The Effect of Citrate on the Morphology of Hydroxyapatite particles through Hydrothermal Synthesis

The focus of this study is on the effect of citrate as chelating agent on the formation of morphology of hydroxyapatite particles synthesized by hydrothermal method. The powder samples were characterized by various techniques. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of crystalline powder and purity in the synthesized hydroxyapatite. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed the importance of Ca/citrate ratio in regulating the particle morphology. In the presence of citrate under hydrothermal process, a two-dimensional monetite phase evolved into three-dimentional hydroxyapatite microspheres with an average diameter of 4-6 µm. The results also indicate that the surface morphology of microspheres can be engineered from nanosheets to nanorods by regulating chelating agent concentration. The BET specific surface analysis showed an increase in the surface area with the increase in the citrate ion concentration. The observed specific surface area of microplates was 30 m2/g in absence of citrate, which increased to100 m2/g for microspheres. The BJH pore size distribution was in the range of 8-20 nm.