Magnet, method for producing same, and magnetic powder contained in same

Abstract

This invention provides a magnet having excellent magnetic characteristics, a method for producing same, and magnetic powder contained in same. The present invention relates to a magnet containing a magnetically oriented granulated product of a flat magnetic powder, and a non-flat magnetic powder having an average particle diameter larger than that of the granulated product.

Description

Magnet, its manufacturing method, and magnetic powder contained therein

[0001] The present invention relates to magnets, methods for their manufacture, and magnetic powders contained therein.

[0002] Patent Document 1 discloses a bonded magnet containing non-flat magnetic powder and flat magnetic powder. By applying pressure that breaks down the flat magnetic powder, the rearrangement of the magnetic powder is promoted, thereby improving density.

[0003] Japanese Patent Application Laid-Open No. 2017-22192

[0004] In the bonded magnet disclosed in Patent Document 1, the flat magnetic particles are not magnetically oriented, which may prevent improvement of the magnetic properties.

[0005] The present disclosure aims to provide a magnet with excellent magnetic properties, a method for producing the same, and the magnetic powder contained therein.

[0006] A magnet according to one embodiment of the present disclosure relates to a magnet including magnetically oriented granules of flat magnetic powder and non-flat magnetic powder having an average particle size larger than that of the granules.

[0007] A magnet manufacturing method according to one embodiment of the present disclosure relates to a magnet manufacturing method including: a molding step of mixing flat magnetic powder with a granulation resin and molding the mixture while magnetically aligning the mixture to obtain a molded body; a granulation step of granulating the molded body to obtain a magnetically oriented granulated product of the flat magnetic powder; and a magnet molding step of molding the granulated product with non-flat magnetic powder having an average particle size larger than that of the granulated product to obtain a magnet.

[0008] A magnetic powder according to one embodiment of the present disclosure relates to a magnetic powder including magnetically oriented granules of flat magnetic powder and non-flat magnetic powder having an average particle size larger than that of the granules.

[0009] According to the present disclosure, the flat magnetic powder is magnetically oriented without agglomeration, making it possible to provide a magnet with excellent magnetic properties.

[0010] FIG. 1 is an image diagram of a magnet including magnetically oriented granules of flat magnetic powder according to one embodiment of the present disclosure, and non-flat magnetic powder having an average particle size larger than that of the granules. FIG. 2 is a flowchart of a method for manufacturing a magnet according to one embodiment of the present disclosure. FIG. 3 is a flowchart of a method for manufacturing a magnet according to one embodiment as a comparative example. FIG. 4 is a flowchart of a method for manufacturing a magnet according to another embodiment as a comparative example. FIG. 5 is an SEM photograph of a mixture of non-flat magnetic powder and flat magnetic powder used to manufacture the magnets in Comparative Example 1 and Example 1, and an SEM photograph of the manufactured magnet.

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are examples for embodying the technical concept of the present invention, and the present invention is not limited to the following. Furthermore, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, in the following embodiments, parts that are identical or equivalent to each other will be described using the same reference numerals.

[0012] <<Magnet>> The magnet 6 of this embodiment is characterized by including magnetically oriented granules 3 of flat magnetic powder 2, and non-flat magnetic powder 1 having an average particle size larger than that of the granules 3. When the flat magnetic powder 2 is mixed directly with the non-flat magnetic powder 1, the flat magnetic powders 2 aggregate together, and when a magnet 6 is made from such a mixture of magnetic powders, the aggregated flat magnetic powder 2 does not increase the density and the magnetic orientation is not uniform, so the magnet does not exhibit sufficient magnetic properties. Even if the flat magnetic powder 2 does not aggregate, when a magnet 6 is made from such a mixture of magnetic powders, the flat magnetic powder 2 is oriented parallel to the surface of the non-flat magnetic powder 1, which has a larger average particle size, so the flat magnetic powder 2 as a whole is not magnetically oriented and does not exhibit sufficient magnetic properties.

[0013] To solve this new problem, the magnet 6 of this embodiment uses a granulated material 3 in which the individual flat magnetic powder particles 2 are magnetically oriented within the granulated material 3. Because the multiple granulated materials 3 are also oriented in the magnetization direction, the magnet 6 has high density and excellent magnetic properties. Figure 1 shows an image of the magnet 6 of this embodiment. The arrows in the figure indicate the magnetization direction of the magnetic powder.

[0014] The flat magnetic powder 2 is a magnetic powder having a flat shape, and preferably has an aspect ratio of 4.0 or more, and more preferably 6.0 or more considering the coercive force distribution of the magnetic powder. The upper limit of the aspect ratio is not particularly limited, but may be 100 or less. The reason why an aspect ratio of 4.0 or more is preferable will be described later. The average particle size of the flat magnetic powder 2 is preferably 30 nm or more and 1000 nm or less, and more preferably 50 nm or more and 500 nm or less considering that the flat magnetic powder (granulated material) is disposed between (in gaps between) multiple non-flat magnetic particles. Here, the average particle size can be determined from a scanning electron microscope (SEM) image.

[0015] The aspect ratio of the flat magnetic powder 2 is the value obtained by dividing the major axis length by the minor axis length. The major axis length refers to the average value of the longest length of the surface (flat plane) with the largest area of ​​the flat magnetic powder 2. The minor axis length refers to the average value of the longest thickness of the length (thickness) between the two flat planes of the flat magnetic powder 2. The average particle size of the flat magnetic powder 2 refers to the above-mentioned major axis length.

[0016] The shapes of the multiple flat magnetic powder particles 2 shown in the SEM image are all different. From these, flat magnetic powder particles 2 are selected that make it easy to determine the longest length on the flat surface. For example, 100 flat magnetic powder particles 2 are selected. Then, the longest lengths of these particles are measured and the average value is calculated. In this way, the major axis length (average particle size) can be determined. The standard deviation of the measured values ​​for the major axis lengths of the 100 flat magnetic powder particles 2 can be evaluated as the measurement error of the major axis length.

[0017] From the multiple flat magnetic powders 2 of various shapes shown in the SEM image, select a flat magnetic powder 2 that is easy to measure the longest thickness between two flat surfaces. In the same manner as for the major axis length, for example, 100 flat magnetic powders 2 are selected. Then, the longest thicknesses of these are measured and the average value is calculated. In this way, the minor axis length is determined. The standard deviation of the measured thicknesses of the 100 flat magnetic powders 2 can be evaluated as the thickness measurement error. Of course, there is no particular limit to the number of flat magnetic powders 2 selected, but it is preferable to measure at least 30 or more.

[0018] As described above, flat magnetic powder 2 suitable for measuring the major axis length and minor axis length is selected. Therefore, the flat magnetic powder 2 whose major axis length is measured differs from the flat magnetic powder 2 whose minor axis length is measured, and the objects for measuring the major axis length and minor axis length are different. However, as described above, 100 pieces of flat magnetic powder 2 are selected for measuring the major axis length and minor axis length. The average values ​​of the major axis length and minor axis length are calculated. Therefore, although the objects for measuring the major axis length and minor axis length are different, it is thought that the influence of the difference in the objects for measurement on the calculated major axis length and minor axis length is small.

[0019] The flat magnetic powder 2 may be a nanoparticle magnetic powder. ０ Among them, FeNi magnetic powder and ferrite magnetic powder having an average particle size of L1 ０ An FeNi magnetic powder having the structure is preferred.

[0020] The magnetically oriented granulated product 3 of the flat magnetic powder 2 is obtained, for example, by molding the flat magnetic powder 2 while magnetically aligning it, and then granulating the resulting molded product by pulverization or the like, and is an aggregate of a plurality of flat magnetic powders 2. It is preferable that the individual flat magnetic powders 2 contained in the granulated product 3 are magnetically oriented in the same direction.

[0021] The magnetically oriented granules 3 of the flat magnetic powder 2 preferably contain a granulation resin 5 to fix the flat magnetic powder 2 in the granulation 3. As the granulation resin 5, not only thermoplastic resins but also thermosetting resins can be used. Examples of thermoplastic resins include nylon, polyester, and polyphenylene sulfide. Examples of thermosetting resins include epoxy resin and phenolic resin. The content of the granulation resin 5 is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the flat magnetic powder, and more preferably 2 parts by mass or more and 10 parts by mass or less from the viewpoint of improving the shape retention and density of the molded body.

[0022] The average particle size of the magnetically oriented granules 3 of the flat magnetic powder 2 is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.2 μm or more and 0.5 μm or less from the viewpoint of improving density. The average particle size of the granules can be measured using a scanning electron microscope, a particle size distribution measuring instrument, or the like.

[0023] The coercive force HcJ (T) of the flat magnetic powder 2 is calculated by the following formula: (HcJ-J Ａ / 3) / J Ｂ -N ａ >0 (in the formula, J Ａ is the magnetization (T) of the non-flat magnetic powder, and J Ｂ is the magnetization (T) of the flat magnetic powder, Na is the demagnetizing factor, and is expressed by the following formula: where m is the aspect ratio of the flat magnetic powder. ) is preferably satisfied. By using a flat magnetic powder 2 that satisfies this formula, a magnet 6 with high magnetic properties can be produced. Here, (HcJ - J Ａ / 3) / J Ｂ is preferably 0.15 or more, and more preferably 0.20 or more in consideration of the coercive force distribution of the magnetic powder.

[0024] (HcJ-J Ａ / 3) / J Ｂ -N ａ The value of (HcJ-J Ａ / 3) / J Ｂ was varied from 0.10 to 0.50 in increments of 0.05, and the aspect ratio of the flat magnetic powder 2 was varied from 1 to 100, and (HcJ-J Ａ / 3) / J Ｂ -N ａ The calculation results are shown in Tables 1 and 2. In Tables 1 and 2, the shaded cells indicate (HcJ-J Ａ / 3) / J Ｂ -N ａ The value of HcJ is a negative value and is excluded. Ａ / 3) / J Ｂ -N ａ If the value is 0 or more, it becomes a magnet. For example, J Ａ 1.42T, J Ｂ If HcJ is 1.50T and HcJ is 0.70T, then (HcJ-J Ａ / 3) / JＢ In this case, it is clear from Table 2 that the aspect ratio is preferably 4.0 or more.

[0025]

[0026]

[0027] In the magnet 6 of this embodiment, from the viewpoint of magnetic properties, it is preferable that the granulated particles 3 of the flat magnetic powder 2 are magnetically oriented.

[0028] In the magnet 6 of this embodiment, in the XRD pattern of the plane perpendicular to the easy axis of magnetization, the hard axis peak of the flat magnetic powder 2 is preferably 1% or less of the main peak, and more preferably 0.5% or less from the viewpoint of improving magnetic properties. ０ In the case of an FeNi magnetic powder having a structure, the (111) peak corresponds to this. When magnetic orientation occurs, the (111) peak disappears. This value can be used to evaluate the magnetic orientation of the flat magnetic powder and the magnetic orientation of the granulated product 3.

[0029] The non-flat magnetic powder 1 is a magnetic powder that is not flat in shape. The aspect ratio is preferably 1.5 or less, more preferably 1.3 or less from the viewpoint of ease of moldability, and even more preferably 1.2 or less. The average particle size of the non-flat magnetic powder 1 is not particularly limited as long as it is larger than the average particle size of the magnetically oriented granules 3 of the flat magnetic powder 2, but is preferably 1.0 μm or more and 10.0 μm or less, and more preferably 1.5 μm or more and 5.0 μm or less considering that the granules 3 are arranged between multiple non-flat magnetic powders 1. Here, the average particle size of the non-flat magnetic powder 1 can be determined from a scanning electron microscope (SEM) image.

[0030] The shapes of the multiple non-flat magnetic powder particles 1 shown in the SEM image vary. From among these, non-flat magnetic powder particles 1 that are nearly spherical are selected. For example, 100 non-flat magnetic powder particles 1 are selected. Then, their diameters are measured and the average value is calculated. In this way, the average diameter value can be determined. The standard deviation of the measured diameters of the 100 non-flat magnetic powder particles 1 can be evaluated as the diameter measurement error.

[0031] The non-flat magnetic powder 1 may be a rare earth magnetic powder or an AlNiCo magnetic powder. The rare earth magnetic powder may be an SmFeN magnetic powder, an NdFeB magnetic powder, an NdFeN magnetic powder, an SmCo magnetic powder, or the like. The flat magnetic powder 2 may be an L1 ０ When using FeNi magnetic powder having the structure, SmFeN magnetic powder is preferable because it has a temperature coefficient close to that of FeNi and is inexpensive at the time of filing this application. SmFeN magnetic powder can be manufactured by a known manufacturing method such as that described in JP 2022-2247 A.

[0032] The content of the magnetically oriented granules 3 of the flat magnetic powder 2 is preferably 0.1 parts by mass or more and 50 parts by mass or less per 100 parts by mass of non-flat magnetic powder having an average particle size larger than that of the granules 3, and more preferably 4 parts by mass or more and 20 parts by mass or less, considering that the granules 3 are disposed between a plurality of non-flat magnetic powders 1. If the content exceeds 20 parts by mass, voids tend to form and the density tends to decrease, and if the content is less than 0.1 parts by mass, it tends to be difficult to obtain the effect of improving density.

[0033] The magnet 6 of this embodiment may be a sintered magnet or a bonded magnet. In the case of a bonded magnet, the magnet of this embodiment includes a molding resin 4. The molding resin 4 may be a thermosetting resin, not just a thermoplastic resin. Examples of thermoplastic resins include nylon, polyester, polyphenylene sulfide, and polyphenylene sulfide. Examples of thermosetting resins include epoxy resin and phenolic resin. The molding resin 4 may be the same as or different from the granulation resin 5 described above. However, if both the granulation resin 5 and the molding resin 4 are thermoplastic resins, the melting point or glass transition temperature of the molding resin 4 is preferably lower than the melting point or glass transition temperature of the granulation resin 5 so that the granulation resin 5 does not flow in the magnet molding step S3. If the granulation resin 5 is a thermoplastic resin and the molding resin 4 is a thermosetting resin, the thermosetting temperature of the molding resin 4 is preferably lower than the melting point (or glass transition temperature) of the granulation resin 5 so that the granulation resin 5 does not flow in the magnet molding step S3.

[0034] When molding resin 4 is included, the content of molding resin 4 is preferably 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the total of flat magnetic powder 2 and non-flat magnetic powder 1, and more preferably 1 part by mass or more and 10 parts by mass or less from the viewpoint of improving shape retention and density.

[0035] <<Magnet Manufacturing Method>> The magnet manufacturing method of this embodiment is characterized by including: a molding step S1 in which flat magnetic powder 2 and granulation resin 5 are mixed and molded while being magnetically oriented to obtain a molded body; a granulation step S2 in which the molded body is granulated to obtain a magnetically oriented granulated product 3 of the flat magnetic powder 2; and a magnet molding step S3 in which the granulated product 3 is molded with non-flat magnetic powder 1 having an average particle size larger than that of the granulated product 3 to obtain a magnet 6.

[0036] Figure 2 shows a flowchart of a method for manufacturing magnet 6 of this embodiment. Figures 3 and 4 show flowcharts of a comparative example of a magnet manufacturing method. In the comparative example, flat magnetic powder 2 and non-flat magnetic powder 1 are mixed as is, so the molding step S1 and granulation step S2 in Figure 2 do not exist. Figure 3 shows a state in which flat magnetic powder 2 is not aggregated, and Figure 4 shows a state in which flat magnetic powder 2 is aggregated.

[0037] In the molding step S1, the flat magnetic powder 2 and the granulation resin 5 are mixed and molded while being magnetically oriented to obtain a molded body. The shape of the molded body is not particularly limited. The flat magnetic powder 2, the granulation resin 5, and the blending amounts of the granulation resin 5 are as described above. The method for mixing the flat magnetic powder 2 and the granulation resin 5 is not particularly limited, and methods such as a ball mill can be used. The molding method for the mixture is not particularly limited as long as it can be molded while being magnetically oriented, and examples include hand pressing, rolling with a roller compactor, injection molding, and compression molding. In the molding step S1, if a thermoplastic resin is used, the mixture must be heated to a temperature above the melting point (or glass transition temperature) of the thermoplastic resin. If a thermosetting resin is used, the mixture must be heated to thermoset. The heating temperature can be set appropriately depending on the characteristics of the respective resins. Magnetic field orientation can be performed using a permanent magnet or an electromagnetic coil. When applying a large magnetic field using an electromagnetic coil, it is preferable to shorten the current flow time to the millisecond level and apply the magnetic field multiple times (pulse magnetic field) to suppress coil heat generation.

[0038] In the granulation step S2, the compact obtained in the molding step S1 is granulated to obtain granules 3 of a predetermined average particle size in which the flat magnetic powder 2 is magnetically oriented. The granulation method is not particularly limited, and a pulverization method such as a planetary mill, jet mill, ball mill, roller mill, pin mill, or bead mill can be used.

[0039] The magnet molding step S3 preferably comprises a magnetic powder mixing step S31 and a magnetic field molding step S32. In the magnetic powder mixing step S31, when a sintered magnet is obtained, granulated material 3 and non-flat magnetic powder 1 are mixed, whereas when a bonded magnet is obtained, granulated material 3, non-flat magnetic powder 1, and molding resin 4 are mixed. Because magnetically oriented granulated material 3 of flat magnetic powder 2 is used, the resulting mixture does not aggregate significantly, allowing granulated material 3 to be positioned between the non-flat magnetic powder. In the magnetic field molding step S32, the mixture is molded while a magnetic field is applied. The molding method is not particularly limited, but examples include hand pressing and rolling with a roller compactor. Heating is performed as necessary during molding. On the other hand, when a bonded magnet is obtained, molding can be performed using methods such as injection molding and compression molding.

[0040] <<Magnetic Powder>> The magnetic powder of the present invention is characterized by comprising magnetically oriented granules 3 of flat magnetic powder 2, and non-flat magnetic powder 1 having an average particle size larger than that of the granules 3. The magnetic powder can contain a molding resin 4, and a bonded magnet can be produced from the magnetic powder.

[0041] The present disclosure will be explained in more detail with reference to the following examples, but the present disclosure is not limited to these examples in any way.

[0042] The chemicals used in the examples are as follows: Flat magnetic powder (L1 ０ FeNi magnetic powder having the structure (prepared in Production Example 1) Average particle size: 0.1 μm, aspect ratio m: 50, magnetization J Ｂ : 1.4T, Coercive force HcJ: 0.5T Non-flat magnetic powder (SmFeN magnetic powder, manufactured by Nichia Chemical Co., Ltd.) Average particle size: 3μm, Aspect ratio m: 1.2, Magnetization J Ａ : 1.3T, coercive force HcJ: 1.5T Granulation resin (epoxy resin, F-6975 manufactured by Somar Co., Ltd.) Molding resin (epoxy resin, F-6975 manufactured by Somar Co., Ltd.)

[0043] Production Example 1 (1) (Synthesis of FeNi Magnetic Powder) The precursor material, FeNiN, can be synthesized using techniques already known or well-known at the time of filing this application. For example, techniques described in Patent Document 1 and Japanese Patent No. 6627818 can be used. Specifically, FeNiN can be synthesized by nitriding FeNi disordered alloy powder produced by, for example, a thermal plasma method, a flame spray method, or a coprecipitation method. Alternatively, FeNiN can be obtained by reducing and nitriding FeNi oxide. The FeNi oxide used in the reduction step may contain Fe oxide or Ni oxide, or may contain an oxide containing Fe and Ni.

[0044] The Fe oxide is not particularly limited, but examples thereof include FeO, Fe ２ O ３ , Fe ３ O ４ Examples of the oxide include oxides obtained by oxidizing raw materials such as metallic iron, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron bromide, iron sulfate, iron nitrate, iron phosphate, and iron oxalate. Examples of Ni oxide include, but are not limited to, NiO. Examples of the oxide include oxides obtained by oxidizing raw materials such as metallic nickel, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel bromide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate. An oxide containing Fe and Ni can be produced by mixing a solution containing Fe and Ni with a precipitant to obtain a precipitate containing Fe and Ni (precipitation step), and then heat-treating the precipitate to obtain an oxide containing Fe and Ni (oxidation step). This method makes it easy to control the average particle size and particle size distribution of the resulting Fe and Ni oxide, and tends to produce a uniform distribution of Fe and Ni in the Fe and Ni oxide.

[0045] The Fe raw material and the Ni raw material are not limited as long as they can be dissolved in an acidic solution. Examples of Fe raw materials include metallic iron, iron oxide, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron sulfate, iron nitrate, iron phosphate, and iron oxalate. Examples of Ni raw materials include metallic nickel, nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate. Examples of acidic solutions include sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid. The concentration of the solution containing Fe and Ni can be appropriately adjusted within a range in which the Fe raw material and the Ni raw material are substantially soluble in the acidic solution. The reaction between the solution containing Fe and Ni and a precipitant may be carried out by adding the precipitant to the solution containing Fe and Ni, or by adding the solution containing Fe and Ni to the precipitant. Furthermore, the solution containing Fe and Ni referred to here may be any solution containing Fe and Ni upon reaction with the precipitant. Alternatively, raw materials containing Fe and Ni may be prepared as separate solutions, and each solution may be added to react with the precipitant. Even when prepared as separate solutions, the contents of each raw material are appropriately adjusted so that they substantially dissolve in the acidic solution. The precipitant is not limited as long as it reacts with the solution containing Fe and Ni to produce a precipitate, and examples thereof include oxalic acid and alkaline solutions such as aqueous sodium hydroxide, aqueous sodium bicarbonate, aqueous potassium hydroxide, and aqueous lithium hydroxide. Furthermore, a precipitate can be obtained by blowing carbon dioxide gas into the solution containing Fe and Ni. Examples of precipitates that can be produced include oxalates, carbonates, and hydroxides. Specifically, FeNiN can be obtained by air-sintering, hydrogen-reducing, and nitriding iron-nickel oxalate powder.

[0046] (2) Coarse Pulverization As a method for coarsely pulverizing FeNiN, a general pulverization method such as a ball mill can be used.

[0047] (3) Flattening Flattening can be easily performed using, but is not limited to, mechanical shearing force. For example, it can be performed by subjecting a slurry containing FeNiN particles to a wet bead mill. Specifically, a slurry is prepared by dispersing coarsely pulverized FeNiN particles in a solvent containing a surfactant. Surfactants that have good coating properties on the FeNiN particles can be used. Examples of surfactants include nitrogen-containing surfactants such as oleylamine and trioctylamine, sulfur-containing surfactants such as octanethiol and triazinedithiol, and polymer surfactants such as polyvinyl alcohol, polyacrylic acid, polyethyleneimine, and polyvinylpyrrolidone. A liquid that can stably disperse FeNiN particles coated with a surfactant can be used as the solvent. Examples include pure water, alcohols such as ethanol and isopropyl alcohol, and nonpolar solvents such as toluene and cyclohexane. In the actual flattening treatment, a slurry containing 5 wt % FeNiN particles in ethanol was placed in a bead mill (e.g., Fritsch Planetary Ball Mill, PL-7) together with zirconia media with a diameter of 0.1 mm, and treated at 600 rpm for 30 minutes.

[0048] (4) Classification: To obtain a high coercive force, small flattened FeNiN particles are extracted. Particle size classification can be performed by centrifuging the slurry. The slurry is centrifuged at 500 G for 10 minutes, 4000 G for 10 minutes, and 4000 G for 120 minutes, in that order, to precipitate the flattened FeNiN particles with larger particle size first, and then collect them.

[0049] (5) Coating The coating layer serves to decouple the magnetic coupling between multiple magnetic particles located nearby within the magnetic material. To this end, the coating layer is formed of a non-magnetic material. Furthermore, the coating layer must be a material that can be subjected to subsequent heat treatment and denitrification treatment and that does not react with the alloy particles. Materials that satisfy these requirements for the coating layer include, for example, oxides of elements from Groups III to VII and XIII to XVI, such as silica, titania, zirconia, yttria, and alumina. Alternatively, films made of insulating materials, such as nitride films, may also be used. The thickness of the insulating film that constitutes the coating layer is arbitrary, but is preferably 1 nm or greater.

[0050] In this manufacturing example, the classified flattened FeNiN particles were coated with silica (silica coat). Coating at this stage suppresses particle sintering due to subsequent heat treatment and denitrification. It also suppresses contact between alloy particles contained in the magnetic body during magnet molding. As a result, deterioration of magnetic properties is suppressed.

[0051] When silica is used as the coating layer, powder of flattened FeNiN particles is mixed with a solvent such as water or ethanol to which tetraethoxysilane has been added, and then an aqueous ammonia solution is poured in. As a result, silica is produced by hydrolysis and condensation of the tetraethoxysilane, and the flattened FeNiN particles are coated with silica. The flattened FeNiN particles are then coated with the coating layer.

[0052] (6) Heat Treatment The flattened FeNiN particles are heat-treated (annealed). This process aligns the atomic arrangement of the flattened FeNiN particles. The flattened FeNiN particles, whose atomic arrangement has been aligned by this annealing, are then denitrified. This increases the degree of ordering and coercivity of the denitrified FeNi ordered alloy. Annealing can be performed, for example, in ammonia gas. Specifically, in this example, the flattened FeNiN particles are placed in an electric furnace capable of introducing ammonia gas, and the heat treatment is performed in ammonia gas. The ambient temperature can be set to 300 to 450°C, and the treatment time can be set to 4 to 48 hours. Since the flattened FeNiN particles may contain sulfur as an impurity or additive, optimal treatment conditions vary depending on the particle size and the amount of sulfur present in the raw materials. However, it is desirable to perform the annealing at a temperature lower than the nitriding temperature. This is because the stabilizing effect of sulfur on FeNiN is weakened after pulverization, making it more susceptible to decomposition at high temperatures.

[0053] (7) Denitrification The denitrification treatment can be performed using the apparatus and method described in Patent Document 1 and Japanese Patent No. 6627818. Specifically, the denitrification treatment can be performed, for example, by heat treatment in a hydrogen atmosphere. The hydrogen flow rate in the denitrification treatment can be set to 0.01 to 10 liters / min, and preferably 0.1 to 5 liters / min, per gram of flattened FeNiN particles. The heat treatment temperature can be set to, for example, 100 to 400°C, and preferably 200 to 350°C. The heat treatment time can be set to, for example, 1 to 24 hours, and preferably 2 to 10 hours.

[0054] Example 1 <Forming step S1> 100 g of the flat magnetic powder produced in Production Example 1 and 10 g of granulated resin were placed in a 1 mm diameter alumina ball container and mixed in a ball mill at a rotation speed of 50 rpm for 10 hours. 4 g of the obtained mixed powder was filled into a molding die having a cavity of 10 mm length, 10 mm width, and 50 mm height, and an upper punch was attached. The mixture was then molded at a temperature of 100 to 150°C and a pressure of 10 ton / cm using a vertical magnetic field molding machine that applies a magnetic field perpendicular to the molding axis direction. ２The mixture was compression molded for 60 seconds under a pressure of 2 T in a magnetic field, and then cured at 150° C. to 200° C. for 1 hour to harden the resin, yielding a rectangular columnar molded body.

[0055] <Granulation step S2> The compact was coarsely pulverized to a particle size of about 2 mm using a mortar, and then pulverized in a bead mill using IPA to granules having an average particle size D50 of 0.5 μm. The granules were then classified, and only the alumina balls were removed using a sieve. The average particle size D50 of the granules was measured using a particle size distribution analyzer (Partica LA-960V2, manufactured by Horiba, Ltd.).

[0056] <Magnet Molding Step S3> <<Mixing Step S31>> 100 g of non-flat magnetic powder, 10 g of granules, 5 g of molding resin, and 100 g of alumina balls were placed in a container and mixed in a ball mill at 50 rpm for 1 hour. <<Magnetic Field Molding Step S32>> 4 g of the mixed powder obtained in the mixing step was filled into a molding die having a cavity 10 mm long, 10 mm wide, and 50 mm high, and an upper punch was attached. A vertical magnetic field molding machine was used to apply a magnetic field perpendicular to the molding axis direction, and the mixture was molded at a molding temperature of 150 to 200°C and a magnetic field of 10 ton / cm. ２ The mixture was compression molded for 60 seconds under a pressure of 2 T in an applied magnetic field, and then cured at 200° C. to 250° C. for 1 hour to harden the resin, thereby obtaining a rectangular magnet.

[0057] Comparative Example 1 <Magnet Molding Step S3> <<Mixing Step S31>> 9.1 g of the flat magnetic powder produced in Production Example 1, 100 g of non-flat magnetic powder, 10 g of molding resin, and 100 g of alumina balls were placed in a container and mixed in a ball mill at 50 rpm for 1 hour, after which only the alumina balls were removed with a sieve. <<Magnetic Field Molding Step S32>> 4 g of the mixed powder obtained in the mixing step was filled into a molding die having a cavity 10 mm long, 10 mm wide, and 50 mm high, and an upper punch was attached. A magnetic field of 10 ton / cm was applied using a vertical magnetic field molding machine that applies a magnetic field perpendicular to the molding axis direction. ２ The mixture was compression molded for 60 seconds under a pressure of 2 T in an applied magnetic field to obtain a rectangular prism-shaped magnet.

[0058] The specific gravity and magnetic properties were evaluated using the magnets produced in Example 1 and Comparative Example 1. The evaluation results are shown in Table 3.

[0059]

[0060] The specific gravity of the bonded magnet of Example 1 was 6.12, confirming a 3% density improvement, compared to 5.95 for the bonded magnet of Comparative Example 1. Additionally, the residual magnetic flux density Br of the compact was 0.85 T for the bonded magnet of Comparative Example 1, while it was 1.00 T for the bonded magnet of Example 1, confirming an 18% improvement. Normally, specific gravity and residual magnetic flux density Br are proportional, but a 3% improvement in specific gravity resulted in an 18% improvement in residual magnetic flux density Br.

[0061] Table 4 also shows the results of comparing peak values ​​in the XRD patterns. In the bonded magnet of Comparative Example 1, 1.1% of the (111) random peak of FeNi was detected, whereas no peak was detected in the bonded magnet of Example 1. From the above, it can be seen that in the bonded magnet of Example 1, the magnetic orientation of FeNi improved the remanence Br more than the improvement in specific gravity.

[0062]

[0063] Figure 5 shows SEM images of the magnetic powder mixture and the produced bonded magnet. In the bonded magnet of Comparative Example 1, the flat magnetic powder aggregated and was larger in particle size than the non-flat magnetic powder. On the other hand, in the bonded magnet of Example 1, the flat magnetic powder did not aggregate and was smaller in particle size than the non-flat magnetic powder.

[0064] <Technical Ideas> This specification includes the following various technical ideas.

[0065] (Item 1) A magnet comprising magnetically oriented granules of flat magnetic powder, and non-flat magnetic powder having an average particle size larger than that of the granules.

[0066] (Item 2) The magnet according to item 1, wherein the granulated material contains a resin for granulated material.

[0067] (Item 3) The magnet according to item 1 or 2, wherein the aspect ratio m of the flat magnetic powder is 4.0 or more.

[0068] (Item 4) The magnet according to any one of Items 1 to 3, wherein the granulated materials are magnetically oriented to each other.

[0069] (Item 5) The coercive force HcJ (T) of the flat magnetic powder is expressed by the following formula (HcJ-J Ａ / 3) / J Ｂ -N ａ >0 (in the formula, J Ａ is the magnetization (T) of the non-flat magnetic powder, and J Ｂ is the magnetization (T) of the flat magnetic powder, Na is the demagnetizing factor, and is expressed by the following formula: 5. The magnet according to any one of items 1 to 4, which satisfies the above condition:

[0070] (Item 6) A magnet according to any one of Items 1 to 5, wherein the non-flat magnetic powder is a rare earth magnetic powder or a ferrite magnetic powder, and the flat magnetic powder is a nanoparticle magnetic powder.

[0071] (Item 7) The magnet according to Item 6, wherein in an XRD pattern in a plane perpendicular to the axis of easy magnetization, the peak of the axis of hard magnetization of the flat magnetic powder is 1% or less of the main peak.

[0072] (Item 8) The magnet according to any one of Items 1 to 7, which contains a molding resin.

[0073] (Item 9) A method for manufacturing a magnet, comprising: a molding step of mixing flat magnetic powder with a granulation resin and molding the mixture while magnetically aligning the mixture to obtain a molded body; a granulation step of granulating the molded body to obtain a granulated product of the flat magnetic powder oriented in a magnetic field; and a magnet molding step of molding the granulated product with non-flat magnetic powder having an average particle size larger than that of the granulated product to obtain a magnet.

[0074] (Item 10) The magnet molding process according to Item 9, comprising: a mixing step of mixing the granulated material, the non-flat magnetic powder, and a molding resin to obtain a resin composition for bonded magnet molding; and a magnet molding step of molding the resin composition for bonded magnet molding while magnetically orienting it to obtain a bonded magnet.

[0075] (Item 11) A magnetic powder comprising magnetically oriented granules of flat magnetic powder and non-flat magnetic powder having an average particle size larger than that of the granules.

[0076] (Item 12) The magnetic powder according to Item 11, which contains a molding resin.

[0077] 1 Non-flat magnetic powder 2 Flat magnetic powder 3 Granules 4 Resin for molding 5 Resin for granulation 6 Magnet S1 Molding process S2 Granulation process S3 Magnet molding process S31 Mixing process S32 Magnetic field molding process

Claims

1. A magnet comprising magnetically oriented granules of flat magnetic powder and non-flat magnetic powder having an average particle size larger than that of the granules.

2. The magnet according to claim 1, wherein the granules contain a granule resin.

3. The magnet according to claim 1 or 2, wherein the aspect ratio m of said flat magnetic powder is 4.0 or more.

4. The magnet according to any one of claims 1 to 3, wherein the granulated materials are magnetically aligned with each other.

5. The coercive force HcJ (T) of the flat magnetic powder is expressed by the following formula (HcJ-J Ａ / 3) / J Ｂ -N ａ >0 (in the formula, J Ａ is the magnetization (T) of the non-flat magnetic powder, and J Ｂ is the magnetization (T) of the flat magnetic powder, Na is the demagnetizing factor, and is expressed by the following formula:

5. The magnet according to claim 1, wherein m is the aspect ratio of the flat magnetic powder.

6. A magnet according to any one of claims 1 to 5, wherein the non-flat magnetic powder is a rare earth magnetic powder or a ferrite magnetic powder, and the flat magnetic powder is a nanoparticle magnetic powder.

7. The magnet according to claim 6, wherein in the XRD pattern of the plane perpendicular to the axis of easy magnetization, the peak of the hard axis of magnetization of said flat magnetic powder is 1% or less of the main peak.

8. The magnet according to any one of claims 1 to 7, which contains a molding resin.

9. A method for manufacturing a magnet, comprising: a molding step of mixing flat magnetic powder with a granulating resin and molding the mixture while magnetically aligning the mixture to obtain a molded body; a granulation step of granulating the molded body to obtain a granulated product of the flat magnetic powder oriented in a magnetic field; and a magnet molding step of molding the granulated product with non-flat magnetic powder having an average particle size larger than that of the granulated product to obtain a magnet.

10. A method for producing a magnet as described in claim 9, wherein the magnet molding process includes a mixing process of mixing the granulated material, the non-flat magnetic powder, and a molding resin to obtain a resin composition for bonded magnet molding, and a magnetic field molding process of molding the resin composition for bonded magnet molding while magnetically orienting it to obtain a bonded magnet.

11. A magnetic powder comprising magnetically oriented granules of flat magnetic powder and non-flat magnetic powder having an average particle size larger than that of the granules.

12. The magnetic powder according to claim 11, which contains a molding resin.

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