Mechanochemical Synthesis of Hydroxyapatite from Calcium Oxide and Brushite

Fine hydroxyapatite (HA) powders were prepared by mechanically activating a mixture of calcium oxide and brushite powders in a high-energy shaker mill. A defective HA phase was formed when the starting powder mixture was activated for ≤20 h. When the mixture was calcined at 800°C, it was converted to β-tricalcium phosphate. In contrast, a nanocrystalline HA phase was formed when the mechanical activation was extended to 30 h. The material was transformed to a HA compound (Ca₁₀(PO₄)₆(OH)₂) of high crystallinity when it was calcined at 800°C.