title: The transformation of single-crystal calcium phosphate ribbon-like fibres to hydroxyapatite spheres assembled from nanorods.
abstract: Two precursors of ribbon-like anhydrous dicalcium phosphate (DCPA) and calcium phosphate fibres were successfully synthesized at 85 °C through a simple and mild pathway from Ca(NO(3))(2)·4H(2)O and (NH(4))(2)HPO(4) upon the hydrolysis of urea. Different molar concentrations of urea resulted in different precursors, including precursor I (DCPA phase) and precursor II (calcium phosphate with DCPA, octacalcium phosphate (OCP) and hydroxyapatite (HAp) phase). By immersing the two precursors in ammonium hydroxide solution (pH = 12), the transformation from precursors to hydroxyapatite could be achieved. X-ray diffraction (XRD) results combined with transmission electron microscopy (TEM) indicated that DCPA fibres (precursor I) were transformed to HAp nanorods in transformation I. In transformation II, dandelion-like spheres assembled by HAp nanorods were obtained from calcium phosphate (precursor II). The mechanisms of transformations I and II are also proposed and discussed based on the XRD and TEM results.
authors.affiliation: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China. Graduate School of the Chinese Academy of Sciences, Beijing, 100039, People's Republic of China.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jinjun
authors.initials: J
authors.lastname: Lu