Papers by Author: Elvia Díaz-Valdés

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Authors: Concepción Mejía-García, Elvia Díaz-Valdés, Marco Alberto Ayala-Torres, Alejandro Sánchez-Sánchez, Ana María Paniagua-Mercado, Josúe Romero-Ibarra
Abstract: We present the synthesis of ZnO nanostructures grown by the hydrothermal method using the rapid microwave heating process. First, 10 mM solutions of zinc acetate dihydrate and 1-propanol were three cycles spin coated on glass substrates at 2000 rpm by 70 s, 90 s and 90 s, respectively. Second, nanostructures were then grown by dipping the substrates in a solution of zinc nitrate hexahydrate, polyethyleneimine (PEI), hexamethylenetetramine and ammonia. The hydrothermal process were carried out with a commercial microwave at 300, and 600 W power settings during 20 min. The structural and morphological properties were investigated using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The influence of the ammonium concentration in the morphology of the nanostructures was analyzed.Keywords: ZnO, nanostructures, XRD, SEM, spin coating, ammonium, hydrothermal process.
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Authors: Concepción Mejía-García, José Luis López-López, Elvia Díaz-Valdés, Claudia Verónica Vázquez-Vera
Abstract: We present a statistical study of the crystalline phase distribution in Pb-Ca-Ba-Cu-O precursor films grown by spray pyrolysis technique, with thickness and composition suitable to incorporate Hg by the sealed quartz tube technique in a subsequent treatment. A series of 9 precursor thin films were deposited on MgO substrates. Interdependence among deposition temperature, solution concentration, annealing temperature and annealed time and the effect in the relative percentage of each precursor phases was studied, applying a fractional factorial design 3IV-II. Chemical composition was obtained from atomic absorption measurements. Crystalline phase identification was performed by X-ray diffraction technique (XRD) and the quantification of each one was carried out by Rietveld method. The BaPbO3, Ba4Pb3O10 ternary phases were obtained at 810°C, and the BaCuO2 phase was got between 835°C and 860°C. Deposition temperature and molarity of the solution have clear influence on the thickness of the film. The effect of deposition temperature on the film composition was observed. Introduction
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