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As technology progresses, lubricant additives are becoming more prevalent and expanding the application areas of modern tribology. This study aimed to investigate the tribological properties of recently used additive particles and their impact on worm gearbox power consumption. To achieve this, hazelnut oil was chosen as the base oil, and graphite, boric acid (BA), and hexagonal boron nitride (hBN) particles were added in certain proportions. The effect of each additive on the coefficient of friction and wear was investigated under different operating speeds and loads using a pin-on-disc tester. Optimal additive ratios for worm gearbox oils were utilized based on the previous studies, and oils using hazelnut oil as the base were prepared accordingly. The efficacy of the additives was evaluated using a worm gearbox test system. [ABSTRACT FROM AUTHOR]

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]

For this article, oleic acid surface-modified zeolitic imidazolate framework-8/graphene oxide (OA-ZIF-8/GO) nanocomposites were prepared by a facile in situ synthetic method. The as-prepared composite samples were analyzed and characterized by means of transmission electron microscope (TEM), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TG). The tribological behaviors of the OA-ZIF-8/GO with different GO contents as the lubricating oil additives were investigated comparatively using a four-ball tribological machine. The results showed that compared with the base oil, the OA-ZIF-8/GO with different GO contents when added to the base oil can all reduce friction and wear. The oil sample with 1.0 wt% of OA-ZIF-8/GO (53%) nanocomposite had the lowest friction coefficient and wear scar diameter. The reduction of friction coefficient and wear scar diameter is attributed to a stable protective film formed on the worn surface via physical deposition and a complicated tribochemical reaction. The study provides a strategy for fabricating graphene-based nanocomposites that were used for lubricating oil additives. [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 tribological performance of polymer-stabilized TiO2 particles dispersed in mineral base oil was investigated. Two polymer–TiO2 mass ratios were investigated, with a constant polymer concentration of 0.3 wt% and two nanoparticle concentrations of 0.1 and 1 wt%. Friction tests were carried out with a pin-on–reciprocating flat test configuration under boundary-lubricated sliding conditions in the presence of a steel–steel contact and at two temperatures (20 and 100 °C). The results show the very good antiwear performance of the nanoparticle-based dispersions. The most promising results were obtained with 0.1 wt% TiO2 particles and at 20 °C. At this temperature, the wear resistance properties of the TiO2 particles surpass those of zinc dialkyldithiophosphate (ZDDP). The tribofilms generated during the friction tests were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS). A tribofilm composed of agglomerates of TiO2 particles embedded in a matrix formed by the polymer was observed. The combination of the polymer used as a dispersant and the TiO2 particles allows good tribological performance that was observed during the friction tests. The formulation including TiO2 particles could improve the antiwear properties of materials in an environment where conventional wear reducing additives do not form tribofilms due to low temperatures. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to evaluate carbon spheres as a green lubricant additive in 5W30 engine oil to reduce friction and wear. Carbon spheres with a diameter of ∼400 nm are synthesized from glucose by using a hydrothermal process. Lubrication is studied using a ball-on-disk tribometer by measuring the friction coefficient and wear in the boundary lubrication regimes. The worn surfaces were analyzed by Raman spectroscopy. Carbon spheres are found to be stably dispersed at 0.5 wt% concentration in base oil. The experiments revealed that carbon spheres are effective in reducing both friction and wear when lubricating by using base oil. Raman results show that the enhanced tribological performance is owing to a carbon-rich boundary film, the formation of which is attributed to the deposit of carbon particles during the sliding process. [ABSTRACT FROM AUTHOR]

This study investigates the performance of three ionic liquids (ILs), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate, trihexyl(tetradecyl)phosphonium decanoate, and 1-butyl-3-methylimidazolium tetrafluoroborate, as lubricant additives in synthetic oil polyalphaolefin (PAO8) and bio-based oil trimethylolpropane trioleate (TMPTO). The ILs were added at 0.5, 1.0, and 1.5 wt% concentrations and evaluated in terms of their miscibility with base oils as well as friction- and wear-reducing abilities. Four-ball and high-frequency reciprocating rig (HFRR) tribotesters were employed to evaluate the tribological performance under a boundary lubrication regime. Worn steel surfaces were characterized using optical microscopy, profilometry, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis. The results suggested that the addition of trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate and trihexyl(tetradecyl)phosphonium decanoate improved the tribological performance of both PAO8 and TMPTO at an optimum concentration of 1 wt%. They showed good friction reduction, lower overall surface wear, and improved surface finishing. 1-Butyl-3-methylimidazolium tetrafluoroborate managed to improve the tribological performance of both base oils only at 0.5 wt%. A further increase in 1-butyl-3-methylimidazolium tetrafluoroborate concentration caused detrimental effects on the steel surface due to the formation of halogenic compounds. [ABSTRACT FROM AUTHOR]

Metal oxide nanoparticles of different nature have been used in different fields such as therapeutics, biomarkers, tribology or environmental remediation, among others. Besides, the surface modification of such nanoparticles is of particular interest to bring designed functions. In this paper we describe the synthesis of CuO nanoparticles with two different geometries (spherical and prolate) and decorated with long alkyl chains in order to use as dye removers by adsorption and/or photo-degradation of a persistent model dye (Congo Red) and as lubricant additives to improve the tribological performance of base lubricant oils. Alkyl-functionalized CuO nanoparticles demonstrated a high stability in oily suspensions and an improvement in the friction reducing the CoF ca. 26%; the alkyl-decorated nanoparticles showed also higher adsorption kinetics for Congo Red than the neat ones following a pseudo-second-order trend, although with lower adsorption efficiency. The synthesis, surface modification and physic-chemical characterization of spherical and prolate CuO nanoparticles are described as well as their applications as lubricant additives and Congo Red photocatalytic removal. [ABSTRACT FROM AUTHOR]