Hydroxyapatite nanocomposites: Synthesis, sintering and mechanical properties

Two different hydroxyapatite based composites reinforced by oxide ceramic (20 wt%) nano crystals were synthesized by high-energy ball milling and sintered by pressure less technique. Alumina and titania nanoparticles as secondary phases improved densification and mechanical behavior of apatite and postponed its decomposition to the tricalcium phosphate (TCP) phases at elevated temperatures. Increasing the relative density of apatite using nano reinforcements leads to enhance the bending strength by more than 40% and 27% (as compared to the pure HA) and increase the hardness from 2.52 to 5.12 (Al₂O₃ composite) and 4.21 (TiO₂ addition) GPa, respectively. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy were employed to study morphologies, fracture surfaces and phase compositions, respectively. The morphological study and micro structural analysis confirm the X-ray diffraction and relative density diagrams.