Highly Ordered Ferromagnetic Mesoporous Materials: Thermal Phase Transformation Pathway and Quantitative Determination

Highly ordered ferromagnetic mesoporous materials with a high abundance and homogeneous dispersion of iron oxide within the mesopores were prepared through thermal oxidation at various temperatures after impregnation of ferrous ions into ordered mesoporous channels. The pathway for the phase transformation to iron oxide in ordered mesoporous channels is found to be different from the conventional transformation pathway. Rokuhnite, feroxychloride, and hematite are formed from Fe2+ ions at oxidation temperatures of 80, 300, and 450 °C, respectively. The transformation pathways are identified from the phase morphology and crystallinity of the obtained products by wide- and small-angle X-ray diffraction and by analyzing the electron diffraction patterns and images. Moreover, the high abundance and homogeneous dispersion of FeO within the mesopores were quantitatively determined up to 1150 ppm/g at various temperatures.