GEOC 133 |
| Iron(III) hydroxides are abundant in near-surface natural environments and play an important role in geochemical processes and the fate of contaminants. The atomic structures of 2- and 6-line ferrihydrite (ferric hydroxide) have been debated in the literature for many years but have not yet been solved. This is primarily due to difficulties in evaluating the structures of nanocrystalline materials using various diffraction techniques. Our recent synchrotron-based experiments using X-ray total-scattering and pair distribution function analysis indicate that the atomic arrangements of 2- and 6-line ferrihydrite are not fundamentally different. The observed differences in diffraction patterns are primarily due to variations in average crystallite sizes, and this reason has not been entirely appreciated in previous work. The sizes of the coherent scattering domains (i.e., minimum average crystallite sizes) estimated from PDF analysis for 2- and 6-line ferrihydrite are on the order of 2-3 nm and 5-6 nm, respectively, and have been corroborated by high-resolution transmission electron microscopy.
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The Structure and Reactivity of Nanoparticles in the Environment
9:00 AM-12:00 PM, Thursday, 14 September 2006 Moscone Center -- Room 262, Oral
Sci-Mix
Division of Geochemistry |
