Preparation method of FeSiBCuNb amorphous nanocrystalline magnetic powder core

Abstract

A preparation method of a FeSiBCuNb amorphous nanocrystalline magnetic powder core relates to the technical field of alloy soft magnetic powder cores, and comprises the following steps: step 1, surface hydroxylation treatment: adding FeSiBCuNb amorphous powder into a nitric acid-hydrogen peroxide solution for surface hydroxylation treatment, and stirring in a water bath; step 2, suction filtration: performing suction filtration, washing with absolute ethyl alcohol, and drying; step 3, ethyl silicate hydrolysis coating: adding into an ethyl silicate-absolute ethyl alcohol solution, adding deionized water, adjusting the pH value of the solution to 8-10 by using ammonia water, and stirring in a water bath until the solution is dried; step 4, coating with resin: adding the FeSiBCuNb amorphous powder and the resin into acetone, continuously stirring until the acetone is completely volatilized, and drying to obtain FeSiBCuNb amorphous powder coated with SiO2 and the resin; step 5, sieving; step 6, pressing; and step 7, performing crystallization to obtain the FeSiBCuNb amorphous nanocrystalline magnetic powder core. The resistivity of the magnetic powder core is improved, the magnetic loss of FeSiBCuNb amorphous nanocrystals is effectively reduced, and the high-frequency integration requirements in the fields of power inductors, energy storage elements, electromagnetic shielding and the like are met.

Description

Technical Field

[0001] This invention relates to the field of alloy soft magnetic powder core technology, specifically to a method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder core. Background Technology

[0002] Metal magnetic powder cores, as a novel type of magnetic composite material, are mainly composed of metallic magnetic powder, an insulating coating layer, and internally distributed air gaps. They possess advantages such as high saturation magnetization, low ferromagnetic loss, and strong anti-saturation capability. These outstanding advantages have attracted the attention of the power electronics industry and are widely used in power electronic equipment such as DC-DC converters and high-frequency switching power supplies. Compared with the metallic magnetic powders used in traditional metal magnetic powder cores, such as carbonyl Fe, FeSi, and FeSiAl, FeSiBCuNb amorphous nanocrystalline magnetic powder has an amorphous nanocrystalline dual-phase structure, exhibiting high resistivity and low loss characteristics, and is considered one of the ideal materials for high-frequency applications.

[0003] The preparation process of metal magnetic powder cores mainly includes raw material mixing, surface passivation, resin coating, compression molding, and heat treatment. Insulation treatment of the magnetic powder is crucial. Although amorphous powders themselves have high resistivity, surface passivation and coating remain the most effective ways to reduce high-frequency eddy current losses in magnetic powder cores. Common insulation coating methods mainly include organic and inorganic coatings. While organic coatings have good adhesion and flexibility, most resins (epoxy resin, phenolic resin, etc.) have poor high-temperature resistance, resulting in insufficient release of internal stress introduced by compression molding. Therefore, increasing attention is being paid to inorganic coatings. The most common inorganic coating involves the reaction of phosphoric acid with Fe in the powder to form a phosphate insulating layer, which has good insulation properties. However, it has been reported that phosphate insulating layers decompose during heat treatment (>500℃), thus reducing their insulation effectiveness. Another inorganic coating method involves preparing inorganic oxide coatings such as SiO2, Al2O3, and MgO through sol-gel methods and chemical co-precipitation. However, the bonding effect between the oxide coating and the magnetic powder surface is poor, and cracking is common during pressing. Therefore, when coating with inorganic oxide coatings, coupling agents (such as polyvinylpyrrolidone, PVP, etc.) are often used to modify the powder surface to improve the bonding effect.

[0004] This invention proposes a method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder cores. The method uses a nitric acid-hydrogen peroxide solution to perform surface hydroxylation treatment on the magnetic powder, which effectively cleans the surface, slightly etches the metal surface to increase surface roughness, and simultaneously creates an oxide surface rich in hydroxyl groups. This provides excellent adhesion sites for SiO2 generated by subsequent hydrolysis of tetraethyl orthosilicate, effectively improving the bonding effect and replacing silane coupling agents. Furthermore, a segmented crystallization technique is employed to control the nanocrystal size, allowing SiO2 to uniformly coat the surface of the FeSiBCuNb spherical amorphous powder, forming an insulating layer. This increases the resistivity of the magnetic powder core and effectively reduces the magnetic loss of the FeSiBCuNb amorphous nanocrystals, meeting the high-frequency integration requirements in fields such as power inductors, energy storage devices, and electromagnetic shielding. Summary of the Invention

[0005] The problem to be solved by this invention is to provide a method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder cores, so as to improve the problem of poor interfacial bonding effect of oxide multi-insulating layers and high magnetic loss of iron-based amorphous nanocrystalline soft magnetic composite materials at high frequencies.

[0006] The technical solution adopted by the present invention to solve the aforementioned technical problem is a method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder cores, characterized by comprising the following steps:

[0007] Step 1. Surface hydroxylation treatment:

[0008] FeSiBCuNb amorphous powder was added to a nitric acid-hydrogen peroxide solution for surface hydroxylation treatment, followed by water...

[0009] Bath stirring;

[0010] Step 2. Filtering:

[0011] The solution from step 1 was filtered, washed with anhydrous ethanol, and dried to obtain the surface-hydroxylated solution.

[0012] FeSiBCuNb amorphous powder;

[0013] Step 3. Ethyl silicate hydrolysis coating:

[0014] The FeSiBCuNb amorphous powder obtained in step 2 was added to a tetraethyl orthosilicate-anhydrous ethanol solution, and then...

[0015] Use deionized water and adjust the pH of the solution to 8-10 with ammonia, then stir in a water bath until dry.

[0016] Step 4. Resin Coating:

[0017] Add the FeSiBCuNb amorphous powder and resin obtained in step 3 to acetone and continue stirring until the acetone is completely dissolved.

[0018] The mixture was completely volatilized and dried to obtain amorphous powder of FeSiBCuNb coated with SiO2 and resin.

[0019] Step 5. Sieve:

[0020] The SiO2 and resin-coated FeSiBCuNb amorphous powder obtained in step 4 were sieved.

[0021] Step 6. Suppression:

[0022] The magnetic powder obtained in step 5 is pressed into shape to obtain a magnetic powder core blank;

[0023] Step 7. Crystallization:

[0024] The magnetic powder core blank obtained in step 6 is subjected to crystallization treatment to obtain the FeSiBCuNb amorphous nanoparticle.

[0025] Microcrystalline magnetic powder core.

[0026] Furthermore, in step 1, the FeSiBCuNb amorphous nanocrystal composition is Fe. 81.4 Si 1.0 B 5.8 Cu 2.6 Nb 9.5 ;

[0027] The nitric acid-hydrogen peroxide solution is prepared by mixing 5-10 wt% nitric acid (65-68% concentration) and 1-5 wt% hydrogen peroxide, based on the mass of anhydrous ethanol. For example, 100g of anhydrous ethanol is mixed with 5-10g of 65-68% nitric acid and 1-5g of hydrogen peroxide.

[0028] For every 1g of FeSiBCuNb spherical amorphous powder, add 1-2ml of nitric acid-hydrogen peroxide solution. The surface hydroxylation treatment temperature is 10-30℃, the stirring speed is 150-350rpm, and the surface hydroxylation treatment time is 3-10min.

[0029] In step 2, the drying temperature is 50–80℃ and the drying time is 8–16 hours.

[0030] In step 3, the volume ratio of ethyl silicate to FeSiBCuNb spherical amorphous powder is 0.05–0.25 ml / g, the volume ratio of deionized water to FeSiBCuNb spherical amorphous powder is 0.15–0.60 ml / g, the pH is adjusted to 8–10, the stirring speed is 150–350 rpm, and the reaction time is 0.5–3 h.

[0031] In step 4, the resin used is a high-temperature silicone resin resistant to 800℃. The mass of the SiO2-coated FeSiBCuNb amorphous powder is used as the calculation basis. The amount of resin used is 2.0-5.0 wt%, the amount of acetone used is 20-60 wt%, the stirring speed is 150-350 rpm, the drying temperature is 40-70℃, and the time is 10-60 min.

[0032] In step 5, the sample is passed through a 40-80 mesh sieve.

[0033] In step 6, the dried magnetic powder obtained in step 5 is mixed evenly with the release agent and then pressed into a magnetic ring to obtain a magnetic powder core blank. The release agent is one of zinc stearate, magnesium stearate, and aluminum stearate. The amount of release agent is 0.1 to 0.5 wt% of the mass of the dried magnetic powder, and the pressing pressure is 600 to 1800 MPa.

[0034] In step 7, the crystallization process is carried out under an argon atmosphere and is performed in stages. First, the temperature is increased to 560°C at a heating rate of 5°C / min and crystallized for 10 min. Then, the temperature is decreased to 520°C and crystallization continues for 30 min.

[0035] This invention proposes a method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder cores. The method uses a nitric acid-hydrogen peroxide solution to perform surface hydroxylation treatment on the magnetic powder, which effectively cleans the surface, slightly etches the metal surface to increase surface roughness, and simultaneously creates an oxide surface rich in hydroxyl groups. This provides excellent adhesion sites for SiO2 generated by subsequent hydrolysis of tetraethyl orthosilicate, effectively improving the bonding effect and replacing silane coupling agents. Furthermore, a segmented crystallization technique is employed to control the nanocrystal size, allowing SiO2 to uniformly coat the surface of the FeSiBCuNb spherical amorphous powder, forming an insulating layer. This increases the resistivity of the magnetic powder core and effectively reduces the magnetic loss of the FeSiBCuNb amorphous nanocrystals, meeting the high-frequency integration requirements in fields such as power inductors, energy storage devices, and electromagnetic shielding. Attached Figure Description

[0036] Figure 1 This is a SEM image of the FeSiBCuNb amorphous nanocrystalline magnetic powder of the present invention. Detailed Implementation

[0037] The core idea of ​​this invention is to perform surface hydroxylation treatment on amorphous powder by adding it to a nitric acid-hydrogen peroxide solution. During this process, the strong oxidizing environment provided by the nitric acid-hydrogen peroxide solution can effectively oxidize and dissolve trace organic contaminants, greases, and metallic impurities on the surface of the alloy powder. The Fe in the amorphous powder is oxidized by the nitric acid and hydrogen peroxide to produce Fe2+. 2+ and Fe 3+ ions, Fe 2+It will react with hydrogen peroxide in solution to produce Fe. 3+ OH - Hydroxyl radicals, as strong oxidants, can effectively oxidize and dissolve trace organic contaminants, grease, and metallic impurities on the surface of alloy powders. They also oxidize the magnetic powder surface to produce slight, uniform etching. This etching increases the surface's physical roughness, providing more reaction sites and a larger specific surface area, which is beneficial for the physical anchoring and surface adhesion of hydrolyzed SiO2, significantly enhancing coating adhesion and thus improving the coating effect. Simultaneously, the strong oxidizing environment generates a thin, dense oxide layer on the magnetic powder surface. This oxide layer is rich in metallic hydroxyl groups. During the subsequent hydrolysis of ethyl silicate, the silanol groups generated by the hydrolysis of ethyl silicate can firmly bind to the metallic hydroxyl groups on the magnetic powder surface through hydrogen bonding and dehydration condensation. By using a nitric acid-hydrogen peroxide solution to perform surface hydroxylation treatment on the magnetic powder, silane coupling agents can be effectively replaced.

[0038] Meanwhile, the crystallization process employs a segmented crystallization treatment. First, crystallization is carried out at a higher temperature to maximize the precipitation of nanocrystalline grains. Then, the crystallization temperature is lowered to allow further precipitation of nanocrystalline grains while inhibiting their growth. By performing segmented crystallization on the formed FeSiBCuNb amorphous magnetic powder core blank, a larger crystal volume fraction and smaller grain size are obtained, resulting in superior magnetic properties.

[0039] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0040] A method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder core, wherein the FeSiBCuNb amorphous nanocrystalline magnetic powder core is composed of FeSiBCuNb amorphous nanocrystals and a coating layer on the surface of the magnetic powder, which, from the inside out, are FeSiBCuNb spherical amorphous nanocrystalline powder, a metal oxide layer, a SiO2 layer and a high-temperature resistant silicone resin layer.

[0041] The specific steps of this invention are as follows:

[0042] Step 1. Surface hydroxylation treatment:

[0043] Weigh out FeSiBCuNb amorphous powder, then add the FeSiBCuNb amorphous powder to a nitric acid-hydrogen peroxide solution for surface hydroxylation treatment, and stir in a water bath;

[0044] Step 2. Filtering:

[0045] The solution from step 1 was filtered and washed 2-3 times with anhydrous ethanol and dried to obtain FeSiBCuNb amorphous powder with surface hydroxylation treatment.

[0046] Step 3. Ethyl silicate hydrolysis coating

[0047] Add the FeSiBCuNb amorphous powder with surface hydroxylation treatment in step 2 to a tetraethyl orthosilicate-anhydrous ethanol solution, add a certain amount of deionized water and adjust the pH of the solution with ammonia water, and stir in a water bath until dry.

[0048] Step 4. Resin Coating:

[0049] The FeSiBCuNb amorphous powder coated with ethyl silicate in step 3 and the resin were added to acetone and stirred continuously until the acetone was completely volatilized. After drying, the FeSiBCuNb amorphous powder coated with SiO2 and resin was obtained.

[0050] Step 5. Sieve:

[0051] The SiO2 and resin-coated FeSiBCuNb amorphous powder from step 4 was sieved.

[0052] Step 6. Suppression:

[0053] The magnetic powder after sieving in step 5 is pressed into shape to obtain a magnetic powder core blank.

[0054] Step 7. Crystallization:

[0055] The magnetic powder core blank obtained in step 6 is subjected to crystallization treatment to obtain the FeSiBCuNb amorphous nanocrystalline magnetic powder core.

[0056] Furthermore, in step 1, the specific composition of the FeSiBCuNb amorphous nanocrystals is Fe. 81.4 Si 1.0 B 5.8 Cu 2.6 Nb 9.5 .

[0057] Regarding the nitric acid-hydrogen peroxide solution, anhydrous ethanol is used as the solvent, and the calculation is based on the mass of anhydrous ethanol as the percentage. If the mass of anhydrous ethanol is 100g, then the amount of nitric acid used is 5-10g, and the amount of hydrogen peroxide used is 1-5g. For every 1g of FeSiBCuNb spherical amorphous powder, 1-2ml of nitric acid-hydrogen peroxide solution is added. The surface hydroxylation treatment temperature is 10-30℃, the stirring speed is 150-350rpm, and the surface hydroxylation treatment time is 3-10min.

[0058] The present invention uses nitric acid with a concentration of 65-68%. The aforementioned "calculation basis based on the mass of anhydrous ethanol" refers to the calculation basis based on the mass of anhydrous ethanol as a percentage. For example, if the mass of anhydrous ethanol is 100g, then the amount of nitric acid with a concentration of 65-68% is 5-10g.

[0059] Furthermore, in step 2, the drying temperature is 50–80°C, and the drying time is 0.5–2 hours.

[0060] Furthermore, in step 3, the volume ratio of added ethyl silicate to the mass of FeSiBCuNb spherical amorphous powder is 0.05–0.25 ml / g, the volume ratio of added deionized water to the mass of FeSiBCuNb spherical amorphous powder is 0.15–0.60 ml / g, the pH is adjusted to 8–10, the stirring speed is 150–350 rpm, and the reaction time is 0.5–3 h.

[0061] Furthermore, in step 4, the resin used is a high-temperature resistant (800℃) silicone resin. The mass of the SiO2-coated FeSiBCuNb amorphous powder is used as the calculation basis. The amount of resin is 2.0-5.0 wt%, the amount of acetone is 20-60 wt%, the stirring speed is 150-350 rpm, the drying temperature is 40-70℃, and the time is 10-60 min.

[0062] Furthermore, in step 5, the sample is passed through a 40-80 mesh sieve.

[0063] Furthermore, in step 6, the pressing process is as follows: the dried magnetic powder obtained in step 5 is mixed evenly with the release agent and then pressed into a magnetic ring to obtain a magnetic powder core blank. The release agent is one of zinc stearate, magnesium stearate, and aluminum stearate. The amount of release agent is 0.1 to 0.5 wt% of the mass of the dried magnetic powder, and the pressing pressure is 400 to 1200 MPa.

[0064] Furthermore, in step 7, the crystallization process is carried out under a protective atmosphere and is performed in stages. First, the temperature is increased to 560°C at a heating rate of 5°C / min and crystallized for 10 min. Then, the temperature is decreased to 520°C and crystallization continues for 30 min.

[0065] Example 1:

[0066] 1) Take 60 ml of anhydrous ethanol. Based on the mass of anhydrous ethanol, weigh 10 wt% nitric acid and 1 wt% hydrogen peroxide. Sonicate until the solution is clear and transparent to obtain a nitric acid-hydrogen peroxide solution. Add 40 g of FeSiBCuNb amorphous powder to the nitric acid-hydrogen peroxide solution for surface hydroxylation treatment. Stir in a water bath at 25°C at a stirring speed of 200 rpm for 10 min.

[0067] 2) Subsequently, the magnetic powder was separated using a vacuum filtration device, washed three times with anhydrous ethanol, and dried at 60°C for 1 hour to obtain FeSiBCuNb amorphous powder with surface hydroxylation treatment.

[0068] 3) Measure 20 ml of anhydrous ethanol and 10 ml of deionized water to prepare a solution, and adjust the pH of the solution to 10 using ammonia. Add 30 g of surface-hydroxylated FeSiBCuNb amorphous powder and 3 ml of ethyl silicate to the solution and stir at 200 rpm for 1 h. Then dry at 60 °C for 30 min to obtain surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder.

[0069] 4) Using the surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder as the calculation basis, the amount of resin is 3wt% and the amount of acetone is 15g. A resin coating solution is prepared. 30g of the surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder is added to the resin coating solution and stirred at 200rpm for 20min. Then, it is dried at 60℃ for 30min and passed through a 50-mesh sieve to obtain the surface-hydroxylated SiO2 and resin-coated FeSiBCuNb amorphous powder.

[0070] 5) The surface-hydroxylated SiO2 and resin-coated FeSiBCuNb amorphous powder were mixed evenly with 0.5wt% zinc stearate; it was pressed into shape under 1000MPa using a 10×6×4mm mold; and crystallized at 560℃ in an argon atmosphere. The crystallization process conditions were as follows: segmented crystallization was adopted. First, the temperature was increased to 560℃ at a heating rate of 5℃ / min and crystallized for 10min. Then, the temperature was decreased to 520℃ and crystallized for another 30min. The powder was cooled in the furnace to obtain FeSiBCuNb amorphous nanocrystalline soft magnetic powder core.

[0071] Example 2:

[0072] 2) 1) Take 60 ml of anhydrous ethanol. Based on the mass of anhydrous ethanol, weigh 10 wt% nitric acid and 3 wt% hydrogen peroxide. Sonicate until the solution is clear and transparent to obtain a nitric acid-hydrogen peroxide solution. Add 40 g of FeSiBCuNb amorphous powder to the nitric acid-hydrogen peroxide solution for surface hydroxylation treatment. Stir in a water bath at 25°C at a stirring speed of 200 rpm for 10 min.

[0073] 2) Subsequently, the magnetic powder was separated using a vacuum filtration device, washed three times with anhydrous ethanol, and dried at 60°C for 1 hour to obtain FeSiBCuNb amorphous powder with surface hydroxylation treatment.

[0074] 3) Measure 20 ml of anhydrous ethanol and 10 ml of deionized water to prepare a solution, and adjust the pH of the solution to 10 using ammonia. Add 30 g of surface-hydroxylated FeSiBCuNb amorphous powder and 3 ml of ethyl silicate to the solution and stir at 200 rpm for 1 h. Then dry at 60 °C for 30 min to obtain surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder.

[0075] 4) Using the surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder as the calculation basis, the amount of resin is 3wt% and the amount of acetone is 15g. A resin coating solution is prepared. 30g of the surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder is added to the resin coating solution and stirred at 200rpm for 20min. Then, it is dried at 60℃ for 30min and passed through a 50-mesh sieve to obtain the surface-hydroxylated SiO2 and resin-coated FeSiBCuNb amorphous powder.

[0076] 5) Mix SiO2 and resin-coated FeSiBCuNb amorphous powder with 0.5wt% zinc stearate evenly; press into shape using a 10×6×4mm mold at 1000MPa; crystallize at 560℃ in an argon atmosphere. Crystallization process conditions: adopt segmented crystallization treatment, first heat to 560℃ at a heating rate of 5℃ / min, crystallize for 10min, then cool to 520℃ and continue crystallizing for 30min; cool with furnace to obtain FeSiBCuNb amorphous nanocrystalline soft magnetic powder core.

[0077] Example 3:

[0078] 3) 1) Take 60 ml of anhydrous ethanol. Based on the mass of anhydrous ethanol, weigh 10 wt% nitric acid and 5 wt% hydrogen peroxide. Sonicate until the solution is clear and transparent to obtain a nitric acid-hydrogen peroxide solution. Add 40 g of FeSiBCuNb amorphous powder to the nitric acid-hydrogen peroxide solution for surface hydroxylation treatment. Stir in a water bath at 25°C at a stirring speed of 200 rpm for 10 min.

[0079] 2) The magnetic powder was separated using a vacuum filtration device, washed three times with anhydrous ethanol, and dried at 60°C for 1 hour to obtain FeSiBCuNb amorphous powder with surface hydroxylation treatment.

[0080] 3) Measure 20 ml of anhydrous ethanol and 10 ml of deionized water to prepare a solution, and adjust the pH of the solution to 10 using ammonia. Add 30 g of surface-hydroxylated FeSiBCuNb amorphous powder and 3 ml of ethyl silicate to the solution and stir at 200 rpm for 1 h. Then dry at 60 °C for 30 min to obtain surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder.

[0081] 4) Using the surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder as the calculation basis, the amount of resin is 3wt% and the amount of acetone is 15g. A resin coating solution is prepared. 30g of the surface-hydroxylated SiO2-coated FeSiBCuNb amorphous powder is added to the resin coating solution and stirred at 200rpm for 20min. Then, it is dried at 60℃ for 30min and passed through a 50-mesh sieve to obtain the surface-hydroxylated SiO2 and resin-coated FeSiBCuNb amorphous powder.

[0082] 5) The surface-hydroxylated SiO2 and resin-coated FeSiBCuNb amorphous powder were mixed evenly with 0.5wt% zinc stearate; it was pressed into shape under 1000MPa using a 10×6×4mm mold; and crystallized at 560℃ in an argon atmosphere. The crystallization process conditions were as follows: segmented crystallization was adopted. First, the temperature was increased to 560℃ at a heating rate of 5℃ / min and crystallized for 10min. Then, the temperature was decreased to 520℃ and crystallized for another 30min. The powder was cooled in the furnace to obtain FeSiBCuNb amorphous nanocrystalline soft magnetic powder core.

[0083] Comparative example:

[0084] 1) Weigh 0.2g of polyvinylpyrrolidone (PVP), add 60ml of anhydrous ethanol, and sonicate until the solution is clear and transparent. Add 40g of FeSiBCuNb amorphous powder to the solution for treatment. Stir in a water bath at 25℃ at a stirring speed of 200rpm for 10min.

[0085] 2) Use a vacuum filter to separate the magnetic powder and dry it at 60℃ for 1 hour.

[0086] 3) Measure 20 ml of anhydrous ethanol and 10 ml of deionized water to prepare a solution, and adjust the pH of the solution to 10 using ammonia. Add 30 g of PVP-modified FeSiBCuNb amorphous powder and 3 ml of ethyl silicate to the solution and stir at 200 rpm for 1 h. Then dry at 60 °C for 30 min to obtain PVP-modified SiO2-coated FeSiBCuNb amorphous powder.

[0087] 4) Using PVP-modified SiO2-coated FeSiBCuNb amorphous powder as the calculation basis, the amount of resin used was 3wt%, and the amount of acetone used was 15g. A resin coating solution was prepared, and 30g of PVP-modified SiO2-coated FeSiBCuNb amorphous powder was added to the resin coating solution and stirred at 200rpm for 20min. Then, it was dried at 60℃ for 30min and passed through a 50-mesh sieve to obtain PVP-modified SiO2 and resin-coated FeSiBCuNb amorphous powder.

[0088] 5) PVP-modified SiO2 and resin-coated FeSiBCuNb amorphous powder were mixed evenly with 0.5wt% zinc stearate; the mixture was pressed into shape using a 10×6×4mm mold at 1000MPa; crystallized at 560℃ in an argon atmosphere. The crystallization process conditions were as follows: segmented crystallization was adopted, firstly, the temperature was increased to 560℃ at a heating rate of 5℃ / min and crystallized for 10min, then the temperature was decreased to 520℃ and crystallized for another 30min; the mixture was cooled in the furnace to obtain FeSiBCuNb amorphous nanocrystalline soft magnetic powder core.

[0089] After winding the FeSiBCuNb amorphous nanocrystalline soft magnetic powder core samples prepared in Examples 1-3 and Comparative Example 1, the resistance and inductance L of the samples were measured using a Tonghui TH2826 precision LCR meter. The effective permeability of the samples was calculated using the formula based on the inductance L. The test conditions were a frequency f = 40 kHz and a typical voltage of 600 mV. The loss performance was tested using an Iwasaki SY-8218 BH analyzer. The loss test conditions were 100 kHz, 50 mT, 25 °C and 1 MHz, 20 mT, 25 °C. The test results are shown in Table 1 below.

[0090] Table 1. Performance test results of FeSiBCuNb amorphous nanocrystalline soft magnetic powder cores obtained in the examples and comparative examples:

[0091]

[0092] The above results show that, compared with the PVP-modified SiO2 hydrolyzed FeSiBCuNb amorphous nanocrystalline soft magnetic powder core, the resistivity of the SiO2-coated FeSiBCuNb amorphous nanocrystalline soft magnetic powder core after surface hydroxylation treatment according to the present invention is increased by 373%, the coercivity is reduced by 50%, and the permeability remains stable. Furthermore, the loss of the SiO2-coated FeSiBCuNb amorphous nanocrystalline magnetic powder core after surface hydroxylation treatment is reduced by 22.0% at 25℃ and 50mT@100kHz, and by 23.5% at 25℃ and 20mT@1MHz.

[0093] Depend on Figure 1It can be seen that after surface hydroxylation treatment, the SiO2 insulating coating is uniformly adhered to the surface of the FeSiBCuNb amorphous nanocrystalline soft magnetic powder.

Claims

1. A method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder cores, characterized in that, Includes the following steps: Step 1. Surface hydroxylation treatment: FeSiBCuNb amorphous powder was added to a nitric acid-hydrogen peroxide solution for surface hydroxylation treatment, followed by water... Bath stirring; Step 2. Filtering: The solution from step 1 was filtered, washed with anhydrous ethanol, and dried to obtain the surface-hydroxylated solution. FeSiBCuNb amorphous powder; Step 3: Ethyl silicate hydrolysis coating: The FeSiBCuNb amorphous powder obtained in step 2 was added to a tetraethyl orthosilicate-anhydrous ethanol solution, and then... Use deionized water and adjust the pH of the solution to 8-10 with ammonia, then stir in a water bath until dry. Step 4. Resin Coating: Add the FeSiBCuNb amorphous powder and resin obtained in step 3 to acetone and continue stirring until the acetone is completely dissolved. The mixture was completely volatilized and dried to obtain amorphous powder of FeSiBCuNb coated with SiO2 and resin. Step 5. Sieve: The SiO2 and resin-coated FeSiBCuNb amorphous powder obtained in step 4 were sieved. Step 6. Compression: The magnetic powder obtained in step 5 is pressed into shape to obtain a magnetic powder core blank; Step 7. Crystallization: The magnetic powder core blank obtained in step 6 is subjected to crystallization treatment to obtain the FeSiBCuNb amorphous nanoparticle. Microcrystalline magnetic powder core.

2. The method for preparing the FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1, characterized in that, In step 1, the FeSiBCuNb amorphous nanocrystal composition is Fe. 81.4 Si 1.0 B 5.8 Cu 2.6 Nb 9.5 ; The nitric acid-hydrogen peroxide solution is prepared by mixing 5-10 wt% nitric acid (calculated based on the mass of anhydrous ethanol), 65-68% nitric acid concentration, and 1-5 wt% hydrogen peroxide. For every 1g of FeSiBCuNb spherical amorphous powder, add 1-2ml of nitric acid-hydrogen peroxide solution. The surface hydroxylation treatment temperature is 10-30℃, the stirring speed is 150-350rpm, and the surface hydroxylation treatment time is 3-10min.

3. The method for preparing the FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1, characterized in that, In step 2, the drying temperature is 50–80℃ and the drying time is 8–16 hours.

4. The method for preparing the FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1, characterized in that, In step 3, the volume ratio of added ethyl silicate to the mass of FeSiBCuNb spherical amorphous powder is 0.05–0.25 ml / g, the volume ratio of added deionized water to the mass of FeSiBCuNb spherical amorphous powder is 0.15–0.60 ml / g, the pH is adjusted to 8–10, the stirring speed is 150–350 rpm, and the reaction time is 0.5–3 h.

5. The method for preparing the FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1, characterized in that, In step 4, the resin used is a high-temperature silicone resin resistant to 800℃. The mass of the SiO2-coated FeSiBCuNb amorphous powder is used as the calculation basis. The amount of resin used is 2.0-5.0 wt%, the amount of acetone used is 20-60 wt%, the stirring speed is 150-350 rpm, the drying temperature is 40-70℃, and the time is 10-60 min.

6. The method for preparing FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1, characterized in that, In step 5, the sample is passed through a 40-80 mesh sieve.

7. The method for preparing the FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1: characterized in that, Step 6 is as follows: After the dried magnetic powder obtained in step 5 is mixed evenly with the release agent, it is pressed into a magnetic ring to obtain a magnetic powder core blank. The release agent is one of zinc stearate, magnesium stearate, and aluminum stearate. The amount of release agent is 0.1 to 0.5 wt% of the mass of the dried magnetic powder. The pressing pressure is 600 to 1800 MPa.

8. The method for preparing the FeSiBCuNb amorphous nanocrystalline magnetic powder core according to claim 1: characterized in that, In step 7, the crystallization process is carried out under an argon atmosphere and is performed in stages. First, the temperature is increased to 560°C at a heating rate of 5°C / min and crystallized for 10 min. Then, the temperature is decreased to 520°C and crystallization continues for 30 min.

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