Composite, electromagnetic wave absorber, noise suppressor, and production method for composite

Abstract

A composite comprising a matrix material and an inorganic material dispersed in the matrix material, wherein the inorganic material has a magnetic base material and a ferromagnetic coating material that coats the base material.

Description

Composite, electromagnetic wave absorber, noise suppressor, and method for manufacturing the composite

[0001] This application claims priority to U.S. Patent Application No. 63 / 542,297, filed October 4, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, with the development of IoT (Internet of Things) devices, electromagnetic interference in electronic devices has become a problem. As a countermeasure against electromagnetic interference, electromagnetic wave absorbers composed of magnetic powder and resin have attracted attention. Electromagnetic wave absorbers have the function of absorbing unwanted electromagnetic waves and converting them into heat.

[0003] However, the electromagnetic wave absorption capacity of an electromagnetic wave absorber depends on the frequency of the electromagnetic wave. With the recent increase in wireless communication speed, this frequency dependency has become a problem. Due to the increase in wireless communication speed, high-frequency electromagnetic waves are increasingly being used. Conventional electromagnetic wave absorbers are capable of absorbing relatively low-frequency electromagnetic waves, but are unable to exhibit sufficient electromagnetic wave absorption capacity for high-frequency electromagnetic waves. Furthermore, the electromagnetic wave absorption capacity of an electromagnetic wave absorber also depends on its thickness. The greater the thickness, the greater the electromagnetic wave absorption capacity. However, in recent years, electronic devices have become increasingly miniaturized. Therefore, there is a demand for electromagnetic wave absorbers that are thin and have high electromagnetic wave absorption capacity.

[0004] Examples of conventionally known electromagnetic wave absorbers are as follows:

[0005] Patent Document 1 discloses a polymer composition for magnetic components, which includes a base polymer and a powder dispersed in the base polymer, the powder consisting of a large number of flat particles, and the material of these particles is an Fe-based alloy containing 6.5% by mass to 32.0% by mass of Ni, 6.0% by mass to 14.0% by mass of Al, 0% by mass to 17.0% by mass of Co, 0% by mass to 7.0% by mass of Cu, and unavoidable impurities.

[0006] Patent Document 2 discloses a soft or semi-hard magnetic material having a first phase with crystals of a bcc or fcc structure containing Fe and Co, and a second phase containing Co, in which the content of Co when the sum of Fe and Co contained in the second phase is taken as 100 atomic % is greater than the content of Co when the sum of Fe and Co contained in the first phase is taken as 100 atomic %.

[0007] In recent years, the construction of mobile communication systems aimed at realizing Society 5.0 and the widespread use of IoT devices have led to an expansion in the need for such systems. The frequencies used are becoming broader and higher, from the UHF band (300 MHz to 3 GHz) to the SHF band (3 GHz to 30 GHz). Concurrently, concerns have arisen about communication failures and device malfunctions due to electromagnetic interference (EMI) in the SHF band, and research and development of countermeasures and methods has been ongoing. The present inventors have focused on the relationship between the anisotropic magnetic field and resonant frequency of permanent magnet materials to develop electromagnetic wave absorbing materials useful in the GHz band. Patent Document 3 discloses that spinodally decomposed flat Fe—Cr—Co alloy materials are effective in absorbing high-frequency electromagnetic waves.

[0008] However, even with these techniques, the electromagnetic wave absorbing ability and noise suppressing ability of the electromagnetic wave absorber for high frequency electromagnetic waves are not sufficient, and there is still room for improvement.

[0009] Japanese Patent Publication No. 2020-152979 International Publication No. 2019 / 059256 International Publication No. 2022 / 264363

[0010] An object of the present invention is to provide a composite, an electromagnetic wave absorber, a noise suppressor, and a method for producing the composite, which have high electromagnetic wave absorption properties and high noise suppression properties in the high frequency band.

[0011] The gist of the present invention is as follows: [1] A composite comprising a substrate and an inorganic material dispersed in the substrate, the inorganic material having a magnetic base material and a ferromagnetic coating material coating the base material.

[0012] [2] The composite according to [1], wherein the coating material contains one or more selected from cubic ferrite, tetragonal ferrite, hexagonal ferrite, and rhombohedral ferrite.

[0013] [3] The cubic ferrite has a spinel crystal structure and AFe ２ O ４ (A is one or more elements selected from Mn, Fe, Co, Ni, Cu, and Zn).

[0014] [4] The composite described in [1], wherein the coating material has a thickness of 10 nm or more and 100 μm or less.

[0015] [5] The composite described in [1], wherein the coating material is composed of a powder of particles having an average particle size of 1 nm or more and 1 μm or less.

[0016] [6] The composite according to [1], wherein the inorganic material has an average aspect ratio of 1 to 100.

[0017] [7] The composite according to [6], wherein the inorganic material has magnetic anisotropy with the in-plane direction of the composite being the direction of easy magnetization.

[0018] [8] The composite according to [1], wherein the base material is an Fe-based magnetic material.

[0019] [9] The composite according to [8], wherein the Fe-based magnetic material is any one selected from an Fe—Co-based alloy, an Fe—Si-based alloy, an Fe—Ni-based alloy, an Fe—Cr—Co-based alloy, an Fe—Cr—Al-based alloy, an Fe—Cr—Si-based alloy, and an Fe—Si—Al-based alloy.

[0020]

[10] The composite according to [1], wherein the base material has a two-phase separated structure composed of a ferromagnetic first phase and a non-ferromagnetic second phase.

[0021]

[11] The composite according to

[10] , wherein the first phase is elongated or flattened.

[0022]

[12] The composite according to

[10] , wherein the first phase has an elliptical plate shape or a circular plate shape elongated in one direction.

[0023]

[13] The composite according to

[12] , wherein the first phase is oriented in an in-plane direction of the composite.

[0024]

[14] The composite according to [9], wherein the base material contains 10 to 50 mass% of Cr, 0 to 30 mass% of Co, and 0 to 5 mass% in total of one or more elements selected from the group consisting of Ti, Zr, Hf, Al, V, Nb, and Si, with the remainder being Fe and impurities.

[0025]

[15] An electromagnetic wave absorber comprising the composite according to [1] or [2].

[0026]

[16] A noise suppressor comprising the composite according to [1] or [2].

[0027]

[17] A method for producing a composite, comprising: a step of preparing a magnetic base material; a step of coating the surface of the base material with a ferromagnetic coating material to form an inorganic material in which the surface of the base material is coated with the coating material; and a step of kneading and molding the inorganic material with a substrate to obtain a composite.

[0028] According to the present invention, it is possible to provide a composite, an electromagnetic wave absorber, a noise suppressor, and a method for manufacturing a composite that have high electromagnetic wave absorption properties and high noise suppression properties in the high frequency band.

[0029] FIG. 1 is a cross-sectional schematic diagram showing a composite according to one embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view of the inorganic material in FIG. 1. FIG. 1 is a diagram showing an example of a production method in which an elongation means and a flattening means are not applied. FIG. 2 is a diagram showing an example of a production method in which powder flattening is applied. FIG. 2 is a diagram showing an example of a production method in which an elongation means for inducing spinodal transformation while applying a magnetic field is applied. FIG. 2 is a diagram showing an example of a production method in which a combination of an elongation means for inducing spinodal transformation while applying a magnetic field and powder flattening is applied. FIG. 2 is a diagram showing an example of a production method in which a combination of powder elongation processing and powder flattening processing is applied. FIG. 2 is a diagram showing a backscattered electron image of a normal Fe—Cr—Co alloy powder in which spinodal decomposition has not occurred. FIG. 2 is a diagram showing a backscattered electron image of an Fe—Cr—Co alloy powder having a two-phase separation structure composed of a first phase and a second phase. FIG. 2 is a diagram showing an example of heat treatment conditions for inducing spinodal decomposition. FIG. 2 is a diagram showing an example of a flattened base material in the case where the base material is an Fe—Cr—Co alloy. FIG. 2 is a diagram showing the results of observation of spherical particles obtained in the examples with an electron microscope. 8A is a diagram showing a cross-sectional view of the spherical particle of FIG. 8A. A diagram showing an image of the base material (C-BM_an) obtained in the examples observed with an electron microscope. A diagram showing a cross-sectional view of the base material of FIG. 9A. A diagram showing the results of observing the surface of the inorganic material obtained in the examples with an electron microscope. A diagram showing the measurement positions when AES analysis was performed on the surface of the base material (C-BM_an) obtained in the examples. A diagram showing the results of AES analysis on the surface of the base material (C-BM_an) obtained in the examples. A diagram showing the measurement positions when AES analysis was performed in the depth direction of the base material (C-BM_an) obtained in the examples. A diagram showing the results of AES analysis of the surface of the base material (C-BM_an) obtained in the examples. A diagram showing the measurement positions when AES analysis was performed on the surface of the inorganic material (C-BM_an / CFO-500°C) obtained in the examples. A diagram showing the results of AES analysis of the surface of the inorganic material (C-BM_an / CFO-500°C) obtained in the examples. 1 shows the measurement positions when AES analysis was performed in the depth direction of the inorganic material (C-BM_an / CFO-500°C) obtained in the example. 2 shows the results of AES analysis in the depth direction of the inorganic material (C-BM_an / CFO-500°C) obtained in the example.1 is a diagram showing the results of XRD analysis of a composite material obtained in an example. FIG. 2 is a diagram showing the results of VSM measurement of a composite material obtained in an example. FIG. 3 is a diagram showing the results of VSM measurement of a composite material obtained in an example. FIG. 4 is a diagram showing the results of VSM measurement of a composite material obtained in an example. FIG. 5 is a diagram showing the results of measuring complex relative permeability versus frequency for a composite material obtained in an example. FIG. 6 is a diagram showing the results of measuring complex relative permeability versus frequency for a composite material obtained in an example. FIG. 7 is a diagram showing the results of measuring the imaginary part of complex relative permeability and resonance frequency for a composite material obtained in an example. FIG. 8 is a diagram showing the results of calculating the value obtained by multiplying each frequency relative to frequency by the imaginary part μr″ of complex relative permeability for a composite material obtained in an example. FIG. 9 is a diagram comparing a composite material obtained in an example with a composite using another material as the inorganic material. FIG. 10 is a diagram explaining a method for evaluating noise suppression properties for a composite material obtained in an example. FIG. 11 is a diagram explaining a method for evaluating noise suppression properties for a composite material obtained in an example. P measured by the method for evaluating noise suppression properties for a composite material obtained in an example. ｌｏｓｓ / P ｉｎ 1 is a graph showing the parameter S measured by the noise suppression characteristic evaluation method for the composite material obtained in the example. ２１ 1 is a graph showing the parameter S measured by the noise suppression characteristic evaluation method for the composite material obtained in the example. １１ 1 is a graph showing ΔP calculated by the noise suppression characteristic evaluation method for the composite materials obtained in the examples. ｌｏｓｓ / P ｉｎ FIG.

[0030] An example of the present invention will be described below with reference to the drawings, but the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Furthermore, when multiple upper and lower limit values ​​are specified for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range.

[0031] <Composite> Fig. 1 is a cross-sectional schematic diagram showing a composite according to one embodiment of the present invention. As shown in Fig. 1, the composite 1 according to this embodiment includes a substrate 11 and an inorganic material 12 dispersed in the substrate 11. The inorganic material 12 includes a magnetic base material 12a and a ferromagnetic coating material 12b that coats the base material 12a. In the composite 1 of this embodiment, the inorganic material 12 has a core-shell structure in which the surface of the base material 12a, which has high magnetic properties, is coated with the ferromagnetic coating material 12b.

[0032] [Substrate] The substrate 11 is composed of a polymer such as resin or rubber. By kneading and molding an inorganic material 12 having a predetermined structure (described below) into the substrate 11, a composite 1 can be obtained in which the inorganic material 12 is dispersed in the substrate 11. The type of polymer constituting the substrate 11 is not particularly limited. The composite 1 exhibits its electromagnetic wave absorption and noise suppression capabilities using the inorganic material 12, rather than the substrate 11. Therefore, as long as the inorganic material 12 can be dispersed and retained without affecting the properties of the inorganic material 12, an appropriate material can be selected for the substrate 11 depending on the intended use of the composite 1. A specific example of a material for the substrate 11 is an epoxy resin. The shape of the substrate 11 is also not particularly limited and can be selected appropriately depending on the intended use of the composite 1. For example, by molding the substrate 11 into a thin plate, sheet, film, or the like using a flexible polymer, the composite 1 can be easily disposed inside an electronic device. A material other than the inorganic material 12 may be kneaded into the substrate 11. For example, the substrate 11 may include processing aids such as lubricants and binders, as well as flame retardants and the like.

[0033] When the total mass of the composite 1 is taken as 100 mass %, the content of the substrate 11 is not particularly limited, but can be 5 to 95 mass %, 5 to 70 mass %, or 5 to 50 mass %.

[0034] The content of inorganic material 12 when the total mass of composite 1 is taken as 100 mass % is not particularly limited, but can be 5 to 95 mass %, 50 to 95 mass %, or 70 to 95 mass %. It is preferable to adjust the content of inorganic material 12 so that it is high when the frequency band used is low, and low when the frequency band used is high.

[0035] The mass ratio of the substrate 11 to the inorganic material 12 is not particularly limited, but may be 5-90:95-10.

[0036] [Inorganic materials]

[0037] Fig. 2 is a partially enlarged cross-sectional view of the inorganic material 12 in Fig. 1. As shown in Fig. 2, the inorganic material 12 of this embodiment has the base material 12a and the coating material 12b as described above.

[0038] The average aspect ratio of the inorganic material 12 is not particularly limited, but is preferably within the range of 1 to 100. By kneading and molding the inorganic material 12 having an average aspect ratio of 1 or more into the substrate 11, the static magnetic properties and magnetic permeability properties of the composite 1 can be improved. The lower limit of the average aspect ratio is preferably 1.5, 3, 5, 8, 10, 15, 18, or 30. Furthermore, from the viewpoint of preventing pulverization of the base material 12a, the upper limit of the average aspect ratio of the base material 12a is preferably 50, 40, 30, or 20.

[0039] The size of the inorganic material 12 is not particularly limited, but the median diameter D ５０ The median diameter D of the inorganic material 12 is preferably 30 μm to 500 μm. ５０ The average thickness of the inorganic material 12 may be 300 μm or less, or may be 100 μm or less. The average thickness of the inorganic material 12 is preferably 10 μm or less, and more preferably 7 μm or less. This is expected to further improve the high frequency characteristics.

[0040] The inorganic material 12 preferably has magnetic anisotropy with the in-plane direction of the composite 1 as the direction of easy magnetization, thereby enabling the composite 1 to have further improved magnetostatic properties and magnetic permeability properties.

[0041] (Base Material) The base material 12a is not particularly limited, but may be, for example, an Fe-based magnetic material, such as an Fe—Co-based alloy, an Fe—Si-based alloy, an Fe—Ni-based alloy, an Fe—Cr—Co-based alloy, an Fe—Cr—Al-based alloy, an Fe—Cr—Si-based alloy, or an Fe—Si—Al-based alloy.

[0042] The matrix 12a preferably has a two-phase separation structure composed of a ferromagnetic first phase 121 and a non-ferromagnetic second phase 122. The two-phase separation structure of the matrix 12a is typically caused by spinodal decomposition. Generally, spinodal decomposition refers to phase separation that corresponds to a change in state from an unstable state to an equilibrium state, and phase separation proceeds by the growth of concentration fluctuations without the need for nucleation. In the matrix 12a of the composite 1 according to this embodiment, the two-phase separation transformation that occurs when the matrix 12a is heated to a temperature range where the metal structure is essentially a single α-phase to a temperature range where the temperature is lowered to a two-phase temperature range is referred to as spinodal decomposition. A spinodally decomposed structure generally exhibits a modulated structure. A modulated structure refers to a structure consisting of regular, fine concentration fluctuations. For example, on page 149 of "Metal Structure Science" by Hajime Sudo, Imao Tamura, and Taiji Nishizawa, published by Maruzen Co., Ltd. on August 31, 1972, a modulated structure is explained, and a Cu-Ni-Fe alloy is given as an example of an alloy that exhibits a modulated structure.

[0043] For example, when the Fe-based magnetic material constituting the base material 12a is an Fe—Cr—Co-based alloy, the base material 12a will contain a first phase (α １ phase) and a Cr-rich second phase (α ２ Specifically, in this two-phase separated structure, the first phase has a higher Fe content and Co content than the second phase, and the second phase has a higher Cr content than the first phase. In an Fe-based alloy, by causing two-phase separation, the peak of the electromagnetic wave absorption property or noise suppression property can be shifted to the high frequency side.

[0044] Furthermore, in the base material 12a of the composite 1 according to this embodiment, the Fe- and Co-rich first phase is preferably elongated or flattened. This further enhances the electromagnetic wave absorption ability of the composite 1 on the high frequency side. By improving the electromagnetic wave absorption ability or noise suppression ability of the composite 1, the thickness of the composite 1 can be reduced. Note that "elongating the first phase" means stretching the first phase along one direction, and "flattening the first phase" means stretching the first phase radially along a plane.

[0045] One example of a means for flattening the first phase contained in the base material 12a is flattening the base material 12a. For example, by inducing spinodal decomposition in the base material 12a and then flattening it, the average aspect ratio of the base material 12a can be set within the range of 3 to 50. This allows the first phase to be flattened, dramatically improving the electromagnetic wave absorption or noise suppression capabilities at high frequencies. However, it should be noted that if spinodal decomposition is performed after flattening, the base material 12a will be flattened, but the first phase will not be flattened. In this case, a granular first phase will be formed inside the flattened base material 12a. Performing a heat treatment at a temperature below the two-phase separation plane to induce spinodal decomposition slightly reduces the workability of the base material 12a, making flattening difficult. Therefore, if the purpose of flattening the base material 12a is to flatten it, it is best to perform the flattening before inducing spinodal decomposition. Even if the first phase is not flattened, some improvement in properties can be expected as long as the base material 12a is flattened. However, according to the knowledge of the present inventors, the factor that crucially influences the effect of flattening on improving electromagnetic properties is not the shape of the base material 12a, but the shape of the first phase contained in the base material 12a. In order to dramatically improve the electromagnetic wave absorption capacity or noise suppression capacity of the composite 1, it is preferable to flatten the first phase.

[0046] One example of a means for elongating the first phase contained in the matrix 12a is to induce spinodal decomposition while applying a magnetic field to the matrix 12a. After normal spinodal decomposition, the first phase is formed in a granular shape, as schematically shown in FIG. 3A , and the average aspect ratio is close to 1. On the other hand, when spinodal decomposition is induced while applying a magnetic field to the matrix 12a, the first phase formed in the matrix 12a assumes a shape similar to that of grains elongated in one direction. This allows the first phase to be elongated without flattening the matrix 12a.

[0047] Another example of a means for elongating the first phase contained in the base material 12 a is elongation processing of the powder after spinodal decomposition. For example, the base material 12 a is subjected to spinodal decomposition, and then filled into a pipe-shaped container, and the container is processed in one direction, thereby elongating the first phase in the same direction as the processing direction of the base material 12 a.

[0048] The above-described means may also be combined as appropriate. Specific examples of manufacturing methods for obtaining a base material 12a having a first phase are described below with reference to the drawings. FIG. 3A shows an example in which the above-described elongation and flattening means are not applied. In the manufacturing method shown in FIG. 3A, a base material 12a having a two-phase separated structure composed of a first phase 121 and a second phase 122 is obtained by performing only a heat treatment that causes spinodal decomposition on a powder before heat treatment (hereinafter referred to as "material powder 12M"). In this case, the base material 12a and the first phase 121 are neither elongated nor flattened.

[0049] 3B shows an example in which the base material 12a is flattened. In the manufacturing method shown in FIG. 3B, first, a material powder 12M is heat-treated to obtain a base material 12a having a phase-separated structure composed of a first phase 121 and a second phase 122. Next, the base material 12a is flattened. This flattens the base material 12a and also flattens the first phase 121 contained in the base material 12a.

[0050] 3C shows an example in which an elongation method is used to induce spinodal transformation while applying a magnetic field. In the manufacturing method shown in FIG. 3C, a heat treatment is performed on a material powder 12M to induce spinodal decomposition while applying a magnetic field in one direction. This results in a base material 12a having a two-phase separated structure composed of a first phase 121 elongated along the magnetic field and a second phase 122. The first phase 121 elongated along the magnetic field is also referred to as an acicular structure. On the other hand, according to the manufacturing method shown in FIG. 3C, the base material 12a is neither elongated nor flattened.

[0051] FIG. 3D illustrates an example in which a combination of an elongation method that induces spinodal transformation while applying a magnetic field and powder flattening is applied. In the manufacturing method illustrated in FIG. 3D , a material powder 12M is first subjected to a heat treatment that induces spinodal transformation while applying a magnetic field, thereby obtaining a matrix 12a in which the first phase 121 is elongated. The matrix 12a is then flattened. According to the manufacturing method illustrated in FIG. 3D , the matrix 12a is flattened. According to the manufacturing method illustrated in FIG. 3D , the first phase 121 has an elliptical plate shape or a circular plate shape elongated in one direction. The shape of the first phase 121 obtained by the manufacturing method illustrated in FIG. 3D is sometimes referred to as a koban (i.e., an oval gold coin from the Edo period in Japan) shape. Furthermore, the first phase 121 is preferably oriented in the in-plane direction of the composite 1.

[0052] 3E shows an example in which a combination of powder elongation processing and powder flattening processing is applied. In the manufacturing method shown in FIG. 3E, a material powder 12M is first subjected to a heat treatment that causes spinodal decomposition, thereby obtaining a base material 12a having a two-phase separated structure composed of a first phase 121 and a second phase 122. Next, the base material 12a is subjected to an elongation processing to obtain a base material 12a elongated in one direction. This elongated base material 12a includes a first phase 121 elongated in one direction. Furthermore, the base material 12a is flattened. This results in a base material 12a having an elliptical plate shape or a disk shape elongated in one direction. The first phase 121 included in this base material 12a also has an elliptical plate shape or a disk shape elongated in one direction.

[0053] In either manufacturing method, the flattening or elongation process needs to be performed on the base material 12a after spinodal transformation has occurred. When the material powder 12M is flattened or elongated and then heat-treated, a flattened or elongated base material 12a is obtained, and the first phase 121 contained therein becomes spherical.

[0054] When the Fe-based magnetic material constituting the base material 12a is an Fe—Cr—Co alloy, the specific components of the Fe—Cr—Co alloy may be those capable of forming a two-phase separation structure composed of an Fe- and Co-rich first phase and a Cr-rich second phase. Elements other than Fe, Cr, and Co may also be included. For example, the Fe—Cr—Co alloy may contain 10 to 50 mass% Cr, 0 to 30 mass% Co, and 0 to 5 mass% total of one or more elements selected from the group consisting of Ti, Zr, Hf, Al, V, Nb, and Si, with the remainder consisting of Fe and impurities. By setting the Cr and Co contents within the above ranges, a suitable two-phase separation structure can be formed.

[0055] Ti is not an essential component for the matrix 12a of the composite 1 according to this embodiment. Therefore, the lower limit of the Ti content is 0%. However, by incorporating an appropriate amount of Ti into the matrix 12a, the matrix 12a before spinodal decomposition can be made into a single α phase, forming a uniform two-phase separated structure. Furthermore, Ti also serves to suppress the reduction in the Cr content due to oxidation. Therefore, 0.5% or more of Ti may be incorporated into the matrix 12a. Furthermore, V, Nb, Zr, Al, Hf, and Si also exhibit similar functions and may be incorporated into the matrix 12a in the same manner as Ti. In this case, the Ti content described above may be applied to the total content of these elements. That is, the matrix 12a may contain one or more elements selected from the group consisting of Ti, Zr, Hf, Al, V, and Nb, and the total content of these elements may be 0 to 5%. Preferably, the total content of one or more elements selected from the group consisting of Ti, Zr, Hf, Al, V, and Nb is 0.5% or more.

[0056] Elements other than Fe, Cr, Co, Ti, V, Nb, Zr, Al, Hf, and Si may also be contained in the base material 12a as impurities or as intentionally added components, as long as they do not impair the magnetic properties and workability of the base material 12a. For example, Mo is an element that increases the coercive force, so it may be contained in the base material 12a.

[0057] On the other hand, elements that impair these properties are preferably excluded from the base material 12a. Furthermore, the base material 12a of the composite 1 according to this embodiment does not contain Ni as an essential component.

[0058] As described above, the average aspect ratio of the base material 12a is preferably within a range of 3 to 50. By kneading and molding the base material 12a having an average aspect ratio of 3 or more into the substrate 11, the Fe- and Co-rich first phase is flattened, a magnetic path is formed inside the composite 1, and the real permeability μ' of the composite 1 can be increased. The lower limit of the average aspect ratio is preferably 5, 8, 10, 15, 18, or 30. Furthermore, from the viewpoint of preventing pulverization of the base material 12a, the upper limit of the average aspect ratio of the base material 12a is preferably 50, 40, 30, or 20.

[0059] The size of the base material 12a is not particularly limited, but for example, it is preferable that the average equivalent circle diameter is 50 μm to 300 μm. The equivalent circle diameter of the base material 12a may be 100 μm or less. On the other hand, by setting the average thickness of the base material 12a to 10 μm or less, further improvement in magnetic properties can be expected.

[0060] The method for evaluating the various properties of the base material 12a of the composite 1 is as follows. The structure of the base material 12a can be evaluated by cutting the composite 1, appropriately preparing the cut surface, and photographing a backscattered electron image with an SEM or TEM. The first and second phases can be clearly confirmed in the backscattered electron image due to the difference in density. As an example, FIG. 4 shows a backscattered electron image of a normal Fe—Cr—Co-based alloy powder in which spinodal decomposition has not occurred, and FIG. 5 shows a backscattered electron image of an Fe—Cr—Co-based alloy powder having a two-phase-separated structure composed of an Fe- and Co-rich first phase and a Cr-rich second phase. A normal Fe—Cr—Co-based alloy powder exhibits a flat appearance in the backscattered electron image. On the other hand, an Fe—Cr—Co-based alloy powder having a two-phase-separated structure exhibits a complex shading pattern in the backscattered electron image. Therefore, the presence or absence of a two-phase-separated structure can be easily confirmed by observing with an SEM or TEM. Furthermore, by measuring the element concentration distribution during TEM observation, it is possible to distinguish between the first phase rich in Fe and Co and the second phase rich in Cr.

[0061] The aspect ratio of the base material 12a can also be evaluated by cutting the composite 1, appropriately preparing the cut surface, and photographing a magnified image using an optical microscope, a laser microscope, an SEM, or a TEM. In the magnified image of the cut surface, the substrate 11 and the base material 12a can be easily distinguished. The aspect ratio of the base material 12a can be obtained by determining the major axis of the base material 12a and the minor axis of the base material 12a measured in a direction perpendicular to the major axis, and then calculating the ratio between them. This procedure can be repeated for multiple base materials 12a, and the average aspect ratio of the obtained aspect ratios can be calculated to determine the average aspect ratio of the base material 12a of the composite 1. When the base material 12a has a flat shape, the aspect ratio of the powder is the ratio of the diameter (a) to the thickness (c) of the powder, i.e., a / c. On the other hand, when the shape of the base material 12a is elongated, the aspect ratio of the powder is the ratio of the average value ((a+b) / 2) of the powder's longitudinal diameter (a) and lateral diameter (b) to the thickness (c), i.e., ((a+b) / 2) / c.

[0062] The components of the base material 12a can be evaluated by measuring the average composition using a SEM equipped with an energy dispersive X-ray spectrometer (EDX), and then measuring the compositions of the first and second phases after separation using a TEM.

[0063] The circle-equivalent diameter of the base material 12a can also be evaluated by cutting the composite 1, appropriately preparing the cut surface, and taking a magnified image using an SEM or TEM. The area of ​​the base material 12a included in the magnified image is determined, and then the cross section of the base material 12a is considered to be a circle and the diameter of that circle is calculated. This procedure is repeated for multiple base materials 12a, and the average of the obtained circle-equivalent diameters is calculated, thereby making it possible to determine the average circle-equivalent diameter of the base materials 12a of the composite 1.

[0064] The coating material 12b is not particularly limited as long as it has ferromagnetic properties, but preferably contains one or more selected from cubic ferrite, tetragonal ferrite, hexagonal ferrite, and rhombohedral ferrite. By containing one or more of the above ferrites in the coating material 12b, it is possible to further improve the electromagnetic wave absorption characteristics and noise suppression characteristics in the high frequency band.

[0065] Cubic ferrite has a spinel crystal structure and is composed of AFe ２ O ４ (A is one or more elements selected from Mn, Fe, Co, Ni, Cu, and Zn). In this case, the coating material 12b is preferably represented by AFe ２ O ４ Ferrite represented by A α O β For example, the cubic ferrite may contain an oxide represented by CoFe ２ O ４ In this case, the coating material is CoFe ２ O ４ and Fe ３ O ４ In addition, when A=Co in the above general formula, the cubic ferrite may contain Co ｘ Fe ３－ｘ O ４ (0<x<1).

[0066] The thickness of the coating material 12b is preferably 10 nm or more and 100 μm or less. By setting the thickness of the coating material 12b within this range, a good balance between improved characteristics and the amount of coating is achieved, and manufacturability can also be improved. The thickness of the coating material 12b may be 15 nm or more, 20 nm or more, or 30 nm or more. The thickness of the coating material 12b may also be 50 μm or less, 10 μm or less, 3 μm or less, or 1 μm or less. The thickness range of the coating material 12b can be a combination of the above upper and lower limit values.

[0067] The form of the coating material 12b is not particularly limited, but is preferably composed of a powder of particles having an average particle size of 1 nm or more and 1 μm or less. The average particle size of the particles constituting the coating material 12b may be 10 nm or more, 30 nm or more, or 50 nm or more. The average particle size of the particles constituting the coating material 12b may be 800 nm or less, 600 nm or less, or 500 nm or less. The range of the average particle size of the particles constituting the coating material 12b can be a combination of the above upper and lower limit values.

[0068] Furthermore, the coating material 12b is preferably made of a sintered body of particle powder, which can further improve the magnetic properties.

[0069] The thickness of the coating material 12b can be measured by an Auger electron spectroscopy (AES) device, and the average particle size of the particles constituting the coating material 12b can be measured by a scanning electron microscope (SEM).

[0070] When the total mass of the inorganic material 12 is taken as 100 mass %, the content of the base material 12a is not particularly limited, but can be 5 to 90 mass %, 50 to 90 mass %, or 70 to 90 mass %.

[0071] When the total mass of the inorganic material 12 is taken as 100 mass %, the content of the coating material 12b is not particularly limited, but can be 5 to 90 mass %, 5 to 50 mass %, or 5 to 30 mass %.

[0072] <Electromagnetic Wave Absorber, Noise Suppressor> The electromagnetic wave absorber according to this embodiment includes the composite 1. The noise suppressor according to this embodiment also includes the composite 1. The electromagnetic wave absorber or noise suppression sheet may be formed from the composite 1. The form of the electromagnetic wave absorber or noise suppressor is not particularly limited, and examples include a film, a sheet, and a plate. This makes it possible to provide an electromagnetic wave absorber or noise suppressor with high electromagnetic wave absorption or noise suppression capabilities, and to dramatically improve the capabilities particularly in the high frequency band.

[0073] <Method for manufacturing composite> Next, a method for manufacturing the composite according to this embodiment will be described. The method for manufacturing the composite according to this embodiment is one example, and the method for manufacturing the composite 1 of the present invention is not limited to the following. The method for manufacturing the composite according to this embodiment includes the steps of preparing a magnetic base material, coating the surface of the base material with a ferromagnetic coating material to form an inorganic material in which the surface of the base material is coated with the coating material, and kneading and molding the inorganic material with a substrate to obtain a composite.

[0074] [Step of Preparing Base Material] The step of preparing the base material 12a is not particularly limited, but may involve, for example, obtaining a metal powder having a predetermined composition, or spraying molten metal compounded to have a predetermined composition at high temperature and solidifying the droplets (atomization method). The base material 12a is not particularly limited, but is preferably an Fe-based magnetic material. Specific examples of the components and composition of the base material 12a may be the same as those described above.

[0075] In this step, it is preferable to cause spinodal decomposition in the metal structure of the base material 12a to form a two-phase separated structure. Specific means for causing spinodal decomposition in the powder are not particularly limited, but the following methods can be used, for example.

[0076] Spinodal decomposition can be induced by first subjecting the base material 12a to a solution treatment to convert its metal structure to a single α phase, followed by a heat treatment to slowly cool the base material 12a. Instead of the solution treatment, an atomization method may be used to produce powder to convert it to a single α phase. Spinodal decomposition can then be induced in the powder by maintaining the powder at a temperature below the two-phase separation surface. For example, a single isothermal aging treatment, a multi-stage aging treatment, or a continuous cooling treatment may be performed at a temperature below the two-phase separation surface. The temperature of the two-phase separation surface varies depending on the powder's components, but can be determined based on a known binary or ternary phase diagram.

[0077] As a specific example of heat treatment conditions, heat treatment conditions when the base material 12a is an Fe-Cr-Co alloy are shown in Figure 6. In Figure 6, As indicates the state after solution treatment, and the heat treatments corresponding to a, b, c, and d are performed by: (A) maintaining the temperature of the base material 12a in a first temperature range of 655°C ± 10°C, which is below the two-phase separation surface temperature, for 80 minutes; (B) reducing the temperature of the base material 12a maintained in the first temperature range to a second temperature range of 620°C ± 10°C and maintaining this temperature for 60 minutes or more; and (C) reducing the temperature of the base material 12a maintained in the second temperature range to a third temperature range of 600°C ± 10°C and maintaining this temperature for 120 minutes or more.

[0078] Solution treatment is a preliminary step to spinodal decomposition. It is estimated that the metal structure of the base material 12a is a single α phase at the completion of solution treatment. The holding temperature is preferably, for example, 700°C or higher, and the alloy is preferably rapidly cooled from the holding temperature to form a supersaturated solid solution. However, the temperature at which the structure transforms to a single α phase varies depending on the components of the binary or ternary alloy. Therefore, it is preferable to set the holding temperature according to the components based on a known phase diagram or the like.

[0079] From the viewpoint of forming a single α-phase structure, it is considered preferable that the temperature holding time in the heat treatment (A) is at least 30 minutes or more. There is no particular upper limit to the temperature holding time, but if the holding time is too long, homogenization will progress, but the manufacturing time and manufacturing cost will increase, and oxidation of the powder surface may occur, which may have an adverse effect on the magnetic properties.

[0080] In the heat treatments (A), (B), (C), and (D), spinodal decomposition of the α single-phase structure occurs, forming a two-phase separated structure. For example, when the base material 12a is an Fe—Cr—Co alloy, the longer the temperature holding time within the range of 500 to 620°C, the greater the difference in Cr concentration between the first and second phases. It is believed that the greater the difference in Cr concentration, the more improved the high-frequency magnetic properties of the composite.

[0081] The first phase may be stretched or flattened at any time before the composite is produced. The specific means for stretching or flattening the first phase is not particularly limited, but may be, for example, the following.

[0082] One example of a specific means for flattening the first phase is to form a two-phase separation structure in the powder and then flatten the powder before mixing and molding the powder with a polymer substrate, as illustrated in FIG. 3B . This flattening process may, for example, set the average aspect ratio of the powder within a range of 3 to 50. Flattening the powder also flattens the first phase contained in the powder. FIG. 7 shows an example of a flattened base material 12a when the base material 12a is an Fe—Cr—Co alloy. The upper part of FIG. 7 is a photograph of the flattened base material 12a viewed from above, and the lower part of FIG. 7 is a photograph of the same viewed from a cross section. As shown in FIG. 7 , the flattened base material 12a has a flat plate shape. Because Fe—Cr—Co alloys are highly workable, they are not crushed even when flattened, and a shape with a high aspect ratio can be obtained. Furthermore, the two-phase separation structure is maintained even after flattening. On the other hand, it should be noted that if spinodal decomposition is induced after flattening, the powder will be flattened, but the first phase will not. If a two-phase separation structure is formed in the powder, the processability of the powder will be slightly reduced, making flattening difficult. If the purpose of flattening is to flatten the powder, the flattening should be carried out before the formation of the two-phase separation structure. However, in the manufacturing method of the composite 1 according to this embodiment, the purpose of the flattening is to flatten the first phase. Therefore, the flattening of the powder is carried out after the formation of the two-phase separation structure.

[0083] The means for flattening is not particularly limited, but it is preferable to use a ball mill, for example. In flattening using a ball mill, the rotation speed and milling time are important parameters. The higher the rotation speed, the higher the degree of processing. Furthermore, the longer the milling time, the higher the degree of processing. However, it should be noted that excessive rotation speed and milling time can pulverize the powder and actually reduce the aspect ratio. Furthermore, according to the inventors' findings, low-load, long-term ball milling with a low rotation speed and a long milling time is advantageous for improving the aspect ratio. The preferred rotation speed is in the range of 50 to 600 rpm, and the preferred milling time is in the range of more than 0 hours and 168 hours. It is preferable to explore a suitable combination of rotation speed and milling time within this range. The preferred combinations discovered by the inventors are shown in the data of the Examples described below.

[0084] One example of a specific means for elongating the first phase is to induce spinodal decomposition while applying a magnetic field to the powder, as illustrated in FIG. 3C . When spinodal decomposition is induced while applying a magnetic field to the powder, the first phase formed in the powder assumes a shape similar to that of grains elongated in one direction. This allows the first phase to be elongated without flattening the powder. Another example of a means for elongating the first phase is powder elongation, as illustrated in FIG. 3E . For example, the powder can be elongated in one direction by filling the powder into a pipe-shaped container and processing the container in one direction. However, like the flattening described above, the elongation should be performed before inducing spinodal decomposition. Both flattening and elongation may be applied to the base material 12a. For example, as illustrated in FIG. 3D , the elongation treatment of the first phase using a magnetic field and the flattening treatment of the first phase by mechanical processing may be combined. 3E, the first phase elongation process by mechanical working may be combined with the first phase flattening process by mechanical working, resulting in a first phase having a flattened and unidirectionally elongated shape, such as an elliptical plate shape or a unidirectionally elongated disk shape.

[0085] [Step of forming inorganic material] In this embodiment, the surface of the base material obtained in the above step is coated with a ferromagnetic coating material to form an inorganic material in which the surface of the base material is coated with the coating material. The method for coating the base material is not particularly limited, but can be performed by a sputtering method.

[0086] When using the sputtering method, a target having a predetermined composition selected to obtain a coating material of a predetermined composition is used, and sputtering is performed in an inert gas atmosphere or vacuum to form a ferromagnetic coating material 12b on the surface of the base material 12a. In this case, particles scattered by glow discharge adhere to the surface of the base material 12a, thereby forming the coating material 12b on the surface of the base material 12a. The median diameter D of the inorganic material 12 is ５０ The thickness and average thickness of the inorganic material 12, as well as the average particle size of the particles that make up the coating material 12b of the inorganic material 12, can be in the same ranges as above.

[0087] For example, when the base material 12a is an Fe—Cr—Co alloy, cobalt iron oxide (CoFe ２ O ４ ) in an inert atmosphere at 80 to 150° C. for 50 to 100 hours, and a CoFe ２ O ４ and Fe ３ O ４ A coating material 12b containing the above is formed.

[0088] In this step, the surface of the base material is coated with a ferromagnetic coating material, and then the coating material may be subjected to a heat treatment. For example, an annealing treatment may be performed in the atmosphere on the inorganic material 12 in which a coating material 12b is formed on the surface of the base material 12a. The heat treatment conditions may be adjusted depending on the components of the coating material 12b, and are not particularly limited. For example, when the coating material 12b is CoFe, ２ O ４ and Fe ３ O ４ When the coating material 12b contains the sintered material, the temperature is 400 to 600° C. and the time is 0.5 to 10 hours. This makes it possible to make the coating material 12b into a sintered body, and further improve the magnetic properties.

[0089] [Step of Obtaining a Composite] In this step, the inorganic material 12 obtained in the above step and the substrate 11 are kneaded and molded to obtain the composite 1. As described above, the specific material of the substrate 11 is not particularly limited and can be selected appropriately depending on the application of the composite 1. Therefore, the kneading and molding conditions may also be selected appropriately based on the substrate 11. The molding method is not particularly limited, but can be powder compaction molding, in which the substrate 11 and the inorganic material 12 are mixed and compacted under a predetermined pressure. The pressure during powder compaction can be, for example, 0.5 GPa to 1.5 GPa or 0.7 GPa to 1.2 GPa. The filling rate during kneading is also not particularly limited, and it is sufficient that the mass of the inorganic material 12 is greater than 0% and less than 100% of the mass of the substrate 11. The functionality of the composite 1 is exhibited even if only a small amount of the inorganic material 12 is contained, and a bulk body can be produced even if only a small amount of the substrate 11 is contained. On the other hand, from the viewpoint of ease of production, it is preferable that the mass of the inorganic material 12 is within a range of 5 to 95% of the total mass of the substrate 11 and the inorganic material 12. The mass ratio of the substrate 11 to the inorganic material 12 may be 5 to 90:95 to 10. The molding method is not particularly limited, and known means such as compression molding, injection molding, extrusion molding, and rolling can be appropriately adopted.

[0090] In the above-described manufacturing method, the chemical composition of the base material 12a before spinodal decomposition may be within the range described above for the chemical composition of the base material 12a of the final composite 1. The average equivalent circular diameter of the base material 12a before spinodal decomposition may also be within the range described above for the equivalent circular diameter of the base material 12a of the final composite 1. However, although the base material 12a of the composite 1 according to this embodiment has high processability, some pulverization may occur during flattening. Therefore, the average equivalent circular diameter of the base material 12a before flattening is typically slightly larger than that of the base material 12a of the final composite 1. Here, when the base material 12a is a spherical powder, it is estimated that the average equivalent circular diameter is preferably several μm (e.g., 2 μm) to 100 μm. The average equivalent circular diameter of the base material 12a may be 3 μm or more, or 5 μm or more. Furthermore, when the base material 12a is a flat powder, it is presumed that the average equivalent circular diameter thereof is preferably several hundred μm or less (for example, 500 μm or less). The average equivalent circular diameter of the base material 12a may be 400 μm or less, or 300 μm or less.

[0091] The effects of one embodiment of the present invention will be explained in more detail using examples. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0092] (Example 1) Fe-25Cr-12Co-1.5Ti atomized powder (average particle size 45 μm or less, median diameter D ５０ The powder (diameter 23 μm) was subjected to various heat treatments in an Ar gas atmosphere to obtain a powder of spherical particles composed of an Fe—Cr—Co alloy. The heat treatment conditions were as follows: (A) The temperature of the base material 12 a was kept at 655° C. for 80 minutes; (B) The temperature of the base material 12 a was reduced to 620° C. and kept for 60 minutes; and (C) The temperature of the base material 12 a was reduced to 600° C. and kept for 120 minutes.

[0093] The results of observing the obtained spherical particles with an electron microscope are shown in Fig. 8A. In addition, as shown in Fig. 8B, in the cross-sectional view of the spherical particles, a first phase (α １phase) and a Cr-rich second phase (α ２ A two-phase separation structure containing a crystalline phase and a crystalline phase was confirmed.

[0094] Next, using a ball mill (Fritch Planetary Ball Mill P-5) with a ball size of 8 mm, 100 rpm, and 15 hours, the particles were flattened into spherical particles. The resulting flat particles (C-BM) were annealed in air at 450°C for 2 hours to obtain a base material (C-BM_an). The results of observing the surface of the obtained base material with an electron microscope are shown in FIG. 9A. Furthermore, as shown in FIG. 9B, in a cross-sectional view of the base material, flat first phases (α １ phase) and the second phase (α ２ A two-phase separation structure containing a crystalline phase and a crystalline phase was confirmed.

[0095] Then, CoFe was used as the target material. ２ O ４ The sputtering was carried out in an Ar gas atmosphere at 100 to 120°C for 80 hours, and CoFe was deposited on the surface of the base material. ２ O ４ and Fe ３ O ４ A coating material consisting of a mixture of the above was formed to obtain an inorganic material (C-BM_an / CFO). The content of the coating material was approximately 25% by mass when the total mass of the inorganic material was taken as 100% by mass. The inorganic material was annealed in air at 500°C for 2 hours. The results of observing the surface of the obtained inorganic material with an electron microscope are shown in Figure 10. As shown in Figure 10, spherical CoFe particles with an average particle size of 100 nm to 300 nm were applied as a coating material to the surface of a base material made of an Fe-Cr-Co alloy. ２ O ４ It was found that powder was deposited.

[0096] The inorganic material (C-BM_an / CFO-500°C) obtained in Production Example 1 and an epoxy resin (Pelpoeder PCE750, manufactured by Pelnox) were mixed and compacted at 0.9 GPa to 1.0 GPa to obtain a composite. The content of the inorganic material was 90% by mass when the total mass of the composite was 100% by mass.

[0097] Example 2 An inorganic material (C-BM_an / CFO-300° C.) and a composite were obtained in the same manner as in Example 1, except that the inorganic material was annealed in air at 300° C. for 2 hours.

[0098] Example 3 An inorganic material (C-BM_an / CFO) and a composite were obtained in the same manner as in Example 1, except that the inorganic material was not subjected to annealing treatment.

[0099] Comparative Example 1 A base material (C-BM_an) and a composite were obtained in the same manner as in Example 1, except that no coating material was formed on the base material.

[0100] (Examples 4 to 10) Composites were obtained in the same manner as in Example 3, except that the mass ratio of the base material and coating material constituting the inorganic material was changed as follows: Example 4 (base material: 80 mass%, coating material: 10 mass%) Example 5 (base material: 75 mass%, coating material: 15 mass%) Example 6 (base material: 70 mass%, coating material: 20 mass%) Example 7 (base material: 65 mass%, coating material: 25 mass%) Example 8 (base material: 50 mass%, coating material: 40 mass%) Example 9 (base material: 25 mass%, coating material: 65 mass%) Example 10 (base material: 10 mass%, coating material: 80 mass%)

[0101] The base materials, inorganic materials, and composites obtained in Examples 1 to 10 and Comparative Example 1 were measured and evaluated by the following methods.

[0102] [AES Analysis] An Auger electron spectroscopy (AES) device (JAMP-9510F, manufactured by JEOL) was used to perform AES analysis of the base material (C-BM_an) obtained in Example 1. As shown in FIGS. 11A and 11B, the surface of the base material was analyzed at position P1 in range A, and the presence of iron (Fe), chromium (Cr), cobalt (Co), and oxygen (O) was confirmed. Furthermore, as shown in FIG. 12A, the depth profile of the base material was analyzed at position P2 in range B. Ar ion sputtering was also used, with an acceleration voltage of 2 kV, a sputtering region of 1.5 mm to 2 mm, a sputtering interval of 1 min / cycle, and a sputtering rate of 6.66 nm / min (SiO ２) and surface etching was performed. As a result, as shown in Figure 12B, the presence of iron (Fe), chromium (Cr), cobalt (Co), titanium (Ti), and oxygen (O) was confirmed at a depth of approximately 600 nm or less (corresponding to 100 or less sputtering cycles). In addition, the oxygen (O) content rapidly decreased at a depth of approximately 50 nm from the base material surface (the position indicated by the dashed line in the figure), suggesting that an oxide film with a thickness of approximately 50 nm had formed on the surface of the base material.

[0103] Similarly, AES analysis was performed on the inorganic material (C-BM_an / CFO-500°C) obtained in Example 1. As shown in Figures 13A and 13B, analysis of the surface of the inorganic material at position P1 in range C confirmed the presence of iron (Fe), cobalt (Co), and oxygen (O). Furthermore, as shown in Figure 14A, analysis of the depth profile of the inorganic material at position P2 in range D was performed. Surface etching was performed under the same conditions as above, using Ar ion sputtering in combination. As a result, the presence of iron (Fe), cobalt (Co), chromium (Cr), titanium (Ti), and oxygen (O) was confirmed at a depth of approximately 600 nm or less (corresponding to 100 sputtering cycles or less). Furthermore, as shown in FIG. 14B, iron (Fe) and chromium (Cr) rapidly increase in the depth direction from the surface to 450 nm to 500 nm (the range indicated by the two dashed lines in the figure), and oxygen (O) rapidly decreases in the same range (FIG. 13B), suggesting that a coating material with a thickness of 450 nm to 500 nm is formed on the surface of the base material.

[0104] [XRD Analysis] XRD analysis was performed on Examples 1 to 3 using an X-ray diffractometer (Rigaku Corporation, SmartLab 9kW ADVANCE). The measurement conditions were as follows: Cu-Kα radiation (λ=0.15418 nm) as the radiation source, tube voltage 45 kV, filament current 200 mA, scan range 20° to 120°, step width 0.01°, and scan speed 3° / min. As a result, as shown in FIG. 15 , in Examples 1 and 2, the peak intensities were detected in the order of (311), (440), (220), (511), and (400), and it was found that the surface of the inorganic material was coated with crystalline Co as a coating material. ｘ Fe ３－ｘ O ４In Example 3, the X-ray diffraction pattern showed that amorphous Co was formed as a coating material on the surface of the inorganic material. ｘ Fe ３－ｘ O ４ It was found that (CFO) was formed.

[0105] [VSM Measurement] For Examples 1 and 3 and Comparative Example 1, the coercive force H ｃ and saturation magnetization σ ｓ The measurement conditions were as follows: a powder sample was placed in a cylindrical Delrin VSM measurement capsule (Riken Denshi Co., Ltd., DPC-625, inner diameter 6 mm, depth 3 mm) and then filled with paraffin from above. The capsule was heated on a hot plate to melt the paraffin and fix the powder. The standard sample was Ni (Riken Denshi Co., Ltd., diameter 5 mm, 2.483 emu), and the maximum applied magnetic field was approximately 400 kA m －１ The calibration was performed under the condition that the sweep speed was 5 min per loop. ｍａｘ Approximately 400 kA m －１ , about 1.6MA・m －１ The measurements were performed using two types of magnetic polarization. No correction was made using the demagnetizing factor. The measured samples were evaluated using mass magnetic polarization, which is the magnetic polarization divided by the mass, and the physical symbol σ was used. The mass saturation magnetic polarization (saturation magnetization) σ was used. ｓ Is H ｍａｘ to 1.6 MA·m －１ On the other hand, the coercive force H ｃ is the value at which the saturation magnetization σ is measured when the applied magnetic field is zero and when a straight line connecting the plots of the demagnetization curve before and after the magnetic polarization value changes from positive to negative is intersected with the axis. The results are shown in Figures 16A, 16B and 17. In Examples 1 and 3, the saturation magnetization σ is measured when compared with Comparative Example 1. ｓ is small and the coercive force H ｃ It was found that the magnetostatic properties were high.

[0106] [Permeability Measurement] For Examples 1 and 3 and Comparative Example 1, the complex relative permeability versus frequency was measured using the NRW (Nicolson-Ross-Weir) method using a vector network analyzer (KEYSIGHT, PNA N5224B). Measurements were performed using a coaxial sample holder (EM Lab, CSH-APC7) for frequencies from 100 MHz to 18 GHz, a waveguide sample holder (EM Lab, WSH-K) for frequencies from 18 GHz to 26.5 GHz, and a waveguide sample holder (EM Lab, WSH-R) for frequencies from 26.5 GHz to 40 GHz, using a materials measurement suite (KEYSIGHT, N1500A). The results are shown in Figures 18A and 18B. In the figures, f is frequency, and μr is complex relative permeability. In Examples 1 and 3, it was found that the real part μr′ and the imaginary part μr″ of the complex relative magnetic permeability were higher in the high frequency band compared to Comparative Example 1. In particular, in Examples 1 and 3, the frequency (resonance frequency fr) at which the imaginary part μr″ of the complex relative magnetic permeability was maximum was shifted to the higher frequency side than in Comparative Example 1, and the imaginary part μr″ of the complex relative magnetic permeability was high at approximately 5 GHz or higher, indicating excellent high-frequency magnetic properties.

[0107] Furthermore, the imaginary part μr″ of the complex relative permeability and the resonance frequency fr were measured for Examples 4 to 10. The results are shown in FIG. 19. It was found that, although the imaginary part μr″ of the complex relative permeability was lower in Examples 4 to 10 compared to Comparative Example 1, the resonance frequency fr was higher and the high-frequency magnetic properties were excellent.

[0108] [Electromagnetic Wave Absorption Evaluation] For Examples 1 and 3 and Comparative Example 1, the value (ω × μr″) obtained by multiplying each frequency ω with the imaginary part μr″ of the complex relative permeability relative to the frequency was calculated. The results are shown in FIG. 20. In Examples 1 and 3, the peak of ω × μr″ was shifted to the higher frequency side compared to Comparative Example 1, and ω × μr″ was large at frequencies of about 5.5 GHz or higher, indicating that the electromagnetic wave absorption characteristics in the high frequency band were excellent. In particular, in Example 1, the peak of ω × μr″ was 1.5 times that of Comparative Example 1, and the frequency of the peak was shifted to a 10 GHz width, from 6 GHz to 16 GHz. For reference, FIG. 21 shows a comparison between Example 1 and a composite using another material as the inorganic material. In Example 1, it was confirmed that the high frequency characteristics were excellent compared to when the base material (C-BM) before annealing treatment was used as a trial material.

[0109] [Noise suppression evaluation] For Examples 1 and 3 and Comparative Example 1, an apparatus as shown in Figs. 22A and 22B was prepared, and the P of the sample made of the composite of each Example and Comparative Example was measured. ｌｏｓｓ / P ｉｎ The measurement conditions are as shown in Table 1. ｌｏｓｓ / P ｉｎ was calculated by the following formulas (1) and (2). In formula (1), W indicates the presence of a sample, W0 indicates the absence of a sample, and in formula (2), S １１ and S ２１ indicates the transmission characteristic. In equation (3), Γ indicates the reflection coefficient, and in equation (4), T indicates the transmission coefficient. The measured P ｌｏｓｓ / P ｉｎ In FIG. 23A, the parameter S １１ and S ２１ are shown in Figures 23B and 23C. ｌｏｓｓ / P ｉｎ (W) and P ｌｏｓｓ / P ｉｎ (WO) to Δ(P ｌｏｓｓ / P ｉｎ The results are shown in Figure 24.

[0110]

[0111]

[0112]

[0113]

[0114]

[0115] From the results of FIG. 24, in Examples 1 and 3, Δ(P ｌｏｓｓ / P ｉｎ ) peak shifts to the high frequency side, and at frequencies above 16 GHz, ｌｏｓｓ / P ｉｎ ) was large, and it was found that the noise suppression characteristics in the high frequency band were excellent. In particular, in Example 1, Δ(P ｌｏｓｓ / P ｉｎ ) was found to have shifted to a 7.3 GHz width from 14 GHz to 21.3 GHz.

[0116] 1 Composite 11 Base material 12 Inorganic material 12a Base material 12b Covering material 121 First phase 122 Second phase 12M Material powder

Claims

1. A composite comprising a substrate and an inorganic material dispersed in the substrate, the inorganic material having a magnetic base material and a ferromagnetic coating material coating the base material.

2. The composite according to claim 1, wherein the coating material contains one or more selected from cubic ferrite, tetragonal ferrite, hexagonal ferrite, and rhombohedral ferrite.

3. The cubic ferrite has a spinel crystal structure and is AFe ２ O ４ (A is one or more elements selected from Mn, Fe, Co, Ni, Cu, and Zn), 4. The composite according to claim 1, wherein the coating material has a thickness of 10 nm or more and 100 μm or less.

5. The composite according to claim 1, wherein the coating material is composed of a powder of particles having an average particle size of 1 nm or more and 1 μm or less.

6. The composite of claim 1, wherein the inorganic material has an average aspect ratio of 1 to 100.

7. The composite according to claim 6, wherein said inorganic material has magnetic anisotropy with the in-plane direction of said composite being the direction of easy magnetization.

8. The composite according to claim 1, wherein the base material is an Fe-based magnetic material.

9. The composite according to claim 8, wherein the Fe-based magnetic material is any one selected from the group consisting of an Fe-Co based alloy, an Fe-Si based alloy, an Fe-Ni based alloy, an Fe-Cr-Co based alloy, an Fe-Cr-Al based alloy, an Fe-Cr-Si based alloy, and an Fe-Si-Al based alloy.

10. The composite of claim 1, wherein the matrix has a two-phase separated structure consisting of a first phase which is ferromagnetic and a second phase which is non-ferromagnetic.

11. The composite of claim 10, wherein the first phase is elongated or flattened.

12. The composite of claim 10, wherein the first phase has the shape of an elliptical plate or a circular plate that is elongated in one direction.

13. The composite of claim 12, wherein said first phase is oriented in an in-plane direction of said composite.

14. The composite according to claim 9, wherein the base material contains 10 to 50 mass% Cr, 0 to 30 mass% Co, and a total of 0 to 5 mass% of one or more elements selected from the group consisting of Ti, Zr, Hf, Al, V, Nb, and Si, with the balance being Fe and impurities.

15. An electromagnetic wave absorber comprising the composite material according to claim 1 or 2.

16. A noise suppressor comprising the composite of claim 1 or 2.

17. A method for producing a composite, comprising: a step of preparing a magnetic base material; a step of coating a surface of the base material with a ferromagnetic coating material to form an inorganic material in which the surface of the base material is coated with the coating material; and a step of kneading and molding the inorganic material with a substrate to obtain a composite.