Lubricant additives can effectively enhance the performance and environmental adaptability of lubricants and reduce the energy loss and machine wear caused by friction. Nanomaterials, as important additive materials, have an essential role in the research and development of new lubricants, whose lubrication performances and mechanisms are not only related to their physical and chemical properties, but also influenced by the geometric shape. In this paper, the friction reduction and antiwear performances of nanomaterials as lubricant additives are first reviewed according to the classification of the dimensions, and their lubrication mechanisms and influence rules are revealed. Second, the recent research progress of composite nanomaterials as lubrication additives is introduced, focusing on their synergistic mechanism to improve the lubrication performance further. Finally, we briefly discuss the challenges faced by nanoadditives and provide an outlook on future research. The review expects to provide new ideas for the selection and development of lubricant additives to expand the application of nanoadditives.

The damping performance of metal rubber is highly correlated with the tribological properties of the internal metal wires. In this paper, the friction and wear characteristics of 316L stainless-steel wire are investigated under different temperatures, loads, crossing angles, and working strokes. Results show that the friction coefficient increases from 0.415 to 0.635 and the wear depth increases from 34 μm to 51 μm, with the temperature rising from 20 °C to 400 °C. High temperature will soften metal materials and promote the oxidation of metal. Softened materials can be easily sheared and removed under friction action, resulting in high wear depth. However, when a continuous oxide film with high hardness is formed under higher temperature, the oxide film can work as a wear-resisting layer to prevent further wear of the wire to a certain degree. At the same temperature, the loads, crossing angles, and working strokes change the wear resistance by affecting the surface stress, debris removal efficiency, etc., and high temperature will aggravate this change. The results pave the way for the design and selection of materials for high-temperature metal rubber components.

Tribotronics represents the modulation of friction via an external electric potential, a field with promising ramifications for intelligent devices, precision manufacturing, and biomedical applications. A profound elucidation of mechanisms that allow for potential-controlled friction is foundational to further research in this tribotronic domain. This article provides a comprehensive review of the research progress in electro-controlled friction over the past few decades, approached from the perspective of the boundary lubrication film at the friction interface, a direct influencer of electro-controlled friction performance. The mechanisms of potential-controlled friction are categorized into three distinct classifications, contingent on the formation mode of the boundary lubrication film: potential-induced interfacial redox reactions, interfacial physical adsorption, and interfacial phase structure transformations. Furthermore, an outlook on the application prospects of electro-controlled friction is provided. Finally, several research directions worth exploring in the field of electro-controlled friction are proposed. The authors hope that this article will further promote the application of electro-controlled friction technology in engineering and provide intellectual inspiration for related researchers.

The fretting wear characteristics of two different energy density 316L stainless steels formed by selective laser melting (SLM) under different friction conditions are studied. The image method was used to study the porosity of two samples with different energy densities (46.88 J/mm³, 98.96 J/mm³) formed by SLM. The dynamic wear test, respectively, evaluates its wear morphology and wear depth under three conditions: dry friction, distilled water, and an 3.5% NaCl solution. The porosity of the samples with SLM forming an energy density of 46.88 J/${\mathrm{mm}}^3$ and 98.96 J/${\mathrm{mm}}^3$ are 7.66% and 1.00%, respectively. Under the three conditions, the friction coefficient and wear depth of the samples with high energy density are smaller than those of the samples with low energy density; the friction of the samples with two energy densities in aqueous solution is faster than dry friction in air and tends to be stable. The friction coefficient in 3.5% NaCl solution is the smallest; when the energy density is constant, the wear depth of the fretting wear is the largest under dry friction and the smallest in distilled water. Under dry-friction conditions, the wear mechanisms of fretting wear are mainly oxidative wear and adhesive wear. In the fretting wear in the distilled water and the 3.5% NaCl solution, both wear mechanisms are abrasive wear and fatigue wear.

受自然界启发, 仿生微结构被广泛用于调控固-液界面的性质. 研究显示, 液滴在微结构表面的各向异性浸润行为可用于实现微流动方向和速度的控制, 且其各向异性浸润与微结构的尺寸和分布等密切相关. 本文研究了微矩形凹槽尺寸对液滴各向异性浸润行为的影响规律. 结果显示, 液滴沿平行沟槽的方向具有较小的运动阻力、易铺展, 因此具有较小接触角; 而垂直于沟槽方向, 由于沟槽的阻隔作用具有较大运动阻力, 因而具有较大接触角, 并且在垂直方向液滴的浸润过程是三相线一系列钉扎和跳跃行为. 在微矩形凹槽表面, 液滴沿平行方向接触角θ_//与肋板宽度R和凹槽宽度G密切相关, 其值与表面固体面积比成反比; 而垂直于沟槽方向的接触角θ_⊥随肋板宽度R和凹槽宽度G变化基本保持不变. 同时各向异性液滴的变形比L/W、特征方向接触角比值θ_⊥/θ_// 与表面固体面积比成正比. 研究结果有助于加深理解微结构表面浸润行为的机制, 并为微矩形凹槽在微流动控制方向的应用提供技术支持.

The influence rules of square micro-pillar array porosity on the liquid motion characteristics of the near-surface layer are investigated by quartz crystal microbalance (QCM). QCM is a powerful and promising technique in studying the interfacial behavior, which exhibits great advantages in investigating the effects of surface microstructure, roughness, and array. In our experiments, three different arrays with the same height of about 280 nm and center distance of 200 μm, but different diameters of about 78 μm, 139 μm, and 179 μm are investigated. The results indicate that when the surface array has a large porosity, its influence on the liquid motion of the near surface layer is slight, thus resulting in a small increase of half-bandwidth variation due to the additional friction energy dissipation. When the surface array has a small porosity, the array tends to make the liquid film trapped in the array oscillating with the substrate, then there may be a layer of liquid film behaving like rigid film, and it also will make the liquid motion near the array layer more complicated. Thus for the #3 surface with a small porosity, both the absolute values of frequency shift |Δf ₃| and half-bandwidth variation ΔΓ ₃ increase obviously. The experimental results show good consistence with the theoretical model of Daikhin and Urbakh. This study sheds light on understanding the influence mechanism of surface array porosity on the liquid motion of near-surface layer.