Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. Includes bibliographical references (leaves 184-188).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1973. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 230-236).

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 257-263).

Th.--Sci. phys.--Nancy--I.N.P.I., 1975.

Literature on the processing, microstructure and properties of NbSi2 and other disilicides have been briefly reviewed, along with earlier work on the alloying behaviour of NbSi2 and the oxidation of both niobium and niobium silicides. Solidification microstructures and phase selection in ingots and melt spun ribbons of binary and ternary NbSi2 based alloys with additions of Cr and Fe have been studied. Low levels of interstitial contamination were achieved in all alloys (< 200wppmO2, < 10wppmH2) using a cold hearth non-consumable tungsten arc melting technique. The following alloys were prepared (at%): Nb-67Si, Nb-58Si, Nb-67Si-8Cr, Nb-60Si-20Cr, Nb-67Si-8Fe and Nb-60Si-20Fe. Evaluation of the microstructure and properties was performed using optical microscopy, SEM, EPMA,TEM,XRD, DSC/TG, isothermal oxidation, room temperature hardness, microhardness, high temperature hardness and nano-indentation. Alloys containing increased levels of Nb or Fe additions exhibited less porosity and cracking in their as-cast structures and lower melt viscosities in comparison to the other alloys. Extensive solubility of Cr in the NbSi2 matrix and of Nb in the CrSi2 matrix was noted and upon heat treatment widescale partitioning between the two phases was evident. Increased Cr additions led to the formation of the ternary phase Nb2Cr3Si6. In contrast the solubility of Nb in both FeSi and FeSi2 was extremely limited along with that of Fe in NbSi2. Rapid solidification refined the microstructures of the alloys by two orders of magnitude. Suppression of Nb5Si3 and NbFeSi2 took place under RS conditions. Segregation free microstructures were formed in zone A of Nb-67Si ribbons. The addition of either Cr or Fe destabilised the S/L front in the ternary alloys preventing the formation of zone A in the ribbons of these alloys. RS processing suppressed the eutectoidal decomposition of betaNb5Si3 to alphaNb5Si3 and the peretectoidal transformation of alphaFeSi2 to betaFeSi2. Three oxidation regimes were identified in binary Nb-67Si, which were associated with the oxidation kinetics of the various niobium oxide forms (NbO2, alphaNb2O5 and betaNb2O5). Pesting of the alloy occurred between 823 and 1123K, but was reduced in the ternary alloys and fully suppressed in Nb-60Si-20Cr. Duplex oxide structures were formed on the ternary alloys consisting of SiO2 and Cr2O3 layers in the Nb-Si-Cr alloys and two silicon oxide layers containing iron oxide particles in the Nb-Si-Fe alloys. Additions of Cr and Fe increased the hardness of the alloys. This was attributed to the volume fraction of the Fe and Cr silicide phases with FeSi and CrSi2 being harder than NbSi2. The elastic moduli of NbSi2 and Nb5Si3 were also measured using the nano-indentation technique. The hardness of Nb-67Si and Nb-67Si-8Cr were retained up to 1173K whilst that of the other ternary alloys decreased rapidly above 950K.

No description available.

Orientador: Luiz Carlos da Silva Filho / Banca: Valdecir Farias Ximenes / Banca: Marco Antonio Barbosa Ferreira / 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 / Resumo: O desenvolvimento de novas estragégias sintéticas para uma eficiente produção de compostos orgânicos é de grande importância. Dentre estes compostos, os derivados quinolínicos apresentam uma variedade de aplicações em diversas áreas e estão presentes em diversas áreas e estão presentes em diversos produtos naturais e drogas. Assim, neste trabalho estudamos a síntese desses derivados utilizando o pentacloreto de nióbio como promotor em reações multicomponentes realizadas entre p-nitroanilina, fenilacetileno e derivados de benzaldeído, a temperatura ambiente, onde obtiveram-se bons rendimentos (54-98%) em um bom tempo reacional. Analisamos também a eficácia do pentacloreto de nióbio comparado a outros catalisadores, que demonstrou então que este é um bom promotor nesta reação. Foi realizada em seguida da redução do grupo nitro presente nos derivados quinolínicos sintetizados. Todos os compostos sintetizados foram submetidos a análises de caracterização estrutural, fotoquímica e fotofísica e os derivados aminoquinolínicos apresentaram maior potencial para aplicação como corantes sensibilizadores de dispositivos fotoeletroquímicos de Gratzel e para utilização em outros dispositivos eletrônicos orgânicos / Abstract: The development of new synthetic strategies for an efficient production of organic compounds is very importante. Among these compounds, quinolites show a variety of applications in various areas and ares present in many natural products and drugs. Thus, in this work we have studied the synthesis of such derivatives by using niobium pentachloride as promoter in multicomponent reactions carried out between p-nitroaniline, phenylacetylene and benzaldehyde derivatives, at room temperature, which were obtained good yields (54-98%) in a good reaction time. We also analyze the effectiveness of niobium pentachloride compared to other catalysts, which showed that the NbCl5 is a good promoter in this reaction. We them carried the reduction of the nitro group present in the synthesized compounds were submitted to analysis of structural, photochemistry and photophysics characterization, aminoquinolines derivatives showed the highest potential for application as sensitizing dyes in photoelectrochemical devices of Gratzel and for use in order organic electronic devices / Mestre

Made available in DSpace on 2018-07-27T18:26:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-24. Added 1 bitstream(s) on 2018-07-27T18:30:35Z : No. of bitstreams: 1 000871607.pdf: 7216802 bytes, checksum: 9abe1632634a9de4ee04f393445edbc7 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O desenvolvimento de novas estragégias sintéticas para uma eficiente produção de compostos orgânicos é de grande importância. Dentre estes compostos, os derivados quinolínicos apresentam uma variedade de aplicações em diversas áreas e estão presentes em diversas áreas e estão presentes em diversos produtos naturais e drogas. Assim, neste trabalho estudamos a síntese desses derivados utilizando o pentacloreto de nióbio como promotor em reações multicomponentes realizadas entre p-nitroanilina, fenilacetileno e derivados de benzaldeído, a temperatura ambiente, onde obtiveram-se bons rendimentos (54-98%) em um bom tempo reacional. Analisamos também a eficácia do pentacloreto de nióbio comparado a outros catalisadores, que demonstrou então que este é um bom promotor nesta reação. Foi realizada em seguida da redução do grupo nitro presente nos derivados quinolínicos sintetizados. Todos os compostos sintetizados foram submetidos a análises de caracterização estrutural, fotoquímica e fotofísica e os derivados aminoquinolínicos apresentaram maior potencial para aplicação como corantes sensibilizadores de dispositivos fotoeletroquímicos de Gratzel e para utilização em outros dispositivos eletrônicos orgânicos / The development of new synthetic strategies for an efficient production of organic compounds is very importante. Among these compounds, quinolites show a variety of applications in various areas and ares present in many natural products and drugs. Thus, in this work we have studied the synthesis of such derivatives by using niobium pentachloride as promoter in multicomponent reactions carried out between p-nitroaniline, phenylacetylene and benzaldehyde derivatives, at room temperature, which were obtained good yields (54-98%) in a good reaction time. We also analyze the effectiveness of niobium pentachloride compared to other catalysts, which showed that the NbCl5 is a good promoter in this reaction. We them carried the reduction of the nitro group present in the synthesized compounds were submitted to analysis of structural, photochemistry and photophysics characterization, aminoquinolines derivatives showed the highest potential for application as sensitizing dyes in photoelectrochemical devices of Gratzel and for use in order organic electronic devices