Formation of dicalcium ferrite at 1273K : effect of pO2 and Al2O3 content

Abstract

As a fundamental study for clarifying the reactions occurring during the early stage of sintering process, formation of dicalcium ferrite in solid state between different kinds of iron oxides and CaO under various P_(O_2 ) at 1273K have been investigated. Additionally, the effect of Al2O3 content on the formation of dicalcium ferrite is also discussed. The dicalcium ferrite formation rates are evaluated by using thermogravimetric methods and the phase identification and quantification of calcium ferrites in the experiment have been carried out by using X-ray diffraction method (the Rietveld method). It has been found that intermediate calcium ferrite phases of CaFe2O4 and CaFe3O5 are formed prior to the Ca2Fe2O5 formation when Fe2O3 and Fe3O4 are used as an initial iron oxide, respectively. When starting from w？stite, intermediate calcium ferrite phases are not formed. The amount of converted Ca2Fe2O5 and its formation rates are found to be different depending on the reactant iron oxide phases and are increased in the order of reactants w？stite > Fe3O4 > Fe2O3. It is also found that the Ca2Fe2O5 formation rate starting from Fe3O4 decreases with increasing P_(O_2 ), but that starting from w？stite is independent of P_(O_2 ). Furthermore, the amount of converted Ca2Fe2O5 and its formation rates are found to be varied with different Al2O3 content.