JP3755023B2 - Radio wave absorber and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio wave absorber and a method for manufacturing the same, and more particularly to a radio wave absorber having a high frequency microwave complex permeability characteristic improved by multilayering and a method for manufacturing the same.
[0002]
[Prior art]
Magnetic fine particles such as ferromagnetic metal fine particles and ferrite fine particles are dispersed and compounded in a binder and used as a radio wave absorber in the form of a magnetic fine particle dispersion.
[0003]
In such an electromagnetic wave absorber, in addition to the magnetic fine particles used as they are dispersed in a resin or the like, a surface treatment agent is applied to the surface of the magnetic fine particles to facilitate the dispersion of the particles, In addition, when the magnetic fine particle is a ferromagnetic metal, there is one in which insulation between particles is obtained by providing a thin layer such as an oxide film on the surface.
[0004]
The surface layer in these magnetic fine particles plays only the role of improving the dispersibility of the particles and weakening the magnetic or electrical coupling between the magnetic particles. Therefore, any of these magnetic fine particles can be regarded as a substantially single-layer magnetic fine particle.
[0005]
Therefore, the present inventors paid attention to new possibilities for electromagnetic field response, such as improving the high-frequency microwave complex permeability characteristics by giving the magnetic particles a multi-layer structure, and conducted research.
[0006]
Incidentally, as the magnetic particles having a layered structure, particles having a ferrite plating layer provided on the surface of a polyacryl sphere have already been developed by the present inventors. However, this is a particle mainly used for medical purposes, and does not improve the high-frequency microwave complex permeability characteristics.
[0007]
In addition, multilayer particles made by using reverse micelles, so-called nano-onion fine particles, have recently been announced and attracted attention as fine particles having a multilayer structure. In these particles, the particle size is limited to the range where reverse micelles are possible. For this reason, the upper limit of the particle size is about 20 to 30 nm in average diameter. Thus reverse micelle nano-onions particles formed with, since its size is limited to very small, the fine particles, the giant magnetoresistive effect minute size is essentially important phenomenon (GMR) etc. are only being researched.
[0008]
[Problem to be Solved by the Invention]
The present inventors have found that with respect to the prior art, instead of the multi-layer structure magnetic fine particles from the conventional single-layer structure, of improving the complex permeability characteristic at high frequency to the microwave band by a multilayer structure I found the necessity and advanced the research.
In further research, one inventors that multilaterally analyze the response to the electromagnetic field of the dispersed magnetic fine particles, as a means to actually form the magnetic fine particles having a multilayer structure, the ferrite plating method of any plating The method was used as a means.
The ferrite plating method is a method in which a ferrite layer is formed on a substrate in an aqueous solution, which was developed by one of the inventors of the present invention. The possible range can be greatly expanded.
[0009]
As one of the applications of the ferrite plating technology, it can be applied to magnetic particles having a multilayer structure of the present invention, that is, a radio wave absorber, thereby enabling a new development of ferrite plating.
[0010]
[Means for Solving the Problems]
The present invention is an invention of a radio wave absorber and a method for producing the same, and by increasing the number of magnetic fine particles to increase the complex permeability and complex dielectric constant at high frequency or microwave of the magnetic fine particle dispersion medium using the same. It is something that can be done.
[0011]
The first wave absorber of the present invention, and a coating layer or layers covering the middle Kokorokaku and central core having a ferromagnetic metallic fine particles, the coating layer formed by the ferrite plating method magnetic multilayer microparticles that have have a ferromagnetic ferrite layer is characterized in that it is dispersed in a binder snake (Snoek) dispersing medium exceeding the limit is formed. The thickness of the coating layer is not particularly limited. In order to sufficiently obtain the effect of the multilayer structure, it is preferable to have an average thickness of, for example, about 1/10 or more of the average diameter of the central core.
[0012]
In the radio wave absorber of the present invention, ferromagnetic metal fine particles such as metallic iron can be used as the central core having ferromagnetism. By using a ferromagnetic metal particle having a large saturation magnetization as the central core of the magnetic multilayer fine particle and providing a coating with a ferrite layer, which is a high-resistance magnetic material, the magnetic multilayer fine particle has a high saturation magnetization, and between the particles. Can have a high specific resistance.
In the radio wave absorber of the present invention, the central core having ferromagnetism may be spinel-type ferrite fine particles, or garnet-type ferrite fine particles or hexagonal ferrite fine particles.
[0013]
If hexagonal ferrite fine particles are used as the central nucleus of the radio wave absorber of the present invention, magnetic multilayer fine particles with easy particle orientation can be obtained by utilizing the strong anisotropy. The unique complex magnetic permeability characteristics of the ferrite fine particles due to the strong anisotropic magnetic field can be controlled by the multilayer structure. Furthermore, even when spinel ferrite is used as the central core and this is coated with spinel ferrite, the complex permeability characteristics can be appropriately controlled by selecting the respective compositions.
[0014]
The second wave absorber of the present invention, the one or more layers chromatic and be covered layer and a coating layer that covers the middle Kokorokaku and central core having ferroelectricity microparticles formed by ferrite plating method magnetic multilayer microparticles that have have a ferromagnetic ferrite layer is characterized in that it is dispersed in a binder snake (Snoek) dispersing medium exceeding the limit is formed.
[0015]
In the present invention, the central core having ferroelectricity includes not only the central core having a ferroelectric material but also the central core having a dielectric constant as high as that of the ferroelectric material. The dielectric constant is preferably 100 or more and more preferably 500 or more in order to obtain a high dielectric constant effect.
[0016]
By having such a central core, magnetic multilayer fine particles having a high complex permeability and a high complex dielectric constant can be obtained. Conventionally, in radio wave absorbers and the like, it has been desired to have a high complex permeability and a high complex dielectric constant. However, a practical material having ferromagnetism and ferroelectricity cannot be obtained at the same time. I could not respond to. The radio wave absorber configured as described above according to the present invention can meet such a demand.
[0017]
In the magnetic multilayer fine particles constituting the radio wave absorber of the present invention, at least one of the coating layers is preferably a ferrite layer, and the ferrite layer is preferably a layer formed by ferrite plating.
[0018]
Ferrite plating is characterized in that a high-quality film can be formed in an aqueous solution under relatively mild conditions such as temperature and pH. Therefore, without alteration of the central core when forming a coating layer, moreover can be provided with excellent be covered layer of magnetic properties good adjusted well thickness.
[0019]
In the magnetic multilayer fine particles constituting the radio wave absorber of the present invention, at least one of the coating layers can be a metal layer. In this case, the metal layer can be formed by electroless plating. By using electroless plating, treatment in an aqueous solution is possible as with ferrite plating.
[0020]
Further, in the magnetic multilayer fine particles constituting the radio wave absorber of the present invention, those having isotropic particle shapes such as those having a spherical central nucleus and shapes having cubic symmetry can be used. If the central core is an isotropic fine particle, it is easy to make the magnetic multilayer fine particle medium isotropic. And by using an isotropic shape magnetic multilayer microparticles, it is easy to produce the magnetic fine particle-dispersed medium having no directionality.
[0021]
In the magnetic multilayer fine particles constituting the radio wave absorber of the present invention, the shape of the central core may be a flat particle shape such as a plate shape. Furthermore, in the magnetic multilayer fine particles of the present invention, those having a central core shape extending in one direction such as a needle shape, a rod shape, or a spun shape can also be used. When the central core has fine particles having such a shape, the obtained magnetic multilayer fine particles can have the same particle shape.
[0022]
If the magnetic multilayer fine particles having the flat particle shape obtained in this way or the magnetic multilayer fine particles having a long particle shape in one direction are used, it is easy to produce a directional radio wave absorber by orienting these particles. In this way, imparting directionality to the dispersion medium, that is, imparting anisotropy, is useful when used as a radio wave absorber.
[0023]
The radio wave absorber of the present invention is characterized in that the magnetic multilayer fine particles are dispersed in a binder. When the magnetic multilayer fine particles of the present invention are dispersed in a binder to form a radio wave absorber, the characteristics of the magnetic multilayer fine particles with respect to the high frequency and the microwave electromagnetic field can be utilized, and a wide range of applications can be obtained.
[0024]
By using the radio wave absorber of the present invention as a radio wave absorber particularly in the quasi-microwave and microwave regions, a large attenuation can be obtained as compared with the conventional radio wave absorber. When used as a radio wave absorber, the magnetic multilayer fine particle dispersion medium is preferably formed in a plate shape, for example, and a metal terminal plate is provided on one surface thereof. In order for the radio wave absorber of the present invention to obtain sufficient radio wave absorption, the average particle size of the magnetic multilayer fine particles is preferably 0.1 μm to 1 mm, more preferably 1 μm to 100 μm.
[0025]
The method for producing a radio wave absorber according to the present invention includes the step of coating a magnetic layer on the surface of fine particles functional with respect to an electromagnetic field by at least one of ferrite plating and electroless plating. Fine particles are produced.
Here, in the present invention, fine particles having a function with respect to an electromagnetic field are fine particles having ferromagnetism, fine particles having ferroelectricity, or fine particles having a high dielectric constant comparable to that of a ferroelectric.
[0027]
In the ferrite plating method, fine particles are dispersed, a reaction solution containing divalent iron ions is added thereto, and the reaction proceeds by oxidation of divalent iron ions and pH adjustment to form a ferrite plating layer on the surface of the fine particles.
[0028]
According to this method, as already described, a well-fixed ferrite layer is formed by formation at a temperature near room temperature, and good crystallinity and good magnetic properties can be obtained. Here, if the ferrite plating layer is formed while applying ultrasonic waves to the reaction solution, ferrite plating can be performed more evenly, and the crystallinity can be further improved.
[0029]
According to the method for manufacturing a radio wave absorber of the present invention, since the surface of the particles is plated in a state in which the fine particles are dispersed in the plating solution, the periphery of the particles can be coated, and the shape and dimensions of the central core and the coating The thickness of the layer can be arbitrarily selected, and magnetic multilayer fine particles well suited for the purpose can be produced.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing several examples of embodiments of magnetic multilayer fine particles 11 in the radio wave absorber of the present invention.
In FIG. 1, (a) shows the core 12 covered with a coating layer 13a, (b) shows the core surrounded by the coating layers 13a and 13b, and (c) shows the core. Is coated with three layers of coating layers 13a, 13b and 13c. (d) shows the central core covered with four layers of coating layers 13a, 13b, 13c and 13d. Although FIG. 1 shows an example in which the central core is coated with up to four layers, the coating layer may be further multilayered if necessary.
[0031]
The particle shape of the central core 12 may be isotropic, such as a spherical shape or a nearly spherical shape as shown in FIG. 1 or a shape close to a regular polyhedron such as a cube, and FIG. ) Covers the anisotropic core 22 such as the flat shape shown in the schematic cross-sectional view of Fig. 2 (b), the rod shape shown in the schematic cross-sectional view of Fig. 2 (b) and the shape of particles that are long in one direction. The magnetic multilayer fine particle 21 provided with the layer 23 may be used.
[0032]
The shape of the central core is spherical or nearly spherical, or a shape close to a regular polyhedron such as a cube, and the magnetic multilayer fine particles using these can have the same shape as the central core. When such magnetic multilayer fine particles are dispersed in a binder resin and molded, it is easy to obtain an isotropic dispersion medium as shown in the schematic cross-sectional view of FIG. In FIG. 3A, magnetic multilayer fine particles 31 are dispersed and molded in a binder resin 34 to form a plate-like magnetic multilayer fine particle dispersion medium 35.
[0033]
In addition, there is no restriction | limiting in particular in the binder used here, According to a use, it can select and use from a well-known material. For example, a resin such as a silicone resin mainly containing siloxane can be selected and used.
[0034]
Further, by forming the central core into a flat shape such as a flat plate shape or a particle shape long in one direction such as a rod shape, the magnetic multilayer fine particles can be formed into a flat shape or a particle shape long in one direction. As described above, the magnetic multilayer fine particles may be formed into a flat plate shape or a rod shape so as to give an appropriate direction to the demagnetizing field in the magnetic particles. In addition, when the magnetic multilayer fine particle has a dielectric such as a ferroelectric at the central core, the shape of the central core is made flat or long in one direction, and the directionality suitable for the counter electric field inside the dielectric May be given.
[0035]
Each of the above figures shows a case where each layer covering the central core is covered with a uniform thickness. However, the coating layer is not necessarily uniform, and the multilayer effect of the present invention can be obtained. In such a range, the layer may be a non-uniform layer as a covering shape, or may partially have a covering layer.
[0036]
By dispersing and orienting these particles in the binder, (b) and (c) in FIG.
As shown in the schematic cross-sectional view, a dispersion medium having anisotropy in which flat tabular grains and rod-shaped grains are dispersed can be obtained. Here, a mechanical method or a magnetic method can be used for the orientation of the particles.
[0037]
As shown in the schematic cross-sectional view of FIG. 4, the magnetic multilayer fine particles in the radio wave absorber of the present invention use ferromagnetic metal fine particles such as metallic iron and metallic cobalt as the central core 42, and around the central core 42, for example, ferrite. You may comprise by coating with the ferrite layer 43 using plating.
[0038]
With such a configuration, magnetic particles 41 having a high resistance and a saturation magnetization larger than that of ferrite are formed. Therefore, the dispersion medium in which the magnetic particles are dispersed is, for example, in the frequency spectrum characteristic of the complex permeability shown in FIG. The limit in the case of ferrite (Snoek limit) can be exceeded.
[0039]
Further, as shown in the schematic cross-sectional view of FIG. 6 (a), a material having a high dielectric constant, for example, ferroelectric particles 62 such as barium titanate, is used as the central core of the magnetic multilayer fine particles in the present invention. Is coated with ferrite plating 63a to obtain magnetic multilayer fine particles 61 having high magnetic permeability and high dielectric constant.
Further, as shown in a schematic cross-sectional view in FIG. 6 (b), a material 62 having such a high dielectric constant is used for the central core, and a metal cobalt metal nickel layer 63b is provided by electroless plating around the material 62. Thereafter, it may be covered with a ferrite plating 63a.
[0040]
Further, as shown in the schematic cross-sectional view of FIG. 7, when using ferrite fine particles for the magnetic multilayer fine particle central core 72 in the radio wave absorber of the present invention, in addition to spinel type ferrite, garnet type ferrite or hexagonal ferrite is used. be able to.
The coating layer covering the central core of the ferrite is provided with a coating layer formed by ferrite plating or a coating layer 73 formed by electroless plating. Further, a layer in which these coating layers are laminated to form a multilayer can also be used.
By such a composite, magnetic multilayer fine particles 71 having composite characteristics that cannot be obtained by a single ferrite particle are obtained.
[0041]
In the production of the magnetic multilayer fine particles in the radio wave absorber of the present invention, the fine particles forming the central core are first immersed in a reaction solution (ferrite plating solution or electroless plating solution) for coating the particle surface, and the fine particles are dispersed as uniformly as possible. To do. Next, the reaction solution is reacted to coat the surface of the dispersed fine particles. Magnetic multilayer fine particles having a multilayer coating layer can be obtained by changing the reaction liquid and further coating the coated particles.
[0042]
As a specific example, a process in which fine particles are coated by ferrite plating will be described with reference to a ferrite plating apparatus shown in FIG. Fine particles 82 forming a central nucleus, for example, barium titanate fine particles are dispersed in water, and divalent metal ions such as FeCl ₂ and divalent metal ions such as MCl _{2 in} a glass vessel 86 immersed in a hot bath 80. Ferrite plating is performed in a ferrite plating reaction solution 87 containing a salt and, if necessary, trivalent iron ions such as FeCl ₃ . Ferrite plating is performed by gradually adding an oxidizing agent such as NaNO ₂ nitrite while applying ultrasonic waves (19.5 kHz, 600 w) with an ultrasonic horn 88, and NH ₄ OH with a pH controller 89. Adjust the pH with.
[0043]
Here, divalent Fe ions and M ions are adsorbed to OH groups, which are adsorption sites on the surface of the barium titanate particles, and hydrogen ions are released. Next, when a reaction in which part of divalent Fe becomes trivalent by oxidation is performed, divalent Fe ions and M ions are adsorbed again on this surface. Then the reaction was carried out in which a part of the divalent Fe is trivalent upon oxidation such Repetitive Rikae said plating layer of spinel ferrite particles surface. The same applies to the case where the central core is another material, for example, metallic iron, and divalent Fe ions and M ions are adsorbed to the OH group, which is an adsorption site existing on the oxidized surface, and the ferrite plating layer is similarly formed. Can be formed.
[0044]
Here, when the ferrite formation reaction is allowed to proceed while irradiating the liquid with ultrasonic waves, it is easy to form a ferrite layer over the entire surface of the fine particles, and a ferrite plating layer with good crystallinity can be formed. Here, the thickness of the coating layer can be easily controlled by adjusting the progress rate of the reaction by oxidation and the time thereof.
[0045]
Next, examples of the present invention will be described.
[0046]
Example 1
(The central core is metallic iron, which is coated with ferrite plating. Moreover, a radio wave absorber using this is prepared.)
A composite of metallic iron and NiZnFe ferrite is formed by forming a ferrite layer with an average thickness of 0.1 μm on the surface using a ferrite plating method with metal iron particles having an average particle size of 0.2 μm and an oxide layer on the surface as the central core. Magnetic multilayer fine particles having a structure were obtained.
[0047]
Here, the ferrite plating was performed using the glass vessel (capacity 500 ml) shown in FIG. 9 under the following conditions while applying ultrasonic waves.
Reaction solution: FeCl ₂ (12 g / l) + NiCl ₂ (4 g / l) + ZnCl ₂ (0.5 g / l), pH = 6.0
Temperature: 80 ℃ Ultrasound: Frequency 19.5kHz, Power 600w
Plating time: 6 minutes [0048]
Next, the magnetic multilayer fine particles were surface-treated with a silane coupling agent, then dispersed in a silicone resin, molded and cured to produce a magnetic multilayer fine particle dispersion medium. The ratio of the fine particles to the nonvolatile resin was 5: 1 by weight, and the volume filling rate of the fine particles was 57%.
[0049]
The frequency characteristics of the complex permeability were measured for this magnetic multilayer fine particle dispersion medium. As a result, the frequency characteristics of complex permeability exceeding the limit of Snoek were obtained.
[0050]
(Example 2)
(The central core is made of barium titanate particles, which are coated with ferrite plating. A radio wave absorber using this is also produced.)
A magnetic multilayer having a composite structure of barium titanate and ferrite, with barium titanate particles with an average particle size of 0.5 μm as the core and a NiZnFe ferrite layer with an average thickness of 0.2 μm formed by ferrite plating on the surface. Fine particles were obtained.
[0051]
Here, the ferrite plating was performed under the following conditions.
Reaction solution: FeCl ₂ (12 g / l) + NiCl ₂ (4 g / l) + ZnCl ₂ (0.5 g / l), pH = 6.0
Temperature: 80 ℃
Ultrasound: frequency 19.5kHz, power 600w
Plating time: 12 minutes [0052]
Next, the produced magnetic multilayer fine particles were surface-treated with a silane coupling agent, then dispersed in a silicone resin, molded and cured to produce a magnetic multilayer fine particle dispersion medium. The ratio of the fine particles to the nonvolatile resin was 6: 1 by weight, and the volume filling rate of the fine particles was 60%.
[0053]
The frequency characteristics of the complex permeability were measured for this magnetic multilayer fine particle dispersion medium. As a result, the frequency characteristics of complex permeability exceeding the limit of Snoek were obtained.
[0054]
[0055]
[0056]
[0057]
[0058]
Example 3
(Ferrite plating is performed on the metallic iron core, then Co electroless plating is performed, and ferrite plating is performed. A radio wave absorber using the same is prepared.)
By the ferrite plating method on the particle surface of the metal iron fine particle powder with an average particle diameter of about 1μm,
Reaction solution: FeCl ₂ (12 g / l) + NiCl ₂ (4 g / l) + ZnCl ₂ (0.5 g / l), pH = 6.0
Temperature: 80 ℃
Ultrasound: frequency 19.5kHz, power 600w
Plating time: A NiZnFe ferrite layer of about 0.4 μm was formed and coated under conditions of 24 minutes. Subsequently, on the surface of the obtained fine particle powder, an Ni base was first formed by electroless plating, and a buffer solution containing a cobalt sulfate solution on the surface was set at 80 ° C. at 80 ° C. About 0.1 μm Co film was formed.
[0059]
Thereafter, the surface of the fine powder, subjected to coating by NiZnFe ferrite layer of approximately 0.4μm by ferrites plating under the same conditions as above again, metallic iron central core, a ferrite layer, the magnetic multilayer comprising a metal layer and a ferrite layer Fine particles were obtained.
[0060]
Next, the magnetic multilayer fine particles were surface-treated with a silane coupling agent, then dispersed in a silicone resin, molded and cured to produce a magnetic multilayer fine particle dispersion medium. The ratio of the fine particles to the nonvolatile resin was 5: 1 by weight, and the volume filling rate of the fine particles was 57%.
[0061]
The frequency characteristics of the complex permeability were measured for this magnetic multilayer fine particle dispersion medium. As a result, the frequency characteristics of complex permeability exceeding the limit of Snoek were obtained.
[0062]
(Example 4)
(Barium titanate / ferrite / Co layer / ferrite layer)
(Production of radio wave absorber using this)
By ferrite plating on the surface of titanium oxide having a rutile structure with an average particle size of about 1 μm,
Reaction solution: FeCl ₂ (12 g / l) + NiCl ₂ (4 g / l) + ZnCl ₂ (0.5 g / l), pH = 6.0
Temperature: 80 ℃
Ultrasound: frequency 19.5kHz, power 600w
Plating time: A NiZnFe ferrite layer of about 0.8 μm was formed and coated at 48 minutes. Subsequently, on the surface of the obtained fine particle powder, an Ni base was first formed by electroless plating, and a buffer solution containing a cobalt sulfate solution on the surface was set at 80 ° C. at 80 ° C. About 0.1 μm Co film was formed.
[0063]
Thereafter, the surface of the fine particle powder was coated with a NiZnFe ferrite layer of about 0.8 μm by a second ferrite plating method to obtain magnetic multilayer fine particles comprising a dielectric core, a ferrite layer, a metal layer, and a ferrite layer.
[0064]
Next, the magnetic multilayer fine particles were surface-treated with a silane coupling agent, then dispersed in a silicone resin, molded and cured to produce a magnetic multilayer fine particle dispersion medium. The ratio of the fine particles to the nonvolatile resin was 6.5: 1 by weight, and the volume filling rate of the fine particles was 62%.
[0065]
The frequency characteristics of the complex permeability were measured for this magnetic multilayer fine particle dispersion medium. As a result, the frequency characteristics of complex permeability exceeding the limit of Snoek were obtained.
[0066]
【The invention's effect】
According to the radio wave absorber of the present invention and the manufacturing method thereof, the material and shape of the central core of the magnetic multilayer fine particle, and the thickness of the coating layer can be arbitrarily selected. You can choose to.
[0067]
For this reason, in the radio wave absorber in which the magnetic multilayer fine particles of the present invention are dispersed, by selecting the central core and the coating layer, it is possible to obtain an elongation exceeding the snake limit line in the frequency characteristics of the complex permeability. Characteristics can be obtained.
[0068]
Furthermore, according to the method for producing a radio wave absorber of the present invention, magnetic multilayer fine particles can be produced in an aqueous solution without using a vacuum, and can be carried out at a temperature close to normal temperature and at normal pressure. Manufacture can be performed with high productivity without requiring a large-scale manufacturing apparatus.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an embodiment of a magnetic multilayer fine particle of a radio wave absorber according to the present invention.
FIG. 2 is a cross-sectional view schematically showing magnetic multilayer fine particles having an anisotropic particle shape such as a flat shape and a rod shape according to another embodiment of the present invention.
FIG. 3 is a cross-sectional view schematically showing an embodiment of a dispersion medium in which magnetic multilayer fine particles of the present invention are dispersed in a binder resin and molded.
FIG. 4 is a schematic cross-sectional view showing magnetic multilayer fine particles according to an embodiment of the present invention, in which ferromagnetic metal fine particles are used as a central nucleus and the periphery is covered with a ferrite layer.
FIG. 5 is a diagram showing a frequency spectrum of complex permeability.
FIG. 6 is a schematic cross-sectional view showing magnetic multilayer fine particles according to an embodiment of the present invention configured by using ferroelectric particles having a high dielectric constant for the central core and covering the periphery with ferrite plating 63.
FIG. 7 is a schematic cross-sectional view showing magnetic multilayer fine particles according to an embodiment of the present invention using ferrite fine particles as a central core.
FIG. 8 is a diagram schematically showing an example of a ferrite plating tank for forming a ferrite plating layer according to an embodiment of the magnetic multilayer fine particle of the present invention.
[Explanation of symbols]
11,21,31,41,61,71 …… Magnetic multilayer fine particles,
12,22,32,42,62,72 …… Central core,
13a, 13b, 13c, 13d, 23, 43, 63a, 63b, 73 …… Coating layer,
34 …… Binder resin
35 …… Magnetic multilayer fine particle dispersion medium,
80 …… Hot bath,
86 …… Glass vessel,
87 …… Reaction liquid,
88 …… Ultrasonic horn,
89 …… pH controller

Claims (3)

A central core having ferromagnetic metal fine particles or ferroelectric fine particles and one or more coating layers covering the central core, and the coating layer has a ferromagnetic ferrite layer formed by a ferrite plating method; wave absorber to magnetic multilayer microparticles are, characterized in that it is dispersed in a binder snake (Snoek) dispersing medium exceeding the limit is formed. 2. The radio wave absorber according to claim 1 , wherein the central core is a ferroelectric fine particle having a dielectric constant of 100 or more. A ferrite-plated coating step of forming a magnetic multilayer microparticles coated with ferromagnetic ferrite layer by ferrite plating method on the surface of the ferromagnetic metal fine particles or ferroelectric particles,
Method for producing a radio wave absorber characterized by having a fine particle dispersion forming step of producing a dispersion medium said magnetic multilayered microparticles were dispersed molded in the binder exceeds snake (Snoek) limit.

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