材料期刊网

铁填充碳纳米管的原位合成

祝巍 , 赵宗彬 , 邱介山

新型炭材料

以无水三氯化铁为催化剂前驱体,乙烯为碳源,采用浮游催化法成功大量合成铁填充型碳纳米管.系统地考察了催化剂输入浓度及载气种类对产物的影响.利用环境扫描电子显微镜、透射电子显微镜、X-射线衍射、拉曼光谱和振动磁强计等多种技术手段对产物进行了表征.结果表明:三氯化铁可以替代传统上惯用的有机金属化合物二茂铁作为催化剂前驱体,具有廉价、可控性好等优点,得到的碳纳米管内腔填充有连续的Fe纳米线;这些Fe填充纳米管具有超顺磁性.

关键词: 碳纳米管 , 原位填充 , 化学气相沉积 , 无水氯化铁

第四届“吴仲华奖励基金”评选出获奖者

工程热物理学报

根据《吴仲华奖励基金章程》（吴奖[2008]01号），经各高等院校、中国工程热物理学会和中国科学院工程热物理研究所认真评选和推荐，吴仲华奖励基金理事会评审并确定授予青年学者戴巍、罗坤、唐桂华“吴仲华优秀青年学者奖”，授予程雪涛等10位同学“吴仲华优秀学生奖”。

关键词: 基金 , 奖励 , 评选 , 获奖者 , 中国科学院 , 青年学者 , 物理研究所 , 高等院校

鼓泡流化床埋管磨损量及其分布的数值研究

桂南 , 樊建人

工程热物理学报

本文采用离散颗粒单元法对流化床内颗粒运动及其与固定埋管受热面的相互作用进行颗粒直接数值模拟,其中颗粒之间的碰撞采用Tsuji等提出的软球碰撞模型处理,而流场的计算采用大涡模拟,其亚网格应力为Smagorinsky涡黏性模型,流动工况为两维鼓泡流化床.磨损量的估计是基于祝京旭等人的埋管磨损试验研究的结论,并结合本文数值模拟的结果,揭示了流化床埋管磨损量及其分布的若干规律.

关键词: 流化床 , 埋管磨损量 , 离散单元法 , 大涡模拟

INVESTIGATION OF HYDROGEN INDUCED DUCTILE BRITTLE TRANSITION IN 7175 ALUMINUM ALLOY

金属学报(英文版)

桑危郑牛樱裕桑牵粒裕桑希巍。希啤。龋伲模遥希牵牛巍。桑危模眨茫牛摹。模眨茫裕桑蹋拧。拢遥桑裕裕蹋拧。裕遥粒危樱桑裕桑希巍。桑巍。罚保罚怠。粒蹋眨停桑危眨汀。粒蹋蹋希?##2##3##4##5INVESTIGATIONOFHYDROGENINDUCEDDUCTILEBRITTLETRANSITIONIN7175ALUMINUMALLOY$R.G.Seng:B.JZhong,MG.ZengandP.Geng(DepartmentofMaterialsScierce,ScienceCollege,NorthearsternUniveisity,Shenyang110006,ChinaMaruscriptreceived4September1995inrevisedform20April1996)Abstrac:Effectsofhydrogenonthemechanicalpropertiesofdifferentlyaged7175aluminumalloyswereinvestigatedbyusingcathodicH-permeation,slowstrainratetensionandsoon.Theresultsindicatethatboththeyieldstressandthepercentagereductionofareadecreasewithincreasinghydrogenchargingtime,andthedegreeofreductiondecreasesasagingtimeincreasesforthesamehydrogenchargingtime.Keywords:hydrogeninducedductile-brittletransition,7175aluminumalloy,mechanicalproperty,cathodicH-permeation1.IntroductionForalongtimehydrogenembrittlementproblemwasthoughttobeabsentinhighstrengthaluminiumalloybecausethesolutiondegreeofhydrogeninaluminumatcommontemperatureandpressureisverysmall.However,hydrogenembrittlementphenomenonwasfoundinaluminumalloyduringtheinvestigationofstresscorrosionandcorrosionfatigue[1-5].Therehavebeenonlyafewreportsofhydrogeninducedsofteningandhardening.Inthispaper,theeffectsofhydrogenonmechanicalpropertiesof7175aluminumalloywereinvestigatedbyusingcathodicalchargingwithhydrogenandslowtensiontests.2.ExperimentalProcedureTheexperimentalmaterialwas7175aluminumalloyforgingintheformofa43mminthicknessandwithcomposition(wt%).5.41Zn,2.54Mg.1.49Cu,0.22Cr,0.1Mn.0.1Ti,0.16Fe.0.11Si,balancedbyA1.Alloyplateof1.5mminthicknesswasobtainedbyhot(465℃)andtoldrollingto83%reductioninthickness.Thelongaxisofhydrogenchargedspecimensisalongtherollingdirection.Allspecimensweresolidsolutionedat480℃for70min,followedtyimmediatequenchinginwaterandthenagedat140℃for6h(A),16h(B)and98h(C).Thetreatmentof6hiscorrespondingtotheunderagedstate.16hthefirstpeak-agedstateand98hthesecondpeak-agedstate.Thespecimenswerepolishedsuccessivelyusingemerypaperbeforehydrogencharging.Thetensilespecimenswerecathodicallychargedina2NH_2SO_4solutionwithasmallamountofAs_2O_3forpromotinghydrogenabsorption,andwithacurrentdensityof20±1mA/cm￣2atroomtemperature.ThehydrogencontentanalysiswascarriedoutonanLT-1Amodelionmassmicroprobeafterthesputteringdepthreached8nm.Theioncurrentsofhydrogenandaluminuminvariousagedstateswererecordedunderthesamecondition.ThetensiletestswereperformedonanAG-10TAmodeltestmachinewhichwascontrolledbycomputer.3.ExperimentalResultsTheratioofioncurrentstrengthofhydrogentoaluminumisrelatedtohydrogenconcentrationinhydrogenchargedspecimen.TheresultswereshowninTable1Thehydrogencontentincreaseswiththeincreaseincharingtime.Ofthethreeagedstates,theunderagedspecimenhasthehighesthydrogencontent.Theratioofyieldstrengthofhydrogenchargedandunchargedspecimenschangeswithhydrogenchargingtime,asshowninFig.1Itcanbeseenthattheyieldstrengthofhydrogenchargedspecimendecreasewithincreasinghydrogenchargingtime.Atthesamechargingtime,theyieldstressdecreasestheleastinthesecondpeak-agedstate,anddecreasesthemostintheunderagedstate.Itindicatesthattheunderagedspecimenismostsensitivetohydrogeninducedsoftening,whichisconsistentwiththeresultsofanotherhighstrengthaluminumalloy[6].TherelativechangesoftheradioofreductionofareawithhydrogenchargingtimearesummarizedinFig.2,whereΨ￣0andΨ￣Harethepercentagereductionofareaofthesamplewithoutandwithhydrogenchargingrespectively.Theradioofreductionofareareduceswhenhydrogenchargingtimeincreases,andthedecreasingdegreeofreductionofareaincreaseswithincreasingagingtime,ie,,theunderagedstateisthemostsensitivetohydrogenembrittlement.4.DiscussionItisknownfromtheresultsabovethatcathodicalchargingwithhydrogenleadstotheobviousdecreaseinthetensilestrengthandplasticityThisisbecausealargeamountofsolidsolutionhydrogenentersthespecimenintheprocessofhydrogenchargingSolidsolutionhydrogenisliabletoenterthecentreofdislocationundertheactionofdislocationtrap,henceraisingthemovabilityofdislocation.Thereforethedislocationsinhydrogenchargedspecimenmoveeasierthaninunchargedspecimen.soresultinginthereductionofyieldstrength[7].Whendislocationstartstomove,thecrystallatticeresistance(P-Nforce)whichitmustovercomeisgivenby:whereμismodulusofshear,visPoissonratio,aisspanofslipplane,bisatomspanofslipdirection.Moreover.theotherresistanceofdislocationmotionmayarisefromtheelasticinteractionofdislocation,theactionwithtreedislocationandetc.,itcanbeexpressedasfollows:whereαisconstant,XisdislocationspanSotheresistanceofdislocationmotioncanbewrittenasfollows:Becausehydrogenatomsreducetheatombondingstrengthafterhydrogencharging,shearmodulusμdecreasesandresultsinthereductionoff,therebytheyieldstressdecreases.Asthecentreofdislocationistheseriousdistortionzoneoflattice.thestresscanberelaxedafterhydrogenatomstuffing,andthesystemenergydecreases.Thusthecentreofdislocationisastrongtrapofhydrogen[8].Therefore,amovabledislocationcaptureshydrogenandmigratestograinboundaries.phaseboundariesorsurfaceofthespecimen,promotingthecrackiesformationandgrowth,thuscausingthelossofplasticity.Sincethelocalenrichmentofhydrogenisrealizedbydislocationtransporting(inthestageofdeformation),thelargerthereductionofyieldstress.theearlierarehydrogenatomstransportedtotheplaceofenrichment.Inaddition,thedamageofatombondingstrengthinducedbyhydrogenmakesthefracturestressdecrease[9]:whereCHishydrogenconcentration.σ_thisfracturestrengthbeforehydrogenchargingandisfracturestrengthafterhydrogencharging.Eq.(4)showsthatthematerialsmaybefracturedatalowerstraini.e.,brittlefractureoccurs.5.Conclusions(1)Hydrogencontentofdifferentlyagedspecimensincreaseswithincreasinghydrogenchargingtimethecapabilityofthealloytoabsorbhydrogeninunderagedstateisthestrongest.(2)Theyieldstressaswellasthepercentagereductionofareaof7175aluminumalloydecreaseashydrogenchargingtimeincreasesundervariousagedstates.(3)Underagedstateismostsensitivetohydrogeninducedsofteningandhardening.(4)Anexplanationwasofferedforthephenomenonofhydrogeninducedsofteninginthestageofdeformation,andhardeninginthestageoffracture.REFERENCES｜｜1G.KKock,Corrosion35(1979)73.2M.K.TsengandH.LMarcus,Scr.Metall.15(1981)427.3PSFao.M.GaoandR.P.Wei,Scr.Metall.19(1985)265.4R.G.SongandM.K.TsengJ.NortheasternUniversity15(1994)5(inChinese).5R.K.Viswanadham,T.S.sunandJ.A.S.Green,Metall.Trans.11A(1980)85.6J.Liu,M.KTsengandB.R.Liu.NonferrousMiningandMetallrgy5(1989)33(inChinese).7LChen,WXChen,ZHLiuandZ.Q.Hu,InFrocofthe1stNationalConfonAl-LiAlloys(Sheryang.China,1991)p.328(inChinese).8Z.HLiuL.ChenW.XChenY.X.ShaoandZ.Q.Hu,InProc.ofthe1stNationalConfonAl-LiAlloys(Shenyang,China,1991)p.334(inChinese).9R.A.OrianiandF.H.Josephic,ActaMetall.22(1974)1065.##61G.KKock,Corrosion35(1979)73.2M.K.TsengandH.LMarcus,Scr.Metall.15(1981)427.3PSFao.M.GaoandR.P.Wei,Scr.Metall.19(1985)265.4R.G.SongandM.K.TsengJ.NortheasternUniversity15(1994)5(inChinese).5R.K.Viswanadham,T.S.sunandJ.A.S.Green,Metall.Trans.11A(1980)85.6J.Liu,M.KTsengandB.R.Liu.NonferrousMiningandMetallrgy5(1989)33(inChinese).7LChen,WXChen,ZHLiuandZ.Q.Hu,InFrocofthe1stNationalConfonAl-LiAlloys(Sheryang.China,1991)p.328(inChinese).8Z.HLiuL.ChenW.XChenY.X.ShaoandZ.Q.Hu,InProc.ofthe1stNationalConfonAl-LiAlloys(Shenyang,China,1991)p.334(inChinese).9R.A.OrianiandF.H.Josephic,ActaMetall.22(1974)1065.##A##BINVESTIGATION OF HYDROGEN INDUCED DUCTILE BRITTLE TRANSITION IN 7175 ALUMINUM ALLOY$$$$R.G.Seng: B.J Zhong, MG. Zeng and P. Geng(Department of Materials Scierce, Science College,Northearstern Univeisity, Shenyang 110006, China Maruscript received 4 September 1995 in revised form 20 April 1996)Abstrac:Effects of hydrogen on the mechanical properties of differently aged 7175 aluminum alloys were investigated by using cathodic H-permeation, slow strain rate tension and so on. The results indicate that both the yield stress and the percentage reduction of area decrease with increasing hydrogen charging time, and the degree of reduction decreases as aging time increases for the same hydrogen charging time.

关键词: :hydrogen induced ductile-brittle transition , null , null , null

ATOMIC FORCE MICROSCOPY OBSERVATION OF MAGNETRON SPUTTERED ALUMINUM-SILICON ALLOY FILMS

金属学报(英文版)

粒裕希停桑谩。疲希遥茫拧。停桑茫遥希樱茫希校佟。希拢樱牛遥郑粒裕桑希巍。希啤。停粒牵危牛裕遥希巍。樱校眨裕裕牛遥牛摹。粒蹋眨停桑危眨停樱桑蹋桑茫希巍。粒蹋蹋希佟。疲桑蹋停?##2##3##4##5ATOMICFORCEMICROSCOPYOBSERVATIONOFMAGNETRONSPUTTEREDALUMINUM-SILICONALLOYFILMSJ.W.Wu,J.H.FangandZ.H.Lu(NationalLaboratoryofMoleculeandBiomoleculeElectronics,SoutheastUniversity,Nanjing210096,ChinaManuscriptreceived27October1995)Abstrcat:Twodifferentsurfacemorphologycharacteristicsofmagnetronsputteredaluminumsilicon(Al-Si)alloyfilmsdepositedat0and200℃wereobservedbyatomicforcemicroscopy(AFM).Oneisirregularlyshapedgrainsputtogtheronaplane.TheotherisirregularlyshapedgrainsPiledupinspace.Nanometer-sizedparticleswithheightsfrom1.6to2.9nmwerefirstobserved.Onthebasisoftheseobservationsthegrowthmechanismofmagnetronsputteredfilmsisdiscussed.Keywords:magnetronsputtering,Al-Sialloy,surfacemorphology,atomicforcemicroscopy,filmgrowthmechanism1.IntroductionTheuseofaluminumalloys[1,2],inparticularAl-Si,isacommonfeatureinmanysinglelevelandmultilevelinterconnectionschemesadoptedinthemanufactureofmicroelectronicdevicesbecauseofseveraldesirableproperties.TheAl-Sigrainmorphology(size.geometryanddistributionofgrainsisassociatedwithstepcoverage[3],electromigration[4]andinterconnectsresistivity[5]etc..Thus,characterizationofAl-Sialloysurfacemorphologyisveryimportant,especiallywhenintegratedintensityincreasesandlinewidthsof0.3to0.5μmbecomecommon.Inthepasttwentyyears,theAl-Sialloysurfacemorphologywhichaffectsthereliabilityofmicroelectronicdeviceshasbeenwidelyinvestigatedbyscanningelectronmicroscopy(SEM),transmissionelectronmicroscopy(TEM)etc.[5-7].However,SEMandTEMhavetheirlimitationorinconvenience,forexample,theverticalresolutionofSEMisnothighandTEMneedscomplexsamplepreparation.Recently,anewgrainboundaryetchingmethodwasproposed￣[8]whichalsoneedstroublesomechemicaletching.Atomicforcemicroscopy(AFM),sinceitsemerging,hasbecomemoreandmoreusefulinphysics,chemistry,materialsscienceandsurfacescience,becauseofitshighresolution,easeofsamplepreparationandrealsurfacetopography.Recently,discussion[9,10]waspresentedonhowAFMwillplayaroleinsemiconductorindustry.Asaresponsetothisdiscussion,weusedAFMtoinvestigateAl-SialloysurfacemorphologyandhaveobtainedsomeresultswhichcannotberevealedbySEMorTEM.ThisindicatesthatAFMisagoodcharacterizationtoolinsemiconductorindustry.2.SamplePreparationInourexperiments,aluminumwith30ppmsiliconwassputteredonsiliconsubstrateinbatchdepositionmodeAllthreefilmswiththicknessof1.6μmweredepositedusinganargonsputteringpressureof4.2×10￣-3Pa.TheotherdepositionparametersaredescribedinTable1.Thesubstratewascleanedusingstandardpremetallizationcleaningtechniquespriortofilmdeposition.3.ExperimentalResultsandDiscussionTheAFMmeasurementswereperformedonacommercialsystem(NanoscopeIII,DigitalInstruments,SantaBarbara).Thetipismadeofmicrofabricatedsiliconnitride(Si_3N_4)Itisattachedtoa200μmcantileverwithaforceconstantofabout0.12N/m.Beforethesurfaceofsamplewasexamined.agoodtipwithananometer-sizedprotrusionatitsendwasselectedbeforehand,whichcanbeobtainedbyimagingtheatomicstructureofmicasubstrateandagoldgrid.AtypicaloperatingforcebetweenthetipandAl-Sisamplesurfaceisoftheorderof10￣-8Nandallimagesweretakenatroomtemperatureinair.AtypicaltopographicviewoftheAl-SifilmsisshowninFig.1(allimagescansizeis5by5μma,bandcarerespectivelyforsample1,2,and3).FromFig.la,itcanbeseenthatirregularlyshapedgrainstiltinginvaryingdegreespileupinspace,andgroovesamongtheirregularlyshapedgrainsaredifficulttodecideatacertainarea(wedefineitascharacteristicA).Toourknowledge,onreportsonthesurfacemorphologyhavebeenpresentedbefore.InFig1b,however,irregularlyshapedgrainsassembleonaPlaneandgroovesamongtheirregularlyshapedgrainsareeasytodecide(wedefineitascharacteristicB),whichisinagreementwithmanypreviousreports[5-7].InFig.1c,bothcharacteristicA(arrowA)andcharacteristicB(arrowB)wereobserved.IndoingAFMexperiments,weselectedfivedifferentscanareastobeimagedforeachsampleandfoundthatallimagesofeachsamplearerespectivelysimilartoFig.1a,bandc.Also,wenotedthatthesurfaceofinFig.1a.WethinkthatdepositionparameterswillinfluenceAl-Sisurfacemorphology,andthetiltedgrainsmaybesusceptibletomicrocracking.Byreducingthescansizeareato2by2μm(Fig.2aandb).Weobtainedmanyidenticalresultsasdescribedabove,suchasirregularlyshapedgrainsetc.Forthefirsttime,wefoundnanometersizedparticlesonirregularlyshapedgrainsurfacewhichcannotberevealedbySEMbecausethediameterofthesenanoparticlesisabout10nmandtheheightofthesenanoparticlesisintherangeof1.6to2.9nm.Inimaging,wenotedthatrotatingthescandirectionandchangingthescanfrequencydidnotaffectthestructureofthesegrainsasshowninFig.2aandb,rulingoutthepossibilitythatscanninginfluencedtheshapeoftheseparticlesorcausedsomesimilarimagingartifacts.Also,wenotedthatthenanoparticleswerenotobservedontheslopesofthegrooves(Fig.2aandb).Thisphenomenoncanbeexplainedasfollows:thepotentialenergyattheslopeislargerthanthatelsewhere,sotheparticlesseemmorelikelytobedepositedontheseareaswithlowerpotentialenergy.Fig.2c,scansize250by250nm,isazoomtopographicimage(whiteoutlineinb).Itshowsunevendistributionofthenanoparticles.Andtheheightdifferenceofthenanoparticlesindicatesdifferentgrowingspeed.Wethinkbasedonthemorphologyofnanoparticles,thattheheightdifferenceandunevendistributionofthesenanoparticlesshowdifferentgrowingadvantageandindicatethatatomshaveenoughenergytomovetoasuitablegrowingspot.Theenergymaybefromthefollowingsources:surfacetemperaturefluctuation,stressdifferenceorcollisionbetweenhighspeedsputteredatoms.Thesenanoparticlesgoongrowingandformmanyirregularlyshapedgrains.AndtheseirregularlyshapedgrainsfurtherconnecteachotheraccordingtocharacteristicAorB,finallyformingtheAl-Sisurfacemorphology.4.ConclusionWecandrawthefollowingconclusionsfromtheabove.First,theexperimentalresultsshowedthatAFMisapowerfultooltoinvestigatethedetailsofAl-Sisurfacemorphologywhichcangreatlyenrichourknowledgeofthefilmgrowthmechanism.Second,depositionconditionsplayanimportantroleindeterminingtheAl-Sisurfacemorphology.Third,thetwoAl-Sisurfacemorphologycharacteristicsarethatirregularlyshapedgrainsassembleonaplaneandirregularlyshapedgrainstiltinginvaryingdegreespileupinspace.Fourth,forthefirsttime,nanoparticleswereobservedonirregularlyshapedgrainsurfacewhichsuggestedthatthefilmgrowthmechanismwasbyinhomogeneousnucleation.Acknowledgements-BeneficialdiscussionswereheldwithDr.ZhenandMr.Zhu.ThisworkwaspartiallysupportedbytheNationalNaturalScienceFoundationofChina.RFFERENCES｜｜1D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)127.2D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)131.3D.pramanikandA.N.Saxena,SolidStateTechnol.33(1990)73.4S.S.IyerandC.Y.Worg,J.Appl.phys.57(1985)4594.5J.F.Smith,SolidStateTechnol.27(1984)135.6D.GerthandD.Katzer,ThinSolidFilm208(1992)67.7R.J.WilsonandB.L.Weiss,ThinSolidFilm207(1991)291.8E.G.Solley,J.H.Linn,R.W.BelcherandM.G.Shlepr,SolidStateTechnol33(1990)409I.SmithandRHowland,SolidStateTechnol.33(1990)53.10L.Peters,SemiconductorInternational16(1993)62.##61D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)127.2D.pramanikandA.N.Saxena,SolidStateTechnol.26(1983)131.3D.pramanikandA.N.Saxena,SolidStateTechnol.33(1990)73.4S.S.IyerandC.Y.Worg,J.Appl.phys.57(1985)4594.5J.F.Smith,SolidStateTechnol.27(1984)135.6D.GerthandD.Katzer,ThinSolidFilm208(1992)67.7R.J.WilsonandB.L.Weiss,ThinSolidFilm207(1991)291.8E.G.Solley,J.H.Linn,R.W.BelcherandM.G.Shlepr,SolidStateTechnol33(1990)409I.SmithandRHowland,SolidStateTechnol.33(1990)53.10L.Peters,SemiconductorInternational16(1993)62.##A##BATOMIC FORCE MICROSCOPY OBSERVATION OF MAGNETRON SPUTTERED ALUMINUM-SILICON ALLOY FILMS$$$$J.W.Wu,J.H. Fang and Z.H.Lu (National Laboratory of Molecule and Biomolecule Electronics,Southeast University,Nanjing 210096, China Manuscript received 27 October 1995)Abstrcat:Two different surface morphology characteristics of magnetron sputtered aluminumsilicon(Al-Si)alloy films deposited at 0 and 200℃ were observed by atomic force microscopy(AFM).One is irregularly shaped grains put togther on a plane.The other is irregularly shaped grains Piled up in space. Nanometer-sized particles with heights from 1.6 to 2.9 nm were first observed. On the basis of these observations the growth mechanism of magnetron sputtered films is discussed.

关键词: :magnetron sputtering , null , null , null , null

CRYSTALLIZATION OF Fe_(38)Ni_(39)Si_(10)B_(13) METALLIC GLASS UNDER HELIUM ION IRRADIATION

金属学报(英文版)

茫遥伲樱裕粒蹋蹋桑冢粒裕桑希巍。希啤。疲錩(38)Ni_(39)Si_(10)B_(13)　METALLIC　GLASS　UNDER　HELIUM　ION　IRRADIATION##2##3##4##5CRYSTALLIZATIONOFFe_(38)Ni_(39)Si_(10)B_(13)METALLICGLASSUNDERHELIUMIONIRRADIATION$YANGQifa(ChinaInstituteofAtomicEnergy,Beijing)ZHANGGuoguang;SHENWanshui(UniversityofScienceandTechnologyBeijing)Manuscriptreceived20February1995ThecrystallizationfeaturesofFe38Hi39Si10B13metallicglassunder100keVand6μA/cm2heliumionirradiationwithdifferentdosesarereported.ItisfoundthattheFe38Ni39Si10B13metallicglasscrystallizedundertheheliumionirradiationatthetemperaturelowerthantheordinarythermalcrystallizationtemperature.ThepreferentialprecipitationphaseisFeSi,andfollowedbytheeutecticphaseα-Fe.Thecriticaldosefortheformationofheliumbubblesinthematerialisaround5x10￣16/cm2.Thesensitivityofcrystallizationduetothetemperaturerisingunderheliumionirradiationandthemechanismofthesequenceofprecipitatedphasearebrieflydiscussed.Keywords:Fe38Ni39Si10B13,metallicglass,crystallization,helium,ionirradiationTheblisteringorflakingoffirstwallmaterialsinducedbyheliumionbombardment,whichisrelevanttothefirstwallsurfaceerosionandplasmacontamination,isacriticalproblemtobeconsideredinfusionengineering.Becauseofthefavourablyphysical,chemicalandotherproperties,especially,thebetterresistanceofblistering,metallicglassesareexpectedtobeapromisingcandidatematerialforthefirstwall.TyagiandNanderkarstudiedsystematicallytheblisteringphenomenaofsomemetallicglassmaterialsunderheliumionandprotonbombardmentwithvariousionenergy,ioncurrentdensityanddose,andfoundthecriticaldoseforblisteringofthesematerials[1-3].However,itisverysuspiciousthatmetallicglasseswillcrystallizeunderheliumionirradiationtolosetheiramorphouscharacter,whichwilldeterioratetheirproperties.GusevaandGordeevareportedthatFe40Ni40B20metallicglassbombardedbyheliumionwithenergyof40keVandionbeamcurrentdensitiesof5-40μA/cm2partiallycrystallizedbelowitsordinarythermalcrystallizationtemperature[4].ByusingXRDexamination,itwasfoundthatα-FeandM3B,M2BandMBwereprecipitated(whereM=FeandNi)underheliumionbombardmentwith5μA/cm2and100μA/cm2ioncurrentdensitiesrespectively.Nevertheless,TyagiandNanderkarfoundthatsomemetallicglassescrystallizedandsomedidnotundersameirradiatedparameters[1-3].Consequently,itisnecessarytoinvestigatetheirradiation-assisted-crystallizationfeatureofmetallicglassesbyheliumionirradiationfortheirapplicationinfusionengineering.Inpresentexperiment,thecrystallizationfeatureofFe38Ni39Si10B13metallicglassunderheliumionirradiationwithenergy100keVandvariousdosesintherangeof5×1016/cm2to1×1018/cm2,andthedistributionofheliumbubblesinmaterialaremeasuredbyusingtransmissionelectronmicroscope(TEM)andX-raydiffraction(XRD).1.ExperimentalApproachTheas-receivedFe-Ni-Si-Bmetallicglassribbonswith10mminwidthand0.2mminthicknessweresuppliedbyBeijingInstituteofMetallurgy.Thenominalcomposition(wt%)ofthematerialisNi47.37,Fe43.91,Si5.81andB2.91fromthechemicalanalysisandthecalculatedconstituentisFe38Ni39Si10B13.TheX-raydiffractogramofas-receivedmaterialdemonstratedthattheas-receivedmaterialhasagoodamoophouscharacter.Thetheimalcrystallizationprocessoftheas-receivedmaterialwastestedbydifferentialthermalanalysis(DTA).Theordinarythermalcrystallizationtemperaturewasdeterminedtobeabout490℃.Rectangularsampleswithanareaof1×2cmanddiscsampleswith3mmindiameterwereemployedrespectivelyforXRDandTEMexperiments.ThesamplesforXRDweremechanicallypolishedtomirrorsurfaee.Ontheotherhand,formakingTEMsamples,thepiecescutfromtheribbonwerethinnedto30μmthicknessfirst,thenpunchedout3mmdiscs,electrothinnedinamixedsolutionof10%perchloricacidand90%ethanolandfinally,thediscswereionmilledtoextendthethinarea.HeliumionirradiationofsampleswascarriedoutonTS51-200/ZKionimplanterinChinaInstituteofAtomicEnergy.ThesampleswerefixedonacopperholderwhichwascooledbyF-113coolant.Thevacuumintargetwasbetterthan3×10-3Paandthescanningareaofionbeamwasabout3×7cm.Thetemperatureridingofthesamplescausedbyionbeambombardmentwasmeasuredbythermalcouple.Undertheirradiationparametersofionbeamenergy100keVandionbeamcurrentdensity6μA/cm2,thetemperaturerisingofsampleswaslowerthan200℃.Theiondosesofimplantedsampleswerechosenfrom5×10￣16/cm2to1×10￣18/cm2inpresentexperiment.AJEOL-100CXTEMoperatedat100kVwasused.Thecalculatedmeanprojectrangeandrangestragghngofheliumionwithenergy100keVinthematerialwere306.9nmand85.5nmrespectively,whichwassimulatedbycodeTRIM86.2.Results2.1CrystallizationunderionirradiationTheselectedareadiffraction(SAD)patternsofun-irradiatedandirradiatedsamplesareshowninFig.l.Fortheun-irradiatedsample,thepatterniscomposedoftwoconcentricringswhichexhibitatypicalamorphousdiffractionfeature(Fig.la).Ontheotherhand,forirradiatedsamples,agroupofnewconcentricringsappearsonthebaseofamorphousdiffractionrings,whichmeanstheoccurrenceofpartialcrystallizationandtheformationofsomenewprecipitationphasesinoriginalamorphousmaterialsbyionirradiation.Withtheincreaseofiondose,theinitialamorpohousdiffractionringsbecomefainterandtheintensitiesofdiffractionringsprodueedbyprecipitatesdevelopehigher.Itisexpectedthatthecrystallizationinsamplesincreaseswiththeincreaseiniondose.Moreover,iftheiondoseislowerthan5×10￣17/cm2,thepatternsshowtypicalpolycrystallinediffractionfeaturewithrandomorientationandveryfinegrains(Figs.lbandlc),butfor1×10￣18/cm2iondose,somebrightspotsarise(Fig.ld),thismeansthatsomerelativelargegrainsformedinsampleunderirradiation.FromtheX-raydiffractogramofthesampleirradiatedbyheliumiontodoseof5×10￣17/cm2,thediffractionpoaksarestillamorpohousfeatureandnonewpeaks.Itispredictedthatthecrystallizationonlyoccursintheprojectedrangeofions.2.2AnalysisofprecipitationphaseFromindexingofdiffractionringsinFig.lbandFig.lc,theprecipitatephaseisanfcccrystallinestructure.InFig.ld,anadditionalbccphaseisfound(ring3,ring5andring8).Thecalculatedlatticeparametersforprecipitatephasesundervariousiondosesareasfollows:5×1016/cm2a=0.412nm(fcc)l×1017/cm2a=0.42lnm(fcc)5×1017/cm2a=0.428nm(fcc)l×1018/cm2a=0.478nm(fcc)a=0.292nm(bcc)UsingASTMindex,itisidentifiedthatthebccphaseisα-Fe(a=0.2866nm).Todeterminethefccprecipitatephase,weinspectedallcompoundswithfcccrystallinestructurecomposedofelementsFe,Ni,SiandB,foundthatthreecompoundsFeSi(a=0.446nm),FeNi3(a=0.353nm)andFe3Si(a=0.564nm),butthemostfavourablecompoundwasFeSi.Therefore,itisassumedthatthepreferentialprecipitatephaseisFeSi,andisfollowedbytheeutectcphaseα-Feundertheheliumionirradiation.2.3HeliumbubbledistributionThemorphologiesofheliumbubblesformedbyagglomerationofimplantedheliumionsareshowninFig.2.Thesmallblackdotspresentbubblesunderbrightfieldwiththeunderfocusingoperation.FromFig.2,itisrevealedthatbubbleslowerthedensity,butinflateinthedimensionwiththeincreaseiniondose.Moreover,underthehigherdosethebubblesjoinedtogether.Fig.3plotsthechangesofdensitiesanddiametersofbubbleswiththeiondose.ItisevidentthatthecriticaldosetoformbubblesinFe38Ni39Si10B13islowerthan5×1016/cm2,whichisslightdifferentfrom1×1017/cm2reportedbyTyagi[1].3.DiscussionAstheresultsreportedbyGusevaandGordeeva[4],theheliumirradiationcantrulybringonthepartialcrystallizationinmetallicglassFe38Ni39Si10B13belowitsordinarythermalcrystallizationtemperature.GusevaandGordeevaconfirmedthattheprecipitatesinFe40Ni40B20wasα-Fephaseunderheliumionirradiationof40keVenergyand5μA/cm2currentdensity,inwhichthetemperaturerisingofthesampleswaslowerthan200℃.Howerve,inpresentexperiment,thoughα-Fephaseisdetermined,notraceofM3B,M2BandMBprecipitatephaseisobserved,whichwasreportedbyaboveauthorsunderirradiationwithenergyof40keVandioncurrentdensityof30μA/cm2.Inaddition,theprecipitationprocessinpresentexperimentissomewhatdifferentfromtheprecipitationprocessreportedbyaboveauthors,thepreferentialprecipitationphaseisFeSi,andfollowedbytheeutecticphaseα-Fe.CrystallizationofamorphousFe40Ni40B20wasnotobservedbyTyagi,whichwasthesamematerialasthatusedbyGusevaandGordeeva,undertheirradiationwith100keVionenergyand30μA/cm2ioncurrentdensity[3].Itmayrelatetothetemperaturerisingofsamplesorsomethingelse.Accordingtothecomparisonandanalysis,itmaybeconcludedthatthecrystallizationofmetallicglassesisverysensitivetothetemperaturerisinginsamplescausedbyionbeamirradiation.ThereasonofthepreferentialphasetobeFeSiandfollowedα-Femaybethatinanamorphousmaterial,themetalloidelementsshouldkeepatthetotalcontentsabove20at%,otherwisesomeelementsorcompoundswillprecipitatetoremainthebalanceofchemicalcomposition.Therefore,astheprecipitationofFeSianddeclineofSicontentsinasample,FeandNimayprecipitateasaneutecticphaseaccordingtoaboveidea.Inthisexperiment,Feprecipitatedfirstly.ThedifferenceoflatticeparametersbetweenexperimentaldataandASTMstandarddatamayresultsintheexistencesofNiandBetcandincompletecrystallizationinsample.Thegeneralviewpointforirradiation-assisted-crystallizationofmetallicglassbelowtheirthermalcrystallizationtemperatureisthedisplacementdamagesinducedbycollosion-cascadebetweenincidentionsandtargetatoms.Thedisplacementdamagesprovidethenucleatingcentresandtheirradiation-assistedmigrationincreasesthecrystallizeddrivingforce,butnodirectrelationshipbetweenheliumandcrystallization.Thegrowthofagrainiscloselyattributedtothediffusionofneighbouringatomstothegrowingnucleus,whichisreliedonthetemperatureextremely,accordingly,thecrystallizationofmetallicglassisverysensitivetothetemperaturerisingfromionbeambombardmentinanirradiatedsample.4.Summary(l)TheFe38Ni39Si10B13metallicglasswillcrystallizebelowitsordinarythermalcrystallizationtemperatureunderheliumionirradiationwith100keVenergyand6μA/cm2ionbeamcurrentdensity.(2)ThepreferentialprecipitationphaseofthemetallicglassisFeSi,andfollowedbyaneutecticphaseα-Fe.(3)Thecriticaldoseformingheliumbubblesinthemetallicglassisabout5×1016/cm2,whichisslightlylowerthanthedosereportedbyTyagi.(4)Theirradiation-assisted-crystallizaofametallicglassesisverysensitivetothetemperaturerisingcausedbyionbeambombardmentinanirradiatedsample.Acknowledgements─TheauthorswouldliketothankthecolleaguesofIonImplantationGroupinChinaInstituteof.AtomicEnergy.forhelpinginsampleirradiation,alsotoProfe

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