AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP3
A Novel Study using XANES Spectroscopy, XPEEM, and Nanoindentation Techniques to Correlate the Microchemistry and Nanomechanical Properties of Zinc-dialkyldithiophosphate Tribofilms on Steel Surfaces

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: M.A. Nicholls, The University of Western Ontario, Canada
Authors: M.A. Nicholls, The University of Western Ontario, Canada
P.R. Norton, The University of Western Ontario, Canada
M. Kasrai, The University of Western Ontario, Canada
G.M. Bancroft, The University of Western Ontario, Canada
T. Do, Atomic Energy of Canada
G. De Stasio, The University of Wisconsin, Madison
Correspondent: Click to Email
Additives with special functions have long been components of engine oils, designed to improve the performance and prolong the life of an engine. One particular additive, zinc-dialkyl-dithiophosphate (ZDDP) has been added to improve the lifespan of an engine by reducing wear at high pressure contacts. ZDDPs have been found to break down under the extreme conditions in an engine and produce products that, under high pressure and temperature, form a sacrificial polyphosphate film that reduces wear. This film has been studied thoroughly for decades, but the origins of its effectiveness still remain a mystery. Advanced synchrotron radiation techniques such as X-ray absorption near edge structure (XANES) spectroscopy and X-ray photoelectron emission microscopy (XPEEM), are now providing the detailed chemical and spatially resolved chemical analysis required to help understand how these films form. In combination with nanoindentation techniques, it is now possible to measure the chemical and nanomechanical properties of these films on the same length scales. We describe how XANES can determine the polyphosphate chain-length in a film, and also illustrate the interaction of ZDDP decomposition products with steel surfaces. Further, XPEEM and nanoindentation have been used to correlate, for the first time, the spatially-resolved chemistry and mechanical properties of the same, selected regions of an antiwear film at a resolution of approximately 200 nm.