材料专业英语第五章

Chapter5

CeramicmaterialsDefinitionAceramicisaninorganic,nonmetallicsolidpreparedbytheactionofheatandsubsequentcooling.

Aceramicmaterialisaninorganic,non-metallic,oftencrystallineoxide,nitrideorcarbidematerial.Ceramicmaterialsmayhaveacrystallineorpartlycrystallinestructure,ormaybeamorphous(e.g.,aglass).ClassificationCeramicmaterialsTraditionalceramicsAdvancedceramicsaremadefromclay,silica,andfeldspar.Chinaanddentalporcelainaretraditionalceramicproducts.alsoclassifiedastechnicalceramicsaremainlypurecompoundsornearlypurecompoundsofprimarilyoxides,carbides,ornitrides.StructuresCeramicshavemorecomplexcrystalstructuresthanmetals.CeramicshavefewfreeelectronsatroomtemperatureTwotypesofbondingmechanismsoccurinceramicmaterials,ionicandcovalent.Oftenthesemechanismsco-existinthesameceramicmaterial.Thereasonthatthemajorityofceramicsarebrittleisthemixedionic-covalentbondingthatholdstheconstituentatomstogether.crystallineSiO2atomspackinperiodic,3DarraysAnaluminiumnitridefracturesurfacePropertiesMaterialPropertiesDiamondsAdvanced

CeramicsMetalsPlasticsTranditionalceramicsThepropertiesofceramicsvarydependingonbonds,composition,microstructure,andprocessing.CeramicsMetalsComparisonmetalsvs.ceramicsTypicalbehaviorofceramicsMosthavearegulararrangementofatoms(exceptglasses)CompoundsofmetallicandNon-metallicelementsDensitylowerthanmetalsStrongerthanmetalsCompressivestrengthistypicallytentimesthetensilestrengthLowresistancetofractureBrittle(lowductility)HighmeltingpointsPoorconductorsofelectricitySuperiorpropertiesofadvancedceramicsAdvancedceramicsarealsoreferredtoas“special”,“technical”,“engineering”,or“high-performance”ceramicsduototheirsuperiorproperties,suchas:SuperiormechanicalpropertiesCorrosion/oxidationresistanceSuperiorthermalresistance(about4000oC)SuperiorelectricalpropertiesOpticalMagneticproperties.ApplicationsandfutureofadvancedceramicsStructuralceramicsElectronicceramicsBioceramicsCompositesnanoceramicsThemostsignificantgrowthoftheglobalceramicsmarketisinadvancedceramics,includes:StructuralceramicsAlsocalledengineeringceramics,includesiliconnitride(Si3N4),siliconcarbide(SiC),zirconia(ZrO2),boroncarbide(B4C),andalumina(Al2O3).Theirrelativepropertiesarehighhardness,lowdensity,high-temperaturemechanicalstrength,creepresistance,corrosionresistance,andchemicalinertness.Theyareusedinapplicationssuchascuttingtools,wearresistingcomponents,andengineparts.CuttingtoolsBrakeDiscsGears(Alumina)wearresistingcomponentsTherearethreekeyissuestosolveinordertoexpandtheuseofstructuralceramics:reducingcostofthefinalproduct,improvingreliabilityandreproducibility.Electronicceramicsincludebariumtitanate(BaTiO3),zincoxide(ZnO),leadzirconatetitanate(Pb(ZrxTi1-x)O3),aluminumnitride(AlN),

indiumoxide(In2O3),andhightemperaturesuperconductor(HTSC).Mobilephones,iPad,highpowerLED(lightsystems)Therearemanychallengesforthefuture:integratingwithexistingsemiconductortechnology,improvingprocessing,andenhancingcompatibilitywithothermaterials.piezoelectricceramics压电陶瓷Bioceramicsareusedinthehumanbody.Theresponseofthesematerialsvariesfromnearlyinerttobioactivetoabsorbable.Nearlyinertbioceramicsincludezirconia(ZrO2)andalumina(Al2O3).Tricalciumphosphateisanexampleofaabsorbablebioceramic;itdissolvesinthebody.Biocompatible生物相容性Ballheadsandcupinsertsforhipjointprostheses.Threeissueswilldeterminefutureprogress:matchingmechanicalpropertiestohumantissues,increasingreliability,andimprovingprocessingmethods.CompositesCompositesmayuseceramicsasthematrixphaseand/orthereinforcingphase.Thepurposeofacompositeistodisplayacombinationofthepreferredcharacteristicsofeachofthecomponents.Thespaceshuttleusereusable,lightweight,highlyporousceramictilestoprotectthealuminumframefromtheheatgeneratedduringre-entryintotheEarth’satmosphere.Mechan.ApplicationsMedicalProductsCuttingToolsMechanicalSystemsChemicalApplicationsElectronicApplicationsMultifunctionalCeramicsArmorCeramicsSuperconductorCeramicsWhatisSuperconductor?Superconductors

havetwooutstandingproperties(superconductivity):1.Zeroelectricalresistance

零电阻Superconductorscancarrycurrentwithoutenergyloss.

bringsuperstrongmagneticfield!2.Perfectdiamagnetism

完全抗磁性Superconductorscanexpel(exclude)allmagneticfields.

float(levitate)abovemagneticfields!Meissnereffect迈斯纳效应SuperconductorTypesISuperconductors(softsuperconductor)

32puremetalswhichexhibitzeroresistivityatlowtemperature.TypeIIsuperconductors:primarilyofalloysorintermetalliccompoundsAlloys,whichhavelowTc.Nb3Sn,NbTi,

Nb-Al-Ge,Nb3Ge,etc.Lowtemperaturesuperconductor-----LTSHightemperaturesuperconductor----HTSCeramet金属陶瓷,whichhaverelative

higherTc.ClassificationofSuperconductor?SuperconductorCeramicsTheceramicmaterialsusedtomakesuperconductorsareaclassofmaterialscalledperovskites.钙钛矿Oneofthesesuperconductorisanyttrium(Y),barium(Ba)andcopper(Cu)composition.ChemicalformulaisYBa2Cu3O7.Thissuperconductorhasacriticaltransitiontemperaturearound90K,wellaboveliquidnitrogen's77Ktemperature.CompoundTc(K)Cs3C6040(15kbarappliedpressure)Ba0.6K0.4BiO330Lal.85Sr0.l5CuO440Ndl.85Ce0.l5CuO422YBa2Cu3O790Tl2Ba2Ca2Cu3O10125HgBa2Ca2Cu3O8+d133

LiquidN2:77KHighTcSuperconductors(HTS)（Tl4Ba）Ba2Ca2Cu7O13+，其转变温度已达254K（-19.6℃）

zeroresistancehighercurrentstableandlargemagneticfieldstrengthshighqualityimageshighHresonancesignalsuperconductorwiresMRI磁共振成像MagneticResonanceImageChemicalstructureanalyzer核磁共振(NuclearMagneticResonance,NMR)IntensityofMagneticfield---NMRTheNMRSpectrometerSincethe1H-NMRand13C-NMR,particularly13C-NMRneedhighmagneticfieldtogivehighqualityimages,superconductorsareupto胜任this.clearpeaksstablebaselinezeroresistance!TransportationIndustryDiamagnetismproducetheeffectoflevitationbyrepulsion;Maglevtrainsfloataboveamagneticfieldwithoutanycontactwiththetracks;Asaresult,highspeedsofupto550km/hrarepossiblewithonlyasmallconsumptionofenergy.---MaglevHTSMagnetDiamagnetism!/v_show/id_XMjA1MzcwNzE2.html

ElectricPowerIndustry---generator,cableHightemperaturesuperconductors(HTS)canbeusedintheproductionofmorecosteffectivemotors发动机andgenerators发电机.AdvantageHigherEfficiencyLowerweightandvolumezeroresistance!OrdinarycablesuperconductivecableHTSpowercablescancarrytwototentimesmorepowerinequallyorsmallersizedcables.zeroresistance!我国第一组实用型高温超导电缆，于2004年3月23日全部