Synthesis of element-substituted hydroxyapatite with controllable morphology and chemical composition using calcium silicate as precursor

In the absence of any surfactants and template-directing reagents, element-substituted hydroxyapatite [Ca-10(PO4)(6)(OH)(2), HAp] powders with controllable morphologies and chemical compositions were synthesized via hydrothermal treatment of a calcium silicate precursor in phosphate solutions. The morphologies (such as nanoparticles, nanowires and nanosheets) of the products could be well tailored through regulating the crystalline nature of the calcium silicate precursors or the type of phosphate solution. While through regulating the chemical compositions of the precursors and the reaction ratio of the precursor/solution, the HAp powders substituted by different kinds and amount of elements (such as Si, Na, Mg, and Sr, etc.) could be facilely obtained. A possible cluster growth mechanism accompanied with ion-releasing and incorporating model was preliminarily proposed for the formation of the controllable structures and compositions. The present work indicated that using calcium silicate as a precursor is an effective strategy to synchronously and delicately control the morphology and chemical composition of HAp crystals.