JP2015148551A - hydrogen response element - Google Patents
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- JP2015148551A JP2015148551A JP2014022347A JP2014022347A JP2015148551A JP 2015148551 A JP2015148551 A JP 2015148551A JP 2014022347 A JP2014022347 A JP 2014022347A JP 2014022347 A JP2014022347 A JP 2014022347A JP 2015148551 A JP2015148551 A JP 2015148551A
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 239000001257 hydrogen Substances 0.000 title claims abstract description 101
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 101
- 108091027981 Response element Proteins 0.000 title claims abstract description 10
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 24
- 239000000956 alloy Substances 0.000 claims abstract description 24
- 239000010409 thin film Substances 0.000 claims abstract description 17
- 239000010419 fine particle Substances 0.000 claims abstract description 6
- 229910052742 iron Inorganic materials 0.000 claims abstract description 6
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 6
- 235000014676 Phragmites communis Nutrition 0.000 claims description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 6
- 230000004043 responsiveness Effects 0.000 abstract description 3
- 230000005291 magnetic effect Effects 0.000 description 26
- 229910021069 Pd—Co Inorganic materials 0.000 description 19
- 239000007789 gas Substances 0.000 description 17
- 239000010408 film Substances 0.000 description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 11
- 239000001301 oxygen Substances 0.000 description 11
- 229910052760 oxygen Inorganic materials 0.000 description 11
- 150000002431 hydrogen Chemical class 0.000 description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 229910001252 Pd alloy Inorganic materials 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- 238000010521 absorption reaction Methods 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 230000005415 magnetization Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000004044 response Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003302 ferromagnetic material Substances 0.000 description 2
- 230000005307 ferromagnetism Effects 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 229920002799 BoPET Polymers 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000007084 catalytic combustion reaction Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000011491 glass wool Substances 0.000 description 1
- 238000012625 in-situ measurement Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
Description
本発明は、水素濃度に応じて磁気特性が変化する水素応答素子に関する。 The present invention relates to a hydrogen responsive element whose magnetic characteristics change according to the hydrogen concentration.
水素は、次世代のエネルギー燃料として期待されているが、水素ガスは可燃性ガスであり、大気中では４％以上になると爆発の危険性がある。
また、水素ガスは拡散が非常に速いことから、一旦漏洩した場合に急速に広範囲に拡散する。
そのため、水素を利用する環境においては広範囲の場所において迅速に水素濃度を検出する必要がある。
また、現在多量の水素ガスを利用したり、発生する場所としては、例えば鉄鋼製造に利用する高炉内，原子炉内，メタン化反応装置等の密閉状態の場合が多く、このような密閉容器に水素ガス検出子の導入穴をあけることなく、外部から非接触で検出，計測できるものが好ましい。
また、今後水素貯蔵タンク，水素供給スタンド，燃料電池関連工場及び施設等の水素を利用した各種工場や施設が増加すると思われる。
このような水素を利用する装置，施設において自発的、且つ無電源で動作するリードスイッチ等の水素濃度検出装置があれば、電源遮断時のトラブルの恐れもなく、水素を利用するインフラでの安全装置の利用が期待できる。
Hydrogen is expected as a next-generation energy fuel, but hydrogen gas is a flammable gas, and there is a risk of explosion when it exceeds 4% in the atmosphere.
Moreover, since hydrogen gas diffuses very quickly, once it leaks, it diffuses rapidly over a wide area.
Therefore, in an environment using hydrogen, it is necessary to quickly detect the hydrogen concentration in a wide range of places.
In addition, there are many cases in which a large amount of hydrogen gas is currently used or generated, for example, in blast furnaces, reactors, methanation reactors, etc., which are used for steel production, in such closed containers. It is preferable to be able to detect and measure from the outside without making a hole for introducing a hydrogen gas detector.
In the future, the number of factories and facilities using hydrogen, such as hydrogen storage tanks, hydrogen supply stands, fuel cell-related factories and facilities, will increase.
If there is a hydrogen concentration detection device such as a reed switch that operates spontaneously and without a power source in such a device or facility that uses hydrogen, there is no risk of trouble when the power is shut off, and safety in the infrastructure that uses hydrogen Use of the device can be expected.
従来の水素ガスの濃度を定量できるものとしては、接触燃焼式，半導体式，Ｐｄ膜抵抗センサ，光学式センサ等が公知である。
接触燃焼式は、簡便で堅牢であるが、測定濃度可能範囲が高い。
逆に半導体式は、測定濃度可能範囲が低すぎる。
Ｐｄ膜抵抗センサは、水素の選択性が高いが、測定濃度可能範囲が高く、酸素に弱い問題がある。
光学式センサは、非接触での計測が可能であるが、複雑な装置が必要になる。
また、水素ガスに対する応答性のあるリードスイッチについては、これまでに報告が見当たらなかった。
As a conventional apparatus capable of quantifying the concentration of hydrogen gas, a contact combustion type, a semiconductor type, a Pd film resistance sensor, an optical sensor, and the like are known.
The catalytic combustion type is simple and robust, but has a high measurable concentration range.
On the other hand, in the semiconductor type, the possible concentration range is too low.
The Pd film resistance sensor has high hydrogen selectivity, but has a high measurable concentration range and is vulnerable to oxygen.
The optical sensor can measure in a non-contact manner, but requires a complicated device.
There has been no report on a reed switch that is responsive to hydrogen gas.
本出願人に係る発明者は、先にＰｄ固体中の水素濃度が磁化率に与える影響を報告し（非特許文献１）、ＰｄとＣｏとの合金が水素の吸収により磁化率が減少することを発表している（非特許文献２）。
しかし、上記論文発表の段階では、水素ガスセンサとしての応用までは明らかでなく、酸素共存下（大気中）での水素ガスによる磁化率の影響についても明確になっていなかった。
さらに上記論文では、Ｐｄ−Ｃｏ合金バルク中の水素濃度と磁気特性について報告したものであって、Ｐｄ−Ｃｏ合金の薄膜化，微粒子化による効果までは言及されていない。
The inventor of the present applicant has previously reported the effect of the hydrogen concentration in the Pd solid on the magnetic susceptibility (Non-Patent Document 1), and that the magnetic susceptibility of an alloy of Pd and Co decreases due to hydrogen absorption. (Non-Patent Document 2).
However, at the stage of the publication of the above paper, the application as a hydrogen gas sensor was not clear, and the influence of magnetic susceptibility due to hydrogen gas in the presence of oxygen (in the atmosphere) was not clear.
Furthermore, in the above paper, the hydrogen concentration and magnetic properties in the bulk of the Pd—Co alloy are reported, and the effects of making the Pd—Co alloy thinner and finer are not mentioned.
本発明は、水素濃度変化に対する応答性に優れた水素応答素子の提供を目的とする。
また、この水素応答素子を用いた水素ガスセンサ及びリードスイッチの提供を目的とする。
An object of this invention is to provide the hydrogen responsive element excellent in the responsiveness with respect to a hydrogen concentration change.
It is another object of the present invention to provide a hydrogen gas sensor and a reed switch using the hydrogen response element.
本発明に係る水素応答素子は、Ｐｄと鉄属元素のいずれか１つ以上との合金であって、厚さ１μｍ以下の薄膜又は平均粒径１００μｍ以下の微粒子からなることを特徴とする。
ここで鉄属元素は、Ｆｅ，Ｃｏ，Ｎｉをいい、ＰｄとこのＦｅ，Ｃｏ，Ｎｉのうち、１つ以上が含まれる合金をいう。
本発明で、厚さ１μｍ以下の薄膜又は平均粒径１００μｍ以下の微粒子にしたのは、質量に対する表面積比率を高くすることで、水素に対する応答性を向上させたものである。
薄膜は、Ｐｄと鉄属元素をスパッタリング等の蒸着法を用いて製作できる。
上記合金を粉末化して微粒子にすることもできる。
The hydrogen responsive element according to the present invention is an alloy of Pd and one or more of iron group elements, and is characterized by comprising a thin film having a thickness of 1 μm or less or fine particles having an average particle diameter of 100 μm or less.
Here, the iron group element refers to Fe, Co, and Ni, and refers to an alloy including one or more of Pd and the Fe, Co, and Ni.
In the present invention, a thin film having a thickness of 1 μm or less or a fine particle having an average particle size of 100 μm or less is obtained by improving the responsiveness to hydrogen by increasing the surface area ratio to the mass.
The thin film can be manufactured using a vapor deposition method such as sputtering of Pd and an iron group element.
The alloy can also be powdered into fine particles.
本発明において、Ｐｄと鉄属元素との合金を用いたのは、Ｐｄの水素吸収性と鉄属元素の強磁性との組み合せに着目したものであり、水素の吸収による磁化率の低下曲線はＰｄ系合金中のＦｅ，Ｃｏ，Ｎｉの配合率により調整可能である。
また、この磁化率変化は温度の影響を受ける。
そこで、常温付近で０．０５％〜１０％までの水素ガス濃度を計測対象にするには、Ｐｄ系合金中のＦｅ，Ｃｏ，Ｎｉのうちの１つ以上含有し、その合計濃度が４〜２０ａｔ％の範囲が好ましい。
なお、ＰｄにＮｉを単独で配合する場合には、４〜５０ａｔ％の範囲でもよい。
In the present invention, an alloy of Pd and an iron group element is used because it pays attention to the combination of hydrogen absorption of Pd and ferromagnetism of an iron group element. It can be adjusted by the mixing ratio of Fe, Co, and Ni in the Pd-based alloy.
This change in magnetic susceptibility is affected by temperature.
Therefore, in order to measure a hydrogen gas concentration of 0.05% to 10% near normal temperature, it contains one or more of Fe, Co, and Ni in the Pd-based alloy, and the total concentration is 4 to 4%. A range of 20 at% is preferred.
In addition, when adding Ni to Pd independently, the range of 4-50 at% may be sufficient.
このような水素応答素子は詳細については後述するが、磁化率変化が水素濃度の１／２乗に比例しており、この水素応答素子の磁化率を計測することにより、水素濃度のレベル計ともなる水素ガス濃度を検知する水素ガスセンサとして利用できる。
また、本発明に係る合金はある濃度範囲において室温で強磁性を示し、また水素を吸収することにより磁化率の大きさが減少する。
つまり、外部から磁石を近づけた場合、水素がない環境では本発明に係るＰｄ合金は磁石に引き付けられるが、水素が一定濃度以上の環境下では磁石に引きつけられない。
この磁石に対する応答の違いから、本発明に係るＰｄ合金を端子として用いたリードスイッチを作成することで、通常は一般のリードスイッチと同様の働きをするが、水素雰囲気化ではスイッチとして機能しなくなるような素子を構築できる。
Although details of such a hydrogen response element will be described later, the change in magnetic susceptibility is proportional to the half power of the hydrogen concentration. By measuring the magnetic susceptibility of this hydrogen response element, both the hydrogen concentration level meter and It can be used as a hydrogen gas sensor for detecting the hydrogen gas concentration.
Moreover, the alloy according to the present invention exhibits ferromagnetism at room temperature in a certain concentration range, and the magnitude of magnetic susceptibility is reduced by absorbing hydrogen.
That is, when the magnet is brought close to the outside, the Pd alloy according to the present invention is attracted to the magnet in an environment where there is no hydrogen, but is not attracted to the magnet in an environment where hydrogen is at a certain concentration or higher.
Due to the difference in response to the magnet, a reed switch using the Pd alloy according to the present invention as a terminal normally functions in the same manner as a general reed switch, but it does not function as a switch in a hydrogen atmosphere. Such an element can be constructed.
本発明に係るＰｄ合金は無酸素下では水素吸収により磁気特性が変化し、その磁気特性変化は非接触で且つ容器の壁を隔てた環境でも読み取ることが可能である。
一方でＰｄ合金は水素酸化触媒として機能する。
そのため、酸素雰囲気下では水素と酸素がＰｄ合金上で反応し、その結果発熱し合金の温度が上昇する。
この温度上昇によりＰｄ合金の磁気特性が変化することから、やはり磁気特性変化を読むことで水素濃度を定量することが可能となる。
また、測定可能な水素濃度は合金の組成を変化させることで対応ができる。
また、本発明に係るＰｄ合金を薄膜化又は微粒子化したので、水素濃度に対する応答性に優れる。
本発明に係る水素応答素子をリードスイッチに展開すると、一般的な水素センサからのフィードバックを利用する安全回路と比較して、本発明の素子は構造が非常に簡単であり、また無電源状態でも素子自身は自発的に動作する。
そのため、耐久性、メンテナンス性に優れ、また水素ガスに対しより高度な安全回路を構築できる。
The Pd alloy according to the present invention changes its magnetic characteristics due to hydrogen absorption in the absence of oxygen, and the change in the magnetic characteristics can be read in an environment that is non-contact and that separates the wall of the container.
On the other hand, the Pd alloy functions as a hydrogen oxidation catalyst.
Therefore, hydrogen and oxygen react on the Pd alloy in an oxygen atmosphere, and as a result, heat is generated and the temperature of the alloy rises.
Since the magnetic characteristics of the Pd alloy change due to this temperature rise, the hydrogen concentration can be quantified by reading the change in the magnetic characteristics.
The measurable hydrogen concentration can be dealt with by changing the composition of the alloy.
Moreover, since the Pd alloy according to the present invention is thinned or finely divided, the response to hydrogen concentration is excellent.
When the hydrogen responsive element according to the present invention is developed in a reed switch, the element of the present invention has a very simple structure as compared with a safety circuit using feedback from a general hydrogen sensor, and even in a non-powered state. The element itself operates spontaneously.
Therefore, it is excellent in durability and maintainability, and a more advanced safety circuit can be constructed against hydrogen gas.
以下、水素ガスセンサに用いた例を説明する。
水素応答素子として、Ｐｄ−Ｃｏ合金薄膜を用いた。
原子数比でＰｄ：Ｃｏが９：１になるようにそれぞれの金属を同時スパッタリングすることで約１μｍの厚さの膜をＰＥＴフィルム上に堆積した。
作成した薄膜は、５ミリ角の大きさに切断した。
この組成のＰｄ−Ｃｏ合金は室温で強磁性体であり、水素を吸うことでその磁気特性が弱くなる。
センサ特性試験装置を、図１に示した。
ガス導入部は２台のマスフローコントローラで、窒素と水素、あるいは空気と水素を所定の比率で混合して導入する仕組みになっている。
図１中央の試料管の内部に、約０．１ｇの薄膜化したＰｄ−Ｃｏ合金を設置し、両端をガラスウールでふさいだ。
試料管内は所定の比率で混合されたガスを毎分１００ｃｃ程度の速度で流し、流したガス内の水素濃度に応じて測定コイルより発生する交流電圧が変化する。
水素濃度１０％から０．２％までの交流電圧の変化を図２に示す。
水素を混合したガスを流すと、急激に交流電圧が大きくなり、ある一定値で止まる。
この値は、水素濃度が低くなるにつれ小さくなる傾向を示している。
これは、Ｐｄ−Ｃｏ合金が水素を吸収することで、磁化率が変化したことを示している。
水素吸収量は流れるガス内の水素の分圧に依存することから、水素濃度が減少することで磁化率の変化が小さくなる。
この磁化率の変化を水素濃度の１／２乗に対してプロットした結果を図３のグラフに示す。
磁化率変化は水素濃度の１／２乗に比例していることがわかる。
一般に水素吸蔵合金の溶解領域での水素溶解量は水素分圧の１／２乗に比例することが知られており、今回の結果は、水素吸収により磁化率が変化することが原因であることを示している。
測定誤差とバックグラウンドの変動を考慮すると、この直線関係より本測定装置により０．０５％の水素濃度まで測定が可能であることが分かる。
一方、酸素存在下での水素濃度の測定も可能であることが図４により示されている。
これは、水素と酸素がＰｄ合金上で反応し水を生成する際の発熱により、合金自身の温度が上昇し、それによって磁化率が変化している。
そのため、図４に示した出力は酸素が存在していない場合の出力とは異なる。
測定条件（雰囲気）に適した校正曲線を利用することで、酸素の存在の有無にかかわらず水素濃度の計測が可能となる。
次に粉末（平均粒径約１００μｍ）及び薄膜（厚さ１μｍ）試料での、水素濃度１％での反応時間を比較したグラフを図５に示す。
粉末での結果は、ｔ９０（最大出力の９０％に到達する時間）が３００ｓｅｃであるのに対して、薄膜での結果は１４０ｓｅｃと短くなった。
これは、水素が薄膜内に入ったのち全体に拡散する時間が必要なためであり、結果として粒径の大きい粉末では薄膜より反応時間が長くなるためである。
よって、反応時間を短くしてセンサとしての機能を高めるためには、より薄い薄膜あるいはナノ粒子の形態のＰｄ−Ｃｏ合金を利用する必要があり、微粒子では少なくとも平均粒子で１００μｍ以下、薄膜で１μｍ以下が好ましい。
Hereinafter, an example used for a hydrogen gas sensor will be described.
A Pd—Co alloy thin film was used as the hydrogen response element.
A film having a thickness of about 1 μm was deposited on the PET film by co-sputtering each metal so that the atomic ratio Pd: Co was 9: 1.
The prepared thin film was cut into a size of 5 mm square.
A Pd—Co alloy having this composition is a ferromagnetic material at room temperature, and its magnetic properties are weakened by absorbing hydrogen.
The sensor characteristic test apparatus is shown in FIG.
The gas introduction unit is a system that introduces a mixture of nitrogen and hydrogen or air and hydrogen at a predetermined ratio with two mass flow controllers.
About 0.1 g of a thinned Pd—Co alloy was placed inside the sample tube in the center of FIG. 1, and both ends were covered with glass wool.
A gas mixed at a predetermined ratio flows in the sample tube at a rate of about 100 cc / min, and the AC voltage generated from the measuring coil changes according to the hydrogen concentration in the flowed gas.
FIG. 2 shows the change in AC voltage from a hydrogen concentration of 10% to 0.2%.
When a gas mixed with hydrogen is flowed, the AC voltage suddenly increases and stops at a certain value.
This value tends to decrease as the hydrogen concentration decreases.
This indicates that the magnetic susceptibility has changed due to the absorption of hydrogen by the Pd—Co alloy.
Since the amount of hydrogen absorption depends on the partial pressure of hydrogen in the flowing gas, the change in magnetic susceptibility decreases as the hydrogen concentration decreases.
The result of plotting this change in magnetic susceptibility against the 1/2 power of the hydrogen concentration is shown in the graph of FIG.
It can be seen that the change in magnetic susceptibility is proportional to the 1/2 power of the hydrogen concentration.
In general, it is known that the amount of hydrogen dissolved in the melting region of a hydrogen storage alloy is proportional to the 1/2 power of the hydrogen partial pressure, and this result is due to the change in magnetic susceptibility due to hydrogen absorption. Is shown.
Considering measurement error and background fluctuation, it can be seen from this linear relationship that the measurement device can measure hydrogen concentration to 0.05%.
On the other hand, FIG. 4 shows that the measurement of the hydrogen concentration in the presence of oxygen is also possible.
This is because the temperature of the alloy itself rises due to the heat generated when hydrogen and oxygen react on the Pd alloy to produce water, thereby changing the magnetic susceptibility.
Therefore, the output shown in FIG. 4 is different from the output when oxygen is not present.
By using a calibration curve suitable for the measurement conditions (atmosphere), the hydrogen concentration can be measured regardless of the presence or absence of oxygen.
Next, FIG. 5 shows a graph comparing the reaction time at a hydrogen concentration of 1% between a powder (average particle diameter of about 100 μm) and a thin film (thickness 1 μm) sample.
The result for the powder was t90 (time to reach 90% of the maximum output) was 300 sec, whereas the result for the thin film was as short as 140 sec.
This is because it takes time for hydrogen to diffuse into the entire thin film, and as a result, a powder having a large particle size has a longer reaction time than the thin film.
Therefore, in order to shorten the reaction time and improve the function as a sensor, it is necessary to use a Pd—Co alloy in the form of a thinner thin film or nanoparticles. At least 100 μm or less for the average particle and 1 μm for the thin film are required for the fine particles. The following is preferred.
図６に今回構築した水素応答リードスイッチの模擬試験装置を示す。
全体は大気圧のガスを一定流量で流すことができる装置となっており、上流側に設置したマスフローコントローラにより水素、アルゴンなどのガスを所定の濃度で混合したうえで、リードスイッチの接触端子部が入っている石英セル内に流すことができる。
接触端子部分には、Ｃｕ棒で対向する１対の電極を作成し、その電極の片側にＣｕ箔上にＰｄ−Ｃｏ薄膜を載せた長方形のフィルムを載せ、その一端を電気的に接触するようＣｕ線などで電極に巻き付けた。
この状態でガラスの外側のある方向から磁石を近づけると、室温で強磁性体であるＰｄ−Ｃｏ薄膜が磁石に引かれることで、Ｐｄ−Ｃｏ／Ｃｕフィルムがもう片方の電極に接触し、電極同士が接触する。
また、磁石を離せばＰｄ−Ｃｏフィルムは重力あるいはＣｕ箔の弾性力により両方の電極が離れるようになっている。
リードスイッチではこの接触の有無を、電気抵抗率の変化により読み取る。
電極の両端に電流を流した際に、電流が流れるか流れないかがそのままＯＮ／ＯＦＦとして利用できる。
この状態で水素を流していない場合、上に説明した通常のリードスイッチのように作動できる。
この装置内に流れるガスに水素を混ぜると、Ｐｄ−Ｃｏ薄膜が水素を吸収し、その磁化率が水素吸収量に従い減少する。
その結果、ある一定濃度以上で磁石による吸引力より重力や弾性力が大きくなり、結果として電極が離れることが予想される。
磁石と電極が入ったセルの外側までの距離を０．７ｃｍとし、Ａｒガス中に水素９％を混合したガスを導入した結果を図７に示す。
スイッチの接触は、ソースメータを用いて電極間に１００ｍＡの定常電流を流し、出力される電圧を読み取ることで判定した。
水素混合ガスを流す前は、出力がほぼ０Ｖを示しており、これは電極同士が接触している、つまりＯＮの状態であることを示している。
時間０ｓｅｃからアルゴンガス中に水素を９％混入し、その時の電圧値を連続的に観測すると、約２００ ｓｅｃ後に突然電圧が１０Ｖの値となった。
これは電極同士が離れ電流が遮断されたこと、つまりＯＦＦの状態になったことを意味する。
この後、水素ガスの混合を止め、アルゴンガスのみを流通させると、約９００ｓｅｃ後に電圧がほぼ０Ｖに戻った。
これはＰｄ−Ｃｏ膜内の水素がアルゴンガス中に放出されることでＰｄ−Ｃｏ膜の磁化率が回復し、その結果再び磁気的な引力が重力を上回り、電極同士が接触したと理解できる。
図７に電極と磁石の距離を０．７ｃｍと固定し、水素濃度を変化させた場合のデータを示す。
水素濃度２％では９％の時と同様、水素混合ガス流通下では電極が離れＯＦＦの状態となるが、水素濃度１％では電極に動きはなく、ＯＮの状態を保持している。
これは、水素濃度が高いほどＰｄ−Ｃｏ膜の磁化が大きく減少するため、低水素濃度ではＰｄ−Ｃｏ膜の磁化を十分に減少させることができなかったことが原因である。
Ｐｄ−Ｃｏ膜の磁化はＣｏ濃度で制御可能なので、Ｃｏ濃度を調整することで、任意の水素濃度以上で作動するスイッチを作成可能である。
また、動作可能な水素濃度は、磁石と電極の距離でも制御可能である。
水素濃度を固定し、磁石と電極の距離を変化させた場合の結果を図８に示す。
磁石と流通セル外側との距離を０．６ｃｍとした場合、水素濃度９％では電極が離れることなくＯＮの状態を保持した。
距離を０．７ｃｍ、０．９ｃｍと大きくすると、水素混合ガス流通下で電極が離れ、ＯＦＦの状態となった。
これは、電極の場所での磁場の大きさによりＰｄ−Ｃｏ電極に作用する力が変化すること考えることで理解できる。
以上の結果より、Ｐｄ−Ｃｏ膜を電極に用い、Ｐｄ−Ｃｏ膜のＣｏ濃度あるいは磁石との距離を調整することで、所定の濃度の水素に反応するリードスイッチが作成可能である。
FIG. 6 shows a simulation test apparatus for the hydrogen responsive reed switch constructed this time.
The whole is a device that can flow atmospheric pressure gas at a constant flow rate, and after mixing gases such as hydrogen and argon at a predetermined concentration by the mass flow controller installed upstream, the contact terminal part of the reed switch Can flow in a quartz cell containing.
In the contact terminal portion, a pair of electrodes facing each other with a Cu rod is created, a rectangular film with a Pd-Co thin film placed on a Cu foil is placed on one side of the electrode, and one end thereof is in electrical contact It wound around the electrode with Cu wire.
In this state, when the magnet is approached from a certain direction outside the glass, the Pd—Co thin film, which is a ferromagnetic material, is attracted to the magnet at room temperature, so that the Pd—Co / Cu film comes into contact with the other electrode. Contact each other.
When the magnet is separated, both electrodes are separated from each other by gravity or the elastic force of the Cu foil.
In the reed switch, the presence / absence of this contact is read by a change in electrical resistivity.
When a current flows through both ends of the electrode, whether the current flows or not flows can be used as it is as ON / OFF.
When hydrogen is not flowing in this state, it can operate like the normal reed switch described above.
When hydrogen is mixed into the gas flowing in the apparatus, the Pd—Co thin film absorbs hydrogen, and the magnetic susceptibility decreases according to the amount of hydrogen absorbed.
As a result, it is expected that the gravitational force and the elastic force become larger than the attractive force by the magnet at a certain concentration or more, and as a result, the electrodes are separated.
FIG. 7 shows the result of introducing a gas in which 9% hydrogen is mixed in Ar gas, with the distance to the outside of the cell containing the magnet and the electrode being 0.7 cm.
The contact of the switch was determined by passing a steady current of 100 mA between the electrodes using a source meter and reading the output voltage.
Before flowing the hydrogen mixed gas, the output shows 0V, which indicates that the electrodes are in contact with each other, that is, in an ON state.
When 9% of hydrogen was mixed in the argon gas from time 0 sec and the voltage value at that time was continuously observed, the voltage suddenly became 10 V after about 200 sec.
This means that the electrodes are separated from each other and the current is cut off, that is, the state is turned off.
Thereafter, when the mixing of the hydrogen gas was stopped and only the argon gas was allowed to flow, the voltage returned to almost 0 V after about 900 seconds.
It can be understood that hydrogen in the Pd—Co film is released into the argon gas, so that the magnetic susceptibility of the Pd—Co film is restored, and as a result, the magnetic attractive force again exceeds gravity, and the electrodes are in contact with each other. .
FIG. 7 shows data when the distance between the electrode and the magnet is fixed to 0.7 cm and the hydrogen concentration is changed.
When the hydrogen concentration is 2%, as in the case of 9%, the electrode is separated and turned off under the hydrogen mixed gas flow. However, when the hydrogen concentration is 1%, the electrode does not move and is kept on.
This is because the magnetization of the Pd—Co film greatly decreases as the hydrogen concentration increases, and therefore the magnetization of the Pd—Co film cannot be sufficiently reduced at a low hydrogen concentration.
Since the magnetization of the Pd—Co film can be controlled by the Co concentration, a switch that operates at an arbitrary hydrogen concentration or higher can be created by adjusting the Co concentration.
The operable hydrogen concentration can also be controlled by the distance between the magnet and the electrode.
FIG. 8 shows the result when the hydrogen concentration is fixed and the distance between the magnet and the electrode is changed.
When the distance between the magnet and the outside of the flow cell was 0.6 cm, the electrode was kept on at a hydrogen concentration of 9% without being separated.
When the distance was increased to 0.7 cm and 0.9 cm, the electrode was released under the hydrogen mixed gas flow, and turned off.
This can be understood by considering that the force acting on the Pd—Co electrode varies depending on the magnitude of the magnetic field at the electrode location.
From the above results, a reed switch that reacts with a predetermined concentration of hydrogen can be produced by using a Pd—Co film as an electrode and adjusting the Co concentration of the Pd—Co film or the distance from the magnet.
Claims (4)
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