Study on the correlation between criterion number derived from Rayleigh–Bénard convective cells and arrangement of nanoporous anodic aluminum oxide

• Anodic alumina in oxalic acid with various viscosity was formed.
• Physical and chemical properties of electrolytes were measured.
• Criterion numbers were estimated.
• Quantitative arrangement analysis was performed.

Anodic aluminum oxide has been formed in 0.3 M oxalic acid with various additions of glycerol (0–100% vol. of glycerol) at voltage range from 20 to 60 V at 30 °C. It was found that properties of the electrolytes, as well as the voltage have strong influence on the type of formed oxide (porous, or non-porous barrier type oxide) and its arrangement. Quantitative arrangement analysis of the nanoporous oxide has been performed with the use of fast Fourier transforms of the FE-SEM images. The obtained data were confronted with criterion number estimated from the operating conditions and electrolytes properties. It was found that the best arrangement of the nanopores is when the criterion number is close to the literature data for other, aqueous electrolytes.

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