Browsing by Author "Birss, Viola I."

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    A study of the protective properties of oxide films formed at reactive Al-Cu and Al-Be alloys
    (2003) Potucek, Rudolf Karel; Birss, Viola I.
    Two Al alloys of interest to the aerospace industry were studied during this research. AA22 l 9 is an Al/Cu alloy containing about 6%-wt Cu, forming Cu-rich particles in a Cu­poor Al-matrix. AlBeMet162 is an Al/Be alloy consisting of ca. 38%-wt Al and 62%-wt Be, forming intermeshed networks of Al and Be. Both alloys do not respond to standard anodization techniques in sulfuric or chromic acid, yielding pitted surfaces and friable anodic coatings. Corrosion protection can be achieved on AA22 l 9 but a significant part of its fatigue strength will be sacrificed as a result of these anodization processes, while no corrosion protection results from the anodization of AlBeMetl 62. Thus, the main goals of this work were preventing the dissolution of the more reactive alloy constituents and electrochemical formation of a passivating surface coating. Cyclic Voltammetry methods (CV) were used as a means of creating barrier and porous oxide layers on AA22 l 9, AlBeMetl 62 and the individual phases making up these alloys. The CV data and measurements of Electrochemical Impedance Spectroscopy (EIS) were used to determine the thickness and dissolution activity of the barrier oxide layers formed. Changes in the barrier oxide thickness during EIS and CV experiments in neutral borate and phosphate buffer as well as H2SO4 and H3PO4 solutions provided a means for predicting whether a stable barrier or porous oxide film would likely be formed in a given electrolyte. This approach was shown to be usable even in the presence of an overlying porous oxide film. The CV data were also examined for an indication of the oxide growth mechanism, with a particular focus on the High Field and Point Defect models, indicating that the High Field Model more closely fits the data acquired. EIS data collected in 5%-wt NaCl solution were shown to give a good indication of the corrosion protection granted by anodic coatings formed on Al alloys and thus to be a suitable method for accelerated corrosion testing. DC anodization at only 2.5 V in neutral buffers and acidic solutions as well as and AC/DC anodization at voltages exceeding 100 V in alkaline silicate solutions were also studied and shown to successfully form anodic oxides without dissolving the reactive constituents of AA22 l 9. Accelerated corrosion testing and microscopic examination of corroded samples suggested that neither of these coatings supplied acceptable corrosion protection, but the silicate coatings appeared very promising, and further optimization of this approach is recommended.
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    Adsorbed lumiflavin at mercury electrode surfaces
    (Elsevier, 1998) Birss, Viola I.; McGarvey, C.; Beck, S.; Quach, S.; Elzanowska, H.
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    Adsorption of quaternary pyridinium compounds at Pt electrodes in neutral and weakly alkaline solutions
    (Elsevier, 2003) Birss, Viola I.; Dang, Kitty; Wong, Jennifer E.; Wong, Rick P.C.
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    Capacitive and kinetic characteristics of Ru-Ti oxide electrodes: influence of variation in the Ru content
    (National Research Council Canada, 1997) Birss, Viola I.; Tilak, B.V.; Chen, C.-P.; Wang, J.
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    Carbon Supported Metal Carbide Catalysts for the Reduction of Carbon Dioxide
    (2018-04-30) Virla Alvarado, Luis Daniel; Hill, Josephine Mary; Pereira Almao, Pedro R.; Birss, Viola I.; Roberts, Edward P. L.; Simakov, David S. A.
    Development of active and selective catalysts for the conversion of CO2 into valuable products is a promising strategy for reducing the environmental impact of CO2 released from the use of fossil fuels. The manufacture of these catalysts should also consider the use of waste materials and reduction of chemicals needed to decrease energy and resource consumption while being economically feasible. The aim of this research was to prepare a molybdenum-carbide catalyst from petroleum coke (petcoke), an abundant waste material from oil refining, with comparable activity and selectivity to other catalysts studied for the reduction of CO2 by H2. The process of converting petcoke into a catalyst involved increasing its porosity and carburizing added Mo using microwaves or electrical heating, focused on eliminating the need for methane and/or hydrogen for its preparation. Due to pyrophoricity risks, a multiple-test rig was built to study the catalysts preventing their exposure to air or passivation gases. The petcoke-based carbon prepared had higher surface areas and pore volumes (~2000 m2/g and > 1 cm3/g) than other commercial carbons (1000-700 m2/g and ~0.5 cm3/g) which enhanced the catalytic performance towards CO2 reduction. Microwave-assisted synthesis reduced the carbide preparation time from 15 h to 8 min. However, the resulting samples showed low CO2 conversion between 1.6-1.2 %. The catalysts prepared using a furnace showed a maximum CO2 conversion of 5.2 % and selectivity towards CO above 95.8 % after 24 h of reaction comparable to that previously reported for Pt based catalysts. Further investigations evaluated the improvement of the catalyst by re-using the petcoke activation chemical as a promoter. Alkali from petcoke activation with KOH moderately improved CO selectivity (97.4 % to 99.5 %) and stability (deactivation from 34 % to 26%) but decreased CO2 conversion by 2 %. Probable site blockage at high loadings of potassium (~5 wt%) indicate that further washing is needed to decrease the potassium concentration and maximize the promotion effect. The findings from this thesis provided insights on the preparation methods of Mo2C catalysts and alternative technologies for CO2 capture and re-utilization that is becoming a major cost in the energy sector.
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    Characteristics of the polyaniline anodic pre-peak
    (Elsevier, 1999) Birss, Viola I.; Dinh, Huyen N.
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    Characterization and optimization of oxide films formed on al-cu alloys
    (2012) Alsrayheen, Enam A.; Birss, Viola I.
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    Characterization of porous aluminum oxide films by metal electrodeposition
    (Elsevier, 1997) Birss, Viola I.; Serebrennikova, I.; Vanysek, P.
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    CHEMICAL ANALYSIS OF THE IONIC CONTENT OF HYDROUS IRIDIUM OXIDE FILMS
    (Elsevier, 1988) Birss, Viola I.; Pickup, Peter G.
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    Complications associated with kinetic studies of hydrous Ir oxide films
    (Elsevier, 1999) Birss, Viola I.; Elzanowska, H.; Segal. J.
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    Composition, Structure, and Electrochemical Behavior of Sol-Gel Derived Nanoparticulate Pt Thin Films
    (The Electrochemical Society, 2002) Birss, Viola I.; Andreas, H. A.
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    Conversion of Methane by Oxidative Coupling
    (Taylor & Francis, 1990) Birss, Viola I.; Amenomiya, Yoshimitsu; Goledzinowski, Maciej; Galuszka, Jan; Sanger, Alan R.
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    Deactivation of Thermally Formed Ru/Ti Oxide Electrodes. An AC Impedance Characterization Study
    (The Electrochemical Society, 2001) Birss, Viola I.; Tilak, B. V.; Wang, J.; Chen, C.-P.; Rangarajan, S. K.
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    Design and optimization of nanoporous carbon for electrochemical applications
    (2012) Banham, Dustin William H; Birss, Viola I.
    The goal of this research was to design porous carbon materials for application as Pt supports in proton exchange membrane fuel cells (PEMFCs) and to understand how the porosity of these Pt/C catalysts influences their activity towards the oxygen reduction reaction (ORR). Through the use of these novel carbon supports, another goal of this work was to improve the Pt nanoparticle utilization vs. commercial carbon supports. Additionally, the supercapacitive properties of some of these porous carbons were also studied. Initial investigations ( experimental work and modelling) of a catalyst layer prepared from commercial Pt/C catalysts confirmed that changes in the catalyst layer thickness (average pore length), conductivity, exchange current density, and average interparticle pore radius can all influence the observed ORR Tafel slope due to ohmic losses through the layer. To gain more control over these four parameters, two types of porous carbons were synthesized and evaluated: colloid imprinted carbons (CICs) and ordered mesoporous carbons (OM Cs). After loading the CICs (having pore diameters of 15, 26, 50, and 80 nm) with Pt, it was determined that the carbon wall thickness has a larger influence on ORR activity than does the pore diameter. This was supported by modelling, which demonstrated that the resistance of the CIC walls must be included in the model for the simulated and experimental ORR Tafel slopes to overlap. Pt-loaded OMCs, all having the same bimodal pore size distribution of ea. 1.8 and 3.5 nm, but different carbon wall (i.e., 'nano-string') diameters were also investigated, showing a precipitous drop in ORR activity for nanostring diameters < 3 nm, due to their high ohmic resistance. A direct comparison between the ORR activity of the most promising Pt/CIC and Pt/OMC catalysts, as well as a conventional Pt/Vulcan carbon catalyst, proved that Pt/CICs are the most promising materials for PEMFC cathodes. This is because CICs have thicker and more crystalline walls, as well as larger pore diameters, vs. OMCs. The CICs were also found to have larger surface areas and pore diameters vs. conventional Vulcan carbon (VC), allowing for more uniform Pt deposition and enhanced Pt utilization. As a further advantage of CICs vs. both OMC and VC, it was shown that the pore depth of CICs can be easily tuned, allowing for control over the depth to which Pt is deposited. This is anticipated to greatly reduce any mass transport limitations that may be encountered in a membrane electrode assembly (MEA). While the OMC supports were not found to be suitable as PEMFC catalyst supports, their extremely high surface areas (> 1000 m2/g) make them ideal as supercapacitor materials. It was shown that OMCs prepared using sucrose as a precursor have a high density of electroactive surface functional groups, resulting in a large ( ~ 0.15 F/m2) specific capacitance. The combination of a high surface area and high specific capacitance resulted in OMC-16 having the largest as yet reported gravimetric capacitance (260 F/g) for a templated carbon material.
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    Development of an electrode mediated glucose sensor using iridium oxide nanoparticles
    (2007) Jhas, Amitpal S.; Birss, Viola I.
    An optimized thin film of Iridium oxide (IrOx) nanoparticles with the presence of Nafion was used to encapsulate the redox enzyme, glucose oxidase (GOx). The resulting films showed an excellent response towards the detection of glucose in both an oxygenated and deoxygenated environment. It was shown that IrOx nanoparticles are mediating the direct transfer of electrons from GOx, and functioning as 4th generation glucose sensors. These sensors (0.2 to 0.008 cm2 ) demonstrated excellent stability and precision when they were tested for glucose strictly under deoxygenated environments; with a linear response up to 40 mM glucose and a sensitivity of 0.5 ?A/cm2/mM (in< 0.3 ?M of dissolved 0 2). In parallel work, an immobilized enzyme kinetic model was derived and the implication of the IrOx/GOx film properties on the apparent Km was presented. This model was also applied to experimental data to assess the interpretation of the parameter.