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Abstract

For biomedical applications the physico-chemical properties of oxide layers, always present in titanium-based materials, are of special interest because the biological system is in direct contact only with these oxides. Using electrochemical impedance spectroscopy and galvanostatic polarization it is shown that the different compositions of c.p.-titanium, Ti6Al4V, and Ti6Al7Nb result in different physico-chemical properties of air formed passive layers and anodic oxide layers. This may have a direct impact on the biocompatibility of these materials. Results of impedance spectroscopy distinctly differ in the flatband potentials as well as in the donor densities of air-formed passive layers with Ti6Al7Nb showing an approximately 50% smaller donor density than the other materials. Anodic galvanostatic polarization results in voltage-charge density curves with distinct differences in the Faraday efficiency epsilon of the oxide formation between Ti6Al7Nb and c.p.-titanium/Ti6Al4V, especially for low current densities. These effects correlate strongly with the donor densities in the air formed passive films of the examined materials. SEM-images of anodic oxide layers show a blister containing surface morphology of the outer part of the oxide layers for all materials. This morphology is probably caused by oxygen evolution, a process which relies on the transfer of electrons through the growing anodic oxide layers and strongly depends on the donor density in the air formed passive layers. Again, the much more pronounced morphology on c.p. titanium/Ti6Al4V agrees with the different donor densities in the air formed passive layers on the materials. These findings correlate with the good biocompatibility of Ti6Al7Nb and suggest that conduction mechanisms, in air formed passive layers and anodic oxide layers, contribute to processes that determine the biocompatibility of these materials.

Biomaterial Interface Investigated by Electrochemical Impedance Spectroscopy

“…[40] Figure 3(c) shows a simple circuit with sufficient fitting results, which is used very often. [4,12,26,29,32,36,[42][43][44][45][46][47][48] As a rule this equivalent circuit is used for a metal in contact with an electrolyte and it consists of the resistance of the solution R sol , a capacitance and the resistance R 1 , which can be a CTR [4,12,32] or the resistance of the passive layer. [32] The CTR represents the limited charge transfer through the interface and the electric double-layer capacitance.…”

Effect of Tantalum Doping on TiO<sub>2</sub> Nanotube Arrays for Water-Splitting

“…The slope of the so-called Mott-Schottky plots allows calculation of the donor density [67]- [70]. The change of the n-semiconductor doping density N D can be estimated using the Mott-Schottky relationship in the linear part of diagram by the equation [66] Table 1.…”

Biological nano-functionalization of titanium-based biomaterial surfaces: a flexible toolbox

“…Because the material is mostly determined for a given application, there exists only a limited choice of alternatives. Generally, the extent of oxygen evolution is lowest for galvanostatic polarization at high current densities (Delplancke & Winand 1988;Blackwood & Peter 1989;Scharnweber et al 2002). However, this recommendation may conflict with the pH drop owing to hydronium ion generation, which is higher for higher current densities.…”