Facile hydrothermal fabrication of hollow hexagonal hydroxyapatite prisms

Abstract

Well-defined hollow hexagonal prisms of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) have been grown facilely on an aluminium oxide anodisc membranevia a hydrothermal reaction of calcium carbonate and phosphoric acid for 6 h at 170 °C in the presence of hydrazine monohydrate in a Teflon-lined autoclave. The sizes and the structures of calcium phosphate crystals are dependent widely on the temperature and the time of the reaction, revealing the formation mechanism of the hollow hexagonal hydroxyapatite prisms. Fourier transform infrared spectra and microscopic images show that irregular nanorods of octacalcium phosphate (Ca₈H₂(PO₄)₆·5H₂O) formed in the early reaction time transform into hollow hexagonal prisms of hydroxyapatite as the reaction time goes by.