Kinetics of Water-Assisted Single-Walled Carbon Nanotube Synthesis Revealed by a Time-Evolution Analysis

Here we investigate the kinetics of water-assisted CVD (henceforth denoted as supergrowth CVD) by a quantitative time-evolution analysis based on a simple growth model. We found that the supergrowth can be well described by a model where the dynamics of the catalyst activity is treated similar to radioactive decay. An in-depth analysis based on this growth model revealed the kinetics of the supergrowth CVD, showing a scale relationship between the carbon source and water, and elucidated the role of water as a catalyst activity enhancer and preserver.

Figure 1

Time evolution of SWNT forest growth. Plot of the SWNT forest height as a function of the growth time. The solid line indicates the excellent curve fitting of the growth equation to the experimental data. Inset photographs show the samples at various stages of growth.

Figure 2

Ethylene dependence on SWNT forest growth. (a) Overlaid plots of the forest heights as a function of growth time for increasing levels of ethylene. The solid lines represent curve fits for each growth condition. (b) Overlaid plots of the lifetime, initial growth rate, and maximum height (histogram), as derived from each growth curve in (a) as a function of the ethylene level.

Figure 3

Water dependence on the SWNT forest growth. (a) Overlaid plots of the forest heights as a function of growth time for increasing levels of water. The solid lines represent curve fits for each growth condition. (b) Overlaid plots of the lifetime, initial growth rate, and maximum height (histogram) as a function of water level.

Figure 4

Two-dimensional mapping of the growth characteristics. Plot of the maximum forest height as a function of ethylene and water.

Figure 5

Water/ethylene ratio. Plot of the maximum height as a function of the water/ethylene ratio, which illustrates the scaling relationship between the carbon source and water. The solid line is drawn to guide the eye.