Abstract Black objects are sometimes associated with black carbon, while shiny, highly reflecting surfaces are typically associated with metals. Here, we discuss several objects in everyday life that upon use take on a black color that is unlikely to be due to black carbon. We propose that this black color is caused by the formation of metallic nanoparticles from abrasion processes. We support this hypothesis using Mie theory and the fact that spherical metal particles are only shiny or bright if the imaginary part of their refractive index and its product with the particle size-parameter are both larger than three. While this is commonly true for bulk metals, the second condition is generally not fulfilled for metallic nanoparticles, and hence, such particles become highly absorbing, i.e., black. For the black grime accumulated on bicycle drivetrains and climbing ropes, we detected metal nanoparticles with electron microscopy, which likely originated from mechanical abrasion processes during use.

中文翻译：

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日常生活中磨损过程中产生的黑色金属纳米粒子：自行车传动系统和攀岩绳索

摘要 黑色物体有时与黑碳有关，而有光泽、高反射的表面通常与金属有关。在这里，我们讨论日常生活中的几种物品，这些物品在使用时呈现黑色，这不太可能是由于碳黑造成的。我们认为这种黑色是由磨损过程形成的金属纳米颗粒引起的。我们使用 Mie 理论和以下事实支持这一假设：球形金属颗粒只有在其折射率的虚部及其与粒度参数的乘积都大于 3 时才具有光泽或明亮。虽然这对于块状金属来说通常是正确的，但对于金属纳米颗粒通常不满足第二个条件，因此，这样的颗粒变得高度吸收，即黑色。