Adesivos de frasco único, tanto auto-condicionantes como condicione-e-lave, são misturas complexas de monômeros resinosos hidrofílicos e hidrofóbicos dissolvidos em combinações de água/solvente.Embora a inclusão de monômeros hidrofílicos tenha conseguido altas forças de adesão imediata, estudos têm mostrado que a interface resina-dentina têm se tornado muito mais fraca através do tempo. Nesse estudo através da microtração, avaliamos a resistência adesiva de 4 sistemas adesivos e através da espectroscopia micro-Raman analisamos quantitativamente a camada híbrida formada por esses adesivos. Para a microtração, os fatores de variação foram 2: o tipo de adesivo (AdperScotchbondMulti-Purpose, AdperSingle Bond 2, Adper SE Plus, AdperEasyOne), e o período de armazenamento, em 3 níveis (1 dia, 30 dias, 180 dias), totalizando 12 níveis de variação. As unidades experimentais foram confeccionadas sobre 120 superfícies de dentina de terceiros molares humanos hígidos e não irrompidos (n= 10).Para análise estatística foi utilizado o teste paramétrico de análise de variância ANOVA e o teste de múltipla comparação de Games Howell.Para a espectroscopia micro-Raman foram utilizados 3 dentes para cada sistema adesivo, totalizando 12 dentes (n=3).Os espectros Raman dos espécimes foram registrados num espectrômetro Micro-Raman RENISHAW InVia com excitação em 785 nm (laser de diodo, RENISHAW) acoplado a um microscópio LEICA DM2500M, com estágio motorizado (x;y;z)RENISHAW MS 20 EncodedStage com resoluções lateral e axial de 100 nm e 1 m. Os adesivos condicione-e-lave ScotchbondMulti-Purpose e SingleBonddesse estudo apresentaram os maiores valores de resistência adesiva, apresentando valores dentro de uma faixa de 44,36 a 50,66 MPa, enquanto que os adesivos AdperSE e Easy One apresentaram valores de 17,97 a 24,60 MPa. O adesivo que apresentou os maiores valores de resistência adesiva foi o ScotchbondMulti-Purpose e o que teve o pior desempenho foi o adesivo Easy One. Todos os adesivos apresentaram queda significativa de resistência de união após 30 e 180 dias. Na análise micro- Raman, o adesivo ScotchbondMulti-Purpose mostrou-se mais homogêneo e com valores de penetração do adesivo semelhantes aos do Single Bond e do Easy One. O adesivo SE Plus apresentou a menor penetração do adesivo e a camada híbrida mais fina. Concluímos neste trabalho que avaliando 4 diferentes tipos de adesivos de uma mesma marca, existe uma relação negativa entre as estratégias de adesão (diminuição do número de passos e frascos) e a resistência de união e a qualidade da camada híbrida. / One-bottle adhesives, both self-etching as etch-and-rinse, are complex mixtures of hydrophilic and hydrophobic monomers resin combinations dissolved in water / solvent. Although the inclusion of hydrophilic monomers has achieved high immediate adhesion forces, studies have shown that dentin-resin interface have become much weaker over time. In this study, bond strength of four adhesive systems was evaluated bymicrotensile test and quantitative analyze ofthe hybrid layer was obtained by micro-Raman spectroscopy. For microtensile test, the factors of variation were 2: the type of adhesive (AdperScotchbondMulti-Purpose, AdperSingle Bond 2, Adper SE Plus, AdperEasy One), and the period of storage at 3 levels (1 day, 30 days, 180 days), totaling 12 levels of variation. The experimental units were made on 120 dentin surfaces of intact humanunerupted third molars (n = 10). The parametric analysis of variance ANOVA and multiple comparison Games Howell was used for statistical analysis. For micro-Raman spectroscopy were used three teeth for each adhesive system, with a total of 12 teeth (n = 3). Raman spectra of the samples were recorded on a Micro-Raman spectrometer RENISHAW invia with 785 nm excitation (laser diode, RENISHAW) coupled to a microscope LEICA DM2500M with motorized stage (x, y, z) RENISHAW MS 20 EncodedStage with lateral and axial resolutionof 100 nm and 1 microns. Etch-and-rinse adhesives ScotchbondMulti-Purposeand SingleBond of this study showed the highest bond strength values, with values within a range from 44.36 to 50.66 MPa, whereas the self-etch adhesives SE Plusand Easy One had values of 17.97 to 24.60 MPa. The adhesive that showed the highest bond strength was ScotchbondMulti-Purpose and the worst performance was fromEasy One.All adhesives showed a significant decrease in bond strength after 30 and 180 days. In micro-Raman analysis, the ScotchbondMulti-Purpose was more homogeneous and had penetration values similar to those of the adhesive Single Bond and Easy One. The SE Plus had the lowest penetration of the adhesive and the thinner hybrid layer. We conclude that evaluating 4 different types of adhesives of the same brand, there is a negative relationship between the strategies of adhesion (decreasing the number of steps and bottles) and bond strength and quality of the hybrid layer.

Adesivos de frasco único, tanto auto-condicionantes como condicione-e-lave, são misturas complexas de monômeros resinosos hidrofílicos e hidrofóbicos dissolvidos em combinações de água/solvente.Embora a inclusão de monômeros hidrofílicos tenha conseguido altas forças de adesão imediata, estudos têm mostrado que a interface resina-dentina têm se tornado muito mais fraca através do tempo. Nesse estudo através da microtração, avaliamos a resistência adesiva de 4 sistemas adesivos e através da espectroscopia micro-Raman analisamos quantitativamente a camada híbrida formada por esses adesivos. Para a microtração, os fatores de variação foram 2: o tipo de adesivo (AdperScotchbondMulti-Purpose, AdperSingle Bond 2, Adper SE Plus, AdperEasyOne), e o período de armazenamento, em 3 níveis (1 dia, 30 dias, 180 dias), totalizando 12 níveis de variação. As unidades experimentais foram confeccionadas sobre 120 superfícies de dentina de terceiros molares humanos hígidos e não irrompidos (n= 10).Para análise estatística foi utilizado o teste paramétrico de análise de variância ANOVA e o teste de múltipla comparação de Games Howell.Para a espectroscopia micro-Raman foram utilizados 3 dentes para cada sistema adesivo, totalizando 12 dentes (n=3).Os espectros Raman dos espécimes foram registrados num espectrômetro Micro-Raman RENISHAW InVia com excitação em 785 nm (laser de diodo, RENISHAW) acoplado a um microscópio LEICA DM2500M, com estágio motorizado (x;y;z)RENISHAW MS 20 EncodedStage com resoluções lateral e axial de 100 nm e 1 m. Os adesivos condicione-e-lave ScotchbondMulti-Purpose e SingleBonddesse estudo apresentaram os maiores valores de resistência adesiva, apresentando valores dentro de uma faixa de 44,36 a 50,66 MPa, enquanto que os adesivos AdperSE e Easy One apresentaram valores de 17,97 a 24,60 MPa. O adesivo que apresentou os maiores valores de resistência adesiva foi o ScotchbondMulti-Purpose e o que teve o pior desempenho foi o adesivo Easy One. Todos os adesivos apresentaram queda significativa de resistência de união após 30 e 180 dias. Na análise micro- Raman, o adesivo ScotchbondMulti-Purpose mostrou-se mais homogêneo e com valores de penetração do adesivo semelhantes aos do Single Bond e do Easy One. O adesivo SE Plus apresentou a menor penetração do adesivo e a camada híbrida mais fina. Concluímos neste trabalho que avaliando 4 diferentes tipos de adesivos de uma mesma marca, existe uma relação negativa entre as estratégias de adesão (diminuição do número de passos e frascos) e a resistência de união e a qualidade da camada híbrida. / One-bottle adhesives, both self-etching as etch-and-rinse, are complex mixtures of hydrophilic and hydrophobic monomers resin combinations dissolved in water / solvent. Although the inclusion of hydrophilic monomers has achieved high immediate adhesion forces, studies have shown that dentin-resin interface have become much weaker over time. In this study, bond strength of four adhesive systems was evaluated bymicrotensile test and quantitative analyze ofthe hybrid layer was obtained by micro-Raman spectroscopy. For microtensile test, the factors of variation were 2: the type of adhesive (AdperScotchbondMulti-Purpose, AdperSingle Bond 2, Adper SE Plus, AdperEasy One), and the period of storage at 3 levels (1 day, 30 days, 180 days), totaling 12 levels of variation. The experimental units were made on 120 dentin surfaces of intact humanunerupted third molars (n = 10). The parametric analysis of variance ANOVA and multiple comparison Games Howell was used for statistical analysis. For micro-Raman spectroscopy were used three teeth for each adhesive system, with a total of 12 teeth (n = 3). Raman spectra of the samples were recorded on a Micro-Raman spectrometer RENISHAW invia with 785 nm excitation (laser diode, RENISHAW) coupled to a microscope LEICA DM2500M with motorized stage (x, y, z) RENISHAW MS 20 EncodedStage with lateral and axial resolutionof 100 nm and 1 microns. Etch-and-rinse adhesives ScotchbondMulti-Purposeand SingleBond of this study showed the highest bond strength values, with values within a range from 44.36 to 50.66 MPa, whereas the self-etch adhesives SE Plusand Easy One had values of 17.97 to 24.60 MPa. The adhesive that showed the highest bond strength was ScotchbondMulti-Purpose and the worst performance was fromEasy One.All adhesives showed a significant decrease in bond strength after 30 and 180 days. In micro-Raman analysis, the ScotchbondMulti-Purpose was more homogeneous and had penetration values similar to those of the adhesive Single Bond and Easy One. The SE Plus had the lowest penetration of the adhesive and the thinner hybrid layer. We conclude that evaluating 4 different types of adhesives of the same brand, there is a negative relationship between the strategies of adhesion (decreasing the number of steps and bottles) and bond strength and quality of the hybrid layer.

Research concerning the formation and removal of black crusts on various historical objects is approached from many different angles. The so-called “yellowing effect”, observed after laser treatment for cleaning purposes, has also received a lot of attention. Evidence regarding this phenomenon differs considerably and the actual mechanisms are still speculated on by researchers. In an attempt to elucidate the processes involved in the yellowing effect associated with laser cleaning, a new analytical technique has been used to investigate the black crust, a region of the sample cleaned by laser irradiation at 1064 nm and another region of the same sample subjected to further laser irradiation at 355 nm, on a limestone sample from the cathedral of Seville in Spain. Micro-Raman spectrometry offers the advantage of spatial chemical characterization of the stone, based upon its molecular makeup and was performed on the bulk body of the stone. Raman and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDXS) results indicate that the surfaces cleaned by irradiation at 1064 nm and by double irradiation at 1064 and 355 nm differed in terms of their calcium sulphate, calcium oxalate and iron oxide content, and that this could contribute to the difference in colour observed.

“Nanomaterials” is a generic term used to describe nano-sized crystals and bulk homogenous materials with a structural disorder at the nanoscale. Ancient (and modern) ceramics and glasses derive some of their properties (eg. pliability and low sintering temperature) from the fact that their raw material namely natural clay is nanosized. Furthermore the pigments used to colour ceramics and glasses need to have particle sizes <500 nm for the object to appear homogenously coloured to the human eye. Raman spectroscopy intrinsically probes chemical bonds and is therefore one of the few techniques that has been proven useful to provide information at the nanoscale. It is an excellent tool to study ceramics and glasses as a Raman spectrum can be used to identify phases, analyse amorphous domains in the silicate network and identify pigments on a nano-scale. The characteristics of a glass, ceramic or ceramic glaze derived through its Raman spectrum can then be linked to the technology used to produce an artefact and in this way provide information about its relative age and provenance. Likewise, the identification of pigments and binders in San rock art might provide information about production techniques and assist in the developement of conservation procedures. In this thesis micro-Raman spectroscopy (with X-ray fluorescence, X-ray powder diffraction, electronmicroscopy and photoluminescence as supportive techniques) was utilised to study archaeological artefacts from the Mapungubwe Collection and San rock art. It was possible to re-date celadon shards excavated on Mapungubwe hill in 1934 to the Yuan or even later Ming dynasty in stead of its original classification as Song. A profile of the glass technology used to produce the Mapungubwe oblates, small trade beads from the “royal burials” on Mapungubwe hill was determined and quite a few unique characteristics of the beads may eventually help to establish their provenance. The possible influence of the presence of rock hyraces at rock art sites on the deterioration of rock art were investigated and during the study very rare polymorphs of CaCO3 (vaterite and monohydrocalcite) were discovered in rock hyrax urine. This study was extended to analyse a San rock art fragment and another first was the identification of animal fat on the fragment, but the exact origin of the fat has to be verified by similar experiments. / Thesis (PhD)--University of Pretoria, 2009. / Physics / unrestricted

Ce travail porte sur la caractérisation optique d'échantillons de 4H-SiC. Les échantillons étudiés ont été répartis en deux groupes : type-n et type-p. La croissance des épitaxies a été réalisée par CVD technique utilisant horizontal, paroi chaude, chauffée par résistance, en utilisant de l'hydrogène comme gaz porteur silane et/propane en tant que précurseurs de Si/C respectivement. Pour atteindre différents dopages : N2 pour le n-type et TMA pour de type p ont été utilisés. Les échantillons ont été étudiés par photoluminescence en basse température, micro-Raman and spectroscopies de masse d'ions secondaires. Pour les échantillons de type-p mesures d'effet Hall ont été utilisés pour déterminer la concentration de porteurs. Avec l'aide de ces techniques, il a été possible de déterminer le niveau de dopage dans une très large gamme pour les deux types. Les deux spectroscopies : Raman et LTPL peut donner des informations sur la concentration, polytype, qualité du cristal et concentration de porteurs, mais seulement LTPL fournit des informations sur la compensation et est indispensable de définir la polarité. Pour les échantillons faiblement dopés les meilleures façons de déterminer le niveau de dopage semble être des mesures LTPL. Pour les échantillons fortement dopés on a remarqué l'avantage de Raman, qui permet de déterminer la concentration en porteurs jusqu'à 10^20cm-3. Enfin en utilisant les mesures électriques et de Fano-paremeters obtenus grâce à micro-Raman, nous avons fait la courbe d'étalonnage pour type p 4H-SiC. / The main topic of this thesis is the optical characterization of 4H-SiC samples. The samples were divided in 2 groups: type-n doped with nitrogen and type-p doped with aluminum. Samples were grown by CVD method performed in a horizontal, hot wall, resistively heated, using hydrogen as a carrier gas and silane/propane as Si/C precursors respectively. To achieve different doping N2 for n-type and TMA for p-type were used. The samples were studied by three different spectroscopies techniques: low temperature photoluminescence, micro-Raman and secondary ion mass spectroscopies. For p-type samples Hall effect measurements were used to determine carrier concentration. With the help of this techniques it was possible to determine doping level in a very large range for both types. Both LTPL and Raman spectroscopy can give information about the polytype, crystal quality and carrier concentration but only LTPL provides information about compensation and is indispensable to define the polarity. For low doped samples since the LOPC & FTA modes of Raman spectra do not exhibit any significant changes the best ways seems to be LTPL measurements. For the highest doped samples notice the advantage of Raman which allows to determine the carrier concentration up to 10^20cm-3. Finally due to electrical measurements and fano-paremeters obtained by micro-Raman spectra we made calibration curve for p –type 4H-SiC.

A series of studies on monomer to polymer conversion in adhesive systems was undertaken using micro-Raman spectroscopy. A database of micro-Raman spectra was compiled for identification of tooth tissues and materials. The degree of conversion was assessed as a function of time and light source. Linear and two-dimensional micro- Raman characterisations of the adhesive-dentine and resin-based composite-adhesivedentine interfaces were performed. The degree of monomer to polymer conversion of adhesive systems was correlated with the amount of eluted monomers obtained by highperformance liquid chromatography. The degree of conversion varied significantly depending on adhesive chemical composition, curing time and light source. It was impossible to specify one curing time applicable to all adhesive systems, due to differences in conversion kinetics. In general, conventional halogen light-curing units at twenty seconds curing time produced similar or higher degree of conversion in adhesive systems compared to high-power LED units at ten seconds. Significantly higher monomer conversion was found in the adhesive layer compared to the hybrid layer in both etch-and-rinse and self-etch systems. Etch-and-rinse adhesive systems formed thicker hybrid layers compared to self-etch systems. Micro-Raman spectroscopy gave a more precise indication of dentine demineralisation and adhesive penetration than scanning electron microscopy and indicated that the hybrid layer is a gradual transitional zone between the adhesive layer and un-affected dentine. The absolute amount and weight percent of eluted monomers varied in all tested adhesive systems. In most adhesive systems, more than 90% of eluted monomers were detected within the first one hour of immersion. Overall, no correlation was found between the degree of conversion and the amount of eluted monomers.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Submitted by Maurílio Figueiredo (maurilioafigueiredo@yahoo.com.br) on 2013-08-29T20:29:58Z No. of bitstreams: 1 TESE_EstudoQuímicoMineralógico.pdf: 8706720 bytes, checksum: 9b3be0c139aa3ef49aa8c71f41e11931 (MD5) / Approved for entry into archive by Gracilene Carvalho (gracilene@sisbin.ufop.br) on 2013-10-10T15:43:00Z (GMT) No. of bitstreams: 1 TESE_EstudoQuímicoMineralógico.pdf: 8706720 bytes, checksum: 9b3be0c139aa3ef49aa8c71f41e11931 (MD5) / Made available in DSpace on 2013-10-10T15:43:00Z (GMT). No. of bitstreams: 1 TESE_EstudoQuímicoMineralógico.pdf: 8706720 bytes, checksum: 9b3be0c139aa3ef49aa8c71f41e11931 (MD5) Previous issue date: 2011 / As áreas alvo do presente estudo encontram-se localizadas em Santa Elena de Uairén, Município Gran Sabana, região sudeste do Estado Bolívar, nas proximidades da fronteira entre a Venezuela e o Brasil, especificamente na Bacia do Rio Caroní, sub-bacia do Rio Icabarú. A região pertence à porção venezuelana do Escudo das Guianas, onde estão presentes as províncias geológicas de Roraima e Cuchivero. A metodologia empregada começa pela seleção e coleta das amostras, destacando-se que com a finalidade de garantir a sua procedência as amostras de diamante foram adquiridas diretamente nas áreas de explotação, coletados nas margens dos rios Icabarú, Uaiparú, Surucún e Mosquito. A caracterização mineralógica consistiu no estudo das propriedades físicas e químicas de 2.000 amostras de diamante entre as variedades gemológica e industrial, o peso médiodos cristais variou de 0,2 a 1,50 ct, não sendo um número expressivo a ser considerado, uma vez que para os depósitos da região reportam-se uma produção de diamante de quilatagem mais elevada. Seu peso específico é representado no intervalo de 3,50 a 3,52, sendo essa variação fruto da presença de algumas inclusões minerais e de defeitos cristalinos. Por meio de microscopia óptica foram estudadas as seções superficiais do diamante permitindo sua caracterização macroscópica. Predominam os octaédricos, seguido dos dodecaédricos, cristais geminados policristalinos, além de exemplares irregulares, subarredondados e fraturados. No que tange à cor, 37% são incolores, 20,5% amarelos, 14% castanhos, 5%verdes, 3% pretos, da amostras estudadas 7,5% apresentam capas verdes e 3,5% apresentam capas marrom. No estudo morfológico dos exemplares molicristalinos analisados se determinou que 57,3% de cristais são irregulares; 11,5% de rombododecaedros; 10,0% de octaedros; 7,8% de octa-rombododecaedros (formas intermediárias entre o octaedro de faces planas e o rombododecaedro de faces curvas); 5,0% de fragmentos de clivagem; 4,2% de agregados cristalinos; 1,5% de geminados e 1,5% de cubos. As demais categorias morfológicas presentes incluindo o cubo piramidado, combinações variadas entre cubo, octaedro e rombododecaedro, formas pseudotetraédricas e diamante policristalino (carbonados, ballas), ocorrem em frequências abaixo de 1,0%. A grade maioria apresentarem figuras de dissolução nas superfícies,o que indica que foram submetidos aos processos de dissolução a altas temperaturas. Com a aplicação do método de Microscopia Eletrônica de Varredura (MEV) mediante a aplicação da técnica de Espectroscopia de Energia Dispersiva (EDS), foram estudadas as superfícies dos cristais de diamante, o que permitiu a interpretação dos fenômenos, processos e/ou eventos quer seja de crescimento, corrosão ou dissolução. Foi possível efetuar o reconhecimento de figuras superficiais dos tipos trigons, quadrons, crescimento em bloco, crescimento laminar, estrias, sulcos e colinas (protuberâncias ou saliências arredondadas), o que permitiu estabelecer a evolução morfológica partindo do octaedro primitivo e passando por fenômenos de dissolução para formas transicionais (111)+(110), (111)+(hkl), proporcionando hábitos rombododecaédricos (110) e hexaoctaédricos (110). A partir de análises de Espectroscopia de Absorção no Infravermelho por Transformada de Fourier (FTIR) foram obtidos dados que permitiram a classificação espectral do diamante a partir da determinação do conteúdo de nitrogênio. Os resultados obtidos indicam as seguintes porcentagem 6% corresponde ao tipo IIa, 2% ao tipo Ib, 18% ao IaA, 26% ao tipo IaB e 48% ao tipo IaAB. A metodologia utilizada para analisar às características estruturais dos cristais de diamante da região consistiu na integração dos métodos analíticos de catodoluminescência (CL), fotoluminescência (PL) e espectroscopia de ressonância paramagnética electrónica (EPR). Foram determinados defeitos estruturais atribuídos à presença de nitrogênio e vacâncias como, por exemplo, o defeito (N-V) o qual foi determinado em vários cristais. Analisando os diamantes de cor marrom observou-se que esses contêm pouca ou nenhuma impureza, porém sendo diamantes puros sua cor pode ser ocasionada por deslocamentos estruturais, conhecidos como deformações plásticas, que são rupturas na simetria de translação da rede cristalina. Os cristais de coloração amarela apresentaram um conjunto de espectros diferenciados, que provam que os defeitos presentes devem-se à presença de impurezas de nitrogênio formando diferentes centros de cor. O primeiro grupo é formado por cristais onde ocorrem principalmente os centros do tipo P1, um segundo grupo onde ocorrem principalmente os centros N1 e N4, um terceiro é representado por cristais cujos principais centros são o P2. E um quarto grupo onde os cristais apresentam espetros que permitem reconhecer um centro N2. Também foram identificados centros S=1. As inclusões minerais presentes nos cristais de diamante, foram analisadas mediante espectroscopia micro-Raman sendo que foi possível identificar inclusões de olivina, granadas e grafita. Mediante analises de microRaman foi determinada uma microinclusão de chaoíta (C – sistema hexagonal) que permite deduzir que a mesma possivelmente pertence a relicto da presença de inclusões gasosas de CO trapeada no interior de microcristais de diamante, sendo que a atividade decorrente da temperatura e pressão de confinamento, localmente produziriam a modificação da estrutura cristalográfica do diamante (cúbica), para hexagonal, segundo hibridizações do tipo SP 3 (chaoíta). A partir das análises de fotoluminescência (PL), catodoluminesência (CL) e ressonância paramagnética eletrônica (EPR) determinaram-se defeitos na estrutura cristalina dos carbonados atribuídos a formação de plaquetas de nitrogênio associada a deslocamentos internos, fato que sugere atuação simultânea de cisalhamento (esforço dirigido) associado ao aumento da temperatura, resultando em condições favoráveis para deformação plástica de diamantes e para a conversão dos centros A para centros B no manto superior. O estudo das amostras de minerais pesados permitiu estabelecer três associações mineralógicas maioritárias: zircão-hematita, ilmenita-zircão e hematita-ilmenita. Nessas amostras, foram identificadas altas concentrações de ouro, esse distribuído ao longo de toda a região de Santa Elena de Uairén. Também foram identificados minerais fosfáticos, tipo Terras Raras, tais como a florencita ________________________________________________________________________________ / ABSTRACT: The target areas in this study are located in SantaElena de Uairén, Municipality of Gran Sabana, southeastern region of the Bolivarian State, near the border between Venezuela and Brazil, specifically in the Caroní River Basin, Icabarú River Sub-basin. The area belongs to the Venezuelan portion of the Guyana Shield, where the geological provinces of Roraima and Cuchivero are. The methodology employed starts by collecting and selecting the samples. It is important to highlight that in order toensure their origin, the diamonds were obtained straight from the exploration areas, i.e. at the Icabarú, Uaiparú, Surucún, and Mosquito River banks. Mineralogical characterization consisted in studying the physical and chemical properties of 2.000 diamond samples among the gemological and industrial varieties. Their average weight ranged from 0.2 to 1.50 ct, which isnot a significant number because the deposits in this area have reportedly produced diamonds of higher carat weights. Their specific weight is represented in the 3.500 to 3.520 interval. This variation derives from the presence of a few mineral inclusions and crystal defects. The superficial sections of the diamonds were studied using optical microscopy, which allowed the morphological characterization. Microscopy revealed the predominance of octahedral, followed by dodecahedral, polycrystalline geminated crystals, as well as irregular, subrounded and fractured samples. As far as color is concerned, 37% are colorless, 20.5% yellow, 14% green, 5% brown, 3% black, 7.5% are green-coated and 3.5% brown-coated. In the morphologic study of diamonds molicristalinos determined that 57.3% of crystals are asymmetrical, 11.5% of rhombic dodecahedron), 10.0% of octaedro, 7.8% of combinations intermediate between octahedrons, of plain faces and rhombic dodecahedron of rounded faces, 5.0% of cleavage fragments, 4.2% of aggregates crystalline; 1.5% of geminados and 1.5% of cubes, The others categories morphologic including tetrahexahedroids combinations varied between cube, octaedro and rhombic dodecahedron, pseudo-dodecahedron forms and diamonds pollycrystaline (carbonado and ballas), presenting in frequency low 1.0%, The majority presented figures of dissolution on the surface features, this indicates that they underwent dissolution processes at high temperatures. Using the ScanningElectron Microscopy (SEM) method and the Energy Dispersive Spectroscopy (EDS) technique, the diamond crystal surfaces were studied. This allowed us to interpret the phenomena and the growth, corrosion or dissolution processes/events. It was possible to recognize superficial figures such as trigons, quadrons,cluster growth, layer growth, grooves, and lumps, which allowed determining their morphological evolution from the primitive octahedron, passing through dissolution phenomena to transitional forms (111)+(110), (111)+(hkl), providing rombododecahedral (110) and hexa-octahedral (110) habits. The Fourier Transform Infrared Spectroscopy (FTIR) analysis obtained chemical composition data that allowed thespectral classification of diamonds based on nitrogen content determination. The results obtained showed the following percentage: 6% corresponds to type IIa, 2% to type Ib, 18% to IaA, 26% to type IaB, and 48%to type IaAB. The methodology used to analyze the structural characteristics of diamond crystals from this area consisted in integrating the Cathodoluminescence (CL), Photoluminescence (PL), and Electron Paramagnetic Resonance Spectroscopy (EPR) analytical methods. Structural defects attributed to the presence of nitrogen and vacancies such as (N-V) defect were determined in several crystals. The analysis of brown diamonds revealed that they have little or no impurities. However, since they are pure Diamonds, their color can be a result of structural displacements, known as plastic deformations, which are disruption in the crystal network translational symmetry. The yellow crystals showed a set of different spectra, which proves that the existing defects are due to nitrogen impuritiesin different forms of centers. The first group ismade of crystals in which mainly type-P1 centers occur, thesecond group with types N1 and N4 centers, and the third group is represented by crystals whose main center are type P2. There is also a fourth group, in which the crystals show spectra that allow indentifying an N2 center. Centers S=1 were also indentified. The mineral inclusions present in the diamond crystals were analyzed using Micro-Raman spectroscopy, which allowed the identification of olivine, grenade, and graphite inclusions. Micro Raman analyses determined a micro-inclusion of chaoite, which allows us to conclude that it belongs to remains of CO gas inclusions trapped within diamond micro-crystals. The activity resulting from the confinement temperature and pressure modified the crystallographic structure of the diamond, from cubic to hexagonal, according to hybridizations such as sp3 (chaoite). Based on Photoluminescence (PL), cathodoluminescence (CL), and Electron ParamagneticResonance (EPR) analyses, we could determine that the defects in the crystal structures of the carbonated attributed to nitrogen platelet formation associated to internal displacements postulates a simultaneous shear forces (directed strength) associated to increased temperature. This resulted in favorable conditions to diamond plastic deformation and conversion of centers A to centers B in the upper mantle. The study of heavy mineral allowed stipulating three major mineralogical associations: zircon-hematite, ilmenite-zircon, and hematite-ilmenite. In these samples, high concentrations of gold were identified, which is spread along almost all the Santa Elenade Uairén area. Phosphate minerals, rare earth type, such as florencite were also identified. The Multivariate Statistical Analysis methodology using discriminant functions is appliedin order to separate individuals (samples) into groups with similar characteristics,according to the different measurements carried out. In other words, it is a multivariate statistical analysis to verify how the elements are grouped and better describe their behavior in similar groups or groupswith affinities.

Analyzing the constituents of meteorites has played an important role in forming the contemporary theories of solar system evolution, planets formation, and stellar evolution. Meteorites are often a complex mixture of common rock forming silicates, such as olivines and pyroxenes, with a range of exotic species including hydrated silicates, and in some cases organic compounds. We used Micro-Raman spectroscopy to analyze the compositions of three carbonaceous chondrites: NWA852, Murchison and Allende. Raman spectra were measured using laser sources with different excitation wavelengths: HeNe 633 nm and Nd:YAG 532 nm. We were able to detect 9 minerals in NWA852, 3 minerals in Murchison and 4 minerals in Allende. Some of these minerals like pyrite in NWA852 and magnetite in NWA852 and Murchison provide evidence for potential previous organic life. Other minerals like ringwoodite in Allende and lizardite in NWA852 reveal information about previous astrophysical and geological events experienced by the meteorites. The detection of graphite in the Murchison and Allende reveals information about the microstructure of these meteorites.

Ce travail porte sur la caractérisation structurale et optique d'échantillons de SiC. Les échantillons étudiés ont été répartis en trois groupes : des échantillons massifs, des couches épitaxiales épaisses et enfin des couches minces. La croissance des échantillons massifs a été réalisée avec la technique CF-PVT, utilisant une géométrie « d'étranglement ». L'objectif était de filtrer les défauts afin de créer des germes de 3C de haute pureté. La croissance de des couches épaisses par sublimation avait comme objectif la maitrise d'un dopage résiduel faible de type n et p pour des applications composants. Enfin, dans le but de réaliser des composants de type LED blanche des impuretés Ga ont été introduites dans des couches minces épitaxiées par VLS afin de créer des échantillons fortement dopé de type p. Tous ces échantillons ont été étudiés par photoluminescence, micro-Raman, SIMS et microscopie électronique à transmission. Il a été possible de déterminer la concentration d'impuretés et d'identifier le caractère n ou p de ces échantillons. L'analyse des échantillons a été faite en utilisant à la fois l'observation des défauts structurels et les informations obtenues à partir des techniques de caractérisation optique. Nous avons pu obtenir des informations sur les paramètres physiques de 3C-SiC, comme l'énergie de liaison de Ga et Al, la structure fine des excitons liés à l'Al et celle des paires donneurs accepteurs Al-N et Ga-N. Enfin l'apparition d'un nouveau défaut de structure appelée le « fourfold twin » a été observée. / The main topic of this thesis is the structural and optical characterization of SiC samples. The samples were divided in three groups: bulk, thick and thin epilayers. The bulk samples were grown with the CF-PVT technique and used a modified crystal holder geometry. The objective was to filter the defects to and create high purity and quality seeds of 3C-SiC. The thick epilayers were grown with the sublimation epitaxy technique, trying to demonstrate the creation of low impurity n and p type layers for device applications. Finally the thin epilayers were grown with the vapour-liquid-solid technique and doped with Ga impurities in an effort to create either heavily p-type doped samples and components for white LED applications. The samples were studied with low temperature photoluminescence, micro-Raman, SIMS and transmission electron microscopy. With the help of these techniques it was possible to determine the impurity concentration and identif y the n or p character of these samples. A qualitative analysis of the quality of the samples was done using both the observation of the structural defects and the information from the optical characterization techniques. We were able to acquire information about physical parameters of 3C-SiC like the binding energy of Ga and Al, the Al bound exciton fine structure and the Al-N and Ga-N donor acceptor pair fine structure. The appearance of a new structural defect called the fourfold twin was observed and presented.