LIA MARIA CARLOTTI ZARPELON

LIA MARIA CARLOTTI ZARPELON

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Effects of magnesium content on structure and electrochemical properties of La-Mg-Pr-Al-Mn-Co-Ni hydrogen storage alloys
2018 - ZARPELON, L.M.C.; BANCZEK, E.P.; MARTINEZ, L.G.; LIMA, N.B.; COSTA, I.; FARIA, R.N.
The discharge capacity, microstructures, and corrosion resistance of some as-cast alloys represented by the formula La0.7−xMgxPr0.3Al0.3Mn0.4Co0.5Ni3.8, where x = 0.0, 0.1, 0.3, 0.5, and 0.7, were investigated by SEM/EDX, XRD, and electrochemical measurements. The partial substitution of La by Mg refined the grain structure while the total substitution changed it from equiaxed to columnar. Three phases were detected: a major phase (M), a grey phase (G), and a dark phase (D). The compositions analyzed by EDX suggested that the M phase was close to a LaNi5 phase. With the increase of the Mg content, the analyses revealed a G phase with composition close to a RMg2Ni9 (R = La,Pr) and a D phase close to a MgNi2 phase. The XRD analysis and Rietveld refinement corroborated the EDX results. The corrosion resistance of the alloys was evaluated in 6.0 mol·L−1 KOH solution, and the results showed that the substitution of La by Mg was beneficial for this alloy property. Nevertheless, Mg addition was deleterious to the discharge capacity of the electrodes.
The influence of Pr and Mg content on the hydrogen decrepitation of LaNi-based battery alloys
2017 - SOARES, E.P.; ZARPELON, L.M.C.; FARIA, R.N.
This paper reports the results of investigations of the hydrogenation and decrepitation of some LaNi-based hydrogen storage cast ingot alloys. A decrepitation procedure for battery negative electrode alloys has been applied using a combination of hydrogen pressure and heating from room temperature to 773K. It has been shown that the Pr and Mg content have a significant influence on the microstructures of the hydrogenated alloys and decrepitation efficiency. Alloys with high concentration of Pr and Mg required an activation quenching treatment for starting the absorption of hydrogen. The decrepitated materials were characterized by scanning electron microscopy (SEM). Electrodes for alloy discharge capacity studies were produced using a nickel screen and electrochemical measurement were carried out in a standard three-electrode cell. The H content of the negative electrode, expressed as the number o H atoms (n) per formula unit, was determined using the measured storage capacity.
Estudo das características eletroquímicas e microestruturais de eletrodos de hidreto metálico à base de LaNi com adições de elementos de liga
2016 - ZARPELON, LIA M.
Neste trabalho avaliou-se a ação positiva da substituição de lantânio por praseodímio e de lantânio por magnésio na performance eletroquímica de eletrodos de ligas de armazenamento de hidrogênio em estado bruto de fusão e com tratamento térmico. O La foi substituído por Mg nas ligas La0,7-xMgxPr0,3Al0,3Mn0,4Co0,5Ni3,8 (x=0,0-0,7) e por Pr nas ligas La0,7-yPryMg0,3Al0,3Mn0,4Co0,5Ni3,8 (y=0,0-0,7). Os parâmetros eletroquímicos analisados foram ativação, capacidade de descarga, retenção da capacidade de descarga, autodescarga e alta taxa de descarga. As ligas apresentaram comportamento passivo em relação à corrosão. As análises por MEV/EDS e por DRX com refinamento por Rietveld revelaram a presença majoritária de fases similares às fases LaNi5, PrNi5, LaMg2Ni9 e PrMg2Ni9 em função das composições das ligas estudadas. Os parâmetros de rede e os volumes da célula unitária das fases diminuíram com a substituição crescente de La por Mg e de La por Pr. As capacidades de descarga máxima decresceram com a substituição crescente de La por Mg e de La por Pr, acompanhando o decréscimo da abundância da fase similar à fase LaNi5 e o aumento da abundância da fase similar à fase LaMg2Ni9. Comparativamente, menores taxas de autodescarga e maior estabilidade cíclica foram observadas para o eletrodo da liga na condição x=0,1, ao passo que o eletrodo da liga na condição y=0,0 apresentou maiores valores de alta taxa de descarga, indicando melhor performance cinética.
Baterias recarregáveis: introdução aos materiais e cálculos
2014 - FARIA JUNIOR, RUBENS N. de; ZARPELON, LIA M.C.; SERNA, MARILENE M.
Self-discharge and microstructure of supercapacitors tested at room temperature and at 333 K
2014 - VISENTINI, VIRGILIO R.S.; ZARPELON, LIA M.C.; FARIA JUNIOR, RUBENS N.
Microstructure and electrochemical characteristics of LaPrMgALMnCoNi hydrogen storage alloys for nickel-metal hydride batteries
2014 - ZARPELON, LIA M.C.; FARIA JUNIOR, RUBENS N.
The effect of the substitution of La with Pr on the microstructure and some electrochemical properties of La0.7-xPrxMg0.3Al0.3Mn0.4Co0.5Ni3.8 (x=0.0, 0.1, 0.3, 0.5, and 0.7) ingot alloys as powder electrode was studied in this paper. XDR and SEM (+EDX) analyses revealed that the as-cast alloys consist mainly of similar LaNi5 and (La,Pr)Mg2Ni9 phases. With the increase in Pr content, both the relative abundance of the phases and microstructure changed. The electrochemical studies showed that the maximum discharge capacity decreased with the increase in Pr content. For the alloy without Pr, the self-discharge studies revealed a major stability of the hydride until the first 984 hours (41 days) of the charge/discharge cycles. The high-rate dischargeability of this alloy electrode showed the best result HRD=88% at a discharge current density of Id=250 mA/g.
Programa de controle analitico do processo de extracao de hafnio no sistema MIBK-HSCN-HCl
1995 - NOBRE, J.S.M.; ZARPELON, L.M.C.; PASCHOAL, J.O.A.
Microstructural and chemical microanalysis studies of rare earth-transition metal-aluminium-magnesium alloys
2006 - ZARPELON, L.M.C.; GALEGO, E.; TAKIISHI, H.; FARIA, R.N.
Microstructure and microanalysis studies of some lanthanum-based hydrogen storage alloys
2007 - ZARPELON, L.M.C.; FERREIRA, E.A.; TAKIISHI, H.; FARIA, R.N.
Microstructures and chemical compositions of some commercial La-Mg based alloys have been investigated. The hydrogen storage alloys can be represented by the formulae La2Mgx, La2Mgx-1Ni and LaMg2Ni9 (x=12 or 17). The determination of the microstructures and phase compositions of these alloys has been carried out using scanning electron microscopy and energy dispersive X-ray analysis.
Estudo de separacao zirconio-hafnio no sistema MIBK-HSCN-HCl
1990 - ZARPELON, L.M.C.; NOBRE, J.S.M.; PASCHOAL, J.O.A.