Magnetoelectric synergistic loss type super-hydrophobic wave-absorbing coating and preparation method thereof

Abstract

The invention discloses a magnetoelectric synergistic loss type super-hydrophobic wave-absorbing coating and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbing coatings. Fluorinated silicon dioxide SiO2-F with low surface energy is grown on the surface of a light iron MOF derivative D-MOF through an in-situ growth method; the light super-hydrophobic wave-absorbing coating with a magnetoelectric synergistic loss mechanism is obtained by uniformly dispersing the hydrophobic wave-absorbing filler subjected to surface modification in hydrophobic polyether sulfone PES and a (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP, the maximum reflection loss of the coating can reach-24.9 dB, the effective absorption bandwidth is 5.2 GHz, and the water contact angle is 151.2 degrees.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorption coatings, and in particular to a magnetoelectric synergistic loss type superhydrophobic wave-absorbing coating and a preparation method thereof. Background Art

[0002] Electromagnetic wave absorption coatings can be widely applied to fields such as electromagnetic pollution prevention and control, multi-frequency electromagnetic compatibility, and equipment stealth technology, and play an extremely important role in the development of the national economy and the construction of national defense and military. However, with the rapid development of the wireless communication technology and the rapid development of information-based and intelligent combat modes, the requirements for electromagnetic wave absorption coatings are getting higher and higher. It is not only required that the coating has the characteristics of "thin, light, wide, and strong", but also has good environmental adaptability, such as good corrosion resistance, high temperature resistance, and self-cleaning performance.

[0003] Currently, the commonly used electromagnetic wave absorption coatings are formed by using ferrite, carbonyl iron powder, magnetic alloy powder, etc. as wave-absorbing fillers, using epoxy resin or acrylic resin as binders, and then mixing with additives and diluents to form a uniform dispersion and coating on a metal substrate. Although magnetic metal powders and alloy powders have strong wave-absorbing ability, their defects such as high density, easy oxidation, and poor corrosion resistance limit their application in wave-absorbing coatings. Moreover, the conventional wave-absorbing agents and binders used do not have hydrophobic and self-cleaning properties and need to be manually cleaned, which is not only time-consuming and laborious, but also accelerates the aging of the wave-absorbing coating. Therefore, some researchers have obtained hydrophobic wave-absorbing fillers through the regulation of the particle size of wave-absorbing agents and surface modification, and used hydrophobic resins to obtain hydrophobic wave-absorbing coatings.

[0004] For example, Patent CN 118240428 A discloses a corrosion-resistant superhydrophobic wave-absorbing coating and a preparation method thereof, which spray an epoxy wave-absorbing bottom layer and a fluorocarbon superhydrophobic surface layer on a substrate in sequence. Through the synergistic effect of the epoxy wave-absorbing bottom layer and the fluorocarbon superhydrophobic surface layer, the present invention exhibits excellent superhydrophobic performance, and the excellent superhydrophobic performance endows the wave-absorbing coating with excellent corrosion resistance and self-cleaning performance. It solves the problems existing in the existing wave-absorbing coating technology, such as easy corrosion in a salt spray environment, unsatisfactory corrosion resistance, limited wave-absorbing performance, and no self-cleaning function. The wave-absorbing coating of the present invention adopts a double-layer structure design of an epoxy wave-absorbing bottom layer and a fluorocarbon superhydrophobic surface layer. While the epoxy wave-absorbing bottom layer exhibits excellent wave-absorbing performance through a multi-level core-shell structure wave-absorbing agent, it can also improve the bonding force of the fluorocarbon superhydrophobic surface layer. On the one hand, the fluorocarbon superhydrophobic surface layer plays a protective role through its superhydrophobic characteristics, improving the corrosion resistance and self-cleaning performance of the wave-absorbing coating. Using a magnetic wave-absorbing agent coated with titanium dioxide and epoxy resin blended as the wave-absorbing bottom layer, and micro-nano hierarchical titanium dioxide powder double-treated with fluorosilane dispersed in fluorocarbon resin as the superhydrophobic surface layer, this method requires the combination of a wave-absorbing bottom layer and a hydrophobic surface layer to achieve wave-absorbing and hydrophobic effects. On the one hand, it increases the application cost and construction process, and on the other hand, it increases the equipment load.

[0005] Patent CN 116855120 A discloses a homogeneous flexible superhydrophobic wave-absorbing coating, its preparation method and application. By modifying wave-absorbing materials with organic-inorganic hybridization, and then synergistically compounding the modified wave-absorbing agent with matrix resin. This method modifies the filler through inverse vulcanization reaction, which can graft sulfur free radicals onto the surface of the wave-absorbing agent. At the same time, the monomer wraps it, which can reduce the dielectric property of the material and improve impedance mismatch. Such a modified wave-absorbing agent can well participate in the blending reaction with the matrix resin and increase the compatibility with the resin matrix. In addition to good flexibility, excellent mechanical properties and electromagnetic wave absorption ability, the coating also has certain superhydrophobicity, low surface energy, self-cleaning function, and reduces the influence of water or pollutants on the coating. By modifying traditional wave-absorbing agents, the problems of self-aggregation and impedance mismatch are improved. The modified wave-absorbing agent powder can be well dispersed in the resin, and it can be observed to be very uniform with the naked eye after curing. The homogeneous flexible superhydrophobic wave-absorbing coating has good flexibility and mechanical properties, good resilience, and can be applied to different application scenarios such as curved surfaces and equipment with complex shapes; the coating surface is smooth, has excellent hydrophobic properties, low surface energy, can reduce the retention of liquid, is easy to self-clean when encountering pollutants, reduces the possibility of adhering pollutants, and can keep the wave-absorbing performance, cleanliness and stability under different conditions, giving the coating a long service life. By modifying the filler through inverse vulcanization reaction and grafting sulfur free radicals onto the surface of the wave-absorbing agent, although the coating exhibits excellent wave-absorbing performance, its water contact angle is only 97.05°, which does not have superhydrophobic properties, and the introduction of sulfur in this method will accelerate the corrosion rate of the metal substrate and greatly reduce the service life of the wave-absorbing coating.

[0006] In recent years, metal-organic framework (MOF) materials have received extensive attention due to their advantages such as high porosity, low density, large specific surface area, adjustable composition and diverse structure. MOF can reasonably design its topological structure and porosity through the change of organic ligands, adjust different particle sizes and different dimensions, and the composition and structure of the derivative materials can be adjusted by controlling the pyrolysis temperature. The derivatives generated by pyrolysis reaction retain good porous structure and ultra-high specific surface area, which is helpful for the multi-stage scattering of electromagnetic waves. The iron-based MOF generates a composite of magnetic metal oxides and porous carbon after pyrolysis. Its rich heterogeneous interface structure and magnetic medium synergistic effect show excellent impedance matching characteristics and diverse loss mechanisms. In addition, its light weight and excellent resistance to harsh environment performance make it an ideal electromagnetic wave absorber. However, a single iron-based MOF derivative as a wave-absorbing filler does not have hydrophobic properties and needs to be surface-modified and hydrophobically modified. Summary of the Invention

[0007] Technical problems to be solved: The purpose of the present invention is to overcome the technical problems of weak loss ability, large mass, and poor stain resistance of the microwave absorbing coating in the prior art. The present application provides a magnetoelectric synergistic loss type superhydrophobic microwave absorbing coating and a preparation method thereof.

[0008] Technical solutions: To achieve the above purpose, the present application is realized through the following technical solutions: A preparation method of a magnetoelectric synergistic loss type superhydrophobic microwave absorbing coating, comprising the following steps: The first step, preparation of iron-based MOF derivative: Dissolve iron salt and organic complex in deionized water at a molar ratio of 1:1, transfer the mixture to a high-pressure reaction kettle after mixing evenly, place the high-pressure reaction kettle in an oven for reaction, centrifuge and collect the precipitate after the reaction is completed, and wash the precipitate with deionized water and ethanol alternately for 3 times. The washed precipitate is dried in a vacuum drying oven for 24 - 48 h to obtain iron MOF powder. Finally, transfer the iron MOF powder to a crucible and pyrolyze it in a tubular furnace with an inert gas flowing through and a heating rate of 5 °C / min to obtain the iron MOF derivative, denoted as D-MOF; The second step, preparation of D-MOF@SiO 2 -F core-shell structure material: Ultrasonically disperse the iron MOF derivative obtained in the first step in a mixed solution of absolute ethanol and ammonia water to form a homogeneous solution A; mix silica sol and absolute ethanol to form solution B, and slowly add solution B dropwise to homogeneous solution A, stir at room temperature for 16 - 20 h to make it hydrolyze completely to obtain a mixed solution, then add fluorosilane to the mixed solution for hydrolysis reaction for 8 h, collect the precipitate by centrifugation, wash the precipitate with absolute ethanol, and vacuum dry the precipitate to constant weight after repeating the centrifugation and absolute ethanol washing steps 3 times to obtain the iron-based MOF derivative coated with fluorinated SiO 2 -F, denoted as D-MOF@SiO 2 -F; The third step, preparation of the microwave absorbing coating: Polyethersulfone PES and polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP are mixed at a mass ratio of 1:3 - 6 as the binder, and D-MOF@SiO 2 -F is used as the microwave absorbing filler. Ultrasonically disperse the binder and the microwave absorbing filler in absolute ethanol for 30 min to obtain a dispersion, and then spray the dispersion on a metal substrate, control the spraying thickness at 1.2 - 1.5 mm, and dry and cure it at 240 °C to form a magnetoelectric synergistic loss type superhydrophobic microwave absorbing coating.

[0009] Preferably, the iron salt in the first step is FeCl 3 ·6H 2 O, Fe 2 (SO 4 ) 3 ·5H 2O or Fe(NO 3 ) 3 ·9H 2 O, and the organic complex is fumaric acid, dimethylimidazole or terephthalic acid.

[0010] Preferably, the oven temperature in the first step is 80 - 110 °C, the reaction time is 3 - 6 h; the temperature of the vacuum drying oven in the first step is 50 - 80 °C.

[0011] Preferably, the inert gas in the first step is a protective gas, and the protective gas is specifically nitrogen or argon, the pyrolysis temperature is 400 - 600 °C, and the pyrolysis time is 30 - 60 min.

[0012] Preferably, the volume ratio of absolute ethanol to ammonia water in the preparation step of homogeneous solution A is (7 - 10):1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of absolute ethanol and ammonia water is 1:(40 - 60).

[0013] Preferably, the silica sol in the preparation step of solution B is one or more of tetraethoxysilane, triethoxysilane, dialkoxysilane, trialkoxysilane, dimethyldialkoxysilane, and the volume ratio of the silica sol to absolute ethanol is 1:(1.3 - 4).

[0014] Preferably, the volume ratio of homogeneous solution A to solution B in the second step is (3 - 5):1.

[0015] Preferably, the fluorosilane in the second step is one or more of 1H,1H,2H,2H - perfluorodecyltriethoxysilane, trifluoropropyltrimethoxy(ethoxy)silane, tridecafluorooctyltrimethoxy(ethoxy)silane, heptadecafluorodecyltrimethoxy(ethoxy)silane, dodecafluoroheptylpropyltrimethoxysilane, hexafluorobutylpropyltrimethoxysilane, and the volume ratio of the fluorosilane to the silica sol in the second step is 1:(8 - 12).

[0016] Preferably, the mass ratio of the binder to the microwave absorption filler in the third step is (3 - 7):(7 - 3), and the total mass of the binder and the microwave absorption filler to absolute ethanol is 1:(8 - 12).

[0017] This application also discloses the magnetoelectric synergistic loss type superhydrophobic microwave absorption coating prepared by any of the above preparation methods.

[0018] The technical principle of the present invention is: preparing D - MOF@SiO with a core - shell structure by an in - situ growth method 2 -F electromagnetic wave absorption filler, the MOF derivative in the core provides the magnetoelectric synergistic loss function, and the low - surface - energy SiO in the shell 2-F provides a self-cleaning function; in addition, the rich low-surface-energy groups in the adhesive further enhance the hydrophobicity of the coating film.

[0019] This application provides a magnetoelectric synergistic loss type superhydrophobic absorbing coating and its preparation method, which have the following beneficial effects compared with the prior art: 1. Using iron-based metal-organic framework derivatives as electromagnetic wave absorption fillers, they have the advantages of rich pores, low density, and large specific surface area. And by a simple in-situ growth method, fluorinated SiO is generated on the surface of the MOF derivative. 2 This "D-MOF@SiO 2 -F" core-shell structure has a rich heterogeneous interface. A large amount of carbon and magnetic metal oxides in D-MOF provide a strong magnetoelectric synergistic loss ability, and the low-surface-energy SiO 2 -F endows the filler with excellent self-cleaning performance; 2. During the co-curing process of D-MOF@SiO 2 -F with PES and PVDF-HFP copolymers, it is rich in low-surface-energy groups, forming a micro / nano-scale structure with a rich papillary structure. The porous D-MOF can allow small molecules such as O 2 and N 2 in the air to enter its internal pore channels, form a coating and effectively capture the surface air, forming a reliable anti-adhesion barrier. In addition, the stable gas film can extend the superhydrophobic life of the coating in harsh environments such as mechanical and chemical damage; 3. PES and PVDF-HFP are used as adhesives for the coating. The O atoms in PES and the F atoms in PVDF-HFP form hydrogen bond interactions with -OH on the matrix substrate, providing strong adhesion for the coating. The D-MOF@SiO 2 -F nanorods intersect and stack to form a multi-level network structure. This organic / inorganic hybrid system makes the superhydrophobic film have a certain structural stability, which can improve the mechanical strength and wear resistance of the coating; 4. A lightweight superhydrophobic absorbing coating with a magnetoelectric synergistic loss mechanism is obtained. The maximum reflection loss of this coating can reach -24.9 dB, the effective absorption bandwidth is 5.2 GHz, and the water contact angle is 151.2°. Specific Embodiments

[0020] To make the technical solutions, advantages, and achieved purposes of the present invention clearer and more definite, the present invention will be described in detail through specific embodiments below. The embodiments are merely illustrative and do not represent limitations on the protection scope of the present invention. All non-essential equivalent changes or adjustments made according to the above-mentioned invention content and spirit belong to the scope protected by the present invention.

[0021] Example 1: A preparation method of a magnetoelectric synergistic loss type superhydrophobic microwave absorbing coating, comprising the following steps: The first step, preparation of iron-based MOF derivative: Dissolve iron salt FeCl 3 ·6H 2 O and organic complex fumaric acid in deionized water at a molar ratio of 1:1, transfer the mixture to a high-pressure reaction kettle after mixing evenly, place the high-pressure reaction kettle in an oven at 100 °C for reaction for 4 h, centrifuge and collect the precipitate after the reaction is completed, and wash the precipitate alternately with deionized water and ethanol for 3 times. The washed precipitate is dried in a vacuum drying oven at 60 °C for 24 h to obtain iron MOF powder. Finally, transfer the iron MOF powder to a crucible and pyrolyze it in a tube furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 500 °C for 30 min to obtain the iron MOF derivative, denoted as D-MOF; The second step, preparation of D-MOF@SiO 2 -F core-shell structure material: Ultrasonically disperse the iron MOF derivative obtained in the first step in a mixed solution of absolute ethanol and ammonia water, where the volume ratio of absolute ethanol to ammonia water is 7:1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of absolute ethanol and ammonia water is 1:56 to form a homogeneous solution A; According to the volume ratio of silica sol: absolute ethanol = 1:1.3, take tetraethoxysilane of silica sol and mix it with absolute ethanol to form solution B; Dropwise add solution B to homogeneous solution A, and the volume ratio of homogeneous solution A to solution B is 3:1. Stir at room temperature for 17 h to completely hydrolyze to obtain a mixed solution, then add 1H,1H,2H,2H-perfluorodecyltriethoxysilane hydrolyzed reaction for 8 h at 10% of the volume of tetraethoxysilane to the mixed solution, centrifuge and collect the precipitate, wash the precipitate with absolute ethanol, and vacuum dry the precipitate to constant weight after repeating the centrifugation and absolute ethanol washing steps 3 times to obtain the fluorinated SiO 2 -coated iron-based MOF derivative, denoted as D-MOF@SiO 2 -F; The third step, preparation of the microwave absorbing coating: Mix polyethersulfone PES and (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP at a mass ratio of 1:3 as the binder, and D-MOF@SiO 2 -F as the microwave absorbing filler. According to the mass ratio of binder: microwave absorbing filler: absolute ethanol = 0.2:0.8:10, ultrasonically disperse the binder and the microwave absorbing filler in absolute ethanol for 30 min, then spray the dispersion on a metal substrate, and the spraying thickness is 1.35 mm. After drying and curing at 240 °C, a magnetoelectric synergistic loss type superhydrophobic microwave absorbing coating is formed.

[0022] Example 2: A preparation method of a magnetoelectric synergistic loss type superhydrophobic microwave absorbing coating, comprising the following steps: Step 1: Preparation of iron-based MOF derivative: Dissolve iron salt FeCl 3 ·6H 2 O and fumaric acid, an organic complex, in deionized water at a molar ratio of 1:1. After mixing evenly, transfer it to a high-pressure reactor. Place the high-pressure reactor in an oven at 80 °C and react for 4 h. After the reaction is completed, centrifuge and collect the precipitate, and wash the precipitate alternately with deionized water and ethanol 3 times. The washed precipitate is dried in a vacuum drying oven at 60 °C for 24 h to obtain iron MOF powder. Finally, transfer the iron MOF powder to a crucible and pyrolyze it in a tube furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 400 °C for 30 min to obtain the iron MOF derivative, denoted as D-MOF; Step 2: Preparation of D-MOF@SiO 2 -F core-shell structure material: Ultrasonically disperse the iron MOF derivative obtained in the first step in a mixed solution of absolute ethanol and ammonia water, where the volume ratio of absolute ethanol to ammonia water is 8:1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of absolute ethanol and ammonia water is 1:56 to form a homogeneous solution A; According to the volume ratio of silica sol: absolute ethanol = 1:1.7, take tetraethoxysilane of silica sol and mix it with absolute ethanol to form solution B; Dropwise add solution B into homogeneous solution A, and the volume ratio of homogeneous solution A to solution B is 3:1. Stir at room temperature for 16 h to completely hydrolyze to obtain a mixed solution. Then add 1H,1H,2H,2H-perfluorodecyltriethoxysilane, which is 10% of the volume of tetraethoxysilane, to the mixed solution and hydrolyze for 8 h. Centrifuge and collect the precipitate, wash the precipitate with absolute ethanol, and repeat the centrifugation and absolute ethanol washing steps 3 times. The precipitate after vacuum drying to constant weight is obtained as the fluorinated SiO 2 -coated iron-based MOF derivative, denoted as D-MOF@SiO 2 -F; Step 3: Preparation of the microwave absorption coating: Polyethersulfone PES and (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP are mixed at a mass ratio of 1:4 as the binder, and D-MOF@SiO 2 -F is used as the microwave absorption filler. According to the mass ratio of binder: microwave absorption filler: absolute ethanol = 0.3:0.7:10, ultrasonically disperse the binder and the microwave absorption filler in absolute ethanol for 30 min, and then spray the dispersion on a metal substrate with a spraying thickness of 1.22 mm. After drying and curing at 240 °C, a magnetoelectric synergistic loss type superhydrophobic microwave absorption coating is formed.

[0023] Example 3: A preparation method of a magnetoelectric synergistic loss type superhydrophobic microwave absorption coating, comprising the following steps: Step 1: Preparation of iron-based MOF derivative: Dissolve iron salt Fe(NO 3 ) 3·9H 2 O and fumaric acid of the organic complex are dissolved in deionized water at a molar ratio of 1:1, and after being mixed evenly, they are transferred to a high-pressure reactor. The high-pressure reactor is placed in an oven at 100 °C for reaction for 5 h. After the reaction is completed, the precipitate is collected by centrifugation, and the precipitate is washed alternately with deionized water and ethanol three times. The washed precipitate is dried in a vacuum drying oven at 70 °C for 36 h to obtain iron MOF powder. Finally, the iron MOF powder is transferred to a crucible and pyrolyzed in a tube furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 500 °C for 30 min to obtain an iron MOF derivative, denoted as D-MOF; Second step, preparation of D-MOF@SiO 2 -F core-shell structure material: The iron MOF derivative obtained in the first step is ultrasonically dispersed in a mixed solution of absolute ethanol and ammonia water, where the volume ratio of absolute ethanol to ammonia water is 9:1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of absolute ethanol and ammonia water is 1:40 to form a homogeneous solution A; according to the volume ratio of silica sol: absolute ethanol = 1:2, tetraethoxysilane of silica sol is mixed with absolute ethanol to form solution B; solution B is added dropwise to homogeneous solution A, and the volume ratio of homogeneous solution A to solution B is 3.5:1, and stirred at room temperature for 18 h to completely hydrolyze to obtain a mixed solution. Then, 1H,1H,2H,2H-perfluorodecyltriethoxysilane of 10% of the volume of tetraethoxysilane is added to the mixed solution for hydrolysis reaction for 8 h. The precipitate is collected by centrifugation, and the precipitate is washed with absolute ethanol. After repeating the centrifugation and absolute ethanol washing steps three times, the precipitate is vacuum dried to constant weight to obtain fluorinated SiO 2 coated iron-based MOF derivative, denoted as D-MOF@SiO 2 -F; Third step, preparation of the wave-absorbing coating: Polyethersulfone PES and (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP are mixed at a mass ratio of 1:5 as the binder, and D-MOF@SiO 2 -F is used as the wave-absorbing filler. According to the mass ratio of binder: wave-absorbing filler: absolute ethanol = 0.4:0.6:10, the binder and the wave-absorbing filler are ultrasonically dispersed in absolute ethanol for 30 min, and then the dispersion is sprayed on a metal substrate with a spraying thickness of 1.28 mm and dried and cured at 240 °C to form a magnetoelectric synergistic loss type superhydrophobic wave-absorbing coating.

[0024] Example 4: A preparation method of a magnetoelectric synergistic loss type superhydrophobic wave-absorbing coating, comprising the following steps: First step, preparation of the iron-based MOF derivative: The iron salt FeCl 3 ·6H 2O and fumaric acid of the organic complex are dissolved in deionized water at a molar ratio of 1:1. After mixing evenly, it is transferred to a high-pressure reactor. The high-pressure reactor is placed in an oven at 110 °C for reaction for 4 h. After the reaction is completed, the precipitate is collected by centrifugation, and the precipitate is washed alternately with deionized water and ethanol 3 times. The washed precipitate is dried in a vacuum drying oven at 70 °C for 36 h to obtain iron MOF powder. Finally, the iron MOF powder is transferred to a crucible and pyrolyzed in a tube furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 600 °C for 30 min to obtain an iron MOF derivative, denoted as D-MOF; Second step, preparation of D-MOF@SiO 2 -F core-shell structure material: The iron MOF derivative obtained in the first step is ultrasonically dispersed in a mixed solution of absolute ethanol and ammonia water, where the volume ratio of absolute ethanol to ammonia water is 10:1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of absolute ethanol and ammonia water is 1:50 to form a homogeneous solution A; According to the volume ratio of silica sol: absolute ethanol = 1:2.5, take tetraethoxysilane of silica sol and mix it with absolute ethanol to form solution B; Solution B is added dropwise to homogeneous solution A, and the volume ratio of homogeneous solution A to solution B is 4:1. Stir at room temperature for 19 h to completely hydrolyze to obtain a mixed solution. Then, 1H,1H,2H,2H-perfluorodecyltriethoxysilane of 10% of the volume of tetraethoxysilane is added to the mixed solution for hydrolysis reaction for 8 h. The precipitate is collected by centrifugation, and the precipitate is washed with absolute ethanol. After repeating the centrifugation and absolute ethanol washing steps 3 times, the precipitate is vacuum dried to constant weight to obtain fluorinated SiO 2 -coated iron-based MOF derivative, denoted as D-MOF@SiO 2 -F; Third step, preparation of the wave-absorbing coating: Polyethersulfone PES and (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP are mixed at a mass ratio of 1:6 as the binder, and D-MOF@SiO 2 -F is used as the wave-absorbing filler. According to the mass ratio of binder: wave-absorbing filler: absolute ethanol = 0.7:0.3:10, the binder and the wave-absorbing filler are ultrasonically dispersed in absolute ethanol for 30 min, and then the dispersion is sprayed on the metal substrate with a spraying thickness of 1.39 mm and dried and cured at 240 °C to form a magnetoelectric synergistic loss type superhydrophobic wave-absorbing coating.

[0025] Example 5: A preparation method of a magnetoelectric synergistic loss type superhydrophobic wave-absorbing coating, comprising the following steps: First step, preparation of the iron-based MOF derivative: Iron salt FeCl 3 ·6H 2O and terephthalic acid as an organic complex are dissolved in deionized water at a molar ratio of 1:1. After mixing evenly, it is transferred to a high-pressure reaction kettle, and the high-pressure reaction kettle is placed in an oven at 90 °C for 4 h. After the reaction is completed, the precipitate is collected by centrifugation, and the precipitate is washed alternately with deionized water and ethanol 3 times. The washed precipitate is dried in a vacuum drying oven at 70 °C for 48 h to obtain iron MOF powder. Finally, the iron MOF powder is transferred to a crucible and pyrolyzed in a tube furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 600 °C for 30 min to obtain an iron MOF derivative, denoted as D-MOF; Second step, preparation of D-MOF@SiO 2 -F core-shell structure material: The iron MOF derivative obtained in the first step is ultrasonically dispersed in a mixed solution of absolute ethanol and ammonia water, where the volume ratio of absolute ethanol to ammonia water is 10:1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of absolute ethanol and ammonia water is 1:60 to form a homogeneous solution A; according to the volume ratio of silica sol: absolute ethanol = 1:3, tetraethoxysilane of silica sol is mixed with absolute ethanol to form solution B; solution B is added dropwise to homogeneous solution A, and the volume ratio of homogeneous solution A to solution B is 4.5:1, and stirred at room temperature for 20 h to completely hydrolyze to obtain a mixed solution. Then, 1H,1H,2H,2H-perfluorodecyltriethoxysilane of 10% of the volume of tetraethoxysilane is added to the mixed solution for hydrolysis reaction for 8 h. The precipitate is collected by centrifugation, and the precipitate is washed with absolute ethanol. After repeating the centrifugation and absolute ethanol washing steps 3 times, the precipitate is vacuum dried to constant weight to obtain fluorinated SiO 2 -coated iron-based MOF derivative, denoted as D-MOF@SiO 2 -F; Third step, preparation of the microwave absorption coating: Polyethersulfone PES and (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP are mixed as a binder at a mass ratio of 1:6, and D-MOF@SiO 2 -F is used as a microwave absorption filler. According to the mass ratio of binder: microwave absorption filler: absolute ethanol = 0.3:0.7:11, the binder and the microwave absorption filler are ultrasonically dispersed in absolute ethanol for 30 min, and then the dispersion is sprayed on a metal substrate with a spraying thickness of 1.3 mm and dried and cured at 240 °C to form a magnetoelectric synergistic loss type superhydrophobic microwave absorption coating.

[0026] Example 6: A preparation method of a magnetoelectric synergistic loss type superhydrophobic microwave absorption coating, comprising the following steps: First step, preparation of iron-based MOF derivative: Iron salt Fe 2 (SO 4 ) 3 ·5H 2O was dissolved in deionized water with the organic complex dimethylimidazole in a molar ratio of 1:1. After mixing evenly, it was transferred to a high-pressure reactor. The high-pressure reactor was placed in an oven at 100 °C and reacted for 4 h. After the reaction was completed, the precipitate was collected by centrifugation, and the precipitate was washed alternately with deionized water and ethanol 3 times. The washed precipitate was dried in a vacuum drying oven at 70 °C for 48 h to obtain iron MOF powder. Finally, the iron MOF powder was transferred to a crucible and pyrolyzed in a tube furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 500 °C for 30 min to obtain an iron MOF derivative, denoted as D-MOF; Second step, preparation of D-MOF@SiO 2 -F core-shell structure material: The iron MOF derivative obtained in the first step was ultrasonically dispersed in a mixed solution of anhydrous ethanol and ammonia water, where the volume ratio of anhydrous ethanol to ammonia water was 10:1, and the mass g of the iron MOF derivative to the volume mL of the mixed solution of anhydrous ethanol and ammonia water was 1:60 to form a homogeneous solution A; According to the volume ratio of silica sol:anhydrous ethanol = 1:4, tetraethoxysilane of silica sol was mixed with anhydrous ethanol to form solution B; Solution B was added dropwise to homogeneous solution A, and the volume ratio of homogeneous solution A to solution B was 5:1. Stir at room temperature for 20 h to completely hydrolyze to obtain a mixed solution. Then, 1H,1H,2H,2H-perfluorodecyltriethoxysilane accounting for 10% of the volume of tetraethoxysilane was added to the mixed solution for hydrolysis reaction for 8 h. The precipitate was collected by centrifugation, and the precipitate was washed with anhydrous ethanol. After repeating the centrifugation and anhydrous ethanol washing steps 3 times, the precipitate was vacuum dried to constant weight to obtain fluorinated SiO 2 -coated iron-based MOF derivative, denoted as D-MOF@SiO 2 -F; Third step, preparation of the microwave absorption coating: Polyethersulfone PES and (polyvinylidene fluoride-hexafluoropropylene) copolymer PVDF-HFP were mixed in a mass ratio of 1:6 as the binder, and D-MOF@SiO 2 -F was used as the microwave absorption filler. According to the mass ratio of binder:microwave absorption filler:anhydrous ethanol = 0.3:0.7:12, the binder and the microwave absorption filler were ultrasonically dispersed in anhydrous ethanol for 30 min, and then the dispersion was sprayed on a metal substrate with a spraying thickness of 1.21 mm and dried and cured at 240 °C to form a magnetoelectric synergistic loss type superhydrophobic microwave absorption coating.

[0027] Comparative example 1: A method for preparing a microwave absorption coating, using 30% polyethersulfone (PES) and (polyvinylidene fluoride-hexafluoropropylene) copolymer (PVDF-HFP) as the binder, 70% of Fe 3 O 4The particles are used as microwave-absorbing fillers. They are ultrasonically dispersed for 30 min according to the mass ratio of binder and microwave absorber to absolute ethanol being 1:10. Then the dispersion is sprayed onto a metal substrate with a spraying thickness of 1.29 mm and dried and cured at 240 °C to form a self-cleaning microwave-absorbing coating.

[0028] Comparative Example 2: A method for preparing a microwave-absorbing coating, comprising the following steps: The first step, preparation of iron-based MOF derivative: Dissolve iron salt FeCl 3 ·6H 2 O and fumaric acid in deionized water according to the molar ratio of 1:1, mix evenly and transfer to a high-pressure reaction kettle. Place the high-pressure reaction kettle in an oven at 100 °C and react for 4 h. After the reaction is completed, centrifuge and collect the precipitate, and alternately wash the precipitate with deionized water and ethanol 3 times. Dry the precipitate in a vacuum drying oven at 60 °C for 24 h to obtain iron MOF powder. Finally, transfer the iron MOF powder to a crucible and pyrolyze it in a tubular furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 500 °C for 30 min to obtain the iron MOF derivative, denoted as D-MOF; The second step, preparation of the microwave-absorbing coating: Polyethersulfone PES and (polyvinylidene fluoride - hexafluoropropylene) copolymer PVDF-HFP are mixed as a binder according to the mass ratio of 1:3, and D-MOF is used as a microwave-absorbing filler. According to the mass ratio of binder:microwave-absorbing filler:absolute ethanol = 0.3:0.7:10, ultrasonically disperse the binder and the microwave-absorbing filler in absolute ethanol for 30 min, then spray the dispersion onto a metal substrate with a spraying thickness of 1.38 mm, and dry and cure it at 240 °C to form a microwave-absorbing coating.

[0029] Comparative Example 3: A method for preparing a microwave-absorbing coating, comprising the following steps: The first step, preparation of iron-based MOF derivative: Dissolve iron salt FeCl 3 ·6H 2 O and fumaric acid in deionized water according to the molar ratio of 1:1, mix evenly and transfer to a high-pressure reaction kettle. Place the high-pressure reaction kettle in an oven at 100 °C and react for 4 h. After the reaction is completed, centrifuge and collect the precipitate, and alternately wash the precipitate with deionized water and ethanol 3 times. Dry the precipitate in a vacuum drying oven at 60 °C for 24 h to obtain iron MOF powder. Finally, transfer the iron MOF powder to a crucible and pyrolyze it in a tubular furnace with nitrogen flowing, a heating rate of 5 °C / min, and a temperature of 500 °C for 30 min to obtain the iron MOF derivative, denoted as D-MOF; The second step, D-MOF@SiO 2- Preparation of Fe@SiO₂-F core-shell structure material: The iron MOF derivative obtained in the first step was ultrasonically dispersed in a mixed solution of absolute ethanol and ammonia water, where the volume ratio of absolute ethanol to ammonia water was 8:1, and the mass ratio of the iron MOF derivative (g) to the volume of the mixed solution of absolute ethanol and ammonia water (mL) was 1:56 to form a homogeneous solution A; according to the volume ratio of silica sol: absolute ethanol = 3:5, tetraethoxysilane of silica sol was mixed with absolute ethanol to form solution B; solution B was added dropwise to homogeneous solution A, and the volume ratio of homogeneous solution A to solution B was 3:1, and stirred at room temperature for 16 h to complete hydrolysis to obtain a mixed solution. Then, 1H,1H,2H,2H-perfluorodecyltriethoxysilane accounting for 10% of the volume of tetraethoxysilane was added to the mixed solution for hydrolysis reaction for 8 h. The precipitate was collected by centrifugation, and the precipitate was washed with absolute ethanol. The precipitate after repeating the centrifugation and absolute ethanol washing steps 3 times was vacuum dried to constant weight to obtain fluorinated SiO₂-coated iron-based MOF derivative, denoted as D-MOF@SiO₂-F; 2 -F 2 -F; - Preparation of the microwave absorption coating in the third step: Using 25% epoxy resin and 5% phenolic amine curing agent as adhesives, and 70% of D-MOF@SiO₂-F as microwave absorption fillers, stirred and dispersed according to the mass ratio of the adhesive and the microwave absorption filler to absolute ethanol of 1:10 for 30 min, and then the dispersion was sprayed on the metal substrate with a spraying thickness of 1.41 mm, and dried and cured at 240 °C to form a microwave absorption coating. 2 -F as microwave absorption filler, stirred and dispersed according to the mass ratio of the adhesive and the microwave absorption filler to absolute ethanol of 1:10 for 30 min, and then the dispersion was sprayed on the metal substrate with a spraying thickness of 1.41 mm, and dried and cured at 240 °C to form a microwave absorption coating.

[0030] The performance test results of the examples and comparative examples of the present invention are as follows: .

[0031] The coatings of Example 1, Example 3 and Example 6 all showed good microwave absorption effect and hydrophobic performance. In Example 2 and Example 5, due to the low hydrothermal reaction temperature, the iron MOF was not completely reacted or the crystal structure of the product was incomplete, so the microwave absorption performance was not shown, but the coatings had certain hydrophobicity. The microwave absorption ability of the coating in Example 4 was poor because the content of the microwave absorber in the coating was small and could not strongly absorb electromagnetic waves, but it still showed certain hydrophobicity. Comparative Example 1 only used conventional Fe₃O₄ particles as microwave absorption fillers, showing certain microwave absorption ability but no obvious hydrophobic effect. In Comparative Example 2, the MOF derivative was not coated with fluorinated SiO₂, still showing good microwave absorption ability, but its hydrophobic effect was much worse than that of Examples 1 to 6. Comparative Example 3 used conventional epoxy resin and amine curing agent as adhesives, with good microwave absorption ability but no hydrophobic effect shown. Through comprehensive analysis of the examples and comparative examples, the coating with iron MOF derivative as filler has better microwave absorption effect than Fe₃O₄ 3 O 4 particles 2 ₂3 O 4 The particulate absorbing coating, especially the iron MOF derivative, has a wider absorption band. The hydrophobic PES and PVDF-HFP binders play a decisive role in the hydrophobic effect of the coating. The micro-nano dual-scale fluorinated SiO 2 coating of the iron MOF derivative core-shell material is beneficial to improving the hydrophobic performance of the coating.

[0032] The above description of the examples is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating, characterized in that: The following steps are involved: The first step is the preparation of iron-based MOF derivatives: the iron salt and the organic complex are dissolved in deionized water at a molar ratio of 1:1, and the mixture is transferred to a high-pressure reactor, which is placed in an oven for reaction. After the reaction is completed, the precipitate is collected by centrifugation, and the precipitate is washed alternately with deionized water and ethanol for 3 times. The washed precipitate is dried in a vacuum drying oven for 24-48 h to obtain an iron MOF powder. Finally, the iron MOF powder is transferred to a crucible and pyrolyzed in a tubular furnace with an inert gas and a heating rate of 5°C / min to obtain an iron MOF derivative, which is recorded as D-MOF. The second step is the preparation of D-MOF@SiO2-F core-shell structure material: the iron MOF derivative obtained in the first step is ultrasonically dispersed in a mixed solution of anhydrous ethanol and ammonia water to form a homogeneous solution A; the silica sol is mixed with anhydrous ethanol to form a solution B, and the solution B is added dropwise to the homogeneous solution A, stirred at room temperature for 16-20 hours to completely hydrolyze it to obtain a mixed solution, and then fluorosilane is added to the mixed solution for a hydrolysis reaction of 8 hours, and the precipitate is collected by centrifugation, and the precipitate is washed with anhydrous ethanol. After repeating the centrifugation and anhydrous ethanol washing steps for 3 times, the precipitate is vacuum dried to a constant weight to obtain a fluorinated SiO2-coated iron-based MOF derivative, which is recorded as D-MOF@SiO2-F; The third step is the preparation of the absorbing coating: polyethersulfone PES and polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP are mixed in a mass ratio of 1:3-6 as an adhesive, D-MOF@SiO2-F is used as an absorbing filler, the adhesive and the absorbing filler are ultrasonically dispersed in anhydrous ethanol for 30 min to obtain a dispersion, and then the dispersion is sprayed on a metal substrate with a spraying thickness controlled at 1.2-1.5mm. After drying and curing at 240°C, a magneto-electric synergistic loss type super-hydrophobic absorbing coating is formed.

2. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The iron salt in the first step is FeCl3·6H2O, Fe2(SO4)3·5H2O or Fe(NO3)3·9H2O, and the organic complex is fumaric acid, dimethylimidazole or terephthalic acid.

3. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The oven temperature in the first step is 80-110°C, and the reaction time is 3-6 h; the vacuum drying oven temperature in the first step is 50-80°C.

4. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The inert gas in the first step is a protective gas, specifically nitrogen or argon, the pyrolysis temperature is 400-600° C., and the pyrolysis time is 30-60 min.

5. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The volume ratio of anhydrous ethanol to aqueous ammonia in the preparation step of homogeneous solution A is (7-10):1, and the ratio of the mass g of the iron MOF derivative to the volume mL of the mixed solution of anhydrous ethanol and aqueous ammonia is 1:(40-60).

6. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The silica sol in the step of preparing solution B is one or more of tetraethoxysilane, triethoxysilane, dialkoxysilane, trialkoxysilane, and dimethyldialkoxysilane, and the volume ratio of the silica sol to anhydrous ethanol is 1:(1.3~4).

7. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The volume ratio of the homogeneous solution A to the solution B in the second step is (3-5):

1.

8. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The fluorosilane in the second step is one or more of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane, trifluoropropyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, dodecafluoroheptylpropyltrimethoxysilane, and hexafluorobutylpropyltrimethoxysilane, and the volume ratio of the fluorosilane to the silica sol in the second step is 1: (8-12).

9. The method for preparing the magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating according to claim 1, characterized in that: The mass ratio of the adhesive to the absorbing filler in the third step is (3-7):(7-3), and the mass ratio of the total amount of the adhesive and the absorbing filler to anhydrous ethanol is 1:(8-12).

10. A magneto-electric cooperative loss type super-hydrophobic wave-absorbing coating prepared by the preparation method according to any one of claims 1 to 9.