Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The pavement construction industry aims to reduce its Greenhouse Gas (GHG) emissions by investigating various energy efficient practices. The industry has focused on reducing energy consumption by producing Warm Mix Asphalt (WMA) surfacing materials that are workable at lower temperatures in relation to Hot Mix Asphalt (HMA), as a means to reduce carbon emissions. Half-Warm Foamed Bitumen Mixtures (HWF) is a relatively new material and is produced at temperatures below 100°C. This translates to large energy savings to overcome the latent heat of steam when exceeding 100°C. The characteristics of HWF mixes are a compromise between those of Foamed Bitumen Stabilised material (BSM-foam) and HMA characteristics. These include to a limited extent the improved tensile strength, particle coating and durability of HMA; and the shear strength of BSM-foam. The use of microwave technology as an efficient heating method to produce improved engineering properties of BSM-foam is proposed in this study. The benefits include energy saving due to its volumetric heating capability as well as rapid heating which improve productivity when using suitable materials. The aspect of recycling material brings forth further energy saving and emissions reduction when reusing materials. The portability of the in-plant recycling machines is an ideal candidate with logistical advantages to implement microwave generators to produce HWF mixes. This study is subdivided into four parts as it progressively investigates the potential to heat aggregates and produce HWF material. Firstly it investigates the heating potential of four aggregates, namely Hornfels, Quartzite, Eucrite, Granite and Reclaimed Asphalt (RA) at various moisture contents using a microwave apparatus. The second part discusses the thermodynamics of the preliminary investigation to provide insight into the third part, the Primary Investigation. The primary investigation evaluates the tensile strength and shear properties of two material blends by respectively implementing Indirect Tensile Strength (ITS) and monotonic triaxial tests on specimens. The two blends were a combination of RA and crushed hornfels. The fourth and final part evaluates the HWF properties in relation to those of the equivalent BSM-foam product by means of a pavement analysis. The highest laboratory production temperature achieved was depicted by the material properties, microwave power capability and production rates. This temperature was consistently recorded at 50°C which theoretically simulates an in-field production rate of approximately 25 tons per hour. ITS test results indicate 100% increase in tensile strengths and an increase in compaction density for the HWF mixes. Large reduction in moisture contents is also observed after curing in relation to BSM-foam. The benefits in improving a layer within a pavement structure have an effect on the pavement’s overall performance. This could assist in reducing the requirement for premium layers e.g. thickness of HMA within the structure, thereby further assisting energy conservation. The evaluation of the microwave heated HWF mixes can be considered economical if designed with a purpose to meet the thermal dynamic requirements of a material considering the microwaves volumetric potential. / AFRIKAANSE OPSOMMING: Die plaveisel konstruksie-industrie poog om hul kweekhuisgas (KHG) uitskeiding te verlaag deur verskeie energie doeltreffende metodes te ondersoek. Die industrie fokus op die vermindering van energie-verbruik deur middel van die produksie van Warm Mengsel Asfalt (WMA) oppervlak materiale wat werkbaar is in laer temperature in verhouding tot “Hete Mengsel Asfalt (HMA)” as `n metode om koolstof uitskeiding te verlaag. Half-Warm Skuim-Bitumen Mengsels (HWS) is `n relatief nuwe materiaal en word vervaardig onder 100 °C. Dit lei tot groot energie besparings en oorkom sodoende die latente hitte van stoom wanneer temperature van 100 °C oorskry word. Die karakter-eienskappe van HWS mengsels is `n kompromie tussen Skuim-Bitumen Gestabiliseerde materiaal (BSM-S) en HMA eienskappe. Dit sluit tot `n beperkte mate in die verbeterde spankrag, partikel bestryking; en die skeer krag van BSM-S. Die gebruik van mikrogolf-tegnologie as effektiewe verwarmingsmetode vir verbeterde ingenieurseienskappe van BSM-S word voorgestel in hierdie studie. Die voordele sluit in energie besparing as gevolg van die volumetriese verwarmingsvermoë sowel as snel verhitting wat produktiwiteit verbeter tydens die gebruik van gepaste materiale. Die gebruik van herwinde materiaal bring verdere energiebesparing en uitskeiding-vermindering mee. Die draagbaarheid van binne-aanleg herwinningsmasjinerie is ‘n ideale kandidate met logistieke voordele vir die installering van mikrogolf-opwekkers vir die produsering van HWS mengsels. Dié studie word onderverdeel in vier dele terwyl dit toenemend ondersoek instel na die potensiaal van hitte versameling asook die produksie van HWS stowwe. Eerstens ondersoek dit die verwarmingspotensiaal van vier versamelings naamlik horingsteen, kwartsiet, eukrite, graniet en Herwinde Asfalt (HA) teenoor verskeie vogskattings-mikrogolf aperate. Die tweede deel bespreek die termodinamika van die voorlopige ondersoek om insig te bied vir die derde deel, die primêre ondersoek. Die primêre ondersoek evalueer die rekbaarheid en skeereienskappe van twee materiaal-mengsels van ITS en monotoniese drieassige toetse onderskeidelik op verskillende monsters. Die twee mengsels was `n kombinasie van HA en gemaalde horingsteen. Die vierde en finale deel evalueer die HWS eienskappe in verhouding tot die van die ekwivalente BSM-S produk deurmiddel van `n sypad-analise. Die hoogste laboratoriumproduksie temperature wat bereik was, was uitgebeeld deur die materiaal-eienskappe, mikrogolf krag kapasiteit en produksiekoers. Hierdie temperature was deurlopend aangeteken teen 50 °C wat `n teoretiese voorstelling is van `n binneveld produksie tempo van ongeveer 25 ton per uur. ITS toets resultate wys `n 100 % verhoging in spankrag asook `n toename in kompakte vir die HWS mengsels. Groot afname in voginhoud is ook waargeneem na bewerking in verhouding tot BSM-S. Die voordeel verbonde aan die verbetering van `n lag binne `n plaveisel-struktuur, het `n impak op die plaveisel se algemene uithoubaarheid. Dit kan bydra tot `n verlaging in die vereiste binne die struktuur en verdere bydra tot energie besparing. Die evaluering van mikrogolf verhitte HWS stowwe kan as ekonomies beskou word wanneer dit doelgerig vervaardig word om te voldoen aan die termodinamika vereistes van `n materiaal, wanneer die mikrogolf volumetriese potensiaal in ag geneem word.

Les inquiétudes concernant la gestion des déchets sont croissantes dans un contexte environnemental préoccupant. De ce fait, il est apparu urgent de trouver des substituts aux plastiques conventionnels et les biopolymères semblent être une réponse prometteuse. Leurs propriétés leur permettent des usages très divers, de l'emballage alimentaire à la bio-ingénierie tissulaire en passant par la formulation cosmétique ou la pharmaceutique. S'ils jouissent d'une image positive et de l'intérêt croissant des scientifiques comme des industriels, on ne connait encore que peu leur comportement lors du vieillissement. Ce travail de thèse se propose d'étudier d'une part le vieillissement en enceinte climatique à paramètres contrôlés de certains polymères bio-sourcés et biodégradable (HPMC, Chitosan, PLA) et d'autre part, l'influence d'un traitement micro-onde sur des films de chitosan dans le cadre d'une utilisation comme le packaging alimentaire. Au cours du vieillissement, les biopolymères subissent plusieurs modifications structurales telles que des ruptures de chaînes et des phénomènes de cristallisation. Ces modifications altèrent les propriétés mécaniques des films de biopolymères. Par ailleurs, les films de chitosan, exposés au micro-onde, vont présenter un phénomène de jaunissement, révélateur de la production de composés néo-formés issus de la réaction de Maillard et susceptibles de migrer vers l'aliment en cas de contact avec le film de biopolymère / Today's increased environmental concerns and the growing questions about disposal management are contributing to growth in biopolymer industry. These materials are used in various fields such as pharmaceutic, bioengineering or tissue engineering as cell support, food formulation or packaging. In spite of a positive perception of biopolymers to improve environmental issues, biopolymers properties remain unknown, even though their biodegradability is well documented. Here we consider the influence of aging in climatic chamber on different biopolymers (HPMC, Chitosan and PLA) and in to what extent it could modify their structure and properties. Moreover, considering the opportunity for theses materials to be used as food packaging, influence of microwave heating was also tested on chitosan films. The food consumption trends tend, indeed, to the development of ready-to-eat meal that is why it is crucial to investigate theses biopolymers behavior when used in microwave oven in food contact. The aim of this study is to bring new knowledge of theses materials and to guarantee an optimal and safe use as a food contact packaging. The results showed several deep modifications in the biopolymers structure such as chain scissions or crystallization. These modifications involved a decrease in the polymer's properties. Chitosan films, exposed to increasing microwave heating times, showed gradually increasing yellowing. Maillard neoformed compounds are responsible for this color change and could be deleterious for consumer safety because of the possibility of migration in case of food contact

De modo geral, os ciclos de cura para resina epóxi demandam algumas horas e elevadas temperaturas. Em busca de novas soluções para a otimização de processos sem perda de qualidade, bem como a economia de energia, diversos processos de cura de resina epóxi não convencionais foram desenvolvidos ao longo dos anos. O uso de irradiação de micro-ondas teve início após a Segunda Guerra Mundial, com a invenção do RADAR. A radiação de micro-ondas é uma radiação não-ionizante, com bom poder de penetração e boa transferência de calor em materiais absorvedores, ou materiais com cargas absorvedoras. A frequência usualmente utilizada em trabalhos de pesquisa e desenvolvimento é de 2,45GHz, a mesma disponível nos equipamentos comerciais e industriais existentes. Para a cura de resinas epóxi não são necessárias alterações no sistema reativo, com iniciadores específicos sensíveis a micro-ondas. O \"efeito micro-ondas\" proporciona um aumento da velocidade de colisão entre os reagentes que, associada à energia absorvida pelo sistema reacional, acelera a reação de cura, possibilitando a cura de resinas de tempo de uso longo (superior a 24 horas, em temperatura ambiente) em questão de minutos. Neste estudo foi utilizado inicialmente um sistema epóxi do tipo DGEBA, com endurecedor à base de anidrido e acelerador à base de amina, nas mesmas condições comerciais indicadas pelo fabricante. Testes iniciais com os fornos de micro-ondas selecionados foram realizados previamente a operação com sistemas epóxi. A cura do sistema já catalisado foi realizada em dois diferentes fornos de micro-ondas adaptados para uso em laboratório. A temperatura de degradação, e a temperatura de transição vítrea, foram avaliadas por técnicas de análise térmica. Cargas, pigmentos e aditivos também foram avaliados, no sentido de determinar suas influências em misturas com o sistema epóxi escolhido. Após estudos preliminares com o sistema epóxi puro, foram realizados testes em compósitos reforçados com fibra de vidro. Os resultados indicam que o processo é promissor, correspondendo ao observado em diversos artigos na literatura. / Generally, the cure cycles epoxy resin demand for few hours, and elevated temperatures. In search of new solutions for process optimization without loss of quality as well as energy saving, various processes of curing epoxy resin unconventional were developed over the years. The use of microwave irradiation began after World War II, with the invention of RADAR. The microwave radiation is non-ionizing radiation, with good power of penetration and good heat transfer in absorbing materials, or materials with absorbing fillers. The frequency usually used in research and development is of 2.45 GHz, the same is available in commercial equipment. For curing epoxy resins are not necessary changes in the system reactive with specific initiators sensitive to microwaves. The \"microwave effect\" provides increased on collision velocity between the reactants, which combined with energy absorbed by the reaction system, its accelerates the reaction curing, allowing the resin to cure long pot-life (times greater than 24 hours) in minutes. In this study, a DGEBA epoxy resin with an anhydride based hardener, and an initiator based on amine was used under the same conditions indicated by the manufacturer. Preliminary tests with the microwave ovens selected were executed before the operation with epoxy systems. The curing of the catalyzed system was performed in two different adapted microwave ovens for use in laboratory. The degradation temperature and the glass transition temperature were evaluated by thermal analysis techniques. Fillers, pigments and additives also were evaluated to determinate the influences with and without the epoxy system. After previous tests with the epoxy system alone, it was realized tests in composites form with glass fiber. The initial results indicate that the curing process by microwave irradiation is promising, and corresponding with the literature.

De modo geral, os ciclos de cura para resina epóxi demandam algumas horas e elevadas temperaturas. Em busca de novas soluções para a otimização de processos sem perda de qualidade, bem como a economia de energia, diversos processos de cura de resina epóxi não convencionais foram desenvolvidos ao longo dos anos. O uso de irradiação de micro-ondas teve início após a Segunda Guerra Mundial, com a invenção do RADAR. A radiação de micro-ondas é uma radiação não-ionizante, com bom poder de penetração e boa transferência de calor em materiais absorvedores, ou materiais com cargas absorvedoras. A frequência usualmente utilizada em trabalhos de pesquisa e desenvolvimento é de 2,45GHz, a mesma disponível nos equipamentos comerciais e industriais existentes. Para a cura de resinas epóxi não são necessárias alterações no sistema reativo, com iniciadores específicos sensíveis a micro-ondas. O \"efeito micro-ondas\" proporciona um aumento da velocidade de colisão entre os reagentes que, associada à energia absorvida pelo sistema reacional, acelera a reação de cura, possibilitando a cura de resinas de tempo de uso longo (superior a 24 horas, em temperatura ambiente) em questão de minutos. Neste estudo foi utilizado inicialmente um sistema epóxi do tipo DGEBA, com endurecedor à base de anidrido e acelerador à base de amina, nas mesmas condições comerciais indicadas pelo fabricante. Testes iniciais com os fornos de micro-ondas selecionados foram realizados previamente a operação com sistemas epóxi. A cura do sistema já catalisado foi realizada em dois diferentes fornos de micro-ondas adaptados para uso em laboratório. A temperatura de degradação, e a temperatura de transição vítrea, foram avaliadas por técnicas de análise térmica. Cargas, pigmentos e aditivos também foram avaliados, no sentido de determinar suas influências em misturas com o sistema epóxi escolhido. Após estudos preliminares com o sistema epóxi puro, foram realizados testes em compósitos reforçados com fibra de vidro. Os resultados indicam que o processo é promissor, correspondendo ao observado em diversos artigos na literatura. / Generally, the cure cycles epoxy resin demand for few hours, and elevated temperatures. In search of new solutions for process optimization without loss of quality as well as energy saving, various processes of curing epoxy resin unconventional were developed over the years. The use of microwave irradiation began after World War II, with the invention of RADAR. The microwave radiation is non-ionizing radiation, with good power of penetration and good heat transfer in absorbing materials, or materials with absorbing fillers. The frequency usually used in research and development is of 2.45 GHz, the same is available in commercial equipment. For curing epoxy resins are not necessary changes in the system reactive with specific initiators sensitive to microwaves. The \"microwave effect\" provides increased on collision velocity between the reactants, which combined with energy absorbed by the reaction system, its accelerates the reaction curing, allowing the resin to cure long pot-life (times greater than 24 hours) in minutes. In this study, a DGEBA epoxy resin with an anhydride based hardener, and an initiator based on amine was used under the same conditions indicated by the manufacturer. Preliminary tests with the microwave ovens selected were executed before the operation with epoxy systems. The curing of the catalyzed system was performed in two different adapted microwave ovens for use in laboratory. The degradation temperature and the glass transition temperature were evaluated by thermal analysis techniques. Fillers, pigments and additives also were evaluated to determinate the influences with and without the epoxy system. After previous tests with the epoxy system alone, it was realized tests in composites form with glass fiber. The initial results indicate that the curing process by microwave irradiation is promising, and corresponding with the literature.

Ce travail vise à étudier l'intérêt duchauffage micro-ondes pour l'inactivation desenzymes dans les jus de fruit, à travers desapproches numériques et aussi expérimentales.En premier lieu, une étude sur les propriétésdiélectriques des jus de fruits modèles est menée,démontrant leur forte sensibilité à la température,à la fréquence et à la composition du produit. Dansune seconde partie, l'inactivation de la peroxydaseest étudiée par chauffage conventionnel et lesdonnées sont ajustées par un modèle cinétique dupremier ordre. Dans la troisième et principalepartie de ce travail, un modèle tridimensionnel,résolu par éléments finis, est proposé pour simulerle chauffage par micro-ondes du jus, en couplantélectromagnétisme, transfert de chaleur etécoulement, avec la cinétique d'inactivation de laperoxydase précédemment déterminée.Cette simulation permet de prédire la distributionspatiale de la température, le profil d’écoulementet l'inactivation de la peroxydase. L’accord entre lemodèle et les expériences est très satisfaisant, cequi confirme la pertinence de l’approche. Dans ladernière partie, les réactivations de la peroxydaseaprès chauffage conventionnel et micro-ondessont évaluées et comparées. Enfin, l’éventuelleexistence d’effets non thermiques des microondesest discutée via des expériencesadditionnelles. En conclusion, ces travauxmontrent tout l’intérêt de la simulation numériquecomme outil de compréhension du processusmultiphysique du chauffage par micro-ondes pourl’inactivation des enzymes, ce qui peut êtreparticulièrement intéressant pour la conception etl’optimisation de traitements micro-ondes. / This work aims at studying the use ofmicrowave heating for enzyme inactivation in fruitjuices by means of numerical and experimentalapproaches. In the first part, a study on thedielectric properties of model fruit juices isconducted, evidencing their high dependence onthe temperature, frequency and composition of theproduct. Then in the second part, the inactivation ofperoxidase is studied using conventional heatingand the data are fitted by a first order kinetic model.In the third and main part of this work, a threedimensionalfinite element model is developed tosimulate the microwave heating of juices, couplingelectromagnetics, heat transfer and fluid flow aswell as the peroxidase inactivation kineticspreviously determined.As a result, spatial temperature distribution, flowpattern and peroxidase inactivation are obtained.The model is experimentally validated and goodagreement is observed, confirming the relevanceof the approach. Finally, in the last part, thepotential peroxidase reactivations afterconventional and microwave heating areassessed and compared. Also, the possibleexistence of non-thermal effects of microwaves isdiscussed thanks to additional experimentations.In conclusion, this work shows the large interest ofcomputer simulation as a tool for understandingthe multiphysics process of microwave heating forenzyme inactivation, which can be particularlyinteresting for further design of optimizedmicrowave processing.

It is widely accepted that palladium is one of the most useful catalysts in organic chemistry, and many palladium(0)-catalysed carbon–carbon bond-forming reactions have been developed over the years. In addition, the ever-growing need for more environmentally benign processes in the chemical industry has driven scientists to look for greener options while developing new methodologies for organic synthesis. This thesis describes a series of studies on Suzuki and Heck coupling reactions in water and the application of palladium(0) catalysis to the development of new HIV-1 integrase inhibitors. The previously described 'transition-metal-free Suzuki-type coupling' reaction was shown to take place due to sub-ppm levels of palladium contaminants present in the commercially available sodium carbonate base. Based on this finding, a new, microwave-assisted Suzuki protocol utilizing ppb/ppm levels of palladium in water was developed. This methodology was adapted to terminal Heck coupling, although the scope of the protocol was found to be rather limited. Finally, both Suzuki and Heck reaction processes were successfully scaled up to 100 mmol using an automated batch stop-flow microwave apparatus. As the methodologies utilizing ultralow palladium concentrations were not applicable to aryl chlorides, attention was shifted towards palladium on carbon. This simple catalyst, together with microwave heating employing simultaneous cooling, was found to be beneficial in the Suzuki coupling of aryl chlorides with phenylboronic acid in water. Ligand-controlled internal arylation of ethylene glycol vinyl ether with aryl halides was shown to be possible in water alone without any additives. Reactions were run under air, using conventional heating and the products formed were isolated as aryl methyl ketones in good to excellent yields. The electron-rich (dippp)2Pd complex was shown to be beneficial for the microwave-assisted internal arylation of some aryl chlorides. Furthermore, the active role of the hydroxyl group of ethylene glycol vinyl ether in the formation of a cationic intermediate leading to internal Heck coupling product was elucidated. Finally, to demonstrate the usefulness of palladium(0) catalysis in the development of new pharmaceutical entities, a series of HIV-1 integrase inhibitors was synthesised and evaluated in strand transfer assays and in vitro. Based on the results and docking studies performed, valuable information related to the structure–activity relationship was obtained.

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Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-05-23T23:17:13Z No. of bitstreams: 1 JoséDAN_DISSERT.pdf: 4366336 bytes, checksum: 608d3dd1b2cdbeef88c6fe49d0d9dfa1 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-05-24T11:15:50Z (GMT) No. of bitstreams: 1 JoséDAN_DISSERT.pdf: 4366336 bytes, checksum: 608d3dd1b2cdbeef88c6fe49d0d9dfa1 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-05-24T11:16:18Z (GMT) No. of bitstreams: 1 JoséDAN_DISSERT.pdf: 4366336 bytes, checksum: 608d3dd1b2cdbeef88c6fe49d0d9dfa1 (MD5) / Made available in DSpace on 2017-05-24T11:16:55Z (GMT). No. of bitstreams: 1 JoséDAN_DISSERT.pdf: 4366336 bytes, checksum: 608d3dd1b2cdbeef88c6fe49d0d9dfa1 (MD5) Previous issue date: 2016-06-02 / Agência Nacional do Petróleo, Gás Natural e Biocombustíveis / With the increasing demand of oil products, the need arises to seek more and more new extraction techniques to increase the production of barrels at the lowest possible cost. With this also comes the concern for the environment and the entire ecosystem near the mining fields. Techniques to increase the recovery factor of these wells has been developed and refined over the past few years. The heating method by microwave is a process where the electromagnetic energy at high frequency is transformed into thermal energy dielectric loss and / or electromagnetic absorption. Research using as a basis the increase of technical electromagnetic heating recovery factor is still poorly developed. The present work aim is to develop a pipeline model filled by brackish water and heavy oil, the main components present in oil wells the Northeast, and heating it using microwaves to reduce its viscosity. This process is intended to prevent the extraction system is blocked by paraffin buildup. Five models were developed for the realization of studies heating by electromagnetic radiation and potential were varied in three steps. The simulations were all developed using multifísico software COMSOL. The simulation results are plotted in graphs in one and two dimensions, in order to compare the performance of each model used to describe the energy conversion efficiency in the system and analyzing the propagation and absorption of electromagnetic radiation in the dielectric / Com a crescente demanda dos produtos derivados do petróleo, surge a necessidade de buscar cada vez mais novas técnicas de extração que aumente a produção de barris com o menor custo possível. Com isso, surge também a preocupação com o meio ambiente e todo o eco sistema próximo aos campos de extração. Técnicas para aumentar o fator de recuperação desses poços vem sendo desenvolvidas e aperfeiçoadas ao longo dos últimos anos. O método de aquecimento por micro-ondas é um processo onde a energia eletromagnética em alta frequência é transformada em energia térmica por perdas dielétricas e/ou absorção eletromagnética. As pesquisas usando como base as técnicas de aumento do fator de recuperação por aquecimento eletromagnético ainda são pouco desenvolvidas. O intuito do presente trabalho é o de desenvolver um modelo de duto totalmente preenchido por água salobra e óleo pesado, principais componentes presentes em poços de petróleo da região nordeste, e aquecer o mesmo usando micro-ondas para diminuir sua viscosidade. Esse processo tem por finalidade evitar que o sistema de extração seja obstruído por acúmulo de parafina. Cinco modelos foram desenvolvidos para a realização dos estudos de aquecimento por radiação eletromagnética e as potencias foram variadas em três etapas. As simulações foram todas desenvolvidas usando o software multifísico COMSOL. Os resultados das simulações foram plotados em gráficos em uma e duas dimensões, com o intuito de comparar o desempenho de cada modelo adotado, descrever a eficiência de conversão de energia no sistema e analisar a propagação e absorção da radiação eletromagnética no dielétrico / 2017-05-23

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Made available in DSpace on 2014-10-09T12:52:09Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:11Z (GMT). No. of bitstreams: 0 / Vidros fosfatos são investigados desde a década de 50, sendo obtidos a partir da fusão de compostos inorgânicos em temperaturas relativamente baixas (1000- 1200oC), apresentando baixas temperaturas de transição vítrea. No entanto, estes vidros são sensíveis a ambientes com altas umidades relativas, mostrando certa fragilidade em relação à durabilidade química. Vidros fosfatos de ferro foram obtidos previamente a partir da fusão de precursores inorgânicos apropriados, tanto em fornos de indução, como em fornos elétricos convencionais. A presença de ferro promove o aumento da durabilidade química, suficiente para possibilitar o uso destes materiais como meio imobilizador de rejeitos radioativos ou como fibras de resistência mecânica, adequadas para aplicações específicas. O uso de microondas tem sido investigado exaustivamente, pois possibilita um aquecimento rápido e homogêneo dos materiais. A radiação de microondas interage diretamente com dipolos e íons presentes na estrutura do material promovendo o seu aquecimento. Vidros fosfatos contendo nióbio também já foram produzidos por meio do aquecimento de precursores em fornos de microondas. Outros vidros contendo ferro em sua estrutura foram produzidos por fornos convencionais e tiveram suas estruturas analisadas. Mas mesmo assim, ainda não foi reportada síntese de vidros fosfatos com ferro a partir da fusão de precursores em fornos de microondas. Neste trabalho, misturas de fosfato de amônia dibásico (NH4)2HPO4 e magnetita (Fe3O4) ou (NH4)2HPO4 e ferrita (Fe2O3) foram expostas às microondas, com radiação eletromagnética de 2,45 GHz. Propõe-se que a absorção desta radiação pelo material à temperatura ambiente cause o aquecimento até a completa fusão e homogeneização do material. Os vidros fosfatos de ferro obtidos foram caracterizados por espectroscopia Mössbauer, Difratometria de raios X e Análise térmica diferencial. Uma comparação é realizada com vidros obtidos por meio da fusão em fornos elétricos. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP