The research presented in this thesis aims to determine the effectiveness of the uptake of toxic gases by several MOFs for future use in gas-mask cartridges, and to attempt to compensate for any deficiencies they show in “real-world” conditions. The main findings of this thesis confirm that MOFs are suitable candidates for the use in respirator cartridge materials and provide high capacity for adsorption of toxic gases like ammonia and STAM-1 in particular showed an impressive improvement in humid conditions, which normally decrease the performance of MOFs made from the same materials, such as HKUST-1. STAM-1's improved performance in humid conditions is attributed to the structural shift it displays upon dehydration and rehydration and this was shown to be the case in a structural analogue, CuEtOip, which was synthesised in the author's research group. This analogue was analysed using a combination of single crystal XRD and solid state MAS-NMR, both of which showed the structural change occurring and displays similar gas sorption behaviours, suggesting that this mechanism is the source of STAM-1's improved performance in humid conditions. This thesis also examines the “Armoured MOF” process and investigates the transferability of the process of deposition of mesoporous silica onto MOFs with vastly different properties and synthetic methods compared to those published in the original publication. Alongside this, attempts to protect MOFs using mesoporous silicates were investigated for their viability.

Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2008. / Includes bibliographical references (p. 54-56). / Landmines and mine-like traps are effective weapons that are difficult to detect and discriminate from a safe distance. The ability to detect landmines in their host environment at a distance and to discriminate them from other objects would be valuable for countering the landmine threat. This paper explores a standoff acoustic/laser technique to discriminate landmines from other forms of man-made objects (clutter) in an urban environment. A novel approach currently under investigation by MIT Lincoln Labs, University of Mississippi, and other groups employs a non-contact acoustic/laser technique to detect landmines from a safe standoff range. This technique uses a sound source to excite vibrations in targets with an acoustic wave. These vibrations are in turn measured remotely with a Laser Doppler Vibrometer (LDV). In this thesis, the vibration responses of landmine variants are measured, analyzed, and compared to those of common urban objects likely to be found on a landmine field or roadside. The Fourier Transform of the vibration of the target as measured by the LDV is used to generate a target vibration spectrum. Target vibration spectra in response to a sound source were experimentally measured for 59 trials, 28 of which were of simulated landmine variants and the remaining trials were of urban clutter objects. Using an algorithm adapted from a methodology for mass spectral analysis, parameters of the target signatures are estimated; then individual target signatures are classified using a Support Vector Machine (SVM) with a training set composed of parameters from the remaining members of the total population. The best results obtained from this methodology had a 71% probability of detection and a 3% false alarm rate corresponding to 20 of 28 of the simulated landmine variants correctly identified and a single clutter object misidentified as a landmine variant. / by John Houston Doherty. / S.M.

Neste trabalho estudamos as propriedades estruturais e eletrônicas de defeitos e impurezas de hidrogênio em MgO. As investigações foram efetuadas através de simulações computacionais baseadas em métodos de primeiros princípios dentro do formalismo da teoria do funcional da densidade e utilizando o método FPLAPW (Full Potential - Linearized Augmented Plane Wave), implementado no código computacional WIEN2k, dentro do esquema de supercelula, com relaxações iônicas tratadas de modo apropriado. Os defeitos estudados foram as vacâncias de oxigênio e de magnésio e as impurezas de hidrogênio foram simuladas em sitos substitucionais e intersticiais da rede do MgO. Em termos de configurações iônicas, a maioria dos centros de defeito ou de impureza apresentam pequenas relaxações do tipo respiratórias, mantendo a simetria local do sito, com exceção de dois dos centros estudados. O primeiro deles é a vacância de magnésio, no estado de carga neutro, que apresenta uma pequena distorção iônica trigonal. O segundo é a impureza intersticial de hidrogênio, no estado de carga positivo, que apresenta uma grande distorção local na rede, com a impureza se deslocando na direção de um dos dois átomos de oxigênio primeiros vizinhos. Nossos resultados para as energias de formação dos defeitos e impurezas nos permitiu avaliar a estabilidade dos centros, em função dos estados de carga, e prever as posicoes energeticas, no gap do material, dos estados de transicao. Para a impureza substitucional de hidrogenio no stio do oxigenio observamos que o centro no estado de carga positivo é o mais estável para qualquer valor do nível de Fermi, indicando que a impureza substitucional de hidrogênio, no sítio do oxigênio, apresenta caráter doador e o MgO pode ser caracterizado como um material tipo-n. Estas características também foram obtidas para as impurezas intersticiais de hidrogênio, mas nestes casos elas são dependentes da posição do nível de Fermi no gap do MgO. / In this work we report the results of the structural and electronic properties of defects and hydrogen impurities in MgO. The investigations were carried by computational simulations using ab initio methods, based on the density functional theory and the FP-LAPW (Full Potential - Linearized Augmented Plane Wave) method, as implemented in the WIEN2k code, considering the supercell approach and atomic relaxations. The studies comprise the oxygen and vacancies and substitutional and interstitial hydrogen impurities. Almost all defects and impurities keeps the crystalline local symmetry, showing breath mode relaxations. The magnesium vacancy, in the neutral charge state conguration, has a very small trigonal, while one of the hydrogen interstitial impurity, in the positive charge state conguration, has a very large local distortion, where the impurity moves toward one of the oxygen next neighbour atom. We have also investigated the energetic stability of these defects, evaluating the transition states related to each defect center. We nd that the substitutional hydrogen impurity in the oxygen site, in the positive charge state conguration, is the most stable one, independent of the Fermi level energy, showing a donor behaviour. Therefore, this impurity can lead to an n-type MgO material. Those characteristics were also observed for the interstitial hydrogen impurities investigated here, but in those cases the donor behaviour are Fermi level dependent.

Made available in DSpace on 2017-07-10T17:31:22Z (GMT). No. of bitstreams: 1 Wagner_de_Aguiar.pdf: 11388693 bytes, checksum: 2d568f29c8d953e3f9cb683f0a508900 (MD5) Previous issue date: 2012-02-27 / The object of this paper is to estimate the mechanical denudation rates for the river basin Quatorze in the sectors of the upper valley and the mouth of the river. The basin is located in the municipality of Francisco Beltrão, in Paraná, draining the left bank of the middle valley of the river basin Marrecas. Monitoring the field began in august 2011, rising daily data of rainfall, flow and concentration of suspended solids in the sections of the channels drained the upper valley and the mouth of the river, to obtain the discharges suspended solids. Carrying out further surveys in ten soil profiles distributed throughout the basin, allowing the identification of the main soil classes (Regolithic Entisols, Inceptisols, Oxisols and Nitossolos) and the measurement of laboratory parameters such as density and real, total porosity and fines content (silt and clay). In the monitored period was recorded daily rainfall, which occurred on august 19, 165 mm, resulting in large peak flows and discharge of suspended solids, contributing to the total rainfall for the month of august 2011, 343 mm, reached the highest monthly index for the month of august, the last 37 years, according to data provided by the Meteorological Station of Francisco Beltrão. Recognizing that the largest fraction pedological removed by the force of runoff is composed of mud (silt and clay), this parameter was quantified for soils of the basin, yielding an average of 91.87%. From the data of total suspended solid discharge (1,616.54 tons. in the upper valley and 5960.38 tons. at the mouth) and the average density (1.05 g.cm-³) of soil profiles were estimated denudation rates for the month of august 2011, 0.0419 mm in the sector of the basin drained by the upper valley and 0.0527 mm in the area drained by the mouth of the river. These results were extrapolated to annual estimates, based on the monitored period of rainfall and monthly average of the years 1974 to 2010. The standard deviations of the average monthly rainfall, for those years, enabled the establishment of maximum and minimum estimates for the annual rates of denudation. The sector of the upper valley had average estimate of 0.2458 mm.yr-¹ can vary over a range of 0.1069 mm.yr-¹ to 0.3848 mm.yr-¹, while the sector had the mouth of the river estimated annual average higher, 0.3092 mm.yr-¹ may, however, vary in a range of 0.1344 mm.yr-¹ to 0.4840 mm.yr-¹. / O objeto de estudo deste trabalho é estimar as taxas de denudação mecânica para a bacia hidrográfica do rio Quatorze, nos setores do Alto Vale e da Foz do rio. A bacia está localizada no município de Francisco Beltrão, no Sudoeste do Paraná, drenando a margem esquerda do médio vale da bacia do rio Marrecas. O monitoramento a campo iniciou-se no mês de agosto de 2011, levantando-se dados diários de pluviosidade, de vazão e de concentração de sólidos em suspensão, nas seções dos canais drenados pelo Alto Vale e pela Foz do rio, para a obtenção das descargas sólidas em suspensão. Realizando-se na sequência levantamentos de solos em dez perfis distribuídos pela bacia, possibilitando a identificação das principais classes de solo (Neossolos regolítico, Cambissolos, Nitossolos e Latossolos) e a quantificação laboratorial dos parâmetros como densidade aparente e real, porosidade total e teor de finos (silte e argila). No período monitorado foi registrada pluviosidade diária, ocorrida no dia 19 de agosto, de 165 mm, provocando grandes picos de vazão e descarga de sólidos em suspensão, contribuindo para que a pluviosidade total do mês de agosto de 2011, 343 mm, atingisse o maior índice mensal, para os meses de agosto, dos últimos 37 anos, de acordo com dados fornecidos pela Estação Meteorológica de Francisco Beltrão. Reconhecendo-se que a maior fração pedológica removida pela força do escoamento superficial é composta pela lama (silte e argila), quantificou-se este parâmetro para os solos da bacia, obtendo-se um valor médio de 91,87%. A partir dos dados de descarga sólida em suspensão total (1.616,54 ton. no Alto Vale e 5.960,38 ton. na Foz) e da densidade aparente média (1,05 g.cm-³) dos perfis de solo, foram estimadas as taxas de denudação, para o mês de agosto de 2011, em 0,0419 mm no setor da bacia drenado pelo Alto Vale e 0,0527 mm no setor drenado pela Foz do rio. Resultados estes extrapolados para estimativas anuais, tendo como base as pluviosidades do período monitorado e das médias mensais dos anos de 1974 a 2010. Os desvios padrões das pluviosidades médias mensais, dos referidos anos, possibilitaram o estabelecimento de estimativas máximas e mínimas para as taxas de denudação anual. O setor do Alto Vale apresentou estimativa média de 0,2458 mm.ano-¹ podendo variar em uma faixa de 0,1069 mm.ano-¹ a 0,3848 mm.ano-¹, enquanto que o setor da Foz do rio apresentou estimativa média anual, mais elevada, de 0,3092 mm.ano-¹, podendo, no entanto, variar em uma faixa de 0,1344 mm.ano-¹ a 0,4840 mm.ano-¹.

A partir de uma investigação empírica, esta pesquisa apresenta dados referentes à formação e atuação da Associação de Recicladores e Catadores de Esteio, a ARCA. Além disso, considerações sobre um processo de educação informal que se institui, inclusão social, relações humanas e trajetórias de vida até à ARCA reúnem-se neste trabalho. Outrossim, apontamentos sobre a problemática de consumo e de resíduos sólidos no planeta, tentam contextualizar a participação especial dos sujeitos naquilo que encaminha para a ruptura de paradigmas ambientalmente destrutivos. Também são descritos aspectos referentes à religiosidade, as relações de gênero, a família e afetos como forma de chamamento reflexivo sobre aquilo que se categoriza por cultural e/ou humano. / From an empirical inquiry, this research presents some information referring to the formation and performance of people, which their job is recycle and catch things, that is, garbage. They are from Esteio, the ARCA. Moreover, considerations about an informal education process which establishes itself, social inclusion, human relations and the history of lives till the ARCA are in this paper. In the same way, registers on a problematical related to the consumption and solids remains in the planet, try contextualize the especial participation of the guys that are being driven to the broken of paradigms environmentally baneful. What is more, are mentioned aspects related to religious, acquaintance of gender, the family and affects as a reflected whoop on what’s being characterized by human and or cultural.

Made available in DSpace on 2017-05-12T14:42:51Z (GMT). No. of bitstreams: 1 Wagner_de_Aguiar.pdf: 11388693 bytes, checksum: 2d568f29c8d953e3f9cb683f0a508900 (MD5) Previous issue date: 2012-02-27 / The object of this paper is to estimate the mechanical denudation rates for the river basin Quatorze in the sectors of the upper valley and the mouth of the river. The basin is located in the municipality of Francisco Beltrão, in Paraná, draining the left bank of the middle valley of the river basin Marrecas. Monitoring the field began in august 2011, rising daily data of rainfall, flow and concentration of suspended solids in the sections of the channels drained the upper valley and the mouth of the river, to obtain the discharges suspended solids. Carrying out further surveys in ten soil profiles distributed throughout the basin, allowing the identification of the main soil classes (Regolithic Entisols, Inceptisols, Oxisols and Nitossolos) and the measurement of laboratory parameters such as density and real, total porosity and fines content (silt and clay). In the monitored period was recorded daily rainfall, which occurred on august 19, 165 mm, resulting in large peak flows and discharge of suspended solids, contributing to the total rainfall for the month of august 2011, 343 mm, reached the highest monthly index for the month of august, the last 37 years, according to data provided by the Meteorological Station of Francisco Beltrão. Recognizing that the largest fraction pedological removed by the force of runoff is composed of mud (silt and clay), this parameter was quantified for soils of the basin, yielding an average of 91.87%. From the data of total suspended solid discharge (1,616.54 tons. in the upper valley and 5960.38 tons. at the mouth) and the average density (1.05 g.cm-³) of soil profiles were estimated denudation rates for the month of august 2011, 0.0419 mm in the sector of the basin drained by the upper valley and 0.0527 mm in the area drained by the mouth of the river. These results were extrapolated to annual estimates, based on the monitored period of rainfall and monthly average of the years 1974 to 2010. The standard deviations of the average monthly rainfall, for those years, enabled the establishment of maximum and minimum estimates for the annual rates of denudation. The sector of the upper valley had average estimate of 0.2458 mm.yr-¹ can vary over a range of 0.1069 mm.yr-¹ to 0.3848 mm.yr-¹, while the sector had the mouth of the river estimated annual average higher, 0.3092 mm.yr-¹ may, however, vary in a range of 0.1344 mm.yr-¹ to 0.4840 mm.yr-¹. / O objeto de estudo deste trabalho é estimar as taxas de denudação mecânica para a bacia hidrográfica do rio Quatorze, nos setores do Alto Vale e da Foz do rio. A bacia está localizada no município de Francisco Beltrão, no Sudoeste do Paraná, drenando a margem esquerda do médio vale da bacia do rio Marrecas. O monitoramento a campo iniciou-se no mês de agosto de 2011, levantando-se dados diários de pluviosidade, de vazão e de concentração de sólidos em suspensão, nas seções dos canais drenados pelo Alto Vale e pela Foz do rio, para a obtenção das descargas sólidas em suspensão. Realizando-se na sequência levantamentos de solos em dez perfis distribuídos pela bacia, possibilitando a identificação das principais classes de solo (Neossolos regolítico, Cambissolos, Nitossolos e Latossolos) e a quantificação laboratorial dos parâmetros como densidade aparente e real, porosidade total e teor de finos (silte e argila). No período monitorado foi registrada pluviosidade diária, ocorrida no dia 19 de agosto, de 165 mm, provocando grandes picos de vazão e descarga de sólidos em suspensão, contribuindo para que a pluviosidade total do mês de agosto de 2011, 343 mm, atingisse o maior índice mensal, para os meses de agosto, dos últimos 37 anos, de acordo com dados fornecidos pela Estação Meteorológica de Francisco Beltrão. Reconhecendo-se que a maior fração pedológica removida pela força do escoamento superficial é composta pela lama (silte e argila), quantificou-se este parâmetro para os solos da bacia, obtendo-se um valor médio de 91,87%. A partir dos dados de descarga sólida em suspensão total (1.616,54 ton. no Alto Vale e 5.960,38 ton. na Foz) e da densidade aparente média (1,05 g.cm-³) dos perfis de solo, foram estimadas as taxas de denudação, para o mês de agosto de 2011, em 0,0419 mm no setor da bacia drenado pelo Alto Vale e 0,0527 mm no setor drenado pela Foz do rio. Resultados estes extrapolados para estimativas anuais, tendo como base as pluviosidades do período monitorado e das médias mensais dos anos de 1974 a 2010. Os desvios padrões das pluviosidades médias mensais, dos referidos anos, possibilitaram o estabelecimento de estimativas máximas e mínimas para as taxas de denudação anual. O setor do Alto Vale apresentou estimativa média de 0,2458 mm.ano-¹ podendo variar em uma faixa de 0,1069 mm.ano-¹ a 0,3848 mm.ano-¹, enquanto que o setor da Foz do rio apresentou estimativa média anual, mais elevada, de 0,3092 mm.ano-¹, podendo, no entanto, variar em uma faixa de 0,1344 mm.ano-¹ a 0,4840 mm.ano-¹.

Neste trabalho estudou-se a copolimerização em emulsão de estireno e acrilato de butila em processo semicontínuo onde o produto final é um látex com alto teor de sólidos. Foi dado enfoque à distribuição de tamanhos de partículas do látex e seus efeitos no produto. Foi realizada uma série de experimentos de copolimerização em emulsão em um reator de vidro, empregando receitas com teores de sólidos de até 64% em massa. Durante os experimentos, amostras eram retiradas periodicamente do reator visando analisar o teor de polímeros (conversão dos monômeros) por gravimetria, a concentração de monômero residual por cromatografia gasosa headspace, o diâmetro médio das partículas por espectroscopia de espalhamento dinâmico de luz e a distribuição de tamanhos de partículas por microscopia eletrônica de transmissão. A viscosidade do látex final era obtida em viscosímetro Brookfield. Aplicando estratégias para renucleação de novas partículas no decorrer do processo, foram obtidos látices com distribuição bimodal de tamanhos de partículas e com viscosidades reduzidas. Aplicou-se um modelo matemático para descrever o processo, incluindo a evolução no tempo da distribuição de tamanhos de partículas, calculada a partir de equações de balanço populacional para as partículas e para os radicais dentro das partículas. Para a solução das equações empregou-se discretização por método de classes e a técnica de pivô fixo. O modelo tem apenas dois parâmetros ajustáveis, referentes às eficiências de captura de radicais por micelas e por partículas. Estes parâmetros foram ajustados para os dados experimentais de um ensaio, e usados, sem reajuste, para outros ensaios em condições diferentes. Os resultados do modelo mostraram boa adequação aos resultados experimentais. / The aim of this work was the study of the high solid contents emulsion copolymerization of styrene and butyl acrylate in semi-batch process. In this context the particle size distribution and its effects on the product viscosity was studied. Copolymerization reactions were carried out in a glass reactor, and recipes with solid contents up to 64 wt.% were used. During each run, samples are periodically taken from the reactor, and analysis are performed to measure the polymer content (monomer conversion) by gravimetry, the concentrations of the residual monomers by head-space gas chromatography, the average particle size by dynamic light scattering, and the particle size distribution by transmission electronic microscopy. The viscosity of the final emulsion is also measured using a Brookfield viscosimeter. By applying operating strategies to nucleate new particles along the process, latexes with bimodal particle size distributions and low viscosities were obtained. A mathematical model was employed for simulating the polymerization process, including the evolution of the particle size distribution along the process, calculated from population balance equations for the particles and the radicals inside the particles. The numerical solution was obtained using the discretized population balance equations by the method of classes and the fixed pivot technique. The model has only two adjustable parameters, the efficiencies for radical capture by micelles and by particles. These two parameters were fitted to the experimental data of one run and used, without further readjustment, for other runs under different conditions. The model results presented satisfactory agreement with the experimental data.

Este trabalho se propôs a avaliar o desempenho de um reator com leito de biomassa aderida de fluxo ascensional em escala plena (159 \'M POT.3\') e com aeração contínua a 7 m acima da base do reator para o tratamento do esgoto sanitário. O leito do reator era formado por carvão ativado granular, carvão antracitoso e areia. O trabalho foi dividido em duas etapas. Na primeira etapa foram feitos ensaios hidrodinâmicos que consistiram da curva de expansão/fluidificação para as biopartículas do leito do reator em escala plena e do ensaio de estímulo-resposta com o traçador \'NA\'CL\'. Na segunda etapa monitorou-se o comportamento do reator com leito de biomassa aderida operado com setor 1 (sem aeração) e setor 2 (com aeração) sobrepostos e foi utilizada a recirculação para expandir o leito. As curvas de expansão/fluidificação das biopartículas constituintes do leito do reator mostraram que o leito do reator no setor 1 encontrava-se sem expansão e no setor 2 estava expandido, sob as condições de operação determinadas para esse trabalho. Do ensaio com o traçador \'NA\'CL\', obtiverem-se tempo de detenção hidráulica médio (TDHM) de 18,45 h para o ensaio sem recirculação e com compressor desligado; e de 16,90 h para o ensaio com recirculação e compressor ligado. Os TDHM obtidos foram maiores que o TDH teórico (igual a 12 h), provavelmente devido à difusão do traçador no biofilme. A Etapa II foi dividida em duas fases, na fase 1 o TDH teórico médio foi de 12 h e na fase 2 foi de 16 h. Verificou-se baixa retenção de sólidos no sistema, visto que o efluente apresentou, durante a maior parte do período de monitoramento, concentrações de sólidos totais e sólidos suspensos totais superiores as do afluente. A maior eficiência de remoção de DQO de amostra bruta aconteceu na fase 2 e foi de 32% sob taxa de carregamento de 0,86kgDQObruta/\'M POT.3\'.d. Os valores médios de DQO de ) amostras filtradas do efluente foram iguais 119 e 116 mg \'O IND.2\'/L, o que equivale a remoções médias de 54% e 63%, respectivamente para a fase 1 e 2. A maior remoção DBO de amostra filtrada no sistema aconteceu na fase 1 e foi de 91%, com o efluente apresentando concentração de 19 mg \'O IND.2\'/L. Com relação à concentração de NTK, o sistema foi pouco eficiente em sua remoção e apresentou concentrações muito baixa de nitrogênio oxidado (menores que 1 mg \'NO IND.3\'POT.-1\'/L). O grau de amonificação foi de 89%, em média, quando considerou a concentração de NTK em amostra filtrada. Concluiu-se que o sistema não é eficiente na remoção de material orgânico e de nutrientes devido ao arraste de sólidos e material biológico no efluente. / This work aimed to evaluate the performance of a full scale up-flow attached biomass bed reactor (159 \'M POT.3\') and with continuous aeration at 7 m above bottom of the reactor to sanitary sewage treatment. The bed of the reactor was constituted for activated granular carbon, anthracite carbon and sand. The work was divided into two stages. In the first stage, hydrodynamics tests were made which consisted of the expansion/fluidization curve for the bioparticles of the bed of the full scale reactor and of the test of stimulus-response with tracer \'NA\'CL\'. In the second stage, it monitored the performance of the attached biomass bed reactor operated with overlapping sector 1 (without aeration) and sector 2 (with aeration) and it utilized the recirculation to expand the bed. The expansion/fluidization curves of the bioparticles of the bed of the reactor showed that the bed of the reactor in the sector 1 was without expansion and in the sector 2 was expanded, under the operating conditions determined for this work. Of the test with \'NA\'CL\' tracer obtained mean hydraulic detention time (HDTM) of 18,45 h for the test without recirculation and compressor off; and of 16,90 h for the test with recirculation and compressor on. The obtained HDTM were bigger than the theoretical HDT (equal at 12 h), probably due to at the diffusion of trace into biofilm. The stage II was divided into two phases, in the phase 1 mean theoretical HDT was of 12 h, and in the phase 2 was of 16 h. It verified low retention of solids in the system, since the effluent presented, during most of the monitoring period, concentrations of total solids and total suspended solids higher than the influent. The greater efficiency of COD removal of raw sample occurred in phase 2 and was of 32% under loading rate of 0,86kgCODraw/\'M POT.3\'.d. The mean amounts COD of filtered samples in the effluent were equal to 119 and 116mg\'O IND.2\'/L, which is equivalent ) to mean removals of 54% and 63%, respectively for phase 1 and 2. The higher efficiency of removal BOD filtered sample in the system was in phase 1 and was of 91%, with effluent presenting concentration of 19mg \'O IND.2\'/L. With respect to the TKN concentration, the system was little efficient in its removal and presented very low concentration of oxidized nitrogen (lower than 1mg \'NO IND.3\'POT.-1\'). The degree of ammonification was 89%, on average, when considered the TKN concentration in the filtered sample. It concluded that the system is not effective removing organic material and nutrients due to drag of solids and biological material in the effluent.

Neste trabalho estudamos as propriedades estruturais e eletrônicas de defeitos e impurezas de hidrogênio em MgO. As investigações foram efetuadas através de simulações computacionais baseadas em métodos de primeiros princípios dentro do formalismo da teoria do funcional da densidade e utilizando o método FPLAPW (Full Potential - Linearized Augmented Plane Wave), implementado no código computacional WIEN2k, dentro do esquema de supercelula, com relaxações iônicas tratadas de modo apropriado. Os defeitos estudados foram as vacâncias de oxigênio e de magnésio e as impurezas de hidrogênio foram simuladas em sitos substitucionais e intersticiais da rede do MgO. Em termos de configurações iônicas, a maioria dos centros de defeito ou de impureza apresentam pequenas relaxações do tipo respiratórias, mantendo a simetria local do sito, com exceção de dois dos centros estudados. O primeiro deles é a vacância de magnésio, no estado de carga neutro, que apresenta uma pequena distorção iônica trigonal. O segundo é a impureza intersticial de hidrogênio, no estado de carga positivo, que apresenta uma grande distorção local na rede, com a impureza se deslocando na direção de um dos dois átomos de oxigênio primeiros vizinhos. Nossos resultados para as energias de formação dos defeitos e impurezas nos permitiu avaliar a estabilidade dos centros, em função dos estados de carga, e prever as posicoes energeticas, no gap do material, dos estados de transicao. Para a impureza substitucional de hidrogenio no stio do oxigenio observamos que o centro no estado de carga positivo é o mais estável para qualquer valor do nível de Fermi, indicando que a impureza substitucional de hidrogênio, no sítio do oxigênio, apresenta caráter doador e o MgO pode ser caracterizado como um material tipo-n. Estas características também foram obtidas para as impurezas intersticiais de hidrogênio, mas nestes casos elas são dependentes da posição do nível de Fermi no gap do MgO. / In this work we report the results of the structural and electronic properties of defects and hydrogen impurities in MgO. The investigations were carried by computational simulations using ab initio methods, based on the density functional theory and the FP-LAPW (Full Potential - Linearized Augmented Plane Wave) method, as implemented in the WIEN2k code, considering the supercell approach and atomic relaxations. The studies comprise the oxygen and vacancies and substitutional and interstitial hydrogen impurities. Almost all defects and impurities keeps the crystalline local symmetry, showing breath mode relaxations. The magnesium vacancy, in the neutral charge state conguration, has a very small trigonal, while one of the hydrogen interstitial impurity, in the positive charge state conguration, has a very large local distortion, where the impurity moves toward one of the oxygen next neighbour atom. We have also investigated the energetic stability of these defects, evaluating the transition states related to each defect center. We nd that the substitutional hydrogen impurity in the oxygen site, in the positive charge state conguration, is the most stable one, independent of the Fermi level energy, showing a donor behaviour. Therefore, this impurity can lead to an n-type MgO material. Those characteristics were also observed for the interstitial hydrogen impurities investigated here, but in those cases the donor behaviour are Fermi level dependent.

Bilayers formed by molecules that possess long alkyl hydrophobic tails are ubiquitous in the natural world manifesting both in biological systems as well as in chemistry. The lipid bilayer is an integral feature of cell membranes of living systems with functions that are of critical importance to the life of the cell. Long chain amphiphilic surfactant molecules can be introduced within the interlamellar region of layered inorganic host lattices to form anchored alkyl chainbilayerswithinthegalleries.Theintercalatedbilayerbearsastriking resemblance to lipid bilayers. However, unlike lipid bilayers where individual molecules can undergo lateral diffusion and also flip-flop between layers the anchored bilayer is characterized by the total absence of translational mobility. The degrees of freedom of the alkyl chains of the anchored bilayer are restricted to changes in conformation. This thesis describes a detailed investigation of the anchored bilayer formed by the intercalation of the anionic surfactant dodecyl sulphate (DDS) in a layered solid, Mg-Al Layered Double Hydroxide(Mg-AlLDH) using both experimental measurements and Molecular Dynamics (MD) simulations (Chapter 2). The thesis is organized as two parts. The first (Chapters 2 -4) deals with the anchored bilayer in the condensed phase -the conditions for the formation of the bilayer arrangement of the intercalated surfactant chains and the conformation and dynamics of the alkyl chains of the surfactant in the galleries of the layered solid. The surfactant intercalated Mg-AlLDH-DDS may be delaminated in nonpolar solvents to give colloidal dispersions of individual Mg-Al LDH sheets with the DDS surfactant chains remaining tethered to the inorganic sheets(Scheme 1).The second part of thesis(Chapters 5 -9)describe studies on the dispersions of the Mg-AlLDH-DDS in toluene. A summary of the results of the of the investigations of the anchored bilayer, formed by the intercalation of DDS ions in Mg-Al LDH, in the condensed and the dispersed phases is presented in the concluding chapter(Chapter10). Layered Double Hydroxides(LDH) are insulating lamellar solids of the general chemical formula[M’(1-x) Mx(OH)2], where M’ is a divalent metal ion and M a trivalent ion. Their structure may be derived from that of Brucite, Mg(OH)2, by isomorphous substitution of apart of the Mg2+ by trivalent ions like Al3+ with electrical neutrality maintained by interlamellar exchangeable ions. The studies reported in this thesis are on an Mg-Al LDH,Mg(1−x)Alx(OH)2, x ranging from 0.17 to 0.37. Dodecyl sulphate surfactant ions have been ion-exchange intercalated in Mg-AlLDH (Chapter 3). By varying the Mg-Al ratio, differing packing densities of the surfactant chains in the interlamellar space of the Mg-Al LDH-DDS are realized. At high packing densities the alkyl chains of the intercalated dodecyl sulphate ions anchored on opposing Mg-Al LDH sheets are arranged as bilayers while at lower packing densities the surfactant chains form a monolayer with the chains oriented flat in the galleries. This composition driven monolayer to bilayer transformation in the surfactant intercalated Mg-AlLDH-DDS is also reproduced by MD simulations. The simulations also indicate that there are profound differences in the factors that decide the arrangement of the surfactant chains. In the bilayer arrangement it is dispersive van der Waals interactions between the chains in opposing layers that is responsible for the cohesive energy of the solid whereas at lower packing densities, where a monolayer arrangement is favored, Coulomb interactions between the positively charged Mg-Al LDH sheets and the negatively charged head-group of the DDS anion dominate. The conformation and dynamics of the alkyl chains of the intercalated surfactant chains in both the monolayer and bilayer arrangements as well as the effect of packing density on these parameters is reported in Chapter 4. The conformation was studied using spectroscopic techniques, infra-red, Raman and 13C Nuclear Magnetic Resonance (NMR) while the dynamics by Variable Contact Time Cross Polarization Magic Angle Spinning(VCT -CPMAS) and2DWidelineSeparation(2DWiSe)NMR techniques. The results showed the expected trends; the concentration of gauche defects and the dynamics of the chains increase with decreasing packing density. There is, however a sharp increase in the gauche concentration and conformational mobilities of the intercalated surfactant chains associated with the bilayer to monolayer transformation. The results of the MD simulations, too, reflect these trends. The second part of thesis describes the delamination of the intercalated anchored bilayer (Mg-AlLDH-DDS) in non-polar solvents. Delamination results in a colloidal dispersion Of the anchored bilayer, isolated Mg-AlLDH sheets with the DDS chains tethered to them, as neutral nanosheets of nanometer thickness and micron size. With increasing concentration of the anchored bilayers in the solvent a gel state is realized. The sol to gel transformation of the dispersions of the anchored bilayer in toluene has been investi-gated. Frequency dependent rheology measurements (Chapter6) were used to investigate the visco-elastic properties of the dispersions and Small Angle X-ray Scattering (SAXS) measurements(Chapter 7) to understand the structure and shape of the nanosheets. The rheology experiments showed that the dispersions irrespective of their concentrations showed shear thinning. The SAXS results indicate a tactoid structure of the dispersions as well as in the gel phase. At higher concentrations, the X-ray scattering curves indicated that the layers stack loosely with an interlamellar space of ~ 39 Å , a value much larger than the interlayer lattice spacing of solid Mg-AlLDH-DDS( ~ 27 Å). The nature of interactions between solvent molecules and the anchored DDS chains were probed by 1Hand 2H NMR measurements(Chapter8). A clear association between the toluene molecules and the alkyl chains of the anchored surfactant was observed. 2D NOESY experiments established that there are toluene molecules in close proximity that interact with the methyl tail of the anchored surfactant. NMR measurements were also able to distinguish two types of solvent molecules based on their widely differing mobilities. MD simulations(Chapter9)of the dispersed anchored bilayer are able to reproduce the essential features of the experimental observations including the formation of a loosely bound lamellar structure. It also provides an explanation on how the spectroscopic observation of motional heterogeneity gives rise to the viscoelastic properties of the dispersed anchored bilayer.