FERNANDO GABRIEL BENITEZ JARA
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Artigo IPEN-doc 30417 Mathematical expressions for simulation of supercapacitor voltammetry curves and capacitance dependence on scan rate2024 - BENITEZ, FERNANDO G.J.; PERUZZI, ALEJANDRO J.B.; FARIA JUNIOR, RUBENS N.A straightforward RC series circuit model was proposed to fit the cyclic voltammetry experimental data of various symmetrical electrochemical supercapacitors. The model simulated the experimental behavior for exponential dependence of capacitance on the scan rate. In this model, the zero-scan rate capacitance was considered as a constant, and the equivalent serial resistance depended on the scan rate. Neither the equivalent parallel resistance nor a possible intrinsic dependence of capacitance on applied voltage was considered in the modelling.Dissertação IPEN-doc 25964 Estudo das microestruturas e características elétricas de supercapacitadores com eletrodos de carbono ativado e grafeno produzido via HDDR e eletrólito biocompatível para aplicações energéticas2018 - BENITEZ JARA, FERNANDO G.Neste trabalho foi proposto investigar as características de capacitores eletroquímicos de dupla camada elétrica (supercapacitores) utilizando como matéria prima um eletrólito biocompatível como rota viável de baixo custo econômico para obtenção de dispositivos eletrônicos para armazenamento de energia. O objetivo principal foi estudar a influência dos vários parâmetros de processamento nas características elétricas de supercapacitores à base de eletrólito neutro, utilizando, na preparação dos eletrodos oxido de grafeno reduzido via HDDR 400°C e o carbono ativado, também com baixa toxidade e impacto ambiental. O primeiro tópico consistiu na preparação de eletrólitos com diferentes concentrações para avaliar este parâmetro na curva de autodescarga dos supercapacitores. Alternativamente realizou-se a caracterização dos eletrodos preparados com oxido de grafeno reduzido via HDDR 400°C e carbono ativado por ensaios de voltametria cíclica em um analisador eletrônico computadorizado de supercapacitores, que resultou na determinação da capacitância específica do material precursor e das resistências internas. Foram utilizadas técnicas adicionais para caracterização dos materiais precursores e processados, tais como: microscopia eletrônica de varredura (MEV-EDS), difração de raios-X (DRX)Resumo IPEN-doc 25388 Low-temperature reduction of graphene oxide using the HDDR process for electrochemical supercapacitor applications2018 - BENITEZ JARA, F.G.; CRUZ, P.V.; BARBOSA, L.P.; CASINI, J.C.S.; PERUZZI, A.J.; SAKATA, S.K.; FARIA, R.N.In the present work, attempts of reducing a graphene oxide powder using a low temperature hydrogenation disproportionation desorption and recombination process (L-HDDR) has been carried out. A lower processing temperature in large scale production is significant as far as costs are concerned. Graphite oxide was prepared using a modified Hummers’ method and dispersed in ethanol, exfoliated using ultrasonication to produce Graphene Oxide (GO). Investigations have been carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results of L-HDDR processing graphene oxide powder using unmixed hydrogen at 400°C and relatively low pressures (<2 bars) have been reported. X-ray diffraction patterns showed a reduction of graphene oxide with the L-HDDR process. The results showed that the L-HDDR process, as the standard HDDR process, can be applied to the reduction of graphene oxide to produce supercapacitor materials. The advantage of employing the L-HDDR process is a relatively a low temperature would reduce the cost of treatment that is a very important factor for producing large amount of material. Thus, the L-HDDR process has been considered a promising alternative method of reducing graphene oxide with efficiency and possibly in large scale production.Resumo IPEN-doc 24832 Thermal reduction of graphene oxide nanocomposite using a low temperature HDDR process for supercapacitors2017 - JARA, FERNANDO G.B.; CRUZ, PEDRO V.D.; GALDINO, GABRIEL S.; CASINI, JULIO C.S.; SAKATA, SOLANGE K.; FARIA JUNIOR, RUBENS N.Recently, it has shown that the hydrogenation disproportionation desorption and recombination (HDDR) process can be an efficient method for the production of reduced graphene oxide for supercapacitors electrodes. The HDDR reduced graphene oxide was processed using a standard temperature (850 o C) for other materials applications. Some improvement in the specific capacitance and in the equivalent serial resistance has been obtained with this particular hydrogen thermal reduction process. The HDDR process has been considered a promising alternative method of reducing graphene oxide with efficiency and possibly in large scale production. A low temperature HDDR process was unreported for this purpose. In the present work, attempts of reducing a graphene oxide powder using a low temperature hydrogenation disproportionation desorption and recombination process (L-HDDR) has been carried out. A lower processing temperature in large scale production is significant as far as costs are concerned. Graphite oxide was prepared using a modified Hummers’ method and dispersed in ethanol, exfoliated using ultrasonication to produce Graphene Oxide (GO). Investigations have been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The experimental results of L-HDDR processing graphene oxide powder using unmixed hydrogen at 400°C and relatively low pressures (<2 bars) have been reported.