Rapid synthesis of hollow nano-structured hydroxyapatite microspheres via microwave transformation method using hollow CaCO3 precursor microspheres

Hollow nano-structured hydroxyapatite [Ca10(PO4)6(OH)2, HAp] microspheres were rapidly synthesized via microwave transformation of a sacrificial hard-template of similarly structured calcium carbonate (CaCO3) hollow microspheres in Na3PO4 aqueous solution. Results showed that the microwave process significantly increased transformation efficiency. Pure hollow HAp microspheres could be obtained within ultra-short-period of 30 min via the microwave transformation process, in comparison to over 48 h in the traditional hydrothermal transformation method. These studies suggest that the microwave assisted hard-template transformation process is an effective approach to synthesize HAp with high efficiency. The resulting hollow nano-structured HAp microspheres may have applications in drug-delivery and serve as materials for chemical and environmental applications.