Alcohols Adsorbed On SiO2 Under Ambient Conditions – From Fundamentals of Adsorption Isotherm and Molecular Orientation to Applications in Tribology

The adsorption isotherm and orientation of small alcohol molecules on clean, hydrophilic silicon oxide surfaces under ambient conditions are studied and their effects on adhesion, friction, and wear of silicon oxide surfaces are explained. The attenuated total reflection infrared spectroscopy (ATR-IR) study reveals that as the isotherm thickness and the molecular orientation of the adsorbed alcohol layers are closely related. Even though the thickness of the adsorbed alcohol layers is only an order on 1 nm, its effects on adhesion, friction, and wear of the silicon oxide surfaces is quite remarkable. The nano-asperity capillary force due to the adsorbed alcohol layer is experimentally measured with an atomic force microscopy (AFM) and theoretically explained. The influence of chain length on friction forces is investigated for ethanol, 1-butanol, and 1-pentanol vapor-phase lubricants on silicon oxide surfaces with AFM. The experimental friciton-load curves are analyzed using contact mechanics to reveal the effects of the adsorbed alcohol layers on friction. Finally, the wear prevention effects of alcohols are experimentally and theoretically investigated.