Papers by Luis Miguel Varela Cabo
The 24th International Electronic Conference on Synthetic Organic Chemistry, 2020
In this work, viscosity, density and electrical conductivity of the ionic liquid, Ethylimidazoliu... more In this work, viscosity, density and electrical conductivity of the ionic liquid, Ethylimidazolium Nitrate pure and doped with lithium nitrate salt were determined in order to check the properties' improvement of the ionic liquid with the salt addition to consider these mixtures as potential electrolytes. Viscosity decreases exponentially as temperature increases, and increases with salt content, as expected. Density values decrease linearly as temperature increases and also increases with salt content. From electrical studies, an increase of conductivity with temperature and a decrease with salt concentration were observed. No significant differences between pure and doped sample were observed on Walden plots.
The 24th International Electronic Conference on Synthetic Organic Chemistry, 2020
Ionic liquids (ILs) represent a real alternative for electrochemical applications due to their re... more Ionic liquids (ILs) represent a real alternative for electrochemical applications due to their remarkable characteristics, namely a very low vapour pressure, low flammability, high thermal stability, wide potential window and high ionic conductivity. In this work, Nyquist plot and impedance spectroscopy at room temperature is proposed as an alternative method to obtain the ionic conductivity for ionic liquids by using an Agilent HP 4284A RLC precision meter. For this propose, the IL 1-butyl-3-methylimidazolium tetrafluoroborate (C4C1Im BF4) was selected and results were compared with the previously obtained from the conductimeter CRISON GLP31.
La relacion entre las propiedades macroscopicas que presenta un material con su estructura intern... more La relacion entre las propiedades macroscopicas que presenta un material con su estructura interna es uno de los objetivos principales de la Fisica de Materiales. En concreto, los modelos que explican las propiedades de las mezclas electroliticas se han de basar necesariamente en un modelo estructural concreto. Este modelo, cuyos principales resultados se resumen en las ecuaciones de Nerst-Einstein y la de Debye-Hucker-Onsager, es perfectamente valido para electrolitos muy diluidos, pero falla a medida que estos se van saturando de sales. Este es el caso de los liquidos ionicos (LIs), que son sales puras en estado liquido a temperatura ambiente, a las que se le pueden anadir disolventes que cambiaran drasticamente sus propiedades (sobre todo las de transporte). A finales del siglo pasado se publico una primera version de un modelo pseudo-reticular para explicar la microestructura de una sal saturada que pronto se extendio al estudio de los liquidos ionicos. Posteriormente, en divers...
International Journal of Molecular Sciences, 2021
This paper presents a comprehensive study of two alkylammonium nitrate ionic liquids. As part of ... more This paper presents a comprehensive study of two alkylammonium nitrate ionic liquids. As part of this family of materials, mainly ethylammonium nitrate (EAN) and also propylammonium nitrate (PAN) have attracted a great deal of attention during the last decades due to their potential applications in many fields. Although there have been numerous publications focused on the measurement of their physical properties, a great dispersion can be observed in the results obtained for the same magnitude. One of the critical points to be taken into account in their physical characterization is their water content. Thus, the main objective of this work was to determine the degree of influence of the presence of small quantities of water in EAN and PAN on the measurement of density, viscosity, electrical conductivity, refractive index and surface tension. For this purpose, the first three properties were determined in samples of EAN and PAN with water contents below 30,000 ppm in a wide range of...
Chemistry Proceedings, 2020
Ionic liquids represent a viable option as electrolytes for electrochemical applications such as ... more Ionic liquids represent a viable option as electrolytes for electrochemical applications such as energy storage devices, due to their high ionic conductivity and wide electrochemical window. However, liquid electrolytes present important problems of safety and performance, and encapsulation in a solid matrix can be a good solution to improve it. In this work, changes in the structure of the mixtures of ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide against the concentration of the salt (0, 0.1, and 1.5 molal), and the effect of nanoconfinement through gelation process were studied using NMR technique.
Proceedings, 2019
Current electrolytes for electrochemical energy storage devices are made of solvents, which often... more Current electrolytes for electrochemical energy storage devices are made of solvents, which often present problems of flammability, corrosion and high toxicity. Ionic liquids and mixtures with metal salts are proposed as a good selection for safer electrolytes due to their properties such as, among others, non-flammability, negligible vapor pressure, high ionic conductivity and wide electrochemical window. In this work, the electrical conductivity of solutions of the ionic liquid 1-ethyl-3-methylimidazolium nitrate ([EIm][NO3]) with lithium nitrate salt in three different concentrations is analyzed for liquid and gel states. The temperature and salt concentration dependences of electrical conductivity are studied for liquid and gel states. As expected, an increase in conductivity with temperature and a decrease with salt concentration were observed, except for the case of gel [EIm][NO3] with a salt concentration of 0.5 m, which shows a small increase in conductivity compared to the ...
Proceedings, 2019
The ionic liquids (ILs) doped with metal salts have become a real alternative as electrolytes for... more The ionic liquids (ILs) doped with metal salts have become a real alternative as electrolytes for batteries, but the right choice of these compounds for reaching the adequate properties and performance is still a challenge, and strategies are therefore needed for achieving it. The thermophysical properties of IL 1-butyl-1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide ([bmpyr] [TFSI]) and its mixture with bis-(trifluoromethane)-sulfonimide lithium salt (from 0.1 m to saturation level) were determined in this work. These properties are density (ρ), speed of sound (U), and corresponding derived magnitudes, such as the bulk modulus and the thermal coefficient, as well as electrical conductivity (σ) against temperature. Density shows a linear decreasing dependence with temperature and a clear increase with the addition of salt, whereas the thermal expansion coefficient increases with temperature and salt addition. Speed of sound decreases with both temperature and salt concentr...
Physical chemistry chemical physics : PCCP, Jan 6, 2018
We present large scale polarizable simulations of mixtures of the ionic liquids 1-ethyl-3-methyli... more We present large scale polarizable simulations of mixtures of the ionic liquids 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-ethyl-3-methylimidazolium dicyanamide with water, where the dielectric spectra, the ion hydration and the conductivity were evaluated. The dielectric decrement, the depression of the dielectric constant of water upon addition of ions, is found to follow a universal functional of Langevin type. Only three physical properties need to be known to describe the complete range of possible concentrations, namely the dielectric constant of pure water, of pure ionic liquid and the linear slope of the dielectric decrement at low ionic liquid concentrations. Both the generalized dielectric constant, as well as the water contribution to the dielectric permittivity follow the functional dependence. We furthermore find that a scaling of van der Waals parameters upon addition of polarizable forces to the force field is necessary to correctly describe the frequ...
Proceedings of The 20th International Electronic Conference on Synthetic Organic Chemistry, 2016
Thermal analysis techniques (DSC and TG) were used to characterize the melting and crystallizatio... more Thermal analysis techniques (DSC and TG) were used to characterize the melting and crystallization temperatures as well as the thermal stability of the ionic liquid ethylammonium nitrate. A detailed analysis of the solid-liquid transition is reported monitoring cooling-heating cycles by means of differential scanning calorimetry (DSC) and thermogravimetric balance, in the interval extending from-75 ºC to 100 ºC. The observed melting and solidification temperatures are in good agreement with previously reported ones in electrical conductivity analysis, and a novel cold crystallization at-40 ºC. The thermal analysis confirms the rich phase behaviour of a good glass-former, with a cold crystallization upon heating and a quite large supercooled region (-28, 17) ºC. Moreover, a fairly good thermal stability was detected by means of the thermogravimetric analysis up to 140-160 ºC, although the onset temperatures both in air and nitrogen atmospheres were found to lie well above this value.
Proceedings of The 18th International Electronic Conference on Synthetic Organic Chemistry, 2014
In this communication the synthesis and physical properties of the new ionic liquid 1ethyl-3-meth... more In this communication the synthesis and physical properties of the new ionic liquid 1ethyl-3-methyl imidazolium decyl sulfate, are shown. The interest of this new salt lies in its tendency to jellify when it is exposed to the atmosphere by absorbing water from moisture up to about a 10% of its own mass; then it keeps the mass ±2% stable depending on the atmospheric humidity grade. The rigid-gel state appears from 15 ºC to 60 ºC. Below 15 ºC it crystallizes and above 60 ºC it liquefies. According to TGA measurements the compound is stable up to 300ºC. The compound 1-ethyl-3-methyl imidazolium decyl sulfate was prepared in two steps. First the alkylation of 1-methylimidazole with diethyl sulfate afforded 1-ethyl-3-methylimidazolium ethyl sulfate. Then a later transesterification reaction allowed to obtain the desired 1-ethyl-3-methyl imidazolium decyl sulfate with high yield and purity. Its structure was confirmed by 1 H, 13 C NMR. Also we performed IR spectroscopy as well as Mass Spectrometry. The FTIR spectrum of this new compound, and the temperature behavior of some physical properties such as electrical conductivity, viscosity, density and refractive index, will be presented.
Documentos De Traballo Analise Economica, 2009
El presente trabajo analiza la evolucion del gasto farmaceutico en Galicia en los ultimos anos, a... more El presente trabajo analiza la evolucion del gasto farmaceutico en Galicia en los ultimos anos, asi como los distintos factores que inciden sobre el. El incremento constante de este capitulo, en torno al 8,5% anual, amenaza la sostenibilidad del sistema y hasta la fecha ninguna de las medidas establecidas ha modificado esta tendencia. La causa principal de esta situacion es la capacidad de la industria farmaceutica para asegurarse un mercado creciente mediante la continua introduccion de nuevos medicamentos, cuya aportacion terapeutica sobre los antiguos es generalmente escasa o nula.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008
In the present paper, we formulate a statistical mechanical framework of amphiphilic self-assembl... more In the present paper, we formulate a statistical mechanical framework of amphiphilic self-assembly that allows a proper understanding of surfactant self-association processes on the basis of an occupation number formalism. In this model, amphiphilic molecules in solution can occupy different levels of well-defined energies corresponding to aggregates of different aggregation numbers. Due to its definition, the occupation number of a
Lecture Notes in Economics and Mathematical Systems, 2016
This chapter aims at reviewing complex network and nonlinear dynamical models and methods that we... more This chapter aims at reviewing complex network and nonlinear dynamical models and methods that were either developed for or applied to socioeconomic issues, and pertinent to the theme of New Economic Geography. After an introduction to the foundations of the field of complex networks, the present summary introduces some applications of complex networks to economics, finance, epidemic spreading of innovations, and regional trade and developments. The chapter also reviews results involving applications of complex networks to other relevant socioeconomic issues.
Book of abstracts of the ILMAT IV. 4th International Conference on Ionic Liquid-based Materials, ... more Book of abstracts of the ILMAT IV. 4th International Conference on Ionic Liquid-based Materials, organized by Universidade da Coruna and Universidade de Santiago de Compostela on 24-27 october 2017 in Santiago de Compostela
En la tesis doctoral titulada "Estudio teorico del equilibrio y del transporte de disolucion... more En la tesis doctoral titulada "Estudio teorico del equilibrio y del transporte de disoluciones de fluidos cargados complejos en la aproximacion de campo medio" presentada por D. Luis Miguel Varela Cabo para la obtencion del grado de Doctor en Fisicas, se realiza una extensa revision de las diversas teorias de equilibrio y de transporte de fluidos ionicos disenadas a lo largo del siglo XX, desde las teorias de campo medio clasicas de Debye-Huckel y de Fuoss-Onsager, a los formalismos estadisticos de funciones de correlacion de los mismos, basados en la resolucion de la ecuacion de Ornstein-Zermike. El objeto central de la tesis es el analisis de la teoria de campo medio exacta de fluidos cargados denominada Teoria del Ion Vestido (DIT). Las contribuciones de la tesis doctoral a este formalismo son la obtencion de la relacion del parametro funcional fundamental de la DIT, la funcion de respuesta lineal, mediante su relacion con el factor estatico de estructura del sistema, y...
In spite of being one the most remarkable and arresting products of late-twentieth-century Britis... more In spite of being one the most remarkable and arresting products of late-twentieth-century British popular culture, Pink Floyd’s The Wall has received little scholarly attention. This paper focuses on how in The Wall and in its companion album, The Final Cut, the individual life history and the present predicament of its protagonist stand for the postwar period in British history as a whole. The latter represent the identitary crossroads at which the nation was placed after the collapse of the welfare state system and the major socio-economic and political transformation it underwent at the dawn of Thatcherism. In order to show this, we draw an outline of the historical context in which The Wall is inscribed and attend closely to the film’s complex temporal structure and rich symbolism. We conclude with a brief discussion on how The Wall leaves in sketch an alternative to the present situation which is based on a retrieval of interhuman affects and on justice as the supreme politica...
Revista Galega De Economia, 2012
Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto
Revista Galega De Economia, 2012
In this contribution we will show that the mainstream of contemporary economics, after its initia... more In this contribution we will show that the mainstream of contemporary economics, after its initial development in XIXth century analytical and conceptual framework of classical Physics, is still anchored to its conceptual core, the general equilibrium theory, neglecting the evolution of physics itself towards the treatment of complex systems, and even the nature of its own knowledge object. For that, after a short summary of classical physics formalism and of the own neoclassical economics, we will analyze the evolution of both disciplines throughout the last century, with particular attention being focused on the development of thermodynamics from its original equilibrium formalism until the formalization of the concept of dissipative structures in nonlinear thermodynamics. Finally, we outpoint some lines along which we consider the adaptation of economics to contemporary physics must be done.
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Papers by Luis Miguel Varela Cabo