ABSTRACT

The synthesis of graphene composites with the matrix of In, In-Ga, or Cu by low-cost methods to achieve uniform distribution of graphene platelets (GPs) is described. Characterization of the microstructure, topography, and distribution of the GPs using optical, scanning electron microscopy (SEM), and x-ray diffraction is presented, and the difculty of evaluation of the volume fraction of GPs is emphasized. Results of measurement of electrical and thermal conductivity coupled with modeling using effective medium approximation are used to determine the volume fraction, electrical conductivity of GPs, and the interface thermal conductance between GPs in the ab plane and the matrix. The electrical conductivity of thin GPs is found to be between 2 and 3 × 106 Ω −1 cm−1 while the average value is between 1 and 2 × 106 Ω−1 cm−1. The thermal conductivity of composites is improved by 100% compared

to that of In and by 25% compared to that of Cu when the volume fraction of GPs is near 0.20. The interface thermal conductance in the ab plane between GPs and the matrix is found to be close to 1 GWm−2 K−1 and thus not a limiting factor in the heat spreading in the composites. Transient thermo reectance (TTR) measurements showed that the composites are better heat spreaders than In and Cu, respectively. These results suggest that composites with In are useful as thermal interface materials and composites with Cu are useful for electrical contact brushes and heat spreaders.