The semiconductor zinc oxide (ZnO) has been widely used because it presents exclusive novel physical and chemical properties at the nanometer scale. In this work, ZnO nanocrystals were synthesized via solochemical processing in a few hours without any subsequent treatment. ZnCl2 and NaOH were adopted as synthesis precursors. ZnO production was realized at different reaction temperatures to verify the effect of this parameter on synthesis. The synthesis temperatures studied were 50 degrees C, 70 degrees C and 90 degrees C. The materials obtained at different reaction temperatures were characterized by X-ray diffraction (XRD) and the Rietveld method. The size and morphology of the ZnO particles obtained at 50 degrees C were evaluated by transmission electron microscopy (TEM). ZnO powders have hexagonal wurtzite structure and nanometric-sized crystallites. Microstrain increased and the average crystallite size decreased with the increase in reaction temperature.

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This work evaluates the effect of ZnCl 2 and Zn(NO 3 ) 2 .6H 2 O as precursors in the synthesis of ZnO nanocrystals. The materials were obtained at 90 °C by a simple solochemical route. The resulting samples were characterized regarding phase composition, particle size and morphology, by means of XRD and TEM. The analysis have provided evidences that the material obtained applying Zn(NO 3 ) 2 .6H 2 O as precursor has hexagonal crystalline structure, typical of the ZnO, and dimensions in the nanoscale. However, applying ZnCl 2 as precursor results in a mixture of ZnO and Zn 5 (OH) 8 Cl 2 .H 2 O phases. For both precursors, the predominant morphology of the obtained ZnO nanocrystals was the rod-like structure.

Sodium bentonites are extensively used in industry because they have specific properties that are wanted for several purposes, such as high swelling, thixotropy, and cation exchange capacity. Otherwise, calcium and polycationic bentonites, which are predominant in Brazil, need to be chemically treated by sodium activation to expand their content of interlayer exchangeable sodium cations, which increases these properties. The present study shows the factorial design of the sodium activation for a polycationic bentonite from Quatro Barras, Paraná. The factors considered in the study were: reagent (NaOH and Na2CO3), concentration (1% and 5%) and contact time (24 and 72 h). The response variables were swelling and cation exchange capacity. Statistical analysis indicated significant effects of all factors over swelling and response surface methodology indicated optimal activation with sodium carbonate at 5% for 24 h.

Substantial efforts have been devoted towards researching routes that provide an appropriate and simple approach for the production of zinc oxide (ZnO) nanocrystals. Here, a rapid and inexpensive solochemical method was employed to synthesize ZnQ nanocrystals through the decomposition of zinc chloride (ZnCl2) and sodium hydroxide (NaOH) at 50 degrees C, 70 degrees C and 90 degrees C. The powders were analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. The products showed high purity, nearly uniform rod-like morphology and nanometric crystallite sizes. With increasing reaction temperature, the crystallites become smaller and rounded. The Raman results reveal correlations between Raman line widths and intensities with ZnO nanorods dimensions. More specifically, the line widths are large and therefore less intense as the nanorod becomes smaller.

Resumo A fabricação de vasos cerâmicos impregnados com prata possibilita o acesso à água potável de uma forma barata e com fabricação relativamente simples. Este estudo teve como objetivo promover a modificação superficial de filtros cerâmicos utilizando APTES e EDTA como agentes ancoradores para melhorar a impregnação da prata e a eficiência e durabilidade dos filtros, avaliando-se diferentes rotas de modificação superficial. A ancoragem e adsorção da prata foram analisadas por espectroscopia FTIR e absorção atômica, e a água filtrada foi analisada quanto à presença de Escherichia coli. Os resultados obtidos demonstraram que a ancoragem melhorou a captura da prata pela cerâmica, em especial com o EDTA, não importando a ordem nas etapas de impregnação. Todos os substratos impregnados com prata, ancorados ou não, apresentaram ausência de E. coli, demonstrando que o procedimento de impregnação atingiu o efeito bactericida esperado e que a ancoragem não interferiu na atuação microbiológica dos filtros.

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