Stresses in Anodic Films

Vermilyea, D. A.

doi:10.1149/1.2425747

Cited by 115 publications

(75 citation statements)

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“…9,11,18,21 Both Vermilyea and Bradhurst observed transitions from compressive to tensile stress with increasing current density. Other studies of porous anodic alumina growth found the same trend.…”

Section: Resultsmentioning

confidence: 96%

“…[14][15][16][17] Like the materials in these experiments, anodic alumina films are amorphous, and stresses large enough to drive significant creep ͑10-100 MPa͒ are found during the growth of both porous and planar anodic alumina. 9,11,[18][19][20][21] Stresses during anodizing may arise from volume constraints at the metaloxide interface, and from electrostatic forces in the oxide dielectric. [22][23][24] In this paper, we present a model for transport in planar anodic films by coupled electrical migration, plastic flow, and migration in the stress field.…”

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confidence: 99%

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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: Resultsmentioning

confidence: 96%

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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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“…Hence, the tensile shift was attributed to processes within the anodic oxide. Vermilyea and Wüthrich suggested that the tensile stress change is due to dehydration of the outer hydrated portion of the oxide, 7,13 and Bradhurst and Leach ascribed it to removal of electrostatic stress. 21 These explanations cannot be valid in view our findings that the tensile open circuit force increases with anodizing current density (Fig.…”

Section: Implications Of the Stress Measurements-mentioning

confidence: 99%

Measurement of Stress Changes during Growth and Dissolution of Anodic Oxide Films on Aluminum

Çapraz

Shrotriya

Hebert

2014

J. Electrochem. Soc.

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While stress is thought to play an important role in the development of self-organized porous films, mechanisms of stress generation during anodizing are not yet understood. In order to reveal depth distributions of stress in anodic films, phase-shifting curvature interferometry was used to monitor force transients (in-plane stress integrated through the sample thickness) during formation of anodic oxides on aluminum in phosphoric acid, as well as subsequent open-circuit dissolution. The measurements were not influenced significantly by electrostatic stress, internal stress in the metal samples, thermal stress, or stress induced by open-circuit dissolution. At typical current densities, the force became more compressive during anodizing, while a net tensile force change was measured after anodizing followed by complete oxide dissolution. Thus, it was revealed that anodizing generates both compressive stress in the oxide and tensile stress near the metal-oxide interface. Analysis of the open-circuit stress change revealed separate contributions from diffusional stress relaxations, and removal of residual oxide stress by dissolution. Residual stress distributions in the oxide, at nanometer depth resolution, were determined from measurements of dissolution rate and stress at open circuit, and validated through variations of the open-circuit dissolution rate.

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“…Thus, without consideration of transport numbers, the densities of anodic oxide and metal phases typically suggest that large compressive stress should be produced, while instead tensile stress may be observed during anodizing of metals such as Al where the metal ions transport appreciable current [54]. Other stress-producing reactions may include hydration/dehydration of the oxide near the solution interface [55,56] and interfacial reactions that produce or consume point defects (as interstitials and vacancies contribute lattice expansion and contraction, respectively) [57,58]. Anodic oxides also exhibit electrostriction stress, that is, elastic stress balancing electrical forces on the dielectric oxide material [59].…”

Section: Phenomenology Of Porous Anodic Oxide Formationmentioning

confidence: 99%

Mathematical Modeling of Self‐Organized Porous Anodic Oxide Films

Hebert

2015

Advances in Electrochemical Sciences and Engineering

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Stresses in Anodic Films

Cited by 115 publications

References 1 publication

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

Measurement of Stress Changes during Growth and Dissolution of Anodic Oxide Films on Aluminum

Mathematical Modeling of Self‐Organized Porous Anodic Oxide Films

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