TUNING THERMAL CONDUCTIVITY WITH MECHANICAL STRAIN

XB Li and J Liu and RG Yang, PROCEEDINGS OF THE ASME INTERNATIONAL HEAT TRANSFER CONFERENCE - 2010, VOL 6: MICROCHANNELS, NANO, NANOFLUIDS, SPRAY COOLING, POROUS MEDIA, 551-558 (2010).

Mechanical strain provides an efficient way for tuning thermal conductivity of materials. In this study, molecular dynamics (MD) simulation is performed to systematically study the strain effects on the lattice thermal conductivity of silicon and carbon based materials (mainly nanostructures: Si nanowire and thin film, single-walled carbon naotube (SWCNT) and single layer graphene) and bulk polymer materials. Results show that thermal conductivity of the strained silicon nanowires and thin films decreases continuously when the strain changes from compressive to tensile. However, the thermal conductivity has a peak value under compressive strain for SWCNT and at zero strain for single layer graphene. In contrast, thermal conductivity of polymer materials increases with increasing tensile strain. The underlying mechanisms are analyzed in this paper for both types of materials. We found that the thermal conductivity of silicon and carbon based materials can be related to the phonon dispersion curve shift and structural buckling under strain and for polymer chains thermal conductivity directly connects to the orientations of the chains. This thermal conductivity dependence with strain can guide us to tune the thermal conductivity for materials in applications.

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