Electron emission (EE) from real metal surfaces occurring during sliding contact with a polytetrafluoroethylene (PTFE) rider has been investigated using the thermodynamic data of metal oxides and the X-ray photoelectron spectroscopy (XPS) intensity ratio of oxygen/metal on the surfaces. EE was termed triboelectron emission (TriboEE). Rolled metal sheets of 18 types were used. The metal‒oxygen bond energy calculated from the heat of the formation of metal oxide, (D(M–O)), was shown to be a key factor in dividing the EE into two routes, the so-called Schottky effect and the tunnel effect, due to the surface oxide layer. The metals in periodic groups 4 (Ti and Zr), 5 (V, Nb, and Ta), and 6 (Mo and W) maintained higher values of D(M–O), while, moving down the groups, the TriboEE intensity increased, being ascribed to the former route. In groups 10 (Ni, Pd, and Pt) and 11 (Cu, Ag, and Au), the D(M–O) values decreased moving down the groups, but the TriboEE intensity increased significantly, which can be attributed to the latter route. Furthermore, with the increase in the electrical conductivity of metals, the TriboEE intensity became remarkably high, while the D(M–O) value fell rapidly and became almost constant. The XPS results showed that the dependence of the D(M–O) and XPS metal core intensity on the O1s intensity and the XPS intensity ratio of the O1s/metal core was different between groups 10 and 11 and groups 4, 5, and 6. It was concluded that, under the electric field caused on the real metal surface by the friction with PTFE, the electron from metals with small D(M–O) values predominantly tunnels the surface oxide layer as a surface barrier, while with large D(M–O) values, the electron passes over the top of the barrier.

中文翻译：

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电子在聚四氟乙烯滑动过程中通过真实金属表面上的天然氧化物层的电子转移：取决于金属氧化物的形成热

使用金属氧化物的热力学数据和表面上氧/金属的X射线光电子能谱（XPS）强度比，研究了在与聚四氟乙烯（PTFE）滑行器滑动接触期间发生的真实金属表面的电子发射（EE）。EE被称为摩擦电子发射（TriboEE）。使用18种轧制金属板。由金属氧化物形成的热量（D（M–O））计算出的金属氧键能被证明是将EE分为两条途径的关键因素，即所谓的肖特基效应和隧道效应。由于表面氧化层的影响。周期族4（Ti和Zr），5（V，Nb和Ta）和6（Mo和W）中的金属保持较高的D（M–O）值，而在各组中向下移动时，TriboEE强度增加，归因于以前的路线。在第10组（Ni，Pd和Pt）和第11组（Cu，Ag和Au）中，D（M–O）值在各组中向下移动，但TriboEE强度显着增加，这可以归因于后者路线。此外，随着金属电导率的增加，TriboEE强度变得非常高，而D（M–O）值迅速下降并几乎保持恒定。XPS结果表明，D（M–O）的依赖性第10组和第11组与第4组，第5组和第6组之间，XPS金属核强度对O1s强度的影响以及O1s /金属核的XPS强度比有所不同。由于与PTFE的摩擦，D（M–O）值小的金属中的电子主要作为表面阻挡层隧穿表面氧化物层，而D（M–O）值较大的金属中的电子越过表面屏障。