Chemically grafted graphite nanosheets dispersed in poly(ethylene-glycol) by γ-radiolysis for enhanced lubrication

Gupta, Bhavana; Panda, Kalpataru; Kumar, N.; Melvin, Ambrose A.; Dash, S.; Tyagi, A.K.

doi:10.1039/c5ra07528a

Cited by 28 publications

(36 citation statements)

References 52 publications

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“…Decrease in friction coefficient and high wear resistance properties could be traditionally explained by deposition of the graphene sheets at the tribo-contact region110. The presence of these sheets in the contact interfaces are directly related to dispersion stability and chemical interaction of the functionalized graphene sheets with the lubricant oil.…”

Section: Resultsmentioning

confidence: 99%

“…In each test, two drops of the ultrasonicated PEG blended with the rGO lubricant were used to thoroughly lubricate the sliding interfaces. A more detailed tribological experimental procedure is described elsewhere310. Two dimensional wear track profile were measured by a Dektak 6 M–stylus profiler in contact mode, at fixed 5 mg contact load and 10 μm/s scanning speed.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Optimization of oxygen functionality in GO/rGO is an important aspect for preserving the chemical stability of the structure while providing sustainable covalent/noncovalent interactions with the lubricant. 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.…”

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confidence: 99%

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Role of oxygen functional groups in reduced graphene oxide for lubrication

Gupta

Kumar

Panda

et al. 2017

Sci Rep

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498

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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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Section: Resultsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Role of oxygen functional groups in reduced graphene oxide for lubrication

Gupta

Kumar

Panda

et al. 2017

Sci Rep

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498

195

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“…Appearance of the quinonoid (CN) and benzenoid ring (CC) vibrations at 1564 and 1461 cm −1 , respectively, clearly indicates presence of PANI on the graphene surface. Band widening and strong absorption peak exhibited by hydroxyl group at 3405 cm −1 signifies formation of PEG‐functionalized rGO and this is only possible through hydrogen bonding when hydroxyl group from the rGO combine with oxygen of PEG . It is noticed that with increase in loading of PANI into graphene network, the absorption of this band is stronger, signifying more hydrogen bonded linkages between rGO and PANI‐PEG (Figure b).…”

Section: Resultsmentioning

confidence: 96%

“…Presently, there is no report of grafted graphene–polyaniline dispersed in a lube medium for tribology applications. Graphite/graphene intercalation with polyethylene glycol (PEG) and functionalization through γ ‐radiolysis for tribology applications has been recently investigated and it was proven to be a promising lubricant . In this material, hydrogen bonding is formed between rGO and PEG molecules which efficiently disperses it in the lube medium, thereby, reducing the frictional and wear resistance.…”

Section: Introductionmentioning

confidence: 99%

Molecular‐Pillar‐Supported Functionalized Reduced Graphene‐Oxide for Energy Efficient Lubrication

Gupta

Kumar

Panda

et al. 2016

Adv Materials Inter

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of anisotropic crystal structure, signifying strong covalent intralayer and weak van der Waals interlayer interactions. The layered lattice structure of graphene and its derivatives in lube oil provide an effective lubrication and antiwear properties. [9][10][11][12][13] However, it is a hydrophobic material and dispersion in a polar hydrophilic lube is unfavorable. In the light of this, oxygen functionalization converts graphene into graphene oxide/reduced graphene oxide (GO/rGO), providing a hydrophilic nature. The GO/rGO is a derivative of graphene containing abundant oxygen functional groups such as carboxyl, hydroxyl, and ether on the basal plane of carbon sheet. [ 14 ] Oxygen functionalization and chemically modifi ed graphene sheet is widely utilized to engineer molecular selfassemblies of organic ingredient for wide range of applications. [15][16][17][18] The presence of hydrophilic oxygen containing groups and hydrophobic aromatic frameworks in GO/rGO makes it an amphiphilic copolymer system, retaining a 2D feature in solution. [ 19 ] Baoli et al. proposed successful grafting of graphene with polyaniline (PANI) through the self assembled amino-propylsilane monolayer and chemical oxidative graft polymerization. [ 20 ] Feng et al. and Fan et al. prepared graphene-PANI composite fi lms by electrochemical process for the use in supercapacitor electrodes. [ 21,22 ] In this composite, the van der Waals interaction dominates between graphene and the conductive polymer. It is well-known that the large surface area of graphene and strong van der Waals force causes severe aggregation in the composite matrix. Therefore, strong interfacial adhesion and compatibility between graphene and the matrix involves dispersion of graphene a prerequisite for its reliable performance. To address these issues, graphene must be functionalized using both covalent and noncovalent approaches. However, covalently bonded polyaniline-graphene hybrids are rarely reported. [ 23,24 ] Kumar et al. reported a chemically bonded graphene-polyaniline hybrid, in which a carboxylic acid ester group linked graphene and PANI. [ 23 ] Novel graphene-polyaniline hybrid based on the PANI nanofi ber was formed through van der Waals interaction. [ 24 ] An et al. reported amide groups linkage between graphene-polyaniline-grafted PANI nanofi bers and graphene. [ 25 ] Presently, there is no report of grafted graphene-polyaniline dispersed in a lube medium for tribology Molecular-pillar-supported basal plane of reduced graphene oxide (rGO)is fabricated by polymerizing polyaniline (PANI). In the presence of poly(ethylene glycol) (PEG200), the γ -radiolysis is used for modifying the functionalization and improving the structural symmetry of PANI and PEG grafted rGO (PANI-PEG-g-rGO). The PANI is covalently and noncovalently grafted onto the surface of the graphene sheets. Carboxyl groups of rGO are linked to the nitrogen atoms in the PANI backbone and an accompanying noncovalent interaction between alkyl chains of grafted PANI and hydrooxylated rGO is formed. ...

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Friction-Induced Transformation from Graphite Dispersed in Esterified Bio-Oil to Graphene

Geng

Zheng

et al. 2016

Tribol Lett

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Chemically grafted graphite nanosheets dispersed in poly(ethylene-glycol) by γ-radiolysis for enhanced lubrication

Abstract: The γ-radiolysis derived chemical grafting of graphite nanosheets with poly(ethylene-glycol) results in a remarkable decrease in the friction coefficient and significantly enhanced antiwear characteristics of steel–steel sliding interfaces.

Cited by 28 publications

References 52 publications

Role of oxygen functional groups in reduced graphene oxide for lubrication

Role of oxygen functional groups in reduced graphene oxide for lubrication

Molecular‐Pillar‐Supported Functionalized Reduced Graphene‐Oxide for Energy Efficient Lubrication

Friction-Induced Transformation from Graphite Dispersed in Esterified Bio-Oil to Graphene

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