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The Origin of High Thermal Conductivity and Ultralow Thermal Expansion in Copper–Graphite Composites

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journal contribution
posted on 08.07.2015, 00:00 by Izabela Firkowska, André Boden, Benji Boerner, Stephanie Reich
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.

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