Nanotechnology’s Wonder Material: Synthesis of Carbon Nanotubes - Hierarchical Nanostructures for Energy Devices - page 52

growth behavior of VACNTs can be related to dynamic changes in the size
of catalyst nanoparticles and their density.

d n 3 r 4 n g | 6

3.2.5 Lessons to the Experimenters from the Growth Models
The previous sections discussed various CNT growth models. While no
single model can explain the totality of experimental observations, we can
still draw several conclusions. First, it is clear that CNT growth and termi-
nation is a complicated process that involves a number of different path-
ways, and thus a simple universal explanation or mechanism may not exist.
Second, the complicated nature of the process places a high requirement on
experiments. For example, the kinetic data can mislead the analyst by failing
to capture a sucient number of data points (Figure 3.10). The low-reso-
lution data give convincing evidence for the exponential decay model, yet

.

Figure 3.10 Sampling rate and CNT growth kinetics. A comparison of the data taken

at high and low sampling rates: circles indicate data points chosen
every 100 sec from in situ data to simulate ex situ data collection.
Dashed lines indicate the fit to the exponential decay model and its first
derivative for growth rate calculation. The fit to the simulated ex situ
data is missing several key features of the growth kinetics.