Thermal transport behavior of polycrystalline graphene: A molecular dynamics study

Abstract

The thermal transport behavior of polycrystalline graphene is studied using molecular dynamics simulations, with focus on the effects of grain size, tensile strain, and temperature on the thermal conductivity. All the simulation samples have the same overall dimensions of 30 Â 30 nm with average grain sizes ranging from 2.5 to 12.5 nm. It is found that polycrystalline graphene exhibits a significant reduction in thermal conductivity compared to single-crystalline graphene, and the smaller the grain size is, the more the thermal conductivity drops. The thermal conductivity of polycrystalline graphene with average grain size of 2.5 nm is only about 20% of single-crystalline graphene. However, the thermal conductivity of polycrystalline graphene is less sensitive to both the applied strain and temperature than that of single-crystalline graphene. The underlying mechanisms for the differences in thermal behavior are examined and discussed. These findings are important for the thermal management of graphene-based devices. V

Scaling properties of polycrystalline graphene: a review

“…, found for a single-grain graphene sample with same length.This is in good agreement with [140] where a reduction of thermal conductivity to about 20% of the value in pristine graphene is observed for an average grain size of ∼2.5nm. This highlights the major role played by GBs in scattering phonons, whose mean free path (MFP) is comparable with the average GB spacing.…”

“…Their multigrain structure, with dimensions down to the microand nanoscale, is likely an important pre-existing cause for the wide range of κ values reported above. However, the systematic investigation of the effect of size, shape, and distribution of grains on thermal transport properties is still ongoing [9,[67][68][69][139][140][141].…”

Scaling Properties of Polycrystalline Graphene: A Review

“…This is in good agreement with Ref. [140] where a reduction of thermal conductivity to about 20 % of the value in pristine graphene is observed for an average grain size of ∼ 2.5 nm. This highlights the major role played by GBs in scattering phonons, whose mean free path (MFP) is comparable with the average GB spacing.…”

“…Their multi-grain structure, with dimensions down to the micro-and nanoscale, is likely an important pre-existing cause for the wide range of κ values reported above. However, the systematic investigation of the effect of size, shape, and distribution of grains on thermal transport properties is still ongoing [9,[67][68][69][139][140][141].…”

Impact of grain boundary characteristics on thermal transport in polycrystalline graphene: Analytical results

“…After that κ(10nm)/κ(2.5nm) gradually goes to unity due to the increasing role of the Umklapp processes. Notice, that MD calculations provide a similar dependence of κ(T )/κ 0 (T ) for the same grain sizes in the temperature range from 300K to 1100K [22].…”