Sintering behavior and mechanical properties of hydroxyapatite ceramics prepared from Nile Tilapia (Oreochromis niloticus) bone and commercial powder for biomedical applications

In this work, Nile tilapia (Oreochromis niloticus) bone was calcined at 800 °C for 5 h in an air atmosphere to obtain hydroxyapatite powder (FB powder). The elemental composition, phase structure, and morphology of the FB powder were investigated and compared with commercial hydroxyapatite powder (SM powder). The FB-powder exhibited 1.01 at. % of Mg while the SM-powder showed Mg in ppm-level. Carbonate groups were detected in the two powders. Both HAp and β-tricalcium phosphate (β-TCP) structures were found in the FB powder, but the SM powder exhibit only the HAp phase. Irregular-shaped particles were observed in the FB powder. After the two HAp powders were sintered at 1200 °C and 1250 °C for 2 h (FB-1200, FB-1250, SM-1200, and SM-1250), the β-TCP intensity peaks of the FB-ceramic samples significantly increased with increasing sintering temperature. The highest relative density, well-packed grains, and β-TCP stabilization by Mg at the Ca5 site of the FB-1250 structure were the dominant factors governing the highest mechanical properties. Although high density was observed in the SM-1200 sample, Vickers hardness of the SM-1200 sample is lower than the FB-1250 sample. This may be attributed to the partial decomposition of HAp into β-TCP, α-tricalcium phosphate (α-TCP), and Ca₁₀(PO₄)₆O phases. In addition, the increase of grain size was the main factor that governs the increasing compressive strength and Young's modulus instead of density and phase decomposition of the SM-ceramic samples.