Excellent Lubrication Research Articles

Fabrication of Surface-carbonated Boron Nitride Nanosheets and Their Application as Water-based Lubrication Additives

As a typical two-dimensional layered material, hexagonal boron nitride nanosheets (BNNSs) have high mechanical strength, good conductivity, and excellent lubrication performance, which have great potential as solid nano lubricant additives in tribology. When BNNS is used as a water-based or oil-based lubricant additive, its inherent chemical inertness and poor dispersion stability make it difficult to achieve optimal anti-friction and anti-wear performance. In this paper, a simple and efficient preparation method for obtaining hexagonal boron nitride nanosheets (C-HPC-BNNSs) with surface carbonization modification and excellent dispersion stability in water-based lubricants was proposed. Using hydroxypropyl cellulose (HPC) as a modifier, a wet ball milling process combined with high-temperature carbonization treatment effectively reduced the thickness of BNNSs while uniformly modifying N-doped carbon layers on the surface of the nanosheets. Benefit from the smaller layer thickness of C-HPC-BNNSs, they exhibit excellent dispersion stability in the water-glycol solution and can maintain no significant agglomeration behavior for up to 30 days, which is the basis for the excellent lubrication performance of lubricant systems. In addition, the N-doped carbon layer modified on the surface is beneficial for enhancing the hydrophilicity of BNNSs and synergistically enhances the tribological properties of the material with BNNSs. The test results of the four-ball friction tester show that compared with the pure water-glycol solution and the water-glycol system with added C-HPC-BNNSs, the friction coefficient (COF) and wear volume of the system with added C-HPC-BNNSs could be as low as 0.095 and 1.99 × 10-4 mm3, respectively. This work has positive significance for the preparation, surface modification, and tribological application expansion of two-dimensional layered material BNNSs, which is conducive to further understanding the relationship between.

Study on the Effectiveness of Okra as an Environmentally Friendly and Economical Lubricant for Drilling Fluid

With the gradual improvement and implementation of unconventional wells drilling and environmental regulations, there is an urgent need for high-performance and more environmentally friendly lubricants for water-based drilling fluids (WD). Developing green oilfield chemicals from natural products is a shortcut. In this work, Abelmoschus esculentus (L.) Moench/okra has been studied as the lubricant in WD. The green drilling fluid lubricant developed demonstrates excellent lubrication performance, as well as good filtration loss reduction and inhibition of bentonite hydration expansion. The results show that with the addition of 2.5% okra slurry to water-based drilling fluid, the coefficient of friction decreased by 51.68%, the apparent viscosity (AV) increased by 51.32%, the plastic viscosity (PV) increased by 42.99%, and the fluid loss decreased by 39.88%. Moreover, through TGA, SEM, FT-IR, particle distribution tests, and contact angle tests, the lubrication mechanism of okra slurry was discussed. Finally, the economic feasibility of using okra as an environmentally friendly lubricant for drilling fluids was analyzed. This work combines agricultural products with industrial production, which not only solves industrial problems but also enhances the added value of agricultural products, providing a reference for the coordinated development of industry and agriculture.

An investigation on tribological behavior of TC bearing materials: Effect of nano-SiO2 concentrations under different loads in the drilling fluid environment

Both Nano-SiO2 (Silicon dioxide nanoparticles) additive concentration and axial load have profound effects on the friction and wear of Tungsten Carbide bearings in the drilling fluid environment. However, the coordinated role of them remains unknown. In this work, the effects of Nano-SiO2 concentrations and axial loads on the tribological behavior of bearing materials were investigated simultaneously. Results show that the water-based drilling fluid containing Nano-SiO2 exhibits more excellent lubrication properties under 200 N as compared with 70 N, and the optimal concentration of Nano-SiO2 additive is 1.0 wt% under all loads. High axial loads are conducive to improve the lubrication performance, and the lubrication mechanisms of Nano-SiO2 under different loads in water-based drilling fluid are the multitudinousness of synergistic effects, including rolling bearing, polishing, shielding, and self-healing effect, which all manifested there is an remarkable load dependence of Nano-SiO2 particles.

Meniscal scaffolds based on self-healable elastomer-hydrogel composites with biomimetic structure and tribological properties for repairing meniscal injuries

Meniscal injuries are increasing dramatically with the aging of the population and the prevalence of sports. Tissue engineering technology is the most promising method for the treatment of meniscal injuries, but the preparation of long-term and durable meniscal scaffolds with mechanical and tribological properties like natural articular cartilage remains a great challenge. Here, inspired by the structure and lubrication mechanism of the meniscus, a durable meniscus scaffold with bionic 3D structure, self-lubrication, and intelligent drug release function is prepared. An elastomer-hydrogel composite consisting of a direct ink writing (DIW) printed elastomer skeleton and a hydrogel matrix is prepared for the meniscus scaffold. The bionic 3D structure of the scaffolds is realized by combining computer-aided structural design and 3D printing technology. The self-healing ability obtained by incorporating dynamic covalent bonds, and the robust interface achieved by co-curing of the elastomer and hydrogel resins, ensure the stability and durability of the composite meniscal scaffolds. Taking advantage of the coexistence of aqueous and oily phases in the emulsion-type hydrogel resin, a hydrophobic phospholipid is loaded into the hydrogel, and achieves excellent boundary lubrication of the composite through its fiction-response release and self-assembly. Moreover, the meniscus scaffolds enable intelligent drug release to adapt to the physiological characteristics during inflammation. In vivo tests in rabbit models validate the protective effect of the scaffold on cartilage. These methods and concepts provide a solid foundation for the preparation of bionic tissue scaffolds.

Mucus-inspired lubricative antibacterial coating to reduce airway complications in an intubation cynomolgus monkey model

Endotracheal intubation-related complications are common in clinical, and there are currently no effective strategies to address these matters. Inspired by the biological characteristics of human airway mucus (HAM), an artificial airway mucus (ARM) coating is straightforwardly constructed by combining carboxymethyl chitosan with methyl cellulose. The ARM coating exhibited excellent lubricity (coefficient of friction (CoF) = 0.05) and hydrophilicity (water contact angle (WCA) = 21.3°), and was capable of coating both the internal and external surfaces of the endotracheal tube (ETT). In vitro experiments demonstrated that the ARM coating not only showed good broad-spectrum antibacterial activity, but also significantly reduced nonspecific protein adhesion. Through an in vivo intubation cynomolgus monkey model, ARM-coated ETT potently mitigated airway injury and inflammation, and was highly potential to prevent bacterial infection and catheter blockage. This work offers a promising avenue for the development of airway-friendly invasive devices.

Mucus-inspired biomass-derived carbon dots-based solvent-free nanofluid with polyelectrolytes networks toward excellent green lubrication

Mechanical friction and wear account for 23 % of global energy, highlighting a need for eco-friendly lubricants. Drawing inspiration from marine organisms' adsorption proteins, we have developed carbon dots-based solvent-free nanofluid. Incorporating hydrophilic polyelectrolytes, the nanofluid forms three-dimensional adsorption-lubrication networks, leveraging carbon dots' strong chelating affinity, synergistically enhancing lubrication. Using the UMT-3 TriboLab and a 3D optical profilometer, we assessed the tribological performance of nanofluid and remarkably reduced the friction coefficient by 47.3 % and wear rate by 90.8 % compared to PEG 200 (Polyethylene Glycol with an average molecular weight of 200). Additionally, the infrared camera detected that nanofluid as water additives, significantly reduce wear and heat generation, decreasing temperature rise by 4.7 times. This biomimetic approach paves the way for green, oil-free, and high-performance water-based lubrication technologies.

Lubrication antagonism mechanism of nano-MoS2 and soot particles in ester base oil

Spherical nano-MoS2 (S-MoS2) has excellent lubricating properties and potential application value in engine oil additives. Engine soot can enter the engine oil, so the tribological interaction between S-MoS2 and diesel combustion soot (DCS) should be investigated. In this study, DCS was used to simulate engine soot. The interaction was investigated in dioctyl sebacate (DOS), and the interaction mechanism was full characterized. Results showed that S-MoS2 and DCS had obvious antagonism effects on lubrication. The 0.5% S-MoS2 exhibited good lubricating properties in DOS, which could reduce friction by ∼22% and wear by ∼54%. However, after 0.5% S-MoS2 was added to the 0.5% DCS contaminated DOS, the lubrication performance was not improved and was even worse than that without S-MoS2. When S-MoS2 was added for DOS lubrication, a tribofilm containing MoS2 formed on the friction surface, but simultaneously adding 0.5% DCS resulted in the disappearance of the MoS2 tribofilm. Moreover, under the action of friction heat, DCS and S-MoS2 could form hard MoxCy, thereby increasing abrasive wear. Finally, a preliminary deantagonism method was provided. After 2.0% zinc isooctyl dithiophosphate was added to the above antagonistic system, the friction coefficient did not show visible changes, but the wear recovered to a level close to that when only S-MoS2 was added. The antiantagonism method is not very satisfactory and some more efficient methods need to be further explored.

Excellent lubricating hydrogels with rapid photothermal sterilization for medical catheters coating

Bacterial infection and tissue damage caused by friction are two major threats to patients’ health in medical catheter implantation. Hydrogels with antibacterial and lubrication effects are competitive candidates for catheter coating materials. Photothermal therapy (PTT) is a highly efficient bactericidal method. Here, a composite hydrogel containing MXene nanosheets and hydrophilic 3-sulfopropyl methacrylate potassium salt (SPMK) is reported, which is synthesized through the one-pot method and heat-initiated polymerization. The hydrogel shows excellent antibacterial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 3 min in the air or 20 min in the water environment under near-infrared light (NIR; 808 nm) irradiation. The friction coefficient of the hydrogel is about 0.11, which is 48% lower than that without SPMK. The rapid photothermal sterilization is attributed to the outstanding antibacterial ability and thermal effect of photoactivated MXene. The ultra-low friction is the result of the hydration lubrication mechanism. This study provides a potential strategy for the surface coatings of biomedical catheters, which enables rapid sterilization and extremely low interface resistance between catheters and biological tissues.

An ionic liquid crystal functionalized nanocellulose lubricant additives

Cellulose, one of nature's most abundant, clean, and sustainable resources, has often shown unsatisfactory results when used as bio-lubricant additives. Herein, nanocellulose (NC) from amorphous waste natural poplar was extracted using deep eutectic solvent encapsulation treatment and chlorine bleaching process. Subsequently, 1-hexadecyl-3-methylimidazolium bromide was integrated onto NC using a one-step hydrothermal treatment (high-temperature and high-pressure environment) to obtain ionic liquid crystal (ILC) functionalized products (named as ILC-NC). After ball-milling process and solid phase separation step, ILC-NC exhibits excellent dispersion stability and lubrication properties in the liquid phase (including water and vegetable oil). Based on the polar and colloidal activity properties of ILC, it can form an ordered molecular layer on NC surface and form a lubricating film-like structure, making NC smoother and sliding well. Compared to ILC/NC aqueous dispersion, ILC-NC reduces the coefficient of friction and wear rate on steel disk surface by 68.75 % and 74.07 %, respectively. The minimum coefficient of friction was further reduced to 0.032 as dispersing ILC-NC in sunflower oil, showing a reduction of 0.134 (77.91 %) compared to pure sunflower oil. Finally, the lubrication theoretical model calculation reveals the lubrication state of ILC-NC on the steel disk surface and proposes the lubrication mechanism.

Silver-modified polydopamine-coated silica core-shell nanospheres as functional additives for lubricants and shear thickening fluids

The limited effectiveness of conventional nano-additives in carrier liquids has prompted research into multi-capable, sustainable, and intelligent application systems. Herein, multifunctional SiO2-PDA@Ag nanoparticles were synthesized by dotting silver (Ag) nanoparticles on polydopamine (PDA)-coated SiO2 nanospheres (SiO2-PDA). The base oil (PAO) containing these synthetic nanoparticles showed excellent lubricity under high contact pressure, and the mechanism was analyzed. The addition of SiO2-PDA@Ag modified with Ag nanoparticles showed better tribological performances compared to PAO and base oils with starting nanomaterials. A concentration of 3 wt% SiO2-PDA@Ag provided the most effective performance. Furthermore, multi-phase STFs were developed by incorporating SiO2-PDA@Ag particles into SiO2-based STFs, significantly enhancing the shear thickening effect. Compared to the pure SiO2-based STF, the peak viscosity of the multi-phase STF increased by about 89.36 %. Notably, the multi-phase STF exhibited higher stress under squeeze, which facilitates the development of high-performance STF devices in extrusion mode. This enhancement is attributed to the nanocore-shell structure of SiO2-PDA@Ag, which effectively prevents the agglomeration of dispersed phase particles in organic carrier medium. The results of this work provide a promising additive nanoparticle in the field of smart materials and lubricants.

The sealing performance of PTFE O-rings at low temperature

Abstract Polytetrafluoroethylene (PTFE) has the advantages of high chemical stability, wide operating temperature range, excellent lubrication, etc. It is widely used in aerospace, automotive industry and other engineering fields and plays an important role in sealing applications of low-temperature media. However, in practical engineering applications, the design of PTFE O-rings in low-temperature variable-temperature working conditions lacks a reference basis. Based on the sealing structure of low-temperature pressure vessel, this paper establishes a two-dimensional axisymmetric model using the finite element analysis software Abaqus to study the sealing performance of PTFE O-rings in the static sealing system, and analyzes the effects of temperature, compression rate, cold shrinkage on the deformation of the PTFE O-rings, the Mises stresses, and the contact pressure.

Synergistic anti-corrosion and anti-wear of epoxy coating functionalized with inhibitor-loaded graphene oxide nanoribbons

The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions. This study reports an epoxy resin coating filled with benzotriazole loaded metal-organic frameworks (BTA-MOFs) functionalized graphene oxide nanoribbons (GONR) that exhibit active anti-corrosion, act as a barrier to corrosive ion, and enhance wear resistance. The GONR@BTA-MOFs composite is synthesized through chemically etching multi-walled carbon nanotubes and subsequent electrostatic self-assembly corrosion inhibitors loaded MOFs onto the GONR. The composite demonstrates improved compatibility with epoxy resins compared to carbon nanotubes. The anti-corrosion performance of the composite coating is investigated using electrochemical impedance spectroscopy. After immersing in a 3.5 wt.% NaCl solution for 25 d, the alternating current impedance of the composite coating is three orders of magnitude higher than that of pure epoxy resin. Simultaneously, the controlled release of the corrosion inhibitor retards the deterioration of the coating after localized damage occurrence, which functions as active corrosion protection. The GONR@BTA-MOFs/EP composite coating exhibits the highest corrosion potential of -0.188 V and the lowest corrosion current of 3.162 × 10−9 A cm−2) in the Tafel test. Tribological studies reveal a reduction in the friction coefficient from 0.62 to 0.08 after incorporating GONR@BTA-MOFs in the coating, with the wear volume being seven times lower than that of pure epoxy resin. The excellent lubrication effect of the nanomaterials reduces the coefficient of friction of the coating, thereby improving the abrasion resistance of the coating. The synergy between the self-lubrication of the two-dimensional layered fillers and the corrosion resistance of the smart inhibitor containers suggests a promising strategy for enhancing the performance of epoxy resins under complex working conditions.

Mechanical properties and tribological behavior of hard phase doped Pb/MoS2 composite films

MoS2 is commonly used as a lubricant in spacecraft applications, and it is necessary to improve the vacuum tribological properties of MoS2 films. Thus, in the current study, hard phase (Ta, Ti, and TiN) and soft metal (Pb) double-doped MoS2 composite films were designed and prepared using an unbalanced magnetron sputtering system. The microstructures and mechanical and tribological properties of the hard-soft phase doped Pb/MoS2 composite films were systematically investigated. The results showed that the synergistic effect of the hard and soft metals gave a denser MoS2 structure denser. In addition, an amorphous structure was generated along with fine crystals, leading to a structure typical of nanocrystals embedded in an amorphous phase. Furthermore, compared with the Ti-doped Pb/MoS2 film, the doped alternative hard phase (i.e. Ta and TiN) improves the mechanical properties, among which the adhesion strength of Ta-Pb/MoS2 film is the highest, and the hardness of TiN-Pb/MoS2 film is the highest. Importantly, the soft metal Pb and its sulfide are excellent lubricants, while the hard phase ensures the long-term reliability of the films. Overall, these soft-hard bimetallic-doped MoS2 films exhibit superior tribological properties to their un-doped equivalents.

Advancements and challenges in bionic joint lubrication biomaterials for sports medicine

AbstractBionic lubricant materials are a class of materials inspired by natural organisms and offer excellent lubrication properties and biocompatibility. In the field of sports medicine, their application opens up new possibilities for the prevention and treatment of sports‐related diseases. The authors will introduce the existing theoretical models of friction in the locomotor system, the characteristics and advantages of biomimetic lubrication materials and discuss in depth their applications in the field of sports medicine. The development of bionic lubrication materials opens up unprecedented opportunities for sports medicine to provide more effective and long‐lasting treatment options for patients.

Borate ester hybrid photothermal nanofluid derived from C3N4/MoS2 catalyzed esterification for efficient organic-inorganic synergistic lubrication

The inferior dispersion stability and simple functionality of MoS2-based nanofluids restrict their efficient application in lubrication. Herein, a novel nanofluid composed of C3N4/MoS2, 3-isocyanatopropyltrimethoxysilane, and C3N4/MoS2-catalyzed product (polyethylene glycol-borate ester, PEG-BA) was proposed. C3N4 nanosheets could induce the formation of regular MoS2 nanospheres. The resulting C3N4/MoS2 showed excellent catalytic activity for the esterification of PEG-BA. The C3N4/MoS2 @PEG-BA nanofluid exhibited favorable dispersion stability in PEG600 with no stratification for ≥ 82 days. The addition of 3.0 wt% C3N4/MoS2 @PEG-BA nanofluid could significantly reduce friction coefficient (30.7 %) and wear scar diameter (28.9 %). The excellent lubrication properties of the nanofluid are attributed to the synergistic lubrication effect of C3N4/MoS2 and PEG-BA. Furthermore, the nanofluid exhibits remarkable photothermal conversion performance in both oil and air mediums.

Skiing-inspired robust lubricating composite coatings from thermally sprayed ceramic template

Inspired by the mechanism of skiing, herein, a novel composite coating with excellent lubrication properties was developed by incorporating solid-liquid reversible lubricating phases into the inherent microcracks and pores of thermally sprayed ceramic coatings. The results indicate that the crystalline-amorphous heterostructure formed within the micro-nano cracks, enhancing their cohesive strength and toughness. Compared to traditional ceramic coatings, the friction coefficient of the composite coating has been reduced by 80 %, while the wear rate decreased from 2.89 × 10−4 to 6.44 × 10−7 mm3∙N−1∙m−1. Under the applied load and friction-induced heat, a thin liquid lubrication film is formed. Importantly, the lubricating phase continuously overflows from defects under the induction of frictional heat to replenish the lubricating film, ensuring long-term lubrication of the coating.

A new application of MoS2@AG@PA prepared by irradiation: Synergizing with magnesium hydroxide to enhance fire safety and other key properties of EVA composites

AbstractTwo‐dimensional molybdenum disulfide (MoS2) nanosheets are seen as highly promising nanofillers for enhancing polymer properties, yet there is a need for methods that are low‐cost, simple, and environmentally friendly to facilitate the large‐scale production of MoS2 nanosheets. Furthermore, it is necessary to functionalize the MoS2 surface to ensure good interfacial compatibility with the polymer matrix. In this study, MoS2@Ag@PA hybrids were created by generating silver nanoparticles directly on the surface of MoS2 via radiation, followed by encapsulation on the surface of MoS2@Ag through the chelating properties of phytic acid. It is significant to note that, due to the excellent lubrication and physical cross‐linking effects of the MoS2@Ag@PA hybrids, adding one part of MoS2@Ag@PA hybrids can enhance the melt flow rate and elongation at break of the ethylene vinyl acetate copolymer (EVA)/MH composites by 140% and 17.3%, respectively. The simultaneous addition of one part of MoS2@Ag@PA hybrids decreased the peak heat release rate, total heat release, and total smoke release of the EVA composites by 48.7%, 42.7%, and 41.2%, respectively. Moreover, the toxic gasses (e.g., CO) generated by burning EVA composites were significantly reduced compared to pure EVA, indicating improved fire safety. This research not only provides significant opportunities for the green mass production of MoS2 nanosheets but also expands their potential applications in high‐performance nanocomposites.

Hyaluronic Acid-Based Microparticles with Lubrication and Anti-Inflammation for Alleviating Temporomandibular Joint Osteoarthritis.

The pathogenesis of temporomandibular joint osteoarthritis (TMJOA) is closely associated with mechanical friction, which leads to the up-regulation of inflammatory mediators and the degradation of articular cartilage. Injectable drug-loaded microparticles have attracted widespread interest in intra-articular treatment of TMJOA by providing lubrication and facilitating localized drug delivery. Herein, a hyaluronic acid-based microparticle is developed with excellent lubrication properties, drug loading capacity, antioxidant activity, and anti-inflammatory effect for the treatment of TMJOA. The microparticles are facilely prepared by the self-assembly of 3-aminophenylboronic acid-modified hyaluronic acid (HP) through hydrophobic interaction in an aqueous solution, which can further encapsulate diol-containing drugs through dynamic boronate ester bonds. The resulting microparticles demonstrate excellent injectability, lubrication properties, radical scavenging efficiency, and antibacterial activity. Additionally, the drug-loaded microparticles exhibit a favorable cytoprotective effect on chondrocyte cells invitro under an oxidative stress microenvironment. Invivo experiments validate that intra-articular injection of drug-loaded microparticles effectively alleviates osteoporosis-like damage, suppresses inflammatory response, and facilitates matrix regeneration in the treatment of TMJOA. The HP microparticles demonstrate excellent injectability and encapsulation capacity for diol-containing drugs, highlighting its potential as a versatile drug delivery vehicle in the intra-articular treatment of TMJOA.

Tribological properties of YG8/steel friction pair in an aqueous lubrication system with an ionic liquid: Experimental results and molecular dynamics simulations

In this work, an ionic liquid (G-RIC) with excellent lubricating performance was successfully prepared, and the tribological properties as an additive in glycerol-water solutions were explored. The results indicated that 2.0 % additive content can reduced the friction coefficient to below 0.1, leading to a decline in the wear volume of 76 %. Gray cast iron corrosion tests revealed that the additive exhibited excellent corrosion resistance. Quantum chemical calculations revealed that the anion RIC has a low energy gap (ΔE = 0.034 Ha), which implies that it is more prone to undergoing tribochemical reactions with the metal substrate under frictional heat. The synergistic action of the liquid lubrication layer, adsorption film, and friction protective film created an interface that easily shears.

Electrothermal-Assisted Photothermal Lubrication Surfaces for Continuous Anti-Icing/Deicing in Multiple Low-Temperature Environments.

Solving the problem of ice accumulation on solid surfaces is of great significance to the economic development of the country and the safety of people's lives. In this work, a coating with multifunctional photothermal/electrothermal solid-state lubrication (PEL) for anti-icing/deicing was prepared in layers based on the intrinsic properties of silicone oil and paraffin wax in combination with conductive graphite and multiwalled carbon nanotubes. Silicone oils and paraffins are used as lubricating media giving the coating excellent lubricity, which results in a water sliding angle (SA) of only 12° on the PEL surface. Meanwhile, PEL shows favorable static and dynamic ice resistance at low temperatures; at -10 °C, the freezing time of water droplets on the PEL surface is extended by at least 4 times compared to the bare substrate. Furthermore, PEL also offers highly efficient photothermal and electrothermal deicing performance, which can effectively remove the accumulated ice at a light intensity of 0.6 kW/m2 or an EPD of 0.1 W/cm2. Meanwhile, the synergistic deicing mechanism of photothermal and electrothermal was verified at -20 °C. Interestingly, the coating shows heat-assisted healing ability due to the phase change characteristic of paraffin wax, which allows the coating to regain lubricating properties after mechanical abrasion. Therefore, this work provides a reliable way for the design of stable all-weather anti-icing/deicing strategies at low temperatures.