Nucleation mechanism of ice crystals under electrical effect

Abstract The electrical effect on ice nucleation from the melt has been studied. Two electrodes of Pt or Ti were immersed in supercooled water. In the case of DC application, the nucleation temperature rose compared with the case of spontaneous nucleation. AC application gave only a slight effect on the nucleation from the melt and the electrostatic field had no effect on it. It is supposed that the bubble generated by electrolysis has an effecton the nucleation. In order to confirm this, a bubble of air of about 200 μ m in radius was attached to the electrode covered with a Teflon tube in advance. At the moment when the bubble detached itself from the electrode, the nucleation occurred. A nucleation mechanism is presented. There must be small protruding parts on the electrode surface in contact with the bubble, and many electric charges concentrate on the protruding parts. Each water molecule with a dipole moment in a bubble is attracted to each surface charge. Consequently, the degree of supersaturation of the water molecules adsorbed on the protruding part must be so high that the heterogeneous nucleation of an ice crystal can occur on the electrode in the vapour phase and the growth proceeds. After the bubble left the electrode, the crystal directly touches the bulk water and acts as the seed crystal to the subsequent growth in the melt.