Effect of sonication time on the characteristics of nanophase hydroxyapatite crystals synthesised by the sol–gel technique

An examination has been conducted of the effect of sonication time (25 kHz) at a constant temperature of 25°C on the structure of hydroxyapatite (HAp). Diammonium hydrogen phosphate and calcium nitrate tetrahydrate were used as starting materials. The gel formed by mixing the starting materials solution was subjected to sonication for 0, 5, 10, 20, 30 and 40 min. After sonication, HAp was dried at room temperature and calcined at 600°C for 2 h. The crystallisation, morphology and functional groups of the prepared nanoHAp were inspected by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. The XRD results revealed crystalline sizes in the range 50-58 nm and 3-5 of the crystalline fraction. The TEM results proved that the particle size of nano-HAp decreased with increasing sonication time. In addition, the FTIR spectroscopy confirmed that an increase of sonication time led to an increase in the concentration of carbonate groups