Abstract
The structures of carbon nanotubes grown from catalytic nanoparticles via plasma-enhanced chemical vapor deposition in CH4 / H2 mixtures show a strong dependence on the H2 -to- CH4 ratio in the feed gas. A suite of characterization techniques, including optical emission, infrared, and Raman spectroscopies combined with convergent-beam and selected-area electron diffraction, and high-resolution (scanning) transmission electron microscopy imaging were used to systematically investigate the interrelation among plasma gas phase composition, catalysts morphology, catalyst structure, and carbon nanotube structure. Hydrogen plays a critical role in determining the final carbon nanotube structure through its effect on the catalyst crystal structure and morphology. At low H2 -to- CH 4 ratios (∼1), iron catalyst nanoparticles are converted to Fe3 C and well-graphitized nanotubes grow from elongated Fe 3 C crystals. High (>5) H2 -to- CH4 ratios in the feed gas result in high hydrogen concentrations in the plasma and strongly reducing conditions, which prevents conversion of Fe to Fe3 C. In the latter case, poorly-graphitized nanofibers grow from ductile bcc iron nanocrystals that are easily deformed into tapered nanocrystals that yield nanotubes with thick walls.
| Original language | English (US) |
|---|---|
| Article number | 053303 |
| Journal | Journal of Applied Physics |
| Volume | 108 |
| Issue number | 5 |
| DOIs | |
| State | Published - Sep 1 2010 |
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ASJC Scopus subject areas
- Physics and Astronomy(all)
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Effect of hydrogen on catalyst nanoparticles in carbon nanotube growth. / Behr, Michael J.; Gaulding, E. Ashley; Mkhoyan, K. Andre; Aydil, Eray.
In: Journal of Applied Physics, Vol. 108, No. 5, 053303, 01.09.2010.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Effect of hydrogen on catalyst nanoparticles in carbon nanotube growth
AU - Behr, Michael J.
AU - Gaulding, E. Ashley
AU - Mkhoyan, K. Andre
AU - Aydil, Eray
PY - 2010/9/1
Y1 - 2010/9/1
N2 - The structures of carbon nanotubes grown from catalytic nanoparticles via plasma-enhanced chemical vapor deposition in CH4 / H2 mixtures show a strong dependence on the H2 -to- CH4 ratio in the feed gas. A suite of characterization techniques, including optical emission, infrared, and Raman spectroscopies combined with convergent-beam and selected-area electron diffraction, and high-resolution (scanning) transmission electron microscopy imaging were used to systematically investigate the interrelation among plasma gas phase composition, catalysts morphology, catalyst structure, and carbon nanotube structure. Hydrogen plays a critical role in determining the final carbon nanotube structure through its effect on the catalyst crystal structure and morphology. At low H2 -to- CH 4 ratios (∼1), iron catalyst nanoparticles are converted to Fe3 C and well-graphitized nanotubes grow from elongated Fe 3 C crystals. High (>5) H2 -to- CH4 ratios in the feed gas result in high hydrogen concentrations in the plasma and strongly reducing conditions, which prevents conversion of Fe to Fe3 C. In the latter case, poorly-graphitized nanofibers grow from ductile bcc iron nanocrystals that are easily deformed into tapered nanocrystals that yield nanotubes with thick walls.
AB - The structures of carbon nanotubes grown from catalytic nanoparticles via plasma-enhanced chemical vapor deposition in CH4 / H2 mixtures show a strong dependence on the H2 -to- CH4 ratio in the feed gas. A suite of characterization techniques, including optical emission, infrared, and Raman spectroscopies combined with convergent-beam and selected-area electron diffraction, and high-resolution (scanning) transmission electron microscopy imaging were used to systematically investigate the interrelation among plasma gas phase composition, catalysts morphology, catalyst structure, and carbon nanotube structure. Hydrogen plays a critical role in determining the final carbon nanotube structure through its effect on the catalyst crystal structure and morphology. At low H2 -to- CH 4 ratios (∼1), iron catalyst nanoparticles are converted to Fe3 C and well-graphitized nanotubes grow from elongated Fe 3 C crystals. High (>5) H2 -to- CH4 ratios in the feed gas result in high hydrogen concentrations in the plasma and strongly reducing conditions, which prevents conversion of Fe to Fe3 C. In the latter case, poorly-graphitized nanofibers grow from ductile bcc iron nanocrystals that are easily deformed into tapered nanocrystals that yield nanotubes with thick walls.
UR - http://www.scopus.com/inward/record.url?scp=77956820902&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77956820902&partnerID=8YFLogxK
U2 - 10.1063/1.3467971
DO - 10.1063/1.3467971
M3 - Article
AN - SCOPUS:77956820902
VL - 108
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 5
M1 - 053303
ER -