FeNi soft magnetic composite material based on tetrabutyl orthosilicate hydrolysis coating and preparation method of FeNi soft magnetic composite material
By growing a dense SiO2 insulating layer in situ on the surface of FeNi powder, the problem of insufficient bonding strength of SiO2 coating was solved, and a FeNi soft magnetic composite material with low loss and high magnetic permeability at high frequencies was realized, which is suitable for high-frequency electronic devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HANGZHOU DIANZI UNIV
- Filing Date
- 2026-03-11
- Publication Date
- 2026-05-12
AI Technical Summary
In the prior art, the bonding strength between SiO2 coating and the surface of metal particles is low, which makes it easy to crack or fall off at high frequencies. The material resistivity is low, so it cannot be used in high-frequency devices. Furthermore, existing methods are difficult to optimize the high-frequency magnetic properties of soft magnetic composite materials.
A dense SiO2 insulating layer is grown in situ on the surface of FeNi powder by using the hydrolysis method of tetrabutyl orthosilicate. By controlling the hydrolysis process, a uniform, dense and ultrathin SiO2 insulating layer is formed, which is firmly bonded, reduces high-frequency eddy current loss and maintains high magnetic permeability.
It significantly reduces high-frequency eddy current losses while maintaining the material's high permeability, making it suitable for devices in the MHz band and applicable to power inductors, transformers, and EMI filters.
Smart Images
Figure CN122025329A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electronic materials technology, and relates to soft magnetic composite materials and their preparation, specifically to a FeNi soft magnetic composite material based on butyl orthosilicate (TBOS) hydrolysis coating and its preparation method. Background Technology
[0002] Under high-frequency conditions, the eddy current loss of soft magnetic composite materials increases sharply with increasing frequency. Coating the surface of magnetic metal powder with a silicon oxide layer using the sol-gel method can improve resistivity, thermal stability, and oxidation resistance, thereby achieving low magnetic loss in soft magnets at high frequencies and meeting the needs of power electronics technology for high-frequency, miniaturized, and high-efficiency development. Among these methods, TEOS hydrolysis is a commonly used method for preparing SiO2 coatings, offering advantages such as uniform film formation, controllable thickness, and pure composition. Furthermore, SiO2 has low conductivity, which can effectively reduce the dielectric constant and dielectric loss of electromagnetic materials. However, because TEOS lacks strongly polar groups, its bonding strength with the metal particle surface is relatively low, resulting in a sparse coating structure. Furthermore, some methods coat SiO2 onto the surface of materials such as iron powder and carbonyl iron powder Fe(CO)5 to obtain soft magnetic composite materials. However, due to the significant difference in physical properties between the SiO2 coating and the internal metal particles, cracks or detachment are prone to occur during subsequent pressing and annealing heat treatment. Therefore, the heat treatment temperature usually cannot exceed 600℃. In addition, the low resistivity of the material leads to large eddy current losses, making it unsuitable for use in high-frequency (MHz) devices.
[0003] In summary, the existing technology lacks a solution that can improve the interfacial bonding strength between the insulating layer and the metal material, and synergistically optimize the high-frequency magnetic properties of soft magnetic composite materials. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention proposes a FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating and its preparation method. By controlling the hydrolysis process of TBOS, a uniform, dense, ultrathin and firmly bonded SiO2 insulating layer is grown in situ on the surface of FeNi powder, thereby significantly reducing the high-frequency eddy current loss of the material while maximizing the preservation of its excellent soft magnetic properties such as high permeability.
[0005] A FeNi soft magnetic composite material based on hydrolyzed tetrabutyl orthosilicate coating is disclosed. The soft magnetic composite material consists of a dense SiO2 insulating layer with a thickness of 5–30 nm coated on the surface of FeNi particles, wherein the mass fraction of the SiO2 insulating layer is 0.2–1.5 wt%. The material exhibits an effective magnetic permeability μ at a frequency of 1 MHz. e Above 100, under test conditions of 1MHz and 50mT, the core loss does not exceed 1000mW / cm. 3 .
[0006] A method for preparing FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating specifically includes the following steps:
[0007] Step 1: Clean and dry the FeNi alloy powder to remove surface grease and oxides.
[0008] Step 2: Mix butyl orthosilicate (TBOS) with anhydrous ethanol, and slowly add deionized water containing the catalyst under stirring conditions, while continuing to stir to form a uniform and transparent SiO2 precursor sol.
[0009] The molar ratio of TBOS, anhydrous ethanol, water, and catalyst is 1:(4~8):(4~6):(0.01~0.1).
[0010] Step 3: Disperse the pretreated FeNi alloy powder in an ethanol solvent to obtain a FeNi alloy powder suspension. The volume ratio of ethanol to water in the ethanol solvent is (2~4):1.
[0011] The SiO2 precursor sol was slowly added dropwise to the FeNi alloy powder suspension, and the temperature was controlled at 30~60℃. The hydrolysis-condensation reaction was carried out under catalytic conditions for 2~6 hours to coat the surface of the FeNi powder with a SiO2 gel layer.
[0012] Step 4: Allow the coated powder system to stand and age, then perform solid-liquid separation, and dry the resulting powder at low temperature to obtain FeNi powder with SiO2 gel coated on the surface.
[0013] Step 5: Heat-treat the FeNi powder coated with SiO2 gel in an inert atmosphere or vacuum at a temperature of 300~600℃ for 0.5~2 hours to transform the SiO2 gel layer into a dense insulating layer. The mass fraction of the SiO2 insulating layer is 0.2~1.5 wt%.
[0014] Preferably, the mass fraction of the SiO2 insulating layer is 0.5~1.0 wt%.
[0015] Preferably, the heat treatment temperature is set to 450~550℃ to avoid excessive growth of FeNi powder grains or adverse phase transformation while forming a dense SiO2 layer.
[0016] Preferably, the heat-treated powder is mixed with an organic insulating binder, wherein the amount of organic insulating binder added does not exceed 0.5 wt% of the total mass of the powder.
[0017] Preferably, the organic insulating adhesive is silicone resin or epoxy resin.
[0018] Application of a FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating in MHz band power inductors, transformers or EMI filters.
[0019] Preferably, the FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating is pressed into a magnetic core of the desired shape under high pressure, and then annealed in a protective atmosphere at a temperature of 600~800℃ to eliminate stress and improve magnetic properties.
[0020] The present invention has the following beneficial effects:
[0021] 1. Excellent insulation layer: Compared with the silicon-based tetraethyl orthosilicate commonly used in existing technologies, tetrabutyl orthosilicate has a relatively long organic carbon chain and better affinity with the alloy. By controlling the hydrolysis rate of tetrabutyl orthosilicate with a catalyst, the SiO2 precursor sol and FeNi alloy powder suspension are mixed and continuously hydrolyzed. The SiO2 gel directly coated on the surface of FeNi powder is uniform and continuous, and is firmly bonded to the matrix alloy powder. Moreover, it is an amorphous structure with high purity and high resistivity, which can effectively block high-frequency eddy currents.
[0022] 2. Good preservation of magnetic properties: The thickness of the synthesized insulating layer is 5~30 nm, the amount of non-magnetic phase introduced is extremely small, the magnetic dilution effect is small, and the high saturation magnetization and initial magnetic permeability of FeNi alloy can be preserved to the maximum extent.
[0023] 3. Low high-frequency loss: The dense SiO2 insulating layer on the surface of the alloy powder can significantly improve the interparticle resistance and greatly reduce eddy current loss. At the same time, appropriate heat treatment not only helps to release powder stress and reduce hysteresis loss, making the total loss of the material extremely low in the MHz band, but also further transforms the SiO2 gel layer into a dense insulating layer, improving the bonding strength and insulation performance.
[0024] 4. Strong process controllability: By adjusting the concentration of butyl orthosilicate, hydrolysis conditions and heat treatment temperature during the preparation process, the hydrolysis rate of butyl orthosilicate can be precisely controlled, thereby controlling the thickness, density and phase of the insulating layer. The process has good repeatability and is suitable for industrial production. Attached Figure Description
[0025] Figure 1 TEM image of the FeNi soft magnetic composite material prepared in Example 1;
[0026] Figure 2 TEM image of the FeNi soft magnetic composite material prepared in Example 2;
[0027] Figure 3 The permeability of FeNi magnetic powder cores prepared in Example 1 at different frequencies;
[0028] Figure 4 The loss performance of FeNi magnetic powder cores prepared in Example 1 at different frequencies was studied.
[0029] Figure 5 The permeability of FeNi magnetic powder cores prepared in Example 2 at different frequencies;
[0030] Figure 6 The loss performance of FeNi magnetic powder cores prepared in Example 2 at different frequencies was studied. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them.
[0032] Example 1
[0033] This embodiment provides a method for preparing FeNi soft magnetic composite material based on hydrolysis coating of tetrabutyl orthosilicate, and uses the obtained soft magnetic composite material to prepare magnetic powder cores. The specific steps are as follows:
[0034] Step 1: Take 50g of atomized Fe with a particle size D50=10 μm. 50 Ni 50 The powder was ultrasonically cleaned with acetone and ethanol and then dried to remove surface grease and oxides.
[0035] Step 2: Mix 0.05 mol TBOS with 0.3 mol anhydrous ethanol, and slowly add 0.25 mol deionized water containing 0.0025 mol ammonia water dropwise under magnetic stirring. Then stir continuously at room temperature for 2 hours to form SiO2 precursor sol.
[0036] Step 3: Clean and dry the Fe 50 Ni 50 The powder was dispersed in 100 mL of ethanol, and the SiO2 precursor sol was slowly added dropwise while stirring. The mixture was then subjected to a hydrolysis-condensation reaction in a 40°C water bath for 4 hours, allowing the SiO2 gel to coat the Fe... 50 Ni 50 Powder surface.
[0037] Step 4: After standing and aging for 12 hours, centrifuge to separate the powder and dry it in an oven at 80°C for 6 hours.
[0038] Step 5: Place the powder in a tube furnace, raise the temperature to 500°C at 5°C / min under an Ar atmosphere, hold for 1 hour, and then cool with the furnace to transform the SiO2 gel layer into a dense insulating layer, thus obtaining a soft magnetic composite material. Figure 1 As shown, in Fe 50 Ni 50A uniform and continuous SiO2 insulating layer with a thickness of about 9.5 nm was formed on the powder surface.
[0039] Step 6: Mix the cooled powder with 0.3 wt% silicone resin until homogeneous and dry. Then press it into a toroidal magnetic core with an outer diameter of 12.7 mm and an inner diameter of 7.6 mm under a pressure of 1500 MPa. Anneal it at 650°C for 1 hour in a pure H2 atmosphere and cool it in the furnace to obtain the magnetic powder core.
[0040] Example 2
[0041] This embodiment provides a method for preparing FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating. Based on Example 1, the amount of TBOS is increased to make Fe... 50 Ni 50 The powder surface was coated with SiO2 containing 1.0 wt%, and then placed in a tube furnace and held at 450°C for 1 hour. Figure 2 As shown, after increasing the amount of TBOS, Fe 50 Ni 50 The thickness of the SiO2 insulating layer on the powder surface has increased to about 15 nm.
[0042] Finally, the obtained soft magnetic composite material was used to prepare magnetic powder cores.
[0043] Example 3
[0044] This embodiment provides a method for preparing FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating. Building upon Example 1, hydrochloric acid is used as a catalyst for the hydrolysis-condensation reaction, and the pH of the reaction system is adjusted to approximately 3. The separated powder is placed in a tube furnace and held at 550°C for 1 hour. Finally, the obtained soft magnetic composite material is used to prepare magnetic powder cores.
[0045] Figure 3 The magnetic permeability of the magnetic powder core prepared in Example 1 at different frequencies shows that the permeability remains almost constant with increasing frequency, maintaining around 100 μm. e The above describes the change in magnetic loss under a 50 mT test condition. Figure 4 As shown, the core loss (Pcv) is also below 1000 mW / cm at 1MHz. 3 .
[0046] Figure 5 , 6 The permeability and loss values of the magnetic powder core prepared in Example 2 are shown in the test conditions of 10mT. The permeability remains above 100 at 3MHz, and the loss of the magnetic core is less than 250 kw / m under the test conditions of 10mT and 3MHz. 3Therefore, the soft magnetic composite material proposed in this invention has excellent comprehensive soft magnetic properties, which are significantly better than existing methods, especially in maintaining stable performance at high frequencies. It can be applied in power inductors, transformers or EMI filters in the MHz band.
Claims
1. A FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating, characterized in that: The soft magnetic composite material comprises FeNi particles and a dense SiO2 insulating layer coating the FeNi particles, wherein the mass fraction of the SiO2 insulating layer is 0.2~1.5wt%; the effective permeability μ of this material at a frequency of 1MHz is... e Above 100, under test conditions of 1MHz and 50mT, the core loss does not exceed 1000mW / cm. 3 .
2. A method for preparing FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating, characterized in that: To prepare a SiO2 precursor sol, butyl orthosilicate was mixed with anhydrous ethanol and deionized water containing a catalyst. FeNi alloy powder was weighed and dispersed in ethanol solvent to obtain a FeNi alloy powder suspension. The SiO2 precursor sol was slowly added dropwise to the FeNi alloy powder suspension, and the temperature was controlled at 30~60℃. A hydrolysis-condensation reaction was carried out under catalytic conditions to coat the FeNi powder surface with SiO2 gel. After static aging and solid-liquid separation, the powder was dried at low temperature and then heat-treated to transform the SiO2 gel layer into a dense insulating layer, thus obtaining the FeNi soft magnetic composite material. The mass fraction of the SiO2 insulating layer was 0.2~1.5 wt%.
3. The preparation method of FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 2, characterized in that: The molar ratio of TBOS, anhydrous ethanol, deionized water and catalyst is 1:(4~8):(4~6):(0.01~0.1).
4. The preparation method of FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 2, characterized in that: The volume ratio of ethanol to water in the ethanol solvent is (2~4):
1.
5. The preparation method of FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 2, characterized in that: The mass fraction of the SiO2 insulating layer is 0.5~1.0 wt%. The mass fraction of the SiO2 insulating layer is controlled by adjusting the proportion of TBOS in the SiO2 precursor sol.
6. The preparation method of FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 2, characterized in that: The heat treatment temperature is set to 450~550℃.
7. An application of a FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating, characterized in that: The FeNi soft magnetic composite material based on hydrolyzed butyl orthosilicate as described in claim 1, or the FeNi soft magnetic composite material based on hydrolyzed butyl orthosilicate prepared by any of the methods in claims 2 to 6, is used to prepare MHz band power inductors, transformers, or EMI filters.
8. The application of the FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 7, characterized in that: The FeNi soft magnetic composite material is mixed with an organic insulating binder, then pressed into a magnetic core of the desired shape under high pressure, and annealed in a protective atmosphere.
9. The application of the FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 8, characterized in that: The organic insulating binder is silicone resin or epoxy resin, and the amount added does not exceed 0.5 wt% of the total mass of the FeNi soft magnetic composite material.
10. The application of the FeNi soft magnetic composite material based on butyl orthosilicate hydrolysis coating as described in claim 8, characterized in that: The annealing temperature is 600~800℃.