The principal materials for implant's fabrication are usually metallic alloys, which have suitable mechanical and corrosion resistant properties. Now, the titanium and its alloys are widely used. In our preliminary work we studied the growth of cells on Ti6Al4V alloy, where the surface was modified either by plasma spraying of Ti microparticles or by electroerosion in liquid medium. The cell growth on these surfaces was compared with those on both the machined and smooth polished surfaces. The influence of the roughness on the cell growth was found, although the similar results of cell adhesion and proliferation were found for both surfaces.
Now, we compared the electroeroded surfaces of pure Ti, Ti6Al4V and Ti5Al2.5Fe alloys. We have characterised the chemical state of the surface by various methods of surface analysis. The presence of carbon based layer was found on all the electroeroded samples by X-ray photoelectron spectroscopy (XPS). The carbon and low traces of oxygen and titanium was observed. This finding indicates the presence of carbonaceous layer with thickness exceeding information depth of XPS. The composition of this layer is only negligibly changed by ion sputtering. The thickness and nature of the surface layer were thus studied using less surface sensitive nuclear analytical methods. The Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analyses (ERDA) was done to measure depth profile of the elemental composition of this layer and hydrogen content. We obtained reasonable profiles of mentioned elements. The maximum of film thickness was ~0.5 mm, unfortunately, the film thickness (and composition) was substantially inhomogeneous. The results of Raman micro-spectroscopy proved the presence of the layer with graphitic structure. The changes in degree of crystallinity between amorphous and crystalline state appeared. The most important features of Raman spectra reflect the evolution in the relation with the dimension of crystallites.
The roughness of sample surfaces was measured using contact profilometer and also by confocal microscopy to obtain 3D surface height mapping. The line and area roughness parameters were obtained; the differences among samples in the roughness were very low.
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