Strong anisotropy in thermoelectric properties of CNT/PANI composites.

The anisotropy in thermoelectric properties of three-dimensional carbon nanotubes (CNTs) and CNT/polyaniline (PANI) composites have been studied by utilizing an orderly aligned CNT arrays with a self-sustained construction. In the length direction of CNT, the electrical conductivity of the CNT array is ∼5 times larger as compared to the direction vertical to the alignment of CNTs, while the difference in thermal conductivity between these two directions is ∼25 times. As a result, strong anisotropic thermoelectric transportation has been also observed in the composites composed of PANI and CNT arrays. An enhanced thermopower in the composites, as compared to the pure PANI or CNTs, is only observed in the direction along the CNTs. This study helps the fundamental understanding on the un-conventional improved thermopower, which is more likely to be realized via adjusting the carrier transportation within the interface between CNTs and PANI rather than across it. [ABSTRACT FROM AUTHOR]