Effects of surface chemistry on the mechanochemical decomposition of tricresyl phosphate.
File(s)
Published version
Author(s)
Ogbomo, Egheosa
Bhuiyan, Fakhrul H
Latorre, Carlos Ayestarán
Martini, Ashlie
Ewen, James P
Type
Journal Article
Abstract
The growth of protective tribofilms from lubricant antiwear additives on rubbing surfaces is initiated by mechanochemically promoted dissociation reactions. These processes are not well understood at the molecular scale for many important additives, such as tricresyl phosphate (TCP). One aspect that needs further clarification is the extent to which the surface properties affect the mechanochemical decomposition. Here, we use nonequilibrium molecular dynamics (NEMD) simulations with a reactive force field (ReaxFF) to study the decomposition of TCP molecules confined and pressurised between sliding ferrous surfaces at a range of temperatures. We compare the decomposition of TCP on native iron, iron carbide, and iron oxide surfaces. We show that the decomposition rate of TCP molecules on all the surfaces increases exponentially with temperature and shear stress, implying that this is a stress-augmented thermally activated (SATA) process. The presence of base oil molecules in the NEMD simulations decreases the shear stress, which in turn reduces the rate constant for TCP decomposition. The decomposition is much faster on iron surfaces than iron carbide, and particularly iron oxide. The activation energy, activation volume, and pre-exponential factor from the Bell model are similar on iron and iron carbide surfaces, but significantly differ for iron oxide surfaces. These findings provide new insights into the mechanochemical decomposition of TCP and have important implications for the design of novel lubricant additives for use in high-temperature and high-pressure environments.
Date Issued
2024-01-07
Date Acceptance
2023-11-28
Citation
Physical Chemistry Chemical Physics, 2024, 26 (1), pp.278-292
ISSN
1463-9076
Publisher
Royal Society of Chemistry
Start Page
278
End Page
292
Journal / Book Title
Physical Chemistry Chemical Physics
Volume
26
Issue
1
Copyright Statement
This journal is © the Owner Societies 2024 This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/38059507
Publication Status
Published
Coverage Spatial
England
Date Publish Online
2023-11-30