Thermal properties of graphene/metal composites with aligned graphene

Graphene holds great potential in metal matrix composites for thermal management due to its excellent thermal properties. However, the graphene/metal composites possessing both high thermal conductivity (TC) and low coefficient of thermal expansion (CTE) have not yet been realized. Herein, we reported an efficient strategy to achieve a high alignment of graphene nanosheets (GNSs) in GNS/Cu composites through a vacuum filtration method followed by spark plasma sintering. Because of the highly aligned GNSs and laminated structure, the GNS/Cu composites exhibited notably anisotropic thermal properties. Intriguingly, the composites showed a reversed anisotropic behavior between TC and CTE as a function of GNS fraction, in which the in-plane TC was substantially higher than through-plane TC, whereas oppositely the through-plane CTE displayed a larger drop than in-plane CTE. Promisingly, the composite with 30 vol% GNSs delivered a high in-plane TC of 458W/mK and a low through-plane CTE of 6.2 ppm/K, corresponding to a 35% TC enhancement and a 64% CTE reduction compared to pure Cu, respectively. The present GNS/Cu composites with high in-plane TC and low through-plane CTE are promising candidates for specific thermal management applications that require an efficient in-plane heat dissipation but a good through-plane dimensional stability. (C) 2017 Elsevier Ltd. All rights reserved.