Researchers at the University of Coimbra in Portugal have developed an innovative and sustainable lubrication system that significantly enhances wear and corrosion resistance in mechanical applications. By integrating gadolinium-doped diamond-like carbon (Gd-DLC) films with ionic liquids, the team addresses environmental concerns associated with conventional lubricant additives, such as zinc dialkyldithiophosphates (ZnDTPs).

“Traditional lubricants rely on additives that can have negative environmental impacts due to high levels of phosphorus, sulfur and zinc”, explains Dr. Fabio Ferreira, the project’s Lead Researcher. “Our goal was to develop a more sustainable alternative that does not compromise performance.”

The research involved doping DLC films with varying concentrations of gadolinium to enhance their wear resistance properties. When combined with specific ionic liquids, the Gd-DLC films not only reduced wear but also provided excellent corrosion protection, even in the presence of bromide-containing ionic liquids that typically corrode steel surfaces.

ToF-SIMS chemical maps and depth profiles revealed PO2- distribution at wear track of undoped and Gd-DLC after tribological tests. Copyright: Takeru Omiya.

“Our experiments showed that increasing the gadolinium content in the DLC films improved their interaction with the ionic liquids, leading to the formation of protective tribofilms”, says PhD candidate Takeru Omiya. “This synergy between the Gd-DLC films and ionic liquids offers a promising path towards more efficient and environmentally friendly lubrication systems.”

Advanced surface analysis techniques, including X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, the key observations in this study, were performed at the University of Namur as part of the NFFA project. The surface analysis techniques revealed that the presence of gadolinium facilitated the adsorption of phosphate ions from the ionic liquids onto the DLC surface. This resulted in the formation of phosphorus-rich tribofilms that enhanced wear resistance.

The project benefited from access to the NFFA-Europe Infrastructure, which provided state-of-the-art facilities and techniques essential for the research. “NFFA-Europe has offered us a unique opportunity to conduct in-depth surface analyses that were critical to understanding the mechanisms behind our findings”, notes Dr. Fabio Ferreira.

The team’s findings not only present a viable alternative to environmentally harmful lubricant additives but also pave the way for further advancements in sustainable lubrication technologies. The research has significant implications for various industries seeking to improve mechanical performance while reducing environmental impact.

Omiya T, Cavaleiro A, Figueiredo N, Gouttebaron R, Felten A, Ferreira F. Sustainable Lubrication through Gd DLC Films and Ionic Liquids for Wear and Corrosion Resistance. Tribology International. 2024:110130. https://doi.org/10.1016/j.triboint.2024.110130

The research utilized advanced surface analysis facilities provided by NFFA-Europe, specifically at the University of Namur's Namur Institute of Structured Matter. Techniques such as X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were essential in analyzing the surface chemistry and understanding the mechanisms behind the enhanced lubrication performance. Access to these state-of-the-art facilities and expertise was instrumental in achieving the project's objectives.

Fábio Ferreira is the pioneer in Portugal and one of the first worldwide in implementing HiPIMS as a technique for developing and producing thin films. Fabio Ferreira got his PhD in Mechanical Engineering in Surface Engineering Specialization in the U. of Coimbra in March 2018. Part of his PhD was done at the highly prestigious Berkeley Lab., CA, USA. During his career, he published more than 50 articles in SCOPUS indexed, some of them in the top 20 most-cited Coatings Journals (Applied Surface Science, Wear, Surface and Coatings Technology) according to the Scimago Rank 2020. The researcher has a SCOPUS h-index of 12 and 514 citations. Dr. Ferreira has participated in 39 international conferences, showcasing his work through a variety of presentations: 1 plenary presentation, 1 keynote presentation, 25 oral presentations, and 12 poster sessions. He has consistently applied for scientific projects at both national and international levels. Despite being in the early stages of his career, he has secured funding for 7 high-level scientific projects. His direct involvement in funded proposals has brought significant funding to CEMMPRE, showcasing his active participation in obtaining competitive funding for research and development activities. Ferreira is the supervisor/co-supervisor of 12 MSc students (9 concluded) and belonged to an MSc jury panel 5 times. Ferreira is a co-supervisor of 5 PhD students in mechanical engineering. Ferreira was distinguished with several awards in the last years, highlighting the best early career award received at the most reputed congress of the area (PSE). Ferreira is the Guest Editor of the special issue "Trends in Coatings and Surface Technology" of Coatings journal and was Guest Editor of the Surface Engineering journal at ICTFPA 2022. He is a member of the Topical Advisory Panel of Coatings Journal. He belonged to the organizing committee of three international congresses, Junior Euromat 2022, ICTFPA 2022 and IECADVAMAP 2023. He is an Invited Professor at the University of Coimbra of several courses. Since 2023, Ferreira is the Co-President of the Portuguese Material Society for the Surface Engineering Area.

Takeru Omiya is a Ph.D. candidate in Mechanical Engineering at the University of Coimbra, specializing in advanced lubrication systems. His research integrates diamond-like carbon (DLC) coatings with innovative additives like copolymers and ionic liquids to enhance lubrication performance and reduce wear in automotive engines. He utilizes high-power impulse magnetron sputtering (HiPIMS) to optimize DLC coatings for improved hardness and adhesion. With four years of industrial experience at Shell Lubricants Japan, Takeru bridges the gap between academia and industry. He has received several awards, including the STLE Early Career Award and the John B. Fenn, Sr. Foundation Endowed Scholarship, and aspires to lead research in sustainable, high-performance lubrication systems.