Preparation method of wave-absorbing, heat-conducting and anti-corrosion coating on surface of aluminum alloy

Abstract

The invention discloses a preparation method of a wave-absorbing, heat-conducting and anti-corrosion coating on the surface of an aluminum alloy, which specifically comprises the following steps: firstly, preparing a magnetic metal-coated wave-absorbing and heat-conducting filler by using BN (boron nitride) fiber, a bimetallic precursor and a reducing agent; secondly, mixing the heat-absorbing and heat-conducting filler with polydopamine, a flatting agent, a dispersing agent and a solvent, and performing oscillation and pulse ultrasonic treatment to prepare a multifunctional spraying coating; then, the surface of the aluminum alloy is subjected to tooth-like micro-groove etching treatment, and chemical activation is carried out; and finally, preparing the wave-absorbing, heat-conducting and anti-corrosion coating with high directional arrangement by adopting a magnetic field auxiliary spraying and gradient thermocuring process. The preparation method provided by the invention is simple in process and easy to operate, and the prepared coating has a wide application prospect in the field of offshore wind power, can effectively improve the operation efficiency and prolong the service life of wind power equipment and reduce the maintenance cost, and has important economic value and social benefit.

Description

Technical Field

[0001] The invention relates to the field of offshore wind power generation equipment protection, and in particular to a method for preparing a wave absorbing-heat conducting-anticorrosive coating on the surface of an aluminum alloy. Background Art

[0002] With the growing global demand for clean energy, offshore wind power generation, as an efficient and renewable energy form, has gradually become an important development direction in the energy field. Aluminum alloys have been widely used in offshore wind power generation equipment due to their low density, high strength, and strong corrosion resistance, especially in key components such as wind turbine blades, towers, and connectors. However, offshore wind power generation equipment faces extremely harsh environmental challenges during operation, including high humidity, high salt spray, and highly corrosive marine environments. In addition, offshore wind power generation equipment will generate electromagnetic interference during operation, which will not only affect the normal operation of its own equipment, but may also interfere with surrounding communication systems. Therefore, the development of an aluminum alloy surface treatment technology that can meet both anti-corrosion requirements and wave-absorbing properties has become a key issue that needs to be urgently addressed in the current offshore wind power generation field.

[0003] The Chinese patent "A method for preparing a conductive, microwave-absorbing and anti-corrosion coating based on Mxene" (application publication number: CN202210642920.8, publication date: 2022.08.05) discloses a method for preparing a conductive, microwave-absorbing and anti-corrosion coating based on Mxene. The GNS / Mxene / magnetic filler composite material maintains the stable performance of Mxene. Although the prepared coating has excellent conductivity, microwave absorption and anti-corrosion properties, the combination with the substrate is not considered.

[0004] The Chinese patent "Composite absorbing and anti-corrosion material with carbonyl iron as core, preparation method and application thereof in corrosion-resistant absorbing coating" (application publication number: CN202311018301.2, publication date: 2023.11.14) discloses a composite absorbing and anti-corrosion material with carbonyl iron as core, a preparation method and application thereof in corrosion-resistant absorbing coating. By using a mesoporous SiO2 coated on the surface of carboxyl iron particles, the composite absorbing and anti-corrosion material with carbonyl iron as core, a preparation method and application thereof in corrosion-resistant absorbing coating are obtained. 2 layer, and loading the corrosion inhibitor on the mesoporous SiO 2 The prepared composite absorbing and anti-corrosion material has excellent absorbing performance, and can also provide anti-oxidation and anti-corrosion effects, thereby delaying or preventing coating aging or metal substrate corrosion, achieving long-term anti-corrosion protection, and improving its adaptability and service life in harsh marine environments. However, its anti-corrosion effect depends on the content of corrosion inhibitors, which is not conducive to long-term anti-corrosion protection. 2 The presence of will cause heat accumulation, which is not conducive to the heat dissipation of the equipment.

[0005] Chinese Patent "A W-Type Ferrite@Clustered MoS 2 Wave Absorbing and Anticorrosive Material and Its Preparation Method" (Application Publication Number: CN202411284066.8, Publication Date: September 13, 2024) proposed a W-type ferrite@clustered MoS 2 Wave absorbing and anticorrosive material and its preparation method. This coating co-cures the W-type ferrite filler coated with clustered MoS 2 with epoxy resin and curing agent to obtain a W-type ferrite@clustered MoS 2 Wave absorbing and anticorrosive material. It effectively improves the wave absorbing performance of pure resin and enhances the anticorrosive performance in harsh environments. However, the uneven dispersion of wave absorbing fillers in the resin will cause heat accumulation.

[0006] Therefore, developing an aluminum alloy surface coating with both anticorrosive, wave absorbing, heat conducting properties and strong bonding force not only has important theoretical significance but also has broad application prospects. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the present invention proposes a preparation method for an aluminum alloy surface wave absorbing - heat conducting - anticorrosive coating, focusing on long-term anticorrosion and stable wave absorbing and heat conducting performance effects, and solving the problems of poor long-term anticorrosive performance and poor bonding force of existing aluminum alloy anticorrosive coatings.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions to achieve:

[0009] A preparation method for an aluminum alloy surface wave absorbing - heat conducting - anticorrosive coating specifically includes the following steps:

[0010] Step 1, in-situ composite preparation of wave absorbing and heat conducting fillers:

[0011] Disperse BN fiber, bimetallic precursor and reducing agent in ethanol by ultrasonic according to the mass ratio, then place it in a high-pressure reaction kettle for hydrothermal treatment, and obtain wave absorbing and heat conducting fillers with magnetic metal-coated BN fiber after filtration, washing, supercritical CO 2 drying and calcination treatment;

[0012] Step 2, preparation of multifunctional spraying coating:

[0013] Mix the wave absorbing and heat conducting fillers obtained in Step 1, polydopamine, leveling agent, dispersant and solvent in proportion, and alternately treat them by oscillation and pulsed ultrasound to ensure uniform dispersion of the fillers and the orientation degree of BN fiber > 60%, and obtain a wave absorbing - heat conducting - anticorrosive spraying coating;

[0014] Step 3, preparation of tooth-like micro-grooves on the aluminum alloy surface:

[0015] The surface of the aluminum alloy is pretreated, coated with photoresist, lithographically developed, and chemically activated to obtain an aluminum alloy surface with dentate microgrooves.

[0016] Step 4, magnetic field-temperature coupling directional solidification process:

[0017] The wave-absorbing, heat-conducting, and anti-corrosion spray coating obtained in Step 2 is magnetically assisted sprayed on the aluminum alloy surface treated in Step 3, and through gradient thermal curing treatment, a wave-absorbing, heat-conducting, and anti-corrosion coating is formed on the aluminum alloy surface.

[0018] Furthermore, in Step 1, the mass ratio of the BN fibers, bimetallic precursor, reducing agent, and ethanol is 1 - 3: 0.5 - 2: 0.1 - 0.5: 10 - 20.

[0019] Furthermore, in Step 1, the bimetallic precursor is any two of copper nitrate, iron nitrate, nickel nitrate, cobalt nitrate, and zinc nitrate, the reducing agent is any one of sodium borohydride, sodium cyanoborohydride, diisobutylaluminum hydride, and lithium triisobutylborohydride, the diameter of the BN fibers is 50 - 200 nm, and the aspect ratio > 20.

[0020] Furthermore, in Step 1, the hydrothermal treatment temperature is 160 - 200 °C, the hydrothermal treatment time is 2 - 40 h; the calcination temperature is 300 - 600 °C, the calcination time is 1.5 - 3.5 h, the calcination atmosphere is argon or nitrogen, and the supercritical CO 2 The drying pressure is 10 - 15 MPa, and the drying temperature is 40 - 60 °C.

[0021] Furthermore, in Step 2, the leveling agent is any one of MODAREZ MF AEX or MODAREZ PW 336, the dispersant is any one of Solsperse TM W60 or Tu Yile DS298, the solvent is any one of ethanol, isopropanol, or deionized water, and the mass ratio of the wave-absorbing and heat-conducting filler, polydopamine, leveling agent, dispersant, and solvent is 1 - 3: 0.1 - 1: 0.1 - 0.4: 0.1 - 0.4: 4 - 6.

[0022] Furthermore, in Step 2, the oscillation speed is 500 - 1000 rpm, the oscillation time is 0.1 - 0.5 h, the pulsed ultrasonic frequency is 1 - 3 MHz, and the number of ultrasonic times is 10 - 20.

[0023] Further, the pretreatment in step 3 includes any one of ultrasonic cleaning, pickling, and alkali washing. In the photolithography and development process, the photolithography light source is an ultraviolet lamp combined with a laser. The power of the ultraviolet lamp is 18 - 36 W, the exposure time is 30 - 150 s, the developing solution is a sodium carbonate solution with a mass fraction of 1%, the solution used in the chemical activation treatment is an acidic ferric sulfate solution with a concentration of 0.1 - 0.5 g / ml, the pH value of the solution is 1 - 6, the treatment time is 100 - 600 s, and the treatment temperature is 20 - 35°C.

[0024] Further, in step 3, ultrasonic cleaning is carried out using an ethanol / acetone mixture for 10 min, pickling is carried out using 5 - 10% nitric acid for etching for 30 s, and alkali washing is carried out using 5% NaOH for etching for 60 s.

[0025] Further, after pretreatment, photoresist coating, photolithography and development, and chemical activation treatment on the aluminum alloy surface in step 3, dentate micro - grooves are formed on the aluminum alloy surface. The tooth height of the micro - grooves is 20 - 50 μm, the spacing of the micro - grooves is 50 - 100 μm, and the inclination angle of the micro - grooves is 45°.

[0026] Further, in step 4, magnetic - field - assisted spraying uses a permanent - magnet array. The intensity of the permanent - magnet array is 0.5 - 1.5 T. The permanent - magnet array is placed below the aluminum alloy substrate. During spraying, the BN fibers are oriented along the magnetic - field direction, and the degree of orientation is ≥80%. The gradient thermal curing includes two stages: In the first stage, pre - heat at 60 - 80°C for 5 - 15 min to level the wave - absorbing, heat - conducting, and anti - corrosion spraying coating and preliminarily cross - link it; in the second stage, apply an alternating magnetic field and simultaneously raise the temperature to 150 - 180°C for curing for 1 - 4 h.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a preparation method for a wave - absorbing, heat - conducting, and anti - corrosion coating on the surface of an aluminum alloy. This method effectively combines the high heat - conductivity of BN fibers and the wave - absorbing performance of magnetic metals through in - situ composite preparation of wave - absorbing and heat - conducting fillers, significantly improving the wave - absorbing and heat - conducting performance of the coating. By using a magnetic - field - temperature coupling directional curing process, highly directional arrangement of the fillers in the coating is achieved, further enhancing the heat - conducting and anti - corrosion effects. At the same time, through dentate micro - groove etching treatment and activation treatment of the aluminum alloy surface, not only the bonding force between the coating and the substrate is increased, but also the anti - corrosion performance is increased. In addition, the preparation method of the present invention has a simple process and is easy to operate. The prepared coating has a wide application prospect in the field of offshore wind power, can effectively improve the operation efficiency and service life of wind power equipment, reduce the maintenance cost, and has important economic value and social benefits. Brief Description of the Drawings

[0029] Figure 1 It is a cross - sectional schematic diagram of the wave - absorbing, heat - conducting, and anti - corrosion coating on the surface of the aluminum alloy prepared by the present invention.

[0030] In the figure, 1 - BN fiber, 2 - bimetallic particle, 3 - composite coating, 4 - Al 2 O 3 layer, 5 - aluminum alloy. Detailed implementation manners

[0031] To enable those skilled in the art to understand the features and effects of the present invention, the following provides only a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meanings understood by those skilled in the art with respect to the present invention. In case of conflicts, the definitions in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0033] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub - ranges and individual numerical values (including integers and fractions) within the ranges.

[0034] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having" or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0035] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as falling within the scope described in this specification.

[0036] A preparation method of an electromagnetic wave absorption - heat conduction - anti - corrosion coating on the surface of an aluminum alloy specifically includes the following steps:

[0037] Step 1, in - situ composite preparation of electromagnetic wave absorption and heat conduction fillers

[0038] Disperse BN fiber, bimetallic precursor and reducing agent in ethanol by ultrasonic wave according to the mass ratio, and then place them in a high - pressure reaction kettle for hydrothermal treatment. After filtration, washing with water, and supercritical CO 2Through drying and calcination treatments, an h-BN fiber absorbing and heat-conducting filler coated with magnetic metal is obtained. Among them, the mass ratio of BN fiber, bimetallic precursor, reducing agent, and ethanol is 1-3: 0.5-2: 0.1-0.5: 10-20. The bimetallic precursor is any two of copper nitrate, iron nitrate, nickel nitrate, cobalt nitrate, zinc nitrate, etc., and the reducing agent is any one of sodium borohydride, sodium cyanoborohydride, diisobutylaluminum hydride, lithium triisobutylborohydride, etc. The diameter of the BN fiber is 50-200 nm, and the aspect ratio > 20. The hydrothermal treatment temperature is 160-200 °C, and the hydrothermal treatment time is 2-40 h. The calcination temperature is 300-600 °C, the calcination time is 1.5-3.5 h, and the calcination atmosphere is argon or nitrogen. Supercritical CO 2 The drying pressure is 10-15 MPa, and the drying temperature is 40-60 °C.

[0039] Step 2, Preparation of the multifunctional spraying coating

[0040] Mix the absorbing and heat-conducting filler obtained in Step 1, polydopamine (PDA), leveling agent, dispersant, and solvent according to the mass ratio of 1-3: 0.1-1: 0.1-0.4: 0.1-0.4: 4-6, and perform alternating treatments of oscillation (oscillation speed is 500 rpm - 1000 rpm, oscillation time is 0.1-0.5 h) and pulsed ultrasound (frequency is 1-3 MHz, number of ultrasound times is 10-20) to ensure that the filler is evenly dispersed and the orientation degree of the BN fiber > 60%, and obtain an absorbing-heat-conducting-corrosion-proof spraying coating. The leveling agent is any one of MODAREZ MF AEX or MODAREZ PW 336, etc., the dispersant is any one of Solsperse TM W60 or Tu Yile DS298, etc., and the solvent is any one of ethanol, isopropanol, or deionized water, etc.

[0041] Step 3, Preparation of the tooth-like micro-grooves on the aluminum alloy surface

[0042] Pre-treat the aluminum alloy (any one of ultrasonic cleaning with an ethanol / acetone mixed solution for 10 min, etching with 5-10% nitric acid for 30 s, and etching with 5% NaOH for 60 s), coat photoresist, perform photolithography and development, and chemical activation treatment to obtain an aluminum alloy surface with a micro-nano structure. Among them, the light source in photolithography is an ultraviolet lamp combined with a laser, the power of the ultraviolet lamp is 18-36 W, the exposure time is 30-150 s, the developing solution is a sodium carbonate solution with a mass fraction of 1%, the solution used for chemical activation treatment is an acidic ferric sulfate solution with a concentration of 0.1-0.5 g / ml, the pH value of the solution is 1-6, the treatment time is 100-600 s, and the treatment temperature is 20-35 °C.

[0043] After the aluminum alloy surface is pretreated, coated with photoresist, lithographed and developed, and chemically activated, a tooth-like microgroove is formed on the aluminum alloy surface. The tooth height of the microgroove is 20-50μm, the microgroove spacing is 50-100μm, and the microgroove inclination angle is 45°.

[0044] Step 4, magnetic field-temperature coupling directional curing process

[0045] The wave-absorbing, heat-conducting and anti-corrosion spray coating obtained in Step 2 is magnetically assisted sprayed on the aluminum alloy surface treated in Step 3, and after gradient thermal curing treatment, a wave-absorbing, heat-conducting and anti-corrosion coating is formed on the aluminum alloy surface. The magnetic field-assisted spraying uses a permanent magnet array, and the intensity of the permanent magnet array is 0.5-1.5T. The permanent magnet array is placed under the aluminum alloy substrate. During spraying, the BN fibers are oriented along the magnetic field direction, and the orientation degree is ≥80%. The gradient curing process includes two stages: the first stage, preheating at 60-80°C for 5-15 minutes to level the wave-absorbing, heat-conducting and anti-corrosion spray coating and preliminarily cross-link it; the second stage, applying an alternating magnetic field and simultaneously heating to 150-180°C for curing for 1-4 hours to finally obtain a wave-absorbing, heat-conducting and anti-corrosion coating on the aluminum alloy surface.

[0046] As Figure 1 shown, the cross-sectional schematic diagram of the wave-absorbing, heat-conducting and anti-corrosion coating on the aluminum alloy surface prepared by the present invention. The composite coating 3 prepared on the aluminum alloy 5 surface contains wave-absorbing and heat-conducting fillers arranged in an oriented manner (where 1 is BN fiber and 2 is bimetallic particles) and a regular tooth-like microgroove structure. The Al 2 O 3 layer 4 is uniformly formed on the microstructure surface.

[0047] The present invention successfully prepares a coating material with high wave absorption, high heat conduction and excellent anti-corrosion performance for the aluminum alloy surface through the in-situ composite preparation of wave-absorbing and heat-conducting fillers, combined with the preparation of multifunctional spray coatings, the etching of tooth-like microgrooves on the aluminum alloy surface, and the magnetic field-temperature coupling directional curing process. By controlling the reaction parameters such as the ratio between BN fibers, bimetallic precursors, and reducing agents, as well as the hydrothermal treatment temperature, time, and calcination conditions, the performance of the wave-absorbing and heat-conducting fillers is ensured to be stable. Through the alternating treatment of oscillation and pulsed ultrasound, the complexation of polydopamine and fillers and the high orientation degree of BN fibers are ensured. By regulating the conditions of aluminum alloy surface pretreatment, lithography and development, and chemical activation treatment, the formation of micro-nano structures on the aluminum alloy surface is ensured, promoting good bonding with the substrate and promoting the formation of Al 2 O 3 to improve the anti-corrosion performance. By adjusting parameters such as the magnetic field strength and direction, preheating temperature and time, application of alternating magnetic field, and curing temperature and time, the directional curing of fillers in the coating is achieved, and the wave absorption, heat conduction, and anti-corrosion performance optimization are fully improved.

[0048] The preparation method of the present invention has a simple process and is easy to operate. The prepared microwave-absorbing - heat - conducting - anti - corrosion coating has broad application prospects in the field of offshore wind power, can effectively improve the operation efficiency and service life of wind power equipment, reduce maintenance costs, and has important economic value and social benefits.

[0049] Example 1

[0050] Step 1, in - situ composite preparation of microwave - absorbing and heat - conducting fillers

[0051] Disperse 1 g of BN fibers (the diameter of BN fibers is 50 nm, and the aspect ratio > 20), 0.5 g of copper nitrate and iron nitrate (0.25 g each), and 0.1 g of sodium borohydride in 20 g of ethanol, ultrasonically disperse for 30 min, and then place in a high - pressure reaction kettle for hydrothermal treatment at 180 °C for 24 h. After filtration and washing with water, perform supercritical CO 2 drying (pressure 12 MPa, temperature 50 °C), and finally calcine in an argon atmosphere at 350 °C for 2 h to obtain microwave - absorbing and heat - conducting fillers.

[0052] Step 2, preparation of multifunctional spraying coating

[0053] Mix 1 g of microwave - absorbing and heat - conducting fillers, 0.2 g of polydopamine, 0.1 g of MODAREZ MF AEX, 0.1 g of Solsperse TM W60 and 5 g of ethanol, oscillate at 800 rpm for 0.3 h and perform pulsed ultrasonic treatment at 2 MHz for 15 times to obtain a spraying coating.

[0054] Step 3, preparation of tooth - like micro - grooves on the aluminum alloy surface

[0055] After ultrasonic cleaning the aluminum alloy in an ethanol / acetone mixed solution for 10 min, apply photoresist and then use a 24 W ultraviolet lamp in combination with laser exposure for 60 s, develop with 1% sodium carbonate solution, and finally treat in a 0.2 g / ml ferric sulfate acidic solution (pH = 3) for 300 s at a temperature of 25 °C. After pretreatment, photoresist coating, photolithography development, and chemical activation treatment on the aluminum alloy surface, tooth - like micro - grooves are formed on the aluminum alloy surface. The height of the micro - groove teeth is 20 μm, the spacing of the micro - grooves is 50 μm, and the inclination angle of the micro - grooves is 45°.

[0056] Step 4, magnetic - field - temperature coupling directional curing process

[0057] Spray the spraying coating on the aluminum alloy surface under the assistance of a 0.8 T magnetic field, and the orientation degree of BN fibers ≥ 80%. Curing process: In the first stage, preheat at 70 °C for 10 min; in the second stage, apply an alternating magnetic field and heat up to 160 °C for curing for 2 h to obtain a microwave - absorbing - heat - conducting - anti - corrosion coating.

[0058] Example 2

[0059] Step 1, In-situ Composite Preparation of Wave Absorbing and Thermal Conductive Filler

[0060] Disperse 2 g of BN fibers (BN fiber diameter is 100 nm, aspect ratio > 20), 1 g of nickel nitrate and cobalt nitrate (0.5 g each), and 0.3 g of sodium cyanoborohydride in 40 g of ethanol, ultrasonically disperse for 40 min, and then place in a high-pressure reaction kettle for hydrothermal treatment at 200 °C for 2 h. After filtration and washing with water, carry out supercritical CO 2 drying (pressure 15 MPa, temperature 60 °C), and finally calcine in a nitrogen atmosphere at 450 °C for 3 h to obtain the wave absorbing and thermal conductive filler.

[0061] Step 2, Preparation of Multifunctional Spraying Coating

[0062] Mix 2 g of wave absorbing and thermal conductive filler, 0.5 g of polydopamine, 0.2 g of MODAREZ PW 336, 0.2 g of Tu Yile DS298 and 6 g of isopropanol, oscillate at 1000 rpm for 0.1 h and perform 3 MHz pulsed ultrasonic treatment 10 times to obtain the spraying coating.

[0063] Step 3, Preparation of Imitation Tooth-shaped Micro-grooves on the Aluminum Alloy Surface

[0064] After the aluminum alloy is etched with 5% nitric acid for 30 s, use a 36 W ultraviolet lamp in combination with laser exposure for 30 s, develop with 1% sodium carbonate solution, and finally treat in a 0.5 g / ml ferric sulfate acidic solution (pH = 4) for 100 s at a temperature of 35 °C. After pretreatment, photolithography development, and chemical activation treatment on the aluminum alloy surface, imitation tooth-shaped micro-grooves are formed on the aluminum alloy surface, with a micro-groove tooth height of 30 μm, a micro-groove spacing of 70 μm, and a micro-groove inclination angle of 45°.

[0065] Step 4, Magnetic Field-Temperature Coupled Directional Curing Process

[0066] Spray the spraying coating on the aluminum alloy surface under the assistance of a 1.5 T magnetic field, and the orientation degree of BN fibers ≥ 80%. Curing process: In the first stage, preheat at 80 °C for 5 min; in the second stage, apply an alternating magnetic field and heat up to 180 °C for curing for 1 h to obtain the wave absorbing-thermal conductive-anti-corrosion coating.

[0067] Example 3

[0068] Step 1, In-situ Composite Preparation of Wave Absorbing and Thermal Conductive Filler

[0069] Disperse 3 g of BN fibers (BN fiber diameter is 150 nm, aspect ratio > 20), 1.5 g of zinc nitrate and iron nitrate (0.75 g each), and 0.5 g of diisobutylaluminum hydride in 45 g of ethanol, ultrasonically disperse for 60 min, and then place in a high-pressure reaction kettle for hydrothermal treatment at 160 °C for 40 h. After filtration and washing with water, carry out supercritical CO 2Dry (pressure 10 MPa, temperature 40 °C), and finally calcine in an argon atmosphere at 300 °C for 3.5 h to obtain the microwave-absorbing and heat-conducting filler.

[0070] Step 2, Preparation of the multifunctional spray coating

[0071] Mix 3 g of the microwave-absorbing and heat-conducting filler, 1 g of polydopamine, 0.4 g of MODAREZ MFAEX, 0.4 g of Solsperse TM W60 and 4 g of deionized water, oscillate at 500 rpm for 0.5 h and perform pulsed ultrasonic treatment at 1 MHz for 20 times to obtain the spray coating.

[0072] Step 3, Preparation of the tooth-like microgrooves on the aluminum alloy surface

[0073] After the aluminum alloy is etched with 5% NaOH for 60 s, expose it with a 24 W ultraviolet lamp in combination with laser for 120 s, develop it with 1% sodium carbonate solution, and finally treat it in a 0.1 g / ml ferric sulfate acidic solution (pH = 6) for 600 s at a temperature of 28 °C. After pretreatment, coating with photoresist, photolithography and development, and chemical activation treatment on the aluminum alloy surface, tooth-like microgrooves are formed on the aluminum alloy surface. The tooth height of the microgrooves is 50 μm, the microgroove spacing is 100 μm, and the microgroove inclination angle is 45°.

[0074] Step 4, Magnetic field-temperature coupling directional curing process

[0075] Spray the spray coating on the aluminum alloy surface with the assistance of a 1.0 T magnetic field, and the orientation degree of BN fibers ≥ 80%. Curing process: In the first stage, preheat at 60 °C for 15 min; in the second stage, apply an alternating magnetic field, heat up to 170 °C and cure for 3 h to obtain the microwave-absorbing - heat-conducting - anti-corrosion coating.

[0076] Example 4

[0077] Step 1, In-situ composite preparation of the microwave-absorbing and heat-conducting filler

[0078] Disperse 1.5 g of BN fibers (the diameter of BN fibers is 200 nm, aspect ratio > 20), 2 g of copper nitrate and nickel nitrate (1 g each), and 0.2 g of lithium triisobutylborohydride in 27 g of ethanol, ultrasonically disperse for 50 min, and then place it in a high-pressure reaction kettle for hydrothermal treatment at 190 °C for 20 h. After filtration and washing with water, perform supercritical CO 2 Dry (pressure 13 MPa, temperature 55 °C), and finally calcine in a nitrogen atmosphere at 600 °C for 1.5 h to obtain the microwave-absorbing and heat-conducting filler.

[0079] Step 2, Preparation of the multifunctional spray coating

[0080] Mix 1 g of microwave-absorbing and heat-conducting filler, 0.1 g of polydopamine, 0.3 g of MODAREZ PW 336, 0.3 g of TUYILE DS298 and 5 g of ethanol, oscillate at 700 rpm for 0.3 h and perform pulsed ultrasonic treatment at 2.5 MHz for 12 times to obtain the spraying coating.

[0081] Step 3, Preparation of dentate micro-grooves on the aluminum alloy surface

[0082] After the aluminum alloy is ultrasonically cleaned with an ethanol / acetone mixture for 10 min, it is exposed to laser for 150 s with an 18 W ultraviolet lamp, developed with a 1% sodium carbonate solution, and finally treated in a 0.1 g / ml ferric sulfate acidic solution (pH = 1) for 200 s at a temperature of 20°C. Dentate micro-grooves are formed on the aluminum alloy surface after pretreatment, photoresist coating, photolithography development, and chemical activation treatment. The tooth height of the micro-grooves is 40 μm, the pitch of the micro-grooves is 90 μm, and the inclination angle of the micro-grooves is 45°.

[0083] Step 4, Magnetic field-temperature coupling directional curing process

[0084] Spray the spraying coating on the aluminum alloy surface with the assistance of a 0.5 T magnetic field, and the orientation degree of BN fibers ≥ 80%. Curing process: In the first stage, preheat at 75°C for 8 min; in the second stage, apply an alternating magnetic field and heat up to 150°C for curing for 4 h to obtain the microwave-absorbing - heat-conducting - anti-corrosion coating.

[0085] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface, characterized in that: The specific steps include: Step 1, in-situ composite preparation of wave-absorbing and heat-conducting fillers: The BN fiber, the bimetallic precursor and the reducing agent are ultrasonically dispersed in ethanol according to the mass ratio, and then placed in a high-pressure reactor for hydrothermal treatment. After filtering, washing, supercritical CO2 drying and calcination, a wave-absorbing and heat-conducting filler with magnetic metal-coated BN fiber is obtained. Step 2, preparation of multifunctional spray coating: The wave-absorbing heat-conducting filler, polydopamine, leveling agent, dispersant and solvent obtained in step 1 are mixed in proportion, and subjected to alternating oscillation and pulsed ultrasonic treatment to ensure that the filler is evenly dispersed and the BN fiber orientation degree is greater than 60%, thereby obtaining a wave-absorbing, heat-conducting and anti-corrosion spray coating; Step 3, preparation of tooth-like micro-grooves on the aluminum alloy surface: The aluminum alloy surface is subjected to pretreatment, photoresist coating, photolithography development and chemical activation treatment to obtain an aluminum alloy surface with tooth-like micro-grooves; Step 4, magnetic field-temperature coupled directional solidification process: The wave-absorbing, heat-conducting and anti-corrosion spray coating obtained in step 2 is sprayed on the surface of the aluminum alloy treated in step 3 with the assistance of a magnetic field, and is subjected to gradient thermal curing treatment to form a wave-absorbing, heat-conducting and anti-corrosion coating on the surface of the aluminum alloy.

2. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: The mass ratio of the BN fiber, the bimetallic precursor, the reducing agent and the ethanol in step 1 is 1-3:0.5-2:0.1-0.5:10-20.

3. The method for preparing a microwave-absorbing, heat-conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: The bimetallic precursors in step 1 are any two of copper nitrate, iron nitrate, nickel nitrate, cobalt nitrate, and zinc nitrate, the reducing agent is any one of sodium borohydride, sodium cyanoborohydride, diisobutylaluminum hydride, and lithium triisobutylborohydride, the BN fiber diameter is 50-200nm, and the aspect ratio is >20.

4. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: The hydrothermal treatment temperature in step 1 is 160-200°C, and the hydrothermal treatment time is 2-40h; the calcination temperature is 300-600°C, and the calcination time is 1.5-3.5h. The calcination atmosphere is argon or nitrogen, the supercritical CO2 drying pressure is 10-15MPa, and the drying temperature is 40-60°C.

5. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: The leveling agent in step 2 is any one of MODAREZ MF AEX or MODAREZ PW 336, and the dispersant is Solsperse TM W60 or Tuyile DS298, the solvent is ethanol, isopropanol or deionized water, and the mass ratio of the wave absorbing and thermally conductive filler, polydopamine, leveling agent, dispersant and solvent is 1-3: 0.1-1: 0.1-0.4: 0.1-0.4: 4-6.

6. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: In step 2, the oscillation speed is 500-1000 rpm, the oscillation time is 0.1-0.5 h, the pulse ultrasound frequency is 1-3 MHz, and the number of ultrasounds is 10-20.

7. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: The pretreatment in step 3 includes any one of ultrasonic cleaning, acid cleaning and alkaline cleaning. In the photolithography development process, the photolithography light source is an ultraviolet lamp combined with a laser, the ultraviolet lamp power is 18-36W, the exposure time is 30-150s, the developing solution is a sodium carbonate solution with a mass fraction of 1%, and the solution used for chemical activation treatment is an acidic ferric sulfate solution with a concentration of 0.1-0.5g / ml, the solution pH value is 1-6, the treatment time is 100-600s, and the treatment temperature is 20-35°C.

8. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 7, characterized in that: In step 3, ultrasonic cleaning is performed using an ethanol / acetone mixture for 10 minutes, acid cleaning is performed using 5-10% nitric acid for 30 seconds, and alkaline cleaning is performed using 5% NaOH for 60 seconds.

9. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1 or 7, characterized in that: In step 3, the aluminum alloy surface is pretreated, coated with photoresist, photolithographically developed, and chemically activated to form tooth-like microgrooves on the aluminum alloy surface. The microgroove tooth height is 20-50 μm, the microgroove spacing is 50-100 μm, and the microgroove inclination angle is 45°.

10. The method for preparing a microwave absorbing, heat conducting and anti-corrosion coating on an aluminum alloy surface according to claim 1, characterized in that: In step 4, the magnetic field assisted spraying adopts a permanent magnetic array with a strength of 0.5-1.5T. The permanent magnetic array is placed under the aluminum alloy substrate. During spraying, the BN fibers are oriented along the magnetic field direction with an orientation degree of ≥80%. The gradient thermal curing includes two stages: the first stage is preheating at 60-80°C for 5-15min to make the wave absorbing, heat conducting and anti-corrosion spray coating leveled and preliminarily cross-linked; In the second stage, an alternating magnetic field is applied and the temperature is raised to 150-180°C for curing for 1-4 hours.

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