N-Oleoyl Sarcosine as an Engine Oil Friction Modifier, Part 1: Tribological Performance of NOS+ZDDP Mixture at 100°C

The friction coefficient when a Fe surface was lubricated with an additive mixture of N-Oleoyl sarcosine (NOS), a commercial organic friction modifier, and zinc dialkyldithiophosphate (ZDDP) was measured at 100°C using a ball-on-disk tribometer under boundary lubrication conditions. The sliding surface was observed with a 3D laser microscope to investigate the tribo-film morphology and to evaluate the anti-wear performance. The findings indicate that this additive mixture enhanced tribological lubrication behavior in terms of friction-reducing and anti-wear properties under extended sliding cycle conditions. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX) studies were conducted to analyze the elemental composition of sliding surfaces after tribo-tests and to estimate the friction reduction mechanism of the additive mixture. The EDX results revealed a noticeable decrease in S, suggesting that the NOS suppresses ZDDP decomposition and reduces the adsorption of the decomposition products

N-Oleoyl Sarcosine as an Engine Oil Friction Modifier, Part 2: Elucidation of Friction-Reducing Mechanism at Room Temperature Focusing on Contribution of NOS in NOS+ZDDP Mixture

The tribological properties of a mixture of a commercial organic friction modifier, N-oleoyl sarcosine (NOS), and a commercial anti-wear additive, zinc dialkyldithiophosphate (ZDDP), were investigated. The results suggest a synergistic effect between these two additives, resulting in a mixture that exhibited the lowest and most stable friction coefficient as well as the smallest wear area. X-ray photoelectron spectroscopy was performed to investigate the chemical composition of the tribo-films formed using this mixture. The results suggest that the tribo-films lacked S as well as PO4³⁻ species. They also suggest that ZDDP mitigates degradation of the NOS, and improve the tribo-film durability thus improving anti-wear/friction-reducing performance. These results elucidate the synergistic friction-reducing tribological mechanism of the NOS+ZDDP mixture

Photocatalytic reduction of CO2 using H-2 as reductant over ATaO(3) photocatalysts (A = Li, Na, K)

ATaO3 (A = Li, Na, K) compound oxides exhibit photocatalytic activity for the reduction of CO2 in the presence of H2. Only CO gas was generated over all samples under photoirradiation. The photocatalytic activity was higher in the order corresponding to KTaO3, NaTaO3 and LiTaO3 (LiTaO3 > NaTaO3 > KTaO3). The order of the photocatalytic activities was consistent with that of the Eg (optical gap) values. After 24 h of photoirradiation, the amount of evolved CO reached 0.42 μmol g−1 over LiTaO3. TPD experiments indicated that the broad peak which is assigned to chemisorbed CO2 gas was observed at 573 K in the case of LiTaO3. On the contrary, there was no peak in the spectra of NaTaO3 and KTaO3. The amount of evolved CO gas almost strongly depends on the amount of chemisorbed CO2 in the case of ATaO3 (A = Li, Na, K). In addition, the photocatalytic activity increased with increasing the calcination temperature of LiTaO3. This means that a smooth charge separation in a LiTaO3 photocatalyst and chemisorption of CO2 on the surface contribute to effective reduction of CO2 in the presence of H2

Relationship between interfacial adsorption of additive molecules and reduction of friction coefficient in the organic friction modifiers-ZDDP combinations

Organic friction modifiers (OFMs) are often used with zinc-dialkyl-dithio-phosphate (ZDDP) in engine oil formulations to reduce boundary friction while maintaining the anti-wear property of ZDDP. This study investigated the interaction between fatty acids and ZDDP. The results showed that the adsorption of fatty acids determines the friction coefficient when fatty acids are used alone. The friction coefficient was smaller when a denser fatty acid adsorbed layer was formed. Neutron reflectivity (NR) measurement revealed that, for a fatty acid-ZDDP combination, the fatty acid also contributes to friction behavior; a synergistic effect occurred only with a reduction in the interface metal thickness. These results suggest that the fatty acid-ZDDP combination promotes metallic soap formation, which reduces friction