Grain growth in ice

Abstract

Grain growth is studied in polycrystalline ice, consisting of elongated grains, of (200/300) um mean width w and (2/3) mm mean length I. The samples are annealed at different temperatures, between 0 °C and — 10 °C. It is found that I is not affected by annealing, while w increases with the annealing time. Below the melting point, w(t) tends to a limit value w3. This behaviour is related to the pinning action of air bubbles, which would be similar to that found for solid inclusions in metals. B y assuming w, — d/f, where d is the mean bubble diameter and / is the volume fraction of air dissolved in water, reasonable values are found for d. The activation energy of the phenomenon is evaluated on the basis of the present and of Jellinek and Gouda’s results. It is found Q — 0.6 eV, which value approximately coincides with that for bulk self-diffusion as it occurs for metals, several degrees below the melting point. This coincidence suggests that, for ice, grain growth would be controlled by bulk impurity diffusion up to the very melting point.