Surface analysis of mixed-conducting ferrite membranes by the conversion-electron Mossbauer spectroscopy
authors Waerenborgh, JC; Tsipis, EV; Yaremchenko, AA; Kharton, VV
nationality International
journal JOURNAL OF SOLID STATE CHEMISTRY
author keywords Dense ceramic membrane; Mixed ionic-electronic conductor; Perovskite-related ferrite; Methane oxidation; Surface states; Phase stability
keywords METHANE OXIDATION; BEHAVIOR; OXYGEN; SYSTEMS; IRON
abstract Conversion-electron Mossbauer spectroscopy analysis of iron surface states in the dense ceramic membranes made of (57)Fe-enriched SrFe(0.7)Al(0.3)O(3-delta) perovskite, shows no traces of reductive decomposition or carbide formation in the interfacial layers after operation under air/CH(4) gradient at 1173 K, within the limits of experimental uncertainty. The predominant trivalent state of iron cations at the membrane permeate-side surface exposed to flowing dry methane provides evidence of the kinetic stabilization mechanism, which is only possible due to slow oxygen-exchange kinetics and enables long-term operation of the ferrite-based ceramic reactors for natural gas conversion. At the membrane feed-side surface exposed to air, the fractions of Fe(4+) and Fe(3+) are close to those in the powder equilibrated at atmospheric oxygen pressure, suggesting that the exchange limitations to oxygen transport are essentially localized at the partially reduced surface. (C) 2011 Elsevier Inc. All rights reserved.
publisher ACADEMIC PRESS INC ELSEVIER SCIENCE
issn 0022-4596
year published 2011
volume 184
issue 9
beginning page 2610
ending page 2614
digital object identifier (doi) 10.1016/j.jssc.2011.07.003
web of science category Chemistry, Inorganic & Nuclear; Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000294835700045

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