无机非金属论文.docx

无机非金属论文.docx

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无机非金属论文

上海理工大学

universityofshanghaiforscienceandtechnology

FinalThesis

RoundupNano-ceramic

Subject：

ScienceofInorganicNonmetallicMaterials

StudentName:

吴昌志

School：

MaterialScienceandTechnology

MajorField：

MaterialsFormingandControlEngineering

StudentIDNo:

1326410222

Advisor：

王丁

DateJanuary1st，2016

Contents

Abstract

Thispapermainlyintroducesthenano-ceramicpreparationandinfluencingfactorsofpreparationandProspectofmechanicalpropertiesintheprocessof.Syntheticmethod,itmainlyintroducesthevaporsynthesisandsolgelsynthesismethodandinfluencingfactorsismainlyeffectofporesizeonthemechanicalproperties,andsolvetheseproblemsway,andliquidity.Theprospectistomakereferencetotheinvestmentofnanometerceramicsthroughthewesterncountries.

Keywords:

nano-ceramic,mechanicalproperties,porosity,fluidity

1Introduction

Ceramicmaterialsasoneofthethreepillarsofmaterialindustry,playsanimportantroleindailylifeandindustrialproduction.Ceramicscanbedividedintostructuralandfunctionalceramics,structuralceramicswithhightemperatureresistance,abrasionresistance,resistancetocorrosionandlightweight,thermalconductivitygoodadvantages;functionalceramicsinmechanical,electrical,thermal,magnetic,opticalandotheraspectshassomespecialfunctions,makeceramichasbeenwidelyusedinallaspects.Buttheexistenceoftheceramicdefectsinbrittle（cracks）anduniformlypoor,toughnessandstrengthofthepoor,sothattheapplicationsubjecttocertainrestrictions

Withthewideapplicationofnanotechnology,nano-ceramics.Nano-ceramicpowderswithnanosizebetweensolidandmolecule（1~100nm）metastableintermediatematerial.Withpowdersuperfining,thesurfaceelectronicstructureandcrystalstructurechange,producethebulkmaterialdonothavethespecialeffectandinthemicrostructureofnanoceramicmaterials,combinedwithgrain,grainboundariesbetweenthemandareinthenanometerlevel,makingthematerialstrength,toughnessandsuperplasticitygreatlyimprovedtoovercomethemanyshortcomingsofEngineeringceramics,andthematerialmechanical,electrical,thermal,electrical,magneticandopticalpropertieshaveasignificantimpact,soastotheapplicationofengineeringceramicsandopenupanewfield.

2Propertiesofnanoceramics

Themechanicalpropertiesofthestructureofnanoceramicmaterialswithconventionalmaterialscomparedtothegreatchangeshavetakenplace,theparticlegroupyuanfinetonanometermagnitude,theinterfacegroupelementgreatlyincreased,thematerialstrength,toughnessandsuperplasticityisgreatlyimproved,andhasimportantinfluenceonthethermal,optical,magnetic,electricalandotherproperties

2.1Mechanicalproperty

Hardnessandfracturetoughness:

onTiO2nanocrystalline,foundintheroomtemperaturecompression,nanoparticleshaveaverygoodcombination,higherthan500DEGCsoondensification,andgrainsizeisonlyaslightincrease,incomeofhardnessandfracturetoughnessvaluesandTiO2singlecrystalsorcoarseparticlecompressionofthecorrespondingvaluethancomparableorbetterperformance.NanocrystallineTiO2thehardnessandfracturetoughnessincreasedwiththeincreaseofsinteringtemperature（i.e.porositydecrease,in800~900DEGCtemperaturerangeofsintering,andcomparedtheoptimizationofsinteringbulkceramics,boththehardnessandfracturetoughnessvaluesareingoodagreement.Aftersinteringatlowtemperature,themechanicalpropertiesofnanocrystallineTiO2canbeobtained.Usuallyhardenedbrittle,resultinginfracturetoughnessdecreased,whilethenanocrystals,hardeningandtougheningbyvoideliminationtoform,thusincreasingtheoverallstrengthofthematerial.NanocrystallineTiO2aftersinteringtemperatureof800DEGC,VickershardnessH=630,fracturetoughnessKIC（Mpam1/2）is2.8,thevoidageis10%;andsinteringof1000DEGC,H=925,Kic=2.8,porosityis5%.

Fig.1RelationshipbetweenrelativedensityofTiO2nanoceramicssinteredat800℃

andmeanparticlesizeofstartingTiO2nanopowders

Fig.2RelationshipbetweenaveragegrainsizeFig.3TEMmicrographofTiO2nanoceramicspressed

ofTiO2nanoceramicsandsinteringtemperatureat720MPaandsinteredat800℃

Table1Averagegrainsize,phasestructure,relativedensityandvickersmicrohardnessofTiO2nanoceramicssinteringat

Plasticityandplasticity:

theplasticofthenanocrystallineceramicshasnothingtodowiththeresidualporosity.ThenanoTiO2sampleswereslottedbendingtestshowedthatnocrackgrowth,plasticdeformationcanbedisplayed.Thereisnoplasticdeformationinthefractureofthenotchedspecimensofbrittleporousmaterials.

Mostinterestedinissuperplasticstructure.Thesuperplasticplaysakeyroleisgrainboundarysliding,grainrotationandregulationofgrainshapeinthediffusionprocess.Infact,thesuperplasticceramicshavebeenreportedasaresultofthetemperatureistoohigh,itisdifficulttoachieve.KnownAl2O3in1750~1950DEGC,Al2O3andCr2O3dopedwithY2O3in1500DEGC,andMgOwithAl2O3dopedin1420DEGChashighstraincreep.Thesuperplasticflowcanbeshownonlyattheinterfacewiththeliquidphaseoftheceramicatlowertemperatures.Thenanoceramicultrafinegrain,comparedwithordinaryceramic,wededucethatthepresentstructureofthesuperplastictemperatureismuchlower.

2.2Thermalperformance

（1）thespecificheat,theinterfacestructureofnanomaterialsinatomicdistributionchaos,comparedwiththeconventionalmaterials,interfacialvolumefractionislarge,sonanomaterialentropycontributiontothespecificheatthantheconventionalmaterials.Thespecificheatofthecorrespondingparticlesizeis80nmAl2O3,whichis8%higherthanthatoftheconventionalcoarsegrainedAl2O3.

（2）thermalexpansion,thethermalexpansioncoefficientofnanoamorphoussiliconnitrideis1to26timeshigherthanthatofconventionalSi3N4.ThereasonisnanoamorphoussiliconnitridestructureandtheconventionalamorphousSi3N4isverydifferent,theformeriscomposedofshort-rangeorderintheamorphoussmallparticlesandtheinterfacebetweenthemaccountedforalargeproportionandarrangementofatomsattheinterfacecomparedwithamorphousparticlesinsidemorechaos.Underthesameconditions,nonlinearthermalvibrationofatomsandtheirbondthanconventionalcrystallineismoreremarkableandsoonthermalexpansioncontributionalsomustbeverylarge.

（3）thermalinsulationmaterialorsuperadiabatic,currentlyinthemiddlestageisstillintheexperimentalresearchandindustrialexperimentinourcountry.Duetotheporositysizetothenanometerlevel,mainlyproducedasnanoeffect:

whenthelightweightmaterialsporesizelessthan50nm,poresintheairmoleculeswilllosethefreeflowandthereforequitetopumpthevacuum,called"zeroconvectioneffect".Duetothevolumeoflowdensitymaterial,poresizeisverysmall,thenthenumberofporewalltendstoinfinity"".Foreveryporewallhascoveredtheroleofhotplate,resultinginnearly"infinitenumberofcoverhotplate"effect,sothattheradiationheattransferdecreasetotheminimumlimit.Duetothenearlyinfiniteinthepresenceofnanopores.Heattransferinsolidscanonlyalongtheporewallofthetransfer,nearinfinitenumberofporewallconstitutethenearly"infinitenumberofpatheffect,thesolidheatconductionabilitydowntoaminimum.

Areusedincalciumsilicatenanocompositeporoussuperthermalinsulationmaterialinconnectionwithfireprotectionofsteelstructurefire-resistanttimefromthegeneralqualitythickfireproofcoatingsfor2hextendedto15h,winningplentyoftimetofire.Thematerialisusedinsolarwaterheater,theheatcollectingefficiencyisincreasedmorethanonetimes,andheatlossdecreasedto30%now.

2.3Opticalperformance

Themicrostructureandtheopticalpropertiesofmaterials,especiallytheelectronstates,defectstatesandstructureofthestatelevel.Nanometermaterialsinthestructureandconventionalmaterialshaveverydifferent,outstandingperformanceinthesmallparticlesizeandlargevolumefractionofinterface,interfaceatomicarrangementandkeyconfigurationofirregularityislargerandtheopticalpropertiesofthenanometermaterialssomearedifferentfromconventionalmaterialsinthenewphenomenon.

（1）:

infraredabsorptionofnanomaterials,infraredabsorption,infraredabsorptionspectrashowedblueshiftandwide.NanoAl2O3,infraredabsorptionspectrahaveabroadabsorptionbandinthe400~1000cm-1wavenumberrange,comparedwiththeAl2O3singlecrystalandinfraredabsorptionpeakisobviouslyexpanded.Thecorrespondingsingle-crystal637cm-1and442cm-1absorptionpeak,innanophasebluemovedto639.7cm-1and442.5cm-1.

（2）:

CrdopednanofluorescenceexcitationwithultravioletlightandFeA12O3,wereobservedinthevisiblelightrangetonewfluorescencephenomenon.

（3）photoluminescence:

annealingtemperaturebelow673kandnonnanocrystalsiliconnitrideblockintheultraviolettovisiblelightrangeofluminescenceandconventionalamorphoussiliconnitridedifferent,sixdiscreteluminescenceband,andconventionalamorphoussiliconnitrideintheultraviolettovisiblelightawiderangeofwavelengthsoflighthasaverybroademissionband.

2.4Electromagneticproperties

Nanomaterialsandconventionalmaterialsinthestructure,especiallyinverydifferentmagneticstructure,sointermsofmagneticwillhasitsuniqueproperties.Exceptforthedifferentmagneticstructureandmagneticcharacteristics,theparticlesofNanocry