Desarrollo de ánodo tubular nio-gdc para soporte de celda de combustible de óxido sólido.
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Date
2025
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Publisher
Universidad de Concepción
Abstract
Esta tesis presenta el desarrollo y caracterización de un ánodo microtubular basado en óxido de níquel (NiO) y de cerio dopado con gadolinio (GDC), optimizado para su aplicación en celdas de combustible de óxido sólido (SOFCs, por sus siglas en inglés). Se aborda todo el proceso, desde la formulación de la pasta cerámica hasta la sinterización final, con especial énfasis en el control reológico y microestructural.
Se demuestra que la extruibilidad está gobernada por el contenido de sólidos (NiO-GDC y α-celulosa), cuantificado mediante el parámetro Pigment Volume Concentration (PVC). Concepto propio de recubrimientos y pinturas, pero que se extrapola al contexto de pastas cerámicas, se define como la fracción volumétrica de fase sólida en la pasta seca, y se utiliza para correlacionar formulación, comportamiento reológico y desempeño en extrusión. Formulaciones con PVC entre 70 y 92 % muestran comportamiento pseudoplástico con esfuerzo de cedencia, adecuadamente modelado con Carreau–Yasuda y validado por ensayos oscilatorios. La pasta VI exhibe la red interna más resistente, mientras que la pasta VII, con PVC excesivo, resulta no extruible.
El secado en cámara de humedad controlada preserva la porosidad y, tras sinterización a 1200 °C, genera ánodos con mayor contenido de carbono residual, menor segregación superficial de Ni y mayor retención de óxidos de tierras raras. Esta temperatura se identifica como óptima para soportes porosos, ya que, a temperaturas superiores, estas diferencias se reducen o desaparecen.
Se concluye que la extrusión reproducible y de alto desempeño se alcanza manteniendo el PVC en el rango 70–92 %, utilizando rampas de sinterización ≤ 0,9 °C/min para evitar defectos, y empleando reómetros adecuados como el Discovery Hybrid Rheometer-3 (DHR-3). Además, se recomienda integrar ensayos tixotrópicos y barridos de frecuencia para ajustar parámetros de extrusión y mejorar la estabilidad mecánica del tubo verde.
Estos hallazgos contribuyen al diseño racional de ánodos microtubulares, clave en la fabricación de SOFCs más eficientes y compatibles con estrategias de transición energética como el hidrógeno verde.
This thesis presents the development and characterization of a microtubular anode based on NiO-GDC, optimized for application in SOFCs. The entire process is addressed—from the formulation of the ceramic paste to final sintering—with particular emphasis on rheological and microstructural control. It is demonstrated that extrudability is governed by the solid content (NiO-GDC and α-cellulose), quantified using the PVC, parameter. Originally a concept from the field of coatings and paints, PVC is extrapolated here to ceramic pastes, defined as the volume fraction of solid phase in the dried paste, and is used to correlate formulation, rheological behavior, and extrusion performance. Formulations with PVC values between 70 and 92% exhibit pseudoplastic behavior with yield stress, accurately modeled using the Carreau–Yasuda equation and validated through oscillatory rheological tests. Paste VI displays the strongest internal network, while paste VII, with an excessive PVC, is not extrudable. Drying in a controlled-humidity chamber preserves porosity, and subsequent sintering at 1200 °C yields anodes with higher residual carbon content, reduced surface nickel segregation, and greater retention of rare earth oxides. This temperature is identified as optimal for porous supports, since at higher temperatures these benefits diminish or disappear. It is concluded that reproducible and high-performance extrusion is achieved by maintaining PVC within the 70–92% range, applying sintering ramps of ≤ 0.9 °C/min to prevent defects, and using appropriate rheometers such as the DHR-3. In addition, it is recommended to incorporate thixotropy tests and frequency sweeps to fine-tune extrusion parameters and improve the mechanical stability of the green tube. These findings contribute to the rational design of microtubular anodes, which are key to the fabrication of more efficient SOFCs compatible with energy transition strategies such as green hydrogen.
This thesis presents the development and characterization of a microtubular anode based on NiO-GDC, optimized for application in SOFCs. The entire process is addressed—from the formulation of the ceramic paste to final sintering—with particular emphasis on rheological and microstructural control. It is demonstrated that extrudability is governed by the solid content (NiO-GDC and α-cellulose), quantified using the PVC, parameter. Originally a concept from the field of coatings and paints, PVC is extrapolated here to ceramic pastes, defined as the volume fraction of solid phase in the dried paste, and is used to correlate formulation, rheological behavior, and extrusion performance. Formulations with PVC values between 70 and 92% exhibit pseudoplastic behavior with yield stress, accurately modeled using the Carreau–Yasuda equation and validated through oscillatory rheological tests. Paste VI displays the strongest internal network, while paste VII, with an excessive PVC, is not extrudable. Drying in a controlled-humidity chamber preserves porosity, and subsequent sintering at 1200 °C yields anodes with higher residual carbon content, reduced surface nickel segregation, and greater retention of rare earth oxides. This temperature is identified as optimal for porous supports, since at higher temperatures these benefits diminish or disappear. It is concluded that reproducible and high-performance extrusion is achieved by maintaining PVC within the 70–92% range, applying sintering ramps of ≤ 0.9 °C/min to prevent defects, and using appropriate rheometers such as the DHR-3. In addition, it is recommended to incorporate thixotropy tests and frequency sweeps to fine-tune extrusion parameters and improve the mechanical stability of the green tube. These findings contribute to the rational design of microtubular anodes, which are key to the fabrication of more efficient SOFCs compatible with energy transition strategies such as green hydrogen.
Description
Tesis presentada para optar al título de Ingeniero/a en Civil Químico/a.
Keywords
Ánodos, Recursos energéticos renovables, Hidrógeno