JP2004115834A - Titanium-chromium-manganese-based hydrogen storage alloy - Google Patents

Titanium-chromium-manganese-based hydrogen storage alloy Download PDF

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JP2004115834A
JP2004115834A JP2002277514A JP2002277514A JP2004115834A JP 2004115834 A JP2004115834 A JP 2004115834A JP 2002277514 A JP2002277514 A JP 2002277514A JP 2002277514 A JP2002277514 A JP 2002277514A JP 2004115834 A JP2004115834 A JP 2004115834A
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hydrogen storage
hydrogen
storage alloy
titanium
chromium
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JP3795443B2 (en
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Yoshitsugu Kojima
小島 由継
Yasuaki Kawai
河合 泰明
Shinichi Towata
砥綿 真一
Masahiko Kanehara
金原 雅彦
Tomoya Matsunaga
松永 朋也
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Toyota Central R&D Labs Inc
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Toyota Central R&D Labs Inc
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storage alloy having a large capacity for storing hydrogen under a high pressure, and a capability of occluding/releasing hydrogen in a wide range from a low temperature to atmospheric temperature. <P>SOLUTION: The hydrogen storage alloy is a titanium-chromium-manganese-based hydrogen storage alloy having a composition formula expressed by Ti<SB>x</SB>Cr<SB>2-y</SB>Mn<SB>y</SB>(1.0<x<1.2, 1.0<y<1.4). The hydrogen storage alloy has a large capacity of storing hydrogen under a high pressure, and a capability of occluding/releasing hydrogen in a wide range of a low temperature to atmospheric temperature, through having a specified range of a content ratio of Mn and Ti (x and y). <P>COPYRIGHT: (C)2004,JPO

Description

【0001】
【発明の属する技術分野】
本発明は、可逆的に水素を吸蔵・放出することのできる水素吸蔵合金に関し、詳しくは、高圧下における水素吸蔵量の大きいチタン−クロム−マンガン系水素吸蔵合金に関する。
【0002】
【従来の技術】
近年、二酸化炭素の排出による地球の温暖化等の環境問題や、石油資源の枯渇等のエネルギー問題から、クリーンな代替エネルギーとして水素エネルギーが注目されている。水素エネルギーは、例えば、電気自動車用電源等に利用される燃料電池を始めとして、様々な用途への利用が期待されている。水素エネルギーを実用化するためには、水素を安全に貯蔵・輸送する技術が重要となる。水素を貯蔵する技術として、例えば、水素を高圧で圧縮したり、また低温で液化してボンベ等の容器に充填する方法がある。一方、容器に水素を吸蔵・放出可能な材料を充填しておき、その材料に水素を吸蔵させて貯蔵する方法もある。水素を吸蔵・放出可能な材料の一つとして、水素吸蔵合金が挙げられる。水素吸蔵合金は、水素を金属水素化物という安全な固体の形で貯蔵できることから、輸送可能な新しい貯蔵媒体として期待されている。
【0003】
これまで、既に数多くの水素吸蔵合金が開発されてきた。例えば、チタン系の水素吸蔵合金としては、一般式Ti−Mn−M(MはV、Cr、Fe、Co、Ni、CuおよびMoからなる群から選ばれる少なくとも一種)で示される合金が開示されている(例えば、特許文献1参照。)。また、一般式Ti1+xCr2−yMn(0<x≦0.4、0<y≦1)で表される合金も開示されている(例えば、特許文献2参照。)。
【0004】
【特許文献1】
特開昭54−62914号公報
【特許文献2】
特公昭59−7774号公報
【0005】
【発明が解決しようとする課題】
しかしながら、上記いずれの水素吸蔵合金も、比較的低圧下では水素を吸蔵・放出するものの、高圧下における水素吸蔵・放出特性は満足いくものではない。すなわち、従来は、1MPa程度の比較的低圧下で、また、常温付近の温度で水素を多量に吸蔵・放出できる合金の開発が主流であった。そのため、15MPa以上の高圧下、あるいは−40℃程度の低温下で多量の水素を吸蔵・放出できる合金の開発は、ほとんど行われていない。
【0006】
本発明は、このような実状に鑑みてなされたものであり、高圧下における水素吸蔵量が大きく、かつ低温から常温までの広い温度範囲で水素を吸蔵・放出できる水素吸蔵合金を提供することを課題とする。
【0007】
【課題を解決するための手段】
本発明のチタン−クロム−マンガン系水素吸蔵合金は、組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表されることを特徴とする。本発明者は、種々の合金の高圧下における水素吸蔵特性について研究を重ねた結果、ある組成を有するチタン−クロム−マンガン系水素吸蔵合金は、高圧下で多量の水素を吸蔵できることを見出した。そして、合金成分であるチタン(Ti)およびマンガン(Mn)の含有割合により、水素の吸蔵・放出量が大きく変化するという知見を得た。ここで、本発明のチタン−クロム−マンガン系水素吸蔵合金の一例として、組成式Ti1.05Cr0.99Mn1.01で表される合金の水素吸蔵量と圧力との関係を図1に示す。図1より、組成式Ti1.05Cr0.99Mn1.01で表される本発明の水素吸蔵合金は、圧力の増加とともに水素吸蔵量が増加し、圧力が15MPa以上で水素吸蔵量が急激に増えることがわかる。
【0008】
後に実施例で詳述するが、例えば、合金中のTiのモル比、つまり上記組成式におけるxの値が1.0以下の場合には、金属水素化物の平衡水素圧(以下「解離圧」と表す。)が上昇し、圧力を35MPa程度まで高くした場合でも、水素はほとんど吸蔵されない。一方、xの値が1.2以上になると、解離圧が低下し、広い範囲の圧力下で水素は吸蔵されやすくなる。しかし、大気圧(約0.1MPa)以上の圧力下で放出される水素の量は減少するため、実用に適さない。特に、−40℃程度の低温下では、大気圧下で水素をほとんど取り出すことができないため、低温下での使用が難しくなる。また、合金中のMnのモル比、つまり上記組成式におけるyの値が1.0以下の場合には、解離圧はあまり変化しないものの、水素を吸蔵できるサイトが少なくなるため、水素吸蔵量が減少する。一方、yの値が1.4以上になると、解離圧が低下し、大気圧以上の圧力下で放出される水素の量は減少する。そのため、特に−40℃程度の低温下での使用が難しくなる。
【0009】
本発明のチタン−クロム−マンガン系水素吸蔵合金は、TiおよびMnの含有割合を上記範囲に特定したため、高圧下における水素吸蔵量が大きく、かつ低温から常温までの広い温度範囲で水素を吸蔵・放出できる水素吸蔵合金となる。また、本発明のチタン−クロム−マンガン系水素吸蔵合金は、低温下でも水素吸蔵・放出速度が大きい。通常、水素吸蔵合金が水素を放出する反応は吸熱反応となる。したがって、水素を放出するにつれ水素吸蔵合金の温度は低下していく。そのため、低温下で水素を放出し難い合金では、水素放出速度が小さくなる。本発明のチタン−クロム−マンガン系水素吸蔵合金は、低温下でも充分水素を放出できるため、水素放出に伴う温度の低下の影響は少なく、水素の放出速度を維持できると考えられる。
【0010】
また、本発明の水素貯蔵装置は、容器と、該容器に収容された水素貯蔵材料とを含む水素貯蔵装置であって、前記水素貯蔵材料は、組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表されるチタン−クロム−マンガン系水素吸蔵合金を含むことを特徴とする。すなわち、上記本発明の水素吸蔵合金を水素貯蔵材料として用いた水素貯蔵装置である。上記本発明の水素吸蔵合金を水素貯蔵材料として用いることで、本発明の水素貯蔵装置は、高圧下で水素を多量に貯蔵することができる装置となる。また、本発明の水素貯蔵装置は、低温から常温までの広い温度範囲で多量の水素を利用できる装置となる。
【0011】
【発明の実施の形態】
以下、本発明のチタン−クロム−マンガン系水素吸蔵合金および水素貯蔵装置について詳細に説明する。なお、説明する実施形態は一実施形態にすぎず、本発明のチタン−クロム−マンガン系水素吸蔵合金および水素貯蔵装置は、下記の実施形態に限定されるものではない。本発明のチタン−クロム−マンガン系水素吸蔵合金および水素貯蔵装置は、下記実施形態を始めとして、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。
【0012】
〈チタン−クロム−マンガン系水素吸蔵合金〉
本発明のチタン−クロム−マンガン系水素吸蔵合金は、組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表される。合金中のTiのモル比、つまり上記組成式におけるxの値の範囲は1.0<x<1.2とする。上述したように、Tiのモル比が1.0以下の場合には、圧力を35MPa程度まで高くしても水素をあまり吸蔵しない。Tiのモル比を1.0より大きくすることで、高圧下で多量の水素を吸蔵させることができる。一方、Tiのモル比が1.2以上であると、大気圧以上の圧力下で取り出すことのできる水素量が減少する。特に、大気圧以上かつ−40℃程度の低温下で、より多くの水素を取り出すことができるという理由から、Tiのモル比を1.1未満(x<1.1)とすることが望ましい。
【0013】
合金中のMnのモル比、つまり組成式におけるyの値の範囲は1.0<y<1.4とする。上述したように、Mnのモル比が1.0以下の場合には、水素の吸蔵サイトが少なくなるため、水素吸蔵量が減少する。Mnのモル比を1.0より大きくすることで、高圧下における水素吸蔵量を大きくすることができる。一方、Mnのモル比が1.4以上であると、大気圧以上の圧力下で取り出すことのできる水素量が減少する。Mnのモル比を1.4未満とすることで、大気圧以上の低温下であっても充分な量の水素を取り出すことができる。
【0014】
また、結晶構造の観点から、本発明のチタン−クロム−マンガン系水素吸蔵合金は、六方晶系C14型結晶構造を有するラーベス相からなり、格子定数aおよびcがそれぞれa:0.4864nm以上0.4877nm以下、c:0.7980nm以上0.8010nm以下であることが望ましい。六方晶系C14型結晶構造を有するラーベス相からなる場合には、水素を吸蔵・放出する際の結晶の相転移がなく、水素の吸蔵・放出速度が大きい。格子定数aおよびcの値は、水素の吸蔵および放出し易さに関係すると考えられる。すなわち、格子定数aおよびcがそれぞれ上記範囲より小さいと、格子体積が小さくなるため、水素を吸蔵し難くなると考えられる。反対に、格子定数aおよびcがそれぞれ上記範囲より大きいと、格子体積が大きくなるため、水素を吸蔵し易くなる。しかし、この場合、一旦吸蔵された水素は放出され難くなると考えられる。
【0015】
本発明のチタン−クロム−マンガン系水素吸蔵合金は、その製造方法が特に限定されるものではない。アーク溶解法等の通常の合金の製造方法、すわわち、原料となる各金属を目的の組成となるように混合、溶解した後、凝固させるというプロセスに従えばよい。
【0016】
〈水素貯蔵装置〉
本発明の水素貯蔵装置は、容器と、該容器に収容された水素貯蔵材料とを含む水素貯蔵装置であって、水素貯蔵材料は、組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表されるチタン−クロム−マンガン系水素吸蔵合金を含む。
【0017】
本発明の水素貯蔵装置を構成する容器は、高圧、低温等の条件で使用できるものであれば、特に限定されるものではない。通常用いられる耐圧容器、ボンベ等種々の容器を使用すればよい。そして、容器に上記本発明の水素吸蔵合金を含む水素蔵貯蔵材料を充填し、圧力や温度を所定の条件に調整することにより、水素を吸蔵・放出させればよい。
【0018】
本発明の水素貯蔵装置は、使用温度、圧力が特に限定されるものではない。上述したように、水素蔵貯蔵材料として収容される本発明のチタン−クロム−マンガン系水素吸蔵合金は、高圧下にて水素を多量に吸蔵する。このことを考慮すると、収容された本発明の水素吸蔵合金に、15MPa以上の圧力下で水素を吸蔵させることが望ましい。つまり、本発明の水素貯蔵装置は、水素を15MPa以上の圧力で充填して使用することが望ましい。水素充填時の圧力を20MPa以上とするとより好適である。
【0019】
【実施例】
上記実施形態に基づいて、本発明のチタン−クロム−マンガン系水素吸蔵合金を種々製造した。そして、各々の水素吸蔵合金に所定の条件下で水素を吸蔵・放出させ、その吸蔵量と放出量とを測定した。以下、製造したチタン−クロム−マンガン系水素吸蔵合金、およびそれらの水素吸蔵・放出特性について述べる。
【0020】
(1)第1シリーズのチタン−クロム−マンガン系水素吸蔵合金
(a)水素吸蔵合金の製造
下記表1に示す9種類の組成のチタン−クロム−マンガン系水素吸蔵合金を、アーク溶解法にて製造した。まず、純度99%以上のTi、Cr、Mnを所定の合金組成となるように混合し、アルゴン雰囲気にて加熱炉で溶解した。その後、鋳型に流し込み急冷することによりインゴットに鋳造した。得られた各水素吸蔵合金のインゴットを粉砕して、以下の種々の測定に用いた。なお、製造された水素吸蔵合金は、いずれも本発明の水素吸蔵合金に相当する。
【0021】
(b)水素吸蔵合金の水素吸蔵・放出量等の測定
上記製造された水素吸蔵合金中のTi、Cr、Mn量を、誘導結合プラズマ(ICP)発光分析法により求めた。また、各水素吸蔵合金について、CuΚα線を用いた粉末法による広角X線回折測定を行った。そして、X線回折パターンにおける(110)面の回折角から格子定数aを求め、(004)面の回折角から格子定数cを求めた。さらに、各水素吸蔵合金に所定の条件下で水素を吸蔵・放出させ、各水素吸蔵合金の水素吸蔵・放出量をPCT特性測定装置(鈴木商館社製)を用いて測定した。水素吸蔵・放出量の測定は、二つの条件で行った。一つは、温度25℃、圧力0.1〜25MPaにて行った。もう一つは、−40℃、圧力0.1〜9MPaにて行った。そして、水素吸蔵合金から放出された水素の質量を、水素吸蔵合金の質量で除した値を有効水素量とした。各々の水素吸蔵合金の水素吸蔵・放出量の測定結果を、合金組成および格子定数とともに表1に示す。
【0022】
【表1】

Figure 2004115834
【0023】
表1より、いずれの水素吸蔵合金も、25℃における有効水素量が1.7wt%以上と大きいことがわかる。また、−40℃における有効水素量も、25℃における値と比較すると若干低下しているが、1.6wt%以上と大きくなった。また、これらの水素吸蔵合金は、いずれも六方晶系C14型結晶構造を有するラーベス相からなり、格子定数aおよびcがそれぞれa:0.4865nm〜0.4876nm、c:0.7981nm〜0.8008nmであることが確認された。以上より、本発明の水素吸蔵合金は、高圧下で多量の水素を吸蔵し、かつ大気圧以上で吸蔵した水素を放出することが確認できた。また、常温付近に限らず、−40℃という低温下であっても、同様に水素を吸蔵・放出できることも確認できた。さらに、25℃において、水素の吸蔵・放出開始からそれぞれ5分後の水素吸蔵・放出量を測定したところ、いずれの水素吸蔵合金も、5分後の水素吸蔵・放出量と、有効水素量とが同じ値となった。これより、本発明の水素吸蔵合金は、水素を吸蔵・放出する速度が大きいことがわかる。
【0024】
(2)第2シリーズのチタン−クロム−マンガン系水素吸蔵合金
(a)水素吸蔵合金の製造
下記表2に示す12種類の組成のチタン−クロム−マンガン系水素吸蔵合金を、上記第1シリーズのチタン−クロム−マンガン系水素吸蔵合金と同様にして、アーク溶解法にて製造した。なお、製造された水素吸蔵合金は、いずれも比較例の水素吸蔵合金となる。
【0025】
(b)水素吸蔵合金の水素吸蔵・放出量の測定
上記製造された水素吸蔵合金中のTi、Cr、Mn量、格子定数(a、c)、および各水素吸蔵合金の水素吸蔵・放出量を、上記第1シリーズのチタン−クロム−マンガン系水素吸蔵合金と同様にして求めた。各々の水素吸蔵合金の水素吸蔵・放出量の測定結果を、合金組成および格子定数とともに表2に示す。なお、参考例として、TiCr1.3361.558について上記同様に測定した結果も併せて示す。
【0026】
【表2】
Figure 2004115834
【0027】
表2からわかるように、本第2シリーズの水素吸蔵合金は、TiおよびMnの少なくとも一方のモル比が、本発明の水素吸蔵合金におけるx、yの範囲外の値となっている。このため、いずれの水素吸蔵合金も、上記表1に示した本発明の水素吸蔵合金と比較して、有効水素量が小さくなった。特に、Tiのモル比が1.0以下の#22、#26および#31の水素吸蔵合金は、25℃における有効水素量が0.25wt%以下と非常に小さいことがわかる。これらの水素吸蔵合金は、解離圧が高いため、25MPaという高圧下であっても水素をほとんど吸蔵しなかったと考えられる。また、#23〜#25、#27、#29、#30および#32の水素吸蔵合金は、−40℃における有効水素量が、25℃における有効水素量と比較して低下した。これらの水素吸蔵合金は、TiおよびMnの少なくとも一方のモル比が、本発明の水素吸蔵合金におけるx、yの範囲の上限を超えているため、解離圧が低く、低温下では水素を放出できなかったと考えられる。
【0028】
また、参考例であるTiCr1.3361.558は、25℃における有効水素量は大きいものの、−40℃における有効水素量は0wt%であった。そして、水素の吸蔵・放出開始からそれぞれ5分後の水素吸蔵・放出量も、有効水素量より小さかった。つまり、TiCr1.3361.558は、水素を吸蔵・放出する速度が小さいことがわかる。
【0029】
さらに、上記第1および第2シリーズの#12、#13、#15〜#17、#19、#22、#23、および#26の水素吸蔵合金における有効水素量のデータを採用し、Tiの含有量と有効水素量との関係を調査した。その結果を図2に示す。図2より、25℃、−40℃のいずれの温度下であっても、Tiの量が1.0を超えると有効水素量が急激に増加することがわかる。また、Tiの量が1.2以上では、有効水素量は低下することがわかる。すなわち、組成式TiおよびMnのモル比がそれぞれ1.0<x<1.2、1.0<y<1.4である本発明のチタン−クロム−マンガン系水素吸蔵合金は、広い温度範囲で多量の水素を吸蔵・放出できることが確認された。
【0030】
(3)水素貯蔵装置の水素貯蔵量の測定
上記#17の水素吸蔵合金(Ti1.02Cr0.99Mn1.01)の12gを内容量35ccの高圧容器に収容して、水素貯蔵装置を作製した。なお、本水素貯蔵装置は、本発明の水素貯蔵装置となる。この水素貯蔵装置に18〜21℃の温度下で水素を充填し、所定の圧力にした。その後、同温度で水素を大気圧となるまで放出させ、水上置換法により各圧力における水素貯蔵量を求めた。一方、何も収容しない空の高圧容器(内容量35cc)を用いて水素貯蔵装置を作製し、比較例の水素吸蔵装置とした。この比較例の水素貯蔵装置に、上記同様に水素を充填し、所定の圧力にした後、各圧力における水素貯蔵量を求めた。図3に、上記二種類の水素貯蔵装置の各圧力における水素貯蔵量を示す。図3より、どちらの水素貯蔵装置も圧力が大きいほど、水素貯蔵量は大きくなっている。しかし、#17の水素吸蔵合金(Ti1.02Cr0.99Mn1.01)を容器に収容した本発明の水素貯蔵装置は、空の容器に水素を充填した比較例の水素吸蔵装置と比較して、すべての圧力において水素貯蔵量が大きくなった。このように、本発明の水素貯蔵装置は、単位体積当たりの水素吸蔵量が大きい水素貯蔵装置となる。
【0031】
【発明の効果】
本発明のチタン−クロム−マンガン系水素吸蔵合金は、組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表される。TiおよびMnのモル比を上記範囲に特定したため、高圧下における水素吸蔵量が大きく、かつ低温から常温までの広い温度範囲で水素を吸蔵・放出できる水素吸蔵合金となる。また、本発明のチタン−クロム−マンガン系水素吸蔵合金は、低温下でも水素吸蔵・放出速度が大きい。
【0032】
本発明の水素貯蔵装置は、水素貯蔵材料として上記本発明のチタン−クロム−マンガン系水素吸蔵合金を含む。このため、高圧下で水素を多量に貯蔵することができ、さらに、低温から常温までの広い温度範囲で多量の水素を利用できる装置となる。
【図面の簡単な説明】
【図1】組成式Ti1.05Cr0.99Mn1.01で表される本発明のチタン−クロム−マンガン系水素吸蔵合金の水素吸蔵量と圧力との関係を示す。
【図2】水素吸蔵合金におけるTiの含有量と有効水素量との関係を示す。
【図3】二種類の水素貯蔵装置の各圧力における水素貯蔵量を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrogen storage alloy capable of reversibly storing and releasing hydrogen, and more particularly to a titanium-chromium-manganese hydrogen storage alloy having a large hydrogen storage amount under high pressure.
[0002]
[Prior art]
BACKGROUND ART In recent years, hydrogen energy has attracted attention as a clean alternative energy due to environmental problems such as global warming due to carbon dioxide emission and energy problems such as depletion of petroleum resources. Hydrogen energy is expected to be used for various applications including, for example, a fuel cell used for an electric vehicle power supply and the like. In order to put hydrogen energy to practical use, technology for safely storing and transporting hydrogen is important. As a technique for storing hydrogen, for example, there is a method of compressing hydrogen at high pressure or liquefying at low temperature and filling it in a container such as a cylinder. On the other hand, there is a method in which a container is filled with a material capable of occluding and releasing hydrogen, and the material is occluding and storing hydrogen. One of the materials capable of storing and releasing hydrogen is a hydrogen storage alloy. Hydrogen storage alloys are expected as a new transportable storage medium because hydrogen can be stored in a safe solid form called metal hydride.
[0003]
Until now, many hydrogen storage alloys have been developed. For example, disclosed as a titanium-based hydrogen storage alloy is an alloy represented by the general formula Ti-Mn-M (M is at least one selected from the group consisting of V, Cr, Fe, Co, Ni, Cu, and Mo). (For example, see Patent Document 1). Further, an alloy represented by the general formula Ti 1 + x Cr 2-y Mn y (0 <x ≦ 0.4,0 <y ≦ 1) is also disclosed (e.g., see Patent Document 2.).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 54-62914 [Patent Document 2]
JP-B-59-7774 [0005]
[Problems to be solved by the invention]
However, any of the above hydrogen storage alloys absorbs and releases hydrogen under relatively low pressure, but does not have satisfactory hydrogen storage and release characteristics under high pressure. That is, conventionally, the development of an alloy capable of storing and releasing a large amount of hydrogen under a relatively low pressure of about 1 MPa and at a temperature near ordinary temperature has been mainly performed. For this reason, alloys capable of storing and releasing a large amount of hydrogen under a high pressure of 15 MPa or more or a low temperature of about −40 ° C. have hardly been developed.
[0006]
The present invention has been made in view of such circumstances, and provides a hydrogen storage alloy having a large hydrogen storage capacity under high pressure and capable of storing and releasing hydrogen in a wide temperature range from low temperature to normal temperature. Make it an issue.
[0007]
[Means for Solving the Problems]
Titanium present invention - chromium - manganese based hydrogen storage alloy be represented by the composition formula Ti x Cr 2-y Mn y (1.0 <x <1.2,1.0 <y <1.4) It is characterized by. As a result of repeated studies on the hydrogen storage properties of various alloys under high pressure, the present inventors have found that a titanium-chromium-manganese hydrogen storage alloy having a certain composition can store a large amount of hydrogen under high pressure. Further, the inventors have found that the amount of hydrogen occlusion / release greatly changes depending on the content ratio of titanium (Ti) and manganese (Mn), which are alloy components. Here, as an example of the titanium-chromium-manganese-based hydrogen storage alloy of the present invention, the relationship between the hydrogen storage amount and the pressure of the alloy represented by the composition formula Ti 1.05 Cr 0.99 Mn 1.01 is shown in FIG. Shown in As shown in FIG. 1, the hydrogen storage alloy of the present invention represented by the composition formula Ti 1.05 Cr 0.99 Mn 1.01 has an increased hydrogen storage amount as the pressure increases, and the hydrogen storage amount increases at a pressure of 15 MPa or more. It can be seen that it increases rapidly.
[0008]
As will be described in detail in Examples later, for example, when the molar ratio of Ti in the alloy, that is, the value of x in the above composition formula is 1.0 or less, the equilibrium hydrogen pressure of the metal hydride (hereinafter, “dissociation pressure”) ) And hydrogen is hardly absorbed even when the pressure is increased to about 35 MPa. On the other hand, when the value of x is 1.2 or more, the dissociation pressure decreases, and hydrogen is easily absorbed under a wide range of pressure. However, since the amount of hydrogen released under a pressure higher than the atmospheric pressure (about 0.1 MPa) decreases, it is not practical. In particular, under a low temperature of about −40 ° C., almost no hydrogen can be taken out under the atmospheric pressure, so that use at a low temperature becomes difficult. Further, when the molar ratio of Mn in the alloy, that is, the value of y in the above composition formula is 1.0 or less, the dissociation pressure does not change much, but the number of sites that can store hydrogen decreases, so that the hydrogen storage amount is low. Decrease. On the other hand, when the value of y becomes 1.4 or more, the dissociation pressure decreases, and the amount of hydrogen released under a pressure higher than the atmospheric pressure decreases. Therefore, it is particularly difficult to use at a low temperature of about −40 ° C.
[0009]
Since the titanium-chromium-manganese-based hydrogen storage alloy of the present invention specifies the content ratio of Ti and Mn in the above range, the hydrogen storage amount under high pressure is large, and hydrogen is stored and stored in a wide temperature range from low temperature to normal temperature. It becomes a hydrogen storage alloy that can be released. Further, the titanium-chromium-manganese hydrogen storage alloy of the present invention has a large hydrogen storage / release rate even at a low temperature. Usually, the reaction of releasing hydrogen from the hydrogen storage alloy is an endothermic reaction. Therefore, the temperature of the hydrogen storage alloy decreases as hydrogen is released. Therefore, in an alloy that does not easily release hydrogen at a low temperature, the hydrogen release rate decreases. The titanium-chromium-manganese-based hydrogen storage alloy of the present invention can release hydrogen sufficiently even at a low temperature. Therefore, it is considered that the effect of a decrease in temperature due to the release of hydrogen is small and the hydrogen release rate can be maintained.
[0010]
The hydrogen storage device of the present invention is a hydrogen storage device comprising a container and a hydrogen storage material contained in the container, the hydrogen storage material, the compositional formula Ti x Cr 2-y Mn y (1 0.0 <x <1.2, 1.0 <y <1.4) and is characterized by containing a titanium-chromium-manganese-based hydrogen storage alloy. That is, a hydrogen storage device using the hydrogen storage alloy of the present invention as a hydrogen storage material. By using the hydrogen storage alloy of the present invention as a hydrogen storage material, the hydrogen storage device of the present invention becomes a device capable of storing a large amount of hydrogen under high pressure. Further, the hydrogen storage device of the present invention is a device that can use a large amount of hydrogen in a wide temperature range from a low temperature to a normal temperature.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the titanium-chromium-manganese-based hydrogen storage alloy and the hydrogen storage device of the present invention will be described in detail. Note that the embodiment to be described is merely an embodiment, and the titanium-chromium-manganese-based hydrogen storage alloy and the hydrogen storage device of the present invention are not limited to the following embodiment. The titanium-chromium-manganese-based hydrogen storage alloy and the hydrogen storage device of the present invention can be implemented in various forms including modifications and improvements that can be made by those skilled in the art, including the following embodiments.
[0012]
<Titanium-chromium-manganese hydrogen storage alloy>
Titanium present invention - chromium - manganese based hydrogen storage alloy represented by the composition formula Ti x Cr 2-y Mn y (1.0 <x <1.2,1.0 <y <1.4). The molar ratio of Ti in the alloy, that is, the range of the value of x in the above composition formula is set to 1.0 <x <1.2. As described above, when the molar ratio of Ti is 1.0 or less, even if the pressure is increased to about 35 MPa, hydrogen is not absorbed much. By making the molar ratio of Ti larger than 1.0, a large amount of hydrogen can be stored under high pressure. On the other hand, when the molar ratio of Ti is 1.2 or more, the amount of hydrogen that can be extracted under a pressure equal to or higher than the atmospheric pressure decreases. In particular, the molar ratio of Ti is desirably less than 1.1 (x <1.1) because more hydrogen can be taken out at atmospheric pressure or higher and at a low temperature of about −40 ° C.
[0013]
The molar ratio of Mn in the alloy, that is, the range of the value of y in the composition formula is set to 1.0 <y <1.4. As described above, when the molar ratio of Mn is 1.0 or less, the number of hydrogen storage sites decreases, and the hydrogen storage amount decreases. By setting the molar ratio of Mn to be larger than 1.0, the hydrogen storage amount under high pressure can be increased. On the other hand, when the molar ratio of Mn is 1.4 or more, the amount of hydrogen that can be taken out under a pressure higher than the atmospheric pressure decreases. By setting the molar ratio of Mn to less than 1.4, a sufficient amount of hydrogen can be taken out even at a low temperature equal to or higher than the atmospheric pressure.
[0014]
Further, from the viewpoint of the crystal structure, the titanium-chromium-manganese-based hydrogen storage alloy of the present invention is composed of a Laves phase having a hexagonal C14 type crystal structure, and has a lattice constant a and c of 0.4864 nm or more, respectively. .4877 nm or less, c: desirably 0.7980 nm or more and 0.8010 nm or less. In the case of the Laves phase having the hexagonal C14 type crystal structure, there is no phase transition of the crystal when storing and releasing hydrogen, and the hydrogen storing and releasing speed is high. It is considered that the values of the lattice constants a and c are related to the ease of storing and releasing hydrogen. That is, when the lattice constants a and c are each smaller than the above range, the lattice volume is reduced, and it is considered that hydrogen is hardly occluded. Conversely, if the lattice constants a and c are larger than the above ranges, respectively, the lattice volume becomes large, and hydrogen is easily absorbed. However, in this case, it is considered that hydrogen once stored becomes difficult to release.
[0015]
The production method of the titanium-chromium-manganese hydrogen storage alloy of the present invention is not particularly limited. An ordinary method of manufacturing an alloy such as an arc melting method, that is, a process of mixing, melting, and solidifying each metal as a raw material so as to have a desired composition may be used.
[0016]
<Hydrogen storage device>
Hydrogen storage device of the present invention is a hydrogen storage device comprising a container and a hydrogen storage material contained in the container, the hydrogen storage material, the compositional formula Ti x Cr 2-y Mn y (1.0 < x <1.2, 1.0 <y <1.4) including a titanium-chromium-manganese hydrogen storage alloy.
[0017]
The container constituting the hydrogen storage device of the present invention is not particularly limited as long as it can be used under conditions such as high pressure and low temperature. Various containers such as a normally used pressure container and a cylinder may be used. Then, the hydrogen storage / storage material containing the hydrogen storage alloy of the present invention is filled in a container, and the pressure and temperature are adjusted to predetermined conditions to store and release hydrogen.
[0018]
The working temperature and pressure of the hydrogen storage device of the present invention are not particularly limited. As described above, the titanium-chromium-manganese hydrogen storage alloy of the present invention stored as a hydrogen storage material stores a large amount of hydrogen under high pressure. In view of this, it is desirable that the stored hydrogen storage alloy of the present invention store hydrogen under a pressure of 15 MPa or more. That is, it is desirable to use the hydrogen storage device of the present invention by filling it with hydrogen at a pressure of 15 MPa or more. It is more preferable to set the pressure at the time of filling hydrogen to 20 MPa or more.
[0019]
【Example】
Various titanium-chromium-manganese hydrogen storage alloys of the present invention were manufactured based on the above embodiments. Then, each of the hydrogen storage alloys was caused to store and release hydrogen under predetermined conditions, and the amounts of stored and released hydrogen were measured. Hereinafter, the manufactured titanium-chromium-manganese hydrogen storage alloys and their hydrogen storage / release characteristics will be described.
[0020]
(1) First series titanium-chromium-manganese hydrogen storage alloy (a) Production of hydrogen storage alloy Titanium-chromium-manganese hydrogen storage alloys having nine compositions shown in Table 1 below were obtained by arc melting. Manufactured. First, Ti, Cr, and Mn having a purity of 99% or more were mixed so as to have a predetermined alloy composition and melted in a heating furnace in an argon atmosphere. Thereafter, the mixture was poured into a mold and rapidly cooled to cast it into an ingot. Each of the obtained hydrogen storage alloy ingots was pulverized and used for the following various measurements. Note that any of the manufactured hydrogen storage alloys corresponds to the hydrogen storage alloy of the present invention.
[0021]
(B) Measurement of hydrogen storage / release amount of hydrogen storage alloy The amounts of Ti, Cr and Mn in the hydrogen storage alloy produced above were determined by inductively coupled plasma (ICP) emission spectrometry. Further, for each hydrogen storage alloy, wide-angle X-ray diffraction measurement was performed by a powder method using CuΚα ray. Then, the lattice constant a was determined from the diffraction angle of the (110) plane in the X-ray diffraction pattern, and the lattice constant c was determined from the diffraction angle of the (004) plane. Furthermore, each hydrogen storage alloy was caused to store and release hydrogen under predetermined conditions, and the amount of hydrogen storage and release of each hydrogen storage alloy was measured using a PCT characteristic measuring device (manufactured by Suzuki Shokan Co., Ltd.). The measurement of the amount of absorbed and released hydrogen was performed under two conditions. One was performed at a temperature of 25 ° C. and a pressure of 0.1 to 25 MPa. The other was performed at −40 ° C. and a pressure of 0.1 to 9 MPa. Then, a value obtained by dividing the mass of hydrogen released from the hydrogen storage alloy by the mass of the hydrogen storage alloy was defined as an effective hydrogen amount. Table 1 shows the measurement results of the amount of hydrogen storage / release of each hydrogen storage alloy together with the alloy composition and lattice constant.
[0022]
[Table 1]
Figure 2004115834
[0023]
Table 1 shows that the effective hydrogen amount at 25 ° C. is as large as 1.7 wt% or more for each of the hydrogen storage alloys. Also, the effective hydrogen amount at -40 ° C is slightly lower than the value at 25 ° C, but increased to 1.6 wt% or more. Each of these hydrogen storage alloys is composed of a Laves phase having a hexagonal C14 type crystal structure, and has lattice constants a and c of a: 0.4865 nm to 0.4876 nm and c: 0.7981 nm to 0. It was confirmed to be 8008 nm. From the above, it was confirmed that the hydrogen storage alloy of the present invention stores a large amount of hydrogen under high pressure and releases the stored hydrogen at atmospheric pressure or higher. Further, it was confirmed that hydrogen can be occluded and released not only at around room temperature but also at a low temperature of -40 ° C. Further, at 25 ° C., when the hydrogen storage and release amounts after 5 minutes from the start of hydrogen storage and release were measured, all the hydrogen storage alloys showed that the hydrogen storage and release amounts after 5 minutes and the effective hydrogen amount Has the same value. This indicates that the hydrogen storage alloy of the present invention has a high rate of storing and releasing hydrogen.
[0024]
(2) Titanium-chromium-manganese hydrogen storage alloy of the second series (a) Production of hydrogen storage alloy Titanium-chromium-manganese hydrogen storage alloys of 12 kinds of compositions shown in Table 2 below were used in the first series. It was manufactured by an arc melting method in the same manner as in the titanium-chromium-manganese hydrogen storage alloy. The manufactured hydrogen storage alloys are all hydrogen storage alloys of comparative examples.
[0025]
(B) Measurement of hydrogen storage / release amount of hydrogen storage alloy The amounts of Ti, Cr, Mn, lattice constants (a, c), and hydrogen storage / release amount of each hydrogen storage alloy in the manufactured hydrogen storage alloy were measured. And the titanium-chromium-manganese hydrogen storage alloy of the first series. Table 2 shows the measurement results of the amount of hydrogen storage / release of each hydrogen storage alloy together with the alloy composition and lattice constant. In addition, as a reference example, the result of the same measurement for Ti 1 Cr 1.336 V 1.558 is also shown.
[0026]
[Table 2]
Figure 2004115834
[0027]
As can be seen from Table 2, in the hydrogen storage alloy of the second series, the molar ratio of at least one of Ti and Mn is outside the range of x and y in the hydrogen storage alloy of the present invention. Therefore, the effective hydrogen amount of each of the hydrogen storage alloys was smaller than that of the hydrogen storage alloy of the present invention shown in Table 1 above. In particular, the hydrogen storage alloys # 22, # 26 and # 31 having a Ti molar ratio of 1.0 or less have an extremely small effective hydrogen amount at 25 ° C. of 0.25 wt% or less. It is considered that since these hydrogen storage alloys have a high dissociation pressure, they hardly absorbed hydrogen even under a high pressure of 25 MPa. In the hydrogen storage alloys # 23 to # 25, # 27, # 29, # 30, and # 32, the effective hydrogen amount at −40 ° C. was lower than the effective hydrogen amount at 25 ° C. These hydrogen storage alloys have a low dissociation pressure and can release hydrogen at low temperatures because the molar ratio of at least one of Ti and Mn exceeds the upper limit of the range of x and y in the hydrogen storage alloy of the present invention. Probably not.
[0028]
Moreover, although Ti 1 Cr 1.336 V 1.558 as a reference example had a large effective hydrogen amount at 25 ° C., the effective hydrogen amount at −40 ° C. was 0 wt%. The amount of hydrogen storage / release after 5 minutes from the start of hydrogen storage / release was also smaller than the effective hydrogen amount. That is, it can be seen that Ti 1 Cr 1.336 V 1.558 has a low rate of absorbing and releasing hydrogen.
[0029]
Further, the data of the effective hydrogen amount in the hydrogen storage alloys # 12, # 13, # 15 to # 17, # 19, # 22, # 23, and # 26 of the first and second series are adopted, The relationship between the content and the effective hydrogen content was investigated. The result is shown in FIG. From FIG. 2, it can be seen that, regardless of the temperature at either 25 ° C. or −40 ° C., if the amount of Ti exceeds 1.0, the effective hydrogen amount sharply increases. Also, it can be seen that when the amount of Ti is 1.2 or more, the effective hydrogen amount decreases. That is, the titanium-chromium-manganese-based hydrogen storage alloy of the present invention in which the molar ratios of the composition formulas Ti and Mn are 1.0 <x <1.2 and 1.0 <y <1.4, respectively, has a wide temperature range. It was confirmed that a large amount of hydrogen could be absorbed and released by the method.
[0030]
(3) Measurement of Hydrogen Storage Amount of Hydrogen Storage Device 12 g of the hydrogen storage alloy (Ti 1.02 Cr 0.99 Mn 1.01 ) of the above # 17 was accommodated in a high-pressure container having a content of 35 cc, and the hydrogen storage device was Was prepared. The present hydrogen storage device is the hydrogen storage device of the present invention. This hydrogen storage device was filled with hydrogen at a temperature of 18 to 21 ° C. and brought to a predetermined pressure. After that, hydrogen was released at the same temperature until the pressure became atmospheric pressure, and the hydrogen storage amount at each pressure was determined by a water displacement method. On the other hand, a hydrogen storage device was produced using an empty high-pressure container (with an internal capacity of 35 cc) that did not accommodate anything, and was used as a hydrogen storage device of a comparative example. The hydrogen storage device of this comparative example was filled with hydrogen in the same manner as described above, and the pressure was adjusted to a predetermined value. Then, the hydrogen storage amount at each pressure was determined. FIG. 3 shows the amount of hydrogen stored at each pressure of the two types of hydrogen storage devices. From FIG. 3, the larger the pressure of both hydrogen storage devices, the larger the hydrogen storage amount. However, the hydrogen storage device of the present invention in which the hydrogen storage alloy # 17 (Ti 1.02 Cr 0.99 Mn 1.01 ) is contained in the container is different from the hydrogen storage device of the comparative example in which an empty container is filled with hydrogen. In comparison, the hydrogen storage was higher at all pressures. Thus, the hydrogen storage device of the present invention is a hydrogen storage device having a large hydrogen storage amount per unit volume.
[0031]
【The invention's effect】
Titanium present invention - chromium - manganese based hydrogen storage alloy represented by the composition formula Ti x Cr 2-y Mn y (1.0 <x <1.2,1.0 <y <1.4). Since the molar ratio of Ti and Mn is specified in the above range, the hydrogen storage alloy has a large hydrogen storage amount under high pressure and can store and release hydrogen in a wide temperature range from low temperature to normal temperature. Further, the titanium-chromium-manganese hydrogen storage alloy of the present invention has a large hydrogen storage / release rate even at a low temperature.
[0032]
The hydrogen storage device of the present invention includes the above titanium-chromium-manganese hydrogen storage alloy of the present invention as a hydrogen storage material. For this reason, a large amount of hydrogen can be stored under high pressure, and a large amount of hydrogen can be used in a wide temperature range from a low temperature to a normal temperature.
[Brief description of the drawings]
FIG. 1 shows the relationship between the hydrogen storage amount and the pressure of a titanium-chromium-manganese-based hydrogen storage alloy of the present invention represented by a composition formula Ti 1.05 Cr 0.99 Mn 1.01 .
FIG. 2 shows the relationship between the Ti content and the effective hydrogen amount in a hydrogen storage alloy.
FIG. 3 shows the hydrogen storage amount at each pressure of two types of hydrogen storage devices.

Claims (5)

組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表されるチタン−クロム−マンガン系水素吸蔵合金。Titanium expressed by a composition formula Ti x Cr 2-y Mn y (1.0 <x <1.2,1.0 <y <1.4) - chromium - manganese based hydrogen storage alloy. 前記組成式におけるxは1.1未満(x<1.1)である請求項1に記載のチタン−クロム−マンガン系水素吸蔵合金。The titanium-chromium-manganese hydrogen storage alloy according to claim 1, wherein x in the composition formula is less than 1.1 (x <1.1). 六方晶系C14型結晶構造を有するラーベス相からなり、格子定数aおよびcがそれぞれa:0.4864nm以上0.4877nm以下、c:0.7980nm以上0.8010nm以下である請求項1に記載のチタン−クロム−マンガン系水素吸蔵合金。The Laves phase having a hexagonal C14 type crystal structure, wherein the lattice constants a and c are each a: 0.4864 nm or more and 0.4877 nm or less, and c: 0.7980 nm or more and 0.8010 nm or less. Titanium-chromium-manganese hydrogen storage alloy. 容器と、該容器に収容された水素貯蔵材料とを含む水素貯蔵装置であって、
前記水素貯蔵材料は、組成式TiCr2−yMn(1.0<x<1.2、1.0<y<1.4)で表されるチタン−クロム−マンガン系水素吸蔵合金を含むことを特徴とする水素貯蔵装置。
A hydrogen storage device including a container and a hydrogen storage material stored in the container,
The hydrogen storage material, titanium expressed by a composition formula Ti x Cr 2-y Mn y (1.0 <x <1.2,1.0 <y <1.4) - chromium - manganese based hydrogen storage alloy A hydrogen storage device comprising:
15MPa以上の圧力下で前記水素吸蔵合金に水素を吸蔵させた請求項4に記載の水素貯蔵装置。The hydrogen storage device according to claim 4, wherein the hydrogen storage alloy stores hydrogen under a pressure of 15 MPa or more.
JP2002277514A 2002-09-24 2002-09-24 Titanium-chromium-manganese hydrogen storage alloy Expired - Fee Related JP3795443B2 (en)

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CN113148947A (en) * 2021-03-03 2021-07-23 中国科学院江西稀土研究院 Rare earth alloy hydrogen storage material and preparation method thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113148947A (en) * 2021-03-03 2021-07-23 中国科学院江西稀土研究院 Rare earth alloy hydrogen storage material and preparation method thereof

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