Preparation of Zirconia Nanorods by Molten Salt Method

Zirconia nanorods were prepared via molten salt route, using zirconia dry gel powder as precursor synthesized by non-hydrolytic sol-gel (NHSG) method. Differential, thermal analysis and thermogravimetric analysis (DTA-TG), X-ray diffraction analysis (XRD), transmission electron microscope (TEM) and field emission scanning electron microscopy (FE-SEM) were employed to characterize the phase transformation process of zirconia, the influences of the type, amount of molten salt and the role of fluoride on the formation of zirconia nanorods. The results show that the optimized molten salt type and dosage are NaVO3 and 1:1 (m(moltensalt):M-xerogel mass ratio), respectively, and the monoclinic zirconia nanorods grow preferentially along the [010] direction in the presence of sodium fluoride. It is found that the F- in the flux plays a vital role in formation of zirconia nanorods: on one hand, the fluoride ions accelerate the mass transfer of Zr4+ ions and the dissolution of zirconia xerogel in molten salt system; on the other hand, fluoride ions adsorb on high-energy facets of the zirconia to block the growth along these facets. The interaction of two aspects promotes the formation of zirconia nanorods in large scale.