Extreme-Pressure Superlubricity of Polymer Solution Enhanced with Hydrated Salt Ions

Li, Shaowei; Bai, Pengpeng; Li, Yuanzhe; Wang, Jia; Li, Xinxin; Meng, Yonggang; Ma, Liran; Tian, Yu

doi:10.1021/acs.langmuir.0c00887

Cited by 17 publications

(13 citation statements)

References 60 publications

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“…It can be observed that the COF of the mixed solution reduced rapidly before stabilizing. A state of superlubricity was achieved in all repeated experiments, with a minimum COF of 0.0038 . However, it was also found that, during the experiment, the frictional force between the friction pairs increased instantaneously, resulting in random “wave peak” features in the COF curve with respect to time.…”

Section: Results and Discussionmentioning

confidence: 77%

“…A state of superlubricity was achieved in all repeated experiments, with a minimum COF of 0.0038. 15 However, it was also found that, during the experiment, the frictional force between the friction pairs increased instantaneously, resulting in random "wave peak" features in the COF curve with respect to time. After the tribo-test, the Si 3 N 4 ball was cleaned with UP, and irregular black abrasive particles were found near the wear scar by optical microscopy (×1000 magnification) (Figure 2b,c).…”

Section: ■ Results and Discussionmentioning

confidence: 94%

“…Superlubricity refers to a state of lubrication with an extremely low friction coefficient. − This phenomenon can potentially be harnessed in energy-saving applications, thus extending the service life of both industrial machinery and human joints. − In the past two decades, great progress has been made in the field of water-based liquid superlubricity, − especially in exploring the ability of various polymers to yield ultralow coefficients of friction (COFs). − In recent years, by applying polymers to bionic synovial fluid, researchers analyzed the mechanisms by which salt solutions influence their lubricating properties. − Zhang et al found that salt solutions can change the strength of polymer adsorption and intermolecular interaction. Li et al showed that the synergistic effect between a polymer and salt solution can result in superlubricity between silicon nitride (Si 3 N 4 ) and sapphire (Al 2 O 3 ) surfaces under extreme pressure conditions. Meanwhile, Han et al demonstrated that a mixed solution of polyethylene glycol and KCl exhibited excellent lubricating properties and revealed that the friction-induced SiO 2 layer played a vital role during the running-in process to realize macroscopic superlubricity .…”

Section: Introductionmentioning

confidence: 99%

“…14−16 Zhang et al 14 found that salt solutions can change the strength of polymer adsorption and intermolecular interaction. Li et al 15 showed that the synergistic effect between a polymer and salt solution can result in superlubricity between silicon nitride (Si 3 N 4 ) and sapphire (Al 2 O 3 ) surfaces under extreme pressure conditions. Meanwhile, Han et al 16 demonstrated that a mixed solution of polyethylene glycol and KCl exhibited excellent lubricating properties and revealed that the friction-induced SiO 2 layer played a vital role during the running-in process to realize macroscopic superlubricity.…”

Section: ■ Introductionmentioning

confidence: 99%

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Effects of Abrasive Particles on Liquid Superlubricity and Mechanisms for Their Removal

Wen

Bai

et al. 2021

Langmuir

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Liquid superlubricity results in a near-frictionless lubrication state, which can greatly reduce friction and wear under aqueous conditions. However, during the running-in process, a large number of abrasive particles are generated, and because these may lead to a breakdown in superlubricity performance, they should be effectively removed. In this paper, the morphology, size, and composition of abrasive particles were verified using scanning electron microscopy with energy-dispersive X-ray spectroscopy, and their influence on liquid superlubricity was explored through friction tests. Subsequently, different solvents were used to remove the abrasive particles, and the optimal cleaning process was determined by macroscopic tribo-tests and microscopic analysis. Finally, droplet-spreading experiments and a force-curve analysis were carried out to understand the abrasive-particle removal mechanism by different solvents. We found that SiO 2 was the main component in the abrasive particles, and micron-sized SiO 2 particles resulted in random "wave peaks" in the coefficient of friction and, thus, the superlubricity. Absolute ethanol + ultrapure water was determined to be the optimal solvent for effectively removing abrasive particles from friction-pair surfaces and helped the lubricant in exhibiting an ultralow friction coefficient for long periods of time. We proposed a "wedge" and "wrap" model to explain the abrasive-particle removal mechanism of different solvents. The SiO 2 removal mechanism outlined in this study can be applied under aqueous conditions to improve the stability and durability of liquid superlubricity in practical engineering applications.

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Section: Results and Discussionmentioning

confidence: 77%

Section: ■ Results and Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of Abrasive Particles on Liquid Superlubricity and Mechanisms for Their Removal

Wen

Bai

et al. 2021

Langmuir

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“…Recent studies have demonstrated that many aqueous lubricants are capable of reducing the friction coefficient (COF) between surfaces down to negligible levels (COF <0.01), thereby achieving superlubricity. These lubricants include polymer solutions, − acid solutions, , mixed solutions of acid and alcohol, surfactant solutions, , salt solutions, and mixed solutions of salt and polymer . Different superlubricity mechanisms have been attributed to interfacial forces, such as double-layer, van der Waals, and hydration forces, caused by the adsorption and aggregation of lubricant molecules onto the frictional interfaces. , …”

Section: Introductionmentioning

confidence: 99%

Potential-Dependent Interfacial Frictional Behavior between Charged Microspheres and Gold in Aqueous Solutions

Bai

et al. 2022

J. Phys. Chem. C

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We study the interfacial frictional behavior between negatively charged hydroxyl- and carboxyl-functionalized and positively charged amino-functionalized colloidal probes and a gold electrode (GE) through electrochemical atomic force microscopy. The charged microspheres exhibit similar potential-dependent frictional behavior, with high and low frictional forces at positive and negative gold potentials, respectively. However, normal force and X-ray photoelectron spectroscopy revealed that the oppositely charged microspheres exhibit differences in the potential-controlled friction mechanism, attributed to a rearrangement of hydrated ions and water molecules due to varying gold potentials and microsphere properties. At the positive potential, surface polar groups on the negatively charged microspheres can directly form hydrogen bonds with an ice-like water layer on the gold surface, thereby increasing friction, whereas the positively charged microspheres rely on the hydrated Cl– ions adsorbed on the surface to form a hydrogen bond with the ice-like water layer. At the negative potential, the lubrication of the hydrated Na+ ions between the negatively charged microspheres and the GE reduced friction and facilitated superlubricity. However, at the interface between the positively charged microspheres and the GE, the electrostatic force generated by the hydration ions with different electrical properties increases frictional energy loss, but the lubrication of hydrated Na+ ions at the interfaces continues to induce superlubricity. The influence of different surface charges/potentials on interfacial adhesion and friction behavior is discussed in line with the mechanism of potential-controlled friction, which aids in the design of controllable friction devices in water-based environments.

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A Self‐Healing Flexible Quasi‐Solid Zinc‐Ion Battery Using All‐In‐One Electrodes

et al. 2021

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Self-healing and flexibility are significant for many emerging applications of secondary batteries, which have attracted broad attention. Herein, a self-healing flexible quasi-solid Zn-ion battery composing of flexible all-in-one cathode (VS 2 nanosheets growing on carbon cloth) and anode (electrochemically deposited Zn nanowires), and a self-healing hydrogel electrolyte, is presented. The free-standing all-in-one electrodes enable a high capacity and robust structure during flexible transformation of the battery, and the hydrogel electrolyte possesses a good self-healing performance. The presented battery remains as a high retention potential even after healing from being cut into six pieces. When bending at 60°, 90°, and 180°, the battery capacities remain 124, 125, and 114 mAh g −1 , respectively, cycling at a current density of 50 mA g −1 . Moreover, after cutting and healing twice, the battery still delivers a stable capacity, indicating a potential use of self-healing and wearable electronics.

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Extreme-Pressure Superlubricity of Polymer Solution Enhanced with Hydrated Salt Ions

Cited by 17 publications

References 60 publications

Effects of Abrasive Particles on Liquid Superlubricity and Mechanisms for Their Removal

Effects of Abrasive Particles on Liquid Superlubricity and Mechanisms for Their Removal

Potential-Dependent Interfacial Frictional Behavior between Charged Microspheres and Gold in Aqueous Solutions

A Self‐Healing Flexible Quasi‐Solid Zinc‐Ion Battery Using All‐In‐One Electrodes

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