Article pubs.acs.org/cm
Ultrahigh Thermal Conductivity of Assembled Aligned Multilayer Graphene/Epoxy Composite Qi Li,† Yufen Guo,†,‡ Weiwei Li,† Shengqiang Qiu,† Chao Zhu,† Xiangfei Wei,† Mingliang Chen,† Chaojun Liu,† Shutian Liao,† Youpin Gong,† Ananta Kumar Mishra,§ and Liwei Liu*,† †
Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123, China ‡ University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing 100049, China § Leibniz Institut fuer Polymer Forschung, Dresden, Germany S Supporting Information *
ABSTRACT: The exceptional thermal conductivity of graphene is expected to endow polymer composites with ultrahigh thermal conductivities, which can be even similar to those of some metals such as stainless steel and aluminum alloy. The thermal conductivities of composites prepared by dispersing multilayer graphene (MLG) in epoxy matrix increase only by an order of magnitude over the pure epoxy. However, the improvement has been limited since the large interfacial thermal resistance exists between graphene and the surrounding epoxy. We have reported an extraordinary increase in thermal conductivity of the MLG/epoxy composites through the fabrication of the vertically aligned and densely packed MLG in the epoxy matrix. The ultrahigh thermal conductivity of 33.54 W/(m K) has been achieved in the aligned MLG/epoxy composite (AG/E). The thermal conductivity of AG/E exhibits a positive temperature response related to the aligned structure while increasing the temperature from 40 °C to 90 °C.
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Aligned carbon nanostructure fillers in polymer matrix are expected to be an efficient way to enhance the thermal conductivity of the resulting composites due to the presence of minimum thermal resistance along the aligned direction.13−16 Marconnet et al. fabricated aligned CNT/polymer nanocomposites using in situ injection of polymers into CNT arrays and obtained the axial thermal conductivity of 4.87 W/(m K) with 16.7 vol % CNTs, which is much greater than the reported values of unaligned CNT-based composites.17 If MLG materials can be vertically stacked in the polymer matrix and assembled interconnected as a network, the thermal conductivity of the composites would be greatly improved. Unfortunately, until now, such inspiring composite structures have not been demonstrated. This is due to the flexible structure of the MLG, which may allow it to transform to complex shapes with different forms during the composite preparation. The vertically aligned free-standing MLG in polymer composites in large scale is very difficult to realize for the flexible nature of ultrathin two-dimensional MLG. Herein, we report a facile and scalable route to fabricate new composites by assembling the aligned and interconnected MLG in an epoxy matrix. The resulting composite exhibits the highest
INTRODUCTION Efficient heat conductivity and heat removal play a vital role for the long service life and high performance of electronic and photonic devices.1,2 In recent years, significant attention has been focused in developing high thermal conductivity composite materials utilizing graphene, because of its extraordinarily high in-plane thermal conductivity, large specific surface area, and high mechanical strength. For instance, the thermal conductivity of graphene has been reported to be ∼5000 W/(m K) at room temperature.3 Enhanced thermal conductivities of the composites over the neat polymers have been achieved by the disordered dispersion of multilayer graphene (MLG) in the polymer matrix.4−9 However, the improvements are very limited, because of the large thermal resistances that exist in the interfacial regions of MLG and polymer.10 So far, the best thermal conductivity of
