Surface analytical studies of surface-additive interactions, by means of in situ and combinatorial approaches

Rossi, Antonella; Eglin, Michael; Piras, Federica M.; Matsumoto, Kazuya; Spencer, Nicholas D.

doi:10.1016/j.wear.2003.10.001

Cited by 41 publications

(35 citation statements)

References 26 publications

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“…Although the majority of the previous studies focused on using mainly ex-situ techniques, there is also a number of studies that attempted to probe the chemistry and composition of various materials using in-situ techniques such as vacuum XPS [39,40], Raman spectroscopy [23,41] and Attenuated Total Reflectance (ATR)-FTIR [42,43]. However, these techniques have some drawbacks in addition to their advantages.…”

Section: Introductionmentioning

confidence: 99%

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

Dorgham

Neville

Ignatyev

et al. 2017

Review of Scientific Instruments

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The complex tribochemical nature of lubricated tribological contacts is inaccessible in real time without altering their initial state. To overcome this issue, a new design of a pin-on-disc tribological apparatus was developed and combined with synchrotron X-ray absorption spectroscopy (XAS). Using the designed apparatus, it is possible to study in situ the transient decomposition reactions of various oil additives on different surfaces under a wide range of realistic operating conditions of contact pressure (1.0–3.0 GPa), temperature (25–120 °C), and sliding speed (30–3000 rpm or 0.15–15 m/s). To test the apparatus, several tribological tests were performed at different shearing times ranging from 2.5 to 60 min. These tests were carried out under helium atmosphere at a temperature of 80 °C, contact pressure of 2.2 GPa, and sliding speed of 50 rpm. The XAS experiments indicate that the zinc dialkyldithiophosphate antiwear additive decomposes in the oil to form a tribofilm on the iron surface at different reaction kinetics from the ones of the thermal film. The tribofilm composition evolves much faster than the one of the thermal film, which confirms that the formation of the tribofilm is a thermally activated process similar to the one of the thermal film but accelerated by shear. Furthermore, the results indicate that the sulfur of the formed film, whether a tribofilm or a thermal film, appears initially in the form of sulfate, with some sulfide, which under heat or shear is reduced into mainly sulfide.

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Section: Introductionmentioning

confidence: 99%

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

Dorgham

Neville

Ignatyev

et al. 2017

Review of Scientific Instruments

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“…This latter characteristic will turn out to be very useful when the method proposed here for chain-length determination is applied to real systems, which very often may contain hydrogen as a cation. ToF-SIMS imaging of elements (Zn, Fe, Ca, P, S) and low-mass ions (PO, PO 2 , PO 3 ) has already been successfully applied to tribological samples [56][57][58][59]. Murase and Ohmori investigated [60] the adsorption and reaction of phosphate-type lubricant additives (zinc-and sulfur-free) on ferrous materials by ToF-SIMS.…”

Section: Introductionmentioning

confidence: 99%

Chain-length-identification strategy in zinc polyphosphate glasses by means of XPS and ToF-SIMS

et al. 2012

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The surface chemistry of amorphous zinc polyphosphates of different compositions (ranging from zinc metaphosphate to zinc orthophosphate) has been investigated by means of X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectroscopy (ToF-SIMS). The identification of the chain length of zinc polyphosphates by XPS was on the basis of the integrated intensity ratio of the bridging (P-O-P) and nonbridging (P = O and P-O-M) oxygen peaks used for fitting the oxygen 1s signal, the shift of the P 2p(3/2) signal towards lower binding energies and the modified Auger parameter towards higher values as the zinc content increases. The discrimination of the polyphosphate chain lengths was also achieved by ToF-SIMS, by comparing the intensities of selected characteristic phosphate fragments. Both techniques appear to be suitable for the investigation of polyphosphate glasses in applications such as tribology, where there is a need to identify the chain length present in the outermost monolayer of the film. Fourier-transform infrared (FT-IR) spectroscopy was used to characterize the bulk compounds. The FT-IR studies showed that long-chain structures linked through P-O-P bonds predominate in the metaphosphate composition, while when the zinc content is increased, the chains become shorter, ultimately being replaced by PO(4) monomers in the orthophosphate composition.

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“…Other than surface characterization of AW films, another ''hot'' research spot is the study on additive interactions between ZDDPs and other additives such as detergents, dispersants and molybdenum dithiophosphates (MoDTCs) [28][29][30][31][32][33]. The fundamental understanding of the reactions between the ZDDPs alone with metallic surfaces is of great importance to the binary additive systems or the formulated package.…”

Section: Introductionmentioning

confidence: 99%

Studies on ZDDP Anti-Wear Films Formed Under Different Conditions by XANES Spectroscopy, Atomic Force Microscopy and 31P NMR

Pereira

Kasrai

et al. 2007

Tribol Lett

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Antiwear (AW) films, generated from a mineral base oil containing a zinc dialkyl dithiophosphate (ZDDP) additive, were studied as a function of formation temperature, load and rubbing time. The surface morphology of these films was investigated using atomic force microscopy (AFM), and surface roughness calculated for the observed differing surface morphologies. The morphology of the films is heterogeneous for all the tested conditions, but the surface roughness is dependent on the rubbing condition. X-ray absorption near edge structure (XANES) spectroscopy has been used to characterize the chemistry of these films, and the intensity of the phosphorus K-edge was also used to monitor their thickness. The thickness of these films is in the range of 10-90 nm depending on the running conditions. Phosphorus L-edge spectra show that these films have a similar chemical nature with variable polyphosphate chain-lengths. 31P NMR was used to study the decomposition of ZDDP in the residual oils. The spectra show that the primary and secondary ZDDP react differently under the various conditions. The tribological characteristics of these AW films were probed by measuring the coefficients of friction (l) and the wear scar width (WSW) of the counter faces. l is highly related to the applied load and the results of WSW measurements show that the wear performance is related to all the tested parameters, temperature, load and rubbing time.

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Surface analytical studies of surface-additive interactions, by means of in situ and combinatorial approaches

Cited by 41 publications

References 26 publications

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

An in situ synchrotron XAS methodology for surface analysis under high temperature, pressure, and shear

Chain-length-identification strategy in zinc polyphosphate glasses by means of XPS and ToF-SIMS

Studies on ZDDP Anti-Wear Films Formed Under Different Conditions by XANES Spectroscopy, Atomic Force Microscopy and 31P NMR

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