氧化铈纳米粒子的制备

关于氧化铈纳米粒子的制备第一页，共二十七页，编辑于2023年，星期二SimplyintroducethestructureandapplicationsofCeO23.Futureworks2.SynthesisofnanocrystallineCeO2bydifferentmethodsOutline第二页，共二十七页，编辑于2023年，星期二BriefintroductionCeO2属于萤石型氧化物。

CeO2晶胞中的Ce4+按面心立方点阵排列，O2-占据所有的四面体位置，每个Ce4+被8个O2-包围，而每个O2-则与4个Ce4+配位。1.StructureofCeO22.功能特性

CeO2的结构中有1/2立方体空隙，可称之为敞型结构。敞型结构允许离子快速扩散。经高温(T＞950℃)还原后，CeO2转化为具有氧空位、非化学计量比的CeO2-X氧化物(0<x<0.5)，而在低温下(T＜450℃)CeO2可形成一系列组成各异的化合物。值得注意的是，即使从晶格上失去相当数量的氧，形成大量氧空位之后，CeO2仍然能保持萤石型晶体结构，这种亚稳氧化物暴露于氧化环境时又易被氧化为CeO2，因而CeO2具有优越的储存和释放氧功能及氧化还原反应能力，同时CeO2也有着良好的化学稳定性和高温快速氧空位扩散能力。

第三页，共二十七页，编辑于2023年，星期二ApplicationsofCeO2

玻璃脱色剂氧化铈大颗粒氧化铈磨料氧化铈抛光粉/液晶显示屏氧化铈抛光粉氧化铈抛光轮CeO2Slurry

此外，CeO2还用作催化材料、高温氧敏材料、pH传感材料、电化学池中膜反应器材料、燃料电池的中间材料、中温固体氧化物燃料电池(SOFC)用电极材料第四页，共二十七页，编辑于2023年，星期二SynthesisofCeO21.DirectprecipitationprecipitationStirandageingstageScouringanddryingtocalcineprecursorThepowerofCeO2Ce3+orCe4+technologyofdirectprecipitationprecipitantNitrate:

Ce(NO3)3or(NH4)2Ce(NO3)6Precipitant:

ammoniaorNH4HCO3

Surfaceactiveagent:

PEG-4000Process:nitrateandPEG-4000weredissolvedindistilledwate.ThenammoniaorNH4HCO3solutionwasaddeddropwiseundervigorousstirringtillthepHreached9.Theprecipitatewasfiltered,washedthricewithdistilledwaterandalcoholanddriedat80℃overnight.第五页，共二十七页，编辑于2023年，星期二(a)(b)(c)(d)Resultsanddiscussion(a)(b)(c)(d)SEMphotoesofprecursorXRDofprecursor(a):Ce(NO3)3+NH3·H2O(b):(NH4)2Ce(NO3)6+NH3·H2O(c):Ce(NO3)3+NH4HCO3(d):(NH4)2Ce(NO3)6+NH4HCO3第六页，共二十七页，编辑于2023年，星期二(a)(c)XRDofCeO2synthesizedat700℃(a)(b)(c)(d)XRDofCeO2synthesizedat500℃(a)(c)XRDofCeO2synthesizedat600℃第七页，共二十七页，编辑于2023年，星期二(a)(c)SEMphotoesofCeO2calcinedat600℃第八页，共二十七页，编辑于2023年，星期二MicrowavehomogeneousprecipitationMicrowavereactionequipmentNitrate:Ce(NO3)3or(NH4)2Ce(NO3)6Precipitant:

ureaSurfaceactiveagent:

PEG-4000CO(NH2)2+H2O→CO2+2NH3NH3+H2O→NH4++OH-CO2+H2O→CO32-+2H+

水解生成的构晶离子OH-、CO32-,在微波辐照作用下,与Ce3+、Ce4+等结合生成不溶前驱物

第九页，共二十七页，编辑于2023年，星期二ResultsanddiscussionXRDofprecursorcalcinedat500℃(a)(b)(c)XRDofprecursor(a)Mean:(a)0.093um(b)0.171um(c)0.210umLSofCeO2calcinedat600℃

(a)Ce(NO3)3+urea,withoutPEG-4000(b)Ce(NO3)3+urea+PEG-4000(c)(NH4)2Ce(NO3)6+urea+PEG-4000第十页，共二十七页，编辑于2023年，星期二600℃700℃XRDofCeO2synthesizedat600℃、700℃

SEMphotoofCeO2calcinedat600℃SEMphotoofprecursor(a)第十一页，共二十七页，编辑于2023年，星期二HydrothermalsynthesisofCeO2nano-particles1.Cerium(IV)hydroxideprecursorA.I.Y.Tok,etal(NanyangTechnologicalUniversity),JournalofMaterialsProcessingTechnology190(2007)217–222H2O2+cerium(III)nitrate,stirredfor5minunderheattoconvertCe3+toCe4++ammonia(pH=8.8),stircontinuouslyat80℃for1hthepaleyellowprecipitates(Ce(OH)4)werewashed,theconductivityofthesupernatant<=2ms30mlofthewashedprecipitates(pH=10)wereplacedintotheTeflonvesselofthehydrothermalbomb,thenplacedintheovenandheatedattherespectivedurations(0–24h)Thefinalproductswerere-washed,conductivity<=2ms,driedat75℃第十二页，共二十七页，编辑于2023年，星期二2.Ceriaacetateprecursorhydrousceriumoxidestabilizedbyacetateions(ceriumacetategel)wasdissolvedindeionizedwatertoyield‘acetatestabilizedcolloidalceriaandwillbeidentifiedasceriaacetateceriaacetatewasdiluted,placing30mlofthesolutionintotheTeflonvesselthebombwasthenplacedintheovenandheatedto250℃atdifferenttreatmenttimestheproductswerelatercentrifugedanddriedat75℃第十三页，共二十七页，编辑于2023年，星期二Fig.1.DTA/TGofCe(OH)4precursorResultsanddiscussionThetotalmeasuredweightlossfrom25to900℃was11.64%,whilethetheoreticalweightlossforthedecompositionofceriumhydrateoxideis17.3%,i.e.Ce(OH)4/CeO2·2H2OtoCeO2ThedecompositionoftheprecursorisaformofdehydrationprocessofthehydratedCeO2thedifferenceinweightlossobservedcouldbeduetothefollowingreasons:(a)precipitateconsistingofapartiallyhydratedformofceria,(i.e.CeO2·xH2O),forwhicha11.64%weightlossondecompositioncorrespondstox=1.35or(b)theprecipitateconsistedofamixtureofphaseslikeCeO2·2H2O+CeO2第十四页，共二十七页，编辑于2023年，星期二Fig.2DTA/TGofceriaacetateprecursorTheprecursormeasuredatotalweightlossof12.55%withfourdistincttemperaturepeaksThefirstendothermicpeakwasdetectedataround100℃.ThisisattributedtothereleaseofthewatermoleculespresentintheprecursorFrom100to200℃,theweightlosswasattributetotheremovalofthesurfaceacetategroupsandlatertheformationoftheaceticacidwhensurfaceacetatehydrolysisoccurs.Thisalsoexplainstheveryweakendothermicpeakdetectedat200℃Therewasasharpweightlossfrom200to400℃andacorrespondingexothermicpeak.Thisexothermicpeaksuggeststheformationofoxyacetateanddioxocarbonatecomplexeswithcerium,Ce(OH)(CH3COO)andCe2O2CO3Astemperatureincreasedto700℃,theCe2O2CO3decomposedendothermallytoproducethefinalproductCeO2第十五页，共二十七页，编辑于2023年，星期二Fig.3DTA/TGforCeO2synthesizedfromceriaacetate:(a)after6htreatment;(b)after24htreatmentafter6and24hofhydrothermaltreatment,weightlossisdramaticallyreducedto2.64and1.37%Thedistincttemperaturepeaksaresimilartothatoftheprecursor.However,thedistinctexothermicpeakforthehydrothermaltreatedsamplesisnolongeraspronouncedasthatoftheprecursorThiscouldbeduetotheamountofacetatecomplexesformationbeingreducedconsiderablyafterhydrothermaltreatment.Tracesofceriumacetatecomplexeswerestillpresentinthesamplesafterhydrothermaltreatment.Theamountishowever,significantlylowerthanthatfoundintheprecursor第十六页，共二十七页，编辑于2023年，星期二Fig.4CeO2usingCe(OH)4precursor(250℃)asafunctionoftimeFig.5CeO2usingceriaacetateprecursor(250℃)asafunctionoftimeFig.4,thenano-particlesexhibitedsomedegreeofcrystallinityanddisplayedallofthemajorpeaksofCeO2withacubicstructureafter6htreatmentNosignificantimprovementincrystallinitywasobservedbetween6and24h,andthepeakswerebroadwithweakintensities.ThistrendissimilarwiththeceriaacetatesystemFig.5,thepeaksaresignificantlynarrowerwithhigherintensitiessuggestinglargercrystallitesizesatanaverageof15.5nmascalculatedandlargerdegreeofcrystallinityascomparedtothecerium(IV)hydroxidesystem.Thepeaksathigher2θanglescanalsobeclearlyobservedforallsamples第十七页，共二十七页，编辑于2023年，星期二Fig.6.LatticeconstantofCeO2afterhydrothermaltreatmentat250℃usingCe(OH)4precursorFig.7LatticeconstantofCeO2afterhydrothermaltreatmentat250℃usingceriaacetateprecursorthelatticeparameterdecreasedbyabout0.2%afterhydrothermaltreatmentat250℃for6h.From6to12hatthesametemperature,thelatticeexpanded.Thelatticeconstantonlyvariedwithinanarrowrange(|a|/a≈0.03%)after12h,indicatingthatthestructurebecamestable.Thelatticeconstantdecreasedbyabout0.5%afterhydrothermaltreatmentat250◦Cfor6h.Furtherchangesoflatticeconstantwereverysmallwhentreatmentdurationwasincreased.Thevariationoflatticeconstantwaslessthan0.03%第十八页，共二十七页，编辑于2023年，星期二Fig.8CeO2fromCe(OH)4(24h)heattreatedat(a)500℃,(b)1000℃Fig.9CeO2fromceriaacetate(24h)heattreatedat(a)500℃,(b)1000℃Inbothfigures,itcanbeseenthatthecharacteristicpeaksaresharperandnarrowerThehigher2θpeaksforthehydroxidesystemcanalsobeobservedafterheattreatment.Thiscrystallitesizeafterheattreatmentat500and1000℃grewto8.8and47.4nm,respectivelyThesamplesfromtheceriaacetatesystemexhibitedalargerdegreeofcrystallinitythanceriumhydroxidesystem.Thecrystallitesizefortheceriaacetatesystemafterheattreatmentwas17.7and53.6nmat500and1000℃,respectively第十九页，共二十七页，编辑于2023年，星期二Fig.10TEMandelectrondiffractionpatternofCeO2fromcerium(IV)hydroxide(a)andceriaacetate(b)after24hhydrothermaltreatment.Fig.10(a)exhibitedveryfineparticles,whichwereagglomerated.Crystallinitycouldbeobservedbasedontheparticlesanditscorrespondingelectrondiffractionpattern.Itscrystallitesizeisabout5–6nmasestimatedfromtheTEMmicrographs.Theparticlesgenerallyshownroundededgesbuttheyarenotwell-definedduetoitssmallsizeFig.10(b),particlesareverywell-definedandrelativelydispersed.GoodcrystallinefacesandcrystallinitystatecouldbeobservedTheparticlesizes,atabout10–15nm,areslightlybiggercomparedtothecerium(IV)hydroxidesystem.ceriaacetatesystemappearstobelessagglomeratedthanthecerium(IV)hydroxidesystem.However,agglomerationoftheparticlesstillappearstobeaproblem.第二十页，共二十七页，编辑于2023年，星期二Salt-assistedultrasonicaerosoldecompositionSalt-assistedaerosoldecomposition(SAD)Conventionalaerosoldecomposition(CAD)thesameoperatingconditions,thesameexperimentalapparatus,withoutthesaltsprecursorsolution:ceriumnitratewasdissolvedindistilledwatera

mixtureofpotassiumandsodiumnitrateswasaddedtotheprecursorsolutionthesolutionwasmistedbyanultrasonictransducer(1.7MHz)intodropletscarriedbyairintoahottubularreactorwheretheywererapidlyheatedanddecomposedtoformparticles,heatingtimewaslessthanfivesecondsCeO2

wereobtainedbywashingtheproductinwatertoremovethesaltsortheirderivativesB.Xia,I.W.LenggoroandK.Okuyama,HiroshimaUniversity,Japan,J.Mater.Chem.,2001,11,2925–2927第二十一页，共二十七页，编辑于2023年，星期二ResultsanddiscussionFig.1SubmicrontomicronCeO2particlessynthesizedbytheCADmethodat800℃:(a)lowermagnificationimage;(b)highermagnificationimageoftheparticlemarkedA,comprisingsinterednano-crystallites.Theparticles(Fig.1a)aresolidandnearlysphericalwithameanparticlesizeof0.74umFig.1showstheTEMimagesoftheCeO2particles,whichweresynthesizedbytheCADmethodat800℃Consistofnanosizedcrystallites(Fig.1b)withmeansizeof13.8nmdeterminedbytheX-raydiffraction(XRD)technique.Thesenanosizedcrystallitesarevirtuallyinseparableduetosintering第二十二页，共二十七页，编辑于2023年，星期二Fig.2NanometernanosizedCeO2particlessynthesizedbytheSADmethodat(a)800℃,and(b)atypicalhighresolutionTEMimageofsample(a),showingthecrystallatticeofaparticleImportantdifferencesbetweentheCADandtheSADproductsareindicatedbelow:First,theSADproduct(Fig.2a)iscomposedofisolatednanoparticles(meansize51nm),whiletheCAD(meansize0.74mm)containingsinterednano-crystallitesSecond,theSADCeO2particlesaresinglecrystalswhiletheCADCeO2particlesarepolycrystalline(asshowninFig.1b)Thesinglecrystalsareevidencedbytheagreementbetweentheparticlesizesandthecrystalliteonesatallsynthesistemperatures,asshowninTable1.ThetypicalcrystallatticeimageshowninFig.2bconfirmsthepresenceofsinglecrystallineparticlesClearly,theparticlesizedistributionoftheSADproducthasbeenremarkablynarrowedincomparisontotheCADproduct第二十三页，共二十七页，编辑于2023年，星期二Table1Comparisonofparticleandcrystallitediameters(inanometers)ofCeO2synthesizedbytheCADandtheSADprocessesFig.3PowderXRDpatternsofroductssynthesizedat(a)CAD,800℃(CeO2);(b)SAD,800℃(CeO2)Third,theSADproducthasamuchhighercrystallinitythantheCADproduct,asshownfromthesharppeaksinFig.3b.ThecrystallitesizeoftheSAD800℃sampleis54.4nm,asshowninTable1.ThisismuchlargerthanthecorrespondingCADsampleDetailsoftheSADprocess:CeO2canparticipateindissolutionandprecipitationintheliquid-statesaltmedia,whichcangreatlyfacilitatemasstrans