Tribological Performance of Silver Nanoparticle–Enhanced Polyethylene Glycol Lubricants

This article introduces a new type of nanoparticle additive for tribological purposes. A nanolubricant was synthesized and studied that consists of metallic silver nanoparticles suspended in polyethylene glycol (PEG). Silver nanoparticles were prepared directly in liquid PEG by introducing aqueous silver nitrate and subsequent reduction by PEG. The nanolubricant exhibits excellent stability due to poly(vinyl pyrollidone) used as the coating agent. Thorough tribological analysis was performed on the nanolubricant, including rheology, friction, wear, and Stribeck curve analysis. Results show that the nanoparticle additives are capable of reducing both friction and wear at low concentrations. Stribeck curve analysis also revealed that the particles are effective in reducing friction in both the boundary and mixed lubrication regimes. The possible friction and wear reduction mechanism of silver nanoparticles is also discussed in the current work.