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1、材料科学导论FundamentalsofMaterialsScienceandEngineering（教案）青岛科技大学材料科学与工程学院1.IntroductionClassesofMaterialsItisconvenienttoclassifymaterialsintobroadcategoriesforstudy.Manyofthecommoncharacteristicsofmaterialswithinacategoryarisefromthelowestlevelofstructure,thenatureoftheatomicbondthatholdsthemtoge
2、ther,andthesesimilaritiesareaidstoorganizingourknowledge.Thetraditionalclassificationsare:•Metals•Ceramics(andglasses,whichareusuallymadeupofthesameelementsbutwithadifferentatomicarrangement)•Polymers(orplastics,tousethemorecommonname)•Composites(whichcombineseveralmaterialstoachieveuniqueorec
3、onomicalcombinationsofproperties)Somepeople(mostlythosewhousethem)alsodistinguishelectronicmaterials(semiconductors)asaseparateclass.Thepropertiesofthesevariousclassesofmaterialsareusuallyratherdistinct.Forinstance,metalsareopaquetolightandreflective.Theyare(usually)ductile,meaningthattheycanb
4、ebentbeforetheybreak.Theyareelectricallyandthermallyconducting.Ontheotherhand,ceramicsandglassesareusuallybrittle,canbetransparenttolight,andaregoodinsulators.Theyareparticularlyusefulathightemperaturesorincorrosiveenvironments,sincetheyretaintheirproperties.Mostpolymers,ontheotherhand,cannotw
5、ithstandhightemperatures.Mostareinsulators,andmanyarehighlydeformable(whichistherealmeaningoftheword,"plastic"),andsomehaveuniqueelasticproperties(rubberbands).Semiconductors,ofcourse,aredistinguishedbytheirelectricalbehavior.Allofthesepropertycharacteristics,andthereasonstheyexist,arediscusse
6、dinsomedetailinthechaptersthatfollow.Itwillbeimportanttounderstandthedifferencesbetweentheseclassesofmaterialsandhowtheyarisefromthenatureoftheatomicbondsandthemicrostructure.Butitwillalsobeimportanttorecognizethatcomparisonsareonlymeaningfulbasedonsimilarmeasurementprocedures.Forexample,mecha
7、nicalstrengthandductility,sensitivitytothepresenceofcracks,andcreepathightemperaturesaremeasuredinthesamewaysforallclassesofmaterials(ofcourse,ahightemperatureforapolymerismuchlowerthanitisforaceramic).Theresponseofthematerialstothesete
