Cuttlebone and Its Hydrothermal Converting to Hydroxyapatite

The composition and morphology of original cuttlebone and hydroxyapatite(HAP)-converted cuttlebone were characterized by means of X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), thermogravimetric-differential thermal analysis(TG-DTA) and scanning electron microscopy (SEM). The mechanism of self-assembly was also discussed. The results show that the mineral of original cuttlebone is rod-like aragonite polymorph of CaCO3 and the chamber-like macroporous architecture is its extrinsic feature. In phosphate solution, the interior aragonite converts hydrothermally to HAP by a solid-state topotactic ion-exchange reaction in which the HAP retains the morphology and the orientation of the original aragonite. Meanwhile, the exterior aragonite converts hydrothermally to HAP via dissolution-recrystallization, with squama-like morphology. These squama-like HAP self-assemble to microspheres with hydrothermal reaction time prolonged.