A molecular dynamics study of thermal boundary resistance over solid interfaces with an extremely thin liquid film

We investigated the characteristics of thermal energy transport over two solid surfaces joined via an extremely thin liquid film where the liquid molecules are under the influence of both solid surfaces simultaneously. Using non-equilibrium molecular dynamics simulations, the thermal resistance between the two solid surfaces was examined for different thickness of liquid film and different alignment (in-plane orientation) of the two solid surfaces. Both solid surfaces were the (1 1 0) plane of face centered cubic lattice, and two different combinations of alignment, i.e., either parallel or crossed to each other, were examined. The thermal resistance between the solid surfaces was decomposed into the thermal boundary resistance at the solid-liquid interfaces and the thermal resistance of the liquid film, which were analyzed separately. The results showed that when the liquid film thickness is equal or less to four molecular dimensions, both the film thickness and the surface alignment have significant influence on the thermal resistance. Specifically, when the liquid film is a single layer of liquid molecules (LLM), the thermal resistance between solid surfaces is extremely low when compared with the cases of more LLM, and increases with increasing liquid density. In contrast, when the film is composed of two or three LLM, the solid-liquid interfacial thermal resistance decreases with increasing liquid density, and a discontinuous increase occurs as the number of LLM changes from two to three. As for the effect of surface alignment, it was found that the parallel surface alignment gives a lower thermal resistance than the crossed surface alignment. (C) 2019 Elsevier Ltd. All rights reserved.