Nanoporous anodic alumina layers obtained from novel deep eutectic solvent formulations

• Published in: Transactions of the Institute of Metal Finishing Vol. 101; no. 1; pp. 19 - 28
• Main Authors: Fernandes, P. M. V., Brincoveanu, O., Pantazi, A., Petica, A., Pereira, C. M., Fernando Silva, A., Enachescu, M., Anicai, L.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 02.01.2023
• Subjects: Aluminium anodisation; anodic oxide layer; choline dihydrogen citrate eutectic mixtures; deep eutectic solvents; ionic liquids; nanoporous anodic alumina
• ISSN: 0020-2967; 1745-9192
• DOI: 10.1080/00202967.2022.2105571

The possible fabrication of porous anodic oxide films on aluminium in ionic liquids based on choline dihydrogen citrate eutectic mixtures both with oxalic acid and isopropyl alcohol and ethylene glycol, has been investigated. The anodisation has been carried out in either potentiostatic or galvanostatic regime, at temperatures of 45-80°C, for different process durations. Quite compact, uniform anodic alumina layers have been obtained. Based on AFM and SEM investigations, pore diameters between 50 and 80 nm and interpore distances in the range of 160-200 nm have been estimated, with values influenced by the electrolyte type and anodisation conditions. The highest anodisation rate of about 0.4 µm min −1 has been determined by applying operation temperatures of 60°C. The recorded EIS spectra showed a pure capacitive behaviour and high anodic oxide resistances of 10 6 -10 7 Ω cm 2  order.