Abstract: When tin oxide thin film is doped with Zn, it grows textured and improves its mechanical properties. The material was synthesized on alkali-free borosilicate glass substrates by spray pyrolysis technique. The elemental composition was determined by X-ray energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The morphology and microstructure of films were examined by electron microscopy techniques, they shown different shapes of crystalline particles according to the dopant content. From X-ray diffraction patterns processed by Rietveld refinement methodology was determine lattice parameters, crystallite sizes and micro strain; it showed that the textural growth of the films depend on the Zn dopant quantity content. The mechanical property was studied as a function of dopants amount, it enhancement due to the texture direction growth. For optimized Zn doped quantity in the film, local measurement of hardness and elastic modulus increased from 12 to 23 GPa and from 137 to 195 GPa, respectively. According to the Zn content, the materials show good correlation between elastic module values and (200) texture growth direction parallel to the substrate.

Nanoestructured TiO2 solar cells modified with MgO (TiO2-MgO) were assembled and characterized; they were sensitized with N791 dye. The MgO modification of the TiO2 films was performed using suspensions with different concentrations of Mg(OH)2 prepared from magnesium nitrate in aqueous solution. One drop of the suspension was placed on top of the film and then was sintered at 530 °C during 30 min. Unsealed cells and sealed cells were obtained, the latter achieved an efficiency of 4.4%, representing an increase of 69% compared to the unmodified sealed cells, which showed an efficiency of 2.6%. Solar efficiency measurements were also performed in darkness and under illumination. It was found that the efficiency diminished 19% in darkness after 22 days, but under illumination diminished 76 % in two days.

Se ensamblaron y se caracterizaron celdas solares basadas en TiO2 nanoestructurado modificado con MgO (TiO2-MgO); las cuales fueron sensibilizadas con el colorante N719. La modificación de las películas de TiO2 con MgO se realizó empleando suspensiones de diferentes concentraciones de Mg(OH)2 preparado a partir de una solución acuosa de nitrato de magnesio. Una gota de la suspensión se colocó sobre el recubrimiento del TiO2, y luego todo el sistema se sinterizó a 530 oC durante 30 min. Se obtuvieron celdas sin sellar y celdas selladas, estas últimas alcanzaron una eficiencia de 4,4%, lo que representó un incremento del 69% con relación a la celda sellada sin modificar, que mostró una eficiencia de 2,6%. Además, se realizaron medidas de la eficiencia solar de una celda sellada bajo iluminación y en oscuridad, y se encontró que la eficiencia disminuyó 19% luego de 22 días en oscuridad, y 76% después de 2 días bajo iluminación.

Abstract Mesoporous silicate were synthesized by a not hydrothermal method and the acid sites were promote by adding zirconium and sulfate ions. The maximum acid strength of the mesoporous silicate was promoted by addition of zirconium during the synthesis process and sulfate ions was add by insipient impregnation, after the mesoporous silicate synthesis. The materials were characterized by TGA, XRD, FT-IR, BET, potentiometric titration with n-butylamine, SEM and TEM techniques. The catalytic activity of the materials was evaluated for the ethanol dehydratation. The zirconium atoms and sulfate ions incorporation had a favorable impact on the acid strength of sites going from -42 to 143 mV. The hexagonal arrangement mesoporous material is slightly affected, indicating that ZrO2 nano crystals are within the silicate matrix. At the same way affected the sulfate ions presence.

Resumen Los silicatos mesoporoso fueron sintetizados por un método no hidrotérmico y los sitios ácidos fueron promovidos por la adición de circonio e iones sulfato. La máxima fuerza ácida del silicato mesoporoso fue promovida por adición de circonio durante el proceso de síntesis del silicato y luego por impregnación insipiente con iones sulfatos, después de la obtención del silicato mesoporoso. Los materiales se caracterizaron por las técnicas TGA, DRX, FT-IR, BET, titulación potenciométrica con n-butilamina, SEM y TEM. La actividad catalítica se evaluó en la deshidratación de etanol. La presencia del óxido de circonio y iones sulfato tuvo un impacto favorablemente en la generación de la fuerza ácida de los sitios, pasando de -42 a 143 mV. El arreglo hexagonal del material mesoporoso es ligeramente afectado, indicando que cristales de ZrO2 están dentro de la matriz del silicato. También de la misma manera afectan la presencia de los iones sulfatos.

This work reports the synthesis of titanium oxide (TiO2) and sulfated titanium oxide (TiO2-SO4(2-)) obtained by thermal hydrolysis of titanium tetrachloride. Titanium hydroxide synthesized by this method was impregnated with a 1 N H2SO4 solution, to give amounts of sulfate ions (SO4(2-)) of 3 and 7 wt%. The synthesized samples were dried at 120 °C during 24 h and then calcined for 3 h at 400 °C. Thermal analyses, X-ray diffraction, nitrogen physisorption, infrared spectroscopy, potentiometric titration with n-butylamine, U.V.-visible diffuse reflectance spectroscopy and scanning electron microscopy were used to characterize the materials. The results of physicochemical characterization revealed that a mixture of crystalline structures, anatase, brookite and rutile developed in the titanium oxide, stabilizing the anatase structure in the sulfated titanium oxides, and coexisting with a small amount of brookite structure. The synthesized mesoporous materials developed specific surface areas between 62 and 70 m² g-1, without detecting an important influence of sulfation on this parameter. The presence of sulfate ions improved the acidity of titanium oxide and modified the characteristics of light absorption in the 425-600 nm region, which suggests the possibility of using these materials in reactions assisted by visible light.

Abstract In this work was conducted the decomposition reaction of 2-propanol to obtain propylene using phosphated zirconia as catalyst. The synthesis of Zr(OH)4 was carried out by the sol-gel method. The materials were modified with phosphoric acid and calcined at 400°C. Characterization tests included X-ray diffraction, nitrogen physisorption, infrared spectroscopy and scanning electron microscopy. The results indicated that were obtained solids with tetragonal structure and the addition of phosphate ion increased the specific surface area in the materials. On the other hand, reaction tests revealed that the phosphated catalysts had higher catalytic activity and the active sites dominant were acid sites.

Resumen En este trabajo se efectuó la reacción de descomposición de 2-propanol para obtener propileno usando circonia fosfatada como catalizador. La síntesis del Zr(OH)4 se realizó por el método sol-gel. Los materiales fueron modificados con ácido fosfórico y calcinados a 400°C. Las pruebas de caracterización incluyeron difracción de rayos X, fisisorción de nitrógeno, espectroscopia de infrarrojo y microscopía electrónica de barrido. Se obtuvieron sólidos con estructura tetragonal y la adición del ión fosfato incrementó el área específica en los materiales. Las pruebas de reacción revelaron que los catalizadores fosfatados tuvieron mayor actividad catalítica y los sitios activos dominantes fueron sitios ácidos.

SnO2 thin films were deposited on glass substrates by intermittent spray pyrolysis technique, using solution of SnCl(4)5H2O in methanol. Thin films obtained were characterized by X-Ray Diffraction (XRD), UV-VIS spectroscopy, Scanning Electron Microscopy (SEM) and resistivity measurements by Van der Pauw method. According to results, high transmittance in visible light spectrum, cassiterite phase of SnO2 and uniformity of the film across the substrate were determined. Optical, electrical and structural features obtained in material synthesis are appropriate for electrodes in Grätzel solar cells such as high transmittance (>80%), low resistivity (9.28 x 10-03 Ω.cm) and high density of carriers (6.24 x 10(19) cm-3). Thickness of the film was determined based on transmittance spectra and the crystallite size from XRD diffractogram by Scherrer's equation.

Se depositaron películas delgadas de SnO2 sobre sustratos de vidrio por la técnica de aspersión pirolítica intermitente utilizando una solución de SnCl(4)5H2O en metanol. Las películas obtenidas fueron caracterizadas por difracción de rayos X (XRD; X-ray diffraction), espectroscopía UV-VIS, microscopía electrónica de barrido (SEM; scanning electron microscopy) y medición de resistividad por el método de Van Der Pauw. De acuerdo con los resultados, se obtuvo alta transmitancia en el espectro de luz visible, se determinó la fase casiterita del SnO2 y se observó uniformidad de la película en todo el sustrato. Las características ópticas, eléctricas y estructurales obtenidas en la síntesis del material fueron adecuadas para su aplicación como electrodos en celdas solares de tipo Grätzel, con una alta transmitancia (>80%), una baja resistividad (9.28 x 10-03 Ω.cm), una alta densidad de portadores (6.24 x 10(19) cm-3). El espesor fue determinado desde el espectro de transmitancia y el tamaño de cristalito fue obtenido desde el difractograma de rayos X por medio de la ecuación de Scherrer.

In this paper, the synthesis and characterization of CoMoW nanostructured oxides, partially sulfided, as well as its application as catalysts in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) is presented. All nanostructures were obtained by a two-step hydrothermal/gas phase reduction. Firstly, CoMoW oxides precursors were prepared using a hydrothermal method. Subsequently, all precursors were reduced and activated under H2S/H2 at 500°C. Nanostructures were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and the specific surface areas of the materials were measured using the BET method. The catalytic activity and selectivity measurements in the HDS of DBT reaction were also presented.

En este trabajo, se presenta la síntesis y caracterización de nanoestructuras de óxidos de CoMoW parcialmente sulfuradas y su aplicación como catalizadores en la reacción de hidrodesulfurización (HDS) de dibenzotiofeno (DBT). Las nanoestructuras se obtuvieron a través de un método en dos etapas: hidrotérmico/reducción en fase gas. En la primera etapa (hidrotérmico) se obtiene el precursor en forma de óxidos de CoMoW. Subsecuentemente, se realizó la reducción y activación de los precursores en atmósfera de H2S/H2 a 500 °C (reducción en fase gas). Se analizó la morfología, estructura cristalina y propiedades texturales de los materiales mediante Microscopía Electrónica de Transmisión (MET), Difracción de Rayos X (DRX), área superficial especifica por el método BET, evaluando la actividad catalítica y la selectividad en la reacción de HDS de DBT.