XRDおよびXAFSによる多成分カルシウムフェライトの還元挙動のその場観察

抄録

Reduction behavior of various multi-component calcium ferrites at 900°C were investigated by using in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy. 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 (Ca₃(Ca,Fe)(Fe,Al)₁₆O₂₈) and SFCA (Ca₂(Fe,Ca)₆(Fe,Al,Si)₆O₂₀) 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 FeO_x then Fe. Intermediate component, Ca₂(Fe,Al)₂O₅ 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°C. SFCA with a high aluminum content indicated lower reducibility than that with a low one.