Structural transformation from NaHTi3O7 nanotube to Na2Ti6O13 nanorod

NaHTi3O7 nanotubes were synthesized by the hydrothermal method. Temperature effects of the nanotubes are examined by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), thermal gravity analysis (TGA), and Raman spectroscopy. With increasing the annealing temperature NaHTi3O7 nanotubes undergo a slight degradation and more degradation of the tubular shape, respectively at 300 and 500 ∘C, and finally become complete Na2Ti6O13 nanorods after annealing at 700 ∘C for 1 hour. The structure characters and lattice dynamics of both nanotubes and nanorods were investigated. The transformation mechanism between NaHTi3O7 nanotubes and Na2Ti6O13 nanorods is discussed to be attributed to release of the structural water in the interlayer space during self-oriented attachments, and to take more stable configuration with low energy.