials utilize the selective transmittance and reflection characteristics of the frequency selective surface coating to electromagnetic waves, and adopt the screen printing process to realize the frequency selective surface preparation. The coating has radar and infrared compatible stealth functions under different temperature conditions. However, due to the influence of the periodic structure design and the screen printing process, such frequency selective surface layer only realizes an infrared emissivity of no more than 0.3 in the 3-5μm band, and it is difficult to achieve the infrared low emissivity characteristics in the 8-14μm band.

[0004] In addition to screen printing technology, commonly used technologies for preparing flat frequency selective surfaces include micro-pen direct writing technology, CNC machining technology, etc. Micro-pen direct writing technology has very high requirements on the flatness of the coating surface and cannot achieve curved surface machining; CNC machining technology uses precision tools to directly etch and process the periodic array structure of the frequency selective surface, but the machining efficiency is low and it is easy to damage the brittle ceramic coating. In addition, Chinese patent ZL201310305384.3 discloses a method for preparing curved frequency selective surfaces using 3D printing technology. This method has low efficiency and long cycle, and it is difficult to meet the requirements for high-precision frequency selective surface preparation. Therefore, how to prepare a dual-band infrared low-emissivity frequency selective surface coating with high temperature resistance, high bonding, excellent thermal shock resistance, and high dimensional accuracy on a brittle ceramic coating has become a key issue for technicians in this field. Summary of the invention

[0005] In view of the above shortcomings, the present invention provides a 950°C high temperature resistant infrared low emissivity frequency selective surface coating, which has high temperature resistance, high bonding, excellent thermal shock resistance, and infrared dual-band low emissivity. The specific technical scheme is as follows:

[0006] A 950°C high temperature resistant infrared low emissivity frequency selective surface coating, the coating is coated on the surface of a substrate material, and comprises a transition bonding layer, a ceramic matching layer and an infrared low emissivity frequency selective surface layer from the inside to the outside; the patch unit periodic structure size a of the infrared low emissivity frequency selective surface layer is 0.5-0.9 mm, the unit side length is a×x, and x is 0.8-0.95, and is made of high melting point Bi 2 O 3 -RE 2 O 3 -SiO 2 The system is composed of microcrystalline glass as the bonding phase and high-temperature oxidation-resistant precious metal alloy powder as the conductive phase.

[0007] The technical principle of the technical solution of the present invention is as follows: based on the radiation principle of the surface of an object, the equivalent emissivity of the low emissivity frequency selective surface coating is jointly determined by the infrared emissivity of the low emissivity layer and the ceramic layer arranged in a periodic structure and the percentage of their occupied area. Based on the radar selective wave transmission requirements, the frequency selective surface periodic structure array pattern is designed, and the high transmittance of a specific radar band and the low emissivity characteristics of the infrared dual band are achieved through the regulation of parameters such as the periodic structure pattern and the unit structure size. The transition bonding layer is to improve the matching characteristics between the ceramic layer and the base material. The ceramic matching layer, as the sintered base of the infrared low emissivity coating, is the key to realizing the preparation of composite coatings on the surfaces of different base materials. At the same time, the infrared emissivity of the ceramic layer will also affect the overall infrared emissivity of the coating.

[0008] Preferably, in the above-mentioned 950°C high temperature resistant infrared low emissivity frequency selective surface coating, the thickness of the transition bonding layer is 0.05mm~0.10mm, the thickness of the ceramic matching layer is 0.10mm~1.00mm, and the thickness of the low emissivity frequency selective surface layer is 0.01mm~0.05mm.

[0009] Preferably, in the above-mentioned 950°C high temperature resistant infrared low emissivity frequency selective surface coating, the substrate material is a high temperature nickel-based alloy, a high temperature iron-based alloy, a high temperature nickel-based single crystal or Ni 3 Al alloy, the transition bonding layer is NiCrAlY, CoNiCrAlY, CoCrAlSiY or NiCoCrAlHfYSi.

[0010] Preferably, in the above-mentioned 950°C high temperature resistant infrared low emissivity frequency selective surface coating, the ceramic matching layer is a multi-component rare earth high entropy zirconate (5RE 0.2 ) 2 Zr 2 O 7 , the RE is five of La, Gd, Nd, Sm, Sc, Yb, Lu, Dy, Ho, and Eu.

[0011] Preferably, in the above-mentioned 950°C high temperature resistant infrared low emissivity frequency selective surface coating, the conductive phase is one or more alloys of Ag, Pd, Au, and Pt, and the mass fraction of the conductive phase in the coating is 75-80%.

[0012] On the other hand, the present invention also provides a method for preparing the above-mentioned 950°C high temperature resistant infrared low emissivity frequency selective surface coating, comprising the following steps:

[0013] (1) Surface roughening of the substrate material: The surface of the substrate material is roughened by sandblasting;

[0014] (2) Preparation of transition bonding layer: preparing a transition bonding layer on the base material of step (1) by using an atmospheric plasma spraying process;

[0015] (3) Preparation of ceramic matching layer: using multi-component rare earth high entropy zirconate ceramic material as raw material, and using a plasma spraying process to spray a ceramic matching layer on the surface of the transition bonding layer prepared in step (2);

[0016] (4) Preparation of infrared low emissivity layer: applying a high-temperature conductor slurry prepared by mixing high-melting-point microcrystalline glass and precious metal alloy powder to the surface of the ceramic matching layer in step (3) by screen printing, and obtaining an infrared low emissivity layer after drying and sintering;

[0017] (5) Preparation of low emissivity frequency selective surface: Based on the low emissivity frequency selective surface pattern design results, the infrared low emissivity layer surface is patterned using a laser etching process to obtain an infrared low emissivity frequency selective surface layer, thereby completing the preparation of the composite coating.

[0018] Preferably, in the above-mentioned preparation method, in the step (1), the sandblasting process parameters are: pressure of 0.2-0.5 MPa, sandblasting distance of 50-120 mm, sand particle size of 30-100 μm, and sandblasting time of 1-4 min;

[0019] In the step (2), the atmospheric plasma spraying process parameters are: argon flow rate is 30-38 L / min, hydrogen flow rate is 6-10 L / min; current size is controlled to be 500-550 A, power is 35-40 kW; powder feeding argon flow rate is 1.0-3.0 L / min, powder feeding amount is 15%-25%; spraying distance is 100-140 mm;

[0020] In the step (3), the atmospheric plasma spraying process parameters are: argon flow rate is 25-45 L / min, hydrogen flow rate is 10-15 L / min; the current size is controlled to be 550-650 A, and the power is 38-50 kW; the powder feeding argon flow rate is 2.0-4.0 L / min, and the powder feeding amount is 20%-40%; the spraying distance is 80-130 mm.

[0021] Preferably, in the above-mentioned preparation method, in the step (4), the drying temperature is 130-200°C, and the drying time is 0.5-2h; the sintering process parameters are: peak sintering temperature is 700-950°C, heating rate is 10-25°C / min, sintering time is 10-60min, and sintering atmosphere is air.

[0022] Preferably, in the above-mentioned preparation method, in the step (5), the laser etching process is performed using a picosecond laser, the laser frequency is 400KHz to 1200KHz, the laser power is 60% to 80%, the etching speed is 500 to 900mm / s, and the number of scans is 2 to 5 times.

[0023] Preferably, in the above-mentioned preparation method, the preparation method of the multi-element rare earth high entropy zirconate ceramic material comprises the following steps:

[0024] ① Synthesis of multi-component rare earth high entropy zirconate ceramics: zirconium oxide and rare earth oxide powders are subjected to high-temperature heat treatment at a temperature of 1000-1300°C for a heat treatment time of 2-12h; different oxide powders are weighed according to the stoichiometric ratio, and the oxide powders and deionized water are added to the ball mill in sequence, with a mass ratio of deionized water: oxide powder: zirconium oxide balls of 1:1:3, and mixed on a horizontal ball mill at a rotation speed of 400r / min-600r / min and a stirring time of 24-96h to obtain a ceramic slurry; the ceramic slurry is dried at a drying temperature of 90-120°C for a drying time of 10-48h; and the dried powder is ground and refined, and the ground powder is sieved through a 100-300 mesh sieve, and the sieved powder is subjected to a high-temperature solid-phase synthesis reaction in a high-temperature box furnace at a synthesis reaction temperature of 1400-1700°C for a reaction time of 24-72h to obtain a multi-component rare earth high entropy zirconate ceramic powder;

[0025] ② Ceramic powder granulation: Multinary rare earth high entropy zirconate ceramic powder, deionized water, gum arabic powder and ammonium citrate are mixed evenly by wet ball milling to form a ceramic slurry, and the ceramic slurry is prepared into spherical particles by spray drying to obtain multinary rare earth high entropy zirconate ceramic material; the specific parameters are: the mass fraction of the deionized water is 45-65%, the mass fraction of the gum arabic powder is 0.8-3.5%, and the mass fraction of the ammonium citrate is 1-4%; The ball milling process is to mix on a horizontal ball mill, the mass ratio of deionized water: ceramic powder: zirconium oxide balls is 1:1:3, the rotation speed of the horizontal ball mill is 400r / min~600r / min, and the stirring time is 24~96h; the spray drying process parameters are: outlet temperature 100~150℃, inlet temperature 200~280℃, slurry feeding speed 1.5~4.0L / min, and atomizing disk rotation speed 15000~20000r / min.

[0026] Preferably, in the above-mentioned preparation method, the preparation method of the high-temperature conductor slurry comprises: mixing glass raw material powders uniformly, melting at a temperature of 1300-1400° C. for 2-4 hours to obtain a glass melt, then directly pouring the glass melt into deionized water for quenching to obtain glass slag, then ball-milling the glass slag into glass powder and uniformly mixing it with precious metal alloy powder to obtain a mixed powder, and finally mixing the mixed powder with an organic carrier and grinding it to obtain a high-temperature conductor slurry;

[0027] The glass raw material powder is mainly composed of the following components in percentage by mass:

[0028] Bi 2 O 3 40%~60%

[0029] RE2 O 3 2%~10%

[0030] Al 2 O 3 1%~5%

[0031] SiO 2 15%~30%

[0032] Li 2 O 3%–8%

[0033] CaO 2%~5%

[0034] MgO 1%~5%

[0035] B 2 O 3 2%~6%

[0036] In the above preparation method, the glass and precious metal mixed powder account for 75% to 80% in the high-temperature conductor slurry, and the organic carrier accounts for 25% to 20% in the coating; the organic carrier is mainly composed of 75% to 85% tributyl citrate, 3% to 7% nitrocellulose and 10% to 25% lecithin with a mass fraction.

[0037] The glass powder and the precious metal alloy powder are mixed in a planetary gravity mixer. The revolution speed of the planetary gravity mixer is 1300 rpm to 1800 rpm, the rotation speed is 35% to 60% of the revolution speed, and the mixing time is 30 min to 60 min.

[0038] The mixing process of the mixed powder of the glass powder and the conductive phase with the organic carrier is carried out in a three-roller grinder, the rotation speed of the three-roller grinder is 200r / min to 450r / min, and the grinding and mixing time is 2h to 4h.

[0039] The viscosity of the high temperature conductor slurry prepared by the above preparation method is 150-280 Pa·s.

[0040] The preparation method of the 950°C high-temperature resistant infrared low-emissivity frequency selective surface coating of the present invention adopts a screen printing process to prepare the infrared low-emissivity coating on the surface of a ceramic layer, and the infrared low-emissivity coating is integrated with the ceramic layer through sintering and curing, and the coating material composition is controlled to achieve the coating's infrared full-band low-emissivity characteristics, thereby solving the coating's temperature resistance and high-temperature infrared low-emissivity characteristics; based on the radar selective wave transmission requirements, a frequency selective surface periodic structure array pattern is designed to achieve radar transmission while having infrared dual-band low-emissivity characteristics, and a laser etching process is used to prepare an infrared low-emissivity layer array pattern, which mainly solves the problem of high-precision dimensional processing of the periodic structure array pattern and realizes the selective function of the low-emissivity frequency selective surface to electromagnetic waves.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The 950°C high temperature resistant infrared low emissivity frequency selective surface coating of the present invention can withstand a high temperature of not less than 950°C, has 3-5μm and 8-14μm dual-band high temperature infrared low emissivity characteristics, and has high radar wave transmission characteristics, high bonding performance, and excellent thermal shock resistance. It effectively solves the contradiction between high radar wave transmission and infrared low emissivity of a single coating surface, promotes the improvement of radar and infrared compatible stealth performance, and meets the new application requirements of aircraft engines, aircraft, etc. for 950°C high temperature resistant low emissivity frequency selective surface materials.

[0043] 2. The present invention adopts a multi-layer gradient structure, and the thermal matching design of each functional layer can alleviate the thermal expansion mismatch between the functional layers, thereby giving the coating excellent thermal shock resistance.

[0044] 3. The present invention adopts a multi-rare earth high-entropy zirconate material system and utilizes the high-entropy effect of multi-rare earth doped ceramic materials to improve the high-temperature thermal expansion characteristics of the coating while exhibiting excellent resistance to high-temperature CMAS corrosion, and giving the coating excellent high-temperature infrared stealth function, thereby realizing the on-demand design of the coating radar wave transmission performance.

[0045] 4. The preparation method of the present invention adopts laser etching process to prepare frequency selective surface pattern, the process is simple, and the pattern size processing accuracy is higher. It has radar wave transmission performance while meeting the infrared low emissivity of 3-5μm and 8-14μm dual-band low emissivity of the coating. At the same time, the high bonding and excellent thermal shock resistance of the coating are guaranteed by optimizing the etching process parameters.

[0046] 5. The high-temperature conductor slurry used in the present invention can be prepared by screen printing and heat treatment process. The rare earth oxide added in the high-temperature conductor slurry can improve the temperature resistance of the coating while regulating the stability of the high-temperature electrical properties of the conductor layer based on the resistance barrier effect. Compared with the precious metal plating process, the low-emissivity coating and the ceramic layer in the composite coating are combined by high-temperature sintering and curing, and it has the advantages of high hardness, strong bonding force, wear resistance, simple process, low cost, and easy preparation of large curved parts.

[0047] 6. The raw materials used in the present invention are simple and easy to obtain, the coating preparation processes used are all mature processes, the equipment is simple, it is easy to realize engineering application, and it is convenient for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0049] Description of main reference numerals:

[0050] 1- low emissivity frequency selective surface layer, 2- ceramic matching layer, 3- transition bonding layer, 4- high temperature metal alloy

[0051] Figure 1 It is a schematic structural diagram of the 950°C high temperature resistant infrared low emissivity frequency selective surface and the composite coating in the present invention.

[0052] Figure 2 It is a schematic diagram of the periodic structural pattern of the low emissivity frequency selective surface layer unit in Example 1 of the present invention.

[0053] Figure 3 This is a diagram of a flat plate sample with a low-emissivity frequency selective surface and a composite coating that is resistant to high temperatures of 950°C in infrared in Example 1 of the present invention.

[0054] Figure 4 This is a microscopic morphology of the 950°C high temperature resistant infrared low emissivity frequency selective surface and the composite coating surface in Comparative Example 1 of the present invention.

[0055] Figure 5 This is a microscopic morphology of the 950°C high temperature resistant infrared low emissivity frequency selective surface and the composite coating etching area in Comparative Example 2 of the present invention.

[0056] Description of main reference numerals:

[0057] 1- low emissivity frequency selective surface layer, 2- ceramic matching layer, 3- transition bonding layer, 4- high temperature metal alloy DETAILED DESCRIPTION

[0058] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0059] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0060] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0061] Example 1

[0062] like Figure 1 As shown, a 950°C high temperature infrared low emissivity frequency selective surface coating comprises, from the inside to the outside, a high temperature nickel-based alloy, a CoNiCrAlY layer, (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic layer and low emissivity frequency selective surface layer; wherein the thickness of the CoNiCrAlY layer is 0.08mm, (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 The thickness of the ceramic layer is 0.90 mm, the thickness of the low emissivity frequency selective surface layer is 0.013 mm, and the total thickness of the coating is 0.993 mm. The unit periodic structure size a of the low emissivity frequency selective surface layer is 0.65 mm, the side length of the patch is a×x, and x is 0.83, such as Figure 2 The low emissivity frequency selective surface layer is made of high melting point Bi 2 O 3 -RE 2 O 3 -SiO 2 It is composed of glass-ceramic bonding phase and Pt conductive phase. 2 O 3 -RE 2 O 3 -SiO 2The mass ratio of Bi-crystalline glass to Pt is 20:80. 2 O 3 -RE 2 O 3 -SiO 2 The mass percentages of the raw materials of each component in the microcrystalline glass are: Bi 2 O 3 50%, La 2 O 3 6%,Gd 2 O 3 3%,Al 2 O 3 3%, SiO 2 22%, Li 2 O4%, CaO 3%, MgO 4%, B 2 O 3 5%.

[0063] The preparation method of the 950°C high temperature resistant infrared low emissivity frequency selective surface coating of this embodiment comprises the following steps:

[0064] (1) The high-temperature nickel-based alloy is placed in a sandblasting machine for surface roughening treatment by sandblasting process, the sandblasting pressure is controlled to be 0.4 MPa, the sandblasting distance is 120 mm, the sand particle size is 60-100 μm, and the sandblasting time is 3 min;

[0065] (2) A CoNiCrAlY transition bonding layer was prepared on the high-temperature nickel-based alloy roughened in step (1) by an atmospheric plasma spraying process, wherein the process parameters were as follows: an argon flow rate of 35 L / min, a hydrogen flow rate of 9 L / min; a current of 530 A, a power of 36 kW; a powder feeding argon flow rate of 2.5 L / min, a powder feeding amount of 20%; and a spraying distance of 100 mm;

[0066] (3) With (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic material is used as raw material, and a high-bonding, low-stress ceramic matching layer is sprayed on the surface of the transition bonding layer prepared in step (2) by plasma spraying process. The process parameters are: argon flow rate is 36L / min, hydrogen flow rate is 12L / min; current size is controlled to be 580A, power is 42kW; powder feeding argon flow rate is 3.0L / min, powder feeding amount is 25%; spraying distance is 100mm;

[0067] (4) applying a high temperature conductor slurry to the surface of the ceramic matching layer prepared in step (3) by screen printing, and obtaining a low emissivity layer after drying and sintering; the drying temperature is 150° C., and the drying time is 1 h; the sintering process parameters are: peak sintering temperature is 900° C., heating rate is 20° C. / min, sintering time is 10 min, and sintering atmosphere is air;

[0068] (5) patterning the low emissivity layer of step (4) using a laser etching process, wherein the laser etching is performed using a picosecond laser, the laser frequency is 800 kHz, the laser power is 70%, the etching speed is 800 mm / s, and the number of scans is 2 times;

[0069] In step (3), (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 The method for preparing the ceramic material comprises the following steps:

[0070] ① The zirconium oxide, lanthanum oxide, europium oxide, neodymium oxide, gadolinium oxide and samarium oxide powders are heat treated at 1000°C for 2h, the zirconium oxide, lanthanum oxide, europium oxide, neodymium oxide, gadolinium oxide and samarium oxide powders are mixed in a molar ratio of 5:1:1:1:1, and the mixed ceramic powder and 50wt% of deionized water are sequentially added to a ball mill, and the mixed ceramic powder is mixed by a horizontal ball mill to obtain a ceramic slurry, wherein the mass ratio of deionized water: mixed ceramic powder: zirconium oxide ball is 1:1:3, the rotation speed of the horizontal ball mill is 500r / min, and the ball milling time is 36h; the ceramic slurry is dried at 100°C for 16h, and the dried powder is ground and sieved through a 200-mesh sieve, and the sieved powder is subjected to a high-temperature solid-phase synthesis reaction at 1600°C in a high-temperature box furnace for 36h to obtain (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic powder;

[0071] ② Will (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7The ceramic powder was added with 50% deionized water, 2.0% gum arabic powder and 3.0% triammonium citrate in mass percentage in sequence, and mixed evenly by ball milling process, the mass ratio of deionized water: ceramic powder: zirconium oxide ball was 1:1:3, the rotation speed of the horizontal ball mill was 500r / min, and the stirring time was 24h; and then the spray drying process was used to prepare spherical powder particles with certain fluidity and uniform particle size distribution, namely (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic material; spray drying process parameters are: outlet temperature 120℃, inlet temperature 230℃, slurry feeding speed 2L / min, atomizing disk speed 18000r / min.

[0072] In step (4), the high temperature conductor slurry is prepared by the following method: mixing glass raw material powders uniformly and then melting them at a temperature of 1300° C. for 5 hours to obtain a glass melt, then directly pouring the glass melt into deionized water for quenching to obtain glass slag, then ball-milling the glass slag into glass powder and uniformly mixing it with a precious metal Pt alloy powder to obtain a mixed powder, and finally mixing the mixed powder with an organic carrier and grinding it to obtain a high temperature conductor slurry;

[0073] The mixing process of glass powder and precious metal Pt alloy powder is carried out in a planetary gravity mixer. The revolution speed of the planetary gravity mixer is 1300rpm, the rotation speed is 40% of the revolution speed, and the mixing time is 60min. The mixing process of the mixed powder of glass and conductive phase and the organic carrier is carried out in a three-roll mill. The rotation speed of the three-roll mill is 400r / min, and the grinding and mixing time is 4h.

[0074] Bi in high temperature conductor paste 2 O 3 -RE 2 O 3 -SiO 2 The glass phase of the microcrystalline glass and the Pt mixed powder account for 77% by mass, and the organic carrier accounts for 23%; the organic carrier is mainly composed of 85% by mass of tributyl citrate, 6% by mass of cellulose nitrate and 9% by mass of lecithin; the viscosity of the high-temperature conductor slurry is 200 Pa·s.

[0075] The flat plate sample with infrared low emissivity and frequency selective surface coating resistant to 950°C prepared in this embodiment is as follows: Figure 3As shown, the total thickness of the composite coating is only 0.993mm, and the bonding strength is 9.5MPa; the pattern prepared in this implementation case is clear, complete and has no adhesion, the actual side length of the etched patch unit size is 0.547mm, the side length design value of the unit periodic structure is 0.540mm, and the etching accuracy reaches ±0.01mm, which meets the design requirements. Meets the design requirements. The infrared emissivity of the coating in the 3-5μm and 8-14μm bands at 950℃ is 0.23 and 0.25 respectively, and the radar transmittance of the coating in the 8-18GHz frequency band is greater than 90%. The number of heat cycles from 950°C to room temperature and air cooling was greater than 500 times. After the coating was subjected to 950°C for a total of 200 hours and 750°C for a total of 400 hours, the coating was intact without obvious cracking, falling off, delamination, etc. After the temperature resistance test, the infrared emissivity of the coating in the 3-5μm and 8-14μm bands at 950°C was 0.28 and 0.29, respectively, indicating that the high-temperature infrared low-emissivity frequency selective surface and composite coating prepared in this embodiment have excellent high temperature resistance, thermal shock resistance, infrared stealth, and high radar wave transmittance.

[0076] Example 2

[0077] A 950°C high temperature infrared low emissivity frequency selective surface coating, which includes a high temperature nickel-based alloy, a CoNiCrAlY layer, (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic layer and low emissivity frequency selective surface layer; wherein the thickness of the CoNiCrAlY layer is 0.06mm, (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 The thickness of the ceramic layer is 0.87 mm, the thickness of the low emissivity frequency selective surface layer is 0.015 mm, and the total thickness of the coating is 0.945 mm. The unit periodic structure size a of the low emissivity frequency selective surface layer is 0.71 mm, the patch side length is a×x, and x is 0.9. 2 O 3 -RE 2 O 3 -SiO 2 The mass ratio of the glass phase to the Pt content in the glass-ceramic is 20:80. 2 O 3 -RE2 O 3 -SiO 2 The mass percentages of the raw materials of each component in the microcrystalline glass are: Bi 2 O 3 50%, La 2 O 3 6%,Gd 2 O 3 3%,Al 2 O 3 3%, SiO 2 22%, Li 2 O 4%, CaO 3%, MgO 4%, B 2 O 3 5%.

[0078] The preparation method of the 950°C high temperature resistant infrared low emissivity frequency selective surface coating of this embodiment comprises the following steps:

[0079] (1) The high-temperature nickel-based alloy is placed in a sandblasting machine for surface roughening treatment by sandblasting process, the sandblasting pressure is controlled to be 0.4 MPa, the sandblasting distance is 120 mm, the sand particle size is 60-100 μm, and the sandblasting time is 3 min;

[0080] (2) A CoNiCrAlY transition bonding layer was prepared on the metal substrate of step (1) by using an atmospheric plasma spraying process, wherein the process parameters were as follows: an argon flow rate of 35 L / min, a hydrogen flow rate of 9 L / min; a current of 530 A, a power of 36 kW; a powder feeding argon flow rate of 2.5 L / min, a powder feeding amount of 20%; and a spraying distance of 100 mm;

[0081] (3) With (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic material is used as raw material, and a high-bonding, low-stress ceramic matching layer is sprayed on the surface of the transition bonding layer prepared in step (2) by plasma spraying process. The process parameters are: argon flow rate is 36L / min, hydrogen flow rate is 12L / min; current size is controlled to be 580A, power is 42kW; powder feeding argon flow rate is 3.0L / min, powder feeding amount is 25%; spraying distance is 100mm;

[0082] (4) applying a high temperature conductor slurry to the surface of the ceramic matching layer prepared in step (3) by screen printing, and obtaining a low emissivity layer after drying and sintering; the drying temperature is 150° C., and the drying time is 1 h; the sintering process parameters are: peak sintering temperature is 900° C., heating rate is 20° C. / min, sintering time is 10 min, and sintering atmosphere is air;

[0083] (5) patterning the low emissivity layer of step (4) using a laser etching process, wherein the laser etching is performed using a picosecond laser, the laser frequency is 1100 kHz, the laser power is 80%, the etching speed is 500 mm / s, and the number of scans is 2 times;

[0084] In step (3), (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 The method for preparing the ceramic material comprises the following steps:

[0085] ① The zirconium oxide, lanthanum oxide, europium oxide, neodymium oxide, gadolinium oxide and samarium oxide powders are heat treated at 1000°C for 2h, the zirconium oxide, lanthanum oxide, europium oxide, neodymium oxide, gadolinium oxide and samarium oxide powders are mixed in a molar ratio of 5:1:1:1:1, and then the mixed ceramic powder and 50wt% of deionized water are sequentially added to a ball mill, and a ceramic slurry is obtained by mixing through a wet ball milling process, wherein the mass ratio of deionized water: mixed ceramic powder: zirconium oxide ball is 1:1:3, the rotation speed of the horizontal ball mill is 500r / min, and the stirring time is 36h; the ceramic slurry is dried at 100°C for 16h, and the dried powder is ground and sieved through a 200-mesh sieve, and the sieved powder is subjected to a high-temperature solid-phase synthesis reaction at 1600°C in a high-temperature box furnace for 36h to obtain (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic powder.

[0086] ② Will (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7The ceramic powder was added with 50% deionized water, 2.0% gum arabic powder and 3.0% triammonium citrate in mass percentage in sequence, and mixed evenly by ball milling process, the mass ratio of deionized water: ceramic powder: zirconium oxide ball was 1:1:3, the rotation speed of the horizontal ball mill was 500r / min, and the stirring time was 24h; and then the spray drying process was used to prepare spherical powder particles with certain fluidity and uniform particle size distribution, namely (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 G 0.2 ) 2 Zr 2 O 7 Ceramic material; spray drying process parameters are: outlet temperature 120℃, inlet temperature 230℃, slurry feeding speed 2L / min, atomizing disk speed 18000r / min.

[0087] In step (4), the high temperature conductor slurry is prepared by the following method: mixing glass raw material powders uniformly and then melting them at a temperature of 1300° C. for 5 hours to obtain a glass melt, then directly pouring the glass melt into deionized water for quenching to obtain glass slag, then ball-milling the glass slag into glass powder and uniformly mixing it with a precious metal Pt alloy powder to obtain a mixed powder, and finally mixing the mixed powder with an organic carrier and grinding it to obtain a high temperature conductor slurry;

[0088] The mixing process of glass powder and precious metal Pt alloy powder is carried out in a planetary gravity mixer. The revolution speed of the planetary gravity mixer is 1300rpm, the rotation speed is 40% of the revolution speed, and the mixing time is 60min. The mixing process of the mixed powder of glass and conductive phase and the organic carrier is carried out in a three-roll mill. The rotation speed of the three-roll mill is 400r / min, and the grinding and mixing time is 4h.

[0089] Bi 2 O 3 -RE 2 O 3 -SiO 2 The glass phase of the microcrystalline glass and the Pt mixed powder account for 76%, and the organic carrier in the high-temperature conductor slurry accounts for 24%; the organic carrier is mainly composed of 83% tributyl citrate, 5% nitrocellulose and 12% lecithin by mass; the viscosity of the high-temperature conductor slurry is 210Pa·s.

[0090] The total thickness of the 950℃ high temperature infrared low emissivity frequency selective surface coating prepared in this embodiment is only 0.945mm, and the bonding strength is 9.7MPa; the pattern prepared in this embodiment is clear, complete and has no adhesion, and the unit periodic structure dimensional accuracy reaches ±0.01mm, meeting the design requirements. The infrared emissivity of the coating in the 3-5μm and 8-14μm bands under 950℃ conditions is 0.23 and 0.26 respectively. The coating falls off after 330 cycles of air cooling from 950℃ to room temperature. The coating falls off after 200 hours at 950℃ and 330 hours at 750℃. Since the laser power of this embodiment is increased compared with that of Example 1, the etching area of ​​the coating is subjected to local high temperature, resulting in the high temperature resistance and thermal shock resistance of the high temperature infrared low emissivity frequency selective surface prepared in this embodiment and the composite coating being lower than that of Example 1, but meeting the design requirements.

[0091] Comparative Example 1:

[0092] The difference between this comparative example and Example 1 is that the low emissivity frequency selective surface layer pattern is prepared by screen printing technology, the parameters and preparation method of steps (1), (2) and (3) are the same as those of Example 1, and when performing the screen printing process in step (4), the pattern processing is directly carried out by screen printing technology, and the other parameters and preparation methods are the same as those of Example 1.

[0093] The total thickness of the 950°C high temperature resistant infrared low emissivity frequency selective surface coating prepared in this comparative example is only 0.994 mm, and the bonding strength is 9.4 MPa; Figure 4 As shown, the pattern prepared in this comparative case has adhesion, and the dimensional accuracy of the coating cannot be guaranteed. The infrared emissivity of the coating prepared in this comparative case at 950°C in the 3-5μm and 8-14μm bands is 0.19 and 0.20 respectively, and the radar transmittance of the coating in the 8-18GHz frequency band is only 63%. This is because the unit periodic structure pattern prepared by the screen printing process has adhesion, and the area proportion of the infrared low emissivity layer has increased, resulting in a decrease in the infrared emissivity of the entire infrared low emissivity frequency selective surface layer, and the radar transmittance has also decreased significantly, which cannot meet the radar wave transmission performance.

[0094] Comparative Example 2:

[0095] The difference between this comparative example and Example 1 is that the low-emissivity frequency-selective surface layer pattern laser etching process uses a picosecond laser for processing, the laser frequency is 1500KHz, the laser power is 90%, the etching speed is 400mm / s, and the number of scans is 2 times; other parameters and preparation methods are the same as Example 1.

[0096] The total thickness of the 950°C high temperature infrared low emissivity frequency selective surface coating prepared in this comparative example is only 0.991mm, and the bonding strength is 5.6MPa; the pattern prepared in this implementation case is clear and complete without adhesion, and the unit periodic structure dimensional accuracy reaches ±0.01mm, which meets the design requirements. However, compared with Example 1, the ceramic layer in the etched area of ​​this comparative example has obvious microcrack defects, such as Figure 5 As shown. Under 950℃ condition, the infrared emissivity of the coating in the 3-5μm and 8-14μm bands is 0.24 and 0.27 respectively, and the radar transmittance of the coating in the 8-18GHz frequency band is greater than 90%. After 230 cycles of air cooling from 950℃ to room temperature, the coating showed local stratification and shedding. After the coating was subjected to 950℃ for a total of 150 hours, obvious cracks, shedding, and stratification appeared in the coating. Due to the excessive laser etching power and frequency, the thermal stress on the ceramic layer in the etching area was also significantly increased, which seriously affected the bonding state of the coating interface, indicating that the high-temperature infrared low-emissivity frequency selective surface and composite coating prepared by laser etching process in this embodiment have high temperature resistance and thermal shock resistance that do not meet the application requirements.

[0097] Comparative Example 3:

[0098] The difference between this comparative example and Example 1 is that the unit periodic structure size a of the low-emissivity frequency selective surface layer pattern is 1.4 mm, the patch side length is a×x, and x is 0.6; other parameters and preparation methods are the same as Example 1.

[0099] The total thickness of the high-temperature infrared low-emissivity frequency selective surface coating on the surface of the high-temperature metal alloy prepared in this comparative example is 0.997 mm, and the bonding strength is 9.7 MPa; the pattern prepared in this comparative example is clear, complete and has no adhesion, and the infrared emissivities of the coating in the 3-5μm and 8-14μm bands at 950°C are 0.29 and 0.64 respectively. The high-temperature infrared low-emissivity frequency selective surface coating prepared in this comparative example cannot meet the infrared dual-band low emissivity requirements.

[0100] Comparative Example 4:

[0101] The difference between this comparative example and Example 1 is that the unit periodic structure size a of the low emissivity frequency selective surface layer pattern is 1.5 mm, the patch side length is a×x, and x is 0.85; other parameters and preparation methods are the same as Example 1.

[0102] The total thickness of the high-temperature infrared low-emissivity frequency selective surface coating on the surface of the high-temperature metal alloy prepared in this comparative example is 0.995 mm, and the bonding strength is 9.5 MPa; the pattern prepared in this comparative example is clear, complete and has no adhesion. The infrared emissivities of the coating in the 3-5μm and 8-14μm bands at 950°C are 0.21 and 0.41 respectively, which cannot meet the infrared dual-band low emissivity requirements.

[0103] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A 950°C high temperature resistant infrared low emissivity frequency selective surface coating and a preparation method thereof, characterized in that: The coating is applied on the surface of the base material, and includes a transition bonding layer, a ceramic matching layer and an infrared low emissivity frequency selective surface layer from the inside to the outside; the patch unit periodic structure size a of the infrared low emissivity frequency selective surface layer is 0.5-0.9 mm, the unit side length is a×x, and x is 0.8-0.95, and it is composed of high melting point Bi2O3-RE2O3-SiO2 series microcrystalline glass as the bonding phase and high temperature oxidation resistant precious metal alloy powder as the conductive phase.

2. The 950°C high temperature resistant infrared low emissivity frequency selective surface coating according to claim 1, characterized in that: The thickness of the transition bonding layer is 0.05 mm to 0.10 mm, the thickness of the ceramic matching layer is 0.10 mm to 1.00 mm, and the thickness of the low emissivity frequency selective surface layer is 0.01 mm to 0.05 mm.

3. The 950°C high temperature resistant infrared low emissivity frequency selective surface coating according to claim 1, characterized in that: The substrate material is a high-temperature nickel-based alloy, a high-temperature iron-based alloy, a high-temperature nickel-based single crystal or a Ni3Al alloy, and the transition bonding layer is NiCrAlY, CoNiCrAlY, CoCrAlSiY or NiCoCrAlHfYSi.

4. The 950°C high temperature resistant infrared low emissivity frequency selective surface coating according to claim 1, characterized in that: The ceramic matching layer is a multi-component rare earth high entropy zirconate (5RE 0.2 )2Zr2O7, the RE is five of La, Gd, Nd, Sm, Sc, Yb, Lu, Dy, Ho, and Eu.

5. The 950°C high temperature resistant infrared low emissivity frequency selective surface coating according to claim 1, characterized in that: The conductive phase is one or more alloys of Ag, Pd, Au and Pt, and the mass fraction of the conductive phase in the coating is 75-80%.

6. A method for preparing a 950°C high temperature resistant infrared low emissivity frequency selective surface coating as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Surface roughening of the substrate material: The surface of the substrate material is roughened by sandblasting; (2) Preparation of transition bonding layer: preparing a transition bonding layer on the base material of step (1) by using an atmospheric plasma spraying process; (3) Preparation of ceramic matching layer: using multi-component rare earth high entropy zirconate ceramic material as raw material, and using a plasma spraying process to spray a ceramic matching layer on the surface of the transition bonding layer prepared in step (2); (4) Preparation of infrared low emissivity layer: applying a high-temperature conductor slurry prepared by mixing high-melting-point microcrystalline glass and precious metal alloy powder to the surface of the ceramic matching layer in step (3) by screen printing, and obtaining an infrared low emissivity layer after drying and sintering; (5) Preparation of low emissivity frequency selective surface: Based on the low emissivity frequency selective surface pattern design results, the infrared low emissivity layer surface is patterned using a laser etching process to obtain an infrared low emissivity frequency selective surface layer, thereby completing the preparation of the composite coating.

7. The preparation method according to claim 6, characterized in that: In the step (3), the atmospheric plasma spraying process parameters are: argon flow rate is 25-45 L / min, hydrogen flow rate is 10-15 L / min; the current size is controlled to be 550-650 A, and the power is 38-50 kW; the powder feeding argon flow rate is 2.0-4.0 L / min, and the powder feeding amount is 20%-40%; the spraying distance is 80-130 mm.

8. The preparation method according to claim 6, characterized in that: In the step (4), the drying temperature is 130 to 200° C. and the drying time is 0.5 to 2 hours; The sintering process parameters are as follows: peak sintering temperature is 700-950°C, heating rate is 10-25°C / min, sintering time is 10-60min, and sintering atmosphere is air.

9. The preparation method according to claim 6, characterized in that: In the step (5), the laser etching process is performed using a picosecond laser, the laser frequency is 400KHz to 1200KHz, the laser power is 60% to 80%, the etching speed is 500 to 900mm / s, and the number of scans is 2 to 5 times.

10. The preparation method according to claim 6, characterized in that: The preparation method of the multi-element rare earth high entropy zirconate ceramic material comprises the following steps: ① Synthesis of multi-component rare earth high entropy zirconate ceramics: zirconium oxide, rare earth oxides and deionized water are added to a ball mill in proportion, and mixed by a wet ball milling process to obtain a ceramic slurry; the ceramic slurry is dried, ground and refined, and then subjected to a high-temperature solid phase synthesis reaction at a reaction temperature of 1400 to 1700°C and a reaction time of 24 to 72 hours to obtain a multi-component rare earth high entropy zirconate ceramic powder; ② Ceramic powder granulation: The multi-component rare earth high entropy zirconate ceramic powder, deionized water, gum arabic powder and triammonium citrate are mixed evenly by a wet ball milling process to form a ceramic slurry, and the ceramic slurry is prepared into spherical particles by a spray drying process to obtain a multi-component rare earth high entropy zirconate ceramic material.

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