Kinoshita Hiroshi, Okamoto Tatsuya, Hirai Yutaro, Sugano Koichi, Naohiro Matsumoto
Department of Mechanical Engineering, Graduate School of Engineering, University of Hyogo, 2167, Shosha, Himeji 671-2280, Japan.
ACS Omega. 2022 Nov 4;7(45):40983-40989. doi: 10.1021/acsomega.2c04181. eCollection 2022 Nov 15.
Previously, isolated nanocarbons in lubricating oils were considered essential for good lubrication. However, we observed that graphene oxide (GO) aggregates in lubricating oil have lower frictional properties than isolated dispersed GO. The GO was dispersed in polyα-olefin (PAO) using alkylamine at different ratios of GO and alkylamine, or it was heated at different temperatures to synthesize high- and low-dispersible GO-dispersed PAO. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy measurements showed that low-dispersible modified GOs retained many of the original GO chemical and structural features. Macrotribological tests between a steel ball and glass disk in GO-dispersed oil were conducted with a load of 5 N under boundary lubrication. The friction interface was observed in situ using an optical microscope. In the low-dispersible GO-dispersed PAO, many GO aggregates were observed through optical microscopy. Surprisingly, the friction coefficients decreased when the GO aggregates entered the friction interface and covered the contact area. The low-dispersible GO-dispersed PAO using alkylamine had the lowest friction coefficient of 0.05, as the GO aggregates covered the contact area. From microtribological tests with a load of 0.8 mN as well, it is assumed that the low friction of the GO aggregates originates due to the sliding between the weakest shear layers in the aligned multiple GO layers.
以前，润滑油中孤立的纳米碳被认为对良好润滑至关重要。然而，我们观察到润滑油中的氧化石墨烯（GO）聚集体的摩擦性能低于孤立分散的GO。使用烷基胺以不同的GO与烷基胺比例将GO分散在聚α-烯烃（PAO）中，或者将其在不同温度下加热以合成高分散性和低分散性的GO分散PAO。X射线光电子能谱（XPS）、傅里叶变换红外光谱（FTIR）和拉曼光谱测量表明，低分散性改性GO保留了许多原始GO的化学和结构特征。在边界润滑条件下，在5 N载荷下对GO分散油中的钢球和玻璃盘进行了宏观摩擦学测试。使用光学显微镜原位观察摩擦界面。在低分散性GO分散的PAO中，通过光学显微镜观察到许多GO聚集体。令人惊讶的是，当GO聚集体进入摩擦界面并覆盖接触区域时，摩擦系数降低。使用烷基胺的低分散性GO分散PAO的摩擦系数最低，为0.05，因为GO聚集体覆盖了接触区域。同样，在0.8 mN载荷的微观摩擦学测试中，可以推测GO聚集体的低摩擦源于排列的多个GO层中最薄弱剪切层之间的滑动。
