Graphene Defies Thermal Conductivity Law
Graphene is a monolayer of carbon atoms arranged in a honeycomb pattern. This arrangement gives it very special properties, including incredible strength and conductivity, while being remarkably lightweight. A group of researchers at the Max Planck Institute for Polymer Research (MPI-P) in connection with the National University of Singapore have demonstrated graphene’s unlimited potential for heat conduction based on the size of the sample, contradicting the law of thermal conduction. The results were published in Nature Communications.
Davide Donadio, Group Leader of MPI-P said in a press release: “We recognized mechanisms of heat transfer that actually contradict Fourier’s law in the micrometer scale. Now all the previous experimental measurements of the thermal conductivity of graphene need to be reinterpreted. The very concept of thermal conductivity as an intrinsic property does not hold for graphene, at least for patches as large as several micrometers.”
Donadio is referring to Fourier’s Law of thermal conduction, which was set forth by French physicist Joseph Fourier in 1822 about how heat is absorbed by solids. Additionally, thermal conductivity in a solid is dictated by the type of material, and not so much in the size or shape of the material. However, this study shows that graphene is an exception to this rule. In both computer simulations and experiments, the researchers found that the larger the segment of graphene, the more heat it could transfer. Theoretically, graphene could absorb an unlimited amount of heat.
The thermal conductivity increases logarithmically, and researchers believe that it is due to the stable rigid bonding pattern as well as being a two-dimensional material. Though researchers have known for a while that graphene was excellent at thermal conductivity, this study was the first to show that it could be varied based on the size of the segment. As graphene is considerably more resistant to tearing than steel and is also lightweight and flexible, its conductivity could have some attractive real-world applications.
Graphene could be applied into electronics, which are getting progressively smaller. As heat transfer in other materials is going to be static, graphene’s unique potential for variable conductivity could be a dream come true for micro- and nano-electronics. Future research will determine if graphene is self-cooling, which would be yet another considerable advantage over other materials.