LUSINETE PEREIRA BARBOSA

LUSINETE PEREIRA BARBOSA

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Low-temperature reduction of graphene oxide using the HDDR process for electrochemical supercapacitor applications
2020 - BENITEZ JARA, F.G.; CRUZ, P.D.V.; BARBOSA, L.P.; CASINI, J.C.S.; SAKATA, S.K.; PERUZZI, A.J.; FARIA, R.N.
In the present work, attempts of reducing a graphene oxide powder using a low temperature hydrogenation disproportionation desorption and the recombination process (L-HDDR) has been carried out. A lower processing temperature in large scale production is significant when costs are concerned. Graphite oxide was prepared using a modified Hummers’ method dispersed in ethanol and 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 both processes, the L-HDDR as well as the standard HDDR, may be applied to the reduction of graphene oxide in order to produce supercapacitor materials. The advantage of employing the L-HDDR process is a relatively low temperature reducing the cost of treatment, what is a very important factor for producing a large amount of material. Thus, the L-HDDR process has been considered a promising alternative method of reducing graphene oxide with efficiency, with the possibility of large scale production.
Influence of separator thickness on the performance of electric double layer supercapacitors in aqueous electrolyte
2020 - SILVA, D.V.; GALDINO, G.S.; BARBOSA, L.P.; CASINI, J.C.S.; FARIA, R.N.
The effects of the separator thickness (δ) upon the equivalent series resistances (ESR) and specific capacitances (Cs) of supercapacitors electrodes have been investigated using commercially available porous filter paper (δ=150 μm, pores size=7.5 μm, 80 gm-2). Commercial activated carbon electrodes immersed in 1molL-1 KOH electrolyte (25°C) have been employed in this study. The specific capacitances were calculated from cyclic voltammetry curves at room temperature employing various scan rates (5, 10, 15 and 30 mVs-1). Internal series resistances of the supercapacitors were measured using the galvanostatic charge discharge curves also at room temperature. A maximum of 28 separators (δ=4200 μm) have been employed in this investigation. It has been shown that the ESR increases substantially with separator thickness (from 3.1 to 7.9 Ωcm2). The specific capacitance decreased somewhat with increasing separator thickness and scan rates (from 64 to 52 Fg-1; at 5 mVs-1). The microstructures of the electrode material have been investigated using scanning electron microscopy (SEM) and chemical microanalyses employing energy dispersive X-ray analysis (EDX). A compositional and morphological evaluation of these electrodes showed a very homogeneous microstructure.
X-ray diffraction evaluation of the average number of layers in thermal reduced graphene powder for supercapacitor nanomaterial
2019 - CARDOSO, QUEZIA de A.; CASINI, JULIO C.S.; BARBOSA, LUZINETE P.; SERNA, MARILENE M.; GALEGO, EGUIBERTO; SOBRINHO, LUIZA F.; SAKATA, SOLANGE K.; FARIA JUNIOR, RUBENS N. de
Graphene oxide (GO) can be partially reduced to graphene-like sheets by removing the oxygen-containing groups and recovering the conjugated structure. In this work, the thermal reduction of GO powder has been carried out using back pumping vacuum pressures and investigated employing X-ray diffraction analysis. The experimental results of estimating the number of graphene layers on the reduced powder at various temperatures (200 – 1000 °C) have been reported. Electrical changes have been produced in a graphene oxide with the vacuum reduction process. This study has shown that the ideal processing temperature for reducing graphene oxide nanomaterial was about 400 oC. It has also been shown that at 600 oC the number of layers in the reduced nanomaterial increased. The internal series equivalent resistance (ESR) has been improved substantially with the vacuum thermal treatment even at temperatures above 400 oC. ESR was reduced from 95.0 to about 13.8 Ω cm2 with this processing. These results showed that the process can be applied to the reduction of graphene oxide to produce supercapacitor nanomaterials. The advantage of employing this method is that the processing is a straightforward and low cost thermal treatment that might be used for large amount of nanocomposite material.
Corrosion characterization of AISI 304 stainless steel filter
2018 - BARBOSA, L.P.; CORREA, O.V.; KARSOKAS FILHO, N.; COSTA, I.
Pre-sintering for removal of lubricants is one of the most important steps in processing of powder metallurgy materials to achieve corrosion resistance. This is often the most neglected step in the sintering process. Incomplete removal of these organic compounds may result in sensitization of sintered parts. The aim of this study is to investigate the effect of lubricant removal process on the corrosion resistance of sintered AISI 304 L stainless steel filters. Pre-sintering was carried out at 450° C and sintering at 1150° C. As lubricant, 1% wax was used. The corrosion resistance of sintered samples was evaluated by polarization and tests, optical and scanning electron microscopy. The results showed that lubricant removal was not complete and during sintering sensitization of the stainless steel occurred decreasing the localized corrosion resistance of the stainless steel.
Recycling and melting process of the zirconium alloy chips
2017 - REIS, LUIS A.M. dos; MUCSI, CRISTIANO S.; TAVARES, LUIZ A.P.; ALENCAR, MAICON C.; GOMES, MAURILIO P.; BARBOSA, LUZINETE P.; ROSSI, JESUALDO L.
Heat treatment and microstructural studies of LaNi-Type battery electrode alloys
2017 - FERREIRA, E.A.; BARBOSA, L.P.; FARIA, R.N.
The effects of annealing on the microstructures and electrochemical characteristics of a La0.7Mg0.3Al0.3Mn0.4Co0.5Ni3.8 hydrogen storage alloy have been studied. The heat treatment by vacuum annealing was carried out at 700 oC, 800 oC, 900 oC and 1000 oC. The microstructure and phase composition of the alloy have been investigated using inductively coupled plasma - atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). The battery anode was prepared using a mixture of the pulverized alloy with carbon black and polytetrafluoroethylene as a binder.
Preparation and characterization of stainless steel filters
1992 - AMBROZIO FILHO, F.; LIMA, L.F.C.P.; MOURISCO, A.J.; BARBOSA, L.P.; POLA, E.J.G.; NEVES, M.D.M.
Caracterizacao do comportamento de corrosao de filtros de aco inoxidavel AISI 316L produzidos com diferentes pressoes de compactacao
1995 - BARBOSA, L.P.; AMBROZIO FILHO, F.; COSTA, I.
Production of Ti-13Nb-13Zr alloy by PM for biomedical applications using zirconium oxide grinding bowl and balls
2011 - DUVAIZEM, J.H.; FAJARDO, A.M.; BARBOSA, L.B.; BRESSIANI, A.H.; TAKIISHI, H.
The influence of heat treatment on the corrosion behavior of titanium (cp) obtained by the hdh process
2011 - BARBOSA, L.B.; SALGADO, L.; KARSOKAS FILHO, N.; DUVAIZEM, J.H.; COSTA, I.