The use of titania (TiO2) nanotubes is becoming one of the most attractive techniques as surface treatment for implants due its combination of morphology (that accelerates osteoblast adhesion and proliferation), bioactivity and possibility of being use as a drug vehicle. Anodic oxidation is one of the cheapest and simplest approaches to obtain highly ordered nanotubes. Parameters such as applied potential, reaction time and fluoride containing in the electrolyte define the nanotubes morphology. However, the mechanical properties of the nanotubes layer do not have been completely elucidated and they play a crucial role in the implant long term stability. The objective of this research was to obtain TiO2nanotubes using anodic oxidation and to determine their elastic modulus and hardness. The TiO2nanotubes layer was obtained in a fluoride containing electrolyte for 1 hour, one group at 15 V and another one at 25 V. The TiO2nanotubes morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elastic modulus and hardness were evaluated by nanoindentation experiments using a spherical tip. SEM images showed highly ordered nanotubes on all titanium surfaces and it was observed that the nanotubes diameters are directly related with the applied potential. Nanotubes diameters are 66 ± 9 nm and 131 ± 22 nm for nanotubes obtained at 15 V and 25 V, respectively. Nanoindentation test results showed a decrease in the elastic modulus comparing with titanium reference and these values approach to cortical bone elastic modulus. These results demonstrate that it was possible to obtain a homogeneous TiO2nanotubes layer that has mechanical properties adequate to improve implant long-term stability.

Titanium and its alloys are biomaterials used in endosseous implants, due to desirable mechanical properties, high corrosion resistance and biocompatibility. Using electrochemical anodization technique these materials can be recovered with self-organized TiO2 nanotubes layer resulting in increased specific surface area and probable bioactivity improvement. This research aimed determine potentiostatic anodization parameters to obtain self-organized TiO2nanotubes layer with reproducibility and ideal diameters for probable bioactive response on Ti - 2 grade (ASTM F67) and Ti6Al4V (ASTM F136) orthopedic alloy and evaluation the electrochemical stability behavior in simulated body fluid media. The self-organized nanotubes layer were obtained by potentiostatic electrochemical method in electrolyte containing fluoride ions, H3PO4/HF for Ti 2 grade and H3PO4/NH4F for Ti6Al4V alloy, the applied potentials were 15 V, 20 V and 25 V for 30, 60 and 90 minutes, for both materials. For morphologic characterization were employed scanning electron microscopy SEM and the Image J software for nanodiameter measurements. The nanoestructure electrochemical stability was evaluated by open circuit potential after immersion for 15, 30 and 60 days in artificial blood plasma, into an electrochemical cell, using SCE (saturated calomel electrode) as reference electrode, in PBS ((phosphate buffered saline) solution electrolyte for 90 minutes. The ideal anodization parameters were 15 V and 20 V for 1 hour and a reproducible, uniform and homogeneous self-organized nanotubes layer were obtained with ideal diameters that probably improve the implant superficial bioactivity with 80 and 120 nm respectively, according to the literature. Open-circuit potentials from metal/oxide system obtained on both materials are stable with potentials in range of -0.031 V to -0,183 V indicating good stability of nanoestructures in simulated body fluid. Nanotubes layer as a superficial treatment is viable with high reproducibility, low cost and electrochemical stability in simulated body fluid media.

Ligas de titânio estão sendo desenvolvidas para uso em implantes ortopédicos devido às suas propriedades mecânicas adequadas, biocompatibilidade e resistência à corrosão. Neste trabalho, foram realizados estudos eletroquímicos nas ligas Ti-Mo com 6, 10 e 20 Mo (% m/m) na estrutura bruta de fusão, em solução de Na2SO4 0,15 mol L-1 e solução fisiológica de Ringer. Os valores dos potenciais de repouso indicam que estas ligas apresentam tendência semelhante à formação de óxido espontâneo, enquanto que os perfis obtidos por voltametria cíclica mostram que estas não sofrem corrosão por pites até potenciais de crescimento iguais a 8,0 V (vs ECS). Nos estudos potenciodinâmicos associados aos cronoamperométricos as análises do potencial de circuito aberto indicaram que a presença do íon cloreto, não afeta a estabilidade dos óxidos anódicos formados.

Ti alloys are being developed to be used in orthopedic implants due their mechanical properties, biocompatibility and corrosion resistance. At this paper are reported electrochemical studies on the as-cast Ti-Mo alloys with 6, 10 and 20 Mo (wt.%), in 0.15 mol/L Na2SO4 solution and Ringer physiological solution. Analyses of the rest-potential indicated that all alloys present the same tendency to a spontaneous passivation, while cyclic voltammograms showed not transpassivation up to potentials of 8,0 V (vs ECS), indicating high corrosion resistance. The comparison among open-circuit profiles of the anodic oxides growth in Ringer and Na2SO4 solutions, are showing that the presence of chloride ions during the anodization is not influencing the oxides chemical stability.

Estudos sobre a estabilidade de óxidos anódicos crescidos sobre zircônio e suas ligas biocompatíveis Ti-50Zr %at. e Zr-2,5Nb %m., em solução fisiológica de Ringer aerada, a 25 e 37 ºC, foram feitos por meio da comparação entre as cargas de sua formação e de sua reconstrução após dissolução a circuito aberto na solução fisiológica. A estabilidade de óxidos crescidos na solução de Ringer e em solução de Na2SO4 0,15 mol L-1 foi comparada. Os resultados obtidos mostram que a estabilidade desses óxidos é aumentada por envelhecimento sob condições potenciostáticas e que ela pode ser decrescida pela presença de íons cloreto no eletrólito durante o processo de anodização.

Studies on the stability of anodic oxides grown on zirconium and its biocompatible alloys Ti-50Zr at.% and Zr-2.5Nb wt.%, in aerated Ringer physiological solution, at 25 and 37 °C, were carried out by comparing their formation charge and their reconstruction charge after dissolution at open circuit in the physiological solution. The stability of oxides grown in the Ringer solution and in a 0.15 mol L-1 Na2SO4 solution was compared. The obtained results show that the stability of these oxides is increased by aging under potentiostatic conditions and can be decreased by the presence of chloride ions in the electrolyte during the anodization process.