Modified FeSiCr soft magnetic material, preparation method thereof and application of modified FeSiCr soft magnetic material in marine environment device

Abstract

The invention discloses a modified FeSiCr soft magnetic material, a preparation method thereof and application of the modified FeSiCr soft magnetic material in marine environment devices, and belongs to the technical field of soft magnetic materials. Comprising flaky FeSiCr soft magnetic powder, and a Ni-P alloy layer, a dopamine-quaternary ammonium salt copolymer grafting layer, a tannic acid-metal ion layer, a nano SiO2-Al2O3 layer and a polysiloxane resin-boron nitride layer which sequentially coat the FeSiCr soft magnetic powder from inside to outside, and the preparation method comprises the steps of chemical plating, grafting modification, sol-gel sintering and hot press molding. Through the synergistic effect of the five coating layers, the modified FeSiCr soft magnetic material achieves comprehensive improvement of corrosion resistance, antibacterial property, insulativity and magnetic performance in the marine environment, is suitable for marine anti-corrosion wave-absorbing coatings, high-frequency electromagnetic elements and other scenes, and has the advantages of being long-acting in service, high in environmental adaptability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of soft magnetic materials, and specifically relates to a modified FeSiCr soft magnetic material, a preparation method thereof, and application in marine environment devices. Background Art

[0002] FeSiCr soft magnetic powder has good soft magnetic properties and certain corrosion resistance, and has application potential in electromagnetic components of marine detection equipment, ship anti-corrosion coatings and other fields. However, when directly applied to the marine environment, it has the following obvious defects:

[0003] First, the corrosion resistance is insufficient: the high salt spray, high humidity, and high chloride ion concentration in the ocean environment easily lead to localized corrosion such as pitting and crevice corrosion. The microbatteries formed by Fe, Si, and Cr accelerate the oxidation and dissolution of Fe, and the oxide layer is prone to peeling during long-term service. The attachment of marine organisms will form a local microenvironment, and their metabolites (such as organic acids and sulfides) may accelerate corrosion.

[0004] Second, magnetic properties deteriorate: salt deposition forms a non-magnetic isolation layer that reduces magnetic permeability, and high humidity causes FeSiCr to oxidize to form a hard magnetic phase, increasing hysteresis loss.

[0005] Third, insulation performance fails: salt deposition and moisture penetration form conductive paths between particles, exacerbating electrochemical corrosion and further deteriorating magnetic properties.

[0006] Based on this, it is extremely important to modify FeSiCr soft magnetic powder to overcome the above technical problems. Summary of the Invention

[0007] The present invention aims to provide a modified FeSiCr soft magnetic material, its preparation method, and its application in marine environmental devices. Through the synergistic effect of a five-component Ni-P alloy layer, a dopamine grafted layer, a tannic acid-metal ion transition layer, a nano-SiO2-Al2O3 layer, and a polysiloxane-BN composite layer, the material achieves comprehensive improvements in corrosion resistance, antibacterial properties, insulation, and magnetic properties in marine environments. The prepared modified FeSiCr soft magnetic material is suitable for applications such as marine anti-corrosion and radar-absorbing coatings and high-frequency electromagnetic components, offering advantages such as long-term service life and strong environmental adaptability.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A modified FeSiCr soft magnetic material comprises FeSiCr soft magnetic powder, and a Ni-P alloy layer, a dopamine-quaternary ammonium salt copolymer graft layer, a tannic acid-metal ion layer, a nano-SiO2-Al2O3 layer and a polysiloxane resin-boron nitride layer, which are sequentially coated on the outside of the FeSiCr soft magnetic powder from the inside out. The FeSiCr soft magnetic powder is FeSiCr flaky powder, the aspect ratio of the FeSiCr flaky powder is 5 to 50 times, and D50 is 5 to 60 μm.

[0010] The present invention achieves comprehensive improvement in the corrosion resistance, antibacterial properties, insulation properties and magnetic properties of FeSiCr soft magnetic materials in marine environments by coating the surface of FeSiCr soft magnetic powder with a Ni-P alloy layer, a dopamine grafted layer, a tannic acid-metal ion transition layer, a nano-SiO2-Al2O3 layer and a polysiloxane-BN composite layer. Through the multi-component synergistic effect among the five coating layers, the corrosion resistance, antibacterial properties, insulation properties and magnetic properties of FeSiCr soft magnetic materials in marine environments are comprehensively improved.

[0011] As some possible implementation methods of the present application, in the nano-SiO2-Al2O3 layer, SiO2 is SiO2 modified by a silane coupling agent; and Al2O3 is Al2O3 modified by an aluminate coupling agent.

[0012] In this solution, the modified nanoparticles create a denser structure in the nano-SiO2-Al2O3 layer, reducing porosity and minimizing the infiltration of corrosive media like seawater, thereby enhancing the material's overall corrosion resistance. Furthermore, the modified nanoparticles disperse more evenly within the organic phase, further stabilizing the insulation properties of the nano-SiO2-Al2O3 layer and improving the material's insulation resistance, thereby preventing insulation failure.

[0013] As some possible implementation methods of the present application, in the nano-SiO2-Al2O3 layer, SiO2 is SiO2 modified by a silane coupling agent. As some possible implementation methods of the present application, in the polysiloxane resin-boron nitride layer, the polysiloxane resin is trimethylsilyl-terminated polysiloxane.

[0014] In this solution, trimethylsilyl-terminated polysiloxane can enhance the chemical stability and hydrophobicity of the polysiloxane resin-boron nitride layer, reduce the probability of Si-O-Si bond hydrolysis, maintain the integrity of the coating in the high humidity environment of the ocean, and prevent the intrusion of corrosive media.

[0015] In addition, to achieve the above object, the present invention also provides a method for preparing FeSiCr soft magnetic material, comprising the following steps:

[0016] S1. FeSiCr soft magnetic powder is pretreated; the FeSiCr soft magnetic powder is FeSiCr flake powder;

[0017] S2. Introduction of a Ni-P alloy layer: coating and sintering by an electroless plating process to obtain a first flaky modified powder;

[0018] S3 introduces dopamine - quaternary ammonium salt grafted layer: the dopamine - quaternary ammonium salt grafted liquid and the first flaky modified powder is thoroughly mixed, washed and dried by centrifugation to obtain a second flaky modified powder;

[0019] S4. Introduction of tannic acid - metal ion layer: The tannic acid - metal ion solution and the second flaky modified powder were thoroughly mixed, washed and dried by centrifugation to obtain a third flaky modified powder;

[0020] S5. Introduction of nano-SiO2-Al2O3 layer: coating and sintering by immersion pulling method to obtain a fourth flaky modified powder;

[0021] S6. Introducing a polysiloxane resin-boron nitride layer: The FeSiCr soft magnetic material is prepared by hot pressing.

[0022] As some possible implementation methods of the present application, in step S3, an imidazole derivative is introduced.

[0023] The marine environment is characterized by high salt (mainly NaCl), high humidity, and active microorganisms. In this environment, the amide bonds and ester bonds in quaternary ammonium salts will hydrolyze after long-term immersion. Marine microorganisms (such as bacteria and algae) will secrete enzymes (such as proteases) after attachment to degrade polymer chains, which will cause the quaternary ammonium salts in the dopamine-quaternary ammonium salt grafted layer to fall off, thus destroying the grafted layer and seriously affecting the corrosion resistance and antibacterial properties.

[0024] To address this issue, the present invention introduces imidazole derivatives, which effectively overcome these technical problems. Specifically, the aromatic structure of the imidazole ring enhances the chemical inertness of the dopamine-quaternary ammonium salt molecular chain, inhibiting the hydrolysis of amide / ester bonds by seawater. Furthermore, the conjugated imidazole system can capture free radicals (such as OH), mitigating oxidative degradation. Imidazole compounds themselves possess antimicrobial activity, and when combined with quaternary ammonium salts, they can reduce enzymatic degradation caused by microbial attachment.

[0025] As some possible implementation methods of the present application, in step S3, sodium molybdate is added to the dopamine-quaternary ammonium salt grafting solution.

[0026] In this scheme, sodium molybdate is introduced into the dopamine-quaternary ammonium salt grafting solution to form MoO4 on the Ni-P surface. 2- The composite passivation film can quickly generate a NiMoO4 repair layer when the local passivation film is destroyed by Cl-, reducing the fluctuation of corrosion current density and improving the corrosion resistance of the material; at the same time, it can effectively inhibit the penetration of H2S.

[0027] As some possible implementation methods of the present application, in step S3, a disulfide bond is introduced.

[0028] Although sodium molybdate can form a repair layer and improve corrosion resistance after being added, it has at least the following defects:

[0029] First, the passive film can only be effectively formed in an oxygen-deficient environment, and the corrosion inhibition effect is significantly reduced in an oxygen-deficient environment (such as crevice corrosion and microbial corrosion areas);

[0030] Second, the film strength and adhesion are insufficient: the passivation film formed by a single molybdate is thin and has weak bonding with the metal surface. It is easy to fall off under mechanical stress, fluid erosion or salt spray erosion, leading to recurrence of local corrosion (such as pitting).

[0031] Third, the lack of antibacterial properties: Sodium molybdate only inhibits corrosion through physical coverage, has no inhibitory effect on microbial attachment and biofilm formation (such as bacteria and algae in the marine environment), and cannot solve the problem of microbial-induced corrosion.

[0032] Based on this, the present invention further introduces a disulfide bond-containing compound on the basis of sodium molybdate, which can overcome the above-mentioned defects of sodium molybdate, as follows:

[0033] First, it can stably exist and function under acidic, alkaline, aerobic or anoxic conditions, making up for the defect of molybdate being sensitive to the environment.

[0034] Secondly, the S atom in the thiol group can form a covalent bond or coordination bond with the metal (Ni, etc.), forming a chemical adsorption film on the metal surface, and the binding force is significantly stronger than the physical adsorption or ionic bond of molybdate; at the same time, the disulfide bond compound is cross-linked through intermolecular sulfur bonds to form a thick and tough composite film layer on the metal surface, which can resist mechanical erosion and penetration of corrosive media.

[0035] Third, sulfur-containing compounds are toxic to microorganisms (such as bacteria and fungi) and can inhibit their metabolic activities or destroy cell membranes, thereby reducing biofilm formation and reducing the risk of microbial corrosion.

[0036] Furthermore, the disulfide bonds can further enhance the self-repairing ability of the grafted layer. When the grafted layer is damaged by external mechanical stress or corrosion, the disulfide bonds can break and then recombine to repair the coating, maintain the material's protective properties, and prevent further corrosion.

[0037] Furthermore, in the synergistic effect with molybdate ions, the molybdate ions are adsorbed on the surface of the positively charged dopamine-quaternary ammonium salt grafted layer through electrostatic action, guiding the uniform distribution of disulfide bond compounds, avoiding local agglomeration, and making the corrosion inhibition film denser and more complete.

[0038] As some possible implementation methods of the present application, in step S5, methyltrimethoxysilane is introduced to hydrolyze and condense in the nano-SiO2-Al2O3 layer to form a Si-O-Si network, thereby enhancing interlayer bonding and structural density, and blocking corrosive media.

[0039] As some possible implementation methods of the present application, in step S6, a fluorine-containing silicone polymer is introduced.

[0040] In this solution, the fluorosilicone polymer reduces surface energy, significantly reducing the adhesion of marine organisms and preventing biocorrosion. It also chemically crosslinks with the polysiloxane matrix through Si-O bonds, improving the coating's stability in marine environments. Furthermore, the network structure formed by methyltrimethoxysilane and the hydrophobicity of the fluorosilicone polymer help improve the material's insulation properties, reducing the impact of moisture and conductive substances on insulation.

[0041] Furthermore, to achieve the above objectives, the present invention also provides the application of FeSiCr soft magnetic materials in marine environmental devices, which are suitable for marine anti-corrosion and wave-absorbing coatings, high-frequency electromagnetic components, and other scenarios.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention effectively improves the corrosion resistance, antibacterial properties, insulation properties, and magnetic properties of FeSiCr soft magnetic powder by coating it with multiple layers (a Ni-P alloy layer, a dopamine-quaternary ammonium salt copolymer graft layer, a tannic acid-metal ion layer, a nano-SiO2-Al2O3 layer, and a polysiloxane resin-boron nitride layer). The specific functions of each coating layer are as follows:

[0044] Ni-P alloy layer: can block O2, Cl - The anodic dissolution of the FeSiCr matrix is suppressed by cathodic protection, thus effectively improving the corrosion resistance of the FeSiCr modified material.

[0045] Dopamine-quaternary ammonium salt copolymer grafted layer: quaternary ammonium salt groups destroy the phospholipid bilayer of bacterial cell membrane through electrostatic action, effectively inhibiting common sulfate-reducing bacteria, iron bacteria, and algae in the ocean, thereby effectively avoiding overcoming the H2S and Ni produced by the metabolism of sulfate-reducing bacteria. 2+ The reaction generates NiS corrosion products, which leads to technical defects such as cracking and peeling of the Ni-P alloy layer.

[0046] Tannic acid-metal ion layer: the polyphenol structure of tannic acid and metal ions (such as Fe 3+ or Cu 2+ etc.) to form a coordination network, depositing a dense protective film on the metal surface to prevent Cl —Penetration; secondly, tannic acid itself has a certain antibacterial effect, and synergizes with quaternary ammonium salts to improve the overall antibacterial properties of the material, reduce the attachment of marine microorganisms and biofilm formation, and increase the antibacterial time; thirdly,

[0047] The polyphenolic structure of tannic acid forms hydrogen bonds with the catechol groups of dopamine, binding to the hydroxyl groups on the oxide surface through metal coordination, enhancing interlayer interlocking. Furthermore, tannic acid, being both hydrophilic and lipophilic, improves the compatibility between the polar oxide (SiO2-Al2O3 layer) and the organic layer (dopamine, polysiloxane resin), reducing interfacial defects such as pores and delamination.

[0048] Nano-SiO2-Al2O3 layer: Nano-sized oxide particles can form a maze effect in the FeSiCr modified material, extending the diffusion path of the corrosive medium and effectively extending the Cl — In addition, the high insulation of the SiO2-Al2O3 layer effectively increases the interlayer resistance and significantly reduces the dielectric loss at high frequencies.

[0049] Polysiloxane resin-boron nitride layer: The Si-O-Si bond network structure of polysiloxane can effectively resist acid and alkali corrosion and improve salt spray resistance; the boron nitride nanosheets are oriented under the induction of the magnetic field to form a heat conduction channel, which quickly dissipates heat and reduces the temperature rise of the magnetic core, avoiding the attenuation of magnetic properties due to temperature.

[0050] In addition, the Ni-P layer 2+ Coordinated with the catechol of dopamine, the amino group of dopamine and the phenolic hydroxyl group of tannic acid are hydrogen-bonded and cross-linked, and the hydroxyl group of tannic acid condenses with the Si-OH of the SiO2-Al2O3 layer to form a cross-layer chemical bond, effectively improving the interlayer bonding strength, thereby effectively blocking Cl — It can effectively maintain the stability of the material's magnetic permeability and extend the service life of the material in the marine environment, ensuring its normal operation in marine electromagnetic equipment.

[0051] In summary, the present invention achieves a comprehensive improvement in the corrosion resistance, antibacterial properties, insulation properties and magnetic properties of FeSiCr soft magnetic materials in marine environments by coating the surface of flaky FeSiCr soft magnetic powder with a Ni-P alloy layer, a dopamine grafted layer, a tannic acid-metal ion transition layer, a nano-SiO2-Al2O3 layer and a polysiloxane-BN composite layer, through the multi-component synergistic effect among the five coating layers. DETAILED DESCRIPTION

[0052] Example 1

[0053] S1. Pretreatment process:

[0054] The FeSiCr flaky soft magnetic powder (aspect ratio of about 30 times, D50 of 25-30 μm) is surface treated by sandblasting process, so that the surface roughness Ra of the treated flaky powder reaches 1.5-2.0 μm.

[0055] S2. Preparation of Ni-P alloy layer:

[0056] S21. Pretreatment: Immerse the pretreated FeSiCr flake soft magnetic powder in a sensitizing solution (10 g / L SnCl2·2H2O + 40 mL / L 37% HCl) and stir at 200 rpm for 10 minutes at room temperature. Filter the filtered FeSiCr flake soft magnetic powder and transfer it to an activation solution (0.5 g / L PdCl2 + 10 mL / L 37% HCl) and stir under the same conditions for 5 minutes. The dosage ratio of the FeSiCr flake soft magnetic powder to the sensitizing solution is: 10 g FeSiCr flake soft magnetic powder: 150 mL sensitizing solution; the dosage ratio of the filtered FeSiCr flake soft magnetic powder to the activation solution is: 10 g FeSiCr flake soft magnetic powder: 165 mL activation solution.

[0057] S22. Electroless plating: To 1 L of deionized water, 25 g of NiSO4·6H2O, 30 g of NaH2PO2·H2O, 20 g of CH3COONa·3H2O, 15 mL of lactic acid, and 2 mg of thiourea were added in sequence, and the pH of the solution was adjusted to 5.0-5.5 to obtain a plating solution. The plating solution was heated to 90°C and kept at this temperature for 15 min, and then pretreated FeSiCr flake soft magnetic powder (loading amount 1.5 dm 2 The plating time was 35 minutes to obtain a coating thickness of approximately 2 μm. A concentrate (with the same composition ratio as the initial plating solution) at 1 / 3 of the initial plating solution was added every 30 minutes to maintain a stable plating solution composition.

[0058] S23. Post-treatment: After plating, the product was washed with deionized water and then vacuum dried at 60°C for 1 h, followed by heat treatment at 200°C under a nitrogen atmosphere for 1 h to obtain a first flaky modified powder.

[0059] S3. Preparation of dopamine-quaternary ammonium salt graft layer:

[0060] S31: Preparation of grafting solution: 2 g / L dopamine hydrochloride and 1 g / L dodecyltrimethylammonium chloride were dissolved in 50 mM Tris-HCl buffer (pH=8.5) to form a homogeneous solution.

[0061] S32: Grafting Reaction: Add the first flaky modified powder to the homogenized solution in S31 at a solid-to-liquid ratio of 1:20. Stir at 150 rpm for 24 hours at room temperature in the dark. After the reaction, centrifuge, wash, and dry under vacuum at 62°C for 10 hours to obtain the second flaky modified powder.

[0062] S4. Tannic acid-Fe 3+ Layer preparation:

[0063] 1.5 g / L tannic acid and 0.8 g / L FeCl3·6H2O were dissolved in an ethanol-water mixed solvent (volume ratio 1:1) to form a coordination solution. The second flaky modified powder was then added (dosage relationship: 18 mL coordination solution: 1 g second flaky modified powder). The reaction was stirred at 200 rpm at 50°C for 1.5 hours. During the reaction, the solution pH was adjusted to 6.5. After the reaction was completed, the solution was centrifuged, washed, and dried under vacuum at 50°C for 7.5 hours to obtain a third flaky modified powder. The tannic acid-Fe 3+ The layer thickness is approximately 15 nm.

[0064] S5. Preparation of nano-SiO2-Al2O3 layer:

[0065] S51: Nanoparticle Surface Modification: 30 nm SiO2 nanoparticles were dispersed in ethanol (20% solid content) and ultrasonically dispersed for 30 minutes. 3 wt% KH-570 silane coupling agent was then added and the mixture was refluxed at 50°C for 2 hours. Ethanol was removed by vacuum distillation and the mixture was vacuum dried at 60°C for 10 hours to obtain modified SiO2. 50 nm Al2O3 nanoparticles were dispersed in toluene (15% solid content) and 2 wt% aluminate coupling agent (DL-411) was added. The mixture was stirred and reacted at 90°C for 1 hour. After filtration and washing, the mixture was dried at 80°C for 8 hours to obtain modified Al2O3.

[0066] S52: Preparation of composite sol: Add 50wt% modified SiO2 and 50wt% modified Al2O3 to ethanol, fully disperse them by ultrasonication, then add 12wt% silica sol (SiO2 content 30%) and 0.5wt% dibutyltin dilaurate, stir at 350rpm for 30min, and let stand at room temperature for 12h.

[0067] S53: Coating and Sintering: The third flaky modified powder was coated using the dip-coating method at a pulling speed of 10 cm / min. After each coating, the powder was dried under hot air at 80°C for 30 minutes. The coating was repeated three times. After coating, the powder was sintered in a nitrogen atmosphere using the following heating program: room temperature → 110°C (2 hours) → 550°C (0.7 hours) at a heating rate of 5°C / min. The powder was then cooled to room temperature (cooling rate ≤ 10°C / min) in the furnace to obtain the fourth flaky modified powder.

[0068] S6. Preparation of polysiloxane resin-BN composite layer

[0069] S61: BN nanosheet pretreatment: BN nanosheets (sheet diameter 2-5 μm, thickness 5-10 nm) were added to anhydrous ethanol (solid content 5%) and ultrasonically dispersed for 90 min (power 500 W, ice-water bath cooling). Subsequently, 0.5 wt% silane coupling agent KH-560 was added and stirred at 50°C for 2 h to obtain a pretreated BN slurry.

[0070] S62: Resin System Preparation: The pretreated BN slurry was mixed with a trimethylsilyl-terminated polysiloxane resin (viscosity 500-1000 mPa·s) in a proportioned manner to achieve a BN content of 0.8 wt%. Ethanol was removed by vacuum distillation at 60°C and -0.09 MPa. Then, 20 wt% methyltriethoxysilane and 0.5 wt% dibutyltin dilaurate were added, and the mixture was stirred under vacuum at 55°C and -0.09 MPa for 18 minutes.

[0071] S63: Hot Pressing: After spraying a fluorocarbon resin release agent and baking (150°C, 30 minutes), a composite system of the resin system and the fourth flaky modified powder component is added to a mold. The mold is then heated at 200°C and maintained at 15 MPa for 1.5 hours. When the temperature reaches 120°C, the mold is vented three times (reducing the pressure to 5 MPa and holding for 30 seconds each time). After demolding, the mold is cured in an air atmosphere at 250°C for 4 hours to obtain the FeSiCr soft magnetic material.

[0072] Example 2

[0073] Compared with Example 1, in step S3, sodium molybdate is added to the dopamine-quaternary ammonium salt grafting solution, and the remaining steps are the same as in Example 1.

[0074] In this embodiment, the specific preparation steps of step S3 are as follows:

[0075] S31: Preparation of grafting solution: Dissolve 2 g / L dopamine hydrochloride and 1 g / L dodecyltrimethylammonium chloride in 50 mM Tris-HCl buffer (pH = 8.5), then slowly add 0.5 g / L sodium molybdate (Na2MoO4·2H2O) and continue stirring for 30 min until completely dissolved to obtain a homogeneous solution;

[0076] S32: Grafting Reaction: Add the first flaky modified powder to the homogenized solution in S31 at a solid-to-liquid ratio of 1:20. Stir at 150 rpm for 24 hours at room temperature in the dark. After the reaction, centrifuge, wash, and dry under vacuum at 60°C for 12 hours to obtain the second flaky modified powder.

[0077] Example 3

[0078] Compared with Example 2, a disulfide bond was introduced in step S3. The remaining steps were the same as Example 2.

[0079] In this embodiment, the specific preparation steps of step S3 are as follows:

[0080] S31: Preparation of grafting solution:

[0081] Dissolve 2 g / L dopamine hydrochloride and 1 g / L dodecyltrimethylammonium chloride in 50 mM Tris-HCl buffer (pH 8.5). Slowly add 0.5 g / L sodium molybdate (Na2MoO4·2H2O) and stir continuously for 30 minutes until completely dissolved. Then, add 0.5 g / L cystamine and continue stirring for 60 minutes to form a homogeneous solution.

[0082] S32: Grafting Reaction: Add the first flaky modified powder to the homogenized solution in S31 at a solid-to-liquid ratio of 1:20. Stir at 150 rpm for 24 hours at room temperature in the dark. After the reaction, centrifuge, wash, and dry under vacuum at 60°C for 12 hours to obtain the second flaky modified powder.

[0083] Example 4

[0084] On the basis of Example 3, an imidazole derivative is introduced in step S3. The remaining steps are the same as in Example 3.

[0085] In this embodiment, the specific preparation steps of step S3 are as follows:

[0086] S31: Grafting solution preparation

[0087] Dissolve 2 g / L dopamine hydrochloride and 1 g / L dodecyltrimethylammonium chloride in 50 mM Tris-HCl buffer (pH 8.5). Slowly add 0.5 g / L sodium molybdate (Na2MoO4·2H2O) and stir continuously for 30 minutes until completely dissolved. Then, add 0.5 g / L cystamine and continue stirring for 60 minutes. Finally, add 0.3 g / L 1-vinyl-3-butylimidazolium bromide and continue stirring under nitrogen for 45 minutes to form a homogeneous solution.

[0088] S32: Grafting reaction

[0089] The first flaky modified powder was added to the homogenous solution of S31 at a solid-to-liquid ratio of 1:20. The mixture was stirred at 150 rpm for 24 hours at room temperature in the dark. After the reaction, the mixture was centrifuged, washed, and dried under vacuum at 60°C for 12 hours to obtain the second flaky modified powder.

[0090] Example 5

[0091] Compared with Example 4, methyltrimethoxysilane and fluorosilicone polymer are introduced in step S62. The remaining steps are the same as Example 4.

[0092] In this embodiment, the specific preparation steps of step S62 are as follows:

[0093] The pretreated BN slurry was mixed with a trimethylsilyl-terminated polysiloxane resin (viscosity 500-1000 mPa·s) in a ratio to achieve a BN content of 0.8 wt%. Ethanol was removed by vacuum distillation at 60°C and -0.09 MPa. Then, 15 wt% methyltrimethoxysilane, 5 wt% Daikin Optool DSX, 20 wt% methyltriethoxysilane curing agent, and 0.5 wt% dibutyltin dilaurate catalyst were added in sequence. The mixture was stirred under vacuum at 55°C and -0.09 MPa for 30 minutes.

[0094] Comparative Example 1

[0095] The unmodified FeSiCr flake powder has an aspect ratio of about 30 times and a D50 of 25 to 30 μm.

[0096] Experimental example

[0097] The flaky FeSiCr modified materials prepared in Examples 1-5 and the flaky powder in Comparative Example 1 were tested for corrosion resistance, antibacterial properties, antibacterial duration, insulation properties, and magnetic properties. The test results are shown in Table 1. The test methods are as follows:

[0098] Corrosion resistance: Salt spray testing was conducted according to ASTM B117. Samples were placed in a 5% NaCl solution for 1000 hours. Surface corrosion was observed and rated (ISO 4628-3). The corrosion rate was also calculated.

[0099] Antibacterial property: With reference to GB / T 21510-2008 standard, the inhibition zone diameter test method was adopted, with Escherichia coli and Staphylococcus aureus as the test bacteria, and the size of the inhibition zone formed around the sample was measured.

[0100] Antibacterial duration: A marine hanging plate test was conducted in accordance with ISO 15181-1. The samples were suspended in a marine environment for 12 months. The biofouling was regularly observed and recorded. The antibacterial duration was assessed by the percentage of biofouling area.

[0101] Insulation: Volume resistivity is tested in accordance with GB / T 1410-2006 standard, and breakdown voltage is measured at the same time.

[0102] Magnetic properties: The saturation magnetization (Ms) and coercive force (Hc) were measured using a vibrating sample magnetometer.

[0103] Table 1:

[0104]

[0105]

[0106] From Table 1 we can see that:

[0107] Compared with Comparative Example 1, Examples 1-5 have achieved significant optimization in corrosion resistance, antibacterial properties, antibacterial duration, insulation and magnetic properties. This series of FeSiCr soft magnetic materials has shown great application potential in marine engineering, ship motors, underwater sensors and other fields, especially Example 5, which has excellent comprehensive performance. While ensuring magnetic properties, it significantly improves corrosion resistance, antibacterial and insulation properties, providing an innovative solution to the problem of material failure in the marine environment.

[0108] Example 2 further introduces molybdate based on Example 1, which can form a passivation film, effectively blocking the erosion of corrosive media, reducing the corrosion rate, and improving the salt spray rating. At the same time, Example 2 also adds molybdate to the antibacterial effect of Example 1, and the two work synergistically to enhance the antibacterial effect.

[0109] Example 3 further adds disulfide bonds based on Example 2, thereby enhancing the density of the coating, making it difficult for corrosive media to penetrate, and thus improving corrosion resistance.

[0110] Example 4 adds imidazole ionic liquid on this basis, effectively overcoming the risk of quaternary ammonium salt shedding, enhancing the antibacterial effect, and extending the antibacterial time.

[0111] In Example 5, fluorosilicone was used to reduce the material's surface energy, making it less susceptible to adhesion of corrosive media. The resulting cross-linked structure further enhanced corrosion resistance, achieving the best performance in the salt spray test, reaching level 0. The introduction of methyltrimethoxysilane significantly improved insulation performance through cross-linking, increasing volume resistivity by multiple orders of magnitude and significantly increasing breakdown voltage.

[0112] Compared with Comparative Example 1, the saturation magnetization Ms of Examples 1-5 all decreased slightly, but the decrease was relatively small. This is mainly because the non-magnetic coating formed on the surface of the material thickened, which to some extent affected the overall magnetic performance of the material. The coercive force increased slightly, which was mainly due to the increase in the interfacial stress formed between the coating and the FeSiCr flaky substrate, which changed the magnetic domain structure inside the material and thus affected the coercive force. However, overall, the magnetic properties of each embodiment still met the basic standards of soft magnetic materials and still had good soft magnetic properties in practical applications.

Claims

1. A modified FeSiCr soft magnetic material, characterized in that: The invention comprises FeSiCr soft magnetic powder, and a Ni-P alloy layer, a dopamine-quaternary ammonium salt copolymer graft layer, a tannic acid-metal ion layer, a nano-SiO2-Al2O3 layer and a polysiloxane resin-boron nitride layer which are sequentially coated on the outside of the FeSiCr soft magnetic powder from the inside to the outside.

2. The modified FeSiCr soft magnetic material according to claim 1, characterized in that: In the nano-SiO2-Al2O3 layer, SiO2 is SiO2 modified by a silane coupling agent; and Al2O3 is Al2O3 modified by an aluminate coupling agent.

3. The modified FeSiCr soft magnetic material according to claim 1, characterized in that: In the polysiloxane resin-boron nitride layer, the polysiloxane resin is trimethylsilyl-terminated polysiloxane.

4. The method for preparing the FeSiCr soft magnetic material according to any one of claims 1 to 3, characterized in that: The steps include: S1. FeSiCr soft magnetic powder is pretreated; the FeSiCr soft magnetic powder is FeSiCr flake powder; S2. Introduction of a Ni-P alloy layer: coating and sintering by an electroless plating process to obtain a first flaky modified powder; S3 introduces dopamine - quaternary ammonium salt grafted layer: the dopamine - quaternary ammonium salt grafted liquid and the first flaky modified powder is thoroughly mixed, washed and dried by centrifugation to obtain a second flaky modified powder; S4. Introduction of tannic acid - metal ion layer: The tannic acid - metal ion solution and the second flaky modified powder were thoroughly mixed, washed and dried by centrifugation to obtain a third flaky modified powder; S5. Introduction of nano-SiO2-Al2O3 layer: coating and sintering by immersion pulling method to obtain a fourth flaky modified powder; S6. Introducing a polysiloxane resin-boron nitride layer: The FeSiCr soft magnetic material is prepared by hot pressing.

5. The method for preparing the FeSiCr soft magnetic material according to claim 4, wherein: In step S3, sodium molybdate is added to the dopamine-quaternary ammonium salt grafting solution.

6. The method for preparing the FeSiCr soft magnetic material according to claim 4, wherein: In step S3, an imidazole derivative is introduced.

7. The method for preparing the FeSiCr soft magnetic material according to claim 5, wherein: In step S3, a disulfide bond is introduced.

8. The method for preparing the FeSiCr soft magnetic material according to claim 4, wherein: In step S5, methyltrimethoxysilane is introduced.

9. The method for preparing the FeSiCr soft magnetic material according to claim 4, wherein: In step S6, a fluorine-containing silicone polymer is introduced.

10. Use of the FeSiCr soft magnetic material according to any one of claims 1 to 3 in marine environment devices.

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