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

Abstract

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. ...

Tribological Properties of Carbon Nanotube and Carbon Nanofiber Blended Polyvinylidene Fluoride Sheets Laminated on Steel Substrates

“…However, PVDF bands are highly shifted in PVDF/CNT composite which indicates chemical intercalation of PVDF with CNT. A strong peak in PVDF/CNT appears at 3270 cm −1 , which is ascribed to the stretching vibration of hydroxyl (O-H), indicating adsorption of water and moisture in the composite [30].…”

“…Ordered sp 2 phase acts as an effective solid lubricant because of frail van der Waals forces acting betwixt the covalently bonded sp 2 phase in the MWCNT structure. A weakly bonded sp 2 plane easily shears and provides a low sliding friction coefficient [30].…”

Lignin from Hardwood and Softwood Biomass as a Lubricating Additive to Ethylene Glycol

“…Strengthening the interactions between the lubricant base and an additive through internal H-bonding seems to be another effective approach to improve the overall lubrication performance [ 27 , 28 ]. For example, the dispersion of reduced graphene oxide (rGO) in poly(ethylene glycol) 200 was improved via the H-bonding between the hydroxyl groups of rGO and the oxygen atoms of PEG200 molecules, thereby reducing the friction coefficient [ 29 , 30 , 31 ].…”

The Self‐Ordered Lamellar Texture of MoS2 Transfer Film Formed in Complex Lubrication

“…Currently, single liquid lubrication and solid lubrication modes are becoming powerless to meet the ever‐increasing requirements for durability and reliability especially under severe operation condition . Complex lubrication, through introducing liquid lubricants into the solid lubricating coating to achieve a comprehensive performance, is considered a promising way for the desired lubrication .…”