Microscopía electrónica: recurso científico- tecnológico disponible en Uruguay

El presente texto describe una visita a la Unidad de Microscopía Electrónica de la Facultad de Ciencias de la UDELAR, los alcances del uso de los microscopios de barrido y transmisión y la disponibilidad de estos instrumentos para uso de organizaciones estatales y particulares con interés científico

In-situ electrochemical synthesis of inorganic compounds for materials conservation: Assessment of their effects on the porous structure

This study refers to the application of in-situ electrochemical synthesis as an alternative method to improve the properties of porous materials against harmful external agents that deteriorate them. It is oriented to an understanding of the effects of crystallisation on the pore structure of different compounds commonly used in the restoration and conservation of porous materials (historical ceramics, building walls, sculptures, or biomedical applications). It analyses the microstructural, chemical details, and stability of the neo-formed phases that modify the pore network. The electrochemical synthesis was carried out at ambient temperature (20 °C), over high porous sandstone for crystallising Ca carbonate, Mg carbonate, Ca phosphate, and Ca oxalate compounds. Based on the neo-formed minerals, a comparison was made depending on their specific properties defining how they affected the pore structure. The characterisation included polarised light optical microscopy, environmental and field-emission scanning electron microscopy, digital image analysis, cathodoluminescence (CL-ESEM),energy-dispersive X-ray spectroscopy, and X-ray microdiffraction. Aragonite, hydromagnesite, hydroxyapatite, and whewellite were identified as the majority phases depending on the treatment. Phase transformation, dehydration, and dissolution-re-precipitation processes suggested different degrees of stability, including aragonite/calcite (CaCO3 treatment) and hydromagnesite/magnesite (MgCO3 treatment) transformations and simultaneous crystallisation of brushite/hydroxyapatite ((Ca3(PO4)2 treatment). Electrocrystallisation induced changes in inter-granular porosity, the development of secondary porosity inherent to the minerals, and differences in pore cementation depending on its mineralogy. Among the treatments, Mg carbonate reduced porosity most effectively, followed in descending order by calcium carbonate and calcium phosphate, being the calcium oxalate the less effective.This work was funded by the following projects: TOP-HERITAGE- (Technologies in Heritage Sciences (S2018/NMT_4372, Community of Madrid); MULTIMAT CHALLENGE: Multifunctional Materials for Society Challenges (S2013/MIT-2862, Community of Madrid); Additive Manufacturing: from material to application, ADITIMAT-CM (S2018/ NMT-4411, Community of Madrid); MAT2016-80875-C3-3-R, (Spanish Ministry of Science, Innovation and Universities); Author J.F.‘s participation was supported by a Spanish Ministry of Sciences, Innovation and Universities Juan de la Cierva grant

Género y ambiente: su inclusión en la agenda pública a partir del covid-19

La relación entre las mujeres y el ambiente ha sido estudiada desde diversos modelos interpretativos que han variado a lo largo de la historia, y que difieren no sólo en razón del tiempo sino también de su ubicación geográfica. Nos enseña Rico en relación a ese vínculo que: “en los países del Norte se asocia con la participación de mujeres en los movimientos ecologista y pacifista y con su crítica a las feministas que hasta el momento no tenían una posición frente a la crisis ambiental, (mientras que) en los países del Sur se relaciona con problemas derivados del sector forestal y la agricultura”. Esto pone en evidencia que la complejidad de cada realidad, en un determinado contexto temporal y espacial, promueve demandas diferenciadas que requieren de soluciones particulares. No obstante tal señalización, resulta primordial a los fines del presente artículo conceptualizar diversas categorías que se presentan útiles como herramienta de análisis, para entender las desigualdades entre hombres y mujeres. Así, en primer lugar entendemos al género como aquella categoría que “refiere a las diferencias de comportamiento, actitudes y actividades que son resultado de un aprendizaje social y de la cultura. El concepto muestra que las diferencias sociales entre mujeres y hombres no están determinadas por la biología, sino por las creencias sobre las diferencias biológicas de los sexos. El mayor valor que la sociedad asigna a los hombres ha originado una posición de desventaja para las mujeres que se traduce en un menor acceso a los recursos, a las oportunidades y a la toma de decisiones. El género se refiere a las relaciones entre hombres y mujeres como relaciones de poder que se caracterizan por la asimetría”. Desde esta perspectiva, resulta entonces fundamental analizar cuestiones como el acceso a los recursos, a la educación y a la salud. A la par de reflexionar sobre la participación de las mujeres en la toma de decisiones, a los fines de verificar su gravitación desde las relaciones de género.Fil: Tello Roldán, María Cecilia. Universidad Nacional de Córdoba. Facultad de Derecho; Argentina.Fil: Villalba, María Eugenia. Universidad Nacional de Córdoba. Facultad de Derecho; Argentina.Fil: González, Candela. Universidad Nacional de Córdoba. Facultad de Derecho; Argentina

El proceso colectivo ambiental en la provincia de Córdoba = The environmental collective process in the province of Córdoba

El artículo tiene por objeto explorar e identificar diversas características del proceso colectivo ambiental. Asimismo, busca precisar las notas procesales en la regulación de esta figura en la provincia de Córdoba. ABSTRACT: The article aims to explore and identify various characteristics of the environmental collective process. Likewise, it seeks to specify the procedural notes in the regulation of this figure in the province of Córdoba

TEM-STEM study of europium doped gadolinium oxide nanoparticles synthesized by spray pyrolysis

Proocedings of: Fourth Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials. Kurashiki, Japan, 02-05 September 2012.Scanning-Transmission and Transmission Electron Microscopy techniques (STEM and TEM) have been applied to the characterization of nanostructured gadolinium oxides doped with europium synthesized by spray pyrolysis. The High Angle Annular Dark Field (HAADF) &- Scanning Transmission Electron Micros-copy (STEM) tools have been used to perform a tomographic study to identify morphological character-istics of nanostructured particles, and to differentiate them according to the heat treatments to which these have been subjected. With these techniques it has been possible to confirm the hollowness and por-ous nature of samples subjected to low temperature annealing (900 ºC). Moreover, the beginning of the densification and sintering processes in samples subjected to thermal treatment at higher temperature (1100 ºC) have been evaluated. Chemical analysis by electron energy loss spectroscopy (EELS) and X ray energy dispersive spectroscopy (EDS) carried out in STEM mode have allowed to confirm the high uni-formity and the expected chemical composition. The high resolution tools either allowed to confirm the presence of a cubic (Ia3 symmetry) and the monoclinic (c2/m symmetry) phases in the nanostructured particles.This work has been supported by the Advanced Structural Materials Program- ESTRUMAT (S2009/MAT-1585) and MAT2010-19837-C06-05. Thanks are extended to NanoPort (FEI)- Eindhoven, especially to Eng. L. Fernando Mendoza and to the Ministry of Science and Technology of Serbia (Project #142010).Publicad

Influence of nanoscale defects on the improvement of photocatalytic activity of Ag/ZnO

This study presents the advances in the field of ZnO/Ag catalysts from the synthesis of hierarchical ZnO nanowires (NWs) decorated with Ag nanoparticles, prepared by a facile solvothermal method at 120°C. It evaluates the photocatalytic efficiency from studying the time reaction of Ag/Zn concentration ratio and the presence of cetyltrimethylammonium bromide (CTAB) as an organic dispersant. X-ray diffraction, scanning electron microscopy, and analytical/high-resolution transmission electron microscopy results confirmed the presence of homogeneous cylindrical ZnO nanowires and quasi-spherical Ag crystals. ZnO NWs exhibited hexagonal wurtzite structure and cubic FCC symmetry in Ag nanoparticles (NPS). Two types of nanostructures, including homogeneous cylindrical ZnO NWs in the absence of Ag and simultaneous presence of ZnO NWs and Ag NPs, formed depending on experimental conditions. The photocatalytic activity was evaluated by studying methylene blue (MB) degradation time under UV light excitation. Diffuse reflectance UV–Vis spectrophotometry (UV–Vis DRS) allowed identifying the ZnO absorption band at ~393 nm. Crystal size varied depending on the reaction time and the addition of CTAB. Synthesis time increased bandgap values, getting better photocatalytic performance in samples synthesized in intermediate times (6 h), higher Ag+/Zn2+ molar ratio (0.2/1.0), and CTAB. According to HRTEM observations, the presence of silver nanocrystals with high content of defects (twinning, stacking faults) could play an essential role in the photocatalytic response. In this context, the specific synthesis conditions of Ag/ZnO might be more appropriate for their use in organic dyes degradation in water and the potential use in protective treatments against materials biodeterioration processes.This work has been supported by the Innovation and Education Ministry (ref. MAT2013-47460-C5-5-P and MAT2016-80875-C3-3-R), the Autonomous Region Program of Madrid (ref. S2018/NMT-4411 and S2013/MIT-2862), the Geomateriales 2 program (S2013/MIT_2914), the TOP Heritage (P2018/NMT-4372) of the Community of Madrid, the Innovation and Education Ministry (MAT201347460-C5-5-P) and the Ministry of Education, Science and Technological Development of Serbia (projects No. 172035 and 45020). Besides, we would like to thank the Master of “Materials Science” of Carlos III University (Spain) for providing financial and laboratory equipment support

Application of magnesium hydroxide nanocoatings on cellulose fibers with different refining degrees

Paper aging and protection are of crucial interest for improving the preservations of library collections and archives. Highly aging-resistant cellulose fiber sheets were obtained by treatment with magnesium hydroxide nanoparticles (Mg(OH)(2)). The procedure was tested on the sheets made of bleached (B) and refined unbleached (UB) pine cellulose fibers as well as their 50%/50% mixture (M). The mor and structural properties of the obtained sheets were studied by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) methods. Stress-strain, smoothness and pH measurements were employed to determine the changes in physical-chemical characteristics of the sheets after mixing two types of the fibers and subsequent treatment with Mg(OH)(2). It has been shown that the sheets made of the fiber mixture show a higher tensile index and smoothness. The modification with Mg(OH)(2) nanoparticles induces an increase in the pH of the sheets to slightly basic values (around pH 8), facilitates the inter-fiber bonding and additionally enhances the smoothness of the sheets. Finally, by exposing the sheets to thermo-hygrometric accelerated artificial ageing, it was found that the physical properties of the treated sheets were not significantly dependent on the environmental factors.This study was supported by the Geomaterials 2 Programme (S2013/MIT_2914),the Innovation and Education Ministry (ref. MAT2013-47460-C5-5-P) and the Autonomous Region Program of Madrid, MULTIMAT CHALLENGE (ref.S2013/MIT-2862

Synthesis and morpho-structural characterization of nanostructured magnesium hydroxide obtained by a hydrothermal method

Controlled magnesium hydroxide particles were successfully synthesized via a simple hydrothermal method. The influence of temperature and reaction time on the hydrothermal synthesis of Mg(OH)(2) was studied. The results provide new parameters to control the morphologies, particle sizes, agglomeration level and crystallographic structures of the brucite nanosized. The physic chemical properties of synthesized Mg(OH)(2) nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HR-TEM) and thermogravimetry/differential scanning calorimetry (TG/DSC). It has been shown that the prolongation of reaction time improves the crystalline degree of magnesium hydroxide particles. It was also possible to detect a relevant increase in the degree of crystallinity and a faster crystal growth with defined hexagonal morphologies in the samples obtained at higher temperature. Our results show that this simple hydrothermal route is highly interesting for the large scale production of these nanomaterials. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.This study has been supported by the Geomaterials Programme (S2009/MAT-1629) and the ESTRUMAT Programme (S2009/MAT-1585) and it has been carried out in the Department of Materials Science and Engineering and Chemical Engineering of the University Carlos III of Madrid, Spain. The authors are grateful to the National Center for Electron Microscopy (CNME) for its support with TEM

Atomic scale study of the dehydration/structural transformation in micro and nanostructured brucite (Mg(OH)(2)) particles: Influence of the hydrothermal synthesis conditions

Micro and nanostructured brucite (Mg(OH2)) particles synthesized by hydrothermal method from solutions with high content of hydrazine (0.14 M) and nitrate (0.24 g) were compared with samples obtained from low hydrazine content (0.0002 M) and nitrate (0.12 g). The samples were heated at 180 degrees C for 4 h, 6 h and 12 h. XRD, TEM-HRTEM, SAED and image analysis techniques were used for the morphological and structural characterization. The effect of electron beam irradiation on the brucite dehydration was observed in atomic resolution images at 300 kV. Hexagonal crystals show differences in crystallinity, strains and kinetic of reaction. High hydrazine/nitrate samples have slightly larger crystals with better crystallinity, showing a strong preferential orientation. Rietveld refinements show how unit cell parameters are bigger in samples obtained with higher hydrazine/nitrate content, confirming also the preferential orientation along the 0001 plane. Differences in the dehydration process show the rapid formation of a porous surface, the amorphised cortex or the presence of highly oriented strains in samples prepared from higher hydrazine/nitrate content. Conversely, crystals slightly smaller with randomly scattered defect surfaces showing the Mg(OH)(2)/MgO interphase in samples prepared with low hydrazine/nitrate content. Significant differences in the kinetic of reaction indicate how the dehydration process is faster in samples prepared with high hydrazine/nitrate content. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.This present research was funded by the Community of Madrid under the GEOMATERIALES II project (S2013/MIT-2914), by the Complutense University of Madrid’s Research Group: “The alteration and conservation of stone heritage” (921349), the Autonomous Region Program of Madrid, MULTIMAT-CHALLENGE (ref. S2013/MIT‐2862), the Innovation and Education Ministry ref. (MAT2013-47460-C5-5-P), the Mat201019837/C06-05 and the Ministry of Education, Science and Technological Development of Serbia (OI 1612046) projects. The authors are indebted to the Petrophysical Laboratory IGEO, affiliated with the Moncloa Campus of International Excellence CEI-09-009(UCM-UPM), the Heritage Laboratory Network in Science and Technology for Heritage Conservation (RedLabPat,) and the Materials Science Department (Carlos III University of Madrid)

Novedades normativas. Ámbito Nacional

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