Preparation method of soft magnetic composite material and soft magnetic composite material

Abstract

This application is applicable to the field of material technology, and provides a preparation method of a soft magnetic composite material and the soft magnetic composite material, including: adding ammonia water to an aqueous and / or alcoholic solution of carbonyl iron powder for sufficient mixing to obtain a pretreated carbonyl iron powder solution; uniformly mixing zirconium butoxide with an alcohol solvent, and then adding the mixture to the pretreated carbonyl iron powder solution for sufficient reaction, followed by filtration, washing, and drying to obtain the product. After the soft magnetic composite material obtained in this application is sintered at 250 °C and tested by a vibrating sample magnetometer, the saturation magnetic induction intensity decreases by 5.58%, while the saturation magnetic induction intensity of the uncoated carbonyl iron powder decreases by 41.13% before and after sintering. Therefore, the carbonyl iron powder coated with zirconia obtained in this application can effectively reduce the decrease in magnetic properties caused by high-temperature oxidation of carbonyl iron powder, improve the high-temperature performance of the soft magnetic material, and is of crucial significance to the application field of future high-temperature soft magnetic composite materials.

Description

Technical Field

[0001] This application belongs to the field of material technology, and particularly relates to a preparation method of a soft magnetic composite material and a soft magnetic composite material. Background Art

[0002] Carbonyl iron powder has a special onion-like structure and features such as high saturation magnetic induction intensity, relatively high magnetic permeability, and high Curie temperature. Therefore, it is widely used in fields such as aerospace and civil applications. However, carbonyl iron powder has a low resistivity and is extremely prone to oxidation above 170 °C, resulting in large eddy current losses when used under high-frequency conditions and a serious decline in magnetic properties when used above 170 °C.

[0003] Currently, there is relatively little research on high-temperature resistant and corrosion-resistant soft magnetic materials in the field of soft magnetic composite materials at home and abroad. Zirconium dioxide is the main oxide of zirconium, with a high melting point and boiling point, a low thermal conductivity coefficient, and features such as good chemical properties and strong corrosion resistance. There have been many studies on compounding zirconium dioxide with other functional materials to improve the high-temperature resistance of raw materials. Therefore, zirconium dioxide can be used to coat the surface of carbonyl iron powder. However, precisely because zirconium dioxide itself has strong chemical stability, it is relatively difficult to directly coat it. Therefore, most scholars first coat a transition layer on the surface of iron powder and then perform the coating of zirconium dioxide.

[0004] However, the current existing technology for coating the surface of carbonyl iron powder with zirconium dioxide mainly involves first preparing acidic zirconium dioxide sol and then directly stirring and coating it by heating, resulting in a problem that the volume fraction of the strong magnetic substance carbonyl iron powder obtained is small and cannot meet the usage requirements. Summary of the Invention

[0005] The purpose of the embodiments of this application is to provide a preparation method of a soft magnetic composite material, aiming to solve the problem that the volume fraction of the strong magnetic substance carbonyl iron powder obtained by the existing technology for coating the surface of carbonyl iron powder with zirconium dioxide is small and cannot meet the usage requirements.

[0006] The embodiments of this application are implemented as follows. A preparation method of a soft magnetic composite material includes:

[0007] Adding ammonia water to an aqueous and / or alcohol solution of carbonyl iron powder for thorough mixing to obtain a pretreated carbonyl iron powder solution;

[0008] After uniformly mixing zirconium n-butoxide with an alcohol solvent, adding it to the pretreated carbonyl iron powder solution for thorough reaction, and then performing filtration, washing, and drying treatments, the product is obtained.

[0009] Another purpose of the embodiments of this application is a soft magnetic composite material, which is prepared by the preparation method of the soft magnetic composite material described above.

[0010] The preparation method of the soft magnetic composite material provided by the embodiment of the present application utilizes the hydrolysis of zirconium butoxide. The generated zirconium dioxide will carry hydroxyl bonds, which will bond with the hydroxyl bonds on the surface of the carbonyl iron powder after surface pretreatment. Through the mechanism of bond bonding, a uniform zirconium dioxide coating layer is formed on the surface of the carbonyl iron powder. After the obtained soft magnetic composite material is sintered at 250 °C and tested by a vibrating sample magnetometer, the saturation magnetic induction intensity decreases by 5.58%. While for the uncoated carbonyl iron powder, the saturation magnetic induction intensity decreases by 41.13% before and after sintering. Therefore, the carbonyl iron powder coated with zirconium dioxide obtained in this application can effectively reduce the decrease in magnetic properties caused by the high-temperature oxidation of carbonyl iron powder, improve the high-temperature performance of soft magnetic materials, and is of crucial significance for the application fields of future high-temperature soft magnetic composite materials. Description of the Drawings

[0011] Figure 1 is the microscopic morphology diagram of the soft magnetic composite material provided by the embodiment of the present application;

[0012] Figure 2 is the M-H diagram of the carbonyl iron powder without zirconium dioxide coating before and after sintering provided by the embodiment of the present application;

[0013] Figure 3 is the M-H diagram of the soft magnetic composite material before and after sintering provided by the embodiment of the present application;

[0014] Figure 4 is the XRD diagram of the soft magnetic composite material provided by the embodiment of the present application. Detailed Embodiments

[0015] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0016] Currently, the hydrolysis method of zirconium alcohol or zirconium salt is often used to prepare zirconium dioxide. Since the most prominent problem in the process of coating zirconium dioxide is that the hydrolysis rate of zirconium salt or zirconium alcohol is too fast, it can be observed in the experiment that the rapid whitening of the solution color is caused by a large number of self-nucleated zirconium dioxide particles generated due to the too fast hydrolysis rate of the zirconium source. The uncontrollable hydrolysis rate leads to serious aggregation between particles. The prior art directly stirs and coats by first preparing acidic zirconium dioxide sol and then heating, resulting in the acidic corrosion of iron powder, the destruction of the original structure, and the reduction of the volume fraction of the ferromagnetic substance carbonyl iron powder.

[0017] In the embodiments of the present application, through the development of coating modification research on carbonyl iron powder-based soft magnetic composites, a preparation method of soft magnetic composites with a controllable reaction rate and excellent performance capable of withstanding temperatures above 200 °C has been developed. By utilizing the hydrolysis of zirconium butoxide, the generated zirconium dioxide will carry hydroxyl bonds, which will bond with the hydroxyl bonds on the surface of the carbonyl iron powder after surface pretreatment. Through the mechanism of bond-bonding, a uniform zirconium dioxide coating layer is formed on the surface of the carbonyl iron powder. After the obtained soft magnetic composites are sintered at 250 °C and tested with a vibrating sample magnetometer, the saturation magnetic induction intensity decreases by 5.58%, while the saturation magnetic induction intensity of the uncoated carbonyl iron powder decreases by 41.13% before and after sintering. Therefore, the carbonyl iron powder coated with zirconium dioxide obtained in the present application can effectively reduce the decrease in magnetic properties caused by high-temperature oxidation of carbonyl iron powder and improve the high-temperature performance of soft magnetic materials, which is of crucial significance for the application fields of future high-temperature soft magnetic composites.

[0018] The embodiments of the present application provide a preparation method of soft magnetic composites, including the following steps:

[0019] Step S1: Add ammonia water to the water and / or alcohol solution of carbonyl iron powder and mix well to obtain a pretreated carbonyl iron powder solution.

[0020] In the embodiments of the present application, the carbonyl iron powder is ultrafine metallic iron powder prepared by the carbonyl method, with an average particle size of 1 - 10 μm.

[0021] In the embodiments of the present application, the water and / or alcohol solution of carbonyl iron powder is a mixed solution of carbonyl iron powder and deionized water, or a mixed solution of carbonyl iron powder and alcohol solvent, or a mixed solution of carbonyl iron powder and water and alcohol solvent.

[0022] In the embodiments of the present application, the concentration of carbonyl iron powder in the water and / or alcohol solution of carbonyl iron powder is 1%. There is a ratio between the water ratio and the zirconium butoxide solution because water is a reactant in the hydrolysis reaction of zirconium butoxide. Therefore, the content of water affects the severity of the hydrolysis reaction of zirconium butoxide, etc.

[0023] In the embodiments of the present application, the volume ratio of the water / alcohol solution of carbonyl iron powder to ammonia water is 5%. The addition ratio of ammonia water in carbonyl iron powder will affect the surface groups of carbonyl iron powder. A pretreatment process is carried out on carbonyl iron powder under weak base conditions, and hydroxyl groups are generated on the surface, which is beneficial for subsequent coating; the optimal ratio of ammonia water is PH = 8 - 8.5 in the mixed solution of carbonyl iron powder, water, and ethanol.

[0024] Step S2: After uniformly mixing zirconium butoxide with an alcohol solvent, add it to the pretreated carbonyl iron powder solution and react fully. After filtration, washing, and drying, the product is obtained.

[0025] In the embodiment of the present application, the volume ratio of zirconium butoxide to the alcohol solvent is 5%. The ratio of carbonyl iron powder to zirconium butoxide determines the thickness of the zirconia coating on the surface of the carbonyl iron powder. The more zirconium butoxide, the thicker the zirconia coating.

[0026] In the embodiment of the present application, the alcohol solvent can only be ethanol and cannot be replaced by other alcohol solvents.

[0027] In the embodiment of the present application, step S2 includes:

[0028] After uniformly mixing zirconium butoxide with the alcohol solvent, it is dropped into the pretreated carbonyl iron powder solution for continuous reaction for 1 to 12 hours. After filtration and washing with absolute ethanol, it is dried at a temperature of 80°C for 5 hours to obtain the product.

[0029] In the embodiment of the present application, if the reaction time exceeds 12 hours, the alcohol and water will evaporate, causing the reaction ratio to change, thereby affecting the material preparation.

[0030] The embodiment of the present application also provides a soft magnetic composite material, which is prepared by the preparation method of the above soft magnetic composite material.

[0031] The following gives examples of certain embodiments of the present application, and the purpose is not to limit the scope of the present application.

[0032] In addition, it should be noted that the values given in the following examples are as accurate as possible. However, those skilled in the art understand that due to inevitable measurement errors and experimental operation problems, each number should be understood as an approximate number rather than an absolutely accurate value.

[0033] Example 1

[0034] (1) Mix 1 g of carbonyl iron powder with 100 mL of absolute ethanol, then add 5 mL of ammonia water and 0.1 mL of deionized water, and stir well with a stirrer to obtain a mixed solution;

[0035] (2) Uniformly mix 0.5 mL of zirconium butoxide in 10 ml of absolute ethanol, and then use a constant pressure separating funnel to drop it into the uniformly mixed solution in step (1). The continuous reaction time is 24 hours. After filtration and washing with absolute ethanol, it is dried in an 80°C drying oven for 5 hours to obtain a high-temperature corrosion-resistant Fe@ZrO2 soft magnetic composite material.

[0036] Example 2

[0037] (1) Mix 1 g of carbonyl iron powder with 100 mL of absolute ethanol, then add 5 ml of ammonia water and 0.1 mL of deionized water, and stir well with a stirrer to obtain a mixed solution;

[0038] (2) Mix 1 mL of zirconium butoxide evenly in 20 mL of absolute ethanol, and then use a constant-pressure separating funnel to drip it into the evenly mixed solution in step (1). Keep reacting for 24 hours. After filtration and washing with absolute ethanol, dry it in an 80 °C drying oven for 5 hours to obtain a high-temperature resistant and corrosion-resistant Fe@ZrO2 soft magnetic composite material.

[0039] Example 3

[0040] (1) Mix 1 g of carbonyl iron powder with 100 mL of absolute ethanol, add 5 mL of ammonia water and 0.1 mL of deionized water, and use a stirrer to fully stir to obtain a mixed solution;

[0041] (2) Mix 1.5 mL of zirconium butoxide evenly in 30 mL of absolute ethanol, and then use a constant-pressure separating funnel to drip it into the evenly mixed solution in step (1). Keep reacting for 24 hours. After filtration and washing with absolute ethanol, dry it in an 80 °C drying oven for 5 hours to obtain a high-temperature resistant and corrosion-resistant Fe@ZrO2 soft magnetic composite material.

[0042] Comparative Example 1

[0043] Soft magnetic material without zirconia coating (carbonyl iron powder purchased from BASF, Germany)

[0044] Perform a scanning electron microscope test on the high-temperature resistant and corrosion-resistant Fe@ZrO2 soft magnetic composite material prepared in Example 2. The morphology of the obtained material is as Figure 1 shown.

[0045] Perform an XRD test on the high-temperature resistant and corrosion-resistant Fe@ZrO2 soft magnetic composite material prepared in Example 2. The results are as Figure 4 shown.

[0046] First perform a vibrating sample magnetometer test on the high-temperature resistant and corrosion-resistant Fe@ZrO2 soft magnetic composite material prepared in Example 2 and the soft magnetic material without zirconia coating in Comparative Example 1. Then sinter them in a tube furnace at 250 °C for 3 h and perform a vibrating sample magnetometer test again. The test results are shown in Table 1 below and Figures 2-3 shown, where Figure 2 is the M-H diagram of the soft magnetic material without zirconia coating in Comparative Example 1 before and after sintering; Figure 3 is the M-H diagram of the high-temperature resistant and corrosion-resistant Fe@ZrO2 soft magnetic composite material prepared in Example 2 before and after sintering.

[0047] Table 1 Main performance indicators of Example 2 and Comparative Example 1 before and after sintering

[0048]

[0049]

[0050] In summary, as can be seen from Table 1, after sintering at 250 °C and tested by VSM, the saturation magnetic induction intensity of the soft magnetic material of carbonyl iron powder without zirconia coating decreased by 41.13%, while that of the Fe@ZrO2 soft magnetic composite with zirconia coating decreased by 5.58%. Therefore, coating carbonyl iron powder with zirconia can effectively reduce the decrease in magnetic properties caused by high-temperature corrosion and oxidation of carbonyl iron powder, and improve the high-temperature magnetic stability of carbonyl iron powder.

[0051] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

[0052] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a soft magnetic composite material, characterized in that, Comprising: Adding ammonia water into an aqueous and / or alcoholic solution of carbonyl iron powder and mixing thoroughly to obtain a pretreated carbonyl iron powder solution; After uniformly mixing zirconium butoxide with an alcohol solvent, dropping it into the pretreated carbonyl iron powder solution and carrying out a continuous reaction for 1 to 48 hours, filtering, washing with absolute ethanol, and then drying at a temperature of 50 to 80 °C for 2 to 10 hours to obtain the product; The volume ratio of zirconium butoxide to the alcohol solvent is 1% to 20%.

2. The preparation method of the soft magnetic composite material according to claim 1, characterized in that, The particle size of the carbonyl iron powder is 1 to 10 μm.

3. The method for preparing the soft magnetic composite material according to claim 1, characterized in that, The volume ratio of the carbonyl iron powder in the aqueous and / or alcoholic solution of carbonyl iron powder is 1% to 10%.

4. The method for preparing the soft magnetic composite material according to claim 1, characterized in that, The volume ratio of the aqueous / alcoholic solution of carbonyl iron powder to ammonia water is 1% to 10%.

5. The method for preparing a soft magnetic composite material according to claim 1, wherein The alcohol solvent is ethanol.

6. A soft magnetic composite material, characterized in that, The soft magnetic composite material is prepared by the preparation method of the soft magnetic composite material according to any one of claims 1-5.

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