Tribological Characterization of Several Silicon-Based Materials Under Ionic-Liquids Lubrication

Abstract

The tribological behaviors of three silicon-based materials (low temperature silicon oxide (LTO), polysilicon (Poly Si) and silicon nitride (Si3N4) films) under ion liquids (ILs) lubrication have been investigated by varying the applied load and the sliding velocity. An atomic force microscope and a nanoindentor were used to characterize the deposited films, and the worn surfaces after frictional tests were analyzed by an optical microscope, a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) and an X-ray photoelectron spectrometer (XPS). The results show the best lubricating properties of the IL lubricants are obtained at the intermediate load of 150 g for the three tribo-pairs. For the Si3N4/Si3N4 tribo-pair, the coefficients of friction (COFs) and the wear rates under ILs lubrication are larger than those under dry friction. The COF values decrease with sliding velocity, and the COFs of the Si3N4/Si3N4 tribo-pair are greater than the ones of the other two tribo-pairs (LTO/Si3N4 and Poly Si/Si3N4) at low velocities. The COF of 1-ethyl-3-methylimidazolium tetrafluoroborate is nearly 3 times larger than the other two IL lubricants (1-butyl-2,3-dimethylimidazolium tetrafluoroborate and N-butylpyridinium tetrafluoroborate) for the Si3N4/Si3N4 tribo-pair. The differences in COFs between the latter two lubricants for the three tribo-pairs are negligible. Different mechanisms of these results have been analyzed in the paper.