The Migration of Metal and Oxygen during Anodic Film Formation

Davies, John; Domeij, Bengt; Pringle, J. P. S.; Brown, F.

doi:10.1149/1.2423662

Cited by 343 publications

(204 citation statements)

References 17 publications

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“…Motion of markers in the anodic film.-Oxide flow may be inferred from experiments in which markers revealed the separate contributions of the two interfaces to film growth. [39][40][41][42] In these papers, the marker position was reported as the metal ion transport number, t M , i.e., the distance between the markers and the filmsolution interface, as a fraction of the film thickness. The term "transport number" derives from the traditional assumptions that the markers are immobile and that ions are transported entirely by electrical migration.…”

Section: Comparison Of Model With Empirical Conduction Behavior-mentioning

confidence: 99%

A Model for Coupled Electrical Migration and Stress-Driven Transport in Anodic Oxide Films

Hebert

Houser

2009

J. Electrochem. Soc.

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A model for transport in amorphous anodic oxide films was developed in which ion migration was driven by gradients of mechanical stress as well as electric potential and which included viscoelastic creep of the oxide. Simulations were presented for the galvanostatic growth of planar barrier-type anodic aluminum oxide films. It is assumed that stress originates at the metal-film interface due to the volume change upon oxidation. The average stress in the film decayed during growth and evolved from compressive to tensile with increasing applied current density. The model was fit to stress-thickness measurements using a viscosity of 1×1012Pas on the same order of magnitude as that of many other amorphous materials displaying viscous creep. The current density increased exponentially with electric field, in agreement with an empirical high field conduction behavior. The metal ion transport number was predicted based on the motion of markers in the film and increased with current density in quantitative agreement with experimental measurements. The model represents a unified quantitative interpretation of ionic conduction, transport numbers, and mechanical stress measurements in anodic films.

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Section: Comparison Of Model With Empirical Conduction Behavior-mentioning

confidence: 99%

A Model for Coupled Electrical Migration and Stress-Driven Transport in Anodic Oxide Films

Hebert

Houser

2009

J. Electrochem. Soc.

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“…The cation transport number is large compared with other examples of nanocrystalline anodic films. For example, the cation transport numbers for nanocrystalline anodic oxide films formed on hafnium and zirconium, which are the best known examples, are ≤0.05 [21,22].…”

Section: Introductionmentioning

confidence: 99%

Effect of current density and behaviour of second phases in anodizing of a Mg-Zn-RE alloy in a fluoride/glycerol/water electrolyte

Němcová

Kuběna

Šmíd

et al. 2015

J Solid State Electrochem

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Anodizing of a Mg-Zn-RE alloy was carried out at constant current densities from 0.1 to 10 mA cm −2 in a fluoride/glycerol/water electrolyte. Rutherford backscattering spectroscopy, nuclear reaction analysis and analytical transmission electron microscopy revealed barrier-type films composed of oxide and fluoride species. The films were formed by outward migration of cations and inward migration of anions. The transport number of cations in the film above the matrix was in the range ∼0.5 to 0.6, and ∼0.1 in the film above the grain boundary Mg-Zn-RE phase. From the oxidation behaviour of the Zn-Zr phases, it is suggested that anions and cations migrate through short-circuit paths in the film.

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“…The passive films, constituted of amorphous niobium pentoxide 3 , can be easily thickened by anodic polarisation [3][4][5][6][7] ; the oxide growth occurs by high-field ion migration in the film 8,9 . Amorphous niobium pentoxide has a density 10 of 4.74 g cm -3 and a rather high concentration of oxygen vacancies (10 19 cm -3 ) that, injected at the metal/oxide interface, act as donor states and make the oxide an n-type semiconductor 11,12 ; Di Quarto et al 4 , studying films of various thickness (21 nm ≤ d ≤ 210 nm) formed in 0.5 mol/L H2SO4, determined their relative permittivity as being equal to 42.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical characterization of thin passive films on Nb electrodes in H3PO4 solutions

Biaggio¹,

Bocchi²,

Rocha‐Filho³

et al. 1997

J. Braz. Chem. Soc.

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The electrical and semiconducting properties of thin anodic passive films potentiostatically formed (1 V ≤ E f ≤ 5 V vs. sce) on polycrystalline niobium electrodes in aqueous 0.5 mol/L H3PO4 solutions (pH 1.3) were studied, at room temperature, using electrochemical impedance spectroscopy. The data were analysed with a transfer function using a non-linear fitting routine, assuming that the resistance of the film is coupled in series with the faradaic impedance of the Nb(0) → Nb(V) reaction, and these in parallel with the capacitance of the passive film/electrolyte interface. The relative permittivity of the films was estimated as about 44. The number concentration of donors (ND) in the films was found to decrease with E f (i.e., with increasing film thickness). A flat band potential value of -0.72 V was also obtained from Mott-Schottky plots.Utilizando-se a espectroscopia de impedância eletroquímica, foram estudadas as propriedades elétricas e semicondutoras de filmes anódicos passivos formados potenciostaticamente (1 V ≤ E f ≤ 5 V vs. ecs) sobre eletrodos de nióbio policristalino em soluções aquosas de H3PO4 0,5 mol/L (pH 1,3), a temperatura ambiente. Os dados foram analisados com uma função de transferência usando uma rotina de ajuste não-linear, supondo que a resistência do filme está acoplada em série com a impedância faradaica da reação Nb(0) → Nb(V) e estas em paralelo com a capacitância da interface filme/eletrólito. A permissividade relativa dos filmes foi estimada como cerca de 44. Encontrou-se que a concentração em número de doadores (ND) nos filmes decresce com E f (isto é, à medida que a espessura do filme aumenta). A partir de gráficos de Mott-Schottky, também obteve-se um valor de -0,72 V para o potencial de banda plana.

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The Migration of Metal and Oxygen during Anodic Film Formation

Cited by 343 publications

References 17 publications

A Model for Coupled Electrical Migration and Stress-Driven Transport in Anodic Oxide Films

A Model for Coupled Electrical Migration and Stress-Driven Transport in Anodic Oxide Films

Effect of current density and behaviour of second phases in anodizing of a Mg-Zn-RE alloy in a fluoride/glycerol/water electrolyte

Electrochemical characterization of thin passive films on Nb electrodes in H3PO4 solutions

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