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ropertiescouldkeepconstant,thereforethealloysshowedaprospectivepracticefuture.Keywords:Ni-Mn-Gaalloy,rearearthTb,crystalstructure,mechanicalproperty
论文题目:快淬La-Mg-Ni系贮氢合金结构与电化学性能的研究
TheInvestigationonStructuresandElectrochemicalPerformances
ofMelt-spinningLa-Mg-NiBasedHydrogenStorageAlloys
研究生姓名:董小平
导师姓名:张羊换教授
专业:材料加工工程
摘 要:
随着科技的进步,环保意识的加强,移动电子产品的日益小型,轻质化,要求小型高容量Ni/MH电池配套,众所周知AB5型贮氢合金的容量已接近其理论值,进一步提升空间较小.这就促使开发有更高能量密度的新一代贮氢电极合金.对于提高容量来说,最具希望的合金之一是La-Mg-Ni系(PuNi3型)合金,但此类贮氢合金存在的主要问题是电化学循环稳定性较差.因此,开展对此系列合金的系统研究,具有重要的学术价值和良好的应用前景.
本文主要应用熔炼法和真空快淬技术制备了La-Mg-Ni系合金,用开口式三电极系统测试了合金的电化学性能,用XRD分析了合金的相组成及相结构,用SEM和光学显微镜观察了合金的微观组织形貌,用TEM观察了快淬态合金的形貌并用SAD确定其晶态.全面系统的研究了快淬工艺对贮氢合金微观结构及电化学性能的影响,得到如下一些主要结论:
1.综合研究了铸态及快淬态La2Mg(Ni0.85Co0.15)9Mx(M等于B,Cr,x等于0,0.05,0.10,0.15,0.20)合金的微观结构及电化学性能.结果表明,B,Cr的加入导致铸态合金的容量下降,快淬使不含硼合金的放电容量随淬速的增加而单调减少,含硼合金的容量随淬速的变化有一个极大值,这主要是由于快淬使Ni2B相消失,从而使LaNi2相的量下降.快淬工艺与B,Cr的加入不同程度的改善合金的循环稳定性,这主要是由于快淬使合金的晶粒细化和非晶相的形成所致.
2.研究了合金La2Mg(Ni0.85-xCo0.15Cux)9(x等于0,0.02,0.05)的微观结构及电化学性能,结果表明,随Cu含量及淬速的增加,合金的容量降低,这主要是由于快淬导致的晶格应力增加以及非晶相的形成.快淬使合金晶粒细化以及非晶相的形成是合金的循环寿命提高的重要原因.
3.导致贮氢合金失效的主要原因是在电化学循环过程中的氧化腐蚀,非晶相的形成能有效的提高合金在腐蚀性电解液中的抗氧化腐蚀性能.因此提高合金表面的抗腐蚀能力是提高La-Mg-Ni系(PuNi3型)贮氢合金循环稳定性的关键.
关 键 词:快淬,La-Mg-Ni系(PuNi3型)贮氢合金,微观结构,循环稳定性
ABSTRACT
Themobileelectronicdevicesincreasinglylessenandlightenwithadvancementofscienceandtechnology,strengthenofenvironmentalprotectionconsciousness.Ni/MHbatteryrequiresmini-typeandhighcapacity.Asweallknow,thedischargecapacityofcurrentlyadvancedAB5-typeelectrodealloyisapproachingitstheoreticalone,itseemstobeverydifficulttofurtherincreasethecapacityoftheAB5-typehydrogenstoragealloy.Therefore,newertypealloyswithhigherenergydensityareurgentlyneededtoreplacestheconventionalrare-basedAB5-typealloy.OneofthemostpromisingcandidatesistheLa-Mg-Nisystem(PuNi3-type)forincreasingthecapacity,butithasonemainquestionthatLa-Mg-Nisystemelectrodehaspoorcyclestability.Therefore,prehensiveinvestigationofLa-Mg-Nisystem(PuNi3-type)alloyhassignificantacademicvalueandexcellentapplicationfuture.
La-Mg-Nisystem(PuNi3-type)hydrogenstoragealloyswerepreparedbycastandrapidlyquenchedtechnologyatvacuumatmosphere.Theelectrochemicalperformancesoftheexperimentalalloysweremeasuredbyanopentri-electrodesystem.Themicrostructuresoftheas-castandquenchedalloyswerestudiedsystematically:thephasestructureswereanalyzedbyXRD,themicrostructuresandmorphologiesofthealloyswereobservedbySEMandOpticsmicroscope,Thecrystallinestateandmorphologiesoftheas-quenchedalloysweredeterminedbyTEMandSAD.Theinfluencesofrapidlyquenchedtechnologyonthemicrostructuresandelectrochemicalperformancesoftheexperimentalalloyswereresearchedindetail,andsomeimportantconclusionwereobtained:
1.Themicrostructuresandelectrochemicalperformancesoftheas-castandquenchedLa2Mg(Ni0.85Co0.15)9Mx(M等于B,Cr,x等于0,0.05,0.10,0.15,0.20)alloysweresyntheticallyinvestigated.TheobtainedresultsshowthattheadditionsofB,Crdecreasecapacityoftheas-castalloy.Thedischargeoftheas-quenchedalloywithoutboronmonotonouslydecreaseswiththeincreaseofquenchingrate,whereasthedischargecapacityoftheas-quenchedalloycontainingboroncanattainamaximumvalueforagivenquenchingrate.ItisascribedtorapidquenchingleadstoadistinctdecreaseoftheNi2Bphase,anddecreasestheamountoftheLaNi2phase.RapidlyquenchedtechnologyandtheadditionsofB,Crcanslightlyenhancethecyclestabilityofthealloy,itismainlyattributedtotheformationofgrainrefinementandamorphousphaseproducedbyrapidquenching.
2.Themicrostructuresandelectrochemicalperformancesoftheas-castandquenchedLa2Mg(Ni0.85-xCo0.15Cux)9(x等于0,0.02,0.05)alloyswereinvestigated.TheobtainedresultsshowthatthecapacityofthealloydecreaseswiththeincreaseofCucontentandquenchingrate,thisismainlyattributedtotheincreaseofthelatticestressandtheformationoftheamorphousphaseafterrapidquenchingtreatment.Theimportantcauseofenhancingthecyclelifeofthealloyistheformationofgrainrefinementandamorphousphaseproducedbyrapidquenching.
3.ThecausesleadingtotheLa-Mg-Nisystem(PuNi3-type)hydrogenstoragealloyefficacylossistheoxidationandcorrosionofthesurfaceofthealloyelectrodeinprocessoftheelectrochemicalcycling.Theformationofamorphousphasecaneffectivelyimprovetheanti-oxidationandcorrosioncapabilitiesofthealloyimmergedincorrosiveelect
电化学有关论文范文素材,与硕士生学位文开题相关毕业论文格式范文参考文献资料：