An oil soluble multifunctional protic ionic liquid (IL) was synthesized and its tribological and antioxidant properties in poly alpha olefin (PAO4) were investigated. The tribological results demonstrated that the IL significantly reduced friction and wear of PAO4. The PAO4 blend with IL resulted in an induced oxidation time of 555 min which is 8.2 and 3.5 times higher than that of pure PAO4 and PAO4 with zinc dialkyl dithiophosphate (ZDDP) for the rotating pressure vessel oxidation test. It is likely that free nonylated diphenylamine acted as a radical scavenger to enhance antioxidant performance, while free bis(2-ethylhexyl) phosphate was more prone to adsorb and react with the metal surface to form a phosphorus-rich tribofilm in order to protect the rubbing surface.

Deep eutectic solvents (DESs) are acknowledged as a novel class of functional liquid. DESs share similar physical properties with ionic liquids (ILs) and have the potential to be a novel class of lubricants. In this study, two DESs, namely tetrabutylammonium chloride-decanoic acid DES (C4-DES) and methyl tricaprylmethylammonium chloride-decanoic acid DES (C8-DES), were synthesized, and their physico-chemical properties and tribological performances were evaluated. Post-analysis of the rubbing surfaces used multiple techniques to gain insights into the lubrication mechanisms. Results show that the coefficient of friction (COF) and wear were reduced by approximately 29% and 91% for the C4-DES, and 36% and 94% for the C8-DES, compared to an ester base oil. The friction reduction behavior of the DESs is attributed to the monolayer adsorption of the polar group in the decanoic acid (DEAC), whose effectiveness is affected by the component of the ammonium salts in the DESs and the operating temperatures. In addition to the adsorbed film, worn surface analysis revealed that an ultra-thin tribochemical film with a thickness of 3–7 nm was formed on the surfaces lubricated with the C8-DES. The composition of the film was studied, and the lubrication mechanisms of the two DESs were discussed.

Fuel and water contents are inevitable in automotive engine oils. This study intends to investigate the impact of the addition of gasoline (3–20%) and water (1%) on the lubricating performance of synthetic base oil (PAO), with or without an anti-wear additive (ZDDP), for a steel-cast iron contact. Fuel-added PAO showed an increase in the load carrying capacity. Oil electrical conductivity and total acid number (TAN) measurements showed slightly increased conductivity and marginally increased acidity at a higher fuel concentration. In contrast, an increased wear rate, proportional to the fuel concentration, was observed in a prolonged test with constant-loading. Results suggested that the fuel addition is a double-edged sword: reducing the scuffing risk by providing stronger surface adsorption and increasing the sliding wear rate by bringing down the oil viscosity. The PAO-water blend formed an emulsion and resulted in a significantly increased load-carrying capacity, again likely due to the higher polarity and possibly acidity. For the ZDDP-containing PAO, the addition of 1% water and 3% fuel generated 24% and 52% higher wear. The phosphate polymerization level was reduced on the worn surfaces by the introduction of water but the thickness of ZDDP tribofilm was not significantly affected.

Notorious Zn dendrites and severe parasitic side reactions severely disrupt the anode–electrolyte interface during Zn plating/stripping, resulting in uncontrollable Zn deposition and limiting the application of aqueous zinc-ion batteries (AZIBs). Although the construction of an artificial interface is a highly desirable strategy, it is often limited by slow Zn²⁺ transport kinetics. To address these issues, we present a bifunctional polymer coating (PEPM) constructed from highly conductive PEDOT:PSS and monolayer MoS₂, where the introduced PEDOT plays an important role in driving the fast Zn ion transfer kinetics as a zincophilic site and 2D MoS₂ acts as a buffer layer to induce uniform Zn nucleation. With this corrosion inhibition and nucleation-oriented coating, the mobility of Zn²⁺ flux and the uniformity of Zn deposition were significantly improved, resulting in a stable plating/stripping performance at an ultra-low overpotential (99.4%) of 1000 cycles without significant dendrite formation. The proposed strategy provides a cost-efficient remedy and opens a new avenue for the development of dendrite-free zinc anodes.

Two kinds of chemically modified silicone oil, diisooctyl phosphate-terminated silicone oil (UCP204) and dioctyl dithiophosphate-terminated silicone oil (UCT2003), were synthesized. The tribological properties of silicone oil were evaluated using an SRV tribometer, and the worn surface and chemical composition were examined by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The friction coefficients of UCP204 and UCT2003 were reduced by approximately 62.7% and 56.7% compared with untreated silicone oil. The results indicated that the incorporation of phosphorus and/or sulfur could significantly enhance the tribological performance of modified silicone oil. Benefiting from their unique chemical structure, chemically modified silicone fluids also exhibit good dispersion stability and excellent anti-foaming properties, which are mainly attributed to the low surface tension properties imparted by the silicone backbone and the better dispersion stability provided by the dialkyl dithiophosphate group in chemically modified silicone fluids. It is also found that lubricants containing modified silicone oil remain clear after three months of storage and still maintain good anti-foaming properties.