Effects of interfacial molecular mobility on thermal boundary conductance at solid-liquid interface

Area of Science:

• Materials Science
• Thermodynamics
• Computational Chemistry

Background:

• Interfacial thermal transport is crucial for thermal management in nanoscale devices.
• Understanding molecular mobility's role in thermal boundary conductance (TBC) is key to optimizing heat dissipation.
• Graphene-water and graphene-perfluorohexane interfaces serve as model systems for studying liquid-solid thermal interactions.

Purpose of the Study:

• To investigate the influence of interfacial molecular mobility on TBC across graphene-water and graphene-perfluorohexane interfaces.
• To elucidate the mechanisms governing thermal transport at these interfaces under varying temperatures.
• To compare the thermal transport behaviors of water and perfluorohexane at the graphene interface.

Main Methods:

• Non-equilibrium molecular dynamics (NEMD) simulations were employed.
• Molecular mobility was controlled by equilibrating nanoconfined liquids (water and perfluorohexane) at different temperatures.
• Thermal boundary conductance was analyzed, including spectral decomposition.

Main Results:

• Perfluorohexane exhibited low molecular mobility and a layered structure across a wide temperature range (200-450 K).
• Water showed increased mobility and diffusion at higher temperatures, significantly contributing to thermal transport.
• Graphene-water TBC showed a quadratic temperature dependence, while graphene-perfluorohexane TBC showed a linear dependence.
• Enhanced spectral transmission and low-frequency modes were observed in interfacial water due to higher molecular mobility.

Conclusions:

• Higher molecular mobility and enhanced spectral transmission in water explain its superior thermal transport compared to perfluorohexane.
• Interfacial molecular mobility is a critical factor determining thermal boundary conductance.
• The distinct thermal transport characteristics are attributed to differences in molecular structure and dynamics between water and perfluorohexane.