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US 2020/0051709A1 Feb.13,2020 3 andgraphite(3-Dgraphiticmaterial).Thecarbonnanotube havinglowerbutnon-zerooxygencontent.Aditionaly, (CNT)referstoatubularstructuregrownwithasinglewal bothGOandRGOcontainahighpopulationofedge-and ormulti-wal.Carbonnanotubes(CNTs)andcarbonnano surface-bornechemicalgroups,vacancies,oxidativetraps, fibers(CNFs)haveadiameterontheorderofafew andothertypesofdefects,andbothGOandRGOcontain nanometerstoafewhundrednanometers.Theirlongitudi oxygenandothernon-carbonelements,e.g.hydrogen[Ref. nal,holowstructuresimpartuniquemechanical,electrical andchemicalpropertiestothematerial.TheCNTorCNFis aone-dimensionalnanocarbonor1-Dnanographitemate rial. [034] Bulk naturalflake graphite isa3-D graphitic materialwitheachparticlebeingcomposedofmultiple grains(agrainbeingagraphitesinglecrystalorcrystalite) 14;J.B.Wu,etal].Incontrast,thepristinegrapheneshets arepracticalydefect-freandcontainnooxygen.Hence, GOandRGOarecommonlyconsideredinthescientific communityasaclasof2-Dnanomaterialthatisfunda mentalydiferentanddistinctfrompristinegraphene. [038]ItmaybefurthernotedthatCVDgraphenefilms, althoughrelativelyoxygen-fre,tendtocontainasignificant withgrainboundaries(amorphousordefectzones)demar amountofothernon-carbonelements,suchashydrogenand catingneighboringgraphitesinglecrystals.Eachgrainis nitrogen.CVD grapheneispolycrystalineandcontains composedofmultiplegrapheneplanesthatareoriented manydefects,e.g.,grainboundaries,linedefects,vacancies, paraleltooneanother.Agrapheneplaneinagraphite andotherlaticedefects,suchasthosemanycarbonatoms crystaliteiscomposedofcarbonatomsoccupyingatwo thatarearangedinpentagons,heptagonsoroctagons,as dimensional,hexagonallatice.Inagivengrainorsingle oposedtothenormalhexagon).Thesedefectsimpedethe crystal,thegrapheneplanesarestackedandbondedviavan flowofelectronsandphonons.Forthesereasons,theCVD derWalforcesinthecrystalographicc-direction(perpen diculartothegrapheneplaneorbasalplane).Althoughal thegrapheneplanesinonegrainareparaleltooneanother, typicalythegrapheneplanesinonegrainandthegraphene graphene is not considered as pristine graphene in the scientificcomunity. [0039]Pristinegraphenecanbeproducedbydirectultra sonicationorliquidphaseproduction,supercriticalfluid planesinanadjacentgrainarediferentinorientation.In exfoliation,alkalimetalintercalationandwater-induced otherwords,theorientationsofthevariousgrainsina explosion,ormoreexpensiveepitaxialgrowth.Pristine graphiteparticletypicalydiferfromonegraintoanother. grapheneisnormalysingle-grainorsingle-crystaline,hav [035]Theconstituentgrapheneplanesofagraphitecrys ingnograinboundaries.Further,pristinegrapheneesen talitecanbeexfoliatedandextracted(orisolated)toobtain individualgrapheneshetsofcarbonatomsprovidedthe inter-planarvanderWaalsforcescanbeovercome.An achemicalspecies,suchasboronornitrogen,tomodifyits isolated,individualgrapheneshetofcarbonatomsiscom electronicandopticalbehaviorinacontroledmanner. monlyreferedtoassingle-layergraphene.Astackof [040]Ahybridmaterialcontainingbothgrapheneoxide multiplegrapheneplanesbondedthroughvanderWaals andCNTwasformedintoathinfilmbyTungetal[Ref.20), forcesinthethicknesdirectionwithaninter-graphene butthefilmdoesnotexhibitasatisfactorybalanceofoptical planespacingof0.354nmiscomonlyreferedtoasa transparencyandelectricalconductivity.Thehighestper multi-layergraphene.Amulti-layergrapheneplatelethasup formancefilmshowsopticaltransmitanceof92%,butthis to30layersofgrapheneplanes(<10nminthicknes). isachievedatanunaceptableshetresistanceof6362/0. Whentheplatelethasupto5-10grapheneplanes,itis Thefilmwiththelowestshetresistance(2402/0with commonlyreferedtoas“few-layergraphene”inthesci un-dopedRGO)shows60%opticaltransmitance,whichis entificcomunity.Single-layergrapheneandmulti-layer grapheneshetsarecolectivelycaled“nanographene platelets”(NGPs).Grapheneshets/plateletsorNGPsarea newclasofcarbonnanomaterial(a2-Dnanocarbon)that isdistinctfromthe0-Dfulerene,the1-DCNT,andthe3-D graphite. notusefulatal.Thegraphenecomponentwasprepared fromheavilyoxidizedgraphiteandthenintenselyreduced [036]Ourresearchgrouppioneredthedevelopmentof graphenematerialsandrelatedproductionprocesesasearly as2002:(1)B.Z.JangandW.C.Huang,"Nano-scaled agonalcarbonatoms,vacancies,dislocations,andgrain GraphenePlates,”U.S.Pat.No.7,071,258(Jul.4,206), aplicationsubmitedonOct.21,2012;(2)B.Z.Jang,etal. “ProcesforProducingNano-scaledGraphenePlates,"U.S. patentaplicationSer.No.10/858,814(Jun.3,204)(U.S. boundaries.Grainboundariesingraphenearelinedefectsat theinterfacesbetwentwodomainswithdiferentcrystal lographicorientations.Duetotheprocesingconditions inherenttotheCVDproces,theCVDgraphenealso containsnon-carbonelements(e.g.hydrogen).Althese Pat.Pub.No.205/0271574)(nowabandoned);and(3)B. Z.Jang,A.Zhamu,andJ.Guo,“ProcesforProducing characteristics(defectsandimpurities)cansignificantly Nano-scaledPlateletsandNanocomposites,”U.S.patent aplicationSer.No.1/509,424(Aug.25,206)(U.S.Pat. Pub.No.2008/0048152)(now abandoned). [0037]ItmaybenotedthatNGPsincludediscreteshets/ plateletsofsingle-layerandmulti-layerpristinegraphene, grapheneoxide,orreducedgrapheneoxidewithdiferent oxygencontents.Pristinegraphenehasesentialy0%oxy [0042]Asdiscusedabove,theCNTmesh,metal gen.Grapheneoxide(GO)has0.01%-46%byweightof nanowiremesh,CVDgraphenefilm,GOfilm(including oxygenandreducedgrapheneoxide(RGO)has0.01%-2.0% RGOfilm),CNT-graphiteflakemesh,CNT-grapheneoxide byweightofoxygen.Inotherwords,RGOisatypeofGO (GO)hybrid,andRGO-protectedAgnanowiremeshhave tialydoesnotcontainoxygenorhydrogen.However,ifso desired,thepristinegraphenecanbeoptionalydopedwith withhydrazine. [041]Anotherhybridmaterial,containingnon-pristine graphene(obtainedbyCVD)andsilvernanowires,was formedintoafilm [Ref.2].Again,CVD-growngraphene isapolycrystalinematerial(notsingle-crystalineandnot pristine)withmanytopologicaldefects,suchasnon-hex impedethetransportofelectronsandphononsinCVD graphenefilms.Evenwiththehelpfromsilvernanowires, thebestCVD graphene-AgNW hybridfilm exhibitsashet resistancevaluethatisstilfarawayfromwhatcanbe theoreticalyachievedwith graphenealone[Ref.2]. Besides,CVD procesesareslow andexpensive.PDF Image | HIGHLY CONDUCTING AND TRANSPARENT FILM AND PROCESS
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