A two-step surface exchange mechanism and detailed defect transport to model oxygen permeation through the La0.9Ca0.1FeO3−mixed-conductor
| Autor: | Ahmed F. Ghoniem, Georgios Dimitrakopoulos |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Argon
020209 energy Diffusion Kinetics Thermodynamics chemistry.chemical_element Filtration and Separation 02 engineering and technology Partial pressure Permeation Kinetic energy Biochemistry Oxygen Membrane chemistry 0202 electrical engineering electronic engineering information engineering General Materials Science Physical and Theoretical Chemistry |
| Zdroj: | Journal of Membrane Science. 510:209-219 |
| ISSN: | 0376-7388 |
| DOI: | 10.1016/j.memsci.2016.03.004 |
| Popis: | A framework to model materials experiencing defect mechanism similar to that of La 1 − x Ca x FeO 3 − δ (LCF) membranes is considered. Using the La 0.9 Ca 0.1 FeO 3 − δ mixed-conductor, we propose a model that incorporates a two-step thermodynamically consistent surface exchange mechanism and charged species transport within the material using the Planck–Nernst–Poisson model. The surface reaction mechanism has been proposed under equilibrium; the current study expands the theory to finite rate kinetics and shows significant kinetic limitations for oxygen incorporation. Existing models describing the diffusion of oxygen vacancies may not be applicable at low oxygen partial pressures. Evidence shows that for the La 1 − x Ca x FeO 3 − δ membrane, simultaneous presence of multiple Fe states should be considered. As a result, the surface chemistry and charged species transport models developed in this study conserve the Fe sites and the electroneutrality condition both at the feed and sweep sides of the membrane. The role of a strict electroneutrality condition within the material is also examined. Using inert argon experimental data, we demonstrate the fidelity of the model. Predictions reveal that no crossover in the concentration of Fe Fe • and Fe Fe ′ takes place within our operating conditions; thus, electronic conductivity within the material is of p-type. |
| Databáze: | OpenAIRE |
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