简介:TherearemanyprocessestoproduceCr2O3fromchrome-ores,DifferentparticlesizerangesofCr2O3powder,finepinmentgradegreenCr2O3andcoarsemetallurgygradeblackCr2O3,aremadebydifferentprocessesinChina,GreenCr2O3assuperfineandadditionandmetallurgygradeblackCr2O3usedtosynthesizeCr2O3graincanbeappliedtorefractories.ItisverydifficultforhighpurityCr2O3tosintertodensificationandTiO2additioniscontributedtodensificationofCr2O3sinteredathightemperature,Cr2O3grainswithrelativedensityof91%-95%aregainedbysinteringCr2O3withTiO2additionandelectrofusingCr2O3rawmaterials.
简介:Thehydrationoftricalciumaluminate(C3A)hasasignificanteffectontheeffectivenessofcement-basedsystems.Inaddition,thecarbonationofhydrationproductsofC3Aisparticularlyimportantinrespectofdurabilityperformance.ThepresentworkinvestigatesthehydrationandcarbonationreactionsofC3AandthechangesinducedbythepresenceoftheheavymetalionssuchasZn2+,Pb2+,Cu2+andCr3+byX-raydiffractometry(XRD).DuringhydrationofC3A,gehlenitehydrate,hydrogarnet,calciummonoaluminate(C4AHx)andcalciumcarboaluminateweredetectedinC3ApastesexcepttheZn2+dopedpaste,wherehydrogarnetdidnotform.Theexaminationsrevealedthatheavymetalscoexistedwithgehlenitehydrate,calciummonoaluminate(C4AHx)andcalciumcarboaluminate,inhibitingtheformationofhydrogarnet.HydratingC3Awasliabletobecarbonatedonexposuretoairandcarbondioxide,especiallyinthepresenceofheavymetals,resultingintheformationofcarboaluminateand/orcalciumcarbonate.Thepresenceofheavymetalsin-fluencedthepolymorphismofcalciumcarbonate,ndicatingthatheavymetalscouldco-precipitatewithcalciumtoformacarbonatesolidsolution.