KR20210094367A - Z-type ferrite, composition of radio wave absorber comprising the same and radio wave absorber sheet - Google Patents

Abstract

In the present invention, single-phase Z-type ferrite can be synthesized by a solid-phase method in air without heat treatment atmosphere control. In the radio wave absorber composition of the present invention, Z-type ferrite having plate-shaped crystal grains is uniformly dispersed without precipitation or agglomeration, and thus, can be used to be easily manufactured into a radio wave absorbent sheet or film. The radio wave absorbent sheet of the present invention has excellent absorption capacity in a GHz band. Specifically, the radio wave absorbent sheet of the present invention can absorb radio waves in the 1 to 18 GHz band.

Description

Z-type ferrite, radio wave absorber composition comprising same, and radio wave absorber sheet comprising same

The present invention relates to a Z-type ferrite, a radio wave absorber composition comprising the same, and a radio wave absorber sheet comprising the same.

As for the conventional ferrite radio wave absorber, a composition having a spinel structure such as Ni-Zn or Mn-Zn was mainly developed and used. These magnetic materials are used in a frequency band of several tens to hundreds of MHz, and in a frequency band of GHz or higher, the magnetic properties are almost lost, and thus the absorber does not function properly.

Meanwhile, in the case of hexaferrite having ferromagnetic resonance characteristics in a band of several to several tens of GHz, it may be used as a radio wave absorber in the GHz band. Hexaferrite has six different crystal structures M, Z, Y, W, X, and U, of which type Z is known to show excellent high-frequency characteristics.

However, there is a problem that Z-type hexaferrite is difficult to synthesize in a single phase. Among _{Ba 3 Co 2 Z (Ba 3} Co 2 Fe 24 O 41) or _{SrBaCo 2 Z (Ba 1. 5} Sr 1. 5 Co 2 Fe 24 O 41) , etc., but the reported synthesis Sr ₃ Co ₂ Z (Sr ₃ Co ₂ Fe ₂₄ O ₄₁ ) phase is very difficult to synthesize as a single phase, so there are few reported cases.

An object of the present invention is to synthesize a single-phase Z-type hexaferrite through two heat treatment in the solid phase in air without adjusting the heat treatment atmosphere, and to provide a radio wave absorber composition and radio wave absorber sheet including the same.

Z-type ferrite according to an embodiment of the present invention is represented by the following formula (1).

[Formula 1]

Sr ₃ Co _2-x M _x Fe _24-d O ₄₁

where x is 0 to 1.0, d is 0 to 1.5,

M is Ni or Mn.

The radio wave absorber composition according to an embodiment of the present invention includes the Z-type ferrite.

The radio wave absorber composition according to an embodiment of the present invention further includes a binder, and the Z-type ferrite is dispersed in the binder.

In the radio wave absorber composition according to an embodiment of the present invention, the Z-type ferrite is included in an amount of 85 wt% to 95 wt%, and the binder is included in an amount of 5 wt% to 15 wt%.

The radio wave absorber composition according to an embodiment of the present invention further includes a solvent, a dispersant, and an anti-settling agent, the solvent is included in an amount of 200 wt % to 250 wt % compared to 100 wt % of Z-type ferrite, and the dispersing agent is Z-type ferrite 100 0.3 wt % to 3.5 wt % compared to wt %, and the anti-settling agent is included in 0.3 wt % to 3.5 wt % compared to Z-type ferrite.

A radio wave absorbing sheet according to an embodiment of the present invention includes a radio wave absorbing layer; and a metal layer disposed on the radio wave absorbing layer, wherein the radio wave absorbing layer includes Z-type ferrite and a binder.

In the radio wave absorption sheet according to an embodiment of the present invention, the metal layer includes aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), It contains at least one selected from the group consisting of tungsten (W) and iron (Fe), graphite, carbon nanotubes (CNT), graphene, graphene oxide, carbon fiber, and fullerene. .

In the present invention, single-phase Z-type ferrite can be synthesized by a solid-phase method in air without heat treatment atmosphere control.

In the radio wave absorber composition of the present invention, Z-type ferrite having plate-like crystal grains is uniformly dispersed without precipitation or agglomeration, and it can be easily manufactured into a radio wave absorber sheet or film using the same.

The radio wave absorption sheet of the present invention has excellent absorption capacity in the GHz band. Specifically, the radio wave absorbing sheet of the present invention can absorb radio waves in the 1 GHz to 18 GHz band.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the synthesis method of Z-type ferrite and the manufacturing method of a radio wave absorber composition.
2 is a schematic schematic diagram of a radio wave absorption sheet.
3 is an XRD graph when d is changed to 0, 0.5, 1, -0.5, -1.0, and FIG. 4 is SEM images.
5 is an XRD graph when M is changed to Ni, Cu, Mn and Non (none).
6 is an XRD graph when x is changed to 0.5, 1.0, 1.5 and 2.0.
7 is an XRD graph when x is changed to 0, 0.3, 0.5, 1.0, 1.5 and 2.0, and FIG. 8 is SEM images.
9 is an XRD graph when x is changed to 0.5, 1.0, 1.5 and 2.0.
10 is a graph showing the complex magnetic permeability and the complex permittivity of the Z-type ferrite of Example 1 when x is changed to 0.0, 0.3 and 0.5.
11 is a graph showing the complex magnetic permeability and the complex permittivity when x of the Z-type ferrite included in the radio wave absorber of Example 2 is changed to 0.0, 0.3, and 0.5.
FIG. 12 is a graph regarding radio wave absorption characteristics when x is 0.0, FIG. 13 is when x is 0.3, and FIG. 14 is when x is 0.5.
15 is a sintered body - a 2D map of a radio wave absorption characteristics corresponding to the type of x in _{- (x Ni x Fe 23 O} 41 -Epoxy Composite Sr 3 Co 2) epoxy composite.
16 is an SEM image of the surface and cross-section, and FIG. 17 is an XRD graph.
18 is a third embodiment propagation of the Z-type ferrite comprising the absorbent sheet Sr ₃ Co _{2 -} and x is from 0.0 _x Ni _x Fe ₂₃ O _41, the magnetic or non holy are complex magnetic permeability and complex permittivity graph.
19 is a third embodiment propagation of Z-type ferrite containing Sr ₂ Co ₃ in the absorbent sheet of _a graph of the wave absorption characteristics when x is in the 0.0 in _x Ni _x Fe ₂₃ O _41.
Fig. 20 is a 2D map of the radio wave absorption characteristics in the case of magnetic or non-magnetic in the radio wave absorption sheet of Example 3;

Hereinafter, various embodiments of the present document will be described with reference to the accompanying drawings. The examples and terms used therein are not intended to limit the technology described in this document to specific embodiments, and should be understood to include various modifications, equivalents, and/or substitutions of the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Z-type ferrite according to an embodiment of the present invention is represented by the following formula (1).

[Formula 1]

Sr ₃ Co _2-x M _x Fe _24-d O ₄₁

where x is 0 to 1.0, d is 0 to 1.5,

M is Ni or Mn.

Preferably, x is 0, 0.3 or 0.5 and d may be 1. Meanwhile, x may be determined according to the sintering temperature when synthesizing Z-type ferrite. For example, when the sintering temperature is 1210 °C when synthesizing Z-type ferrite, x may be 0 or 0.3. Alternatively, when the sintering temperature is 1235° C. when synthesizing Z-type ferrite, x may be 0.5.

The Z-type ferrite according to an embodiment of the present invention may have a plate shape.

Referring to FIG. 1, the method of manufacturing Z-type ferrite according to an embodiment of the present invention includes the steps of weighing powder (S100), mixing (S200), calcining (S300), pulverizing and sieving ( S400), and sintering (S500) may be included.

First, in the step (S100) of weighing the powder, Fe ₂ O ₃ , SrCO ₃ , CoO, MeO (Me = dislocation metal) powders may be weighed according to the molar ratio of the target composition.

Next, in the mixing step ( S200 ), the weighed powder may be mixed with the Zr-ball and ball milled wet.

Next, in the calcining step (S300), it may be calcined at a temperature at which a target phase can be made or an intermediate phase (eg, Y-type or M-type) of the target phase can be made. For example, in the calcining step, it may be calcined at 1100 °C to 1160 °C.

Next, in the pulverizing and sieving step (S400), the calcined powders may be ground in a mortar and sieved through a #80 sieve.

Next, in the sintering step (S500), the sieved powder may be sintered at 1160 °C to 1300 °C. Preferably, in the sintering step (S500), it may be sintered at 1210 °C to 1235 °C.

Through such a specific calcination temperature and sintering temperature, it is possible to synthesize the desired Z-type ferrite in the present invention.

The radio wave absorber composition according to an embodiment of the present invention may include the above-described Z-type ferrite and the binder. The plate-shaped Z-type ferrite may be dispersed in the binder. In this case, the binder may include at least one selected from the group consisting of an epoxy-based compound, a silane-based compound, an amino-based compound, a silicone-based compound, a polyolefin-based resin, and combinations thereof. Preferably, the binder may be an epoxy. Alternatively, the binder may include a styrene-ethylene (Styrene-Ethylene), and a butylene-styrene (Butylene-Styrene) polymer.

In the radio wave absorber composition according to an embodiment of the present invention, the Z-type ferrite may be included in an amount of 85 wt% to 95 wt%, and the binder may be included in an amount of 5 wt% to 15 wt%.

The radio wave absorber composition according to an embodiment of the present invention may further include a solvent, a dispersant, and an anti-settling agent.

The solvent may be at least one selected from the group consisting of hexane, benzene, acetone, butanol, toluene, and xylene. The solvent may be included in an amount of 200 wt % to 250 wt % compared to 100 wt % of Z-type ferrite.

The dispersant may be any one selected from the group consisting of a polyacrylate-based dispersant, a polyester-containing dispersant, a polyether-containing dispersant, and a polyurethane-based dispersant. For example, the dispersant may be texaphor. The dispersant can stabilize the dispersion of Z-type ferrite. The dispersant may be included in an amount of 0.3 wt % to 3.5 wt % relative to 100 wt % of Z-type ferrite.

The anti-settling agent may be at least one selected from the group consisting of attapulgite, garamite, acrylonitrile, methylene chloride, and methylmethacrylate. . The anti-settling agent may be included in an amount of 0.3 wt% to 3.5 wt% compared to 100 wt% of Z-type ferrite. When the amount of the anti-settling agent is less than 0.5 wt %, the anti-settling effect of the Z-type ferrite may be reduced. If the amount of the anti-settling agent is more than 3.0 wt %, the electromagnetic properties may be lost.

In the radio wave absorber composition of the present invention, Z-type ferrite having plate-like crystal grains is uniformly dispersed without precipitation or agglomeration, and it can be easily manufactured into a radio wave absorber sheet or film using the same.

A radio wave absorber can be obtained by preparing such a radio wave absorber composition in the form of a film or sheet.

The method of manufacturing a radio wave absorber composition according to an embodiment of the present invention, referring to FIG. 1 , may include a step of pulverizing and sieving the Z-type ferrite sintered body synthesized above (S600) and a step of mixing with a binder (S700). can Specifically, the previously synthesized Z-type ferrite sintered body may be sieved through a #200 sieve, and mixed with a binder, a solvent, an anti-settling agent, and the like. In the step of pulverizing and sieving the Z-type ferrite sintered compact (S600), the Z-type ferrite may be obtained in plate-shaped grain units.

Referring to FIG. 2, a radio wave absorbing sheet according to an embodiment of the present invention includes a radio wave absorbing layer; and a metal layer disposed on the radio wave absorbing layer, wherein the radio wave absorbing layer may include Z-type ferrite and a polymer binder. That is, the radio wave absorbing layer may be obtained from the radio wave absorber composition described above.

In the radio wave absorbing sheet according to an embodiment of the present invention, the metal layer is aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), tungsten (W) and iron (Fe), graphite (Graphite), carbon nanotube (CNT), graphene (Graphene), graphene oxide, carbon fiber and at least one selected from the group consisting of fullerene (Fullerene) may include there is.

The radio wave absorption sheet of the present invention has excellent absorption capacity in the GHz band. Specifically, the radio wave absorbing sheet of the present invention can absorb radio waves in the 1 GHz to 18 GHz band.

Hereinafter, it will be described in detail through specific embodiments of the present invention.

However, the following examples are only for illustrating the present invention, and the present invention is not limited by the following examples.

Example 1- Preparation of Z-type ferrite sintered body

_{Powder of Fe 2} O ₃ (Kojundo Chemical, 99.5%), SrCO ₃ (Kojundo Chemical, 99.5%), CoO (Sigma-Aldrich, 99%) to make the desired composition of Sr ₃ Co ₂ Fe ₂₄ O _{41 (CoZ)} After weighing the products of the elements and the additive elements according to the molar ratio of the target composition, they were mixed with Zr-balls in a 9:1 ratio and mixed wet (Ball milling). After drying the mixed powder, it was calcined for 4 hours at a temperature at which a desired phase can be formed or a temperature at which an intermediate phase (Y-type, M-type) can be formed (1100 to 1160° C.). The calcined powders were ground in a mortar, sieved through a #80 sieve, and anisotropically molded by dry anisotropic molding in a disk-type mold with a diameter of 8 mm and 15 mm. The molded sample and the sieved powder were sintered at 1160 to 1300° C. for 2 hours, respectively. The calcination and sintering were all raised at a rate of 5° C. per minute to each temperature, and cooled at room temperature.

Example 2-Sintered body containing Z-type ferrite-Epoxy composite preparation

The sintered body of Example 1 and the epoxy binder were composited. After the sintered powder was sieved through a #200 sieve, 90 wt% and 10 wt% of an epoxy binder (YD014, Kukdo Chemical) powder were weighed and mixed. The mixed powder was made into a molded body of a donut (Toroidal) type (inner diameter 3.03, outer diameter 7.00 mm). The donut shaped body was cured at 180° C. for 30 minutes. The epoxy volume ratio of the final sample is on the order of 50%.

Example 3 - Preparation of radio wave absorption sheet

The sintered body of Example 1 was prepared as a ferrite powder sample, and after mixing an epoxy binder, a solvent and an additive, the ferrite powder sample was mixed. Rotate Mill operation was carried out for about 4 hours while checking the internal heating temperature. After that, the dispersed crude liquid was subjected to Pilot Comma coating and a roll sample was produced. Thereafter, the shielding sheet was peeled off the release film to prepare a radio wave absorbing sheet.

Experimental Example 1 - Observation of the microstructure of Z-type ferrite according to d at a sintering temperature of 1210 °C

The calcination temperature is 1160 ℃, and when the sintering temperature is 1210 ℃, the sintered body according to the first embodiment to the _{Sr 3 Co 2 - x M x} Fe 24 -d O 41 (x = o) of the fine Z-type ferrite according to d in The structure was observed. Crystal phase analysis was performed with an X-ray diffraction (XRD, D8 Advance, Bruker) analyzer using Cu Kα radiation (λ = 0.154056 nm). To observe the microstructure, the fracture surface of the sintered body was photographed using a field emission scanning electron microscope (FE-SEM, JSM-7610F, JEOL). The fracture surface of the sintered compact for SEM imaging and the powder for XRD measurement were taken from the sintered compact molded in a disk (diameter 8mm) mold.

3 is an XRD graph when d is changed to 0, 0.5, 1, -0.5, -1.0, and FIG. 4 is SEM images.

Referring to FIGS. 3 and 4 , it can be confirmed that when d is 1, Z-type hexaferrite close to a single phase is manufactured. In addition, referring to FIG. 4 , it was confirmed that the smaller the Fe content, the larger the grain growth.

Experimental Example 2 - Observation of the crystal phase of Z-type ferrite according to the type of M at a sintering temperature of 1210 °C

The type of M on the _{x M x Fe 24 -d O 41} (x = 0.3, d = 1) - calcining temperature was 1160 ℃ and, according to the first to the embodiment when the sintering temperature is 1210 ℃ sintered Sr ₃ Co ₂ A crystalline phase of Z-type ferrite was observed.

5 is an XRD graph when M is changed to Ni, Cu, Mn and Non (none). Referring to FIG. 5 , it can be seen that a Z-type ferrite phase is observed when M is Ni or Mn.

Experimental Example 3 - Observation of the crystal phase of Z-type ferrite according to x at a sintering temperature of 1185 °C

The type of x in _{x M x Fe 24 -d O 41} (M = Ni, d = 1) - calcining temperature was 1160 ℃, and when the sintering temperature is 1185 ℃, according to the first embodiment in the sintered Sr ₃ Co ₂ A crystalline phase of Z-type ferrite was observed.

6 is an XRD graph when x is changed to 0.5, 1.0, 1.5 and 2.0. Referring to FIG. 6 , when the sintering temperature is 1185° C., it can be seen that all secondary phases occur regardless of the value of x, and it can be seen that it is difficult to obtain a single phase.

Experimental Example 4 - Observation of the crystalline phase of Z-type ferrite according to x at a sintering temperature of 1210 °C

The type of x in _{x M x Fe 24 -d O 41} (M = Ni, d = 1) - calcining temperature was 1160 ℃, and when the sintering temperature is 1210 ℃, according to the first embodiment in the sintered Sr ₃ Co ₂ A crystalline phase of Z-type ferrite was observed.

7 is an XRD graph when x is changed to 0, 0.3, 0.5, 1.0, 1.5 and 2.0, and FIG. 8 is SEM images. 7 and 8, when the sintering temperature is 1210 °C, it can be seen that the Z-type ferrite phase is observed when x is 0 or 0.3. Secondary phases were observed when x was 0.5, 1.0, 1.5 and 2.0.

Experimental Example 5 - Observation of the crystal phase of Z-type ferrite according to x at a sintering temperature of 1235 ° C.

The type of x in _{x M x Fe 24 -d O 41} (M = Ni, d = 1) - calcining temperature was 1160 ℃, and when the sintering temperature is 1235 ℃, according to the first embodiment in the sintered Sr ₃ Co ₂ A crystalline phase of Z-type ferrite was observed.

9 is an XRD graph when x is changed to 0.5, 1.0, 1.5 and 2.0. Referring to FIG. 9 , it can be seen that when the sintering temperature is 1235° C., a Z-type ferrite phase is observed when x is 0.5. A secondary phase was observed when x was 1.0, 1.5 and 2.0.

Experimental Example 6 - Observation of complex permeability and complex permittivity

The calcination temperature is 1160 ℃, and subjected to a sintering temperature of 1210 ℃ manufactured by Z-type ferrite of Example 1. _{Sr 3 Co 2 - x M x} Fe 24 -d O 41 (M = Ni, d = 1) and said containing them epoxy composite _- for the complex permeability and the complex dielectric according to the type of x in the (Sr ₃ Co _2-x Ni _x Fe ₂₃ O ₄₁ -Epoxy composite) was observed in the sintered body according to the embodiment 2.

The sintered body according to Example 2 - the complex magnetic permeability (μ = μ' - jμ'') and the complex dielectric constant (ε = ε' - ε'') of the epoxy composite are of a Toroidal type (inner diameter 3.03 mm, outer diameter 7.00 mm) After molding in a mold, the cured composite sample was measured in a frequency range of 1 to 18 GHz using a VNA (Vector Network Analyzer, Vector Network Analyzer, E50356A, Keysight) together with an Airline Kit (85052BR03).

10 is a graph showing the complex magnetic permeability and the complex permittivity of the Z-type ferrite of Example 1 when x is changed to 0.0, 0.3 and 0.5. 11 is a graph showing the complex permeability and the complex permittivity when x of the Z-type ferrite included in the radio wave absorber of Example 2 is changed to 0.0, 0.3, and 0.5.

Referring to FIG. 11, the imaginary part peak of the permeability and the imaginary part peak of the permittivity coexist within the measured GH range as a radio wave absorption mechanism through magnetic and dielectric loss by ferromagnetic resonance and dielectric resonance. It can be seen that the characteristics of

Experimental Example 7 - Observation of radio wave absorption characteristics

Epoxy composite _- a wave absorption characteristics corresponding to the type of x in the (Sr ₃ Co _2-x Ni _x Fe ₂₃ O ₄₁ -Epoxy Composite) was observed according to the embodiment 2, the sintered body. From the values of dielectric constant and permeability (spectrum according to frequency) measured with a network analyzer, it was calculated as the reflection loss (RL, indicating radio wave absorption characteristics) specta according to the thickness of the sinter-epoxy composite. The results are shown in FIGS. 12 to 14 .

12 is a graph relating to radio wave absorption characteristics when x is 0.0, FIG. 13 is when x is 0.3, and FIG. 14 is when x is 0.5.

On the other hand, Figure 15 is a sintered body - a 2D map of a radio wave absorption characteristics corresponding to the type of x in _{- (x Ni x Fe 23 O} 41 -Epoxy Composite Sr 3 Co 2) epoxy composite. 15 shows the thickness and frequency domain for absorbing radio waves in the region of the contour line, and shows a 90% absorption area within the range of the first contour line, 99% absorption area of the second contour line, and a 99.9% absorption area of the third contour line. That is, the first solid line region is RL<-10 dB (radio energy absorbed more than 90%), the second solid line region is RL<-20 dB (radio wave energy absorbed more than 99%), and the solid line region within it is RL It means the region of <-30 dB (absorbing 99.9% of radio wave energy).

Experimental Example 8 - Observation of the microstructure of the radio wave absorption sheet

The microstructure of the radio wave absorbing sheet according to Example 3 was observed.

16 is an SEM image of the surface and cross-section, and FIG. 17 is an XRD graph.

16 and 17 , it can be seen that the (00l) peak is greatly increased, and through this, it can be seen that the z-axis direction of the hexaferrite grains is oriented in the vertical direction of the film.

Experimental Example 9- Observation of complex permeability and complex permittivity of radio wave absorption sheet

18 is a third embodiment propagation of the Z-type ferrite comprising the absorbent sheet Sr ₃ Co _{2 -} and x is from 0.0 _x Ni _x Fe ₂₃ O _41, the magnetic or non holy are complex magnetic permeability and complex permittivity graph.

Experimental Example 10 - Observation of radio wave absorption properties of radio wave absorbing sheet

19 is a third embodiment propagation of Z-type ferrite containing Sr ₂ Co ₃ in the absorbent sheet of _a graph of the wave absorption characteristics when x is in the 0.0 in _x Ni _x Fe ₂₃ O _41. From the values of dielectric constant and permeability (spectrum according to frequency) measured by a network analyzer, it was calculated as a reflection loss (RL, indicating radio wave absorption characteristics) specta according to the thickness of the radio wave absorbing sheet, and the results are shown in FIG. 19 .

Meanwhile, FIG. 20 is a 2D map of the radio wave absorption characteristics in the case of magnetic or non-magnetic in the radio wave absorption sheet of Example 3. FIG. 20 shows the thickness and frequency domain for absorbing radio waves in the region of the contour line, and shows a 90% absorption region within a range of a first contour line, a 99% absorption region with a secondary contour line, and a 99.9% absorption region with a third contour line. That is, the first solid line region is RL<-10 dB (radio energy absorbed more than 90%), the second solid line region is RL<-20 dB (radio wave energy absorbed more than 99%), and the solid line region within it is RL It means the region of <-30 dB (absorbing 99.9% of radio wave energy).

Features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiments have been described above, these are merely examples and do not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are exemplified above in a range not departing from the essential characteristics of the present embodiment It can be seen that various modifications and applications that have not been made are possible. For example, each component specifically shown in the embodiments may be implemented by modification. And the differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (8)

Z-type ferrite represented by the following formula (1).
Sr ₃ Co _2-x M _x Fe _24-d O ₄₁
where x is 0 to 1.0, d is 0 to 1.5,
M is Ni or Mn.
containing Z-type ferrite,
The Z-type ferrite is a radio wave absorber composition represented by the following formula (1).
Sr ₃ Co _2-x M _x Fe _24-d O ₄₁
where x is 0 to 1.0, d is 0 to 1.5,
M is Ni or Mn.
3. The method of claim 2,
The radio wave absorber composition further comprises a binder,
The Z-type ferrite is a radio wave absorber composition, characterized in that dispersed in the binder.
4. The method of claim 3,
The Z-type ferrite is included in 85 wt% to 95 wt%,
The binder is a radio wave absorber composition, characterized in that it is included in an amount of 5 wt % to 15 wt %.
4. The method of claim 3,
The radio wave absorber composition further comprises a solvent, a dispersant and an anti-settling agent,
The solvent is included in 200 wt % to 250 wt % compared to 100 wt % of Z-type ferrite, the dispersant is included in 0.3 wt % to 3.5 wt % compared to 100 wt % of Z-type ferrite, and the anti-settling agent is 0.3 wt % compared to Z-type ferrite % to 3.5 wt% of the radio wave absorber composition.
radio wave absorption layer; and
a metal layer disposed on the radio wave absorbing layer;
The radio wave absorbing layer includes a Z-type ferrite and a binder.
7. The method of claim 6,
The Z-type ferrite is a radio wave absorption sheet represented by the following formula (1).
Sr ₃ Co _2-x M _x Fe _24-d O ₄₁
where x is 0 to 1.0, d is 0 to 1.5,
M is Ni or Mn.
7. The method of claim 6,
The metal layer includes aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), tin (Sn), zinc (Zn), tungsten (W) and iron (Fe), graphite ( Graphite), carbon nanotubes (CNT), graphene (Graphene), graphene oxide, carbon fiber, and a radio wave absorption sheet comprising at least one selected from the group consisting of fullerene (Fullerene).

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