Diffusion- and Reaction-Limited Growth of Carbon Nanotube Forests

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560−800 °C and 10−5 to 14 mbar partial pressure range, using acetylene as the feedstock and Al2O3-supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P0.6 and activation energies of <1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging

Diffusion- and Reaction-Limited Growth of Carbon Nanotube Forests

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560−800 °C and 10−5 to 14 mbar partial pressure range, using acetylene as the feedstock and Al2O3-supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P0.6 and activation energies of <1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging

In-situ X-ray Photoelectron Spectroscopy Study of Catalyst−Support Interactions and Growth of Carbon Nanotube Forests

We study catalyst support interactions during chemical vapor deposition of carbon nanotubes by in situ X-ray photoelectron spectroscopy over a wide range of pressures. We observe Fe 2+ and 3+ interface states for metallic Fe on Al2O3 in the absence of measurable Al reduction. This support interaction is much stronger than that on SiO2, and it restricts Fe surface mobility. The resulting much narrower Fe catalyst particle size distribution on Al2O3 leads to a higher carbon nanotube nucleation density and a vertical nanotube alignment due to proximity effects. We record the growth kinetics of carbon nanotube forests by optical imaging to understand effects that contribute to growth termination

In-situ X-ray Photoelectron Spectroscopy Study of Catalyst−Support Interactions and Growth of Carbon Nanotube Forests

We study catalyst support interactions during chemical vapor deposition of carbon nanotubes by in situ X-ray photoelectron spectroscopy over a wide range of pressures. We observe Fe 2+ and 3+ interface states for metallic Fe on Al2O3 in the absence of measurable Al reduction. This support interaction is much stronger than that on SiO2, and it restricts Fe surface mobility. The resulting much narrower Fe catalyst particle size distribution on Al2O3 leads to a higher carbon nanotube nucleation density and a vertical nanotube alignment due to proximity effects. We record the growth kinetics of carbon nanotube forests by optical imaging to understand effects that contribute to growth termination

In-situ X-ray Photoelectron Spectroscopy Study of Catalyst−Support Interactions and Growth of Carbon Nanotube Forests

We study catalyst support interactions during chemical vapor deposition of carbon nanotubes by in situ X-ray photoelectron spectroscopy over a wide range of pressures. We observe Fe 2+ and 3+ interface states for metallic Fe on Al2O3 in the absence of measurable Al reduction. This support interaction is much stronger than that on SiO2, and it restricts Fe surface mobility. The resulting much narrower Fe catalyst particle size distribution on Al2O3 leads to a higher carbon nanotube nucleation density and a vertical nanotube alignment due to proximity effects. We record the growth kinetics of carbon nanotube forests by optical imaging to understand effects that contribute to growth termination