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In this study, the wear failure behaviour of coated self-lubricating spherical plain bearings under different working conditions in the light-load and low-frequency range was studied using a swing wear life tester. The commercial GE17ES bearing was the main research object, and the wear state of the bearing was monitored in real time using torque and temperature rise signals. Furthermore, a scanning electron microscope and an energy dispersive X-ray spectroscope were adopted to analyse the wear failure mechanism of bearings. The results indicated that the friction torque and temperature rise signal changes were mainly divided into three stages, and the characteristics of similar changes could be maintained under different working conditions. Furthermore, at the end of the bearing life, the torque and temperature rise had abrupt changes almost at the same time, which indicated the occurrence of bearing failure. In general, the wear failure mechanisms of bearings included abrasive wear and adhesive wear. Moreover, fatigue wear and oxidation wear were under some conditions. The torque and temperature rise comprehensively reflected the service state of coated self-lubricating spherical plain bearings, which could be used as a physical criterion for determining bearing failure. These results had a strong prospect of engineering application, and were expected to provide a reference for determining the failure behaviour of multi-type coated self-lubricating spherical plain bearings in the future, and provided theoretical support for establishing relevant test standards.

Exploring a rapid, reliable, and practical means to detect blockages and leakages in liquid pipelines and accurately locate their positions is of great importance in practical engineering applications. Here, we report a bubble motion-based triboelectric sensor (BM-TES) for detecting and locating the blockages and leaks inside a plastic tube. This simple-designed, environment-friendly, non-damaging sensor is composed of several ring-shaped Cu electrodes distributed on a polytetrafluoroethylene tube. The self-powered movement of the bubble under the action of buoyancy makes the inner wall of the tube change from the original solid-liquid phase to the gas-solid-liquid phase, which results in a short-term contact and separation between the liquid and the wall. Based on the fractional triboelectric effect of the liquid-solid contact, an obvious real-time stable voltage peak will be generated where the detection bubble passes. The obvious peaks of the open-circuit voltage with respect to time correspond with the electrode distribution. Then, the peaks can be utilized as a robust and sensitive indicator for detecting blockage and leakage, as the number of obvious peaks of the open-circuit voltage is directly related to the blockage and leakage location. The blockage and leakage in a fluid tube were successfully detected using the BM-TES with an accuracy of 10 cm. In addition, the BE-TES was able to detect the water flow velocity in the pipe. The experimental results showed that BM-TES can provide a new strategy and method for liquid tube monitoring and has great potential application value in related fields.

3D printing of hydrogels with high intrinsic mechanical performance has significant applications in many fields yet has been proven to be a fundamental challenge. Here, 3D printing of ultrahigh strength hydrogels is achieved by constructing cross-linkingDPC networks based on poly(vinyl alcohol) (PVA) and chitosan (CS). The hybrid ink with moderate rheology for direct ink writing is employed to manufacture complex hydrogel structures, first. Then, the cyclic freezing–thawing followed by sodium citrate solution soaking realize the first network of PVA crystallization and the second one of CS ionic interaction between amino and carboxyl groups. The optimized DPC hydrogel displays a tensile strength of 12.71 ± 1.32 MPa at a strain of 302.27 ± 15.70%, Young’s modulus of 14.01 ± 1.35 MPa, and work of extension at fracture Wextof 22.10 ± 2.36 MJ m–3because of the dominant energy dissipation of the stiff CS ionic network. Moreover, the tearing test supports that this DPC hydrogel possesses a high toughness of 9.92 ± 1.05 kJ m–2. This protocol can readily realize not only the hydrogel lattice, honeycomb, and spring, but also secondary-shaping hydrogel objects including whale, octopus, and butterfly via a local DPC strategy. Integrating the advanced 3D-printing technique with high-performance hydrogels uncovers a feasible strategy to broad practical applications in engineering, intelligent machine, and soft robotics.

Inspired by the gas-trapped mechanism underwater of Argyroneta aquatica, we prepared a superhydrophobic yarn with a fiber network structure via a facile and environmentally friendly method. Attributed to the low surface energy, the superhydrophobic fiber network structure on the yarn is able to trap and transport bubbles directionally underwater. The functional yarn has good superhydrophobic and superaerophilic properties underwater to realize the directional transport of bubbles underwater without being pumped. We designed demonstration experiments on the antibuoyancy directional bubble transportation, which indicated the feasibility in the applications of gas-related fields. Significantly, on further testing, where the superhydrophobic yarn is put into a U-shaped pipe, we obtain a gas-siphon underwater with a high flux. The superhydrophobic fiber structure yarn can trap the gas underwater to enable the self-starting behavior while no manual intervention is used. The gas-siphon can convey gas over the edge of a vessel and deliver it at a higher level without energy input, which is driven by the differential pressure. The relationship between the differential pressure and the volume flux of transport bubbles is investigated. The experimental results show that the prepared superhydrophobic yarn has the advantages of good stability, easy preparation, and low cost in bubble continuous transportation underwater, which provides a novel strategy for the development and application of new technologies such as directional transportation, separation, exhaustion, and collection of gases in water.

An efficient Fe(TPP)Cl catalyzed insertion reaction of in situgenerated benzylic carbenes from N-tosylhydrazones into X–H (X = Si, Sn, Ge) was developed. Silanes bearing tertiary, secondary, and primary (3°, 2°, and 1°) Si–H bonds all reacted well to afford insertion products in moderate to high yields (up to 97%), and the reaction time could be significantly shortened to 1 h under microwave irradiation. A programmable stepwise double insertion strategy was developed for the synthesis of unsymmetrical tetrasubstituted silanes.

A new ratiometric nanosystem has been developed for selective and ultrasensitive detection of etimicin based on citrate-stabilized silver nanoparticles (AgNPs) and N,N′-bis-(1-pyrenecarboxaldehyde)-1,12-dodecanediamine (probe 1). Probe 1, a bispyrene Schiff base derivative, was designed to function as an ideal dual-emission fluorophore because of its special monomer and excimer bands at around 396 and 483 nm, respectively. Meanwhile, AgNPs can serve as an excellent light-absorber as well as a colorimetric probe. In the presence of etimicin, the fluorescence intensity at 396 nm increases owing to the turn-on of the fluorescence of probe 1. Moreover, etimicin can induce the aggregation of AgNPs and subsequently enhance the emission quenching of probe 1at 483 nm due to the restriction of the conformational change of bispyrene molecules, thus leading to the corresponding ratiometric fluorescence measurement of the analyte. Additionally, analyte-caused aggregation of AgNPs also favors ratiometric colorimetric detection of etimicin. Under the optimum conditions, this convenient ratiometric nanosensor can be applied to the fluorescence and colorimetric analysis of etimicin in human urine with the detection limit as low as 0.05 and 0.25 nM (S/N = 3), respectively.

New lanthanide metal-organic framework(MOF) nano/microrods, [C4mim]Cl-Eu-MOF, [C8mim]Cl-Eu- MOF and [C12mim]Cl-Eu-MOF, were conveniently synthesized via an ionic liquid-assisted hydrothermal method and characterized by means of powder X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG) and transmission electron microscopy(TEM). The obtained nano/microrods with low surface areas were efficient for the removal of Congo red(CR) from aqueous solutions. Under the optimum conditions, [C4mim]Cl-Eu-MOF with a specific surface area of 5.1 m2/g exhibited an ultrahigh adsorption capacity of 2606 mg/g toward CR. Notably, the adsorption efficiency of [C4mim]Cl-Eu-MOF for CR vianano/microscale stacking can be directly demonstrated by TEM. In-depth understanding of CR removal by [C4mim]Cl-Eu-MOF nano/microrods was also supported by FTIR, Raman spectroscopy and zeta potential analyses.

Oil-impregnated self-lubricating polymers are widely used in the field of aviation and aerospace, petrochemical industry and mechanical engineering due to their excellent self-lubrication, maintenance-free and environmental stability. Traditionally, they are fabricated by the two-step method, i.e. fabrication of porous structure followed by filling the lubricant in the pores, which is not only specific equipment requirement and time-consuming, but results poor lubricating and mechanical performance due to the uneven distribution of lubricant and the high porosity. Herein, the oil-impregnated polymer with superior self-lubricating and mechanical performances is achieved with a novel one-pot strategy by pre-embedding the oil-impregnated cotton fibres in the polymer matrix. With the pre-embedding of the oil-impregnated cotton fibre, the oil-impregnated cotton fibres/polymer composites (OCFP) with the oil content rate up to 42.86% were achieved in one step. Moreover, the oil impregnated in OCFP was found nearly no leak. The resultant OCFP thus exhibited the average friction coefficient reduced by 98.63% and the compression strength improved by 367.74%. The oil-impregnated polymers with excellent self-lubricating and mechanical performance fabricated by the facile one-pot fabricating strategy are promising to be widely used in the engineering fields.

Despite many years of research, the current-carrying friction interface still strongly depends on the lubricating film between the friction pairs, because this film can reduce the probability of arc occurrence. However, this film has poor conductivity, cannot self-heal, and is prone to be greasy, which reduces the efficiency of current conduction, which seriously affects the contact status. In order to solve this problem, graphite materials with excellent lubricating properties and electrical conductivity are used to make current-carrying friction materials. Graphite and graphite-based composite materials are the most widely used current-carrying friction materials in various industries. Graphite has excellent lubricity, conductivity, and high temperature resistance to steel and many other metal materials. However, with the passage of time, due to the continuous deterioration of the application conditions and the environment, such as arc under high current density, spark phenomenon, severe mechanical wear under high load, etc., the lubricating film is destroyed, which greatly weakened the performance of protecting friction pairs. Therefore, improving the working stability of the current-carrying friction pair is the key to ensuring that the contact pair does not spark. In this review, we mainly discuss how to improve the stability of the current-carrying friction system, reduce the wear of the current-carrying friction system, and thereby extend the service life of the current-carrying friction material. At first, we discussed the latest research progress of current-carrying friction from the electrical properties, contact resistance, thermal effect, and arc of current-carrying friction materials to tribological characteristics. Secondly, the influence of contact resistance parameters and structural function parameters on the wear life of current-carrying friction pairs is discussed. The current research status of current-carrying performance and tribological performance of current-carrying friction pairs under the coupled effects of temperature field and current field is discussed. It is necessary to combine experiment, theory, and simulation to study the temperature field of the current-carrying friction pair, especially the influence of complicated conditions such as oil and dust on the friction performance of the current-carrying. Thirdly, the influence of arcing, sparking, and dynamic characteristics on the friction performance of the current-carrying friction system is reviewed. At the same time, the prediction model of current-carrying friction and wear should be studied systematically to detect current-carrying friction and wear online. Finally, it introduces in detail that new current-carrying friction materials are developing in the direction of tissue functionalization and structural composite.