Lattice thermal conductivity of graphene flakes: Comparison with bulk graphite

Abstract

The authors proposed a simple model for the lattice thermal conductivity of graphene in the framework of Klemens approximation.

Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism

“…For instance, theoretical calculations have revealed a superior lifetime of the bending modes in twodimensional graphene. 52,53,56 Our auto-correlation function calculations are consistent with these results. The TW and LA modes have much shorter lifetime than the bending modes at 300 K. From the comparison between these curves for 300K and 1200 K, we find that the lifetime for the two bending modes and the LA mode decrease considerably with increasing temperature.…”

“…The surface or boundary scattering is a common mechanism in low-dimensional NW structures, which is closely related to weaker phonon-phonon scattering. 51,52,53,54 The experimental value for the exponent is above 1.0, which is attributed to other phonon scattering mechanisms be- sides the phonon-phonon scattering, 28 for example intrinsic vacancy point defects or isotropic disorder. In our simulations, all ZnO NWs are pristine without defects, so the temperature exponents from our calculations are smaller than the experimental values.…”

“…This preserving mechanism for the bending mode is crucial for the much higher thermal conductivity of the free ZnO NW because it is well-known that thermal energy is mainly transported by the bending modes in both two-dimensional and one-dimensional nanosystems. 52,53,56 Hence, the preservation of the bending mode directly leads to much higher thermal conductivity in the free ZnO NW.…”

Anomalous Size Dependence of the Thermal Conductivity of Graphene Ribbons

“…Although the strong size dependence was reported in many studies of heat conduction in graphene or CNTs [13,[16][17][19][20][21][25][26][27][28][29][30][31][32][33], it is usually difficult to distinguish among the various possible mechanisms. Among them are the K(L) dependence in the ballistic thermal transport regime where L<< the K dependence on the nanoribbon width due to the acoustic phonon -rough edge scattering, or the fundamental K size dependence in 1D or 2D lattices where anharmonic interactions are not sufficient for establishing finite K over the given length scale L. These important questions call for a rigorous study of the lateral size effects on the thermal conductivity of graphene ribbons and graphite slabs.…”

“…Substituting the expression for the phonon Umklapp relaxation time scattering to the first order [27,30,35]. This model is not suitable for the large graphene samples when other scattering mechanisms, e.g.…”