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

Abstract

Porous hydroxyapatite and hydroxyapatite/oxide composites, with 10 wt% addition of Y 2O 3, ZrO 2 or TiO 2 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 Y 2O 3 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 ZrO 2 or TiO 2 enhances the decomposition of hydroxyapatite into Ca 3(PO 4) 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% β-Ca 3(PO 4) 2, exhibited the best mechanical properties. The failure of hydroxyapatite-10Y 2O 3 during the flexure tests was no catastrophic in contrast to the catastrophic behaviour found in the other materials.