Oxide/aqueous and metal/metal oxide interfaces are essential for environmental remediation, catalysis, and corrosion inhibition, in addition to their potential implementation as energy transducers, consumer electronics, and coating products. While these interfaces are critically important, they are difficult to access experimentally under aqueous flow conditions. This thesis describes results obtained with the goal to overcome this capability gap. First, second harmonic generation (SHG) spectroscopy has been applied to probe charged silica/water interfaces in contact with aqueous solutions of alkali halides at concentrations as low as a few tens of µM. We have obtained evidence that 1) the relative permittivity of the diffuse layer is that of bulk water, with other possible values as low as 30, 2) the surface charge density varies with salt concentration and ion identity, and 3) the diffuse layer properties to which SHG spectroscopy is sensitive are invariant with ion identity, while the Stern layer properties are subject to ion specificity. Second, atom probe tomography (APT) analysis of zero-valent iron (ZVI) nanofilms, with potential applications in a variety of environmental remediation and energy technologies, reveals, after exposure to ambient air, the presence of dendritic iron-oxide features that extend from a thermal oxide overlayer into the ZVI bulk. The dendrites are determined by APT to be in the 5 nm x 10 nm size range, and their growth into the metal film, within the limit of our three-month long study, is self-limiting. The atomistic views obtained shed first light on the atmospheric corrosion process of Fe(0)-bearing engineered materials and their surfaces in the limit of low bulk impurities. Third, we also report stable, metal/metal oxide nanostructures synthesized in a single step that generate electrical currents when alternating salinity gradients flow along its surface in a liquid flow cell. Nanolayers of Fe/FeOx or Ni/NiOx produce several tens of mV and several µA cm-2 at aqueous flow velocities of just a few cm s-1. The principle of operation is sensitive to charge-carrier motion in the oxide nano-overlayer that forms spontaneously in air, and then self terminates. The nanolayers generate currents in various modes of application with moving liquids and droplets.

Creator

• Boamah, Mavis Dufie

DOI

• https://doi.org/10.21985/n2-j7j0-gz05

Subject

• Chemistry

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:14724
• etdadmin_upload_670561

Keyword

• Zero-Valent Iron
• Second Harmonic Generation Spectroscopy
• Nanolayers
• Passivation
• Interface
• Atom Probe Tomography

Date created

• 2019-01-01

Resource type

• Dissertation

Rights statement

• In Copyright