Preparation and Characterization of Hydroxyapatite-Alumina-Zirconia Composite

In this present work, hydroxyapatite-alumina-zirconia composites were prepared and subsequent characterization was performed. This work makes zirconia as a central layer, alumina as an intermediate layer and then hydroxyapatite as an outer shell. The resultant composite was expected to have both improved mechanical properties and improved phase purity because of separation of two reactive phases, zirconia and hydroxyapatite by the alumina layer. In the first step of work synthesis of hydrous zirconia was prepared by using zirconium oxychloride and ammonium hydroxide solution and from it stabilization of tetragonal zirconia was performed after doping 3mol% Y2O3 during synthesis of hydrous zirconia. Treating yttria stabilized zirconia (YSZ) as core and using urea as the precipitant, subsequent coating on particle surface was performed in two steps, first aluminum nitrate as the source of Al3+ to generate alumina coating on YSZ and secondly using calcium nitrate as a source of Ca2+ and diammonium hydrogen phosphate as the source of P(Ca/P ratio 1.67) to produce hydroxyapatite coating on top of alumina coating on YSZ. Layered coating was ensured by drop wise addition of aluminum nitrate solution on zirconia precipitate and the similar procedure was followed for coating of hydroxyapatite on ZrO2-Al2O3 particles synthesized using urea decomposition method above 85oC in aqueous media. The resultant precipitate was freeze dried and then calcined at 800oC/4h followed by compaction of calcined powder into pellets and sintering at 1300oC. Particle size distribution, phase composition and microstructural analysis of sintered compacts were performed using TEM, XRD and FESEM respectively