JP5207425B2 - Hydrogen gas sensor and manufacturing method thereof - Google Patents
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims description 57
- 238000004519 manufacturing process Methods 0.000 title claims description 20
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 46
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 44
- 239000010409 thin film Substances 0.000 claims description 33
- 229910052697 platinum Inorganic materials 0.000 claims description 23
- 239000000758 substrate Substances 0.000 claims description 23
- 239000010408 film Substances 0.000 claims description 22
- 229910052763 palladium Inorganic materials 0.000 claims description 22
- 229910001069 Ti alloy Inorganic materials 0.000 claims description 21
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical group [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 14
- 239000010936 titanium Substances 0.000 claims description 14
- 229910052719 titanium Inorganic materials 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 11
- 238000007743 anodising Methods 0.000 claims description 10
- 239000012212 insulator Substances 0.000 claims description 6
- 238000001659 ion-beam spectroscopy Methods 0.000 claims description 4
- 229910000510 noble metal Inorganic materials 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 2
- 239000000956 alloy Substances 0.000 claims description 2
- 102000029749 Microtubule Human genes 0.000 claims 1
- 108091022875 Microtubule Proteins 0.000 claims 1
- 210000004688 microtubule Anatomy 0.000 claims 1
- 230000035945 sensitivity Effects 0.000 description 24
- 239000001257 hydrogen Substances 0.000 description 17
- 229910052739 hydrogen Inorganic materials 0.000 description 17
- 230000004044 response Effects 0.000 description 17
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 14
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 14
- 238000001514 detection method Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 9
- 239000010407 anodic oxide Substances 0.000 description 7
- 150000002431 hydrogen Chemical class 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 238000002048 anodisation reaction Methods 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 229910002070 thin film alloy Inorganic materials 0.000 description 3
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- 229910001252 Pd alloy Inorganic materials 0.000 description 2
- 229910001260 Pt alloy Inorganic materials 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000000635 electron micrograph Methods 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- UUWCBFKLGFQDME-UHFFFAOYSA-N platinum titanium Chemical compound [Ti].[Pt] UUWCBFKLGFQDME-UHFFFAOYSA-N 0.000 description 2
- 238000004904 shortening Methods 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910000808 amorphous metal alloy Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000007084 catalytic combustion reaction Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
Description
本発明は、水素ガスセンサ及びその製造方法に関し、自動車用燃料電池や家庭用燃料電池などの水素ガスを扱う各種装置から漏れる水素ガスを検知するのに用いる水素ガスセンサ又は水素ガスを扱う装置内の水素ガス濃度を制御するなどの用途に適した水素ガスセンサ及びその製造方法に関する。 The present invention relates to a hydrogen gas sensor and a method of manufacturing the same, and relates to a hydrogen gas sensor used for detecting hydrogen gas leaking from various devices handling hydrogen gas, such as automobile fuel cells and household fuel cells, or hydrogen in a device handling hydrogen gas. The present invention relates to a hydrogen gas sensor suitable for applications such as controlling gas concentration and a method for manufacturing the same.
水素ガスセンサとしては、光学式、接触燃焼式、半導体式、起電力式、電流検知式(電
池型)などの種々のものが考案されている。水素ガスセンサとしては、高い検出感度と良
好な応答性を有し、水素ガス選択性に優れ、しかも高耐久性と安価であること求められている。この目標を狙った技術として、例えば、特許文献１（特開2003-166972号公報）に
は、水素選択性に優れるセンサとして、プロトンと酸化物イオンを伝導する固体電解質の表面に二つの電極を配置し、電極間の電流を計測し水素濃度を検知するセンサが開示されている。また、特許文献２（特開2005-172756号公報）には、一対の電極間に挟まれた水
素を吸排可能な粒状の水素吸収層を有し、この層の体積と静電容量の変化を計測する技術が開示されている。さらに、特許文献３（特開2006-317196号公報）には、小型で安価な
センサとして、アモルファス合金を検出層とし水素吸蔵により電気抵抗や電磁気的性質が変化することを利用したセンサに関する技術が開示されている。また、非特許文献１には、陽極酸化により形成された酸化チタンナノチューブアレイの表面にパラジウムをコーティングした水素ガスセンサが開示されている。
Various hydrogen gas sensors such as an optical type, catalytic combustion type, semiconductor type, electromotive force type, and current detection type (battery type) have been devised. Hydrogen gas sensors are required to have high detection sensitivity and good responsiveness, excellent hydrogen gas selectivity, high durability, and low cost. As a technique aiming at this goal, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-166972) discloses two electrodes on the surface of a solid electrolyte that conducts protons and oxide ions as a sensor having excellent hydrogen selectivity. A sensor that disposes and measures the current between the electrodes and detects the hydrogen concentration is disclosed. Patent Document 2 (Japanese Patent Laid-Open No. 2005-172756) has a granular hydrogen absorption layer capable of absorbing and discharging hydrogen sandwiched between a pair of electrodes, and changes in volume and capacitance of this layer. Techniques for measuring are disclosed. Furthermore, Patent Document 3 (Japanese Patent Laid-Open No. 2006-317196) discloses a technique relating to a sensor that uses an amorphous alloy as a detection layer and changes in electrical resistance and electromagnetic properties due to hydrogen storage as a small and inexpensive sensor. It is disclosed. Non-Patent Document 1 discloses a hydrogen gas sensor in which palladium is coated on the surface of a titanium oxide nanotube array formed by anodization.
しかしながら、簡便な構造で耐久性が高く、しかも高い検出感度と良好な応答時間を有し、水素選択性に優れるという実用化に十分な条件を満たす水素センサは依然として得られておらず、その製造方法も知られていない。 However, a hydrogen sensor that has a simple structure, high durability, high detection sensitivity, good response time, and excellent hydrogen selectivity has not yet been obtained. The method is not known.
本発明は上記事情に鑑みなされたもので、その目的とするところは、簡便な構造で耐久性が高く、しかも高い検出感度と良好な応答時間を有し、水素ガス選択性に優れた水素センサを提供することにある。 The present invention has been made in view of the above circumstances, and an object thereof is a hydrogen sensor having a simple structure, high durability, high detection sensitivity, good response time, and excellent hydrogen gas selectivity. Is to provide.
本発明者は、上記未解決の課題を解決するため種々の試験研究を行い、本発明を完成させた。本発明の主旨は、以下の通りである。 In order to solve the above-mentioned unsolved problems, the present inventor conducted various test studies and completed the present invention. The gist of the present invention is as follows.
本発明の水素ガスセンサの構成は、絶縁体の基板表面に、微細孔又は微細筒が形成された貴金属を含むチタン合金の陽極酸化被膜からなるセンサ素子を備え、前記センサ素子が、パラジウム又は白金を質量百分率０．０１％以上含むチタン合金の陽極酸化皮膜であることを特徴とする。 Configuration of a hydrogen gas sensor of the present invention, the substrate surface of the insulator, comprising a sensor element composed of an anode oxide film of the titanium alloy containing fine holes or fine tube is formed noble metal, wherein the sensor element is palladium or platinum Is an anodized film of a titanium alloy containing 0.01% or more by mass percentage.
本発明の水素ガスセンサの第１の製造方法は、絶縁体の基板表面にパラジウム又は白金を質量百分率０．０１％以上含むチタン合金の薄膜を作製する作製ステップと、前記薄膜を陽極酸化し、内径500nm以下の微細孔あるいは外径1000nm以下の微細筒が形成された陽極酸化被膜を生成する生成ステップとを備えることを特徴とする。 The first manufacturing method of the hydrogen gas sensor of the present invention includes a production step of producing a thin film of a titanium alloy containing 0.01% or more by mass of palladium or platinum on the surface of an insulating substrate, anodizing the thin film, And a generation step of generating an anodic oxide film in which fine holes of 500 nm or less or fine cylinders of an outer diameter of 1000 nm or less are formed.
本発明の水素ガスセンサの第２の製造方法は、上記第１の製造方法において、前記生成ステップでは、前記内径500nm以下の微細孔として、内径50nm以下の微細孔が形成され、前記外径1000nm以下の微細筒として、外径100nm以下の微細筒が形成されることを特徴とする。 The second manufacturing method of the hydrogen gas sensor of the present invention is the above-described first manufacturing method, wherein in the generating step, a fine hole having an inner diameter of 50 nm or less is formed as the fine hole having an inner diameter of 500 nm or less, and the outer diameter is 1000 nm or less. As the fine cylinder, a fine cylinder having an outer diameter of 100 nm or less is formed .
本発明の水素ガスセンサの第３の製造方法は、絶縁体の基板表面にパラジウム又は白金を質量百分率０．０１％以上含むチタン合金の薄膜を作製するステップと、前記薄膜を陽極酸化し、微細孔又は微細筒が形成された陽極酸化被膜を生成するステップとを備えることを特徴とする。 A third method for producing a hydrogen gas sensor according to the present invention comprises a step of producing a titanium alloy thin film containing 0.01% or more by mass of palladium or platinum on the surface of an insulating substrate , anodizing the thin film, Or a step of generating an anodized film on which a fine cylinder is formed .
本発明の水素ガスセンサの第４の製造方法は、第１乃至第３の製造方法のいずれかにおいて、前記薄膜をイオンビームスパッタ法で作製することを特徴とする。 A fourth method for producing a hydrogen gas sensor according to the present invention is characterized in that, in any of the first to third production methods, the thin film is produced by an ion beam sputtering method.
本発明の水素ガスセンサは、水素検知部に非常に表面積の広い微細孔あるいは微細筒状構造を有するチタン酸化物を用いているため低濃度の水素ガスを高感度に検知することができる。また、必要に応じて微量のパラジウムや白金などの貴金属を含むチタン合金の陽極酸化皮膜を検知手段とすることで、さらに感度及び応答時間が向上し、且つ耐久性が高く実用に適している。さらに、水素ガスセンサの製造方法としても、絶縁体の基板表面にチタン薄膜又はチタン合金薄膜を形成した後、チタン薄膜又はチタン合金薄膜を陽極酸化する手法であるため、製造工程が簡便で低コスト化を図ることができる。 The hydrogen gas sensor of the present invention uses a titanium oxide having a very large surface area of fine holes or a fine cylindrical structure in the hydrogen detection part, so that low concentration hydrogen gas can be detected with high sensitivity. Further, if necessary, an anodized film of a titanium alloy containing a trace amount of noble metal such as palladium or platinum is used as a detection means, so that sensitivity and response time are further improved and durability is high and suitable for practical use. Furthermore, as a method for manufacturing a hydrogen gas sensor, the titanium thin film or titanium alloy thin film is formed on the surface of the insulator substrate, and then the titanium thin film or titanium alloy thin film is anodized. Can be achieved.
以下に、本発明を実施するための最良の形態について述べる。しかしながら、かかる実施の形態例が、本発明の技術的範囲を限定するものではない。 The best mode for carrying out the present invention will be described below. However, such an embodiment does not limit the technical scope of the present invention.
図１及び図２は、本発明の実施形態にかかる水素ガスセンサの概略構成図を示す。図１は断面図、図２は正面図である。本発明は、水素濃度に依存してセンサ素子の電気抵抗が変化することを利用した水素ガスセンサであり、電気絶縁性の基板３上のセンサ素子１、すなわち微細孔又は微細筒（いわゆるナノチューブ）１０を有する構造のチタン酸化物を基本構成要素としている。 1 and 2 are schematic configuration diagrams of a hydrogen gas sensor according to an embodiment of the present invention. 1 is a cross-sectional view, and FIG. 2 is a front view. The present invention is a hydrogen gas sensor that utilizes the change in electrical resistance of a sensor element depending on the hydrogen concentration, and is a sensor element 1 on an electrically insulating substrate 3, that is, a fine hole or a fine tube (so-called nanotube) 10. The basic component is a titanium oxide having a structure having
このチタン酸化物からなるセンサ素子１は、絶縁体の基板３上に形成されている必要がある。これは、水素濃度に依存してセンサ素子１の電気抵抗のみを検出するために必須である。そして、センサ素子１の微細孔及び微細筒１０の長軸方向が基板の法線方向に配向している必要がある。実施例で後述するとおり、微細孔及び微細筒１０の長軸方向が基板の法線方向に配向していないと、センサ感度が低くなり、実用上充分な感度を得ることができない。 The sensor element 1 made of titanium oxide needs to be formed on an insulating substrate 3. This is essential for detecting only the electrical resistance of the sensor element 1 depending on the hydrogen concentration. And the micro hole of the sensor element 1 and the major axis direction of the micro cylinder 10 need to be oriented in the normal direction of the substrate. As will be described later in Examples, if the major axis direction of the micropores and the microcylinder 10 is not oriented in the normal direction of the substrate, the sensor sensitivity is lowered, and practically sufficient sensitivity cannot be obtained.
センサ素子１は、基板３上の純チタンあるいはチタン合金薄膜２を陽極酸化して得られる陽極酸化被膜として形成され、センサ素子１に導電性ペースト（例えば銀ペースト）４を塗布してリード線を接続し、抵抗計５により電気抵抗変化を計測する。また、電気抵抗は計測が容易でありセンサ構造を簡易化、小型化、低コスト化することが容易である。 The sensor element 1 is formed as an anodic oxide film obtained by anodizing a pure titanium or titanium alloy thin film 2 on a substrate 3. A conductive paste (for example, silver paste) 4 is applied to the sensor element 1 to provide lead wires. Connect and measure the electrical resistance change with the resistance meter 5. In addition, the electrical resistance can be easily measured, and the sensor structure can be easily simplified, reduced in size, and reduced in cost.
図３は、微細孔及び微細筒の拡大模式図である。図２の点線円ａの拡大模式図であり、図３（ａ）は微細孔１０ａ、図３（ｂ）は微細筒１０ｂを示す。本明細書では、微細孔１０ａ及び微細筒１０ｂを総称して、微細孔及び微細筒１０と記載する。 FIG. 3 is an enlarged schematic view of the fine holes and the fine cylinders. FIG. 3 is an enlarged schematic diagram of a dotted circle a in FIG. 2, FIG. 3A shows a fine hole 10a, and FIG. 3B shows a fine cylinder 10b. In the present specification, the fine hole 10a and the fine cylinder 10b are collectively referred to as a fine hole and a fine cylinder 10.
図４は、微細筒１０ｂの電子顕微鏡写真を示す図（断面図）である。図４は、白金が添加されたチタン合金の陽極酸化被膜であり、微細筒１０ｂに含まれる白金粒子（黒粒状に見えるもの）も示される。 FIG. 4 is a diagram (sectional view) showing an electron micrograph of the fine cylinder 10b. FIG. 4 shows an anodized film of a titanium alloy to which platinum is added, and also shows platinum particles (those that appear black) contained in the fine cylinder 10b.
微細孔及び微細筒１０の形成により、微細孔の内面及び微細筒の中空部分の内周面が、水素ガスに接触する表面積を増大させる。微細孔及び微細筒は、センサ素子１の水素ガスに接触する表面積を増大させる点で同一の機能を有する。また、微細筒の中空部分（内周面）の内径は微細筒の外径に相関する。従って、微細孔の内径又は微細筒の外径を小さくするほど、一定面積における微細孔又は微細筒の数は増大し、それに応じて、センサ素子（チタン酸化物）１の表面積を増大させることができる。なお、微細筒については、隣接する微細筒との間に空間が存在する場合は、微細筒の外周面もセンサ素子１の表面積となる。 By forming the fine holes and the fine cylinder 10, the inner surface of the fine holes and the inner peripheral surface of the hollow part of the fine cylinder increase the surface area in contact with the hydrogen gas. The fine hole and the fine cylinder have the same function in that the surface area of the sensor element 1 that contacts the hydrogen gas is increased. The inner diameter of the hollow portion (inner peripheral surface) of the fine cylinder correlates with the outer diameter of the fine cylinder. Therefore, the smaller the inner diameter of the microholes or the outer diameter of the microcylinders, the greater the number of microholes or microcylinders in a certain area, and accordingly, the surface area of the sensor element (titanium oxide) 1 can be increased. it can. In addition, about a fine cylinder, when space exists between adjacent fine cylinders, the outer peripheral surface of a fine cylinder also becomes a surface area of the sensor element 1.
本発明では、センサ素子１を、内径500nm以下の微細孔あるいは外径1000nm以下の微細
筒が形成されたチタン酸化物を主成分とするものとしている。ここで言う主成分とは、体積分率として５０パーセント以上がチタン酸化物であることである。チタン酸化物に水素ガスが吸着あるいは吸蔵されると電気抵抗が変化する特性を有し、水素選択性に優れており、該特性を利用して水素ガスが検出されるが、チタン酸化物の体積分率５０％を下回ると、水素ガス濃度に依存して抵抗値が大きく変化するセンサ素子を提供することはできなくなる。
In the present invention, the sensor element 1 is mainly composed of titanium oxide in which a fine hole having an inner diameter of 500 nm or less or a fine cylinder having an outer diameter of 1000 nm or less is formed. The main component here means that 50% or more of the volume fraction is titanium oxide. When hydrogen gas is adsorbed or occluded in titanium oxide, it has the property that electric resistance changes and is excellent in hydrogen selectivity, and hydrogen gas is detected using this property. If the fraction is less than 50%, it becomes impossible to provide a sensor element whose resistance value varies greatly depending on the hydrogen gas concentration.
また、水素ガスに接触するチタン酸化物の表面積を大きくするほど、電気抵抗の変化率も高まり、水素ガスの検出感度も高くなる。実用上充分な感度を得るためには、チタン酸化物表面に微細孔を作製する場合、その内径は500nm以下とする必要がある。これよりも
内径が大きいと、電気抵抗の変化が小さくなり、応答時間も遅くなるので、実用には不適である。また、早い応答時間（例えば、１桁超の抵抗値変化するまでの時間が１０秒以内）での充分な感度を得るには、内径を50nm以下とすることが好ましい。
Further, as the surface area of the titanium oxide in contact with the hydrogen gas is increased, the rate of change in electrical resistance is increased and the detection sensitivity of hydrogen gas is increased. In order to obtain a practically sufficient sensitivity, when a micropore is formed on the titanium oxide surface, the inner diameter needs to be 500 nm or less. If the inner diameter is larger than this, the change in electrical resistance becomes small and the response time becomes slow, which is not suitable for practical use. In order to obtain sufficient sensitivity with a fast response time (for example, the time until the resistance value changes by more than one digit is within 10 seconds), the inner diameter is preferably 50 nm or less.
また、チタン酸化物表面に微細筒を作製する場合、その外径は1000nm以下とする必要がある。外径は小さいほど好ましいが、1000nm以下であれば実用上充分な性能が得られる。また、早い応答時間（例えば、１桁超の抵抗値変化するまでの時間が１０秒以内）での充分な感度を得るには、外径を100nm以下とすることが好ましい。なお、ここで、実用上充
分な感度とは、体積分率で1000ppm程度の水素ガスに対して一桁以上の抵抗値変化を得ら
れる感度を意味している。
Moreover, when producing a fine cylinder on the titanium oxide surface, the outer diameter needs to be 1000 nm or less. The smaller the outer diameter, the better. However, if it is 1000 nm or less, practically sufficient performance can be obtained. In order to obtain sufficient sensitivity with a fast response time (for example, the time until the resistance value changes by more than one digit is within 10 seconds), the outer diameter is preferably 100 nm or less. Here, the practically sufficient sensitivity means a sensitivity capable of obtaining a resistance value change of one digit or more with respect to hydrogen gas having a volume fraction of about 1000 ppm.
センサ素子１としては、必要に応じて、質量百分率で０．０１％以上のパラジウムもしくは０．０１％以上の白金を含むチタン合金の陽極酸化被膜を用いることができる。パラジウムと白金は貴金属であり、水素吸着あるいは水素吸蔵反応の触媒として機能し、センサ感度及び応答時間を向上させる機能がある。チタン酸化物内には、パラジウム又は白金がナノ粒子として均一分散し、水素ガスが接触する面全域にわたってパラジウム又は白金のナノ粒子が存在するため、感度及び応答時間の向上に大きく資する。質量百分率０．０１％以上の添加により、感度及び応答時間を向上させる効果が得られる。 As the sensor element 1, an anodic oxide film of titanium alloy containing 0.01% or more palladium or 0.01% or more platinum by mass percentage can be used as necessary. Palladium and platinum are noble metals, function as a catalyst for hydrogen adsorption or hydrogen storage reaction, and have a function of improving sensor sensitivity and response time. In the titanium oxide, palladium or platinum is uniformly dispersed as nanoparticles, and palladium or platinum nanoparticles exist over the entire surface in contact with hydrogen gas, which greatly contributes to improvement in sensitivity and response time. By adding 0.01% or more by mass percentage, the effect of improving sensitivity and response time can be obtained.
パラジウム又は白金を含むチタン合金薄膜の陽極酸化被膜とすることで、純チタン薄膜の陽極酸化被膜にパラジウム又は白金をコーティングした構成と比較して、パラジウム又は白金をコーティングする工程を省略することができ、製造工程が簡略化され、製造コストが低減される。また、パラジウム又は白金をコーティングする場合は、陽極酸化被膜に対してパラジウム又は白金層が剥離しやすい欠点を有するが、パラジウム又は白金を含むチタン合金薄膜の陽極酸化被膜とすることで、パラジウム又は白金が陽極酸化被膜と一体化して存在するので、剥離の問題は生じず、取り扱いも容易となり、耐久性が向上する。なお、当該効果は、微細孔又は微細筒の径を問わない。 By using an anodized film of a titanium alloy thin film containing palladium or platinum, the step of coating palladium or platinum can be omitted compared to a structure in which an anodized film of pure titanium thin film is coated with palladium or platinum. The manufacturing process is simplified and the manufacturing cost is reduced. In addition, when palladium or platinum is coated, the palladium or platinum layer has a defect that the anodic oxide film is easily peeled off. However, by forming an anodic oxide film of a titanium alloy thin film containing palladium or platinum, palladium or platinum is used. Since it is integrated with the anodized film, there is no problem of peeling, handling becomes easy, and durability is improved. In addition, the said effect does not ask | require the diameter of a fine hole or a fine cylinder.
センサ素子１の製造方法は次の通りである。センサ素子１は、絶縁体の基板表面に純チタン薄膜又はチタン合金薄膜を形成した後、純チタン薄膜又はチタン合金薄膜の全量を陽極酸化することにより製造される。 The manufacturing method of the sensor element 1 is as follows. The sensor element 1 is manufactured by forming a pure titanium thin film or a titanium alloy thin film on an insulating substrate surface and then anodizing the entire amount of the pure titanium thin film or the titanium alloy thin film.
陽極酸化は電解液中で合金を陽極に接続して電圧を加える方法であり、電圧と電流を制御することでセンサ素子を、内径500nm以下の微細孔あるいは外径1000nm以下の微細筒が
形成され且つ微細孔及び前記微細筒の長軸方向が基板の法線方向に配向する構造のチタン酸化物であり陽極酸化被膜を容易に作製することができる。陽極酸化処理時間を制御することで、微細孔の内径及び微細筒の外径を制御可能である。
Anodization is a method in which an alloy is connected to an anode in an electrolyte and a voltage is applied. By controlling the voltage and current, a fine hole with an inner diameter of 500 nm or less or a fine cylinder with an outer diameter of 1000 nm or less is formed. In addition, it is a titanium oxide having a structure in which the long axis direction of the fine holes and the fine cylinder is oriented in the normal direction of the substrate, and an anodized film can be easily produced. By controlling the anodizing time, the inner diameter of the fine holes and the outer diameter of the fine cylinders can be controlled.
予め絶縁体の基板表面に純チタン薄膜又はチタン合金薄膜を形成した後、純チタン薄膜又はチタン合金薄膜の全量を陽極酸化することで、センサ素子と絶縁基板を一体化して製造することができ、センサ素子を作製した後、基板に貼り合わせるよりもコスト的に安価になる。また、両層の接着剤が電気抵抗変化を検出する際の障害となるという要因を排除することも可能となる。なお、微細孔配列構造又は微細筒配列構造のいずれにするかは、陽極酸化処理における各種条件（例えば、電解液組成、温度、電流密度）を制御することにより制御可能である。 After forming a pure titanium thin film or a titanium alloy thin film on the substrate surface of the insulator in advance, the whole amount of the pure titanium thin film or the titanium alloy thin film can be anodized, so that the sensor element and the insulating substrate can be integrated and manufactured. After the sensor element is manufactured, the cost is lower than when the sensor element is bonded to the substrate. It is also possible to eliminate the factor that the adhesives of both layers become an obstacle when detecting a change in electrical resistance. It should be noted that either the fine hole arrangement structure or the fine cylinder arrangement structure can be controlled by controlling various conditions (for example, electrolyte composition, temperature, current density) in the anodizing treatment.
さらに、純チタン薄膜又はチタン合金薄膜として、イオンビームスパッタ法で作製した薄膜を用いることで組成及び厚さが面内で一定に制御される。その結果、微細孔及び微細筒の長軸方向が基板の法線方向に配向しやすくなり、感度が高くなる。 Furthermore, as a pure titanium thin film or a titanium alloy thin film, a composition and a thickness are controlled to be constant in a plane by using a thin film manufactured by an ion beam sputtering method. As a result, the major axis direction of the microholes and microcylinders is easily oriented in the normal direction of the substrate, and the sensitivity is increased.
表１に示す組み合わせでセンサ素子１を有する水素ガスセンサを作製し、水素ガスの検出を行った。いずれの場合も、イオンビームスパッタ蒸着装置を用い、市販のスライドガラスを基板として、純チタン、チタン−パラジウム合金及びチタン−白金合金の薄膜を基板上に170nmの厚さで形成した。その後、グリセリンと水を１：１に混合した溶液に質量
百分率で０．５％のNH4を添加した溶液中で、白金を対極として試験片に３〜２５Vの電圧を加えた。試験片は基板の中央部分のみを陽極酸化した。この際、センサのセンサ素子となる試験片の中央部分については、170nmの厚さ全量を陽極酸化した。その後、５００℃
で５時間の熱処理を加えた。
Hydrogen gas sensors having sensor elements 1 with the combinations shown in Table 1 were produced, and hydrogen gas was detected. In either case, a thin film of pure titanium, titanium-palladium alloy and titanium-platinum alloy was formed on the substrate with a thickness of 170 nm using a commercially available slide glass as a substrate using an ion beam sputtering deposition apparatus. Thereafter, a voltage of 3 to 25 V was applied to the test piece using platinum as a counter electrode in a solution obtained by adding 0.5% by mass of NH4 to a solution in which glycerin and water were mixed 1: 1. Only the center part of the substrate was anodized. At this time, the entire thickness of 170 nm was anodized for the central portion of the test piece serving as the sensor element of the sensor. Then 500 ° C
And 5 hours heat treatment was applied.
図５は、陽極酸化処理及び熱処理を行った試験片の形状を示す図（正面図）である。熱処理後、図５に示すように両端を切断し、中央部分のみとし、そこに図１及び図２に示すように銀ペースト４を塗り、そこに抵抗計測のためのリード線を取り付けた。熱処理は４００〜７００℃で試したが、センサ特性には差異は見られなかった。水素ガスの検出試験は、水素が体積比率で1000ppmの水素−窒素混合を流し、290℃の条件でセンサ素子１の抵抗値の変化をエレクトロメータ（抵抗計）で計測した。なお、微細孔や微細筒の寸法や配向状態は走査電子顕微鏡観察により計測した。 FIG. 5 is a diagram (front view) showing the shape of a test piece subjected to anodization treatment and heat treatment. After the heat treatment, both ends were cut as shown in FIG. 5 to form only the central portion, and silver paste 4 was applied thereto as shown in FIGS. 1 and 2, and lead wires for resistance measurement were attached thereto. The heat treatment was tried at 400 to 700 ° C., but no difference was found in the sensor characteristics. In the hydrogen gas detection test, a hydrogen-nitrogen mixture with 1000 ppm by volume of hydrogen was flowed, and the change in the resistance value of the sensor element 1 was measured with an electrometer (resistance meter) under the condition of 290 ° C. In addition, the dimension and orientation state of the fine hole and the fine cylinder were measured by observation with a scanning electron microscope.
表１において、感度の評価は、1000ppmの水素−窒素混合を導入する前（１００％窒素
）と後での抵抗値の変化が１桁以内のものを×とし、１桁超のものを△、○、◎とした。△、○、◎、◎◎、◎◎◎は応答時間で判別した。すなわち、ガスを切り替えた後、１桁超の抵抗値低下が認められるまでに１００秒以上かかったものを△、３０秒未満１０秒以上のものを○、１０秒未満３秒以上のものを◎、３秒未満１秒以上のものを◎◎、そして１秒未満のものを◎◎◎と示す。
In Table 1, the sensitivity is evaluated by x when the change in resistance value is within one digit before and after introducing 1000 ppm of hydrogen-nitrogen mixture (100% nitrogen), and Δ when the change is more than one digit. ○ and ◎. Δ, ○, ◎, ◎◎, ◎◎◎ were determined by response time. That is, after switching the gas, it took △ for more than 100 seconds until a resistance value decrease of more than one digit was recognized, ○ for less than 30 seconds for 10 seconds or more, ○ for less than 10 seconds for 3 seconds or more Those with less than 3 seconds and 1 second or more are shown as ◎, and those with less than 1 second are shown as ◎.
まず、番号１は本発明の比較例である。陽極酸化の電圧を低く、処理時間を短くすることで、陽極酸化皮膜表面が平滑なもの（微細孔又は微細筒を有しない）を作製した例であるが、センサ感度の評価が悪いことが分かる。番号２も比較例である。これは、微細孔を形成したものであるが、微細孔の内径が1000nmであり、必要なセンサ感度を得られなかった。 First, number 1 is a comparative example of the present invention. This is an example in which the anodized film has a smooth surface (no micropores or microcylinders) by lowering the anodizing voltage and shortening the processing time, but the sensor sensitivity is poorly evaluated. . Number 2 is also a comparative example. This is a micropore formed, but the inner diameter of the micropore was 1000 nm, and the required sensor sensitivity could not be obtained.
これに対して、微細孔の内径を490nmから10nmの範囲で変化させた番号３〜６では、セ
ンサ感度が充分高くなっていることが分かる。特に、番号５及び６に示すように、微細孔の内径を50nm以下に制御すると更に応答時間も向上することが分かる。
On the other hand, it can be seen that the sensor sensitivity is sufficiently high in the numbers 3 to 6 in which the inner diameter of the micropore is changed in the range of 490 nm to 10 nm. In particular, as shown by numbers 5 and 6, it can be seen that the response time is further improved when the inner diameter of the micropores is controlled to 50 nm or less.
次いで、番号７は、チタン酸化物を微細筒状としたものであるが、微細筒の外径が1350nmであり、センサ感度としても不充分なものとなっている。これに対して、番号８〜１１は、微細筒の外径を950nmから20nmに制御したものであるが、高いセンサ感度（抵抗値の変化が１桁超）が得られている。特に、番号１０及び１１に示すように、微細筒の外径を100nm以下にしたものであるが、更に応答時間も向上していることが分かる。 Next, number 7 is titanium oxide in a fine cylinder shape, but the outer diameter of the fine cylinder is 1350 nm, which is insufficient as sensor sensitivity. On the other hand, numbers 8 to 11 are those in which the outer diameter of the fine cylinder is controlled from 950 nm to 20 nm, and high sensor sensitivity (change in resistance value is more than one digit) is obtained. In particular, as indicated by numbers 10 and 11, the outer diameter of the fine cylinder is 100 nm or less, but it can be seen that the response time is further improved.
番号１２は比較例である。陽極酸化の電圧は高く、処理時間を極端に短くすることで、微細筒の長軸方向が絶縁体の基板の法線方向に配向していない場合である。この場合にも必要なセンサ感度（抵抗値の変化が１桁超）を得られなかった。 Number 12 is a comparative example. This is a case where the anodization voltage is high and the long axis direction of the fine cylinder is not oriented in the normal direction of the insulating substrate by shortening the processing time extremely. Also in this case, the necessary sensor sensitivity (resistance value change over one digit) could not be obtained.
番号１３〜２３は、チタン−パラジウム合金の陽極酸化被膜を用いた例である。添加割合は、質量百分率で０．０１％、０．２％、２％であり、それぞれ微細孔の内径又は微細筒の外径の寸法を変えて計測した。全例とも、1000pppmの水素−窒素混合ガスに対して抵抗値の変化が１桁超であるが、特に、微細筒の外径100nm以下又は微細孔の内径50nm以下
のものは、その応答時間が、純チタンの陽極酸化被膜（番号１〜１１）と比較して、同等又はそれ以上であり、さらに、パラジウムの添加割合が多いほど向上していることが分かる。微細筒の外径100nm以下又は微細孔の内径50nm以下であって且つパラジウムを０．２
％以上含むもの（番号１９〜２３）は、応答時間が３秒未満と高速であり、特に、番号２３の条件では、１秒未満という極めて高速な応答時間が得られた。
Numbers 13 to 23 are examples using an anodized film of a titanium-palladium alloy. The addition ratio was 0.01%, 0.2%, and 2% in terms of mass percentage, and the measurement was performed by changing the inner diameter of the fine hole or the outer diameter of the fine cylinder. In all cases, the change in resistance value is more than an order of magnitude with respect to 1000 pppm hydrogen-nitrogen mixed gas. Especially, the response time is less than 100 nm for the outer diameter of the fine cylinder or 50 nm for the inner diameter of the fine hole. It can be seen that it is equal to or higher than that of pure titanium anodic oxide coatings (Nos. 1 to 11), and further improved as the proportion of palladium added increases. The outer diameter of the fine cylinder is 100 nm or less or the inner diameter of the fine hole is 50 nm or less, and palladium is 0.2
% (Numbers 19 to 23) includes a high response time of less than 3 seconds. In particular, under the condition of number 23, an extremely high response time of less than 1 second was obtained.
同じく、番号２４〜３６は、チタン−白金合金の陽極酸化被膜を用いた例である。パラジウム添加の例（番号１３〜２３）と同様に、添加割合は、０．０１％、０．２％、２％であり、それぞれ微細孔の内径又は微細筒の外径の寸法を変えて計測した。全例とも、1000pppmの水素−窒素混合ガスに対して抵抗値の変化が１桁超であるが、特に、微細筒の外径100nm以下又は微細孔の内径50nm以下のものは、その応答時間が、純チタンの陽極酸化被膜（番号１〜１１）と比較して、同等又はそれ以上であり、さらに、白金の添加割合が多いほど向上していることが分かる。微細筒の外径100nm以下又は微細孔の内径50nm以下であって且つ白金を０．２％以上含むもの（番号３０〜３４）は、応答時間が３秒未満と高速であり、特に、番号３４の条件では、１秒未満という極めて高速な応答時間が得られた。 Similarly, numbers 24 to 36 are examples using an anodized film of titanium-platinum alloy. Similar to the examples of palladium addition (Nos. 13 to 23), the addition ratios are 0.01%, 0.2%, and 2%, and the measurement is performed by changing the inner diameter of the fine holes or the outer diameter of the fine cylinder, respectively. did. In all cases, the change in resistance value is more than an order of magnitude with respect to 1000pppm hydrogen-nitrogen mixed gas. It can be seen that it is equal to or higher than that of pure titanium anodic oxide coatings (numbers 1 to 11), and further improved as the addition ratio of platinum increases. The fine cylinder having an outer diameter of 100 nm or less or an inner diameter of the fine hole of 50 nm or less and containing 0.2% or more of platinum (numbers 30 to 34) has a high response time of less than 3 seconds. Under these conditions, an extremely fast response time of less than 1 second was obtained.
本発明の活用例としては、自動車用燃料電池、家庭用燃料電池などの水素ガスを扱う各種装置から漏れる比較的低濃度の水素ガスを検知するのに用いる水素ガスセンサ 、ある
いは水素ガスを扱う装置内の比較的高濃度の水素ガスを制御するなどの用途に適した水素ガスセンサおよび製造方法として利用可能である。
Examples of the use of the present invention include a hydrogen gas sensor used to detect hydrogen gas at a relatively low concentration leaking from various devices that handle hydrogen gas, such as automobile fuel cells and household fuel cells, or a device that handles hydrogen gas. It can be used as a hydrogen gas sensor and a manufacturing method suitable for applications such as controlling a relatively high concentration of hydrogen gas.
１：センサ素子、２：純チタン薄膜あるいはチタン合金薄膜、３：絶縁基板、４：導電性ペースト、５：抵抗計 1: sensor element, 2: pure titanium thin film or titanium alloy thin film, 3: insulating substrate, 4: conductive paste, 5: resistance meter
Claims (5)
前記薄膜を陽極酸化し、内径500nm以下の微細孔あるいは外径1000nm以下の微細筒が形成された陽極酸化被膜を生成する生成ステップとを備えることを特徴とする水素ガスセンサの製造方法。 A production step of producing a thin film of a titanium alloy containing 0.01% or more by mass of palladium or platinum on the substrate surface of the insulator;
A method for producing a hydrogen gas sensor, comprising: anodizing the thin film to produce an anodized film in which fine holes having an inner diameter of 500 nm or less or fine cylinders having an outer diameter of 1000 nm or less are formed.
前記生成ステップでは、前記内径500nm以下の微細孔として、内径50nm以下の微細孔が形成され、前記外径1000nm以下の微細筒として、外径100nm以下の微細筒が形成されることを特徴とする水素ガスセンサの製造方法。 In claim 2 ,
In the generating step, micropores with an inner diameter of 50 nm or less are formed as the micropores with an inner diameter of 500 nm or less, and microtubes with an outer diameter of 100 nm or less are formed as the microtubules with an outer diameter of 1000 nm or less. Manufacturing method of hydrogen gas sensor.
前記薄膜を陽極酸化し、微細孔又は微細筒が形成された陽極酸化被膜を生成するステップとを備えることを特徴とする水素ガスセンサの製造方法。 Producing a thin film of a titanium alloy containing palladium or platinum in a mass percentage of 0.01% or more on the substrate surface of the insulator;
And a step of anodizing the thin film to produce an anodized film in which fine holes or fine cylinders are formed .
前記薄膜をイオンビームスパッタ法で作製することを特徴とする水素ガスセンサの製造方法。 In any of claims 2 to 4 ,
A method for producing a hydrogen gas sensor, wherein the thin film is produced by an ion beam sputtering method.
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