Synthesis and Nanocomposite Sintering of Hydroxyapatite-coated Zirconia Nanopowders

Hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is a well-known and a valuable implantmaterial with biocompatibility and bioactive properties. Full utilisation of the unique properties ofhydroxyapatite bulk ceramics is, however, enhanced by a proper reinforcement, i.e. by preparationof composites. The goal of this study was to synthesize a HAP-coated zirconia composite powderby the precipitation of HAP in presence of zirconia. The idea was to avoid uncontrolledagglomeration of the zirconia nanostructured reinforcement during the sintering step. ZrO2nanopowders, previously synthesized by hydrothermal crystallisation, were added in an appropriateamount to an intensively stirred aqueous suspension of Ca(OH)2. HAP was precipitated by additionof H2PO4 at controlled pH in order to obtain a 50:50 composite powders. The obtained powders,fully characterized by TEM, XRD, TG-DTA and BET, were used for the preparation of thenanostructured composite speciments. The sintered materials were characterized in order toevaluate their structural and morphological properties.