HRTEM study of the variation of TNTs morphology synthesized via hydrothermal method at different reaction times

•Titanate nanotubes were synthesized via hydrothermal method.•The influence of reaction time on the evolution of nanotubes morphology was investigated.•The HRTEM results are compared to those obtained by XRD.•The outer diameter as well as the number of layers increases with the increase of the reaction time.

Titanate nanotubes were synthesized via hydrothermal treatment of rutile TiO2. The reaction conditions were: particles sizes of TiO2 having diameter between 0.05 and 0.5 μm, 10 M NaOH solution and a temperature of 150 °C. The effect of reaction time on the morphology and the crystalline structure were investigated by X-ray diffraction (XRD), Raman spectroscopy and High Resolution Transmission Electron Microscopy (HRTEM). Results showed that the reaction products are composed of nanotubes having 3, 4 and 5 layers. All the three forms coexist together in each sample with different fractions. The number of layers of the major form increases from 3 to 5 layers when reaction time increases from 12 to 120 h. At the same time, internal and external diameters vary from 3 nm to 5 nm and from 7 nm to 11 nm respectively. Deformation of nanotubes as well as nanotubes assembling and the formation of nanoribbons appear clearly for high reaction times (120 h).