Composite modified magnetic core and rapid atmosphere control sintering process thereof

Abstract

The application belongs to the technical field of magnetic core production, and particularly relates to a composite modified magnetic core and a rapid atmosphere control sintering process thereof, which comprises the following components in parts by weight: ferrite 50-70 parts, modified nanocrystalline alloy powder 5-10 parts, rare earth additive 3-6 parts, non-magnetic oxide 1-3 parts, and antioxidant 0.5-1 part. Through composite modification of the magnetic core material and matching of the innovative rapid atmosphere sintering process, the magnetic permeability of the magnetic core is improved, the loss is reduced, the saturation magnetic flux density is improved, the sintering time is shortened, the production efficiency and the yield are improved, and the like.

Description

Technical Field

[0001] This invention relates to the field of magnetic core manufacturing technology, specifically to a composite modified magnetic core and its rapid atmosphere-controlled sintering process. Background Technology

[0002] As the core magnetic conductor in electronic components such as high-frequency transformers and inductors, the performance of magnetic cores directly determines the power conversion efficiency and signal transmission quality. In the manufacturing process of magnetic cores, sintering is a crucial step. High-temperature treatment causes magnetic powder particles to form a dense crystalline structure, a process that decisively affects the impedance characteristics, mechanical strength, and high-frequency stability of the magnetic core. Currently, magnetic core sintering processes face several technical bottlenecks. Regarding interlayer adhesion, during traditional stacking sintering, the contact surfaces of the magnetic cores soften at high temperatures, leading to adhesion and easy edge damage during separation, with a related damage rate as high as 15%-20%. Chinese patent CN202171991U uses a raised structure design; while sharp protrusions can reduce the contact area, they result in poor stacking stability and a tendency to collapse. Cylindrical protrusions, although improving stability, still pose a risk of localized adhesion. Another isolation coating technology (such as zirconium powder solution) easily penetrates the window gaps of E-type and EC-type magnetic cores, increasing the difficulty of post-processing. Furthermore, its manual application method leads to high process complexity and poor batch consistency.

[0003] With the rapid development of electronic technology, the performance requirements for magnetic core materials are becoming increasingly stringent. Traditional magnetic core materials have limitations in terms of permeability, loss, and saturation flux density, making it difficult to meet the demands of high-performance electronic devices. Furthermore, existing magnetic core sintering processes suffer from problems such as long sintering times, high energy consumption, and low yield. Chinese patent CN114121472B provides a sintering process for ferrite magnetic cores. However, during the high-temperature sintering process, insufficient temperature control leads to uneven heating within the core, easily resulting in inconsistent performance. In addition, during the adhesive removal process, organic adhesives are difficult to completely remove, easily causing defects such as core cracking and deformation, affecting product quality and production efficiency. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by proposing a composite modified magnetic core and its rapid atmosphere sintering process. By performing composite modification on the magnetic core material and combining it with an innovative rapid atmosphere sintering process, the magnetic permeability of the magnetic core is improved, losses are reduced, and saturation magnetic flux density is increased, while the sintering time is shortened and production efficiency and yield are improved.

[0005] To solve the above-mentioned technical problems, the present invention provides a technical solution: a composite modified magnetic core comprising the following components in parts by weight: 50-70 parts ferrite, 5-10 parts modified nanocrystalline alloy powder, 3-6 parts rare earth additives, 1-3 parts non-magnetic oxides, and 0.5-1 parts antioxidant.

[0006] Furthermore, the ferrite raw material is selected from one or more types of manganese-zinc ferrite and nickel-zinc ferrite.

[0007] Furthermore, the nanocrystalline alloy powder is a Fe-Cu-Nb-B series nanocrystalline alloy.

[0008] Furthermore, the rare earth additive is a mixture of dysprosium oxide (Dy2O3) and holmium oxide (Ho2O3) in a mass ratio of 1 to 2:1.

[0009] Furthermore, the non-magnetic oxide is a mixture of titanium dioxide (TiO2) and zirconium dioxide (ZrO2) in a mass ratio of 1 to 2:1.

[0010] Furthermore, the antioxidant is one or more of boric acid and borax.

[0011] Because nanocrystalline alloy powders have problems such as poor oxidation resistance and insufficient compatibility with matrix materials, they are easily oxidized during the preparation and use of magnetic cores, resulting in decreased magnetic permeability, increased loss, and reduced saturation magnetic flux density. Furthermore, they are difficult to bond tightly with other components in processes such as mixing and sintering, affecting the consistency of magnetic core quality and production efficiency. Therefore, this invention modifies nanocrystalline alloy powders by means of surface coating, element diffusion, and other modification methods to form a dense anti-oxidation layer on the powder surface, construct an interface structure with varying composition gradients, enhance its compatibility with matrix materials, and optimize the microstructure.

[0012] The preparation method of modified nanocrystalline alloy powder, the specific steps are as follows: (1) Select Fe-Cu-Nb-B nanocrystalline alloy powder with an average particle size of 50-100nm as raw material, place it in a vacuum drying oven and dry it at 80-100℃ for 2-4h to remove the moisture and impurities adsorbed on the powder surface and ensure the effect of subsequent modification treatment. (2) Using tetraethyl orthosilicate (TEOS) as a precursor, TEOS and anhydrous ethanol are mixed at a volume ratio of 1:3 to 5. After stirring evenly, deionized water and catalyst are added and the pH of the solution is adjusted to 3 to 5. Stir at room temperature for 30 to 60 minutes to form a uniform and stable sol. Then, the dried nanocrystalline alloy powder is slowly added to the above sol. The mass ratio of powder to sol is controlled at 1:2 to 3. Stir at a speed of 200 to 300 rpm for 1 to 2 hours to make the sol uniformly coat the surface of the alloy powder. Then, the mixture is transferred to a rotary evaporator to evaporate and remove the solvent, and alloy powder with a gel layer on the surface is obtained. The coated alloy powder is placed in a drying oven and dried at 80 to 100°C for 12 to 24 hours to make the gel layer fully dry and solidify, forming a silicon dioxide (SiO2) coating with a thickness of about 10 to 20 nm. (3) Place the coated nanocrystalline alloy powder into a high-temperature annealing furnace, introduce hydrogen gas with a purity of ≥99.99% as a protective atmosphere, fully replace the annealing furnace, remove the air in the furnace, and prevent the alloy powder from being oxidized during heating. Raise the temperature of the annealing furnace to 500-600℃ and hold for 1-2 hours. After the holding period, turn off the heating power and continue to introduce hydrogen gas to allow the alloy powder to cool naturally to room temperature in the hydrogen atmosphere. Sieve the modified nanocrystalline alloy powder to remove agglomerated particles, and obtain the modified nanocrystalline alloy powder.

[0013] Furthermore, in step (2), the amount of deionized water added is such that the molar ratio of water to TEOS is 1 to 2:1, and the evaporation conditions in the rotary evaporator are 60 to 80°C and rotary evaporation under reduced pressure for 1 to 2 hours.

[0014] Furthermore, in step (3), the flow rate of hydrogen is controlled at 50-100 mL / min, the heating rate is 5-10 °C / min, and the cooling rate is controlled at 5-10 °C / min.

[0015] This invention uses tetraethyl orthosilicate (TEOS) as the silicon source and employs an acid-catalyzed sol-gel reaction (core reaction: Si(OC2H5)4 + 2H2O → SiO2 + 4C2H5OH) to uniformly construct an amorphous silica (SiO2) coating with a thickness of approximately 10–20 nm on the surface of pre-dried Fe-Cu-Nb-B nanocrystalline alloy powder particles. This step creates an initial, silicon (Si)-rich and almost iron (Fe)-free chemical region on the powder surface, forming a distinct chemical interface with the iron (Fe)-rich nanocrystalline alloy core within.

[0016] The subsequent hydrogen atmosphere annealing treatment (500~600℃) involves a crucial interfacial reduction reaction between the coated SiO2 layer and hydrogen under this high-temperature reducing atmosphere (high-purity H2): SiO2 + 2H2 → Si + 2H2O. This reaction effectively breaks down the barrier of the inert SiO2 coating, converting the bound silicon into highly reactive free silicon (Si) atoms, which accumulate on the surface of the alloy particles, creating the kinetic conditions for subsequent atomic diffusion.

[0017] Driven by high-temperature thermal energy, silicon (Si) and iron (Fe) atoms begin to interdiffused across the original sharp interface. Due to the large concentration gradient on both sides of the interface—Si-rich and Fe-poor on the surface, and Fe-rich and Si-poor inside—this constitutes a strong diffusion driving force. Microscopically, smaller silicon atoms tend to rapidly diffuse into the interior of the iron-based alloy through interstitial mechanisms. Simultaneously, larger iron atoms diffuse towards the surface primarily through vacancy mechanisms. Since the diffusion coefficient of silicon atoms is typically greater than that of iron atoms, this asymmetry in diffusion rates, combined with the initial step distribution of concentration, prevents instantaneous homogenization at the diffusion front. According to Fick's diffusion law, the concentration of silicon atoms is highest near the surface (Si-rich region). As the particle penetrates deeper, the silicon concentration decreases exponentially, while the iron concentration increases exponentially, eventually transitioning to the unaffected core region of the original Fe-rich nanocrystalline alloy. This naturally forms a compositional gradient transition layer where the silicon concentration continuously decreases from the surface to the interior, and the iron concentration continuously increases from the surface to the interior—a compositional gradient interface layer that gradually changes from Si-rich to Fe-rich.

[0018] The microstructure of the nanocrystalline alloy itself plays a crucial role in this process. Powder with a particle size of only 50-100 nm has an extremely high grain boundary density. These grain boundaries act as "fast channels" for atomic migration (the grain boundary diffusion rate can be several orders of magnitude higher than bulk diffusion), greatly accelerating the interdiffusion process of silicon and iron atoms, allowing a gradient layer of moderate thickness to be formed within a relatively short holding time. At the same time, silicon atoms diffusing into the grain boundary region can also generate the Zener pinning effect, which helps to suppress the growth of nanocrystals at high temperatures and maintain the excellent magnetic properties of the material.

[0019] The resulting gradient interface layer exhibits a continuous structural change: the outermost layer is a silicon-rich (Si > 70 at%) amorphous / microcrystalline silicon-iron compound region; the middle layer is a transitional solid solution region with continuously varying silicon-iron concentration; and the inner layer gradually transforms into an iron-rich (Fe > 80 at%) nanocrystalline alloy region that retains its original composition. This gradient structure, through the continuous transition of chemical composition, effectively solves the physical and chemical incompatibility problem between the nanocrystalline alloy and the ferrite matrix, significantly improves oxidation resistance, and thus optimizes the overall performance of the magnetic core.

[0020] To solve the above-mentioned technical problems, another technical solution provided by the present invention is: a rapid atmosphere sintering process for composite modified magnetic cores, the specific steps of which are as follows: S1 blank preparation: Ferrite, modified nanocrystalline alloy powder, rare earth additives, non-magnetic oxides, and antioxidants are added to a sealed mixer in the above proportions. Nitrogen gas with a purity of ≥99.99% is introduced to maintain an inert environment with an oxygen content of <50ppm. Polyvinyl alcohol solid and deionized water are added and mixed at 250-300rpm for 3-5 hours to form a uniform slurry. The slurry is then transported to a nitrogen-protected spray drying equipment, with the inlet air temperature controlled at 180-200℃ and the outlet air temperature at 80-90℃, to produce magnetic core blank particles with an average particle size of 50-100μm. The entire granulation process is carried out in a nitrogen environment. S2 Debinding Process: The magnetic core blank is placed in a debinding furnace. The temperature is first raised to 200-250℃ at a heating rate of 1-2℃ / min and held for 1-2 hours. During this stage, a mixed gas is introduced to initially decompose most of the organic adhesive. Then, the temperature is raised to 400-450℃ at a heating rate of 2-3℃ / min and held for 2-3 hours. At the same time, the mixed gas is switched to a reducing gas to further and thoroughly remove the organic adhesive. During the debinding process, the gas flow rate is precisely controlled at 50-100L / h through a gas flow control system. S3 Rapid Atmosphere Sintering: The debinding magnetic core blank is placed in a rapid atmosphere sintering furnace equipped with microwave-assisted heating. A mixed atmosphere is introduced into the furnace to fully replace and remove air from the furnace chamber. The sintering process uses a combination of microwave and resistance heating, rapidly raising the temperature to 1000-1200℃ at a heating rate of 10-20℃ / s. During the heating process, the selective heating characteristics of microwaves are utilized to allow the modified nanocrystalline alloy powder and other components in the magnetic core blank to rapidly absorb energy, achieving rapid heating. At the same time, resistance heating ensures overall temperature uniformity. After reaching the target temperature, the temperature is held for 10-20 minutes. After the holding period, the microwave power supply and resistance heating are turned off, and the magnetic core is cooled to room temperature at a cooling rate of 5-10℃ / min under the protection of the mixed atmosphere. S4 Post-processing: The sintered magnetic core is first subjected to plasma cleaning treatment. In a mixed gas environment of argon and hydrogen with a volume ratio of 4:1, it is treated with 100-150W power for 8 minutes to remove the surface oxide layer and impurities. Then, a silicon carbide (SiC) coating with a thickness of 50-100nm is deposited at 600-700℃ using chemical vapor deposition (CVD) technology. After cooling to room temperature, the magnetic core is obtained.

[0021] Furthermore, in step S1, the amounts of polyvinyl alcohol solids and deionized water added are 1.0% to 1.2% and 15% to 18% of the total mass of the raw materials, respectively.

[0022] Further, in step S2, the mixed gas is 5%–10% oxygen and 90%–95% nitrogen, and then it is switched to a reducing gas of 2%–5% hydrogen and 95%–98% nitrogen.

[0023] Furthermore, in step S3, a mixed atmosphere of 80%–90% argon and 10%–20% hydrogen is introduced into the furnace, with the gas flow rate controlled at 100–200 L / h.

[0024] This invention overcomes the limitations of traditional technologies by constructing a compositional gradient interface layer that transitions from Si-rich to Fe-rich through surface coating and elemental diffusion modification of nanocrystalline alloy powder. During the multi-field coupled heating stage of rapid atmosphere sintering, this gradient interface works synergistically with microwaves to promote more uniform atomic diffusion during high-speed heating (10–20 °C / s), effectively improving the magnetic permeability of the core and significantly enhancing its high-frequency performance.

[0025] Traditional nanocrystalline alloys exhibit low energy absorption efficiency during microwave sintering, often requiring the addition of absorbers and prone to localized overheating and grain coarsening. This invention utilizes the selective microwave absorption characteristics of a modified nanocrystalline alloy powder surface SiO2 coating to create "micro-hot spots" during rapid atmosphere sintering. Combined with precise atmosphere control and multi-field synergistic heating, this not only accelerates the core densification process but also avoids the drawbacks of traditional microwave sintering, shortening sintering time, refining grain size, and reducing core losses.

[0026] This invention integrates a dual mechanism of physical coating and elemental diffusion alloying for oxidation resistance, achieved through modification of nanocrystalline alloy powder, throughout the entire sintering process. From nitrogen-protected mixing and granulation during billet preparation to precise atmosphere control during binder removal and sintering, this method reduces oxidation weight gain and improves the retention rate of soft magnetic properties of the nanocrystalline alloy compared to traditional processes in 800℃ high-temperature oxidation tests. This close integration of the modified oxidation resistance with each stage of the sintering process ensures stable application of the magnetic core in harsh environments.

[0027] Furthermore, this invention integrates the modification process with a rapid atmosphere sintering process, closely linking coating-diffusion modification with mixing, debinding, and sintering steps to form a complete system, significantly improving production efficiency. Simultaneously, this process can improve both the static and dynamic properties of the magnetic core, effectively overcoming the limitations of traditional magnetic core materials in terms of permeability, loss, and saturation flux density, meeting the requirements of high-performance electronic devices, and greatly expanding the application scenarios of magnetic cores.

[0028] The beneficial effects of this invention are as follows: 1. Significantly improved magnetic properties and stability: Through composite modified material design and nanocrystalline alloy surface modification, the magnetic permeability of the magnetic core is improved in the 1-10MHz frequency band, the loss is reduced at 100kHz, the weight gain from high-temperature oxidation is reduced, and the oxidation resistance is significantly enhanced.

[0029] 2. Significantly improved sintering efficiency and yield: The rapid sintering process combining microwave and resistance heating achieves a heating rate of 10-20℃ / s, greatly shortening the sintering time. At the same time, segmented atmosphere control avoids core cracking and adhesion, significantly reducing the breakage rate.

[0030] 3. Process integration and application scenario expansion: The modification technology and sintering process are integrated into the design to solve the problems of poor compatibility of traditional materials and high sintering energy consumption. The performance of the magnetic core simultaneously meets the application requirements of high-frequency electronic components and harsh environments. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments, but this does not limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0032] Example 1 A composite modified magnetic core comprises the following components by weight: 50 parts ferrite, 5 parts modified nanocrystalline alloy powder, 3 parts rare earth additives, 1 part non-magnetic oxide, and 0.5 parts antioxidant.

[0033] Furthermore, the ferrite raw material is selected from one or more types of manganese-zinc ferrite and nickel-zinc ferrite.

[0034] Furthermore, the nanocrystalline alloy powder is a Fe-Cu-Nb-B series nanocrystalline alloy.

[0035] Furthermore, the rare earth additive is a mixture of dysprosium oxide (Dy2O3) and holmium oxide (Ho2O3) in a mass ratio of 1:1.

[0036] Furthermore, the non-magnetic oxide is a mixture of titanium dioxide (TiO2) and zirconium dioxide (ZrO2) in a mass ratio of 1:1.

[0037] Furthermore, the antioxidant is one or more of boric acid and borax.

[0038] The preparation method of modified nanocrystalline alloy powder, the specific steps are as follows: (1) Select Fe-Cu-Nb-B nanocrystalline alloy powder with an average particle size of 50nm as raw material, place it in a vacuum drying oven and dry it at 80℃ for 2h to remove the moisture and impurities adsorbed on the powder surface and ensure the effect of subsequent modification treatment. (2) Using tetraethyl orthosilicate (TEOS) as a precursor, TEOS and anhydrous ethanol were mixed at a volume ratio of 1:5. After stirring evenly, deionized water and catalyst with a molar ratio of 1:1 to TEOS were added, and the pH of the solution was adjusted to 3. The mixture was stirred at room temperature for 30 min to form a uniform and stable sol. Then, the dried nanocrystalline alloy powder was slowly added to the above sol. The mass ratio of powder to sol was controlled at 1:3. The mixture was stirred at 200 rpm for 1 h to make the sol uniformly coat the surface of the alloy powder. The mixture was then transferred to a rotary evaporator and evaporated at 60°C under reduced pressure for 1 h to remove the solvent and obtain alloy powder with a gel layer on the surface. The coated alloy powder was placed in a drying oven and dried at 80°C for 12-24 h to allow the gel layer to dry and solidify fully, forming a silicon dioxide (SiO2) coating with a thickness of about 10 nm. (3) The coated nanocrystalline alloy powder is placed in a high-temperature annealing furnace, and hydrogen gas with a purity of ≥99.99% is introduced as a protective atmosphere. The gas flow rate is controlled at 50 mL / min. The annealing furnace is fully replaced to remove the air in the furnace and prevent the alloy powder from being oxidized during heating. The temperature of the annealing furnace is raised to 500℃ at a heating rate of 5℃ / min and held for 1 hour. After the holding period, the heating power is turned off and hydrogen gas is introduced to allow the alloy powder to cool naturally to room temperature in the hydrogen atmosphere. The cooling rate is controlled at 5℃ / min. The modified nanocrystalline alloy powder is sieved to remove agglomerated particles, thus obtaining the modified nanocrystalline alloy powder.

[0039] A rapid atmosphere sintering process for composite modified magnetic cores, the specific steps of which are as follows: S1 blank preparation: Ferrite, modified nanocrystalline alloy powder, rare earth additives, non-magnetic oxides, and antioxidants are added to a sealed mixer in the above proportions. Nitrogen gas with a purity of ≥99.99% is introduced to maintain an inert environment with an oxygen content of <50ppm. Polyvinyl alcohol solid is added at 1.0% of the total mass of raw materials, and deionized water is added at 15% of the total mass. The mixture is mixed at 250rpm for 3 hours to form a uniform slurry. The slurry is then transported to a nitrogen-protected spray drying equipment, with the inlet air temperature controlled at 180℃ and the outlet air temperature at 80℃, to produce magnetic core blank particles with an average particle size of 50μm. The entire granulation process is carried out in a nitrogen environment. S2 Debinding Process: The magnetic core blank is placed in a debinding furnace. The temperature is first raised to 200℃ at a heating rate of 1℃ / min and held for 1 hour. During this stage, a mixed gas containing 5% oxygen and 90% nitrogen is introduced to initially decompose most of the organic adhesive. Then, the temperature is raised to 400℃ at a heating rate of 2-3℃ / min and held for 2 hours. At the same time, the mixed gas is switched to a reducing gas containing 2% hydrogen and 95% nitrogen to further and thoroughly remove the organic adhesive. During the debinding process, the gas flow rate is precisely controlled at 50L / h through a gas flow control system. S3 Rapid Atmosphere Sintering: The debinding magnetic core blank is placed in a rapid atmosphere sintering furnace equipped with microwave-assisted heating. A mixed atmosphere consisting of 80% argon and 10% hydrogen is introduced into the furnace at a flow rate of 100 L / h to fully replace the furnace chamber and remove air. The sintering process uses a combination of microwave and resistance heating to rapidly raise the temperature to 1000℃ at a heating rate of 10℃ / s. During the heating process, the selective heating characteristics of microwaves are utilized to allow the modified nanocrystalline alloy powder and other components in the magnetic core blank to rapidly absorb energy, achieving rapid heating. At the same time, resistance heating ensures overall temperature uniformity. After reaching the target temperature, the temperature is held for 10 minutes. After the holding period, the microwave power supply and resistance heating are turned off, and the magnetic core is cooled to room temperature at a cooling rate of 5℃ / min under the protection of the mixed atmosphere. S4 Post-processing: The sintered magnetic core is first subjected to plasma cleaning treatment. In a mixed gas environment of argon and hydrogen with a volume ratio of 4:1, it is treated with 100W power for 8 minutes to remove the surface oxide layer and impurities. Then, a 50nm thick silicon carbide (SiC) coating is deposited at 600℃ using chemical vapor deposition (CVD) technology. After cooling to room temperature, the magnetic core is obtained.

[0040] Example 2 A composite modified magnetic core comprises the following components by weight: 70 parts ferrite, 10 parts modified nanocrystalline alloy powder, 6 parts rare earth additives, 3 parts non-magnetic oxide, and 1 part antioxidant.

[0041] Furthermore, the ferrite raw material is selected from one or more types of manganese-zinc ferrite and nickel-zinc ferrite.

[0042] Furthermore, the nanocrystalline alloy powder is an Fe-Cu-Nb-B nanocrystalline alloy with an average particle size of 50-100 nm.

[0043] Furthermore, the rare earth additive is a mixture of dysprosium oxide (Dy2O3) and holmium oxide (Ho2O3) in a mass ratio of 2:1.

[0044] Furthermore, the non-magnetic oxide is a mixture of titanium dioxide (TiO2) and zirconium dioxide (ZrO2) in a mass ratio of 2:1.

[0045] Furthermore, the antioxidant is one or more of boric acid and borax.

[0046] The preparation method of modified nanocrystalline alloy powder, the specific steps are as follows: (1) Select Fe-Cu-Nb-B nanocrystalline alloy powder with an average particle size of 100nm as raw material, place it in a vacuum drying oven and dry it at 100℃ for 4h to remove the moisture and impurities adsorbed on the powder surface and ensure the effect of subsequent modification treatment. (2) Using tetraethyl orthosilicate (TEOS) as a precursor, TEOS and anhydrous ethanol were mixed at a volume ratio of 1:3. After stirring evenly, deionized water and catalyst with a molar ratio of 2:1 to TEOS were added, and the pH of the solution was adjusted to 5. The mixture was stirred at room temperature for 60 min to form a uniform and stable sol. Then, the dried nanocrystalline alloy powder was slowly added to the above sol. The mass ratio of powder to sol was controlled at 1:2. The mixture was stirred at 300 rpm for 2 h to make the sol uniformly coat the surface of the alloy powder. The mixture was then transferred to a rotary evaporator and rotary evaporated at 80°C under reduced pressure for 2 h to remove the solvent and obtain alloy powder with a gel layer on the surface. The coated alloy powder was placed in a drying oven and dried at 100°C for 24 h to allow the gel layer to dry and solidify fully, forming a silicon dioxide (SiO2) coating with a thickness of about 20 nm. (3) The coated nanocrystalline alloy powder is placed in a high-temperature annealing furnace, and hydrogen gas with a purity of ≥99.99% is introduced as a protective atmosphere. The gas flow rate is controlled at 100 mL / min. The annealing furnace is fully replaced to remove the air in the furnace and prevent the alloy powder from being oxidized during heating. The temperature of the annealing furnace is raised to 600℃ at a heating rate of 10℃ / min and held for 2 hours. After the holding period, the heating power is turned off and hydrogen gas is introduced to allow the alloy powder to cool naturally to room temperature in the hydrogen atmosphere. The cooling rate is controlled at 10℃ / min. The modified nanocrystalline alloy powder is sieved to remove agglomerated particles, thus obtaining the modified nanocrystalline alloy powder.

[0047] A rapid atmosphere sintering process for composite modified magnetic cores, the specific steps of which are as follows: S1 blank preparation: Ferrite, modified nanocrystalline alloy powder, rare earth additives, non-magnetic oxides, and antioxidants are added to a sealed mixer in the above proportions. Nitrogen gas with a purity of ≥99.99% is introduced to maintain an inert environment with an oxygen content of <50ppm. Polyvinyl alcohol solid is added at 1.2% of the total mass of raw materials, and deionized water is added at 18% of the total mass of raw materials. The mixture is mixed at 300rpm for 5 hours to form a uniform slurry. The slurry is then transported to a nitrogen-protected spray drying equipment, with the inlet air temperature controlled at 200℃ and the outlet air temperature at 90℃, to produce magnetic core blank particles with an average particle size of 100μm. The entire granulation process is carried out in a nitrogen environment. S2 Debinding Process: The magnetic core blank is placed in a debinding furnace. The temperature is first raised to 250°C at a heating rate of 2°C / min and held for 2 hours. During this stage, a mixed gas containing 10% oxygen and 95% nitrogen is introduced to initially decompose most of the organic adhesives. Then, the temperature is raised to 450°C at a heating rate of 3°C / min and held for 3 hours. At the same time, the mixed gas is switched to a reducing gas containing 5% hydrogen and 98% nitrogen to further and thoroughly remove the organic adhesives. During the debinding process, the gas flow rate is precisely controlled at 100L / h through a gas flow control system. S3 Rapid Atmosphere Sintering: The debinding magnetic core blank is placed in a rapid atmosphere sintering furnace equipped with microwave-assisted heating. A mixed atmosphere consisting of 90% argon and 20% hydrogen is introduced into the furnace at a flow rate of 200 L / h to fully replace the furnace chamber and remove air. The sintering process uses a combination of microwave and resistance heating to rapidly raise the temperature to 1200℃ at a heating rate of 20℃ / s. During the heating process, the selective heating characteristics of microwaves are utilized to allow the modified nanocrystalline alloy powder and other components in the magnetic core blank to rapidly absorb energy, achieving rapid heating. At the same time, resistance heating ensures overall temperature uniformity. After reaching the target temperature, the temperature is held for 20 minutes. After the holding period, the microwave power supply and resistance heating are turned off, and the magnetic core is cooled to room temperature at a cooling rate of 10℃ / min under the protection of the mixed atmosphere. S4 Post-processing: The sintered magnetic core is first subjected to plasma cleaning treatment. In a mixed gas environment of argon and hydrogen with a volume ratio of 4:1, it is treated with 150W power for 8 minutes to remove the surface oxide layer and impurities. Then, a 100nm thick silicon carbide (SiC) coating is deposited at 700℃ using chemical vapor deposition (CVD) technology. After cooling to room temperature, the magnetic core is obtained.

[0048] Example 3 A composite modified magnetic core comprises the following components by weight: 60 parts ferrite, 7.5 parts modified nanocrystalline alloy powder, 4.5 parts rare earth additives, 2 parts non-magnetic oxide, and 0.75 parts antioxidant.

[0049] Furthermore, the ferrite raw material is selected from one or more types of manganese-zinc ferrite and nickel-zinc ferrite.

[0050] Furthermore, the nanocrystalline alloy powder is an Fe-Cu-Nb-B nanocrystalline alloy with an average particle size of 75 nm.

[0051] Furthermore, the rare earth additive is a mixture of dysprosium oxide (Dy2O3) and holmium oxide (Ho2O3) in a mass ratio of 1.5:1.

[0052] Furthermore, the non-magnetic oxide is a mixture of titanium dioxide (TiO2) and zirconium dioxide (ZrO2) in a mass ratio of 1.5:1.

[0053] Furthermore, the antioxidant is one or more of boric acid and borax.

[0054] The preparation method of modified nanocrystalline alloy powder, the specific steps are as follows: (1) Select Fe-Cu-Nb-B nanocrystalline alloy powder with an average particle size of 75nm as raw material, place it in a vacuum drying oven and dry it at 90℃ for 3h to remove the moisture and impurities adsorbed on the powder surface and ensure the effect of subsequent modification treatment. (2) Using tetraethyl orthosilicate (TEOS) as a precursor, TEOS and anhydrous ethanol were mixed at a volume ratio of 1:4. After stirring evenly, deionized water and catalyst with a molar ratio of 3:2 to TEOS were added, and the pH of the solution was adjusted to 4. The mixture was stirred at room temperature for 45 min to form a uniform and stable sol. Then, the dried nanocrystalline alloy powder was slowly added to the above sol. The mass ratio of powder to sol was controlled at 1:2.5. The mixture was stirred at 250 rpm for 1.5 h to make the sol uniformly coat the surface of the alloy powder. The mixture was then transferred to a rotary evaporator and evaporated at 70 °C under reduced pressure for 1.5 h to remove the solvent and obtain alloy powder with a gel layer on the surface. The coated alloy powder was placed in a drying oven and dried at 90 °C for 18 h to make the gel layer fully dry and solidify, forming a silicon dioxide (SiO2) coating with a thickness of about 15 nm. (3) The coated nanocrystalline alloy powder is placed in a high-temperature annealing furnace, and hydrogen gas with a purity of ≥99.99% is introduced as a protective atmosphere. The gas flow rate is controlled at 75 mL / min. The annealing furnace is fully purged to remove air and prevent the alloy powder from being oxidized during heating. The annealing furnace temperature is raised to 550℃ at a heating rate of 7.5℃ / min and held for 1.5 h. After the holding period, the heating power is turned off and hydrogen gas is introduced to allow the alloy powder to cool naturally to room temperature in the hydrogen atmosphere. The cooling rate is controlled at 7.5℃ / min. The modified nanocrystalline alloy powder is then sieved to remove agglomerated particles, thus obtaining the modified nanocrystalline alloy powder.

[0055] A rapid atmosphere sintering process for composite modified magnetic cores, the specific steps of which are as follows: S1 blank preparation: Ferrite, modified nanocrystalline alloy powder, rare earth additives, non-magnetic oxides, and antioxidants are added to a sealed mixer in the above proportions. Nitrogen gas with a purity of ≥99.99% is introduced to maintain an inert environment with an oxygen content of <50ppm. Polyvinyl alcohol solid is added at 1.1% of the total mass of raw materials, and deionized water is added at 16.5% of the total mass of raw materials. The mixture is mixed at 275rpm for 4 hours to form a uniform slurry. The slurry is then transported to a nitrogen-protected spray drying equipment, with the inlet air temperature controlled at 190℃ and the outlet air temperature at 85℃, to produce magnetic core blank particles with an average particle size of 75μm. The entire granulation process is carried out in a nitrogen environment. S2 Debinding Process: The magnetic core blank is placed in a debinding furnace. The temperature is first raised to 225℃ at a heating rate of 1.5℃ / min and held for 1.5h. During this stage, a mixed gas containing 7.5% oxygen and 92.5% nitrogen is introduced to initially decompose most of the organic adhesive. Then, the temperature is raised to 425℃ at a heating rate of 2.5℃ / min and held for 2.5h. At the same time, the mixed gas is switched to a reducing gas containing 3.5% hydrogen and 96.5% nitrogen to further and thoroughly remove the organic adhesive. During the debinding process, the gas flow rate is precisely controlled at 75L / h through a gas flow control system. S3 Rapid Atmosphere Sintering: The debinding magnetic core blank is placed in a rapid atmosphere sintering furnace equipped with microwave-assisted heating. A mixed atmosphere consisting of 85% argon and 15% hydrogen is introduced into the furnace at a flow rate of 150 L / h to fully replace the furnace chamber and remove air. The sintering process uses a combination of microwave and resistance heating to rapidly raise the temperature to 1100℃ at a heating rate of 15℃ / s. During the heating process, the selective heating characteristics of microwaves are utilized to allow the modified nanocrystalline alloy powder and other components in the magnetic core blank to rapidly absorb energy, achieving rapid heating. At the same time, resistance heating ensures overall temperature uniformity. After reaching the target temperature, the temperature is held for 15 minutes. After the holding period, the microwave power supply and resistance heating are turned off, and the magnetic core is cooled to room temperature at a cooling rate of 7.5℃ / min under the protection of the mixed atmosphere. S4 Post-processing: The sintered magnetic core is first subjected to plasma cleaning treatment. In a mixed gas environment of argon and hydrogen with a volume ratio of 4:1, it is treated with 125W power for 8 minutes to remove the surface oxide layer and impurities. Then, a 75nm thick silicon carbide (SiC) coating is deposited at 650℃ using chemical vapor deposition (CVD) technology. After cooling to room temperature, the magnetic core is obtained.

[0056] Comparative Example 1: This Comparative Example 1 is basically the same as Example 3, except that the nanocrystalline alloy powder has not been modified.

[0057] Comparative Example 2: This Comparative Example 2 is basically the same as Example 3, except that the magnetic core blank did not undergo the glue removal process in step (S2).

[0058] Test experiment: Five magnetic cores from Examples 1-3 and Comparative Examples 1-2 were used as test samples and the test results are shown in Tables 1 and 2 below.

[0059] 1. Basic physical performance testing Testing items: bulk density, flexural strength, surface hardness, coefficient of thermal expansion Testing standards: GB / T 5163-2006, GB / T 6569-2006, ISO 6507-1, GB / T 4339-2008.

[0060] Table 1 Performance Test Results 2. Core Indicators of Electromagnetic Performance Test items: initial permeability μi, saturation magnetic flux density Bs, power loss Pcv, high-frequency impedance characteristics Test conditions: IEC 60401-3 (10kHz), IEC 60404-4 (1194A / m), IEC 62044-3 (100kHz / 200mT) Table 2 Electromagnetic performance test results Based on the comparative test data of the embodiments and comparative examples, in terms of basic physical properties, Embodiment 3 exhibits the best overall performance: a bulk density of 4.91 g / cm³, a flexural strength of 138 MPa, and a low coefficient of thermal expansion of 7.9 × 10⁻⁻⁻⁻⁶. 6 / K. Comparative Example 1, lacking nanocrystalline modification treatment, showed a 3.3% decrease in bulk density (4.75 g / cm³) and a 14.5% decrease in flexural strength (118 MPa) compared to Example 3, demonstrating the crucial role of gradient interface modification in enhancing particle bonding and material densification. Comparative Example 2, omitting the segmented adhesive removal process, experienced a catastrophic drop in flexural strength to 9 MPa, while its coefficient of thermal expansion increased to 8.8 × 10⁻⁻⁻⁶. 6 / K clearly reveals that residual organic matter can cause microcracks and thermal mismatch problems, which in turn confirms the necessity of the segmented atmosphere debinding process.

[0061] In the field of electromagnetic performance, the embodiments achieved comprehensive breakthroughs: the power loss Pcv of Embodiment 3 was as low as 320 kW / m³, which was significantly reduced by 44.8% compared with Comparative Example 1 (580 kW / m³). This is attributed to the effective suppression of eddy current and hysteresis losses by the fine grain structure formed by the modified interface; the initial permeability μi (5600) and saturation magnetic flux density Bs (0.52T) were increased by 16.7% and 15.6% respectively compared with Comparative Example 1, which confirmed that the gradient interface promotes domain wall movement and the high magnetic saturation characteristics of the modified nanocrystalline alloy; the high-frequency impedance value at 10MHz reached 20.1Ω (compared to only 15.3Ω in Comparative Example 1), highlighting the blocking effect of SiC coating on eddy currents and meeting the high-frequency requirements of 5G / new energy equipment.

[0062] The parameter optimization trend shows that with the increase of the proportion of nanocrystals (5→7.5 parts) and the optimization of the sintering temperature (1000→1100℃), the core performance of Examples 1 to 3 continues to improve: the bulk density increases by 1.9%, the magnetic permeability increases by 7.7%, and the power loss decreases by 8.6%, establishing Example 3 as the optimal balance point between composition and process. The comparative experiments further enhance the inventiveness of the invention: Comparative Example 1, due to lack of modification, resulted in a surge of 81.3% in Pcv and a decrease of 13.5% in Bs, exposing the inherent defects of nanocrystal oxidation; Comparative Example 2, due to the lack of binder removal, caused a collapse in flexural strength (9 MPa vs. normal value >100 MPa) and the lowest bulk density (4.68 g / cm³), further demonstrating the destructive impact of organic residues on the material structure.

[0063] This invention addresses oxidation compatibility issues through gradient interface modification, eliminates organic residues through segmented atmosphere debinding, and achieves grain refinement and energy consumption control through microwave-resistance synergistic rapid sintering—ultimately achieving significant results such as a 44.8% reduction in high-frequency loss, a more than 80% reduction in sintering energy consumption, and improved stability over a wide temperature range.

[0064] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A composite modified magnetic core, characterized in that, It includes the following components in parts by weight: 50-70 parts ferrite, 5-10 parts modified nanocrystalline alloy powder, 3-6 parts rare earth additives, 1-3 parts non-magnetic oxides, and 0.5-1 parts antioxidant.

2. The composite modified magnetic core according to claim 1, characterized in that, The ferrite raw material is selected from one or more of manganese-zinc ferrite and nickel-zinc ferrite, and the nanocrystalline alloy powder is Fe-Cu-Nb-B series nanocrystalline alloy.

3. The composite modified magnetic core according to claim 1, characterized in that, The rare earth additive is a mixture of dysprosium oxide (Dy2O3) and holmium oxide (Ho2O3) in a mass ratio of 1 to 2:1, and the antioxidant is one or more of boric acid and borax.

4. The composite modified magnetic core according to claim 1, characterized in that, The preparation method of the modified nanocrystalline alloy powder includes the following specific steps: (1) Select Fe-Cu-Nb-B nanocrystalline alloy powder with an average particle size of 50-100nm as raw material, place it in a vacuum drying oven and dry it at 80-100℃ for 2-4h to remove the moisture and impurities adsorbed on the powder surface and ensure the effect of subsequent modification treatment. (2) Using tetraethyl orthosilicate (TEOS) as a precursor, TEOS and anhydrous ethanol are mixed at a volume ratio of 1:3 to 5. After stirring evenly, deionized water and catalyst are added and the pH of the solution is adjusted to 3 to 5. Stir at room temperature for 30 to 60 minutes to form a uniform and stable sol. Then, the dried nanocrystalline alloy powder is slowly added to the above sol. The mass ratio of powder to sol is controlled at 1:2 to 3. Stir at a speed of 200 to 300 rpm for 1 to 2 hours to make the sol uniformly coat the surface of the alloy powder. Then, the mixture is transferred to a rotary evaporator to evaporate and remove the solvent, and alloy powder with a gel layer on the surface is obtained. The coated alloy powder is placed in a drying oven and dried at 80 to 100°C for 12 to 24 hours to make the gel layer fully dry and solidify, forming a silicon dioxide (SiO2) coating with a thickness of about 10 to 20 nm. (3) Place the coated nanocrystalline alloy powder into a high-temperature annealing furnace, introduce hydrogen gas with a purity of ≥99.99% as a protective atmosphere, fully replace the annealing furnace, remove the air in the furnace, and prevent the alloy powder from being oxidized during heating. Raise the temperature of the annealing furnace to 500-600℃ and hold for 1-2 hours. After the holding period, turn off the heating power and continue to introduce hydrogen gas to allow the alloy powder to cool naturally to room temperature in the hydrogen atmosphere. Sieve the modified nanocrystalline alloy powder to remove agglomerated particles, and obtain the modified nanocrystalline alloy powder.

5. A composite modified magnetic core according to claim 4, characterized in that, In step (2), the amount of deionized water added is 1 to 2:1 in molar ratio of water to TEOS, and the evaporation conditions in the rotary evaporator are 60 to 80°C and rotary evaporation under reduced pressure for 1 to 2 hours.

6. A composite modified magnetic core according to claim 4, characterized in that, In step (3), the flow rate of hydrogen is controlled at 50-100 mL / min, the heating rate is 5-10 °C / min, and the cooling rate is controlled at 5-10 °C / min.

7. The sintering process of the composite modified magnetic core according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: S1 blank preparation: Ferrite, modified nanocrystalline alloy powder, rare earth additives, non-magnetic oxides, and antioxidants are added to a sealed mixer in the above proportions. Nitrogen gas with a purity of ≥99.99% is introduced to maintain an inert environment with an oxygen content of <50ppm. Polyvinyl alcohol solid and deionized water are added and mixed at 250-300rpm for 3-5 hours to form a uniform slurry. The slurry is then transported to a nitrogen-protected spray drying equipment, with the inlet air temperature controlled at 180-200℃ and the outlet air temperature at 80-90℃ to produce magnetic core blank particles with an average particle size of 50-100μm. The entire granulation process is carried out in a nitrogen environment. S2 Debinding Process: The magnetic core blank is placed in a debinding furnace. The temperature is first raised to 200-250℃ at a heating rate of 1-2℃ / min and held for 1-2 hours. During this stage, a mixed gas is introduced to initially decompose most of the organic adhesive. Then, the temperature is raised to 400-450℃ at a heating rate of 2-3℃ / min and held for 2-3 hours. At the same time, the mixed gas is switched to a reducing gas to further and thoroughly remove the organic adhesive. During the debinding process, the gas flow rate is precisely controlled at 50-100L / h through a gas flow control system. S3 Rapid Atmosphere Sintering: The debinding magnetic core blank is placed in a rapid atmosphere sintering furnace equipped with microwave-assisted heating. A mixed atmosphere is introduced into the furnace to fully replace and remove air from the furnace chamber. The sintering process uses a combination of microwave and resistance heating, rapidly raising the temperature to 1000-1200℃ at a heating rate of 10-20℃ / s. During the heating process, the selective heating characteristics of microwaves are utilized to allow the modified nanocrystalline alloy powder and other components in the magnetic core blank to rapidly absorb energy, achieving rapid heating. At the same time, resistance heating ensures overall temperature uniformity. After reaching the target temperature, the temperature is held for 10-20 minutes. After the holding period, the microwave power supply and resistance heating are turned off, and the magnetic core is cooled to room temperature at a cooling rate of 5-10℃ / min under the protection of the mixed atmosphere. S4 Post-processing: The sintered magnetic core is first subjected to plasma cleaning treatment. In a mixed gas environment of argon and hydrogen with a volume ratio of 4:1, it is treated with 100-150W power for 8 minutes to remove the surface oxide layer and impurities. Then, a silicon carbide (SiC) coating with a thickness of 50-100nm is deposited at 600-700℃ using chemical vapor deposition (CVD) technology. After cooling to room temperature, the magnetic core is obtained.

8. The method for preparing the composite modified magnetic core according to claim 7, characterized in that, In step S1, the amounts of polyvinyl alcohol solids and deionized water added are 1.0% to 1.2% and 15% to 18% of the total mass of the raw materials, respectively.

9. The method for preparing the composite modified magnetic core according to claim 7, characterized in that, In step S2, the mixed gas is 5%–10% oxygen and 90%–95% nitrogen, and then it is switched to a reducing gas of 2%–5% hydrogen and 95%–98% nitrogen.

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