Abstract
Porous hydroxyapatite (Ca10 (PO4) 6 (OH) 2; HAp) ceramics were prepared using hollow spherical agglomerates and hydrogen peroxide (H2O2) as a foaming agent. The hollow spherical HAp agglomerates with diameters of around 1μm were prepared by the spray pyrolysis of the mixed solution containing 0.5 mol·dm-3 of Ca (NO3) 2 and 0.3 mol·dm-3 of (NH4) 2HPO4 at 600°C. After the slurry was prepared by mixing 1 g of HAp powder with 5cm3 of H2O2 solution (concentration : 0-20 mass%), the excess amount of H2O2 solution was filtered off to form a compact with a diameter of 20 mm and a thickness of 4 mm. The compact was heated at 50°C for 1 h in order to form large pore sizes with 100-500μm and small pore sizes with 0.5μm or less within agglomerates, due to the pyrolysis of H2O2. The compact was fired between 900°Cand 1200°Cfor 5 h. By changing the concentration of H2O2 solution from 0 to 20 mass%, the total porosity of HAp compact fired at 1000°C for 5 h could be changed linearly from 61.2% to 71.7%. Pore sizes of the HAp compact with maximum porosity (71.7%) were around 0.7μm, 5-100μm and 100-200μm.
