Facile preparation of hydroxyapatite nanotubes assisted by needle-like calcium carbonate

Hydroxyapatite (HA) is a famous biomaterial and its performance depends greatly on its morphology and 3D architecture. So the synthesis for HA with specific structures has been widely paid attention. In this research, a cost-effective way to prepare HA nanotubes with no post-processing template removal step was presented through Kirkendall effect-assisted ion-exchange process by using inexpensive needle-like CaCO3 nanoparticles as templates and calcium sources. The effects of reaction time, temperature and pH value on the formation of HA nanotubes were investigated. The as-prepared HA nanotube products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET). It was found that HA nanotubes had uniform tubular hollow structures with big openings, a length of 2–4 μm, the average inner diameters at the two ends of 300–400 nm and 150–250 nm, respectively, as well as a wall thickness of approximately 35 nm and a specific surface area of 60 m2/g.