Sol-gel derived nanocrystalline hydroxyapatite coatings preparation, characterization, evaluation of the bioactivity and corrosion protection behavior

Abstract

The aim of this work was to prepare bioactive hydroxyapatite coatings by sol-gel method and to study the effect of thermal treatment temperature upon the bioactivity and corrosion protection of these coatings on Titanium alloy Ti6Al4V. The application of DTA/TGA and XRD has provided valuable information about the phase transformation, mass loss, identification of the phases developed, crystallite size, degree of crystallinity, lattice parameters, and unit cell volume. ICP has been used to analyze the evolution of ion release from hydroxyapatite tablets versus the immersion time in SBF. SEM/EDX has been applied to study the surface morphology of HA tablets before and after immersion in SBF to detect the biomimetic precipitation of secondary hydroxyapatite. FTIR has been also applied for studying the structure changes of the samples after being immersed in SBF. The obtained results show that all the prepared samples are ceramic nanopowders with crystal structure and composition like hydroxyapa tite, with small deviations from that present in the human bone. The bioactivity of the studied samples is found to be closely related to the thermal treatments applied. That is, the bioactivity decreases as the temperature of the thermal treatment increase. Coatings from such prepared hydroxyapatite sol have been accomplished by dip-coating technique on non-toxic Ti6Al4V alloy for biomedical applications. The corrosion behaviour of the resulting hydroxyapatite coatings in a simulated body fluid (SBF) has been studied by electrochemical impedance spectroscopy. The hydroxyapatite coated Ti6Al4V alloy displayed excellent bioactivity when soaked in the SBF and acceptable corrosion protection behaviour.