Effect of the addition ZrO2-Al2O3 on nanocrystalline hydroxyapatite bending strength and fracture toughness

Nanocrystalline hydroxyapatite powder has been synthesized from a Ca(NO3)(2).4H(2)O and (NH4)(2)HPO4 solution by the precipitation method. In the next step we prepared Zro(2)-Al2O3 powder. After preparation, the powder was dried at 80 degrees C and calcined at 1200 degrees C for 1 h. Various amounts (HAP-15 wt% ZA, HAP-30 wt% ZA) of powder were mixed with the hydroxyapatite by ball milling. The powder mixtures were pressed and sintered at 1000 degrees C, 1100 degrees C and 1200 degrees C for I h. In order to study the structural evolution, X-ray diffraction (XRD) was used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to estimate the particle size of the powder and observe fracture surfaces. Results show that the bending strength of pressed nanocrystalline HAP was improved significantly by the addition 15 wt% of ZrO2-Al2O3 powders at 1200 degrees C, but the fracture toughness was not changed, however when 30 wt% of ZA powders were added to nanocrystalline HAP, the bending strength and fracture toughness of the specimens decreased at all sintering temperature. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.