Researchers at the Swedish university have developed a graphene assembled film that has over 60% higher thermal conductivity than graphite film – despite the fact that graphite simply consists of many layers of graphene.
The graphene film shows 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 higher thermal conductivity than graphite film.
Single layer graphene has a thermal conductivity between 3500 and 5000 W/mK. If you put two graphene layers together, then it theoretically becomes graphite, as graphene is only one layer of graphite.
Today, graphite films, which are practically 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.
Chalmers’ researchers have recently changed this situation. They discovered that the thermal conductivity of graphene assembled film can reach up to 3200 W/mK, which is over 60% higher than the best graphite films.
The research team have done this through careful control of both grain size and the stacking orders of graphene layers.
The high thermal conductivity is a result of large grain size, high flatness, and weak interlayer binding energy of the graphene layers.
With these important features, phonons, whose movement and vibration determine the thermal performance, can move faster in the graphene layers rather than interact between the layers, thereby leading to higher thermal conductivity.
Furthermore, the researchers discovered that the graphene film has almost three times higher mechanical tensile strength than graphite film, reaching 70 MPa.
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 commercialisation of the technology.