Marisa Frechero

National Scientific and Technical Research Council | conicet

In this work the relationship between the structure of a solid ionic material and its ionic dynamics has been studied by impedance spectroscopy, differential scanning calorimetry and molecular dynamics simulation. Nanometric samples of AgI were synthesized to study the cation dynamics when it reaches its superionic behavior. The observed thermal ev...

When applying the Molecular Dynamics (MD) formalism to the short-time dynamics on a paradigmatic lithium metasilicate glass system, it reveals the major features of the mobility. Experimental evidence of the physical phenomenon known as the Nearly Constant Loss (NCL) can be attributed to the independent motion of a small proportion of uncorrelated...

As a result of the increasing need for highly efficient energy storage systems, Li-solid-state batteries emerge as the next-generation energy storage devices to satisfy high energy density and safety requirements. Particularly, solid polymer-based electrolytes have attracted attention as a promising alternative due to their high mechanical flexibil...

A family of doped-NASICON-type structures according to the chemical compositions: Li1.2 Zr1.9M0.1(PO4)3 [with M = Ca²⁺, Mg²⁺, Zn²⁺]; Li1.1 Zr1.9Y0.1(PO4)3 and Li1.0 Zr1.9Ce0.1(PO4)3 have been synthesized by solid state reaction. The modification on the thermal treatment proposed in this work makes possible to obtain a high purity phase confirmed by...

Energy solar harvesting through low environmental impact resources is an underlying objective for future technological developments. In this work, an innovative design of a vitro-metallic composite material is developed with Cu0, Zn0 and ZnO microparticles dispersed in a glass-ceramic matrix. The uppermost feature of these materials is that they ar...

el "1er Encuentro Nacional sobre Litio: hacia una política para el desarrollo integral". Este evento está dirigido a docentes-investigadores, estudiantes, empresas, industrias, representantes del Estado, organizaciones sociales, ambientales, y público en general de todo el país, con el propósito de generar un ámbito de debate científico y político...

Marisa A. Frechero Grupo de Fisicoquímica de conductores iónicos de estado sólido (GFQCIES) Departamento de Química, Universidad Nacional del Sur- INQUISUR-CONICET. Bahía Blanca, Buenos Aires. frechero@uns.edu.ar La Ciencia de los Materiales busca comprender las propiedades de los Materiales con el objeto de ampliar sus aplicaciones tecnológicas c...

El cuidado y la preservación del medio ambiente requiere de diversas metodologías para medir en qué grado la contaminación del hombre lo afecta. El cálculo de la Huella Ecológica y de la Huella de Carbono nos permiten determinar la superficie de tierra que se necesita para absorber todo aquello que producimos, desechamos y el CO2 emitido. En los úl...

The interactions between the [BMIM][PF6] -ionic liquid- and a phosphate glassy surface is studied through calorimetric, structural and impedance spectroscopy methods. A soft solid conductor material is obtained mixing the ionic glass powder with the ionic liquid in a low proportion (2 and 4%). At microscopic level, the interactions of this ionic li...

Physics Nobel Prize winner P.W. Anderson famously wrote in 1995: “The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of the glass and the glass transition”. Despite much effort in the intervening years, the problem is still unsolved. We contribute a novel mathematical approach to this problem...

The electrical behavior of a bismuth-phosphate glass lithium ion conductor is studied in a very wide temperature range, from 39 K to 843 K, encompassing the glassy state, passing through the glass transition temperature, and reaching devitrification. The relationship between the structural changes caused by the thermal treatment and the resulting e...

In this work a modified glassy micro-particles glucose sensor was developed applying a new and effective procedure to anchor glucose oxidase on glassy micro particles using urea medium. The resulting sensor, in the presence of glucose, generates a color development in 60 seconds working at room temperature. The intensity of the resulting color show...

New materials based on V2O5, TeO2 and a combination of graphite, graphene oxide and multiwalled carbon nanotubes were developed and tested as potential electrochemical sensors. A mixture design with three components in combination with multi-response assays based on the desirability function was used as multivariate optimization for the system comp...

Structural features of the glass family xLi2O- yMgO (4.8 Bi2O3 47.6 P2O5) obtained by melt quenching technique were studied taking into account the density, FTIR and UV–vis spectra and also the electrical response observed by impedance spectroscopy. In this work it becomes clarified how the alkaline earth oxides stabilize the glassy matrix and also...

Mixed alkaline-earth effect (MAEE) on the transition metal oxides (TMO)-tellurite glasses [TMO = MoO3, Nb2O5 and WO3] modified with BaO/MgO mix is analyzed to understand how feasible it is to tune structural and optical properties of a tellurite glass. Changes induced by the three transition metal oxides on the tellurite polyhedral produce some mod...

In this work, nitrogen-doped hierarchical porous carbon (NPC) was obtained from an effective and facile synthesis route based on metal-organic framework (MOF)-drive approach using Zr-metal-organic framework (UiO-66-NH2) as a template. The structural analysis of synthesized NPC using different heat treatment was performed through X-ray diffraction,...

Glasses formed by different oxides are of uppermost importance because they are developed for many applications in electronics, optics, biology, etc. Oxide glasses are built by a three-dimensional network of corner connected oxygen polyhedral that can be modified by the inclusion of other oxides such as transition metal oxides. In this work, the po...

Glasses formed by different oxides are of uppermost importance because they are developed for many applications in electronics, optics, biology, etc. Oxide glasses are built by a three-dimensional network of corner connected oxygen polyhedral that can be modified by the inclusion of other oxides such as transition metal oxides. In this work, the po...

When a liquid is quenched, a disordered solid is obtained. That solid can be a glass or a poly-crystalline material. If a glass is obtained, understanding the variation of time dependence of its physical properties-such as the glasses' structural relaxation-is crucial. The glass transition process is commonly associated with a frozen liquid structu...

Silver iodide (AgI) is one of the most extensively studied superionic conductors. In this work, we have applied the standard Buckingham pair potential and standard charge. For the first time the microscopic dynamic events that allow the achievement of the superionic transition are revealed. A collaborative effect among cations and anions that makes...

New mixed composite conductors of compositions: Li 3 V 2−x [Cu] x (PO 4 ) 3 /C and Li 3 V 2−x [Nb] x (PO 4 ) 3 /C (x = 0.1; 0.2 and 0.3) have been synthesized by the sol-gel method using Citric and Oxalic acids as a primary carbon source and Carbon Black or Carbon Nano-Fibers as secondary carbon sources. The combination of these carbon forms with t...

NiFe 2O4 spinel – phosphate (Bi-Ba-Li) glass composite was synthesized by solid-state reaction. New crystalline magnetic phases was developed inside the glassy matrix through a controlled heat treatment. New NF-LBPB4 magnetic nanocomposite material was study. Complex impedance analysis has shown that mobile ions inside the matrix induce the develop...

Lithium borate glasses modified with molybdenum oxide according to the formula: xMoO3 (1-x)[0.25 Li2O 0.75 B2O3] prepared by the melt quenching technique were studied. Density, differential thermal analysis, FTIR and impedance spectroscopic were used to analyze these systems. It was confirmed that the glassy matrix of these systems was based on the...

Oxide glasses are the oldest ever-known glasses. Probably, silicate glasses are the most ancient material of industrial interest. However, glasses formed by another kind of oxides are of uppermost importance because of the special properties which they are able to develop for many applications in electronics, optics, biology, etc. Every oxide that...

En este trabajo se ha diseñado un material innovador que permite la transformación de la luz solar en energía calórica con alta eficiencia, consiguiendo además, cumplir un doble propósito: reaprovechar desechos industriales (parabrisas de automotores y cenizas)y contribuir al cuidado del medioambiente mediante el desarrollo de un nuevo método de ge...

Green Energy sources Lithium in Argentina Glassy electrolytes Hybrid electrolytes Batteries’ prototipes

Atomic Resolution STEM-EELS Studies of Defects and Local Structural Distortions in Oxide Interfaces - Volume 23 Issue S1 - G. Sánchez-Santolino, M. A. Roldan, Qiao Qiao, L. Begon-Lours, M. A. Frechero, J. Salafranca, R. Mishra, C. Leon, S. T. Pantelides, S. J. Pennycook, J. E. Villegas, J. Santamaría, M. Varela

The reinforcement of the ionic conductivity in a lithium-vanadium-molybdenum tellurite glass is possible by modified with zinc oxide {0.7 [x ZnO (1− x) Li2O] 0.3 [0.5 V2O5. 0.5 MoO3]. 2TeO2}. Structural features induced by zinc cation on the glassy matrix have a positive effect on the electrical behavior of the modified glass. The electrical respon...

The world demand for new alternatives of energy storage has inevitably led the scientific and technological community to develop new devices that must have an environmentally clean, efficient performance, and renewable use for a sustainable development. Considering this scenario, lithium ion batteries play a leading role today. In this chapter, we...

A new modified lithium-phosphate glass has been obtained by environmentally friendly components. This glass has provided a remarkable lithium ion solid electrolyte. Frequency-dependent electrical data of several lithium-phosphate glass compositions has been discussed in the framework of the electric modulus representation. The origin of the non-Deb...

Electrical response changes due to the incorporation of alkaline-earth oxides in the vanadium–molybdenum tellurite glassy matrix have been studied. The results are explained by analyzing the electric formalisms representations. A non-straightforward relationship to the modifier oxide ionic radius was found and the results suggest poor charge carrie...

Glasses of composition 0.8 [xBaO.(1 − x)MgO]. 0.2TM.2TeO2 with TM: MoO3, WO3, V2O5 or Nb2O5 (x = mol content) were obtained by the melt quenching technique. Raman Spectroscopy, Density and Differential Scanning Calorimetry were used to infer their microscopic structure and electrical properties were studied using Impedance Spectroscopy. Some singul...

We evaluate the distribution of female physicists in the Argentinean workforce, analyzing the distribution of women at different levels of education and research using several indicators. Although important imbalances still occur, our findings are encouraging and the distribution of female physicists seems to be changing for the better.

The blocking of ion transport at interfaces strongly limits the performance of electrochemical nanodevices for energy applications. The barrier is believed to arise from space-charge regions generated by mobile ions by analogy to semiconductor junctions. Here we show that something different is at play by studying ion transport in a bicrystal of yt...

From the results of molecular dynamic simulations of lithium metasilicate glass–at temperatures above and below their transition temperature ( )–we propose a simple graphical representation to search for the broken ergodicity in an ionic oxide glass. Knowing when ergodicity is lost is critical for the proper use of statistical mechanics as a tool f...

In this paper we present the study of the glassy systems of formula: xMgO(1 − x)(0.5V2O5·0.5MoO3)2TeO2, with (0 < x < 1). The aim of the work is to understand the relationship between in the induced changes in the glassy matrix by the incorporation of MgO in a vanadium–tellurite glass and the electrical response of the material. It has been found t...

Monolayers of n-eicosane phosphonic acid, EPA, were studied using a Langmuir balance and a Brewster angle microscope at different subphase pH values to change the charge of the polar headgroups (Zav) from zero to -2. Molecular dynamics simulations (MDS) results for Zav = 0, 1 and 2 were compared with the experimental ones. EPA monolayers behave a...

Performing Molecular Dynamic simulations and using the isoconfigurational ensemble method, we studied the effect of the potassium cation replacing the half part of lithium ions in glassy Li2SiO3. This so-constructed glassy system has the main ingredients present in an immediate forthcoming definition of mixed alkali effect (MAE) in glasses. We show...

El objetivo principal es explorar las energías renovables con nuevos sistemas de generación y mínimos efectos medioambientales. En este contexto, el diseño de un generador eléctrico de flujo transversal con imanes permanentes posee una geometría modular ideal para analizar la aplicación de materiales nanocristalizados que permitirían menor pérdida...

We compute for an archetypical glass-forming system the excess of particle mobility distributions over the corresponding distribution of dynamic propensity, a quantity that measures the tendency of the particles to be mobile and reflects the local structural constraints. This enables us to demonstrate that, on supercooling, the dynamical trajectory...

We summarize recent studies of oxide ion dynamics in ionically conducting defect pyrochlores of general formulae Ln2Ti2−yZryO7. Unit cell volume, structural disorder, and ion–ion interactions, are all relevant in determining ion hopping probability and thus the mobility of oxide ions at high temperatures. At enough low temperatures ion hopping is s...

In this work, we suggest an explanation of the electrical conductivity behavior of tellurite glassy systems modified with barium when transition metal oxides (V2O5-MoO3) present in the glassy matrix are replaced progressively by barium oxide. These glasses of formula x BaO (1 − x) (0.5V2O5 · 0.5MoO3) 2 TeO2 are obtained by the standard quenching te...

In the context of the ionic transport in glasses, the concept of conduction channels (or pathways) has proved to be useful to rationalize both experimental and computational results. While the concept of a transport “channel” is well defined for crystalline solid conductors, for the case of glasses this concept mainly refers to a finite region of t...

In this paper we study the structural and electrical behavior of glass-ceramic material of general formula: xMgO (1-x) (0.5V2O5.0.5MoO3)2TeO2 (0≤x≤0.9) through measurements of density, molar volume, oxygen packing density (OPD), differential scanning calorimetry (DSC) and Raman spectroscopy: electric behavior was studied by impedance spectroscopy....

This chapter is devoted to show our research results on glassy systems (made with mixtures of oxides) where the main objective is to improve not only the ionic conductivity but also some other physical properties of the glassy matrix, e.g. glass transition temperature (T g), enthalpy of matrix relaxation and stress reduction during the synthesis, i...

The nature of the glass transition, that is, the dramatic dynamic slowing down that a glass-forming system experiences when supercooled below its melting point, continues to be one of the major open questions in condensed-matter physics. To elucidate the physical underpinnings of such slowing down, we compute for an archetypical glass-forming syste...

We present ac conductivity spectra of tellurite glasses at several temperatures. For the first time, we report oscillatory modulations at frequencies around MHz. This effect is more pronounced the lower the temperature, and washes out when approaching the glass transition temperature $T_g$. We show, by using a minimal model, how this modulation may...

In this paper, we analyze using differential scanning calorimetry (DSC) how a disordered structure, obtained by the quenching of oxides melted into glass, is related to the nature of the modifier cation. We estimated the enthalpy relaxation in based tellurite oxide glasses of formula xM2O (1−x)(0.5 V2O5·0.5MoO3) 2TeO2 when they are modified with un...

Surprisingly, there is not a complete and general working theory for the ionic conduction on structurally disordered inorganic solids at present. In this context, lithium metasilicate glasses appear as paradigmatic and they have been extensively used for investigation in order to identify the main ingredients for a working theory of ionic conductin...

It has been proposed that disk-like micelles may be precursors to the formation of lamellar liquid crystals. The possibility of obtaining n-decane phosphonic acid (DPA) disk-like micelles in aqueous solution without the addition of a second ionic surfactant led us to study in detail the low-concentration range of this system by both a battery of ex...

Data collected 10 years ago in Argentina concluded that women in physics were underrepresented in many instances and that a "crystal ceiling" was firmly in place. We have collected updated data for several indicators and compared them with those obtained 10 years ago. Although there is not a clear conclusion to be drawn from this comparison, we try...

The demand for batteries with high energy densities has inevitably led to the research and development of systems involving thermodynamically more stable than aqueous electrolytes. In this chapter, we review our results of the last ten years research in tellurite glassy systems where the main ionic carrier is the Lithium cation. The main objectives...

The aggregation properties of 2-, 3-, and 4-fluorobenzoic acids (2FBA, 3FBA, and 4FBA, respectively) and their salts with hexadecyltrimethylammonium cations (HTA2FB, HTA3FB, and HTA4FB) in water were studied with a battery of techniques. Their activity at the air/solution interface has been also studied. The position of the fluorine atom in the aci...

Here we show impedance spectroscopy measurements on a bicrystal of the ionically conducting yttria stabilized zirconia (YSZ). By using micrometer sized electrodes it is possible to measure ionic transport perpendicular to a single grain boundary, and characterize its electrical properties. We are thus able to obtain the microscopic parameters that...

In the context of the ionic transport in glasses, the concept of conduction “channels” (or pathways) has proved to be useful to rationalize both experimental and computational results.While the concept of transport channel is well defined for crystalline solid conductors, in the case of glasses the concept of transport channel is related to an ephe...

We study the structure and orientation of water molecules at model hydrophobic surfaces by means of molecular dynamics. We focus here on the role of geometry in water hydration by comparing the situation for a planar graphene sheet with convex surfaces with different curvature: the exterior surfaces of carbon nanotubes and fullerenes of different r...

The effect of the partial replacement of lithium oxide by silver oxide in a glassy vanadium–molybdenum–tellurite oxides matrix is analyzed by means of impedance spectroscopy. We find that a weak mixed mobile ion effect (MMIE) is due to the different kind of modifications silver and lithium oxides induce in the glass of formula 0.7[x Ag2O (1−x) Li2O...

Exhaustive nonredundant dataset of 2661 monomeric uncomplexed PDB-reported proteins lacking prosthetic groups or ion coordination. (4.10 MB DOC)

Soluble proteins must maintain backbone hydrogen bonds (BHBs) water-tight to ensure structural integrity. This protection is often achieved by burying the BHBs or wrapping them through intermolecular associations. On the other hand, water has low coordination resilience, with loss of hydrogen-bonding partnerships carrying significant thermodynamic...

Impedance spectroscopy of nickel manganite NiMn2O4 obtained from different synthesis routes

In this paper we present the structural, magnetic and dielectric properties of ceramic nickel manganite NiMn 2 O 4+δ produced by using nickel permanganate Ni(MnO 4) 2 xH 2 O as a precursor. We have characterized the NiMn 2 O 4+δ stoichiometry using quantitative energy-dispersive analysis of X-rays and thermal gravimetry under reducing conditions. I...

By means of molecular dynamics simulations we study the structure and dynamics of water molecules in contact with a model hydrophobic surface: a planar graphene-like layer. The analysis of the distributions of a local structural index indicates that the water molecules proximal to the graphene layer are considerably more structured than the rest an...

Amiodarone aqueous systems at concentrations C<or=3mg/mL were studied with different techniques (conductivity, solubility, ion-selective electrodes, pH, viscosity, polarizing microscopy, computational simulation, electron microscopy and fluorescence at various temperatures. The Krafft point (T(K)=70.6 degrees C) was determined. A partial phase diag...

The use of the isoconfigurational method has enabled one to determine the existence of particles with high and low dynamic propensity (tendency to be mobile) and particles with preferred directionality for motion (directional particles) in supercooled liquids. On the other hand, dynamical studies have shown that the relaxation of such systems evolv...

Supercooled liquids have been shown to be dynamically heterogeneous with different regions of the system presenting dynamics that vary from each other even by orders of magnitude. Computer simulations have confirmed such a picture by detecting that the mobile particles in model glass formers are not homogeneously distributed within the system but a...

Mesoporous titania was synthesized by a surfactant template route and was doped with Ag2O by treatment with AgNO3. Commercial anatase was also used as reference material. The obtained materials were characterized by nitrogen adsorption, scanning and transmission electron microscopy, solid state conductivity and X-ray diffraction. The inclusion of A...

The aim of the present paper is to give structural information in order to set a correlation between the electrical conductivity behavior and structures of lithium and silver vanadium–tellurite based glasses. We report our structural studies and compare the effect of the nature of the metallic cation on glasses of the form XM2O · (1 − X)V2O5 · 2TeO...

Dynamics in glass-forming liquids in the supercooled regime vary considerably from one point of the sample to another suggesting the existence of regions with different degrees of jamming. In fact, the existence of relatively compact regions with particles with an enhanced propensity for motion has been detected in model glassy systems. In turn, th...

In this work, we assess the relevance of different range particle displacements and string motions to the metabasin (MB) dynamics of a simple glass former. We find that MB transitions are triggered by the occurrence of massive rearrangements termed as “democratic clusters” or d-clusters which last on average less than 1% of the α-relaxation time. T...

The electrical properties of mixed ion-polaron conducting vanadium tellurite glasses of the form XLi2O·(1 − X)[0.5V2O5·0.5MoO3]2TeO2 have been studied by using the impedance spectroscopy in a wide range of temperature and composition. The obtained results confirm the existence of a transition from a typically electronic (polaronic) conductive regim...

The discovery that the propensity for particle motion in a supercooled liquid is completely determined by the initial structure pointed to the existence of a causal link between structure and dynamics in glassy systems. Here we demonstrate that this underlying influence of structure is only local in time, fading out beyond the metabasin lifetime mu...

Within the landscape approach the dynamical heterogeneities presented by model glasses at low temperatures have been shown to represent well-defined elemental activated events in the exploration of the potential energy surface, PES. This last picture relies on the validity of a timescale separation hypothesis: Transitions within basins of attractio...

The landscape paradigm has become a widespread picture within the realm of complex systems. Complex systems include a great variety of systems, ranging from glasses to biopolymers, which display a common dynamical behavior. Within this framework, the dynamics of a such a system can be envisioned as the search it performs on its (potential energy) l...

We perform a series of molecular dynamics simulations in a binary Lennard-Jones system at temperatures close to its mode-coupling temperature, Tc. We demonstrate that the string-like movements carried out by a fraction of the particles are of ballistic nature. Depending on temperature these ballistic strings are found to become rare events related...

In this work we investigate by means of molecular dynamics simulations the detailed time evolution of string-like cooperative motions in a binary Lennard-Jones system at temperatures close to its mode-coupling temperature, Tc. The strings will be fully geometrically and dynamically characterised, making evident the correlated and concerted nature o...

In a previous paper, the effect of the Ag2O on the electrical conductivity of vanadium tellurite glasses of the form XAg2O·(1−X)V2O5·2TeO2 has been studied by using the impedance spectroscopy in a wide range of temperature and composition. The obtained results confirm the existence of a transition from a typically electronic (polaronic) conductive...