Surface charge on materials is important due to its wide range of consequences and applications in many industries (e.g., semiconductor). One important parameter needed for the design of devices and selection of materials is the polarity of charge of solid surfaces after the surfaces are charged by contact electrification. Currently, it is only known that one surface charges positively, whereas the other surface charges negatively after contact (i.e., in accordance to the law of conservation of charge). This manuscript describes a previously unreported anomalous charging behavior of a general class of materials: the inorganic materials. Both contacting inorganic materials charged either both positively (e.g., mica and NaCl) or both negatively (e.g., quartz and CaF₂). A close monitoring of the charge in real time showed that charge was conserved immediately after contact; however, an active interaction of the separated surfaces and the surrounding atmosphere unexpectedly changed the polarity of one surface rapidly (e.g., 1 s), thus resulting in both positively or both negatively charged surfaces. This anomalous charging behavior fundamentally changes our understanding of the design of devices related to contact electrification of inorganic materials and the triboelectric series.

中文翻译：

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无机材料的异常充电行为

材料的表面电荷之所以重要，是因为其后果和在许多行业（例如半导体）中的广泛应用。器件设计和材料选择所需的一个重要参数是固体表面通过接触带电充电后的电荷极性。目前，仅已知一个表面在接触后带正电，而另一个表面在接触后即带负电（即根据电荷守恒定律）。该手稿描述了一般材料（无机材料）以前从未报道过的异常充电行为。两种接触的无机材料都带正电（例如云母和NaCl）或带负电（例如石英和CaF _2））。实时密切监控电荷显示，接触后电荷立即被保存；然而，分离的表面与周围大气的主动相互作用出乎意料地迅速改变了一个表面的极性（例如1 s），从而导致两个带正电的表面或两个带负电的表面。这种异常的充电行为从根本上改变了我们对与无机材料和摩擦电系列接触带电有关的设备设计的理解。