Thermal conductivity of graphene nanofluids via defect engineering: a computational approach

Abstract

We present a molecular dynamics study on the thermal conductivity () of graphene-based nanofluids, examining monolayer (mG), bilayer (bG), and trilayer (tG) graphene immersed in liquid argon. At 300 K, pristine mG displayed the highest = 2700 W/mK, confirming its outstanding phonon transport capacity. Introducing 5% centralized vacancies (mG5C) reduced to 2257 W/mK, whereas decentralized defects (mG5D) caused a steeper decline to 2080 W/mK. The random-defect configuration (mG5R) exhibited an even stronger suppression, reaching only 1824 W/mK, which highlights the disruptive effect of stochastic defect topology on phonon propagation. Increasing the vacancy concentration to 15% further reduced the thermal response: dropped to 1847 W/mK for mG15C and to 1647 W/mK for mG15D. This systematic reduction demonstrates that both defect density and spatial distribution critically modulate phonon scattering. The same tendency was maintained throughout the 100–800 K range and was reproduced in the bG and tG models.To elucidate the underlying mechanisms, we computed the vibrational density of states (VDOS) from velocity autocorrelation functions. Defective models exhibited the suppression of high-frequency phonon modes ( 50 THz) and an enhancement of low-frequency localized vibrations ( 30 THz), indicating increased phonon scattering and confinement of vibrational modes. Radial distribution function (RDF) analysis revealed that centralized defects promote more ordered argon layering near the graphene surface, enhancing interfacial thermal coupling. In contrast, decentralized vacancies reduced this structural order and likely increased interfacial resistance.These findings demonstrate that thermal conductivity in graphene nanofluids can be tuned through defect engineering, balancing intrinsic phonon transport with interfacial coupling. This provides valuable guidance for optimizing nanofluids in thermal management technologies.