Thermal Conductivity Measurement of Graphene Composite
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Thermal Conductivity Measurement of Graphene Composite Jiuning Hu1, 2, Wonjun Park1, 2, Xiulin Ruan3, 2, Yong P. Chen4, 2, 1 1 School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, U.S.A. 2 Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, U.S.A. 3 School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, U.S.A. 4 Department of Physics, Purdue University, West Lafayette, IN 47907, U.S.A. ABSTRACT Graphene composites (GCs) have attracted much attention recently. It is interesting to explore thermal properties of GCs in which graphene filler concentrations are tunable. Here, we use 3ω method to measure the thermal conductivity of GCs synthesized from reduced graphene oxide (RGO) dispersed in polystyrene. To avoid the detrimental effect of lithography processes to GCs, we have developed a novel method employing polyvinyl alcohol and poly(methyl methacrylate) (PMMA) as a holder film to transfer micrometer-sized metal heaters/sensors onto GC surface. Room temperature measurements of the thermal conductivity of GCs are performed. The thermal conductivity is enhanced by ~ 35 % when adding 5 vol.% of RGO filler concentration. Our measurements will be helpful to probe and understand the thermal transport properties of graphene based composites. INTRODUCTION Graphene composite (GC) materials have drawn much attention recently mainly due to its potential of large scale applications through mass production and abilities to tune their various properties by material engineering [1]. GCs exhibit excellent properties, such as extremely low percolation threshold of electrical conductivity [1]. Similarly, the thermal properties of GCs can be tuned by controlling graphene concentrations. It has been shown that adding graphene flakes to host materials, such as epoxy [2] and nanostructured phase change materials [3] can dramatically increase the thermal conductivity of the composite materials. However, there are few experiments to study the thermal transport in graphene-polystyrene composite which is inherently uniform through chemically compatible processes. It is interesting to investigate the thermal properties of such GCs, and in particular, the graphene concentration dependence of thermal conductivities. EXPERIMENT GCs of several different volume concentrations are made from polystyrene and graphene oxide [2]. Graphene oxide (GO) is produced by following Hummer’s method [4]. The uniform mixture of GO and polystyrene in dimethylformamide is treated by hydrazine (Figure 1a) to convert GO to reduced GO (RGO, referred simply as graphene in the following text). The solution is then polymerized using methanol and filtered to collect GC, followed by drying it in a
vacuum oven. The dried GC is milled into fine powders (Figure 1b) and hot pressed into bulk dense composite plate as shown in Figure 1c. The thickness of the GC plate is about 1.3 mm.
Figure 1. Main fabrication processes of graphene composite are shown in (a)-(c). The thickness of the hot press
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