Analysis of tribochemical decomposition of two imidazolium ionic liquids on Ti–6Al–4V through Mechanically Stimulated Gas Emission Spectrometry

Abstract

Mechanochemical degradation of imidazolium bis(trifluoromethanesulfonyl)imide room-temperature ionic liquids (RTIL) with alkyl and mPEG side groups on Ti¿6Al¿4V substrate was studied through analysis of gas triboemission and Raman spectroscopy. In vacuum the RTIL with longer mPEG chain had better lubricity due to its higher capacity for tribochemical passivation. Raman spectroscopy showed possible bonding of fluorine to the substrate. Mechanical stimulus caused degradation of both anionic and the cationic moieties that further reacted with the substrate and with each other. The relevant decrement of water content during rubbing was found attributable to the proper RTIL and not only to the absorption on the substrate. No volatile sulphur compounds were found supporting the hypothesis of their bonding to Ti substrate.This work was financially supported by the Spanish Ministry of Economy and Competitiveness with the participation of the European Regional Development Fund under the projects RYC-2009-0412, BIA2011-25653 and IPT-2012-1167-120000. The authors acknowledge the contribution of the COST Action CM1207