Composite wave-absorbing anticorrosive material of nano-graphite flake loaded with iron-cobalt alloy nanoparticles, preparation method of composite wave-absorbing anticorrosive material and application of composite wave-absorbing anticorrosive material in anticorrosive wave-absorbing coating

Abstract

The invention provides a composite wave-absorbing anti-corrosion material of a nano-graphite flake loaded with iron-cobalt alloy nanoparticles, a preparation method of the composite wave-absorbing anti-corrosion material and application of the composite wave-absorbing anti-corrosion material in an anti-corrosion and wave-absorbing coating, and the composite wave-absorbing anti-corrosion material is formed by loading the iron-cobalt alloy nanoparticles on the surface of the nano-graphite flake. Meanwhile, the composite wave-absorbing anticorrosive material is applied to an anticorrosive wave-absorbing coating, and the coating containing the composite wave-absorbing anticorrosive material provided by the invention not only has excellent anticorrosive performance, but also has relatively strong electromagnetic wave-absorbing performance, and meanwhile, has good mechanical properties with the surface of a substrate.

Description

Technical Field

[0001] The present application relates to the technical field of anti-corrosion and wave-absorbing coatings, and in particular to a composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, a preparation method thereof, and application thereof in anti-corrosion and wave-absorbing coatings. Background Art

[0002] With the rapid development of information technology and the popularization of 5G communications, electronic products are becoming increasingly widespread, and the resulting electromagnetic radiation and pollution are becoming increasingly serious. At the same time, in the defense sector, further improvements in radar technology are placing higher demands on electromagnetic stealth materials. Therefore, the development of advanced absorbing materials has become a hot topic for many researchers.

[0003] However, in the actual service of absorbing materials, adverse environmental conditions can cause a reduction in their absorbing performance. For example, the actual application effect of absorbing materials in the marine environment where ships serve is poor. The absorbing coating on the surface of the ship is exposed to harsh marine environments such as high heat, high humidity, high salt fog, strong light, and high ultraviolet rays for a long time. As well as being affected by various factors such as sea fog, tides, and seawater splash, the ship's surface is extremely susceptible to corrosion. Corrosion will gradually change the morphology and structure of the absorbing material in the absorbing coating. Various corrosion factors gradually spread through coating defects, causing the coating's electromagnetic wave absorption performance to decay until it is completely lost, and its service life is greatly shortened compared to other application environments. Therefore, in order to better maintain the stability of absorbing performance, materials with both excellent anti-corrosion and absorbing properties have become a research and development focus. Summary of the Invention

[0004] The present application provides a composite absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, a preparation method, and its application in an anti-corrosion and absorbing coating to solve the above-mentioned problems mentioned in the background technology. The coating can effectively prevent corrosion of the metal substrate in harsh environments and at the same time has excellent electromagnetic wave absorption performance.

[0005] In one aspect, the present application provides a method for preparing a composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, the preparation method comprising: (1) Preparation of nanographite sheets: Expandable graphite was placed in an environment with a heat shock of 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation to obtain nanographite sheets. (2) Preparation of hydroxylated nanographite flakes: The nanographite flakes were dispersed in concentrated nitric acid, ultrasonically treated for 0.5-2 h, washed, and dried to obtain hydroxylated nanographite flakes. (3) Preparation of iron-cobalt alloy nanoparticles: dissolve ferric nitrate, cobalt nitrate and urea in deionized water, adjust the pH value to 8-9 with alkali to obtain a reaction solution, place the reaction solution in a reactor for hydrothermal reaction to obtain a preliminary product of iron-cobalt alloy nanoparticles, then soak the preliminary product of iron-cobalt alloy nanoparticles in an aqueous solution of polydienyldimethylammonium chloride, and ultrasonically treat for 1-1.5 hours, wash and dry to obtain iron-cobalt alloy nanoparticles; (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles are dispersed in anhydrous ethanol at a weight ratio of (0.2-0.4):1, ultrasonically treated for 0.5-1.5 h, washed, and dried to obtain a composite wave-absorbing and anti-corrosion material.

[0006] Optionally, in the step of preparing the nanographite sheet, the particle size of the expandable graphite is 200-500 mesh, and the weight-to-volume ratio of the expandable graphite to anhydrous ethanol is 1 g: 200-300 mL.

[0007] Optionally, the thickness of the nanographite flakes is 10-50 nm and the diameter is 10-50 um.

[0008] Optionally, in the step of preparing hydroxylated nanographite flakes, the reaction temperature is 60-70° C., and the weight-to-volume ratio of nanographite flakes to concentrated nitric acid is 1 g:100-120 mL.

[0009] Optionally, the molar ratio of ferric nitrate, cobalt nitrate and urea is (1-2): (1-2): (0.5-0.75), and the weight-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate and urea to deionized water is 1 g: 100-200 mL.

[0010] Optionally, the temperature of the hydrothermal reaction is 180-240° C., and the reaction time is 12-13 h.

[0011] Optionally, the weight-to-volume ratio of the primary iron-cobalt alloy nanoparticles to the polydienyldimethylammonium chloride aqueous solution is 1 g: 100-200 mL, and the mass concentration of the polydienyldimethylammonium chloride aqueous solution is 0.5%.

[0012] On the other hand, the present application provides a composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles. The composite wave-absorbing and anti-corrosion material is obtained by the above-mentioned preparation method.

[0013] On the other hand, the present application provides an application of a composite wave-absorbing and anti-corrosion material of nano-graphite sheets loaded with iron-cobalt alloy nanoparticles in an anti-corrosion and wave-absorbing coating. The composite wave-absorbing and anti-corrosion material is used to prepare an anti-corrosion and wave-absorbing coating. The composite wave-absorbing and anti-corrosion material is obtained by the above-mentioned preparation method, or is the above-mentioned composite wave-absorbing and anti-corrosion material.

[0014] Optionally, the raw materials of the anti-corrosion and microwave-absorbing coating include a composite microwave-absorbing and anti-corrosion material, an epoxy resin, a curing agent, and a solvent in a weight ratio of (0.5-0.75):1:(0.3-0.35):1; The solvent is obtained by mixing xylene and n-butanol in a weight ratio of 7:3.

[0015] The composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, the preparation method thereof, and the application thereof in the anti-corrosion and microwave-absorbing coating provided in the present application realize the preparation of the composite microwave-absorbing and anti-corrosion material. Compared with the prior art, it has the following beneficial effects: (1) Expandable graphite is exfoliated by ultrasonic treatment to obtain nanographite flakes, which are then treated with concentrated nitric acid to introduce hydroxyl groups on the surface of the nanographite flakes, resulting in a negative charge on the surface of the nanographite flakes. Using ferric nitrate as an iron source, cobalt nitrate as a cobalt source, and urea as a reducing agent, a hydrothermal reaction is performed to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles is soaked in an aqueous solution of polydienyldimethylammonium chloride to obtain a positive charge on the surface of the preliminary product of iron-cobalt alloy nanoparticles. Finally, the hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles are dispersed in anhydrous ethanol, and the iron-cobalt alloy nanoparticles are loaded on the surface of the nanographite flakes by electrostatic adsorption to obtain a composite anti-corrosion material. The composite anti-corrosion material retains the excellent electrical conductivity and mechanical properties of the nanographite flakes and introduces the strong magnetism of the iron-cobalt alloy nanoparticles. The synergistic effect of the two improves the anti-corrosion and anti-corrosion performance of the composite anti-corrosion material.

[0016] (2) By combining polydienyldimethylammonium chloride with the initial product of iron-cobalt alloy nanoparticles, the surface of the iron-cobalt alloy nanoparticles is made positively charged, and the nanographite flakes are hydroxylated, which makes it easier to combine with the negatively charged groups on the surface of the hydroxylated nanographite flakes, so that the iron-cobalt alloy nanoparticles are more easily and evenly loaded on the surface of the hydroxylated nanographite flakes, thereby obtaining a composite absorbing and anti-corrosion material. The composite absorbing and anti-corrosion material retains the excellent electrical conductivity and mechanical properties of the nanographite flakes and introduces the strong magnetism of the iron-cobalt alloy nanoparticles to optimize the impedance matching performance of the filler.

[0017] (3) Composite absorbing and anti-corrosion materials are used as fillers in anti-corrosion and anti-corrosion coatings. The coating of the anti-corrosion and anti-corrosion coating includes composite absorbing and anti-corrosion materials, epoxy resin, curing agent and solvent. Iron-cobalt alloy nanoparticles can effectively absorb and attenuate electromagnetic waves through their magnetic properties, improve the absorbing performance of the coating and enhance the impedance matching of the material. Nanographite sheets have small pore size, high resistance and good conductivity, which enable the graphite sheets to absorb, scatter and reflect electromagnetic waves, thereby playing the role of electromagnetic wave shielding. Cobalt alloy nanoparticles are loaded on nanographite sheets to obtain composite absorbing and anti-corrosion materials. The composite absorbing and anti-corrosion materials have both magnetic loss and dielectric loss properties. The synergistic effect of cobalt alloy nanoparticles and nanographite sheets can significantly improve the impedance matching of the material and further enhance the absorbing effect of the coating. At the same time, the oxygen-containing groups on the composite absorbing and anti-corrosion materials can improve the adsorption of the coating on the substrate surface, jointly promoting the mechanical strength and adhesion of the anti-corrosion and anti-corrosion coating on the substrate surface.

[0018] (4) The anti-corrosion and wave-absorbing coating provided in this application has excellent anti-corrosion performance and strong electromagnetic wave absorption performance. The frequency range of the electromagnetic wave reflectivity of the coating is ≤-8dB, which is 9.6GHz-18GHz, and the coating thickness is 1.5mm.

[0019] (5) The anti-corrosion and wave-absorbing materials and coatings provided in this application are environmentally friendly and easy to prepare. The preparation method is simple and environmentally friendly, and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0020] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts also fall within the scope of protection of this application.

[0021] In one aspect, the present application provides a method for preparing a composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, the preparation method comprising: (1) Preparation of nanographite sheets: Expandable graphite was placed in an environment with a heat shock of 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation to obtain nanographite sheets. (2) Preparation of hydroxylated nanographite flakes: The nanographite flakes were dispersed in concentrated nitric acid, ultrasonically treated for 0.5-2 h, washed, and dried to obtain hydroxylated nanographite flakes. (3) Preparation of iron-cobalt alloy nanoparticles: dissolve ferric nitrate, cobalt nitrate and urea in deionized water, adjust the pH value to 8-9 with alkali to obtain a reaction solution, place the reaction solution in a reactor for hydrothermal reaction to obtain a preliminary product of iron-cobalt alloy nanoparticles, then soak the preliminary product of iron-cobalt alloy nanoparticles in an aqueous solution of polydienyldimethylammonium chloride, and ultrasonically treat for 1-1.5 hours, wash and dry to obtain iron-cobalt alloy nanoparticles; (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles are dispersed in anhydrous ethanol at a weight ratio of (0.2-0.4):1, ultrasonically treated for 0.5-1.5 h, washed, and dried to obtain a composite wave-absorbing and anti-corrosion material.

[0022] Specifically, expandable graphite is subjected to a thermal shock at 800°C for 5 seconds to produce nanographite flakes. After ultrasonic treatment, the nanographite flakes, containing anhydrous ethanol, are dried at 60-80°C to a constant weight, yielding dried nanographite flakes. The nanographite flakes are then dispersed in concentrated nitric acid. Hydroxyl groups are introduced onto the surface of the nanographite flakes under ultrasonic conditions. The nanographite flakes are then washed with water multiple times until neutral, and dried at 60-80°C to a constant weight, imparting a negative charge to the surface of the nanographite flakes. Furthermore, the concentrated nitric acid treatment imparts a large number of oxygen-containing functional groups to the surface of the nanographite flakes, enhancing their adhesion to subsequent coatings and, in turn, the adhesion between the coating and the substrate surface, improving the coating's corrosion resistance and microwave absorption properties, and thus extending the service life of mechanical components.

[0023] Using ferric nitrate as the iron source, cobalt nitrate as the cobalt source, and urea as the reducing agent, a hydrothermal reaction was performed to obtain preliminary iron-cobalt alloy nanoparticles. These nanoparticles were then immersed in an aqueous solution of polydienyldimethylammonium chloride at room temperature (25-35°C) and ultrasonically treated to impart a positive surface charge to the nanoparticles. Following ultrasonic treatment, the nanoparticles were washed multiple times with deionized water or anhydrous ethanol and dried at 60-80°C to constant weight, yielding the iron-cobalt alloy nanoparticles. These nanoparticles exhibit excellent electromagnetic properties, further enhancing electromagnetic wave loss and improving their absorption performance. Finally, hydroxylated nanographite flakes and the iron-cobalt alloy nanoparticles were dispersed in anhydrous ethanol and ultrasonically treated for 0.5-1.5 hours to electrostatically attach the iron-cobalt alloy nanoparticles to the nanographite flakes. The composite anti-corrosion material was then dried at 60-80°C to constant weight. A stable composite structure was formed through physical adsorption or chemical bonding. The composite wave-absorbing and anti-corrosion material retains the excellent electrical conductivity and mechanical properties of nanographite sheets and introduces the strong magnetism of iron-cobalt alloy nanoparticles to optimize the impedance matching performance of the composite wave-absorbing and anti-corrosion material.

[0024] The present application realizes the preparation of composite wave-absorbing and anti-corrosion materials through the above scheme. Expandable graphite is exfoliated by ultrasonic treatment to obtain nanographite flakes. The nanographite flakes are then treated with concentrated nitric acid to introduce hydroxyl groups on the surface of the nanographite flakes, so that the surface of the nanographite flakes has a negative charge. Using ferric nitrate as the iron source, cobalt nitrate as the cobalt source, and urea as the reducing agent, a hydrothermal reaction is performed to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles is soaked in an aqueous solution of polydienyldimethylammonium chloride to give the preliminary product a positive charge on the surface of the iron-cobalt alloy nanoparticles, thereby obtaining iron-cobalt alloy nanoparticles. Finally, the hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles are dispersed in anhydrous ethanol, and the iron-cobalt alloy nanoparticles are loaded on the surface of the nanographite flakes by electrostatic adsorption to obtain a composite wave-absorbing and anti-corrosion material. This composite wave-absorbing and anti-corrosion material retains the excellent electrical conductivity and mechanical properties of the nanographite flakes and introduces the strong magnetism of the iron-cobalt alloy nanoparticles. The two work synergistically to improve the anti-corrosion and wave-absorbing properties of the composite wave-absorbing and anti-corrosion material.

[0025] In the preparation steps of iron-cobalt alloy nanoparticles, the base used is strong sodium oxide, and the pH value of the reaction liquid is adjusted to 8-9. Urea is used as a reducing agent. The suitable acid-base environment is conducive to the hydrothermal reaction, which is conducive to controlling the quality and particle size uniformity of the iron-cobalt alloy nanoparticles, and thus helps the composite absorbing and anti-corrosion material to have better anti-corrosion and absorbing properties.

[0026] Preferably, the particle size of the iron-cobalt alloy nanoparticles is controlled at 5-50 nm, and more preferably, the particle size of the iron-cobalt alloy nanoparticles is 20-40 nm. This not only makes the iron-cobalt alloy nanoparticles have good dispersibility, but also has good electromagnetic properties. As a result, when the composite absorbing and anti-corrosion material is applied to the metal surface as an absorbing and anti-corrosion coating, the dispersion stability and uniformity of the coating are improved, thereby improving the adhesion and stability of the coating, which is conducive to the formation of a dense protective film between the substrate and the external environment, extending the coating's protection period for absorbing and anti-corrosion of the metal substrate, and thereby extending the service life of mechanical components in harsh environments such as the ocean.

[0027] Optionally, in the step of preparing the nanographite sheet, the particle size of the expandable graphite is 200-500 mesh, and the weight-to-volume ratio of the expandable graphite to anhydrous ethanol is 1 g: 200-300 mL.

[0028] Specifically, selecting expandable graphite with a suitable particle size is beneficial to the exfoliation between graphite sheets, while controlling the weight-to-volume ratio of expandable graphite to anhydrous ethanol not only achieves the exfoliation of graphite sheets but also avoids the waste of anhydrous ethanol.

[0029] Optionally, the thickness of the nanographite flakes is 10-50 nm and the diameter is 10-50 um.

[0030] Specifically, the expandable graphite is ultrasonically stripped using an ultrasonic stripper to separate the graphite flakes. Ultrasonication is performed until the thickness of the obtained nanographite flakes is 10-50nm and the diameter is 10-50um. Controlling the particle size specifications of the nanographite flakes is beneficial to the subsequent uniform loading of the iron-cobalt alloy nanoparticles, thereby improving the anti-corrosion and anti-corrosion quality and performance of the composite anti-corrosion absorbing material.

[0031] Optionally, in the step of preparing hydroxylated nanographite flakes, the reaction temperature is 60-70° C., and the weight-to-volume ratio of nanographite flakes to concentrated nitric acid is 1 g:100-120 mL.

[0032] Optionally, the molar ratio of ferric nitrate, cobalt nitrate and urea is (1-2): (1-2): (0.5-0.75), and the weight-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate and urea to deionized water is 1 g: 100-200 mL.

[0033] Optionally, the temperature of the hydrothermal reaction is 180-240° C., and the reaction time is 12-13 h.

[0034] Specifically, the molar ratio of ferric nitrate, cobalt nitrate and urea is controlled, and urea is used as a reducing agent to ensure the stable progress of the hydrothermal reaction. At the same time, the amount of deionized water is controlled to promote the rapid progress of the reaction.

[0035] Optionally, the weight-to-volume ratio of the primary iron-cobalt alloy nanoparticles to the polydienyldimethylammonium chloride aqueous solution is 1 g: 100-200 mL, and the mass concentration of the polydienyldimethylammonium chloride aqueous solution is 0.5%.

[0036] Specifically, polydienyldimethylammonium chloride is combined with a preliminary product of iron-cobalt alloy nanoparticles, so that the surface of the iron-cobalt alloy nanoparticles is positively charged, which can then more easily combine with the negatively charged groups on the surface of the hydroxylated nano-graphite flakes, making it easier and more uniform for the iron-cobalt alloy nanoparticles to be loaded on the surface of the hydroxylated nano-graphite flakes, thereby obtaining a composite absorbing and anti-corrosion material. The composite absorbing and anti-corrosion material retains the excellent electrical conductivity and mechanical properties of the nano-graphite flakes, and introduces the strong magnetism of the iron-cobalt alloy nanoparticles to optimize the impedance matching performance of the filler.

[0037] On the other hand, the present application provides a composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles. The composite wave-absorbing and anti-corrosion material is obtained by the above-mentioned preparation method.

[0038] On the other hand, the present application provides an application of a composite wave-absorbing and anti-corrosion material of nano-graphite sheets loaded with iron-cobalt alloy nanoparticles in an anti-corrosion and wave-absorbing coating. The composite wave-absorbing and anti-corrosion material is used to prepare an anti-corrosion and wave-absorbing coating. The composite wave-absorbing and anti-corrosion material is obtained by the above-mentioned preparation method, or is the above-mentioned composite wave-absorbing and anti-corrosion material.

[0039] Optionally, the raw materials of the anti-corrosion and microwave-absorbing coating include a composite microwave-absorbing and anti-corrosion material, an epoxy resin, a curing agent, and a solvent in a weight ratio of (0.5-0.75):1:(0.3-0.35):1; The solvent is obtained by mixing xylene and n-butanol in a weight ratio of 7:3.

[0040] Specifically, the composite absorbing and anti-corrosion material is applied to the anti-corrosion and absorbing coating, which includes the composite absorbing and anti-corrosion material, epoxy resin, curing agent and solvent. The epoxy resin is the main film-forming agent with good adhesion. It can combine the components with the substrate surface to form a coating, forming a protective film between the substrate surface and the external environment. At the same time, the composite absorbing and anti-corrosion material is used as a filler to further improve the anti-corrosion and absorbing performance of the coating. The curing agent can promote the chemical reaction between the coating and the oxygen in the air, thereby accelerating the drying process of the coating and shortening the coating time. At the same time, it can improve the hardness and brightness of the coating, enhance the stability of the coating and the anti-corrosion and absorbing performance. The solvent is a mixture of xylene and n-butanol, which increases the fluidity of the coating, helps the coating to better adhere to the surface of the object, and improves the drying speed and glossiness of the coating. At the same time, it enables the components in the coating to be evenly dispersed, which is beneficial to the uniformity of the coating after application, thereby improving the anti-corrosion and absorbing performance of the coating.

[0041] Iron-cobalt alloy nanoparticles can effectively absorb and attenuate electromagnetic waves through their magnetic properties, improving the coating's absorbing properties and enhancing the material's impedance matching. The small pore size, high electrical resistance, and good electrical conductivity of the nanographite flakes enable them to absorb, scatter, and reflect electromagnetic waves, thereby providing electromagnetic shielding. Cobalt alloy nanoparticles are loaded onto nanographite flakes to create a composite absorbing and anti-corrosion material that combines both magnetic and dielectric loss properties. The synergistic effect of the cobalt alloy nanoparticles and nanographite flakes significantly improves the material's impedance matching, further enhancing the coating's absorbing properties. Furthermore, the oxygen-containing groups on the composite absorbing and anti-corrosion material enhance the coating's adsorption to the substrate surface, contributing to the mechanical strength and adhesion of the anti-corrosion and absorbing coating to the substrate surface.

[0042] The technical solution of this application is described in detail below with reference to specific embodiments.

[0043] Example 1 A preparation method of a composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles and its application in an anti-corrosion and microwave-absorbing coating, the preparation method comprising: (1) Preparation of nanographite flakes: 200-mesh expandable graphite was thermally shocked at 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation until the nanographite flakes had a thickness of 10 nm and a diameter of 10 μm. After ultrasonic treatment, the nanographite flakes were dried at 60°C to constant weight to obtain the nanographite flakes. The weight-to-volume ratio of expandable graphite to anhydrous ethanol was 1 g:200 mL.

[0044] (2) Preparation of hydroxylated nanographite flakes: At 60°C, nanographite flakes were dispersed in concentrated nitric acid at a weight-to-volume ratio of 1 g:100 mL. After ultrasonic treatment for 0.5 h, the nanographite flakes were washed with water several times until neutral, and dried at 60°C to constant weight to obtain hydroxylated nanographite flakes.

[0045] (3) Preparation of iron-cobalt alloy nanoparticles: Ferric nitrate, cobalt nitrate, and urea were dissolved in deionized water at a molar ratio of 1:1:0.5, and the pH value was adjusted to 8 with sodium hydroxide to obtain a reaction solution. The reaction solution was placed in a reactor and subjected to a hydrothermal reaction at 180°C for 12 hours to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles was then immersed in a 0.5% polydimethylammonium chloride aqueous solution and ultrasonically treated for 1 hour. The product was washed with water several times and dried at 60°C to a constant weight to obtain iron-cobalt alloy nanoparticles. The weight-to-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate, and urea to deionized water was 1 g:100 mL. The weight-to-volume ratio of the preliminary product of iron-cobalt alloy nanoparticles to the polydimethylammonium chloride aqueous solution was 1 g:100 mL.

[0046] (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles were dispersed in anhydrous ethanol at a weight ratio of 0.2:1, ultrasonically treated for 0.5 h, washed with water several times, and dried at 60 °C to constant weight to obtain a composite wave-absorbing and anti-corrosion material.

[0047] (5) Preparation of anti-corrosion and microwave-absorbing coating: A composite microwave-absorbing and microwave-absorbing material, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating was sprayed onto the surface of the pretreated steel plate, with the sprayed wet film thickness not exceeding 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm to obtain an anti-corrosion and microwave-absorbing coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3.

[0048] The steel plate is made of Q235 steel, and the surface roughness after sandblasting is Ry=40-80μm.

[0049] Example 2 A preparation method of a composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles and its application in an anti-corrosion and microwave-absorbing coating, the preparation method comprising: (1) Preparation of nanographite flakes: 300-mesh expandable graphite was thermally shocked at 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation until the nanographite flakes had a thickness of 20 nm and a diameter of 20 μm. After ultrasonic treatment, the nanographite flakes were dried at 70°C to constant weight to obtain nanographite flakes. The weight-to-volume ratio of expandable graphite to anhydrous ethanol was 1 g:250 mL.

[0050] (2) Preparation of hydroxylated nanographite flakes: Nanographite flakes were dispersed in concentrated nitric acid at a weight-to-volume ratio of 1 g:110 mL at 65°C. After ultrasonic treatment for 1 h, they were washed with water several times until neutrality was achieved and dried at 70°C to constant weight to obtain hydroxylated nanographite flakes.

[0051] (3) Preparation of iron-cobalt alloy nanoparticles: Ferric nitrate, cobalt nitrate, and urea were dissolved in deionized water at a molar ratio of 1:2:0.75, and the pH value was adjusted to 8 with sodium hydroxide to obtain a reaction solution. The reaction solution was placed in a reactor and subjected to a hydrothermal reaction at 180°C for 12 hours to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles was then immersed in a 0.5% polydimethylammonium chloride aqueous solution and ultrasonically treated for 1.2 hours. The product was washed with water several times and dried at 70°C to a constant weight to obtain iron-cobalt alloy nanoparticles. The weight-to-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate, and urea to deionized water was 1 g:150 mL. The weight-to-volume ratio of the preliminary product of iron-cobalt alloy nanoparticles to the polydimethylammonium chloride aqueous solution was 1 g:150 mL.

[0052] (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles were dispersed in anhydrous ethanol at a weight ratio of 0.2:1, ultrasonically treated for 1 h, washed with water several times, and dried at 70°C to constant weight to obtain a composite wave-absorbing and anti-corrosion material.

[0053] (5) Preparation of anti-corrosion and microwave-absorbing coating: A composite microwave-absorbing and microwave-absorbing material, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating was sprayed onto the surface of the pretreated steel plate, with the sprayed wet film thickness not exceeding 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm to obtain an anti-corrosion and microwave-absorbing coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3.

[0054] Example 3 A preparation method of a composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles and its application in an anti-corrosion and microwave-absorbing coating, the preparation method comprising: (1) Preparation of nanographite flakes: 300-mesh expandable graphite was subjected to thermal shock at 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation until the nanographite flakes had a thickness of 20 nm and a diameter of 30 μm. After ultrasonic treatment, the nanographite flakes were dried at 80°C to constant weight to obtain nanographite flakes. The weight-to-volume ratio of expandable graphite to anhydrous ethanol was 1 g:300 mL.

[0055] (2) Preparation of hydroxylated nanographite flakes: Nanographite flakes were dispersed in concentrated nitric acid at a weight-to-volume ratio of 1 g:120 mL at 60-70°C. After ultrasonic treatment for 2 h, they were washed with water several times until neutrality was achieved and dried at 80°C to constant weight to obtain hydroxylated nanographite flakes.

[0056] (3) Preparation of iron-cobalt alloy nanoparticles: Ferric nitrate, cobalt nitrate, and urea were dissolved in deionized water at a molar ratio of 2:1:0.75, and the pH value was adjusted to 9 with sodium hydroxide to obtain a reaction solution. The reaction solution was placed in a reactor and subjected to a hydrothermal reaction at 200°C for 12 hours to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles was then immersed in a 0.5% polydimethylammonium chloride aqueous solution and ultrasonically treated for 1.5 hours. The product was washed with water several times and dried at 80°C to a constant weight to obtain iron-cobalt alloy nanoparticles. The weight-to-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate, and urea to deionized water was 1 g:200 mL. The weight-to-volume ratio of the preliminary product of iron-cobalt alloy nanoparticles to the polydimethylammonium chloride aqueous solution was 1 g:200 mL.

[0057] (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles were dispersed in anhydrous ethanol at a weight ratio of 0.2:1, ultrasonically treated for 1.5 h, washed with water several times, and dried at 80 °C to constant weight to obtain a composite wave-absorbing and anti-corrosion material.

[0058] (5) Preparation of anti-corrosion and microwave-absorbing coating: A composite microwave-absorbing and microwave-absorbing material, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating was sprayed onto the surface of the pretreated steel plate, with the sprayed wet film thickness not exceeding 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm to obtain an anti-corrosion and microwave-absorbing coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3.

[0059] Example 4 A preparation method of a composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles and its application in an anti-corrosion and microwave-absorbing coating, the preparation method comprising: (1) Preparation of nanographite flakes: 500-mesh expandable graphite was thermally shocked at 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation until the nanographite flakes had a thickness of 40 nm and a diameter of 40 μm. After ultrasonic treatment, the nanographite flakes were dried at 80°C to constant weight to obtain the nanographite flakes. The weight-to-volume ratio of expandable graphite to anhydrous ethanol was 1 g:300 mL.

[0060] (2) Preparation of hydroxylated nanographite flakes: Nanographite flakes were dispersed in concentrated nitric acid at a weight-to-volume ratio of 1 g:120 mL at 70°C. After ultrasonic treatment for 2 h, they were washed with water several times until neutrality and dried at 80°C to constant weight to obtain hydroxylated nanographite flakes.

[0061] (3) Preparation of iron-cobalt alloy nanoparticles: Ferric nitrate, cobalt nitrate, and urea were dissolved in deionized water at a molar ratio of 1:1:0.5, and the pH value was adjusted to 9 with sodium hydroxide to obtain a reaction solution. The reaction solution was placed in a reactor and subjected to a hydrothermal reaction at 220°C for 12 hours to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles was then immersed in a 0.5% polydimethylammonium chloride aqueous solution and ultrasonically treated for 1 hour. The product was washed with water several times and dried at 80°C to a constant weight to obtain iron-cobalt alloy nanoparticles. The weight-to-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate, and urea to deionized water was 1 g:00 mL. The weight-to-volume ratio of the preliminary product of iron-cobalt alloy nanoparticles to the polydimethylammonium chloride aqueous solution was 1 g:200 mL.

[0062] (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles were dispersed in anhydrous ethanol at a weight ratio of 0.3:1, ultrasonically treated for 1.5 h, washed with water several times, and dried at 80 °C to constant weight to obtain a composite wave-absorbing and anti-corrosion material.

[0063] (5) Preparation of anti-corrosion and microwave-absorbing coating: A composite microwave-absorbing and microwave-absorbing material, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating was sprayed onto the surface of the pretreated steel plate, with the sprayed wet film thickness not exceeding 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm to obtain an anti-corrosion and microwave-absorbing coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3.

[0064] Example 5 A preparation method of a composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles and its application in an anti-corrosion and microwave-absorbing coating, the preparation method comprising: (1) Preparation of nanographite flakes: 500-mesh expandable graphite was thermally shocked at 800°C for 5 seconds, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation until the nanographite flakes had a thickness of 50 nm and a diameter of 50 μm. After ultrasonic treatment, the nanographite flakes were dried at 80°C to constant weight to obtain nanographite flakes. The weight-to-volume ratio of expandable graphite to anhydrous ethanol was 1 g:300 mL.

[0065] (2) Preparation of hydroxylated nanographite flakes: Nanographite flakes were dispersed in concentrated nitric acid at a weight-to-volume ratio of 1 g:120 mL at 70°C. After ultrasonic treatment for 2 h, they were washed with water several times until neutrality and dried at 80°C to constant weight to obtain hydroxylated nanographite flakes.

[0066] (3) Preparation of iron-cobalt alloy nanoparticles: Ferric nitrate, cobalt nitrate, and urea were dissolved in deionized water at a molar ratio of 1:1:0.5, and the pH value was adjusted to 9 with sodium hydroxide to obtain a reaction solution. The reaction solution was placed in a reactor and subjected to a hydrothermal reaction at 240°C for 13 h to obtain a preliminary product of iron-cobalt alloy nanoparticles. The preliminary product of iron-cobalt alloy nanoparticles was then immersed in a 0.5% polydimethylammonium chloride aqueous solution and ultrasonically treated for 1.5 h. The product was washed with water several times and dried at 80°C to a constant weight to obtain iron-cobalt alloy nanoparticles. The weight-to-volume ratio of the sum of the weights of ferric nitrate, cobalt nitrate, and urea to deionized water was 1 g:200 mL. The weight-to-volume ratio of the preliminary product of iron-cobalt alloy nanoparticles to the polydimethylammonium chloride aqueous solution was 1 g:200 mL.

[0067] (4) Preparation of composite wave-absorbing and anti-corrosion materials: Hydroxylated nanographite flakes and iron-cobalt alloy nanoparticles were dispersed in anhydrous ethanol at a weight ratio of 0.3:1, ultrasonically treated for 1.5 h, washed with water several times, and dried at 80 °C to constant weight to obtain a composite wave-absorbing and anti-corrosion material.

[0068] (5) Preparation of anti-corrosion and microwave-absorbing coating: A composite microwave-absorbing and microwave-absorbing material, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating was sprayed onto the surface of the pretreated steel plate, with the sprayed wet film thickness not exceeding 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm to obtain an anti-corrosion and microwave-absorbing coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3.

[0069] Comparative Example 1 The difference from Example 3 is that: The step (2) of hydroxylating the nanographite sheets is not performed, and in the step (3) of preparing the iron-cobalt alloy nanoparticles, the primary iron-cobalt alloy nanoparticles are obtained after the hydrothermal reaction is completed, and no polydienyldimethylammonium chloride aqueous solution is added for treatment.

[0070] (5) Preparation of anti-corrosion and microwave-absorbing coating: nano-graphite sheets and primary iron-cobalt alloy nanoparticles are mixed in a weight ratio of 0.2:1 to obtain a composite microwave-absorbing and anti-corrosion material; A composite absorbing and anti-corrosion material, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to produce a coating. The coating was sprayed onto a pretreated steel plate surface to a wet film thickness of no more than 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm, thereby producing an anti-corrosion and anti-corrosion coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3.

[0071] Comparative Example 2 The difference from Example 3 is that: (5) Preparation of anti-corrosion and microwave-absorbing coating: Nanographite flakes, epoxy resin, curing agent, and solvent were mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating was sprayed onto the surface of the pretreated steel plate to a wet film thickness of no more than 200 μm. After curing at room temperature for 24 hours, the coating was sprayed again until the dry film thickness reached 1.5 mm to obtain an anti-corrosion and microwave-absorbing coating. The solvent was a mixture of xylene and n-butanol in a weight ratio of 7:3. No iron-cobalt alloy nanoparticles were added to the coating.

[0072] Comparative Example 2 The difference from Example 3 is that: In step (3) of preparing the iron-cobalt alloy nanoparticles, the primary iron-cobalt alloy nanoparticles are obtained after the hydrothermal reaction is completed, without adding the polydienyldimethylammonium chloride aqueous solution for treatment.

[0073] (5) Preparation of anti-corrosion and wave-absorbing coating: The iron-cobalt alloy nanoparticles, epoxy resin, curing agent and solvent are mixed in a weight ratio of 0.5:1:0.3:1 to obtain a coating. The coating is sprayed on the surface of the pretreated steel plate, and the spray wet film thickness does not exceed 200 μm. After curing at room temperature for 24 hours, it is sprayed again until the dry film thickness reaches 1.5 mm to obtain an anti-corrosion and wave-absorbing coating. The solvent is a mixture of xylene and n-butanol in a weight ratio of 7:3. No nanographite flakes are added to the coating. Experimental Example 1 Wave absorption performance test The reflectivity of the anti-corrosion absorbing coatings provided in Examples 1-5 and Comparative Examples 1-3 was accurately tested in the 2-12 GHz range using the standard GJB 2038A-2011 radar absorbing material (RAM) reflectivity test. The test frequency range was 1-18 GHz, and the difference in the frequency range where the reflection loss was less than -8 dB was taken as the effective absorption bandwidth. Three parallel runs were performed for each test example, and the results were averaged. The results are shown in Table 1.

[0074] Table 1 Effective absorption frequency GHz Effective absorption bandwidth GHz Example 1 8.4 Comparative Example 1 5.2 Example 2 7.8 Comparative Example 2 4.6 Example 3 8.5 Comparative Example 3 4.3 Example 4 7.2 - - Example 5 7.6 - - As can be seen from Table 1, the anti-corrosion and absorbing coating provided by the present application has a good electromagnetic wave loss function. In the composite absorbing and anti-corrosion material, the iron-cobalt alloy nanoparticles have a strong saturation magnetization and high magnetic permeability, which can adjust the impedance matching performance of a single nanographite flake as a filler, thereby allowing more electromagnetic waves to enter the coating. It also enhances the coating's ability to reduce electromagnetic waves and makes the coating thinner. The frequency range of the coating's electromagnetic wave reflectivity ≤-8dB is 9.6GHz-18GHz, and the coating thickness is 1.5mm.

[0075] Experimental Example 2 Anti-corrosion performance test 2.1 Neutral salt spray resistance time test method: According to the national standard GB / T 1771-2007 "Paints and varnishes, determination of resistance to neutral salt spray", three parallel tests were set up for each test group, and the average value was taken. The test results are shown in Table 2.

[0076] 2.2 Electrochemical impedance spectroscopy (EIS) method to test the anti-corrosion performance of anti-corrosion and microwave-absorbing coatings The anti-corrosion and absorbing coatings provided in Examples 1 to 5 and Comparative Examples 1 to 3 were immersed in 3.5 wt.% NaCl solution for 1 day to test their anti-corrosion performance. A conventional three-electrode system was used with a surface exposure area of 1 cm 2 The waterborne acrylic acid composite coating / Q235 steel sample was used as the working electrode, the calomel electrode (SCE) was used as the reference electrode, and the platinum electrode was used as the counter electrode. The frequency range of electrochemical impedance spectroscopy (EIS) measurement was 10 −2 -10 5 Hz, AC amplitude of 10mV, and the test was performed after the open circuit potential stabilized. Three parallel tests were set up for each test group, and the average value was taken. The data obtained are shown in Table 2.

[0077] Table 2 Neutral salt spray resistance time / h <![CDATA[Electrochemical impedance / Ωcm 2 > Example 1 2560 <![CDATA[1.4×10 11 ]]> Example 2 2540 <![CDATA[1.35×10 11 ]]> Example 3 3010 <![CDATA[1.62×10 11 ]]> Example 4 3000 <![CDATA[1.54×10 11 ]]> Example 5 2650 <![CDATA[1.43×10 11 ]]> Comparative Example 1 1800 <![CDATA[4.35×10 6 ]]> Comparative Example 2 900 <![CDATA[2.57×10 5 ]]> Comparative Example 3 950 <![CDATA[8.44×10 4 ]]> The corrosion resistance of the anti-corrosion and absorbing coating provided by the present application was tested by neutral salt spray resistance and electrochemical impedance spectroscopy. As shown in Table 2, the corrosion resistance of the anti-corrosion and absorbing coating provided by the present application is good. In the composite absorbing and anti-corrosion material, the nanographite flakes have good physical and chemical stability, and the two-dimensional flake shape can effectively isolate the corrosive medium from the metal substrate. At the same time, the iron and cobalt in the iron-cobalt alloy nanoparticles are more easily combined with the metal surface, and the nitrogen atoms in the polydienyldimethylammonium chloride are more likely to form coordination bonds with the empty d orbitals on the metal surface, thereby forming an adsorption film on the metal surface. The nanographite flakes and the iron-cobalt alloy nanoparticles work synergistically to improve the corrosion resistance of the coating on the substrate surface, thereby delaying the corrosion process.

[0078] Experimental Example 3 Mechanical properties testing The anti-corrosion and radar-absorbing coatings provided in Examples 1, 3, and 5, as well as Comparative Examples 1 and 3, were tested for adhesion to metal in accordance with the standard GB / T 5210-2006, "Paint and Varnish Adhesion Test by Pull-Off Method." Three replicates were run for each test, and the average results were calculated. The results are shown in Table 3.

[0079] Table 3 The anti-corrosion and wave-absorbing coating provided in the present application has strong adhesion to the metal surface. The nanographite flakes enhance the mechanical strength and toughness of the coating, allowing the coating to remain stable under complex stress environments. At the same time, the iron and cobalt in the iron-cobalt alloy nanoparticles are more easily combined with the metal surface, and the nitrogen atoms in the polydienyldimethylammonium chloride are more easily formed with the empty d orbitals on the metal surface, thereby improving the adhesion of the coating to the metal surface and further improving the mechanical strength of the coating, which is conducive to the formation of a dense and stable adsorption film between the metal surface and the external environment, thereby extending the protection period of the coating on the surface of mechanical parts.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, characterized in that: The preparation method comprises: (1) Preparation of nanographite sheets: Expandable graphite was placed in an 800°C environment for 5 seconds for thermal shock, then dispersed in anhydrous ethanol and subjected to ultrasonic exfoliation to obtain nanographite sheets. (2) Preparation of hydroxylated nanographite flakes: dispersing the nanographite flakes in concentrated nitric acid, ultrasonically treating for 0.5-2 h, washing, and drying to obtain the hydroxylated nanographite flakes; (3) Preparation of iron-cobalt alloy nanoparticles: dissolving ferric nitrate, cobalt nitrate and urea in deionized water, adjusting the pH value to 8-9 with alkali to obtain a reaction solution, placing the reaction solution in a reactor for hydrothermal reaction to obtain a preliminary product of iron-cobalt alloy nanoparticles, then immersing the preliminary product of iron-cobalt alloy nanoparticles in an aqueous solution of polydienyldimethylammonium chloride, and ultrasonically treating the solution for 1-1.5 hours, washing and drying the solution to obtain the iron-cobalt alloy nanoparticles; (4) Preparation of composite wave-absorbing and anti-corrosion material: The hydroxylated nano-graphite flakes and the iron-cobalt alloy nanoparticles are dispersed in anhydrous ethanol at a weight ratio of (0.2-0.4):1, ultrasonically treated for 0.5-1.5 hours, washed, and dried to obtain the composite wave-absorbing and anti-corrosion material.

2. The method for preparing the composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 1, characterized in that: In the step of preparing the nanographite sheet, the particle size of the expandable graphite is 200-500 mesh, and the weight-to-volume ratio of the expandable graphite to the anhydrous ethanol is 1 g: 200-300 mL.

3. The method for preparing the composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 1, characterized in that: The thickness of the nanographite flakes is 10-50 nm, and the diameter is 10-50 μm.

4. The method for preparing the composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 1, characterized in that: In the step of preparing the hydroxylated nanographite flakes, the reaction temperature is 60-70° C., and the weight-to-volume ratio of the nanographite flakes to the concentrated nitric acid is 1 g:100-120 mL.

5. The method for preparing the composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 1, characterized in that: The molar ratio of the ferric nitrate, the cobalt nitrate and the urea is (1-2):(1-2):(0.5-0.75), and the weight-to-volume ratio of the sum of the weights of the ferric nitrate, the cobalt nitrate and the urea to the deionized water is 1 g:100-200 mL.

6. The method for preparing the composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 5, characterized in that: The temperature of the hydrothermal reaction is 180-240° C., and the reaction time is 12-13 hours.

7. The method for preparing the composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 6, characterized in that: The weight-to-volume ratio of the primary iron-cobalt alloy nanoparticles to the polydienyldimethylammonium chloride aqueous solution is 1 g: 100-200 mL, and the mass concentration of the polydienyldimethylammonium chloride aqueous solution is 0.5%.

8. A composite wave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles, characterized in that: The composite wave-absorbing and anti-corrosion material is a composite wave-absorbing and anti-corrosion material obtained by the preparation method described in any one of claims 1 to 7.

9. Application of a composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles in an anti-corrosion and microwave-absorbing coating, characterized in that: The composite wave-absorbing and anti-corrosion material is used to prepare an anti-corrosion and wave-absorbing coating. The composite wave-absorbing and anti-corrosion material is obtained by the preparation method described in any one of claims 1 to 7 above, or is the composite wave-absorbing and anti-corrosion material described in claim 8.

10. Use of the composite microwave-absorbing and anti-corrosion material of nanographite sheets loaded with iron-cobalt alloy nanoparticles according to claim 9 in an anti-corrosion and microwave-absorbing coating, characterized in that: The raw materials of the anti-corrosion and wave-absorbing coating include the composite wave-absorbing and anti-corrosion material, epoxy resin, curing agent and solvent in a weight ratio of (0.5-0.75):1:(0.3-0.35):1; The solvent is obtained by mixing xylene and n-butanol in a weight ratio of 7:3.

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