he effects of substrate composition on oxide layer properties following plasma electrolytic oxidation under similar conditions have been evaluated for α-cpTi, α/β-Ti6Al7Nb, β-Ti35Zr10Nb and β-Ti45Nb alloys. All oxidised surfaces revealed enhanced wettability, surface free energy and roughness relative to the non-oxidised surfaces. Nevertheless, the resultant oxides differed with respect to average pore size, pores density, layer chemistry and phase composition. The β-titanium alloys developed oxides with a larger average pore size and lower pore density relative to the α-cpTi and α/β-Ti6Al7Nb substrates. Anatase dominated the oxide layer formed on α-cpTi and β-Ti45Nb alloys, a mixture of anatase and rutile was present on the oxidised α/β-Ti6Al7Nb surface, whereas Ti2ZrO6 was the only phase detected on the oxidised surface of the β-Ti35Zr10Nb alloy.@en

This research was aimed at investigating the growth mechanism of TiO(2)-Ag antibacterial coatings during plasma electrolytic oxidation (PEO) of Ti6Al7Nb biomedical alloy in an electrolyte based on calcium acetate/calcium glycerophosphate bearing Ag nanoparticles. The focus was on the mechanism of incorporation of Ag nanoparticles, their distribution and chemical composition within the porous coatings using high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) imaging techniques combined with energy dispersive X-ray spectroscopy (EDX) for chemical analyses. The PEO coatings were grown using different oxidation times, 10, 30, 60, 90, 120, 180, 240 and 300 s. The electron microscopy results confirmed the formation of a porous coating with incorporated Ag nanoparticles from the initial stages of oxidation (i.e. 10s). with further Ag incorporation as the PEO process was continued for longer durations. The Ag nanoparticles were embedded in the dense oxide layer, fused into the pore walls and on the surface of the coatings without any change in their morphology or chemistry as detected by HRTEM, SEM and EDX. Ag seems to be delivered to the sites of coating growth (where dielectric breakdown occurs) through different transport pathways, i.e. open pores, cracks and short-circuit channels.@en