Vendredi 23 février à 11h, salle des séminaires IRPHE
Abstract: Collisions within a granular medium can cause large buildups of electric charge, a well-documented phenomenon encountered in settings as varied as volcanic eruptions, industrial powder flow or space exploration. The underlying causes of the charge separation, however, are still an open question. Using acoustic trapping to isolate a single grain allows us to cause individual collisions on a substrate, measure charge with high precision, and discharge grains using ionizing radiation to reset the system. Using this setup, we examine the fundamental processes behind contact electrification. We observe the initial breaking of symmetry and examine its causes. We find that the charge-driving parameter is global on the scale of the sample, is a function of the sample's history, and is irreversibly affected by changes in humidity. Ultimately, our results point to a mechanism where adsorbates play a driving role.
Galien Grosjean / Soft and Electrified Materials Lab, Institute of Science and Technology Austria