Synthesis of nanocrystalline hydroxyapatite from Ca(OH)2 and H3PO4 assisted by ultrasonic irradiation

This work is focused on the synthesis of hydroxyapatite powders by precipitation assisted by a tip ultrasonic irradiation (UI) from Ca(OH)2 and H3PO4. The effect of UI time, applied UI power during the synthesis, initial Ca2+ concentration and ageing time of the mixture on phase composition, morphology and specific surface area of the obtained powders was analysed. Particles obtained from the precipitation method using UI or mechanical agitation were compared with a nanosized hydroxyapatite of reference in terms of crystal size, phase composition and thermal stability. This study revealed the feasibility to produce hydroxyapatite powders with controlled crystal size between 31.7 and 70.6 nm by ultrasonic assisted precipitation method. Hydroxyapatite powder with similar surface area to the reference material can be obtained adjusting experimental conditions. The used method allowed us to synthesise hydroxyapatite powders with thermal stability up to 1100 °C.