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In-situ reflection-XANES study of ZDDP and MoDTC lubricant films formed on steel and diamond like carbon (DLC) surfaces

DOI: 10.1016/j.apsusc.2014.01.116 DOI Help

Authors: Ardian Morina (University of Leeds) , Hongyuan Zhao (University of Leeds) , Fred Mosselmans (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Surface Science , VOL 297 , PAGES 167-175

State: Published (Approved)
Published: February 2014
Diamond Proposal Number(s): 6209 , 6926

Abstract: Chemical characterisation of boundary lubricated interfaces is essential for developing mechanistic models that describe lubricant additive interactions with the surface and their effect on tribological performance. In this study the potential for using the synchrotron-based reflection mode X-ray absorption spectroscopy (XAS) technique for in-situ chemical characterisation of lubricant films has been studied. Thermal films formed from zinc dialkyl dithio phosphate (ZDDP) and molybdenum dialkyl dithio carbamate (MoDTC) lubricant additives have been formed and analysed in-situ using the X-ray absorption near edge structure (XANES) spectroscopy technique. The surface sensitivity of this approach was improved by doing the analysis in reflection mode, enabling analysis of only top layer (up to around 10 nm) of the solid surface. In addition, in-lubro analysis of pre-formed tribofilms from the same additives was done using non-vacuum conditions. The results are discussed in conjunction with XANES and X-ray photoelectron spectroscopy (XPS) analysis of similar additives published in the literature. The results obtained are consistent with the existing ZDDP and MoDTC literature and provide some new insight into intermediate species not reported before. The advantages and disadvantages of the developed XANES methodology for in-situ surface chemical analysis of lubricated conditions are discussed.

Journal Keywords: Lubricant additives; Tribofilm; XANES; MoDTC; ZDDP

Subject Areas: Materials, Engineering, Chemistry

Instruments: I18-Microfocus Spectroscopy

Added On: 19/02/2014 14:27

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