Low-temperature vitrified coated high-resistance soft magnetic powder and production process thereof

Abstract

The invention relates to low-temperature vitrified coated high-resistance soft magnetic powder and a production process thereof. The low-temperature vitrified coated high-resistance soft magnetic powder is prepared from the following raw materials in parts by mass: 80-100 parts of soft magnetic powder, 4-8 parts of low-melting-point glass powder, 0.5-3 parts of a silane coupling agent, 0.3-0.8 part of a nucleating agent, 0.2-0.5 part of an external field response component, 0.01-0.15 part of a thermal expansion adjusting component, 0.1-0.8 part of a lubricating agent and 0.1-0.4 part of a dispersing agent. The low-temperature vitrified coated high-resistance soft magnetic powder provided by the invention has high impedance matching performance and high and low temperature stability.

Description

Technical Field

[0001] This application relates to a microwave absorbing material, and more specifically, to a low-temperature vitrified high-resistivity soft magnetic powder, its production process, and its application. Background Technology

[0002] With the increasing demands for electromagnetic compatibility and stealth performance in fields such as aerospace, advanced electronic warfare, and high-end new energy, the preparation of low-temperature vitrifiable high-resistivity soft magnetic powders is becoming increasingly crucial. These powders must possess high surface resistivity to prevent circuit breakdown under high power, excellent impedance matching, and structural stability. They are indispensable in high-end applications such as stealth coatings for military aircraft, radar absorbing components, and high-frequency motor cores for new energy vehicles, effectively addressing the core pain points of traditional soft magnetic powders, such as low surface resistivity, insufficient high-temperature resistance, and insufficient insulation, which can easily lead to conductivity interference with equipment performance.

[0003] In existing technologies, the vitrification coating of soft magnetic powders often employs methods such as sol-gel and mechanical mixing sintering. However, these methods generally suffer from several significant technical problems: First, the coating uniformity is poor, easily resulting in localized areas of no coating, large thickness fluctuations, and powder agglomeration, leading to insufficient product performance consistency. Second, the significant difference in the thermal expansion coefficients between the soft magnetic powder and the glass coating layer generates interfacial thermal stress during cooling and use, causing cracking and peeling of the coating layer, severely affecting insulation stability and service life. Especially during large-scale preparation, uneven glass powder melting and powder agglomeration lead to deterioration, making it difficult to prepare soft magnetic powders with uniform glass powder molten coating.

[0004] To address the above problems, existing solutions mostly improve interfacial bonding by adding coupling agents and alleviate stress by optimizing sintering temperature curves. However, there are still obvious drawbacks: coupling agents are prone to decomposition and failure at high temperatures, which cannot fundamentally solve the problem of mismatched expansion coefficients. Traditional processes are difficult to accurately control the coating thickness, and agglomeration is not effectively suppressed, resulting in large fluctuations in powder surface resistance and poor microwave absorption performance.

[0005] Therefore, developing a high-performance, low-temperature vitrifiable coating technology for high-resistivity soft magnetic powder is both necessary and valuable for research and development. This technology can fill the gap in high-end applications for micron-sized soft magnetic powders with high consistency, insulation stability, high impedance matching, and high temperature resistance, significantly improving the electromagnetic compatibility and stealth performance of related equipment, and has broad application prospects. Summary of the Invention

[0006] In order to improve the wave absorption performance and high and low temperature stability of glass-insulated coated soft magnetic powder, this application provides a low-temperature vitrifiable coated high-resistivity soft magnetic powder and its production process.

[0007] In a first aspect, this application provides a low-temperature vitrifiable coated high-resistivity soft magnetic powder, comprising the following raw materials in parts by weight: 80-100 parts soft magnetic powder, 4-8 parts low-melting-point glass powder, 0.5-3 parts silane coupling agent, 0.3-0.8 parts nucleating agent, 0.2-0.5 parts external field response component, 0.01-0.15 parts thermal expansion regulating component, 0.1-0.8 parts lubricant, and 0.1-0.4 parts dispersant.

[0008] By taking the above steps, the soft magnetic powder constitutes a large proportion of the main phase, ensuring the core contribution of magnetic loss and avoiding excessive dilution of magnetic properties by glass powder. The low-melting-point glass powder can achieve a good balance between insulation coating and magnetism, forming a dense insulating layer without significantly reducing the saturation magnetization. The addition of a certain mass of silane coupling agent enhances the interfacial chemical bonding, the addition of a certain mass of nucleating agent induces glass microcrystallization, and the addition of a certain mass of external field response component balances external field response and performance. This allows the product preparation process to achieve micro-flow and stirring effects by applying an external field, promoting uniform coating of the glass phase medium. The magnetic and dielectric complementarity of the soft magnetic powder and glass powder, and the additive system is optimized from multiple dimensions such as interfacial bonding, structural regulation, and external field response, avoiding performance degradation caused by excessive single component. The product has a good glass phase coating effect, combining the impedance matching and insulation effects of glass-coated soft magnetic materials. At the same time, the coating is uniform, and it is not prone to cracking during cooling and use, resulting in stable performance.

[0009] Preferably, the external field response component includes cobalt-doped magnetic iron oxide.

[0010] By taking the above steps and adding a certain mass of magnetic iron oxide, a better response effect is achieved under a directional magnetic field. This can drive the glass powder and molten glass to disperse evenly, forming a more uniform coating layer with smaller fluctuations in coating thickness. The silane coupling agent is anchored on the Fe3O4 surface through Si-O-Fe bonds, and the other end forms a chemical bond with the Si-O network of the glass powder, preventing Fe3O4 from agglomerating and improving the adsorption force with the glass powder. The magnetic enhancement effect of Co doping and the interfacial compatibility effect of silane modification work synergistically, making the magnetic field response component a bridge between the external field and the glass powder. The glass powder coating is more uniform, and the product has better microwave absorption performance and more stable performance.

[0011] Preferably, the raw materials for preparing Co-doped magnetic iron oxide include Fe3O4 and Co(NO3)2·6H2O in a mass ratio of (50-70):1.

[0012] By taking the above steps, the Co content is appropriate, the magnetic permeability does not change significantly, and the magnetic response enhancement effect is obvious. At this ratio, there are sufficient active sites on the Fe3O4 surface, which reacts more fully with the silane coupling agent. The surface hydrophobicity is moderate, and it has both high magnetic response intensity and interfacial bonding stability.

[0013] Preferably, the field response component also includes MXene.

[0014] By taking the above steps, the layered structure of MXene provides high dielectric loss, which, in conjunction with the magnetic loss of the soft magnetic powder, optimizes impedance matching. At the same time, the local thermal deviation after the application of microwaves can better promote the uniform melting and coating effect of the glass powder. The above-mentioned microwave response of MXene and the magnetic field response of silane-modified Co-doped Fe3O4 form a "dual external field response system". The magnetic field orientation and microwave heating work together to improve the coating uniformity, and the dielectric and magnetic losses work together to enhance the microwave absorption performance. The performance of the low-temperature vitrifiable coated high-resistivity soft magnetic powder is further improved.

[0015] Preferably, the nucleating agent comprises zirconium dioxide and titanium dioxide in a mass ratio of 1:(1-2).

[0016] By taking the above steps, Zr 4+ Ti has strong nucleation ability. 4+ With precise crystallization control, the combined use induces the formation of certain nanocrystalline regions in the glass, resulting in a better match between the thermal expansion coefficient and the soft magnetic powder. At the same time, the degree of crystallization is appropriate, making the product stronger and less brittle.

[0017] Preferably, the mass ratio of MXene to cobalt-doped magnetic iron oxide is 1:(3-5).

[0018] By taking the above steps, at this ratio, the magnetic field response dominates to ensure the directional dispersion of glass powder, while MXene provides a small amount to supplement microwave absorption and dielectric loss, thus achieving both microwave absorption performance and uniform coating.

[0019] Preferably, the MXene particle size is 30-80 nm, and the cobalt-doped magnetic iron oxide particle size is 30-80 nm.

[0020] By taking the above steps, the particle sizes of the two particles are similar, and particle size matching avoids hierarchical agglomeration. During mixing, stratification will not occur due to density differences, thus improving dispersion uniformity. At the same time, the external field response sensitivity remains at a good level, which is suitable for the raw material settings of the system.

[0021] Synergistic effect: Particle size matching enables the dual external field response components to be uniformly distributed on the surface of the soft magnetic powder, and they can perform their functions synchronously under the action of the external field, avoiding performance fluctuations caused by local enrichment.

[0022] Preferably, the soft magnetic powder is an acidified soft magnetic powder, which includes the following preparation steps: adding the soft magnetic powder to a 0.3-0.5 wt% aqueous solution of phosphoric acid and stirring at 60-90°C for 20-40 minutes.

[0023] Secondly, this application provides a production process for a low-temperature vitrifiable coated high-resistivity soft magnetic powder, comprising the following preparation steps: weighing raw materials according to mass parts, mixing, nitrogen protection, applying a DC magnetic field and microwave, gradient heating, stirring, and obtaining the powder.

[0024] Preferably, the gradient heating includes the following steps: heating at 4-5℃ / min to 280-300℃, holding for 4-6 min, heating at 2-3℃ / min to 490-500℃, holding for 12-15 min, heating at 1-2℃ / min to 350℃, holding for 5-8 min; and cooling down to room temperature at 1-2℃ / min.

[0025] Preferably, the DC magnetic field strength is 0.1-0.3T and the microwave power is 300-500W.

[0026] By adopting the above steps, the preparation process is relatively simple. Nitrogen protection prevents oxidation of the soft magnetic powder. A DC magnetic field drives the Co-doped Fe3O4 to be oriented, resulting in uniform coating of the glass powder. Microwaves, through MXene absorption, achieve localized heating, leading to higher glass melting uniformity. Under gradient heating conditions, the dispersant is thoroughly removed to avoid residual carbon. The glass melts, and the amorphous structure of the soft magnetic powder is relatively stable. Slow cooling releases internal stress, and the glass coating layer does not produce obvious defects. The product is uniform, stable, and has a reasonable structure.

[0027] In summary, this application has the following beneficial effects: This application utilizes dual external field components with magnetic and microwave responses to achieve a superior structural control effect with nucleating agents and thermal expansion regulating components, simultaneously improving interfacial bonding, structural stability, and insulation. A better balance between expansion matching and stress release is achieved through control of microcrystalline effects and gradient temperature control. The final product exhibits a variety of excellent properties, including high magnetic properties, superior insulation, wideband strong microwave absorption, and stability in extreme environments, making it suitable for various applications such as high-frequency electronic devices, electromagnetic shielding, and microwave absorbing materials. Attached Figure Description

[0028] Figure 1 This is a simplified schematic diagram of the low-temperature vitrifiable coating high-resistivity soft magnetic powder of this application. Detailed Implementation

[0029] To further aid in understanding the technical solution of this invention, several specific implementation examples are provided below to describe the technical solution of this invention in more detail. All of these described embodiments are only some embodiments of this invention, and not all of them. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments; and the reaction devices, monomer compounds, etc. involved in the following embodiments are all commercially available.

[0030] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0031] The following examples are further illustrations of the present invention, but the present invention is not limited thereto.

[0032] Iron-silicon-aluminum magnetic powder (85 wt% Fe, 9 wt% Si, 6 wt% Al) was purchased from Zhejiang Keda Magnetoelectric Co., Ltd. (KS039-125A); low-melting-point glass powder was purchased from Anmi Micro-Nano (D240); and titanium dioxide was purchased from SunChemical. WHITE 0022K; magnetic iron oxide was purchased from Jiupeng CY-EF05; nano magnesium oxide was purchased from Jinghuang JH-348-D30n-B40; zirconium dioxide was purchased from Lanabai lnb-1135; MXene was purchased from Xianfeng Nano XFK01; zinc stearate was purchased from Singapore San Yi SUNACE SAK-ZS-PLB.

[0033] Preparation Example 1: Co-doped magnetic iron oxide 30g of magnetic iron oxide was dispersed in 1500mL of anhydrous ethanol, sonicated at 300W and 40kHz for 10min, 0.6g of Co(NO3)2·6H2O was added, stirred at 50℃ for 30min, centrifuged at 8000r / min for 10min, and vacuum dried at 60℃ for 3h to obtain Co-doped magnetic iron oxide.

[0034] Preparation Example 2: Co-doped magnetic iron oxide 30g of magnetic iron oxide was dispersed in 1500mL of anhydrous ethanol, sonicated at 300W and 40kHz for 10min, 0.4g of Co(NO3)2·6H2O was added, stirred at 50℃ for 30min, centrifuged at 8000r / min for 10min, and vacuum dried at 60℃ for 3h to obtain Co-doped magnetic iron oxide.

[0035] Preparation Example 3: Co-doped magnetic iron oxide 30g of magnetic iron oxide was dispersed in 1500mL of anhydrous ethanol, sonicated at 300W and 40kHz for 10min, 0.9g of Co(NO3)2·6H2O was added, stirred at 50℃ for 30min, centrifuged at 8000r / min for 10min, and vacuum dried at 60℃ for 3h to obtain Co-doped magnetic iron oxide.

[0036] Preparation Example 4: Acidified iron-silicon-aluminum magnetic powder: Iron-silicon-aluminum magnetic powder was added to a 0.4 wt% phosphoric acid aqueous solution, stirred at 70°C for 30 minutes, filtered, washed with water, and dried to obtain acidified iron-silicon-aluminum magnetic powder.

[0037] Preparation Example 5: Acidified iron-silicon-aluminum magnetic powder: Iron-silicon-aluminum magnetic powder was added to a 0.4 wt% phosphoric acid aqueous solution, stirred at 25°C for 10 minutes, filtered, washed with water, and dried to obtain acidified iron-silicon-aluminum magnetic powder. Example

[0038] Example 1 Raw material preparation: 100g iron-silicon-aluminum magnetic powder, 6g low melting point glass powder, 1g silane coupling agent KH560, 0.4g titanium dioxide, 0.4g Co-doped magnetic iron oxide prepared in Preparation Example 1, 0.1g nano magnesium oxide, 0.5g zinc stearate, and 0.2g PEG-400.

[0039] Production process: The raw materials weighed according to the mass ratio are mixed evenly, under nitrogen protection, a DC magnetic field and microwave are applied, the DC magnetic field strength is 0.3T and the microwave power is 400W, the temperature is raised and stirred to react, the temperature is raised to 280℃ at 5℃ / min and held for 5min, the temperature is raised to 490℃ at 3℃ / min and held for 12min, the temperature is raised to 350℃ at 2℃ / min and held for 6min; the temperature is lowered to room temperature at 1℃ / min to obtain a low-temperature vitrifiable coated high-resistivity soft magnetic powder.

[0040] Example 2 The only difference between this embodiment and Example 1 is that the Co-doped magnetic iron oxide was prepared in Example 2.

[0041] Example 3 The only difference between this embodiment and Example 1 is that the Co-doped magnetic iron oxide was prepared in Example 3.

[0042] Example 4 The only difference between this embodiment and Example 1 is the following raw materials: 100g of iron-silicon-aluminum magnetic powder, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.4g of titanium dioxide, 0.3g of Co-doped magnetic iron oxide prepared in Example 1, 0.1g of MXene, 0.1g of nano-magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0043] Example 5 The only difference between this embodiment and Example 1 is the following raw materials: 100g of iron-silicon-aluminum magnetic powder, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.4g of titanium dioxide, 0.1g of Co-doped magnetic iron oxide obtained in Preparation Example 1, 0.3g of MXene, 0.1g of nano-magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0044] Example 6 The only difference between this embodiment and Example 1 is the raw materials: 100g of iron-silicon-aluminum magnetic powder, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.4g of titanium dioxide, 0.4g of MXene, 0.1g of nano magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0045] Example 7 The only difference between this embodiment and Example 1 is the following raw materials: 100g of iron-silicon-aluminum magnetic powder, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.2g of titanium dioxide, 0.2g of zirconium dioxide, 0.3g of Co-doped magnetic iron oxide obtained in Preparation Example 1, 0.1g of MXene, 0.1g of nano-magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0046] Example 8 The only difference between this embodiment and Example 1 is the following raw materials: 100g of iron-silicon-aluminum magnetic powder, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.4g of zirconium dioxide, 0.3g of Co-doped magnetic iron oxide prepared in Example 1, 0.1g of MXene, 0.1g of nano-magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0047] Example 9 The only difference between this embodiment and Example 1 is the raw materials: 100g of iron-silicon-aluminum magnetic powder prepared in Example 4, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.2g of titanium dioxide, 0.2g of zirconium dioxide, 0.3g of Co-doped magnetic iron oxide prepared in Example 1, 0.1g of MXene, 0.1g of nano-magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0048] Example 10 The only difference between this embodiment and Example 1 is the raw materials: 100g of iron-silicon-aluminum magnetic powder prepared in Example 5, 6g of low-melting-point glass powder, 1g of silane coupling agent KH560, 0.2g of titanium dioxide, 0.2g of zirconium dioxide, 0.3g of Co-doped magnetic iron oxide prepared in Example 1, 0.1g of MXene, 0.1g of nano-magnesium oxide, 0.5g of zinc stearate, and 0.2g of PEG-400.

[0049] Comparative Example Comparative Example 1 Raw material preparation: 100g iron-silicon-aluminum magnetic powder, 6g low melting point glass powder, 1g silane coupling agent KH560, 0.4g titanium dioxide, 0.4g magnetic iron oxide, 0.1g nano magnesium oxide, 0.5g zinc stearate, 0.2g PEG-400.

[0050] Production process: The raw materials weighed according to the mass ratio are mixed evenly, under nitrogen protection, a DC magnetic field and microwave are applied, the DC magnetic field strength is 0.3T and the microwave power is 400W, the temperature is raised and stirred to react, the temperature is raised to 280℃ at 5℃ / min and held for 5min, the temperature is raised to 490℃ at 3℃ / min and held for 12min, the temperature is raised to 350℃ at 2℃ / min and held for 6min; the temperature is lowered to room temperature at 1℃ / min to obtain a low-temperature vitrifiable coated high-resistivity soft magnetic powder.

[0051] Performance testing test 1: The peak reflectivity of the 2mm thick product in the 2-18GHz frequency band was tested according to the test standard GJB2038A-2011. The test results are summarized in Table 1. Test 2: Measuring the equilibrium dielectric constant ε r With permeability μ r Calculate the matching coefficient ε corresponding to the free space impedance. r The results are summarized in Table 1.

[0052] Test 3: Place the product in a high and low temperature alternating test chamber, raise the temperature from room temperature to 300℃ at a rate of 5℃ / min, hold for 30min, then introduce a -50℃ dry ice gas stream, lower the temperature at a rate ≥20℃ / min, hold for 30min, and after a total of 50 cycles, test the surface ε. r / μ', observe the appearance under a microscope.

[0053] Table 1 Combined with Examples 1-3 and Comparative Example 1 and Table 1, it can be seen that the product of this application has good microwave absorption performance, is resistant to rapid cooling and heating, and the appropriate amount of Co doping does not lead to obvious lattice distortion. The structure is stable after rapid cooling and heating, and the matching coefficient increases little.

[0054] As can be seen from Examples 1, 4-6 and Table 1, adding a certain mass ratio of MXene to supplement dielectric loss results in good matching coefficient and microwave absorption performance; the microwave heating effect of MXene makes the coating layer more uniform, and the matching coefficient increases less after rapid cooling and heating.

[0055] As can be seen from Examples 1 and 7-8 and Table 1, this application induces the formation of microcrystalline regions in the glass phase through composite nucleating agents. The difference between the thermal expansion coefficient and FeSiAl is small, the matching coefficient is suitable, the microwave absorption performance is good, the thermal expansion matching is excellent, and the matching coefficient only increases less after rapid cooling and heating.

[0056] As can be seen from Examples 1, 9-10 and Table 1, this application exhibits better interfacial bonding and a more stable interfacial chemical network through appropriate phosphoric acid treatment. In contrast, Example 10 may have resulted in a loose interface, leading to slight peeling of the passivation layer after rapid cooling and heating.

[0057] The structures of Examples 2, 4, 7, and 8 are relatively stable, with small increases in the matching coefficient due to excellent thermal expansion matching and tight interfacial chemical bonds. Examples 3, 5, 6, 10, and Comparative Example 1 have structural defects due to lattice distortion, uneven coating, or poor interfacial bonding, which lead to ε-strain caused by rapid cooling and heating. r As μ' increases, the matching coefficient deteriorates.

[0058] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A low-temperature vitrifiable high-resistivity soft magnetic powder, characterized in that: The raw materials include the following components by weight: 80-100 parts soft magnetic powder, 4-8 parts low melting point glass powder, 0.5-3 parts silane coupling agent, 0.3-0.8 parts nucleating agent, 0.2-0.5 parts external field response component, 0.01-0.15 parts thermal expansion regulating component, 0.1-0.8 parts lubricant, and 0.1-0.4 parts dispersant.

2. The low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 1, characterized in that: The soft magnetic powder is an acidified soft magnetic powder, which includes the following preparation steps: adding the soft magnetic powder to a 0.3-0.5 wt% phosphoric acid aqueous solution and stirring at 60-90℃ for 20-40 minutes.

3. The low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 1, characterized in that: The external field response component includes cobalt-doped magnetic iron oxide.

4. The low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 3, characterized in that: The raw materials for preparing the Co-doped magnetic iron oxide include Fe3O4 and Co(NO3)2·6H2O in a mass ratio of (50-70):

1.

5. The low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 3, characterized in that: The field response component also includes MXene.

6. The low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 1, characterized in that: The nucleating agent comprises zirconium dioxide and titanium dioxide in a mass ratio of 1:(1-2).

7. The preparation steps of a low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 5, characterized in that: The mass ratio of MXene to cobalt-doped magnetic iron oxide is 1:(3-5).

8. A production process for low-temperature vitrifiable coated high-resistivity soft magnetic powder according to any one of claims 1-7, characterized in that: The preparation process includes the following steps: weighing the raw materials according to their mass percentages, mixing them, protecting them with nitrogen, applying a DC magnetic field and microwave, gradually increasing the temperature, stirring, and obtaining the final product.

9. The production process of low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 8, characterized in that: The gradient heating process includes the following steps: heating at 4-5℃ / min to 280-300℃, holding for 4-6 min, heating at 2-3℃ / min to 490-500℃, holding for 12-15 min, heating at 1-2℃ / min to 350℃, holding for 5-8 min, and cooling down to room temperature at 1-2℃ / min.

10. The production process of low-temperature vitrifiable coated high-resistivity soft magnetic powder according to claim 9, characterized in that: The DC magnetic field strength is 0.1-0.3T, and the microwave power is 300-500W.

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