NanoTribochemical Investigation of Advanced Lubricants

Energy and resource losses in moving mechanical components as a result of friction and wear impose an enormous cost on national economies and thus call for the development of new design strategies, engineering systems, and materials with improved properties. Besides allowing significant economic savings, the reduction of frictional losses and the protection of mechanical components from wear can also have beneficial environmental effects, i.e. a reduction in the emission of carbon dioxide or other greenhouse gases.
The goal of the proposed project is to develop an understanding of the mechanism(s) of surface molecular reactivity of a new class of “green” lubricants, i.e. ionic liquids (ILs), under mechanical stress. The gap in our understanding concerning the interaction(s) between ILs and solid surfaces leading to a reduction in friction and wear drastically hinders our ability to predict, control, and improve the behaviour of ILs and motivated the current project.
Through the use of novel analytical methodologies that allow a multi-scale investigation of the processes occurring at buried sliding interfaces in the presence of ILs, insights into the origin of the promising tribological properties of ILs are gained. The project has a strong multidisciplinary character and greatly benefit from the expertise that the fellow acquired from his mobility between research institutions in different countries.
The broader impact of NanoTrIAL is to aid in the rational design and synthesis of new, modified, and improved ILs that can reduce energy and resource consumption in advanced tribological applications. Furthermore, the project implies highly innovative, direct methodological developments that can be broadly applied, thus enhancing European academic and commercial competitiveness.

The project required the use of an highly multidisciplinary, multi-technique approach to gain insights into the reactivity of a class of ionic liquids (imidazolium-based ionic liquids, ILs). As a starting point, the fellow investigated the thermally-induced degradation of neat ILs, thus gaining fundamental information about the chemical reactions occurring in these fluids at elevated temperatures. The outcomes of the experiments were critical for unambiguously interpreting the results of the subsequent tests aimed to shed light on the reactivity of ILs on silicon at elevated temperatures or upon sliding. The systematic study of the effect of the cation (i.e. influence of the length of the alkyl chains attached to the methyl imidazole unit) and the chemical nature of the anion on the stability of the ILs at elevated temperatures and on the formation of reaction layers on silicon upon annealing or sliding allowed the fellow, for the first time, to develop a fundamental understanding of the relationship between the chemical structure of the IL and the resulting functional behavior. These results, which are in the process of being published, are scientifically relevant and of high technological importance, since they can effectively open the path for the rational design of ILs with task-specific performance.

Significant progress beyond the state of the art were made during the reporting period. In particular, the development of a fundamental understanding of the chemical reactions occurring in ionic liquids at elevated temperatures has never received significant attention in the literature. The experiments performed by the fellow demonstrated, for the first time, how these liquids degrade upon annealing. This knowledge is critical for interpreting stress-assisted chemical reactions that take place at tribological interfaces. The potential impact of these new insights is considered very significant since they provide new ideas for rationally designing ILs with task-specific performance

Periodic Reporting for period 1 - NanoTrIAL (NanoTribochemical Investigation of Advanced Lubricants)

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