Electromagnetic wave absorbing particle in GHz band and Electromagnetic wave absorbing material comprising the same

Abstract

The present invention relates to electromagnetic wave absorbing particles in the GHz band and electromagnetic wave absorbing materials containing the same, and more specifically, to electromagnetic wave absorbing particles in the GHz band capable of absorbing electromagnetic waves by a magnetic loss mechanism due to spin vibration in the GHz band and electromagnetic wave absorbing materials containing the same. The electromagnetic wave absorbing particles in the GHz band according to one embodiment of the present invention are represented by the following [Composition Formula 1] and are characterized by the formation of M-type hexagonal ferrite as a major phase. [Cho Seong-sik 1] Sr1-xRxFey-2zM2zOa Here, R is one or more selected from Ba, Ca and La, M is one or more selected from Co, Ti and Zr, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, 0 < z ≤ 1.5, and a = 19.

Description

Technology Field

[0001] The present invention relates to electromagnetic wave absorbing particles in the GHz band and electromagnetic wave absorbing materials containing the same, and more specifically, to electromagnetic wave absorbing particles in the GHz band capable of absorbing electromagnetic waves by a magnetic loss mechanism due to spin vibration in the GHz band and electromagnetic wave absorbing materials containing the same. Background Technology

[0003] Many electrical and electronic components are used in automobiles, and as a result, problems related to electromagnetic interference are arising.

[0004] Therefore, in automobiles, materials capable of shielding electromagnetic waves are adopted for components surrounding parts that generate electromagnetic waves and for parts that need to be protected from them.

[0005] While components applied to conventional automobiles protected parts by shielding electromagnetic waves, a problem arose where the shielding process unnecessarily reflected electromagnetic waves, causing adverse effects on other parts.

[0006] Therefore, this technology was researched based on the idea that absorbing electromagnetic waves—that is, shielding them rather than reflecting them—could prevent them from having an adverse effect on other parts of the vehicle.

[0007] In addition, as interest in autonomous vehicles has recently increased, automotive radar technology and wireless communication technologies such as 5G are being applied to enable autonomous driving, and the electromagnetic waves used in this process have increasingly higher frequency bands, with high frequencies in the range of several to tens of GHz being used.

[0008] Accordingly, research on materials capable of absorbing electromagnetic waves in the range of several to tens of GHz is necessary.

[0009] Conventionally, a technology that absorbs electromagnetic waves by a conductive mechanism by mixing carbon-based (graphite, carbon black, carbon nanotubes, carbon fibers, etc.) and metal-based powders into a polymer resin as absorbers that absorb electromagnetic waves in the tens of GHz band has been utilized and applied to automotive parts.

[0010] However, components of this type have limitations in their ability to absorb electromagnetic waves due to absorption mechanisms based on genetic or conductive loss, and because of the possibility of scattering by reflected waves, fundamental electromagnetic wave cancellation was not possible.

[0011] In addition, electromagnetic wave absorbers using Mn-Zn ferrite and Ni-Zn ferrite have been developed as absorbers using magnetic powder, but they have not been effective absorbers in the tens of GHz band because they lose almost all permeability values ​​at high frequencies in the GHz band to an extent similar to the relative permeability in a vacuum.

[0013] The content described above as background technology is intended only to help understand the background of the present invention and should not be construed as an acknowledgment that it constitutes prior art already known to those skilled in the art. Prior art literature

[0015] Registered Patent Publication No. 10-2011343 (2019.08.09) The problem to be solved

[0016] The present invention provides electromagnetic wave absorbing particles in the GHz band capable of absorbing electromagnetic waves by a magnetic loss mechanism caused by spin vibration, and an electromagnetic wave absorbing material containing the same. means of solving the problem

[0018] The electromagnetic wave absorbing particles in the GHz band according to one embodiment of the present invention are represented by the following [Composition Formula 1] and are characterized by the formation of M-type hexagonal ferrite as a major phase.

[0019] [Cho Seong-sik 1]

[0020] Sr 1-x R x Fe y-2z M 2z O a

[0021] Here, R is one or more selected from Ba, Ca and La, M is one or more selected from Co, Ti and Zr, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, 0 < z ≤ 1.5, and a = 19.

[0022] Preferably, the electromagnetic wave absorbing particles are characterized by being represented by the following [Composition Formula 2].

[0023] [Cho Seong-sik 2]

[0024] Sr 1-x R x Fe y-2z Co z Ti z O 19

[0025] Here, R is one or more selected from Ba, Ca and La, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, and 0 < z ≤ 1.5.

[0026] The above electromagnetic wave absorbing particles are characterized by maximally absorbing electromagnetic waves in the 8 to 15 GHz band when the Z value is 1.2.

[0027] The above electromagnetic wave absorbing particles are characterized by having an x ​​value of 0.094 to 0.15.

[0029] Meanwhile, an electromagnetic wave absorbing material for the GHz band according to one embodiment of the present invention is characterized by being formed by mixing a polymer resin and electromagnetic wave absorbing particles represented by the following [Composition Formula 1], wherein M-type hexagonal ferrite is formed as the major phase.

[0030] [Cho Seong-sik 1]

[0031] Sr 1-x Rx Fe y-2z M 2z O a

[0032] Here, R is one or more selected from Ba, Ca and La, M is one or more selected from Co, Ti and Zr, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, 0 < z ≤ 1.5, and a = 19.

[0033] Preferably, the electromagnetic wave absorbing particles are characterized by being represented by the following [Composition Formula 2].

[0034] [Cho Seong-sik 2]

[0035] Sr 1-x R x Fe y-2z Co z Ti z O 19

[0036] Here, R is one or more selected from Ba, Ca and La, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, and 0 < z ≤ 1.5.

[0037] The above electromagnetic wave absorbing material is characterized by the addition of a dielectric constant adjusting agent.

[0038] The above dielectric constant modifier is characterized by being graphite.

[0039] The above dielectric constant modifier is characterized by being contained in an amount of 5 wt% or less relative to 100 wt% of the mass of the electromagnetic wave absorbing particles.

[0040] The above electromagnetic wave absorbing material is characterized by absorbing electromagnetic waves in the 24 GHz band. Effects of the invention

[0042] According to an embodiment of the present invention, M-type hexagonal ferrite is used as an absorbing particle, and by utilizing the high ferromagnetic resonance frequency in the GHz band due to their high crystal magnetic anisotropy, it is possible to expect an effect of absorbing electromagnetic waves up to the tens of GHz band or higher through a mechanism of magnetic loss (increase in the imaginary part of permeability) caused by spin vibration.

[0043] In addition, by including a modifier capable of adjusting the dielectric constant in an absorbing material containing electromagnetic wave absorbing particles in which M-type hexagonal ferrite is formed as the major phase, it is possible to expect an effect of absorbing electromagnetic waves in a desired band. Brief explanation of the drawing

[0045] Figure 1 is a graph showing the change in permeability according to the change in the content of Sr and La in [Composition Formula 1], and Figure 2a is a graph showing the change in the real part of the dielectric constant according to the change in the mixing amount of graphite, and FIG. 2b is a graph showing the change in the imaginary part of the permittivity according to the change in the mixing amount of graphite, and FIG. 2c is a graph showing the change in the real part of the permeability according to the change in the mixing amount of graphite, and FIG. 2d is a graph showing the change in the imaginary part of the permeability according to the change in the mixing amount of graphite, and Figure 3a is a graph showing the change in the real part of the permittivity according to the change in the mixing amount of graphite, and Figure 3b is a graph showing the change in the imaginary part of the permittivity according to the change in the mixing amount of graphite, and Figure 3c is a graph showing the change in reflection loss values ​​according to the change in the mixing amount of graphite. Specific details for implementing the invention

[0046] Hereinafter, embodiments of the present invention will be described in more detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms, and these embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention.

[0048] An electromagnetic wave absorbing material in the GHz band according to one embodiment of the present invention is formed by mixing absorbing particles, in which M-type hexagonal ferrite is formed as a major phase, with a polymer resin.

[0049] In addition, a dielectric constant modifier capable of adjusting the dielectric constant can be further added to the electromagnetic wave absorbing material.

[0050] At this time, the absorbing particles are represented by the following [Composition Formula 1].

[0051] [Cho Seong-sik 1]

[0052] Sr 1-x R x Fe y-2z M 2z O a

[0053] Here, R is one or more selected from Ba, Ca and La, M is one or more selected from Co, Ti and Zr, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, 0 < z ≤ 1.5, and a = 19.

[0054] In this case, R must include at least one of Ba, Ca, and La, and may also include rare earth elements that can be substituted in the Sr position.

[0055] And, M is a transition metal that can be substituted at the Fe site, and the value of y-2z is the Fe content that maintains the hexagonal system as the main phase, 8 ≤ y ≤ 14, and it is desirable to maintain 0 < z ≤ 1.5.

[0056] The value of a, which is the oxygen content, is an important factor in maintaining the hexagonal system, and it is desirable to maintain a value of about 19.

[0057] Meanwhile, the absorbing particles can be represented by the following [Composition Formula 2], with Co and Ti selected as M.

[0058] [Cho Seong-sik 2]

[0059] Sr 1-x R x Fe y-2z Co z Ti z O 19

[0060] With the composition as described above, electromagnetic waves in the desired frequency range from several to tens of GHz can be absorbed.

[0062] Next, the process of deriving [Formula 1] as described above will be explained.

[0063] First, the magnetic resonance frequency corresponding to the frequency with the maximum absorption rate follows [Snoek's law] below.

[0064] [Snoek's law]

[0065]

[0066] Here, μ s : Permeability, γ: gyromagnetic ratio, M s : saturation magnetization, fr: refers to magnetic resonance frequency.

[0067] In this case, since the magnetic rotation ratio of the material is a constant depending on the material's characteristics, fr (magnetic resonance frequency) is the saturation magnetization value (M s ) and (μ s It is determined by the value of - 1).

[0068] Therefore, in the above [Composition Formula 1], M was determined through BH curve measurement for the composition in which the x value was fixed at 0.094, the y value at 11, and the z value was changed. s and μs The value was measured.

[0069] Then, the fr (magnetic resonance frequency) at which the electromagnetic wave absorption rate of each sample is maximized was derived using [Snoek's law], and the results are as shown below and in [Table 1].

[0070] Classification (No.) z m s -1 fr (μs-1)fr M S (μs-1)fr / M s 1 0 0.242 14.56 3.52352 2000 0.00176176 2 0 0.036 >50 3.06 2000 0.00153 3 0.8 0.076 40 3.04 1660 0.00183133 4 1 0.154 20 3.08 1630 0.00188957 5 1.2 0.298 10.1 3.0098 1630 0.0018465 6 1.4 Slope 3.2 　- - -

[0071] Through Table 1 above, it was confirmed that when the z value is 0 < z ≤ 1.5, the fr (magnetic resonance frequency) value can be derived in the range of several to tens of GHz.

[0072] For example, for the fr (magnetic resonance frequency) value to be 24 GHz, (μ s It can be seen that the value of - 1) shows the most similar value when z = 1. Preferably, using [Snoek's law], theoretically, a fr (magnetic resonance frequency) value of 24 GHz is obtained (μ s If you calculate the value of - 1) (μ s The value of - 1) is 0.128.

[0073] Accordingly, several samples were prepared to control the content of Sr and La in the composition where z = 1, and (μ s An experiment was conducted to derive a sample with a value of - 1) close to 0.128, and the results are shown in Figure 1.

[0074] As can be seen in Figure 1, as the amount of La increases or decreases, μ s It was confirmed that the value decreased in steps, and at x = 0.15, the fr (magnetic resonance frequency) value became 24 GHz (μ s - 1) The theoretical value of 0.128, i.e., μ s It was confirmed that it approaches the theoretical value of 1.128. At this time, μ s represents the real part of the permeability value in the vicinity where the real part of the permeability with respect to frequency does not change significantly.

[0075] Therefore, the absorbing particle having an absorption mechanism based on the ferromagnetic resonance phenomenon at 24 GHz is Sr 0.85 La 0.15 Fe9Co 1.0 Ti 1.0 O 19 It was confirmed that this could be achieved through the composition of...

[0076] Based on this, it was found that the absorbing particle with an x ​​value of 0.094 and a Z value of 1.2 has the highest absorption capacity in the 8 to 15 GHz band.

[0077] And, it was found that the absorbing particle with an x ​​value of 0.094 and a z value of 1 has the highest absorption capacity in the 7 GHz band.

[0079] Next, in order to match the impedance of the absorbent material mixed with absorbent particles and polymer resin, the dielectric constant of the absorbent material was controlled.

[0080] In this embodiment, graphite was added to the absorbent as a dielectric constant modifier to control the dielectric constant of the absorbent.

[0081] In this case, the absorbent is Sr 0.85 La 0.15 Fe9Co 1.0 Ti 1.0 O 19 It was manufactured with the composition of [the material], and the permeability and permittivity were measured while changing the amount of graphite mixed into the absorbent.

[0082] FIG. 2a is a graph showing the change in the real part of the permittivity according to the change in the mixing amount of graphite, FIG. 2b is a graph showing the change in the imaginary part of the permittivity according to the change in the mixing amount of graphite, FIG. 2c is a graph showing the change in the real part of the permeability according to the change in the mixing amount of graphite, and FIG. 2d is a graph showing the change in the imaginary part of the permeability according to the change in the mixing amount of graphite.

[0083] As can be seen in Figures 2a to 2d, when the amount of graphite mixed is changed, the permeability hardly changes, but the dielectric constant changes.

[0084] In particular, as can be inferred from Fig. 2a, it was confirmed that the point where ε′ = 7.0 and the point where ε” = 0.2 ~ 0.5 correspond to the frequency 24GHz point.

[0085] Therefore, it was confirmed that the dielectric constant can be adjusted without changing the permeability of the absorbent by mixing graphite as a dielectric constant modifier and appropriately adjusting the mixing amount.

[0087] On the other hand, just because the value of fr (magnetic resonance frequency) of the absorbing particle matches the frequency of the electromagnetic wave to be absorbed does not mean that the absorbing particle absorbs the electromagnetic wave well at fr (magnetic resonance frequency). To address this, it is necessary to match the impedance in a vacuum with the impedance of the absorbing material.

[0088] At this time, the impedance in vacuum (Zo) and the impedance of the absorbing particle (Z in ) can be calculated using the following [relationship].

[0089] [Relationship]

[0090]

[0091] Therefore, the impedance in vacuum (Zo) and the impedance of the absorbing particle (Z in In order to match ) Z in By adjusting the value of / Zo to be as close as possible to 1, a material having the highest electromagnetic wave absorption rate in the desired frequency band can be derived.

[0092] What can be inferred from the above relationship is Z in The value of / Zo can be adjusted by controlling the permittivity under the condition that the permeability does not change.

[0093] Therefore, as explained earlier, when graphite is used as a dielectric modifier, since it is possible to change only the dielectric constant without changing the permeability, by mixing graphite into the absorbent material Z in It can be derived that by adjusting the value of / Zo to a value as close as possible to 1, the absorption rate can be matched with fr (magnetic resonance frequency) of the absorbing material in the desired frequency band.

[0095] Next, the dielectric constant and reflection loss of the absorbent were measured by changing the amount of graphite mixed as a dielectric constant modifier.

[0096] In this case, the absorbent is Sr 0.906 La 0.094 Fe9Co 1.0 Ti 1.0 O 19 It was fabricated with the composition of [the material], and the permeability and reflection loss were measured while changing the amount of graphite mixed into the absorbent.

[0097] Figure 3a is a graph showing the change in the real part of the permittivity according to the change in the mixing amount of graphite, Figure 3b is a graph showing the change in the imaginary part of the permittivity according to the change in the mixing amount of graphite, and Figure 3c is a graph showing the change in the reflection loss value according to the change in the mixing amount of graphite.

[0098] As can be seen in Figures 3a to 3d, it was confirmed that the dielectric constant changes when the amount of graphite mixed is changed.

[0099] In addition, as can be seen in Fig. 3c, it was confirmed that an absorber with maximum absorption rates in the 8, 9, and 15 GHz bands can be realized depending on the amount of graphite added.

[0100] Therefore, it was confirmed that when graphite is added as a dielectric constant modifier, if it is contained in an amount of 5 wt% or less relative to 100 wt% of the mass of the electromagnetic wave absorbing particles, it can effectively absorb electromagnetic waves in the range of several to tens of GHz.

[0102] Although the present invention has been described with reference to the accompanying drawings and the aforementioned preferred embodiments, the present invention is not limited thereto but is defined by the claims set forth below. Accordingly, those skilled in the art can make various modifications and variations to the present invention within the scope of the technical spirit of the claims set forth below without departing from the technical spirit of the present invention.

Claims

Claim 1 Electromagnetic wave absorbing particles in the GHz band represented by the following [Composition Formula 2], characterized by the formation of M-type hexagonal ferrite as a major phase. [Composition Formula 2] Sr 1-x R x Fe y-2z Co z Ti z O 19 Here, R is one or more selected from Ba, Ca, and La, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, Z = 1.2, and absorbs electromagnetic waves in the 8 ~ 15 GHz band to the maximum, and the electromagnetic wave absorbing particle is characterized by having an x ​​value of 0.094 ~ 0.

15. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 An electromagnetic wave absorbing material for the GHz band, comprising a polymer resin and electromagnetic wave absorbing particles represented by the following [Composition Formula 1], wherein M-type hexagonal ferrite is formed as the major phase, and further comprising an added dielectric constant modifier, wherein the dielectric constant modifier is contained in an amount of 5 wt% or less relative to 100 wt% of the mass of the electromagnetic wave absorbing particles. [Composition Formula 1] Sr 1-x R x Fe y-2z M 2z O a Here, R is one or more selected from Ba, Ca and La, M is one or more selected from Co, Ti and Zr, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, 0 < z ≤ 1.5, and a = 19. Claim 6 An electromagnetic wave absorbing material in the GHz band according to claim 5, wherein the electromagnetic wave absorbing particles are represented by the following [Composition Formula 2]. [Composition Formula 2] Sr 1-x R x Fe y-2z Co z Ti z O 19 Here, R is one or more selected from Ba, Ca and La, 0 < x ≤ 0.8, 8 ≤ y ≤ 14, and 0 < z ≤ 1.

5. Claim 7 delete Claim 8 An electromagnetic wave absorbing material in the GHz band according to claim 5, characterized in that the dielectric constant adjusting agent is graphite. Claim 9 delete Claim 10 A GHz band electromagnetic wave absorbing material according to claim 5, characterized in that the electromagnetic wave absorbing material absorbs electromagnetic waves in the 24 GHz band.

Images