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Graphene film can have higher thermal conductivity than graphite film

Researchers at Chalmers University of Technology in Sweden have developed a graphene-assembled film that possesses over 60% higher thermal conductivity than graphite film – even though graphite simply consists of many layers of graphene. The graphene film shows great potential as a novel heat-spreading material for form factor-driven electronics and other high power-driven systems.

Until now, scientists in the graphene research community have assumed that graphene-assembled film cannot have a higher thermal conductivity than graphite film. Single layer graphene has a thermal conductivity between 3500W/mK and 5000W/mK. If you put two graphene layers together, then it theoretically becomes graphite, as graphene is a single, atom-thick layer of graphite.

Graphite films, which are currently used for heat dissipation and spreading in mobile phones and other power devices, have a thermal conductivity of up to 1950W/mK. A graphene-assembled film, being essentially graphite, should not have higher thermal conductivity than this.

Johan Liu and his research team at Chalmers University of Technology have now challenged this assumption. In a paper in Small, they report that the thermal conductivity of graphene-assembled film can reach up to 3200W/mK, over 60% higher than the best graphite films.

Liu and his team achieved this high thermal conductivity through careful control of both grain size and the stacking orders of the layers in a graphene film. The high thermal conductivity is a result of large grain size, high flatness and a weak interlayer binding energy between the layers. With these important features, phonons, whose movement and vibration determine thermal performance, can move faster within the graphene layers than between them, leading to higher thermal conductivity.

"This is indeed a great scientific breakthrough, and it can have a large impact on the transformation of the existing graphite film manufacturing industry," says Liu. The researchers also discovered that the mechanical tensile strength of graphene film is almost three times higher than graphite film, reaching 70MPa.

"With the advantages of ultra-high thermal conductivity, and thin, flexible and robust structures, the developed graphene film shows great potential as a novel heat spreading material for thermal management of form factor-driven electronics and other high power-driven systems," asserts Liu.

As a consequence of never-ending miniaturization and integration, the performance and reliability of modern electronic devices and many other high-power systems are greatly threatened by severe thermal dissipation issues.

"To address the problem, heat spreading materials must get better properties when it comes to thermal conductivity, thickness, flexibility and robustness, to match the complex and highly integrated nature of power systems," says Liu. "Commercially available thermal conductivity materials like copper, aluminum and artificial graphite film will no longer meet and satisfy these demands."

The intellectual property in the high-quality manufacturing process for this graphene film belongs to SHT Smart High Tech AB, a spin-off company from Chalmers, which is going to focus on commercializing the technology.

This story is adapted from material from Chalmers University of Technology, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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