Ultra-High Vacuum Studies of Model Boundary Layer Lubricants

Surface Analytical Techniques have been used to probe the structure and surface chemistry of model boundary layer lubricants adsorbed onto single-crystal metal surfaces under ultra-high vacuum conditions. Chapter 3 presents results from the adsorption of a set of straight-chain carboxylic acids and perfluorinated carboxylic acids onto the Ag(110) surface. The carboxylic acids are found to desorb reversibly from the clean Ag(110) surface. For monolayer coverages of the acids, the corresponding peak temperature maximum in the Temperature Programmed Desorption spectrum increases by roughly 10-15 K as the alkyl chain length is increased. This corresponds to an increase in the activation energy of desorption by 0.94 $\pm$ 0.01 kcal/mol/-CH$\sb2$ group. On the preoxidized Ag(110) surface, the carboxylic acids undergo an acid-base reaction with the adsorbed oxygen to form water and the corresponding carboxylate. The carboxylates then decompose under heating to form CO$\sb2,$ hydrocarbons, and other products. The perfluorinated acids adsorbed onto the clean Ag(110) surface spontaneously deprotonate to form the perfluorocarboxylate. Perfluorination of the alkyl chain lowers the barrier for deprotonation of the acid which increases the rate of formation of the perfluorocarboxylate intermediate. The perfluorocarboxylates decompose near 600 K to give CO$\sb2$ and fluorine-containing products.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Parker, Bryan Robert

Contributors dc:contributor

• Gellman, A.J.

• Chemistry, Physical

Identifier

(UMI)AAI9411748

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/72292