Studies of Defect Behavior in Large-Grain, Polycrystalline Ice Using Synchrotron X-ray Topography

Abstract

Synchrotron White Beam X-ray Topography (SWBXT) has been used to conduct in situ, low temperature studies of the behavior of defects introduced into large-grain, polycrystalline ice of very low “as-grown” defect density. The generation of faulted and unfaulted interstitial dislocation loops as a function of imposed temperature changes was observed. Variations in the distribution of these loops in the vicinity of grain boundaries are discussed in the context of diffusion mobilities on the basal plane and the relative orientation between the basal plane and the grain boundary plane. Dislocation generation mechanisms under applied compressive stresses were also investigated in situ using a specially-designed compression stage. This has led to the novel observation of dislocation nucleation at stress concentrations on grain boundaries. The utility of SWBXT in dynamic studies of this general nature is demonstrated.