Thesis (Ph.D.)--University of South Florida, 2004. / Includes vita. Includes bibliographical references (leaves 144-164).

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on July 1, 2010). Includes bibliographical references.

Made available in DSpace on 2014-12-17T14:07:12Z (GMT). No. of bitstreams: 1 RaimisonBA_DISSERT.pdf: 2147079 bytes, checksum: db6881c15458f1e487de74465b7088a0 (MD5) Previous issue date: 2013-07-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Magnetic ceramics have been widely investigated, especially with respect to intrinsic and extrinsic characteristics of these materials. Among the magnetic ceramic materials of technological interest, there are the ferrites. On the other hand, the thermal treatment of ceramic materials by microwave energy has offered various advantages such as: optimization of production processes, high heat control, low consumption of time and energy among others. In this work were synthesized powders of Ni-Zn ferrite with compositions Ni1- xZnxFe2O4 (0.25 ≤ x ≤ 0.75 mols) by the polymeric precursor route in two heat treatment conditions, conventional oven and microwave energy at 500, 650, 800 and 950?C and its structural, and morphological imaging. The materials were characterized by thermal analysis (TG/ DSC), X-ray diffraction (XRD), absorption spectroscopy in the infrared (FTIR), scanning electron microscopy (SEM), X-ray spectroscopy and energy dispersive (EDS) and vibrating sample magnetometry (VSM). The results of X-ray diffraction confirmed the formation of ferrite with spinel-type cubic structure. The extrinsic characteristics of the powders obtained by microwave calcination and influence significantly the magnetic behavior of ferrites, showing particles ferrimagn?ticas characterized as soft magnetic materials (soft), is of great technological interest. The results obtained led the potential application of microwave energy for calcining powders of Ni-Zn ferrite / Cer?micas magn?ticas t?m sido amplamente investigadas, principalmente com rela??o as caracter?sticas intr?nsecas e extr?nsecas destes materiais. Dentre os materiais cer?micos magn?ticos de interesse tecnol?gico, destacam-se as ferritas. Por outro lado, o tratamento t?rmico de materiais cer?micos por energia de microondas tem oferecido diversas vantagens, tais como: otimiza??o dos processos de obten??o, alto controle de aquecimento, menor consumo de tempo e energia entre outras. Neste trabalho, foram sintetizados p?s de ferritas Ni-Zn com composi??es Ni1-xZnxFe2O4 (0,25 ≤ x ≤ 0,75 mols) pela rota dos precursores polim?ricos em duas condi??es de tratamento t?rmico, em forno convencional e por energia de microondas a 500, 650, 800 e 950?C, e sua caracteriza??o estrutural, morfol?gica e magn?tica. Os materiais obtidos foram caracterizados por an?lises t?rmicas (TG/DSC), difra??o de raios x (DRX), espectroscopia de absor??o na regi?o do infravermelho (FTIR), microscopia eletr?nica de varredura (MEV), espectroscopia de raios X por dispers?o de energia (EDS) e magnetometria de amostra vibrante (VSM). Os resultados da difra??o de raios X confirmaram a forma??o da ferrita com estrutura c?bica do tipo espin?lio. As caracter?sticas extr?nsecas dos p?s obtidos e a calcina??o por microondas influenciaram de forma significativa o comportamento magn?tico das ferritas, apresentando part?culas ferrimagn?ticas, caracterizadas como materiais magn?ticos moles (macias), sendo de grande interesse tecnol?gico. Os resultados obtidos induziram o potencial de aplica??o de energia de microondas para a calcina??o de p?s de ferritas Ni-Zn

L'éruption de 2010 du Merapi est la première grande éruption explosive du volcan qui a été observée instrumentalement. Dans ce travail, nous étudions les précurseurs de l'éruption et le comportement du volcan avant l'éruption en reliant les caractéristiques sismiques avec d'autres observations disponibles. Nous présentons les principaux aspects de l'activité sismique au cours de la crise de 2010, tels que la chronologie de la sismicité, l'évolution spatio-temporelle des positions de source de séisme et les changements de vitesse sismique. En effectuant des localisations absolues et relatives, nous obtenons des preuves de l'existence de zones asismiques, concordant avec des études antérieures, que nous interprétons comme des zones plus ductiles. La migration du magma de la partie profonde à la partie superficielle du conduit à travers la zone asismique supérieure est mise en évidence par un déplacement vers le haut des hypocentres. Nous analysons l'énergie sismique quantifiée par le RSAM calculé pour plusieurs bandes de fréquences. Ces fonctions affichent des accélérations claires dans les dernières semaines avant l'éruption. Ce comportement est utilisé pour effectuer des prévisions d'éruption volcanique rétrospective avec la méthode « Material Failure Forecast » ou FFM. Le début de la première éruption est estimé avec une bonne précision. Nous proposons une méthode originale de détection d'événement basée sur un rapport d'énergie. En utilisant cette méthode et la corrélation de la forme d'onde, nous identifions 10 familles de séismes similaires. Ces multiplets sismiques sont situés en dessous ou au -dessus de la zone asismique supérieure et sont composés soit d'événements volcano-tectoniques soit d'événements basse fréquence. Certains de ces groupes ont été actifs pendant plusieurs mois avant la crise éruptive alors qu'une famille qui comprend 119 événements répétitifs est apparue 20 heures avant le début de l'éruption. Nous estimons des variations de vitesse sismique, liées principalement à l'activité magmatique, en utilisant la coda des multiplets et les fonctions d'intercorrélation du bruit sismique. Ces variations montrent une forte variabilité spatiale et temporelle de leur amplitude et de leur signe. Bien qu'elles ne puissent pas être décrites par une simple tendance unique, ces variations de vitesse peuvent être considérées comme un précurseur de l'éruption. En utilisant les résultats précédents ainsi que d'autres observations, nous déterminons les particularités associées à la grande éruption explosive de 2010. En outre, nous proposons un scénario chronologique de l'activité pré- éruptive du Merapi. / The 2010 eruption of Merapi is the first large explosive eruption of the volcano that has been instrumentally observed. In this work, we study the eruption precursors and the pre-eruptive volcano behaviour by linking seismic features with other available observations. The main characteristics of the seismic activity during the 2010 crisis, including the chronology of seismicity, the spatio-temporal evolution of earthquake source positions and the seismic velocity changes, are presented. By performing absolute and relative locations, we obtain evidences of aseismic zones which are consistent with earlier studies and are interpreted as more ductile zones. Magma migration from the deep to the shallow part of the conduit through the upper aseismic zone is revealed by an upward shift of the hypocenters. We analyse the seismic energy quantified by RSAM calculated for several frequency bands. These functions display clear accelerations in the last few weeks before the eruption. This behaviour is used to perform hindsight eruption forecasting with the Material Failure Forecast method (FFM). The onset of the first eruption is estimated with a good precision. We propose an original method of event detection based on energy ratio. Using this method and waveform correlation, we identify 10 families of similar earthquakes. The seismic multiplets are located either below or above the upper aseismic zone and are composed of either volcano-tectonic or low-frequency events. Some of the clusters were active during several months before the eruptive crisis while a family that includes 119 repeating events appeared 20 hours before the eruption onset. Seismic velocity variations associated mainly with magmatic activity are estimated using the coda of both multiplets and noise cross correlation functions. These variations display strong temporal and spatial variability of their amplitude and sign. Although they cannot be described by a unique simple trend, these velocity variations can be considered as an eruption precursor. Using the preceding results together with other observations, we determine the specific features associated with the large explosive eruption of 2010. Furthermore, we propose a chronological scenario of the pre-eruptive activity of Merapi 2010 unrest.

Per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants used in industrial applications and are globally distributed in the environment. A group of PFASs that are difficult to measure with today’s method are perfluoroalkyl acid precursors (PFAA precursors) that, when degraded, serves as indirect sources of PFAAs. This study has optimized a previously developed method for quantification of PFAA precursors in soil; through total oxidizable precursor assay (TOP assay) under alkaline conditions, to be applicable on sewage sludge. To achieve and maintain an alkaline environment during the entire oxidative treatment, several parameters were tested: concentrations of NaOH, persulfate and sample; additional clean-up with graphitized non-porous carbon and reaction time. Solid phase extraction-weak anion exchange (SPE-WAX) was used for clean-up and separation of analytes, and LC-MS/MS was used for quantification. The optimal conditions with the highest levels of PFAAs detected was obtained with 1.33 M NaOH, 60 mM persulfate, 3.57 g/L sludge with a reaction time of 6 hours. The use of graphitized non-porous carbon reduced matrix effects on oxidative conversion resulting in a higher pH as well as a higher degree of oxidation, but with some analyte loss.

Per- and polyfluoroalkyl substances (PFASs) are synthetic chemicals which are used in a wide range of applications such as aqueous film forming foam (AFFF) for firefighting, paint, coating and cosmetics. For almost a decade, PFASs have received worldwide attention because of the ubiquitous detection of PFAS in the environment and their bioaccumulative, persistent and give toxic effects on animals and humans. A number of study have shown many unknown organofluorine present in environmental samples. The total oxidizable precursor (TOP) method is an oxidation method to convert any precursor compounds of PFASs into measurable perfluorinated carboxylic acids (PFCAs) or sulfonic acids (PFSAs). The aims of this project are to evaluate if the use of total oxidizable precursor (TOP) assay may help improve the mass balance analysis between the quantifiable PFASs and extractable organofluorine in samples. In this study, three water samples: landfill leachate water, contaminated groundwater and adiluted Sthamex AFFF with tap water were undergone TOP assay to reveal the present of any unidentified precursor compounds. To obtain the extractable organofluorine and quantifiable PFAS levels in the samples, combustion ion chromatography (CIC) and liquid chromatography – tandem mass spectrometry (LC-MS/MS) were used, respectively. Results suggested the presence of unidentified precursor compounds in the samples with the aid of TOP assay reaction. Although after the oxidative conversion, a large portion of unidentified PFASs compounds were still present in the samples. The quantifiable PFASs in the samples were up to 7 % of the EOF; in other word, there were still around 93 % of unidentified compounds present in the samples. Further development of analytical method for characterization or identification of these unknown PFAS compounds is needed.

Made available in DSpace on 2014-10-09T12:50:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 1 10459.pdf: 5417083 bytes, checksum: ed654658e2629338a19dc7ae0a312583 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:50:22Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:54Z (GMT). No. of bitstreams: 1 10891.pdf: 10297564 bytes, checksum: e2cbc8792530f432498c2945ee2cc670 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:01/12269-7

Made available in DSpace on 2015-05-14T13:21:33Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1872624 bytes, checksum: 82d5c5729cedad38a0a2aa4e489a50cd (MD5) Previous issue date: 2009-11-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Biodiesel production is based on the is transesterification of vegetable oils or animal fat, using homogeneous or heterogeneous catalysts. Wheres, the heterogeneous-based processing presents slower conversions compared to homogenous ones, such processes lead to noncorrosive manufacturing and avoids the occurrence of saponification reactions. Thus, this work aims at evaluating the catalytic activity of the SnO2 supported on vermiculite clay [(Mg, Fe, Al)3(Al, Si)4O10(OH)2.4H2O] for the transesterification of soybean oil. The several catalysts were obtained by impregnation of vermiculite with tin resin, previously synthesized by the polymeric precursor method. All samples were characterized thermal analysis (TG/DTA), X-ray diffraction (XRD), grazing angle XRD, X-ray fluorescence (XRF), scanning electron microscopy (SEM), infrared (IR) and confocal Raman spectroscopy is Biodiesels were synthesized using a molar ratio of 1:10 (soybean oil: ethanol), 5,0 % (wt / wt) catalys treational temperature q 65 °C, besing characterized by dynamic and kinematic viscosities. In this work the vermiculite was treated with nitric acid (HNO3). The leaching process did not modifi, the thermal stability of inorganic solids. XRF date indicates satisfactory impregnation of the catalyst supports by the precursor resins. The XRD patterns identified the presence of cassiterite phase as well as the presence of characteristic phases of clay minerals which was confirmed by grazing incidence XRD. The spectroscopic data indicated the presence of peaks characteristic of the catalytic support as well as the active phase of catalyst (SnO2). The formation of active species (alkoxide) at low temperature, on the surface of catalysts, favored the soybean oil transesterification process. Rheological studies gave preliminary evidence that the catalytic reaction occurred with reduction of 40 % in the viscosity. / A produção de biodiesel é baseada na transesterificação de óleos vegetais ou gorduras animais, utilizando catalisadores homogêneos ou heterogêneos. O processo de transesterificação heterogênea apresenta conversões mais baixas em comparação com o homogêneo, porém, não apresenta problemas de corrosão e reduz à ocorrência de reações paralelas como saponificação. Neste sentido, este trabalho visa avaliar a atividade catalítica do SnO2 suportado em vermiculita [(Mg, Fe, Al)3(Al, Si)4O10(OH)2.4H2O] para a transesterificação do óleo de soja. Os diversos catalisadores foram obtidos pela impregnação da vermiculita com resina de estanho previamente sintetizada pelo método dos precursores poliméricos. Todas as amostras foram caracterizadas por análise térmica (TG/DTA), difração de raios-X (DRX), DRX de ângulo rasante, fluorescência de raios-X (FRX), microscopia eletrônica de varredura (MEV), espectroscopia vibracional na região do infravermelho (IV), espectroscopia Raman confocal. Os biodieseis foram sintetizados utilizando uma razão molar de 1:10 (óleo de soja: etanol) e 5,0 % (wt/catalisador) em peso, a 65 °C, e cujas caracterizações foram feitas por intermédio de medidas de viscosidade dinâmica e cinemática. Neste trabalho a vermiculita foi submetida a tratamento ácido utilizando ácido nítrico. O processo de lixiviação não causou mudanças na estabilidade térmica do sólido inorgânico. Dados da FRX apresentaram resultados satisfatórios de impregnação dos suportes catalíticos pelas resinas precursoras. Os DRX tanto identificaram a presença da fase cassiterita como também a presença das fases características dos argilominerais, confirmada pelas análises do DRX de ângulo rasante. Os dados espectroscópicos indicaram a presença dos picos típicos do suporte catalítico como também da fase ativa do catalisador (SnO2). A formação da espécie ativa (alcóxido) a baixa temperatura sobre a superfície dos catalisadores favoreceu o processo de transesterificação do óleo de soja comercial. Os estudos reológicos deram uma confirmação preliminar de que ocorreu o fenômeno da catálise, com redução de até 40 % da viscosidade.

Made available in DSpace on 2015-05-14T13:21:45Z (GMT). No. of bitstreams: 1 parte1.pdf: 2235233 bytes, checksum: 90091ce5e150c5df82bb72929b3cb2f0 (MD5) Previous issue date: 2008-08-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / SnO2 pigments, when doped with chromium, lead to violet or purple colors, depending on chromium oxidation state. There is a need to control the chromophore oxidation state, as Cr(VI) is toxic and carcinogenic, while Cr(III) leads to no risk to living beings. Cr(VI) formation may be avoided with the addition of counterions, that lead to a charge imbalance. In this work, SnO2:Cr pigments were synthesized by the polymeric precursor method, with the addition of molybdenum as counterion. The powder precursor decomposition was evaluated by thermogravimetry (TG) and differential thermal analysis (DTA). The influence of the counterion in the crystalline structure was evaluated by Xray diffraction. The materials were also characterized by infrared spectroscopy, colorimetry and UV-vis spectroscopy. All pigments are crystalline and single phase with cassiterite structure. Chromium formation with hexavalent state was observed in all samples, while Sn0.90Cr0.06Mo0.04O2 presented the lowest amount of this cation, comparing to the other pigments, being the less toxic one. Violet and rose colors were obtained for materials doped with chromium and chromium/molybdenum, respectively, being related to the formation of Cr(IV) in the material structure. / O SnO2 quando dopado com cromo forma pigmentos de coloração violeta e rósea, dependendo dos diferentes estados de oxidação do cromo. Contudo, há necessidade de um controle sobre o estado de oxidação do metal, já que o Cr(VI) é tóxico e cancerígeno, enquanto que o Cr(III) não oferece perigo aos seres vivos. Uma forma de evitar a formação de Cr(VI) é pela adição de contraíons, que levam a um balanço de cargas. Neste trabalho, pigmentos cerâmicos de SnO2:Cr na presença de contra-íon molibdênio foram sintetizados pelo método dos precursores poliméricos. A decomposição dos pós precursores foi estudada por termogravimetria (TG) e análise térmica diferencial (DTA). Foi realizado também o estudo da influência dos contra-íons na evolução da fase cristalina por meio de Difração de Raios-X (DRX). Os materiais foram caracterizados por infravermelho, colorimetria e espectroscopia de UV-vis. Os pigmentos mostraram-se cristalinos e monofásicos com a obtenção da fase cassiterita para todos os sistemas. A formação do cromo no seu estado hexavalente foi observada para todos os sistemas, contudo o pigmento Sn0,90Cr0,06Mo0,04O2 apresentou a menor quantidade formada desse cátion, quando comparado com os demais, tornando-se o menos tóxico dos pigmentos estudados. As cores violeta e rósea foram obtidas para os materiais dopado com cromo e cromo/molibdênio, respectivamente, que está associado à formação de Cr(IV) na estrutura do material.