The Effects of Surface Curvature and Temperature on Charge Transfer During Ice‐Ice Collisions

Abstract

Repetitive collisions of sublimating ice surfaces, created by freezing liquid water, produced charge separation Q of a magnitude (pC) comparable to earlier results of vapour-grown ice crystals repetitively collided in a saturated environment. Those results had been explained by a theory of charge distribution in a quasi-liquid surface layer QLL mediated at the moment of impact by collisional melting. The present results are from long duration contacts (15ms) with transfer of kinetic energy estimated to be a factor of 104 greater, and charging-rate 98% slower. They do not support an assumption in that proposed mechanism of collisional melting, and are contrary to the basic assumptions of that theory: that significant Q occurs only in growing surfaces (that is, in a supersaturated condition which implies the presence of liquid water), that were originally grown from vapour, and for which contact is less than 1ms. The results are opposite to a rule that in the case of differing surfaces (vapour-grown, and rimed) that which is greater sublimating charges negatively. Here, for surfaces of frozen water, the surface further from equilibrium becomes positively charged. The results are not inconsistent with recent reports of simulations that suggest that the thickness of a quasi-liquid layer QLL in sublimating surfaces may not be less than the equilibrium value. Apparently, for differing ice surfaces, Q is of the order of 1fC whereas for collisions of similar ices on metal substrates (whether both vapour-deposited, or both frozen liquid water) Q is of the order of 1pC.