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Purpose: This study aims to prepare thymol-based deep eutectic solvents (DESs) and use them as lubricates for friction and wear tests to simulate the wear conditions of hybrid bearings. Design/methodology/approach: Through the characterization and analysis of the morphology of wear scars and the elemental composition of friction films, the tribological behavior and wear mechanism of sample materials as lubricants were investigated and the anti-wear mechanism of thymol-based DESs was discussed. Findings: The findings demonstrate that because of the formation of a fluid lubrication film and excellent kinematic viscosity, the lubrication effect of the prepared DES is improved by about 50% compared to the base lubricating oil. The prepared [Ch]Cl-thymol DES has a better anti-friction and lubrication effect than citric-thymol, EG-thymol and urea-thymol DESs, with an average friction coefficient of about 0.04. Originality/value: In this work, the friction reduction properties of thymol-based DESs were studied as lubricants for the first time, and the lubrication mechanism of sample materials was investigated. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to prepare ZnFe2O4 nanospheres, sheet MoS2 and three ZnFe2O4@MoS2 core-shell composites with various shell thicknesses, and add them to the base oil for friction and wear tests to simulate the wear conditions of hybrid bearings. Design/methodology/approach: Through the characterization and analysis of the morphology of wear scars and the elemental composition of friction films, the tribological behavior and wear mechanism of sample materials as lubricant additives were investigated and the effects of shell thickness and sample concentration on the tribological properties of core–shell composite lubricant additives were discussed. Findings: The findings demonstrate that each of the five sample materials can, to varying degrees, enhance the lubricating qualities of the base oil and that the core–shell nanocomposite sample lubricant additive has superior lubricating properties to those of ZnFe2O4 and MoS2 alone, among them ZnFe2O4@MoS2-2 core–shell composites with moderate shell thickness performed most ideally. In addition, the optimal concentration of the ZnFe2O4@MoS2 lubricant additive was 0.5 Wt.%, and a concentration that was too high led to particle deposition and affected the friction effect. Originality/value: In this work, ZnFe2O4@MoS2 core–shell composites were synthesized for the first time using ZnFe2O4 as the carrier and the lubrication mechanism of core–shell composites and single materials were compared and studied, which illustrated the advantages of core–shell composite lubricant additives. At the same time, the influence of different shell thicknesses on the lubricant additives of core–shell composites was studied. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2022-0367/ [ABSTRACT FROM AUTHOR]

In this study, polydopamine-modified graphene oxide (PGO) nanomaterials were prepared based on the self-polymerization of dopamine in a weakly alkaline environment. In the friction experiment, the lubricants with 0.15 wt% PGO nanomaterials have optimal friction properties. Subsequently, X-ray photoelectron spectroscopy (XPS), X-ray energy spectroscopy (EDS), and laser Raman spectroscopy were performed on the wear scar. Compared to pure oil, the friction coefficient was reduced by 31%, and the trace width was reduced by 47.69%. In addition, molecular dynamics simulations showed that PGO has the lowest diffusion coefficient among n-hexadecane and the interaction energy between PGO and n-hexadecane molecules was the largest, and oil droplets containing PGO exhibited the best adsorption performance on the surface of the Si3N4/GCr15. The results showed that compared with other additives, PGO as a lubricant additive can play a significant role in reducing friction and anti-wear. [ABSTRACT FROM AUTHOR]

Abstract: The zinc perrhenate used as oil additive was synthesised via aqua‐solution method and was dispersed into pentaerythritol ester with the surface‐active agents. The tribological properties of lubricants were examined by 4‐ball tester and ball‐on‐disc testing machine. Additional investigations were performed using XRD, XPS, SEM‐EDS, and DTA/TG to probe the possible lubricating mechanism. Four‐ball test results showed compared to base oil, the friction coefficient and wear scar diameter of oil with zinc perrhenate additive were reduced by 14.9% and 16.6%, suggesting that zinc perrhenate additive could improve the lubricating property of base oil under 4‐ball test condition. Frictional tests under a wide temperature range indicated that oil with zinc perrhenate additive exhibited friction‐reducing performance during elevated temperature process because of its intrinsic shear susceptible property and could form a protective layer with native oxides of the disc sample at the interface, thus significantly minimised friction. [ABSTRACT FROM AUTHOR]

Recently, the engineering structural ceramics as friction and wear components in manufacturing technology and devices have attracted much attention due to their high strength and corrosion resistance. In this study, the tribological properties of Si3N4/Si3N4 sliding pairs were investigated by adding few-layer graphene to base lubricating oil on the lubrication and cooling under different experimental conditions. Test results showed that lubrication and cooling performance was obviously improved with the addition of graphene at high rotational speeds and low loads. For oil containing 0.1 wt% graphene at a rotational speed of 3000 r·min−1 and 40 N loads, the average friction coefficient was reduced by 76.33%. The cooling effect on Si3N4/Si3N4 sliding pairs, however, was optimal at low rotational speeds and high loads. For oil containing 0.05 wt% graphene at a lower rotational speed of 500 r·min−1 and a higher load of 140 N, the temperature rise was reduced by 19.76%. In addition, the wear mark depth would decrease when adding appropriate graphene. The mechanism behind the reduction in friction and anti-wear properties was related to the formation of a lubricating protective film. [ABSTRACT FROM AUTHOR]