| This dissertation covers three areas which I have worked on while pursuing my degree. The first chapter includes an introduction of the work presented. The second and third chapters are devoted to the corrosion of Mg and electrochemical measurements of corrosion. Mg corrodes readily in aqueous environments, producing hydrogen gas, localized alkalinity and various ionic Mg compounds. Chapter two covers corrosion of Mg4Y alloy and the comparison of behavior when silane epoxy coatings are applied to Mg. Electrochemical impedance spectroscopy (EIS), open circuit potential, and pH changes used to examine the corrosion of magnesium 4% yttrium alloy (Mg4Y) in a stirred 0.154 M NaCl solution at 37° C. For a good quality silane-epoxy-coating (SEC) a relatively low non-faradaic resistance of 266 Ω cm2 was observed. I compared electrochemical measurements of bare Mg4Y corrosion, Mg4Y with a SEC that remained intact, and a SEC that did not protect the Mg from corrosion.;In chapter three, details of Mg4Y corrosion in various biologically relevant solutions is presented. Electrochemical sensing techniques, EIS, pH, and hydrogen response at a Pt electrode were used to monitor the corrosion of Mg4Y in H 2O, 0.154 M NaCl, phosphate buffered saline, cell culture media, and fetal bovine serum at 37° C. The electrochemical impedance spectra of the Mg4Y sample, the pH, and the response of a platinum electrode to dissolved H2 levels in solution were monitored with electrochemical sensors. The corrosion behavior for each of the solutions tested was reported.;In chapter four, the growth of bipyramidal gold nano-particles is explored. Bipyramidal gold nano-particles were grown using a seed mediated process. The nanoparticles were characterized both by their physical dimensions determined by transmission electron microscopy and by the wavelength position of their localized surface plasmon resonance peaks. The physical dimensions of the bipyramidal gold nanoparticles corresponded to particular initial conditions, and distinct modes of temporal evolution during growth were observed. A relationship between the radius of the nano-particle tip and wavelength of the longitudinal localized surface plasmon resonance absorption peak was determined. The effects of varying silver nitrate concentration and growth time were also studied. Critical parameters for synthesizing bipyramidal nanoparticles with sharp tips and desirable length were determined.;In chapter five the effects of electrochemical oxidation of carbon nanotubes in NaOH solutions was examined. Towers of aligned multi-walled carbon nanotubes were electrochemically oxidized in 1 M NaOH solutions. Amperometry was used to monitor the oxidation current at a fixed potential. Characterization by cyclic voltammetry in potassium ferricyanide before and after oxidation produced a large increase in background current and increased electrode capacitance without significantly affecting the reduction current from ferricyanide. Oxidation in NaOH caused morphological changes and increased hydrophilicity of the nanotubes. Cyclic voltammetry, atomic force microscopy, Raman microscopy and light microscopy were used to evaluate these changes due to oxidation. |
