The interlayer coupling interaction of bentonite (BT) material behave superior performance and unique functionality by introducing guest functional molecules. As intercalation agents, ionic liquids ...(ILs) with high polarity and molecular structure regulation can provide excellent lubricity and multifunctionality. Herein, the novel IL-modified intercalation bentonite (IL-BT) were designed and prepared by functionalization of the imidazolium-based and phosphorus-based ILs. And ultra-thin lamellar structure morphology is obtained, which contributes to the enhanced dispersion and stability in base oils. For IL -BT, their strong interlayer slip can significantly improve lubrication properties. Besides, FIB-TEM results show that unique tribofilm is detected at the sliding asperity. The excellent tribological properties are attributed to the synergistic lubricity of interlayer slip, tribo-chemical reaction and repair effect during friction.
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•Novel IL functionalized bentonite composite (IL-BT) was designed and prepared.•Ultra-thin lamellar morphology for IL-BT was obtained, as well as excellent dispersion stability.•Superior tribological properties can be noticed even at 2.74 GPa.•The synergistic lubricity and unique triboflim induced by IL-BT is explored on the metal surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study aimed to investigate the formation and alteration of tribofilm during pure rolling contact under sufficient lubrication. The surface state changes were also analyzed. Rolling contact ...experiments with varying stress cycles were conducted using a ball-rod testing machine. Characterizations on surface state including morphology, roughness and plastic deformation were executed and chemical composition and valence state of tribofilm were detected for different rolling periods. The results indicated tribofilm was formed and evolved due to the effect of Hertz Contact stress. Surface morphology changes and plastic deformation were caused by Hertz Contact, simultaneously. The micro-sliding destroyed the tribofilm to a certain degree, resulting in the change of surface state and tribofilm composition compared to the pure rolling region.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Magnesium (Mg) and its alloys are crucial for energy-efficient vehicles due to their strong and lightweight properties, necessitating high-temperature fabrication and lubrication to reduce oxidation, ...friction, and wear. This paper investigated the tribological performance of lubricating oil using different particles to a Mg alloy subjected to contact sliding in an open system at high temperatures up to 250 °C. The overall experimental results showed improved tribological performances by using the two types of nanoparticles / nanoparticle-clusters (concentration ≥ 0.5 wt%) compared with the base silicone oil. The mechanisms by which the two types of nano lubricants improved the tribological performance are different. Al2O3 particles provided a more stable Al-rich anti-wear surface at higher temperatures in the range of 200–250 °C, while a tribo-chemical reaction film was formed with MoS2 additives, generating MoO3 and MgSO4. It is generally concluded that Al2O3 has more positive effect in terms of reduced coefficient of friction and wear rate as comparison to MoS2.
•Two types of silicone oil based nano lubricants for the sliding contact of a Mg alloy in an open system at high temperatures.•The tribological characteristics with different types of nano lubricants at elevated temperatures.•Tribofilm formation and removal during contact sliding of the contact pair due to high concentration Al2O3 nano lubricants at high temperatures.•Pits on the Mg AZ31B disc surface due to the clustering of MoS2 nanoparticles in the lubricant.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lubrication properties of imidazolium and phosphonium bis(oxalato)borate ionic liquids (ILs) are compared in a reciprocating sliding contact at 80 °C and 140 °C. Both the influence of the alkyl chain ...length and the cation architecture on friction, wear and lubricant breakdown are investigated. Imidazolium ILs showed lower friction than phosphonium ILs though only phosphonium-based ILs reduced wear. A longer alkyl chain reduced friction only in the case of the imidazolium-based ILs. Analysis of the wear scars was consistent with chemical breakdown solely of the anion. Chemical changes in the ILs after the tribotests were more pronounced for imidazolium-based ILs, and comparison of breakdown and tribofilm formation implicated catalysis by the imidazolium center, which, in turn, had a strong dependence on the surface self-assembly.
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•The effects of the nature of the cation of an ionic liquid on its lubrication properties are revealed.•The Lewis acidity of the imidazolium cation is responsible for the different extent of lubricant breakdown.•Chemical reactivity is shown to be modulated by self-assembly at the surface.•Breakdown of the anion is a prerequisite for sacrificial tribofilm formation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A robust superlubricity under high load (300 N) and speed (0.461 m/s) is realizes.•The superlubricity system exhibits good anti-corrosion and high carrying capacity.•The superlubricity mechanism is ...attributed to tribofilm, multilayer lubrication film.•The evolution of tribofilm formed by tribochemical reaction is revealed.•The application of superlubricity system in the field of cutting fluid is explored.
Superlubricity technology is one of the fastest growing fields of tribology in recent years because it can fundamentally reduce friction and wear. However, the current challenges for liquid superlubricity are the bearing capacity of lubricants and the stable superlubricity behavior at high shear rates. In this work, four imidazole-phosphate ionic liquids (ILs) with different chain lengths were prepared and used as pure water additives to achieve stable superlubricity with the friction coefficient of 0.008 under high loading (300 N) and high speed (0.461 m/s) between steel interfaces. The evoluation progress and tribochemical reaction of superlubricity is explored by the staged experiment. The results showed that a key factor of achieving superlubricity is the running-in period, in which, on the one hand, the contact pressure greatly reduce to maintain a suitable bearing range. On the other hand, the ordered accumulation of hydrogen ions, organic anions and cations, and ion of hydration formed a multi-layer electrostatic layer at the interface of the friction pair, which not only provides a protective layer to avoid serious corrosion, but also enhances the bearing capacity of the lubricating film attributed to the electrostatic repulsion. In addition, the tribochemical reaction between ILs and the surface of metal forms a functional tribofilm composed of carbides, iron oxides, nitrides and phosphides, which prevents the direct contact of the friction pair and reduces wear. Consequently, this research offers valuable insights into the optimal IL structure, revealing the tribochemical reaction of the superlubricity process and holding the significant potential of water-based superlubricity systems for practical applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Graphene has emerged as one of the most promising solid lubricants owing to their exceptional lubricity. The atomically thin nature and its ability to conformally adsorb on the sliding surfaces ...provide unprecedented pathways for modifying the friction and wear behaviors of the mechanical moving parts. Here, the tribological responses of several representative tribo-couples including bare steel, diamond-like carbon and ceramic materials are investigated to explore the potentials of graphene as surface modifier. Specific emphasis is devoted to the graphene-induced reconstruction of the sliding interface and the growth mechanism of nanostructured tribofilms formed on the contact surface using high-resolution microscopic technique. The results reveal the unique properties of graphene regarding the friction reduction and wear protection irrespective of the types of counterpart materials, graphene-processed methods, dry or humid tests environments. Nevertheless, the interfacial features and the bonding characteristics of the tribofilms are diversified in each specific rubbing case, demonstrating the distinguished adaption capacity of graphene to the tribo-testing conditions. The present findings shed light on the lubrication phenomenon of graphene at the microscale and may provide useful design criterion for 2D-based solid lubricants.
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•Graphene-processed lubricants with effective friction-reducing effects are achieved.•The lubricity depends strongly on the material characteristics of the tribo-couple.•The anti-friction tribofilms formed on the contact areas are analyzed to reveal the lubricating mechanisms.•The present findings show the promising application of graphene-based lubricants in engineering fields.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Zinc dialkyldithiophosphate (ZDDP) is added to engine lubricants to reduce wear and ensure reliable operation. ZDDP reacts under rubbing conditions to form protective zinc/iron phosphate tribofilms ...on steel surfaces. Recently, it has been demonstrated that this process can be promoted by applied stresses in lubricated contacts, as well as temperature, and is thus mechanochemical in origin. In this study, a tribology test rig, capable of applying very high loads, has been developed to generate ZDDP tribofilms under full-film elastohydrodynamic lubrication (EHL) conditions in steel/steel ball-on-disk contacts. This provides a well-defined temperature and stress environment with negligible direct asperity contact in which to study mechanochemical processes. ZDDPs with branched primary and secondary alkyl substituents have been studied in three base oils, two with high EHL friction and one with low EHL friction. In the high EHL friction base oils, the tribofilm growth rate increases exponentially with shear stress and temperature for both ZDDPs, as predicted by a stress-augmented thermal activation model. Conversely, under otherwise identical conditions, negligible ZDDP tribofilm formation takes place in the low EHL friction base oil. This confirms that the ZDDP reaction is driven by macroscopic shear stress rather than hydrostatic pressure. The secondary ZDDP forms tribofilms considerably faster than the primary ZDDP under equivalent conditions, suggesting that the initial decomposition reaction is the rate-determining step for tribofilm formation. The rate of tribofilm growth is independent of ZDDP concentration over the range studied, indicating that this process follows zero-order kinetics. Under full-film EHL conditions, ZDDP tribofilm formation is promoted by macroscopic shear stress applied through the base oil molecules, which induces asymmetric stress on adsorbed ZDDP molecules to promote their decomposition and initiate rapid phosphate polymerization.
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IJS, KILJ, NUK, PNG, UL, UM
Solid tribofilm plays a vital role in lubricating and separating friction pairs during relative movement especially under mixed/boundary conditions. However, the present of the ultra-low sulfur ...diesel retrogrades the formation of the high-performance tribofilm on the counter steel. Two-dimensional (2D) transition metal carbides, carbonitrides or nitrides (MXene) with abundant surface functional groups are promising for forming robust tribofilm at the sliding interface when adding it into self-lubricating polymer. Herein, the design of MXene/epoxy (EP) nanocomposites with enhanced tribology performance is reported. Furthermore, we demonstrated an efficient approach for realizing superlubricity and extraordinary low wear rates (97% off) by incorporating 0D Al2O3 and 2D MXenes. Here, we ascribed the splendid tribological properties to the hybrid tribofilm which can effectively avoid direct contact of the friction pairs. This study provides a basis for exploring the structure-properties relationship of tribofilms, also exploring the potentials of MXene for developing advanced functional materials.
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•Tribological mechanisms of EP composites lubricated by ULSD were studied.•MXene is promising for forming robust tribofilm at the sliding interface.•Superlubricity was realized by incorporating MXene, Al2O3 and EP resin.•MXene-Al2O3 has a synergistic effect on reducing wear rate of EP by 97% off.•Hybrid nanostructure tribofilm is crucial on enhancing tribological performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•One oil-soluble ionic liquids (IL) combining rigid imidazole ring and flexible alkyl chain was synthesized.•The IL shows outstanding lubrication performance significant than ZDDP and existing ...oil-soluble ILs.•The minimum effective addition of IL is only 0.1 wt% as well as the ability to lubricate effectively at 400 N.•The lubrication mechanism of IL was studied in detail by examining frictional electron transfer and tribofilm analysis.
The various forms of friction and wear present in mechanical systems consume a huge amount of the world’s energy sources. Ionic liquids (ILs) have drawn great attention as emerging lubricant materials and currently increasing efforts to drive their commercialization and engineering. Herein, one oil-soluble IL lubricant additive, 2-N-undecylimidazolium bis(2-ethylhexyl) phosphate (C11-IMDEHP), has been prepared by “bottom-up” structural design. Compared to the commercially available lubricant additive zinc dialkyl dithiophosphates (ZDDPs) and existing oil-soluble ILs, C11-IMDEHP shows significantly superior lubrication performance even at high normal loads (400 N). Its minimum effective concentration (0.1 wt%) is at least tenfold smaller than conventional additives. This extremely low effective concentration is vital to lower the total phosphorus content in the lubricating compounds for environmental protection and cost reduction. Furthermore, the lubrication mechanism was studied in detail by examining the electron transfer at the frictional interface and tribofilm analysis, which further reveal the lubrication nature at electronic scales for ILs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of two types of additives, trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate and tricresyl phosphate on the tribological behavior of the polyolester based lubricant (POE) has been ...studied. Experiments revealed the lubricant equipped with both additives had friction reduction (up to 4 times) and a smaller wear rate (by almost 2 orders) of sliding steel surfaces in a wide range of temperature conditions in comparison to original POE and POE with each additive separately. Characterization revealed the formation of the phosphorous-rich film on the wear track that was responsible for observed friction and wear reduction. The rate of the film formation evaluated using Quartz Crystal Microbalance was found to increase with temperatures thus suggesting better efficiency of the steel surface protection during sliding.
•The individual and synergy effects of ionic liquid and TCP on lubrication of polyolester lubricants are investigated.•Addition of additives results in up to 4 times reduction in friction and 2 orders of magnitude reduction in wear of steel.•The improvement in the lubrication characteristics is attributed to the formation of a protective phosphorous-rich tribofilm.•The rate of the tribofilm formation is accelerated with increased temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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