Freezing Potentials and Currents in Potassium Fluoride Solutions at Constant Growth Rates

• Published in: Journal of Glaciology
• Main Authors: Hanley, T. O’D., Weber, A. H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1973
• Subjects: Earth-Surface Processes; Workman; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000031890; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000031890

The Workman–Reynolds effect was studied in the growth of ice on a monocrystalline seed, at constant growth rates and under steady-state conditions, from KF solutions at concentrations from 2 × 10 −5 to 10 × 10 −5 Normal. Freezing potentials increased with growth rate to a maximum of 12 V at 11.2 μ m/s. Discharge currents through a 10 5 Ω shunt generally increased with freezing rate until a maximum of 1.5 μ A at 11.2 μ m/s. The charge transfer decreased with growth rate to 200 μ C at 10.3 μ m/s and then reached a maximum of 850 μ C at 11.2 μ m/s. Apparent diffusion coefficients of about 2 × 10 −3 mm 2 /s increased slowly with growth rate until a rapid increase began, apparently associated with interface breakdown. Distribution coefficients of the order of 10 −3 , calculated from a criterion for constitutional supercooling, increased with concentration. Parameters for LeFebre’s model of the interface showed an interface thickness of about 6 mm, an interface capacitance near one-half pF/mm 2 , and an interface resistance of about 6 × 10 4 Ω/mm 2 . Several empirical relations between these quantities were disclosed. Comparison with values obtained for KC1 solutions with the same freezing cell shows that the KF solutions yielded higher values of freezing potential, charge transfer, and distribution coefficient, and lower values of diffusion coefficient, interface capacitance, and interface resistance.