Similar to the interfacial thermal resistance, i.e., Kapitza resistance, the

thermal resistance R at the constrictions can be defined as (4) where J and ∆T, respectively, correspond to the heat current across the constrictions and the associated temperature jump (as shown in Figure 2). In order to reduce the error, in this paper, the constriction resistance R is calculated by fitting the curve between the temperature jump and the heat current. The results are shown in Figure 4, where w is the width of one constriction, with larger w meaning weaker strength of GSK2118436 supplier the constriction. The results show that the nanosized constriction resistance is on the order of 107 to 109 K/W. And as mentioned before, the constriction resistance has an obvious size effect, which Nirogacestat molecular weight decreases from 4.505 × 108 to 9.897 × 106 K/W with the increasing width, and it is almost inversely proportional to the width of the constrictions. Figure 4 Constriction resistance versus Stattic width of constriction. The dots are MD results and the curve is the theoretical prediction given by Equation 9. To quantitatively describe the effect of the nanosized constrictions on thermal transport properties,

we introduce a dimensionless parameter: the thermal conductance ratio η = σ/σ 0, where σ and σ 0 are the thermal conductance of the graphene with constrictions and that of the corresponding pristine graphene, respectively.

Figure 5 shows the dependence of the thermal conductance ratio on the width. As shown, various-sized constrictions have a significant influence on the thermal conductance of graphene and the thermal conductance is reduced by 7.7% to 90.4%. Thus, we can conclude that it is quite feasible to tune the thermal conductance of graphene over a wide range by introducing the nanosized constriction or controlling the Dapagliflozin configuration of the embedded extended defect in graphene. Figure 5 Thermal conductance ratio versus width of constriction. The inset is the corresponding pristine graphene. Recently, some model-based analyses on the constriction resistance have been carried out [30–33]. The models mainly involve the following three parameters: the phonon mean free path (l), the characteristic size of the constriction (a), and the dominant phonon wavelength (λ d). In the completely diffusive regime when a is much larger than l, the diffusive constriction resistance (R d) is given by the Maxwell constriction resistance model [30]: (5) where κ denotes the thermal conductivity. But in the other limit, that is, a < < l, phonon transport across the constriction is ballistic.