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According to the redox ability of dopamine in a weak alkaline environment, silver nanoparticles were uniformly loaded on the surface of polydopamine-modified graphene oxide (Ag/PGO). The results show that the base oil containing Ag/PGO nanoparticles exhibits a better tribological property than base oil. The maximum decrease in wear rate and friction coefficient at different temperatures amounted to 68% and 53.6%, respectively. The tribofilm containing C, O, N, and Ag exists and plays an important role in reducing friction and increasing wear resistance. Molecular dynamics simulations show that the microscopic oil film composed of Ag/PGO and n-hexadecane has low shear deformation during the shearing process, and the oil film has low interaction energy with the upper and lower shear walls. [ABSTRACT FROM AUTHOR]

In the boundary lubrication regime, the addition of long as well as straight alkyl chain containing additive exhibit a serendipitous impact on protecting various metallic surfaces or machinery components from friction and subsequent wear. In quest of environment-friendly, proficient friction-reducing, surface protective and cost-effective lubricant additives; herein, two diazomethine functionalised long-chain consisting organic molecules, namely (3E)-N-((E)-2-(octadecylimino)ethylidene)octadecan-1-amine (ODE) and (3E)-N-((E)-2-(dodecylimino)ethylidene)dodecan-1-amine (DDE) were synthesized through a one-pot condensation reaction. The surface protective film-forming, as well as wear and friction reducing properties of these organic additives on steel balls within paraffin oil (PO), were thoroughly explored using a four-ball tester with variation in time, load and speed. The addition of these additives showed a remarkable reduction of coefficient of friction (COF) and wear amount in compared to the pure base oil. ODE exhibited better performance with a ∼62% reduction in COF and ∼23% reduction in wear amount for steels in contact. Electronic level analysis for elucidating the tribofilm formation capability of the additives was rationalized using computational approaches such as density functional theory (DFT) and Fukui indices. Additionally, the molecular dynamics (MD) simulation which is an efficient computational approach was used to explore the spontaneous adsorption insight of additives; and also radial distribution function (RDF) were analysed to impressively explore the molecular-level interactions and adsorption mechanism of the additives with the metal atoms. Thereby, the mechanism of surface adhesive tribofilm formation and its metal protection capability has been explained in a comprehensive manner. Diazomethine functionalised organic molecules were synthesized with a variation of aliphatic chain length. Long aliphatic chain containing ODE additive showed enhanced surface protective performances in paraffin oil exhibiting lower COF value in comparison to DDE. Possible formation of ODE-based efficient tribofilm in metal-solution interface which exhibits enhanced surface adsorption property on the metal surface. Substantial decrease in wear upon addition of ODE in the base oil, which was confirmed by FE-SEM and 3D surface profilometer study. MD simulation has been used to investigate the adsorption competence of ODE and DDE on the iron surface. [ABSTRACT FROM AUTHOR]

With the EU aiming for net-zero greenhouse gas emissions by 2050, conventional production cycles must be transformed into cradle-to-cradle approaches. Spent coffee grounds are often dumped in landfills, with their potential as high-quality feedstock for biofuel or bio-lubricant production. Spent coffee grounds oil (SCGO) was investigated for its physicochemical properties while having more free acid groups compared to the reference polyalphaolefin 8 (PAO 8), which may cause faster oxidation. TGA results displayed comparable thermal stability of SCGO and PAO 8 for inert/oxidative atmosphere. The oil composition was characterized by ATR-FTIR, elemental analysis, and GC-EI-MS, where a higher oxygen content was found for SCGO, referring to functional ester/acid groups. The tribological behavior of SCGO was studied as lubricant base oil and as a 5% additive in PAO 8. The condition of fresh and tribologically used oils was investigated with High-Resolution-ESI-MS, and the worn surfaces were evaluated by light microscopy and topographic analysis. The results showed a superior friction coefficient of pure SCGO (μ = 0.092) to PAO 8 (μ = 0.129). The 5% SCGO additive in PAO 8 (μ = 0.095) could significantly reduce friction compared to pure PAO 8 on an unpolished 100Cr6 surface. [ABSTRACT FROM AUTHOR]

n the last few years, there is a general shift observable toward greener lubrication, fueled amongst others by policy initiatives such as the European Green Deal in consistency with the UN Sustainable Development Goals. At least 70 vol% of a lubricant is composed of a specific base oil, the rest is a variation of additives altering the lubricant properties (enhancing or suppressing existent base oil properties or adding new properties) to be operational for a particular field of application. So, in terms of sustainability, biodegradability, bioaccumulation, and toxicity the type of base oil plays a major role, which makes environmentally harmful petroleum-based lubricant formulations highly problematic for future applications. Hence, this leads to an ever-growing demand of environmentally friendly lubricant alternatives. Within the scope of this review lies the investigation of bio-based, bio-derived, and other sustainable lubricant components that could serve as promising replacements for conventional petroleum-based formulations, in accordance with the principles of green chemistry and tribology. As recycling is embraced by the term sustainability, waste-derived components of non-biological origin are also included in this work. An overview of studies on the tribological performance such as friction and wear properties of these sustainable and benign lubricant components is given. [ABSTRACT FROM AUTHOR]

Oils and grease have beneficial effects on moving parts such as connecting rod, gears, shafts, and engine to reduce wear and friction. The properties of lubricants such as tribological and rheological properties are an important role in oils and grease characterization. Nano additives on lubricant oils play an important role in anti-wear; reduce the coefficient of friction and enhance the rheological properties. The Tribological and rheological behavior of base oil 15W50 which have different concentrations of multi-wall Carbon Nanotubes (MWCNTs) (0.5, 1, 1.5, and 2 wt%), and constant amount of graphene nanosheets (GNSs) (0.5 wt%) were investigated. This research is the first one in studying the effect of hybrid nano additives of (MWCNTs) and (GNs) on the tribological and rheological properties of lubricant oils. Tribological characterization was carried out on four ball testing model under different loads (200, 400, 600, and 800 N). The kinematic viscosity, flash point, pour point, and thermal conductivity of nanofluid added 15W50 lubricant are estimated and compared with base oil. The results showed that nano additives improve the wear scar and coefficient of friction by 78% and 48%, respectively. The flash point, thermal conductivity, kinematic viscosity, and pour point, were improved by 15%, 77%, 76.8%, and 20%, respectively compared with the base oil. The hybrid addition of CNTs/GNs nanoparticles enhanced the properties of 15W50 engine oil. [ABSTRACT FROM AUTHOR]

The proposed work deals with the investigation of magnetorheological based minimum quantity lubrication of graphene oxide (GO) based jojoba oil as bio-lubricant on machinability and tool wear mechanism of turning Monel K500 alloy. Experiments were carried out for dry, flooded, minimum quantity lubrication (MQL) and magnetorheological (MR–MQL) conditions using medium duty lathe. The process parameters include the cutting speed 95, 110, 125 m/min, feed rate 0.050, 0.075, 0.1 mm/rev and depth of cut 0.25, 0.50, 0.75 mm for the output responses such as surface roughness, cutting temperature and tool flank wear. The results indicated that GO-based bio-lubricant MR–MQL reduced coefficient of friction (COF) of 0.051 and wetting angle of 6°, as well as improved machining performance such as cutting temperature of 145 °C, the surface roughness of 0.614 µm, flank wear of 0.18 mm with enhanced lubrication regime under extreme wear conditions. [ABSTRACT FROM AUTHOR]