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US 8,696,938B2 78 Furthermore,Kaschak,etal.55didnotprovideanyevi dencetoshowtheexistenceofnano-scaledgraphiteparticles thattheyclaimedtheyproducedwiththismethod.Inparticu lar,theyclaimedthat“oneadvantageoftheinventionisthat theaforementionedmethodsmaybeusedtomanufacture graphiteinaformthathasathicknessoflesthanabout10 microns,preferablylesthanabout1micron,morepreferably lesthanabout100nm,evenmorepreferablylesthanabout 10nm,andmostpreferablylesthanabout1nm.”However, theydidnotfairlysuggesttheconditionsunderwhichgraph iteparticleswithathicknesslesthan10nmor1nmcouldbe produced.Thiswastrulyabigclaimandshouldhavebeen Supported by solid experimental evidence; unfortunately, absolutelynoevidencewhatsoeverwaspresented. Gulari,etal. 56 proposedamethodofdelaminatinga graphitestructurewithacoatingagentsolubilizedinaSuper criticalfluid.AccordingtoGulari,etal. 56,thecoating agentwasapolymer,monomer,oroil.Themethodcomprises difusingacoatingagentinaSupercriticalfluidbetween layeredparticlesofagraphitestructureandcatastrophicaly depressurizingtheSupercriticalfluidtodelaminatethecoat ingagent-intercalatedgraphiteparticles.However,Gultari,et al.56 failedtomentionanythingaboutthethicknesofthe delaminatedparticles.Itwasnotclearifandhowgraphite plateletswithathickneslesthan100nmcouldbeproduced withthismethod.Gulari,etal.presumedthatacoatingagent wasneededtopreventthereformationofthecovalentbonds betweengraphiteparticleswhentheywerebrokenduring delamination.Thisisratherconfusingormisleadingsinceit ducingsuchthinflakes.U.S.Pat.No.5,019,446(May28, iswell-knownthatthebondingbetweengraphitelayersisvan 1991). derWaalsforceratherthancovalentbond.Furthermore,a30 coatingagentisproblematicifapuregrapheneproductis desired.Gulari,etal.56 didnotteachifasupercriticalfluid withoutacoatingagentsolubilizedthereinwouldbecapable ofdelaminatinggraphitelayers.NeitherKaschak,etal.55 norGulari,etal.56 discusthepropertiesoftheresulting exfoliatedgraphite. Bycontrast,afteranintensiveresearchanddevelopment efort,wehavefoundthatasupercriticalfluid,alonewithout acoatingagent,wascapableofbothintercalatingandexfo liatingagraphiticmaterialwithoutinvolvinganaditional intercalationoroxidationstep(asrequiredinKaschak,etal.40 12.Bunnell,Sr.L.R.Methodforproducingthingraphite flakeswithlargeaspectratios.U.S.Pat.No.5,186,919 (Feb.16,193). 55).Further,thissupercriticalfluid-basedprocessiscapable ofproducingnanographeneplateletsthatareultra-thin(<10 nm)and,inmanycases,thinnerthan1nm.Wehavealso discoveredthatitwasnotnecessarytodischargetheSuper criticalfluid-intercalatedgraphiteoutofapressurechamber toachievegraphiteexfoliation.Instead,exfoliationofgraph itefortheNGPproductioncouldbecariedoutbyrapidly de-presurizingorreleasingthegasfromthechamberwhere agraphiticmaterialwastentativelyintercalatedbyaSuper criticalfluid.BykeepingtheexfoliatedgraphiteorNGPsin50 thechamber,thechambercanbere-presurizedandthen de-pressurizedtofurtherseparatemulti-layerNGPs.This procedurecanberepeateduntilalormostoftheNGPsare single-layeredstructures. carbonnanofilm.Apl.Phys.Let.84,2403-2405(2004); paperreceivedon8Sep.2003. 15.Hirata,M.&Horiuchi,S.Thin-film-likeparticleshaving skeletonconstructedbycarbonsandisolatedfilms. U.S. Pat.No.6,596,396(Jul2,2003). 16.Hirata,M.& Horiuchi,S.Compositescontainingthin filmparticleshavingcarbonskeleton,methodofreducing thethin-filmparticles,andprocessfortheproductionofthe composite.U.S.Pat.No.6,828,015(Dec.7,2004). Hence,itwasanobjectofthepresentinventiontoprovide apristinenanographeneplateletmaterialthathasgoodelec tricalconductivity. Itwasanotherobjectofthepresentinventiontoprovidea processformass-producingpristineNGPswithoutinvolving theuseofanyundesirablechemical. Itwasafurtherobjectofthepresentinventiontoprovidea processforproducingultra-thinNGPs(e.g.,thosewitha thicknesslesthan1nm). ReferencesCited 1.Novoselov,K.S.,etal.Electricfieldefectinatomically thincarbonfilms.Science306,666-669(2004). 55 60 65 No.2,798,878,Jul.9,1957. 18.Liu,P.&Gong,K.Synthesisofpolyaniline-intercalated graphiteoxidebyaninsituoxidativepolymerizationreac tion.Carbon37,706-707(1999). 19.Dekany,I.,Kruger-Grasser,R.&Weiaa,A.Selective liquidsorptionpropertiesofhydrophobizedgraphiteoxide nanostructures.ColloidPolymerSci.276,570-576(1998). 20.Chen,G.H.Preparationandcharacterizationofgraphite nanosheetsfromultrasonicpowderingtechnique.Carbon 42,753-759(204). 21.Jang,B.Z.,Wong,S.C.&Bai,Y.Processforproducing nano-scaledgrapheneplates. U.S.patentaplicationSer. No.10/858,814(Jun.3,2004);Pub.No.US2005/0271574 (Pub.Dec.8,2005). 2.Petrik,V.I.Massproductionofcarbonnanostructures. U.S.patentaplicationSer.No.11/007,614(Dec.7,2004); PublNo.US2006/0121279(Pub.Jun.8,2006). 23.DrzalL.T.& Fukushima,H.Expandedgraphiteand productsproducedtherefrom.U.S.patentaplicationSer. No.11/363,336(Feb.27,2006);Ser.No.11/361,255(Feb. 24,2006);Ser.No.10/659,577(Sep.10,2003). 10 2.Novoselov,K.S.,etal.Twodimensionalatomiccrystals. Proc.Natl.Acad.Sci.102,10451-10453(205). 3.Jang,B.Z.&Huang,W.C.Nano-scaledgraphemeplates. U.S.Pat.No.7,071,258,(submittedonOct.21,2002and issuedonJul.4,2006). 4.Jang,B.Z.Processfornano-scaledgrapheneplates.U.S. patentaplicationSer.No.11/442,903(Jun.20,2006);a divisionalofSer.No.10/274,473(Oct.21,2002). 5.McAlister,M.J.,etal.Singlesheetflinctionalized graphenebyoxidationandthermalexpansionofgraphite. Chem.Materials19(18),4396-4404(2007). 6.Li,J.L.,etal.Oxygen-drivenunzippingofgraphiticmate 15 rials.Phys.Rev.Let.96,176101-1-4(206). 7.Schniepp,H.C.,etal.Functionalizedsinglegraphene shetsderivedfrom splitinggraphiteoxide.J.Phys. Chem.B110,8535-8547(206). 8.Li,X.Wang,X.Zhang,L.,Lee,S.&Dai,H.,Chemically derived,ultraSmoothgraphenenanoribbonsemiconductor. Science319,1229-1232(2008). 9.BorZ.JangandAZhamu,“ProcessingofNanoGraphene Platelets(NGPs)andNGPNanocomposites:AReview.”J. MaterialsSci.43(2008)5092-5101. 10.Bunnell,Sr.L.R.Enhancementofthemechanicalprop ertiesbygraphiteflakeadition.U.S.Pat.No.4,987,175 (Jan.22,191). ofpolymersbythinflakeaditionandapparatusforpro 25 1.Bunnell,Sr.L.R.Enhancementofmechanicalproperties 13.Zaleski,P.L.,etal.Methodforexpandinglamelarforms ofgraphiteandresultantproduct.U.S.Pat.No.6,287,694 (Sep.1,2001). 35 14.Horiuchi,S.,etal.Singlegrapheneshetdetectedina 45 17.Hummers,W.S.Preparationofgraphiticacid.U.S.Pat.PDF Image | SCO2 Producing Nanographine Platelets
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