A Transforming Metal Nanocomposite with Large Elastic Strain(5)

REPORTS

InsitusynchrotronHE-XRDwasusedtocharacterizethedeformationandphasetransfor-mationevolutionsoftheNbnanowiresandtheNiTimatrix,duringthepretreatment(Fig.4A,inset)andthesubsequenttensilecycle(Fig.4C,inset).Afterthepretreatment,theNbnanowiressustainedanelasticcompressivestrainof–1.4%(pointD),whereastheNiTimatrixsustainedanelastictensilestrainof1%(pointE)(Fig.4A).ThereisalsosomeretainedB19′phaseinthematrix(Fig.4B).Theseresultscanbeunderstoodasfollows.Uponremovalofthepretreatmentload,theplasticallydeformedNbnanowires(AtoBinFig.4A)hinderedtherecoveryoftheNiTimatrixbecauseoftheB19′→B2transfor-mation(15,16),whichcausedlargeresidualstrainsinthenanowiresandtheSMAwithsomeretainedB19′phase.Thisdemonstratesthatstrongcouplingbetweenthenanowiresandthematrixtookplaceduringthepretreatment.Inthesubse-quenttensilecycle(Fig.4C),theelasticstrainachievedintheNbnanowireswasupto5.6%(AtoB),consistingofthepreexistingelasticcompressivestrainof–1.4%(OtoB)andanelastictensilestrainof4.2%(OtoA).TheNiTimatrixwentthroughcontinuousSIMTthrough-outthetensileloadingandexhibitedanultralowtangentialeffectivemodulus(Fig.4,DandE)ratherthanundergoinganinitialelasticdefor-mationfollowedbyanabruptSIMTtransition,aswouldoccurinamonolithicSMA(16).ThecontinuousSIMTcanbeascribedtothecontri-butionofthepreexistinginternaltensilestressandtheretainedB19′phaseinthematrix.Uponunloading,theNiTimatrixunderwentareversetransformationfromthestress-inducedmartens-itetotheparentphase(Fig.4,DandE),in-troducingasmallhysteresisinthestress-straincurveresultingfromenergydissipationduringtheprocess.TheexperimentalevidencepresentedabovedemonstratesthattheNbnanowiresex-periencedanultrawideelasticstrainof4.2%–(–1.4%)=5.6%,whichcloselymatchesthephasetransformationstrainof~7%ofNiTi.ThismatchingofelasticandtransformationstrainsresultsintheextraordinarypropertiesofNICSMA.

ReferencesandNotes

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(CambridgeUniv.Press,Cambridge,1998).

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25.D.C.Hofmannetal.,Nature451,1085(2008).Acknowledgments:WethankG.H.Wu,H.B.Xu,andY.F.ZhengforvaluablediscussionsonthedeformationmechanismofNICSMA.ThisworkissupportedbythekeyprogramprojectofNationalNaturalScienceFoundationofChina(NSFC)(51231008),theNational973programsofChina(2012CB619400and2009CB623700),andthe

NSFC(51071175,51001119,50831001,and10825419).J.L.alsoacknowledgessupportbyNSFDMR-1008104andDMR-1120901.X.D.H.acknowledgessupportbytheBeijingHigh-levelTalents(PHR20100503),theBeijingPXM201101420409000053,andBeijing211project.

D.E.B.acknowledgessupportbytheInstituteforNanoScience,Engineering,andTechnology(INSET)ofNorthernIllinois

eoftheAdvancedPhotonSourcewassupportedbytheU.S.DepartmentofEnergy,OfficeofScience,undercontractno.DE-AC02-06CH11357.

SupplementaryMaterials

/cgi/content/full/339/6124/1191/DC1MaterialsandMethodsFigs.S1toS12References(26–30)

9August2012;accepted10January201310.1126/science.1228602

TerrestrialAccretionUnderOxidizingConditions

JulienSiebert,1*JamesBadro,2DanieleAntonangeli,1FrederickJ.Ryerson2,3

Theabundanceofsiderophileelementsinthemantlepreservesthesignatureofcoreformation.

Onthebasisofpartitioningexperimentsathighpressure(35to74gigapascals)andhightemperature(3100to4400kelvin),wedemonstratethatdepletionsofslightlysiderophileelements(vanadiumandchromium),aswellasmoderatelysiderophileelements(nickelandcobalt),canbeproducedbycoreformationundermoreoxidizingconditionsthanpreviouslyproposed.Enhancedsolubilityofoxygeninthemetalperturbsthemetal-silicatepartitioningofvanadiumandchromium,precludingextrapolationofpreviousresults.WeproposethatEarthaccretedfrommaterialsasoxidizedasordinaryorcarbonaceouschondrites.Transferofoxygenfromthemantletothecoreprovidesamechanismtoreducetheinitialmagmaoceanredoxstatetothatofthepresent-daymantle,reconcilingtheobservedmantle

vanadiumandchromiumconcentrationswithgeophysicalconstraintsonlightelementsinthecore.hedepletionofsiderophile(i.e.,“iron-loving”)elementsinEarth’smantlerelativetochondritescanconstraintheredoxstateofaccretingmaterialsduringterrestrialaccretionandcoredifferentiation(1–4).Forexample,metal-InstitutdeMinéralogieetdePhysiquedesMilieuxCondensés,UniversitéPierreetMarieCurie,UMRCNRS7590,InstitutdePhysiqueduGlobedeParis,75005Paris,France.2InstitutdePhysiqueduGlobedeParis,UniversitéParisDiderot,75005Paris,France.3LawrenceLivermoreNationalLaboratory,Livermore,CA94551,USA.

*Towhomcorrespondenceshouldbeaddressed.E-mail:julien.siebert@impmc.upmc.fr

1

T

silicatepartitioningexperimentsatatmospher-icpressureindicatethattheobserveddepletionofslightlysiderophileelements(SSEs)suchasVandCrcanonly …… 此处隐藏：5390字，全部文档内容请下载后查看。喜欢就下载吧 ……