Dissertation
Understanding superlubricity of in situ formed tribofilms by magnesium hydrosilicate nanoparticles
Doctor of Philosophy (PhD), Washington State University
01/2015
Handle:
https://hdl.handle.net/2376/118393
Abstract
Numerous members of the broad magnesium hydrosilicates family were successfully employed as solid powder anti-wear additives to oil-based liquid lubricants. This research shows that such powders dispersed in hydrocarbon lubricating media interact with steel rubbing surfaces and form tribofilms with unique self-regulating properties, this inspired the idea to characterize the result as a "self-repair effect" and friction coefficient reaching superlubricity levels (< 0.01) under conditions where boundary lubrication is typically observed. However, the mechanism of such film formation and its structure are yet to be understood.
The parametric study of the tribofilm formation process and its dependence on the structural composition of employed natural and synthesized powders is performed. Friction and wear tests had been done in reciprocating pin on plate, four ball and block on ring configurations. Source powders and the resulting film were characterized by means of Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Focused Ion Beam Imaging,
Transmission Electron Microscopy, Electron Energy Loss Spectroscopy, X-ray Diffractometry, Time of Flight Secondary Ions, Fourier Transform Infrared and Raman spectroscopy. This characterization allowed to resolve the debate regarding the mechanism of protective film formation. The mechanism for the film formation process proposed includes selective adherence of nanoparticles to a surface, tribochemical change in powder structure due to hydration level, the catalytic promotion of oil carburization and oxidation and selective diffusion of ions into the matrix. The very top layer of the film found to be a silica rich amorphous carbon in Diamond Like Nanocomposite structure. Following an explanation of the effects of powder material hydration and structure, as well as film formation mechanism, the thermodynamic model is proposed to screen and design new class of film forming lubricating oil additives with superior tribological properties tailored for industrial use. A wide implementation of such additives will help to reduce wear, save resources and energy.
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Details
- Title
- Understanding superlubricity of in situ formed tribofilms by magnesium hydrosilicate nanoparticles
- Creators
- Pavlo Rudenko
- Contributors
- Amit Bandyopadhyay (Advisor)Susmita Bose (Committee Member)Konstantin Matveev (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Materials Science and Engineering Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 209
- Identifiers
- 99900581732701842
- Language
- English
- Resource Type
- Dissertation