In Situ Tribochemical Characterization of Nanolubricants
Abstract
Lubrication plays important roles in mechanical systems in motion. The challenge in understanding the characteristics of a lubricant under working conditions lies in its dynamic nature, and it is impossible to observe the target directly. The objective of this thesis research is to obtain better fundamental understanding of nanolubricants under shear. Specifically, a methodology that enables in situ detection of a rubbing pair is developed. Using this approach, the properties and performance of nanoluricants are studied. The resulting tribochemical products as tribofilms are investigated.
This research consists investigation in three aspects. The first is to develop in situ triboelectrochemical techniques enabling basic study. An integrated tribotesting system combined a disc-on-disc tribotesting with electrochemical impedance measurement.
The second is to study the properties of working lubricants, their electrical and thermal properties. The electrical conductivity against the oil film thickness was examined. Results showed the non-ohmic behavior of a lubricating film in the hydrodynamic regime. Properties of lubricants and testing conditions are some of the factors affecting the conductivity. The study on thermal performance over a mineral oil and polyalphaolefin (PAO) were carried out. Results showed that thermal properties of lubricants depended on the shear and they were not constants as being known. This research revealed the potential existence of dynamic properties of a working lubricant.
The third is to investigate tribochemical interactions between nanolubricants and rubbing surfaces of a substrate. Using α-ZrP nanoparticles as additives, a nanolubricant produced a tribofilm with consistent electrical properties that reduced friction for 40% and wear 90%. Research results showed that under shear, a tribofilm consisting of pyrophosphate.
Citation
Chen, Yan (2021). In Situ Tribochemical Characterization of Nanolubricants. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /200834.