UC Santa Cruz

ZrO₂ nanoparticles were synthesized by a vapor-phase hydrolysis process, and characterized in terms of crystalline structures, hardness and microstructures by X-ray diffraction, Vickers hardness test method, and atomic force microscopy (AFM) measurements. Moreover, in vitro cytotoxicity evaluation and hemolysis assay showed that the nanoparticles possessed good biocompatibility. Hardness investigations and AFM measurements indicated that both the sintering temperature and compression force played an important role in determining the physical behaviors (hardness, roughness and density) of flakes of the ZrO₂ nanoparticles. When ZrO₂ nanoparticles synthesized at 500 °C were pressed into flakes under 6 MPa and sintered at 1400 °C, the resulting flakes exhibited an optimal combination of hardness (534.58 gf·mm^-2), roughness (0.07 μm) and density (4.41 g·cm^-3). As the Vickers hardness value of human bones is of 315~535 gf·mm^-2 and the density of adult femuris about 1.3~1.7 g·cm^-3, the experimental results showed that the ZrO₂ flakes were comparable to human bones with a higher density. As a result, the synthesized ZrO₂ NPs may be useful for biomedical applications, especially for bone repair and replacement in future.