Non-equilibrium Molecular Dynamics Study of the Tribological Behavior of Lubricated Amorphous Carbon

Abstract Non-equilibrium molecular dynamics (NEMD) simulations were carried out to investigate the lubrication of two amorphous carbon surfaces by a confined fluid of n-hexadecane molecules. Interatomic interactions were described by the AIREBO-M potential. An external pressure of 1 GPa and shear rates in the range of $$10^9$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>9</mml:mn> </mml:msup> </mml:math> – $$10^{10}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>10</mml:mn> </mml:msup> </mml:math> s $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:math> were applied to the system. Subjected to this high shear rates, above the critical shear rate, the n-hexadecane fluid behaved as a non-Newtonian fluid. Slip-boundary behavior was not observed, but the system demonstrated shear localization. Due to stronger interactions at the solid–lubricant interface, where some n-hexadecane molecules were adsorbed, the corresponding sublayers of lubricant molecules moved with the same velocity of the sliding surfaces. Away from the interfaces, a linear velocity profile, consistent with Couette flow, developed towards the center of the fluid channel. The friction coefficients calculated from the mean shear stresses were in the ultra-low friction region, which is compatible with experimental data for similar tribosystems.