Solvothermal Synthesis and Morphological Control of TiO2 Nanorods Modified with Oleic Acid

TiO2 nanorods were prepared by solvothermal method in two reaction systems. The structure, morphology and surface modification state of the as-obtained nanorods were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and thermalgravimetric method (TG). The results indicate that the surface modification and crystallization process are the main factors that affect the morphology of TiO2 nanorods. In the nonaqueous reaction system, the aspect ratio of as-prepared TiO2 nanorods increase to 11.5 with the mole ratio of tetrabutyl titanate to oleic acid at 1: 10, which is 2.3 times of that obtained in the hydrolyzation system under the same ratio of reactants. The reason for this phenomenon is that the selective adsorption of oleic acid on the surface of TiO2 limits the one-dimensional orientation growth of crystals. The aspect ratio of TiO2 nanorods can be enhanced by increasing the amount of oleic acid. Furthermore, nonaqueous reaction facilitates the adequate growth of crystals and the oriented attachment of nanorods due to its lower reaction velocity, leading to the significant increase of aspect ratio of nanorods. The as-obtained nanorods with the optimum aspect ratio exhibit good modification effect on the positive impulse breakdown strength of transformer oil.