Broad low-frequency phonon resonance for increased across-tube heat transport
Lin Qiu, Fengcheng Li, Ning Zhu, Yanhui Feng, Xiaoliang Zhang, Xiaohua Zhang
Abstract
The poor heat conduction between carbon nanotubes (CNTs) has become a severe obstacle, hindering the applications for thermal management. Considering that the across-tube heat transport is limited by the small fraction of low-frequency phonons (LFPs), it is of great necessity to develop a strategy to excite LFPs without modifying the tube contacts. Herein, a mechanism of LFP resonance is proposed by assigning soft long-chain polymers (e.g., polyurethane and polyethylene) to the groove sites of contacted CNTs. The resonance takes places at multiple points and in wide ranges of frequencies and wave vectors, originating from the rich low-frequency vibrations localized at the soft segments of the polymer. More excited phonons lead to an extraordinary improvement on the across-tube heat conductance, by a factor of 79%, which opens a route to develop advanced CNT-based thermal functional materials.