Introducing thermally stable inter-tube defects to assist off-axial phonon transport in carbon nanotube films

J Wang and D Chen and J Wallace and J Gigax and XM Wang and L Shao, APPLIED PHYSICS LETTERS, 104, 191902 (2014).

DOI: 10.1063/1.4874624

Through integrated molecular dynamics (MD) simulations and experimental studies, we demonstrated the feasibility of an ion-irradiation-and- annealing based phonon engineering technique to enhance thermal conductivity of carbon nanotube (CNT) films. Upon ion irradiation of CNT films, both inter-tube defects and intra-tube defects are introduced. Our MD simulations show that inter-tube defects created between neighboring tubes are much more stable than intra-tube defects created on tube graphitic planes. Upon thermal annealing, intra-tube defects are preferentially removed but inter-tube defects stay. Consequently, axial phonon transport increases due to reduced phonon scattering and off- axial phonon transport is sustained due to the high stability of inter- tube defects, leading to a conductivity enhancement upon annealing. The modeling predictions agree with experimental observations that thermal conductivities of CNT films were enhanced after 2MeV hydrogen ion irradiations and conductivities were further enhanced upon post irradiation annealing. (C) 2014 AIP Publishing LLC.

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