Oxide Microstructural Changes Accompanying Pore Formation During Anodic Oxidation of Aluminum
| Autor: | Kurt R. Hebert, Ömer Özgür Çapraz, Pranav Shrotriya, Shinsuke Ide |
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| Rok vydání: | 2017 |
| Předmět: |
Materials science
Anodizing 020209 energy General Chemical Engineering Surface force Metallurgy Oxide 02 engineering and technology 021001 nanoscience & nanotechnology Stress (mechanics) chemistry.chemical_compound Chemical engineering chemistry Residual stress 0202 electrical engineering electronic engineering information engineering Electrochemistry Cyclic voltammetry 0210 nano-technology Porosity Dissolution |
| Zdroj: | Electrochimica Acta. 232:303-309 |
| ISSN: | 0013-4686 |
| Popis: | Porous anodic oxide formation results from a morphological instability of uniform barrier oxide growth leading to the establishment of pores. To gain insight into this process, evidence for microstructural changes in the oxide accompanying pore initiation in anodic alumina was sought through two types of experiments: potentiodynamic anodizing and stress measurements during dissolution of the anodic films. Cyclic voltammetry during anodizing in sulfuric acid shows that pore formation coincides with the appearance of localized ohmic- conducting regions close to the oxide-solution interface of individual pores. These defects induce large current increases which are apparently responsible for growth of concave scalloped features on the metal-oxide interface at the pore base. It is argued that interface defects are generated by surface forces in the oxide that accompany flow contributing to pore initiation. Stress measurements reveal that pore initiation introduces tensile residual stress into the oxide at the pore base, suggesting the formation of vacancy-type defects in the film. Such defects are explained by increases of local conduction current density due to the concentration of anodizing current in pores. Both sets of experiments reveal that pore formation generates locally defective oxide, which may help explain the phenomenon of burning during high-rate anodizing. |
| Databáze: | OpenAIRE |
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