Structure of a HAp/TiOy Nanocomposite Studied by Vibrational Spectroscopy Techniques

Abstract

A hydroxyapatite/TiO_y nanocomposite material has been studied by X-ray diffraction, infrared spectroscopy, and Raman spectroscopy. The results demonstrate that annealing at 400°C changes the valence state of the titanium and leads to the formation of [Ti(OH)₂]²⁺ and [TiHPO₄]²⁺ surface groups and terminal carbonyls and partial heterovalent cation substitutions of Ti³⁺ and Ti⁴⁺ for Ca²⁺. As the annealing temperature is raised to 600°C, surface groups disappear. The amount of inflowing oxygen is insufficient for the complete oxidation of TiO_0.92 to TiO₂ in hydroxyapatite/TiO_0.92. The result is the formation of an intermediate nanophase with the composition Ti_4.5O₅.