Synthesis of Nanosize Silica in a Nonionic Water-in-Oil Microemulsion_Effects of the Water_Surfactant Molar Ratio and Ammonia Concentration

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1、JournalofColloidandInterfaceScience211,210±220(1999)ArticleIDjcis.1998.5985,availableonlineathttp://www.idealibrary.comonSynthesisofNanosizeSilicainaNonionicWater-in-OilMicroemulsion:EffectsoftheWater/SurfactantMolarRatioandAmmoniaConcentration12F.J.ArriagadaandK.Osseo-AsareDepar

2、tmentofMaterialsScienceandEngineering,ThePennsylvaniaStateUniversity,UniversityPark,Pennsylvania16802ReceivedDecember15,1997;acceptedNovember18,1998genides,metalhalides,carbonates,oxides,andorganicTheeffectofammoniaconcentrationontheregionofexistencepolymers(1±6).ofsingle-phasewa

3、ter-in-oilmicroemulsionshasbeeninvestigatedInourlaboratoryweareinvestigatingtherelationshipbe-forthesystempolyoxyethylene(5)nonylphenylether(NP-5)/tweenmicroemulsionpropertiesandthecharacteristicsofthecyclohexane/ammoniumhydroxide.Thepresenceofammoniade-ensuingnanoparticles(7±13)

4、.Inanearlierpaper(7)were-creasesthesizeofthemicroemulsionregion.Aminimumconcen-portedonthepreparationofnanosizemonodispersesilicatrationofsurfactant(estimatedatabout1.1wt%)isrequiredforsolubilizationoftheaqueousphase;thisvalueisnotsigni®cantlyparticlesbycontrolledhydrolysisoftetr

5、aethoxysilane(TEOS)affectedbyammoniaconcentration.Asindicatedby¯uorescenceinanonionicsurfactant/cyclohexane/ammoniumhydroxidespectraldata,thetransitionbetweenboundandfreewateroccurswater-in-oilmicroemulsionsystem.Particlesintherangeof50whenthewater-to-surfactantmolarratioisabout1

6、andthepres-to70nmwereproducedwithstandarddeviationsbelow8.5%enceofammoniumhydroxidedoesnotappeartohaveasigni®-aroundthemeandiameter.Asthewater-to-surfactantmolarcanteffectonthis.Ultra®ne(30±70nmdiameter),monodisperseratio(R)increasedfrom0.7to2.3,theparticlesizedecreasedsilicapart

7、iclesproducedbyhydrolysisoftetraethoxysilaneandthesizedistributionbecamenarrower.Furtherworkhas(TEOS)inthemicroemulsionshowacomplexdependenceofthenowshownthatthedependenceofparticlesizeonthewater-particlesizeonthewater-to-surfactantmolarratio(R)andontheto-surfactantmolarratiobeco

8、mesmuchmorecomplicatedasaconcentrationof