Mechanical characteristics of porous hydroxyapatite/oxide composites produced by post-sintering hot isostatic pressing

Porous hydroxyapatite and hydroxyapatite/oxide composites, with 10 wt% addition of Y2O3, ZrO2 or TiO2 have been prepared by hot isostatic pressing after pressureless sintering, and their phase composition, mechanical properties and microstructure investigated. The quantitative X-ray diffraction analyses reveal that the addition of Y2O3 inhibits the hydroxyapatite decomposition completely during the consolidation processes as a result of the Y ion dissolution into the hydroxyapatite lattice. On the contrary, it is found that the addition of ZrO2 or TiO2 enhances the decomposition of hydroxyapatite into Ca-3(PO4)(2), which causes the transformation of the starting oxides. The mechanical characterization of the materials has been accomplished by three-point flexure tests, and nanoindentation and microhardness measurements. Post-sintering hot isostatic pressed pure hydroxyapatite, which resulted in a porous biphasic material with 13.2 wt% beta-Ca-3(PO4)(2), exhibited the best mechanical properties. The failure of hydroxyapatite-10Y(2)O(3) during the flexure tests was no catastrophic in contrast to the catastrophic behaviour found in the other materials. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.