Hollow porous magnetic carbon fiber framework material, composite coating with electromagnetic wave absorption and anti-corrosion functions, preparation method and application

Abstract

The invention belongs to the technical field of functional composite materials, and particularly relates to a hollow porous magnetic carbon fiber framework material, a composite coating with electromagnetic wave absorption and anti-corrosion functions, a preparation method and application. The hollow porous magnetic carbon fiber framework material is prepared by adopting a method comprising the following steps: transferring a mixture of nickel nitrate hexahydrate, 2, 5-dihydroxyterephthalic acid and DMF (Dimethyl Formamide) into a reaction kettle, and heating for reaction to obtain a nickel metal organic framework material; taking a mixture of PAN, copper nitrate monohydrate, a nickel metal organic framework material and PMMA as a shell layer solution, taking a polymethyl methacrylate solution as a core layer solution, and performing coaxial electrostatic spinning to obtain a core-shell structure nanofiber felt; and carrying out pre-oxidation, template sacrifice and carbonization treatment. Impedance matching of the coating filler can be effectively optimized, and excellent electromagnetic wave absorption performance is achieved through the synergistic effect of dielectric loss, magnetic loss and multi-interface polarization.

Description

Hollow porous magnetic carbon fiber skeleton material, composite coating with both electromagnetic wave absorption and corrosion resistance functions, preparation method and application Technical Field

[0001] This invention belongs to the field of functional composite materials technology, specifically relating to a hollow porous magnetic carbon fiber skeleton material, a composite coating with both electromagnetic wave absorption and corrosion protection functions, its preparation method, and its application. Background Technology

[0002] Electromagnetic wave absorbing materials have wide applications in military equipment and new energy fields. However, in harsh environments such as the ocean with high humidity and high salt spray, electromagnetic wave absorbing materials face serious corrosion problems, leading to structural degradation and functional failure. Single-function electromagnetic wave absorbing coatings are insufficient to meet the long-term use requirements in complex environments.

[0003] Currently, materials such as carbon nanotubes, ferrites, graphene, and metal-organic framework (MOF) derivatives have shown great potential in electromagnetic wave absorption. Among them, MOF derivatives, due to their ability to form porous carbon-metal / metal oxide composites, show great promise in the field of electromagnetic wave absorption. However, MOF derivatives are prone to structural collapse and particle agglomeration during high-temperature carbonization, limiting their large-scale practical application. On the other hand, organic coatings used for metal protection are prone to generating micropores and defects during curing, providing channels for the penetration of corrosive media such as water molecules and chloride ions, accelerating the corrosion of the metal substrate, and causing blistering, deformation, and even peeling of the coating, seriously affecting the long-term stability of electromagnetic wave absorption performance.

[0004] Superhydrophobic coatings have attracted widespread attention due to their excellent water repellency and antifouling properties, serving as an effective physical barrier against the penetration of corrosive media. However, the practical application of existing superhydrophobic surfaces in marine environments still faces technical bottlenecks such as limited functionality, complex fabrication processes, and insufficient durability.

[0005] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0006] The purpose of this invention is to provide a hollow porous magnetic carbon fiber skeleton material, a composite coating with both electromagnetic wave absorption and corrosion protection functions, a preparation method, and applications, so as to help solve or improve the problems of limited application of MOF derivatives and / or severe corrosion of metal substrates affecting electromagnetic wave absorption performance in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a hollow porous magnetic carbon fiber skeleton material, wherein the hollow porous magnetic carbon fiber skeleton material is prepared by a method comprising the following steps: A1, transferring a mixture of nickel nitrate hexahydrate, 2,5-dihydroxyterephthalic acid and N,N-dimethylformamide into a reaction vessel and heating it to react, thereby obtaining a nickel metal-organic framework material; A2, using a mixture of polyacrylonitrile, copper nitrate monohydrate, the nickel metal-organic framework material and polymethyl methacrylate as a shell layer solution and a polymethyl methacrylate solution as a core layer solution, coaxially electrospinning to obtain a core-shell structured nanofiber felt; A3, subjecting the core-shell structured nanofiber felt to pre-oxidation, template sacrificial and carbonization treatments, thereby obtaining the hollow porous magnetic carbon fiber skeleton material.

[0008] Preferably, in step A1, the mass ratio of nickel nitrate hexahydrate to 2,5-dihydroxyterephthalic acid is 1:1.5-1:2; the mass ratio of nickel nitrate hexahydrate to N,N-dimethylformamide is 1:55-1:60; the heating reaction temperature is 110-120℃, and the reaction time is 22-24h.

[0009] Preferably, in step A2, the mass ratio of copper nitrate monohydrate to the nickel metal-organic framework material is (0.8-1.1):(0.07-0.1); in the shell solution, the mass ratio of polyacrylonitrile to the nickel metal-organic framework is 1:0.07-1:0.1; the mass ratio of polyacrylonitrile to polymethyl methacrylate is 1:(0.9-1.1); the mass ratio of polyacrylonitrile to N,N-dimethylformamide is 1:330-1:333; and in the core solution, the mass ratio of polymethyl methacrylate to N,N-dimethylformamide in the polymethyl methacrylate solution is 1:3.5-1:4.

[0010] Preferably, in step A2, the voltage of the electrospinning is 14-16kV and the receiving distance is 10-14cm.

[0011] Preferably, in step A3, the pre-oxidation temperature is 200-250℃, and the pre-oxidation time is 1.5-2h; the template sacrifice and carbonization are carried out under an argon atmosphere; the template sacrifice temperature is 300-350℃, and the template sacrifice time is 1.5-2h. The carbonization temperature is 750-800℃, and the carbonization time is 1.5-2h; the heating rate during carbonization is 3-5℃ / min.

[0012] The present invention also provides a method for preparing a composite coating with both electromagnetic wave absorption and corrosion protection functions, which adopts the following technical solution: A method for preparing a composite coating with both electromagnetic wave absorption and corrosion protection functions includes the following steps: (1) dispersing the hollow porous magnetic carbon fiber skeleton material as described above in an epoxy resin system to obtain a bottom layer solution; dispersing superhydrophobic modified nano titanium dioxide in a fluorocarbon resin system to obtain a surface layer solution; (2) first coating the bottom layer solution onto the substrate surface, allowing it to dry to form a bottom layer; then coating the surface layer solution onto the bottom layer surface, allowing the surface layer solution to cure to form a surface layer; the composite coating includes the bottom layer and the surface layer.

[0013] Preferably, in step (1), the superhydrophobic modified nano-titanium dioxide is prepared by a method including the following steps: dispersing nano-titanium dioxide in ethanol, adding perfluorooctyltrimethoxysilane and tetraethyl orthosilicate for surface modification reaction, and obtaining superhydrophobic modified nano-titanium dioxide after stirring, sonication, filtration and drying.

[0014] Preferably, the mass-to-volume ratio of the nano-titanium dioxide to anhydrous ethanol is 3g:(45-50)mL; the volume ratio of the perfluorooctyltrimethoxysilane to tetraethyl orthosilicate is 1:(0.6-1); during the surface modification reaction, the mixture is first stirred at 50-60℃ for 22-24h, and then stirred at room temperature for 6-8h.

[0015] Preferably, in step (1), the epoxy resin system comprises epoxy resin and a curing agent, and the mass ratio of the hollow porous magnetic carbon framework material to the epoxy resin is 1:19-1:21; the fluorocarbon resin system comprises fluorocarbon resin, hexamethyl diisocyanate, and a solvent, and the mass ratio of the fluorocarbon resin to hexamethyl diisocyanate is 6.5:1-7:1; the mass ratio of the superhydrophobic modified nano-titanium dioxide to the fluorocarbon resin is 2.5:1-3:1; the solvent is butyl acetate; preferably, the epoxy resin is E44 epoxy resin, and the curing agent is butyl acetate. The curing agent is polyamide resin, and the mass ratio of epoxy resin to curing agent is 5:(4-4.5); the mass ratio of fluorocarbon resin to hexamethylene diisocyanate is 6.5:1-7:1; the mass ratio of superhydrophobic modified nano titanium dioxide to fluorocarbon resin is 2.5:1-3:1; the solvent is butyl acetate; the surface solution is coated by spraying, and the spraying conditions are: air pressure 1 atm, spray gun distance 10-15cm, spraying time 20-30s, spraying 2-3 times; the curing conditions of the surface solution are curing at 40-50℃ for 10h.

[0016] This invention provides a composite coating that combines electromagnetic wave absorption and corrosion protection functions, which adopts the following technical solution: a composite coating that combines electromagnetic wave absorption and corrosion protection functions, wherein the composite coating that combines electromagnetic wave absorption and corrosion protection functions is prepared by the method described above.

[0017] The present invention also provides a marine engineering component, which adopts the following technical solution: a marine engineering component having a composite coating as described above that has both electromagnetic wave absorption and corrosion protection functions.

[0018] Beneficial effects: This invention constructs a hollow porous magnetic carbon framework material with a hollow porous structure and copper-nickel alloy nanoparticles, which can effectively optimize the impedance matching of the coating filler. Through the synergistic effect of dielectric loss, magnetic loss and multiple interface polarization, it achieves excellent electromagnetic wave absorption performance and obtains minimum reflection loss and effective absorption bandwidth with thin matching thickness.

[0019] The composite coating of the present invention, which combines electromagnetic wave absorption and corrosion protection, adopts a double-layer structure design. The superhydrophobic modified nano titanium dioxide in the surface layer not only provides excellent water repellency and self-cleaning ability, but its low dielectric constant can also form a functional gradient impedance matching structure with the hollow porous magnetic carbon framework high-loss layer in the bottom layer, which promotes the incidence of electromagnetic waves and effectively blocks the penetration of water and corrosive media.

[0020] The composite coating of this invention, which combines electromagnetic wave absorption and corrosion protection, exhibits excellent long-term corrosion resistance. After being immersed in 3.5wt% NaCl solution for 30 days, its low-frequency impedance modulus is still three orders of magnitude higher than that of the pure epoxy coating.

[0021] Simulation results of radar cross section show that the composite coating of the present invention, which combines electromagnetic wave absorption and corrosion protection, can achieve omnidirectional and multi-polarization electromagnetic wave absorption on complex ship models, proving its great application potential in engineering radar stealth.

[0022] The composite coating of the present invention, which combines electromagnetic wave absorption and corrosion protection, has a simple preparation process, readily available raw materials, good environmental adaptability, and is suitable for large-area coating. It has good prospects for promotion and application in the field of marine equipment and coastal facility protection. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. In which: Figure 1 is a scanning electron microscope (SEM) image; wherein, (a) is a SEM image of the carbon framework material of Comparative Example 1, (b) is a SEM image of the magnetic carbon framework material of Comparative Example 2, and (c) is a SEM image of the hollow porous magnetic carbon fiber skeleton material of Example 1.

[0024] Figure 2 shows the X-ray diffraction patterns of the hollow porous magnetic carbon fiber skeleton material of Example 1, the carbon framework material of Comparative Example 1, and the magnetic carbon framework material of Comparative Example 2.

[0025] Figure 3 shows the Raman spectra of the hollow porous magnetic carbon fiber skeleton material of Example 1, the carbon framework material of Comparative Example 1, and the magnetic carbon framework material of Comparative Example 2.

[0026] Figure 4 shows the reflection loss diagrams; where (a) is the reflection loss diagram of the carbon framework material in Comparative Example 1, (b) is the reflection loss diagram of the magnetic carbon framework material in Comparative Example 2, (c) is the reflection loss diagram of the hollow porous magnetic carbon fiber skeleton material in Example 1, (d) is the reflection loss diagram of the magnetic carbon framework material with increased copper nitrate concentration in Example 2, (e) is the reflection loss diagram of the magnetic carbon framework material with decreased copper nitrate concentration in Example 3, (f) is the reflection loss diagram of the magnetic carbon framework material without copper nitrate in Comparative Example 8, and (g) is the reflection loss diagram of the magnetic carbon framework material without the sacrificial template step in Comparative Example 9.

[0027] Figure 5 shows the radar scattering cross-section curve of the hollow porous magnetic carbon fiber skeleton material in Example 1. Among them: (a) and (b) are front views, (c) and (d) are overview views; (a) and (c) represent horizontally polarized electromagnetic wave incidence, and (b) and (d) represent vertically polarized electromagnetic wave incidence.

[0028] Figure 6 shows the reflection loss test results of the superhydrophobic modified nano-titanium dioxide obtained in step (1) of Example 1.

[0029] Figure 7 shows the wettability test results of the composite coating of Example 1 of the present invention with different types of liquids.

[0030] Figure 8 is an electrochemical characterization diagram of Example 1 of the present invention; wherein: (a), (d), and (g) are enlarged views of the Bode plot, Nyquist plot, and Nyquist plot of Example 1, respectively; (b) and (e) are the Bode plot and Nyquist plot of Comparative Example 4, respectively; and (c), (f), and (h) are enlarged views of the Bode plot, Nyquist plot, and Nyquist plot of Comparative Example 3, respectively. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0032] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0033] This invention addresses the limitations of MOF derivatives in the prior art and / or the serious impact of metal matrix corrosion on electromagnetic wave absorption performance by providing a hollow porous magnetic carbon fiber skeleton material.

[0034] The hollow porous magnetic carbon fiber skeleton material of this invention is prepared by a method including the following steps: A1, a mixture of nickel nitrate hexahydrate, 2,5-dihydroxyterephthalic acid and N,N-dimethylformamide is transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated to react, thereby obtaining a nickel metal-organic framework material; A2, a mixture of polyacrylonitrile, copper nitrate monohydrate, nickel metal-organic framework material and polymethyl methacrylate is used as the shell layer solution, and a polymethyl methacrylate (PMMA) solution is used as the core layer solution, and coaxial electrospinning is performed to obtain a core-shell structured nanofiber felt; A3, the core-shell structured nanofiber felt is subjected to pre-oxidation, template sacrificial and carbonization treatments to obtain the hollow porous magnetic carbon fiber skeleton material. In this invention, copper nitrate plays two roles: firstly, copper catalyzes carbonization, promoting the formation of a highly conductive network and laying the foundation for strong conductive loss; secondly, the introduced copper element can form a CuNi alloy phase with nickel, and this synergistic effect can finely adjust complex electromagnetic parameters and create abundant heterogeneous interfaces, thereby synergistically optimizing impedance matching and significantly enhancing interface polarization loss, ultimately achieving strong broadband absorption (if copper nitrate is replaced with copper acetate, the structure and electromagnetic properties of the final product will deteriorate significantly). In step A3, the template sacrifice treatment step can pyrolyze the core layer (polymethyl methacrylate) in the core-shell structured nanofiber felt, leaving a hollow structure and generating gas to form a porous structure; if the template sacrifice treatment step is omitted, the pyrolysis of the polymethyl methacrylate in the core layer may be incomplete, which will affect the structure of the hollow porous magnetic carbon fiber skeleton material of this invention, and thus affect its microwave absorption performance.

[0035] This invention utilizes PMMA as a thermally decomposable template, enabling its complete decomposition and gas release during template sacrifice and carbonization. This successfully constructs a magnetic carbon framework material with unique cavities and abundant hierarchical pores. This material effectively traps air to form a low dielectric constant region, which, when applied to coatings, significantly improves the impedance matching characteristics of the coating. In the hollow porous magnetic carbon framework material of this invention, copper-nickel alloy nanoparticles are uniformly distributed within the carbon framework, providing not only considerable magnetic loss capability but also enhancing the interfacial polarization effect through the heterojunction formed between them and the carbon interface. The preparation route, employing coaxial electrospinning combined with self-templating carbonization, allows for precise control of the fiber's core-shell structure and its evolution during heat treatment, ensuring a regular hollow porous morphology (if...). Using polymethyl methacrylate (PMMA) solution as the shell solution and a mixture of polyacrylonitrile (PAN), copper nitrate monohydrate, nickel metal-organic framework (MOF), and PMMA as the core solution results in the PMMA shell decomposing and disappearing first during the initial carbonization stage due to the thermal decomposition template effect of PMMA. This causes the overall fiber structure to collapse or break before the PAN core is fully stabilized, making it difficult to form a complete and continuous tubular structure. It also degrades the conductive network: even if some structure remains, the carbon fibers derived from the core may stick together, agglomerate, or form discontinuous carbon particles due to the missing shell, failing to construct the three-dimensional interconnected, highly conductive fiber network of the original design, severely damaging conductive loss and structural integrity. The hollow porous magnetic carbon skeleton material of this invention effectively optimizes the impedance matching of the coating filler. Through the synergistic effect of dielectric loss, magnetic loss, and multiple interface polarizations, it achieves excellent electromagnetic wave absorption performance, obtaining minimum reflection loss and effective absorption bandwidth at a thin matching thickness.

[0036] In a preferred embodiment of the hollow porous magnetic carbon fiber skeleton material of the present invention, in step A1, the mass ratio of nickel nitrate hexahydrate to 2,5-dihydroxyterephthalic acid is 1:(1.5-2) (e.g., 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2); the mass ratio of nickel nitrate hexahydrate to N,N-dimethylformamide is 1:(55-60) (e.g., 1:55, 1:56, 1:57, 1:58, 1:59 or 1:60); the reaction temperature is 110-120℃ (e.g., 110℃, 112℃, 114℃, 116℃, 118℃ or 120℃); and the reaction time is 22-24h (e.g., 22h, 22.5h, 23h, 23.5h or 24h).

[0037] In a preferred embodiment of the hollow porous magnetic carbon fiber skeleton material of the present invention, in step A2, the mass ratio of copper nitrate monohydrate to nickel metal-organic framework material is (0.8-1.1):(0.07-0.1) (e.g., 0.8:0.07, 0.8:0.09, 0.8:0.1, 0.9:0.07, 0.9:0.08, 0.9:0.1, 1.1:0.07, 1.1:0.1, or 1.1:0.08); in the shell solution, the mass ratio of polyacrylonitrile to nickel metal-organic framework is 1:(0.07-0.1) (e.g., 1:0.07, 1:0.08, 1:0.08). 0.09 or 1:0.1); the mass ratio of polyacrylonitrile to polymethyl methacrylate is 1:(0.9-1.1) (e.g., 1:0.9, 1:1, 1:1.1); the mass ratio of polyacrylonitrile to N,N-dimethylformamide is 1:(330-333) (e.g., 1:330, 1:331, 1:332, 1:333); in the core layer solution, the mass ratio of polymethyl methacrylate to N,N-dimethylformamide in the polymethyl methacrylate solution is 1:(3.5-4) (e.g., 13.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9 or 1:4). If the proportion of copper nitrate is too large, too much gas will be generated during the carbonization process, which will seriously affect the continuity of the prepared hollow porous magnetic carbon fiber skeleton material. At the same time, it will cause the overall electrical conductivity of the material to increase excessively and weaken the magnetic permeability of the material. If the proportion of copper nitrate is too small, the copper-nickel alloying will be insufficient, which will reduce the natural resonance ability of the material, break the balance between dielectric constant and magnetic permeability, and reduce the number of heterojunctions and polarization effect.

[0038] In a preferred embodiment of the hollow porous magnetic carbon fiber skeleton material of the present invention, in step A2, the voltage of electrospinning is 14-16kV (e.g., 14kV, 15kV or 16kV), and the receiving distance is 10-14cm (e.g., 10cm, 11cm, 12cm, 13cm or 14cm).

[0039] Preferably, in step A2, the inner diameter of the spinning needles in the coaxial electrospinning is 0.5-0.7 mm (e.g., 0.5 mm, 0.6 mm, or 0.7 mm), and the outer diameter is 0.8-1.0 mm (e.g., 0.8 mm, 0.9 mm, or 1.0 mm); the shell solution velocity is 0.04-0.06 mm / min (e.g., 0.04 mm / min, 0.05 mm / min, or 0.06 mm / min), and the core solution velocity is 0.009-0.011 mm / min (e.g., 0.009 mm / min, 0.010 mm / min, or 0.011 mm / min).

[0040] In a preferred embodiment of the hollow porous magnetic carbon fiber skeleton material of the present invention, in step A3, the pre-oxidation temperature is 200-250℃ (e.g., 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃), and the pre-oxidation time is 1.5-2h (e.g., 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, or 2h); template sacrifice and carbonization are carried out under an argon atmosphere, and the template sacrifice temperature is 300-350℃ (e.g., 300℃, 310℃, 320℃, 330℃, or 340℃). The carbonization temperature is 750-800℃ (e.g., 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃), and the carbonization time is 1.5-2h (e.g., 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h); the heating rate during carbonization is 3-5℃ / min (e.g., 3℃ / min, 4℃ / min or 5℃ / min). The template sacrifice and carbonization processes are carried out under an argon atmosphere. Argon possesses excellent chemical inertness, a moderate density (beneficial for maintaining a stable furnace atmosphere), and relatively economical cost. It can effectively isolate oxygen during carbonization while allowing reducing gases (such as H2 and CO) generated from precursor pyrolysis to form a localized reducing environment, promoting the formation of CuNi alloys. This makes it the optimal choice for achieving a balance between performance, reliability, and economy in this process. If nitrogen is used instead of argon, nitrogen may react with components such as metallic nickel at high temperatures to form nitrides, altering the phase composition and electromagnetic properties of the target product.

[0041] The present invention also proposes a method for preparing a composite coating with both electromagnetic wave absorption and corrosion protection functions. The method for preparing the composite coating with both electromagnetic wave absorption and corrosion protection functions in the embodiments of the present invention includes the following steps: (1) dispersing the hollow porous magnetic carbon fiber skeleton material as described above in an epoxy resin system to obtain a bottom layer solution; dispersing superhydrophobic modified nano titanium dioxide in a fluorocarbon resin system to obtain a surface layer solution; (2) first coating the bottom layer solution onto the substrate surface, allowing it to dry to form a bottom layer; then coating the surface layer solution onto the bottom layer surface, allowing the surface layer solution to solidify to form a surface layer; the composite coating includes a bottom layer and a surface layer.

[0042] In the composite coating prepared by the method of this invention, the hollow porous magnetic carbon fiber skeleton material in the bottom solution can significantly improve the impedance matching characteristics of the coating; and the copper-nickel alloy nanoparticles are uniformly distributed in the carbon skeleton, which can provide considerable magnetic loss capability, and the heterojunction formed between it and the carbon interface also enhances the interfacial polarization effect; the superhydrophobic modified nano-titanium dioxide achieves effective reduction of surface energy through the introduction of perfluoroalkyl chains, and works synergistically with the micro-nano hierarchical rough structure to endow the coating surface with stable superhydrophobic properties; the design of the double-layer structure of the composite coating of this invention constructs a functional gradient from the low-loss impedance matching layer on the upper surface to the high-loss absorption layer on the lower surface, which not only promotes the incident and dissipation of electromagnetic waves, but also achieves multiple barriers to corrosive media through the synergy of the superhydrophobic barrier and the physical shielding of the bottom layer.

[0043] In a preferred embodiment of the method for preparing the composite coating with both electromagnetic wave absorption and corrosion protection functions of the present invention, in step (1), the superhydrophobic modified nano-titanium dioxide is prepared by a method including the following steps: nano-titanium dioxide is dispersed in ethanol, perfluorooctyltrimethoxysilane and tetraethyl orthosilicate are added for surface modification reaction, and after stirring, sonication, filtration and drying, superhydrophobic modified nano-titanium dioxide is obtained. The superhydrophobic modified nano-titanium dioxide effectively reduces surface energy through the introduction of perfluoroalkyl chains, and works synergistically with the micro-nano hierarchical rough structure (the micro-nano hierarchical rough structure formed on the surface of the coating obtained by spraying a surface solution containing superhydrophobic modified nano-titanium dioxide) to impart stable superhydrophobic properties to the coating surface.

[0044] In a preferred embodiment of the method for preparing the composite coating with both electromagnetic wave absorption and corrosion protection functions of the present invention, the mass-to-volume ratio of nano-titanium dioxide to anhydrous ethanol is 3g:(45-50)mL (e.g., 3g:45mL, 3g:46mL, 3g:47mL, 3g:48mL, 3g:49mL, 3g:50mL); the volume ratio of perfluorooctyltrimethoxysilane to tetraethyl orthosilicate is 1:(0.6-1); during the surface modification reaction, the mixture is first stirred at 50-60℃ (e.g., 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃) for 22-24h (e.g., 22h, 23h or 24h), and then stirred at room temperature for 6-8h (e.g., 6h, 7h or 8h).

[0045] In a preferred embodiment of the method for preparing the composite coating with both electromagnetic wave absorption and corrosion protection functions of the present invention, in step (1), the epoxy resin system comprises epoxy resin and curing agent, and the mass ratio of the hollow porous magnetic carbon framework to the epoxy resin is 1:(19-21) (e.g., 1:19, 1:20 or 1:21); the fluorocarbon resin system comprises fluorocarbon resin, hexamethyl diisocyanate and solvent, and the mass ratio of the fluorocarbon resin to hexamethyl diisocyanate is (6.5-7):1 (e.g., 6.5:1, 6.6:1, 6.7:1, 6.8:1, 6.9:1 or 7:1); the mass ratio of the superhydrophobic modified nano titanium dioxide to the fluorocarbon resin is (2.5-3):1 (e.g., 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1); the solvent is butyl acetate.

[0046] In a preferred embodiment of the preparation method of the composite coating with both electromagnetic wave absorption and corrosion protection functions of the present invention, the solvent is butyl acetate; the surface solution is coated by spraying, and the spraying conditions are: air pressure 1 atm, spray gun distance 10-15cm (e.g., 10cm, 11cm, 12cm, 13cm, 14cm or 15cm), spraying time 20-30s (e.g., 20s, 22s, 24s, 26s, 28s or 30s), spraying 2-3 times; the surface solution is cured at 40-50℃ (e.g., 40℃, 42℃, 44℃, 46℃, 48℃ or 50℃) for 10h.

[0047] This invention also proposes a composite coating that combines electromagnetic wave absorption and corrosion protection functions. The composite coating with these functions, as described above, is prepared using the method described in this invention. The composite coating of this invention employs a two-layer structure design. The superhydrophobic modified nano-titanium dioxide in the surface layer not only provides excellent water repellency and self-cleaning ability, but its low dielectric constant also forms a functionally graded impedance matching structure with the hollow porous magnetic carbon framework high-loss layer in the bottom layer. This promotes the incidence of electromagnetic waves while effectively blocking the penetration of water and corrosive media.

[0048] The present invention also proposes a marine engineering component, wherein the marine engineering component of the present invention has a double-sided composite coating as described above, which has both efficient electromagnetic wave absorption and long-term corrosion protection functions.

[0049] Preferably, the marine engineering components of the present invention include, but are not limited to, at least one of the following: ship equipment, missiles, and coastal facility metal components.

[0050] The hollow porous magnetic carbon fiber skeleton material, the composite coating with both electromagnetic wave absorption and corrosion resistance functions, its preparation method, and its application are described in detail below through specific embodiments.

[0051] The main raw materials used in the following examples are sourced from: polyacrylonitrile (PAN, Mw=150,000), polymethyl methacrylate (Mw=100,000-120,000), nickel nitrate hexahydrate ( ), 2,5-dihydroxybenzoic acid (C8H6O6), copper nitrate monohydrate ( All of the above (99.8%) were derived from Aladdin; nano-particles TiO2 (nano TiO2, 25nm, 99.8%), 1H,1H,2H,2H-perfluoroethyltrimethoxysilane, and tetraethyl orthosilicate (C8H) were derived from Aladdin. 20 O4Si, 98%), hexamethyl diisocyanate (99%), anhydrous ethanol ( AR), N,N-dimethylformamide (DMF, 99%), and butyl acetate (Yinghua, Arkansas) were all sourced from Maclean's; epoxy resin E-44 and polyamide resin (low molecular weight 650) were purchased from Zhenjiang Danbao Resin Chemical Co., Ltd.; fluorocarbon resin (FC) was purchased from Shandong Huafu Chemical Co., Ltd. All chemicals were used in their original form without any additional treatment.

[0052] Example 1: The hollow porous magnetic carbon fiber skeleton material of this example was prepared by the following steps: A1. A mixture of 0.72 g of nickel nitrate hexahydrate and 1.245 g of 2,5-dihydroxyterephthalic acid was added to 45 mL of N,N-dimethylformamide and mixed evenly under ultrasonic magnetic stirring; then the uniformly mixed solution was transferred to a 50 mL high-pressure reactor lined with polytetrafluoroethylene and placed in an oven at 110 °C for 22 h; after cooling to room temperature, the sample was centrifuged and washed several times with N,N-dimethylformamide, and then dried at 60 °C to collect the product to obtain the nickel metal-organic framework material; A2. 0.6 g of polyacrylonitrile and 0.5 g of copper nitrate monohydrate were dispersed in 10 g of N,N-dimethylformamide. In N,N-dimethylformamide, 0.045 g of nickel-organic framework material was added to the above solution and stirred for 2 h; 0.6 g of polymethyl methacrylate was added to the above solution and stirred evenly to form the shell solution; simultaneously, a 20 wt% polymethyl methacrylate solution was used as the core solution; coaxial electrospinning was performed (the coaxial electrospinning process was carried out at room temperature, 30% humidity, 14 kV voltage, and a working distance of 14 cm; the inner diameter of the spinning needle for coaxial electrospinning was 0.6 mm and the outer diameter was 0.9 mm); The shell solution velocity was 0.05 mm / min, and the core solution velocity was 0.01 mm / min, to obtain a core-shell structured nanofiber felt; A3, the core-shell structured nanofiber felt prepared above was dried in an oven at 60°C overnight; then, it was pre-oxidized at 250°C for 2 h; then, it was heated to 300°C and heat-treated for 2 h under an argon atmosphere (template sacrifice); finally, it was heated to 800°C at a heating rate of 5°C / min for 2 h to obtain the hollow porous magnetic carbon fiber skeleton material of this embodiment.

[0053] The preparation method of the composite coating with electromagnetic wave absorption and anti-corrosion functions in this embodiment includes the following steps: (1) 3g of nano titanium dioxide is added to 50mL of anhydrous ethanol and stirred evenly to obtain solution A; 3mL of perfluorooctyltrimethoxysilane and 2mL of tetraethyl orthosilicate are dissolved in 10mL of anhydrous ethanol, stirred for 10min, and ultrasonically treated for 20min to obtain solution B; solution B is added dropwise to solution A, and the mixture is continuously stirred at 60℃ for 24h, and then stirred for another 6h at room temperature; the reaction solution is filtered, centrifuged and dried to obtain superhydrophobic modified nano titanium dioxide; (2) 0.1g of the hollow porous magnetic carbon fiber skeleton material of this embodiment is uniformly dispersed in 2g of ethanol to obtain a dispersion; then, 2g of the above dispersion is added to the above dispersion. E44 epoxy resin and 1.6g polyamide resin were stirred for 30min to ensure that the sample and epoxy resin were mixed evenly to obtain the bottom layer solution; the above superhydrophobic modified nano titanium dioxide was added to 40mL butyl acetate and stirred evenly, then fluorocarbon resin was added dropwise, while stirring was continued until evenly mixed, and then hexamethylene diisocyanate was added (the mass ratio of superhydrophobic modified nano titanium dioxide, fluorocarbon resin and hexamethylene diisocyanate was 21:7:1), and mixed evenly to obtain the surface layer solution; (3) the bottom layer solution was coated on Q235 low carbon steel (before this, the surface of Q235 low carbon steel was sanded with sandpaper, cleaned with anhydrous ethanol and dried), and placed in a 40℃ oven to dry for 20min to reach the surface dry state, and the bottom layer solution was cured to obtain the bottom layer; the surface layer solution was sprayed onto the surface-dried bottom layer with a spray gun and cured in a 40℃ oven for 10h to obtain the surface layer; the composite coating of this embodiment includes the bottom layer and the surface layer.

[0054] Example 2 The only difference between this example and Example 1 is that in A2, 0.6g of polyacrylonitrile and 1g of copper nitrate monohydrate are dispersed in 10g of N,N-dimethylformamide, and the rest is the same as in Example 1.

[0055] Example 3 The only difference between this example and Example 1 is that in A2, 0.6g of polyacrylonitrile and 0.1g of copper nitrate monohydrate are dispersed in 10g of N,N-dimethylformamide, and the rest is the same as in Example 1.

[0056] Example 4 The only difference between this example and Example 1 is that in the preparation of the composite coating with both electromagnetic wave absorption and anti-corrosion functions, waterborne epoxy resin (E44) and low molecular weight polyamide curing agent are mixed in a weight ratio of 5:4 and uniformly coated on the metal substrate (titanium alloy) with a glass rod. All other aspects are the same as in Example 1.

[0057] Comparative Example 1: The carbon framework of this comparative example was prepared by the following steps: 0.6 g of polyacrylonitrile was dissolved in 10 g of N,N-dimethylformamide and magnetically stirred to obtain a spinning solution; the spinning solution was transferred to a 10 mL syringe and uniaxial electrospinning was performed (at room temperature, 30% humidity, 14 kV voltage, and a working distance of 14 cm) to obtain a fiber membrane; the obtained fiber membrane was dried overnight in an oven at 60 °C; subsequently, the fiber membrane was pre-oxidized at 250 °C for 2 h, and then carbonized at 800 °C for 2 h in an argon atmosphere at a heating rate of 5 °C / min to obtain the carbon framework of this comparative example.

[0058] Comparative Example 2: The magnetic carbon framework of this comparative example was prepared by a method comprising the following steps: 0.6 g of polyacrylonitrile and 0.5 g of copper nitrate monohydrate were dissolved in 10 g of N,N-dimethylformamide; 0.045 g of nickel metal-organic framework material (prepared according to the same method as step A1 in Example 1) was added to the above solution, and the mixture was magnetically stirred to obtain a spinning solution. The spinning solution was transferred to a 10 mL syringe and uniaxial electrospinned to obtain a fiber membrane; the obtained fiber membrane was dried overnight in an oven at 60 °C; subsequently, the fiber membrane was pre-oxidized at 250 °C for 2 h, and then carbonized at 800 °C for 2 h in an argon atmosphere at a heating rate of 5 °C / min to obtain the magnetic carbon framework of this comparative example.

[0059] Comparative Example 3 provides a pure resin coating, which is prepared by a method including the following steps: waterborne epoxy resin (E44) and low molecular weight polyamide curing agent are mixed in a weight ratio of 5:4, and uniformly coated on a metal substrate (carbon steel) with a glass rod. The coating is applied three times and placed in an oven at 60°C for 20 minutes until the coating reaches a surface dry state, thus obtaining the pure resin coating of this comparative example.

[0060] Comparative Example 4 provides a method for preparing a hollow porous magnetic carbon framework / epoxy composite coating. The only difference from Example 1 is that the step of spraying the surface solution onto the dried substrate using a spray gun is omitted in step (3) (that is, the substrate solution is applied to Q235 low carbon steel and the surface is dried. After obtaining the substrate, it is directly placed in an oven and dried at 40°C for 10 hours to obtain the hollow porous magnetic carbon framework / epoxy composite coating); other steps and parameters are the same as in Example 1.

[0061] The only difference between Comparative Example 5 and Example 1 is that in A2, 0.6 g of polyacrylonitrile and 0.5 g of copper nitrate monohydrate were dispersed in 20 g of N,N-dimethylformamide, while the rest remained the same as in Example 1.

[0062] In this comparative example, the solution concentration was too low during the electrospinning process, resulting in the failure to form filaments and thus sample preparation failure.

[0063] The only difference between Comparative Example 6 and Example 1 is that in the preparation of the composite coating with both electromagnetic wave absorption and corrosion protection functions, superhydrophobic modified nano-titanium dioxide was added to 40 mL of butyl acetate and stirred evenly to obtain a surface solution (i.e., no fluorocarbon resin and hexamethylene diisocyanate were added to the surface solution); all other aspects were the same as in Example 1.

[0064] In this comparative example, since no fluorocarbon resin and hexamethylene diisocyanate were added to the surface solution, the titanium dioxide powder on the dried coating surface fell off with a light touch, and the final stabilized coating was basically the same as that of comparative example 4.

[0065] The only difference between Comparative Example 7 and Example 1 is that the top layer solution was sprayed directly onto the bottom layer coating after the bottom layer solution was applied to Q235 low carbon steel (i.e., the top layer solution was sprayed before the bottom layer solution was surface dry). All other aspects were the same as in Example 1.

[0066] In this comparative example, the surface solution was sprayed directly before the bottom solution was completely dry, which damaged the bottom coating and resulted in unsuccessful sample preparation.

[0067] The only difference between Comparative Example 8 and Example 1 is that the step of adding copper nitrate monohydrate in step A2 is omitted; otherwise, they are the same as Example 1.

[0068] The only difference between Comparative Example 9 and Example 1 is that the step of heat treatment at 300°C for 2 hours in an argon atmosphere (template sacrifice) in step A3 is omitted; all other steps are the same as in Example 1.

[0069] Experiment 1, Scanning Electron Microscopy Test: The surfaces of each sample were observed under a scanning electron microscope, and the SEM images are shown in Figure 1. Figure 1(a) is the SEM image of the carbon framework of Comparative Example 1, showing no obvious breaks or collapses in the three-dimensional network structure, thus forming a relatively complete conductive path. Figure 1(b) is the SEM image of the magnetic carbon framework of Comparative Example 2, exhibiting a bead-like structure, which may originate from nickel metal-organic framework particles. Figure 1(c) is the SEM image of the hollow porous magnetic carbon fiber skeleton material of Example 1. Due to the pyrolysis of polymethyl methacrylate and the release of carbon dioxide, pores appear on the surface of the carbon framework while maintaining a relatively continuous state. After the pyrolysis of polymethyl methacrylate, the core of the fiber exhibits a hollow nanofiber structure.

[0070] 2. XRD Testing: Figure 2 shows the XRD patterns of the hollow porous magnetic carbon fiber skeleton material of Example 1, the carbon framework of Comparative Example 1, and the magnetic carbon framework material of Comparative Example 2. As shown in Figure 3, all three samples exhibit diffraction peaks at 2θ = 26.5°, which is consistent with the characteristic peak position of the graphite (002) crystal plane. After carbonization treatment, both the hollow porous magnetic carbon framework and the magnetic carbon framework sample formed well-crystallized metal solid solutions, and their XRD patterns showed three different diffraction peaks at 2θ = 43.3°, 50.4°, and 74.1°. It is worth noting that compared with the standard diffraction peaks of pure copper (Cu, PDF#00-004-0836), these peak positions are slightly shifted to higher angles, corresponding to the characteristic peaks of pure nickel (Ni, PDF#00-004-0850), which are approximately 44.5°, 51.8°, and 76.4°, respectively. The absence of characteristic peaks in pure nickel indicates that its content is significantly lower than that of copper. Combined with the observed shifts in diffraction peak positions, these results indicate that during reduction, nickel is primarily incorporated into the copper matrix in an elemental state, leading to the formation of a copper-rich substituted solid solution (Cu(Ni)). This dissolution causes the diffraction peaks to systematically shift to higher angles. Furthermore, a diffraction peak for cuprous oxide is observed at 2θ≈36.4º, which is likely due to slight oxidation of a small amount of copper on the surface during the later stages of carbonization.

[0071] 3. Raman Spectroscopy Test: Figure 2 shows the Raman spectra of the hollow porous magnetic carbon fiber skeleton material of Example 1, the carbon framework of Comparative Example 1, and the magnetic carbon framework material of Comparative Example 2. The spectra at 1350 cm⁻¹... -1 (D peak) and 1590cm -1 The characteristic peaks at (G peak) reflect the degree of disorder and ordered graphitization of the carbon structure in the composite material. The ratio of the intensity of the D peak to the intensity of the G peak (ID / IG) is a key parameter for evaluating the degree of graphitization of carbon materials. The comparative results show that the sample in Example 1 has the highest ID / IG value, indicating a higher concentration of defects in its carbon microstructure.

[0072] 4. Electromagnetic wave reflection loss (RL) test: Figure 4 shows the RL diagrams for Example 1, Comparative Example 1, Comparative Example 2, Example 2, Example 3, Comparative Example 8, and Comparative Example 9. Specifically, Figure 4(a) shows the RL of the hollow porous magnetic carbon framework material (Example 1) at 17.6 GHz and a matching thickness of 1.9 mm. min The effective absorption bandwidth is -43.06 dB, covering 6.45 GHz (12.56–18 GHz); Figure 4(b) shows the magnetic carbon framework (Comparative Example 2) with an RL of 7.7 mm matching thickness. min The effective absorption bandwidth is -43.51 dB, covering 5.33 GHz. Figure 4(c) shows the RL of the carbon frame (Comparative Example 1) with a matching thickness of 2.1 mm. minThe dielectric loss is -32.65 dB, with an effective absorption bandwidth covering 6.29 GHz. Introducing copper-nickel alloy particles into the carbon framework matrix generates numerous heterojunctions, which significantly enhance dielectric loss through strong interfacial polarization, enabling the magnetic carbon framework to achieve excellent RL (hydrodynamic) performance. min During the transformation from a magnetic carbon framework to a hollow porous magnetic carbon framework, the resulting hollow porous structure maintained high attenuation capability while broadening the EAB to 16% and reducing the matching thickness by 75%, achieving synergistic optimization of broadband, strong absorption, and ultrathinness. However, changing the amount of copper nitrate added, as seen in Example 2, increased the dielectric constant of the sample, leading to significant electromagnetic wave reflection and weakening the absorption performance. At a matching thickness of 6.4 mm, the RL... min Only -45.23dB was achieved (Figure 4d); however, when the amount of copper nitrate added in Example 3 was reduced, the dielectric loss of the sample was greatly reduced, which also reduced its microwave absorption performance. The RL value was lower when the thickness was 2.4mm. min The absorption rate only reached -25.8 dB (Figure 4e). When copper nitrate was not added in Comparative Example 8, the balance between dielectric and magnetic losses was disrupted, resulting in dielectric loss being significantly greater than magnetic loss, which affected its microwave absorption performance. At a matching thickness of 2.2 mm, the RL... min The absorption rate was only -35.53 dB (Figure 4f). When the template sacrifice step was not performed in Comparative Example 9, the PMMA pyrolysis was incomplete, the morphology and structure of the sample changed, resulting in a decrease in the microwave absorption performance. When the matching thickness was 2.7 mm, RLmin only reached -40.92 dB (Figure 4g).

[0073] Figure 6 shows the reflection loss test results of the superhydrophobic modified nano-titanium dioxide obtained in step (1) of Example 1; when the matching thickness is 6.8 mm, the minimum reflection loss value reaches -19.46 dB, indicating that the superhydrophobic modified nano-titanium dioxide can effectively absorb about 98.8% of the incident electromagnetic wave energy.

[0074] 5. Radar Cross Section (RCS): The radar stealth capability of the hollow porous magnetic carbon frame was further evaluated on complex ship-scale targets to determine its practical applicability. A conformal coating of the absorber was applied to a simplified destroyer model, and its electromagnetic wave absorption characteristics were systematically simulated. The coordinate system was defined with the ship located in the xy plane, its bow aligned with the positive x-axis, and the positive z-axis designated as the zenith. The incident direction of the electromagnetic wave was parameterized by spherical coordinates θ and φ. Horizontal (HP) and vertical (VP) polarization were simulated at 17.6 GHz. RCS reduction was analyzed in two key observation scenarios: the forward-looking zone (receiver angle θ = 90°, φ ranging from 0° to 360°) and the downward-looking zone (receiver angle θ = 90°, φ ranging from -180° to 180°).

[0075] The test results are shown in Figures 5(a)-(d). When the perfect electrical conductor (PEC) reference is used as the baseline, the RCS response of the conformal coating model of the hollow porous magnetic carbon framework is significantly suppressed in both polarization states. This result clearly verifies the ability of the hollow porous magnetic carbon framework material of Example 1 to achieve effective electromagnetic attenuation over a wide range and in multiple polarization modes on complex geometries.

[0076] 6. Wettability Test: The contact angle of the coating was determined using a coating contact angle measuring instrument. At room temperature, the sample was placed on the surface of the instrument, and different 3μL droplets were placed on the coating surface for measurement. Measurements were taken at five different locations, and the average value was calculated. The wettability test results of the composite coating in Example 1 are shown in Figure 7; Figure 7 illustrates the repulsion performance of the composite coating against various complex liquids. Water, Coca-Cola, milk, fruit juice, 3.5wt% NaCl solution, and tea leaves all exhibited contact angles ≥150°.

[0077] The test results fully demonstrate that the composite coating of Example 1 not only exhibits superhydrophobic properties to pure water, but also to aqueous dispersions and emulsions containing complex components such as salt, sugar, protein, organic acid or pigment, showing excellent anti-fouling and anti-corrosion potential.

[0078] 7. Electrochemical Testing: The electrochemical performance of the coating was measured using a conventional three-electrode system. A platinum electrode was used as the counter electrode, and the working electrode had an area of ​​0.1 cm². 2 The coating was used, with a saturated silver chloride electrode as the reference electrode. The coating was immersed in a 3.5% sodium chloride solution, and the system was tested after stabilization. The Bode plots of Example 1, Comparative Example 4, and Comparative Example 3 are shown in Figures 8(a)-(c) respectively; The value gradually decreased with increasing soaking time; Examples 1, 4, and 3 The values ​​are respectively , and This indicates that all three coatings provide substantial protection for the Q235 carbon steel substrate. Specifically, the initial coating of Example 1... The value was two orders of magnitude higher than that of Comparative Example 4, and this significant difference may be due to the formation of a superhydrophobic interface; after soaking for 10 days, the value of Comparative Example 3 was... This represents a reduction of two orders of magnitude. After 30 days, as the corrosive medium penetrates the coating defects, the performance of Comparative Example 3... Further down to This indicates that the corrosion resistance of Comparative Example 3 has significantly decreased, and it cannot effectively protect the metal substrate. In stark contrast, after immersion for 30 days, the corrosion resistance of Examples 1 and 4... Keep each at and Compared with Comparative Example 3, the results were improved by three and two orders of magnitude, respectively; this is attributed to the incorporation of the hollow porous magnetic carbon fiber skeleton material of Example 1 and the magnetic carbon framework of Comparative Example 2 as nanofillers into the coating matrix.

[0079] The Nyquist plots of Example 1, Comparative Example 4 and Comparative Example 3 are shown in Figure 8 (d)-(f) respectively ((g) is a partial enlarged view of (d), and (h) is a partial enlarged view of (f)); As can be seen from the figure, compared with Comparative Example 3, Example 1 and Comparative Example 4 exhibit larger capacitance-resistance radii throughout the immersion cycle.

[0080] In summary, this invention provides a multifunctional composite coating with a dual-layer structure, which successfully integrates efficient electromagnetic wave absorption and long-term corrosion protection through innovative material design and manufacturing processes. The coating uses a hollow porous magnetic carbon framework as the bottom absorber, optimizing impedance matching and synergistically enhancing dielectric and magnetic losses through a unique cavity structure and copper-nickel alloy nanoparticles. The top layer utilizes superhydrophobic modified nano-titanium dioxide to construct an excellent water-repellent barrier and self-cleaning surface. This functionally graded structure not only enables the coating to exhibit excellent electromagnetic wave absorption performance at ultra-thin thicknesses but also significantly improves corrosion resistance through the synergistic effect of physical shielding and superhydrophobicity, maintaining extremely high impedance modulus even after long-term immersion in salt spray environments. Radar cross-section simulation further verifies its engineering potential for achieving omnidirectional, multi-polarized electromagnetic stealth on complex components. This invention features controllable processes and good environmental adaptability, providing an effective technical solution for addressing the integrated electromagnetic stealth and corrosion protection needs of equipment in harsh environments such as the ocean, and has broad prospects for widespread application.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hollow porous magnetic carbon fiber skeleton material, characterized in that, The hollow porous magnetic carbon fiber skeleton material is prepared by a method including the following steps: A1, a mixture of nickel nitrate hexahydrate, 2,5-dihydroxyterephthalic acid and N,N-dimethylformamide is transferred to a reaction vessel and heated to react, thereby obtaining a nickel metal-organic framework material; A2, a mixture of polyacrylonitrile, copper nitrate monohydrate, the nickel metal-organic framework material and polymethyl methacrylate is used as the shell solution, and the polymethyl methacrylate solution is used as the core solution, and coaxial electrospinning is performed to obtain a core-shell structured nanofiber felt; A3. The core-shell structured nanofiber felt is subjected to pre-oxidation, template sacrifice, and carbonization treatment to obtain the hollow porous magnetic carbon fiber skeleton material.

2. The hollow porous magnetic carbon fiber skeleton material as described in claim 1, characterized in that, In step A1, the mass ratio of nickel nitrate hexahydrate to 2,5-dihydroxyterephthalic acid is 1:1.5-1:2; the mass ratio of nickel nitrate hexahydrate to N,N-dimethylformamide is 1:55-1:60; the heating reaction temperature is 110-120℃, and the reaction time is 22-24h.

3. The hollow porous magnetic carbon fiber skeleton material as described in claim 1, characterized in that, In step A2, the mass ratio of copper nitrate monohydrate to the nickel metal-organic framework material is (0.8-1.1):(0.07-0.1); in the shell solution, the mass ratio of polyacrylonitrile to the nickel metal-organic framework is 1:0.07-1:0.1; the mass ratio of polyacrylonitrile to polymethyl methacrylate is 1:(0.9-1.1); the mass ratio of polyacrylonitrile to N,N-dimethylformamide is 1:330-1:333; in the core solution, the mass ratio of polymethyl methacrylate to N,N-dimethylformamide in the polymethyl methacrylate solution is 1:3.5-1:

4.

4. The hollow porous magnetic carbon fiber skeleton material as described in claim 1, characterized in that, In step A2, the voltage of the electrospinning is 14-16kV and the receiving distance is 10-14cm.

5. The hollow porous magnetic carbon fiber skeleton material as described in claim 1, characterized in that, In step A3, the pre-oxidation temperature is 200-250℃ and the pre-oxidation time is 1.5-2h; the template sacrifice and carbonization are carried out under an argon atmosphere; the template sacrifice temperature is 300-350℃ and the template sacrifice time is 1.5-2h; the carbonization temperature is 750-800℃ and the carbonization time is 1.5-2h; the heating rate during carbonization is 3-5℃ / min.

6. A method for preparing a composite coating that combines electromagnetic wave absorption and corrosion protection functions, characterized in that, The steps include: (1) dispersing the hollow porous magnetic carbon fiber skeleton material as described in any one of claims 1-5 in an epoxy resin system to obtain a bottom layer solution; dispersing superhydrophobic modified nano titanium dioxide in a fluorocarbon resin system to obtain a surface layer solution; (2) First, the bottom solution is coated onto the substrate surface and allowed to dry to form the bottom layer; Subsequently, the surface solution is coated onto the bottom layer surface, and the surface solution is cured to form the surface layer; the composite coating includes the bottom layer and the surface layer.

7. The method for preparing the composite coating with both electromagnetic wave absorption and corrosion protection functions as described in claim 6, characterized in that, In step (1), the superhydrophobic modified nano-titanium dioxide is prepared by a method including the following steps: nano-titanium dioxide is dispersed in ethanol, perfluorooctyltrimethoxysilane and tetraethyl orthosilicate are added for surface modification reaction, and after stirring, sonication, filtration and drying, superhydrophobic modified nano-titanium dioxide is obtained; preferably, the mass-volume ratio of nano-titanium dioxide to anhydrous ethanol is 3g:(45-50)mL; the volume ratio of perfluorooctyltrimethoxysilane to tetraethyl orthosilicate is 1:(0.6-1); during the surface modification reaction, the mixture is first stirred at 50-60℃ for 22-24h, and then stirred at room temperature for 6-8h.

8. The method for preparing the composite coating with both electromagnetic wave absorption and corrosion protection functions as described in claim 6, characterized in that, In step (1), the epoxy resin system comprises epoxy resin and a curing agent, and the mass ratio of the hollow porous magnetic carbon framework material to the epoxy resin is 1:19-1:21; the fluorocarbon resin system comprises fluorocarbon resin, hexamethyl diisocyanate, and a solvent, and the mass ratio of the fluorocarbon resin to hexamethyl diisocyanate is 6.5:1-7:1; the mass ratio of the superhydrophobic modified nano-titanium dioxide to the fluorocarbon resin is 2.5:1-3:1; the solvent is butyl acetate; preferably, the epoxy resin is E44 epoxy resin, and the curing agent... The resin is polyamide resin, and the mass ratio of epoxy resin to curing agent is 5:(4-4.5); the mass ratio of fluorocarbon resin to hexamethylene diisocyanate is 6.5:1-7:1; the mass ratio of superhydrophobic modified nano titanium dioxide to fluorocarbon resin is 2.5:1-3:1; the solvent is butyl acetate; the surface solution is coated by spraying, and the spraying conditions are: air pressure 1 atm, spray gun distance 10-15 cm, spraying time 20-30 s, spraying 2-3 times; the curing conditions of the surface solution are curing at 40-50℃ for 10 h.

9. A composite coating that combines electromagnetic wave absorption and corrosion protection functions, characterized in that, The composite coating that combines electromagnetic wave absorption and corrosion protection is prepared using the method described in any one of claims 1-8.

10. A marine engineering component, characterized in that, The marine engineering component has a composite coating as described in claim 9, which combines electromagnetic wave absorption and corrosion protection.

Images