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Baer A, Wawra SE, Bielmeier K, Uttinger MJ, Smith DM, Peukert W, Walter J, Smith AS. The Stokes-Einstein-Sutherland Equation at the Nanoscale Revisited. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2304670. [PMID: 37806757 DOI: 10.1002/smll.202304670] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 09/05/2023] [Indexed: 10/10/2023]
Abstract
The Stokes-Einstein-Sutherland (SES) equation is at the foundation of statistical physics, relating a particle's diffusion coefficient and size with the fluid viscosity, temperature, and the boundary condition for the particle-solvent interface. It is assumed that it relies on the separation of scales between the particle and the solvent, hence it is expected to break down for diffusive transport on the molecular scale. This assumption is however challenged by a number of experimental studies showing a remarkably small, if any, violation, while simulations systematically report the opposite. To understand these discrepancies, analytical ultracentrifugation experiments are combined with molecular simulations, both performed at unprecedented accuracies, to study the transport of buckminsterfullerene C60 in toluene at infinite dilution. This system is demonstrated to clearly violate the conditions of slow momentum relaxation. Yet, through a linear response to a constant force, the SES equation can be recovered in the long time limit with no more than 4% uncertainty both in experiments and in simulations. This nonetheless requires partial slip on the particle interface, extracted consistently from all the data. These results, thus, resolve a long-standing discussion on the validity and limits of the SES equation at the molecular scale.
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Affiliation(s)
- Andreas Baer
- Department of Physics, PULS Group, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058, Erlangen, Germany
| | - Simon E Wawra
- Department of Physics, PULS Group, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058, Erlangen, Germany
- Institute of Particle Technology (LFG), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 4, 91058, Erlangen, Germany
| | - Kristina Bielmeier
- Department of Physics, PULS Group, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058, Erlangen, Germany
- Institute of Particle Technology (LFG), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 4, 91058, Erlangen, Germany
| | - Maximilian J Uttinger
- Department of Physics, PULS Group, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058, Erlangen, Germany
- Institute of Particle Technology (LFG), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 4, 91058, Erlangen, Germany
| | - David M Smith
- Interdisciplinary Center for Functional Particle Systems (FPS), Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstr. 9a, 91058, Erlangen, Germany
| | - Wolfgang Peukert
- Department of Physics, PULS Group, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058, Erlangen, Germany
- Institute of Particle Technology (LFG), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 4, 91058, Erlangen, Germany
| | - Johannes Walter
- Department of Physics, PULS Group, Interdisciplinary Center for Nanostructured Films (IZNF), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, 91058, Erlangen, Germany
- Institute of Particle Technology (LFG), Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 4, 91058, Erlangen, Germany
| | - Ana-Sunčana Smith
- Interdisciplinary Center for Functional Particle Systems (FPS), Friedrich-Alexander-Universität Erlangen-Nürnberg, Haberstr. 9a, 91058, Erlangen, Germany
- Division of Physical Chemistry, Group of Computational Life Sciences, Ruđer Bošković Institute, Bijenička 54, Zagreb, 10000, Croatia
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Sharuddin MHB, Sulaiman MH, Kamaruddin S, Dahnel AH, Abd Halim NFH, Ridzuan MJM, Abdul-Rani AM. Properties and tribological evaluation of graphene and fullerene nanoparticles as additives in oil lubrication. PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS, PART J: JOURNAL OF ENGINEERING TRIBOLOGY 2023; 237:1647-1656. [DOI: 10.1177/13506501231175540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
In this study, SAE-0W20 engine oil was mixed with graphene and fullerene nanoparticles. The goal of this study was to evaluate and compare the effects of different carbon nanoparticles on the thermal, rheological, and tribological properties of engine oil, such as thermal degradation, viscosity, friction, and wear. Using a two-step process, graphene and fullerene nanostructures were dispersed in low-viscosity SAE-0W20 engine oil at a concentration of 0.05 wt.%. The friction and wear characteristics were evaluated in a customized cylindrical block-on-ring tribology test according to the ASTM G77 standard. Graphene and fullerene nanoparticles protect contact surfaces by forming a very thin protective film between moving mechanical parts thus resulting in wear and friction reduction. The results showed graphene nanoparticles have improved significantly the tribological performance of SAE-0W20 engine oil.
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Affiliation(s)
- Muhammad Hazman bin Sharuddin
- Department of Manufacturing and Materials Engineering, International Islamic University Malaysia, Gombak, Selangor, Malaysia
| | - MH Sulaiman
- Department of Mechanical and Manufacturing Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
| | - S Kamaruddin
- Department of Manufacturing and Materials Engineering, International Islamic University Malaysia, Gombak, Selangor, Malaysia
| | - AH Dahnel
- Department of Manufacturing and Materials Engineering, International Islamic University Malaysia, Gombak, Selangor, Malaysia
| | - NFH Abd Halim
- Department of Manufacturing and Materials Engineering, International Islamic University Malaysia, Gombak, Selangor, Malaysia
| | - MJM Ridzuan
- Faculty of Mechanical Engineering Technology, Universiti Malaysia Perlis, Arau, Perlis, Malaysia
| | - Ahmad Majdi Abdul-Rani
- Department of Mechanical Engineering, Universiti Teknologi Petronas, Ser Iskandar, Perak, Malaysia
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