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3. Optimisation of the electrochemical performance of (Nd,Gd)1/3Sr2/3CoO3−δ cathode for solid oxide fuel cells via spray-pyrolysis deposition and decoration with Ag nanoparticles

Author

Santos, Paula Rosendo, primary, Pérez-Coll, Domingo, additional, Azcondo, M. Teresa, additional, Mather, Glenn C., additional, Muñoz-Noval, Álvaro, additional, Salas-Colera, Eduardo, additional, Amador, Ulises, additional, Boulahya, Khalid, additional, and Muñoz-Gil, Daniel, additional

Published
2024
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4. Optimisation of the electrochemical performance of (Nd,Gd)1/3Sr2/3CoO3−δ cathode for solid oxide fuel cells via spray-pyrolysis deposition and decoration with Ag nanoparticles.

Author

Santos, Paula Rosendo, Pérez-Coll, Domingo, Azcondo, M. Teresa, Mather, Glenn C., Muñoz-Noval, Álvaro, Salas-Colera, Eduardo, Amador, Ulises, Boulahya, Khalid, and Muñoz-Gil, Daniel

Abstract

Single-step synthesis and deposition of composite solid oxide fuel cell cathodes of composition (Nd,Gd)1/3Sr2/3CoO3−δ : Ce0.9(Gd,Nd)0.1O1.95 (70 : 30 w : w) with and without the addition of Ag nanoparticles (Ag NPs) was achieved employing spray pyrolysis and low-temperature sintering at 900 °C. Spray-pyrolysis-prepared materials offered improved microstructure with smaller particle size and higher porosity (extended triple phase boundary) in comparison to slurry-coated electrodes of analogous composition. Impedance spectroscopy of symmetrical cells of the composite air electrodes indicated a lower resistive response of the spray-pyrolysis-prepared electrodes with lower overall polarisation resistance (Rp), attributable to improved oxygen surface exchange and oxide-ion diffusion processes. Further reduction in Rp was achieved on decoration of the composite air electrodes with Ag NPs; the decorated composites were characterised by high resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Ag K-edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) of Ce0.9Gd0.1O2−δ:Ag spray-pyrolysed composites indicated that the Ag nanoparticles exhibit a core–shell structure with a Ag2O outer layer calculated to be two unit cells in thickness. The outer particle shell is suggested to participate in the enhanced electrochemical response, lowering the electrode polarisation response of symmetrical cells below 700 °C. Anode-supported single-cell fuel cells corresponding to the composite air electrode with Ag NPs and a thin YSZ-CGO electrolyte provided a maximum power density of 0.6 W cm−2 at 700 °C. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Sodium Rich Vanadium Oxy‐Fluorophosphate – Na3.2Ni0.2V1.8(PO4)2F2O – as Advanced Cathode for Sodium Ion Batteries

Author

Essehli, Rachid, primary, Yahia, Hamdi Ben, additional, Amin, Ruhul, additional, Li, Mengya, additional, Morales, Daniel, additional, Greenbaum, Steven G., additional, Abouimrane, Ali, additional, Parejiya, Anand, additional, Mahmoud, Abdelfattah, additional, Boulahya, Khalid, additional, Dixit, Marm, additional, and Belharouak, Ilias, additional

Published
2023
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7. Elaboración de material audiovisual de uso en asignaturas prácticas y teórico prácticas de grados y dobles grados que tratan la química

Author

Isasi Marín, Josefa, Alcolea Palafox, Mauricio, Fernández-Ramos Humanes, Miguel, Rapp Diez de la Cortina, María, Hernán García, Esther, de la Lastra Martínez, Jaime, Alba Isasi, Pablo, Cáceres Ramos, Silvia, Alba Isasi, Carlos, Herranz Muñoz, Irene, Gordo Lozano, Marta, Luliana Ionita, Andrea, García Calvo, Elena, Espada Morán, Luis, Villa García, Mª Isabel, Martín Gandul, Mª del Carmen, Arévalo Cid, Pablo, Martinez Pacheco, Andrea, Boulahya, Khalid, Arquero Avilés, Mª del Rosario, Marco Arquero, Alexia, Marco Arquero, Carla, Marco Arquero, María, Marco Cuenca, Gonzalo, Criado García, Mª Rosario, Sánchez Calero, Luisa, Isasi Marín, Josefa, Alcolea Palafox, Mauricio, Fernández-Ramos Humanes, Miguel, Rapp Diez de la Cortina, María, Hernán García, Esther, de la Lastra Martínez, Jaime, Alba Isasi, Pablo, Cáceres Ramos, Silvia, Alba Isasi, Carlos, Herranz Muñoz, Irene, Gordo Lozano, Marta, Luliana Ionita, Andrea, García Calvo, Elena, Espada Morán, Luis, Villa García, Mª Isabel, Martín Gandul, Mª del Carmen, Arévalo Cid, Pablo, Martinez Pacheco, Andrea, Boulahya, Khalid, Arquero Avilés, Mª del Rosario, Marco Arquero, Alexia, Marco Arquero, Carla, Marco Arquero, María, Marco Cuenca, Gonzalo, Criado García, Mª Rosario, and Sánchez Calero, Luisa

Abstract

En el desarrollo del proyecto se han elaborado un total de 25 tutoriales que se convertirán en la guía con la que los estudiantes y el profesorado podrán recordar el funcionamiento de todos los softwares utilizados durante el grado (Excel, Origin, Avogadro, ChemSketch, Vesta, X´pert, Checkell, Hyperchem y Fullprof), pudiendo aprender además aquello que no se asimiló bien o lo que nunca se llegó a conocer de estos programas. Este material está ya a disposición de todos los estudiantes de la UCM y de otras universidades en el canal QuimIsasi (https://www.youtube.com/channel/UCNG3-lLP2AetTksEBC0hAw) en el espacio de título "Material audiovisual de uso en asignaturas prácticas de grados que tratan la Química", siendo de suma utilidad para el alumnado que vaya a cursar o que cursará diferentes asignaturas prácticas y teórico-prácticas incluidas en grados y dobles grados que tratan la Química. El análisis y evaluación del material audiovisual elaborado podrá permitir un aprendizaje más eficaz del manejo de distintos programas que, como se verá, va a permitir llevar a cabo: cálculos generales y estadísticos, creación de bases de datos, dibujos de moléculas y su simetría, representación de estructuras de compuestos inorgánicos/orgánicos y cálculos de parámetros de celdilla de esas estructuras o de sus momentos magnéticos., A total of 25 tutorials have been prepared in the development of the project which will become the guide with which students and teachers will be able to remember the operation of all the software used during the degree (Excel, Origin, Avogadro, ChemSketch, Vesta, X'pert, Checkell, Hyperchem and Fullprof), being able to also learn what was not well assimilated or what was never known about these programs. This material is now available to all UCM students and other universities on the QuimIsasi channel (https://www.youtube.com/channel/UCNG3-lLP2AetTksEBC0hAw) in the title space "Audiovisual material for use in subjects degree practices that deal with Chemistry", being extremely useful for students who are going to take or will be taking different practical and theoretical-practical subjects included in degrees and double degrees that deal with Chemistry. The analysis and evaluation of the audiovisual material produced may allow a more effective learning of the management of different programs that, as will be seen, will allow carrying out: general and statistical calculations, creation of databases, drawings of molecules and their symmetry, representation of structures of inorganic/organic compounds and calculations of cell parameters of those structures or of their magnetic moments., Dans le développement du projet, un total de 25 tutoriels ont été préparés qui deviendront le guide avec lequel les étudiants et les enseignants pourront se souvenir du fonctionnement de tous les logiciels utilisés pendant le diplôme (Excel, Origin, Avogadro, ChemSketch, Vesta , X'pert, Checkell, Hyperchem et Fullprof), pouvant aussi apprendre ce qui n'a pas été bien assimilé ou ce qui n'a jamais été connu de ces programmes. Ce matériel est désormais disponible pour tous les étudiants de l'UCM et d'autres universités sur la chaîne QuimIsasi (https://www.youtube.com/channel/UCNG3-lLP2AetTksEBC0hAw) dans l'espace titre "Matériel audiovisuel à utiliser dans les pratiques de diplômes traitant de la chimie ", extrêmement utile pour les étudiants qui vont suivre ou suivront différentes matières pratiques et théoriques-pratiques incluses dans les diplômes et doubles diplômes traitant de la chimie. L'analyse et l'évaluation du matériel audiovisuel produit pourront permettre un apprentissage plus efficace de la gestion de différents programmes qui, comme on le verra, permettront d'effectuer : des calculs généraux et statistiques, la création de bases de données, des dessins de molécules et leur symétrie, la représentation des structures de composés inorganiques/organiques et calculs des paramètres cellulaires de ces structures ou de leurs moments magnétiques.

Published
2023

8. Sodium Rich Vanadium Oxy‐Fluorophosphate – Na3.2Ni0.2V1.8(PO4)2F2O – as Advanced Cathode for Sodium Ion Batteries.

Author

Essehli, Rachid, Yahia, Hamdi Ben, Amin, Ruhul, Li, Mengya, Morales, Daniel, Greenbaum, Steven G., Abouimrane, Ali, Parejiya, Anand, Mahmoud, Abdelfattah, Boulahya, Khalid, Dixit, Marm, and Belharouak, Ilias

Subjects
SODIUM ions, TRANSITION metal oxides, CATHODES, VANADIUM, TRANSITION metals, HIGH voltages, ELECTROCHEMICAL analysis
Abstract

Conventional sodium‐based layered oxide cathodes are extremely air sensitive and possess poor electrochemical performance along with safety concerns when operating at high voltage. The polyanion phosphate, Na3V2(PO4)3 stands out as an excellent candidate due to its high nominal voltage, ambient air stability, and long cycle life. The caveat is that Na3V2(PO4)3 can only exhibit reversible capacities in the range of 100 mAh g−1, 20% below its theoretical capacity. Here, the synthesis and characterizations are reported for the first time of the sodium‐rich vanadium oxyfluorophosphate, Na3.2Ni0.2V1.8(PO4)2F2O, a tailored derivative compound of Na3V2(PO4)3, with extensive electrochemical and structural analyses. Na3.2Ni0.2V1.8(PO4)2F2O delivers an initial reversible capacity of 117 mAh g−1 between 2.5 and 4.5 V under the 1C rate at room temperature, with 85% capacity retention after 900 cycles. The cycling stability is further improved when the material is cycled at 50 °C within 2.8–4.3 V for 100 cycles. When paired with a presodiated hard carbon, Na3.2Ni0.2V1.8(PO4)2F2O cycled with a capacity retention of 85% after 500 cycles. Cosubstitution of the transition metal and fluorine in Na3.2Ni0.2V1.8(PO4)2F2O as well as the sodium‐rich structure are the major factors behind the improvement of specific capacity and cycling stability, which paves the way for this cathode in sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Published
2023
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12. Enseñanza de química con fundamento. Ensayos virtuales

Author

Isasi Marín, Josefa, Arquero Avilés, Rosario, Marco Cuenca, Gonzalo, Fernández-Ramos Humanes, Miguel, Rap diez de la Cortina, María, Martínez Pacheco, Andrea, Gómez Prados, Sergio, Lozano Vilches, Yaiza, Alba Isasi, Pablo, Alba Isasi, Carlos, Marco Arquero, María, Alba Isasi, María Teresa, Alcolea Palafox, Mauricio, Espada Morán, Luis, Marco Arquero, Carla, Marco Arquero, Alexia, Herranz Muñoz, Irene, Cáceres Ramos, Silvia, Hernán García, Esther, de la Lastra Martínez, Jaime, Veas Porlán, Manuel, Pareja García, Arturo, García Calvo, Elena, Ferreiro de Aguiar, Adriana, Fernández Rivero, Adrian, Gordo Lozano, Marta, Arévalo Cid, Pablo, Boulahya, Khalid, Sanchez Calero, María Luisa, Isasi Marín, Josefa, Arquero Avilés, Rosario, Marco Cuenca, Gonzalo, Fernández-Ramos Humanes, Miguel, Rap diez de la Cortina, María, Martínez Pacheco, Andrea, Gómez Prados, Sergio, Lozano Vilches, Yaiza, Alba Isasi, Pablo, Alba Isasi, Carlos, Marco Arquero, María, Alba Isasi, María Teresa, Alcolea Palafox, Mauricio, Espada Morán, Luis, Marco Arquero, Carla, Marco Arquero, Alexia, Herranz Muñoz, Irene, Cáceres Ramos, Silvia, Hernán García, Esther, de la Lastra Martínez, Jaime, Veas Porlán, Manuel, Pareja García, Arturo, García Calvo, Elena, Ferreiro de Aguiar, Adriana, Fernández Rivero, Adrian, Gordo Lozano, Marta, Arévalo Cid, Pablo, Boulahya, Khalid, and Sanchez Calero, María Luisa

Abstract

24 vídeos se han elaborado en el desarrollo del trabajo. Estos vídeos muestran grabaciones de experimentos sencillos que tratan contenidos de Química general y su explicación. El trabajo está teniendo una buena aceptación, tal y como lo demuestran las muchas entradas al canal de YouTubehttps://www.youtube.com/channel/UCNG3-lLP2AetT-ksEBC0hAw/video

Published
2022

13. First Principles Study on the Features of Ca x Sr 2−x Ta 2 O 7 (x = 0, 1) as a Photocatalytic Material †.

Author

Gómez-Toledo, Marianela, Boulahya, Khalid, and Arroyo-de Dompablo, M. Elena

Subjects
PHOTOCATALYSIS, HYDROGEN production, CARBONIZATION, ABSORPTION, SUBSTITUTION reactions
Abstract

With hydrogen as one of the energetic vectors craved for use in the future, the successful de-carbonization of the energy sector will require an increase in hydrogen production from renewable resources. Materials that are able to catalyze the water-splitting reaction through sunlight absorption have been widely studied as an adequate solution for green hydrogen generation. Among the proposed tantalum-based oxide materials, Sr2Ta2O7 displays moderate photocatalytic activity. Aiming to improve the photocatalytic properties by means of compositional modifications, this work presents a DFT study of the Sr substitution with Ca. The structural, energetic, and electronic features of the phases of CaxSr2−xTa2O7 (0 < x < 1) have been examined. The computational results utilizing the SCAN functional show that there is a slight decrement in the band gap value (from 3.65 eV for x = 0 to 3.50 eV for x = 1) concomitant to a minor distortion of the crystal structure. [ABSTRACT FROM AUTHOR]

Published
2023
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22. Ventana virtual a un laboratorio de química

Author

Isasi Marín, Josefa, Abuín Vences, Natalia, Arévalo Cid, Pablo, Alcaraz Romo, Lorena, Alcolea Palafox, Mauricio, Fernández González, Mario, Caballero Sánchez, Elena, González Rodríguez, Diego, Espada Morán, Luis, Villa García, María Isabel, Boulahya, Khalid, Morocho Chávez, Erika Patricia, Rodríguez Boehm, Íñigo, Martínez Fernández, Alejandro, Criado García, Rosario Presentación, Gómez de Castro, Consuelo, Pañeda de la Peña, Victoria, Fernández Sola, Julia, Torres Álvarez, Sergio, Isasi Marín, Josefa, Abuín Vences, Natalia, Arévalo Cid, Pablo, Alcaraz Romo, Lorena, Alcolea Palafox, Mauricio, Fernández González, Mario, Caballero Sánchez, Elena, González Rodríguez, Diego, Espada Morán, Luis, Villa García, María Isabel, Boulahya, Khalid, Morocho Chávez, Erika Patricia, Rodríguez Boehm, Íñigo, Martínez Fernández, Alejandro, Criado García, Rosario Presentación, Gómez de Castro, Consuelo, Pañeda de la Peña, Victoria, Fernández Sola, Julia, and Torres Álvarez, Sergio

Abstract

El proyecto desarrollado pone a disposición de los centros docentes en un canal de YouTube, https://www.youtube.com/channel/UCNG3-lLP2AetT-ksEBC0hAw, una ventana virtual a un laboratorio de química. Se visualizan vídeos de prácticas diseñadas para hacer mucho más comprensible el estudio de la química general.

Published
2019

28. Las TIC en el fomento de nuevas vocaciones científicas

Author

Isasi Marín, Josefa, Gómez de Castro, Consuelo, Criado García, Rosario, Abuín Vences, Natalia, Arévalo Cid, Pablo, Alcaraz Romo, Lorena, Espada Morán, Luis, Fernández del Río, Beatriz, Caballero Sánchez, Elena, Arribas Delgado, Andrés, González Rodriguez, Diego, Isasi Campillo, Miriam, Boulahya, Khalid, De la Puente Viedma, Carlos, Isasi Marín, Josefa, Gómez de Castro, Consuelo, Criado García, Rosario, Abuín Vences, Natalia, Arévalo Cid, Pablo, Alcaraz Romo, Lorena, Espada Morán, Luis, Fernández del Río, Beatriz, Caballero Sánchez, Elena, Arribas Delgado, Andrés, González Rodriguez, Diego, Isasi Campillo, Miriam, Boulahya, Khalid, and De la Puente Viedma, Carlos

Abstract

El objetivo de este proyecto es poner de manifiesto la relación existente entre la investigación básica y la aplicada. Se han editado dos documentales que muestran la síntesis,caracterización y estudio de nanocomposites que pueden resultar de utilidad como membranas adsorbentes de especies contaminantes en aguas y como dispositivos optoelectrónicos.

Published
2018

30. Superior Performance as Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cells of the Ruddlesden–Popper n= 2 Member Eu2SrCo0.50Fe1.50O7−δwith Low Cobalt Content

Author

Muñoz Gil, Daniel, Boulahya, Khalid, Santamaria Santoyo, María, Azcondo, M. Teresa, and Amador, Ulises

Abstract

The effects of the contents of iron and cobalt on the crystal structure, oxygen content, thermal expansion coefficient, and electrical–electrochemical properties of materials Eu2SrCoxFe2–xO7−δ(x= 0.50 and 1.00) are reported. These oxides are well-ordered new members of the Ruddlesden–Popper series (Eu,Sr)n+1(Co,Fe)nO3n+1system with n= 2 as determined by selected area electron diffraction and high-resolution transmission electron microscopy and X-ray diffraction studies. The two materials are semiconductors of p-type, with much higher total conductivity under working conditions for the low cobalt compound, Eu2SrCo0.50Fe1.50O7−δ. Composite cathodes prepared with this oxide present much lower area-specific resistance values (0.08 Ω·cm2at 973 K in air) than composites containing Eu2SrCo1.00Fe1.00O7−δ(1.15 Ω·cm2). This significant difference is related to the much higher total conductivity and a sufficiently high content of oxygen vacancies in the Fe-rich phase. The excellent electrochemical performance of Eu2SrCo0.50Fe1.50O7−δwith low cobalt content, which shows one of the lowest area-specific resistance reported so far for a Ruddlesden–Popper oxide, makes it a good candidate for application as a cathode material for solid oxide fuel cells at intermediate temperatures in real devices.

Published
2021
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31. Las TIC en investigación avanzada: técnicas de caracterización e información aportada

Author

Isasi Marín, Josefa, Abuín Vences, Natalia, Criado García, Rosario, Arévalo Cid, Pablo, Alcaraz Romo, Lorena, De la Puente Viedma, Carlos, Fernández González, Mario, Pradillo Orellana, Mónica, Boulahya, Khalid, Martínez García, Marina, Parra Núñez, Pablo, Villa García, María Isabel, Espada Morán, Luis, Martín Majadas, Raúl, Isasi Marín, Josefa, Abuín Vences, Natalia, Criado García, Rosario, Arévalo Cid, Pablo, Alcaraz Romo, Lorena, De la Puente Viedma, Carlos, Fernández González, Mario, Pradillo Orellana, Mónica, Boulahya, Khalid, Martínez García, Marina, Parra Núñez, Pablo, Villa García, María Isabel, Espada Morán, Luis, and Martín Majadas, Raúl

Abstract

Se emplean las TIC para describir la información proporcionada por difractogramas, espectros, micrografías, capturas de microscopía y diferentes gráficas obtenidos empleando técnicas avanzadas de caracterización. En un canal creado en YouTube se da difusión del trabajo realizado que se plasma en un conjunto de diez vídeos.

Published
2017

32. Síntesis y caracterización de nuevos óxidos funcionales avanzados basados en cobalto

Author

Boulahya, Khalid, Hassan, Manar, Boulahya, Khalid, and Hassan, Manar

Abstract

El objetivo fundamental de este trabajo es la preparación, caracterización microestructural y estudio de las propiedades magnéticas y electroquímicas de óxidos derivados de la serie de RP An+1BnO3n+1 (A=Sr, Nd y Eu y B= Co, Mn y Fe) para su uso como cátodos de temperatura intermedia para pilas de combustible (IT-SOFC). Se han estudiado los efectos de la sustitución parcial del Sr por Nd y Eu en las posiciones A de la serie An+1BnO3n+1. También se han evaluaddo los efectos de la sustitución del Co por otros elementos de transición en la estructura cristalina como el Mn y Fe y su influencia en las propiedades electroquímicas de materiales derivados de Srn+1ConO3n+1. Con objeto de ampliar el margen de sustitución del Co por el Fe y Mn, se han estudiado óxidos en el sistema (Eu,Sr)3(Co,Mn/Fe)2O7 Estos compuestos presentan buenos valores de ASR. También se han estudiado los efectos de la sustitución de elementos de Tierra rara por el Sr en la estructura cristalina y propiedades magnéticas derivados de NdCoO3 y SrCoO2.5. En particular, se han estudiado nuevos óxidos preparados en los sistemas Sr2-xNdxCoO4, Sr2-xNdxCo0.75Fe0.25O4, Sr2-xNdxCo0.75Mn0.25O4, Eu2SrCo1.5M0.5O7 (M=Mn y Fe) y Sr1-xNdxCoO3..., The aim of this work is the synthesis, microstructural characterization and physical properties (magnetic and electrochemical properties) of new oxides based on cobalt, members of the homologous series (RP) An+1BnO3n+1 (A=Sr, Nd y Eu y B= Co, Mn y Fe) for use at intermediate temperature as cathodes in solid oxide fuel cells (IT-SOFCs). We have studied the effect of the partial substitution of Sr atoms by Nd and Eu and the effects of substituting Co by other transition metal elements as Mn and Fe in the homologous series Srn+1ConO3n+1, on their magnetic and electrochemical properties. With the aim of increasing the substitution of Fe/Mn for Co, we have studied the (Eu,Sr)3(Co,Mn/Fe)2O7 system. These oxides show excellent area specific resistance (ASR) values. We have studied the effect of the substitution of Nd for Sr in the structural characterisation and magnetic properties of compounds based on NdCoO3 and SrCoO2.5. In particular, this work has focused on the study of 3 different members (n=1,2 and ∞) the RP series (RE,Sr)n+1(Co,M)nO3n+1 (RE=Nd, Eu) and M=Mn, Fe); Sr2-xNdxCoO4, Sr2-xNdxCo0.75Fe0.25O4, Sr2-xNdxCo0.75Mn0.25O4, Eu2SrCo1.5M0.5O7 (M=Mn, Fe) and Sr1-xNdxCoO3 systems...

Published
2017

34. Structural characterization and NMR study of NMR study of NaNbW[O.sub.6] and its proton-exchanged derivatives

Author

Kuhn, Alois, Azcondo, Maria T., Amador, Ullses, Boulahya, Khalid, Sobrados, Isabel, and Sanz, Jesus

Subjects
Nuclear magnetic resonance spectroscopy -- Analysis, Sodium compounds -- Structure, Sodium compounds -- Optical properties, Sodium compounds -- Spectra, Tungsten compounds -- Structure, Tungsten compounds -- Optical properties, Tungsten compounds -- Spectra, X-rays -- Diffraction, X-rays -- Observations, Chemistry
Abstract

The structural characterization of NaNbE[O.sub.6], prepared by the ceramic route is performed. The observation of this study relates to the proton conductivity displayed by exchanged products under a humid atmosphere.

Published
2007

37. The Effects of Sr Content on the Performance of Nd1–xSrxCoO3−δAir-Electrode Materials for Intermediate Temperature Solid Oxide Fuel Cells under Operational Conditions

Author

Muñoz-Gil, Daniel, Azcondo, M. Teresa, Ritter, Clemens, Fabelo, Oscar, Pérez-Coll, Domingo, Mather, Glenn C., Amador, Ulises, and Boulahya, Khalid

Abstract

The potential of the perovskite system Nd1–xSrxCoO3−δ(x= 1/3 and 2/3) as cathode material for solid oxide fuel cells (SOFCs) has been investigated via detailed structural, electrical, and electrochemical characterization. The average structure of x= 1/3 is orthorhombic with a complex microstructure consisting of intergrown, adjacent, perpendicularly oriented domains. This orthorhombic symmetry remains throughout the temperature range 373–1073 K, as observed by neutron powder diffraction. A higher Sr content of x= 2/3 leads to stabilization of the cubic perovskite with a homogeneous microstructure and with a higher oxygen vacancy content and cobalt oxidation state than the orthorhombic phase at SOFC operation temperature. Both materials are p-type electronic conductors with high total conductivities of 690 and 1675 S·cm–1at 473 K in air for x= 1/3 and 2/3, respectively. Under working conditions, both compounds exhibit similar electronic conductivities, since x= 2/3 loses more oxygen on heating than x= 1/3, associated with a greater loss of p-type charger carriers. However, composite cathodes prepared with Nd1/3Sr2/3CoO3−δand Ce0.8Gd0.2O2−δpresent lower ASR values (0.10 Ω·cm2at 973 K in air) than composites prepared with Nd2/3Sr1/3CoO3−δand Ce0.8Gd0.2O2−δ(0.34 Ω·cm2). The high activity for the oxygen electrochemical reaction at intermediate temperatures is likely attributable to a large disordered oxygen-vacancy concentration, resulting in a very promising SOFC cathode for real devices.

Published
2020
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38. Unprecedented rock-salt ordering of A and B cations in the double perovskite Nd2−xCaxMgTiO6−δ and defect association.

Author

Teresa Azcondo, M., Boulahya, Khalid, Ritter, Clemens, García-Alvarado, Flaviano, and Amador, Ulises

Subjects
*ION traps, *ACTIVATION energy, *OXYGEN, *RARE earth ions, *CATIONS
Abstract

The partial substitution of up to 5% Nd+3 by Ca+2 results in the oxide Nd1.90Ca0.10MgTiO5.94 that presents some remarkable structural features with a noticeable influence on its properties. In this oxide with a monoclinic perovskite-like structure and an octahedral tilting scheme (a−a−b+), both A- and B-ions are arranged in a rock-salt like manner, representing therefore the first example of a type of perovskite theoretically predicted. Besides this unprecedented arrangement of A- and B-ions, the oxygen vacancies created through doping with acceptor ions are trapped by association with the acceptor defects and hence the mobility of these vacancies is strongly limited. The oxygen conductivity of the substituted material is lower and the activation energy for oxygen motion is higher than those of the parent oxide, in which the concentration of anion vacancies is only due to intrinsic defects. [ABSTRACT FROM AUTHOR]

Published
2019
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39. Eu2SrCo1.5Fe0.5O7 a new promising Ruddlesden–Popper member as a cathode component for intermediate temperature solid oxide fuel cells.

Author

Boulahya, Khalid, Muñoz-Gil, Daniel, Gómez-Herrero, Adrián, Azcondo, M. Teresa, and Amador, Ulises

Abstract

A new oxide of the Ruddlesden–Popper series in the (Eu,Sr)n+1(Co,Fe)nO3n+1 system has been isolated and structurally characterized. X-ray diffraction and electron microscopy show that polycrystalline Eu2SrCo1.5Fe0.5O7 constitutes the n = 2 member of a homologous series, the essential feature of which is the existence of two connected Co/Fe octahedral layers with a perovskite-like structure, linked by an EuO rock-salt like layer. Random distributions of 3d-metals in the perovskite blocks and interstitial and oxygen vacancies in the rock-salt layers (anti Frenkel defects) are observed by electron microscopy. Such facts are commonly associated with high electronic conduction and ionic conductivity. The electrochemical study shows that the area-specific resistance of this compound is 0.26 Ω cm2 at 700 °C in air, a value which is comparable to those of the best state-of-the-art Ruddlesden–Popper materials used as cathodes in intermediate temperature solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Published
2019
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40. Síntesis y caracterización de nuevos óxidos funcionales avanzados basados en cobalto

Author

Hassan, Manar, Boulahya, Khalid, Hassan, Manar, and Boulahya, Khalid

Abstract

El objetivo fundamental de este trabajo es la preparación, caracterización microestructural y estudio de las propiedades magnéticas y electroquímicas de óxidos derivados de la serie de RP An+1BnO3n+1 (A=Sr, Nd y Eu y B= Co, Mn y Fe) para su uso como cátodos de temperatura intermedia para pilas de combustible (IT-SOFC). Se han estudiado los efectos de la sustitución parcial del Sr por Nd y Eu en las posiciones A de la serie An+1BnO3n+1. También se han evaluaddo los efectos de la sustitución del Co por otros elementos de transición en la estructura cristalina como el Mn y Fe y su influencia en las propiedades electroquímicas de materiales derivados de Srn+1ConO3n+1. Con objeto de ampliar el margen de sustitución del Co por el Fe y Mn, se han estudiado óxidos en el sistema (Eu,Sr)3(Co,Mn/Fe)2O7 Estos compuestos presentan buenos valores de ASR. También se han estudiado los efectos de la sustitución de elementos de Tierra rara por el Sr en la estructura cristalina y propiedades magnéticas derivados de NdCoO3 y SrCoO2.5. En particular, se han estudiado nuevos óxidos preparados en los sistemas Sr2-xNdxCoO4, Sr2-xNdxCo0.75Fe0.25O4, Sr2-xNdxCo0.75Mn0.25O4, Eu2SrCo1.5M0.5O7 (M=Mn y Fe) y Sr1-xNdxCoO3...

Published
2016

41. Empleo de las TIC como herramienta divulgativa de la metodología experimental inherente a investigaciones de interés social

Author

Isasi Marín, Josefa, Cuervo Rodríguez, Mª Rocio, Criado García, Rosario, Pradillo Orellana, Mónica, Alcaraz Romo, Lorena, Arévalo Cid, Pablo, de la Puente Viedma, Carlos, Donald Rivera, Minerva, Boulahya, Khalid, Fernández González, Mario, Martín Majadas, Raul, Parra Núñez, Pablo, Espada Morán, Luis, Martínez García, Marina, González Izquierdo, Jesús, Isasi Marín, Josefa, Cuervo Rodríguez, Mª Rocio, Criado García, Rosario, Pradillo Orellana, Mónica, Alcaraz Romo, Lorena, Arévalo Cid, Pablo, de la Puente Viedma, Carlos, Donald Rivera, Minerva, Boulahya, Khalid, Fernández González, Mario, Martín Majadas, Raul, Parra Núñez, Pablo, Espada Morán, Luis, Martínez García, Marina, and González Izquierdo, Jesús

Abstract

Diseño, elaboración y procesado de vídeos en los que se incluye la metodología empleada en una investigación avanzada.

Published
2016

43. Aprendizaje de la Química con soporte material y virtual

Author

Isasi Marín, Josefa, Alba Isasi, Teresa, Pradillo Orellana, Mónica, Alcaraz Romo, Lorena, Arevalo Cid, Pablo, de la Puente Viedma, Carlos, Criado García, Rosario, Donald Rivera, Minerva, Boulahya, Khalid, Fernandez Gonzalez, Mario, Isasi Marín, Josefa, Alba Isasi, Teresa, Pradillo Orellana, Mónica, Alcaraz Romo, Lorena, Arevalo Cid, Pablo, de la Puente Viedma, Carlos, Criado García, Rosario, Donald Rivera, Minerva, Boulahya, Khalid, and Fernandez Gonzalez, Mario

Abstract

El estudio de la Química básica resulta en ocasiones difícil de abordar. Una gran mayoría de estudiantes aprenden los conceptos a base de memorizarlos, sin detenerse a buscar la manera de relacionarlos. El diseño y elaboración de una temario básico e interactivo que facilite el proceso de enseñanza-aprendizaje en esta materia ha sido el objetivo perseguido a la hora de realizar este trabajo.

Published
2015

47. Structure evolution with Sr content of the perovskite-like materials La2-xSrxCoTiO6 (0 ≤x≤ 0.5)

Author

Ministerio de Ciencia e Innovación (España), Gómez-Pérez, Alejandro, Pérez-Flores, Juan Carlos, Ritter, Clemens, Boulahya, Khalid, Castro, Germán R., García-Alvarado, Flaviano, Amador, Ulises, Ministerio de Ciencia e Innovación (España), Gómez-Pérez, Alejandro, Pérez-Flores, Juan Carlos, Ritter, Clemens, Boulahya, Khalid, Castro, Germán R., García-Alvarado, Flaviano, and Amador, Ulises

Abstract

The oxide series La2-x Sr x CoTiO6 (0 ≤ x ≤ 1.0) belong to the perovskite family with general formula ABO3. The evolution of the room-temperature structure as a function of the Sr content was studied using complementary techniques by applying the symmetry-adapted modes formalism (AMPLIMODES). In the compositional range presented in this article (0 ≤ x ≤ 0.5), the compounds adopt distorted perovskite structures of monoclinic (space group P21/n) or orthorhombic (space group Pnma) symmetry, both with octahedral tilting scheme (a - a - c +) (out of phase along two perovskite main directions and in phase along the third direction). The main difference between these structures is the existence of rock-salt order of B ions in the monoclinic symmetry, which is lost for x ≥ 0.30. As the Sr content increases, a better matching of the A - O and B - O distances occurs. This is produced by an elongation of the A - O distance as La3+ is replaced by the larger ion Sr2+, and the shortening of the B - O distance due to the oxidation of Co2+ to Co3+ induced by the aliovalent substitution. As a result, the cuboctahedral A-site cavity becomes less and less distorted; the A ion tends to occupy its ideal positions, increasing its coordination and giving rise to a more symmetrical structure. In the whole compositional range, the symmetry-adapted atomic displacements (modes) responsible for the out-of-phase tilting of the BO6 octahedra remain active but those associated with the in-phase tilting become negligible, anticipating for x ≥ 0.6 a transition to a new structure with tilting scheme either (a 0 a 0 c -) (space group I4/mcm) or (a - a - a 0) (space group Imma) or (a - a - a -) (space group R3c). © 2014.

Published
2014

48. New Instrumentation for TEM Electron Diffraction Structure Analysis: Electron Diffractometry Combined with Beam Precession

Author

Stavros Nicolopoulos, Jean-Luc Delplancke, Alexey Kuligin, Kiril Kuligin, Anatoly Avilov, Boulahya Khalid, Gregory Lepeshov, Maximilian S. Nickolsky, and Arturo Ponce

Subjects
Materials science, Reflection high-energy electron diffraction, Electron diffraction, Electron crystallography, Spinel, Resolution (electron density), Analytical chemistry, engineering, Electron, Atomic physics, engineering.material, Beam (structure), Electron backscatter diffraction
Abstract

Electron diffractometry has been used in the past in combination with electron diffraction cameras (EDC) and has been prooved very succesfull for electron crystalography work; by measuring electron diffraction intensities with high precision ( up to 1 %) structure resolution of many minerals with even refined light atoms like H,O positions has been resolved this way. We are reporting for the first time a new generation of electron diffractometry equipment (combined with beam precession technique to avoid dynamical interactions). The device could be pontentially interfaced to any commercial TEM in order to measure precisely ED data and resolve structures of nm size. The technique has a strong potential for electron crystallography as any voltage TEM may be used (> 100 kv); preliminary results are presented with a case study where light lithium atoms are revealed in a spinel structure.

Published
2006

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