Role of subsurface diffusion and Ostwald ripening in catalyst formation for single-walled carbon nanotube forest growth.
Here we show that essentially any Fe compounds spanning Fe salts, nanoparticles, and buckyferrocene could serve as catalysts for single-walled carbon nanotube (SWNT) forest growth when supported on AlO(x) and annealed in hydrogen. This observation was explained by subsurface diffusion of Fe atoms into the AlO(x) support induced by hydrogen annealing where most of the deposited Fe left the surface and the remaining Fe atoms reconfigured into small nanoparticles suitable for SWNT growth. Interestingly, the average diameters of the SWNTs grown from all iron compounds studied were nearly identical (2.8-3.1 nm). We interpret that the offsetting effects of Ostwald ripening and subsurface diffusion resulted in the ability to grow SWNT forests with similar average diameters regardless of the initial Fe catalyst.
Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan.
Shunsuke
S
Sakurai
Hidekazu
H
Nishino
Don N
DN
Futaba
Satoshi
S
Yasuda
Takeo
T
Yamada
Alan
A
Maigne
Yutaka
Y
Matsuo
Eiichi
E
Nakamura
Motoo
M
Yumura
Kenji
K
Hata
D000537:Aluminum Oxide / Q000737:chemistry*; D002384:Catalysis; D004058:Diffusion; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties
D005290:Ferric Compounds; D005296:Ferrous Compounds; D000075163:Metallocenes; D037742:Nanotubes, Carbon; D000537:Aluminum Oxide; C004998:ferrocene