[Zurück]

K. Psychogyiopoulou, A. Tomala, W.S.M. Werner, I. Gebeshuber, N. Dörr, H. Störi:
"Tribochemistry of isomer and oligomer lubricant films";
Poster: Electrochem 2008, Liverpool/UK; 15.09.2008 - 17.09.2008; in: "Book of Abstracts, Electrochem 2008", (2008), S. P-34.

Additives are of crucial importance in lubrication technology. Additive molecules physisorbed or chemisorbed onto surfaces form lubricating films fundamentally influencing wear and friction properties of two rubbing surfaces.
Earlier experiments in the macrorange as well as in the nanorange showed that the oligomers of ethanolamine and isomers of hydroqyquinoline have different lubrication properties on 100Cr6 steel and copper, respectively. Ethanolamines act as multidentate ligands on the base of amino, hydroxyl and deprotonated hydroxyl groups of the total formula NH3-nRn (R = CH2CH2OH, n = 1 to 3). Mono-, di- and triethanolamine are readily water soluble and are utilised as additives in metalworking fluids. The understanding of the lubrication mechanisms of the additive layer chemisorbed on the specimens investigated yields important information regarding lubrication optimisation concerning the type of additive, type of isomer or oligomer and amount.
The aim of this present study was to find out the influence of oxygen and nitrogen containing substances on tribological behaviour. X-ray photoelectron spectroscopy is used to obtain insight into the molecular mechanisms leading to the macroscopic lubricity. Monomolecular lubricant films were deposited onto ultra thin copper films sputtered onto silicon wafers and on finely polished 100Cr6 steel blocks. The surfaces prepared with the three ethanolamine oligomers and hydroxyquinoline isomers were investigated by X-ray Photoelectron Spectroscopy with an electrochemistry adsorption device extension.
X-ray photoelectron spectroscopy investigations were performed using a VG ESCALAB Mk III equipment with a prototype preparation chamber, permitting the transfer of samples from liquid to the analysis chamber under Helium protective gas preventing exposure to ambient conditions. The solution with a concentration of 250 ppm ethanolamine oligomer and hydroxyquinoloine isomer, respectively, in double distilled water was transferred into the adsorption device, which is an extension of the spectrometer. The structure of the molecular film is elucidated using angular resolved X-ray photoelectron spectroscopy. The results showed that ethanolamine oligomer molecules are packed differently on the copper and on the steel surface. Furthermore hydroxyquinoline isomers bond to surface by the hydroqyl group, and have the amino group on the top, comparable to the ethanolamine oligomer on the steel surface. On copper, ethanolamines bond to the surface by the amino group and have the hydroxyl group on the top.