Biological bone is a nanostructured composite that consists of hydroxyapatite (HA) nanoparticles in a polymeric collagen matrix. HA has widely been used as an implant material in clinical applications owing to its desirable properties such as osteoconductivity and bioactivity. Its low mechanical properties are not suitable for load bearing cases. One way to solve this problem is to apply HA coating onto substrates in order to achieve the necessary mechanical strength and bioactive properties, simultaneously. HA coating and metal substrate could not form a chemically bonding interface. The addition of ZrO 2 particles on the HA coating has been got considerable attention because the ZrO 2 particles increase the bonding strength between HA coating and substrate. Sol-gel technique can be used to produce nanostructured HA coating and the metallic implant. In this study HA/yttria stabilized zirconia(YSZ) nanopowders and also nanostructured coatings were prepared by a sol–gel method. The HA sol was prepared by dissolving (C 2 H 5 O) 3 P and Ca(NO 3 ) 2 .4H 2 O in the ethanol absolute, under vigorous stirring at room temperature. Appropriate amount of Zr(OC 3 H 7 ) 4 OC 3 H 8 , were used as the source of zirconia. The yttrium precursor was obtained by dissolution of 0, 3, 5 and 8 mol% (CH 3 CO 2 ) 3 Y.xH 2 O in 2-propanol alkohol. The reinforcements were prepared by 30 wt% ZrO 2 sol. X-ray diffraction(XRD), Thermal Gravity Analysis(TGA), Fourier Transform Infrared(FTIR), Scanning Electron Microscopy(SEM) and Transmission Electron Microscopy(TEM) methods were used to characterize and evaluate of the phase composition, thermal behavior, functional groups, morphology and particle size of products. HA/YSZ composite coatings were performed on 316L stainless steel substrate by the sol-gel technique. Structural characterization techniques including XRD, SEM and EDX were used to investigate the microstructure and morphology of the coatings. The dissolution rates of the coatings were measured in a physiological saline solution and the dissolved Ca 2+ ion concentration was measured by atomic absorption spectroscopy (AAS) method. It was found that at temperatures ranging from 850 to 1050?C, the dominant phases of the powder were HA and tetragonal (t)-zirconia in 3YSZ, cubic (c)-zirconia in 8 YSZ and t-c-Zirconia in 5YSZ phases with the small amounts of ?-tricalcium phosphate (?-TCP) and CaZrO 3 . The crystallinity and the crystallite size of the coating were about 80% and ~20-30 nm for tetragonal and cubic zirconia grain size and 60-80 nm for hydroxyapatite grain size, respectively. Crack-free and homogeneous HA/YSZ composite coatings were obtained with no observable defects. The
