hide
Free keywords:
hydrogen dynamics; carbon nanotubes; point defects
Abstract:
The first mechanical spectroscopy experiments in HiPco carbon nanotubes
from room temperature to 3 K revealed a thermally activated relaxation
process at about 25 K for frequencies in the kHz range. The peak is due
to the presence of a very mobile species performing about 103 jumps per
second at the peak temperature. The activation energy obtained by the
peak shift with frequency is E-a = 54.7 meV; the value of the
pre-exponential factor of the Arrhenius law for the relaxation time, co
= 10(-14) s, which is typical of point defect relaxation and suggests
that the process is originated by the dynamics of hydrogen or by H
complexes. The peak is much broader than a single Debye relaxation
process, indicating the presence of intense elastic interactions in the
highly disordered bundle structure. There are indications that the
relaxation process is governed by a quantum mechanism.
