Tribochemistry in the analytical UHV tribometer

The knowledge of tribochemical reactions in boundary lubrication in the pre sence of lubricant additives is fundamental in order to improve chemical en gineering of new molecules, multifunction compounds and to predict interact ions between these additives. Experiments with in lubro, ex situ or post-mo rtem analyses are difficult and even dangerous to exploit because of numero us artefacts. We introduce two special approaches to simulate boundary lubr ication tribochemistry. Basically, these approaches use a dedicated analyti cal UHV tribotester allowing in situ AES/XPS analysis of both counterfaces and introduction of partial pressure of gases during friction. The first mo del experiment is UHV friction on previously formed tribofilms from a lubri cated test. The second experiment is gas phase lubrication with ethyl phosp hate. The results reveal some fundamental aspects of the origin of friction -reduction by transfer of MoS2 single sheets. The reaction of friction-acti vated nascent surfaces with gases is also emphasised. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.