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[doc] Surface Modfication of Fe3O4 Nanoparticles

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[doc] Surface Modfication of Fe3O4 Nanoparticles

    Surface Modfication of Fe3O4

    Nanoparticles

    Sept.2006J.ChinaUniv.ofMining&Tech.(EnglishEdition)VblJ16No.3 ;SurfaceModficationofFe304Nanoparticles

    ;LIUYong~ian,JIAHong.yi,ZHUANGHong

    ;DepartmentofChemistry,SuzhouCollegeofScienceandTechnology,Suzhou.Jiangsu215011.ina

    ;~SchoolofChemistryandEnvironmentEngineering,ChinaUniversityofMining&Technology,Beijing100083.China

    ;Abstract:Nanometerparticlesareimportantportionofmagneticfluid.FeO4magneticnanoparticleswerestudiedifl

    ;thispaperandthesurfacemodificationofFe3O4nanoparticleswasinvestigatedbyaseriesofexperiments.Fe3O4mag.

    ;neticnanoparticlesweresynthesizedwithpHvalue,temperature,andthedosageofsurfactant.Thephase,structure,size

    ;andmagnetismofnanoparticlesweretestedbyXraydiffration(XRD),tran

    smissionelectronmicroscopy(TEM)and

    ;magneticbalance.Onthebasisofthesurfacemodificationcoatingmechanism,theexperimentalphenomenaandthe

    ;effectsonthevariationofsize,magnetismandstabilityofFe3O4nanoparticle

sweretheoreticallyanalyzed.XRaydif-

    ;fractionspectrumandTEMphotographshowthat1)thenanoparticlesstructureisperfect.2)thediameterofnamoparti.

    ;clesissmallandhavegooddeliquescence,and3)Sodiumoleateistheanionsurfactant.Therefore1)thegoodcondition

    ;ofsurfacemodificationisinanacidicsolution,2)thebesttemperatureofsurfacemodificationisat80?.and3)the

    ;dosageofsurfactantshouldbeabout0.6timesOftllatOfFe. ;Keywords:Fe3O4nanoparticles;magneticgrain:surfacemodification;mechanism

    ;CLCnumber:061

    ;Consistingofmagneticnanometerparticles,

    ;surfactant,andbasicliquid,themagneticfluidisa

    ;l(indofman.mademultifunctionalfluidwitl1high

    ;magnetization.Withboththemagneticpropertyof

    ;solidandtherheologyofliquid.itisbeingwidelyof

    ;interestforenvironmentalconservation,medical

    ;treatment

    ;

    ;,chemicalengineering,electronics,and

    ;printetciii.Themagnetismandstabilityofmagnetic

    ;fluidbasicallylieonmagneticnanoparticles.

    ;Inthemagneticfluid.therearethreetypesofin. ;teractionalpowerbetweensuper.microparticleslZl: ;VanderWaalsforce,magneticforces,doubleelec. ;tricallayerrepulsion.Inthestablemagneticfluid,the ;repulsionhastoconquertheforinertwointeractional ;forces.Whilelateoneisveryweak.usuallyinorder ;topreventnanoparticlesfromagglomeratingandto ;improvetheirdispersibilityinthenonmagnericliquid. ;theyarecoveredwithsurfactantsothatitcanproduce ;therepulsionbyspaceposition.Atthesametime,the

    ;surfacemodificationofnanorparticlescanimprove ;thecontactangleandthewettabilityalongwiththe ;abilityofdispersednessinthebaseliquid. ;Today,therearelotsofmagneticmaterialsfor ;thepreparationofmagneticfluid,whileFe04 ;nanoparticlesisthepreferredoneforitiseasyin ;preparation,lowinprice,innocuityandnopollution. ;Inthispaper,weuseFe3O4nanoparticlesasmagnetic ;materialtoinvestigatethesurfacemodificationofthe ;materia1.

    ;2Experimental

    ;2.1Mainreagentsandinstruments

    ;Instrumentsincludeelectricstirrer,constant ;temperaturewater-bath.ultrasonicwave.Gouymag. ;neticbalance(MB.1A),transmissionelectronmicro. ;scope(JEM2OOCXstyle),X-raydiffraction(D/Max- ;3DwithCuK?radiationtooperateat3OKvand

    ;30mA).

    ;MainreagentsareanalyticalofFeSO4.H20, ;Fe2(SO4)3.xHzO,sodiumhydroxide(NaOH7.0 ;mol/L)andsodiumoleate.

    ;2.2Magneticfluidsynthes~

    ;SolutionofFe3andFe(molarratiois3:21was ;well-proportionedmixedinathreemeatusbottle.

    ;Themixturewasputintothewater-bathtoheatto65 ;?.withacertainamountofethanoladdedandround. ;Thenthesodiumhydroxide(7.0moI/L)wasquickly ;drippedinthemixturetomakethePHreach11.Atier ;itwaslaidfor10min.theblackmagneticparticles ;couldbeseen.Whenthetemperaturereaches8O?.

    ;theacidityisregulatedandthesurfactantwasadded ;forthesurfacemodificationofnonoparticles.Atier30 ;min,themixturewasputonmagneticplatformto ;filteranddeposit.Aherthat.itwaswashedwitl1

    ;ethanolanddistilledwater~Finally,itwasdriedand ;calcinedtoproducetheflourymagnetismofFe3O4. ;Received13March2006;accepted23April2006 ;Correspondingauthor.Tel:+86-13915589019;Emailaddress:yjliul215@y

    ahoo.com.cu

    ;

    ;J.ChinaUniv.ofMining&Tech.(EnglishEdition)V_0I.16No.3

    ;3ResultandDiscussion

    ;3.1XRDanalysis

    ;AsshowninFig.1.thepowderofFe304hasa

    ;goodcrysta1structure.thecharacteristicpeakofthe ;crysta1isveryclear,comparedwiththestandardchart. ;thepeakisquitewide,thatisbecauseparticlesareall ;nanoparticles.FromFig.1wecanseesomecharac- ;teristicpeaksofFe20,becausethereactiontakes ;placeintheairandnanoparticleshavebiggersurface, ;makingthenanoparticleseasytobeoxidized.And ;someofFe3O4particlesarechangedtocrystalstruc- ;tnrey-Fe203

    ;20(.)

    ;Fig.1XRDpatternsoftheFe304nanoparticles ;3.2TEManalysis

    ;IntheFig.2,thatisthedistributionofmagnetic ;particlesin.Heptanewhicharerandomcapturedby ;Cu.net.The.Heptanebasedmagneticfluidisthat ;themagneticpowderisdisperseddirectlyinbase- ;liquidbyultrasonicirradiation,nobigparticlewas ;separated.Fig.2showsthat,afterthesurfacemodifi- ;cation,themagneticparticlesaredistributedequably ;inbase.1iquid.observedinthe1ens,themagneticpar- ;ticlesareallbal1.shaped.Theaveragediameterof ;particlesisabout8nmcalculatedaccordingthe ;enlargedphoto.Andtheoveralldistributionisvery ;good.

    ;Fig.2TEMphotographsofFe304nanoparticles ;3.3InfluencesofpHvaluesurfacemodification ;Foundby1waski3l

    ;,

    ;theequipotentialpointof

    ;Fe304isatpH=6.5.IfpH>6.5,thesurfacenanoparti

    ;clesofFe304isnegative,whileifpH<6.5,itisposi

    ;tive.Theoleicacidsodiumisananionsurfactant.so ;itiseasytobeadsorbedintheacid.However,the ;acidvalueisnothighbecause1,theacidvalueof

    ;liquorissohighthatFe304nanoparticlesmaybedis- ;solvedinit.and2thepHvalueofcarboxy1.acidis ;usually4-5.andiftheacidvalueistoohigh,thenthe ;reaction

    ;RC00Na+HC1RCOOH+NaC1

    ;willtakeplace,andtheelectricdissociationformof ;oleicacidis1ikethereactionof

    ;RCOOH===RCOO.+H.

    ;whichisadynamicequilibrium;Ifthehydrogenion ;istoohigh,itwillstoptheformationofoleicacidion, ;whichisnotfavorableforformingthestablecoating. ;ForpH=5,thecoatingcangaintheblackwell-dis- ;tributedmagneticparticles.

    ;3.4Affectsoftemperature

    ;FromtheIRpicture,theFe3O4adsorptionof ;oleic.acidionischemicaladsorption,sorisingthe ;temperatureisbenefittocoating,whiletheadsorption ;isareversibleequilibriumprocess.F0rf>70?.itis

    ;easyindesorptionAndatthesametime.themag

    ;netismofnanoparticlesincreaseasthetemperature ;risesaccordingtotheexperimentatdifferenttern- ;peratures.Fort=80?.themagnetismisthehighest

;(Fig.3).

    ;tf?1

    ;Fig.3Magneticvariationofnanoparticles ;vs.modificationtemperature

    ;3.5Affectsofsurfactant

    ;Usually.thesurfactantoncrystalisamonomo- ;lecular.Theadsorptioniseitherbyelectrostaticin- ;teraction(Fig.4a)orthroughsuperficialcomplexa- ;tion(Fig.4b),theformeristhephysicaladsorption, ;thelaterischemica1.Theadsorptionofsodiumoleate ;changefrom(a)to(b)asthetemperaturerises.The ;polarityheadoflong.chainalkvladsorbsnanoparti- ;cles(Fig.5),thenonpolarityheadproducetherepul-

    ;sionbyspaceposition,whichcanpreventnanoparti

    ;clesfromagglomeratingandimprovetheaffinityof ;nanoparticleswithbaseliquid,thesolubilityin

    ;baseliquid.whichisfavorableforformingastable ;so1.Ifsomeethanolisaddedduringthemodification, ;betterresultwillbeacquiredbecausetheethanolacts ;asasubsidiarysurfactanttodebasethesurfaceten

    ;sionandeliminatenonbridgehydroxylamongnano-

    ;particles,andavoidtheparticlesreunitingatcalcin-

;ing.

    ;一?u一五一slIul0口巴龋一盆

    ;g—g?口辱g

    ;IoEoI?>

    ;

    ;LIUYong-jianeta1.SurfaceModficationofFe304Nanoparticles361

    ;(b)viasuperficialcomplexation

    ;Fig.4Sketchofcoatingmethods

    ;Ha

    ;Fig.5Sketchofmodifiedparticlesinbasedfluid ;(Thereisastateofsterticstabilizationbetweenparticles) ;3.6Effectofdosageofsurfactant

    ;Thesurfactantonparticlesisstablemonomo

    ;lecular,thelongchainalkylofsurfactantisoutside, ;thepolarityheadadsorbsontheparticles.Basedon ;experiment,whendosageisinshort,thennotallpar- ;ticlesarecoated,resultinginformingbigparticles; ;whileifthedosageisabundant,multilayeradsorp

    ;tionappearsontheparticles,makingthecoatedparti

    ;clesbecomedifficulttOseparate,andthelongchain

    ;alky1ofsodiumoleatebecomplectedeachOtheThis ;makesthesmallmagneticparticlesagglomerate,de

;creasingthestabilityofthemagneticfluid,weaken

    ;ingthemagnetismofmagneticparticles.According ;whatmentionedabove,thedosageofsurfactant ;shouldbemoderate.Theformerexperimentsshow ;tllat.whenthedosageofsurfactantis0.6timesasthat ;ofFefmolarratio)l,themagneticparticlesare ;smal1andhighmagnetic.

    ;4Conclnsions

    ;1)Sodiumoleateistheanionsurfactant,the ;goodconditionofsurfacemodificationiSpH=5. ;21Thebesttemperatureofsurfacemodification ;isat8O?.

    ;3)XRaydiffractionspectrumandTEMphoto?

    ;graphshowthatthenanoparticlesstructureisperfect, ;thediameterofnamoparticlesissmallandhavegood ;deliquescence.

    ;References

    ;JiangBZ,YangJM.Applicationandprocessofmagneticfluid.ChemistryPro

    cess,1997,9(1):69-78.(InChinese)

    ;LiuYJ.ThestudyofdysprosiumcompositeFerritesuperpowder.JournalofC

    hinaUniversityofMiningandTechnology,

    ;2003,6(6):45_52.(InChinese)

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