Abstract
Sum-frequency vibrational spectroscopy has been used to obtain the vibrational spectra of oleic acid dissolved in PAO and stearic acid dissolved in ethanol adsorbed at iron-based materials-lubricants interface. The surface structures inferred from the vibrational spectra. The relative intensities of the d^+ (symmetric stretch of methylene group) and r^+ (symmetric stretch of terminal methyl group) modes, which provide a useful measure of the conformational order of hydrocarbon chain, were varied depending on the substrate material. This result indicates that the surface structures of adsorbed oleic acid and stearic acid depend on the substrate material and additives.
