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Polyprenols (PPs) are compounds with excellent biological activities and are applied in food, pharmaceutical, and cosmetic industries. However, its strong non-polar nature makes it difficult to separate with many saturated impurities (such as saturated fatty acids) extracted together. Complexation extraction is an effective method for separating saturated and polyunsaturated compounds. In this study, mesoporous silica MCM-41 was modified by imidazole-based ionic liquids (IL) followed by coating these MCM-41-supported IL compounds with silver salt to construct π-complexing adsorbent (AgBF 4 /IL•MCM-41) to enrich PPs from Ginkgo biloba leaves (GBL) extract. The mesoporous π-complexing sorbent was characterized by small-angle X-ray scattering (SAXS), FTIR, and nitrogen adsorption-desorption. The effect of the ratio of silver salt to IL•MCM-41 on the adsorption capacity of polyprenols from GBL was compared, and the dosage of AgBF 4 was determined to be 1.5 mmol/g IL•MCM-41. Adsorption isotherms and kinetics indicate that the π-complexing adsorbent has excellent PPs adsorption performance (153 mg/g at 30 °C) and a fast adsorption rate (the time to reach adsorption equilibrium is 210 s). The PPs were separated using the fixed bed after treatment for only one cycle with AgBF 4 /IL•MCM-41, and the content of PPs in the product was increased from 38.54% to 70.2%, with a recovery rate of 86.6%. The π-complexing adsorbent showed excellent reusability for ≥3 adsorption-desorption cycles., Competing Interests: Declaration of competing interest The authors state that they have no conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this communication we report the first preparation of ionic liquid-modified carbon nanotubes with reversibly switchable solubility between aqueous and organic solvents, induced by anion exchange.

In this study, the direct intercalation of gemini ionic liquids (ILs) with different alkyl chains into the bentonite (BT) interlayer as a high-performance lubricating additive for base oil 500SN was investigated. The purpose of modifying BT with an IL is to improve the dispersion stability and lubricity of BT in lubricating oil. The dispersibility and tribological properties of IL—BT as oil-based additives for 500SN depend on the increase in interlamellar space in BT and improve as the chain length is increased. More importantly, the IL—BT nanomaterial outperforms individual BT in improving wear resistance, owing to its sheet layers were deformed and sprawled in furrows along the metal surface, thereby resulting in low surface adhesion. Because of its excellent lubrication performance, IL-modified BT is a potential candidate for the main component of drilling fluid. It can be used as a lubricating additive in oil drilling and oil well construction to reduce equipment damage and ensure the normal operation of equipments. [ABSTRACT FROM AUTHOR]

A series of new halogen-free dicationic ionic liquids (ILs) with different alkyl chain lengths were prepared, and the relationship between the alkyl chain length, physicochemical and tribological properties of ILs, and their role as neat lubricant for steel-steel friction pairs, was investigated. Evaluation of stability during hydrolysis and copper strip corrosion test results show that synthetic ILs are stable and not corrosive to metal contacts, due to the halogen-free anions. The friction and wear test results indicate that ILs with long alkyl chains have excellent friction-reducing and anti-wear properties, especially at high temperatures. Based on the surface three-dimensional (3D) profiles, electrical contact resistance, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and the X-ray photoelectron spectrometry (XPS) analysis of the worn surfaces of steel discs, we can conclude that the efficiency of ILs is due to the formation of high quality tribofilms that consist of both tribochemical reaction and ordered absorption films. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have emerged as potential lubricants in 2001. Subsequently, there has been tremendous research interest in ILs from the tribology society since their discovery as novel synthetic lubricating materials. This also expands the research area of ILs. Consistent with the requirement of searching for alternative and eco-friendly lubricants, IL lubrication will experience further development in the coming years. Herein, we review the research progress of IL lubricants. Generally, the tribological properties of IL lubricants as lubricating oils, additives and thin films are reviewed in detail and their lubrication mechanisms discussed. Considering their actual applications, the flexible design of ILs allows the synthesis of task-specific and tribologically interesting ILs to overcome the drawbacks of the application of ILs, such as high cost, poor compatibility with traditional oils, thermal oxidization and corrosion. Nowadays, increasing research is focused on halogen-free ILs, green ILs, synthesis-free ILs and functional ILs. In addition to their macroscopic properties, the nanoscopic performance of ILs on a small scale and in small gaps is also important in revealing their tribological mechanisms. It has been shown that when sliding surfaces are compressed, in comparison with a less polar molecular lubricant, ion pairs resist "squeeze out" due to the strong interaction between the ions of ILs and oppositely charged surfaces, resulting in a film that remains in place at higher shear forces. Thus, the lubricity of ILs can be externally controlled in situ by applying electric potentials. In summary, ILs demonstrate sufficient design versatility as a type of model lubricant for meeting the requirements of mechanical engineering. Accordingly, their perspectives and future development are discussed in this review. [ABSTRACT FROM AUTHOR]

Fatty acid ionic liquids (FAILs) were designed and synthesized by combining quaternary ammonium cations with a range of biobased fatty acid anions. They were found to be good and universal lubricants for steel-steel, steel-copper, and steel-aluminum friction pairs, which possess low corrosivities, moderate viscosity indexes, and thermal stabilities compared to commercially available synthetic oil polyalphaolefin (PAO) 10 and traditional ionic liquid (IL) L-F104. Among them, N1444Oct and N4444Oct were found to have far lower toxicity than L-F104. Investigation of the lubricating mechanism revealed that firm and effective physical adsorption and tribochemical reaction films can be easily formed on the sliding surface due to the polarity of the fatty acid anions and the aliphatic tails, which prevent metal-metal contact and further antiwear and reduce friction. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a “green” way of in situ forming ionic liquids (ILs) as high‐temperature lubricants by dissolving high content of lithium bis(trifluoromethylsulfonyl)imide in lard oil (LO). Nuclear magnetic resonance spectroscopy result indicated that lithium bis(trifluoromethylsulfonyl)imide could have a reaction with triacylglycerols, which are the major component of LO and formed the IL (Li[triacylglycerol])bis(trifluoromethylsulfonyl)imide. Differential scanning calorimetry result shown that ILs could effectively enhance the thermal‐oxidation stability of LO. Tribological behaviours of lubricant application in steel/steel contacts were evaluated on an Optimol SRV‐IV oscillating reciprocating friction and wear tester at 250°C. It was found that the in situ formed ILs possessed excellent friction‐reducing and antiwear properties in LO compared with perfluoropolyether (as a reference lubricant) under the same conditions. The wear mechanisms are tentatively discussed according to the morphology observation of worn surfaces of steel discs by scanning electron microscope and the surface composition analysis by X‐ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

The study aims to explore the physicochemical and tribological properties of perfluorooctane sulfonate ionic liquids (PSILs) CFSON and CFSOP. The results showed that CFSOP exhibited excellent friction-reducing and anti-wear properties at both room and high temperatures, and CFSON presented excellent tribological properties at high temperature when they were used as lubricants for steel/steel, steel/copper, and steel/aluminum friction pairs. As compared with traditional fluorine-containing ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide (L-F104), increasing the fluorocarbon chain length of the anion is proven to be an effective way to improve the performance of the PSILs in terms of hydrophobicity, corrosion resistance, and tolerance to extreme pressure, thereby making them more suitable to be used as lubricants under harsh conditions. The X-ray photoelectron spectroscopy analysis indicated that physical adsorption and tribochemical reactions occurred and generated protective films on the sliding surface during the rubbing process, which reduced the friction and elevated the anti-wear efficiency of the PSILs. [ABSTRACT FROM AUTHOR]

Purpose - The aim of this paper was to inhibit the serious corrosion of conventional ionic liquids, a series of new ionic liquids (ILs) containing the triazole functionality, as the anti-corrosion groups were synthesized in this work. Design/methodology/approach - It is well known that nitrogen and sulfur containing organic compounds have been traditionally used as corrosion inhibitors. Among them, triazole derivatives are most often used as corrosion inhibitors. To alleviate the corrosion of the ILs and further improve the anti-wear property, the authors prepared a series of imidazolium ILs modified with the triazole functionality in the present study. Findings - The corrosion behavior of the ILs was evaluated with the iron disk corrosion test and their tribological properties were investigated on an Optimol SRV IV oscillating friction and wear tester at elevated temperatures. The results showed that the ILs with the triazole functionality could effectively reduce the corrosion and exhibit a smaller friction coefficient and wear volume than the unmodified counterpart. The ILs containing the triazole functionality can be used as the single component anti-corrosion base oils even at elevated temperatures. Originality/value - The results showed that the ILs with the triazole functionality could effectively reduce the corrosion and exhibit a smaller friction coefficient and wear volume than the unmodified counterpart. The ILs containing the triazole functionality can be used as the single component anti-corrosion base oils even at elevated temperatures. [ABSTRACT FROM AUTHOR]

Three kinds of protic ionic liquids with ammonium salts, dodecylamine salt of S-(1-carboxyl)-propyl- N, N-diethyldithiocarbamate (coded as DDED), dodecylamine salt of S-(1-carboxyl)-propyl- N, N-dibutyldithiocarbamate (coded as DDBD), dodecylamine salt of S-(1-carboxyl)-propyl- N, N-dioctyldithiocarbamate (coded as DDOD) were synthesized, characterized, and their tribological behaviors as additives in lithium complex grease were studied for steel/steel contact. The tribological properties were evaluated on an Optimol SRV-I oscillating reciprocating friction and wear tester and a MRS-10A lever-type fourball tester in details. The results of tests demonstrated that the novel additives were able to remarkably improve the extreme pressure, friction-reducing, and anti-wear properties of the base lithium complex grease when added at a low adding concentration (<3 %). Based on the performance comparison of three novel additives with different chain lengths in DTCs groups and a commercial additive with similar DTCs groups but no PILs groups, methylene bis dibutyldithiocarbamate (T323), a number of primary conclusions were drawn. The carboxylic acid ammonium salts, the typical function groups of the PILs existing in the molecule structures of three additives, could not only greatly enhance the physical and/or chemical adsorption on the metal surface to reduce friction of the base grease, and also have better synergism with DTCs groups in improving anti-wear performance of base grease. Based on the characterization and analysis of the worn surface by a PHI-5702 multifunctional X-ray photoelectron spectrometer (XPS) and a JSM-5600LV scanning electron microscope (SEM), a protective film consisting of FeS, organic compound was formed on the surface. The ordered adsorbed film and chemical reactive film on the sliding steels contributed to the main factor in improving the tribological properties of base lithium complex grease. [ABSTRACT FROM AUTHOR]

A novel polyelectrolyte‐grafted multiwalled carbon nanotubes (MWCNTs‐g‐PILs) which possesses a hard backbone of MWCNTs and a soft shell of brush‐like poly (ionic liquids) (PILs) has been synthesized via the surface atom transfer radical polymerization (ATRP). Chemical structure and the grafted PILs quantities of MWCNTs‐g‐PILs were determined by FTIR, TGA, and XPS. TEM and FE‐SEM observations indicate that the nanotubes were coated with a PILs layer, exhibiting core‐shell nanostructures with the PILs chains as the brush‐like or hairy shell and the MWCNTs as the hard backbone. Furthermore, the effect of counter‐anions on the solubility of MWCNTs‐g‐PILs was investigated. The results indicate that relative solubility of MWCNTs‐g‐PILs in various solvents could be switched by anion exchange. This tunable solubility results in the formation of the cycle of reversible phase‐transition. Tribological property of MWCNTs‐g‐PILs as additives in base lubricant 1‐methyl‐3‐butylimidaaolium hexafluorophosphate (LP104) was evaluated using an Optimol SRV oscillating friction and wear tester, confirming that MWCNTs‐g‐PILs are the excellent antiwear and friction‐reducing additives, which can amend the tribological properties of base lubricant significantly. This is attributed to the good dispersibility and core‐shell structure of MWCNTs‐g‐PILs. These results reported in this work may open primarily toward constructing a bridge among carbon nanotues (CNTs), ILs, and lubricant additives and secondarily to prove that CNTs (modified CNTs) as lubricant additives are promising candidates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7225–7237, 2008 [ABSTRACT FROM AUTHOR]

In order to increase the solubility of ionic liquids in base oils and to improve the lubricating performance of light alloys, two new ionic liquids comprised of sulfonate base anion and phosphonium based cation are designed and synthesized. The difference between these two ionic liquids is the cation: One has only one organophosphate group (P88816DOSS) and the other has two organophosphate group (P888PDOSS). The copper strip corrosion test is used to evaluate the anticorrosion properties of new developed ionic liquids. Tribological properties of the ionic liquids are investigated by an optimal SRV‐IV oscillating tribometer. The results indicate that the new designed ionic liquids show very good solubility in traditional mineral‐based oils. P88816DOSS and P888PDOSS show excellent friction reduction, antiwear performance accompanied with effective anticorrosion properties for the mineral base oil. Surface analysis results show that the superior properties of P88816DOSS and P888PDOSS are attributed to surface chemical reactions between ionic liquids and light metal. The designed task specific ionic liquids (ILs) not only have very good solubility in nonpolar hydrocarbon base oils, but also can significantly improve the lubricity and antiwear properties of base oils for light alloys. The excellent tribology properties of ILs can be attributed to their physical and chemical adsorption on the light metal surface and the further generation of tribofilm. [ABSTRACT FROM AUTHOR]

[Display omitted] • The poly(ionic liquid) functionalized COFs were prepared via surface-initiated ATRP of ionic liquid monomer. • The as-obtained PIL-PF 6 @DT-COF as lubricant additive can significantly reduce friction and wear. • The PIL-PF 6 @DT-COF nano-additive and protective tribo-film synergize and contribute to the good lubrication effect. Recently, covalent organic frameworks (COFs) have been extensively studied due to their abundant active sites for functionalization and the derived various applications. Herein, we prepared poly(ionic liquid) functionalized COFs via mechanochemical reaction to bond with initiator and the following surface-initiated polymerization. Firstly, the initiator 2-bromo-2-methylpropionyl bromide bonded with the hydroxyl group of DT-COF through ball milling driven mechanochemical reaction, then the ionic liquid monomer (IL-Cl) can grow on COF skeleton from the active sites of initiator via surface-initiated atom transfer radical polymerization (SI-ATRP) to obtain the poly(ionic liquid) functionalized COF (PIL-Cl@DT-COF). The as-prepared PIL-Cl@DT-COF as well as the PIL-PF 6 @DT-COF sample after anion exchange with PF 6 − served as oil-based lubricant additives, significantly reducing the friction coefficient and wear volume of base oil PAO10, especially PIL-PF 6 @DT-COF can reduce the average friction coefficient from 0.169 to 0.094 and decrease the wear volume by 82.9 %. The outstanding tribological properties mainly benefited from the tough protective tribo-film, which was built via tribological reaction on the friction interface, containing the absorbed PIL-PF 6 @DT-COF, ferric oxides and anti-wear F, P compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two novel amino acid-based ionic liquids (AAILs) were prepared and employed as water-ethylene glycol (W-EG) lubricant additives. • Two AAILs as additives can significantly reduce the corrosion of W-EG to cast iron, while demonstrating excellent friction-reducing and anti-wear properties. • The physical adsorption film and the tribochemical reaction film act synergistically to enhance the tribological properties of W-EG. • These two sulfur-free and halogen-free AAILs are promising for application in metal working fluids and hydraulic fluids. Two novel amino acid-based ionic liquids (AAILs) were synthesized and their tribological properties as water-ethylene glycol (W-EG) lubricant additives were investigated. The addition of 1 wt% of both AAILs to W-EG can significantly enhance the anti-corrosion, friction-reducing and anti-wear properties of the lubricants. Compared to W-EG, the coefficient of friction and wear volume are reduced by about 50% and 75%, respectively. The physical adsorption film and the tribochemical reaction film derived from AAILs collectively establish a protective barrier at the friction interface, endowing the lubricants with superior lubricity and load-carrying capacity. These two sulfur-free and halogen-free AAILs are promising for application in metal working fluids and hydraulic fluids. [ABSTRACT FROM AUTHOR]

Introducing functional ILs into the water-glycol system can significantly improve its lubrication and corrosion resistance, therefore, it is meaningful to investigate the interaction between IL and the interface or water-ethylene glycol system. Herein, we designed two IL additives to achieve the construction of water-glycol lubricating system. The unique interfacial behavior between the IL and the sliding asperity makes it critical to the friction reduction and anti-wear effect. And the adsorbed layer with certain viscosity and elastic modulus was obtained on the metal surface, which is ascribed to the strong hydrogen bonding network structure and a hydration layer, thus showing excellent load-bearing capacity. Additionally, the tribofilm formed on the friction pair behave superior mechanical properties (high Young's modulus and hardness). [Display omitted] • An ILs-WG lubrication system was constructed by task-specific ionic liquid. • The ILs-WG lubrication system can form a hydration layer between the friction pairs. • The formed tribofilm on the metal surface show certain mechanical properties. • Broadening the application of IL additives in water-ethylene glycol hydraulic fluids. [ABSTRACT FROM AUTHOR]

Three halogen-free poly(ionic liquid)s (PILs), composed of polycations (poly(PEGMA-co-METAC), PPM) and different amino acid anions as counterions, were synthesized. The physicochemical properties of three PILs were characterized to confirm their efficacy as viscosity-enhancing additives. The tribological properties of aqueous lubricants containing PILs were investigated by the SRV-IV test. The addition of three PILs to water resulted in remarkable improvements in kinematic viscosity, lubricity, and anti-wear properties. Among them, PPM-Try demonstrated the best tribological performance due to the formation of the more superior protective film on the friction interface through a tribochemical reaction. Furthermore, PPM-Try is non-toxic to environment and demonstrates favorable antibacterial properties, rendering it a promising eco-friendly aqueous lubricant additive for applications in the metalworking and food industry. [Display omitted] • Three halogen-free PILs with amino acids counterions were prepared and employed as water-based lubricant additives. • PILs can significantly enhance the viscosity, corrosion resistance, friction reduction and anti-wear properties of water. • Three types of tribofilms act synergistically to endow PILs with superior tribological properties. • PPM-Try demonstrates favorable antimicrobial activities and low biotoxicity towards earthworm. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ultra-low friction is achieved by using the inorganic salts and the proton-based ionic liquid. • The addition of the proton-based ionic liquid and the inorganic salts can enhance the P B value to 3090 N. • The system is suitable for a wide range of applications, including load ranges, sliding speed range and different alcohol types. • The proton ionic liquid not only can be adsorbed on the surface of the friction pairs, but also can form a triple film to get ultra-low friction. • The addition of inorganic salts that can form hydrated molecular layer to withstand high normal loads is the key factor. Macroscale facilitated lubrication is a forward-looking strategy in modern tribology that can significantly reduce friction and wear in mechanical equipment. However, it has been studied experimentally mainly for special friction pairs or point-to-surface contact. In the present work, we have achieved the ultra-low friction for point-to-point contact at the steel/steel interfaces by using the inorganic salts (NaCl and KCl) and the proton-based ionic liquid possessing a simple synthesis step and good solubility stability in aqueous 1,3-propylene glycol (PDO aq). Besides, the addition of the proton-based ionic liquid (PIL) can enhance the maximum non-seizure load (P B value) in PDO aq to 3090 N and the addition of inorganic salts don't lower the P B value. Results show: (1) The proton ionic liquid can be adsorbed on the surface of the friction pairs through electrostatic interactions, and undergo a friction chemical reaction to form a triple film that can effectively cushion the direct contact and collision of the microgrooves. (2) The addition of inorganic salts can form hydrated ions, which can shape a hydrated molecular layer to withstand high normal loads and balance the van der Waals attraction by hydration repulsion, which is a key factor in realizing the ultra-low friction. This discovery greatly expands the application of facilitated lubrication for point-to-point contact on steel surfaces in engineering applications. [ABSTRACT FROM AUTHOR]

Abstract Extreme pressure lubrication is a great challenge for many mechanical systems like bearings and gears. Here, an novel functional material based on Ga-based liquid metal has been applied to successfully lubricate the steel-ceramic sliding pairs at extreme high load (1500 N), which significantly outperforms other liquid lubricants like oil and ionic liquid. Ga-based liquid metal provides a low friction coefficient (0.11–0.23) and wear rate (10−8-10−7 mm3/Nm) of AISI 52100 steel disc (C 0.98-1.10 Mn 0.25-0.45 P ≤0.025 S ≤0.025 Si 0.15-0.30 Cr 1.30-1.60 Fe 96.5-97.32 , mass %; American Iron and Steel Institute standard) when it slides against Si 3 N 4 balls over a load range 100–1500 N. To elucidating these interesting results, the lubrication mechanisms of Ga-based liquid metal are studied by tribo-surface analysis. Highlights • Liquid metal (LM) provides a new strategy for lubricating the steel-ceramic pairs. • LM displays good lubricity and extraordinary load-bearing for steel-ceramic pairs. • This good property is due to boundary lubrication of LM and nano-scale Ga tribo-film. [ABSTRACT FROM AUTHOR]

Two novel PN type ionic liquids (ILs) surfactants, N-(3-(diethoxyphosphoryl) propyl)-N,N-dimethyloctadecan-1-aminium-6-methyl-4-oxo-4H-1,2,3-oxathiazin-3-ide-2,2-dioxide and N-(3-(diethoxyphosphoryl)propyl) -N,N-dimethyl octadecan-1-aminium-2,3,4,5,6-pentahydroxyhexanoate were synthesized and investigated as a potential water-based lubricant additive. Unlike other ILs with low solubility, these ILs surfactants are stable and miscible with water-diethylene glycol. Remarkably, these additives reduce the corrosion of water on the steel and improve friction and antiwear function for the steel surface with lower friction coefficient and wear volume. Based on the results of mechanism analysis, we speculate a boundary lubricating protection film containing phosphorus and nitrogen formed on the sliding steel surfaces, achieving excellent tribological properties by a phosphorus-nitrogen synergy. [ABSTRACT FROM AUTHOR]

This research into environmentally-friendly ionic liquids (ILs) used a series of choline amino acid ILs ([Ch][AA] ILs) prepared from choline cations and several amino acid anions. Their physicochemical and tribological properties were tested, and the results showed that [Ch][AA] ILs had good lubricating properties for different friction pairs at room temperature (RT). Their toxicities were checked against three aquatic organisms: brine shrimp, zebrafish and green algae. The results showed that they have a remarkably low toxicity. Versus traditional IL 1-butyl-3-methyl imidazolium tetrafluoroborate (L-B104), the [Ch][AA] ILs had comparable or even better physicochemical and tribological properties. More importantly, they had the environmentally features of biodegradability and non-toxicity. [ABSTRACT FROM AUTHOR]

A series of dicarboxylic acid ionic liquids (DAILs) were synthesized from the neutralizing reaction of variable dicarboxylic acids with tetrabutylammonium hydroxide. The ionic liquids (ILs) exhibit good performance in terms of corrosion, viscosity–temperature characteristic, and thermal and hydrolysis stabilities. Tribological test results indicated that these DAILs possess superior behavior in reducing both the friction coefficient and wear volume compared with monocarboxylic acid ionic liquids (MAILs), especially when used on steel–copper and steel–aluminum friction pairs. The enhanced lubricating property is attributed to the two introduced carboxyl groups that enable DAIL molecules to adsorb more efficiently on sliding metal surfaces. Toxicity test data also show that DAIL lubricants possess lower toxicity than MAILs. [ABSTRACT FROM AUTHOR]

A new N-(3-(diethoxyphosphoryl)propyl)-N,N-dimethyloctadecan- 1-ammonium bromide (NP) surfactant was synthesized. The NP together with 1 wt% sodium D -gluconate or 1 wt% triethanolamine displays remarkable lubricating property as the water-based lubricant additive and provides a non-corrosive environment for steel in aqueous solution. The lubricating mechanism was tentatively discussed according to electrical contact resistance, X-ray photoelectron spectroscopy and Quartz Crystal Microbalance measurement. These results show a stable protective film is formed on the contact surface by physical adsorption and tribo-chemical reactions. Surprisingly, the water-based additive has excellent anti-friction properties comparable to oil-based lubricants and superior to cationic surfactant analogue. Therefore, this NP is a potential efficient additive in water-based lubricating fluids. [ABSTRACT FROM AUTHOR]

To clarify the lubricating mechanism, two kinds of oil-soluble ionic liquids (ILs) with the same cation but different anions are synthesized, and then they are added into PAO10 as additives with different mass concentration. The tribological results indicate that the mixtures perform better lubricating performance than neat PAO10 for steel/steel contacts. Then quartz crystal monitor (QCM), X-ray photoelectron spectroscopy (XPS), plasma treatment, and external potential are introduced to clarify the lubricating mechanism of ILs as additives. The lubricating mechanism of the kind of ILs can be attributed to the good adsorptivity of cations and tribochemical films on the sliding surfaces. [ABSTRACT FROM AUTHOR]

A new class of ionic liquid gels (ionogels) is prepared through the supramolecular self-assembly of imidazolium-based ionic liquids (ILs) bearing the urea group as gelators in normal ILs. The ILs gelator can self-assemble through hydrogen bonding and hydrophobic interaction to form analogous lamellar structures and solidify base ILs. The obtained ionogels exhibit superior anticorrosion and conductivity characteristics. Moreover, ionogels show fully thermoreversible and favorable thixotropic characteristics, such that they can be used as high-performance semisolid conductive lubricants. The tribological tests reveal that these ionogels lubricants can effectively reduce the friction of sliding pairs effectively and have better tribological performance than the pure ILs under harsh conditions. Ionogel lubricants not only maintain the excellent tribological properties and conductivity of ILs, but also prevent base liquids from creeping and leakage. Therefore, ionogel lubricants can be potentially used in the conductive parts of electrical equipments. [ABSTRACT FROM AUTHOR]

This study firstly reports a series of novel functional polyhedral oligomeric silsesquioxane-based ionic liquids (POSS-ILs) with remarkable lubrication performance as well as resistance to space atomic oxygen (AO) irradiation. The enhancement in both anti-irradiation properties and the lubrication performance can be attributed to the synergistic effect produced by POSS group along with the tribochemical reactions. The approximate cube-octameric POSS framework as a significant contributor converts the original sliding friction into a rolling mode. The key benefit of POSS-ILs derives from the active elements N and P present in ILs and corresponding tribochemical reaction film formed. These ILs are bound to have substantial applicability in the aviation lubrication field. [Display omitted] • Oligomeric silsesquioxane-based ionic liquids (POSS ILs) were synthesized. • These POSS ILs have resistance to space AO irradiation. • These POSS ILs convert the original sliding friction into a rolling mode. • These POSS ILs has good antifriction and wear resistance. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) were modified by imidazolium-based ionic liquid (IL), 1-hydroxyethyl-3-hexyl imidazolium tetrafluoroborate and used as an additive in base stock IL 1-methyl-3-butylimidazolium tetrafluoroborate as the base lubricant. The effectiveness of using the IL- modified MWCNTs as lubricant additive was evaluated using a ball-on-plate configuration on an Optimol SRV oscillating friction and wear tester. The worn surfaces were examined using scanning electron microscope and the chemical composition on wear tracks was analyzed on an X-ray photoelectron spectrometer. Results suggest excellent anti-wear properties for the IL-modified MWCNTs as lubricant additive. [ABSTRACT FROM AUTHOR]

DOSS–(dioctyl sulfosuccinate) based quaternaryammonium ionic liquids (QAILs) were synthesized and used as both neatlubricants and lubricant additives. The influence of structure ontheir miscibility, thermal stability, and tribological property wasdiscussed. These QAILs are low cost as compared with conventionalhalogen-containing ionic liquids (ILs). They are noncorrosive andhydrolysis stable because of their halogen-free characteristics. Thetribological properties of these QAILs as neat lubricants for steel/steeland steel/copper contacts are found to be better than conventionalhalogen-containing ILs 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(L-F104) and far better than traditional synthetic lubricant poly-α-olefin(PAO). Moreover, oil-soluble ILs were obtained by properly adjustingthe chain length and cation asymmetry of these QAILs, which can beeasily dissolved in nonpolar synthetic-oil PAO. They are found tobe effective lubricant additives for improving the friction-reducingand antiwear properties of PAO. It is a great advantage as comparedwith conventional ILs, which have extremely low solubility in PAOand are difficult to be used as lubricant additives for this kindof base oil. Furthermore, the coking test results indicated that thesynthesized QAILs have high deterging ability when used as lubricantadditives for PAO. Thus, they can restrain carbonaceous depositionas well as oil sludge and varnish formation on the metal contactsduring the sliding process. They can also disperse, loosen, and removethe already formed harmful substances and keep the metal contactsclean. The present work may make obvious progress toward preparinglow cost, noncorrosive, and environmentally benign IL lubricants inlubrication engineering. [ABSTRACT FROM AUTHOR]

Abstract: Two kinds of lithium-based and sym-triazine- or cyclotriphosphazene-functionalized ionic liquids (ILs, L-C3N3 and L-P3N3) were synthesized by simply blending an appropriate molar ratio of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with tri(methoxyethoxyethoxyethoxy)triazine (C3N3(OR)3) or hexa(methoxyethoxyethoxyethoxy) cyclotriphosphazene (P3N3(OR)6). The ILs were evaluated as high temperature lubricants for Si3N4/steel contact and found to have significantly improved friction–reducing and anti-wear proprieties compared with conventional alkylimidazolium ILs, 1-ethyl-3-methylimidazolium bis(trifluoro methylsulfonyl)imide (L-F102) and 1-butyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (L-F104), at some condition. The morphologies of the worn surfaces were analyzed by scanning electron microscope (SEM). The wear mechanisms were discussed according to the surface composition analysis by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]

Abstract: Imidazolium ionic liquids (ILs) containing sterically hindered phenol and benzotriazole groups were synthesized and evaluated as combined antiwear (AW), antioxidation, and anticorrosion additive in poly(ethylene glycol) (PEG) for steel/steel contacts at room temperature and 100°C. The physical properties of the synthetic ILs and PEG with the additive were measured. The antioxidation and anticorrosion properties of the synthetic ILs were assessed via the thermal analysis, an accelerated corrosion test and copper strip corrosion test, which showed the excellent antioxidation and anticorrosion properties in comparison with the pure PEG and the selected conventional ILs having no functional groups. Tribological results indicated that these ILs as the additives could effectively reduce friction and wear of sliding pairs in PEG. The tribological properties were generally better than the common IL (L-P106) in PEG. The wear mechanisms are tentatively discussed according to the morphology observation of worn surfaces of steel discs by scanning electron microscope (SEM) and the surface composition analysis was obtained by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]

Abstract: In order to improve the lubrication performance and inhibit the serious corrosivity of conventional ionic liquids (ILs) at elevated temperatures, a series of vinyl functionalized ILs were synthesized in this work. The corrosion behavior of the ILs was evaluated with copper sheet corrosion test and their tribological properties were investigated on an Optimol SRV-IV oscillating friction and wear tester at elevated temperatures. The results showed that ILs with vinyl group, such as 1-vinyl-3-butyl imidazolium tetrafluoroborate (VBImBF4), can reduce corrosion effectively and its extreme pressure reached up to 1500N at 150°C. Based on the XPS analysis, ILs with vinyl group could interact with the iron surface and a protecting layer would form on the surface of steel possibly. Thus, ILs lubricants with good lubricating performance and low corrosivity at elevated temperature were achieved. [Copyright &y& Elsevier]

Abstract: Ionic liquids of α, -diimidazoliumalkylene hexafluorophosphate were synthesized. The tribological properties of the synthetic ionic liquid and the ionic liquid contained additive for contacts of steel/steel were investigated by Optimol SRV oscillating friction and wear tester under ambient conditions. The synthetic ionic liquid presented low friction coefficients and small wear volumes, especially under higher temperatures. The ionic liquid doped with benzotriazole (BTA) showed excellent anti-wear ability. The worn surfaces and chemical nature of the boundary films generated on the metal surfaces were analyzed by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). SEM results showed slight abrasion on the worn surfaces and XPS results indicated the formation of FeF2, FeF3, Fe3O4, and FePO4 by the tribochemical reactions of ionic liquid with iron during the sliding process. [Copyright &y& Elsevier]

Abstract: A series of asymmetrical tetraalkylphosphonium ionic liquids were synthesized and evaluated as a new kind of lubricant for the contacts of steel/Al using an Optimol SRV oscillating friction and wear tester in ambient condition. The phosphonium ionic liquid shows excellent tribological performance and is superior to the conventional ionic liquids 1-ethy-3-hexylimidazolium hexafluorophosphate (P206) in terms of anti-wear performance and load-carrying capacity. The chemical compositions of the boundary film generated on different contact surfaces were analyzed on a scanning electron microscope with a Kevex energy dispersive X-ray analyzer attachment (SEM/EDS) and X-ray photoelectron spectrometer (XPS). The friction-reduction and anti-wear mechanism were proposed to originate from the layered structure of ionic liquid under boundary lubrication and the tribochemical reaction of anions with the fresh surface, respectively. [Copyright &y& Elsevier]

The lubrication of Ti-6Al-4V tribopairs with various tetraalkyl phosphonium perfluorosulfonate ionic liquids (TPP ILs, C 6 F 13 SO 3 P 4444 , C 8 F 17 SO 3 P 4444 and C 8 F 17 SO 3 P 8888) was systematically investigated and compared with conventional ILs lubricants based on BF 4 − or PF 6 − and TFSI− anions. The results show that the TPP ILs have superior lubricating properties to existing IL lubricants on Ti-6Al-4V. Analysis of the lubrication mechanism showed that both physicochemically adsorbed films and tribochemical reaction films were produced on Ti alloy tribopair surfaces during sliding when lubricated with the TPP ILs. The formation of physicochemically adsorbed films between the TPP ILs and the friction surfaces were mainly responsible for the superior tribological properties compared to the reference samples. By comparing the tribological properties of TPP ILs with those of the tetrabutyl ammonium perfluorosulfonate IL C 8 F 17 SO 3 N 4444 and tetrabutyl phosphonium carboxylate IL C 8 F 15 O 2 P 4444 , the chemical structures of the perfluorosulfonate ILs was found to have significant influence on the lubricating ability. The introduction of the sulfonate group and P-containing functional group effectively improved the lubricating properties of the TPP ILs to lubricate Ti alloy tribopairs. This work provides insight into the behavior of IL lubricants on Ti alloy surfaces, and will inspire further studies into use of liquid lubricants for titanium alloys. • Sulfonate ionic liquids have remarkable tribological property on titanium alloy. • Physicochemically adsorbed film formation is the main reason for the property. • Sulfonate and P-containing groups introducing can effectively improve the property. [ABSTRACT FROM AUTHOR]

Abstract: Room Temperature Ionic Liquid (RTIL)/Multi-Walled Carbon Nanotubes (MWNTs) composite was prepared by chemical modification. The composite was analyzed by using laser Raman spectroscopy and X-ray photoelectron spectroscopy. The RTIL/MWNTs composite was evaluated as lubricant additive in ionic liquid due to their excellent dispersibility. Tribological performances of RTIL/MWNTs composite as lubricant additive were performed on a universal UMT-2MT Tribo-tester. It is found that RTIL/MWNTs composite showed good friction-reduction and anti-wear properties in friction process. It is concluded that RTIL/MWNTs composite might play the role of roller bearing during friction process. [Copyright &y& Elsevier]

Cr-doped graphite-like carbon (Cr-GLC) coatings and Cr-doped diamond-like carbon (Cr-DLC) coatings were prepared by PVD and PECVD, respectively. The lubrication behaviour of the solid-liquid composite lubrication systems was investigated using two ionic liquids (ILs) as lubricants. The results show that the friction coefficient was reduced by approximately 40% compared with that under the dry condition, and the composite system exhibited a good synergistic lubrication effect. The Cr-DLC coating showed better tribological behaviour than the Cr-GLC coating, which can be ascribed to a better physicochemical film formation under friction and the compact microstructure of the Cr-DLC coating. The synergistic effect of the composite systems was affected by the viscosity and corrosiveness of the ILs and the microstructure of the coatings. Image 1 • The Cr-GLC and Cr-DLC coatings were prepared by PVD and PECVD method, respectively. • The friction coefficient decreases from 0.11 (dry condition) to 0.045–0.06 (ILs condition). • The lubrication of solid-liquid systems is mainly affected by the wettability of ionic liquids. • The tribological properties of Cr-GLC in ionic liquids are more affected by the corrosion effect. [ABSTRACT FROM AUTHOR]

• A new kinds of low cost proton-type ionic liquids additives (PILs) were synthesized. • PILs as additives for water have good solubility and anticorrosion property. • PILs additives significantly enhance lubricity and antiwear performances of water. • Interface assembly behavior and tribochemistry work together to enhance lubricity. • Torque test indicate that PILs have great potential as water-based additives. With the increasingly serious environmental pollution and energy issues, water-based lubricating materials will gradually replace oil-based lubricating materials in some specific applications, which has become a trend. As a water-soluble lubricating additive, the synthesized proton-type ionic liquids (PILs) have the advantages of simple synthesis, good solubility stability, and excellent corrosion resistance properties, providing a method to better solve the problems of traditional water-based additives. The physical-chemical properties and lubrication functions of additives were characterized by foam corrosion test and tribological trials, with the detailed exploration of their lubricating mechanism obtained from QCM, TEM, TOF-SIMS, XPS and MD analysis. The results show that PILs display excellent friction-reducing and anti-wear performances, and improve the carrying capacity for water, which is mainly attributed to the formed tribofilm on the friction surface. The tribofilm is probably triggered by ions pair adsorption on the substrate surfaces, equipping with a typical bilayer structure self-assembly between two convexs. When it worked on the interface, a double layer structure is formed by the way of self-assembly, resulting in the formation of a continuous boundary protective film induced by tribochemical reaction, which can effectively reduce the shear damping during friction. Torque testing system results show that PILs have the smaller torque values, indicating their better lubricating performance in the small-scale platform test, which can make it to be used as a potential additive with excellent properties in water-based cutting fluids. [ABSTRACT FROM AUTHOR]