Excellent Lubrication Research Articles

Converting “sliding” to “rolling” design for high-performance lubricating hydrogel

Despite the excellent lubricity of conventional hydrogel materials due to their wet-soft properties, they produce severe mechanical elastic deformation at higher interfacial contact stresses. Balancing the load-bearing capacity and lubricating properties of hydrogel material is the difficulty of the current research work for articular cartilage substitutes. Great progress has been made in developing bionic joint materials with high load-bearing and low-friction hydrogels based on gradient designs. However, most bionic materials are based on sliding friction greatly limiting the improvement of lubrication performance. Herein, we designed and prepared a new hydrogel material with high load-bearing capacity and stable lubrication performance, breaking through the traditional friction method and turning to “sliding” for “rolling”. The network on the hydrogel surface was dissociated by UV irradiation and the pores on the surface were filled with SiO2 nanoparticles. The dense network structure of the underlying layer endows the hydrogel material with good load-bearing properties, while the high degree of hydration of the surface layer and the rolling friction effect of SiO2 nanoparticles greatly enhance the lubrication property. With the synergistic effect of these designs, the multi-layered hydrogel with nanoparticles on the surface achieved an ultra-low average coefficient of friction (COF) of ∼0.00809 at a high load of 50 N during 30,000 cycles. This idea of hydrogel material design provides a new strategy for the replacement of biomimetic articular cartilage materials.

Screening of low-friction two-dimensional materials from high-throughput calculations using lubricating figure of merit

Two-dimensional materials are excellent lubricants with inherent advantages. However, superlubricity has been reported for only a few of these materials. Unfortunately, other promising two-dimentional (2D) materials with different physical properties cannot be discovered or applied in production; thus, energy consumption can be greatly reduced. Here, we carry out high-throughput calculations for 1,475 2D materials and screen for low-friction materials. To set a standard, we propose, for the first time, a geometry-independent lubricating figure of merit based on the conditions for stick-slip transition and our theory of Moiré friction. For the efficient calculation of this figure of merit, an innovative approach was developed based on an improved registry index model. Through calculations, 340 materials were found to have a figure of merit lower than 10−3. Eventually, a small set of 21 materials with a figure of merit lower than 10−4 were screened out. These materials can provide diverse choices for various applications. In addition, the efficient computational approach demonstrated in this work can be used to study other stacking-dependent properties.

Enhanced long-term performance of ureteral stents with functional coating: Combating bacterial adhesion and inhibiting encrustation

Long-term indwelling ureteral stents in urology surgeries often lead to severe encrustation and challenging clinical complications, necessitating an effective medical response. Although many researchers have started with antibacterial, anti-fouling and other aspects, the lack of direct urinary pertinence or develop drug resistance have not really improved the current situation of crust. Therefore, while giving full play to the excellent properties of coated anti-bacterial adhesion, it is still a challenging problem to ensure that it can be effectively applied to ureteral stents and urinary tract environment. Herein, this work proposes a practical functional coating to inhibit encrustation, achieved by incorporating the urinary crystal inhibitor citric acid to crosslink the polyvinylpyrrolidone with hydrophilic lubrication properties (PVP/CA). The coating based on charge interaction has excellent stability (peel strength up to 600 N/m) excellent wettability (contact angle reduced by 60°), lubricity (friction coefficient reduced by 4 times) and biocompatibility. More importantly, the synergistic anti-bacteria adhesion (>90 %) and inhibition of urinary tract crystallization properties of the coated ureteral stent demonstrate superior performance in preventing encrustation over a 4-week period in an in vitro model. This innovative coating strategy holds promising prospects for ureteral stents, offering a potential solution to alleviate pain in urological patients.

Novel biomimetic macromolecules system for highly efficient lubrication, ROS scavenging and osteoarthritis treatment

The early stages of osteoarthritis (OA) in the joints are typically characterized by two key factors: the dysfunction of articular cartilage lubrication and inflammation resulting from the excessive production of reactive oxygen species (ROS). Synthetic injectable macromolecular materials present great potential for preventing the progression of early OA. In this study, to mimic the excellent lubricity of brush-like aggregates found in natural synovial fluid, we develop a novel macromolecular biolubricant (CS-PS-DA) by integrating adhesion and hydration groups onto backbone of natural biomacromolecules. CS-PS-DA exhibits a strong affinity for cartilage surfaces, enabling the formation of a stable lubrication layer at the sliding interface of degraded cartilages to restore joint lubrication performance. In vitro results from ROS scavenging and anti-inflammatory experiments indicate the great advantage of CS-PS-DA to decrease the levels of proinflammatory cytokines by inhibiting ROS overproduction. Finally, in vivo rats OA model demonstrates that intra-cavitary injection of CS-PS-DA could effectively resist cartilage wear and mitigated inflammation in the joints. This novel biolubricant provides a new and timely strategy for the treatment of OA.

The synthesis of hyperbranched polysiloxane-functionalized graphene oxide with excellent water lubrication performance

Water, esteemed for its sustainable and environmentally friendly lubricating qualities, faces constraints due to its limited load-bearing capacity and diminished lubrication performance, restricting its applications. This study endeavors to overcome these challenges by synthesizing a hyperbranched polysiloxane (HBPSi) and grafting it onto graphene oxide (GO) surfaces. The remarkable lubricating properties and hydrophilicity of HBPSi enable the stable dispersion of GO in water, thereby enhancing overall lubrication performance. This novel approach not only increases water's carrying capacity but also enhances its lubricating ability. Consequently, the resultant HBPSi-GO exhibits exemplary tribological properties. By elucidating this methodology, our research establishes a practical foundation for the development of high-performance water lubrication additives.

A State of the Art on Sustainable Metal Working Fluids in Machining Applications

Metalworking fluids (MWFs) play a crucial role in machining processes by lubricating and cooling cutting tools, reducing friction, and improving overall machining efficiency. These fluids can be classified into various types, including cutting oils, water-based fluids, and semi-synthetic or synthetic fluids. Cutting oils are often mineral-based, providing excellent lubrication in heavy-duty applications. Water-based fluids, on the other hand, are more environmentally friendly and commonly used in light to moderate machining operations. Semi-synthetic and synthetic fluids offer a balance between performance and eco-friendliness, incorporating additives to enhance their properties. Proper selection and management of MWFs are essential for optimizing tool life, surface finish, and overall productivity in metal machining applications. Research has shown that the cost of cutting fluid in machining constitutes 17% of the total production cost. In the same research, it was stated that the cutting tool cost was around 4%. This review provides an overview of the current advancements in sustainable MWFs within machining applications. It explores state-of-the-art technologies, formulations, and practices aimed at minimizing environmental impact while maintaining optimal performance in metalworking processes. The review encompasses eco-friendly additives, recycling methods, and emerging trends in the development of MWFs, emphasizing the importance of sustainable practices in the manufacturing industry.

Performance evaluation of trimethylolpropane ester as high-temperature resistant lubricant for high performance water-based drilling fluids

As drilling operations increasingly target large-displacement wells, horizontal wells, deep wells, and ultra-deep wells, the challenges of excessive drilling resistance and downhole safety have become more prominent. During the drilling process, one of the primary technical methods for preventing and addressing drilling safety issues is the reduction of downhole frictional resistance through the addition of lubricants to the drilling fluid. In this study, a high-temperature and high-salt-resistant drilling fluid lubricant was synthesized using raw materials such as oleic acid and trimethylolpropane. The lubricant exhibited excellent lubrication performance under high-temperature and high-salt conditions. When added at a 1.5% dosage to a 4% freshwater-based slurry, HZ-1 resulted in a 95.2% reduction in the lubrication coefficient. After aging at 200 °C, the HZ-1-containing slurry maintained an 87.9% reduction, and when used with a NaCl dosage of 36%, the slurry still exhibited an 80.5% reduction. Furthermore, HZ-1 exhibited favorable compatibility with both polymer drilling fluid and polysulfone drilling fluid systems. It had basically no effect on the rheological properties of the drilling fluid and reduced filtration loss. Moreover, HZ-1 exhibited a lubrication coefficient reduction rate of 94.5% in freshwater-based slurry and 85.5% in brine-based slurry, outperforming domestic and foreign lubricants. It outperformed these comparative lubricants in terms of lubrication and drag reduction within the same period. The analysis of the lubrication and drag-reduction mechanism revealed that HZ-1, when adsorbed onto a metal surface, formed a hydrophobic and high-strength physical adsorption film. This film prevented direct contact between drilling tools and the friction surface of the well wall, resulting in a significant reduction in the lubrication coefficient. Furthermore, using the drilling fluid system containing HZ-1 lubricant, the wear scar diameter formed on the surface of the four-ball friction experimental body was the smallest, measuring only 0.78 mm. This property significantly enhances the extreme-pressure and anti-wear performance of the friction sub-surface. Consequently, HZ-1 effectively prevents complications such as pressure support, stuck drilling, and high frictional resistance, thereby significantly reducing costs and improving efficiency.

The enhanced tribological performance of fabric‐reinforced resin composites by biomimetic surface modification of fillers

The poor dispersion of multiwalled carbon nanotubes (MWCNTs) and weak interfacial adhesion of fabric and resin matrix seriously affect the tribological performance of fabric‐reinforcement resin composites. Tannic acid (TA), a plant‐derived compound, which is similar to mussel‐inspired polydopamine, can adhere to various substrates under a weak basic buffer solution. Therefore, in this work, TA‐modified MWCNTs were incorporated into TA functionalized fabric composite to improve the tribological performance of the fabric composite. The results indicate that the MWCNTs and fabric were successfully modified with TA. The wear tests revealed that the TA‐MWCNTs reinforcement TA‐fabric resin composites exhibited the best tribological performance, in which the friction coefficient and volume wear rate decreased by 16.9% and 40%, respectively, compared with pristine fabric composite. The favorable interfacial bonding between fabric and resin is beneficial to the friction force transfer to the load‐bearing fabric, decreasing the stress focus and thus reducing the damage to composite materials. Meanwhile, the good dispersion of MWCNTs contributes to the excellent lubrication performance. This simple and eco‐friendly method of treating fillers with TA provides a new approach to achieve high‐performance tribological materials.

Durable bionic honeycomb slippery liquid-infused porous surfaces with anti-icing and water-collecting properties

The slippery liquid-infused porous surfaces with nanostructures have emerged as a high-performance multifunctional surface with super-liquid repellency, low contact angle hysteresis and self-healing. However, the amount of lubricant captured by the nanostructures is extremely low, and such oil-filled functional surfaces are susceptible to lubricant loss depletion. In this research, we developed a honeycomb-inspired multidimensional lubricant-infused surface that has a good ability to lock in lubricant while providing excellent mechanical durability. The honeycomb-shaped hexagonal micropores store lubricant to stabilize the smooth oil layer, while the pine-needle shaped nano-needles in the pores retain the lubricant in the pores, making it more difficult to lose the lubricant and increasing durability. Compared to conventional nanostructured slippery liquid-infused porous surfaces, this surface ensures excellent long-term lubrication performance under extreme conditions such as cooling, high shear and water spray impact. Meanwhile the honeycomb mesh lubricant injected into the surface is able to rapidly coalesce and remove water droplets during condensation due to the presence of coarsening effect, and it also retards the formation of ice. This structure provides a new idea for anti-icing and water collection research

Tribological behavior of sulfonitrided tribofilm generated from non-corrosive dimercaptobenzothiadiazole-based additives as effective boundary lubrication layer

Lubricant additives are essential to protect mechanical devices. Although sulfur (S)-based dialkylpentasulfide (RC2540) exhibits acceptable extreme pressure (EP) performance, a high amount of S causes severe corrosion and poorer anti-wear (AW) performance. Herein, dimercaptobenzothiadiazole-based additives (DMTDs) consist of four and five S atoms, namely 2-(benzyldisulfanyl)-5-(benzylsulfanyl)-1,3,4-thiadiazole (4SBZ), 2-(octyldisulfanyl)-5-(octylsulfanyl)-1,3,4-thiadiazole (4SC8), 2,5-bis(benzyldisulfanyl)-1,3,4-thiadiazole (5SBZ), and 2,5-bis(octyldisulfanyl)-1,3,4-thiadiazole (5SC8) were synthesized. The synthesized DMTDs are non-corrosive (Grade 1a-1b) compared to RC2540 (Grade 4c). The 10 wt% 5SBZ demonstrated exceptional EP and AW performance than RC2540. The 10 wt% 5SBZ has improved weld load and reduced wear scar area by 5.0 folds and 94.1% compared to naphthenic base oil. The exceptional tribological properties of 5SBZ are attributed to the strong non-covalent interaction between the benzene ring and metal surfaces, high S content, and synergistic effect between S and N. Alternatively, the DMTDs exhibit better AW performance compared to RC2540. The XPS depth profiling demonstrated the formation of sulfonitrided tribofilm after lubrication with synthesized DMTDs. This tribofilm contributed to an excellent boundary lubrication layer for wear protection. The lubrication mechanism was discussed and proposed. This work provides promising DMTDs as EP and AW additives for industrial applications.

Friction Characteristics and Lubrication Properties of Spherical Hinge Structure of Swivel Bridge

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation.

Design and tribological performance of graphene nanofluids dispersed by dragging effect of bicomponent gelator

Nanofluids have excellent lubrication and high thermal conductivity. However, the agglomeration and sedimentation produced by the large surface energy of nanoparticles in base liquid threaten the long-term dispersion stability and impact the wide application of nanofluid. In this work, based on the self-assemble behavior and continuous network structure formed by low molecular weight organic gelator, the uniform clusters were formed through regulating the kinetics behavior in the gelling process. The dragging effect was demonstrated by oleic acid - sodium dodecyl sulfate (OA-SDS) bicomponent gelator and graphene oxide (GO) nanosheets. The results showed that GO nanofluids dispersed by OA-SDS were stable for more than 12 months. The well-dispersed GO nanofluid exhibited better anti-friction and anti-wear properties under both immersion and electrostatic minimum quantity lubrication conditions. Moreover, the lower contact angle, surface tension and droplet size of nanofluids after charging improved the wettability on the frictional interface. The GO adsorption film formed on the friction interface protected the tribochemical reaction film of iron oxide and prevented the occurrence of sintering of base oil.

Excellent lubricating performance of a novel polysaccharide lubricant on reducing friction-induced deformation

Minimizing the deformation caused by friction on surfaces enabled to maintain a stable friction force and coefficient of friction (COF), and valuable insights could be gained from studying bio-based lubrication systems. A natural polysaccharide was derived from fresh okras in order to enhance the lubricating efficiency of aqueous system. The lubricating performance and mechanism of okra polysaccharide were unveiled through the implementation of multiple wear tests between the steel and PA66. Particular attention was paid to the relationship between the deformation, friction force and COF. The results indicated that the surface fluctuated deformations caused comparable fluctuations in both the friction force and the COF. However, the inclusion of okra polysaccharide at a concentration of 2 wt% significantly diminished the amplitudes of friction force by decreasing surface deformations. As a result, almost 50% decrease in both COF and wear loss were observed. The lubricating mechanism of okra-polysaccharide lubricant could be described as the interaction between the hydrophilic groups and water molecules, which forms a hydration layer on the surfaces in contact, thus reducing shear force. The acquired knowledge in this study was used to develop a green lubricant that addresses the issue of instability in frictional systems caused by friction-induced deformation.

Excellent hydration lubrication based on Zwitterionic Poly (N-vinylpyrrolidone-co-methacrylic acid) for hair combing improvement

In the present work, Poly (N-vinylpyrrolidone-co-methacrylic acid) (P(NVP-co-MAA)) was synthesized with free radical polymerization, and the hydration lubrication of the zwitterionic copolymer were investigated. P(NVP-co-MAA) as a lubricant to improve hair combing was also explored. The contact angle measurement showed that P(NVP-co-MAA) could adsorb onto both PDMS and hair surfaces. Adsorption equilibrium was achieved at the polymeric concentration of 0.2% and 0.3% on the surfaces of PDMS and hair, leading to a decrease in the contact angles by 5° and 11°, respectively. The hydration lubricity of P(NVP-co-MAA) was tested, and the results demonstrated that P(NVP-co-MAA) exhibited excellent lubricity properties in both boundary lubrication and mixed lubrication. It provided stable lubricity for up to 2 h with continuous friction. Scanning electron microscope (SEM) and atomic force microscope (AFM) showed that the copolymer adsorbed on hair surfaces, mainly concentrated around the cuticles. It implied that the adsorption of the copolymer on hair surfaces relied on electrostatic interactions as well as hydrophobic interactions. The polymeric solution could lower the friction coefficient of wet hair compared to polyquaternium-10 (JR-400), a commonly used hair conditioner. When the concentration of copolymer was greater than 0.2%, the friction coefficient of wet hair was 0.129. At this concentration, copolymer molecules formed a hydration layer on the hair surface, which reduced the friction coefficient by 34.1%.

Implementation of hybrid CryoMQL sustainable lubri-cooling to enhance the grindability and surface integrity of tool steel

The current demand for surface finishing processes that are both technically proficient and environmentally friendly is increasing, necessitating the advancement of more efficient sustainable methods. Minimum quantity lubrication (MQL) provides excellent lubrication in the tool-work interaction but insufficient cooling impact. Besides, cryogenic enhances the chilling effect but has inadequate lubrication. This research revealed the synergistic impact of hybrid CryoMQL with eco-friendly Al2O3 NFs while grinding AISI D2 tool steel. CryoMQL facilitates the application of MQL-based soybean oil and deionized water (SO+DW) emulsion with 0.5 wt% and 1 wt% concentration of Al2O3 NPs and liquid nitrogen (LN2) through two individual nozzles in the cutting region. The results indicated that CryoMQL reduced grinding force (tangential force, Ft, and normal force, Fn), specific grinding energy (Ug), surface roughness (Ra), and grinding temperature (Tg) by 3.64–25.66 % in Ft, 3.52–12.87 % in Fn, 3.64–25.66 % in Ug, 8.81–25.02 % in Ra and 57.59–58.30 % in Tg, respectively, compared to MQL environment at 0.04 mm downfeed and 150 mm/s table feed rate. Eventually, it was observed that 1 wt% Al2O3 NFs improve Ft, Fn, Ug, Ra and Tg by up to 32.71 %, 20.33 %, 32.71 %, 23.55 %, and 6.81 % in comparison to 0.5 wt% Al2O3 NFs in the CryoMQL mode. The effectiveness of Al2O3 nanofluids with CryoMQL has resulted in good tribological conditions in the grinding zone with enhanced cooling/lubricating action of vegetable oil. Furthermore, negligible chip adhesion over finished surfaces was seen with 0.5 wt% and 1 wt% Al2O3 NFs under CryoMQL grinding. This study provides numerous scientific assistance in the automotive and tooling sectors, such as a better selection of environmentally friendly coolants and sustainable parameters for excellent surface properties, to provide the solution to highly complex and close tolerances of tool steel parts using CryoMQL finishing.

Grindability Evaluation of Ultrasonic Assisted Grinding of Silicon Nitride Ceramic Using Minimum Quantity Lubrication Based SiO2 Nanofluid

Minimum quantity Lubrication (MQL) is a sustainable lubrication system that is famous in many machining systems. It involve the spray of an infinitesimal amount of mist-like lubricants during machining processes. The MQL system is affirmed to exhibit an excellent machining performance, and it is highly economical. The nanofluids are understood to exhibit excellent lubricity and heat evacuation capability, compared to pure oil-based MQL system. Studies have shown that the surface quality and amount of energy expended in the grinding operations can be reduced considerably due to the positive effect of these nanofluids. This work presents an experimental study on the tribological performance of SiO2 nanofluid during grinding of Si3N4 ceramic. The effect different grinding modes and lubrication systems during the grinding operation was also analyzed. Different concentrations of the SiO2 nanofluid was manufactured using canola, corn and sunflower oils. The quantitative evaluation of the grinding process was done based on the amount of grinding forces, specific grinding energy, frictional coefficient, and surface integrity. It was found that the canola oil exhibits optimal lubrication performance compared to corn oil, sunflower oil, and traditional lubrication systems. Additionally, the introduction of ultrasonic vibrations with the SiO2 nanofluid in MQL system was found to reduce the specific grinding energy, normal grinding forces, tangential grinding forces, and surface roughness by 65%, 57%, 65%, and 18% respectively. Finally, regression analysis was used to obtain an optimum parameter combinations. The observations from this work will aid the smooth transition towards ecofriendly and sustainable machining of engineering ceramics.

A Review on the Impact of Bio-Additives on Tribological Behavior of Diesel Fuels

Automobile engines require lubrication to lessen the impact of friction due to the high levels of wear and frictional heat generated by the sliding parts. Wear and friction will cause engine parts to endure for less time, be less reliable, and require more maintenance. Diesel fuel can potentially be replaced with biodiesel among other fuels. Diesel engines have a serious problem with equipment that is lubricated by the fuel itself. This study’s goal is to assess the influence of bio-additives on the diesel fuel tribological behavior and energy balance during the car’s idle running, acceleration, constant speed, and braking. Lubricity issues with reformulated diesel and lubricity test procedures are explained. The relationship between tribology and bio-additives is also briefly illustrated. According to the literature, adding bio-additives to fuel boosts its lubricity. Biodiesel has long been considered an additive with excellent lubricant properties. Even in small amounts, adding biodiesel to diesel fuel can increase its lubricity without the need for conventional lubricity additives. This is especially true for diesel fuel with ultralow sulfur. Diesel fuel characteristics determine the precise blending percentage needed to provide the proper lubricity of maximum 520 μm testing wear scars with a high-frequency reciprocating rig (HFRR), although 2% biodiesel nearly invariably imparts adequate lubricity to biodiesel blends. Tall oil fatty acid (TOFA) was one of the bio-additives investigated by HFRR. When the additive concentration was raised from 0 to 500 g/g, the wear scar diameter (WSD) of nonadditive diesel fuel was lowered by 60.3%, from 630 to 250 μm, and the coefficient of friction (COF) was lowered by 95.7%, from 0.47 to 0.02.

Tribological behaviors of siver@Ti3C2Tx nanocomposite as a water-based lubrication additive

Recently, issues related to reforming the lubricating performance of water by adding nanocomposite have received more and more attention. This paper demonstrated a special adsorption and self-reduction route to prepare siver@Ti3C2Tx nanocomposite (Ag@Ti3C2Tx). Various characterization methods confirmed its successful preparation. The tribology experiments of Ag@Ti3C2Tx as a water-based lubrication additive demonstrated that 1.5 wt% addition of such nanocomposite could reduce coefficient of friction and wear rate by 22.2 % and 81.4 %, respectively. Importantly, the Ag@Ti3C2Tx had good compatibility with benzotriazole which was a frequently-used antirusting agent. Detailed surface analysis revealed that the Ag NPs capable of self reparing abraded surface and the lamellar Ti3C2Tx which can form stable protective film worked in coordination to endow Ag@Ti3C2Tx with excellent lubrication properties in water.

Transient mixed-lubrication and contact behavior analysis of metal liquid film under magneto-thermal effect

To investigate the contact state and interface behavior of the armature-rail (A/R) interface under magneto-thermal shock, this study employs the lubrication theory and considers the coupling effect of electromagnetic and temperature fields. A transient mixed hydrodynamic lubrication model is established using the finite difference method. The study investigates the evolution mechanism of rough surface metal liquid film, electrical contact behavior, and transient mixed lubrication characteristics at the interface under complex magneto-thermal excitation. The study suggests that the electrical contact behavior of the metal liquid film during electromagnetic launch process exhibits significant fluctuation characteristics, which have a crucial influence on the temperature distribution of the metal liquid film. Moreover, due to the fluctuation behavior of electrical contact and factors such as surface roughness, the temperature of the metal liquid film exhibits a complex spatial distribution pattern. The temperature peak continuously increases as the electromagnetic launch progresses. Furthermore, the initially uniform distribution of the metal liquid film gradually transforms into a non-uniform, island morphology due to the joint action of the magneto-thermal effect. However, the liquid metal film still exhibits excellent lubricating properties, which play a crucial role in reducing friction and wear in the electromagnetic launcher system (EMLs).

Excellent corrosion inhibition and lubrication performance of MMT based ionic liquids as ester oil additives

In this work, electrochemical experiments and friction tests were conducted to investigate anti-corrosion properties and lubrication performance of the 2-mercapto-5-methyl thiadiazole (MMT) based ILs as additives of ester oil. The outcomes of electrochemical experiments were further supported by quantum chemical simulation which clarified the reason for corrosion inhibition from a microscopic perspective. Electrochemical impedance spectroscopy obtained from different temperatures (from 293 K to 323 K) showed that the inhibitors could reach a higher corrosion inhibition efficiency at 293 K. The experimental data exhibited that the adsorption behavior obeys Langmuir adsorption isotherm and the inhibitors adsorbed on the surface in a laying way seen from the results of theoretical simulation. Besides, SEM and XPS were employed to analyze the corrosion morphologies of immersion tests corroborating the presence of adsorption film on the steel surface. The tribological performance of MMT based ILs as base oil additives were examined by four-ball tester. The friction coefficient dropped by 47% and wear scar diameter decreased by 28% contrast to the base oil sample. The outstanding corrosion inhibition properties and friction-reducing and anti-wear performance could make it prospect for some industrial applications in energy saving.