Investigations on Tribological Mechanisms of Graphene Oxide and Oxidized Wood-Derived Nanocarbons as Water-Based Lubricating Additives
Investigations on Tribological Mechanisms of Graphene Oxide and Oxidized Wood-Derived Nanocarbons as Water-Based Lubricating Additives
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DOI：
10.2474/trol.11.235
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发表时间：
2016-04
期刊：
影响因子：
1
通讯作者：
H. Kinoshita;Y. Nishina
中科院分区：
文献类型：
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作者：
H. Kinoshita;Y. Nishina
氧化石墨烯（GO）包含石墨单层片，而氧化木基纳米碳（oWNC）由石墨纳米壳组成。由于这两种材料都被许多含氧官能团彻底氧化，go和ownc在水中都形成稳定的分散体。我们发现，在使用钢板和碳化钨球的情况下，GOs和ownc在水中的分散润滑导致摩擦系数非常低，低于0.04，只有轻微的板表面磨损。润滑后，在滑动表面形成较厚的摩擦膜，使摩擦减小。在本研究中，为了阐明导致如此低摩擦系数的摩擦学机制，我们使用带有光学数据存储系统的共聚焦激光扫描显微镜（CLSM）、x射线光电子能谱（XPS）、扫描电子显微镜（SEM）和原子力显微镜（AFM）进行了摩擦学测试，并分析了氧化石墨烯在水中分散形成的摩擦膜。氧化石墨烯摩擦膜是由许多碳和一些氧组成的，这些氧来自于无序和聚集的氧化石墨烯薄片。氧化石墨烯摩擦膜具有比钢板更高的硬度和亲水性，具有较低的摩擦磨损。研究发现，氧化石墨烯摩擦膜和氧化石墨烯都是达到尽可能低摩擦系数所必需的。oWNC摩擦膜可能具有与氧化石墨烯分散体相似的摩擦和磨损降低效果。
Graphene oxide (GO) contains graphitic single-layered sheets, while oxidized wood-based nanocarbon (oWNC) is composed of graphitic nanoshells. Since both materials are thoroughly oxidized with many oxygen-containing functional groups, both GOs and oWNCs form stable dispersions in water. We found that lubrication by dispersions of GOs and oWNCs in water resulted in very low friction coefficients below 0.04 with only slight plate surface wear using a steel plate and tungsten carbide ball. After lubrication, thick tribofilms are formed on the sliding surfaces, which would decrease the friction. In this study, in order to clarify the tribological mechanisms that result in such low friction coefficients, we have performed tribological tests and analyzed the tribofilms formed by dispersions of GO in water using confocal laser scanning microscopy (CLSM) with an optical data storage system, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The GO tribofilm is composed of many carbons and some oxygen, derived from the disordered and aggregated GO sheets. The GO tribofilm have higher hardness and hydrophilic properties than the steel plates, which would provide low friction and wear. It is found that both the GO tribofilm and GOs are necessary to achieve the lowest possible coefficient of friction. It is likely that the oWNC tribofilm has similar friction and wear decreasing effects to that of the GO dispersion.