Thermal boundary resistance between single-walled carbon nanotubes and surrounding matrices

Thermal boundary resistance (TBR) between a single-walled carbon nanotube (SWNT) and matrices of solid and liquid argon was investigated by performing classical molecular-dynamics simulations. Thermal boundary conductance (TBC), i.e., inverse of TBR, was quantified for a range of nanotube lengths by applying a picosecond heat pulse to the SWNT and observing the relaxation. The SWNT-length effect on the TBC was confirmed to be absent for SWNT lengths from 20 to 500 A. The heat transfer mechanism was studied in detail and phonon spectrum analysis provided evidence that the resonant coupling between the low-frequency modes of the SWNT and the argon matrix is present both in solid and liquid argon cases. The heat transfer mechanism was qualitatively analyzed by calculating the spectral temperature of the SWNT in different frequency regimes. It was found that the low-frequency modes that are resonantly coupled to the argon matrix relaxes roughly ten times faster than the overall TBC time scale, depending on the surrounding matrix. However, such resonant coupling was found to transfer little energy despite a popular picture of the linear transfer path. The analysis suggests that intrananotube energy transfer from high-frequency modes to low-frequency ones is slower than the interfacial heat transfer to the argon matrix.