Article

An Investigation on the Effect of Morphologies on Corrosion Behaviour of Nanostructured Hydroxyapatite-Titania Scaffolds

Journal of Bionanoscience 01/2011; Vol-4:1-5. DOI: 10.1166/jbns.2010.1038

ABSTRACT The viable application of hydroxyapatite (HAp) scaffolds requires to posses the unison of properties:
porosity, bioactivity, mechanical toughness etc. Such properties strongly depend on the geometric
factors such as the size, morphology/microstructure of HAp. We have developed a hydrothermal
based approach to synthesize HAp-titania scaffold with different morphologies ranging from smooth
film to cauliflower to urchin like structures. The structural characterization by XRD reveals the formation
of HAp phase. The SEM analysis suggests the formation of HAp nanosheets or their subsequent
assembly when reaction carried out under basic conditions without and with the oxidizing
agent H2O2, respectively. The detailed investigation of corrosion behaviour of all HAp-titania scaffold
samples was undertaken by potentiodynamic technique in Ringer’s simulated body fluid solution at
close to human body temperature i.e., 37 �C. The shift in the OCP values of HAp-titania scaffold
samples towards nobler side and the relatively more posivite Ecorr values observed for these samples
than that of bare Ti-foil, suggesting superior corrosion resistance in case of HAp-titania scaffold
samples than that of bare Ti-foil. The detailed results on structural characterization and discussion
on corrosion behaviour of HAp-titania scaffold samples with different morphologies/microstructures
are presented.

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    ABSTRACT: NiTi alloy is used as biomaterial due to its unique properties, but the high content of Ni (about 50 at.%) in biomedical NiTi is of concern. Hydroxyapatite/titania composite coating was directly electrodeposited on the surface of NiTi alloy. The coated samples were characterized using X-ray diffraction, scanning electron microscopy, infrared spectroscopy, bonding strength test, polarization and electrochemical impedance spectroscopy (EIS). Results showed that addition of TiO2 to the electrolyte changed the morphology of hydroxyapatite from thin flake-flower-like crystals to needle-flower-like crystals, and the coating was much denser. Besides, hydroxyapatite crystal grains in the coating were preferentially arranged in the [001] direction, which was perpendicular to the surface of NiTi alloy. The addition of TiO2 improved the bonding strength between the coating and the substrate. Corrosion resistance of NiTi in the simulated body fluid at 37 °C was significantly improved by more than 50 times by electrodeposition of the hydroxyapatite/titania composite coating.Research Highlights► HAP/TiO2 coating was directly fabricated on NiTi by electrodeposition. ► Corrosion behavior of NiTi coated with HAP/TiO2 coating was studied. ► HAP/TiO2 coating can protect the NiTi from corrosion availably in the SBF.
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