高等固体物理-碳纳米管及石墨烯

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1、专题一：纳米碳管Outline•WhatareNanotubes?•Fabrication•Properties•Applications•ConclusionsWhatareNanotubes?•DiscoveredbyIijima(1991,NEC)•Rolledupsheetofgraphene•CappedattheendswithhalfafullereneMultiWalledNanotube(MWNT)•Concentrictubes~50innumber•Innerdiameters:1.5–15nm•Outerdiameters:2.5–3

2、0nmSingleWalledNanotube(SWNT)•Singleatomiclayerwall•Diameterof0.4–5nmStructureofCNT•Chiralvector-DefinedonthehexagonallatticeasCanˆwhereandmaˆaˆaˆh1212areunitvectors,andmandareintegers.nThediagramhasbeenconstructedfor(n,m)=(4,2)infigure(a).•Chiralangle,ismeasuredrelativetothedir

3、ectiondefinedbyaˆ122d.0078nnmmd:diameterarctan[3m/(m2n)]mnintergermetallicifnotsemicondutor3NomenclatureofthenanotubesCommonorientations:•Armchair(5,5)•Zigzag(9,0)•Chiral(10,5)FabricationTechniques•Arc-dischargeHe(50–760torr)–CriticallydependentonP,T,IHe+-+Goodquali

4、ty,yield+MWNT,SWNT(ModifiedV:10–30VElectrodes)I:50–300A-CoveredwithamorphousC•LaserVaporization(unclean)GraphitetargetWaterCooledNd:YAGLaserCopperCollector+LargeandalignedSWNTyield+Greatercontrolovergrowthcondition+absenceofhighelectricfield-expensiveprocessMetalNanoparticlesDCatal

5、yticDecompositionEC+SWNT,MWNTonanysubstrateOM-nanotubesweaker,oftenuncappedHydrocarbonPO-Faultygraphitization,oftenattheStipsENanotubeproperties•Electronic:–Dresselhausetal.(1995):(n-m)/3:integerMetallicconduction(allarmchairs):non-integerSemiconductor(two-thirdofzigzag,chiral)–E

6、ffectofmagneticfield•Energybandgapcanbeaffectedbyincreasingthemagneticfieldalongtheaxis–Bandgap(localbendingcurvature)-1Energybandgap–Bandgap~100meV(IRregion)B•Magnetic:–Diamagnetic–Pronouncedanisotropicsusceptibility>>

7、

8、GrapheneEEFkkxykykxNanotubeProperties:contd.•Mechanical:–

9、YoungModulus~1TPa(SWNT)and1.25TPa(MWNT)(Steel:230GPa)–HighAspectRatio:1000–10,000–Density:1.3–1.4g/cm3–MaximumTensileStrength:30GP•Thermal:–Conductivity:2000W/m.K(Copperhas400W/m.K)Nanotubetorturetest:repeatedbendingtofailure?InterestingFactsAboutTinyStripsMulti-WalledCarbonNanotub

10、esofGraphitesheets,rolled1