a recent study at rice university has examined the thermal transport capability of pillared graphene, a theoretical material that was hypothesized by university researchers, and determined that asymmetric junctions that caused wrinkles would enhance the thermal conductivity of the material.

heat transport through pillared graphene could be made faster by manipulating the junctions between sheets of graphene and the nanotubes that connect them. (lei tao)

according to a report on the university website, the researchers worked with computer models of pillared graphene, which are sheets of graphene connected with covalently-bonded carbon nanotubes.

“they found that manipulating the joints between the nanotubes and graphene has a significant impact on the material’s ability to direct heat,” the article explained. “that could be important as electronic devices shrink and require more sophisticated heat sinks.”

rice researchers found that replacing six heptagons (that form a seamless connection with the carbon nanotubes) with three octagons would stress the graphene and form wrinkles in the graphene sheets without breaking the junctions.

these wrinkles were expected to alter thermal conductivity, but not for the better. what the scientists found was that reducing the number of rings in the junctions meant less scattering of phonons. the models with octagons performed 20 percent better than those without.

“the researchers thought phonon transport through the nanotubes, which they already knew was slower than in graphene, might be slower still under the influence of the octagons, but the altered interface didn’t appear to have a significant effect,” the article continued.

the new research was recently published in applied materials and interfaces. the abstract stated:

“hybrid 3d nanoarchitectures by covalent connection of 1d and 2d nanomaterials are currently in high demands to overcome the intrinsic anisotropy of the parent materials. this letter reports the junction configuration-mediated thermal transport properties of pillared graphene (pgn) using reverse nonequilibrium molecular dynamics simulations.

“the asymmetric junctions can offer ∼20% improved in-plane thermal transport in pgn, unlike the intuition that their wrinkled graphene sheets cause phonon scattering.

“this asymmetric trait, which entails lower phonon scattering provides a new degree of freedom to boost thermal properties of pgn and potentially other hybrid nanostructures.”