Mar 27, 2013
Non-covalently functionalized graphene enhances thermal transport
Modern thermal management through advanced cooling is essential for the safety and the daily operations of modern micro- and nanoelectronic devices, as well as energy systems such as batteries and solar thermal cells, which dissipate more heat as they become more powerful. Graphene, due to its excellent thermal conductivity, can be added to traditional thermal grease to enhance heat-transfer efficiency. However, there are significant barriers for heat transfer at the graphene/grease interfaces.
To reduce this heat-transfer barrier, researchers at MIT used atomistic simulations to design decorated graphene surfaces with alkyl-pyrene molecules. The alkyl-pyrene molecules possess vibrational (phonon spectra) features of both graphene and octane (to model grease) and therefore can bridge the vibrational mismatch at the graphene/octane interface. These alkyl-pyrene molecules are deliberately chosen and denoted here as “phonon-spectra linkers”.
In support of their hypothesis, the team found that the best alkyl-pyrene candidate can enhance the interfacial thermal conductance by ~22%, attributed to its capability to compensate the low-frequency vibrational frequency of graphene in the normal-to-sheet direction.
The scientists also found that the length of the alkyl chain indirectly affects the interfacial thermal conductance through different orientations of these chains by dictating the contribution of the out-of-plane high-frequency carbon–hydrogen bond vibrations to the overall phonon transport.
Their study advances our understanding of the less destructive non-covalent functionalization method and design principles for suitable linker molecules to enhance the thermal performance of graphene nanocomposite-based thermal grease, while retaining the intrinsic chemical, thermal and mechanical properties of pristine graphene.
Full details can be found in the journal Nanotechnology.
About the author
Dr Shangchao Lin is a postdoctoral associate at the Laboratory for Atomistic and Molecular Mechanics (LAMM), in the Department of Civil and Environmental Engineering at MIT. LAMM is led by Prof. Markus Buehler, whose research emphasizes multiscale computational mechanics and materials design from the atomistic to the macroscopic level. An area of particular interest is the design of nanoscale heat-transfer materials based on phonon engineering, to achieve advanced thermal-management systems to enhance the efficiency of energy harvesting and storage.