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The present paper reports on the influence of the addition of TiO 2 and SiO 2 oxides as sub-layer, on the morphological and mechanical properties of the hydroxyapatite (HAP) bioceramic coatings deposited on 316L stainless steel by sol-gel method in order to improve the properties of hydroxyapatite and expand its clinical application. The stability of the sols suspensions was evaluated by measuring the time dependence of the viscosity. Annealed properties of the coatings were analyzed by XPS, XRD, SEM, and EDS. The Vickers microhardness of the coatings is obtained under the same indentation load of 10 g. The hydroxyapatite coating deposited on the surface of the 316L SS substrate exhibits a porous carbonated apatitic structure. The results clearly demonstrate that HAP-TiO 2 and HAP-SiO 2 bilayer coatings where hydroxyapatite is deposited on the surface of TiO 2 -and SiO 2 -coated 316L SS substrate systems were highly homogeneous and uniform and show higher microhardness compared to HAPcoated 316L SS. A gap of nearly 10 pct is observed. The addition of TiO 2 and SiO 2 as sub-layer of a hydroxyapatite coating results in changes in surface morphology as well as an increase of the microhardness.

This study investigated the effectiveness of titania (TiO 2) as a reinforcing phase in the hydroxyapatite (HAP) coating and silica (SiO 2) single layer as a bond coat between the TiO 2-reinforced hydroxyapatite (TiO 2 /HAP) top layer and 316L stainless steel (316L SS) substrate on the corrosion resistance and mechanical properties of the underlying 316L SS metallic implant. Single layer of SiO 2 film was first deposited on 316L SS substrate and studied separately. Water contact angle measurements, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrophotometer analysis were used to evaluate the hydroxyl group reactivity at the SiO 2 outer surface. The microstructural and morphological results showed that the reinforcement of HAP coating with TiO 2 and SiO 2 reduced the crystallite size and the roughness surface. Indeed, the deposition of 50 vol pct TiO 2-reinforced hydroxyapatite layer enhanced the hardness and the elastic modulus of the HAP coating, and the introduction of SiO 2 inner layer on the surface of the 316L SS allowed the improvement of the bonding strength and the corrosion resistance as confirmed by scratch studies, nanoindentation, and cyclic voltammetry tests.

In this work, hydroxyapatite (HA) and fluorohydroxyapatite (FHA) coatings have been successfully synthesized with an electrochemical deposition method, using pulsed current deposition mode on smooth and rough 316L stainless steel implant surfaces. The impact of the variation of the current density was also studied. The surface morphology and chemical composition of the coatings were characterized by scanning electron microscopy associated with energy-dispersive X-ray spectroscopy (SEM-EDX), and X-ray photoelectron spectroscopy (XPS). The structural characterization is carried out by X-ray diffraction (XRD) and Fourier-transformed infrared (FT-IR) spectroscopy. Furthermore, thickness, roughness, and wettability of the coating are determined. The experimental results showed that the electrodeposition on rough surface promotes deposition of dense and homogeneous layers. It also shows that uniform and smooth films were obtained at low current densities compared to high current densities. Potentiodynamic polarization results in simulated body fluid (SBF) indicate that the coatings thickness and the incorporation of the fluorine ions into hydroxyapatite crystals play an important role in improving the corrosion resistance of the substrate. Moreover, cyclic voltammetry studies clearly suggest that the addition of H 2 O 2 and F À ions into the electrolyte solution catalyses a reduction reactions and favorites fluorohydroxyapatite formation. *bir.fatima@yahoo.fr