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Ultra-low friction is crucial for the anti-friction, anti-wear, and long-life operation of nanodevices. However, very few two-dimensional materials can achieve ultra-low friction, and they have some limitations in their applications. Therefore, exploring novel materials with ultra-low friction properties is greatly significant. The emergence of ternary two-dimensional materials has opened new opportunities for nanoscale ultra-low friction. This study introduced nickel phosphorous trisulfide (NiPS3, referred to as NPS), a novel two-dimensional ternary material capable of achieving ultralow friction in a vacuum, into the large nanotribology family. Large-size and high-quality NPS crystals with up to 14 mm × 6 mm × 0.3 mm dimensions were grown using the chemical vapor transport method. The NPS nanosheets were obtained using mechanical exfoliation. The dependence of the NPS nanotribology on layer, velocity, and angle was systematically investigated using lateral force microscopy. Interestingly, the coefficient of friction (COF) of NPS with multilayers was decreased to about 0.0045 under 0.005 Pa vacuum condition (with load up to 767.8 nN), achieving the ultra-low friction state. The analysis of the frictional dissipation energy and adhesive forces showed that NPS with multilayers had minimum frictional dissipation energy and adhesive forces since the interlayer interactions were weak and the meniscus force was excluded under vacuum conditions. This study on the nanoscale friction of a ternary two-dimensional material lays a foundation for exploring the nanoscale friction and friction origin of other two-dimensional materials in the future. [ABSTRACT FROM AUTHOR]

Nature has successfully combined soft matter and hydration lubrication to achieve ultralow friction even at relatively high contact pressure (e.g., articular cartilage). Inspired by this, hydrogels are used to mimic natural aqueous lubricating systems. However, hydrogels usually cannot bear high load because of solvation in water environments and are, therefore, not adopted in real applications. Here, a novel composite surface of ordered hydrogel nanofiber arrays confined in anodic aluminum oxide (AAO) nanoporous template based on a soft/hard combination strategy is developed. The synergy between the soft hydrogel fibers, which provide excellent aqueous lubrication, and the hard phase AAO, which gives high load bearing capacity, is shown to be capable of attaining very low coeffcient of friction (<0.01) under heavy load (contact pressures ≈2 MPa). Interestingly, the composite synthetic material is very stable, cannot be peeled off during sliding, and exhibits desirable regenerative (self-healing) properties, which can assure long-term resistance to wear. Moreover, the crosslinked polymethylacrylic acid hydrogels are shown to be able to promptly switch between high friction (>0.3) and superlubrication (≈10−3) when their state is changed from contracted to swollen by means of acidic and basic actuation. The mechanisms governing ultralow and tunable friction are theoretically explained via an in-depth study of the chemomechanical interactions responsible for the behavior of these substrate-infiltrated hydrogels. These findings open a promising route for the design of ultra-slippery and smart surface/interface materials. [ABSTRACT FROM AUTHOR]

Friction was the main way of energy loss in society, and reducing friction has become a focal point in current research. Inspired by special wetting phenomena, an asymmetric multiphase composite (AMPC) friction system was constructed. Tribological behavior of the friction system was evaluated using hydrogel on anodized aluminum as friction pair and superhydrophobic alumina with micro/nano-composite as substrate. Ultra-low friction coefficients (∼10−3) were measured under both Cassie and Wenzel regimes. Especially in Wenzel state, increased contact stress or extended shear rate promoted the formation of transfer lubricant film, thus enabling the ultra-low friction coefficient. Moreover, the system showed mechanical stability during prolonged water lubrication. This novel lubrication approach may provide valuable scientific solutions for specific tribology applications. [Display omitted] • Inspired by superwetting phenomena, a green, asymmetric multiphase composite (AMPC) friction system is developed. • By forming a transfer lubricant film, ultra-low friction behavior under various wetting regimes was realized. • The tribological prototype showed exceptional mechanical stability, maintaining ultra-low friction over an extended period. [ABSTRACT FROM AUTHOR]

Maintaining the condition of the friction pair is an important measure to reduce mechanical failure. This paper integrates a vacuum elastohydrodynamic oil film measurement device and a current amplifier to simultaneously observe the optical interference image, friction coefficient and triboelectric signal during the friction process. In a high vacuum environment, the discharge phenomenon of steel balls corresponds to the time when the friction pair wears. Changes in the friction state in high vacuum environments have a significant impact on triboelectricity. Based on the relationship between the two, a sensor for real-time monitoring of the friction and wear status of the friction pair is designed, which provides a reliable real-time monitoring method for friction pair monitoring in vacuum machinery. [Display omitted] [ABSTRACT FROM AUTHOR]

Using superlubricants to reduce friction and wear can dramatically reduce energy consumption and economic losses in industrial production. In this paper, we report a natural and environmentally friendly lubricant based on phytic acid solution (PA-0) that can achieve robust macroscale liquid superlubrication between PDMS and glass interfaces, and the superlubrication state can be maintained for at least 13 h. Significantly, its superlubrication can also be extended to other friction pair materials, reflecting its robustness and universality as a superlubricant. The calculation of the lubricating film thickness reveals that the superlubrication realized by the PA-0 solution belongs to the mixed lubrication state that comprises boundary lubrication and hydrodynamic lubrication. These findings may advance the practical application of liquid superlubrication. [Display omitted] • Phytic acid (PA) is widely found in plant seeds and has the advantages of natural abundance, non-toxicity and low cost. • The superlubricating state achieved by PA-0 lubricant can be maintained for up to 13 h. • The superlubrication of the obtained PA-0 lubricating material can be realized between PDMS and various friction pairs. [ABSTRACT FROM AUTHOR]

Deep eutectic solvent (DES), as a promising electrolyte for composite electrodeposition, can effectively reduce the agglomeration of nanoparticles in the electroplating bath and increase the content of nanoparticles in the metal matrix compared with aqueous solution. However, uniform distribution of nanoparticle within metal matrix remains a difficult challenge. In this work, it is demonstrated that a novel in-situ synthesis of SiO 2 nanoparticles in DES can effectively improve the distribution uniformity of SiO 2 nanoparticles in the Ni matrix compared with the conventional addition method, producing a homogenous Ni/SiO 2 nanocomposite coating. The friction and wear tests showed that the uniformly distributed SiO 2 nanoparticles in the Ni matrix significantly improved the tribological properties of the composite coating with stable friction coefficient and wear resistance. The in-situ synthesized method is a promising way to fabricate homogenous nanocomposite coating has better tribological properties than the conventional composite coatings produced by solid particle adding method. [ABSTRACT FROM AUTHOR]

Wear and corrosion are one of the main causes of material loss and equipment failure in mechanical equipment, especially under current-carrying friction conditions, which interact and exacerbate each other. Herein, a new ionic liquid additive (IL-16) was studied to simultaneously improve the anti-wear and anti-corrosion properties of steel-steel friction pair under conductive conditions. The coefficient of friction decreased by 58.8% at 1.6 wt% IL-16 content under the load current of 1.5 A, the wear was reduced 10 times, and the contact resistance was only 37 mΩ, owing to the IL-16 ionic liquids additive forming a stable physical adsorption film on the surface of the friction pair to hinder the transfer of charges and products related to the corrosion reaction. [Display omitted] • IL-16 additive can reduce the friction and wear and improve the electrical conductivity and corrosion resistance. • IL-16 ionic liquid can form coordination bonds with metals to improve the corrosion resistance of metals. • The long alkyl chain of IL-16 can form an effective lubricating film to reduce friction and wear. [ABSTRACT FROM AUTHOR]

Triboelectrification typically occurs in the friction process. In this study, we investigated the effect of liquid lubricants of various polarities on triboelectrification in a friction pair consisting of a steel ball and polyvinylidene fluoride blocks. The results revealed that alkanes and alkenes enhanced triboelectrification. On addition of PAO 4, the friction coefficient reduced considerably, and the short-circuit current could be output stably for a long time. With the increase in the viscosity of PAO, the triboelectric signal gradually decreased. This study revealed that the appropriate lubricant and the quantity of liquid can increase the size of the triboelectric signal to achieve a stable output for a long time. Monitoring the lubrication status of the machine was very important to the life of the machine. Through the change of the triboelectric signal, the state of the lubricant in the friction pair could be reflected in real-time, and the lubrication of the friction pair in the mechanical system can be monitored online to improve Machine life and safety. This research provides a real-time and online strategy for monitoring the lubrication status of friction pairs. [Display omitted] • Alkanes and alkenes enhanced triboelectrification. • Under dry friction, air breakdown changed short-circuit current. • After adding PAO 4, the short-circuit current could be output stably for a long time. • With the increase in the viscosity of PAO, the triboelectric signal gradually decreased. [ABSTRACT FROM AUTHOR]