Synthesis and sinterability of hydroxyapatite from fishery by-products

Hydroxyapatites (HAps) were synthesized using the powdered waste of fishery products, i.e., fish scales and crab shells, as starting materials. HAp was synthesized by a wet-chemistry method followed by calcination at 600 and 800°C. Calcined crabshell powder revealed a single HAp phase and fine powder, while calcined fish-scale powder showed a ß-TCP secondary phase, even at the higher calcination temperature. Dense HAp pellets were obtained from the crab-shell powder by spark plasma sintering at 1000°C for 10 min under applied pressures of 40 and 80 MPa in a vacuum state, giving sample densities of 2.93 and 3.06 g/cm³, respectively. The estimated grain size of HAp was 448 ± 96 and 283 ± 59 nm for applied pressures of 40 and 80 MPa, respectively. In contrast, the HAp obtained using the pressureless sintering technique showed excessive grain growth without further densification.