HR: 0830h
AN: C21C-0824    [PDF]
TI: Fabric Measurements of Ice Crystallized Within the Pore Networks of Chalk and Diatomite
AU: * Swainson, I P
EM: Ian.Swainson@nrc.gc.ca
AF: Neutron Program for Materials Research, National Research Council of Canada, Chalk River Labs, Chalk River, ON K0J 1J0 Canada
AU: Schulson, E M
EM: Erland.M.Schulson@Dartmouth.EDU
AF: Thayer School of Engineering, Dartmouth College, 8000 Cummings, Hanover, NH 03755-8000 United States
AB: The phenomenon of the crystallization of ice through porous bodies is a concern in many branches of science; e.g., porous materials; biological cells and related cell damage; and permafrost on earth and other planetary bodies. Whereas in unconsolidated sediments particle-pushing and ice lens formation occur, these are not significant processes within rock, and the ice must crystallize through a pre-existing pore network. At issue is whether the pore walls act as efficient nucleation sites or whether a coherent crystallization front of ice moves through the connected porosity. In the former case each pore can be considered independent and in the latter case the state (frozen/unfrozen) is dependent on the states of its neighbors, and the ice crystallization front advances through the porosity in a manner analogous to models of invasion percolation of fluids through pores. In the latter case, one would also predict the development of strong fabric (crystallographic texture) of ice as the ice front grows through the network. We present neutron diffraction measurements of deuterated ice Ih forming {\it within}\/ the pores of bulk specimens of chalk and diatomite. Preliminary neutron ``powder diffraction'' measurements suggested a very highly textured nature to the ice. Subsequently, we built a Peltier cooler device to form ice within the pore networks of highly porous rocks. This device was placed in a Eulerian cradle and mounted on a neutron diffractometer. The pole figures we measured strongly suggest the advance of a coherent crystallization front throughout the connected porosity.
DE: 1823 Frozen ground
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5462 Polar regions
SC: Cryosphere [C]
MN: 2003 Fall Meeting