Pei Lulu, Ji Li, Li Hongxuan, Cai Haichao, Xue Yujun
School of Mechatronics Engineering, Henan University of Science and Technology, Luoyang 471003, China.
Henan Key Laboratory for Machinery Design and Transmission System, Henan University of Science and Technology, Luoyang 471003, China.
Materials (Basel). 2024 Oct 10;17(20):4941. doi: 10.3390/ma17204941.
Amorphous carbon is recognized as an excellent lubricating material; however, its tribological properties are significantly influenced by humidity. To elucidate the mechanism underlying this humidity dependence and to propose a novel enhancement method, we investigated and compared the tribological properties of hydrogenated amorphous carbon (a-C:H) and amorphous carbon/gold (a-C/Au) composite films. First, the friction coefficient of these carbon films under different humidity conditions was tested using a rotational ball-on-disk tribometer. Subsequently, we analyzed the morphology and structure of the sliding interface employing optical microscopy (OM), Raman spectroscopy, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Finally, first-principle calculations were carried out to calculate the adsorption energy of water molecules on different surfaces. The results indicate that the friction coefficient of a-C:H film and the area of transfer film increase with the increase of humidity. This phenomenon can be attributed to the fact that water molecules enhance the interaction between the a-C:H film and steel counterfaces. Notably, in contrast, the friction coefficient of a-C/Au film demonstrates low sensitivity to humidity due to the formation of an Au transfer film that exhibits weak interaction with water molecules. These findings provide a promising strategy for developing environment-adaptive amorphous carbon films and play an important role in promoting the development of intelligent lubricating film.
非晶碳被认为是一种优异的润滑材料；然而，其摩擦学性能受湿度的影响显著。为阐明这种湿度依赖性的潜在机制并提出一种新的增强方法，我们研究并比较了氢化非晶碳（a-C:H）和非晶碳/金（a-C/Au）复合薄膜的摩擦学性能。首先，使用旋转式球盘摩擦磨损试验机测试了这些碳薄膜在不同湿度条件下的摩擦系数。随后，我们采用光学显微镜（OM）、拉曼光谱、透射电子显微镜（TEM）和高分辨率透射电子显微镜（HRTEM）分析了滑动界面的形貌和结构。最后，进行了第一性原理计算以计算水分子在不同表面上的吸附能。结果表明，a-C:H薄膜的摩擦系数和转移膜面积随湿度增加而增大。这种现象可归因于水分子增强了a-C:H薄膜与钢对偶面之间的相互作用。值得注意地是，相比之下，a-C/Au薄膜的摩擦系数对湿度表现出低敏感性，这是由于形成了与水分子相互作用较弱的金转移膜。这些发现为开发环境适应性非晶碳薄膜提供了一种有前景的策略，并在推动智能润滑薄膜的发展中发挥重要作用。
