Low-temperature-SEM study of dihedral angles in the ice-I/sulfuric acid partially molten system.

The transport and mechanical properties of partially molten materials are influenced by the wetting behaviour of the melt with respect to the crystalline solid. The equilibrium microstructure of an ice + melt system was examined using low-temperature scanning electron microscopy. The samples were prepared by spraying a liquid solution of H(2) O-H(2) SO(4) into liquid nitrogen and packing the frozen particulates into aluminium capsules. Samples were then sintered at -35°C or -55°C (above the eutectic temperature, T(E) =-62°C) for various durations and were quenched in liquid nitrogen to capture the equilibrium microstructure. This paper reports the first quantitative measurements of dihedral angle in this system. The measured median dihedral angle between the solid and vitrified melt is approximately 26 ± 2° at -35°C and increases slightly as temperature decreases and approaches the solidus (32 ± 3° at -55°C).