(a)
(b)
(c)
Figure 4:
SEM images of N-TiO
2
samples prepared from precursors with different N : Ti molar ratios, fired at 250°C, 3 h, and 500°C 1 min. Ramp: 10°C/min. (a) N : Ti, 0 (TiO
2
); (b) N : TI, 4 : 1; (c) N : Ti, 8 : 1.
