A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item SOLUBLE SALTS REDUCTION AND METALS BEHAVIOR OF DREDGED SEDIMENT FOR REUSE IN HIGHWAY SLOPE APPLICATIONS(2019) Huffert, Michelle B; Davis, Allen P.; Aydilek, Ahmet H.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Waterways are dredged routinely to maintain navigation channels, resulting in large quantities of dredged materials (DM) that require disposal. This study examines the innovative reuse of DM as a topsoil alternative in highway slopes. The dredged material met Maryland Department of Transportation, State Highway Administration (MDOT SHA) topsoil requirements for pH, organic matter, and particle size distribution, and required 122 cm (48 inches) of rainwater to leach soluble salts to below limits. Column leach tests were performed on DM and topsoil to evaluate metal leaching behavior; extractions were performed to determine total and potentially mobile metals content. DM leached metals concentrations below drinking water maximum contaminant levels (MCLs) for >95% of the samples tested, and passed a toxicity characteristic leaching procedure (TCLP). Extraction data showed higher total concentrations of arsenic, chromium, and lead as compared to topsoil, but similar concentrations in the EDTA-extracted fractions indicating that metals are strongly bound.Item Metals and Metallic Alloys for Energy Harvesting and Storage(2018) Gong, Chen; Leite, Marina S; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Metals have been widely used for harvesting and storing energy in devices such as superabsorbers and Li-ion batteries. However, incorporating metals into a wider range of energy applications is severely limited by their intrinsic optical and electrochemical properties. Therefore, in this thesis, we provide a new class of metallic materials by forming binary mixtures of Ag, Au, Cu, and Al with novel physical properties for photonics, and a comprehensive understanding of the fundamental electrochemistry in Al and Si anode all-solid-state batteries for energy storage. The first part of my thesis focuses on developing metallic alloys with a tunable optical response. We realize a new family of metallic materials by alloying Ag, Au, and Cu with on-demand dielectric functions, which can be used in superabsorbers and hot carrier devices. We design and fabricate alloyed nanostructures with engineered optical response and spatially resolve the electric field distribution at the nanoscale by utilizing near-field scanning optical microscopy, which can potentially enhance the performance of optoelectronic devices. To understand the physical origin of the optical response of the alloys, we measure the valence band spectra and calculate the band structures of Ag-Au alloys, providing direct evidence that the change in the electronic bands is responsible for its optical property. Further, we obtain a photonic device with superior performance using metallic alloys. Specifically, an Al-Cu/Si bilayer superabsorber is reached in a lithography-free manner with maximum absorption > 99%, which can be used for energy harvesting. The second part of my thesis highlights the importance of understanding the reactions and ion distribution in energy storage devices. We inspect how the Al electrode surface changes upon cycling and directly map the Li distribution in 3-dimensions within all-solid-state batteries by implementing time-of-flight secondary ion mass spectroscopy. This research indicates that undesired chemical reactions, including the formation of an insulating layer on the Al anode surface and the trapping of Li ions at the interfaces, hinder the cycling performance of the devices. Overall, our results will contribute to the design of energy storage devices with enhanced electrochemical performance.Item Release of inorganic and organic contaminants from fly ash amended permeable reactive barriers(2008-01-25) Morar, Doina Lorena; Aydilek, Ahmet H.; Seagren, Eric A.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Large quantities of fly ash are generated in the United States via coal combustion, most of which is disposed of in lagoons or landfills. The overall goal of this research was to assess the feasibility of using high carbon content (HCC) fly ashes as a reactive medium in permeable reactive barriers (PRBs) for remediation of petroleum hydrocarbon contaminated groundwater. A series of column and batch tests were performed to evaluate the leaching of selected metals from the fly ash, and adsorption/desorption of two target hydrocarbons (naphthalene and o-xylene) onto/from this PRB medium. Leaching of metals in the column experiments exhibited a first-flush, followed by a tailing slope elution pattern for all fly ashes. The naphthalene and o-xylene adsorption/desorption on/from the fly ashes were directly correlated with the organic carbon of the fly ash as measured by loss in ignition. Adsorption/desorption hysteresis was obvious in column and batch tests, suggesting that the adsorption/desorption was not completely reversible during the testing.