纳米材料 复习题

纳米材料复习题关键词翻译：1、Nanomaterials)（扫描隧道显微镜）ScanningTunnelingMicroscope(STM)Zero(one,two,（零、一、二、三维）SizeEffect-Kubo（尺寸效应-库伯理论）(1)Quantumsizeeffect（量子尺寸效应）(2)SmallsizeSurfaceeffect（表面效应）CoulombblockadeandQuantumtunnelingeffect（库仑堵塞和量子隧穿效应）Dielectricconfinement2Clusters（团簇）Nanoparticle（纳米微粒）SupersaturatedVapor（过饱和蒸气）Heterogeneousnucleation（异相成核）Homogeneousnucleation（均相成核）（幻（魔）数）MagicNumbers3、Primaryparticles（初始颗粒、一次颗粒）Secondaryparticles（二次颗粒）AgglomerationScanningelectronmicroscope(SEM)扫描电镜Transmissionelectronmicroscope(TEM)（透射电镜）High-resolutiontransmissionelectronmicroscope(HRTEM)（高分辨率透射电镜）4、MechanicalAttrition/MechanicalAlloying(MA)（机械研磨、机械合金化）High-energyBallMilling（高能球磨）Contamination（污染物）Comminution（破碎、粉碎）Intermetallic（金属间化合物）Oxide-dispersionstrengthenedsuperalloys（弥散氧化物强化合金）NanocompositesDislocation（位错）5sol-gel溶胶凝胶alkoxidesolution醇盐溶液colloidalsols胶体溶液microporousmonoliths多孔块体材料anisotropic/isotropicshrinkage各向异性、各向同性收缩polymerpyrolysis聚合物高温分解hydrolysis水解6Agreen（素坯）Pressurelesssintering（无压烧结）Inhomogeneoussintering（非均一烧结）Densification（致密化）Porosity（多孔性）PressureAssistedSintering（压力辅助烧结）Sinter-forging（烧结锻压）7、Electroniceffects(电子效应)Supporteffects()Shapeeffects（形状效应）Zeolite(Molecularsieve)(沸石、分子筛)Catalyst（催化剂）Adsorbent（吸附剂）8、YieldStrengthHall-Petchequation（霍尔佩奇方程）Diffusioncreeprate（扩散蠕变速率）Coblecreep（扩散蠕变－Coble蠕变）Triplejunctions（三叉晶界）Superplasticity（超塑性）9Massspectra电弧Nuclearmagneticresonance核磁共振Pentagon/hexagon五边形、六边形名词解释及问答：质谱Fullerene富勒烯Buckyball巴基球High-performanceliquidchromatography高效液相色谱法Allotrope同素异形体Electricarc一、ThedefinitionofNanomaterialsMaterialshavingacharacteristiclengthscalelessthanaboutahundrednanometers.（长度尺寸小于一百纳米的材料）Classificationaccordingtodimensions1）Three-dimensionNanomaterials(Zeolite)（2Two-dimensionfilm,superlattice（）One-dimensionnanowire,nanotube1（4）Zero-dimensionparticle,clusterBasictheoryofnanoparticles1.SizeEffect-Kubotheory（尺寸效应的尺寸、第二相粒子的尺寸减少时，纳米材料的性质会发生变化，当组成尺寸小到某一临界尺寸相当时，材料的性能将发生明显的变化或突变。小尺寸效应：随着颗粒尺寸量变，在一定条件下，会引起颗粒性质突变，由于颗粒尺寸变小所引起的宏观物理性质的变化称为小尺寸效应。量子尺寸效应：电子能量被量子化，形成分立的电子态能级，电子在该系统中的运动道的能隙变宽的效应。2.Surface有大量晶界，因而晶界上的原子占有相当高的比例，晶界原子结构不同于块体材料，使纳米微粒自由能增加，处于不稳定状态。3.Coulombblockadee2和放电过程是不连续的，充入一个电子所需能量为：ECC其中Ec导致对一个小体电子输运行为称为库仑堵塞效应。Quantum点上的单电子穿过能垒到达另一个量子点上的行为称为量子隧穿效应。4.Dielectricconfinementeffect（介电限域效应）纳米微粒分散在异质介质中，由于界面引起的体系介电增强的现象。二、1、Howdoyoubuildsomethingsosmall?“Topdown”and“Bottomup”？“Topdown”–buildingsomethingbystartingwithalargercomponentandcarvingawaymaterial(likeasculpture).Innanotechnology:patterning(usingphotolithography)andetchingawaymaterial,asinbuildingintegratedcircuits。“Bottomup”–buildingsomethingbyassemblingsmallercomponents(likebuildingacarengine).Innanotechnology:self-assemblyofatomsandmolecules,asinchemicalandbiologicalsystems。2Basicconcepts(Clusters（团簇）smallernanoparticlescontainingfewerthan104atomsormolecules.（包含少于104MagicNumbers（幻数）theunusuallyhighmassspectralabundancesthatoccurforcertainclustersizeswhichrepresentspecialelectronicorgeometricconfigurations（具有异乎寻常;Nanoparticle（纳米微粒）:物质颗粒体积效应和表面效应两者之一显著变化或者两者都显著出现的颗粒。)3、Howtoachievesupersaturationvapor?(1)thephysicalcoolingofavaporbysonicorsupersonicexpansiontechniques;(2)agasphasechemicalorphotochemicalreactionthatcanproducenonvolatilecondensableproducts;2(3)directlybythermalevaporation,sputtering,orlaserablation.Educetheformulaofsurfacetovolumeratioofclusters4n1F3sTwoimportantdifferencesbetweenthenanoparticlesandtheclustersFirst,nanoparticlesareusuallylargerthantheclusters.Theyrangeinsizefrom1to100nm.Secondly,inmuchlargerquantitiesthantheclustersReasons：highparticle；Outofthevacuumchamber。三、(1)Theadvantagesandpotentialdifficultiesadvantages1).versatilityindesigningandsynthesizingnewmaterials2).themanipulationofmatteratthemolecularlevel：mixingatthemolecularlevel；goodchemicalhomogeneitycanbeachieved；3).molecularsyntheticchemistrycanbetailordesignedtopreparenovelstartingcomponents4).Bettercontroloftheparticlesize,shape,andsizedistributioncanbeachievedinparticlesynthesispotentialdifficulties：thechemistryiscomplexandhazardousEntrapmentofimpuritiesinthefinalproductScalingupfortheeconomicalproductionofalargequantityofmaterialmayberelativelyeasyforsomebutnotallsystemsundesirableagglomerationatanystageofthesynthesisprocesscanchangetheproperties(2)PrimaryparticlesandsecondaryparticlesThesmallsubunitsaredefinedastheprimaryparticlesandtheagglomeratesoftheseprimaryparticlesarecalledsecondaryparticles.(3)FactorsinfluencingtherateofprecipitatedreactionsFactorsinfluencingtherateofreactionsincludetheconcentrationofreactants,thereactiontemperature,thepH,andtheorderinwhichthereagentsareaddedtothesolution。(4)ThereasonsofagglomerationAgglomerationoffineparticlesiscausedbytheattractivevanderWaalsforceand/orthedrivingforcethattendstominimizethetotalsurfaceenergyofthesystem。(5)Measurestoagainstagglomeration：Repulsiveinterparticleforcesarerequiredtopreventtheagglomerationoftheseparticles（为了防止分散的粒子团聚，可以加四、(1)high-energyballmilling料进行强烈撞击、研磨或搅拌，把金属或合金粉末粉碎成纳米级微粒的方法。mechanicalattrition球磨罐中进行高能球磨，粉末通过压延压合-碾碎的反复过程最后获得组织和成分分布均匀的合金粉末，由于该方法利用机械能达到合金化，而不用热电能，所以把高能球磨制备合金粉末的方法称为机械研磨。(2)Whatisthemajorproblemofmechanicalattrition(orthedisadvantagesofMA)?Explainthemandwhichmeasurescanbetotake?surfaceandinterfacecontamination。themillingtools(Fe)andatmosphere3(traceelementsofO2,N2inraregases)canbeaproblem.Measures:minimizingthemillingtime;usingthepurest,mostductilemetalpowders,athincoatingofthemillingtools;sealingthevialwithaflexible'O'ringafterthepowderhasbeenloadedinaninertgasglovebox.(3)MechanismofGrain-sizeReduction(Theprocessesleadingtothegrainsizerefinementincludethreebasicstages).(i)Initially,thedeformationislocalizedinshearbandsconsistingofanarrayofdislocationswithhighdensity.(ii)Atacertainstrainlevel,thesedislocationsannihilateandrecombineassmall-anglegrainboundariesseparatingtheindividualgrains.Thesubgrainsformedviathisroutearealreadyinthenanometerrange(~20–30nm).(iii)Theorientationsofthesingle-crystallinegrainswithrespecttotheirneighboringgrainsbecomecompletelyrandom.五、1)Thereactionsinalkoxidesolutionhydrolysistomakethesolutionactive(reactionI)condensationpolymerization(reactionII)alongwithfurtherhydrolysisThesereactionsincreasethemolecularweightoftheoxidepolymer(reactionsIIIandIV).sol–geltransition:thesolutionreactstoapointwherethemolecularstructureisnolongerreversible2)ThefundamentaldifferencebetweenalkoxideprecursorsandcolloidalsolprecursorsColloidalsolsarealsoreferredtoasprecursorsforsol–gelprocessing。Inthiscase,the„sol‟insol–gelprocessingisnotshorthandforsolution,but,infact,acolloidalsolution.theaggregationofsolparticlesiscausedbychangingthepHorchangingtheconcentration(Ludox)differencebetweenalkoxideprecursorsandcolloidalsolprecursorsdiscretefeatures。poreswithinsecondaryparticlesandporesbetweensecondary。3)Powder-freeProcessingofGelShapes(monoliths,fibers,thinfilms)4)Theprocessingstepsofsol-gelthatarecommontoallgeometries(I)dissolvingandreactingtheprecursors;(II)formingandgellingtheshapes;(III)drying;(IV)firingtopartialorfulldensity.4六、1、Thedefinitionsofpressurelesssintering,pressureassistedsinteringandsinter-forging无压烧结：纳米晶粉末压制成型后，高温烧结致密化而不需压力。压力辅助烧结：对样品施加一个大于大气压的外力进行烧结。行。2Whywecan'tusewetprocessedtofabricatemetals?Becauseparticlescanslideandrearrangemuchmoreeasilyinaliquidmedium,itisoftenadvantageoustofabricatepowdercompacts,particularlyceramicpowdercompactsbywet-processingtechniques.Note:metalparticlesaretypicallynotwetprocessedduetotheirrelativelygoodbehaviorindrypressingandtheirtendencytoformoxidelayersduringexposuretoaqueousmedia3、Threestagesofdensificationofnanocrystallineceramicsduringpressurelesssintering.1）.Neckgrowthoccursatthecontactpointsbetweenadjacentparticles2）.Theceramichasasponge-likestructureconsistingofanextensivenetworkoftubularporesopentotheoutsidesurfaceoftheceramicsample.Mostoftheactualdensificationtakesplaceduringthissecondstage,asthetubularporesshrinktosmallerandsmallerdiameters.Oncetheseporesareverynarrowrelativetotheirlength,theybecomeunstableandpinchofftoformisolated,closed,sphericalpores.3）.Theeliminationofclosedpores.4、Howtoovercometheproblemofinhomogeneoussintering?Forsmallsamples:onemightcanbetousefastheatingratesforthedensificationofnanocrystallinethinfilmsFormoderate-to-large-sizedsamples:)slowingheatingratesduringsintering)changingthesample‟sstartingmicrostructure('precoarsening'treatment,inwhichthesampleisheatedatalowtemperaturelongenoughforporesandgrainstogrowsomewhat))choosinglowsinteringtemperatureswithlongtimes薄膜样品,使用快的升温速率.；中、大型样品采用慢的升温速率；改变样品的初始微结构；低温长时间烧结。)5、MinimizingGrainGrowthandMaximizingDensificationduringPressurelessSintering(Principlesformetalsandceramicsduringpressurelesssintering)Somesimpleprinciplesfortheproductionoffullydensematerialswithsub-100nmgrainsizefromultrafinestartingpowders.8.1Metals(i)Compacttothehighestpossibledensitypriortosintering(ii)Sinteratalowtemperature(toavoidgraingrowth)foraslongasnecessarytoremoveresidualporosityandestablishequilibriumgrainboundariesbetweenneighboringparticles.8.2Ceramics(i)Chooseanon-agglomeratedstarting。(ii)Maximizedensificationratesbyminimizingtheporesizewithinthestartingcompact:Forsmallsamples,narrowporescanbeachievedbycompactingatlarge5pressures;forlargersamples,fabricatingthepowdercompactbywet-processingtechniquesisanoption.(iii)Minimizegraingrowthkineticsbychoosingalow-sintering-temperature/long-sintering-timecombination.(iv)Avoidfastheatingrates,especiallyinceramicswhicharenotthermallyconductive(v)Forselectceramicsinwhichgraingrowthislimitedbythepresenceofpores,graingrowthwillbeseverelycurtailedupto≈90%density.七、1.Surfacechemistryisofvitalimportanceinnumerousprocessesandthisisfortworeasons.Pleaseexplainthemrespectively?First,thehugesurfaceareasofthenanostructuredmaterialdictatethatmanyoftheatomsareallthesurface,thusallowinggood``atomeconomy''insurface-gas,surface-liquid,orevensurface-solidreactions.Second,nanoparticlesfeatureisenhancedintrinsicchemicalreactivityassizegetssmaller.(纳米结构材料具有很大表面积,表明表面有很多原子,原子利用率高.而且增强了本征化学反应,尺寸降低.)Thereasonsforthisenhancedreactivityaremostlikelyduetochangesincrystalshape.However,thereareotherfeaturesthatcanaffect``surfaceenergy.''Ascrystalsizebecomessmaller,anion/cationvacanciesoftheFrenkelorSchottkytypebecomeprevalent.Also,atomsonthesurfacecanbedistortedintheirbondingpatterns.2.Whymetallicnanoparticlescanbeusedascatalysts,thereexistthreeeffects,explainthemrespectively?电子效应:Electrondensitychangesatcatalyticsitescanvaryduetoparticlesize.由于粒子尺寸改变,催化中心电子密度发生变化)载体效应:一些载体在金属表面进行沉积从而形成一些活性点.(thephenomenonisthetendencyofsomesupportstoformdepositsonthecatalyticmetalparticles,therebyformingcatalyticallyactiveinterfacesites.）形状效应：（1）Certainchemicalreactionsare``structure-sensitive''(hydrogenolysisofcyclopropane,dehydrocyclization,etc.).Thismeans,thatasthereactantapproaches,severaladjacentsurfacemetalatomsarerequiredfortheadsorptionandcatalytictransformationtoproceed.（2Inanothermanifestationofshapeeffects,itisoftenassumedthattheactivesitesareatlowcoordination(edges,corners),andthesmallnessofthecatalyticparticlecanaffectcrystalshapeandthereforesurfaceconcentrationofedge/cornersites.(forexample)3.Asabsorbents,whynanostructuredmaterialsaresousefulinchemistry?First,theypossessverylargesurfaceareas.Second,nano-crystalshapesusuallyaffordlargesurfaceconcentrationsofedge/cornerandvariousdefectsites,orotherunusualstructuralfeatures,suchaschannelsorwell-definedcavities.Third,inadditiontotheseaspectsnano-structuredmaterials,whenconsolidated,canexhibitunusualporestructure,andinthiswayexhibitstericeffectsonadsorptionprocesses.八、ListthefivedifferentregulationsofHall-Petcheffectinnanometermaterialsandexplainthepossibleexistentreasons.FirstwriteouttheHall-PetchequationEmpiricalHall–Petchequationrelatesyieldstresssytoaveragegrainsizedincommonmulticrystalmaterials。kkHHy0v0dd6whereisafrictionstress,isaconstant,istheaveragegrainsize,andHkd0isahardness.PositiveHPslope(K>0)(2)NegativeHPslope(K<0)(3)Positive-NegativeHPsloped(K>0,asd>dc,andK<0,asd<dc)where(4)Deviat