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The latest advances in technology and materials science have catalyzed a transformative shift towards the adoption of environmentally conscious and lightweight materials across key sectors such as aeronautics, biomedical, and automotive industries. Noteworthy among these innovations are the magnesium-aluminum (Mg-Al) alloys employed in aeronautical applications, contributing to the overall reduction in aircraft weight and subsequently diminishing fuel consumption and mitigating atmospheric emissions. The present work delves into a study of the anti-corrosive properties inherent in various sol-gel coatings, leveraging a range of environmentally friendly corrosion inhibitors, specifically tailored for samples of the AZ61 alloy. Methodologically, the work involves the synthesis and application of sol-gel coatings on AZ61 alloy containing eco-friendly inhibitors: L-cysteine, N-acetyl-cysteine, curcumin and methylene blue. Subsequently, an accelerated corrosion test in a simulated saline environment is performed. Through microstructural and compositional analyses, the best inhibitors responses are achieved with inhibitors containing S, N heteroatoms and conjugated double bonds in their structure, probably due to the creation of a continuous MgCl2 layer. This research contributes to the ongoing discourse on protective eco-coatings, aligning with the broader paradigm shift towards sustainable and lightweight materials in key industries.

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RL_(min)) = −21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe_(73.5)Si_(13.5)B_(9)Cu_(1)Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (−53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a f_(min) tunability is demonstrated, maintaining similar RL_(min) and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs., Ministerio de Ciencia e Innovación (España), Ministerio de Asuntos Economicos y Transformacion Digital (España), Comunidad de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, Instituto de Magnetismo Aplicado (IMA), TRUE, pub

2023 Acuerdos transformativos CRUE, The identification of the active phase of a catalyst under operando conditions is probably the most relevant task in basic catalysis research. In this respect, the Ru(0001) surface during CO oxidation is a traditional studied model, for both its importance in applied catalysis and for its peculiar behavior. In this work, we study the CO catalytic oxidation reaction on flat and defective Ru(0001) surfaces, concluding that the highest activity is achieved in oxidizing conditions when a disordered and thin Ru oxide is formed at the surface. Also, we find that in defective surfaces, with a high density of surface steps, this reaction is enhanced, related to the facile sub-surface incorporation of atomic oxygen and to the easier formation of the oxide. Thus, the CO catalytic oxidation on Ru(0001) is a structure-sensitive reaction, being active on the surface of the oxide formed in reaction conditions., Ministerio de Economía y Competitividad (España), Ministerio de Ciencia e Innovación (España), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Today’s environmental needs require the reduction of the weight of vehicles, thus reducing fuel consumption and associated emissions. For this reason, the use of light alloys is being studied, which, due to their reactivity, must be protected before use. In this work, the effectiveness of a hybrid sol-gel coating doped with various organic environmentally friendly corrosion inhibitors applied to an AA2024 lightweight aluminium alloy is evaluated. Some of the inhibitors tested are pH indicators, acting as both corrosion inhibitors and optical sensors for the surface of the alloy. Samples are subjected to a corrosion test in a simulated saline environment and characterised before and after the test. The experimental results regarding their best inhibitor performance for their potential application in the transport industry are evaluated., Ministerio de Ciencia, Innovación y Universidades (España), Ministerio de Economía, Comercio y Empresa (España), Depto. de Física de Materiales, Fac. de Ciencias Físicas, Instituto de Magnetismo Aplicado (IMA), TRUE, pub

© 2015 Macmillan Publishers Limited. Financial support from the Spanish Ministry of Economy and Competitiveness under projects MAT2012-38045-C04-03 and MAT2012-38045-C04-04 is acknowledged. A.M. also acknowledges project MAT2010-21156-C03-02 for financial support. We thank A. Tejeda for critical discussions. We acknowledge the Spanish Ministry of Economy and Competitiveness and Consejo Superior de Investigaciones Científicas for both financial support under project PIE 201060E013 and provision of synchrotron radiation facilities. We would also like to thank the SpLine beamline staff for their assistance during the SR experiments. GSS and the microscopy effort were supported by the ERC starting Investigator Award, grant #239739 STEMOX. Electron microscopy observations were carried out at the Centro Nacional de Microscopía Electrónica, CNME-UCM. Part of the XRD measurements were performed at the C.A.I. de Difracción de Rayos X-UCM. Computational calculations were performed at the Supercomputing Centre of Galicia (CESGA). Author contributions: O.R.d.l.F. conceived the project and coordinated the research. B.M., I.P. and O.R.d.l.F. prepared the samples and performed the Auger and LEED measurements and the ion beam modifications. B.M., I.P., A.M., J.L.-S, O.R.d.l.F., J.R.-Z., P.F. and G.C. performed the X ray diffraction measurements. G.S.-S. and M.V. performed the STEM measurements. J.I.B. and M.C.M. carried out the Density Functional Theory calculations. All authors wrote and revised the manuscript and extensively discussed the results and their interpretation. Supplementary Information: accompanies this paper at http://www.nature.com/ naturecommunications., A plethora of technological applications justify why titanium dioxide is probably the most studied oxide, and an optimal exploitation of its properties quite frequently requires a controlled modification of the surface. Low-energy ion bombardment is one of the most extended techniques for this purpose and has been recently used in titanium oxides, among other applications, to favour resistive switching mechanisms or to form transparent conductive layers. Surfaces modified in this way are frequently described as reduced and defective, with a high density of oxygen vacancies. Here we show, at variance with this view, that high ion doses on rutile titanium dioxide (110) induce its transformation into a nanometric and single-crystalline titanium monoxide (001) thin film with rocksalt structure. The discovery of this ability may pave the way to new technical applications of ion bombardment not previously reported, which can be used to fabricate heterostructures and interfaces., Unión Europea. FP7, Ministerio de Economía y Competitividad (MINECO), España, Consejo Superior de Investigaciones Científicas (CSIC), España, ERC starting Investigator Awards, European Research Council (ERC), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2008 The American Physical Society. The authors acknowledge financial support from the Comunidad de Madrid Project No. CAM-S-0505/PPQ/0316, from Santander-UCM Project No.PR27/05-13926, and from the Spanish Ministerio de Educación y Ciencia Project No. MAT2006-13149-C02-01., Titanium dioxide rutile crystals have been nanoindented and studied by a combination of atomic force microscopy imaging and analysis of force vs penetration curves. In all the experiments, gold crystals have been used as a reference. A concept of nanoindentation effective volume is introduced to differentiate the bulk behavior from that of a small defect-free volume around the indentation. In the latter volume, a reversible Hertzian elastic stage is identified with a Young modulus comparable to that of the bulk. At higher loads, an incipient plastic range is recognized in which the load is linear on the penetration and permanent traces are left behind at the surface upon tip retraction. In that range, the hardness is constant, about five times smaller than the yield strength and more than three times smaller than the corresponding bulk value. This reduced hardness is explained in terms of the operation of dislocation sources with a low-energy barrier., Comunidad de Madrid, Santander-UCM, Spanish Ministerio de Educacion y Ciencia, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2012 American Physical Society Spanish Ministry of Science and Innovation [MAT2009-4578-C03-01, MAT2009-14578-C03-02, MAT2010-21156-C03-02]; Office of Basic Energy Sciences, Division of Materials and Engineering Sciences, US Department of Energy [DE-AC04-94AL85000]; European Union [226716-ELISA]; Spanish Ministry of Science and Innovation through FPI, The oldest known magnetic material, magnetite, is of current interest for use in spintronics as a thin film. An open question is how thin can magnetite films be and still retain the robust ferrimagnetism required for many applications. We have grown 1-nm-thick magnetite crystals and characterized them in situ by electron and photoelectron microscopies including selected-area x-ray circular dichroism. Well-defined magnetic patterns are observed in individual nanocrystals up to at least 520 K, establishing the retention of ferrimagnetism in magnetite two unit cells thick., Ministerioo de Ciencia e Innovación, Office of Basic Energy Sciences, Division of Materials and Engineering Sciences, US Department of Energy, European Union, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2008 The American Physical Society. The authors thank J.E. Ortega for providing us the Au(788) sample. Financial support from the Spanish MEC, Project No. MAT2006-13149-C02-01 and from the CAM Projects Nos. CAM-S-0505/PPQ/0316 and GR/ MAT/0632/2004 are gratefully acknowledged. V. N. thanks MEC through No. MAT2003-08627-C02-01., Gold vicinal surfaces (788), with a high density of steps, along with (111) flat surfaces taken as a reference, have been nanoindented and their resulting penetration curves and related defect structure comparatively analyzed by AFM and atomistic simulations. Stepped surfaces are shown to yield at smaller loads than (111) ones in agreement with calculations of the critical resolved shear stress needed to nucleate a dislocation. In the stepped surfaces, a novel intermediate state is identified in which the penetration curves depart from a Hertzian behavior prior to the appearance of pop-ins. This state is shown to result from heterogeneous nucleation at preexisting surface steps of dislocation loops, most of which retract and vanish when the indenter load is removed., Spanish MEC, CAM, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Today’s environmental needs require the reduction of the weight of vehicles, thus reducing fuel consumption and associated emissions. For this reason, the use of light alloys is being studied, which, due to their reactivity, must be protected before use. In this work, the effectiveness of a hybrid sol-gel coating doped with various organic environmentally friendly corrosion inhibitors applied to an AA2024 lightweight aluminium alloy is evaluated. Some of the inhibitors tested are pH indicators, acting as both corrosion inhibitors and optical sensors for the surface of the alloy. Samples are subjected to a corrosion test in a simulated saline environment and characterised before and after the test. The experimental results regarding their best inhibitor performance for their potential application in the transport industry are evaluated.

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RLmin) = ¿21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe73.5Si13.5B9Cu1Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (¿53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a fmin tunability is demonstrated, maintaining similar RLmin and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs.

Few-layered mesoporous graphene (FLMG) is employed as a sensing material to develop an innovative and high-sensitivity room temperature NO_(2) sensor through a simple manufacturing process. For this purpose, sensing material is optimized at 100 min by a high-energy milling process where natural graphite is used as a precursor: it is an inexpensive, sustainable and suitable active material. The large number of defects created and the enhanced degree of mesoporosity produced during the milling process determine the physical principles of operation of the designed device. NO_(2) gas sensing tests reveal an improved and selective performance with a change in resistance of ∼16 % at 0.5 ppm under ultraviolet photo-activation, establishing a detection limit around ∼25 ppb. Interestingly, the response of the developed sensor to humidity is independent in the measured range (0–33 % relative humidity at 25 °C) and the dependency to the presence of NH3 is rather poor as well (∼1.5 % at 50 ppm)., Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), Fondo Europeo de Desarrollo Regional (Unión Europea), Comunidad de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, Instituto de Magnetismo Aplicado (IMA), TRUE, pub

© 2022 by the authors. Licensee MDPI The present work has been supported by the Ministerio Español de Ciencia e Innovación (MICINN) and the Consejo Superior de Investigaciones Cientificas (CSIC) through the projects PIE-2010-OE-013-200014, PIE 2021-60-E-030, and RTI2018-095303-A-C52. A.S. acknowledges financial support from the program “Atracción de Talento Investigador” Contract (2017-t2/IND5395, Comunidad de Madrid)., A temperature-dependent Raman experiment between 80 and 600 K was performed in a nanoparticulated coating of single-phase hematite grown on a silica substrate. In that range, a thermal Raman shift hysteresis was identified in the vibrational modes that accompanies the Morin transition, observing large effects in the two-magnon Raman frequency position and in its relative intensity. Interestingly, no decrease in coercivity occurs when the hematite crosses the Morin transition below 230 K. The spin-flop processes produced in the coating leads to a strong decompensation of the surface spins, generating a ferromagnetic component over the whole temperature range studied. Such unusual effects might be promoted by a certain degree of structural disorder and the stresses produced by the nanoparticulation growth approach of the hematite coating. As a result, a high stability of the two-magnon excitation is obtained over a wide temperature range and considerable advances are made for the development of spintronic devices based on semiconductor antiferromagnetic materials., Ministerio de Ciencia e Innovación (MICINN)/ FEDER, Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2021) ©2021 The Author(s). Published by Elsevier This work has been supported by the Ministerio de Ciencia e Innovación (MCINN, Spain) through the projects PIE: 2021-60-E-030, PIE: 2010-6-OE-013, PID2019-104717RB-I00 (2020–2022), MAT2017- 86540-C4-1-R, RTI2018-095856-B-C21 (2019–2021), RTI2018- 097895-B-C43 and RTI2018-095303-A-C52. The authors are grateful to The ESRF (France), MCINN and Consejo Superior de Investigations Científicas (CSIC, Spain) for the provision of synchrotron radiation facilities and to the BM25-SpLine Staff for their valuable help. A.S. and A.M.-N acknowledge financial support from Comunidad de Madrid (Spain) for an “Atracción de Talento Investigador” Contract 2017-t2/IND5395 and 2018-T1/IND-10360, respectively, Epsilon iron oxide (epsilon-Fe_2O_3) coatings on Si(100) substrates are obtained by an easy one-pot sol-gel recipe assisted by glycerol in an acid medium. Glycerol, given its small dimensions, enables the formation of epsilon-Fe_2O_3 nanoparticles with a size of a few nanometers and the highest purity is reached in coatings after a densification treatment at 960 degrees C. The structural and compositional evolution up to 1200 degrees C is studied by confocal Raman microscopy and X-ray absorption spectroscopy techniques, correlating the existing magnetic properties. We report a novel characterization method, which allows monitoring the evolution of the precursor micelles as well as the intermediate and final phases formed. Furthermore, the inherent industrial technology transfer of the sol-gel process is also demonstrated with the epsilon-Fe_2O_3 polymorph, impelling its application in the coatings form., Ministerio de Ciencia e Innovacion (MICINN), Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Physiological human fluid is a natural corrosive environment and can lead to serious corrosion and mechanical damages to light Mg–Al alloys used in prosthetics for biomedical applications. In this work, organic–inorganic hybrid coatings doped with various environmentally friendly and non-toxic corrosion inhibitors have been prepared by the sol-gel process for the corrosion protection of AZ61 magnesium alloys. Effectiveness has been evaluated by pH measurements, optical microscopy, and SEM during a standard corrosion test in a Hanks’ Balanced Salt Solution. The results showed that the addition of an inhibitor to the sol-gel coating can improve significantly the corrosion performance, being an excellent barrier for the L-cysteine-doped hybrid sol-gel films. The incorporation of TiO nanoparticles, 2-Aminopyridine and quinine organic molecules slowed down the corrosion rate of the Mg–Al alloy. Graphene oxide seemed to have the same response to corrosion as the hybrid sol-gel coating without inhibitors.

Few-layered mesoporous graphene (FLMG) is employed as a sensing material to develop an innovative and high-sensitivity room temperature NO sensor through a simple manufacturing process. For this purpose, sensing material is optimized at 100 min by a high-energy milling process where natural graphite is used as a precursor: it is an inexpensive, sustainable and suitable active material. The large number of defects created and the enhanced degree of mesoporosity produced during the milling process determine the physical principles of operation of the designed device. NO gas sensing tests reveal an improved and selective performance with a change in resistance of ∼16 % at 0.5 ppm under ultraviolet photo-activation, establishing a detection limit around ∼25 ppb. Interestingly, the response of the developed sensor to humidity is independent in the measured range (0–33 % relative humidity at 25 °C) and the dependency to the presence of NH is rather poor as well (∼1.5 % at 50 ppm).

©2019 The Author(s) This journal is © The Royal Society of Chemistry 2019 Artículo firmado por más de diez autores. Dr Paloma Almodovar is acknowledged for her fruitful discussions about CRM and SEM characterization. The authors also acknowledge the Spanish Ministry of Industry, Economy and Competitiveness for financing the project MAT2015-65445-C2-1-R, MAT2017-86450-C4-1-R, MAT2015-67557-C2-1-P, by the Comunidad de Madrid S2013/MIT-2850 NANOFRONTMAG and H2020 AMPHIBIAN Project ID: 720853. The authors are also grateful to the BM25-SpLine staff for their valuable technical support beyond their duties and for the financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) and The Spanish National Research Council (CSIC) under Grant No. PIE 2010-6OE-013, The ESRF - The European Synchrotron, MICIU and CSIC are acknowledged for provision of synchrotron radiation facilities. A. S. acknowledges the financial support from the Comunidad de Madrid for an "Atraccion de Talento Investigador" contract (No. 2017-t2/IND5395)., The purpose of this work is to fabricate self-assembled microstructures by the sol-gel method and study the morphological, structural and compositional dependence of epsilon-Fe_2O_3 nanoparticles embedded in silica when glycerol (GLY) and cetyl-trimethylammonium bromide (CTAB) are added as steric agents simultaneously. The combined action of a polyalcohol and a surfactant significantly modifies the morphology of the sample giving rise to a different microstructure in each of the studied cases (1, 3 and 7 days of magnetic stirring time). This is due to the fact that the addition of these two compounds leads to a considerable increase in gelation time as GLY can interact with the alkoxide group on the surface of the iron oxide precursor micelle and/or be incorporated into the hydrophilic chains of CTAB. This last effect causes the iron oxide precursor micelles to be interconnected forming aggregates whose size and structure depend on the magnetic stirring time of the sol-gel synthetic route. In this paper, crystalline structure, composition, purity and morphology of the sol-gel coatings densified at 960 degrees C are examined. Emphasis is placed on the nominal percentage of the different iron oxides found in the samples and on the morphological and structural differences. This work implies the possibility of patterning epsilon-Fe_2O_3 nanoparticles in coatings and controlling their purity by an easy one-pot sol-gel method., Unión Europea. H2020, Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Consejo Superior de Investigaciones Científicas (CSIC), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

An economical approach to synthesize superhydrophobic surfaces with silica and alumina nanoparticles on a polyurethane-based paint is presented. The surfaces have been prepared by spraying functionalized nanoparticles on the partially cured polymer matrix, and they have been characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and water contact angle measurements. Results show that the gel point is reached 26 min after the application of the paint when it is cured at 70 degrees C. At that moment, rather than submerging into the paint, the sprayed nanoparticles remain partially exposed at the surface. Following this approach, we have found that, for samples including 0.5 wt% of polydimethylsiloxane-functionalized nanoparticles, water droplets show contact angles higher than 150 degrees, have a negligible attachment to the substrate and easily roll off the substrates. The application method is fast and scalable to relatively wide areas. Also, nanoparticles are located only at the surface, thus reducing manufacturing costs., Universidad Complutense de Madrid, Fundación para la Investigación, Desarrollo y Aplicación de Materiales Compuestos, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

[EN] The purpose of this work is to fabricate self-assembled microstructures by the sol–gel method and study the morphological, structural and compositional dependence of 3-Fe2O3 nanoparticles embedded in silica when glycerol (GLY) and cetyl-trimethylammonium bromide (CTAB) are added as steric agents simultaneously. The combined action of a polyalcohol and a surfactant significantly modifies the morphology of the sample giving rise to a different microstructure in each of the studied cases (1, 3 and 7 days of magnetic stirring time). This is due to the fact that the addition of these two compounds leads to a considerable increase in gelation time as GLY can interact with the alkoxide group on the surface of the iron oxide precursor micelle and/or be incorporated into the hydrophilic chains of CTAB. This last effect causes the iron oxide precursor micelles to be interconnected forming aggregates whose size and structure depend on the magnetic stirring time of the sol–gel synthetic route. In this paper, crystalline structure, composition, purity and morphology of the sol–gel coatings densified at 960 ºC are examined. Emphasis is placed on the nominal percentage of the different iron oxides found in the samples and on the morphological and structural differences. This work implies the possibility of patterning 3-Fe2O3 nanoparticles in coatings and controlling their purity by an easy one-pot sol–gel method.

©AIP Publishing. This work has been supported by the Ministerio Español de Economía, Industria y Competitividad (MINECO) through the Project Nos. MAT2017-86540-C4-1-R, MAT2013-48009-C4-1-P, and FIS-2008-06249. Project supported by a 2016 BBVA Foundation Grant for Researchers and Cultural Creators. F. R-M. is also indebted to MINECO for a “Ramon y Cajal” contract (Ref: RyC-2015-18626), which is co-financed by the European Social Fund., We present here a study on the modification of morphological and plasmonic properties of Ag thin films deposited on glass substrates upon annealing in air at different temperatures. Initially, Ag films are continuous and exhibit extended surface plasmons with a resonant absorbance that depends on the film thickness. The dewetting process promotes the formation of nanoparticles with different sizes, shapes, and agglomerations states, besides a partial oxidation from Ag to AgO at surface level. The final Ag-AgO nanostructures are dependent on the annealing temperature and initial film thickness. The optical properties evolve from those typical of metallic films with high reflectivity and extended surface plasmon resonance toward localized surface plasmons characteristic of nanoparticles. The optical evolution and the final plasmonic response are evaluated according to the morphological and structural features of nanostructures. Published by AIP Publishing., Ministerio de Economía y Competitividad (MINECO), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Esta tesis se centra en la síntesis de partículas ¿-Fe2O3 mediante la técnica sol-gel de una forma sencilla, reproducible y de bajo coste. Este material presenta unas propiedades físicas inusuales para tratarse de un óxido de hierro convencional. Las más destacadas son su campo coercitivo de 20 kOe y ferroelectricidad a temperatura ambiente, es un semiconductor intrínseco tipo p con una energía del gap ~2.1 eV, y posee una frecuencia de resonancia ferromagnética por encima de los 80 GHz. Por todas estas propiedades tan interesantes se diseñan diferentes rutas químicas sol-gel para obtener partículas de ¿-Fe2O3.En la primera parte de la tesis se obtienen nanopartículas de ¿-Fe2O3 embebidas en sílice en forma de polvo con tamaños de partícula comprendidos entre 4 y 35 nm. La sílice proporciona una matriz tridimensional mesoporosa donde se alojan las partículas evitando la agregación entre micelas precursoras y promoviendo fases metaestables, como es la fase ¿-Fe2O3. La pureza de estas muestras sintetizadas es cercana al 90%. Los resultados obtenidos mediante XAS y CRM suponen los primeros espectros de ¿-Fe2O3 conocidos y con ellos, aparecen nuevas características y propiedades para diferenciarlos de otros óxidos de hierro. Además, se realiza un estudio magnético en función de la temperatura (5-1000 K) y se detectan dos transiciones magnéticas asociadas a ¿-Fe2O3...

Esta tesis se centra en la síntesis de partículas ¿-Fe2O3 mediante la técnica sol-gel de una forma sencilla, reproducible y de bajo coste. Este material presenta unas propiedades físicas inusuales para tratarse de un óxido de hierro convencional. Las más destacadas son su campo coercitivo de 20 kOe y ferroelectricidad a temperatura ambiente, es un semiconductor intrínseco tipo p con una energía del gap ~2.1 eV, y posee una frecuencia de resonancia ferromagnética por encima de los 80 GHz. Por todas estas propiedades tan interesantes se diseñan diferentes rutas químicas sol-gel para obtener partículas de ¿-Fe2O3.En la primera parte de la tesis se obtienen nanopartículas de ¿-Fe2O3 embebidas en sílice en forma de polvo con tamaños de partícula comprendidos entre 4 y 35 nm. La sílice proporciona una matriz tridimensional mesoporosa donde se alojan las partículas evitando la agregación entre micelas precursoras y promoviendo fases metaestables, como es la fase ¿-Fe2O3. La pureza de estas muestras sintetizadas es cercana al 90%. Los resultados obtenidos mediante XAS y CRM suponen los primeros espectros de ¿-Fe2O3 conocidos y con ellos, aparecen nuevas características y propiedades para diferenciarlos de otros óxidos de hierro. Además, se realiza un estudio magnético en función de la temperatura (5-1000 K) y se detectan dos transiciones magnéticas asociadas a ¿-Fe2O3...

[EN] We present here a study on the modification of morphological and plasmonic properties of Ag thin films deposited on glass substrates upon annealing in air at different temperatures. Initially, Ag films are continuous and exhibit extended surface plasmons with a resonant absorbance that depends on the film thickness. The dewetting process promotes the formation of nanoparticles with different sizes, shapes, and agglomerations states, besides a partial oxidation from Ag to AgO at surface level. The final Ag-AgO nanostructures are dependent on the annealing temperature and initial film thickness. The optical properties evolve from those typical of metallic films with high reflectivity and extended surface plasmon resonance toward localized surface plasmons characteristic of nanoparticles. The optical evolution and the final plasmonic response are evaluated according to the morphological and structural features of nanostructures.

©American Institute of Physics. This work was supported by projects MAT2012-38045- C04-03, FIS2014-61839-EXP, MAT2014- 52477-C5-2-P and MAT2013-48009-C4-1-P from the Spanish Ministry of Economy and Competitiveness and a 2016 BBVA Foundation Grant for Researchers and Cultural Creators. S.R.-G. thanks a FPI MINECO fellowship. J. Romero from the C.A.I de Tecnicas Fısicas-UCM is acknowledged for the SQUID measurements., We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single- crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity. Published by AIP Publishing., Ministerio de Economía y Competitividad (MINECO), BBVA Foundation Grant for Researchers and Cultural Creators, FPI MINECO fellowship, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

El programa: Diseño e implementación de un laboratorio virtual para el estudio de "Defectos puntuales en cristales iónicos" enseña de forma interactiva las reglas de balance necesarias para escribir las ecuaciones de defectos en los cristales iónicos, usando la notación de Kröger-Vink para los defectos puntuales.

We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single-crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity.

In this work, surface plasmon resonance (SPR) spectroscopy has been employed as a probe to study modifications in nanostructured systems based on Au. Those modifications include a) structural and morphological changes induced by annealing and b) electronic modifications upon X-ray irradiation. The use of SPR spectroscopy to follow the evolution of modifications in nanostructures (especially, in situ and in real time) has been scarcely explored and its study results interesting and relevant for the plasmonic technology. In this first part of the work, we have grown nanostructures from Au films and Au/Fe bilayers which have been later annealed under different conditions. These nanostructures have been characterized morphologically and analyzed by SPR spectroscopy, in order to follow the morphological changes of the systems varying the sample features (i.e., initial thickness) and the annealing conditions. With the purpose of studying changes induced upon X-ray irradiation using SPR as a probe, we have designed and developed a SPR system based on the Kretschmann-Raether configuration compatible with a X-ray absorption spectroscopy (XAS) beamline (SPR-XAS setup). Using this device, a study of the effects of the X-rays on glasses and Co-Phthalocyanines (CoPcs) has been carried out. For the study on glasses, two different types are analyzed: soda-lime and silica substrates, and for the case of the CoPcs, these have been grown varying the film thickness and the growth conditions

In this work, surface plasmon resonance (SPR) spectroscopy has been employed as a probe to study modifications in nanostructured systems based on Au. Those modifications include a) structural and morphological changes induced by annealing and b) electronic modifications upon X-ray irradiation. The use of SPR spectroscopy to follow the evolution of modifications in nanostructures (especially, in situ and in real time) has been scarcely explored and its study results interesting and relevant for the plasmonic technology. In this first part of the work, we have grown nanostructures from Au films and Au/Fe bilayers which have been later annealed under different conditions. These nanostructures have been characterized morphologically and analyzed by SPR spectroscopy, in order to follow the morphological changes of the systems varying the sample features (i.e., initial thickness) and the annealing conditions. With the purpose of studying changes induced upon X-ray irradiation using SPR as a probe, we have designed and developed a SPR system based on the Kretschmann-Raether configuration compatible with a X-ray absorption spectroscopy (XAS) beamline (SPR-XAS setup). Using this device, a study of the effects of the X-rays on glasses and Co-Phthalocyanines (CoPcs) has been carried out. For the study on glasses, two different types are analyzed: soda-lime and silica substrates, and for the case of the CoPcs, these have been grown varying the film thickness and the growth conditions, En este trabajo se ha empleado la espectroscopía de resonancia de plasmones de superficie (SPR) para estudiar modificaciones en sistemas nanoestructurados basados en Au. Estas modificaciones incluyen a) cambios estructurales y morfológicos inducidos mediante tratamientos térmicos y b) modificaciones electrónicas bajo irradiación con rayos X. El uso de la espectroscopía de SPR para seguir la evolución de modificaciones en nanoestructuras (especialmente, in situ y en tiempo real) ha sido escasamente explorado y su estudio resulta interesante y relevante para el campo de la plasmónica. En la primera parte de este trabajo se ha llevado a cabo la fabricación de nanoestructuras a partir de películas de Au y bicapas Au/Fe tratadas térmicamente bajo diferentes condiciones. Estas nanoestructuras han sido caracterizadas morfológicamente y analizadas mediante espectroscopía de SPR con el fin de estudiar los cambios estructurales inducidos en las muestras al variar parámetros como el espesor y las condiciones del tratamiento térmico. Con el objetivo de estudiar modificaciones inducidas en la materia bajo irradiación con rayos X usando la SPR como sonda, se ha diseñado y desarrollado un sistema experimental de SPR basado en la configuración de Kretschmann-Raether y compatible con la espectroscopía de absorción de rayos X (dispositivo SPR-XAS). Mediante este montaje experimental se han analizado los efectos inducidos por los rayos X en vidrios y en Ftalocianinas de Co (CoPcs), in situ y en tiempo real. Para el caso de los vidrios, dos tipos diferentes han sido empleados como substratos: sodicocálcicos y de sílice. Por otro lado, las CoPcs estudiadas han sido crecidas variando su espesor y las condiciones de crecimiento

© 2013 American Institute of Physics. This work has been supported by the Spanish Ministerio de Ciencia e Innovacion (MICINN) through Project Nos. FIS-2008-06249 and MAT2009-14578-C03-02 and by Comunidad de Madrid, Project NANOBIOMAGNET (S2009/MAT-1726). A. Serrano thanks the CSIC for JAEPredoctoral fellowship. We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and the Spanish Ministerio de Economıa y Competitividad (MECC) and Consejo Superior de Investigaciones Cientıficas (CSIC) for financial support (PE- 2010 6 0E 013) and for provision of synchrotron radiation facilities. We would like to thank the BM25-SpLine staff for the technical support and help far beyond their duties. Finally, the authors acknowledge C. de Julian Fernandez for the access to the spectrophotometer at the Dipartimento di Chimica, University of Firenze. We would like to thank the referee for valuable comments and suggestions., We present here a study of hard X-ray irradiation of soda-lime glasses performed in situ and in real time. For this purpose, we have used a Au thin film grown on glass and studied the excitation of its surface plasmon resonance (SPR) while irradiating the sample with X-rays, using a recently developed experimental setup at a synchrotron beamline [Serrano et al., Rev. Sci. Instrum. 83, 083101 (2012)]. The extreme sensitivity of the SPR to the features of the glass substrate allows probing the modifications caused by the X-rays. Irradiation induces color centers in the soda-lime glass, modifying its refractive index. Comparison of the experimental results with simulated data shows that both, the real and the imaginary parts of the refractive index of soda-lime glasses, change upon irradiation in time intervals of a few minutes. After X- ray irradiation, the effects are partially reversible. The defects responsible for these modifications are identified as non-bridging oxygen hole centers, which fade by recombination with electrons after irradiation. The kinetics of the defect formation and fading process are also studied in real time., Ministerio de Ciencia e Innovacion (MICINN), Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Consejo Superior de Investigaciones Científicas (CSIC), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

En este trabajo hemos realizado un estudio, mediante espectroscopías de infrarrojo y de electrones, de las especies adsorbidas en superficie y su evolución durante la descomposición de metanol sobre rutenio (0001). A continuación, se describen las principales contribuciones que hemos realizado a este amplio tema de estudio. Por una parte, la investigación aquí descrita se ha realizado bajo condiciones que hemos tratado que sean cercanas a las existentes en la catálisis real. El rango de presiones con el que hemos trabajado abarca desde el ultra-alto vacío hasta los 1x10-2 mbar. Las superficies han sido expuestas a exposiciones de hasta 2x107 L, llegando a un estado que corresponde prácticamente a la saturación y que ha sido estudiado con detenimiento. Por razones similares, la temperatura se ha mantenido alrededor de los 300 K. Por otra parte, hemos comparado el comportamiento de superficies planas con el de superficies modificadas, en las que una gran densidad de escalones han sido generados de modo controlado. Así, hemos estudiado el papel de estos defectos a la hora de activar nuevos caminos de reacción. Además, hemos llevado a cabo otro conjunto de experimentos coadsorbiendo oxígeno y metanol sobre la superficie de rutenio, y hemos analizado estos resultados en términos de modificación química de la superficie de rutenio. Para la realización de los experimentos hemos diseñado y construido un nuevo sistema de ultra-alto vacío que permite la incorporación de la técnica FT-IRAS. El sistema experimental está compuesto por dos campanas que trabajan en el rango de presiones del ultra-alto vacío: una campana de preparación que incluye varias técnicas típicas de caracterización superficial, y una cámara de infrarrojo (conectada pero aislada de la campana principal) donde se llevan a cabo los experimentos de espectroscopía de infrarrojo. Esta cámara, normalmente en ultra-alto vacío, puede alcanzar altas presiones. En el caso de la adsorción de metanol, el resultado princ

En este trabajo hemos realizado un estudio, mediante espectroscopías de infrarrojo y de electrones, de las especies adsorbidas en superficie y su evolución durante la descomposición de metanol sobre rutenio (0001). A continuación, se describen las principales contribuciones que hemos realizado a este amplio tema de estudio. Por una parte, la investigación aquí descrita se ha realizado bajo condiciones que hemos tratado que sean cercanas a las existentes en la catálisis real. El rango de presiones con el que hemos trabajado abarca desde el ultra-alto vacío hasta los 1x10-2 mbar. Las superficies han sido expuestas a exposiciones de hasta 2x107 L, llegando a un estado que corresponde prácticamente a la saturación y que ha sido estudiado con detenimiento. Por razones similares, la temperatura se ha mantenido alrededor de los 300 K. Por otra parte, hemos comparado el comportamiento de superficies planas con el de superficies modificadas, en las que una gran densidad de escalones han sido generados de modo controlado. Así, hemos estudiado el papel de estos defectos a la hora de activar nuevos caminos de reacción. Además, hemos llevado a cabo otro conjunto de experimentos coadsorbiendo oxígeno y metanol sobre la superficie de rutenio, y hemos analizado estos resultados en términos de modificación química de la superficie de rutenio. Para la realización de los experimentos hemos diseñado y construido un nuevo sistema de ultra-alto vacío que permite la incorporación de la técnica FT-IRAS. El sistema experimental está compuesto por dos campanas que trabajan en el rango de presiones del ultra-alto vacío: una campana de preparación que incluye varias técnicas típicas de caracterización superficial, y una cámara de infrarrojo (conectada pero aislada de la campana principal) donde se llevan a cabo los experimentos de espectroscopía de infrarrojo. Esta cámara, normalmente en ultra-alto vacío, puede alcanzar altas presiones. En el caso de la adsorción de metanol, el resultado princ

En esta tesis se ha mostrado cómo la técnica de nanoindentación realizada con un microscopio de fuerzas atómicas (AFM) permite el estudio a escala nanométrica de las propiedades mecánicas de un material. Se han realizado experimentos en oro y en dióxido de titanio, asistidos por simulaciones atomísticas. Para las superficies planas metálicas, se aprecian regiones elástica y plástica. En la región elástica se observa una deformación reversible, mientras que en la región plástica se observa una huella permanente. En la tesis se demuestra la relevancia del estado de la superficie en la deformación incipiente, y en particular, cómo los escalones actúan como centros de nucleación heterogénea de dislocaciones. Así se explica la aparición de una nueva región en las curvas fuerza vs penetración, que se ha denominado cuasiplástica. Esta región presenta un comportamiento con características propias tanto de la región elástica como de la plástica (se observa nucleación reversible de dislocaciones). Además, el límite elástico se ve reducido un 30% por los defectos, respecto al valor en la superficie plana. Se han estudiado también las propiedades mecánicas de superficies de oro nanoestructuradas mediante bombardeo iónico. Se ha propuesto un mecanismo de deformación similar al de la muestra escalonada. En el caso de la superficie plana de TiO2(110), se ha propuesto un mecanismo de plasticidad similar al de los metales: se llega al límite elástico cuando se alcanza la tensión crítica teórica. Superada ésta se ha observado una dureza inusualmente reducida en comparación a la dureza a escala micrométrica. Este hecho se ha explicado proponiendo un mecanismo de deformación a escala nanométrica mediante la creación de dislocaciones por fuentes de baja barrera.

En esta tesis se ha mostrado cómo la técnica de nanoindentación realizada con un microscopio de fuerzas atómicas (AFM) permite el estudio a escala nanométrica de las propiedades mecánicas de un material. Se han realizado experimentos en oro y en dióxido de titanio, asistidos por simulaciones atomísticas. Para las superficies planas metálicas, se aprecian regiones elástica y plástica. En la región elástica se observa una deformación reversible, mientras que en la región plástica se observa una huella permanente. En la tesis se demuestra la relevancia del estado de la superficie en la deformación incipiente, y en particular, cómo los escalones actúan como centros de nucleación heterogénea de dislocaciones. Así se explica la aparición de una nueva región en las curvas fuerza vs penetración, que se ha denominado cuasiplástica. Esta región presenta un comportamiento con características propias tanto de la región elástica como de la plástica (se observa nucleación reversible de dislocaciones). Además, el límite elástico se ve reducido un 30% por los defectos, respecto al valor en la superficie plana. Se han estudiado también las propiedades mecánicas de superficies de oro nanoestructuradas mediante bombardeo iónico. Se ha propuesto un mecanismo de deformación similar al de la muestra escalonada. En el caso de la superficie plana de TiO2(110), se ha propuesto un mecanismo de plasticidad similar al de los metales: se llega al límite elástico cuando se alcanza la tensión crítica teórica. Superada ésta se ha observado una dureza inusualmente reducida en comparación a la dureza a escala micrométrica. Este hecho se ha explicado proponiendo un mecanismo de deformación a escala nanométrica mediante la creación de dislocaciones por fuentes de baja barrera.

© World Scientific Publishing Company., We review here our recent results of experimental observation of room temperature magnetism in gold nanoparticles (NPs) and thin. films. Capping gold surfaces with certain organic molecules leads to the appearance of magnetism at room temperature. The surface bonds between the organic molecules and Au atoms give rise to magnetic moments. These magnetic moments are blocked along the bond direction showing huge anisotropy. In the case of atomically. at surfaces, the magnetic moments are giants. An explanation of this orbital ferromagnetism is given. These results point out the possibility to observe magnetism at nanoscale in materials without typical magnetic atoms ( transition metals and rare earths), and are of fundamental value to understand the magnetic properties of surfaces., Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Hemos estudiado los defectos superficiales en Au(001) 5x20 generados mediante dos diferentes técnicas experimentales: bombardeo iónico de baja energía y nanoindentación. Hemos analizado estos defectos con microscopía de efecto túnel (STM). Los experimentos de bombardeo de iones Ar+ con energía E=600 eV revelan que los defectos producidos a muy bajas dosis son dipolos de dislocación bidimensionales. Se forman mediante la difusión anisótropa y agregación de las vacantes generadas por cada uno de los impactos iónicos. A dosis media observamos transformaciones estructurales en la reconstrucción, que puede rotar o desaparecer. Finalmente, a altas dosis, observamos una superficie nanoestructurada, con cráteres formando un red que puede llegar a tener un cierto orden a corto alcance. Respecto a los defectos producidos por nanoindentación identificamos los mecanismos incipientes de deformación plástica en una superficie fcc (001). Por un lado, se emiten dislocaciones helicoidales que mediante deslizamiento dan lugar a terrazas alrededor del punto de indentación. Por otro lado, observados y caracterizamos la emisión, hasta distancias del orden de cientos de angstroms, de semilazos de dislocación disociados emergentes, que son fruto del desplazamiento plástico expulsado a lo largo de un sistema de deslizamiento principal del cristal

Hemos estudiado los defectos superficiales en Au(001) 5x20 generados mediante dos diferentes técnicas experimentales: bombardeo iónico de baja energía y nanoindentación. Hemos analizado estos defectos con microscopía de efecto túnel (STM). Los experimentos de bombardeo de iones Ar+ con energía E=600 eV revelan que los defectos producidos a muy bajas dosis son dipolos de dislocación bidimensionales. Se forman mediante la difusión anisótropa y agregación de las vacantes generadas por cada uno de los impactos iónicos. A dosis media observamos transformaciones estructurales en la reconstrucción, que puede rotar o desaparecer. Finalmente, a altas dosis, observamos una superficie nanoestructurada, con cráteres formando un red que puede llegar a tener un cierto orden a corto alcance. Respecto a los defectos producidos por nanoindentación identificamos los mecanismos incipientes de deformación plástica en una superficie fcc (001). Por un lado, se emiten dislocaciones helicoidales que mediante deslizamiento dan lugar a terrazas alrededor del punto de indentación. Por otro lado, observados y caracterizamos la emisión, hasta distancias del orden de cientos de angstroms, de semilazos de dislocación disociados emergentes, que son fruto del desplazamiento plástico expulsado a lo largo de un sistema de deslizamiento principal del cristal