简介:O'-sialon-ZrO2compositebasedonthecheapcommercialavailablezirconandsiliconasrawmaterialscanbeachievedbyusingreac-tionnitridationmethod,Moreattentionwasgiventothenitridingprocessandtheeffectofadditivesonit.Theexperimentalresultsshowthattherearetwonitridationpaths:oneisthedirectnitridationofsiliconpowderandtheotheristhroughthereactionbetweenthemedi-umcompoundZrSi2andthenitrogen.Theeffectsofadditionofcalciaandtheincorpora-tionofBNonthenitridingreactionwerealsoinvestigated,theprimitiveexperimentalresultsdemonstratedthatbothofcalciaandBNcoulddeterioratethenitridingdegree.
简介:Thereactionofsillimanitewithaluminaattemperatures1650℃an1750℃hasbeeninvestigated.Theresultshaveshownthat,inthelaboratorytestconditions,thehigherthealuminacontent,thelowerwillbetheamountsofglass-phseofthefiredbodyandthehigherwillbetheformationofmullite.Inthepresenttests,however,thereactioninconcernhasnotbeencompleted,thereactioninconcernhasnotbeencompleted.Someuncombinedresidualaluminastillexistintheformofcorundum.
简介:Thestabilizationofγ-aluminiumoxyni-tridespinel(γ-AlON)hasbeeninvestigatedbyadditionofMgO,MgAl2O4,etc.,inreactionprocess.Theresultsindicatedthattherearewidersolidsolutionareasnear,Al2O3-richsideinAlN-Al2O3-MgOternarysystems,ThecontentofstabilizedAlONphaseinsamplesisrelatedtoheatingtemperatures,additives,etc.ThelatticeparametersoftheirAlONphasescouldbewelldescribedbytheequation:a0=0.7900+0.0375[MgO]+0.015[AlN](nm)
简介:Thespecimenswerepreparedbymoldingthemixtureofsilicafume(w(SiO2)=94.5%;averageparticlesize:0.08μm)andsiliconnitride(≤0.074mm)withamassratioof11,carbonembeddedfiringat1300℃,1450℃,1500℃,1550℃and1600℃for3hinair,andthenwater-cooling,respectively.Themicrostructureandphasecompositionofthespecimenswereanalyzed.Theresultsshowthat:(1)silicafumereactsobviouslywithSi3N4formingSi2N2Oabove1550℃.TheedgesandcornersofSi3N4grainsbecomesmoothandtheSi3N4grainsdistributeinthecontinuouscementationphaseofSi2N2OformingthedensestructureofSi2N2OpackedSi3N4;(2)below1500℃,theedgesandcornersofSi3N4grainsareclear,Si2N2Odoesn'tform,andonlySiO2crystallizesfromsilicafumewhichhappensobviouslyat1300℃.
简介:β-sialon/alumina/silicamixturesweresinteredinflowingnitrogenat1500℃and1600℃respectively.ThesinteringpropertiesandmorphologyofsampleswereinvestigatedbySEM,EDSandXRD.Resultsshowthatsinteredpropertiesofthesamplesareinfluencedbysoakingtemperaturesandcompositions.Bulkdensitiesofsamplesareincreasedwiththeincreaseofthesoakingtemperature,whereastheapparentporositiesaredecreased.Masslossofthesinteredsamplesat1500℃islowerthanthatat1600℃,butallthemasslossremainsapproximatelyconstantwiththeincreaseofsialoncontent.Fromthepointofthermodynamicanalysis,ComplexchemicalreactionstakeplaceinsamplesduringsinteringprocessandthevolatileofSiO(g)isresponsibleforthemasslossofsamples.Comparedtocrosssectionmicrostructureofβ-sialon/Al2O3/SiO2mixturessinteredincokepowderbedconsistingofthedensecenterwithwell-developedcolumnofsialonphase,thetransitionalpartwithneedlelikegrainnitrogen-containingphaseandtheloosepartwithshortgranularAl2O3phase,thoseofmixturessinteredinflowingnitrogenisofwell-developedsialonindensecenterandslightlyloosepartwithsialondebris.
简介:Reactionsintereddensezirconia-mullitecompositeswerepreparedbyisostaticallypressingfromzirconflourandreactivealuminawithdifferentproportionsofTiO2andCr2O3additives.Thepressedcompactsweresinteredatdifferentelevatedtemperatureswithvariablesoakingtimes.Microstructuresandphasedevelopmentinthesinteredcompactswereanalysedtoassesstheinfluenceoftheadditivesonthepropertiesofthezirconiamullitecomposite.