Interactions between Friction Modifiers and Dispersants in Lubricants: The Case of Glycerol Monooleate and Polyisobutylsuccinimide-Polyamine.

The structural and frictional properties of 10 wt % solutions of the amphiphilic molecules glycerol monooleate (GMO) and polyisobutylsuccinimide-polyamine (PIBSA-PAM) in squalane are studied using molecular dynamics simulations in bulk and under confinement between iron oxide surfaces. GMO is a friction modifier, PIBSA-PAM is a dispersant, and squalane is a good model for typical base oils. A range of liquid compositions and applied pressures is explored, and the formation and stability of reverse micelles are determined under quiescent and shear conditions.

Industrial Gear Oils: Tribological Performance and Subsurface Changes.

This study examined the tribological performance of three gear oils (Oils A, B and C), in relation to surface and microstructural changes. Oil A contains molybdenum dithiophosphate friction modifier, Oil B contains amine molybdate combined with zinc dialkyl dithiophosphate antiwear additive, while Oil C contains phosphonate and a commercial gear oil package. Following sliding tests of a hardened AISI 52100 steel ball on a spheroidized AISI 52100 steel disc, the worn surfaces were chemically studied using Raman and energy-dispersive X-ray spectroscopy.

Property Self-Optimization During Wear of MoS.

Knowledge of their bulk physical properties often guides selection of appropriate tribological coating materials. However, these properties as well as the microstructure evolve dramatically under the extreme conditions imposed during mechanical wear. The dynamic response ultimately governs the material's wear performance; thus, understanding the dynamic evolution of the system is critical.

Mechanical Properties of Molybdenum Disulfide and the Effect of Doping: An in Situ TEM Study.

Direct observations on nanopillars composed of molybdenum disulfide (MoS2) and chromium-doped MoS2 and their response to compressive stress have been made. Time-resolved transmission electron microscopy (TEM) during compression of the submicrometer diameter pillars of MoS2- and Cr-doped MoS2 (Cr: 0, 10, and 50 at %) allow the deformation process of the material to be observed and can be directly correlated with mechanical response to applied load. The addition of chromium to the MoS2 changed the failure mode from plastic deformation to catastrophic brittle fracture, an effect that was more pronounced as chromium content increased.

Structure and friction of stearic acid and oleic acid films adsorbed on iron oxide surfaces in squalane.

The structure and friction of fatty acid surfactant films adsorbed on iron oxide surfaces lubricated by squalane are examined using large-scale molecular dynamics simulations. The structures of stearic acid and oleic acid films under static and shear conditions, and at various surface coverages, are described in detail, and the effects of unsaturation in the tail group are highlighted. At high surface coverage, the measured properties of stearic acid and oleic acid films are seen to be very similar.

Effect of fuel and lube oil sulfur on the performance of a diesel exhaust gas continuously regenerating trap.

The continuously regenerating trap (CRT) is a diesel exhaust emission control that removes nearly all diesel particulate matter on a mass basis, but under some circumstances oxidation of sulfur leads to the formation of nanoparticles. The objective of the four year study was to determine CRT performance under controlled, real-world, on-road conditions, and to develop quantitative relationships between fuel and lubrication oil sulfur concentration and particle number exhaust emissions. It was shown that nanoparticle emissions are minimized by the use of ultralow sulfur fuels and specially formulated low sulfur lubrication oil.

The influence of polyacid molecular weight on some properties of glass-ionomer cements.

The influence of the molecular weight of the poly(acrylic acid) component on some properties of glass-ionomer cement has been investigated. The results can be explained by treatment of glass-ionomer cements as thermoplastic composites. Many of the concepts of polymer science can be applied successfully in a qualitative way to these cements, including the ideas of entanglements and reptation.