A soft magnetic powder composite and a method of making and a composite magnetic powder core material and a method of making

Abstract

The application discloses a soft magnetic powder composite and a preparation method and a composite magnetic powder core material and a preparation method, the soft magnetic powder composite has a core-shell structure; the core is a soft magnetic powder; the shell is an insulating coating layer; the material of the insulating coating layer is obtained by reacting a mixed solution of phytic acid and silane with the soft magnetic powder; and the soft magnetic powder is selected from metal and / or alloy materials containing at least one of Fe, Co and Ni-based elements. The application adopts mixed coating of phytic acid and silane, the coating process is simple, time-consuming is short, coating conditions are easy to realize, the environment is friendly, a uniform and dense stable insulating coating film is obtained after the reaction is completed, the conductivity between the soft magnetic powders is effectively reduced, the eddy current loss is effectively reduced, meanwhile, the direct current bias performance of the magnetic powder core is improved, and the film thickness of the magnetic powder surface is controlled by adjusting parameters such as time and concentration.

Description

Technical Field

[0001] This application relates to a soft magnetic powder composite and its preparation method, and a composite magnetic powder core material and its preparation method, belonging to the field of magnetic powder core preparation technology. Background Technology

[0002] Soft magnetic composite magnetic powder cores are composite materials prepared by mixing magnetic powder with an insulating medium. The pressing and molding technology of the magnetic powder and the insulating medium largely determines the density of the magnetic powder core. The amount and volume fraction of magnetic powder and insulating coating material, the thickness of the insulating coating film, the uniformity of the insulating coating layer, and the bonding effect between the coating layer and the matrix are crucial to the resistivity, permeability, coercivity, hysteresis loss, and eddy current loss of the magnetic powder core.

[0003] Eddy current loss is the main reason for the high high-frequency loss of soft magnetic composite powder cores. Eddy current loss is divided into intraparticle eddy current loss and interparticle eddy current loss. The former can be reduced by increasing the powder resistivity and reducing the particle size, while the latter can be reduced by coating the particles with a high-resistivity insulating layer. Currently, the industry requirements for the insulating coating layer include high resistivity, high thermal stability, tight bonding with the magnetic powder, and complete coating.

[0004] Currently, the commonly used coating methods are classified into four categories: inorganic, organic, organic-inorganic composite coating, and magnetic phase coating.

[0005] (1) The commonly used organic coatings are thermosetting resins, including epoxy resins, phenolic resins and silicone resins. However, the heat resistance of the resins is very poor, which limits the temperature range of the subsequent annealing treatment. The increase in temperature will cause the resin to decompose, resulting in a decrease in resistivity and losing the purpose of coating.

[0006] Thermoplastic resins were used earlier in organic coating, but their disadvantages were quickly exposed. They are easily soluble in industrial solutions and have a low melting point that limits the heat treatment temperature. Therefore, thermosetting resins such as epoxy resins were applied and promoted. However, their thermal stability is not high enough, and most resins have weak anti-aging ability and short service life.

[0007] On the other hand, in terms of the affinity between magnetic powder and resin, resin is hydrophobic and magnetic powder is hydrophilic. Therefore, their surface properties are opposite, which weakens the wetting between magnetic powder and organic coating agent. This results in the organic coating agent not being able to completely and uniformly coat the surface of magnetic powder, which increases the effective particle size, reduces resistivity, and increases eddy current loss.

[0008] (2) Inorganic coating can be divided into two categories. One is the sol-gel method where the magnetic powder does not participate in the formation of the insulating layer. The coating material is mainly inorganic oxides with high resistivity and high thermal decomposition temperature, such as ZrO2, SiO2, Al2O3, and TiO2. For example, Al(NO3)3 hydrolyzes and precipitates on the surface of FeSiAl magnetic powder to generate Al(OH)3, which forms a coating layer mainly composed of Al2O3 after annealing heat treatment. Because this type of material does not react with the surface of the magnetic powder, the bonding force between the insulating layer and the magnetic powder is low, and it is easy to fall off during the pressing process. The other type is to react directly with the magnetic powder using phosphoric acid, chromic acid, or oxidizing nitric acid to generate an insulating coating film on its surface. This coating method gives the insulating layer and magnetic powder high bonding force, high uniformity, and controllable thickness. However, substances such as phosphoric acid and chromic acid will cause environmental pollution, which also limits its application.

[0009] Because organic coating agents generally have low thermal decomposition temperatures, inorganic coating agents are gradually emerging. Currently, commonly used inorganic coating methods include phosphate coating, metal oxide coating, and ferrite coating.

[0010] (a) Phosphate coating: This method was used earlier. It generates a uniform, dense and controllable insulating layer in situ using acidic solution and magnetic powder. However, the resistivity of phosphate coating materials is low, resulting in high eddy current loss at high frequencies. The plating solution is unstable and the operation is complicated. At the same time, harmful substances such as phosphoric acid are highly harmful to the human body, making it unsuitable for large-scale industrial production and application.

[0011] (b) Metal oxide coating: This type of method is currently the mainstream coating method because it generally has high thermal stability and good electrical insulation ability, which meets the requirements of heat treatment. However, it is brittle and has poor bonding force with magnetic powder. The insulating coating layer is prone to cracking during the pressing process, resulting in poor coating effect.

[0012] (c) Ferrite coating: The above two methods reduce the magnetic permeability and saturation magnetic induction of the magnetic powder core due to the addition of non-magnetic materials. Ferrite coating is widely used because it can minimize the influence of the coating material on the magnetic properties of the matrix and ensure the stability of magnetic properties in the megahertz range. However, ferrite coating has low uniformity and low compaction density.

[0013] (3) Organic-inorganic composite coating combines the advantages of inorganic and organic coatings and has been widely used and researched in recent years. Nanoscale metal oxides, such as nano-silica, nano-calcium carbonate, and nano-Y2O3, are added to the resin to improve the resistivity of the coating layer and the thermal stability of the resin. However, due to the agglomeration of nanoscale metal oxides during the coating process, poor dispersion leads to an uneven coating layer and uncontrollable thickness.

[0014] (4) Magnetic phase coating is due to the magnetic dilution effect. The addition of non-magnetic phase insulating materials will inevitably lead to a decrease in the permeability and saturation magnetic induction intensity of soft magnetic composite materials. Therefore, materials with ferromagnetic magnetic properties are used as coating / binders to enhance or maintain the soft magnetic coupling effect between powder particles in soft magnetic composite materials, thereby increasing the overall saturation magnetic induction intensity or suppressing the decrease in the overall magnetic induction intensity.

[0015] Currently, most coating methods are limited to inorganic coatings such as phosphate coating and metal oxide coating, and organic coatings such as silicone resin coating. These existing insulating coating methods suffer from drawbacks such as high preparation difficulty, poor process stability, high environmental pollution, significant health hazards, easy cracking of the coating layer, low temperature stability, and poor coating uniformity. Existing acid passivation methods for generating insulating layers mostly use phosphoric acid, chromic acid, nitric acid, etc., resulting in low resistivity of the coating layer, but also causing significant environmental pollution. Summary of the Invention

[0016] To address the problems of existing technologies, this application utilizes an organic-inorganic hybrid solution generated by the reaction of phytic acid and silane to passivate metal powder, forming a uniform and controllable-thickness dense insulating layer in situ, thereby insulating the powder. The insulating film increases resistivity, reduces eddy currents between magnetic powder particles, and lowers eddy current losses in the magnetic powder core. The coating film thickness is thin and controllable, effectively reducing eddy currents between magnetic powder particles and maintaining high DC bias performance without compromising other properties.

[0017] One aspect of this application provides a soft magnetic powder composite having a core-shell structure;

[0018] The core is a soft magnetic powder;

[0019] The shell is an insulating coating layer;

[0020] The insulating coating material is obtained by reacting a mixed solution containing phytic acid and silane with soft magnetic powder;

[0021] The soft magnetic powder is selected from metals and / or alloys containing at least one Fe, Co, or Ni-based element.

[0022] Optionally, the thickness of the insulating coating layer is 100~1000 nm.

[0023] Optionally, the thickness of the insulating coating is independently selected from any value among 100 nm, 168 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, and 1000 nm, or any range between any two of the above points.

[0024] Optionally, the median diameter of the soft magnetic powder D 50 ≤150 μm.

[0025] Optionally, the median diameter of the soft magnetic powder D 50 The range is 1~150 μm.

[0026] Optionally, the median diameter of the soft magnetic powder D 50 The value is independently selected from any value among 1 μm, 30 μm, 60 μm, 90 μm, 120 μm, and 150 μm, or any range between any two of the above points.

[0027] In another aspect, this application provides a method for preparing the above-mentioned soft magnetic powder composite, the method comprising:

[0028] (1) Prepare coating solution; mix phytic acid solution and silanol solution, react I to obtain phytic acid silane organic-inorganic hybrid coating solution (PAS solution).

[0029] (2) Mix the soft magnetic powder with the phytic acid silane organic-inorganic hybrid coating solution (PAS solution) and react II to obtain the soft magnetic powder composite.

[0030] Optionally, the concentration of the phytic acid solution is 1 g / L to 10 g / L.

[0031] Optionally, the concentration of the phytic acid solution is independently selected from any value among 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, and 10 g / L, or any range between any two of the above points.

[0032] Optionally, the silanol solution comprises a silane and an alcohol solvent, wherein the silane is selected from at least one of γ-glycidoxypropyltrimethoxysilane, aminopropyltriethoxysilane, and methyltriethoxysilane;

[0033] The alcohol solvent is at least one of ethanol, methanol, and isopropanol;

[0034] Optionally, the concentration of silane in the silanol solution is 0.001 g / L to 0.01 g / L.

[0035] Optionally, the concentration of the silane is independently selected from any value among 0.001 g / L, 0.002 g / L, 0.005 g / L, 0.006 g / L, 0.008 g / L, 0.01 g / L, or any range between any two of the above points.

[0036] Optionally, the mass ratio of phytic acid to silane is 1 to 30.

[0037] Optionally, the mass ratio of phytic acid to silane is independently selected from any value of 1, 5, 10, 15, 20, 25, 30 or any range between any two of the above points.

[0038] Optionally, the temperature of reaction I is 30~80 °C;

[0039] The reaction time for reaction I is 0.5~20 h;

[0040] Reaction I was carried out under isothermal conditions.

[0041] Optionally, the temperature of reaction I is independently selected from any value among 30 ℃, 40 ℃, 50 ℃, 55 ℃, 60 ℃, 70 ℃, and 80 ℃, or any range between any two of the above points.

[0042] Optionally, the reaction time I is independently selected from any value among 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, or any range between any two of the above points.

[0043] Optionally, in step (2),

[0044] The volume-to-mass ratio of the phytate silane organic-inorganic hybrid coating solution (PAS solution) to the soft magnetic powder is 1~5 mL / g.

[0045] Optionally, the volume-to-mass ratio of the phytate silane organic-inorganic hybrid coating solution (PAS solution) to the soft magnetic powder is independently selected from any value among 1 mL / g, 2 mL / g, 2.5 mL / g, 3 mL / g, 4 mL / g, and 5 mL / g, or any range between any two of the above points.

[0046] Optionally, the temperature of reaction II is 15~40 °C;

[0047] The reaction time for reaction II is 0.5 to 3 hours;

[0048] Reaction II was carried out under isothermal conditions.

[0049] Optionally, the temperature of reaction II is independently selected from any value of 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃ or any range between any two of the above points.

[0050] Optionally, the reaction time II is independently selected from any value among 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, or any range between any two of the above points.

[0051] As one specific implementation method, the preparation method of the soft magnetic powder composite includes:

[0052] First, clean the magnetic powder with alcohol or acetone to remove oil or impurities from its surface. Dry the cleaned powder for later use. Transfer the phytic acid solution to a three-necked flask and heat it in a water bath to 55 °C. Transfer the silanol solution to a constant pressure funnel and add it dropwise to the phytic acid solution. React at a constant temperature for 5 hours to obtain a slightly white organic-inorganic hybrid solution, which is called PAS solution. Then, according to the standard of 2.5 mL / g, under mechanical stirring, add 20 g of magnetic powder to 50 mL of PAS solution and react at a constant temperature of 30 °C for 30 min to generate a high-quality insulating layer on the surface of the magnetic powder.

[0053] The coating method used in this application produces films with high uniformity, thin and controllable film thickness, effectively isolates interparticle eddy currents, ensures the magnetic permeability of the matrix, and has strong bonding force between the coating layer and the magnetic powder, which can reduce the amount of binder used, is easy to press and mold, reduces the dilution effect of non-magnetic phase, further improves the magnetic properties of the matrix, and has low hazard. The preparation process is simple and easy to repeat.

[0054] In another aspect of this application, a composite magnetic powder core material is provided, the composite magnetic powder core material comprising the soft magnetic powder composite described above or the soft magnetic powder composite prepared by the above preparation method.

[0055] Optionally, the composite magnetic powder core material further includes a binder;

[0056] The mass ratio of the binder to the soft magnetic powder composite is 0.5:100 to 5:100;

[0057] The adhesive is selected from at least one of epoxy resin (W-6C), silicone resin, and phenolic resin.

[0058] Optionally, the mass ratio of the binder to the soft magnetic powder composite is independently selected from any value among 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, and 5:100, or any range between any two of the above.

[0059] Another aspect of this application provides a method for preparing the above-mentioned composite magnetic powder core material, the method comprising:

[0060] The soft magnetic powder composite is mixed with a binder, pressed into shape, cured, and then heat-treated to obtain the composite magnetic powder core material.

[0061] Optionally, the pressing method is cold pressing;

[0062] The process parameters for cold pressing are: pressure of 300~2000 MPa and holding time of 0~600 s;

[0063] The curing temperature is 150~260 ℃, and the curing time is 2~24 h;

[0064] The heat treatment temperature is 300~580 ℃, and the heat treatment time is 10 min~3 h.

[0065] Optionally, the pressure for cold pressing is independently selected from any value among 300 MPa, 500 MPa, 800 MPa, 1000 MPa, 1100 MPa, 1200 MPa, 1500 MPa, 1800 MPa, and 2000 MPa, or any range between any two of the above points.

[0066] Optionally, the holding time for cold pressing is independently selected from any value among 0 s, 60 s, 120 s, 180 s, 240 s, 300 s, 360 s, 420 s, 480 s, 540 s, and 600 s, or any range between any two of the above points.

[0067] Optionally, the curing temperature is independently selected from any value among 150 ℃, 180 ℃, 200 ℃, 250 ℃, and 260 ℃, or any range between any two of the above.

[0068] Optionally, the curing time is independently selected from any value among 2 h, 3 h, 6 h, 12 h, 18 h, 24 h, or any range between any two of the above points.

[0069] Optionally, the temperature of the heat treatment is independently selected from any value among 300 ℃, 400 ℃, 480 ℃, 500 ℃, and 580 ℃, or any range between any two of the above points.

[0070] Optionally, the heat treatment time is independently selected from any value among 10 min, 1 h, 2 h, 3 h, or any range between any two of the above points.

[0071] As one specific implementation method, the preparation method of the composite magnetic powder core material includes:

[0072] First, clean the magnetic powder with alcohol or acetone to remove oil or impurities from its surface. Dry the cleaned powder for later use. Transfer 300 mL of phytic acid solution to a three-necked flask and heat it in a water bath to 55 °C. Transfer the silanol solution to a constant pressure funnel and add it dropwise to the phytic acid solution. React at a constant temperature for 5 h to obtain a slightly white organic-inorganic hybrid solution, which is called PAS solution. Then, according to the standard of 2.5 mL / g, under mechanical stirring, add 20 g of magnetic powder to 50 mL of PAS solution and react at a constant temperature of 30 °C for 30 min to generate a high-quality insulating layer on the surface of the magnetic powder. The magnetic powder treated with the mixed solution was washed three times with distilled water and dried at 60 °C for 3 h. 2 wt.% epoxy resin was added to the dried powder and dissolved in an appropriate amount of acetone. The acetone was evaporated under ultrasonic and stirring conditions, thus coating the surface of the magnetic powder with epoxy resin. The resin in this operation acts as a binder. The treated powder was then dried, and about 1 g of the dried powder was weighed. The magnetic powder with the insulating coating was pressed into shape at 1100 MPa, cured at 180 °C for 3 h, and then vacuum stress-relief annealed at 480 °C for 1 h.

[0073] In this application, the hybrid solution of phytic acid and silane possesses multiple functional groups from both phytic acid and silane. Phytic acid can react with magnetic powder through chelation. After silane hydrolysis, the alkoxy groups are converted into silanol groups, which are adsorbed onto the metal surface through hydrogen bonds. After dehydration, they form strong covalent bonds, namely Si-O-Fe. The P-OH groups of phytic acid react with the Si-OH groups after silane hydrolysis to form Si-OP bonds that bind phytic acid molecules to silicon-oxygen chains. In addition, the P-OH groups in phytic acid can also bond with the epoxy bonds of γ-glycidoxypropyltrimethoxysilane in the epoxy ring-opening reaction, further increasing the crosslinking degree between phytic acid and Si-O-Si and increasing the number of P-OH groups in the PAS solution. This forms a phytic acid-bonded siloxane network structure. The soft magnetic powder forms a dense and uniform insulating layer through the reaction with phytic acid and silane. This ensures a strong bond between the PAS insulating coating layer and the soft magnetic powder, effectively maintaining magnetic permeability while reducing the conductivity between magnetic powders.

[0074] In this application, the thickness of the organic insulating film can be adjusted by changing the experimental parameters.

[0075] In this application,

[0076] (1) Magnetic loss: When a metal magnetic powder core works in an alternating magnetic field, it is magnetized on the one hand and loses energy on the other. The total value of energy loss is called magnetic loss. Magnetic loss consists of magnetostrictive loss, eddy current loss and residual loss.

[0077] (2) Eddy current loss: When the external magnetic field changes with frequency, an induced current will be generated in the material due to electromagnetic induction, which will cause eddy current loss. The higher the frequency of the alternating magnetic field, the greater the eddy current. The insulating coating can block the eddy current inside the magnetic powder particles, thereby reducing the eddy current between the magnetic powder particles and thus reducing the eddy current loss of the magnetic powder core.

[0078] (3) Resistivity: The property of a substance to impede the flow of electric current, which is related to the type of material, pressure, temperature, magnetic field and other factors.

[0079] (4) Saturation magnetic induction intensity: The maximum magnetization intensity that a magnetic material can achieve when magnetized in an applied magnetic field is called the saturation magnetic induction intensity, which provides the conditions for miniaturization of electronic components. The saturation magnetic induction intensity directly affects the power output capability of the magnetic core and is a core performance characteristic of power devices, thus providing the conditions for miniaturization of electronic components. For magnetic powder cores, under the same main magnetic powder conditions, the higher the proportion of soft magnetic powder participating in magnetization, the higher the saturation magnetic induction intensity. In this experiment, the ultra-thin insulating film thickness maintained the good high saturation magnetic induction intensity of the amorphous magnetic powder core.

[0080] (5) Permeability: A physical quantity that characterizes the magnetism of a magnetic medium. It represents the resistance to the generation of magnetic flux after a current flows through a coil in space or in the magnetic core, or its ability to conduct magnetic lines of force in a magnetic field.

[0081] The beneficial effects that this application can produce include:

[0082] (1) This application uses a mixture of phytic acid and silane for coating. The coating process is simple, time-saving, and the coating conditions are easy to achieve. It is also environmentally friendly. After the reaction is completed, a uniform, dense, and stable insulating coating film is obtained, which effectively reduces the conductivity between soft magnetic powders and improves the DC bias performance of the magnetic powder core. The film thickness on the surface of the magnetic powder can be controlled by adjusting parameters such as time and concentration. A dense coating layer can be seen on the surface of the magnetic powder under a scanning electron microscope, and the thickness of the insulating coating layer is 168.8–400.6 nm under a transmission electron microscope. The ultra-thin film thickness can reduce the core loss while improving the resistivity of the magnetic powder core and maintaining good soft magnetic properties such as high permeability and high saturation magnetization.

[0083] (2) In this application, phytic acid and silane are used to coat magnetic powder. Phytic acid can form a dense insulating layer on the surface of magnetic powder through chelation reaction. The alkoxy group of silane can be hydrolyzed into silanol group. When the metal powder is immersed in silane solution, the silanol is adsorbed onto the oxide layer on the surface of the metal powder through hydrogen bonding, and then dehydrated to form a strong covalent bond (Si-O-Fe). The P-OH group of phytic acid reacts with the Si-OH group to form Si-OP bond that binds the phytic acid molecule to the silicon-oxygen chain. In addition, the P-OH in phytic acid and the epoxy bond of γ-glycidoxypropyltrimethoxysilane can also bond in the epoxy ring-opening reaction, which further improves the crosslinking degree of phytic acid and Si-O-Si and increases the P-OH group in PAS solution. A siloxane network structure bound by phytic acid is formed, which reduces the conductivity between magnetic powders while effectively ensuring magnetic permeability. In addition, the reaction process is simple and can be completed without complicated instruments and steps. The thickness of the insulating layer is uniform and controllable, and the bonding force with the magnetic powder is strong.

[0084] (3) The insulating coated magnetic powder was pressed into shape at 1100 MPa and stress-relieved annealed at 300~500 ℃. Compared with the uninsulated coated magnetic powder under the same preparation conditions, the magnetic powder core obtained showed a 26.78%~35.4% reduction in core loss (100kHz, 50mT) and a 27.82%~37.70% reduction (1MHz, 50mT). Due to the thin insulating layer and the addition of less non-magnetic material, the magnetic dilution effect was small, and the permeability was maintained at 33~36 and achieved stability in the range of 500 kHz~1 MHz. The DC bias performance was 73.56%~90.54% under 100 Oe conditions. Attached Figure Description

[0085] Figure 1 This is a flowchart of the phytate silane theater coating method of this application;

[0086] Figure 2 The images show SEM images of the surface morphology of the raw powder in Comparative Example 1 and the soft magnetic powder composites obtained in Examples 1-3 of this application. The scale bar in the images is 5 μm. Among them, (a) shows the surface morphology of the raw powder, (b) shows the surface morphology of the soft magnetic powder composite obtained in Example 1, (c) shows the surface morphology of the soft magnetic powder composite obtained in Example 2, (d) shows the surface morphology of the soft magnetic powder composite obtained in Example 3, and (e)-(h) show the surface elemental distribution of the soft magnetic powder composite obtained in Example 2.

[0087] Figures 3a-3c These are FIB-SEM images of the cross-sectional morphology of the soft magnetic powder composites obtained in Examples 1-3 of this application. Figures 3a-3c The scale bars in the text are all 1 μm, where, Figure 3a The figure shows the cross-sectional morphology of the soft magnetic powder composite obtained in Example 1. Figure 3bThe figure shows the cross-sectional morphology of the soft magnetic powder composite obtained in Example 2. Figure 3c The figure shows the cross-sectional morphology of the soft magnetic powder composite obtained in Example 3. Figure 3d The image shows a magnified cross-sectional image and corresponding elemental distribution after 3 g / L insulation treatment. Detailed Implementation

[0088] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0089] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially. Zinc stearate, phytic acid solution (70 wt.%), and γ-(2,3-epoxypropoxy)propyltrimethoxysilane (γ-GPS) were purchased from Aladdin Biochemical Technology Co., Ltd.; W-6C epoxy resin was purchased from Chenghua Adhesive Co., Ltd.

[0090] Example 1

[0091] according to Figure 1 Flowchart:

[0092] (1) Prepare a phytic acid solution with a concentration of 1 g / L. Transfer 300 mL of the phytic acid solution into a three-necked flask and heat it in a water bath to 55 °C.

[0093] (2) Weigh 0.093 g of γ-GPS and dissolve it in 15.78 g of anhydrous ethanol to obtain a silanol solution. Transfer 15.873 g of the silanol solution to a constant pressure funnel and add it dropwise to the phytic acid solution obtained in step (1). React at a constant temperature of 55 °C for 5 h to obtain a slightly white organic-inorganic hybrid solution. This solution is called phytic acid silane (PAS) solution.

[0094] (3) Take 20 g of particles with a diameter D 50 30 μm spherical Fe 73 Si 11 B 11 Cr2C3 powder was distributed in 50 mL of ethanol and subjected to ultrasonic treatment and mechanical stirring for 30 min to remove oil or impurities from the surface of the magnetic powder. After washing three times with distilled water, the powder was dried to obtain the dried powder for later use.

[0095] (4) Heat the dried powder obtained in step (3) in a water bath and continuously stir mechanically in 50 mL of phytic acid silane (PAS) solution obtained in step (2) at 30 °C for 30 min. A high-quality insulating layer can be generated on the surface of the magnetic powder to obtain soft magnetic powder composite 1#.

[0096] (5) Filter the precipitate obtained after stirring in step (4) and dry it at 80 °C for 3 h. Add 0.2 g of W-6C epoxy resin and 0.05 g of zinc stearate (zinc stearate is used to promote demolding) to 10 g of the dried soft magnetic powder composite 1# and mix them. Dissolve them in acetone solution and mix them evenly. Then, stir the mixture with ultrasound to evaporate the acetone. Then, take out the mixed powder and put it into a vacuum drying oven to dry at 60 °C for 3 h. In this way, the epoxy resin is coated on the surface of the soft magnetic powder composite 1#.

[0097] (6) Place 1 g of the dry mixed powder obtained in step (5) into a hydraulic molding machine, use 1100 MPa pressure and hold for 60 s, and cure at 180 ℃ for 3 h to obtain a ring-shaped powder magnetic core sample.

[0098] The above-mentioned annular powder magnetic core sample was placed in a vacuum heat treatment furnace and annealed at 480 °C for 60 min to obtain composite magnetic powder core material S1.

[0099] Example 2

[0100] according to Figure 1 Flowchart:

[0101] (1) Prepare a phytic acid solution with a concentration of 3 g / L. Transfer 300 mL of the phytic acid solution into a three-necked flask and heat it in a water bath to 55 °C.

[0102] (2) Weigh 0.093 g of γ-GPS and dissolve it in 15.78 g of anhydrous ethanol to obtain a silanol solution. Transfer 15.873 g of the silanol solution to a constant pressure funnel and add it dropwise to the phytic acid solution obtained in step (1). React at 55°C for 5 hours to obtain a slightly white organic-inorganic hybrid solution. This solution is called phytic acid silane (PAS) solution.

[0103] (3) Take 20 g of particles with a diameter D 50 30 μm spherical Fe 73 Si 11 B 11 Cr2C3 powder was distributed in 50 mL of ethanol and subjected to ultrasonic treatment and mechanical stirring for 30 min to remove oil or impurities from the surface of the magnetic powder. After washing three times with distilled water, it was dried to obtain the dried powder.

[0104] (4) Heat the dried powder obtained in step (3) in a water bath and continuously stir mechanically in 50 mL of phytic acid silane (PAS) solution obtained in step (2) at 30 °C for 30 min. A high-quality insulating layer can be generated on the surface of the magnetic powder to obtain soft magnetic powder composite 2#.

[0105] (5) Filter the precipitate obtained after stirring in step (4) and dry it at 80 °C for 3 h. Add 0.2 g of W-6C epoxy resin and 0.05 g of zinc stearate (zinc stearate is used to promote demolding) to 10 g of the dried soft magnetic powder composite 1# and mix them. Dissolve them in acetone solution and mix them evenly. Then, stir the mixture with ultrasound to evaporate the acetone. Then, take out the mixed powder and put it into a vacuum drying oven to dry at 60 °C for 3 h. In this way, the epoxy resin is coated on the surface of the soft magnetic powder composite 2#.

[0106] (6) Place 1 g of the dry mixed powder obtained in step (5) into a hydraulic molding machine, use 1100 MPa pressure and hold for 60 s, and cure at 180 ℃ for 3 h to obtain a ring-shaped powder magnetic core sample.

[0107] The above-mentioned annular powder magnetic core sample was placed in a vacuum heat treatment furnace and annealed at 480 °C for 60 min to obtain composite magnetic powder core material S2.

[0108] Example 3

[0109] according to Figure 1 Flowchart:

[0110] (1) Prepare a phytic acid solution with a concentration of 5 g / L. Transfer 300 mL of the phytic acid solution into a three-necked flask and heat it in a water bath to 55 °C.

[0111] (2) Weigh 0.093 g of γ-GPS and dissolve it in 15.78 g of anhydrous ethanol to obtain a silanol solution. Transfer 15.873 g of the silanol solution to a constant pressure funnel and add it dropwise to the phytic acid solution obtained in step (1). React at a constant temperature of 55 °C for 5 h to obtain a slightly white organic-inorganic hybrid solution. This solution is called phytic acid silane (PAS) solution.

[0112] (3) Take 20 g of particles with a diameter D 50 30 μm spherical Fe 73 Si 11 B 11 Cr2C3 powder was distributed in 50 mL of ethanol and subjected to ultrasonic treatment and mechanical stirring for 30 min to remove oil or impurities from the surface of the magnetic powder. After washing three times with distilled water, it was dried to obtain the dried powder.

[0113] (4) Heat the dried powder obtained in step (3) in a water bath and continuously stir mechanically in 50 ml of phytic acid silane (PAS) solution obtained in step (2) at 30 °C for 30 minutes. A high-quality insulating layer can be generated on the surface of the magnetic powder to obtain soft magnetic powder composite 3#.

[0114] (5) Filter the precipitate obtained after stirring in step (4) and dry it at 80 °C for 3 h. Add 0.2 g of W-6C epoxy resin and 0.05 g of zinc stearate (zinc stearate is used to promote demolding) to 10 g of the dried soft magnetic powder composite 1# and mix them. Dissolve them in acetone solution and mix them evenly. Then, stir the mixture with ultrasound to evaporate the acetone. Then, take out the mixed powder and put it into a vacuum drying oven to dry at 60 °C for 3 h. In this way, the epoxy resin is coated on the surface of the soft magnetic powder composite 1#.

[0115] (6) Place 1 g of the dry mixed powder obtained in step (5) into a hydraulic molding machine, use 1100 MPa pressure and hold for 60 s, and cure at 180 ℃ for 3 h to obtain a ring-shaped powder magnetic core sample.

[0116] The above-mentioned annular powder magnetic core sample was placed in a vacuum heat treatment furnace and annealed at 480 °C for 60 min to obtain composite magnetic powder core material S3.

[0117] Comparative Example 1

[0118] (1) Take 20 g of particle size D 50 30 μm spherical Fe 73 Si 11 B 11 Cr2C3 powder was distributed in 50 mL of ethanol and subjected to ultrasonic treatment and mechanical stirring for 30 min to remove oil or impurities from the surface of the magnetic powder. After washing three times with distilled water, it was dried to obtain the dried powder.

[0119] (2) Add 0.4 g of W-6C epoxy resin and 0.1 g of zinc stearate (zinc stearate is used to promote demolding) to the 20 g dried powder obtained in step (1), mix them, and dissolve them in acetone solution. After mixing evenly, stir ultrasonically to evaporate the acetone. Then take out the mixed powder and put it into a vacuum drying oven at 60 °C for 3 h to dry. In this way, the epoxy resin will coat the surface of the soft magnetic powder #4.

[0120] (3) Place 1 g of the dry mixed powder obtained in step (2) into a hydraulic molding machine, use 1100 MPa pressure and hold for 60 s, and cure at 180 ℃ for 3 h to obtain a ring-shaped powder magnetic core sample.

[0121] The above-mentioned annular powder magnetic core sample was placed in a vacuum heat treatment furnace and annealed at 480 °C for 60 min to obtain composite magnetic powder core material S4.

[0122] Comparative Example 2

[0123] (1) Take 20 g of weight D 50 300 μm spherical Fe 73Si 11 B 11 Cr2C3 powder was passivated using chromic acid, and then dried by stirring in a water bath at 50 °C to obtain passivated magnetic powder. The chromic acid accounted for 0.8% of the total weight of the magnetic powder. The passivated magnetic powder was then coated with an insulating material using a sol-gel method.

[0124] (2) Dissolve 4 g of aluminum isopropoxide in 30 g of anhydrous ethanol, add nitric acid to adjust the pH of the solution to 4, stir evenly for 30 min to obtain a sol, take 25 mL of the sol and add it to the passivated magnetic powder, mix and stir for 20 min to obtain a suspension, add 4 mL of deionized water dropwise, stir in a 70 ℃ water bath until completely dry, and obtain the composite coated magnetic powder #5.

[0125] (3) Add 1.2% of barium stearate by weight of the coated magnetic powder to the coated magnetic powder and mix evenly to obtain the magnetic powder to be formed. Press the magnetic powder to be formed into a magnetic ring under a pressure of 1800 MPa for 20 s. Using nitrogen as a protective atmosphere, place the magnetic ring in an environment of 750 ℃ ​​for 50 min to obtain the iron-silicon-aluminum soft magnetic composite material S5.

[0126] Comparative Example 3

[0127] (1) 0.1 mol tetraethyl orthosilicate and 0.002 mol methyltriethoxysilane were mixed and added to 200 g anhydrous ethanol. 0.25 mol deionized water was added dropwise for the first time. After the addition was complete, the mixture was stirred for 25 min. 120 g iron powder with an average particle size of 200 μm after oil removal with acetone was added and stirred for 28 min. 0.8 mol deionized water was added dropwise for the second time and the mixture was stirred for another 50 min. The mixture was filtered, washed with anhydrous ethanol, dried at 60 ℃, and then dried at 100 ℃ to obtain insulating coated powder #6.

[0128] (2) Add 0.3% zinc stearate by weight of the insulating coating powder to each powder, stir evenly, pre-press at 850MPa for 38 s, then press at 2100MPa for 37 s to form the powder, then heat at 100℃ for 30 min in nitrogen, heat to 230℃ for 40 min, heat to 420℃ for 40 min, and finally heat to 725℃ for 120 min and cool down to obtain metal soft magnetic composite material S6.

[0129] Comparative Example 4

[0130] (1) Add 10 g of concentrated nitrous acid to 40 g of anhydrous ethanol and stir for 10 min to obtain a passivation solution. Add 20 g of iron-nickel powder to the passivation solution after sieving and particle size distribution, and stir evenly for 15 min. Then filter and dry to obtain passivated magnetic powder #7.

[0131] (2) Add a binder accounting for 1.5% of the mass of the passivated magnetic powder to the passivated magnetic powder, and stir thoroughly under heating conditions until the mixture is dry and uniformly mixed. The binder is silicone resin. Finally, add a release agent accounting for 0.5% of the total weight of the passivated magnetic powder to the passivated magnetic powder and mix evenly. The release agent is barium stearate, to obtain the magnetic powder to be shaped. Press the magnetic powder to be shaped into a ring-shaped soft magnetic composite material under a pressure of 1400 MPa. Using nitrogen as a protective atmosphere, place the soft magnetic composite material in a 600°C environment for 120 min to prepare the soft magnetic composite material S7.

[0132] Test Example 1

[0133] (1) The microstructure and elemental distribution of the surface morphology of the original powder of Comparative Example 1 and the soft magnetic powder composites obtained in Examples 1-3 were analyzed by scanning electron microscopy (SEM, ZEISS EVO 18) and energy dispersive X-ray spectroscopy (EDS).

[0134] Among them, the surface morphology of the raw powder is as follows Figure 2 As shown in Figure (a), the surface morphologies of the soft magnetic powder composites obtained in Examples 1-3 are shown in Figures (b), (c), and (d), respectively. The surface of the original powder is smooth and clean, which is beneficial to improving the adhesion and uniformity of the subsequent insulating coating. The insulating coating layer was prepared using a 1 g / L phytic acid solution, and the surface morphology of the obtained soft magnetic powder composites (as shown in Figure (a)) is shown in Figure (b), (c), and (d), respectively. Figure 2 As shown in Figure (b), the surface roughness becomes slightly rougher, and a very thin insulating layer forms, slightly improving the insulation performance. Phytic acid solution concentrations ranged from 1 g / L to 5 g / L, with a continuous insulating layer coated on the surface of all spherical powders. With increasing phytic acid concentration, the surface roughness and coating thickness of the soft magnetic powder composite gradually increased. Figure 2 As shown in Figure (c), the soft magnetic powder composite prepared with a 3 g / L phytic acid solution exhibits the best and most uniform insulating coating. As the concentration is further increased to 5 g / L, as... Figure 2 As shown in Figure (d), the insulation layer becomes rougher and exhibits localized cracks due to its thickness. Furthermore, excessive insulation material reduces the final molding density of the particles; the optimal phytic acid concentration is 3 g / L phytic acid.

[0135] To further determine the composition of the insulating coating, the surface of the soft magnetic powder composite obtained in Example 2 (with a concentration of 3 g / L phytic acid) was analyzed using SEM and EDS (see [link to example]). Figure 2 (Figures e to h). The elemental signals of Fe, O, Si, and P are widely and uniformly distributed on the powder, indicating that the insulating coating has excellent adhesion. This is beneficial for improving the resistivity of the powder and reducing eddy current losses after the magnetic powder core is prepared.

[0136] (2) The cross-sectional morphology of the soft magnetic powder composites obtained in Examples 1-3 was observed using a focused ion beam / scanning electron microscope (FIB / SEM, Carl Zeiss Auriga). The test results are as follows: Figures 3a-3c As shown.

[0137] Depend on Figures 3a-3c It can be seen that the insulating coating exhibits a core-shell structure. The outer milky white layer is a platinum deposit that protects the insulating layer from ion beam damage. Furthermore, the uniform dark black layer in the center of the yellow line represents the insulating layer, and the magnetic powder matrix lies beneath the yellow line. With increasing PA concentration, the thickness of the insulating layer on the magnetic powder surface increases from 168.8 nm (…). Figure 3a As shown in the figure, the PA concentration gradually increased from 1 g / L to 400.6 nm. Figure 3c As shown in the figure, the PA concentration is 5 g / L. Figure 3b The insulation layer shown in the figure has a thickness of 251.2 nm, corresponding to a PA concentration of 3 g / L. Figure 3d A magnified cross-sectional image of the 3 g / L insulation treatment is shown, along with the corresponding elemental distribution obtained by EDS spectroscopy (line scan). The elements are uniformly distributed within the powder. When the scan position reaches the insulating layer, the signal intensity of Fe drops sharply, while the signal intensities of Si, P, and O increase accordingly. The thickness dimension, i.e., the width of the signal intensity variation range, is 251.2 nm. These results demonstrate the success of the method in this study and the highly uniformity of the resulting insulating layer.

[0138] Test Example 2

[0139] The DC bias performance under a 100 Oe DC magnetic field was measured using an LCR meter (Tong Hui TH2828A), and the results are shown in Table 1. The composite magnetic powder core material obtained from the original powder (coated only with pure epoxy resin) had a DC bias performance of only 67% at 100 Oe. With the increase of phytic acid concentration, the DC bias performance of the composite magnetic powder core materials obtained in Examples 1-3 gradually increased to 73.56%, 80.825%, and 90.54%, respectively, which means that the FeSiBCCr / PAS powder core is not easily saturated under an applied magnetic field. The structure of the insulating layer between magnetic powder particles affects the DC bias performance of the powder core. A uniform and dense insulating layer helps to reduce the effective magnetic field applied to the magnetic powder, thereby improving its DC bias performance.

[0140] Test Example 3

[0141] Using a broadband power analyzer (Iwatsu SY-8218, Japan) at a maximum magnetic flux density of 0.1 T ( B m ) Measure core loss at 100 kHz frequency ( P cv The test results are shown in Table 1. Table 1 shows that for all samples, core loss gradually increases with increasing test frequency. However, the growth rates differ significantly between different samples. Furthermore, with increasing PA concentration, P cv First decrease, then gradually increase. The lowest... P cv @ 0.1T / 50kHz (S2) is 267.8 mW / cm². 3 Compared to the uninsulated core sample (366.4 mW / cm²), 3 It is about 26.91% lower.

[0142] Test Example 4

[0143] An Agilent 4294A precision impedance analyzer was used in the frequency range of 1 kHz - 110 MHz, with an applied magnetic field. H The permeability of the magnetic powder core was measured under operating conditions of approximately 0.1 A / m, where the number of coil turns N1 = 20 and N2 = 5. The test results are shown in Table 1. With the increase of phytic acid content, the content of PAS insulation layer increases, and the amount of non-magnetic material in the magnetic core increases, resulting in a decrease in the effective permeability of the magnetic core with the increase of phytic acid content.

[0144] Table 1

[0145]

[0146] As can be seen from the table above, comparing the iron loss and initial permeability data measured under the conditions of 0.1 T excitation and 50 kHz frequency, Examples 1, 2, and 3 of this application show lower losses than Comparative Examples 1, 2, 3, and 4. Meanwhile, Examples 1, 2, and 3 show higher DC bias performance compared to Comparative Examples 1, 2, and 3, while still maintaining high initial permeability. In summary, the insulation coating process, adhesive coating process, and cold pressing process described in this application have significant advantages in the preparation of magnetic powder cores, achieving high initial permeability, low iron loss, and excellent high-frequency stability characteristics.

[0147] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A soft magnetic powder composite, characterized in that, The soft magnetic powder composite has a core-shell structure; The core is a soft magnetic powder; The shell is an insulating coating layer; The insulating coating material is obtained by reacting a mixed solution containing phytic acid and silane with soft magnetic powder; The soft magnetic powder is selected from metals and / or alloys containing Fe. The method for preparing the soft magnetic powder composite includes: (1) Mix phytic acid solution with silanol solution, react I, and obtain phytic acid silane organic-inorganic hybrid coating solution; (2) Mix the soft magnetic powder with the phytic acid silane organic-inorganic hybrid coating solution, and react II to obtain the soft magnetic powder composite. In step (1), The concentration of the phytic acid solution is 1 g / L to 10 g / L; The mass ratio of phytic acid to silane is 1~30; The temperature of reaction I is 30~80 ℃; The reaction time for reaction I is 0.5~20 h; Reaction I was carried out under isothermal conditions; In step (2), The volume-to-mass ratio of the phytate silane organic-inorganic hybrid coating solution to the soft magnetic powder is 1~5 mL / g; The temperature of reaction II is 15~40℃; The reaction time for reaction II is 0.5 to 3 hours; Reaction II was carried out under isothermal conditions.

2. The soft magnetic powder composite according to claim 1, characterized in that, The thickness of the insulating coating layer is 100~1000 nm.

3. The soft magnetic powder composite according to claim 1, characterized in that, The median diameter of the soft magnetic powder D 50 ≤150 μm.

4. The soft magnetic powder composite according to claim 3, characterized in that, The median diameter of the soft magnetic powder D 50 The range is 1~150 μm.

5. The soft magnetic powder composite according to claim 1, characterized in that, The silanol solution comprises a silane and an alcohol solvent, wherein the silane is selected from at least one of γ-glycidoxypropyltrimethoxysilane, aminopropyltriethoxysilane, and methyltriethoxysilane. The alcohol solvent is selected from at least one of ethanol, methanol, and isopropanol; The concentration of silane in the silanol solution is 0.001 g / L to 0.01 g / L.

6. A composite magnetic powder core material, characterized in that, The composite magnetic powder core material includes the soft magnetic powder composite as described in any one of claims 1 to 5.

7. The composite magnetic powder core material according to claim 6, characterized in that, The composite magnetic powder core material also includes a binder; The mass ratio of the binder to the soft magnetic powder composite is 0.5:100 to 5:100; The adhesive is selected from at least one of epoxy resin, silicone resin, and phenolic resin.

8. A method for preparing the composite magnetic powder core material according to any one of claims 6-7, characterized in that, The preparation method includes: The soft magnetic powder composite is mixed with a binder, pressed into shape, cured, and then heat-treated to obtain the composite magnetic powder core material.

9. The preparation method according to claim 8, characterized in that, The pressing and molding method is cold pressing; The process parameters for cold pressing are: pressure of 300~2000 MPa and holding time of 0~600 s; The curing temperature is 150~260 ℃, and the curing time is 2~24 h; The heat treatment temperature is 300~580 ℃, and the heat treatment time is 10 min~3 h.

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