碳纳米管的制备和应用

CONTENTBackgroundCarbonNanotubes(CNTs)HistoryandApplicationsTheFormationofCNTsonBimetallicAlloys-StructureControl-ReactionConditionsControl-MechanismsConclusionsMg2Ni(200)Mg2Ni(110)Mg2Ni(213)Mg2Ni(216)MgxNi(1-x)O(311)MgxNi(1-x)O(400)Figure1.TEMmicrographsofnano-MgNialloyaftercalcinedwithvacuumat500℃for5hr(a)andcorrespondingSADpattern(b).Thescalebaris20nmNano-MgNiAlloyCatalyst20304050607080Ni(111)RawMg-NiAlloyCalcinedwithvaccumat500oCfor5hrNi(200)(220)MgxNi(1-x)ONi(200)Ni(111)MgxNi(1-x)O(200)(111)MgxNi(1-x)OIntensity2ThetaFigure2.XRDresultsofnano-MgNialloybeforeandaftercalcinedwithvacuumat500℃for5hr.XRDPatternsofNano-MgNiAlloyCarbonnanotubeis1-Dhollowstructure,thewallsconsistofhexagoncarbon.ThecapsofCNTarehalfcagesofC60(fullerene)AtomicstructureofCNT(a)armchair(b)zig-zag(a)C60(b)C36(c)C20CarbonNanotubeStructuresArcDischargeSyntheticMethodsofCarbonNanotubeSyntheticMethodsofCarbonNanotubeLaserVaporizationCVDSystemForCNTsGrowth-Typicalgrowthprocedure:Catalystweight=50mgcatalystCH4flowrate=100sccmGrowingtemperature=670℃,30minChangeconditions:(a)CH4concentration(b)CH4flowrate(c)Catalystweight(d)Temperature(e)H2additioneffectVacuumPumpGasVentQuartzBoatFurnaceQuartzTubeArH2CatalystMFCCH4ReactionConditionsControl600℃Ar10℃/minReactionTemperatureH250sccm30minAr5℃/minFlowingCH4Temp.Time(min)ThereactortemperatureisanimportantfactortosynthesizeCNTs.ThedifferentreactingprocessesrequireaproperreactingtemperaturetogrowCNTS.ItappearsthattheCNTsgrowat640℃,andonlyimpurecarbonaceouscomponentsformatothertemperatures.Therefore,theoptimumtemperatureregionsoftheformationoftheCNTsinthisstudyisabout640℃～670℃ContinuousTEMimageofCNT(tipgrowthmode)TEMimageshowsthatcatalystiscoveredinsideofCNTTheEffectofCH4FlowRateonCNTGrowth01002003004005006007008009000102030405060708090100110a10sccmb20sccmc40sccmd60sccme80sccmf100sccmg120sccm80sccm120sccm100sccm60sccm40sccm20sccm10sccmWeight%Temperature(oC)20304050607080Catalyst(220)MgxNi(1-x)ONi(200)Ni(111)(200)MgxNi(1-x)O(111)MgxNi(1-x)OCH4=140sccmCH4=120sccmCH4=100sccmCH4=80sccmCH4=60sccmCH4=40sccmNi(220)Graphate(100)Graphate(002)CH4=20sccmCH4=10sccmIntensity2ThetaTGAresultsofCNTgrowthwithvariousCH4flowrateXRDresultsofCNTgrowthwithvariousCH4flowrateTheconcentrationgradientisreducedandtheCH4diffusionisreachedtoasteadystatewhentheflowratereachingto100-120cm3/min.Thus,theCH4conversionandcarbonyieldarenotenhancedwhentheflowrateincreasingto140cm3/min.GrowingtemperatureeffectonCNTgrowth01002003004005006007008009000102030405060708090100110670oC600oC650oC700oC550oC500oCa500oCb550oCc600oCd650oCe670oCf700oCWeight%Temperature(oC)20304050607080d=0.3409nmd=0.3411nm,33.7%d=0.3381nm,68.6%d=0.3388nm,60.5%d=0.3394nm,53.4%d=0.3411nm,33.7%Catalyst700oC670oC650oC600oC550oC500oCGraphate(100)MgxNi(1-x)O(220)Ni(200)Ni(111)(111)MgxNi(1-x)O(200)MgxNi(1-x)OGraphate(002)Intensity2ThetaXRDresultsofCNTgrowthwithvariousgrowingtemperature.TGAresultsofCNTgrowthwithvariousgrowingtemperature.Theinterlayerspacingofgraphite(002)isneartothe0.3354nmofidealgraphitecrystalat650℃,itappearsthatthegraphitizationdegreeofsynthesizedCNTishigher.TheEffectofGrowingTemperatureonCNTGrowth20304050607080WithoutH2additionH2additionGraphate(110)Ni(220)Ni(220)Graphate(004)Ni(200)Ni(200)Ni(111)Graphate(100)Graphate(100)Ni(111)d=0.3398nmd=0.3411nmGraphate(002)Graphate(002)Intensity2ThetaThetheXRDresultsindicatethattheintensityofgraphite(002)increaseswiththepresenceofhydrogenandtheinterlayerspacingshiftsfrom0.3411to0.3398nmwhichisneartotheinterlayerspacingofidealgraphitecrystal(0.3354nm).ThehydrogenadditioncanenhancethegraphitizationdegreeofsynthesizedCNTandkeepslowerresidualcatalyst.XRDresultsofCNTgrowthwithandwithouthydrogenaddition.CNTPurification0100200300400500600700800900-100102030405060708090100110dacbaRawCNTbAirTreatmentcAirandHCltreatmentsdHCltreatmentWeight%Temperature(oC)TGAresultsofCNTpurifiedwithvariousprocedures.20304050607080AirandHCltreatmentsOnlyHCltreatmentAirtreatmentRawCNTCatalystNi(200)Ni(200)(220)MgxNi(1-x)OMgxNi(1-x)O(200)MgxNi(1-x)O(111)Ni(111)Graphate(100)Ni(111)Graphate(002)Graphate(100)MgxNi(1-x)O(220)Ni(200)Ni(111)(200)MgxNi(1-x)O(111)MgxNi(1-x)OIntensity2ThetaXRDresultsofCNTpurifiedwithvariousprocedures.TEMImagesofCNTsFigure15.TEMimagesofCNTs.(a)RawCNTs,(b)purifiedwithairoxidation,(c)purifiedwithbothairoxidationandHCltreatments(a)(c)(b)InRamanspectroscopystudies,thepeakisusuallynamedD-band(Disorderband)inthevicinityof1350cm-1,andthebondischaracteristicofthesp3structure.G-band(Graphiticband)invicinityof1580cm-1incharacteristicofthesp2bondstructure.G-bandcorrespondstothedegreeofgraphitecrystallinedefectRamanSpectroscopyAnalysisRamanSpectroscopyAnalysisInRamanspectroscopystudies,thepeakisusuallynamedD-band(Disorderband)inthevicinityof~1400cm-1,andthebondischaracteristicofthesp3structure.G-band(Graphiticband)invicinityof~1580cm-1incharacteristicofthesp2bondstructure.G-bandcorrespondstothedegreeofgraphitecrystallinedefect50010001500200025003000350077455665010881335157423242673232714201568Intensity(ArbitraryUnits)RamanShift(cm-1)Vi