Bao Jin,Guangyan Chen,Jun Zhao,Yongyong He,Yulong Li,Jianbin Luo
Reducing the friction and wear of dynamic interfaces has been a constant endeavor in the field of sustainability. Lubricants with two-dimensional atomic materials are operative frameworks proposed as promising candidates: they can together generate both a boundary tribofilm and a liquid hydrodynamic film in the interfacial domain. However, a quantitative characterization of the film formation and their coupling behaviors in the finite domain is lacking. Here, we report the coupling effect of tribofilms and hydrodynamic films regulated by typical representatives of two-dimensional material family (graphene, hBN, MoS 2 , and WS 2 ). The anti-wear properties of the interfaces are attributed to the behavior of the tribofilm, whereas the anti-friction properties of the interfaces are attributed to the viscosity behavior of the hydrodynamic film. This study provides an understanding of the intrinsic coupling mechanism of a tribofilm and a hydrodynamic film and a possible strategy for the design of interfacial lubricating systems.
Ao Xie,Jiaying Zhang,Hao-Zhe Xu,Xin-Gang Wang,Qiangliang Yu,Wenquan Lv,Meirong Cai,Feng Zhou
This manuscript developed a novel DLC–supramolecular gel (HTG) composite lubrication system to achieve long-life outstanding lubrication under extreme contact stress while avoiding sealing challenges relying on the unique thixotropic properties of the gel. DLC–HTG exhibited ultra-low wear and excellent friction reduction performance under a maximum contact stress of 2.24 GPa. DLC films with designed double transition layers possess high interfacial bond strength and mechanical properties, providing the basis for high wear resistance. The establishment of a robust tribofilm and the confinment effect of HTG on wear debris dominate the achievement of ultra-low wear. This ultra-low wear sliding extends the service life of the lubrication system with the broad implications for mechanical engineering , transportation, and wind power generation .
Jin Ran,Min Hu,Dongbo Yu,Yubin He,Muhammad Aamir Shehzad,Liang Wu,Tongwen Xu
The development of polymeric anion exchange membranes (AEMs) for recycling acid is facing a serious difficulty, the desired acid passage and undesired salt leakage dilemma. Ionic domains are the only channels to conduct H + ions and metallic ions, and thus viable modifications on ionic domains render the permeation of two ions simultaneously enhanced or limited, leading to “trade-off” effect. Herein, we propose an origin strategy of “three-phase” AEMs to beat this “rade-off” effect. Apart from typical hydrophobic polymer backbone and hydrophilic cation phase domains, the auxiliary phase domains built by graphene oxide (GO) sheets were added. Due to the abundant oxygen containing groups distributing on GO, the auxiliary phase domains not only aid to transport H + ions, but also capture metallic ions. With only 0.5 wt% GO loadings, the “three-phase” AEM increased acid recovery efficiency and separation factor by 40% and 51% for the FeCl 2 /HCl system respectively, compared with the “two-phase” AEM. To explain these results, density functional theory (DFT) simulation was applied to study the interactions between GO and Fe 2+ ions.
Youheng Wang,Xianjun Hou,Longxiang Zhang,Mohamed Kamal Ahmed Ali,Hua Jiang,Yuxin Ma
Nano-materials, given their excellent anti-friction and anti-wear characteristics, have attracted significant attention in tribological applications. However, conventional nano-materials have difficulty meeting the development requirements of the eco-friendly lubricants . In this study, nano biochar derived from sesame stalk was synthesized and used as a lubricant additive in poly-alpha olefin-6 (PAO6). The tribological properties were evaluated by four ball tribological tests with steel and ceramic balls as the friction pair . Following the friction experiment, the worn surface on the steel ball was analyzed by X-ray photoelectron spectrometry . The steel ball friction results showed that the lubricants containing 0.2 wt% nano biochar achieved a maximum wear volume reduction of 46% compared to PAO6, and the friction coefficient decreased by 34.6% for the ceramic balls. Analysis indicated that the enhanced wettability of nano biochar lubricant contributed to improving the anti-wear properties. Characterization of the worn surface revealed that the addition of nano biochar facilitated the formation of strong Fe 3 O 4 tribofilms. This study demonstrated that nano biochar could serve as an environmentally friendly additive in the liquid lubricant industry.
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