A Benzaldehyde Derivative as a Chelating Ligand: Helical Manganese(II) Coordination Polymers Assembling into a Porous Solid

A molecular, porous crystalline material constructed from neutral helical coordination polymers incorporating manganese(II) ions and two types of bridging ligands, namely the deprotonated form of 2-hydroxy-5-methoxy-3-nitrobenzaldehyde (HL) and isobutyrate (iB−), has been obtained and structurally characterized. Structural analysis reveals that within the coordination polymer each benzaldehyde derivative ligates two manganese ions in 6-membered chelating rings, and the isobutyrate ligands cooperatively chelate either two or three manganese ions. The solid state assembly of the resulting polymeric chains of formula [Mn4(L)2(iB)6]n (1), described in the polar space group R3c, is associated with tubular channels occupied by MeCN solvent molecules (1·xMeCN; x ≤ 9). TGA profiles and PXRD measurements demonstrate that the crystallinity of the solid remains intact in its fully desolvated form, and its stability and crystallinity are ensured up to a temperature of 190 °C. Gas adsorption properties of desolvated crystals were probed, but no remarkable sorption capacity of N2 and only a limited one for CO2 could be observed. Magnetic susceptibility data reveal an antiferromagnetic type of coupling between adjacent manganese(II) ions along the helical chains with energy parameters J1 = −5.9(6) cm−1 and J2 = −1.8(9) cm−1.

In situ dehydration behavior of zeolite-like pentagonite: A single-crystal X-ray study

The structural modifications upon heating of pentagonite, Ca(VO)(Si4O10)·4H2O (space group Ccm21, a=10.3708(2), b=14.0643(2), c=8.97810(10) Å, V=1309.53(3) Å3) were investigated by in situ temperature dependent single-crystal X-ray structure refinements. Diffraction data of a sample from Poona district (India) have been measured in steps of 25 up to 250 °C and in steps of 50 °C between 250 and 400 °C. Pentagonite has a porous framework structure made up by layers of silicate tetrahedra connected by V4+O5 square pyramids. Ca and H2O molecules are extraframework occupants. Room temperature diffraction data allowed refinement of H positions. The hydrogen-bond system links the extraframework occupants to the silicate layers and also interconnects the H2O molecules located inside the channels. Ca is seven-fold coordinated forming four bonds to O of the tetrahedral framework and three bonds to extraframework H2O. The H2O molecule at O9 showing a high displacement parameter is not bonded to Ca. The dehydration in pentagonite proceeds in three steps. At 100 °C the H2O molecule at O8 was released while O9 moved towards Ca. As a consequence the displacement parameter of H2O at O9 halved compared to that at room temperature. The unit-cell volume decreased to 1287.33(3) Å3 leading to a formula with 3H2O per formula unit (pfu). Ca remained seven-fold coordinated. At 175 °C Ca(VO)(Si4O10)·3H2O transformed into a new phase with 1H2O molecule pfu characterized by doubling of the c axis and the monoclinic space group Pn. Severe bending of specific TOT angles led to contraction of the porous three-dimensional framework. In addition, H2O at O9 was expelled while H2O at O7 approached a position in the center of the channel. The normalized volume decreased to 1069.44(9) Å3. The Ca coordination reduced from seven- to six-fold. At 225 °C a new anhydrous phase with space group Pna21 but without doubling of c had formed. Release of H2O at O7 caused additional contraction of TOT angles and volume reduction (V=1036.31(9) Å3). Ca adopted five-fold coordination. During heating excursion up to 400 °C this anhydrous phase remained preserved. Between room temperature and 225 °C the unit-cell volume decreased by 21% due to dehydration. The dehydration steps compare well with the thermo-gravimetric data reported in the literature.

Correlation between Accurate Electron Density and Linear Optical Properties in Amino Acid Derivatives: L-Histidinium Hydrogen Oxalate

The accurate electron density and linear optical properties of L-histidinium hydrogen oxalate are discussed. Two high-resolution single crystal X-ray diffraction experiments were performed and compared with density functional calculations in the solid state as well as in the gas phase. The crystal packing and the hydrogen bond network are accurately investigated using topological analysis based on quantum theory of atoms in molecules, Hirshfeld surface analysis, and electrostatic potential mapping. The refractive indices are computed from couple perturbed Kohn-Sham calculations and measured experimentally. Moreover, distributed atomic polarizabilities are used to analyze the origin of the linear susceptibility in the crystal, in order to separate molecular and intermolecular causes. The optical properties are also correlated with the electron density distribution. This compound also offers the possibility to test the electron density building block approach for material science and different refinement schemes for accurate positions and displacement parameters of hydrogen atoms, in the absence of neutron diffraction data.

Observations of the northern seasonal polar cap on Mars II: HiRISE photometric analysis of evolution of northern polar dunes in spring

We present an overview of our analyses of HiRISE observations of spring evolution of selected dune areas of the north polar erg. The north polar erg is covered annually by seasonal volatile ice layer, a mixture of CO2 and H2O with mineral dust contamination. In spring, this layer sublimes creating visually enigmatic phenomena, e.g. dark and bright fan-shaped deposits, dark–bright–dark bandings, dark down-slope streaks, and seasonal polygonal cracks. Similar phenomena in southern polar areas are believed to be related to the specific process of solid-state greenhouse effect. In the north, it is currently unclear if the solid-state greenhouse effect is able to explain all the observed phenomena especially because the increased influence of H2O on the time scales of this process has not yet been quantified. HiRISE observations of our selected locations show that the ground exhibits a temporal behaviour similar to the one observed in the southern polar areas: a brightening phase starting close to the spring equinox with a subsequent darkening towards summer solstice. The resolution of HiRISE enabled us to study dunes and substrate individually and even distinguish between different developments on windward and slip face sides of single dunes. Differences in the seasonal evolution between steep slip faces and flatter substrate and windward sides of dunes have been identified and compared to CRISM data of CO2 and H2O distributions on dunes. We also observe small scale dark blotches that appear in early observations and tend to sustain a low reflectivity throughout the spring. These blotches can be regarded as the analogue of dark fan deposits in southern polar areas, leading us to the conclusion that both martian polar areas follow similar spring evolutions.

Calculation Methodology and Fabrication Procedures for Particle Accelerator Strip-Line Kickers: Application to the CTF3 Combiner Ring Extraction Kicker and TL2 Tail Clippers

A particle accelerator is any device that, using electromagnetic fields, is able to communicate energy to charged particles (typically electrons or ionized atoms), accelerating and/or energizing them up to the required level for its purpose. The applications of particle accelerators are countless, beginning in a common TV CRT, passing through medical X-ray devices, and ending in large ion colliders utilized to find the smallest details of the matter. Among the other engineering applications, the ion implantation devices to obtain better semiconductors and materials of amazing properties are included. Materials supporting irradiation for future nuclear fusion plants are also benefited from particle accelerators. There are many devices in a particle accelerator required for its correct operation. The most important are the particle sources, the guiding, focalizing and correcting magnets, the radiofrequency accelerating cavities, the fast deflection devices, the beam diagnostic mechanisms and the particle detectors. Most of the fast particle deflection devices have been built historically by using copper coils and ferrite cores which could effectuate a relatively fast magnetic deflection, but needed large voltages and currents to counteract the high coil inductance in a response in the microseconds range. Various beam stability considerations and the new range of energies and sizes of present time accelerators and their rings require new devices featuring an improved wakefield behaviour and faster response (in the nanoseconds range). This can only be achieved by an electromagnetic deflection device based on a transmission line. The electromagnetic deflection device (strip-line kicker) produces a transverse displacement on the particle beam travelling close to the speed of light, in order to extract the particles to another experiment or to inject them into a different accelerator. The deflection is carried out by the means of two short, opposite phase pulses. The diversion of the particles is exerted by the integrated Lorentz force of the electromagnetic field travelling along the kicker. This Thesis deals with a detailed calculation, manufacturing and test methodology for strip-line kicker devices. The methodology is then applied to two real cases which are fully designed, built, tested and finally installed in the CTF3 accelerator facility at CERN (Geneva). Analytical and numerical calculations, both in 2D and 3D, are detailed starting from the basic specifications in order to obtain a conceptual design. Time domain and frequency domain calculations are developed in the process using different FDM and FEM codes. The following concepts among others are analyzed: scattering parameters, resonating high order modes, the wakefields, etc. Several contributions are presented in the calculation process dealing specifically with strip-line kicker devices fed by electromagnetic pulses. Materials and components typically used for the fabrication of these devices are analyzed in the manufacturing section. Mechanical supports and connexions of electrodes are also detailed, presenting some interesting contributions on these concepts. The electromagnetic and vacuum tests are then analyzed. These tests are required to ensure that the manufactured devices fulfil the specifications. Finally, and only from the analytical point of view, the strip-line kickers are studied together with a pulsed power supply based on solid state power switches (MOSFETs). The solid state technology applied to pulsed power supplies is introduced and several circuit topologies are modelled and simulated to obtain fast and good flat-top pulses.

Sintering and microstuctural characterization of W6+, Nb5+ and Ti4+ iron-substituted BiFeO3

The sintering behaviour and the microstructural evolution of W6+, Nb5+ and Ti4+iron-substituted BiFeO3 ceramics have been analyzed. The obtained results show that W6+ and Nb5+ ions interact with the secondary phases usually present in these materials, thus altering the solid state formation of the BiFeO3 phase. In contrast, Ti4+ ions incorporate into the perovskite structure, leading to an exceptionally low proportion of secondary phases. In addition to this, BiFe0.95Ti0.05O3 materials present a dense microstructure with submicronic and nanostructured grains, clearly smaller than those in the undoped materials.

Physical characterization of laser interaction and shock generation in laser shock processing: coupled theoretical-experimental analysis

Laser Shock Processing is developing as a key technology for the improvement of surface mechanical and corrosion resistance properties of metals due to its ability to introduce intense compressive residual stresses fields into high elastic limit materials by means of an intense laser driven shock wave generated by laser with intensities exceeding the 109 W/cm2 threshold, pulse energies in the range of 1 Joule and interaction times in the range of several ns. However, because of the relatively difficult-to-describe physics of shock wave formation in plasma following laser-matter interaction in solid state, only limited knowledge is available in the way of full comprehension and predictive assessment of the characteristic physical processes and material transformations with a specific consideration of real material properties. In the present paper, an account of the physical issues dominating the development of LSP processes from a moderately high intensity laser-matter interaction point of view is presented along with the theoretical and computational methods developed by the authors for their predictive assessment and new experimental contrast results obtained at laboratory scale.

On the Absence of Carrier Drift in Two-Terminal Devices and the Origin of Their Lowest Resistance per Carrier RK= h/q^2

After a criticism on today’s model for electrical noise in resistors, we pass to use a Quantum-compliant model based on the discreteness of electrical charge in a complex Admittance. From this new model we show that carrier drift viewed as charged particle motion in response to an electric field is unlike to occur in bulk regions of Solid-State devices where carriers react as dipoles against this field. The absence of the shot noise that charges drifting in resistors should produce and the evolution of the Phase Noise with the active power existing in the resonators of L-C oscillators, are two effects added in proof for this conduction model without carrier drift where the resistance of any two-terminal device becomes discrete and has a minimum value per carrier that is the Quantum resistance RK/(2pi)

Contribution to active multi-beam reconfigurable antennas for L and S bands

La presente tesis doctoral con título "Contribution to Active Multi-Beam Reconfigurable Antennas for L and S Bands" ha sido desarrollada por el investigador ingeniero de telecomunicación estudiante de doctorado Javier García-Gasco Trujillo en el Grupo de Radiación del Departamento de Señales, Sistemas y Radiocomunicaciones de la ETSI de Telecomunicación de la Universidad Politécnica de Madrid bajo la dirección de los doctores Manuel Sierra Pérez y José Manuel Fernández González. Durante décadas, el desarrollo de antenas de apuntamiento electrónico ha estado limitado al área militar. Su alto coste y su gran complejidad eran los mayores obstáculos que frenaban la introducción de esta tecnología en aplicaciones comerciales de gran escala. La reciente aparición de componentes de estado sólido prácticos, fiables, y de bajo coste ha roto la barrera del coste y ha reducido la complejidad, haciendo que las antenas reconfigurables de apuntamiento electrónico sean una opción viable en un futuro cercano. De esta manera, las antenas phased array podrían llegar a ser la joya de la corona que permitan alcanzar los futuros retos presentes en los sistemas de comunicaciones tanto civiles como militares. Así pues, ahora es el momento de investigar en el desarrollo de antenas de apuntamiento electrónico de bajo coste, donde los nuevos componentes de estado sólido comerciales forman el núcleo duro de la arquitectura. De esta forma, el estudio e implementación de estos arrays de antenas activas de apuntamiento electrónico capaces de controlar la fase y amplitud de las distintas señales implicadas es uno de los grandes retos de nuestro tiempo. Esta tesis se enfrenta a este desafío, proponiendo novedosas redes de apuntamiento electrónico e innovadores módulos de transmisión/recepción (T/R) utilizando componentes de estado sólido de bajo coste, que podrán integrar asequibles antenas activas reconfigurables multihaz en bandas L y S. En la primera parte de la tesis se realiza una descripción del estado del arte de las antenas phased array, incluyendo su base teórica y sus ventajas competitivas. Debido a que las contribuciones obtenidas en la presente tesis han sido realizadas dentro de distintos proyectos de investigación, donde se han manejada antenas de simple/doble polarización circular y simple/doble banda de trabajo, se describen detenidamente los dos proyectos más relevantes de la investigación: el radar de basura espacial de la Agencia Espacial Europea (ESA), Space Situational Awareness (SSA); y la estación base de seguimiento y control de satélites de órbita baja, GEOdesic Dome Array (GEODA). Sin lugar a dudas, los dispositivos desfasadores son uno de los componentes clave en el diseño de antenas phased arrays. Recientemente se ha observado una gran variación en el precio final de estos dispositivos, llegando en ocasiones a límites inasequibles. Así pues, se han propuesto distintas técnicas de conformación de haz alternativas a la utilización de componentes desfasadores comerciales: el desfasador de líneas conmutadas, la red de haz conmutado, y una novedosa red desfasadora divisora/combinadora de potencia. Para mostrar un uso práctico de las mismas, se ha propuesto el uso de las tres alternativas para el caso práctico del subarray de cinco elementos de la celda GEODA-SARAS. Tras dicho estudio se obtiene que la novedosa red desfasadora divisora/combinadora de potencia propuesta es la que mejor relación comportamiento/coste presenta. Para verificar su correcto funcionamiento se construye y mide los dos bloques principales de los que está compuesta la red total, comprobando que en efecto la red responde según lo esperado. La estructura más simple que permite realizar un barrido plano es el array triangular de tres elementos. Se ha realizado el diseño de una nueva red multihaz que es capaz de proporcionar tres haces ortogonales en un ángulo de elevación _0 y un haz adicional en la dirección broadside utilizando el mencionado array triangular de tres elementos como antena. En primer lugar se realizar una breve introducción al estado del arte de las redes clásicas multihaz. Así mismo se comentan innovadores diseños de redes multihaz sin pérdidas. El estudio da paso a las redes disipativas, de tal forma que se analiza su base matemática y se muestran distintas aplicaciones en arrays triangulares de tres elementos. Finalmente, la novedosa red básica propuesta se presenta, mostrando simulaciones y medidas de la misma para el caso prácticoo de GEODA. También se ha diseñado, construido y medido una red compuesta por dos redes básicas complementarias capaz de proporcionar seis haces cuasi-ortogonales en una dirección _0 con dos haces superpuestos en broadside. La red propuesta queda totalmente validada con la fabricación y medida de estos con prototipos. Las cadenas de RF de los módulos T/R de la nueva antena GEODA-SARAS no son algo trivial. Con el fin de mostrar el desarrollo de una cadena compleja con una gran densidad de componentes de estado sólido, se presenta una descripción detallada de los distintos componentes que integran las cadenas de RF tanto en transmisión como en recepción de la nueva antena GEODA-SARAS. Tras presentar las especificaciones de la antena GEODA-SARA y su diagrama de bloques esquemático se describen los dos bloques principales de las cadenas de RF: la celda de cinco elementos, y el módulo de conversión de panel. De la misma manera también se presentará el módulo de calibración integrado dentro de los dos bloques principales. Para comprobar que el funcionamiento esperado de la placa es el adecuado, se realizará un análisis que tratará entre otros datos: la potencia máxima en la entrada del transmisor (comprobando la saturación de la cadena), señal de recepción mínima y máxima (verificando el rango de sensibilidad requerido), y el factor G/T (cumpliendo la especificación necesaria). Así mismo se mostrará un breve estudio del efecto de la cuantificación de la fase en el conformado de haz de RF. Los estudios muestran que la composición de las cadenas de RF permite el cumplimiento de las especificaciones necesarias. Finalmente la tesis muestra las conclusiones globales del trabajo realizado y las líneas futuras a seguir para continuar con esta línea de investigación. ABSTRACT This PhD thesis named "Contribution to Active Multi-Beam Reconfigurable Antennas for L and S Bands", has been written by the Electrical Engineer MSc. researcher Javier García-Gasco Trujillo in the Grupo de Radiación of the Departamento de Señales, Sistemas y Radiocomunicaciones from the ETSI de Telecomunicación of the Universidad Politécnica de Madrid. For decades, the implementation of electronically steerable phased array antennas was confined to the military area. Their high cost and complexity were the major obstacles to introduce this technology in large scale commercial applications. The recent emergence of new practical, low-cost, and highly reliable solid state devices; breaks the barrier of cost and reduces the complexity, making active phased arrays a viable future option. Thus, phased array antennas could be the crown jewel that allow to meet the future challenges in military and civilian communication systems. Now is time to deploy low-cost phased array antennas, where newly commercial components form the core of the architecture. Therefore, the study and implementation of these novel low-cost and highly efficient solid state phased array blocks capable of controlling signal phase/amplitude accurately is one of the great challenges of our time. This thesis faces this challenge, proposing innovative electronic beam steering networks and transmitter/ receiver (T/R) modules using affordable solid state components, which could integrate fair reconfigurable phased array antennas working in L and S bands. In the first part of the thesis, a description of the state of art of phased array antennas, including their fundamentals and their competitive advantages, is presented. Since thesis contributions have been carried out for different research projects, where antennas with single/double circular polarization and single/double working frequency bands have been examined, frameworks of the two more important projects are detailed: the Space Situational Awareness (SSA) programme from the European Space Agency (ESA), and the GEOdesic Dome Array (GEODA) project from ISDEFE-INSA and the ESA. Undoubtedly, phase shifter devices are one of the key components of phased array antennas. Recent years have witnessed wide fluctuations in commercial phase shifter prices, which sometimes led to unaffordable limit. Several RF steering technique alternatives to the commercial phase shifters are proposed, summarized, and compared: the switched line phase shifter, the switched-beam network, and the novel phase shifter power splitter/combiner network. In order to show a practical use of the three different techniques, the five element GEODA-SARAS subarray is proposed as a real case of study. Finally, a practical study of a newly phase shifter power splitter/combiner network for a subarray of five radiating elements with triangular distribution is shown. Measurements of the two different phase shifter power splitter/combiner prototypes integrating the whole network are also depicted, demonstrating their proper performance. A triangular cell of three radiating elements is the simplest way to obtain a planar scanner. A new multibeam network configuration that provides three orthogonal beams in a desired _0 elevation angle and an extra one in the broadside steering direction for a triangular array of three radiating elements is introduced. Firstly, a short introduction to the state of art of classical multi-beam networks is presented. Lossless network analysis, including original lossless network designs, are also commented. General dissipative network theory as well as applications for array antennas of three radiating elements are depicted. The proposed final basic multi-beam network are simulated, built and measured to the GEODA cell practical case. A combined network that provides six orthogonal beams in a desired _0 elevation angle and a double seventh one in the broadside direction by using two complementary proposed basic networks will be shown. Measurements of the whole system will be also depicted, verifying the expected behavior. GEODA-SARAS T/R module RF chains are not a trivial design. A thorough description of all the components compounding GEODA-SARAS T/R module RF chains is presented. After presenting the general specifications of the GEODA-SARAS antenna and its block diagrams; two main blocks of the RF chains, the five element cell and the panel conversion module, are depicted and analyzed. Calibration module integrated within the two main blocks are also depicted. Signal flow throw the system analyzing critical situations such as maximum transmitted power (testing the chain unsaturation), minimum and maximum receiving signal (verifying sensitivity range), maximum receiver interference signals (assuring a proper reception), and G/T factor (fulfilling the technical specification) are evaluated. Phase quantization error effects are also listed. Finally, the manuscript contains the conclusions drawn of the present research and the future work.

Contribución al diseño de lazos de realimentación electrónica para microsistemas electromecánicos (MEMS) resonantes: ruido de fase generado en lazos osciladores por sus realimentaciones

En 1966, D. B. Leeson publicó el artículo titulado “A simple model of feedback oscillator noise spectrum” en el que, mediante una ecuación obtenida de forma heurística y basada en parámetros conocidos de los osciladores, proponía un modelo para estimar el espectro de potencia que cuantifica el Ruido de Fase de estos osciladores. Este Ruido de Fase pone de manifiesto las fluctuaciones aleatorias que se producen en la fase de la señal de salida de cualquier oscilador de frecuencia f_0. Desde entonces, los adelantos tecnológicos han permitido grandes progresos en cuanto a la medida del Ruido de Fase, llegando a encontrar una estrecha “zona plana”, alrededor de f_0, conocida con el nombre de Ensanchamiento de Línea (EL) que Leeson no llegó a observar y que su modelo empírico no recogía. Paralelamente han ido surgiendo teorías que han tratado de explicar el Ruido de Fase con mayor o menor éxito. En esta Tesis se propone una nueva teoría para explicar el espectro de potencia del Ruido de Fase de un oscilador realimentado y basado en resonador L-C (Inductancia-Capacidad). Al igual que otras teorías, la nuestra también relaciona el Ruido de Fase del oscilador con el ruido térmico del circuito que lo implementa pero, a diferencia de aquellas, nuestra teoría se basa en un Modelo Complejo de ruido eléctrico que considera tanto las Fluctuaciones de energía eléctrica asociadas a la susceptancia capacitiva del resonador como las Disipaciones de energía eléctrica asociadas a su inevitable conductancia G=1⁄R, que dan cuenta del contacto térmico entre el resonador y el entorno térmico que le rodea. En concreto, la nueva teoría que proponemos explica tanto la parte del espectro del Ruido de Fase centrada alrededor de la frecuencia portadora f_0 que hemos llamado EL y su posterior caída proporcional a 〖∆f〗^(-2) al alejarnos de f_0, como la zona plana o pedestal que aparece en el espectro de Ruido de Fase lejos de esa f_0. Además, al saber cuantificar el EL y su origen, podemos explicar con facilidad la aparición de zonas del espectro de Ruido de Fase con caída 〖∆f〗^(-3) cercanas a la portadora y que provienen del denominado “exceso de ruido 1⁄f” de dispositivos de Estado Sólido y del ruido “flicker” de espectro 1⁄f^β (0,8≤β≤1,2) que aparece en dispositivos de vacío como las válvulas termoiónicas. Habiendo mostrado que una parte del Ruido de Fase de osciladores L-C realimentados que hemos denominado Ruido de Fase Térmico, se debe al ruido eléctrico de origen térmico de la electrónica que forma ese oscilador, proponemos en esta Tesis una nueva fuente de Ruido de Fase que hemos llamado Ruido de Fase Técnico, que se añadirá al Térmico y que aparecerá cuando el desfase del lazo a la frecuencia de resonancia f_0 del resonador no sea 0° o múltiplo entero de 360° (Condición Barkhausen de Fase, CBF). En estos casos, la modulación aleatoria de ganancia de lazo que realiza el Control Automático de Amplitud en su lucha contra ruidos que traten de variar la amplitud de la señal oscilante del lazo, producirá a su vez una modulación aleatoria de la frecuencia de tal señal que se observará como más Ruido de Fase añadido al Térmico. Para dar una prueba empírica sobre la existencia de esta nueva fuente de Ruido de Fase, se diseñó y construyó un oscilador en torno a un resonador mecánico “grande” para tener un Ruido de Fase Térmico despreciable a efectos prácticos. En este oscilador se midió su Ruido de Fase Técnico tanto en función del valor del desfase añadido al lazo de realimentación para apartarlo de su CBF, como en función de la perturbación de amplitud inyectada para mostrar sin ambigüedad la aparición de este Ruido de Fase Técnico cuando el lazo tiene este fallo técnico: que no cumple la Condición Barkhausen de Fase a la frecuencia de resonancia f_0 del resonador, por lo que oscila a otra frecuencia. ABSTRACT In 1966, D. B. Leeson published the article titled “A simple model of feedback oscillator noise spectrum” in which, by means of an equation obtained heuristically and based on known parameters of the oscillators, a model was proposed to estimate the power spectrum that quantifies the Phase Noise of these oscillators. This Phase Noise reveals the random fluctuations that are produced in the phase of the output signal from any oscillator of frequencyf_0. Since then, technological advances have allowed significant progress regarding the measurement of Phase Noise. This way, the narrow flat region that has been found around f_(0 ), is known as Line Widening (LW). This region that Leeson could not detect at that time does not appear in his empirical model. After Leeson’s work, different theories have appeared trying to explain the Phase Noise of oscillators. This Thesis proposes a new theory that explains the Phase Noise power spectrum of a feedback oscillator around a resonator L-C (Inductance-Capacity). Like other theories, ours also relates the oscillator Phase Noise to the thermal noise of the feedback circuitry, but departing from them, our theory uses a new, Complex Model for electrical noise that considers both Fluctuations of electrical energy associated with the capacitive susceptance of the resonator and Dissipations of electrical energy associated with its unavoidable conductance G=1/R, which accounts for the thermal contact between the resonator and its surrounding environment (thermal bath). More specifically, the new theory we propose explains both the Phase Noise region of the spectrum centered at the carrier frequency f_0 that we have called LW and shows a region falling as 〖∆f〗^(-2) as we depart from f_0, and the flat zone or pedestal that appears in the Phase Noise spectrum far from f_0. Being able to quantify the LW and its origin, we can easily explain the appearance of Phase Noise spectrum zones with 〖∆f〗^(-3) slope near the carrier that come from the so called “1/f excess noise” in Solid-State devices and “flicker noise” with 1⁄f^β (0,8≤β≤1,2) spectrum that appears in vacuum devices such as thermoionic valves. Having shown that the part of the Phase Noise of L-C oscillators that we have called Thermal Phase Noise is due to the electrical noise of the electronics used in the oscillator, this Thesis can propose a new source of Phase Noise that we have called Technical Phase Noise, which will appear when the loop phase shift to the resonance frequency f_0 is not 0° or an integer multiple of 360° (Barkhausen Phase Condition, BPC). This Phase Noise that will add to the Thermal one, comes from the random modulation of the loop gain carried out by the Amplitude Automatic Control fighting against noises trying to change the amplitude of the oscillating signal in the loop. In this case, the BPC failure gives rise to a random modulation of the frequency of the output signal that will be observed as more Phase Noise added to the Thermal one. To give an empirical proof on the existence of this new source of Phase Noise, an oscillator was designed and constructed around a “big” mechanical resonator whose Thermal Phase Noise is negligible for practical effects. The Technical Phase Noise of this oscillator has been measured with regard to the phase lag added to the feedback loop to separate it from its BPC, and with regard to the amplitude disturbance injected to show without ambiguity the appearance of this Technical Phase Noise that appears when the loop has this technical failure: that it does not fulfill the Barkhausen Phase Condition at f_0, the resonance frequency of the resonator and therefore it is oscillating at a frequency other than f_0.

Diseño y síntesis de materiales nanoestructurados basados en aluminatos de estroncio con propiedades fotoluminiscentes

Durante la última década, se han llevado acabo numeroso estudios sobre la síntesis de materiales fotoluminiscentes sub-micrónicos, en gran medida, al amplio número de aplicaciones que demandan este tipo de materiales. En concreto dentro de los materiales fosforescentes o también denominados materiales con una prolongada persistencia de la luminiscencia, los estudios se han enfocado en la matriz de SrAl2O4 dopada con Europio (Eu2+) y Disprosio (Dy3+) dado que tiene mayor estabilidad y persistencia de la fosforescencia con respecto a otras matrices. Estos materiales se emplean mayoritariamente en pinturas luminiscentes, tintas, señalización de seguridad pública, cerámicas, relojes, textiles y juguetes fosforescentes. Dado al amplio campo de aplicación de los SrAl2O4:Eu, Dy, se han investigado múltiples rutas de síntesis como la ruta sol-gel, la síntesis hidrotermal, la síntesis por combustión, la síntesis láser y la síntesis en estado sólido con el fin de desarrollar un método eficiente y que sea fácilmente escalable. Sin embargo, en la actualidad el método que se emplea para el procesamiento a nivel industrial de los materiales basados en aluminato de estroncio es la síntesis por estado sólido, que requiere de temperaturas de entre 1300 a 1900oC y largos tiempos de procesamiento. Además el material obtenido tiene un tamaño de partícula de 20 a 100 μm; siendo este tamaño restrictivo para el empleo de este tipo de material en determinadas aplicaciones. Por tanto, el objetivo de este trabajo es el desarrollo de nuevas estrategias que solventen las actuales limitaciones. Dentro de este marco se plantean una serie de objetivos específicos: Estudio de los parámetros que gobiernan los procesos de reducción del tamaño de partícula mediante molienda y su relación en la respuesta fotoluminiscente. Estudio de la síntesis por combustión de SrAl2O4:Eu, Dy, evaluando el efecto de la temperatura y la cantidad de combustible (urea) en el proceso para la obtención de partículas cristalinas minimizando la presencia de fases secundarias. Desarrollo de nuevas rutas de síntesis de SrAl2O4:Eu, Dy empleando el método de sales fundidas. Determinación de los mecanismos de reacción en presencia de la sal fundida en función de los parámetros de proceso que comprende la relación de sales y reactivos, la naturaleza de la alúmina y su tamaño, la temperatura y atmósfera de tratamiento. Mejora de la eficiencia de los procesos de síntesis para obtener productos con propiedades finales óptimas en procesos factibles industrialmente para su transferencia tecnológica. Es este trabajo han sido evaluados los efectos de diferentes procesos de molienda para la reducción del tamaño de partícula del material de SrAl2O4:Eu, Dy comercial. En el proceso de molienda en medio húmedo por atrición se observa la alteración de la estructura cristalina del material debido a la reacción de hidrólisis generada incluso empleando como medio líquido etanol absoluto. Con el fin de solventar las desventajas de la molienda en medio húmedo se llevo a cabo un estudio de la molturación en seco del material. La molturación en seco de alta energía reduce significativamente el tamaño medio de partícula. Sin embargo, procesos de molienda superiores a una duración de 10 minutos ocasionan un aumento del estado de aglomeración de las partículas y disminuyen drásticamente la respuesta fotoluminiscente del material. Por tanto, se lleva a cabo un proceso de molienda en seco de baja energía. Mediante este método se consigue reducir el tamaño medio de partícula, d50=2.8 μm, y se mejora la homogeneidad de la distribución del tamaño de partícula evitando la amorfización del material. A partir de los resultados obtenidos mediante difracción de rayos X y microscopia electrónica de barrido se infiere que la disminución de la intensidad de la fotoluminiscencia después de la molienda en seco de alta energía con respecto al material inicial se debe principalmente a la reducción del tamaño de cristalito. Se observan menores variaciones en la intensidad de la fotoluminiscencia cuando se emplea un método de molienda de baja de energía ya que en estos procesos se preserva el dominio cristalino y se reduce la amorfización significativamente. Estos resultados corroboran que la intensidad de la fotoluminiscencia y la persistencia de la luminiscencia de los materiales de SrAl2O4:Eu2+, Dy3+ dependen extrínsecamente de la morfología de las partículas, del tamaño de partícula, el tamaño de grano, los defectos superficiales e intrínsecamente del tamaño de cristalito. Siendo las características intrínsecas las que dominan con respecto a las extrínsecas y por tanto tienen mayor relevancia en la respuesta fotoluminiscente. Mediante síntesis por combustión se obtuvieron láminas nanoestructuradas de SrAl2O4:Eu, Dy de ≤1 μm de espesor. La cantidad de combustible, urea, en la reacción influye significativamente en la formación de determinadas fases cristalinas. Para la síntesis del material de SrAl2O4:Eu, Dy es necesario incluir un contenido de urea mayor que el estequiométrico (siendo m=1 la relación estequiométrica). La incorporación de un exceso de urea (m>1) requiere de la presencia de un agente oxidante interno, HNO3, para que la reacción tenga lugar. El empleo de un mayor contenido de urea como combustible permite una quelación efectiva de los cationes en el sistema y la creación de las condiciones reductoras para obtener un material de mayor cristalinidad y con mejores propiedades fotoluminiscentes. El material de SrAl2O4:Eu, Dy sintetizado a una temperatura de ignición de 600oC tiene un tamaño medio 5-25 μm con un espesor de ≤1 μm. Mediante procesos de molturación en seco de baja energía es posible disminuir el tamaño medio de partícula ≈2 μm y homogenizar la distribución del tamaño de partícula pero hay un deterioro asociado de la respuesta luminiscente. Sin embargo, se puede mejorar la respuesta fotoluminiscente empleando un tratamiento térmico posterior a 900oC N2-H2 durante 1 hora que no supone un aumento del tamaño de partícula pero si permite aumentar el tamaño de cristalito y la reducción del Eu3+ a Eu2+. Con respecto a la respuesta fotoluminiscente, se obtiene valores de la intensidad de la fotoluminiscencia entre un 35%-21% con respecto a la intensidad de un material comercial de referencia. Además la intensidad inicial del decaimiento de la fosforescencia es un 20% de la intensidad del material de referencia. Por tanto, teniendo en cuenta estos resultados, es necesario explorar otros métodos de síntesis para la obtención de los materiales bajo estudio. Por esta razón, en este trabajo se desarrollo una ruta de síntesis novedosa para sintetizar SrAl2O4:Eu, Dy mediante el método de sales fundidas para la obtención de materiales de gran cristalinidad con tamaños de cristalito del orden nanométrico. Se empleo como sal fundente la mezcla eutéctica de NaCl y KCl, denominada (NaCl-KCl)e. La principal ventaja de la incorporación de la mezcla es el incremento la reactividad del sistema, reduciendo la temperatura de formación del SrAl2O4 y la duración del tratamiento térmico en comparación con la síntesis en estado sólido. La formación del SrAl2O4 es favorecida ya que se aumenta la difusión de los cationes de Sr2+ en el medio líquido. Se emplearon diferentes tipos de Al2O3 para evaluar el papel del tamaño de partícula y su naturaleza en la reacción asistida por sales fundidas y por tanto en la morfología y propiedades del producto final. Se obtuvieron partículas de morfología pseudo-esférica de tamaño ≤0.5 μm al emplear como alúmina precursora partículas sub-micrónicas ( 0.5 μm Al2O3, 0.1 μm Al2 O3 y γ-Al2O3). El mecanismo de reacción que tiene lugar se asocia a procesos de disolución-precipitación que dominan al emplear partículas de alúmina pequeñas y reactivas. Mientras al emplear una alúmina de 6 μm Al2O3 prevalecen los procesos de crecimiento cristalino siguiendo un patrón o plantilla debido a la menor reactividad del sistema. La nucleación y crecimiento de nanocristales de SrAl2O4:Eu, Dy se genera sobre la superficie de la alúmina que actúa como soporte. De esta forma se desarrolla una estructura del tipo coraza-núcleo («core-shell» en inglés) donde la superficie externa está formada por los cristales fosforescentes de SrAl2O4 y el núcleo está formado por alúmina. Las partículas obtenidas tienen una respuesta fotoluminiscente diferente en función de la morfología final obtenida. La optimización de la relación Al2O3/SrO del material de SrAl2O4:Eu, Dy sintetizado a partir de la alúmina de 6 μm permite reducir las fases secundarias y la concentración de dopantes manteniendo la respuesta fotoluminiscente. Comparativamente con un material comercial de SrAl2O4:Eu, Dy de referencia, se han alcanzado valores de la intensidad de la emisión de hasta el 90% y de la intensidad inicial de las curvas de decaimiento de la luminiscencia de un 60% para el material sintetizado por sales fundidas que tiene un tamaño medio ≤ 10μm. Por otra parte, es necesario tener en cuenta que el SrAl2O4 tiene dos polimorfos, la fase monoclínica que es estable a temperaturas inferiores a 650oC y la fase hexagonal, fase de alta temperatura, estable a temperaturas superiores de 650oC. Se ha determinado que fase monoclínica presenta propiedades luminiscentes, sin embargo existen discordancias a cerca de las propiedades luminiscentes de la fase hexagonal. Mediante la síntesis por sales fundidas es posible estabilizar la fase hexagonal empleando como alúmina precursora γ-Al2O3 y un exceso de Al2O3 (Al2O3/SrO:2). La estabilización de la fase hexagonal a temperatura ambiente se produce cuando el tamaño de los cristales de SrAl2O4 es ≤20 nm. Además se observó que la fase hexagonal presenta respuesta fotoluminiscente. El diseño de materiales de SrAl2O4:Eu,Dy nanoestructurados permite modular la morfología del material y por tanto la intensidad de la de la fotoluminiscencia y la persistencia de la luminiscencia. La disminución de los materiales precursores, la temperatura y el tiempo de tratamiento significa la reducción de los costes económicos del material. De ahí la viabilidad de los materiales de SrAl2O4:Eu,Dy obtenidos mediante los procesos de síntesis propuestos en esta memoria de tesis para su posterior escalado industrial. ABSTRACT The synthesis of sub-micron photoluminescent particles has been widely studied during the past decade because of the promising industrial applications of these materials. A large number of matrices has been developed, being SrAl2O4 host doped with europium (Eu2+) and dysprosium (Dy3+) the most extensively studied, because of its better stability and long-lasting luminescence. These functional inorganic materials have a wide field of application in persistent luminous paints, inks and ceramics. Large attention has been paid to the development of an efficient method of preparation of SrAl2O4 powders, including solgel method, hydrothermal synthesis, laser synthesis, combustion synthesis and solid state reaction. Many of these techniques are not compatible with large-scale production and with the principles of sustainability. Moreover, industrial processing of highly crystalline powders usually requires high synthesis temperatures, typically between 1300 a 1900oC, with long processing times, especially for solid state reaction. As a result, the average particle size is typically within the 20-100 μm range. This large particle size is limiting for current applications that demand sub-micron particles. Therefore, the objective of this work is to develop new approaches to overcome these limitations. Within this frame, it is necessary to undertake the following purposes: To study the parameters that govern the particle size reduction by milling and their relation with the photoluminescence properties. To obtain SrAl2O4:Eu, Dy by combustion synthesis, assessing the effect of the temperature and the amount of fuel (urea) to synthesize highly crystalline particles minimizing the presence of secondary phases. To develop new synthesis methods to obtain SrAl2O4:Eu, Dy powders. The molten salt synthesis has been proposed. As the method is a novel route, the reaction mechanism should be determine as a function of the salt mixture, the ratio of the salt, the kind of Al2O3 and their particle size and the temperature and the atmosphere of the thermal treatment. To improve the efficiency of the synthesis process to obtain SrAl2O4:Eu, Dy powders with optimal final properties and easily scalable. On the basis of decreasing the particle size by using commercial product SrAl2O4:Eu2+, Dy3+ as raw material, the effects of different milling methods have been evaluated. Wet milling can significantly alter the structure of the material through hydrolysis reaction even in ethanol media. For overcoming the drawbacks of wet milling, a dry milling-based processes are studied. High energy dry milling process allows a great reduction of the particle size, however milling times above 10 min produce agglomeration and accelerates the decrease of the photoluminescence feature. To solve these issues the low energy dry milling process proposed effectively reduces the particle size to d50=2.8 μm, and improves the homogeneity avoiding the amorphization in comparison with previous methods. The X-ray diffraction and scanning electron microscope characterization allow to infer that the large variations in PL (Photoluminescence) values by high energy milling process are a consequence mainly of the crystallite size reduction. The lesser variation in PL values by low energy milling proces is related to the coherent crystalline domain preservation and the unnoticeable amorphization. These results corroborate that the photoluminescence intensity and the persistent luminescence of the SrAl2O4:Eu2+, Dy3+ powders depend extrinsically on the morphology of the particles such as particle size, grain size, surface damage and intrinsically on the crystallinity (crystallite size); being the intrinsically effects the ones that have a significant influence on the photoluminescent response. By combustion method, nanostructured SrAl2O4:Eu2+, Dy3+ sheets with a thickness ≤1 μm have been obtained. The amount of fuel (urea) in the reaction has an important influence on the phase composition; urea contents larger than the stoichiometric one require the presence of an oxidant agent such as HNO3 to complete the reaction. A higher amount of urea (excess of urea: denoted m>1, being m=1 the stoichiometric composition) including an oxidizing agent produces SrAl2O4:Eu2+,Dy3+ particles with persistent luminescence due to the effective chelation of the cations and the creation of suitable atmospheric conditions to reduce the Eu3+ to Eu2+. Therefore, optimizing the synthesis parameters in combustion synthesis by using a higher amount of urea and an internal oxidizing agent allows to complete the reaction. The amount of secondary phases can be significantly reduced and the photoluminescence response can be enhanced. This situation is attributed to a higher energy that improves the crystallinity of the powders. The powders obtained have a particle size c.a. 5-25 μm with a thickness ≤1 μm and require relatively low ignition temperatures (600oC). It is possible to reduce the particle size by a low energy dry milling but this process implies the decrease of the photoluminescent response. However, a post-thermal treatment in a reducing atmosphere allows the improvement of the properties due to the increment of crystallinity and the reduction of Eu3+ to Eu2+. Compared with the powder resulted from solid state method (commercial reference: average particle size, 20 μm and heterogeneous particle size distribution) the emission intensity of the powder prepared by combustion method achieve the values between 35% to 21% of the reference powder intensity. Moreover, the initial intensity of the decay curve is 20% of the intensity of the reference powder. Taking in account these results, it is necessary to explore other methods to synthesize the powders For that reason, an original synthetic route has been developed in this study: the molten salt assisted process to obtain highly crystalline SrAl2O4 powders with nanometric sized crystallites. The molten salt was composed of a mixture of NaCl and KCl using a 0.5:0.5 molar ratio (eutectic mixture hereafter abbreviated as (NaCl-KCl)e). The main advantages of salt addition is the increase of the reaction rate, the significant reduction of the synthesis temperature and the duration of the thermal treatment in comparison with classic solid state method. The SrAl2O4 formation is promoted due to the high mobility of the Sr2+ cations in the liquid medium. Different kinds of Al2O3 have been employed to evaluate the role of the size and the nature of this precursor on the kinetics of reaction, on the morphology and the final properties of the product. The SrAl2O4:Eu2+, Dy3+ powders have pseudo-spherical morphology and particle size ≤0.5 μm when a sub-micron Al2O3 ( 0.5 μm Al2O3, 0.1 μm Al2O3 and γ-Al2O3) has been used. This can be attributed to a higher reactivity in the system and the dominance of dissolution-precipitation mechanism. However, the use of larger alumina (6 μm Al2O3) modifies the reaction pathway leading to a different reaction evolution. More specifically, the growth of SrAl2O4 sub-micron particles on the surface of hexagonal platelets of 6μm Al2O3 is promoted. The particles retain the shape of the original Al2O3 and this formation process can be attributed to a «core-shell» mechanism. The particles obtained exhibit different photoluminescent response as a function of the final morphology of the powder. Therefore, through this study, it has been elucidated the reaction mechanisms of SrAl2O4 formation assisted by (NaCl-KCl)e that are governed by the diffusion of SrCO3 and the reactivity of the alumina particles. Optimizing the Al2O3/SrO ratio of the SrAl2O4:Eu, Dy powders synthesized with 6 μm Al2O3 as a precursor, the secondary phases and the concentration of dopant needed can be reduced keeping the photoluminescent response of the synthesized powder. Compared with the commercial reference powder, up to 90% of the emission intensity of the reference powder has been achieved for the powder prepared by molten salt method using 6μm Al2O3 as alumina precursor. Concerning the initial intensity of the decay curve, 60% of the initial intensity of the reference powder has been obtained. Additionally, it is necessary to take into account that SrAl2O4 has two polymorphs: monoclinic symmetry that is stable at temperatures below 650oC and hexagonal symmetry that is stable above this temperature. Monoclinic phase shows luminescent properties. However, there is no clear agreement on the emission of the hexagonal structure. By molten salt, it is possible to stabilize the hexagonal phase of SrAl2O4 employing an excess of Al2O3 (Al2O3/SrO: 2) and γ-Al2O3 as a precursor. The existence of nanometric crystalline domains with lower size (≤20 nm) allows the stabilization of the hexagonal phase. Moreover, it has been evidenced that the hexagonal polymorph exhibits photoluminescent response. To sum up, the design of nanostructured SrAl2O4:Eu2+, Dy3+ materials allows to obtain different morphologies and as consequence different photoluminescent responses. The reduction of temperature, duration of the thermal treatment and the precursors materials needed imply the decrease of the economic cost of the material. Therefore, the viability, suitability and scalability of the synthesis strategy developed in this work to process SrAl2O4:Eu2+, Dy3+ are demonstrated.

Analysis of single and binary phases in cerium doped sodium bismuth titanate -Na0.5Bi0.5TiO3 materials

The pure and cerium doped sodium bismuth titanate inorganic powders were synthesized by solid state reaction method. The presence of rhombohedral phase was observed in cerium doped NBT compounds. At 1200 ºC, the 5% of cerium doped NBT compound forms single perovskite phase. The samples of x = 0.10 and 0.15 were heat treated to 1350 ºC, the binary phases with cerium and bismuth oxides were observed. The X-ray diffraction, fourier transform infrared spectroscopy, reflectance spectra, differential thermal analysis and thermo gravimetric analysis were used to analyze the various properties of samples. Moreover, the effects of cerium doping and calcining temperature on NBT samples were investigated. In this work we present our recent results on the synthesis and characterization of Ce doped sodium bismuth titanate materials.

Investigação da estabilidade de fases da zircônia-escândia

Nesse trabalho foi proposto investigar a estabilidade de fases do sistema zircônia-escândia (ScSZ) por meio do estudo termodinâmico de nanopartículas, na faixa de 0 a 20% em mol de Sc2O3, e a partir da introdução de um segundo aditivo (Dy2O3 e Nb2O5) ao ZrO2 contendo 10% em mol de Sc2O3 (10ScSZ). A estabilidade de fases do ScSZ foi avaliada com base em dados termodinâmicos determinados pelas técnicas de microcalorimetria de adsorção de água e calorimetria de dissolução à alta temperatura. As soluções sólidas foram sintetizadas pelo método de coprecipitação de hidróxidos. Dados termodinâmicos foram determinados para as formas polimórficas encontradas (monoclínica, tetragonal, cúbica, romboédrica β e γ) por difração de raios X no ScSZ. Esse trabalho resultou no diagrama de fases em nanoescala de tamanho de partícula-composição. Os efeitos produzidos pela introdução de aditivos na matriz de 10ScSZ foram investigados visando obter a possível estabilização da estrutura cúbica (c) e a supressão da transformação de fase c-β, característica do sistema binário. As composições foram sintetizadas por coprecipitação de hidróxidos e por reações em estado sólido para fins comparativos. Os materiais foram sinterizados convencionalmente e por sinterização assistida por campo elétrico. A estabilização completa da fase cúbica ocorreu a partir de teores molares de 1% de Dy2O3 e 0,5% de Nb2O5. O menor teor de Nb2O5 necessário para a estabilização da fase foi atribuído à provável formação da fase líquida durante a sinterização e ao menor tamanho do íon Nb5+. Os resultados de difratometria de raios X em alta temperatura e análise térmica mostraram que houve supressão da transição c-β. As amostras contendo 0,5% mol de Nb2O5 apresentaram valores de condutividade iônica similares aos do 10ScSZ sem aditivos em uma ampla faixa de temperatura com elevada estabilidade em um período de 170 h a 600 °C.

Generalized isotropic Lipkin-Meshkov-Glick models: ground state entanglement and quantum entropies

We introduce a new class of generalized isotropic Lipkin–Meshkov–Glick models with su(m+1) spin and long-range non-constant interactions, whose non-degenerate ground state is a Dicke state of su(m+1) type. We evaluate in closed form the reduced density matrix of a block of Lspins when the whole system is in its ground state, and study the corresponding von Neumann and Rényi entanglement entropies in the thermodynamic limit. We show that both of these entropies scale as a log L when L tends to infinity, where the coefficient a is equal to (m  −  k)/2 in the ground state phase with k vanishing magnon densities. In particular, our results show that none of these generalized Lipkin–Meshkov–Glick models are critical, since when L-->∞ their Rényi entropy R_q becomes independent of the parameter q. We have also computed the Tsallis entanglement entropy of the ground state of these generalized su(m+1) Lipkin–Meshkov–Glick models, finding that it can be made extensive by an appropriate choice of its parameter only when m-k≥3. Finally, in the su(3) case we construct in detail the phase diagram of the ground state in parameter space, showing that it is determined in a simple way by the weights of the fundamental representation of su(3). This is also true in the su(m+1) case; for instance, we prove that the region for which all the magnon densities are non-vanishing is an (m  +  1)-simplex in R^m whose vertices are the weights of the fundamental representation of su(m+1).

Estudo da substituição da fluorita por alumina ou sodalita e de cal por resíduo de mármore em escórias sintéticas dessulfurantes.

A siderurgia vem sofrendo transformações que buscam inovação e matérias-primas alternativas. Dentro deste contexto, o uso de resíduos industriais para a formação de escórias sintéticas é tido como alternativa na busca de novos materiais e rotas de reaproveitamento de resíduos. Portanto, este trabalho teve como objetivo estudar o uso de escórias sintéticas na etapa de dessulfuração do ferro-gusa, aço e ferro fundido. Assim como, propor a utilização da sodalita e da alumina em substituição à fluorita e o resíduo de mármore em substituição à cal convencional. Inicialmente, o resíduo foi caracterizado utilizando as seguintes técnicas: análise química, análise granulométrica, área de superfície específica, difração de raios-X, microscopia eletrônica de varredura (MEV) e análise de espectroscopia por energia dispersiva (EDS). Os resultados da caracterização mostraram que aproximadamente 90% das partículas do resíduo de mármore estão abaixo de 100m e sua área superficial foi de 0,24m²/g. Através da difração de raios-X foi observado que o resíduo é composto por CaCO3, MgCO3 e SiO2. Na sequência, foram feitas simulações com o software Thermo-Calc para obter dados termodinâmicos das fases presentes nas misturas e compará-los com os resultados experimentais. Além disso, também foram calculados dados de capacidade de sulfeto (Cs), partição de enxofre (Ls) e basicidade ótica () das misturas iniciais. Posteriormente, foram realizados os ensaios experimentais em escala laboratorial para ferro-gusa, ferro fundido e aço, respectivamente nas temperaturas de 1400°C, 1550°C e 1600°C. Nos ensaios de dessulfuração do aço e do ferro-gusa, utilizou-se um rotor de alumina com o objetivo de favorecer a agitação no metal e aumentar a remoção de enxofre. Na etapa de dessulfuração do ferro-gusa, constatou-se que a fase sólida de CaO é a responsável pela remoção de enxofre e que a presença das fases silicato tricálcio e aluminato tricálcio (3CaO.SiO2 e 3CaO.Al2O3) limitam a reação, sendo maiores suas concentrações nas escórias que utilizaram o resíduo de mármore e sodalita, devido a presença de SiO2 e Al2O3 nestas matérias-primas. Já para o aço e o ferro fundido, que foram estudados com escórias à base de CaO e Al2O3, observou-se que o aumento da fase líquida favoreceu a dessulfuração. Verificou-se que a dessulfuração no ferro fundido foi por escória de topo e no aço por um processo misto, onde a fase líquida e fase sólida participaram da dessulfuração.