A magnetic powder core and preparation method thereof

Abstract

The present application discloses a magnetic powder core and a preparation method thereof, and relates to the technical field of magnetic materials. The present application provides a preparation method of a magnetic powder core, comprising: mixing amorphous magnetic powder with an acid solution, acidifying the surface of the amorphous magnetic powder to form an acidified magnetic powder; mixing the acidified magnetic powder with a silicate sol, so that the silicate sol is coated on the surface of the acidified magnetic powder to form a sol magnetic powder; dehydrating the sol magnetic powder, and the silicate sol is dehydrated to form a silicon dioxide layer coated on the surface of the acidified magnetic powder, so that the sol magnetic powder is converted into a coated magnetic powder; and the coated magnetic powder is pressed into a magnetic powder core. The magnetic powder core and the preparation method thereof provided by the present application can obtain a uniform and dense insulating layer on the surface of the amorphous magnetic powder that is not easy to break during the pressing process.

Description

Technical Field

[0001] The present application relates to the technical field of magnetic materials, and in particular to a magnetic powder core and a preparation method thereof. Background Art

[0002] With the rapid development of electronic power and information industries, electronic equipment and devices are developing towards miniaturization, high frequency and high current. Traditional magnetic powder cores such as iron powder cores, iron silicon powder cores, iron silicon aluminum powder cores, iron nickel powder cores and iron nickel molybdenum powder cores have problems such as high loss, heavy weight, low power and poor stability, which cannot meet their development needs. Therefore, in order to meet the trend of electronic components developing towards high frequency, miniaturization and high current, it is necessary to develop a soft magnetic composite material with excellent comprehensive properties such as high saturation magnetic induction intensity, high magnetic permeability, low loss, good frequency stability and DC bias performance. Amorphous soft magnetic materials are one of the ideal materials for preparing high magnetic permeability and low loss soft magnetic composite materials due to their high magnetic permeability, high resistivity and low coercive force.

[0003] Insulating amorphous magnetic powder to reduce the energy loss in the electromagnetic conversion process of magnetic powder core is the key to achieve high frequency and low loss of electronic components. However, amorphous magnetic powder has good corrosion resistance, and it is difficult to form a uniform and dense insulation layer on the surface of magnetic powder by acid passivation. In addition, the high pressing pressure of amorphous magnetic powder core causes the insulation layer on the surface of magnetic powder to rupture, making it difficult to obtain amorphous soft magnetic composite materials with good comprehensive performance, thus limiting the development and application of such materials. Summary of the invention

[0004] The purpose of the present application is to provide a magnetic powder core and a preparation method thereof, which can obtain a uniform and dense insulating layer on the surface of amorphous magnetic powder and is not easy to break during the pressing process.

[0005] On the one hand, an embodiment of the present application provides a method for preparing a magnetic powder core, comprising: mixing amorphous magnetic powder with an acid solution, acidifying the surface of the amorphous magnetic powder to form acidified magnetic powder; mixing the acidified magnetic powder with a silicate sol, so that the silicate sol is coated on the surface of the acidified magnetic powder to form a sol magnetic powder; dehydrating the sol magnetic powder, the silicate sol is dehydrated to form a silicon dioxide layer coated on the surface of the acidified magnetic powder, so that the sol magnetic powder is converted into a coated magnetic powder; and pressing the coated magnetic powder into a magnetic powder core.

[0006] As an practicable manner, before mixing the acidified magnetic powder with silicate sol so that the silicate sol is coated on the surface of the acidified magnetic powder to form sol magnetic powder, the method for preparing the magnetic powder core further includes: mixing the acidified magnetic powder with an emulsifier to increase the surface wettability of the acidified magnetic powder.

[0007] As an practicable method, amorphous magnetic powder is mixed with an acid solution and the amorphous magnetic powder is acidified to form the acidified magnetic powder, including: acidifying the amorphous magnetic powder to form an inorganic salt layer on the surface of the amorphous magnetic powder to convert the amorphous magnetic powder into acidified magnetic powder, and the inorganic salt material in the inorganic salt layer grows at multiple points on the surface of the amorphous magnetic powder to form a rough surface.

[0008] As an practicable method, the amorphous magnetic powder is mixed with an acid solution to acidify the amorphous magnetic powder to form the acidified magnetic powder, which includes: mixing the amorphous magnetic powder with a phosphoric acid solution and stirring at a temperature of 40-60°C for 10-30 minutes, wherein the surface of the amorphous magnetic powder reacts with the phosphoric acid to generate phosphate attached to the surface of the amorphous magnetic powder, so that the amorphous magnetic powder is converted into the acidified magnetic powder.

[0009] As an practicable manner, the mass ratio of phosphoric acid to amorphous magnetic powder is between 0.25:100 and 0.75:100.

[0010] As an practicable manner, the phosphoric acid solution is formed by mixing phosphoric acid and alcohol, wherein the mass ratio of phosphoric acid to alcohol is between 1:10 and 2:10.

[0011] As an practicable method, the acidified magnetic powder is mixed with a silicate sol so that the silicate sol is coated on the surface of the acidified magnetic powder to form a sol magnetic powder, which includes: mixing the acidified magnetic powder with an aqueous sodium silicate solution, and stirring at a temperature of 40-80° C. for 10-50 minutes, so that the silicate sol generated by the reaction of sodium silicate and water is coated on the surface of the acidified magnetic powder; and filtering the sodium silicate sol not coated on the surface of the acidified magnetic powder.

[0012] As an practicable manner, the mass ratio of sodium silicate to acidified magnetic powder is between 1.8:100 and 2.2:100.

[0013] As an practicable method, pressing the coated magnetic powder into a magnetic powder core includes: granulating the coated magnetic powder and then drying it to form dry magnetic powder; vibrating and screening the dry magnetic powder and cold pressing it into a magnetic powder core preform; and annealing the magnetic powder core preform to form a magnetic powder core.

[0014] On the other hand, an embodiment of the present application provides a magnetic powder core, which is made by the above-mentioned magnetic powder core preparation method. The magnetic powder core is pressed into a preset shape by coated magnetic powder, and the coated magnetic powder includes: a matrix; a mixed layer of inorganic salt and silicon dioxide formed on the surface of the matrix; wherein the inorganic salt forms a rough surface structure on the surface of the matrix, and the silicon dioxide fills the rough surface structure and coats the inorganic salt to form a mixed layer of inorganic salt and silicon dioxide.

[0015] The beneficial effects of the embodiments of the present application include:

[0016] The preparation method of the magnetic powder core provided in the present application comprises: mixing amorphous magnetic powder with an acid solution, acidifying the surface of the amorphous magnetic powder to form acidified magnetic powder, wherein the atoms on the surface of the amorphous magnetic powder react with the acid solution to generate inorganic salts attached to the surface of the acidified magnetic powder, and hydroxyl sites are formed on the surface of the acidified magnetic powder; mixing the acidified magnetic powder with a silicate sol, so that the silicate sol is coated on the surface of the acidified magnetic powder to form a sol magnetic powder, and the hydroxyl groups in the silicate sol are combined with the hydroxyl sites on the surface of the acidified magnetic powder, so that the silicate sol is coated with the hydroxyl groups on the surface of the acidified magnetic powder. On the surface of the acidified magnetic powder, since silicon atoms are evenly distributed in the silicate sol, the sol has a network structure, so that the silicon atoms are evenly and densely coated on the surface of the acidified magnetic powder; the sol magnetic powder is dehydrated, and the silicate sol is dehydrated to form a silicon dioxide layer coating the surface of the acidified magnetic powder, so that the sol magnetic powder is converted into coated magnetic powder, and the silicon dioxide layer is evenly and densely coated on the surface of the acidified magnetic powder; the coated magnetic powder is pressed into a magnetic powder core, and since silicon dioxide has a strong strength, it is not easy to break during the pressing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 One of the flow charts of a method for preparing a magnetic powder core provided in an embodiment of the present application;

[0019] Figure 2 One of the schematic diagrams of the state of coated magnetic powder provided in an embodiment of the present application;

[0020] Figure 3 The second schematic diagram of a state of coated magnetic powder provided in an embodiment of the present application;

[0021] Figure 4 The third schematic diagram of a state of coated magnetic powder provided in an embodiment of the present application;

[0022] Figure 5 A fourth schematic diagram of a state of coated magnetic powder provided in an embodiment of the present application;

[0023] Figure 6 The SEM image of the uncoated amorphous magnetic powder;

[0024] Figure 7 This is the SEM image of phosphate-coated amorphous magnetic powder;

[0025] Figure 8 This is the SEM image of amorphous magnetic powder coated with sodium silicate;

[0026] Fig. 9 This is a SEM image of the coated magnetic powder provided in the embodiment of the present application;

[0027] Fig.10 This is a second flow chart of a method for preparing a magnetic powder core provided in an embodiment of the present application.

[0028] Icon: 110-amorphous magnetic powder; 120-inorganic salt layer; 130-silicon dioxide layer. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0032] Amorphous magnetic powder has the characteristics of high magnetic permeability, high resistivity and low coercivity. It is one of the ideal materials for preparing high magnetic permeability and low loss soft magnetic composite materials. However, it is not easy to coat a dense and uniform insulating layer on the surface of amorphous magnetic powder, which limits the development and application of this type of material.

[0033] The present application provides a method for preparing a magnetic powder core, such as Figure 1 As shown, including:

[0034] S10: Figure 2 As shown, the amorphous magnetic powder 110 is mixed with an acid solution to acidify the surface of the amorphous magnetic powder 110 to form an acidified magnetic powder;

[0035] In order to clearly illustrate the preparation method of the present invention, the embodiment of the present invention uses Fe-containing magnetic powder as the amorphous magnetic powder 110 and phosphoric acid as the acid solution to illustrate the specific implementation steps. Of course, the amorphous magnetic powder 110 of the present invention is not limited to the magnetic powder containing Fe, and the acid solution is not limited to phosphoric acid. For example, the Fe atoms on the surface of the amorphous magnetic powder 110 are mixed with the phosphoric acid solution. Phosphoric acid is a medium-strong acid and will react chemically with the Fe atoms on the surface of the amorphous magnetic powder 110 to form acidified magnetic powder. The specific reaction formula is as follows:

[0036] Fe+H3PO4→Fe 2+ +HPO4 2- +H2↑ (1)

[0037] 3Fe 2+ +2PO4 3- →Fe3(PO4)2 (2)

[0038] 4Fe 2+ +O2+4PO4 3- +4H + →4FePO4+2H2O (3)

[0039] After the Fe-containing magnetic powder is mixed with amorphous magnetic powder 110 as a phosphoric acid solution, the Fe atoms on the surface of the amorphous magnetic powder 110 react with the phosphoric acid, and the hydrogen generated in formula (1) will escape into the external environment. The Fe3(PO4)2 and FePO4 generated in formula (2) and formula (3) nucleate and grow on the surface of the amorphous magnetic powder 110, and the crystals of Fe3(PO4)2 and FePO4 are rapidly formed. Since the crystal nuclei of Fe3(PO4)2 and FePO4 are formed at multiple points on the surface of the amorphous magnetic powder 110, and the growth direction of each crystal nucleus is inconsistent, the surface of the inorganic salt layer 120 formed by the combination of Fe3(PO4)2 and FePO4 generated on the surface of the amorphous magnetic powder 110 is uneven. In addition, Fe3(PO4)2 and FePO4 are generated by the reaction of Fe atoms on the surface of the amorphous magnetic powder 110 with the phosphoric acid solution. Therefore, Fe3(PO4)2 and FePO4 are firmly combined with the surface of the amorphous magnet and have good adsorption, corrosion resistance and electrical insulation.

[0040] In addition, the phosphoric acid solution forms many hydroxyl sites on the surface of the amorphous magnetic powder 110 during the reaction, so that the surface of the acidified magnetic powder has multiple hydroxyl sites, so that the hydroxyl groups of the silicate sol can be combined with the hydroxyl sites on the surface of the acidified magnetic powder during S20.

[0041] S20: Figure 2 As shown, the acidified magnetic powder is mixed with the silicate sol, so that the silicate sol is coated on the surface of the acidified magnetic powder to form sol magnetic powder;

[0042] The embodiment of the present invention uses sodium silicate sol as silicate sol. Specifically, sodium silicate is dissolved in water to form sodium silicate sol. The specific reaction formula is as follows:

[0043] Na2·nSiO2+(2n+1)H2O→2NaOH+nSi(OH)4 (4)

[0044] Among them, nSi(OH)4 acts as the colloidal particles in the sol, and NaOH acts as the solvent in the sol, so that nSi(OH)4 is evenly dispersed in the solvent. When the silicate sol coats the acidified magnetic powder, due to the uneven surface of the acidified magnetic powder, the colloidal sodium silicate sol can fill the uneven surface of the acidified magnetic powder and coat the surface of the acidified magnetic powder, so that the colloidal particles in the sol are evenly distributed on the surface of the acidified magnetic powder.

[0045] The hydroxyl groups in the sodium silicate sol can combine well with the hydroxyl sites on the surface of the acidified magnetic powder to form a strong coating layer.

[0046] S30: dehydrating the sol magnetic powder, the silicate sol is dehydrated to form a silicon dioxide layer 130 coated on the surface of the acidified magnetic powder, so that the sol magnetic powder is converted into coated magnetic powder;

[0047] Specifically, the reaction equation for dehydration of colloidal Si(OH)4 is as follows:

[0048]

[0049] S40: Pressing the coated magnetic powder into a magnetic powder core.

[0050] The specific shape of the magnetic powder core is not limited in the embodiments of the present application, and can be an E-type magnetic core, a ring-shaped magnetic core, an I-type magnetic core or an F-type magnetic core. The magnetic powder core formed by pressing the coated magnetic powder in the embodiments of the present application has a dense and uniform coating layer on the coated magnetic powder, so that the magnetic powder core formed by pressing the coated magnetic powder has good insulation and compression resistance.

[0051] The preparation method of the magnetic powder core provided in the present application comprises: mixing an amorphous magnetic powder 110 with an acid solution, acidifying the surface of the amorphous magnetic powder 110 to form an acidified magnetic powder, wherein the atoms on the surface of the amorphous magnetic powder 110 react with the acid solution to generate inorganic salts attached to the surface of the acidified magnetic powder, and hydroxyl sites are formed on the surface of the acidified magnetic powder; mixing the acidified magnetic powder with a silicate sol, so that the silicate sol is coated on the surface of the acidified magnetic powder to form a sol magnetic powder, and the hydroxyl groups in the silicate sol are combined with the hydroxyl sites on the surface of the acidified magnetic powder, so that the silicate sol is coated on the surface of the acidified magnetic powder to form a sol magnetic powder. The surface of the acidified magnetic powder is coated. Since silicon atoms are evenly distributed in the silicate sol and the sol has a network structure, the silicon ions are evenly and densely coated on the surface of the acidified magnetic powder. The sol magnetic powder is dehydrated. The silicate sol is dehydrated to form a silicon dioxide layer 130 coated on the surface of the acidified magnetic powder, so that the sol magnetic powder is converted into coated magnetic powder. The silicon dioxide layer 130 is evenly and densely coated on the surface of the acidified magnetic powder. The coated magnetic powder is pressed into a magnetic powder core. Since silicon dioxide has a strong strength, it is not easy to break during the pressing process.

[0052] In order to further prove that the phosphoric acid treatment followed by silica sol coating provided in the embodiment of the present application has the above advantages, the embodiment of the present application provides a comparison table of various properties of magnetic powder cores coated with phosphoric acid only, coated with silica sol only, and coated in the present application, as shown in Table 1, Figure 6 , Figure 7 , Figure 8 and Fig. 9 shown.

[0053] It can be seen from Table 1 that the coating method of phosphoric acidization followed by silica sol coating provided in the embodiment of the present application enables the magnetic powder core to have a larger resistivity, lower loss and larger crush stress.

[0054] Depend on Figure 6 , Figure 7 , Figure 8 and Fig. 9 It can be seen that the coating method of phosphoric acidization followed by silica sol coating provided in the embodiment of the present application makes the surface of the coated magnetic powder more dense and uniform.

[0055] Table 1 Performance comparison of magnetic powder cores prepared by different coating methods

[0056]

[0057] Optionally, before mixing the acidified magnetic powder with silicate sol so that the silicate sol is coated on the surface of the acidified magnetic powder to form sol magnetic powder, the method for preparing the magnetic powder core further includes mixing the acidified magnetic powder with an emulsifier to increase the surface wettability of the acidified magnetic powder.

[0058] The acidified magnetic powder is mixed with an emulsifier to improve the wettability of the surface of the acidified magnetic powder. When the acidified magnetic powder is mixed with the silicate sol, the acidified magnetic powder can react with the silicate sol quickly to achieve silica sol coating, thereby increasing the coating rate of the acidified magnetic powder, thereby shortening the reaction time of the acidified magnetic powder and the silicate sol. Because the silicate sol usually contains water, the acidified magnetic powder is prevented from being corroded by the water in the silicate sol during the coating process, thereby destroying the originally uniform and dense coating layer.

[0059] In one achievable method of an embodiment of the present application, the amorphous magnetic powder 110 is mixed with an acid solution, and the amorphous magnetic powder 110 is acidified to form the acidified magnetic powder, including: the amorphous magnetic powder is acidified to form an inorganic salt layer on the surface of the amorphous magnetic powder to convert the amorphous magnetic powder into the acidified magnetic powder, and the inorganic salt material in the inorganic salt layer 120 grows at multiple points on the surface of the amorphous magnetic powder 110 to form a rough surface.

[0060] The amorphous magnetic powder 110 is mixed with the acid solution, and the atoms on the surface of the amorphous magnetic powder 110 react with the acid to form an inorganic salt, and the inorganic salt forms an inorganic salt layer 120 on the surface of the amorphous magnetic powder 110. The inorganic salt nucleates and grows to form crystals on the surface of the amorphous magnetic powder 110. The growth directions of multiple crystal nuclei on the surface of the amorphous magnetic powder 110 are inconsistent, making the surface of the acidified magnetic powder rough. When the acidified magnetic powder with a rough surface reacts with the silicate sol, it can improve the bonding strength between the silicate sol and the surface of the acidified magnetic powder, thereby improving the firmness of the coating.

[0061] Optionally, mixing the amorphous magnetic powder 110 with an acid solution to acidify the amorphous magnetic powder 110 to form the acidified magnetic powder includes:

[0062] The amorphous magnetic powder 110 is mixed with the phosphoric acid solution and stirred at a temperature of 40-60° C. for 10-30 minutes. The surface of the amorphous magnetic powder 110 reacts with the phosphoric acid to generate phosphate attached to the surface of the amorphous magnetic powder 110 , so that the amorphous magnetic powder 110 is converted into an acidified magnetic powder.

[0063] The acid solution uses a phosphoric acid solution because phosphoric acid is a medium-strong acid. When a strong acid is selected as the acid solution, the strong acid reacts too violently with the atoms on the surface of the amorphous magnetic powder 110, making the reaction difficult to control. When a weak acid is selected as the acid solution, the weak acid reacts too slowly with the amorphous magnetic powder 110, making the reaction time longer and prolonging the preparation time of the magnetic powder core. The embodiment of the present application uses phosphoric acid to reduce the acidification time while ensuring that the reaction is within a controllable range. Based on the fact that the acid solution is a phosphoric acid solution, the present application sets the reaction temperature at 40-60°C and the reaction time at 10-30min. Preferably, the reaction temperature is set at 50°C, the reaction time is set at 20min and stirred. When the atoms on the surface of the amorphous magnetic powder 110 react with phosphoric acid, the high temperature will not cause the reaction rate to be too fast, making the reactants uneven, nor will the temperature be too low, causing the reaction to stop. The reaction time is also moderate. Too short a reaction time will result in incomplete reaction, while too long a time will prolong the preparation time. The atoms on the surface of the amorphous magnetic powder 110 can fully react with phosphoric acid to form an inorganic salt layer 120 wrapped on the surface of the amorphous magnetic powder 110. In order to make the reaction of the metal magnetic powder and the phosphoric acid solution more uniform and complete, the reaction can be stirred to ensure full and uniform mixing.

[0064] In one achievable manner of the embodiment of the present application, the mass ratio of phosphoric acid to the amorphous magnetic powder 110 is between 0.25:100 and 0.75:100.

[0065] When the phosphoric acid solution and the amorphous magnetic powder 110 are mixed and reacted to form the acidified magnetic powder, the phosphoric acid actually reacts with the atoms on the surface of the amorphous magnetic powder 110. To ensure that the amorphous magnetic powder 110 is fully acidified, the mass ratio of phosphoric acid to amorphous magnetic powder 110 is set between 0.25:100 and 0.75:100.

[0066] Optionally, the phosphoric acid solution is formed by mixing phosphoric acid and alcohol, wherein the mass ratio of phosphoric acid to alcohol is between 1:10 and 2:10.

[0067] The amorphous magnetic powder 110 usually contains metals such as Fe that are easily corroded by water. In order to prevent the phosphoric acid solution from containing moisture, which may corrode the amorphous magnetic powder 110 when the amorphous magnetic powder 110 is mixed with the phosphoric acid aqueous solution and cause an increase in the loss of the amorphous magnetic powder 110, the embodiment of the present application sets the phosphoric acid solution to a mixed solution of phosphoric acid and alcohol. The amorphous magnetic powder 110 usually contains atoms such as Fe that are not easy to react with alcohol, thereby avoiding the occurrence of the above situation.

[0068] In addition, when the phosphoric acid solution is mixed with the amorphous magnetic powder 110 to form the acidified magnetic powder, in order to enable the phosphoric acid in the phosphoric acid solution to react with the atoms on the surface of the amorphous magnetic powder 110 and increase the probability of the phosphoric acid ions contacting the amorphous surface, the mass ratio of phosphoric acid to alcohol can be set between 1:10 and 2:10.

[0069] In one achievable manner of the embodiment of the present application, mixing the acidified magnetic powder with the silicate sol so that the silicate sol is coated on the surface of the acidified magnetic powder to form the sol magnetic powder includes:

[0070] The acidified magnetic powder is mixed with the sodium silicate aqueous solution and stirred at a temperature of 40-80° C. for 10-50 minutes, so that the silicate sol generated by the reaction of the sodium silicate and water is coated on the surface of the acidified magnetic powder;

[0071] When sodium silicate is mixed with water to form sodium silicate sol, the specific reaction formula is as follows:

[0072] Na2·nSiO2+(2n+1)H2O→2NaOH+nSi(OH)4 (4)

[0073] In order to allow sodium silicate to react with water to generate sodium silicate sol, the present application sets the reaction temperature at 40-80°C and the reaction time at 10-50 minutes. The high temperature will not cause the reaction rate to be too fast, resulting in uneven distribution of the colloid particles, nor will the temperature be too low, resulting in a slow reaction or even stopping. The reaction time is also moderate. If the reaction time is too short, the reaction will be incomplete, while if the time is too long, the preparation time will be prolonged.

[0074] The sodium silicate sol not coated on the surface of the acidified magnetic powder is filtered out to filter out the sol magnetic powder.

[0075] Optionally, the mass ratio of sodium silicate to acidified magnetic powder is between 1.8:100 and 2.2:100.

[0076] The sodium silicate solution is mixed with the acidified magnetic powder, and the sodium silicate solution forms a sodium silicate sol, so that the sodium silicate sol is coated on the surface of the acidified magnetic powder. In order to make the sodium silicate sol evenly coated on the surface of the acidified magnetic powder, the mass ratio of sodium silicate to the acidified magnetic powder is set between 1.8:100 and 2.2:100, which can ensure that the sodium silicate sol completely coats the acidified magnetic powder.

[0077] In one achievable manner of the embodiment of the present application, pressing the coated magnetic powder into a magnetic powder core includes: Fig.10 As shown:

[0078] S41: granulating the coated magnetic powder and drying it to form dry magnetic powder;

[0079] Granulation is to sieve the powder that is evenly stirred and agglomerated. The mesh number of the granulation sieve is 40-250 mesh, so that the powder has good fluidity and similar particle size, so that the insulation performance of the coated magnetic powder is relatively uniform. After granulation, the coated magnetic powder still contains some organic solvents, which need to be volatilized and dried in a drying oven to make it powdery.

[0080] S42: vibrating and screening the dried magnetic powder, and cold pressing to form a magnetic powder core preform;

[0081] Vibration screening is used to select coated magnetic powder of 50-200 mesh, and large and small particles in the powder are removed to make the coated magnetic powder uniform in size. In order to avoid agglomeration and facilitate demoulding, 0.3wt.% barium stearate lubricant can be used for lubrication.

[0082] The coated magnetic powder is then cold pressed into a shape that can be used in electronic components. Specifically, the magnetic core can be made into any shape according to actual needs. The cold pressing pressure is 400-2000MPa, and the holding time is 2s-60s. For example, the cold pressing pressure of the embodiment of the present invention is 800MPa, and the holding time is 5s.

[0083] S43: annealing the magnetic powder core preform to form a magnetic powder core.

[0084] The annealing treatment increases the strength of the magnetic powder core preform to form a magnetic powder core. The specific curing conditions are: heating from 20°C-35°C to 160°C-200°C within 2 hours, and then curing and keeping warm for 0.5h-2.5h. For example, the curing conditions of the embodiment of the present invention are heating from room temperature to 180°C within 0.5h, and then keeping warm at 180°C for 1.5h to fully cure it.

[0085] The embodiment of the present application also discloses a magnetic powder core, which is made by the above-mentioned magnetic powder core preparation method. The magnetic powder core is pressed into a preset shape by coated magnetic powder, and the coated magnetic powder includes: a matrix; an inorganic salt and silicon dioxide mixed layer formed on the surface of the matrix; wherein the inorganic salt forms a rough surface structure on the surface of the matrix, and silicon dioxide fills the rough surface structure and coats the inorganic salt to form an inorganic salt and silicon dioxide mixed layer. The mixed layer is densely and evenly coated on the matrix, so that the magnetic powder core has good insulation and pressure resistance.

[0086] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a magnetic powder core, characterized in that: include: Mixing amorphous magnetic powder with an acid solution to acidify the surface of the amorphous magnetic powder to form acidified magnetic powder; Mixing the acidified magnetic powder with silicate sol so that the silicate sol covers the surface of the acidified magnetic powder to form sol magnetic powder; Dehydrating the sol magnetic powder, wherein the silicate sol is dehydrated to form a silicon dioxide layer coated on the surface of the acidified magnetic powder, so that the sol magnetic powder is converted into coated magnetic powder; Pressing the coated magnetic powder into a magnetic powder core; The mixing of the amorphous magnetic powder with the acid solution to acidify the amorphous magnetic powder to form the acidified magnetic powder comprises: The amorphous magnetic powder is acidified to form an inorganic salt layer on the surface of the amorphous magnetic powder to convert the amorphous magnetic powder into the acidified magnetic powder. The inorganic salt material in the inorganic salt layer grows at multiple points on the surface of the amorphous magnetic powder to form a rough surface.

2. The method for preparing a magnetic powder core according to claim 1, characterized in that: Before mixing the acidified magnetic powder with silicate sol so that the silicate sol covers the surface of the acidified magnetic powder to form sol magnetic powder, the method further includes: The acidified magnetic powder is mixed with an emulsifier to increase the surface wettability of the acidified magnetic powder.

3. The method for preparing a magnetic powder core according to claim 1, characterized in that: The mixing of the amorphous magnetic powder with the acid solution to acidify the amorphous magnetic powder to form the acidified magnetic powder comprises: The amorphous magnetic powder is mixed with a phosphoric acid solution and stirred at a temperature of 40-60° C. for 10-30 minutes. The surface of the amorphous magnetic powder reacts with the phosphoric acid to generate phosphate attached to the surface of the amorphous magnetic powder, so that the amorphous magnetic powder is converted into an acidified magnetic powder.

4. The method for preparing a magnetic powder core according to claim 3, characterized in that: The mass ratio of the phosphoric acid to the amorphous magnetic powder is between 0.25:100 and 0.75:

100.

5. The method for preparing a magnetic powder core according to claim 3, characterized in that: The phosphoric acid solution is formed by mixing phosphoric acid and alcohol, wherein the mass ratio of phosphoric acid to alcohol is between 1:10 and 2:

10.

6. The method for preparing a magnetic powder core according to claim 1, characterized in that: Mixing the acidified magnetic powder with silicate sol so that the silicate sol covers the surface of the acidified magnetic powder to form sol magnetic powder comprises: The acidified magnetic powder is mixed with a sodium silicate aqueous solution, and stirred at a temperature of 40-80° C. for 10-50 minutes, so that the silicate sol generated by the reaction of the sodium silicate and water is coated on the surface of the acidified magnetic powder; The sodium silicate sol not coated on the surface of the acidified magnetic powder is filtered out.

7. The method for preparing a magnetic powder core according to claim 6, characterized in that: The mass ratio of the sodium silicate to the acidified magnetic powder is between 1.8:100 and 2.2:

100.

8. The method for preparing a magnetic powder core according to claim 1, characterized in that: The step of pressing the coated magnetic powder into a magnetic powder core comprises: Granulating the coated magnetic powder and then drying it to form dry magnetic powder; Vibrating and screening the dry magnetic powder and cold pressing the dry magnetic powder into a magnetic powder core preform; The magnetic powder core preform is annealed to form the magnetic powder core.

9. A magnetic powder core, characterized in that: The magnetic powder core is made by the method for preparing the magnetic powder core according to any one of claims 1 to 8, wherein the magnetic powder core is pressed into a preset shape by coated magnetic powder, and the coated magnetic powder comprises: matrix; A mixed layer of inorganic salt and silicon dioxide is formed on the surface of the substrate; wherein the inorganic salt forms a rough surface structure on the surface of the substrate, and silicon dioxide fills the rough surface structure and covers the inorganic salt to form the mixed layer of inorganic salt and silicon dioxide.

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