Size-selective growth of double-walled carbon nanotube forests from engineered iron catalysts.
We have succeeded in synthesizing vertically aligned doubled-walled carbon nanotube (DWNT) forests with heights of up to 2.2 mm by water-assisted chemical vapour deposition (CVD). We achieved 85% selectivity of DWNTs through a semi-empirical analysis of the relationships between the tube type and mean diameter and between the mean diameter and the film thickness of sputtered Fe, which was used here as a catalyst. Accordingly, catalysts were engineered for optimum DWNT selectivity by precisely controlling the Fe film thickness. The high efficiency of water-assisted CVD enabled the synthesis of nearly catalyst-free DWNT forests with a carbon purity of 99.95%, which could be templated into organized structures from lithographically patterned catalyst islands.
Yamada
Takeo
T
Research Center for Advanced Carbon Materials, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
Namai
Tatsunori
T
Hata
Kenji
K
Futaba
Don N
DN
Mizuno
Kohei
K
Fan
Jing
J
Yudasaka
Masako
M
Yumura
Motoo
M
Iijima
Sumio
S
D003460:Crystallization / Q000379:methods*; D007501:Iron / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry*; D008422:Materials Testing; D036103:Nanotechnology / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure*
D046911:Macromolecular Substances; D037742:Nanotubes, Carbon; D007501:Iron