Tesi sul tema "Tellurium"
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Tellurium.
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Tellurium".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Rooms, John Frederick. "A matrix isolation investigation of tellurium crochemistry using hydrogen telluride and tellurium dimers as precursors". Thesis, University of Hull, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419789.
Testo completo
2
Pathirana, Hema M. K. K. "Ligand chemistry of tellurium". Thesis, Aston University, 1985. http://publications.aston.ac.uk/14516/.
Testo completo
3
West, Anthony A. "Structural studies in tellurium chemistry". Thesis, Aston University, 1989. http://publications.aston.ac.uk/9705/.
Testo completoAbstract (sommario):
The primary theme of this research was the characterisation of new and novel organo-tellurium complexes, using the technique of single crystal X-ray analysis to establish more firmly the various coordination modes of tellurium. In each study the unit cell dimensions and intensity data were collected using an Enraf-Nonius CAD-4, four circle diffractometer. The raw data collected in turn was transferred to the Birmingham University Honeywell Multics System and processed using the appropriate computer packages for the determination of crystal structures. The molecular and crystal structures of: bis[2-(2-pyridyl)phenyl]tritelluride, bis[2-(N-hydroxy)iminophenyl] ditelluride, 2-(2-pyridyl)phenyltellurium(IV) tribromide, (2-N,N-dimethylbenzylamine-C,N')tellurium(IV)tribromide, 2-dichloro(butyl)tellurobenzaldehyde, 2-dichlorobutotelluro-N-dimethylbenzyl ammonium chloride, dimethyldithiocarbamato[2-(2-pyridyl)phenyl]tellurium(II), dimethyldithiocarbamato[2-(2-quinolinyl)phenyl]tellurium(II) and para-ethoxypheny[2-(2-pyridyl)phenyl]telluride are described. In each structure, the Lewis acidity of tellurium appears to be satisfied by autocomplex formation, through short-range intramolecular secondary bonds between tellurium and an electron denoting species, (generally nitrogen in these structures) with long range weak inter molecular contacts forming in the majority of the tellurium(IV) structures. The order of Lewis acidity in each structure can be considered to be reflected by the length of the short range intramolecular secondary bond, identified, that is, when tellurium has a low Lewis acidity this interaction is long. Interestingly, no primary bonds are found trans to a Te-C covalent bond in any of the above structures, highlighting the strong trans effect of aromatic and aryl groups in tellurium complexes.
4
Swan, R. "Experimental studies of thin tellurium films". Thesis, London South Bank University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618631.
Testo completo
5
Swan, Ronnie. "Experimental studies of thin tellurium films". Thesis, London South Bank University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316966.
Testo completo
6
Espinosa, Ortiz Erika. "Bioreduction of selenite and tellurite by Phanerochaete chrysosporium". Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1193/document.
Testo completoAbstract (sommario):
Le sélénium et le tellurium partagent des propriétés chimiques communes et appartiennent à la colonne des éléments chalcogènes de la classification périodique des éléments. Ces métalloïdes ont des propriétés physico-chimiques remarquables et ils ont été utilisés dans un grand nombre d'applications dans le domaine des hautes technologies (électronique, semi-conducteurs, alliages). Ces éléments, qui se retrouvent généralement sous formes d'oxyanions, sont extrêmement solubles dans l'eau et présentent une forte toxicité. Leur libération dans l'environnement est donc d'un enjeu capital. Différentes méthodes physico-chimiques ont été développées pour la récupération de ces metalloïdes, en particulier pour le sélénium. Néanmoins, ces méthodes requièrent un équipement lourd et couteux et ne sont pas très recommandables sur le plan écologique. Le traitement biologique est donc une bonne alternative pour la récupération de Se et de Te provenant des effluents pollués. Cette approche réside dans la bioréduction des différents oxyanions sous formes métalliques. Ceux-ci sont moins toxiques et d'intérêts commerciales notables surtout lorsqu'ils se présentent sous forme nanométrique. L'utilisation de micro-champignons comme microorganismes catalyseur de la réduction de Se et de Te a été démontrée dans cette étude. La réactivité du champignon responsable de la pourriture blanche, Phanerochaete chrysosporium en présence de sélénite et de tellurite a été évaluée, ainsi que son application potentielle pour le traitement des eaux contaminées et la production de nanoparticules. La présence de Se et de Te a une influence importante sur la croissance et la morphologie du champignon. Il s'avère que P. chrysosporium est très sensible à la présence de sélénites. La synthèse de Se° et de Te° sous forme de nanoparticules piégées dans la biomasse fongique a été observée, ainsi que la formation de nano-composites Se-Te lorsque le champignon était cultivé simultanément en présence des deux métalloïdes. L'usage potentiel de biofilm fongiques pour le traitement des effluents semi-acides (pH 4.5) contenant du Se et du Te a été suggéré. De plus, le traitement en mode continu de sélénite dans un réacteur à biofilm fongique granulaire a été évalué. Le réacteur a montré un rendement d'élimination du sélénium en régime permanent de 70% pour differentes conditions opératoires. Celui-ci s'est montré efficace pendant une période supérieure à 35 jours. La bonne sédimentation du biofilm granulaire facilite la séparation du sélénium de l'effluent traité. L'utilisation du biofilm granulaire contenant du sélénium élémentaire comme bio-sorbant a également été étudiée. Cet adsorbant hybride s'est montré prometteur pour l'immobilisation du zinc présent dans les effluents semi-acides. La plupart des recherches effectuées se sont focalisées sur l'utilisation des biofilms granulaires. Toutefois, la croissance du champignon suite à l'exposition à des concentrations différentes de sélénites a également été étudiée. Des micro-électrodes à oxygène et un microscope confocal à balayage laser ont été utilisées pour évaluer l'effet du sélénium sur la structure des biofilms fongiques. Quel que soit le mode de croissance de P. chrysosporium, le mécanisme de réduction du sélénite semble être toujours le même tout en menant à la formation de sélénium élémentaire. Cependant, l'architecture des biofilms et l'activité en oxygène sont influencées par la présence de séléniumSelenium (Se) and tellurium (Te) are particular elements, they are part of the chalcogens (VI-A group of the periodic table) and share common properties. These metalloids are of commercial interest due to their physicochemical properties, and they have been used in a broad range of applications in advanced technologies. The water soluble oxyanions of these elements (i.e., selenite, selenate, tellurite and tellurate) exhibit high toxicities, thus their release in the environment is of great concern. Different physicochemical methods have been developed for the removal of these metalloids, mainly for selenium. However, these methods require specialized equipment, high costs and they are not ecofriendly. The biological treatment is a green alternative to remove Se and Te from polluted effluents. This remediation technology consists on the microbial reduction of Se and Te oxyanions in wastewater to their elemental forms (Se0 and Te0), which are less toxic, and when synthesized in the nano-size range, they can be of commercial value due to their enhanced properties. The use of fungi as potential Se- and Te-reducing organisms was demonstrated in this study. Response of the model white-rot fungus, Phanerochaete chrysosporium, to the presence of selenite and tellurite was evaluated, as well as their potential application in wastewater treatment and production of nanoparticles. The presence of Se and Te had a clear influence on the growth and morphology of the fungus. P. chrysosporium was found to be more sensitive to selenite. Synthesis of Se0 and Te0 nanoparticles entrapped in the fungal biomass was observed, as well as the formation of unique Se-Te nanocomposites when the fungus was cultivated concurrently in the presence of Se and Te. Potential use of fungal pellets for the removal of Se and Te from semi-acidic effluents (pH 4.5) was suggested. Moreover, the continuous removal of selenite in a fungal pelleted reactor was evaluated. The reactor showed to efficiently remove selenium at steady-state conditions (~70%), and it demonstrated to be flexible and adaptable to different operational conditions. The reactor operated efficiently over a period of 35 days. Good settleability of the fungal pellets facilitated the separation of the selenium from the treated effluent. The use of elemental selenium immobilized fungal pellets as novel biosorbent material was also explored. This hybrid sorbent was promising for the removal of zinc from semi-acidic effluents. The presence of selenium in the fungal biomass enhanced the sorption efficiency of zinc, compared to Se-free fungal pellets. Most of the research conducted in this study was focused on the use of fungal pellets. However, the response of the fungus to selenite in a different kind of growth was also evaluated. Microsensors and confocal imaging were used to evaluate the effects of selenium on fungal biofilms. Regardless of the kind of fungal growth, P. chrysosporium seems to follow a similar selenite reduction mechanism, leading to the formation of Se0. Architecture of the biofilm and oxygen activity were influenced by the presence of selenium
7
Bates, C. M. "Pentamethylcyclopentadienyl (Cp*) compounds of selenium and tellurium". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636056.
Testo completoAbstract (sommario):
Successful preparations were: (1) bis(pentamethylcyclopentadienyl)selenium, prepared by the reaction of selenium diethydithiocarbamate with lithiated pentamethylcyclopentadiene; (2) Cp*SenLi (n = 2,3,4), prepared by the reaction of elemental selenium with lithiated pentamethylcyclopentadiene in THF and its subsequent reaction with iodomethane to produce (3) methyl(pentamethylcyclopentadienyl)selenium or water to produce the polyselenide mixture (4) Cp*2Sen (n = 2,3,4). (4) was also produced by the low temperature reaction of selenium chloride with lithiated pentamethylcyclopentadiene. The compounds were characterised by conventional methods including 77Se NMR spectroscopy. The x-ray structural determination was obtained for compound (1) revealing the largest C-Se-C bond angle recorded for a simple diorganoselenide. The reactivities of the compounds (1) (3) and (4) were investigated in reactions with unsaturated transition metal fragments. In the reactions of (1) with sources of the tungsten and chromium carbonyl compounds [W(CO)5THF], [W(CO)3(CH3CN)3], [Cr(CO)5THF], [Cr(CO)4nbd] and [Cr(CO)3(CH3CN)3] the first example of reduction of a selenide to form a diselenide within the transition metal coordination sphere was observed. These produced the complexes [M(CO)2{Se2Cp*2}] (M = W, Cr). The x-ray structure determinations are included. These complexes contain the longest Se-C bonds recorded. A 1,2 metal shift was observed for the tungsten complex using the technique of two dimensional exchange NMR spectroscopy. (3) reacts with [W(CO5THF] or [Cr(CO)5THF] to produce the complexes [W(CO)5{Se(Me)Cp*}] and [Cr(CO)5{Se(Me)Cp*}]. The first recorded Se-W satellites are reported for the former. The compounds (1), (3) and (4) were reacted with diiron nonacarbonyl to produce the complex [Fe3Se2(CO)5]. Compound (1) was reacted with a half molar equivalent of [PdCl2(PhCN)2] to produce the complex [Pd2Cl4(SeCp*2)].
8
Conibeer, Gavin John. "Zinc diffusion in tellurium doped gallium antimonide". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262103.
Testo completo
9
Abid, K. Y. "Synthetic approaches to organoselenium and tellurium semiconductors". Thesis, Aston University, 1987. http://publications.aston.ac.uk/9723/.
Testo completo
10
Ahmed, Mohammed A. K. "Synthesis and physical investigation of tellurium dithiocarbamates". Thesis, Aston University, 1985. http://publications.aston.ac.uk/11726/.
Testo completo
11
Abbott, Jonathan D. "Carbon Coated Tellurium for Optical Data Storage". BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2360.
Testo completoAbstract (sommario):
A highly durable optical disk has been developed for data archiving. This optical disk uses tellurium as the write layer and carbon as a dielectric and oxidation prevention layer. The sandwich style CTeC film was deposited on polycarbonate and silicon substrates by plasma sputtering. These films were then characterized with SEM, TEM, EELS, ellipsometry, ToF-SIMS, etc, and were tested for writability and longevity. Results show the films were uniform in physical structure, are stable, and able to form permanent pits. Data was written to a disk and successfully read back in a commercial DVD drive.
12
Chau, Hei. "Synthesis and properties of tellurium-containing long chain fatty acid derivatives /". [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13554566.
Testo completo
13
Mullins, J. T. "Properties of Tellurium-based II-VI semiconducting materials". Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6004/.
Testo completoAbstract (sommario):
Opto-electronic devices operating as radiation detectors in the infra-red region of the electromagnetic spectrum are currently of interest. By operating in the infra-red, particularly in the 8-12 µm wavelength range, it is possible to detect the infra-red radiation emitted by objects at ordinary temperatures and so to image in darkness. Furthermore, at such wavelengths, vision is also possible in mist, fog or smoke. Semiconducting materials which have an energy gap corresponding to the photon energy of the radiation of interest are suitable for fabricating such devices. The growth and characterisation of two such materials both formed from elements in groups IIB and VIA of the periodic table and generally refered to as II-VI compounds, forms the subject matter of this thesis. The first of these materials is the ternary compound mercury cadmium telluride ((Hg,Cd)Te). This is a well established infra-red material and was grown for this work in thin film form by Metal Organic Vapour Phase Epitaxy (MOVPE) using the Inter- diffused Multilayer Process (IMP). The resulting layers were characterised optically and electrically and were shown to be of excellent compositional uniformity, an important consideration for infra-red devices, but to contain extremely high acceptor concentrations in the as grown state. These high acceptor concentrations were attributed to mercury vacancies present due to the inherent weakness of the material. Fitting of the electrical data obtained from p-type samples using a multicarrier/multilayer transport model suggested that the mercury vacancy concentrations were also highly non-uniform. A more novel alternative to (Hg(_1)Cd)Te is the HgTe:ZnTe superlattice system. By forming a superlattice from the two constituent binary compounds, rather than alloy, quantum confinement and strain effects may, in principle, be used to tailor the optical and electronic properties to some extent independently of the composition. The resulting material may also be structurally more stable than an equivalent alloy. Here the development of a thermal MOVPE growth process for this superlattice system is described and it is shown that such superlattices may be preferable to the equivalent alloys as they are easier to grow by MOVPE. Initial structural and optical studies and theoretical calculations have confirmed the suitability of MOVPE for the growth of this superlattice system and its applicability for infra-red applications.
14
Bello, Yusuf O. "Tellurium and selenium precipitation from copper sulphate solutions". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95895.
Testo completoAbstract (sommario):
Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: The copper sulphate leach solutions produced during the final pressure leach stages in base metal refinery processes contain low concentrations of other precious metals (OPMs, namely Rh, Ru and Ir ) and impurities in addition to the base metals (BMs) of interest. Se and Te impurities, in particular, must be removed from the leach solution before it is fed to copper electrowinning because these species have adverse effects on electrowinning efficiency. Currently, these elements are being precipitated from the leach solution with sulphurous acid. Se precipitation is satisfactory but Te removal still proves challenging. Previous studies have shown that tellurium can either be precipitated as cuprous telluride from copper sulphate solutions by reduction with sulphurous acid alone, or by the addition of SO2 as a precipitating agent and metallic copper as an additional precipitating agent. The objective of this study was to evaluate the effects of different process variables on Te and Se recovery in order to propose operating conditions at which increased tellurium precipitation can be achieved with minimal co-precipitation of base metals of interest (notably Cu and Ni). This would also aid in the development of a better understanding of tellurium and selenium precipitation mechanisms in CuSO4-H2SO4 medium.
AFRIKKANSE OPSOMMING: Die kopersulfaat logingsoplossing wat gedurende die finale druklogingstadia in basis metaal raffinaderye produseer word bevat, behalwe vir die basis metale van belang, ook lae konsentrasies ander edelmetale (AEM, naamlik Rh, Ru, en Ir) sowel as onsuiwerhede. Se en Te onsuiwerhede, in die besonder, moet vanuit die logingsoplossing verwyder word voordat die oplossing na die koper elektrowinning gevoer word omdat hierdie spesies negatiewe effekte op die elektrowinning effektiwiteit het. Hierdie elemente word tans met swaweligsuur vanuit die logingsoplossing gepresipiteer. Se presipitasie is voldoende, maar die Te verwydering bly steeds problematies. Vorige studies het getoon dat tellurium as kuprotelluried vanuit kopersulfaat oplossings presipiteer kan word deur middel van reduksie met swaweligsuur alleen, of met die byvoeging van SO2 as presipiteermiddel en metallieke koper as addisionele presipiteermiddel. Die doelwit van hierdie studie was om die effekte van verskillende prosesveranderlikes op Te en Se presipitasie te ondersoek ten einde bedryfstoestande voor te stel wat verbeterde tellurium presipitasie toelaat met minimale kopresipitasie van basis metale van belang (hoofsaaklik Cu en Ni). Dit sal ook bydra tot die ontwikkeling van ʼn beter begrip van die tellurium en selenium presipitasie meganisme in ʼn CuSO4-H2SO4 medium.
15
Poon, Jia-fei. "Exploring Catalytic Tellurium-Based Antioxidants : Synthesis and Evaluation". Doctoral thesis, Uppsala universitet, Organisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302475.
Testo completoAbstract (sommario):
This thesis is concerned with the synthesis and evaluation of various tellurium-based chain-breaking antioxidants. The purpose is to find novel regenerable compounds with improved radical-trapping capacity. In the first part of this work, we explore the possibilities to incorporate tellurium into tocopherols and aromatic amines. Overall, tocopherols carrying alkyltelluro groups are better radical-trapping agents than the corresponding sulfur- and selenium analogues. Among them, 7-octyltelluro δ-tocopherol showed a ca. 17-fold higher reactivity than recorded for α-tocopherol and much better regenerability. Even longer inhibition times were recorded for the corresponding bis(tocopheryl) tellurides. In the aromatic amine series, diphenyl amines carrying alkyltelluro groups were shown to function as efficient radical-quenchers capable of inhibiting peroxidation for 460 min in the presence of N-acetylcysteine. Thiol-consumption experiments suggested that the long inhibition times are due to efficient quenching of in-situ formed alkoxyl radicals in a solvent cage. In the second part of the thesis, we study how the antioxidant properties are affected by variations in the electron density at tellurium and the number of alkyltelluro substituents in the molecule. Evaluation of a series of aryltelluro phenols carrying electron donating and electron withdrawing groups in the para-position of the aryl moiety suggested that a high electron density at the heteroatom prolonged the inhibition time. Among alkyltelluro phenols, alkyltelluro resorcinols and bis(alkyltelluro) phenols, phenols carrying alkyltelluro groups in both ortho positions were superior when it comes to radical-trapping activity and regenerability.
16
Hall, Bradley Devin. "Powder processing, powder characterization, and mechanical properties of LAST (lead-antimony-silver-tellurium) and LASTT (lead-antimony-silver-tellurium-tin) thermoelectric materials". Diss., Connect to online resource - MSU authorized users, 2008.
Cerca il testo completoAbstract (sommario):
Thesis (M.S.)--Michigan State University. Materials Science and Engineering, 2008.Title from PDF t.p. (viewed on Aug. 7, 2009) Includes bibliographical references (p. 151-159). Also issued in print.
17
Aucoin, Sandblom Nicole Therese. "Experimental and theoretical studies of multiply bonded tellurium compounds". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0015/NQ47912.pdf.
Testo completo
18
Elaseer, Abdusalam S. "Transmethylation of selenium and tellurium : analytical and environmental aspects". Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240775.
Testo completo
19
Wilhelm, Allison Anne. "Tellurium Based Glasses for Bio-Sensing and Space Applications". Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195158.
Testo completoAbstract (sommario):
Te2As3Se5 (TAS) fibers are often used in bio-sensing applications requiring direct contact between the fiber and live cells. However, the toxicity and stability of chalcogenide glasses typically used in such bio-sensing applications are not well known. The stability and toxicity of TAS glass fibers were therefore examined. The surface of TAS fibers stored for up to three years in air were analyzed using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), and atomic force microscopy (AFM). It is shown that an oxide layer develops on the surface of TAS fibers stored in air. This oxide layer is highly soluble in water and therefore easily removed. Additional studies using cyclic voltammetry show that the fresh TAS glass surface is insoluble in water for at least a few days, and attenuation measurements show that oxidation does not affect the transmission properties of the glass fibers. It was also determined that old, oxidized fibers pose a toxic threat to cells, while washed and new fibers show no toxic effect. Therefore, it is concluded that a soluble oxide layer forms on the surface of TAS fibers stored in air and that this layer has a toxic effect on cells in an aqueous environment. However, through etching, the oxide layer and the toxicity can be easily removed.In other applications of telluride glasses, such as the search for possible signs of life on exoplanets, a glass transmitting further into the IR is required in order to detect molecules, such as CO2. A new family of Tellurium based glasses from the Ge-Te-I ternary system has therefore been investigated for use in space and bio-sensing applications. A systematic series of compositions has been synthesized in order to explore the ternary phase diagram in an attempt to optimize the glass composition for the fiber drawing and molding process. The resulting glass transition temperature range lies between 139°C and 174°C, with deltaT values between 64°C and 124°C. The most stable glass composition was found to be Ge20Te73I7. The Ge-Te-I glasses were found to have an effective transmission window between 2-20 microns, encompassing the region of interest for the identification of biologically relevant species such as carbon dioxide. Furthermore, the successful fibering and molding of the composition Ge20Te73I7 are shown. Lastly, an investigation into glass conductivity was completed resulting in a maximum conductivity value on the order of 10^-4 Ohm-1 cm-1 for the composition Ge20Te73I7.In an attempt to take advantage of the high conductivity of telluride glasses, a new approach to virus detection in an aqueous environment has been developed using the electrophoretic deposition of protein and viruses on the charged glass surface for in situ infrared characterization and identification. A proof of concept experiment has been completed using a germanium ATR plate and an indium tin oxide (ITO) plate as the experimental electrodes. Charged proteins and viruses were driven to the surface of the oppositely charged germanium ATR crystal, once a potential was applied to the system. FTIR/ATR spectroscopy was used before and throughout electro-deposition to enable the in situ observation of the deposition with time. This technique resulted in the successful deposition and removal of the protein Bovine Serum Albumin (BSA), and deposition of the virus MS2, a bacteriophage that infects only bacteria, with an applied voltage of only 1.1V. Furthermore, based on analysis of the ATR spectra, distinct spectral features were identified for the protein and virus showing the potential for identification and characterization of biological molecules in an aqueous environment. A Ge20Te73I7 ATR plate was synthesized but unsuccessfully applied as an electrode in these experiments, likely due to an inconsistent conductivity along the plate. A glass from the Ge-As-Te system with a lower but more consistent conductivity was thereafter synthesized and successfully used as an electrode and sensing element in the electro-deposition experiment.
20
MESTNIK, SONIA A. C. "Separacao do Mo-99 do Te-132 usando tioureia como agente complexante .Aplicacao a separacao do Mo-99 dos produtos de fissao". reponame:Repositório Institucional do IPEN, 1987. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9881.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-10-09T12:32:25Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:31Z (GMT). No. of bitstreams: 1 03134.pdf: 2064767 bytes, checksum: 2ee561f5c7d60b299f3f1a26c7b85831 (MD5)
Tese(Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
21
周晞 e Hei Chau. "Synthesis and properties of tellurium-containing long chain fatty acidderivatives". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31233478.
Testo completo
22
Badaye, Massoud. "Fabrication and investigation of tellurium thin film CO2 laser detectors". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61901.
Testo completo
23
Nwambaekwe, Kelechi Chiemezie. "Tellurium attenuation of kesterite band-gap for improved photovoltaic efficiency". University of the Western Cape, 2019. http://hdl.handle.net/11394/6656.
Testo completoAbstract (sommario):
>Magister Scientiae - MScTellurium is a member of the chalcogen group in the periodic table and is known to be a better semiconductor material when compared to sulfur and selenium. By introducing tellurium into the kesterite structure there would be an improvement in the semiconducting property of the kesterite material. This research focused on incorporating tellurium into kesterite structure in order to reduce its band-gap thereby improving its light absorption and ultimately lead to a more efficient photovoltaic effect. For a typical synthesis, kesterite nanoparticles were synthesized by anion hot injection process which involved the injection of the anion precursor comprising of sulfur, selenium and tellurium in diethylene glycol into a solution containing the cation precursor which are copper (II) chloride, Zinc chloride and tin (II) chloride which are dissolved in diethylene glycol. The synthesized nanoparticles were copper zinc tin sulfide (CZTS), copper zinc tin sulfide selenide telluride (CZTSSeTe) and copper zinc tin sulfide telluride (CZTSTe). Morphological characterization of the synthesized nanoparticles was carried out by high-resolution scanning electron microscopy (HRSEM) and high-resolution transmission electron microscopy (HRTEM) to obtain the shape of the surface and internal structure of the nanoparticles respectively. The micrograph obtained from HRSEM shows that all synthesized nanoparticles had a flower-like surface appearance which is a common morphology obtained for non-vacuum synthesized kesterite nanoparticles. The micrograph obtained from TEM showed that all nanoparticles were agglomerated and had a black surface covering which attributable to the solvent used during synthesis, washing and centrifugation. The internal structure of the synthesized nanoparticles was obtained through small angle x-ray scattering (SAXS) plot of the shapes. The shape obtained for the nanoparticles were core shell hollow sphere for CZTS, core shell dumb-bell for CZTSSeTe and solid sphere for CZTSTe.
24
Mbogo, S. A. "The co-ordination chemistry of tellurium and related selenium ligands". Thesis, Aston University, 1990. http://publications.aston.ac.uk/25359/.
Testo completoAbstract (sommario):
2-(2-pyridyl)phenyl(p-ethoxyphenyl)tellurium(II), (RR1Te) reacts with HgCl2 at room temperature to give white HgCl2.RR1Te. On setting aside, or on warming the reaction mixture a yellow material, [R1HgCl.(RTeCl)2] is formed. Multinuclear NMR(125Te, 199Hg, 1H) and mass spectroscopy confirm the formulation, and confirm the ease of transfer of the p-ethoxyphenyl group (R1) between the metal centres. The crystal structure of the yellow material consists of two discrete RTeCl molecules together with a R1HgCl molecule. There is no dative bond formation between these species, hence the preferred description of the formation of an inclusion complex. The reaction of RR1Te with Copper(I) chloride in the cold gives an air sensitive yellow product Cu3Cl3(RR1Te)2(0.5CH3CN); under reflux in air changes to the green Cu2Cl(RR1Te)(0.5 EtOH). By contrast, the reaction of RR1Te with acetonitrile solution of Copper(II) salts under mild conditions affords the white materials CuCl(RR1Te) and CuBr(RR1Te)H2O. RR1Te reacts with PdCl2 and PtCl2 to give materials albeit not well defined, can be seen as intermediates to the synthesis of inorganic phase of the type M3XTe2XCl2X. Paramagnetism is associated with some of the palladium and platinum products. The 195Pt NMR measurement in DMSO establishes the presence of six platinum species, which are assigned to Pt(IV), Pt(III) or Pt(II). The reactions show that in the presence of PdCl2 or PtCl2 both R and R1 are very labile. The reaction of RHgCl(R= 2-(2-pyridyl)phenyl) with SeX4(X= Cl, Br) gives compounds which suggest that both Trans-metallation and redox processes are involved. By varying reaction conditions materials which appear to be intermediates in the trans-metallation process are isolated. Potentially bidentate tellurium ligands having molecular formula RTe(CH2)nTeR,Ln, (R= Ph,(t-Bu). C6H4, n = 5,10) are prepared. Palladium and Platinum complexes containing these ligands are prepared. Also complex Ph3SnC1L(L = p-EtO.C6H4) is prepared.
25
Al-Salim, Najih I. "The synthesis and properties of some novel tellurium-containing ligands". Thesis, Aston University, 1987. http://publications.aston.ac.uk/14522/.
Testo completo
26
Johnston, Murray. "Thermodynamics of selenium and tellurium in molten metallurgical slags and alloys". University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0064.
Testo completoAbstract (sommario):
There are a number of impurity elements present in sulphide ores that can have a deleterious effect on the properties of the final copper metal product. In this thesis, an equilibrium distribution technique was used to determine the thermodynamic behaviour of selenium and tellurium in molten slags used in copper production. Calcium ferrite based slags and copper or silver alloy were equilibrated in magnesia crucibles at temperatures of 1200 to 1400 °C and oxygen partial pressures of 10-11 to 10-0.68 atm. Under conditions typical of those employed during copper converting, the minor elements were found to enter the slag as negatively charged species. The partitioning of selenium and tellurium to the slag was greatest at high temperature, low oxygen partial pressure and at highest concentration of basic oxide (CaO or BaO). The experimentally derived data were combined with published information to calculate the selenide and telluride capacities of the slag, and also to generate fundamental thermodynamic activity data for selenium and tellurium in the slag phase. It was found that the activity coefficients of selenium and tellurium were independent of their concentration in the slag over the range studied, but were strongly dependent on the temperature, slag chemistry and oxidation state of the slag. Experiments were also designed and carried out to determine what effect the presence of iron oxide and its oxidation state has on the behaviour of selenium in the slag. A series of experiments involving iron oxide additions to a calcium aluminate slag was conducted under increasingly oxidising conditions to assess the effect of total iron on the selenide capacity as the dominant oxidation state of iron in the slag changed. It was shown that at a constant ratio of CaO:Al2O3, the selenide capacity increased with total iron in the slag. However, the effect on the selenide capacity did not appear any more significant as the Fe3+:Fe2+ ratio changed in a particular direction. 4 Another series of experiments was carried out with iron calcium silicate slags to determine the stability of phases within the slag, and how this affected the equilibrium distribution and activity coefficient of selenium in the slag. A number of solid phases were identified and their composition determined by scanning electron microscopy, energy dispersive spectroscopy and electron microprobe analysis. The composition and minor element content of the remaining liquid was calculated using a thermodynamic model. From this it was found that the capacity of the liquid slag has a region of independence against slag chemistry, before increasing strongly with increasing lime content to the calcium ferrite composition. Some of the implications of this work are discussed with reference to the practicality of adjusting the process variables in a large-scale industrial process for the purpose of managing minor element content of the molten phases. Considerations include the effect on copper recovery and rate of wear of furnace refractory materials.
27
Landvogt, Christian Rudolf [Verfasser]. "Gold-Tellurium Clusters and Tetrachloridoaurates with Divalent Cations / Christian Rudolf Landvogt". Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1159955131/34.
Testo completo
28
Richards, Martyn W. "Chemical reactions of caesium, tellurium and oxygen with transition metal alloys". Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276201.
Testo completo
29
Ma, Yi. "Thermoelectric Properties of P-Type Nanostructured Bismuth Antimony Tellurium Alloyed Materials". Thesis, Boston College, 2009.
Cerca il testo completoAbstract (sommario):
Thesis advisor: Zhifeng RenSolid-state cooling and power generation based on thermoelectric effects are attractive for a wide range of applications in power generation, waste heat recovery, air-conditioning, and refrigeration. There have been persistent efforts on improving the figure of merit (ZT) since the 1950's; only incremental gains were achieved in increasing ZT, with the (Bi1-xSbx)2(Se1-yTey)3 alloy family remaining the best commercial material with ZT ~ 1. To improve ZT to a higher value, we have been pursuing an approach based on random nanostructures and the idea that the thermal conductivity reduction that is responsible for ZT enhancement in superlattices structures can be realized in such nanostructures. The synthesis and characterization of various nanopowders prepared by wet chemical as well as high energy ball milling methods will be discussed in this dissertation. The solid dense samples from nanopowders were prepared by direct current induced hot press (DC hot press) technique. The thermoelectric properties of the hot pressed samples have been studied in detail. By ball milling ingots of bulk alloy crystals and hot pressing the nanopowders, we had demonstrated a high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this dissertation, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 can be achieved. Our material also exhibits a ZT of 0.7 at 250 °C, close to the value reached when ingot was used. This process is more economical and environmentally friendly than starting from bulk alloy crystals. The ZT improvement is caused mostly by the low thermal conductivity, similar to the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the high density grain boundaries and defects. The performance of thermoelectric materials is determined by its dimensionless figure-of-merit (ZT) which needs to be optimized within a specific temperature range for a desired device performance. Hence, we show that by varying the Bi/Sb ratio, the peak ZT can be shifted to a higher or lower temperature for power generation applications or a cooling mode operation. A peak ZT of about 1.3 is achieved from a Bi0.4Sb1.6Te3 composition which is highest among the different compositions. These nanostructured bulk samples have a significantly low lattice thermal conductivity compared to the bulk samples due to the increased phonon scattering in the grain boundaries and defects. This study shows that Bi0.5Sb1.5Te3 may potentially perform better for cooling devices, while Bi0.3Sb1.7Te3 should be able to show better power generation efficiency. Several issues related to accurate measurement of thermoelectric properties were identified and many of them were solved during my studies and these are discussed in this thesis. With the data we obtained, it is clear that nanopowder-based thermoelectric materials hold significant promise. Therefore, a review of synthesis of nanostructured materials by solution-based methods, including a hydrothermal process for the Bi2Te3, Bi2Se3, and Bi2Te2.25Se0.75 nanoparticles, a solvothermal route for Sb2Te3 nanostructures, and a polyol process for the preparation of Bi nanostructures is presented in this dissertation. These new nanostructures may find applications in enhancing the thermoelectric performance. Although small sized and well dispersed nanopowders of various thermoelectric materials could be prepared by a solution method in large scale, contamination and partial oxidation are always big challenges in a chemical approach. Hence, a high energy ball milling technique to prepare thermoelectric nanopowders in large scale and without major contamination is still found to be more efficient and preferred
Thesis (PhD) — Boston College, 2009
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
30
Hesford, Matthew James. "Synthesis and coordination chemistry of acyclic and macrocyclic tellurium-containing ligands". Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/361577/.
Testo completo
31
Moffett, Christina. "Characterization of Tellurium Back Contact Layer for CdTe Thin Film Devices". Thesis, Colorado State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10826197.
Testo completoAbstract (sommario):
Cadmium Telluride (CdTe) thin film photovoltaic technology has shown favorable progress due to inexpensive and efficient processing techniques. However, efficiencies have yet to reach the overall projected CdTe device efficiency, with the back contact being a main source of CdTe performance limitations. Tellurium (Te) applied as a back contact has led to significant increases in fill factor and an overall progress in device efficiency. Devices deposited with Te show significant improvement in uniformity, even without intentional Cu doping, when compared to devices without Te. In current - density measurements, Te shows stability even at low temperatures, which is indicative of a low barrier developed at the CdTe/Te interface. X-ray and ultra-violet photoelectron spectroscopy were carried out to examine the valence band offset at the CdTe/Te back contact interface. The valence band offset was shown to be highly dependent on the Te thickness and was largely affected by oxidation and contamination at the surface. Capacitance measurements were carried out to study the effect Te has on the absorber depletion width. Data indicate a decreased depletion width with Te applied at the back of thin film CdTe devices, which agrees with increased device performance. Te thickness was varied in all studies to understand the effect of application thickness on device performance and material characteristics. With a thicker Te layer leading to overall improvement in device performance and favorable device characteristics.
32
Culshaw, Peter Norman. "Generation and reactivity of carbon, sulphur and tellurium centred free radicals". Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/14841.
Testo completoAbstract (sommario):
Using ESR dimer-radical equilibrium techniques the heat of formation, △Hf0, of the pentamethylcyclopentadienyl radical was determined as 7.4 kcal mol−1, and hence SEMeH was calculated to be 37.9 kcal mol−1. It was attempted to determine △Hf0 for the pentaethyl- and pentamethoxycarbonylcyclopentadienyl radicals, but this proved unsuccessful. From appearance energy measurements, △Hf0 (Pentadienyl) was determined to be 49.6 kcal mol−1 Using photoacoustic calorimetry, the C3-H bond dissociation energy of penta−1,4-diene and several 3-substituted pentadienes were determined; i.e. for penta−1,4-diene (DH° (C3-H) = 76.6±0.6 kcal mol−1), 3-methyl- penta−1,4-diene (DH°(C3-H) = 76.6±0.6 kcal mol−1) and 3-hydroxypenta−1,4-diene (DH°(C3-H) = 69.0±0.6 kcal mol−1). ESR exchange broadening methods were used to show that SEESR (3-methylpentadienyl) is virtually the same as that of the parent pentadienyl radical, (i.e. 25 kcal mol−1). The 3-hydroxypentadienyl, l-hydroxy-3-methylpentadienyl and l-trimethylsilyloxy-3-methylpentadienyl radicals were generated, but exchange broadening was not observed in the accessible temperature range. Sulphonate esters were examined as a potential source of free radicals. The reaction of simple alkyl alkanesulphonates with photochemically generated trimethyltin radicals in the cavity of an ESR spectrometer gave the corresponding alkanesulphonyl radicals. Good ESR spectra were obtained when sulphonyl radicals, generated from sulphonate esters, were used to form adduct radicals with alkenes of the type CH2=CHR where R is an electron releasing substituent, (R = OMe, OBun, SPh, SiME3). Delocalised radicals were generated from sulphonate esters which contained a terminal alkenyl or alkynyl substituent. For example, the reaction of allyl methanesulphonate with photochemically generated trimethyltin radicals in the cavity of an ESR spectrometer gave good spectra of the allyl radical. The pent-4-ene-1-sulphonyl radical was generated from the corresponding sulphonyl chloride using several different radical initiator systems (tri-n-butyltin hydride, triphenylsilane, hexa-n-butylditin, 9-trimethylstannyl-9,10-dihydroanthracene, copper (II) chloride and tris (triphenylphosphine) ruthenium (II) chloride). The radical was found to cyclise in a predominantly endo-fashion to give 3-chlorotetrahydrothiopyran-1,1-dioxide, the exact proportion of endo- and exo-products depending on the temperature. The hex-5-ene-1-sulphonyl radical was found to give thiepane-1,1- dioxide, also the product of endo-cyclisation. The inclusion of a bulky ring substituent forced the cyclohexenylethanesulphonyl radical to cyclise in the exo-mode to give 2-chloro-9-thiabicyclo[4.3.0]nonane-9,9-dioxide. Dialkyltellurides and dialkylditellurides gave the corresponding alkyl radical on photolysis in the cavity of an ESR spectrometer. For example, diallyltelluride gave good spectra of the allyl radical. Under thermolysis conditions, a nitrosodurene spin trap was employed to observe the trapped alkyl radicals. It is believed that certain of the trapped radicals were tellurium-centred species.
33
Silva, Robson Rosa da [UNESP]. "Estudo da preparação de nanocompósitos magneto-luminescentes unidimensionais baseados em telúrio". Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/97932.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-06-11T19:29:10Z (GMT). No. of bitstreams: 0
Previous issue date: 2012-03-15Bitstream added on 2014-06-13T20:38:23Z : No. of bitstreams: 1
silva_rr_me_araiq.pdf: 6153824 bytes, checksum: 99fdc68a43b515fbf9a4f98f2d7ce84b (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho baseou-se no estudo da preparação de novos nanomateriais multifuncionais baseados em nanoestruturas 1D de telúrio (Te1D), as quais foram obtidas pela redução de óxido de telúrio através da síntese por modelagem assistida de protetores de colóide. Os protetores de colóide utilizados foram baseados em surfactantes iônicos e não iônicos, copolímeros em blocos ou carboidratos de cadeias lineares. Nanoestruturas de Te1D na forma de filamentos ou fios longos e flexíveis, ou ainda bastões rígidos, foram obtidas em dispersões aquosas estáveis. A morfologia e tamanho das nanoestruturas de Te1D foram dependentes da razão molar Te: H3PO2 e da natureza do protetor de colóide empregados. Novos nanobiocompósitos de Te1D foram obtidos pelo crescimento de nanoestruturas de Te1D em molde sólido formado pela rede tridimensional de nanofibras entrecruzadas de celulose bacteriana (CB-hidrogel). O arranjo das nanofibras de CB atua como barreira de difusão no controle da formação de nanoestruturas de Te1D. Além disso, a formação de nanofios de Te1D foi dependente da proporção mássica de telúrio/CB empregada. Nanopartículas de maghemita de diâmetro médio de 11 nm (-Fe2O3) foram obtidas pela oxidação de magnetita previamente sintetizada pelo método de coprecipitação de íons ferro em meio alcalino. As nanopartículas apresentaram perfil superparamagnético e foram funcionalizadas com camada de sílica (-Fe2O3@SiO2) pelo método modificado de Stöber. Novos nanocompósitos bifuncionais magneto-luminescentes foram obtidos pela associação de nanopartículas...
This work was based on the study of the preparation of novel nano multifunctional 1D nanostructures based on tellurium (Te1D), which were obtained by reduction of tellurium oxide at template synthesis by a colloid protector. The colloid protectors used were based on ionic and nonionic surfactants, block copolymers or carbohydrates of linear chains. Te1D nanostructures in the shape of filaments or wires long and flexible, or rigid rods were obtained in stable aqueous dispersions. The morphology and size of Te1D nanostructures were dependent to the molar ratio of Te:H3PO2 and the nature of the colloid protector employed. New Te1D nanobiocomposites were obtained by the growth of Te1D nanostructures into solid template of the intersecting three-dimensional network of bacterial cellulose nanofibers (BC-hydrogel). The arrangement of nanofibers CB acts as a diffusion barrier into control of the nanostructures Te1D formation. Moreover, the formation of Te1D nanostructure was dependent to the weight proportion between tellurium and CB employed. Maghemite nanoparticles with average diameter about 11 nm (-Fe2O3) were obtained by oxidation of magnetite previously synthesized by the coprecipitation method of iron ions in alkaline media. The nanoparticles exhibits a superparamagnetic profile and they were functionalized with a silica layer (SiO2@Fe2O3) by the modified Stöber method. New magneto-luminescent bifunctional nanocomposites were prepared by anchoring the visible emitter... (Complete abstract click electronic access below)
34
Brown, Daniel Edward. "Low temperature nuclear orientation studies of nuclei far from stability". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257942.
Testo completo
35
Alzahrani, Ali. "DETERMINATION AND SPECIATION OF TELLURIUM IN ENVIRONMENTAL SAMPLES USING HYDRIDE GENERATION ATOMIC FLUORESCENCE SPECTROSCOPY (HG-AFS)". Thesis, Laurentian University of Sudbury, 2014. https://zone.biblio.laurentian.ca/dspace/handle/10219/2133.
Testo completoAbstract (sommario):
This thesis focuses on developing a new method to measure trace tellurium (Te) in
different environmental samples such as lake waters, mine tailings and sediments. The developed
technique is based on Hydride Generation Atomic Fluorescence Spectroscopy (HG-AFS), a
technique that can measure low concentration of Te and also allows for Te speciation at low cost
and high efficiency in various environmental samples.
To validate the method that could be used to determine Te speciation in various types of
environmental samples, a series of tests has been designed for finding the best conditions to
measure Te(IV) using HG-AFS and obtain accurate and reliable results. Those tests include the
stability of the signal, the acidity of the solution, the volatility of Te after digestion of solids, the
reduction from Te(VI) to Te(IV), the detection limit of the technique, and the validity of two
digestion methods under the optimum (HG-AFS) instrumental settings.
An interference study including the most common elements in the Earth’s crust such as
(Ni, Fe, Pb, Cr, Cu, Co, Zn, Mn and Mo) was also performed. The results of this study showed
that Cu(II) can severely interfere with Te quantification decreasing the Te signal to almost zero.
Therefore, different masking agents such as 8-hydroxyquinoline, 1,10-phenanthroline, urea and
thiourea were tested to reduce and eliminate this interference.
36
Silva, Robson Rosa da. "Estudo da preparação de nanocompósitos magneto-luminescentes unidimensionais baseados em telúrio /". Araraquara, 2012. http://hdl.handle.net/11449/97932.
Testo completoAbstract (sommario):
Orientador: Sidney José Lima RibeiroBanca: Osvaldo Novais de Oliveira Junior
Banca: Cid Bartolomeu de Araujo
Resumo: Este trabalho baseou-se no estudo da preparação de novos nanomateriais multifuncionais baseados em nanoestruturas 1D de telúrio (Te1D), as quais foram obtidas pela redução de óxido de telúrio através da síntese por modelagem assistida de protetores de colóide. Os protetores de colóide utilizados foram baseados em surfactantes iônicos e não iônicos, copolímeros em blocos ou carboidratos de cadeias lineares. Nanoestruturas de Te1D na forma de filamentos ou fios longos e flexíveis, ou ainda bastões rígidos, foram obtidas em dispersões aquosas estáveis. A morfologia e tamanho das nanoestruturas de Te1D foram dependentes da razão molar Te: H3PO2 e da natureza do protetor de colóide empregados. Novos nanobiocompósitos de Te1D foram obtidos pelo crescimento de nanoestruturas de Te1D em molde sólido formado pela rede tridimensional de nanofibras entrecruzadas de celulose bacteriana (CB-hidrogel). O arranjo das nanofibras de CB atua como barreira de difusão no controle da formação de nanoestruturas de Te1D. Além disso, a formação de nanofios de Te1D foi dependente da proporção mássica de telúrio/CB empregada. Nanopartículas de maghemita de diâmetro médio de 11 nm (-Fe2O3) foram obtidas pela oxidação de magnetita previamente sintetizada pelo método de coprecipitação de íons ferro em meio alcalino. As nanopartículas apresentaram perfil superparamagnético e foram funcionalizadas com camada de sílica (-Fe2O3@SiO2) pelo método modificado de Stöber. Novos nanocompósitos bifuncionais magneto-luminescentes foram obtidos pela associação de nanopartículas... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work was based on the study of the preparation of novel nano multifunctional 1D nanostructures based on tellurium (Te1D), which were obtained by reduction of tellurium oxide at template synthesis by a colloid protector. The colloid protectors used were based on ionic and nonionic surfactants, block copolymers or carbohydrates of linear chains. Te1D nanostructures in the shape of filaments or wires long and flexible, or rigid rods were obtained in stable aqueous dispersions. The morphology and size of Te1D nanostructures were dependent to the molar ratio of Te:H3PO2 and the nature of the colloid protector employed. New Te1D nanobiocomposites were obtained by the growth of Te1D nanostructures into solid template of the intersecting three-dimensional network of bacterial cellulose nanofibers (BC-hydrogel). The arrangement of nanofibers CB acts as a diffusion barrier into control of the nanostructures Te1D formation. Moreover, the formation of Te1D nanostructure was dependent to the weight proportion between tellurium and CB employed. Maghemite nanoparticles with average diameter about 11 nm (-Fe2O3) were obtained by oxidation of magnetite previously synthesized by the coprecipitation method of iron ions in alkaline media. The nanoparticles exhibits a superparamagnetic profile and they were functionalized with a silica layer (SiO2@Fe2O3) by the modified Stöber method. New magneto-luminescent bifunctional nanocomposites were prepared by anchoring the visible emitter... (Complete abstract click electronic access below)
Mestre
37
Kalb, Johannes Andreas. "Crystallization kinetics in antimony and tellurium alloys used for phase change recording". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979086299.
Testo completo
38
Rai, Vidisha. "An ab initio study of electronic states and transitions of tellurium monohalides". [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968337449.
Testo completo
39
Sheng, Jia. "Synthesis, Structure and Function Studies of Selenium and Tellurium Derivatized Nucleic Acids". Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/chemistry_diss/30.
Testo completoAbstract (sommario):
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.
40
Burgess, M. R. "Synthetic, spectroscopic, structural and electrochemical studies on selenium- and tellurium-substituted ferrocenes". Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636180.
Testo completoAbstract (sommario):
This work is divided into seven chapters. Chapter one contains a brief introduction to the chemistry of ferrocene, selenium and tellurium, together with an outline of relevant electrochemical techniques. Chapter two introduces 77 Se and 125 Te NMR spectroscopy, and contains a discussion of the electrochemistry and multinuclear NMR spectroscopy of diferrocenyl diselenide and diferrocenyl ditelluride. The molecular structure of the latter has been determined and is also described and related to its electrochemical behaviour. Chapter three contains the results of multinuclear NMR spectroscopic and electrochemical studies of progressive series of ferrocenyl alkyl chalcogenides and bis(ferrocenyl selenide) derivatives and discusses trends within the data. It is proposed that the 77Se chemical shift of diferrocenyl selenide is anomalous. Chapter four contains details of the synthesis and characterisation by multinuclear spectroscopy and electrochemistry of pentamethylcyclopentadienyl ferrocenyl selenide. The molecular structure of the compound, which is the first example of a crystalline mono(pentamethylcyclopentadienyl)selenium derivative, has been determined and is described. The synthesis and characterisation of the analogous tetramethyl compound is also presented in chapter four. Chapter five contains a discussion of the reactions of diferrocenyl diselenide and diferrocenyl ditelluride with metal carbonyl complexes and includes characterisation by multinuclear NMR spectroscopy, cyclic voltammetry, and differential pulse voltammetry of some of the products. The molecular structure of the [W(SeFc)(CO)4]2 has also been determined and is presented. Chapter six discusses miscellaneous reactions carried out, whilst chapter seven gives experimental details of all the work described in this thesis.
41
Yates, Carol Ann. "An investigation into adduct formation between dialkyl tellurium and dialkyl cadmium compounds". Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292770.
Testo completo
42
Girkin, J. M. "Development of a tellurium frequency standard for laser spectroscopy of atomic hydrogen". Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382167.
Testo completo
43
Podchezertsev, Stanislav. "Magnetoelectric coupling in cobalt-based tellurium (VI) oxides with complex spin structures". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC228.
Testo completoAbstract (sommario):
La thèse actuelle est consacrée à une étude complexe de diffusion de neutrons sur des séries de spinelles de tellure à base de cobalt (VI) dopées au zinc. Il a été constaté que le composé parent peut être obtenu sous deux formes structurelles: centrosymétrique désordonnée (groupe d'espace # 227) et non-centrosymétrique ordonnée (groupe d'espace # 212). Alors que le polymorphe désordonné soit un ferrimagnet typique de type Néel avec une transition magnétique à 40 K, le polymorphe ordonné possède deux transitions de phase magnétiques incommensurables à 45 K et 27 K. Grâce à l'approche de symétrie super-spatiale, il a été découvert que la structure de spin d'un polymorphe ordonné est une spirale ferrimagnétique. La frustration magnétique et l'interaction Dzyaloshinskii-Morya stabilisent cet ordre magnétique. Le système montre la stabilité de la structure magnétique contre la dilution magnétique, qui occupe de préférence l'environnement tétraédrique: ce n'est que lorsque la moitié des sites A est remplacée par du zinc que l'ordre magnétique à longue distance est supprimé. Ce qui est remarquable, ce sont les deux polymorphes qui démontrent une diffusion diffuse magnétique bien au-dessus des températures de transition à longue distance. L'analyse de polarisation Neutron XYZ a révélé: quand le polymorphe est ordonné, l'ordre à courte portée a la même nature en spirale ferrimagnétique que l'état ordonné. L'ordre à courte portée du polymorphe ordonné fortement dilué est similaire au composé parent. La spectroscopie diélectrique du composé désordonné et ordonné a révélé un comportement magnétoélectrique en chaque casThe current thesis is dedicated to a complex neutron scattering study of magnetic behaviour cobalt-based tellurium (VI) spinel series doped with zinc. It was found that the parent compound may be obtained in two structural forms: disordered centrosymmetric (space group #227) and ordered non-centrosymmetric (space group #212). While the disordered polymorph is a typical Néel-type ferrimagnet with a magnetic transition at 40 K, the ordered polymorph possesses two incommensurate magnetic phase transitions at 45 K and 27 K. With a help of the superspace symmetry approach the spin structure of the ordered polymorph was found to be ferrimagnetic spiral. Both magnetic frustration and Dzyaloshinskii-Morya interaction stabilize such a magnetic ordering. The system shows stability of the magnetic structure against magnetic dilution, which occupies tetrahedral environment preferably: only when the half of A-sites is substituted with zinc the long range magnetic ordering is suppressed. Remarkably, both polymorphs demonstrate magnetic diffuse scattering far above long-range transition temperatures. Neutron XYZ polarization analysis revealed that in the case of the ordered polymorph the short-range ordering has the same ferrimagnetic spiral nature as the ordered state. Short-range ordering of the highly diluted ordered polymorph is similar to the parent compound. Dielectric spectroscopy of the disordered and ordered compound revealed magnetoelectric behaviour in each case
44
Lizárraga, Olivares Kevin Angello. "Excitons in monolayer tellurium studied with QPMBPT and a hydrogen-like model /". São Paulo, 2019. http://hdl.handle.net/11449/183101.
Testo completoAbstract (sommario):
Orientador: Alexandre Reily RochaResumo: Os excitons desempenham um papel fundamental em aplicações fotovoltaicas (FV). Atualmente, a tecnologia FV de filme fino possui 9% da produção mundial. Em particular, o telúrio foi ligado ao cádmio (Cd-Te) e utilizado no fabrico de células solares de película fina. No entanto, a tecnologia de telúrio pode ser melhorada se estruturas de menor dimensão forem usadas, por exemplo, a forma de monocamada conhecida como telureno. O telureno pode ser sintetizado com sucesso em um substrato (por exemplo, grafeno), tem alta mobilidade dos portadores, a condutividade térmica mais baixa entre monocamadas de átomos e um gap de banda óptica sintonizável que o torna em um candidato proeminente para o desenvolvimento de tecnologia. Neste trabalho, realizamos cálculos ab-initio da teoria da perturbação do muitos corpos (QPMBPT) para analisar os efeitos excitônicos na absorção de luz pelo telureno. Como telúrio é um elemento pesado, nossa análise foi estendida para a presença de acoplamento spin-órbita, que faz uma mudança significativa na estrutura da banda, bem como na parte imaginária da constante dielétrica. A anisotropia da telurena é evidente no espectro de absorção, que é semelhante ao fósforo preto, com a mais forte excitação ao longo da direção em ziguezague e energias de ligação de excitons semelhantes a outros semicondutores 2D. Além disso, comparamos nossos resultados com um modelo efetivo de hidrogênio, no qual o elétron e o buraco interagem através de uma interação anisotrópica d... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre
45
Kennard, David R. "The chemistry of the corrosion of transition metals by caesium, tellurium and oxygen". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357966.
Testo completo
46
Nordheider, Andreas. "Phosphorus-tellurium heterocycles and their lighter chalcogen analogues : from small rings to macrocycles". Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/5546.
Testo completoAbstract (sommario):
The research on phosphorus-chalcogen compounds enjoys a long tradition in the field of inorganic chemistry, which has led to applications such as strike-anywhere matches, precursors for metal chalcogenide thin films and versatile reagents in organic synthesis. Whereas a wide range of phosphorus-sulfur and -selenium systems is known, the literature lacks information about compounds incorporating phosphorus-tellurium bonds. This thesis describes fundamental studies that develop the basic understanding of the synthesis of phosphorus-tellurium systems and the structural characteristics of these species. The focus will be on cyclic structural motifs as these offer novel bonding modes and often an interesting reactivity. In addition, the novel compounds are compared with the properties of the sulfur and selenium analogues. Three different approaches were developed to stabilise and study compounds incorporating phosphorus-tellurium bonds: a) Stabilisation of binary organophosphorus-tellurium heterocycles by bulky substituents, b) the utilisation of P₂N₂ rings based on the dianions [{EP(NtBu)(μ-NtBu)}₂]²⁻ (E = S, Se, Te) and c) the peri-substitution of phosphorus and tellurium atoms on an acenaphthene backbone. The use of sterically demanding substituents led to the isolation of the first series of structurally characterised organophosphorus(III)-tellurium heterocycles of the type (RP)[sub]nTe[sub]m including three- to six-membered ring systems. The mild oxidation of [{EP(NtBu)(μ-NtBu)}₂]²⁻ (E = S, Se, Te) with iodine yielded macrocyclic (S, Se) or oligomeric systems (Te). Furthermore, a collection of novel P₂N₂-supported phosphorus-chalcogen heterocycles incorporating main group elements was synthesised employing [{EP(NtBu)(μ-NtBu)}₂]²⁻ (E = S, Se, Te) in metathetical reactions with main group element halides. Extension of this approach to transition metal halides generated some unusual metallocycles, as well as macrocycles and ladders incorporating coinage metals. The first peri-substituted phosphorus-tellurium species were studied regarding their interatomic and intermolecular forces. Systems of the general formula RTe–Acenap–P(iPr)₂ were shown to exhibit extensive through-space spin-spin coupling. In addition, the influence of oxidation and complexation on these interactions was investigated and the formation of peri-substituted phosphorus-tellurium cations exhibiting P–Te bonds was observed.
47
Majeed, Zulfiqar. "The reactions of directly related tellurium and selenium heterocyclic compounds with triiron dodecacarbonyl". Thesis, Aston University, 1999. http://publications.aston.ac.uk/9622/.
Testo completoAbstract (sommario):
The reactions of directly related tellurium and selenium heterocyclic compounds with triiron dodecacarbonyl are described. The reaction of 2-telluraphthalide, C8H8OTe with [Fe3(CO)12 gave [Fe{C6H4(CH2)Te}(CO)3]2, (1). An iron atom has inserted into the telluracyclic ring, and it is probable that one co-ordinated CO ligand arises from the initially organic carbonyl group. X-ray analysis of compound (1) showed that the compound has a Fe2Te2 core, which is achieved by dimerisation. The reaction of telluraphthalic anhydride, C8H402Te with [Fe3(CO)12] gave a known, but unexpected, organic phthalide product, C8H602, which was confirmed by X-ray crystallography. Selenaphthalic anhydride, C8H4O2Se gave intractable products on reaction with [Fe3(CO)12], 2-selenaphthalide, C8H6OSe, on reaction with [Fe3(CO)12] gave a major product [Fe2{C6H4(CH2)Se}(CO)6], (2) and a minor product [Fe3{C6H4(CH2)Se}(CO)8], (3) which is an intermediate in the formation of (2). X-ray analysis of (2) shows that compound (2) is very similar to (1) except that the 18 electron rule is satisfied by co-ordination of a Fe(CO)3 moiety, rather than dimerisation. Compound (3), also studied by X-ray crystallography, differs from (2) mainly in the addition of an Fe(CO)2 moiety. Telluraphtbalic anhydride, C8H402Te, and selenaphthalic anhydride, C8H402Se, are both monoclinic and crystallise in space group P21/n. 2-Selenaphthalide, C8H402Se, is also monoclinic, space group P21/C. The reactions of the following compounds (l,3-dihydrobenzo[c]selenophene, 1,3,7,9-tetrahydrobenzo[1,2c; 4,5c'] ditellurophene, dibenzoselenophene, phenoxselenine, 3, 5-naphtho-1-telluracyclohexane and 3,5-naphtho-1-selenacyclohexane) with [Fe3lCO)12] are reported. It is unfortunate that the above compounds do not react under the conditions employed; this may be due to differing degrees of ring strain. 1,8-bis(bromomethyl)naphthalene, C12H10Br2 is monoclinic and crystallises in space group C2/c. 1,1-diiodo-3,5-naphthotelluracyclohexane, C12H10TeI2 and 3,5-naphtho-l-telluracyclohexane, C12H10Te are monoclinic and crystallise in space group P21/c. 3,5-naphtho-l-selenacyclohexane, C12H10Se and 2,2,8,8-tetraiodo-1,3,7,9-tetrahydrobenzo[1,2c;4,5c']ditellurophene are also monoclinic, space group P21/a. The syntheses of intramolecular stabilised organo-tellurium and selenium compounds are reported, having a general formula of REX (where R = phenylazophenyl; E = Se, Te; X = electronegative group, for example C1, Br or I). The crystal structures of R'TeBr, RTeI, RSeCI, RSeCI/I and RSeI (where R = phenylazophenyl) are reported. The tellurium containing X-ray structures are triclinic and have a space group P-1. The selenium containing X-ray structures are monoclinic with space group P21/n. The inclusion of nitrogen in selenium heterocycles provides access to an entirely new area of organometallic chemistry. The reaction of 2-methylbenzoselenazole with [Fe3(CO)12] gave [Fe2{C6H4(NCH2CH3)Se}(CO)6]. The reactions of 2-(methyltelluro)benzanilide or 2-(methylseleno)benzanilide with [Fe3(CO)12] gave reaction products [Fe2(μTeMe)2(CO)6] and [Fe2 (μ-SeMe)2(CO)6] respectively, which were confmned by X-ray crystallography. The use of Mossbauer spectroscopy on the products obtained from the reactions of heterocyclic compounds with [Fe3(CO)12] can give useful information, for example the number of iron sites and the environments of these iron sites within the products.
48
Khan, Rana. "Structural studies of halogen, interhalogen and pseudohalogen compounds of phosphorus, selenium and tellurium". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/structural-studies-of-halogen-interhalogen-and-pseudohalogen-compounds-of-phosphorus-selenium-and-tellurium(b1ba6ec9-198c-4de5-be73-f136a4db3ee0).html.
Testo completoAbstract (sommario):
A series of compounds with the general formula R3PX2 and R3PX4 (where R = o-tolyl, m-tolyl, p-tolyl, o-anisyl, m-anisyl, p-anisyl, o-thioanisyl, p-thioanisyl, p-fluorophenyl, p-chlorophenyl, mesityl and X = Cl, Br, I) have been synthesised and studied by X-ray crystallography, multinuclear NMR spectroscopy and Raman spectroscopy. A study of the conformational features of the aryl groups in these structures was undertaken in order to investigate the role of steric effects and crystal packing on P-X and X-X bond lengths. Compounds with the general formula RSeX / RSeX3 (where R = p-fluorophenyl, p-chlorophenyl, p-bromophenyl, p-iodophenyl and X = Cl, Br, I) have been synthesised by reacting the diselenides with halogens in the stoichiometric ratios. The X-ray crystal structure of p-ClC₆H₄SeI.I₂ is the first crystallographically characterised example of a compound of stoichiometry RSeI₃, although it is better represented as an I₂ adduct of a Se(II) iodide than a Se(IV) compound. In contrast, (p-FC₆H₄)Se-Se(I)₂(p-FC₆H₄) is an I₂ adduct where the Se-Se bond has not been cleaved by iodine. Both structures are stabilised by weak Se...I and I...I interactions. p-FC₆H₄SeCl₃ is an example of a dimeric structure with bridging chlorines. [Ph₄PX] and Ph₃PX₂ were reacted with PhEX (where E = Se, Te and X = I, Br, Cl) to produce salts containing [PhEX₂]- and [PhEX₄] anions. Where possible all the products were then analysed via NMR and Raman spectroscopy and X-ray crystallography. The reactions of the ligand tris-p-fluorophenyl phosphine with sulfur and selenium are presented along with the subsequent reactions of these compounds with diiodine. All of the compounds are characterised via X-ray crystallography.
49
Yildirim, Emrah. "Tellurium Speciation Using Hydride Generation Atomic Absorption Spectrometry And In-situ Graphite Cuvette Trapping". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610967/index.pdf.
Testo completoAbstract (sommario):
In recent years speciation analysis is becoming more important as it is known that each chemical form of an element behaves differently in biological and environmental media. Since abundance of tellurium in earth crust is extremely low, very sensitive and accurate methods are needed to determine the concentration of tellurium. Hydride generation atomic absorption is a sensitive, fast and economical technique applied for the determination of tellurium. Speciation of tellurium can be achieved by making use of different kinetic behaviors of Te(IV) and Te(VI) upon its reaction with sodiumborohydride.
A continuous flow hydride generation system was developed and parameters that affect the analytical signal were optimized. Sample solutions were prepared in 4.0 mol/L HClas reductant 0.5 % (w/v) sodiumborohydride in 0.5 % (w/v) NaOH was used. Quantitative reduction of Te(VI) was achieved through application of a microwave assisted prereduction of Te(VI) in 6.0 mol/L HCl solution. Sensitivity of the system was further enhanced by in-situ trapping of the formed H2Te species in a previously heated graphite furnace whose surface was modified using Pd or Ru. Overall efficiency of pyrolytic coated graphite surface was found to be 15% when hydrides are trapped for 60 seconds at 300 oC. LOD and LOQ values were calculated as 86 pg/mL and 287 pg/mL according to peak height values. Efficiency was increased by 46% and 36% when Pd and Ru modifiers were used, respectively. With Ru modified graphite tube 173 fold enhancement was obtained over 180 seconds trapping period with respect to direct ETAAS. LOD values were 6.4 and 2.2 pg/mL for Pd and Ru treated systems, respectively, for 180 s collection of 9.6 mL sample solution.
50
Allen, Matthew David. "The oxidation and ammoxidation of propene using mixed oxides of iron, antimony and tellurium". Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385111.
Testo completo