Date of Award

August 2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Jesse Bond

Second Advisor

Mathew M. Maye

Keywords

Core/Alloy Nanoparticles, Corrosion Resistance, Hollow Nanoparticles, Internal Voids, Stainless-Steel Nanoparticles, Transition Metal Alloys

Subject Categories

Physical Sciences and Mathematics

Abstract

The objective of my graduate research is to understand the oxidation in heterostructured transition metal-based core/alloy nanostructures and to design protocol towards the synthesis of oxidation resistant stainless-steel nanoparticles. To this effect, I employed bottom-up wet chemistry approach to synthesize multi-shell Fe/CrxNi1-x NPs, bimetallic FexCr1-x alloy NPs, and Fe/Ni core/shell NPs. I performed the morphological analysis of these NPs via transmission electron microscopes (TEM/HRTEM), structural characterization via X-ray diffraction (XRD), surface analysis via X-ray photoelectron spectroscopy (XPS), thermal property analysis via thermogravimetric analysis (TGA), organic ligand characterization using infrared spectroscopy (FTIR), and absorption spectra using UV-visible spectroscopy (UV-Vis). In chapter 2, synthesis of mixed shell Fe/Cr/Ni, Fe/Ni/Cr, and Fe/CrxNi1-x core/alloy nanoparticles (CA-NPs) is investigated, where chromium and nickel carbonyl-based precursors are used for depositing various shell combinations. Oxidation in these NPs is studied as a function of shell thickness and shell-deposition routes, and diffusion data for Fe/Cr, Fe/Ni, and Fe/CrNi core/shell NP systems is provided. In chapter 3, I describe the synthesis of cube-shaped FexCr1-x alloy NPs, oxidation and the subsequent formation of internal voids. HRTEM images of oxidized alloy NPs are analyzed to understand the extent of internal void formation as a function of oxidation conditions. In chapter 4, I explore how grain boundary diffusion and interfacial thermodynamics dictates the alloying of core-shell nanoparticles as a function of annealing temperature. The importance of interfacial effects on thermodynamics and diffusion kinetics is described and examined in light of the observed temperature dependent alloying of synthesized α- phase Fe/Ni nanoparticles, into γ-phase Fe/FexNi1-x core alloy nanoparticles. In final chapter, I summarize the research, discuss the scope and future prospects in this research area.

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Open Access

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