SUBJECT: Ph.D. Proposal Presentation
BY: Sergey Tereshko
TIME: Tuesday, March 31, 2009, 9:30 a.m.
PLACE: MARC Building, 401
TITLE: Study of Space Charge Layers of Hydrocarbon-based Lubricants at Au Surfaces
COMMITTEE: Dr. Steven Danyluk, Chair (ME)
Dr. Peter Hesketh (ME)
Dr. Minami Yoda (ME)
Dr. Valeria Milam (MSE)
Dr. Dennis Hess (CHBE)


This thesis will investigate space charge layers in hydrocarbon based lubricants at Au surfaces using measurements of steady state and transient currents. The characterization of the properties of the electrical double layer (EDL) formed on Au substrates will be made. Finally, the modifications of lubricant chemistry will be linked to electrical measurements and models of electrical conduction will be developed. In this thesis, the indirect measurement of the EDL will be performed by using two parallel plates immersed in oil while an external low frequency waveform is applied to the electrodes. The charge and discharge transient currents will be recorded. The electrodes will be made of Au in order to avoid corrosion effects. The response in the amount of charge stored on the electrodes will be correlated to the composition of the space charge layer, namely, a concentration of a particular chemical component in the oil. Additionally, the screening length, Debye length, will be calculated from the measured transient characteristics and given constants. Direct EDL measurement method plausibility will be assessed based on the results obtained from the transient current measurement and will involve a Vibrating Kelvin probe scan of an interface between a metal and a lubricant in and out of an external electrical field. This method was reported to had been successfully used while measuring potential distributions in dielectric media. The scanning results, obtained using the direct method, could be correlated with the actual EDL's structure, which is expected to contain unique features due to different charge separation phenomena in different samples. A study of the dependence of the EDL's parameters on the known composition of lubricating oil will be performed. In order to validate the results, a theoretical model will be constructed by incorporating known adsorption theories.