IoNanoFluids – ‘ionic liquid-nanocarbon’ hybrids as superlubricants in metal-polymer friction pairs

Funding: 1 458 764 PLN

Duration: 4 October 2021 – 3 October 2024

Leader: Silesian University of Technology, Gliwice

Partner: Poznan University of Technology, Poznan

Abstract

Carbon nanomaterials (CNs) such as carbon nanotubes (CNTs) and graphene reveal exceptional physical and chemical properties in many aspects outperforming numerous conventional materials. Thus, CNs attract worldwide scientific interest. One of the most notable CNs’ properties is superlubricity – a state where the friction between two sliding surfaces nearly vanishes. Until now, this effect was confirmed in several studies, however, the vast majority of the measurements were performed on the nanoscale using electron microscopes – and for surfaces as small as invisible to the unarmed eye.

Contrary to the above high-cost and time-consuming studies, our preliminary tests performed using a tribometer, and on the macro-scale surfaces, as large areas as for typical rotating and sliding machines parts, also confirmed the superior lubricating properties of CN-based liquids. And so, when introducing our initially elaborated grease containing CNTs between plastic blocks sliding on the steel ring, we observed friction incomparably lower than for any high-quality commercially available grease. Importantly, it should be noted that, nowadays, plastic components are extensively used in cars, aircraft, home printers, and practically any general application. Plastic sliding elements are used in inexpensive and simple mechanisms but critically in safety-relevant applications such as key elements of car steering systems. In the future, a new class of lubricants reducing friction and wear on plastic surfaces will make the field of CNs’ applications even wider, eventually making the products broadly available, less expensive but more efficient.

What we have also observed was that the friction depended strongly on the CNTs’ purity, type of the plastic sliding on the metal ring, and type of the liquid in which CNTs were dispersed. Consequently, the goal of our project is to develop and produce lab-scale lubricants containing CNs that outperform conventional greases in the reduction of friction on polymer surfaces. Targeting this goal, we will apply ionic liquids and their solutions allowing us, on one hand, to obtain time- and operation-stable dispersions and to increase lubricant affinity to the sliding surface while maintaining their non-harmful character (both for surfaces as well as the environment), from the other hand. For the same reason, we plan to modify the surface of CNs and synthesize more complex, hierarchical structures based on carbon nanomaterials, intentionally designed to reduce friction.

We will apply atomistic simulations which are intended to provide interpretative support for the experimental research. The planned simulations are meant to give insights into the molecular picture of lubrication and friction processes. This approach will allow us to identify and better understand physicochemical phenomena which occur in the considered lubricants. In the next research step, the numerically designed CNs will be produced in our laboratories. The proposed synthetic steps shall also allow the carbon atoms to self-organize. These 3D-organized CNs will be purified and modified predominantly using wet chemistry. Finally, functionalized CNs will be admixed to pre-designed liquids and tested in the tribometers. The plastic and metal elements from the tribometer will be comprehensively tested under microscopes like scanning electron microscope allowing us to understand details of the phenomena occurring on the sliding surface. One of the possible mechanisms of tribo-action emerges as a permanent incorporation of CNs delivered with lubricants onto plastic surfaces making it more slippery. The gained knowledge about the lubricant and plastic interactions will close the loop suggesting how to optimize CNs for further friction lowering to the level of superlubricity.

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