AVS 45th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS-MoM

Paper AS-MoM4
An Investigation of the Surface Chemistry of Lubricant Additives on Steel by NEXAFS Spectroscopy

Monday, November 2, 1998, 9:20 am, Room 307

Session: Materials Analysis (including Small Dimensions and Synchrotron)
Presenter: T.S. Rufael, Texaco Inc.
Authors: T.S. Rufael, Texaco Inc.
J.K. Mowlem, Texaco Inc.
D.A. Fischer, National Institute of Standards and Technology
Correspondent: Click to Email
Molecular level investigations of highly complex adsorption systems, such as the lubrication process in automotive parts, provide a challenge for mechanistic understanding and spectroscopic identification of surface intermediates. In this study, Near-Edge X-ray Absorption Fine Structure Spectroscopy is used to probe the surface reactions of a well-known anti-wear additive, zinc dialkyl dithiophosphate (ZDDP), and a novel friction modifier, molybdenum dithiocarbamate (MoDTC) on a polished steel alloy surface. Thin films from representative concentrations of ZDDP and MoDTC in base oil have been studied individually as well as in combination with each other following thermal processing at temperatures conducive for ZDDP decomposition. Soft X-ray absorption at the oxygen K-, carbon K-, iron-L, zinc L-, and molybdenum M-edges has been used to examine the structural and chemical changes taking place at the interface. In addition, we have investigated the effect of a model pro-oxidant, cumene hydroperoxide (CHP), on the above systems. We discuss the suitability of NEXAFS spectroscopy to study such complex adsorption systems by presenting results from these model lubricant systems.