Defense Date

2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Everett Carpenter

Abstract

Magnetism lies at the core of modern technology and can be found in industries such as oil refining, automotive, telecommunications, personal electronics, and power generation that are integral to our day to day lives. This permeation into everyday life has been enhanced in the past several decades with improvements in material design based upon the principles of nanotechnology leading to smaller, faster, and more efficient devices. The presented research will discuss the synthesis and processing of multiple magnetic nanoparticle structures designed for the enhancement of various, application specific, properties. In the first experiments a tunable core/shell structure was developed with either enhanced optical properties or enhanced catalytic reactivity based solely upon small manipulations in the synthesis resulting in alternate morphologies. Essentially reaction times were controlled to direct core nucleation followed by shell growth and based upon addition times and concentration the final product could be manipulated as either a Fe/Ag or Ag/Fe core/shell. The modifications also resulted in Fe particles decorated with Ag islands that showed significant Plasmon shifts while still maintaining their high magnetization. These particles present applications in catalysts, sensors, and separations. Secondly FexCo100-x alloys were generated in order to determine the atomic compositions with the best magnetic properties. Several post-processing cleaning and annealing regimes were used to determine the most effective method of preparing the particles for utilization in devices. Annealing temperatures of 450°C were found most effective at enhancing magnetic properties while minimizing grain growth. Finally the synthesis of exchange-coupled hard magnetic core/shell nanoparticles was conducted. In this synthesis SmCo5 was synthesized via solvent assisted ball milling in oleic acid. Once completed these particles were processed in a multistep cleaning process which removed excess solvent and much of the surface oxidation. The particles were then suspended in a non-aqueous solvent and a magnetically coupled Co shell was carefully grown under sub-zero conditions. The resulting composite material demonstrated greatly enhanced magnetic properties and a unique laminated structure that had been elusive in nanoparticle research. Several magnetic nanoparticles and compositions were studied resulting in increased functionality based upon the bottom-up nanostructuring of materials. This work allows for the understanding of the effect of synthetic conditions on the control of nucleation and growth dynamics within nanoparticle synthesis and the generation of high quality functional magnetic materials.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

December 2013

Available for download on Wednesday, December 13, 2023

Included in

Chemistry Commons

Share

COinS