Microscopic mechanisms of thermal transport at the SiO2-water interface under the influence of wettability: A molecular dynamics study

Abstract

Amorphous silica (a-SiO₂) nanoparticles play an important role in the fields of solar thermal utilization, nanofluids and thermomagnetic therapy. However, there is still a lack of understanding of the microscopic mechanism of heat transfer between nanoparticles and water, especially the wettability of nanoparticles. Here, we use molecular dynamics (MD) simulation to study the microscopic mechanism of heat transport between a-SiO₂ and water under the different wettability. The results show that the hydrogen bonds(H-bonds) heat conduction network is formed at the interface of the a-SiO₂ nanoparticles due to the H-bonds interaction between water molecules. In addition, with the increase of wettability, the thermal boundary conductance also increases. This is due to the formation of more H-bonds between water molecules at the interface of the a-SiO₂ nanoparticles, which slows down the exchange frequency of water molecules between the a-SiO₂ nanoparticles interface and the bulk water, increases the time scale of stay on the a-SiO₂ nanoparticles surface, and increases the probability of heat transfer between a-SiO₂ nanoparticles and water. The change of wettability leads to the change of water structure at the a-SiO₂ nanoparticles interface, forming a tetrahedral hydrogen bond structure similar to that of solid ice. The analysis of VDOS further confirms the key role of the vibration of the H-bonds network in the heat transport at the solid-liquid interface. Consequently, these insights provide a valuable theoretical framework for comprehending heat transport mechanisms at soft-hard interfaces.