UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    The effect of boric acid on the growth mechanism of electrodeposited metal nanostructures
    (2014) Graham, Lauren M.; Lee, Sang Bok; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Electrochemical deposition (ECD) has been a primary method of metal plating for a variety of applications for nearly 100 years. Its popularity is due to its straightforward design, low cost, uniform results, and successful application to a wide range of metals and substrates. Many factors have been shown to influence the composition, texture, and chemical properties of the resultant deposit, such as the current density, the nature and concentration of metal ions, the solution temperature and composition, the applied current waveform, the substrate surface, and agitation. In particular, additives play a complex role in metal deposition due to their ability to greatly alter the growth mechanism and resultant deposit structure. There exists a vast body of work related to the role of additives in various plating solutions, however the majority of investigations on additive effects are focused on planar deposition. For instance, boric acid is a common additive found in nearly all aqueous transition metal plating solutions, yet its influence on metal nanostructure deposition has not been well studied. In this work, we focus on the impact of additives on the growth of metal nanostructures. Specifically, we investigate the role of boric acid in the ECD of nickel nanotubes (NTs) and nanowires (NWs). First, we demonstrate the difference in the growth mechanism and nanostructure morphology in the presence and absence of boric acid with electron microscopy and electrochemical analyses. The ECD conditions are modified to further probe the role of boric acid in the 1D growth of nickel nanostructures. The results confirm the function of boric acid in the surface-directed growth of nickel nanostructures. Second, we employ the boric acid-controlled growth mechanism in the synthesis of advanced nickel nanostructures. The potential for the role of boric acid to be applied to the deposition of additional metals is realized through the synthesis of nickel alloy NTs and NWs. Additionally, the advantage of the boric acid-controlled surface-directed growth mechanism is demonstrated through the straightforward synthesis of segmented nanostructures and a 3D interconnected nanotube network.
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    DLC Thin Film Assisted ZnO Nanowires Growth
    (2008-08-12) YOUNG, SHENG-YU; Salamanca-Riba, Lourdes; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In this study, we successfully fabricated dense, uniform, vertically aligned ZnO NWs on top of DLC films. The NWs' length, diameter and separation distance were controllable by fine tuning the growth parameters and changing the DLC film deposition temperature. HRTEM examination confirms the NWs were single crystalline with c-axis preferred orientation (lattice parameter c = 0.519 nm). From our experiment results, a ZnO polycrystalline layer forms first and then ZnO NWs grow on top of it. The NW has two sections. The bottom section has wider diameter of 100nm ~ 1 , and the upper thinner section were about 20 ~ 80 nm and it extends for in length. EDS maps by SEM and TEM showed the elemental concentration of the Zn, O and C in NWs. From all the investigations, we established a model of growth mechanism for ZnO NWs growth on DLC film.