Formula design and preparation method of high-permeability soft magnetic composite powder

Abstract

The invention discloses a formula design and a preparation method of high-permeability soft magnetic composite powder, and the high-permeability soft magnetic composite powder comprises the following components in parts by weight: 20-30 parts of amorphous magnetic powder with D50 distribution of 25 [mu] m; 70-80 parts of carbonyl iron powder, wherein D50 distribution is 9 [mu] m; the adhesive is composed of epoxy resin, an anhydride curing agent and gamma-aminopropyltriethoxysilane, the anhydride curing agent accounts for 20% of the weight of the adhesive, the gamma-aminopropyltriethoxysilane accounts for 6.7% of the weight of the adhesive, and two molecular ends of the gamma-aminopropyltriethoxysilane are chemically bonded with hydroxyl on the surface of the magnetic powder and the epoxy resin respectively; the particle size ratio of the amorphous magnetic powder to the carbonyl iron powder is controlled to be (2.5-3): 1. According to the formula design, the magnetic powder with a specific proportion and a specific particle size ratio is mixed, and a special adhesive is matched to enhance the interface bonding force, so that the defect of single magnetic powder is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of soft magnetic materials, in particular to a formula design and preparation method of high permeability soft magnetic composite powder. BACKGROUND

[0002] At present, the traditional soft magnetic composite powder faces many technical bottlenecks when applied to small-size hot-pressed products.

[0003] From the formula level, the prior art mostly adopts a single magnetic powder or a simple magnetic powder mixing system. For example, although the carbonyl iron powder has a certain magnetic permeability, the magnetic loss is high in small-size products. The forming strength of single amorphous magnetic powder is difficult to meet the requirements of hot-pressing process. Moreover, the absence of coupling agent in the traditional adhesive system makes the interface bonding force between the magnetic powder particles and the adhesive weak, which not only leads to insufficient strength of the magnetic core, but also has a negative impact on the magnetic permeability.

[0004] In terms of preparation process, the traditional method has the problem of extensive control of process parameters. For example, the particle size distribution is not accurately controlled during mixing of the magnetic powder, the drying temperature and time are not reasonably set during the granulation process, and the pressure and temperature parameters cannot balance the magnetic permeability and strength during hot-pressing forming. These will cause unstable performance of the final product, which is difficult to meet the strict requirements of small-size hot-pressed products on high magnetic permeability and high strength.

[0005] With the increasing demand for small-size, high-power-density electronic components in the fields of 5G communication and new energy vehicles, it has become a key technical problem to be solved in the field to develop a soft magnetic composite powder with high magnetic permeability and high strength under small-size conditions and a preparation method thereof. Therefore, a formula design and preparation method of high magnetic permeability soft magnetic composite powder are provided. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a formula design and preparation method of high magnetic permeability soft magnetic composite powder to solve the problems raised in the background art.

[0007] To achieve the above purpose, the present application provides the following technical scheme: a formula design and preparation method of high magnetic permeability soft magnetic composite powder, comprising the following components and weight parts: Amorphous magnetic powder 20-30 parts, D50 distribution is 25 μm, select iron-based amorphous magnetic powder to use its high saturation magnetic induction intensity characteristics, lay the foundation for the magnetic permeability improvement; carbonyl iron powder 70-80 parts, D50 distribution is 9 μm; adhesive 3-3.8 parts, composed of epoxy resin, acid anhydride curing agent and gamma-aminopropyl triethoxysilane, wherein the acid anhydride curing agent accounts for 20% of the weight of the adhesive to ensure the epoxy resin is fully crosslinked and cured, gamma-aminopropyl triethoxysilane accounts for 6.7% of the weight of the adhesive, the molecular ends of gamma-aminopropyl triethoxysilane are chemically bonded to the surface hydroxyl of the magnetic powder and the epoxy resin respectively, enhancing the interfacial bonding force between the magnetic powder and the adhesive and improving the strength of the composite powder; release agent 0.1 part is graphite fluoride, the layered structure of the release agent can form a lubricating film during hot pressing to prevent the magnetic powder from adhering to the mold, the particle size ratio of the amorphous magnetic powder and the carbonyl iron powder is controlled at 2.5-3:1, the different particle size magnetic powders are graded and filled to reduce the porosity between the magnetic powders and optimize the magnetic flux conduction path, thereby improving the magnetic permeability; The mixture of amorphous magnetic powder and carbonyl iron powder can be uniformly mixed in a high-speed mixer at an appropriate speed after accurate weighing to ensure that the particle size ratio meets the requirements of 2.5-3:1, the adhesive is prepared by adding epoxy resin, acid anhydride curing agent and gamma-aminopropyl triethoxysilane in proportion and stirring at 40-50°C for 30 min until complete dissolution, and the release agent graphite fluoride is uniformly added in the subsequent process to ensure that a good lubricating film is formed during hot pressing; By accurately controlling the particle size ratio and weight of amorphous magnetic powder and carbonyl iron powder, efficient grading and filling between magnetic powders are realized, the porosity is significantly reduced, the magnetic flux conduction path is optimized, thereby improving the magnetic permeability, the reasonable ratio of epoxy resin and acid anhydride curing agent in the adhesive ensures the full crosslinking and curing of the epoxy resin, enhances the structural strength of the composite powder, the addition of gamma-aminopropyl triethoxysilane further enhances the interfacial bonding force between the magnetic powder and the adhesive, improves the impact and compression strength of the composite powder, the layered structure of the release agent graphite fluoride forms a lubricating film during hot pressing, effectively preventing the magnetic powder from adhering to the mold, improving the production efficiency, overall, the formula design is scientific and reasonable, and the synergistic effect between the components is significant.

[0008] Preferably, the amorphous magnetic powder is an iron-based amorphous magnetic powder, which has high saturation magnetic induction intensity characteristics, high saturation magnetic induction intensity can store more magnetic energy in the same magnetic field strength, combined with the high magnetic permeability characteristics of carbonyl iron powder, the two synergistically improve the magnetic permeability of the composite powder, the low magnetic crystal anisotropy of the iron-based amorphous magnetic powder is conducive to the stability of the magnetic permeability at high frequency; During preparation, the purity and particle uniformity of the iron-based amorphous magnetic powder are ensured, the heat treatment process parameters such as annealing temperature and time are accurately controlled to maintain its amorphous structure, thereby maintaining high saturation magnetic induction intensity and low magnetic crystal anisotropy; The amorphous magnetic powder adopts an iron-based amorphous material, which has the remarkable characteristic of high saturation magnetic induction, which enables the magnetic powder to store more magnetic energy under the same magnetic field strength, and the high magnetic permeability characteristic of the carbonyl iron powder complements each other, thereby improving the magnetic permeability of the composite powder. In addition, the low magnetic crystalline anisotropy of the iron-based amorphous magnetic powder effectively reduces the magnetic permeability fluctuation under high frequency application, thereby ensuring the stability of the magnetic performance.

[0009] Preferably, the carbonyl iron powder is a high-purity iron powder with low oxygen content. The high purity reduces the obstruction of impurities to the rotation of magnetic domains and reduces the magnetic hysteresis loss, while the low oxygen content avoids the formation of iron oxide impurities to reduce eddy current loss, thereby ensuring that the carbonyl iron powder still maintains excellent magnetic permeability performance under high frequency, meeting the high frequency application requirements of small-sized hot-pressed products. In the preparation process, vacuum melting technology is adopted, and crushing and screening are carried out under inert gas protection to avoid oxidation. In addition, the purity of the raw materials is strictly controlled, high-purity iron is used as the starting material, and chemical analysis method is used to verify the purity and oxygen content of the final product, thereby ensuring that the patent requirements are met. The use of high-purity, low-oxygen carbonyl iron powder as a key component of the soft magnetic composite powder has significant advantages. The high purity ensures the smoothness of the rotation of magnetic domains and reduces the obstruction of impurities to the magnetic domains, thereby effectively reducing the magnetic hysteresis loss. At the same time, the low oxygen content avoids the formation of iron oxide impurities, which can form resistive paths and increase eddy current loss. Through this technical improvement, the carbonyl iron powder still maintains excellent magnetic permeability performance under high frequency application, which is particularly important for small-sized hot-pressed products, as they often need to work under high frequency conditions. Therefore, the use of this high-purity, low-oxygen carbonyl iron powder not only improves the overall performance of the soft magnetic composite powder, but also meets the demand for high-frequency, high-efficiency magnetic materials in modern electronic equipment.

[0010] Preferably, the acid anhydride curing agent reacts with the epoxy resin to form a crosslinked network, which has high heat resistance and mechanical strength, and can provide sufficient structural strength to the composite powder after hot pressing and curing. The ethoxy groups of the gamma-aminopropyl triethoxysilane hydrolyze to form silicon hydroxyl groups, which form covalent bonds with the hydroxyl groups on the surface of the amorphous magnetic powder and the carbonyl iron powder. The amino groups crosslink with the epoxy resin to form a chemical bonding bridge between the magnetic powder and the adhesive, significantly enhancing the interfacial bonding force and improving the impact strength and compressive strength of the composite magnetic powder. By precisely controlling the mixing ratio of the anhydride curing agent and the epoxy resin, and carrying out the reaction under suitable temperature and stirring conditions, the crosslinking network is fully formed to achieve the required heat resistance and mechanical strength. Meanwhile, the hydrolysis and crosslinking reaction of the γ-aminopropyl triethoxysilane can also be optimized by adjusting the reaction conditions (such as pH value, temperature, stirring speed, etc.) to ensure that its ethoxy groups and amino groups effectively react with the amorphous magnetic powder, carbonyl iron powder, and epoxy resin, respectively, to build a stable chemical bonding bridge. The crosslinking network formed by the reaction of the anhydride curing agent and the epoxy resin significantly improves the structural strength of the composite powder after hot pressing and curing, enabling it to withstand greater mechanical stress and thermal stress without deformation or damage. Meanwhile, the chemical bonding bridge built by the γ-aminopropyl triethoxysilane between the magnetic powder and the adhesive greatly enhances the interfacial bonding force and improves the impact strength and compressive strength of the composite magnetic powder. This strengthening effect helps maintain the stability and reliability of the composite magnetic powder during long-term use.

[0011] Preferably, the adhesive further includes a solvent, acetone. As a low-boiling polar solvent, acetone can effectively dissolve the epoxy resin and dilute the adhesive system, reducing its viscosity. The adhesive uniformly coats the magnetic powder particles during the mixing process, forming a thin and uniform insulating layer that prevents direct contact between the magnetic powder particles, thereby reducing eddy current loss. Additionally, the addition of acetone facilitates the subsequent granulation process, ensuring the uniformity of the granulated particles. When preparing the adhesive, the epoxy resin, anhydride curing agent, and γ-aminopropyl triethoxysilane are mixed in proportion, and then acetone solvent is slowly added while continuously stirring to ensure that the epoxy resin is completely dissolved and the adhesive system has moderate viscosity, allowing it to uniformly coat the magnetic powder particles during the subsequent mixing process. Using acetone as the solvent for the adhesive has significant advantages in the preparation of high magnetic permeability soft magnetic composite powder. As a low-boiling polar solvent, acetone not only effectively dissolves the epoxy resin and reduces the viscosity of the adhesive system, but also ensures that the adhesive uniformly coats each magnetic powder particle during the mixing process, forming a thin and uniform insulating layer. This process effectively prevents direct contact between the magnetic powder particles, thereby reducing the generation of eddy current loss. Additionally, the addition of acetone facilitates the subsequent granulation process, ensuring the uniformity of the granulated particles.

[0012] Preferably, when the amorphous magnetic powder and carbonyl iron powder are mixed in a particle size ratio of 2.5-3:1, the carbonyl iron powder fills the gaps between the amorphous magnetic powder, forming a multi-level stacking structure and reducing the pore volume in the mixed system. In the mixing of amorphous magnetic powder and carbonyl iron powder, by accurately weighing 20-30 parts of amorphous magnetic powder with D50 of 25 μm and 70-80 parts of carbonyl iron powder with D50 of 9 μm, and ensuring that the particle size ratio of the two is strictly controlled in the range of 2.5-3:1, the mechanical stirring equipment is used for sufficient mixing, so that the carbonyl iron powder is uniformly filled in the gap of the amorphous magnetic powder, forming a compact multi-level accumulation structure, thereby effectively reducing the pore volume in the mixed system and improving the packing density of the magnetic powder; Mixing amorphous magnetic powder and carbonyl iron powder according to a specific particle size ratio and forming a multi-level accumulation structure significantly optimizes the packing density of the magnetic powder, reduces the pore volume in the mixed system, which not only improves the conduction efficiency of the magnetic flux, because tighter packing means less magnetic resistance and better magnetic circuit, but also enhances the interaction between the magnetic powders, which is beneficial to the improvement of the magnetic permeability. At the same time, this structure also helps to reduce the eddy current loss and hysteresis loss, because smaller pore volume reduces the direct contact between the magnetic powder particles, reducing the formation of resistive paths, thereby improving the performance stability of the soft magnetic composite powder in high frequency applications.

[0013] Preferably, the γ-aminopropyl triethoxysilane chemically bonds with the hydroxyl groups on the surface of the magnetic powder and the epoxy resin, enhancing the interfacial bonding force; During the preparation of the adhesive, the ethoxy groups of the γ-aminopropyl triethoxysilane hydrolyze to form silicon hydroxyl groups, which form covalent bonds with the hydroxyl groups on the surface of the amorphous magnetic powder and the carbonyl iron powder. At the same time, its amino group crosslinks with the epoxy resin, thereby building a stable chemical bonding bridge between the magnetic powder and the adhesive, significantly enhancing the interfacial bonding force; The chemical bonding between the γ-aminopropyl triethoxysilane and the hydroxyl groups on the surface of the magnetic powder and the epoxy resin brings significant benefits to the high magnetic permeability soft magnetic composite powder. This chemical bonding process not only enhances the interfacial bonding force between the magnetic powder and the adhesive, but also improves the impact strength and compressive strength of the composite powder. During the preparation of the composite powder, this strong interfacial bonding force helps to maintain the stability and uniformity of the magnetic powder particles, reduces the voids between the particles, optimizes the magnetic flux conduction path, and thus improves the magnetic permeability. In addition, the strong interfacial bonding force also enhances the structural strength of the composite powder after hot pressing and curing, making it better meet the high frequency application requirements of small size hot pressed products.

[0014] A preparation method of a high magnetic permeability soft magnetic composite powder, which adopts the formula design of the high magnetic permeability soft magnetic composite powder described above, comprising the following steps: Step one, soft magnetic powder ratio mixing: Soft magnetic powder ratio mixing: 20-30 parts of amorphous magnetic powder with D50 distribution of 25 μm and 70-80 parts of carbonyl iron powder with D50 distribution of 9 μm are mixed according to weight parts to obtain mixed magnetic powder; Step two, adhesive preparation: The epoxy resin, acid anhydride curing agent and γ-aminopropyl triethoxysilane are mixed in proportion, acetone solvent is added, and stirring is carried out at 40-50°C for 30 min to prepare the adhesive; Step three, mixing the adhesive with the magnetic powder: The adhesive is added to the mixed magnetic powder, and stirring is carried out at 20-50°C for 15-25 min; Step four, granulation after stirring: The mixture is granulated and placed in a vacuum box for vacuum drying at 50-60°C for 30 min; Step five, mixing the release agent: 0.1 parts of fluorinated graphite is added to the dried material and mixed for 20 min; Step six, compacting the magnetic ring: 2.000 g of the composite soft magnetic powder is weighed, and hot pressing is carried out at a pressure of 4.5 t and a temperature of 210°C to form a magnetic ring with an inner diameter of 8 mm and an outer diameter of 14 mm, and the pressure is maintained for 110 s; Step seven, curing the magnetic ring: The magnetic ring is cured at 170°C for 120 min; Step eight, performance test: The cured magnetic ring is wound, and the electrical parameters are measured at a frequency of 1 MHz; The hot pressing equipment in step six can be a hydraulic press with precise pressure and temperature control to ensure stable molding at a pressure of 4.5 t and a temperature of 210°C. Meanwhile, the size of the magnetic ring can be accurately controlled through customized molds to ensure an inner diameter of 8 mm and an outer diameter of 14 mm. The preparation method of the high magnetic permeability soft magnetic composite powder realizes the high-performance preparation of the composite powder through fine proportioning, adhesive preparation, and subsequent processing steps. The different particle size gradations of amorphous magnetic powder and carbonyl iron powder reduce porosity, optimize the magnetic flux conduction path, and improve magnetic permeability. The crosslinking of epoxy resin and curing agent in the adhesive forms a high-strength network, and the silane coupling agent enhances the interfacial bonding force between the magnetic powder and the adhesive, improving the mechanical strength of the composite powder. The hot pressing and curing process further optimizes the magnetic core structure, making it have high density and excellent magnetic properties. Finally, performance tests verify the stable performance of the composite powder at high frequencies.

[0015] Preferably, the vacuum drying process in step four reduces the environmental gas pressure to volatilize the solvent, while isolating oxygen to prevent oxidation of the surface of the magnetic powder particles, thereby avoiding the decrease in magnetic permeability caused by oxidation and ensuring that the dried magnetic powder still maintains excellent magnetic properties; In the vacuum drying process of step four, in order to realize vacuum drying and isolate oxygen, the granulated mixture can be placed in a vacuum drying box, and after sealing, the air in the box is extracted by a vacuum pump to form a negative pressure environment, so that the solvent can quickly volatilize at a lower temperature, at the same time, the vacuum drying box should have good sealing performance and be equipped with an oxygen monitoring device to ensure that the oxygen content is controlled at a very low level during the drying process, thereby effectively preventing the surface oxidation of the magnetic powder particles and maintaining their excellent magnetic properties. By reducing the environmental pressure, the solvent can quickly volatilize at a lower temperature, avoiding the performance decline of the magnetic powder caused by high temperature, and at the same time, the oxygen-free environment effectively prevents the surface oxidation of the magnetic powder particles, which is an important factor leading to the decrease of magnetic permeability. Therefore, this step is crucial for ensuring that the dried magnetic powder still maintains high magnetic permeability and other excellent magnetic properties. This drying method not only improves production efficiency, but also ensures product quality.

[0016] Preferably, the pressure and temperature parameters of the hot pressing forming in step six work together to fill the gaps between the magnetic powders after the adhesive melts, and at the same time, promote the close packing of magnetic powders of different particle sizes to form a high-density magnetic core structure, thereby improving the magnetic permeability and mechanical strength of the composite soft magnetic powder to meet the performance requirements of small-size hot-pressed products. During hot pressing, the pressure (4.5t) and temperature (210℃) need to be accurately controlled, and the pressure holding time (110s) needs to be maintained to ensure that the adhesive is fully melted and fills the gaps between the magnetic powders. At the same time, the mold design is adjusted to optimize the packing method of the magnetic powders, promoting the close combination of magnetic powders of different particle sizes, thereby forming a high-density and uniform magnetic core structure. The hot pressing process of step six realizes the effective filling of the adhesive to the gaps between the magnetic powders by accurately adjusting the pressure and temperature parameters, and promotes the close packing of magnetic powders of different particle sizes to form a high-density magnetic core structure. This process not only improves the magnetic permeability of the composite soft magnetic powder, but also enhances its mechanical strength, ensuring the performance stability of the product under small-size hot pressing conditions. The high-density magnetic core structure optimizes the magnetic flux conduction path and reduces magnetic loss.

[0017] In summary, compared with the prior art, the present application provides a formula design and preparation method of a high-magnetic-permeability soft magnetic composite powder, which has the following beneficial effects: The application realizes complementary advantages of the two kinds of magnetic powders by mixing amorphous magnetic powder and carbonyl iron powder according to specific weight parts and particle size ratio, the amorphous magnetic powder can improve the forming strength and meet the requirement of hot pressing process, the carbonyl iron powder provides certain magnetic permeability, the combination of the two kinds of magnetic powders solves the defects of single magnetic powder in the application of small size products, meanwhile, the adhesive composed of epoxy resin, acid anhydride curing agent and gamma-aminopropyl triethoxysilane is adopted, the two ends of the gamma-aminopropyl triethoxysilane molecule are chemically bonded with the hydroxyl on the surface of the magnetic powder and the epoxy resin respectively, the interface bonding force between the magnetic powder particles and the adhesive is enhanced, the problems of insufficient magnetic core strength and affected magnetic permeability caused by the lack of coupling agent in the traditional adhesive system are avoided, and the overall performance of the magnetic core is improved. By accurately controlling the process parameters, the stable improvement of the product performance is realized, when the magnetic powders are mixed, the particle size distribution is strictly controlled to ensure the uniformity of mixing, in the granulation process, the drying temperature is reasonably set to ensure the granulation quality, in the hot pressing forming, the pressure holding is reasonably set to balance the magnetic permeability and the strength, in addition, the curing process further improves the performance stability of the product, the accurate control of these process parameters solves the problem of unstable product performance caused by extensive control of process parameters in the traditional method, and the strict requirements of small size hot pressing products on high magnetic permeability and high strength are met. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a step diagram of the preparation method of the high magnetic permeability soft magnetic composite powder of the application; Figure 2 is an embodiment and a comparative example of the preparation method of the high magnetic permeability soft magnetic composite powder of the application. DETAILED DESCRIPTION

[0019] The application provides a technical solution, a formula design and a preparation method of a high magnetic permeability soft magnetic composite powder, please refer to Figure 2 : Example one, formula design: amorphous magnetic powder (D50 distribution is 25 mu m): 20 parts; carbonyl iron powder (D50 distribution is 9 mu m): 80 parts; adhesive: epoxy resin: 3 parts; acid anhydride curing agent (20% of the weight of the adhesive): 0.6 parts; gamma-aminopropyl triethoxysilane (6.7% of the weight of the adhesive): 0.2 parts; acetone solvent: appropriate amount (used for diluting the adhesive system); release agent (fluorinated graphite): 0.1 part; preparation method: soft magnetic powder ratio mixing: Mix 20 parts of amorphous magnetic powder with 80 parts of carbonyl iron powder by weight to obtain mixed magnetic powder; Configure the adhesive: Mix the epoxy resin, acid anhydride curing agent, and γ-aminopropyl triethoxysilane in proportion, add acetone solvent, and stir at 40-50°C for 30 min to prepare the adhesive; Mix the adhesive with the magnetic powder: Add the adhesive to the mixed magnetic powder and stir at 20-50°C for 20 min; Granulate after stirring: Granulate the mixture and place it in a vacuum box for vacuum drying at 50-60°C for 30 min; Mix the release agent: Add 0.1 part of fluorinated graphite to the dried material and mix for 20 min; Compact the magnetic ring: Weigh 2.000g of composite soft magnetic powder, hot press it into a magnetic ring with an inner diameter of 8mm and an outer diameter of 14mm at a pressure of 4.5t and a temperature of 210°C, and hold the pressure for 110s; Cure the magnetic ring: Cure the magnetic ring at 170°C for 120 min; Performance test: Wind the cured magnetic ring and measure the electrical parameters at a frequency of 1MHz; Technical effect: Permeability μ@1MHz: 59.2; Strength of the cured magnetic ring (kgf): 42.93; Magnetic core density (g / cm³): 5.91; Example two, The difference between this example two and example one is: Formulation design: Amorphous magnetic powder (D50 distribution of 25μm): 30 parts; Carbonyl iron powder (D50 distribution of 9μm): 70 parts; Adhesive: Epoxy resin: 3 parts; Acid anhydride curing agent (20% of the weight of the adhesive): 0.6 parts; γ-aminopropyl triethoxysilane (6.7% of the weight of the adhesive): 0.2 parts; Acetone solvent: appropriate amount (used to dilute the adhesive system); Release agent (fluorinated graphite): 0.1 part; Preparation method: Mix the soft magnetic powder by weight: Mix 30 parts of amorphous magnetic powder with 70 parts of carbonyl iron powder by weight to obtain mixed magnetic powder; Preparation of adhesive: The epoxy resin, acid anhydride curing agent and γ-aminopropyl triethoxysilane were mixed in proportion, and acetone solvent was added. The mixture was stirred at 40-50°C for 30 min to prepare the adhesive; Mixing of adhesive and magnetic powder: The adhesive was added to the mixed magnetic powder and stirred at 20-50°C for 20 min; Granulation after stirring: The mixture was granulated and placed in a vacuum box for vacuum drying at 50-60°C for 30 min; Mixing of release agent: 0.1 parts of fluorinated graphite was added to the dried material and mixed for 20 min; Compaction of magnetic ring: 2.000 g of composite soft magnetic powder was weighed and hot-pressed into a magnetic ring with an inner diameter of 8 mm and an outer diameter of 14 mm at a pressure of 4.5 t and a temperature of 210°C, with a holding pressure of 110 s; Curing of magnetic ring: The magnetic ring was cured at 170°C for 120 min; Performance test: The cured magnetic ring was wound and the electrical parameters were measured at a frequency of 1 MHz; Technical effect: Permeability μ@1MHz: 52.36; Strength of cured magnetic ring (kgf): 37.34; Magnetic core density (g / cm³): 5.82.

[0020] Comparative Example 1 (based on Example 1), Formulation design: The same as Example 1, but γ-aminopropyl triethoxysilane was removed; Preparation method: The same as Example 1, but γ-aminopropyl triethoxysilane was removed when preparing the adhesive; Technical effect: Permeability μ@1MHz: 60.7 (slightly increased permeability, but significantly decreased strength); Strength of cured magnetic ring (kgf): 38.67; Magnetic core density (g / cm³): 6.02; Explanation: After removing γ-aminopropyl triethoxysilane, although the permeability increased slightly, the strength of the cured magnetic ring decreased significantly, indicating that γ-aminopropyl triethoxysilane played an important role in enhancing the interfacial bonding force and improving the impact strength and compressive strength of the composite magnetic powder; Comparative Example 2 (based on Example 2), Formulation design: The same as Example 2, but removing γ-aminopropyl triethoxysilane; Preparation method: The same as Example 2, but removing γ-aminopropyl triethoxysilane when configuring the adhesive; Technical effect: Magnetic permeability μ@1MHz: 54.61 (magnetic permeability decreased, and the strength also decreased slightly); Magnetic ring strength after curing (kgf): 35.81; Magnetic core density (g / cm³): 5.85; Explanation: After removing γ-aminopropyl triethoxysilane, the magnetic permeability and the magnetic ring strength after curing both decreased, further proving the importance of γ-aminopropyl triethoxysilane in improving the performance of composite magnetic powder.

[0021] A formulation design and preparation method of a high magnetic permeability soft magnetic composite powder, comprising the following components and weight parts: Amorphous magnetic powder 20-30 parts, D50 distribution of 25 μm, iron-based amorphous magnetic powder is selected to take advantage of its high saturation magnetic induction strength characteristics, laying a foundation for improving magnetic permeability; carbonyl iron powder 70-80 parts, D50 distribution of 9 μm; adhesive 3-3.8 parts, composed of epoxy resin, anhydride curing agent and γ-aminopropyl triethoxysilane, wherein the anhydride curing agent accounts for 20% of the weight of the adhesive to ensure that the epoxy resin is fully cross-linked and cured, and the γ-aminopropyl triethoxysilane accounts for 6.7% of the weight of the adhesive, the two ends of the γ-aminopropyl triethoxysilane molecule are chemically bonded to the surface hydroxyl group of the magnetic powder and the epoxy resin, respectively, to enhance the interfacial bonding force between the magnetic powder and the adhesive and improve the strength of the composite powder; release agent 0.1 part is graphite fluoride, the layered structure of the release agent can form a lubricating film during hot pressing to prevent the magnetic powder from sticking to the mold, the particle size ratio of amorphous magnetic powder to carbonyl iron powder is controlled at 2.5-3:1, the porosity between the magnetic powders is reduced by grading and filling different particle sizes of magnetic powders, and the magnetic flux conduction path is optimized, thereby improving the magnetic permeability; The mixture of amorphous magnetic powder and carbonyl iron powder can be uniformly mixed in a high-speed mixer at an appropriate speed after being accurately weighed to ensure that the particle size ratio meets the requirements of 2.5-3:1, the adhesive is prepared by adding epoxy resin, anhydride curing agent and γ-aminopropyl triethoxysilane in proportion, and stirring at 40-50°C for 30 min until complete dissolution, and the release agent graphite fluoride is uniformly added in the subsequent process to ensure that a good lubricating film is formed during hot pressing; By precisely controlling the particle size ratio and weight of amorphous magnetic powder and carbonyl iron powder, efficient grading and filling between magnetic powders are realized, porosity is significantly reduced, and magnetic flux conduction path is optimized, thereby improving magnetic permeability. The reasonable ratio of epoxy resin and anhydride curing agent in the adhesive ensures the full crosslinking and curing of the epoxy resin, enhances the structural strength of the composite powder, the addition of gamma-aminopropyl triethoxysilane further enhances the interfacial bonding force between the magnetic powder and the adhesive, and improves the impact and compression strength of the composite powder. The layered structure of the release agent fluorinated graphite forms a lubricating film during hot pressing, effectively preventing the adhesion of the magnetic powder to the mold and improving the production efficiency. Overall, the formula design is scientific and reasonable, and the synergistic effect between the components is significant.

[0022] Please refer to Figure 1 , the amorphous magnetic powder is iron-based amorphous magnetic powder, which has high saturation magnetic induction strength characteristics. High saturation magnetic induction strength can store more magnetic energy in the same magnetic field intensity. Combined with the high magnetic permeability characteristics of carbonyl iron powder, the two work together to improve the magnetic permeability of the composite powder. The magnetic crystal anisotropy of the iron-based amorphous magnetic powder is low, which is beneficial to the stability of the magnetic permeability at high frequency. During preparation, the purity and particle uniformity of the iron-based amorphous magnetic powder are ensured. The annealing temperature and time are precisely controlled to maintain the amorphous structure, thereby maintaining high saturation magnetic induction strength and low magnetic crystal anisotropy. The amorphous magnetic powder uses iron-based amorphous material, which has the significant characteristic of high saturation magnetic induction strength. This characteristic allows the magnetic powder to store more magnetic energy in the same magnetic field intensity. Combined with the high magnetic permeability characteristics of carbonyl iron powder, the two work together to improve the magnetic permeability of the composite powder. In addition, the low magnetic crystal anisotropy of the iron-based amorphous magnetic powder effectively reduces the magnetic permeability fluctuation at high frequency, ensuring the stability of the magnetic properties.

[0023] Please refer to Figure 1 , the carbonyl iron powder is high-purity iron powder with low oxygen content. High purity can reduce the obstruction of impurities to magnetic domain rotation and reduce hysteresis loss. Low oxygen content can avoid the formation of resistive paths by iron oxide impurities and reduce eddy current loss, ensuring that the carbonyl iron powder still maintains excellent magnetic permeability performance at high frequency, meeting the high-frequency application requirements of small-size hot-pressed products. During preparation, vacuum melting technology is used, and crushing and screening are carried out under inert gas protection to avoid oxidation. At the same time, the purity of the raw materials is strictly controlled, high-purity iron is used as the starting material, and the purity and oxygen content of the final product are verified by chemical analysis method to ensure that the requirements of the patent are met. The high-purity and low-oxygen content carbonyl iron powder is used as the key component of the soft magnetic composite powder, which has significant advantages. The high purity ensures the smoothness of magnetic domain rotation and reduces the obstruction of impurities to the magnetic domain, thereby effectively reducing the magnetic hysteresis loss. At the same time, the low oxygen content avoids the formation of iron oxide impurities, which can form resistive paths and increase eddy current loss. Through this technical improvement, the carbonyl iron powder can still maintain excellent magnetic permeability performance under high-frequency application. This is particularly important for small-sized hot-pressed products, as they often need to work under high-frequency conditions. Therefore, the use of high-purity and low-oxygen content carbonyl iron powder not only improves the overall performance of the soft magnetic composite powder, but also meets the demand for high-frequency and high-efficiency magnetic materials in modern electronic equipment.

[0024] Please refer to Figure 1 The acid anhydride curing agent reacts with the epoxy resin to form a crosslinked network, which has high heat resistance and mechanical strength, enabling the composite powder to have sufficient structural strength after hot pressing and curing. The ethoxy groups of γ-aminopropyl triethoxysilane hydrolyze to form silicon hydroxyl groups, which form covalent bonds with the hydroxyl groups on the surface of the amorphous magnetic powder and the carbonyl iron powder. The amino groups crosslink with the epoxy resin, forming a chemical bonding bridge between the magnetic powder and the adhesive, significantly enhancing the interfacial bonding force and improving the impact strength and compressive strength of the composite magnetic powder. By precisely controlling the mixing ratio of the acid anhydride curing agent and the epoxy resin and reacting under suitable temperature and stirring conditions, the crosslinked network is fully formed to achieve the required heat resistance and mechanical strength. At the same time, the hydrolysis and crosslinking reaction of γ-aminopropyl triethoxysilane can be optimized by adjusting the reaction conditions (such as pH value, temperature, stirring speed, etc.) to ensure that its ethoxy groups and amino groups effectively react with the amorphous magnetic powder, carbonyl iron powder, and epoxy resin, respectively, to form a stable chemical bonding bridge. The crosslinked network formed by the reaction of the acid anhydride curing agent and the epoxy resin significantly improves the structural strength of the composite powder after hot pressing and curing, enabling it to withstand greater mechanical and thermal stresses without deformation or damage. At the same time, the chemical bonding bridge formed by γ-aminopropyl triethoxysilane between the magnetic powder and the adhesive greatly enhances the interfacial bonding force and improves the impact strength and compressive strength of the composite magnetic powder. This strengthening effect helps to maintain the stability and reliability of the composite magnetic powder during long-term use.

[0025] Please refer to Figure 1 The adhesive also includes solvent acetone, which as a low-boiling polar solvent can effectively dissolve the epoxy resin and dilute the adhesive system, reducing its viscosity. The adhesive uniformly coats the magnetic powder particles during the mixing process, forming a thin and uniform insulating layer that prevents direct contact between the magnetic powder particles, thereby reducing eddy current loss. This also facilitates the smooth progress of the subsequent granulation process, ensuring the uniformity of the granulated particles. In the configuration of the adhesive, the epoxy resin, the anhydride curing agent and the gamma-aminopropyl triethoxysilane are mixed in proportion, then the acetone solvent is slowly added and the stirring is continued to ensure that the epoxy resin is completely dissolved and the viscosity of the adhesive system is moderate, so that the magnetic powder particles can be uniformly coated in the subsequent mixing process; Using acetone as the solvent of the adhesive has significant advantages in the preparation of high magnetic permeability soft magnetic composite powder. As a low-boiling polar solvent, acetone can not only effectively dissolve the epoxy resin and reduce the viscosity of the adhesive system, but also ensure that the adhesive uniformly coats each magnetic powder particle during the mixing process, forming a thin and uniform insulation layer. This process effectively avoids direct contact between the magnetic powder particles, thereby reducing the generation of eddy current loss. At the same time, the addition of acetone also facilitates the smooth progress of the subsequent granulation process, ensuring the uniformity of the granulation particles.

[0026] Please refer to Figure 1 When the amorphous magnetic powder and the carbonyl iron powder are mixed in a particle size ratio of 2.5-3:1, the carbonyl iron powder fills the gaps in the amorphous magnetic powder, forming a multi-level packing structure and reducing the pore volume in the mixed system. When mixing amorphous magnetic powder and carbonyl iron powder, 20-30 parts of amorphous magnetic powder with a D50 of 25 μm and 70-80 parts of carbonyl iron powder with a D50 of 9 μm are accurately weighed, and the particle size ratio of the two is strictly controlled within the range of 2.5-3:1. The mixture is thoroughly mixed using a mechanical stirring device, so that the carbonyl iron powder uniformly fills the gaps in the amorphous magnetic powder, forming a compact multi-level packing structure, thereby effectively reducing the pore volume in the mixed system and improving the packing density of the magnetic powder. Mixing amorphous magnetic powder and carbonyl iron powder in a specific particle size ratio and forming a multi-level packing structure significantly optimizes the packing density of the magnetic powder and reduces the pore volume in the mixed system. This not only improves the conduction efficiency of the magnetic flux, as a tighter packing means less magnetic resistance and better magnetic circuit, but also enhances the interaction between the magnetic powders, which is beneficial to the improvement of magnetic permeability. At the same time, this structure also helps to reduce eddy current loss and hysteresis loss, as smaller pore volume reduces direct contact between the magnetic powder particles, reducing the formation of resistive paths and improving the performance stability of the soft magnetic composite powder in high-frequency applications.

[0027] Please refer to Figure 1 The gamma-aminopropyl triethoxysilane chemically bonds with the hydroxyl groups on the surface of the magnetic powder and the epoxy resin, enhancing the interfacial bonding force. During the configuration of the adhesive, the ethoxy groups of the gamma-aminopropyl triethoxysilane hydrolyze to form silicon hydroxyl groups, which form covalent bonds with the hydroxyl groups on the surface of the amorphous magnetic powder and the carbonyl iron powder. At the same time, the amino groups of the gamma-aminopropyl triethoxysilane crosslink with the epoxy resin, thereby building a stable chemical bonding bridge between the magnetic powder and the adhesive, significantly enhancing the interfacial bonding force. The chemical bonding of γ-aminopropyl triethoxysilane with the surface hydroxyl groups of the magnetic powder and the epoxy resin brings significant benefits to the high magnetic permeability soft magnetic composite powder, and this chemical bonding process not only enhances the interfacial bonding force between the magnetic powder and the adhesive, but also improves the impact strength and compression strength of the composite powder. In the preparation process of the composite powder, the strong interfacial bonding force helps to maintain the stability and uniformity of the magnetic powder particles, reduces the gap between the particles, optimizes the magnetic flux conduction path, and thus improves the magnetic permeability. In addition, the strong interfacial bonding force also enhances the structural strength of the composite powder after hot pressing and curing, so that it can better meet the high-frequency application requirements of small-size hot-pressed products.

[0028] A preparation method of a high magnetic permeability soft magnetic composite powder, which adopts the formula design of the high magnetic permeability soft magnetic composite powder described above, please refer to Figure 1 , comprising the following steps: Step one, soft magnetic powder ratio mixing: Soft magnetic powder ratio mixing: 20-30 parts of amorphous magnetic powder with D50 distribution of 25 μm and 70-80 parts of carbonyl iron powder with D50 distribution of 9 μm are mixed according to weight parts to obtain mixed magnetic powder; Step two, configuration of adhesive: Mix the epoxy resin, acid anhydride curing agent and γ-aminopropyl triethoxysilane in proportion, add acetone solvent, and stir at 40-50℃ for 30min to prepare the adhesive; Step three, mixing of adhesive and magnetic powder: Add the adhesive to the mixed magnetic powder and stir at 20-50℃ for 15-25min; Step four, granulation after stirring: Granulate the mixture and place it in a vacuum box for vacuum drying at 50-60℃ for 30min; Step five, mixing of release agent: Add 0.1 parts of fluorinated graphite to the dried material and mix for 20min; Step six, compaction of magnetic ring: Weigh 2.000g of composite soft magnetic powder, and hot-press it into a magnetic ring with an inner diameter of 8mm and an outer diameter of 14mm at a pressure of 4.5t and a temperature of 210℃, and keep the pressure for 110s; Step seven, curing of magnetic ring: Cure the magnetic ring at 170℃ for 120min; Step eight, performance test: Wind the cured magnetic ring and measure the electrical parameters at a frequency of 1MHz; The hot-pressing equipment in step six can be a hydraulic machine with precise pressure and temperature control to ensure stable molding at 4.5t pressure and 210℃, and the size of the magnetic ring can be precisely controlled by a customized mold to ensure the accuracy of the inner diameter of 8mm and the outer diameter of 14mm. The preparation method of the high magnetic permeability soft magnetic composite powder realizes high-performance preparation of the composite powder through fine proportioning, adhesive preparation, and subsequent processing steps. The different particle size gradations of amorphous magnetic powder and carbonyl iron powder reduce porosity, optimize the magnetic flux conduction path, and improve magnetic permeability. The cross-linking of epoxy resin and curing agent in the adhesive forms a high-strength network, while the silane coupling agent enhances the interfacial bonding force between the magnetic powder and the adhesive, improving the mechanical strength of the composite powder. The hot-pressing and curing process further optimizes the magnetic core structure, making it have high density and excellent magnetic properties. Finally, performance tests verify the stable performance of the composite powder at high frequencies.

[0029] Please refer to Figure 1 , the vacuum drying process in step four reduces the environmental air pressure to make the solvent evaporate, while isolating oxygen to prevent the surface oxidation of the magnetic powder particles, thereby avoiding the decrease in magnetic permeability caused by oxidation and ensuring that the dried magnetic powder still maintains excellent magnetic properties. During the vacuum drying process in step four, to achieve vacuum drying and isolate oxygen, the granulated mixture can be placed in a vacuum drying oven, sealed, and then the air in the oven is extracted by a vacuum pump to form a negative pressure environment, allowing the solvent to evaporate quickly at a lower temperature. At the same time, the vacuum drying oven should have good sealing performance and be equipped with an oxygen monitoring device to ensure that the oxygen content during the drying process is controlled at a very low level, thereby effectively preventing the surface oxidation of the magnetic powder particles and maintaining their excellent magnetic properties. By reducing the environmental air pressure, the solvent can evaporate quickly at a lower temperature, avoiding the performance decline of the magnetic powder that may be caused by high temperature. At the same time, the oxygen-free environment effectively prevents the surface oxidation of the magnetic powder particles, which is an important factor leading to a decrease in magnetic permeability. Therefore, this step is crucial for ensuring that the dried magnetic powder still maintains high magnetic permeability and other excellent magnetic properties. This drying method not only improves production efficiency but also ensures product quality.

[0030] Please refer to Figure 1 , the pressure and temperature parameters of hot-pressing in step six work together to fill the gaps between the magnetic powders after the adhesive melts, while also promoting the close packing of magnetic powders of different particle sizes to form a high-density magnetic core structure, thereby improving the magnetic permeability and mechanical strength of the composite soft magnetic powder to meet the performance requirements of small-sized hot-pressed products. In hot-pressing, the pressure (4.5t) and temperature (210℃) are accurately controlled, and the pressure holding time (110s) is kept to ensure that the adhesive is fully melted and fills the gap between the magnetic powders. At the same time, the mold design is adjusted to optimize the accumulation of magnetic powders and promote the close combination of magnetic powders of different particle sizes, thereby forming a high-density and uniform magnetic core structure. The hot-pressing process of step six realizes the effective filling of the adhesive gap between the magnetic powders by accurately regulating the pressure and temperature parameters, and promotes the close accumulation of magnetic powders of different particle sizes to form a high-density magnetic core structure. This process not only improves the magnetic permeability of the composite soft magnetic powder, but also enhances its mechanical strength, ensuring the performance stability of the product under small-size hot-pressing conditions. The high-density magnetic core structure optimizes the magnetic flux conduction path and reduces magnetic loss.

[0031] It should be noted that in this text, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual such relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0032] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A recipe for a high permeability soft magnetic composite powder, characterized in that, The composition and weight parts include: Amorphous magnetic powder 20-30 parts, D50 distribution is 25 μm; carbonyl iron powder 70-80 parts, D50 distribution is 9 μm; adhesive 3-3.8 parts, which is composed of epoxy resin, acid anhydride curing agent and gamma-aminopropyl triethoxysilane, wherein the acid anhydride curing agent accounts for 20% of the weight of the adhesive, the gamma-aminopropyl triethoxysilane accounts for 6.7% of the weight of the adhesive, and the molecular ends of the gamma-aminopropyl triethoxysilane are chemically bonded with the hydroxyl groups on the surface of the magnetic powder and the epoxy resin; release agent 0.1 part is graphite fluoride, the particle size ratio of the amorphous magnetic powder to the carbonyl iron powder is controlled at 2.5-3:

1.

2. The formulation of high permeability soft magnetic composite powder according to claim 1, characterized in that: The amorphous magnetic powder is iron-based amorphous magnetic powder, and the magnetic crystal anisotropy of the iron-based amorphous magnetic powder is low.

3. The formulation of the high permeability soft magnetic composite powder according to claim 1, characterized in that: The carbonyl iron powder is high-purity iron powder, and the oxygen content is low.

4. The formulation of the high permeability soft magnetic composite powder according to claim 1, characterized in that: The acid anhydride curing agent reacts with the epoxy resin to form a crosslinked network; the ethoxyl groups of the gamma-aminopropyl triethoxysilane are hydrolyzed to form silicon hydroxyl groups, which form covalent bonds with the hydroxyl groups on the surface of the amorphous magnetic powder and the carbonyl iron powder, and the amino groups crosslink with the epoxy resin to form a chemical bonding bridge between the magnetic powder and the adhesive.

5. The formulation of high permeability soft magnetic composite powder of claim 1, wherein: The adhesive also includes a solvent, acetone, which is a low-boiling polar solvent that uniformly coats the magnetic powder particles during the mixing process, forming an insulating layer.

6. The formulation of a high permeability soft magnetic composite powder of claim 1, wherein: When the amorphous magnetic powder and the carbonyl iron powder are mixed at a particle size ratio of 2.5-3:1, the carbonyl iron powder fills the gaps between the amorphous magnetic powder, forming a multi-level accumulation structure.

7. The formulation of high permeability soft magnetic composite powder of claim 1, wherein: The gamma-aminopropyl triethoxysilane chemically bonds with the hydroxyl groups on the surface of the magnetic powder and the epoxy resin.

8. A method for preparing a high permeability soft magnetic composite powder, using a formulation design according to any one of claims 1 to 7, characterized in that, The method includes the following steps: Step one, soft magnetic powder mixing: Mix 20-30 parts of D50 distribution 25 μm amorphous magnetic powder with 70-80 parts of D50 distribution 9 μm carbonyl iron powder by weight to obtain mixed magnetic powder; Step two, configure the adhesive: Mix the epoxy resin, acid anhydride curing agent, and gamma-aminopropyl triethoxysilane in proportion, add acetone solvent, and stir at 40-50°C to obtain the adhesive; Step three, mix the adhesive with the magnetic powder: Add the adhesive to the mixed magnetic powder and stir at 20-50°C for 15-25 min; Step four, granulation after stirring: Granulate the mixture and place it in a vacuum box for vacuum drying at 50-60°C; Step five, mix the release agent: Add graphite fluoride to the dried material and mix; Step six, compact the magnetic ring: Weigh the composite soft magnetic powder and hot-press it into a magnetic ring; Step seven, solidify the magnetic ring: Solidify the magnetic ring; Step eight, performance test: Wind the solidified magnetic ring and measure the electrical parameters at 1 MHz frequency.

9. The method of claim 8, wherein the soft magnetic composite powder has a high magnetic permeability. The vacuum drying process in step four reduces the environmental pressure to make the solvent volatilize and isolate oxygen.

10. The method of claim 8, wherein the soft magnetic composite powder has a high magnetic permeability. The pressure and temperature parameters of the hot-pressing in step six work together to fill the gaps between the magnetic powder after the adhesive melts.

Images