Influence of temperature and ZDDP concentration on tribochemistry of surface-capped molybdenum sulfide nanoparticles studied by XANES spectroscopy

Abstract

The tribological behavior of surface-capped MoS 3 nanoparticles (nano-MoS 3 ) in hydrocarbon oils was studied in combination with ZDDP at test temperatures in the range of 100-160°C and at ZDDP content of 0-1.0 wt% in oil. It was demonstrated that this combination of additives demonstrates high antiwear and antifriction efficiency, especially at high temperatures and low ZDDP content. X-ray Absorption Near Edge Structure (XANES) spectroscopy at the sulfur, molybdenum, and phosphorus edges was used to identify the chemical species in the tribochemical films. It was established that the tribofilms formed by combination of ZDDP and nano-MoS 3 contain phosphate-based layers incorporating MoS 2 -type fragments. An increase in temperature and ZDDP content results in an increase in tribofilm thickness, while the relative Mo content in tribofilm decreases. Under the tested conditions, the best tribological properties are demonstrated by the composition comprising 500 ppm Mo and 0.1 wt% ZDDP in oil.

Plasma-Functionalized Polytetrafluoroethylene Nanoparticles for Improved Wear in Lubricated Contact

“…It is used to determine the local coordination of the elements, and the information can be obtained from both the surface and the bulk of the sample. XANES spectra provide detailed information concerning both the geometric makeup and electronic structure of the absorbing atom. , XANES analyses have played a particularly significant role in tribological studies, and it has been broadly employed in investigating the chemical composition of the tribofilms formed from different oil additives. ,,,,,, In the present case, the XANES study focused on phosphorus and sulfur chemistry in the tribofilms. It included fluorescence yield (FLY) mode spectra, which provide information from the bulk of the sample, and total electron yield (TEY) mode spectra, which are more surface-sensitive, for both K and L shell electrons.…”

An analytical study of tribofilms generated by the interaction of ashless antiwear additives with ZDDP using XANES and nano-indentation

“…Sulfur L-edge spectra provides a useful information regarding the local co-ordination/oxidation state of sulfur near the surface of the tribofilms [23,53,[58][59][60]. The S L-edge spectra are plotted for the tribofilms derived from ZDDP and combinations of ZDDP with ashless PFC18 & SSC18 compounds and compared with the spectra of several model compounds in figure 7 (a) and (b).…”

A Redox Couple Strategy Enables Long‐Cycling Li‐ and Mn‐Rich Layered Oxide Cathodes by Suppressing Oxygen Release

“…Peak 1 corresponds to sulfide‐type sulfur atoms (S 2− ), and peaks 2 and 3 correspond to sulfate‐type sulfur atoms (SO 3 2− ). [ 43 ] The intensity of the SO 3 2− peaks increases and then decreases during charging and discharging, respectively, suggesting that the reversible S 2− /SO 3 2− redox reaction occurs in one charge/discharge cycle. The relative atomic ratios of SO 3 2− and S 2− during the first cycle for the different Na 2 S‐modified electrodes were determined from the XPS results (Figure 3e,f and Figure S14, Supporting Information).…”