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1、PERGAMONCarbon39(2001)1307±1318HydrothermalsynthesisofgraphitetubesusingNicatalystJosephLibera,YuryGogotsiab,*aUniversityofIllinoisatChicago,DepartmentofMechanicalEngineering,842W.TaylorSt.(M/C251),Chicago,IL60607-7022,USAbDrexelUniversity,DepartmentofMaterialsEngineerin
2、g,Philadelphia,PA19104,USAReceived19April2000;accepted4September2000AbstractWhilemanyformsofcarbonnanotubesand®lamentouscarbonhavebeenreported,bothalargeinsidediameterandhighlygraphiticwallstructurehavenotbeencreated.Thispaperdescribessuchtubesfrom70to1300nmindiameterwhi
3、chweresynthesizedhydrothermallyintheC±H±O±Nisystemat100MPaand730±8008Cby®rstestablishingapost-pyrolysisC±H±Oequilibriumfollowedbyanincreaseinpressureduringwhichtimegrowthofgraphiticcarbonoccurred.DependingonthesizeoftheNicatalystparticles,¯ake-likegraphiteorcarbontubules
4、wereformed.Tubeswerealsosynthesizedwithoutwater,i.e.,intheC±H±Nisystem,butthesetubeshadmultipleinternalcapswhilethoseproducedwithwaterpresenthadveryfewinternalobstructionsandalargeinsidediameter.Theexceptionalqualityofthetubewallsisdemonstratedbystraightandperfectlattice
5、fringinginthetubewallsandelectrondiffractionspotpatternsfreeofdiffuseamorphousrings.Ramanspectralevidenceshowshighsimilaritytothespectraobtainedfromhighpuritynaturalgraphite.Thehighintegrityofhydrothermalnanotubesisdemonstratedbytheexistenceofliquidinclusionstrappedinsid
6、ethetubesduringsynthesis.Thepropertiesofhydrothermalgraphitetubessuggesttheiruseinnano-¯uidicdevicesandaslightweightreinforcementforcomposites.Ó2001ElsevierScienceLtd.Allrightsreserved.Keywords:A.Carbonnanotubes,Graphite;B.Hydrothermaltreatment;C.Ramanspectroscopy,Electr
7、onmicroscopy1.Introduction®rst,thelayersofgraphenecomprisingthewallsofthetubesare®niteinlength,i.e.,theyterminateonboththeThediscoveryofsinglewallcarbonnanotubeswasinnerandoutersurfacesofthetubesbyvirtueofhavingaprecededbydecadesofresearchin®lamentouscarbonconicalgeometr
8、yofarbitraryconicalangle.Suchcon®gu-withahollowarrangementofaxiallyorderedgraphenerationshavebeendescri
