In situ Observation of Reduction Behavior of Multicomponent Calcium Ferrites by XRD and XAFS

Reduction behavior of various multi-component calcium ferrites at 900 degrees C were investigated by using in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy. Reaction products (intermediate components) were determined by XRD and change in X-ray absorption spectra of Fe and Ca K-edges were analyzed to determine reaction rate constants. SFCA-I (Ca-3(Ca,Fe)(Fe,Al)(16)O-28) and SFCA (Ca-2(Fe,Ca)(6)(Fe,Al,Si)(6)O-20) consist of layered structure of spinel and pyroxene. Early stage of reduction reaction, diffraction peaks of spinel structure were observed which indicating SFCA-I and SFCA decomposed into these units at the first step of the reduction reactions. The spinel was reduced sequentially into FeOx then Fe. Intermediate component, Ca-2(Fe,Al)(2)O-5 originated in pyroxene module was hard to reduce and reaction was controlled by decomposition of this phase. Reduction of SFCA-I started later than SFCA (with 5.7 mol% Al2O3) under hydrogen gas reduction condition at 900 degrees C. SFCA with a high aluminum content indicated lower reducibility than that with a low one.

Automated summary

The reduction behavior of various multi-component calcium ferrites at 900 degrees Celsius was studied, revealing that calcium ferrites with higher aluminum content showed lower reducibility compared to those with lower aluminum content.