外文翻譯--利用超音速射流分散納米粒子的新型濕式粉碎機.doc

英文原文Dispersionofnanoparticlesbynovelwet-typepulverizerutilizedsupersonicjetflowAbstract.Wehaveexaminedthedispersionofbariumtitanatenanoparticles(BT-NPs)andhavediscussedtheeffectofairpressuresuppliedtothenozzleonthedispersionbyusingnovelwet-typepulverizerutilizedsupersonicjetflow(SSJM).Theaggregatedparticlesizewasdecreasedwithincreasingtheairpressureandthecollisiontimes.Intheoptimizedcondition,almosttheBT-NPsweredispersedwiththeprimaryparticles,however,furtherexcessivecollisionhadcausedreaggregations.Thedegreeofdispersionhasbeenaffectedbytheairpressure.Theinjecteddropletshadformedalmostthesamediameterregardlessofairpressureandthevelocitywasincreasedwithincreasingoftheairpressureandreached300m/s.WehavespeculatedthattheshockwavedominatesthedispersionofBT-NPs.1.IntroductionNanoparticlesarerequiredhighlyinmanyapplicationssuchasdielectricmaterialsforelectronicdevices,electrodematerialsforsecondarybatteries,etc.Thenanoparticleshavebeenfrequentlyproducedbytheso-calledbuildupprocessessuchashydrothermalprocess,coprecipitationprocess,andsol-gelmethod.Forexploitingsizeeffectofnanoparticles,itiscrucialtocontrolthedispersionandaggregationofthenanoparticlesinsuspension.However,nanoparticlesaggregatemoreeasilyandstronglythansubmicronsizedparticles,andaggregatednanoparticlesdonotfragmenteasily.Therefore,itisquitedifficulttodispersenanoparticlesperfectly,andthedispersionofnanoparticleshasbecomeafundamentaltechniqueforhandlingnanoparticlesinindustries.Ithasbeenreportedthathenanoparticleswerewell-dispersedbyusingbeadsmill1.Beadmillingwithballsseveraltensofmicrometersindiameterhasrecentlybeendevelopedasanewmethodtodispersenanoparticlestoalmostprimaryparticlesize1.However,thecontaminationcausedbythegrindedballinbeadmillingwastentimeshigherthanthatcausedbydrygrinding2.Forprovidingnanoparticlesdispersingmethodthatcansolvetheaboveproblem,wehavedevelopednovelwet-typepulverizerutilizedsupersonicjetflow(hereafterreferredtoassupersonicwetjetmill；SSJM).Inthisstudy,wehavereportedthedispersingresultofbariumtitanatenanoparticles(BT-NPs)andhavediscussedtheeffectofairpressureonthedispersionbyusingtheSSJM.2.Experimentalapparatusandprocedure2.1.ExperimentalapparatusFigure1showsschematicdiagramoftheSSJM(left).Therightpartofdescribesshowstheinternalconfigurationofthenozzlepart.Thecompressedair(maximumairpressurewas0.6MPa)wassuppliedatthetoppartofthenozzle.TheLavalnozzle,whichwasusedfortheSSJMasshowninFigure1,isusedtoaccelerateacompressedairpassingthroughittoasupersonicspeed,anduponexpansion,toformtheexhaustflowsothattheheatenergypropellingtheflowismaximallyconvertedintokineticenergy.Asaresult,theinjecteddropletspassingthroughthenozzlewereacceleratedtosupersonicandwerenaturallycooled.Thesuspensioninthefeedtankwassuppliedtothethroatofthenozzle,whilecontrollingthevolumeflowthroughthepumptubing.Thesuppliedsuspensionhadbeenformeddropletsbyjetflowandhadbeenacceleratedinsidethenozzle.TheaccelerateddropletshadcollidedwiththeSiCplate.Mostoftheprocessedsuspensionwascollectedatthebottomtank,andsomeoftheprocessedsuspensionwasevacuatedalongwiththejetflow,therefore,thesolventrecoverytankunitattachedtotheexhaustline.Figure1.Schematicdiagramsofsupersonicwetjetmill(left)andthenozzlepart(right),showingapproximateflowvelocity(V),togetherwiththeeffectontemperature(T)andpressure(P).2.2.ExperimentalprocedureTwokindsofBT-NPwereusedinthiswork.BT-NPswiththeaverageparticlesizeof30nmweresynthesizedbythesol-gelmethod3(referredtoassol-gelBT).CommerciallyavailableBT-NPs(BT-01,SakaiChemicalIndustry,Japan)withtheaverageparticlesizeof100nmweremanufacturedbyhydrothermalmethod(referredtoashydrothermalBT).Adispersantusedinthisstudywasanammoniumsaltofpoly(acrylicacid)(PAA-NH4+,Mw8000,Touagousei,Japan).Thesol-gelBTwasaddedtoethyleneglycolmonomethyletherin2volume%(referredtoassol-gelBTsuspension).PAA-NH4+wasaddedtodistilledwaterin5wt%againstpowderweightandthenthehydrothermalBTwasaddedin20volumepercentsagainstdistilledwater(referredtoashydrothermalBTsuspension).Eachsuspensionwasinjectedundervariousairpressuresfrom0.3to0.6MPa.Anaggregatedparticlesizewasevaluatedbydynamiclightscatteringmethod(DLS,Nano-ZS,Malvern,UK).AshapeandmicrostructureoftheBT-NPswereexaminedwithatransmissionelectronmicroscope(TEM,JEM-3200EX,JEOL,Japan)andafieldemissionscanningelectronmicroscope(FESEM,S-4800,Hitachi,Japan).FordiscussingtheeffectofairpressureonthedispersionbyuseoftheSSJM,sizeandvelocitydistributionsofdropletsweremeasuredasfollows.Distilledwaterwasinjectedundervariousairpressuresfrom0.3to0.6MPa.Thesizeandvelocitydistributionofdropletsatadistanceof100mmawayfromthenozzleexitweremeasuredsimultaneouslybyPhaseDopplerAnemometry(DantecDynamics,Denmark)3.ResultanddiscussionFigure2.Effectofcollisionnumberoncumulativemeandiameterofsol-gelBTsuspensionsundervariousairpressures.Figure4.FESEMimagesofhydrothermalBT-NPs:(A)and(B)werebeforecollisionprocess,and(C)and(D)wereaftercollisionprocessfor3timesat0.6MPa3.1.DispersionofBT-NPsFigure2showschangeofcumulativemeandiameterDA,ofwhichthevaluerepresentstheaverageaggregatedsize,withcollisionnumberundervariousairpressuresforsol-gelBT.TEMimagesofBT-NPscollidedundervariousconditionswereshowninFigure3.DAoftheBT-NPscollidedat0.3MPawasdecreasedwithincreasingcollisionnumber.TheBT-NPscollidedfor3timesat0.3MPaweredispersedwithalmosttheprimaryparticles(asshowninFigure3(B),however,furtherexcessivecollisionhadcausedreaggregations.AlthoughDAcollidedat0.4and0.6MPawerealsodecreasedbythecollisionatonceortwice,DAwasincreasedimmediately.AsshowninFigure3(D),sol-gelBT-NPswerepulverizedtofinerBT-NPswiththesizeunder10nmthantheinitialparticlesize,andwereformedaggregationswiththesizeover100nmconsistedofthepulverizedfinerparticles.Figure4showsFESEMimagesofthehydrothermalBT-NPs.As-recievedhydrothermalBT-NPswereaggregatedwiththesizesover1masshowninFigure4(A),andwerewidelydistributedinrangeoffrom100to200nmandunder100nm(Figure4(B).Afterthecollisionfor3timesat0.6MPa,BT-NPswiththesizeunder100nmwereclearlyincreasedandtheaggregatedparticleswerenotexistedasfarasFESEMobservationwasconcerned.Figure5showsthehydrothermalBTparticlesizedistributionscollidedat0.3MPaand0.6MPa.LiketheFESEMobservation,theaggregatedparticlesweredecreasedandtheparticleswiththesizeunder100nmwereincreasedwithincreasingcollisionnumber.However,reaggregationswiththesizeover1mandquitefineBT-NPsunder10nmhadbeengeneratedbythecollisionfor5timesat0.6MPaasshowninFigure5.Excessivecollisionat0.6MPahadcausedreaggregations,similarlythesol-gelBT-NPsdispersionresult.Thedegreeofdispersionhasbeenaffectedbyairpressure.3.2.EffectofairpressureonthedispersionbySSJM.Figure6showsthesizeandthevelocitydistributionofinjecteddropletsundertheairpressuresfrom0.3to0.6MPameasuredatadistanceof100mmawayfromthenozzleexit.Theinjecteddropletsformedalmostthesamediameterregardlessofairpressureandthemediandiameterwasabout7m.Thedropletsvelocitywasincreasedwithincreasingoftheairpressureandthevelocityinallmeasurementsreached300m/s.Incaseofdry-typejetmill,ofwhichthepulverizingprincipalissimilartotheSSJM,ithasbeenreportedthatthedrivingforceofpulverizingweretheshockwavegeneratedbythec