Graduation Semester and Year

2016

Language

English

Document Type

Thesis

Degree Name

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

First Advisor

Pranesh Aswath

Abstract

Stringent government regulation on environment emissions and demand to develop energy efficient and durable modern mechanical systems has imposed a significant challenge on the lubricant additive manufacturer to develop environment friendly and high performance additives for the lubricating medias like oil and grease. The current industrial additive technology is dominated by phosphorus and sulfur containing the liquid antiwear additive, Zinc dialkyl dithiophosphate and extreme pressure solid additives like Graphite, Molybdenum disulfide. This current additive package possesses harm to the environment and has already met performance limit for applications working under severe operating condition. A proposed solution to combat with this problem is the use of ionic liquid as the next generation green lubricant additive. The unique properties of the ionic liquids such as negligible volatility, nonflammability, and high thermal stability make them potential candidate as an antiwear additive. Also, with the advent of nanotechnology, nanoparticles have recognized considerable attention as solid additives in lubricating oils and greases. In this research study, the nature of the interaction between ionic liquids and carbonaceous materials like carbon nanotube and soot is considered and is correlated with the tribological performance of the lubricating media, engine oil, and grease. This thesis work is divided into two main section, first section deals with the tribological performance of the combined solid and liquid additive chemistry of multi-walled carbon nanotube (MWCNT) and ionic liquid in lithium lubricating greases, while, the second section is about evaluating the potential of ionic liquid in minimizing the detrimental effect of the increased soot contamination in the engine oil. As an attempt to study the interaction of MWCNT and ionic liquids, the first approach was to determine the optimal concentration of MWCNT as an antiwear additive in lithium based grease is investigated by analyzing the friction and wear results generated during four ball standard ASTM D2266 test. The results indicate the MWCNTs at optimal concentration of 1wt% decreases the wear by 25% and friction by 39%. Secondly, the antiwear and antifriction performance of the four different ionic liquids in lithium grease was investigated. The excellent antiwear property of the ionic liquid is attributed to the formation of protective phosphate tribofilms on the interacting surfaces. In addition, ionic liquids were blended with the MWCNT to study the synergism between novel solid-liquid combined chemistry. The addition of hydroxyl functionalized MWCNT at 1wt% with the ionic liquid having phosphonium cation and dithiophosphate anion results in the comparable tribological behavior to the grease blends with the MWCNT and ionic liquid alone. Second Section of the thesis describes the influence of the increased soot contamination on the diesel engine wear. First, the abrasive nature of the soot was examined by using X-ray absorption near edge spectroscopy and high temperature X-ray diffraction. Then the oil formulations were prepared by dispersing the diesel engine soot with three different antiwear additives, namely, ashed Zinc dialkyldithiophosphate, ashless alkyl dithiophospahte and an ionic liquid. The soot concentration at 10wt% exhibits the extremely high wear in the presence of all the three additives. The soot abrades the protective tribofilms formed by antiwear additives and results in sever wear.

Keywords

Ionic Liquid, Multiwalled Carbon nanotubes, Diesel engine soot, lithium grease, wear

Disciplines

Engineering | Materials Science and Engineering

Comments

Degree granted by The University of Texas at Arlington

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