Soft magnetic composite material and preparation method and application thereof

Abstract

The invention provides a soft magnetic composite material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing alloy powder with a chlorine salt solution to obtain a mixture; the mixture is dried, and coated powder is obtained; the coated powder and a binder are mixed and cured, and then cured powder is obtained; and sequentially carrying out compression molding and annealing treatment on the cured powder to obtain the soft magnetic composite material. According to the preparation method, the alloy powder is etched by the chlorine salt at a high temperature, so that insulation coating of the surfaces of alloy powder particles is realized, and the soft magnetic composite material with high direct current bias performance and high frequency stability is obtained.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic materials technology, and relates to a soft magnetic composite material, its preparation method and application. Background Technology

[0002] With the rapid development of the new energy field, electronic devices are constantly evolving towards miniaturization, high frequency, and low loss. Soft magnetic materials, as common component materials, primarily undertake important functions such as energy conversion and filtering. To meet the ever-increasing performance requirements of electronic devices, soft magnetic materials need to possess comprehensive properties such as high magnetic flux density, low high-frequency loss, and good DC bias performance. Compared to traditional soft magnetic alloys, soft magnetic composite materials have advantages such as three-dimensional isotropy, high permeability, and low loss, making them one of the most promising soft magnetic materials currently available. Soft magnetic composite materials effectively suppress large eddy currents between alloy particles by insulating the surface of the soft magnetic alloy, thereby maintaining excellent high-frequency performance and low power loss. Currently, research and development of soft magnetic composite materials mainly focus on controlling high permeability and low loss, with research emphasis on the selection of coating layer types and the optimization of coating processes.

[0003] While common soft magnetic composite materials possess advantages such as high permeability and low loss, their DC bias performance is not excellent. The key issue is that the DC bias performance of soft magnetic materials measures their ability to withstand DC bias fields, primarily depending on the saturation magnetization of the magnetic powder, the magnetic anisotropy field, and the air gap distribution of the powder core. However, in conventional soft magnetic composite materials, the coating layer mainly serves as electrical insulation, offering limited control over the magnetic domain structure between powder particles. Therefore, soft magnetic composite materials are significantly limited in applications requiring high DC bias performance. Developing a soft magnetic composite material and its preparation method that effectively improves DC bias characteristics while maintaining good high-frequency soft magnetic properties is of great significance.

[0004] For example, CN113560570A discloses a method for preparing an iron-silicon-aluminum-nickel powder core. This method involves preparing alloy magnetic powder with high saturation magnetization through mechanical ball milling and high-temperature solution treatment. Subsequently, nano-silica is applied to the surface for insulating coating, ultimately achieving a synergistic improvement in both high saturation magnetic polarization and high DC bias performance. Another example is CN118248450A, which discloses a low-loss, high DC bias FeSi soft magnetic composite material and its preparation method. This method involves ball milling FeSi powder and FeSiAl powder to obtain a core-shell FeSi@FeSiAl composite powder. The composite powder is then subjected to insulating treatment, successfully preparing a soft magnetic composite material with both high permeability and low loss. In addition, CN115116689A discloses a low-loss and high DC bias magnetic powder core and its preparation method. The process involves pretreating the magnetic powder with phosphoric acid and organosilicon resin to obtain intermediate powder, then treating it with chromic acid, and finally adding water glass and binder for pressing and molding. Through this inorganic-organic multilayer coating structure, the stability and uniformity of the insulation layer are ensured, and the final magnetic core has high permeability, good DC superposition performance and low loss.

[0005] While the methods disclosed in the prior art can improve DC bias performance to some extent, they still have problems such as limited improvement in bias performance, complex preparation process, and difficulty in controlling the stability and uniformity of multilayer coating structure. In order to address these shortcomings, it is necessary to develop a simple preparation method that can significantly improve the DC bias characteristics of soft magnetic composite materials and maintain excellent high-frequency magnetic properties. Summary of the Invention

[0006] The purpose of this invention is to provide a soft magnetic composite material, its preparation method and application. The preparation method utilizes the etching effect of molten chloride salt on alloy powder at high temperature to achieve insulating coating on the surface of alloy powder particles, thereby obtaining a soft magnetic composite material with both high DC bias performance and high frequency stability.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a soft magnetic composite material, the method comprising the following steps:

[0009] (1) Mix the alloy powder with a chloride salt solution to obtain a mixture;

[0010] (2) The mixture described in step (1) is dried to obtain a coated powder;

[0011] (3) After mixing and curing the coating powder described in step (2) with the binder, a cured powder is obtained;

[0012] (4) The cured powder described in step (3) is pressed and annealed in sequence to obtain the soft magnetic composite material.

[0013] The preparation method of the present invention first mixes and dries the alloy powder with a chloride solution to achieve chloride coating. The chloride can achieve controlled corrosion of the alloy powder surface at high temperature. The mechanism is mainly that the corrosion of the alloy powder by the molten chloride is a self-continuous process and the corrosion is penetrating, which can penetrate the oxide protective layer on the alloy surface to make the reaction continue. This corrosion reaction needs to be activated at high temperature, so that the etching of the alloy powder can be completed simultaneously during the annealing process. In addition, since the etching product contains highly insulating oxides, the surface of the alloy powder is insulated during the etching process, thereby obtaining a soft magnetic composite material with both high frequency stability and high DC bias performance.

[0014] It is worth noting that under low temperature and dry conditions, the corrosion of alloy powder by chloride salts is negligible and has a limited impact on the service life of the device.

[0015] Preferably, the chloride salt in the chloride salt solution in step (1) is 0.075wt%-1.5wt% of the alloy powder mass, for example, it can be 0.075wt%, 0.1wt%, 0.25wt%, 0.5wt%, 0.75wt%, 1wt%, 1.25wt% or 1.5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.15wt%-1.5wt%.

[0016] This invention can effectively control the corrosion rate and depth of alloy powder by controlling the amount of chloride coating, thereby achieving targeted regulation of the comprehensive performance of soft magnetic composite materials. During high-temperature corrosion, some chlorine will be discharged in gaseous form; a higher amount of chloride coating can provide a more sufficient chlorine source, thus ensuring that the corrosion reaction continues and is fully carried out, resulting in a faster corrosion rate and a deeper degree of corrosion. However, if the amount of chloride coating is too high, the excessive amount of chloride will over-erode the magnetic powder matrix, causing an excessively thick corrosion layer to form on the surface of the magnetic powder particles. This not only increases the magnetic dilution effect but also reduces the effective permeability of the magnetic core, leading to increased hysteresis loss.

[0017] Preferably, the chloride salt in the chloride salt solution in step (1) includes stannous chloride dihydrate.

[0018] The chloride salt used in this invention is stannous chloride, which melts at a lower temperature than other chloride salts, forming a uniform liquid phase coating on the alloy powder surface and ensuring the uniformity of the corrosion reaction. Simultaneously, the matrix can be oxidized to Sn during the corrosion reaction. 4+It forms a highly insulating SnO2 coating layer; on the other hand, Fe and Si in the matrix also form oxide layers on the particle surface during the corrosion process, ultimately achieving integrated synergy of 'etching-film formation'.

[0019] Preferably, the solvent in the chloride salt solution in step (1) includes anhydrous ethanol.

[0020] Preferably, the mass ratio of the solvent to the alloy powder in the chloride salt solution in step (1) is 1:(1.8-2.2), for example, it can be 1:1.8, 1:1.9, 1:2.0, 1:2.1 or 1:2.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the alloy powder in step (1) comprises Fe-Si based alloy powder.

[0022] Preferably, the silicon content in the Fe-Si based alloy powder is 3wt%-6.5wt%, for example, it can be 3wt%, 4wt%, 5wt%, 6wt% or 6.5wt%, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the alloy powder in step (1) has a mesh size of 160-700 mesh, for example, it can be 160 mesh, 200 mesh, 300 mesh, 400 mesh, 500 mesh, 600 mesh or 700 mesh, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the temperature at which the alloy powder is mixed with the chloride solution in step (1) is 20℃-30℃, for example, 20℃, 22℃, 24℃, 26℃, 28℃ or 30℃, and the time is 0.5h-3h, for example, 0.5h, 1h, 1.5h, 2h or 3h, and the stirring rate is ≤500rpm, for example, 500rpm, 450rpm, 400rpm, 350rpm, 300rpm or 250rpm, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the drying temperature in step (2) is 80℃-120℃, for example, it can be 80℃, 90℃, 100℃, 110℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the drying time in step (2) is ≤12h, for example, it can be 12h, 10h, 8h, 6h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the coating powder in step (2) is pre-oxidized before step (3).

[0028] To reduce the impact of chloride residue on device stability in certain special scenarios, this invention also pre-oxidizes the coating powder, performs preliminary etching in air, and removes most of the chlorine.

[0029] Preferably, the temperature of the pre-oxidation treatment is 200℃-500℃, for example, 200℃, 300℃, 400℃ or 500℃, and the time is ≤2h, for example, 2h, 1.5h, 1h or 0.5h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the atmosphere for the pre-oxidation treatment is an oxygen atmosphere or an air atmosphere.

[0031] Preferably, the adhesive in step (3) comprises an epoxy resin solution.

[0032] Preferably, the epoxy resin solution includes epoxy resin and organic solvent.

[0033] Preferably, the epoxy resin is 0.5wt%-3wt% of the alloy powder mass, for example, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] This invention controls the amount of binder added by controlling the content of epoxy resin in the epoxy resin solution, thereby controlling the performance of the soft magnetic composite material. On the one hand, the decomposition of epoxy resin at high temperature introduces impurities such as H2O, promoting the corrosion reaction driven by impurities. On the other hand, its addition amount directly affects the pressing performance of magnetic powder, and the gas generated by decomposition affects the microstructure of the magnetic powder core, introducing more air gaps, which helps to improve DC bias performance.

[0035] Preferably, the mass ratio of the organic solvent in the epoxy resin solution to the coating powder in step (2) is 1:(0.8-1.2), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1 or 1:1.2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the organic solvent includes acetone.

[0037] Preferably, the temperature at which the coating powder and the binder are mixed in step (2) is 40℃-50℃, for example, 40℃, 42℃, 44℃, 46℃, 48℃ or 50℃, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, in step (2), the coating powder and the binder are mixed until the organic solvent in the binder is evaporated.

[0039] Preferably, the curing temperature in step (3) is 90℃-110℃, for example, 90℃, 95℃, 100℃, 105℃ or 110℃, and the time is ≤3h, for example, 3h, 2.5h, 2h, 1.5h or 1h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the pressing pressure in step (4) is 1GPa-2GPa, for example, it can be 1GPa, 1.2GPa, 1.4GPa, 1.6GPa, 1.8GPa or 2GPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the annealing temperature in step (4) is 400℃-800℃, for example, it can be 400℃, 500℃, 600℃, 700℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 600℃-800℃.

[0042] The annealing temperature described in this invention affects the performance of soft magnetic composite materials. Since the chloride corrosion process is controlled by the mass diffusion rate, the corrosion rate increases exponentially with increasing temperature. Higher temperatures can achieve deeper etching, potentially resulting in higher DC bias performance even with lower chloride coating. However, excessively high annealing temperatures and rapid reaction rates can lead to uneven corrosion and localized over-corrosion areas. Furthermore, some chlorine rapidly vaporizes at high temperatures, significantly reducing its effective contact time on the substrate surface, thus weakening the corrosion effect and hindering the uniform formation of the insulating layer. In addition, excessively high annealing temperatures can cause irreversible changes in the magnetic domain structure of the iron-silicon alloy, resulting in a decrease in magnetic properties.

[0043] Preferably, the annealing holding time in step (4) is 1h-8h, for example, it can be 1h, 3h, 5h, 7h or 8h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the annealing atmosphere in step (4) includes an inert atmosphere.

[0045] In a second aspect, the present invention provides a soft magnetic composite material, which is prepared by the preparation method described in the first aspect.

[0046] Thirdly, the present invention provides an application of a soft magnetic composite material, including its use in electronic devices.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention uses molten chloride coating to achieve controllable corrosion of alloy powder. Unlike traditional processes such as phosphoric acid passivation, this corrosion process is a self-circulating reaction that can continue under suitable conditions. The corrosion products can directly form a uniform insulating layer, which can significantly improve the DC bias performance of the magnetic powder core and also greatly improve its high-frequency magnetic properties.

[0049] (2) The process of the present invention is simple, the raw materials are readily available, and there is no need for multiple coatings or large amounts of additives, which effectively reduces production costs. In addition, the process has low requirements for the uniformity of the coating layer, and only depends on the distribution and reaction state of the molten chloride salt, which has good process stability and scalability.

[0050] (3) The present invention can control the corrosion rate and residual amount of chloride ions by adjusting parameters such as annealing temperature and reaction atmosphere; it can also adjust the amount of chloride salt added to regulate the degree of reaction, thereby realizing the directional control of DC bias performance of soft magnetic composite materials and adapting to the needs of different application scenarios. Attached Figure Description

[0051] Figure 1 The graph shows a comparison of the magnetic properties of the soft magnetic composite materials obtained in Examples 1-5, Comparative Example 1, and Comparative Example 2 of this invention.

[0052] Figure 2 This is a comparison diagram of the magnetic properties of the soft magnetic composite materials obtained in Examples 1 and 6-9 of the present invention.

[0053] Figure 3 This is a comparison diagram of the magnetic properties of the soft magnetic composite materials obtained in Examples 1 and 10-13 of the present invention.

[0054] Figure 4 This is a cross-sectional SEM image of the soft magnetic composite material obtained in Example 1 of the present invention.

[0055] Figure 5 The images shown are XRD patterns before and after annealing after the material is pressed and molded according to the preparation method described in Example 1 of this invention. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] Example 1

[0058] This embodiment provides a method for preparing a soft magnetic composite material, the method comprising the following steps:

[0059] (1) Dissolve stannous chloride dihydrate completely in anhydrous ethanol to obtain stannous chloride ethanol solution;

[0060] The stannous chloride dihydrate is 0.15 wt% of the Fe-Si based alloy powder in step (2), and the mass ratio of the anhydrous ethanol to the Fe-Si based alloy powder in step (2) is 1:2.

[0061] (2) Add 300-mesh Fe-Si based alloy powder (silicon content of 6.5wt%) to stannous chloride ethanol solution, and mechanically stir at 25°C for 1 h with the mechanical stirring speed set to 500 rpm to obtain a mixture;

[0062] (3) Place the mixture from step (2) in an oven to dry at 100°C for 3 hours to obtain coated powder;

[0063] (4) Dissolve the epoxy resin in acetone solution to obtain epoxy resin acetone solution, wherein the epoxy resin is 1 wt% of the Fe-Si based alloy powder in step (2).

[0064] Add the coating powder described in step (3) to the epoxy resin acetone solution and stir with ultrasonic assistance at 50°C until the solution is completely evaporated. The mass ratio of acetone to coating powder is 1:1.

[0065] (5) The powder obtained in step (4) is cured by placing it in a vacuum drying oven, setting the curing temperature at 100℃ and the curing time at 3h.

[0066] (6) The cured powder is pressed into shape at a pressure of 1.6 GPa and a holding time of 1 min; then it is annealed in an argon atmosphere to obtain the soft magnetic composite material, wherein the annealing temperature is 700℃ and the holding time is 2 h.

[0067] Example 2

[0068] This embodiment provides a method for preparing a soft magnetic composite material. The preparation method is the same as in Example 1, except that the stannous chloride dihydrate in step (1) is 0.075 wt% of the Fe-Si based alloy powder in step (2).

[0069] Example 3

[0070] This embodiment provides a method for preparing a soft magnetic composite material. The preparation method is the same as in Example 1, except that the stannous chloride dihydrate in step (1) is 0.3 wt% of the Fe-Si based alloy powder in step (2).

[0071] Example 4

[0072] This embodiment provides a method for preparing a soft magnetic composite material. The preparation method is the same as in Example 1, except that the stannous chloride dihydrate in step (1) is 0.6 wt% of the Fe-Si based alloy powder in step (2).

[0073] Example 5

[0074] This embodiment provides a method for preparing a soft magnetic composite material. The preparation method is the same as in Example 1, except that the stannous chloride dihydrate in step (1) is 1.5 wt% of the Fe-Si based alloy powder in step (2).

[0075] Example 6

[0076] This embodiment provides a method for preparing a soft magnetic composite material. Except that the epoxy resin in step (4) is 0.5 wt% of the Fe-Si based alloy powder in step (2), the preparation method is the same as in Example 1.

[0077] Example 7

[0078] This embodiment provides a method for preparing a soft magnetic composite material. Except that the epoxy resin in step (4) is 1.5 wt% of the Fe-Si based alloy powder in step (2), the preparation method is the same as in Example 1.

[0079] Example 8

[0080] This embodiment provides a method for preparing a soft magnetic composite material. Except that the epoxy resin in step (4) is 2 wt% of the Fe-Si based alloy powder in step (2), the preparation method is the same as in Example 1.

[0081] Example 9

[0082] This embodiment provides a method for preparing a soft magnetic composite material. Except that the epoxy resin in step (4) is 3 wt% of the Fe-Si based alloy powder in step (2), the preparation method is the same as in Example 1.

[0083] Example 10

[0084] This embodiment provides a method for preparing a soft magnetic composite material. Except for the annealing temperature of 500°C in step (6), the preparation method is the same as that in Example 1.

[0085] Example 11

[0086] This embodiment provides a method for preparing a soft magnetic composite material. Except for the annealing temperature of 550°C in step (6), the preparation method is the same as that in Example 1.

[0087] Example 12

[0088] This embodiment provides a method for preparing a soft magnetic composite material. Except for the annealing temperature of 600°C in step (6), the preparation method is the same as that in Example 1.

[0089] Example 13

[0090] This embodiment provides a method for preparing a soft magnetic composite material. Except for the annealing temperature of 800°C in step (6), the preparation method is the same as that in Example 1.

[0091] Example 14

[0092] This embodiment provides a method for preparing a soft magnetic composite material. Except for step (3), in which the coated powder is pre-oxidized before step (4), specifically by placing the coated powder in a muffle furnace and holding it at 400°C for 0.5 hours in an air atmosphere, the preparation method is the same as in Example 1.

[0093] Example 15

[0094] This embodiment provides a method for preparing a soft magnetic composite material, the method comprising the following steps:

[0095] (1) Dissolve stannous chloride dihydrate completely in anhydrous ethanol to obtain stannous chloride ethanol solution;

[0096] The stannous chloride dihydrate is 0.15 wt% of the Fe-Si based alloy powder in step (2), and the mass ratio of the anhydrous ethanol to the Fe-Si based alloy powder in step (2) is 1:1.8.

[0097] (2) Add 160-300 mesh Fe-Si based alloy powder (silicon content of 6.5wt%) to stannous chloride ethanol solution, and mechanically stir at 30°C for 0.5h with the mechanical stirring speed set to 500rpm to obtain a mixture;

[0098] (3) Place the mixture from step (2) in an oven to dry at 120°C for 10 hours to obtain coated powder;

[0099] (4) Dissolve the epoxy resin in acetone solution to obtain epoxy resin acetone solution, wherein the epoxy resin is 1 wt% of the Fe-Si based alloy powder in step (2).

[0100] Add the coating powder described in step (3) to the epoxy resin acetone solution and stir with ultrasonic assistance at 40°C until the solution is completely evaporated. The mass ratio of acetone to coating powder is 1:0.8.

[0101] (5) The powder obtained in step (4) is cured by placing it in a vacuum drying oven, setting the curing temperature at 110°C and the curing time at 2 hours.

[0102] (6) The cured powder is pressed into shape at a pressure of 1 GPa and a holding time of 1 min; then it is annealed in an argon atmosphere to obtain the soft magnetic composite material, wherein the annealing temperature is 700℃ and the holding time is 1 h.

[0103] Example 16

[0104] This embodiment provides a method for preparing a soft magnetic composite material, the method comprising the following steps:

[0105] (1) Dissolve stannous chloride dihydrate completely in anhydrous ethanol to obtain stannous chloride ethanol solution;

[0106] The stannous chloride dihydrate is 0.15 wt% of the Fe-Si based alloy powder in step (2), and the mass ratio of the anhydrous ethanol to the Fe-Si based alloy powder in step (2) is 1:2.2.

[0107] (2) Fe-Si based alloy powder (silicon content of 6.5wt%) that can pass through an 800-mesh sieve is added to the stannous chloride ethanol solution and mechanically stirred at 20°C for 3 hours with a mechanical stirring speed of 400 rpm to obtain a mixture;

[0108] (3) Place the mixture from step (2) in an oven to dry at 80°C for 12 hours to obtain coated powder;

[0109] (4) Dissolve the epoxy resin in acetone solution to obtain epoxy resin acetone solution, wherein the epoxy resin is 1 wt% of the Fe-Si based alloy powder in step (2).

[0110] Add the coating powder described in step (3) to the epoxy resin acetone solution and stir with ultrasonic assistance at 50°C until the solution is completely evaporated. The mass ratio of acetone to coating powder is 1:1.2.

[0111] (5) The powder obtained in step (4) is cured by placing it in a vacuum drying oven, setting the curing temperature at 90°C and the curing time at 3 hours.

[0112] (6) The cured powder is pressed into shape at a pressure of 1.6 Gpa and a holding time of 1 min; then it is annealed in an argon atmosphere to obtain the soft magnetic composite material, wherein the annealing temperature is 700℃ and the holding time is 6 h.

[0113] Comparative Example 1

[0114] This comparative example provides a method for preparing a soft magnetic composite material. The preparation method is the same as that in Example 1 except that steps (1)-(3) are omitted and Fe-Si based alloy powder is directly subjected to steps (4)-(6).

[0115] Comparative Example 2

[0116] This comparative example provides a method for preparing a soft magnetic composite material. The preparation method is the same as in Example 1, except that the concentration of stannous chloride ethanol solution is replaced with phosphoric acid solution.

[0117] The magnetic properties of the soft magnetic composite materials obtained in Examples 1-5, Comparative Example 1, and Comparative Example 2 are compared as follows: Figure 1 As shown, Figure 1 The left side shows the effective permeability of the soft magnetic composite materials obtained in Examples 1-5, Comparative Examples 1 and 2 at different frequencies, and the right side shows the DC bias performance; the magnetic properties comparison diagram of the soft magnetic composite materials obtained in Examples 1 and 6-9 is shown above. Figure 2 As shown, Figure 2 The left side shows the effective permeability of the soft magnetic composite materials obtained in Examples 1 and 6-9 at different frequencies, and the right side shows the DC bias performance. Figure 3 This is a comparison diagram of the magnetic properties of the soft magnetic composite materials obtained in Examples 1 and 10-13 of the present invention. Figure 3 The left side shows the effective permeability of the soft magnetic composite materials obtained in Examples 1 and 10-13 at different frequencies, and the right side shows the DC bias performance. Figures 1-3The comparison shows that the soft magnetic composite materials obtained in Examples 1-13 possess excellent magnetic properties; the cross-sectional SEM images of the soft magnetic composite material obtained in Example 1 are shown below. Figure 4 As shown (from left to right: 20μm scale, 5μm scale, and 1μm scale); Figure 5 The images shown are XRD patterns before and after annealing after the material is pressed and molded according to the preparation method described in Example 1 of this invention.

[0118] The effective permeability of the soft magnetic composite materials obtained in the above embodiments and comparative examples at 50 kHz, the effective permeability at 2 MHz, and the DC bias performance are shown in Table 1:

[0119] Table 1

[0120]

[0121] As can be seen from Table 1 above:

[0122] (1) As can be seen from Examples 1-16, the present invention uses chloride salt coating, which can achieve controllable corrosion on the surface of alloy powder at high temperature and simultaneously form a complete insulating layer on its surface, so that the soft magnetic composite material can maintain good high-frequency magnetic properties while significantly improving DC bias performance; As can be seen from Examples 1-5, by adjusting the amount of chloride salt added, the corrosion rate and depth of chloride salt on alloy powder can be effectively controlled, thereby achieving directional regulation of the comprehensive performance of magnetic powder core; As can be seen from Examples 1 and Examples 6-9, the amount of binder added will also affect the performance of soft magnetic composite material; As can be seen from Examples 1 and Examples 10-13, the annealing temperature is a key parameter affecting the performance of soft magnetic composite material. Higher temperatures can achieve deeper etching, which may result in higher DC bias performance even with a lower amount of chloride salt coating; As can be seen from Examples 1 and Examples 14, adding a pre-oxidation step can further improve the bias performance of the material to a certain extent. The reason is that chloride salt can cause corrosion in an oxygen-containing atmosphere and at relatively low temperatures. Pre-oxidation treatment helps to introduce more oxygen elements to promote the formation of the insulating layer, and may also help to remove excess chloride elements.

[0123] (2) As can be seen from Example 1 and Comparative Example 1, simple organic coating alone cannot make the soft magnetic composite material obtain good high-frequency magnetic performance stability and its DC bias performance is poor. In contrast, the chloride salt coating process can significantly improve the high-frequency magnetic performance of the soft magnetic composite material, significantly improve the permeability frequency stability, and obtain excellent DC bias performance. As can be seen from Example 1 and Comparative Example 2, the traditional phosphoric acid passivation process only forms a passivation layer on the surface. The reaction terminates when the phosphoric acid is completely consumed, and only a passivation layer of fixed thickness can be formed. However, the chloride salt corrosion process of the present invention has continuity and penetration, which can modify the matrix at a deeper level, thereby greatly improving the DC bias performance of the material.

[0124] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a soft magnetic composite material, characterized in that, The preparation method includes the following steps: (1) Mix the alloy powder with a chloride salt solution to obtain a mixture; (2) The mixture described in step (1) is dried to obtain a coated powder; (3) After mixing and curing the coating powder described in step (2) with the binder, a cured powder is obtained; (4) The cured powder described in step (3) is pressed and annealed in sequence to obtain the soft magnetic composite material.

2. The preparation method according to claim 1, characterized in that, In step (1), the chloride salt in the chloride salt solution is 0.075wt%-1.5wt% of the alloy powder mass, preferably 0.15wt%-1.5wt%. Preferably, the chloride salt in the chloride salt solution in step (1) includes stannous chloride dihydrate; Preferably, the solvent in the chloride salt solution in step (1) includes anhydrous ethanol; Preferably, the mass ratio of the solvent to the alloy powder in the chloride salt solution in step (1) is 1:(1.8-2.2).

3. The preparation method according to claim 1 or 2, characterized in that, The alloy powder in step (1) includes Fe-Si based alloy powder; Preferably, the silicon content in the Fe-Si based alloy powder is 3wt%-6.5wt%; Preferably, the alloy powder in step (1) has a mesh size of 160-700 mesh; Preferably, in step (1), the temperature for mixing the alloy powder with the chloride solution is 20℃-30℃, the time is 0.5h-3h, and the stirring rate is ≤500rpm.

4. The preparation method according to claim 1 or 2, characterized in that, The drying temperature in step (2) is 80℃-120℃; Preferably, the drying time in step (2) is ≤12h.

5. The preparation method according to claim 1 or 2, characterized in that, The coating powder described in step (2) underwent a pre-oxidation treatment before step (3); Preferably, the pre-oxidation treatment is performed at a temperature of 200℃-500℃ for a time of ≤2 hours. Preferably, the atmosphere for the pre-oxidation treatment is an oxygen atmosphere or an air atmosphere.

6. The preparation method according to claim 1 or 2, characterized in that, The adhesive in step (3) includes an epoxy resin solution; Preferably, the epoxy resin solution comprises epoxy resin and an organic solvent; Preferably, the epoxy resin is 0.5wt%-3wt% of the alloy powder mass; Preferably, the mass ratio of the organic solvent in the epoxy resin solution to the coating powder in step (2) is 1:(0.8-1.2); Preferably, the organic solvent includes acetone.

7. The preparation method according to claim 1 or 2, characterized in that, The temperature at which the coating powder and the binder are mixed in step (2) is 40℃-50℃; Preferably, in step (2), the coating powder and the binder are mixed until the organic solvent in the binder is evaporated; Preferably, the curing temperature in step (3) is 90℃-110℃ and the time is ≤3h.

8. The preparation method according to claim 1 or 2, characterized in that, The pressing pressure in step (4) is 1 GPa-2 GPa; Preferably, the annealing temperature in step (4) is 400℃-800℃, and more preferably 600℃-800℃; Preferably, the annealing holding time in step (4) is 1h-8h; Preferably, the annealing atmosphere in step (4) includes an inert atmosphere.

9. A soft magnetic composite material, characterized in that, The soft magnetic composite material is prepared by the preparation method according to any one of claims 1-8.

10. An application of the soft magnetic composite material as described in claim 9, characterized in that, The applications include those used in electronic devices.

Images