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1、NanoStructuredMaterials,Vol.11,No.8,pp.1231±1237,1999ElsevierScienceLtdPergamonCopyright©2000ActaMetallurgicaInc.PrintedintheUSA.Allrightsreserved.0965-9773/99/$±seefrontmatterPIIS0965-9773(99)00413-4STRUCTURALSTABILITYOFTITANIATHINFILMSP.I.Gouma,P.K.DuttaandM.J.MillsCenterforIndustrialSe
2、nsorsandMeasurements,TheOhioStateUniversity,Columbus,OH43210(ReceivedSeptember27,1999)(AcceptedNovember21,1999)AbstractÐThispaperstudiesthestabilityofthinfilmsofnanostructuredtitaniaatelevatedtemperatures.Thinfilmsoftitaniaareintendedforuseinmanyapplications,includinghigh-temperaturegasse
3、nsingdevices.Theinitialstructureofthefilmsconsistsofnanocrystallineanatase(;8nm).Exposureofthefilmstotemperatures.400°Cresultsinthenucleationandsubsequentrapidgrowthofrutilegrains(finalgrainsize.300nm).In-situ,hot-stageexperimentsintheTEMwerecarriedout,whichrevealeddetailsaboutthenucleati
4、onandabnormalgraingrowthprocessesinthissystem.Itisarguedthatcoarseningofthenano-structurefollowingthetransformationisacharacteristicofpolymorphicreactionsfrommetastabletostablephases.Thenucleationprocessisacriticalrate-controllingprocessformaintainingnanosizegrainsinthetransformedmaterial
5、.©2000ActaMetallurgicaInc.1.IntroductionTitaniaisawell-knownoxidesystemintendedforuseinawidevarietyofapplications.EarlierworkattheCenterforIndustrialSensorsandMeasurements(CISM)hasidentifiedtitaniaalsoasacandidatematerialforcarbonmonoxide(CO)sensingelementsoperatingathightemperaturesandho
6、stileenvironments(suchasintheautomotiveexhaustmanifold)(1).Manyoftheapplicationstitania-basedsystemsaredesignedforrequirednanocrystallinepowdermaterialshavinglargesurfacetobulkratios(e.g.sensors,catalysts,solarcells).Nanocrystallinetitaniacanbedepositedonsubstratesintheformofthickandthinf
7、ilms.Thinfilmtechnologiesarebecomingevermorepopular,sincesuchminiaturizeddesignsarefarmoreattractivethanbulkarrangementsintermsofcost,weight,andspacesavings(2).Thereexistsconsiderableinterestintheprocessingofnanostructuredtitania(e.g.sol-gelroutes(3),mesoporousªcora
