HR: 0830h
AN: GP11B-0264    [PDF]
TI: Rock Magnetic and HRTEM Study of Iron Oxyhydroxide Nanoparticles
AU: * Guyodo, Y
EM: guyodo@umn.edu
AF: Institute for Rock Magnetism, Dept. of Geology and Geophysics, Univ. of Minnesota, 108 Pillsbury Hall, Minneapolis, MN 55455 United States
AU: Banerjee, S K
EM: banerjee@umn.edu
AF: Institute for Rock Magnetism, Dept. of Geology and Geophysics, Univ. of Minnesota, 108 Pillsbury Hall, Minneapolis, MN 55455 United States
AU: Burleson, D
EM: burle001@tc.umn.edu
AF: Dept. of Chemistry, Univ. of Minnesota, 139 Smith Hall, Minneapolis, MN 55455 United States
AU: Penn, R L
EM: penn@chem.umn.edu
AF: Dept. of Chemistry, Univ. of Minnesota, 139 Smith Hall, Minneapolis, MN 55455 United States
AU: Seda, T
EM: sedat@physics.wwu.edu
AF: Dept. of Physics and Astronomy, Western Washington Univ., 152 Bond Hall, Bellingham, WA 98225 United States
AU: Solheid, P
EM: peat@umn.edu
AF: Institute for Rock Magnetism, Dept. of Geology and Geophysics, Univ. of Minnesota, 108 Pillsbury Hall, Minneapolis, MN 55455 United States
AB: Low-crystallinity, nanophase iron oxyhydroxide minerals such as ferrihydrite are common environmentally-relevant magnetic minerals, and have recently been proposed as possible building blocks for larger, more crystalline phases such as goethite or hematite (Schwertmann et al., {\it J. Coll. Inter. Sci. 209}, 215-223, 1999; Banfield et al., {\it Science 289}, 751-754, 2000; Guyodo et al., {\it Geophys. Res. Lett. 30}, 10.1029/2003GL017021, 2003). Despite the ubiquitous presence of iron oxyhydroxides in soils and sediments, their detection and quantification in natural samples is often difficult due to their low-crystallinity and the poor resolution of their x-ray diffraction (XRD) spectra. Highly sensitive, low-temperature rock magnetic techniques may therefore provide a crucial additional tool for the detection and quantification of such minerals in complex mixtures. In this presentation, we address major aspects of the growth and evolution of synthetic ferrihydrite nanoparticles prepared under systematically different synthesis conditions. These nanoparticles have been studied by low-temperature magnetometry and susceptometry, M\"{o}ssbauer spectroscopy, and high-resolution transmission electron microscopy (HRTEM). We provide examples of relationships between the low-temperature magnetic properties of the samples and (1) nanoparticle crystallinity (e.g., 2-line versus 6-line ferrihydrite), (2) particle aggregation (isolated primary nanoparticles versus oriented aggregates), and (3) phase transformations (e.g., ferrihydrite-to-goethite or to-hematite).
DE: 1519 Magnetic mineralogy and petrology
DE: 1540 Rock and mineral magnetism
DE: 3929 NMR, Mossbauer spectroscopy, and other magnetic techniques
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting