Effect of Annealing on Microstructure of Hydroxyapatite Coatings and their Behaviours in Simulated Body Fluid

Abstract

In this study, hydroxyapatite (HA) coatings on Ti6Al4V substrate were deposited using an ion beam sputtering technique. Owing to its medical applications, the crystalline phases present in the HA must be controlled. This study investigated the effect of post-deposition heat treatment at different temperatures and evaluated the microstructure of the HA coatings and their behaviours in simulated body fluid (SBF). The post-deposition treatment of the as-deposited samples was carried out in an air-circulated furnace at a temperature between 300 0C and 600 0C. The XRD patterns reveal that the minimum temperature to transform the HA coating from amorphous to crystalline phase is 400 0C. A higher temperature at 600 0C leads to a growth of the crystalline HA phases. Fourier transform infrared spectroscopy (FTIR) measurements show the existence of hydroxyl and PO-bonds in all coatings and the amounts varied with temperature. Atomic Force Microscopy (AFM) study suggests that the nanostructured crystalline HA starts to grow at 400 0C and becomes more obvious at a higher temperature of 600 0C. The simulated body fluid (SBF) test reveals that better apatite formation with post deposition heat treatment at 600 0C would potentially enhance the formation of new bone (osseointegration).