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1、NanoStructaredMaterials,Vol.12,pp.95-100,1999ElsevierScienceLtdPergamon01999ActaMetallurgicaInc.PrintedintheUSA.Allrightsreserved0965-9113l99/$seefrontmatterPI1SO9659773(99)00073-ZDIFFERENTZIRCONIA-ALUMINANANOPOWDERSBYMODIFICATIONSOFCHEMICALVAPORSYNTHESISV
2、.V.Srdics,M.Winterer,G.Miehe*andH.HahnThinFilmsDivision,*StructuralAnalysisDivision,MaterialsScienceDepartment,DarmstadtUniversityofTechnology,Germany$Onleavefrom:FacultyofTechnology,InorganicTechnologyandMaterialsScienceDepartment,UniversityofNoviSad,Yugo
3、slaviaAbstract--Ultra-fine,nanocrystallinezirconia/alumina(n-ZrOz/A/203)powdersaresynthesizedbychemicalvaporsynthesis(CVS)usingavariable,modulargasflowreactor.Resultsforthreediflerentn-ZrOz/AhO3powdersarepresented:singlephaseparticlesformedbydopingzirconia
4、withalumina,coatedparticles,andcompositepowderconsistingofmixedparticlesofn-Ah03andn-Z&k.01999ActaMetallurgicaInc.INTRODUCTIONRecently,anovelgasphaseprocess,chemicalvaporsynthesis(CVS),hasbeendevelopedforthesynthesisofn-ZrOzpowders(1,2).Inthisprocessvolati
5、lemetalorganicprecursorsaredecomposedinahotwallreactoratreducedpressuresformingnon-agglomeratednanocrystallineparticles.TheinherentadvantagesoftheCVSprocessare:(a)theformationofnanoparticlesfrommolecularoratomicspeciesinacompletelyhomogeneousstate(vapor),(
6、b)awelldefinedreactionzoneinwhichtemperature,pressureandmassflowsarecontrolableandreproducible.Inthispaper,theopportunitiesofthis“bottom-up”strategyaredemonstratedbythemicrostructuralvariationsofnanoparticlesobtainedbymodificationsofthereactorgeometry.TheZ
7、rOz/3mol%Al203systemwaschosenasanexampletodemonstratetheuniqueopportunitiesofCVS.EXPERIMENTALThedifferentassembliesofthemodularCVSreactorusedinthepresentworkareshownschematicallyinFigure1.Generally,thereactorconsistsofprecursordeliveryunits,differenttypeso
8、freactionzones,apowdercollectionzoneandapumpingunitconsistingofarootspumpandabackingpump.Theprecursorsaredeliveredtothereactionzonesbybubblingcontrolledheliumgasflowsthroughbubblerswithliquidzirconium-t-butox
