From Zirconium Nanograins to Zirconia Nanoneedles

Abstract

Combinations of three simple techniques were utilized to gradually form zirconia nanoneedles from zirconium nanograins. First, a physical vapor deposition magnetron sputtering technique was used to deposit pure zirconium nanograins on top of a substrate. Second, an anodic oxidation was applied to fabricate zirconia nanotubular arrays. Finally, heat treatment was used at different annealing temperatures in order to change the structure and morphology from nanotubes to nanowires and subsequently to nanoneedles in the presence of argon gas. The size of the pure zirconium nanograins was estimated to be approximately 200-300 nm. ZrO2 nanotubular arrays with diameters of 70-120 nm were obtained. Both tetragonal and monoclinic ZrO2 were observed after annealing at 450 degrees C and 650 degrees C. Only a few tetragonal peaks appeared at 850 degrees C, while monoclinic ZrO2 was obtained at 900 degrees C and 950 degrees C. In assessing the biocompatibility of the ZrO2 surface, the human cell line MDA-MB-231 was found to attach and proliferate well on surfaces annealed at 850 degrees C and 450 degrees C; however, the amorphous ZrO2 surface, which was not heat treated, did not permit extensive cell growth, presumably due to remaining fluoride.