The sliding electrical contact behavior on the perpendicular surface of highly oriented pyrolytic graphite has been systematically studied under various electric current densities and environmental atmospheres. The results indicated that the friction coefficient decreased from 0.30 to 0.23 in wet air, and it increased from 0.32 to 0.39 in dry N2 with increasing electric current density from 0 to 50 A/cm2. The opposite tribological behavior induced by electric current between wet air and dry N2 was attributed to the changes in the microstructure and carbon dangling bonds. Electric current caused the nanostructure defects and carbon dangling bonds to increase in both wet air and dry N2. In wet air, these carbon dangling bonds were passivated by –H and –OH, which reduced the sliding force and caused the debris parallel to the sliding direction, thereby decreasing the friction coefficient. In dry N2, however, the carbon dangling bonds could not be passivated for the lack of water molecules. As a result, electric current oriented the debris perpendicular to the sliding direction, and the friction coefficient increased. In addition, it provided a novel strategy for tuning the tribological behavior of carbon materials in situ by adjusting the environmental atmospheres and electric current density.

中文翻译：

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电流对高取向热解石墨微观结构演变和摩擦学行为的影响

在各种电流密度和环境气氛下，系统研究了高取向热解石墨垂直表面上的滑动电接触行为。结果表明，随着电流密度从0增加到50 A/cm2，摩擦系数在湿空气中从0.30降低到0.23，在干N2中从0.32增加到0.39。由电流在湿空气和干 N2 之间引起的相反摩擦学行为归因于微观结构和碳悬键的变化。电流导致湿空气和干 N2 中的纳米结构缺陷和碳悬挂键增加。在潮湿的空气中，这些碳悬空键被-H和-OH钝化，降低了滑动力并导致碎片平行于滑动方向，从而降低摩擦系数。然而，在干燥的 N2 中，由于缺乏水分子，碳悬空键无法钝化。结果，电流使碎屑垂直于滑动方向，摩擦系数增加。此外，它还提供了一种通过调节环境气氛和电流密度来原位调节碳材料摩擦学行为的新策略。