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Subject: search.filters.subject.Hydrothermal synthesis

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    Phase transformation during the zeolitization of fly ashes
    (Elsevier, 2017) Monzón, Jorge; Pereyra, Andrea; Conconi, Susana; Basaldella, Elena
    The reactivity of a fly ash discarded from a thermoelectric power station was evaluated in terms of its hydrothermal conversion into NaA-containing products. The influence of ash pretreatments and the effect of changes in the synthesis mixture composition on the evolution of the solid phase toward its conversion into zeolitic materials were studied. Activation by milling was not as effective as alkaline fusion. The highest levels of fly ash reactivity were obtained by applying an alkaline fusion treatment using sodium carbonate at 800 C. It was observed that this particular ash activatiorn induces a solid reordering that generates crystalline materials identified as NaAlSiO2 polymorphs that in turn are easily transformed into zeolite structures. Synthesis conditions for ash zeolitization as high as 60% were established.
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    Electrochemical characterization of nickel hydroxide nanomaterials as electrodes for NiMH batteries
    (Springer, 2016-08-23) Real, Silvia; Ortiz, Mariela; Castro, Élida Beatriz
    β-Nickel hydroxide was successfully synthesized by a hydrothermal method. Nano-nickel hydroxide material was characterized by X-ray diffraction, infrared absorption spectroscopy, and transmission electron microscopy. They were employed as additives to the positive electrode of Ni-MH batteries. Working electrodes, with mixtures of commercial nickel hydroxide and nano-nickel hydroxide (0–10 wt.%) as active material, were prepared. Cyclic voltammetry, charge discharge profiles, and electrochemical impedance spectroscopy studies were carried out to evaluate the electrochemical performance of the nickel electrode, in 7 M KOH electrolyte, at 25 °C. The presence of nano-nickel hydroxide improves the electrochemical behavior of the active material. The electrochemical impedance spectroscopy (EIS) results were analyzed employing a modified version of previously developed physicochemical model that takes into account the main structural and physicochemical parameters that control these systems.