Evaluation of thermal transport in composite SWCNT films with pseudo-heterogeneous interfaces obtained by blending different SWCNTs

Abstract

Single-walled carbon nanotubes (SWCNTs) are used in numerous functional devices as they possess excellent properties. Functional devices that manage thermal transport require film structures composed of numerous individual SWCNTs, and the device performance is directly linked to the thermal transport properties of the SWCNT films. In particular, composite SWCNT films blended with multiple types of SWCNTs have the potential to control thermal transport owing to their pseudo-heterogeneous interfaces. However, their properties, including their lattice thermal conductivity, sound velocity, and phonon mean free path (MFP), have not been well investigated. In this study, we investigated the thermal transport properties of composite SWCNT films with pseudo-heterogeneous interfaces that were prepared using SWCNT inks by varying the blending ratio of two SWCNTs (CNT-A and CNT-B). The SWCNT inks were characterized using rheometry and rheoimpedance measurements. SEM images of the composite SWCNT films revealed that the two types of SWCNTs formed independent bundles. Therefore, pseudo-heterogeneous interfaces were obtained between the bundles of each SWCNT. The sound velocity increased for SWCNT films with pseudo-heterogeneous interfaces. However, the thermal conductivity increased linearly with the blending content of CNT-B. The measured phonon MFP of the composite SWCNT films was lower than the linear fitting value that considered only the homogeneous interfaces. This phenomenon occurred because phonon scattering and trapping were enhanced at the pseudo-heterogeneous interfaces in the composite SWCNT films. These findings improve our understanding of the thermal transport in materials with different interfaces.