Introduction
In1985,ProfessorKroto,aspectrographerfromtheUniversityofSussexintheUnitedKingdomandProfessorSmalleyandCurlfromRiceUniversityintheUnitedStates,foundthatcarboncanbeformedbyC60andC70moleculeswithahighlysymmetricalcagestructurecomposedof60or70carbonatomsarecalledBuckyballs.In1991,Iijima,aJapaneseNECscientist,usedahigh-resolutiontunnelelectronmicroscopeforthefirsttimeinthepreparationofC60cathodescarsanddiscoveredacarbonwithanouterdiameterof515nmandaninnerdiameterof213nm,whichiscomposedofonlytwolayersofcoaxialgraphite-likecylindricalsurfaces.nanotube.Thenin1993,theresearchteamofIijimaandBethunesimultaneouslyreportedthesynthesisofsingle-walledcarbonnanotubeswithaverysimplestructure,whichprovidedexperimentalpossibilitiesfortheoreticalpredictionoftheperformanceofcarbonnanotubes,andfurtherbroadenedtherangeofcarbonclustermaterials.Ithasalsogreatlypromotedthetheoreticalandexperimentalresearchoncarbonnanotubes,makingthisfieldahotspotinglobalresearchtoday.
Characteristics
Theuniquestructureofcarbonnanotubesdeterminesthatithasmanyspecialphysicalandchemicalproperties.TheC=Ccovalentbondthatmakesupcarbonnanotubesisthemoststablechemicalbondinnature,socarbonnanotubeshaveveryexcellentmechanicalproperties.Theoreticalcalculationsshowthatcarbonnanotubeshaveextremelyhighstrengthandgreattoughness.ThetheoreticalvalueestimatesthattheYoung'smoduluscanreach5TPa,thestrengthisabout100timesthatofsteel,andtheweightdensityisonly1/6thatofsteel.Forthefirsttime,Treacyetal.usedTEMtomeasurethemeansquareamplitudeofmulti-walledcarbonnanotubesinthetemperaturerangefromroomtemperatureto800degrees,anddeducedthattheaverageYoung'smodulusofmulti-walledcarbonnanotubeswasabout1.8Tpa.Salvetatetal.measuredtheYoung'smodulusofsmalldiametersingle-walledcarbonnanotubesandderiveditsshearmodulusas1Tpa.Wongetal.usedanatomicforcemicroscopetomeasuretheaveragebendingstrengthofmulti-walledcarbonnanotubestobe14.2±10.8GPa,whilethebendingstrengthofcarbonfiberwasonly1GPa.Carbonnanotubesarefarsuperiortoanyfiberintermsofstrengthandtoughness,andareconsideredtobethe"superfiber"inthefuture.
Developmentprospects
Itispredictedthatcarbonnanotubesmaybecomeanewtypeofhigh-strengthcarbonfibermaterial,whichnotonlyhastheinherentnatureofcarbonmaterials,butalsohastheelectricalandthermalconductivityofmetalmaterials.,Theheatandcorrosionresistanceofceramicmaterials,theweaveabilityoftextilefibers,andthelightweightandeasyprocessingofpolymermaterials.Usingcarbonnanotubesasacompositematerialreinforcementisexpectedtoexhibitgoodstrength,elasticity,fatigueresistanceandisotropy.Itcanbeexpectedthatcarbonnanotubereinforcedcompositematerialsmaybringaleapincompositeperformance.Theresearchonusingnanotubestomakecompositematerialswasfirstcarriedoutonmetalsubstrates,suchas:Fe/carbonnanotubes,Al/carbonnanotubes,Ni/carbonnanotubes,Cu/carbonnanotubes,etc.Theresearchfocusofcarbonnanotubecompositematerialshasshiftedtopolymer/carbonnanotubecompositematerials.Forexample,inlightweightandhigh-strengthmaterials,carbonfiberisusedasareinforcingmaterial.ThemechanicalpropertiesofcarbonnanotubesandtheirsmalldiameterandlargediameterTheaspectratiowillbringbetterenhancementeffect.