Session: 15-01-01: ASME International Undergraduate Research and Design Exposition

Paper Number: 151795

151795 - Choline Amino Acid Ionic Liquids: Sustainable and High-Performance Lubricants and Additives 

Friction and wear are processes that occur between two interacting surfaces in relative motion. The outcomes of these interactions affect the material condition over time, often in a deteriorating way. In tribology, researchers develop lubricants to introduce between the contacting surfaces, reducing friction and wear in machine elements. Lubricants also carry significant economic benefits by reducing energy consumption and maintenance costs. However, conventional lubricants are non-biodegradable and can negatively impact the environment. Therefore, there is an increasing demand for eco-friendly alternatives, and choline amino acid ionic liquids (CHAAILs) have emerged as promising environmentally-friendly lubricants. In this work, the tribological performance of the three CHAAILs, each with the same choline cation and different amino acid anions (leucine, isoleucine, and aspartic acid), is studied both as neat lubricants and additives to a low viscosity polar oil at different loads. 

The three CHAAILs were synthesized in our laboratory using leucine, isoleucine, and aspartic acid as acids and choline hydroxide as the base. Viscosity measurements at different temperatures and thermogravimetric analysis were carried out to characterize the three CHAAILs. Each of the CHAAILs was mixed at 1 wt.% with a commercially available low-viscosity esterex polyol ester (EST) base oil to form a stable mixture. Using a ball-on-flat tribometer, three friction tests were run by placing AISI 52100 steel balls against AISI 52100 steel polished disks, and 2 ml of each lubricant was added at the initial of the test. All tests were performed with a controlled frequency of 5 Hz, a stroke length of 3 mm, and a sliding distance of 108 m. Three different loads were studied: 0.5N, 3N, and 6N to investigate the effect of the pressure on the lubricating behavior of the CHAAILs. After each friction test, optical and electron microscopy, 3D profilometry, and energy dispersive spectroscopy (EDS) and Raman spectroscopy were employed to characterize the worn disk surfaces and elucidate the lubricating mechanism.

Results show variations in friction and wear among the different CHAAILs and the load used. For all lubricants, friction was higher at the lower load studied. This may be due to the initial asperity contacts at low loads taking longer to smooth out, combined with wear debris at higher loads potentially acting as a third body to reduce friction. Additionally, the formation of a tribolayer at higher pressures that effectively reduced friction may also contribute to this phenomenon. As neat lubricants, the use of any CHAAILs resulted in lower friction than the polar base oil. Adding 1 wt.% of any of the CHAAILs slightly reduced friction at the highest load studied. At all loads studied, tests lubricated with neat CHAAILs exhibited less steel wear than that observed with the polar EST base oil. No major differences were found in steel wear when the 1 wt.% of any CHAAILs was added to EST at 0.5N and 3N. However, a 15% wear reduction was observed when choline leucinate was used as a 1 wt. additive to the base oil at the highest load of 6N. Preliminary results showed the formation of oxygen- and carbon-rich layers when lubricating with CHAAILs may be responsible for their improved lubricating ability. Further research work is ongoing to explore the practical viability of CHAAILs as green lubricants in real-world applications.

Presenting Author: Esmond Lau Rochester Institute of Technology

Presenting Author Biography: Esmond Lau was born and grew up in Flushing, New York City, in 2002. He graduated from Townsend Harris High School at Queens College in 2021. He is currently a fourth-year student at Rochester Institute of Technology, Rochester, NY, where he is pursuing a dual degree in Mechanical Engineering (BS/ME) and a minor in Business. From the summer to winter of 2023, he worked as an intern for the Sensors and Electron Devices program at DEVCOM Army Research Laboratory, Adelphi, MD, administered by Oak Ridge Associated Universities. Last summer of 2024, he worked as a research assistant for the Tribology lab at RIT, exploring tribological behavior of Choline Amino Acid Protic Ionic Liquids as neat lubricants and additives. His areas of interest in Mechanical Engineering include mechanical design, powertrain system, and mechatronics.

Authors:

Esmond Lau Rochester Institute of Technology
Moni Chavez Rochester Institute of Technology
Davis Kipkania Kiboi Rochester Institute of Technology
Patricia Iglesias Rochester Institute of Technology