Agata Sotniczuk

Literature data has shown that reactive oxygen species (ROS), generated by immune cells during post‐operative inflammation, could induce corrosion of standard Ti‐based biomaterials. For Ti6Al4V alloy, this process can be further accelerated by the presence of albumin. However, this phenomenon remains unexplored for Ti β‐phase materials, such as TiNb alloys. These alloys are attractive due to their relatively low elastic modulus value. This study aims to address the question of how albumin influences the corrosion resistance of TiNb alloy under simulated inflammation. Electrochemical and ion release tests have revealed that albumin significantly enhances corrosion resistance over both short (2 and 24 h) and long (2 weeks) exposure periods. Furthermore, post‐immersion XPS and cross‐section TEM analysis have demonstrated that prolonged exposure to an albumin‐rich inflammatory solution results in the complete coverage of the TiNb surface by a protein layer. Moreover, TEM studies revealed that H₂O₂‐induced oxidation and further formation of a defective oxide film were suppressed in the solution enriched with albumin. Overall results indicate that contrary to Ti6Al4V, the addition of albumin to the PBS + H₂O₂ solution is not necessary to simulate the harsh inflammatory conditions as could possibly be found in the vicinity of a TiNb implant.

The aim of this work was to improve the surface properties of cp-Ti Grade 2 and β-Ti alloy TNTZ (Ti-29Nb-13Ta-4.6Zr) for biomedical applications. A hybrid surface treatment consisting of shot peening and chemical etching was conducted. Subsequently, the physicochemical properties and topography of the modified surfaces were analysed. Microhardness measurements of the shot-peened samples revealed a great increase in the surface hardness to the similar level as can be achieved for the ultrafine-grained and nanostructured materials. Roughness tests and microscopic observations showed significant topographical differences, depending on the material and modification process involved. Moreover, in this paper we demonstrate the influence of the substrate and treatments on the wettability. Obtained results confirmed that designed hybrid modification of Ti Grade 2 and TNTZ has significant potential for biomedical applications.

Two approaches can be taken when designing properties of the native oxide layers formed on Ti-based biomedical materials: (i) changing the chemical composition of the substrate by adding biocompatible, valve alloying elements, and (ii) changing the microstructure of the substrate—especially its level of defectiveness—through large plastic deformation. However, especially in the aggressive fluoridated oral environment, it is still unknown what factor is more effective in terms of enhancing oxide layer protectiveness against biocorrosion: (i) the presence of valve alloying elements, or (ii) a high number of structural defects. To gain knowledge about the separate influence of both of these factors, surface properties were examined for commercially pure Ti and Ti–Nb–Ta–Zr alloy in microcrystalline state as well as after multiple-pass cold rolling, a process that can be readily scaled up to the industrial level. This study showed that while valve-alloying elements and structural defects individually have a beneficial effect on Ti oxide layer properties in fluoridated medium, they not have to act in a synergistic manner. These findings have to be taken into account when designing future Ti-based dental materials together with analyzing their mechanical performance with respect to mechanical strength and elastic properties.

In this work, the influence of bending an AA5457 alloy sheet and the resulting microstructural changes on its corrosion behavior was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to perform detailed microstructural analyses of the alloy in its original form and after bending. After immersion in naturally-aged NaCl under open-circuit conditions (0.5 M, adjusted to 3 by HCl), post-corrosion observations were made, and electrochemical polarization measurements were performed to investigate the corrosion mechanisms occurring on both surfaces. The results showed that the corrosion of AA5457 is a complex process that mainly involves trenching around coarse Si-rich particles, crystallographically-grown large pits, and the formation of multiple tiny pits around Si-rich nanoparticles. The experimental data showed that bending AA5457 changed the shape and distribution of Si-rich coarse particles, cumulated a higher dislocation density in the material, especially around Si-rich nanoparticles, and all of these factors caused that corrosion behavior of the AA5754 in the bending area was lowered.