Iron-based nanocrystalline magnetic powder core, preparation method and application thereof

Abstract

The application relates to an iron-based nanocrystalline magnetic powder core and a preparation method and application thereof. The preparation method of the iron-based nanocrystalline magnetic powder core comprises the following steps: obtaining iron-based amorphous powder through treatment of iron-based amorphous strip; mixing preprocessed alumina, grinding aids and the iron-based amorphous powder through ball milling to obtain iron-based amorphous magnetic powder; sequentially performing washing, drying and annealing on the iron-based amorphous magnetic powder to obtain iron-based nanocrystalline magnetic powder; mixing glue and the iron-based nanocrystalline magnetic powder until solvent volatilization, then performing compression molding and baking to obtain the iron-based nanocrystalline magnetic powder core. The iron-based nanocrystalline magnetic powder core is prepared by adopting a short-time high-energy ball milling method, high-strength alumina is used as a coating layer, and the prepared iron-based nanocrystalline magnetic powder core has high soft magnetic performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soft magnetic composite materials, and relates to a magnetic powder core and a preparation method and application thereof, in particular to an iron-based nanocrystalline magnetic powder core and a preparation method and application thereof. BACKGROUND

[0002] The iron-based amorphous nanocrystalline soft magnetic alloy has the advantages of high saturation magnetic induction, high initial permeability, low coercivity and low loss. The iron core made of the amorphous strip prepared by rapid quenching has excellent soft magnetic properties after proper heat treatment, and has been widely used in the fields of transformers, sensors and switching power supplies. However, the winding lamination soft magnetic core has large loss at high frequency, which limits its application at high frequency. The magnetic powder core has the advantages of high saturation magnetic induction, small coercivity and low loss, and can be used in high-frequency environment.

[0003] In the preparation process of the magnetic powder core, the insulating coating is a key process. Common insulating coating methods include phosphoric acid passivation and organic glue coating process, but the chemical corrosion of phosphoric acid to the magnetic powder will cause the loss to increase, and the phosphate insulating layer is easy to be ablated at high temperature, thereby limiting the optimization of the performance of the soft magnetic composite material; meanwhile, the epoxy resin coating layer is easy to break, thereby greatly increasing the eddy current loss of the powder; in addition, the epoxy resin coating layer does not have magnetic properties, so that the magnetic properties such as permeability and saturation magnetization of the original magnetic powder will be reduced after coating.

[0004] CN 103745791A discloses a preparation method of an iron-based nanocrystalline magnetic powder core with ultra-high permeability; comprising the following steps: step one, mechanically crushing the iron-based nanocrystalline thin strip to obtain an iron-based nanocrystalline powder; step two, screening and proportioning the iron-based nanocrystalline powder, and then mixing the coarse powder and the fine powder to obtain a mixed powder; step three, sequentially performing passivation, coupling, insulating coating treatment on the mixed powder by using a passivating agent, a coupling agent, an insulating agent and a binder respectively, and then pressing into a shape; and step four, sequentially performing annealing treatment and insulating spraying treatment on the shaped magnetic powder core. However, the powder prepared by the mechanical crushing method has sharp corners, which is difficult to insulate during coating, resulting in high loss of the magnetic powder core and poor direct current bias resistance.

[0005] CN 105132786A provides a preparation method of a high-strength soft magnetic composite material, which selects Fe with abundant reserves as the magnetic powder material, and the raw material is cheap; a passivated iron powder is obtained by using a liquid phase reduction method, and high-purity magnesium oxide powder is ball milled by using a high-energy ball mill to obtain particles with a particle size of 80nm-100nm; the passivated iron powder and the refined magnesium oxide powder are uniformly mixed by using a mechanical mixing method, and a high-strength soft magnetic composite material is obtained through pressing and heat treatment. The composite material prepared by the method has good mechanical properties, but the soft magnetic properties need to be further improved.

[0006] In view of the deficiencies of the prior art, it is urgent to provide a magnetic powder core material with high soft magnetic performance and low loss. SUMMARY

[0007] The purpose of the present application is to provide an iron-based nanocrystalline magnetic powder core and its preparation method and application. The iron-based nanocrystalline magnetic powder core is prepared by short-time high-energy ball milling method, and high-strength aluminum oxide is used as the coating layer. The prepared iron-based nanocrystalline magnetic powder core has high soft magnetic performance and low loss, and is suitable for industrial production.

[0008] To achieve the purpose of the present application, the following technical solutions are adopted:

[0009] In a first aspect, the present application provides a preparation method of an iron-based nanocrystalline magnetic powder core, which comprises the following steps:

[0010] (1) The iron-based amorphous strip is sequentially subjected to heat treatment, mechanical crushing, sieving, wet grinding, washing and drying to obtain an iron-based amorphous powder;

[0011] (2) The obtained iron-based amorphous powder in step (1) is mixed with pre-processed aluminum oxide and grinding aid by ball milling to obtain an iron-based amorphous magnetic powder;

[0012] (3) The obtained iron-based amorphous magnetic powder in step (2) is sequentially subjected to washing, drying and annealing to obtain an iron-based nanocrystalline magnetic powder;

[0013] (4) The obtained iron-based nanocrystalline magnetic powder in step (3) is mixed with glue, and then the solvent is volatilized, followed by compression molding and baking to obtain the iron-based nanocrystalline magnetic powder core;

[0014] The pre-processed aluminum oxide in step (2) is obtained by sequentially subjecting nano-aluminum oxide to water immersion treatment, acid immersion treatment and alkali immersion treatment;

[0015] The rotation speed of the ball milling in step (2) is 1050-1150 r / min, and the time is 4-6 min.

[0016] The preparation method of the iron-based nanocrystalline magnetic powder core provided by the present application uses short-time high-energy ball milling method to prepare the iron-based nanocrystalline magnetic powder core. While avoiding powder crystallization caused by high temperature, the high impact energy applied by the ball mill breaks the edges and protrusions of the iron-based amorphous powder, achieving the purpose of spheroidization. Meanwhile, the pre-processed aluminum oxide is adsorbed on the surface of the iron-based amorphous powder under the action of micro-molecular force, forming a dense aluminum oxide coating insulation layer, thereby reducing the core loss of the magnetic powder core.

[0017] The rotation speed of the ball-milling mixing is 1050-1150 r / min, for example, it can be 1050 r / min, 1080 r / min, 1100 r / min, 1120 r / min or 1150 r / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0018] The time of the ball-milling mixing is 4-6 min, for example, it can be 4 min, 4.5 min, 5 min, 5.5 min or 6 min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0019] Preferably, the iron-based amorphous ribbon in step (1) comprises Fe 78 Si 15 B3P3Cu1.

[0020] Preferably, the heat treatment in step (1) comprises a first heat treatment and a second heat treatment performed in sequence.

[0021] Preferably, the step of the first heat treatment comprises: heating to 390-410 ℃ at a rate of 9-11 ℃ / min in a nitrogen atmosphere, and holding for 18-22 min.

[0022] The heating rate of the first heat treatment is 9-11 ℃ / min, for example, it can be 9 ℃ / min, 9.5 ℃ / min, 10 ℃ / min, 10.5 ℃ / min or 11 ℃ / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] The end point of the heating of the first heat treatment is 390-410 ℃, for example, it can be 390 ℃, 395 ℃, 400 ℃, 405 ℃ or 410 ℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0024] The holding time of the first heat treatment is 18-22 min, for example, it can be 18 min, 19 min, 20 min, 21 min or 22 min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0025] Preferably, the step of the second heat treatment comprises: heating to 440-460 ℃ at a rate of 4-6 ℃ / min in a nitrogen atmosphere, and holding for 28-32 min.

[0026] The heating rate of the second heat treatment is 4-6 ℃ / min, for example, it can be 4 ℃ / min, 4.5 ℃ / min, 5 ℃ / min, 5.5 ℃ / min or 6 ℃ / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0027] The temperature rising end point of the second heat treatment is 440-460℃, for example, it can be 440℃, 445℃, 450℃, 455℃ or 460℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0028] The holding time of the second heat treatment is 28-32min, for example, it can be 28min, 29min, 30min, 31min or 32min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0029] Preferably, after the heat treatment of step (1) and before mechanical crushing, it further includes a step of cooling in liquid nitrogen at -210℃ to -190℃, for example, it can be -190℃, -195℃, -200℃, -205℃ or -210℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0030] Furnace cooling can cause the iron-based amorphous powder to form irregular polyhedrons or flakes with many sharp corners and protrusions, while liquid nitrogen quenching helps the iron-based amorphous powder to form spherical powder, thereby forming a high-strength cladding layer.

[0031] Preferably, the particle size range of the powder after sieving in step (1) is 100-150 mesh, for example, it can be 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh or 150 mesh, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0032] Preferably, the ball-to-material mass ratio of wet milling in step (1) is (4-6):1, for example, it can be 4:1, 4.5:1, 5:1, 5.5:1 or 6:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] Preferably, the wet milling balls of wet milling in step (1) include large balls and small balls with a mass ratio of (1.5-2.5):1, for example, it can be 1.5:1, 2:1 or 2.5:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0034] Preferably, the medium of wet milling in step (1) includes ethanol.

[0035] Preferably, the amount of ethanol is 70-80wt% of the total amount of powder, for example, it can be 70wt%, 72wt%, 75wt%, 78wt% or 80wt%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0036] Preferably, the rotation speed of the wet milling in step (1) is 140-160 r / min, for example, it can be 140 r / min, 145 r / min, 150 r / min, 155 r / min or 160 r / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] Preferably, the time of the wet milling in step (1) is 3.5-4.5 h, for example, it can be 3.5 h, 3.8 h, 4 h, 4.2 h or 4.5 h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0038] Preferably, the temperature of the drying in step (1) is 100-120℃, for example, it can be 100℃, 105℃, 110℃, 115℃ or 120℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0039] Preferably, the time of the drying in step (1) is 60-120 min, for example, it can be 60 min, 75 min, 90 min, 105 min or 120 min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0040] Preferably, the mass ratio of the pre-processed alumina to the iron-based amorphous powder in step (2) is (4-6):1, for example, it can be 4:1, 4.5:1, 5:1, 5.5:1 or 6:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0041] Preferably, the grinding aid in step (2) comprises polyethyleneimine and / or deionized water.

[0042] Preferably, the amount of the polyethyleneimine is 0.8-1.2 wt% of the pre-processed alumina, for example, it can be 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt% or 1.2 wt%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0043] The present application adds polyethyleneimine with a purity of 99% as a grinding aid, which can avoid the agglomeration of the pre-processed alumina, and the pre-processed alumina can be adsorbed on the surface of the amorphous powder in a large amount and uniformly after high-energy ball milling, so that a complete coating layer can be formed, thereby reducing the loss.

[0044] Preferably, the number average molecular weight of the polyethyleneimine is 2000-5000, for example, it can be 2000, 2500, 3000, 4000 or 5000, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0045] The polyethylene imine is selected to have a lower number average molecular weight, so that the pre-processed alumina can be fully dispersed in the deionized water, and the prepared alumina coating layer has higher strength.

[0046] Preferably, the amount of deionized water is 80-90wt% of the pre-processed alumina, for example, it can be 80wt%, 82wt%, 85wt%, 88wt% or 90wt%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0047] Preferably, the ball-to-material mass ratio of the ball milling in step (2) is (45-55):1, for example, it can be 45:1, 48:1, 50:1, 52:1 or 55:1, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0048] Preferably, the ball milling in step (2) uses tungsten carbide balls.

[0049] Preferably, the ball milling in step (2) is carried out in an argon atmosphere.

[0050] Preferably, the ball milling in step (2) is carried out 4-6 times, for example, it can be 4 times, 5 times or 6 times.

[0051] Preferably, the ball milling tank is subjected to water circulation cooling treatment during the ball milling in step (2).

[0052] Preferably, the water immersion treatment step includes uniformly mixing the nano-alumina with deionized water, and drying the solid-liquid separated water immersion treatment powder.

[0053] Preferably, the water immersion treatment step is repeated 2-3 times.

[0054] Preferably, the acid immersion treatment step includes uniformly mixing the water immersion treatment powder with a hydrochloric acid solution, and washing and drying the solid-liquid separated acid immersion treatment powder.

[0055] Preferably, the concentration of hydrochloric acid in the hydrochloric acid solution is 0.08-0.12mol / L, for example, it can be 0.08mol / L, 0.09mol / L, 0.1mol / L, 0.11mol / L or 0.12mol / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0056] Preferably, the alkali immersion treatment step includes uniformly mixing the acid immersion treatment powder with a sodium hydroxide solution, and washing and drying the solid-liquid separated pre-processed alumina.

[0057] Preferably, the concentration of sodium hydroxide in the sodium hydroxide solution is 0.08-0.12 mol / L, for example, it can be 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L or 0.12 mol / L, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0058] The present application performs water immersion, acid immersion and alkali immersion treatment on nano-alumina, so that the alumina is uniformly and fully adsorbed on the surface of the iron-based amorphous powder after high-energy ball milling, thereby forming a complete alumina coating layer.

[0059] Preferably, the washing in step (3) comprises ultrasonic cleaning.

[0060] Preferably, the reagent used in the washing in step (3) comprises ethanol.

[0061] Preferably, the drying in step (3) is performed at a temperature of 100-120℃, for example, it can be 100℃, 105℃, 110℃, 115℃ or 120℃, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0062] Preferably, the drying in step (3) is performed for a time of 60-120 min, for example, it can be 60 min, 75 min, 90 min, 105 min or 120 min, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0063] Preferably, the annealing in step (3) is performed at a temperature of 535-545℃, for example, it can be 535℃, 538℃, 540℃, 542℃ or 545℃, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0064] The annealing temperature needs to be controlled within a reasonable range, and an excessively high annealing temperature will cause the nanocrystals to be excessively crystallized, thereby reducing the magnetic permeability of the iron-based nanocrystalline magnetic powder core, and an excessively low annealing temperature cannot form a nanocrystalline phase structure.

[0065] Preferably, the annealing in step (3) is performed for a time of 55-65 min, for example, it can be 55 min, 58 min, 60 min, 62 min or 65 min, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0066] Preferably, the annealing in step (3) is performed in a nitrogen atmosphere.

[0067] Preferably, the glue in step (4) comprises a mixture of epoxy resin and polyamide resin acetone solution.

[0068] Preferably, the mass of the epoxy resin is 0.18-0.22wt% of the iron-based nanocrystalline magnetic powder, for example, it can be 0.18wt%, 0.19wt%, 0.2wt%, 0.21wt% or 0.22wt%, but is not limited to the listed values, other values not listed in the value range are also applicable.

[0069] Preferably, the concentration of the polyamide resin in the polyamide resin acetone solution is 0.08-0.12%, for example, it can be 0.08%, 0.09%, 0.1%, 0.11% or 0.12%, but is not limited to the listed values, other values not listed in the value range are also applicable.

[0070] Preferably, the pressure of the press forming in step (4) is 18-22t / cm 2 , for example, it can be 18t / cm 2 , 19t / cm 2 , 20t / cm 2 , 21t / cm 2 or 22t / cm 2 , but is not limited to the listed values, other values not listed in the value range are also applicable.

[0071] As a preferred technical solution of the preparation method of the first aspect of the present application, the preparation method comprises the following steps:

[0072] (1) The iron-based amorphous strip is sequentially subjected to first and second heat treatments, mechanical crushing, sieving, wet grinding at 140-160r / min for 3.5-4.5h, washing and drying at 100-120℃ for 60-120min to obtain an iron-based amorphous powder;

[0073] The first heat treatment step comprises: heating to 390-410℃ at a rate of 9-11℃ / min in a nitrogen atmosphere, and holding for 18-22min; the second heat treatment step comprises: heating to 440-460℃ at a rate of 4-6℃ / min in a nitrogen atmosphere, and holding for 28-32min; after the heat treatment and before the mechanical crushing, the step of cooling in liquid nitrogen at -210℃ to -190℃ is further included;

[0074] The particle size range of the powder after sieving is 100-150mesh; the ball-to-material mass ratio of the wet grinding is (4-6):1; the medium of the wet grinding comprises 70-80wt% of the total amount of the powder of ethanol;

[0075] (2) The iron-based amorphous powder obtained in step (1) is ball milled with pre-treatment alumina and grinding aid in an argon atmosphere at 1050-1150r / min for 4-6min, and the ball milling is performed 4-6times to obtain an iron-based amorphous magnetic powder;

[0076] The pre-processed alumina is obtained by sequentially subjecting nano-alumina to water immersion treatment, acid immersion treatment and alkali immersion treatment; the water immersion treatment step comprises uniformly mixing the nano-alumina with deionized water, and drying the water immersion treatment powder obtained after solid-liquid separation; the acid immersion treatment step comprises uniformly mixing the water immersion treatment powder with a 0.08-0.12 mol / L hydrochloric acid solution, and washing and drying the acid immersion treatment powder obtained after solid-liquid separation; and the alkali immersion treatment step comprises uniformly mixing the acid immersion treatment powder with a 0.08-0.12 mol / L sodium hydroxide solution, and washing and drying the pre-processed alumina obtained after solid-liquid separation.

[0077] The mass ratio of the pre-processed alumina to the iron-based amorphous powder is (4-6):1; the grinding aid comprises polyethyleneimine and / or deionized water; the amount of the polyethyleneimine is 0.8-1.2 wt% of the pre-processed alumina; the number average molecular weight of the polyethyleneimine is 2000-5000; the amount of the deionized water is 80-90 wt% of the pre-processed alumina; and the ball-to-material mass ratio of the ball milling is (45-55):1.

[0078] (3) sequentially subjecting the iron-based amorphous magnetic powder obtained in step (2) to washing, drying at 100-120℃ for 60-120 min, and annealing at 535-545℃ for 55-65 min under a nitrogen atmosphere to obtain an iron-based nanocrystalline magnetic powder;

[0079] (4) mixing an epoxy resin, a polyamide resin acetone solution and the iron-based nanocrystalline magnetic powder obtained in step (3) until the solvent volatilizes, and then pressing and molding under a pressure of 18-22 t / cm 2 and baking to obtain the iron-based nanocrystalline magnetic powder core.

[0080] The mass of the epoxy resin is 0.18-0.22 wt% of the iron-based nanocrystalline magnetic powder; and the concentration of the polyamide resin in the polyamide resin acetone solution is 0.08-0.12%.

[0081] In a second aspect, the present application provides an iron-based nanocrystalline magnetic powder core prepared by the preparation method of the first aspect.

[0082] In a third aspect, the present application provides an application of the iron-based nanocrystalline magnetic powder core of the second aspect, wherein the iron-based nanocrystalline magnetic powder core is used in an inductor, a switching converter, a filter or an antenna tuning circuit.

[0083] Compared with the prior art, the present application has the following beneficial effects:

[0084] (1) The preparation method of the iron-based nanocrystalline magnetic powder core provided by the application adopts a short-time high-energy ball milling method to prepare the iron-based nanocrystalline magnetic powder core, so that the edges and protrusions of the iron-based amorphous powder are broken to be spherical, and a dense aluminum oxide coating insulation layer is formed, so that the loss of the iron-based nanocrystalline magnetic powder core at f = 100 KHz, Bm = 100 mT is reduced to 87 mW / cm 3 ; the loss at f = 500 KHz, Bm = 50 mT is reduced to 358 mW / cm 3 ; the magnetic permeability can reach 93, and it is suitable for industrial scale production;

[0085] (2) The iron-based nanocrystalline magnetic powder core provided by the application does not need to be phosphatized for insulation coating treatment, so that the addition of glue such as epoxy resin and other inorganic substances can be greatly reduced, so as to improve the soft magnetic properties of the iron-based nanocrystalline magnetic powder core, and at the same time, the application of nanocrystalline in high temperature scenes is widened, the preparation method has low requirements on equipment, simple process and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0086] Figure 1 is the SEM graph of the iron-based amorphous magnetic powder provided by example 1 after washing and drying;

[0087] Figure 2 is the XRD graph of the iron-based amorphous magnetic powder provided by example 1 after washing and drying;

[0088] Figure 3 is the XRD graph of the iron-based nanocrystalline magnetic powder provided by example 1. DETAILED DESCRIPTION

[0089] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application, and should not be regarded as specific limitations on the application.

[0090] Example 1

[0091] The embodiment provides an iron-based nanocrystalline magnetic powder core, and a preparation method of the iron-based nanocrystalline magnetic powder core comprises the following steps:

[0092] (1) The iron-based amorphous strip with a composition of Fe 78 Si 15 B3P3Cu1 is sequentially subjected to first heat treatment and second heat treatment, mechanical crushing, sieving, 150 r / min wet grinding for 4 h, washing and 110℃ drying for 90 min to obtain an iron-based amorphous powder;

[0093] The first heat treatment step includes: heating to 400℃ at a rate of 10℃ / min under nitrogen atmosphere, and holding for 20min; the second heat treatment step includes: heating to 450℃ at a rate of 5℃ / min under nitrogen atmosphere, and holding for 30min; and the powder is cooled in liquid nitrogen at -200℃ after the heat treatment;

[0094] The median particle size of the sieved powder is 120 mesh; the ball-to-material mass ratio of the wet milling is 5:1; and the medium of the wet milling includes 75wt% of the total amount of the powder of ethanol;

[0095] (2) Ball-mixing the pretreated alumina, polyethyleneimine, deionized water and the iron-based amorphous powder obtained in step (1) for 5min at 1100r / min under argon atmosphere, and ball-mixing 5 times to obtain an iron-based amorphous magnetic powder;

[0096] The pretreated alumina is obtained by sequentially subjecting nano-alumina to water immersion treatment, acid immersion treatment and alkali immersion treatment; the water immersion treatment step includes: uniformly mixing the nano-alumina and deionized water, and drying the solid-liquid separated water immersion treated powder; the acid immersion treatment step includes: uniformly mixing the water immersion treated powder and 0.1mol / L hydrochloric acid solution, and washing and drying the solid-liquid separated acid immersion treated powder; and the alkali immersion treatment step includes: uniformly mixing the acid immersion treated powder and 0.1mol / L sodium hydroxide solution, and washing and drying the solid-liquid separated pretreated alumina;

[0097] The mass ratio of the pretreated alumina to the iron-based amorphous powder is 5:1; the amount of the polyethyleneimine is 1wt% of the total amount of the powder; the number average molecular weight of the polyethyleneimine is 3000; the amount of the deionized water is 85wt% of the total amount of the powder; and the ball-to-material mass ratio of the ball-mixing is 50:1;

[0098] (3) The iron-based amorphous magnetic powder obtained in step (2) is sequentially subjected to ultrasonic ethanol washing, 110℃ drying for 90min, and 540℃ annealing for 60min under nitrogen atmosphere to obtain an iron-based nanocrystalline magnetic powder;

[0099] (4) Mixing epoxy resin, polyamide resin acetone solution and the iron-based nanocrystalline magnetic powder obtained in step (3) until the solvent volatilizes, and then pressing and molding under 20t / cm 2 and baking to obtain the iron-based nanocrystalline magnetic powder core;

[0100] The mass of the epoxy resin is 0.2wt% of the iron-based nanocrystalline magnetic powder; and the concentration of the polyamide resin in the polyamide resin acetone solution is 0.1%.

[0101] The SEM image of the iron-based amorphous magnetic powder after washing and drying is as shown in Figure 1As shown, the sphericity of the iron-based amorphous magnetic powder is good, without obvious sharp corners and protrusions; the XRD pattern of the iron-based amorphous magnetic powder after washing and drying is as shown in Figure 2 As shown, there is no obvious diffraction peak in the figure, only a broad diffuse scattering peak, indicating that the prepared magnetic powder is amorphous; the XRD pattern of the iron-based nanocrystalline magnetic powder is as shown in Figure 3 As shown, the iron-based nanocrystalline magnetic powder has an amorphous / nanocrystalline dual-phase structure, and the crystallized phase is a single α-Fe phase.

[0102] Example 2

[0103] The present embodiment provides an iron-based nanocrystalline magnetic powder core, and a preparation method thereof includes the following steps:

[0104] (1) The composition of the iron-based amorphous strip is Fe 78 Si 15 B3P3Cu1, which is sequentially subjected to first heat treatment and second heat treatment, mechanical crushing, sieving, 145 r / min wet milling for 4.2 h, washing, and 105℃ drying for 105 min, to obtain an iron-based amorphous powder;

[0105] The step of the first heat treatment includes: heating to 395℃ at a rate of 9.5℃ / min under a nitrogen atmosphere, and holding for 21 min; the step of the second heat treatment includes: heating to 445℃ at a rate of 4.5℃ / min under a nitrogen atmosphere, and holding for 31 min; and the heat-treated product is cooled in liquid nitrogen at -195℃;

[0106] The median particle size of the sieved powder is 110 mesh; the ball-to-material mass ratio of the wet milling is 4.5:1; and the medium of the wet milling includes 72wt% of the total amount of the powder of ethanol;

[0107] (2) The iron-based amorphous powder is obtained by ball milling the pretreated alumina, polyethyleneimine, deionized water, and the iron-based amorphous powder obtained in step (1) in an argon atmosphere at 1080 r / min for 5.5 min, with 5 ball milling times;

[0108] The pretreated alumina is obtained by sequentially subjecting nano-alumina to water immersion treatment, acid immersion treatment, and alkali immersion treatment; the step of the water immersion treatment includes: uniformly mixing the nano-alumina and deionized water, drying after solid-liquid separation to obtain a water immersion treated powder; the step of the acid immersion treatment includes: uniformly mixing the water immersion treated powder and a 0.09 mol / L hydrochloric acid solution, washing and drying after solid-liquid separation to obtain an acid immersion treated powder; and the step of the alkali immersion treatment includes: uniformly mixing the acid immersion treated powder and a 0.09 mol / L sodium hydroxide solution, washing and drying after solid-liquid separation to obtain the pretreated alumina;

[0109] The mass ratio of the pre-processed alumina to the iron-based amorphous powder is 4.5:1; the amount of the polyethyleneimine is 0.9wt% of the total amount of the powder; the number average molecular weight of the polyethyleneimine is 3000; the amount of the deionized water is 82wt% of the total amount of the powder; the ball-to-powder mass ratio of the ball milling is 48:1;

[0110] (3) The iron-based amorphous magnetic powder obtained in step (2) is sequentially subjected to ultrasonic ethanol washing, drying at 105℃ for 105min, and annealing at 538℃ for 62min under a nitrogen atmosphere, to obtain an iron-based nanocrystalline magnetic powder;

[0111] (4) The epoxy resin, the polyamide resin acetone solution, and the iron-based nanocrystalline magnetic powder obtained in step (3) are mixed until the solvent evaporates, and then are pressed into a shape under a pressure of 19t / cm 2 and baked to obtain the iron-based nanocrystalline magnetic powder core;

[0112] The mass of the epoxy resin is 0.19wt% of the iron-based nanocrystalline magnetic powder; the concentration of the polyamide resin in the polyamide resin acetone solution is 0.09%.

[0113] Example 3

[0114] The present embodiment provides an iron-based nanocrystalline magnetic powder core, and a preparation method thereof includes the following steps:

[0115] (1) An iron-based amorphous strip with a composition of Fe 78 Si 15 B3P3Cu1 is sequentially subjected to a first heat treatment and a second heat treatment, mechanical crushing, sieving, wet milling at 155r / min for 3.8h, washing, and drying at 115℃ for 75min, to obtain an iron-based amorphous powder;

[0116] The step of the first heat treatment includes: heating to 405℃ at a rate of 10.5℃ / min under a nitrogen atmosphere, and maintaining for 19min; the step of the second heat treatment includes: heating to 455℃ at a rate of 5.5℃ / min under a nitrogen atmosphere, and maintaining for 29min; and the heat-treated product is cooled in liquid nitrogen at -205℃;

[0117] The median particle size of the sieved powder is 135 mesh; the ball-to-powder mass ratio of the wet milling is 5.5:1; and the medium of the wet milling includes 78wt% of the total amount of the powder of ethanol;

[0118] (2) The pre-processed alumina, the polyethyleneimine, the deionized water, and the iron-based amorphous powder obtained in step (1) are ball-mixed in an argon atmosphere at 1120r / min for 4.5min, with 5 times of ball-mixing, to obtain an iron-based amorphous magnetic powder;

[0119] The pre-processed alumina is obtained by sequentially subjecting nano-alumina to water immersion treatment, acid immersion treatment and alkali immersion treatment; the water immersion treatment step comprises uniformly mixing the nano-alumina with deionized water, and drying the water immersion treatment powder obtained after solid-liquid separation; the acid immersion treatment step comprises uniformly mixing the water immersion treatment powder with a 0.11 mol / L hydrochloric acid solution, and washing and drying the acid immersion treatment powder obtained after solid-liquid separation; the alkali immersion treatment step comprises uniformly mixing the acid immersion treatment powder with a 0.11 mol / L sodium hydroxide solution, and washing and drying the pre-processed alumina obtained after solid-liquid separation;

[0120] The mass ratio of the pre-processed alumina to the iron-based amorphous powder is 5.5:1; the amount of the polyethyleneimine is 1.1 wt% of the total amount of the powder; the number average molecular weight of the polyethyleneimine is 3000; the amount of the deionized water is 88 wt% of the total amount of the powder; and the ball-to-powder mass ratio of the ball milling is 52:1;

[0121] (3) The iron-based amorphous magnetic powder obtained in step (2) is sequentially subjected to ultrasonic ethanol washing, 115℃ drying for 75 min and annealing at 542℃ for 58 min under a nitrogen atmosphere to obtain an iron-based nanocrystalline magnetic powder;

[0122] (4) Mixing epoxy resin, polyamide resin acetone solution and the iron-based nanocrystalline magnetic powder obtained in step (3) until the solvent volatilizes, and then pressing and molding under a pressure of 21 t / cm 2 and baking to obtain the iron-based nanocrystalline magnetic powder core;

[0123] The mass of the epoxy resin is 0.21 wt% of the iron-based nanocrystalline magnetic powder; and the concentration of the polyamide resin in the polyamide resin acetone solution is 0.11%.

[0124] Example 4

[0125] The present embodiment provides an iron-based nanocrystalline magnetic powder core, and a preparation method thereof comprises the following steps:

[0126] (1) An iron-based amorphous strip with a composition of Fe 78 Si 15 B3P3Cu1 is sequentially subjected to first heat treatment and second heat treatment, mechanical crushing, sieving, 140 r / min wet milling for 4.5 h, washing and 100℃ drying for 120 min to obtain an iron-based amorphous powder;

[0127] The first heat treatment step comprises heating to 390℃ at a rate of 9℃ / min under a nitrogen atmosphere, and maintaining the temperature for 22 min; the second heat treatment step comprises heating to 440℃ at a rate of 4℃ / min under a nitrogen atmosphere, and maintaining the temperature for 32 min; and the heat-treated product is cooled in liquid nitrogen at -190℃;

[0128] The median particle size of the sieved powder is 115 mesh; the ball-to-material mass ratio of the wet milling is 4:1; the medium of the wet milling includes 70wt% of the total amount of the powder of ethanol;

[0129] (2) Ball-mixing the pretreated alumina, polyethyleneimine, deionized water and the iron-based amorphous powder obtained in step (1) for 6 minutes at 1050 r / min under argon atmosphere, ball-mixing 4 times, to obtain an iron-based amorphous magnetic powder;

[0130] The pretreated alumina is obtained by sequentially subjecting nano-alumina to water immersion treatment, acid immersion treatment and alkali immersion treatment; the step of water immersion treatment includes uniformly mixing the nano-alumina and deionized water, drying after solid-liquid separation to obtain a water immersion treatment powder; the step of acid immersion treatment includes uniformly mixing the water immersion treatment powder and a 0.08 mol / L hydrochloric acid solution, washing and drying after solid-liquid separation to obtain an acid immersion treatment powder; the step of alkali immersion treatment includes uniformly mixing the acid immersion treatment powder and a 0.08 mol / L sodium hydroxide solution, washing and drying after solid-liquid separation to obtain the pretreated alumina;

[0131] The mass ratio of the pretreated alumina to the iron-based amorphous powder is 4:1; the amount of the polyethyleneimine is 0.8wt% of the total amount of the powder; the number average molecular weight of the polyethyleneimine is 3000; the amount of the deionized water is 80wt% of the total amount of the powder; the ball-to-material mass ratio of the ball-mixing is 45:1;

[0132] (3) The iron-based amorphous magnetic powder obtained in step (2) is sequentially subjected to ultrasonic ethanol washing, drying at 100℃ for 120 minutes and annealing at 535℃ for 65 minutes under nitrogen atmosphere, to obtain an iron-based nanocrystalline magnetic powder;

[0133] (4) Mixing an epoxy resin, a polyamide resin acetone solution and the iron-based nanocrystalline magnetic powder obtained in step (3) until the solvent evaporates, and then pressing and molding under 18t / cm 2 and baking to obtain the iron-based nanocrystalline magnetic powder core;

[0134] The mass of the epoxy resin is 0.18wt% of the iron-based nanocrystalline magnetic powder; the concentration of the polyamide resin in the polyamide resin acetone solution is 0.08%.

[0135] Example 5

[0136] The present embodiment provides an iron-based nanocrystalline magnetic powder core, and a preparation method thereof includes the following steps:

[0137] (1) The composition of Fe 78 Si 15The iron-based amorphous strip of B3P3Cu1 is sequentially subjected to a first heat treatment and a second heat treatment, mechanical crushing, sieving, wet milling at 160 r / min for 3.5 h, washing, and drying at 120℃ for 60 min to obtain an iron-based amorphous powder;

[0138] The first heat treatment includes: heating to 410℃ at a rate of 11℃ / min under a nitrogen atmosphere, and holding for 18 min; the second heat treatment includes: heating to 460℃ at a rate of 6℃ / min under a nitrogen atmosphere, and holding for 28 min; and the heat-treated product is cooled in liquid nitrogen at -210℃;

[0139] The medium particle size of the sieved powder is 130 mesh; the ball-to-material mass ratio in wet milling is 6:1; and the medium in wet milling includes 80wt% of the total amount of the powder of ethanol;

[0140] (2) The iron-based amorphous powder obtained in step (1) is ball-mixed with pretreated alumina, polyethyleneimine, and deionized water in an argon atmosphere at 1150 r / min for 4 min, and the ball-mixing is performed 6 times to obtain an iron-based amorphous magnetic powder;

[0141] The pretreated alumina is obtained by sequentially subjecting nano-alumina to water immersion treatment, acid immersion treatment, and alkali immersion treatment; the water immersion treatment includes: uniformly mixing the nano-alumina and deionized water, drying after solid-liquid separation to obtain a water immersion treated powder; the acid immersion treatment includes: uniformly mixing the water immersion treated powder and a 0.12 mol / L hydrochloric acid solution, washing after solid-liquid separation, and drying to obtain an acid immersion treated powder; and the alkali immersion treatment includes: uniformly mixing the acid immersion treated powder and a 0.12 mol / L sodium hydroxide solution, washing after solid-liquid separation, and drying to obtain the pretreated alumina;

[0142] The mass ratio of the pretreated alumina to the iron-based amorphous powder is 6:1; the amount of the polyethyleneimine is 1.2wt% of the total amount of the powder; the number average molecular weight of the polyethyleneimine is 3000; the amount of the deionized water is 90wt% of the total amount of the powder; and the ball-to-material mass ratio in ball-mixing is 55:1;

[0143] (3) The iron-based amorphous magnetic powder obtained in step (2) is sequentially subjected to ultrasonic ethanol washing, drying at 120℃ for 60 min, and annealing at 545℃ for 55 min under a nitrogen atmosphere to obtain an iron-based nanocrystalline magnetic powder;

[0144] (4) The epoxy resin, polyamide resin acetone solution, and the iron-based nanocrystalline magnetic powder obtained in step (3) are mixed until the solvent evaporates, and then are pressed and formed under a pressure of 22 t / cm 2 and baked to obtain the iron-based nanocrystalline magnetic powder core;

[0145] The mass of the epoxy resin is 0.22wt% of the iron-based nanocrystalline magnetic powder; the concentration of the polyamide resin in the polyamide resin acetone solution is 0.12%.

[0146] Example 6

[0147] This example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, except that the annealing temperature in step (3) is adjusted to 520℃, the rest is the same as example 1.

[0148] Example 7

[0149] This example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, except that the annealing temperature in step (3) is adjusted to 560℃, the rest is the same as example 1.

[0150] Example 8

[0151] This example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, except that the cooling step after heat treatment in step (1) is adjusted to furnace cooling, the rest is the same as example 1.

[0152] Example 9

[0153] This example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, except that the composition of Fe 78 Si 15 B3P3Cu1 in step (1) is replaced by iron-based amorphous strip with composition Fe 78 Si9B 13 , the rest is the same as example 1.

[0154] Example 10

[0155] This example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, except that the number average molecular weight of polyethyleneimine in step (2) is adjusted to 10000, the rest is the same as example 1.

[0156] Example 11

[0157] This example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, no polyethyleneimine is added in step (2), and the rest is the same as example 1.

[0158] Comparative example 1

[0159] This comparative example provides an iron-based nanocrystalline magnetic powder core, which is different from example 1 in that, the pre-processed alumina in step (2) is replaced by unprocessed nano-alumina, and the rest is the same as example 1.

[0160] Comparative Example 2

[0161] This comparative example provides an iron-based nanocrystalline magnetic powder core, which is different from Example 1 in that, in addition to adjusting the rotation speed of the ball milling in step (2) to 900 r / min, the rest is the same as Example 1.

[0162] Comparative Example 3

[0163] This comparative example provides an iron-based nanocrystalline magnetic powder core, which is different from Example 1 in that, in addition to adjusting the rotation speed of the ball milling in step (2) to 1300 r / min, the rest is the same as Example 1.

[0164] Comparative Example 4

[0165] This comparative example provides a magnetic powder core, which is prepared by the preparation method of the low-loss soft magnetic powder core disclosed in CN 111370193A.

[0166] The iron-based nanocrystalline magnetic powder cores provided in Examples 1-11 and Comparative Examples 1-4 are tested for permeability (test conditions: 1 MHz, 1 V) and loss (test conditions: f = 100 KHz, Bm = 100 mT; f = 500 KHz, Bm = 50 mT), and the results are shown in Table 1.

[0167] Table 1

[0168]

[0169] As can be seen from Table 1, the iron-based nanocrystalline magnetic powder core provided by the present application is prepared by short-time high-energy ball milling and reasonable heat treatment process, and has high permeability and low loss, which can meet the requirements of high-performance soft magnetic material;

[0170] As can be seen from Table 1, the iron-based nanocrystalline magnetic powder core provided by the present application is prepared by short-time high-energy ball milling and reasonable heat treatment process, and has high permeability and low loss, which can meet the requirements of high-performance soft magnetic material; 78 Si 15The poor adsorption between the iron-based amorphous ribbon of B3P3Cu1 and the pretreated alumina leads to insufficient strength of the coating layer, thereby reducing the permeability of the magnetic powder core and increasing the loss; as can be known from the comparison between Example 1 and Example 10, the use of high-molecular-weight polyethyleneimine for assisting in ball milling reduces the dispersion effect of the pretreated alumina in deionized water, and finally leads to a decrease in the strength of the coating layer; as can be known from the comparison between Example 1 and Example 11, without adding polyethyleneimine for ball milling, the pretreated alumina is agglomerated, the adsorption amount of the pretreated alumina on the surface of the iron-based amorphous powder is small and uneven after high-energy ball milling, and an integrated coating layer is not formed, finally leading to an increase in the loss;

[0171] As can be known from the comparison between Example 1 and Comparative Example 1, the nano-alumina is not pretreated, the adsorption amount of the nano-alumina on the surface of the iron-based amorphous powder is small and uneven after high-energy ball milling, and an integrated coating layer is not formed, thereby leading to a decrease in the permeability; as can be known from the comparison between Example 1 and Comparative Examples 2 and 3, the lower ball milling speed cannot completely break the edges and protrusions of the iron-based amorphous powder, and the loss is increased; the higher ball milling speed also has an adverse effect on the subsequent coating; as can be known from the comparison between Example 1 and Comparative Example 4, the magnetic powder core prepared by using the prior art phosphoric acid passivation and glue as the coating layer is prone to breakage, thereby leading to a significant decrease in the soft magnetic performance.

[0172] In summary, the preparation method of the iron-based nanocrystalline magnetic powder core provided by the application uses a short-time high-energy ball milling method to prepare the iron-based nanocrystalline magnetic powder core, breaks the edges and protrusions of the iron-based amorphous powder to achieve spheroidization, and forms a dense alumina coating insulation layer, so that the loss of the iron-based nanocrystalline magnetic powder core at f=100KHz, Bm=100mT is reduced to 87mW / cm 3 ; the loss at f=500KHz, Bm=50mT is reduced to 358mW / cm 3 ; the permeability can reach 93, and the method is suitable for industrial-scale production.

[0173] The application does not need phosphoric acid passivation for insulation coating treatment, can greatly reduce the addition of glue such as epoxy resin and inorganic matter, thereby improving the soft magnetic performance of the iron-based nanocrystalline magnetic powder core, and at the same time, widens the application of nanocrystalline in high-temperature scenarios, the preparation method has low requirements on equipment, simple process and low cost.

[0174] The above merely describes specific embodiments of the application, but the protection scope of the application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the application.

Claims

1. A method for preparing an iron-based nanocrystalline magnetic powder core, characterized in that: The preparation method comprises the following steps: (1) The iron-based amorphous strip is subjected to heat treatment, mechanical crushing, screening, wet grinding, washing and drying in sequence to obtain iron-based amorphous powder; (2) ball milling the pretreated alumina, the grinding aid, and the iron-based amorphous powder obtained in step (1) to obtain iron-based amorphous magnetic powder; (3) The iron-based amorphous magnetic powder obtained in step (2) is washed, dried, and annealed in sequence to obtain iron-based nanocrystalline magnetic powder; (4) mixing the glue and the iron-based nanocrystalline magnetic powder obtained in step (3) until the solvent evaporates, and then performing compression molding and baking to obtain the iron-based nanocrystalline magnetic powder core; The pretreated alumina in step (2) is obtained by sequentially subjecting nano-alumina to water leaching, acid leaching, and alkali leaching. The ball milling mixing in step (2) is performed at a rotation speed of 1050-1150 r / min for 4-6 min; The grinding aid in step (2) comprises polyethyleneimine and deionized water; the number average molecular weight of the polyethyleneimine is 2000-5000.

2. The preparation method according to claim 1, characterized in that The iron-based amorphous strip in step (1) comprises Fe 78 Si 15 B3P3Cu1.

3. The preparation method according to claim 1, characterized in that The heat treatment in step (1) includes a first heat treatment and a second heat treatment performed sequentially.

4. The preparation method according to claim 3, characterized in that The first heat treatment step includes: heating to 390-410° C. at a rate of 9-11° C. / min under a nitrogen atmosphere, and keeping the temperature for 18-22 minutes.

5. The preparation method according to claim 3, characterized in that The second heat treatment step includes: heating to 440-460° C. at a rate of 4-6° C. / min under a nitrogen atmosphere, and keeping the temperature for 28-32 minutes.

6. The preparation method according to claim 1, characterized in that After the heat treatment in step (1) and before the mechanical crushing, the step of cooling in liquid nitrogen at -210°C to -190°C is also included.

7. The preparation method according to claim 1, characterized in that The particle size range of the powder after sieving in step (1) is 100-150 mesh.

8. The preparation method according to claim 1, characterized in that The mass ratio of the balls and materials in the wet grinding of step (1) is (4-6):

1.

9. The preparation method according to claim 1, characterized in that The medium for wet grinding in step (1) includes ethanol.

10. The preparation method according to claim 9, characterized in that The amount of ethanol used is 70-80 wt% of the total amount of powder.

11. The preparation method according to claim 1, characterized in that The rotation speed of the wet grinding in step (1) is 140-160 r / min.

12. The preparation method according to claim 1, characterized in that The wet grinding time in step (1) is 3.5-4.5h.

13. The preparation method according to claim 1, characterized in that The drying temperature in step (1) is 100-120°C.

14. The preparation method according to claim 1, characterized in that The drying time in step (1) is 60-120 minutes.

15. The preparation method according to claim 1, characterized in that The mass ratio of the pretreated alumina to the iron-based amorphous powder in step (2) is (4-6):

1.

16. The preparation method according to claim 1, characterized in that The amount of polyethyleneimine used is 0.8-1.2 wt % of the pretreated alumina.

17. The preparation method according to claim 1, characterized in that The amount of deionized water used is 80-90 wt % of the pretreated alumina.

18. The preparation method according to claim 1, characterized in that The mass ratio of the ball to material in the ball milling mixture in step (2) is (45-55):

1.

19. The preparation method according to claim 1, characterized in that The ball milling balls for the ball milling mixture in step (2) include tungsten carbide balls.

20. The preparation method according to claim 1, characterized in that The ball milling mixing in step (2) is carried out in an argon atmosphere.

21. The preparation method according to claim 1, characterized in that The number of ball milling mixing in step (2) is 4-6 times.

22. The preparation method according to claim 1, characterized in that The water immersion treatment step includes: uniformly mixing nano-alumina and deionized water, separating the solid and liquid, and drying to obtain water immersion treatment powder.

23. The preparation method according to claim 22, characterized in that The acid leaching step includes: uniformly mixing the water-leaching powder and the hydrochloric acid solution, separating the solid and the liquid, washing, and drying to obtain the acid leaching powder.

24. The preparation method according to claim 23, characterized in that The concentration of hydrochloric acid in the hydrochloric acid solution is 0.08-0.12 mol / L.

25. The preparation method according to claim 23, characterized in that The alkaline leaching treatment step includes: uniformly mixing the acid leaching treated powder with a sodium hydroxide solution, and washing and drying after solid-liquid separation to obtain pretreated alumina.

26. The preparation method according to claim 25, characterized in that The concentration of sodium hydroxide in the sodium hydroxide solution is 0.08-0.12 mol / L.

27. The preparation method according to claim 1, characterized in that The drying temperature in step (3) is 100-120°C.

28. The preparation method according to claim 1, characterized in that The drying time in step (3) is 60-120 minutes.

29. The preparation method according to claim 1, characterized in that The annealing temperature in step (3) is 535-545°C.

30. The preparation method according to claim 1, characterized in that The annealing time in step (3) is 55-65 minutes.

31. The preparation method according to claim 1, characterized in that The annealing in step (3) is performed in a nitrogen atmosphere.

32. The preparation method according to claim 1, characterized in that The glue in step (4) comprises a mixture of epoxy resin and polyamide resin acetone solution.

33. The preparation method according to claim 32, characterized in that The mass of the epoxy resin is 0.18-0.22 wt % of the iron-based nanocrystalline magnetic powder.

34. The preparation method according to claim 32, characterized in that The concentration of the polyamide resin in the polyamide resin acetone solution is 0.08-0.12%.

35. The preparation method according to claim 1, characterized in that The pressure of the compression molding in step (4) is 18-22t / cm 2 .

36. The preparation method according to claim 1, characterized in that The preparation method comprises the following steps: (1) The iron-based amorphous strip is subjected to a first heat treatment, a second heat treatment, mechanical crushing, screening, wet grinding at 140-160 r / min for 3.5-4.5 h, washing, and drying at 100-120° C. for 60-120 min to obtain an iron-based amorphous powder; The first heat treatment step comprises: heating to 390-410°C at a rate of 9-11°C / min under a nitrogen atmosphere and holding the temperature for 18-22 minutes; the second heat treatment step comprises: heating to 440-460°C at a rate of 4-6°C / min under a nitrogen atmosphere and holding the temperature for 28-32 minutes; after the heat treatment and before the mechanical crushing, the step of cooling in liquid nitrogen at -210°C to -190°C is also included; The particle size of the sieved powder is in the range of 100-150 mesh; the ball-to-material mass ratio of the wet grinding is (4-6):1; the wet grinding medium comprises ethanol in an amount of 70-80 wt% of the total powder; (2) ball milling the pretreated alumina, the grinding aid, and the iron-based amorphous powder obtained in step (1) at 1050-1150 r / min in an argon atmosphere for 4-6 minutes, and ball milling for 4-6 times to obtain iron-based amorphous magnetic powder; The pretreated alumina is obtained by sequentially subjecting nano-alumina to water leaching, acid leaching, and alkali leaching. The water leaching step comprises: uniformly mixing the nano-alumina with deionized water, separating the solid and liquid, and drying to obtain a water-leached powder. The acid leaching step comprises: uniformly mixing the water-leached powder with a 0.08-0.12 mol / L hydrochloric acid solution, separating the solid and liquid, washing, and drying to obtain an acid-leached powder. The alkali leaching step comprises: uniformly mixing the acid-leached powder with a 0.08-0.12 mol / L sodium hydroxide solution, separating the solid and liquid, washing, and drying to obtain the pretreated alumina. The mass ratio of the pretreated alumina to the iron-based amorphous powder is (4-6):1; the grinding aid includes polyethyleneimine and deionized water; the amount of the polyethyleneimine is 0.8-1.2wt% of the pretreated alumina; the number average molecular weight of the polyethyleneimine is 2000-5000; the amount of the deionized water is 80-90wt% of the pretreated alumina; the mass ratio of the ball and material in the ball milling mixture is (45-55):1; (3) The iron-based amorphous magnetic powder obtained in step (2) is washed, dried at 100-120° C. for 60-120 min, and annealed at 535-545° C. for 55-65 min in a nitrogen atmosphere to obtain iron-based nanocrystalline magnetic powder; (4) Mixing epoxy resin, polyamide resin acetone solution and iron-based nanocrystalline magnetic powder obtained in step (3) until the solvent evaporates, and then 2 Pressing, forming and baking to obtain the iron-based nanocrystalline magnetic powder core; The mass of the epoxy resin is 0.18-0.22 wt% of the iron-based nanocrystalline magnetic powder; and the concentration of the polyamide resin in the polyamide resin acetone solution is 0.08-0.12%.

37. An iron-based nanocrystalline magnetic powder core, characterized in that: The iron-based nanocrystalline magnetic powder core is prepared by the preparation method according to any one of claims 1 to 36.

38. A use of the iron-based nanocrystalline magnetic powder core as claimed in claim 37, characterized in that: The iron-based nanocrystalline magnetic powder core is used for inductance, switching converter, filter or antenna tuning loop.

Images