Synthesis of ultra-long super-aligned double-walled carbon nanotube forests.

The pre-treatment (catalyst reduction with H2) time effect on the carbon nanotube (CNT) growth is reported. The total CNT height, the initial growth rate, the diameter, the number of walls, and the alignment in the CNT forests change with the catalyst reduction time. Densely packed, vertically super-aligned, double-walled CNT (DWCNT) forests with 9 mm height were synthesized in 10 hrs. We find that the density and the size of catalysts plays an important role in the alignment of the DWCNT forests, which is evidenced by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy.