Dense mullite zirconia composites obtained from the reactionsintering of milled stoichiometric alumina zircon mixtures by SPS

N.M. RENDTORFF(1)(2), G. SUÁREZ (1), Y. SAKKA(2), E.F. AGLIETTI

CERAMICS INTERNATIONAL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2014 vol. 40 p. 4461 - 4470

0272-8842

The mainobjectiveofthisarticleistoobtaindense(porosityunder0.5%)polyphasicceramicsbelongingtotheAl2O3?SiO2?ZrO2 system by SPS sinteringofhighenergypowdersmilleddrily;thestoichiometric(54.45:45.54zircon?alumina, weightbasis)mixturewasexploredinthis work. Particularlytheprincipalsinteringvariables:sinteringtemperatureanddwelltimewereinvestigated.Thetextural,structuraland microstructural changeswereevaluatedtogetherwiththehardnessandtoughnessoftheobtainedceramicsandtheirmicrostructure.Theeffectof the mechanicalpre-treatmentwascarriedoutbyX-raydiffractionandparticledistributionevaluation.Duetotherapidheatingprocessan incomplete reactionwasachievedinseveralcases,asaconsequencemultiphasicceramicswithdifferentalumina,mullite,zirconandzirconia contents wereobtained. The mechanicalpretreatmentusedresultedinahomogeneousdrymixturewithapartial(E20%) zircondissociation,apparentlyenhancedby the aluminapresence.ThistogetherwiththeposteriorSPSprocessingpermittedtoobtainfullydenseceramiccompositesataverylow temperature (1300 1C) withouttherequirementofanyadditive.Thereactionsfromaluminazirconmixturestomullitezirconiaoccur200 1C below conventionalprocessingroutesandatleast50 1C belowthereportedSPSbasedmaterialsprocessedfromun-milledmixtures.The microstructure andmechanicalpropertiesobtainedwerecomparabletotheonesobtainedbyotherprocessingroutes.Finallysomeinteresting group correlationswerefoundforthedevelopedmaterialswhilethehardnessisdirectlycorrelatedwiththedensityandthefracturetoughnessis correlated withthezirconia(mþt) content. 2O3?SiO2?ZrO2 system by SPS sinteringofhighenergypowdersmilleddrily;thestoichiometric(54.45:45.54zircon?alumina, weightbasis)mixturewasexploredinthis work. Particularlytheprincipalsinteringvariables:sinteringtemperatureanddwelltimewereinvestigated.Thetextural,structuraland microstructural changeswereevaluatedtogetherwiththehardnessandtoughnessoftheobtainedceramicsandtheirmicrostructure.Theeffectof the mechanicalpre-treatmentwascarriedoutbyX-raydiffractionandparticledistributionevaluation.Duetotherapidheatingprocessan incomplete reactionwasachievedinseveralcases,asaconsequencemultiphasicceramicswithdifferentalumina,mullite,zirconandzirconia contents wereobtained. The mechanicalpretreatmentusedresultedinahomogeneousdrymixturewithapartial(E20%) zircondissociation,apparentlyenhancedby the aluminapresence.ThistogetherwiththeposteriorSPSprocessingpermittedtoobtainfullydenseceramiccompositesataverylow temperature (1300 1C) withouttherequirementofanyadditive.Thereactionsfromaluminazirconmixturestomullitezirconiaoccur200 1C below conventionalprocessingroutesandatleast50 1C belowthereportedSPSbasedmaterialsprocessedfromun-milledmixtures.The microstructure andmechanicalpropertiesobtainedwerecomparabletotheonesobtainedbyotherprocessingroutes.Finallysomeinteresting group correlationswerefoundforthedevelopedmaterialswhilethehardnessisdirectlycorrelatedwiththedensityandthefracturetoughnessis correlated withthezirconia(mþt) content.