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A friendly solid-liquid lubrication system, which is the key to solve the environmental harm caused by phosphorus and sulfur additives in lubricants, has attracted the attention. In this paper, the TiN-Cu/PAO solid-liquid composite system was constructed in situ by tribochemical reaction based on the performance of nitride film and base oil. The results show that when rubbing in PAO, the carbon-based films deriving from PAO will form at the contacting interface. From the perspectives of surface energy, friction products and simulation calculation, the mechanisms of friction and wear reduction of the solid-liquid composite system was systematically investigated. Meanwhile, the degradation process of PAO molecules during friction was revealed from the molecular level, including adsorption, dehydrogenation, C-C bond breaking and reconstruction. [ABSTRACT FROM AUTHOR]

Surface texturing plays an increasingly important role as it can directly influence the tribological behaviors of contact surfaces in many ways. In texturing, tribological performance depends upon the types of design texture used and methods of fabricating texture on the surface. In this research work, friction and wear behaviors of surface textured EN-31 alloy steel have been investigated under wet condition by using DUCOM linear reciprocating tribometer. The textured dimples are fabricated by micro-EDM and micro-drilling CNC machining processes. Initially un-textured surfaces of EN-31 alloy steel with EN-8 steel pin are experimented for friction and wear under ISO-68 and ISO-220 lubricant oil. Under the different normal load conditions, it has been observed that the ISO 68 oil gives better friction-wear characteristics with respect to ISO-220 oil. Then after textured surfaces were investigated by using optimized ISO-68 lubricant. Experimental results on micro-EDM provide better friction and wear properties with respect to micro-drilling CNC. Surface texturing may act as wear debris trapper, lubricant reservoirs, hydrodynamic lift, and retarding the lubricant molecules flow in a particular path where potential exists. In this work, it has observed that texturing by micro-EDM enhanced mixed lubrication and minimum friction in mixed lubrication leads to decrement of wear loss. [ABSTRACT FROM AUTHOR]

The authors investigate the structure‐surface property relationship of different amide‐based waxes, which can be beneficial for designing new anti‐friction materials. Five different amide‐based samples (derived from soybean oil) and a carnauba wax sample are tested. The effect of normal load, sliding velocity, and environmental temperature on the coefficient of friction (COF) and wear loss is investigated. COF and wear loss of different materials respond to these factors very differently. The long carbon chain and high hardness of polyamide and Amidecoat result in low COF and less wear loss. The lower glass transition point of Amidecoat results in higher COF and more wear loss when tested at a high environmental temperature. Crystal morphology and crystallinity of these materials are found to have no apparent correlation with their friction and wear behaviors. Practical Applications: It is shown in this research that the soybean oil based polyamide and Amidecoat have comparable friction and wear behavior as the high‐priced carnauba wax. The Amidecoat and polyamide can be suitable substitutes for carnauba wax for anti‐friction purposes, and this study is expected to provide some practical guidance for the application of amide‐based materials (derived from soybean oil) in the tribological field. The work should be a great interest in the coating and lubricant industries that are looking for green and renewable alternatives for the expensive natural waxes with limited availability. [ABSTRACT FROM AUTHOR]

In the present work, three kinds of halogen-free ionic liquids (ILs) incorporating long-chain quaternary phosphonium as cations and dioctylsulfosuccinate (DOSS) as the anion were synthesized and characterized and the tribological properties of phosphonium ionic liquids were investigated as neat lubricants for steel ball–steel disc friction pairs at room temperature (RT) and elevated temperature (100 °C). The ILs were found to be noncorrosive and highly thermally stable and showed better antiwear and friction reduction performance than commercially available synthetic lube base oil poly-α-olefin (PAO10) and conventionally used IL 1-methyl-3-hexylimidazolium hexafluorophosphate (L-P106). Scanning electron microscopy (SEM) and energy-dispersive spectroscopic (EDS) analysis of the worn-out surfaces of the steel discs was performed and the results revealed that physical adsorption and tribochemical reactions occurred and formed a protective boundary film on the worn steel surface to prevent direct steel–steel contact between rubbing surfaces. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of magnesium silicate hydroxide (MSH) nanoparticles and their synergistic tribological properties combined with amphiphilic molecules (AMs) as additives in base oil. This combination reduces wear losses substantially due to the formation of a double well-arranged molecular layer or tribofilm on the rubbing surfaces under certain test conditions. From the results of nonequilibrium molecular dynamics (NEMD) simulations, lamellate MSH nanoparticles provide a medium for the adsorption of AMs thus further decreasing the contact of rough peaks. In addition, with the increase of load, a tribofilm containing element Mg, Si, O forms on the worn surfaces and greatly improves the anti-wear property of base oil. [ABSTRACT FROM AUTHOR]

In this work, the anti-friction and anti-wear capacity of 0.05 wt% graphene or/and 0.5 wt% MoDTC were investigated in PAO base oil at different test temperatures. Sliding surfaces were analyzed by scanning electron microscope, X-ray energy dispersive spectrometer, and Raman spectroscopy. Results indicated that graphene alone as an additive mildly reduced the friction coefficient at low test temperatures due to its easy shear and ultrathin lamellar structure. MoDTC alone effectively reduced the friction coefficient at different test temperatures because of the formation of MoS 2 tribo-film. The excellent mechanical and thermal properties of graphene tribo-film and the good lubricity of MoS 2 tribo-film contributed to the enhanced anti-wear capacity of graphene and MoDTC additives, respectively. Graphene-MoDTC dual additive further improved the lubricating performance of PAO base oil. It was shown that MoS 2 tribo-film derived from MoDTC dominated the friction behavior of graphene-MoDTC dual additive and graphene nanosheets further improved the anti-wear characteristics of the dual additive. It suggests that the combination of graphene and MoDTC supplies a feasible additive formulation design for PAO base oil at steel/steel interface. [Display omitted] • Graphene mildly reduces the friction coefficient at low test temperature. • MoDTC effectively reduces friction coefficient at different temperatures. • Graphene-MoDTC dual additive provides synergistic wear improvement. • MoS 2 tribofilm facilitates the synergistic improvement of dual additive. [ABSTRACT FROM AUTHOR]

Possibility to produce the biogrease using rapeseed oil as a base oil, beeswax as a thickener and its modification with functional anti-wear and antioxidant additives and carbon nanoparticles of graphene oxide and thermally expanded graphite nanoparticles were evaluated. Tribological tests were performed using a four-ball tribo-tester and the rheological characterization using a cone-plate Brookfield rheometer. The rheological parameters were correlated with the physico-chemical properties of the greases. The resulting variation of the rheological parameters with the temperature exhibits non-Newtonian behavior. Although the increasing proportion of beeswax worsens the tribological properties of investigated grease, the functional additives and nanoparticles significantly improve the thermal properties of the lubricant, yield stress, viscosity and tribological properties reducing the wear rate. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnO@SiO 2 have better dispersion in lubricants than ZnO/SiO2 mixed nanoparticles. • ZnO@SiO 2 composite nanoparticles can form a stable tribo-film on the worn surface. • SiO 2 shell absorb long chain molecule of base oil, forming a high viscosity layer. Nano additives have been widely proven to significantly improve the tribological properties of traditional greases, and the synergistic effect of multiple nanomaterials to improve the performance of greases is a promising research direction. In this paper, based on the hardness of the bearing material GCr15 steel, harder SiO 2 nanoparticles and softer ZnO nanoparticles were selected to synthesize hard-shelled soft-core composite nanoparticles (ZnO@SiO 2) by chemical deposition, and it was used as grease additive for the first time. The composite ZnO@SiO 2 nanoparticles have better dispersion and tribological properties than the physically mixed nanoparticles (ZnO/SiO 2). When 1 wt% ZnO@SiO 2 was added to the grease, the coefficient of friction and wear scar diameter were reduced by 11.5% and 25%, respectively. The special hard-shell-soft-core structure of the composite not only has good dispersion, but also forms a special solid friction film on the surface of the friction pairs. The SiO 2 shell can absorb a large number of long-chain lubricant molecules and increase the viscosity of the lubricant in the friction zone, thus forming a solid-liquid phase composite lubricating film, which plays a significant role in friction reduction and anti-wear. [ABSTRACT FROM AUTHOR]

In the field of tribology, graphene has become a potential candidate material for lubricating oil and lubricant additives at multiple scales due to their high thermal conductivity and impermeability. In order to further improve the anti-wear and anti-friction properties of graphene, Ni/polydopamine-functionalized graphene composites (Ni/pDA/GR) were successfully prepared by a wet chemical reduction method. In this paper, The GR, pDA/GR, Ni/GR and Ni/pDA/GR were added into the base oil as lubricant additives respectively to explore their lubrication properties. The results showed that the friction coefficient of Ni/pDA/GR group is the lowest, which is about 15 % lower than base oil. Ni/pDA/GR also exhibited good wear resistance in wear tests. At the same time, the optimal concentration of the composite is 0.1 wt% in base oil, and the optimal lubrication load is 5 N. [Display omitted] • Polydopamine was used to modify graphene which is facile and environmental. • Spherical Ni NPs can improve the load-bearing capacity of base oil. • The composite can improve the anti-wear and anti-friction performance of base oil. • We report a facile method to prepare metal-nanomaterial composites. [ABSTRACT FROM AUTHOR]

MoS 2 nanoparticles have been extensively applied as lubricating additives enhancing tribological behavior of base oils over the past decades. But how MoS 2 nanoparticles specially behave in formulated engine oil is still poorly understood, and even some contradictory conclusions have been obtained. Herein, ultrathin MoS 2 nanosheets were synthesized through a chemical method and their friction-reducing and antiwear capabilities in formulated engine oil was investigated. In addition, the tribofilm formation, interface structure and friction mechanism were studied in terms of the surface characterization and chemical analysis. The research contributed to comprehending the lubrication mechanism of MoS 2 nanoparticles within formulated engine oil. • The ultrathin shape of MoS 2 nanosheets with 1–4 layer were fabricated. • Ultrathin MoS 2 nanosheets showed positive tribological response in formulated engine oil. • Ultrathin MoS 2 nanosheets restrained the oxidation of substrate at high temperature. • A tribofilm with embedment of MoS 2 nanosheets was formed to protect rubbing surfaces. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are very potential lubricant additives for their strong adsorption and tribochemical reactions at the interface. In this work, poly(ionic liquid) of PImC 6 NTf 2 is used as lubricant additive in base oil of PEG, which can reduce the wear volume by around 65 times under 2.5 GPa. The lubricity is much more advantageous than the geminal dicationic IL of BIm 5 -(NTf 2) 2. The adsorption strength of lubricants is studied by employing the microcalorimeter to evaluate the adsorption heat, AFM to test the adhesion force, and molecular dynamics simulation to calculate the interfacial binding energy. As a result, the adsorption strength of PImC 6 NTf 2 is obviously higher than BIm 5 -(NTf 2) 2 , and the lubricity is strongly dependent on the adsorption strength of ILs. • Poly(ionic liquid) (PIL) of PImC 6 NTf 2 is used as lubricant additive in PEG. • The wear volume is reduced by around 65 times comparing with PEG. • The lubricity of PImC 6 NTf 2 is better than the geminal dicationic IL of BIm 5 -(NTf 2) 2. • The adsorption strength is studied by microcalorimeter, AFM and MD simulation. • The lubrication of ILs/base oil is strongly dependent on the adsorption of ILs. [ABSTRACT FROM AUTHOR]

The development of eco-friendly lubricant is the requirement of the times. In this paper, the modified IF-WS 2 nanoparticles are added to castor oil as additives to prepare mixed lubricant. The lubrication performances of the mixed oil are investigated by ball-on-disc rotary friction tester, and then the surface scratches are characterized by depth of field digital microscope, scanning electron microscope and Raman spectrometer. Experiments reveal that compared with the base oil, the friction coefficient and worn volume decrease by 27.4% and 47.2% after adding modified IF-WS 2 as additives under 300 rpm and 5 N conditions, respectively. From mechanism analysis, this improvement in lubrication performance is attributed to the polarity of castor oil and the unique pressure bearing structure and dispersion stability of modified IF-WS 2 , which makes that the castor oil molecules can better adsorb around the modified IF-WS 2 to form heavy loading bearing friction oil film so as to reduce friction and wear. In summary, results indicate the mixture of modified IF-WS 2 nanoparticles and vegetable lubricating oil has an attractive prospect in the field of environmentally-friendly products. [Display omitted] • The chemical modification of IF-WS 2 is successfully carried out by oleic acid. • A new environment-friendly and efficient lubricating oil is synthesized. • Friction coefficient and worn volume decrease by 27.4% and 47.2%. • Anti-wear mechanism of modified IF-WS 2 nanoparticles in castor oil is studied. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of the tribological and vibration performance of the synthesized lithium complex grease (LCG) containing Carbon black, Fe 3 O 4 and Al 2 O 3 nanoparticles on rolling bearing. The micromorphology, friction coefficient, worn surface and bearing vibration experiment of four greases were studied. The results show that in presence of nanoparticles friction and wear behaviors are improved compared to LCG without nanoparticles. The best tribological performance is obtained in presence of Al 2 O 3 nanoparticle, which is mainly attributed to its high hardness, cylindrical shape and deposition on the worn surface. Further, the wettability test shows that Al 2 O 3 nanoparticles can effectively promote the flow of base oil on the LCG soap fibers, which results in the most effective bearing vibration suppression. • The Al 2 O 3 nano-particles have the largest hardness and show cylindrical microscopic morphology. • The Al 2 O 3 nano-particles were intensively deposited on the surface of worn steel ball. • The Al 2 O 3 nanoparticles effectively promote the flow of base oil on the LCG soap fibers. [ABSTRACT FROM AUTHOR]

A high quality three dimensional graphene nanosheets (3D GNS) with few layers' thickness was prepared by the arc-discharge method. The 3D GNS is used as oil additive to explore its tribological performance under different working conditions. The results demonstrate that with the help of 3D GNS, the anti-wear and friction-reduction capabilities of base oil are improved in a wide range of speed and load. Especially under low speed and heavy load condition (4.2 mm/s and 1.0 GPa contact pressure), the reduction in coefficient of friction and wear volume loss can be as high as 29.1% and 55%, respectively. Raman spectrum and its mapping together confirmed the existence of protective film consisted by 3D GNS on rubbing surface, which avoids the direct contact of tribo-pairs and thus enhances the tribological performance of oil. In the case of heavier load condition, the lubricating performance of 3D GNS was reduced owing to the deteriorated 3D structure of the GNS. For higher speed, the thicker oil film brings better tribological properties to oil and minute 3D GNS is needed to participate in the friction process. The results are in good agreement with the Stribeck curve prediction. In brief, 3D GNS is helpful for improving the tribological properties of base oil under low speed and heavy load; thus providing a new insight for practical application as lubricant additive. Image 1 • A high quality three dimensional graphene nanosheets (3D GNS) as oil additive is investigated. • 3D GNS improve tribological performanceof base oil, in particular under low speed and heavy load. • This discovery on 3D GNS provides a new insight for developing effective oil additive. [ABSTRACT FROM AUTHOR]

In this study, magnesium matrix composites reinforced with 5 wt% WS 2 and 15–20 wt% SiC particles were sintered via powder processing. The friction and wear behaviour were studied using a ball-on-disc tribometer against Al 2 O 3 ball, subjected to normal loads of 1–4 N, room temperature and 110 °C, sliding speed of 22.5 mm/s, and lubricant of PAO base oil. The wear track and tribo-layer generated were investigated by optical profilometry and scanning electron microscopy. The average friction coefficient for Mg metal matrix composites (MMCs) was found to be 0.1–0.2 compared with 0.16–0.46 for pure Mg. Under all testing conditions, the Mg MMCs exhibited much lower friction coefficient and outstanding anti-wear property compared with unreinforced Mg and the Mg alloy AZ31. • Lightweight magnesium matrix reinforced with SiC and WS 2 (Mg MMCs) were sintered via powder processing. • Friction and wear tests were conducted under both room and elevated temperature. • Mg MMCs exhibited outstanding anti-wear and self-lubricating properties in addition to enhanced mechanical strength. • Mg MMCs provide a competitive advantage as greener components operating in tribological applications. [ABSTRACT FROM AUTHOR]

Natural serpentine powders are applicable as additives for various lubricating oils. However, no uniform theories explain their tribological performance, lubrication, and wear mechanism, especially their self-repairing mechanism. Herein, the influence of different nano serpentine powders (NSPs) contents in liquid paraffin on the friction and wear characteristics of steel balls and the self-repairing process of NSPs on the worn surface were studied. Results show that the optimal amount of NSPs was 0.5 wt %. Relative to those of the base oil, the friction coefficients and wear spot diameters were reduced by 22.8% and 34.2%, respectively. Moreover, the long-term tribological test shows that the wear scar diameter decreased slightly after 3 h, reaching the state of dynamic balance between wear and repair. The outstanding tribological performance should be attributed to the formed bilayer tribofilm, the first layer of which contains nanoparticles surrounded by lubricants and the second layer of which contains nanoparticles compacted onto the surface of the steel ball. [ABSTRACT FROM AUTHOR]