Dealing with degradation in solid oxide electrochemical cells: novel materials and spectroscopic probes

In this PhD thesis, we have focused on two of the main issues regarding solid oxide fuel cells and electrolysers. On the one hand, the high temperatures at which they work (800-1000ºC) is detrimental for their long-term performance, and novel combinations of electrolyte and oxygen electrode materials have been tested in order to establish their suitability to work in intermediate temperature (600-800ºC) solid oxide fuel cells. On the other hand, degradation issues affect these devices greatly when working in the electrolyser mode, often assigned to the development of high oxygen partial pressures within the electrolyte. Regarding this topic, we have developed an analytical procedure to monitor the oxygen activity inside a YSZ electrolyte using redox dopants as spectroscopic probes and used it in cells tested in different conditions in the electrolysis mode.First, an aluminium-doped lanthanum silicate compound (LSAO) with the apatite structure was chosen as electrolyte, and eight different strontium and cobalt-free compounds with a perovskite structure with the general formula LaMxN1-xO3 (where M: Fe, Mn, Cr; and N: Ni, Cu) were selected to be tested with the apatite electrolyte. The solid-state synthesis of the apatite and perovskite-type compounds was optimised, achieving perovskite compounds free from secondary phases or decomposition, both in powder form and also after sintering them in pellet form, as it was proven by X-ray diffraction and Raman spectroscopy. The chemical compatibility of the electrolyte and electrode materials was tested by mixing and heating the powders at temperatures above the operational and sintering ones, and no reaction between the compounds took place, as proven again by X-ray diffraction. The thermomechanical compatibility between sintered materials was tested by dilatometry, and no big differences could be found regarding the thermal expansion behaviour of the apatite and perovskites in a wide range of temperatures.Then, the electrochemical performance of the compounds was tested by electrochemical impedance spectroscopy. The LSAO ionic conductivity at intermediate temperatures (9.4·10-3 S·cm-1 at 800ºC) was close to the one shown by a conventional YSZ electrolyte, and the electrical conductivity of the oxygen electrode materials ranged from 10 to 100 S·cm-1 at 800ºC, with activation energies in the high temperature range between 0.1 and 0.3 eV. Among the perovskite materials, the ones containing manganese and copper showed the highest electrical conductivities and the lowest activation energies. The iron-containing compounds (LFN and LFC) exhibited a different activation behaviour with temperature than the rest of the compounds.The following step consisted on manufacturing symmetrical cells with the apatite electrolyte and perovskite electrodes. For that purpose, slurries of the electrode materials were prepared and the electrolyte pellet was coated with them by dip-coating and sintered. The microstructure of the cells was checked in terms of electrode thickness, porosity, particle size, and adherence of the electrodes. Among the compositions tested, LFC showed the lowest ASR with just 4.3 Ω·cm2 at 700ºC, value comparable to the state-of-the-art oxygen electrodes. When applying a small DC bias, the activation energies of the electrodes decreased, as well as their polarization resistances. Promising results were found in this thesis about novel electrolyte/electrode combinations for IT-SOFC, with room for improvement regarding electrode microstructure and the fabrication of composite electrodes with the LFC material.In order to examine the degradation issues concerning SOEC devices, the research began with finding a suitable spectroscopic probe that allowed us to track the oxygen activity in the cells. First, the optical signals in a YSZ electrolyte doped with redox ions were investigated. The objective was to select the ones suitable to track the oxygen activity, allow for a detection in the backscattering configuration and be operative at high temperatures. The samples tested in this part of the thesis were either commercial or solidified on purpose YSZ single-crystals doped with Ce, Mn, Mn-Nd, V or Tb; or polycrystalline ceramics of Tb or Pr-doped YSZ.Among the commercial samples, it was found that YSZ-Ce showed strong change in its optical signal upon redox treatment, and the Ce3+ backscattering signal could be used to monitor the oxygen activity, although the signal disappeared at temperatures above 300ºC. In the case of YSZ-Mn and YSZ-V, even though a change in the optical signal upon oxidation/reduction could be found, there were no backscattering signals that could be used for tracking the oxygen activity. The luminescence of minority rare earth dopants in these samples (Pr3+, Er3+ or Nd3+) was measured and a change in the backscattering signal could be observed upon redox treatment. Nevertheless, the quantification of these signals would have been complicated due to a possible interaction with the major dopants, and these commercial samples were not used to track the oxygen activity within the electrolyte.In the case of praseodymium-doped YSZ, a change in optical signal was observed by diffuse reflectance, and bands due to Pr3+ and Pr4+ could be found. In the case of backscattering signal, Pr3+ ions exhibited an intense luminescence band which decreases upon oxidation to Pr4+, and this signal held up to 700ºC. This could be useful to make in-situ or in-operando measurements of the oxygen activity inside the electrolyte. Nevertheless, ion-ion interaction and concentration quenching of the luminescence band prevented an easy quantification of the oxygen activity, and this probe was also discarded.Terbium-doped YSZ was found suitable in order to track the oxygen activity within YSZ. Changes in optical and luminescence signals could be observed and attributed to different oxidation states of terbium (Tb3+ and Tb4+) upon redox treatments. Tb3+ was not affected by concentration quenching and a quantitative analysis could be carried out. It was found that Tb4+ absorbance was proportional to PO2^(1⁄4), as expected for the electron trapping model. A relation between the Tb3+ luminescence intensity and the oxygen partial pressure could be found, and it proved to be useful in the high PO2 range (10-4-100 bar). Terbium was therefore the selected probe in order to carry out the electrochemical experiments to detect degradation mechanisms in electrolysers.3%Tb-doped 8YSZ shows appropriate oxide ion conductivity to be used as the electrolyte in solid oxide cells. Then, an electrolyte-supported solid oxide cell was prepared using a LSM/YSZ composite for the oxygen electrode and a NiO/YSZ composite for the fuel electrode, and its electrochemical properties were tested in a bicameral cell at 800ºC. Using EIS and changing the atmosphere in the oxygen side, the electrochemical properties of the system were described, and the polarization resistance of each electrode was assigned. After those measurements, several experiments were carried out polarising different cells using a range of biases in the electrolyser mode. When a steady-state was reached around 48 hours after applying a constant voltage, cells were quenched to freeze the high temperature polarization state.The post-mortem cells were analysed in terms of the Tb3+ luminescence across the electrolyte thickness. The luminescence values were transformed into oxygen partial pressures using the relation mentioned above and profiles of the oxygen activity within the electrolyte could be obtained. These measurements were noisy and a couple of corrections were made in order to obtain a suitable signal. An edge-correction due to the loss of signal near the electrodes and a saturation correction due to microstructural aspects of the cell were applied. The method presented here has potential to visualize PO2 profiles in SOEC. Further experiments should be done in order to achieve higher accuracies.Finally, numerical solutions to the transport equations for describing the oxygen activity within the electrolyte were found and compared with the experimental results. It was found that the simulations assuming polarization resistances as derived from EIS spectra at the beginning of the CA experiments did not agree with the oxygen activity profiles obtained from the luminescence experiments. By analysing the SEM micrographs of the post-mortem cells, we could find that the most degradation had occurred near the fuel electrode. The nickel particles tended to agglomerate, especially for high polarization biases, and the porosity of the electrode decreased with applied bias. Besides, cracks within the electrolyte were found near this electrode and even a complete delamination of the fuel electrode was observed for the highest polarization experiment. These observations allowed us to assign a higher polarization resistance to the fuel electrode and then the numerical model results were closer to the results of the luminescence measurements. In order to get better insights of the degradation conditions of the cell while working on electrolyser mode, more experiments should be done.<br /

Escenarios de evaluación en el contexto de la pandemia por la COVID-19: la opinión del profesorado

En España, tras el Real Decreto 463/2020, de 14 de marzo, por el que se declara el estado de alarma para la gestión de la situación de crisis sanitaria ocasionada por la COVID-19, más de diez millones de estudiantes están intentando finalizar el curso desde sus casas. Para hacer esto posible, los docentes han realizado en este tiempo una impresionante transición de la educación presencial a la educación a distancia contando con recursos limitados, muy poco tiempo para la planificación y escasas instrucciones por parte de la Administración educativa. Una de las consecuencias del cierre de los centros educativos es la incertidumbre respecto a la evaluación del tercer trimestre y la evaluación final del curso 2019-2020. Por un lado, resulta tremendamente complicado organizar de manera improvisada una experiencia satisfactoria de aprendizaje a distancia y aún mucho más de evaluación en línea. Por otro lado, existe un número indeterminado de estudiantes cuyo derecho a la educación se ve amenazado por cuestiones sanitarias, familiares, socioeconómicas o tecnológicas. En todo caso, hay dudas razonables acerca de cómo están transcurriendo la enseñanza y el aprendizaje en estas circunstancias y sobre cómo se debe realizar la evaluación en esta situación de confinamiento y rodeados por una pandemia todavía por controlar. Por ello, el objetivo de este documento es realizar un análisis de escenarios para la evaluación del curso 2019-2020 y saber la opinión de los docentes respecto a estos escenarios. Conocer el futuro es imposible, pero plantearnos posibles futuros alternativos es una manera de reducir la incertidumbre y de prepararnos para tomar las mejores decisiones llegado el momento. Ese empeño preside estas páginas y cada palabra de este texto

Dehydrofluorination Process of Poly(vinylidene difluoride) PVdF-Based Gel Polymer Electrolytes and Its Effect on Lithium-Sulfur Batteries

Gel polymer electrolytes (GPEs) are emerging as suitable candidates for high-performing lithium-sulfur batteries (LSBs) due to their excellent performance and improved safety. Within them, poly(vinylidene difluoride) (PVdF) and its derivatives have been widely used as polymer hosts due to their ideal mechanical and electrochemical properties. However, their poor stability with lithium metal (Li0) anode has been identified as their main drawback. Here, the stability of two PVdF-based GPEs with Li0 and their application in LSBs is studied. PVdF-based GPEs undergo a dehydrofluorination process upon contact with the Li0. This process results in the formation of a LiF-rich solid electrolyte interphase that provides high stability during galvanostatic cycling. Nevertheless, despite their outstanding initial discharge, both GPEs show an unsuitable battery performance characterized by a capacity drop, ascribed to the loss of the lithium polysulfides and their interaction with the dehydrofluorinated polymer host. Through the introduction of an intriguing lithium salt (lithium nitrate) in the electrolyte, a significant improvement is achieved delivering higher capacity retention. Apart from providing a detailed study of the hitherto poorly characterized interaction process between PVdF-based GPEs and the Li0, this study demonstrates the need for an anode protection process to use this type of electrolytes in LSBs.This work was funded by the European Union’s Horizon 2020 research and innovation program Graphene Flagship Core Project 3 (GrapheneCore3) under grant agreement 881603. The project was also supported by Ministerio de Ciencia, Innovación y Universidades (MCIU), Agencia Estatal de Investigación (AEI), and the European Regional Development Fund (ERDF) (RTI2018-098301–B-I00)

Design and implementation of an embedded system for image acquisition of inserts in a headtool machine

Basados ​​en la idea de combinar sistemas integrados, cámaras industriales y procesamiento de imágenes, en este documento presentamos el diseño de un sistema de adquisición de imágenes integrado y portátil en una Raspberry PI 2 y otra en una notebook. El sistema de adquisición de imágenes se ha desarrollado utilizando dos lenguajes de programación diferentes, como Python y C ++. La biblioteca OpenCV Computer Vision, en su nueva versión 3.0.0, se utilizó para llevar a cabo todo el procesamiento de la visión artificial

Panorama de la Educación en España tras la Pandemia de COVID-19: La opinión de la comunidad educativa

Este informe recoge el análisis de la visión de la comunidad educativa (profesorado, estudiantado y familias) sobre la educación en España tras la pandemia por COVID-19. Las opiniones de la comunidad educativa se recogen mediante un diseño mixto de investigación mediante cuestionario y grupos de discusión

What can we learn from the innovative school for initial and ongoing teacher training? Research proposal

La formación inicial y permanente del profesorado es señalada como una de las claves fundamentales para la mejora del sistema. Sin embargo, para que esto ocurra, la formación del profesorado debe estar vinculada con prácticas educativas de calidad. En este artículo se defiende la investigación cualitativa en innovación educativa a través de los principios de la Teoría Fundamentada como una manera eficaz de construir una teoría sobre la innovación educativa que sea válida y útil para la transformación positiva del sistema educativo

A chromosome-level genome assembly enables the identification of the follicule stimulating hormone receptor as the master sex-determining gene in the flatfish Solea senegalensis

Sex determination (SD) shows huge variation among fish and a high evolutionary rate, as illustrated by the Pleuronectiformes (flatfishes). This order is characterized by its adaptation to demersal life, compact genomes and diversity of SD mechanisms. Here, we assembled the Solea senegalensis genome, a flatfish of great commercial value, into 82 contigs (614 Mb) combining long- and short-read sequencing, which were next scaffolded using a highly dense genetic map (28,838 markers, 21 linkage groups), representing 98.9% of the assembly. Further, we established the correspondence between the assembly and the 21 chromosomes by using BAC-FISH. Whole genome resequencing of six males and six females enabled the identification of 41 single nucleotide polymorphism variants in the follicle stimulating hormone receptor (fshr) consistent with an XX/XY SD system. The observed sex association was validated in a broader independent sample, providing a novel molecular sexing tool. The fshr gene displayed differential expression between male and female gonads from 86 days post-fertilization, when the gonad is still an undifferentiated primordium, concomitant with the activation of amh and cyp19a1a, testis and ovary marker genes, respectively, in males and females. The Y-linked fshr allele, which included 24 nonsynonymous variants and showed a highly divergent 3D protein structure, was overexpressed in males compared to the X-linked allele at all stages of gonadal differentiation. We hypothesize a mechanism hampering the action of the follicle stimulating hormone driving the undifferentiated gonad toward testisEuropean Union's Horizon 2020 research and innovation programme under grant agreement (AQUA-FAANG). Grant Number: 81792. Junta de Andalucía-FEDER Grant. Grant Number: P20-00938. Spanish Ministry of Economy and Competitiveness, FEDER Grants. Grant Numbers: RTI2018-096847-B-C21, RTI2018-096847-B-C22S

Natural History of MYH7-Related Dilated Cardiomyopathy

BACKGROUND Variants in myosin heavy chain 7 (MYH7) are responsible for disease in 1% to 5% of patients with dilated cardiomyopathy (DCM); however, the clinical characteristics and natural history of MYH7-related DCM are poorly described. OBJECTIVES We sought to determine the phenotype and prognosis of MYH7-related DCM. We also evaluated the influence of variant location on phenotypic expression. METHODS We studied clinical data from 147 individuals with DCM-causing MYH7 variants (47.6% female; 35.6 +/- 19.2 years) recruited from 29 international centers. RESULTS At initial evaluation, 106 (72.1%) patients had DCM (left ventricular ejection fraction: 34.5% +/- 11.7%). Median follow-up was 4.5 years (IQR: 1.7-8.0 years), and 23.7% of carriers who were initially phenotype-negative developed DCM. Phenotypic expression by 40 and 60 years was 46% and 88%, respectively, with 18 patients (16%) first diagnosed at <18 years of age. Thirty-six percent of patients with DCM met imaging criteria for LV noncompaction. During follow-up, 28% showed left ventricular reverse remodeling. Incidence of adverse cardiac events among patients with DCM at 5 years was 11.6%, with 5 (4.6%) deaths caused by end-stage heart failure (ESHF) and 5 patients (4.6%) requiring heart transplantation. The major ventricular arrhythmia rate was low (1.0% and 2.1% at 5 years in patients with DCM and in those with LVEF of <= 35%, respectively). ESHF and major ventricular arrhythmia were significantly lower compared with LMNA-related DCM and similar to DCM caused by TTN truncating variants. CONCLUSIONS MYH7-related DCM is characterized by early age of onset, high phenotypic expression, low left ventricular reverse remodeling, and frequent progression to ESHF. Heart failure complications predominate over ventricular arrhythmias, which are rare. (C) 2022 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation

Innocampus Explora: una aproximación multidisciplinar a la problemática ambiental

[ES] Presentamos las actividades del proyecto de innovación Innocampus Explora desarrollado en el campus de Burjassot-Paterna de la Universitat de València y cuyo objetivo principal es mostrar la interrelación existente entre los diferentes grados científicos y técnicos del campus. En la presente anualidad, el equipo de trabajo integrado por estudiantes y profesores de todos las facultades y escuelas del campus de Burjassot-Paterna, ha desarrollado actividades en torno a la problemática medioambiental. Una visión transversal e interdisciplinar de los problemas de los usos del plástico y de la energía nuclear que enlaza con varios de los Objetivos de Desarrollo Sostenible (ODS) dictados por Naciones Unidas. Con el desarrollo de este proyecto contribuimos a una formación transversal de calidad para todos los estudiantes participantes.[EN] We present the activities of the Innocampus Explora innovation project developed on the Burjassot-Paterna campus of the Universitat de València and whose main objective is to show the interrelation between the different scientific and technical degrees on campus. In this year, the work team made up of students and professors from all the faculties and schools of the Burjassot-Paterna campus, have carried out activities around environmental issues. A cross-sectional and interdisciplinary vision of the problems of the uses of plastic and nuclear energy that link with several of the Sustainable Development Goals (SDGs) dictated by the United Nations. With the development of this project we contribute to quality transversal training for all participating students.Moros Gregorio, J.; Quílez Asensio, A.; Jimenez Romero, D.; Blas Medina, A.; Giménez Escamilla, I.; Amorós Hernández, L.; Giner, L.... (2021). Innocampus Explora: una aproximación multidisciplinar a la problemática ambiental. En IN-RED 2020: VI Congreso de Innovación Educativa y Docencia en Red. Editorial Universitat Politècnica de València. 1003-1014. https://doi.org/10.4995/INRED2020.2020.11996OCS1003101

TIC Y SISTEMAS INTELIGENTES como herramientas de soporte para el manejo, educación y prevención del trauma

La corporación ecuatoriana para el desarrollo de la investigación y la academia,. CEDIA, promueve la exploración y resultados de proyectos innovadores que vinculan a instituciones ecuatorianas. A inicios del año 2014, CEDIA conformó grupos de trabajo en varias áreas d einterés; una de ellas fue Telemedicina y Telesalud debido al gran impacto que tiene dentro de la investigación. Este grupo cuenta con la participación de seis universidades ecuatorianas: Universidad de Cuenca, Universidad Salesiana, Universidad Católica de Cuenca, Universidad del Azuay, Universidad Regional Autónoma de los Andes y Universidad Nacional de Chimborazo. El objetivo de este grupo de trabajo es fortalecer, impulsar y motivar actividades de investigación entre las instituciones miembros de CEDIA en bienestar d ela comunidad. En este libro se visualiza el trabajo realizado por el Grupo de Trabajo en temas de trauma utilizando múltiples formas de tecnología, desde aplicaciones móviles, e-learning, objetos de aprendizaje, hasta sistemas de recolección automatizada de datos; desarrollando programas que impactan en la atención de la salud en el área pre-hospitalaria, prevención de lesiones, registro de trauma, modalidades de educación y aprendizaje, mediante el uso de las TIC