title: The Origin of High Thermal Conductivity and Ultralow Thermal Expansion in Copper-Graphite Composites.
abstract: We developed a nanocomposite with highly aligned graphite platelets in a copper matrix. Spark plasma sintering ensured an excellent copper-graphite interface for transmitting heat and stress. The resulting composite has superior thermal conductivity (500 W m(-1) K(-1), 140% of copper), which is in excellent agreement with modeling based on the effective medium approximation. The thermal expansion perpendicular to the graphite platelets drops dramatically from ∼20 ppm K(-1) for graphite and copper separately to 2 ppm K(-1) for the combined structure. We show that this originates from the layered, highly anisotropic structure of graphite combined with residual stress under ambient conditions, that is, strain-engineering of the thermal expansion. Combining excellent thermal conductivity with ultralow thermal expansion results in ideal materials for heat sinks and other devices for thermal management.
authors.affiliation: Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Izabela
authors.initials: I
authors.lastname: Firkowska
authors.affiliation: Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Boden
authors.affiliation: Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Benji
authors.initials: B
authors.lastname: Boerner
authors.affiliation: Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Reich
keywords: Metal−matrix composites; graphene; graphite; strain; thermal conductivity; thermal expansion; thermal stress