Fig. 1.
The FESEM figures of TNTs prepared at 20 °C for 1 h under different oxidation voltages (a) 10 V (b) 30 V and (c) 60 V. The FESEM figures of TNTs prepared at 20 °C under 30 V for (d) 10 min (e) 60 min (f) 180 min. The FESEM figures of TNTs prepared under 30 V for 1 h at different reaction temperature (g) 0 °C (h) 60 °C (i) 100 °C.