Made available in DSpace on 2014-12-17T14:06:58Z (GMT). No. of bitstreams: 1 GilbertoM_DISSERT_PARCIAL.pdf: 494543 bytes, checksum: da2d1ceb188b373977eacdb9f150846c (MD5) Previous issue date: 2011-01-31 / In this work, was studied the formation of a composite of the refractory metal niobium with copper, through the process of high-energy milling and liquid phase sintering. The HEM can be used to synthesize composite powders with high homogeneity and fine size particle distribution. It may also produce the solid solubility in immiscible systems such as Nb-Cu, or extend the solubility of systems with limited solubility. Therefore, in the immiscible system Cu-Nb, the high-energy milling was successfully used to obtain the composite powder particles. Initially, the formation of composite particles during the HEM and the effect of preparation technique on the microstructure of the material was evaluated. Four loads of Nb and Cu powders containing 20%wt Cu were synthesized by MAE in a planetary type ball mill under different periods of grinding. The influence of grinding time on the metal particles is evaluated during the process by the withdrawal of samples at intermediate times of milling. After compaction under different forces, the samples were sintered in a vacuum furnace. The liquid phase sintering of these samples prepared by HEM produced a homogeneous and fine grained. The composite particles forming the sintered samples are the addition of a hard phase (Nb) with a high melting point, and a ductile phase (Cu) with low melting point and high thermal and electrical conductivities. Based on these properties, the Nb-Cu system is a potential material for many applications, such as electrical contacts, welding electrodes, coils for generating high magnetic fields, heat sinks and microwave absorbers, which are coupled to electronic devices. The characterization techniques used in this study, were laser granulometry, used to evaluate the homogeneity and particle size, and the X-ray diffraction, in the phase identification and to analyze the crystalline structure of the powders during milling. The morphology and dispersion of the phases in the composite powder particles, as well the microstructures of the sintered samples, were observed by scanning electron microscopy (SEM). Subsequently, the sintered samples are evaluated for density and densification. And finally, they were characterized by techniques of measuring the electrical conductivity and microhardness, whose properties are analyzed as a function of the parameters for obtaining the composite / Neste trabalho, foi estudada a forma??o de um comp?sito do metal refrat?rio ni?bio com o cobre, atrav?s do processo de moagem de alta energia e sinteriza??o por fase l?quida. A MAE pode ser usada para sintetizar p?s comp?sitos com alta homogeneidade e fina distribui??o de tamanho de part?culas. Ela tamb?m pode produzir a solubilidade s?lida em sistemas imisc?veis como o Nb-Cu, ou, estender a solubilidade de sistemas com limitada solubilidade. Portanto, no sistema imisc?vel Nb-Cu, a moagem de alta energia foi utilizada com sucesso para a obten??o das part?culas do p? comp?sito. Inicialmente a forma??o das part?culas comp?sitas durante a MAE e o efeito dessa t?cnica de prepara??o na microestrutura do material foi avaliada. Quatro cargas de p?s de Nb e Cu contendo 20% em massa de Cu foram sintetizados por MAE em um moinho de bolas tipo planet?rio, sob diferentes per?odos de moagem. A influ?ncia do tempo de moagem nas part?culas met?licas ? avaliada no decorrer do processo, atrav?s da retirada de amostras em tempos parciais da moagem. Ap?s a compacta??o sob diferentes for?as, as amostras foram sinterizadas em um forno ? v?cuo. A sinteriza??o por fase l?quida destas amostras preparadas por MAE produziu uma estrutura homog?nea e com granula??o refinada. As part?culas comp?sitas que formam as amostras sinterizadas, s?o a jun??o de uma fase dura (Nb) com alto ponto de fus?o, e uma fase d?ctil (Cu) de baixo ponto de fus?o e de elevadas condutividades t?rmica e el?trica. Com base nestas propriedades, o sistema Nb-Cu ? um material em potencial para in?meras aplica??es, como contatos el?tricos, eletrodos de solda, bobinas para gera??o de altos campos magn?ticos, dissipadores de calor e absorvedores de microondas, que s?o acoplados a dispositivos eletr?nicos. As t?cnicas de caracteriza??o utilizadas neste estudo, foram a granulometria ? laser para avaliar a homogeneidade e o tamanho das part?culas, e a difra??o de raios-X, na identifica??o das fases e an?lise da estrutura cristalina dos p?s durante a moagem. J? a morfologia e a dispers?o das fases nas part?culas do p? comp?sito, assim como as microestruturas das amostras sinterizadas, foram observadas atrav?s de microscopia eletr?nica de varredura (MEV). Posteriormente, as amostras sinterizadas foram avaliadas quanto ? densidade e densifica??o. E, finalmente, foram caracterizadas atrav?s de t?cnicas de medi??o da condutividade el?trica e microdureza Vickers, cujas propriedades s?o analisadas em fun??o dos par?metros de obten??o do comp?sito

Made available in DSpace on 2014-12-17T14:16:38Z (GMT). No. of bitstreams: 1 RandRM.pdf: 491733 bytes, checksum: 93fd5e529dea72386495c9d4b3d94d8f (MD5) Previous issue date: 2006-08-18 / Hormone therapy is an important tool in the treatment of breast cancer and tamoxifen represents one of the most important drugs used in this type of treatment. Recently other drugs based on the inhibition of aromatase had been developed, this enzyme is responsible for the synthesis of estrogenic esteroids from the androgenic ones. The objective of this study would be the development of a quantitative cytological model of murine estral analysis that allowed the characterization of different hormone drugs effect over vaginal epithelium. The technique of monochromatic staining with Evans blue (C.I. 23860) showed to be efficient in the qualitative and quantitative classification of the cycle. It had been observed differences in the cytological standard of animals submitted to the studied drugs; tamoxifen presented a widening of phases of lesser maturation (diestrais), while anastrozole and exemestane increased the duration of the phases of larger maturation (estrais). The data were analysed through a cubical non linear regression (spline) which allowed a better characterization of the drugs, suggesting a proper cytological profile to the antagonism of the estrogen receptor (tamoxifen), aromatase competition (anastrozole) and inhibition of the enzyme (exemestane) / A hormonioterapia ? um importante recurso no tratamento do c?ncer de mama e o tamoxifeno representa o f?rmaco mais empregado neste tipo de tratamento. Recentemente foram desenvolvidos outros f?rmacos baseados na inibi??o da aromatase, enzima respons?vel pela s?ntese de ester?ides estrog?nicos a partir de androg?nios. O objetivo deste estudo seria o desenvolvimento de um modelo citol?gico quantitativo de analise estral murina que permitisse a caracteriza??o dos efeitos farmacol?gicos de diferentes hormonioter?picos sob epit?lio vaginal. A t?cnica de colora??o monocrom?tica com Azul de Evans (C.I. 23860) mostrou-se eficaz na classifica??o qualitativa e quantitativa do ciclo. Observou-se diferen?as no padr?o citol?gico de animais submetidos aos f?rmacos em estudo; onde o tamoxifeno apresentou alargamento das fases de menor matura??o (diestrais), enquanto que o anastrozol e o exemestano incrementaram a dura??o das fases de maior matura??o (estrais). O tratamento dos dados atrav?s de uma regress?o n?o linear por spline c?bica permitiu melhor caracteriza??o dos f?rmacos, sugerindo um perfil citol?gico pr?prio ao antagonismo do receptor de estr?geno (tamoxifeno), competi??o da aromatase (anastrozol) e inibi??o da enzima (exemestano)