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This work compares the anticorrosion features of polysiloxane hybrid films deposited on carbon steel substrates by dip-coating. To assess the influence of the components, sol-gel coatings were prepared from condensation and polymerization of TEOS and MPTS, TEOS and MTES, TMOS and MPTS or TMOS and MTES mixtures in three molar ratios. The corrosion protection of the coatings was evaluated by means of polarization curves and electrochemical impedance spectroscopy measurements. The coatings' thickness was quantified by field emission-scanning electron microscopy. The results indicate that all the coatings improved the corrosion resistance of carbon steel in an alkaline environment contaminated with 3. wt.%NaCl solution and show that the protective properties of the coating were especially improved when MTES was added to the formulations and when the TMOS/MPTS mixture was used, probably due to a highly cross-linked network and a greater coating thickness, capable of delaying the corrosion process. © 2014 Elsevier B.V.

The apatite-type compounds Ca2-xBaxLa 6Bi2(SiO4)6O2 (0 ≤ x ≤ 2) have been prepared by high temperature solid-state reaction technique. Samples have been investigated by powder X-ray diffraction (XRD), infrared absorption spectroscopy (IR), Raman scattering spectroscopy (Raman) and 29Si MAS-NMR spectroscopy. IR, Raman and NMR techniques have been used to demonstrate the presence of isolated SiO4 groups and to investigate the cation distribution around the silicate tetrahedra. The analysis of 29Si MAS-NMR spectra indicates that Ca and Ba distribution becomes disordered at intermediate compositions. An impedance analysis has been used to analyze the electrical behavior of samples as a function of frequency at different temperatures. Evidences of temperature-dependent electrical relaxation phenomena have been observed. © 2014 Elsevier B.V. All rights reserved.

Universal dielectric response (UDR) and nearly constant loss (NCL) dispersive regimes have been investigated in fast ion conductors with perovskite and NASICON structure by using NMR and impedance spectroscopy (IS). In this study, the electrical behavior of La0.5Li0.5TiO 3 (LLTO-05) perovskite and Li1.2Ti1.8Al 0.2(PO4)3 (LTAP0-02) NASICON compounds was investigated. In both systems a three-dimensional network of conduction paths is present. In the Li-rich LLTO-05 sample, lithium and La are randomly distributed on A-sites of perovskites, but in LTAP0-02 Li and cation vacancies are preferentially disposed at M1 and M2 sites. In perovskite compounds, local motions produced inside unit cells are responsible for the large >near constant loss> regime detected at low temperatures, however, in the case of NASICON compounds, local motions not participating in long-range charge transport were not detected. In both analyzed systems long-range correlated motions are responsible for dc-conductivity values of ceramic grains near 10-3 S cm-1 at room temperature, indicating that low-temperature local motions, producing large NCL contribution, are not required to achieve the highest ionic conductivities. This journal is © the Partner Organisations 2014.

All rights reserved. Mesocrystals (superstructures of crystallographically-oriented inorganic nanocrystals) represent sophisticated configurations generated from biomineralization processes, and an example of nonclassical crystallization mechanisms. Being the closest relatives to single-crystals at the nanoscale, porous mesocrystals are considered as ideal configurations to improve functional properties, and to correlate structural and textural features with materials functionality. Here we show that TiO2 anatase mesoporous colloidal mesocrystals, synthesized by a self-assembly/seeding method, can be easily processed as active materials in anode composites. These anode composites can be efficiently infiltrated during battery operation with safe aprotic ionic liquid electrolytes down to the mesoporosity of mesocrystals (3-4 nm), and operate over a wider temperature window than organic carbonates. For example, after continuous galvanostatic cycling for 1 month at high temperatures (15 days at 60 °C + 15 days at 80 °C, ∼130 cycles), these anode composites sustain a capacity at 67 mA g-1 that is still remarkable for TiO2-based anodes (155 mAh g-1 or 200 mAh cm-3, coulombic efficiency of ∼99%). On contrast, in organic carbonates the capacity decays down to 80 mAh g-1 after only 15 days at 60 °C. Our results suggest that the principles derived from porous anatase mesocrystal/ionic liquid electrolyte combinations could constitute the basis for battery applications in which safety, durability and variability in operating temperature represent the primary concerns.

Hybrid organic-inorganic films have been prepared by hydrolysis and condensation of several silicon compounds: 3-methacryloxypropyltrimethoxysilane (MPTS) or methyltriethoxysilane (MTES) and tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS) precursors using four [TEOS] or [TMOS]/[MPTS] or [MTES] molar ratios: 0, 0.5, 1 and 2. The progress on the organic and inorganic polymerizations was followed employing thermogravimetric analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), 13C and 29Si nuclear magnetic resonance (NMR). These techniques have provided information about the hybrid network formation inside films. The formation of the hybrids prepared from [TEOS]/[MPTS] and [TMOS]/[MPTS] mixtures was accomplished through the reaction of SiOR groups, via condensation of silanols (inorganic condensation), and opening of the CC double bond in MPTS (organic polymerization). The formation of the hybrids prepared from [TEOS]/[MTES] and [TMOS]/[MTES] mixtures was mainly accomplished through the reaction of SiOR groups. The increment of TEOS or TMOS in MPTS mixtures favored the inorganic (Q3 and Q4 units) condensation. Total degrees of condensation for hybrids synthetized with [TEOS] or [TMOS]/[MTES] were higher than those obtained with [TEOS] or [TMOS]/[MPTS], so MTES favored the formation of hybrids with branched organic structures.

En las últimas décadas el número de trabajos centrados en encontrar alternativas que permitan resolver las necesidades actuales de fuentes de energías ligeras, económicas, no contaminantes y fiables ha aumentado considerablemente. Aunque en la actualidad las fuentes fósiles y nucleares sean las principales proveedoras de energía, la conciencia ambiental y lo limitado de algunos recursos ha fortalecido la búsqueda de nuevas formas de generación, almacenamiento y distribución de energía. Los electrolitos sólidos debido a su capacidad de transportar carga al interior de su estructura por medio de iones, han llamado la atención para su uso en dispositivos electroquímicos tales como celdas de combustible y baterías recargables. La investigación generada en torno a estos materiales se ha dirigido principalmente hacia tres campos: 1. El estudio de los mecanismos de transporte y difusión en materiales. 2. La optimización de las propiedades de transporte presentadas por materiales iónicos. 3. El estudio de dispositivos para generación y almacenamiento de energía. Nuestro trabajo se ha centrado en los dos primeros puntos, para lo cual se han escogido materiales cristalinos con estructura conocida que presentan altos valores para la conducción del ion Litio y que sirven de referencia a la hora de entender el fenómeno de conducción. Estos materiales son sistemas de la familia La2/3-xLi3xTiO3 (LLTO) con estructura tipo Perovskita y muestras Li1+xTi2-xAlx(PO4)3 (LTAPO) con estructura tipo NASICON. Además se abordara la sustitución de Lantano por un catión más grande (Sr2+) en la familia LLTO. El estudio comparativo de estas dos familias nos permitirá analizar algunos de los problemas planteados sobre la dinámica de los portadores en conductores iónicos rápidos. El objetivo principal de este proyecto ha sido estudiar los mecanismos de conducción en los dos tipos de compuestos, analizando el efecto que tiene el aumento/disminución del contenido en vacantes y/o portadores de carga

Lithium extraction from the Li-excess Li1.10Mn 1.90O4 spinel has been performed by chemical and electrochemical methods in aqueous and in organic media, respectively. De-lithiated samples have been investigated by XRD, SEM, TG, 7Li and 1H MAS-NMR techniques. The comparative study has allowed demonstrating that the intermediate de-intercalated samples prepared during the chemical extraction by acid titration are similar to those prepared by the electrochemical way in a non-aqueous electrolyte. LiMn2O4 based spinel with a tailored de-lithiation degree can be prepared as a single phase by controlling the pH used in chemical extraction. 7Li MAS-NMR spectroscopy has been used to follow the influence of the manganese oxidation state on tetra and octahedral Li-signals detected in Li-extracted samples. The oxidation of Mn(iii) ions goes parallel to the partial dissolution of the spinel, following Hunter's mechanism. Based on this mechanism, a generalized chemical reaction has been proposed to explain the formation of intermediate Li+ de-intercalated samples during acid treatment in aqueous media. By the 1H MAS NMR study, no evidence of Li-H topotactic exchange in the bulk of the acid treated material was found. This journal is © the Owner Societies 2014.

Rat model of Obstructive Sleep Apnea (OSA) is a realistic approach for studying physiological mechanisms involved in sleep. Rats are usually anesthetized and autonomic nervous system (ANS) could be blocked. This study aimed to assess the effect of anesthesia on ANS activity during OSA episodes. Seven male SpragueDawley rats were anesthetized intraperitoneally with urethane (1 g/kg). The experiments were conducted applying airway obstructions, simulating 15s-apnea episodes for 15 minutes. Five signals were acquired: respiratory pressure and flow, Sa02, ECG and photoplethysmography (PPG). In total, 210 apnea episodes were studied. Normalized power spectrum of Pulse Rate Variability (PRV) was analyzed in the Low Frequency (LF) and High Frequency (HF) bands, for each episode in consecutive 15s intervals (before, during and after the apnea). All episodes showed changes in respiratory flow and Sa02 signal. Conversely, decreases in the amplitude fluctuations of PPG (DAP) were not observed. Normalized LF presented extremely low values during breathing (median=7,67%), suggesting inhibition of sympathetic system due to anesthetic effect. Subtle increases of LF were observed during apnea. HRV and PPG analysis during apnea could be an indirect tool to assess the effect and deep of anesthesia., Peer Reviewed, Postprint (published version)

Metal oxides structures, formed by ordered self-assembling of crystalline nanoparticles aggregates, are attracting growing attention in fields such as catalysis or solar cells. The properties of these structures are influenced not only by their morphology and nanoparticles composition but also by the assembled particles boundaries. In order to determine the influence of these boundaries on the structures properties, the present investigation has been devoted to study the characteristics of anatase nanoparticles boundaries in titania aggregates prepared by TiCl4 hydrolysis at low temperature. Proton magic angle spinning nuclear magnetic resonance and high resolution transmission electron microscopy show that these samples mainly contain amorphous TiO 2 strongly bound to specific faces of anatase particles. This amorphous titania-mediated attachment induces the ordered self-assembling of the anatase particles, with favored formation of mesopores in the nanoparticles boundaries. Photocatalytic degradation of 4-methoxybenzyl alcohol in water, test reaction used as a method to get information on the boundaries properties, indicates that the mesoporous amorphous TiO2 offers active sites for the alcohol catalytic partial oxidation, but it strongly hampers inter-particles electron transfer. These effects, characteristic of amorphous oxide chain morphology, can be expected when low dispersed dopants or promoters are incorporated to metal oxides. © 2013 Elsevier B.V. All rights reserved.

The structures of K-rich feldspar, (K>Na)AlSi3O8, are currently described as >ideal> crystals with periodic average structures from Bragg diffraction maxima obtained by reciprocal-space techniques. Polymorphism is explained by variable substitutional disorder of framework Si and Al cations in tetrahedral T sites, and positional disorder of cavity alkali cations in a single M site. Here, high-resolution magic angle spinning multinuclear magnetic resonance spectroscopy, leading to 29Si, 27Al, and 23Na spectra at 9.4 as well as 27Al, 39K, and 23Na spectra at 19.6 T, has been used to investigate the >real> structures along the order-disorder series of K-feldspar crystals. The >ideal> and >real> structure coincides only in the perfectly long-range ordered triclinic end-member of the low-microcline structure. Long-range disordered structures (either with monoclinic or triclinic symmetry by X-ray diffraction) show non-random disorder at the medium-range scale, triclinic-like distortions with four sets of T sites for framework atoms, two sets of M sites for alkali atoms, and Al-O-(K,Na) multi-site correlations by NMR spectroscopy. The K-feldspar structures can be described by a medium-range structure using the number of Al atoms per four-membered rings of tetrahedra, with >...-2-0-2-0-...> chains for microcline and orthoclase where the Al-occupancies t1O > t2m > t2O ≈ t1m, and with >...-1-1-1-1-...> chains for valencianite and sanidine, in which t1O > t2m ≈ t2O ≈ t1m. Framework cations respect Loewenstein's rule (Al-O-Al avoidance), as well as some additional constraints of charge dispersion involving deficiency of Si atoms in Q4 (4Si,0Al), (1Si,3Al), and (0Si,4Al) environments, constraints which are particularly strong in valencianite. These >real> structure features cannot be described by >ideal> structures owing to the lack of resolving power of the reciprocal-space techniques.

The properties and structures of three commercial metakaolins were evaluated for their use in geopolymer materials. The dehydroxylation processes used on these three metakaolins (rotary, flash or oven processes) induce varying reactivities and purities according to the results obtained by FTIR spectroscopy, XRD, 27Al MAS-NMR, TEM characterization, and DTA. The flash-calcined metakaolin is the most reactive one. After geopolymerization, the impurities (such as quartz or micas) and the reactivities of the raw metakaolins induce the formation of different networks within the geopolymer material. This study demonstrates the main role of the metakaolin dehydroxylation process, the effect of impurities and the use of the wettability as an indicator of metakaolin reactivity. © 2013 Elsevier B.V.

Geopolymer materials are obtained by the alkaline activation of aluminosilicate sources, the best of which is metakaolin. However, every raw material is different, and very few comparative studies have been done on different metakaolin sources. The aim of this work is to develop methods for the prediction of the working properties of geopolymer materials based on the reactivity of the metakaolin employed. Infrared spectroscopy showed direct relationships between the wettability, the Si/Al ratio and the kinetics of conversion of Si-O-Si bonds to Si-O-Al bonds. Moreover, it was demonstrated that the presence of impurities and the reactivity of the metakaolin can generate the formation of one or several networks. Finally, a descriptive model of the mechanism of geopolymer formation was proposed that takes into account the quality of metakaolin used. © 2013 Elsevier Inc.

A complex impedance of oxyapatites Ca2-xBaxLa 4Bi4(SiO4)6O2 (0≤x≤2) prepared by solid state reaction has been investigated. The formation of apatites has been checked by X-ray diffraction, FTIR, Raman and 29Si MAS-NMR techniques. The electric impedance data indicate that relaxation phenomena are strongly dependent on temperature in the 923-1048 K range. The bulk resistance decreases with increasing temperature, showing a typical negative temperature coefficient of resistance (NTCR). ac-Conductivity measurements have been performed on a wide range of frequencies and temperatures. The complex modulus plots have confirmed the presence of bulk contributions. The complex impedance analysis suggests the presence of non-Debye relaxations that would be associated with correlation on ions motion. © 2013 Elsevier Ltd and Techna Group S.r.l.

Procedimiento de obtención de materiales multifuncionales y renovables a partir del rechazo de pipa procedente de la producción de aceite de girasol. La presente invención se refiere al procedimiento de obtención de materiales renovables, a partir de residuos precedentes de la fabricación de aceite de girasol, para su uso como matrices biocompatibles en ingeniería de tejidos, administración controlada de sustancias de interés biológico (drogas, proteínas, genes, etc.) y como catalizadores en procesos activados por centros básicos, utilizando tanto calentamiento dieléctrico, como activación solar, para aumentar la sostenibilidad del proceso.

Incorporation of silver nanoparticles enhances the biocide functionality of Ag supported kaolinite/metakaolite materials. In this regard, structural evolution of supports in the presence of silver nanoparticles is investigated. For this purpose, 27Al and 29Si magic-angle-spinning nuclear magnetic resonance spectroscopy was applied to investigate the bonding between silver nanoparticles and kaolinite/metakaolin materials. The incorporation of silver nanoparticles, following a chemical or thermal reduction, does not change the structure of kaolin, whereas in the case of metakaolin, a preferential interaction with tetrahedral sheets was observed and some stabilization of hexacoordinated aluminium is favoured.

In a recent work, it has been proved that soda-lime glasses, belonging to the SiO2–Na2O–CaO–B2O3 system with a high content of calcium oxide (15 to 20 wt.%), are efficient biocides against Gram positive, negative bacteria and yeast. In the present work we discuss the possible mechanism responsible for the biocide action of these series of glasses against Escherichia coli microorganisms. The local structure of these glasses has been investigated by MAS-NMR spectroscopy. The importance of the strength with which calcium is retained in the glass structure has been pointed out. This strength decreases as the condensation degree of tetrahedral in the glass structure decreases, as a consequence the biocide activity also increases.

The complexity of the ZrO2–CeO2 phase diagram arises from several factors: the low solubility of each compound into the other one, the slow kinetics of cation diffusion, the occurrence of Ce reduction at high temperatures, and the existence of several metastable phases whose appearance and evolution depend on synthesis method and thermal history of the sample. Identification of phase content is moreover complicated because the X-ray diffractograms of some ZrO2–CeO2 phases are very close or even indistinguishable, which imposes the use of other techniques more sensitive to small oxygen displacements. In this work we present a Raman spectroscopic study of phase segregation in the ZrO2–CeO2 system between 1300 and 1650 °C, focusing on the effect of Ce reduction at high temperatures and its relation with the appearance of metastable phases upon cooling. The nature of the high-temperature defective cubic phase is discussed.

Análisis de medios audiovisuales. Vídeo online y nuevas narrativas. Analysis of media. Online video and new storytelling

[ES] Alguna vez, puede que en la misma Escuela donde estudiamos, oímos esa reflexión que argumenta lo siguiente: si los proyectos estuvieran perfectamente descritos y si el constructor supiera exactamente lo que tiene que hacer, la figura del Aparejador no tendría razón de ser.

Partially deuterated Ca3Al2(SiO4)y(OH)12−4y–Al(OH)3 mixtures, prepared by hydration of Ca3Al2O6 (C3A), Ca12Al14O33 (C12A7) and CaAl2O4 (CA) phases in the presence of silica fume, have been characterized by 29Si and 27Al magic-angle spinning–nuclear magnetic resonance (MAS–NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca3Al2(OH)12 and Al(OH)3 phases were detected. From the quantitative analysis of 27Al NMR signals, the Al(OH)3/Ca3Al2(OH)12 ratio was deduced. The incorporation of Si into the katoite structure, Ca3Al2(SiO4)3−x(OH)4x, was followed by 27Al and 29Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of 27Al MAS–NMR components associated with Al(OH)6 and Al(OSi)(OH)5 environments. The 29Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C–S–H and C–A–S–H for short. From 29Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures.

[EN] A structural and spectroscopic characterization of crystalline rods of Ce0.4Zr0.6O2 grown by the laser floating zone (LFZ) method is presented. A precursor rod of Ce0.4Zr0.6O2 composition was sintered at 1500 ºC in air atmosphere and then processed by the LFZ technique with a CO2 laser. The processed material was characterized by XRD, SEM and Raman spectroscopy. In the as-grown, dark-color processed rod, the Raman spectrum evolves radially from a t’-like one, corresponding to Ce0.37Zr0.63O2 composition, at the edge of the rod, to a very broad and weak, cubic-like one, at the center. The degree of cerium reduction and oxygen non-stoichiometry were determined through measurements of the electronic Raman spectrum of Ce3+. A strong Ce3+ signal was found at the core of the rod, indicating strong reduction, whereas no Ce3+ signal was detected at the edge. To restore oxygen and Ce4+ content a section of the fiber was reoxidized at 620 ºC for 24 h. A very homogeneous spectrum was found in the reoxidized sample, that was assigned to a t’-phase of composition Ce0.42Zr0.58O2., [ES] Presentamos una caracterización estructural y espectroscópica de fibras cristalinas de Ce0.4Zr0.6O2 crecidas mediante fusión zonal asistida por láser (LFZ). Una barra del material precursor, de composición Ce0.4Zr0.6O2, fue sinterizada a 1500 ºC en atmósfera de aire y después procesada por LFZ con un láser de CO2. El material procesado fue caracterizado por difracción de rayos X, microscopía electrónica de barrido y espectroscopía Raman. En la fibra recién procesada, de color gris oscuro, el espectro Raman varía radialmente desde un espectro de tipo t’, correspondiente a una composición Ce0.37Zr0.63O2, en el borde de la fibra, hasta un espectro muy ensanchado y débil, de aspecto cúbico, en el centro. El grado de reducción del cerio y la no estequiometría del oxígeno se determinaron a través de las medidas del Raman electrónico del Ce3+. La señal de Ce3+ era muy intensa en el centro de la fibra, lo que indica una fuerte reducción, mientras que no se detectó en el borde. Para restablecer el contenido de oxígeno y de Ce4+ una parte de la fibra fue reoxidada a 620 ºC durante 24 h. El espectro de la muestra reoxidada, de color amarillo pálido y muy homogénea, fue asignado a una fase t’ de composición Ce0.42Zr0.58O2.

Nuclear magnetic resonance (NMR) spectroscopy provides information on both the structural and dynamic aspects of solids, including clay minerals. The application of multinuclear high-resolution NMR spectroscopy over the past two decades provided valuable information on the structures of phyllosilicates, such as crystallographic sites, cation coordination, silicate network distortion, and cation distributions. However, conventional low-resolution NMR spectroscopy is still useful for investigating the surface orientation of adsorbed molecules and their mobility. In situ reactions among co-adsorbed molecules or between adsorbed species and clay mineral surfaces can now be studied by high-resolution NMR—magic-angle spinning (MAS) and cross-polarization MAS (CP-MAS) techniques. The formation of pillared clays was extensively studied by multinuclear NMR spectroscopy. The same can be said for zeolite formation by alkali treatment of clay minerals. These developments have important implications for the industrial applications of clays and clay minerals.

[ES] Se han muestreado y estudiado ochenta y seis microclinas con textura pertítica procedentes de siete pegmatitas graníticas por difracción de rayos-X (DRX), fluorescencia de rayos-X (FRX) y microscopía óptica de luz transmitida (MLT). La tendencia hacia la bimodalidad estructural y la coexistencia de multitud de estados estructurales se describe considerando las microclinas pegmatíticas no como pseudomorfos heterogéneos sino como cristales complejos. Según ésta descripción, los estados estructurales no están distribuidos al azar sino que están organizados según patrones estructurales en torno a las interfases con el feldespato sódico en venas macropertíticas. La tendencia a la bimodalidad en el estado estructural permite distinguir entre microclinas desordenadas y ordenadas, cuyo origen se puede correlacionar con una dualidad en su evolución al estado sólido según un régimen genético estático y otro dinámico durante el enfriamiento. El régimen estático produce un re-equilibrado limitado porque la recristalización de regiones con mayor orden Si/Al es superficial. El ordenamiento Si/Al está localizado en las proximidades de las superficies con circulación acanalada de fluidos acuosos catalizadores de las transformaciones estructurales. El régimen dinámico es adaptativo y el re-equilibrado es extenso operando por recristalización global. Este comportamiento se explica por el flujo volumétrico de las moléculas de agua catalizadoras del re-equilibrado. La penetración parcial del agua a través de la estructura produce un régimen transicional entre los dos anteriores., [EN] Eighty six microclines with perthitic texture from seven granitic pegmatites have been collected and studied by X-ray diffraction (XRD), X-ray fluorescence (XRF) and optical microscopy (OM). The statistical distribution of the structural state of the microclines shows a tendency to bimodality and also the coexistence of different triclinicities. Pegmatitic microclines are better described when considered as complex crystals and not as heterogeneous pseudomorphic assemblages after sanidine transformation, because the structural state is organized following structural patterns around the interfase with Na-feldspar veins in macroperthitic texture. This tendency to bimodality allows to distinguish among disordered and ordered microclines linked with static and dynamic genetic regimes of solid state evolution on cooling. The static regime produces limited reequilibration since a surface re-crystallization process of regions with high local Si/Al order occurs along boundaries. The ordering is located next to circulation surfaces because the catalyst aqueous fluids have mainly a channeled motion. The dynamic regime is adaptative and important volumes are re-equilibrated by bulk re-crystallization give rise to an ordered microcline. This behavior can be explained considering that a volumetric flow of catalyst water molecules promote global Si/Al ordering. A transitional regime can be distinguished by partial penetration of water through the structures.

El objetivo de esta Tesis es el estudio de la respuesta dinámica de iones móviles mediante espectroscopia de admitancias y resonancia magnética nuclear en diferentes materiales conductores iónicos. En la memoria se presentan fundamentalmente resultados obtenidos en óxidos de zirconio e ytrio, y titanatos de lantano y litio. Se investiga la respuesta eléctrica en estos materiales de los iones en el proceso de conducción iónica. Se discute el proteceo microscópico de salto iónico y la influencia que tiene en él la concentración del portadores y la dimensionalidad de la conducción. Se presenta el estudio de la conductividad a largo alcance basado en una solución sólida cristalina derivada de los titanatos de lantano y litio en la cual los iones presentan un fenómeno de percolación al sustituir litio por sodio, bloqueando las vacantes necesarias para el transporte iónico. Por último se realiza un estudio detallado del régimen de pérdidas constantes, que domina la respuesta eléctrica de los conductores iónicos para tiempos muy cortos y/o temperaturas bajas, cuando la mayoría de los iones portdores están confinados en sus pozos de potencial

Reaction products formed during alkaline activation, with 8M NaOH solutions, of fly ashes have been characterized with 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MASNMR) spectroscopy. In particular, the influence of curing conditions (time and temperature of reaction) has been analyzed. NMR results show the formation of amorphous tecto-silicates in which the amount of aluminum decreases in the two consecutive formed phases. The Si/Al ratio of zeolite precursor obtained at 85°C changes from 0.95 to 1.86 when curing time is increased from 5 h to 1 week. The evolution of the mechanical properties of prepared cements has also been discussed in terms of the phases formed and texture and morphology of samples.

El objetivo de esta Tesis es el estudio de la respuesta dinámica de iones móviles mediante espectroscopia de admitancias y resonancia magnética nuclear en diferentes materiales conductores iónicos. En la memoria se presentan fundamentalmente resultados obtenidos en óxidos de zirconio e ytrio, y titanatos de lantano y litio. Se investiga la respuesta eléctrica en estos materiales de los iones en el proceso de conducción iónica. Se discute el proteceo microscópico de salto iónico y la influencia que tiene en él la concentración del portadores y la dimensionalidad de la conducción. Se presenta el estudio de la conductividad a largo alcance basado en una solución sólida cristalina derivada de los titanatos de lantano y litio en la cual los iones presentan un fenómeno de percolación al sustituir litio por sodio, bloqueando las vacantes necesarias para el transporte iónico. Por último se realiza un estudio detallado del régimen de pérdidas constantes, que domina la respuesta eléctrica de los conductores iónicos para tiempos muy cortos y/o temperaturas bajas, cuando la mayoría de los iones portdores están confinados en sus pozos de potencial