2.4. Characterizations
The morphology of the CNT films was investigated using a field
emission scanning electron microscope (FE-SEM, Model S-4300,
Hitachi). The mass of the CNT films (m) were measured by a high-precision
Sartorius microbalance. The density (ρ) of the film was then calculated
by ρ=m/lwt, where l, w and t were the length, width and
thickness of the sample.