简介:HightemperatureoxidationbehavioroftwokindsofnitridebondedSiCbasedrefractorieswasinvestigatedat11001500℃bymeansofX-raydiffractometer,scanningelectronicmicroscopyandthermogravimetry.Theresultsshowthat:(1)withthetemperatureincreasing,theoxidationmassincrementrateofthespecimenincreasesfirstandthendecreases,andoxidationpassivationoccurs;(2)theoxidationresistanceofSiAlONbondedSiCrefractoriesissuperiortothatofSi3N4bondedSiCrefractories;(3)hightemperatureoxidationresultsintheincreaseofcompressivestrengthatroomtemperatureofSiCbasedrefractoriescomparedwithspecimenbeforeoxidation;thecompressivestrengthofSiAlONbondedSiCspecimensoxidizedathightemperaturesdecreaseswiththeincreaseofthetemperatureasaresultofformationandburstofsurfacebubble,whilethedecreaseofcompressivestrengthofSi3N4bondedSiCspecimensoxidizedathightemperaturesisowingtotheincreaseoftheconsistencyofnet-likecrackassociatedwithcristobalitetransformationduringcooling.
简介:Theeffectsofcorundum,magnesiaandspineladditionsonrheologicalpropertiesofmatrixofbauxite-basedcastableswerestudiedusingbauxite,fusedwhitecorundum,magnesia,spinel,microsilica,ultra-fineα-Al2O3andcementasstartingmaterialsandtrimericsodiumphosphateasdispersant.Theresultsshow:(1)thematrixslurryofbauxite-basedcastablesbelongstoBinghamfluidandshowsthixotropybehavior;(2)appropriatecorundumadditionimprovesrheologicalpropertiesofthematrix;(3)magnesiaadditionisdetrimentaltomatrixrheologicalproperties;(4)spineladditionhasslightlynegativeeffectsonmatrixrheologicalproperties.
简介:Cr2O3canbesinteredwellat1500℃incarbon-embeddedconditionorH2atmosphere.Butthehighchromebearingrefractoriescannotreachdensificationwhensinteredat1700℃for10hinweakreducingatmosphereformedbythecombustionoffuel,anditsapparentporosityisabout18%.Thehighchromebearingrefractoriesaremainlyusedincoalgasifiers.Thetemperatureinthefurnaceisabout1500℃andtheproductsareH2andCO,whicharejustthesinteringconditionsofthedensechromerefractorieswithapparentporositylessthan10%.Thehighchromebearingrefractoriesusedincoalgasifiersmaybesinteredagainandthenshrink,destroyingthegasifierlining.Thethermodynamiccalculationshowsthatitissafeaboutthehighchromebearingrefractoriesusedingasifiers.Itisalsoexplainedthatthehighchromebearingrefractoriescan’tbesintereddenselyinweakreducingatmosphereformedbythecombustionoffuel.Thenewsinteringtechnologiescanbeusedtoimprovethebulkdensityofthehighchromebearingrefractories.