A new way to form carbon nanotubules, where polyyne-containing carbon
is heated and irradiated by an electron beam in TEM, was developed. This
way is compatible to in-situ and real-time observation of the nanotubule
growth1-4).
The obtained information would be of great importance to understand
the formation mechanism. A time-series of photographs of carbon nanotubule
growth were taken by a TEM with this technique.
The photographs show that the growth is comprised of two steps: quick
formation of carbon rod (step I), and subsequent formation of a hollow
inside of the rod (step II). The step I is completed in less than 1 s.
A sheath of the rod, which is supposed to be a loose graphine-like
network of carbon, is already formed. The rod is stuffed with liquid-like
carbon or salts at the core of the rod.
The diameter and the length of the rod does not change after this step.
The whole outline of the carbon nanotubule is assumed to be formed
at this step. The step II proceeds gradually and is completed in 30 to
60 s.
The hollow develops in three ways: from the top of the tubule to the
bottom, from the bottom to the top, from both the top and the bottom to
the middle.
The formation of the hollow is assumed to be evaporation of the liquid-like
carbon or salts, not flow of these. During this step, the sheath of the
rod does not get thick and graphitization may proceed. At the end on the
evaporation, a cap at the top of the rod is formed.
References
1. N. Kawase et al., Carbon 36, 1234 - 1235, 1998.
2. N. Kawase et al., Carbon, in press.
3. N. Kawase et al., Carbon, in press.
4. A. Yasdua et al., Reactive and Functional Polymers, in press.