Microwave band electromagnetic wave absorbing material and manufacturing method thereof

Abstract

One embodiment of the present invention provides a method for manufacturing an electromagnetic wave absorbing material, the method comprising: a step of mixing a powder containing at least one selected from the group consisting of a Ca precursor, a Ba precursor, a Sr precursor, an Re precursor, an Me precursor, a Co precursor, and an Fe precursor; a step for performing a first heat treatment on the mixed powder; a step of ball-milling the powder after the heat treatment; and a step of performing a second heat treatment on the powder after the ball milling, thereby manufacturing an electromagnetic wave absorbing material including W-type hexagonal ferrite represented by the chemical formula 1. The present invention is a research result of a development subject of a microwave absorber for 5G communication (28GHz), which is supported by the Chang star (strain) and is executed by a first university production and study association group.

Description

Technical Field

[0001] This invention relates to an electromagnetic wave absorbing material and a method for manufacturing the same, and more specifically, to a method for manufacturing an electromagnetic wave absorbing material for the Ka-band (26.5 GHz to 40 GHz) in the field of 5G communication, wherein the material contains little or no Fe. 2+ W-type hexaferrite of ions. Background Technology

[0002] With the development of information and communication technologies, next-generation technologies such as autonomous vehicles, the Internet of Things (IoT), smartphones, artificial intelligence (AI), and virtual reality are actively developing.

[0003] Furthermore, electronic devices are becoming increasingly miniaturized, their usable operating frequencies are gradually increasing, and the amount of data and communication being processed is growing dramatically. Consequently, communication between electronic devices has become more complex and diverse, leading to problems such as communication errors caused by frequency interference, thus increasing the necessity for electromagnetic shielding and absorption.

[0004] Hexagonal ferrites possess high magnetic anisotropy, making them suitable materials for use as electromagnetic wave absorbers in the GHz frequency range. Therefore, to achieve stable communication of electronic devices in the Ka-band (26.5 GHz to 40 GHz) of 5G communication, electromagnetic interference must be eliminated. Consequently, the application of hexagonal ferrites, which exhibit excellent absorption characteristics in the several GHz to tens of GHz frequency bands, in 5G communication technology is gradually increasing.

[0005] However, in the traditional case, with the increase of electronic devices and communication volume, interference from signals from surrounding devices will occur, resulting in electromagnetic interference (EMI) problems that may lead to functional degradation or malfunction.

[0006] In particular, it could pose serious problems for electronic devices that are closely related to life, such as drones, self-driving cars, and implantable biosensors.

[0007] To mitigate this EMI problem, electromagnetic compatibility (EMC), as an international standard, has been legislated and regulated as a mandatory requirement. Therefore, one method introduced during the product design phase to meet EMC standards is electromagnetic shielding and absorption technology, which blocks the entry and exit of electromagnetic waves. This technology minimizes unwanted electromagnetic radiation from the final product and maximizes the device's immunity to unwanted electromagnetic waves.

[0008] However, as operating frequencies gradually shift towards higher frequency bands, traditional materials such as Ni-Zn Ferrite, Mn-Zn Ferrite, and Sendust are unsuitable for use as electromagnetic shielding and absorption materials in the range of several GHz to tens of GHz due to their low magnetic anisotropy in crystal structure.

[0009] Currently, with the advent of fifth-generation wireless communication (5G), the need for electromagnetic wave absorbing materials in the 3.5GHz and 28GHz bands is increasing, especially for absorbing materials in the 28GHz band, but the supply of suitable materials is insufficient.

[0010] Existing technical documents Korean Patent Registration No. 10-2621490 Summary of the Invention The problem the invention aims to solve This invention aims to provide a method for manufacturing an electromagnetic wave absorbing material for the Ka-band (26.5GHz to 40GHz) in the field of 5G communication, wherein the material contains little or no Fe. 2+ W-type hexaferrite of ions.

[0011] The technical problems to be solved by the present invention are not limited to those mentioned above. Other technical problems not mentioned can be clearly understood by those skilled in the art through the following description.

[0012] means for solving problems To address the aforementioned technical challenges, one embodiment of the present invention provides a method for manufacturing an electromagnetic wave absorbing material.

[0013] A method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention includes: mixing a powder comprising at least one selected from the group consisting of a Ca precursor, a Ba precursor, a Sr precursor, a Re precursor, a Me precursor, a Co precursor, and an Fe precursor; subjecting the mixed powder to a first heat treatment; ball milling the heat-treated powder; and subjecting the ball-milled powder to a second heat treatment, thereby manufacturing an electromagnetic wave absorbing material comprising W-type hexaferrite represented by the following chemical formula 1.

[0014] Chemical Formula 1 Ca a Ba b Sr 1-a-b-c Re c Co 2+x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 1, Re is at least one selected from the group consisting of rare earth elements, and Me 2+ It is selected from at least one of the group consisting of divalent transition metals, wherein a is 0.0 to 1.0, b is 0.0 to 1.0, c is 0.0 to 1.0, and x is 0.0 to 2.0.

[0015] Furthermore, in a method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention, x in the chemical formula 1 is 0.0 to 0.3.

[0016] Furthermore, according to a method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention, in the chemical formula 1, the Me... 2+ Is it a free choice of Zn? 2+ Fe 2+ Ni 2+ Mn 2+ and Mg 2+ At least one of the groups.

[0017] Furthermore, according to an embodiment of the present invention, in the chemical formula 2, the Me 2+ Is it a free choice of Zn? 2+ Fe 2+ Ni 2+ Mn 2+ and Mg 2+ At least one of the groups, characterized in that the method for manufacturing the electromagnetic wave absorbing material.

[0018] Furthermore, in a method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention, the first heat treatment step is performed in a temperature range of 1200°C to 1400°C.

[0019] Furthermore, according to a method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention, in the W-type hexaferrite represented by the chemical formula 1, in the 2 moles of divalent transition metal contained in the chemical formula 1, Fe 2+ The ion content is less than 0.5 moles.

[0020] Furthermore, in a method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention, the second heat treatment step is performed in a temperature range of 1200°C to 1400°C.

[0021] Furthermore, in a method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention, the second heat treatment step involves sintering in air.

[0022] To address the aforementioned technical challenges, another embodiment of the present invention provides an electromagnetic wave absorbing material.

[0023] According to one embodiment of the present invention, an electromagnetic wave absorbing material is provided, which comprises W-type hexaferrite represented by the following chemical formula 1.

[0024] Chemical Formula 1 Ca a Ba b Sr 1-a-b-c Re c Co 2+ x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 1, Re is at least one selected from the group consisting of rare earth elements, and Me 2+ It is selected from at least one of the group consisting of divalent transition metals, wherein a is 0.0 to 1.0, b is 0.0 to 1.0, c is 0.0 to 1.0, and x is 0.0 to 2.0.

[0025] That is, the W-type hexaferrite has a composition that simultaneously contains the Ba and Sr elements in the chemical formula 1.

[0026] Furthermore, according to one embodiment of the present invention, in the W-type hexagonal ferrite represented by the chemical formula 1, in the 2 moles of divalent transition metal contained in the chemical formula 1, Fe 2+ The ion content is less than 0.5 moles.

[0027] Furthermore, according to one embodiment of the present invention, the electromagnetic wave absorbing material has a ferromagnetic resonance (FMR) frequency in the frequency band of 26.5 GHz to 40 GHz.

[0028] Furthermore, according to one embodiment of the present invention, in the chemical formula 1, x is 0.0 to 0.3.

[0029] Furthermore, according to one embodiment of the present invention, the thickness of the electromagnetic wave absorbing material ranges from 0.97 mm to 1.05 mm.

[0030] Furthermore, according to an embodiment of the present invention, in chemical formula 1 and chemical formula 2, the Me 2+ Is it a free choice of Zn? 2+ Fe 2+ Ni 2+ Mn 2+ and Mg 2+ At least one of the groups.

[0031] Invention Effects According to one embodiment of the present invention, a method for manufacturing an electromagnetic wave absorbing material for the Ka-band (26.5 GHz to 40 GHz) in the field of 5G communication can be provided, wherein the material contains only a very small amount of Fe. 2+ W-type hexaferrite of ions.

[0032] According to an embodiment of the present invention, a method for manufacturing an electromagnetic wave absorbing material comprising W-type hexagonal ferrite can be provided, wherein, by means of Me in the W-type hexagonal ferrite 2+ Replace Zn in position 2+ Co 2+ Ni 2+ Mn 2+ Cu 2+ Mg 2+ Plasma gives it a high complex permittivity and complex permeability in the high-frequency region.

[0033] According to one embodiment of the present invention, a compositional design for adjusting the ferromagnetic resonance frequency can be provided to have excellent absorption capability in the Ka band (26.5 GHz to 40 GHz) in the field of 5G communication.

[0034] The beneficial effects of the present invention are not limited to those described above, but should be understood to include all effects that can be derived from the composition of the invention as described in the specification or claims of the present invention. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating a method for manufacturing an electromagnetic wave absorbing material comprising W-type hexagonal ferrite according to an embodiment of the present invention.

[0036] Figure 2 illustrates the electromagnetic wave absorbing material according to an embodiment of the present invention, with Co... 2+ Curves of complex permeability and complex permittivity with varying content (powder content volume fraction of 30%).

[0037] Figure 3 illustrates the electromagnetic wave absorbing material according to an embodiment of the present invention, with Co... 2+A graph showing the results of ferromagnetic resonance frequency regression analysis of content changes.

[0038] Figure 4 This illustrates an electromagnetic wave absorbing material according to an embodiment of the present invention, in which Co... 2+ A graph showing the absorption characteristics (minimum reflection loss) of composite sheets with varying content.

[0039] Figure 5 This is a graph showing the absorption characteristics of a composite sheet as a function of thickness in an electromagnetic wave absorbing material according to an embodiment of the present invention.

[0040] Figure 6 illustrates the electromagnetic wave absorbing material according to an embodiment of the present invention, with Co... 2+ A graph showing the absorption characteristics of composite sheets with varying content (contour plots of absorption characteristics as a function of thickness and frequency).

[0041] Figure 7 shows the effect of Fe (Fe) 2+ Mg 2+ Mn 2+ Ni 2+ )-Co 2+ A graph showing the change in complex magnetic permeability (the volume fraction of powder in epoxy resin is 30%) with varying content.

[0042] Figure 8 This shows the variation of various divalent transition metals and Co. 2+ A graph showing the ferromagnetic resonance frequency regression analysis of changes in ion content. Detailed Implementation

[0043] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that it includes all modifications, equivalents, and even substitutions that fall within the scope of the concept and technology of the present invention.

[0044] Furthermore, in order to clearly illustrate the embodiments of the present invention, parts unrelated to the description have been omitted in the accompanying drawings, and similar reference numerals have been used for similar parts throughout the specification.

[0045] Throughout the instruction manual, when a part is referred to as being "connected (joined, contacted, joined)" to another part, this includes not only the case of "direct connection" but also the case of "indirect connection" with other components in between.

[0046] Furthermore, when a layer, film, region, plate, or other part is referred to as being "above" another part, this includes not only the case where it is "directly above" the other part, but also the case where the other part exists in between. Additionally, in this specification, when a layer, film, region, plate, or other part is referred to as being formed on another part, the formation direction is not limited to the upper direction, but also includes cases where it is formed in the side or lower direction. Conversely, when a layer, film, region, plate, or other part is referred to as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where the other part exists in between.

[0047] In this specification, "upper surface" and "lower surface" are relative concepts used for ease of understanding the technical concept of the present invention. Therefore, "upper surface" and "lower surface" do not refer to a specific direction, position, or constituent element, and can be used interchangeably.

[0048] For example, "upper surface" can be interpreted as "lower surface," and "lower surface" can also be interpreted as "upper surface." Therefore, "upper surface" can be referred to as "first," and "lower surface" can be referred to as "second," or "lower surface" can be referred to as "first," and "upper surface" can be referred to as "second." However, within one embodiment, "upper surface" and "lower surface" are not used interchangeably.

[0049] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms such as those defined in general dictionaries shall be interpreted as having a meaning consistent with their meaning in the relevant technical context, and shall not be interpreted in an idealized or overly formalized sense unless expressly defined in this application.

[0050] Furthermore, when a part is said to "contain" a certain constituent element, it means that unless there is a specific contrary statement, it does not exclude other constituent elements, but may further possess other constituent elements.

[0051] The terminology used in this specification is for illustrative purposes only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the presence of features, numbers, steps, operations, constituent elements, components, or combinations thereof described in the specification, and should not be construed as pre-excluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, constituent elements, components, or combinations thereof.

[0052] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0053] Figure 1This is a flowchart illustrating a method for manufacturing an electromagnetic wave absorbing material comprising W-type hexagonal ferrite according to an embodiment of the present invention.

[0054] Referring to the above Figure 1 A method for manufacturing an electromagnetic wave absorbing material according to an embodiment of the present invention will be described.

[0055] As an example of the above embodiment, a method for manufacturing an electromagnetic wave absorbing material includes: mixing a powder comprising at least one selected from the group consisting of a Ca precursor, a Ba precursor, a Sr precursor, a Re precursor, a Me precursor, a Co precursor, and an Fe precursor; subjecting the mixed powder to a first heat treatment; ball milling the heat-treated powder; and subjecting the ball-milled powder to a second heat treatment.

[0056] Chemical Formula 1 Ca a Ba b Sr 1-a-b-c Re c Co 2+ x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 1, Re is at least one selected from the group consisting of rare earth elements, and Me 2+ It is selected from at least one of the group consisting of divalent transition metals, wherein a is 0.0 to 1.0, b is 0.0 to 1.0, c is 0.0 to 1.0, and x is 0.0 to 2.0.

[0057] At this point, the hexagonal ferrite is a magnetic material with a hexagonal crystal structure. Due to its large magnetic anisotropy, it is an electromagnetic wave absorber material with great application potential in the high-frequency field of the GHz band.

[0058] Furthermore, the hexagonal ferrite exists in various types according to its chemical composition. Among them, the W-type hexagonal ferrite has greater potential as an absorber in the higher GHz band due to its magnetic anisotropy in the c-axis direction compared with other hexagonal ferrites.

[0059] As an example of the described embodiment, in chemical formula 1, the Me 2+ Is it a free choice of Zn? 2+ Fe 2+ Ni 2 + Mn 2+ and Mg 2+At least one of the groups.

[0060] In the case of the described embodiment, a method for manufacturing an electromagnetic wave absorber comprising a W-type hexagonal ferrite can be provided, wherein, by means of Me in the W-type hexagonal ferrite... 2+ Replace Zn in position 2+ Fe 2+ Ni 2+ Mn 2+ Mg 2+ Plasma gives it a high complex permittivity and complex permeability in the high-frequency region.

[0061] Furthermore, a compositional design for adjusting the ferromagnetic resonance frequency is provided to achieve excellent absorption in the Ka band (26.5 GHz to 40 GHz) in the 5G communication field, and the correlation between the ferromagnetic resonance frequency and absorption characteristics is elucidated.

[0062] The ferromagnetic resonance phenomenon refers to the phenomenon that when a magnetic body is exposed to high-frequency electromagnetic waves, its magnetic spin begins to precess, thereby absorbing electromagnetic waves in a specific region. The ferromagnetic resonance frequency represents the frequency at this time.

[0063] At this point, as mentioned above, the reason for adjusting the ferromagnetic resonance frequency is that by doing so, electromagnetic wave absorbing materials with excellent absorption characteristics can be manufactured in the desired frequency band.

[0064] The composition of the W-type hexagonal ferrite is typically Sr (or Ba)Me2Fe. 16 O 27 Where Me represents Mn 2+ Zn 2+ Mg 2 + Ni 2+ Co 2+ Cu 2+ Divalent metal ions.

[0065] Reference Figure 1 The process of manufacturing an electromagnetic wave absorbing material comprising W-type hexaferrite represented by the chemical formula 1 can be confirmed by the following steps: a step (S10) of mixing powder comprising at least one selected from the group consisting of Ca precursor, Ba precursor, Sr precursor, Re precursor, Me precursor, Co precursor and Fe precursor; a step (S20) of subjecting the mixed powder to a first heat treatment; a step (S30) of ball milling the heat-treated powder; and a step (S40) of subjecting the ball-milled powder to a second heat treatment.

[0066] In one embodiment, the Sr precursor can be SrCO3, the Fe precursor can be Fe2O3, the Co precursor can be CoO, and the Me precursor can be MeO.

[0067] Referring to the above Figure 1 It can be confirmed that the process of using precursor powders such as SrCO3, Fe2O3, CoO, and MeO to manufacture W-type hexagonal ferrites substituted with divalent transition metal ions can be confirmed.

[0068] At this time, the manufacturing process used can be a solid-state reaction, and the sample can be either in powder form or tablet form during the first heat treatment step (S20).

[0069] In the step (S30) of ball milling the heat-treated powder, a conventional grinding mill using grinding beads can be used.

[0070] Basically, in the chemical formula 1, x is from 0.0 to 2.0.

[0071] More preferably, x is 0.0 to 0.3.

[0072] As can be confirmed in the experimental examples, with the Co 2+ As the content of x increases, the ferromagnetic resonance frequency gradually shifts to a lower frequency band, and when the value of x is in the range of 0.0 to 0.3, the ferromagnetic resonance frequency value near 28 GHz can be confirmed.

[0073] Most preferably, x is 0.25 to 0.3.

[0074] The absorption characteristics are optimal for the target frequency of 28 GHz when x is in the range of 0.25 to 0.3.

[0075] In one embodiment, the Re (rare earth element) is at least one selected from the group consisting of La, Ce, and Y.

[0076] In one embodiment, in the step of forming the powder, if only Ba precursor, Me precursor, Co precursor and Fe precursor powders are mixed, an electromagnetic wave absorbing material comprising W-type hexaferrite represented by the following chemical formula 2 instead of the chemical formula 1 can be produced.

[0077] Chemical formula 2 BaCo 2+ x Me 2+ 2-x Fe3+ 16 O 27 In the chemical formula 2, the Me 2+ It is selected from at least one of the group consisting of divalent transition metals, and the x is 0.0 to 2.0.

[0078] As another example of the embodiment, in the step of forming the powder, if only Sr precursor, Me precursor, Co precursor and Fe precursor powders are mixed, an electromagnetic wave absorbing material containing W-type hexaferrite represented by the following chemical formula 3 instead of the chemical formula 1 can be produced.

[0079] Chemical formula 3 SrCo 2+ x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 3, the Me 2+ It is selected from at least one of the group consisting of divalent transition metals, and the x is 0.0 to 2.0.

[0080] According to an embodiment of the present invention, in a method for manufacturing an electromagnetic wave absorbing material, in the chemical formula 2, the Me 2+ It is selected from at least one of the group consisting of divalent transition metals.

[0081] Unlike chemical formulas 2 and 3, the W-type hexaferrite represented by chemical formula 1 not only contains the Sr and Ba elements, but also contains both Ba and Re (rare earth elements).

[0082] In the chemical formula 1, when a, c and b are 0, it is the same as in the chemical formula 3.

[0083] In chemical formula 1, when a and c are 0 and b is 1, it is the same as chemical formula 2.

[0084] More preferably, a is 0.0 to 0.5.

[0085] More preferably, b is 0.0 to 1.0.

[0086] More preferably, c is 0.0 to 0.5.

[0087] According to one embodiment of the present invention, the first heat treatment step is performed in a temperature range of 1200°C to 1400°C.

[0088] The first heat treatment step can be carried out by calcination.

[0089] Furthermore, the first heat treatment step can be carried out in air and can last for a period of 5 to 7 hours.

[0090] At this time, when the first heat treatment step is carried out at a temperature below 1200°C, there is a problem of mixed crystal phases of W-type hexagonal ferrite, M-type hexagonal ferrite and spinel ferrite.

[0091] As the heat treatment temperature increases, around 1300℃, the M-type and spinel ferrite phases can be synthesized into the W-type hexagonal ferrite phase.

[0092] Conversely, if the second heat treatment step is carried out at a temperature exceeding 1400°C, it will exist in the form of magnetite and liquid phase, making phase synthesis difficult.

[0093] As an example of the embodiment, in the W-type hexagonal ferrite represented by Formula 1, in the 2 moles of divalent transition metal contained in Formula 1, Fe 2+ The ion content is less than 0.5 moles.

[0094] At this time, the second heat treatment step can be carried out in a temperature range of 1200°C to 1400°C, and the second heat treatment step can also be sintered in air.

[0095] At this point, if the second heat treatment step is carried out at a temperature below 1200°C, there is a problem of mixed crystal phases of W-type hexagonal ferrite, M-type hexagonal ferrite, and spinel ferrite.

[0096] As the heat treatment temperature increases, around 1300℃, the M-type and spinel ferrite phases can be synthesized into the W-type hexagonal ferrite phase.

[0097] Conversely, when the second heat treatment step is carried out at a temperature exceeding 1400°C, the problem arises that phase synthesis is difficult because the magnetite exists in the form of a liquid phase.

[0098] Furthermore, the second heat treatment step can be carried out in an air atmosphere by sintering.

[0099] In traditional cases, the W-type phase is typically a high-temperature stable phase, and Fe in air... 2+ Ions are easily oxidized to Fe 3+The phase decomposition caused by ions necessitates heat treatment under low oxygen partial pressure.

[0100] However, in the case of the embodiment described above, since Fe is present in the 2 moles of divalent transition metal contained in Formula 1... 2+ The ion content is less than 0.5 moles, thus it has the advantage of being heat-treated in air.

[0101] When Fe is present in 2 moles of divalent transition metal contained in the chemical formula 1, 2+ When the ion content is 0.5 moles or higher, a stable W-type hexagonal ferrite phase without phase decomposition can be synthesized if accompanied by gas conditioning or quenching. Compared with the case where oxygen partial pressure needs to be adjusted, the second heat treatment step has the advantage of reducing process costs because it does not require additional gas conditioning.

[0102] An electromagnetic wave absorbing material according to another embodiment of the present invention will be described.

[0103] The electromagnetic wave absorbing material is a different type of invention with practically the same technical features as the aforementioned method for manufacturing electromagnetic wave absorbing materials. Therefore, the content described above in the description of the method for manufacturing electromagnetic wave absorbing materials can be applied.

[0104] As an example of the above embodiment, an electromagnetic wave absorbing material comprises a W-type hexaferrite represented by the following chemical formula 1.

[0105] Chemical Formula 1 Ca a Ba b Sr 1-a-b-c Re c Co 2+ x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 1, Re is at least one selected from the group consisting of rare earth elements, and Me 2+ It is selected from at least one of the group consisting of divalent transition metals, wherein a is 0.0 to 1.0, b is 0.0 to 1.0, c is 0.0 to 1.0, and x is 0.0 to 2.0.

[0106] As an example of the above embodiment, an electromagnetic wave absorbing material comprises a W-type hexaferrite represented by the following chemical formula 2.

[0107] Chemical formula 2 BaCo 2+ x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 2, the Me 2+ It is selected from at least one of the group consisting of divalent transition metals, and the x is 0.0 to 2.0.

[0108] As another example of the embodiments described, an electromagnetic wave absorbing material comprises a W-type hexaferrite represented by the following chemical formula 3.

[0109] Chemical formula 3 SrCo 2+ x Me 2+ 2-x Fe 3+ 16 O 27 In the chemical formula 3, the Me 2+ It is selected from at least one of the group consisting of divalent transition metals, and the x is 0.0 to 2.0.

[0110] Unlike chemical formulas 2 and 3, the W-type hexaferrite represented by chemical formula 1 not only contains the Sr and Ba elements, but also contains both Ba and Re (rare earth elements).

[0111] In chemical formula 1, when a, c, and b are 0, it is the same as in chemical formula 3. In chemical formula 1, when a and c are 0 and b is 1, it is the same as chemical formula 2.

[0112] More preferably, a is 0.0 to 0.5.

[0113] More preferably, b is 0.0 to 1.0.

[0114] More preferably, c is 0.0 to 0.5.

[0115] As an example of the embodiment, in the W-type hexagonal ferrite represented by Formula 1, in the 2 moles of divalent transition metal contained in Formula 1, Fe 2+ The ion content is less than 0.5 moles.

[0116] As an example of the embodiment, the electromagnetic wave absorbing material has a ferromagnetic resonance frequency in the range of 26.5 GHz to 40 GHz.

[0117] As an example of the embodiment, in the chemical formula 1, x is 0.0 to 0.3.

[0118] As an example of the embodiment, the thickness of the electromagnetic wave absorbing material ranges from 0.97 mm to 1.05 mm.

[0119] As an example of the embodiment, in the chemical formula 1, the Zn 2+ Fe 2+ Ni 2+ Mn 2+ and Mg 2+ At least one of the groups.

[0120] In one embodiment, the Re (rare earth element) is at least one selected from the group consisting of La, Ce, and Y.

[0121] The characteristics of the electromagnetic wave absorbing material described in the embodiments will be explained in detail through the following experimental examples.

[0122] Manufacturing Example 1. Electromagnetic wave absorbing material (SrCo) according to an embodiment of the present invention x Zn 2-x Fe 16 O 27 ).

[0123] This paper illustrates the process of manufacturing W-type hexagonal ferrites substituted with divalent transition metal ions using precursor powders of SrCO3, Fe2O3, CoO, and ZnO. The manufacturing process used is a solid-state reaction, and the sample can be in powder or tablet form during calcination.

[0124] The ball mill uses a common grinding mill that utilizes grinding beads.

[0125] 1. Add 1 mole of SrCO 3， x moles of CoO, (2-x) moles of ZnO, and 8 moles of Fe2O3 precursor powder were ball-milled for 24 hours.

[0126] The total amount of the substance is 20g, and it is manufactured separately by adjusting the value of x. The applicable values ​​of x are detailed below.

[0127] 2. Calcine in air at 1250°C for 6 hours.

[0128] 3. After that, ball milling is carried out again for 24 hours.

[0129] 4. Next, sinter in air at 1300°C for 2 hours.

[0130] The shredder used for crushing was a zirconia ball, with the weight of the zirconia ball being 12 times that of the 20g precursor, or 240g.

[0131] There are three types of balls used, with diameters of 1 mm, 0.5 mm and 0.3 mm respectively, and 80g of each type of ball is used.

[0132] The ball milling temperature and rpm were based on 150 rpm at room temperature.

[0133] SrCo is produced through the above process. x Zn 2-x Fe 16 O 27 Hexagonal ferrite powder.

[0134] The manufacturing process involves adjusting the amount of precursor used to produce x values ​​of 0.0, 0.1, 0.2, 0.225, 0.250, 0.275, and 0.3.

[0135] Experimental Example 1. Co 2+ Analysis of the effects of the content and thickness of the material on the properties of electromagnetic wave absorbing materials.

[0136] Figure 2 illustrates the electromagnetic wave absorbing material according to an embodiment of the present invention, with Co... 2+ Curves of complex permeability and complex permittivity with varying content (powder content volume fraction of 30%).

[0137] Figure 3 illustrates the electromagnetic wave absorbing material according to an embodiment of the present invention, with Co... 2+ A graph showing the results of ferromagnetic resonance frequency regression analysis of content changes.

[0138] Figure 4 This illustrates an electromagnetic wave absorbing material according to an embodiment of the present invention, in which Co... 2+ A graph showing the absorption characteristics (minimum reflection loss) of composite sheets with varying content.

[0139] Figure 5 This is a graph showing the absorption characteristics of a composite sheet as a function of thickness in an electromagnetic wave absorbing material according to an embodiment of the present invention.

[0140] Figure 6 illustrates the electromagnetic wave absorbing material according to an embodiment of the present invention, with Co... 2+A graph showing the absorption characteristics of composite sheets with varying content (contour plots of absorption characteristics as a function of thickness and frequency).

[0141] The experimental example is illustrated by Figures 2 to 6.

[0142] In Figure 2, in order to evaluate SrCo according to an embodiment of the present invention x Zn 2-x Fe 16 O 27 (0≤x≤0.3) Absorption characteristics of hexagonal ferrite composition: After mixing epoxy solid resin, composite sheets were manufactured according to different contents.

[0143] The type of resin can be varied as needed, using epoxy resin, acrylic resin, silicone resin, polyurethane, paraffin, etc.

[0144] To evaluate the absorption performance of the fabricated composite sheet, the complex permeability and complex permittivity, which are material constants, were obtained using a network analyzer.

[0145] Ferromagnetic resonance frequency can usually be determined by the complex permeability (μ). r The region where the inflection point of the real permeability (μ') and the maximum value of the imaginary permeability (μ'') in the equation =μ'- jμ'' can be identified.

[0146] Referring to Figure 2, it can be confirmed that, with Co 2+ As the content of Co increases, the ferromagnetic resonance frequency gradually shifts to lower frequency bands, and in Co 2+ The content (x value) is in the range of 0.25 to 0.3, and it has a ferromagnetic resonance frequency value around 28 GHz.

[0147] This can also be confirmed using Table 1 below.

[0148] Table 1

[0149] The values ​​in Table 1 also confirm, as mentioned earlier, that with Co... 2+ As the content of Co increases, the ferromagnetic resonance frequency gradually shifts to lower frequency bands, and in Co 2+ The content (x value) is in the range of 0.25 to 0.3, and it has a ferromagnetic resonance frequency value around 28 GHz.

[0150] In Figure 3, it can be confirmed that Co 2+ The results of ferromagnetic resonance frequency regression analysis of the content changes.

[0151] Referring to Figure 3, similarly, it can be confirmed that with Co...2+ As the content of Co increases, the ferromagnetic resonance frequency gradually shifts to lower frequency bands, and in the Co... 2+ The content (x value) is in the range of 0.25 to 0.3, and it has a ferromagnetic resonance frequency value around 28 GHz.

[0152] exist Figure 4 In order to evaluate the following Co 2+ The absorption characteristics of composite sheets with varying content are determined by first calculating the impedance value using the following mathematical formula 1, based on transmission line theory.

[0153] Then, substituting into the following mathematical formula 2, the reflection loss (RL) value expressed in terms of absorption characteristics was calculated.

[0154] Mathematical Formula 1

[0155] Mathematical formula 2 Reference Figure 4 With Co 2+ The increase in substitution content causes the frequency of maximum absorption capacity (lowest RL) to shift to a lower frequency band, which is consistent with the behavior of ferromagnetic resonance frequency shift.

[0156] In the composition with x=0.3 exhibiting a ferromagnetic resonance frequency of 26.9 GHz.

[0157] It exhibits maximum absorption capacity at 27.7 GHz and also demonstrates excellent absorption capacity of over 99.99% at 28 GHz.

[0158] Therefore, it can be confirmed that by adjusting Co 2+ and Zn 2+ With its high content, excellent absorbers can be developed not only in the 28 GHz band, but also in other bands of the Ka frequency.

[0159] exist Figure 5 In this study, the absorption characteristics of the composite sheet can be confirmed as the thickness of the absorbing material varies.

[0160] Reference Figure 5 It can be confirmed that, according to the mathematical formula 1, the absorber with a thickness of 1.01 mm exhibits the best absorption capacity, and the absorption capacity decreases with the change of thickness.

[0161] In actual commercial applications, the thickness deviation may be around 5%. Even with a difference of + to -0.04 mm on a reference thickness of 1.01 mm, the absorption capacity can still be maintained at over 99.0% based on a frequency of 28 GHz.

[0162] In Figure 6, it can be confirmed that Co 2+ Absorption characteristics of composite sheets with varying content (contour plot of absorption characteristics as a function of thickness and frequency).

[0163] Referring to Figure 6, it can be seen that as Co... 2+ With increasing content, the absorption peak gradually shifts to lower frequency bands. This is consistent with the previously observed shift in ferromagnetic resonance frequencies.

[0164] Table 2 below compares the reflection loss and absorption characteristics.

[0165] Table 2

[0166] Table 2 is a conversion table of reflection loss and absorption capacity expressed in decibels.

[0167] At this point, if the reflection loss (RL) is -20 dB, it means that 99.0% of the electromagnetic waves incident on the absorber sample from the outside are absorbed inside the absorber, and only 1.0% are reflected to the outside.

[0168] Table 3 below summarizes the results of the study on the effects of Co. 2+ A table showing the ferromagnetic resonance frequencies, volume fractions, maximum absorption peak frequencies and thicknesses, and frequency ranges above 99% absorption (-20dB) for variations in the amount of substitution.

[0169] Table 3

[0170] In summary, it can be seen that with Co 2+ As the content of increases, the magnetic anisotropy of the C-axis decreases, thereby gradually reducing the ferromagnetic resonance frequency.

[0171] And it was confirmed that the ferromagnetic resonance frequency was in the Co 2+ When the content is around 0.25 to 0.3, it moves toward the target value of around 28 GHz.

[0172] Based on transmission line theory, the reflection loss value, represented by absorption characteristics, was calculated.

[0173] The results confirmed that when Co 2+ When the content is 0.25 to 0.3 and the thickness is 0.97 mm to 1.05 mm.

[0174] It exhibits an absorption characteristic of -65.5 dB at 27.7 GHz and achieves an excellent absorption characteristic of -50.3 dB at 28.0 GHz.

[0175] In addition, it was confirmed that when Co 2+ When the content is 0.3 and the volume fraction is 30%.

[0176] Excellent absorption properties were achieved in thicknesses ranging from 0.97 mm to 1.05 mm.

[0177] At this point, the characteristic is that it absorbs more than 99% of values ​​below -20dB.

[0178] These findings demonstrate that setting the ferromagnetic resonance frequency to 1.0 to 1.5 GHz lower than the target frequency can yield excellent absorption characteristics.

[0179] Furthermore, the ferromagnetic resonance frequency can be effectively adjusted by changing the content of substituted ions and powder. Therefore, it can be applied not only to the Ka band (26.5GHz to 40GHz) in the field of 5G communication, but also to other application frequencies.

[0180] Experimental Example 2. Variation of ferromagnetic resonance frequency with changing transition metal In SrCo 2+ x Me 2+ 2-x Fe 3+ 16 O 27 Medium fixed Co 2+ Ions, in the Me 2+ In terms of position, use excluding Zn 2+ Substitution with divalent transition metals applicable outside of ions confirmed the change in ferromagnetic resonance frequency.

[0181] Fe 2+ Mg 2+ Mn 2+ , and Ni 2+ By performing substitution, the change in ferromagnetic resonance frequency was confirmed, which allows the fabrication of magnetic composite sheets with excellent absorption characteristics at the target frequency.

[0182] Figure 7 shows the effect of Fe (Fe) 2+ Mg 2+ Mn 2+ Ni 2+ )-Co 2+ A graph showing the change in complex magnetic permeability (the volume fraction of powder in epoxy resin is 30%) with varying content.

[0183] Figure 8 This is a graph showing the ferromagnetic resonance frequency regression analysis as the content of various divalent transition metals and Co2+ ions changes.

[0184] Table 4 below is a table summarizing the changes in ferromagnetic resonance frequency with the change of transition metal.

[0185] Table 4

[0186] Refer to Figure 7, Table 4 and Figure 8 The experimental example 2 will be described below.

[0187] Referring to Figure 7 and Table 4, it can be confirmed that in SrCo 2+ x Me 2+ 2-x Fe 3+ 16 O 27 Medium fixed Co 2+ Ions, and in the Me 2+ In terms of position, use excluding Zn 2+ Fe, a divalent transition metal applicable outside of ions 2+ Mg 2+ Mn 2+ and Ni 2+ When substitution is performed, the ferromagnetic resonance frequency gradually shifts within the Ka band as the composition changes.

[0188] This indicates that specific ferromagnetic resonance frequencies can be tuned through various formulations and can be used as fillers in absorbers for applications operating at corresponding frequencies.

[0189] Reference Figure 8 It can be confirmed that according to Co 2+ -Me 2+ (Fe) 2+ Zn 2+ Mg 2+ Mn 2+ Ni 2+ The results of regression analysis were obtained by replacing the measured ferromagnetic resonance frequency values ​​with the original composition.

[0190] Through the above Figure 8 It can be confirmed that the Co required to obtain the ferromagnetic resonance frequency values ​​of each substance is... 2+ The content range.

[0191] The foregoing description of the invention is illustrative, and those skilled in the art will understand that it can be readily modified into other specific forms without altering the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, the constituent elements described as a single form may also be implemented separately, and similarly, the constituent elements described as separate may be implemented in combination.

[0192] The scope of this invention is defined by the following claims, and it should be understood that all modifications or variations derived from the meaning and scope of the claims and their equivalents are included within the scope of this invention.

Claims

1. A method for manufacturing an electromagnetic wave absorbing material, comprising: The step of mixing a powder comprising at least one selected from the group consisting of Ca precursor, Ba precursor, Sr precursor, Re precursor, Me precursor, Co precursor and Fe precursor; The step of performing a first heat treatment on the mixed powder; The step of ball milling the heat-treated powder; and The step of subjecting the ball-milled powder to a second heat treatment. This allows for the manufacture of electromagnetic wave absorbing materials containing W-type hexagonal ferrite represented by the following chemical formula 1: Chemical Formula 1 Approx a Ba b Sr 1-a-b-c Re c Co 2+ x Along with 2+ 2-x Feb 3+ 16 O 27 Wherein, in the chemical formula 1, The Re is selected from at least one of the group consisting of rare earth elements; The Me 2+ It is selected from at least one of the group consisting of divalent transition metals; The value of a is between 0.0 and 1.0; The value of b is between 0.0 and 1.0; The value of c is between 0.0 and 1.0; And x is between 0.0 and 2.

0.

2. The method for manufacturing the electromagnetic wave absorbing material according to claim 1, characterized in that, In the chemical formula 1, x is from 0.0 to 0.

3.

3. The method for manufacturing the electromagnetic wave absorbing material according to claim 1, characterized in that, In the chemical formula 1, the Me 2+ Is it a free choice of Zn? 2+ Fe 2+ Ni 2+ Mn 2+ and Mg 2+ At least one of the groups.

4. The method for manufacturing the electromagnetic wave absorbing material according to claim 1, characterized in that, The first heat treatment step is carried out in a temperature range of 1200°C to 1400°C.

5. The method for manufacturing the electromagnetic wave absorbing material according to claim 1, characterized in that, In the W-type hexagonal ferrite represented by chemical formula 1, of the 2 moles of divalent transition metal contained in chemical formula 1, Fe 2+ The ion content is less than 0.5 moles.

6. The method for manufacturing the electromagnetic wave absorbing material according to claim 1, characterized in that, The second heat treatment step is carried out in a temperature range of 1200°C to 1400°C.

7. The method for manufacturing the electromagnetic wave absorbing material according to claim 1, characterized in that, The second heat treatment step involves sintering in air.

8. An electromagnetic wave absorbing material, characterized in that, Contains W-type hexagonal ferrite represented by the following chemical formula 1: Chemical Formula 1 Approx a Ba b Sr 1-a-b-c Re c Co 2+ x Along with 2+ 2-x Feb 3+ 16 O 27 Wherein, in the chemical formula 1, The Re is selected from at least one of the group consisting of rare earth elements; The Me 2+ It is selected from at least one of the group consisting of divalent transition metals; The value of a is between 0.0 and 1.0; The value of b is between 0.0 and 1.0; The value of c is between 0.0 and 1.0; And x is between 0.0 and 2.

0.

9. The electromagnetic wave absorbing material according to claim 8, characterized in that, In the W-type hexagonal ferrite represented by chemical formula 1, in the 2 moles of divalent transition metal contained in chemical formula 1, Fe 2+ The ion content is less than 0.5 moles.

10. The electromagnetic wave absorbing material according to claim 8, characterized in that, The electromagnetic wave absorbing material has a ferromagnetic resonance (FMR) frequency in the frequency band above 26.5 GHz and below 40 GHz.

11. The electromagnetic wave absorbing material according to claim 8, characterized in that, In the chemical formula 1, x is from 0.0 to 0.

3.

12. The electromagnetic wave absorbing material according to claim 8, characterized in that, In the chemical formula 1, the Me 2+ Is it a free choice of Zn? 2+ Fe 2+ Ni 2+ Mn 2+ and Mg 2+ At least one of the groups.

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