Graphene-Based Engine Oil Nanofluids for Tribological Applications
21 Oct 2011-ACS Applied Materials & Interfaces (American Chemical Society)-Vol. 3, Iss: 11, pp 4221-4227
TL;DR: The improvement in FC, AW, and EP properties of nanofluids is respectively by 80, 33, and 40% compared with base oil and can be attributed to the nanobearing mechanism of graphene in engine oil and ultimate mechanical strength of graphene.
Abstract: Ultrathin graphene (UG) has been prepared by exfoliation of graphite oxide by a novel technique based on focused solar radiation. Graphene based engine oil nanofluids have been prepared and their frictional characteristics (FC), antiwear (AW), and extreme pressure (EP) properties have been evaluated. The improvement in FC, AW, and EP properties of nanofluids is respectively by 80, 33, and 40% compared with base oil. The enhancement can be attributed to the nanobearing mechanism of graphene in engine oil and ultimate mechanical strength of graphene.
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TL;DR: In this article, the authors present a review of four main types of friction modifier additive and outline their history, research and the mechanisms by which they are currently believed to function, including organic friction modifiers, functionalised polymers, soluble organo-molybdenum additives and dispersed nanoparticles.
Abstract: The need for energy efficiency is leading to the growing use of additives that reduce friction in thin film boundary and mixed lubrication conditions. Several classes of such friction modifier additive exist, the main ones being organic friction modifiers, functionalised polymers, soluble organo-molybdenum additives and dispersed nanoparticles. All work in different ways. This paper reviews these four main types of lubricant friction modifier additive and outlines their history, research and the mechanisms by which they are currently believed to function. Aspects of their behaviour that are still not yet fully understood are highlighted.
374 citations
TL;DR: There are three types of friction modifiers for liquid lubricants: organomolybdenum compounds, organic friction modifiers, as well as nanoparticles as mentioned in this paper, and the problems and some suggestions for the future directions of research on friction modifiers are proposed.
Abstract: Due to the increasing demand of low emission and fuel economy, friction modifiers have been widely used in lubricating compositions to adjust friction and wear properties of lubricants. Recent achievements in the application of friction modifiers for liquid lubricants (2007–present) are reviewed in this paper. There are three types of friction modifiers for liquid lubricants: organomolybdenum compounds, organic friction modifiers, as well as nanoparticles. The tribological properties and lubrication mechanisms of these friction modifiers are discussed. The problems and some suggestions for the future directions of research on friction modifiers are proposed.
329 citations
TL;DR: In this paper, the effect of shear, solvent and chemical modification on the dispersion of graphene (including graphene oxide and reduced graphene oxide) is discussed in the context of manufacturing and commercialisation.
Abstract: Harnessing the exceptional physical properties of graphene often requires its dispersion into aqueous or organic media. Dispersion must be achieved at a concentration and stability appropriate to the final application. However, the strong interaction between graphene sheets means it disperses poorly in all but a few high boiling organic solvents. This review presents an overview of graphene dispersion applications and a discussion of dispersion strategies: in particular the effect of shear, solvent and chemical modification on the dispersion of graphene (including graphene oxide and reduced graphene oxide). These techniques are discussed in the context of manufacturing and commercialisation.
319 citations
Cites background from "Graphene-Based Engine Oil Nanofluid..."
...respectively by the following: 14% and 17% [84], 9% and 26% [85], and 33% and 80% [86] in base fluids ranging from water [87] to organic...
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TL;DR: In this paper, the authors highlight the future prospects of nanoparticles in the context of the lubricant industry and highlight the use of nano-scale particles for enhancing certain properties, such as friction and wear resistance.
296 citations
01 Mar 2010
TL;DR: Using friction force microscopy, the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide, niobium diselenide, and hexagonal boron nitride are compared to those of their bulk counterparts, suggesting that the trend arises from the thinner sheets’ increased susceptibility to out-of-plane elastic deformation.
Abstract: Thin Friction The rubbing motion between two surfaces is always hindered by friction, which is caused by continuous contacting and attraction between the surfaces. These interactions may only occur over a distance of a few nanometers, but what happens when the interacting materials are only that thick? Lee et al. (p. 76; see the Perspective by Müser and Shakhvorostov) explored the frictional properties of a silicon tip in contact with four atomically thin quasi–two dimensional materials with different electrical properties. For all the materials, the friction was seen to increase as the thickness of the film decreased, both for flakes supported by substrates and for regions placed above holes that formed freely suspended membranes. Placing graphene on mica, to which it strongly adheres, suppressed this trend. For these thin, weakly adhered films, out-of-plane buckling is likely to dominate the frictional response, which leads to this universal behavior. A universal trend is observed for the friction properties of thin films on weakly adhering substrates. Using friction force microscopy, we compared the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide (MoS2), niobium diselenide, and hexagonal boron nitride exfoliated onto a weakly adherent substrate (silicon oxide) to those of their bulk counterparts. Measurements down to single atomic sheets revealed that friction monotonically increased as the number of layers decreased for all four materials. Suspended graphene membranes showed the same trend, but binding the graphene strongly to a mica surface suppressed the trend. Tip-sample adhesion forces were indistinguishable for all thicknesses and substrate arrangements. Both graphene and MoS2 exhibited atomic lattice stick-slip friction, with the thinnest sheets possessing a sliding-length–dependent increase in static friction. These observations, coupled with finite element modeling, suggest that the trend arises from the thinner sheets’ increased susceptibility to out-of-plane elastic deformation. The generality of the results indicates that this may be a universal characteristic of nanoscale friction for atomically thin materials weakly bound to substrates.
244 citations
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TL;DR: The process yields a wrinkled sheet structure resulting from reaction sites involved in oxidation and reduction processes, and functionalized graphene produced by this method is electrically conducting.
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3,353 citations