Influence of hydrothermal treatment on the surface characteristics and electrochemical behavior of Ti-6Al-4V bio-functionalized through plasma electrolytic oxidation

• Published in: Surface & coatings technology 2019-09, Vol.374, p.222-231
• Main Authors: Fazel, M., Salimijazi, H.R., Shamanian, M., Apachitei, I., Zadpoor, A.A.
• Format: Article
• Language: English
• Subjects: Biomedical materials; Calcium compounds; Corrosion resistance; Electrochemical analysis; Electrochemical impedance spectroscopy; Hydrothermal treatment; Hydroxyapatite; Hydroxyapatite nanocrystals; Morphology; Nanocrystals; Organic chemistry; Orthopedics; Oxidation; Plasma electrolytic oxidation (PEO); Protective coatings; Surface properties; Surgical implants; Titanium base alloys; Water absorption; Wettability
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.05.088

The performance of biomaterials in general and orthopaedic biomaterials in particular is dependent on both the chemistry and topography of their surfaces. It is therefore important to tailor both of those aspects through an appropriate surface modification technique. Here, we examined the influence of hydrothermal treatment on the surface characteristics and electrochemical behavior of Ti-6Al-4V specimens whose surfaces were modified using plasma electrolytic oxidation (PEO). Even though no calcium-phosphorous related crystalline compound was identified in the XRD spectra of PEO layers, hydroxyapatite crystals were clearly detectable after the applied hydrothermal treatment. The partial water absorption of the HA crystals and their needle-like morphology resulted in a significant increase in the wettability of the surfaces. However, the application of post-PEO hydrothermal treatment also decreased the corrosion resistance of the PEO layers. The numerical results of electrochemical impedance spectroscopy demonstrated that the optimized surface properties and corrosion resistance were achieved in one of the groups, namely PEO-HT3, where the HA nanocrystals homogenously covered the entire surface of the specimens. •Ca-P contained PEO layers were successfully synthesized on Ti6Al4V alloy using a constant current-constant voltage regime.•A developed structure of uniformly distributed HA nanocrystals was formed after the hydrothermal treatment of PEO layers.•The presence of the HA nanocrystals caused a remarkable increase in the wettability of the hydrothermally treated groups.•PEO-HT3 specimens showed both high corrosion resistance and uniform coverage of their surfaces by HA nanocrystals.