Lightning protection composite coating and preparation method thereof

Abstract

This invention belongs to the field of protective coatings, specifically disclosing a lightning protection composite coating and its preparation method. The composite coating comprises a high-temperature oxidation-resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer stacked sequentially from the inside out. The thickness of the ceramic heat insulation layer is 150–350 μm. The raw materials for preparing the silver-based conductive layer include organic silver salts and complexing agents. The composite coating of this invention utilizes a high-temperature oxidation-resistant layer, a low thermal conductivity ceramic heat insulation layer, and a high conductivity silver-based conductive layer. Through the synergistic effect of these three layers, the composite coating exhibits high bonding strength and low sheet resistance, effectively conducting current to form protection. Under a current of 20 kA, neither the coating nor the substrate material showed any peeling, deformation, cracking, or damage, demonstrating good lightning protection and thermal protection effects.

Description

Technical Field

[0001] This invention belongs to the field of protective coatings, specifically relating to a lightning protection composite coating and its preparation method. Background Technology

[0002] Research on lightning protection coatings for aircraft engines is one of the key technologies to ensure the safe and reliable operation of aircraft. When the high temperature and electromagnetic effects of lightning current act on the surface of the engine, it often causes the ablation or delamination of structural materials with poor conductivity, such as ceramic matrix composites (CMC). At present, metal conductive layers are mainly used to disperse lightning current.

[0003] Compared with traditional metallic materials such as aluminum alloys and titanium alloys, composite materials have poor electrical conductivity. When an aircraft is struck by lightning, the composite material cannot effectively conduct the lightning current. The charge accumulates in large quantities near the lightning strike point and is converted into heat energy, which may cause the composite material to burn, melt, explode, and deform. At the same time, the overvoltage and overcurrent of lightning will also generate a powerful electromagnetic pulse, which will interfere with or damage the electronic systems and components inside the aircraft. Composite material aircraft structures are more likely to suffer serious damage in extreme environments such as lightning strikes, and are more likely to cause catastrophic tragedies. Therefore, lightning protection of composite materials is a very important task in the aircraft design process.

[0004] The damage process of lightning to composite materials is very complex, and the damage is usually caused by the thermo-electric-magnetic-mechanical coupling effect generated by the lightning current. For example, the overpressure effect caused by the instantaneous thermal expansion of the lightning channel, the Joule heating effect of the lightning current on the composite material, and the resulting vaporization recoil effect, all contribute to the immense energy instantaneously transferred from the discharge channel to the composite material, which can cause physicochemical changes such as thermal expansion, phase transition, and high-temperature thermal decomposition on the surface and subsurface of the composite material. Furthermore, when the composite material burns and pyrolyzes to a certain extent, the carbon fibers sublimate, resulting in pits in the matrix, and the pressure of the pyrolysis gases causes delamination of the composite material.

[0005] With the increasing use of composite materials in aircraft, the safety threat posed by lightning is growing. In my country, lightning protection measures for composite materials mainly involve laying metal mesh on their surface. While this method offers some protection, the high thermal conductivity of metal means it doesn't protect against the instantaneous thermal shock of a lightning strike, resulting in poor overall protection and potential damage to the composite material. This still poses significant safety risks and fails to meet the required standards. Summary of the Invention

[0006] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a composite coating that has a better lightning protection effect.

[0007] The second objective of this invention is to provide a method for preparing a composite coating.

[0008] The third objective of this invention is to provide a product.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] The first aspect of the present invention provides a composite coating comprising a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer stacked sequentially from the inside out;

[0011] The material of the high-temperature resistant oxide layer includes at least one of NiCrAlY, CoCrAlY, and NiCoCrAlY;

[0012] The ceramic heat insulation layer is made of zirconium oxide and rare earth oxides doped in the zirconium oxide; the thickness of the ceramic heat insulation layer is 150-350 μm.

[0013] The raw materials for preparing the silver-based conductive layer include organic silver salts and complexing agents.

[0014] In this invention, the composite coating is applied to the surface of the substrate material. From the inside out, "inside" refers to the surface of the substrate material, and "outside" refers to the outer surface of the composite coating, which is furthest from the substrate material. In this invention, the high-temperature oxidation resistant layer is applied to the surface of the substrate material.

[0015] In some embodiments of the present invention, the sheet resistance of the silver-based conductive layer does not exceed 100 mΩ / sq. When the sheet resistance of the silver-based conductive layer is ≤100 mΩ / sq, a conductive path can be formed, thereby achieving the effect of lightning protection. If the sheet resistance of the silver-based conductive layer is >100 mΩ / sq, the conductivity is poor, and it cannot effectively conduct lightning current. Charge accumulates in large quantities near the lightning strike point and is converted into heat energy, which may cause the substrate material to burn, melt, explode, and become structurally deformed, thus failing to achieve an effective lightning protection effect.

[0016] In some embodiments of the present invention, the thermal conductivity of the ceramic insulation layer is 0.8–1 W / mK. The ceramic insulation layer of the present invention has a low thermal conductivity, reducing the longitudinal transfer of heat along the surface of the composite coating to the interior of the substrate material during lightning strikes, thus protecting the substrate material from ablation and structural damage.

[0017] In some embodiments of the present invention, the density of the ceramic heat insulation layer is 4.5–5.5 g / cm³. 2 .

[0018] In some embodiments of the present invention, the thickness of the ceramic heat insulation layer can be selected from any value or a range formed by any two of the following: 150μm, 170μm, 175μm, 200μm, 220μm, 240μm, 250μm, 260μm, 275μm, 280μm, 300μm, 320μm, 340μm, and 350μm. If the thickness of the ceramic heat insulation layer is too small, it cannot provide adequate lightning protection, and the substrate material is easily damaged under lightning strikes. If the thickness of the ceramic heat insulation layer is too large, it will result in excessive weight, failing to meet the lightweight requirements of aircraft and other similar applications, and significantly increasing costs.

[0019] In some embodiments of the present invention, the sheet resistance of the silver-based conductive layer is 15 to 40 mΩ / sq; in some embodiments of the present invention, the sheet resistance of the silver-based conductive layer can be selected from any value of 15 mΩ / sq, 17 mΩ / sq, 19 mΩ / sq, 20 mΩ / sq, 22 mΩ / sq, 24 mΩ / sq, 26 mΩ / sq, 28 mΩ / sq, 30 mΩ / sq, 32 mΩ / sq, 34 mΩ / sq, 36 mΩ / sq, 38 mΩ / sq, 40 mΩ / sq, or a range formed by any two of these values.

[0020] In some embodiments of the present invention, the thickness of the silver-based conductive layer is 1 to 10 μm; in some embodiments of the present invention, the thickness of the silver-based conductive layer is any value of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or a range formed by any two of these values.

[0021] In some embodiments of the present invention, the thickness of the high-temperature oxidation-resistant layer is 50–250 μm; in some embodiments of the present invention, the thickness of the high-temperature oxidation-resistant layer is any value or a range formed by any two of the following: 50 μm, 70 μm, 75 μm, 90 μm, 100 μm, 120 μm, 140 μm, 150 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, and 250 μm.

[0022] In some embodiments of the present invention, the silver-based conductive layer is prepared by coating the raw materials for preparing the silver-based conductive layer onto the ceramic heat insulation layer, and then reacting at 180℃ to 580℃ to precipitate metallic silver. In the preparation of the silver-based conductive layer, the present invention uses an organic silver salt as the silver source. The organic silver salt and a complexing agent are complexed and coated onto the surface of the ceramic heat insulation layer. Upon heating, silver precipitates and is in situ loaded onto the surface of the ceramic heat insulation layer, forming a conductive network on the surface of the ceramic heat insulation layer. This results in good conductivity and can effectively prevent lightning strikes. Furthermore, the present invention uses organic silver salts and a complexing agent to prepare the silver-based conductive layer, which significantly reduces the preparation cost compared to coating with silver paste.

[0023] In some embodiments of the present invention, the reaction time is 10 to 60 min; in some embodiments of the present invention, the reaction time is any value of 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, or a range formed by any two of them.

[0024] In some embodiments of the present invention, the reaction temperature may be selected from any value or a range formed by any two of 180°C, 200°C, 220°C, 230°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, and 582°C.

[0025] In some embodiments of the present invention, the rare earth oxide includes at least one of Y2O3, Gd2O3, and Yb2O3.

[0026] In some embodiments of the present invention, the rare earth oxide comprises 3-8% by mass of Gd2O3 and 3-8% by mass of Yb2O3.

[0027] In some embodiments of the present invention, the rare earth oxide comprises 6-10% Y2O3 by mass.

[0028] In some embodiments of the present invention, the organic silver salt is selected from at least one of silver formate, silver oxalate, silver citrate, and silver benzoate.

[0029] In some embodiments of the present invention, the complexing agent is selected from at least one of ethylamine, n-butylamine, ethanolamine, ethylenediamine, diethanolamine, isopropanolamine, and aniline.

[0030] In some embodiments of the present invention, the raw materials for preparing the silver-based conductive layer also include organic solvents.

[0031] In some embodiments of the present invention, the organic solvent includes at least one selected from acetone, methanol, ethanol, ethylene glycol, propylene glycol, n-butanol, isobutanol, n-pentanol, and cyclohexanol; in some embodiments of the present invention, the organic solvent includes n-butanol, n-pentanol, and cyclohexanol.

[0032] In some embodiments of the present invention, the raw materials for preparing the silver-based conductive layer also include a purification agent.

[0033] In some embodiments of the present invention, the impurity remover is selected from at least one of sodium dodecylbenzenesulfonate (LAS), methyl diethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), phenyl dimethyl ketone (BHT), and ethanolamine (MEA). With the assistance of the impurity remover, organic matter in the raw materials for preparing the silver-based conductive layer is converted into carbon dioxide and discharged at a temperature of 180°C to 580°C, while silver ions are precipitated to form a silver-based conductive layer. The material of the silver-based conductive layer is silver. The impurity remover can significantly reduce the content of non-silver impurities in the silver-based conductive layer, avoiding the influence of non-silver impurities on the conductivity of the silver-based conductive layer, ensuring that the sheet resistance of the silver-based conductive layer does not exceed 100 mΩ / sq.

[0034] In some embodiments of the present invention, the mass ratio of organic silver salt to complexing agent is (0.2-7):1.

[0035] In some embodiments of the present invention, the silver-based conductive layer comprises the following raw materials in parts by weight: 1-7 parts of organic silver salt, 4-7 parts of organic solvent, 0.1-3 parts of impurity remover, and 1-6 parts of complexing agent.

[0036] In some embodiments of the present invention, the material of the ceramic heat insulation layer is yttrium-stabilized zirconium oxide.

[0037] In some embodiments of the present invention, the high-temperature oxidation-resistant layer is disposed on a substrate material, the substrate material being selected from carbon fiber, ceramic materials, or metal alloys.

[0038] In some embodiments of the present invention, the metal alloy is a lightweight alloy.

[0039] In some embodiments of the present invention, the metal alloy is selected from aluminum alloys or magnesium alloys.

[0040] In some embodiments of the present invention, the ceramic material may be a ceramic material used in aircraft engines.

[0041] The second aspect of the present invention provides a method for preparing the composite coating described in the first aspect of the present invention, comprising the following steps:

[0042] The composite coating is prepared by sequentially forming a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer on a substrate material.

[0043] In some embodiments of the present invention, the preparation method includes the following steps:

[0044] The preparation material is prepared by first spraying a high-temperature resistant oxidation layer onto a substrate material, then spraying a ceramic heat insulation layer, and then coating the raw material for the silver-based conductive layer onto the ceramic heat insulation layer. The mixture is then reacted at 180℃~580℃ to precipitate metallic silver.

[0045] In some embodiments of the present invention, the high-temperature resistant oxide layer and the ceramic heat insulation layer are respectively prepared by at least one method selected from supersonic flame spraying, atmospheric plasma spraying, low-pressure plasma spraying, plasma-physical vapor deposition, and magnetron sputtering.

[0046] In some embodiments of the present invention, the high-temperature oxidation-resistant layer is prepared by atmospheric plasma spraying or low-pressure plasma spraying.

[0047] In some embodiments of the present invention, the ceramic heat insulation layer is prepared by atmospheric plasma spraying or plasma-physical vapor deposition.

[0048] In some embodiments of the present invention, the high-temperature oxidation-resistant layer and / or ceramic heat insulation layer are prepared by atmospheric plasma spraying. The parameters for atmospheric plasma spraying are: argon flow rate 25-50 L / min, hydrogen flow rate 5-30 L / min, current 500-700 A, powder feeding rate 10-30 g / min, and spraying distance 100-300 mm. Spraying under the parameters of the present invention is beneficial to the control and formation of ceramic-ceramic and ceramic-metal interfaces, thereby improving the bonding strength and lightning protection performance of the composite coating.

[0049] In some embodiments of the present invention, the argon flow rate is any value or a range formed by any two of the following: 25 L / min, 27 L / min, 30 L / min, 35 L / min, 37 L / min, 40 L / min, 45 L / min, 47 L / min, and 50 L / min.

[0050] In some embodiments of the present invention, the hydrogen flow rate is any value or a range formed by any two of the following: 5 L / min, 7 L / min, 10 L / min, 13 L / min, 15 L / min, 17 L / min, 20 L / min, 23 L / min, 25 L / min, 27 L / min, and 30 L / min.

[0051] In some embodiments of the present invention, the current is any value or a range formed by any two of the following: 500A, 520A, 540A, 550A, 560A, 570A, 580A, 600A, 620A, 640A, 660A, 680A, and 700A.

[0052] In some embodiments of the present invention, the powder feeding rate is any value of 10 g / min, 15 g / min, 20 g / min, 25 g / min, 30 g / min, or a range formed by any two of these values.

[0053] In some embodiments of the present invention, the spraying distance is any value of 100mm, 120mm, 150mm, 170mm, 200mm, 220mm, 250mm, 270mm, 300mm, or a range formed by any two of them.

[0054] In some embodiments of the present invention, the high-temperature oxidation-resistant layer is prepared by atmospheric plasma spraying; the parameters of atmospheric plasma spraying are: argon flow rate 25-50 L / min, hydrogen flow rate 5-30 L / min, current 500-600 A, powder feeding rate 10-20 g / min, and spraying distance 100-300 mm.

[0055] In some embodiments of the present invention, the ceramic heat insulation layer is prepared by atmospheric plasma spraying; the parameters of atmospheric plasma spraying are: argon flow rate 25-50 L / min, hydrogen flow rate 5-30 L / min, current 500-700 A, powder feeding rate 10-30 g / min, and spraying distance 100-300 mm.

[0056] A third aspect of the invention provides a product comprising the composite coating described in the first aspect of the invention, the product being selected from aircraft, ships, trains, or automobiles.

[0057] In some embodiments of the present invention, the product further includes a surface skin and a load-bearing structural component, wherein the surface skin is provided on the surface of the load-bearing structural component, and the surface skin is provided with the composite coating described in the first aspect of the present invention. The surface skin is the base material described above.

[0058] In some embodiments of the present invention, the aircraft is selected from airplanes and drones.

[0059] The beneficial effects of this invention are as follows: The composite coating of this invention adopts a high-temperature oxidation-resistant layer, a low thermal conductivity ceramic heat insulation layer, and a high conductivity silver-based conductive layer. Through the synergistic effect between the three layers, the composite coating has high bonding strength (30-50MPa) and low sheet resistance (not exceeding 100mΩ / sq). It can effectively conduct current to form protection. Under a current of 20kA, neither the coating nor the substrate material showed any peeling, deformation, cracking, or damage. It has good lightning protection and thermal protection effects.

[0060] The high-temperature oxidation layer and the ceramic heat insulation layer in the composite coating of this invention both have low thermal conductivity. The combined thermal protection and thermal matching of the two form a gradient protection against the longitudinal energy transfer during a lightning strike, and provide effective protection against the thermal shock during a lightning strike, thus enabling the coating to serve reliably. Attached Figure Description

[0061] Figure 1This is a schematic diagram of the lightning protection composite coating in Example 1.

[0062] Figure 2 This is a physical image of the lightning protection composite coating in Example 1.

[0063] Figure 3 This is a diagram illustrating the mechanism of the silver benzoate complexation reaction in Example 1.

[0064] Figure 4 This is a photograph of the silver-based conductive layer precursor solution in Example 1.

[0065] Figure 5 This is a measured surface resistance diagram of the lightning protection composite coating in Example 1.

[0066] Figure 6 The image shows the actual product of the lightning protection composite coating in Example 2 after being subjected to a 40KA lightning strike test using a simulated resistor-inductor (RL). Detailed Implementation

[0067] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0068] The material information used in the following embodiments and comparative examples is as follows:

[0069] The YSZ layer is yttrium oxide-stabilized zirconium oxide, wherein the mass percentage of yttrium oxide is 8% and the mass percentage of zirconium oxide is 92%.

[0070] The NiCrAlY layer is composed of elements such as Ni, Cr, Al, and Y. Its raw material is NiCrAlY powder, which is composed of the following components by mass percentage: Ni 67%, Cr 22%, Al 10%, and Y 1%.

[0071] Example 1

[0072] This example provides a lightning protection composite coating, which is applied to the surface of a skin substrate (the material of which is carbon fiber). The coating includes a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer sequentially stacked on the skin substrate. The high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100 μm; the ceramic heat insulation layer is a YSZ layer with a thickness of 175 μm; and the silver-based conductive layer is made of silver benzoate with a thickness of 10 μm.

[0073] The structural schematic diagram of the lightning protection composite coating in this example is shown below. Figure 1As shown in the picture, the actual product is as follows. Figure 2 As shown. By Figure 1 It can be seen that a ceramic-ceramic interface is formed between the high-temperature resistant oxide layer and the ceramic heat insulation layer, and a ceramic-metal interface is formed between the ceramic heat insulation layer and the silver-based conductive layer, thus giving the composite coating a good interface bonding effect and good performance.

[0074] This example also provides a method for preparing a lightning protection composite coating, the specific steps of which are as follows:

[0075] (1) Carbon fiber is selected as the skin substrate, and the thickness of the skin substrate is 30mm.

[0076] (2) NiCrAlY powder was sprayed onto the surface of the skin substrate to prepare a NiCrAlY high-temperature oxidation resistant layer with a thickness of 100μm by atmospheric plasma spraying. Spraying parameters: spraying distance 300mm, argon flow rate 27L / min, hydrogen flow rate 7L / min, current 450A, powder feeding rate 10g / min.

[0077] (3) YSZ powder was sprayed onto the surface of the high-temperature oxidation layer to prepare a YSZ ceramic heat insulation layer with a thickness of 175μm by atmospheric plasma spraying. Spraying parameters: spraying distance 300mm, argon flow rate 30L / min, hydrogen flow rate 15L / min, current 500A, powder feeding rate 10g / min.

[0078] (4) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to form an organic solvent and mix it with the impurity remover diisopropanolamine (DIPA) until the diisopropanolamine is fully dissolved to obtain a mixed solvent. The amount of diisopropanolamine used is 0.5 parts by weight.

[0079] (5) Add silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mix evenly by magnetic stirring. Under ice bath conditions, add a complexing agent composed of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine dropwise, and continue stirring until the solution is clear and transparent to obtain a silver-based conductive layer precursor solution. The complexation reaction mechanism of silver benzoate and the complexing agent is as follows: Figure 3 As shown in the image, a physical diagram of the silver-based conductive layer precursor solution is as follows: Figure 4 As shown;

[0080] (6) The silver-based conductive layer precursor solution obtained in step (5) is uniformly brushed onto the surface of the ceramic heat insulation layer obtained in step (3), and placed in an oven at 180°C for 30 minutes to obtain the lightning protection composite coating in this example.

[0081] The adhesion and surface resistivity of the composite coating in this example were tested according to HB5476 and GB / T 40007-2021 standards. The adhesion strength of the coating was 34 MPa, and the surface resistivity was 30 mΩ / sq. A photograph of the actual product is shown below. Figure 5 As shown. In this example, the lightning protection composite coating did not peel off or crack after being tested for 5 seconds with a 20kA current on a simulated resistor-inductor (RL) lightning strike test platform. At the point of lightning strike, the coating surface material underwent a phase change, resulting in partial discoloration, but the skin substrate and coating remained intact and undamaged.

[0082] The density of the ceramic insulation layer obtained in step (2) of this example was tested, and its thermal diffusivity, thermal conductivity and specific heat capacity were tested at different temperatures. The specific test results are shown in Table 1 below.

[0083]

[0084] Example 2

[0085] This example provides a lightning protection composite coating, which is applied to the surface of a skin substrate (made of aluminum alloy). The coating includes a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer sequentially stacked on the skin substrate. The high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100 μm; the ceramic heat insulation layer is a YSZ layer with a thickness of 175 μm; and the silver-based conductive layer is made of silver benzoate with a thickness of 9 μm.

[0086] This example also provides a method for preparing a lightning protection composite coating, the specific steps of which are as follows:

[0087] (1) Aluminum alloy is selected as the skin substrate, and the thickness of the skin substrate is 30mm.

[0088] (2) NiCrAlY powder was sprayed onto the surface of the skin substrate to prepare a NiCrAlY high-temperature oxidation resistant layer with a thickness of 100μm by atmospheric plasma spraying. Spraying parameters: spraying distance 200mm, argon flow rate 27L / min, hydrogen flow rate 7L / min, current 500A, powder feeding rate 10g / min.

[0089] (3) YSZ powder was sprayed onto the surface of the high-temperature oxidation layer to prepare a YSZ ceramic heat insulation layer with a thickness of 175μm by atmospheric plasma spraying. Spraying parameters: spraying distance 200mm, argon flow rate 30L / min, hydrogen flow rate 15L / min, current 600A, powder feeding rate 10g / min.

[0090] (4) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to form an organic solvent and mix it with the impurity remover diisopropanolamine (DIPA) until the diisopropanolamine is fully dissolved to obtain a mixed solvent. The amount of diisopropanolamine used is 0.5 parts by weight.

[0091] (5) Add silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mix it evenly by magnetic stirring. Add a complexing agent composed of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine dropwise under ice bath conditions and continue stirring until the solution is clear and transparent to obtain silver-based conductive layer precursor solution.

[0092] (6) The silver-based conductive layer precursor solution obtained in step (5) is uniformly brushed onto the surface of the high-temperature resistant oxide layer obtained in step (3), and placed in an oven at 180°C for 30 minutes to obtain the lightning protection composite coating in this example.

[0093] Referring to HB5476 and GB / T 40007-2021 standards, the adhesion strength and surface resistivity of the composite coating in this example are as follows: the coating adhesion strength is 41 MPa, and the surface resistivity is 18 mΩ / sq. In this example, the lightning protection composite coating was subjected to a 40 kA current for 5 seconds on a simulated resistor-inductor (RL) lightning strike test platform. After the test, the coating did not peel or crack. At the lightning strike point, the coating surface material underwent a phase change, resulting in partial discoloration, but the skin substrate and coating remained intact. A photograph of the actual product is shown below. Figure 6 As shown.

[0094] Comparative Example 1

[0095] This example provides a composite coating disposed on the surface of a skin substrate (the material of which is aluminum alloy). The coating includes a high-temperature oxidation resistant layer and a ceramic heat insulation layer sequentially stacked on the skin substrate. The high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100 μm, and the ceramic heat insulation layer is a YSZ layer with a thickness of 175 μm.

[0096] This example also provides a method for preparing a composite coating, the specific steps of which are as follows:

[0097] (1) Aluminum alloy is selected as the skin substrate, and the thickness of the skin substrate is 30mm.

[0098] (2) NiCrAlY powder was sprayed onto the surface of the skin substrate to prepare a NiCrAlY high-temperature oxidation resistant layer with a thickness of 100μm. The spraying parameters were: spraying distance 200mm, argon flow rate 27L / min, hydrogen flow rate 7L / min, current 500A, and powder feeding rate 10g / min.

[0099] (3) YSZ powder was sprayed onto the surface of the high-temperature oxidation layer to prepare a YSZ ceramic heat insulation layer with a thickness of 175μm by atmospheric plasma spraying. The spraying parameters were: spraying distance of 200mm, argon flow rate of 30L / min, hydrogen flow rate of 15L / min, current of 600A, and powder feeding rate of 10g / min. The composite coating in this example was obtained.

[0100] Referring to HB5476 and GB / T 40007-2021 standards, the adhesion strength and surface resistivity of the composite coating in this example are as follows: the coating adhesion strength is 47 MPa, and the sheet resistivity is 10 Ω·cm. 7 Ω / sq, non-conductive, during the simulated lightning strike test, the center of the impact point cracked, the coating surface was ablated and partially peeled off, the back of the skin substrate was deformed, and there was no lightning protection effect.

[0101] Comparative Example 2

[0102] This example provides a lightning protection composite coating, which is applied to the surface of a skin substrate (made of aluminum alloy). The coating includes a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer sequentially stacked on the skin substrate. The high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100 μm; the ceramic heat insulation layer is a YSZ layer with a thickness of 75 μm; and the silver-based conductive layer is made of silver benzoate with a thickness of 9 μm.

[0103] This example also provides a method for preparing a lightning protection composite coating, the specific steps of which are as follows:

[0104] (1) Aluminum alloy is selected as the skin substrate, and the thickness of the skin substrate is 30mm.

[0105] (2) NiCrAlY powder was sprayed onto the surface of the skin substrate to prepare a NiCrAlY high-temperature oxidation resistant layer with a thickness of 100μm. The spraying parameters were: spraying distance 200mm, argon flow rate 27L / min, hydrogen flow rate 7L / min, current 500A, and powder feeding rate 10g / min.

[0106] (3) YSZ powder was sprayed onto the surface of the high-temperature oxidation layer to prepare a YSZ ceramic heat insulation layer with a thickness of 75μm by atmospheric plasma spraying. Spraying parameters: spraying distance 200mm, argon flow rate 30L / min, hydrogen flow rate 15L / min, current 600A, powder feeding rate 10g / min.

[0107] (4) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to form an organic solvent and mix it with the impurity remover diisopropanolamine (DIPA, amount of 0.5 parts by weight) until the diisopropanolamine is fully dissolved to obtain a mixed solvent.

[0108] (5) Add silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mix it evenly by magnetic stirring. Add a complexing agent composed of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine dropwise under ice bath conditions and continue stirring until the solution is clear and transparent to obtain silver-based conductive layer precursor solution.

[0109] (6) The silver-based conductive layer precursor solution obtained in step (5) is uniformly brushed onto the surface of the ceramic heat insulation layer obtained in step (3), and placed in an oven at 180°C for 30 minutes to obtain the lightning protection composite coating in this example.

[0110] Referring to HB5476 and GB / T 40007-2021 standards, the bonding strength and surface resistivity of the composite coating in this example are as follows: the coating bonding strength is 53 MPa, and the surface resistivity is 14 mΩ / sq. In this example, after a 40 kA current test was applied to the simulated resistor-inductor (RL) lightning strike test platform, the coating partially detached at the strike point, without edge cracking. The coating surface material at the strike point underwent a phase change, resulting in partial discoloration, and the back of the skin substrate deformed. This was because the ceramic insulation layer was too thin to effectively protect the low-melting-point lightweight aluminum alloy skin substrate, causing the skin substrate material to fail. Furthermore, due to the large instantaneous thermal shock, the skin substrate and composite coating could not bond effectively, resulting in partial coating detachment.

[0111] Comparative Example 3

[0112] This example provides a lightning protection composite coating, which is applied to the surface of a skin substrate (the material of which is aluminum alloy). The coating includes a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer sequentially stacked on the skin substrate. The high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100 μm; the ceramic heat insulation layer is a YSZ layer with a thickness of 175 μm; and the silver-based conductive layer is made of silver benzoate with a thickness of 10 μm.

[0113] This example also provides a method for preparing a lightning protection composite coating, the specific steps of which are as follows:

[0114] (1) Aluminum alloy is selected as the skin substrate, and the thickness of the skin substrate is 30mm.

[0115] (2) NiCrAlY powder was sprayed onto the surface of the skin substrate to prepare a NiCrAlY high-temperature oxidation resistant layer with a thickness of 100μm by atmospheric plasma spraying. Spraying parameters: spraying distance 200mm, argon flow rate 27L / min, hydrogen flow rate 7L / min, current 500A, powder feeding rate 10g / min.

[0116] (3) YSZ powder was sprayed onto the surface of the high-temperature oxidation layer to prepare a YSZ ceramic heat insulation layer with a thickness of 175μm by atmospheric plasma spraying. Spraying parameters: spraying distance of 200mm, argon flow rate of 30L / min, hydrogen flow rate of 15L / min, current of 600A, and powder feeding rate of 10g / min.

[0117] (4) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to form an organic solvent and mix it with the impurity remover diisopropanolamine (DIPA, the amount of which is 0.5 parts by weight) until the diisopropanolamine is fully dissolved to obtain a mixed solvent.

[0118] (5) Add silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mix it evenly by magnetic stirring. Add a complexing agent composed of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine dropwise under ice bath conditions and continue stirring until the solution is clear and transparent to obtain silver-based conductive layer precursor solution.

[0119] (6) The silver-based conductive layer precursor solution obtained in step (5) is uniformly brushed onto the surface of the ceramic heat insulation layer obtained in step (3), and placed in an 80°C oven for 30 minutes to obtain the lightning protection composite coating in this example.

[0120] Referring to the HB5476 standard and GB / T 40007-2021 standard, the bonding strength and surface resistance of the composite coating in this example are as follows: the coating bonding strength is 39MPa and the surface resistance is 32Ω / sq. Due to the low reduction temperature of the silver-based conductive layer precursor, less conductive silver elemental is precipitated, resulting in extremely poor conductivity of the coating surface. During the simulated lightning strike test, the center of the impact point cracked, the coating surface was ablated and partially detached, the back of the skin substrate was deformed, and there was no lightning protection effect.

[0121] Comparative Example 4

[0122] This example provides a conductive coating disposed on the surface of a skin substrate (the material of which is aluminum alloy). The coating is a silver-based conductive layer. The material used to prepare the silver-based conductive layer includes silver benzoate, and the thickness of the silver-based conductive layer is 10 μm.

[0123] This example also provides a method for preparing a conductive coating, the specific steps of which are as follows:

[0124] (1) Aluminum alloy is selected as the skin substrate, and the thickness of the skin substrate is 30mm.

[0125] (2) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to form an organic solvent and mix it with the impurity remover diisopropanolamine (DIPA, the amount of which is 0.5 parts by weight) until the diisopropanolamine is fully dissolved to obtain a mixed solvent.

[0126] (3) Add silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (2) and mix it evenly by magnetic stirring. Add a complexing agent composed of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine dropwise under ice bath conditions and continue stirring until the solution is clear and transparent to obtain silver-based conductive layer precursor solution.

[0127] (4) The silver-based conductive layer precursor solution obtained in step (3) is uniformly brushed onto the surface of the skin substrate and placed in an oven at 180°C for 30 minutes to obtain the conductive coating in this example.

[0128] Referring to the adhesion strength test using the cross-cut adhesion test and the bonding strength and surface resistivity of the composite coating in this example according to GB / T 40007-2021 standard, the coating adhesion strength is HB grade, the sheet resistance is 2.6mΩ / sq, and the conductivity is excellent. After applying a 4kA current to the conductive coating prepared in this example on a simulated resistor-inductor (RL) lightning strike test platform, both the coating and the skin substrate showed melting at the impact point, and the skin substrate was severely deformed. This was because the low-melting-point lightweight alloy skin substrate was not protected by a ceramic heat insulation layer, causing the skin substrate material to fail.

[0129] In summary, the composite coating in this invention exhibits good bonding strength (over 30 MPa) with the skin substrate, excellent electrical conductivity, and a sheet resistance of 18–30 mΩ / sq, enabling charge conduction on the aircraft surface. Furthermore, the low thermal conductivity ceramic insulation layer provides instantaneous thermal shock protection to the skin substrate. By ion-complexing highly conductive metals, rapid preparation of the silver-based conductive layer and good compatibility with the ceramic insulation layer are achieved, making it suitable for lightning protection of carbon fiber or aluminum alloy skins for aircraft.

[0130] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A composite coating, characterized in that: It includes a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer, which are stacked sequentially from the inside out; The material of the high-temperature resistant oxide layer includes at least one of NiCrAlY, CoCrAlY, and NiCoCrAlY; The ceramic heat insulation layer is made of zirconium oxide and rare earth oxides doped in the zirconium oxide; the thickness of the ceramic heat insulation layer is 150~350μm. The silver-based conductive layer comprises the following raw materials in parts by weight: 1-7 parts organic silver salt, 4-7 parts organic solvent, 0.1-3 parts impurity remover, and 1-6 parts complexing agent; The impurity remover is selected from at least one of sodium dodecylbenzenesulfonate, methyl diethanolamine, diethanolamine, diisopropanolamine, phenyl dimethyl ketone, and ethanolamine; The sheet resistance of the silver-based conductive layer does not exceed 30 mΩ / sq.

2. The composite coating according to claim 1, characterized in that: The thickness of the silver-based conductive layer is 1~10μm; And / or, the thickness of the high-temperature resistant oxide layer is 50~250μm.

3. The composite coating according to claim 1, characterized in that: The silver-based conductive layer is prepared by coating the raw materials for preparing the silver-based conductive layer onto the ceramic heat insulation layer, and then reacting at 180℃~580℃ to precipitate metallic silver.

4. The composite coating according to claim 1, characterized in that: The rare earth oxides include at least one of Y2O3, Gd2O3, and Yb2O3; And / or, the organic silver salt is selected from at least one of silver formate, silver oxalate, silver citrate, and silver benzoate; And / or, the complexing agent is selected from at least one of ethylamine, n-butylamine, ethanolamine, ethylenediamine, diethanolamine, isopropanolamine, and aniline.

5. The composite coating according to claim 1, characterized in that: The ceramic insulation layer is made of yttrium-stabilized zirconium oxide.

6. The composite coating according to any one of claims 1 to 5, characterized in that: The high-temperature oxidation resistant layer is disposed on a substrate material, which is selected from carbon fiber, ceramic materials or metal alloys.

7. The method for preparing the composite coating according to any one of claims 1 to 6, characterized in that: Includes the following steps: The composite coating is prepared by sequentially forming a high-temperature oxidation resistant layer, a ceramic heat insulation layer, and a silver-based conductive layer on a substrate material.

8. The method for preparing the composite coating according to claim 7, characterized in that: The high-temperature resistant oxide layer and the ceramic heat insulation layer are respectively prepared by at least one method selected from supersonic flame spraying, atmospheric plasma spraying, low-pressure plasma spraying, plasma-physical vapor deposition, and magnetron sputtering.

9. The method for preparing the composite coating according to claim 8, characterized in that: The high-temperature oxidation-resistant layer and / or ceramic heat insulation layer are prepared by atmospheric plasma spraying. The parameters of atmospheric plasma spraying are: argon flow rate 25~50L / min, hydrogen flow rate 5~30L / min, current 500~700A, powder feeding rate 10~30g / min, and spraying distance 100~300mm.

10. A product, characterized in that: The product includes the composite coating described in any one of claims 1 to 6, wherein the product is selected from aircraft, ships, trains, or automobiles.

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