Tribology Letters ( IF 2.9 ) Pub Date : 2021-07-16 , DOI: 10.1007/s11249-021-01475-1 Alper Özoğul 1 , Enrico Gnecco 1 , Benedykt R. Jany 2 , Franciszek Krok 2 , Mehmet Z. Baykara 3
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We present the results of friction experiments performed by manipulation of oxidized platinum nanoislands on highly oriented pyrolytic graphite (HOPG) substrates through atomic force microscopy (AFM). The oxidation of the platinum nanoislands, performed via mild plasma exposure, is confirmed through X-ray photoelectron spectroscopy (XPS) and high-resolution energy-dispersive X-ray spectroscopy (EDX), the latter of which reveals partial oxidation on the sliding surfaces of the nanoislands. Oxidized platinum nanoislands are found to exhibit higher friction than non-oxidized islands, with a ~ 70% increase in mean shear stress over the investigated contact size regime. An increase in chemical interaction forces between the oxidized platinum and the graphite substrate is proposed to explain the increase in friction forces. Our results reveal that alteration of interfacial chemistry through oxidation leads to a noticeable modulation of friction forces, but not a total breakdown of the superlubric state (as evidenced by the signature observation of decreasing shear stress with increasing contact size), providing further feasibility for the design of superlubric mechanical systems to be operated under ambient conditions.
Graphic Abstract
中文翻译：
超润滑结构中界面氧化对摩擦的影响
我们展示了通过原子力显微镜 (AFM) 在高度取向的热解石墨 (HOPG) 基板上操作氧化铂纳米岛进行的摩擦实验的结果。X 射线光电子能谱 (XPS) 和高分辨率能量色散 X 射线能谱 (EDX) 证实了通过轻度等离子体暴露进行的铂纳米岛的氧化，后者显示滑动表面的部分氧化的纳米岛。发现氧化的铂纳米岛比非氧化的岛表现出更高的摩擦力，平均剪切应力在所研究的接触尺寸范围内增加了约 70%。提出氧化铂和石墨基材之间化学相互作用力的增加来解释摩擦力的增加。
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