简介:TheencapsulationofstearicacidcoatednanometerCaCO3byapolystyrene(PS)networkviaemulsionpolymerizationisdescribed,whereγ-methacryloxypropyltrimethoxysilane(MPS)wasusedasanefficientcrosslinker.TheimportantfactorssuchasthetypeandamountofsurfactantandinitiatorandthecontentofCaCO3areinvestigatedaswellastheroleofMPS.IthasbeenshownthatlittlePSwasextractablewithonly0.6wt%ofMPS(relativetostyrene).Thecationicsurfactantcetyltrimethylammoniumbromide(CTAB)provedmoreeffectivethantheanionicsurfactantsodiumdodecylsulfonate(SDS).Theyieldrises,particlesbecomesmallerandsizedistributionbroadenswithincreasedamountofCTAB.Itisalsofoundthateither2,2′-azobis(isobutyronitrile)(AIBN)orammoniumpersulfate(APS)issuitableforattaininghighmonomerconversion.WithincreasedamountofCaCO3,theencapsulationratiocanbevariedfrom17.9to3.6,whilemonomerconversionandyielddecreaseslightly.FT-IRspectraoftheproductsafterextractionindicatetightencapsulationbetweenPSandCaCO3,andTEMphotographsofcompositeparticleswithwell-definedcore-shellstructuregivedirectevidenceofencapsulation.
简介:Lens-likevateriteCaCO3microringscomposedofCaCO3nanoparticlesweresynthesizedviaamicro-emulsion-mediatedrouteatroomtemperaturewithethanolandn-hexanolasco-surfactant.Thisprocessdidnotde-mandanyadditionalenergysuchasheatingorcontinuousagitation.Itwasthefirsttimetouseethanolasco-surfactantinthesynthesisofmicroornanomaterials.AndtheethanolwasbelievedtoplayanimportantroleintheaggregationfashionofCaCO3nanoparticles.Moreover,shuttle-shapednanorods,hexagonalnanoplates,andrice-likenanoparticleswerealsofabricatedbymodulatingthegrowthparameters.Additionally,theintroduceofethanolintomicroemulsionsasco-surfactantmaybegeneralizedasanovelgreenroutetocontrolthestructureofotherfunctionalmaterials.
简介:TheeffectsofHDPEmatrixtoughnessonthebrittle-ductiletransitionofHDPE/CaCO3blendsareinvestigated.NotallHDPEcanbetoughenedbyCaCO3particles.TheabilityofthematrixtoyieldplaysafundamentalroleindetermingwhetherHDPEcanbetoughenedornot.Thereexistsacriticalmatrixtoughness(Isc≈45J/m)belowwhichHDPEcannotbetoughenedobservablybyCaCO3particleatgivenaveragesize,andabovewhichthecriticalmatrixligamentthickness(τ?)isproportionaltomatriximpactstrength.
简介:ThisstudypresentsanovelprocessofinsitusurfacemodificationofCaCChnanoparticlesusingamultipleorificedispersionmicroreactor.CO2/Ca(OH)2precipitationreactionwasemployedtoprepareCaCO3nanoparticleswithsodiumstearatesurfactant.SynthesizedCaCChproductswerecharacterizedbythermogravimetricanalysis(TGA),infra-red(IR),X-raydiffraction(XRD),transmissionelectronmicroscopy(TEM)andBrunauer-Emmet-Telleranalysis(BET).Theeffectofvariousoperationparametersonnanoparticlesandthedosageofsodiumstearateweredetermined.Theresultsshowedthatthepreparationprocesscouldbepreciselycontrolledwithefficientmasstransferprocess.Theparticleswerehighlyhydrophobicwithacontactangleof117andmonodispersewithanaveragesizeof30nm.Theadsorptionsofsodiumstearateandcalciumiononsolidparticlesduringtheinsitusurfacemodificationprocesswereinvestigated.
简介:TheeffectofyttriaonthesolidreactionmechanismofaCaHPO4·2H2O+CaCO3systematdifferenttemperatureswasexperimentallystud-ied.Thesampleswithandwithoutyttriaweresubjectedtothermogravimetric/differentialscanningcalorimetrymeasurement.ThesampleswereheattreatedatthetemperaturescorrespondingtothepeaksontheDSCspectra,andtheresultedphasecompositionswereidentifiedbyX-raydiffraction.Thetransformationmechanismwasdeducedbycomparingthephasesobtainedatdifferenttemperatures.Theresultsshowthatthetransformationsatbelow1073Karenotaffectedbyyttria,butallthoseatabove1073Karecompletelyaltered.Theformationtem-peratureofhydroxyapatitedecreasesby134K,andthedecompositiontemperatureincreasesby38K.ThepolymorphoustransformationofCa3(PO4)2fromβphasetoαphaseincreasesby47K.Thethermodynamicpropertiesofthetransformationsatabove1073Karealsomodi-fiedbytheadditionofyttria;thatis,theendothermalpeaksaresubstitutedbyexothermalpeaks.