Structured electrodes with tailored nanoscale morphology and chemistry are highly desirable for a range of applications. In particular, emerging energy storage applications such as thick Lithium-ion battery (LIB) electrodes and photoanodes for watersplitting require new electrode structures that simultaneously optimise electron, ion, and thermal transport. In this PhD thesis, advanced structured electrodes are fabricated by creating 3D carbon-inorganic hybrid architectures. In this process, patterned vertically aligned carbon nanotubes (CNT) were used as the structural scaffolds to shape the electrodes while inheriting the excellent thermal and electrical properties of CNTs. First, UV and colloidal lithographic patterning processes were developed to create micro- and nanopores respectively within the CNT structures. Those structures provide high surface area and conductive backbone for the synthesis of hybrid CNT-inorganic structures. Specifically, the parameter space to create honeycomb shaped CNT structures with pores ranging from 300~nm to 30~$\mu$m has been established. Next, the micro-pore CNT structures have been chemically modified with iron oxide using microwave-assisted, hydrothermal synthesis for fabricating high areal loading LIB anodes. The areal loading was increased by 120\% compared to a standard battery film while at the same time retaining a high capacity (900 mAhg$^{-1}$ at 0.2 C). Then thick electrodes with optimised diffusion pathways were created by coating the nanopatterned CNTs with silicon using physical vapour deposition. These electrode structures are up to 50\% thicker than previously reported structures and still retain a stable capacity (650 mAhg$^{-1}$) and a good high-rate performance. Finally, the honeycomb shaped CNT structures have been coated with bismuth vanadate using a hotcasting process and the electrode architecture has been optimized for good conductivity by the addition of a Pd/Au layer between the CNTs and the BiVO$_{4}$. The photoelectrode performance was measured and shows a clear increase in current density when exposed to light. Each of these novel electrodes illustrate how patterning vertically aligned carbon nanotube structures combined with inorganic surface modification enables the creation of advanced electrodes with new formfactors and improved performance in comparison to literature and to classic drop-casted battery films of the same materials.

This thesis includes five main studies/ first, in order to enhance the conductivity of LiTi204, a new doping strategy is used and LiTi204−xCx ramsdellite is successfully fabricated. It is found that unit cell parameters a and b decline while c increases with more carbon inserted. The conductivity of LiTi204−xCx increases with more carbon insertion. Material with more carbon shows better reversibility and lower electrochemical polarization observed from potentiostatic curve. The material has better retention rate and rate ability with more carbon substitute doped. LiTi203.925C0.0375 has 151 mAh∙g−1 capacity under current density of 100 mAh∙g−1 and capacity decreased by 5.57% after 100 cycles. Second, in order to improve the capacity of LiTi204−xCx, Ti204−xCx is successfully fabricated through topotactic oxidation. It is found that the lattice parameters b and c decline while a keeps stable. With more carbon inserted, the retention ability increases. Ti01.9625C0.0375 has the capacity 320 mAh∙g−1 under 200 mAh∙g−1 and capacity retention loss by 9.1% per 100 cycles due to the balance of high conductivity and disordered channel resistance. Third, in order to study the process of lithium insertion, the structures and the atom sites of LiTi204−xCx ( R ) are obtained through refinement of the neutron diffraction patterns. The unit cell parameters a and b increase while c keeps stable for more lithium, atoms insertion. The channels for lithium insertion become wider and more round with lithium arranged in a line when x rises in the range of 0 < x < 0.5. When the x increases to 1, the channels turn into ordered parallelogram. Fourth, the lithium-contained spinelloid (a potential cathode material) is explored, but it is not found in this work. But spinels LI1−0.5xFe2.5xM1−xP1−xO4 (M=Fe, Co, Ni, Mn) are found and phosphorous insertion makes the structure stable during cycling. At last, to enhance the energy density, the 3D electrode is fabricated in in-situ growth by infiltration method. By powder infiltration, the load of activity material reaches over 60% of electrode mass. The morphology is porous and the particle size of the activity material is 20nm. The energy density based on LiCoO2 (250 WH∙g−1) is much higher than that of the traditional (200 WH∙g−1) 2D electrode reported.

Made available in DSpace on 2014-06-11T19:26:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-30Bitstream added on 2014-06-13T19:06:10Z : No. of bitstreams: 1 souza_cl_me_bauru.pdf: 1683744 bytes, checksum: 01408dd015968c885377375501713f24 (MD5) / Esta pesquisa tem como objetivo identificar as empresas produtoras de baterias automotivas esstão lidando com as barreiras e as motivações para a adoção de práticas de green supply chain managment (GSCM). O método de pesquisa utilizado foi o estudo de múltiplos casos nas cinco principais empresas produtoras de baterias automotivas instaladas no Brasil. Os resultados dessa pesquisa apontam que as principais práticas de GSCM adotadas pelas empresas estudadas são a gestão ambiental interna e a logística reversa e consequentemente as mais afetadas pelos fatores interno Processo de melhoria interno e externo Regulamentações Governamentais e Legislações. A forma como as empresas lidam com o fator interno é através da implantação de certificações, auditorias frequentes e respeito às exigências dos padrões de qualidade e, externamente é cumprido com as legislações e regulamentações vigentes e pertinentes ao setor. Adicionalmente, esta pesquisa apresenta guidelines para o setor de baterias automotivas instaladas no Brasil no que concernem as oportunidades e desafios para a adoção de práticas de GSCM / This research aims to identify how automotive batteries enterprisess are dealing with the barriers and drivers for the adoption of green supply chain management practices. The research method used was a multiple case study in five major automotive batteries enterprises installed in Brazil. The results of this study indicate that the main GSCM practices adopted by companies studied are internal environmental management and reverse logistics, and therefore most affected by internal factors Internal process improvement and external Government Regulations and Laws. The way companies deal with the internal factor is thorugh the deployment of certificates, frequent audits and compliance with the requirements of quality standards, and externally is complying with laws and regulations and relevant to the sector. Additionally, this research presents guidelines for the sector of automotive batteries enterprises installed in Brazil that concern the opportunities and challenges for the adoption of GSCM practices

Orientador: Ana Beatriz Lopes de Sousa Jabbour / Banca: Andrea Lago da Silva / Banca: Daniel Jugend / Resumo: Esta pesquisa tem como objetivo identificar as empresas produtoras de baterias automotivas esstão lidando com as barreiras e as motivações para a adoção de práticas de green supply chain managment (GSCM). O método de pesquisa utilizado foi o estudo de múltiplos casos nas cinco principais empresas produtoras de baterias automotivas instaladas no Brasil. Os resultados dessa pesquisa apontam que as principais práticas de GSCM adotadas pelas empresas estudadas são a gestão ambiental interna e a logística reversa e consequentemente as mais afetadas pelos fatores interno "Processo de melhoria interno" e externo "Regulamentações Governamentais e Legislações". A forma como as empresas lidam com o fator interno é através da implantação de certificações, auditorias frequentes e respeito às exigências dos padrões de qualidade e, externamente é cumprido com as legislações e regulamentações vigentes e pertinentes ao setor. Adicionalmente, esta pesquisa apresenta guidelines para o setor de baterias automotivas instaladas no Brasil no que concernem as oportunidades e desafios para a adoção de práticas de GSCM / Abstract: This research aims to identify how automotive batteries enterprisess are dealing with the barriers and drivers for the adoption of green supply chain management practices. The research method used was a multiple case study in five major automotive batteries enterprises installed in Brazil. The results of this study indicate that the main GSCM practices adopted by companies studied are internal environmental management and reverse logistics, and therefore most affected by internal factors "Internal process improvement" and external "Government Regulations and Laws". The way companies deal with the internal factor is thorugh the deployment of certificates, frequent audits and compliance with the requirements of quality standards, and externally is complying with laws and regulations and relevant to the sector. Additionally, this research presents guidelines for the sector of automotive batteries enterprises installed in Brazil that concern the opportunities and challenges for the adoption of GSCM practices / Mestre

Made available in DSpace on 2018-08-01T21:58:48Z (GMT). No. of bitstreams: 1 tese_10827_Dissertação Jenifer Rigo Almeida - FINAL.pdf: 2105933 bytes, checksum: 17fccc5751be81765e75282388ce4b0c (MD5) Previous issue date: 2017-03-27 / Baterias de íon-Lítio (LIBs) exauridas são consideradas resíduos sólidos perigosos devido à presença de metais e compostos orgânicos em sua composição, representando desperdício de recursos naturais não renováveis e de metais valiosos quando descartadas. Este trabalho tem por objetivo fornecer dados quantitativos sobre a composição química do material ativo do cátodo (MAC) de diferentes LIBs exauridas visando monitorar variações com o passar dos anos e auxiliar nos processos de reciclagem do material. Os elementos Al, Co, Cr, Cu, Ga, Li, Mg, Mn, Ni, Ti e Zn foram determinados por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) após lixiviação ácida empregando 2,0 mol.L-1 de ácido cítrico (HCit) e H2O2 (0,25 mol.L-1) como alternativa ambientalmente favorável. As condições otimizadas para adequação do meio às curvas analíticas foram: para Al, Cu: Curva de HCit diluído 10 vezes sem padrão interno (PI); para Co, Li, Mn, Ni: Curva de HCit diluído 500 vezes sem PI; para Ga, Zn: Curva de HCit diluído 10 vezes com Y. O procedimento analítico empregado alcançou limites de detecção de 0,01 mg.L-1 para Al; 0,20 mg.L-1 para Co; 0,006 mg.L-1 para Cr; 0,02 mg.L-1 para Cu; 0,004 mg.L-1 para Ga; 0,02 mg.L-1 para Li; 0,0005 mg.L-1 para Mg; 0,07 mg.L-1 para Mn; 0,70 mg.L-1 para Ni; 0,0005 mg.L-1 para Ti e 0,007 mg.L-1 para Zn. A exatidão do procedimento foi confirmada por testes de adição e recuperação dos analitos obtendo-se valores entre 92-113 %. Os elementos majoritários Co (43-67 % m/m), Li (5,3-6,8 % m/m), Mn (0,8-8,2 % m/m), Ni (0,1-11,7 % m/m) e Al (0,06-3,2 % m/m) e os elementos minoritários Cr (0,0005-0,002 % m/m), Cu (0,01-0,05 % m/m), Mg (0,005-0,02 % m/m), Ti (0,001-0,07 % m/m), Ga (0,0009-0,03 % m/m) e Zn (0,009-0,05 % m/m) demonstraram que a composição do MAC pode variar de acordo com a capacidade e ano de fabricação. As baterias mais antigas foram as que apresentaram maiores teores de Co e Li. As baterias de menor capacidade foram as que continham os maiores teores de Mn e Ni, indicando que o Co foi substituído. O pó do MAC e o resíduo após lixiviação foram caracterizados por difratometria de raios X (DRX) obtendo-se LiCoO2 como composto principal, podendo ser reutilizado.

In today’s world, we have reached the point where conventional energy forms are inevitably running out. At the same time, the technology for alternative energy harnessing is improving with big steps, especially with society rethinking their high consumption of finite energy and material. This opens the opportunity und increases acceptance for projects and research to prove its actual implementation and to push the boundaries of current technology further.One particular area of application is the automotive sector showcasing raise of costs due to depleting fuel. Solar powered cars are raising interest as it could be a way to complete independence of any resource that has to be produced, mined or in any way transported to the place of consumption. Involvement with the view to enhance their research in this field has become interesting for universities.With solar powered cars, new problems emerge, amongst others the amount of harnessed sun power and the storage to have it available at the point of use. Due to the low energy available, energy storage as light and as efficient as possible is needed. A system is required that allows to be operated independently of its surrounding in a way it is controllable.Lithium-ion based batteries were seen as the most applicable way to execute this, as they give the highest energy density with lower losses than stable, commercially available energy storage mediums.It was decided to design, build and integrate a battery system with its safety circuit into a solar car. After material selection suppliers were searched and contacted. With the successful manufacturing of this system combining different processing methods, partially at university and partially in the industry, the project included a monitoring and management system and protective measures. It was implemented so that neither the limitations of the chemistry and the physical cells nor the vibration occurring while driving the car prevents its proper use. Besides this, communication and dimensions to operate within the car followed, allowing the driver and convoy to access information and control the system.This battery system proved to be practical in street use comparable with that of regular cars and posed as a safe and effective energy supply for an electrically driven car, meeting the given demands.

Les batteries lithium-ion s'affichent comme de bons candidats pour assurer le stockage réversible de l'énergie électrique sous forme électrochimique. Toutefois, elles sont à l'origine d'un certain nombre d'incidents aux conséquences plus ou moins dramatiques. Ces incidents sont souvent liés au phénomène d'emballement thermique. La sécurité des batteries Li-ion représente par conséquent un enjeu technique et sociétal très important. C'est dans ce contexte que vient s'inscrire ce travail de thèse dans le cadre d'une collaboration entre IFPEN, l'INERIS et le LISE. Une double approche de modélisation et expérimentation a été retenue. Un modèle 3D du comportement thermique a été développé à l'échelle de la cellule, couplant les phénomènes thermiques et chimiques, et prenant en compte le vieillissement par croissance de la SEI sur l'électrode négative. Le modèle a été calibré pour la chimie LFP/C sur deux technologies A123s (2,3 Ah) et LifeBatt (15 Ah), puis validé expérimentalement. Le modèle permet d'identifier les paramètres critiques d'emballement de cellules, il permet également de discuter l'effet du vieillissement sur l'emballement thermique. Grâce à l'expérimentation, les connaissances en termes d'amorçage et de déroulement d'un emballement thermique d'une batterie Li-ion, ont pu être enrichies, en particulier pour les cellules commerciales LFP/C cylindriques A123s, LifeBatt, et pour les cellules NMC/C prismatiques en sachet souple PurePower (30 Ah). Cette étude ouvre de nouvelles possibilités pour améliorer la prédiction des différents événements qui ont lieu lors de l'emballement thermique des batteries Li-ion, à différentes échelles. / Li-ion secondary batteries are currently the preferred solution to store energy since a decade for stationary applications or electrical traction. However, because of their safety issues, Li-ion batteries are still considered as a critical part. Thermal runaway has been identified as a major concern with Li-ion battery safety. In this context, IFPEN, INERIS and LISE launched a collaboration to promote a PhD thesis so called « understanding and modeling of thermal runaway events pertaining to new and aged Li-ion batteries ». To achieve this goal, a double approach with modeling and experimental investigation is used. A 3D thermal runaway model is developed at cell level, coupling thermal and chemical phenomena, and taking into account the growth of the SEI layer as main ageing mechanism on negative electrode. Advanced knowledge of cells thermal behavior in over-heated conditions is obtained particularly for commercial LFP / C cylindrical cells: A123s (2,3Ah), LifeBatt (15Ah), and NMC / C pouch cells: PurePower (30 Ah). The model was calibrated for LFP / C cells, and then it was validated with thermal abuse tests on A123s and LifeBatt cells. This model is helpful to study the influence of cell geometry, external conditions, and even ageing on the thermal runaway initiation and propagation. This study opens up new possibilities for improving the prediction of various events taking place during Li-ion batteries thermal runaway, at various scales for further practical applications for safety management of LIBs.

Polymer electrolyte membrane fuel cell (PEMFC) stacks require sealing around the perimeter of the cells to prevent the gases inside the cell from leaking. Elastomeric materials are commonly used for this purpose. The overall performance and durability of the fuel cell is heavily dependent on the long-term stability of the gasket. In this study, the degradation of three elastomeric gasket materials (silicone rubber, commercial EPDM and a developed EPDM 2 compound) in an accelerated ageing environment was investigated. The change in properties and structure of a silicone rubber gasket caused by use in a real fuel cell was studied and compared to the changes in the same silicone rubber gasket material brought about by accelerated aging. The accelerated aging conditions were chosen to relate to the PEM fuel cell environment, but with more extreme conditions of elevated temperature (140°C) and greater acidity. Three accelerated ageing media were used. The first one was dilute sulphuric acid solution with the pH values of 1, 2 and 4. Secondly, Nafion® membrane suspended in water was used for accelerated ageing at a pH 3 to 4. Finally, diluted trifluoroacetic acid (TFA) solution of pH 3.3 was chosen. Weight change and the tensile properties of the aged gasket samples were measured. In addition, compression set behaviour of the elastomeric seal materials was investigated in order to evaluate their potential sealing performance in PEM fuel cells. The results showed that acid hydrolysis was the most likely mechanism of silicone rubber degradation and that similar degradation occurred under both real fuel cell and accelerated aging conditions. The effect of TFA solution on silicone rubber was more aggressive than sulphuric acid and Nafion® solutions with the same acidity (pH value) suggesting that TFA accelerated the acid hydrolysis of silicone rubber. In addition, acid ageing in all three acidic solutions caused visible surface damage and a significant decrease in tensile strength of the silicone rubber material, but did not significantly affect the EPDM materials. EPDM 2 compound had a desirable (low) compression set value which was similar to silicone rubber and much better than the commercial EPDM. It also showed a very good performance in the fuel cell test rig conforming that it a potential replacement for silicone rubber in PEMFCs.

This thesis is a study of the properties of thin GaAs films grown on molybdenum substrates by the close spaced vapour transport (CSVT) deposition technique with the intention that the GaAs/Mo structure would be used as the semiconductor and substrate for economic solar cells. The GaAs films were polycrystalline cubic crystals with no preferred orientation. The crystallite area increased with the temperature at which the substrate was held during growth and at 710°C grain sizes of 100 μm² were observed. The crystallites formed a columnar-like structure with crystal size comparable to the film thickness. No impurities of foreign instrus-ions existed in the films in quantities observable on the electron micro-probe. The resistivity of the GaAs films was 220 Ω cm, hence acceptable for thin film solar cells, however, the GaAs/Mo contact was mildly rectifying. Diodes were fabricated by the deposition of Au onto the GaAs films and the resulting barriers showed values of barrier height of approximately 0.8 eV, ideality factor n = 1.5 to 2, and depletion-layer majority carrier concentration of roughly 10¹⁶ cm⁻³ as measured by J-V and C-V methods. The GaAs films show promise for use in solar cells provided that the Mo/GaAs interface resistance can be reduced. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Orientadores: Amauri Garcia, Wislei Riuper Ramos Osório / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-22T04:44:23Z (GMT). No. of bitstreams: 1 Peixoto_LeandroCesardeLorena_D.pdf: 28075319 bytes, checksum: 2535b56f95b9fb469e95bb5f7f810eff (MD5) Previous issue date: 2013 / Resumo: O presente trabalho pretende contribuir para o entendimento do desenvolvimento microestrutural e das propriedades de ligas diluídas dos sistemas Pb-Ag e Pb-Bi que apresentam importância para a indústria na fabricação de componentes de baterias automotivas e estacionárias. As amostras foram obtidas através de experimentos de solidificação unidirecional realizados em dispositivo no qual o calor é extraído somente pelo sistema de resfriamento a água, localizado na base do conjunto lingote/lingoteira (solidificação vertical ascendente). Taxas e velocidades de solidificação são determinadas a partir do registro de temperaturas a partir de termopares posicionados dentro da lingoteira em diferentes posições. As amostras foram utilizadas para analisar as influências das variáveis térmicas de solidificação e da concentração de soluto das ligas nas macro e microestruturas resultantes e na resistência mecânica. São determinados os limites de resistência à tração e escoamento e alongamentos específicos em função de espaçamento dendrítico e celular. A influência do arranjo microestrutural no comportamento eletroquímico é também avaliada por intermédio dos ensaios de espectroscopia de impedância eletroquímica, extrapolação de Tafel nas curvas de polarização potenciodinâmicas e análise por circuito equivalente em solução eletrolítica de 0,5 M de ácido sulfúrico à temperatura ambiente. Observa-se que as resistências à corrosão e à tração das ligas Pb-Ag aumentam com o refino microestrutural. O surgimento de espaçamentos terciários na liga Pb-2,4%Ag influencia negativamente na resistência à corrosão e contribui para o aumento do alongamento específico desta liga. Para as ligas Pb-Bi, a microestrutura é caracterizada por espaçamentos celulares e a resistência à corrosão é maior para um arranjo celular mais grosseiro. O teor de bismuto influi negativamente na resistência à corrosão e não tem influência na resposta mecânica. Embora da ordem de 10 vezes mais cara, por conta do valor da prata, as ligas Pb-Ag apresentam valores de resistência mecânicos mais altos e melhor resistência à corrosão induzindo que o uso dessas ligas pode aumentar o ciclo de vida desses componentes em até 5 vezes quando comparado com ligas tradicionais usadas para componentes de baterias chumbo-ácido / Abstract: The present work aims to contribute to the understanding of the microstructural development and properties of dilute PbAg and PbBi alloys which are widely applied in the manufacture of automobile and stationary lead-acid batteries. A water-cooled vertical upward unidirectional solidification system was used to obtain the samples. The experimental set-up was designed in such a way that the heat was extracted only through the water-cooled bottom, promoting upward directional solidification. Thermal readings were obtained by thermocouples positioned at different distances from the heat-extracting surface at the casting bottom. Both PbAg and PbBi alloys were used to analyze the effects of the cooling rate and growth rates and solute content on the resulting macro and microstructures and on the mechanical properties. The ultimate tensile and yield strengths and the elongations were determined as a function of the cellular and dendritic spacing. The effect of the resulting microstructure on the electrochemical corrosion behavior was also analyzed based on electrochemical parameters, determined by Tafel plots at potentiodynamic polarization curves and on equivalent circuit analysis after corrosion tests carried out in a 0.5 M sulphuric acid solution. It was observed that both the corrosion resistance and the ultimate tensile strength increased with the decrease in the dendritic spacing for Pb-Ag alloys. The tertiary spacing's, which occurred for the Pb-2.4 wt.% Ag alloy showed a deleterious effect on the corrosion response increased the elongation. A cellular microstructure characterized the Pb-Bi casting alloys, and the corrosion resistance was shown to be higher for coarse cells than for fine ones. The bismuth content has negatively affected the corrosion resistance, while no effect was observed for the mechanical behavior. Although the higher cost of Pb-Ag alloys due to the presence of silver, these alloys have evidenced high values of both mechanical properties and corrosion resistance. This indicates that Pb-Ag alloys can provide higher life-time cycle (up to five times) of the lead-acid battery components when compared with other traditional and commonly commercialized Pb-based alloys / Doutorado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica