Magnetic material

Abstract

This magnetic material comprises magnetic nanoparticles (10) and a low-carbon organic substance (20) having 4 or less carbon atoms. The low-carbon organic substance (20) comprises C, N, O, and H, and has a structure having an amide bond. The magnetic nanoparticles (10) are each formed of Fe, an Fe-containing alloy material, or an Fe-containing compound. The magnetic nanoparticles (10) each have a mean particle diameter of 20-200 nm when being calculated as a ball having the same volume, and have a volume fraction of 80-95 vol%.

Description

magnetic material CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Patent Application No. 2024-117825, filed on July 23, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to magnetic materials having magnetic nanoparticles and low carbon number organic matter.

[0003] In recent years, carbon dioxide (CO ２ In order to reduce power consumption, the electrification of various devices is being promoted. These devices use, for example, powder magnetic cores and permanent magnets obtained by pressure molding magnetic materials using magnetic nanoparticles. In order to improve the performance of these types of devices, it is effective to increase the density of magnetic nanoparticles in the magnetic bodies obtained by processing the magnetic materials.

[0004] For example, Patent Document 1 describes a powder magnetic core using a magnetic material containing magnetic nanoparticles with an average particle size of 1 to 300 nm and saturated fatty acid having 12 or 20 to 30 carbon atoms.

[0005] Patent No. 7332283

[0006] The magnetic material described in Patent Document 1 has saturated fatty acids with at least 12 carbon atoms and long molecular chains, and these saturated fatty acids occupy a considerable volume, so there is a limit to how much the volume fraction of magnetic nanoparticles can be increased, and there is still room for improvement.

[0007] The present disclosure relates to magnetic materials that can be densified by increasing the volume fraction of magnetic nanoparticles.

[0008] According to one aspect of the present disclosure, a magnetic material comprises magnetic nanoparticles and a low-carbon organic substance containing four or less carbon atoms.

[0009] This magnetic material is composed of magnetic nanoparticles and a low-carbon organic substance containing four or less carbon atoms, and has a higher volume fraction of magnetic nanoparticles than conventional materials. Therefore, by using this magnetic material, it is possible to obtain a molded body with a higher density than conventional materials.

[0010] FIG. 1 is a diagram showing a magnetic material according to an embodiment; FIG. 2 is an explanatory diagram of the manufacture of a magnetic material and the processing of a magnetic core; FIG. 3 is a flowchart showing the manufacturing process of a magnetic core using the magnetic material according to an embodiment; FIG. 4 is a diagram showing the analysis results of magnetic nanoparticles coated with a polymer material by time-of-flight secondary ion mass spectrometry (TOF-SIMS), illustrating the detected cations; FIG. 5 is a diagram showing the analysis results of magnetic nanoparticles after a polymer decomposition treatment, illustrating the detected cations; FIG. 6 is a diagram showing the analysis results of magnetic nanoparticles after a polymer decomposition treatment, illustrating the detected anions; and FIG. 7 is a diagram showing the measurement results of the volume density and saturation magnetization of magnetic cores using magnetic nanoparticles with different coating types.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

[0012] (Embodiment) A magnetic material 1 according to an embodiment will be described.

[0013] The magnetic material 1 of this embodiment comprises magnetic nanoparticles 10 and a low-carbon organic substance 20, as shown in Fig. 1 for example. As shown in Fig. 2 for example, the magnetic material 1 is obtained by adding and dispersing a polymer material 30 to the magnetic nanoparticles 10, coating the magnetic nanoparticles 10 with the polymer material 30, and then decomposing the polymer material 30 to form the low-carbon organic substance 20. The magnetic material 1 can be produced, for example, by pressure molding, to produce a magnetic body 2 that is a high-density molded body having a filling rate of the magnetic nanoparticles 10 equal to or higher than a predetermined level. Examples of the magnetic body 2 include a powder magnetic core.

[0014] The magnetic nanoparticles 10 are magnetic particles composed of, for example, Fe (iron), Fe-containing alloy materials, or Fe-containing compounds, with diameters on the order of nanometers. Examples of Fe-containing alloy materials include, but are not limited to, FeCo alloy materials containing Co (cobalt) in addition to Fe, and FeNi alloy materials containing Ni (nickel). Other known Fe alloy materials may also be used. Furthermore, the Fe-containing alloy material may be composed of, for example, one type of alloy material, or multiple types of alloy materials. Examples of Fe-containing compounds include oxides and nitrides of Fe and Fe-containing alloy materials.

[0015] The magnetic nanoparticles 10 may be, for example, commercially available Fe-containing alloy nanoparticles with an average particle diameter in the range of 20 nm to 200 nm. The average particle diameter of the magnetic nanoparticles 10 can be calculated, for example, by the following method. First, the diameter distribution of magnetic nanoparticles 10 dispersed in a solvent such as ethanol is measured using a dynamic light scattering particle size distribution analyzer when converted into spheres of the same volume. As the particle size distribution analyzer, for example, a Zetasizer (ZEN1600) manufactured by Malvern can be used. Then, the average particle diameter, which is the average value of the diameters, is calculated based on the diameter distribution of the magnetic nanoparticles 10 obtained by the measurement.

[0016] If the average particle diameter is less than 20 nm, the volume fraction of the magnetic nanoparticles 10 in the magnetic material 1 decreases relatively, making it difficult to improve the filling rate of the magnetic nanoparticles 10 in the magnetic body 2. On the other hand, if the average particle diameter exceeds 200 nm, the effect of the low-carbon organic matter 20 on the magnetic nanoparticles 10 becomes relatively small, and it is thought that the filling rate of the magnetic nanoparticles 10 in the magnetic body 2 will be about the same as when a magnetic material coated with a polymer material 30 is used. Note that there are no particular restrictions on the shape of the magnetic nanoparticles 10, as long as the average particle diameter is within the above range.

[0017] The low-carbon organic material 20 is an organic material that is composed of C, N, O, and H and has a structure with an amide bond, and that covers the magnetic nanoparticles 10. The low-carbon organic material 20 contains four or fewer carbon atoms. The low-carbon organic material 20 can be obtained, for example, by covering the magnetic nanoparticles 10 with a polymer material 30 such as a nitrogen-containing polyvinyl polymer, and then performing a decomposition process. Note that the polymer material 30 used to form the low-carbon organic material 20 only needs to have molecular chains that are sufficient to ensure the dispersibility of the magnetic nanoparticles 10 in the manufacturing process described below, and the number of carbon atoms is at least four, but there is no particular upper limit to the number of carbon atoms.

[0018] The magnetic material 1 has a volume fraction of magnetic nanoparticles 10 of 80 vol% or more and 95 vol% or less, and it is possible to form a high-density magnetic body 2 compared to conventional magnetic materials, for example, in which magnetic nanoparticles are coated with a polymer material having 10 or more carbon atoms.

[0019] [Manufacturing Method] Next, a manufacturing method for the magnetic material 1 and the magnetic body 2 will be described.

[0020] As shown in FIG. 3, the magnetic material 1 is manufactured through two steps: coating the magnetic nanoparticles 10 with the polymer material 30 in step S10, and decomposing the polymer material 30 in step S11.

[0021] In step S10, first, magnetic nanoparticles 10 having an average particle size in the range of 20 nm to 200 nm and a polymer material 30 of an N-containing vinyl polymer are prepared. Then, for example, the magnetic nanoparticles 10 and the polymer material 30 are dispersed and dissolved in a solvent at a desired ratio, mixed, and then the solvent is dried and removed, and the magnetic nanoparticles 10 can be coated with the polymer material 30.

[0022] Specifically, magnetic nanoparticles 10 and 10 wt % to 50 wt % of polymer material 30 relative to the weight of the magnetic nanoparticles 10 are prepared. These materials are then added to an organic solvent such as ethanol while applying ultrasonic waves, and dispersed and dissolved. The organic solvent is used in an amount of, for example, 80 mL / g relative to the weight of the magnetic nanoparticles 10. The magnetic nanoparticles 10 are then recovered from the organic solvent by magnetic separation using a magnet or precipitation using a centrifuge. The recovered magnetic nanoparticles 10 are then re-dispersed in an organic solvent such as ethanol while applying ultrasonic waves. This washes the magnetic nanoparticles 10 and removes excess polymer material 30. After recovering the magnetic nanoparticles 10 from the organic solvent using the magnetic separation or precipitation methods described above, the recovered magnetic nanoparticles 10 are dried and the organic solvent is removed. This allows the magnetic nanoparticles 10 coated with polymer material 30 to be obtained.

[0023] At this time, the polymer material 30 has a carbon number greater than 4 and a molecular chain length greater than a predetermined value, thereby ensuring the dispersibility of the magnetic nanoparticles 10. For ease of explanation, the magnetic nanoparticles 10 coated with the polymer material 30 obtained in step S10 will be referred to as "polymer-coated particles" below.

[0024] Next, in step S11, the polymer-coated particles are subjected to a heat treatment to decompose the polymer material 30. Specifically, for example, the polymer-coated particles are subjected to a heat treatment at 250°C for 5 hours while heated hydrogen gas is supplied to the polymer-coated particles, thereby decomposing the polymer material 30. This makes it possible to obtain magnetic nanoparticles 10 coated with low-carbon organic matter 20, i.e., magnetic material 1. Note that the conditions for the decomposition treatment in step S11 need only be such that the polymer material 30 can be decomposed, and can be changed as appropriate depending on the polymer material 30, such as a temperature of about 200°C to 300°C and a heating time of about several hours.

[0025] Here, the results of analysis of the magnetic nanoparticles 10 before and after the decomposition treatment in step S11 by time-of-flight secondary ion mass spectrometry (TOF-SIMS) will be described with reference to FIGS.

[0026] As shown in FIG. 4, the molecular weight of the cations detected by TOF-SIMS of the magnetic nanoparticles 10 before the decomposition treatment in step S11, i.e., the polymer-coated particles, was in the range of 15 to 138. Specifically, in the polymer-coated particles, ３ ), 23(Na), 27(C ２ H ３ ), 39(K), 41(C ３ H ５ ), 43 (C ３ H ７ ), 45 (C ２ H ５ O), 55 (C ４ H ７ ), 56 (Fe), and 58 (Ni) molecular weight cations were detected. ６０ Ni), 69(C ４ H ５ O), 73 (FeOH), 86 (C ４ H ８ In addition, a cation with a molecular weight of 98 (C ５ H ８ NO), 112 (C ６ H １０ NO), 124 (C ７ H １０ NO), 138 (C ８ H １２ Cations with a molecular weight of NO, i.e., organic ions with a carbon number of more than 4, were detected. The description in parentheses after the molecular weight indicates the composition estimated from the molecular weight. Of the detected cations, those containing metal elements are thought to originate from the magnetic nanoparticles 10, and the organic ions are thought to originate from the polymer material 30. This result suggests that the polymer-coated particles contain organic compounds with molecular chains with a carbon number of more than 4.

[0027] On the other hand, the magnetic nanoparticles 10 after the decomposition treatment in step S11, i.e., the magnetic material 1, had cation molecular weights detected by TOF-SIMS in the range of 15 to 73, as shown in Figure 5. Specifically, in the magnetic material 1, in addition to molecular weights of 15, 23, 27, 39, 41, 55, 58, 69, and 73, which are the same as those of the polymer-coated particles, there was also a cation molecular weight of 43 (C ３H ７ ), 45 (C ２ H ５ O), 56 (Fe), 60 ( ６０ In the magnetic material 1, since no organic cations with a carbon number of more than 4 were detected by TOF-SIMS, it is presumed that the polymer material 30 has been decomposed and that the magnetic material 1 contains low-carbon organic matter 20.

[0028] In addition, as shown in FIG. 6, in the magnetic material 1, 13(CH), 16(O), 19(F), 26(CN), 32(O) were detected by TOF-SIMS. ２ ), 35 (Cl), 42 (CNO), 45 (CHO ２ In magnetic material 1, anions with a molecular weight of 60 (SiO ２ ), 77(SiO ３ H), 88(FeO ２ ), 91(NiO ２ Anions with a molecular weight of 1H were also detected, which are thought to be derived from the magnetic nanoparticles 10. According to the results of TOF-SIMS, the magnetic material 1 is thought to be in a state of having the magnetic nanoparticles 10 and a low-carbon organic substance 20 consisting of C, N, O, and H, with a total carbon number of 4 or less, and a structure having an amide bond.

[0029] Next, in step S12, for example, the magnetic material 1 obtained in step S11 is filled into a mold (not shown), heated, and pressure-molded. This makes it possible to manufacture a magnetic body 2 densely packed with magnetic nanoparticles 10. The pressure-molding in step S12 can be performed, for example, in a vacuum atmosphere of 30 Pa or less, at a temperature of 250 to 400°C (or higher than 250°C), and at a pressure of 500 MPa to 1.5 GPa.

[0030] It may seem possible to obtain magnetic nanoparticles 10 coated with low-carbon organic material 20 by performing a process similar to step S10 using magnetic nanoparticles 10 and low-carbon organic material 20. However, in this case, the molecular chain of the low-carbon organic material 20 is short, making it difficult to ensure the dispersibility of the magnetic nanoparticles 10. As a result of intensive research by the present inventors, it was found that if magnetic nanoparticles 10 are coated with polymer material 30 and then the polymer material 30 is decomposed to convert it into low-carbon organic material 20, the dispersibility of the magnetic nanoparticles 10 is maintained and the density of the magnetic body 2 can be increased. The magnetic material 1 and high-density magnetic body 2 were obtained through the above process.

[0031] Here, the filling rate and saturation magnetization were evaluated for magnetic body 2 obtained using magnetic material 1, a magnetic body obtained using only magnetic nanoparticles 10, and a magnetic body obtained using polymer-coated particles, and the results shown in Figure 7 were obtained.

[0032] In the column for the type of coating in Fig. 7, "none" corresponds to the case where only magnetic nanoparticles 10 were used, "polymer" corresponds to the case where polymer-coated particles were used, and "low-carbon organic matter" corresponds to the case where magnetic material 1 was used. The filling rate shown in Fig. 7 is a value obtained by taking the total amount of material used in the pressure molding as 100%, measuring the mass and volume of the magnetic body after pressure molding, and calculating the proportion of the volume occupied by the magnetic nanoparticles 10. The saturation magnetization (unit: T) was measured using Versalab, a small-sized refrigerant-free PPMS (registered trademark) manufactured by Quantum Design Co., Ltd. ＴＭ The value was obtained by measuring the temperature.

[0033] The magnetic material obtained using only magnetic nanoparticles 10 had a filling rate of 91.7% and a saturation magnetization of 1.38 T. Note that the magnetic material obtained using only magnetic nanoparticles 10 has low mechanical strength because it does not contain a binder to bond the magnetic nanoparticles 10 together.

[0034] The magnetic material obtained using polymer-coated particles has higher mechanical strength than that obtained without coating because the polymer material 30 functions as a binder, but the filling rate was 85.1% and the saturation magnetization was 1.28 T, which was low.

[0035] In contrast, magnetic body 2 had a filling rate of 87.0% and a saturation magnetization of 1.31 T, which were improved in filling rate and saturation magnetization compared to the magnetic body made of polymer-coated particles. This is thought to be because in magnetic material 1, in which magnetic nanoparticles 10 are covered with low-carbon organic matter 20, the volume fraction of magnetic nanoparticles 10 is greater than that of polymer-coated particles.

[0036] The magnetic material 1 of this embodiment comprises magnetic nanoparticles 10 and a low-carbon organic substance 20 containing 4 or less carbon atoms, and has an improved volume ratio of the magnetic nanoparticles 10 compared to conventional materials. Therefore, by using the magnetic material 1, it is possible to manufacture a magnetic body 2, which is a high-density molded body with an improved filling rate of the magnetic nanoparticles 10.

[0037] The magnetic material 1 also has the following characteristics: (1) The low-carbon organic material 20 is composed of C, N, O, and H and has a structure with an amide bond. (2) The magnetic nanoparticles 10 are composed of Fe, an Fe-containing alloy material, or an Fe-containing compound. (3) The magnetic nanoparticles 10 have an average particle diameter of 20 nm or more and 200 nm or less when converted into spheres of the same volume. (4) The volume fraction of the magnetic nanoparticles 10 is 80 vol% or more and 95 vol% or less.

[0038] (Other Embodiments) While the present disclosure has been described with reference to examples, it is understood that the present disclosure is not limited to those examples or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one, or less than one, are also within the scope and spirit of the present disclosure.

[0039] It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, values, amounts, and ranges of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle.

[0040] (Aspects of the Present Disclosure) The above-described present disclosure can be understood from the following perspectives, for example. [First Aspect] A magnetic material comprising magnetic nanoparticles (10) and a low-carbon organic material (20) containing 4 or less carbon atoms. [Second Aspect] The magnetic material according to the first aspect, wherein the low-carbon organic material is composed of C, N, O, and H and has a structure having an amide bond. [Third Aspect] The magnetic material according to the first or second aspect, wherein the magnetic nanoparticles are composed of Fe, an Fe-containing alloy material, or an Fe-containing compound. [Fourth Aspect] The magnetic material according to any one of the first to third aspects, wherein the magnetic nanoparticles have an average particle diameter of 20 nm or more and 200 nm or less when converted into spheres of the same volume. [Fifth Aspect] The magnetic material according to any one of the first to fourth aspects, wherein the volume fraction of the magnetic nanoparticles is 80 vol% or more and 95 vol% or less.

Claims

1. A magnetic material comprising magnetic nanoparticles (10) and a low-carbon organic substance (20) containing 4 or less carbon atoms.

2. The magnetic material according to claim 1, wherein the low-carbon organic substance is composed of C, N, O, and H and has an amide bond structure.

3. The magnetic material of claim 1, wherein the magnetic nanoparticles are composed of Fe, an Fe-containing alloy material, or an Fe-containing compound.

4. The magnetic material according to claim 1, wherein the magnetic nanoparticles have an average particle diameter of 20 nm or more and 200 nm or less when converted into spheres of the same volume.

5. The magnetic material according to any one of claims 1 to 4, wherein the volume fraction of the magnetic nanoparticles is 80 vol % or more and 95 vol % or less.

Images