A model for time-dependent grain boundary diffusion of ions and electrons through a film or scale, with an application to alumina
File(s)
Accepted version
Author(s)
Tautschnig, MP
Harrison, NM
Finnis, MW
Type
Journal Article
Abstract
A model for ionic and electronic grain boundary transport through thin films, scales or membranes with columnar grain structure is introduced. The grain structure is idealized as a lattice of identical hexagonal cells – a honeycomb pattern. Reactions with the environment constitute the boundary conditions and drive the transport between the surfaces. Time-dependent simulations solving the Poisson equation self-consistently with the Nernst-Planck flux equations for the mobile species are performed. In the resulting Poisson-Nernst-Planck system of equations, the electrostatic potential is obtained from the Poisson equation in its integral form by summation. The model is used to interpret alumina membrane oxygen permeation experiments, in which different oxygen gas pressures are applied at opposite membrane surfaces and the resulting flux of oxygen molecules through the membrane is measured. Simulation results involving four mobile species, charged aluminum and oxygen vacancies, electrons, and holes, provide a complete description of the measurements and insight into the microscopic processes underpinning the oxygen permeation of the membrane. Most notably, the hypothesized transition between p-type and n-type ionic conductivity of the alumina grain boundaries as a function of the applied oxygen gas pressure is observed in the simulations. The range of validity of a simple analytic model for the oxygen permeation rate, similar to the Wagner theory of metal oxidation, is quantified by comparison to the numeric simulations. The three-dimensional model we develop here is readily adaptable to problems such as transport in a solid state electrode, or corrosion scale growth.
Date Issued
2017-06-15
Date Acceptance
2017-04-25
Citation
Acta Materialia, 2017, 132 (1), pp.503-516
ISSN
1359-6454
Publisher
Elsevier
Start Page
503
End Page
516
Journal / Book Title
Acta Materialia
Volume
132
Issue
1
Copyright Statement
© 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
BP International Limited (0946)
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000405881500046&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
75195 / ICAM8 (UoM+IC)
EP/P023118/1
EP/G001723/1
Subjects
Science & Technology
Technology
Materials Science, Multidisciplinary
Metallurgy & Metallurgical Engineering
Materials Science
Grain boundary diffusion
Oxide-film growth kinetics
Ceramic membrane
Alumina
Poisson-Nernst-Planck
OXYGEN POTENTIAL GRADIENTS
THERMAL BARRIER COATINGS
HIGH-TEMPERATURES
POLYCRYSTALLINE ALUMINA
MASS-TRANSFER
TRANSPORT
AL2O3
PERMEABILITY
ALPHA-AL2O3
CHANNELS
Materials
0204 Condensed Matter Physics
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status
Published
Date Publish Online
2017-04-28