Lightning protection composite coating and preparation method thereof

Abstract

The invention belongs to the field of protective coatings, and particularly discloses a lightning protection composite coating and a preparation method thereof. The composite coating comprises a high-temperature-resistant oxidation layer, a ceramic heat insulation layer and a silver-based conductive layer which are sequentially arranged in a stacked mode from inside to outside. The thickness of the ceramic heat insulation layer is 150 to 350 microns; the preparation raw materials of the silver-based conductive layer comprise organic silver salt and a complexing agent. According to the composite coating, the high-temperature-resistant oxidation layer, the low-heat-conductivity ceramic heat insulation layer and the high-conductivity silver-based conductive layer are adopted, through the synergistic effect of the three layers, the composite coating has high bonding strength and low square resistance, current can be effectively conducted to form protection, and the service life of the composite coating is prolonged. Under the current of 20kA, the coating and the base material do not fall off, deform, crack or damage, and the like, so that the coating has better lightning protection effect and thermal protection effect.

Description

Technical Field

[0001] The present invention belongs to the field of protective coatings, and in particular relates to a lightning protection composite coating and a preparation method thereof. Background Art

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

[0003] Compared with traditional metal materials such as aluminum alloy and titanium alloy, composite materials have poor electrical conductivity. When an aircraft is struck by lightning, the composite materials cannot effectively conduct the lightning current. The charges accumulate in large quantities near the lightning strike point and are converted into heat energy, which may cause the composite materials to burn, melt, explode and deform the structure. At the same time, the overvoltage and overcurrent caused by lightning will also generate powerful electromagnetic pulses, causing interference or damage to the electronic systems and components inside the aircraft, which can easily cause serious damage to the composite aircraft structure in extreme environments such as lightning, making catastrophic tragedies more likely to occur. Therefore, in the aircraft design process, lightning protection of composite materials is a very important task.

[0004] The damage process of lightning on composite materials is highly complex, typically caused by the thermal-electrical-magnetic-mechanical coupling effects of lightning currents. These include the overvoltage effect caused by the instantaneous thermal expansion of the lightning channel, the Joule heating of the composite material caused by the lightning current, and the resulting vaporization recoil effect of the composite material. The enormous energy instantly transmitted from the discharge channel to the composite material can cause physical and chemical changes such as thermal expansion, phase transitions, and high-temperature thermal decomposition on the composite surface and subsurface. Furthermore, when the composite material burns and pyrolyzes to a certain extent, the carbon fibers sublime, resulting in pits in the matrix. The pressure of the pyrolysis gases causes the composite material to delaminate.

[0005] With the increasing use of composite materials in aircraft, the threat posed by lightning to aircraft safety is becoming increasingly significant. my country's lightning protection measures for composite materials primarily involve laying metal mesh on the composite surface. While this method can provide some lightning protection, due to the high thermal conductivity of metal, it provides no protection against the instantaneous thermal shock of lightning strikes, resulting in poor lightning protection and some damage to the composite material. This still presents significant safety risks and fails to meet operational requirements. Summary of the Invention

[0006] In order to overcome at least one technical problem existing in the above-mentioned prior art, one of the objectives of the present invention is to provide a composite coating having a good lightning protection effect.

[0007] The second object of the present invention is to provide a method for preparing a composite coating

[0008] A third object of the present invention is to provide a product.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

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

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

[0012] The material of the ceramic heat-insulating layer includes zirconium oxide and rare earth oxide doped in the zirconium oxide; the thickness of the ceramic heat-insulating layer is 150 to 350 μm;

[0013] The raw materials for preparing the silver-based conductive layer include organic silver salt and a complexing agent.

[0014] The composite coating in the present invention is provided on the surface of the substrate. From inside to outside, "inside" refers to the surface of the substrate, and "outside" refers to the outer surface of the composite coating, which is the farthest away from the substrate. The high-temperature oxidation resistant layer in the present invention is provided on the surface of the substrate.

[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 providing lightning protection. However, if the sheet resistance of the silver-based conductive layer is greater than 100 mΩ / sq, the conductivity is poor and the lightning current cannot be effectively conducted. Charge accumulates near the lightning strike point and is converted into heat energy, potentially causing the base material to burn, melt, explode, and deform, thus failing to provide effective lightning protection.

[0016] In some embodiments of the present invention, the ceramic thermal insulation layer has a thermal conductivity of 0.8 to 1 W / mK. The ceramic thermal insulation layer of the present invention has a low thermal conductivity, which reduces the longitudinal transfer of heat from the composite coating surface to the interior of the substrate during a lightning strike, thereby protecting the substrate from ablation and structural damage.

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

[0018] In some embodiments of the present invention, the thickness of the ceramic thermal insulation layer can be selected from any one of 150 μm, 170 μm, 175 μm, 200 μm, 220 μm, 240 μm, 250 μm, 260 μm, 275 μm, 280 μm, 300 μm, 320 μm, 340 μm, and 350 μm, or a range formed by any two of these values. If the thickness of the ceramic thermal insulation layer is too small, it will not effectively protect against lightning strikes, and the base material will be easily damaged by lightning strikes. If the thickness of the ceramic thermal insulation layer is too thick, it will be too heavy, which will not meet the requirements of lightweight aircraft and other equipment, and the cost will increase significantly.

[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 one 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, and 40 mΩ / sq, or a range formed by any two of the 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 one of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, or a range formed by any two of the values.

[0021] In some embodiments of the present invention, the thickness of the high-temperature oxidation resistant layer is 50 to 250 μm; in some embodiments of the present invention, the thickness of the high-temperature oxidation resistant layer is 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, 250 μm, or a range formed by any two of the values.

[0022] In some embodiments of the present invention, the silver-based conductive layer is prepared by coating raw materials for preparing the silver-based conductive layer onto the ceramic insulation layer, followed by reaction at 180°C to 580°C to precipitate metallic silver. In the present invention, an organic silver salt is used as the silver source in preparing the silver-based conductive layer. The organic silver salt is complexed with a complexing agent and then coated on the surface of the ceramic insulation layer. Upon heating, silver is precipitated and in-situ loaded onto the surface of the ceramic insulation layer, forming a conductive network on the surface of the ceramic insulation layer. This provides excellent electrical conductivity and can effectively prevent lightning strikes. Furthermore, the present invention uses an organic silver salt and a complexing agent to prepare the silver-based conductive layer, significantly reducing preparation costs 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 one 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 can be selected from any value of 180°C, 200°C, 220°C, 230°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 582°C, or a range formed by any two of them.

[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% by mass of Y2O3.

[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 further include an organic solvent.

[0031] In some embodiments of the present invention, the organic solvent includes at least one of 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 further include an impurity remover.

[0033] In some embodiments of the present invention, the impurity remover is selected from at least one of sodium dodecylbenzenesulfonate (LAS), methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), phenyldimethyl ketone (BHT), and ethanolamine (MEA). With the assistance of the impurity remover, the 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, and silver ions are precipitated to form a silver-based conductive layer, the material of the silver-based conductive layer being silver. The impurity remover can significantly reduce the content of non-silver impurities in the silver-based conductive layer, prevent the non-silver impurities from affecting the conductive properties of the silver-based conductive layer, and ensure that the sheet resistance of the silver-based conductive layer does not exceed 100mΩ / sq.

[0034] In some embodiments of the present invention, the mass ratio of the organic silver salt to the 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 to 7 parts of an organic silver salt, 4 to 7 parts of an organic solvent, 0.1 to 3 parts of an impurity remover, and 1 to 6 parts of a complexing agent.

[0036] In some embodiments of the present invention, the material of the ceramic thermal insulation layer is yttria-stabilized zirconia.

[0037] In some embodiments of the present invention, the high temperature oxidation resistant layer is provided on a base material, and the base material is selected from carbon fiber, ceramic material or metal alloy.

[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 alloy or magnesium alloy.

[0040] In some embodiments of the present invention, the ceramic material may be a ceramic material on an aircraft engine.

[0041] A second aspect of the present invention provides a method for preparing the composite coating according to the first aspect of the present invention, comprising the following steps:

[0042] A high-temperature oxidation resistant layer, a ceramic heat-insulating layer and a silver-based conductive layer are sequentially formed on a base material to prepare the composite coating.

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

[0044] The high-temperature oxidation resistant layer is first sprayed on the base material, and then the ceramic heat insulation layer is sprayed. The raw materials for preparing the silver-based conductive layer are then coated on the ceramic heat insulation layer. The reaction is then carried out at 180°C to 580°C to precipitate metallic silver.

[0045] In some embodiments of the present invention, the high-temperature oxidation resistant layer and the ceramic thermal 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 thermal 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 thermal insulation layer are produced by atmospheric plasma spraying; the atmospheric plasma spraying parameters are: argon flow rate of 25-50 L / min, hydrogen flow rate of 5-30 L / min, current of 500-700 A, powder feed rate of 10-30 g / min, and spraying distance of 100-300 mm. Spraying under these spraying parameters facilitates the regulation 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 one of 25 L / min, 27 L / min, 30 L / min, 35 L / min, 37 L / min, 40 L / min, 45 L / min, 47 L / min, 50 L / min, or a range formed by any two of the values.

[0050] In some embodiments of the present invention, the hydrogen flow rate is any one of 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, 30 L / min, or a range formed by any two of the values.

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

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

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

[0054] In some embodiments of the present invention, the high-temperature oxidation resistant layer is obtained by atmospheric plasma spraying; the parameters of the 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 thermal insulation layer is prepared by atmospheric plasma spraying; the parameters of the 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 present invention provides a product comprising the composite coating according to the first aspect of the present invention, wherein the product is selected from an aircraft, a ship, a train or a car.

[0057] In some embodiments of the present invention, the product further comprises a surface skin and a load-bearing structure, wherein the surface of the load-bearing structure is provided with a surface skin, and the surface of 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 an airplane and a drone.

[0059] The beneficial effects of the present invention are as follows: the composite coating of the present invention adopts a high-temperature oxidation resistant layer, a low thermal conductivity ceramic insulation layer and a high-conductivity silver-based conductive layer. Through the synergistic effect between the three layers, the composite coating has a high bonding strength (30-50 MPa) and a low sheet resistance (not exceeding 100 mΩ / sq), can effectively conduct current to form protection, and under a current of 20 kA, the coating and the base material do not show any shedding, deformation, cracking or damage, etc., and has good lightning protection and thermal protection effects.

[0060] The high-temperature oxidation resistant layer and the ceramic thermal insulation layer in the composite coating of the present invention both have low thermal conductivity. The comprehensive thermal protection and thermal matching of the two form a gradient protection against the longitudinal energy transfer at the moment of lightning strike, forming effective protection against the thermal shock at the moment of lightning strike, and can realize the reliable service of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1Schematic diagram of the structure of the lightning protection composite coating in Example 1.

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

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

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

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

[0066] Figure 6 This is a real picture of the lightning protection composite coating in Example 2 after being subjected to a 40KA lightning strike test using a simulated resistor and inductor (RL). DETAILED DESCRIPTION

[0067] The specific implementation of the present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

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

[0069] The YSZ layer is yttria-stabilized zirconia, wherein the mass percentage of yttria is 8% and the mass percentage of zirconia is 92%;

[0070] The NiCrAlY layer is composed of elements such as Ni, Cr, Al, and Y. The raw material for preparing the NiCrAlY layer is NiCrAlY powder, which is composed of the following components in 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 arranged on the surface of a skin substrate (whose material is carbon fiber). The coating includes a high-temperature oxidation resistant layer, a ceramic thermal insulation layer and a silver-based conductive layer stacked in sequence on the skin substrate; wherein the high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100μm; the ceramic thermal insulation layer is a YSZ layer with a thickness of 175μm; the preparation material of the silver-based conductive layer includes silver benzoate, and the thickness of the silver-based conductive layer is 10μm.

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

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

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

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

[0077] (3) YSZ ceramic thermal insulation layer with a thickness of 175 μm was prepared by spraying YSZ powder onto the surface of the high-temperature oxidation layer using atmospheric plasma spraying. The spraying parameters were as follows: spraying distance 300 mm, argon flow rate 30 L / min, hydrogen flow rate 15 L / min, current 500 A, and powder feeding rate 10 g / min.

[0078] (4) uniformly mixing an organic solvent prepared by mixing 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol, and 2 parts by weight of cyclohexanol with an impurity remover diisopropanolamine (DIPA), and stirring until diisopropanolamine is fully dissolved to obtain a mixed solvent, wherein the amount of diisopropanolamine used is 0.5 parts by weight;

[0079] (5) Adding silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mixing uniformly by magnetic stirring, adding dropwise a complexing agent prepared by mixing 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and continuously stirring until the solution becomes clear and transparent to obtain a silver-based conductive layer precursor solution. The complexing reaction mechanism between silver benzoate and the complexing agent is as follows: Figure 3 As shown, the actual picture 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 evenly brushed on the surface of the ceramic 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 bonding strength and surface resistance of the composite coating in this example were tested with reference to the HB5476 standard and the GB / T 40007-2021 standard. The bonding strength and surface resistance of the coating were 34 MPa and 30 mΩ / sq, respectively. Figure 5 The lightning protection composite coating in this example showed no peeling or cracking after being tested on a simulated resistor and inductor (RL) lightning strike test platform with a 20kA current for 5s. The coating surface at the lightning strike point underwent a phase change, with partial discoloration, but the skin substrate and coating remained intact.

[0082] The density of the ceramic thermal insulation layer obtained in step (2) of this example was tested, and its thermal diffusivity, thermal conductivity and specific heat capacity data at different temperatures were tested. 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 arranged on the surface of a skin substrate (whose material is aluminum alloy). The coating includes a high-temperature oxidation resistant layer, a ceramic thermal insulation layer and a silver-based conductive layer stacked in sequence on the skin substrate; wherein, the high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100μm; the ceramic thermal insulation layer is a YSZ layer with a thickness of 175μm; the preparation material of the silver-based conductive layer includes silver benzoate, and the thickness of the silver-based conductive layer is 9μm.

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

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

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

[0089] (3) YSZ ceramic thermal insulation layer with a thickness of 175 μm was prepared by spraying YSZ powder onto the surface of the high-temperature oxidation layer using atmospheric plasma spraying. The spraying parameters were as follows: spraying distance 200 mm, argon flow rate 30 L / min, hydrogen flow rate 15 L / min, current 600 A, and powder feeding rate 10 g / min.

[0090] (4) uniformly mixing an organic solvent prepared by mixing 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol, and 2 parts by weight of cyclohexanol with an impurity remover diisopropanolamine (DIPA), and stirring until diisopropanolamine is fully dissolved to obtain a mixed solvent, wherein the amount of diisopropanolamine used is 0.5 parts by weight;

[0091] (5) adding silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mixing uniformly by magnetic stirring, adding dropwise a complexing agent prepared by mixing 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and continuously stirring until the solution becomes clear and transparent, thereby obtaining a silver-based conductive layer precursor solution;

[0092] (6) The silver-based conductive layer precursor solution obtained in step (5) is evenly brushed on the surface of the high-temperature oxidation resistant 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] The bonding strength and surface resistance of the composite coating in this example are measured with reference to the HB5476 standard and the GB / T 40007-2021 standard. The coating bonding strength is 41 MPa and the surface resistance is 18 mΩ / sq. The lightning protection composite coating in this example was subjected to a 40 kA current for 5 seconds on a simulated resistor and inductor (RL) lightning strike test platform. After the test, the coating showed no peeling or cracking. The surface material of the coating at the lightning strike point underwent a phase change, with partial discoloration. However, the skin substrate and coating were intact and undamaged. The actual physical picture is as follows: Figure 6 shown.

[0094] Comparative Example 1

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

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

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

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

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

[0100] The bonding strength and surface resistance of the composite coating in this example are determined by referring to the HB5476 standard and the GB / T 40007-2021 standard. The bonding strength of the coating is 47 MPa and the sheet resistance is 10 7 Ω / sq, no conductivity, during the simulated lightning strike test, the center of the strike point cracked, the coating surface was ablated and partially fell 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 arranged on the surface of a skin substrate (whose material is aluminum alloy). The coating includes a high-temperature oxidation resistant layer, a ceramic thermal insulation layer and a silver-based conductive layer stacked in sequence on the skin substrate; wherein the high-temperature oxidation resistant layer is a NiCrAlY layer with a thickness of 100μm; the ceramic thermal insulation layer is a YSZ layer with a thickness of 75μm; the preparation material of the silver-based conductive layer includes silver benzoate, and the thickness of the silver-based conductive layer is 9μm.

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

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

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

[0106] (3) YSZ ceramic thermal insulation layer with a thickness of 75 μm was prepared by spraying YSZ powder on the surface of the high temperature oxidation layer by atmospheric plasma spraying method. The spraying parameters were as follows: spraying distance 200 mm, argon flow rate 30 L / min, hydrogen flow rate 15 L / min, current 600 A, and powder feeding rate 10 g / min;

[0107] (4) uniformly mixing an organic solvent prepared by mixing 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol, and 2 parts by weight of cyclohexanol with an impurity remover diisopropanolamine (DIPA, used in an amount of 0.5 parts by weight), and stirring until the diisopropanolamine is fully dissolved to obtain a mixed solvent;

[0108] (5) adding silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mixing uniformly by magnetic stirring, adding dropwise a complexing agent prepared by mixing 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and continuously stirring until the solution becomes clear and transparent, thereby obtaining a silver-based conductive layer precursor solution;

[0109] (6) The silver-based conductive layer precursor solution obtained in step (5) is evenly brushed on the surface of the ceramic 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] With reference to the HB5476 standard and the 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 53MPa and the surface resistance is 14mΩ / sq. After the lightning protection composite coating in this example was tested on a simulated resistor and inductor (RL) lightning strike test platform with a current of 40kA, the coating partially fell off at the strike point, with no cracking at the edge. The surface material of the coating at the lightning strike point underwent a phase change, with partial discoloration, and deformation of the back of the skin substrate. This is because the thickness of the ceramic thermal insulation layer is too small to effectively protect the lightweight aluminum alloy skin substrate with a low melting point, causing the skin substrate material to fail. In addition, due to the large instantaneous thermal shock, the skin substrate and the composite coating cannot be effectively bonded, resulting in partial coating shedding.

[0111] Comparative Example 3

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

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

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

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

[0116] (3) YSZ ceramic thermal insulation layer with a thickness of 175 μm was prepared by spraying YSZ powder on the surface of the high-temperature oxidation layer using atmospheric plasma spraying method. The spraying parameters were as follows: spraying distance 200 mm, argon flow rate 30 L / min, hydrogen flow rate 15 L / min, current 600 A, and powder feeding rate 10 g / min.

[0117] (4) uniformly mixing an organic solvent prepared by mixing 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol, and 2 parts by weight of cyclohexanol with an impurity remover diisopropanolamine (DIPA, used in an amount of 0.5 parts by weight), and stirring until the diisopropanolamine is fully dissolved to obtain a mixed solvent;

[0118] (5) adding silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (4) and mixing uniformly by magnetic stirring, adding dropwise a complexing agent prepared by mixing 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and continuously stirring until the solution becomes clear and transparent, thereby obtaining a silver-based conductive layer precursor solution;

[0119] (6) The silver-based conductive layer precursor solution obtained in step (5) is evenly brushed on the surface of the ceramic 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 the 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 39 MPa and the surface resistance is 32 Ω / sq. Due to the low reduction temperature of the silver-based conductive layer precursor and the less precipitation of the conductive phase silver element, the conductivity of the coating surface is extremely poor. During the simulated lightning strike test, the center of the striking point cracks, the coating surface is ablated and partially falls off, the back of the skin substrate is deformed, and there is no lightning protection effect.

[0121] Comparative Example 4

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

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

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

[0125] (2) uniformly mixing an organic solvent prepared by mixing 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol, and 2 parts by weight of cyclohexanol with an impurity remover diisopropanolamine (DIPA, used in an amount of 0.5 parts by weight), and stirring until the diisopropanolamine is fully dissolved to obtain a mixed solvent;

[0126] (3) adding silver benzoate powder (1 part by weight) to the mixed solvent obtained in step (2) and mixing uniformly by magnetic stirring, adding dropwise a complexing agent prepared by mixing 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and continuously stirring until the solution becomes clear and transparent, thereby obtaining a silver-based conductive layer precursor solution;

[0127] (4) The silver-based conductive layer precursor solution obtained in step (3) was evenly brushed on 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 Hundred Grids adhesion strength test and the GB / T 40007-2021 standard, the bonding strength and surface resistance of the composite coating in this example were HB-grade, with a sheet resistance of 2.6 mΩ / sq and excellent conductivity. After applying a 4kA current to a simulated resistor and inductor (RL) lightning strike test platform, the conductive coating prepared in this example melted at the strike point, and the skin substrate was severely deformed. This is due to the lack of protection of the lightweight alloy skin substrate with a lower melting point by the ceramic insulation layer, resulting in the failure of the skin substrate material.

[0129] In summary, the composite coating in the present invention has good bonding strength with the skin substrate (over 30 MPa), good electrical conductivity, and a sheet resistance of 18 to 30 mΩ / sq. It has good electrical conductivity, can enable charge to be conducted on the surface of the aircraft, and provides instantaneous thermal shock protection to the skin substrate through a low thermal conductivity ceramic insulation layer; by ion complexing of highly conductive metals, the rapid preparation of the silver-based conductive layer and good adaptation to the ceramic insulation layer are achieved, which is suitable for lightning protection of aircraft carbon fiber skins or aluminum alloy skins.

[0130] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A composite coating, characterized in that: It includes a high-temperature oxidation resistance layer, a ceramic heat insulation layer and a silver-based conductive layer stacked in sequence from the inside to the outside; The material of the high temperature oxidation resistant layer includes at least one of NiCrAlY, CoCrAlY, and NiCoCrAlY; The material of the ceramic heat-insulating layer includes zirconium oxide and rare earth oxide doped in the zirconium oxide; the thickness of the ceramic heat-insulating layer is 150 to 350 μm; The raw materials for preparing the silver-based conductive layer include organic silver salt and a complexing agent.

2. The composite coating according to claim 1, characterized in that: The thickness of the silver-based conductive layer is 1 to 10 μm; and / or, the sheet resistance of the silver-based conductive layer is no more than 100 mΩ / sq; And / or, the thickness of the high-temperature oxidation resistant layer is 50 to 250 μm.

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 on the ceramic heat-insulating layer, and then reacting the raw materials at 180° C. to 580° C. to precipitate metallic silver.

4. The composite coating according to claim 1, characterized in that: The rare earth oxide includes 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 material of the ceramic heat insulation layer is yttria-stabilized zirconia.

6. The composite coating according to any one of claims 1 to 5, characterized in that: The high-temperature oxidation resistant layer is arranged on a base material, and the base material is selected from carbon fiber, ceramic material or metal alloy.

7. The method for preparing the composite coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: A high-temperature oxidation resistant layer, a ceramic heat-insulating layer and a silver-based conductive layer are sequentially formed on a base material to prepare the composite coating.

8. The method for preparing the composite coating according to claim 7, wherein: The high-temperature oxidation resistant layer and the ceramic heat-insulating 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, wherein: The high-temperature oxidation resistant layer and / or ceramic thermal insulation layer is prepared by atmospheric plasma spraying; the parameters of the 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.

10. A product characterized by: The composite coating comprises the composite coating according to any one of claims 1 to 6, wherein the product is selected from an aircraft, a ship, a train or a car.

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