The effect of the electrical double layer on hydrodynamic lubrication: a non-monotonic trend with increasing zeta potential

Abstract

In the present study, a modified Reynolds equation including the electrical double layer (EDL)-induced electroviscous effect of lubricant is established to investigate the effect of the EDL on the hydrodynamic lubrication of a 1D slider bearing. The theoretical model is based on the nonlinear Poisson–Boltzmann equation without the use of the Debye–Hückel approximation. Furthermore, the variation in the bulk electrical conductivity of the lubricant under the influence of the EDL is also considered during the theoretical analysis of hydrodynamic lubrication. The results show that the EDL can increase the hydrodynamic load capacity of the lubricant in a 1D slider bearing. More importantly, the hydrodynamic load capacity of the lubricant under the influence of the EDL shows a non-monotonic trend, changing from enhancement to attenuation with a gradual increase in the absolute value of the zeta potential. This non-monotonic hydrodynamic lubrication is dependent on the non-monotonic electroviscous effect of the lubricant generated by the EDL, which is dominated by the non-monotonic electrical field strength and non-monotonic electrical body force on the lubricant. The subject of the paper is the theoretical modeling and the corresponding analysis.

A comparative study of the nanoscale and macroscale tribological attributes of alumina and stainless steel surfaces immersed in aqueous suspensions of positively or negatively charged nanodiamonds

“…These systems also exhibited an abrupt drop in f and an increase in R when re-exposed to pure DI water. The latter behavior is potentially explained by the suspended −ND nanoparticles acting as a lubricious slurry reducing resistance at the solid–liquid interface through potentially electrostatic repulsion with the rest of the −NDs in the surrounding suspension [ 20 , 43 ]. This suggestion, which is somewhat analogous to boundary lubrication and steric repulsion effects by mucinous glycoproteins boundary layers in aqueous biological settings [ 18 ], remains an intriguing possibility for the future investigations.…”

“…The surface chemical treatments employed in the production of the ND might therefore dominate the tribological performance. The surface charges on ND are also expected to affect the interfacial solid–fluid slip lengths attributes, and therefore the apparent fluid viscosity, via electroviscous and/or steric mechanisms [ 18 – 20 ]. Fundamental studies at the nanoscale are clearly essential at this time in order for the field to progress and for accurate model predictions to be developed.…”

Lubrication Performance under Electrical Regulation: Investigating the Mechanism of Graphene/Ionic Liquid Composite Materials

“…5(b), exhibited an inverse relationship with the friction coe cient changes, further con rming the direct association between friction coe cient variations and current application. The possible cause is the electric double layer (EDL) effect [23] and the subsequent electrorheological (ER) phenomenon induced by the current. These involve the transition of the liquid from a Newtonian uid to a high-yield stress viscoelastic solid on the millisecond time scale and the liquid's ability to quickly revert to its original low-viscosity state after the removal of the electric eld.…”

QCM Study of Tribotronic Control in Ionic Liquids and Nanoparticle Suspensions

“…This emerging field is referred to as "tribotronics", and is defined as the "active" or "smart" control of friction by combining machine elements with electronics [13][14][15][16][17]. A vast range of materials can be employed in tribotronic applications, including magnetorheological fluids, cryogenic liquids [8,18,19], ionic liquid suspensions, electrical double layers, and charged nanoparticles [7,[20][21][22][23].…”