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5/16/2017  |   10:55 AM - 11:20 AM   |  3

Switchable Thermal conductivity of High-Quality Graphene Paper

This presentation reports on the discovery of switchable ultra-high thermal conductivity of high purity graphene paper (GP) when its temperature is reduced from room temperature down to 10 K. The thermal conductivity after switch-on (1732 to 3013 W m-1 K-1) is 4~8 times that before switch-on. The triggering temperature is 245~260 K. The switch-on behavior is attributed to thermal expansion mismatch between pure graphene flakes and impurity-embedded flakes. This is confirmed by switch behavior of the temperature coefficient of resistance. Before switch-on, the interactions between pure graphene flakes and surrounding impurity-embedded flakes efficiently suppress phonon transport in GP. After switch-on, the structure separation frees the pure graphene flakes from the impurity-embedded neighbors, leading to several-fold thermal conductivity increase. By conducting comparison studies with pyrolytic graphite, graphene oxide paper and partly reduced graphene paper, the whole physical picture is illustrated clearly. The thermal expansion induced switch-on is feasible only for high purity GP materials. This finding points out a novel way to switch on/off the thermal conductivity of graphene paper based on substrate-phonon scattering.

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Yangsu Xie (POC,Primary Presenter,Author), Iowa State University,;
Xinwei Wang (Author,Co-Author), Iowa State University, ;

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