A boron-silicon coated metal soft magnetic powder core and a method for producing the same

Abstract

The application provides a boron-silicon coated metal soft magnetic powder core and a preparation method thereof. The preparation method comprises the following steps: (1) mixing a siloxane, boric acid powder, a first solvent, a catalyst and water to perform a hydrolysis reaction, and performing a polycondensation reaction on a hydrolysis product to obtain a boron-silicon containing coating agent; (2) mixing the boron-silicon containing coating agent, soft magnetic powder and a second solvent to obtain coated soft magnetic powder; and (3) mixing the coated soft magnetic powder, a binder and a release agent, and sequentially performing press forming and annealing treatment to obtain the boron-silicon coated metal soft magnetic powder core. The preparation method uniformly coats the boron-silicon containing coating agent on the surface of the soft magnetic powder by chemical organic synthesis, effectively improves the insulation coating of the surface of the soft magnetic powder, and further greatly improves the resistance of the metal soft magnetic powder core, reduces the eddy current loss under high frequency use, and has large-scale industrialization application prospects.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic metal materials technology, and in particular to a borosilicate-coated soft magnetic metal powder core and its preparation method. Background Technology

[0002] Soft magnetic materials are important magnetic functional materials with excellent electromagnetic conversion properties. Electronic components made from them are widely used in communications, power equipment, information technology, and automatic control. Metallic soft magnetic materials possess advantages such as high saturation magnetization and good frequency characteristics. When mixed with insulating binders and then processed through molding, annealing, and impregnation curing, metallic soft magnetic powder cores are prepared for high-frequency, high-efficiency, high-current, and miniaturized electronic component applications.

[0003] Surface coating of metal magnetic powder can increase the surface resistivity of the powder core and reduce eddy current losses under high-frequency use. Current technology mainly focuses on coating the surface of magnetic powder particles with silicon-containing compounds, and the methods include inorganic coating, organic coating, and inorganic-organic coating.

[0004] CN110246679A discloses a method for preparing a metal soft magnetic powder core based on an organic / inorganic composite insulation process. The technical solution involves first organically insulating the metal magnetic powder with epoxy resin, then modifying and coupling the nano-silica powder generated from the hydrolysis of epoxy resin and tetraethyl orthosilicate using a silane coupling agent. This achieves composite insulation of the metal magnetic powder by epoxy resin and silica. The insulated powder is then cold-pressed and the green blank is subjected to high-temperature annealing to obtain a metal soft magnetic powder core with excellent DC bias performance and low high-frequency loss. However, this process does not significantly improve the interparticle insulation, resulting in a metal soft magnetic powder core with relatively high magnetic loss.

[0005] CN101599334A discloses a method for manufacturing a high-resistivity, high-permeability iron-silicon-aluminum material. This method involves adding 1-10 wt% Ni powder to FeSiAl magnetic powder and coating the powder surface with a SiO2 layer. This significantly reduces conductivity without altering the original magnetic properties, greatly reducing losses. Furthermore, the thickness of the SiO2 coating can be adjusted based on the concentration of added tetraethyl orthosilicate. The method also includes surface treatment of the coated powder to improve dispersibility, processability, and significantly enhance the product's physicochemical properties. However, this method is technically challenging and the process is difficult to control.

[0006] CN103247403A discloses a method for preparing a soft magnetic powder core, which includes six parts: raw material sieving, insulating coating, preparing the magnetic powder to be shaped, pressing and molding, heat treatment, and surface spraying. The manufacturing process is simple, and the equipment used is basic. Using this nano-oxide dispersion for insulating coating of the magnetic powder results in good performance, is environmentally friendly, and has low raw material costs. The preparation process does not use organic solvents or organic binders, and does not require impregnation and curing treatment, resulting in low cost and no pollution. The soft magnetic powder core prepared by this method exhibits good magnetic property stability, a high quality factor, and low core loss. However, the coating effect of this preparation method is relatively poor.

[0007] Therefore, it is of great significance to develop a borosilicate-coated soft magnetic powder core with good insulation coating effect, which can improve the surface resistance of the magnetic powder core and reduce eddy current loss under high frequency use, and its preparation method. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a borosilicate-coated metal soft magnetic powder core and its preparation method. The borosilicate-coated material is uniformly coated onto the surface of the soft magnetic powder using chemical organic synthesis. The preparation process is easy to control, and the insulating coating effect is excellent, making it promising for large-scale industrial application.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0011] (1) Mix siloxane, boric acid powder, first solvent, catalyst and water, and carry out hydrolysis reaction. The hydrolysis product is subjected to polycondensation reaction to obtain borosilicate coating agent.

[0012] (2) Mix the boron-silicon coating agent, soft magnetic powder and second solvent to obtain the coated soft magnetic powder;

[0013] (3) The coated soft magnetic powder, binder and release agent are mixed and then pressed and annealed in sequence to obtain borosilicate coated metal soft magnetic powder core.

[0014] The method for preparing borosilicate-coated metal soft magnetic powder cores according to the present invention involves sequentially hydrolyzing and polycondensing raw materials siloxane, boric acid powder, a first solvent, a catalyst, and water to obtain a borosilicate-containing coating agent. This agent can form a glassy network structure on the surface of the soft magnetic powder particles, effectively improving the insulating coating of the soft magnetic powder surface, thereby significantly increasing the resistance of the metal soft magnetic powder core and reducing eddy current losses under high-frequency use. The preparation process of the method described in this invention is easy to control, and the insulating coating effect is excellent.

[0015] Preferably, step (1) of mixing siloxane, boric acid powder, first solvent, catalyst and water includes: first mixing siloxane and boric acid powder to obtain a mixed solution, then adding the first solvent and catalyst, stirring and heating to 50-100°C, and then adding water. The stirring and heating to 50-100°C can be, for example, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the siloxane in step (1) includes polydimethylsiloxane and / or dimethyldiethoxysilane.

[0017] Preferably, the purity of the boric acid powder is 99.9% or higher, for example, it can be 99.9%, 99.91%, 99.92%, 99.94%, 99.95% or 99.98%, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the boric acid powder has a particle size of 5 to 50 μm, such as 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the mass ratio of the siloxane to the boric acid powder is 10:(0.5-3), for example, it can be 10:0.5, 10:0.8, 10:1, 10:1.5, 10:2 or 10:3, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] In this invention, the preferred mass ratio of siloxane to boric acid powder is 10:(0.5-3). This facilitates the formation of a borosilicate coating with a glass mesh structure on the surface of the soft magnetic powder particles, thereby increasing the surface resistance of the metal soft magnetic powder core and reducing eddy current losses under high-frequency use. When the mass ratio of siloxane to boric acid powder is lower than 10:0.5, the silicon content of the powder coating is low, resulting in poor eddy current loss reduction. When the mass ratio of siloxane to boric acid powder is higher than 10:3, the silicon content of the powder coating is too high, significantly reducing the permeability of the borosilicate-coated metal soft magnetic powder core.

[0021] Preferably, in step (1), the first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol or n-butanol, wherein typical but non-limiting combinations include a combination of methanol and ethanol, a combination of isopropanol and n-butanol, a combination of ethanol and isopropanol, or a combination of n-butanol, methanol and isopropanol.

[0022] Preferably, the catalyst comprises any one or a combination of at least two of hydrochloric acid, sulfuric acid, or nitric acid, wherein typical but non-limiting combinations include a combination of hydrochloric acid and sulfuric acid, a combination of nitric acid and hydrochloric acid, or a combination of sulfuric acid, nitric acid, and hydrochloric acid.

[0023] Preferably, the mass concentration of the catalyst is 2 to 10 mol / mL, for example, it can be 2 mol / mL, 3 mol / mL, 5 mol / mL, 7 mol / mL, 8 mol / mL or 10 mol / mL, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the volume ratio of the first solvent to the catalyst is 10:(0.1 to 0.5), for example, it can be 10:0.1, 10:0.2, 10:0.3, 10:0.4 or 10:0.5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the water comprises deionized water.

[0026] Preferably, the amount of water added is 1 to 5% of the mass of siloxane and boric acid powder, for example, it can be 1%, 2%, 3%, 4% or 5%, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the hydrolysis reaction time is 0.5 to 5 hours, for example, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the polycondensation reaction in step (1) is carried out in a distillation apparatus.

[0029] Preferably, the hydrolysis product is subjected to vacuum distillation in the distillation apparatus.

[0030] Preferably, the vacuum degree of the reduced pressure distillation is 0.02 to 0.15 MPa, for example, it can be 0.02 MPa, 0.05 MPa, 0.1 MPa, 0.12 MPa, 0.14 MPa or 0.15 MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the temperature of the polycondensation reaction is 80 to 150°C, for example, 80°C, 90°C, 100°C, 130°C, 140°C or 150°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the polycondensation reaction time is 1 to 20 hours, for example, 1 hour, 3 hours, 5 hours, 10 hours, 15 hours or 20 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the mass ratio of the borosilicate coating agent, soft magnetic powder, and second solvent in step (2) is (0.01-0.5):10:(0.5-1.5), for example, it can be 0.01:10:0.5, 0.05:10:0.8, 0.1:10:0.9, 0.2:10:1, 0.3:10:1.2, or 0.5:10:1.5, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the soft magnetic powder includes any one or a combination of at least two of the following: iron-nickel magnetic powder, iron-silicon magnetic powder, iron-silicon-aluminum magnetic powder, iron-nickel-molybdenum magnetic powder, amorphous magnetic powder, or nanocrystalline magnetic powder. Typical but non-limiting combinations include combinations of iron-nickel magnetic powder and iron-silicon magnetic powder, combinations of iron-silicon-aluminum magnetic powder and iron-nickel-molybdenum magnetic powder, combinations of iron-nickel magnetic powder and iron-silicon-aluminum magnetic powder, or combinations of iron-nickel-molybdenum magnetic powder, iron-nickel magnetic powder, and iron-silicon magnetic powder.

[0035] Preferably, the second solvent comprises acetone.

[0036] Preferably, the coated soft magnetic powder is further subjected to drying and sieving processes in sequence.

[0037] Preferably, step (3) of mixing the coated soft magnetic powder, binder and release agent includes: first mixing the coated soft magnetic powder and binder, drying the mixture and then adding the release agent.

[0038] Preferably, the mass ratio of the coated soft magnetic powder, binder, and release agent is 10:(0.01~0.1):(0.01~0.1), for example, it can be 10:0.01:0.01, 10:0.02:0.03, 10:0.05:0.05, 10:0.06:0.07, 10:0.08:0.09, or 10:0.1:0.1, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the adhesive comprises any one or a combination of at least two of silicone resin, epoxy resin, or phenolic resin, wherein typical but non-limiting combinations include a combination of silicone resin and epoxy resin, a combination of phenolic resin and silicone resin, or a combination of epoxy resin, phenolic resin, and silicone resin.

[0040] Preferably, the release agent comprises any one or a combination of at least two of zinc stearate, aluminum stearate, or graphite, wherein typical but non-limiting combinations include a combination of zinc stearate and aluminum stearate, a combination of graphite and zinc stearate, or a combination of aluminum stearate, graphite, and zinc stearate.

[0041] Preferably, the pressing pressure in step (3) is 1000 to 3000 MPa, for example, it can be 1000 MPa, 1050 MPa, 2000 MPa, 2500 MPa or 3000 MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] The present invention preferably uses a pressing pressure of 1000-3000 MPa, which has the advantages of improving the density of the borosilicate-coated metal soft magnetic powder core and ensuring that the insulation layer is not damaged.

[0043] Preferably, the annealing process is carried out in a nitrogen atmosphere.

[0044] Preferably, the annealing temperature is 500 to 800°C, for example, 500°C, 550°C, 600°C, 700°C, 770°C or 800°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] The annealing temperature of the present invention is preferably 500-800℃, which has the advantages of stress removal and reduction of hysteresis loss.

[0046] Preferably, the annealing time is 0.1 to 8 hours, for example, it can be 0.1 hours, 0.5 hours, 1 hour, 2 hours, 5 hours or 8 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0048] (1) First, mix siloxane and boric acid powder in a mass ratio of 10:(0.5~3) to obtain a mixed solution. Then, add a first solvent and catalyst in a volume ratio of 10:(0.1~0.5), stir and heat to 50~100℃, add water, and carry out a hydrolysis reaction for 0.5~5h. In a distillation apparatus, perform vacuum distillation on the hydrolysis product and carry out a polycondensation reaction at a temperature of 80~150℃ for 1~20h to obtain a borosilicate coating agent.

[0049] The siloxane includes polydimethylsiloxane and / or dimethyldiethoxysilane; the boric acid powder has a purity of 99.9% or higher; the boric acid powder has a particle size of 5–50 μm; the first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, or n-butanol; the catalyst includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, or nitric acid; the catalyst has a mass concentration of 2–10 mol / mL; the water includes deionized water; the amount of water added is 1–5 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.02–0.15 MPa.

[0050] (2) The boron-silicon coating agent, soft magnetic powder and second solvent are mixed in a mass ratio of (0.01~0.5):10:(0.5~1.5) to obtain the coated soft magnetic powder;

[0051] The soft magnetic powder includes any one or a combination of at least two of the following: iron-nickel magnetic powder, iron-silicon magnetic powder, iron-silicon-aluminum magnetic powder, iron-nickel-molybdenum magnetic powder, amorphous magnetic powder, or nanocrystalline magnetic powder; the second solvent includes acetone; the coated soft magnetic powder is further subjected to drying and sieving processes in sequence.

[0052] (3) First, mix the coated soft magnetic powder and binder, dry them, then add a release agent, and then successively press them under a pressure of 1000-3000MPa and anneal them in a nitrogen atmosphere at a temperature of 500-800℃ for 0.1-8h to obtain a borosilicate coated metal soft magnetic powder core.

[0053] The mass ratio of the coated soft magnetic powder, binder, and release agent is 10:(0.01-0.1):(0.01-0.1); the binder includes any one or a combination of at least two of silicone resin, epoxy resin, or phenolic resin; the release agent includes any one or a combination of at least two of zinc stearate, aluminum stearate, or graphite.

[0054] Secondly, the present invention also provides a borosilicate-coated metal soft magnetic powder core, wherein the metal soft magnetic powder core is prepared by the method for preparing the borosilicate-coated metal soft magnetic powder core described in the first aspect.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] (1) The method for preparing borosilicate coated metal soft magnetic powder core provided by the present invention utilizes boric acid powder as raw material to chemically and organically synthesize borosilicate coating, which effectively improves the insulating coating on the surface of the metal soft magnetic powder core and increases the resistance of the magnetic powder core.

[0057] (2) The borosilicate-coated metal soft magnetic powder core provided by the present invention has superior magnetic properties, high permeability and low magnetic loss, and has the prospect of large-scale industrial application. Detailed Implementation

[0058] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0059] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0060] Example 1

[0061] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0062] (1) First, polydimethylsiloxane and boric acid powder are mixed in a mass ratio of 10:0.5 to obtain a mixed solution. Then, ethanol and hydrochloric acid are added in a volume ratio of 10:0.3. After stirring and heating to 50°C, deionized water is added to carry out a hydrolysis reaction for 0.5 h. The hydrolysis product is then subjected to vacuum distillation in a distillation apparatus and a polycondensation reaction is carried out at 80°C for 1 h to obtain a borosilicate coating agent.

[0063] The purity of the boric acid powder is 99.9%; the particle size of the boric acid powder is 30 μm; the mass concentration of the catalyst is 5 mol / mL; the amount of water added is 2 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.02 MPa.

[0064] (2) The boron-silicon coating agent, iron-nickel magnetic powder and the second solvent acetone are mixed in a mass ratio of 0.5:10:1 to obtain the coated soft magnetic powder; the coated soft magnetic powder is then dried and sieved in sequence.

[0065] (3) First, mix the coated soft magnetic powder and the binder silicone resin, dry it, and then add the mold release agent zinc stearate. Then, press it under a pressure of 1500 MPa and anneal it in a nitrogen atmosphere at a temperature of 600°C for 5 hours to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder and mold release agent is 10:0.05:0.05.

[0066] Example 2

[0067] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0068] (1) First, polydimethylsiloxane and boric acid powder are mixed in a mass ratio of 10:0.5 to obtain a mixed solution. Then, ethanol and sulfuric acid are added in a volume ratio of 10:0.3. After stirring and heating to 80°C, deionized water is added and hydrolysis is carried out for 5 hours. The hydrolysis product is then subjected to vacuum distillation in a distillation apparatus and polycondensation is carried out at 100°C for 1 hour to obtain a borosilicate coating agent.

[0069] The purity of the boric acid powder is 99.93%; the particle size of the boric acid powder is 10 μm; the mass concentration of the catalyst is 2–10 mol / mL; the amount of water added is 1–5 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.05 MPa.

[0070] (2) The boron-silicon coating agent, iron-nickel magnetic powder and the second solvent acetone are mixed in a mass ratio of 0.05:10:1 to obtain the coated soft magnetic powder; the coated soft magnetic powder is then dried and sieved in sequence.

[0071] (3) First, mix the coated soft magnetic powder and the binder epoxy resin, dry them, and then add the release agent aluminum stearate. Then, press them under a pressure of 1500 MPa and anneal them in a nitrogen atmosphere at a temperature of 650°C for 2 hours to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder and release agent is 10:0.01:0.05.

[0072] Example 3

[0073] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0074] (1) First, polydimethylsiloxane and boric acid powder are mixed in a mass ratio of 10:0.5 to obtain a mixed solution. Then, ethanol and nitric acid are added in a volume ratio of 10:0.5. After stirring and heating to 50°C, deionized water is added and hydrolysis is carried out for 2 hours. The hydrolysis product is then subjected to vacuum distillation in a distillation apparatus and polycondensation is carried out at 80°C for 1 hour to obtain a borosilicate coating agent.

[0075] The purity of the boric acid powder is 99.95%; the particle size of the boric acid powder is 25 μm; the mass concentration of the catalyst is 4 mol / mL; the amount of water added is 4 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.05 MPa.

[0076] (2) The boron-silicon coating agent, iron-silicon magnetic powder and the second solvent acetone are mixed in a mass ratio of 0.05:10:1 to obtain the coated soft magnetic powder; the coated soft magnetic powder is then dried and sieved in sequence.

[0077] (3) First, mix the coated soft magnetic powder and the binder phenolic resin, dry them, and then add the release agent graphite. Then, press them under a pressure of 1500 MPa and anneal them in a nitrogen atmosphere at a temperature of 700°C for 7 hours to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder and release agent is 10:0.09:0.03.

[0078] Example 4

[0079] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0080] (1) First, polydimethylsiloxane and boric acid powder are mixed in a mass ratio of 10:0.5 to obtain a mixed solution. Then, ethanol and sulfuric acid are added in a volume ratio of 10:0.5. After stirring and heating to 50°C, deionized water is added and hydrolysis reaction is carried out for 5 hours. The hydrolysis product is subjected to vacuum distillation in a distillation apparatus and polycondensation reaction is carried out at 120°C for 6 hours to obtain a borosilicate coating agent.

[0081] The purity of the boric acid powder is above 99.9%; the particle size of the boric acid powder is 50 μm; the mass concentration of the catalyst is 10 mol / mL; the amount of water added is 2.4 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.1 MPa.

[0082] (2) The boron-silicon coating agent, iron-silicon-aluminum magnetic powder and the second solvent acetone are mixed in a mass ratio of 0.05:10:1 to obtain the coated soft magnetic powder; the coated soft magnetic powder is then dried and sieved in sequence.

[0083] (3) First, mix the coated soft magnetic powder and the binder epoxy resin, dry them, and then add the release agent zinc stearate. Then, press them under a pressure of 1500 MPa and anneal them in a nitrogen atmosphere at a temperature of 700°C for 5.5 h to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder and release agent is 10:0.08:0.01.

[0084] Example 5

[0085] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0086] (1) First, dimethyldiethoxysilane and boric acid powder are mixed in a mass ratio of 10:3 to obtain a mixed solution. Then, methanol and nitric acid are added in a volume ratio of 10:0.1. After stirring and heating to 100°C, deionized water is added and hydrolysis is carried out for 5 hours. The hydrolysis product is then subjected to vacuum distillation in a distillation apparatus and polycondensation is carried out at 150°C for 20 hours to obtain a borosilicate coating agent.

[0087] The purity of the boric acid powder is 99.92%; the particle size of the boric acid powder is 5 μm; the mass concentration of the catalyst is 2 mol / mL; the amount of water added is 1 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.02 MPa.

[0088] (2) The boron-silicon coating agent, iron-silicon magnetic powder and second solvent acetone are mixed in a mass ratio of 0.01:10:0.5 to obtain coated soft magnetic powder; the coated soft magnetic powder is then dried and sieved in sequence.

[0089] (3) First, mix the coated soft magnetic powder and the binder silicone resin, dry it, and then add the mold release agent aluminum stearate. Then, press it under a pressure of 1000MPa and anneal it in a nitrogen atmosphere at a temperature of 500℃ for 8 hours to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder and mold release agent is 10:0.01:0.1.

[0090] Example 6

[0091] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0092] (1) First, polydimethylsiloxane and boric acid powder are mixed in a mass ratio of 10:0.5 to obtain a mixed solution. Then, ethanol and sulfuric acid are added in a volume ratio of 10:0.5. After stirring and heating to 80°C, deionized water is added to carry out a hydrolysis reaction for 0.5 h. The hydrolysis product is then subjected to vacuum distillation in a distillation apparatus and a polycondensation reaction is carried out at 80°C for 1 h to obtain a borosilicate coating agent.

[0093] The purity of the boric acid powder is 99.98%; the particle size of the boric acid powder is 50 μm; the mass concentration of the catalyst is 10 mol / mL; the amount of water added is 5 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.15 MPa.

[0094] (2) The boron-silicon coating agent, iron-silicon-aluminum magnetic powder and the second solvent acetone are mixed in a mass ratio of 0.5:10:1.5 to obtain the coated soft magnetic powder; the coated soft magnetic powder is then dried and sieved in sequence.

[0095] (3) First, mix the coated soft magnetic powder and the binder silicone resin, dry it, and then add the mold release agent zinc stearate. Then, press it under a pressure of 3000MPa and anneal it in a nitrogen atmosphere at a temperature of 800℃ for 0.1h to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder and mold release agent is 10:0.1:0.5.

[0096] Example 7

[0097] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Example 1, except that the mass ratio of siloxane to borate powder in step (1) is replaced with 10:0.1 instead of 10:0.5.

[0098] Example 8

[0099] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Example 1, except that the mass ratio of siloxane to borate powder in step (1) is replaced with 10:4 instead of 10:0.5.

[0100] Example 9

[0101] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Embodiment 1, except that the pressing pressure in step (3) is replaced with 500 MPa instead of 1500 MPa.

[0102] Example 10

[0103] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Embodiment 1, except that the pressing pressure in step (3) is replaced with 3500 MPa instead of 1500 MPa.

[0104] Example 11

[0105] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Example 1, except that the annealing temperature in step (3) is replaced with 400°C instead of 600°C.

[0106] Example 12

[0107] This embodiment provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Example 1, except that the annealing temperature in step (3) is replaced with 900°C instead of 600°C.

[0108] Comparative Example 1

[0109] This comparative example provides a method for preparing a borosilicate-coated metal soft magnetic powder core, the method comprising the following steps:

[0110] 500-mesh iron-nickel magnetic powder was passivated in phosphoric acid, then coated with 0.5 wt% kaolin for insulation, followed by a second coating with 0.3 wt% silicone resin. Phenolic resin was added as a binder and zinc stearate as a release agent to the coated magnetic powder. The mixture was then molded at 1500 MPa and annealed at 600℃ under a nitrogen atmosphere to obtain ring-shaped samples.

[0111] Comparative Example 2

[0112] This comparative example provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as in Example 1, except that boric acid powder is not added in step (1).

[0113] Comparative Example 3

[0114] This comparative example provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as that of Comparative Example 1, except that the iron-nickel powder is replaced with iron-silicon magnetic powder.

[0115] Comparative Example 4

[0116] This comparative example provides a method for preparing a borosilicate-coated metal soft magnetic powder core. The preparation method is the same as that of Comparative Example 1, except that the iron-nickel powder is replaced with iron-silicon-aluminum magnetic powder.

[0117] The permeability and magnetic loss results of the borosilicate-coated metal soft magnetic powder cores obtained in the above embodiments and comparative examples are shown in Table 1.

[0118] Table 1

[0119]

[0120] As can be seen from Table 1:

[0121] (1) As can be seen from Examples 1 to 6, when the raw material is iron-nickel magnetic powder, the permeability of the obtained borosilicate-coated metal soft magnetic powder core can reach over 125, and the loss can reach 133 mW / cm under the conditions of 50 kHz and 100 mT. 3 Below, under conditions of 100kHz and 100mT, the loss can reach 287mW / cm. 3 The following applies: When the raw material is iron-silicon magnetic powder, the permeability of the obtained borosilicate-coated soft magnetic powder core can reach over 56, and the loss can reach 749 mW / cm under conditions of 50 kHz and 100 mT. 3 Below, under conditions of 100kHz and 100mT, the loss can reach 1783mW / cm. 3The following applies: When the raw material is iron-silicon-aluminum magnetic powder, the permeability of the obtained borosilicate-coated soft magnetic powder core can reach over 60, and the loss can reach 132 mW / cm under conditions of 50 kHz and 100 mT. 3 Below, under conditions of 100kHz and 100mT, the loss can reach 272mW / cm. 3 the following;

[0122] (2) It can be seen from the combined results of Examples 1 and Examples 7-8 that in Example 7, the mass ratio of siloxane to boric acid powder in step (1) is 10:0.1, and the permeability of the borosilicate-coated metal soft magnetic powder core is significantly lower than that in Example 1; however, the loss is comparable to that in Example 1 under the conditions of 50kHz and 100mT and under the conditions of 100kHz and 100mT; in Example 8, the mass ratio of siloxane to boric acid powder in step (1) is 10:4, and the permeability of the borosilicate-coated metal soft magnetic powder core is 132, which is slightly improved, but the loss is significantly increased.

[0123] (3) It can be seen from the combined results of Examples 1 and Examples 9-10 that the pressing pressure in step (3) of Example 9 is relatively low, and the permeability of the borosilicate-coated metal soft magnetic powder core is relatively low, at 76; the pressing pressure in step (3) of Example 10 is relatively high, and the permeability of the borosilicate-coated metal soft magnetic powder core is higher than that of Example 1, at 141; however, the losses of the borosilicate-coated metal soft magnetic powder cores obtained in Examples 9 and 10 are much higher than those in Example 1.

[0124] (4) Combining Examples 1 and 11-12, it can be seen that the annealing temperature in step (3) of Example 11 is relatively low, and the permeability of the borosilicate-coated metal soft magnetic powder core obtained is slightly lower than that of Example 1, but the loss is much higher than that of Example 1; the annealing temperature in step (3) of Example 12 is relatively high, and the permeability of the borosilicate-coated metal soft magnetic powder core obtained is comparable to that of Example 1, but the loss is as high as 1210mW / cm under the conditions of 100kHz and 100mT. 3 ;

[0125] (5) It can be seen from the comprehensive comparison of Example 1 and Comparative Example 1, Example 3, Example 5 and Comparative Example 3, Example 4, Example 6 and Comparative Example 4 that the borosilicate-coated metal soft magnetic powder core preparation method provided by the present invention is applied to raw materials such as iron-nickel, iron-silicon, and iron-silicon-aluminum magnetic powder. Compared with the methods of Comparative Example 1, Comparative Example 3 and Comparative Example 4, the obtained borosilicate-coated metal soft magnetic powder core has high permeability and low loss.

[0126] (6) It can be seen from the combined results of Example 1 and Comparative Example 2 that in Comparative Example 2, step (1) does not involve the addition of boric acid powder. The resulting metal soft magnetic powder core has a slightly lower permeability than that of Example 1, but its loss is much higher than that of Example 1.

[0127] In summary, the method for preparing borosilicate-coated metal soft magnetic powder cores provided by this invention employs a specific mass ratio of siloxane to boric acid powder, and utilizes the raw material boric acid powder to chemically and organically synthesize a borosilicate-containing coating under specific pressing pressure and annealing temperature conditions. This effectively improves the insulating coating on the surface of the metal soft magnetic powder core, increases the resistance of the powder core, and results in a borosilicate-coated metal soft magnetic powder core with superior magnetic properties, high permeability, and low magnetic loss.

[0128] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a borosilicate-coated metal soft magnetic powder core, characterized in that, The preparation method includes the following steps: (1) Mix siloxane, boric acid powder, first solvent, catalyst and water, and carry out hydrolysis reaction. The hydrolysis product is subjected to polycondensation reaction to obtain borosilicate coating agent; (2) Mix the boron-silicon coating agent, soft magnetic powder and second solvent to obtain the coated soft magnetic powder; (3) The coated soft magnetic powder, binder and release agent are mixed and then pressed and annealed in sequence to obtain a borosilicate coated metal soft magnetic powder core; The mass ratio of the siloxane to boric acid powder is 10:(0.5~3).

2. The preparation method according to claim 1, characterized in that, Step (1) involves mixing siloxane, boric acid powder, first solvent, catalyst and water. The steps include: first mixing siloxane and boric acid powder to obtain a mixed solution, then adding the first solvent and catalyst, stirring and heating to 50~100℃, and then adding water.

3. The preparation method according to claim 1, characterized in that, The siloxane in step (1) includes polydimethylsiloxane and / or dimethyldiethoxysilane.

4. The preparation method according to claim 1, characterized in that, The boric acid powder has a purity of 99.9% or higher.

5. The preparation method according to claim 1, characterized in that, The boric acid powder has a particle size of 5~50μm.

6. The preparation method according to claim 1, characterized in that, Step (1) The first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol or n-butanol.

7. The preparation method according to claim 1, characterized in that, The catalyst includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, or nitric acid.

8. The preparation method according to claim 1, characterized in that, The mass concentration of the catalyst is 2~10 mol / mL.

9. The preparation method according to claim 1, characterized in that, The volume ratio of the first solvent to the catalyst is 10:(0.1~0.5).

10. The preparation method according to claim 1, characterized in that, The water includes deionized water.

11. The preparation method according to claim 1, characterized in that, The amount of water added is 1 to 5% of the mass of siloxane and boric acid powder.

12. The preparation method according to claim 1, characterized in that, The hydrolysis reaction takes 0.5 to 5 hours.

13. The preparation method according to claim 1, characterized in that, The polycondensation reaction in step (1) is carried out in a distillation apparatus.

14. The preparation method according to claim 13, characterized in that, The hydrolysis products are subjected to vacuum distillation in the distillation apparatus.

15. The preparation method according to claim 14, characterized in that, The vacuum degree of the vacuum distillation is 0.02~0.15MPa.

16. The preparation method according to claim 1, characterized in that, The temperature of the polycondensation reaction is 80~150℃.

17. The preparation method according to claim 1, characterized in that, The polycondensation reaction takes 1 to 20 hours.

18. The preparation method according to claim 1, characterized in that, The mass ratio of the borosilicate coating agent, soft magnetic powder and second solvent in step (2) is (0.01~0.5):10:(0.5~1.5).

19. The preparation method according to claim 1, characterized in that, The soft magnetic powder includes any one or a combination of at least two of the following: iron-nickel magnetic powder, iron-silicon magnetic powder, iron-silicon-aluminum magnetic powder, iron-nickel-molybdenum magnetic powder, amorphous magnetic powder, or nanocrystalline magnetic powder.

20. The preparation method according to claim 1, characterized in that, The second solvent includes acetone.

21. The preparation method according to claim 1, characterized in that, The coated soft magnetic powder is then subjected to drying and sieving processes.

22. The preparation method according to claim 1, characterized in that, Step (3) of mixing the coated soft magnetic powder, binder and release agent includes: first mixing the coated soft magnetic powder and binder, drying them, and then adding the release agent.

23. The preparation method according to claim 1, characterized in that, The mass ratio of the coated soft magnetic powder, binder, and release agent is 10:(0.01~0.1):(0.01~0.1).

24. The preparation method according to claim 1, characterized in that, The adhesive includes any one or a combination of at least two of silicone resin, epoxy resin, or phenolic resin.

25. The preparation method according to claim 1, characterized in that, The release agent includes any one or a combination of at least two of zinc stearate, aluminum stearate, or graphite.

26. The preparation method according to claim 1, characterized in that, The pressing pressure in step (3) is 1000~3000MPa.

27. The preparation method according to claim 1, characterized in that, The annealing process is carried out in a nitrogen atmosphere.

28. The preparation method according to claim 1, characterized in that, The annealing temperature is 500~800℃.

29. The preparation method according to claim 1, characterized in that, The annealing process takes 0.1 to 8 hours.

30. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) First, mix siloxane and boric acid powder in a mass ratio of 10:(0.5~3) to obtain a mixed solution. Then, add a first solvent and catalyst in a volume ratio of 10:(0.1~0.5), stir and heat to 50~100℃, add water, and carry out hydrolysis reaction for 0.5~5h. Then, perform vacuum distillation on the hydrolysis product in a distillation apparatus and carry out polycondensation reaction at a temperature of 80~150℃ for 1~20h to obtain borosilicate coating agent. The siloxane includes polydimethylsiloxane and / or dimethyldiethoxysilane; the boric acid powder has a purity of 99.9% or higher; the boric acid powder has a particle size of 5-50 μm; the first solvent includes any one or a combination of at least two of methanol, ethanol, isopropanol, or n-butanol; the catalyst includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, or nitric acid; the catalyst has a mass concentration of 2-10 mol / mL; the water includes deionized water; the amount of water added is 1-5 wt% of the mass of the siloxane and boric acid powder; the vacuum degree of the vacuum distillation is 0.02-0.15 MPa; (2) The boron-silicon coating agent, soft magnetic powder and second solvent are mixed in a mass ratio of (0.01~0.5):10:(0.5~1.5) to obtain the coated soft magnetic powder; The soft magnetic powder includes any one or a combination of at least two of the following: iron-nickel magnetic powder, iron-silicon magnetic powder, iron-silicon-aluminum magnetic powder, or iron-nickel-molybdenum magnetic powder; the second solvent includes acetone; the coated soft magnetic powder is further subjected to drying and sieving processes in sequence. (3) First, mix the coated soft magnetic powder and binder, dry them, then add a release agent, and then press them under a pressure of 1000~3000MPa and anneal them in a nitrogen atmosphere at a temperature of 500~800℃ for 0.1~8h to obtain a borosilicate coated metal soft magnetic powder core. The mass ratio of the coated soft magnetic powder, binder, and release agent is 10:(0.01~0.1):(0.01~0.1); the binder includes any one or a combination of at least two of silicone resin, epoxy resin, or phenolic resin; the release agent includes any one or a combination of at least two of zinc stearate, aluminum stearate, or graphite.

31. A borosilicate-coated metal soft magnetic powder core, characterized in that, The metal soft magnetic powder core is prepared by the method for preparing borosilicate-coated metal soft magnetic powder core according to any one of claims 1 to 30.

Images