Compatible coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and particularly relates to a compatible coating and a preparation method and application thereof. In the use process of the compatible coating prepared by the invention, electromagnetic waves firstly enter through the frequency selective surface layer, a small part of the incident electromagnetic waves continuously enter into the wave absorbing layer through the frequency selective surface layer, the wave absorbing layer absorbs a part of the electromagnetic waves, and the unabsorbed part penetrates through the wave absorbing layer and encounters the metal matrix to be reflected; the electromagnetic waves pass through the wave absorbing layer and the frequency selective surface layer in sequence and are finally received by the radar, the wave absorbing layer absorbs part of the electromagnetic waves again in the reflecting process, the frequency selective surface layer blocks part of the electromagnetic waves, the electromagnetic waves which are absorbed and blocked for multiple times are finally received by the radar, and the stealth capability of the electromagnetic waves can reach-5.5 db; the infrared emissivity of the frequency selective surface layer is between 0.1 and 0.3 when the frequency selective surface layer is 3-5 microns and 8-14 microns, and the infrared emissivity is relatively low, so that radar stealth and infrared stealth can be realized at the same time.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a compatible coating, its preparation method, and its application. Background Technology

[0002] With the rapid development of modern high technology and the continuous improvement of various reconnaissance methods, new detection systems and precision-guided equipment have emerged, placing higher demands on the stealth performance of equipment. Currently, single-function stealth materials are no longer sufficient; multi-band compatible stealth materials, especially radar-infrared compatible stealth materials, have become a key research focus. Radar stealth materials require low reflectivity in the radar band, while infrared stealth materials require high infrared reflectivity. This contradiction presents significant challenges to the fabrication of radar-infrared compatible stealth materials. Therefore, resolving this contradiction through material design is crucial for achieving radar-infrared compatible stealth.

[0003] Currently available compatible coatings generally have good absorption performance at high frequencies, but poor absorption performance at low frequencies.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a compatible coating, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution: On one hand, the present invention provides a compatible coating comprising a radar absorbing layer and an infrared stealth layer stacked sequentially on a metal substrate from bottom to top; the radar absorbing layer comprising an adhesive layer and an absorbing layer stacked sequentially on the metal substrate, and the infrared stealth layer comprising an adhesive layer for improving adhesion, a matching layer for relieving thermal stress, and a low emissivity layer stacked sequentially on the absorbing layer. The low emissivity layer includes a frequency selective surface layer, which comprises M×N frequency selective structures, where M and N are both integers greater than or equal to 1. Each frequency selective structure includes a first part, a second part, a third part, and a fourth part, which are clockwise closely arranged and are all square layer structures. The frequency selective structures are symmetrical about the center. The first part and the third part are diagonally symmetrical about the frequency selective structures, and the second part and the fourth part are diagonally symmetrical about the frequency selective structures. The first part, the second part, the third part, and the fourth part are square structures of the same size.

[0007] Specifically, the first part contains 5×5 square metal layer structures. The metal layer structures in the first part are diagonally symmetrical. A largest metal layer structure is located at one corner of the first part. The side length of the largest metal layer structure is X, which is greater than or equal to the minimum value required to successfully fabricate a frequency-selective structure, and X is not zero. The side lengths of the other metal layer structures on the same horizontal or vertical direction as the largest metal layer structure are 0.9X, 0.8X, 0.75X, and 0.55X to 0.65X (i.e., any value between 0.55X and 0.65X). Two of the largest metal layer structures are symmetrical about a line of symmetry L. The side lengths of the metal layer structures on any diagonal line parallel to the line of symmetry L are the same, and the distance between the center points of adjacent squares is the same. The second part consists of four proportionally reduced and centrally symmetrical first parts.

[0008] Specifically, the adhesive layer is made of commercially available nickel-cobalt-chromium-aluminum-yttrium powder with a thickness of 85μm to 115μm; the absorbing layer is made of a mixture of ceramic binder matrix, absorber, and filler with a thickness of 1mm to 1.5mm; the bonding layer is made of one of nickel-based solder, aluminum phosphate glue, and silica sol with a thickness of 1μm to 50μm; the matching layer is made of a mixture of alumina and silicon carbide, and is a gradient layer formed by alumina and silicon carbide with a thickness of 50μm to 300μm, wherein the alumina content gradually decreases and the silicon carbide content gradually increases, and the mass ratio of alumina to silicon carbide changes from an initial 90:10 to a final 10:90; the low emissivity layer is made of one of gold, silver, aluminum, copper, nickel, and chromium with a thickness of 0.01mm to 0.5mm.

[0009] Furthermore, in the microwave absorbing layer, the proportions of each substance by mass percentage are as follows: ceramic binder matrix: 40%–70%, absorber: 20%–50%, filler: 5%–20%.

[0010] Furthermore, in the absorbing layer, the ceramic binder matrix includes one or more of silicon carbide, alumina, zirconium oxide, or silicon oxide; the absorber includes one of manganese zinc ferrite metal powder, graphene, silicon carbide, or barium titanate; and the filler includes one of alumina, zirconium oxide, boron nitride, hollow ceramic microspheres, conductive magnetic fillers, and functional ceramics. The particle size of the ceramic binder matrix, absorber, and filler powders is 1 μm to 150 μm. When alumina is used as the ceramic binder matrix, its particle size is less than 100 nm; when alumina is used as the filler, its particle size is 1 μm to 10 μm, or it is alumina whiskers with an aspect ratio greater than 10.

[0011] On the other hand, the present invention provides a method for preparing the compatible coating as described above, comprising the following steps: Step 1: Pre-treat the substrate surface; specifically, sandblast the substrate surface to remove oxide scale and contaminants, and create an uneven surface to improve the interlocking between the substrate and the coating, thereby increasing the tensile bond strength. The sandblasting process uses SiC sand with a particle size of 100 mesh, a sandblasting speed of 4 cm / s to 6 cm / s, a sandblasting distance of 10 cm to 15 cm, and a sandblasting pressure of 10 psi to 20 psi.

[0012] Step 2: Spray an adhesive layer onto the pretreated substrate surface; specifically: use plasma spraying technology and nickel-cobalt-chromium-aluminum-yttrium powder as raw material to spray an adhesive layer onto the substrate surface. The parameters for preparing the adhesive layer are as follows: spraying current 490A~510A, powder feed rate 40g / min~50g / min, argon flow rate 48L / min~52L / min, hydrogen flow rate 2.8L / min~3.2L / min, spray gun moving speed 490mm / s~510mm / s, spraying spacing 2.5mm~3.5mm, and spraying distance 8cm~10cm.

[0013] Step 3: First, spray an absorbing layer onto the surface of the adhesive layer, then perform a first heat treatment and cool. Specifically, use one or more of silicon carbide, alumina, zirconium oxide, or silicon oxide as the ceramic binder matrix, use one of manganese zinc ferrite metal powder, graphene, silicon carbide, or barium titanate as the absorber, and use one of alumina, zirconium oxide, boron nitride, hollow ceramic microspheres, conductive magnetic fillers, and functional ceramics as fillers. Prepare the absorbing layer on the adhesive layer using plasma spraying technology and a mixed powder of ceramic binder matrix, absorber, and filler as raw material. Place the substrate with the absorbing layer in an oven and heat it to 690℃~710℃ within 190min~210min, hold it at that temperature for 110min~130min, and then cool it to room temperature with the oven after the holding time. The parameters for preparing the microwave absorbing layer are as follows: spraying current 540A~560A, powder feed rate 35g / min~45g / min, argon flow rate 33L / min~37L / min, hydrogen flow rate 8.8L / min~9.2L / min, spray gun moving speed 490mm / s~510mm / s, spraying spacing 2.5mm~3.5mm, and spraying distance 8cm~10cm.

[0014] Step 4: First, prepare a bonding layer on the surface of the absorbing layer, and then perform a second heat treatment followed by cooling; specifically, use magnetron sputtering technology and one of nickel-based solder, aluminum phosphate glue, or silica sol as raw materials to prepare the bonding layer; The parameters for preparing the bonding layer are: sputtering power of 140W to 160W, sputtering gas pressure of 0.25Pa to 0.35Pa, target-substrate distance of 50mm to 70mm, and single-point coating time of 10min. The second heat treatment specifically involves placing the substrate with the bonding layer into an oven, starting from room temperature, heating it to 485℃~515℃ at a heating rate of 2℃ / min~3℃ / min, holding it at that temperature for 25min~35min, and then cooling it to room temperature with the oven after the holding period.

[0015] Step 5: First, prepare a matching layer on the surface of the bonding layer, and then perform a third heat treatment followed by cooling; specifically: use magnetron sputtering technology and alumina and silicon oxide as raw materials to prepare the matching layer, which is a gradient layer; The parameters for preparing the matching layer are: sputtering power of 110W to 130W, sputtering gas pressure of 0.25 Pa to 0.35 Pa, target-substrate distance of 50mm to 70mm, and single-point coating time of 8min. The third heat treatment specifically involves placing the substrate with the matching layer into an oven and heating it to 490℃~510℃ at a heating rate of 2℃~3℃, holding it at that temperature for 30 minutes, and then cooling it to room temperature with the oven after the holding period. It should also be noted that the following two methods can be used to prepare the matching layer: 1) Layered preparation method: Prepare a mixture of 9 parts alumina and silicon oxide (raw material) according to the mass ratio of alumina to silicon oxide of 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90. Spray the mixture of alumina and silicon oxide onto the surface of the bonding layer in the above order until all nine parts of raw material are sprayed to obtain the matching layer of the gradient layer. 2) Electroplating method: When preparing the matching layer of the microwave absorbing coating by electroplating, an electrolytic deposition is used to form a coating on the surface of the bonding layer. The matching layer is made into a gradient layer by real-time control of the composition ratio of alumina and silicon oxide.

[0016] Step 6: First, prepare a low emissivity layer on the surface of the matching layer, then perform a fourth heat treatment and cool to obtain the desired compatible coating; Specifically, magnetron sputtering technology is used, and a low emissivity layer is prepared using one of gold, silver, aluminum, copper, nickel, and chromium as raw materials. The parameters of the magnetron sputtering technology are: sputtering power of 70W to 90W, sputtering gas pressure of 0.2Pa to 0.3Pa, and target-substrate distance of 50nm to 70nm. The fourth heat treatment is as follows: the entire substrate is placed in a heating furnace and heated from room temperature for 190min to 210min, raising the furnace temperature to 690℃ to 710℃, and finally held at that temperature for 110min to 130min. After the holding time, the substrate is cooled to room temperature with the furnace.

[0017] Furthermore, the present invention provides an application of the as-described compatible coating in the fields of radar and infrared stealth.

[0018] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: During use, the compatible coating of this invention first transmits electromagnetic waves through the frequency-selective surface layer. A small portion of the transmitted electromagnetic waves then passes through the frequency-selective surface layer and continues to the absorbing layer, where it absorbs a portion of the waves. The unabsorbed portion eventually passes through the absorbing layer and is reflected by the metal substrate. It then passes through the absorbing layer and the frequency-selective surface layer again before being received by the radar. During the reflection process, the absorbing layer absorbs a portion of the electromagnetic waves again, and the frequency-selective surface layer blocks a portion of the electromagnetic waves. Therefore, the electromagnetic waves ultimately received by the radar are those that have been absorbed and blocked twice. The stealth capability in the low-frequency band of electromagnetic waves can reach -5.5 dB. Furthermore, since the infrared emissivity of the frequency-selective surface layer is between 0.1 and 0.3 in the 3-5 μm and 8-14 μm ranges, it can simultaneously achieve low-frequency radar stealth and infrared stealth. Attached Figure Description

[0019] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 This is a cross-sectional schematic diagram of the coating compatible with the present invention; Figure 3 This is a schematic diagram of the structure of the low reflectivity layer of the present invention; Figure 4This is a schematic diagram of the microwave absorption test results of the compatible coatings prepared in Examples 1-3. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] See Figure 2 and 3 As shown, the present invention provides a compatible coating comprising a radar absorbing layer and an infrared stealth layer stacked sequentially on a metal substrate from bottom to top; the radar absorbing layer comprises an adhesive layer and an absorbing layer stacked sequentially on the metal substrate, and the infrared stealth layer comprises an adhesive layer for improving adhesion, a matching layer for relieving thermal stress, and a low emissivity layer stacked sequentially on the absorbing layer. The low emissivity layer includes a frequency selective surface layer, which comprises M×N frequency selective structures, where M and N are both integers greater than or equal to 1. Each frequency selective structure includes a first part, a second part, a third part, and a fourth part, which are clockwise closely arranged and are all square layer structures. The frequency selective structures are symmetrical about the center. The first part and the third part are diagonally symmetrical about the frequency selective structures, and the second part and the fourth part are diagonally symmetrical about the frequency selective structures. The first part, the second part, the third part, and the fourth part are square structures of the same size.

[0025] Specifically, the first part contains 5×5 square metal layer structures. These metal layer structures are diagonally symmetrical. A largest square is located at one corner of the first part, with a side length of X. X is greater than or equal to the minimum value required to successfully fabricate a frequency-selective structure, and X is not zero. The side lengths of the remaining squares on the same horizontal or vertical axis as the largest metal layer structure are, in order: 0.9X, 0.8X, 0.75X, and 0.55X to 0.65X (i.e., any value between 0.65X and 0.55X). Two of the largest squares are symmetrical about a line of symmetry L (e.g., ...). Figure 3 As shown, the symmetry line L is Figure 3The squares on any diagonal line parallel to the line of symmetry L (the red line in the middle) have the same side length, and the distance between the center points of adjacent squares is the same; the second part consists of four proportionally reduced and centrally symmetrical first parts.

[0026] Specifically, the adhesive layer is made of commercially available nickel-cobalt-chromium-aluminum-yttrium powder with a thickness of 85μm to 115μm; the absorbing layer is made of a mixture of ceramic binder matrix, absorber, and filler with a thickness of 1mm to 1.5mm; the bonding layer is made of one of nickel-based solder, aluminum phosphate glue, and silica sol with a thickness of 1μm to 50μm; the matching layer is made of a mixture of alumina and silicon carbide, and is a gradient layer formed by alumina and silicon carbide with a thickness of 50μm to 300μm, wherein the alumina content gradually decreases and the silicon carbide content gradually increases, and the mass ratio of alumina to silicon carbide changes from an initial 90:10 to a final 10:90; the low emissivity layer is made of one of gold, silver, aluminum, copper, nickel, and chromium with a thickness of 0.01mm to 0.5mm.

[0027] Furthermore, in the microwave absorbing layer, the proportions of each substance by mass percentage are as follows: ceramic binder matrix: 40%–70%, absorber: 20%–50%, filler: 5%–20%.

[0028] Furthermore, in the absorbing layer, the ceramic binder matrix includes one or more of silicon carbide, alumina, zirconium oxide, or silicon oxide; the absorber includes one of manganese zinc ferrite metal powder, graphene, silicon carbide, or barium titanate; and the filler includes one of alumina, zirconium oxide, boron nitride, hollow ceramic microspheres, conductive magnetic fillers, and functional ceramics. The particle size of the ceramic binder matrix, absorber, and filler powders is 1 μm to 150 μm. When alumina is used as the ceramic binder matrix, its particle size is less than 100 nm; when alumina is used as the filler, its particle size is 1 μm to 10 μm, or it is alumina whiskers with an aspect ratio greater than 10.

[0029] See Figure 1 As shown, the present invention provides a method for preparing the compatibility coating as described above, comprising the following steps: Step 1: Pre-treat the substrate surface; specifically, sandblast the substrate surface to remove oxide scale and contaminants, and create an uneven surface to improve the interlocking between the substrate and the coating, thereby increasing the tensile bond strength. The sandblasting process uses SiC sand with a particle size of 100 mesh, a sandblasting speed of 4 cm / s to 6 cm / s, a sandblasting distance of 10 cm to 15 cm, and a sandblasting pressure of 10 psi to 20 psi.

[0030] Step 2: Spray an adhesive layer onto the pretreated substrate surface; specifically: use plasma spraying technology and nickel-cobalt-chromium-aluminum-yttrium powder as raw material to spray an adhesive layer onto the substrate surface. The parameters for preparing the adhesive layer are as follows: spraying current 490A~510A, powder feed rate 40g / min~50g / min, argon flow rate 48L / min~52L / min, hydrogen flow rate 2.8L / min~3.2L / min, spray gun moving speed 490mm / s~510mm / s, spraying spacing 2.5mm~3.5mm, and spraying distance 8cm~10cm.

[0031] Step 3: First, spray an absorbing layer onto the surface of the adhesive layer, then perform a first heat treatment and cool. Specifically, use one or more of silicon carbide, alumina, zirconium oxide, or silicon oxide as the ceramic binder matrix, use one of manganese zinc ferrite metal powder, graphene, silicon carbide, or barium titanate as the absorber, and use one of alumina, zirconium oxide, boron nitride, hollow ceramic microspheres, conductive magnetic fillers, and functional ceramics as fillers. Prepare the absorbing layer on the adhesive layer using plasma spraying technology and a mixed powder of ceramic binder matrix, absorber, and filler as raw material. Place the substrate with the absorbing layer in an oven and heat it to 690℃~710℃ within 190min~210min, hold it at that temperature for 110min~130min, and then cool it to room temperature with the oven after the holding time. The parameters for preparing the microwave absorbing layer are as follows: spraying current 540A~560A, powder feed rate 35g / min~45g / min, argon flow rate 33L / min~37L / min, hydrogen flow rate 8.8L / min~9.2L / min, spray gun moving speed 490mm / s~510mm / s, spraying spacing 2.5mm~3.5mm, and spraying distance 8cm~10cm.

[0032] Step 4: First, prepare a bonding layer on the surface of the absorbing layer, and then perform a second heat treatment followed by cooling; specifically, use magnetron sputtering technology and one of nickel-based solder, aluminum phosphate glue, or silica sol as raw materials to prepare the bonding layer; The parameters for preparing the bonding layer are: sputtering power of 140W to 160W, sputtering gas pressure of 0.25Pa to 0.35Pa, target-substrate distance of 50mm to 70mm, and single-point coating time of 10min. The second heat treatment specifically involves placing the substrate with the bonding layer into an oven, starting from room temperature, heating it to 485℃~515℃ at a heating rate of 2℃ / min~3℃ / min, holding it at that temperature for 25min~35min, and then cooling it to room temperature with the oven after the holding period.

[0033] Step 5: First, prepare a matching layer on the surface of the bonding layer, and then perform a third heat treatment followed by cooling; specifically: use magnetron sputtering technology and alumina and silicon oxide as raw materials to prepare the matching layer, which is a gradient layer; The parameters for preparing the matching layer are: sputtering power of 110W to 130W, sputtering gas pressure of 0.25 Pa to 0.35 Pa, target-substrate distance of 50mm to 70mm, and single-point coating time of 8min. The third heat treatment specifically involves placing the substrate with the matching layer into an oven and heating it to 490℃~510℃ at a heating rate of 2℃~3℃, holding it at that temperature for 30 minutes, and then cooling it to room temperature with the oven after the holding period. It should also be noted that the following two methods can be used to prepare the matching layer: 1) Layered preparation method: Prepare a mixture of 9 parts alumina and silicon oxide (raw material) according to the mass ratio of alumina to silicon oxide of 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90. Spray the mixture of alumina and silicon oxide onto the surface of the bonding layer in the above order until all nine parts of raw material are sprayed to obtain the matching layer of the gradient layer. 2) Electroplating method: When preparing the matching layer of the microwave absorbing coating by electroplating, an electrolytic deposition is used to form a coating on the surface of the bonding layer. The matching layer is made into a gradient layer by real-time control of the composition ratio of alumina and silicon oxide.

[0034] Step 6: First, prepare a low emissivity layer on the surface of the matching layer, then perform a fourth heat treatment and cool to obtain the desired compatible coating; Specifically, magnetron sputtering technology is used, and a low emissivity layer is prepared using one of gold, silver, aluminum, copper, nickel, and chromium as raw materials. The parameters of the magnetron sputtering technology are: sputtering power of 70W to 90W, sputtering gas pressure of 0.2Pa to 0.3Pa, and target-substrate distance of 50nm to 70nm. The fourth heat treatment is as follows: the entire substrate is placed in a heating furnace and heated from room temperature for 190min to 210min, raising the furnace temperature to 690℃ to 710℃, and finally held at that temperature for 110min to 130min. After the holding time, the substrate is cooled to room temperature with the furnace.

[0035] To demonstrate the effectiveness of the preparation method of the present invention, the following examples are provided for verification.

[0036] Example 1 See Figure 1 As shown, this embodiment provides a method for preparing a compatible coating, the specific steps of which are as follows: Step 1: The substrate surface is sandblasted with 100-mesh SiC sand at a speed of 5 cm / s, a distance of 13 cm, and a pressure of 15 psi to remove oxide scale and contaminants from the substrate surface and to create an uneven surface to improve the interlocking between the substrate and the coating and increase the tensile bond strength. Step 2: Using plasma spraying technology and nickel-cobalt-chromium-aluminum-yttrium powder as raw material, an adhesive layer is prepared by spraying it onto the surface of the pretreated substrate. The parameters for preparing the adhesive layer are as follows: spraying current is 500A, powder feed rate is 45g / min, argon flow rate is 50L / min, hydrogen flow rate is 3L / min, spray gun moving speed is 500mm / s, spraying spacing is 3mm, and spraying distance is 9cm. Step 3: Using alumina and zirconium oxide as ceramic binder matrix, manganese zinc ferrite metal powder as absorbent, and boron nitride as filler, a microwave absorbing layer is prepared on the surface of the binder layer using plasma spraying technology and a mixture of ceramic binder matrix, absorbent and filler powder as raw material. The matrix with microwave absorbing layer is then placed in an oven and heated to 700℃ within 200 minutes, held at that temperature for 120 minutes, and then cooled to room temperature with the oven after the holding time is completed. The parameters for preparing the microwave absorbing layer are as follows: spraying current is 550A, powder feed rate is 40g / min, argon flow rate is 35L / min, hydrogen flow rate is 9L / min, spray gun moving speed is 500mm / s, spraying spacing is 3mm, and spraying distance is 9cm. Step 4: Using magnetron sputtering technology and nickel-based solder as raw material, a bonding layer is prepared on the surface of the microwave absorbing layer. The substrate with the bonding layer is then placed in an oven and heated from room temperature to 500°C at a heating rate of 2°C / min. The temperature is held for 30 minutes, and then cooled to room temperature with the furnace after the holding period. The parameters for preparing the bonding layer were: sputtering power of 150W, sputtering pressure of 0.3Pa, target-substrate distance of 60mm, and single-point coating time of 10min. Step 5: Using magnetron sputtering technology and alumina and silicon oxide as raw materials, a matching layer is prepared on the surface of the bonding layer by multi-target co-sputtering. The alumina and silicon oxide raw materials are respectively loaded into two magnetron sputtering devices, and the power and sputtering speed of each target are adjusted to form a matching layer with a gradient layer. The substrate with the matching layer is placed in an oven and heated to 500°C at a heating rate of 3°C, held at that temperature for 30 minutes, and then cooled to room temperature with the furnace after the holding time. The parameters for preparing the matching layer were: sputtering power of 120W, sputtering pressure of 0.3Pa, target-substrate distance of 60mm, and single-point coating time of 8min. Step 6: Using magnetron sputtering technology and silver as the raw material, a low emissivity layer is prepared on the surface of the matching layer. The parameters of the magnetron sputtering technology are: sputtering power of 80W, sputtering gas pressure of 0.3Pa, and target-substrate distance of 60nm. After completion, the entire substrate is placed in a heating furnace and heated from room temperature for 200min, so that the furnace temperature rises to 700℃, and held at that temperature for 120min. After the holding time is completed, the substrate is cooled to room temperature with the furnace to obtain the required compatible coating.

[0037] Example 2 See Figure 1 As shown, this embodiment provides a method for preparing a compatible coating, the specific steps of which are as follows: Step 1: The substrate surface is sandblasted with 100-mesh SiC sand at a speed of 4 cm / s, a distance of 10 cm, and a pressure of 10 psi to remove oxide scale and contaminants from the substrate surface and to create an uneven surface to improve the interlocking between the substrate and the coating and increase the tensile bond strength. Step 2: Using plasma spraying technology and nickel-cobalt-chromium-aluminum-yttrium powder as raw material, an adhesive layer is prepared by spraying it onto the surface of the pretreated substrate. The parameters for preparing the adhesive layer are as follows: spraying current is 490A, powder feed rate is 40g / min, argon flow rate is 48L / min, hydrogen flow rate is 2.8L / min, spray gun moving speed is 490mm / s, spraying spacing is 2.5mm, and spraying distance is 8cm. Step 3: Using silicon carbide as the ceramic binder matrix, graphene as the absorber, and zirconium oxide as the filler, a microwave absorbing layer is prepared on the surface of the binder layer using plasma spraying technology and a mixed powder of ceramic binder matrix, absorber, and filler as raw material. The matrix with microwave absorbing layer is then placed in an oven and heated to 690℃ within 190 minutes, held at that temperature for 110 minutes, and then cooled to room temperature with the oven after the holding time is completed. The parameters for preparing the microwave absorbing layer are as follows: spraying current is 540A, powder feed rate is 35g / min, argon flow rate is 33L / min, hydrogen flow rate is 8.8L / min, spray gun moving speed is 490mm / s, spraying spacing is 2.5mm, and spraying distance is 8cm. Step 4: Using magnetron sputtering technology and silica sol as raw material, a bonding layer is prepared on the surface of the microwave absorbing layer. The substrate with the bonding layer is then placed in an oven and heated from room temperature to 485°C at a heating rate of 2°C / min. The temperature is held for 25 minutes, and then cooled to room temperature with the oven after the holding period. The parameters for preparing the bonding layer were: sputtering power of 140W, sputtering pressure of 0.25Pa, target-substrate distance of 50mm, and single-point coating time of 10min. Step 5: Using magnetron sputtering technology and alumina and silicon oxide as raw materials, a matching layer is prepared on the surface of the bonding layer using a layered preparation method. Specifically, a mixture of 9 parts of alumina and silicon oxide (raw materials) is prepared according to the mass ratio of alumina to silicon oxide of 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90. The mixture of alumina and silicon oxide is then sprayed onto the surface of the bonding layer in the above order until all nine parts of raw materials are sprayed, resulting in a gradient matching layer. The substrate with the matching layer is placed in an oven and heated to 490°C at a heating rate of 2°C, held at that temperature for 30 minutes, and then cooled to room temperature with the oven after the holding period. The parameters for preparing the matching layer were: sputtering power of 110W, sputtering pressure of 0.25 Pa, target-substrate distance of 50mm, and single-point coating time of 8min. Step 6: Using magnetron sputtering technology and copper as the raw material, a low emissivity layer is prepared on the surface of the matching layer. The parameters of the magnetron sputtering technology are: sputtering power of 70W, sputtering gas pressure of 0.2Pa, and target-substrate distance of 50nm. After completion, the entire substrate is placed in a heating furnace and heated from room temperature for 190min, so that the furnace temperature rises to 690℃, and held at that temperature for 110min. After the holding time is completed, the substrate is cooled to room temperature with the furnace to obtain the required compatible coating.

[0038] Example 3 See Figure 1 As shown, this embodiment provides a method for preparing a compatible coating, the specific steps of which are as follows: Step 1: The substrate surface is sandblasted with 100-mesh SiC sand at a speed of 6 cm / s, a distance of 15 cm, and a pressure of 20 psi to remove oxide scale and contaminants from the substrate surface and to create an uneven surface to improve the interlocking between the substrate and the coating and increase the tensile bond strength. Step 2: Using plasma spraying technology and nickel-cobalt-chromium-aluminum-yttrium powder as raw material, an adhesive layer is prepared by spraying it onto the surface of the pretreated substrate. The parameters for preparing the adhesive layer are as follows: spraying current is 510A, powder feed rate is 50g / min, argon flow rate is 52L / min, hydrogen flow rate is 3.2L / min, spray gun moving speed is 510mm / s, spraying spacing is 3.5mm, and spraying distance is 10cm. Step 3: Using silicon dioxide as the ceramic binder matrix, silicon carbide as the absorbent, and alumina as the filler, a microwave absorbing layer is prepared on the surface of the adhesive layer using plasma spraying technology and a mixed powder of ceramic binder matrix, absorbent, and filler as raw material. The substrate with microwave absorbing layer is then placed in an oven and heated to 710℃ within 210 minutes, held at that temperature for 130 minutes, and then cooled to room temperature with the oven after the holding time is completed. The parameters for preparing the microwave absorbing layer are as follows: spraying current is 560A, powder feed rate is 45g / min, argon flow rate is 37L / min, hydrogen flow rate is 9.2L / min, spray gun moving speed is 510mm / s, spraying spacing is 3.5mm, and spraying distance is 10cm. Step 4: Using magnetron sputtering technology and aluminum phosphate gel as raw material, a bonding layer is prepared on the surface of the microwave absorbing layer. Then, the substrate with the bonding layer is placed in an oven and heated from room temperature to 515°C at a heating rate of 3°C / min. The temperature is held for 35 minutes and then cooled to room temperature with the oven after the holding period. The parameters for preparing the bonding layer were: sputtering power of 160W, sputtering pressure of 0.35Pa, target-substrate distance of 70mm, and single-point coating time of 10min. Step 5: Using magnetron sputtering technology and alumina and silicon oxide as raw materials, a matching layer is prepared on the surface of the bonding layer by multi-target co-sputtering. That is, the alumina and silicon oxide raw materials are respectively loaded into two magnetron sputtering devices, and the power and sputtering speed of each target are adjusted to form a matching layer with a gradient layer. The substrate with the matching layer is placed in an oven and heated to 510°C at a heating rate of 3°C, held at that temperature for 30 minutes, and then cooled to room temperature with the furnace after the holding time. The parameters for preparing the matching layer were: sputtering power of 130W, sputtering pressure of 0.35Pa, target-substrate distance of 70mm, and single-point coating time of 8min. Step 6: Using magnetron sputtering technology and chromium as the raw material, a low emissivity layer is prepared on the surface of the matching layer. The parameters of the magnetron sputtering technology are: sputtering power of 90W, sputtering gas pressure of 0.3Pa, and target-substrate distance of 70nm. After completion, the entire substrate is placed in a heating furnace and heated from room temperature for 210 minutes, so that the furnace temperature rises to 710℃, and held at that temperature for 130 minutes. After the holding time is completed, the substrate is cooled to room temperature with the furnace to obtain the required compatible coating.

[0039] It should also be noted that the ceramic binder matrix includes one or more of silicon carbide, alumina, zirconium oxide, or silicon oxide. When several materials are selected as the ceramic binder matrix, there is no strict ratio relationship, because these materials have similar properties. Therefore, selecting one or more mixed materials will not affect the effect of the absorbing layer.

[0040] See Figure 4The figure shows the absorption test results of the compatible coatings prepared in Examples 1-3 of this invention. The horizontal axis represents the wavelength and the vertical axis represents the absorption capability. As can be seen from the figure, in the low-frequency band, the absorption capability of the compatible coating prepared by this invention reaches -3.75 when the wavelength is 2.4 Hz; and -5.6 when the wavelength is 3.2 Hz. Therefore, the compatible coating prepared by this invention can meet the radar stealth requirements in the low-frequency band.

[0041] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0042] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A compatible coating, characterized in that, It includes a radar absorbing layer and an infrared stealth layer stacked sequentially on a metal substrate from bottom to top; the radar absorbing layer includes an adhesive layer and an absorbing layer stacked sequentially on the metal substrate, and the infrared stealth layer includes an adhesive layer for improving bonding strength, a matching layer for relieving thermal stress, and a low emissivity layer stacked sequentially on the absorbing layer. The low emissivity layer includes a frequency selective surface layer, which includes M×N frequency selective structures, where M and N are both integers greater than or equal to 1; each frequency selective structure includes a first part, a second part, a third part, and a fourth part arranged clockwise closely and each being a square layer structure, and each frequency selective structure is symmetrical about the center.

2. The compatible coating according to claim 1, characterized in that, The first part contains 5×5 square metal layer structures, which are diagonally symmetrical. A largest metal layer structure is located at one corner of the first part, with a side length of X (not zero). The side lengths of the remaining metal layer structures on the same horizontal or vertical axis as the largest metal layer structure are 0.9X, 0.8X, 0.75X, and 0.55X to 0.65X, respectively. Two of the largest metal layer structures are symmetrical about a line of symmetry L. The side lengths of the metal layer structures on any diagonal line parallel to the line of symmetry L are the same, and the distance between the center points of adjacent metal layer structures is the same. The second part consists of four proportionally reduced and centrally symmetrical first parts.

3. The compatible coating according to claim 1, characterized in that, The adhesive layer is made of nickel-cobalt-chromium-aluminum-yttrium and has a thickness of 85μm to 115μm; the absorbing layer is made of a mixture of ceramic binder matrix, absorber and filler and has a thickness of 1mm to 1.5mm; the bonding layer is made of one of nickel-based solder, aluminum phosphate glue and silica sol and has a thickness of 40μm to 70μm; the matching layer is made of a mixture of alumina and silicon carbide and is a gradient layer formed by alumina and silicon carbide and has a thickness of 50μm to 300μm; the low emissivity layer is made of one of gold, silver, aluminum, copper, nickel and chromium and has a thickness of 0.01 mm to 0.5mm.

4. The compatible coating according to claim 3, characterized in that, In the microwave absorbing layer, the proportions of each substance by mass percentage are as follows: ceramic binder matrix: 40%–70%, absorbent: 20%–50%, filler: 5%–20%.

5. The compatible coating according to claim 3, characterized in that, In the absorbing layer, the ceramic binder matrix includes one or more of silicon carbide, alumina, zirconium oxide, or silicon oxide; the absorber includes one of manganese zinc ferrite metal powder, graphene, silicon carbide, or barium titanate; and the filler includes one of alumina, zirconium oxide, boron nitride, hollow ceramic microspheres, conductive magnetic fillers, and functional ceramics. When alumina is used as the ceramic binder matrix, its particle size is less than 100 nm; when alumina is used as the filler, its particle size is 1 μm to 10 μm, or it is alumina whiskers with an aspect ratio greater than 10.

6. A method for preparing a compatible coating based on any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Pre-treat the substrate surface; Step 2: Spray an adhesive layer onto the pretreated substrate surface; Step 3: First, spray an absorbing layer onto the surface of the adhesive layer, then perform a first heat treatment and cool it. Step 4: First, prepare a bonding layer on the surface of the absorbing layer, then perform a second heat treatment and cool it. Step 5: First, prepare a matching layer on the surface of the bonding layer, then perform a third heat treatment and cool it. Step 6: First, prepare a low emissivity layer on the surface of the matching layer, then perform a fourth heat treatment and cool to obtain the desired compatible coating.

7. The method for preparing the compatible coating according to claim 6, characterized in that, In step 2, an adhesive layer is prepared on the substrate surface using plasma spraying technology. The specific parameters for preparation are as follows: spraying current is 490A~510A, powder feed rate is 40g / min~50g / min, argon flow rate is 48L / min~52L / min, hydrogen flow rate is 2.8L / min~3.2L / min, spray gun moving speed is 490mm / s~510mm / s, spraying spacing is 2.5mm~3.5mm, and spraying distance is 8cm~10cm.

8. The method for preparing the compatible coating according to claim 6, characterized in that, In step 3, a microwave absorbing layer is prepared on the adhesive layer using plasma spraying technology. The parameters for preparation are as follows: spraying current is 540A to 560A, powder feed rate is 35g / min to 45g / min, argon flow rate is 33L / min to 37L / min, hydrogen flow rate is 8.8L / min to 9.2L / min, spray gun moving speed is 490mm / s to 510mm / s, spraying spacing is 2.5mm to 3.5mm, and spraying distance is 8cm to 10cm.

9. The method for preparing the compatible coating according to claim 6, characterized in that, In step 6, a low emissivity layer is prepared using magnetron sputtering technology. The parameters for preparation are: sputtering power of 70W to 90W, sputtering gas pressure of 0.2Pa to 0.3Pa, and target-substrate distance of 50nm to 70nm.

10. The application of the compatible coating according to any one of claims 1 to 5, characterized in that, Applications in radar and infrared stealth.

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