Robust and durable superlubricity enabled by carboxylated graphene quantum dots in lubricated steel contacts

Nadeem, Irfan (author), Finšgar, Matjaž (author), Dražić, Goran (author), Malok, Matjaž (author), Morina, Ardian (author), Kalin, Mitjan (author)

Achieving macroscale superlubricity on engineering steel by utilizing aqueous green lubricants has gained growing interest, given its substantial potential to reduce energy consumption and carbon footprint. However, maintaining superlubricity under diverse sliding conditions over a prolonged duration is a major obstacle for real-scale applications. Herein, we report that a robust and durable tribofilm enabled by a unique lubrication mechanism based on carboxylated graphene quantum dots (CGQDs) in aqueous glycerol triggers macroscale superlubricity in self-mated steel contacts. A dedicated intermittent test was designed to show the superlubricity's robustness and the ability of the tribofilm to adapt to a variety of relevant sliding conditions. Moreover, the boundary film provides an average coefficient of friction of around 0.007 and up to 69 % wear reduction (compared to the base lubricant), resulting in the maintenance of superlubricity at a real final contact pressure of 123 MPa, which increases the upper limit of the contact pressure compared to current aqueous-lubricated steel contacts. The new superlubricity mechanism was enabled by the chemical adsorption of the CGQDs onto the worn metal surface, coupled with the tribo-induced structural degradation and transformation of the CGQDs into layered graphitic structures that generate an adaptable low-shear interface. This work provides new insights into the role of chemical adsorption and structural transformation of CGQDs in achieving superlubricity and is an important step forward for implementing energy-efficient and green lubrication technologies for industrial applications.

• Language: English
• Keywords: graphene quantum dots, superlubricity, boundary lubrication, aqueous glycerol, green tribology, steel
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 16 str.
• Numbering: Vol. 226, art. 119226
• PID: 20.500.12556/RUL-156374
• UDC: 539.92:621.8
• ISSN on article: 1873-3891
• DOI: 10.1016/j.carbon.2024.119226
• COBISS.SI-ID: 196343811
• Publication date in RUL: 23.05.2024

Record is a part of a journal

• Title: Carbon
• Publisher: Elsevier
• ISSN: 1873-3891
• COBISS.SI-ID: 22990853

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: grafenske kvantne pike, super mazljivost, mejno mazanje, vodni glicerol, zelena tribologija, jeklo