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Orientador: João Batista Fogagnolo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-27T20:13:02Z (GMT). No. of bitstreams: 1 RodriguezPerez_JessicaMarlena_M.pdf: 4283527 bytes, checksum: 428a287377aaab009ef368ca3005561b (MD5) Previous issue date: 2015 / Resumo: O interesse em ligas do sistema titânio-nióbio para aplicações ortopédicas se deve à excelente resistência mecânica e biocompatibilidade, sendo que o módulo de elasticidade pode ser controlado pelo teor de nióbio. Existem diversos processos que podem tornar estas ligas adequadas para uso como biomaterial e que resultam em diferentes fases com diferentes propriedades. O presente trabalho teve como objetivo modificar peças sinterizadas de ligas do sistema titânio-nióbio por refusão superficial por laser. Foram utilizadas ligas com diferentes composições químicas, variando-se o teor de nióbio de 5 a 45% em peso. Foram analisados os efeitos da variação dos parâmetros de processamento, potência e velocidade de deslocamento do feixe laser, sobre a morfologia de cordões isolados. Foram obtidas camadas contínuas de refusão por sobreposição de cordões de isolados. As amostras sinterizadas com teores de nióbio entre 5 e 20% apresentaram as fases ? e ?. A amostra com teor de nióbio de 25% e maiores apresentam regiões com fase ? completamente estabilizada e regiões com as fases ? e ? devido à heterogeneidade química na distribuição de nióbio. A amostra com teor de nióbio de 45% apresenta apenas a fase ?, porém também se observa nessa amostra a heterogeneidade na distribuição de nióbio. Constatou-se que a potência do feixe de laser é o parâmetro de maior influência na morfologia e dimensões da zona fundida dos cordões isolados. Dependendo do teor de nióbio, diferentes fases são formadas nas camadas continuas de refusão. Para teor de nióbio de 5%, obtém-se a fase martensítica ?', de estrutura hexagonal. Para teor de nióbio de 15%, obtém-se majoritariamente a fase ?' com presença da fase martensítica ortorrômbica ?''. Para teor de nióbio de 25%, obtém-se a fase ?'', com pequena fração de fase ?. Para teor de nióbio de 35 e 45%, obtém-se a fase ? em toda a zona fundida e a fase ?'' na zona termicamente afetada. Tanto os cordões isolados como as camadas refundidas das amostras com teores de 15, 25, 35 e 45% em peso de nióbio apresentaram heterogeneidade química devido à microssegregação de soluto durante a solidificação. Os valores de módulo de elasticidade medidos por nanoindentação foram decrescentes para aumentos da quantidade de nióbio, tanto nas zonas modificadas pelo laser quanto no substrato sinterizado. Os valores de nanodureza mantiveram-se constantes, dentro da variação estatística dos resultados / Abstract: The interest in alloys of the titanium-niobium system for orthopedic applications is due to their excellent mechanical resistance and biocompability, as the elastic modulus may be controlled by niobium content. There are several processes that can make those alloys adequate to be used as biomaterials and that result in different metallic phases with different properties. The objective of this study was to modify, by laser surface remelting, sintered parts of alloys from the titanium-niobium system. Alloys with different chemical compositions were used; the niobium content varied from 5 to 45wt%. The effects of the variation of processing parameters (laser beam power and scan speed) on the morphology of the isolated tracks were analyzed. Continuous remelting layers were obtained by overlapping isolated tracks. The sintered samples with niobium content between 5 and 20% exhibited both ? and ? phases. The sample with a niobium content of 25% or more had regions of completely stabilized ? phase and regions of ? and ? phases due to the chemical heterogeneity in the niobium distribution. The sample with a 45% niobium content showed only the ? phase, but heterogeneity in the niobium distribution is also seen. It was found that the laser beam power is the parameter that most influences the morphology and dimensions of the molten area of isolated tracks. Depending on the niobium content, different phases are formed in the continuous remelting layers. For a niobium content of 5%, the martensitic ?' phase of hexagonal structure is obtained. For a niobium content of 15%, the ?' phase is mostly obtained, with the presence of orthorhombic, martensitic ?'' phase. For a niobium content of 25%, the ?'' phase, with a small fraction of ? phase, is obtained. For niobium contents of 35 and 45%, ? phase throughout the molten area and ?'' phase in the heat affected zone are obtained. Both the isolated tracks and the continuous remelting layers on the samples with niobium weight contents of 15,25,35 and 45wt% presented chemical heterogeneity due to solute microsegregation during solidification. The values of elastic modulus measured by nanoindentation decreased as the niobium content increased, both in the laser modified zones and in the sintered substrates. The values of nanohardness remained constant within the results' statistical variation / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

This thesis relates a technique for increasing the optical strength of NaCl and KCl single-crystal samples. The 1.06-μm pulsed laser damage thresholds were increased by factors as large as 4.6 for a bulk NaCl single-crystal sample. The bulk laser damage breakdown threshold (LDBT) of the crystal was measured prior to and after heat treatment at 800*C using a Nd:YAG laser operating at 1.06 μm. Bulk and surface LDBTs were also studied on samples annealed at 400° C. These samples showed differences in damage morphology on both cleaved and polished surfaces, and the cleaved surfaces had improved damage thresholds. However, neither the polished surfaces nor the bulk showed improved threshold at the lower annealing temperature.

Thesis (Elec.E)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 172-176. / by Chon Meng Wong. / Elec.E

This thesis presents studies on a novel ‘meta-material’ as a potential candidate to replace the traditional Electro-Optic crystals (GaP, ZnTe) used in ultrashort bunch monitors for electron/positron accelerators. This study is aimed at showing the linear and non-linear optical properties of such materials, and creating a toolbox for both optical characterisation and manipulation of their properties using an ultra-short pulsed laser. The material studied throughout this thesis is a composite of silver nanoparticles (a “nanocomposite”) embedded within soda-lime glass. The Surface Plasmon Resonance (SPR) is a feature of these particles that is responsible for its unique optical properties. It is shown in this work how SPR is utilised for shape modification of silver nanoparticles with the use of a ps- pulsed laser with various laser beam polarisations. The impact of linear polarisation irradiation is investigated. It is found that multipulse irradiation has the effect of elongating nanoparticles to form prolate spheroids, which results in a dichroic effect on the composite as a whole, caused by the anisotropic SPR band shift. It is also shown that changing the laser polarisation from linear to radial and/or azimuthal changes the character of the reshaped nanoparticles. It was observed that a localised change of ellipsoid orientation is achieved, resulting in a non-directionally-dependent SPR band shift. Second Harmonic Generation (SHG) has been observed from reshaped nanoparticles embedded in soda-lime glass. A comparison of the effect was made between ps-pulsed reshaped, fs-pulsed reshaped and mechanically stretched samples containing silver nanoparticles. Multiphoton Absorption Induced Luminescence (MAIL) was observed along with the SHG and characterised for the various laser polarisation components. The dependence of the aforementioned effects on the elongated nanoparticle aspect ratio was shown to have a great impact. A novel method for reshaped nanoparticles characterisation is presented. It is based on the laser-induced SHG and MAIL signal and is proved to give a precise measurement of the nanoparticle shape and orientation. Frequency Resolved Optical Gating (FROG) measurement of a fs-pulse is measured with great accuracy, in the case where the BBO nonlinear crystal is replaced by the reshaped nanoparticle composite. This was demonstrated to be caused by the anisotropic SHG of the ellipsoidal nanoparticles. Preliminary THz based measurements were performed as a part of a feasibility study of the application of these composites in the EO-based detection of ultrashort electron bunches. Future work is suggested in order to achieve more efficient EO detection.

Graduation date: 1993

Two-dimensional thermal, mechanical and optical simulations are carried out to investigate the effect of Nd3+ concentration on thermal, mechanical and optical behavior of Nd:YAG ceramic laser materials under continuous wave laser operation. In the analyses, rods are pumped longitudinally with laser diodes, in three, six, nine and twelve fold structures. Rods having diameters of 3 and 6 mm are pumped with 808 nm and 885 nm sources separately having Nd+3 concentrations of 0.6, 1, 2, 3, 4 and 6 at. %. Total absorbed pump power are kept constant for all rods. Absorbed pump power distribution are obtained for each rod using ray tracing method and Beer&amp / #8217 / s Law. In the analysis, temperature dependent material properties are incorporated. Nonlinear numerical solutions of thermal and stress equations have been performed. Temperature and stress results are obtained to investigate the effect of Nd concentration on the optical properties of ceramic YAG laser material. Analysis results reveal that, increase in Nd3+ concentration of YAG ceramic laser material, decreases the temperature and stress developed during optical pumping. Rods pumped with 808 nm source have large temperature and stress values compared to 885 nm pumped ones. Optical path difference (OPD) of each ray passed trough the material is calculated using thermal and elastic strain results together with photo-elastic constants of Nd:YAG material. Focal length and depolarization of each rod is calculated numerically from OPD results. Focal length of each rod is found to increase, in contrary depolarization is found to decrease with increase in the dopant concentration.

Facilement excitable au moyen de diode InGaAs, l’ion Ytterbium trivalent présenteune émission infrarouge intéressante pour des applications laser. Les matériaux étudiés sontnombreux. Parmi eux, les borates sont des composés stables, transparents dans l’UV et présentant un seuil élevé au dommage. Ils sont par conséquent des bons candidats pour desapplications optiques. D’un point de vue structural, ils présentent une diversité de sitesd’accueil pour la terre rare ce qui permet de moduler les émissions obtenues en fonction de lacomposition.Nous avons mené une étude d’élaboration et de caractérisation sur un borate (à fusioncongruente) et deux oxyborates (à fusion non congruente) de composition : Li6Ln(BO3)3 ;LiGd6O5(BO3)3 ; Na3La9O3(BO3)8.Les différentes croissances cristallines, par la méthode Czochralski ou par la méthodedu flux, nous ont permis d’obtenir des cristaux de taille centimétrique comportant de largeszones transparentes, utiles pour les tests en cavité laser. L’étude spectroscopique de l’ionytterbium nous a permis d’évaluer l’éclatement des niveaux d’énergie et de localiser les ionsterres rares dans ces matrices. Différentes caractérisations thermiques, mécaniques et optiquesont aussi été réalisées sur les cristaux afin de pouvoir estimer les paramètres laser.Finalement, de premiers tests lasers ont été réalisés et ont montré la potentialité de cesmatériaux en tant que matériaux amplificateurs. / By the mean of InGaAs diode, trivalent ytterbium ions can give rise to an interestinginfrared emission for laser applications. Numerous compounds are in study. Among them,borates are stable, UV-transparent compounds and they have a high damage threshold. Thusthey are good candidates for optical applications. From a structural point of view, they exhibita diversity of host sites for the rare earth which allows to modulate emission withcomposition.We carry out an elaboration and characterization study on a borate and two oxyboratecompounds of formula Li6Ln(BO3)3 ; LiGd6O5(BO3)3 ; Na3La9O3(BO3)8.Crystal growth, by Czochralski or flux method depending on the meltingcharacteristic, enable us to obtain centimetric sized crystals with large transparent areas.Ytterbium ion spectroscopy study enables us to estimate energy levels splitting and to locaterare earth ions in these matrices. Several thermal, mechanical and optical characterizations were also performed on the crystals to estimate laser parameters. Finally, first laser tests werecarried out and have shown the potentiality of these materials as amplifier media.

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Made available in DSpace on 2014-10-09T12:41:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:03Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:08/10721-9