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1、UNIT–IIICARBONNANOSTRUCTURESSPECIALNANOMATERIALS:Introduction:Inthepreviouschapters,wehaveintroducedthefundamentalsandgeneralmethodsforthesynthesisandfabricationofvariousnanostructuresandnanomaterialsincludingnanoparticles,nanowiresandthinfilms.However,thereareanumberofimportantnanomateri
2、alsnotincluded,sincetheirsynthesisisuniqueanddifficulttogroupintopreviouschapters.Examplesofsuchnanomaterialsarecarbonfullerenesandnanotubes.Inaddition,bulkmaterialswithnanosizedbuildingblocks,suchasnanograinedceramicsandnanocompositeshavenotbeendiscussedsofar.Inthischapter,wewilldiscusst
3、hesynthesisofthesespecialnanomaterials.Mostofthesenanomaterialsareunique,donotexistinnature,andaretruly“man-made”relativelyrecently,therefore,abriefintroductiontothematerials,suchastheirpeculiarstructuresandproperties,hasalsobeenincludedinthischapter. Carbonisauniquematerial,and
4、canbeagoodmetallicconductorintheformofgraphite,awidebandgapsemiconductorintheformofdiamond,orapolymerwhenreactedwithhydrogen.Carbonprovidesexamplesofmaterialsshowingtheentireregimeofintrinsicnanometerscaledstructuresfromfullerenes,whicharezero-dimensionalnanoparticles,tocarbonnanotubes,on
5、e-dimensionalnanowirestographite,atwodimensionallayeredanisotropicmaterial,tofullerenesolids,athreedimensionalbulkmaterialswiththefullerenemoleculesasthefundamentalbuildingblockofthecrystallinephase.Carbonfullerenes:Carbonfullerenecommonlyreferstoamoleculewith60carbonatoms,C60,andwithanic
6、osahedralsymmetry,butalsoincludeslargermolecularweightfullerenesCn(n>60).ExamplesoflargermolecularweightfullerenesareC70,C76,C78,C80,andhighermassfullerenes,whichpossessdifferentgeometricstructures,e.g.C70hasarugby-ballshapedsymmetry.ThefollowingfigureshowsthestructureandgeometryofC60mole
7、cule.Figure:TheicosahedralC60molecule.ThenameoffullerenewasgiventothisfamilyofcarbonmoleculesbecauseoftheresemblanceofthesemoleculestothegeodesicdomedesignedandbuiltbyR.BuckminsterFuller,whereasthenameofBuckminsterFullereneorbuckyballwasspecificallygiventotheC60mole
