In situ synchrotron Х-ray diffraction study of heat-induced structural changes in TiO_y/HAp nanocomposites

In situ synchrotron Х-ray diffraction (XRD) was used to study the interactions between an important biomaterial for tissue engineering and regenerative medicine, hydroxyapatite, and titanium monoxide additives of different stoichiometry, in nanocomposite materials. The study was carried out in the temperature range from ambient to 900 °C in a flow of dry air. During the temperature evolution of the nanocomposites, the mutual influences of the matrix and additives were observed. The dynamics of changes in the phase composition and the effects of TiO_y on the thermal stability of the matrix were considered. The addition of 10 wt% TiO_y increased the decomposition temperature of HAp by approximately 100 °C. Different additive stoichiometries shifted the temperature ranges of the phase transitions in the nanocomposites. Opposite trends were observed for the dependence of the weight content of the matrix and that of the additive on temperature in the range from 300 to 800 °C. This behaviour was explained by a partial substitution of Ti atoms for Ca atoms. After heat treatment to 900 °C, all nanocomposite phases were biocompatible. The oxyapatite and TiO₂ phases retained the nanostates of their initial components, while the α- and β-ТСР phases were microcrystalline. In situ synchrotron XRD method proved to be a highly informative and precise technique for studying new biomaterials.