水溶液を反応場としたビスマス鉄複合酸化物の生成と粒子特性

概要

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The formation diagram of Bi-Fe-OH- system in the aqueous solution was studied using hydrothermal or "wet" method. Three kinds of bismuth-ferricoxides, Bi25FeO40 (Fe-sillenite), BiFeO3 and Bi2Fe4O9 were obtained depending on their reaction conditions. The stoichiometric Bi25FeO40 has two kinds of particle shapes, the cubic and the tetrahedral, depend on its reaction conditions, although formation mechanism of the two kinds of particle shapes is not clear yet. The precipitate obtained below 100°C from starting materials with higher ratio of Fe/Bi than 3.8mole% showed interesting feature as follows. The precipitate gave only analogous XRD spectrum of Bi25FeO40, but observations by SEM and Mossbauer effect showed the surface of the precipitate was coated homogenously with fine particles of amorphous Fe oxide. The Bi25FeO40 coated with amorphous fine particles of Fe oxide (hereafter described as pseudo Fe-sillenite) reacted with CO2 gas or CO32- in aqueous solution and easily converted to Bi2O2(CO3) at the mild reaction conditions. The gradual conversion took place even at the room temperature during the prolonged period. The phenomena may be applied to the immobilization of the CO2 in the air and in the aqueous solution.
社団法人粉体粉末冶金協会の論文
2003-05-15