title: High through-plane thermal conduction of graphene nanoflake filled polymer composites melt-processed in an L-shape kinked tube.
abstract: Design of materials to be heat-conductive in a preferred direction is a crucial issue for efficient heat dissipation in systems using stacked devices. Here, we demonstrate a facile route to fabricate polymer composites with directional thermal conduction. Our method is based on control of the orientation of fillers with anisotropic heat conduction. Melt-compression of solution-cast poly(vinylidene fluoride) (PVDF) and graphene nanoflake (GNF) films in an L-shape kinked tube yielded a lightweight polymer composite with the surface normal of GNF preferentially aligned perpendicular to the melt-flow direction, giving rise to a directional thermal conductivity of approximately 10 W/mK at 25 vol % with an anisotropic thermal conduction ratio greater than six. The high directional thermal conduction was attributed to the two-dimensional planar shape of GNFs readily adaptable to the molten polymer flow, compared with highly entangled carbon nanotubes and three-dimensional graphite fillers. Furthermore, our composite with its density of approximately 1.5 g/cm(3) was mechanically stable, and its thermal performance was successfully preserved above 100 °C even after multiple heating and cooling cycles. The results indicate that the methodology using an L-shape kinked tube is a new way to achieve polymer composites with highly anisotropic thermal conduction.
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Haejong
authors.initials: H
authors.lastname: Jung
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Seunggun
authors.initials: S
authors.lastname: Yu
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Nam-Seok
authors.initials: NS
authors.lastname: Bae
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Suk Man
authors.initials: SM
authors.lastname: Cho
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Richard Hahnkee
authors.initials: RH
authors.lastname: Kim
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Cho
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Ihn
authors.initials: I
authors.lastname: Hwang
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Beomjin
authors.initials: B
authors.lastname: Jeong
authors.affiliation: ‡Carbon Convergence Materials Research Center, Korea Institute of Science and Technology, Jeonbuk 565-905, Republic of Korea.
authors.forename: Ji Su
authors.initials: JS
authors.lastname: Ryu
authors.affiliation: ‡Carbon Convergence Materials Research Center, Korea Institute of Science and Technology, Jeonbuk 565-905, Republic of Korea.
authors.forename: Junyeon
authors.initials: J
authors.lastname: Hwang
authors.affiliation: §Materials Architecturing Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea.
authors.forename: Soon Man
authors.initials: SM
authors.lastname: Hong
authors.affiliation: §Materials Architecturing Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea.
authors.forename: Chong Min
authors.initials: CM
authors.lastname: Koo
authors.affiliation: †Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Republic of Korea.
authors.forename: Cheolmin
authors.initials: C
authors.lastname: Park
keywords: L-shape kinked tube; graphene nanoflake; orientation; poly(vinylidene fluoride); polymer composite; thermal conductivity