This work examines the deposition of metallic and semiconductor elements onto self-assembled DNA templates for the fabrication of nanodevices. Biological molecules like DNA can self-assemble into a variety of complex 2-D and 3-D architectures without the need for expensive patterning tools. In addition, self-assembled DNA templates can be designed to controllably place functional nanomaterials with molecular precision. These characteristics make DNA an attractive template for fabricating electronic circuits from biological molecules. However, electrically conductive structures are required for electronic applications. While metallized DNA nanostructures have been demonstrated, the ability to make thin, continuous wires that are electrically conductive still represents a formidable challenge. DNA-templated wires have generally been granular in appearance with a resistivity approximately two to three orders of magnitude higher than that of the bulk material. An improved method for the metallization of DNA origami is examined in this work that addresses these challenges of size, morphology and conductivity of the metallized structure. Specifically, we demonstrated a metallization process that uses gold nanorod seeds followed by anisotropic electroless (autocatalytic) plating to provide improved morphology and greater control of the final metallized width of conducting metal lines. Importantly, growth during electroless deposition occurs preferentially in the length direction at a rate that is approximately four times the growth rate in the width direction, which enables fabrication of narrow, continuous wires. The electrical properties of 49 nanowires with widths ranging from 13 nm to 29 nm were characterized, and resistivity values as low as 8.9 x 10-7 Ω-m were measured, which represent some of the smallest nanowires and the lowest resistivity values reported in the literature. The metallization procedure developed on smaller templates was also successfully applied to metallize bigger DNA templates of tens of micrometers in length. In addition, a polymer-assisted annealing process was discovered to possibly improve the resistivity of DNA metal nanowires. Following metallization of bigger DNA origami structures, controlled placement of gold nanorods on a DNA breadboard (~100 x 100 nm2) to make rectangular, square and T-shaped metallic structures was also demonstrated. For site-specific placement of nanorods to a DNA template, we modified the surface of the gold nanorods with single-stranded DNA. The rods were then attached to DNA templates via complementary base-pairing between the DNA on the nanorods and the attachment strands engineered into the DNA "breadboard" template. Gaps between the nanorods were then filled controllably via anisotropic plating to make 10 nm diameter continuous metallic structures. Finally, controlled placement of metal (gold) - semiconductor (tellurium) materials on a single DNA origami template was demonstrated as another important step toward the fabrication of DNA-based electronic components. The combination of molecularly directed deposition and anisotropic metallization presented in this work represents important progress towards the creation of nanoelectronic devices from self-assembled biological templates.

This thesis is concerned with the synthesis and evaluation of regenerable chalcogen containing antioxidants. Variously substituted 2,3-dihydrobenzo[b]selenophene-5-ol antioxidants were evaluated in order to gain information about structure/reactivity-relationships. Within the series explored, the most regenerable unsubstituted compound inhibited lipid peroxidation for more than 320 minutes when assayed in a two-phase lipid peroxidation model in the presence of N-acetylcysteine (NAC). α-Tocopherol which could inhibit lipid peroxidation for 90 minutes under similar conditions was therefore easily outperformed. The antioxidant activity of the parent was also documented in an aqueous environment. The best catalyst quenched/inhibited ROS production by neutrophils and PMA-stimulated macrophages more efficiently than Trolox. In addition, over a period of seven days, no disruption in proliferation for the cell lines used was observed when exposed to our synthetic compound or Trolox at a concentration of 60 µM. 3-Pyridinols substituted with alkyltelluro groups in the ortho-position were more regenerable in the two-phase model than their corresponding para-substituted analogues in the presence of NAC and also inhibited autoxidation of styrene in a catalytic fashion in homogenous phase in the presence of N-tert-butoxycarbonyl cysteine methyl ester (LipCys), a lipid-soluble analogue of NAC. The best inhibitors quenched peroxyl radicals more efficiently than α-tocopherol. They could also catalyze reduction of organic hydroperoxides in the presence of thiols and therefore mimic the action of the glutathione peroxidase enzymes. Mechanisms for the catalysis are proposed. Octylthio, octylseleno and octyltelluro analogues of butylated hydroxyanisole (BHA) were synthesized and evaluated. Among these, the tellurium compound was superior to α-tocopherol in the presence of NAC both when it comes to quenching capacity and regenerability.  Organochalcogen substituent effects in phenolic compounds were studied by using EPR, IR and computational methods.

Nucleic acids play important roles in living systems by storing and transferring genetic information and directing protein synthesis. Recently, it was found that nucleic acids can catalyze chemical and biochemical reactions similar to protein enzymes. In addition, they can also serve as drug targets for the treatment of deadly diseases such as AIDS and cancers. As a result, the 3D structure study of nucleic acids and proteinnucleic acids complexes by X-ray crystallography has become one of the most active research areas. However, the two intrinsic bottlenecks of macromolecule X-ray crystallography, including crystallization and phase determination, have significantly limited its application in study and discovery of the new structures and folds, as well as in exploration of the biological mechanisms. So far, the selenium derivatization (Se-Met) of proteins and multiple anomalous dispersion (MAD) or single anomalous dispersion (SAD) technology have revolutionized the protein crystallography field by providing a rational solution to solve the phase determination problem. Similarly, it’s important and urgent to develop a corresponding methodology for nucleic acid X-ray crystallography. The work presented here includes two general research directions: the selenium derivatized nucleic acids (SeNA) and tellurium derivatized nucleic acids (TeNA): 1) The SeNA strategy by site-specifically replacing oxygen with selenium at the 2’ and 4 positions of thymidine and uridine has been developed. We found that the selenium derivatization at both sites are relatively stable and doesn’t cause significant structure perturbations by comparing with their corresponding native counterparts. In addition to the phase determination, the 2’-Se modification can also facilitate crystal growth of many oligonucleotides. Moreover, we have observed colorful DNAs and RNAs with the 4-Se modification for the first time. 2) The TeNA strategy by covalently incorporating tellurium functionalities into different positions of nucleic acids, particularly at the 2’ and 5 position of thymidine, has been developed. We have demonstrated the compatibility of the tellurium modification and solid-phase synthesis, as well as the potential application of the tellurium modifications in anti-viral drug synthesis and DNA-damage investigation.

Durch diese Arbeit konnten einerseits neuartige sowie bereits bekannte molekulare Tellurringe in Clusterverbindungen und quasi-eindimensionalen Koordinationspolymeren erhalten werden. Die Stabilisierung der zyklischen, homonuklearen Einheiten erfolgt dabei stets durch die Koordination an elektronenreiche Übergangsmetallatome, wobei die koordinierenden Telluratome gegenüber diesen als Zwei-Elektronendonoren fungieren. Die molekularen Clusterverbindungen [M(Te10)](TeX4)2(TeX3)2 (M = Rh, Ir X = Cl, Br) sowie [Ru2(Te10)](TeI4)2(TeI2)2 beinhalten eine übergangsmetallstabilisierte, neutrale Te10-Einheit, wobei jedes Übergangsmetallatom zusätzlich zwei terminale Halogenidotelluratliganden koordiniert. Im neuartigen, zehngliedrigen (Te04Te+0,54Te2)-Fragment finden sich zwei nahezu linear umgebende Telluratome, die als "Tellurbrücke", zwei gefaltete Te4-Ringe zur Vervollständigung der tricyclo[5.1.1.13;5]-Einheit koordinieren. Die Bindungssituation der nahezu linearen Te3-Sequenzen im homonuklearen Fragment sowie die [X-Te-X]-Sequenzen der Halogenidotelluratliganden lassen sich mit 3c4e-Bindungen verstehen. Anhand quantenchemischer Rechnungen konnte die Mehrzentrenbindung sowie die Aussage eines übergangsmetallstabilisierten Fragments bestätigt werden. In den inkommensurabel modulierten Kristallstrukturen (M2Te14I12)(TeI4) Te2I2) (M = Rh, Ir) existieren hingegen zweifach positiv geladene (M2Te14I12)2+-Cluster (M = Rh, Ir) neben nahezu planaren Schichten bestehend aus (TeI4)2--Gruppen und (Te2I2) Molekülen. Das (Te+I2I2) Molekül konnte anhand quantenchemischer Rechnungen als stabiles Molekül in der Gasphase bestätigt werden und stellt ein schweres Homologes des S2Cl2 dar. Die quaternäre Verbindung (Ir2Te14Br12)2(InBr4)2 enthält ebenfalls einen zweifach positiv geladenen Cluster, {[Ir3+2(Te0)4(Te+0,5)4(Te-)2]Te2+2Br-6)2}2+, dessen Ladung durch zwei einfach negativ geladene (In3+Br4)--Gruppen ausgeglichen wird sowie einem neutralen Cluster, [Ir3+2(Te0)4(Te3.-)2](Te2+2Br-6)2, mit einem Te3.--Radikalanion, dessen Existenz mittels ESR-Spektroskopie nachgewiesen wurde. Die aus diskreten Molekülen aufgebaute Verbindung [Ru2(Te6)]TeBr3)4(TeBr2)2 kann je nach Betrachtungsweise entweder als Te6-Ring, der durch zwei (Ru2+Te2+3Br-8)-Kappen umgeben ist oder als [Ru2Te6]4+-Heterokuban, welcher zusätzlich mit Bromidotelluratliganden koordiniert ist, beschrieben werden. In den Kristallstrukturen der ternären Koordinationspolymere [M(Te6)]X3 (M = Rh, Ir; X = Cl, Br, I) verlaufen entlang der c-Achse lineare, positiv geladene [M(Te6)]3+-Ketten (M = Rh,Ir), in denen abwechselnd ein ektronenreiches Übergangsmetallatom und sechsgliedrige Tellurringe koordinativ gebunden sind, wodurch eine hoch symmetrische Anordnung realisiert wird. Dabei zeigt sich aufgrund der starken Bindung an die Übergangsmetallatome eine erhebliche Ringspannung im Vergleich zu den bekannten sechsgliedrigen Tellureinheiten. Isolierte Halogenidionen, welche sich in der Ebene der Übergangsmetallatome befinden, dienen einerseits zum Ladungsausgleich der positiv geladenen Ketten und verbrücken andererseits innerhalb eines Stranges benachbarte Te6-Ringe. Im Koordinationspolymer [Ru(Te8)]Cl2 konnte ein neutraler Te8-Ring mit einer bislang für achtgliedrige Chalkogenmoleküle unbekannten Konformation röntgenographisch nachgewiesen werden. Die Abweichung von der bevorzugten Kronenform, ist wiederum ein E ekt der starken Bindung zwischen den Telluratomen und den Rutheniumatomen. In den linearen, positiv geladenen [Ru(Te8)]2+-Strängen binden 3+3 Telluratome an zwei benachbarte Rutheniumatome. Isolierte Chlorid-Ionen, die zwischen den positiven Strängen eingelagert sind, dienen in der Kristallstruktur zum Ladungsausgleich. Das quaternäre Koordinationspolymer [Ru(Te9)](InCl4)2 beinhaltet eine neuartige, zyklische Te9-Einheit, welche die Vielfalt der tellurreichen Ringstrukturen erweitert. Analog zum ternären Koordinationspolymer [Ru(Te8)]Cl2 gliedert sich die Kristallstruktur in [Ru(Te9)]2+-Stränge, die entlang der c-Achse verlaufen, und dem komplexen Anion (InCl4)-. Ein besonders interessantes Strukturmerkmal der positiv geladenen Stränge stellt das käfigartige Fragment [Ru-(Te9)-Ru] dar, dessen hexazyklischer Aufbau aus kondensierten Fünfringen den isolierten Undecapniktiden Pn113- (Pn = P, As, Sb) topologisch äquivalent ist. Für einen genaueren Einblick in die chemische Bindung der tellurreichen Koordinationspolymere [Rh(Te6)]Cl3, [Ru(Te8)]Cl2 und [Ru(Te9)](InCl4)2 wurden quantenchemische Rechnungen durchgeführt. Eine topologische Analyse der Elektronendichte und des Elektronenlokalisierbarkeitsindikators (ELI-D) an koordinierenden und freien Tellurmolekülen sollte zu detaillierten Aussagen über Gründe der extremen Ringspannung aufgrund der Koordination führen. Zusammenfassend kann feststellt werden, dass die Verzerrung der Tellurringe in den Koordinationspolymeren einerseits der gerichteten Bindung zu den Übergangsmetallatomen geschuldet ist und andererseits um Platz für die sich abstoßenden freien Elektronenpaare zu bekommen. Für weitere Arbeiten könnten zunächst einerseits die Untersuchungen zur Löslichkeit der Clusterverbindung Re4Q4(TeCl2)4Cl8 (Q = S, Se, Te) in organischen Lösungsmitteln als Ausgangspunkt für die Austauschreaktionen der terminalen Halogenidotelluratliganden durch neue verbrückenden Gruppen von Interesse sein. Andererseits kann auch innerhalb des untersuchten Systems, durch Variation der Eduktzusammensetzung, neuartige Tellurmoleküle erwartet sowie die bereits erworbenen Erkenntnisse zur Übertragung auf das leichtere Homologon Selen genutzt werden.

SALOMÃO, Francisco Carlos Carneiro Soares. Estruturas Híbridas de Nanotubos de Carbono de Parede Simples e Telúrio. 2011. 82 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2011. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-04-23T21:29:45Z No. of bitstreams: 1 2011_dis_fccssalomao.pdf: 4413944 bytes, checksum: 498642e6b8eef08e5f36f566e477e377 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-04-29T17:48:04Z (GMT) No. of bitstreams: 1 2011_dis_fccssalomao.pdf: 4413944 bytes, checksum: 498642e6b8eef08e5f36f566e477e377 (MD5) / Made available in DSpace on 2015-04-29T17:48:04Z (GMT). No. of bitstreams: 1 2011_dis_fccssalomao.pdf: 4413944 bytes, checksum: 498642e6b8eef08e5f36f566e477e377 (MD5) Previous issue date: 2011 / In this work we use Raman spectroscopy and electron microscopy to characterize hybrid carbon nanotube single-wall and tellurium nanostructures. Carbon nanotubes are important nanostructures due to their electrical, optical and mechanical properties, which makes them attractive for many applications in nanotechnology. However, for a wide range of applications requires the functionalization of the nanotubes in order to better exploit their potential application. Within this area of hybrid structures formed with carbon nanotubes, we highlight the carbon nanotubes interacting with the family of the chalcogen elements, which make them suitable for applications ranging from photonics to biology. The hybrid SWCNT-Te samples were prepared through the generation of anionic species of CNTs, followed by capture of elemental tellurium, using single-wall carbon nanotubes prepared by different methods. Raman spectroscopy data show that the characteristics present in the samples of single wall carbon nanotubes and tellurium used in the functionalization and show differences in comparison with the characteristics observed in the hybrid samples. Changes in the G band frequency, asymmetry and width were observed after the functionalization. We noticed an increase in the relative intensity of band D in the sample in relation to the hybrid single-wall nanotubes used in the functionalization. In the observation of the modes between 100 and 1000 cm-1 we note the contribution of the RBM modes of single wall carbon nanotubes and the modes of tellurium. Raman modes associated with tellurium oxide were found in two of three hybrids samples, which are resonant modes for the laser line of 532 nm (2.33 eV). The process of removal of oxides, by dissolving in acetone PA in ultrasonic bath, proved to be efficient. Even after the removal of oxides, we can still observe the modes related to tellurium and carbon nanotubes in the Raman spectrum of hybrid sample. The electron microscope images show that the hybrid system is presented carbon nanotubes clusters with tellurium nanostructures. / Neste trabalho utilizamos as Técnicas de Espectroscopia Raman e microscopia Eletrônica para caracterizar sistemas híbridos de nanotubos de carbono de parede simples e Telúrio. Os nanotubos de Carbono são nanoestruturas importantes devido às suas propriedades elétricas, óticas e mecânicas, que os torna atraentes para muitas aplicações em nanotecnologia. Porém, para uma grande gama de aplicações se requer a funcionalização dos nanotubos de modo a explorar mais amplamente seu potencial de aplicação. Dentro desta área de estruturas híbridas formadas com nanotubos de carbono, destacamos os nanotubos de carbono interagindo com elementos da família dos calcogênios, que permitiria aplicações desde a fotônica até biológicas. As amostras híbridas SWCNT-Te foram preparadas através de uma técnica de funcionalização chamada Geração de carbânios, utilizando nanotubos de parede simples do tipo HipCo e não HipCo. No estudo de espectroscopia Raman, observamos as características presentes nas amostras de nanotubos de carbono de parede simples e Telúrio utilizados na funcionalização e comparamos com as características observadas nas amostras híbridas. Mudanças na banda G como freqüência, assimetria e largura foram observadas após a funcionalização. Notou-se um aumento na intensidade relativa da banda D na amostra híbrida em relação aos nanotubos de parede simples utilizados na funcionalização. Na observação dos modos entre 100 e 1000 cm-1 notamos a contribuição dos modos RBM dos nanotubos de carbono de parede simples e dos modos do Telúrio. Modos associados a óxido de Telúrio foram encontrados em duas das três amostras híbridas, sendo estes modos ressonantes para a linha de laser de 532 nm (2,33 eV). O processo de retirada dos óxidos, pela dissolução em Acetona P.A, em ultra-som de banho mostrou-se eficiente. Mesmo após a retirada dos óxidos, ainda podemos observar os modos relacionados ao Telúrio e aos nanotubos de carbono no espectro da amostra híbrida. As imagens de microscopia eletrônica mostram que o sistema híbrido se apresenta como nanocabos coaxias, de nano tubos de carbono envolvidos por Telúrio.

Diversas classes de compostos orgânicos de telúrio foram exploradas neste trabalho. Inicialmente foi estudada a transmetalação entre teluretos alílicos e dibutil cianocupratos de lítio de ordem superior, levando aos respectivos cianocupratos alílicos de lítio. Estes, por sua vez, foram acoplados com triflatos vinílicos, importantes intermediários sintéticos preparados previamente a partir de teluretos vinílicos, levando a sistemas altamente insaturados em ótimos rendimentos (Esquema 1). (Ver no arquivo em PDF) Em seguida, foi explorada a reatividade de teluretos aromáticos frente a reagentes organometálicos. Cianocupratos arílicos, gerados a partir da transmetalação entre teluretos aromáticos com cianocupratos de lítio de ordem superior, foram adicionados a cetonas α,β -insaturadas, levando aos produtos de adição 1,4 em bons rendimentos (Esquema 2). (Ver no arquivo em PDF) Teluretos vinílicos funcionalizados de configuração Z também foram alvo de estudo visando a formação de ligação carbono-carbono. Reações de substituição entre estes teluretos e cianocupratos de lítio de ordem inferior levaram a cetonas e ésteres α,β- insaturados com estereoquímica defInida em ótimos rendimentos (Esquema 3). (Ver no arquivo em PDF) De agosto/20OJ a março/2004, a aluna realizou um estágio sanduíche na University of California, Santa Barbara, sob a orientação do Prof. Bruce H. Lipshutz, onde realizou estudos sobre a ciclização de Bergman, visando a síntese do fragmentobiarílico A-B da vancornicina. Diversas condições para a ciclização foram estudadas com um composto modelo (Esquema 4) (Ver no arquivo em PDF) e parte da síntese total do fragmento da vancomlcma, onde a ciclização seria a etapa-chave, foi realizada com sucesso (Esquema 5). (Ver no arquivo em PDF) / Several classes of organotellurium compounds were explored in this work. First, transmetallation reaction between allylic tellurides and higher order dilithium dibutyl cyanocuprates was carried out, leading to the corresponding allylic cyanocuprates. Then these reagents performed cross-coupling reactions with vinylic triflates, important synthetic intermediates prepared previously from vinylic tellurides, affording highly unsaturated systems in high yields (Scheme 1). (See in file PDF) Next, the reactivity of aryl tellurides was explored with some organometallic reagents. Aryl cyanocuprates, generated by transmetallation reaction between aryl tellurides and higher order lithium cyanocuprates, were reacted with α,&$946;-unsaturated ketones, yielding 1,4-addition products (Scheme 2). (See in file PDF) Functionalized Z-vinylic tellurides were also investigated in reactions aiming carbon-carbon bond formation. Substitution reactions of these tellurides with lower order lithium cyanocuprates gave α,β-unsaturated ketones and esters with defined stereochemistry in good yields (Scheme 3). From Aug/03 to Mar/04, the student worked in the University of California, Santa Barbara, under the supervision of Prof. Bruce H. Lipshutz, where studies concerning the Bergman cyclization were performed, aiming the synthesis of the vancomycin A-B biaryl fragment. Several conditions for this cyclization were investigated using a model compound (Scheme 4) (See in file PDF) and part of the total synthesis of the vancomycin fragment, in which the Bergman cyclization would be the key-step, was accomplished (Scheme 5). (See in file PDF)

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Orientador: Eudes Borges de Araújo / Banca: Keizo Yukimitu / Banca: Antonio Carlos Hernandes / Banca: Noelio Oliveira Dantas / Banca: Antonio Medina Neto / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: No presente estudo, quatro vidros 20 'Li IND. 2' O-80Te 'O IND. 2' foram preparados com composição nominal idêntica mas com diferentes histórias térmicas. As técnicas de difração de raios-X, espectroscopia no infravermelho, espectroscopia Raman e calorimetria diferencial de varredura foram usadas para compreender os efeitos da história térmica sobre as propriedades térmicas e estruturais dos vidros estudados. Observou-se que as propriedades investigadas dependem fortemente da história térmica dos vidros. Os resultados de difração de raios-X revelaram a presença de três fases cristalinas distintas у-Te 'O IND. 2', α-Te 'O IND. 2, у-Te 'O IND. 2', α-Te 'O IND. 2 e α- 'Li IND. 2'Te 'O IND. 2'O IND. 5' nos vidros estudados com a seguinte sequência de cristalização у-Te 'O IND. 2' 'seta' α-Te 'O IND. 2 'seta' у-Te 'O IND. 2', α-Te 'O IND. 2 'seta' α- 'Li IND. 2'Te 'O IND. 2'O IND. 5". A fase у-Te 'O IND. 2' é metaestável enquanto as fases cristalinas у-Te 'O IND. 2' e α- 'Li IND. 2'Te 'O IND. 2'O IND. 5' persistem até os estágios finais da cristalização. A estrutura das bandas no espectro infravermelho é similar àquelas observadas em vidros Te "O IND. 2'. Para vidros selecionados, as energias de ativação associadas as fases cristalinas foram calculadas considerando que os picos de cristalização das curvas de DSC possam ser representados por três funções lorentzianas reportados em diferentes tamanhos de partículas. Os resultados de DSC sugerem ainda que tratamentos térmicos a longos tempos, em torno de 'T IND. g', imediatamente após o quenching são favoráveis para a produçao de regiões ordenadas nos vidros sem necessariamente aumentar o número de núcleos na matriz vítrea. / Abstract: In the present study, four 20 'Li IND. 2' O-80Te 'O IND. 2', glasses were prepared with identical nominal composition but with different histories. X-Ray Diffraction, Infrared Sprectroscopy, Raman Spectroscopy and Differential Scanning Calorimetry techniques were used to understand the effects of the thermal histories on the thermal and structural properties of the studied glasses. It was observed that investigated properties depend strongly on the thermal histories of the glasses. X-ray Diffraction results reveal the presence of three distinct у-Te 'O IND. 2', α-Te 'O IND. 2 and α- 'Li IND. 2'Te 'O IND. 2'O IND. 5' crystalline phases in the studied glasses with the following crystallization у-Te 'O IND. 2' 'seta' α-Te 'O IND. 2 'seta' у-Te 'O IND. 2', α-Te 'O IND. 2 'seta' α- 'Li IND. 2'Te 'O IND. 2'O IND. 5" sequence. The у-Te 'O IND. 2' is a mestastable phase while α- 'Li IND. 2'Te 'O IND. 2'O IND. 5' crystalline phases persist up to the final stages of the in situ bulk crystallization. The infrared band structure of the studied glasses is similar to the one observed in glassy Te 'O IND. 2'. For selected glasses, activation energies were evaluated from lorentzian three-peak deconvolution of the DSC crystallization peak recorded at different particle sizes. DSC results suggested that heat annealing immediately after quenching at temperatures around 'T IND. g' and longer times are favorable to produce local ordered regions in the glass without necessarily the nuclei number in the glass matrix. / Doutor

Orientador: Amauri Garcia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-23T00:16:48Z (GMT). No. of bitstreams: 1 Paula_MarcoAntoniode_M.pdf: 6257043 bytes, checksum: 67fa65ec75efb5c07d163b22b9b530c2 (MD5) Previous issue date: 1997 / Resumo: Este trabalho objetiva, essencialmente, analisar de formas teórica e experimental os aspectos relativos à purificação do telúrio, utilizando o método da fusão zonal.Processaram-se amostras de telúrio, partindo de matérias primas com pureza de 99,95 % , com 9 (nove) passadas de três zonas líquidas simultâneas, de 70 mm de largura cada uma, a uma velocidade constante de 5mm/h, em uma barra de 200 mm de comprimento. Para a caracterização do material processado foram feitas análises da composição química do material e comparadas com as do material de partida, juntamente com análises macro e micrográfica e medidas de dureza sob carga reduzida, para verificação do grau de pureza do material. Os resultados demonstraram a eficiência do processo e pela presença silmutânea de impurezas de k<1 e de k>1 há a necessidade de utilização de uma dupla fusão zonal para alcançar-se elevadas purezas / Abstract: The present work is a theoretical and practical analysis related to the tellurium purification by zone melting. The starting material was 99,95 % purity Te. The zone melting process was carried out by using three simultaneous liquid zones with 70 mmwide each one and a constant displacement speed of 5mm/h in a 200 mm long rodo Chemical analysis was performed to compare with the starting material.Both macro and micrographic analysisand also hardness testing were conducted to verify the final degree of purity. The obtained results have demonstrated the efficiencyof the processoThe simultaneous presence of k < 1 and k > 1 impurities suggests the need of using a double zone melting system to reach purity levels higher than 99.99 / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica