Electron microscopy study of the formation of hydroxyapatite through sol-gel processing

A study of the stages involved in the formation of hydroxyapatite synthesized by a sol-gel route was performed using scanning and transmission electron microscopic techniques as the primary characterization tools. Scanning electron microscopy enabled examination of the samples of the gel heat treated at various temperatures and for different time periods to determine the morphology and size of grains along with the presence and extent of any porosity in the sample surfaces. Thus, phase development could be studied as a function of heat treatment time and temperature. The gel was prepared using calcium acetate and triethyl phosphate as precursors added in a Ca/P molar ratio of 1.67. Characterization of the samples using transmission electron microscopy allowed a closer examination of the interaction between individual particles and also the detection of features on a much finer scale. Results deduced from these techniques were compared with those obtained from X-ray diffraction and FTIR spectroscopy.