JP4784517B2 - Radio wave absorber - Google Patents

Radio wave absorber Download PDF

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JP4784517B2
JP4784517B2 JP2007007270A JP2007007270A JP4784517B2 JP 4784517 B2 JP4784517 B2 JP 4784517B2 JP 2007007270 A JP2007007270 A JP 2007007270A JP 2007007270 A JP2007007270 A JP 2007007270A JP 4784517 B2 JP4784517 B2 JP 4784517B2
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謙一郎 松野
綱 伊藤
守 伊藤
達哉 川口
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TDK Corp
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Description

本発明は、電波吸収体に関するものである。   The present invention relates to a radio wave absorber.

近年、建築構造物や電波暗室等の壁材に用いられるタイルとして、フェライト製の板状電波吸収体が知られている。このような電波吸収体は、例えば下記特許文献１等において開示されている。
特公平７−１１４３１８号公報 2. Description of the Related Art In recent years, ferrite-made plate-shaped wave absorbers are known as tiles used for wall materials such as building structures and anechoic chambers. Such a radio wave absorber is disclosed in, for example, Patent Document 1 below.
Japanese Patent Publication No.7-114318

しかしながら、前述した従来の電波吸収体においては、タイルとしての強度（抗折強度）が十分ではなく、そのため、さらなる強度の向上が望まれていた。   However, the above-described conventional radio wave absorber does not have sufficient strength (bending strength) as a tile, and therefore, further improvement in strength has been desired.

そこで、本発明は、上述の課題を解決するためになされたもので、十分な強度向上が図られた電波吸収体を提供することを目的とする。   Therefore, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radio wave absorber that is sufficiently improved in strength.

本発明に係る電波吸収体は、３０ＭＨｚ〜４００ＭＨｚの周波数帯において、吸収特性が１８ｄＢより大きく、整合厚さが８ｍｍより薄く、且つ、組成比が、Ｆｅ２Ｏ３：４９．１〜４９．７ｍｏｌ％、ＺｎＯ：３０．０〜３１．５ｍｏｌ％、ＣｕＯ：５．０〜９．１ｍｏｌ％、ＭｇＯ：５．０〜９．９ｍｏｌ％、ＮｉＯ：４．０〜７．０ｍｏｌ％である。 The radio wave absorber according to the present invention has an absorption characteristic larger than 18 dB, a matching thickness smaller than 8 mm, and a composition ratio of Fe 2 O 3 : 49.1 to 49.7 mol in a frequency band of 30 MHz to 400 MHz. %, ZnO: 30.0 to 31.5 mol%, CuO: 5.0 to 9.1 mol%, MgO: 5.0 to 9.9 mol%, NiO: 4.0 to 7.0 mol%.

この電波吸収体においては、実用的な周波数帯（３０ＭＨｚ〜４００ＭＨｚ）において、十分な吸収特性（＞１８ｄＢ）、及び、十分に薄い整合厚さ（＜８ｍｍ）が得られ、且つ、高い抗折強度を実現することができる。   In this radio wave absorber, a sufficient absorption characteristic (> 18 dB) and a sufficiently thin matching thickness (<8 mm) are obtained in a practical frequency band (30 MHz to 400 MHz), and a high bending strength is obtained. Can be realized.

また、本発明に係る電波吸収体は、３０ＭＨｚ〜４００ＭＨｚの周波数帯において、吸収特性が１８ｄＢより大きく、整合厚さが７ｍｍより薄く、且つ、組成比が、Ｆｅ２Ｏ３：４９．２〜４９．６ｍｏｌ％、ＺｎＯ：３０．０〜３０．３ｍｏｌ％、ＣｕＯ：６．２〜７．６ｍｏｌ％、ＭｇＯ：７．２〜８．２ｍｏｌ％、ＮｉＯ：５．４〜６．５ｍｏｌ％である。 The radio wave absorber according to the present invention has an absorption characteristic larger than 18 dB, a matching thickness smaller than 7 mm, and a composition ratio of Fe 2 O 3 : 49.2 to 49 in a frequency band of 30 MHz to 400 MHz. 0.6 mol%, ZnO: 30.0-30.3 mol%, CuO: 6.2-7.6 mol%, MgO: 7.2-8.2 mol%, NiO: 5.4-6.5 mol%.

この電波吸収体においては、実用的な周波数帯（３０ＭＨｚ〜４００ＭＨｚ）において、十分な吸収特性（＞１８ｄＢ）、及び、十分に薄い整合厚さ（＜７ｍｍ）が得られ、且つ、高い抗折強度を実現することができる。   In this radio wave absorber, a sufficient absorption characteristic (> 18 dB) and a sufficiently thin matching thickness (<7 mm) are obtained in a practical frequency band (30 MHz to 400 MHz), and a high bending strength is obtained. Can be realized.

なお、ＣｕＯの組成比に対するＭｇＯの組成比の割合（ＭｇＯ／ＣｕＯ）を０．９３〜１．９２とすることで高い抗折強度が得られる。   A high bending strength can be obtained by setting the ratio of the MgO composition ratio to the CuO composition ratio (MgO / CuO) to be 0.93 to 1.92.

本発明によれば、十分な強度向上が図られた電波吸収体が提供される。   ADVANTAGE OF THE INVENTION According to this invention, the electromagnetic wave absorber by which sufficient intensity | strength improvement was achieved is provided.

以下、添付図面を参照して本発明を実施するにあたり最良と思われる形態について詳細に説明する。なお、同一又は同等の要素については同一の符号を付し、説明が重複する場合にはその説明を省略する。   DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments that are considered to be the best in carrying out the invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the same or equivalent element, and the description is abbreviate | omitted when description overlaps.

本発明に係る電波吸収体１０は、図１に示すように板状であり、その寸法は縦１００ｍｍ×横１００ｍｍ×厚さ８ｍｍとなっている。   The radio wave absorber 10 according to the present invention has a plate shape as shown in FIG. 1 and has dimensions of 100 mm in length × 100 mm in width × 8 mm in thickness.

この電波吸収体１０は、Ｆｅ２Ｏ３と、ＺｎＯと、ＣｕＯと、ＭｇＯと、ＮｉＯとを含むフェライト材料によって構成されている。そして、電波吸収体１０の組成比の範囲は、Ｆｅ２Ｏ３：４９．１〜４９．７ｍｏｌ％、ＺｎＯ：３０．０〜３１．５ｍｏｌ％、ＣｕＯ：５．０〜９．１ｍｏｌ％、ＭｇＯ：５．０〜９．９ｍｏｌ％、ＮｉＯ：４．０〜７．０ｍｏｌ％（以下、「組成範囲Ａ」と称す。）となっている。 The radio wave absorber 10 is made of a ferrite material containing Fe 2 O 3 , ZnO, CuO, MgO, and NiO. The range of the composition ratio of the electromagnetic wave absorber 10, Fe 2 O 3: 49.1~49.7mol% , ZnO: 30.0~31.5mol%, CuO: 5.0~9.1mol%, MgO : 5.0 to 9.9 mol%, NiO: 4.0 to 7.0 mol% (hereinafter referred to as “composition range A”).

発明者らは、鋭意研究の末、電波吸収体１０の構成材料に上記組成範囲Ａとなるフェライト材料を用いることにより、実用的な周波数帯（３０ＭＨｚ〜４００ＭＨｚ）において、十分な吸収特性（＞１８ｄＢ）、及び、十分に薄い整合厚さ（＜８ｍｍ）が得られ、且つ、高い抗折強度を実現することができることを新たに見出した。   As a result of diligent research, the inventors have used a ferrite material having the composition range A as a constituent material of the radio wave absorber 10, thereby providing sufficient absorption characteristics (> 18 dB) in a practical frequency band (30 MHz to 400 MHz). ) And a sufficiently thin matching thickness (<8 mm) can be obtained, and a high bending strength can be realized.

さらに、発明者らは、電波吸収体１０の構成材料に、Ｆｅ２Ｏ３：４９．２〜４９．６ｍｏｌ％、ＺｎＯ：３０．０〜３０．３ｍｏｌ％、ＣｕＯ：６．２〜７．６ｍｏｌ％、ＭｇＯ：７．２〜８．２ｍｏｌ％、ＮｉＯ：５．４〜６．５ｍｏｌ％の組成範囲（以下、「組成範囲Ｂ」と称す。）であるフェライト材料を用いることで、より薄い整合厚さ（＜７ｍｍ）を実現でき、且つ、実用的な周波数帯（３０ＭＨｚ〜４００ＭＨｚ）において、十分な吸収特性（＞１８ｄＢ）と高い抗折強度が得られることを新たに見出した。 Further, the inventors have included in the constituent material of the radio wave absorber 10 Fe 2 O 3 : 49.2-49.6 mol%, ZnO: 30.0-30.3 mol%, CuO: 6.2-7.6 mol. %, MgO: 7.2 to 8.2 mol%, NiO: 5.4 to 6.5 mol% (hereinafter referred to as “composition range B”). It was newly found that a thickness (<7 mm) can be realized and sufficient absorption characteristics (> 18 dB) and high bending strength can be obtained in a practical frequency band (30 MHz to 400 MHz).

以下、発明者らによる上記電波吸収体を構成するフェライト材料の実施例及び比較例について説明する。   Hereinafter, examples and comparative examples of the ferrite material constituting the radio wave absorber by the inventors will be described.

発明者らは、上記組成範囲Ｂに適合する５種類のフェライト材料（試料１〜５）と、上記組成範囲Ａに適合する７種類のフェライト材料（試料６〜１２）と、上記組成範囲Ａ及び組成範囲Ｂのいずれにも適合しない１３種類のフェライト材料（試料１３〜２５）の計２５種類の試料を準備し、そのそれぞれについて、「整合厚さ」、「吸収特性」及び「抗折強度」を測定した。   The inventors have five types of ferrite materials (samples 1 to 5) conforming to the composition range B, seven types of ferrite materials (samples 6 to 12) conforming to the composition range A, the composition range A and A total of 25 types of samples of 13 types of ferrite materials (samples 13 to 25) that do not conform to any of composition range B are prepared, and for each of these, “matching thickness”, “absorption characteristics”, and “bending strength” Was measured.

なお、吸収特性（すなわち、減衰量）の測定は、外径１９．８ｍｍ、内径８．７ｍｍ、厚さ７ｍｍの寸法に成形したフェライト焼結体（トロイダルコア）に対し、インピーダンスアナライザで同軸管を用いておこなった。この吸収特性は、発明者らがおこなった実験によれば、図２に示すとおり、同じ整合厚さでみた場合、周波数の上限値（４００ＭＨｚ）に比べて下限値（３０ＭＨｚ）のほうが小さい値となるため、この下限値を用いて吸収特性の測定をおこなった。また、抗折強度は、５．５ｍｍ×１．２ｍｍの長方形金型を用いて、フェライト顆粒１０ｇを２ｔｏｎ／ｃｍ２の成型圧で成型した焼結コアを、三点法（二点間距離３０ｍｍ）により測定した。 The absorption characteristics (that is, the amount of attenuation) are measured by using an impedance analyzer to measure the coaxial tube of a ferrite sintered body (toroidal core) formed to have dimensions of an outer diameter of 19.8 mm, an inner diameter of 8.7 mm and a thickness of 7 mm. It was done using. According to the experiment conducted by the inventors, the absorption characteristic is lower in the lower limit (30 MHz) than the upper limit (400 MHz) of the frequency when viewed at the same matching thickness as shown in FIG. Therefore, the absorption characteristics were measured using this lower limit value. The bending strength is a three-point method (distance between two points: 30 mm) using a 5.5 mm × 1.2 mm rectangular mold and a sintered core obtained by molding 10 g of ferrite granules with a molding pressure of 2 ton / cm 2. ).

それらの測定結果は、図３の表に示すとおりとなった。   The measurement results were as shown in the table of FIG.

つまり、組成範囲Ｂに適合する試料１〜５においては、いずれも整合厚さが７ｍｍより小さく、吸収特性は１８ｄＢより大きく、且つ、抗折強度は１００ＭＰａよりも大きかった。   That is, in Samples 1 to 5 that conform to the composition range B, the matching thickness was less than 7 mm, the absorption characteristics were greater than 18 dB, and the bending strength was greater than 100 MPa.

また、組成範囲Ａに適合する試料６〜１２においては、いずれも整合厚さが８ｍｍより小さく、吸収特性は１８ｄＢより大きく、且つ、抗折強度は１００ＭＰａよりも大きかった。   In Samples 6 to 12 that conform to the composition range A, the matching thickness was less than 8 mm, the absorption characteristics were greater than 18 dB, and the bending strength was greater than 100 MPa.

一方、その他の試料１３〜２５においては、整合厚さ、吸収特性及び抗折強度のいずれかが上記条件を満たしていない。   On the other hand, in the other samples 13 to 25, any of the matching thickness, the absorption characteristic, and the bending strength does not satisfy the above condition.

すなわち、試料１３，１４はいずれもＦｅ２Ｏ３が組成範囲外となっており、そのため、減衰量が１８ｄＢよりも低くなっている。 That is, in both samples 13 and 14, Fe 2 O 3 is out of the composition range, and therefore the attenuation is lower than 18 dB.

また、試料１５，１６はいずれもＺｎＯが組成範囲外となっており、そのため、試料１５では減衰量が１８ｄＢよりも低くなっており、試料１６では整合厚さが８ｍｍ以上となっている。   Further, in both samples 15 and 16, ZnO is out of the composition range. Therefore, in sample 15, the attenuation is lower than 18 dB, and in sample 16, the matching thickness is 8 mm or more.

さらに、試料１７〜２０はいずれもＣｕＯ若しくはＮｉＯが組成範囲外となっており、そのため、減衰量が１８ｄＢよりも低くなっている。   Further, in all of Samples 17 to 20, CuO or NiO is out of the composition range, and therefore the attenuation is lower than 18 dB.

試料２１〜２４はいずれもＭｇＯが組成範囲外となっており、そのため、試料２１では整合厚さが８ｍｍ以上となっており、試料２２〜２４では減衰量が１８ｄＢよりも低くなっている。なお、試料２５はＭｇＯを全く添加していない材料である。   In all of the samples 21 to 24, MgO is out of the composition range. Therefore, in the sample 21, the matching thickness is 8 mm or more, and in the samples 22 to 24, the attenuation is lower than 18 dB. Sample 25 is a material to which no MgO is added.

加えて、比較例である試料１３〜２５においては、いずれも抗折強度が１００ＭＰａ未満であった。   In addition, in samples 13 to 25 as comparative examples, the bending strength was less than 100 MPa.

ここで、ＭｇＯの組成比と抗折強度との関係を図４のグラフに示す。この図４のグラフは、縦軸が抗折強度（ＭＰａ）であり、横軸がＭｇＯの組成比（ｍｏｌ％）である。   Here, the relationship between the composition ratio of MgO and the bending strength is shown in the graph of FIG. In the graph of FIG. 4, the vertical axis represents the bending strength (MPa), and the horizontal axis represents the composition ratio (mol%) of MgO.

この図４のグラフから明らかなように、ＭｇＯの組成比が所定の範囲（５．０〜９．９ｍｏｌ％）である場合には１００ＭＰａよりも高い抗折強度が得られるのに対し、その範囲外である場合には１００ＭＰａ以下の抗折強度しか得られない。この結果から、上述した組成範囲Ａ及び組成範囲Ｂでは、ＭｇＯの組成比が適切な範囲となっているために、得られる電波吸収体の抗折強度の向上が図られていると考えられる。   As is apparent from the graph of FIG. 4, when the composition ratio of MgO is in a predetermined range (5.0 to 9.9 mol%), a bending strength higher than 100 MPa is obtained, whereas that range When it is outside, only a bending strength of 100 MPa or less can be obtained. From this result, since the composition ratio of MgO is in an appropriate range in the composition range A and the composition range B described above, it is considered that the bending strength of the obtained radio wave absorber is improved.

図５は、ＣｕＯの組成比に対するＭｇＯの組成比の割合（ＭｇＯ／ＣｕＯ比）と、抗折強度との関係を示したグラフである。この図５のグラフにおいて、縦軸は抗折強度（ＭＰａ）であり、横軸はＭｇＯ／ＣｕＯ比である。   FIG. 5 is a graph showing the relationship between the ratio of the MgO composition ratio to the CuO composition ratio (MgO / CuO ratio) and the bending strength. In the graph of FIG. 5, the vertical axis represents the bending strength (MPa), and the horizontal axis represents the MgO / CuO ratio.

この図５のグラフから、ＭｇＯ／ＣｕＯ比が所定の範囲（０．９３〜１．９２）である場合には１００ＭＰａよりも高い抗折強度が得られるのに対し、その範囲外である場合には１００ＭＰａ以下の抗折強度しか得られない。この結果から、ＭｇＯ／ＣｕＯ比が上記範囲である場合に、得られる電波吸収体の抗折強度の向上が図られるものと考えられる。   From the graph of FIG. 5, when the MgO / CuO ratio is in a predetermined range (0.93 to 1.92), a bending strength higher than 100 MPa is obtained, but when it is out of the range. Only has a bending strength of 100 MPa or less. From this result, it is considered that when the MgO / CuO ratio is in the above range, the bending strength of the obtained radio wave absorber can be improved.

以上で説明したとおり、本発明の実施形態に係る電波吸収体１０は、上述した組成範囲Ａ若しくは組成範囲Ｂであるフェライト材料により構成されているため、実用的な周波数帯において、十分な吸収特性、及び、十分に薄い整合厚さが得られ、且つ、高い抗折強度を実現することができる。   As described above, since the radio wave absorber 10 according to the embodiment of the present invention is made of the ferrite material having the composition range A or the composition range B described above, sufficient absorption characteristics can be obtained in a practical frequency band. A sufficiently thin matching thickness can be obtained, and a high bending strength can be realized.

本発明の実施形態に係る電波吸収体を示した斜視図である。It is the perspective view which showed the electromagnetic wave absorber which concerns on embodiment of this invention. 減衰量（吸収特性）と周波数との関係を整合厚さ毎に示したグラフである。It is the graph which showed the relationship between attenuation amount (absorption characteristic) and frequency for every matching thickness. 本発明の実施例に係る測定結果を示した表である。It is the table | surface which showed the measurement result which concerns on the Example of this invention. 本発明の実施例に係る測定結果を示したグラフである。It is the graph which showed the measurement result which concerns on the Example of this invention. 本発明の実施例に係る測定結果を示したグラフである。It is the graph which showed the measurement result which concerns on the Example of this invention.

符号の説明Explanation of symbols

１０…電波吸収体。   10 ... A radio wave absorber.

Claims (3)

３０ＭＨｚ〜４００ＭＨｚの周波数帯において、吸収特性が１８ｄＢより大きく、整合厚さが８ｍｍより薄く、且つ、組成比が、
Ｆｅ２Ｏ３：４９．１〜４９．７ｍｏｌ％、
ＺｎＯ：３０．０〜３１．５ｍｏｌ％、
ＣｕＯ：５．０〜９．１ｍｏｌ％、
ＭｇＯ：５．０〜９．９ｍｏｌ％、
ＮｉＯ：４．０〜７．０ｍｏｌ％
である、電波吸収体。 In the frequency band of 30 MHz to 400 MHz, the absorption characteristics are larger than 18 dB, the matching thickness is thinner than 8 mm, and the composition ratio is
Fe 2 O 3: 49.1~49.7mol%,
ZnO: 30.0-31.5 mol%,
CuO: 5.0 to 9.1 mol%,
MgO: 5.0 to 9.9 mol%,
NiO: 4.0-7.0 mol%
A radio wave absorber. ３０ＭＨｚ〜４００ＭＨｚの周波数帯において、吸収特性が１８ｄＢより大きく、整合厚さが７ｍｍより薄く、且つ、組成比が、
Ｆｅ２Ｏ３：４９．２〜４９．６ｍｏｌ％、
ＺｎＯ：３０．０〜３０．３ｍｏｌ％、
ＣｕＯ：６．２〜７．６ｍｏｌ％、
ＭｇＯ：７．２〜８．２ｍｏｌ％、
ＮｉＯ：５．４〜６．５ｍｏｌ％
である、電波吸収体。 In the frequency band of 30 MHz to 400 MHz, the absorption characteristics are larger than 18 dB, the matching thickness is thinner than 7 mm, and the composition ratio is
Fe 2 O 3: 49.2~49.6mol%,
ZnO: 30.0-30.3 mol%,
CuO: 6.2 to 7.6 mol%,
MgO: 7.2-8.2 mol%,
NiO: 5.4 to 6.5 mol%
A radio wave absorber. ＣｕＯの組成比に対するＭｇＯの組成比の割合（ＭｇＯ／ＣｕＯ）が０．９３〜１．９２である、請求項１又は２に記載の電波吸収体。   The electromagnetic wave absorber according to claim 1 or 2, wherein a ratio of the composition ratio of MgO to the composition ratio of CuO (MgO / CuO) is 0.93 to 1.92.
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