0000000000136120
AUTHOR
Peter Skeldon
showing 6 related works from this author
Growth and Characterization of Anodic Films on Al-Nb Alloys
2006
Abstract The anodizing behaviours of sputtering-deposited aluminium, niobium and Al-Nb alloys, containing 0.4, 7.5, 21, 40 and 55 at.% niobium, have been examined in 0.1 M ammonium pentaborate electrolyte with interest in the morphology, structure and electronic properties of the anodic oxides. Transmission electron microscopy revealed amorphous oxides, containing units of Nb2O5 and Al2O3, with formation ratios intermediate between those of anodic alumina and anodic niobia. Photocurrent spectroscopy provided increased understanding of the electronic properties of the anodic films, suggesting the formation of “mixed oxides” with insulating behaviours. The estimated band gap values are correl…
Effect of Composition on the Photoelectrochemical Behavior of Anodic Oxides on Binary Aluminum Alloys
2006
The photoelectrochemical behavior of anodic films on Al alloys, containing titanium, tantalum, and tungsten (valve metals), has been studied as a function of alloy composition and anodizing conditions. Photocurrent spectroscopy has been used to get information on bandgap and the flatband potential values of different mixed oxides. Both insulator-like and semiconducting behavior has been observed for anodic oxides grown on Al-W and Al-Ti alloys dependent on alloy initial composition. Optical bandgap values, E opt g , of different oxides are in accordance with predictions based on the correlation between E opt g and the difference of electronegativities of the oxide constituents, indicating p…
Behavior of alloying elements during anodizing of Mg-Cu and Mg-W alloys in a fluoride/glycerol electrolyte
2015
Anodizing of sputtering-deposited magnesium and Mg-0.75at.%Cu and Mg-1.23at.%W alloys has been carried out in a fluoride/ glycerol electrolyte. The aims of the study were to investigate the enrichment of alloying elements in the alloy immediately beneath the anodic film and the migration of alloying element species in the film. The specimens were examined by electron microscopy and ion beam analysis. An enrichment of copper is revealed in the Mg-Cu alloy that increases with the anodizing time up to ∼6×1015 Cu atoms cm-2. Copper species are then incorporated into the anodic film and migrate outwards. In contrast, no enrichment of tungsten occurs in the Mg-W alloy, and tungsten species are im…
Tailoring of the Solid State Properties of Al–Nb Mixed Oxides: A Photoelectrochemical Study
2013
Al–Nb containing mixed oxides were grown by anodizing sputter-deposited Al–Nb alloys of different compositions. A photoelectrochemical investigation was carried out in order to estimate the band gap, flat band potential, and conductivity type of these oxides as a function of their composition. The dependence of the band gap on the composition of mixed sp–d metal oxides has been rationalized by using a semiempirical correlation between the difference of electronegativity and band gap of oxides proposed in the literature some years ago and recently tested for regular d–d metal mixed oxides. The band gap increase observed as a function of Al content into the oxides seems mainly depending on th…
Formation of anodic films on sputtering-deposited Al–Hf alloys
2009
Abstract The growth of barrier-type anodic films at high efficiency on a range of sputtering-deposited Al–Hf alloys, containing from 1 to 95 at.% Hf, has been investigated in ammonium pentaborate electrolyte. The alloys encompassed nanocrystalline and amorphous structures, the latter being produced for alloys containing from 26 to 61 at.% Hf. Except at the highest hafnium content, the films were amorphous and contained units of HfO 2 and Al 2 O 3 distributed relatively uniformly through the film thickness. Boron species were confined to outer regions of the films. The boron distributions suggest that the cation transport number decreases progressively with increasing hafnium concentration i…
Photocurrent spectroscopy study of passive films on hafnium and hafnium–tungsten sputtered alloys
2003
Abstract Anodic and air-formed films on sputtered Hf and W–Hf alloys of different composition have been investigated by Rutherford back scattering, photocurrent spectroscopy (PCS) and transmission electron microscopy (TEM) techniques. In alkaline solutions the PCS data suggest the formation on Hf metal of a duplex layer with anodic hafnia covered by an external layer of composition close to HfO(OH) 2 . This last compound is also present on Hf air-formed films. In acidic solutions the initial oxy-hydroxide film disappears at high anodising potentials ( V f >10 V). In the case of W–Hf alloys films of different composition and semiconducting behaviour are formed by air exposure or by anodising…