AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Black Metal Nanoparticles from Abrasion Processes in Our Everyday Lives: Bicycle Chains, Rock Climbing Ropes, and Motor Oil
HANS MOOSMULLER, Ramesh Giri, Matthew Berg, Christopher Sorensen, Desert Research Institute
Abstract Number: 308 Working Group: Aerosol Physics
Abstract Black carbon is often thought to dominate particle light absorption due to its high bulk absorption coefficient. Here, we examine some manifestations of small black particles in our everyday lives including the ubiquitous blackening of bicycle chains, climbing ropes, and motor oil. We present experimental and theoretical evidence that this blackening is caused by black metal nanoparticles, not by black carbon. While metals are commonly thought of being highly reflective, this is only true if the imaginary part of the refractive index and its product with the size parameter x are both larger than ~3 (Sorensen et al., 2019); this is generally true for metals in our everyday experience. However, for metallic nanoparticles, the second condition is generally not fulfilled and metal particles become black and highly absorbing with a very low single scattering albedo (Moosmüller and Sorensen, 2018) and with an appearance resembling that of black carbon.
References: [1] Sorensen, C. M., J. B. Maughan, and H. Moosmüller (2019). Spherical Particle Absorption over a Broad Range of Imaginary Refractive Index. J. Quant. Spectrosc. Radiat. Transfer, accepted for publication. [2] Moosmüller, H. and C. M. Sorensen (2018). Small and Large Particle Limits of Single Scattering Albedo for Homogeneous, Spherical Particles. J. Quant. Spectrosc. Radiat. Transfer, 204, 250-255, https://doi.org/10.1016/j.jqsrt.2017.09.029.