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1、Microstructure-Properties:II CrystallizationofGlass27-302Lecture4Fall,2002Prof.A.D.Rollett1MaterialsTetrahedronMicrostructurePropertiesProcessingPerformance2ObjectiveTheobjectiveofthislectureistoprovidesomebackgroundfortheexperimentinvolvingcrystallizationofglass-ceramic.Thematerialdiscussedinthi
2、slectureshouldbefamiliartostudentsfromthelecturesonnucleationandgrowth.3ReferencesPhasetransformationsinmetalsandalloys,D.A.Porter,&K.E.Easterling,Chapman&Hall.PhysicalCeramics(1997),Y.-T.Chiang,D.P.BirnieIII,W.D.Kingery,Wiley,NewYork,pp430-450.MaterialsPrinciples&Practice,ButterworthHeinemann,Ed
3、itedbyC.Newey&G.Weaver.Glass-Ceramics(1979),P.W.McMillan,AcademicPress,NewYork.Glass-CeramicTechnology(2002),W.Höland&G.Beall,TheAmericanCeramicSociety,Westerville,OH.Applications,Production,andCrystallizationBehaviorofanUltra-LowExpansionGlass-Ceramic:Zerodur,presentationbyDr.MarkJ.Davis,SchottG
4、lassTechnologies,Oct.17thatCMU.4GrowthRatesCrystallizationinglassesisgenerallyaphenomenontobeavoidedifatallpossible.Crystallizationmakesglassopaque,forexample,anddoesimproveitsotherproperties.Theexceptionisthecaseofglass-ceramics.Mostglass-ceramicsarevaluedforacombinationofchemicalinertnessandthe
5、rmalshockresistance.ThermalshockresistancedependsonlowCTE.LowCTEmeansthatstrainsdevelopedoncoolingfromhightemperaturesgeneratesmallstressesandthebreakingstrengthislesslikelytobeexceeded.Ourparticularexampleisopposite:highCTEisneededforcompatibilitywithmetals.5GlassCeramicsOtherglassceramicmateria
6、lsareoptimizedfor:HighmechanicalstrengthHightemperaturecapabilityPhotosensitivityLowdielectricconstant(electronicpackaging)Dielectric-breakdownresistanceBiologicalcompatibilityMachinability(throughtheinclusionofmicaceousphases)6ApplicationsofGlassCeramicsRadomes-Corning9606,cordieriteglass-cerami
7、c.Requiredproperties:transparencytoradar,lowdielectricconstant,lowCTE,highstrength,highabrasionresistance,highthermalshockresistance.Photosensitiveglass-ceramicsbasedonlithiumdisilicate,Li2Si2O5,asthecrystallinephaseth
