Hydrothermal Soft Chemical Process for Synthesis of Manganese Oxides with Tunnel Structures
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- Feng, Q., Yanagisawa, K. & Yamasaki, N. Journal of Porous Materials (1998) 5: 153. doi:10.1023/A:1009657724306
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A soft chemical process is used for the synthesis of manganese oxides with tunnel structures. This process comprises two steps: the first step is the preparation of a precursor with layered structure and insertion of templates (structure-directing agents) into its interlayer space by a soft chemical reaction , and the second step is the transformation of the template-inserted precursor into a tunnel structure by hydrothermal treatment. The usefulness of this process was demonstrated by synthesizing six kinds of tunnel manganese oxides from a birnessite-type manganese oxide with layered structure. The transformation reactions from layered structure to tunnel structures were investigated by X-ray, DTA-TG, and chemical analyses, and IR spectroscopy. Spinel-, hollandite-, romanechite-, and todorokite-type manganese oxides, which have (1×3), (2×2), (2×3), and (3×3) tunnel structures, can be obtained by using Li+, K+, Ba2+, and Mg2+ ions as the templates, respectively. Pyrolusite- and ramsdellite-type manganese oxides with (1×1) and (1×2) tunnel structures can be obtained in acidic solutions. The size of the resulting tunnels correspond to the size of the templates.