In the mechanical condensation method [37], the as-prepared CNT
films were firstly straightened and fixed in between two sheets of A4
paper by the following procedures: one end of the CNT film was first
fixed on the paper by plastic tape; second, the film was slightly straightened
until it closely attached to the paper and the other end of the film
was fixed by plastic tape; and then the other sheet of paperwas covered
on the film. These steps helped to ensure that the CNT film would not
get damaged during the mechanical densification process but at the
same time allowed the force to be applied directly on the CNT film. A
stainless steel spatula with a flat end was used to compress the A4
paper and CNT film from one end of the film and slid across, along the
direction of the CNT axis. The applied force was approximately 100 N,
45° above the flat surface [37]. This densification process was repeated
10 times for each sample.