Prediction of the viscosity of water confined in carbon nanotubes

Abstract

In this paper, the viscosity of water confined in single-walled carbon nanotubes (SWCNTs) with the diameter ranging from 8 to 54 Å is evaluated, which is crucial for the research on the nanoflow but difficult to be obtained. An ''Eyring-MD'' (molecular dynamics) method combining the Eyring theory of viscosity with the MD simulations is proposed to tackle the particular problems. For the critical energy which is a parameter in the ''Eyring-MD'' method, the numerical experiment is adopted to explore its dependence on the temperature and the potential energy. To demonstrate the feasibility of the proposed method, the viscosity of water at high pressure is computed and the results are in reasonable agreement with the experimental results. The computational results indicate that the viscosity of water inside SWCNTs increases nonlinearly with enlarging diameter of SWCNTs, which can reflect the size effect on the transports capability of the SWCNTs. The trend of the viscosity is well explained by the variation of the hydrogen bond of the water inside SWCNTs. A fitting equation of the viscosity of the confined water is given, which should be significant for recognizing and studying the transport behavior of fluid through the nanochannels.

Diameter-dependent ion transport through the interior of isolated single-walled carbon nanotubes

“…Water confined in nanopores of diameter similar to its molecular size demonstrates slip-flow at the walls 31 , reduced viscosity 42 and increased proton transport rates 23 . Both protons and blocking ions within a SWNT will feel these effects and our simple model, illustrated in Fig.…”

Structural and dynamical properties of water confined in carbon nanotubes

“…Most of its importance may be attributed to its anomalous properties, not found in any other substance. When confined in nanopores or nanochannels its behavior become even more intriguing: it experiences a liquid-solid transition at room temperature [2] and presents large size-dependent viscosity [3] and thermal conductivity [4], among other properties. Besides, hundreds of studies have focused on the remarkable fast diffusion properties of water in nanochannels, with applications in fields as diverse as desalinisation, filtering, gas separation, ion transport and others [5].…”

Effect of critical thickness on nanoconfined water fluidity: review, communication, and inspiration

“…Based on the previous experiments and molecular dynamic simulations (Raviv et al 2001;Thomas and McGaughey 2008;Kelly et al 2015;Qin and Buehler 2015;Wei et al 2014;Haria et al 2013;Babu and Sathian 2011;Ye et al 2011;Zhang et al 2011;Petravic and Harrowell 2009;Chen et al 2008;Liu et al 2005), a quadratic equation is proposed to reveal the relationship between the viscosity ratio ( i ∞ ) and contact angle, as shown in the following equation: Wu et al (2017) proposed a linear equation to model the relationship between the viscosity ratio ( i ∞ ) and contact angle. While their equation fitted well with experiments and molecular dynamic simulations, the linear relationship may neglect some underlining physics that is still not well understood at present.…”