材料科学进展 张奇课件

材料科学进展主要内容材料发展电卡材料多孔膜石墨烯苏美“有些事不懂，就先放下，不急，假以时日，像是枝头的葡萄，自然会熟，落下来，尝了，就懂了。”材料发展历史人类文明的发展水平很大程度上取决于该文明所处时期的材料的特征和功能材料革命有机化学的发展1825年，德国化学家维勒制备了尿素1856年，英国化学家博金合成染料–马尾紫19世纪90年代称为“紫红色十年”，这期间诞生了有机化学的另一分支–聚合物化学，这一领域对新材料的发展产生了巨大的影响材料革命新材料的发现1865年，英国发明家亚历山大帕克斯，硝酸纤维素1900年，美国化学家贝兰德，酚醛塑料20世纪20-30年代许多聚合物新材料的发明和商品化，包括：脲醛塑料、聚氯乙烯、聚苯乙烯、尼龙、聚甲基丙烯酸甲酯、聚乙烯、密胺塑料等。材料革命新金属的发展铁碳合金英国冶金学家---亨利贝莫西现代炼钢法：向熔化的铁水中吹入热空气，可得到含碳比例适当的钢材料革命其它非铁合金铝铜镁锰合金–硬铝，1908年，德国工程师维尔姆发明。之后Al-Cu-Mg合金系、Al-Zn-Mg-(Cu)合金系、Al-Li合金系相继发明。镍铬合金镍钛合金铜合金镁合金材料研究进展纳米材料材料研究目前最具有发展前景的领域是纳米材料。科学家将采用自下而上的顺序从分子和原子层次来合成新物质。纳米技术不仅能够对现有材料进行变革，同时还能够为新的化合物的设计和制造提供新的方式。化学状态分类物理性质分类导电橡胶不锈钢铝箔复合材料螺母单晶硅透光混凝土铁氧体环氧树脂状态分类物理效应分类组成分类材料应用智能材料定义能感知外界的变化后以某种形式对其作出反应，从而改变自己的行为的材料种类压电和电致伸缩材料、磁致伸缩材料、现状记忆合金、电流变液和磁流变液材料、光致变色或热致变色材料智能材料形状记忆合金的应用形状记忆合金被广泛地应用于卫星、航空、生物工程、医药、能源和自动化等方面。如：“阿波罗”11号登月舱携带的天线。先在相变温度以上把天线做好，然后在相变温度以下把它压缩成一团，塞进登月舱，到登月舱进入轨道后，加热天线到相变温度以上，天线完全打开。智能材料压电和电致伸缩材料压电效应是1880年杰克斯、居里俩兄弟首先发现的。压电效应：某些电介质在沿一定方向上受到外力的作用而变形时，其内部会产生极化现象，同时在它的两个相对表面上出现正负相反的电荷。当外力去掉后，它又会恢复到不带电的状态，这种现象称为正压电效应。当作用力的方向改变时，电荷的极性也随之改变。相反，当在电介质的极化方向上施加电场，这些电介质也会发生变形，电场去掉后，电介质的变形随之消失，这种现象称为逆压电效应。逆压电效应属于一种典型的电致伸缩效应压电材料智能材料-压电材料正压电效应当对压电材料施以物理压力时，材料体内之电偶极矩会因压缩而变短，此时压电材料为抵抗这变化会在材料相对的表面上产生等量正负电荷，以保持原状。这种由于形变而产生电极化的现象称为“正压电效应”。正压电效应实质上是机械能转化为电能的过程。 P=dσ其中，P为晶体的电极化率，单位是C/m2，d为压电常数，单位是C/N，σ为应力，单位是N/m2。智能材料-压电材料逆压电效应当在压电材料表面施加电场（电压），因电场作用时电偶极矩会被拉长，压电材料为抵抗变化，会沿电场方向伸长。这种通过电场作用而产生机械形变的过程称为“逆压电效应”。逆压电效应实质上是电能转化为机械能的过程。 S=dt

E其中，S为晶体的杨氏模量，dt为压电常数，单位是m/V，E为电场强度，单位是V/m。智能材料–压电原理智能材料-压电应用原子力显微镜和扫描隧道显微镜采用逆压电保持传感针靠近探针。喷墨打印机：在某些喷墨打印机，特别是那些爱普生生产的，压电晶体是用来控制从喷墨头到纸张上墨水的流量。柴油发动机：高性能的共轨柴油发动机使用压电喷油器，最先由罗伯特博世有限公司研发的，替代了更常见的电磁阀装置。智能材料-压电材料压电材料的研究发展方向驰豫型铁电单晶压电复合材料主要用于水听器，理论未完全建立，开发未充分发掘高居里温度复合材料必须在高温下具有压电性能三元及多元系压电材料压电薄膜满足器件的小型化需求细晶粒压电陶瓷智能材料-压电材料压电材料的研究发展方向无铅压电材料目前所用的压电材料绝大部分为铅基压电陶瓷，对人和环境有污染。无铅压电材料的性能还远远落后于铅基压电陶瓷材料，要达到铅基压电材料的性能还需要做大量的研究工作。日本在无铅压电材料研究开发上的论文和专利最多。智能材料-铁电材料铁电材料的主要特征值智能材料-铁电材料自发极化

在没有外施电场的情况下，晶体的正、负电荷中心也不重合而呈现电偶极矩这种现象称为自发极化。凡是呈现自发极化，并且自发极化的方向能因施加外场而改变的晶体称为铁电体(ferroelectrics)。

智能材料-铁电材料电畴具有自发极化的晶体中存在一些自发极化取向一致的微小区域，称为电畴。两畴之间的界壁称为畴壁。若两个电畴的自发极化方向互成90°，则其畴壁叫90°畴壁。此外，还有180°畴壁等。180º90º智能材料-铁电材料电滞回线铁电体的基本特征是在外电场的作用下，晶体的自发极化强度能随外电场而转向。从电畴的角度出发，在无外场时，各小电畴在晶体中的分布是无规律的，晶体呈电中性，也即从宏观的整体来说，晶体是不极化的。但当有外电场加于晶体时，由于电场同方向的电畴增长，逆电场方向的电畴逐渐消失，以及由于其他方向分布的电畴转向电场方向等原因，使极化矢量P随电场E的增大而增加，且它们之间的关系曲线完全相似于铁磁性物质的H—B曲线，这种曲线叫做电滞回线。

智能材料-压电材料居里温度居里温度是指材料从铁电性转变成非铁电性的温度。TεTc介电反常BaTiO3铁电体的研究历史与现状1920年，法国人瓦拉赛克（Valasek）发现罗息盐（酒石酸甲纳），具有铁电性。第一阶段：1920-1939,发现了两种铁电结构，即罗息盐和KH2PO4系列。第二阶段：1940-1958，铁电热力学理论。第三阶段：1959-1970年代，钙态矿时期-铁电软模理论出现。第四阶段：1980年代-今，铁电薄膜及器件时期-小型化。智能材料-铁电压电关系

压电体热释电体铁电体介电体电卡效果（Electrocaloriceffect)热释电热释电效应（pyroelectriceffect)在某些绝缘物质中，由于温度的变化引起极状态改变的现象称为热释电效应。ΔPs=ρΔTΔPs为自发式极化强度变化量；ΔT为温度变化；ρ为热释电系数。热释电热释电系数

ρ=ΔPs/ΔT=dPs/dTPTTcVIZT1T2>T1T1T1T2热释电热释电材料LiTaO3单晶PZT陶瓷硫酸三甘钛电卡效果（electrocaloriceffect)电卡效应是在极性材料中因外电场的改变从而导致极化状态的改变而产生的绝热温度或等温熵的改变。Whenanelectricfieldisappliedtoorremovedfromadielectricmaterial,underadiabaticconditions,itwillinduceachangeinthepolarizationandconsequentlyachangeintheentropyandtemperatureinthematerial.Suchanelectricfield-inducedtemperatureandentropychangeinadielectricmaterialisknownastheelectrocaloriceffect(ECE).RefrigerationcyclebasedonECE-3-好心情T1(=RoomT),S1E1(=0)

T2(=T1+ΔT),S1E2=EmaxT1,S2(<S1)ΔS<0Ejectheattoaheatsink(Th)E2=EmaxE1(=0)T3=T1–ΔT,S2

Adiabatic(绝热）

dQ=0AdiabaticdQ=0Absorbheatfromaload(TC)ΔS>0ΔS=0ΔS=0S(E1,T1)=S(E2,T2)S(E2,T1)=S(E1,T3)PossiblepracticalusesofECEAllsolid-statecoolingdevicesOn-chipdevicesRefrigerationfridges,air-conditioners(moreenvironmentallyfriendly)电卡效应heaterKaptonfilmECEfilm+-IRsensor电卡测试装置OperatingPrincipleofElectrocaloricRefrigeration

A-BAdiabaticpolarizationB-CHeattransferC-DAdiabaticdepolarizationD-AEntropytransferOperatingPrincipleofElectrocaloricRefrigeration

NetElectricalEnergy:CoefficientofPerformance(COP):RelativeEfficiency:Foridealreversiblecycle:Forrealcycle:WhyECEBasedCoolingDevicesAreInteresting?EnergyandEnvironment

Refrigeration,air-conditioning,andcoolingoverallconsumemorethan20%ofelectricityinthedevelopedcountriesAirconditioningisakeydriverofpeakelectricitydemandThemechanicalVaporCompressionCyclecooling(VCC)deviceshaveCOP~2to4(<20%ofCarnotefficient)andhardtoimprovefurtherSimulationresultsindicatethatcoolingdevicesbasedondielectricswithlargeECEcanhavemuchhigherCOP(>70%ofCarnotefficient)Environmentalconcerns:therefrigerantgases(HFC)inthemechanicalVCCcoolingdevicesarestronggreenhousegases.Theycontributetoabout25%oftotalgreenhousegases!ECEofbulkmaterialsInbulkceramics,itwasfoundthat-ΔT~afewKelvin(2.5KinPb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)O3),-Asmallchangeofheat~0.2kJkg-1and-Asmallbreakdownfield≤50kVcm-1.Allofthesearetoosmalltobeofpracticaluse.ElectrocaloricpropertiesofPZTthinfilmsassociatedwiththeFE-PEphasetransitionA.S.Mischenko，Q.Zhang,etal.Science311,1270(2006)Hysteresislosses~4%Jouleheating~10-3K220°CAssessmentofElectrocaloricRefrigerantsCostEnvironmentImpactEfficiency/PowerAssessmentofElectrocaloricMaterialsCostEnvironmentImpactEfficiency/PowerAssessmentofElectrocaloricMaterialsIrreversibleProcesses(Thermalandelectricalhysteresis)HeatingSpan/RefrigerantCapacityElectrocaloricDSandDTAssessmentofElectrocaloricMaterialsHighBreakdownField(Thinfilms)Highpyroelectriccoefficient(Phasetransition)ElectrocaloricDSandDTAssessmentofElectrocaloricRefrigerantsPbSc0.5Ta0.5O3ThinFilm(Partially-ordered)ElectrocaloricDSandDTT.M.Correia,etal.J.ofPhys.D:Appl.Phys.44,165407(2011).AssessmentofElectrocaloricMaterialsPbSc0.5Ta0.5O3ThinFilm(Partially-ordered)ElectrocaloricDSandDTAssessmentofElectrocaloricMaterialsIrreversibleProcesses(Thermalandelectricalhysteresis)DeviationfromidealreversibleCarnotcycleMaterialirreversibleprocesses

Thermalhysteresis(first-orderphasetransitions,glassystateinrelaxors,…)ElectricalhysteresisThermodynamicCycleLossesduringheatexchangeAssessmentofElectrocaloricRefrigerantsIrreversibleProcesses(Thermalandelectricalhysteresis)Relaxor0.93PbMg1/3Nb2/3O3-0.07PbTiO3ThinFilmNon-ergodicphaseThermalHysteresisAssessmentofElectrocaloricMaterialsIrreversibleProcesses(Thermalandelectricalhysteresis)Relaxor0.93PbMg1/3Nb2/3O3-0.07PbTiO3ThinFilmLowElectricalHysteresis<9%AssessmentofElectrocaloricRefrigerantsHeatingSpan/RefrigerantCapacity(RC)RefrigerationCapacity(RC)Gshneideretal.Wood&PotterAssessmentofElectrocaloricMaterialsCostEnvironmentImpactEfficiency/PowerAssessmentofElectrocaloricRefrigerantsRawMaterialsThinFilmgrowthOperationInexpensiveSol-Gelmethod:Cost-effectivetechniqueLow-costoperatingdevice(noneedforexpensivemagnetslikemagnetocaloricrefrigerants)AssessmentofElectrocaloricMaterialsCostEnvironmentImpactEfficiency/PowerAssessmentofElectrocaloricMaterials(Leadisatoxicelementforwhichspecialfacilitiesarerequiredduringhandlinginordertominimizerisktohealthandtotheenvironment.)Eliminategreenhousegasemissionsoriginatedbydomesticandindustrialvapour-compressionrefrigerationandairconditioning(HFCgases).

Electrocaloricrefrigeration

donotinvolveharmfulgasesLead-basedelectrocaloricthinfilmsMembraneTechnologiesForCO2CaptureTitleContentsIntroductionWhycaptureCO2?SourcesofCO2emission?CO2separationtechnologiesGasseparationtechnologiesBasicconceptsContents–cont’dMembranesMechanismofmembraneseparationprocessesSelectionofMembranesPermeabilitySelectivityPolymericMembranesInorganicMembranesOthermembranesConclusionsOutcomesRealizetheCO2separationmechanismbymembranes.WhataretheadvantagesoftheuseofmembranesforCO2separation?Realizecurrentdevelopmentofpolymericandinorganicmembranes.Realizethefuturedevelopmentdirectionofmembranes.Introduction~85%oftheworld’stradeenergyneedsisprovidedbymineralfuelsthatarelargelyresponsiblefortheincreaseinCO2emissions.Climatechangeisoneofthemostsignificantfactorsfacedbyhumanityandsocietyasawhole.Withthecurrentstructureofglobalpower,therearenoviablealternativeenergysourcestomineralfuels,capabletofullyreplacethem.Whycapturecarbon?Introduction–cont’dArapidchangeofenergysourcesofnonmineraloriginwouldresultinamajordisruptiontotheinfrastructureofenergysupply,withsignificantconsequencesfortheglobaleconomy.TheCO2captureandstorage(CCS)isseenasafundamentalandindispensablemeasuretoreducetheenvironmentalimpactsassociatedwiththispotentiallycatastrophicphenomenon.Introduction–cont’dCommercialCO2capturetechnologythatexiststodayisveryexpensiveandenergyintensive.Itisnecessarytodeveloptechnologiesthatwillallowustoutilizethefossilfuelswhilereducingtheemissionofgreenhousegases.Introduction–cont’dThislecturepresentsasummaryofmembrancetechnologyofcapture/separationofCO2.Introduction—Cont’dCurrentlythelargestsinglepointsourcesofCO2emissionarepowerplantsthatproducestreamsoffluegas,exhaustedcombustionsmoke,withCO2concentrationsofca.15%at1atm.SourcesofCO2emissionFossilfuel（化石燃料）

Naturalgas(powerplant)MixedgasesreusetransportseparationCO2StorageIntroduction--CO2EmissionSourcesNaturalgasgenerationMixedgasesCO2,CH4,H2,etcseparationCO2SeparationTechnologiesCryogenicdistillationSorbentabsorption（吸附剂吸附）MembraneSeparationTechnologies-cont’dBasicconceptsAdsorption–istheadhesionofatoms,ions,biomoleculesormoleculesofgas,liquid,ordissolvedsolidstoasurface.Absorption–inchemistry,isaphysicalorchemicalphenomenonoraprocessinwhichatoms,molecules,orionsentersomebulkphase-gas,liquidorsolidmaterial.BasicconceptsAdsorbent–isasubstance,usuallyporousinnatureandwithahighsurfaceareathatcanadsorbsubstancesontoitssurfacebyintermolecularforces.Adsorbate–themoleculesoratomsbeingaccumulatedonthesurfaceoftheadsorbent.Surfaceenergy–theexcessenergyatthesurfaceofamaterialcomparedtothebulk.BasicconceptsPhysisorption–alsocalledphysicaladsorption,isaprocessinwhichtheelectronicstructureoftheatomormoleculeisbarelyperturbeduponadsorption.BasicconceptsChemisorption

isasub-classofadsorption,drivenbyachemicaloccurringattheexposedsurface.Anewchemicalspeciesisgeneratedattheadsorbentsurface(e.g.corrosion,metallicoxidation).Thestronginteractionbetweentheadsorbateandthesubstratesurfacecreatesnewtypesofelectronicbonds–ionicorcovalent,dependingonthereactivechemicalspeciesinvolved.BasicconceptsVanderWaalsforce–isthesumoftheattractiveorrepulsiveforcesbetweenmolecules(orbetweenpartsofthesamemolecule)otherthanthoseduetocovalentbondsortotheelectrostaticinteractionofionswithoneanotherorwithneutralmolecules.Micropores,ofdimensionsbelow2nm,Mesopores,between2and50nm,andMacropores,>50nm.Membranes–cont’d

Gasseparationmembranesallowonecomponentinagasstreamtopassthroughfasterthantheothers.Therearemanydifferenttypesofgasseparationmembrane,includingporousinorganicmembranes,palladiummembranes,polymericmembranesandzeolites.

86MembranesMembranesMembranes–cont’dMembranescannotusuallyachievehighdegreesofseparation,somultiplestagesand/orrecycleofoneofthestreamsisnecessary.Thisleadstoincreasedcomplexity,energyconsumptionandcosts.89ProcessesofMembraneSeparation(PMS)Thetransportofchemicalspeciesthroughamembraneoccurswhenthereisadrivingforceactingonit.Ingeneral,chemicalpotentialgradientisthedrivingforce.Chemicalpotentialgradientcanbeexpressedintermsofpressuregradientandconcentrationgradient.MechanismofmembraneseparationprocessesAsuccessfulmembraneallowsthedesiredgasmoleculetoadsorbtothesurfaceononeside,oftenathigherpressure(solubility).Themoleculethenabsorbsintothemembraneinterior,eventuallyreachingtheothersideofthemembrane(mobility)whereitcandesorbunderdifferentconditions,suchaslowpressure.Solution-diffusionmechanismtheseparationofpermeatesduetotwofactorsSolubility(thermodynamicfactor)mobilityofthepermeatesintothemembranematrixdiffusion(kineticfactor)SolubilityMobilityTypesofmembranesIntegralCompositeisotropicAnisotropicThefirstFick’slawJ:thespecificgasflowD:diffusioncoefficient(m2s-1)C:gasconcentrationinmaterial(molm-3)d:filmthicknessPermeability–cont’dThepermeabilityperunitthickness:SelectivityTheselectivityofamembraneSelectionofmembraneSelectthemostsuitablematerialforseparatinggasmixtures,leadingtobetterselectivityandpermeabilityratio.Studytheyieldandpurityoftheproduct.Thismeansthatthepermeabilityandselectivityforthetransportofgasshouldbehigh.SelectmembraneTheanisotropicmembranewithappropriatemorphologyforgasseparationmustpresentacoating,freefromdefects,favouringthetransportsolutionbydiffusion.SelectionofMembranesInordertoobtainefficiency,areducedcoatingthicknessshouldbeused,whichprovideshigherpermeateflux.SelectionofMembranePoroussublayerwithlowresistancetothetransportofpermeate.Thissublayermustoperateonlyasaporoussupport,providingmechanicstrengthtofinish.PolymericmembranesThechallengeforpolymerchemistsistodeveloppolymerswithmuchhigherpermeability,whilstretainingadequateselectivityandmeetingotherrequirements,suchasprocessabilityandlong-termstability.PolymericmembranesManypolymershavebeeninvestigatedasgasseparationmembranematerials,butuptonowonlyahandfulhavefoundcommercialsuccess.Theseinclude

RubberypolymersPoly(dimethylsiloxane)

Glassypolymers

PolysulfoneCelluloseacetatePolyimidePoly(phenyleneoxide)PolymericmembranesGlassypolymercontainsmicropores(<2nm)highselectivitygoodmechanicstrengthPolymericmembranesPlotofselectivityvspermeabilitySolidline1991DashedLine2008∆PTMSP;▲polyacetylene2e;×TeflonAF2400;+poly(trimethylsilylnorbornene)□PIM-1;■PIM-1aftermethanoltreatment○6FDA-DMNpolyimide◊PIM-PI-8PolymericmembranesPerformanceofpolymericmembranesseparatingCO2/N2(PowellandQiao,2006)TransportmechanismthroughmicroporousmembranesCarbonmembranesCarbonmembranesPorousaluminaPolymerprecursorsolutionCarbonizedundervacuumorhighTPreparationofmembranesTheCO2affinityofatypicalcarbonmembranewasenhancedtoimprovetheseparationperformanceofthemembranebasedontheconceptofSchemeI.InorganicmembranesZeolitesarecrystallinealuminosilicateswithauniformporestructureandaminimumchanneldiameterrangeof0.3to1.0nm.Selectivelyadsorbmoleculesbysizeandpolarity.Separationoccursinzeolitemembranesbybothmolecularsievingandsurfacediffusionmechanisms.ZeolitemembranesInorganicmembranesIncorporationofmolecularsieveswithinapolymermembranepossiblyprovidesboththeprocessibilityofpolymersandselectivityofmolecularsieves.Thepermeabilityofagasthroughazeolite-filledpolymericmembranedependsontheintrinsicpropertiesofthezeoliteandpolymer.Examples:polyimide-carbonmolecularsieve;polyimide-silica;etc.Mixed-matrixmembranesInorganicmembranesAporousinorganicsupportmaterialissurface-modifiedwithchemicalswhichhavegoodaffinitywithCO2.ThishelpsCO2separationintwoways:porousinorganicmaterialsallowlargefluxwhilethechemicalprovidesselectivity.Examples:Trichlorosilane-γ-alumina;tetrapropylammonium-silica,etc.HybridmembranesInorganicmembranesPolymericmembranesRelativelyeasytomanufactureandwell-suitedforlowtemperatureapplications.Bycarbonizingthesepolymericmaterialsitispossibletoobtainamolecularsievecapability.InorganicmembranesMuchgreaterthermalandchemicalstability.ConclusionsFossilfuelcontinuestobetheprimaryenergysource,atleastforthiscentury.Therearemanytechnicaloptionsforseparationand/orcaptureofCO2fromcombustionfluegasandotherindustrialeffluents.Membraneseparationprocessesprovideseveraladvantagesoverotherconventionalseparationtechniques;Amembranecombininghighflux,highselectivityandhighstabilityisrequired,butisnotrealisticatthisstage.ConclusionsMixed-matrixmembranesprovidehopes.Membraneprocessasenergy-saving,spacesaving,easytoscale-up,couldbethefuturetechnologyforCO2separation.Graphene（石墨烯）ContentsBasicdefinitionsCarbonIntroductionOccurrenceandproductionPropertiesPotentialapplicationsExamplesConclusionBasicDefinitionsGraphene–aone-atom-thickplannarsheetofcarbonatomsthataredenselypackedinahoneycombcrystallattice.Graphite–manygraphenesheetsstacktogether2Dcrystal–asingleatomicplaneisa2Dcrystal,whereas100layersshouldbeconsideredasathinfilmofa3Dmaterial.Composite–thematerialismadeoftwoormoredifferentparts;oneormorediscontinuousphasesdistributedinonecontinuousphase.Graphite(石墨）STMimageofgraphitesurfaceatomsSideviewoflayerstackingGraphite（石墨）Graphitehasalayered,planarstructure.Ineachlayer,thecarbonatomsarearrangedinahexagonallatticewithseparationof0.142

nm,andthedistancebetweenplanesis0.335

nm.Graphiteisanelectricalconductor,asemimetal.Graphiteisthemoststableformofcarbonunderstandardconditions(273ºC,0.986atm.byIUPAC). IUPAC–InternationalUnionofPureandAppliedChemistryGraphiteGraphitecanconductelectricityduetothevastelectrondelocalizationwithinthecarbonlayers.Thesevalenceelectronsarefreetomove,soareabletoconductelectricity.However,theelectricityisonlyconductedwithintheplaneofthelayers.Diamondface-centeredcubiccrystalstructurelessstablethangraphitestrongcovalentbondingbetweenitsatomsthehighesthardnessandthermalconductivityofanybulkmaterialDiamond（钻石）Graphite（石墨）钻石和石墨的外表CarbonNanotubesGrapheneorgraphiterollsandformscarbonnanotubes,theformersinglewallandthelatermulti-walls.碳纳米管IntroductionThehexagonalgridstructureofgraphene

Monolayergraphenewasfirstobtainedasatransferablematerialin2004.Thisdevelopmenthasrecentlyculminatedintheawardofthe2010NobelPrizetoAndreGeimandKonstantinNovoselovoftheUniversityofManchester,UK,for“groundbreakingexperimentsregardingthetwo-dimensionalmaterialgraphene.”IntroductionGraphenecanbewrappedupinto0Dfullerences,rolledinto1Dnanotubesorstackedinto3Dgraphite.Nature,2007,6,183.石墨碳纳米管石墨烯足球烯ProductionofgrapheneIn2004,theresearchersintheUniversityofManchester,obtainedgraphenebymechanicalexfoliationofgraphite[1].Theyusedcohesivetapetorepeatedlysplitgraphitecrystalsintoincreasinglythinnerpieces.Earlierattemptstoisolategrapheneconcentratedonchemicalexfoliation[2].

[1]Science,306,666(2004)[2]Adv.Phys.,51,1(2002)ProductionofgrapheneNowsingle-andfew-layergraphenehavebeengrownepitaxiallybychemicalvapourdepositionofhydrocarbonsonmetalsubstratesandbythermaldecompositionofSiC[3,4,5].[3]Surf.Sci.,291,93(1993)[4]Surf.Sci.,48,463(1975)[5]J.Phys.Chem.B108,19912(2004).ProductionofgrapheneStartingmaterialwas1-mm-thickplateletsofhighly-orientedpyrolyticgraphite（热解石墨）.Graphiteflakes（小薄片）wererepeatedlypeeledoffusingascotchtape.Afterrepeatedpeeling,thegraphenesweretransferredto300nmSiO2/Sisubstratesbyadheringandtakingoffthetape.1.Mechanicalexfoliation（剥落）ofgraphiteProductionofgrapheneThen-layergraphenesleftonthewaferwerefirstselectedbasedontheircolourcontrastinanopticalmicroscope.Thisapproachisveryreliableandfewlayergraphenefilmsupto10µminsizecanbeprepared.A:

Photograph(innormalwhitelight)ofarelativelylargemultilayergrapheneflakewiththickness~3nmontopofanoxidizedSiwafer.B:

Atomicforcemicroscope(AFM)imageof2mmby2mmareaofthisflakenearitsedge.3nmheightSiO23nmheightProductionofgrapheneSiO20.8nmheight1.2nmheight2.5nmheightAFMimageofsingle-layergrapheneProductionofgrapheneImagesofathingraphiticflakeinoptical(Left)andscanningelectron(Right)Microscopes.Few-layergrapheneisclearlyvisibleinSEMbutnotinoptics.ProductionofgrapheneOpticalphotoinwhitelightofgraphiticfilmsofvariousthicknessd.TheindicatedvalueofdweremeasuredbyAFM.Notetheareawithd=2nm,whichisbarelyvisibleinopticsinthetop-leftcorner.ColorindicationofthicknessProductionofgrapheneSiO22nm0.5nmfoldingStartingfromgraphite.Graphiteintercalationreactions–forexample,rapidthermalexpansionofsulfuricacid-intercalatedgraphite,followedbyasuitabletreatmenttoproduceplatelets/nanoplateletsfromtheexpandedmaterial(ballmillingorexposuretoultrasound).

2.ChemicalexfoliationgraphiterapidthermalexpansiongraphiteoxideballmillingorultrasoundgrapheneflakesProductionofgrapheneInsummary,thethicknessforsinglelayerisabout0.4nmandfordoublelayeritis0.8nm.Today,thesizeofgraphenefilmsproducedbychemicalexfoliationislimitedtosmallsizes(usually<1000µm2)becausethefilmsareproducedmostlybyexfoliatinggraphite,whichisnotascalabletechnique.ProductionofgrapheneAlthoughgraphenehasbeengrownonanumberofmetals,therestillarethechallengesofgrowinglarge-areagraphene,ofpresenceofmultilayersatthegrainboundaries,andthehighsolubilityofcarbon.Large-areagraphenehasbeengrownoncopperfoilattemperaturesupto1000ºCbyCVDofcarbonusingamixtureofmethaneandhydrogen[1].[1]Science,325,1312(2009)3.Chemicalvapourdeposition(CVD)onmetalfoilsProductionofgraphene4.Growthofgraphenefromsolidcarbonsources

SpincoatingaPMMA(poly(methylmethacrylate))thinfilmonaCufilm.Sinteringthefilmat800–1000ºCinH2/Arandunderlowpressureconditions.ProductionofgrapheneUltrahighvacuumannealingofsinglecrystalSiC[1-2]AnnealingSiC[1]Sicence,312,1191(2006)[2]Nat.Mater.8,203(2009)CharacterizationofgrapheneDespitethedevelopmentofvariousmethodsofproducinggraphene,theidentificationandcountingofgraphenelayersisamajorhurdle.Monolayersareagreatminorityamongstaccompanyingthickerflakes.Invisibleinanopticalmicroscopeonmostsubstrates.CharacterizationofgrapheneOnlyvisiblewhendepositedonoxidizedSisubstrateswithafinelytunedthicknessoftheoxidelayer(typically,300nmofSiO2),because,inthiscase,evenamonolayeraddstotheopticalpathofreflectedlighttochangetheinterferencecolorwithrespecttotheemptysubstrate.CharacterizationofgrapheneAtomicforcemicroscopya,SEManddigitalimage(inset)ofnaturalgraphite.b,AtypicalAFMnon-contact-modeimageofgraphiteoxidesheetsdepositedontoamicasubstratefromanaqueousdispersion(inset)withsuperimposedcross-sectionMeasurementstakenalongtheredlineindicatingasheetthicknessof~1nm.c,AFMofgraphiteoxidesheetsonmicaandproshowingthe~1nmthickness.CharacterizationofgrapheneAFMisagoodmethodtoidentifysingleandfewlayersbutitislowthroughput.Inaddition,thereisa0.5nminstrumentaloffsetcausedbydifferentinteractionforces,whichisevenlargerthanthethicknessofagraphenemonolayer.RamanSpectroscopyAspectroscopictechniqueusedtostudyvibrational,rotational,andotherlow-frequencymodesinasystem.ItreliesoninelasticscatteringorRamnascattering,ofmonochromaticlight,usuallyfromalaser.Thelaserlightinteractswithmolecularvibrations,phononsorotherexcitationsinthesystem,resultingintheenergyofthelaserphotonsbeingshiftedupordown.Theshiftinenergygivesinformationaboutthephononmodesinthesystem.Infraredspectroscopyyieldssimilar,butcomplementary,information.RamanspectroscopyElasticscatteringInelasticscatteringIfthefinalvibrationalstateofthemoleculeismoreenergeticthantheinitialstate,thentheemittedphotonwillbeshiftedtoalowerfrequencyinorderforthetotalenergyofthesystemtoremainbalanced.ThisshiftinfrequencyiscalledStockshift.Ifthefinalvibrationalstateislessenergeticthantheinitialstate,thentheemittedphotonwillbeshiftedtoahigherfrequency,andthisisdesignatedasanAnti-Stokesshift.Ramanscatt