Modified graphene as novel lubricating additive with high dispersion stability in oil
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ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Modified graphene as novel lubricating additive with high dispersion stability in oil Pu WU1, Xinchun CHEN1, Chenhui ZHANG1,*, Jiping ZHANG2, Jianbin LUO1, Jiyang ZHANG3,* 1
State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
2
Tianjin Research Institute for Advanced Equipment, Tsinghua University, Tianjin 300300, China
3
Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms, Beijing Institute of Control Engineering, Beijing 100094, China
Received: 15 July 2019 / Revised: 15 September 2019 / Accepted: 20 September 2019
© The author(s) 2019. Abstract: Graphene is a promising material as a lubricant additive for reducing friction and wear. Here, a dispersing method which combines chemical modification of graphene by octadecylamine and dicyclohexylcarbodiimide with a kind of effective dispersant has been successfully developed to achieve the remarkable dispersion stability of graphene in base oil. The stable dispersion time of modified graphene (0.5 wt%) with dispersant (1 wt%) in PAO-6 could be up to about 120 days, which was the longest time reported so far. At the same time, the lubricant exhibits a significant improvement of tribological performance for a steel ball to plate tribo-system with a normal load of 2 N. The coefficient of friction between sliding surfaces was ~0.10 and the depth of wear track on plate was ~21 nm, which decreased by about 44% and 90% when compared to pure PAO-6, respectively. Furthermore, the analysis of the lubricating mechanisms in regard to the sliding-induced formation of nanostructured tribo-film has been contacted by using Raman spectra and TEM. Keywords: modified graphene; dispersity; lubricant additives; tribo-film
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Introduction
Graphene has attracted a great deal of attention in recent years because of its unique structure and remarkable mechanical, electrical, optical and thermal properties [1–5]. In particular, graphene has been proved as an excellent candidate for both solid lubricant and lubricant additive owing to its excellent mechanical strength, low shear strength, high thermal and chemical stability, atomically smooth surface, notable specific surface area, and ultrathin film thickness [6–10]. Friction and wear can lead to energy wastage, material losses and shorter life of moving components in mechanical processes. It is reported that the direct losses from tribological contacts are closed to 23% of total fuel energy lost [11]. In order to save energy as well as to protect the mechanical components,
lubrication has been demonstrated as an effective method to reduce friction and wear in multiple industrial applications. Liquid lubricant is one kind of versatile lubricant which has a wide range of uses, and graphene also has gained large interest in recent years as lubricating additives due to their low shear resistance between the layer structure, suitable size to enter the contact areas and good thermal conductivity to dissipate the heat genera
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