Towards ecological nanolubricants

The two main constituents of tribology are friction and wear, the control and reduction of both parameters is critical to proper functionality of machine elements.

Agnieszka Maria Tomala

High friction will lead to energy losses, while extensive wear can lead to catastrophic failure of the mechanical systems. The performance of current mechanical components made of steel is limited by the tribological properties of the surfaces. Steel components require stricter high-quality lubricants, very often containing toxic additives to enable them to withstand high contact pressures and temperatures. The stringent requirements from environmental legislation on reducing harmful elements is constantly forcing lubricant manufacturers to produce and implement greener additives. In the same way, equipment manufacturers are encouraged to develop and implement novel materials in machine elements’ contacts, with better mechanical, wear and frictional properties.

Diamond-like carbon (DLC) coatings in conjunction with nanolubricants are considered to hold great promise for such objectives and are of paramount interest to researchers. Nowadays, however, a major challenge involved in using coated materials is ensuring satisfactory tribological performance with conventional lubricant additives. This is because existing lubricant additives (e.g. AW/EP, friction modifiers, detergents, dispersants, etc.) were designed to work with ferrous surfaces (e.g. steel on steel) and no adequate confidence exists as to whether they can work and effectively reduce friction and wear with non-ferrous surfaces (e.g. DLC coatings).

The TriNoIS NovA (Tribology of Non-ferrous Interacting Surfaces Lubricated with Fluids Containing Novel Additives) project approach addresses grid issues by focusing on novel types of lubrication additives in the form of inorganic fullerene-like (IF) and nano-tubular structures as nanolubricants suitable for both ferrous and non-ferrous materials. Using lamellar nanoparticles such as IF-MoS2 as novel additives in the nanolubricants, a superior lubrication ability can be achieved due to their low-shear resistance to any applied shear stress. Multiwall IF-MoS2 nanotubes (NTs) are easily exfoliated and deposited on the interacting surfaces. Such a physically-based mechanism can be used for the lubrication of materials with lower chemical reactivity, e.g. DLC coatings. Accordingly, the TriNoIS NovA project’s main achievement is the design of nanolubricants which are suitable for steel coated and uncoated surfaces combining modern machine components interacting with ecological nanolubricants.

In the following steps, newly developed nanolubricants based on fully-formulated gear and engine oils with incorporated MoS2 and MoO3 NTs are evaluated using an FZG gear test rig and engine component test. Further, when the nanoparticles are added to coolants/lubricants (nanofluids), they show better heat dissipation ability at the machining zone, which enables substantial enhancement of the machining process.

The outcomes of these implementations will be mutually benefited by reduced emissions (e.g. social, environmental, ecological societies), optimised savings (e.g. economic body) and will facilitate sustainable development of energy-efficient and greener products. The expected impact on civilisation and society involves improved fuel economy and, importantly, with an environmental/ecological interest to reduce harmful emissions.

How did you benefit from the POLONEZ fellowship?

The POLONEZ fellowship has served as a continuation of my career and an extension of the research excellence in tribology and lubrication. The fellowship has helped me to increase my interdisciplinary renown, leading in future to my achieving a doctor habilitatus degree. In addition to the scientific work, I have developed my skills in management, personal effectiveness, scientific writing and preparation of European Commission (EC) project proposals.

Dr Eng. Agnieszka Tomala received her PhD in Physics from the Vienna University of Technology in 2010. She participated in EC Marie Skłodowska-Curie Actions PhD exchange programmes at SKF Engineering and Research Centre and Imperial College London. She published over 20 peer-reviewed papers in the field of tribology while working at Austrian Excellence Center for Tribology. Experience gained during the POLONEZ fellowship evolved into funding awarded from the M ERA.NET Call 2018: HOTselflub project at Łukasiewicz Research Network – The Institute for Sustainable Technologies in collaboration with teams from Austria and Estonia. She is currently working on bioengineering and biomaterials at Cracow University of Technology, Faculty of Materials Engineering and Physics.