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Synthesis and Characterization of Nanostructured Ceria Obtained by the Reverse Microemulsion Method
|Marcin Molenda , Roman Dziembaj , Marek Drozdek , Barbara Dudek|
Jagiellonian University, Faculty of Chemistry, Ingardena 3, Kraków 30-060, Poland
Ceria (CeO2) crystallizes in a very stable fluorite like structure, showing no phase changes up the melting point (~2700°C). Nevertheless, due to many structural defects formed in an activation procedure, it shows anionic conductance and catalytic activity in redox reactions. Doping of the ceria matrixes with Ge or Sm results in formation of very effective anionic conductors applicable as solid electrolytes in the intermediate temperature solid oxide fuel cells (IT-SOFC). Wide application of the cerium oxide materials demands developing of synthesis methods of the nanosized particles being prerequisite for high performance of these materials in their application as well catalysts as anionic conductors, due to participation of nearly whole bulk of such small particles. These attractive properties may be lost during calcinations or even prolonged work at elevated temperatures owing to sintering processes. That is why further searching for new preparation methods are pursued.
In the present work we propose modification of the reverse microemulsion method to obtain a nanosized particles being precursors for the nanostructured ceria crystallites. The parameters of the precursors decomposition were optimized in a series of experiments performed in a thermal analyzer measuring simultaneously mass changes (TG/DTG), thermal effects (DTA) and chemical composition of the evolved gaseous products with quadruple mass spectrometer (MS-EGA). Crystal structure and morphology of the obtained ceria particles were characterized using XRD, BET and SEM techniques. The average grain size obtained from micro-emulsion was estimated as equal to 8 nm, which is an order of magnitude lower than those obtained by the standard precipitation route - about 140 nm. The catalytic activity of the obtained ceria towards volatile organic compounds (VOC’s) degradation was tested in benzene and ethylene total oxidation and discussed in terms of ceria samples structure and morphology.
Presentation: Oral at E-MRS Fall Meeting 2007, Symposium A, by Roman Dziembaj
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-21 10:52 Revised: 2009-06-07 00:44