Biomimetic formation of hydroxyapatite investigated by analytical techniques with high resolution.

Morphology, phase and chemical compositions of atmospheric plasma-sprayed (APS) hydroxyapatite (HAp) coatings were investigated by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), proton-induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS). The study involved as-sprayed coatings and coatings incubated in simulated body fluid (rSBF) for up to 56 days. The results obtained using combined contributions from three complementary analytical techniques confirm that secondary Ca-deficient defect hydroxyapatite precipitated by a biomimetic process from the simulated body fluid onto the HAp coating surface after a prolonged induction time. Owing to its sensitivity proton-induced X-ray emission (PIXE) provides information on in vitro resorption of calcium phosphate ceramics and dynamic dissolution/precipitation events occurring during the incubation process.