Potentiostatic formation of titanium nanotubes in the presence and absence of cerium. Impact on the parameters that characterize roughness

CAJIAO CHECCHIN VALENTINA CHIARA; GRAVINA ANABELA NOEL; FERNÁNDEZ LORENZO MÓNICA

Conferencia; 2020 Express Conference on the Physics of Materials and its applications in Energy and Environment (e-CPM2020); 2020

Anodic oxidation is a widely used electrochemical technique for surface modification of oxide films of some metals such as Ti. During anodizing in aggressive media, generally acidic media, there is a competition between the formation and dissolution of the oxide that, depending on the conditions, induces the formation of markedly different topographies. The resulting nanostructure is conditioned by the composition of the electrolytic solution. The aim of this work is to study the modification produced by anodizing at different potentials and the incorporation of Ce into the electrolyte in the process of potentiostatic formation of titanium oxide nanotubes (TiNT), and also to study the surface properties of the material. Consequently, electrochemical and topographic parameters will be analyzed.Mirror polished Grade 2 Titanium (DTi) discs that were anodized at 5, 7 and 10 V, in two cycles of two hours each, were used to obtain TiNT. A high-density polyethylene (PE-HD) cell with a graphite bar as the cathode, the DTi as the anode and an aqueous solution of HF/H3PO4 were used. During anodizing, the current was recorded as a function of time to study the curves comparatively. Subsequently, the samples were calcined at 400 °C. In the TiNT anodized record, in the 5 V condition a peak is generated, then the current (J) stabilizes. This peak is showed at short times, around 4 minutes, showing a characteristic J vs t record of the formation of porous oxides. (1) On the other hand, the condition of 7 V presents a double peak in the registry, the first at the same time as that observed at 5 V and the second after 14 minutes. This result would indicate that in the condition of 7 V there is a double formation of pores, and self-organization of them for the generation of a greater exposed area, unlike the other potential conditions. Then, J stabilizes giving rise to the stage of aging and growth of the NT.Moreover, Ce was incorporated into the anodized surfaces using a solution of CeCl3.7H2O as electrolyte (2) and a new potentiostatization was performed at + 0.8 V (SCE) and, as a last step, calcination. The observations by AFM of the samples with and without Ce, showed that nanotubes formed on the anodized surfaces, depending on the potential, present different diameters. The comparative roughness analysis for TiNT samples with and without Ce in a field of 15μm2 showed similar Rq and Ra values between both conditions, but the values of % of the area difference (SAD), Rz and Rku were higher and Rsk lower for TiNT-CeO2 samples. These results suggest that there would be a nano/microstructural difference between the samples with and without Ce that would imply, in the case of the TiNT-CeO2 samples, a predominance of sharper peaks and deeper valleys around the mean of the record. Also, when measuring the diameter in each condition (TiNT with/without Ce) it was observed that the formation of Ce oxides on the NT generates an increase in diameter. Thus, for example, in the 7 V condition, the corresponding average diameters are 75.4nm without Ce and 90nm with Ce.Based on this results, it was possible to conclude that there are nano/microstructural changes during anodizing at different potentials to form the TiNTs and that the 7 V condition has a special reorganization in anodizing with a distinctive record in current transients. On the other hand, the addition of Ce during the potentiostatic transient modifies parameters that characterize the shape of the TiNT (sharp peaks and deep valleys). These results could imply important consequences in the use of Ti in medical implants, particularly in the adhesion of cells.