FRM - I+D+i - Artículo Publicado
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Item Evaluación técnica y ambiental de un calefón solar de bajo costo(2013-01-01) Arena, Pablo; Gardey Merino, María; Rivarola, DoraSe presenta un calefón solar de bajo costo construido con materiales reciclables y de reuso. Midiendo tanto la temperatura ambiente, como la de entrada y salida del colector solar, se provee una estimación del rendimiento del sistema en la que se alcanzó una interesante cobertura energética cercana al 70%. Se llevó a cabo el Análisis de Ciclo de Vida del calefón solar usando el software SimaPro, permitiendo cuantificar la carga ambiental asociada con cada componente del sistema. Los mayores impactos están asociados con el combustible requerido para transporte y compra de los materiales, al proceso de generación de electricidad y de caños de PVC, todos expresados en kg de CO2 . Se propusieron también algunas modificaciones sobre el modelo original con el objeto de mejorar el rendimiento y vida útil del dispositivo, pero el impacto ambiental de este último sistema es mayor que el del modelo construidoItem Estudio de carbones activados para el uso en sistemas de refrigeración solar por adsorción(2017-01-01) Gardey Merino, MaríaEl objetivo de este trabajo es evaluar diferentes carbones activados, tres de origen local y uno de origen internacional, y compararlas con las correspondientes al carbón activado de referencia CNR 115. Se busca un carbón activado de bajo costo y accesible en el mercado local. Los carbones se caracterizaron mediante técnicas como FT-IR, TGA-DSC, TP, BET, y SEM. Se determinó que el carbón granular C2 de la empresa Concarb es el que presenta mayor similitud con el carbón de referencia, sobre todo porque es el que presenta una mayor superficie específica.Item Síntesis y caracterización de nanopartículas Co3O4 para uso como pigmento en pinturas absorbedoras solares(2010-01-01) Gardey Merino, MaríaEl objetivo de este trabajo es presentar una caracterización físico-química de los polvos de Co3O4 obtenidos mediante una vía de combustión estequiométrica utilizando dos combustibles, Lisina y ácido aspártico, y demostrar su aptitud para utilizarlo en pinturas absorbedoras solares. Los polvos obtenidos fueron caracterizados por Difracción de Rayos X, Microscopía Electrónica de Transmisión y Espectrofotometría UV-VIS-IR cercano. En ambos casos se obtuvieron partículas de Co3O4 con un tamaño promedio de 50nm y forma poliédrica. La absorbancia solar para los polvos de Co3O4 más cubeta de cuarzo dio un valor de 0,883 en el caso de los polvos sintetizados con Lisina, mientras que para el aspártico fue de 0,863. Ambos valores de absorción se encuentran cercanos al rango de valores de absorción solar medidos para superficies selectivas formadas por películas de aluminio cubiertas con pinturas fabricadas con pigmentos de Co3O4 ; entonces podrían utilizarse como pigmentos en pinturas absorbedoras.Item Síntesis y caracterización de pinturas selectivas de Co3O4 para superficies selectivas en colectores solares de baja temperatura(2009-01-01) Gardey Merino, MaríaPara aumentar el rendimiento energético de los calefones solares se recubre su colector con superficies selectivas siendo las pinturas selectivas una alternativa económica, empleandose como pigmento para fabricarlas Co3O4 obtenido por diferentes métodos. Como se encuentran pocas referencias sobre su síntesis por combustión, se han obtenido para este trabajo micropartículas de Co3O4 empleando una ruta de combustión. Luego, por Difracción de Rayos X se constató la estructura cúbica del Co3O4 obtenido. Además, por Microscopía Electrónica de Barrido, se observó una morfología compacta y aglomeración de las micropartículas y mediante Microscopía Electrónica de Transmisión se apreciaron tamaños de partícula de 1 µm aprox. La absorbancia espectral en un rango de 500 a 1100 nm de longitud de onda de las películas formadas a partir de este pigmento sobre vidrio y aluminio resultó entre 0.92 y 0.96, valor menor al obtenido para una pintura comercial que resultó entre 0.95 y 0.97.Item Combustion synthesis of Co-Cu-Mn oxides deploying different fuels(2015-01-01) Gardey Merino, MaríaTernary spinel-like oxides such as CuFeMnO4, CoCuMnOx and CuCr2O4 are attractive materials due to their absorbent properties when used as pigments for selective surfaces thus improving solar heaters efficiency. These materials are obtained through sol-gel and sol-gel-combustion methods. This work proposes the synthesis of mixed oxides of Co, Cu and Mn by means of original one-step stoichiometric combustion methods starting from Mn(NO3)2, Co(NO3)26H2O, Cu(NO3)23H2O and Aspartic acid (Asp) or Lysine( Lys) as fuels. The resulting ashes after the combustion were calcined at 500 °C. The obtained ashes and the calcined powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and by Brunauer–Emmett– Teller method (BET), and TG-DTA analysis. In calcined powders obtained with Lys (CoCuMnOx-Lys), the phase corresponding to CoCuMnOx and others segregated phases were identified. However, in calcined powders obtained with Asp (CoCuMnOx-Asp) only the phase corresponding to CoCuMnOxwas identified. The sample CoCuMnOx-Lys presented an average crystallite size of 44 nm and a specific surface area of 23 m 2 /g while in CoCuMnOx-Asp, 54 nm and 13 m2 /g values were obtained throughout FT-IR vibrational modes associated with spinel metallic oxides for both calcined powders (Asp and Lys) were observed. Additionally, by means of TEM, polyhedral particles with an average size of 20 to 100 nm were observed. In particular, it was determined in CoCuMnOx-Lys an average size of 44nm. According to the different fuels used (Asp and Lys), an evident variation in the obtained phases was observed. However, it was not obtained any difference in crystallite size and specific area surface values. It is of considerable importance the study of further syntheses processes to verify this trend.Item Combustion synthesis of ultrafine powders of Co3O4 for selective surfaces of solar collectors(2015-01-01) Gardey Merino, MaríaSolar selective paints, with the addition of Co3O4 as a pigment, are used to improve energetic efficiency in solar collectors. Although Co3O4 has been obtained by different methods, references about combustion synthesis are scarce. Co3O4 powders have been synthesized by stoichiometric and non-stoichiometric routes using aspartic acid (Asp) or tri-hydroxi-methyl-aminomethane (Tris) as fuels. The samples were calcined in air at 500 °C. They were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectrum and the specific surface area of the samples was determined by means of the Brunauer–Emmett–Teller technique. The optical properties of pigments were assessed by means of a spectrophotometer. In all cases, powders exhibited the crystalline structure of Co3O4. A minimum crystallite average size of 29 nm was observed for powders obtained by the “stoichiometric/Asp” combustion route, while a maximum value of 41 nm was stated for powders obtained by the “nonstoichiometric/Asp” combustion process. The average particle size ranged between 50 and 100 nm. The powders obtained by the “stoichiometric/Asp” method were selected to study their optical properties; their solar absorption value was 86%. Solar selective surfaces composed by Co3O4 pigments and an alkyd resin were obtained and applied over copper or aluminum substrates. In both cases, solar absorptance was of 93% and comparable with similar solar selective surfaces, but the thermal emittance value was higher than 90%, as a consequence of the large width of the films.Item Combustion Syntheses of Co3O4 Powders Using Different Fuels(2015-01-01) Gardey Merino, MaríaCo3O4 powders are used as pigment in solar selective paints. In this work, two new gel-combustion processes for the synthesis of Co3O4 nanopowders with lysine (Lys) or ethylenediaminetetraacetic acid (Edta) as fuel are presented. The first route is a conventional, stoichiometric process, while the second one is a non-stoichiometric, pH-controlled process. The samples were calcined in air at 500 ºC. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and the optical properties of the pigments were assessed with a spectrophotometer. In all cases, powders exhibited the Co3O4 crystalline structure. A minimum crystallite average size of 19 nm for powders obtained by the “stoichiometric/Lys” combustion route was observed, meanwhile, a maximum value of 47 nm was stated for powders obtained by the “non-stoichiometric/Edta” combustion process. The average particle size ranged between 50 and 100 nm. The powders obtained by the stoichiometric nitrate–lysine route were selected to study its optical properties, their solar absorption was 88%, compared with the references, evidencing their aptitude to be used in solar absorbent paintsItem Combustion Syntheses of CoAl2O4 Powders Using Different Fuels(2015-01-01) Gardey Merino, MaríaThis research intends to analyse the potential use of CoAl2O4 as an opaque pigment for solar collector selective paints. The opacity of the pigment occurs when the average crystallite size is micrometric. The CoAl2O4 samples were synthesized through combustion methods using aspartic acid (Asp) or lysine (Lys) as fuels. The powders obtained were calcined at temperatures between 600°C and 1100°C. Afterwards, the product was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR). It was observed a CoAl2O4 phase in all the samples. The lowest average crystallite size was ≈24nm corresponding to the sample obtained with Asp and calcined at 600°C, while both powders calcined at 1100°C showed sizes higher than 200nm. In the light of these results it is suggested the use of even higher calcination temperatures so as to obtain opaque pigments for solar collectors selective paints.Item Combustion synthesis of Co3O4 nanoparticles : fuel ratio effect on the physical properties of the resulting powders(2012-01-01) Gardey Merino, MaríaCo3O4 nanoparticles have been obtained by stoichiometric combustion synthesis: in particular 4 nitrates-aspartic routes each with different fuel ratio (ranging 0.5-2.5) have been studied. It has been determined through XRD that the crystalline structure present in all obtained powders was the face-centered cubic corresponding to Co3O4 and it has been evaluated an average crystallite size ranging between 21 and 76 nm. As regards to the effect of fuel ratio on physical properties, an increment on the crystallite average size and a drop on the specific surface area with the increase of the fuel ratio has been observed.Item Nanostructured aluminium oxide powders obtained by aspartic acid–nitrate gel-combustion routes(2009-10-01) Gardey Merino, MaríaIn this work, two new gel-combustion routes for the synthesis of Al2O3 nanopowders with aspartic acid as fuel are presented. The first route is a conventional stoichiometric process, while the second one is a non-stoichiometric, pH-controlled process. These routes were compared with similar synthesis procedures using glycine as fuel, which are well-known in the literature. The samples were calcined in air at different temperatures, in a range of 600–1200 ◦C. They were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and BET specific surface area. Different phases were obtained depending on the calcination temperature: amorphous, (metastable) or (stable). The amorphous-to- transition was found for calcination temperatures in the range of 700–900 ◦C, while the -to- one was observed for calcination temperatures of 1100–1200 ◦C. The retention of the metastable phase is probably due to a crystallite size effect. It transforms to the phase after the crystallite size increases over a critical size during the calcination process at 1200 ◦C. The highest BET specific surface areas were obtained for both nitrate–aspartic acid routes proposed in this work, reaching values of about 50 m2/g.