Inorganic nanofillers prepared from LDHS to obtain polymer matrix nanocomposites. Determination of the impact of the preparation method on their properties

[ES] El presente trabajo de investigación se ha centrado en la obtención de nanorrellenos inorgánicos a partir de Hidróxidos Dobles Laminares (LDHs) que puedan ser de utilidad en la preparación de composites y nanocomposites de matriz polimérica modificando sus propiedades. Las propiedades de este tipo de nanorrellenos están estrechamente ligadas a las condiciones empleadas durante su síntesis; así, parámetros como el pH, medio de reacción, temperatura de síntesis e historial térmico, relación molar de cationes, velocidad de precipitación, etc., repercuten en las propiedades físicas y de superficie de los sólidos finales. En el presente trabajo se ha llevado a cabo la síntesis de LDHs de Zn y Al en relaciones molares 2:1 y 3:1 mediante el método de coprecipitación empleando aminas de carácter básico más débil que las clásicamente utilizadas. Concretamente, se han empleado aminas con diferente grado de sustitución y longitud de cadena, como agentes precipitantes empleando una metodología de síntesis más sencilla que la empleada en la hidrolisis de la urea. Los sólidos resultantes se han caracterizado atendiendo a sus propiedades morfológicas y estructurales y se ha estudiado su viabilidad para ser utilizados como nanorrellenos en nanocomposites de matriz polimérica. Los nanocomposites se han preparado utilizando polipropileno como matriz polimérica, dispersando LDHs de Zn y Al sintetizados en diferentes condiciones. Finalmente, se estudió la repercusión que supone el uso de estos solidos a modo de nanorrellenos sobre la estabilidad térmica y las propiedades mecánicas de los nanocomposites resultantes. La metodología de síntesis empleando aminas como agentes de precipitación se extendió a la preparación de LDHs de Ni y Al que resultan de gran interés como precursores de catalizadores en la reacción de Sabatier de hidrogenación de CO2 para obtener metano. La síntesis de este tipo de sólidos se llevó a cabo utilizando dimetilamina como agente precipitante, ya que no se observó con esta amina la formación de compuestos de coordinación con el Ni(II) y, además, resultó ser la amina con la que los sólidos de Zn y Al ofrecían las mejores propiedades, en cuanto a grado de cristalinidad y distribución de tamaño de partículas. El estudio de la actividad catalítica de este tipo de solidos se amplió con la síntesis de los catalizadores promovidos por cationes de elementos de tierras raras, como Ce y La. La efectividad de los catalizadores resultantes de Ni-Al2O3, Ni-Ce2O3-Al2O3 y Ni-La2O3-Al2O3 se estudió en la producción de CH4, atendiendo tanto a la conversión como a la selectividad frente a la formación de productos secundarios. El test catalítico se realizó entre 200 y 400 ºC, observándose que a 275 ºC se lograba una conversión superior al 60% y que se mantenía hasta 400 ºC, con una selectividad del 95% en la producción de metano. [EN] The present research work has focused on obtaining inorganic nanofillers from Layered Double Hydroxides (LDHs) that can be useful in the preparation of polymer matrix composites and nanocomposites with modified properties. The properties of this type of nanofillers are closely linked to their synthesis conditions; so, parameters such as pH, reaction medium, molar ratio of cations, precipitation rate, synthesis temperature and hydrothermal treatments, etc., have an important impact on the physical and surface properties of the final solids. Thus, in the present work, the synthesis of Zn,Al LDHs with molar ratios 2:1 and 3:1 has been carried out by the coprecipitation method using amines, which are softer bases than the classically used bases. Specifically, amines with different substitution degree and chain length have been used as precipitating agents using a simpler synthesis methodology than the hydrolysis of urea. The resulting solids have been characterised in terms of their morphological and structural properties and their feasibility for use as nanofillers in polymer matrix nanocomposites has been studied. Thus, nanocomposites have been prepared using polypropylene as polymeric matrix, dispersing Zn,Al LDHs synthesised under different conditions. Finally, the impact of the use of these solids as nanofillers on the thermal stability and mechanical properties of the resulting nanocomposites was studied. On the other hand, the synthesis methodology using amines as precipitating agents was extended to the preparation of Ni,Al LDHs which are of great interest as catalyst precursors in the Sabatier reaction of CO2 hydrogenation to obtain methane. The synthesis of this type of solids was carried out using dimethylamine as precipitating agent, since the formation of coordination compounds with Ni(II) was not observed and, in addition, it turned out to be the amine with which the Zn,Al LDHs offered the best properties, in terms of crystallinity degree and particle size distribution. The study of the catalytic activity of this type of solids was extended with the synthesis of catalysts promoted by cations of rare earth elements, such as Ce and La. Thus, the effectiveness of the resulting Ni-Al2O3, Ni-Ce2O3-Al2O3 and Ni-La2O3-Al2O3-Al2O3 catalysts was studied in the production of CH4, taking into account both the conversion and the selectivity towards secondary products. The catalytic test was carried out between 200 and 400 ºC, and it was observed that at 275 ºC a conversion larger than 60% was achieved, maintained up to 400 ºC, with a selectivity of 95% in methane production

Buscadores académicos como herramientas útiles para el aprendizaje de química para estudiantes de ESO y/o bachillerato

El desarrollo de Internet en las últimas décadas ha provocado que la cantidad de información de la que se dispone crezca de forma exponencial a cada día que pasa. Este hecho, junto a la incorporación de las Tecnologías de Información y Comunicación (TIC) en la sociedad, ha modificado la percepción del aprendizaje y la comunicación. De ahí que el nuevo modelo educativo trate de garantizar la adquisición de competencias digitales en el alumnado, Debido al gran volumen de información que contiene la Red, es necesario el uso de herramientas tecnológicas que permitan encontrar la información deseada; estas herramientas son los motores de búsqueda. Sin embargo, no toda la información mostrada es veraz; por ello, es necesario el uso de buscadores académicos, que están indexados con fuentes de información confiables. No obstante, la obtención de información relevante también depende de las habilidades del usuario a la hora de concretar la estrategia de búsqueda, seleccionar el motor de búsqueda adecuado, la construcción de las palabras clave adecuadas y del conocimiento del mismo para elegir si la información es correcta o no. En este Trabajo de Fin de Máster se ha realizado una propuesta metodológica para integrar el uso de los buscadores académicos en el proceso de enseñanza-aprendizaje de los estudiantes de Educación Secundaria Obligatoria y de Bachillerato en el estudio de la Física y la Química. Con esto se pretende que los estudiantes posean herramientas y recursos que les sean de utilidad en la búsqueda de información fiable, ya sea a lo largo de su vida académica, como en la vida laboral e incluso personal. Además, las actividades propuestas les sirven de ayuda en el proceso de aprendizaje de la Química y contribuyen al desarrollo de un pensamiento crítico ante la información.Internet's development over the last decades has led to an exponential increase in the amount of information available with each new day. This fact, together with the incorporation of Information and Communication Technologies (ICT) into society, has changed the perception of learning and communication. Hence, the new educational model in Spain tries to guarantee the acquisition of e-learning skills in students. Due to the large volume of information available through the Web, it is necessary to use technological tools to find the desired information; these tools are the search engines. However, not all the information displayed is true; therefore, it is necessary to use academic search engines, which are indexed with reliable sources of information. However, getting relevant information also depends on the user's skills in specifying the search strategy, selecting the right search engine, constructing the right keywords and its knowledge of the search engine to choose if the information is correct or not. In this Master's thesis, a methodological proposal has been made to integrate the use of academic search engines in the teaching-learning process of Educación Secundaria Obligatoria and Bachillerato students in the study of Physics and Chemistry. The aim is to provide the students with tools and resources that will be useful in their search for reliable information, whether in their academic, working or even personal life. In addition, the proposed activities help them in the process of learning chemistry and contribute to the development of their critical thinking about new information.Departamento de Química OrgánicaMáster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idioma

Preparation of Ca2Al1–mFem(OH)6Cl 2H2O-doped hydrocalumites and application of their derived mixed oxides in the photodegradation of ibuprofen

Aluminum from saline slags generated during the recycling of this metal, extracted under reflux conditions with aqueous NaOH, was used in the synthesis of hydrocalumite-type solids with the formula Ca2Al1–mFem(OH)6Cl 2H2O. The characterization of the obtained solids was carried out by powder X-ray diffraction, infrared spectroscopy, thermal analysis, element chemical analysis, N2 adsorption-desorption at -196ºC and electron microscopy. The results showed the formation of Layered Double Hydroxide-type compounds whose characteristics varied as the amount of incorporated Fe3+ increased. These solids were calcined at 400ºC and evaluated for the catalytic photodegradation of ibuprofen, showing promising results in the elimination of this drug by advanced oxidation processes. The CaAl photocatalyst (without Fe) showed the best performance under UV light for the photodegradation of ibuprofen.This research was funded by Universidad de Salamanca (Plan I-B2)

Palladium(II)-catalyzed Intramolecular C-H Alkenylation for the Synthesis of Chromanes

The intramolecular Pd(II)-catalyzed alkenylation of aryl homoallyl ethers constitutes a mild, versatile, and efficient procedure for the synthesis of highly and diversely substituted chromanes, and 2H-chromenes. The use of p-TsOH as additive allows more efficient reactions that could be carried out a room temperature in most cases. The procedure has a wide scope, allowing the synthesis of alkylidenechromanes and 2H-chromenes substituted at C-2 or C-3 of the chromene moiety, thus accessing relevant flavenes and isoflavenes, and even coumarins, in high yields (59 to 91%, 32 examples)Ministerio de Economía y Competitividad (CTQ2016-74881-P) // Gobierno Vasco (IT1045-16

Metodologías activas para la mentorización y la cultura emprendedora en las titulaciones de la facultad de Ciencias Químicas

Memoria ID-031 Ayudas de la Universidad de Salamanca para la innovación docente, curso 2020-2021

Ruhe, bitte! - Was Lärmreduktion im Flugzeug mit dem Klimaschutz verbindet

Aktive Systeme zur Lärmreduktion sind seit Jahren Gegenstand zahlreicher Forschungsvorhaben. Im Bereich der Flugzeugkabine hebt das EU­Projekt ACASIAS (EU Horizon 2020, Grant Nr. 723167) aktive Systeme auf eine neue technologische Entwicklungsstufe. Gemeinsam mit Partnern aus der Industrie gelingt die Integration aller Komponenten in einem autarken, für die Serienfertigung geeigneten Flugzeug­Seitenwandpaneel. Seine kompakte Bauweise und die sehr gute Reduktion von tieffrequentem Lärm sind ein Türöffner für energieeffiziente, aber laute Antriebe im Flugzeugbau

Use of Ethylamine, Diethylamine and Triethylamine in the Synthesis of Zn,Al Layered Double Hydroxides

Amines with two carbon atoms in the organic chain [ethylamine (EA), diethylamine (DEA), triethylamine (TEA)] have been used as precipitant agents to obtain a hydrotalcite-like compound with Zn (II) and Al (III) as layered cations and with nitrate anions in the interlayered region to balance the charge. This Layered Double Hydroxide was prepared following the coprecipitation method, and the effect on the crystal and particle sizes was studied. Also, the effect of submitting the obtained solids to hydrothermal post-synthesis treatment by conventional heating and microwave assisted heating were studied. The obtained solids were exhaustively characterized using several instrumental techniques, such as X-ray diffraction, Thermal Analysis (DTA and TG), Chemical Analysis, Infrared Spectroscopy (FT-IR), determination of Particle Size Distribution and BET-Surface area. Well crystallized solids were obtained showing two possible LDH phases, depending on the orientation of the interlayer anion with respect to the brucite-like layers. The results indicated that there is a certain influence of the amine, when used as a precipitating agent, and as a consequence of the degree of substitution, on the crystallinity and particle size of the final solid obtained. The LDHs obtained using TEA exhibited higher crystallinity, which was improved after a long hydrothermal treatment by conventional heating. Regarding the shape of the particles, the formation of aggregates in the former solid was detected, which could be easily disintegrated using ultrasound treatments, producing solid powder with high crystallinity and small particle size, with homogeneous size distribution

Active Lining for the Reduction of Rotor Noise

The participants of the EU-project ACASIAS develop advanced concepts for aero-structures with multifunctional capabilities. Within work package 3 an active system for noise reduction is integrated into a lining panel. The application scope includes current propeller driven aircraft and future aircraft with counterrotating open rotor (CROR) engines. The drawback of these CO2-efficient engines is their high sound emission in the frequency band up to 500 Hz. Active noise reduction systems are able to achieve performance in this frequency band while passive sound insulation materials fall behind. In this paper an integration concept for the actuators and sensors of an active noise reduction system is presented. It includes the protection of the components from humidity, dust, etc. and the integration into industrial manufacturing processes. A tool- and connector-free assembly of the components allows a fast and reliable maintenance. The concept is implemented on a lining with size 1300×1690 mm^2