Browsing by Author "Silva, Glaura G."

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    Facile Graphene Oxide Preparation by Microwave-Assisted Acid Method
    (Sociedade Brasileira de Química, 2015) Viana, Marcelo M.; Lima, Meiriane C.F.S.; Forsythe, Jerimiah C.; Gangoli, Varun S.; Cho, Minjung; Cheng, Yinhong; Silva, Glaura G.; Wong, Michael S.; Caliman, Vinicius
    Few-layered graphene oxide (GO) was prepared using a fast and energy-saving method by microwave-assisted acid technique. The oxygenated groups existing on the GO surface were determined using UV-Vis, X-ray photoelectron and Fourier-transform infrared spectroscopies. An oxygenated group percentage of 30% in mass for the GO was observed by thermogravimetric analysis. The reduced few-layered graphene oxide (rGO) film annealed at 110 °C deposited onto a silicon/silica wafer showed expanded graphite-like structure with 0.70 nm between the rGO sheets, as determined by X-ray diffraction. This rGO film exhibited a relatively high electrical conductivity value of 7.36 × 102 S m-1 confirming the good restoration of the π-conjugated system. The prepared GO sample exhibited good stability in water from pH 4 to 12, as determined by its zeta potential, and contained 5 to 9 layers, as determined by atomic force microscopy (AFM) and transmission electron microscopy (TEM).
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    Supercapacitor Operating At 200 Degrees Celsius
    (Nature Publishing Group, 2013) Borges, Raquel S.; Reddy, Arava Leela Mohana; Rodrigues, Marco-Tulio F.; Gullapalli, Hemtej; Balakrishnan, Kaushik; Silva, Glaura G.; Ajayan, Pulickel M.
    The operating temperatures of current electrochemical energy storage devices are limited due to electrolyte degradation and separator instability at higher temperatures. Here we demonstrate that a tailored mixture of materials can facilitate operation of supercapacitors at record temperatures, as high as 2006C. Composite electrolyte/separator structures made from naturally occurring clay and room temperature ionic liquids, with graphitic carbon electrodes, show stable supercapacitor performance at 2006C with good cyclic stability. Free standing films of such high temperature composite electrolyte systems can become versatile functional membranes in several high temperature energy conversion and storage applications.