Large magnetoelectric effects mediated by electric-field-driven nanoscale phase transformations in sputtered (nanoparticulate) and electrochemically dealloyed (nanoporous) Fe-Cu films

Large magnetoelectric effects are observed in as-sputtered (nanoparticulate-like) and electrochemically dealloyed (nanoporous) 200 nm thick Fe-Cu films. Large magnetoelectric effects are observed in as-sputtered (nanoparticulate-like) and electrochemically dealloyed (nanoporous) 200 nm thick Fe-Cu films. Application of positive voltages decreases both the saturation magnetization (M ) and coercivity (H ) of the films, while negative voltages cause the reverse effect (increase of M and H ). The relative variations are as high as 20% for M and beyond 100% for H , both for the as-sputtered and dealloyed states. These changes in magnetic properties are caused by controlled and reversible electric-field-driven nanoscale phase transformations between face-centered cubic (fcc) and body-centered cubic (bcc) structures. These phase transitions are in turn due to selective redox reactions induced by the applied voltage, which can be regarded as a "magnetoionic effect." The controlled tuning of H and M with the moderate values of applied voltage, together with the sustainable composition of the investigated alloys (not containing noble metals, as opposed to many previous works on magnetoelectric effects in thin films), pave the way towards the implementation of magnetic and spintronic devices with enhanced energy efficiency and functionalities

Environmental evaluation of a self-compacted clay based concrete with natural superplasticizers

[EN] Cement concrete is the most widely used construction material worldwide due to its favourable mechanical characteristics. However, it is responsible for 8% of the total carbon emissions in the world, which are generated mainly during the production of clinker. Due to that fact, finding alternatives to cement for some applications in which it is not strictly needed should be a priority. In this study, a self-compacted clay-based concrete with natural superplasticizers based on natural tara tannins is presented. The main objective of the study is to determine if this clay-based concrete can be a sustainable alternative to conventional cement concrete as the main component in structural slabs. The methodology of the study is divided into two parts. First, the self-compacting clay concrete is characterized to determine its mechanical properties. Secondly, a comparative Life Cycle Assessment is conducted to determine the difference between the impacts generated by one square meter of self-compacting cement concrete and one of self-compacting clay concrete. The characterization of the material showed that this self-compacting clay concrete is suitable for some building elements such as structural slabs while avoiding the energy consumption needed to produce conventional concrete. The environmental impact results showed that using self-compacting clay concrete instead of the cement-based material decreases 90% of the carbon emissions and 80% of the overall environmental impact. After the completion of the study, it can be stated that the presented material is a sustainable alternative to conventional concrete for building structural slabs.Romero Clausell, J.; Quintana-Gallardo, A.; Hidalgo Signes, C.; Serrano Lanzarote, AB. (2021). Environmental evaluation of a self-compacted clay based concrete with natural superplasticizers. Materials and Structures. 54(1):1-16. https://doi.org/10.1617/s11527-020-01586-611654

Fabricació d'òxids de molibdè per electrodeposició

Els òxids de metalls de transició són un material indispensable per a molts processos industrials. Una de les tècniques que s'utilitza per fabricar-los en forma de capa és l'electrodeposició, que consisteix en el creixement d'un material sobre un substrat mitjançant l'aportació d'electrons a ions presents en una dissolució. En aquest treball s'estudia com afecten certs paràmetres químics al tipus d'òxid de molibdè obtingut i les seves característiques i es presenta una forma senzilla de fabricar matrius ordenades d'estructures submicromètriques d'òxid de molibdè.Los óxidos de metales de transición son un material indispensable para muchos procesos industriales. Una de las técnicas que se utiliza para fabricarlos en forma de capa es la electrodeposición, que consiste en el crecimiento de un material sobre un sustrato mediante la aportación de electrones a iones presentes en una disolución. En este trabajo se estudia cómo afectan ciertos parámetros químicos al tipo de óxido de molibdeno obtenido y a sus características y se presenta una forma sencilla de fabricar matrices ordenadas de estructuras submicrométricas de óxido de molibdeno.Transition metal oxides are an essential material for many industrial processes. Electrodeposition, which consists in the growth of a material on a substrate through the reduction (gain of electrons) of an ion present in an electrolyte (dissolution), allows preparing transition metal oxides in thin film form. This work investigates to what extent certain chemical parameters affect the type of molybdenum oxide obtained and its features, and presents a simple route to build up ordered arrays of submicrometer molybdenum oxides

A Comparative Approach to Integration and Trade Openness in the Economic Growth of the European Union and Latin America

El objetivo de esta investigación consiste en probar si la integración económica y la apertura comercial en los países de la Unión Europea (UE) y América Latina (AL), ayudaron a aliviar los desequilibrios de balanza de pagos previos. La principal contribución del trabajo descansa en el análisis comparativo entre la UE y AL en dos periodos distintos de tiempo (de acuerdo con su integración económica) utilizando la técnica de panel cointegrados de Westerlund (2007 y 2008) para probar la validez de la ley de Thirlwall. Con los resultados, se encontró que los precios relativos no influyeron de manera relevante en los periodos de integración y apertura comercial, por lo que resultó más adecuado trabajar con el multiplicador dinámico del comercio de Harrod. Es importante mencionar que, aunque el enfoque contrafactual se aplica a momentos históricos de Europa y América Latina distintos, con sus resultados se pudo concluir que la integración económica ayudó a aliviar los desequilibrios de balanza de pagos en los países europeos y la apertura comercial provocó un mayor crecimiento compatible con el equilibrio de balanza de pagos, para la mayoría de los países de América Latina.The aim of this research is to prove whether Economic Integration and Trade Openness in countries of the European Union (EU) and Latin America (LA) helped alleviate previous Balance of Payments imbalances. The main contribution of the work consists on the comparative analysis between the EU and LA in two different periods of time (according to their economic integration) using the Westerlund panel cointegration technique (2007 and 2008) to prove the validity of Thirlwalls Law. The results show that the relative prices are not relevant in periods of Economic Integration and Trade Openness, consequently it was more appropriate to work with Harrods Dynamic Trade Multiplier. It is important to mention that, although the counterfactual approach is applied to different historicalmoments in Europe and Latin America, the results showed that the Economic Integration helped alleviate the Balance of Payments imbalances in European countries and Trade Openness caused a greater growth compatible with the Balance of Payments equilibrium for most Latin American countries

Caracterización estructural de FCXTH 1 y FCXTH 2 asociados al desarrollo y maduración del fruto de Fragaria chiloensis (L). Duch.

78 p.La frutilla chilena (Fragaria chiloensis) surge como una nueva alternativa comercial, debido a sus excelentes características organolépticas. Su fruto es de rápido ablandamiento, reflejado en la alteración de la textura del fruto, que influye negativamente en la sobrevida de postcosecha y calidad, limitando su comercialización. Estudios previos han demostrado que el ablandamiento esta relacionado con la alteración de la pared celular, lo que corresponde a una serie de modificaciones de los polisacáridos que la componen. Los xiloglucanos (XG), polisacáridos abundantes en la pared celular, entrecruzan las microfibras de celulosa otorgándole rigidez a la pared. Se piensa que la modificación de las cadenas de XG estaría involucrada en la alteración observada en la pared, lo que resulta en el ablandamiento del fruto. La enzima xiloglucano endotransglicosilasa / hidrolasa (XTH) presente en todos los tejidos vegetales, presenta alta afinidad a xiloglucano y posee actividad endotransglicosilasa (XET), endohidrolasa (XEH), o ambas. En F. chiloensis se han identificado dos genes, que presentan alta similitud de secuencia con miembros de la familia de las XTH. Fc-XTH1, presenta alta acumulación de transcritos especialmente en fruto y Fc-XTH2 relacionado con los procesos vegetativos como el crecimiento de las hojas. Con el fin de aportar nuevos antecedentes en el proceso de ablandamiento del fruto, y obtener una perspectiva sobre el mecanismo de acción a nivel molecular de las enzimas FcXTH1 y FcXTH2, se realizó modelamiento comparativo para construir las estructuras de éstas enzimas. Además, se exploró la interacción de sustratos xiloglucano (XG) con la proteína, usando simulaciones de acoplamiento molecular. Ambas enzimas mostraron energías favorables de afinidad para sustratos XG, sin embargo, la estabilidad del complejo depende del estado de glicosilación de FcXTH. Simulaciones de dinámica molecular evidenciaron una marcada estabilidad de ambas proteínas al estar glicosiladas con 9 manosas (9m). La estabilidad de los complejos fue evaluada a través de cálculos de energía libre de unión con el método MM-GBSA. Los datos son congruentes con un probable papel de XTH durante el desarrollo y maduración del fruto./ABSTRACT: The chilean strawberry (Fragaria chiloensis) appears as a new commercial alternative, due to its excellent organoleptics. Fragaria chiloensis’s fruit with fast softening, which is reflected in the alteration of the texture of the fruit that affects negatively the survival and quality of the postharvest, restricting its merchandising. Previous studies have demonstrated that the softening is related to the alteration of the cell wall, which corresponds to modifications of the constituent polysaccharides. The xyloglucans(XG), abundant polysaccharides in the cell wall, crisscross microfibers of cellulose providing stiffness to the wall. This phenomenon could be due to that the modification of XG chains would be involved in the alteration observed in the wall, which results in softening of the fruit. The xyloglucan endotransglycosylase enzyme / hydrolase (XTH) present in all vegetables tissues, exhibits high affinity to xyloglucan and possesses endotransglycosylase actvity (XET),endohydrolase activity (XEH) , or both. In F. chiloensis have been identified two genes that show high similitude of sequence with members of the XTH family. Fc-XTH1, presents high accumulation of transcripts, especially in fruit and Fc-XTH2 is related to the vegetative processes such as leaf growth. With the purpose of providing new information in the process of fruit softening and obtaining a perspective about the mechanism of action to molecular level of enzymes FcXTH1 and FcXTH2, comparative modeling was performed to build the structures of these enzymes. Moreover, the interaction of xyloglucan (XG) substrates with the protein was explored, by using molecular Docking simulations. Both enzymes showed favorable energies of affinity for XG substrates. However, the stability of the complex depends on the state of FcXTH glycosylation. Molecular dynamics simulations showed a marked stability of both proteins by being glycosylated with 9 mannose (9m). The stability of the complexes was evaluated through calculations of binding free energy with the MM-GBSA method. The data are consistent with a probable role of XTH during development and the fruit ripening

Unraveling the origin of magnetism in mesoporous Cu-doped SnO₂ magnetic semiconductor

The origin of magnetism in wide-gap semiconductors doped with non-ferromagnetic 3d transition metals still remains intriguing. In this article, insights in the magnetic properties of ordered mesoporous Cu-doped SnO₂ powders, prepared by hard-templating, have been unraveled. Whereas, both oxygen vacancies and Fe-based impurity phases could be a plausible explanation for the observed room temperature ferromagnetism, the low temperature magnetism is mainly and unambiguously arising from the nanoscale nature of the formed antiferromagnetic CuO, which results in a net magnetization that is reminiscent of ferromagnetic behavior. This is ascribed to uncompensated spins and shape-mediated spin canting effects. The reduced blocking temperature, which resides between 30 and 5 K, and traces of vertical shifts in the hysteresis loops confirm size effects in CuO. The mesoporous nature of the system with a large surface-to-volume ratio likely promotes the occurrence of uncompensated spins, spin canting, and spin frustration, offering new prospects in the use of magnetic semiconductors for energy-efficient spintronics

Structural and magnetic properties of FexCu1-x sputtered thin films electrochemically treated to create nanoporosity for high-surface-area magnetic components

Sputter deposition is a facile and widely used technique for fabricating thin-film materials. Electrochemical dealloying, on the other hand, is a promising method for creating nanoporosity, and therefore increasing surface area, in metallic materials. Surprisingly, little work has been done on the application of electrochemical dealloying to sputter-deposited thin films. Here, we prepare FexCu1-x thin films by sputter deposition to be then electrochemically treated to create porosity. We investigate the structural and magnetic properties of as-sputtered and electrochemically treated films. We find that the morphology, crystal structure, and magnetic properties are highly dependent on initial film composition. For high copper content films (Fe29Cu71), relative Cu content is found to decrease during the dealloying process. For these films, the crystal structure is not greatly affected by the induced porosity and the porous films show increased saturation magnetization. However, for the more Fe-rich compositions (Fe63Cu37), we find that Fe is preferentially lost and making the films nanoporous induces a crystal structure change from body-centered cubic (bcc) to a mixture of face-centered cubic (fcc) and bccphases. These same porous films show a decrease in saturation magnetization and a large increase in coercivity compared to the as-sputtered films. These films are attractive as high-surface-area magnetic components because of the tunability of their magnetic properties and their high surface area due to porosity. To the best of our knowledge, these results constitute the first example of nanoporous, magnetic thin films by prepared by sputtering and subsequent electrochemical treatment

Reversible, electric-field induced magneto-tonic control of magnetism in mesoporous cobalt ferrite thin films

The magnetic properties of mesoporous cobalt ferrite films can be largely tuned by the application of an electric field using a liquid dielectric electrolyte. By applying a negative voltage, the cobalt ferrite becomes reduced, leading to an increase in saturation magnetization of 15% (M) and reduction in coercivity (H) between 5-28%, depending on the voltage applied (−10 V to −50 V). These changes are mainly non-volatile so after removal of −10 V M remains 12% higher (and H 5% smaller) than the pristine sample. All changes can then be reversed with a positive voltage to recover the initial properties even after the application of −50 V. Similar studies were done on analogous films without induced porosity and the effects were much smaller, underscoring the importance of nanoporosity in our system. The different mechanisms possibly responsible for the observed effects are discussed and we conclude that our observations are compatible with voltage-driven oxygen migration (i.e., the magneto-ionic effect)

Voltage control of magnetism with magneto-ionic approaches : beyond voltage-driven oxygen ion migration

Magneto-ionics is an emerging field in materials science where voltage is used as an energy-efficient means to tune magnetic properties, such as magnetization, coercive field, or exchange bias, by voltage-driven ion transport. We first discuss the emergence of magneto-ionics in the last decade, its core aspects, and key avenues of research. We also highlight recent progress in materials and approaches made during the past few years. We then focus on the "structural-ion"approach as developed in our research group in which the mobile ions are already present in the target material and discuss its potential advantages and challenges. Particular emphasis is given to the energetic and structural benefits of using nitrogen as the mobile ion, as well as on the unique manner in which ionic motion occurs in CoN and FeN systems. Extensions into patterned systems and textures to generate imprinted magnetic structures are also presented. Finally, we comment on the prospects and future directions of magneto-ionics and its potential for practical realizations in emerging fields, such as neuromorphic computing, magnetic random-access memory, or micro- and nano-electromechanical systems

"Interruptor magnètic", inducció o supressió del ferromagnetisme mitjançant voltatge elèctric

La manipulació magnètica a través de camps elèctrics és una de les propostes més prometedores per reduir el consum energètic de la nostra societat. Investigadors del departament de física de la UAB juntament amb altres grups nacionals i internacionals han demostrat per primer cop la manera d'induir ferromagnetisme (alteració de propietats magnètiques) a temperatura ambient en una capa de 100 nm de gruix de Co3O4. Fins ara, s'havien utilitzat materials amb mobilitat iònica i per tant, les temperatures superaven l'ambient per tal d'incrementar la cinètica dels processos implicats. Aquest article descriu la possibilitat de tenir un "interruptor magnètic" simplement controlat a través de l'aplicació de voltatge elèctric. Aquesta nova perspectiva podria contribuir notablement al desenvolupament de tecnologies de baix consum.La manipulación magnética a través de campos eléctricos es una de las propuestas más prometedoras para reducir el consumo energético de nuestra sociedad. Investigadores del departamento de física de la UAB junto a otros grupos nacionales e internacionales han demostrado por primera vez la manera de inducir el ferromagnetismo (alteración de propiedades magnéticas) a temperatura ambiente en una capa de 100 nm de grosor de Co3O4. Hasta ahora, se tenían que utilizar materiales de movilidad iónica y por tanto, las temperaturas superaban la del ambiente incrementando así la cinética de los procesos implicados. Este artículo describe la posibilidad de un "interruptor magnético" controlado simplemente por la aplicación de voltaje eléctrico. Esta nueva perspectiva podría contribuir notablemente al desarrollo de tecnologías de bajo consumo.The magnetic manipulation through electric fields is one of the most promising approaches to reduce energy consumption of our society. Researchers from the department of physics at the UAB jointly with other national and international groups have proved for the first time the induction of ferromagnetism (alteration of magnetic properties) at ambient temperature in a layer of 100 nm thick of Co3O4. Until now, ionic mobility materials have been used and, therefore, the temperature exceeded the ambient temperature to increase the kinetics of the processes involved. This article describes the possibility of a "magnetic switch" controlled simply by the application of an electrical voltage. This new perspective could contribute significantly to the development of low consumption technologies