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Anisotropic Percolation of SiC–Carbon Nanotube Hybrids: A New Route Towards Thermally Conductive High-k Polymer Composites Jinkai Yuan, Shenghong Yao, Weilong Li, Alain Sylvestre, and Jinbo Bai J. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 19 May 2017 Downloaded from http://pubs.acs.org on May 21, 2017
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The Journal of Physical Chemistry
Anisotropic Percolation of SiC–Carbon Nanotube Hybrids: A New Route towards Thermally Conductive High-k Polymer Composites
Jinkai Yuan†‡, Shenghong Yao§, Weilong Liǁ, Alain Sylvestre§, Jinbo Bai∗,‡
†
Centre de Recherche Paul Pascal, CNRS, Université de Bordeaux, 115 Avenue Schweitzer, 33600 Pessac, France. ‡ Lab. MSSMat, CNRS UMR 8579, Centrale-Supélec, Université Paris-Saclay, ChâtenayMalabry, 92290, France. § Univ. Grenoble Alpes, CNRS, Grenoble INP1, G2Elab, F-38000 Grenoble, France. ǁ Institute of Photonics & Photon-Technology, Northwest University, Xi’an 710069, China
1
Institute of Engineering Univ. Grenoble Alpes, France.
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The Journal of Physical Chemistry
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ABSTRACT Percolation of carbon nanotube (CNT) has been widely exploited in various polymer matrices to largely improve the dielectric constant or thermal conductivity of heterogeneous polymer composites. However, so far it is still very challenging to simultaneously enhance both while maintaining the low losses of polymers. Herein, we demonstrate a thermally conductive highk material with low losses by establishing anisotropic percolation of multiscale SiC–CNT hybrids within poly(vinylidene fluoride) (PVDF) matrix. Indeed, the SiC–CNT/PVDF composite exhibits a much lower electrical percolation threshold (1.23 wt%) along the inplane direction than that (1.89 wt%) perpendicular to it. By locating CNT content (1.5 wt%) between them, the composite displays unprecedented dielectric properties in the out-of-plane direction, with a dielectric constant as high as 714 and the loss tangent of 0.49, while a thermal conductivity improved by 200% as compared with the virgin polymer along the inplane direction. The true anisotropy in electrical, dielectric and thermal properties is elucidated by invoking percolation theory on the basis of the rod geometry and spatial orientation of the hybrids.
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The Journal of Physical Chemistry
1. INTRODUCTION In last decades, high-dielectric-constant (high-k) materials have been actively pursued due to their critical role in modern electronic and electrical applications, such as energy storage and pulsed power generation,1-4 electromechanical actuators,5-7 electrocaloric cooling,8, 9 and even mechanical energy harvesting.10 Compared to the inorganic ceramics, polymer dielectrics are flexible, scalable, light weight and low cost. They have high voltage rating and low power dissipations, and particularly can be easily molded (melt or solution casting) into various intricate configurations.11 The best commercially available dielectric polymers, such as biaxially oriented polypropylene (BOPP), can sustain an electrical field as high as ~700 MV m-1 and exhibit dielectric losses less than 0.02%. However, their low dielectric constant (
