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Seminars and Events

Seminars and Events

PhD Thesis


03 September 2021, 10:30 h. online

EUTECTIC MIXTURES RESULTING FROM DILUTION OF DEEP EUTECTIC SOLVENTS: TOOLS FOR CHARACTERIZATION

Huan Zhang
Bioinspired Materials Group

Supervisor(s): Prof. Francisco del Monte & Dra. María Concepción Gutiérrez

This thesis focuses on the research of DESs and its mixtures with different solvents for the determination of its eutectic composition and the dilution range of the so-called “solvent-in-DES” regime, that is, the dilution of DESs where their intriguing features remain but some of their typical drawbacks (e.g., high viscosity, low electrical conductivity, etc.) are mitigated. Therefore, the knowledge of tools for the prediction (and eventually extending) of the dilution range of the “solvent-in-DES” regime is obviously of interest. To this aim, differential scanning calorimetry (DSC), 1H nuclear magnetic resonance (NMR) and Brillouin spectroscopies of DES solutions as well as the excess molar volume and the deviation in viscosity (calculated from density and viscosity measurements) of the different mixtures were evaluated. Besides, we analyzed an interesting question that arises for DES dilutions related to if DESs themselves should be considered as a mixture of two components or as a pseudo-component. The different treatment yields different results for the determination of their thermodynamic properties that have been used to understand microscopic structures and solute-solvent interactions between DES components and also to predict the dilution range where DES dilutions can better perform in different applications.

Link





26 July 2021, 17:00 h. Salón de Actos

Novel Developments and Applications of
Bimodal Atomic Force Microscopy and 3D-AFM

Simone Benaglia
ForceTool group

Supervisor(s): Ricardo Garcia

Understanding surface and interfacial properties of materials is fundamental to employ them for novel applications. The Atomic Force Microscope is one of the most versatile tools for that purpose. Among the different AFM techniques developed so far, dynamic modes stand out for their flexibility. Dynamic AFM methods consist of an oscillatory excitation of the AFM cantilever [1]. Recently, novel advanced dynamic AFM techniques have been developed with three general purposes: (i) higher sensitivity, (ii) faster acquisition time, (iii) ability to analyse material properties not accessible before. In particular, bimodal AFM and 3D-AFM are the advanced dynamic methods of interest. Bimodal AFM is a multifrequency AFM technique based on the simultaneous excitation of two eigeinmodes of the AFM cantilever. Here, it is shown how it can be applied to unravel different types of elastic and viscoelastic properties of soft matters at the nanoscale. The reliability of the technique was verified on test samples; then, bimodal AFM was applied to understand the mechanical behaviour of organic electronic materials. 3D-AFM is a volume AFM technique that allows to obtain an atomic resolution of a three-dimensional space. In particular, it can be used to visualize the solid-liquid interface (SLIs) of a variety of liquids on surfaces of different nature with sub-nm resolution. 3D-AFM was employed to map the particular behaviour that hydrophobic layered materials have in contact with water. Moreover, the technique was used to visualise the SLI of highly concentrated solutions in contact with charged surfaces





20 July 2021, 10:30 h. online

ENHANCING THE PERFORMANCE OF CARBON/CARBON SUPERCAPACITORS VIA AQUEOUS SOLVENT-IN-SALT ELECTROLYTES

Xuejun Lu
Bioinspired Materials Group

Supervisor(s): Prof. Francisco del Monte & Dra. María Concepción Gutiérrez

This Thesis is devoted to study various combinations of new aqueous electrolytes not only in terms of selection and synthesis of salts and solvents but also interaction mechanisms. The so-called aqueous eutectic-in-salt (AEIS), bi-solvent in zwitterionic-based protic ionic liquids (BS-in-ZPIL) and tri-solvent-in-salt (TSIS) have been exhaustively studied and efforts have been taken to demonstrate the formation and evolution of the different concentrated solvation species and electrochemically active hydrogen bond complex structures following by techniques (such as Raman and NMR spectroscopies, and MD simulations) with the aim of developing low cost and excellently functional electrolytes,. Ultimately, this essay is dedicated to present the high attractiveness of designing new and low-cost aqueous electrolytes that offered an improved performance.

Link





14 July 2021, 12:00 h. Salón de Actos

Caracterización física y láser de monocristales de granates desordenados tipo Ca3(NbGa)5012 dopados con Yb+3

Jorge Omar Álvarez Pérez


Supervisor(s): Carlos Zaldo

Se aborda un estudio detallado de las propiedades físicas de los granates de Calcio-Niobio-Galio (CNGG) y de las propiedades espectroscópicas y láser del Yb3+ en este tipo de monocristales que, mediante el empleo de una metodología diferente a la encontrada en la literatura, puede ayudar a optimizar el rendimiento láser





07 July 2021, 11:00 h. Salón de Actos

Orbital Selective Spin-Fluctuations physics in iron-based superconductors

Raquel Fernández Martín
Universidad Autónoma de Madrid (UAM)

Supervisor(s): Belén Valenzuela Requena y Laura Fanfarillo

There is no temperature below absolute zero. Researchers have tried to reach this lower limit and this has led to the discovery of new physical phenomena, e.g. superconductivity, which understanding is still unknown. Since its discovery, hundreds of new superconductors have been found. In this Thesis we focus on the family of iron-based superconductors (IBS). Although the crystallographic and electronic structures are very similar in these materials, they present a very different phenomenology. The development of a theory that can explain the complex phenomenology of IBS within a common framework is one of the most important theoretical challenges in the field.

This Thesis shows how the diverse phenomenology of various families of IBS can be understood within a common framework: the Orbital Selective Spin Fluctuations scenario. Thanks to the orbital selectivity of the magnetic excitations of the system, a spin-orbital interplay arises in the magnetic susceptibility, superconducting gaps and velocity and the scattering rate in the nematic phase of IBS. This model has been extensively used to study the phenomenology of FeSe and 122 systems. The generalization to a five-pockets model, also performed in this Thesis, put the basis to exploit this model to analyze more IBS compounds.

Beyond IBS, orbital selectivity might also appear in other compounds in which the multiorbital character has a significant role to play. Without doubt, there are numerous avenues where orbital selectivity may play an important role, leaving many possibilities to be explored.





29 April 2021, 11:00 h.

Estudio del efecto del desorden en las propiedades fotónicas de materiales autoensamblados.

Jose Ángel Pariente
ICMM-CSIC

Supervisor(s): Ceferino López
Álvaro Blanco

Enlace
Código de acceso: 168538

Esta tesis doctoral trata sobre la explotación de las propiedades fotónicas de sistemas autoensamblados con el fin de caracterizar dos fenómenos físicos fundamentales: las transiciones de fase y la introducción de desorden en materiales nanoestructurados.





23 April 2021, 11:00 h. Sala de Seminarios, 182

Dinámica resuelta en tiempo de una única pared de dominio y procesos de imanación en microhilos magnéticos

Esther Calle Ramírez
Instituto de Magnetismo Aplicado Salvador Velayos

Supervisor(s): Rafael Pérez del Real
Manuel Vázquez Villalabeitia

El control del desplazamiento de paredes de dominio a lo largo de nanoestructuras magnéticas es un tema que ha cobrado interés en los últimos años por su importancia para el desarrollo de nuevos dispositivos espintrónicos y memorias, en los cuales la velocidad de operación está determinada por la velocidad de propagación de estas paredes.
Los microhilos magnéticos estudiados en esta tesis son materiales amorfos que poseen una estructura muy particular de dominios, relacionada con la elevada anisotropía magnetoelástica que se induce durante su proceso de fabricación y que hace posible el estudio de la dinámica de propagación de una única pared.
Esta tesis se ha centrado en el estudio y control de la dinámica resuelta en tiempo de la pared de dominio en microhilos altamente magnetostrictivos. Usando el efecto Mateucci intrínseco que presentan microhilos amorfos de magnetostricción positiva, se ha desarrollado un método de medida de la velocidad de la pared con resolución temporal que ha permitido identificar los procesos de nucleación, aceleración y propagación de la pared bajo la aplicación de un campo constante. Asimismo, se ha inducido el frenado local de la pared de dominio y estudiado el movimiento de paredes inyectadas en el microhilo bajo la aplicación combinada de un campo de propagación uniforme y un campo local no homogéneo, obteniendo que para campos mínimos del orden del campo de fricción se produce un atrapamiento estocástico de la pared que ha sido atribuido al carácter dinámico del campo de fricción. El estudio del movimiento alterno de la pared ha puesto de manifiesto la importancia de su inercia, determinando la existencia de un rango de frecuencias crítico por encima del cual la pared oscila sin llegar a detenerse, como cabría esperar por efecto de la fricción. Por último, se ha puesto de manifiesto la capacidad de emplear una corriente eléctrica aplicada al microhilo para inducir y controlar el movimiento de la pared de dominio, a partir de la interacción entre el campo Oersted generado por la corriente en el interior del hilo y la componente azimutal de la imanación.





22 April 2021, 11:00 h. online

Studies on secondary electron emission induced charging in dielectric materials: Novel methods and applications for space and plasma technologies

Leandro Olano García
Universidad Autónoma de Madrid

Supervisor(s): Isabel Montero y María Eugenia Dávila

Link





26 March 2021, 11:00 h. Salón de Actos

Fenomenos de orden-desorden en oxidos con estructura tpo rutilo y su aplicación como soportes en catalizadores heterogéneos

Jon Canca Ruiz
Universidad Autónoma de Madrid

Supervisor(s): Fernando Agulló Rueda y Jorge Hernández








     

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