SYNTHESIS OF ULTRAFINE HYDROXYAPATITE IN A Ca(OH)2-H3PO4-H2O REACTION SYSTEM USING ULTRASOUND IRRADIATION

This paper reports the application of ultrasound irradiation in the synthesis of ultrafine hydroxyapatite (HAp) with a high specific surface area of 300 m/g. We examined the effects of initial temperature, horn diameter and suspension concentration on the powder properties, especially specific surface area, of ultrafine HAp. Amorphous calcium phosphate (ACP), which is a precursor of HAp, was formed in the early stage of the reaction, and then rapidly crystallized to form HAp. In the case of an initial temperature at 30oC, the largest specific surface areas of 250 m/g and 300 m/g were obtained using horn diameters of 19 mm and 6 mm, respectively. Based on particle size distribution measurements, the mode and average diameters of the HAp powders were found to be 5.0 and 6.3 nm, respectively. These values were well-agreed with the average diameter calculated from the specific surface area. (Received Sep 12, 2019; Accepted Oct 25, 2019)