Energy efficient reduced graphene oxide additives: Mechanism of effective lubrication and antiwear properties

Gupta, Bhavana; Kumar, N.; Panda, Kalpataru; Dash, S.; Tyagi, AK

doi:10.1038/srep18372

Cited by 93 publications

(70 citation statements)

References 43 publications

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“…Lubrication enhancement by GO/rGO additives was described by the formation of low-shear-strength graphene tribofilm by adsorption to metal surfaces1210. However, the lubrication mechanism was effective also without forming mechanically stable graphene tribofilms within the sliding interfaces11. In this case, lubrication acts through shearing of the physisorbed functionalized graphene sheets under the contact.…”

mentioning

confidence: 99%

Role of oxygen functional groups in reduced graphene oxide for lubrication

Gupta

Kumar

Panda

et al. 2017

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Functionalized and fully characterized graphene-based lubricant additives are potential 2D materials for energy-efficient tribological applications in machine elements, especially at macroscopic contacts. Two different reduced graphene oxide (rGO) derivatives, terminated by hydroxyl and epoxy-hydroxyl groups, were prepared and blended with two different molecular weights of polyethylene glycol (PEG) for tribological investigation. Epoxy-hydroxyl-terminated rGO dispersed in PEG showed significantly smaller values of the friction coefficient. In this condition, PEG chains intercalate between the functionalized graphene sheets, and shear can take place between the PEG and rGO sheets. However, the friction coefficient was unaffected when hydroxyl-terminated rGO was coupled with PEG. This can be explained by the strong coupling between graphene sheets through hydroxyl units, causing the interaction of PEG with the rGO to be non- effective for lubrication. On the other hand, antiwear properties of hydroxyl-terminated rGO were significantly enhanced compared to epoxy-hydroxyl functionalized rGO due to the integrity of graphene sheet clusters.

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mentioning

confidence: 99%

Role of oxygen functional groups in reduced graphene oxide for lubrication

Gupta

Kumar

Panda

et al. 2017

Sci Rep

Self Cite

498

195

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“…Patel et al, 2019, investigated the tribological effects of highly reduced graphene oxide (H-rGO) nanoplatelets as additives to mineral base oil, aiming to exploit the fewer oxygen groups present between the microlayers, allowing spacing between the surfaces to accommodate the lubricant [58]. Liñeira del Río et al, 2019, [59] studied the tribological properties of nanolubricants formed by trimethylolpropane trioleate (TMPTO) or polyalphaolefin (PAO 40) base oils with reduced graphene oxide sheets (rGO) [60][61][62][63] whose reduction was carried out in order to obtain a good stability of the nanoadditives in the fluids, observing 24% and 20% friction enhancement for the PAO 40 and the TMPTO base oils, respectively. Mungse et al, 2019, prepared alkylated graphene oxide (GO)/reduced graphene oxide (rGO) by covalent interaction with octadecyltrichlorosilane (OTCS) and octadecyltriethoxysilane (OTES), finding that the variable oxygen functionalities in the GO/rGO and hydrolysis rate of octadecylsilanes governed the grafting density of octadecyl chains on the GO and rGO.…”

Section: Rgo/go Lubrication Mechanismmentioning

confidence: 99%

rGO/GO Nanosheets in Tribology: From the State of the Art to the Future Prospective

et al. 2020

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In the last few decades, in the lubricant industry, the request for new performing additives has been becoming imperative. In this scenario, control at the nanoscale can be the key factor for the improvement of more efficient nanolubricants. Herein, after a discussion about the nanoparticles’ four main lubrication mechanisms, considerable attention is devoted to the usage of reduced graphene oxide/graphene oxide (rGO/GO) nanosheets in tribology. Moreover, graphene surface functionalization is reviewed, also including unexplored results in the field of lubrication. As far as the literature is concerned, it can be postulated that rGO/GO nanosheets can reduce wear and friction. Wear reduction is obtained by deposition and film formation, while friction reduction is related more to the shear and lamination of the sheets on the contacting surfaces. Nevertheless, the two phenomena are interrelated and work in sync. In this context, it is of high importance to form a homogenous suspension for a continuous nanosheet supply after deposition and shearing. The focus of this review was placed on the main issues still to be overcome, e.g., the literature results in rationalization; dispersion stability enhancement; and finding the optimum concentration in the delicate balance of different components. Possible solutions for their efficient overcoming are eventually reported.

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“…Thus, an optimal concentration of 0.75 wt.% was found for both friction and wear. Optimal concentrations were also found for other nanolubricants [24,[46][47][48][49][50][51][52][53][54], including those containing h-BN nanoparticles [16,17]. At lower concentrations, the base oil governs the behavior because the quantity of nanoparticles is not sufficient to prevent wear whereas when the concentration is too high, the agglomeration allows the creation of new asperities.…”

Section: Tribological Characterizationmentioning

confidence: 99%

Tribological and Thermophysical Properties of Environmentally-Friendly Lubricants Based on Trimethylolpropane Trioleate with Hexagonal Boron Nitride Nanoparticles as an Additive

et al. 2019

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Dispersions based on hexagonal boron nitride, h-BN, nanoparticles, at 0.50, 0.75 and 1.0 wt.% mass concentrations, in an ester base oil composed mainly of trimethylolpropane trioleate, were investigated as potential nanolubricants. The stability of the dispersions was assessed to determine the reliability of the tribological, thermophysical and rheological measurements. Density and viscosity were measured from 278.15 to 373.15 K, while rheological behavior was analyzed at shear rates from 1 to 1000 s −1 at 283.15 K. Newtonian behavior was exhibited by all nanolubricants at the explored conditions, with the exception of the highest concentration at the lowest shear rates, where possible non-Newtonian behavior was observed. Tribological tests were performed under a normal load of 2.5 N. Wear was evaluated by means of a 3D profiler, scanning electron microscopy and confocal Raman microscopy. The best tribological performance was achieved by the 0.75 wt.% nanolubricant, with reductions of 25% in the friction coefficient, 9% in the scar width, 14% in the scar depth, and 22% of the transversal area, all with respect to the neat oil. It was observed that physical protective tribofilms are created between rubbing surfaces.Coatings 2019, 9, 509 2 of 17 relatively weak van der Waals interactions between loosely stacked h-BN sheets that provide excellent lubrication characteristics [9]. h-BN, the softest and most lubricious polymorph of BN, has both high thermal stability and thermal conductivity as well as numerous industrial applications, especially in metalworking processes where cleanliness of the working environment is required [10][11][12]. Additionally, h-BN is an environmentally-friendly material [13], which is being studied as a nanoadditive for liquid lubricants [14-22] because, compared with solid lubricants, liquid lubricant additives present advantages such as faster entrance and replenishment of the sliding interface, and easier removal of wear debris from the contact zone [23].With respect to the tribological behavior of nanolubricants containing h-BN nanoparticles, Mosleh et al. [14] found that when nanoparticles of h-BN, with irregular flake-like shapes and an average size of 70 nm, were dispersed in commercial sheet metal forming fluids, the friction coefficient for titanium-steel pairs showed little or no improvement; nevertheless, the wear reduction using the 1 wt.% h-BN nanodispersion was 55%. Çelik et al. [15] found that an engine oil (Society of Automotive Engineers (SAE) 10 W) containing h-BN nanoparticles of disk-like shape with an average diameter of 114 nm and thickness of 30-70 nm, led to a 14.4% improvement in the friction coefficient and a 65% decrease in the wear rate with respect to the neat oil for an AISI 4140 steel material. Wan et al. [16] studied nanolubricants composed of a formulated oil 15W-40, a dispersant, and h-BN nanoparticles (disks with average diameter of 120 nm and a single layer thickness of around 30 nm), finding that the nanolubricants with low nanoparticle concentrations s...

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Energy efficient reduced graphene oxide additives: Mechanism of effective lubrication and antiwear properties

Cited by 93 publications

References 43 publications

Role of oxygen functional groups in reduced graphene oxide for lubrication

Role of oxygen functional groups in reduced graphene oxide for lubrication

rGO/GO Nanosheets in Tribology: From the State of the Art to the Future Prospective

Tribological and Thermophysical Properties of Environmentally-Friendly Lubricants Based on Trimethylolpropane Trioleate with Hexagonal Boron Nitride Nanoparticles as an Additive

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