Date of Graduation

Spring 2011

Degree

Master of Science in Materials Science

Department

Physics, Astronomy and Materials Science

Committee Chair

Robert Mayanovic

Keywords

radiolysis of iron Fe₃O₄ nanoparticles, ferrimagnetism, superparamagnetism, blocking temperature, inverted magnetic hysteresis, micro hydrothermal reactor

Subject Categories

Materials Science and Engineering

Abstract

The increased demand in higher efficiency of energy conversion requires power reactors to operate under elevated temperatures, pressures and extreme radiation conditions. This requires development of novel materials and a greater understanding of the behavior of materials under such extremes. In this study I investigated reactions of iron species with radiolytic products and Fe3O4 nanoparticles with metal ions under hydrothermal conditions. In one experiment, I studied the effects of synchrotron x-ray-induced radiolysis of iron species in aqueous solution at 300 to 500 °;C. I observed that oxidation reactions occur at 300 °;C and reduction of iron species occurs at 400°;C and 500 °;C. In the second set of experiments, we hydrothermally treated Fe3O4 nanoparticles (~20nm) in the presence of Ni2+, Co2+ or Zn2+ species inside a micro-reactor. The magnetic properties of the untreated and hydrothermally reacted Fe3O4 nanoparticles were then investigated. I found that the particle size does not significantly change with the hydrothermal treatment but the blocking temperature of the nanoparticles changes significantly, depending on the metal species present during the treatment. Magnetic hysteresis measurements show evidence for two-phase behavior of both the untreated and hydrothermally reacted Fe3O4 nanoparticles.

Copyright

© Hingure Arachchilage Naveen Dharmagunawardhane

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