O presente trabalho determinou a concentração dos metais zinco, manganês, cádmio, chumbo, níquel, cobre e cromo no efluente e solo de quatro colunas de latossolo indeformadas. Duas colunas foram contaminadas por pilhas do tipo zinco-carbono e duas colunas foram utilizadas como referência, além de pilhas isoladas, foram todas lixiviadas por uma solução \"água de chuva\" (HNO3 + H2SO4, pH 4,0). Os metais no efluente e no solo foram determinados pela técnica de ICP-OES. A avaliação do efluente e do solo das colunas contaminadas pelas pilhas mostrou um incremento das concentrações dos metais, principalmente de zinco, manganês e chumbo. A sequência das massas acumuladas dos metais no efluente e no solo da coluna contaminada apresentaram uma sequência semelhante a da lixiviação isolada da pilha (Zn > Mn > Pb > Cr > Cu > Ni > Cd), confirmando a influência da pilha nas concentrações dos metais no efluente e solo das colunas. Observou-se também que a contaminação de Zn e Mn tende a migrar da camada superior da coluna de solo para as camadas inferiores. O estudo mostrou que as pilhas podem causar uma contaminação significativa do solo para os metais Zn, Mn e Pb e possivelmente também para Cd. Esta contaminação do solo poderia vir a causar uma contaminação da água subterrânea para os metais Zn, Mn e Pb, dependo das características do perfil do solo. / The aim of the present study was to determine the concentration of Zn, Mn, Pb, Cd, Cu, Cr, and Ni in an oxisol column contaminated with zinc-carbon batteries. Two control and two contaminated columns, and batteries alone were leached for a periods of six months and one year with aqueous solution of HNO3 and H2SO4 (1:1, pH 4,0) to simulate rainwater. The metal concentrations in effluent and soil were measured by means of ICP-OES technique. Results from the contaminated column showed enhanced concentrations in both effluent and soil (mainly zinc, manganese and lead). In addition, the total amount of metals in effluent and soil showed similar sequence order as observed for batteries alone (Zn > Mn > Pb > Cr > Cu > Ni > Cd) indicating that batteries can be considered the main source of contamination. We also observed migration of Zn and Mn from the top to the lower layers of the soil columns. The study gives further evidence that batteries can significantly contaminate the soil with metals like Zn, Mn and Pb, and maybe Cd too. This soil contamination combined with the enhanced concentrations found in the effluent can point out a probable groundwater contamination.

O presente trabalho determinou a concentração dos metais zinco, manganês, cádmio, chumbo, níquel, cobre e cromo no efluente e solo de quatro colunas de latossolo indeformadas. Duas colunas foram contaminadas por pilhas do tipo zinco-carbono e duas colunas foram utilizadas como referência, além de pilhas isoladas, foram todas lixiviadas por uma solução \"água de chuva\" (HNO3 + H2SO4, pH 4,0). Os metais no efluente e no solo foram determinados pela técnica de ICP-OES. A avaliação do efluente e do solo das colunas contaminadas pelas pilhas mostrou um incremento das concentrações dos metais, principalmente de zinco, manganês e chumbo. A sequência das massas acumuladas dos metais no efluente e no solo da coluna contaminada apresentaram uma sequência semelhante a da lixiviação isolada da pilha (Zn > Mn > Pb > Cr > Cu > Ni > Cd), confirmando a influência da pilha nas concentrações dos metais no efluente e solo das colunas. Observou-se também que a contaminação de Zn e Mn tende a migrar da camada superior da coluna de solo para as camadas inferiores. O estudo mostrou que as pilhas podem causar uma contaminação significativa do solo para os metais Zn, Mn e Pb e possivelmente também para Cd. Esta contaminação do solo poderia vir a causar uma contaminação da água subterrânea para os metais Zn, Mn e Pb, dependo das características do perfil do solo. / The aim of the present study was to determine the concentration of Zn, Mn, Pb, Cd, Cu, Cr, and Ni in an oxisol column contaminated with zinc-carbon batteries. Two control and two contaminated columns, and batteries alone were leached for a periods of six months and one year with aqueous solution of HNO3 and H2SO4 (1:1, pH 4,0) to simulate rainwater. The metal concentrations in effluent and soil were measured by means of ICP-OES technique. Results from the contaminated column showed enhanced concentrations in both effluent and soil (mainly zinc, manganese and lead). In addition, the total amount of metals in effluent and soil showed similar sequence order as observed for batteries alone (Zn > Mn > Pb > Cr > Cu > Ni > Cd) indicating that batteries can be considered the main source of contamination. We also observed migration of Zn and Mn from the top to the lower layers of the soil columns. The study gives further evidence that batteries can significantly contaminate the soil with metals like Zn, Mn and Pb, and maybe Cd too. This soil contamination combined with the enhanced concentrations found in the effluent can point out a probable groundwater contamination.

The decarbonization of the energy system is one of the most complex and consequential challenges of the 21st century. Meeting this challenge will require the deployment of existing low carbon technologies at unprecedented scales and rates and will necessitate the development of new technologies that have the ability to transform variable renewable energy into high energy density products. Reversible Solid Oxide Cells (RSOCs) are electrochemical devices that can function both as fuel cells or electrolyzers: in fuel cell mode, RSOCs consume a chemical fuel (H₂, CO, CH₄, etc.) to produce electrical power, while in electrolysis mode they consume electric power and chemical inputs (H₂O, CO₂) to produce a chemical fuel (H₂, CO, CH₄, etc.). As such, RSOC systems can be thought of as flexible “energy hubs” that have unique potential to bridge the low power density renewable infrastructure with that of high energy density fuels in an efficient, dynamic, and bidirectional fashion. This dissertation explores the different operational sensitivities and design trade-offs of a methane based RSOC system, investigates the optimum operating strategies for a system that adapts to variations in the hourly spot electricity and fuel prices in Western Denmark, and provides an economic analysis of the system under a wide variety of design assumptions, operational strategies, and fuel and electricity market structures. In order to perform such comprehensive analyses, a 0-D computational model of a methane based RSOC system was developed in Python. In fuel cell mode, the system generates power by consuming natural gas, while in electrolysis mode the system generates synthetic natural gas (SNG) by electrolyzing steam and catalytically hydrogenating recycled CO₂ into CH₄ downstream of the RSOC. The model's flexibility enables the simulation of “part-load” operation, allowing the user to assess the changes in output, efficiency, and operating cost as the system is operated across multiple points. The model has the ability to evaluate the impact that changes in design choices and operating parameters (Area Specific Resistance, temperatures, current density, etc.) have on the system as it interfaces with time varying exogenous factors such as fuel and electricity prices. As such, one of the main contributions of this model is the ability to run simulations in which the operating strategy of the RSOC system responds and adapts to varying market signals. The computational model is used to develop a series of hourly optimizations for finding the optimal operating strategy for an RSOC system that can buy or sell electricity and gas in the spot electricity and natural gas markets in Western Denmark. After receiving an electricity and gas price signal, the optimization determines the operating mode (fuel cell, electrolysis or idle) and operating point (e.g., current density) that maximize the operating profits every hour for the given electricity and gas price pair. In order to avoid the speculation associated with traditional energy storage simulations, the system is “opened” at both ends, allowing it to instantaneously buy and sell any electricity or gas that is generated. Thus, the system never stores any of the products and it buys and sells them at the instantaneously available market price. By assuming that market prices reflect all existing information, this design choice removes the necessity of having to speculate about the future in order to determine the optimum operating strategy. This approach is one of the innovations presented in this work. The optimizations aim at maximizing the operating profits at each hour of the year, and decisions of operating mode and point are based on marginal operating costs for each electricity and natural gas price pair. The full economic analysis, however, requires the understanding of how design choices (e.g. operating limits, heat management, gas recycling systems, etc.) affect the investment costs, and therefore a Total Plant Cost (TPC) model is developed. For each design choice, the TPC model is used to compute a cost of the system per m² of active electrode area or kW of output. This value, assumed to be a sunk cost that does not affect the operating decision, together with the operating profits resulting from the optimization is used to assess the overall profitability of the system. For a system with 100m² of active electrode area, conventional costing metrics suggest that the balance of plant (BoP) components for managing the system's heat (Heat exchangers, evaporators, condensers) are the main cost drivers and represent roughly 50% of the TPC. The cost of the electrochemical RSOC stack, assembly, power inverter and piping represent 35% of the cost, with the other 15% coming from pumps, compressors and the methanation system. Twenty different optimization scenarios are developed in order to quantify the effect that system design choices, operating limits, and market prices have on the operating profile and on the overall economics of the system. The first 12 case studies are based on real hourly spot electricity and natural gas prices for the years 2009-2014 in Western Denmark. For the last 8 scenarios, a forecasted hourly time-series for electricity in the Danish grid for the year 2050 and two fixed SNG prices (high and a low) are used. The 2050 prices, which assume a fossil fuel free system, are used to understand the role and value that RSOC systems can offer in deeply decarbonized energy systems. For each optimization, different parameters such as the initial ASR and the operating limits (maximum current densities for each mode of operation) are varied in order to find the impact that these changes have on the system's design (balance of plant components), hourly operating mode, investment costs, hourly operating profits, and overall plant profits. For the 2009-2014 optimizations, it is found that the sale of electricity (fuel cell mode) and fuel (electrolysis mode) is not large enough to cover the fixed costs associated with the plant. Fuel cell mode dominates the operation (61% of the time) with electrolysis representing only ~ 4% of the operating hours. ASR is found to have an important impact on the system's economics, due to the fact that a lowering of the ASR leads to a reduction in the size of the heat management system, which in turn reduces the Total Plant Cost. For the 2050 dataset, it is found that under the high gas price scenario electrolysis mode dominates (50% of the time), and fuel cell operation represents 15% of the hours in the year. For the low SNG price, electrolysis still dominates (48% of the time), and fuel cell operation increases to 30% of the operating hours. Furthermore, for the high SNG scenario, the sale of fuel and electricity are large enough to cover the system's fixed cost, making the system attractive from an investment perspective. For the low SNG price, the system also becomes profitable when using ASR values of 0.4 ASR or below.

The objective of the proposed research is to investigate the design of Self-Aware Radio Frequency Circuits and Wireless Communication Systems that can adapt to environmental and process variations to always operate at minimum power levels possible, extending battery life. The explosive growth of portable battery operated devices has mandated design of low power circuits and systems to prolong battery life. These devices fabricated in modern nanoscale CMOS technologies suffer from severe process variation due to the reduced controllability of the fabrication process, causing yield loss. This calls for integrated low power and process tolerant design techniques, or design of systems that can adapt to its process and environment to maintain its performance while minimizing power consumption. Currently, most of the wireless circuits are designed to meet minimum quality-of-service requirements under worst-case wireless link conditions (interference, noise, multi-path effects), leading to high power consumption when the channel is better than worst-case. In this research, we develop a multi-dimensional adaptation approach for wireless transmitters and receivers that optimally trades-off power vs. performance across temporally changing operating conditions by concurrently tuning control parameters in the RF front end to lower power consumption. Tunable circuits (e.g. LNA) with built-in tuning knobs providing independent controllability of important specifications allow optimal adaptation. Process sensing using intelligent test and calibration facilitates yield improvement and the design of process tolerant environment adaptive systems. Low cost testing methodologies are developed for identification of the health of the wireless circuit/system. These are used in conjunction with tuning algorithms that tune a wireless system under process variation to meet performance specifications and recover yield loss. This testing and adaptation is performed once during the post manufacture test/tune phase to compensate for manufacturing variations. This can also be applied periodically during in field operation of a device to account for performance degradation due to ageing. Finally, process tolerant environment adaptive systems are designed.

As the world's power needs grow, the demand for power from renewable resources, such as wind or solar is increasing. One major drawback associated with these renewable resources is that the power output is dependent on environmental factors, such as cloud cover and wind speeds. This allows the possibility of either power output exceeding or falling short of forecast levels that may lead to grid instabilities. Therefore, Large Scale Energy Storage (LSES) systems are critical to store excess power when the output exceeds demand in order to supplement output power when it falls short of demand.¹ The Zinc/Bromine Redox Flow Battery (RFB) is a promising technology because of previously reported long cycle-life (CL) capability, high efficiencies, low cost materials, and scalable operating conditions.² The excellent energy storage performance of the Zinc/Bromine system was confirmed by measuring both Faradaic and Coulombic electrochemical cell efficiency dependence on temperature of a bench scale Zinc/Bromine flow cell. At room temperature, near 75% Faradaic efficiency was measured when cycling the system between 20% and 100% State of Charge (SOC), which is in good agreement with published values,³ and was measured to be over 80% efficient when operating at an elevated temperature of 50°C. To elucidate capital and operational costs, key system operation parameters especially focused on degradation mechanisms were investigated. Since deep discharge cycling is perceived as highly damaging to electrochemical systems, a system was cycled between 0% and 5% (SOC) 10,000 times. Performance was quantified by measuring the frequency factor (i[subscript 0]) and relative activation energy (α) for the reactions using Tafel scans. No statistically significant degradation or change to the electrodes was observed during the zero point cycling experiment. However, it was found that under conventional operation damage to the electrodes does accumulate, presumably due to the highly oxidative environment caused by the presence of high concentrations of dissolved bromine or tri-bromide. While the performance of both electrodes shows decreases in frequency factor attributed to the damage process, the bromide oxidation process seems to be more damaging (i.e., at the positive electrode during the charging process). Long term measurements show a degradation of the electrocatalytic parameters at an applied overpotential of 100 mV from ca. 40 mA/cm² to ca. 5 mA/cm² at the positive electrode and from ca. 20 mA/cm² to ca. 10 mA/cm² for the negative electrode. A degradation rate model was proposed to predict the service life expectancy of graphite electrodes in a bromine system based on processes showing a combined second order reaction rate coupled with a negative first order reaction rate. The model can be used to predict the cost of energy when operating any device using graphite electrodes, based on the operating power ratio, defined here as the quotient between operating power and system rated power. This damage could be partially reversed by exposing the electrode surfaces to concentrated potassium hydroxide dissolved in isopropanol, presumably due to exfoliation of the electrocatalytic surface leading to the exposure of a clean surface with electrocatalytic performance close to the original. Further, a chemical pretreatment for the graphite surface imparting enhanced stability in aqueous bromine systems was developed that shows negligible damage when similar amounts of current have passed through the electrode surface. After bromide oxidation equivalent to passing ca. 10 Ah/cm² the treated surface showed a change in steady state current density at an applied overpotential of 100 mV from ca. 50 mA/cm² to ca. 48 mA/cm². / Graduation date: 2013 / Access restricted to the OSU Community at author's request from April 1, 2013 - April 1, 2015

Thesis (M.S.)--Air Force Institute of Technology, 2008. / Title from title page of PDF document (viewed on: Dec 10, 2009).

A inserção e a expansão da geração distribuída (GD) trazem desafios intrínsecos relacionados, sobretudo, a confiabilidade e operação do sistema elétrico de potência (SEP), o que resulta em uma mudança de paradigma imposta aos sistemas de distribuição de energia. Dentre os desafios e oportunidades associados à geração distribuída, destaca-se a operação ilhada dos sistemas de distribuição e microrredes. Nesse contexto, esse trabalho propõe estratégias operacionais e de controle para viabilizar a operação de sistema eólicos. O controle proposto baseia-se em uma malha de controle suplementar, adicionada à malha de controle de velocidade da unidade eólica. A malha de controle proposta consiste em uma quebra de paradigma para o controle da tensão no barramento CC, pois nos sistemas tradicionais essa tensão é normalmente controlada apenas pelo banco de baterias. Através do controle suplementar proposto, torna-se possível reduzir o número e a duração de atuações do banco de baterias, aumentando sua vida útil. Propõe-se ainda, como contribuição, uma metodologia para o dimensionamento mínimo do sistema de armazenamento de energia baseado em banco de baterias para permitir a operação ilhada autônoma de sistemas eólicos. Esse dimensionamento considera um degrau de carga máximo que deverá ser atendido pelo sistema. Por fim, as estratégias operacionais e de controle propostas em conjunto com o sistema de armazenamento de energia são avaliadas e validadas por meio de análises matemáticas e simulações no domínio do tempo utilizando o sistema proposto. Os resultados obtidos demonstraram que o controle proposto permitiu a operação autônoma de um sistema eólico baseado em gerador síncrono com conversor estático completo. / The insertion and expansion of distributed generation bring about intrinsic challenges, especially concerning to the reliability and operation of the electric power system, which results in a paradigm shift imposed on power distribution systems. Among the challenges and opportunities associated to distributed generation, the islanded operation of distribution systems and microgrids has grown considerably. In this context, this paper proposes operational and control strategies to properly allow the operation of a wind generation system. The proposed control is based on a supplementary control loop, added to the speed control loop of the wind turbine. The proposed control loop consists of a paradigm shift to control the DC-link voltage, since in traditional systems the DC-link voltage is usually controlled only by the BESS. The proposed supplementary control loop reduces the number and duration of the BESS actuations. Furthermore, the proposed strategy can contribute to enhance the reliability and the life cycle of the energy storage device. This work also proposes a new methodology for minimum sizing of battery energy storage systems to allow the islanded operation of wind power systems. The methodology considers a maximum load step to be supplied by the system. Finally, the proposed control and operational strategies with the BESS are evaluated and validated throughout mathematical analysis and simulation in the time domain using the proposed system. The proposed control strategy was effective in regulating the DC-link voltage, allowing the islanded operation of a wind power system based on synchronous generator with full-size power converters.

O desenvolvimento de tecnologias para a obtenção de energias renováveis tem recebido crescente atenção nos dias atuais. Células a combustível microbianas (CCMs) são dispositivos bioeletroquímicos que utilizam microrganismos sob condições anaeróbicas para catalisar reações redox em compostos orgânicos visando geração de energia elétrica. Pesquisas recentes estão voltadas para otimizar o desempenho e a eficiência das CCMs. Um dos desafios é a necessidade de se testar novos materiais condutores como eletrodos visando aumentar o potencial elétrico destes dispositivos. O polipirrol é um polímero orgânico condutor que possui boa condutividade elétrica, elevada área superficial, biocompatibilidade e baixo custo. Neste trabalho foi construída uma CCM de dupla câmara para a geração de energia elétrica a partir da degradação de glucose por Escherichia coli. Foram avaliados 2 tipos de eletrodos: um de grafite, normalmente utilizado em estudos com CCMs, outro de grafite modificado pela eletrodeposição de polipirrol, obtido após síntese. A diferença de potencial foi verificada utilizando um multímetro data logger ligado em série com a CCM e conectado a um computador para a aquisição de dados em tempo real. Para avaliação da formação de biofilme na superfície dos eletrodos foi utilizada a técnica de microscopia eletrônica de varredura (MEV). As CCMs apresentaram valores de densidade de potência que variaram entre 15 mW.m-2, no experimento com eletrodo de grafite e 20 mW.m-2, obtida no experimento utilizando eletrodo de grafite com polipirrol. Com a modificação da superfície de um eletrodo de grafite pela adição do polipirrol foi possível observar um incremento de atividade elétrica e aumento de área superficial do eletrodo. Em termos da eficiência da célula foi possível observar um acréscimo em termos de eficiência coulombica no sistema contendo polipirrol (17,18%) em relação ao sistema que não possuía (7,31%), o que representa um melhor aproveitamento dos elétrons do substrato que podem de fato ser convertidos em energia elétrica. Portanto, foi mostrado que o eletrodo de grafite modificado pela eletrodeposição de polipirrol pode ser uma alternativa viável e proveitosa para uso em CCMs. / The development of technologies to obtain renewable energy has received increasing attention nowadays. Microbial fuel cells (MFC) are chemical devices that uses microorganisms under anaerobic conditions to catalyze redox reactions in organic compounds for electricity generation. Recent research is focused to optimize the performance and efficiency of MFCs. One challenge is the need to test new conductive materials as electrodes in order to increase the electric potential in these devices. Polypyrrole is a conductive organic polymer which presents good electrical conductivity, high surface area, low cost and also biocompatibility. In this work, a double chamber MFC was built to generate electricity from glucose degradation by Escherichia coli. We assessed two types of electrodes: a graphite one, normally used in studies with MFCs, and graphite modified by electrodeposition of polypyrrole, obtained after synthesis. The potential difference was recorded using a data logger multimeter connected in series with the MFC and connected to a computer to obtain data in real time. For evaluation of biofilm formation on the surface of the electrodes scanning electron microscopy (SEM) was carried out. The MFCs had power density values ranging from 15 MW.m-2, in the experiment using graphite electrode 20 and MW.m-2 in the experiment using graphite electrode with polypyrrole. By the modification of the graphite surface with polypyrrole it was observed an increase in electrical activity and increased surface area of the electrode. In terms of cell efficiency, it was possible to observe an increased coulombic efficiency in the system containing polypyrrole (17.18%) compared with the system that lacked (7.31%), representing an improvement in flow of electrons from the substrate that can be converted into electricity. Therefore, it was shown in this work that the graphite electrode modified by electrodeposition of polypyrrole can be a viable and profitable alternative for use in MCC.

Em um momento em que questões ambientais e a segurança energética estão numa posição de destaque, Veículos Elétricos (VEs) estão no centro das atenções. Entretanto, ainda é difícil para eles substituir os tradicionais veículos de combustão interna e a razão principal para isso é o seu sistema de energia. Normalmente, devido a suas características, baterias são usadas como banco de energia para VEs. No entanto, baterias também apresentam algumas limitações para essa aplicação e o problema no sistema de energia é relacionado a essas limitações. Uma das soluções propostas é se colocar baterias e supercapacitores (SC) em paralelo, resultando em um Sistema Híbrido de Armazenamento de Energia (SHAE). Para fazer essa configuração possível e o fluxo de potência controlável em um SHAE, um conversor CC-CC bidirecional interfaceando a bateria e o SC é necessário. Levando isso em consideração, o estudo de topologias CC-CC bidirecionais é apresentado nessa Dissertação de Mestrado. Primeiro, o estudo de um conversor CC-CC bidirecional com indutor dividido, envolvendo sua análise teórica em regime permanente, análise dinâmica e uma metodologia de projeto com resultados de simulação, é apresentado, resultando na construção de um protótipo experimental com as seguintes especificações de projeto: Fonte de tensão 1 de 300 V, fonte de tensão 2 de 96 V, frequência de comutação de 20 kHz e potência nominal de 1000 W. Então, o estudo de uma segunda topologia, um conversor CC-CC Buck-Boost ZVS bidirecional, envolvendo sua análise em regime permanente e uma metodologia de projeto com resultados de simulação, também é apresentado. / In an era where environmental issues and the energetic safety are in an outstanding position, Electric Vehicles (EVs) are in the spotlight. However, it is difficult for them to replace the ICE vehicles and the main reason for that it is their energy system. Normally, due to some of their characteristics, batteries are used as energy bank in Electric Vehicles. Nevertheless, batteries also present some limitations for this application and the energy system problem is related to these limitations. One of the proposed solutions is to place batteries and Supercapacitors (SC) in parallel, resulting in a Hybrid Energy Storage System (HESS). To make this configuration possible and the power flow controllable in the HESS, a bidirectional DC-DC converter interfacing the battery and the SC is necessary. Taking this into account, the study of bidirectional DC-DC topologies is presented in this Master’s Thesis. First, a study of a bidirectional DC-DC converter with tapped inductor, involving its theoretical steady state analysis, dynamic analysis and design methodology with simulation results, is presented, resulting in the design of an experimental prototype with the following design specifications: Voltage source 1 of 300 V, voltage source 2 of 96 V, switching frequency of 20 kHz and rated power of 1000 W. Then, the study of a second topology, a bidirectional ZVS Buck-Boost DC-DC converter, involving he steady state analysis and a design methodology with simulation results, is also presented.

Submitted by Mery Piedad Zamudio Igami (mery@ipen.br) on 2017-03-10T15:20:01Z No. of bitstreams: 1 22060.pdf: 3959215 bytes, checksum: 0a58b276270c30e02d2f6935bafba229 (MD5) / Made available in DSpace on 2017-03-10T15:20:01Z (GMT). No. of bitstreams: 1 22060.pdf: 3959215 bytes, checksum: 0a58b276270c30e02d2f6935bafba229 (MD5) / 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. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP