High thermal conductivity and ultralow friction of two-dimensional ice by molecular dynamics simulations

• Published in: International journal of heat and mass transfer Vol. 220; p. 124938
• Main Authors: Zou, Hongyi, Yang, Lijun, Huang, Zhiyuan, Dong, Yuan, Dong, Ruo-Yu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2024
• Subjects: Lubricity; Molecular dynamics; Thermal conductivity; Two-dimensional ice; Lubricity; Molecular dynamics; Thermal conductivity; Two-dimensional ice
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2023.124938

•Thermal and friction properties of two-dimensional (2D) ice were systematically studied and compared with one bulk ice phase, ice Ih.•High thermal conductivity of 2D ice compared to Ih phase was revealed and the underlying mechanism was uncovered from phonon analyses.•The friction coefficient of 2D ice when sliding between graphene sheets could be as low as ∼0.005, indicating superlubricity. Two-dimensional ice (2D ice) is a relatively new family member of ice polymorphs. While the phase transitions and growth kinetics of 2D ice have aroused intensive investigation, its thermal and mechanical properties are seldom studied. The unique 2D structure of this polymorph suggests that it may possess distinct physical characteristics compared to its bulk counterparts. In this work, the thermal conductivities and friction of 2D ice were systematically studied by molecular dynamics (MD) simulations. It was found that the thermal conductivities of 2D ice show a strong dependence on their length and the extrapolated value of the infinite system can achieve ∼4.7 W/(m∙K), which is notably higher than that of bulk phase of ice Ih ∼1.5 W/(m∙K). Decreasing temperature or applying mechanical strains can both increase the thermal conductivity of 2D ice, which can be explained by structure or phonon analyses. 2D ice also exhibits an ultralow friction of ∼0.24 nN when sliding upon a graphene substrate, lower than that of ice Ih ∼0.70 nN at the same sliding conditions. With the decrease in temperature or the increase in normal load, the friction coefficient of 2D ice exhibits a downward trend, and it could be as low as ∼0.005, indicating superlubricity. The analysis on structural lubricity suggests that ordered but mismatched crystal-crystal contacts have lower friction than disordered case. The results on high thermal conductivity and ultralow friction would guide the potential application of 2D ice in efficient thermal management or design of nanofluidic devices.