JP3930638B2 - Hydrogen storage alloy and method for producing the same - Google Patents
Hydrogen storage alloy and method for producing the same Download PDFInfo
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- JP3930638B2 JP3930638B2 JP11697398A JP11697398A JP3930638B2 JP 3930638 B2 JP3930638 B2 JP 3930638B2 JP 11697398 A JP11697398 A JP 11697398A JP 11697398 A JP11697398 A JP 11697398A JP 3930638 B2 JP3930638 B2 JP 3930638B2
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- 229910045601 alloy Inorganic materials 0.000 title claims description 124
- 239000000956 alloy Substances 0.000 title claims description 124
- 238000003860 storage Methods 0.000 title claims description 80
- 239000001257 hydrogen Substances 0.000 title claims description 74
- 229910052739 hydrogen Inorganic materials 0.000 title claims description 74
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims description 69
- 238000004519 manufacturing process Methods 0.000 title claims description 19
- 238000010438 heat treatment Methods 0.000 claims description 29
- 229910018007 MmNi Inorganic materials 0.000 claims description 14
- 239000002994 raw material Substances 0.000 claims description 12
- 229910001122 Mischmetal Inorganic materials 0.000 claims description 9
- 229910004247 CaCu Inorganic materials 0.000 claims description 8
- 239000013078 crystal Substances 0.000 claims description 8
- 239000011261 inert gas Substances 0.000 claims description 5
- 238000007712 rapid solidification Methods 0.000 claims description 4
- 238000000889 atomisation Methods 0.000 claims description 2
- 230000006698 induction Effects 0.000 claims description 2
- 239000000203 mixture Substances 0.000 description 51
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 32
- 229910052782 aluminium Inorganic materials 0.000 description 19
- 238000010298 pulverizing process Methods 0.000 description 19
- 239000010949 copper Substances 0.000 description 17
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 16
- 238000010828 elution Methods 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 10
- 229910052742 iron Inorganic materials 0.000 description 10
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 8
- 229910017052 cobalt Inorganic materials 0.000 description 7
- 239000010941 cobalt Substances 0.000 description 7
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 7
- 230000006866 deterioration Effects 0.000 description 7
- 238000005204 segregation Methods 0.000 description 7
- 239000007789 gas Substances 0.000 description 6
- 229910052786 argon Inorganic materials 0.000 description 5
- 230000001771 impaired effect Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000001816 cooling Methods 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 229910018185 Al—Co Inorganic materials 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 238000005266 casting Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- HMUNWXXNJPVALC-UHFFFAOYSA-N 1-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)C(CN1CC2=C(CC1)NN=N2)=O HMUNWXXNJPVALC-UHFFFAOYSA-N 0.000 description 1
- WWSJZGAPAVMETJ-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]-3-ethoxypyrazol-1-yl]-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C=1C(=NN(C=1)CC(=O)N1CC2=C(CC1)NN=N2)OCC WWSJZGAPAVMETJ-UHFFFAOYSA-N 0.000 description 1
- ZRPAUEVGEGEPFQ-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]pyrazol-1-yl]-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C=1C=NN(C=1)CC(=O)N1CC2=C(CC1)NN=N2 ZRPAUEVGEGEPFQ-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000010410 dusting Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Images
Classifications
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- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Powder Metallurgy (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は水素吸蔵合金及びその製造方法に関し、詳しくは合金中にコバルトを含有させることなく、鉄を含有させ、微粉化特性に優れ、しかも初期活性が良好で、鉄の偏析がなく、アルミニウムの溶出量も少ない水素吸蔵合金及びその製造方法に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
近年、ニッケル−カドミウム蓄電池に代わる高容量アルカリ蓄電池として、水素吸蔵合金を負極に用いたニッケル−水素蓄電池が注目されている。この水素吸蔵合金は、現在では希土類系の混合物であるＭｍ（ミッシュメタル）とＮｉ、Ａｌ、Ｍｎ、Ｃｏとの５元素の水素吸蔵合金が汎用されている。
【０００３】
このＭｍ−Ｎｉ−Ｍｎ−Ａｌ−Ｃｏ合金は、Ｌａ系のそれに比べて比較的安価な材料で負極を構成でき、サイクル寿命が長く、過充電時の発生ガスによる内圧上昇が少ない密閉形ニッケル水素蓄電池を得ることができることから、電極材料として広く用いられている。
【０００４】
現在用いられているＭｍ−Ｎｉ−Ｍｎ−Ａｌ−Ｃｏ合金は、合金の微粉化を抑制してサイクル寿命を長くしているが、一般的にこの微粉化抑制のためには１０重量％程度のＣｏ（原子比で０．６〜１．０）を必要とすることが知られている。また、優れた水素吸蔵特性及び耐食性を得るためにも一定量のＣｏの含有は必要とされている。
【０００５】
しかしながら、Ｃｏの含有率が高いとそれだけ原料コストが高くなり、原料コストの面から問題視されている。特に、電気自動車用電源（ＥＶ：Electric vihicle）等の大型電池への適用やニッケル−水素蓄電池のさらなる市場の増大に対しては、原料コストは、電極負極材料の選定において大きな割合を占め、このことが問題となっていた。
【０００６】
このような問題を解決するために、特開平９−２１３３１９号公報には、Ｍｍ−Ｎｉ−Ｍｎ−Ａｌ−Ｃｏ系合金の組成を変化させ、これにさらに少量の１元素を加えることが提案されている。同公報に記載の水素吸蔵合金粉末を負極に用いることによって、Ｃｏが少量にもかかわらず、合金の微粉化による負極の劣化を一定限度抑制し、電池のサイクル寿命を長くすることができる。
【０００７】
しかるに、同公報に開示の水素吸蔵合金を用いた場合には、安定した良好な初期特性が得られないという問題がある。また、微粉化特性及び水素吸蔵特性も必ずしも満足し得るものではない。
【０００８】
Ｆｅを含有し、Ｃｏを含有しない水素吸蔵合金は、耐微粉化特性が向上し有望であるが、Ｆｅの偏析やＡｌの溶出が問題となり、時として性能差が著しく、例えば高温での保存時に合金の腐食が著しくなったり、充放電サイクル初期の容量の劣化が起こったりするため性能の安定性を得るのが非常に難しく、基本的性能向上は認められたものの、安定性に欠け、実用化の大きな障壁となっていた。
【０００９】
従って、本発明の目的は、コバルトを含有しないことによって製造コストを低減し、かつ微粉化特性に優れると共に、良好な初期特性を有し、しかも鉄の偏析がなく、アルミニウム溶出量も少ない水素吸蔵合金及びその製造方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明者等は種々の研究を重ねた結果、コバルトを含有することなく、鉄を含有するＡＢ5 型合金組成を特定の非化学量論組成（Ｂサイトリッチ）とし、かつｃ軸が一定範囲にある水素吸蔵合金によって、上記目的を達成し得ることを知見した。また、このような水素吸蔵合金は、上記特定の組成において、熱処理条件とが一定の関係にある場合に得られることを見い出した。
【００１１】
本発明は、上記知見に基づきなされたもので、
一般式
ＭｍＮｉa Ｍｎb Ａｌc Ｆｅd Ｃｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）
で表されるＣａＣｕ5 型の結晶構造を有するＡＢ5 型水素吸蔵合金であって、
ｃ軸の格子長が４０７．３ｐｍ以上であることを特徴とする水素吸蔵合金を提供するものである。
【００１２】
また、本発明は、本発明の水素吸蔵合金の好ましい製造方法として、
水素吸蔵合金原料を加熱溶解し、これを水冷型の鋳型に流し込んで１３５０〜１５５０℃で鋳造した後、不活性ガス雰囲気中で熱処理し、下記一般式で表されるＣａＣｕ5型の結晶構造を有するＡＢ5型水素吸蔵合金を製造する方法であって、該熱処理条件が、下記一般式において、ａ＋ｂ＋ｃ＋ｄ＋ｅが５．１０〜５．２５未満の場合、１０４０〜１０８０℃、３〜６時間であり、ａ＋ｂ＋ｃ＋ｄ＋ｅが５．２５〜５．３５の場合、１０６０〜１１００℃、３〜６時間であることを特徴とする水素吸蔵合金の製造方法を提供するものである。
一般式
ＭｍＮｉaＭｎbＡｌcＦｅdＣｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）
【００１３】
更に、本発明は、本発明の水素吸蔵合金の好ましい製造方法として、
水素吸蔵合金原料を加熱溶解し、これを超急冷凝固又はアトマイズした後、不活性ガス雰囲気中で熱処理し、下記一般式で表されるＣａＣｕ5型の結晶構造を有するＡＢ5型水素吸蔵合金を製造する方法であって、該熱処理条件が１０００〜１１００℃、１０分〜６時間であることを特徴とする水素吸蔵合金の製造方法。
一般式
ＭｍＮｉaＭｎbＡｌcＦｅdＣｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）
【００１４】
【発明の実施の形態】
本発明の水素吸蔵合金は、一般式
ＭｍＮｉa Ｍｎb Ａｌc Ｆｅd Ｃｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）
で表されるＣａＣｕ5 型の結晶構造を有するＡＢ5 型水素吸蔵合金である。
【００１５】
ここで、ＭｍはＬａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ等の希土類系の混合物であるミッシュメタルである。また、この水素吸蔵合金は、ＣａＣｕ5 型の結晶構造を有するＡＢ5 型水素吸蔵合金で、ＡＢ5.10`5.35 のＢサイトリッチの非化学量論組成である。
【００１６】
この水素吸蔵合金において、Ｎｉa Ｍｎb Ａｌc Ｆｅd Ｃｕe の組成割合（原子比）は、下記の関係を有するものである。すなわち、Ｎｉの割合は３．９≦ａ≦４．３であり、Ｍｎの割合は０．３≦ｂ≦０．５５であり、Ａｌの割合は０．１５≦ｃ≦０．５であり、Ｆｅの割合は０．１≦ｄ≦０．４であり、Ｃｕの割合は０．０５≦ｅ≦０．３５であり、かつａ＋ｂ＋ｃ＋ｄ＋ｅが５．１０〜５．３５の範囲にある。
【００１７】
上記のように、Ｎｉの割合ａは３．９〜４．３であり、ａが３．９未満では水素吸蔵量が損なわれ、４．３を超えると微粉化や寿命特性劣化が認められる。
【００１８】
Ｍｎの割合ｂは０．３〜０．５５であり、ｂが０．３未満ではプラトー圧力が高くなり、かつ水素吸蔵量が損なわれ、０．５５を超えると合金の腐食が激しくなり、合金の早期劣化が認められる。
【００１９】
Ａｌの割合ｃは０．１５〜０．３であり、ｃが０．１５未満では水素吸蔵合金放出圧力であるプラトー圧力が高くなり、充放電のエネルギー効率が悪くなり、０．５を超えると水素吸蔵量が少なくなるだけでなく、合金が単相化しにくい。
【００２０】
Ｆｅの割合ｄは０．１〜０．４であり、ｄが０．１未満では微粉化特性に劣り、０．４を超えるとＦｅの偏析を防ぐことができず、またＡｌの溶出を抑えることができない。
【００２１】
Ｃｕの割合ｅは０．０５〜０．３５であり、ｅが０．０５未満では微粉化特性の向上は見られず、０．３５を超えると水素吸蔵特性が損なわれ、またＣｕが析出する場合が生じる。
【００２２】
ａ＋ｂ＋ｃ＋ｄ＋ｅ（以下、場合によってｘと総称する）は５．１０〜５．３５であり、ｘが５．１０未満では電池寿命や微粉化特性が損なわれ、５．３５を超えた場合には、水素吸蔵特性が損なわれる。
【００２３】
本発明の水素吸蔵合金は、ｃ軸の格子長が４０７．３ｐｍ以上、好ましくは４０７．６〜４０８．０ｐｍである。ｃ軸の格子長が４０７．３ｐｍ未満では、微粉化特性に劣るのみならず、初期特性も低下する。また、４０８．０ｐｍを超えるような水素吸蔵合金は、製造において困難性が伴うし、水素吸蔵量の大幅な減少を伴う。
【００２４】
さらに、本発明の水素吸蔵合金のａ軸の格子長は、特に限定されないが、一般には５００．０〜５０３．０ｐｍである。
【００２５】
次に、本発明の水素吸蔵合金の製造方法について説明する。
先ず、上記で示したような合金組成となるように、水素吸蔵合金原料を秤量、混合し、例えば誘導加熱による高周波加熱溶解炉を用いて、上記水素吸蔵合金原料を溶解して金属溶湯となす、これを水冷型の鋳型に流し込んで水素吸蔵合金を１３５０〜１５５０℃で鋳造する。
【００２６】
次に、得られた水素吸蔵合金を不活性ガス雰囲気中、例えばアルゴンガス中で熱処理する。熱処理を行うのは、鋳造された合金の組織には通常Ｍｎ又はＦｅ主体の微細な粒界偏析が認められるが、これを加熱することによって均質化するためである。
【００２７】
熱処理条件はａ＋ｂ＋ｃ＋ｄ＋ｅ（ｘ）の値によって異なり、ｘが５．１０〜５．２５未満の時は、１０４０〜１０８０℃、３〜６時間であり、ｘが５．２５〜５．３５の時は、１０６０〜１１００℃、３〜６時間である。
【００２８】
また、本発明の水素吸蔵合金の他の製造方法としては、上記で示したような合金組成となるように、水素吸蔵合金原料を秤量、混合して得られた金属溶湯を、１０3 〜１０5 Ｋ程度の速い冷却速度で超急冷凝固させる超急冷凝固法（メルトスピン法）や上記金属溶湯を圧縮空気等を作用させ、多数の液滴に分割し、凝固させるアトマイズ法によって水素吸蔵合金を製造してもよい。
【００２９】
この場合の熱処理条件は、１０００〜１１００℃、１０分〜６時間、好ましくは１０分〜３時間である。
【００３０】
このようにして、鉄を含有し、コバルトを含有しないにも拘わらず、微粉化特性に優れると共に、良好な初期特性を有し、かつ鉄の偏析が生じず、アルミニウムの溶出量が少ない水素吸蔵合金が得られる。
【００３１】
この水素吸蔵合金は、粗粉砕、微粉砕後、アルカリ蓄電池の負極として好適に用いられる。かかるアルカリ蓄電池は、初期特性が良好で、合金の微粉化による負極の劣化が抑制され、サイクル寿命が長いものとなる。
【００３２】
【実施例】
以下、本発明を実施例等に基づき具体的に説明する。
【００３３】
［実施例１−１〜１−３及び比較例１−１〜１−２］
Ｍｍ、Ｎｉ、Ｍｎ、Ａｌ、Ｆｅ及びＣｕを合金組成でＭｍＮｉ4.05Ｍｎ0.45Ａｌ0.3 Ｆｅ0.28Ｃｕ0.22（ｘ＝５．３０）になるように、各水素吸蔵合金原料を秤量、混合し、その混合物をルツボに入れて高周波溶解炉に固定し、１０-3Ｔｏｒｒまで真空状態にした後、アルゴンガス雰囲気中で加熱溶解した後、水冷式銅鋳型に流し込み、１４５０℃で鋳造を行い、合金を得た。更に、この合金をアルゴンガス雰囲気中で、表２に示す条件で熱処理を行い、それぞれ水素吸蔵合金を得た。
【００３４】
［実施例２−１〜２−３及び比較例２−１〜２−２］
合金組成を表１に示される合金組成Ｂとし、表２に示す条件で熱処理を行った以外は、実施例１−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００３５】
［比較例３−１〜３−３］
合金組成を表１に示される合金組成Ｃとし、表２に示す条件で熱処理を行った以外は、実施例１−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００３６】
［比較例４−１〜４−５］
合金組成を表１に示される合金組成Ｄとし、表２に示す条件で熱処理を行った以外は、実施例１−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００３７】
［実施例５−１〜５−３及び比較例５−１〜５−２］
合金組成を表１に示される合金組成Ｅとし、表３に示す条件で熱処理を行った以外は、実施例１−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００３８】
［実施例６−１〜６−３及び比較例６−１〜６−２］
合金組成を表１に示される合金組成Ｆとし、表３に示す条件で熱処理を行った以外は、実施例１−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００３９】
［実施例７−１〜７−３及び比較例７−１〜７−２］
合金組成を表１に示される合金組成Ｇとし、表３に示す条件で熱処理を行った以外は、実施例１−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００４０】
［実施例８−１］
合金組成を表１に示される合金組成Ｈとし、表３に示す条件で熱処理を行った以外は、実施例１−１と同様にして水素吸蔵合金を得た。
【００４１】
［実施例９−１］
合金組成を表１に示される合金組成Ｉとし、表３に示す条件で熱処理を行った以外は、実施例１−１と同様にして水素吸蔵合金を得た。
【００４２】
［実施例１０−１〜１０−３及び比較例１０−１〜１０−２］
Ｍｍ、Ｎｉ、Ｍｎ、Ａｌ、Ｆｅ及びＣｕを合金組成でＭｍＮｉ4.05Ｍｎ0.45Ａｌ0.3 Ｆｅ0.28Ｃｕ0。22（ｘ＝５．３０）（合金組成Ａ）になるように、各水素吸蔵合金原料を秤量、混合し、その混合物をルツボに入れて高周波溶解炉に固定し、１０-3Ｔｏｒｒまで真空状態にした後、アルゴンガス雰囲気中で加熱溶解した後、１０3 〜１０5 Ｋ程度の冷却速度で超急冷凝固させ合金を得た。更に、この合金をアルゴンガス雰囲気中で、表４に示す条件で熱処理を行い、それぞれ水素吸蔵合金を得た。
【００４３】
［実施例１１−１〜１１−３及び比較例１１−１〜１１−２］
合金組成を表１に示される合金組成Ｇとし、表４に示す条件で熱処理を行った以外は、実施例１０−１と同様にしてそれぞれ水素吸蔵合金を得た。
【００４４】
［特性評価］
実施例及び比較例で得られた水素吸蔵合金について、格子長、アルミニウム溶出率、初期容量劣化の有無及び微粉化残存率の評価を行った。その結果を表２〜４に示す。なお、格子長、アルミニウム溶出率及び微粉化残存率は下記の方法に基づいて行った。そして、これらの評価に基づいて総合評価を行い、◎を良好、×を不良とした。
【００４５】
＜格子長＞
Ｘ線回折試験に基づいて行い、粒径２２μｍ以下の合金粉末をディフラクトメータで測定し、１００゜≦２θ≦１５０゜の間のピークを用いて、格子定数の精密化を実施した。
【００４６】
＜アルミニウム溶出率＞
アルミニウム溶出試験を行い、試験片を３０重量％ＫＯＨ水溶液（６５℃）中に放置し、ＩＣＰ分析を行った。そして、比較例３−１の値を１００％とした指数表示とした。
【００４７】
＜微粉化残存率＞
ＰＣＴ装置で、３０ｂａｒの水素ガスを粒度２２〜５３ミクロンに調整した水素吸蔵合金に導入し、その後脱蔵排気する処理を１０回繰り返した後、サイクル試験前の平均粒度に対するサイクル試験後の平均粒度の比で計算した。
【００４８】
【表１】
【表２】
【表３】
【表４】
表２〜４の結果から明らかなように、実施例はコバルトを含有しない比較例よりも、一般的にアルミニウム溶出率が小さく、初期容量劣化もなく、また微粉化残存率が高いため総合評価において優れている。また、コバルトを含有する比較例は、総合評価に優れているものの、経済性に劣り、また実施例に比べてアルミニウム溶出率が大きい。
【００５３】
［実験例１］
ＭｍＮｉ4.05Ｍｎ0.45Ａｌ0.3 Ｆｅ0.28Ｃｕ0。22（ｘ＝５．３０）（合金組成Ａ）とＭｍＮｉ3.95Ｍｎ0.4 Ａｌ0.3 Ｆｅ0.3 Ｃｕ0。25（ｘ＝５．２０）（合金組成Ｂ）の熱処理条件と格子長（ｃ軸）の関係を評価した。結果を図１に示す。なお、合金組成Ａ及びＢはいずれも鋳造によって得られたものである。
【００５４】
図１の結果から、合金組成Ａは熱処理条件が１０８０℃、３時間で最もｃ軸長が長くなり、合金組成Ｂは熱処理条件が１０６０℃、６時間で最もｃ軸長が長くなる。このように合金組成Ａ及びＢではｘの値によって、最適熱処理条件が異なることが判る。
【００５５】
［実験例２］
ＭｍＮｉ4.05Ｍｎ0.45Ａｌ0.3 Ｆｅ0.28Ｃｕ0。22（ｘ＝５．３０）（合金組成Ａ）、ＭｍＮｉ3.55Ｍｎ0.4 Ａｌ0.3 Ｃｏ0.75（ｘ＝５．００）（合金組成Ｃ）及びＭｍＮｉ3.95Ｍｎ0.45Ａｌ0.3 Ｃｏ0.4 Ｃｕ0.1 （ｘ＝５．２０）（合金組成Ｄ）の熱処理条件とアルミニウム溶出量の関係を評価した。結果を図２に示す。なお、合金組成Ａ、Ｃ、Ｄはいずれも鋳造によって得られたものである。また、アルミニウム溶出量は合金組成Ｃを１００％とした指数表示で示した。
【００５６】
図２の結果から、合金組成Ｃ及びＤは熱処理条件に拘わらず、アルミニウム溶出量が一定であるのに対し、合金組成Ａは１０８０℃、３〜６時間で最もアルミニウム溶出量が少ない。このように合金組成Ａでは、アルミニウム溶出量において最適熱処理条件があることが判る。
【００５７】
【発明の効果】
以上説明したように、本発明の水素吸蔵合金は、コバルトを含有しないため製造コストが低減され、かつ微粉化特性に優れると共に、良好な初期特性を有し、しかも鉄の偏析がなく、アルミニウム溶出量も少ない。
また、本発明の製造方法によって、上記水素吸蔵合金が安定して、かつ効率よく得られる。
【図面の簡単な説明】
【図１】各合金組成における熱処理条件と格子長（ｃ軸）の関係を示すグラフ。
【図２】各合金組成における熱処理条件とアルミニウム溶出量の関係を示すグラフ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrogen storage alloy and a method for producing the same. More specifically, the alloy does not contain cobalt, contains iron, has excellent pulverization characteristics, has good initial activity, has no segregation of iron, and does not contain aluminum. The present invention relates to a hydrogen storage alloy with a small amount of elution and a method for producing the same.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, nickel-hydrogen storage batteries using a hydrogen storage alloy as a negative electrode have attracted attention as high-capacity alkaline storage batteries that can replace nickel-cadmium storage batteries. As this hydrogen storage alloy, a five-element hydrogen storage alloy of Mm (Misch metal), which is a rare earth-based mixture, and Ni, Al, Mn, and Co is currently widely used.
[0003]
This Mm-Ni-Mn-Al-Co alloy can form a negative electrode with a relatively inexpensive material compared to that of La-based, has a long cycle life, and has a low internal pressure increase due to gas generated during overcharge. Since a storage battery can be obtained, it is widely used as an electrode material.
[0004]
The currently used Mm-Ni-Mn-Al-Co alloy suppresses the pulverization of the alloy and extends the cycle life. Generally, about 10% by weight is required for suppressing the pulverization. It is known that Co (at an atomic ratio of 0.6 to 1.0) is required. In order to obtain excellent hydrogen storage characteristics and corrosion resistance, it is necessary to contain a certain amount of Co.
[0005]
However, the higher the Co content, the higher the raw material cost, which is regarded as a problem from the viewpoint of raw material cost. In particular, for application to large batteries such as electric vehicle power supplies (EVs) and further market growth of nickel-hydrogen storage batteries, raw material costs account for a large proportion in the selection of electrode negative electrode materials. That was a problem.
[0006]
In order to solve such a problem, Japanese Patent Laid-Open No. 9-213319 proposes changing the composition of the Mm-Ni-Mn-Al-Co alloy and adding a small amount of one element to the composition. ing. By using the hydrogen storage alloy powder described in the publication for the negative electrode, it is possible to suppress the deterioration of the negative electrode due to the pulverization of the alloy to a certain limit and extend the cycle life of the battery even though the amount of Co is small.
[0007]
However, when the hydrogen storage alloy disclosed in the publication is used, there is a problem that stable and good initial characteristics cannot be obtained. Further, the pulverization characteristics and the hydrogen storage characteristics are not always satisfactory.
[0008]
Hydrogen storage alloys that contain Fe and do not contain Co are promising due to improved anti-dusting properties, but segregation of Fe and elution of Al are problematic, and sometimes there are significant performance differences, for example during storage at high temperatures. It is very difficult to obtain performance stability due to significant corrosion of the alloy and deterioration of capacity at the beginning of the charge / discharge cycle, and although basic performance improvement has been recognized, it is not stable and practical use It became a big barrier.
[0009]
Accordingly, the object of the present invention is to reduce the manufacturing cost by not containing cobalt, and to have excellent pulverization characteristics, good initial characteristics, no segregation of iron, and little aluminum elution. It is to provide an alloy and a manufacturing method thereof.
[0010]
[Means for Solving the Problems]
As a result of various studies by the inventors, the AB 5 type alloy composition containing iron has a specific non-stoichiometric composition (B site rich) without containing cobalt, and the c-axis is in a certain range. It has been found that the above object can be achieved by the hydrogen storage alloy in FIG. Further, it has been found that such a hydrogen storage alloy can be obtained when the specific composition has a certain relationship with the heat treatment conditions.
[0011]
The present invention has been made based on the above findings,
Formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
In a AB 5 type hydrogen storage alloy having a CaCu 5 type crystal structure represented by,
The present invention provides a hydrogen storage alloy having a c-axis lattice length of 407.3 pm or more.
[0012]
Further, the present invention provides a preferred method for producing the hydrogen storage alloy of the present invention,
The hydrogen storage alloy raw material is heated and melted , poured into a water-cooled mold and cast at 1350 to 1550 ° C., and then heat-treated in an inert gas atmosphere to obtain a CaCu 5 type crystal structure represented by the following general formula. a method of manufacturing a AB 5 type hydrogen storage alloy having, heat treatment conditions, the following formula, when a + b + c + d + e is less than 5.10-5.25, 1,040 to 1,080 ° C., is 3-6 hours, When a + b + c + d + e is 5.25 to 5.35, it provides a method for producing a hydrogen storage alloy characterized by being 1060 to 1100 ° C. and 3 to 6 hours .
General formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
[0013]
Furthermore, the present invention is a preferred method for producing the hydrogen storage alloy of the present invention,
A hydrogen storage alloy raw material is heated and melted, and this is subjected to ultra-rapid solidification or atomization, followed by heat treatment in an inert gas atmosphere, and an AB 5 type hydrogen storage alloy having a CaCu 5 type crystal structure represented by the following general formula: A method for producing a hydrogen-absorbing alloy, characterized in that the heat treatment conditions are 1000 to 1100 ° C. and 10 minutes to 6 hours.
General formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The hydrogen storage alloy of the present invention have the general formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
In a AB 5 type hydrogen storage alloy having a CaCu 5 type crystal structure represented.
[0015]
Here, Mm is a misch metal which is a rare earth-based mixture of La, Ce, Pr, Nd, Sm and the like. This hydrogen storage alloy is an AB 5 type hydrogen storage alloy having a CaCu 5 type crystal structure, and has a B site rich non-stoichiometric composition of AB 5.10`5.35 .
[0016]
In this hydrogen storage alloy, the composition ratio (atomic ratio) of Ni a Mn b Al c Fe d Cu e has the following relationship. That is, the proportion of Ni is 3.9 ≦ a ≦ 4.3, the proportion of Mn is 0.3 ≦ b ≦ 0.55, the proportion of Al is 0.15 ≦ c ≦ 0.5, The proportion of Fe is 0.1 ≦ d ≦ 0.4, the proportion of Cu is 0.05 ≦ e ≦ 0.35, and a + b + c + d + e is in the range of 5.10 to 5.35.
[0017]
As described above, the Ni ratio “a” is 3.9 to 4.3, and when a is less than 3.9, the hydrogen storage amount is impaired, and when it exceeds 4.3, pulverization and deterioration of life characteristics are observed.
[0018]
The ratio b of Mn is 0.3 to 0.55. If b is less than 0.3, the plateau pressure becomes high and the hydrogen storage amount is impaired. If it exceeds 0.55, the corrosion of the alloy becomes severe. Early deterioration is observed.
[0019]
The ratio c of Al is 0.15 to 0.3. If c is less than 0.15, the plateau pressure, which is the hydrogen storage alloy discharge pressure, becomes high, the energy efficiency of charge / discharge deteriorates, and if it exceeds 0.5, Not only does the hydrogen storage amount decrease, but the alloy is less likely to become a single phase.
[0020]
The ratio d of Fe is 0.1 to 0.4. If d is less than 0.1, the pulverization characteristics are inferior. If it exceeds 0.4, segregation of Fe cannot be prevented and the elution of Al is suppressed. I can't.
[0021]
The ratio e of Cu is 0.05 to 0.35. When e is less than 0.05, improvement of the pulverization property is not observed, and when it exceeds 0.35, the hydrogen storage property is impaired and Cu is precipitated. Cases arise.
[0022]
a + b + c + d + e (hereinafter, collectively referred to as x in some cases) is 5.10 to 5.35. When x is less than 5.10, the battery life and pulverization characteristics are impaired, and when it exceeds 5.35, hydrogen The storage characteristics are impaired.
[0023]
The hydrogen storage alloy of the present invention has a c-axis lattice length of 407.3 pm or more, preferably 407.6 to 408.0 pm. When the c-axis lattice length is less than 407.3 pm, not only the pulverization characteristics are inferior but also the initial characteristics are deteriorated. Moreover, a hydrogen storage alloy exceeding 408.0 pm is accompanied by difficulty in production and accompanied by a significant decrease in the amount of hydrogen storage.
[0024]
Further, the a-axis lattice length of the hydrogen storage alloy of the present invention is not particularly limited, but is generally 500.0 to 503.0 pm.
[0025]
Next, the manufacturing method of the hydrogen storage alloy of this invention is demonstrated.
First, the hydrogen storage alloy raw material is weighed and mixed so as to have the alloy composition as described above, and the hydrogen storage alloy raw material is melted into a molten metal using, for example, an induction heating high-frequency heating melting furnace. , which is cast at 1,350 to 1,550 ° C. a hydrogen storage alloy is poured into water cooling type template.
[0026]
Next, the obtained hydrogen storage alloy is heat-treated in an inert gas atmosphere, for example, argon gas . Perform thermal processing, the fine grain boundary segregation of normal Mn or Fe mainly observed in the tissue of the cast alloy, in order to homogenize by heating it.
[0027]
Heat treatment conditions depend on the value of a + b + c + d + e (x), when x is less than 5.10 to 5.25 is, 1 040-1,080 ° C., is 3-6 hours, x is from the 5.25 to 5.35 time, 1 060~1100 ℃, 3 to 6 hours.
[0028]
Further, as another method for producing the hydrogen storage alloy of the present invention, a metal melt obtained by weighing and mixing the hydrogen storage alloy raw materials so as to have the alloy composition as described above is 10 3 to 10. Manufactures hydrogen storage alloys by ultra-rapid solidification method (melt spin method), in which ultra-rapid solidification is performed at a high cooling rate of about 5 K, and the atomized method in which the molten metal is divided into a large number of droplets by the action of compressed air. May be.
[0029]
The heat treatment conditions in this case are 1000-1100 ° C., 10 minutes-6 hours, preferably 10 minutes-3 hours.
[0030]
In this way, although it contains iron and does not contain cobalt, it has excellent pulverization characteristics, has good initial characteristics, does not cause segregation of iron, and has a low aluminum elution amount. An alloy is obtained.
[0031]
This hydrogen storage alloy is suitably used as a negative electrode for an alkaline storage battery after coarse pulverization and fine pulverization. Such an alkaline storage battery has good initial characteristics, suppresses deterioration of the negative electrode due to the pulverization of the alloy, and has a long cycle life.
[0032]
【Example】
Hereinafter, the present invention will be specifically described based on examples and the like.
[0033]
[Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2]
Each hydrogen storage alloy raw material is weighed and mixed so that MmNi 4.05 Mn 0.45 Al 0.3 Fe 0.28 Cu 0.22 (x = 5.30) in the alloy composition of Mm, Ni, Mn, Al, Fe and Cu, and the mixture Is put in a crucible and fixed in a high-frequency melting furnace, vacuumed to 10 -3 Torr, heated and melted in an argon gas atmosphere, poured into a water-cooled copper mold, and cast at 1450 ° C to obtain an alloy. It was. Furthermore, this alloy was heat-treated in an argon gas atmosphere under the conditions shown in Table 2 to obtain hydrogen storage alloys.
[0034]
[Examples 2-1 to 2-3 and Comparative examples 2-1 to 2-2]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was alloy composition B shown in Table 1 and heat treatment was performed under the conditions shown in Table 2.
[0035]
[Comparative Examples 3-1 to 3-3]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1, except that the alloy composition was alloy composition C shown in Table 1 and heat treatment was performed under the conditions shown in Table 2.
[0036]
[Comparative Examples 4-1 to 4-5]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was alloy composition D shown in Table 1 and heat treatment was performed under the conditions shown in Table 2.
[0037]
[Examples 5-1 to 5-3 and Comparative Examples 5-1 to 5-2]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was alloy composition E shown in Table 1 and heat treatment was performed under the conditions shown in Table 3.
[0038]
[Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-2]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was alloy composition F shown in Table 1 and heat treatment was performed under the conditions shown in Table 3.
[0039]
[Examples 7-1 to 7-3 and Comparative Examples 7-1 to 7-2]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was alloy composition G shown in Table 1 and heat treatment was performed under the conditions shown in Table 3.
[0040]
[Example 8-1]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was the alloy composition H shown in Table 1 and heat treatment was performed under the conditions shown in Table 3.
[0041]
[Example 9-1]
A hydrogen storage alloy was obtained in the same manner as in Example 1-1 except that the alloy composition was alloy composition I shown in Table 1 and heat treatment was performed under the conditions shown in Table 3.
[0042]
[Examples 10-1 to 10-3 and Comparative Examples 10-1 to 10-2]
Mm, Ni, Mn, Al, Fe and Cu are alloy compositions of MmNi 4.05 Mn 0.45 Al 0.3 Fe 0.28 Cu 0.22 (x = 5.30) (alloy composition A). Weigh and mix, put the mixture in a crucible and fix it in a high-frequency melting furnace, evacuate to 10 -3 Torr, heat and dissolve in an argon gas atmosphere, then cool at a cooling rate of about 10 3 to 10 5 K The alloy was obtained by ultra-cooling and solidification. Furthermore, this alloy was heat-treated in an argon gas atmosphere under the conditions shown in Table 4 to obtain hydrogen storage alloys.
[0043]
[Examples 11-1 to 11-3 and Comparative Examples 11-1 to 11-2]
A hydrogen storage alloy was obtained in the same manner as in Example 10-1, except that the alloy composition was alloy composition G shown in Table 1 and heat treatment was performed under the conditions shown in Table 4.
[0044]
[Characteristic evaluation]
The hydrogen storage alloys obtained in Examples and Comparative Examples were evaluated for lattice length, aluminum elution rate, presence / absence of initial capacity deterioration, and residual pulverization rate. The results are shown in Tables 2-4. The lattice length, aluminum elution rate, and pulverization residual rate were determined based on the following methods. Then, comprehensive evaluation was performed based on these evaluations, with 良好 being good and × being bad.
[0045]
<Lattice length>
Based on the X-ray diffraction test, an alloy powder having a particle size of 22 μm or less was measured with a diffractometer, and the lattice constant was refined using a peak between 100 ° ≦ 2θ ≦ 150 °.
[0046]
<Aluminum dissolution rate>
An aluminum elution test was performed, and the test piece was left in a 30 wt% KOH aqueous solution (65 ° C.) for ICP analysis. And it was set as the index display which made the value of the comparative example 3-1 100%.
[0047]
<Micronized residual rate>
After the process of introducing 30 bar hydrogen gas into a hydrogen storage alloy adjusted to a particle size of 22-53 microns and then evacuating and exhausting 10 times with a PCT device, the average particle size after the cycle test with respect to the average particle size before the cycle test is repeated. The ratio was calculated.
[0048]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
As is clear from the results of Tables 2 to 4, the examples generally have a lower aluminum elution rate, no initial capacity deterioration, and a higher pulverization residual rate than the comparative examples not containing cobalt. Are better. Moreover, although the comparative example containing cobalt is excellent in comprehensive evaluation, it is inferior to economical efficiency, and its aluminum elution rate is large compared with an Example.
[0053]
[Experimental Example 1]
MmNi 4.05 Mn 0.45 Al 0.3 Fe 0.28 Cu 0.22 (x = 5.30) (alloy composition A) and MmNi 3.95 Mn 0.4 Al 0.3 Fe 0.3 Cu 0.25 (x = 5.20) (alloy composition B) The relationship between the heat treatment conditions and the lattice length (c-axis) was evaluated. The results are shown in FIG. Alloy compositions A and B are both obtained by casting.
[0054]
From the results of FIG. 1, the alloy composition A has the longest c-axis length at 1080 ° C. for 3 hours, and the alloy composition B has the longest c-axis length at 1060 ° C. for 6 hours. Thus, it can be seen that the optimum heat treatment conditions differ depending on the value of x in the alloy compositions A and B.
[0055]
[Experiment 2]
MmNi 4.05 Mn 0.45 Al 0.3 Fe 0.28 Cu 0.22 (x = 5.30) (alloy composition A), MmNi 3.55 Mn 0.4 Al 0.3 Co 0.75 (x = 5.00) (alloy composition C) and MmNi 3.95 Mn 0.45 The relationship between the heat treatment conditions of Al 0.3 Co 0.4 Cu 0.1 (x = 5.20) (alloy composition D) and the aluminum elution amount was evaluated. The results are shown in FIG. Alloy compositions A, C, and D are all obtained by casting. Moreover, the aluminum elution amount was shown by an index display with the alloy composition C as 100%.
[0056]
From the results of FIG. 2, the alloy compositions C and D have a constant aluminum elution amount regardless of the heat treatment conditions, whereas the alloy composition A has the smallest aluminum elution amount at 1080 ° C. for 3 to 6 hours. Thus, it can be seen that the alloy composition A has optimum heat treatment conditions for the aluminum elution amount.
[0057]
【The invention's effect】
As described above, the hydrogen storage alloy of the present invention does not contain cobalt, so the production cost is reduced, and it is excellent in pulverization characteristics, has good initial characteristics, has no segregation of iron, and dissolves aluminum. The amount is also small.
Moreover, the hydrogen storage alloy can be obtained stably and efficiently by the production method of the present invention.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between heat treatment conditions and lattice length (c-axis) in each alloy composition.
FIG. 2 is a graph showing the relationship between heat treatment conditions and aluminum elution amount in each alloy composition.
Claims (5)
ＭｍＮｉaＭｎbＡｌcＦｅdＣｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）
で表されるＣａＣｕ5型の結晶構造を有するＡＢ5型水素吸蔵合金であって、
ｃ軸の格子長が４０７．３ｐｍ以上であることを特徴とする水素吸蔵合金。General formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
In a AB 5 type hydrogen storage alloy having a CaCu 5 type crystal structure represented by,
A hydrogen storage alloy having a c-axis lattice length of 407.3 pm or more.
一般式
ＭｍＮｉaＭｎbＡｌcＦｅdＣｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）The hydrogen storage alloy raw material is heated and melted , poured into a water-cooled mold and cast at 1350 to 1550 ° C., and then heat-treated in an inert gas atmosphere to obtain a CaCu 5 type crystal structure represented by the following general formula. a method of manufacturing a AB 5 type hydrogen storage alloy having, heat treatment conditions, the following formula, when a + b + c + d + e is less than 5.10-5.25, 1,040 to 1,080 ° C., is 3-6 hours, When a + b + c + d + e is 5.25-5.35, it is 1060-1100 degreeC and it is 3 to 6 hours , The manufacturing method of the hydrogen storage alloy characterized by the above-mentioned.
General formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
一般式
ＭｍＮｉaＭｎbＡｌcＦｅdＣｕe
（式中、Ｍｍはミッシュメタル、３．９≦ａ≦４．３、０．３≦ｂ≦０．５５、０．１５≦ｃ≦０．５、０．１≦ｄ≦０．４、０．０５≦ｅ≦０．３５、５．１０≦ａ＋ｂ＋ｃ＋ｄ＋ｅ≦５．３５）A hydrogen storage alloy raw material is heated and melted, and this is subjected to ultra-rapid solidification or atomization, followed by heat treatment in an inert gas atmosphere, and an AB 5 type hydrogen storage alloy having a CaCu 5 type crystal structure represented by the following general formula: A method for producing a hydrogen-absorbing alloy, characterized in that the heat treatment conditions are 1000 to 1100 ° C. and 10 minutes to 6 hours.
General formula MmNi a Mn b Al c Fe d Cu e
(In the formula, Mm is misch metal, 3.9 ≦ a ≦ 4.3, 0.3 ≦ b ≦ 0.55, 0.15 ≦ c ≦ 0.5, 0.1 ≦ d ≦ 0.4, 0 .05 ≦ e ≦ 0.35, 5.10 ≦ a + b + c + d + e ≦ 5.35)
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