Browsing by Autor "Dachamir Hotza"

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    Characterization of SOFCS: A Crystallographic Analysis and First Steps towards an Impedance Spectroscopy Approach
    (Trans Tech Publications, 2012) Albert Avila; Juan Carlos Poveda; Darwing Villalta Gómez; Dachamir Hotza; Jairo Arturo Escobar
    Solid oxide fuel cells (SOFCs) have emerged as an efficient way to transform chemical energy into electrical energy. However, a major disadvantage of this technology is related to the high temperatures required for SOFC operation. In this way, new materials are necessary to maintain the electrical properties of the cell at intermediate temperatures. Based on these ideas, it is necessary to study both the structural variation of the cells components at different temperatures and their electrochemical behavior. In this work, a crystallographic characterization is presented, which was performed in a commercial SOFC cell using X-ray diffraction (XRD). An equivalent linear electrical model to predict SOFC losses is developed as well. Keywords: Solid oxide fuel cells (SOFCs); AC impedance; Electrochemical impedance spectroscopy (EIS); Equivalent circuit models.
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    Manufacture and Characterization of Alumina Ceramic Foams for Porous Burners
    (Trans Tech Publications, 2012) Ana María Herrera; Verônica Moreno; Amir Antônio Martins Oliveira; Dachamir Hotza; Óscar Álvarez; Jairo Arturo Escobar
    Hazardous byproducts emissions such as nitrogen oxides (NOx) and carbon monoxide (CO) might be controlled by the use of radiant porous burners. Those heaters require a solid porous matrix where combustion reaction takes place, reason why the heat transfer is much more efficient. This project was based on a rheology study of an alumina slurry, where parameters like viscosity and tixotropy were the guide to select the appropriate formulation to be used in the fabrication of ceramic foams by the replica method. Low strength samples were produced after the first thermal treatment, explained by the absence of a plasticizer when using PVA as a binder. Incomplete sintered foams were obtained due to an insufficient soak time.