The impact of viscosity of the electrolyte on the formation of nanoporous anodic aluminum oxide

• Anodization of aluminum in solutions with various viscosity was done.
• FE-SEM images of formed AAO were taken.
• Quantitative images analyses were performed.
• Relations between current density and viscosity were found.
• Relations between AAO geometry and viscosity were found > 

Anodic aluminum oxide was formed in 0,3 M oxalic acid at various content of glycerol (from 0 to 100 vol. %), at voltage range from 20 to 60 V (30 °C, 1 h long steps). Due to the influence of viscosity on the ionic mobility, current density, as well as on the thickness of the grown oxide, current density and thickness of the grown oxide were found to be linear functions of the inversed viscosity. Quantitative FE-SEM images analyses revealed surprising relation: interpore distance increases with the viscosity (logarithmic function). Additionally, pore diameter, porosity and pores density were also influenced by viscosity of the electrolyte. We have found that viscosity of the electrolyte, one of the most important factors in electrochemistry, has significant influence on the anodic alumina formation.

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