Frequency-selective high-temperature-resistant wave-absorbing anti-oxidation coating and preparation method thereof

Abstract

The invention discloses a frequency-selective high-temperature-resistant wave-absorbing anti-oxidation coating and a preparation method thereof. The frequency-selective high-temperature-resistant wave-absorbing anti-oxidation coating comprises a transition layer, a dielectric layer, a frequency selective surface layer and a surface protection layer which are sequentially arranged from inside to outside, the transition layer is SiC ceramic, the dielectric layer and the surface protection layer are yttrium oxide partially stabilized zirconia coatings, and the frequency selective surface layer is a FeCrAl coating. The frequency-selective high-temperature-resistant wave-absorbing anti-oxidation coating disclosed by the invention realizes high temperature resistance, wave-absorbing performance and anti-oxidation performance of the coating, and can adapt to a more complex working environment.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic wave absorbing materials, and relates to a frequency selective high temperature resistant wave absorbing and anti-oxidation coating and a preparation method thereof. Background Art

[0002] With the rapid development of aerospace and national defense, especially in the field of stealth thermal protection materials, the performance requirements for materials are becoming increasingly stringent. The stability, thermal fatigue resistance, and oxidation resistance of these materials in extreme environments, especially under conditions of high temperature, severe aerodynamic heat load, and strong radiation, are constantly increasing. In-depth research on the behavior of materials under these harsh conditions has become a key factor in improving the performance of stealth thermal protection materials and promoting technological progress in military equipment. Therefore, studying the performance of materials in extreme environments is not only crucial to the development of materials science, but also an important measure to enhance the strength of national defense science and technology and ensure national security. For modern aircraft, stealth performance is often crucial, and the material's wave absorption ability is directly related to the concealment and survivability of weapons and equipment.

[0003] Carbon / carbon composites are carbon-based composites with carbon fibers or graphite fibers as reinforcements. As a cutting-edge high-performance material, they have a series of excellent comprehensive properties such as light weight, high specific strength, high specific modulus and ultra-high temperature resistance. Even in extreme environments with temperatures exceeding 2000°C, carbon / carbon composites can still maintain good mechanical properties, which makes it an ideal lightweight structural material in the aerospace field. It has immeasurable value in reducing aircraft weight and improving flight efficiency.

[0004] However, in a high-temperature oxygen environment, carbon / carbon composites show extremely strong oxidation sensitivity. Once in such an environment, oxidation reactions will rapidly occur on the surface of the material, resulting in a sharp decline in performance or even complete failure. This greatly limits its application in the aerospace field, especially in components that need to withstand high temperatures for a long time. In addition, carbon / carbon composites have high conductivity, will reflect electromagnetic waves, and have weak electromagnetic wave absorption capabilities. The above limitations of carbon / carbon composites have become a key factor restricting their application as stealth thermal protection structural materials. Therefore, it is necessary to develop carbon / carbon composite absorbing and anti-oxidation coatings that can serve at high temperatures. Summary of the invention

[0005] The purpose of the present invention is to provide a frequency selective high temperature resistant wave absorbing and anti-oxidation coating and a preparation method thereof, so as to solve the problem that carbon / carbon composite materials have oxidation sensitivity at high temperature and insufficient wave absorbing ability.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A frequency selective high temperature resistant wave absorbing and oxidation resistant coating, comprising a transition layer, a dielectric layer, a frequency selective surface layer and a surface protective layer arranged in sequence from the inside to the outside; The transition layer is SiC ceramics, the dielectric layer and the surface protection layer are both yttria partially stabilized zirconia coatings, and the frequency selective surface layer is FeCrAl coating.

[0007] Furthermore, the thickness of the transition layer is 70-200 μm, the thickness of the dielectric layer is 1-1.5 mm, the thickness of the frequency selective surface layer is 10-100 μm, and the thickness of the surface protection layer is 20-100 μm.

[0008] Furthermore, a cross-shaped pattern is provided on the frequency selective surface layer by means of a mask.

[0009] A method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating comprises: SiC ceramics are prepared on the pretreated substrate by embedding method to form a transition layer; The transition layer is preheated, and a yttria-partially stabilized zirconium oxide layer is prepared on the surface of the preheated transition layer by a plasma spraying method to form a dielectric layer; A mask is laid on the dielectric layer, and a FeCrAl coating is sprayed thereon by a plasma spraying method to form a frequency selective surface layer with a cross-shaped pattern; A yttria partially stabilized zirconia coating is sprayed on the frequency selective surface layer by a plasma spraying method to form a surface protective layer, thereby obtaining a frequency selective high temperature resistant wave absorbing and oxidation resistant coating.

[0010] Furthermore, the pretreatment process of the substrate includes: The substrate is placed in anhydrous ethanol, surface impurities are removed by ultrasonic cleaning, and then the substrate is dried; The temperature of the drying process is 80-100° C., and the time of the drying process is 5-6 hours.

[0011] Furthermore, the method for preparing SiC ceramics on a pretreated substrate by the embedding method comprises: Si powder, C powder and Al2O3 powder were mixed and ball-milled for 2-8 hours in a mass ratio of 6-9:1-4:1-4 to prepare a mixed powder; The pretreated substrate is fully coated with the mixed powder, and heat treated at 1700-2100°C in an Ar atmosphere, kept at this temperature for 1-4 hours, and then cooled to room temperature; After the heat treatment is completed, the surface residue is removed to obtain the SiC ceramic coated on the substrate.

[0012] Furthermore, the temperature of the preheating treatment is 70-170° C., and the time of the preheating treatment is 10-20 minutes.

[0013] Furthermore, the spraying process of the yttria partially stabilized zirconia layer includes: current of 220-290A, voltage of 80-150V, spraying distance of 80-120mm, main gas flow of 60-65splm, and auxiliary gas flow of 2.2-3.2splm.

[0014] Furthermore, the spraying process of the FeCrAl coating includes: a current of 200-240A, a voltage of 80-100V, a spraying distance of 80-120mm, a main gas flow rate of 60-65splm, and an auxiliary gas flow rate of 2.2-3.2splm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a frequency selective high temperature resistant wave absorbing and anti-oxidation coating, comprising a transition layer, a dielectric layer, a frequency selective surface layer and a surface protective layer sequentially arranged on the surface of a substrate from the inside to the outside, wherein the transition layer is a SiC ceramic matching the thermal expansion coefficient of a carbon / carbon composite material, ensuring that the coating and the substrate have similar thermal expansion behaviors when the temperature changes, thereby effectively avoiding the problem of cracking or peeling of the coating caused by thermal stress differences, and greatly enhancing the high temperature resistance and long-term stability of the coating. The dielectric layer is a low dielectric constant yttria partially stabilized zirconia coating, which has a high melting point, low thermal conductivity, good chemical stability and wave transmission characteristics. By introducing the concept of a super surface, the yttria partially stabilized zirconia is used as a dielectric layer, and a periodic structure super surface is prepared on its surface, and a sudden phase is introduced at the interface reflection of the electromagnetic wave, and the principle of interference destructiveness is used to achieve effective absorption of electromagnetic waves in a specific frequency band. The frequency selective surface layer is a highly conductive FeCrAl layer, which can selectively absorb electromagnetic waves of a specific frequency. The surface protective layer is a yttria partially stabilized zirconia coating with good oxidation resistance, which can effectively resist oxidation erosion in high temperature environments and extend the service life of the coating. The frequency selective high temperature resistant wave absorbing and oxidation resistant coating prepared by the present invention realizes the high temperature resistance, wave absorption and oxidation resistance of the coating, and can adapt to more complex working environments, such as extreme conditions such as high temperature and strong electromagnetic radiation.

[0016] The present invention also provides a method for preparing a frequency selective high temperature resistant wave absorbing and anti-oxidation coating, wherein a SiC ceramic transition layer is prepared on a substrate by an embedding method; a yttria partially stabilized zirconium oxide dielectric layer is then prepared by a plasma spraying method; a frequency selective surface FeCrAl coating is then prepared by a plasma spraying method; and finally, a yttria partially stabilized zirconium oxide surface protective layer is prepared by a plasma spraying method to obtain a frequency selective high temperature resistant wave absorbing and anti-oxidation coating. The embedding method is used to prepare the transition layer, which can provide a relatively uniform coating distribution and a good interface bonding force, and is helpful to improve the overall stability and service life of the coating. Subsequently, a dielectric layer, a frequency selective surface layer and a surface protective layer are prepared by a plasma spraying method. The plasma spraying method has the advantages of high efficiency, good coating quality, and high bonding strength between the coating and the substrate, and can ensure a relatively close bonding between the layers, which can significantly improve the production efficiency, thereby improving the overall performance of the coating. The present invention can accurately control the electromagnetic properties, high temperature resistance and anti-oxidation properties of the coating by selecting different materials and preparation processes. At the same time, there is good connectivity between the steps, which reduces unnecessary repetitive labor and material waste, thereby reducing the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. The following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a schematic structural diagram of a frequency selective high temperature resistant, microwave absorbing and anti-oxidation coating prepared in Example 1 of the present invention.

[0019] Figure 2 This is a reflection loss diagram of the frequency selective high temperature resistant wave absorbing and anti-oxidation coating prepared in Example 1 of the present invention at room temperature. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0022] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0023] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0024] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0025] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0026] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0027] The present invention is described in further detail below: The present invention provides a frequency selective high temperature resistant wave absorbing and oxidation resistant coating, comprising a transition layer, a dielectric layer, a frequency selective surface layer and a surface protection layer arranged in sequence from the inside to the outside. The transition layer is SiC ceramics having a thermal expansion coefficient similar to that of a carbon / carbon composite material, the dielectric layer is a yttria partially stabilized zirconia coating with a certain thickness and a low dielectric constant, the frequency selective surface layer adopts a highly conductive FeCrAl coating, and the surface protection layer is made of the same material as the dielectric layer, and adopts yttria partially stabilized zirconia with good oxidation resistance.

[0028] The thickness of the transition layer is 70~200μm, the thickness of the dielectric layer is 1~1.5mm, the thickness of the frequency selective surface layer is 10~100μm, the thickness of the surface protection layer is 20~100μm, and a cross-patterned frequency selective surface is prepared by masking.

[0029] The present invention also provides a method for preparing a frequency selective high temperature resistant wave absorbing and anti-oxidation coating, which specifically comprises the following steps: Step 1: Process the carbon / carbon composite into appropriate dimensions.

[0030] Step 2: Substrate pretreatment: Place the carbon / carbon composite material in anhydrous ethanol for ultrasonic cleaning for 2 to 3 hours to remove surface impurities, and then dry it at 80 to 100° C. for 5 to 6 hours.

[0031] Step 3: Preparation of transition layer. A SiC ceramic transition layer is prepared on a carbon / carbon composite material substrate by an embedding method. During the preparation process using the embedding method, the process is as follows: ① Si powder, C powder, and Al2O3 powder are mixed in a mass ratio of 6~9:1~4:1~4 and ball-milled for 2~8 hours to make a mixed powder; ② The mixed powder and the C / C composite material sample are placed in a graphite crucible, and the mixed powder fully wraps the C / C composite material sample; ③ The sealed graphite crucible is placed in a high-temperature heat treatment furnace, and heat-treated in an Ar atmosphere at a temperature of 1700~2100°C, and then cooled to room temperature with the furnace after keeping warm for 1~4 hours; ④ After the heat treatment is completed, it is taken out from the crucible, and the surface residue is removed to obtain SiC ceramics coated on the C / C composite material sample.

[0032] Step 4: Preparation of dielectric layer, drying 8YSZ powder at 70~110℃ for 1~4h, preheating the embedded carbon / carbon composite material at 70~170℃ for 10~20min to improve the bonding strength between the coating and the substrate. Plasma spraying was used to prepare yttria partially stabilized zirconia 8YSZ coating on the surface of the transition layer. During the preparation process, the current was set to 220~290A, the voltage was 80~150V, the spraying distance was 80~120mm, the main gas flow rate was 60~65splm, and the auxiliary gas flow rate was 2.2~3.2splm.

[0033] Step 5: Preparation of frequency selective surface layer. Dry the FeCrAl powder at 70~170℃ for 1~4h. Use plasma spraying method to lay a mask on the dielectric layer first, and then spray FeCrAl coating on it to prepare a cross-pattern frequency selective surface. During the spraying process, set the current to 200~240A, the voltage to 80~100V, the spraying distance to 80~120mm, the main gas flow rate to 60~65splm, and the auxiliary gas flow rate to 2.2~3.2splm.

[0034] Step 6: Preparation of the surface protection layer. Use plasma spraying to spray the yttria partially stabilized zirconia coating on the frequency selective surface layer. During the spraying process, set the current to 220~290A, the voltage to 80~150V, the spraying distance to 80~120mm, the main gas flow rate to 60~65splm, and the auxiliary gas flow rate to 2.2~3.2splm, and finally obtain the required frequency selectively designed high temperature resistant, microwave absorbing and antioxidant coating.

[0035] The present invention is further described in detail below in conjunction with specific embodiments: Embodiment 1: (1) Substrate pretreatment: The carbon / carbon composite material is processed into the required size, and the substrate is placed in anhydrous ethanol for ultrasonic cleaning for 2 h to remove impurities, and then placed in an oven for treatment at 80 ° C for 5 h, and then taken out for use.

[0036] (2) Preparation of transition layer: A 70 μm SiC ceramic transition layer was prepared on the surface of the pretreated carbon / carbon composite material by the embedding method. During the preparation process by the embedding method, the process is as follows: ① Si powder, C powder and Al2O3 powder were mixed in a mass ratio of 9:1:1 and ball-milled for 2 h to prepare a mixed powder; ② The mixed powder and the C / C composite material sample were placed in a graphite crucible, and the mixed powder fully wrapped the C / C composite material sample; ③ The sealed graphite crucible was placed in a high-temperature heat treatment furnace and heat treated in an Ar atmosphere at a temperature of 1700°C. After keeping the heat for 1 h, it was cooled to room temperature with the furnace; ④ After the heat treatment was completed, it was taken out from the crucible, and the surface residue was removed to obtain SiC ceramic coated on the C / C composite material sample.

[0037] (3) Preparation of dielectric layer: 8YSZ powder was treated in an oven at 80°C for 1 hour and then taken out for later use. The embedded carbon / carbon composite material was preheated at 70°C for 10 minutes to improve the bonding strength between the coating and the substrate. During the plasma spraying process, the current was 290A, the voltage was 150V, the spraying distance was 90mm, the main gas flow rate was 60splm, and the auxiliary gas flow rate was 2.2splm. A 1.35mm thick 8YSZ coating was prepared on the embedded carbon / carbon composite material.

[0038] (4) Preparation of frequency selective surface layer: FeCrAl powder was treated in an oven at 80°C for 1 h and then taken out for later use. Before spraying, a mask was laid on the layer obtained in (3). During the plasma spraying process, a current of 200A, a voltage of 80V, a spraying distance of 90mm, a main gas flow rate of 60splm, and an auxiliary gas flow rate of 2.2splm were used. With the mask, a cross-shaped FeCrAl coating with a thickness of 30μm was prepared on the coating obtained in (3).

[0039] (5) Preparation of surface protection layer: On the coating obtained in (4), a plasma spraying method was used with a current of 290A, a voltage of 150V, a spraying distance of 90mm, a main gas flow rate of 60splm, and an auxiliary gas flow rate of 2.2splm to prepare a 100μm thick 8YSZ coating, and finally a frequency selective high temperature resistant, microwave absorbing and anti-oxidation coating was obtained. Figure 1 As shown, the frequency selective high temperature resistant wave absorbing and anti-oxidation coating prepared in this embodiment is Figure 1 It can be seen that the surface 8YSZ protective layer can play an anti-oxidation protection role for the FeCrAl frequency selective surface layer. At the same time, the thin thickness and wave transmission of the 8YSZ protective layer hardly affect the wave absorbing effect of the frequency selective surface layer on the entire composite coating. The reflection loss of the coating prepared in this embodiment is tested at room temperature. The results are as follows: Figure 2 As shown, from Figure 2 It can be seen that the effective absorption bandwidth (RL<-10dB) is about 3.5GHz, which means that the coating prepared by the present invention has the ability to stably absorb electromagnetic waves, can exert a good stealth effect, and improve the concealment of the equipment.

[0040] Embodiment 2: (1) Substrate pretreatment: The carbon / carbon composite material is processed into the required size, and the substrate is placed in anhydrous ethanol for ultrasonic cleaning for 2 h to remove impurities, and then placed in an oven for treatment at 80 ° C for 5 h, and then taken out for use.

[0041] (2) Preparation of transition layer: A 90 μm SiC ceramic transition layer was prepared on the surface of the pretreated carbon / carbon composite material by the embedding method. During the preparation process by the embedding method, the process is as follows: ① Si powder, C powder and Al2O3 powder were mixed in a mass ratio of 8:1:1 and ball-milled for 4 h to prepare a mixed powder; ② The mixed powder and the C / C composite material sample were placed in a graphite crucible, and the mixed powder fully wrapped the C / C composite material sample; ③ The sealed graphite crucible was placed in a high-temperature heat treatment furnace and heat treated in an Ar atmosphere at a temperature of 1800°C. After keeping the heat for 1 h, it was cooled to room temperature with the furnace; ④ After the heat treatment was completed, it was taken out from the crucible, and the surface residue was removed to obtain SiC ceramic coated on the C / C composite material sample.

[0042] (3) Preparation of dielectric layer: 8YSZ powder was treated in an oven at 80°C for 1 hour and then taken out for later use. The embedded carbon / carbon composite material was preheated at 70°C for 10 minutes to improve the bonding strength between the coating and the substrate. During the plasma spraying process, the current was 270A, the voltage was 140V, the spraying distance was 100mm, the main gas flow rate was 60splm, and the auxiliary gas flow rate was 2.2splm. A 1.4mm thick 8YSZ coating was prepared on the embedded carbon / carbon composite material.

[0043] (4) Preparation of frequency selective surface layer: FeCrAl powder was treated in an oven at 80°C for 1 h and then taken out for later use. Before spraying, a mask was laid on the coating obtained in (3). During the spraying process using plasma spraying, the current was 200A, the voltage was 85V, the spraying distance was 100mm, the main gas flow rate was 60splm, and the auxiliary gas flow rate was 2.2splm. With the mask, a 40μm thick cross-pattern FeCrAl coating was prepared on the coating obtained in (3).

[0044] (5) Preparation of surface protective layer: On the coating obtained in (4), a plasma spraying method was used with a current of 270 A, a voltage of 140 V, a spraying distance of 100 mm, a main gas flow rate of 60 splm, and an auxiliary gas flow rate of 2.2 splm to prepare a 70 μm thick 8YSZ coating, and finally a frequency selective high temperature resistant, microwave absorbing and antioxidant coating was obtained.

[0045] Embodiment 3: (1) Substrate pretreatment: The carbon / carbon composite material is processed into the required size, and the substrate is placed in anhydrous ethanol for ultrasonic cleaning for 3 h to remove impurities, and then placed in an oven for treatment at 80 ° C for 6 h, and then taken out for use.

[0046] (2) Preparation of transition layer: A 100 μm SiC ceramic transition layer was prepared on the surface of the pretreated carbon / carbon composite material by the embedding method. During the preparation process by the embedding method, the process is as follows: ① Si powder, C powder and Al2O3 powder were mixed in a mass ratio of 8:2:1 and ball-milled for 3 h to make a mixed powder; ② The mixed powder and the C / C composite material sample were placed in a graphite crucible, and the mixed powder fully wrapped the C / C composite material sample; ③ The sealed graphite crucible was placed in a high-temperature heat treatment furnace and heat treated in an Ar atmosphere at a temperature of 1900°C. After keeping the heat for 3 h, it was cooled to room temperature with the furnace; ④ After the heat treatment was completed, it was taken out from the crucible, and the surface residue was removed to obtain SiC ceramic coated on the C / C composite material sample.

[0047] (3) Preparation of dielectric layer: 8YSZ powder was treated in an oven at 80°C for 1 hour and then taken out for later use. The embedded carbon / carbon composite material was preheated at 100°C for 20 minutes to improve the bonding strength between the coating and the substrate. During the plasma spraying process, the current was 260A, the voltage was 100V, the spraying distance was 110mm, the main gas flow rate was 62splm, and the auxiliary gas flow rate was 2.4splm. A 1.3mm thick 8YSZ coating was prepared on the embedded carbon / carbon composite material.

[0048] (4) Preparation of frequency selective surface layer: FeCrAl powder was treated in an oven at 100°C for 2 h and then taken out for later use. Before spraying, a mask was laid on the coating obtained in (3). During the spraying process using plasma spraying, the current was 220A, the voltage was 90V, the spraying distance was 110mm, the main gas flow rate was 62splm, and the auxiliary gas flow rate was 2.4splm. With the mask, a 50μm thick cross-pattern FeCrAl coating was prepared on the coating obtained in (3).

[0049] (5) Preparation of surface protective layer: On the coating obtained in (4), a plasma spraying method was used with a current of 260 A, a voltage of 100 V, a spraying distance of 110 mm, a main gas flow rate of 62 splm, and an auxiliary gas flow rate of 2.4 splm to prepare a 50 μm thick 8YSZ coating, and finally a frequency selective high temperature resistant, microwave absorbing and antioxidant coating was obtained.

[0050] Embodiment 4: (1) Substrate pretreatment: The carbon / carbon composite material is processed into the required size, and the substrate is placed in anhydrous ethanol for ultrasonic cleaning for 3 h to remove impurities, and then placed in an oven for treatment at 80 ° C for 6 h, and then taken out for use.

[0051] (2) Preparation of transition layer: A 100 μm SiC ceramic transition layer was prepared on the surface of the pretreated carbon / carbon composite material by the embedding method. During the preparation process by the embedding method, the process is as follows: ① Si powder, C powder and Al2O3 powder were mixed in a mass ratio of 8:2:1 and ball-milled for 3 h to make a mixed powder; ② The mixed powder and the C / C composite material sample were placed in a graphite crucible, and the mixed powder fully wrapped the C / C composite material sample; ③ The sealed graphite crucible was placed in a high-temperature heat treatment furnace and heat treated in an Ar atmosphere at a temperature of 1900°C. After keeping the heat for 3 h, it was cooled to room temperature with the furnace; ④ After the heat treatment was completed, it was taken out from the crucible, and the surface residue was removed to obtain SiC ceramic coated on the C / C composite material sample.

[0052] (3) Preparation of dielectric layer: 8YSZ powder was treated in an oven at 80°C for 1 hour and then taken out for later use. The embedded carbon / carbon composite material was preheated at 100°C for 20 minutes to improve the bonding strength between the coating and the substrate. During the plasma spraying process, the current was 260A, the voltage was 100V, the spraying distance was 110mm, the main gas flow rate was 62splm, and the auxiliary gas flow rate was 2.4splm. A 1.3mm thick 8YSZ coating was prepared on the embedded carbon / carbon composite material.

[0053] (4) Preparation of frequency selective surface layer: FeCrAl powder was treated in an oven at 100°C for 2 h and then taken out for later use. Before spraying, a mask was laid on the coating obtained in (3). During the spraying process using plasma spraying, the current was 220A, the voltage was 90V, the spraying distance was 110mm, the main gas flow rate was 62splm, and the auxiliary gas flow rate was 2.4splm. With the mask, a 50μm thick cross-pattern FeCrAl coating was prepared on the coating obtained in (3).

[0054] (5) Preparation of surface protective layer: On the coating obtained in (4), a plasma spraying method was used with a current of 260 A, a voltage of 100 V, a spraying distance of 110 mm, a main gas flow rate of 62 splm, and an auxiliary gas flow rate of 2.4 splm to prepare a 50 μm thick 8YSZ coating, and finally a frequency selective high temperature resistant, microwave absorbing and antioxidant coating was obtained.

[0055] Embodiment 5: (1) Substrate pretreatment: The carbon / carbon composite material is processed into the required size, and the substrate is placed in anhydrous ethanol for ultrasonic cleaning for 3 h to remove impurities, and then placed in an oven for treatment at 80 ° C for 6 h, and then taken out for use.

[0056] (2) Preparation of transition layer: A 100 μm SiC ceramic transition layer was prepared on the surface of the pretreated carbon / carbon composite material by the embedding method. During the preparation process by the embedding method, the process is as follows: ① Si powder, C powder and Al2O3 powder were mixed in a mass ratio of 8:2:2 and ball-milled for 5 h to make a mixed powder; ② The mixed powder and the C / C composite material sample were placed in a graphite crucible, and the mixed powder fully wrapped the C / C composite material sample; ③ The sealed graphite crucible was placed in a high-temperature heat treatment furnace and heat treated at 2000°C in an Ar atmosphere. After keeping the heat for 3 h, it was cooled to room temperature with the furnace; ④ After the heat treatment was completed, it was taken out from the crucible, and the surface residue was removed to obtain SiC ceramic coated on the C / C composite material sample.

[0057] (3) Preparation of dielectric layer: 8YSZ powder was treated in an oven at 80°C for 1 hour and then taken out for later use. The embedded carbon / carbon composite material was preheated at 120°C for 10 minutes to improve the bonding strength between the coating and the substrate. During the plasma spraying process, the current was 280A, the voltage was 120V, the spraying distance was 110mm, the main gas flow rate was 64splm, and the auxiliary gas flow rate was 2.8splm. A 1.2mm thick 8YSZ coating was prepared on the embedded carbon / carbon composite material.

[0058] (4) Preparation of frequency selective surface layer: FeCrAl powder was treated in an oven at 100°C for 2 h and then taken out for later use. Before spraying, a mask was laid on the coating obtained in (3). During the spraying process using plasma spraying, the current was 240A, the voltage was 90V, the spraying distance was 110mm, the main gas flow rate was 64splm, and the auxiliary gas flow rate was 2.8splm. With the mask, a 50μm thick cross-pattern FeCrAl coating was prepared on the coating obtained in (3).

[0059] (5) Preparation of surface protective layer: On the coating obtained in (4), a plasma spraying method was used with a current of 280 A, a voltage of 120 V, a spraying distance of 110 mm, a main gas flow rate of 64 splm, and an auxiliary gas flow rate of 2.8 splm to prepare a 50 μm thick 8YSZ coating, and finally a frequency selective high temperature resistant, microwave absorbing and antioxidant coating was obtained.

[0060] Embodiment 6: (1) Substrate pretreatment: The carbon / carbon composite material is processed into the required size, and the substrate is placed in anhydrous ethanol for ultrasonic cleaning for 3 h to remove impurities, and then placed in an oven for treatment at 80 ° C for 6 h, and then taken out for use.

[0061] (2) Preparation of transition layer: A 100 μm SiC ceramic transition layer was prepared on the surface of the pretreated carbon / carbon composite material by the embedding method. During the preparation process by the embedding method, the process is as follows: ① Si powder, C powder and Al2O3 powder were mixed in a mass ratio of 6:2:1 and ball-milled for 3 h to prepare a mixed powder; ② The mixed powder and the C / C composite material sample were placed in a graphite crucible, and the mixed powder fully wrapped the C / C composite material sample; ③ The sealed graphite crucible was placed in a high-temperature heat treatment furnace and heat treated in an Ar atmosphere at a temperature of 2100°C. After keeping the heat for 3 h, it was cooled to room temperature with the furnace; ④ After the heat treatment was completed, it was taken out from the crucible, and the surface residue was removed to obtain SiC ceramic coated on the C / C composite material sample.

[0062] (3) Preparation of dielectric layer: 8YSZ powder was treated in an oven at 80°C for 1 hour and then taken out for later use. The embedded carbon / carbon composite material was preheated at 100°C for 10 minutes to improve the bonding strength between the coating and the substrate. During the plasma spraying process, the current was 240A, the voltage was 100V, the spraying distance was 110mm, the main gas flow rate was 65splm, and the auxiliary gas flow rate was 2.6splm. A 1.1mm thick 8YSZ coating was prepared on the embedded carbon / carbon composite material.

[0063] (4) Preparation of frequency selective surface layer: FeCrAl powder was treated in an oven at 100°C for 2 h and then taken out for later use. Before spraying, a mask was laid on the coating obtained in (3). During the spraying process using plasma spraying, the current was 230A, the voltage was 80V, the spraying distance was 110mm, the main gas flow rate was 65splm, and the auxiliary gas flow rate was 2.6splm. With the mask, a 40μm thick cross-pattern FeCrAl coating was prepared on the coating obtained in (3).

[0064] (5) Preparation of surface protective layer: On the coating obtained in (4), a plasma spraying method was used with a current of 240 A, a voltage of 100 V, a spraying distance of 110 mm, a main gas flow rate of 65 splm, and an auxiliary gas flow rate of 2.6 splm to prepare a 100 μm thick 8YSZ coating, and finally a frequency selective high temperature resistant, microwave absorbing and antioxidant coating was obtained.

[0065] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A frequency selective high temperature resistant microwave absorbing and anti-oxidation coating, characterized in that: It includes a transition layer, a dielectric layer, a frequency selective surface layer and a surface protective layer which are arranged in sequence from the inside to the outside; The transition layer is SiC ceramics, the dielectric layer and the surface protection layer are both yttria partially stabilized zirconia coatings, and the frequency selective surface layer is FeCrAl coating.

2. The frequency selective high temperature resistant microwave absorbing and anti-oxidation coating according to claim 1, characterized in that: The thickness of the transition layer is 70-200 μm, the thickness of the dielectric layer is 1-1.5 mm, the thickness of the frequency selective surface layer is 10-100 μm, and the thickness of the surface protection layer is 20-100 μm.

3. The frequency selective high temperature resistant microwave absorbing and anti-oxidation coating according to claim 1, characterized in that: The frequency selective surface layer is provided with a cross-shaped pattern by means of a mask.

4. A method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating according to any one of claims 1 to 3, characterized in that: include: SiC ceramics are prepared on the pretreated substrate by embedding method to form a transition layer; The transition layer is preheated, and a yttria-partially stabilized zirconium oxide layer is prepared on the surface of the preheated transition layer by a plasma spraying method to form a dielectric layer; A mask is laid on the dielectric layer, and a FeCrAl coating is sprayed thereon by a plasma spraying method to form a frequency selective surface layer with a cross-shaped pattern; A yttria partially stabilized zirconia coating is sprayed on the frequency selective surface layer by a plasma spraying method to form a surface protective layer, thereby obtaining a frequency selective high temperature resistant wave absorbing and oxidation resistant coating.

5. The method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating according to claim 4, characterized in that: The pretreatment process of the substrate comprises: The substrate is placed in anhydrous ethanol, surface impurities are removed by ultrasonic cleaning, and then the substrate is dried; The temperature of the drying process is 80-100° C., and the time of the drying process is 5-6 hours.

6. The method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating according to claim 4, characterized in that: The method for preparing SiC ceramics on a pretreated substrate by embedding method comprises: Si powder, C powder and Al2O3 powder were mixed and ball-milled for 2-8 hours in a mass ratio of 6-9:1-4:1-4 to prepare a mixed powder; The pretreated substrate is fully coated with the mixed powder, and heat treated at 1700-2100°C in an Ar atmosphere, kept at this temperature for 1-4 hours, and then cooled to room temperature; After the heat treatment is completed, the surface residue is removed to obtain the SiC ceramic coated on the substrate.

7. The method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating according to claim 4, characterized in that: The temperature of the preheating treatment is 70-170° C., and the time of the preheating treatment is 10-20 minutes.

8. The method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating according to claim 4, characterized in that: The spraying process of the yttria partially stabilized zirconia layer includes: a current of 220-290A, a voltage of 80-150V, a spraying distance of 80-120mm, a main gas flow rate of 60-65splm, and an auxiliary gas flow rate of 2.2-3.2splm.

9. The method for preparing the frequency selective high temperature resistant wave absorbing and anti-oxidation coating according to claim 4, characterized in that: The spraying process of the FeCrAl coating includes: a current of 200-240A, a voltage of 80-100V, a spraying distance of 80-120mm, a main gas flow rate of 60-65splm, and an auxiliary gas flow rate of 2.2-3.2splm.

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