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 Characterization of Copper Covetic Bulk and Films: Copper with High Carbon Content(2016) Isaacs, Romaine Antonio; Salamanca-Riba, Lourdes G; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Incorporation of carbon nanostructures in metals is desirable to combine the strongly bonded electrons in the metal and the free electrons in carbon nanostructures that give rise to high ampacity and high conductivity, respectively. Carbon in copper has the potential to impact industries such as: building construction, power generation and transmission, and microelectronics. This thesis focuses on the structure and properties of bulk and thin films of a new material, Cu covetic, that contains carbon in concentrations up to 16 at.%. X-ray photoelectron spectroscopy (XPS) shows C 1s peak with both sp2 and sp3 bonded C measuring up to 3.5 wt.% (16 at.%). High resolution transmission electron microscopy and electron diffraction of bulk covetic samples show a modulated structure of ≈ 1.6 nm along several crystallographic directions in regions that have high C content suggesting that the carbon incorporates into the copper lattice forming a network. Electron energy loss spectra (EELS) from covetics reveal that the level of graphitization from the source material, activated carbon, is maintained in the covetic structure. Bulk Cu covetics have a slight increase in the lattice constant, as well as <111> texturing, or possibly a different structure, compared to pure Cu. Density functional theory calculations predict bonding between C and Cu at the edges and defects of graphene sheets. The electrical resistivity of bulk covetics first increases and then decreases with increasing C content. Cu covetic films were deposited using e-beam and pulsed laser deposition (PLD) at different temperatures. No copper oxide or any allotropes of carbon are present in the films. The e-beam films show enhanced electrical and optical properties when compared to pure Cu films of the same thickness even though no carbon was detected by XPS or EELS. They also have slightly higher ampacity than Cu metal films. EELS analysis of the C-K-edge in the PLD films indicate that graphitic carbon is transferred from the bulk into the films with uniform carbon distribution. PLD films exhibit flatter and higher transmittance curves and sheet resistance two orders of magnitude lower than e-beam films leading to a high figure of merit as transparent conductors.Item COPPER CORROSION IN THE FLOWERS OF SULFER TEST ENVIRONMENT(2015) Mahadeo, Dinesh Michael; Pecht, Michael G; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sulfur, present in the environment in the form of sulfur dioxide and hydrogen sulfide, can produce failure in electronics. In particular, copper, which is used extensively in electronic products, is subject to corrosion in the presence of sulfur. This thesis examines the corrosion of copper under the Flowers of Sulfur (FoS) test at varying temperatures and durations. The FoS test setup, described in ASTM B809, was initially designed to evaluate surface finish porosity, but this setup may have boarder application. To expand the applicability of the FoS test, it is important to characterize the test environment. To this end, a systematic study of copper corrosion was conducted through weight gain measurements of copper coupons that were subjected to FoS test environments. From the test results, a model was developed that correlates copper sulfide thickness to temperature and time under the FoS test. This model can be used to determine test conditions given a target field environment.Item FORENSIC INVESTIGATION TECHNIQUES FOR INSPECTING ELECTRICAL CONDUCTORS INVOLVED IN FIRES FOR ARC AND MELT BEADS(2012) Hussain, Nasir; Sunderland, Peter B; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The objective of this research was to determine, experimentally, if distinguishing characteristics exist between the beads formed on energized and non-energized wires exposed to various thermal insults. Most of research published in the literature has not tested energized and non-energized wires under the same thermal conditions. The tests in this study were conducted using convective, radiative and combined convective/radiative thermal exposures. Wires were tested in both energized and non-energized states. Energized wires were tested under "load" and "no load" conditions. Beads formed on both the energized and non-energized wires as results of thermal exposure. Beads were analyzed externally and internally with stereo microscope, SEM/EDS, and a metallurgical microscope. No clear trends or distinguishing visual or microscopic characteristics between the beads formed on energized and non-energized wires were found. The bead analysis methods used during this research showed that it is not possible to distinguish between the beads formed on energized and non-energized wires exposed to various thermal insults.