Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 34: New Methods and Developments III: Spectroscopy and Tribology

O 34.2: Vortrag

Dienstag, 2. April 2019, 14:15–14:30, H13

Ultrasensitive charge detection to study contact electrification between a steel ball and a gold surface — •Andre Mölleken, Hüseyin Azazoglu, Doris Tarasevitch, Tobias Roos, Detlef Utzat, Hermann Nienhaus, and Rolf Möller — Fakultät für Physik/Cenide, Universität Duisburg-Essen, Germany

Contact electrification and charge transfer between particles in granular matter are of high technological and fundamental interest. As a model system, we have studied the free fall of a single steel ball of 1mm in diameter on a gold coated copper plate of a parallel plate capacitor. The ball hits the surface with an initial velocity of approximately 0.6m/s and bounces afterwards repeatedly on the surface. If the moving steel ball is charged it creates an image charge in the plate which is measured as a function of time. The induced and the transferred charge is measured using an extremely sensitive and fast charge detector [1], capable of detecting a few thousand elementary charges with a 50 kHz bandwidth. Kinetic parameters and energy transfer coefficients can be extracted from the data. In addition, the charge transfer between ball and plate is precisely determined for every collision. Different kinds of charge transfer are found, e.g., reduction and increase of the charge on the ball as well as polarity changes. A complete discharging as expected for a metallic contact occurs only very rarely. However, there is a significant tendency that the charges before and after collision are related to each other and the total amount of transferred charge correlates with the impact velocity. [1] P. Graf. et al., Rev. Sci. Instrum. 88, 084702 (2017).