Magnetic powder core and preparation method thereof

Abstract

The invention discloses a magnetic powder core and a preparation method thereof.The magnetic powder core comprises ferromagnetic powder and a composite coating layer arranged on the surface of the ferromagnetic powder in a coating mode, and the composite coating layer comprises a first inorganic oxide mixing layer arranged on the surface of the ferromagnetic powder, the first inorganic oxide mixing layer comprises SiO2 with the content of W1; the first inorganic oxide mixing layer is coated with the SiO2 transition layer, and the SiO2 transition layer comprises SiO2 with the content of W2; the SiO2 transition layer is coated with the second inorganic oxide mixing layer, and the second inorganic oxide mixing layer comprises SiO2 with the content of W3; w2gt; w1, and W2gt; w3. According to the magnetic powder core, the phenomena of cracking and falling easily occurring in the forming and pressing process can be effectively improved, and therefore the electromagnetic performance of the magnetic powder core is improved.

Description

Technical Field

[0001] This application relates to the technical field of electronic components, and particularly to a magnetic powder core and a preparation method thereof. Background Art

[0002] By insulating and coating ferromagnetic powders such as metals or alloys, the eddy current loss of the magnetic powder core under high-frequency conditions can be reduced, thereby improving the high-frequency performance of the magnetic powder core. Inorganic oxide insulating materials such as SiO2, MgO, TiO2, and Al2O3 have excellent high-temperature stability and have become widely used coating materials at present. However, at present, the multi-layer coating layers formed by combining different inorganic oxides are extremely prone to cracking and peeling during the molding and pressing process of the magnetic powder core, resulting in a decrease in the insulation effect between ferromagnetic powders. Summary of the Invention

[0003] In order to improve the cracking and peeling phenomena that easily occur during the molding and pressing process of the magnetic powder core, this application provides a magnetic powder core and a preparation method thereof.

[0004] In a first aspect, an embodiment of this application provides a magnetic powder core.

[0005] A magnetic powder core includes ferromagnetic powders and a composite coating layer coated on the surface of the ferromagnetic powders. The composite coating layer includes:

[0006] A first inorganic oxide mixed layer provided on the surface of the ferromagnetic powders, and the first inorganic oxide mixed layer includes SiO2 with a content of W1;

[0007] A SiO2 transition layer coating the first inorganic oxide mixed layer, and the SiO2 transition layer includes SiO2 with a content of W2;

[0008] A second inorganic oxide mixed layer coating the SiO2 transition layer, and the second inorganic oxide mixed layer includes SiO2 with a content of W3;

[0009] W2 > W1, and W2 > W3.

[0010] As an optional implementation manner, in the embodiment of this application, in the first inorganic oxide mixed layer, the W1 is 10wt.% to 70wt.%; and / or, in the SiO2 transition layer, the W2 is greater than 95wt.%; and / or, in the second inorganic oxide mixed layer, the W3 is 10wt.% to 60wt.%.

[0011] As an optional implementation manner, in the embodiment of this application, the structure of the composite coating layer is selected from any one of the following:

[0012] On the surface of the first inorganic oxide mixed layer, a single layer of the SiO2 transition layer and a single layer of the second inorganic oxide mixed layer are distributed;

[0013] On the surface of the first inorganic oxide mixed layer, at least two periodically arranged units formed by alternately arranging the SiO2 transition layer and the second inorganic oxide mixed layer are distributed.

[0014] As an optional implementation manner, in the embodiments of the present application, the thickness of the first inorganic oxide mixed layer is 10 nm to 100 nm;

[0015] When a single layer of the SiO2 transition layer and a single layer of the second inorganic oxide mixed layer are distributed on the surface of the first inorganic oxide mixed layer, the thickness of the SiO2 transition layer is 10 nm to 50 nm, and the thickness of the second inorganic oxide mixed layer is 10 nm to 100 nm;

[0016] When at least two of the periodically arranged units are distributed on the surface of the first inorganic oxide mixed layer, the thickness of the periodically arranged unit is 20 nm to 150 nm.

[0017] As an optional implementation manner, in the embodiments of the present application, in the periodically arranged unit, the thickness ratio of the SiO2 transition layer to the second inorganic oxide mixed layer is 1:(1 to 10).

[0018] As an optional implementation manner, in the embodiments of the present application, the ferromagnetic powder contains at least Fe element and Si element.

[0019] As an optional implementation manner, in the embodiments of the present application, in the ferromagnetic powder, the content of the Si element is 1 wt.% to 15 wt.%.

[0020] As an optional implementation manner, in the embodiments of the present application, the first inorganic oxide includes at least one of Al2O3, Fe3O4, Fe2O3, Cr2O3, Nb2O5, TiO2, and rare earth oxides;

[0021] and / or;

[0022] The second inorganic oxide includes at least one of Al2O3, Fe3O4, Fe2O3, Cr2O3, Nb2O5, TiO2, MgO, ZrO2, CeO2, HfO2, NiO, and rare earth oxides;

[0023] and / or,

[0024] The morphology of the ferromagnetic powder includes one or a mixture of spherical, quasi-spherical, and flaky.

[0025] and / or

[0026] The ferromagnetic powder includes any one or a mixture of FeSi magnetic powder, FeSiAl magnetic powder, FeSiBNbCu magnetic powder, and FeSiBNbCu magnetic powder.

[0027] In a second aspect, an embodiment of the present application provides a method for preparing the magnetic powder core as mentioned in the first aspect.

[0028] The method for preparing the magnetic powder core includes the following steps:

[0029] Form the SiO2 transition layer and the second inorganic oxide mixed layer that coat the surface of the ferromagnetic powder on the surface of the ferromagnetic powder in sequence to obtain a magnetic powder core precursor;

[0030] Perform oxidation treatment to oxidize the surface layer of the ferromagnetic powder near the SiO2 transition layer and form the first inorganic oxide mixed layer to obtain the magnetic powder core.

[0031] As an optional implementation manner, in the embodiment of the present application, the oxidation treatment is carried out in an oxygen-containing atmosphere, the oxygen-containing atmosphere includes air and / or oxygen, and the oxidation treatment is to keep the temperature at 350°C to 600°C for 1h to 2h.

[0032] As an optional implementation manner, in the embodiment of the present application, the SiO2 transition layer and the second inorganic oxide mixed layer are prepared by sol-gel method, vapor phase method, hydrothermal synthesis method or atomic layer deposition method.

[0033] As an optional implementation manner, in the embodiment of the present application, the method for preparing the SiO2 transition layer and the second inorganic oxide mixed layer by the hydrothermal synthesis method includes the following steps:

[0034] Place the ferromagnetic powder, coupling agent, surfactant, silicon dioxide hydrolysis source and pH regulator in a mixed solvent of organic solvent and water, stir and react for 2h to 8h, and form the SiO2 transition layer on the surface of the ferromagnetic powder;

[0035] Continue to add water and the second inorganic oxide hydrolysis source, stir and react at 50°C to 80°C for 2h to 8h, and form the second inorganic oxide mixed layer with the SiO2 and the second inorganic oxide bonded to each other on the surface of the SiO2 transition layer facing away from the ferromagnetic powder;

[0036] and / or

[0037] The method for preparing the SiO2 transition layer and the second inorganic oxide mixed layer by the atomic layer deposition method includes the following steps:

[0038] Using trimethylsilane as a gas source, cyclic deposition is carried out to form the SiO2 transition layer;

[0039] Using the trimethylsilane and at least one precursor for forming the second inorganic oxide as gas sources, alternating cyclic deposition is carried out to form the second inorganic oxide mixed layer.

[0040] Compared with the prior art, the beneficial effects of the present application are as follows:

[0041] A magnetic powder core provided by an embodiment of the present application, by sequentially arranging a composite coating layer including a first inorganic oxide mixed layer, a SiO2 transition layer, and a second inorganic oxide mixed layer on the surface of the magnetic powder, and making the SiO2 transition layer have the highest SiO2 content. This structural design not only enables SiO2 to cooperate with the first inorganic oxide and the second inorganic oxide to give play to the complementary advantages of the materials, but also makes full use of the strengthening effect of the Si-O network to achieve interlayer stress buffering and lattice matching effect improvement. In the first inorganic oxide mixed layer and the second inorganic oxide mixed layer, SiO2 is mixed with the first inorganic oxide and the second inorganic oxide. The silanol groups (-Si-OH) on the surface of SiO2 can chemically react with the active groups on the surfaces of the first inorganic oxide and the second inorganic oxide to form chemical bonds, thereby enhancing the connection strength between the layers. At the same time, this low-high-low SiO2 content distribution forms a continuous and stable chemical bonding network between the first inorganic oxide mixed layer, the SiO2 transition layer, and the second inorganic oxide mixed layer, which can effectively transfer stress and improve the overall stability and anti-shedding ability of the composite coating layer 2.

[0042] Moreover, since SiO2 is distributed in the first inorganic oxide mixed layer, the SiO2 transition layer, and the second inorganic oxide mixed layer, it can adjust the lattice parameters of each layer, make the lattice structures between the first inorganic oxide mixed layer, the SiO2 transition layer, and the second inorganic oxide mixed layer more matched, reduce the internal stress generated due to lattice mismatch between the layers, and reduce the risk of cracking of the composite coating layer due to stress concentration during the molding pressing process.

[0043] During the molding pressing process of the magnetic powder core, the stress generated under the action of external force can be evenly dispersed between the layers, rather than concentrated in a certain layer or a specific area of a certain layer, thereby ensuring the integrity and stability of the composite coating layer during the pressing process, and effectively solving the problems of easy cracking and shedding of the composite coating layer during the molding pressing process of the magnetic powder core. Description of the Drawings

[0044] To more clearly illustrate the technical solutions in the embodiments of the present application, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0045] Figure 1 is a schematic structural diagram of the magnetic powder core disclosed in the embodiments of the present application;

[0046] Figure 2 is a scanning electron microscope scanning image of the focused ion beam of the magnetic powder core disclosed in Embodiment 1 of the present application;

[0047] Figure 3 is a transmission electron microscope image disclosed in Embodiment 3 of the present application.

[0048] Reference numerals: 100, magnetic powder core; 1, magnetic powder; 2, composite coating layer; 21, first inorganic oxide mixed layer; 22, SiO2 transition layer; 23, first inorganic oxide mixed layer. Detailed implementation manners

[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0050] In the present application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation or be constructed and operated in a specific orientation.

[0051] Moreover, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to the specific situation.

[0052] In addition, the terms "installed", "set up", "provided with", "connected", and "linked" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there can be internal communication between two devices, components, or constituent parts. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0053] In addition, terms such as "first", "second", etc. are mainly used to distinguish different devices, components, or constituent parts (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, components, or constituent parts. Unless otherwise specified, the meaning of "a plurality" is two or more.

[0054] Hereinafter, the technical solutions of this application will be further described in conjunction with embodiments and the accompanying drawings.

[0055] In a first aspect, referring to Figure 1 , an embodiment of this application provides a magnetic powder core 100.

[0056] A magnetic powder core 100 includes ferromagnetic powder (hereinafter referred to as magnetic powder 1) and a composite coating layer 2 coated on the surface of the magnetic powder 1. The composite coating layer 2 includes:

[0057] A first inorganic oxide mixed layer 21 is provided on the surface of the magnetic powder 1. The first inorganic oxide mixed layer 21 includes SiO2 with a content of W1;

[0058] An SiO2 transition layer 22 coats the first inorganic oxide mixed layer 21. The SiO2 transition layer 22 includes SiO2 with a content of W2;

[0059] A second inorganic oxide mixed layer 23 coats the SiO2 transition layer 22. The second inorganic oxide mixed layer 23 includes SiO2 with a content of W3;

[0060] W2 > W1 and W2 > W3.

[0061] In this application, a composite coating layer 2 including a first inorganic oxide mixed layer 21, a SiO2 transition layer 22, and a second inorganic oxide mixed layer 23 is sequentially provided on the surface of the magnetic powder 1, and the SiO2 transition layer 22 has the highest SiO2 content. This structural design not only enables SiO2 to cooperate with the first inorganic oxide and the second inorganic oxide to give play to the complementary advantages of the materials, but also makes full use of the strengthening effect of the Si-O network to achieve the improvement of interlayer stress buffering and lattice matching effect. In the first inorganic oxide mixed layer 21 and the second inorganic oxide mixed layer 23, SiO2 is mixed with the first inorganic oxide and the second inorganic oxide, and the silanol groups (-Si-OH) on the surface of SiO2 can chemically react with the active groups on the surfaces of the first inorganic oxide and the second inorganic oxide to form chemical bonds, thereby enhancing the connection strength between the layers. At the same time, this low-high-low SiO2 content distribution forms a continuous and stable chemical bonding network between the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23, which can effectively transfer stress and improve the overall stability and anti-shedding ability of the composite coating layer 2.

[0062] Moreover, since SiO2 is distributed in the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23, it can adjust the lattice parameters of each layer, make the lattice structures between the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23 more matched, reduce the internal stress generated by lattice mismatch between layers, and reduce the risk of cracking of the composite coating layer 2 due to stress concentration during the forming and pressing process.

[0063] During the pressing and forming process of the magnetic powder core 100, the stress generated under the action of external force can be evenly dispersed among the layers instead of concentrating in a certain layer or a specific area of a certain layer, thereby ensuring the integrity and stability of the composite coating layer 2 during the pressing process and effectively solving the problems of easy cracking and shedding of the composite coating layer 2 during the pressing process of the magnetic powder core 100.

[0064] In some embodiments, in the first inorganic oxide mixed layer 21, W1 is 10 wt.% to 70 wt.%; and / or, in the SiO2 transition layer 22, W2 is greater than 95 wt.%; and / or, in the second inorganic oxide mixed layer 23, W3 is 10 wt.% to 60 wt.%.

[0065] By limiting the content of SiO2 in each layer, it can be ensured that there are sufficient active groups between SiO2 and the first inorganic oxide and the second inorganic oxide in the first inorganic oxide mixed layer 21 and the second inorganic oxide mixed layer 23 to carry out chemical reactions, forming a more solid chemical bonding interface and further improving the bonding strength of the coating layer. At the same time, by controlling the content of SiO2 in each layer, the lattice parameters of each layer can be adjusted more accurately, making the lattice structures of the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23 more matched, reducing the internal stress generated due to lattice mismatch, and further optimizing the stability and reliability of the coating layer.

[0066] In some embodiments, the structure of the composite coating layer 2 is selected from any of the following:

[0067] A single-layer SiO2 transition layer 22 and a single-layer second inorganic oxide mixed layer 23 are distributed on the surface of the first inorganic oxide mixed layer 21;

[0068] At least two periodically arranged units formed by alternately arranged SiO2 transition layers 22 and second inorganic oxide mixed layers 23 are distributed on the surface of the first inorganic oxide mixed layer 21.

[0069] The present application provides two structural arrangements of the composite coating layer 2: one is that a single-layer SiO2 transition layer 22 and a single-layer second inorganic oxide mixed layer 23 are distributed on the surface of the first inorganic oxide mixed layer 21; the other is that at least two periodically arranged units formed by alternately arranged SiO2 transition layers 22 and second inorganic oxide mixed layers 23 are distributed on the surface of the first inorganic oxide mixed layer 21.

[0070] For the first arrangement, the structure of the composite coating layer 2 is relatively simple, easy to prepare and control, can improve the performance of the magnetic powder core 100, ensure the stability and reliability of the composite coating layer 2, and has certain economic advantages in large-scale production.

[0071] For the second arrangement, the risks of micropores and cracks in the composite coating layer 2 are limited to a single periodically arranged unit, preventing the penetration and expansion of defects, thereby further improving the overall stability and reliability of the composite coating layer 2 and optimizing the performance of the magnetic powder core 100. This periodically arranged unit can provide better performance under more complex working conditions. For example, under harsh conditions such as high stress and high frequency, the integrity of the composite coating layer 2 can still be maintained to ensure the normal operation of the magnetic powder core 100.

[0072] In some embodiments, the thickness of the first inorganic oxide mixed layer 21 is 10 nm to 100 nm;

[0073] When a single-layer SiO2 transition layer 22 and a single-layer second inorganic oxide mixed layer 23 are distributed on the surface of the first inorganic oxide mixed layer 21, the thickness of the SiO2 transition layer 22 is 10 nm to 50 nm, and the thickness of the second inorganic oxide mixed layer 23 is 10 nm to 100 nm;

[0074] When at least two periodic units are distributed on the surface of the first inorganic oxide mixed layer 21, the thickness of the periodic unit is 20 nm to 150 nm.

[0075] By controlling the thickness of each layer, a more reasonable stress buffer structure can be formed between the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23, effectively dispersing the stress generated during the pressing process and reducing the risk of rupture of the composite coating layer 2 caused by stress concentration. At the same time, the reasonable setting of the thickness of each layer helps to further optimize the lattice matching, reduce the lattice mismatch caused by the thickness difference, and improve the overall stability and reliability of the composite coating layer 2.

[0076] In addition, on the premise of ensuring the insulation performance, reasonably controlling the thickness of the composite coating layer 2 and avoiding excessive increase in the material usage helps to reduce the production cost and improve the economy of the product.

[0077] In some embodiments, in the periodic unit, the thickness ratio of the SiO2 transition layer 22 to the second inorganic oxide mixed layer 23 is 1∶(1 - 10).

[0078] By controlling this thickness ratio, the stress distribution inside the periodic unit can be made more uniform, reducing the risk of formation of micropores and cracks caused by excessive thickness difference, and further improving the integrity and stability of the composite coating layer 2. Moreover, different thickness ratios can meet the performance requirements under different working conditions to a certain extent. For example, under conditions such as high frequency and high magnetic field strength, by appropriately adjusting the thickness ratio, the insulation performance and mechanical properties of the composite coating layer 2 can be further optimized to ensure the reliable operation of the magnetic powder core 100.

[0079] In some embodiments, the magnetic powder 1 contains at least Fe element and Si element.

[0080] By using magnetic powder 1 containing at least Fe element and Si element, through oxidation reaction, a first inorganic oxide mixed layer 21 with better interfacial bonding strength between the magnetic powder 1 and the SiO2 transition layer 22 can be formed, realizing further improvement of the interfacial bonding strength between layers. When the magnetic powder core 100 is made and undergoes oxidation treatment, oxygen can contact the magnetic powder 1 near the SiO2 transition layer 22 through the SiO2 transition layer 22 and the second inorganic oxide mixed layer 23. The constituent elements in the magnetic powder 1 react with oxygen, and a first inorganic oxide mixed layer 21 is formed on the side close to the SiO2 transition layer 22. At the same time, the combination of Fe and Si elements can improve the compatibility and bonding strength between the first inorganic oxide mixed layer 21 and the magnetic powder 1, further enhancing the overall strength of the magnetic core powder and reducing the possibility of cracking during the pressing and forming process. In addition, the reasonable combination of Fe and Si elements can optimize the soft magnetic properties of the magnetic powder 1, improve key indicators such as the magnetic permeability and saturation magnetic induction intensity of the magnetic powder core 100, and meet the performance requirements of the magnetic powder core 100 in different application scenarios.

[0081] In some embodiments, in the magnetic powder 1, the content of Si element is 1 wt.% to 15 wt.%.

[0082] When the content of Si element is within this range, it is beneficial to form an appropriate amount and evenly distributed SiO2 during the oxidation treatment, improve the content and quality of SiO2 in the first inorganic oxide mixed layer 21, and thus enhance the interfacial bonding strength between the first inorganic oxide mixed layer 21 and the SiO2 transition layer 22. At the same time, an appropriate amount of Si element can ensure that the first inorganic oxide mixed layer 21 has good stability and reliability, avoiding insufficient formation of the first inorganic oxide mixed layer 21 caused by too low content of Si element or other adverse effects caused by too high content, such as increased internal stress in the composite coating layer 2. In addition, within the range of Si element content, on the basis of ensuring that the magnetic powder core 100 has excellent insulation performance, mechanical properties and soft magnetic properties, the production cost can be reasonably controlled, avoiding increasing the raw material cost due to too high content of Si element and improving the market competitiveness of the product.

[0083] In some embodiments, the first inorganic oxide includes at least one of Al2O3, Fe3O4, Fe2O3, Cr2O3, Nb2O5, TiO2 and rare earth oxides;

[0084] and / or;

[0085] The second inorganic oxide includes at least one of Al2O3, Fe3O4, Fe2O3, Cr2O3, Nb2O5, TiO2, MgO, ZrO2, CeO2, HfO2, NiO and rare earth oxides;

[0086] and / or,

[0087] The morphology of the magnetic powder 1 includes one or a mixture of spherical, quasi-spherical and flaky shapes;

[0088] and / or,

[0089] The magnetic powder 1 includes any one or a mixture of FeSi magnetic powder, FeSiAl magnetic powder, FeSiBNbCu magnetic powder, FeSiBNbCu magnetic powder.

[0090] The metal elements contained in the above-mentioned first inorganic oxide are often added to the magnetic powder 1, and through an oxidation reaction, the corresponding first inorganic oxide is formed.

[0091] The above-mentioned second inorganic oxide has high thermal stability and chemical stability, can improve the stability and reliability of the magnetic powder core 100 in harsh environments such as high temperature and humidity, forms complementary material advantages with SiO2, and extends the service life of the magnetic powder core 100.

[0092] In a second aspect, an embodiment of the present application provides a preparation method of the magnetic powder core 100 as mentioned in the first aspect.

[0093] A preparation method of a magnetic powder core 100 includes the following steps:

[0094] Form a SiO2 transition layer 22 and a second inorganic oxide mixed layer 23 on the surface of the magnetic powder 1 in sequence to obtain a precursor of the magnetic powder core 100;

[0095] Perform an oxidation treatment to oxidize the surface layer of the magnetic powder 1 close to the SiO2 transition layer 22 and form a first inorganic oxide mixed layer 21 to obtain the magnetic powder core 100.

[0096] By first forming the SiO2 transition layer 22 and the second inorganic oxide mixed layer 23, and then performing an oxidation treatment to form the first inorganic oxide mixed layer 21, the interlayer bonding strength between the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23 can be effectively improved, thereby improving the stability of the magnetic powder core 100.

[0097] In some embodiments, the oxidation treatment is carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere includes any one or both of air and / or oxygen. The oxidation treatment is to keep the temperature at 350°C to 600°C for 1h to 2h.

[0098] In some embodiments, the SiO2 transition layer 22 and the second inorganic oxide mixed layer 23 are prepared by a sol-gel method, a vapor phase method, a hydrothermal synthesis method or an atomic layer deposition method.

[0099] The above methods can all achieve the deposition of the SiO2 transition layer 22 and the second inorganic oxide mixed layer 23. By providing multiple preparation methods, the present application not only enriches the process options, but also can meet the diverse requirements for the performance and cost of the magnetic powder core 100 in different application scenarios, further improving the flexibility and adaptability of the preparation of the magnetic powder core 100.

[0100] In some embodiments, the method for preparing the SiO2 transition layer 22 and the second inorganic oxide mixed layer 23 by the hydrothermal synthesis method includes the following steps:

[0101] Put the magnetic powder 1, coupling agent, surfactant, silicon dioxide hydrolysis source, and pH regulator into a mixed solvent of an organic solvent and water, stir and react for 2 h to 8 h, and a SiO2 transition layer 22 is formed on the surface of the magnetic powder 1;

[0102] Continue to add water and the second inorganic oxide hydrolysis source, and stir and react at 50 °C to 80 °C for 2 h to 8 h. A second inorganic oxide mixed layer 23 with SiO2 and the second inorganic oxide bonded to each other is formed on the surface of the SiO2 transition layer 22 facing away from the magnetic powder 1.

[0103] In some embodiments, the method for preparing the SiO2 transition layer 22 and the second inorganic oxide mixed layer 23 by the atomic layer deposition method includes the following steps:

[0104] Using trimethylsilane as a gas source, perform cyclic deposition to form the SiO2 transition layer 22;

[0105] Using trimethylsilane and at least one precursor for forming the second inorganic oxide as gas sources, perform alternating cyclic deposition to form the second inorganic oxide mixed layer 23.

[0106] In the hydrothermal synthesis method, by putting the magnetic powder 1, coupling agent (such as: KH550 (γ-

[0107] aminopropyltriethoxysilane), KH560 (γ-glycidoxypropyltrimethoxysilane), KH570 (γ-methacryloxypropyltrimethoxysilane), etc.), surfactant (such as polyvinylpyrrolidone), silicon dioxide hydrolysis source (such as tetraethyl orthosilicate, tetramethyl orthosilicate, etc.), and pH regulator (such as ammonia water, etc.) into a mixed solvent of an organic solvent (such as absolute ethanol, etc.) and water, stir and react for 2 h. During this process, the silicon dioxide hydrolysis source (such as tetraethyl orthosilicate, etc.) hydrolyzes and transforms into SiO2, and this SiO2 is uniformly deposited on the surface of the magnetic powder 1 to form the SiO2 transition layer 22. Subsequently, add water and the second inorganic oxide hydrolysis source (such as tetrabutyl titanate, etc.), and continue to stir and react at 50 °C to 80 °C for 2 h to 8 h. During this process, the silicon dioxide hydrolysis source and the second inorganic oxide hydrolysis source are fully mixed and both undergo hydrolysis reactions, transforming into SiO2 and the second inorganic oxide. The silicon-oxygen tetrahedron of SiO2 is [SiO4]4- is directly connected to the second inorganic oxide through Si-O-M (M is a non-oxygen element in the second inorganic oxide) bridge bonds to form a three-dimensional interpenetrating network, realizing the interpenetration and bonding of the structural units of SiO2 and the second inorganic oxide, thereby constructing a uniformly mixed second inorganic oxide mixed layer 23. Exemplarily, when the second inorganic oxide is TiO2, the titanium octahedron [TiO6] of TiO2 8- and the silicon tetrahedron [SiO4] of SiO2 4- are connected through Si-O-Ti bridge bonds.

[0108] In the atomic layer deposition method, trimethylsilane is used as a gas source for cyclic deposition to form a SiO2 transition layer 22, and then trimethylsilane and at least one precursor for forming the second inorganic oxide (such as trimethylaluminum) are used as gas sources for alternating cyclic deposition. For example, trimethylsilane is introduced for deposition reaction, purged, and then trimethylaluminum is introduced for deposition reaction, purged, to complete one cycle of deposition. Through multiple cycles of deposition, a second inorganic oxide mixed layer 23 with a specific thickness is formed. This method can precisely control the thickness and composition of each layer, achieve atomic-level uniform coating, and effectively improve the quality and performance of the composite coating layer 2.

[0109] The technical solutions of the present application will be further described below in combination with more specific embodiments.

[0110] Example 1

[0111] The embodiment of the present application provides a magnetic powder core. The preparation method of the magnetic powder core includes the following steps:

[0112] Prepare a SiO2 transition layer: Dissolve KH550 coupling agent and polyvinylpyrrolidone in absolute ethanol, and then add spherical Fe-6.5Si magnetic powder (i.e., magnetic powder containing 6.5% silicon), and continuously stir while adding. Then, add 5 ml of tetraethyl orthosilicate and continuously stir, and then slowly add a mixed solution composed of 2 ml of ammonia water and 50 ml of deionized water, and continuously stir for 2 h to form a SiO2 transition layer with a thickness of 15 nm on the surface of the magnetic powder.

[0113] Prepare a second inorganic oxide mixed layer: Continue to add a mixed solution of 10 ml of deionized water and 5 ml of tetrabutyl titanate to the mixed solution that has been continuously stirred for 2 h, and continuously stir for 2 h under the condition of a 60 °C water bath to form a second inorganic oxide mixed layer with a thickness of 60 nm and composed of SiO2 and TiO2, wash several times with deionized water, and collect by magnetic separation to obtain a magnetic powder core precursor.

[0114] Preparation of the first inorganic oxide mixed layer: Place the magnetic powder core precursor in a resistance furnace at 600 °C. After heat preservation for 2 h, cool it to room temperature in air. During the heating process, the magnetic powder is oxidized under the action of high-temperature air, and a first inorganic oxide mixed layer containing SiO2 with a thickness of 20 nm is formed at the interface between the magnetic powder and the SiO2 transition layer, obtaining a magnetic powder core;

[0115] Preparation of the toroidal soft magnetic composite material: Add the magnetic powder core treated in the preparation of the first inorganic oxide mixed layer to an acetone solution containing epoxy resin, and mechanically stir until the acetone volatilizes completely. After drying at 90 °C for 2 h, press the above powder into a toroidal magnetic powder core, and perform heat treatment on the magnetic powder core at 550 °C - 700 °C for 30 min - 60 min under nitrogen protection, namely obtaining the toroidal soft magnetic composite material.

[0116] Example 2

[0117] This application example provides a magnetic powder core, which is different from that in Example 1 in that: spherical FeSiAl magnetic powder is used to replace Fe-6.5Si magnetic powder;

[0118] 3 ml of tetraethyl orthosilicate is used to replace 5 ml of tetraethyl orthosilicate;

[0119] The temperature of the resistance furnace is replaced with 500 °C instead of 600 °C;

[0120] The rest is the same as that in Example 1.

[0121] Example 3

[0122] This application example provides a magnetic powder core, and the preparation method of the magnetic powder core includes the following steps:

[0123] Drying: Dissolve KH550 coupling agent and polyvinylpyrrolidone in absolute ethanol, add spherical FeSiAl magnetic powder, stir for 30 min, then collect the magnetic powder and dry it at 60 °C for 4 h.

[0124] Preparation of the magnetic powder core precursor composed of periodic units:

[0125] Preparation of the SiO2 transition layer: Perform atomic layer deposition on the dried magnetic powder, use trimethylsilane as the precursor, the deposition temperature is 210 °C, and cycle deposition is carried out 30 times to form a SiO2 transition layer with a thickness of 10 nm - 12 nm;

[0126] Preparation of the second inorganic oxide mixed layer: Introduce trimethylsilane and control the deposition temperature at 210 °C for deposition reaction and purge. Then introduce trimethylaluminum and control the deposition temperature at 210 °C for deposition reaction and purge. Complete one cycle of deposition, and cycle deposition is carried out 300 times to form a second inorganic oxide mixed layer composed of SiO2 and Al2O3 with a thickness of 95 nm - 100 nm;

[0127] Prepare 10 periodic units in the order of first preparing the SiO2 transition layer and then preparing the second inorganic oxide mixed layer to obtain a magnetic powder core precursor.

[0128] Prepare the first inorganic oxide mixed layer: Place the magnetic powder core precursor in a resistance furnace at 400 °C and keep it warm for 2 h, then cool it to room temperature in air. During the heating process, the magnetic powder is oxidized under the action of high-temperature air, and a first inorganic oxide mixed layer containing SiO2 with a thickness of 20 nm is formed at the interface between the magnetic powder and the SiO2 transition layer to obtain a magnetic powder core.

[0129] Prepare a toroidal soft magnetic composite material: Add the magnetic powder core treated in the preparation of the first inorganic oxide mixed layer to an acetone solution containing epoxy resin, mechanically stir until the acetone volatilizes completely, dry it at 90 °C for 2 h, then press the above powder into a toroidal magnetic powder core, and perform heat treatment on the magnetic powder core at 550 °C - 700 °C for 60 min under nitrogen protection to obtain a toroidal soft magnetic composite material.

[0130] Example 4

[0131] An embodiment of the present application provides a magnetic powder core, which is different from Example 3 in that: in the preparation of the second inorganic oxide mixed layer, the number of cyclic depositions is 100 times, and the thickness of the prepared second inorganic oxide mixed layer is between 25 nm and 30 nm; the rest is the same as Example 3.

[0132] Example 5

[0133] An embodiment of the present application provides a magnetic powder core, which is different from Example 3 in that: in the preparation of the first inorganic oxide mixed layer, the magnetic powder core precursor is placed in a resistance furnace at 560 °C and heated for 1 h; the rest is the same as Example 3.

[0134] Comparative Example 1

[0135] A comparative example of the present application provides a magnetic powder core, which is different from Example 1 in that: the oxidation treatment step in the preparation of the first inorganic oxide mixed layer is omitted, and only the SiO2 transition layer and the second inorganic oxide mixed layer are retained, and the rest is the same as Example 1.

[0136] Comparative Example 2

[0137] A comparative example of the present application provides a magnetic powder core, which is different from Example 2 in that: the step of preparing the first inorganic oxide mixed layer and the step of preparing the second inorganic oxide mixed layer are omitted, and the rest is the same as Example 2.

[0138] Comparative Example 3

[0139] A comparative example of this application provides a magnetic powder core, which is different from Example 3 in that: in the step of preparing the magnetic powder core precursor composed of periodic units, trimethylaluminum is used only as the gas source, the deposition temperature is 170 °C, and the cyclic deposition is carried out 300 times, so that the thickness of the Al2O3 layer prepared on the surface of the magnetic powder is between 95 nm and 100 nm; the rest is the same as Example 3.

[0140] Experiment 1

[0141] The magnetic powder core prepared in Example 1 was scanned by a focused ion beam scanning electron microscope, and the obtained image is Figure 2 .

[0142] The magnetic powder core prepared in Example 3 was scanned by a transmission electron microscope, and the obtained transmission electron microscope image is Figure 3 (a), Figure 3 (a) After elemental surface scanning analysis, Figure 3 (b) and Figure 3 (c).

[0143] From Figure 2 the test results, it can be seen that the composite coating layer on the surface of the magnetic powder is divided into three layers, corresponding to the first inorganic oxide mixed layer 21, the SiO2 transition layer 22, and the second inorganic oxide mixed layer 23 respectively. Figure 3 In the composite coating layer shown in (a), several periodic units formed by alternately arranged SiO2 transition layers 22 and second inorganic oxide mixed layers 23 are distributed on the surface of the first inorganic oxide mixed layer 21.

[0144] Figure 3 In the elemental surface scanning test results of, blue represents aluminum element, red represents silicon element, and green represents iron element. Figure 3 (b) marks aluminum element, silicon element and iron element at the same time. From Figure 3 (b), it can be seen that the green-enriched area is the magnetic powder. The first inorganic oxide mixed layer 21 on the surface of the magnetic powder appears as a yellow thin layer in Figure 3 (b), indicating that this layer contains both SiO2 formed by the silicon element representing red and oxides formed by the iron element representing green. The surface of the first inorganic oxide mixed layer 21 is the SiO2 transition layer 22, which appears as a red thin layer in Figure 3 (b). The surface of the SiO2 transition layer 22 is the second inorganic oxide mixed layer 23, which appears as a thin layer of intertwined red and blue in the figure.

[0145] Figure 3(c) Both silicon and iron elements are marked, while aluminum element is not marked. From this figure, it can be clearly seen that SiO2 always exists in the entire composite coating layer. The content of SiO2 is the highest in the SiO2 transition layer 22, and relatively lower in the first inorganic oxide mixed layer 21 and the second inorganic oxide mixed layer 23. The setting of this composite coating layer effectively improves the chemical bonding and lattice matching between the SiO2 transition layer 22 and the first inorganic oxide mixed layer 21 and the second inorganic oxide mixed layer 23 on both sides, thereby enhancing the interfacial bonding strength between the SiO2 transition layer 22 and the first inorganic oxide mixed layer 21 and the second inorganic oxide mixed layer 23, and further improving the problem of poor interfacial bonding strength, reducing the phenomenon of shedding during the molding and pressing process of the magnetic powder core.

[0146] Experiment Two

[0147] The magnetic powder cores prepared in the above examples and comparative examples were tested for the optimum molding pressure, magnetic powder core density and electromagnetic properties, where:

[0148] The test method for the optimum molding pressure is as follows: According to the IEC 60404-4 and IEC 62044-3 standards, by testing the effective magnetic permeability and total loss of the magnetic powder core under different pressure conditions, and through the optimal performance combination of "effective magnetic permeability and total loss", the optimum molding pressure is confirmed.

[0149] The test method for the magnetic powder core density is as follows: According to the GB / T 5163 standard, the Archimedes drainage method is adopted, and the density of the toroidal magnetic powder core is measured by a precision electronic density balance.

[0150] The test method for magnetic permeability is as follows: According to the IEC 60404-4 standard, the magnetic permeability of the toroidal magnetic powder core is measured at 100 kHz using an impedance analyzer.

[0151] The test method for loss is as follows: According to the IEC 62044-3 standard, a high-frequency power analyzer is used in combination with a B-H analyzer to measure the magnetic loss of the toroidal magnetic powder core.

[0152] The test method for DC bias is as follows: According to the IEC 60404-13 standard, the DC superposition method is adopted. A static bias magnetic field is provided by a DC power supply, and the DC bias performance of the magnetic permeability under an external magnetic field of 100 Oe is measured in combination with an impedance analyzer.

[0153] The test method for resistivity is as follows: According to the IEC 60404-11 standard, a standardized voltage (100 V) is applied to the toroidal magnetic powder core using the four-probe method, and the current is measured to calculate the bulk resistivity.

[0154] The test results of the above examples and comparative examples are shown in Table 1.

[0155] Table 1

[0156]

[0157]

[0158] From the data comparison between Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that the optimal molding pressure of Examples 1 to 3 has increased significantly compared to Comparative Examples 1 to 3. This indicates that by constructing a composite coating layer structure of the first inorganic oxide mixed layer, the SiO2 transition layer, and the second inorganic oxide mixed layer, the interfacial bonding strength between the magnetic powder and the composite coating layer is enhanced, making the composite coating layer less likely to break or fall off during the high-pressure molding process of the magnetic powder core, thus allowing a higher molding pressure.

[0159] At the same time, the density, DC bias, and resistivity of Examples 1 to 3 have increased compared to Comparative Examples 1 to 3, while the losses of Examples 1 to 3 are significantly lower than those of Comparative Examples 1 to 3. This result can be attributed to the fact that the higher molding pressure promotes the closer packing of magnetic powder particles, and the lattice matching between the SiO transition layer and the first inorganic oxide mixed layer and the second inorganic oxide mixed layer on both sides effectively reduces the risk of microcrack generation during the pressing process, thus increasing the density. In addition, the improvement of the interfacial bonding strength of the composite coating layer reduces the possibility of damage to the insulating composite coating layer during the molding pressing process, avoids magnetic permeability loss, and at the same time blocks the eddy current path through the high resistivity characteristics of the composite coating layer, significantly reducing the high-frequency loss and improving the overall insulation performance.

[0160] Furthermore, further analysis reveals that the improvement in the optimal molding pressure, density, DC bias, and resistivity of Example 3 compared to Comparative Example 3 is more obvious, and the reduction in loss is also increased. This benefits from the periodic unit design that confines the risk of micropores or cracks within a single periodic unit and achieves better stress buffering and lattice matching through the alternately arranged SiO2 transition layer and the second inorganic oxide mixed layer. The second inorganic oxide mixed layer composed of a mixture of SiO2 and Al2O3 constructed by atomic layer deposition technology in Example 3 not only improves the chemical bonding strength between the composite coating layers but also suppresses local electric field concentration through the uniform distribution of oxides, thus showing lower eddy current loss and higher resistivity. This design significantly enhances the stability and reliability of the magnetic powder core under high-pressure and high-frequency conditions by optimizing the interlayer compatibility.

[0161] The above has introduced in detail the magnetic powder core and its preparation method disclosed in the embodiments of the present application. Specific examples are used herein to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the magnetic powder core and its preparation method of the present application and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A magnetic powder core, characterized in that, It includes ferromagnetic powder and a composite coating layer coated on the surface of the ferromagnetic powder. The composite coating layer includes: A first inorganic oxide mixed layer, which is provided on the surface of the ferromagnetic powder. The first inorganic oxide mixed layer includes SiO2 with a content of W1; A SiO2 transition layer, which coats the first inorganic oxide mixed layer. The SiO2 transition layer includes SiO2 with a content of W2; A second inorganic oxide mixed layer, which coats the SiO2 transition layer. The second inorganic oxide mixed layer includes SiO2 with a content of W3; W2 > W1 and W2 > W3.

2. The magnetic powder core according to claim 1, wherein In the first inorganic oxide mixed layer, W1 is 10wt.% - 70wt.%; and / or, in the SiO2 transition layer, W2 is greater than 95wt.%; and / or, in the second inorganic oxide mixed layer, W3 is 10wt.% - 60wt.%.

3. The magnetic powder core according to claim 1, wherein The structure of the composite coating layer is selected from any of the following: A single layer of the SiO2 transition layer and a single layer of the second inorganic oxide mixed layer are distributed on the surface of the first inorganic oxide mixed layer; At least two periodically arranged units formed by alternating the SiO2 transition layer and the second inorganic oxide mixed layer are distributed on the surface of the first inorganic oxide mixed layer.

4. The magnetic powder core according to claim 3, wherein, The thickness of the first inorganic oxide mixed layer is 10nm - 100nm; When a single layer of the SiO2 transition layer and a single layer of the second inorganic oxide mixed layer are distributed on the surface of the first inorganic oxide mixed layer, the thickness of the SiO2 transition layer is 10nm - 50nm, and the thickness of the second inorganic oxide mixed layer is 10nm - 100nm; When at least two of the periodically arranged units are distributed on the surface of the first inorganic oxide mixed layer, the thickness of the periodically arranged unit is 20nm - 150nm.

5. The magnetic powder core according to claim 4, wherein In the periodically arranged unit, the thickness ratio of the SiO2 transition layer to the second inorganic oxide mixed layer is 1:(1 - 10).

6. The magnetic powder core according to claim 4, characterized in that, The ferromagnetic powder contains at least Fe element and Si element.

7. The magnetic powder core according to claim 6, wherein In the ferromagnetic powder, the content of the Si element is 1wt.% - 15wt.%.

8. The magnetic powder core according to any one of claims 1-7, characterized in that, The first inorganic oxide includes at least one of Al2O3, Fe3O4, Fe2O3, Cr2O3, Nb2O5, TiO2, and rare earth oxides; and / or; The second inorganic oxide includes at least one of Al2O3, Fe3O4, Fe2O3, Cr2O3, Nb2O5, TiO2, MgO, ZrO2, CeO2, HfO2, NiO, and rare earth oxides; and / or, The morphology of the ferromagnetic powder includes one or a mixture of spherical, quasi-spherical, and flaky; and / or, The ferromagnetic powder includes any one or a mixture of FeSi magnetic powder, FeSiAl magnetic powder, FeSiBNbCu magnetic powder, and FeSiBNbCu magnetic powder.

9. A preparation method of a magnetic powder core, characterized in that, The preparation method of the magnetic powder core according to any one of claims 1 - 8 includes the following steps: The SiO2 transition layer and the second inorganic oxide mixed layer are successively formed on the surface of the ferromagnetic powder to obtain a magnetic powder core precursor; An oxidation treatment is carried out to oxidize the surface layer of the ferromagnetic powder close to the SiO2 transition layer and form the first inorganic oxide mixed layer to obtain the magnetic powder core.

10. The preparation method of the magnetic powder core according to claim 9, characterized in that, The oxidation treatment is carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere includes air and / or oxygen. The oxidation treatment is carried out at 350°C to 600°C for 1 h to 2 h.

11. The preparation method of the magnetic powder core according to claim 9, characterized in that, The SiO2 transition layer and the second inorganic oxide mixed layer are prepared by a sol-gel method, a gas-phase method, a hydrothermal synthesis method or an atomic layer deposition method.

12. The preparation method of the magnetic powder core according to claim 11, characterized in that, The method for preparing the SiO2 transition layer and the second inorganic oxide mixed layer by the hydrothermal synthesis method includes the following steps: The ferromagnetic powder, a coupling agent, a surfactant, a silica hydrolysis source and a pH regulator are placed in a mixed solvent of an organic solvent and water, and stirred and reacted for 2 h to 8 h to form the SiO2 transition layer on the surface of the ferromagnetic powder; Water and a second inorganic oxide hydrolysis source are continuously added, and stirred and reacted at 50°C to 80°C for 2 h to 8 h to form the second inorganic oxide mixed layer having the SiO2 and the second inorganic oxide bonded to each other on the surface of the SiO2 transition layer facing away from the ferromagnetic powder; and / or The method for preparing the SiO2 transition layer and the second inorganic oxide mixed layer by the atomic layer deposition method includes the following steps: Using trimethylsilane as a gas source, cyclic deposition is carried out to form the SiO2 transition layer; Using the trimethylsilane and at least one precursor for forming the second inorganic oxide as gas sources, alternating cyclic deposition is carried out to form the second inorganic oxide mixed layer.

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