title: Combinatorial electrochemistry on Al-Fe alloys.
abstract: Combinatorial material development was combined with high throughput microelectrochemistry to allow an efficient but comprehensive investigation of the interface chemistry of Al rich Al-Fe alloys as a function of their chemical composition. Composition spread thin films with a linear composition gradient were produced by thermal codeposition. A scanning droplet cell was used to determine the open circuit potential and to perform successive anodic oxide formation with intermittent impedance spectroscopy. The film formation factor, the relative permittivity of the oxides and the onset potential of oxide formation were determined quantitatively as function of the composition with a resolution of 0.5 at.%. An unexpected synergistic effect is found in a very narrow composition range between 9 and 12 at.% Fe. This effect, which shifts the onset potential by nearly 1 V, is discussed in terms of a local accumulation of Fe resulting in a redox stabilisation of space charge layer formation during high-field oxide growth. The results are supported by composition and depth dependent XPS measurements.
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany.
authors.forename: Andrei Ionut
authors.initials: AI
authors.lastname: Mardare
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany.
authors.forename: Amar Prasad
authors.initials: AP
authors.lastname: Yadav
authors.affiliation: Ruhr-Universität Bochum, 44780 Bochum, Germany.
authors.forename: Andreas Dirk
authors.initials: AD
authors.lastname: Wieck
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Stratmann
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany.
authors.forename: Achim Walter
authors.initials: AW
authors.lastname: Hassel
keywords: anodic oxide film; combinatorial libraries; microelectrochemistry; scanning droplet cell