A Ferrous-Based Soft Magnetic Composite Material and Its Preparation Method

Abstract

This invention belongs to the field of soft magnetic composite material technology, specifically relating to an iron-based soft magnetic composite material and its preparation method. The preparation method of an iron-based soft magnetic composite material includes the following steps: 1) reacting phosphoric acid aqueous solution with iron powder to obtain modified iron powder; 2) mixing the modified iron powder with zirconium oxide gel and calcining to obtain the iron-based soft magnetic composite material. This application obtains a core-shell structured soft magnetic composite material of phosphate-nano zirconium dioxide bilayer coated iron powder through a sol-gel method and subsequent heat treatment. Simultaneously, by adjusting the amount of zirconium dioxide added and the subsequent heat treatment process, eddy current loss is effectively reduced, and a significant increase in magnetic loss is effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic composite materials technology, specifically relating to an iron-based soft magnetic composite material and its preparation method. Background Technology

[0002] In recent years, the demand for high-performance iron-based soft magnetic composite materials has been gradually increasing. These materials can be used in automotive stators and rotors to effectively improve motor efficiency. Among these materials, iron phosphide powder exhibits excellent performance and is therefore widely used. However, research shows that the phosphide insulating layer decomposes at temperatures above 500°C, failing to block the annular eddy currents within the device and deteriorating the performance of the magnetic powder core. Therefore, oxide-based inorganic coating materials with high resistivity and higher heat resistance have attracted researchers' attention. ZrO2, as a novel metal oxide coating material, has seen relatively few reports on soft magnetic composite materials, but it also possesses high heat resistance and resistivity due to the strong Zr-O atom covalent bonds between Zr and O atoms. Therefore, SiO2 and ZrO2 can serve as excellent phosphate substitutes. Motors made from uncoated Fe powder experience significant eddy current losses at high frequencies, generating substantial heat, causing unnecessary energy loss, and reducing magnetic properties, thus lowering motor efficiency. The large eddy current losses caused by soft magnetic composite materials coated with a single SiO2, ZrO2 and phosphating insulating layer will still limit the application of motors. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an iron-based soft magnetic composite material and its preparation method to solve the problems in the prior art.

[0004] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0005] One objective of this invention is to provide a method for preparing an iron-based soft magnetic composite material, comprising the following steps:

[0006] 1) Modified iron powder is obtained by reacting phosphoric acid aqueous solution with iron powder;

[0007] 2) The modified iron powder is mixed with zirconium oxide gel and calcined to obtain the iron-based soft magnetic composite material.

[0008] Preferably, the concentration of the phosphoric acid aqueous solution is 0.1–0.5 wt%.

[0009] Preferably, the mass-to-volume ratio of the iron powder to the phosphoric acid aqueous solution is (1-5) g: 1 mL.

[0010] Preferably, the reaction temperature is 50–100°C; the reaction continues until all water has evaporated.

[0011] Preferably, the iron powder is selected from water-atomized iron powder, with a purity >99.7%, a particle size of 50μm to 200μm, and a loose packing density of 2.5 to 3.0 g / cm³. 3 .

[0012] Preferably, the mass ratio of the modified iron powder to the zirconium oxide gel is (10-50):1.

[0013] Preferably, the calcination temperature is 600–900°C.

[0014] Preferably, the calcination time is 60 to 120 minutes.

[0015] Preferably, the zirconium oxide gel is prepared by reacting ammonia water with an aqueous solution of zirconium oxychloride and sintering to obtain the zirconium oxide gel.

[0016] More preferably, the aqueous solution of zirconium oxychloride is prepared by stirring and mixing zirconium oxychloride and water at 50-100°C for 1-4 hours.

[0017] More preferably, the concentration of the aqueous solution of zirconium oxychloride is 0.2 to 3 mol / L.

[0018] More preferably, the reaction temperature is 50–90°C.

[0019] More preferably, the reaction time is 1 to 6 hours.

[0020] More preferably, the reaction is carried out under magnetic stirring.

[0021] More preferably, the reaction is cooled to room temperature afterward.

[0022] More preferably, the sintering temperature is 400–800°C.

[0023] More preferably, the sintering time is 30 to 120 minutes.

[0024] More preferably, the sintering is carried out in a protective atmosphere. Specifically, the protective atmosphere is argon.

[0025] More preferably, the sintering process further includes cooling to room temperature.

[0026] More preferably, the mass-to-volume ratio of zirconium oxychloride to ammonia is (1-10) g:mL.

[0027] The second objective of this invention is to provide an iron-based soft magnetic composite material prepared by the preparation method described above.

[0028] Preferably, the iron-based soft magnetic composite material comprises iron powder and zirconium dioxide; based on the total mass of the iron-based soft magnetic composite material, the mass percentage of zirconium dioxide is 0.5% to 4%.

[0029] In this application, the zirconium dioxide content cannot be too high or too low. If it is too high or too low, the resulting iron-based soft magnetic composite material will have low magnetic loss, which is not ideal.

[0030] Preferably, the amplitude permeability of the iron-based soft magnetic composite material is 40-90, and the specific total loss is 0.1-20 W / kg.

[0031] This application uses a phosphate passivation solution to directly react with iron powder, generating a uniform and dense phosphate insulating coating layer on the iron powder surface through an in-situ method to form modified iron powder. Zirconia gel-coated modified iron powder is then prepared using a sol-gel method and heat treatment, ultimately yielding an iron-based composite soft magnetic material. The iron-based soft magnetic composite material of this invention has a core-shell structure, with an inner phosphate coating layer exhibiting high resistivity and an outer zirconia coating layer.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The iron particles used in the method of this application are water-atomized pure iron powder, which is inexpensive. At the same time, the cost of phosphating solution is also very low, and the reagents used in the preparation of zirconium oxide gel are also inexpensive.

[0034] 2) The preparation method of this application is simple, easy to operate, and requires less skill from the operator.

[0035] 3) By adding an appropriate amount of zirconium dioxide, this application can obtain a phosphate-nano zirconium dioxide double-layer coated iron-based soft magnetic composite material with a core-shell structure. This material has the advantages of low magnetic loss and less decrease in magnetic permeability. Attached Figure Description

[0036] Figure 1 The diagram shown is a process flow chart of the preparation method of the present invention.

[0037] Figure 2 The amplitude permeability U of the iron-based soft magnetic composite materials obtained in Examples 2-5 of this application is shown. a and the total loss P s picture.

[0038] Figure 3 The figure shows the saturation magnetization M of the iron-based soft magnetic composite materials obtained in Examples 2-5 of this application. s picture.

[0039] Figure 4The image shown is a cross-sectional metallographic image of the iron-based soft magnetic composite material obtained in Example 5 of this application after being treated at 400°C for 30 min and then further treated at 450°C, 500°C, 550°C and 600°C for 30 min respectively.

[0040] in, Figure 4 The figures in the figures are as follows: (a) cross-sectional metallographic image of iron-based soft magnetic composite material after heat treatment at 450℃ for 30 min, (b) cross-sectional metallographic image of iron-based soft magnetic composite material after heat treatment at 500℃ for 30 min, (c) cross-sectional metallographic image of iron-based soft magnetic composite material after heat treatment at 550℃ for 30 min, and (d) cross-sectional metallographic image of iron-based soft magnetic composite material after heat treatment at 600℃ for 30 min.

[0041] Figure 5 The image shown is a cross-sectional metallographic image of the iron-based soft magnetic composite material obtained in Examples 2-5 of this application.

[0042] in, Figure 5 The icons in the accompanying drawings are as follows: 1 corresponds to Embodiment 2, 2 corresponds to Embodiment 3, 3 corresponds to Embodiment 4, and 4 corresponds to Embodiment 5.

[0043] Figure 6 The images shown are SEM images and energy dispersive spectroscopy (EDS) analyses of the modified iron powder used as a comparative example in this application.

[0044] in, Figure 6 The attached figures are as follows: (a) SEM image of Fe powder; (b) SEM image of modified iron powder; (c) Energy dispersive spectroscopy (EDS) analysis of modified iron powder. Detailed Implementation

[0045] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0046] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0047] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0048] In this embodiment, a soft magnetic AC measuring instrument (model MATS-2010SA / 500K) from Hunan Lianzhong Technology Co., Ltd. is used to measure the amplitude permeability U of the iron-based soft magnetic composite material. a and the total loss P s Before measurement, the appropriate range of coil turns N1 and N2 was calculated using the turns calculation formula provided with the testing instrument. Suitable turns were selected: N1 = 120, N2 = 100. The testing conditions used were H... m = 35000 and 10000 are two maximum magnetic field strengths.

[0049] In this embodiment, the atomized iron powder used is commercially available ordinary water-atomized pure iron powder. The water-atomized iron powder has a purity of 99.8%, a particle size of 150 μm, and a loose packing density of 2.8 g / cm³. 3 .

[0050] In this application, the process flow diagram for the preparation of iron-based soft magnetic composite materials is detailed in [reference needed]. Figure 1 .

[0051] Example 1

[0052] In this embodiment, the preparation of zirconia gel includes the following steps:

[0053] 1) In a three-necked flask, add 13g of zirconium oxychloride and 70mL of water, stir magnetically at 75℃ for 2h, and cool to room temperature to obtain an aqueous solution of zirconium oxychloride.

[0054] 2) Add 5 mL of ammonia water dropwise to the above-mentioned zirconium oxychloride aqueous solution, and continue to stir magnetically at 75 °C for 2 h. Cool to room temperature to obtain ZrO2 sol.

[0055] 3) Weigh 3g of ZrO2 sol, put it into a U-shaped quartz tube and place it in a muffle furnace. Sinter at 600℃ for 60min under an Ar protective atmosphere, and cool to room temperature to obtain zirconia gel.

[0056] Example 2

[0057] In this embodiment, the zirconia gel obtained in Example 1 is used to prepare the iron-based soft magnetic composite material, including the following steps:

[0058] 1) Mix 30g of iron powder with 15mL of 0.2wt% phosphoric acid aqueous solution, react and stir in an 80℃ constant temperature water bath until the water evaporates completely, and then dry in a vacuum oven to obtain modified iron powder.

[0059] 2) Stir 10g of modified iron powder with 0.1g of zirconia gel for 30min, then dry in a vacuum oven at 100℃ for 1h, and then calcine in a muffle furnace at 600℃ for 60min under argon protection to obtain iron-based soft magnetic composite material.

[0060] In this embodiment, the mass fraction of zirconium oxide is 1% based on the total mass of the iron-based soft magnetic composite material.

[0061] Example 3

[0062] In this embodiment, the zirconia gel obtained in Example 1 is used to prepare the iron-based soft magnetic composite material, including the following steps:

[0063] 1) Mix 30g of iron powder with 15mL of 0.2wt% phosphoric acid aqueous solution, react and stir in an 80℃ constant temperature water bath until the water evaporates completely, and then dry in a vacuum oven to obtain modified iron powder.

[0064] 2) Stir 10g of modified iron powder with 0.2g of zirconia gel for 30min, then dry in a vacuum oven at 100℃ for 1h, and then calcine in a muffle furnace at 600℃ for 60min under argon protection to obtain iron-based soft magnetic composite material.

[0065] In this embodiment of the application, the mass fraction of zirconium oxide is 2% based on the total mass of the iron-based soft magnetic composite material.

[0066] Example 4

[0067] In this embodiment, the zirconia gel obtained in Example 1 is used to prepare the iron-based soft magnetic composite material, including the following steps:

[0068] 1) Mix 30g of iron powder with 15mL of 0.2wt% phosphoric acid aqueous solution, react and stir in an 80℃ constant temperature water bath until the water evaporates completely, and then dry in a vacuum oven to obtain modified iron powder.

[0069] 2) Stir 10g of modified iron powder with 0.3g of zirconia gel for 30min, then dry in a vacuum oven at 100℃ for 1h, and then calcine in a muffle furnace at 600℃ for 60min under argon protection to obtain iron-based soft magnetic composite material.

[0070] In this embodiment, the mass fraction of zirconium oxide is 3% based on the total mass of the iron-based soft magnetic composite material.

[0071] Example 5

[0072] In this embodiment, the zirconia gel obtained in Example 1 is used to prepare the iron-based soft magnetic composite material, including the following steps:

[0073] 1) Mix 30g of iron powder with 15mL of 0.2wt% phosphoric acid aqueous solution, react and stir in an 80℃ constant temperature water bath until the water evaporates completely, and then dry in a vacuum oven to obtain modified iron powder.

[0074] 2) Stir 10g of modified iron powder with 0.4g of zirconia gel for 30min, then dry in a vacuum oven at 100℃ for 1h, and then calcine in a muffle furnace at 600℃ for 60min under argon protection to obtain iron-based soft magnetic composite material.

[0075] In this embodiment of the application, the mass fraction of zirconium oxide is 4% based on the total mass of the iron-based soft magnetic composite material.

[0076] Comparative Example

[0077] In this embodiment, the preparation of modified iron powder includes the following steps:

[0078] 1) Mix 60g of iron powder with 15mL of 0.2wt% phosphoric acid aqueous solution, react and stir in an 80℃ constant temperature water bath until the water evaporates completely, and then dry in a vacuum oven to obtain modified iron powder.

[0079] Modified iron powder and zinc stearate were mixed evenly at a mass ratio of 100:0.5 and then pressed into a composite material with an outer diameter of 20 mm, an inner diameter of 12 mm, and a height of about 3.4 mm under a pressure of 800 MPa for 180 s. The composite material was then tested.

[0080] Figure 2 The diagrams show the amplitude permeability Ua and specific total loss Ps of the iron-based soft magnetic composite materials prepared in Examples 2-5 at different frequencies.

[0081] Figure 3 The image shows the saturation magnetization Ms of the iron-based soft magnetic composite materials prepared in Examples 2-5.

[0082] Figure 4The cross-sectional metallographic images of the iron-based soft magnetic composite material prepared in Example 5 after being kept at 400℃ for 30 min are shown in (a) after being kept at 450℃ for 30 min, (b) after being kept at 500℃ for 30 min, (c) after being kept at 550℃ for 30 min, and (d) after being kept at 600℃ for 30 min. In Figure (d), the box indicates that the phosphate distribution on the surface of the iron powder after phosphating is uneven.

[0083] Figure 5 The images show cross-sectional metallographic images of the iron-based soft magnetic composite materials prepared in Examples 2-5. 1 corresponds to the iron-based soft magnetic composite material obtained in Example 2, 2 corresponds to the iron-based soft magnetic composite material obtained in Example 3, 3 corresponds to the iron-based soft magnetic composite material obtained in Example 4, and 4 corresponds to the iron-based soft magnetic composite material obtained in Example 5.

[0084] Figure 6 The images show the SEM images and energy dispersive spectroscopy (EDS) analysis results of the modified iron powder used as a comparative example.

[0085] from Figure 2 It can be seen that increasing the amount of ZrO2 added can effectively reduce magnetic loss.

[0086] from Figure 3 It can be seen that the addition of ZrO2 leads to a decrease in saturation magnetization, but the decrease is small when the content is below 3%.

[0087] from Figure 4 It can be seen that after phosphating, a uniform phosphate layer is formed on the surface of the iron powder in the iron-based soft magnetic composite material, which plays an insulating role.

[0088] from Figure 5 It can be seen that the addition of ZrO2 forms a uniform insulating layer on the surface of iron powder.

[0089] from Figure 6 It can be seen that an insulating phosphate coating is formed on the surface of the modified iron powder.

[0090] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing an iron-based soft magnetic composite material, characterized in that, Includes the following steps: 1) Modified iron powder is obtained by reacting phosphoric acid aqueous solution with iron powder; 2) The modified iron powder is mixed with zirconium oxide gel and calcined to obtain the iron-based soft magnetic composite material; The iron-based soft magnetic composite material has a core-shell structure, with the core being iron powder, the inner layer being a phosphate coating layer, and the outer layer being a zirconium dioxide coating layer; Based on the total mass of the iron-based soft magnetic composite material, the mass percentage of zirconium dioxide is 1-4%.

2. The preparation method according to claim 1, characterized in that, The concentration of the phosphoric acid aqueous solution is 0.1–0.5 wt%. And / or, the mass-to-volume ratio of the iron powder to the phosphoric acid aqueous solution is (1-5) g: 1 mL; And / or, the reaction temperature is 50 ~ 100°C; the reaction continues until all water has evaporated; And / or, the iron powder is selected from water-atomized iron powder, with a purity >99.7%, a particle size of 50μm to 200μm, and a loose packing density of 2.5 to 3.0 g / cm³. 3 .

3. The preparation method according to claim 1, characterized in that, The calcination temperature is 600–900°C; And / or, the calcination time is 60 to 120 minutes.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the modified iron powder to the zirconium oxide gel is (10-50):

1.

5. The preparation method according to claim 1, characterized in that, The method for preparing the zirconia gel is as follows: Ammonia water is reacted with an aqueous solution of zirconium oxychloride, and then sintered to obtain the zirconium oxychloride gel.

6. The preparation method according to claim 5, characterized in that, The reaction temperature for the reaction between the ammonia water and the aqueous solution of zirconium oxychloride is 50–90°C. And / or, the reaction time of the ammonia water and the aqueous solution of zirconium oxychloride is 1 to 6 hours; And / or, the sintering temperature is 400–800°C; And / or, the sintering time is 30 to 120 minutes; And / or, the sintering is carried out in a protective atmosphere.

7. The preparation method according to claim 5, characterized in that, The concentration of the aqueous solution of zirconium oxychloride is 0.2–3 mol / L; And / or, the mass-to-volume ratio of zirconium oxychloride to ammonia is (1-10) g: 1 mL.

8. The iron-based soft magnetic composite material prepared by the preparation method according to any one of claims 1-7.

9. The iron-based soft magnetic composite material according to claim 8, characterized in that, The amplitude permeability of the iron-based soft magnetic composite material is 40–90, and the specific total loss is 0.1–20 W / kg.

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