Physicochemical investigation of pulsed laser deposited carbonated hydroxyapatite films on titanium

Carbonated hydroxyapatite (CHA)-coated titanium can find wide applications as bone substitute implant in bone and dental surgery and orthopedics, promoting osseointegration with a host bone and ensuring biocompatibility and bioactivity. In this work, carbonated hydroxyapatite films were prepared on titanium substrates by pulsed laser deposition at different substrate temperatures ranging from 30 to 750 °C. The properties of films were investigated by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray diffraction, and Fourier transform infrared spectroscopy. Vickers microhardness measurements of the composite film-substrate systems were performed, and the intrinsic hardness of films was separated from the composite hardness using a “law-of-mixtures” approach and taking into account the indentation size effect. The prepared CHA films are nearly stoichiometric with a Ca/P atomic ratio of 2.0-2.2. The films deposited in the 30-500 °C temperature range are about 9 ¼m thick, amorphous, having an average roughness of 60 nm. At higher temperature, 700-750 °C, the films are about 4 ¼m thick, show a finer surface morphology and an average roughness of 20 nm. At 750 °C the films are amorphous, whereas at 700 °C they are crystalline and textured along the (202) and (212) directions. The intrinsic hardness of the films increased with an increase in substrate temperature, being as low as 5 GPa at 30 °C and reaching a high value of 28 GPa at 700 °C. The rich information gained by the joint use of the mentioned techniques allowed a comprehensive characterization of this system.