Synthesis, Characterization and Thermal Stability of Highly Crystallized Titania Nanotubes
- PDF / 581,644 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 205 Views
L1.8.1
Synthesis, Characterization and Thermal Stability of Highly Crystallized Titania Nanotubes B. Poudel, 1 W. Z. Wang ,1 C. Dames, 2 J. Y. Huang, 1 S. Kunwar, 1 D. Z. Wang, 1 D. Banerjee, 1 G. Chen, 2 and Z. F. Ren 1 1 Department of Physics, Boston College, Chestnut Hill, MA 02467 2 Department of Mechanical Engineering, MIT, Cambridge, MA 02139 ABSTRACT Gram quantities of titania (TiO2) nanotubes, with typical outside diameter about 9 nm, wall thickness about 2.5 nm, and length about 600 nm, were synthesized from anatase nano- and micro-powder using the hydrothermal method. The crystallization, structure, and phase stability of the nanotubes at high temperatures were systematically studied. A morphology change from nanotube to nanowire was observed at 650oC. The as-prepared nanotubes were usually contaminated with sodium impurities, other TiO2-derived phases and were poorly crystallized, but under optimized synthesis conditions the impurity phases was completely removed, resulting in highly crystallized pure nanotubes. The volume filling fraction of the autoclave as well as the concentration of the acid treatment were found to be particularly important for controlling the purity and crystallinity of the resulting nanotubes. INTRODUCTION Low-dimensional titania (TiO2) nanostructures such as nanotubes, nanowires, and nanobelts have attracted much attention in recent years because they have potential applications in electronics, optics, catalysts, sensors, and energy conversion [1-7]. For example, titania nanotubes have shown more than a two-fold increase in short-circuit current density compared to nanoparticles in thin film dye-sensitized solar cells [8]. For all of these applications, purity, crystallinity, and stability at elevated temperatures are particularly important. Titania nanotubes of various dimensions have been synthesized by different groups using techniques like anodization [9], template method [10], and hydrothermal method [1, 2]. A simple and cost-effective hydrothermal method for the large-scale production of titania nanotubes with small diameters has been introduced by Kasuga et al. There is currently much discussion about the formation mechanism and phases of the resulting nanotubes. The formation mechanism has been described in various reports [11-16]. In this context, we have systematically studied the synthesis conditions in order to determine optimal parameters for the growth of pure crystalline anatase nanotubes from the hydrothermal method. By systematically studying the alkali treatment and acid washing steps, we have identified conditions leading to each of the various phases reported previously by different groups, and established the optimal conditions for the formation of pure crystalline titania nanotubes.
EXPERIMENTAL DETAILS Titania nanotubes were synthesized following the method of Kasuga et al. [1].The starting materials were anatase nano-powder or micro-powder, NaOH, and HCl. In the optimized synthesis using micro-powder, 3 g of anatase powder was first mixed with 168 mL of 1
Data Loading...
