Synthesis of HAp by Means of Sonoprecipitation Method.

Biomaterials, like hydroxyapatite (HAp), are the subject of many scientific investigations. Their specific application, however, is determined by the form and some characteristic features of the resulting material. Synthesis methods and optimization procedures leading to a product of predetermined characteristics are therefore of great interest. To broaden the existing knowledge, sonoprecipitation was investigated as a potential method for the production of nanosized HAp particles. The research was carried out in a static mixer (STM) immersed in the ultrasonic bath. The influence of operating conditions, e.g., ultrasonic power P US ( ε US ), ultrasonic frequency (f US ), and unit mixing power ( ε mix ), was investigated in terms of nucleation intensity, product quality, and characteristics (particle size distribution ( PSD ), mean size, shape, etc.). As a result, the optimal conditions for the HAp nanoparticles synthesis (mean size: d ~150 nm; length: L 1 ~250 nm; width: L 2 ~80 nm) in the form of needles/whiskers/rods-similar to the shape of the HAp present in natural human bones, free from agglomerates, with negligible signs of particle destruction-were determined. The formation of HAp of smaller sizes ( d ≤ 100 nm) and more compact shapes ( L 1 ~155 nm, L 2 ~90 nm), useful in bone regeneration processes, was also discussed.