Thermal wave propagation in graphene studied by molecular dynamics simulations

Networked nanoconstrictions: An effective route to tuning the thermal transport properties of graphene

“…W/(m·K), which is reduced by as much as 96% because of the specific arrangement. This thermal conductivity is lower than the minimum value of the reduced graphene oxide films and compatible with that of the graphene oxide films measured by Renteria et al [28], and about three order of magnitude lower than the bulk graphene [1,41]. Thus, the combined effect of the above three factors,…”

“…Further, for other cases, the inset of figure 3c shows the theoretical resistance of a 1-µm-wide graphene sheet with a bulk thermal conductivity of 3082 W/(m·K) [41], we can find that the ballistic resistance is always one or two orders of magnitude larger than the diffusive one. So, for a single-constriction with its constriction width much smaller than the MFP of graphene, it is feasible to ignore the diffusive resistance and predict the total constriction resistance with the model of the 2D ballistic resistance we proposed.…”

“…We employed the NEMD method [38][39][40][41] and constructed a series of simulation systems, as illustrated in figure 1. Figure 1a depicts the simplest system having one variable-width-constriction, constructed by introducing two linear vacancy defects in a pristine graphene sheet.…”

Phonon wave propagation in ballistic-diffusive regime

“…The superposition results in serious dispersions of thermal waves and broadening of PWs in simulations with LE stated above which would be aggravated once the frequency dependence of the phonon group velocity are taken into considerations. 41 Due to that the temperature profiles of the thermal wave obtained from the C-V model and the MC simulation with DE are similar with the temperature wave 22,42 in cases of Fourier heat conduction, it should be noted that the thermal wave and the temperature are actually quite different. The thermal wave in ultrafast thermal transport (we call it ballistic thermal wave) is due to the ballistic transport of heat, while the temperature wave resulting from the periodic boundary condition is still under the regime of diffusive transport and just a kind of transient case of the Fourier heat conduction.…”

“…21 Yao and Cao first studied the propagation of the heat pulse in graphene by MD simulations and indicated that the heat pulse propagates in ballistic-diffusive regime. 22 Xu and Wang developed a LBM scheme with which he studied the ultrafast process of the pico-and femto-second pulse laser heating process in single-crystal silicon and pointed out that the parabolic equation and the hyperbolic equation are neither applicable to the ballistic condition due to the failure of the continuum and local equilibrium approximation. 23 Author to whom correspondence should be addressed.…”