Formation of Calcium Ferrites under Controlled Oxygen Potentials at 1273 K

다국어 초록 (Multilingual Abstract)

<P>Solid state calcium ferrite formation reactions between different kinds of iron oxides and CaO under various <I>P</I>O<SUB>2</SUB> at 1273 K have been investigated. The calcium ferrite formation rates are evaluated by using thermogravimetric method. 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 CaFe<SUB>2</SUB>O<SUB>4</SUB> and CaFe<SUB>3</SUB>O<SUB>5</SUB> are formed prior to the Ca<SUB>2</SUB>Fe<SUB>2</SUB>O<SUB>5</SUB> formation when Fe<SUB>2</SUB>O<SUB>3</SUB> and Fe<SUB>3</SUB>O<SUB>4</SUB> are used as a starting iron oxide, respectively. When starting from wüstite, intermediate calcium ferrite phases are not formed. The rates of Ca<SUB>2</SUB>Fe<SUB>2</SUB>O<SUB>5</SUB> formation are found to be different depending on the starting reactant iron oxide phases. The Ca<SUB>2</SUB>Fe<SUB>2</SUB>O<SUB>5</SUB> formation rate from wüstite is faster than that from Fe<SUB>3</SUB>O<SUB>4</SUB>, and that from Fe<SUB>3</SUB>O<SUB>4</SUB> is faster than that from Fe<SUB>2</SUB>O<SUB>3</SUB>. It is also found that the Ca<SUB>2</SUB>Fe<SUB>2</SUB>O<SUB>5</SUB> formation rate starting from Fe<SUB>3</SUB>O<SUB>4</SUB> decreases with <I>p</I>O<SUB>2</SUB>, but that starting from wüstite is independent from <I>p</I>O<SUB>2</SUB>.</P>