This study investigates the formation of electrical fluting erosion on bearing surfaces using a lubricated ball-on-disc tribometer. The “washboarding effect” is firstly proposed to account for fluting evolution during electrical erosion. Results show that elevated voltage extends the discharge region beyond the Hertzian contact area. Thicker oil films, resulting from higher velocity or viscosity, increase the critical breakdown voltage and decrease the fluting spacing. Additionally, mechanical-electrical coupling under slide-roll conditions significantly exacerbates surface degradation. Fluting is observed to evolve from initial frosting damage. Analogous to the “washboard” phenomenon on the unpaved roads, it is thought the initial ridge/flute morphology is irreversibly recorded and progressively amplified under follow-up rolling, forming fluting erosion with alternating “bright” and “dark” areas.

Designing lubricant additives capable of simultaneously improving lubrication and impact resistance remains a significant challenge in tribological systems operating under complex loading conditions. In this work, hollow mesoporous silica nanoparticles (HMSNs) encapsulating high-viscosity polyethylene glycol (PEG6000) were fabricated and further modified with a polydopamine shell to construct PEG6000@HMSN@PDA nano-additives dispersed in PEG200 base fluid. Rheological measurements revealed pronounced shear-thickening behavior at high particle concentrations, while tribological tests demonstrated a substantial reduction in friction coefficient and wear compared with the base lubricant. The optimized additive concentration produced stable boundary lubrication conditions and reduced peak impact force, indicating enhanced energy dissipation capability under cyclic impact loading. Surface analyses suggest that the improved performance originates from the synergistic effects of nanoparticle deposition, physical surface protection, and pressure-induced release of viscous PEG6000 within the contact zone. These findings provide a feasible strategy for designing multifunctional lubricant additives capable of adapting to both sliding and impact conditions.

The present study reports the synthesis of polyol esters from trimethylolpropane (TMP) and fatty acids via an esterification process catalyzed by a series of mixed-linker sulfonic acid-functionalized UiO-66 catalysts with varying sulfonic ligand ratios. A comprehensive structural analysis revealed the successful attachment of sulfonic acid groups (–SO3H) to the UiO-66 framework while preserving its characteristic topology. An increase in sulfonic ligand content progressively enhanced the total acidity from 1.67 to 3.71 mmol g−1, but resulted in a decline in crystallinity and surface area. The UiO-66 containing 40 mol% of the sulfonic acid-containing benzenedicarboxylate linker exhibited the highest catalytic activity. This optimal performance was attributed to the best balance achieved between Brønsted acid site density and Lewis acid site accessibility at this intermediate ligand ratio, enabling effective Brønsted-Lewis acid synergy under pore-diffusion conditions. Furthermore, the catalyst demonstrated excellent reusability over multiple cycles. The present work elucidates the influence of sulfonic ligand ratio on the structure and catalytic performance of UiO-66, providing a robust heterogeneous catalyst for the green synthesis of polyol esters.

High-temperature lubricant additives face significant challenges in maintaining stable tribological performance under extreme conditions due to thermal degradation and insufficient interfacial protection. This study develops a novel MWCNT@FCTF nanocomposite through mechanochemical synthesis, combining one-dimensional multiwalled carbon nanotubes with a two-dimensional fluorinated covalent triazine framework to address these limitations. The resulting core-shell structure exhibits exceptional thermal stability and oil dispersibility, enabling stable operation across a wide temperature range (50-250 degrees C). Tribological testing demonstrates outstanding performance, with a 45.3 % reduction in friction coefficient and 68.7 % lower wear rate compared to the base oil. Multiscale characterization reveals a synergistic lubrication mechanism involving FCTF-derived adsorption films, MWCNT-generated graphitic layers, and in situ formed fluorinated iron oxide tribofilms, collectively reducing friction and wear. The system maintains robust performance under high contact pressures and prolonged operation, while the lubrication mechanism elucidates the fluorine-enhanced tribochemical reactions at the interface. This work provides a materials design strategy for high-performance, wide-temperature lubricant additives through dimensional hybridization and interface engineering.

Biobased lubricants have garnered significant attention due to their environmentally friendly characteristics. In this study, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) was employed as a thickener to successfully prepare four biobased greases with identical NLGI consistency grades. Scanning electron microscopy (SEM) characterization revealed that the P34HB thickener formed a three-dimensional lamellar network microstructure, elucidating the grease formation mechanism of the P34HB thickener. Rheological tests demonstrated that this grease system exhibited typical non-Newtonian fluid behavior and pronounced shear-thinning effects. Tribological performance evaluation indicated that the grease formulated with acetyl triethyl citrate (ATEC) as base oil displayed optimal friction-reducing and anti-wear properties. This research provided expanded base oil options for developing eco-friendly lubricants, extended the application scope of biobased materials in grease technology, and held substantial engineering value for promoting innovative development in green lubrication technologies

High-performance transformer oils require excellent thermal stability and electrical insulation, making polyol esters (POE) synthesized from trimethylolpropane (TMP) and fatty acids ideal base oils for advanced transformers. The synthesis efficiency of POE is largely dependent on the catalytic system employed. This work employs acetic acid (HAc) as a green, low-cost modulator to fabricate defective UiO-66 for the esterification of TMP esters, a key reaction in transformer base oil production. The UiO-66 were characterized, and their catalytic performance was evaluated via single-factor tests, response surface methodology (RSM)-Box-Behnken design (BBD) optimization, density functional theory (DFT) calculations, and reusability experiments. HAc modification introduced controllable linker defects while preserving the crystal framework, creating abundant coordinatively unsaturated Zr4+ (CUS-Zr4+) Lewis acid sites, raising specific surface area by 40.89% and total acidity by 10.20%. Under optimized conditions, esterification conversion exceeded 95%, and the catalyst showed outstanding reusability and stability. DFT revealed that CUS-Zr4+ strengthened substrate adsorption, promoted electron transfer, polarized n-octanoic acid C--O, and weakened TMP O-H bonds, thus activating key sites and accelerating the nucleophilic step of esterification.

Although extensive research has found that ionic liquid additives can effectively improve tribological performance, the true industrial application may be to exert lubricating effects under parts per million levels of ionic liquid additives. For the performance requirements of aviation oil under the standard MIL-PRF-23699G Enhanced Ester (EE), the introduction of in situ ionic liquids may become a solution. Herein, in situ introducing of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) at 500 ppm could form molecular structures with enhanced polarity. When it comes to harsh conditions, the in situ ionic liquid could easily adsorb to the asperity contact zone of a metal surface for smooth lubrication. Excellent tribological properties are attributed to the physical adsorption of polarity-induced films of in situ formed ionic liquids on the surfaces, as well as the further tribochemical reaction of TFSI- with sliding metallic surfaces.

Driven by the goals of sustainable development and environmental protection, this study aims to address the reliance of conventional lubricant additives on non-renewable petrochemical resources. To this end, a green deep eutectic solvent (DES) type lubricant additive was designed and prepared using renewable bio-based phytic acid (PA) as the raw material. The tribological performance of the DES in PEG400 under various testing parameters was evaluated using a reciprocating friction and wear tribometer (SRV). Findings indicate that the DES markedly enhances the friction-reducing and anti-wear performance of Polyethylene glycol 400 (PEG400) under various loads (50-300 N), a wide temperature range (25-150 degrees C), and multiple frequencies (5-45 Hz). When 0.25 wt% is added, the average coefficient of friction (ACOF) of PEG400 was reduced by up to 48.69%, the wear volume decreased by 97.68%. The lubrication mechanism of the PA-based DES was elucidated by analyzing the microstructure and chemical composition of the wear surfaces. It was found that the DES forms an in situ organic-inorganic hybrid composite lubricating film at the friction interface through chemical adsorption and tribochemical reactions, thereby delivering excellent lubrication performance. The work thus proposes a new direction for creating sustainable, high-performance lubricant additives.

Immersion cooling technology enables efficient heat dissipation through direct heat exchange between coolants and components. Ester oils are considered potential cooling media owing to their biodegradability and excellent thermal stability; however, their low thermal conductivity limits further improvement in cooling performance. Thus, this study proposed and implemented a synergistic mechanism combining chemical bonding and physical adsorption through the surface modification of h-BN with KH550 and Span 80. Nanofluids were prepared using ester oil 1190 as the base fluid, and their dispersion stability, rheological properties, and thermal conductivity were evaluated. Numerical simulations were further conducted to assess the cooling performance of the BNKS nanofluid in an immersion cooling system. The results demonstrated that the modified BNKS nanosheets exhibited improved short-term dispersion stability in ester oil 1190 compared with h-BN, maintaining stable dispersion after 7 days of static sedimentation. Moreover, surface modification reduced the viscosity increase of high-concentration nanofluids. At 20 °C, the BNKS-5 nanofluid achieved a thermal conductivity of 0.1693 W·m−1·K−1, corresponding to an 8.27% enhancement compared with ester oil 1190. At a flow rate of 4 L/min, the BNKS-5 nanofluid decreased the maximum temperature difference of the battery module to 4.80 °C and maintained an average temperature of 26.78 °C, indicating enhanced temperature uniformity and cooling performance. This study proposed a synergistic surface modification strategy that integrated KH550-induced chemical bonding with the physical adsorption of Span 80 to improve the dispersion stability and thermal transport properties of ester oil-based h-BN nanofluids, highlighting their potential for immersion cooling applications

In this study, an elastoplastic finite element (FE) contact model was developed to evaluate the plastic deformation of a surface induction-hardened tapered roller bearing used in wind turbines, incorporating depth-dependent material properties and heat treatment-induced residual stress distribution. The validity of this model was confirmed by comparing the calculated plastic deformation with measured profiles from static compression experiments. The results show that the residual stresses generated by induction hardening have a significant influence on the elastoplastic behavior of bearings. Based on this model, a parametric analysis was performed to investigate the effects of surface hardening depth (SHD), contact pressure, and residual stress on surface plastic deformation. Empirical formulas were developed to predict surface plastic deformation and evaluate material yielding for surface-hardened tapered roller bearings, thereby preventing excessive deformation during service. This allows for the rapid estimation of the maximum plastic deformation for different hardening depths and provides an efficient approach for assessing the yielding risk.

To address the challenges in green synthesis and efficient catalyst separation for high-grade polyol ester lubricants, a Fe3O4-SnO-SiO2 composite catalyst with high activity, magnetic separability, and cycling stability was designed for efficient esterification of trimethylolpropane trioleate (TMPTO). Characterizations, including XRD, VSM, SEM-EDS, XPS, and BET, confirm that Fe3O4 provides magnetic separation, SnO offers Lewis acid sites, and SiO2 improves dispersion and structural stability, realizing the integration of efficient catalysis, fast magnetic separation, and stable recycling. At 200 degrees C for 4 h, the TMPTO conversion reaches 91.3% and remains 87.8% after 5 cycles. The product shows no byproducts and improved structural regularity. Tribological tests exhibit a stable coefficient of friction (0.08-0.10), with wear volume and rate about one-third of the uncatalyzed system, reaching or exceeding commercial products. DFT and FTIR reveal that Sn2+ acts as the active center to activate oleic acid and reduce the energy barrier. This work provides a new catalyst system and theoretical basis for green industrial production of high-end ester lubricants.

Traditional metalworking fluids contain a variety of components to perform the functions of lubrication, cooling, and rust prevention. However, traditional additives are prone to failure under long-term operating conditions and have insufficient basic lubrication performance, resulting in significant fluctuations in the friction coefficient under mixed lubrication states. In view of the research demand for enhancing the lubrication performance and anti-corrosion property of aqueous solutions, this study specifically designed and synthesized four types of watersoluble fatty alcohol polyoxyethylene ether phosphates (C10PPE-M) functionalized with distinct metal ions (i.e., Ce, La, Zn, and Ca). When C10PPE-M was introduced into pure water, the friction coefficient of the lubrication system decreased from 0.393 to 0.078, and the contact interface exhibited an extremely low wear volume (0.29 x10-3 mm3) and wear rate (6.66 mu m3 center dot N-1 center dot m-1). Analysis of the lubrication mechanism revealed that C10PPE-M tends to adsorb on the metal surface to form a deposition film, thereby reducing the sliding resistance at the friction interface. In addition, tapping torque tests further verified their low-torque characteristics in micro-platform lubrication scenarios, indicating great potential in water-based cutting fluids.

Lithium 12-hydroxystearate (Li12HS) and its derivatives serve as primary thickeners in grease formulations; however, the mechanistic pathway governing thickener network scaffolding via crystallization remains incompletely elucidated. This study systematically investigates the non-isothermal crystallization kinetics of Li12HS in synthetic ester oil using differential scanning calorimetry (DSC). Results demonstrate that the Avrami model adequately describes the melt-recrystallization process, revealing a two-dimensional flake-like growth mechanism followed by agglomeration into macrocrystalline assemblies. Notably, base oil molecules significantly constrain the conformational mobility of Li12HS molecular chains, thereby inducing crystallization retardation within the grease matrix. Jeziorny kinetic analysis of DSC thermograms and scanning electron microscopy (SEM) further reveals that the fibrillar growth mechanism—characterized by the progressive assembly and elongation of fibrils into bundled fibers—is the key process governing the formation of the lithium-grease network.

Lubrication systems constructed with responsive additives exhibit real-time changes in the coefficient of friction (CoF) as the external environment changes to achieve controllable friction. However, the CoF of the currently investigated responsive additives is virtually impossible to modulate in real time. Herein, this work presents a magnetic composite material that exhibits a friction curve with a step change in an applied magnetic field. Importantly, the composites can degrade common contaminants in aqueous solutions through a tribocatalytic effect, exhibiting superior eco-friendly properties. Compared to the base oil at 250°C, the composite lubrication system showed a 19.8% and 66.8% reduction in CoF (0.131 to 0.105) and wear volume (21.1 × 10 5 µm 3 to 7.0 × 10 5 µm 3 ), respectively. The carbon deposition film and tribofilm formed during the friction process are the dominant factors in high-temperature resistant lubrication. Additionally, the finite element analysis (FEA) results indicate that the applied magnetic field exerts a vertically downward load on the tribopairs, causing an increase in the CoF. This research provides a new strategy for the design of multifunctional nano-additives with high-temperature intelligent lubrication.

Modern mechanical transmission components face the multiple challenges of friction, wear, and electrical corrosion. To address these issues, the development of multifunctional additives that integrate superior tribological performance with high electrical conductivity has emerged as a critical strategy. In this study, CuS@MXene nanohybrids possessing both excellent tribological and conductive characteristics were designed and synthesized as multifunctional additives for supramolecular gels. The in-situ uniform loading of CuS nanoparticles onto the Mo2C MXene surface was achieved via molten salt etching and electrostatic adsorption strategies. Its tribological performance and lubrication mechanisms as a lubricant additives in supramolecular gels were investigated using a reciprocating friction and wear tester, X-ray photoelectron spectroscopy, and Focused Ion Beam-Transmission Electron Microscopy. Tribological evaluations revealed that, compared to the pure gel, the gel containing 2.0 wt% CuS@MXene reduced the average coefficient of friction by 56.1% and the wear volume by 83.9%, while enhancing the load-carrying capacity by two times. The lubrication mechanism of CuS@MXene is attributed to the formation of a "hard-soft" synergistic composite tribofilm at the sliding interface; this film leverages the complementary advantages of its components to deliver exceptional lubrication performance. Furthermore, the nanohybrids significantly enhanced the electrical conductivity of the gel, thereby reducing the electrical resistance of the tribofilm. This work provides a novel strategy for developing multifunctional additives with robust lubricating and conductive capabilities to mitigate friction and electrical corrosion in mechanical components.

To address electrical erosion in rolling bearings of the motor systems of electrical vehicles, this study presents an in situ functionalization of graphene oxide (GO) with an amino-functionalized ionic liquid, [Bmim]PF6, resulting in a reduced graphene oxide-ionic liquid composite (rGOIL) with excellent electrical conductivity and outstanding friction-reducing and anti-wear performances. A series of conductive urea-based greases are formulated by optimizing the rGOIL content. The structure and morphology of rGOIL are characterized by FTIR, XRD, Raman spectroscopy, SEM, TEM, and XPS. Tribological tests using an SRV tribometer and electrical erosion evaluation on a bearing test rig show that grease containing 0.5 wt% rGOIL maintains a low and stable friction coefficient (0.102) under a 200 N load at 50 degrees C, with a 93 % reduction in wear volume compared to conventional polyurea grease. In electrical erosion tests, the bearing vibration amplitude stabilizes at 1.1 mm/s2, only 15 % of that measured for the reference grease. XPS and TEM analyses reveal the formation of a tribochemical film consisting of graphene nanosheets, ionically bonded liquid layers, and metal fluorides and phosphates. This film forms a conductive lubrication layer through a synergistic "lubrication-conductivity-lubrication" mechanism, effectively mitigating electrical erosion and enhancing bearing durability.

The development of conductive greases with friction-reducing, anti-wear, and anti-electrical corrosion performance provides an effective solution to mitigate bearing electrical erosion in electrical vehicles. In this study, a titanium carbide MXene (Ti3C2Tx)-based eutectic hydrogen-bonded thickener is successfully synthesized through micro-interface reactions by exploiting the different reaction rates of -NH3, H2O, and -CNO functional groups. Tribological experiments indicate that the hydrogen bonding within the Ti3C2Tx-based eutectic thickener facilitates the co-release of the thickener and Ti3C2Tx nanosheets at tribological interfaces, thereby enhancing the lubricating film thickness. Moreover, the M-0.5 system (Ti3C2Tx concentration of 0.5 wt%) achieves a 91 % reduction in wear volume, significantly decreases contact resistance, and effectively mitigates electrical corrosion. This study presents a feasible strategy for the design of two-dimensional oil-soluble complexes for the protection of grease lubricated bearings.

Rolling contact fatigue(RCF)failures in critical components such as precision gears and high-performance bearings have become increasingly prominent under demanding conditions.Conventional lubricant additives struggle to reduce friction simultaneously,resist wear,and repair dynamic micropitting.To address this challenge,a composite material of ionic liquid-functionalized magnesium silicate hydroxide(MSH)([DDP][TOA]/MSH(DDP=dialkyl dithiophosphate,TOA=trioctylamine))was synthesized using hydrothermal synthesis and noncovalent modification.This composite exhibited remarkable dispersion stability and copper corrosion inhibition,as well as superior tribological properties,including friction reduction,wear mitigation,and micropitting repair during rolling-sliding contact.Tribological evaluations revealed that 1.0 wt%[DDP][TOA]/MSH reduced the friction coefficient by 17.2%and the wear volume by 52.5%,demonstrating unprecedented load-bearing capacity and frequency adaptability.Notably,under rolling-sliding contact fatigue conditions,commercial gear oil exacerbated micro-pitting damage continuously,whereas the composite material repaired damage,with a repair efficiency of 72.0%.Surface characterization reveals a three-stage mechanism for the dynamic repair of worn metal surfaces:(1)micro-asperities are removed through mechanical grinding,(2)micro-cracks are filled via tribochemical deposition of FeS/phosphate phases,and(3)a hybrid a-SiC/a-SiOx repair layer is formed with improved mechanical strength,effectively preventing fatigue wear propagation.This work demonstrates the synergistic effect of ionic liquids and layered silicate additives on micropitting repair under rolling contact fatigue,expanding the application of MSH in the field of commercial lubricant additives.

Biaxially oriented polypropylene stretchers and wood hot presses operate continuously at 90–120 ℃, demanding lubricants with superior thermal resistance and long-term tribological durability. Traditional mineral oils easily undergo thermal oxidation and boundary film failure under such harsh medium–high temperature working conditions. Herein, citric acid-modified trimethylolpropane oleate (TMPTO-CA) is synthesized via DFT-guided esterification and comprehensively characterized by thermogravimetry (TG), 1H/ 13C NMR, 2D COSY NMR, EDS, XPS, Raman spectroscopy, and FIB-SEM. DFT simulations identify the low-energy esterification pathway to stabilize intermediates, and a high esterification conversion rate of 92.02% is achieved within 6h. NMR and 2D COSY spectra verify the cross-linked molecular network formed by covalently grafted citric acid. TG tests confirm the improved thermal stability of TMPTO-CA compared with neat TMPTO. Tribological tests across 90–120 °C reveal that TMPTO-CA delivers remarkable friction-reducing and anti-wear superiority over unmodified TMPTO. XPS, Raman, and FIB-SEM characterizations demonstrate that abundant citric acid-derived oxygen-containing groups strengthen interfacial adsorption, accompanied by temperature-responsive tribofilm evolution: amorphous carbon prevails at 90 °C, while disordered sp2 carbon layers form at 120 °C with I(D)/I(G)≈0.98. The temperature-adaptive lubrication mechanism is clarified: liquid adsorption films dominate lubrication at moderate temperatures, and citric acid triggers ester cleavage and in-situ carbonization to construct dense hybrid carbon–oxygen solid protective films at critical high temperatures. This work provides a tailored ester lubricant for hot industrial processing devices and deepens the understanding of temperature-dependent steel interfacial tribochemistry.