Tribological Performance of an Imidazolium Ionic Liquid-Functionalized SiO₂@Graphene Oxide as an Additive

Abstract

A graphene oxide (GO)-wrapped SiO2 nanosphere was modified with a 1-methylimidazolium bis­(salicylato)­borate (MEIMBScB) ionic liquid to form a SiO2@GO@MEIMBScB nanocomposite. The SiO2@GO@MEIMBScB nanocomposite exhibited a core–shell structure, which was characterized by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, photoluminescence spectroscopy, dynamic light scattering, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The SiO2@GO@MEIMBScB nanocomposite was dispersed into poly­(ethylene glycol) 400 (PEG400) as a lubricant additive, and its tribological performance was evaluated with a four-ball tribometer under 392 N at 1450 rpm for 30 min. The results showed that the SiO2@GO@MEIMBScB nanocomposite can reduce the friction coefficient by 57.27% and reduce the wear scar diameter by 16.98% at an optimized concentration. Its tribological performance was much better than the individual SiO2@GO and MEIMBScB ionic liquid and the SiO2@GO/MEIMBScB mixture. The SiO2@GO@MEIMBScB nanocomposite exhibited a synergistic effect, which was confirmed by surface analysis on a wear track. It showed that SiO2@GO@MEIMBScB can be adsorbed on the rubbing surface and form a tribo-boundary film to reduce friction and wear. A possible lubrication mechanism was proposed, which might guide the development of a novel nanolubricant additive.

Artificial Intelligence-Based Rapid Design of Grease with Chemically Functionalized Graphene and Carbon Nanotubes as Lubrication Additives

“…In practice, the frictional interfaces are similar to those of steel balls when friction occurs, in which the surface is not as smooth as it appears to the naked eye (Figure S8). There are a lot of craters and bulges on the surface of the steel ball, which makes the frictional interfaces very rough and lead to a high friction coefficient (Figure a). , Meanwhile, the high friction coefficient deteriorates the tribological environment even further during the friction process, for example, the increasing friction coefficient of curve (a) in Figure e. FGR can be rapidly deposited at the friction interfaces (Figure b), filling the craters through the repair effect and forming a lubricating and protective film to avoid direct contact with the bulges through the protection effect. , The repair and protection effects effectively improve the morphology of the frictional interfaces.…”

“…Grease can stick better than lubricating oils through their excellent adhesion on frictional interfaces where gravity and centrifugal force cause serious loss. , Recently, the continuous development of productivity has required a higher grease performance. It has been confirmed that the addition of lubricant additives may enhance their tribological properties. − The dispersibility of nanoadditives is the most critical factor to influence their performance in lubricants, and chemical functionalization is the most common method to improve its dispersibility. − Ismail et al performed a reaction at 80 °C for 24 h and successfully grafted the straight alkyl chain onto graphene oxide to enhance its hydrophobicity and tribological properties in lubricants. In addition, the functionalized additive has excellent lipophilic properties and improves the solubility of the additive in the oil .…”

“…Some engineering problems still need to be resolved for the rapid design of high-performance lubricants, although both chemically functionalized additives and multi-additives can further improve the tribological properties of lubricants. The chemical functionalization of additives often requires long or complex chemical reactions. ,,− In addition, there is an optimum concentration of additives in lubricants . The introduction of multi-additives increases the complexity of the friction system; therefore, the optimum concentration of multi-additives requires extensive experiments to determine, and the lubrication mechanism becomes more complex. − , Microwaves have been proven to reduce activation energy and promote chemical reactions .…”

Ionic Liquid Crystals Confining Ultrathin MoS2 Nanosheets: A High-Concentration and Stable Aqueous Dispersion

“…It is noteworthy that the aromatic ring of ILCs is capable of attractive π−π stacking interactions. 24 In a previous work, the ILC-assisted hydrothermal exfoliation method was developed for exfoliation and functionalization of fluorinated graphene, and encouraging results were obtained concerning the performance of ILCs as colloidal dispersants. 25 In this study, a scalable and facile approach to exfoliate bulk MoS 2 into high-quality MoS 2 ultrathin nanosheets in water via sonication using ILCs as green exfoliating/dispersing agents is reported.…”

“…Amphiphilic ionic liquid crystals (ILCs) are commonly composed of cationic alkyl chains of more than 12 carbon atoms with hydrophilic anions. It is noteworthy that the aromatic ring of ILCs is capable of attractive π–π stacking interactions . In a previous work, the ILC-assisted hydrothermal exfoliation method was developed for exfoliation and functionalization of fluorinated graphene, and encouraging results were obtained concerning the performance of ILCs as colloidal dispersants .…”