JULIO CESAR SERAFIM CASINI

JULIO CESAR SERAFIM CASINI

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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.
Effect of Sn and Cu on corrosion resistance of LaMgAlMnCoNi type alloys
2017 - CASINI, JULIO C.S.; SAEKI, MARGARIDA J.; GUO, ZAIPING; LIU, HUA K.; FARIA, RUBENS N. de; TAKIISHI, HIDETOSHI
This paper reports the results of investigation carried out to evaluate the corrosion resistance of tin and copper in as-cast alloys represented by two sequential series, first: La0.7Mg0.3Al0.3Mn0.4Co0.5-xSnxNi3.8 (x = 0.0, 0.1, 0.2, 0.3 and 0.5) and second: La0.7Mg0.3Al0.3Mn0.4Sn0.5-yCuyNi3.8 (y = 0.0, 0.1, 0.2, 0.3 and 0.5). Electrochemical methods, specifically, polarization curves have been employed in this study. Copper substitution yielded good overall performance of the alloys.
Supercapacitor application of powder prepared using the Hydrogenation Disproportionation Desorption and Recombination (HDDR) process in graphene oxide
2017 - CASINI, JULIO C.S.; FERNANDEZ, ANTONIO P.R.; OLIVEIRA, RENE R. de; SAKATA, SOLANGE K.; FARIA JUNIOR, RUBENS N.
Graphene (G) has been attracted great interest for its excellent electrical properties. However, the large-scale production of graphene is presently unfeasible. Graphene oxide (GO) can be (partly) reduced to graphene-like sheets by removing the oxygen-containing groups with the recovery of a conjugated structure. It can be produced using inexpensive graphite as raw material by cost-effective chemical methods. Although hydrogen (mixed with argon) at high temperature (1100°C) has been employed to reduce GO powder, the hydrogenation disproportionation desorption and recombination (HDDR) process in particular was unreported for this purpose. In the present work, attempts of reducing GO powder using the HDDR process have been carried out and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The experimental results of processing graphene oxide powder using unmixed hydrogen at moderate temperatures (about 850°C) and relatively low pressures (<2 bars) have been reported.
Processamento de ligas à base de terras raras e metais de transição para fabricação de eletrodos de bateriais de Ni-MH
2008 - CASINI, JULIO C.S.; TAKIISHI, HIDETOSHI; FARIA JUNIOR, RUBENS N. de
Effect of Sn and Cu on corrosion resistance of LaMgAlMnCoNi type alloys
2015 - CASINI, JULIO C.S.; SAEKI, MARGARIDA J.; GUO, ZAIPING; LIU, HUA K.; FARIA, RUBENS N. de; TAKIISHI, HIDETOSHI
Supercapacitor application of powder prepared using the hydrogenation disproportionation desorption and recombination (HDDR) process in graphene oxide
2015 - CASINI, JULIO C.S.; FERNANDEZ, ANTONIO P.R.; OLIVEIRA, RENE R. de; SAKATA, SOLANGE K.; FARIA JUNIOR, RUBENS N.
Effects of Cu substitution for Sn on the electrochemical performance of Lasub(0.7)Mgsub(0.3)Mnsub(0.4)Snsub(0.5-x)Cusub(x)Nisub(3.8)(x=0-05) alloys for Ni-MH batteries
2015 - CASINI, JULIO C.S.; GUO, ZAIPING; LIU, HUA K.; FARIA, RUBENS N.; TAKIISHI, HIDETOSHI
The effects of substitution of Cu for Sn on the electrochemical discharge capacity performance of La0.7Mg0.3Al0.3Mn0.4Sn0.5−xCuxNi3.8 (x = 0.0, 0.1, 0.2, 0.3, and 0.5) negative electrode alloys were investigated. Results indicate that increasing Cu content enhanced electrochemical behavior by increasing the maximum discharge capacity from 239.8 mA·h/g (x = 0) to 305.2 mA·h/g (x = 0.5), the discharge capacity retention at the 100th cycle from 78.0% (x = 0) to 81.8% (x = 0.5), and the high rate dischargeability (HRD) from 25.7% (x = 0) to 80.6% (x = 0.5).
Influência da substituição do cobalto por estanho e cobre na microestrutura e propriedades elétricas em ligas a base de LaMgAlMnCoNi
2015 - CASINI, JULIO C.S.
Neste trabalho, avaliou-se inicialmente o efeito da substituição de elementos em ligas à base de LaMgAlMnCoNi do tipo AB5 com adição de estanho (Sn) e cobre (Cu) em substituição ao cobalto (Co), para utilização em ligas absorvedoras de hidrogênio e em eletrodos negativos de baterias de Ni-HM. Avaliou-se a influência desta substituição na microestrutura do material. Notou-se que o aumento da concentração de estanho promove a formação da fase LaNiSn nas ligas, bem como a diminuição das duas fases principais: LaNi5 e (La,Mg)Ni3. Adicionalmente, utilizou-se o refinamento de Rietveld para quantificar as fases em cada composição. Posteriormente, propôs-se um estudo da absorção de hidrogênio. Notou-se que a liga com cobalto apresentou a melhor capacidade de absorção de hidrogênio. Ademais, verificou-se o comportamento destas ligas na capacidade de descarga, estabilidade cíclica e na alta taxa de descarga de baterias de Ni-HM. A maior capacidade de descarga medida foi para a liga de cobalto, atingindo 337,1 mAh/g. Notou-se, posteriormente uma melhora na estabilidade cíclica das baterias com o aumento do teor de cobre. Além disso, observou-se que a alta taxa de descarga apresenta melhores valores com a adição de cobre na composição. Por fim, avaliou-se o efeito da susceptibilidade a corrosão. Notou-se que o estanho promove um aumento na resistência à corrosão das ligas em eletrólito alcalino.
Effect of heat treatment on microstructure and mechanical properties of Ti-13Nb-13Zr alloy produced by powder metallurgy
2014 - DUVAIZEM, J.H.; MENDES, N.M.F.; CASINI, J.C.S.; BRESSIANI, A.H.; TAKIISHI, H.
Effect of Sn substitution for Co on microstructure and electrochemical performance of ABsub(5) type Lasub(0.7)Mgsub(0.3)Mnsub(0.4)Cosub(0.5)-sub(x)Snsub(3.8)(x=0-0.5) alloys
2015 - CASINI, JULIO C.S.; GUO, ZAIPING; LIU, HUA K.; FERREIRA, ELINER A.; FARIA, RUBENS N.; TAKIISHI, HIDETOSHI
: The effects of substitution of Sn for Co on the microstructure, hydrogen storage and electrochemical discharge capacity of La0.7Mg0.3Al0.3Mn0.4Co0.5−xSnxNi3.8 (x=0, 0.1, 0.2, 0.3 and 0.5) alloys were investigated using X-ray diffraction (XRD), pressure composition isotherm (PCT) and electrochemical discharge cycle. XRD, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tests showed that all of alloys are mainly composed of LaNi5 and MgNi2 phases, but when increasing the content of Sn in alloys, the LaNiSn phase appears and microstructure is refined. The PCT showed that increasing substitution of Sn for Co results in decrease of the maximum hydrogen storage capacity from 1.48% (x=0) to 0.85% (x=0.5). The electrochemical tests indicated that the maximum discharge capacity decreases from 337.1 mA·h/g (x=0) to 239.8 mA·h/g (x=0.5); however, the discharge capacity retention at the 100th cycle increases from 70.2% (x=0) to 78.0% (x=0.5).