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27 pages, 5523 KB

Open AccessReview

Tribological Aspects of Graphene and Its Derivatives

by Çağla Gizem Acar and Audrius Žunda

Lubricants 2025, 13(6), 232; https://doi.org/10.3390/lubricants13060232 - 22 May 2025

Cited by 7 | Viewed by 3122

Tribology is the branch of science and engineering that focuses on understanding friction, wear, and lubrication, which is essential for saving energy, improving performance, reducing vibration, and creating eco-friendly lubricants and wear resistance. Over the past decade, nanomaterials have captured the immense interest of tribology science. This review aimed to analyze how graphene and its derivatives can be incorporated into lubricants to enhance their properties, particularly in mitigating friction and wear. This is due to graphene’s excellent specific properties, such as a low friction coefficient, mechanical strength, high thermal and electrical conductivity, biocompatibility, high load-carrying capacity, wear resistance, and chemical stability. This study briefly introduces graphite, graphene, and graphene oxide, as well as presents graphene as a material for tribological applications. Among other things, the environmentally friendly possibilities of chemical reduction of reduced graphene oxide are analyzed here, as well as the macro-, micro-, and nano-tribological examination of graphene and its derivatives. Despite what is already known about graphene in tribology, further research is needed to gain a deeper understanding of development regarding integration with different materials, long-term performance, eco-friendly synthesis using green reducing agents, and comprehending how these approaches may affect systems at various scales. Full article

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19 pages, 7828 KB

Open AccessArticle

Comparative Study on Macro-Tribological Properties of PLL-g-PEG and PSPMA Polymer Brushes

by Fue Ren, Shuyan Yang, Yang Wu, Feng Guo and Feng Zhou

Polymers 2022, 14(9), 1917; https://doi.org/10.3390/polym14091917 - 8 May 2022

Cited by 13 | Viewed by 4512

Abstract

An ultra-low friction and high load capacity could be obtained on the surfaces grafted by a polymer brush even at relatively slow friction speeds in aqueous lubrication environments, which has attracted widespread attention to study the lubrication mechanism of polymer brushes; however, it has yet to be fully understood. The macroscopic tribological performance of two different polymer brushes, which were prepared by the method of “grafting to” and “grafting from” and named as PLL-g-PEG and PSPMA, respectively, were investigated. The friction results demonstrated that PLL-g-PEG obtained a lower friction coefficient than polymer brush PSPMA, which was ascribed to its unique “self-healing” behavior. The lubrication film was in situ observed and the film thickness induced by the polymer brush was measured using a laboratory set for film thickness measurement apparatus based on interference technology. It was found that PSPMA exhibited excellent lubrication performance not found in PLL-g-PEG, and two film-forming mechanisms highly dependent on velocity were revealed, which may be important to interpret the lubrication mechanism of polymer brushes in aqueous lubricants. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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18 pages, 8924 KB

Open AccessArticle

Effect of Fe and Cr on the Macro/Micro Tribological Behaviours of Copper-Based Composites

by Zhongyi Zhang, Haibin Zhou, Pingping Yao, Kunyang Fan, Yongqiang Liu, Lin Zhao, Yelong Xiao, Taimin Gong and Minwen Deng

Materials 2021, 14(12), 3417; https://doi.org/10.3390/ma14123417 - 20 Jun 2021

Cited by 17 | Viewed by 2924

Abstract

Fe and Cr are regarded as two of the most important friction components in Cu-based composites (Cu–BCs). In this study, the microstructural detection and micro- and macro-tribology evaluation of Cu–BCs containing Fe and Cr were performed. The results indicated that both Fe and Cr formed diffusion interfaces with the copper matrix. Because of the generation of a defect interface layer, the Cr/Cu interface exhibited a low bonding strength. Owing to the excellent binding interface between Fe and Cu, the high coefficient of friction (COF) of Fe, and the formation of a mechanical mixing layer promoted by Fe, the Cu–BCs containing Fe presented better friction performance under all braking energy per unit area (BEPUA) values. The main wear mechanism of Cu–BCs containing Fe and Cr changed from abrasion to delamination with an increase in BEPUA, and the delamination of Cu–BCs containing Fe was induced by breaks in the mechanical mixed layer (MML). Full article

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14 pages, 7996 KB

Open AccessArticle

Micro and Macro-Tribology Behavior of a Hierarchical Architecture of a Multilayer TaN/Ta Hard Coating

by César D. Rivera-Tello, E. Broitman, Francisco Javier Flores-Ruiz, J. Perez-Alvarez, M. Flores-Jiménez, O. Jiménez and M. Flores

Coatings 2020, 10(3), 263; https://doi.org/10.3390/coatings10030263 - 11 Mar 2020

Cited by 19 | Viewed by 4014

Abstract

The micro- and macro-tribological behaviors of a novel hierarchical TaN/Ta coating deposited on Ti6Al4V biomedical alloy by direct current magnetron sputtering were analyzed in the present work. This analysis was associated with the morphological, structural, and mechanical properties, as well as the roughness changes during and after the tribological tests. The wear track of the coating after the macro-tribology tests was evaluated by Raman spectroscopy in order to detect the compounds formed as a result of the tribo-reactions that occurred during the tests. Micro- and macro-tribology behaviors showed a significant wear rate reduction of the hierarchical coating in comparison to the Ti6Al4V substrate. For the case of the micro-tribology tests, this reduction was attributed to the high hardness of the coating (31.4 GPa); however, this hardness caused a considerable increment in the friction coefficient. On the other hand, the macro-tribology performance was associated with the hardness and the ability of the hierarchical architecture to prevent the propagation of cracks. Moreover, the friction coefficient increased considerably at the end of the test; this increment was associated with the tantalum oxides in the wear track detected by Raman spectroscopy. Full article

(This article belongs to the Special Issue Tribological Coatings: Nanomaterials for Macroscale)

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47 pages, 11742 KB

Open AccessFeature PaperReview

Scaling Effects on Materials Tribology: From Macro to Micro Scale

by Pantcho Stoyanov and Richard R. Chromik

Materials 2017, 10(5), 550; https://doi.org/10.3390/ma10050550 - 18 May 2017

Cited by 63 | Viewed by 15855

Abstract

The tribological study of materials inherently involves the interaction of surface asperities at the micro to nanoscopic length scales. This is the case for large scale engineering applications with sliding contacts, where the real area of contact is made up of small contacting asperities that make up only a fraction of the apparent area of contact. This is why researchers have sought to create idealized experiments of single asperity contacts in the field of nanotribology. At the same time, small scale engineering structures known as micro- and nano-electromechanical systems (MEMS and NEMS) have been developed, where the apparent area of contact approaches the length scale of the asperities, meaning the real area of contact for these devices may be only a few asperities. This is essentially the field of microtribology, where the contact size and/or forces involved have pushed the nature of the interaction between two surfaces towards the regime where the scale of the interaction approaches that of the natural length scale of the features on the surface. This paper provides a review of microtribology with the purpose to understand how tribological processes are different at the smaller length scales compared to macrotribology. Studies of the interfacial phenomena at the macroscopic length scales (e.g., using in situ tribometry) will be discussed and correlated with new findings and methodologies at the micro-length scale. Full article

(This article belongs to the Special Issue Nanoscale Friction, Adhesion and Wear Characteristics of Surfaces and Interfaces of Micro/Nanostructures)

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