Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

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 give thesis/dissertation in DRUM

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

Browse

Filters

2011 - 20132

Settings

Subject: search.filters.subject.coating

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Functionally Coated Faceted Aluminum Nanocrystals: Aerosol Synthesis and Reactivity
    (2013) Kaplowitz, Daniel Alan; Zachariah, Michael R; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The demand for large scale manufacture of nanoaluminum for use in propellant applications has motivated research into development of an aerosol production scheme. In addition, the reactive nature of aluminum in the presence of oxygen has inspired investigation into functionally coating bare nanoaluminum prior to exposure to the atmosphere. Faceted aluminum crystals are fabricated in the aerosol phase via thermal pyrolysis of triisobutylaluminum, a low temperature gas-phase synthesis route, and combustion tests of oxygen passivated product in thermite combination show an increase in energy release compared to commercial nanoaluminum. Three different coatings on this bare nanoaluminum are developed: a decoration of Ni/Ni2O3 particles by thermal decomposition of Ni(CO)4, a homogeneous layer of Fe3O4 by thermal decomposition of Fe(CO)5, and a monolayer of perfluoropentanoic acid via bridge bonding between aluminum and carboxylate groups. X-ray photoelectron spectroscopy analysis indicates that the metal oxide coatings have facilitated formation of an expanded aluminum oxide layer during an air bleed, but perfluoropentanoic acid has successfully passivated aluminum. The protection from significant oxide formation for the perfluoropentanoic acid coating is evident in a 16% increase in active fuel content by thermogravimetric analysis compared to the untreated case. Subsequent temperature jump fine wire combustion tests show decreased ignition temperatures for all three coatings. Combustion chamber tests in thermite combinations display poor pressure output for the Ni/Ni2O3 coated case, but reasonable response for the Fe3O4 product. Flame ignition of perfluoropentanoic acid coated product is shown to produce AlF3 by chemical analysis of char, indicating the passivation coating also functions in direct oxidizer delivery.
  • Thumbnail Image
    Item
    PROBING ATMOSPHERIC AEROSOL AND GAS PROPERTIES WITH PHOTOACOUSTIC SPECTROSCOPY
    (2011) Bueno, Pedro Antonio; Zachariah, Michael R; Dickerson, Russell R; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Absorption by atmospheric aerosols is the wild card for global climate change. Issues regarding atmospheric gases and aerosols have been at the forefront and the work presented within is directed at those issues. Specifically, work has been performed in order to help understand the issue of absorption in the atmosphere and whether this contributes towards positive forcing or warming of the atmosphere. In the process of conducting this research a custom, first-principles photoacoustic spectrometer was improved, calibrated and used extensively in order to obtain knowledge of the interaction of light with atmospherically relevant gases and make the first measurements of absorbing aerosols. The absorption cross-section of uncoated and coated soot was measured and quantified and found to be consistent with other work where amplifications on the order of nearly 100% were observed with uncertainty levels much lower than previously reported. Soot was also found to be optically thin where the total mass of the soot contributes to the absorption. Consequential to the soot work, the photoacoustic spectrometer developed to measure the absorption was utilized as a high precision greenhouse gas sensor. The photoacoustic spectrometer was found to produce results on the absorption of CO2 to within 3% of the theoretically predicted line profile Moreover, the photoacoustic spectrometer was used to determine measurable coating thicknesses of less than 10 nanometers on 100 nm soot particles.