[16p-PA11-1~2] 22.1 Joint Session M "Phonon Engineering"

▲ [16p-PA11-1] Highly Thermally Conductive Freestanding CNT/Polymer Composite Film with Aligned CNTs Fabricated via Direct Ink Writing

〇(PC)Nikita Kumari¹, Ryo Abe¹, Naofumi Okamoto¹, Manish Pandey¹, Masakazu Nakamura¹ (1.NAIST)

Keywords:Carbon nanotube, Orientation, Thermal conductivity

Thermal management has attracted a great deal of research interest for high-density integrated circuits, power electronics, electric vehicles, etc. Large thermal conductivity (k) of carbon nanotubes (CNTs) qualifies them as a potential candidate for efficient heat conductors. However, entanglement due to high aspect ratio and strong van der Waals interaction is one of the challenges to the high k in practical applications. Many orientation techniques have been developed in recent decades, there are still significant possibilities for further improvement. We have recently reported the CNT orientation by drawing the extruded ink through a needle to form ribbon like films on a substrate, also known as direct ink writing (DIW). Here ribbon-like CNT/polymer composite films (CNT ribbons) were drawn via DIW, and the CNT orientation was estimated by polarized Raman mapping (average-G band ratios). The dispersion quality of the CNT/polymer composite ink, substrate wettability, drawing parameters (i.e., relative drawing speed, dispensing speed, needle inner-diameter (2r), and the gap between the needle tip and the substrate), and their inter-relation were noticed to produce a net effect on the degree and distribution of CNT orientation. Via systematic tuning of these parameters, the optimum CNT alignment was attained. Among these parameters the CNT alignment was found to be more susceptible to the 2r, i.e., for certain ink narrower needle leads to higher CNT alignment while the ink can pass through without getting squeezed. Further, the ink composition was varied while the ribbons were drawn using optimized conditions and 2r was required to be increased with CNT concentration. Finally, k of the peeled ribbons was measured by mounting them on a cross-junction platform. Under optimum conditions k of the CNT/polymer composite ribbons reached up to 319.4 W/mK which is comparable to that of aligned pristine CNT films.