Effect of stabilised ZrO2, Al2O3 and TiO2 on sintering of hydroxyapatite

In this work, the hydroxyapatite was prepared from cortical bone after calcination at 700 C during 1 hour. In order to improve mechanical properties of HA, 5 wt% of the ZrO2 (stabilized with 12.0 wt% CeO2), Al2O3 and TiO2 were added to HA powder as a reinforcing phase. All the powders were sintered at 1300 degrees C for 2 hours. The XRD was utilized to identify the phases composition. It was found that the initial calcined powder is hydroxyapatite with the following chemical composition Ca-5(PO4)(3)OH. In addition, the phenolphthalein test has put into evidence the existence of free CaO. For powders containing ZrO2, the XRD spectra has showed a little percent of formed beta-tricalcium phosphate ((beta-TCP); the HA was decomposed to ((beta-TCP) and CaO which forms with ZrO2 the calcium zirconate (CaZrO3). Nevertheless, in powders containing TiO2, the XRD spectra showed that a partial decomposition of HA to beta-TCP was occurred with formation of calcium titanium oxide (CaTiO3 However, for powders containing Al2O3, a nearly full decomposition of HA to beta-TCP was occurred, the free Al2O3 was present. Finally, it has been found that HA composites containing a large amount of beta-tricalcium phosphate are resorbale than HA composites containing a small amount of beta-TCP and they were not well densified. The microhardness values of HA-ZrO2 composites were greater than those of HA-Al2O3 and HA-TiO2 composites.