Stress-generating electrochemical reactions during the initial growth of anodic titanium dioxide nanotube layers. (1st February 2019)

• Record Type: Journal Article
• Authors: Dou, Qi; Shrotriya, Pranav; Li, Wenfang; Hebert, Kurt R.
• Is Part Of: Electrochimica acta. Volume 295(2019)
• Page Start: 418
• Page End: 426
• Publication Date: 2019-02-01
• Subjects: Anodic oxidation -- Titanium -- Self-organized nanotube layers; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2018.10.094
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: Titanium dioxide nanotube layers are widely investigated for diverse applications as functional materials. Previously, we demonstrated the importance of mechanical stress-generating open-circuit electrochemical reactions or chemical reactions in the initiation and growth of nanotube layers. These reactions were investigated here through analysis of stress and potential transients after interrupted anodization followed by open-circuit oxide dissolution. Large tensile stress increases after complete dissolution occur at potentials near the TiH2 /Ti2 O3 equilibrium potential, and are attributed to cathodic hydride formation at exposed metal surfaces. Tensile increases accompanying initiation of nanotubes during anodization itself were also explained by the hydride mechanism. The observation of tensile stress changes after both complete oxide dissolution and nanotube formation supports the view that nanotube initiation involves detachment of oxide at the metal interface. Tensile stress changes during anodization were followed by compressive transients that were also found during open-circuit dissolution, but not associated with a specific range of open-circuit potentials. The compressive stress change was explained by chemical oxidation of Ti +3 ions in nanotube walls by H + ions, along with absorption of charge-compensating anionic species. Hydrogen ion absorption is promoted by large decreases of surface pH that accompany anodization in organic-based solutions.