Degree Type

Dissertation

Date of Award

1990

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Patricia A. Thiel

Abstract

We have studied the interactions of water and perfluorodiethyl ether on Ru(100) in order to model the effects of surface structure and humidity on the bonding and decomposition of perfluoroalkyl ether lubricants with metal surfaces. In order to understand the interactions on Ru(100), we have first investigated the interactions of each of these adsorbates alone on the clean surface;The interactions of perfluorodiethyl ether on Ru(100) have been compared to published results on the Ru(001) surface in order to understand the effect of surface morphology on the bonding and decomposition of this molecule. Thermal desorption studies of this system show very little change in the surface-ether bond energy due to the change in surface morphology (37 and 39 kJ/mol on Ru(100) vs. 42 kJ/mol on Ru(001)) and no change whatsoever in the degree of decomposition;The interactions of water with Ru(100) have been studied using both thermal desorption spectroscopy (TDS) and electron energy loss spectroscopy (EELS). From these studies we conclude that a small amount of water dissociates on this surface (5-10% of a monolayer), but water is adsorbed in a predominantly molecular form on this surface with an increasing degree of hydrogen-bonding with increasing coverage;The effects of hydrogen ad oxygen coadsorption on the interactions of water with this surface have also been studied using TDS. We observe an upward shift in the temperature of the multilayer water chemisorption feature due to the presence of either of these coadsorbates, and at low water coverages we observe an upward shift of as much as 65 K in the monolayer water feature due to the presence of coadsorbed oxygen;Finally, the interactions of coadsorbed water and perfluorodiethyl ether on Ru(100) have been investigated using TDS. We observe an interesting competition between these two Lewis bases on Ru(100). Both form weaker metal-adsorbate bonds due to the presence of the other. We postulate that this effect is either a site-blocking phenomenon or that some sort of through-metal effect occurs. These experiments highlight the possible importance of humidity on surface-lubricant bonding for perfluoropolyether lubricants.

DOI

https://doi.org/10.31274/rtd-180813-10281

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Pamela Kaye Leavitt

Language

en

Proquest ID

AAI9035091

File Format

application/pdf

File Size

172 pages

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