Influence of Surface Defects on the Thermal Conductivity of Hexagonal Boron Nitride/Poly(dimethylsiloxane) Nanocomposites: A Molecular Dynamics Simulation

Abstract

In this simulation, the reverse nonequilibrium molecular dynamics simulation is employed to explore how the surface defects in hexagonal boron nitride (h-BN) influence the thermal conductivity of poly(dimethylsiloxane) (PDMS)-based composites. First, the interfacial thermal conductivity and the intrinsic thermal conductivity of h-BN are obtained by tuning the defect density, the inhomogeneity of the defect distribution, and the number of h-BN layers. The defects enhance the interfacial thermal conductivity, especially for h-BNs with high inhomogeneity of the defect distribution and multilayer. However, the intrinsic thermal conductivity of h-BN is declined significantly by the defects. They can be explained well by the vibrational density of states of PDMS and h-BNs and their overlap. Then, by combining the effective medium approximation model with the simulation, the overall thermal conductivity of composites is obtained. It exhibits a gradual decrease with increasing defect density or reducing the inhomogeneity of the defect distribution. Meanwhile, the enhancement extent of the overall thermal conductivity by improving the concentration and size of h-BNs depends on the defect density and the defect distribution. Finally, the comparison between the simulation and experiment is discussed. In summary, our work provides some valuable insights into how the defect density, the defect distribution, and the number of layers influence the thermal conductivity of the PDMS-based composite.

Excellent Medium-Temperature Thermoelectric Performance of Monolayer BiOCl

“…By contrast, some high-frequency optical modes determined by O atom vibrations also possess the same level of group velocities because the presence of the phonon gap blocks the redistribution of phonon energy between the high-frequency optical modes with other phonon modes mentioned above. It also means that the high-frequency optical phonons also play an important role in thermal transport. , More importantly, under tensile strain from 1 to 1.5%, the group velocity of all phonon branches changes slightly, showing that the harmonic effect does not play the dominant role in the phonon transport. To distinguish the contribution ratio of different phonons branches, we have plotted the mode-wise total phonon thermal conductivity in Figure c.…”

“…It also means that the high-frequency optical phonons also play an important role in thermal transport. 63,64 More importantly, under tensile strain from 1 to 1.5%, the group velocity of all phonon branches changes slightly, showing that the harmonic effect does not play the dominant role in the phonon transport. To distinguish the contribution ratio of different phonons branches, we have plotted the mode-wise total phonon thermal conductivity in Figure 5c.…”

Improved out-of-plane thermal conductivity of boron nitride nanosheet-filled polyamide 6/polyethylene terephthalate composites by a rapid solidification method

“…This high-frequency peak was derived from the isolated B and N atoms on the edge of BNNSs that are fully exposed to the heat flow, which can promote the interaction of phonons and then enhance the interfacial heat transfer. 52 The PDOS overlap region of BNNSs and PA6/PET is mainly distributed over 0-45 THz. In addition, the PDOS of BNNSs can be divided into the in-plane and out-of-plane values, as shown in Fig.…”

Structure and properties of polymer/two-dimensional nanomaterials studied via molecular dynamics simulation: a review

“…However, the defect is detrimental to the overall thermal conductivity. Zhang et al 90 explored (Fig. 20) the impact of the defect density, the inhomogeneity of the defect distribution, and the number of h-BN layers on the interfacial and overall thermal conductivity.…”