Date of Award

Spring 5-15-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical and Aerospace Engineering

Advisor(s)

Ahn, Jeongmin

Keywords

Biometallic Corrosion, Dynamic Interfacial Chemical Reactions, Electrochemistry, Electromagnetic Radiation, Heterogeneous Catalysis, Surface Chemistry

Subject Categories

Automotive Engineering | Biomedical Engineering and Bioengineering | Engineering | Materials Science and Engineering

Abstract

This research effort investigates the manipulation of surface electrochemical reactions induced by oscillating electric potentials on the surface of metal-based electrodes. Specifically, this research presents experimental data identifying modified electrochemical surface reactions caused by low magnitude electric potential oscillations on multilayered catalytic membranes and on implanted biometallic alloys. The scope of this effort consists of four major components: (1) perform an exhaustive literature review and analysis of the current understanding in applied surface electrochemistry and develop potential theoretical frameworks by which to interpret the experimental results; (2) identify the electrochemical manipulation via electrical oscillation while reacting nitric oxide on a multilayered ceramic membrane in combustion exhaust; (3) demonstrate that low magnitude electric potential oscillation are sufficient to induce corrosion of implanted biometallic alloys; (4) evaluate ambient electromagnetic radiation as a contributing factor to the complex corrosion of implanted ASTM F1537 CoCrMo.Although electrochemistry has been a driving force of many modern technologic advancements and the fundamental relations of electrochemistry have existed for over 100 years, current techniques do not adequately address the possibility for high frequency spatially and temporally varying electromagnetic potential fields and their effects on surface reactivity. Modern electrochemical theory remains focused on quasi-steady state reduction and oxidation reactions. Expanding upon existing theoretical models, such as the Newns-Anderson model for surface adsorbate systems, three feasible mechanisms of action are proposed by which spatially and temporally varying electromagnetic fields may interact to alter surface chemical reactions at the boundary of a metal-based electrode: direct shifting of the d-band center on the metallic surface, a photon-phonon interaction leading to the creation of a phonon-polariton, and/or the evolution of a complex three dimensional field with surface normal. When investigating a multilayered ceramic electrochemical catalytic membrane for automotive emission reduction, it was concluded that the presence of high frequency, low magnitude electric potential oscillations resulted in a manipulation of the predicted chemical pathway during the conversion of NO into diatomic nitrogen and oxygen. The electrical activity altered the initial surface electrochemical reaction toward the less probable formation of N2O, instead of NO2, ultimately resulting in greater NO reduction efficacy, compared to a Pt catalyst. Electrical stimulation (at 200 mVpp, >25MHz) of ASTM F1537 CoCrMo within a simulated synovial fluid resulted in significant corrosion activity. The chemical composition of corrosion products grown via electrical stimulation match that of recovered in vivo corrosion products. The corrosion products contain primarily Cr2O3, CrO3, phosphates, molybdates, CrOH, and CoOH, with varying concentrations of Ca, P, and Co. Furthermore, this work demonstrates that the ambient electromagnetic field in a standard university laboratory can induce sufficient electrical activity to initiate the corrosion of ASTM F1537 CoCrMo in a simulated synovial fluid environment. Samples shielded from electrical activity did not demonstrate corrosion activity, whereas samples subjected to ambient electromagnetic activity showed formation of Cr2O3 and potentially CrO3 with significant concentrations of Ca, P, N, and Na. The work presented throughout this thesis provides foundational experimental data which identifies a novel electrochemical reaction manipulation phenomenon arising from temporally and spatially varying electromagnetic fields. This electrochemical phenomenon is believed to persist across a general electrochemical system and deserves significant future study.

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