Mechanism of aluminium and oxygen ions transport in the barrier layer of porous anodic alumina films

Patermarakis, G; Diakonikolaou, J

dc.contributor.author	Patermarakis, G	en
dc.contributor.author	Diakonikolaou, J	en
dc.date.accessioned	2014-03-01T02:11:24Z
dc.date.available	2014-03-01T02:11:24Z
dc.date.issued	2012	en
dc.identifier.issn	14328488	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/29894
dc.subject	Al3+ and O2- transport	en
dc.subject	Barrier layer	en
dc.subject	Ions clusters	en
dc.subject	Porous anodic alumina	en
dc.subject	Two-step mechanism	en
dc.subject.other	Acid electrolytes	en
dc.subject.other	Barrier layers	en
dc.subject.other	Electrolyte concentration	en
dc.subject.other	Faraday's laws	en
dc.subject.other	High field	en
dc.subject.other	Ion transports	en
dc.subject.other	Kinetic equations	en
dc.subject.other	Low current density	en
dc.subject.other	Low temperatures	en
dc.subject.other	Oxalic Acid	en
dc.subject.other	Oxide interfaces	en
dc.subject.other	Oxide lattices	en
dc.subject.other	Oxygen evolution	en
dc.subject.other	Oxygen ions	en
dc.subject.other	Porous anodic alumina	en
dc.subject.other	Porous anodic alumina films	en
dc.subject.other	Production efficiency	en
dc.subject.other	Rate-controlling steps	en
dc.subject.other	Transformed structure	en
dc.subject.other	Transport number	en
dc.subject.other	Two-step mechanisms	en
dc.subject.other	Activation energy	en
dc.subject.other	Current density	en
dc.subject.other	Efficiency	en
dc.subject.other	Electrolytes	en
dc.subject.other	Integral equations	en
dc.subject.other	Interfaces (materials)	en
dc.subject.other	Ions	en
dc.subject.other	Organic acids	en
dc.subject.other	Oxide films	en
dc.subject.other	Oxygen	en
dc.subject.other	Sulfuric acid	en
dc.subject.other	Aluminum	en
dc.title	Mechanism of aluminium and oxygen ions transport in the barrier layer of porous anodic alumina films	en
heal.type	journalArticle	en
heal.identifier.primary	10.1007/s10008-012-1683-x	en
heal.identifier.secondary	http://dx.doi.org/10.1007/s10008-012-1683-x	en
heal.publicationDate	2012	en
heal.abstract	Aluminium was anodised in oxalic acid electrolyte at concentrations 0.125-0.5 M, current densities 25- 100 Am-2 and low temperatures 0 and 5 °C. The efficiencies of Al consumption and oxide production in the metal\| oxide interface and the transport numbers of Al3+ and O2- in the barrier layer of porous anodic alumina films were determined. The Al consumption efficiency essentially coincides with that by Faraday's law while that of oxygen evolution, visually detected at these temperatures, is negligible. The oxide production efficiency and O2- transport number decrease with temperature, increase with current density and are almost independent of electrolyte concentration. The transport numbers combined with literature ones for oxalate and sulphuric acid electrolytes were treated by high field kinetic equations describing independent Al3+ and O2- transport to penetrate its mechanism. The half jump activation distances were found comparable to ions radii. This mechanism embraces two steps, equilibrium established between ordinary oxide lattice hardly allowing transport and locally emerging transformed structure dispersed in barrier layer consisting of pairs of Al3+ and O2- clusters enabling transport and the rate-controlling step of actual ion transport within clusters. The transformed structure then returns to ordinary while it emerges at other sites. The real activation energy of Al3+ transport is higher than that of O2-, e.g. by ≈19 kJ mol-1 at low current densities, but the fraction of really mobile Al3+ is ≈103-104 times larger than that of O2- justifying the not excessively different values of O2- and Al3+ transport numbers. © Springer-Verlag 2012.	en
heal.journalName	Journal of Solid State Electrochemistry	en
dc.identifier.doi	10.1007/s10008-012-1683-x	en
dc.identifier.volume	16	en
dc.identifier.issue	9	en
dc.identifier.spage	2921	en
dc.identifier.epage	2939	en