First stages of bioactivity of glass-ceramics thin films prepared by magnetron sputtering technique

Implant type coatings were prepared by magnetron sputtering (MS) technique onto medical grade Ti6Al4V alloy substrates starting from biological 45S5 glass system powders. The as-deposited thin layers were annealed 2 h at 700 °C in ambient air, followed by a slow cooling (2 °C/min) in order to induce crystallization. The behavior of the coatings was investigated by soaking the samples in simulated body fluids (SBF) and extracting them after 24 and 72 h. The changes in the films' structure were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) analysis and by Fourier transform infrared spectroscopy (FTIR). A pitched, pore free microstructure with 6 μm agglomerates of submicron grains in a continuous matrix was revealed by the SEM images of the annealed samples. Complex silicates as Na4Ca4Si6O18-combeite and phosphates NaCaPO4 as crystalline phases were identified in the XRD diffraction patterns. In-growths after 24 h show the enrichment in Si-O (s) non-bonding oxygen (NBO). The polymerization reaction in the surface layer appears for the sample immersed 72 h in SBF. No crystalline hydroxyapatite (HA) was evidenced for those samples. Subsequent dissolution processes of the surface layers were noticed from XRD patterns and SEM images.