Metathetic reaction in reverse micelles: Synthesis of nanostructured alkaline-earth metal phosphates

For the past few years, hydroxyapatite (HAp) has been identified as a potential biomaterial due to its excellent biocompatibility and bioactivity. The preparation of nanostructured HAp with controlled powder characteristics is a pre-requisite for processing it into useful biocomposites. Here, the synthesis of nanorods of calcium hydroxyapatite (Ca-HAp), strontium hydroxyapatite (Sr-HAp), and barium hydroxyapatite (Ba-HAp) by exploiting the metathetic reaction taking place in reverse micelles in the presence of cetyltrimethylammonium bromide has been reported. Powder X-ray diffraction analysis and thermogravimetric measurements confirm the formation of monophasic Ca-HAp and Sr-HAp. The growth of nanorods was further confirmed using transmission electron microscopy studies. The average lengths of Ca-HAp and Sr-HAp were ∼60 and 30 nm, respectively. However, the preparation of Ba-HAp invariably yielded a multiphasic mixture with other competitive phases like BaHPO and Ba(HPO). © 2007 The American Ceramic Society.