Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Conventional structural analysis of buildings in reinforced concrete is performed considering beam-column connections as rigid. However, experimental results prove the existence of relative rotations in beam-column connections of reinforced concrete structures, showing the partial transfer of bending moment. In this study the influence of the stiffness of beam-column connections on the structural behavior of multi-storey buildings in reinforced concrete was investigated. On a first stage, the value of the rotation restriction of connections was varied, observing the impact on horizontal displaceability of the structure, on the γz coefficient, on the negative and positive moments of the beams and on the longitudinal reinforcement of the pillars. This analysis was performed for buildings with 05, 10, 15 and 19 floors. The results show that the reduction of the rotation restriction of connections increases the values of the horizontal displacements, of the γz coefficient, of the positive moments and of the reinforcement of the pillars. The increases that occur on the values of the analyzed parameters become larger as the number of floors of buildings increases. On a second stage, the same building was calculated with rigid connections and deformable connections. In order to determine the factor αR of deformable connections, two analytical models available in literature were used, and a comparison between the results obtained by each analytical model was also performed. Based on the results, it is concluded that neglecting the influence of the stiffness of the beam-column connections on the analysis of monolithic reinforced concrete structures may result in different solutions compared to the real behavior of the structure. The stiffness values obtained with the analytical models that were used differ considerably from the condition of rigid connections, suggesting an adjustment on the standard consideration of rigid connections adopted by the computer programs of structural calculation. / A análise estrutural convencional de edificações em concreto armado é realizada considerando as ligações viga-pilar como rígidas. Entretanto, resultados experimentais comprovam a existência de rotações relativas nas ligações viga-pilar de estruturas de concreto armado, evidenciando a transmissão parcial de momento fletor. Neste trabalho foi investigada a influência da rigidez das ligações viga-pilar no comportamento estrutural de edificações de múltiplos pavimentos em concreto armado. Em uma primeira etapa, variou-se o valor de restrição à rotação das ligações observando os impactos na deslocabilidade horizontal da estrutura, no coeficiente γz, nos momentos negativos e positivos das vigas e nas armaduras longitudinais dos pilares. Esta análise foi realizada para edificações com 05, 10, 15 e 19 pavimentos. Observou-se por meio dos resultados que a redução da rigidez à rotação das ligações provoca aumento nos valores dos deslocamentos horizontais, do coeficiente γz, dos momentos positivos das vigas e das armaduras dos pilares. Os acréscimos ocorridos nos valores dos parâmetros analisados são maiores à medida em que se aumentam o número de pavimentos das edificações. Em uma segunda etapa, calculou-se uma mesma edificação com ligações rígidas e com ligações deformáveis. Para determinação da restrição à rotação das ligações deformáveis, utilizaram-se dois modelos analíticos disponíveis na literatura, realizando-se, também, uma comparação entre os resultados obtidos pelos modelos. Com base nos resultados, conclui-se que negligenciar a influência da rigidez das ligações viga-pilar na análise de estruturas monolíticas em concreto armado pode gerar soluções muito diferentes do comportamento real da estrutura na prática. Os valores de rigidez obtidos pelos modelos analíticos utilizados divergem consideravelmente da condição de ligações rígidas, sugerindose a adequação na consideração padrão de ligações rígidas adotada pelos programas computacionais de cálculo estrutural. / Mestre em Engenharia Civil

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-01-09T14:43:53Z No. of bitstreams: 1 rafaelmarques.pdf: 2550703 bytes, checksum: 4694887625f47f1d8d4f3dbed5d78f1d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-01-23T11:20:19Z (GMT) No. of bitstreams: 1 rafaelmarques.pdf: 2550703 bytes, checksum: 4694887625f47f1d8d4f3dbed5d78f1d (MD5) / Made available in DSpace on 2018-01-23T11:20:19Z (GMT). No. of bitstreams: 1 rafaelmarques.pdf: 2550703 bytes, checksum: 4694887625f47f1d8d4f3dbed5d78f1d (MD5) Previous issue date: 2017-09-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta tese de doutorado aborda o preparo, a caracterização e a utilização de fases estacionárias monolíticas para uso em colunas de separação cromatográfica em escala capilar. As fases estacionárias foram preparadas pela polimerização do monômero 3-(metacriloxipropil)-trimetoxisilano em duas etapas envolvendo primeiramente um processo sol-gel e depois um processo de adição radicalar fotoiniciado. A fotopolimerização foi feita in situ em capilares de sílica fundida transparentes à radiação UV com 100 μm de diâmetro interno. As colunas produzidas foram aplicadas qualitativamente com sucesso na separação de cinco hidrocarbonetos policíclicos aromáticos e três hormônios esteroides, tanto por cromatografia a líquido capilar quanto por eletrocromatografia capilar em um equipamento de eletroforese capilar. A eletrocromatografia foi usada para analisar quantitativamente uma amostra de emulsão transdérmica contendo estriol e 17-β-estradiol. Como tentativa de melhorar a separação entre alguns analitos, foi feita a modificação do polímero adicionando o monômero benzil metacrilato, porém sem sucesso. As colunas foram caracterizadas com relação à sua homogeneidade física usando um microscópio óptico e um detector condutométrico sem contato capacitivamente acoplado. O detector foi usado como um scanner não invasivo deslocando-se longitudinalmente ao longo da coluna externamente ao capilar. A caracterização química do polímero foi feita através da espectroscopia de ressonância magnética nuclear no estado sólido dos núcleos de 13C e de 29Si. Foi possível propor uma estrutura para o arranjo da cadeia carbônica e o grau de substituição do grupo silil indicando a reticulação das cadeias poliméricas através da formação de dímeros e trímeros condensação de grupos alcoxisilanos. / This doctoral thesis adresses the preparation, characterization and use of monolithic stationary phases for chromatographic separation columns in capillary scale. The stationary phases were prepared by polymerizing the 3- (methacryloxypropyl) trimethoxysilane monomer in two steps involving a sol-gel process followed by a photoinitiated radical addition. The photopolymerization was carried out in UV transparent coating fused silica capillaries with 100 μm of internal diameter. The columns were applied in the qualitative separation of five polycyclic aromatic hydrocarbons and three steroid hormones, both by capillary liquid chromatography and capillary electrochromatography in a capillary electrophoresis equipment. Electrochromatography was used to quantitative analyzis of a transdermal emulsion sample containing estriol and 17-β-estradiol. In an attempt to improve the separation between some analytes, the polymer was modified by adding the benzyl methacrylate monomer, but without success. The columns were characterized with respect to their physical homogeneity using an optical microscope and a capacitively coupled contactless conductivity detector. The detector was used as a non-invasive scanner moving longitudinally along the column externally to the capillary. The chemical characterization of the polymer was done by the solid state 13C and 29Si nuclear magnetic resonance spectroscopy. It was possible to propose a carbon chain strucuture and the substitution degree of the silyl group indicating the cross-linking of the polymer chains through the formation of dimers and trimers by condensation of the alkoxysilane groups.

Foram desenvolvidas metodologias de cromatografia a líquido de fase reversa baseadas em injeção sequencial (SIC) e em cromatografia a líquido de alta eficiência (HPLC) para determinação de triclosan em amostras de produtos de higiene pessoal e em estudos de adsorção em argilominerais naturais e modificados, visando determinar parâmetros de adsorção de triclosan frente a alguns de seus metabólitos. A determinação de triclosan em enxaguadores bucais foi realizada por SIC com eluição isocrática usando fase móvel constituída por acetonitrila: tampão fosfato de trietilamina 70 mM pH 3,5 na proporção 70:30 (v v-1), obtendo-se limites de detecção e de quantificação de 0,22 e 0,72 mg L-1, respectivamente. Taxas de recuperação entre 96 e 98% foram obtidas da aplicação a amostras reais, sendo que os resultados obtidos pelo método proposto não apresentaram evidências de diferenças estatisticamente significativas em comparação a uma metodologia de referência baseada em HPLC com coluna empacotada. A separação de triclosan (TCS), 2-clorofenol (2-CP), 2,4-diclorofenol (2,4-DCP), 2,4,6-triclorofenol (2,4,6-TCP), 2,3,4-triclorofenol (2,3,4-TCP) e metiltriclosan (MTCS) foi estudada por SIC, obtendo-se a separação de TCS, 2-CP, 2,4-DCP e 2,4,6-TCP com duas etapas de eluição isocrática, a primeira delas com fase móvel 60:40 (v v-1) metanol: tampão acetato de amônio 20 mM (pH 5,5) seguida de eluição com fase móvel 70:30 (v v-1) metanol : tampão acetato de amônio 20 mM (pH 5,5). Nesse caso, os isômeros 2,4,6-TCP e 2,3,4-TCP coeluem. Metiltriclosan, o menos polar desses compostos, pode ser separado de TCS com etapas subseqüentes de eluição. Os métodos foram aplicados para estudar a adsorção de triclosan e seus metabólitos 2,4-DCP, 2,4,6-TCP e metiltriclosan em montmorilonita homoiônica (K+) e modificada com sal de hexadeciltrimetilamônio (HDTMA), observando-se forte adsorção de triclosan e metiltriclosan em comparação a 2-CP, 2,4-DCP e 2,4,6-TCP. A incorporação de HDTMA no argilomineral causou significativo aumento da capacidade de adsorção desses metabólitos, determinada a partir do ajuste dos dados experimentais à equação linearizada de Langmuir, observando-se que a ordem de adsorção é 2,4,6-TCP > 2,4-DCP > 2-CP / Reversed-phase liquid chromatography methodologies based on sequential injection (SIC) and high performance liquid chromatography (HPLC) have been developed for determination of triclosan in samples of personal hygiene products and in studies of adsorption on natural and modified clay minerals aiming to determine kinetic and thermodynamic parameters of adsorption of triclosan in comparison with some of its metabolites. The determination of triclosan in oral rinses with SIC was performed by isocratic elution using a mobile phase of acetonitrile : 70 mM triethylamine phosphate buffer pH 3.5 at the ratio 70:30 (v v-1), obtaining limits of detection and quantification of 0.22 and 0.72 mg L-1, respectively. Recovery rates between 96 and 98 % were obtained from the application to commercial samples, and the results obtained by the proposed method showed no evidence of statistically significant differences compared to the reference methodology based on HPLC with packed column. The separation of triclosan (TCS), 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4 trichlorophenol (2,3,4-TCP) and methyltriclosan (MTCS) was studied by SIC, resulting in the separation of TCS, 2-CP, 2,4-DCP and 2,4,6-TCP with two isocratic elution steps, the first of them with a mobile phase 60:40 (v v-1) methanol: 20 mM ammonium acetate buffer (pH 5.5) followed by elution with 70:30 (v v-1) mobile phase of methanol : 20 mM ammonium acetate buffer (pH 5.5). In this case, the isomers 2,4,6-TCP and 2,3,4-TCP coeluted. Methyltriclosan, the less polar of these compounds, can be separated from TCS with subsequent elution steps. The methods were applied to study the adsorption of triclosan and its metabolites 2-CP, 2,4-DCP, 2,4,6-TCP and methyltriclosan on homoionic montmorillonite (K+) as well as in hexadecyltrimethylammonium salt (HDTMA) modified montmorillonite, noticing a stronger adsorption of triclosan and methyltriclosan compared with 2-CP, 2,4-DCP and 2,4,6-TCP. Incorporation of HDTMA in the clay mineral caused significant increase in adsorption capacity of these metabolites. This capacity was determined by fitting the experimental data to the linearized Langmuir equation. The adsorption order was 2,4,6-TCP > 2,4-DCP > 2-CP.

Estudou-se o emprego da Cromatografia a Líquido por Injeção Seqüencial (SIC) explorando o uso de uma cela de longo caminho óptico com guia de onda (LCW) de 100 cm para a melhora dos limites de detecção (LOD) e quantificação (LOQ) na determinação de atrazina (ATR), propazina (PRO) e simazina (SIM). Para isto, utilizou-se uma fase móvel com composição de 44:56 (v v-1) metanol : tampão acetato de amônio 1,25 mM, pH 4,7, coluna monolítica e a detecção espectrofotométrica em 238 nm. Obtiveram-se valores de LOD e LOQ, respectivamente, de 1,76 e 5,86 µg L-1 para ATR, 4,51 e 15 µg L-1 para PRO e 2,25 e 7,5 µg L-1 para SIM. Com o emprego da cela de longo caminho óptico os valores de LOD ficaram abaixo dos recomendados pela US-EPA, que permite para águas potáveis uma concentração de 3 µg L-1 para ATR, 4 µg L-1 para SIM e 10 µg L-1 para PRO. Realizaram-se estudos de adsorção de SIM, PRO e ATR e seus metabólitos desisopropilatrazina (DIA), desetilatrazina (DEA) e 2-hidroxiatrazina (HAT) em solo, ácido húmico e solo modificado com ácido húmico. Para isso foi utilizado um sistema de monitoramento on-line composto por um filtro tangencial e uma bomba peristáltica para circulação da suspensão. Foram realizados estudos cinéticos em duas etapas e, em ambas, foi utilizado um mix dos compostos com concentração inicial de 1,0 mg L-1 e gradiente de eluição passo a passo para a separação dos compostos utilizando três fases móveis com composições de 15 ou 28, 40 e 50% (v v-1) metanol : tampão acetato de amônio 1,25 mM pH 4,7. Na primeira etapa o tempo de contato entre triazinas e adsorventes foi de 90 min. Na segunda etapa foi utilizado apenas o solo como adsorvente e o tempo de contato foi de 24 h. Para a primeira etapa do estudo só foi possível aplicar modelo cinético de pseudo-segunda ordem, o qual permitiu estimar os valores de massa adsorvida de triazina por massa de adsorvente, sendo que o ácido húmico é o material com maior capacidade adsortiva (1470 ± 43µg g-1 para DIA a 2380 ± 51 µg g-1 para PRO). O composto mais adsorvido em solo é PRO (26,5 ± 0,1 µg g-1). A presença de ácido húmico no solo aumentou a adsorção de ATR (de 19,4 ± 0,7 para 23 ± 2 µg g-1), de HAT (10,9 ± 0,7 para 18 ± 2 µg g-1) e de PRO (26,5 ± 0,7 para 29,8 ±0,2 µg g-1), mas diminuiu a adsorção de SIM e não afetou DIA e DEA. No estudo com tempo de contato de 24 h foi possível aplicar modelos de pseudo-primeira e segunda ordem. Os resultados obtidos confirmaram a maior adsorção de PRO, seguidos da ATR. HAT, SIM, DEA e DIA apresentaram as menores taxas de adsorção em solo, sendo que os dois últimos apresentaram uma tendência de dessorção após 4 h de contato, tendo maior potencial de lixiviação para corpos d\'água próximos aos locais de aplicação. / This work describes the use of Sequential Injection Liquid Chromatography (SIC) coupled to a long path length optical flow cell with 100 cm long Liquid Core Waveguide (LCW) to improve the limits of detection (LOD) and quantification (LOQ) for determination of atrazine (ATR), propazine (PRO) and simazine (SIM). Separation was achieved with a mobile phase composition of 44:56 (v v-1) methanol:1.25 mM ammonium acetate buffer, pH 4.7, monolithic column and spectrophotometric detection at 238 nm. The values of LOD and LOQ were, respectively, 1.76 and 5.86 µg L-1 for ATR, 4.51 and 15 µg L-1 for PRO and 2.25 and 7.5 µg L-1 for SIM. The LOD values achieved with the employment of long optical path cell were lower than those recommended by US-EPA, which allows for drinking water, maximum concentration levels of 3 µg L-1 for ATR, 4 µg L-1 for SIM and 10 µg L-1 for PRO. Adsorption of SIM, PRO and ATR, as well as their metabolites desisopropylatrazine (DIA), desethylatrazine (DEA) and 2-hidroxyatrazine (HAT) on soil, humic acid and soil modified with humic acidic was studied. An on-line monitoring system was assembled, composed of a tangential filter and a peristaltic pump for circulation of the suspension. Kinetic studies were carried out in two steps, and in both, it was used a mix of compounds with initial concentration of 1,0 mg L-1 and a stepwise gradient elution for separation of the compounds using three mobile phases with compositions of 15 or 28, 40 and 50% (v v-1) methanol: 1.25 mM ammonium acetate buffer, pH 4.7. In the first step the contact time between triazines and adsorbents was 90 minutes. In a second study made only with soil, the contact time was 24 h. Data obtained in the first stage of the study was only fitted to pseudo-second order kinetic equation, which allowed one to estimate the values of the adsorbed mass of triazine per mass of adsorbent. Humic acid was the material with higher adsorptive capacity (from 1470 ± 43 µg g-1 for DIA to 2380 ± 50 µg g-1 for PRO). In soil, PRO exhibited the highest adsorption (26.5 ± 0.1 µg g-1). The presence of humic acid in the soil increased adsorption of ATR (19.4±0.7 to 23±2 µg g-1), HAT (10.9 ± 0.7 to 18 ± 2 µg g-1) and PRO (26.5 ± 0.7 to 29.8 ± 0.2 µg g-1), but decreased adsorption of SIM, not affecting DIA and DEA. In the study with contact time of 24 h, it was possible apply pseudo-first and pseudo-second order equations for SIM, ATR and PRO. The results confirmed the greatest adsorption of PRO, followed by ATR. HAT, SIM, DEA and DIA had low rates of adsorption on soil, the latter two showed a trend of desorption after 4 h of contact, having the greatest potential for leaching to water bodies near to the places of application.

A introdução de separações cromatográficas expandiu a aplicabilidade de sistemas de análises em fluxo. No entanto, a seletividade e sensibilidade de procedimentos são restritos devido à escassa disponibilidade de fases estacionárias que operam a baixas pressões. Sendo assim, foram desenvolvidos quatro procedimentos analíticos visando a melhoria destes aspectos. A primeira proposta explorou pioneiramente colunas de núcleo fundido em sistemas de análises por injeção em fluxo. A separação de metil, etil e propil parabenos foi selecionada com aplicação. As eficiências cromatográficas de quatro colunas (C18, RPamida, F5 e fenil-hexil) foram avaliadas criticamente. Acetonitrila e uma solução de ácido fosfórico pH 2,5 foram utilizadas como fase móvel. A fase RP-amida apresentou melhor desempenho com a separação dos três analitos em 8,0 min, com resoluções > 1,72, simetrias de pico < 1,66, LOD entre 0,12 e 0,39 mg L-1, resposta linear até 5,0 mg L-1 (r > 0,996) e CV para altura dos picos < 3,5 % (n=10). O procedimento foi aplicado à determinação de parabenos em produtos de cuidados pessoais e os resultados concordaram com o procedimento de referência a 95% de confiança. Um procedimento envolvendo o acoplamento de extração em fase sólida (SPE) a um sistema de cromatografia por injeção sequencial (SIC) foi proposto para pré-concentração e separação de oito sulfonamidas. A fase estacionária pentafluorofenilpropil foi selecionada após comparação crítica da eficiência apresentada por três colunas de núcleo fundido e duas colunas de fases monolíticas. Acetonitrila e tampão fosfato (pH 5,0) foram utilizados como fase. Fatores de enriquecimento de até 39,2 foram alcançados com volume de amostra de 500 ?L. O procedimento apresentou tempo de análise < 10,5 min, resoluções > 1,83 com simetrias de pico <= 1,52, LOD entre 4,9 e 27 ?g L-1, faixa de resposta linear entre 30,0 e 1000,0 ?g L-1 (r > 0,997) e CV da altura dos picos, 2,9% (n=6). Um procedimento empregando fase estacionária micelar foi desenvolvido para determinação de melamina em leite. A fase móvel foi composta por uma solução aquosa de dodecil sulfato de sódio (SDS) e 1-propanol (92,5:7,5 v/v). O procedimento de preparo de amostra foi implementado em linha pela diluição da amostra com SDS. Resposta linear foi observada entre 2,0 e 6,0 mg L-1 de melamina com LOD estimado em 0,6 mg L-1 e CV da altura dos picos de 2,9% (n=6). Os resultados para diferentes amostras de leite foram concordantes com aqueles obtidos pelo procedimento cromatográfico de referência em um nível de 95% de confiança. Uma estratégia envolvendo pré-concentração on-column de parabenos em um sistema SIC foi proposta. Resposta linear foi observada entre 0,25 e 1,00 ?g mL-1 (r >= 0,999) e LODs estimados entre 40 e 60 ng mL-1. Tempos de retenção e altura dos picos apresentaram CV < 2,1%. Fatores de enriquecimento entre 30,0 e 34,8 foram alcançados. As estratégias propostas são viáveis para melhoria de seletividade e sensibilidade de separações cromatográficas em sistemas de análises em fluxo, além de apresentarem vantagens frente a procedimentos análogos na literatura / The introduction of chromatographic separations expanded the applicability of flow systems. However, selectivity and sensitivity of the procedures are limited due the poor options of stationary phases available for low-pressure. Therefore, four procedures were developed aiming the improvement of these aspects. The first proposal exploited pioneered fused-core columns in a flow injection analysis system. The separation of methyl, ethyl and propel parabens was selected as an application. The chromatographic efficiency of four columns (C18, RP-amide, F5 and fenyl-hexyl) were crítically evaluated. Acetonitrile and a phosphoric acid solution at pH 2.5 were used as mobile phase at different proportions for each column. The RP-amide phase presented the best performance by separating the analytes in 8.0 min with resolution > 1.72, peak symmetry < 1.66, LOD between 0.12-0.39 mg L-1, linear response range up to 5.0 mg L-1 (r > 0.996) and coefficients of variation of peak heights < 3.5% (n=10). The procedure was applied to parabens determination in personal care products and the results agreed with the HPLC reference procedure at the 95% confidence level. A procedure coupling solid phase extraction (SPE) to a sequential injection chromatography (SIC) was proposed for preconcentration and separation of eight sulfonamides. The pentafluorophenylpropyl (F5) phase was selected after a critical comparison of the performance achieved by three fused-core columns and two monolithic columns. Acetonitrile and acetate buffer pH 5.0 were used as mobile phase. Enrichment factors up to 39.2 were achieved with a 500 ?L sample volume. The developed procedure showed analysis time < 10.5 min, resolutions > 1.83 with peak symmetry <= 1.52, LODs between 4.9 and 27 ?g L-1, linear response ranges from 30.0 to 1000.0 ?g L-1 (r > 0.997) and CV of peak heights < 2.9% (n=6). Micelar chromatography was for the first time exploited in SIC and the performance was demonstrated by determination of melamine in milk. Mobile phase was composed by a sodium dodecyl sulfate (SDS) solution and propanol (92.5:7.5). The sample pretreatment procedure was on-line implemented by dilution of the sample with SDS. A linear response was observed within 2.0 and 6.0 mg L-1 of melamine with a LOD estimated at 0.6 mg L-1 and coefficients of variation at 2.9% (n=6). Results for different milk samples agreed with those obtained by high performance liquid chromatography at the 95% confidence level. A procedure involved on-column preconcentration of parabens in a SIC system was based on the injection of relatively high volume of an aqueous sample in a reversed-phase column. After preconcentration, a suitable mobile phase was inserted to perform chromatographic separation (acetonitrile/phosphoric acid pH 2.5 (75:25, v/v)). A linear response was achieved from 0.25 to 1.00 ?g mL-1 (r > 0.999) and LOD estimated within 40 and 80 ng mL-1. Coefficients of variation for retention time and peak heights were below 2.1%. Enrichment factors within 30.0 and 34.8 were achieved. The proposed strategies are feasible for improving selectivity and sensitivity of chromatographic separations in flow analysis systems, besides having advantages compared to similar procedures in the literature

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-27T12:33:46Z No. of bitstreams: 1 fernandoantoniosimasvaz.pdf: 40063052 bytes, checksum: f272ddc4d930b7d243c50223436e02b2 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-13T13:00:49Z (GMT) No. of bitstreams: 1 fernandoantoniosimasvaz.pdf: 40063052 bytes, checksum: f272ddc4d930b7d243c50223436e02b2 (MD5) / Made available in DSpace on 2017-05-13T13:00:49Z (GMT). No. of bitstreams: 1 fernandoantoniosimasvaz.pdf: 40063052 bytes, checksum: f272ddc4d930b7d243c50223436e02b2 (MD5) Previous issue date: 2011-07-22 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Nesta tese é descrita a preparação de novas fases estacionárias monolíticas (FEM) polimerizadas por fotoiniciação, através do método sol-gel, em capilares de sílica fundida revestidos com poliacrilato, para aplicação em eletrocromatografia capilar (ECC). Dentre as principais técnicas de separação em Química Analítica, a ECC tem despertado grande interesse no meio acadêmico, pelo fato desta combinar as vantagens tanto da cromatografia a líquido de alta eficiência quanto da eletroforese capilar. Grande parte do desenvolvimento da ECC se deve ao uso das FEM, as quais são semelhantemente aplicadas em outras técnicas cromatográficas. Ao contrário do revestimento de poliimida, amplamente empregado, o revestimento de poliacrilato, transparente acima de 370 nm e à luz visível, facilita a visualização da solução de sol no interior do capilar, o que permite controlar a injeção desta e de outras soluções, bem como observar a formação in situ da FEM. Além disso, é possível que seja feita a polimerização fotoiniciada sem a necessidade de remoção do revestimento polimérico que protege a coluna. O objetivo central deste trabalho foi entender e aprimorar o processo de fabricação das FEM para aplicações em ECC. Para isso, foram feitas modificações da câmara fotorreatora homemade utilizada para a polimerização das FEM, como uma correção na faixa espectral de trabalho de 350 a 700 nm para 350 a 400 nm; e instalação de dispositivos de segurança tanto para o operador quanto para o sistema elétrico. Para que fosse alcançado um melhor controle de injeção de fases líquidas no interior de tubos com dimensões capilares, a construção de um dispositivo de alta pressurização (DAP) que forneceu, além da pressão, grande precisão foi indispensável. O DAP, além de simples, teve ótima relação custo-benefício, comparado a modelos comerciais. O preparo das FEM foi otimizado mediante auxílio de planejamento fatorial fracionário 24-1, onde se buscou analisar propriedades eletrocromatográficas frente diferentes proporções dos reagentes empregados e tempo de incidência de luz ultravioleta (UV). Este último fator não apresentou significância e foi desconsiderado, de forma que o planejamento fosse devidamente reduzido para um planejamento fatorial completo 23, o que possibilitou uma análise mais apurada dos efeitos significativos. O fator mais influente foi a proporção de porogênio (tolueno), sendo que a melhor condição obtida foi utilizando 80,0 % (v/v) de solução porogênica; 3,5 % (m/m) de fotoiniciador óxido de bis(2,4,6-trimetilbenzoil)-fenilfosfino (Irgacure 819); razão molar água/ metacriloxipropiltrimetoxisilano (MPTMS) igual a 4 e tempo de incidência de luz UV de 10 minutos. As características morfológicas, espectroscópicas e porosidade foram avaliadas através de microscopia eletrônica de varredura, infravermelho e porosimetria por adsorção de nitrogênio, respectivamente. As FEM foram testadas em ECC pela separação de hidrocarbonetos policíclicos aromáticos (naftaleno, acenafteno, fluoreno, fenantreno e antraceno) e alquilbenzenos (etilbenzeno, propilbenzeno, butilbenzeno e hexilbenzeno), todos compostos eletricamente neutros, diluídos em metanol (1 mmol L-1 cada), utilizando tiouréia como marcador de fluxo. Como fase móvel foi utilizada a mistura de acetato de amônio 16,7 mmol L-1 pH 7,0 (60 %) e acetonitrila (40 %). A voltagem aplicada foi -20 kV; a temperatura de análise foi 20 ºC; a injeção dos analitos foi -25 mbar por 5 s; e a detecção no UV foram nos comprimentos de onda de 220 nm e 250 nm. Foi utilizado o modo ECC-rápida, que consiste na inversão do sentido de análise e injeção de padrões pela extremidade curta do capilar. Este modo se mostrou muito mais rápido, repetitivo e eficiente do que o modo normal, fornecendo em pouco mais de 12 minutos de análise, mais de 51400 pratos/m de coluna e desvios padrão relativos em tempo de migração/retenção entre 0,09 e 3,3 % e em área de pico relativa entre 0,14 e 1,6 %. Os perfis de separação em ECC corroboraram com os resultados de porosidade e morfologia obtidos. / This thesis describes the preparation of new monolithic stationary phases (MSP) polymerized by photoinitiation through sol-gel approach in polyacrylate-coated fused silica capillary, for application in capillary electrochromatography (CEC). CEC has been concentrated much attention among the major separation techniques in analytical chemistry because it combines the advantages of both high performance liquid chromatography and capillary electrophoresis. Much of the CEC development is due to the use of MSP, which are similarly applied to other chromatographic techniques. Unlike polyimide-coating, widely used, the polyacrylate-coating, which is transparent above 370 nm and visible, enables the visualization of the sol solution within the capillary, allowing one to control the injection of sol and other solutions, in addition to observe the in situ formation of the MSP. Furthermore, it is possible to perform the photoinitiated polymerization without removing this polymeric coating that protects the capillary. The main purpose of this work was to comprehend and improve the fabrication process of MSP, for CEC applications. For this, some changes were set in the homemade photo reactor chamber, used for the MSP polymerization, like correction in the work range from 350 – 700 nm to 350 – 400 nm; and installation of security devices for both operator and electric system safeties. For better control of liquid phases injection within tubes with capillary dimensions, the build of a high-pressure device (HPD) that provides a great precision, in addition to the high-pressure, was essential. HPD is simpler and relatively cheaper when compared to commercial models. The preparation of the MSP has been optimized through assistance of a 24-1 fractional factorial design, with the intention to investigate electrochromatographic properties with different amounts of employed reagents and ultraviolet (UV) light incidence time. The later factor did not show significance and was unconsidered, making the design possible to be reduced to a 23 complete factorial design, which allowed analyzing the significant effects accurately. The most influent factor was the porogen (toluene) proportion, and the best condition was obtained using 80.0 % (v/v) of porogenic solution; 3.5 % of photoinitiator bis(2,4,6 trimetylbenzoyl)-phenylphosphine oxide (Irgacure 819); water to metacryloxypropyltrimethoxysilane (MPTMS) molar ratio equal to 4 and 10 minutes of UV light incidence time. The MSP morphological, spectroscopic characteristics and porosity were evaluated through scanning electron microscopy, infrared spectroscopy and nitrogen adsorption porosimetry, respectively. The MSP has been tested in CEC through the separation of polycyclic aromatic hydrocarbons (naphthalene, acenaphthene, fluorene, phenanthrene and anthracene) and alkylbenzenes (ethylbenzene, propylbenzene, butylbenzene and hexylbenzene), which are electrically neutral compounds, after dilution in methanol (1 mmol L-1 each), using thiourea as the flow marker. As mobile phase a mixture of ammonium acetate 16.7 mmol L-1 at pH 7.0 (60.0 %) and acetonitrile (40.0 %) was used. The applied voltage was -20 kV, the temperature of analysis was 20 °C, the analyte injection was -25 mbar for 5 s, and UV detection was done at 220 and 250 nm. A fast-CEC mode, which consists to reverse the analysis direction and to introduce the analyte by capillary short-end injection, was performed. This mode was much more fast, repetitive and efficient than the normal one, providing in a little more than 12 minutes over than 51400 plates per meter of column and relative standard deviations ranging from 0.09 to 3.3 % for migration/retention time and from 0.14 to 1.6 % for relative peak area. The separation profiles in CEC corroborate with the porosity and morphology results.

The finite element method (FEM) is a widely-used numerical tool in the fields of structural dynamics, acoustics and electromagnetics. In this work, our goal is to develop robust FEM strategies for solving problems in the areas of acoustics, structures and electromagnetics, and then extend these strategies to solve multi-physics problems such as magnetohydrodynamics and structural acoustics. We now briefly describe the finite element strategies developed in each of the above domains. In the structural domain, we show that the trapezoidal rule, which is a special case of the Newmark family of algorithms, conserves linear and angular momenta and energy in the case of undamped linear elastodynamics problems, and an ‘energy-like measure’ in the case of undamped acoustic problems. These conservation properties, thus, provide a rational basis for using this algorithm. In linear elastodynamics variants of the trapezoidal rule that incorporate ‘high-frequency’ dissipation are often used, since the higher frequencies, which are not approximated properly by the standard displacement-based approach, often result in unphysical behavior. Instead of modifying the trapezoidal algorithm, we propose using a hybrid FEM framework for constructing the stiffness matrix. Hybrid finite elements, which are based on a two-field variational formulation involving displacement and stresses, are known to approximate the eigenvalues much more accurately than the standard displacement-based approach, thereby either bypassing or reducing the need for high-frequency dissipation. We show this by means of several examples, where we compare the numerical solutions obtained using the displacementbased and hybrid approaches against analytical solutions. We also present a monolithic formulation for the solution of structural acoustic problems based on the hybrid finite element approach. In the area of electromagnetics, since our goal is to ultimately couple the electromagnetic analysis with structural or fluid variables in a ‘monolithic’ framework, we focus on developing nodal finite elements rather than using ‘edge elements’. It is well-known that conventional nodal finite elements can give rise to spurious solutions, and that they cannot capture singularities when the domains are nonconvex and have sharp corners. The commonly used remedies of either adding a penalty term or using a potential formulation are unable to address these problems satisfactorily. In order to overcome this problem, we first develop several mixed finite elements in two and three dimensions which predict the eigenfrequencies (including their multiplicities) accurately, even for non-convex domains. In this proposed formulation, no ad-hoc terms are added as in the penalty formulation, and the improvement is achieved purely by an appropriate choice of the finite element spaces for the different variables. For inhomogeneous domains, ‘double noding’ is used to enforce the appropriate continuity conditions at an interface. Although the developed mixed FEM works very accurately for all 2D geometries and regular Cartesian 3D geometries, it has so far not yielded success for curved 3D geometries. Therefore, for 3D harmonic and transient analysis problems, we propose and use a modified form of the potential formulation that overcomes the disadvantages of the standard potential method, especially on non-convex domains. Electromagnetic radiation and scattering in an exterior domain traditionally involved imposing a suitable absorbing boundary condition (ABC) on the truncation boundary of the numerical domain to inhibit reflection from it. In this work, based on the Wilcox asymptotic expansion of the electric far-field, we propose an amplitude formulation within the framework of the nodal FEM, whereby the highly oscillatory radial part of the field is separated out a-priori so that the standard Lagrange interpolation functions have to capture a relatively gently varying function. Since these elements can be used in the immediate vicinity of the radiator or scatterer (with few exceptions which we enumerate), it is more effective compared to methods of imposing ABCs, especially for high-frequency problems. We show the effectiveness of the proposed formulation on a wide variety of radiation and scattering problems involving both conducting and dielectric bodies, and involving both convex and non-convex domains with sharp corners. The Time Domain Finite Element Method (TDFEM) has been used extensively to solve transient electromagnetic radiation and scattering problems. Although conservation of energy in electromagnetics is well-known, we show in this work that there are additional quantities that are also conserved in the absence of loading. We then show that the developed time-stepping strategy (which is closely related to the trapezoidal rule) mimics these continuum conservation properties either exactly or to a very good approximation. Thus, the developed numerical strategy can be said to be ‘unconditionally stable’ (from an energy perspective) allowing the use of arbitrarily large time-steps. We demonstrate the high accuracy and robustness of the developed method for solving both interior and exterior domain radiation problems, and for finding the scattered field from conducting and dielectric bodies. In the field of magneto-hydrodynamics, we develop a monolithic strategy based on a continuous velocity-pressure formulation that is known to satisfy the Babuska-Brezzi (BB) conditions. The magnetic field is interpolated in the same way as the velocity field, and the entire formulation is within a nodal finite element framework. Both transient and steady-state formulations are developed for two- and three-dimensional geometries. An exact linearization of the monolithic strategy ensures that rapid (quadratic) convergence is achieved within each time (or load) step, while the stable nature of the interpolations used ensure that no instabilities arise in the solution. Good agreement with analytical solutions, even with the use of very coarse meshes, shows the efficacy of the developed formulation.

Dans un contexte où les limites intrinsèques des matériaux classiques de l’industrie CMOS sont en passe d’être atteintes du fait de la forte miniaturisation des composants, le développement de la microélectronique requiert la définition de nouvelles solutions pour combiner sur un même substrat (le silicium) des matériaux différents aux propriétés physiques variées. Ceci devrait permettre d’intégrer sur silicium des fonctionnalités nouvelles. Parmi les matériaux d’intérêt, les oxydes fonctionnels de la famille des pérovskites offrent une large gamme de propriétés et attirent donc une attention particulière. D’autre part, la recherche se porte aussi sur les semi-conducteurs de la classe III-V et le Ge pour leurs propriétés optiques ou de transport de charges. Cependant, la grande hétérogénéité chimique et cristallographique entre ces matériaux rend leur association sur silicium par voie épitaxiale particulièrement délicate. Dans ce contexte, ce travail de thèse consiste en une étude approfondie de l’interface Ge sur SrTiO3et des mécanismes à l’origine des modes d’accommodation et de croissance du semi-conducteur sur le substrat pérovskite. Les échantillons, fabriqués par épitaxie par jets moléculaires, ont été étudiés par caractérisations in situ, au synchrotron, diffraction de rayons X en incidence rasante et spectroscopie de photoémission. Des images de microscopie électronique en transmission sont venues compléter cette étude. La combinaison de ces résultats a permis de comprendre et de décrire deux aspects spécifiques des systèmes III-V et Ge sur SrTiO3. Le mode de croissance Volmer-Weber et la compétition entre les orientations cristallines(001) et (111) du Ge sont décrits dans une première partie. La relation d’épitaxie de Ge/SrTiO3est identifiée et l’influence des énergies d’adhésion et de surface libre du semi-conducteur sur sa croissance est élucidée. Dans une deuxième partie, le mode d’accommodation du Ge est plus spécifiquement étudié. La mise en place d’un réseau de dislocations d’interface est observée expérimentalement et analysée à l’aide d’un modèle numérique. Ce travail de thèse a permis de discuter de l’interface d’un système épitaxié très hétérogène et il ouvre des perspectives intéressantes, liées aux spécificités de l’accommodation aux interfaces semi-conducteurs/oxydes, pour l’intégration monolithique de Ge et de III-V sur des substrats d’oxydes/Si. / With the recent developments of the microelectronic industry, the intrinsic limits of the classical CMOS materials are being reached because of the strong miniaturization. Thus, the microelectronic industry is waiting for new solutions for combining, on the same substrate (silicon), different materials with various physical properties in the framework of integrating new functionalities on silicon. Research is now focusing on perovskite oxides because of the very wide range of properties they are offering (electronic, magnetic, etc.), but also on III-V semiconductors for the development of integrated photonic devices and on Ge for its electronic transport properties. However, combining these materials is challenging due to their strong chemical and crystallographic heterogeneity. Thus, this thesis focuses on the Ge/SrTiO3 system. The accommodation mode and growth mechanism have been studied by in situ, synchrotron-based, characterization methods like grazing incidence X-ray scattering and X-ray photoemission spectroscopy. The samples were prepared by molecular beam epitaxy. Transmission electron microscopy images complemented the study. The combination of these results have allowed for highlighting two specificities of the III-V or Ge/SrTiO3epitaxial systems. In a first chapter, the Volmer-Weber growth mode and a competition between (001)and (111)-oriented Ge islands is described. Epitaxial relationship between Ge and SrTiO3, chemical bonds at the interface and influence of adhesion and surface energies on the growth mode are described. In a second part, the specific accommodation mode of the Ge/SrTiO3 interface is studied. The development of a misfit dislocation network during the growth is experimentally observed and analyzed on the basis of a numerical model of the interface. This work provides state of the art understanding of the interface of weakly bonded epitaxial systems and opens interesting perspectives, especially related to the accommodation mode of semiconductors/oxides interfaces, for the monolithic integration of III-V or Ge on oxides/Si substrates.

Micromagnetics is a continuum mechanics theory of magnetic materials widely used in industry and academia. In this thesis we describe a complete numerical method, with a number of novel components, for the computational solution of dynamic micromagnetic problems by solving the Landau-Lifshitz-Gilbert (LLG) equation. In particular we focus on the use of the implicit midpoint rule (IMR), a time integration scheme which conserves several important properties of the LLG equation. We use the finite element method for spatial discretisation, and use nodal quadrature schemes to retain the conservation properties of IMR despite the weak-form approach. We introduce a novel, generally-applicable adaptive time step selection algorithm for the IMR. The resulting scheme selects error-appropriate time steps for a variety of problems, including the semi-discretised LLG equation. We also show that it retains the conservation properties of the fixed step IMR for the LLG equation. We demonstrate how hybrid FEM/BEM magnetostatic calculations can be coupled to the LLG equation in a monolithic manner. This allows the coupled solver to maintain all properties of the standard time integration scheme, in particular stability properties and the energy conservation property of IMR. We also develop a preconditioned Krylov solver for the coupled system which can efficiently solve the monolithic system provided that an effective preconditioner for the LLG sub-problem is available. Finally we investigate the effect of the spatial discretisation on the comparative effectiveness of implicit and explicit time integration schemes (i.e. the stiffness). We find that explicit methods are more efficient for simple problems, but for the fine spatial discretisations required in a number of more complex cases implicit schemes become orders of magnitude more efficient.

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