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ContributorsDaval, Charles (Performer) / ASU Library. Music Library (Publisher)
Created2018-03-26
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DescriptionThe purpose of this project is to explore the influence of folk music in guitar compositions by Manuel Ponce from 1923 to 1932. It focuses on his Tres canciones populares mexicanas and Tropico and Rumba.
ContributorsGarcia Santos, Arnoldo (Author) / Koonce, Frank (Thesis advisor) / Rogers, Rodney (Committee member) / Rotaru, Catalin (Committee member) / Arizona State University (Publisher)
Created2014
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Description
The behavior of a solid oxide fuel cell (SOFC) cermet (ceramic-metal composite) anode under reaction conditions depends significantly on the structure, morphology and atomic scale interactions between the metal and the ceramic components. In situ environmental transmission electron microscope (ETEM) is an important tool which not only allows us to

The behavior of a solid oxide fuel cell (SOFC) cermet (ceramic-metal composite) anode under reaction conditions depends significantly on the structure, morphology and atomic scale interactions between the metal and the ceramic components. In situ environmental transmission electron microscope (ETEM) is an important tool which not only allows us to perform the basic nanoscale characterization of the anode materials, but also to observe in real-time, the dynamic changes in the anode material under near-reaction conditions. The earlier part of this dissertation is focused on the synthesis and characterization of Pr- and Gd-doped cerium oxide anode materials. A novel spray drying set-up was designed and constructed for preparing nanoparticles of these mixed-oxides and nickel oxide for anode fabrication. X-ray powder diffraction was used to investigate the crystal structure and lattice parameters of the synthesized materials. Particle size distribution, morphology and chemical composition were investigated using transmission electron microscope (TEM). The nanoparticles were found to possess pit-like defects of average size 2 nm after subjecting the spray-dried material to heat treatment at 700 °C for 2 h in air. A novel electron energy-loss spectroscopy (EELS) quantification technique for determining the Pr and Gd concentrations in the mixed oxides was developed. Nano-scale compositional heterogeneity was observed in these materials. The later part of the dissertation focuses mainly on in situ investigations of the anode materials under a H2 environment in the ETEM. Nano-scale changes in the stand-alone ceramic components of the cermet anode were first investigated. Particle size and composition of the individual nanoparticles of Pr-doped ceria (PDC) were found to affect their reducibility in H2 gas. Upon reduction, amorphization of the nanoparticles was observed and was linked to the presence of pit-like defects in the spray-dried material. Investigation of metal-ceramic interactions in the Ni-loaded PDC nanoparticles indicated a localized reduction of Ce in the vicinity of the Ni/PDC interface at 420 °C. Formation of a reduction zone around the interface was attributed to H spillover which was observed directly in the ETEM. Preliminary results on the fabrication of model SOFCs and in situ behavior of Ni/Gd-doped ceria anodes have been presented.
ContributorsSharma, Vaneet (Author) / Crozier, Peter A. (Thesis advisor) / Sharma, Renu (Thesis advisor) / Adams, James B (Committee member) / Dey, Sandwip (Committee member) / Arizona State University (Publisher)
Created2011
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Description
As world energy demands increase, research into more efficient energy production methods has become imperative. Heterogeneous catalysis and nanoscience are used to promote chemical transformations important for energy production. These concepts are important in solid oxide fuel cells (SOFCs) which have attracted attention because of their potential to provide an

As world energy demands increase, research into more efficient energy production methods has become imperative. Heterogeneous catalysis and nanoscience are used to promote chemical transformations important for energy production. These concepts are important in solid oxide fuel cells (SOFCs) which have attracted attention because of their potential to provide an efficient and environmentally favorable power generation system. The SOFC is also fuel-flexible with the ability to run directly on many fuels other than hydrogen. Internal fuel reforming directly in the anode of the SOFC would greatly reduce the cost and complexity of the device. Methane is the simplest hydrocarbon and a main component in natural gas, making it useful when testing catalysts on the laboratory scale. Nickel (Ni) and gadolinium (Gd) doped ceria (CeO2) catalysts for potential use in the SOFC anode were synthesized with a spray drying method and tested for catalytic performance using partial oxidation of methane and steam reforming. The relationships between catalytic performance and structure were then investigated using X-ray diffraction, transmission electron microscopy, and environmental transmission electron microscopy. The possibility of solid solutions, segregated phases, and surface layers of Ni were explored. Results for a 10 at.% Ni in CeO2 catalyst reveal a poor catalytic behavior while a 20 at.% Ni in CeO2 catalyst is shown to have superior activity. The inclusion of both 10 at.% Gd and 10 at.% Ni in CeO2 enhances the catalytic performance. Analysis of the presence of Ni in all 3 samples reveals Ni heterogeneity and little evidence for extensive solid solution doping. Ni is found in small domains throughout CeO2 particles. In the 20 at.% Ni sample a segregated, catalytically active NiO phase is observed. Overall, it is found that significant interaction between Ni and CeO2 occurs that could affect the synthesis and functionality of the SOFC anode.
ContributorsCavendish, Rio (Author) / Crozier, Peter (Thesis advisor) / Adams, James (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2012
ContributorsKotronakis, Dimitris (Performer) / ASU Library. Music Library (Publisher)
Created2018-03-01
ContributorsDavin, Colin (Performer) / ASU Library. Music Library (Publisher)
Created2018-10-05
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Description
Because of their favorable ionic and/or electronic conductivity, non-stoichiometric oxides are utilized for energy storage, energy conversion, sensing, catalysis, gas separation, and information technologies, both potential and commercialized. Charge transport in these materials is influenced strongly by grain boundaries, which exhibit fluctuations in composition, chemistry and atomic structure within Ångstroms

Because of their favorable ionic and/or electronic conductivity, non-stoichiometric oxides are utilized for energy storage, energy conversion, sensing, catalysis, gas separation, and information technologies, both potential and commercialized. Charge transport in these materials is influenced strongly by grain boundaries, which exhibit fluctuations in composition, chemistry and atomic structure within Ångstroms or nanometers. Here, studies are presented that elucidate the interplay between macroscopic electrical conductivity, microscopic character, and local composition and electronic structure of grain boundaries in polycrystalline ceria-based (CeO2) solid solutions. AC impedance spectroscopy is employed to measure macroscopic electrical conductivity of grain boundaries, and electron energy-loss spectroscopy (EELS) in the aberration-correction scanning transmission electron microscope (AC-STEM) is used to quantify local composition and electronic structure. Electron diffraction orientation imaging microscopy is employed to assess microscopic grain boundary character, and links these macro- and nanoscopic techniques across length scales.

A model system, CaxCe1-xO2-x-δ, is used to systematically investigate relationships between nominal Ca2+ concentration, grain boundary ionic conductivity, microscale character, and local solute concentration. Grain boundary conductivity varied by several orders of magnitude over the composition range, and assessment of grain boundary character highlighted the critical influence of local composition on conductivity. Ceria containing Gd3+ and Pr3+/4+ was also investigated following previous theoretical work predicting superior ionic conductivity relative to state-of-the-art GdxCe1-xO2-x/2-δ. The grain boundary conductivity was nearly 100 times greater than expected and a factor four enrichment of Pr concentration was observed at the grain boundary, which suggested electronic conduction that was cited as the origin of the enhanced conductivity. This finding inspired the development of two EELS-based experimental approaches to elucidate the effect of Pr enrichment on grain boundary conductivity. One employed ultra-high energy resolution (~10 meV) monochromated EELS to characterize Pr inter-bandgap electronic states. Alternatively, STEM nanodiffraction orientation imaging coupled with AC-STEM EELS was employed to estimate the composition of the entire grain boundary population in a polycrystalline material. These compositional data were the input to a thermodynamic model used to predict electrical properties of the grain boundary population. These results suggest improved DC ionic conduction and enhanced electronic conduction under AC conditions.
ContributorsBowman, William John (Author) / Crozier, Peter A. (Thesis advisor) / Chan, Candace K. (Committee member) / McCartney, Martha (Committee member) / Sieradzki, Karl (Committee member) / Arizona State University (Publisher)
Created2016
ContributorsSanchez, Armand (Performer) / Nordstrom, Nathan (Performer) / Roubison, Ryan (Performer) / ASU Library. Music Library (Publisher)
Created2018-04-13
ContributorsMiranda, Diego (Performer)
Created2018-04-06
ContributorsChan, Robbie (Performer) / McCarrel, Kyla (Performer) / Sadownik, Stephanie (Performer) / ASU Library. Music Library (Contributor)
Created2018-04-18