Nucleation and Growth of Bubbles at an Ice–Water Interface

Nucleation and growth of bubbles during freezing of solutions of air and helium in water has been investigated experimentally using different techniques to give freezing rates between 1μm s−1and 10 mm s−1. Bubbles grow as cylinders below 5μm s−1, becoming egg shaped, the narrow ends towards the freezing interlace, at higher ice growth velocities. Bubble concentration increases and size decreases with increase of growth rate. The detail of bubble size and concentration is influenced appreciably by the particulate content of the water sample. Very high freezing rates give initially clear ice. Subsequently, bubbles nucleate and grow at grain boundaries within the ice. Bubbles do not move with recrystallization, their spatial distribution showing the grain boundary positions at the time of nucleation. Observations are interpreted in terms of nucleation on particles in suspension in the water and a significant incorporation of air molecules into the ice lattice. The relevance of the results to bubble-containing ice formed under natural conditions is discussed.