Different methods (EFTEM, XPS, XANES, and ToF-SIMS) are used to determine particles size and detailed chemical composition of overbased calcium alkyl benzene sulfonate (OCABS) micelles. Colloids are ...obtained by carbonation of calcium hydroxide in hydrocarbon phase used in lubricant in the presence of ABS surfactant. The reaction leads to well-defined nanoparticles. This paper describes the location in the nanoparticle of expected molecular species and the quantity of each species. The originality of this study is to show the presence of residual calcium hydroxide in overbased detergents. As calcium carbonate has a highly amorphous character despite a local order close to calcite one, calcium hydroxide is suspected to be present in the core even at the end of the reaction. Its quantity and location are determined by the complementarities of these surface analysis techniques.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Overbased detergents are well known in the tribology field as anti-wear additives. In boundary lubrication, they generate a quite thick tribofilm on rubbing surfaces. They were studied by coupling ...XPS and AES depth profiles with XANES and ToF-SIMS analyses. Under friction, we show by ToF-SIMS analysis that detergent molecules are split into smaller structural units. Moreover, ionic bonds do not resist high pressure and shearing, and sulfur disappears from the contact zone. The overbased calcium carbonate core finally collapses and crystallizes to give a good anti-wear film between rubbing surfaces.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Inorganic Fullerene-like (IF)-MoS
2 nanoparticles were tested under boundary lubrication and ultra-high vacuum (UHV) and were found to give an ultra-low friction coefficient in both cases compared to ...hexagonal (h)-MoS
2 material. Previous works made by Rapoport et al. with IF-WS
2 revealed that the benefit effect of the inorganic fullerene-like materials decreases at high loads and sliding velocities. Nevertheless, under the conditions used in our experiments using high contact pressure (maximum pressure above 1.1 GPa in oil and 400 MPa in high vacuum) and slow sliding velocities (1.7 mm/s in oil test and 1 mm/s in high vacuum), friction always decreases and stabilizes at about 0.04 for 800 cycles in both cases. Therefore, IF-MoS
2 material appears to be a good candidate for use in various environments in regard to other MoS
2 crystal structures. Wear mechanisms were investigated using both High Resolution TEM and surface analyses (XPS) on the wear tracks. Wear particles collected from the flat wear scar show several morphologies, suggesting at least two lubricating mechanisms. As spherical particles are found in the wear debris, rolling may be a possible event. However, flattened and unwrapped IF-MoS
2 particles are often observed after friction. In this case, low friction is thought to be due either to sliding between IF-MoS
2 external flattened planes or to slip between individual unwrapped MoS
2 sheets.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
