Properties of hydroxyapatite produced by annealing of bovine bone

The properties of porous hydroxyapatite (HA) bioceramic produced by heat treatment (annealing) of bovine bone were evaluated over temperatures between 400 °C and 1200 °C. The annealed body was characterized by thermal analysis (thermogravimetric analysis (TG)/differential thermal analysis (DTA)), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transformed infrared (FTIR) spectroscopy. The XRD results showed that the annealing process enhanced the crystallinity of HA phase in the bone matrix particularly when annealed above 700 °C. There was no secondary phase formation in bones annealed between 600 °C and 1000 °C. However, decomposition of HA to β-tricalcium phosphate (TCP) was observed for samples heat-treated at 1100 °C and 1200 °C. The FTIR spectra and the TG/DTA thermogram of as-received bovine bone indicated the presence of organic compounds, which upon annealing at temperatures above 600 °C was completely removed from the matrices. Bovine bone annealed between 800 °C and 1000 °C revealed the characteristics of a natural bone with the interconnecting pore network being retained in the structure.