Neste trabalho foi feito um estudo das propriedades estruturais e eletroquímicas de eletrodos formados por pó de liga de hidreto metálico Zr0,9Ti0,1Ni1,04Mn0,64V0,46 (tipo AB2) preparadas em forno a arco e tratadas por moagem em moinho de bolas na presença de pó de Ni ou da liga LaNi4,7Sn0,3. Também foram estudadas ligas à base de Mg-Ni preparadas por moagem de alta energia, com e sem a inclusão de um terceiro elemento (Ti ou Pt). Neste último caso, foi realizada deposição eletroquímica para o revestimento da superfície da liga Mg-Ni com paládio. Os estudos nos dois sistemas foram conduzidos utilizando-se as técnicas de EDX (energia dispersiva de raios X), DRX (difração de raios X) e MEV (microscopia eletrônica de varredura) para a caracterização física dos materiais. Também foram realizados experimentos espectroscopia de absorção de raios X (XAS) e de microscopia eletrônica de transmissão (MET). Os estudos eletroquímicos incluíram medidas da polarização dos eletrodos ao longo dos ciclos de carga/descarga, com o monitoramento da capacidade de descarga em função do número de ciclos. Medidas de espectroscopia de impedância eletroquímica em diferentes estado de carga, temperaturas e números de ciclos foram realizadas nos eletrodos formados com as diferentes ligas. Foi observado que a capacidade de armazenamento de carga da liga AB2 sem tratamento, aumenta muito lentamente com o decorrer do número de ciclos de carga/descarga, enquanto que os eletrodos formados com essa mesma liga, porém submetida aos tratamentos superficiais pela moagem com os diferentes aditivos, apresentam ativação muito mais rápida. Pelas medidas de impedância eletroquímica, observou-se alta similaridade da cinética reacional nas várias amostras AB2 analisadas. A substituição parcial da liga MgNi pela Pt levou à uma maior estabilidade aos ciclos de carga e descarga, inibindo a formação de hidróxido de Mg e proporcionando uma cinética tanto de absorção quanto de dessorção do hidreto maior que sua correspondente liga base. A eletrodeposição de Pd nestas ligas, leva à um incremento adicional na estabilidade do eletrodo. / This work reports results of studies on the structure and electrochemical properties of hydrogen storage alloy electrodes, formed by Zr0,9Ti0,1Ni1,04Mn0,64V0,46 (AB2-type), prepared in arc furnace and processed by ball milling in the presence of Ni and/or LaNi4,7Sn0,3 powder additives. The Mg- Ni based alloys with and without incorporation of Ti and Pt, processed by mechanical alloying were also investigated. In this case, electrochemical deposition of palladium was carried out on the surface of Mg-Ni based alloy particles aiming at improving the alloy stability. The structure of all materials were characterized by energy dispersive X-ray (EDS) analyses, X-ray diffraction (XRD) and scanning electronic microscopy (SEM). X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) were also employed for this purpose. Electrochemical studies involved measurements of the electrode polarization along the charge/discharge cycles and also monitoring total discharge capacity as a function of the cycle number. Reaction kinetics were investigated by electrochemical impedance spectroscopy (EIS) measurements, conducted at different states of charge, temperatures and cycle numbers for the different metal hydride electrodes. It was found that the charge storage capacity increased very slowly along the initial charge/discharge cycles for the bare AB2 alloy, but a significant decrease of the activation time, due to a raise on the active area caused by the milling treatment was seen, independent of the additive nature. Electrochemical impedance showed similar reaction kinetics for different AB2 samples. The inclusion of small content of Pt in the Mg-Ni alloy leaded to a significant increase of the material stability for the charge/discharge cycles, probably because of a reduction in the corrosion processes. Consistently, the electrochemical coatings of Pd lead to a raise in the cycling stability of these alloys.

Ni - MH batteries have superior properties which are long cycle life, low maintenance, high power, light weight, good thermal performance and configurable design. Hydrogen storage alloys play a dominant role in power service life of a Ni - MH battery and determining the electrochemical properties of the battery. LaNi5, belonging to the CaCu5 crystal structure type, satisfy many of the properties. The most important property of LaNi5 is fast hydrogen kinetics. Recently, CaNi5, belonging to same crystal type, has taken some attention due to its low cost, higher hydrogen storage capacity, good kinetic properties. However, the main restriction of its use is its very low cycle life. The aim of the study is to obtain a more stable structure providing higher cycle life by the addition of different alloying elements. In this study, the effect of sixteen alloying elements (Mn, Sm, Sn, Al, Y, Cu, Si, Zn, Cr, Mg, Fe, Dy, V, Ti, Hf and Er) on cycle life was investigated. Sm, Y, Dy, Ti, Hf and Er were added for replacement of Ca and Mn, Sn, Al, Cu, Si, Zn, Cr, Mg, Fe and V were added for replacement of Ni. Alloys were produced by vacuum casting and heat treating followed by ball milling. The cells assembled, using the produced active materials as anode, which were cycled for charging and discharging. As a result, replacement of Ca with Hf, Ti, Dy and Er, and replacement of Ni with Si and Mn were observed to show better cycle durability rather than pure CaNi5.

The topic of this study is to develop a battery capacity management system. The main purpose is to monitor the state of battery during charging and discharging. Form this, user can know the battery status and to avoid loss of data before sudden system power down caused by a spent battery. Different states of battery were collected in different conditions by a battery measurement system, after which characteristics were analyzed. A fast-charge and residual capacity estimation system was developed according to the battery characteristics. The fast-charge system is a technique that emphasizes not only fastness charging but also safety. In this study a fast-charge end method was adopted to terminate the fast charging state of the battery and the initial state had been estimated before charging. Furthermore, the battery was charged with the optimum method according to the battery initial state. That can recover the capacity of the battery within a short period without causing any side effects from repeated usage. The residual capacity estimation system works by first estimating the initial capacity of the batteries, and then recording the current of batteries continuously using the coulomb counting method to make compensation for the effects of battery aging, environmental temperature, self-discharging, and output current.

Neste trabalho foi feito um estudo das propriedades estruturais e eletroquímicas de eletrodos formados por pó de liga de hidreto metálico Zr0,9Ti0,1Ni1,04Mn0,64V0,46 (tipo AB2) preparadas em forno a arco e tratadas por moagem em moinho de bolas na presença de pó de Ni ou da liga LaNi4,7Sn0,3. Também foram estudadas ligas à base de Mg-Ni preparadas por moagem de alta energia, com e sem a inclusão de um terceiro elemento (Ti ou Pt). Neste último caso, foi realizada deposição eletroquímica para o revestimento da superfície da liga Mg-Ni com paládio. Os estudos nos dois sistemas foram conduzidos utilizando-se as técnicas de EDX (energia dispersiva de raios X), DRX (difração de raios X) e MEV (microscopia eletrônica de varredura) para a caracterização física dos materiais. Também foram realizados experimentos espectroscopia de absorção de raios X (XAS) e de microscopia eletrônica de transmissão (MET). Os estudos eletroquímicos incluíram medidas da polarização dos eletrodos ao longo dos ciclos de carga/descarga, com o monitoramento da capacidade de descarga em função do número de ciclos. Medidas de espectroscopia de impedância eletroquímica em diferentes estado de carga, temperaturas e números de ciclos foram realizadas nos eletrodos formados com as diferentes ligas. Foi observado que a capacidade de armazenamento de carga da liga AB2 sem tratamento, aumenta muito lentamente com o decorrer do número de ciclos de carga/descarga, enquanto que os eletrodos formados com essa mesma liga, porém submetida aos tratamentos superficiais pela moagem com os diferentes aditivos, apresentam ativação muito mais rápida. Pelas medidas de impedância eletroquímica, observou-se alta similaridade da cinética reacional nas várias amostras AB2 analisadas. A substituição parcial da liga MgNi pela Pt levou à uma maior estabilidade aos ciclos de carga e descarga, inibindo a formação de hidróxido de Mg e proporcionando uma cinética tanto de absorção quanto de dessorção do hidreto maior que sua correspondente liga base. A eletrodeposição de Pd nestas ligas, leva à um incremento adicional na estabilidade do eletrodo. / This work reports results of studies on the structure and electrochemical properties of hydrogen storage alloy electrodes, formed by Zr0,9Ti0,1Ni1,04Mn0,64V0,46 (AB2-type), prepared in arc furnace and processed by ball milling in the presence of Ni and/or LaNi4,7Sn0,3 powder additives. The Mg- Ni based alloys with and without incorporation of Ti and Pt, processed by mechanical alloying were also investigated. In this case, electrochemical deposition of palladium was carried out on the surface of Mg-Ni based alloy particles aiming at improving the alloy stability. The structure of all materials were characterized by energy dispersive X-ray (EDS) analyses, X-ray diffraction (XRD) and scanning electronic microscopy (SEM). X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) were also employed for this purpose. Electrochemical studies involved measurements of the electrode polarization along the charge/discharge cycles and also monitoring total discharge capacity as a function of the cycle number. Reaction kinetics were investigated by electrochemical impedance spectroscopy (EIS) measurements, conducted at different states of charge, temperatures and cycle numbers for the different metal hydride electrodes. It was found that the charge storage capacity increased very slowly along the initial charge/discharge cycles for the bare AB2 alloy, but a significant decrease of the activation time, due to a raise on the active area caused by the milling treatment was seen, independent of the additive nature. Electrochemical impedance showed similar reaction kinetics for different AB2 samples. The inclusion of small content of Pt in the Mg-Ni alloy leaded to a significant increase of the material stability for the charge/discharge cycles, probably because of a reduction in the corrosion processes. Consistently, the electrochemical coatings of Pd lead to a raise in the cycling stability of these alloys.

Made available in DSpace on 2016-12-23T14:41:49Z (GMT). No. of bitstreams: 1 Vinicius Emmanuel de Oliveira.pdf: 5229003 bytes, checksum: 7bc46aad5447805d1e99c00c4deb6f3b (MD5) Previous issue date: 2012-08-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho, um método hidrometalúrgico para a recuperação dos metais terras raras, cobalto, níquel, ferro e manganês dos eletrodos negativos exauridos das baterias de telefone celular é desenvolvido. Os compostos das terras raras foram obtidos por precipitação química em pH 1,5 com NaCe(SO4)2.H2O e La2(SO4)3.H2O como os principais componentes recuperados. A composição e a concentração relativa dos elementos químicos que constituem os materiais recuperados foram determinados por espectroscopia de emissão óptica com plasma indutivamente acoplado (ICP-OES).Esta análise confirma que os elementos níquel, cobalto,ferro e manganês permanecem em solução após a precipitação do cério e lantânio. O ferro é recuperado como Fe(OH)3 e FeO. Além disso o precipitado de hidróxido de manganês inicialmente formado sofre um processo de envelhecimento em soluções alcalinas e na presença de oxigénio, manganês é obtido como Mn3O4. Níquel e cobalto foram recuperados como β -Ni(OH)2 e Co(OH)2. Os hidróxidos recuperados de cobalto e níquel são subsequentemente utilizados para sintetizar materiais de cátodos LiCoO2,LiNiO2 e CoO para uso em baterias de Li-ion. Os ânodos e materiais reciclados são caracterizados por difração de raios - X (DRX), microscopia eletrônica de varredura (MEV), energia dispersiva de raios-X, (EDX), espectroscopia de infravermelho com transformada de fourier (FT-IR), termogravimetria (TG/DTG) e espectroscopia de emissão óptica com plasma indutivamente acoplado (ICP-OES). Métodos químicos e eletroquímicos para reciclagem de Ni, Co, Zn e Mn dos eletrodos positivos exauridos de baterias de Ni-MH foram desenvolvidos. Os materiais reciclados por precipitação química tem a composição β - Ni(OH)2, Co(OH)2, Zn(OH)2 e Mn3O4. O pó retém, nitrato,sulfato e carbonato de ânios a partir da solução mãe, bem como água adsorvida.Estudos utilizando voltametria cíclica mostram que a densidade de corrente diminui para taxas de varredura maiores que 10 mVs-1 por causa da formação de filmes de hidróxido. As quantidades de Ni2+,Co2+,Zn2+ e Mn2+ foram obtidas por análise da solução utilizando espectroscopia de emissão óptica com plasma indutivamente acoplado (ICP-OES), que demonstraram que o método de eletrodeposição exibe um comportamento anómalo. As quantidades de íons de níquel depositado está relacionado com a composição dos banho de sulfamato. A presença de manganês nos eletrodepósitos é devido à precipitação do Mn(OH)2 e Zn(OH)42- não sofre redução no intervalo investigado de potencial. O material eletrodepositado contém Ni, Co, CoO, Co(OH)2, e Mn3O4. Uma eficiência da carga de 83,7 % foi obtida para os eletrodepósitos formados por aplicação de -1,1 V vs Ag /AgCl a uma densidade de corrente de - 90 Ccm-2. A dissolução dos eletrodepósitos depende do potencial aplicado / In this work, a hydrometallurgical method for the recovery of rare earth metals, cobalt, nickel, iron, and manganese from the negative electrodes of spent Ni-MH mobile phone batteries is developed. The rare earth compounds are obtained by chemical precipitation at pH 1.5 with NaCe(SO4)2.H2O and La2(SO4)3.H2O as the major recovered components. The composition and relative concentration of the chemical elements that constitute the recovered material are determined by inductively coupled plasma optical emission Spectroscopy (ICP-OES). This analysis confirms that the elements cobalt, nickel, iron, and manganese remain in solution after precipitation of the cerium and lanthanum. Iron is recovered as Fe(OH)3 and FeO. In addition, because manganese hydroxide precipitate initially undergoes an aging process in alkaline solutions and in the presence of oxygen, manganese is obtained as Mn3O4. Nickel and cobalt are recovered as β-Ni(OH)2 and Co(OH)2. The recovered cobalt and nickel hydroxides are subsequently used to synthesize the cathode materials LiCoO2, LiNiO2 and CoO for use in Li-ion batteries. The anodes and recycled materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG/DTG) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Chemical and electrochemical recycling methods for the Ni, Co, Zn and Mn from the positives electrodes of spent Ni-MH batteries were developed. The materials recycled by chemical precipitation has the composition β-Ni(OH)2, Co(OH)2, Zn(OH)2 and Mn3O4. The powder retains, sulphate, nitrate and carbonate anions from the mother solution as well as adsorbed water. Studies using cyclic voltammetry show that the current density decreases for scan rates greater than 10 mV s-1 because of the formation of hydroxide films. The amounts of Ni2+, Co2+, Zn2+ and Mn2+ were obtained by analysis of the solution using the inductively coupled plasma with optical emission spectroscopy technique, which demonstrated that the electrodeposition method exhibits anomalous behavior. The amount of deposited nickel ions is related to the composition of the sulfamate bath. The presence of manganese in the electrodeposits is due to the precipitation of Mn(OH)2, and Zn(OH)42- does not undergo reduction in the investigated potential range. The electrodeposited material contains Ni, Co, CoO, Co(OH)2, and Mn3O4. A charge efficiency of 83.7% was attained for the electrodeposits formed by the application of -1.1 V vs. Ag/AgCl at a current density of -90 C cm-2. The dissolution of the electrodeposits depends on the applied potential

Cette thèse vise à améliorer les propriétés d'alliage à mémoire de forme et de stockage d'hydrogène du TiNi par des substitutions chimiques sur le sous-réseau de Ni. L'effet de la substitution de Ni par Pd, Cu et Co sur les propriétés structurales, la transformation martensitique et les propriétés d'hydrogénation de TiNi, a été étudiée par des techniques structurales (diffraction des Rayons-X et des neutrons sur poudre), calorimétriques, par réaction solide-gaz et par mesure électrochimique. Des calculs de type DFT ont été effectués pour mettre en évidence les modifications de la structure électronique sur les propriétés d'hydrogénation. Les trois substitutions, TiNi1-zMz (M = Pd, Cu et Co; z ≤ 0,5), conduisent à la formation de composés pseudo-binaires. La substitution par Pd et par Cu augmentent le volume de la maille de TiNi, alors que celle par Co possède un effet inverse. Les températures de transformation martensitique suivent la même tendance que les changements de volume. Ils augmentent fortement pour M = Pd et légèrement pour M = Cu, tandis qu'elles diminuent pour M = Co. Les propriétés d'hydrogénation sont très sensibles à la nature chimique des substitutions. La capacité diminue fortement avec la substitution par Pd, modérément avec le Cu et reste stable pour le M = Co. Contrairement à l'effet attendu par des considérations géométrique, la substitution par Pd et par Cu diminuent la stabilité des hydrures. Les calculs DFT montrent qu'un effet électronique, et non géométrique, régit la stabilité des hydrures pour M = Pd. La substitution par le cobalt induit une formation de plusieurs hydrures par étapes successives, observée par mesure d'isothermes pression-composition en multiple plateaux. Pour les applications, la substitution de Ni par Cu avec une faible teneur (z = 0,2) augmente la capacité de décharge électrochimique de TiNi de 150 à 300 mAh/g en raison de la déstabilisation de l'hydrure. Cela ouvre de nouvelles perspectives pour l'utilisation d'alliages TiNi comme électrodes de batteries Ni-MH. En revanche, la substitution par Pd ou Cu (avec z = 0,5) est très efficace pour réduire la réactivité de TiNi avec l'hydrogène, et est donc intéressante pour des applications à mémoire de forme sous un environnement réducteur / The PhD thesis aims to improve shape memory and hydrogen storage properties of TiNi by chemical substitutions in the Ni sub-lattice. The effect of Pd, Cu and Co substitutions on crystal structure, martensitic transformation and hydrogenation properties of TiNi has been studied by structural (X-ray and neutron powder diffraction), calorimetric, solid-gas and electrochemical means. Ab initio DFT calculations were done to highlight electronic effects on hydrogenation properties. The three substitutions, TiNi1-zMz (M = Pd, Cu and Co; z ≤ 0.5), lead to the formation of pseudobinary compounds. Substitutions by Pd and Cu increase the unit-cell volume of TiNi, whereas the reverse effect occurs for Co. Martensitic transformation temperatures correlate with volume variations. They increase strongly for M = Pd and slightly for M = Cu, whereas M = Co decreases it. Hydrogenation properties are very sensitive to chemical elements substitution. The capacity decreases strongly for M = Pd, moderately for M = Cu and remains stable for M = Co. Contrary to expected effect by geometric model, both Pd and Cu substitutions decrease the stability of hydrides. DFT calculations show that electronic rather than geometric effects govern hydride stability for M = Pd. Co substitution induces step-wise formation of hydrides with a multi-plateau behaviour in pressure-composition isotherms. As concerns applications, low amount of Cu substitution (z =0.2) increases the electrochemical discharge capacity of TiNi from 150 to 300 mAh/g due to hydride destabilization. This opens new perspectives for using TiNi-based alloys in Ni-MH batteries. In contrast, Pd and high amount of Cu substitution (z = 0.5) are effective to decrease TiNi reactivity towards hydrogen, and therefore attractive for shape memory applications under reductive environment

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. / In this work, it has firstly been evaluated the effect of tin (Sn) and copper (Cu) substituting cobalt (Co) in LaMgAlMnCoNi AB5-type alloys for use in hydrogen storage materials and negative electrodes of Ni-MH batteries. The influence of this substitution on the microstructure of these materials has been evaluated. It could be noted that increasing the tin concentration promotes the formation of LaNiSn phase and decrease of two main phases of these alloys: LaNi5 and (La,Mg)Ni3. Additionally, the Rietveld refinement has been evaluated to quantify phases in each composition. Subsequently, it has been proposed a study of the hydrogen absorption in these alloys. It could be observed that the cobalt alloy showed the best hydrogen absorption capacity. Moreover, the behavior of these alloys has been investigated in the discharge capacity, cyclic stability and high rate dischargeability of Ni-MH batteries. The highest discharge capacity has been measured for cobalt alloy, reaching 337.1 mAh/g. It has been noted, further improvement in the cyclic stability batteries with increasing copper content in the alloys. Furthermore, it has been observed that the high rate dischargeability has better values with the addition of copper in the composition. Finally, it has been evaluated the effect of susceptibility to corrosion. It has been noted that tin promotes an increase in corrosion resistance of the alloys in an alkaline electrolyte.

Neste trabalho foram estudadas ligas La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0,7) no estado bruto de fusão, para utilização em eletrodos negativos de baterias de níquel-hidreto metálico (Ni-HM). A caracterização das ligas foi realizada através das seguintes técnicas: microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e difração de raios X. Foi também determinada capacidade de absorção de hidrogênio destas ligas. A hidrogenação do material foi realizada em dois processos sendo: o primeiro denominado de baixa pressão (0,2 MPa de hidrogênio e temperatura de 500ºC) e o segundo de alta pressão (1 MPa e de hidrogênio e temperatura de 25ºC). Foi observado que com o aumento do teor de Pr a capacidade de absorção de hidrogênio diminui. Para o estudo da capacidade de descarga das baterias foi utilizado um analisador digital de quatro canais e observou-se um decréscimo na capacidade de descarga das baterias com adição de praseodímio para as composições La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0,3). A maior capacidade de descarga (386 mAhg-1) e estabilidade cíclica foi obtida para a liga La0,2Pr0,5Mg0,3Al0,3Mn0,4Co0,5Ni3,8. Esta capacidade obtida pode estar relacionada com a maior proporção da fase LaMg2Ni9 encontrada na liga com adição de 0,5 % at. de Pr. / The La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0.7) as-cast alloys to apply in negative electrodes for nickel-metal hydride batteries (Ni-MH). The characterizations of the alloys were realized by: scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction techniques. A study of hydrogen absorption capacity of the alloys realized. The hydrogenation of the material was performed in two processes: the low pressure (0.2 MPa of hydrogen and temperature of the 773 K) and high pressure (1 MPa of hydrogen and temperature of the 298 K). It was observed that with increasing Pr content occurred a decrease the hydrogen absorption capacity. The capacity of discharge of the batteries was determined utilizing an analyzer digital computerized composed of four channels. It was observed decreases of the discharge capacity of the batteries when increase praseodymium content in La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0.3) alloys. The highest discharge capacity (386 mAhg-1) and stability cyclic were obtained to La0.2Pr0.5Mg0.3Al0.3Mn0.4Co0.5Ni3.8 alloy. This capacity can be related to the higher proportion of phase LaMg2Ni9 in the alloy with the addition of 0.5 at.% Pr.

Neste trabalho foram estudadas ligas La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0,7) no estado bruto de fusão, para utilização em eletrodos negativos de baterias de níquel-hidreto metálico (Ni-HM). A caracterização das ligas foi realizada através das seguintes técnicas: microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e difração de raios X. Foi também determinada capacidade de absorção de hidrogênio destas ligas. A hidrogenação do material foi realizada em dois processos sendo: o primeiro denominado de baixa pressão (0,2 MPa de hidrogênio e temperatura de 500ºC) e o segundo de alta pressão (1 MPa e de hidrogênio e temperatura de 25ºC). Foi observado que com o aumento do teor de Pr a capacidade de absorção de hidrogênio diminui. Para o estudo da capacidade de descarga das baterias foi utilizado um analisador digital de quatro canais e observou-se um decréscimo na capacidade de descarga das baterias com adição de praseodímio para as composições La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0,3). A maior capacidade de descarga (386 mAhg-1) e estabilidade cíclica foi obtida para a liga La0,2Pr0,5Mg0,3Al0,3Mn0,4Co0,5Ni3,8. Esta capacidade obtida pode estar relacionada com a maior proporção da fase LaMg2Ni9 encontrada na liga com adição de 0,5 % at. de Pr. / The La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0.7) as-cast alloys to apply in negative electrodes for nickel-metal hydride batteries (Ni-MH). The characterizations of the alloys were realized by: scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction techniques. A study of hydrogen absorption capacity of the alloys realized. The hydrogenation of the material was performed in two processes: the low pressure (0.2 MPa of hydrogen and temperature of the 773 K) and high pressure (1 MPa of hydrogen and temperature of the 298 K). It was observed that with increasing Pr content occurred a decrease the hydrogen absorption capacity. The capacity of discharge of the batteries was determined utilizing an analyzer digital computerized composed of four channels. It was observed decreases of the discharge capacity of the batteries when increase praseodymium content in La0,7-xPrxMg0,3Al0,3Mn0,4Co0,5Ni3,8 (x= 0 a 0.3) alloys. The highest discharge capacity (386 mAhg-1) and stability cyclic were obtained to La0.2Pr0.5Mg0.3Al0.3Mn0.4Co0.5Ni3.8 alloy. This capacity can be related to the higher proportion of phase LaMg2Ni9 in the alloy with the addition of 0.5 at.% Pr.

Les accumulateurs Ni-MH (Nickel-Métal-Hydrure) sont un sujet prometteur et largement étudié dans les recherches d’une énergie propre et durable. Trouver le matériau idéal pour l'électrode négative à haute densité volumétrique et gravimétrique est la clé pour l’application de cette technologie. Les hydrures métalliques à base de Ti-Ni ont des propriétés équilibrées entre la capacité d’hydrogène et les performances électrochimiques.L’objectif de cette thèse est d’étudier les effets de substitutions/additions d’éléments et de la mécanosynthèse sur la structure et les propriétés d’hydrogène des alliages Ti-Ni. Dans cette étude, une série d’alliages à base de Ti-Ni avec des substitutions/additions de Mg ou de Zr ont été systématiquement étudiés.Les alliages (TiNi)1-xMgx, (TiH2)1.5Mg0.5Ni, and Ti2-xZrxNi ont été synthétisés par mécanosynthèse à partir de poudres élémentaires. Dans un premier temps, l’influence du temps de broyage et les effets de substitutions/additions sur les microstructures ont été caractérisés par des techniques telles que la DRX, le MEB et le MET. Dans un second temps, les propriétés d’hydrogénation des différents alliages ont été mesurées par des réactions solid-gaz et par cyclage électrochimique.La théorie de la fonctionnelle de la densité (DFT) en utilisant le programme CASTEP a permis de calculer les enthalpies de formation afin de comparer la stabilité thermodynamique des alliages obtenus. Dans ces travaux de recherche, nous avons identifié les priorités d’alliage des ternaires Ni-Ti-Mg et Ti-Ni-Zr dans des conditions de broyage. La transformation structurale du Ti en phase CFC, induite par l’introduction d’éléments étrangers, a été mise en évidence.Les courbes PCI (Pression-Composition-Isothermes) et les capacités de décharge en fonction du nombre de cycles indiquent les propriétés d’hydrogène des alliages obtenus, y compris TiNi, Ti2Ni (amorphe), Ti-Mg et Ti-Zr. / Ni-MH (Nickel-Metal-Hydride) batteries have been a promising and extensively studied topic among clean and sustainable energy researches. Finding the ideal material for the negative electrode with high volumetric and gravimetric densities is the key to apply this technology on broader applications. Metal hydrides based on Ti-Ni have balanced properties between hydrogen capacity and electrochemical performances in cycling.The objective of this thesis is to study the effects of element substitution/doping and mechanical alloying on the structural and hydrogen properties of Ti-Ni alloys. In this study, a series of Ti-Ni based systems with Mg or Zr doping/substitution have been systematically investigated.The metallic compounds (TiNi)1-xMgx, (TiH2)1.5Mg0.5Ni, and Ti2-xZrxNi were synthesized by mechanically alloying from elemental powders.The milling time and effects of Mg, Zr substitution/doping were studied firstly in respect of their microstructures, using characterization techniques including XRD, SEM, TEM (EDX support), followed by the hydrogen properties measurements of the samples by hydrogen solid-gas reaction and electrochemical cycling.A first principle calculation tool based on DFT (Density Functional Theory) was carried out to further investigate the enthalpy of formation in order to compare the thermodynamical stability of the obtained compounds. In the study, we have found the alloying priorities in the ternary alloys Ti-Ni-Mg and Ti-Ni-Zr under milling conditions.A structure transformation of Ti to FCC induced by foreign elements is reported and investigated. Enthalpy of formation per atom of the compounds were obtained by DFT calculations, which helped interpreting the experimental results. PCI (Pressure Composition Isotherms) curves and discharge capacities as the function of cycling numbers revealed the hydrogen properties of the obtained compounds, including TiNi, Ti2Ni (amorphous), Ti-Mg and Ti-Zr.