Effects of the Filler Property, Electron-Phonon Coupling on Thermal Conductivity, and Strain Rate on the Mechanical Property of Polyethylene Nanocomposites
B Zhang and YM Liang and W Liu and ZC Liu, JOURNAL OF PHYSICAL CHEMISTRY C, 124, 26001-26011 (2020).
Electron-phonon interaction (EPI) plays an important role in the transport property of metals. Nevertheless, EPI in polymer nanocomposites containing metal fillers has not been fully investigated due to the complicated physical mechanisms. In this work, the copper- polyethylene (Cu-PE) nanocomposite is used as a model system, and nonequilibrium molecular dynamics (NEMD) simulation combined with the two-temperature model (TTM) is conducted to reveal the role of EPI in Cu-PE systems. The effects of filler length, filler property, and EPI strength on thermal conductivity are revealed. A dimensionless number (T) is defined to characterize the electron-phonon nonequilibrium (EPN) degree. The results show that the EPN degree has a significant impact on thermal conductivity. When the system is in a strong EPN state, the effects of EPI on thermal conductivity can be negligible. However, when the EPN degree gradually decreases, ignoring EPI can severely underestimate the thermal conductivity. Furthermore, the temperature profile of electrons and phonons is extracted and the equivalent thermal circuit is presented. The additional thermal resistances induced by the nonlocal and nonequilibrium effects are revealed. Phonon spectra analysis and heat current decomposition are performed to uncover the underlying mechanisms. In addition, the effects of atomic mass density and filler types on thermal conductivity are revealed. Stress-strain simulation is conducted to unravel the effects of strain rates on the mechanical property. The results are useful for designing polymer nanocomposites with controlled thermal conductivity.
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