Characterization of the Fe-Doped Mixed-Valent Tunnel Structure Manganese Oxide KOMS-2
| Autor: | Steven L. Suib, Xiongfei Shen, Mark Aindow, Jianming Bai, Jia Liu, Jonathan C. Hanson, Aimee Morey, William A. Hines, Jun Cai, William M. Reiff, Anatoly I. Frenkel, Qi Wang, Wen Wen, Jason P. Durand, Yun-Shuang Ding |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Materials science
Extended X-ray absorption fine structure Doping Inorganic chemistry Analytical chemistry engineering.material Surfaces Coatings and Films Electronic Optical and Magnetic Materials Magnetization General Energy Octahedron X-ray crystallography engineering Cryptomelane Thermal stability Nanorod Physical and Theoretical Chemistry |
| Zdroj: | The Journal of Physical Chemistry C. 115:21610-21619 |
| ISSN: | 1932-7455 1932-7447 |
| DOI: | 10.1021/jp206046k |
| Popis: | A sol-gel-assisted combustion method was used to prepare Fe-doped manganese oxide octahedral molecular sieve (Fe-KOMS-2) materials with the cryptomelane structure. Characterization of the nanopowder samples over a wide range of Fe-doping levels (0 {le} Fe/Mn {le} 1/2) was carried out using a variety of experimental techniques. For each sample, Cu K{alpha} XRD and ICP-AES were used to index the cryptomelane structure and determine the elemental composition, respectively. A combination of SEM and TEM images revealed that the morphology changes from nanoneedle to nanorod after Fe doping. Furthermore, TGA scans indicated that the thermal stability is also enhanced with the doping. Anomalous XRD demonstrated that the Fe ions replace the Mn ions in the cryptomelane structure, particularly in the (211) planes, and results in a lattice expansion along the c axis, parallel to the tunnels. Reasonable fits to EXAFS data were obtained using a model based on the cryptomelane structure. Moessbauer spectra for selected Fe-KOMS-2 samples indicated that the Fe is present as Fe{sup 3+} in an octahedral environment similar to Mn in the MnO{sub 6} building blocks of KOMS-2. Magnetization measurements detected a small amount of {gamma}-Fe{sub 2}O{sub 3} second phase (e.g., 0.6 wt % for the Fe/Mn = 1/10more » sample), the vast majority of the Fe being in the structure as Fe{sup 3+} in the high-spin state.« less |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|