{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,26]],"date-time":"2026-04-26T22:36:59Z","timestamp":1777243019123,"version":"3.51.4"},"reference-count":46,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2025,2,14]],"date-time":"2025-02-14T00:00:00Z","timestamp":1739491200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"European Network for Joint Doctoral-Level Training in Green Tribology\u2014Horizon 2020\u2014GreenTRIBOS","award":["860246"],"award-info":[{"award-number":["860246"]}]},{"name":"European Network for Joint Doctoral-Level Training in Green Tribology\u2014Horizon 2020\u2014GreenTRIBOS","award":["UID\/00285"],"award-info":[{"award-number":["UID\/00285"]}]},{"name":"European Network for Joint Doctoral-Level Training in Green Tribology\u2014Horizon 2020\u2014GreenTRIBOS","award":["LA\/P\/0112\/2020"],"award-info":[{"award-number":["LA\/P\/0112\/2020"]}]},{"name":"National Funds Through FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["860246"],"award-info":[{"award-number":["860246"]}]},{"name":"National Funds Through FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["UID\/00285"],"award-info":[{"award-number":["UID\/00285"]}]},{"name":"National Funds Through FCT\u2014Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["LA\/P\/0112\/2020"],"award-info":[{"award-number":["LA\/P\/0112\/2020"]}]},{"name":"Centre for Mechanical Engineering, Materials and Processes (CEMMPRE)","award":["860246"],"award-info":[{"award-number":["860246"]}]},{"name":"Centre for Mechanical Engineering, Materials and Processes (CEMMPRE)","award":["UID\/00285"],"award-info":[{"award-number":["UID\/00285"]}]},{"name":"Centre for Mechanical Engineering, Materials and Processes (CEMMPRE)","award":["LA\/P\/0112\/2020"],"award-info":[{"award-number":["LA\/P\/0112\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>To address modern tribological challenges\u2014reducing friction and wear to conserve resources while minimising environmental impact\u2014cobalt-doped DLC (Co-DLC) coatings were developed. These nanometric multilayer coatings, designed to retain key properties such as hardness, reduced modulus, and substrate adhesion, were fabricated using non-reactive DC magnetron sputtering (DCMS). The multilayer structure was achieved by controlling the planetary substrate holder\u2019s rotational speed. Characterisation of microscopic, chemical, structural, and mechanical properties was performed using techniques including FEI-SEM, EDS, XRD, TEM, Raman spectroscopy, scratch adhesion testing, and nanoindentation. Tribological performance was evaluated under boundary and fully flooded lubrication using PAO4 base oil and formulations with ashless, sulphur-free AW and EP additives. The coatings exhibited a granular surface morphology, columnar cross-sections, and amorphous structure. Increased dopant concentrations slightly enhanced graphitisation and significantly improved adhesion, though hardness and reduced modulus decreased. Tribological testing revealed superlubricity in several coating\u2013oil combinations and significantly reduced wear rates with higher dopant levels and new additives. A phosphate ester additive without an amine group achieved the lowest COF values, while one with an amine group yielded minimal wear rates. These findings highlight the potential of Co-DLC coatings and tailored additives to minimise friction and wear effectively.<\/jats:p>","DOI":"10.3390\/ma18040847","type":"journal-article","created":{"date-parts":[[2025,2,17]],"date-time":"2025-02-17T12:36:57Z","timestamp":1739795817000},"page":"847","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Achieving Superlubricity: Development of Multilayer Co-Doped DLC Coatings and Tribological Evaluation with Eco-Friendly Base Oil and Low-SAPS Oil Formulations"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9930-456X","authenticated-orcid":false,"given":"Mobeen","family":"Haneef","sequence":"first","affiliation":[{"name":"ARISE\u2014Advanced Production and Intelligent Systems, Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Dos Santos, 3030-788 Coimbra, Portugal"},{"name":"CEMMPRE\u2014Centre for Mechanical Engineering Materials and Processes, Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Dos Santos, 3030-788 Coimbra, Portugal"},{"name":"Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2606-2782","authenticated-orcid":false,"given":"Manuel","family":"Evaristo","sequence":"additional","affiliation":[{"name":"ARISE\u2014Advanced Production and Intelligent Systems, Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Dos Santos, 3030-788 Coimbra, Portugal"},{"name":"CEMMPRE\u2014Centre for Mechanical Engineering Materials and Processes, Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Dos Santos, 3030-788 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0935-3921","authenticated-orcid":false,"given":"Liuquan","family":"Yang","sequence":"additional","affiliation":[{"name":"Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK"}]},{"given":"Ardian","family":"Morina","sequence":"additional","affiliation":[{"name":"Institute of Functional Surfaces (iFS), School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2971-8465","authenticated-orcid":false,"given":"Bruno","family":"Trindade","sequence":"additional","affiliation":[{"name":"ARISE\u2014Advanced Production and Intelligent Systems, Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Dos Santos, 3030-788 Coimbra, Portugal"},{"name":"CEMMPRE\u2014Centre for Mechanical Engineering Materials and Processes, Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Dos Santos, 3030-788 Coimbra, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,2,14]]},"reference":[{"key":"ref_1","unstructured":"Tri, P.N., Rtimi, S., and Plamondon, C.M.O. 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