A modified milling system, using a bimodal distribution of highly resistant ceramics. Part 1. A natural hydroxyapatite study

A careful combination of the main parameters controlling natural hydroxyapatite (NHA: Ca10(PO4)6(OH)2) production such as milling techniques, sintering temperature and holding time may lead to an interesting NHA based bio-ceramics without any foreign oxide additions. In this way, an original wet milling setup has been proposed to obtain sub-micron sized NHA powders. In order to avoid any possible NHA decomposition, a precise Ca/P ratio of NHA derived from animals was selected accordingly. Also, an alternative direct visual approach of the bone age classification was also proposed. A relative density of about 95% was obtained for powders sintered at 1300°C for 2h. The best Vickers micro-hardness and 3 point bending strength values for these sintered samples, using this proposed milling system and without any additions, were 4.7±0.3GPa and 37MPa, respectively. Finally, a complete correlation between the powder microstructure and the final product properties has been established. •A new simple and a multidirectional wet milling system was proposed.•A complete combination between parameters controlling NHA sintering was studied.•Sub-micron sized NHA powders were obtained using the proposed milling system.•A direct visual approach of the age bone animal classification was also proposed.•NHA promising density and mechanical properties were obtained using this system.