Insulating soft magnetic metal powder, its preparation method, and magnetic powder core

Abstract

The present invention discloses an insulating soft magnetic metal powder, a preparation method thereof, and a magnetic powder core. The insulating soft magnetic metal powder includes a soft magnetic metal powder and an insulating layer coating the soft magnetic metal powder. The insulating layer includes multiple layers of hexagonal boron nitride layers sequentially distributed in the radial direction of the soft magnetic metal powder. The structure of each layer of the hexagonal boron nitride layer is a single-layer hexagonal network structure, and boron atoms and nitrogen atoms are cross-distributed at the vertices of the hexagon. Adjacent hexagonal boron nitride layers are connected by van der Waals forces. The D50 particle size of the soft magnetic metal powder is 10 μm to 60 μm, and the thickness of the insulating layer is 5 nm to 100 nm. The insulating soft magnetic metal powder of the present invention simultaneously has excellent properties of high inductance value, low loss, and high insulation.

Description

Technical Field

[0001] The present invention relates to the field of magnetic functional materials, and more specifically, to an insulating soft magnetic metal powder, a preparation method thereof, and a magnetic powder core. Background Art

[0002] With the development of electromagnetic conversion electronic components towards miniaturization, high power, high frequency, and high efficiency, the required magnetic powder cores are expected to have higher saturation magnetic induction intensity, DC bias performance, and resistivity, as well as lower losses.

[0003] Surface insulation coating of soft magnetic metal powder can effectively block the contact between powder particles, thereby increasing the resistivity, reducing the eddy current loss of the magnetic powder core, and improving the saturation magnetic induction intensity, DC bias performance, and resistivity of the magnetic powder core, thus improving the high-frequency performance of the magnetic powder core.

[0004] The main methods to reduce the loss of the magnetic powder core are: reducing the particle size of the soft magnetic metal powder or increasing the thickness of the insulating layer on the surface of the soft magnetic metal powder. Among them, reducing the particle size of the soft magnetic metal powder, the finer the particle size, the lower the inductive eddy current loss. However, the finer the particle size, the smaller the magnetic permeability, which is not conducive to increasing the inductance; increasing the thickness of the insulating layer on the surface of the soft magnetic metal powder, the thicker the insulating layer, the higher the resistivity, and the lower the inductive eddy current loss. However, with the increase in the thickness of the insulating layer, the filling ratio of the soft magnetic metal powder in the magnetic powder core decreases, resulting in a decrease in magnetic permeability.

[0005] There is an urgent need to develop a magnetic powder core with high inductance value and low loss, and a magnetic powder core with high insulation resistance to meet the market demand. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art, and provide an insulating soft magnetic metal powder with high inductance value, low loss, and high insulation resistance, a preparation method thereof, and a magnetic powder core to meet the market demand.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows:

[0008] An insulating soft magnetic metal powder, comprising a soft magnetic metal powder and an insulating layer coating the soft magnetic metal powder. The insulating layer includes multiple layers of hexagonal boron nitride layers distributed in sequence along the radial direction of the soft magnetic metal powder. The structure of each layer of hexagonal boron nitride layer is a single-layer hexagonal network structure, with boron atoms and nitrogen atoms cross-distributed at the vertices of the hexagon. Adjacent hexagonal boron nitride layers are connected by van der Waals forces. The D50 particle size of the soft magnetic metal powder is 10 μm to 60 μm, and the thickness of the insulating layer is 5 nm to 100 nm.

[0009] The present invention also discloses a preparation method of the above-mentioned insulating soft magnetic metal powder, including the following process:

[0010] Place the soft magnetic metal powder on a fluidized bed, and charge the boron nitride precursor into the fluidized bed reaction chamber from below the fluidized bed along with the fluidizing gas stream. The fluidizing gas stream passes through the fluidized bed, causing the soft magnetic metal powder to be suspended and flow. The boron nitride precursor reacts in the fluidized bed reaction chamber to generate boron nitride, and the boron nitride deposits on the surface of the soft magnetic metal powder to form a multi-layer hexagonal boron nitride layer coating the soft magnetic metal powder, thereby obtaining the insulated soft magnetic metal powder.

[0011] The present invention also discloses a magnetic powder core prepared from the above-mentioned insulated soft magnetic metal powder.

[0012] Implementing the embodiments of the present invention will have the following beneficial effects:

[0013] In the embodiments of the present invention, a multi-layer hexagonal boron nitride layer is sequentially deposited on the surface of the soft magnetic metal powder by chemical vapor deposition (CVD). Chemical vapor deposition (CVD) is a layer-by-layer growth method. Therefore, each layer of the grown hexagonal boron nitride layer is a single-layer boron nitride network structure coating the surface of the soft magnetic metal powder. Therefore, the surface of the insulating layer of the present invention is atomically smooth, has no dangling bonds, and the insulating layer structure is more stable and is not easily detached during the process of pressing to form a magnetic powder core. Therefore, it can provide properties of high magnetic induction, high insulation, and ultra-low loss.

[0014] The through holes of the present invention are prepared by a fluidized bed - chemical vapor deposition method, making the structure of each layer of the grown hexagonal boron nitride layer more regular and the thickness of the insulating layer more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Among them:

[0017] Figure 1 is a schematic structural diagram of a single-layer hexagonal boron nitride coating the surface of the soft magnetic metal powder obtained by the present invention.

[0018] Figure 2 is a scanning electron microscope image of the insulated soft magnetic metal powder obtained in Example 1 of the present invention.

[0019] Figure 3 is a scanning electron microscope image of the insulated soft magnetic metal powder obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] The present invention discloses an insulating soft magnetic metal powder, which includes a soft magnetic metal powder and an insulating layer coating the soft magnetic metal powder. The insulating layer includes multiple layers of hexagonal boron nitride layers sequentially distributed in the radial direction of the soft magnetic metal powder. The structure of each layer of hexagonal boron nitride layer is a single-layer hexagonal network structure, and boron atoms and nitrogen atoms are cross-distributed at the vertices of the hexagon. Adjacent hexagonal boron nitride layers are connected by van der Waals forces. The D50 particle size of the soft magnetic metal powder is 10 μm to 60 μm, and the thickness of the insulating layer is 5 nm to 100 nm.

[0022] Since the present invention uses chemical vapor deposition (CVD) to sequentially deposit multiple layers of hexagonal boron nitride layers on the surface of the soft magnetic metal powder, and chemical vapor deposition (CVD) is a layer-by-layer growth method, therefore, each layer of grown hexagonal boron nitride layer is a single-layer boron nitride network structure coating the surface of the soft magnetic metal powder, as Figure 1 shown. Therefore, the surface of the insulating layer of the present invention is atomically smooth, without dangling bonds, and the structure of the insulating layer is more stable and not easily detached during the process of pressing to form a magnetic powder core. Therefore, it can provide properties of high magnetic induction, high insulation, and ultra-low loss.

[0023] In the prior art, there is a method of ball milling, in which the soft magnetic metal powder and hexagonal boron nitride are ball milled together to prepare a composite of the soft magnetic metal and hexagonal boron nitride. Hexagonal boron nitride is similar to the graphite structure and is a multi-layer structure. There is no chemical bond between layers. After ball milling the multi-layer hexagonal boron nitride, the obtained hexagonal boron nitride powder is usually still a multi-layer structure and is difficult to directly become a single-layer structure (similar to the single-layer graphene structure). Therefore, after ball milling, the multi-layer hexagonal boron nitride powder is stacked and attached to the surface of the soft magnetic metal powder in a dot-like manner. The surface of the insulating layer is relatively rough and there are dangling bonds, which is completely different from the insulating layer structure formed by the present invention.

[0024] In a specific embodiment, the soft magnetic metal powder can be selected from one or more of iron-based soft magnetic powder, iron-silicon-based soft magnetic powder, iron-silicon-aluminum-based soft magnetic powder, and iron-nickel-based soft magnetic powder, etc.

[0025] In a specific embodiment, the number of layers of the hexagonal boron nitride layer is 10 layers to 200 layers, and the corresponding thickness of the insulating layer is about 5 nm to 100 nm.

[0026] The present invention also provides a method for preparing the above-mentioned insulating soft magnetic metal powder, which adopts the fluidized bed-chemical vapor deposition method, making the hexagonal boron nitride layer structure grown in each layer more regular and the thickness of the insulating layer more uniform. Specifically, it includes the following processes:

[0027] Place the soft magnetic metal powder on the fluidized bed, and charge the boron nitride precursor into the fluidized bed reaction chamber together with the fluidizing gas flow from below the fluidized bed. The fluidizing gas flow passes through the fluidized bed, causing the soft magnetic metal powder to suspend and flow. The boron nitride precursor reacts in the fluidized bed reaction chamber to generate boron nitride, and the boron nitride is deposited on the surface of the soft magnetic metal powder to form multiple layers of hexagonal boron nitride layers coating the soft magnetic metal powder, obtaining the insulating soft magnetic metal powder.

[0028] In the above embodiment, the boron nitride precursor can be a solid powder, a gas, or a mixture of a solid powder and a gas. When the boron nitride precursor includes a solid powder, a powder feeder can be used to slowly and continuously feed the solid powder into the gas pipeline of the fluidizing gas flow, and the fluidizing gas flow is used to blow the solid powder into the fluidized bed reaction chamber. When the boron nitride precursor includes a gas, the gas can be directly transported into the gas pipeline of the fluidizing gas flow.

[0029] In a specific embodiment, the pressure in the fluidized bed reaction chamber is 50 Pa to 150 Pa, the reaction temperature in the fluidized bed reaction chamber is 600 °C to 1000 °C, the reaction time in the fluidized bed reaction chamber is 10 min to 120 min, the flow rate of the fluidizing gas flow is 30 sccm to 100 sccm, the feeding amount of the boron nitride precursor is 1 g / min to 10 g / min, and the mass ratio of the boron nitride precursor to the soft magnetic metal powder is 1000:20 to 120.

[0030] In the above embodiment, the pressure in the fluidized bed reaction chamber and the flow rate of the fluidizing gas flow jointly determine whether the soft magnetic metal powder can suspend and flow in the fluidized bed reaction chamber, and the reaction time and the feeding amount of the boron nitride precursor jointly determine the thickness of the insulating layer.

[0031] In a specific embodiment, the boron nitride precursor includes one or more of ammonia borane, borazine, binary precursor B2H6 / NH3, binary precursor BCl3 / NH3, and binary precursor BF3 / NH3.

[0032] In a specific embodiment, the fluidizing gas flow includes one or more of a mixed gas of argon and hydrogen, argon, nitrogen, and helium.

[0033] In a specific embodiment, before placing the soft magnetic metal powder on the fluidized bed, it further includes: cleaning the soft magnetic metal powder, and the cleaning includes:

[0034] Step 1: Pickling the soft magnetic metal powder with an acid solution to remove the oxide layer on the surface of the soft magnetic metal powder.

[0035] In the above steps, the acid solution for pickling includes one or more of hydrochloric acid, phosphoric acid and sulfuric acid, and the hydrogen ion concentration of the acid solution is 0.1 mol / L to 0.5 mol / L.

[0036] Step 2: The soft magnetic metal powder after pickling is sequentially cleaned with a hydrophilic organic solvent and then washed with water.

[0037] Hydrophilic organic solvent cleaning is used to remove organic impurities on the surface of soft magnetic metal powder, and water washing is used to remove washing liquid residue and other impurities.

[0038] The hydrophilic organic solvent may be selected from acetone and / or ethanol.

[0039] In this embodiment, the soft magnetic metal powder after acid washing is washed with acetone and ethanol in sequence.

[0040] Step 3: Drying the soft magnetic metal powder.

[0041] In a specific embodiment, nitrogen gas may be used to dry the soft magnetic metal powder.

[0042] The invention also discloses a magnetic powder core, which is prepared from the above insulating soft magnetic metal powder.

[0043] Specifically, the insulating soft magnetic metal powder is sieved and granulated, and then evenly mixed with a silane coupling agent, a resin binder, a release agent, etc., and then pressed and annealed to produce a finished soft magnetic powder core.

[0044] The silane coupling agent may be selected from KH550 and / or KH560, preferably KH550.

[0045] The resin binder may be one or more selected from phenolic resin, epoxy resin, silicone resin, polyvinyl fluoride and melamine resin.

[0046] The release agent may be selected from one or more of zinc stearate, barium stearate, calcium stearate and molybdenum disulfide.

[0047] The following are specific examples.

[0048] Example 1

[0049] 1. Ultrasonic cleaning of 1000g of sendust soft magnetic powder (D50 particle size is 40μm) in 50mL of dilute hydrochloric acid solution (0.1mol / L) for 30min, followed by ultrasonic cleaning with 50mL of acetone, 50mL of ethanol, and 50mL of deionized water for 10min respectively to remove impurities on the surface of the magnetic powder, and blow dry with nitrogen for later use.

[0050] 2. Place 20 g of the ammonia borane precursor in a powder feeder. Add the iron-silicon-aluminum magnetic powder treated in step 1 into a fluidized bed reactor. Place the ammonia borane precursor in the powder feeder and slowly and continuously feed it into the gas pipeline of the fluidizing gas stream by the powder feeder. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 1 g / min. The fluidizing gas stream is argon with a flow rate of 50 sccm. The pressure in the fluidized bed reactor is 50 Pa, the temperature is 1000 °C, and the reaction time is 20 min to obtain iron-silicon-aluminum soft magnetic powder coated with HBN insulation. Measure that the thickness of the insulation layer of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is 20 nm, the number of layers of the hexagonal boron nitride layer is 40 layers, and the D50 particle size of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is about 40 μm.

[0051] 3. Pass the iron-silicon-aluminum powder coated with HBN insulation obtained in step 2 through a 200-mesh sieve, perform screening and granulation, then weigh 200 g of the granulated powder, add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate, mix evenly, and press into a magnetic powder core.

[0052] Example 2

[0053] The difference between Example 2 and Example 1 lies in the different usage amounts of the ammonia borane precursor.

[0054] 1. Ultrasonically clean 1000 g of iron-silicon-aluminum soft magnetic powder (D50 particle size is 40 μm) in 50 mL of dilute hydrochloric acid solution (0.1 mol / L) for 30 min, and then ultrasonically clean it with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min each to remove impurities on the surface of the magnetic powder, and dry it with nitrogen for standby.

[0055] 2. Place 80 g of the ammonia borane precursor in a powder feeder. Add the iron-silicon-aluminum magnetic powder treated in step 1 into a fluidized bed reactor. Place the ammonia borane precursor in the powder feeder and slowly and continuously feed it into the gas pipeline of the fluidizing gas stream by the powder feeder. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 1 g / min. The fluidizing gas stream is argon with a flow rate of 50 sccm. The pressure in the fluidized bed reactor is 50 Pa, the temperature is 1000 °C, and the reaction time is 80 min to obtain iron-silicon-aluminum soft magnetic powder coated with HBN insulation. Measure that the thickness of the insulation layer of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is 60 nm, the number of layers of the hexagonal boron nitride layer is 120 layers, and the D50 particle size of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is 40 μm.

[0056] 3. Pass the iron-silicon-aluminum powder coated with HBN insulation obtained in step 2 through a 200-mesh sieve, perform screening and granulation, then weigh 200 g of the granulated powder, add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate, mix evenly, and press into a magnetic powder core.

[0057] Example 3

[0058] Example 3 is different from Example 1 in that the usage amount of the ammonia borane precursor is different.

[0059] 1. Ultrasonically clean 1000 g of FeSiAl soft magnetic powder (D50 particle size is 40 μm) in 50 mL of dilute hydrochloric acid solution (concentration 0.1 mol / L) for 30 min, and then ultrasonically clean it with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min each to remove impurities on the surface of the magnetic powder, and dry it with nitrogen for standby.

[0060] 2. Place 120 g of the ammonia borane precursor in a powder feeder. Add the FeSiAl magnetic powder treated in step 1 into a fluidized bed reactor. Place the ammonia borane precursor in the powder feeder and slowly and continuously feed it into the gas pipeline of the fluidizing gas stream. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 1 g / min. The fluidizing gas stream is argon, the argon flow rate is 50 sccm, the pressure of the fluidized bed reactor is 50 Pa, the temperature is 1000 °C, and the reaction time is 120 min to obtain FeSiAl soft magnetic powder coated with HBN insulation. Measure that the thickness of the insulation layer of the FeSiAl soft magnetic powder coated with HBN insulation is 100 nm, the number of layers of the hexagonal boron nitride layer is 200 layers, and the D50 particle size of the FeSiAl soft magnetic powder coated with HBN insulation is 40 μm.

[0061] 3. Pass the FeSiAl powder coated with HBN insulation obtained in step 2 through a 200-mesh sieve, perform screening and granulation, then weigh 200 g of the granulated powder, and add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate and mix evenly, and press it into a magnetic powder core.

[0062] Example 4

[0063] Example 4 is different from Example 1 in that the average particle size of the FeSiAl soft magnetic powder is different.

[0064] 1. Ultrasonically clean 1000 g of FeSiAl soft magnetic powder (D50 particle size is 20 μm) in 50 mL of dilute hydrochloric acid solution (concentration 0.1 mol / L) for 30 min, and then ultrasonically clean it with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min each to remove impurities on the surface of the magnetic powder, and dry it with nitrogen for standby.

[0065] 2. 20 g of ammonia borane precursor is placed in a powder feeder. The iron-silicon-aluminum magnetic powder treated in step 1 is added to a fluidized bed reactor. The ammonia borane precursor is placed in the powder feeder and slowly and continuously fed into the gas pipeline of the fluidizing gas stream by the powder feeder. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 1 g / min. The fluidizing gas stream is argon, the argon flow rate is 50 sccm, the pressure of the fluidized bed reactor is 50 Pa, the temperature is 1000 °C, and the reaction time is 20 min to obtain iron-silicon-aluminum soft magnetic powder coated with HBN insulation. The thickness of the insulation layer of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is measured to be 30 nm, the number of layers of the hexagonal boron nitride layer is 60 layers, and the D50 particle size of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is 20 μm.

[0066] 3. The iron-silicon-aluminum powder coated with HBN insulation obtained in step 2 is sieved through a 200-mesh sieve for screening granulation. Then, 200 g of the granulated powder is weighed, and 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate are added and mixed evenly, and then pressed into a magnetic powder core.

[0067] Example 5

[0068] The difference between Example 5 and Example 1 is that the average particle size of the iron-silicon-aluminum soft magnetic powder is different.

[0069] 1. 1000 g of iron-silicon-aluminum soft magnetic powder (D50 particle size is 60 μm) is ultrasonically cleaned in 50 mL of dilute hydrochloric acid solution (concentration 0.1 mol / L) for 30 min, and then ultrasonically cleaned with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min to remove the impurities on the surface of the magnetic powder, and then dried with nitrogen for standby.

[0070] 2. 20 g of ammonia borane precursor is placed in a powder feeder. The iron-silicon-aluminum magnetic powder treated in step 1 is added to a fluidized bed reactor. The ammonia borane precursor is placed in the powder feeder and slowly and continuously fed into the gas pipeline of the fluidizing gas stream by the powder feeder. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 1 g / min. The fluidizing gas stream is argon, the argon flow rate is 50 sccm, the pressure of the fluidized bed reactor is 50 Pa, the temperature is 1000 °C, and the reaction time is 20 min to obtain iron-silicon-aluminum soft magnetic powder coated with HBN insulation. The thickness of the insulation layer of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is measured to be 15 nm, the number of layers of the hexagonal boron nitride layer is 20 layers, and the D50 particle size of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is 20 μm.

[0071] 3. The iron-silicon-aluminum powder coated with HBN insulation obtained in step 2 is sieved through a 200-mesh sieve for screening granulation. Then, 200 g of the granulated powder is weighed, and 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate are added and mixed evenly, and then pressed into a magnetic powder core.

[0072] Example 6

[0073] Example 6 is different from Example 1 in that the fluidization parameters are different.

[0074] 1. Ultrasonically clean 1000 g of FeSiAl soft magnetic powder (D50 particle size is 40 μm) in 50 mL of dilute hydrochloric acid solution (concentration 0.1 mol / L) for 30 min, and then ultrasonically clean with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min each to remove impurities on the surface of the magnetic powder, and dry it with nitrogen for standby.

[0075] 2. Place 20 g of ammonia borane precursor in a powder feeder. Add the FeSiAl magnetic powder treated in step 1 into a fluidized bed reactor. Place the ammonia borane precursor in the powder feeder and slowly and continuously feed it into the gas pipeline of the fluidizing gas flow. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 1 g / min. The fluidizing gas flow is argon, the argon flow rate is 30 sccm, the pressure of the fluidized bed reactor is 50 Pa, the temperature is 600 °C, and the reaction time is 20 min to obtain FeSiAl soft magnetic powder coated with HBN insulation. Measure that the thickness of the insulation layer of the FeSiAl soft magnetic powder coated with HBN insulation is 10 nm, the number of layers of the hexagonal boron nitride layer is 20 layers, and the D50 particle size of the FeSiAl soft magnetic powder coated with HBN insulation is 40 μm.

[0076] 3. Pass the FeSiAl powder coated with HBN insulation obtained in step 2 through a 200-mesh sieve for screening and granulation, then weigh 200 g of the granulated powder, and add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate and mix evenly, and press it into a magnetic powder core.

[0077] Example 7

[0078] Example 7 is different from Example 1 in that the fluidization parameters are different.

[0079] 1. Ultrasonically clean 1000 g of FeSiAl soft magnetic powder (average particle size is 40 μm)) in 50 mL of dilute hydrochloric acid solution (concentration 0.1 mol / L) for 30 min, and then ultrasonically clean with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min each to remove impurities on the surface of the magnetic powder, and dry it with nitrogen for standby.

[0080] 2. Place 20 g of the ammonia borane precursor in the powder feeder. Add the iron-silicon-aluminum magnetic powder treated in Step 1 to the fluidized bed reactor. Place the ammonia borane precursor in the powder feeder and slowly and continuously feed it into the gas pipeline of the fluidizing gas stream. The powder dropping rate (i.e., the feeding amount) of the ammonia borane precursor is 10 g / min. The fluidizing gas stream is argon, the argon flow rate is 100 sccm, the pressure of the fluidized bed reactor is 150 Pa, the temperature is 1000 °C, and the reaction time is 20 min to obtain iron-silicon-aluminum soft magnetic powder coated with HBN insulation. Measure the thickness of the insulation layer of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation to be 30 nm, the number of layers of the hexagonal boron nitride layer is 60 layers, and the D50 particle size of the iron-silicon-aluminum soft magnetic powder coated with HBN insulation is 40 μm.

[0081] 3. Pass the iron-silicon-aluminum powder coated with HBN obtained in Step 2 through a 200-mesh sieve for screening and granulation. Then weigh 200 g of the granulated powder, add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate, mix evenly, and press into a magnetic powder core.

[0082] Comparative Example 1

[0083] Prepared by the ball milling method.

[0084] 1. Ultrasonically clean 1000 g of iron-silicon-aluminum soft magnetic powder (D50 particle size is 40 μm) in 50 mL of dilute hydrochloric acid solution (concentration 0.1 mol / L) for 30 min. Then ultrasonically clean with 50 mL of acetone, 50 mL of ethanol, and 50 mL of deionized water in sequence for 10 min each to remove impurities on the surface of the magnetic powder, and dry with nitrogen for standby.

[0085] 2. Mix the iron-silicon-aluminum magnetic powder treated in Step 1 with 20 g of HBN. After mixing, place it in a ball mill, use alcohol as the solvent, ball mill for 2 h, and the rotation speed is 150 r / min to obtain a composite powder.

[0086] 3. Dry the material obtained in Step 2 with nitrogen.

[0087] 4. Pass the composite powder obtained in Step 3 through a 200-mesh sieve for screening and granulation. Then weigh 200 g of the granulated powder, add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate, mix evenly, and press into a magnetic powder core.

[0088] Comparative Example 2

[0089] Pass the commercially available ordinary coated iron-silicon-aluminum powder (phosphate-coated iron-silicon-aluminum powder) through a 200-mesh sieve for screening and granulation. Then weigh 200 g of the granulated powder, add 0.2 g of coupling agent, 1.0 g of resin binder, and 1.2 g of zinc stearate, mix evenly, and press into a magnetic core.

[0090] Test Example 1

[0091] The HBN-insulated iron-silicon-aluminum soft magnetic powder materials prepared in Example 1 and Comparative Example 1 were characterized morphologically, as Figure 2 and Figure 3 shown. It can be clearly seen from Figure 2 that the HBN coating layer on the surface of the HBN-insulated iron-silicon-aluminum soft magnetic powder material prepared by the method of the present invention is a thin-layer stacked structure. Each thin layer is a single-layer boron nitride layer, and the overall surface is very smooth. Referring to Figure 3 , the surface of the product prepared by the ball milling method is massive boron nitride, the thickness of the boron nitride is thick and uneven, resulting in larger pores and being significantly very rough.

[0092] Test Example 2

[0093] The electrical properties of the magnetic powder cores prepared in Examples 1 to 7 and Comparative Examples 1 to 2 were measured. A 30-turn inductance coil was wound on the magnetic powder core, and an impedance tester TH2839 and a DC bias current source TH1778A were used in combination to test the initial permeability μ(1V / 1MHz) and the inductance value under the superimposed current. The current value (A) at which the inductance decreased by 30% was the change value of the scanning inductance with the increase of the current, and the current value at which the inductance decreased by 30% was recorded. The insulation resistance of the magnetic powder core was tested with a CH-333 tester. The magnetic powder core loss (100mT&100KHz) was tested with an SY-8218 type B-H analyzer. The results are shown in Table 1.

[0094] Table 1: Electrical property indexes of the magnetic powder cores prepared in Examples 1 to 7 and Comparative Examples 1 to 2

[0095]

[0096] Referring to Table 1, first, comparing Example 1 with Comparative Example 1, it can be seen that the insulation resistance (1200 MΩ) of the magnetic powder core prepared by the preparation method of the present invention is significantly improved compared with that of Comparative Example 1 (700 MΩ), the initial permeability is significantly increased from 45 of Comparative Example 1 to 50, the loss is significantly reduced from 540 mW / cm 3 to 498 mW / cm 3 , and the current value at which the inductance decreases by 30% is significantly increased from 13.5 A of Comparative Example 1 to 18.2 A. It can be seen that the layer-by-layer preparation method of the present invention can produce a magnetic powder core with more excellent performance than the existing ball milling method.

[0097] Second, compared with Comparative Examples 1 and 2, the magnetic powder cores obtained in Examples 1 to 7 have higher initial permeability, insulation resistance and current value at which the inductance decreases by 30% and lower loss, and significant performance improvement effects are obtained.

[0098] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing an insulating soft magnetic metal powder, characterized in that, The insulating soft magnetic metal powder includes a soft magnetic metal powder and an insulating layer coating the soft magnetic metal powder. The insulating layer includes multiple layers of hexagonal boron nitride layers sequentially distributed in the radial direction of the soft magnetic metal powder. The structure of each layer of the hexagonal boron nitride layer is a single-layer hexagonal network structure, with boron atoms and nitrogen atoms cross-distributed at the vertices of the hexagon. Adjacent hexagonal boron nitride layers are connected by van der Waals forces. The D50 particle size of the soft magnetic metal powder is 10 μm to 60 μm, the thickness of the insulating layer is 5 nm to 100 nm, and the preparation method includes the following process: Place the soft magnetic metal powder on a fluidized bed, and introduce the boron nitride precursor into the fluidized bed reaction chamber from below the fluidized bed together with the fluidizing gas stream. The fluidizing gas stream passes through the fluidized bed, causing the soft magnetic metal powder to be suspended and flow. The boron nitride precursor reacts in the fluidized bed reaction chamber to generate boron nitride, and the boron nitride deposits on the surface of the soft magnetic metal powder to form multiple layers of hexagonal boron nitride layers coating the soft magnetic metal powder, obtaining the insulating soft magnetic metal powder; The boron nitride precursor includes one or more of ammonia borane, borazine, binary precursor B2H6 / NH3, binary precursor BCl3 / NH3, and binary precursor BF3 / NH3.

2. The preparation method of the insulating soft magnetic metal powder according to claim 1, wherein, The feeding amount of the boron nitride precursor is 1 g / min to 10 g / min; The mass ratio of the soft magnetic metal powder to the boron nitride precursor is 1000:20 to 120.

3. The preparation method of the insulating soft magnetic metal powder according to claim 1, characterized in that the pressure in the fluidized bed reaction chamber is 50 Pa to 150 Pa; the reaction temperature in the fluidized bed reaction chamber is 600 °C to 1000 °C; the reaction time in the fluidized bed reaction chamber is 10 min to 120 min; the flow rate of the fluidizing gas stream is 30 sccm to 100 sccm.

4. The preparation method of the insulating soft magnetic metal powder according to claim 1, characterized in that, The fluidizing gas stream includes one or more of a mixed gas of argon and hydrogen, argon, nitrogen, and helium.

5. The preparation method of the insulating soft magnetic metal powder according to claim 1, wherein, Before placing the soft magnetic metal powder on the fluidized bed, it further includes: cleaning the soft magnetic metal powder, and the cleaning includes: pickling the soft magnetic metal powder with an acid solution to remove the oxide layer on the surface of the soft magnetic metal powder; successively cleaning the pickled soft magnetic metal powder with a hydrophilic organic solvent and water; drying the soft magnetic metal powder.

6. The preparation method of the insulating soft magnetic metal powder according to claim 1, characterized in that, The number of layers of the hexagonal boron nitride layer is 10 layers to 200 layers.

7. The preparation method of the insulating soft magnetic metal powder according to claim 1, characterized in that, The soft magnetic metal powder is selected from one or more of iron-based soft magnetic powder, iron-silicon-based soft magnetic powder, iron-silicon-aluminum-based soft magnetic powder, and iron-nickel-based soft magnetic powder.

8. A magnetic powder core, characterized in that, It is prepared from the insulating soft magnetic metal powder prepared by the preparation method according to any one of claims 1 to 7.

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