A TECHNIQUE FOR THE SCANNING ELECTRON MICROSCOPY AND MICROANALYSIS OF UNCOATED ICE CRYSTALS

摘要

Recently, we developed a technique to examine the microstructural location of impurities in ice that involves sublimation in a low vacuum scanning electron microscope equipped with a liquid nitrogen-cooled cold stage. One effect of the sublimation is that it leaves behind concentrated impurities, which can be identified using x-ray microanalysis. Observations on ice specimens from Greenland, Antarctica, and laboratory-grown doped ice are presented. The polar ice cores revealed impurities such as Cl, S, Na, and Ca throughout the material. Filaments, of mainly Na and Cl, or Mg and S, were observed in the grain boundaries. These are thought to have formed by the coalescence of impurities located in the grain boundary plane as a result of the sublimation. Similar filaments were observed in the grain boundaries of recrystallized, laboratory-grown KCl-doped ice. Hexagonal voids were also observed in the polar ice. A brief survey is presented of uncoated snow in the SEM, which shows the impact of sublimation.