Date of Graduation

Spring 2012

Degree

Master of Science in Materials Science

Department

Physics, Astronomy and Materials Science

Committee Chair

Robert Mayanovic

Keywords

energy, nanoparticles, xanes, LDOS, adsorption

Subject Categories

Materials Science and Engineering

Abstract

This work focuses on the reactive properties of ferrite nanoparticles (NPs) in extreme environments, such as in supercritical water cooled reactors, having direct relevance to the spalling of ferrite NPs. The spalling results from the oxidation and corrosion of steel-alloyed pipes and reactor vessel walls of water-cooled conventional and nuclear power reactors. The reactivity, structural, magnetic and other physical properties of ferrite NP can be affected by the interactions (e.g., adsorption) between the NPs and other corrosion byproducts (e.g., Fe3+, Ni2+, Co2+), depending upon the thermodynamic conditions of the system. Modeling of in situ x-ray absorption near edge structure (XANES) shows that cobalt and nickel ions adsorb on octahedral sites whereas zinc ions adsorb on tetrahedral sites on the surface of magnetite nanoparticles. XANES analyses using FEFF 9.0 show little alteration in the angular momentum projected density of states (LDOS) of the Ni:Fe3O4 NP system and a significant change in the LDOS of the Co:Fe3O4 NP system from 400 to 500 oC, respectively. Analyses reveal that the Co:Fe3O4 NP system pre-edge resonance feature centroid shifts to lower energy level relative to that of bulk CoFe2O4. Transmission electron microscopy (TEM) results indicate that the structure and morphology of Co:Fe3O4, Ni:Fe3O4, and Zn:Fe3O4 NPs is unaltered post synthesis.

Copyright

© Joseph Wesley Demster

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