Researchers at Chalmers University of Technology in Sweden, have developed a graphene assembled film that has over 60% higher thermal conductivity than graphite film – despite the fact that graphite 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. The IP of the high-quality manufacturing process for the graphene film belongs to SHT Smart High Tech AB, a spin-off company from Chalmers, which is going to focus on the commercialization of the technology.

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

Today, graphite films, which are useful for heat dissipation and spreading in mobile phones and other power devices, have a thermal conductivity of up to 1950 W/mK. Therefore, the graphene-assembled film should not have higher thermal conductivity than this. Research scientists at Chalmers University of Technology have recently changed this conception by discovering that the thermal conductivity of graphene assembled film can reach up to 3200 W/mK.

The manufacturing method of the graphene film is based on simultaneous graphene oxide film formation and reduction, on aluminum substrate, dry-bubbling film separation, followed by high-temperature treatment as well as mechanical pressing. These conditions enable the formation of the graphene film with large grain size, good atomic alignment, thin-film structure, and low interlayer binding energy. All these features have great benefit for the transfer of both high-frequency diffusive phonons and low-frequency ballistic phonons, and thereby lead to the improvement of in-plane thermal conductivity of the graphene film. Phonons are quantum particles that describe the thermal conductivity of a material.

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