Title: Granular Electrostatics

Author (Invited): Troy Shinbrot, Rutgers University

Abstract:

Pound for pound, common wheat flour contains nearly twice the explosive power of TNT. To harness this power requires only that fine flour particles be suspended in an oxygenated cloud and exposed to a single spark. For this reason, industries expend significant efforts to control electrostatic charging in powder silos and processing plants. Electrostatic charging of fine materials has also been put to important uses, including Xerography , thin film manufacture , and air filtration . Electrostatics may also play an important role in geophysical processes involving granular materials under dry conditions, for example strong electrostatic charging has been observed during volcanic eruptions as well as during aeolian transport of grains. We present experimental data demonstrating that charging of grains can cause spontaneous self-assembly that may generate lasting geological patterns resembling “Razorbacks” observed on Mars. We also describe experiments in which charged grains, including both colored sand and pharmaceutical materials, segregate profoundly in very simple flow arrangements, to concentration extremes of 5% and 90%.