材料科学导论英文前言.ppt

1、IntroductionofMaterialsScienceIntroductionofMaterialsScienceChapter1Introduction1.1HistoricalPerspectiveMaterialsaremoredeep-seatedinourculturethanmostofusrealize.Transportation,housing,clothing,communication,recreation,andfoodproduction-virtuallyeverysegmentofoureverydaylivesisinfluencedtoonedegree

2、oranotherbymaterials.Chapter1IntroductionHistorically,thedevelopmentandadvancementofsocietieshavebeenintimatelytiedtothemembersabilitytoproduceandmanipulatematerialstofilltheirneeds.Earlycivilizationshavebeendesignatedbytheleveloftheirmaterialsdevelopment(StoneAge,BronzeAge,etal.,)Chapter1Introducti

3、onFirstly,theearliesthumanhadaccesstoonlyaverylimitednumberofmaterials,thosethatoccurnaturally:stone,wood,clay,skins,andsoon.Secondly,thehumandiscoveredtechniquesforproducingmaterialsthathadpropertiessuperiortothoseofthenaturalones,thesenewmaterialsincludedpotteryandvariousmetals.Chapter1Introductio

4、nFurthermore,itwasdiscoveredthatthepropertiesofamaterialscouldbealteredbyheattreatmentsandbytheadditionofothersubstances.Nowthescientistscometounderstandtherelationshipsbetweenthestructuralelementsofmaterialsandtheirproperties.Chapter1IntroductionThus,tensofthousandsofdifferentmaterialshaveevolvedwi

5、thratherspecializedcharacteristicsthatmeettheneedsofourmodernandcomplexsociety;theseincludemetals,plastics,glasses,andfibers.Thedevelopmentofmanytechnologiesthatmakeourexistencesocomfortablehasbeenintimatelyassociatedwiththeaccessibilityofsuitablematerials.Chapter1IntroductionAnadvancementintheunder

6、standingofamaterialtypeisoftentheforerunnertothestepwiseprogressionofatechnology.In our contemporary era,sophisticatedelectronic devices rely on componentsthat are made from what are calledsemiconductingmaterials.Chapter1Introduction1.2MaterialsScienceandEngineeringThedisciplineofmaterialsscienceinv

7、olvesinvestigatingtherelationshipsthatexistbetweenthestructuresandpropertiesofmaterials.Materialsengineeringis,onthebasisofthesestructure-propertytoproduceapredeterminedsetofproperties.Chapter1Introduction“Structure”is a nebulous term thatdeservessomeexplanation.In brief,the structure of a materialu

8、suallyrelatestothearrangementofitsinternalcomponents.Subatomic structure involves electronswithintheindividualatomsandinteractionswiththeirnuclei.(ElectronicStructure)Chapter1IntroductionOnanatomiclevel,structureencompassestheorganizationofatomsormoleculesrelativetooneanother.(AtomicStructure)Thenex

9、tlargerstructuralrealm,whichcontainslargegroupsofatomsthatarenormallyagglomeratedtogether,istermed“microscopic”.(MicroscopicStructure)Chapter1IntroductionFinally,structuralelementsthatmaybeviewedwiththenakedeyearetermed“macroscopic.”(Macroscopicstructure)Thenotionof“property”deserveselaboration.Whil

10、einserviceuse,allmaterialsareexposedtoexternalstimulithatevokesometypeofresponse.Chapter1IntroductionApropertyisamaterialtraitintermsofthekindandmagnitudeofresponsetoaspecialimposedstimulus.Generally,definitionsofpropertiesaremadeindependentofmaterialshapeandsize.Virtuallyallimportantpropertiesofsol

11、idmaterialsmaybegroupedintosixdifferentcategories:Chapter1Introduction1.Mechanicalproperties2.Electricalproperties3.Thermalproperties4.Magneticproperties5.Opticalproperties6.DeteriorativepropertiesChapter1IntroductionForeachthereisacharacteristictypeofstimuluscapableofprovokingdifferentresponses.Mec

12、hanicalpropertiesrelatedeformationtoanappliedloadorforce(includingelasticmodulusandstrength).Chapter1IntroductionForelectricalproperties,suchaselectricalconductivityanddielectricconstant,thestimulusisanelectricfield.Thethermalpropertiesofsolidscanberepresentedintermsofheatcapacityandthermalconductiv

13、ity.Magneticpropertiesdemonstratetheresponseofamaterialtotheapplicationofmagneticfield.Chapter1IntroductionForopticalproperties,thestimulusiselectro-magneticorlightradiation.(indexofrefractionandreflectivity)Deteriorativecharacteristicsindicatethechemicalreactivityofmaterials.Chapter1IntroductionIna

14、dditiontostructureandproperties,twootherimportantcomponentsareinvolvedinthescienceandengineeringofmaterialsnamely“processing”and“performance.”Withregardtotherelationshipsofthesefourcomponents,thestructureofamaterialwilldependonhowitisprocessed.Chapter1IntroductionFurthermore,amaterialsperformancewil

15、lbeafunctionofitsproperties.Theinterrelationshipbetweenprocessing,structure,properties,andperformanceisshownasFigure1.1Chapter1IntroductionStructureProcessingPropertiesPerformanceFigure 1.1 The relationships of structure,properties,precessing and performanceChapter1IntroductionWenowpresentanexampleo

16、ftheseprocessing-structure-properties-performanceprinciples.Allofthesespecimensareofthesamematerials:aluminumoxide(Al2O3)Chapter1IntroductionAsinglecrystal-thatis,itishighlyperfect-whichgivesrisetoitstransparency,soitistransparent;Theotheroneiscomposedofnumerousandverysmallsinglecrystalsthatareallco

17、nnected(polycrystals);Chapter1Introductiontheboundarybetweenthesesmallcrystalsscatteraportionofthelightreflectedfromtheprintedpage,whichmakesthismaterialsopticallytranslucent.Finally,thethirdspecimeniscomposednotonlyofmanysmall,interconnectedcrystals,butalsoofalargenumberofverysmallporesorvoidspaces

18、.(Ceramics)Chapter1IntroductionTheseporesalsoeffectivelyscatterthereflectedlightandrenderthismaterialopaque.Thus,thestructuresofthesethreespecimensaredifferentintermsofcrystalboundariesandpores,whichaffecttheopticaltransmittanceproperties.Chapter1IntroductionFurthermore,eachmaterialwasproducedusinga

19、differentprocessingtechniques.Andofcause,ifopticaltransmittanceisanimportantparameterrelativetotheultimatein-serviceapplication,theperformanceofeachmaterialwillbedifferent.Chapter1Introduction1.3WhystudyMaterialsScienceandEngineering?Manyanappliedscientistorengineer,whethermechanical,civil,chemical,

20、orelectrical,willatonetimeoranotherbeexposedtoadesignprobleminvolvingmaterials.Chapter1IntroductionOfcourse,materialsscientistsandengineersarespecialistswhoaretotallyinvolvedininvestigationanddesignofmaterials.Manytimes,amaterialsproblemisoneofselectingtherightmaterialfromthemanythousandsthatareavai

21、lable.Thereareseveralcriteriaonwhichthefinaldecisionisnormallybased.Chapter1IntroductionFirstofall,thein-serviceconditionsmustbecharacterized,forthesewilldictatethepropertiesrequiredofthematerial.Ononlyrareoccasionsdoesamaterialpossessthemaximumoridealcombinationofproperties.Chapter1IntroductionThus

22、,itmaybenecessarytotradeoffonecharacteristictoanother.Chapter1Introduction The classic example involves strengthandductility;normally,amaterialhavingahigh strength will have only a limitedductility.A second selection consideration isany deterioration of material propertiesthatmayoccurduringserviceop

23、eration.Chapter1IntroductionForexample,significantreductionsinmechanicalstrengthmayresultfromexposuretoelevatedtemperaturesorcorrosiveenvironments.Finally,theoverridingconsiderationisthat of economics:what will the finishproductcost?Chapter1IntroductionAmaterialmaybefoundhastheidealset of properties

24、 but is prohibitivelyexpensive.Hearagain,somecompromiseisinevitable.The cost of a finished piece alsoincludes any expense incurred duringfabricationtoproducethedesiredshape.Chapter1Introduction1.4ClassificationofMaterialsSolidmaterialshavebeenconvenientlygroupedintothreebasicclassifications:metals,c

25、eramicsandpolymers.Thisschemeisbasedprimarilyonchemicalmakeupandatomicstructure.Chapter1IntroductionInaddition,therearethreeothergroupsofimportantengineeringmaterials-composites,semiconductorsandbiomaterials.METALSMetallicmaterialsarenormallycombinationsofmetallicelements.They have large numbers of

26、nonlocated electrons:that is,these electrons are notboundtoparticularatoms.Chapter1IntroductionMany properties of metals are directlyattributabletotheseelectrons.Metals are extremely good conductorsof electricity and heat and are nottransparenttovisitlight;apolishedmetalsurfacehasalustrousappearance

27、.Metalsarequitestrong,yetdeformable,whichaccountsfortheirextensiveuseinstructureapplicationsChapter1IntroductionCERAMICSCeramicsarecompounds betweenmetallic and nonmetallic elements;theyaremostfrequentlyoxides,nitrides,andcarbides.The wide range of materials that fallwithinthisclassificationincludes

28、ceramicsare composedof clay minerals,cement,andglass.Chapter1IntroductionCeramicsaretypicallyinsulativetothepassage of electricity and heat,and aremoreresistanttohightemperaturesandharsh environments than metals andpolymers.With regard to mechanical behavior,ceramicsarehardbutverybrittle.Chapter1Int

29、roductionPOLYMERSPolymersincludethefamiliarplasticandrubbermaterials.Many of them are organic compoundsthat are chemically based on carbon,hydrogen,andothernonmetallicelements;theyhaveverylargemolecularstructures.Thesematerialstypicallyhavelowdensitiesandmaybeextremelyflexible.Chapter1IntroductionCO

30、MPOSITESAnumberofcompositematerialshavebeenengineeredthatconsistofmorethanonematerialtype.Acompositeisdesignedtodisplayacombinationofthebestcharacteristicsofeachofthecomponentmaterial.Chapter1IntroductionFiberglass is a familiar example,inwhichglassfibersareembeddedwithinapolymericmaterial.Fiberglas

31、s acquires strength from theglassandflexibilityfromthepolymer.Chapter1IntroductionSEMICONDUCTORSemiconductorshaveelectricalpropertiesthatareintermediatebetweentheelectricalconductorsandinsulators.Furthermore,the electrical characteristicsofthesematerialsareextremelysensitivetothe presence of minute

32、concentrations ofimpurityatoms;theseconcentrationsmaybecontrolledoververysmallspatialregions.Chapter1IntroductionBIOMATERIALSBiomaterialsareemployedincomponents implanted into the humanbody for replacement of diseased ordamagedbodyparts.Thesematerialsmustnotproducetoxicsubstancesandmustbecompatiblew

33、ithbodytissues.Chapter1IntroductionAll of the above materials-metals,ceramics,polymers,composites,and semiconductors-may be used as biomaterials.1.5 Advanced Materials Materials that are utilized in high-technology(or high-tech)application are sometimes termed advanced materials.Chapter1Introduction

34、By high technology we mean a device or product that operates or functions using relatively intricate and sophisticated principles;examples include electronic equipment(VCRs,CD players,etc.),computers,fiberoptical systems,spacecraft,aircraft,and military rocketry.Chapter1IntroductionThese advanced ma

35、terials are typicallyeithertraditionalmaterialswhosepropertieshavebeenenhancedornewlydeveloped,high-performancematerials.Chapter1IntroductionFurthermore,they may be of all material types(e.g.,metals,ceramics,polymers)and are normally relatively expensive.For example,advanced materials are materials

36、that used for lasers,integrated circuits,magnetic information storage,liquid crystal displays(LCDs),fiber optics and the thermal protection system for the Space Shutter Orbiter.Chapter1Introduction1.6METRIALSOFTHEFUTURESMARTMATERIALSSmart(or intelligent)materials are agroupofnewandstate-of-the-artma

37、terials now being developed that willhave a significant influence on many ofourtechnologies.Chapter1IntroductionTheadjective“smart”impliesthatthesematerialsareabletosensechangesintheirenvironmentsandthenrespondtothesechangesinpredeterminedmanners-traitsthatarealsofoundinlivingorganisms.Chapter1Intro

38、ductionInaddition,this“smart”conceptisbeingextendedtorathersophisticatedsystemsthatconsistofbothsmartandtraditionalmaterials.Componentsofasmartmaterial(orsystem)includesometypeofsensor(thatdetectsaninputsignal),andanactuator(thatperformsaresponsiveandadaptivefunction).Chapter1IntroductionActuators m

39、ay be called upon to changeshape,position,naturalfrequency,ormechanical characteristics in response tochange in temperature,electric fields,and/ormagneticfields.Fourtypesofmaterialsarecommonlyusedforactuators:shapememoryalloys,piezo-electricceramics,magnetostrictivematerials,Chapter1Introductionande

40、lectrorheological/magnetorheologicalfluids.Shapememoryalloysaremetalsthat,afterhavingbeendeformedrevertbacktotheiroriginalshapeswhentemperatureischanged.Piezoelectricceramicsexpandandcontractinresponsetoanappliedelectricfield(orvoltage);conversely,theyalsogenerateanChapter1Introductionelectricfieldw

41、hentheirdimensionsarealtered.Thebehaviorofmagnetostrictivematerialsisanalogoustothatofthepiezoelectricceramics,exceptthattheyareresponsivetomagneticfields.Chapter1IntroductionAlso,electrorheological and magneto-rheologicalfluidsareliquidsthatexperiencedramaticchangesinviscosityupon the application o

42、f electric andmagneticfield,respectively.Forexample,onetypeofsmartsystemisusedinhelicopterstoreduceaerodynamiccockpitnoisethatiscreatedbytherotatingrotorblades.Chapter1Introduction Piezoelectricsensorsinsertedintotheblades,monitorbladestressanddeformations;feedbacksignalsfromthesesensorsarefedintoac

43、omputer-controlledadaptivedevice,whichgeneratesnoise-cancelingantinoise.Chapter1IntroductionNANOTECHNOLOGYUntilveryrecenttimesthegeneralprocedureutilizedbyscientiststounderstandthechemistryandphysicsofmaterialshasbeentobeginbystudyinglargeandcomplexstructures,andthentoinvestigatethefundamentalbuildi

44、ngblocksofthesestructuresthataresmallerandsimpler.Chapter1IntroductionThisapproachissometimestermed“top-down”science.However,withtheadventofscanningprobemicroscopes,whichpermitobservationofindividualatomsandmolecules,ithasbecomepossibletomanipulatesandmoveatomsandmoleculestoformnewstructuresand,thus

45、,designnewmaterialsthatarebuiltfromsimpleatomicleveltoconstituents(i.e.,”materialsbydesign”).Chapter1IntroductionThisabilitytocarefullyarrangeatomsprovidesopportunitiestodevelopmechanical,electrical,magnetic,andotherpropertiesthatarenototherwisepossible.Wecallthisthe“bottom-up”approach,andthestudyof

46、thepropertiesofthesematerialsistermed“nanotechnology”;the“nano”prefixdenotesthatarethedimensionsofthesestructuralentitiesareontheorderofanano-meter(10-9m)-asarule,lessthan100nano-meters(equivalenttoapproximately500atomdiameters).Chapter1IntroductionOneexampleofamaterialofthistypeisthecarbonnanotube.

47、In the future,we undoubtedly find thatincreasinglymoreofourtechnologicaladvanceswillutilizethesenano-engineeredmaterials.Chapter1Introduction1.7MODERNMATERIALS”NEEDSIn spite of the tremendous progressthat has been made in the discipline ofmaterialsscienceandengineeringwithinthe past few years,there

48、still remaintechnological challenges,including thedevelopmentofevenmoresophisticatedand specialized materials,as well asconsiderationoftheenvironmentalimpactofmaterialsproduction.Chapter1IntroductionNuclear energy holds some promise,but the solutions to the many problemsthatremainwillnecessarilyinvo

49、lvematerials,from fuels to containmentstructurestofacilitiesforthedisposalofradioactivewaste.Significantquantitiesofenergyareinvolvedintransportation.Chapter1IntroductionReducingtheweightoftransportationvehicles(automobiles,aircraft,trains,etc.),as well as increasing engineoperating temperatures,wil

50、l enhancedfuelefficiency.Newhigh-strength,low-densitystructurematerialsremaintobedeveloped,aswellasmaterialsthathavehigher-temperaturecapabilities,foruseinenginecomponents.Chapter1IntroductionFurthermore,there is a recognizedneedtofindnew,economicalsourcesofenergyandtousepresentresourcemoreefficient