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1、NaaoStmcturedMaterials,Vol.12,pp.65-70,1999ElsevierScienceLtdPergamon01999ActaMetallurgicaInc.PrintedintheUSA.Alltightsreserved0965-9773/99/S-seefrontmatterPIIs0%5-9773(99)00067-7SYNTHESISANDREACTIVITYOFNANOPHASEFERRITESINREVERSEMICELLARSOLUTIONSCharlesJ.O’Connor,CandaceT.S
2、eip,EverettE.Carpenter,SichuLi,andVijayT.JohnAdvancedMaterialsResearchInstitute,UniversityofNewOrleans,NewOrleans,LA70148,USA.Abstract--Selfassemblypreparativetechniquesinconfinedmediathatleadtomagneticmaterialswithnanometerdimensionsaredescribed.Synthesisofnanoparticlesusi
3、ngtherestrictedenvironmentsofferedbysurfactantsystemssuchaswater-in-oilmicroemulsions(reversemicelles)provideexcellentcontroloverparticlesize,inter-particlespacing,andparticleshape.TheseenvironmentshavebeenusedinthesynthesisofFFezOj,Fes04,MnFez04,andCoFe204withparticlesizes
4、rangingfrom1O-20nm.Thecontrolledenvironmentofthereversemicellealsoallowssequentialsynthesiswhichcanproduceacore-shelltypestructure,forexampleFe304nanoparticleswithMnOcoatings.Lyotropicliquidcrystalmediaalsooffertemplateeffectsforthesynthesisofmagneticnanostructures.Thenanos
5、caleorderingofmagneticparticleswhensynthesizedinlyotropicliquidcr?/stalgelsischaracterized.Thestructures,theoryandmodelingconcepts,andnovelphysicalpropertiesofthesematerialsarediscussedwithemphasisgiventothedifferencesbetweencourseandjnegrainedmagneticmaterials.01999ActaMet
6、allurgicaInc.INTRODUCTIONAninterestingapproachthatisusedinsynthesisofnanophasematerialsistoemploythespatiallyandgeometricallyrestricted,self-assemblingmediaofreversemicellesandmicrostructuredgelphases.,Reversemicelles,forexample,arewater-in-oilmicroemulsionswheremicrodrople
7、tsofwaterarestabilizedinnon-aqueoussolutionbyasurfactant.Ourearlierstudiesonferritesynthesisinthesesystemshaveshownparticlegrowthrestrictedtothenanometerrangewithanarrowsizedistribution.Thesepreparationsemployedreversemicellesformedwithatwin-tailedanionicsurfactantbis-(2-et
8、hylhexyl)sodiumsulfosuccinate(AOT).Ferritenanoparticlesexhibitclassicalsuperparama