Multifunctional polysiloxane in-situ coated metal soft magnetic material, its preparation method and application

Abstract

The application belongs to the technical field of metal soft magnetic materials, and particularly relates to a multifunctional polysiloxane in-situ coated metal soft magnetic material and a preparation method and application thereof. The method realizes uniform coating on the surface of the metal soft magnetic material through surface modification and in-situ polysiloxane coating, protects the oxide layer and enhances the insulation, and simultaneously introduces a plurality of adjustable functional groups. The technology solves the problem of poor adaptability of the oxide coating layer and other components, the polysiloxane can form a continuous and dense insulating barrier, improve the resistivity, reduce the eddy current loss, the flexibility can buffer stress, avoid processing damage, and effectively block water and oxygen and corrosive media, prolong the service life of the material.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic metal materials technology, and particularly relates to a soft magnetic metal material with in-situ coating of multifunctional polysiloxane, its preparation method and application. Background Technology

[0002] Soft magnetic metallic materials are a class of magnetic materials that are easily magnetized and demagnetized in a magnetic field, possessing characteristics such as high permeability, low coercivity, and low hysteresis loss. Coating metal magnetic cores with oxides can significantly improve the resistivity of the material and effectively reduce eddy current losses in the composite material. However, the oxide on the surface of the metal magnetic core is a rigid inorganic material, typically hard and brittle. During subsequent powder pressing, the extrusion and friction between particles may cause localized detachment of the oxide coating. Moreover, the oxide coating is usually only a few nanometers thick, potentially containing micropores and cracks, resulting in insufficient resistance to acids and alkalis, hydrophobicity, and weathering, which can corrode the metal magnetic core and reduce its service life. Furthermore, the surface of the oxide coating lacks abundant active functional groups, leading to poor compatibility with other substrates such as resin materials. Microscopic phase separation can occur after blending, affecting the application and expansion of the composite material.

[0003] Polysiloxanes are a class of molecules primarily composed of inorganic silicon-oxygen chains and organic hydrocarbon chains. Their Si-O-Si molecular structure exhibits good flexibility, and their side chains are linked to various functional organic groups via silicon atoms, combining the properties of both organic polymers and inorganic materials. They demonstrate excellent performance in high and low temperature resistance, weather resistance, corrosion resistance, electrical insulation, radiation resistance, and resistance to swelling. However, low molecular weight polysiloxanes have poor film-forming properties and thermal stability, making them unsuitable for coating soft magnetic metal materials. High molecular weight polysiloxanes, on the other hand, have high viscosity, poor flowability, and low solubility, making it difficult to achieve uniform coating of soft magnetic metal powder surfaces. Therefore, polysiloxanes, as in-situ coating layers, not only provide a dense insulating layer but also allow for the development of compatible systems suitable for different substrate materials through functional group design, leading to wider applications in inductors, sensors, transformers, and electromagnetic shielding. Summary of the Invention

[0004] The purpose of this invention is to provide a multifunctional polysiloxane-coated metal soft magnetic material, its preparation method, and its application. This technology is applied to the surface of metal soft magnetic materials with oxide coating layers. Through in-situ reaction, uniform coating of the metal soft magnetic material can be achieved, protecting the oxide coating layer, improving insulation performance, and introducing various tunable functional group structures onto the surface of the metal soft magnetic material. This solution aims to solve the problem of poor compatibility between the oxide coating layer and other components. Furthermore, because polysiloxane is used as an in-situ coating, it can form a more continuous and denser insulating barrier. This not only imparts high resistivity to the material, reducing eddy current losses, but also buffers stress due to its good flexibility and elasticity, preventing physical damage to the oxide coating layer during processing. It can also more effectively prevent water, oxygen, and corrosive media from penetrating to the surface of the metal core, effectively extending its service life.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a multifunctional polysiloxane-coated in-situ metallic soft magnetic material includes the following steps:

[0007] S1 Surface Modification: A silane coupling agent is used to modify the surface of a metal soft magnetic material with an oxide coating under alkaline conditions. The specific steps are as follows: ammonia, deionized water, and ethanol are mixed, and then the metal soft magnetic material with an oxide coating and the silane coupling agent are added to modify the surface under alkaline conditions. Surface modification of the oxide coating on the metal soft magnetic material improves its surface reactivity and dispersibility in the solvent. After the surface modification reaction is complete, the material is washed with ethanol and deionized water. After solid-liquid separation, polysiloxane coating can be directly applied.

[0008] S2 Polysiloxane Coating: Short-branched siloxane monomers and siloxane monomers with active functional groups are added to surface-modified metal soft magnetic material powder. Under the action of an acidic catalyst, an in-situ hydrolysis-condensation-copolymerization reaction occurs to produce a metal soft magnetic material with multifunctional polysiloxane in-situ coating. Thus, a uniform polysiloxane coating layer with multiple functional groups is formed on the oxide surface. The selected monomers all contain alkoxy groups, which hydrolyze to generate silanols. Condensation reactions can occur between silanols and between silanols and alkoxy groups. At the same time, copolymerization reactions occur between multiple monomers. After the polysiloxane coating reaction is completed, the mixture is washed with deionized water and ethanol. By selecting siloxane monomers with specific functional groups and carrying out hydrolysis-condensation-copolymerization reactions under acidic conditions, the required polysiloxane coating layer can be flexibly designed and customized based on the type and functionality of the monomers.

[0009] Furthermore, the metal soft magnetic material with oxide coating is preferably composed of iron, iron-nickel alloy, or iron-cobalt alloy as its core powder, with a particle size of 0.5–5 micrometers. The oxide on the surface of the metal soft magnetic material with oxide coating is preferably composed of silicon oxide, aluminum oxide, or titanium oxide, with a thickness controlled at 1–10 nanometers. The oxide coating surface is rich in hydroxyl groups, and especially after surface modification under alkaline conditions, it can significantly enhance the interfacial bonding with the subsequent organic polysiloxane coating layer. Simultaneously, this oxide layer acts as a transition and bridge between the inorganic metal and the organic polymer, enhancing their compatibility and bonding performance.

[0010] In some embodiments of the present invention, preferably, the siloxane monomer containing the active functional group is selected from any one or more of the following: γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldiethoxysilane, β-(3,4) (Epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, aminoethylaminoethylaminopropyltrimethoxysilane, aminophenyltrimethoxysilane, N-methylaminopropyltrimethoxysilane, methyl(γ-aminopropyl)diethoxysilane, anilinemethyltriethoxysilane, anilinemethyltrimethoxysilane, hexamethylenediaminemethyltriethoxysilane, methyl(γ-epoxypropoxy)diethoxysilane, methyl(N-β-aminoethyl-γ-aminopropyl)dimethoxysilane.

[0011] In some embodiments of the present invention, the mass of the oxide-coated metal soft magnetic material powder is 30% to 60% of the mass of ethanol, preferably 35% to 55%. Excessive powder addition can lead to dispersion difficulties, resulting in agglomeration and uneven coating during surface modification and coating processes; insufficient addition is detrimental to large-scale production.

[0012] In some embodiments of the present invention, the mass of the silane coupling agent in the surface modification step is 0.1% to 5% of the mass of ethanol, preferably 1% to 4%.

[0013] In some embodiments of the present invention, the molar ratio of water to alkoxy groups in the siloxane monomer is 1.0 to 1.5:1. This ratio provides sufficient water molecules to drive the hydrolysis of alkoxy groups to generate silanols, promoting the reaction towards complete hydrolysis.

[0014] In some embodiments of the present invention, the short-branched siloxane monomer is selected from any one or more of the following: dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, and propyltrimethoxysilane.

[0015] In some embodiments of the present invention, the acidic catalyst in the polysiloxane coating includes at least one of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid, or citric acid. The process requires adjusting the pH of the reaction system to 3-5, preferably 4. This pH range can significantly increase the hydrolysis rate of alkoxy groups while effectively inhibiting the condensation reaction rate of silanols, thereby ensuring sufficient hydrolysis while avoiding excessive condensation, resulting in a uniform and stable polysiloxane coating layer.

[0016] In some embodiments of the present invention, in the polysiloxane coating, the ratio of amino to epoxy groups in the polysiloxane is determined by the amount of corresponding monomers added, thereby designing polysiloxane coating layers with different requirements; at the same time, the molar ratio of short-chain branched siloxane monomers to siloxane monomers with active functional groups is 1:0.3 to 0.8, preferably 1:0.45 to 0.55; the molar ratio of the two functional groups, amino and epoxy, can be synthesized according to specific needs.

[0017] In some embodiments of the present invention, the surface modification step may be performed at a temperature of 25 to 60°C and a reaction time of 5 to 24 hours, preferably at 25°C for 18 hours.

[0018] In some embodiments of the present invention, in the polysiloxane coating step, the reaction temperature is 50~80℃, preferably 60℃, and the reaction time is 10~24 hours, preferably 18 hours.

[0019] In some embodiments of the present invention, in the surface modification step, after ethanol, ammonia and deionized water are mixed evenly, a soft magnetic metal material with an oxide coating is added, and then stirred for 30 minutes to make the soft magnetic material powder evenly dispersed before adding a silane coupling agent.

[0020] In some embodiments of the present invention, the polysiloxane coating step is performed in the following order: first, the siloxane monomer is mixed evenly with ethanol, then a soft magnetic metal material with an oxide coating layer is added, and the mixture is stirred continuously for 30 minutes to ensure that the powder is fully suspended and evenly dispersed, and finally deionized water is added. This order of addition helps to ensure that the soft magnetic metal material is fully dispersed in the solvent and the reactant monomer, while avoiding premature hydrolysis of the siloxane monomer before the reaction begins.

[0021] In some embodiments of the present invention, during the polysiloxane coating step, the acidic catalyst is slowly added dropwise after the reaction system has been heated to a predetermined temperature. This operation avoids excessive hydrolysis caused by excessively high local concentrations of the catalyst, thereby ensuring a uniform and dense coating layer.

[0022] In some embodiments of the present invention, the metal soft magnetic material powder with oxide coating (including powder before and after surface modification) needs to be added to the reaction system in batches or slowly and continuously, with the total addition time controlled within 10 minutes. Specifically, the slow and controlled addition method can effectively prevent local agglomeration of powder due to instantaneous accumulation and ensure that the powder particles are in uniform contact with the reaction medium as much as possible.

[0023] The advantages of this invention are:

[0024] 1. Compared with non-in-situ coating technology, in-situ polysiloxane coating technology can directly initiate and complete the polymerization of siloxane monomers on the surface of the oxide coating layer of the metal soft magnetic material, thereby forming a denser, more uniform coating layer with higher bonding strength at the particle-polymer interface, constructing a metal soft magnetic material with a double-layer coating structure. This structure can effectively block the electrical contact between metal particles, significantly reducing eddy current losses at high frequencies. At the same time, the thin and uniform coating layer helps to achieve a higher metal filling rate, thereby improving the effective permeability of the material and improving its frequency characteristics. In addition, the double-layer coating structure enhances the resistance to external environmental factors. The polysiloxane outer coating layer can provide better protection for the internal oxide layer and metal core, effectively ensuring the insulation integrity and magnetic performance stability, ultimately contributing to the improvement of the overall performance of the soft magnetic composite material.

[0025] 2. This invention significantly enhances the functionality and application potential of the coated powder by rationally designing the active functional groups (such as amino and epoxy groups) in the polysiloxane coating layer. These functional groups can greatly improve the interfacial compatibility and chemical bonding ability between the composite material and the polymer matrix (such as epoxy resin), coatings, and other subsequent application systems. For example, in the epoxy resin system, polar functional groups can effectively enhance the compatibility between the two phases, making the material more uniformly dispersed during processing and improving the interfacial bonding strength. In addition, the dense polysiloxane coating layer also has a good anti-corrosion barrier effect and provides the possibility of further chemical modification for metal soft magnetic powders that already have oxide coating layers, expanding their application prospects in high-performance composite materials, electromagnetic shielding, inductor devices, and other fields. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a double-layered coated soft magnetic metal material.

[0027] Figure 2 The image shows the microstructure of the soft magnetic metal material with a double-layer coating structure provided in Example 1. Detailed Implementation

[0028] The present invention is described below through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention based on the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Based on different viewpoints and applications, various modifications or changes can be made to the details described in this specification without departing from the spirit of the present invention.

[0029] It should be noted that the embodiments described in this specification are merely exemplary and are not intended to exhaustively describe or limit the scope of protection of this invention. Other embodiments that can be obtained by those skilled in the art based on the embodiments disclosed in this invention without creative effort should all be considered to fall within the scope of protection of this invention.

[0030] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art; the raw materials and reagents used, unless otherwise specified, are all raw materials and reagents that can be obtained from conventional markets and other commercial channels.

[0031] Example 1

[0032] A method for preparing iron powder with a silicon oxide coating layer in situ coated by polysiloxane includes the following steps:

[0033] (1) Surface modification of iron powder (Fe@SiOx) with a silicon oxide coating includes the following steps:

[0034] First, place 100 g of ethanol in a beaker and stir with a stirrer at 300 rpm. Then, add 10 g of 28 wt% ammonia and 10 g of deionized water and stir for 5 minutes. Next, take 50 g of Fe@SiOx and slowly add it spoonful by spoonful to the solution being stirred, completing the addition within 10 minutes. Then, maintain stirring at 300 rpm for 30 minutes. Next, take 3 g of γ-aminopropyltriethoxysilane and slowly add it dropwise to the above solution. React at room temperature for 18 hours. After the reaction is complete, wash several times with ethanol and deionized water, ensuring that the final wash is with ethanol. During each wash, stir with a stirrer at 300 rpm for 3 minutes and use a magnet to achieve solid-liquid separation. Vacuum dry at 80 degrees Celsius for 3 hours for in-situ polysiloxane coating, or use it directly for in-situ polysiloxane coating after solid-liquid separation.

[0035] (2) In-situ polysiloxane coating of the surface-modified powder includes the following steps: First, 12 g of dimethyldimethoxysilane and 11.8 g of γ-glycidyl etheroxypropyltrimethoxysilane were added to 119 g of ethanol and stirred continuously at 300 rpm for 10 minutes; then, 47.6 g of the surface-modified powder was slowly added spoonful by spoonful to the solution being stirred, and the addition was completed within 10 minutes, and then stirred at 300 rpm for 30 minutes; then, 6.3 g of deionized water was added dropwise, and then the reaction temperature was slowly increased from room temperature to 60°C, and 3 g of 1 M HCl was gradually added; finally, the reaction was continued at 60°C for 18 hours to complete the hydrolysis-condensation-copolymerization reaction. After the reaction was completed, the powder was washed several times with ethanol and deionized water, and it was ensured that the final wash was with ethanol. During each wash, the powder was stirred at 300 rpm for 3 minutes with a stirrer, and solid-liquid separation was achieved with a magnet. The powder was then vacuum dried at 80°C for 3 hours.

[0036] In this embodiment, the surface is modified with the silane coupling agent γ-aminopropyltriethoxysilane, and then hydrolyzed, condensed and copolymerized with dimethyldimethoxysilane and γ-glycidoxypropyltrimethoxysilane to prepare a polysiloxane coating with epoxy groups. The inner coating layer is silicon oxide and the metal core is iron.

[0037] Example 2

[0038] A method for preparing iron powder with silicon oxide coating in situ using polysiloxane differs from Example 1 in that: the siloxane monomer with active functional groups in the polysiloxane coating step is changed to two types, and γ-aminopropyltriethoxysilane is added to the original method. The molar ratio of γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane is maintained at 1:1, and the total molar number of the two is 0.5:1 compared with the molar ratio of dimethyldimethoxysilane.

[0039] Example 3

[0040] A method for preparing iron powder with silicon oxide coating in situ using polysiloxane differs from Example 2 in that the molar ratio of γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane in the polysiloxane coating step is changed from 1:1 to 3:1, and the total molar number of the two is 0.5:1 compared with the molar ratio of dimethyldimethoxysilane.

[0041] Example 4

[0042] A method for preparing iron powder with silicon oxide coating in situ using polysiloxane differs from Example 1 in that γ-glycidoxypropyltrimethoxysilane in the polysiloxane coating step is replaced with γ-aminopropyltriethoxysilane, while maintaining the molar ratio of γ-aminopropyltriethoxysilane to dimethyldimethoxysilane at 0.5:1.

[0043] Example 5

[0044] A method for preparing polysiloxane-coated iron-nickel alloy powder with silica coating, which differs from Example 1 in that the iron powder with silica coating in the surface modification step is replaced with iron-nickel alloy powder with silica coating.

[0045] Example 6

[0046] A method for preparing polysiloxane-coated iron-cobalt alloy powder with silica coating, which differs from Example 1 in that the iron powder with silica coating in the surface modification step is replaced with iron-cobalt alloy powder with silica coating.

[0047] Example 7

[0048] A method for preparing iron powder with polysiloxane in situ coating of alumina coating, which differs from Example 1 in that the iron powder with silicon oxide coating in the surface modification step is replaced with iron powder with aluminum oxide coating.

[0049] Example 8

[0050] A method for preparing iron powder with titanium oxide coating in situ coated with polysiloxane, which differs from Example 1 in that the iron powder with silicon oxide coating in the surface modification step is replaced with iron powder with titanium oxide coating.

[0051] Example 9

[0052] A method for preparing polysiloxane-coated iron powder with silica coating, differing from Example 1 in that dimethyldimethoxysilane is replaced with propyltrimethoxysilane, the amount of propyltrimethoxysilane added is changed to 0.1314 g, the amount of γ-glycidyl etheroxypropyltrimethoxysilane added is changed to 0.0945 g, and the amount of deionized water is changed to 0.648 g, while the rest remain the same.

[0053] Example 10

[0054] A method for preparing iron powder with a silicon oxide coating layer in situ coated by polysiloxane is different from that in Example 1, except that the surface modification step is omitted and the coating step is performed directly.

[0055] Comparative Example 1

[0056] A method for preparing iron powder coated with a silica coating by polysiloxane condensation of a single monomer:

[0057] Unlike Example 1, γ-glycidoxypropyltrimethoxysilane was not added in the polysiloxane coating step, while the total number of monomer moles remained unchanged. 0.05 mol of dimethyldimethoxysilane was added, and other operations remained the same as in Example 1.

[0058] Comparative Example 2

[0059] A method for preparing polysiloxane-coated iron powder with silica coating by single monomer condensation: Unlike Example 1, dimethyldimethoxysilane is not added in the polysiloxane coating step, while keeping the total molar number of monomers unchanged, and 0.1 mol of γ-glycidoxypropyltrimethoxysilane is added. Other operations remain unchanged from Example 1.

[0060] Comparative Example 3

[0061] A method for preparing iron powder with a silica coating layer directly coated by non-in-situ polysiloxane: The surface of the iron powder with the silica coating layer is modified by the surface modification step in Example 1; 6 g of dimethyldimethoxysilane and 5.9 g of γ-glycidyl etheroxypropyltrimethoxysilane are taken and stirred evenly, and then 3.15 g of deionized water is added dropwise. After the reaction temperature is raised to 60°C, 50 mg of 1 M HCl is gradually added, and the reaction is carried out for 18 hours; then the product is added to 59.5 g of ethanol and stirred evenly, and then 25 g of iron powder with the silica coating layer is added. The mixture is stirred at 300 rpm at room temperature for 18 hours; after the reaction is completed, the mixture is washed with deionized water and ethanol and then dried.

[0062] Comparative Example 4

[0063] Iron powder with a silicon oxide coating (a product manufactured by our company).

[0064] The iron powder soft magnetic composite material with a silicon oxide coating and in situ polysiloxane coating prepared in Example 1 was subjected to scanning electron microscopy. The morphology of the obtained material is as follows: Figure 2 As shown.

[0065] The soft magnetic composite materials prepared in Examples 1-10 and Comparative Examples 1-4 were subjected to contact angle and dual-probe powder compaction resistance tests. The resistivity, compaction density, contact angle, and coefficients of variation of the compaction resistance at 100 MPa are shown in Table 1. Compared with the untreated control sample (Comparative Example 4), coating the powder surface with a polysiloxane layer significantly improved its resistivity and hydrophobicity. This confirms the successful introduction of a new insulating layer onto the oxide coating layer. Although the resistivity of the samples obtained by in-situ coating with different polysiloxanes was similar, the compaction density and contact angle varied due to differences in their branched functional groups. Specifically, short-chain siloxane monomers achieved higher compaction densities because their steric hindrance was less than that of siloxane monomers containing active functional groups (such as amino and epoxy groups), but their resistivity improvement was not significant. Meanwhile, the contact angle test showed that epoxy functional groups were more hydrophobic than amino functional groups. Therefore, as the proportion of epoxy groups in the polysiloxane coating increases, the hydrophobicity of the material also increases. This clearly demonstrates that the physicochemical properties of the material surface can be effectively adjusted by controlling the surface functional group composition of the polysiloxane coating. Simultaneously, the in-situ prepared polysiloxane coating exhibits a more uniform and consistent coating compared to the non-in-situ prepared coating, as multiple measurements of the same batch of samples in powder resistance testing show more stable test results, i.e., a smaller coefficient of variation. Furthermore, under these coating conditions, the insulation provided by the polysiloxane coating reaches its limit; that is, the effective thickness of the coating in the examples has entered the "insulation plateau region," where the resistance is insensitive to minor changes in thickness and process variations. The significant differences between the comparative examples (especially Comparative Example 4) and the examples precisely demonstrate the crucial role of the coating. The deviation coefficients of Examples 9 and 10 highlight the importance of coating uniformity. Meanwhile, the contact angles in the examples are generally high (>90°), indicating that the material surface is hydrophobic after polysiloxane coating, proving the success of the coating. However, this parameter is mainly determined by the chemical composition and microstructure of the solid surface and is unrelated to the thickness of the polysiloxane coating layer, the inner oxide coating layer, and the core magnetic core. The examples only adjusted the proportion of end groups related to surface chemistry, but still showed a regular variation of nearly 20°, particularly significantly different from Comparative Example 4 (without polysiloxane coating). Furthermore, Example 10 shows that although the surface modification step does not affect the resistance of subsequent in-situ coating, the uniformity of the surface coating is particularly limited, thus affecting the subsequent magnetic ring performance (Table 2). Therefore, the surface modification step is a crucial step before coating.

[0066] Table 1. Contact Angle and Powder Compaction Resistance Test with Dual Probes

[0067]

[0068] The soft magnetic composite materials prepared in Examples 1-10 and Comparative Examples 1-4 were pressed and their magnetic properties were tested. The steps were as follows: The soft magnetic composite material powder prepared in the experiment was mixed evenly with an epoxy resin ethanol solution binder. The epoxy resin content was 0.2% of the mass of the soft magnetic composite material powder, and the binder solid content was 15%. The mixture was injected into a ring mold, held under pressure of 600 MPa for 1 minute, and then annealed at 150°C for 120 minutes under argon protection to obtain a magnetic ring. By comparing the examples and comparative examples, it was found that although introducing an insulating coating layer on the surface of the magnetic core powder can improve resistivity and reduce eddy current loss, it will also degrade its inherent magnetic properties. Compared with non-in-situ coating, the in-situ polysiloxane coating process can more effectively mitigate this negative impact on magnetic properties. Its key advantage lies in the fact that the coating layer formed by this process has better uniformity and thinner thickness. It is particularly important to note that Examples 5 and 6 differ significantly from other examples. This is entirely due to the fundamental difference in the microscopic magnetic mechanism between the soft magnetic alloys (iron-nickel, iron-cobalt) used in them and pure iron. This also further illustrates the scalability of the process of this invention. The coated soft magnetic material is competitive in low-frequency and mid-to-high-frequency applications by changing the core alloy. However, this is still a comprehensive choice based on performance, application, and cost. For applications requiring extremely high saturation magnetic induction (such as high-power, miniaturized magnetic components), Example 6 (FeCo alloy) is a better choice. The addition of cobalt optimizes the arrangement of iron atom magnetic moments. The resulting iron-cobalt (Fe-Co) alloy is known to have the highest saturation magnetization at room temperature, so its data being significantly higher than pure iron is in line with theoretical expectations. Conversely, in iron-nickel alloys (such as the classic permalloy containing 78% nickel), the addition of nickel dilutes the ferromagnetism of iron. The specific arrangement of nickel and iron atom magnetic moments results in a lower saturation magnetization than pure iron, which is determined by the intrinsic electronic structure of the alloy. Finally, compared with the three types of embodiments or comparative examples of non-in-situ coating, no coating, and no surface treatment, the process described in this invention can maintain lower core loss with a lower magnetic dilution effect.

[0069] Table 2 Magnetic Performance Tests

[0070]

Claims

1. A method for preparing a multifunctional polysiloxane-coated in-situ metallic soft magnetic material, characterized in that, Includes the following steps: S1 Surface Modification: The surface of the metal soft magnetic material with oxide coating is modified under alkaline conditions using a silane coupling agent; the alkaline conditions are adjusted to pH 9-13 by ammonia water; the metal soft magnetic material with oxide coating consists of an inorganic insulating oxide coating on the surface of metal core powder, the metal core being one of iron, iron-nickel alloy, or iron-cobalt alloy, with a particle size of 0.5-5 micrometers, the oxide coating thickness being 1-10 nanometers, and the oxide being one of silicon oxide, titanium oxide, or aluminum oxide; S2 Polysiloxane Coating: Short-branched siloxane monomers and siloxane monomers with active functional groups are added to surface-modified metal soft magnetic material powder, and an in-situ hydrolysis-condensation-copolymerization reaction is carried out under the action of an acidic catalyst to obtain a metal soft magnetic material with polyfunctional polysiloxane in situ coating; the acidic catalyst is at least one of hydrochloric acid, sulfuric acid, nitric acid, formic acid, acetic acid or citric acid, with a pH of 3 to 5; the siloxane monomer with active functional group is a siloxane monomer with one or more functional groups of amino or epoxy groups; the short-branched siloxane monomer is a siloxane monomer without side chains or with branches shorter than those with active functional groups.

2. The method for preparing the in-situ coated metal soft magnetic material with multifunctional polysiloxane as described in claim 1, characterized in that: In the surface modification step, based on the total mass of ethanol, the total amount of the soft magnetic metal material with oxide coating is 30–60 wt%, and the total amount of silane coupling agent is 0.1–5 wt%. In the polysiloxane coating step, based on the molar number of short-branched siloxane monomers and siloxane monomers having one or more functional groups such as amino and epoxy groups, the molar ratio of short-branched siloxane monomers to siloxane monomers having one or more functional groups such as amino and epoxy groups is 1:0.3 to 0.

8.

3. The method for preparing the in-situ coated metal soft magnetic material with multifunctional polysiloxane as described in claim 1, characterized in that: The siloxane monomer having an active functional group is selected from any one or more of the following: γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, aminoethylaminoethylaminopropyltrimethoxysilane, aminophenyltrimethoxysilane, N-methylaminopropyltrimethoxysilane, methyl(γ-aminopropyl)diethoxysilane, anilinemethyltriethoxysilane, anilinemethyltrimethoxysilane, hexamethylenediaminemethyltriethoxysilane, methyl(γ-epoxypropoxy)diethoxysilane, methyl(N-β-aminoethyl-γ-aminopropyl)dimethoxysilane.

4. The method for preparing the in-situ coated metal soft magnetic material with multifunctional polysiloxane as described in claim 1, characterized in that: The short-branched siloxane monomer is selected from any one or more of the following: dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, cyclohexylmethyldimethoxysilane, and propyltrimethoxysilane.

5. The method for preparing the in-situ coated metal soft magnetic material with multifunctional polysiloxane as described in claim 1, characterized in that: In the surface modification step, the treatment temperature is 25–60℃ and the reaction time is 5–24 hours; In the polysiloxane coating step, the reaction temperature is 50~80℃ and the reaction time is 10~24 hours.

6. The multifunctional polysiloxane-coated metal soft magnetic material prepared by any one of claims 1-5, characterized in that: The material has a double-layer coating structure. On top of the oxide coating layer of the metal soft magnetic material, a multifunctional polysiloxane layer is further coated through in-situ reaction. The polysiloxane layer contains amino and epoxy active functional groups, and the molar ratio of each functional group is controlled by the amount of corresponding monomers added.

7. The application of the multifunctional polysiloxane-coated metal soft magnetic material as described in claim 6, characterized in that: This soft magnetic metallic material is used in the fields of inductors, sensors, transformers, and electromagnetic shielding.

Images