纳米材料与微型机器外文文献翻译中英文翻译.docx

纳米材料与微型机器外文文献翻译中英文翻译.docx

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纳米材料与微型机器外文文献翻译中英文翻译

外文资料

NanotechnologyandMicro-machine

原文

（一）:

Nanomaterial

Nanomaterialsandnanotechnologyhavebecomeamagicwordinmodernsociety.

Nanomaterialsrepresenttoday’scuttingedgeinthedevelopmentofnoveladvancedmaterialswhichpromisetailor-madefunctionalityandunheardapplicationsinallkeytechnologies.Sonanomaterialsareconsideredasagreatpotentialinthe21thcenturybecauseoftheirspecialpropertiesinmanyfieldssuchasoptics,electronics,magnetics,mechanics,andchemistry.Theseuniquepropertiesareattractiveforvarioushighperformanceapplications.Examplesincludewearresistantsurfaces,lowtemperaturesinterablehigh-strengthceramics,andmagneticnanocomposites.Nanostructuresmaterialspresentgreatpromisesandopportunitiesforanewgenerationofmaterialswithimprovedandmarvelousproperties.

Itisappropriatetobeginwithabriefintroductiontothehistoryofthesubject.Nanomaterialsarefoundinbothbiologicalsystemsandman-madestructures.Naturehasbeenusingnanomaterialsformillionsofyears,asDiscksonhasnoted:

“Lifeitselfcouldberegardedasananophasesystem”.Examplesinwhichnanostructuredelementsplayavitalrolearemagnetotacticbacteria,ferritin,andmolluscanteeth.Severalspeciesofaquaticbacteriausetheearth’smagneticfieldtoorientthenselves.Theyareabletodothisbecausetheycontainchainsofnanosized,single-domainmagnetiteparticles.Becausetheyhaveestablishedtheirorientation,theyareabletoswimdowntonutrimentsandawayfromwhatislethaltothem,oxygen.Anotherexampleofnanomaterialsinnatureisthatherbivorousmollusksuseteethattachedtoatonguelikeorgan,theradula,toscrapetheirfood.Theseteethhaveacomplexstructurecontainingnanocrystallineneedles.Wecanutilizebiologicaltemplatesformakingnanomaterials.Apoferritinhasbeenusedasaconfinedreactionenvironmentforthesynthesisofnanosizedmagnetiteparticles.Somescholarsconsiderbiologicalnanomaterialsasmodelsystemsfordevelopingtechnologicallyusefulnanomaterials.

Scientificworkonthissubjectcanbetracedbackover100years.In1861theBritishchemistThomasGrahamcoinedthetermcolloidtodescribeasolutioncontaining1to100nmdiameterparticlesinsuspension.Aroundtheturnofthecentury,suchfamousscientistsasRayleigh,Maxwell,andEinsteinstudiedcolloids.In1930theLangmuir-Blodgettmethodfordevelopingmonolayerfilmswasdeveloped.By1960Uyedahadusedelectronmicroscopyanddiffractiontostudyindividualparticles.Ataboutthesametime,arc,plasma,andchemicalflamefurnaceswereemployedtoprouducesubmicronparticles.Magneticalloyparticlesforuseinmagnetictapeswereproducedin1970.By1980,studiesweremadeonclusterscontainingfewerthan100atoms.In1985,ateamledbySmalleyandKrotofoundspectroscopicevidencethat

clusterswereunusuallystable.In1991,Lijimareportedstudiesofgraphiticcarbontubefilaments.

Researchonnanomaterialshasbeenstimulatedbytheirtechnologicalapplications.Thefirsttechnologicalusesofthesematerialswereascatalystsandpigments.Thelargesurfaceareatovolumeratioincreasesthechemicalactivity.Becauseofthisincreasedactivity,therearesignificantcostadvantagesinfabricatingcatalystsfromnanomaterials.Thepeopertiesofsomesingle-phasematerialscanbeimprovedbypreparingthemasnanostructures.Forexample,thesinteringtemperaturecanbedecreasedandtheplasticityincreasedonsingle-phase,structuralceramicsbyreducingthegrainsizetoseveralnanometers.Multiphasenanostructuredmaterialshavedisplayednovelbehaviorresultingfromthesmallsizeofheindividualphases.

Technologicallyusefulpropertiesofnanomaterialsarenotlimitedtotheirstructural,chemical,ormechanicalbehavior.Multilayersrepresentexamplesofmaterialsinwhichonecanmodifyoftuneapropertyforaspecificapplicationbysensitivelycontrollingtheindividuallayerthickness.ItwasdiscoveredthattheresistanceofFe-CrmultilayeredthinfilmsexhibitedlargechangesinanappliedmagneticfieldofseveraltensofkOe.Thiseffectwasgiventhenamegiantmagnetoresistance（GMR）.Morerecently,suitablyannealedmagneticmultilayershavebeendevelopedthatexhibitsignificantmagnetoresistanceeffectseveninfieldsaslowas5to10Oe（Oersted）.Thiseffectmayprovetobeofgreattechnologicalimportanceforuseinmagneticrecordingreadheads.

Inmicroelectronics,theneedforfasterswitchingtimesandeverlargerintegrationhasmotivatedconsiderableefforttoreducethesizeofelectroniccomponents.Increasingthecomponentdensityincreasesthedifficultyofsatisfyingcoolingrequirementsandreducestheallowableamountofenergyreleasedonswitchingbetweenstates.Itwouldbeidealiftheswitchingoccurredwiththemotionofasingleelectron.Onekindofsingle-electrondeviceisbasedonthechangeintheCoulombicenergywhenanelectronisaddedorremovedfromaparticle.Forananoparticlethisenerychangecanbelargeenoughthataddingasingleelectronwilleffectivelyblockstheflowofotherelectrons.TheuseofCoulombicrepulsioninthiswayiscalledCoulombblockade.

Inadditiontotechnology,nanomaterialsarealsointerestingsystemsforbasicscientificinvestigations.Forexample,smallparticlesdisplaydeviationsfrombulksolidbehaviorsuchasreductiosinthemeltingtemperatureandchanges（usuallyreductions）inthelatticeparameter.Thechangesnthelatticeparameterobservedformetalandsemiconductorparticlesresultfromtheeffectofthesurfacefreeenergy.Boththesurfacestressandsurfacefreeenergyarecausedbythereducedcoordinationofthesurfaceatoms.Bystudyingthesizedependenceofthepropertiesofparticles,itispossibletofindthecriticallengthscalesatwhichparticlesbehaveessentiallyasbulkmatter.Generally,thephysicalpropertiesofananoparticleapproachbulkvaluesforparticlescontainingmorethanafewhundredatoms.

Newtechniqueshavebeendevelopedrecentlythathavepermittedresearcherstoproducelargerquantitiesofothernanomaterialsandtobettercharacterizethesematerials.Eachfabricationtechniquehasitsownsetofadvantagesanddisadvantages.Generallyitisbesttoproducenanoparticleswithanarrowsizedistribution.Inthisregard,freejetexpansiontechniquespermitthestudyofverysmallclusters,allcontainingthesamenumberofatoms.Ithasthedisadvantageofonlyproducingalimitedquantityofmaterial.Anotherapproachinvolvestheproductionofpelletsofnanostructuredmaterialsbyfirstnucleatingandgrowingnanoparticlesinasupersaturatedvaporandthenusingacoldfingertocollectthenanoparticle.Thenanoparticlesarethenconsolidatedundervacuum.Chemicaltechniquesareveryversatileinthattheycanbeappliedtonearlyallmaterials（ceramics,semiconductors,andmetals）andcanusuallyproducealargeamountofmaterial.Adifficultywithchemicalprocessingistheneedtofindtheproperchemicalreactionsandprocessingconditionsforeachmaterial.Mechanicalattrition,whichcanalsoproducealargeamountofmaterial,oftenmakeslesspurematerial.Oneproblemcommontoallofthesetechniquesisthatnanoparticlesoftenformmicron-sizedagglomerates.Ifthisoccurs,thepropertiesofthematerialmaybedeterminedbythesizeoftheagglomerateandnotthesizeoftheindividualnanoparticles.Forexample,thesizeoftheagglomeratesmaydeterminethevoidsizeintheconsolidatednanostructuredmaterial.

Theabilitytocharacterizenanomaterialshasbeenincreasedgreatlybytheinventionofthescanningtunnelingmicroscope（STM）andotherproximalprobessuchastheatomicforcemicroscope（AFM）,themagneticforcemicroscope,andtheopticalnear-fieldmicroscope.SMThasbeenusedtocarefullyplaceatomsonsurfacestowritebitsusingasmallnumberofatmos.Ithasalsobeenemployedtoconstructacirculararrangementofmetalatomsonaninsulatingsurface.Sinceelectronsareconfinedtothecircularpathofmetalatoms,itservesadaquantum‘corral’ofatoms.Thisquantumcorralwasemployedtomeasurethelocalelectronicdensityofstatesofthesecircularmetallicarrangements.Bydoingthis,researcherswereabletoverifythequantummechanicaldescriptionofelectronsconfinedinthisway.

Othernewinstrumentsandimprovementsofexistinginstrumentsareincreasinglybecomingimportanttoolsforcharacterizingsurfacesoffilms,biologicalmaterials,andnanomaterials.Thedevelopmentofnanoindentorsandtheimprovedabilitytointerpretresultsfromnanoindentationmeasurementshaveincreasedourabilitytostudythemechanicalpropertiesofnanostructuredmaterials.Improvedhigh-resolutionelectronmicroscopesandmodelingoftheelectronmicroscopeimageshaveimprovedourknowledgesofthestructureofthetheparticlesandtheinterphaseregionbetweenparticlesinconsolidatednanomaterials.

Nanotechnology

1.Introduction

Whatidnanotechnology?

itisatermthatenteredintothegeneralvocabularyonlyinthelate1970’s,mainlytodescribethemetrologyassociatedwiththedevelopmentofX-ray,opticalandotherveryprecisecomponents.Wedefinednanotechnologyasthetechnologywheredimensionsandtolerancesintherange0.1～100nm（fromthesizeoftheatomtothewavelengthoflight）playacriticalrole.

Thisdefinitionistooall-embracingtobeofpracticalvaluebecauseitcouldinclude,forexample,topicsasdiverseasX-raycrystallography,atomicphysicsandindeedthewholeofchemistry.Sothefieldcoveredbynanotechnologyislaternarroweddowntomanipulationandmachiningwithinthedefineddimensionalrange（from0.1nmto100nm）bytechnologi