纳米材料与微型机器外文文献翻译中英文翻译.docx
- 文档编号:26776919
- 上传时间:2023-06-22
- 格式:DOCX
- 页数:27
- 大小:43.98KB
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》由会员分享,可在线阅读,更多相关《纳米材料与微型机器外文文献翻译中英文翻译.docx(27页珍藏版)》请在冰豆网上搜索。
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
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 纳米 材料 微型 机器 外文 文献 翻译 中英文