Hexagonal boron nitride (h-BN) is an environmentally friendly lubricant that shows great potential in lubrication applications. However, there is currently a lack of research on the synergistic mechanisms of carboxylic acid-modified h-BN at different friction interfaces. In this study, the tribological mechanism of carboxylic acid-modified h-BN across various contact interfaces was investigated through experimental and molecular dynamics simulations. At the steel-steel contact, wear reductions relative to the base oil were 21.74% for unmodified h-BN, 58.94% for oleic acid (OA)-modified h-BN, and 55.80% for stearic acid (SA)-modified h-BN. At the alumina-steel contact, the corresponding wear reductions were 8.50%, 25.30%, and 23.54%, respectively. Additionally, at the alumina-steel contact, OA-modified and SA-modified h-BN reduced the coefficients of friction by 35.18% and 23.32%, respectively, compared with the base oil. Simulations revealed the adsorption mechanism of carboxylic acids: the carboxyl group anchors to the metal or oxide surfaces, while the alkyl end is compatible with the base oil. Among these, the conformational flexibility of the C=C bond in the OA molecule enables the synergistic anti-wear effect between OA and h-BN. This research outcome can guide the development of high-performance nano-lubricants suitable for multiple interfaces.

O3-type Ni-Mn-based layered oxides as cathode materials have received much attention due to their high theoretical capacity in sodium-ion batteries (SIBs). However, the occurrence of irreversible phase transition during the charge-discharge process will lead to poor structural stability and cycling performance. Herein, a high-entropy layered oxide of Na0.85Ni0.25Cu0.12Ti0.15Li0.08Ca0.02Fe0.15Mn0.31O2 (NCFMTLC-1) was prepared by optimizing the ratio of Fe to Mn. It is found that Fe element plays a significant role in the optimization of crystal lattice and the regulation of configurational entropy, improving the cycling and rate performance of materials. In-situ X-ray diffraction combined with DFT calculations reveal that NCFMTLC-1 exhibits superior structural stability with minor reversible phase transition during charge/discharge processes, in stark contrast to its Fe-free counterpart. Therefore, the prepared NCFMTLC-1 cathode demonstrates impressive rate performance (discharge capacity of 96.1 mAh/g at 5C) and cycling stability (83.4% capacity retention after 400 cycles). This work demonstrates that adjusting Fe/Mn ratio is an effective strategy to improve the electrochemical properties of high-entropy materials, offering valuable guidance for the future design of advanced cathode materials for SIBs.

The stability of tribological performance in lubricants under extreme temperature conditions presents a significant challenge in the field of lubrication. Enhancing the overall performance of lubricating materials across a wide temperature range is essential for the reliable operation of equipment in extreme environments. To tackle this issue, this study formulated a nano-lubricant by incorporating modified graphene oxide (GO) powder as a high-performance nano-additive into PAO6 base oil. The objective was to achieve exceptional and stable tribological performance across a broad temperature spectrum. In the study of low-concentration GO nano-lubricants (0.01-0.2 wt%), systematic testing and analysis of dispersion stability, rheological properties, and thermal performance were conducted to establish a foundation for subsequent tribological evaluations. Following this, comprehensive tribological performance evaluations were carried out on the GO nano-lubricants at varying concentrations using a four-ball friction tester. Tests were performed under conditions of a 147 N load and a rotational speed of 1200 r/min across a broad temperature range (- 15 C to 100 C), elucidating the anti-friction and anti-wear mechanisms of GO powder. The results indicated that, compared to pure PAO6 base oil, the optimal formulation was a nano-lubricant containing 0.05 wt% GO, which reduced the average coefficient of friction by 32% and decreased the wear scar diameter by 40% to 74%. Advanced surface analysis techniques (SEM, EDS, Raman spectroscopy, and XPS) confirmed that the exceptional tribological performance is attributed to the unique powder characteristics of GO. Specifically, this is manifested in the interlayer sliding effect of GO nanosheets, the formation of a robust induced protective film during friction, and the synergistic effect of catalyzing FeO/Fe2O3 friction film formation through tribochemical processes. This study underscores the multifunctional application potential of GO powder as a lubricant additive under extreme temperature conditions and provides crucial theoretical support and practical references for the rational design and performance optimization of next-generation powder-based lubricants.

To address the common problem of insufficient heat dissipation performance of lubricants in the power systems of new energy vehicles, this study investigated the physicochemical properties of Fe3O4/CNTs composite nanomaterials as an additive for PAO7 lubricating oil. The wettability and rheological properties of different nanofluids were studied. In addition, the thermal stability and thermal conductivity of the nanofluids were further evaluated. The results showed that the addition of Fe3O4/CNTs composite nanomaterials significantly reduced the contact angle with the steel interface by 42.7%. The viscosity of the nanofluids decreased slightly with increasing shear rate, exhibiting significant shear-thinning behavior. Simultaneously, the high-temperature oxidative degradation time was prolonged, showing excellent high-temperature stability. The thermal conductivity of hybrid nanolubricant (HL) was increased by approximately 11.04% compared to the base oil, significantly improving heat transfer performance. This composite nano-lubricant is expected to be applied to the cooling system of new energy vehicles, thereby improving their overall performance.

Eco-friendly lubricant additives play a pivotal role in saving energy and advancing sustainable development. Focusing on the tribological properties of biomass-derived carbon microspheres (CSs), this study successfully synthesized by a one-step glucose hydrothermal method and systematically evaluated as lubricant additives in water-based polyethylene glycol (PEG400), non-polar polyalphaolefin base oil (PAO6), and commercial full synthetic motor oil (0W-20). Results demonstrate that CSs exhibit excellent dispersion stability and significant friction-reduction and anti-wear effects in all three lubricants. Specifically, CSs maintained colloidal stability for 180 days in PEG400, achieved a maximum 32.7 % friction coefficient reduction in 0W-20, and a maximum wear volume decrease of 65.6 % in PAO6. Analysis indicates that the excellent lubrication performance is mainly ascribed to the enhanced interfacial adhesion force derived from improved wettability, which contributes to the rapid formation of homogeneous adsorption oil films at the sliding interface. Simultaneously, the nanobearing effect generated by the spherical structure of CSs and the friction-induced formation of Fe3O4/CS composite films synergistically interact to achieve high-efficiency lubrication. This study systematically evaluates the application potential of CSs in both polar and non-polar lubricant systems, providing valuable insights for the future development of high-performance lubricants.

Variations in the wettability of nanolubricants, which crucially influence tribological performance, are driven by physical factors such as substrate morphology, material composition, surface tension, and lubricant viscosity. In the study, the tert-butylhydroquinone-modified silver/carbon black (Ag@CB) nanoparticles are employed to develop an effective lubricant. Herein, the influence of nano-Ag@CB concentration, surface tension, oil viscosity, and substrate morphology on the surface wettability is explored by quantifying the contact angle in experimental and molecular dynamics simulation results. The maximum deviation between experiment and simulation is 4.2 %. It is jointly verified that the strong adsorption effect, driven by the high synergy between hybrid nanoparticles, optimally enhances the wettability of the composite nanolubricant by 54.2 %, with a minimum contact angle of 22.4 degrees, compared to single additive and basic lubricant. The effect on tribological performance is investigated by innovatively varying the wettability of the friction sub-materials. By analyzing mean square displacement, radial distribution function, energy profiles, microscopic atomic motion trajectories, and adsorption processes, the underlying mechanisms for the wettability enhancement of nano-bio-lubricants are elucidated. The results of this study can shed lights on the design of nanolubrication with high wettability and superior lubricating properties.

Enhancing the heat transfer capability and understanding the rheological properties of automotive lubricants are essential for improving engine performance and durability. This study investigated the important parameters influencing the above-mentioned performance, namely the thermal conductivity and dynamic viscosity of the nanofluid (NF) based on poly-alpha-olefin (PAO6) and nano-silicon carbide (SiC) via experiments and molecular dynamics (MD) simulations. The fascinating novelty of this approach lies in exploring the effects of the coating layer formed on nano-SiC within the lubricant interface, as well as its influence on viscosity and the mechanisms that facilitate enhanced heat conduction between lubricant layers. The experiment and MD simulation revealed that NF exhibited shear thinning behavior and the dynamic viscosity values of SiC NF from 20 degrees C to 60 degrees C were exponentially reduced. Moreover, the thermal conductivity of NF is improved by 4.7 % and 10.5 % than that of base oils for experiemnt and simulation outcomes, which were influenced by temperatures and nano-SiC concentrations. The distribution diagram of the atom radial distribution function (RDF), based on the structural and interactional data at the molecular level, indicates that the presence of nano-SiC transforms the microstructure from a liquid phase to a nanolaminar solid state. This alteration increases the orderliness of the NF molecules and facilitates more efficient energy exchange, thereby improving their thermal conductivity and viscosity. Finally, this study assists the design of NF in accordance with specified operating requirements.

Lubricant degradation under elevated temperatures is a critical challenge in the automobile and manufacturing sectors, which reduces the durability of machinery components. In this study, a new environmentally friendly castor oil-based lubricant was developed utilizing tert-butylhydroquinone (TBHQ)-functionalized silver/carbon black (Ag/CB@TBHQ) nano-additives. Herein, the mechanism of thermal conductivity improvement in Ag/ CB@TBHQ nanolubricant was investigated by experimental tests and molecular dynamics simulations. Furthermore, the hybrid Ag/CB@TBHQ nano-additive presented superior thermal conductivity compared to individual nano-additives (Ag or CB) under various concentrations and temperatures. Additionally, the study presented the improved tribological performance of a novel nanolubricant under various temperatures. In summary, our results will offer promising insights to enhance the heat transfer capability and tribological performance of mechanical systems.

The development of green lubrication requires nano-lubricants to possess more environmentally friendly fabrication modes and materials with superior tribological properties. This study investigates the tribological properties of nano-biochar in PAO6 base oil and in combination with different additives. The effect of adsorption on friction reduction and anti-wear performance is demonstrated by replacing the friction sub-materials in the four-ball friction test. Based on the comparison of wear region characterization, the incorporation of nano-biochar improves the friction reduction performance of detergent and dispersant base oils with a reduction in coefficient of friction (COF) by 16.7% and 19.0%, respectively, and produces a synergistic effect on the anti-wear performance. When nano-biochar is compounded with anti-wear agents and friction reducer, there is a synergistic effect on friction reduction performance, and COF decreases by 9.4% and 4.5% compared with anti-wear agents and friction reducer base oils, respectively. A method to analyze the friction reduction and anti-wear mechanism of nano-additives in complex lubrication system is proposed, which reveals in depth the interaction law and synergistic lubrication mechanism between NBC and additives in the friction process.

The study breaks new ground by creatively exploring the blended base oils of 0W20 with PAO7 (0WP7), introducing composite aluminum/zinc nanoparticles, which offers a novel approach to lubricant formulation. In view of the intricate molecular composition of lubricants, a nanolubricant molecular dynamics model coupled with multicarbon (C20 + C30) is built. Through simulating diffusion effect, atomic disordering, and liquid-solid interaction, it uncovers microscopic mechanisms that govern lubrication, providing more in-depth understanding compared to traditional macroscopic studies. Results indicated that friction coefficient (COF) and wear scar diameter (WSD) with the composite NL lubrication were significantly reduced by approximately 36.4% and 20.3% compared with the reference. Eventually, the vital mechanism for the tribological improvement from mechanical tribology and electrostatic and interfacial science was presented.

Compared to friction clutches, dog clutches have the advantages of high efficiency, small size, low cost, and large transmission torque; therefore, they are selected for use in hybrid electric vehicles (HEVs) with a single electric motor (EM) driving the rear axle. In the dog clutch coupling process, the meshing of the teeth produces an impact, and dynamic control of the clutch faces problems of backlash and flexible shaft control. For an advanced dynamic study and subsequent improved performance, a novel dynamic estimation algorithm is proposed. This algorithm includes an observer for estimating the clutch torque, two piecewise-affine (PWA) estimators for estimating the torsion angle and half-shaft torque, and a state machine for indicating the backlash position. To demonstrate its feasibility, the convergence rate and observation error are investigated. Based on the information obtained through dynamic estimation, a second-order receding horizon sliding control (RHSC) approach is proposed. In dog clutch coupling, the speed deviation and tracing torque set points, which correspond to different backlash positions, are the control targets. Based on the second-order sliding mode structure, an optimization algorithm is developed and its convergence is studied. The performance of the estimator and control method is verified through road tests. The results show that the estimator can correctly indicate the system state and that the control method can improve the performance of the powertrain.

In this paper, the effect of branched hydrocarbon molecules, i.e., polymethylene olefins (PAO), on the boundary lubrication of ZnO nanofluids is investigated using large-scale molecular dynamics (MD) simulations. The film structure and friction of the lubricated film on the atomic scale are discussed, and the slip distance of the iron wall is calculated. The results show that the nanofluid forms a layered structure under stronger liquid-solid interactions; the higher the number of PAO branches, the higher the number of atoms between the contact surfaces, which significantly reduces the friction force in the event of inhomogeneous contacts; the higher the number of PAO branches, the higher the number of atoms between the contact surfaces, which significantly reduces the friction force in the case of inhomogeneous contact, with a maximum reduction of about 95%; as the number of PAO branches increases, the wall slip distance of the system increases.

Lubricants are indispensable ingredients for alleviating friction and wear in mechanical components especially in automobile. However, due to its poor heat transfer capabilities, traditional lubricants are denatured under extreme working conditions, leading to lubrication failure during the friction process. Therefore, this study elaborately put forward to a novel MoS2/h-BN hybrid nanoparticle as efficient nano-additive for engine oil. The results of experiments and molecular dynamics simulation jointly show that compared with mono nanoparticles, hybrid nano-lubricants (NL) thermal conductivity was significantly improved than that of base oil owing to the synergistic effect. The corresponding mechanism for the improving heat transfer performance was suitably proposed based on the Mean Square Displacement (MSD) and Radial Distribution Function (RDF) results at the microscopic atomic level.

Vegetable oils are being increasingly studied in tribology due to their environmental benefits. This study investigates the physicochemical and tribological properties of carbon black/silver (CB/Ag) hybrid nanomaterials modified by tertiary-butylhydroquinone (TBHQ) as lubricant additives. The composition of the tribolayer formed were characterized using an FE-SEM, 3D surface profilometer, and XPS analysis. The results reveal a substantial decrease in the coefficient of friction (COF) value for the hybrid nanolubricant, with an approximate 31% reduction compared to the baseline oil. Finally, the characterization of worn surfaces strongly supports the noteworthy improvement in friction performance, primarily ascribed to the synergistic effects of CB, Ag nanoparticles, and TBHQ antioxidant surfactants. This study affirms that TBHQ-modified CB/Ag hybrid nanoparticles serve as eco-friendly lubricant additives.

Automotive engine oils demand superior tribological properties to prolong the lifespan of mechanical components. This study contributes to that objective by investigating the impact of nickel-coated multi-walled carbon nanotubes (Ni-MWCNTs) as additives to engine oil on tribological properties. Tribological tests were conducted utilizing a reciprocating motion tribometer to simulate the tribo-system of the piston ring and cylinder liner in automobile engines. Additionally, advanced characterization techniques were employed to study wear and lubrication mechanisms. Ni-MWCNTs nano-additives diminished the friction coefficient and wear rate by 15–23% and 68–87%, respectively, compared to baseline oil. The lubrication process is ascribed to the generation of a tribofilm brought about by thermophysical and tribochemical mechanisms. Ultimately, this study offers new insights into improving lubrication performance in automobile engines to enhance engine durability and fuel economy.

As an environmentally friendly material, biochar is increasingly being utilized in the field of heat transfer and thermal conduction. In this study, nano-biochar was prepared from high-pressure homogenization (HPH) using sesame stalks as the raw material. It was incorporated into ethylene glycol (EG) and its dispersion stability, viscosity, and thermal conductivity were investigated. The nano-biochar was stably dispersed in EG for 28 days. When the concentration of the nano-biochar added to EG was less than 1%, the impact on viscosity was negligible. The addition of 5 wt.% nano-biochar to EG improved the thermal conductivity by 6.72%, which could be attributed to the graphitized structure and Brownian motion of the nano-biochar. Overall, nano-biochar has the potential to be applied in automotive thermal management.

This study mainly investigated the physicochemical characteristics of ethylene glycol/ water (EG/W) based hydroxyl-functionalized boron nitride (BN-OH) and graphite (G) hybrid nanofluids. A novel simple and efficient annealing method was proposed to have hexagonal boron nitride (h-BN) nanoparticles func-tionalized to improve the synergistic role between hybrid G/BN-OH nanoparticles. Meanwhile, the dis-persion stability, thermal stability, and rheological behavior of diverse nanofluids (h-BN, BN-OH, G, G/ BN and G/BH-OH) were comprehensively evaluated. The results showed that the G/BN-OH hybrid nanofluids demonstrate both better dispersion stability and thermal stability, as well as a lower increase in viscosity. In addition, the thermal conductivity of G/BN-OH hybrid nanofluids was increased by up to 18.05% with a concentration of 0.2 wt% when compared to the base fluid. Ultimately, the complicated theoretical mechanism of thermophysical performance augment for G/BH-OH hybrid nanofluids was reli-ably presented. The enhanced thermal conductivity of nanofluids may be attributed to the formation of adsorption layers and the synergistic effect of the thermal conductivity network.(c) 2023 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.

Nano-materials, given their excellent anti-friction and anti-wear characteristics, have attracted significant attention in tribological applications. However, conventional nano-materials have difficulty meeting the development requirements of the eco-friendly lubricants. In this study, nano biochar derived from sesame stalk was synthesized and used as a lubricant additive in poly-alpha olefin-6 (PAO6). The tribological properties were evaluated by four ball tribological tests with steel and ceramic balls as the friction pair. Following the friction experiment, the worn surface on the steel ball was analyzed by X-ray photoelectron spectrometry. The steel ball friction results showed that the lubricants containing 0.2 wt% nano biochar achieved a maximum wear volume reduction of 46% compared to PAO6, and the friction coefficient decreased by 34.6% for the ceramic balls. Analysis indicated that the enhanced wettability of nano biochar lubricant contributed to improving the anti wear properties. Characterization of the worn surface revealed that the addition of nano biochar facilitated the formation of strong Fe3O4 tribofilms. This study demonstrated that nano biochar could serve as an environmentally friendly additive in the liquid lubricant industry.

This study comprehensively investigated physicochemical and tribological performance of polyalphaolefin (PAO4) oil introducing oleic acid (OA)-functionalized SiC/TiN hybrid nanomaterials. The dispersion stability, wettability, thermal stability, and friction properties of the nanolubricants (NL) system were greatly improved following the application of hybrid NL. Additionally, the anti-wear and reducing-friction behavior were assessed via a four-ball tribometer. The results showed that the COF and WSD values of wear scar lubricated by hybrid NL were greatly reduced by approximately 32.7% and 35.1%, respectively, compared with the base oil. Finally, it is strongly confirmed that the significant improvement of friction performance is mainly due to improved interfacial effect of NL, the stable chemical tribo-film generated onto the friction surface, and the synergistic effect among SiC, TiN nanoparticles, and OA surfactant.