Heat Pulse Analysis in Single-Wall and Double-Wall Carbon Nanotubes

Abstract

This paper investigates thermal transport in single wall carbon nanotubes (SWCNTs) and the interfacial thermal interaction in double-wall carbon nanotubes (DWCNTs) using molecular dynamics (MD) simulation and wavelet methods. The simulations are performed on three groups of carbon nanotubes (CNTs), as shown in Figure 1: 200 nm SWCNTs, 200 nm DWCNTs with 50 nm cut in the middle, and 100 nm complete DWCNTs. A heat pulse is applied in the middle of the CNTs, and wavelike responses of temperature as well as its three components (radial, tangential, and longitudinal) along the CNTs are analyzed to explore the underlying thermal transport mechanism. Wavelet analysis is carried out on the three components of velocity to investigate the evolution of frequency spectrum along CNTs in time. The heat pulse analysis in SWCNTs shows that the longitudinal components propagate as the leading wave packet of heat at the largest speed but only carry a small fraction of the total energy. The high frequency radial components carry most of the energy and dominate in the middle diffusion regions. In DWCNTs, the radial components and tangential components carry most of the total energy while the longitudinal components carry only a small fraction of the total energy. We observe dramatic energy transfer from outer tube to inner tube of a DWCNT without any cut during the heating period. This energy transferred to inner tube is primarily contained in the slowly moving radial modes indicating that energy can be transferred effectively by the radial modes. However, the energy transfer between tubes of DWCNTs through tangential and longitudinal components is quite ineffective.