Strengthening mechanism of tribological properties of graphene oxide / multiwalled carbon nanotubes hybrid nanofluids: Molecular dynamics and experimental validation

Abstract

A novel water-based hybrid nanofluid incorporating graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) has been successfully formulated. To elucidate the lubrication mechanisms underpinning this nanofluid's performance, a friction model was constructed employing molecular dynamics (MD) simulations. This approach enabled an in-depth examination of how GO and MWCNTs, along with their interfacial interactions, contribute to enhanced lubrication between contacting surfaces. The MD simulations highlighted that the stable layered architecture generated by the adsorption of GO and MWCNTs within the hybrid nanofluid plays a crucial role in diminishing the coefficient of friction. Building on these insights, dispersion experiments were undertaken to investigate strategies for improving the long-term suspension stability of the water-based GO/MWCNTs hybrid nanofluid. The impact of varying particle concentrations on tribological characteristics was also assessed through comprehensive friction and wear testing. Findings revealed that polyvinylpyrrolidone (PVP) is an optimal surfactant for ensuring sustained stability of the nanofluid when dispersed in a base liquid. Benefiting from interfacial effects, GO and MWCNTs coalesce into a robust stacked-layer structure, exhibiting superior anti-wear and friction-reducing attributes during operation. Optimal tribological performance was observed at GO and MWCNT concentrations of 1.0 wt% each, achieving the lowest mean friction coefficient and material volume wear rate. Compared with conventional CNC water-based cutting coolants, this optimized hybrid nanofluid formulation resulted in reductions of 22.3 % in average friction coefficient and 40.2 % in material volume wear rate, underscoring its potential as an advanced lubricant in industrial applications.

Keywords: Graphene oxide; Molecular dynamics; Multiwalled carbon nanotube; Nanofluids; Tribological performance.